Analyte sensing device

Abstract

A sensing device for detecting analytes within a package or container is disclosed. The sensing device may include a substrate, one or more electrodes, and a sensor array disposed on the substrate. The sensor array may include a plurality of carbon-based sensors coupled to the one or more electrodes. Each of the sensors may be configured to react with a unique group of analytes in response to an electromagnetic signal received from an external device. In some cases, a first sensor may be functionalized with a first material configured to detect the presence of each analyte in the first group of analytes, and a second sensor may be functionalized with a second material configured to detect the presence of each analyte in the second group of analytes. The second group of analytes may be a subset of the first group of analytes, and the second material may be different from the first material.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to detecting analytes, and more particularly to increasing the accuracy of analyte sensing devices. [Background technology]

[0002] Chemical sensors operate by generating a signal in response to the presence of a particular chemical. Conventional analyte sensors typically require a relatively high output energy source to detect relatively low concentrations of analyte (e.g., less than one part per billion (ppb)), which makes widespread adoption of such sensors impractical. Further improvements in chemical and vapor sensors are desirable. Summary of the Invention

[0003] This Summary is provided to introduce some concepts in a simplified form that are further described below in the Detailed Description. It is not intended to identify key features or important features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0004] One innovative aspect of the subject matter described in this disclosure may be implemented as a sensing device for detecting analytes. The sensing device may include a substrate and a sensor array. The sensor array may be disposed on the substrate and may include a plurality of carbon-based sensors. In some embodiments, a first carbon-based sensor disposed between a first pair of electrodes may be configured to detect the presence of each analyte in a first group of analytes, and a second carbon-based sensor disposed between a second pair of electrodes may be configured to detect the presence of each analyte in a second group of analytes, where the second group of analytes is a subset of the first group of analytes. In some cases, the first group of analytes may include at least twice as many different analytes as the second group of analytes. In some embodiments, the first carbon-based sensor may be configured to generate a first output signal in response to detecting the presence of one or more analytes in the first group of analytes, and the second carbon-based sensor may be configured to generate a second output signal in response to confirming the presence of one or more analytes detected by the first carbon-based sensor. In one embodiment, the first and second output signals may be currents based at least in part on alternating currents applied to the first and second carbon-based sensors. In some cases, a ratio of the current of the first output signal to the alternating current may indicate a concentration of at least one of the detected analytes, and a ratio of the current of the second output signal to the alternating current may indicate a concentration of at least one of the confirmed analytes.

[0005] In other embodiments, the first and second output signals may indicate the impedance of the first and second carbon-based sensors, respectively. In some aspects, the first output signal may indicate a change in impedance of the first carbon-based sensor caused by exposure to one or more analytes of a first group of analytes, and the second output signal may indicate a change in impedance of the second carbon-based sensor caused by exposure to one or more analytes of a second group of analytes. In some other embodiments, the first and second output signals may indicate the frequency responses of the first and second carbon-based sensors, respectively. In some cases, the frequency response of the first carbon-based sensor may indicate the presence or absence of each analyte of the first group of analytes, and the frequency response of the second carbon-based sensor may indicate the presence or absence of each analyte of the second group of analytes. The frequency responses may be based on electrochemical impedance spectroscopy (EIS) sensing or resonant impedance spectroscopy (RIS) sensing.

[0006] In various embodiments, a first carbon-based sensor may be functionalized with a first material configured to react with each analyte of a first group of analytes, and a second carbon-based sensor may be functionalized with a second material configured to react only with analytes of a second group of analytes. In some cases, the first material may be a cobalt-decorated carbon nano-onion (CNO) configured to detect the presence of one or more of triacetone triperoxide (TATP), toluene, ammonia, or hydrogen sulfide (HS), and the second material may be an iron-decorated three-dimensional (3D) graphene-containing structure configured to detect the presence of toluene.

[0007] The substrate may be paper, a flexible polymer, or other suitable material. In some embodiments, the substrate and sensor array may be integrated within a label configured to be removably printed on the surface of a package or container. In some aspects, each of the carbon-based sensors may be printed on the substrate using a different carbon-based ink, and the electrode pair may be printed on the substrate using an ohmic-based ink. In some cases, the first and second carbon-based sensors may be stacked on top of each other. In other cases, the first and second carbon-based sensors may be positioned next to each other.

[0008] In some embodiments, each of the carbon-based sensors may include a plurality of different graphene allotropes. In some embodiments, the different graphene allotropes of each of the carbon-based sensors may include one or more microporous or mesoporous pathways. Each of the carbon-based sensors may include a polymer configured to bond the plurality of different graphene allotropes to one another. The polymer may include a humectant configured to reduce the sensitivity of each of the carbon-based sensors to humidity.

[0009] Another innovative aspect of the subject matter described in this disclosure may be implemented as a sensing device for detecting analytes in a package or container. In various embodiments, the sensing device may include a substrate, one or more electrodes, and a sensor array. The sensor array may be disposed on the substrate and may include a plurality of carbon-based sensors coupled to the one or more electrodes. In some embodiments, the carbon-based sensors may be configured to react with unique groups of analytes in response to electromagnetic signals received from an external device. In some cases, the carbon-based sensors may be configured to resonate at different frequencies in response to the electromagnetic signals. Each of the one or more electrodes may be configured to provide an output signal indicative of whether the corresponding carbon-based sensor detects one or more analytes in each of the unique groups of analytes. In some cases, each output signal may indicate the impedance or reactance of the corresponding carbon-based sensor.

[0010] Additionally or alternatively, a first frequency response of a first carbon-based sensor to the electromagnetic signal may indicate the presence or absence of a first group of analytes in the package or container, and a second frequency response of a second carbon-based sensor to the electromagnetic signal may indicate the presence or absence of a second group of analytes in the package or container. In some cases, the first frequency response may be based at least in part on exposing the first carbon-based sensor to the electromagnetic signal for a first period of time, and the second frequency response may be based at least in part on exposing the second carbon-based sensor to the electromagnetic signal for a second period of time that is longer than the first period of time. In some cases, the second period of time is at least twice as long as the first period of time. The first and second frequency responses may be based on resonant impedance spectroscopy (RIS) sensing.

[0011] In various embodiments, a first carbon-based sensor may be functionalized with a first material configured to detect the presence of each analyte in a first group of analytes, and a second carbon-based sensor may be functionalized with a second material configured to detect the presence of each analyte in a second group of analytes. The second group of analytes may be a subset of the first group of analytes, and the second material may be different from the first material. In some embodiments, the first group of analytes may include at least twice as many different analytes as the second group of analytes. In some cases, the first material may be a cobalt-decorated carbon nano-onion (CNO) configured to detect the presence of one or more of triacetone triperoxide (TATP), toluene, ammonia, or hydrogen sulfide (HS), and the second material may be an iron-decorated three-dimensional (3D) graphene-containing structure configured to detect the presence of toluene. In various embodiments, the third carbon-based sensor may be functionalized with a third material configured to detect the presence of each analyte in a third group of analytes, where the third group of analytes may be a different subset of the first group of analytes, and the third material may be different from the first and second materials.

[0012] In some embodiments, at least two of the carbon-based sensors may be juxtaposed in a planar arrangement on a substrate. In other embodiments, the carbon-based sensors may be stacked on top of each other in a vertical arrangement. For example, in one embodiment, the carbon-based sensors may form a dielectric gradient. In some embodiments, a single electrode may be configured to provide an output signal indicating whether the stacked carbon-based sensors detect one or more analytes. The single electrode may also be configured to provide the output signal to an external device.

[0013] The substrate may be paper, a flexible polymer, or other suitable material. In some embodiments, the substrate and sensor array may be integrated within a label that can be removably printed on the surface of a package or container. In some aspects, each of the carbon-based sensors may be printed on the substrate using a different carbon-based ink, and the one or more electrodes may be printed on the substrate using an ohmic-based ink. In some embodiments, each of the carbon-based sensors may include multiple different graphene allotropes. In some aspects, the different graphene allotropes of each carbon-based sensor may include one or more microporous or mesoporous pathways. Each of the carbon-based sensors may include a polymer configured to bond the multiple different graphene allotropes to one another. The polymer may include a humectant configured to reduce the sensitivity of each carbon-based sensor to humidity.

[0014] Another innovative aspect of the subject matter described in this disclosure may be implemented as a sensing device for monitoring a battery pack. The sensing device may include a substrate and a plurality of carbon-based sensors disposed on the substrate. Each of the carbon-based sensors may be coupled between a corresponding pair of electrodes. In some embodiments, the 3D graphene-based sensing material of a first carbon-based sensor may be functionalized with a first material configured to detect the presence of each analyte in a first group of analytes, and the 3D graphene-based sensing material of a second carbon-based sensor may be functionalized with a second material configured to detect the presence of each analyte in a second group of analytes. In some embodiments, the second group of analytes may be a subset of the first group of analytes, and the first group of analytes may include at least twice as many different analytes as the second group of analytes. In some cases, the first and second carbon-based sensors may be stacked on top of each other. In other cases, the first and second carbon-based sensors may be positioned next to each other. In some embodiments, the carbon-based sensors may be carbon-based ink printed on the substrate. In some cases, the first carbon-based sensor may be a first carbon-based ink and the second carbon-based sensor may be a second carbon-based ink that is different from the first carbon-based ink.

[0015] The first carbon-based sensor may be configured to generate a first output signal in response to detecting the presence of one or more analytes of the first group of analytes, and the second carbon-based sensor may be configured to generate a second output signal in response to confirming the presence of the one or more analytes detected by the first carbon-based sensor. In some embodiments, the sensing device may include an input terminal for receiving an alternating current, and the first and second output signals may be currents based at least in part on the alternating current. In some cases, a first difference between the alternating current and the first output signal may indicate the presence or absence of one or more analytes of the first group of analytes, and a second difference between the alternating current and the second output signal may indicate the presence or absence of one or more analytes of the second group of analytes.

[0016] In other embodiments, the first output signal may indicate a change in impedance of a first carbon-based sensor caused by exposure to one or more analytes of a first group of analytes, and the second output signal may indicate a change in impedance of the carbon-based sensor caused by exposure to one or more analytes of a second group of analytes. In some cases, a relatively small change in impedance of each carbon-based sensor may indicate the absence of the corresponding group of analytes, and a relatively large change in impedance of each carbon-based sensor may indicate the presence of the corresponding group of analytes.

[0017] In some other embodiments, the sensing device may include an antenna configured to receive an electromagnetic signal from an external device, and the first and second output signals may be frequency responses of the 3D graphene-based sensing material of the first and second carbon-based sensors, respectively, to the electromagnetic signal. For example, the frequency response of the 3D graphene-based sensing material of the first carbon-based sensor may indicate the presence or absence of one or more analytes of a first group of analytes, and the frequency response of the 3D graphene-based sensing material of the second carbon-based sensor may indicate the presence or absence of one or more analytes of a second group of analytes. In some embodiments, the frequency responses may be based on resonant impedance spectroscopy (RIS) sensing.

[0018] In various embodiments, at least one of the output signals may indicate an operating mode of the battery pack. In some embodiments, the at least one output signal may indicate a normal mode based on the absence of any analyte from the first group of analytes, a maintenance mode based on the presence of one or more analytes from the first group of analytes not exceeding a threshold level, or an emergency mode based on the presence of one or more analytes from the first group of analytes exceeding a threshold level. Additionally, or alternatively, the first output signal may indicate a concentration level of one or more analytes from the first group of analytes, and the second output signal may indicate a concentration level of one or more analytes from the second group of analytes.

[0019] In some embodiments, the analytes of the first and second groups of analytes may include one or more volatile organic compounds (VOCs), including any one or more of carbon dioxide (CO), carbon monoxide (CO), nitrogen dioxide (NO), one or more hydrocarbons including methane (CH), ethylene (C2H4), ethane (C2H6), or propane (C3H8), one or more acids including hydrochloric acid (HCl) or hydrofluoric acid (HF), one or more fluorinated hydrocarbons including phosphorus oxyfluorides, hydrogen cyanide (HCN), one or more aromatic compounds including benzene (C6H6), toluene (C7H8), or ethanol (C2H5OH), hydrogen carbonate including ethylene carbonate (C3H4O3), dimethyl carbonate (C3H6O3), or propylene carbonate (C4H3O3), a carbonate ester-based electrolyte, or one or more reduced sulfur compounds including thiols having the form R-SH. In some embodiments, each of the 3D graphene-based sensing materials may be configured to adsorb VOCs. In some embodiments, each of the carbon-based sensors may include a plurality of different graphene allotropes. The plurality of different graphene allotropes in each carbon-based sensor may include one or more microporous or mesoporous pathways.

[0020] Another innovative aspect of the subject matter described in this disclosure may be embodied as a container for storing one or more items. The container may include a surface defining a volume of the container and a label printed on the container. In various embodiments, the label may include a substrate, a plurality of carbon-based sensors printed on the substrate, and one or more electrodes printed on the substrate. The carbon-based sensors may be collectively configured to detect the presence of one or more analytes in the container. In some embodiments, each of the carbon-based sensors may be configured to react with a unique group of analytes in response to an electromagnetic signal received from an external device. One or more electrodes may be coupled to at least some of the carbon-based sensors and configured to provide one or more output signals indicative of the presence or absence of one or more analytes in the container. In some embodiments, a first electrode coupled to a first carbon-based sensor may be configured to indicate the presence of one or more analytes of a first group of analytes, and a second electrode coupled to a second carbon-based sensor may be configured to confirm the presence of the analyte detected by the first carbon-based sensor. In some embodiments, the carbon-based sensors may be configured to resonate at different frequencies in response to the electromagnetic signal.

[0021] In some embodiments, a first carbon-based sensor may be functionalized with a first material configured to detect the presence of each analyte in a first group of analytes, and a second carbon-based sensor may be functionalized with a second material configured to detect the presence of each analyte in a second group of analytes, where the second group of analytes may be a subset of the first group of analytes. In some embodiments, the first group of analytes may include at least twice as many different analytes as the second group of analytes. The second material may be different from the first material. For example, in one embodiment, the first material may be a cobalt-decorated carbon nano-onion (CNO) configured to detect the presence of one or more of triacetone triperoxide (TATP), toluene, ammonia, or hydrogen sulfide (HS), and the second material may be an iron-decorated three-dimensional (3D) graphene-containing structure configured to detect the presence of toluene. In another example, the third carbon-based sensor may be functionalized with a third material configured to detect the presence of each analyte in a third group of analytes, where the third group of analytes is a different subset of the first group of analytes, and where the third material is different from the first and second materials.

[0022] In some embodiments, each output signal may indicate a frequency response of the corresponding carbon-based sensor to the electromagnetic signal. In some cases, a first frequency response of a first carbon-based sensor to the electromagnetic signal may indicate the presence or absence of a first group of analytes in the container, and a second frequency response of a second carbon-based sensor to the electromagnetic signal may indicate the presence or absence of a second group of analytes in the container. The first frequency response may be based at least in part on exposing the first carbon-based sensor to the electromagnetic signal for a first period of time, and the second frequency response may be based at least in part on exposing the second carbon-based sensor to the electromagnetic signal for a second period of time that is longer than the first period of time. In some embodiments, the second period of time is at least twice as long as the first period of time. The first and second frequency responses may be based on resonant impedance spectroscopy (RIS) sensing.

[0023] In various embodiments, the antenna may be printed on the substrate and configured to pass a current through the carbon-based sensor in response to an electromagnetic signal. In some embodiments, each output signal may indicate the impedance or reactance of the corresponding carbon-based sensor to the current. The impedance or reactance of the carbon-based sensor may indicate the presence or absence of one or more analytes in the container. For example, the impedance or reactance of a first carbon-based sensor may indicate the presence or absence of an analyte in a first group of analytes, and the impedance or reactance of a second carbon-based sensor may indicate the presence or absence of an analyte in a second group of analytes. In some cases, at least two of the carbon-based sensors are juxtaposed in a planar arrangement on the substrate. In other cases, the carbon-based sensors are stacked on top of each other. In some embodiments, the carbon-based sensors may form a dielectric gradient.

[0024] In some embodiments, each of the carbon-based sensing materials may include multiple different graphene allotropes. In some embodiments, the different graphene allotropes of each carbon-based sensor may include one or more microporous or mesoporous pathways. Each of the carbon-based sensors may include a polymer configured to bond the multiple different graphene allotropes to one another. The polymer may include a humectant configured to reduce the sensitivity of each carbon-based sensor to humidity.

[0025] The details of one or more embodiments of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. Note that the relative dimensions of the following figures may not be drawn to scale. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 illustrates an example of a sensing device configured to detect an analyte, according to some embodiments. [Figure 2] FIG. 2 illustrates the sensing device of FIG. 1 coupled to a receptor, according to some embodiments. [Figure 3] FIG. 2 illustrates the sensing device of FIG. 1 configured to detect an analyte with a battery pack, according to some embodiments. [Figure 4] FIG. 2 illustrates the sensing device of FIG. 1 configured to detect an analyte with a battery pack, according to some embodiments. [Figure 5] 2 illustrates a reaction between one or more analytes and the sensing device of FIG. 1, according to some embodiments. [Figure 6] 2 is a block diagram of an analyte detection system including the sensing device of FIG. 1 according to some embodiments. [Figure 7A] FIG. 1 illustrates a sensor array configured to detect an analyte, according to various embodiments. [Figure 7B] FIG. 1 illustrates a sensor array configured to detect an analyte, according to various embodiments. [Figure 7C] FIG. 1 illustrates a sensor array configured to detect an analyte, according to various embodiments. [Figure 7D] FIG. 1 illustrates a sensor array configured to detect an analyte, according to various embodiments. [Figure 7E] FIG. 1 illustrates a sensor array configured to detect an analyte, according to various embodiments. [Figure 8] 1 shows a flowchart depicting exemplary operations for manufacturing at least some of the sensing devices disclosed herein, according to some embodiments. [Figure 9] FIG. 1 illustrates another sensor array according to some embodiments. [Figure 10A] FIG. 1 illustrates an exemplary sensor configuration, according to some embodiments. [Figure 10B] FIG. 10 illustrates an exemplary sensor configuration according to another embodiment. [Figure 11A] 1A-1C illustrate various structured carbon materials that can be used in the sensing devices disclosed herein, according to some embodiments. [Figure 11B]1A-1C illustrate various structured carbon materials that can be used in the sensing devices disclosed herein, according to some embodiments. [Figure 11C] 1A-1C illustrate various structured carbon materials that can be used in the sensing devices disclosed herein, according to some embodiments. [Figure 11D] 1A-1C illustrate various structured carbon materials that can be used in the sensing devices disclosed herein, according to some embodiments. [Figure 11E] 1A-1C illustrate various structured carbon materials that can be used in the sensing devices disclosed herein, according to some embodiments. [Figure 11F] 1A-1C illustrate various structured carbon materials that can be used in the sensing devices disclosed herein, according to some embodiments. [Figure 11G] 1A-1C illustrate various structured carbon materials that can be used in the sensing devices disclosed herein, according to some embodiments. [Figure 12A] 1A-1C illustrate examples of frequency responses of resonant impedance sensors to various analytes, according to some embodiments. [Figure 12B] 1A-1C illustrate examples of frequency responses of resonant impedance sensors to various analytes, according to some embodiments. [Figure 12C] 1A-1C illustrate examples of frequency responses of resonant impedance sensors to various analytes, according to some embodiments. [Figure 12D] 1A-1C illustrate examples of frequency responses of resonant impedance sensors to various analytes, according to some embodiments. [Figure 12E] 1A-1C illustrate examples of frequency responses of resonant impedance sensors to various analytes, according to some embodiments. [Figure 12F] 1A-1C illustrate examples of frequency responses of resonant impedance sensors to various analytes, according to some embodiments. [Figure 13A]FIG. 1 shows the actual (Z′) impedance component of an example frequency response of an electrochemical impedance sensor, according to some embodiments. [Figure 13B] FIG. 1 shows the hypothetical (Z") impedance component of an example frequency response of an electrochemical impedance sensor, according to some embodiments. [Figure 14A] 1A-1C illustrate an example of a baseline frequency response and an example of a frequency response to hydrogen peroxide, according to some embodiments. [Figure 14B] FIG. 10 illustrates example frequency responses for acetone and water, according to some embodiments. [Figure 14C] FIG. 1 illustrates an example of frequency response for ethanol and ammonia, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0027] Like reference numbers and designations in the various drawings indicate like elements. The following description is directed to several exemplary embodiments for the purpose of illustrating the innovative aspects of the present disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in numerous different ways. The described embodiments can be implemented in any environment to detect the presence of multiple different analytes in or near any device, battery pack, package, container, structure, or system that may be susceptible to the analytes. Furthermore, embodiments of the subject matter disclosed herein can be used to detect the presence of harmful or hazardous chemicals, gases, or vapors. Thus, the disclosed embodiments should not be limited by the examples provided herein, but rather encompass all embodiments contemplated by the appended claims. Additionally, well-known elements of the present disclosure will not be described in detail or will be omitted so as not to obscure the relevant details of the present disclosure.

[0028] Batteries typically contain multiple electrochemical cells that can be used to power a wide variety of devices, including, for example, mobile phones, laptops, and electric vehicles (EVs), factories, and buildings. When batteries are exposed to harsh environmental conditions or damaged, toxic chemicals and vapors within the electrochemical cells can leak from the battery's casing, posing serious health and safety risks. When released from the battery, these toxic chemicals and vapors can cause respiratory problems, allergic reactions, and even explosions. Chemicals typically used in lithium-ion battery cells can be particularly dangerous because they are highly reactive and prone to explosion if inadvertently released from the battery's casing. Therefore, it is necessary to quickly and accurately determine whether a particular battery or battery pack is leaking such toxic chemicals or vapors. Furthermore, if the presence of one or more analytes (or other toxic chemicals or vapors) is detected, it may be desirable to determine the concentration of such analytes. It may also be desirable to predict battery failure and / or determine the operational integrity of such batteries.

[0029] Various aspects of the presently disclosed subject matter relate to detecting the presence of one or more analytes in an environment. According to various embodiments of the presently disclosed subject matter, a sensing device may include a plurality of carbon-based sensors configured for the presence of a variety of different analytes. In some embodiments, at least some of the carbon-based sensors may include different types of three-dimensional (3D) graphene-based sensing materials configured to react with different analytes or different groups of analytes. In some embodiments, the sensing materials of the different sensors may be functionalized with different materials, for example, to enhance the sensitivity of each sensor to one or more corresponding analytes.

[0030] In some embodiments, a change in the impedance of the sensor may be used to determine the presence of one or more analytes near the sensing device. In other embodiments, a change in the current through the sensor may be used to determine the presence of one or more analytes near the sensing device. In some embodiments, a frequency response of the sensor may be used to determine the presence of one or more analytes near the sensing device. In some aspects, the frequency response of the sensor may be compared to one or more reference frequency responses corresponding to one or more analytes to identify which analytes are present in the environment. In this manner, the sensor systems disclosed herein can accurately detect the presence of a variety of different analytes in a given environment.

[0031] In one embodiment, a first sensor may be configured to detect the presence of a relatively large number of different analytes, and one or more second sensors may be configured to confirm the presence of one or more analytes detected by the first sensor. Specifically, a first sensor may be configured to react with each analyte in a first group of analytes, and one or more second sensors may be configured to react with a corresponding second group of analytes that is a unique subset of the first group of analytes. In some cases, a first sensor may be exposed to the ambient environment for a relatively short period of time to provide an initial rough indication of whether an analyte in the first group of analytes is present, and each of the second sensors may be exposed to the ambient environment for a relatively long period of time to provide a detailed indication of whether any analyte in the corresponding second group of analytes is present. For example, while a first sensor may be capable of detecting more analytes than any of the second sensors, configuring each of the second sensors to detect only one or two different analytes may increase the sensitivity of the second sensors to each "target" analyte, thereby improving the accuracy with which the sensing device can detect the presence of various analytes. In this way, when the indication provided by the second sensor is used to confirm the indication provided by the first sensor, the number of false positive indications is reduced, which in turn increases the overall accuracy of the sensing device.

[0032] Certain embodiments of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages: In some embodiments, the sensing devices disclosed herein can detect the presence of various analytes and other harmful chemicals and gases, as well as reduce the occurrence of false positives. Specifically, by using a first sensor to quickly detect the presence of one or more analytes in a group of analytes and one or more second sensors to confirm the presence of the analyte detected by the first sensor, embodiments of the present disclosure can reduce the number of false positives exhibited by the sensing device. This is in contrast to conventional analyte sensors that are not only insensitive to differences between different analytes in a group of analytes, but also do not employ a multi-layer analyte detection system.

[0033] FIG. 1 illustrates an example of a sensing device 100 configured to detect an analyte, according to some embodiments. The sensing device 100 may include an array 110 of carbon-based sensors 120 disposed on a substrate 130. In some embodiments, each of the carbon-based sensors 120 may include a carbon-based sensing material 125 disposed between a corresponding pair of electrodes 121-122, for example, as shown in FIG. 1. In other embodiments, a carbon-based sensor 120 may be coupled to only one electrode. The carbon-based sensors 120, as well as their respective carbon-based sensing materials 125, may be formed from any suitable material that can be configured to respond to, or react with, a variety of different analytes. Reactions between the carbon-based sensors 120 and the various analytes may be used to detect the presence of a particular analyte or a particular group of analytes. For example, the reaction may cause a change in current through one or more of the carbon-based sensors 120, cause a change in impedance or reactance of one or more of the carbon-based sensors 120, produce unique or different frequency responses in one or more of the carbon-based sensors 120, or any combination thereof.

[0034] In the example of Figure 1, multiple different analytes 151-155 are in the presence of sensing device 100. Although only five analytes 151-155 are shown in Figure 1, sensing device 100 is capable of detecting many more different analytes. In some embodiments, analytes 151-155 can include vapor phase and / or fluid compositions including one or more volatile organic compounds (VOCs), such as, but not limited to, carbon dioxide (CO), carbon monoxide (CO), nitrogen dioxide (NO), one or more hydrocarbons including methane (CH), ethylene (C2H4), ethane (C2H6), or propane (C3H8), one or more acids including hydrochloric acid (HCl) or hydrofluoric acid (HF), one or more fluorinated hydrocarbons including phosphorus oxyfluorides, hydrogen cyanide (HCN), one or more aromatic compounds including benzene (C6H6), toluene (C7H8), ethanol (C2H5OH), hydrogen, or one or more reduced sulfur compounds including thiols having the form R-SH.

[0035] In some embodiments, the carbon-based sensors 120 may include carbon particulates or 3D graphene structures that react (or can be configured to react) with analytes associated with the battery, for example, to determine whether a particular battery is leaking analytes that may be harmful or hazardous. In other embodiments, the carbon-based sensors 120 may include carbon particulates or 3D graphene structures that react (or can be configured to react) with a group of analytes considered harmful or hazardous, either individually or in combination with one another. For example, the carbon-based sensors 120 may be configured to produce a detectable response when exposed to acetone and hydrogen peroxide to detect the presence of acetone peroxide (which is highly explosive). In another example, one or more of the carbon-based sensors 120 may be configured to detect the presence of triacetone triperoxide (TATP) or tricyclic acetone peroxide (TCAP), which are trimers of acetone peroxide.

[0036] In some embodiments, each of the sensors 120 may be configured to react with a unique group of analytes. In some aspects, the sensors 120 may be functionalized with different materials configured to detect different analytes or different groups of analytes. In one embodiment, a first sensor of the sensor array 110 may be functionalized with a first material configured to detect the presence of a first group of analytes, and one or more second sensors of the sensor array 110 may be functionalized with a second material configured to detect the presence of one or more corresponding second groups of analytes, where the second materials are different from each other and from the first material, and the second group of analytes is a unique subset of the first group of analytes. For example, a first sensor may be configured to detect each of the five analytes 151-155, while each of the second sensors may be configured to detect only one of the five analytes 151-155. The first sensor may sense the environment for a relatively short period of time to provide a general detection of any of the analytes 151-155, and each of the second sensors may sense the environment for a relatively long period of time to confirm the presence of a respective one of the five analytes 151-155. In this manner, one or more second sensors 120 may be used to verify the detection of various analytes by the first sensor 120, thereby reducing or eliminating false positives.

[0037] In other embodiments, the sensors 120 may be configured to react with overlapping groups of analytes. In some other embodiments, the sensors 120 may be configured to react with the same or similar groups of analytes.

[0038] The substrate 130 may be any suitable material. In some cases, the substrate may be paper or a flexible polymer. In other examples, the substrate 130 may be a rigid or semi-rigid material, such as, for example, a printed circuit board.

[0039] FIG. 2 is a diagram 200 illustrating the sensing device 100 of FIG. 1 coupled to a receptor 180, according to some embodiments. The receptor 180 can be any suitable device, component, or mechanism capable of collecting, directing, or directing analytes 151-155 present in the surrounding environment toward the sensing device 100. As shown, the receptor 180 includes an inlet 182 and multiple outlets 184. The inlet 182 can be configured to accept or attract the analytes 151-155 to the receptor 180, and the outlets 184 can be configured to direct the analytes 151-155 toward one or more exposed surfaces of the sensing device 100. In some embodiments, for example, each of the outlets 184 of the receptor 180 can be aligned with a corresponding sensor 120 such that the analytes 151-155 that enter the receptor 180 can be released and exposed to each of the sensors 120 of the array 110. In this manner, receptor 180 may concentrate analytes 151-155 on or near corresponding sensing materials 125 of array 110, thereby increasing the likelihood of detection by sensing device 100. For example, if sensing device 100 is printed on the surface of a shipping package, a portion of the shipping package (e.g., a foldable flap) may be used as receptor 180.

[0040] FIG. 3 is a diagram 300 illustrating the sensing device 100 of FIG. 1 configured to detect the presence of an analyte at or near a battery pack 310, according to some embodiments. The battery pack 310 is shown to include a plurality of battery cells 320 arranged in a planar array on a substrate 312. One or more sensing devices 100 may be disposed near or coupled to a corresponding number of battery cells 320 of the battery pack 310. In some embodiments, a subset of the battery cells 320 may be associated with a sensing device 100 such that the number of sensing devices 100 is less than the number of battery cells 320, as shown in the example of FIG. 3 . In other embodiments, each of the battery cells 320 may be associated with or coupled to a corresponding sensing device 100. In some cases, the sensors 120 of each sensing device 100 may be stacked on top of each other (e.g., in a vertical arrangement). In other cases, the sensors 120 of each sensing device 100 may be positioned next to each other (e.g., in a planar arrangement).

[0041] The sensing device 100 may be configured to detect the presence of analytes 340 leaked from one or more of the battery cells 320 of the battery pack 310 in a manner similar to that described above with reference to FIG. 1 . Specifically, each of the sensors 120 may be coupled between a corresponding pair of electrodes 121-122 and may include multiple 3D graphene-based sensing materials 125 configured to detect the presence of specific analytes (e.g., analytes 151-155 in FIG. 1 ). In some embodiments, the sensing materials 125 in different sensors 120 may be configured to detect the presence of different analytes or different groups of analytes. For example, in some cases, the sensing material 125 of a first sensor 1201 may be functionalized with a first material configured to detect the presence of each analyte in a first group of analytes, and the sensing material 125 of a second sensor 1202 may be functionalized with a second material configured to detect the presence of each analyte in a second group of analytes, where the second group of analytes is a subset of the first group of analytes. In other embodiments, the sensing materials 125 in different sensors 120 may be configured to detect the same analyte or the same group of analytes.

[0042] In various embodiments, each of the sensors 120 in each sensing device 100 may be configured to provide an output signal in response to detecting the presence of one or more analytes. In some embodiments, the output signal may be a current generated in response to an alternating current provided to each sensor 120. In some cases, a difference between the alternating current and the output signal may indicate the presence or absence of one or more analytes of a first group of analytes. In other embodiments, the output signal may indicate a change in impedance of the corresponding sensor 120 caused by exposure to one or more analytes. In some cases, a relatively small change in impedance of a sensor 120 may indicate the absence of one or more analytes, and a relatively large change in impedance of a sensor 120 may indicate the presence of one or more analytes.

[0043] In some other embodiments, one or more of the sensing devices 100 may include an antenna (not shown for simplicity) configured to receive an electromagnetic signal from an external device, and the output signal may be a frequency response of the sensing material 125 to the electromagnetic signal. For example, the frequency response of the sensing material 125 of the first sensor 1201 may indicate the presence or absence of a first group of analytes, and the frequency response of the sensing material 125 of the second sensor 1202 may indicate the presence or absence of a second group of analytes. In some embodiments, the frequency response may be based on resonant impedance spectroscopy (RIS) sensing.

[0044] In various embodiments, the output signal generated by each sensing device 100 may indicate an operational mode of the corresponding battery cell 320 of the battery pack 310. In some embodiments, the output signal may indicate a normal mode for the corresponding battery cell 320 based on the absence of analyte, a maintain mode for the corresponding battery cell 320 based on the presence of analyte not exceeding a threshold level, or an emergency mode for the corresponding battery cell 320 based on the presence of analyte exceeding a threshold level. The output signal may also indicate the concentration level of each analyte detected by the sensing device 100.

[0045] FIG. 4 is a diagram 400 illustrating the sensing device 100 of FIG. 1 configured to detect an analyte in a shipping package 410, according to some embodiments. The shipping package 410 is shown to include a surface 412 defining a volume in which one or more items (not shown for simplicity) may be contained. The defined volume of the shipping package 410 also includes a plurality of analytes 414, which may be, for example, one or more of the analytes 151-155 of FIG. 1. As shown, the sensing device 100 may be a label 430 printed on the surface 412 of the shipping package 410. In various embodiments, the label 430 may include a substrate 432, a plurality of carbon-based sensors 434 printed on the substrate, and one or more electrodes 436 printed on the substrate. The sensors 434, which may be examples of the carbon-based sensors 120 of FIG. 1, may collectively be configured to detect the presence of the analyte 414 in the shipping package 410.

[0046] In some embodiments, each of the sensors 434 may be configured to react with a unique group of analytes in response to an electromagnetic signal 442 received from an external device 440. For example, the first sensor 4341 may be configured to detect the presence of a first group of analytes, and the second sensor 4342 may be configured to detect the presence of a second group of analytes that is a first subset of the first group of analytes. In one embodiment, the third sensor 4343 may be configured to detect the presence of a third group of analytes that is a second subset of the first group of analytes. As previously mentioned, the first sensor 4341 may be functionalized with a first material configured to react with the first group of analytes, the second sensor 4342 may be functionalized with a second material configured to react with the second group of analytes, and the third sensor 4343 may be functionalized with a third material configured to react with the third group of analytes. Thus, the second sensor 4342 may be used to confirm the detection of a first subset of analytes by the first sensor 4341, and the third sensor 4343 may be used to confirm the detection of a second subset of analytes by the first sensor 4341. In other embodiments, one or more groups of sensors 434 may be configured to react with overlapping groups of analytes in response to the electromagnetic signal 442.

[0047] Electrodes 436, which may be examples of electrodes 121-122 in FIG. 1, may be coupled to sensors 434. In some embodiments, each sensor 434 may be coupled between a corresponding pair of electrodes 436. The first electrode 436 of each electrode pair may be configured to receive an electromagnetic signal 442, and the second electrode 436 of each electrode pair may be configured to provide an output signal indicative of whether the corresponding sensor 434 has detected the presence of an analyte.

[0048] In some embodiments, each output signal may indicate the frequency response of the corresponding sensor 434 to the electromagnetic signal 442. For example, the frequency response of the first sensor 4341 may indicate the presence (or absence) of a first group of analytes in the shipping package 410, the frequency response of the second sensor 4342 may confirm the presence (or absence) of a second group of analytes, and the frequency response of the third sensor 4343 may confirm the presence (or absence) of a third group of analytes. In some cases, the first sensor 4341 may be exposed to the electromagnetic signal 442 for a relatively short period of time to provide a rough indication of whether analytes of the first group of analytes are present, while the second and third sensors 4342 and 4343 may be exposed to the electromagnetic signal 442 for a relatively long period of time to confirm the indication of the presence of the second and third groups of analytes by the first sensor 4341. In this manner, the sensors 4341-4343 may collectively reduce the number of false positives exhibited by the sensing device 100.

[0049] In at least some embodiments, an antenna (not shown for simplicity) may be printed on the substrate 432 and configured to pass an alternating current through the sensor 434 in response to the electromagnetic signal 442. The sensors 434 may be functionalized with different materials, which may have different electrical and / or chemical properties, such that the resulting sensor output currents may indicate the presence (or absence) of different analytes. For example, in some cases, each output signal may indicate the impedance or reactance of the corresponding carbon-based sensor 434 to an alternating current. The impedance or reactance of each sensor 434 can be measured and compared to a reference impedance or reactance to determine whether one or more analytes associated with the sensor 434 are present in the shipping package 410. In some cases, the reference impedance or reactance may be determined by passing an alternating current through the sensor 434 in the absence of all analytes and measuring the impedance or reactance of the output signal from the sensor 434.

[0050] In some embodiments, sensors 434 may be juxtaposed in a planar arrangement on substrate 432. In other cases, sensors 434 may be stacked on top of each other in a vertical arrangement. In some implementations, sensors 434 may form a dielectric gradient.

[0051] As previously mentioned, the analyte sensing devices disclosed herein can be integrated into products or packages, such as cardboard boxes or food packages. The analyte sensing devices disclosed herein can be positioned adjacent to the product or package and can detect analytes on or within the product or package. For example, the analyte sensing device can be integrated into or positioned adjacent to a scale used to weigh shipping containers, and the analyte sensing device can be used to detect analytes on or within shipping packages weighed by the scale. In another example, the analyte sensing device can be integrated into or positioned adjacent to a component of a medium used to transport shipping containers, such as in a mail car, and the analyte sensing device can be used to detect analytes on or within shipping packages transported by the medium. As yet another example, the analyte sensing device can be integrated into a conveyor belt or attached to a portion of a mechanical transport device. Additionally or alternatively, the analyte sensing device can be integrated into handling equipment, such as a robotic arm, or handling apparel, such as gloves, and the analyte sensing device can be used to detect analytes on or within any shipping packages being transported or handled.

[0052] In one embodiment, a suction device, such as a fan or vacuum pump, may be used to direct ambient gas (which may contain one or more analytes) toward the analyte sensing device and / or into a housing containing the analyte sensing device. For example, the analyte sensing device may be disposed in a housing, and the fan or vacuum pump may draw the ambient ambient gas into the housing such that analytes present in the ambient gas are exposed to the analyte sensing device. In another example, the analyte sensing device may be disposed adjacent to a set of objects, such as a shipping package, a mouse pad, or other product, and may be monitored for the presence of one or more analytes.

[0053] FIG. 5 is a diagram 500 illustrating an example of a reaction between one or more analytes and the sensor 120 of FIG. 1 , according to some embodiments. As previously described, the sensor 120 may include a 3D graphene-based sensing material 125 disposed on a substrate 130, which may be functionalized with a material 126 configured to detect the presence of analytes 151-152. In some embodiments, the sensing material 125 may include multiple different graphene allotropes having one or more microporous or mesoporous pathways. While not shown for simplicity, a polymer may bond the multiple different graphene allotropes to one another. In some cases, the polymer may include a humectant configured to reduce the sensitivity of the carbon-based sensor to humidity.

[0054] As shown, analytes 151-152 may follow various pathways to penetrate and react with the sensing material 125. Specifically, inset 510 shows analytes 151-152 being adsorbed by various exposed surfaces of the functionalized material 126 and / or the sensing material 125. Inset 520 shows carbon particulates 522 from which the sensing material 125 may be formed. In some cases, reactive chemical additives (e.g., salts dissolved in a carrier solvent) may be deposited on and within exposed surfaces, pores, and / or pathways of the particulate carbon 522. In some cases, reactive chemical additives may be incorporated into the particulate carbon 522 to enhance the sensitivity of the sensor 120 to one or more specific analytes.

[0055] 6 is a block diagram of an analyte detection system 600 according to some embodiments. The analyte detection system 600 is shown to include an input circuit 610, a sensor array 620, a measurement circuit 630, and a controller 640. The input circuit 610 may be coupled to the controller 640 and the sensor array 620 and provide an interface by which current, voltage, and electromagnetic signals may be applied to the sensor array 620. The sensor array 620, which may be an example of the sensor array 110 of FIG. 1, is shown to include eight carbon-based sensors 1201-1208 coupled between respective pairs of electrodes 1211 and 1221 to 1218 and 1228. In some cases, the first electrode 121 1~ Each of the second electrodes 1218 may be coupled to a corresponding terminal of the input circuit 610, and each of the second electrodes 1221-1228 may be coupled to a corresponding terminal of the measurement circuit 630. In another example, each terminal of the input circuit 610 may be coupled to a corresponding group of the sensors 1201-1208.

[0056] The controller 640 then selects the carbon-based sensors 1201 to 120 nThe controller 640 may generate an excitation signal or electric field whose current level, voltage level, impedance, and / or frequency response can be measured or determined by the measurement circuitry 630. For example, in some embodiments, the controller 640 may be a current source configured to drive either a direct or alternating current through each of the sensors 1201-1208. In other embodiments, the controller 640 may be a voltage source capable of applying various voltages to the sensors 1201-1208 via corresponding pairs of electrodes 121 and 122. In some cases, the controller 640 can adjust the sensitivity of each sensor 120 to a particular analyte by varying the voltage applied to each sensor 120. For example, the controller 640 can increase the sensitivity of each sensor 120 by decreasing the applied voltage or decrease the sensitivity of each sensor 120 by increasing the applied voltage. In other embodiments, an antenna (not shown for simplicity) coupled to the sensor array 620 can receive one or more electromagnetic signals from an external device. In some aspects, the first electrodes 1211-1218 may be configured to receive electromagnetic signals.

[0057] As previously mentioned, the sensors 1201-1208 may include each sensing material 1251-1258, which may be functionalized with different materials configured to react with and / or detect different analytes or different groups of analytes. In some embodiments, the sensors 1201-1208 may include cobalt in particulate form, and the sensing materials 1251-1258 may include carbon nano-onions (CNO). Specifically, the active sites on the exposed surface of the CNO may, in some embodiments, be solid-phase cobalt (Co) that reacts with carbon available on the exposed surface of the CNO. (S) ) (e.g., Co particles) and / or cobalt oxide (Co2O3) (e.g., via surface modification). For example, the chemical reaction associated with using cobalt oxide to detect the presence of hydrogen peroxide (H2O2) may be represented as follows:

[0058]

number

[0059] Additionally or alternatively, cobalt-based functionalization can be used to detect TATP according to the following chemical reaction:

[0060]

number

[0061] In another embodiment, the presence of TATP may be detected based on the following steps or procedures. Exposed carbon surface (300-700m 2 Adsorption of TATP (50 ppb) onto a carbon (C) surface (C / g) that is effectively acidified by the addition of an acid (e.g., HCl at a concentration level of about 0.1 m). An example acid treatment level includes 10 mg of carbon (C) corresponding to 100 mg of HCl at 0.1 m diluted in a suitable carrier solvent. Over time, the adsorbed HCl evaporates, protonating hydroxyl and / or carboxyl groups on the exposed carbon surface, leaving such surfaces in a relatively acidic state. · Hydrolysis of TATP to acetone and peroxides; The peroxide oxidation performance shown by the above formulas (1) to (3); and · The generation of free electrons and the associated observable change in one or more electrical or chemical properties of the sensing device.

[0062] In some embodiments, cobalt-decorated CNO may provide the most selective and sensitive response to triacetone triperoxide (TATP) compared to other types of 3D graphene-based sensing materials. Applicants note that because hydrogen peroxide has a somewhat similar chemical structure to triacetone triperoxide (TATP) or tricyclic acetone peroxide (TCAP), a sensing device configured to detect the presence of hydrogen peroxide can also be used to detect the presence of TATP.

[0063] The exact chemical reactivity and / or interaction between an analyte and the exposed carbon surfaces of the materials 1251-1258 may depend on the type of analyte and the structure or mechanism of the corresponding materials 1251-1258. For example, certain analytes, such as hydrogen peroxide (HO) and TATP, may be detected by one or more oxidation-reduction ("redox") type chemical reactions with metals decorated on the exposed carbon surfaces of the sensing materials 1251-1258. In some embodiments, some of the sensing materials 1251-1258 may be prepared or engineered to contain free amines that may react with electron-deficient aromatic nitro analytes, such as TNT and DNT.

[0064] The measurement circuit 630 may measure the output signals provided by the sensors 1201-1208 to determine whether a particular analyte is present in the surrounding environment. For example, when the sensor array 120 is pinged with an electromagnetic signal (e.g., received from an external device such as device 440 of FIG. 4), the measurement circuit may measure the frequency responses of the sensors 1201-1208 and compare the measured frequency responses to one or more reference frequency responses. If the measured frequency response of the sensor 120 matches a particular reference frequency response, the measurement circuit 630 may indicate the presence of the analyte associated with the particular reference frequency response. Conversely, if the measured frequency response of the sensor 120 does not match any of the reference frequency responses, the measurement circuit 630 may indicate the absence of the analyte associated with the particular reference frequency response.

[0065] In another example, application of an alternating current to the sensor array 120 may cause one or more electrical and / or chemical properties of the sensors 1201-1208 to change (e.g., increase or decrease). The measurement circuit 630 can detect the resulting change in the electrical and / or chemical properties of the sensors 1201-1208 and determine whether a particular analyte is present based on the change. In some embodiments, the measurement circuit 630 can measure the output current of the sensors 1201-1208 caused by the alternating current and compare the measured output current to one or more reference currents to determine whether a particular analyte is present. Specifically, if the measured output current of a sensor 120 matches a particular reference current, the measurement circuit 630 may indicate the presence of the analyte associated with the particular reference current. Conversely, if the measured output current of a sensor 120 does not match any of the reference currents, the measurement circuit 630 may indicate the absence of the analyte associated with the particular reference current.

[0066] In other embodiments, the measurement circuit 630 can measure the impedance or reactance of the sensors 1201-1208 in response to an alternating current and compare the measured impedance or reactance to one or more reference impedances or reactances to determine whether a particular analyte is present. Specifically, if the measured impedance or reactance of a sensor 120 matches the reference impedance or reactance, the measurement circuit 630 may indicate the presence of the analyte associated with the reference impedance or reactance. Conversely, if the measured impedance or reactance of a sensor 120 does not match any of the reference impedances or reactances, the measurement circuit 630 may indicate the absence of the analyte associated with the reference impedance or reactance.

[0067] FIG. 7A illustrates another sensor array 700A according to some embodiments. As shown, the sensor array 700A includes multiple sensors 701-704 arranged in a planar arrangement, each of the sensors 701-704 including a different carbon-based sensing material. In some embodiments, the sensors 701-704 may be examples of the sensors 120 of FIGS. 1-3 and 5-6. In other embodiments, the sensors 701-704 may be examples of the sensors 434 of FIG. 4. While the example 700A of FIG. 7A illustrates four sensors 701-704 arranged in a two-by-two array, other embodiments can include other numbers of sensors arranged in other suitable configurations.

[0068] The sensors 701-704 may include routing channels between individual deposits of carbon-based sensing material. These routing channels may provide a path through which electrons can flow through the sensors 701-704. The resulting current through the sensors 701-704 may be measured via ohmic contact with each of the electrode pairs E1-E4. For example, a measurement M1 of the first sensor 701 may be obtained via electrode pair E1, a measurement M2 of the second sensor 702 may be obtained via electrode pair E2, a measurement M3 of the third sensor 703 may be obtained via electrode pair E3, and a measurement M4 of the fourth carbon-based sensor 704 may be obtained via electrode pair E4.

[0069] In various embodiments, each of the sensors 701-704 can be configured to react with and / or detect a corresponding analyte or group of analytes. For example, the first sensor 701 can be configured to react with or detect a first group of analytes in a coarse-grained manner, while the second sensor 702 can be configured to react with or detect a subset of the first group of analytes in a fine-grained manner. In some cases, the sensors 701-704 can be printed on a substrate using different carbon-based inks. Ohmic contacts can be used to capture measurements M1-M4 simultaneously or sequentially.

[0070] FIG. 7B illustrates another sensor array 700B according to some embodiments. The sensor array 700B includes multiple carbon-based sensors 701-704 stacked on top of each other in a vertical or stacked arrangement. In some embodiments, the sensors 701-704 may be examples of the sensors 120 of FIGS. 1-3 and 5-6. In other embodiments, the sensors 701-704 may be examples of the sensors 434 of FIG. 4. The sensors 701-704 (and their respective sensing materials) may be sequentially deposited on top of each other to form a stacked array. In some cases, separators (not shown for simplicity) may be provided between the sensors 701-704. As previously mentioned, the sensors 701-704 may be functionalized with different materials and / or may include different types of carbon-based sensing materials that may be printed in successive layers on a substrate or label.

[0071] As the demand for low-cost analyte sensors continues to increase, it is becoming increasingly important to reduce or even eliminate the need for electronic components in analyte sensors. For example, the high-cost electronic components typically found in conventional analyte sensors make widespread deployment in shipping containers, packages, and packaging materials impractical. Thus, some embodiments of the presently disclosed subject matter may provide a cost-effective solution to the long-standing problem of monitoring large numbers of shipping containers, packages, and packaging materials for the presence of harmful chemicals and gases, such as the various analytes described herein.

[0072] 7C is a diagram 700C illustrating an inkjet or bubble-jet printhead 720 for printing various sensing devices disclosed herein onto the surface of a shipping container, package, or packaging material, according to some embodiments. Specifically, FIG. 700C illustrates a process by which multiple layers of different carbon-based sensing materials 711-714 can be printed onto a substrate 710. As shown, the printhead 720 can print a first layer 711 of carbon-based sensing material onto the substrate 710 using a first carbon-based ink 721, a second layer 712 of carbon-based sensing material onto the substrate 710 using a second carbon-based ink 722, a third layer 713 of carbon-based sensing material onto the substrate 710 using a third carbon-based ink 723, and a fourth layer 714 of carbon-based sensing material onto the substrate 710 using a fourth carbon-based ink 724. In some cases, the carbon-based inks 721-724 may be different from one another, so that, for example, the resulting sensing material layers 711-714 are configured to react with and / or detect different analytes or different groups of analytes. The printhead 720 may also use an ohmic-based ink 725 to print the electrodes E1-E4 of the different sensing material layers 711-714, respectively. The ohmic contacts may be printed into portions of the substrate 710 and / or the sensing material layers 711-714 using multiple passes of the multi-jet printhead 720. In some implementations, the sensing device may include vias that provide access to the resulting electrodes E1-E4. In other implementations, other suitable mechanisms may be used to provide ohmic contacts to the electrodes E1-E4.

[0073] FIG. 7D is a diagram 700D illustrating a printhead 720 for printing various sensing devices disclosed herein onto the surface of a shipping container, package, or packaging material, according to some embodiments. Specifically, FIG. 700D illustrates a process by which multiple layers of different carbon-based sensing materials 711-714 can be printed in a pyramidal arrangement on a substrate 710. FIG. 700D also illustrates ohmic contacts 705 printed on the sensing material layers 711-714 using an ohmic-based ink 725. In some embodiments, the different sizes and exposed surface areas of the sensing material layers 711-714 may cause each sensor to have different electrical and / or chemical properties, which in turn may be configured to react with and / or detect different types of analytes.

[0074] Further details regarding various carbon-based sensing materials, tuning, and calibration techniques that can be used to form the carbon-based sensors disclosed herein are summarized in Table 1 below.

[0075] [Table 1]

[0076] As noted above, different materials may resonate at different frequencies, and many materials may resonate at different frequencies depending on whether one or more particular analytes are present. In some embodiments, the dielectric constant of the carbon-based sensing materials described herein can be modified by exposing the material to ultraviolet (UV) radiation.

[0077] FIG. 7E is a diagram 700E illustrating UV radiation emitted toward the sensor 701. As shown, a UV source 753 may be used to expose the sensor 701 to UV radiation. The power and wavelength of the UV radiation may be controlled by a power control unit 751 and a wavelength control unit 752, respectively. In some embodiments, adjusting the power level and / or wavelength of the UV radiation may change the dielectric constant of each of the sensing material layers 711-714. That is, after being irradiated with UV radiation, each of the sensing material layers 711-714 may resonate at a different frequency. In some embodiments, the different dielectric constants of the sensing material layers 711-714 may collectively form a dielectric constant gradient 725. The dielectric constant gradient 725 may correspond to a step-shaped gradient 761, a linear-shaped gradient 762, or a curve-shaped gradient 763.

[0078] FIG. 8 shows a flowchart 800 depicting example operations for fabricating at least some of the sensing devices disclosed herein, according to some embodiments. In various embodiments, the dielectric constant of the carbon-based sensing material can be altered to induce specific resonance characteristics in the carbon-based sensing material when exposed to a particular analyte. In some cases, different portions of the carbon-based sensing material may be configured to have different dielectric constant values specifically selected to induce specific resonant frequencies and / or resonance characteristics. In particular, it may be desirable for a first portion of the carbon-containing material to have a first dielectric constant tuned to resonate with a specific resonance characteristic when the first portion of the carbon-containing material absorbs a first analyte of interest, while a second portion of the carbon-containing material has a second dielectric constant tuned to resonate with a specific resonance characteristic when the second portion of the carbon-containing material absorbs a second analyte of interest.

[0079] Forming different portions of carbon-containing material with different dielectric constant values can be achieved using a combination of masking and UV treatment. At block 802, a carbon-containing material is deposited on a substrate or electrode 811. At block 804, a UV opaque mask is deposited or printed on the carbon-containing material. At block 806, the carbon-containing material is activated, for example, via irradiation with UV photons. This results in a first portion 8121 of the carbon-containing material having a first dielectric constant and a second portion 8122 of the carbon-containing material having a second dielectric constant different from the first dielectric constant. At block 808, the mask can be washed away, ablated, or otherwise removed. Two or more of the resulting analyte sensing devices can be used as multi-element, multi-analyte sensors and / or high-sensitivity analyte sensors. Additionally, or alternatively, the resulting analyte sensing device can be exposed to additional irradiation with UV photons at block 810, for example, to further modify portions of the carbon-containing material previously under the UV opaque mask.

[0080] Some examples of alternative embodiments are summarized in Table 2 below.

[0081] [Table 2]

[0082] FIG. 9 illustrates another sensor array 900 according to some embodiments. The sensor array 900 includes multiple layers 911-914 of individually functionalized carbon-containing materials. As shown, the layers 911-914 are arranged sequentially to form a stack of layers, with the first layer 911 disposed on a substrate 910. Each layer is formed with a corresponding individually functionalized carbon-containing matrix (e.g., Carbon Matrix 1, Carbon Matrix 2, Carbon Matrix 3, Carbon Matrix 4), and each individually functionalized carbon-containing matrix includes a respective additive A-D. The combination of carbon-containing matrix and additive may be selected based on the sensitivity of the particular combination to a particular analyte of interest.

[0083] In forming the analyte sensor array, the different layers can be deposited using any known technique. Furthermore, each of the different layers can be configured to be of a particular thickness. Strictly by way of example and as shown, a first deposited layer can have a first thickness 924 in a first range (e.g., 10 nm to 100 nm), while another deposited layer can have a thickness in a different range (e.g., 500 nm to 1000 nm), etc. The particular thickness of a particular layer can be any combination of the following: the properties of the additive for that particular layer, and / or the properties of the analyte of interest, and / or · Can be selected based on the inherent binary and ternary interactions of and between the layer components.

[0084] In some embodiments, the open pore structure of the carbon-based sensing materials disclosed herein may allow certain analytes to more easily penetrate the material and / or interact with the carbon matrix within the material, and therefore, these open pores may increase the sensitivity of the sensors disclosed herein to the analyte over conventional analyte detection systems.

[0085] FIG. 10A illustrates an example sensor configuration 1000A according to some embodiments. Sensor configuration 1000A, according to some embodiments, includes a mapping between sensors and various analytes in an analyte detection system. For example, the 3D graphene-based sensing material of the carbon-based sensor 120 in FIG. 1 may be or include the carbon recipe shown in sensor configuration 1000A. That is, in a configuration in which the sensor array 120 includes eight carbon-based sensors 120, each sensor may have a corresponding carbon recipe as illustrated by exemplary sensor configuration 1000A. For example, the first sensor may be CNO decorated with cobalt oxide (Co2O3) and may produce a percent change in current (% ΔI) relative to an initial current (I0) and / or a measured impedance increase of 9.26244%, etc. In this manner, the carbon recipe of sensor configuration 1000A may be used to configure carbon-based sensors to detect and identify various analytes (e.g., TATP, DNT, HS) even at relatively low concentration levels based on their respective chemical fingerprints. Thus, the sensing devices disclosed herein may be capable of detecting relatively low concentrations of analytes and / or other chemical threat agents, even in the presence of common interfering substances.

[0086] 10B shows another example of a sensor configuration 1000B according to some embodiments. The sensor configuration 1000B may be similar to the sensor configuration 1000A of FIG. 10A, for example, as follows:

[0087] Sensor No. 1: Carbon #29, corresponding to carbon nano-onion (CNO) oxide produced in a thermal reactor; cobalt(II) acetate (C4H6CoO4), a cobalt salt of acetic acid (often found as tetrahydrate Co(CH3CO2)2·4H2O, abbreviated Co(OAc)2·4H2O) entered the thermal reactor at a ratio of approximately 59.60 wt.%, corresponding to 40.40 wt.% carbon (referring to carbon in the CNO form), resulting in functionalization of the active sites of the CNO oxide with cobalt, representing cobalt-decorated CNO at levels of 15,000 and 100,000 times, respectively; suitable gas mixtures used to produce carbon #29 and / or cobalt-decorated CNO include the following steps: · Ar purge at 0.75 standard cubic feet per minute (scfm) for 30 minutes; · Ar purge changed to 0.25scfm for running; A temperature increase from 25°C to 300°C in 20 minutes; and This may include a temperature increase from 300°C to 500°C in 15 minutes.

[0088] Sensor No. 2: corresponds to TG JM (thermal graphene jet mill; the carbon in the thermal reactor is not functionalized) as shown in Figure 11A.

[0089] Sensor No. 3: Carbon #19, corresponding to carbon of the "DXR" type or configuration (characterized in Figures 5A and / or 5B) produced in a microwave reactor (e.g., a reactor coupled to a microwave source such that microwave energy propagates through the reactor, exciting a carbon-containing gas and / or plasma within the reactor). Silver acetate (CHCOAg), a white crystalline solid particulate material suspended in a carrier gas to produce silver acetate vapor, enters the microwave reactor at a ratio of approximately 58.18 wt.%, corresponding to 41.82 wt.% carbon (referring to carbon in the DXR form), resulting in the functionalization of active sites on the DXR-configured carbon with silver, substantially as shown in Figure 11D (undecorated form) and / or Figure 11G (showing actual decoration with cobalt instead of silver). An example of a gas mixture used to produce carbon #19 and / or silver-decorated DXR carbon, substantially as shown in Figures 11D and 11G, involves the following steps: This may involve flowing a carrier gas over the DXR carbon structure at a volume ratio of 6.7% H2 per 93.3% Ar for approximately 1 minute and 8 seconds.

[0090] Sensor No. 4: CNO (carbon nano-onion; non-functionalized carbon in a thermal reactor) as shown in Figure 11B.

[0091] Sensor No. 5: Carbon #16, corresponding to carbon of the "DXR" type or configuration (characterized in Figures 5A and / or 5B) produced in a microwave reactor; iron(II) acetate, a white solid particulate material suspended in a carrier gas to produce iron acetate vapor, enters the microwave reactor at a ratio of approximately 65.17 wt. %, corresponding to 34.83 wt. % carbon (referring to carbon in the DXR form), resulting in silver functionalization of the active sites on the DXR-configured carbon, substantially as shown in Figure 11D (undecorated form) and / or Figure 11G (showing actual decoration with cobalt instead of iron). An example of a gas mixture used to produce carbon #16 and / or iron-decorated DXR carbon, substantially as shown in Figures 11D and 11G, involves the following steps: A flow of carrier gas over the DXR carbon structure at a volume ratio of 6.7% H2 per 93.3% Ar for approximately 1 minute and 13 seconds may be included.

[0092] Sensor No. 6: Carbon #1, corresponding to carbon of the "Anvel" (characterized in FIG. 7C) type or configuration produced in a microwave reactor; platinum(II) bis(acetylacetonate), abbreviated Pt, a coordination compound with the formula Pt(OCH) flows as fine particles dispersed in a carrier gas to produce platinum(II) bis(acetylacetonate) vapor, which enters the microwave reactor in a proportion of about 76.62 wt. %, corresponding to 23.38 wt. % carbon (referring to the Anvel form of carbon), resulting in functionalization of the active sites on the Anvel-configured carbon with platinum, as substantially shown in FIG. 11C (undecorated form); a suitable gas mixture used to produce carbon #1 and / or undecorated Anvel carbon, substantially as shown in FIG. 11C, involves the following steps: A flow of carrier gas over the Anvel carbon structure at a volume ratio of 6.7% H2 per 93.3% Ar for approximately 15 minutes may be included.

[0093] Sensor No. 7: Carbon #6, corresponding to carbon of the type or composition "Anvel" (characterized in Figure 7C) produced in the microwave reactor; formula [Pd(OCCH)] n , abbreviated as [Pd(OAc)2] n Palladium(II) acetate, a compound of palladium described by [the inventors], flows as fine particles dispersed in a carrier gas to produce palladium(II) acetate vapor, which enters the microwave reactor at a ratio of about 65.17 wt. %, corresponding to 34.83 wt. % carbon (referring to carbon in its Anvel form), resulting in platinum functionalization of the active sites on the Anvel-configured carbon, substantially as shown in Figure 11C (undecorated form). An example of a gas mixture used to produce carbon #6 and / or platinum-decorated Anvel carbon, substantially as shown in Figure 11C, involves the following steps: A flow of carrier gas over the Anvel carbon structure at a volume ratio of 6.7% H2 per 93.3% Ar for approximately 15 minutes may be included. Sensor No. 8: 1,3-diaminonaphthalene, which forms a complex with TG-JM to produce organically modified carbon, such as that shown in Figure 11A.

[0094] 11A-11G show diagrams of various structured carbon materials that can be used in sensing devices disclosed herein, according to some embodiments. For example, FIG. 11A shows a photomicrograph 1100A of thermogravimetric (TG) carbon, according to various embodiments. FIG. 11B shows a photomicrograph 1100B of undecorated CNO, according to various embodiments. FIG. 11C shows a photomicrograph 1100C of Anvel carbon, according to various embodiments. FIG. 11D shows a photomicrograph 1100D of DXR carbon, according to various embodiments. FIG. 11E shows a photomicrograph 1100E of cobalt-decorated CNO at a 15,000x magnification level, according to various embodiments. FIG. 11F shows a photomicrograph 1100F of cobalt-decorated CNO at a 100,000x magnification level, according to various embodiments. FIG. 11G shows a photomicrograph 1100G of cobalt-decorated DXR carbon, according to various embodiments.

[0095] In contrast to conventional 2D graphene materials, the 3D graphene sensing materials disclosed by the present embodiments may be designed with complex 3D structures to prevent graphene restacking, avoiding some of the drawbacks of using 2D graphene as a sensing material. This process also increases the areal density of the material, resulting in a high level of analyte adsorption sites per unit area, thereby improving chemical sensitivity, as enabled by the corresponding library of carbon allotropes used to customize the sensor arrays disclosed herein to chemically differentiate leaked analytes for multiple applications.

[0096] The structured carbon materials shown in Figures 11A-11G may be produced using a flow-through microwave plasma reactor configured to continuously generate pristine 3D graphene particles from hydrocarbon gases at near-atmospheric pressure. In operation, as hydrocarbons flow through a relatively high-temperature zone in the plasma reactor, carbon free radicals are formed that flow further down the length of the reactor to a growth zone, where 3D carbon microparticles (based on multiple 2D graphenes bonded together) are formed and collected as a fine powder. The density and composition of the gas species, including the free-radical carbon, may be adjusted by gas chemistry and microwave (MW) power level. By controlling the reactor process parameters, these reactors may produce carbon with a wide but tunable range of morphology, crystalline order, and size (and distribution). For example, possible sizes and distributions may vary from flakes (hundreds of nanometers to micrometers wide and a few nanometers thin) to spherical particles (tens of nanometers in diameter) to graphene clusters (tens of micrometers). The 3D nature of the material effectively prevents agglomeration, allowing the material to be dispersed as unagglomerated particles. As a result, highly responsive and selective sensing materials can be fabricated.Graphene, an atomically thin two-dimensional (2D) material, has many advantageous properties for sensing, including excellent chemical and mechanical strength, high carrier mobility, high electrical conductivity, large surface area, and gate-tunable carrier density.

[0097] To improve chemical selectivity, the 3D graphene of the presently disclosed graphene may be functionalized with various reactive materials in such a way that binding between target molecules and carbon may be optimized. This functionalization step, along with the ability to measure complex impedances of the exposed sensor, may be important for efficient and selective detection of analytes. For example, various metal or metal oxide nanoparticles may be decorated on the surface of the 3D graphene to selectively detect hydrogen peroxide (a TATP decomposition product), since peroxide is known to react with various metals. Furthermore, nanoparticle-decorated graphene structures may act synergistically to provide desirable and advantageous properties for sensing applications.

[0098] 12A-12F show example frequency responses of resonant impedance sensors to various analytes, according to some embodiments. Specifically, FIG. 12A shows an example frequency response 1200A of the sensor 120 alongside a baseline or reference frequency response. Specifically, FIG. 12B shows an example frequency response 1200B of the sensor 120 alongside a baseline or reference frequency response. FIG. 12C shows an example frequency response 1200C of the sensor 120 to ethanol alongside a baseline or reference frequency response. FIG. 12D shows an example frequency response 1200A of the sensor 120 to isopropanol alongside a baseline or reference frequency response. FIG. 12E shows an example frequency response 1200E of the sensor 120 to water alongside a baseline or reference frequency response. FIG. 12F shows an example frequency response 1200F of the sensor 120 to xylene alongside a baseline or reference frequency response.

[0099] FIG. 13A is a graph 1300A showing the actual (Z') impedance component of an example frequency response of sensor 120 to acetone, ethanol (EtOH), water, and hydrogen peroxide (H2O2) alongside a baseline or reference frequency response, according to some embodiments. FIG. 13A is a graph 1300B showing the hypothetical (Z") impedance component of an example frequency response of sensor 120 to acetone, ethanol (EtOH), water, and hydrogen peroxide (H2O2) alongside a baseline or reference frequency response, according to some embodiments.

[0100] Figure 14A shows an example of the frequency response of sensor 120 to hydrogen peroxide alongside a baseline or reference frequency response, according to some embodiments. Figure 14B shows an example of the frequency response of sensor 120 to acetone and water, according to some embodiments. Figure 14C shows an example of the frequency response to ethanol and ammonia, according to some embodiments.

[0101] As used herein, a reference to "at least one" or "one or more" of a list of items refers to any combination of those items, including single members. "At least one of a, b, or c" is intended to cover the possibilities of a alone, b alone, c alone, a and b combinations, a and c combinations, b and c combinations, and a, b, and c combinations.

[0102] The various illustrative components, logic circuits, logic blocks, modules, circuits, operations, and algorithmic processes described in connection with the embodiments disclosed herein, including the structures disclosed herein and structural equivalents thereof, may be implemented as electronic hardware, firmware, software, or a combination of hardware, firmware, or software. The interoperability of hardware, firmware, and software is generally described in terms of the functionality and illustrated in the various illustrative components, blocks, modules, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the application and design constraints imposed on the overall system.

[0103] Various modifications to the embodiments described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the scope of the claims is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with this disclosure, the principles and novel features disclosed herein.

[0104] Moreover, various features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Moreover, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Thus, while features may be described above in combination with each other and may even be initially claimed as such, one or more features from a claimed combination may, in some cases, be carved out of the combination, and the claimed combination may be directed to a subcombination or variation of the subcombination.

[0105] Similarly, while operations are shown in the figures in a particular order, this should not be understood as requiring such operations to be performed in the particular order or sequential order shown, or that all of the operations shown be performed, to achieve desirable results. Additionally, the figures may generally depict another exemplary process in the form of a flowchart or flow diagram. However, other operations not shown may be incorporated into the generally described exemplary process. For example, one or more additional operations may be performed before, after, simultaneously with, or between the operations shown in the figures. In some situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the program components and systems described may generally be integrated together in a single software product or may be embodied in multiple software products.

Claims

1. A container for storing one or more items, comprising: a surface defining a volume of the container; a label printed on the container, the label comprising: A substrate; a plurality of carbon-based sensors printed on the substrate and collectively configured to detect the presence of one or more analytes in the container, each of the carbon-based sensors configured to react with a unique group of analytes, and the label further comprising: one or more electrodes printed on the substrate and coupled to at least some of the carbon-based sensors, the one or more electrodes configured to provide one or more output signals indicative of the presence or absence of the one or more analytes in the container in response to an electromagnetic signal received from an external device; a first carbon-based sensor functionalized with a first material configured to detect the presence of an analyte of a first group of analytes; A container wherein a second carbon-based sensor is functionalized with a second material configured to detect the presence of an analyte of a second group of analytes, said second material being different from said first material.

2. The container of claim 1 , wherein the carbon-based sensors are configured to resonate at different frequencies in response to the electromagnetic signal.

3. The vessel of claim 1 , wherein each output signal comprises a frequency response of a corresponding carbon-based sensor to the electromagnetic signal.

4. 10. The container of claim 1, further comprising an antenna printed on the substrate, the antenna configured to pass an electrical current through the carbon-based sensor in response to the electromagnetic signal.

5. 5. The container of claim 4, wherein each output signal is indicative of an impedance or reactance of a corresponding carbon-based sensor to the current, the impedance or reactance being indicative of the presence or absence of at least one analyte of a corresponding unique group of analytes.

6. 10. The container of claim 1, wherein the first group of analytes comprises at least twice as many different analytes as the second group of analytes.

7. The first material may be triacetone triperoxide (TATP), toluene, ammonia, or hydrogen sulfide (H ２ S), 10. The container of claim 1, wherein the second material comprises an iron-decorated three-dimensional (3D) graphene-containing structure configured to confirm the presence of toluene.

8. 10. The container of claim 1, wherein a third carbon-based sensor is functionalized with a third material configured to detect the presence of each analyte in a third group of analytes, the third group of analytes comprising a different subset of the first group of analytes, and the third material is different from the first and second materials.

9. a first frequency response of the first carbon-based sensor to the electromagnetic signal indicative of the presence or absence of the analyte of the first group of analytes in the container; 10. The container of claim 1, wherein a second frequency response of the second carbon-based sensor to the electromagnetic signal indicates the presence or absence of the analyte of the second group of analytes in the container.

10. the first frequency response is based at least in part on exposure of the first carbon-based sensor to the electromagnetic signal for a first period of time; 10. The container of claim 9, wherein the second frequency response is based at least in part on exposure of the second carbon-based sensor to the electromagnetic signal for a second period of time that is longer than the first period of time.

11. 11. The container of claim 10, wherein the second period of time is at least twice as long as the first period of time.

12. The one or more electrodes a first electrode coupled to the first carbon-based sensor and configured to indicate the presence of one or more analytes of the first group of analytes; a second electrode coupled to the second carbon-based sensor and configured to confirm the presence of the analyte detected by the first carbon-based sensor.

13. The container of claim 1 , wherein the first and second carbon-based sensors form a dielectric gradient.

14. The container of claim 1 , wherein the substrate comprises paper or a flexible polymer.

15. A container for storing one or more items, comprising: a surface defining a volume of the container; a label printed on the container, the label comprising: A substrate; a plurality of carbon-based sensors printed on the substrate and collectively configured to detect the presence of one or more analytes in the container, each of the carbon-based sensors configured to react with a unique group of analytes, and the label further comprising: one or more electrodes printed on the substrate and coupled to at least some of the carbon-based sensors, the one or more electrodes configured to provide one or more output signals indicative of the presence or absence of the one or more analytes in the container in response to an electromagnetic signal received from an external device; Each of the carbon-based sensors comprises a different carbon-based ink printed on the substrate.

16. A container for storing one or more items, comprising: a surface defining a volume of the container; a label printed on the container, the label comprising: A substrate; a plurality of carbon-based sensors printed on the substrate and collectively configured to detect the presence of one or more analytes in the container, each of the carbon-based sensors configured to react with a unique group of analytes, and the label further comprising: one or more electrodes printed on the substrate and coupled to at least some of the carbon-based sensors, the one or more electrodes configured to provide one or more output signals indicative of the presence or absence of the one or more analytes in the container in response to an electromagnetic signal received from an external device; each of the carbon-based sensors comprising a plurality of different graphene allotropes.

17. 17. The container of claim 16, wherein the plurality of different graphene allotropes of each carbon-based sensor comprises one or more microporous or mesoporous pathways.

18. 17. The container of claim 16, wherein each of the carbon-based sensors comprises a polymer configured to bond the plurality of different graphene allotropes to one another.

19. 20. The container of claim 18, wherein the plurality of different graphene allotropes comprises at least one of graphene flakes or carbon nano-onions (CNOs).

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