Abstract: The promotion of silicon (Si) from being the key material for microelectronics to an interesting material for optoelectronic application is a consequence of the possibility to reduce its device dimensionally by a cheap and easy technique. In fact, electrochemical etching of Si under controlled conditions leads to the formation of nanocrystalline porous silicon (PS) where quantum confinement of photo excited carriers and surface species yield to a band gap opening and an increased radiative transition rate resulting in efficient light emission. In the present study, the nanostructured PS samples were prepared using anodic etching of p-type silicon. The effect of current density on structural and optical properties of PS, has been investigated. XRD studies confirm the presence of silicon nanocrystallites in the PS structure. By increasing the current density, the average estimated values of grain size are found to be decreased. SEM images indicate that the pores are surrounded by a thick columnar network of silicon walls. The observed PL spectra at room temperature for all the current densities confirm the formation of PS structures with nanocrystalline features. PL studies reveal that there is a prominent visible emission peak at 606 nm. The obtained variation of intensity in PL emission may be used for intensity varied light emitting diode applications. These studies confirm that the PS is a versatile material with potential for optoelectronics application.
Abstract: Mg-Co-Zn nanoferrite particles were prepared by combustion method using stoichiometric compositions of magnesium nitrate, cobalt nitrate and zinc nitrate as oxidizers and urea as a fuel. The structure of the sample is studied with X-ray diffraction (XRD) using Cu-Kα radiation. The X-ray diffraction analysis revealed the nanocrystalline nature in the prepared ferrite samples. Dielectric and a. c. conductivity studies have been undertaken over a wide range of frequencies (100-5MHz) for Mg-Co-Zn nanoferrites at room temperature. The dielectric properties such as dielectric loss tangent (D), dielectric constant (ε′) and dielectric loss factor (ε″) were found to decrease with an increase in the frequency. Further, a. c. conductivity of the Mg-Co-Zn nanoferrite was found to increase with the increase in the frequency. The electrical conduction mechanism in the Mg-Co-Zn nanoferrite has been understood on the basis of the electron hopping model.
Abstract: Nanoscale Nickel ferrite particles were prepared by combustion method using nickel nitrate as oxidizer and urea as a fuel. The structure of the sample is studied with X-ray diffraction (XRD) using Cu-Kα radiation. The X-ray diffraction analysis revealed the nanocrystalline nature in the prepared ferrite samples. Dielectric studies have been undertaken over a wide range of frequencies (100Hz-5MHz) for Nickel nanoferrites at room temperature. Dielectric properties such as dielectric loss tangent (D), dielectric constant (ε′ ) and dielectric loss factor (ε″) are found to decrease with the increase in the frequency. Observed variations are understood on the basis of Koop’s phenomenological model. Further, a. c. conductivity of the Nickel nanoferrite was found to increase with the increase in the frequency. Observed variation in the a. c. conductivity with the frequency has been understood on the basis of electron hopping model.
Abstract: Abstract. The Yttria substituted BaCeO3 nanocomposites were prepared by modified Pechini technique followed by novel microwave sintering at 1400°C. The powder XRD results show that the material exhibit orthorhombic crystalline structure. The average grain size was calculated to be as 55 nm. SEM results show that the homogeneous distribution of particles in the lower nanometer range leads to dense microstructure. DTA peaks at 575 and 648°C indicate that the crystallization of the material and the associated weight losses were observed in the TG curve. The 96% of theoretical density was measured for the sintered sample through Archimedes principle. The maximum power density of 788mWcm2 and the maximum open voltage (OCV) of about 0.991 V was measured from the I-V and I-P results. The results confirm that the microwave sintering technique enhances the material properties in the nanometer scale with large potential for SOFC applications.
Abstract: The Gd substituted BaCe0.8Y0.1O3-δ nanocomposites were prepared by a modified Pechini route and then the prepared material was subjected to conventional sintering at 1400°C. The powder XRD results show that the material exhibit orthorhombic crystalline structure and the mean particle size were calculated to be ~40 nm. SEM micrographs indicate that the particle sizes were observed in the nanometer range with dense microstructure, which leads to increase in the densification of the material. FT-IR result confirms the presence of metal bondings in the material. DTA peaks observed at 725°C and 880°C show the crystallization of the material and the corresponding weight loss was recorded in the TG spectrum. I-V & I-P results show that the maximum open cell voltage (OCV) was measured at 1.1V and the maximum power density of about 801mWcm2 was observed which may be due to the substitution of Gd ions into the BaCeYO3 sites showing an improved electrochemical performance of IT-SOFC electrolytes.
Abstract: Highly fluorescent Cadmium based II-VI CQD’s plays a vital role in third generation photovoltaic’s design. In this paper, a novel approach for rapid synthesis of two different high quality cadmium based CQD’s in aqueous phase was presented and the optical stability and the structural properties of those materials were studied out. In this work Tellurium composed CQD’s along with cadmium were prepared by colloidal route. In the above procedure Thio Glycolic Acid (TGA) as well as Mercapto succinic acids (MSA) was used as the capping agents. All these procedures were carried out in aqueous medium at air atmosphere. The size dependent band gaps of the prepared quantum dots were determined from UV-Vis spectra and compared with the other one. The fluorescent properties of CdTe CQDs were investigated by using fluorescence spectra. The surface and structural morphologies were determined by using HRSEM and X-ray diffraction studies. The formation of CdTe quantum dots and the capping effect of the thiol group were investigated from EDAX and FTIR analysis.
Abstract: Synthesis of aligned ZnO nanorods (NRs) is important for electronic and optoelectronic devices. In this work we demonstrate the growth of ZnO nanorods by co-precipitation method using zinc nitrate and hexamine precursors. The samples were characterized by X-ray diffraction analysis, Scanning electron microscopy and Raman spectroscopy. On introducing the seeded substrate into the growth solution, the seeds offer nucleation sites for one-dimensional growth of ZnO nanorods. ZnO nanorod arrays grown on the successive ionic layer adsorption and reaction (SILAR) seed layer found to be irregular and non-uniform due to the etching of the seed substrate by growth solution. However, dip-coated seed substrate yielded uniform growth of ZnO nanostructures. ZnO nanostructures with flower-like morphology were obtained for pH of 9. On reducing the pH of the growth solution the flower morphology transformed into rod-like morphology with rod diameter of 200nm. On reducing the pH to 3 the diameter of the nanorods is decreased to 20 to 25nm. On reducing the precursor concentration the faceted morphology of the nanorods changed into needle-like shape (with sharp tips) along with reduction in diameter (about 20nm). The growth of uniform and vertically aligned ZnO nanorods is observed in dip-coated seed substrate with 5 pH. The results indicate that the diameter of ZnO nanorod array could be controlled by varying the precursor concentration.
Abstract: Cobalt hexacynoferrate decorated carbon spheres (CoHCF@C) with few micron dimensions was synthesized by sequential deposition method in which the carbon sphere previously modified with cobalt ion exposed into potassium ferricyanide. The thickness of the CoHCF layer was restricted to five cycles. The formation of layer CoHCF was confirmed by FT-IR, XRD, HRSEM, EDX and cyclic voltammeter technique. The CoHCF decorated carbon sphere modified GCE was utilized as electron transfer mediator for electrocatalytic oxidation of hydrazine in phosphate buffer medium. The electrocatalytic behavior of modified electrode on oxidation of hydrazine is compared with bare GCE. The amperometry method was adapted for the quantitative detection of hydrazine in water samples.
Abstract: Nanocrystalline lead oxide was prepared by solvo-thermal technique at a temperature of 75 °C. X-ray diffraction studies show the formation of stable β - PbO at 75 °C and heat treated from 200 to 500 °C for 2 h. Scanning electron micrograph images reveal the change in morphology of PbO particles from spherical to rhombus shape at higher temperatures. The band gap of the material was estimated by Diffused Reflectance Spectroscopy (DRS) found to be 2.67 eV. Photoluminescence spectrum of all the samples exhibits several band peaks due to radiative transitions from defect levels and recombination process.
Abstract: Selective detection of dopamine (DA) in presence of ascorbic (AA) is an important analytical problem, due to its combined existence in the biological system. In the present study, we are reporting an electrochemical detection method for dopamine (DA) in the presence of ascorbic acid (AA) using graphitized nanoporous carbon (NPC) modified glassy carbon electrode (GCE/NPC) in 0.1 M phosphate buffer solution. The modified electrode shows excellent electrocatalytic activities towards the oxidations of DA and AA in neutral pH buffer solution. Compared to unmodified GCE, GCE/NPC shows well separated and enhanced oxidation peak currents. Differential pulse voltammetric technique used as qualitative analytical tool for the detection of DA. The oxidation peak potentials for DA and AA were at -80 and 136 mV vs Ag/AgCl respectively. The modified electrode shows good stability and reproducibility with the relative standard deviation value of 2.6 %. The analytical application of the modified electrode (GCE/NPC) was demonstrated for the individual determination of DA in clinical injection and pharmaceutical tablet by using standard addition method.