Synthesis and Characterization of CDS/SIO2 Nanocomposites

Core-shell nanocomposites are gaining lots of interest due to their potential application in different field like catalysis, sensor, electronic, biomedical ect. In addition, they show better properties when two different element nanoparticles coating each other than a single nanoparticles is used. In this thesis, we studied the synthesis Rout and characterization of CdS/PVA nanoparticles by hydrothermal method with different concentration of cadmium acetate deposited in a PVA matrix. SiO2 nanoparticles by the sol-gel method with different concentrations of TEOS and CdS / SiO2core-shell nanocomposites by encapsulation Stober method. The result obtain by analysis of the product of CdS/PVA, SiO2 and CdS / SiO2core-shell nanocomposites have successful. The result of X-ray diffraction (XRD) analysis shows the cubic and hexagonal structure of the CdS nanoparticles, amorphous phase of SiO2 and CdS/SiO2 core-shell nanocomposites, The electrical properties including the d.c. conductivity of CdS/PVA were found to be 2 x 10-7 S/cm, and optical band gap energy 2.53 eV respectively. To improve conductivity of SiO2 nanoparticles when prepared CdS/SiO2 nanocomposites were found to be 6 x 10-10 S/cm . The FTIR measurement absorption centred at 690 cm-1 corresponding to the Cd–O. And at 1200 cm-1 is assigned to Si-O group. However, The peak of PVA/CdS/SiO2 particles was wider at about 3500 cm–1.The morphology of nanopatricles and nanocomposite study by (TEM) mentioned that the composites were estimated as being from 5-15 nm for CdS, 25- 140 nm for SiO2, and the CdS/SiO2 was estimated to be around 15 nm for the core and above 30 nm for the shell

Up-scalable synthesis of size-controlled copper ferrite nanocrystals by thermal treatment method

Close-packed cubic copper ferrites (CuFe2O4) nanoparticles were synthesized using an effective thermal-treatment method directly from an aqueous solution containing copper and iron nitrates as metal precursors and poly(vinyl pyrrolidone) as a capping agent. The FTIR spectra of the calcined samples revealed the vibration bands of Fe–O and Cu–O at 315 and 535 nm respectively. The structural, morphological, optical and magnetic properties of the nanocrystal powder samples were analyzed using various characterization techniques. The powder X-ray diffraction unveiled the formation of spinel phase of CuFe2O4 with the average particle size determined from TEM images increased from 24 to 34 nm at the calcination temperatures between 773 and 1173 K. The band gap calculated using Kubelka–Munk function from the UV–visible diffuse reflectance spectra decreased from 2.64 to 2.45 eV with increasing calcination temperature. The electron spin resonance (ESR) spectroscopy confirmed the presence of unpaired electrons in the calcined samples. The g-factor increased from 2.10497 to 2.57056 and the resonance magnetic field decreased from 3.11599×10−7 to 2.55161×10−7 A/m with increasing calcination temperature

Physical properties of ZnSe and CdSe semiconductor nanoparticles synthesized by thermal treatment and gamma irradiation routes

Several methods have been utilized previously to synthesize metal chalcogenide nanoparticles with enhanced chemical and physical properties. However, most of these methods have used a complicated procedure, longer reaction times, and employed toxic reagents of expensive materials. Current study employed two physical methods, the thermal treatment to synthesis pure ZnSe and CdSe semiconductor nanoparticles and their (Cd0.5Zn0.5)Se nanocomposite under a constant N2 gas flow. Gamma radiation method was used to prepare pure ZnSe and CdSe semiconductor nanoparticles. For the first method, an aqueous solutions of metal nitrate at different concentrations were mixed with 2 g of PVP, ethylenediamine(en) as a solvent of Se and deionized water as a solvent were prepared at calcination temperatures of 450-700°C. The samples were characterized by TGA, FTIR, EDX, XRD, TEM, and UV-Vis. FTIR analysis results confirmed the removal of organic matters and the presence of semiconductor nanoparticles at calcination temperatures 450-700°C. The elemental composition of the samples obtained by EDX spectroscopy has further evidence that the formation of ZnSe and CdSe nanoparticles and their nanocomposites. It was found that the phase formations of ZnSe and CdSe nanoparticles were cubic and hexagonal face-centered, respectively. The TEM images confirmed the increment of particle size from 12 to 26 nm for ZnSe and from 6 to 37 nm for CdSe and as well as from 12 to 24 nm for (Cd0.5Zn0.5)Se nanocomposites due to elevated calcination temperature and material concentration. The particle size of nanocrystals was also determined from XRD spectra. The estimated average sizes in the range 10.5-24 nm for ZnSe, 6-33 nm for CdSe nanoparticles and 10.5-25 nm for (Cd0.5Zn0.5)Se nanocomposites. While the optical properties were measured using UV-Vis spectrometer and the band gap ranged (3.956-4.158), (2.31-3.69) and (2.24-3.71) eV for ZnSe, CdSe and (Cd0.5Zn0.5)Se nanostructures, respectively. ZnSe and CdSe semiconductor nanoparticles were also synthesized using a single-step radiolytic approach in aqueous solution containing metal sulfite were mixed with 2 g of PVP, ethylenediamine(en), deionized water, and IPA alcohol under irradiation with Co-60 gamma rays at dose of 120 kGy. The hydrate electrons created in water are responsible for the formation of CdSe and ZnSe nanoparticles. The final samples were characterized by EDX, XRD, TEM, and UV-Vis. The X-ray powder diffraction patterns reveal successful hexagonal crystal structure for both CdSe and ZnSe nanoparticles, with the average crystallite sizes of 16.3 and 10.7 nm, respectively. The EDX was used to confirm the stoichiometric elemental composition of Zn, Cd and Se in the samples. The TEM micrograph shows that CdSe and ZnSe nanoparticles are spherical in shape, with an average diameter of 17.3 and 11.2 nm, respectively. The optical band gaps determined from UV-Visible absorption spectra are between 2.87 and 3.58 eV for the CdSe and ZnSe nanoparticles, respectively

Simple synthesis of ZnSe nanoparticles by thermal treatment and their characterization

A simple thermal treatment was used to synthesize ZnSe nanoparticles at different calcination temperatures in a nitrogen flowing. The samples of ZnSe nanoparticles were prepared by reacting zinc nitrate (source of zinc) and selenium powder with Polyvinylpyrrolidone (capping agent). Analysis of their X-ray diffraction patterns suggested the formation of an amorphous phase of the unheated material before calcination, which then transformed into a cubic crystalline structure of ZnSe nanoparticles after calcination. The phase analyses using energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy confirmed the presence of Zn and Se as the original compounds of prepared ZnSe nanoparticle samples. The average particle size of the samples increased from 7 ± 5 to 18 ± 3 nm as the calcination temperature was increased from 450 to 700 °C, which is also supported by the transmission electron microscopy results. Diffuse UV–visible reflectance spectra were used to determine the optical band gap through the Kubelka–Munk equation; the energy band gap was found to decrease from 4.24 to 3.95 eV with increasing calcination temperature

Formation of a colloidal CdSe and ZnSe quantum dots via a gamma radiolytic technique

Colloidal cadmium selenide (CdSe) and zinc selenide (ZnSe) quantum dots with a hexagonal structure were synthesized by irradiating an aqueous solution containing metal precursors, poly (vinyl pyrrolidone), isopropyl alcohol, and organic solvents with 1.25-MeV gamma rays at a dose of 120 kGy. The radiolytic processes occurring in water result in the nucleation of particles, which leads to the growth of the quantum dots. The physical properties of the CdSe and ZnSe nanoparticles were measured by various characterization techniques. X-ray diffraction (XRD) was used to confirm the nanocrystalline structure, energy-dispersive X-ray spectroscopy (EDX) was used to estimate the material composition of the samples, transmission electron microscopy (TEM) was used to determine the morphologies and average particle size distribution, and UV-visible spectroscopy was used to measure the optical absorption spectra, from which the band gap of the CdSe and ZnSe nanoparticles could be deduced