Method and apparatus

Abstract

One aspect of the present disclosure provides a system for collecting a neutral gaseous fluid sample desorbed from a solid or liquid sample of a substance of interest, the system comprising: a sample collection substrate having an activated surface suitable for surface enhanced Raman spectroscopy (SERS), the activation surface is configured for collecting a sample of the substance of interest; a substrate receiving region in which the sample collection substrate is disposed; a SERS analyzer configured to perform SERS on the surface of the substrate in the substrate receiving area; and a desorber configured to desorb the substance of interest from the sample collection substrate to provide a neutral gaseous fluid sample suitable for further analysis.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to methods and devices for collecting solid and liquid samples, and to analysing and processing such samples for further analysis. BACKGROUND

[0002] A number of methods of sample collection and processing have been proposed. These include:

[0003] • P. D. Fedick et al., Forensic Sampling and Analysis from a Single Substrate: Surface-Enhanced Raman Spectroscopy Followed by Paper Spray Mass Spectrometry, Anal. Chem. 89, 10973-10979, 2017. DOI: 10.1021 / acs.analchem.7b02798.

[0004] • Z. Gong et al., Fabrication of SERS Swab for Direct Detection of Trace Explosives in Fingerprints, ACS Appl. Mater. Interfaces 6, 21931-21937, 2014. DOI: https: / / doi.org / 10.1021 / am507424v.

[0005] • T. Liyanage et al., Fabrication of a self-assembled and flexible SERS nanosensor for explosive detection at parts-per-quadrillion levels from fingerprint, Analyst 143, 9, 2012-2022, 2018. DOI: https: / / doi.org / 10.1039 / C8AN00008E.

[0006] • C. H. Lee et al., Paper-Based SERS Swab for Rapid Trace Detection on Real-World Surfaces, ACS Appl. Mat. Inter. 2, 12, 3429-3435, 2010. DOI: https: / / doi.org / 10.1021 / am1009875.

[0007] • L. Lan et al., Inkjet-printed paper-based semiconducting substrates for surface-enhanced Raman spectroscopy, Nanotechnology 31, 5, 055502, 2020. DOI: 10.1088 / 1361-6528 / ab4f11.

[0008] • M. S. S. Bharati, V. R. Soma, Flexible SERS substrates for hazardous materials detection: recent advances, Opto-Electr. Adv. 4, 11, 210048, 2021. DOI: https: / / doi.org / 10.29026 / oea.2021.210048.

[0009] • H.-C. Chen et al., Surface-enhanced Raman scattering substrate and manufacturing method thereof, US Patent No. 9,518,927 B2, December 13th 2016.

[0010] • Y. Shi et al., A positively charged silver nanowire membrane for rapid on-site swabbing extraction and detection of trace inorganic explosives using a portable Raman spectrometer, Nano Res. 9, 8, 2487-2497, 2016. DOI: 10.1007 / s12274-016-1135-5.

[0011] • W.-C. Shih, Method of stamping surface-enhanced Raman spectroscopy for label-free, multiplexed, molecular sensing and imaging, US Patent No. 9,546,958 B2, April 29th 2015.

[0012] A variety of analytical techniques are known. For example, surface enhanced Raman spectroscopy or surface enhanced Raman scattering (SERS) is a surface sensitive technique that enhances Raman scattering by molecules adsorbed on a suitably decorated surface with nanostructures, such as plasmonic nanoparticles. The most common way of performing SERS measurements is by depositing a sample onto a silicon or glass surface with nanostructured noble metal inclusions. The surface is usually prepared using a distribution of metal nanoparticles on the surface. The most commonly used visible SERS metals are silver and gold. Aluminium has also been proposed for UV SERS. To reduce costs, SERS active particles can be provided on a substrate, for example nanoparticles can be provided on a substrate so that SERS can be performed on a sample on that substrate.

[0013] Other analytical techniques are also known, such as ion mobility spectroscopy and mass spectrometry, and other techniques are also used to analyse ions obtained from a sample.

[0014] Embodiments of the present disclosure provide a single sample collection substrate (e.g. a "swab") that provides suitable desorption mechanisms and arrangements for sample transport. Embodiments can address or at least ameliorate some or all of the following problems:

[0015] • Efficiently collect solid or potentially liquid substances for detection and screening of hazardous, explosive, contaminating or illegal substances;

[0016] • In-situ non-destructive rapid detection and identification (chemical fingerprinting) by SERS;

[0017] • Possible sample transfer, for example for off-site analysis;

[0018] • Desorption and extraction of samples in the gas phase for further analytical characterisation and / or forensic analysis,

[0019] For example (but not exclusively) using an analyser or spectroscopy.

[0020] In one embodiment, a swab according to the present disclosure, such as any SERS-active swab described or claimed herein, can be inserted into a benchtop or handheld trace detection system, such as an explosive trace detector (sometimes referred to as an ETD). Thus, when a user inserts a swab, a SERS analysis is performed, and then the swab is thermally desorbed for analysis in an IMS. SUMMARY

[0021] Aspects of the invention are set out in the independent claims. Embodiments are set out in the dependent claims.

[0022] There is provided in one aspect a system for collecting a sample of a neutral gaseous fluid desorbed from a solid or liquid sample of a substance of interest, the system comprising:

[0023] a sample collection substrate having an active surface suitable for surface enhanced Raman spectroscopy (SERS), the active surface being configured for collecting the sample of the substance of interest;

[0024] a substrate receiving region for receiving the sample collection substrate;

[0025] a SERS analyser configured for performing SERS on the surface of the substrate in the substrate receiving region;

[0026] a desorber configured for desorbing the substance of interest from the sample collection substrate to provide a sample of a neutral gaseous fluid.

[0027] The system can include a gaseous sample collection device arranged to collect a gaseous fluid desorbed from a sample carried by a swab, and to provide the gaseous fluid to a receptacle, such as a container, or to an inlet of a detector.

[0028] The system can also include a detector, and the detector can be configured to ionise the gaseous fluid. Examples of such detectors include ion mobility spectrometers (IMS) and mass spectrometers. Other detectors can be used.

[0029] The sample collection substrate can be configured for thermal desorption of a solid or liquid sample. For example, the material can be substantially free of outgassing at the temperature used for thermal desorption.

[0030] The substrate can be configured for single use, for example it can include at least one heat-sensitive use indicator. Such an indicator can be configured to degrade in response to being heated above a selected temperature threshold. For example, the substrate can be configured to at least partially discolour to provide a visual indication of previous use and / or at least partially disintegrate to inhibit reuse of the substrate.

[0031] The material of the substrate can be hydrophobic.

[0032] In one aspect there is provided a sample collection substrate having an activated surface suitable for surface enhanced Raman spectroscopy (SERS), the activated surface being configured for collecting a sample of a substance of interest, wherein the substrate is further configured for desorbing the substance from the substrate to provide a gaseous fluid.

[0033] The substrate can be a flexible material. Examples of such materials include plastic films, colloidal dispersions on solid substrates, paper-based materials, structured materials such as porous glass or porous alumina, silica or other glass-based films or fibres, homo- or hetero-structured semiconductor films, nanostructures and graphene, and cloth-like substrates such as carbon cloth.

[0034] The substrate is typically SERS-activated and / or enhanced by at least one of nanoparticles, nanostructures and photonic crystals.

[0035] The material of the substrate can be substantially free of background fluorescence at wavelengths of 850 to 450 nm.

[0036] In one aspect there is provided a method of collecting a neutral gaseous fluid sample for analysis, the method comprising:

[0037] collecting a solid or liquid sample of a substance of interest on a sample collection substrate having an activated surface suitable for surface enhanced Raman spectroscopy (SERS);

[0038] desorbing the sample from the substrate to provide a neutral gaseous fluid sample; and

[0039] collecting the neutral gaseous fluid sample for analysis.

[0040] The method can further comprise performing SERS on the surface of the substrate to obtain SERS data corresponding to the sample.

[0041] Collecting a gaseous fluid sample for analysis can comprise providing the neutral gaseous fluid to: (a) a container for storage and / or transport; and (b) an inlet of a detector.

[0042] Desorbing the sample from the substrate can comprise at least one of: (a) heating the substrate; (b) chemical modification, for example acid volatilisation.

[0043] General desorption methods can be used (e.g., thermal desorption and / or current-based desorption, vacuum desorption, etc.). However, in some cases, methods specific to a particular substance or class of compounds can be used. Examples include chemical extraction, acid volatilization, optical resonance and non-resonance desorption, etc. The extraction can be performed in a separate device or reactor and then transferred for further analysis, or directly in an instrument equipped with a suitable desorber. For example, SERS active swabs can be exposed to thermal desorption cycles in IMS or MS.

[0044] For example, graphene- and semiconductor-based substrates can be suitable for current-induced desorption, potentially allowing for conductivity / resistivity measurements. Chemically inert materials such as graphene or graphite, silica-based glasses, or other glasses can be suitable for selective or non-selective chemical extraction, such as by acid evaporation. Optically transparent materials can be used in conjunction with light- or laser-induced desorption, resonant or non-resonant desorption, thereby enabling the use of SERS-active nanoparticles for plasma-enhanced optical desorption.

[0045] As another example, the desorption step can be performed in the desorber of a detector such as an IMS or mass spectrometer.

[0046] Embodiments of this disclosure provide an apparatus comprising a surface-enhanced Raman spectroscopy (SERS) active sample collection substrate for collecting solid or liquid samples, and a desorber arranged to desorb the samples to obtain a gaseous fluid sample. Typically, the gaseous fluid sample is electrically neutral, for example, it is substantially unionized.

[0047] The desorber may include a thermal desorption device, such as a heater. In some embodiments, additional devices for chemical desorption may be provided, such as a device for acid volatilization of the sample. For example, a device for acid volatilization may be provided that provides acid to a solid or liquid sample on a swab to chemically generate a more volatile material. This more volatile material may still bind to the swab, and thermal desorption may still be required to desorb this more volatile material, for example, for desorbing (now more volatile) substances of interest from a sample collection substrate to provide a neutral gaseous fluid sample.

[0048] Embodiments of this disclosure are intended to provide rapid in-situ SERS detection and chemical identification, storage, and transportation. For example, samples can be collected on an SERS-active substrate and then desorbed into a container for containing the gaseous fluid sample. Examples of such containers include bags and other types of sealable packaging. Ex-situ release of the sample into the gaseous phase (e.g., gas or vapor) allows for further analysis or optical analysis. The embodiments thus provide multi-step detection and analysis protocols.

[0049] For example, in one embodiment, a method is provided that includes collecting a solid or liquid sample using a SERS-active sample collection substrate (such as a swab), performing SERS analysis of the sample in situ on the sample collection substrate, and desorbing the sample from the substrate to obtain a gaseous fluid sample for analysis.

[0050] The gaseous fluid sample can be provided to a detector for further analysis, such as by ion mobility spectrometry (IMS), mass spectrometry (MS), gas chromatography, and conventional Raman or optical spectroscopy of the vapor, or any suitable combination of these.

[0051] Embodiments of the present disclosure can allow spatial and / or temporal separation of the identification of a sample in the field, and further analysis or forensic investigation at mobile or fixed facilities.

[0052] Embodiments of the present disclosure can allow a single collection method to support a variety of different analyses and / or spectroscopic investigations, including rapid SERS detection. Embodiments can provide a SERS-based chemical fingerprint, followed by a suitable desorption mechanism (including but not limited to thermal desorption or acid volatilization) and other destructive or non-destructive analysis.

[0053] The desorption can be configured to provide a gaseous fluid containing only neutral species (i.e., the sample is not directly ionized during desorption).

[0054] Embodiments of the present disclosure can be particularly useful in detecting explosives, toxic or illegal substances (such as chemical warfare agents (CWAs), toxic industrial chemicals (TICs), or narcotics) in solid phases or solutions. BRIEF DESCRIPTION OF DRAWINGS

[0055] Embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which Figure 1 A schematic diagram of an apparatus according to the present disclosure is shown. DETAILED DESCRIPTION

[0056] Figure 1 An apparatus 10 is shown that includes a chamber 14 for introducing a substrate 1 having a SERS-active surface, a SERS analyzer 12, a desorber, and a gaseous sample collection device 18.

[0057] The substrate 1 is adapted to physically collect ("swab") particulate residue and / or to be deposited from a liquid solution. For example, it is typically flexible and can include a cloth-like material or other suitable material to allow it to wipe a surface to collect a sample of a substance of interest from the surface. The substrate material is typically adapted to allow it to be subjected to a desorption process, for example it can be non-flammable and / or capable of being heated to at least 200°C without significant off-gassing. The surface of the substrate 1 is SERS-active. For example, it carries a material suitable for performing SERS, such as silver nanoparticles.

[0058] like Figure 1 As shown, substrate 1 can be supported on sample collection rod 22 or the like. As illustrated, substrate 1 can be introduced into chamber 14 of the device, either on such rod 22 or via other means. Chamber 14 can be provided with a housing to collect gaseous fluids, such as vapor or gas, desorbed from the sample. Figure 1 In the example shown, the chamber 14 of the device 1 includes a port 24 to allow the substrate 1 to be introduced into the chamber, for example, such that a sample collection rod 22 carrying the substrate 1 can be inserted into the chamber 14.

[0059] Desorber 16 can also be provided in chamber 14. Figure 1 In the illustrated embodiment, the desorber 16 includes a heater arranged such that heat can be applied to the substrate 1 to desorb the sample therefrom when the substrate 1 is introduced into the chamber 14 and after SERS analysis.

[0060] A gas sample collection device 18 is connected to the chamber for collecting gaseous fluid desorbed from the substrate 1 by the desorber 16. Typically, the sample collection device 18 includes a blower, such as a pump, connected to move the gaseous fluid from the chamber 14 to the inlet of a receiver, such as a container or detector.

[0061] In addition, the device also includes a SERS analyzer 12. As shown in the figure, this includes optics for providing radiation to the sample and for collecting Raman scattered radiation from the sample.

[0062] The controller 20 can be connected to the SERS analyzer 12 to obtain SERS data from the SERS analyzer 12. The controller 20 may have a data output interface for providing the SERS data to another device, such as a detector, which can use the SERS data for analysis of neutral gaseous fluids and / or ionized substances obtained therefrom.

[0063] In operation, the SERS-active substrate 1 is rubbed against its surface to collect solid or liquid substances on the substrate. The substrate carrying the solid or liquid sample is introduced into chamber 14 and positioned such that the SERS-active surface of substrate 1 and the sample are provided to the SERS analyzer 12. The SERS analyzer 12 is then operated to provide excitation radiation with typical Raman bands to the active surface of the substrate, such as near-infrared (e.g., 850 nm or 780 nm), visible light (e.g., 635 nm or 532 nm), and latent UV (e.g., 250 nm). The SERS analyzer 12 collects the radiation scattered by substrate 1 and analyzes the scattered radiation to provide spectral data corresponding to the chemical Raman characteristics of the sample. This spectral data can be provided to controller 20, which can store the data or provide it for transmission to other devices.

[0064] The desorber 16 is then operated according to its operating principle (e.g. thermal, optical and optionally additional chemical desorption) to cause volatilisation of the sample carried by the substrate 1. This process produces a gaseous fluid comprising vapour and / or gas. Typically, this is done such that the gaseous fluid remains neutral (i.e. not ionised). The neutral gaseous fluid is then collected and provided to a receptor such as a container for storage or an inlet of a detector. Examples of suitable detectors for this purpose include ion mobility spectrometers (IMS), mass spectrometers and other types of detector in which neutral gas can be introduced into an inlet of the device for analysis.

[0065] This enables a multi-stage analysis to be performed, with one stage being SERS, which can be controlled automatically or manually by an operator. The substrate containing the collected material will be used for SERS spectroscopy to rapidly identify the chemical species, and in appropriate locations using suitable desorption or extraction mechanisms for at least another optical or analytical technique which requires use of the gas phase. As the extracted molecules are primarily in a neutral charge state, the next analysis can include ionisation of the extracted / vaporised material. It can thus be seen that the collection substrate described herein can provide significant advantages in matching the requirements of SERS and subsequent extraction for chemical or physical analysis by detection methods such as IMS and other techniques.

[0066] Figure 1 The illustrated apparatus uses a sample collection swab, but any suitable device can be used to immobilise the SERS-active substrate ("swab"). The swab can be mounted in a suitable sampling tool (e.g. a sampling stick or forceps) or instrument (e.g. but not exclusively any mechanical construct capable of autonomous or guided movement), but can also be simply manually operated by an individual.

[0067] The SERS-active substrate can be designed in any form factor suitable to match the requirements of the instrument one prefers to use. The same applies to the materials: depending on the envisaged application and / or the chosen desorption mechanism (see below), SERS-active swabs can be implemented, for example (but not limited to) plastic films and organic polymers, colloidal dispersions on solid substrates, paper-based materials, microscopically structured materials (e.g. porous glass, porous alumina), silica or other glass-based films or fibres, homo- or hetero-structured semiconductor films or nanostructures and graphene, and cloth-like substrates, for example (but not limited to) carbon cloth.

[0068] SERS activity can be introduced and / or enhanced with any known technique, including for example (but not limited to) decoration with nanoparticles or nanostructures, photonic crystals, etc.

[0069] Methods for extracting the collected substance for subsequent study with instruments other than the SERS spectrometer can be general (e.g., thermal desorption and / or current-based desorption, vacuum desorption, etc.) or specific to the substance or class of compounds (e.g., chemical extraction, acid volatilization, optical resonance and non-resonance desorption, etc.) as described. Extraction can be performed in a separate device or reactor, with subsequent transfer for further analysis, or directly in the instrument equipped with a suitable desorber. For example, the SERS-active swab can be exposed to a thermal desorption cycle in an IMS or MS.

[0070] For example, but not limiting the scope of the invention to these materials and methods of operation, graphene and semiconductor-based substrates can be suitable for current-induced desorption, potentially allowing for conductivity / resistivity measurements. Chemically inert materials like graphene or graphite, silica-based glass or other glasses can be suitable for selective or non-selective chemical extraction, for example by acid volatilization. Optically transparent materials can be used in conjunction with light or laser-induced desorption, resonance or non-resonance, whereby one can also take advantage of SERS-active nanoparticles for plasmon-enhanced optical desorption.

[0071] The gas sample collection device can provide a system for maintaining the integrity of the collected sample (e.g., a sealed vapor bag) and for extracting neutral molecules from the collected sample via a suitable desorption mechanism, such as thermal desorption, light-induced desorption or chemical volatilization.

[0072] A significant advantage is that the neutral gaseous fluid sample provides the possibility of transferring the collected sample to off-site facilities after rapid SERS characterization. The SERS data collected together with the relevant sample can be provided together with the sample itself.

[0073] As explained above with reference to Figure 1 The combination of SERS with IMS is a preferred embodiment of the invention, as explained above. Such an embodiment can provide in a single integrated system, where both types of analysis are performed by a single device. However, other embodiments can be contemplated. For example, after SERS analysis of a solid or liquid sample carried on a swab, desorption and analysis with instruments and techniques other than SERS can be performed separately (in space and / or time) from the instrument used for SERS detection. This can also imply the possibility of transferring the SERS-active substrate ("swab") to a different location after SERS analysis.

[0074] As described above, the present disclosure provides a sample collection substrate having an activated surface suitable for surface-enhanced Raman spectroscopy, SERS, the activated surface being configured for collecting a sample of a substance of interest, wherein the substrate is further configured for desorbing the substance from the substrate to provide a gaseous fluid.

[0075] Such a substrate can be configured for high collection efficiency.

[0076] In one embodiment, the substrate can have surface porosity and / or low adsorption energy and / or chemical affinity with a compound of interest. It can be disposable and configured for single use.

[0077] It can be configured for desorption mechanisms, such as thermal desorption and / or current-based desorption, vacuum desorption, etc.) or techniques specific to a class of substances or compounds (such as chemical extraction, acid volatilization, optical resonance and non-resonance desorption, etc.).

[0078] Typically, the substrate and the material from which it is made are flexible to facilitate surface adhesion of a solid or liquid sample. It can be configured to inhibit adsorption of background gases and / or it can be provided in a sealed packaging. Typically, the active (e.g. SERS active) surface of the substrate has an area of at least 1 cm 2 .

[0079] The material and / or the substrate can be configured for attachment to a sample collection rod, or it can be configured for application to a surface by hand.

[0080] Typically, the substrate comprises a hydrophobic material.

[0081] The substrate can be configured for thermal desorption of the solid or liquid sample. Typically, such a substrate can be configured for single use, e.g. it can comprise at least one heat-sensitive use indicator. Such an indicator can be configured to degrade in response to being heated above a selected temperature threshold. For example, the substrate can be configured to at least partially change color to provide a visual indication about previous use and / or at least partially disintegrate to inhibit reuse of the substrate.

[0082] A substrate configured for thermal desorption can have a melting point much greater than 200 °C, e.g. at least 600 °C, e.g. at least 800 °C, e.g. 1500 °C or more. Typically, such a substrate has a glass transition temperature greater than 200 °C.

[0083] Typically, a substrate configured for thermal desorption consists only of materials that have limited or negligible outgassing at the desorption temperature. Typically, a substrate configured for thermal desorption has a surface extraction potential that is less than the ionization potential of a species of interest, e.g. a chemical warfare agent, a controlled substance, a toxic industrial chemical, etc. For example, a substrate configured for thermal desorption can have a low adsorption energy, e.g. of the order of about 0.1 eV. Typically, a substrate configured for thermal desorption has a thickness of less than 1 mm.

[0084] The substrate can be configured for electrodesorption of the solid or liquid sample. Such a swab can include electrically conductive members, which can be at least partially electrically insulated, for example so that they carry current preferably along their length (for example between uninsulated contact points disposed at opposite ends of the electrically conductive members). Such a swab can be adapted to be clamped between electrodes, and can include a contact region which can be arranged to provide electrical contact between the electrically conductive members and a power supply of the desorber. The contact region can be arranged to make electrical contact with a clamp holding the swab to the desorber. The electrically conductive members can be incorporated into the substrate, for example by being woven or embedded into the substrate material. Typically, a substrate configured for electrodesorption has a thickness of less than 1 mm. Typically, a substrate configured for electrodesorption consists only of a material which has limited or negligible outgassing at the desorption temperature.

[0085] The substrate can be configured for acid volatilisation of the solid or liquid sample. Typically, such a substrate is chemically inert and stable, for example it can not react with an acid, for example an acid used for volatilisation. The substrate can include a material which is capable of being coated with a polymer such as Nafion. In some embodiments, the substrate includes a polymer coating. Such a substrate can be adapted to be humidified prior to desorption. A substrate configured for acid volatilisation can further be configured for electro and / or thermal desorption as described above.

[0086] The substrate can be configured for optical desorption of the solid or liquid sample. For example, it can be substantially optically transmissive in the short wavelength visible light range. In some examples, the wavelength can be in the near ultraviolet range. For example, it can be substantially optically transmissive for wavelengths less than or equal to about 540 nm, for example less than or equal to about 532 nm (i.e. λ < 532 nm). It can be substantially optically transmissive for wavelengths greater than or equal to about 300 nm. A substrate configured for optical desorption can have a low absorption energy, for example of the order of about 0.1 eV (Eads~10-1 eV).

[0087] All substrates of the present disclosure can be configured for single use. For example, they can carry elements configured to inhibit reuse of the substrate, such as elements which change state in response to a desorption process being performed on the swab, for example elements which degrade or discolour by the desorption process.

[0088] Substrates of the present disclosure can be decorated with SERS-active nanoparticles such as gold (Au) nanoparticles. The nanoparticles can be disposed on the substrate in a regular arrangement.

[0089] The substrate of the present disclosure can comprise (or consist only of) a material that provides reduced or substantially no background fluorescence at SERS wavelengths, e.g. between 850 nm and 400 nm, e.g. less than 780 nm, e.g. less than 633 nm, e.g. less than 532 nm, e.g. greater than 400 nm. The material can be transparent, e.g. substantially transparent, e.g. partially transparent at such wavelengths.

[0090] The substrate of the present disclosure can comprise (or consist only of) a material that provides reduced or substantially no background fluorescence at SERS wavelengths, e.g. between 400 nm and 850 nm, e.g. greater than 532 nm, e.g. greater than 633 nm, e.g. greater than 780 nm, e.g. less than 850 nm. The material can be transparent, e.g. substantially transparent, e.g. partially transparent at such wavelengths.

[0091] Typically, the material is sufficiently robust to be manipulated by hand or a stick. The SERS active region is typically about 1 cm 2 .

[0092] Preferably, the material(s) have surface porosity and / or low adsorption energy and / or chemical affinity with the compound of interest. Preferably, the swab is configured for single use and is capable of retaining the sample for at least one day, e.g. at least 5 days, e.g. at least 28 days, e.g. 90 days. Preferably, the material is suitable for at least one of the desorption mechanisms listed above. Preferably, the material is flexible and exhibits low levels of outgassing, e.g. substantially no outgassing at temperatures used for thermal desorption. Preferably, the material is decorated with nanoparticles on the SERS active region. The nanoparticles can be gold or silver.

[0093] In some embodiments, the swab of the present disclosure has a shelf life longer than 3 months and is suitable for both hand sampling and stick sampling.

[0094] The material can comprise or consist essentially of a paper-based substrate decorated with Au (or Ag) nanoparticles and other cellulose-based substrates.

[0095] The material can comprise or consist essentially of a membrane-based substrate decorated with Au (or Ag) nanoparticles, e.g. PTFE, micro / nano-porous glass, etc. One commercial example of such a material is

[0096] Zitex G by Saint-Gobain.

[0097] The material can comprise or consist essentially of a cloth-based substrate decorated with Au (or Ag) nanoparticles. For example, carbon cloth.

[0098] The material can comprise or consist essentially of graphene or graphite sheets decorated with Au (or Ag) nanoparticles.

[0099] In some embodiments, silicon or semiconductor structures decorated with Au (or Ag) nanoparticles can be used.

[0100] The above materials can provide useful performance even with different nanostructures that provide plasmon-like responses that can lead to SERS enhancement.

[0101] The controller of the apparatus described herein can comprise an ADC and digital logic configured to perform the operations described herein. In some examples, the functionality of the controller can be provided by a general purpose processor, which can be configured to perform a method according to any of those described herein. In some examples, the controller can comprise digital logic, such as a field programmable gate array, FPGA, an application specific integrated circuit, ASIC, a digital signal processor, DSP, or any other appropriate hardware. In some examples, one or more memory elements can store data and / or program instructions for implementing the operations described herein. Embodiments of the disclosure provide a tangible, non-transitory storage medium comprising program instructions operable to program a processor to perform any one or more of the methods described and / or claimed herein and / or to provide a data processing apparatus as described and / or claimed herein. The controller can comprise analog control circuitry providing at least a portion of this control functionality. Embodiments provide an analog control circuitry configured to perform any one or more of the methods described herein.

[0102] It will be understood from the above discussion that the embodiments shown in the figures are exemplary only and include features that can be generalized, removed or replaced as described herein and according to the claims.

[0103] Referring generally to the drawings, it will be understood that the schematic functional block diagrams are used to indicate functionality of the systems and apparatuses described herein. However, it will be understood that functionality need not be divided in this manner and should not be taken to imply any particular hardware structure other than that described and claimed below. The functionality of one or more elements shown in the drawings can be further subdivided and / or distributed throughout the apparatus of the disclosure. In some embodiments, the functionality of one or more elements shown in the drawings can be integrated into a single functional unit.

[0104] The above examples are to be understood as illustrative examples. Further embodiments can be envisaged. It will be appreciated that any feature described in relation to any one embodiment can be used alone or in combination with other features described, and can also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above can also be employed without departing from the scope of the application, which is defined in the claims below.

Claims

1. A system for collecting a neutral gaseous fluid sample desorbed from a solid or liquid sample of a substance of interest, the system comprising: A sample collection substrate having an activated surface suitable for surface-enhanced Raman spectroscopy (SERS), the activated surface being configured to collect a sample of the substance of interest; A substrate storage area, wherein the sample collection substrate will be placed; A SERS analyzer is configured to perform SERS on the surface of the substrate in the substrate housing region. A desorber configured to desorb the substance of interest from the sample collection substrate to provide a neutral gaseous fluid sample suitable for further analysis.

2. The system of claim 1, wherein the sample collection substrate is configured for single use, for example, wherein the sample collection substrate carries or includes at least one thermal use indicator.

3. The system according to claim 1 or 2, wherein the sample collection substrate is provided with a hydrophobic material.

4. The system according to any one of the preceding claims, wherein the sample collection substrate is provided with a material that has substantially no background fluorescence in wavelengths between 850 nm and 450 nm.

5. The system according to any one of the preceding claims, comprising a gaseous sample collection device arranged to collect the neutral gaseous fluid sample and provide the sample to a receiver.

6. The system of claim 5, wherein the receiver comprises one of: (a) a container and (b) an inlet to the detector.

7. The system of claim 6, wherein the receiver includes the inlet of the detector, and the system further includes the detector, wherein the detector is configured to ionize the gaseous fluid.

8. A sample collection substrate having an activated surface suitable for surface-enhanced Raman spectroscopy (SERS), the activated surface being configured to collect a sample of a substance of interest, wherein the substrate is further configured to desorb the substance from the substrate to provide a gaseous fluid.

9. The sample collection substrate of claim 8, wherein the sample collection substrate is configured for single use, for example, wherein the sample collection substrate carries or includes at least one thermal use indicator.

10. The sample collection substrate according to claim 8 or 9, wherein the sample collection substrate is provided with a hydrophobic material.

11. The sample collection substrate according to any one of claims 8 to 10, wherein, The sample collection substrate was provided with a material that has virtually no background fluorescence in wavelengths between 850 nm and 450 nm.

12. The sample collection substrate according to any one of claims 8 to 11 or the system according to claim 7, wherein the substrate is made of a flexible material.

13. The sample collection substrate according to any one of claims 8 to 12 or the system according to claim 7, wherein the substrate comprises at least one of: a plastic film, a colloidal dispersion on a solid substrate, a paper-based material, a structured material such as porous glass or porous alumina, silica or other glass-based films or fibers, a homogeneous or heterogeneous semiconductor film, nanostructures and graphene, and a cloth substrate such as carbon cloth.

14. The sample collection substrate of any one of claims 8-13 or the system of any one of claims 1-7, wherein the substrate is activated and / or enhanced by SERS through at least one of nanoparticles, nanostructures and photonic crystals.

15. A method for collecting a neutral gaseous fluid sample desorbed from a solid or liquid sample for analysis, the method comprising: Solid or liquid samples of the substance of interest are collected on a sample collection substrate with an activated surface suitable for surface-enhanced Raman spectroscopy (SERS). Desorb the solid or liquid sample from the substrate to provide a neutral gaseous fluid sample; as well as The neutral gaseous fluid sample was collected for further analysis.

16. The method of claim 15, further comprising performing SERS on the surface of the substrate to obtain SERS data corresponding to the sample.

17. The method of claim 15 or 16, wherein collecting the gaseous fluid sample for analysis comprises: The neutral gaseous fluid is provided to one of the following: (a) a container for storage and / or transport; (a) and (b) the detector's entrance.

18. The method according to any one of claims 15 to 17, wherein desorbing the sample from the substrate comprises at least one of: (a) heating the substrate; (b) chemical extraction, such as acid evaporation; (c) optical desorption; and (d) current-induced desorption.

19. The method according to any one of claims 15 to 18, wherein the desorption step is performed in the desorber of a detector such as an IMS or mass spectrometer.

20. The method according to any one of claims 15 to 19, wherein the sample collection substrate is provided by the sample collection substrate according to any one of claims 8 to 14.

21. The system according to any one of claims 1 to 7, wherein the desorber is provided in a separate device separate from the SERS analyzer.

22. The system according to any one of claims 1 to 7 or claim 21, wherein, The further analysis is spatially and / or temporally separate from the SERS analysis.

Images