Optical properties of cadmium sulfide nanocrystals obtained by the sol-gel method in gelatin

Abstract

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...

Synthesis of cadmium sulfide CdS nanoparticles in a silicate glass matrix

“…The reduction in the total amount of nanoparticles may be due to the dissolution of small particles, which may lead to the growth of large particles. Such a particle growth mech anism corresponds to Ostwald ripening [8,[24][25][26].…”

Cytocompatible Fluorescent Quantum Dot/PEG‐Chitosan Bioconjugates for Nanomedicine Applications

“…The average CdS nanoparticle sizes were determined by using Henglein's empirical model,38 which relates the diameter of the CdS nanoparticle (2 R ) to the exciton absorption transition onset ( λ exc ) in the UV/Vis spectra according to Equation (1). …”

Electronic Properties of Surface Vacancies in CdS Nanocrystals

“…Дослідженню фотолюмінесцентних властивостей та встановленню механізмів випромінювальної рекомбінації нанокристалів CdS присвячена ціла серія робіт [14][15][16][17][18][19]. Проте, ще багато факторів є невизначеними, зокрема нез'ясованою залишається природа центрів випромінювальної рекомбінації в НК CdS.…”

“…Проте, ще багато факторів є невизначеними, зокрема нез'ясованою залишається природа центрів випромінювальної рекомбінації в НК CdS. В багатьох роботах висувалось припущення, що висвічування відбувається через поверхневі дефекти невідомої природи, через центри V Cd -V S [15,19] чи через акцепторні центри V Cd [16][17][18].…”