Wet-chemistry processing of powdery raw material for high-tech ceramics

The purpose of this study was to develop wet-chemistry approaches for the synthesis of ultradispersed and mesoporous metal oxide powders and powdery composites intended for usage in the production of ceramic materials with desired properties. The focus is on the development of template synthesis of mesoporous metal silicates as well as obtaining nano- and subnanopowders by a modified sol-gel technique and template methods. Families of mesoporous (2 to 300 nm) metal silicates and nano-oxides and subnanopowders (4 to 300 nm) were synthesized by the template method and modified sol-gel technique, respectively. Texture and morphology of the obtained objects have been studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and N2 adsorption-desorption. It was found that morphological parameters of the metal oxide obtained by the modified sol-gel technique depend nonlinearly on the initial molar ratio value of the sol stabilizer and metal in the reaction medium as well as the nature of the stabilizer. It has been shown that the nature of structure-directing components determines the morphology of the silicate obtained by the template method: dispersion and shape of its particles. The developed laboratory technology corresponds to the conception of soft chemistry and may be adapted to the manufacture of ultradispersed materials for catalysis, solar cells, fuel cells, semiconductors, sensors, low-sized electronic devices of new generation, etc

Two-stage ZnS Shell Coating on the CuInS2 Quantum Dots for Their Effective Solubilization

High-precision diagnostics is one of the necessary conditions for effective treatment of diseases. Bioimaging is one of the most promising modern methods of tumor diagnosis. High-quality luminophores are necessary for effective bio-imaging. CuInS2(CIS) quantum dots (QDs) are very promising luminophores for these applications due to their low toxicity and long-term stability of their properties. Two batches of CIS QDs with different positions of the luminescence maximum have been obtained. The position of the luminescence maximum can be controlled by changing the Cu to In ratio; a decrease in this ratio cause a blue shift of the luminescence. The standard procedure of CIS synthesis yields QDs covered with thiols, which form strong bonds with the surface and prevent the ligand exchange; hence, it is very hard to adapt CIS QDs for biological tasks using the standard hydrophobic to hydrophilic ligand exchange procedure. We have developed a two-stage shell coating procedure yielding CIS QDs covered with amines, which is suitable for ligand exchange; hence,the resultant QDs can be adapted for modern biological and medical applications. Keywords: Quantum dots, CuInS2, solubilization

The Effect of Quantum Dot Shell Structure on Fluorescence Quenching By Acridine Ligand

The current strategy for the development of advanced methods of tumor treatment focuses on targeted drug delivery to tumor cells. Quantum dot (QD) - semiconductor fluorescent nanocrystal, conjugated with a pharmacological ligand, such as acridine, ensures real-time tracking of the delivery process of the active substance. However, the problem of QD fluorescence quenching caused by charge transfer can arise in the case when acridine is bound to the QD. We found that QD shell structure has a defining role on photoinduced electron transfer from QD on acridine ligand which leads to quenching of QD photoluminescence. We have found that multishell CdSe/ZnS/CdS/ZnS QD structure provides minimal reduction of photoluminescence quantum yield at minimal shell thickness compared to classical thin ZnS or “giant” shells. Thus, CdSe/ZnS/CdS/ZnS core/multishell QD could be an optimal choice for engineering of small-sized acridine-based fluorescent labels for tumor diagnosis and treatment systems. Keywords: Quantum dot, photoluminescence quenching, DNA ligand, acridine derivative