Synthesis Of Silicon Nanoparticles Research Articles

Nonthermal plasma synthesis of silicon nanoparticles and their thermal transport properties

Silicon-based nanostructured materials have been studied to utilize and observe the novel properties of silicon nanoparticles (SiNPs). Nonthermal plasma was employed to synthesize SiNPs, producing particles below 10 nm with narrow size distribution. The synthesis process of nonthermal plasma is discussed including the parameters that determine the particle size, yield and crystallinity of SiNPs. In this study, nanostructured material of SiNP/polystyrene (PS) nanocomposite has been observed to have a significant decrease in thermal conductivity. In this paper, post-processing of thermal annealing was applied, and the thermal conductivity measurement result shows the increase of thermal conductivity values. Although there is no significant enhancement of SiNP dispersion in the PS matrix, the thermal annealing induced molecular structure change, resulting in thermal transport enhancement at the interfacial region. The preservation of unique properties of nanoscale materials and low-cost fabrication by a silicon ink process at room temperature provide the promising potential of the SiNP-based nanostructured material. In addition, the combination of interfacial region engineering and post-processing provides controllable thermal transport properties for application in heat transfer management.

Low temperature chemical synthesis of silicon nanoparticles as anode materials for lithium-ion batteries

In this study, silicon (Si) nanoparticles have been prepared by a chemical reaction of calcium silicide (CaSi2), sulfur and metallic sodium in an autoclave at 250 °C. X-ray powder diffraction pattern indicates that the obtained sample is cubic phase Si with the calculated lattice constant a = 5.436 Å. Electron microscopy images show the obtained Si sample is composed of nanoparticles with an average size of 50 nm. As an anode for lithium ion batteries, the as-prepared Si nanoparticles exhibit a reversible capacity of 1409 mA h g−1 at a current density of 2 A g−1 over 300 cycles.

Extraction of silica from cassava periderm using modified sol-gel method

Cassava peridem wastes are generated and disposed indiscriminately or burnt due to zero economic value. In this study, modified sol-gel synthesis of amorphous silica nanoparticles from cassava periderm (CP) was investigated. The wastes were pretreated with HCl to remove soluble metallic impurities. Both treated and untreated CP flakes were calcined at 700 o C to obtain their respective ashes. The ashes were leached with HCl to remove soluble metallic oxides and thereafter sol-gelled to obtain silica gel modified with ethylene glycol. The gel was dried at 80 o C for 18 hours and then characterized using SEM, EDX, XRD, FT-IR, Raman, TEM and PSA. The SEM micrographs showed that silica modified with ethylene glycol is less agglomerated with higher silica yield and lower particle sizes. All the silica produced showed similar functional groups and non-crystallinity. The silica nanoparticles could be used as starting materials for synthesis of silicon nanoparticles. Keywords: agricultural waste, cassava periderm, amorphous silica, agglomeration, sol-gel

Synthesis of Silicon Nanoparticles from Rice Husk and their Use as Sustainable Fluorophores for White Light Emission

Silicon nanoparticles (Si NPs) exhibiting observable luminescence have many electronic, optical, and biological applications. Owing to reduced toxicity, they can be used as cheap and environmentally friendly alternatives for cadmium containing quantum dots, organic dyes, and rare earth-based expensive phosphors. Here, we report an inexpensive silicon precursor, namely rice husk, which has been employed for the synthesis of Si NPs by rapid microwave heating. The Si NPs of ∼4.9 nm diameter exhibit observable green luminescence with a quantum yield of ∼60%. They show robust storage stability and photostability and have constant luminescence during long-term UV irradiation extending over 48 h, in contrast to other luminescent materials such as quantum dots and organic dyes which quenched their emission over this time window. Green luminescent Si NPs upon mixing with synthesized red and blue luminescent Si NP species are shown to be useful for energy-efficient white light production. The resulting white light ...

Synthesis of Si/SiO2 nanoparticles using nanosecond laser ablation of silicate-rich garnet in water

During the nanosecond pulsed laser ablation of naturally occurring garnet in water, silicon and silicon dioxide nanoparticles are synthesized. These nanoparticles have an average size of 25 nm and 23 nm when the target is ablated for 20 and 30 min, respectively. The synthesized silicon nanoparticles are crystalline in nature and have cubic structure with 3.0 Å interplanar distance. The effects of laser ablation time on the yield of synthesized nanoparticles in the solution are investigated and it is observed that the optimum ablation time of 20 min is required for the efficient synthesis of silicon nanoparticles while operating at an input pulse energy of 90 mJ. We also report the elemental analysis of the garnet using laser induced breakdown spectroscopy.

The Synthesis of Hybrid Gold-Silicon Nano Particles in a Liquid

We show that the laser ablation method can be efficiently employed for the synthesis of silicon nanoparticles (NP), which are characterized by a strong resonant optical response in the visible spectral range. A single layer composed of silicon NPs has been deposited from the colloidal solution generated by laser ablation. The formation of hybrid silicon-gold NPs as a result of the laser action on a mixed colloidal solution is observed. These hybrid NPs are characterized by broadening of the near-field photoluminescence spectra compared to pure silicon NPs. These results may be used for the realization of functional metasurfaces consisting of randomly distributed resonant NPs.

A-few-second synthesis of silicon nanoparticles by gas-evaporation and their self-supporting electrodes based on carbon nanotube matrix for lithium secondary battery anodes

Rapid gas-evaporation method is proposed and developed, which yields Si nanoparticles (SiNPs) in a few seconds at high yields of 20%–60% from inexpensive and safe bulk Si. Such rapid process is realized by heating the Si source to a temperature ≥2000 °C, much higher than the melting point of Si (1414 °C). The size of SiNPs is controlled at tens to hundreds nanometers simply by the Ar gas pressure during the evaporation process. Self-supporting films are fabricated simply by co-dispersion and filtration of the SiNPs and carbon nanotubes (CNTs) without using binders nor metal foils. The half-cell tests showed the improved performances of the SiNP-CNT composite films as anode when coated with graphitic carbon layer. Their performances are evaluated with various SiNP sizes and Si/CNT ratios systematically. The SiNP-CNT film with a Si/CNT mass ratio of 4 realizes the balanced film-based capacities of 618 mAh/gfilm, 230 mAh/cm3, and 0.644 mAh/cm2 with a moderate Si-based performance of 863 mAh/gSi at the 100th cycle.

A scalable synthesis of silicon nanoparticles as high-performance anode material for lithium-ion batteries

In this work, a scalable and cost-effective method including mechanical milling, centrifugation and spray drying was developed to fabricate Si nanoparticles. The synthesized Si nanoparticles show an average size of 62 nm and exhibit a narrow particle size distribution. The influence of particle sizes on electrochemical performance of Si-based electrode was investigated, and it is found that as the particle size decreases in the studied range, the Si particles show a lower specific capacity and a higher irreversible capacity loss (ICL). Furthermore, an oxide layer with thickness of ~3 nm was detected on the surface of the as-received Si nanoparticles, and this layer can be effectively removed by hydrofluoric acid (HF) etching, resulting in much improved electrochemical performance over the as-received samples.

Facile Synthesis of Silicon Nanoparticles Embedded in 3D N-doped Graphene as Anode Materials for High-Performance Lithium Ion Batteries

Facile Synthesis of Silicon Nanoparticles Embedded in 3D N-doped Graphene as Anode Materials for High-Performance Lithium Ion Batteries

One-Pot Microwave Synthesis of Water-Dispersible, High Fluorescence Silicon Nanoparticles and Their Imaging Applications in Vitro and in Vivo.

Silicon nanoparticles (SiNPs) have been reported to be synthesized by microwave-assisted methods under high pressure. However, there is still a lack of knowledge about the synthesis of SiNPs via microwave-assisted methods under normal pressure. Here we developed a new, facile, one-pot microwave-assisted method for the synthesis SiNPs (∼4.2 nm) with excellent water solubility under normal pressure by employing glycerol as the solvent. Furthermore, glycerol might be responsible for the photoluminescence quantum yield (PLQY) value up to 47% for the resultant SiNPs. The use of organic solvent could afford less nanoparticle surface defects compared with those prepared in aqueous solution, thus improving the fluorescent efficiency. The as-prepared SiNPs simultaneously featured bright blue-green fluorescence, long lifetime (∼12.8 ns), obvious up-conversion luminescence originating from two-photon absorption, superbly strong photostability, and favorable low toxicity. As a satisfactory probe, the as-synthesized SiNPs were successfully applied in fluorescence imaging of human cervical carcinoma cell lines (HeLa) and zebrafish.

Synthesis of Silicon Nanoparticles in Nonthermal Capacitively-Coupled Flowing Plasmas: Processes and Transport

Control of the size and material properties of silicon nanoparticles plays a critical role in optimizing applications using those nanoparticles, such as photovoltaics and biomedical devices. While synthesis of silicon nanoparticles in low temperature plasmas has many attractive features, the basic mechanisms leading to formation of nanoparticles in these plasmas are poorly understood. A two-dimensional numerical model for synthesis of silicon nanoparticles (<5 nm in diameter) in radio frequency (RF) discharges was developed and used to investigate mechanisms for particle growth for Ar/He/SiH4 gas mixtures. Algorithms for the kinetics of nanoparticle formation were self-consistently embedded into a plasma hydrodynamics simulation to account for nucleation, growth, charging, and transport of nanoparticles. We found that with RF excitation in narrow tubes at pressures of a few Torr, the electric field does not fully confine charged nanoparticles in the axial direction, which then results in a finite residence time of particles in the plasma. We found that because of the high neutral nanoparticle density, coagulation plays a significant role in growth. The model predicts the possibility of synthesizing crystalline silicon nanoparticles under these conditions. Trends in the growth of nanoparticles as a function of power are discussed.

Synthesis of Silicon Nanoparticles and Nanowires by a Nontransferred Arc Plasma System

Silicon nanomaterials were synthesized from solid silicon powder in microsize using a nontransferred arc plasma system. Synthesized silicon nanomaterials were sphere or wire in morphology according to the input power of arc plasma, the flow rate of plasma forming gas, and the collecting position of product. The product was spherical nanoparticles at a high input power for complete evaporation, while it was nanowires at a relatively low input power. The mean diameter of synthesized silicon nanoparticles was increased from 20.52 nm to 40.01 nm by increasing the input power from 9 kW to 13 kW. On the other hand, the diameter of silicon nanowires was controllable by changing the flow rate of plasma forming gas. The mean diameter of silicon nanowires was increased from 16.69 nm to 23.03 nm by decreasing the plasma forming gas flow rate from 15 L/min to 12 L/min.

Hollow silicon carbide nanoparticles from a non-thermal plasma process

We demonstrate the synthesis of hollow silicon carbide nanoparticles via a two-step process involving the non-thermal plasma synthesis of silicon nanoparticles, followed by their in-flight carbonization, also initiated by a non-thermal plasma. Simple geometric considerations associated with the expansion of the silicon lattice upon carbonization, in combination of the spherical geometry of the system, explain the formation of hollow nanostructures. This is in contrast with previous reports that justify the formation of hollow particles by means of out-diffusion of the core element, i.e., by the Kirkendall nanoscale effect. A theoretical analysis of the diffusion kinetics indicates that interaction with the ionized gas induces significant nanoparticle heating, allowing for the fast transport of carbon into the silicon particle and for the subsequent nucleation of the beta-silicon carbide phase. This work confirms the potential of non-thermal plasma processes for the synthesis of nanostructures composed of high-melting point materials, and suggests that such processes can be tuned to achieve morphological control.

Controllable synthesis of silicon nano-particles using a one-step PECVD-ionic liquid strategy

Silicon nano-particles (SiNPs) with various sizes can be controllably synthesized by a facile and novel PECVD-IL method.

Silicon nanoparticles by the oxidation of [Si4](4-)- and [Si9](4-)-containing Zintl phases and their corresponding yield.

The Zintl phases with nominal compositions Na4Si4, Rb7NaSi8, and A12Si17 (A = K, Rb, Cs) were utilized as precursors in the synthesis of silicon nanoparticles (Si NPs). The present study characterizes and compares the yields of Si NPs synthesized from Na4Si4, Rb7NaSi8, and A12Si17 (A = K, Rb, Cs). Na4Si4 and Rb7NaSi8 Zintl phases consist of anionic silicon tetrahedra stabilized by group I cations. The A12Si17 (A = K, Rb, Cs) Zintl phases that contain [Si9](4-) and [Si4](4-) clusters have been speculated to be more soluble than the A4Si4 (A = Na, Rb, Cs) Zintl phases that contain solely [Si4](4-) clusters due to the lower charge density of the [Si9](4-) cluster. The Zintl phases were reacted with NH4Br in dimethylformamide (DMF) and subsequently capped with allylamine. The Si NPs were characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), UV-vis, and photoluminescence (PL) spectrophotometry. Furthermore, the Si yields were characterized by inductively coupled plasma mass spectrometry (ICP-MS) to evaluate if the reactions of [Si9](4-) cluster containing Zintl phases resulted in higher yields of Si NPs. The yield of Si increased with larger or mixed alkali metal Zintl phases, leading to the conclusion that Coulombic interactions between the cations and anions affect the Zintl phase's reactivity. The size of the Si NPs also increased with larger and mixed alkali metal cations, resulting in similar NP concentrations regardless of the starting material. With respect to ease of synthesis and yield, Na4Si4 remains the most practical precursor for the solution synthesis of Si NPs; however, the larger and mixed alkali metal precursors show promise for further development.

Improved Low Temperature Solution Synthesis of Silicon Nanoparticles for Lithium-Ion Batteries

Silicon nanoparticles have extraordinary electrochemical performance for lithium-ion batteries. This paper gives an improved low temperature solution synthesis route of Si NPs. Reduced by magnesium and then passivated by four kinds of amines/amides respectively, stable yellow Si NPs ranging from 5-50 nm were prepared. When passivated by N-methyl-2-pyrrolidone, grape-like aggregation of 5-20 nm particles were generated. FTIR, XRD, SEM and Electrochemical Characterization were performed to confirm the product. The Si NPs passivated by NMP achieve good electrochemical performance with a first discharge capacity of 1154 mAhg-1at a current density of 200 mAg-1and good capacity retention of 95.3% after 5 cycles.

A parametric study of non-thermal plasma synthesis of silicon nanoparticles from a chlorinated precursor

Silicon nanoparticles (Si NPs) synthesized in non-thermal plasma with silicon tetrachloride (SiCl4) are anticipated as a non-toxic and inexpensive Si source for important applications. This study examines the crystallinity, yield, and size distribution of Si NPs in terms of specific energy input (SEI) for 2.5–65 J cm‒3 and the H2/SiCl4 ratio (1–10). The particle growth mechanism is discussed comprehensively. Atomic hydrogen (H) production using non-thermal plasma is the primary important step for SiCl4 dechlorination at low temperatures. The Si NP yield increases with SEI (plasma power divided by total gas flow) because SiCl4 conversion increases with energy fed into the unit volume of the feed gas. At low SEI, Si NPs were mostly in amorphous material because of insufficient plasma heating. A maximum yield of 50 wt% was obtained when SEI = 10 J cm‒3 (H2/SiCl4 = 10) with a crystal fraction of about 1%. Increased SEI is necessary to improve crystal fraction, but excessive SEI decreases the NP yield remarkably. The NP yield losses correspond to increasing NP-free thin film growth on the reactor wall. Mass spectrometry shows that SiCl4 is highly decomposed with greater SEI. Hydrogen chloride (HCl) increases as a by-product. At higher SEI, particle nucleation and subsequent growth are suppressed.

Global sensitivity analysis of a model for silicon nanoparticle synthesis

This paper presents a global sensitivity analysis of the detailed population balance model for silicon nanoparticle synthesis of Menz & Kraft [2013a, A new model for silicon nanoparticle synthesis, Combustion & Flame, 160:947–958]. The model consists of a gas-phase kinetic model, fully coupled with a particle population balance. The sensitivity of the model to its seven adjusted parameters was analysed in this work using a High Dimensional Model Representation (HDMR). An algorithm is implemented to generate response surface polynomials with automatically selected order based on their coefficient of determination. A response surface is generated for 19 different experimental cases across a range of process conditions and reactor configurations. This enables the sensitivity of individual experiments to certain parameters to be assessed. The HDMR reveals that particle size was most sensitive to the heterogeneous growth process, while the particle size distribution width is also strongly dependent on the rate of nucleation.

Electrical Explosion Synthesis of Si/C Nanocomposites for Li Secondary Batteries

A novel technique of electrical explosion has been used for nanomaterial synthesis by a single-step process [1-5]. However, it was known that in principle the electrical explosion of Si is not possible due to the fact that applying a high voltage on Si wire having relatively high electrical resistance leads to a current flow through surface plasma formed along the wire which disables the resistive heating of Si. In this presentation, we will show the successful application of electrical explosion to silicon nanoparticle synthesis and the electrochemical properties of Si/C nanocomposites derived from the nanoparticles.The electrical explosion of Si was successfully applied using a liquid media to suppress the unfavorable surface plasma generation. The physical and chemical properties of the produced materials were analyzed by XRD, FE-SEM, HR-TEM and the performances of the Si/C composites as an anode for Li ion batteries were investigated by electrochemical charge/discharge measurements. The Si/C composites obtained under the explosion in hexane and ethanol consist of a core-shell structure with a compact graphitic carbon on the Si particle surface which cause detrimental effects against Li ion diffusion. However, we found that Si explosion in methanol minimized the formation of the carbon phase on the surface of nano-sized Si. The Si/C nanocomposite after a simple pyrolysis with carbon precursor showed a high capacity with an excellent cycle performance.[1] Cho, C., Choi, Y.W., Kang, C., Lee, G.W. Effects of the medium on synthesis of nanopowders by wire explosion process (2007) Applied Physics Letters, 91 (14), p. 141501.[2] Cho, C., Ha, Y.-C., Kang, C., Jin, Y.-S., Rim, G.-H. Preparation of a nickel nanopowder by wire explosion in liquid media (2010) Journal of the Korean Physical Society, 57 (61), pp. 1807-1810.[3] Ha, Y.-C., Cho, C. Production of highly-dispersed nano-sized Sn powders in a liquid medium by using a high-energy electrical explosion (2010) Journal of the Korean Physical Society, 57 (61), pp. 1574-1576.[4] Cho, C., Ha, Y.-C., Kang, C., Jin, Y.-S., Rim, G.-H. Electrical explosion of silicon rod in distilled water (2011) Japanese Journal of Applied Physics, 50 (10 PART 1).[5] Ha, Y.-C., Kang, C., Cho, C., Kim, Y.-U., Park, C.-M., Sohn, H.-J. Wire explosion synthesis of a Sn/C nanocomposite as an anode material for Li secondary batteries (2011) Journal of the Korean Physical Society, 59 (61), pp. 3458-3462.

Electrical Explosion Synthesis of Si/C Nanocomposites for Li Secondary Batteries

A novel technique of electrical explosion has been used for nanomaterial synthesis by a single-step process [1-5]. However, it was known that in principle the electrical explosion of Si is not possible due to the fact that applying a high voltage on Si wire having relatively high electrical resistance leads to a current flow through surface plasma formed along the wire which disables the resistive heating of Si. In this presentation, we will show the successful application of electrical explosion to silicon nanoparticle synthesis and the electrochemical properties of Si/C nanocomposites derived from the nanoparticles.The electrical explosion of Si was successfully applied using a liquid media to suppress the unfavorable surface plasma generation. The physical and chemical properties of the produced materials were analyzed by XRD, FE-SEM, HR-TEM and the performances of the Si/C composites as an anode for Li ion batteries were investigated by electrochemical charge/discharge measurements. The Si/C composites obtained under the explosion in hexane and ethanol consist of a core-shell structure with a compact graphitic carbon on the Si particle surface which cause detrimental effects against Li ion diffusion. However, we found that Si explosion in methanol minimized the formation of the carbon phase on the surface of nano-sized Si. The Si/C nanocomposite after a simple pyrolysis with carbon precursor showed a high capacity with an excellent cycle performance.