Based on analysis of optical absorption data for CdS nanocrystals obtained by sol-gel technology in gelatin, we have studied the effect of technological factors (reagent concentrations, gelatin concentration) on the growth process and size distribution of the synthesized nanocrystals. Depending on the reagent concentration, we synthesized CdS nanocrystals with mean radii in the range r _ = 1.9-2.4 nm. We have shown that for a low gelatin content (1%), nanocrystals of different sizes are formed (1.7 nm and 2.6 nm). With an increase in the gelatin concentration, the size dispersion decreases and nanocrystals of a single mean radius (2.3 nm) are formed. We have established a correlation between the size dispersion and the shape of the photoluminescence spectrum of the CdS nanocrystals.Introduction. The physics of nanosized objects is a rapidly developing field, where studies of polymer nanosystems with inorganic semiconductors have stimulated considerable interest. This is because of both their original electrophysical, physicochemical, optical, and other properties, and the possible practical implementation in various instruments and devices, in particular light-emitting diodes [1, 2], photoluminescent and solar cells, biological sensors [3, 4], etc. An important aspect of successful solution of fundamental and applied problems in the physics of nanoparticles and nanosystems is development of the technology for obtaining them. One method for preparing nanoparticles is the colloidal chemical method ("sol-gel" technology), based on chemical reaction between the reagents in solution in the presence of stabilizers. The stabilizer prevents joining of the particles and their further growth, where the particles remain in solution. The colloidal chemical synthesis of nanoparticles is affected by a large number of factors, including the concentration of the starting materials, the type and concentration of the stabilizers, the temperature, the pH of the solution, and the reaction time. The possibility of controlling the synthesis by varying the indicated parameters, with the aim of achieving the required properties of the material (size and crystalline structure, dispersed distribution, electrophysical and optoelectronic properties) is one of the advantages of chemical methods for obtaining semiconductor nanoparticles. An advantage of sol-gel technology is also the possibility of making homogeneous thin films and modifying the sample material to obtain a specific form of the devices with low material costs.The most frequently used stabilizers are organic compounds such as polyphosphates [5][6][7][8], trioctylphosphines [9], and thiols [10]. Using trioctylphosphine/trioctylphosphine oxide, cadmium chalcogenide compounds have been obtained with a narrow particle size distribution. The characteristics of semiconductor materials obtained in the above-indicated stabilizers are presented in [11].The choice of stabilizer is determined by many factors. The major factor is the ability to hinder coagulation of the particles, preventi...

In this study we investigated the mechanisms of action and effect of plant growth promoting rhizobacteria (PGPR) Bacillus subtilis No.2 when utilized alone and in conjunction with a humic fertilizer (HF). Different mechanisms of action of B. subtilis No.2 and HF Stimulife on tomato plants Original Research Article

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Photoluminescent (PL) porous layers were formed on p-type silicon by a metal-assisted chemical etching method using H 2 O 2 as an oxidizing agent. Silver particles were deposited on the (100) Si surface prior to immersion in a solution of HF and H 2 O 2 . The morphology of the porous silicon (PS) layer formed by this method was investigated by atomic force microscopy (AFM). Depending on the metal-assisted chemical etching conditions, the macro-or microporous structures could be formed. Luminescence from metal-assisted chemically etched layers was measured. It was found that the PL intensity increases with increasing etching time. This behaviour is attributed to increase of the density of the silicon nanostructure. It was found the shift of PL peak to a green region with increasing of deposition time can be attributed to the change in porous morphology. Finally, the PL spectra of samples formed by high concentrated solution of AgNO 3 showed two narrow peaks of emission at 520 and 550 nm. These peaks can be attributed to formation of AgF and AgF 2 on a silicon surface.