COMPARISON OF THE EFFICIENCY OF DIFFERENT DETECTORS OF THE SCANNING ELECTRONIC MICROSCOPE «MIRA-LMH» FOR STUDYING MICROSTRUCTURE OF NANOMATERIALS

На первом этапе были синтезированы объекты исследования - диоксид кремния методом Штобера, где в качестве прекурсора использовали тетраэтоксисилан, и нанокомпозит ZnO - Au золь-гель методом с использованием в качестве прекурсора 2 - водного ацетата цинка. На втором этапе, микроструктуру и морфологию полученных образцов исследовали методом растровой электронной микроскопии на сканирующем электронном микроскопе «MIRA-LMH» фирмы «Tescan» с применением как классического детектора вторичных электронов, так и дополнительных детекторов - внутрилинзового детектора вторичных электронов и детектора отраженных электронов. В результате исследований установлено, что при использовании детектора вторичных электронов получаются изображения с топографическим контрастом и практически без шумов. При использовании внутрилинзового детектора вторичных электронов создаются изображения только материального контраста, без влияния рельефа поверхности. Также использование данного детектора позволило получить высококачественные изображения с большим разрешением на расстоянии от образца 5 мм. При использовании детектора отраженных электронов с рабочим расстоянием до образца 8 мм и увеличении разрешающей способности микроскопа, полученные изображения имеют низкий контраст границ, но представляют композиционную информацию с высокой чувствительностью. Таким образом, установлено, что внутрилинзовый детектор вторичных электронов, с рабочим расстоянием до образца 5 мм, является оптимальным для получения четких изображений микроструктры поверхности наноматериалов при многократном увеличении. At the first stage, the objects of study were synthesized - silicon dioxide by the Stober method, where tetraethoxysilane was used as a precursor, and a nanocomposite ZnO - Au by the sol-gel method using the aqueous zinc acetate dihydrate as a precursor. At the second stage, the microstructure and morphology of the obtained samples were investigated by scanning electron microscopy on a «MIRA-LMH» scanning electron microscope (Tescan company) using both a classical secondary electron detector and additional detectors - intralens secondary electron detector and back-scattered electrons detector. As a result of the research, it was found that when using the secondary electron detector, practically no noise images with topographic contrast are obtained. When using the intralens secondary electron detector, images of only material contrast are created, without the influence of the surface relief. Also, the use of this detector made it possible to obtain high-quality images with a high resolution at a distance of 5 mm from the sample. When using a back-scattered electrons detector with a working distance to the sample of 8 mm and increasing the resolution of the microscope, the resulting images have low border contrast, but represent compositional information with high sensitivity. Thus, it was found that the intralens secondary electron detector with a working distance of 5 mm to the sample is optimal for obtaining clear images of the microstructure of the surface of nanomaterials at multiple magnifications.

A Facile Synthesis of Fe3O4@SiO2@ZnO for Curcumin Delivery

This paper proposed an engineered silica-coated Fe3O4 with ZnO nanoparticle, prepared by a coprecipitation/Stöber method as a curcumin delivery system. To this end, the structural characterization of the nanocomposite was performed by Fourier transform infrared spectroscopy (FT-IR), ray diffraction (XRD), VSM, and TEM. The findings show that the synthesized nanocomposite has a semispherical structure with an average particle size of 50-70 nm and excellent magnetization properties (21.4 emu/g).

Calcium Carbonate@silica Composite with Superhydrophobic Properties

In this paper, spherical calcium carbonate particles were prepared by using CaCl2 aqueous solution + NH3·H2O + polyoxyethylene octyl phenol ether-10 (OP-10) + n-butyl alcohol + cyclohexane inverse micro emulsion system. Then, nanoscale spherical silica was deposited on the surface of micron calcium carbonate by Stöber method to form the composite material. Scanning electron microscope (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and structure of the composite material. It is found that the surface of the composite material has a micro-nano complex structure similar to the surface of a “lotus leaf”, making the composite material show hydrophobicity. The contact angle of the cubic calcium carbonate, spherical calcium carbonate and CaCO3@SiO2 composite material were measured. They were 51.6°, 73.5°, and 76.8°, respectively. After modification with stearic acid, the contact angle of cubic and spherical CaCO3 were 127.1° and 136.1°, respectively, while the contact angle of CaCO3@SiO2 composite was 151.3°. These results showed that CaCO3@SiO2 composite had good superhydrophobicity, and the influence of material roughness on its hydrophobicity was investigated using the Cassie model theory.

Synthesis and Characteristics of Multifunctional Magneto-luminescent Nanoparticles by an Ultrasonic Wave-assisted Stӧber Method

Multifunctional magneto-luminescent nanoparticles (NPs) were synthesised by an ultrasonic wave-assisted Stöber method. The multifunctional NPs are composed of magnetic NPs (Fe3O4) and photoluminescent quantum dots (QDs) (ZnS:Mn) in amorphous silica (SiO2) matrix, which was confirmed by X-ray diffraction, Raman scattering spectroscopy, and transmission electron microscopy (TEM). The multifunctional NPs have high saturation magnetisation at room temperature simultaneously with strong photoluminescence (PL) in visible light, which is promising for biomedical applications.

Removal of Oil Pollution in water using hydrophobic silica

Nowadays the contamination in waters by oily substances turns out to be a problem of world-wide scope and although some methods of removal of oils in water exist; these present some limitations; therefore, this project proposes the use of hydrophobic silicas as absorbent materials for oily substances. Modified silicas (R-SiO2) were synthesized using the Stöber method, modifying the surface by co-condensation. Tetraethyl-orthosilicate (TEOS) and two surface modifiers were used as silica former: Methyl-trimethoxysilane (MeTEOS) and n-octyl-triethoxysilane (nOctyl-TEOS). The R-SiO2 were characterized by infrared spectroscopy identifying the modifying groups and their hydrophobicity was qualitatively evaluated according to the change in solubility in water. Finally, the removability of an automotive motor oil was evaluated by determining the amount of oil removed per gram of modified silica.

Fabrication, Characterization of SiO2 Nanospheres and SiO2 Opal Photonic Crystals

In this report, we presented the usage of Stober method to fabricate SiO2 nanospheres and self-assembly method to make SiO2 opal photonic crystals based on the fabricated SiO2 nanospheres. An averaged size of SiO2 nanospheres was controlled by varying concentrations of NH4OH and TEOS. Crystal structure and morphology of particles was investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Experimental results showed that SiO2 nanospheres possess amorphous crystal structure with sizes ranged from 150 to 300 nm. The diffuse reflection spectra show the reflection peaks of the SiO2 opal photonic crystals from 410 nm to 520 nm.