Fozia Z. Haque

Synthesis and Characterization of SiO2 Nanoparticles by Sol-Gel Process and Its Degradation of Methylene Blue

Nanomaterials are used for the miniaturization of particular electronic device. But new era of technology demands a cheaper and more commercial method to produce excellent material especially silicon dioxide. The present work deals with the sol-gel synthesis of SiO2 material and also provides a basic understanding of the effect of calcination temperature on the growth of SiO2 by hydrolysis of TEOS with ethanol, deionized water and catalyst mixture. The properties of resulting materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), AFM and optical properties through UV-visible spectroscopy and Photo Luminescence (PL). The XRD study of pure SiO2 with calcination temperature at 300°C shows well crystalline characteristics and having hexagonal crystal structure. SEM results show obtained silica particles were having spherical morphology. The proper temperature the PL intensity was reduced and the shape of the emission spectrum slightly split into sharp peaks. UV-visible absorbance spectra of the silica samples having wide band gap showing absorbance in the ultra violet region. The

PVP Assisted Shape-Controlled Synthesis of Self-Assembled 1D ZnO and 3D CuO Nanostructures

Self-assembled one-dimensional (1D) zinc oxide (ZnO) rods and three-dimensional (3D) cupric oxide (CuO) cubes like nanostructures with a mean crystallite size of approximately 33 and 32 nm were synthesized through chemical route in the presence of polyvinylpyrrolidone (PVP) under mild synthesis conditions. The technique used for the synthesis of nanoparticles seems to be an efficient, inexpensive and easy method. X-Ray diffraction patterns confirmed well crystallinity and phase purity of the as prepared samples, followed by the compositional investigation using Fourier Transform Infrared (FT-IR) spectroscopy. The formation of ZnO nanorods and CuO nanocubes like structures were through Scanning Electron Microscopy (SEM) images. The mechanism and the formation factors of the self-assembly were discussed in detail. It was clearly observed from results that the concentration of precursors and PVP were important factors in the synthesis of self-assembly ZnO and CuO nanostructures. These self-assembly nanostructures maybe used as novel materials in various potential applications.

Rare earth ion (La, Ce, and Eu) doped ZnO nanoparticles synthesized via sol-gel method: Application in dye sensitized solar cells

Dye-sensitized solar cells (DSSCs) were fabricated by using ZnO nanoparticles as working electrode material synthesized via simple and cost effective sol-gel method. Crystallography and morphology was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM), respectively. Among various rare earth ions, 1.0 mol % La, Ce, and Eu doped ZnO nanoparticles based photoanodes were used to test DSSC performance. Lower efficiency (η = 1.14%) for La ion doped ZnO nanoparticles based cell was observed. A much lower photocurrent Jsc = 2.52 mA/cm2 with 0.60% efficiency (η) for the Ce ion doped ZnO nanoparticles based prototype was observed as compared to that (Jsc = 3.86 mA/cm2 with η = 1.24%) of the undoped one which may be due to the formation of opposite internal electric potential difference in the cell. Furthermore, the improvement in efficiency (η = 1.36%) and Jsc = 3.99 mA/cm2 for Eu ion doped ZnO can be attributed to enhanced electron injection and transport abilities. This indicates that 1.0 mol % Eu ion doped ZnO film possesses better electrical conductivity probably due to the existence of high-valance Eu ions in the ZnO matrix which might be promising in ZnO-based dye sensitized solar cell.

Optical investigation of various morphologies of ZnO nanostructures prepared by PVP-assisted wet chemical method

Various morphologies of zinc oxide have been successfully synthesized via simple poly-vinylpyrrolidone (PVP) assisted wet chemical method. Herein, a comparative study between three different morphologies of ZnO, namely nanoparticles (NP’s), nanowalls (NW’s) and nanorods (NR’s) has been presented. The structural and spectroscopic results reveal that the addition of PVP as capping agent greatly influences the structural and optical behavior of ZnO. X-ray diffraction (XRD) results confirmed pure phase ZnO nanostructures with well crystallinity. It was observed from results that increasing concentration of poly-vinylpyrrolidone from half to equimolar ratio lattice imperfections decrease. ZnO nanorods have biggest crystallite size compared with nanowalls and nanoparticles, confirmed through X-ray diffraction study. The formation of three different morphologies was observed through scanning electron microscopy (SEM). The FTIR and Raman spectroscopic results reveal significant shifts for these ZnO nanostructures in the typical modes assigned to Zn-O, which intercorrelated with the XRD results. The optical band gap energies were found to be decreased from ∼3.22 eV for ZnO nanoparticles to 3.14 eV for ZnO nanorods. It was investigated from photoluminescence study that PVP capped ZnO nanostructures have reduced surface trap states and therefore the UV emission and visible emission regions overlap to form a single band. The physical properties and optical behavior realized that, as prepared samples might be applied in energy storage devices and solar cells.

Controlled synthesis of flower like zinc oxide nanostructures using ionic liquid through a simple alkaline aqueous solution growth technique

This article describes the synthesis of ZnO nanostructures with different morphologies such as, flakes-like, flowers or mixture of both morphologies. The growth rate is enhanced by adjusting the concentration of ionic liquid (IL): Benzyltrimethylammoium hydroxide (BTMAH) and sodium hydroxide in reaction mixture. Different structures are obtained including a unique flower like ZnO nanostructures. These structures show three-order symmetry, groups of many oriented flakes and leaves grown on the branches symmetrically, indicating an interesting fractal growth. The products have been investigated by XRD, Scanning Electron Microscopy (SEM), Atomic force microscopy (AFM), Fourier Transform Infrared (FTIR), UV-Vis and photolumincence (PL). According to the investigation on the growth process, it was confirmed that as-prepared samples of ZnO nanoparticles morphologies and properties strongly dependant on the ratio of alkaline and IL.

pH-Dependent Single-Step Rapid Synthesis of CuO Nanoparticles and Their Optical Behavior

This paper reports the pH-dependent growth of copper oxide (CuO) nanoparticles by wet chemical precipitation method using pH value of the samples as the only variable parameter. The phase purity, morphology, optical behavior, and elemental analysis of synthesized nanoparticles are shown to be critically dependent on the pH of the samples. Scanning electron microscope (SEM) results shows that a higher pH results well-defined CuO nanoflakes. X-ray powder diffraction (XRD) results disclosed that the growth of pure CuO with monoclinic structure at higher pH 8, whereas mixed phase was formed at lower pH 7. The average crystallite size of samples prepared at pH 8 to 10 was varying from 23.36 to 25.78 nm. The infrared spectroscopy showed that the O–H stretching peaks become narrow with an increase in the pH value. Optical results revealed the existence of the sharp absorption edges with precise excitonic features and photoluminescence bands both located at visible and near infrared spectral region attributed to the excellent optical behavior and narrow size distribution of particles. The additional near infrared band in photoluminescence spectrum located at 860 nm is attributed the defect-related luminescence. The growth mechanism of CuO nanostructures was discussed in the light of our findings.

Optical study and ruthenizer (II) N3 dye-sensitized solar cell application of ZnO nanorod-arrays synthesized by combine two-step process

Highly dense ZnO nanorod-arrays were successfully synthesized with uniform c-axis growth by using combine two-step process: sol-gel spin coating followed by the aqueous solution growth method. Structural and optical properties of ZnO nanorod-arrays were investigated. The X-ray diffraction results revealed that ZnO nanorod arrays exhibit wurtzite hexagonal crystal structure with a dominant (002) peak with high crystallinity. Nanorods of 3–4 μm length and 500 nm diameter, with surface roughness ∼20 nm were observed. Furthermore, Raman spectroscopic results revealed the presence of E2 peak ∼438 cm–1 which again corroborated the existence of wurtzite crystal structures assigned to ZnO. The optical transmittance spectrum indicated that the transmittance of more than 80% was observed in the visible and infrared (IR) regions with the optical band-gap energy ∼3.35 eV. Photoluminescence spectrum showed peaks in ultra-violet (382.0 nm) and green region (524.9 nm), which specified good-quality crystallite formation containing high density of surface defects, zinc interstitials and oxygen-vacancies. Ruthenizer (II) N3-dye loaded sensitized solar cell test illustrated that the uniform ZnO nanorod-arrays as working electrode with a short circuit current density of 3.99 mA/cm2, fill factor ∼50% and overall power conversion efficiency (η) ∼1.36% might be a promising electrode material of dye sensitized solar cell application.

Effect of Different Acids and Solvents on Optical Properties of SiO2 Nanoparticles Prepared by the Sol-Gel Process

SiO2 nanoparticles are prepared via a simple solgel method to provide a basic understanding of the effect of different acids, acetic acid [CH3COOH], hydrochloric acid (HCl), sulfuric acid (H2SO4) and oleic acid [C18H34O2] and solvents dimethylformamide and formamide on the morphological and optical properties. The resulting SiO2 nanoparticle were characterized by photoluminescence spectrophotometry (PL) for the study of optical properties, Transmission electron microscopy (TEM) to determine particle size and Fourier transform infrared spectroscopy (FTIR) for identification of materials and impurities. SiO2 formed with formamide and HCl shows high crystallinity and transperancy in the material. PL spectra reveal that SiO2 nanoparticles show absorbance in the UV region. For each solvent, the PL emission intensity of the SiO2 sample prepared with acid was reduced which shows the formation of well-defined lattice sites and decrease of deffects. The PL intensity of SiO2 prepared with dimethyl-formamide to acetic-acid (SD1) and SiO2 prepared with formamide to acetic-acid (SF1) samples increased. The particle size is confirmed by TEM which was indicative of the successful synthesis of SiO2 nanoparticles in spherical shape. The estimated particle size is in the range of 2-4 nm. The chemical changes were observed from the FTIR results. Strong and broad bands appeared at 3459 cm1-3458 cm−1 and 1640 cm−1-1638 cm−1 corresponding to the bending vibrations of -OH groups and carbon impurity atoms. The peaks that appeared at 989 cm−1-801 cm1 and at 966 cm-1-802 cm1 show the bending vibrations of Si-O-Si and Si-OH bonds in prepared samples.

Optimization of process parameters and its effect on structure and morphology of CuO nanoparticle synthesized via the sol−gel technique

AbstractThis article describes systematic basic research on the optimization of the processing parameters of sol−gel technique for synthesis of the high purity CuO nanoparticles. Effect of the synthesis parameters such as copper salt concentration, solvent and gelating agent, optimized one at a time, was investigated by employing XRD, TEM, FESEM, micro-Raman, UV-visible-NIR and PL spectroscopies. XRD results clearly demonstrate the monoclinic structure of CuO nanoparticles with traceable impurities at a lower molar concentration of Cu2+, transition of nucleation system from homogeneous to heterogeneous state with the increase in concentration of Cu2+ from 0.05 to 0.15 M. It was also found that the isopropyl alcohol offers better results in comparison to ethanol and water. Moreover, the lattice parameters, space group, and crystal system were determined by powder X-ray diffraction method. Further we propose the optimization of synthesis process using ethylene glycol and citric acid (EG:CA). The Raman analysis confirmed the influence of ethylene glycol and citric acid ratio and TEM observations confirmed that EG:CA 1:2 ratio formulate homogenous flower-like nanostructures. The optical absorption of CuO nanostructures can be easily tuned by varying the concentration of citric acid without changing other conditions; it shows the role of synthesis parameters more significant. Our results suggest that the prepared CuO nanostructures have a potential to be used as absorbing material in solar cell applications. HighlightsCuO nanoparticles are successfully synthesized via simple non-aqueous sol-gel method.The effect of various process parameters on the morphology and structure of CuO nanoparticles are investigated.Vibrant modifications in the morphology of CuO nanoparticles are detected via TEM and SEM.Isopropyl alcohol gives better crystallization of CuO nanostructures in comparison to ethanol.1:2 ratio of ethylene glycol and citric acid yield superior assembly of CuO nanostructures.

Structural and Optical Characterization of ZnO Nanoparticles Synthesized Via Low Temperature Precipitation Method

ZnO nanoparticles were successfully synthesized via a low temperature and simple precipitation method. Crystallinity, phase purity and structural properties of as prepared material were analyzed by X-ray diffraction pattern (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) with 32 nm average crystallite size. Additionally, the optical properties of the sample were investigated by using Uv-Vis-NIR and Photoluminescence spectroscopy with an energy band gap at 3.09 eV. These results should be useful in developing optoelectronic devices such as UV-LEDs and laser diodes.