阅读说明：本技术 制备纳米粒子的方法 (Method for producing nanoparticles ) 是由 J·A·凯西 C·塞拉诺 D·L·威特科尔 于 2020-03-31 设计创作，主要内容包括：本发明公开了一种用于在包括具有内表面的反应室的等离子体反应器中制备硅纳米粒子的方法。该方法包括将卤素气体引入等离子体反应器的反应室中。该方法还包括在卤素气体存在于反应室内时点燃反应室内的等离子体。卤素气体的原子至少部分地在反应室的内表面上形成涂层。该方法包括将包含硅前体气体和第一惰性气体的反应物气体混合物引入等离子体反应器的反应室中。该方法还包括在等离子体反应器中形成硅纳米粒子。本发明还公开了一种硅纳米粒子组合物。该硅纳米粒子组合物包含根据该方法制备的硅纳米粒子。(A method for preparing silicon nanoparticles in a plasma reactor comprising a reaction chamber having an inner surface is disclosed. The method includes introducing a halogen gas into a reaction chamber of a plasma reactor. The method also includes igniting a plasma within the reaction chamber while the halogen gas is present within the reaction chamber. The atoms of the halogen gas form a coating at least partially on the inner surface of the reaction chamber. The method includes introducing a reactant gas mixture comprising a silicon precursor gas and a first inert gas into a reaction chamber of a plasma reactor. The method also includes forming silicon nanoparticles in the plasma reactor. The invention also discloses a silicon nanoparticle composition. The silicon nanoparticle composition includes silicon nanoparticles prepared according to the method.)

1. A method for preparing silicon nanoparticles in a plasma reactor comprising a reaction chamber having an inner surface, the method comprising:

i) introducing a halogen gas into the reaction chamber of the plasma reactor;

ii) igniting a plasma within the reaction chamber while the halogen gas is present within the reaction chamber, wherein atoms of the halogen gas at least partially form a coating on the inner surface of the reaction chamber, the coating comprising halogen atoms;

iii) introducing a reactant gas mixture comprising a silicon precursor gas and a first inert gas into the reaction chamber of the plasma reactor; and

iv) forming the silicon nanoparticles in the plasma reactor.

2. The method of claim 1, wherein the interior surface has a first coating comprising silicon atoms, and wherein the coating formed with the halogen gas comprises silicon atoms and halogen atoms.

3. The method of claim 1 or 2, wherein the halogen gas is introduced into the reaction chamber prior to introducing the reactant gas mixture, and wherein an initial inert gas is introduced into the reaction chamber with the halogen gas.

4. A method according to any preceding claim, wherein a halogen gas is introduced into the reaction chamber with the reactant gas mixture after the reactant gas mixture is first introduced into the reaction chamber.

5. The method of claim 2, wherein igniting a plasma within the reaction chamber while the halogen gas is present within the reaction chamber forms halosilanes in the reaction chamber from the first coating layer comprising silicon atoms and the halogen gas.

6. The method of any one of claims 1-3 and 5, wherein a halogen gas is present in the reaction chamber with the reactant gas mixture during the preparation of the silicon nanoparticles.

7. The method of any preceding claim, wherein the halogen gas is chlorine gas and the halogen atom is a chlorine atom.

8. The method of any preceding claim, wherein the reactant gas mixture further comprises a second precursor gas comprising an element selected from carbon, germanium, boron, phosphorus, and nitrogen.

9. The method of any preceding claim, further comprising collecting the silicon nanoparticles in a capture fluid in a vacuumed particle collection chamber, wherein the pressure of the vacuumed particle collection chamber is less than the pressure of the reaction chamber.

10. The method of claim 9, wherein the capture fluid comprises a hydrocarbon fluid, a silicon-containing fluid, or a fluorocarbon fluid.

11. The method of claim 9 or 10, wherein the capture fluid further comprises a doping compound.

12. The method of any preceding claim, wherein igniting a plasma comprises applying a preselected radio frequency having a continuous frequency of 10MHz to 500MHz and a coupled power of 5W to 1000W to the reaction chamber.

13. The method of any preceding claim, further comprising:

introducing the silicon nanoparticles from the plasma reactor into a diffusion pump;

heating the trapped fluid in a reservoir to form a vapor and transporting the vapor through a spray assembly;

discharging the vapor through a nozzle into a chamber of the diffusion pump and condensing the vapor to form a condensate comprising the capture fluid;

flowing said condensate back to said reservoir; and

trapping the silicon nanoparticles in the condensate comprising the trapping fluid.

14. The method of claim 2, further comprising forming the first coating on the inner surface of the reaction chamber.

15. Silicon nanoparticles prepared by the method of any one of the preceding claims.

Technical Field

The present disclosure relates to a method of preparing nanoparticles, and more particularly, to a method of preparing silicon nanoparticles in a plasma reactor.

Background

Nanoparticles are known in the art and can be prepared via various processes. Nanoparticles are generally defined as particles having at least one dimension less than 100 nanometers. The nanoparticles are made of bulk material that is initially larger than the nanoparticles, or are made of particles, such as ions and/or atoms, that are smaller than the silicon nanoparticles. Nanoparticles are particularly unique in that they can have properties that are significantly different from the bulk material or the smaller particles from which the silicon nanoparticles are derived. For example, bulk materials used as insulators or semiconductors may be conductive or photoluminescent when in nanoparticle form.

An important characteristic of smaller (diameter <5nm) silicon nanoparticles is that they photo-emit visible light when stimulated. Silicon nanoparticles are useful in a variety of applications, including use in photovoltaics, diagnostics, analysis, and cosmetics. The silicon nanoparticles have additional physical properties different from the bulk material, such as melting point, which varies with particle size.

Disclosure of Invention

The present invention provides a method for preparing silicon nanoparticles in a plasma reactor comprising a reaction chamber having an inner surface. The method includes introducing a halogen gas into a reaction chamber of a plasma reactor. The method also includes igniting a plasma within the reaction chamber while the halogen gas is present within the reaction chamber. The atoms of the halogen gas form a coating at least partially on the inner surface of the reaction chamber. The method also includes introducing a reactant gas mixture comprising a silicon precursor gas and a first inert gas into the reaction chamber of the plasma reactor. The method also includes forming silicon nanoparticles in the plasma reactor.

The invention also provides silicon nanoparticles prepared by the method.

The invention also provides a silicon nanoparticle composition. The silicon nanoparticle composition includes silicon nanoparticles prepared according to the above-described method.

Drawings

Other advantages and aspects of the invention described in the following detailed description may be further understood when considered in conjunction with the accompanying drawings, wherein:

FIG. 1 shows one embodiment of a low pressure, high frequency pulsed plasma reactor for producing silicon nanoparticles;

FIG. 2 shows an embodiment of a system including a low pressure pulsed plasma reactor to produce silicon nanoparticles and a diffusion pump to collect the silicon nanoparticles;

FIG. 3 shows a schematic diagram of one embodiment of a diffusion pump for collecting silicon nanoparticles produced via a reactor;

FIG. 4 shows emission intensities of nanoparticles formed in examples 1 and 2 and comparative example 1; and is

FIG. 5 shows the emission intensity of the nanoparticles formed in examples 3-5.

Detailed Description

The present invention provides a method for preparing silicon nanoparticles, silicon nanoparticles prepared by the method, and a composition comprising silicon nanoparticles. Silicon nanoparticles have excellent physical properties and are suitable for a myriad of end-use applications ranging from photovoltaic to cosmetic.

The method is performed in a plasma reactor comprising a reaction chamber having an inner surface. The plasma reactor and the reaction chamber are described in more detail below.

The method includes introducing a halogen gas into a reaction chamber of a plasma reactor. The method also includes igniting a plasma within the reaction chamber while the halogen gas is present within the reaction chamber. The atoms of the halogen gas form a coating at least partially on the inner surface of the reaction chamber.

Non-limiting examples of halogen gases include gaseous diatomic molecules consisting of elements selected from group 17 of the periodic table, such as chlorine (Cl)₂) Fluorine gas (Fl)₂) Bromine gas (Br)₂) Iodine gas (I)₂) And mixtures thereof. Alternatively, the halogen gas may comprise a metal halide or other halogen-containing gas. However, the halogen gas is typically a diatomic halogen gas that does not contain non-halogen atoms.

Generally, the method includes introducing a halogen gas into the reaction chamber prior to introducing the reactant gas mixture, as described below. In such embodiments, the introduction of the halogen gas into the reaction chamber is separate and distinct from the introduction of the reactant gas mixture into the reaction chamber, although the reactant gas mixture may optionally also comprise a halogen gas. Unlike introducing the reactant gas mixture, introducing the halogen gas does not include introducing a precursor gas. Introducing a halogen gas into the reaction chamber prior to introducing the reactant gas mixture improves the physical properties of the silicon nanoparticles formed from the reactant gas mixture in the process.

In certain embodiments, a halogen gas is introduced into the reaction chamber and the plasma is ignited prior to each process of preparing silicon nanoparticles in the plasma reactor. However, it is contemplated that there may be a time delay or additional process in the plasma reactor between the introduction of the halogen gas into the reaction chamber and the preparation of nanoparticles from the reactant gas mixture described below with the plasma reactor.

In certain embodiments, introducing the halogen gas into the reaction chamber further comprises introducing an initial inert gas into the reaction chamber with the halogen gas.

The initial inert gas is generally not reactive within any molecule or atom of the halogen gas or with the reaction chamber itself. Examples of inert gases include noble gases such as helium, neon, argon, krypton, xenon, and combinations thereof. When used, the initial inert gas is typically used in an amount of 1% to 99% v/v based on the total volume of halogen gas and initial inert gas. The halogen gas and the initial inert gas may be introduced separately or together into the reaction chamber, for example in a single stream or in separate streams combined in the reaction chamber. In certain embodiments, the halogen gas and the initial inert gas are introduced into a reactor that is free of any other reactant or precursor gas, alternatively completely free of any other gas.

The reaction chamber typically contains materials suitable for plasma processes. In certain embodiments, the reaction chamber comprises quartz, alternatively quartz. In certain embodiments, the interior surfaces of the reaction chamber comprise a first coating comprising silicon atoms. Those skilled in the art will readily understand how to form a first coating layer comprising silicon atoms, alternatively consisting essentially of silicon atoms, on the inner surfaces of the reaction chamber. For example, the first coating layer may be formed by a chemical or physical method. For example, the first coating may be formed via a silane deposition process known in the art. Alternatively, the first coating layer may be formed by previously using a reaction chamber to generate silicon nanoparticles, since silicon is generally deposited to form the first coating layer when such preparation of silicon nanoparticles is performed.

The method also includes igniting a plasma within the reaction chamber while the reactant gas is present within the reaction chamber. The parameters for igniting the plasma are described below with respect to the production of silicon nanoparticles via a plasma process. The parameters for igniting the plasma may be the same as or different from the parameters for igniting the plasma when preparing the silicon nanoparticles, and each step of igniting the plasma is independently selected. However, for the sake of brevity, the parameters for igniting the plasma are described collectively below with reference to the preparation of silicon nanoparticles.

The method forms a coating at least partially on an inner surface of the reaction chamber when a plasma is ignited in the reaction chamber in the presence of a halogen gas in the reaction chamber. By at least partially forming the coating, it is meant that the coating on the inner surface may be continuous or discontinuous and may vary in any characteristic (e.g., composition, thickness, etc.). The coating typically contains halogen atoms. When the first coating is present on the inner surface of the reaction chamber, the coating comprises silicon atoms and halogen atoms. For example, the coating may comprise a halosilane. When the coating comprises, alternatively consists of, silicon atoms and halogen atoms, the silicon atoms and halogen atoms may be bonded together (e.g., in the case of halosilane atoms) and/or may be physically adjacent to each other in the coating. The formation of the coating layer may cause the first coating layer to degrade, and the first coating layer and the coating layer may not be distinguishable from each other when the coating layer is formed. The coating is typically used to passivate the silicon nanoparticles as they are formed via the method of the invention, thereby imparting improved and superior physical properties, particularly optical properties.

In various embodiments, the amount of halogen gas used is based on the desired coating properties. In certain embodiments, a halogen gas is used at a flow rate to selectively control the molar ratio of silicon atoms to halogen atoms in the coating. This molar ratio of silicon atoms to halogen atoms can also be selectively controlled throughout the process of the present invention, for example, if the coating degrades during the preparation of silicon nanoparticles, then a greater amount of halogen gas is used later in the process (e.g., in the reactant gas mixture).

In various embodiments, the plasma process for preparing silicon nanoparticles (alternatively referred to simply as nanoparticles) is carried out in a plasma reactor. In various embodiments, the silicon nanoparticles comprise an independently selected group IV element in addition to silicon. As used herein, the group designations of the periodic table of the elements are generally from CAS or old IUPAC nomenclature, where the group IV elements are referred to as group 14 elements according to the modern IUPAC system, as is readily understood in the art. As used herein, group IV elements include C, Si, Ge, Sn, Pb, and Fl. Typically, the group IV element of the silicon nanoparticles is selected from Si, Ge, Sn, and combinations thereof.

In certain embodiments in which the plasma process is carried out in a low pressure reactor, the plasma process comprises forming a nanoparticle aerosol in the low pressure reactor, wherein the aerosol comprises silicon nanoparticles entrained in a gas. The silicon nanoparticles are typically collected as they are formed. In certain embodiments, as described below, the silicon nanoparticles are collected by trapping the silicon nanoparticles in a trapping fluid that is typically in fluid communication with the low pressure reactor.

Regardless of the particular plasma system and process used to prepare the silicon nanoparticles, the plasma system typically relies on a silicon precursor gas. The silicon precursor gas is typically selected based on the desired silicon nanoparticle composition.

The precursor gas is typically selected based on the desired nanoparticle composition. For example, as described above, the precursor gas typically comprises silicon. When the silicon nanoparticles comprise at least one other element, the precursor gas typically comprises atoms selected from germanium, tin, and/or other group IV elements.

In certain embodiments, the precursor gas comprises a compound that may be silicon (including silane, disilane, halogen-substituted silane, halogen-substituted disilane, C₁-C₄Alkylsilane, C₁-C₄Alkyldisilanes, and the like, as well as derivatives and/or combinations thereof). For example, in some embodiments, the precursor gas comprises 0.1% to 2%, alternatively 0.1% to 50%, of the silicon compound, measured by volume of the precursor gas. In some such embodiments, the reactant gas mixture comprises 0.1% to 2%, alternatively 0.1% to 50%, of the silicon compound, measured by volume of the reactant gas mixture.

Typical examples of silicon compounds suitable for use in or as a precursor gas include alkyl silanes and aromatic silanes. Some specific examples of silicon compounds suitable for use in or as precursor gases include dimethylsilane (H)₃C-SiH₂-CH₃) Tetraethyl silane ((CH)₃CH₂)₄Si) and diphenylsilane (Ph-SiH)₂Ph), disilane (Si)₂H₆) Silicon tetrachloride (SiCl)₄) Trichlorosilane (HSiCl)₃) Dichlorosilane (H)₂SiCl₂). In certain embodiments, the silicon compound comprises SiCl₄、HSiCl₃And/or H₂SiCl₂。

In some embodiments, the precursor gas further comprises a compound that may be germanium (including germane, digermane, halo-substituted germane, halo-substituted digermane, C₁-C₄Alkyl germane, C₁-C₄Alkyldigermane, and the like, as well as derivatives and/or combinations thereof). Specific examples of germanium compounds suitable for use in or as precursor gases include tetraethylgermane ((CH)₃CH₂)₄Ge) and diphenylgermane (Ph-GeH)₂-Ph). The precursor gas may comprise both silicon and germanium, as well as any other group IV element.

In some embodiments, the precursor gas further comprises an organometallic precursor compound comprising a group IV metal. Examples of such organometallic precursor compounds include organosilicon compounds, organogermanium compounds, and organotin compounds, such as alkylgermanium compounds, alkylsilane compounds, alkylstannane compounds, chlorosilane compounds, chlorogermanium compounds, chlorottannane compounds, aromatic silane compounds, aromatic germanium compounds, aromatic stannane compounds, and the like, as well as derivatives and/or combinations thereof. In these or other embodiments, the precursor gas comprises hydrogen, a halogen gas (e.g., chlorine, bromine, etc.), or both. In a particular embodiment, the precursor gas comprises a compound containing atoms of a group IV element and H and/or halogen atoms.

Typically, the reactant gas mixture comprises the precursor gas in an amount of 0.1% to 50%, alternatively 1% to 50%, based on the total volume of the reactant gas mixture.

In some embodiments, the reactant gas mixture further comprises a halogen gas (e.g., chlorine gas (Cl))₂)). The halogen gas may be present in the precursor gas, for example in the form of a combined feed, or used as a separate feed together with or separately from the precursor gas. The relative amount of halogen gas (if used) can be optimized based on a variety of factors, such as the precursor gas selected, etc. For example, when the precursor gas comprises a halogen atom, a lesser amount of halogen gas may be required to prepare the halogen-functionalized nanoparticlesAnd (4) adding the active ingredients. In certain embodiments, the halogen gas is used in an amount greater than 0% to 25%, alternatively 1% to 10% v/v of the total volume of the reactant gas mixture.

The reactant gas mixture may comprise other gases, i.e. gases other than precursor gases. In certain embodiments, the reactant gas mixture comprises an inert gas. During operation of the plasma reactor, the inert gas is generally not reacted within any molecules or atoms present within the plasma stream. Examples of inert gases include noble gases such as helium, neon, argon, krypton, xenon, and combinations thereof. When used, the inert gas is typically present in an amount of 1% to 99% v/v based on the total volume of the reactant gas mixture.

The reactant gas mixture may comprise a dopant, such as a source of atoms to be integrated (i.e., "doped") into nanoparticles formed in the plasma reactor during the process. In such embodiments, the dopant may alternatively be referred to as a second precursor gas. In some embodiments, the nanoparticles are subjected to gas phase doping in a plasma, wherein the reactant gas mixture comprises a first precursor gas containing silicon to form silicon nanoparticles, and a second precursor gas containing another element that dissociates and incorporates into the nanoparticles upon nucleation of the nanoparticles. Of course, the nanoparticles may also or alternatively be doped (i.e. once formed), for example downstream of the preparation of the nanoparticles but prior to collection of the nanoparticles in the capture fluid. In some embodiments, the reactant gas mixture includes a dopant containing carbon, germanium, boron, phosphorus, and/or nitrogen, such as trimethylsilane, disilane, trisilane, BCl₃、B₂H₆、PH₃、GeH₄、GeCl₄And the like, as well as combinations thereof. In certain embodiments, the reactant gas mixture comprises the dopant in an amount of 0.1% to 49.9% v/v based on the total volume of the reactant gas mixture. In some embodiments, the reactant gas mixture comprises the precursor gas and the dopant in a combined amount of 0.1% to 50% v/v, based on the total volume of the reactant gas mixture.

In a particular embodiment, the reactant gas mixture comprises hydrogen. Typically, in such embodiments, the reactant gas mixture comprises 1% to 50%, alternatively 1% to 2%, alternatively 1% to 10%, by volume of hydrogen gas, based on the total volume of the reactant gas mixture.

In one form of the present disclosure, the silicon nanoparticles may comprise an alloy of a group IV element, such as a silicon alloy. Silicon alloys that may be formed include, but are not limited to, silicon carbide, silicon germanium, silicon boron, silicon phosphorous, and silicon nitride. The silicon alloy may be formed by mixing at least one first precursor gas with a second precursor gas or using precursor gases containing different elements. However, other methods of forming alloyed silicon nanoparticles are also contemplated.

In various embodiments, the plasma reactor is a component of a plasma system (alternatively referred to as a plasma reactor system). Specific embodiments of a plasma reactor system particularly suited for use in the method of the present invention are described below. It should be understood that the specific embodiments described below are merely exemplary of exemplary plasma processes suitable for preparing silicon nanoparticles.

The plasma reactor is not particularly limited, so that any plasma reactor or system including a plasma reactor can be used to produce the nanoparticle aerosol. In certain embodiments, the plasma reactor is a component of a plasma reactor system (alternatively referred to as a plasma system), which may be, for example, an extremely high frequency low pressure plasma reactor system, a low pressure high frequency plasma reactor system, or the like. Such a plasma reactor system is illustrated in fig. 1, which shows a plasma reactor system, generally indicated at 20. Plasma reactor system 20 includes a plasma generation chamber 22, a particle collection chamber 26 in fluid communication with plasma generation chamber 22, and a vacuum source 28 in fluid communication with particle collection chamber 26 and plasma generation chamber 22.

The plasma generation chamber 22 (which may alternatively be referred to as a plasma reactor and/or discharge tube) includes a High Frequency (HF) or Very High Frequency (VHF) Radio Frequency (RF) power source (not shown). A variable frequency RF power amplifier 21, triggered via an arbitrary function generator, is supplied with power from a power source to establish a high frequency pulsed plasma (alternatively simply referred to as plasma) in the region shown at 23. Typically, rf power is capacitively coupled into the plasma in a gas using a ring electrode, parallel plate or anode/cathode arrangement, thereby producing a capacitively coupled plasma discharge. Alternatively, RF coils disposed around the discharge tube 22 may be used in an Inductively Coupled Plasma (ICP) reactor arrangement to inductively couple radio frequency power into the plasma.

The plasma generation chamber 22 further comprises an electrode arrangement 24 attached to the variable RF power amplifier 21. The plasma-generating chamber 22 further comprises a second electrode arrangement 25. The second electrode arrangement 25 may be grounded, DC biased or operated in a push-pull manner with respect to the electrode arrangement 24. The plasma generation chamber 22 also includes a reactant gas inlet 29 and an outlet 30 defining a hole or orifice 31. The plasma generation chamber 22 may also include a dielectric discharge tube (not shown). In various embodiments, the plasma generation chamber 22 comprises quartz.

In some embodiments, the electrode configurations 24, 25 of the plasma generation chamber 22 comprise a flow-through showerhead design in which an upstream porous electrode plate 24 of VHF radio frequency bias is separated from a downstream porous electrode plate 25, with the pores of the plates 24, 25 aligned with one another. The holes may be circular, rectangular or any other desired shape.

Particle collection chamber 26 (alternatively referred to as a deposition chamber and/or a vacuum particle collection chamber) typically contains a container 32.

The vacuum source 28 typically comprises a vacuum pump. However, in certain embodiments, the vacuum source 28 may include a mechanical pump, a turbomolecular pump, a diffusion pump, or a cryopump. During operation, portions of the plasma generation chamber 22 may be evacuated to a reduced pressure (i.e., vacuum level), such as 1x10^-7To 500 torr, alternatively 100 millitorr to 10 torr.

In operation, the electrode arrangements 24, 25 are used to couple HF or VHF power to the reactant gas mixture to ignite and sustain a glow discharge of the plasma (i.e., "ignite the plasma") within the region identified as shown at 23. In certain embodiments, the reactant gas mixture (alternatively referred to as the first reactive precursor gas) enters a dielectric discharge tube (not shown) that generates a plasma. Regardless, the molecular components of the reactant gas mixture dissociate in the plasma into charged atoms that nucleate to form nanoparticles from the reactant gas mixture and produce an aerosol containing silicon nanoparticles in the gas (i.e., a "nanoparticle aerosol"). The aerosol is then transported to the particle collection chamber 26, and in particular to the container 32.

More specifically, particle collection chamber 26 generally includes a trapping fluid 27 disposed within a container 32 for trapping nanoparticles. The container 32 or the captured fluid 27 may be adapted for agitation (e.g., stirring, rotating, inverting, sonicating, etc.), such as via a rotatable support, stirring mechanism, or the like (not shown). In some embodiments, the trapped fluid 27 is agitated to renew the surface of the trapped fluid 27 and force the trapped nanoparticles therein away from the centerline of the orifice 32. In this way, the rate of absorption of nanoparticles into the trapping fluid 27 can be increased by increasing the agitation of the trapping fluid 27. For example, in certain embodiments, sonication may be used as an added method of agitating the trapped fluid 27. Typically, the trapping fluid 27 is a liquid at the operating temperature of the plasma reactor system 20.

Generally, nanoparticles produced via plasma reactor system 20 can be varied/controlled in nanoparticle diameter by varying the distance between aperture 31 in outlet 30 of plasma generation chamber 22 and the surface of trapping fluid 27 (i.e., "collection distance"). The collection distance is typically in the range of 5 to 50 times the diameter of the aperture 31 (i.e., 5 to 50 times the "aperture diameter"). Positioning the surface of the trapping fluid 27 too close to the aperture 31 can result in undesirable interactions of the plasma with the trapping fluid 27. Conversely, positioning the surface of trapped fluid 27 too far from aperture 31 may reduce nanoparticle collection efficiency. Since the collection distance is a function of the diameter of the aperture 31 and the pressure drop between the plasma generation chamber 22 and the collection chamber 26, acceptable collection distances are typically 1cm to 20cm, alternatively 5cm to 10cm, alternatively 6cm to 12cm, based on the operating conditions described herein.

In some embodiments, an HF or VHF radio frequency power source (not shown) operates at a preselected RF in the frequency range of 10MHz to 500MHz to generate a plasma for a time sufficient to form a nanoparticle aerosol. The pre-selected radio frequency may be a continuous frequency of 10MHz to 500MHz, alternatively 30MHz to 150MHz, and typically corresponds to a coupled power of 5W to 1000W, alternatively 1W to 200W, respectively. In certain embodiments, the preselected radio frequency is a continuous frequency of 100MHz to 150 MHz.

In some embodiments, the plasma generation chamber 22 can include an electrode 24 coupled to the VHF radio frequency power source and having a tip (not shown) spaced a variable distance from a ground ring (not shown) inside the plasma generation chamber 22. Alternatively, the tips may be positioned at a variable distance from the VHF radio frequency power ring operating in push-pull mode (180 ° out of phase). In some embodiments, the electrode arrangements 24, 25 include an induction coil (not shown) coupled to a VHF radio frequency power source such that the radio frequency power is delivered to the reactant gas mixture by an electric field formed by the induction coil.

The plasma in region 23 is initiated (alternatively referred to as ignited) via an RF Power amplifier such as, for example, an AR world wide KAA2040 type or Electronics and Innovation 3200L type or an EM Power RF Systems, inc. The amplifier may be driven (or pulsed) by an arbitrary function generator (e.g., Tektronix AFG3252 function generator) capable of generating up to 200 watts of power at 0.15MHz to 150 MHz. In some embodiments, the arbitrary function may be able to drive the power amplifier with a burst, amplitude modulation, frequency modulation, or a different waveform. The power coupling between the amplifier and the reactant gas mixture generally increases as the frequency of the RF power increases. Higher frequency drive power may allow more efficient coupling between the power source and the discharge. The increased coupling may be manifested as a decrease in Voltage Standing Wave Ratio (VSWR) according to equation 1:

where p is the reflection coefficient:

where Zp and Zc represent the plasma and coil impedances, respectively. At frequencies below 30MHz, only 2-15% of the power is delivered to the plasma discharge, resulting in high reflected power in the RF circuit, which can lead to increased heating and limited power source life. In contrast, higher frequencies may be used to allow more power to be delivered to the plasma discharge, thereby reducing the amount of reflected power in the RF circuit.

In some embodiments, the power and frequency of the plasma discharge are preselected to create an optimal operating space for forming nanoparticles. Generally, tuning both power and frequency will produce the appropriate ion and electron energy distributions in the plasma discharge to help dissociate the molecules of the reactant gas mixture and nucleate the silicon nanoparticles. The power of the plasma discharge controls the temperature of individual particles within the plasma discharge. By controlling the temperature of the individual particles within the plasma discharge, the crystallinity of the silicon nanoparticles formed within the plasma discharge can be controlled. Generally, higher power produces crystalline particles, while lower power produces amorphous particles. Controlling both power and frequency may also be used to prevent silicon nanoparticles from overgrowing.

The plasma reactor system 20 may be pulsed to directly manage the residence time for nanoparticle nucleation, thereby controlling the particle size distribution and agglomeration kinetics in the plasma. Generally, pulsing system 20 allows for controlled tuning of particle residence time in the plasma, which affects the size of the silicon nanoparticles formed therein. By reducing the "on" time of the plasma, the nucleating particles have less time to agglomerate, and thus the average size of the silicon nanoparticles can be reduced (i.e., the nanoparticle distribution can be shifted to smaller diameter particle sizes). Also, the distance between the nanoparticle synthesis site and the surface of the trapping fluid 27 is typically selected to be sufficiently short to avoid unwanted agglomeration of entrained nanoparticles.

The particle size distribution of the silicon nanoparticles can also be controlled by controlling the plasma residence time, the high ion energy/density region of the VHF radio frequency low pressure glow discharge, relative to the residence time of the precursor gas molecules through the discharge. Generally, at constant operating conditions (e.g., discharge drive frequency, drive amplitude, discharge tube pressure, chamber pressure, plasma power density, precursor mass flow rate, collection distance from the plasma source electrode, etc.), a shorter plasma residence time for the VHF radio frequency low pressure glow discharge corresponds to a decrease in average nano-sample diameter at constant operating conditions relative to the gas molecule residence time. For example, as the plasma residence time of a VHF radio frequency low pressure glow discharge increases relative to the gas molecule residence time, the average nanoparticle diameter follows y ═ y₀-exp(-t_rExponential growth model of the form/C), where y is the mean nanoparticle diameter, y₀Is an offset, t_rPlasma residence time, and C constant. The particle size distribution can also be increased by increasing the plasma residence time at other constant operating conditions.

In some embodiments, the average particle size of the nucleated nanoparticles (and the nanoparticle size distribution) can be controlled by controlling the mass flow rate of at least one precursor gas in the VHF radio frequency low pressure glow discharge. For example, as the mass flow rate of the precursor gas (or gases) is increased in a VHF radio frequency low pressure plasma discharge, the average nanoparticle diameter synthesized may follow y-y₀An exponential decay model of the form + exp (-MFR/C'), where y is the average nanoparticle diameter, y₀For offset, MFR is the precursor mass flow rate, and C' is a constant for constant operating conditions. Typical operating conditions may include discharge drive frequency, drive amplitude, discharge tube pressure, chamber pressure, plasma power density, gas molecule residence time through the plasma, and collection distance from the plasma source electrode. The average nanoparticle size distribution of the synthesized nanoparticles can also be determined according to the ratio of y to y₀An exponential decay model decrease of the form + exp (-MFR/K), where y is the mean nanoparticle diameter, y₀Is an offset amountMFR is the precursor mass flow rate and K is constant for constant operating conditions.

Generally, operating the plasma reactor system 20 at a higher frequency range and pulsing the plasma provides the same conditions as conventional pinch/filament discharge techniques that use plasma instability to produce high ion energy/density, but with the added advantage that the user can control the operating conditions to select and produce a predetermined size of nanoparticles that can affect certain characteristic physical properties (e.g., photoluminescence).

For pulsed implantation, the synthesis of nanoparticles (alternatively referred to as deposition) can be achieved using a pulsed energy source, such as a pulsed very high frequency RF plasma, or a pulsed laser for pyrolysis. Typically, the VHF radio frequency is pulsed at a frequency in the range of 1kHz to 50 kHz.

As described above, the aerosol comprising silicon nanoparticles is transferred from the plasma reactor 22 to the collection chamber 26, in particular to the capture fluid 27 disposed in the vessel 32. In certain embodiments, the silicon nanoparticles are transferred to the trapping fluid 27 by the input of a pulsed reactant gas mixture while the plasma is ignited. For example, in some such embodiments, the plasma is ignited with a first reactive precursor gas present to synthesize silicon nanoparticles, and at least one other gas, such as an inert gas, present to sustain the discharge. The synthesis of silicon nanoparticles is stopped by stopping the flow of the first reactive precursor gas (e.g., with a mass flow controller), and then resumed by flowing the first reactive precursor gas again. This pulse flow technique may be used, for example, to increase the concentration of nanoparticles in trapping fluid 27 when the flux of functional nanoparticles impacting trapping fluid 27 is greater than the absorption rate of silicon nanoparticles into trapping fluid 27. In certain embodiments, silicon nanoparticles are evacuated from the plasma reactor 22 to the particle collection chamber 26 (e.g., to a capture fluid 27 disposed in a vessel 32) by cycling the plasma to a low ion energy state and/or turning off the plasma.

In some embodiments, the silicon nanoparticles are prepared byThe transfer from plasma generation chamber 22 to trapping fluid 27 is by the pressure differential between plasma generation chamber 22 and particle collection chamber 26, which can be controlled in a variety of ways, and can be sufficient to produce an ultrasonic jet of nanoparticles flowing from plasma generation chamber 22. The ultrasonic jet minimizes gas phase particle-particle interactions, thereby keeping the silicon nanoparticles monodisperse in the gas stream. In certain embodiments, the discharge tube 22 has an inner diameter that is much smaller than the inner diameter of the particle collection chamber 26, thereby creating a pressure differential (e.g., where the pressure of the particle collection chamber 26 is less than the pressure of the reaction chamber 22). In various embodiments, the pressure of the deposition chamber is less than 1x10^-5A tray, which can be controlled via a vacuum source 28. In some embodiments, the aperture 31 is adapted to force the plasma to reside partially within the aperture 31, e.g., based on the debye length of the plasma and the size of the plasma generation chamber 22. In certain embodiments, the orifice 31 may be electrostatically varied to create a concentric positive charge that forces the negatively charged plasma through the orifice 31.

As described above, after the dissociation of the molecules of the reactant gas mixture in the plasma generation chamber 22, nanoparticles are formed and entrained in the gas phase. The distance between the nanoparticle synthesis site and the surface of the trapping fluid 27 must be short enough that no unwanted nucleation or functionalization occurs when the silicon nanoparticles are entrained in the gas phase, but instead the silicon nanoparticles interact in the gas phase and agglomerates of many individual small nanoparticles form and are trapped in the trapping fluid 27. If too many interactions occur in the gas phase, the silicon nanoparticles can sinter together and form nanoparticles with a larger average diameter.

Additional examples relating to reactors suitable for use in embodiments of the present invention are described in the disclosures of international (PCT) publications nos. WO 2010/027959 and WO 2011/109229, each of which is incorporated herein by reference in its entirety. Such a reactor may be, but is not limited to, a low pressure high frequency pulsed plasma reactor.

It should be understood that other plasma reactors and plasma reactor systems may be used. For example, in certain embodiments, the method may be performed using a plasma reactor system exemplified by a plasma reactor system shown generally at 50 in fig. 2. In these embodiments, the silicon nanoparticles are prepared in a plasma reactor system 50, similar to the previous plasma reactor systems described above, including a plasma generation chamber 22.

In these embodiments, the plasma reactor system 50 includes a diffusion pump 120. Thus, silicon nanoparticles may be collected by the diffusion pump 120. The particle collection chamber 26 can be in fluid communication with the plasma generation chamber 22. Diffusion pump 120 may be in fluid communication with particle collection chamber 26 and plasma generation chamber 22. In other forms of the present disclosure, plasma reactor system 50 may not include particle collection chamber 26. For example, the outlet 30 may be coupled to the inlet 103 of the diffusion pump 120, or the diffusion pump 120 may be in substantially direct fluid communication with the plasma generation chamber 22.

Fig. 3 is a schematic cross-sectional view of an exemplary diffusion pump 120 suitable for use in the plasma reactor system 50 of the embodiment of fig. 2. Diffusion pump 120 may include a chamber 101 having an inlet 103 and an outlet 105. The inlet 103 may have a diameter of 5cm to 140cm, and the outlet may have a diameter of 1cm to 21 cm. The inlet 103 of the chamber 101 is in fluid communication with the outlet 30 of the reactor 20. The diffusion pump 120 may have a pumping speed of, for example, 65 to 65,000 liters/second or greater than 65,000 liters/second.

Diffusion pump 120 also includes a reservoir 107 in fluid communication with chamber 101. The reservoir 107 supports or contains a capture fluid. The reservoir may have a volume of 30ml to 15 litres. The volume of trapped fluid in the diffusion pump may be 30ml to 15 liters. Diffusion pump 120 may also include a heater 109 for vaporizing the trapped fluid in reservoir 107. Heater 109 heats and vaporizes the capture fluid to form a vapor (e.g., liquid to vapor phase conversion). For example, the capture fluid may be heated to 100 to 400 ℃, alternatively 180 to 250 ℃.

The injection assembly 111 may be in fluid communication with the reservoir 107, and the injection assembly 111 may include a nozzle 113 for discharging vaporized trapped fluid into the chamber 101. The vaporized trap fluid flows and rises through the injection assembly 111 and is discharged from the nozzle 113. The flow of vaporized capture fluid is shown in fig. 3 using arrows. The vaporized capture fluid condenses and flows back to reservoir 107. For example, the nozzles 113 may discharge the vaporized trapped fluid against the walls of the chamber 101. The walls of the chamber 101 may be cooled with a cooling system 114, such as a water cooling system. The cooled walls of the chamber 101 may cause the vaporized trapped fluid to condense. The condensed capture fluid may then flow down the walls of the chamber 101 under gravity and back to the reservoir 107. The capture fluid may be continuously circulated through the diffusion pump 120. The flow of the capture fluid causes the gas entering the inlet 103 to diffuse from the inlet 103 to the outlet 105 of the chamber 101. The vacuum source 33 may be in fluid communication with the outlet 105 of the chamber 101 to assist in removing gas from the outlet 105.

As the gas flows through the chamber 101, nanoparticles entrained in the gas (e.g., silicon nanoparticles of a nanoparticle aerosol) may be absorbed by the trapping fluid, which thereby collects the silicon nanoparticles from the gas. For example, the surface of the silicon nanoparticles may be wetted by the vaporized and/or condensed trapping fluid. The agitation cycle trapping fluid can further increase the absorption rate of the silicon nanoparticles compared to a static fluid. The pressure within the chamber 101 may be less than 1 millitorr.

The capture fluid with the silicon nanoparticles may be removed from the diffusion pump 120. For example, the trapping fluid with silicon nanoparticles may be continuously removed and replaced with a trapping fluid that contains substantially no silicon nanoparticles.

Advantageously, the diffusion pump 120 can be used not only to collect silicon nanoparticles, but also to evacuate the plasma generation chamber 22 and collection chamber 26. For example, the operating pressure in the plasma generation chamber 22 may be a low pressure, such as less than atmospheric pressure, less than 760 torr, or between 1 torr and 760 torr. The collection chamber 26 may be, for example, in the range of 1 to 5 millitorr, or have less than 1x10^-5The pressure of the tray. Other operating pressures are also contemplated.

The plasma reactor system 50 may also include a vacuum pump or source 33 in fluid communication with the outlet 105 of the diffusion pump 120. The vacuum source 33 may be selected so that the diffusion pump 120 operates normally. In one form of the embodiment of the invention, the vacuum source 33 comprises a vacuum pump (e.g., an auxiliary pump). The vacuum source 33 may include a mechanical pump, a turbo-molecular pump, or a cryopump. However, other vacuum sources may alternatively or additionally be utilized.

In some embodiments, the method includes forming a nanoparticle aerosol in the plasma generation chamber 22 using the plasma reactor system 50 of fig. 2. The nanoparticle aerosol may comprise silicon nanoparticles in a gas, and the method further comprises introducing the nanoparticle aerosol from the plasma generation chamber 22 into the diffusion pump 120. In such embodiments, the method may further include heating the trapped fluid in the reservoir 107 to form a vapor, transporting the vapor through the spray assembly 111, discharging the vapor through the nozzle 113 into the chamber 101 of the diffusion pump 120, condensing the vapor to form a condensate, and flowing the condensate back to the reservoir 107. The method may further comprise capturing and collecting the silicon nanoparticles of the nanoparticle aerosol in a capture fluid condensate in the reservoir 107. The silicon nanoparticles of the nanoparticle aerosol may be captured in the capture fluid condensate in the same manner as the silicon nanoparticles of the nanoparticle aerosol are collected in the capture fluid. The method may further include removing gas from the diffusion pump 120 with the vacuum source 33. In contrast to the embodiment described above with reference to fig. 1, in which silicon nanoparticles are directly collected in the capture fluid 27, the plasma reactor system 50 utilizes a vaporized form of the capture fluid condensed in a diffusion pump 120, where the capture fluid is used to capture/collect silicon nanoparticles from the nanoparticle aerosol.

As described above, the nanoparticle aerosol formed in the plasma reactor contains nanoparticles in a gas. With respect to gases, those skilled in the art will readily appreciate that gases include those gases introduced into the plasma reactor, such as the various gaseous components of the silicon nanoparticle-forming reactant gas mixture, which components will be described in detail below.

Regardless of the particular low pressure reactor used to produce the nanoparticle aerosol, the silicon nanoparticles are optionally collected in a capture fluid or diffusion pump fluid (which may also be used as a capture fluid).

The capture fluid, if used, may comprise any compound, component, or fluid that may be suitable for capturing silicon nanoparticles. For example, conventional components used in conventional capture fluids may be used as the capture fluid. Specific examples of conventional trapping fluids include silicone fluids such as polydimethylsiloxane, phenylmethyl-dimethylcyclosiloxane, tetramethyltetraphenyltrisiloxane, and/or pentaphenyltrimethyltrisiloxane; a hydrocarbon; a phenyl ether; fluorinated polyphenylene ether; sulfoxides (e.g., anhydrous methyl sulfoxide); a hydrocarbon fluid; a silicon-containing fluid; a fluorocarbon fluid; and an ionic liquid. Combinations of different components may be used in the current capture body. The trapping fluid can have a dynamic viscosity of 0.001 to 1Pa · s, 0.005 to 0.5Pa · s, alternatively 0.01 to 0.2Pa · s at 23 ± 3 ℃. Further, the trapping fluid may have a size of less than 1x10^-4The vapor pressure of Torr. A low viscosity trapping fluid is required to allow the silicon nanoparticles to be injected into or absorbed by the trapping fluid without forming a film on the surface of the trapping fluid. In some embodiments, the capture fluid is at a temperature in the range of-20 ℃ to 150 ℃ and a pressure in the range of 1 to 5 millitorr (0.133Pa to 0.665 Pa). In some embodiments, the trapping fluid has a vapor pressure that is less than the pressure in particle collection chamber 26.

It is contemplated that the trapped fluid may be used as a material handling and storage medium. In one embodiment, the capture fluid is selected to allow the nanoparticles to be absorbed and dispersed into the capture fluid as the silicon nanoparticles are collected, thereby forming a dispersion or suspension of nanoparticles in the capture fluid.

Due to quantum confinement effects, silicon nanoparticles can exhibit a number of unique electronic, magnetic, catalytic, physical, optoelectronic, and optical properties. For example, many semiconductor nanoparticles exhibit a photoluminescence effect that is significantly greater than that of macroscopic materials of similar composition.

The diameter of the silicon nanoparticles can be calculated by the following formula:

such as Proot et al, appl.phys.lett, 61,1948 (1992); delerue et al, Phys.Rev.B.,48,11024 (1993); and Ledoux et al, Phys. Rev.B.,62,15942(2000), wherein h is the Planckian constant, c is the speed of light, and E is_gIs the bulk bandgap of silicon.

The functionalized nanoparticles and/or silicon nanoparticles may independently have a maximum or average maximum dimension of less than 50nm, alternatively less than 20nm, alternatively less than 10nm, alternatively less than 5 nm. Optionally, the silicon nanoparticles have a largest dimension greater than 0.1 nm. Furthermore, the maximum or average maximum size of the silicon nanoparticles may be between 1nm and 50nm, alternatively between 2nm and 20nm, alternatively between 2nm and 10nm, alternatively between 2.2nm and 4.7 nm. The maximum size of the silicon nanoparticles can be measured by a variety of methods, such as with Transmission Electron Microscopy (TEM). For example, as understood in the art, particle size distributions are typically calculated via TEM image analysis of hundreds of different nanoparticles. In various embodiments, the silicon nanoparticles may comprise quantum dots, typically silicon quantum dots. Quantum dots have excitons confined in all three spatial dimensions and may comprise individual crystals, i.e. each quantum dot is a single crystal.

In various embodiments, the silicon nanoparticles may be photoluminescent when excited by exposure to UV light. Depending on the average diameter of the silicon nanoparticles, the silicon nanoparticles may be photoluminescent at any wavelength in the visible spectrum and may visually appear red, orange, green, blue, violet, or any other color in the visible spectrum. For example, visible photoluminescence can be observed when the silicon nanoparticles have an average diameter of less than 5nm, and near Infrared (IR) luminescence can be observed when the silicon nanoparticles have an average diameter of less than 10 nm. In one form of the disclosure, the silicon nanoparticles have an excitation wavelength of at least 1x10 at 365nm⁶The photoluminescence intensity of (a). Fluorol with 450W Xe excitation source, excitation monochromator, sample holder, sideband filter (400nm), emission monochromator, and silicon detector photomultiplier can be usedAn og3 spectrofluorometer (commercially available from Horiba (Edison, NJ)) measures the photoluminescence intensity. To measure the photoluminescence intensity, the excitation and emission slit widths were set to 2nm and the integration time was set to 0.1 s. In these or other embodiments, the silicon nanoparticles can have a quantum efficiency of at least 4% at an excitation wavelength of 395nm, as on an HR400 spectrophotometer (commercially available from Ocean Optics (Dunedin, Florida)) via a 1000 micron optical fiber coupled to an integrating sphere and the absorbance of incident photons>10% of the total mass of the sample. The quantum efficiency was calculated by placing the sample in an integrating sphere and exciting the sample via a 395nm LED driven by an Ocean Optics LED driver. The system was calibrated with a known lamp source to measure the absolute irradiance from the integrating sphere. The quantum efficiency is then calculated by the ratio of the total photons emitted by the silicon nanoparticles to the total photons absorbed by the silicon nanoparticles. Furthermore, in these or other embodiments, the silicon nanoparticles may have a full width half maximum emission of 20 to 250 at an excitation wavelength of 270-500 nm.

Without wishing to be bound by a particular theory, it is believed that photoluminescence of silicon nanoparticles is caused by quantum confinement effects that occur when the diameter of the silicon nanoparticles is smaller than the excitation radius, which can lead to band gap bending (i.e., gap increase). The band gap energy of the nanoparticles varies according to the diameter of the nanoparticles. Although silicon is an indirect bandgap semiconductor in the bulk, silicon nanoparticles with diameters less than 5nm can mimic direct bandgap materials, which can be achieved by interfacial trapping of excitons.

Furthermore, both the photoluminescence intensity and the luminescence quantum efficiency may continue to increase over time, especially when the silicon nanoparticles are exposed to air to passivate the surface of the silicon nanoparticles. In another form of the present disclosure, the maximum emission wavelength of the silicon nanoparticles shifts to shorter wavelengths (i.e., a blue shift of the emission spectrum) over time when passivated (e.g., exposed to oxygen). When passivated, the luminescent quantum efficiency of the silicon nanoparticles can increase by 200% to 2500%. However, other increases in the luminous quantum efficiency are also contemplated. The photoluminescence intensity can be increased from 400% to 4500%, depending on the degree of time of passivation and the concentration of silicon nanoparticles in the fluid in which they are suspended. However, other increases in photoluminescence intensity are also contemplated. The wavelength spectrum of light emitted from the silicon nanoparticles undergoes a blue shift as the silicon nanoparticles are passivated. In one form of the present disclosure, the maximum emission wavelength undergoes a blue shift of 100nm, corresponding to a reduction in nanoparticle size of about 1nm, depending on the duration of passivation. However, other maximum emission wavelength shifts are also contemplated herein. An alternative passivation approach includes contacting the silicon nanoparticles with a nitrogen-containing gas, such as ammonia, to produce a surface layer on the silicon nanoparticles, where the surface layer comprises a nitride.

The following examples, which are illustrative of the compositions and methods of the present disclosure, are intended to illustrate and not to limit the present disclosure.

Examples 1 and 2 and comparative example 1

An optical emission spectrometer (Ocean Optics PlasCalc-2000-UV/VIS/NIR) was attached to the very high frequency low pressure plasma reactor. The spectrometer is a fiber-based spectrometer with a spectral range of 200 and 1100nm and a Full Width Half Maximum (FWHM) optical resolution of 1 nm. The spectrometer was placed over the plasma and the axis of the discharge tube was viewed through a quartz window rather than looking radially down to eliminate wall deposition attenuation. Optical emission spectrometer spectra were analyzed offline using Ocean Optics SpecLine software to identify atomic and molecular emissive species.

Silicon nanoparticles are prepared in a plasma reactor. In examples 1 and 2, the method of preparing nanoparticles includes first introducing a halogen gas (Cl) into a reaction chamber of a plasma reactor before introducing a reactant gas mixture into the reaction chamber to prepare silicon nanoparticles₂) And argon (Ar) and ignite the plasma. In comparative example 1, the same process as in examples 1 and 2 was performed to prepare silicon nanoparticles, but there was no first step of introducing a halogen gas into the reaction chamber and igniting plasma in the reaction chamber before preparing the silicon nanoparticles. The silicon nanoparticles of examples 1 and 2 had higher emission intensities (1.5-2.25 times peak intensity) than the silicon nanoparticles of comparative example 1 when measured at a right angle on a Horiba FL3 spectrofluorometer.

Tables 1 and 2 below show parameters/conditions related to examples 1 and 2 and comparative example 1. In tables 1 and 2, the gas precursor values are gas volume percent and the frequency is the RF of the plasma, P_FIs forward power, P_RTo reflect power, P_CTo couple power, and P_effIs power efficiency. PDMS represents polydimethylsiloxane. PDMS had a viscosity of 10cSt at 25 ℃.

TABLE 1：

Table 2:

as shown in FIG. 4, the nanoparticles formed in examples 1 and 2 had higher emission intensities (1.5-2.25 times peak intensity) than the nanoparticles formed in comparative example 1 when measured with a Horiba FL3 spectrofluorometer.

Examples 3 to 5

Examples 3-5 are identical to each other, but some attention is required. Example 3 the method of the invention was utilized and examples 1 and 2 were followed (except for certain parameters, including time). Each of examples 3-5 utilized a short deposition time (20 minutes). Examples 4 and 5 were performed after example 3, but without the additional step of introducing a halogen gas into the reaction chamber prior to preparing the nanoparticles. Thus, examples 4 and 5 utilize only the steps of introducing a halogen gas and igniting the plasma of example 3. The peak emission intensity of the silicon nanoparticles of example 3 was almost 6 times greater than the peak emission intensity of the silicon nanoparticles of examples 4 and 5, as measured with a Horiba FL3 spectrofluorometer, as shown in FIG. 5.

Tables 3 and 4 below show the parameters/conditions associated with examples 3-5. In tables 3 and 4, the gas precursor values are gas volume percent and the frequency is the RF of the plasma, P_FIs forward power, P_RTo reflect power, P_CTo couple power, and P_effIs power efficiency. PDMS represents polydimethylsiloxane. PDMS had a viscosity of 10cSt at 25 ℃.

TABLE 3：

TABLE 4：

It is to be understood that the appended claims are not limited to the specific and specific compounds, compositions, or methods described in the detailed description, which may vary between specific embodiments falling within the scope of the appended claims. For any markush group relied upon herein to describe a particular feature or aspect of various embodiments, different, special and/or unexpected results may be obtained from each member of the respective markush group independently of all other markush members. Each member of the markush group may be relied upon individually and/or in combination and provide adequate support for specific embodiments within the scope of the appended claims.

Moreover, any ranges and subranges relied upon in describing the various embodiments of the invention are independently and collectively within the scope of the appended claims, and it is understood that all ranges including all and/or some values therein are described and contemplated, even if such values are not explicitly written herein. Those skilled in the art will readily recognize that the enumerated ranges and subranges sufficiently describe and enable various embodiments of the present invention, and such ranges and subranges may be further delineated into relevant halves, thirds, quarters, fifths, and so on. As but one example, a range of "0.1 to 0.9" may be further delineated into a lower third (i.e., 0.1 to 0.3), a middle third (i.e., 0.4 to 0.6), and an upper third (i.e., 0.7 to 0.9), which are individually and collectively within the scope of the appended claims, and which may be relied upon individually and/or collectively and provide adequate support for specific embodiments within the scope of the appended claims. Further, with respect to language such as "at least," "greater than," "less than," "no more than," and the like, defining or modifying a range, it is to be understood that such language includes subranges and/or an upper or lower limit. As another example, a range of "at least 10" inherently includes at least a sub-range of 10 to 35, at least a sub-range of 10 to 25, a sub-range of 25 to 35, and the like, and each sub-range may be relied upon individually and/or collectively and provide adequate support for specific embodiments within the scope of the appended claims. Finally, independent numerical values within the disclosed ranges may be relied upon and provide sufficient support for specific embodiments within the scope of the appended claims. For example, a range of "1 to 9" includes individual integers such as 3, and individual numbers including decimal points (or fractions) such as 4.1, which may be relied upon and provide adequate support for specific embodiments within the scope of the appended claims.