Properties Of Silicon Nanoparticles Research Articles

Silicon nanoparticles in sustainable agriculture: synthesis, absorption, and plant stress alleviation.

Silicon (Si) is a widely recognized beneficial element in plants. With the emergence of nanotechnology in agriculture, silicon nanoparticles (SiNPs) demonstrate promising applicability in sustainable agriculture. Particularly, the application of SiNPs has proven to be a high-efficiency and cost-effective strategy for protecting plant against various biotic and abiotic stresses such as insect pests, pathogen diseases, metal stress, drought stress, and salt stress. To date, rapid progress has been made in unveiling the multiple functions and related mechanisms of SiNPs in promoting the sustainability of agricultural production in the recent decade, while a comprehensive summary is still lacking. Here, the review provides an up-to-date overview of the synthesis, uptake and translocation, and application of SiNPs in alleviating stresses aiming for the reasonable usage of SiNPs in nano-enabled agriculture. The major points are listed as following: (1) SiNPs can be synthesized by using physical, chemical, and biological (green synthesis) approaches, while green synthesis using agricultural wastes as raw materials is more suitable for large-scale production and recycling agriculture. (2) The uptake and translocation of SiNPs in plants differs significantly from that of Si, which is determined by plant factors and the properties of SiNPs. (3) Under stressful conditions, SiNPs can regulate plant stress acclimation at morphological, physiological, and molecular levels as growth stimulator; as well as deliver pesticides and plant growth regulating chemicals as nanocarrier, thereby enhancing plant growth and yield. (4) Several key issues deserve further investigation including effective approaches of SiNPs synthesis and modification, molecular basis of SiNPs-induced plant stress resistance, and systematic effects of SiNPs on agricultural ecosystem.

Preparation and properties of silicon nanoparticles by pulse discharge and ball milling

In this paper, nano silicon particles were prepared by pulse discharge and ball milling. Firstly, the bulk silicon material was gasified and melted by high temperature in the process of...

Laser Ablation of Silicon Nanoparticles and Their Use in Charge-Coupled Devices for UV Light Sensing via Wavelength-Shifting Properties.

This study explores the controlled laser ablation and corresponding properties of silicon nanoparticles (Si NP) with potential applications in ultraviolet (UV) light sensing. The size distribution of Si NPs was manipulated by adjusting the laser scanning speed during laser ablation of a silicon target in a styrene solution. Characterization techniques, including transmission electron microscopy, Raman spectroscopy, and photoluminescence analysis, were employed to investigate the Si NP structural and photophysical properties. Si NP produced at a laser scanning speed of 3000 mm/s exhibited an average diameter of ~4 nm, polydispersity index of 0.811, and a hypsochromic shift in the Raman spectrum peak position. Under photoexcitation at 365 nm, these Si NPs emitted apparent white light, demonstrating their potential for optoelectronic applications. Photoluminescence analysis revealed biexponential decay behavior, suggesting multiple radiative recombination pathways within the nanoscale structure. Furthermore, a thin film containing Si NP was utilized as a passive filter for a 2nd generation CCD detector, expanding the functionality of the non-UV-sensitive detectors in optics, spectrometry, and sensor technologies.

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.

Study of Colloidal Suspensions of Silicon Nanoparticles: Effect of Surface Oxidation on the Photoluminescence Property

Nanosilicon is currently under intensive research owing to its extremely promising properties, particularly in photonics domain. However, the photoluminescence (PL) mechanism of silicon nanocrystal remains unclear. We propose, in this paper, a simple method to investigate the PL properties of silicon nanoparticles by exposing the nanoparticles directly to the solvents. The interaction between the nanoparticles and different solvents allows us to assume that not only the quantum size effect but also the surface defect states play a critical role in the PL mechanism, especially at high energy region. This can be confirmed by the results of Transmission Electron Microscopy, FTIR and Raman Spectroscopy.

Morphology and Laser-Induced Photochemistry of Silicon and Nickel Nanoparticles

The structural and photoinduced properties of silicon nanoparticles obtained by plasmachemical and electrolytic techniques and the nickel particles deposited on aluminum oxide film in ultra-high vacuum are investigated by Auger electron spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy and time-of-flight spectroscopy. It is found that substantial increase of silicon nanoparticle photoinduced luminescence can be attributed to particle specific structure, as well as to the SiO2 thin film which is formed on the nanocrystalline silicon surface. In case of Ni particles deposited on aluminum oxide film at low mean coverage of about 0.04 monolayers, when the film can be viewed as consisting of separated single adsorbed atoms or very small clusters, the photon irradiation by nanosecond pulsed laser leads to NO desorption. At monolayer Ni coverage formed at a substrate temperature of 80 K laser irradiation causes dissociation of NO molecules. Efficiency of this process at the initial stage is notably enhanced compared to that of NO on the bulk Ni (111) crystal. This enhancement can be attributed to the effect of underlying aluminum oxide support.

Structural properties of silicon nanoparticles formed by pulsed laser ablation in liquid media

Silicon nanoparticles have been formed as a result of the irradiation of single-crystal silicon targets in distilled water and liquid nitrogen, by, respectively, picosecond and femtosecond laser pulses. The main structural properties of these nanoparticles have been investigated by atomic force microscopy, transmission electron microscopy, electron diffraction, Raman scattering, and photoluminescence spectroscopy. These particles are found to be mainly spherical. The presence of crystalline and amorphous silicon phases under picosecond ablation in water is established experimentally. Irradiation by femtosecond pulses in liquid nitrogen can yield nanoparticles smaller than 5 nm in size, which are quantum dots with a characteristic photoluminescence peak near 750 nm.

Photoluminescent biocompatible silicon nanoparticles for cancer theranostic applications

Silicon nanoparticles (SiNPs) obtained by mechanical grinding of porous silicon have been used for visualization of living cells in vitro. It was found that SiNPs could penetrate into the cells without any cytotoxic effect up to the concentration of 100 μg/ml. The cell cytoplasm was observed to be filled by SiNPs, which exhibited bright photoluminescence at 1.6 eV. SiNPs could also act as photosensitizers of the singlet oxygen generation, which could be used in the photodynamic therapy of cancer. These properties of SiNPs are discussed in view of possible applications in theranostics (both in therapy and in diagnostics).

Effects of Process Conditions on the Properties of Silicon Nanoparticles Synthesized by Gas Phase Reactions Using Inductive Coupled Plasma

Silicon nanoparticles were synthesized by passing monosilane through a quartz tube wrapped with Inductive Coupled Plasma (ICP) coil. Microstructures of synthesized silicon nanoparticles were investigated with various process conditions. To research the effects of process parameters on the properties of nanoparticles, we verified the partial pressure of monosilane, the plasma power and the working pressure. The highly crystalline silicon nanoparticles were only achieved at the proper partial pressure of the reactive gas and plasma power. Partial pressure determined not only the particle size but also the crystallinity of the nanoparticles. The plasma power was controlled from 50 to 100 W which determined not the particle size but the crystallinity of nanoparticles. Especially, too low a power resulted in amorphous particles with an average sizes of 5.25 nm. As the working pressure increased, the amount of produced nanoparticles linearly increased and the maximum production yield was at 76 mg/hr. Controlling those parameters, we achieved monodispersed single crystalline silicon nanoparticles with an average diameter of 7.52 nm. Silicon nanoparticles in this study can be applied to light absorbing material for solar cells and the wavelength down-converter material of Light Emitting Diode (LED).

Modeling of electronic properties of silicon nanoparticles with dense atomic packing

Results of optimization of the atomic structure and calculation of electronic and transfer characteristics of Si13 silicon clusters with dense atomic packing and silicon nanoparticles encapsulated by transitive metal atoms (Cu, Zn, Fe, and Ni) are presented. It is demonstrated that an external electric field and a silicon nanostructure charge change significantly their energy spectrum and kinetic properties.

Topographic analysis of silicon nanoparticles-based electroluminescent devices

Electroluminescent properties of silicon nanoparticles embedded in MOS devices have been studied. Silicon rich oxide (SRO) films with 4 at.% of silicon excess were used as active layers. Intense and stable light emission is observed with the naked eye as shining spots at the surface of devices. AFM measurements on these devices exhibit a remarkably granular surface where the EL spots are observed. The EL measurements show a broad visible spectrum with various peaks between 420 and 870 nm. These EL spots are related with charge injection through conductive paths created by adjacent Si-nps within the SRO.

Optical properties of silicon nanoparticles synthesised at different heating rates via physical vapour condensation method

A physical vapour condensation method is employed to fabricate the silicon nanoparticles at different heating rates. We have grown silicon nanoparticles at two different heating rates i.e., 10°C/min and 20°C/min. It is observed that the nanoparticles synthesise at low heating rate (10°C/min) are more uniform and spherical with size varying between 10nm to 40 nm. The average surface roughness is about 160 nm as evident from the AFM images. Whereas, the silicon nanoparticles grown at higher heating rate i.e., 20°C/min looks like aggregated and appears as nanoclusters. The size of these nanoparticles varies between 5 nm to 10 nm and the average surface roughness is about 140 nm. The photoluminescence (PL) observed from silicon (Si) nanoparticles has been explained with the help of oxygen-related surface state mechanism.

Structural and optical properties of silicon nanoparticles prepared by pulsed laser ablation in hydrogen background gas

We studied the structural and optical properties of silicon (Si) nanoparticles (np-Si) prepared by pulsed laser ablation (PLA) in hydrogen (H2) background gas. The mean diameter of the np-Si was estimated to be approximately 5 nm. The infrared absorption corresponding to Si-Hn (n=1,2,3) bonds was observed at around 2100 cm-1, and a Raman scattering peak corresponding to crystalline Si was observed at around 520 cm-1. These results indicate that nanoparticles are not an alloy of Si and hydrogen but Si nanocrystal covered by hydrogen or hydrogenated silicon. This means that surface passivated Si nanoparticles can be prepared by PLA in H2 gas. The band-gap energy of np-Si prepared in H2 gas (1.9 eV) was larger than that of np-Si prepared in He gas (1.6 eV) even though they are almost the same diameter. After decreasing the hydrogen content in np-Si by thermal annealing, the band-gap energy decreased, and reached the same energy level as np-Si prepared in He gas. Thus, the optical properties of np-Si were affected by the hydrogenation of the surface of np-Si.

Optical Properties of Silicon Nanoparticles in Silica Gel Monoliths

ABSTRACTWe have synthesized highly photoluminescent monoliths by incorporating nanocrystalline Silicon (nc-Si) from Porous Silicon (PSi) into a Sol Gel Silica matrix. The optically transparent samples are the result of mixing an acid catalyzed solution of Sol-Gel and nc-Si that forms a solution of Si-nanoclusters (Si-n) that eventually after condensation for three days produces the final luminescent material. Photoluminescence (PL) basic studies show a very high orange emission band with a maximum peak that ranges between 600 nm and 750 nm. The PL emission intensity was increased up to ten times the luminescence of the native nano material PSi, the mechanical and thermal stability properties were also greatly improved. The PL corresponds to different concentrations or preparations of Sol-Gel with Si-n (Sol-Si) with a broad size distribution that produces orange and blue emissions, and for this reason we take as our future work to tailor samples with very high Si-n densities for semiconducting and photonic applications.

Properties of Silicon Nanoparticles Produced by Picosecond Pulsed Laser Ablation

AbstractSilicon nanocrystals have been fabricated by picosecond pulsed laser ablation. Size control over the nanocrystals can be achieved by careful selection of experimental geometry, laser fluence, laser wavelength, backing gas pressure and distance from plume center. Measurements of optical absorption and photoluminescence confirm that particle size variation does significantly affect bandgap and emission efficiency. Differences between results published previously for nanosecond pulsed laser ablation will also be discussed.

Excitation Intensity and Temperature Dependent Photoluminescence Behavior of Silicon Nanoparticles

AbstractThe luminescence properties of silicon nanoparticles have been studied as a function of the excitation light intensity, the temporal Nature of the excitation source, and of sample temperature. The excitation intensity dependence of the luminescence was found to depend strongly on the temporal Nature of the excitation source. Under high intensity excitation from a pulsed 355 nm source, the photoluminescence (PL) intensity saturates and the peak PL wavelength shifts to the blue at room temperature. This behavior persists at reduced temperature. In contrast, under high intensity excitation using a cw 488 nm source at room temperature, the PL intensity saturates but does not shift in wavelength. At reduced temperatures, there is no saturation of luminescence intensity with high intensity cw excitation. These differences indicate that photogenerated carrier recombination occurs via different pathways depending on the temporal profile of the excitation, with cw excited samples following the expected Auger pathway while pulsed samples exhibit a state filling mechanism. Auger models for the pulsed behavior are found to be inconsistent with the experimental data. The temperature dependence of the PL from a pulsed excited sample for a constant excitation intensity was also monitored. The variation of the peak emission wavelength was found to be similar in magnitude to that observed for amorphous silicon, suggesting that structural disorder may play a role in the luminescence. The change in emission intensity was fairly weak, indicating enhanced carrier confinement, as would be expected in a quantum confined system.