Synthesis Of Silicon Nanoparticles Research Articles

Large-Scale Aqueous Synthesis of Fluorescent and Biocompatible Silicon Nanoparticles and Their Use as Highly Photostable Biological Probes

A large-scale synthetic strategy is developed for facile one-pot aqueous synthesis of silicon nanoparticles (SiNPs) yielding ∼0.1 g SiNPs of small sizes (∼2.2 nm) in 10 min. The as-prepared SiNPs feature strong fluorescence (photoluminescence quantum yield of 20-25%), favorable biocompatibility, and robust photo- and pH-stability. Moreover, the SiNPs are naturally water dispersible, requiring no additional post-treatment. Such SiNPs can serve as highly photostable bioprobes and are superbly suitable for long-term immunofluorescent cellular imaging.

Synthesis, properties, and applications of silicon nanocrystals

Silicon nanocrystals have been widely investigated for several years because of their many interesting properties and their potential use in several applications. This field has grown enormously after the observation of quantum confinement in porous silicon and remains an area of great interest for different reasons. Most importantly, silicon is already widely used in the semiconductor industry, is nontoxic at least in its bulk form, is the second most earth-abundant element in the crust, and is relatively cheap to process. A large number of groups have investigated silicon in the form of nanocrystals, and the authors intend to provide a comprehensive review of their contribution to the field. The author has decided to address first the synthesis and properties of silicon nanocrystals. Several different techniques, such as nucleation in substoichiometric thin films or gas-phase nucleation and growth in silane-containing nonthermal plasmas, have been proposed for the controlled synthesis of silicon nanoparticles. The author outlines the strengths and weaknesses of each approach and identify the research groups that have advanced each particular synthesis technique. The understanding of the properties of silicon nanocrystals has evolved as new synthetic approaches were developed, and for that reason the material properties are discussed together with its production approach. The use of silicon nanocrystals for the development of novel electronic devices, light emitting devices, photovoltaic cells, and for biorelated applications will be discussed. Waste heat recovery and energy storage applications are also discussed.

A new model for silicon nanoparticle synthesis

This work presents a novel multivariate particle model to simulate the synthesis of silicon nanoparticles across a wide range of process conditions. The gas-phase mechanism of Ho et al. (1994, J. Phys. Chem. 98, 10138–10147) is simultaneously solved with a stochastic population balance incorporated a detailed multidimensional particle model. A systematic parameter estimation procedure is used to adjust gas-phase and heterogeneous pre-exponential factors to obtain fits with experimental results. The model is tested against a six different experimental configurations, with excellent fit observed for the majority of cases. It was found that primary particles were too large under conditions of finite-rate sintering, leading to the recommendation that the model could be made more robust by development of accurate sintering kinetics for silicon nanoparticles.

Plasma Synthesis of Silicon Nanoparticles: Optimization of Yield, Size Distribution, and Crystallinity

Plasma Synthesis of Silicon Nanoparticles: Optimization of Yield, Size Distribution, and Crystallinity

One-pot synthesis of silicon nanoparticles trapped in ordered mesoporous carbon for use as an anode material in lithium-ion batteries

Silicon nanoparticles trapped in an ordered mesoporous carbon composite were prepared by a one-step self-assembly with solvent evaporation using the triblock copolymer Pluronic F127 and a resorcinol–formaldehyde polymer as the templating agent and carbon precursor respectively. Such a one-pot synthesis of Si/ordered mesoporous carbon nanocomposite is suitable for large-scale synthesis. Characterization confirmed that the Si nanoparticles were trapped in the ordered mesoporous carbon, as evidenced by transmission electron microscopy, x-ray diffraction analysis and nitrogen sorption isotherms. The composite showed a high reversible capacity above 700 mA h g−1 during 50 cycles at 2 A g−1. The improved electrochemical performance of the composite can be ascribed to the buffering effect of spaces formed in the ordered pore channels during the volume expansion of silicon and the rapid movement of lithium ions through the uniform cylindrical pore structure of the mesopores.

Modelling for the optimization of the reaction chamber in silicon nanoparticle synthesis by a radio-frequency induction thermal plasma

The optimization of the reaction chamber for the silicon nanoparticle synthesis process by a radio-frequency induction thermal plasma is addressed using a plasma thermo-fluid-dynamic model coupled with electromagnetic field equations and with a moment model for nanoparticle transport. Various reaction chamber geometries composed of two parts—a conical top and a cylindrical bottom—are evaluated in terms of the yield of the synthesis process, the presence of recirculation flow patterns that may affect the uniformity of the produced nanoparticles and the size distribution of nanoparticles at the chamber outlet. Turbulent diffusion is suggested as the physical phenomenon that leads to nanoparticle deposition onto the walls of the reaction chamber. The injection of a suitable gas along the walls of the reaction chamber at the axial position, where the nanoparticle nucleation takes place, is proven to be effective in increasing the synthesis process yield.

Studies on Optical Limiting Characteristics of Silicon Nanoparticles Synthesized by Laser Ablation

We present synthesis of silicon nanoparticles dispersed in toluene by laser ablation and studies on their optical limiting properties with nanosecond laser pulses at 532 nm. Silicon nanoparticles in toluene show better optical limiting compared to standard optical limiter fullerene C60 in toluene. Optical limiting threshold of silicon nanoparticles is about three times less than that of C60. Detailed studies using Z-scan experiments, angle dependent scattering, intensity dependent transmission and temporal profile measurements indicate that apart from non-linear scattering, nonlinear absorption and nonlinear refraction also contribute to the optical limiting behavior of silicon nanoparticles.

Process control strategies for the gas phase synthesis of silicon nanoparticles

In this contribution the identification of new reaction conditions for the production of nearly monodisperse silicon nanoparticles via the pyrolysis of monosilane in a hot wall reactor is considered. For this purpose a full finite volume model has been combined with a state-of-the-art trust-region optimisation algorithm for process control. Verified against experimental data, specific process conditions are determined accomplishing a versatile range of prescribed product properties. The main achievement of the optimisation is the possibility to control the different mechanisms in the particle formation process by mainly adjusting the temperature profile. Due to a successful separation of the nucleation and growth process, significantly narrower particle size distributions are obtained. Moreover, the presented optimisation framework establishes rate constants based on measured data.

Facile synthesis of silicon nanoparticles inserted into graphene sheets as improved anode materials for lithium-ion batteries

Silicon nanoparticles have been successfully inserted into graphene sheets via a novel method combining freeze-drying and thermal reduction. The as-obtained Si/graphene nanocomposite exhibits remarkably enhanced cycling performance and rate performance compared with bare Si nanoparticles for lithium-ion batteries.

Synthesis of silicon nanoparticles with a narrow size distribution: A theoretical study

This work presents a study of the processes involved in synthesis of narrowly distributed silicon nanoparticles from the thermal decomposition of silane. Two models are proposed, one which simultaneously solves the kinetic mechanism of Swihart & Girshick (1999, Journal of Physical Chemistry B 103, 64–76) while adjusting the sintering parameters; and another which adjusts the kinetic and surface growth mechanisms while neglecting coagulation and sintering. The models are applied to simulate the centreline of the hot-wall reactor and process conditions of Körmer et al. (2010, Journal of Aerosol Science 41, 998–1007). Both models are shown to give good agreement with experimental PSDs at a range of process conditions. However, it is reported that an unphysical sintering process is obtained when attempting to use Swihart & Girshick's kinetic mechanism, while solving for the sintering parameters. The model with adjusted gas-phase and surface growth processes gives better quantitative and qualitative agreement with experimental results. It is therefore recommended that further study into the kinetic and heterogeneous growth mechanisms be conducted in order to better understand the fundamental processes occurring in this hot-wall reactor.

Silicon nanoparticle synthesis by short-period thermal anneals at atmospheric pressure in argon

Silicon nanoparticles have been studied for a wide variety of applications including nanoelectronic, photovoltaic, and optoelectronic devices. In this work, silicon nanoparticles were synthesized by short-period annealing of silicon-on-insulator substrates to temperatures ranging between 600 and 900 °C in argon gas at atmospheric pressure. Two different top silicon layers were deposited by ion-beam sputtering onto oxidized substrates. The thinner 6 nm top layer samples were annealed to temperatures for 30 s periods while thicker 15 nm top layer samples were annealed for 60 s periods. For both sets of samples, nanoparticles were observed to form at all the anneal temperatures through imaging by AFM. One long-period UHV anneal study, with 30-min anneal times, observed nanoparticle formation at temperatures similar to the current work while another similar long-period UHV anneal reported nanoparticle formation only above well-defined formation temperatures that depended upon the starting top layer thickness. In the current work, the average nanoparticle radius was found to increase both with the final anneal temperature and anneal period. For the highest anneal temperatures of the 6 nm top layer samples, a changing surface topography indicated that the thinner Si source layer was becoming depleted and the nanoparticle formation process was nearing completion. No such changes were observed for the thicker 15 nm samples at the same temperatures.

Synthesis of luminescent Si Nanoparticles using the laser-induced pyrolysis

The synthesis of silicon nanoparticles in the reaction of the silane pyrolysis is presented. The reaction of the silane decomposition is performed in a flow reactor in the presence of the cw CO2-laser irradiation. As-prepared Si nanoparticles are studied with the aid of transmission electron microscope, fiber spectrometer, and FTIR spectrometer. Spherical Si nanoparticles with a diameter of about 15 nm are produced. The luminescence of the as-prepared nanoparticles is virtually absent. The nanoparticles are etched in acid vapor and are oxidized to increase the luminescence quantum yield. After the chemical treatment, the mean size of the crystalline core of nanoparticles decreases to 5 nm and the luminescence spectrum exhibits the band peaked at 730 nm.

Aerosol synthesis of silicon nanoparticles with narrow size distribution—Part 2: Theoretical analysis of the formation mechanism

This work investigates the mechanisms which lead to the formation of silicon nanoparticles with narrow size distributions by means of population balance modeling. The model accounts for the full aerosol process, including chemical reaction, nucleation from supersaturated vapor, growth and agglomeration. The results are in good agreement with experimental data. The effects of the process parameters temperature, silane concentration and reactor total pressure are systematically investigated. The simulation allows an in-depth insight into the particle formation mechanism and reveals the key requirements which are necessary for the generation of narrow particle size distributions. In this mechanism, only a short nucleation burst occurs, while surface growth plays the dominant role in silane precursor consumption. A key role is attributed to condensation, because the numerical calculations can only reflect the experimental observations, if the condensation mechanism is included in the model.

Aerosol synthesis of silicon nanoparticles with narrow size distribution—Part 1: Experimental investigations

A study on the feasibility of aerosol processing of nearly monodisperse silicon nanoparticles via pyrolysis of monosilane in a hot wall reactor is presented. For optimal conditions silicon nanoparticles with a geometric standard deviation of 1.06 were synthesized at a production rate of 0.7 g/h. The size of the particles could be precisely controlled in the range of 20–40 nm, whilst maintaining a geometric standard deviation in the range of 1.06–1.08, by proper choice of the governing parameters temperature, residence time and precursor concentration. The results show that narrow particle size distributions can only be obtained in the temperature range between 900 and 1100 °C, as long as both the initial silane concentration (1 mbar silane partial pressure) and the reactor total pressure are low (25 mbar). This regime for the production of narrow particle size distributions has not been identified in prior work on the thermal decomposition of silane. Narrowly distributed particles can be obtained under conditions where nucleation and particle growth are separated and the agglomeration rates are negligible.

High-yield synthesis of silicon nanoparticles via the perpendicular pulsed laser ablation in the inert gas

Si nanoparticles are synthesized at a high rate (400–500 mg/h) using the perpendicular pulsed laser ablation (PPLA) on the silicon target at room temperature in Ar atmosphere. The PPLA method can also be used to obtain Si nanocrystal films with large areas on the glass substrate. These particles are etched with a mixture of hydrofluoric acid (HF) and nitric acid (HNO3) to reduce their sizes and the surfaces of these particles are passivated by the high-pressure water vapor annealing (HWA). After treating the particles exhibit blue emission (with maximum photoluminescence (PL) intensity at 404 nm) at room temperature.

Synthesis of Silicon Nano-particles for Thin Film Electrodes Preparation

AbstractThe present work concerns novel approaches to fabricate silicon-based electrodes. In this study silicon nano-particles are synthesized via two aerosol routes: Laser assisted Chemical Vapour Pyrolysis (LaCVP) and Spark Discharge Generation (SDG). These two techniques allow the generation of uniformly sized particles, with a good control over the composition and the range of sizes. Herein, particles with size ranging from 2 to 70 nm were obtained. Starting from these nano-particles, nano-structured porous thin films are produced either by electrospraying a polymeric solution in which LaCVP-produced particles were previously dispersed, or by inertial impacting the SDG-produced particles directly from gas phase onto a substrate. The Electro- Spray (ES) is used to produce composite films for Li-ion battery applications, whereas the Inertial Impaction (II) is used to produce pure silicon films for other purposes (i.e.: sensors).

Silicon nanoparticles with chemically tailored surfaces

AbstractSilicon nanoparticles are useful materials for optoelectronic devices, solar cells and biological markers. The synthesis of air‐stable nanoparticles with tunable optoelectronic properties is highly desirable. The mechanochemical synthesis of silicon nanoparticles via high‐energy ball milling produces a variety of covalently bonded surfaces depending on the nature of the organic liquid used in the milling process. The use of the C8 reactants including octanoic acid, 1‐octanol, 1‐octaldehyde and 1‐octene results in passivated surfaces characterized by strong SiC bonds or strong SiO bonds. The surfaces of the nanoparticles were characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy. The nanoparticles were soluble in common organic solvents and remarkably stable against agglomeration and air oxidation. The luminescence and optical properties of the nanoparticles were very sensitive to the nature of their passivating surface. Copyright © 2009 John Wiley & Sons, Ltd.

Gas-Phase Synthesis of Silicon Nanoparticles and Mixing with Graphite Powders by Using Counter-Flow Injection

Mixing between nano-sized silicon particles and micro-sized graphite powders was performed for anode materials of lithium ion batteries, in which the silicon nanoparticles were synthesized by silane pyrolysis under optimized conditions and were subsequently coated onto the surface of graphite powders at mixing chamber by counter-flow injection. The counter-flow injection was employed as a dry particle mixing process in order to generate uniform silicon-coated graphite powders. Furthermore, this method also made it possible to combine particle synthesis and mixing into one single operation. Energy dispersive X-ray spectroscopy (EDS) was utilized to examine the degree of mixing through surface chemical composition analysis of the mixture. Experimental results indicate that the jet Reynolds number can be considered as the key parameter to determine the homogeneity of the mixture and its critical value may be in the range of 120 to 180 for good mixing performance, being in reasonable agreement with previous studies.

Thermally Induced Hydrosilylation at Deuterium-Terminated Silicon Nanoparticles: An Investigation of the Radical Chain Propagation Mechanism

Isotopic labeling techniques were employed to study alkene addition to hydrogen- and deuterium-terminated silicon nanoparticles. Deuterium-terminated silicon nanoparticle synthesis is described, as is the characterization of fresh deuterium-terminated particles by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and in situ Fourier transform infrared spectroscopy (FTIR). Particles were refluxed in pure 1-dodecene and subsequently characterized by FTIR and nuclear magnetic resonance (NMR) spectroscopy. (1)H NMR results showed features consistent with dodecyl-terminated nanoparticles. Infrared absorption spectra of refluxed particles showed strong evidence of new C-D bond formation, which is consistent with a radical chain mechanism for alkene addition by hydrosilylation.

Computational Modeling of Silicon Nanoparticle Synthesis: II. A Two-Dimensional Bivariate Model for Silicon Nanoparticle Synthesis in a Laser-Driven Reactor Including Finite-Rate Coalescence

In this work, a two-dimensional model was developed for silicon nanoparticle synthesis by silane thermal decomposition in a six-way cross laser-driven aerosol reactor. This two-dimensional model incorporates fluid dynamics, laser heating, gas phase and surface phase chemical reactions, and aerosol dynamics, with particle transport and evolution by convection, diffusion, thermophoresis, nucleation, surface growth, coagulation, and coalescence processes. Because of the complexity of the problem at hand, the simulation was carried out via several sub-models. First, the chemically reacting flow inside the reactor was simulated in three dimensions in full geometric detail, but with no aerosol dynamics and with highly simplified chemistry. Second, the reaction zone was simulated using an axisymmetric two-dimensional CFD model, whose boundary conditions were obtained from the first step. Last, a two-dimensional aerosol dynamics model was used to study the silicon nanoparticle formation using more complete silane decomposition chemistry, together with the temperature and velocities extracted from the reaction zone CFD simulation. A bivariate model was used to describe the evolution of particle size and morphology. The aggregates were modeled by a moment method, assuming a lognormal distribution in particle volume. This was augmented by a single balance equation for primary particles that assumed locally equal number of primary particles per aggregate and fractal dimension. The model predicted the position and size at which the primary particle size is frozen in, and showed that increasing the peak temperature was a more effective means of improving particle yield than increasing silane concentration or flowrate.