Прыжковая проводимость Мотта и Эфроса-Шкловского в пленках из наночастц Si, легированных фосфором и бором

The electrical characteristics of thin films formed from Si nanoparticles (nc-Si) with various degrees of doping are studied. To exclude the influence of ionic conductivity, the current parameters of the films were recorded in an ultrahigh vacuum (P ~ 3 – 5∙10–9 Torr) with preliminary high-temperature (9500C) annealing. An analysis of the temperature dependences of the conductivity showed that in nc-Si films formed from heavily doped nanoparticles (the concentration of free electrons ne is greater than 1019 cm-3), the transport is determined by variable-length hopping (VRH). In these samples, the Mott conductivity prevails at temperatures above 300C and at lower temperatures, the Efros-Shklovskii type variable range hopping conduction is dominate. In films with a medium level of doping of nanoparticles (ne <1019 cm-3), transport is realized by the Mott, Efros - Shklovskii and thermally activated conductivities. At the same time, thermally activated conductivity is dominated at temperatures above 560K. In nc-Si films formed from undoped nanoparticles, the transport parameters are determined by thermally activated conductivity and Mott's conductivity. Conductivity of Efros - Shklovskii is not observed in such films. From the analysis of the parameters corresponding to the Mott and Efros - Shklovsky conductivities, the localization lengths of wave functions, the density of states at the Fermi level (g (EF)), and average hopping lengths are found. The average hopping lengths in nc-Si films from nanoparticles pre-etched in HF are in the range 56 - 86 nm, which indicates that hopping in such films occurs via intermediate nanoparticles.

Iodine and Selenium Biofortification of Chervil Plants Treated with Silicon Nanoparticles

Production of functional food with high levels of selenium (Se) and iodine (I) obtained via plant biofortification shows significant difficulties due to the complex interaction between the two elements. Taking into account the known beneficial effect of silicon (Si) on plant growth and development, single and joint foliar biofortification of chervil plants with potassium iodide (150 mg L−1) and sodium selenate (10 mg L−1) was carried out in a pot experiment with and without Si nanoparticles foliar supplementation. Compared to control plants, nano-Si (14 mg L−1) increased shoot biomass in all treatments: by 4.8 times with Si; by 2.8 times with I + Si; by 5.6 times with Se + Si; by 4.0 times with I + Se + Si. The correspondent increases in root biomass were 4.5, 8.7, 13.3 and 10.0 times, respectively. The growth stimulation effect of Se, I and I + Se treatments resulted in a 2.7, 3.5 and 3.6 times increase for chervil shoots and 1.6, 3.1 and 8.6 times for roots, respectively. Nano-Si improved I biofortification levels by twice, while I and Se enhanced the plant content of each other. All treatments decreased nitrate levels, compared to control, and increased the photopigment accumulation. Improvement of total antioxidant activity and phenolic content was recorded only under the joint application of Se + I + Si. Foliar nano-Si treatment affected other element content in plants: decreased Na+ accumulation in single and joint supplementation with Se and I, restored Fe, Mn and Cr amount compared to the decreased levels recorded in separately Se and I fortified plants and promoted Al accumulation both with or without Se and I biofortification. The results of this research suggest high prospects of foliar nano-Si supply for enhancing both growth and joint I/Se biofortification of chervil.

Nano Silicon Composite with Gelatin/Melamine Derived N-doped Carbon as an Efficient Anode Material for Li-ion Batteries

Silicon (Si) has a high theoretical capacity and low working potential vs. Li/Li+, and has been investigated as the most capable negative electrode material for lithium-ion batteries (LIBs). However, Si undergoes significant volume changes during the Li+ alloying/ dealloying processes, leading to unstable cycle life and limiting its practical applicability in anodes. Introducing carbon into the Si anodes can effectively address the Si drawbacks, while providing advantages of improved conductivity and structural stability. In this study we choose gelatin/ melamine combination as an eco-friendly and cost-effective source for nitrogendoped carbon to make a Si composite. The prepared composite was studied as an anode material for LIBs, and it delivered excellent cyclability with 2175 mAh g-1 capacity after 50 cycles with 86% capacity retention at 200 mA g-1. The composite exhibited superior rate capability and improved Li+ diffusion properties compared with bare Si nanoparticles (Si NP). The significant enhancement could be attributed to the structural stability and conductivity provided by the nitrogen-doped carbon matrix. This work promotes emerging batteries with low-cost materials as a promising solution for increasing energy storage requirements.

Effect of temperature on the structure of Cu/Si composite Janus nanoparticles

This work determined the effect of temperature on the formation of composite Cu/Si nanoparticles by the molecular dynamics (MD) method. For the first time, the temperature dependence of the potential energy of hybrid nanoparticles, which were single-crystal spherical clusters cut from an ideal lattice, was studied. It is shown that phase transitions and structural ordering cause a sharp change in the potential energy of composite nanoparticles. The structural arrangement of copper nanoparticles at high temperatures was found.

Structure and Magnetic Properties Of Fe/Si Nanoparticles Prepared by High Energy Milling Process

The structure and magnetic properties of Fe/Si nanoparticle prepared by high energy milling process have been examined, focusing on the phase transition. Fe/Si nanoparticles were processed by high energy milling (HEM) for 10 hours to 50 hours with a weight per cent ratio of 9:1. Based on the X-ray diffraction (XRD) pattern, transmission electron microscope (TEM) observations, and vibrating sample magnetometer (VSM) analysis, the phase transition induced by HEM, were evidenced. The effect of structural state and the particle size on the magnetic properties such as magnetization was also studied. It was found that iron and iron oxides (-Fe2O3/ Fe3O4) phase were exhibited on all milled samples. The magnetization value of Fe/Si nanoparticles increased up to 20 hours with 142 emu/gr saturated magnetization and then decreased linearly with increasing milling time. Referring to the XRD result, this decline was initially caused by the iron oxide formation and magnetic interaction between iron and iron oxides nanoparticles. The phase and magnetic properties value changes related to the interaction mechanism between Fe atoms caused by interstitial occupied of Si atoms, particle size reduction, and oxidation process.

Temperature oscillations during photoinduced heating of aqueous suspensions of silicon nanoparticles

Temperature oscillations (pulsations) were detected in aqueous suspensions of silicon (Si) nanoparticles NPs under laser irradiation with highly absorbed light. The temperature pulsation frequency was found to depend on the NPs concentration in suspension and laser irradiation power. The observed phenomenon is assumed to be caused by the local overheating of Si NPs close to the boiling point of water, while the average heating of the surrounding liquid was insignificant. The observed phenomenon is discussed in view of potential applications in local photo-induced hyperthermia of cancer.