Polymers comprising silicon nanoparticles dispersed therein from silicon nanoparticle coated polymer sheets

Abstract

A polymeric host matrix material having silicon nanoparticles dispersed therein is prepared by: (a) providing a sheet of polymeric host matrix material coated with silicon nanoparticles; (b) softening the sheets of polymeric host matrix material coated with silicon nanoparticles to form softened sheets of polymeric host matrix material; and (c) blending the softened sheets of polymeric host matrix material with the silicon nanoparticles on the surface of the softened sheets of polymeric host matrix material to form a single substance of polymeric host matrix material in which the silicon nanoparticles are dispersed.

Description

Technical Field

[0001] The present invention relates to polymeric materials having silicon nanoparticles dispersed therein and methods for preparing such polymeric materials from polymer sheets coated with silicon nanoparticles.

[0002] introduction

[0003] The advent of nanotechnology has led to paradigm shifts in many technological fields, as the properties of many materials change at the nanoscale. For example, reducing the dimensions of some structures to the nanometer scale can increase the surface-to-volume ratio, leading to changes in the material's electrical, magnetic, reactive, chemical, structural, and thermal properties. Nanomaterials are already found in commercial applications and are likely to be present in a wide variety of technologies over the coming decades, including computing, photovoltaics, optoelectronics, medicine / pharmaceuticals, structural materials, military applications, and many others.

[0004] Silicon nanoparticles are an ideal type of nanoparticle. A key property of small (average size less than 10 nanometers (nm)) silicon nanoparticles is that they photoluminesce in the visible when stimulated by a relatively low-wavelength (UV) light source. This is believed to be caused by a quantum confinement effect that occurs when the nanoparticle diameter is smaller than the excitation radius, leading to bandgap bending (i.e., an increase in the bandgap). Researchers have shown that the bandgap energy (measured in electron volts) of nanoparticles varies depending on the nanoparticle diameter.

[0005] Although silicon is an indirect bandgap semiconductor in the bulk, silicon nanoparticles with an average size of less than 10 nm can simulate direct bandgap materials, which can be achieved by interface trapping of excitons. Direct bandgap materials can be used as silicon quantum dot materials in optoelectronic applications. Silicon quantum dots are particularly desirable relative to other quantum dot materials because they do not require environmentally unfriendly components such as lead, selenide, cadmium, indium, arsenide or even germanium. Another interesting property of nanomaterials is the melting point reduction that follows the surface phonon instability theory. Researchers have shown that the melting point of nanomaterials formed by nanoparticles varies depending on the diameter of the nanoparticles.

[0006] There is the application that benefits from making silicon nanoparticles be dispersed in composition (commonly referred to as " host matrix ", such as polymer).But, may be difficult to nanoparticles be directly dispersed in the host matrix, particularly under the situation that does not experience the agglomeration of silicon nanoparticles.Some efforts in the prior art have described nanoparticles being dispersed in monomer, then make monomer polymerization to obtain the polymer host matrix that nanoparticles are dispersed in therein.But, this needs the preparation personnel to adapt to handle monomer and carry out polymerization.Expect to determine a kind of for silicon nanoparticles being directly dispersed in the polymer host matrix material and do not have to handle monomer and polymerization procedure with nanoparticles being dispersed in the effective method in the polymer matrix. Summary of the Invention

[0007] The present invention provides an efficient method for dispersing silicon nanoparticles directly into a polymer host matrix, rather than dispersing the silicon nanoparticles into monomers and then polymerizing the monomers into the polymer matrix material. This method also provides a means of concentrating the silicon nanoparticles within the polymer matrix material using differential flow rates of the polymer and silicon nanoparticles.

[0008] The present invention is the result of the discovery that not only can silicon nanoparticles be deposited onto a polymer host matrix material during the manufacture of the silicon nanoparticles, but that the silicon nanoparticles are sufficiently thermally and physically stable to allow melt blending of silicon nanoparticle-coated sheets of the polymer host matrix material, and even to be hot pressed to form a polymer host matrix in which the silicon nanoparticles are dispersed throughout the polymer host matrix. Even when the silicon nanoparticles are silicon quantum dots, they can withstand the temperatures of melt blending and hot pressing to produce a polymer composition in which the silicon quantum dots are dispersed. Even more surprisingly, flowing a thermoplastic polymer host matrix containing dispersed silicon nanoparticles can result in a differential flow between the silicon nanoparticles and the thermoplastic polymer host matrix, so as to produce a concentration effect of the silicon nanoparticles by inducing flow of the thermoplastic polymer host matrix material. This result appears to be a result of the phenomenon that the silicon nanoparticles flow slower than the thermoplastic polymer host matrix, which results in a concentration effect of the silicon nanoparticles within the thermoplastic polymer host matrix, which avoids agglomerating the silicon nanoparticles. This concentration procedure allows obtaining a higher concentration of silicon nanoparticles within the thermoplastic polymer host matrix than can be obtained by mixing the nanoparticles directly into the thermoplastic polymer host matrix without agglomeration.

[0009] In a first aspect, the present invention is a method for preparing a polymer host matrix material having silicon nanoparticles dispersed therein, the method comprising: (a) providing sheets of polymer host matrix material coated with silicon nanoparticles; (b) softening the sheets of polymer host matrix material coated with silicon nanoparticles to form softened sheets of polymer host matrix material; and (c) blending the softened sheets of polymer host matrix material together with the silicon nanoparticles on the surfaces of the softened sheets of polymer host matrix material to form a single substance of polymer host matrix material having silicon nanoparticles dispersed therein.

[0010] The method of the present invention is suitable for dispersing silicon nanoparticles into a polymer host matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A schematic diagram of the VHFLPP apparatus used in the preparation of the Examples herein is shown. DETAILED DESCRIPTION

[0012] Products identified by their trade names refer to compositions available under those trade names on the priority date of this document.

[0013] "A plurality of" means two or more. "And / or" means "and, or as an alternative." Unless otherwise indicated, all ranges are inclusive.

[0014] "Cx to Cy", "C x -C y ”, “C x-y ” are used interchangeably and refer to compositions having a number of carbon atoms in the range of x to y.

[0015] "Silicon nanoparticles" refers to silicon-based particles having an average particle size of less than 1 micron, typically 100 nanometers (nm) or less, and an average particle size of 1 nm or greater. Dynamic light scattering or transmission electron microscopy image analysis are common methods for determining the average particle size of silicon nanoparticles. Silicon nanoparticles include silicon quantum dots.

[0016] "Silicon-based" refers to compositions that contain silicon. Silicon-based materials typically contain 40 percent (%) or more, and may contain 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or even 100% silicon atoms, or a combination of silicon atoms and oxygen atoms, based on all atoms in the material.

[0017] "Silicon quantum dots" refer to silicon nanoparticles that have a crystalline silicon structure and photoluminesce when exposed to light. Typically, the average particle size of silicon quantum dots ranges from 1 to 10 nanometers, preferably from 1 to 6 nanometers, and more preferably from 1 to 5 nanometers. Silicon quantum dots are characterized by luminescence when exposed to light with a wavelength in the range of 300 to 477 nanometers, corresponding to blue and ultraviolet light.

[0018] The present invention is a method for preparing a polymer host matrix material in which silicon nanoparticles, preferably silicon quantum dots, are dispersed. The polymer host matrix material is a softenable material, which means that it can be softened by heating and / or adding a solvent and becomes stronger when cooled and / or the solvent is removed. Desirably, the polymer host matrix material is a polymer, preferably a thermoplastic polymer. The polymer host matrix material can be crystalline, semi-crystalline or amorphous. Examples of suitable polymers that can be polymer host matrix materials include homopolymers and copolymers. Examples of suitable polymers that can be polymer host matrix materials include any polymer or any combination of more than one polymer selected from the group consisting of polyethylene, polypropylene, polybutadiene, poly(methyl methacrylate), polystyrene, polyisoprene, poly(vinyl butyral), poly(lactic acid) and poly(amide). Polyethylene includes variants of polyethylene, such as low density polyethylene, linear low density polyethylene and high density polyethylene.

[0019] The method of the present invention involves providing sheets of a polymer host matrix material coated with silicon nanoparticles, softening the sheets of polymer host matrix material to form softened sheets of polymer host matrix material; and then blending the softened sheets of polymer host matrix material with the silicon nanoparticles on the surfaces of the softened sheets of polymer host matrix material to form a single mass of polymer host matrix material in which the silicon nanoparticles are dispersed. "Sheets" with respect to sheets of polymer host matrix material can be in any form, such as, for example, any one or any combination of more than one of pellets, powders, granules, flakes, plates, chips, blocks, and sheets or films.

[0020] Within the broadest scope of the present invention, providing a sheet of a polymer host matrix material coated with silicon nanoparticles can be accomplished in any manner. Exemplary methods of providing a sheet of a polymer host matrix material coated with silicon nanoparticles include the following: (1) spray coating a sheet of a polymer host matrix material with silicon nanoparticles; (2) depositing the silicon nanoparticles directly onto a sheet of host matrix material after they are prepared; and (3) depositing the silicon nanoparticles into a capture fluid containing a sheet of polymer host matrix material after they are prepared. Each of these methods desirably uses a very high frequency low pressure plasma (VHFLPP) process to prepare the silicon nanoparticles.

[0021] VHFLPP process

[0022] The VHFLPP process is a commonly known process for producing nanoparticles, and in this case, silicon nanoparticles, including silicon quantum dots. The VHFLPP process offers greater control over particle size and size distribution when producing nanoparticles than other processes for producing nanoparticles. Examples of the VHFLPP process are described in the prior art, including US2013 / 0189446, US2012 / 0326089, and WO2020 / 205850. Below is a basic description of the VHFLPP process.

[0023] The VHFLPP process uses a gas stream containing at least one nanoparticle precursor, which flows through a quartz tube at a pressure below 13,333 Pascals (Pa). To produce silicon nanoparticles, the nanoparticle precursor is or comprises a silicon-containing material, typically selected from the group consisting of silane, disilane, halogen-substituted silanes, halogen-substituted disilanes, C1 to C4 alkylsilanes, C1 to C4 alkyldisilanes, and mixtures thereof. The gas stream may contain additional precursors (dopants), typically comprising a component or any combination thereof selected from the group consisting of halogens, germanium, boron, phosphorus, and nitrogen. The combined concentration of the nanoparticle precursor and dopant in the gas stream typically ranges from 0.1 volume percent (vol%) to 50 volume percent (vol%) relative to the gas stream composition. The remainder of the gas stream is primarily an inert gas or a combination of more than one inert gas, such as argon (Ar), helium (He), neon (Ne), krypton (Kr), xenon (Xe), and radon (Rn).

[0024] Concentrically and externally of the quartz tube are two ring electrodes, typically copper, spaced apart, with one ring electrode positioned "upstream" (relative to the gas flow) relative to the other. Plasma is generated within the quartz tube by powering the upstream ring electrode with an RF source while grounding the other ring electrode. RF is a very high frequency (typically ranging from 30 MHz to 500 MHz) and is coupled to a power typically ranging from 80 watts to 1000 watts.

[0025] When the nanoparticle precursor flows through the plasma, it decomposes, nucleates and grows into nanoparticles.The pressure of the plasma is 6666 Pascal (Pa) or less, preferably 667 Pa or less, and typically 133 Pa or greater.

[0026] The nanoparticles continue to flow in the airflow and leave the quartz tube through the orifice into the collection chamber. When the airflow is flowing, the pressure in the collection chamber is less than 13.33 Pascals (Pa). When the airflow is not flowing, the pressure in the collection chamber is typically 6.67×10 -5 Pa.

[0027] The VHFLPP process can be run as a continuous or pulsed process. A continuous VHFLPP process uses a constant, continuous radio frequency on the upstream ring electrode. In contrast, a pulsed VHFLPP process uses an amplitude-modulated very high frequency (VHF) radio frequency signal applied to the upstream ring electrode. This amplitude-modulated signal typically operates with a square wave function ranging from 1 kHz to 50 kHz, which is multiplied by a continuous VHF sinusoidal waveform. Advantages of a pulsed process include using pulse energy to control the size of the nanoparticles, which are produced by controlling the residence time of the nanoparticle precursors as they are exposed to the high-power plasma while passing through the VHF glow discharge. In a continuous (non-modulated) VHF plasma process, nanoparticle size can be controlled by the concentration of the nanoparticle precursors—in the case of silicon nanoparticles, the concentration of silicon—as well as by the residence time of the precursors in the VHF plasma.

[0028] Spraying method

[0029] In spray coating methods that provide a sheet of polymeric host matrix material, it is desirable to collect the nanoparticles in a capture fluid, transfer them to a solvent, and then spray coat them onto the sheet of polymeric host matrix material.

[0030] When collecting silicon nanoparticles in a capture fluid, the capture fluid is positioned in the collection chamber of the VHFLPP process in the flow path of the air flow containing nanoparticles. The distance between the surface of the capture fluid and the orifice of the quartz tube is ideally in the range of 5 to 50 orifice diameters. The air flow containing nanoparticles impacts the surface of the capture fluid, thereby introducing the nanoparticles into the capture fluid, and the nanoparticles are collected in the capture fluid. Usually, in order to help nanoparticles to be dispersed in the capture fluid, during the nanoparticle collection, the capture fluid is stirred (for example, stirred or subjected to ultrasonic agitation) and / or the reservoir containing the capture fluid is rotated during the nanoparticle collection. After capture is complete, the capture fluid containing nanoparticles is subjected to ultrasonic treatment and also helps to promote the dispersion of nanoparticles.

[0031] The capture fluid should have a sufficiently low vapor pressure so as to remain substantially intact in the reservoir within the collection chamber during the VHFLPP process. The capture fluid is ideally non-aqueous. Examples of suitable capture fluids include mineral oil, silicone oil (such as polydimethylsiloxane (PDMS), phenylmethyl-dimethylcyclosiloxane, tetramethyltetraphenyltrisiloxane and pentaphenyltrimethyltrisiloxane), fluorocarbons, and alkylene oxide oils. The capture fluid can be a blend of more than one fluid. Other desired properties and examples of suitable capture fluids are proposed in paragraphs

[0070] to

[0077] of WO2020 / 205850, and these teachings are incorporated herein by reference because they are ideally suited for the capture fluids of the present invention.

[0032] The capture fluid may contain additives dissolved or dispersed therein. Desirable additives may include surface modifiers (functionalizing agents) that adhere to the surface of the nanoparticles as the nanoparticles are collected. Surface modifiers may act as compatibilizers, making the nanoparticles more compatible with the capture fluid or some other medium with which the nanoparticles need to be combined, may make the surface of the nanoparticles reactive to further chemical reactions, or may impart both compatibility and reactivity. Examples of additives that may be included in the capture fluid include hydrocarbons (such as 1-olefins) that help disperse the nanoparticles in hydrophobic media; oligoethylene glycols (such as allyl ethers) that help disperse the nanoparticles in hydrophilic media; terminal olefins containing functional groups such as alcohols, carboxylates, amines, and protected forms of these for post-passivation conversion and extraction; and fluorocarbons with terminal olefins that help disperse the nanoparticles in fluoropolymers.

[0033] The capture fluid can be recycled or reused in the VHFLPP process. That is, for multiple runs of the VHFLPP process, nanoparticles can be collected in the same capture fluid. Typically, the nanoparticles are separated from the capture fluid before the capture fluid is reused, but this is not required. For example, the nanoparticles can be collected in the capture fluid, passivated, and then separated from the capture fluid (e.g., by filtration or centrifugation). The remaining capture fluid can then be used in subsequent VHFLPP processes.

[0034] After the silicon nanoparticles are collected in the capture fluid, it is desirable to passivate them, particularly if they are silicon nanoparticles, in order to provide stability for exposure to air. Silicon nanoparticles are readily passivated in a capture fluid by exposing the capture fluid containing the silicon nanoparticles to a relatively humid atmosphere, typically at a temperature above 25°C for a period of time. The moisture slowly penetrates the capture fluid and reacts to form a passivating oxide layer on the silicon nanoparticles. For example, one way to perform passivation of the silicon nanoparticles in the capture fluid is to subject the nanoparticles and the capture fluid to a temperature of 23°C or higher, typically 50°C or higher, 60°C or higher, 65°C or higher, or even 70°C or higher, while typically 80°C or lower, or 70°C or lower, or even 65°C or lower, and an atmosphere of 85% relative humidity, preferably air, for a period of time typically between 12 hours and 72 hours, and may even be longer than 72 hours. In some cases, this period of time can be 168 hours or longer. Longer time periods can result in a greater degree of oxidation of the silicon nanoparticle surface, particularly in fluids with low oxygen and moisture permeabilities.

[0035] From the capture fluid, separate the silicon nanoparticles, usually by centrifugation, remove fluid and / or filter subsequently.Then the silicon nanoparticles are dispersed into a sprayable fluid such as a solvent (for example, toluene).Then the dispersion of the silicon nanoparticles in the sprayable fluid is sprayed onto the sheet of the polymeric host matrix material, and they are dried.The polymer thermal material sheet of gained is coated with silicon nanoparticles.

[0036] Direct deposition method

[0037] When the silicon nanoparticles are directly collected on substrate (such as the sheet of polymer host matrix material), substrate is positioned in the collecting chamber in the flow path of the air-flow that contains nanoparticles.When nanoparticles contact substrate, they gather on the surface of substrate.When the air-flow that contains nanoparticles hits substrate, what is desired is to move substrate, so that help nanoparticles are distributed on the surface of substrate, rather than coalesce into agglomerates.For example, substrate can be in an open container, and this open container rotates or translates under the air-flow that contains nanoparticles in the collecting chamber.Gained substrate (such as the sheet of polymer host matrix material) is coated with silicon nanoparticles.

[0038] It is desirable to passivate the silicon nanoparticles on the substrate before exposing the substrate to air, particularly if the silicon nanoparticles are silicon quantum dots. One method of passivating the silicon nanoparticles is to immerse the host matrix particles coated with silicon nanoparticles in a protective fluid in a vacuum or under a dry inert atmosphere and then expose the fluid to air in a controlled manner to control the rate at which oxygen and moisture reach the silicon nanoparticles so that a protective oxide layer forms on the silicon nanoparticles without undergoing catastrophic exothermic degradation. Suitable protective fluids include capture fluids

[0039] One way to passivate a silicon nanoparticle-coated substrate in a protective fluid, such as a capture fluid, is to subject the nanoparticles and the protective fluid to a temperature of 23° C. or higher, typically 50° C. or higher, 60° C. or higher, 65° C. or higher, or even 70° C. or higher, while typically 80° C. or lower, or 70° C. or lower, or even 65° C. or lower, and an atmosphere of 85% relative humidity, preferably air, for a period of time typically of 12 hours to 72 hours, and may even be longer than 72 hours. In some cases, the period may be 168 hours or longer. Longer periods of time may result in greater oxidation of the silicon nanoparticle surface, particularly in protective fluids with low oxygen and moisture permeability.

[0040] Trapped Fluid Deposition

[0041] The most desirable method for providing a sheet coated with silicon nanoparticles of a polymeric host material is to directly coat the sheet in a capture fluid while collecting the silicon nanoparticles in the capture fluid. This method captures the silicon nanoparticles in the capture fluid as described above for the spray coating method. However, the capture fluid has a sheet of polymeric host material that is at least partially immersed (preferably, completely immersed) in the capture fluid when capturing the silicon nanoparticles. In this method, the silicon nanoparticles enter the capture fluid and tend to disperse, and then coat the sheet of polymeric host material in the capture fluid. This method generally results in a more uniform coating of the sheet of polymeric host material than can be achieved by a direct deposition method because the capture fluid acts as a dispersant for the silicon nanoparticles before the silicon nanoparticles contact the sheet of polymeric host material. It is desirable to have the capture fluid in a container and to move the container while collecting the nanoparticles so as to help disperse the nanoparticles throughout the capture fluid. For example, a container containing particles of the polymeric host matrix material is positioned in a collection chamber and the container is rotated or translated when an airflow containing the nanoparticles flows into the capture fluid.

[0042] The capture fluid may contain additives dissolved or dispersed therein. Desirable additives may include surface modifiers (functionalizing agents) that adhere to the surface of the nanoparticles as the nanoparticles are collected. Surface modifiers may act as compatibilizers, making the nanoparticles more compatible with the capture fluid or some other medium with which the nanoparticles need to be combined, may make the surface of the nanoparticles reactive to further chemical reactions, or may impart both compatibility and reactivity. Examples of additives that may be included in the capture fluid include hydrocarbons (such as 1-olefins) that help disperse the nanoparticles in hydrophobic media; oligoethylene glycols (such as allyl ethers) that help disperse the nanoparticles in hydrophilic media; terminal olefins containing functional groups such as alcohols, carboxylates, amines, and protected forms of these for post-passivation conversion and extraction; and fluorocarbons with terminal olefins that help disperse the nanoparticles in fluoropolymers.

[0043] It is desirable to passivate the silicon nanoparticles coated on the sheet of polymer host material before exposing them to air. It is most desirable to passivate the silicon nanoparticles in the capture fluid. Silicon nanoparticles are readily passivated in the capture fluid by exposing the capture fluid containing the silicon nanoparticles to a relatively humid atmosphere, typically at a temperature above 25°C for a period of time. The moisture slowly penetrates the capture fluid and reacts to form a passivating oxide layer on the silicon nanoparticles. For example, one way to passivate the silicon nanoparticles in the capture fluid is to subject the nanoparticles and the capture fluid to a temperature of 23°C or higher, typically 50°C or higher, 60°C or higher, 65°C or higher, or even 70°C or higher, and typically 80°C or lower, or 70°C or lower, or even 65°C or lower, and an atmosphere of 85% relative humidity, preferably air, for a period of time typically from 12 hours to 72 hours, and can even be longer than 72 hours. In some cases, the period can be 168 hours or longer. Longer time periods can result in a greater degree of oxidation of the silicon nanoparticle surface, particularly in fluids with low oxygen and moisture permeabilities.

[0044] The silicon nanoparticle-coated sheet of polymer host matrix material can be separated from the capture fluid by, for example, filtration. Flushing with a solvent may be desirable to remove residual capture fluid. The capture fluid can be reused if desired.

[0045] In the widest scope of the present invention, can soften the sheet of the polymer host matrix material that is coated with silicon nanoparticle by any way.For example, softening can occur with the polymer host matrix material that is coated with silicon nanoparticle by heating and / or adding solvent thereto to soften the polymer host matrix material.The polymer host matrix material should fully soften to allow the sheet of the host matrix material to be blended together to form the single substance of the polymer host matrix material.Blending can for example be carried out manually by using agitator or scraper, carry out with mechanical mixer, or carry out by guiding through forcing machine.After the softening sheet of mixed polymer host matrix material, produce the single substance form of the polymer host matrix material that silicon nanoparticle is dispersed in therein.

[0046] Can further process the single substance of the host matrix material that silicon nanoparticle is dispersed in therein.For example, can further fully soften the host matrix material to form flowable composition, can allow or cause flowable composition to flow then and do not mix.Surprisingly, the silicon nanoparticle that is dispersed in the host matrix material tends to flow with the speed different from the host matrix material, thereby causes the concentration effect of silicon nanoparticle in the host matrix material.Usually, silicon nanoparticle flows slower than host matrix material, causes the concentration in the host matrix material higher, and wherein host matrix material flows and does not carry silicon nanoparticle with proportional concentration.Alternately or additionally, by the softening single substance of the polymer host matrix material wherein compressed silicon nanoparticle is dispersed in, the single substance of the polymer host matrix material wherein silicon nanoparticle is dispersed in can form the film of the host matrix material wherein silicon nanoparticle is dispersed in.This compression that forms film can be carried out with batch process (batch process) in press, or carries out in a continuous manner (such as by roller). Such films can be used as agricultural films in particular, especially when silicon nanoparticles are silicon quantum dots that absorb light of less agricultural friendly wavelengths (for example, light with a wavelength less than 400 nanometers) and emit light under the light of more agricultural friendly wavelengths. The friendly wavelength of light of agriculture is generally in the range of 600-750 nanometers. Then, the gained agricultural films are used to convert the light of less useful or even harmful wavelengths into light of useful wavelengths. For example, the light of less useful or harmful wavelengths can be the ultraviolet light that damages plants, and the light of more useful wavelengths can be the blue, green or red wavelengths that plants can use in photosynthesis. Agricultural films are suitable for use as coverings for plants or even as coverings for greenhouses.

[0047] A single mass of host matrix material with silicon nanoparticles dispersed therein may also or instead be extruded to form various types of polymeric compositions including pellets of host matrix material with silicon nanoparticles dispersed therein.

[0048] Example

[0049] Material

[0050] Table 1 lists the components used to prepare the following samples.

[0051] Table 1

[0052]

[0053] SentryGlas is a trademark of Kuraray Amberica.

[0054] Using samples deposited onto particles of a polymer host matrix material in a trapping fluid

[0055] Preparation of SiQD-coated LDPE particles

[0056] The following program reference Figure 1 , which is a general image of the components of the VHFLP process used to prepare silicon quantum dots (SiQDs).

[0057] In the glove box 1, 8 grams (g) of mineral oil and 7.1 g of LDPE pellets were placed in an open container ("capture fluid reservoir") 6, which was then transferred to the load lock 2 through the gate valve 2a. The load lock 2 was evacuated to a pressure below 2.67 Pa using a roughing pump. The main collection chamber 4 was evacuated to a pressure below 6.67×10 Pa using a high vacuum pump 11 (a turbomolecular pump with a pumping speed of 600 liters / second supported by a roughing pump (an Ebara S50 semiconductor pump with a pumping speed of 5,000 liters / minute)). -5 Pa. Use transfer arm 2c to transfer capture fluid reservoir 6 through gate valve 3 into main collection chamber 4 and position it on capture fluid reservoir holder 7. Use capture fluid reservoir holder 7 to position capture fluid reservoir 6 6.5 cm below orifice 5b. Close gate valve 3 and evacuate main collection chamber 4 to 6.67×10 -5 The pressure is 100 Pa. The capture fluid reservoir holder 7 (and therefore the capture fluid reservoir 6) is rotated at a rate of 12 revolutions per minute.

[0058] A flow of 35 standard cubic centimeters per minute (SCCM) of nanoparticle precursor and 55 SCCM of Ar carrier gas was fed into the inlet port 5a and passed through the dielectric discharge tube 5 and out of the discharge tube orifice 5b into the main collection chamber 4. A plasma 9 was ignited in the discharge tube 5 by applying an AC sinusoidal bias to electrodes 8a and 8b of the double copper electrode 8. The sinusoidal bias was generated using a Tektronix AFG3252 function generator and an Electronic and Innovation 3200L Class A RF generator connected to the electrodes. The sinusoidal bias on the electrodes generated a capacitively coupled very high frequency (90 MHz to 500 MHz) plasma within the dielectric discharge tube. The frequency source was tuned to provide maximum power coupled into the plasma while minimizing the driving amplitude of the sinusoidal wave. The coupled power density of the plasma was greater than 130 watts per square centimeter (W / cm 2 ). Silicon nanoparticles are formed in the plasma 9 and exit the dielectric discharge tube through the discharge tube orifice 5b in the main collection chamber 4 into the capture fluid in the capture fluid reservoir and coat the LDPE pellets in the capture fluid.

[0059] The production and collection of silicon nanoparticles continued in this manner for 70 minutes, after which the power to electrodes 8a and 8b was turned off. The gate valve 3 was opened, and the capture fluid reservoir was transferred back to the load lock 2 using the transfer arm 2c. The capture fluid reservoir was transferred to the glove box, and the contents of the capture fluid reservoir were poured into a glass jar. The glass jar was transferred to a humidity chamber (Associated Environmental Systems, Model LH-10) maintained at 60°C and 85% relative humidity. The glass jar was left uncovered in the humidity chamber for 7 days to allow the silicon nanoparticles to slowly passivate by forming an oxide coating.

[0060] The silicon nanoparticle-coated LDPE pellets were separated from the capture fluid by transferring the contents of the capture fluid reservoir 6 into a syringe (COVIDIENT Luer lock sterile syringe, 60 cc, Grainger catalog number 9VZF7) equipped with a filter (polytetrafluoroethylene syringe filter, 0.22 micron CELLTREAT brand filter). The plunger on the syringe was pressed to drive the capture fluid through the filter and out of the syringe, while retaining the silicon nanoparticle-coated LPDE pellets in the syringe. Toluene was added to the syringe with the silicon nanoparticle-coated LPDE pellets to rinse the pellets, and then the toluene was pressed out through the filter and out of the syringe. Rinse again with toluene in a similar manner. The resulting silicon nanoparticle-coated LPDE pellets were dried in an oven at 60°C. The dried silicon nanoparticle-coated LPDE pellets were dried under UV light (from a BLACKOUT with a filter from Waveform Lighting) and then dried under UV light (from a BLACKOUT with a filter from Waveform Lighting). TM The silicon nanoparticles exhibited visible photoluminescence when flashed with a real UV LED lamp (Cat. No. 7023) at a wavelength of 365 nm using Filter Technology, indicating that the silicon nanoparticles were silicon quantum dots.

[0061] Sample 1: LDPE film with silicon quantum dots dispersed in it

[0062] 3-4 grams of silicon nanoparticle coated LDPE pellets were placed between two PTFE sheets, and the resulting PTFE sheet and silicon nanoparticle coated LDPE pellets were placed in a vacuum bag (FoodSaver vacuum sealing roller, item number 191396). The vacuum bag was evacuated (using FoodSaver part number FSSMSL0160-000), and then while in the vacuum bag, the two PTFE sheets were compressed onto the silicon nanoparticle coated LDPE pellets at 150° C. using a clamshell hot press (Geo Knight & Co., model DK16) and a pressure in the range of 4-6 on the pressure scale of the clamshell hot press for 30 minutes to create an LDPE film between the PTFE sheets. The LDPE film and PTFE sheet were removed from the vacuum bag. When exposed to UV light (from a BLACKOUT with waveform lighting) TM When exposed to a 365 nm wavelength of a real UV LED flash lamp from Filter Technology (Cat. No. 7023), the LDPE film glowed, indicating that it contained silicon quantum dots dispersed therein.

[0063] Sample 2: LDPE monolith from silicon nanoparticle coated LPDE pellets mixed with uncoated LDPE pellets

[0064] The silicon nanoparticle coated LDPE pellets were manually blended with the uncoated silicon nanoparticle coated LDPE pellets while being heated to a temperature sufficient to soften and flow the LDPE pellets to form a single molten polymer mixture. The single molten polymer mixture was allowed to cool to form a LDPE monolith. When exposed to UV light (from a BLACKOUT with waveform lighting) TM When exposed to a 365 nm wavelength of a real UV LED flash lamp from Filter Technology (Cat. No. 7023), the LDPE monolith glowed, indicating that it contained silicon quantum dots dispersed therein.

[0065] Use samples deposited directly onto particles of a polymer host matrix material

[0066] In the glove box, one gram of LDPE pellets was placed in an open container ("capture fluid reservoir") 6 without any trapping fluid, and the trapping fluid reservoir was then transferred to the load lock 2. The load lock 2 was evacuated to a pressure below 2.67 Pa using a roughing pump. The main collection chamber 4 was evacuated to a pressure below 6.67×10 Pa using a high vacuum pump 11 (a turbomolecular pump with a pumping speed of 600 L / s supported by a roughing pump (an Ebara S50 semiconductor pump with a pumping speed of 5,000 L / min)). -5 Pa. Use transfer arm 2c to transfer the capture fluid reservoir through gate valve 3 into the main collection chamber 4 and position it on the capture fluid reservoir holder 7. Use capture fluid reservoir holder 7 to position the capture fluid reservoir 6.5 cm below the orifice 5b. Close gate valve 3 and evacuate the main collection chamber 4 to 6.67×10-5 The pressure is 100 Pa. The capture fluid reservoir holder 7 (and hence the capture fluid reservoir) is rotated at a rate of 12 revolutions per minute.

[0067] 35 SCCM of nanoparticle precursor, 50 SCCM of Ar carrier gas, 3 SCCM of H2 carrier gas and 0.3 SCCM of chlorine dopant were fed into the inlet port 5a and passed through the dielectric discharge tube 5 and out of the discharge tube orifice 5b into the main collection chamber 4. A plasma 9 was ignited in the discharge tube 5 by applying an AC sinusoidal bias to electrodes 8a and 8b of the double copper electrode 8. The sinusoidal bias was generated using a Tektronix AFG 3252 function generator and an Electronic and Innovation 3200L Class A RF generator connected to the electrodes. The sinusoidal bias on the electrodes generated a capacitively coupled very high frequency (90 MHz to 500 MHz) plasma in the dielectric discharge tube. The frequency source was tuned to provide maximum power coupled into the plasma while minimizing the driving amplitude of the sinusoidal wave. The coupled power density of the plasma was greater than 130 watts per square centimeter (W / cm 2 ). Silicon nanoparticles are formed in the plasma 9 and exit the dielectric discharge tube through the discharge tube orifice 5b in the main collection chamber 4 onto the LDPE pellets in the capture fluid reservoir to coat the LDPE pellets with the silicon nanoparticles.

[0068] Continue to generate and collect silicon nanoparticles in this manner for 45 minutes, then turn off the power to electrode 8a and electrode 8b. Open the gate valve 3 and use the transfer arm 2c to transfer the capture fluid reservoir back to the load lock 2. The capture fluid reservoir is transferred to the glove box and 12g of mineral oil is added to the capture fluid reservoir. The contents of the capture fluid reservoir are poured into a glass jar. The glass jar is transferred to a humidity chamber (Associated Environmental Systems, Model LH-10) maintained at 60°C and 85% relative humidity. The glass jar is opened in the humidity chamber for 7 days to allow the silicon nanoparticles to slowly passivate by forming an oxide coating.

[0069] The silicon nanoparticle-coated LDPE pellets were separated from the mineral oil by transferring the contents of the capture fluid reservoir to a syringe (COVIDIENT Luer lock sterile syringe, 60 cubic centimeters, Grainger catalog number 9VZF7) equipped with a filter (polytetrafluoroethylene syringe filter, 0.22 micron CELLTREAT brand filter). The plunger on the syringe was pressed to drive the mineral oil through the filter and out of the syringe, while retaining the silicon nanoparticle-coated LPDE pellets in the syringe. Toluene was added to the syringe with the silicon nanoparticle-coated LPDE pellets to rinse the pellets, and then the toluene was pressed out through the filter and out of the syringe. Rinse again with toluene in a similar manner. The resulting silicon nanoparticle-coated LPDE pellets were dried in an oven at 60°C. The dried silicon nanoparticle-coated LPDE pellets were dried under UV light (from a BLACKOUT with waveform lighting) and then irradiated with water. TM The silicon nanoparticles exhibited visible photoluminescence when flashed with a real UV LED lamp (Cat. No. 7023) at a wavelength of 365 nm using Filter Technology, indicating that the silicon nanoparticles were silicon quantum dots.

[0070] Sample 3: LDPE film with silicon quantum dots dispersed in it

[0071] The process of Sample 1 was repeated using silicon nanoparticle-coated LPDE pellets prepared by direct deposition onto particles of a polymer host matrix material. When exposed to UV light (from a BLACKOUT with waveform illumination) TM When exposed to a 365 nm wavelength of a real UV LED flash lamp from Filter Technology (Cat. No. 7023), the LDPE film glowed, indicating that it contained silicon quantum dots dispersed therein.

[0072] Samples using silicon nanoparticles sprayed onto particles of a polymer host matrix material

[0073] For these samples, a dispersion of silicon nanoparticles in a fluid was prepared and then sprayed onto particles of a polymer host matrix material to form silicon nanoparticle-coated particles. The silicon nanoparticle-coated particles were then used to form a polymeric material.

[0074] Preparation of silicon nanoparticle dispersion

[0075] In the glove box, 12 g of mineral oil trapping fluid was placed in an open container ("trapping fluid reservoir") 6. The trapping fluid was a 5 wt% solution of 1-octadecene in mineral oil. The trapping fluid reservoir was transferred to the load lock 2. The load lock 2 was evacuated to a pressure below 2.67 Pa using a rough vacuum pump. The main collection chamber 4 was evacuated to a pressure below 6.67 × 10-5 Pa. Use transfer arm 2c to transfer the capture fluid reservoir through gate valve 3 into the main collection chamber 4 and position it on the capture fluid reservoir holder 7. Use capture fluid reservoir holder 7 to position the capture fluid reservoir 6.5 cm below the orifice 5b. Close gate valve 3 and evacuate the main collection chamber 4 to 6.67×10 -5 The pressure is 100 Pa. The capture fluid reservoir holder 7 (and hence the capture fluid reservoir) is rotated at a rate of 12 revolutions per minute.

[0076] 50 SCCM of nanoparticle precursor and 7 SCCM of H2 carrier gas were fed into the inlet port 5a and passed through the dielectric discharge tube 5 and out of the discharge tube orifice 5b into the main collection chamber 4. Plasma 9 was ignited in the discharge tube 5 by applying an AC sinusoidal bias to electrodes 8a and 8b of the double copper electrode 8. The sinusoidal bias was generated using a Tektronix AFG 3252 function generator and an Electronic and Innova tion 3200L Class A RF generator connected to the electrodes. The sinusoidal bias on the electrodes generated a capacitively coupled very high frequency (90 MHz to 500 MHz) plasma in the dielectric discharge tube. The frequency source was tuned to provide maximum power coupled into the plasma while minimizing the driving amplitude of the sinusoidal wave. The coupled power density of the plasma was greater than 130 watts per square centimeter (W / cm 2 ). Silicon nanoparticles are formed in the plasma 9 and exit the dielectric discharge tube through the discharge tube orifice 5b in the main collection chamber 4 into the capture fluid in the capture fluid reservoir.

[0077] The production and collection of silicon nanoparticles continued in this manner for 95 minutes, after which the power to electrodes 8a and 8b was turned off. The gate valve 3 was opened, and the capture fluid reservoir was transferred back to the load lock 2 using the transfer arm 2c. The capture fluid reservoir was transferred to a glove box, and the contents of the capture fluid reservoir were poured into a glass jar, which was placed in a sonic bath (Branson 2510, 40 kHz) and subjected to ultrasonic agitation for one hour. The glass jar was then transferred to a humidity chamber (Associated Environmental Systems, Model LH-10) maintained at 60°C and 85% relative humidity. The glass jar was left uncovered in the humidity chamber for 7 days to allow the silicon nanoparticles to slowly passivate by forming an oxide coating.

[0078] The solution of capture fluid and silicon nanoparticles was transferred to a centrifuge tube and centrifuged using a Sorvall BiofugePrimo centrifuge. The supernatant capture fluid was removed from the centrifuge tube using a pipette, leaving the silicon nanoparticles. The centrifuge tube was filled with toluene and gently stirred manually to rinse the silicon nanoparticles, and then the centrifuge tube was centrifuged to separate the toluene from the silicon nanoparticles. The toluene was aspirated. The toluene rinse and centrifugation were repeated three times. Toluene was then added to the centrifuge tube containing the silicon nanoparticles and sonicated as described above to produce a clear dispersion of silicon nanoparticles in toluene. The dispersion was then exposed to UV light (from a BLACKOUT with waveform illumination) and the silicon nanoparticles were separated. TM The silicon nanoparticles exhibited visible photoluminescence when flashed with a real UV LED lamp (Cat. No. 7023) at a wavelength of 365 nm using Filter Technology, indicating that the silicon nanoparticles were silicon quantum dots.

[0079] Sample 4: Spraying silicon quantum dots on LDPE to form a L-shaped LDPE with silicon quantum dots dispersed therein DPE film

[0080] Using a spray gun (Central Pneumatic, item 95810), a dispersion of silicon nanoparticles in toluene was sprayed onto the LDPE pellets to form silicon nanoparticle-coated LDPE pellets. 10 ml of 1,000 parts by weight of silicon nanoparticles per million parts by weight of toluene was sprayed onto the LDPE pellets. The silicon nanoparticle-coated LDPE pellets were dried in an oven at 60° C. for 24 hours. The dried silicon nanoparticle-coated LDPE pellets were exposed to UV light (from a BLACK OUT lamp with waveform lighting). TM The silicon nanoparticles exhibited visible photoluminescence when flashed with a real UV LED lamp (Cat. No. 7023) at a wavelength of 365 nm using Filter Technology, indicating that the silicon nanoparticles were silicon quantum dots.

[0081] 3-4 grams of silicon nanoparticle coated LDPE pellets were placed between two PTFE sheets, and the resulting PTFE sheet and silicon nanoparticle coated LDPE pellets were placed in a vacuum bag (FoodSaver vacuum sealing roller, item number 191396). The vacuum bag was evacuated (using FoodSaver part number FSSMSL0160-000), and then while in the vacuum bag, the two PTFE sheets were compressed onto the silicon nanoparticle coated LDPE pellets at 150° C. using a clamshell hot press (Geo Knight & Co., model DK16) and a pressure in the range of 4-6 on the pressure scale of the clamshell hot press for 30 minutes to create an LDPE film between the PTFE sheets. The LDPE film and PTFE sheet were removed from the vacuum bag. When exposed to UV light (from a BLACKOUT with waveform lighting) TMWhen exposed to a 365 nm wavelength of a real UV LED flash lamp from Filter Technology (Cat. No. 7023), the LDPE film glowed, indicating that it contained silicon quantum dots dispersed therein.

[0082] Sample 5: Spraying silicon quantum dots onto a PVB sheet to form a PVB film with silicon quantum dots dispersed therein

[0083] The PVB sheet was cut into two PVB sheets measuring 7.62 cm x 2.54 cm. Using a spray gun (Central Pneumatic, item 95810), a dispersion of silicon nanoparticles in toluene was sprayed onto one side of each of the two PVB sheets to form a silicon nanoparticle-coated PVB sheet. 10 ml of 1,000 parts by weight of silicon nanoparticles per million parts by weight of toluene was sprayed onto the PVB sheet. The silicon nanoparticle-coated PVB sheet was dried at 25° C. The silicon nanoparticle-coated PVB sheets were placed on top of each other with the silicon nanoparticle-coated surfaces in contact with each other and placed between two PTFE sheets in a vacuum bag (FoodSaver vacuum sealing roller, item number 191396). The vacuum bag was evacuated (using FoodSaver part number FSSMSL0160-000) and then, while in the vacuum bag, two PTFE sheets were compressed onto the silicon nanoparticle coated PVB sheet using a clamshell hot press (GeoKnight & Co., model DK16) and a pressure in the range of 4-6 on the pressure scale of the clamshell hot press at 150°C for 30 minutes to create a single PVB film between the PTFE sheets. The PVB film and PTFE sheet were removed from the vacuum bag. When exposed to UV light (from a BLACKOUT with waveform lighting) TM When exposed to a 365 nm wavelength of a real UV LED flash lamp from Filter Technology (Cat. No. 7023), the PVB film glowed, indicating that it contained silicon quantum dots dispersed therein.

[0084] The resulting PVB film containing silicon nanoparticles was placed between two glass microscope slides and placed in a vacuum bag (FoodSaver vacuum sealing roller, product number 191396). The vacuum bag was evacuated (using FoodSaver part number FSSMSL0160-000), and then while in the vacuum bag, two PTFE sheets were compressed onto the silicon nanoparticle coated PVB sheet using a clamshell hot press (Geo Knight & Co., model DK16) and a pressure in the range of 4-6 on the pressure scale of the clamshell hot press at 120°C for 10 minutes to produce two sheets of glass laminated together with the silicon nanoparticle-containing PVB laminated between them. When exposed to ultraviolet light (from a BLACKOUT with waveform lighting) TMWhen flashed with a real UV LED lamp (catalog number 7023) from Filter Technology at a wavelength of 365 nanometers, the laminated glass sample glowed, indicating that it contained silicon quantum dots.

[0085] Sample 6: Silicon quantum dots were sprayed onto PLA to form a PLA with silicon quantum dots dispersed therein. A film

[0086] Two pieces of PLA ("PLA sheets") were cut from a cold cup of PLA to provide sheets measuring 7.62 cm x 2.54 cm. Using a spray gun (Central Pneumatic, Item 95810), a dispersion of silicon nanoparticles in toluene was sprayed onto one side of each of the two PLA sheets to form silicon nanoparticle-coated PLA sheets. 10 ml of 1,000 parts by weight silicon nanoparticles per million parts by weight toluene was sprayed onto the PLA sheets. The silicon nanoparticle-coated PLA sheets were dried at 25°C. The silicon nanoparticle-coated PLA sheets were placed on top of each other with the silicon nanoparticle-coated surfaces in contact with each other and placed between two PTFE sheets in a vacuum bag (FoodSaver Vacuum Sealing Roll, Item No. 191396). The vacuum bag was evacuated (using FoodSaver part number FSSMSL0160-000) and then, while in the vacuum bag, two PTFE sheets were compressed onto the silicon nanoparticle-coated PLA sheet using a clamshell hot press (Geo Night & Co., Model DK16) and a pressure in the range of 4-6 on the pressure scale of the clamshell hot press at 180°C for 30 minutes to create a single PLA film between the PTFE sheets. The PLA film and PTFE sheet were removed from the vacuum bag. When exposed to UV light (from a BLACKOUT with waveform lighting) TM When exposed to a 365 nm wavelength of a real UV LED flash lamp from Filter Technology (Cat. No. 7023), the PLA film glowed, indicating that it contained silicon quantum dots dispersed therein.

[0087] A one-centimeter by one-centimeter piece was cut from a PLA film and dissolved in a 50% aqueous potassium hydroxide solution. The PLA rapidly decomposed into potassium lactate, and the silicon quantum dots were etched into potassium silicate, as evidenced by a rapid loss of orange photoluminescence. This demonstrates that a sample of a polymer film with silicon quantum dots dispersed therein can rapidly degrade at the end of its useful life.

Claims

1. A method for preparing a polymer host matrix material in which silicon nanoparticles are dispersed, the method comprising: a. providing a sheet of a polymer host matrix material coated with silicon nanoparticles; b. softening the sheet of polymer host matrix material coated with silicon nanoparticles to form a softened sheet of polymer host matrix material; as well as c. blending the softened pieces of polymeric host matrix material together with the silicon nanoparticles on the surface of the softened pieces of polymeric host matrix material to form a single mass of polymeric host matrix material in which the silicon nanoparticles are dispersed. The method of claim 1 , wherein the silicon nanoparticles are silicon quantum dots. The method of claim 2 , wherein the silicon nanoparticles are passivated silicon quantum dots. 4 . The method according to claim 3 , further comprising forming an oxide coating on the silicon quantum dots after preparing the silicon quantum dots, so as to form a passivating oxide coating on the silicon quantum dots.

5. A method according to any preceding claim, further comprising providing the sheet of polymer host matrix material coated with silicon nanoparticles by any one or any combination of the following methods: a. When preparing the silicon nanoparticles, the silicon nanoparticles are deposited directly onto a sheet of the polymer host matrix material; b. When preparing the silicon nanoparticles, depositing the silicon nanoparticles into a capture fluid containing a sheet of a polymer host matrix material; and c. Spray coating a sheet of polymer host matrix material with a solvent dispersion of silicon nanoparticles. The method of claim 5 , further comprising forming the silicon nanoparticles using a VHFLPP process. 7 . The method of claim 6 , wherein the VHFLPP process comprises capturing the silicon nanoparticles in a capture fluid comprising a functionalizing agent.

8. A method according to any preceding claim, wherein the polymeric host matrix material is a thermoplastic polymer composition.

9. The method of any preceding claim, wherein the single substance of a polymer host material in which silicon nanoparticles are dispersed is further formed into a polymer film, and the silicon nanoparticles are quantum dots that absorb light of less agriculturally friendly wavelengths having a wavelength of less than 400 nanometers and emit light at more agriculturally friendly wavelengths having a wavelength in the range of 600 nanometers to 750 nanometers.

10. The method according to any preceding claim, further comprising the steps of: If the single substance of the polymer host matrix material in which the silicon nanoparticles are dispersed is not already in a flowable state, it is softened to form a flowable polymer composition, and then the flowable polymer composition is allowed or caused to flow without mixing to achieve the differential concentration of silicon nanoparticles in the polymer host matrix material.

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