Search

We report here the zeta potential study of Bi2S3 nanoparticles (NPs), synthesized by facile polyol method using CTAB and EDTA as surfactants or capping agents. X-ray diffraction (XRD), Rietveld refinement of XRD data and Raman spectroscopy confirms the single phase orthorhombic crystal structure of Bi2S3 with space group Pnma. In Energydispersive X-ray spectroscopy (EDAX) data ratio of Bi to S was little deviated from 2:3 due to excess sulfur taken during synthesis. Field Emission Scanning Electron Microscope (FESEM) images show the agglomeration of rod-like Bi2S3. Effect of different capping agents on the surface charge of Bi2S3 NPs was studied using Zeta potential measurement with ethanol as dispersion medium at different pH values. It reveals that these NPs are more stable when it was synthesized in presence of EDTA than that of CTAB or without capping agent. The isoelectronic point was found at pH = 4.2 for pure sample and 3.2 and 7.3 for CTAB and EDTA capped Bi2S3 samples. [ABSTRACT FROM AUTHOR]

we synthesized successfully SnS nanoparticles (NPs) by polyol method using diethylene glycol as the surfactant as well as the stabilizing agent. Further, the crystallographic and morphological studies have been carried out. The X-ray diffraction (XRD) data confirms the single-phase formation with orthorhombic crystal structure and average crystallite size as 35 nm. The field emission scanning electron microscopic (FESEM) study confirms the flake-like shape. Seebeck coefficient (S) and electric resistivity (ρ = 1/σ) data analysis confirm p-type semiconductor nature of these NPs. They result in the highest thermoelectric power factor (PF = S²σ) of 0.013μW/mK² at 325 K. [ABSTRACT FROM AUTHOR]

Wurtzite CdS nanoparticles (NPs) synthesized by a facile polyol method at 220 °C without extra surfactant were investigated using X-ray diffraction (XRD), Raman spectroscopy, dynamic light scattering (DLS) and zeta potential techniques. XRD data confirms hexagonal crystal structure with P63mc space group and no impurity peaks. Presence of two distinct Raman modes further confirms their stoichiometric formation. Dispersion medium-dependent stability of the NPs studied using zeta potential (ξ) data in the pH range from 3 to 10.5 reveals that these NPs are highly stable above pH 6.49 in basic medium with highest ξ of -39.32 mV at pH 10.28 in de-ionized water (DIW), but unstable in toluene and ethanol as dispersing medium. HD distribution curve shows that the particles agglomerate more rapidly in toluene and ethanol in comparison with that in DIW. This information is expected to be useful for many applications like ceramics, batteries, biological labeling, as a pigment in paints, as photocatalyst in degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

We have demonstrated a simple strategy for improvement of thermoelectric performance of Ag2S based composites by modifying reaction conditions in polyol method. The existence of two-phased heterostructure in Ag2S@Ag nanocomposites is confirmed from dual phase Rietveld refinement of its powder X-ray diffraction. The FESEM images confirmed the formation of nanodisks of average thickness 80 nm and width in few hundreds of nm. A systematic reduction in electrical resistivity with increasing Ag-content is observed which leads an enhancement in power factor. The values of Seebeck coefficient are positive or negative depend on fraction of Ag-content in Ag2S matrix. Finally, a significantly high power factor is obtained for Ag2S@Ag nanocomposites synthesized at 245 °C. This work open a new way for reduction of electrical resistivity of resistive Ag2S and hence improved its thermoelectric efficiency. [ABSTRACT FROM AUTHOR]

We report here the thermoelectric (TE) properties of CuS nanoparticles (NPs), synthesized by a facile polyol method using CTAB and PVP as surfactants. Systematic characterizations using powder XRD, Rietveld refinement of XRD and Raman spectroscopy confirm their single phase, hexagonal-closed structure with space group P63/mmc and stoichiometric composition, respectively. The presence of surfactants during synthesis of CuS NPs seemingly prevents the volatility of S, making the capped samples a little S-rich and hence enhanced electrical conductivity and thermopower. Consequently, a significant improvement of more than 50% in thermoelectric power factor at 300 K is observed for CTAB and PVP capped CuS NPs as compared to pure one. [ABSTRACT FROM AUTHOR]

Analysis of Rietveld refinement of XRD data confirms single phase orthorhombic crystal structure of pure and polyvinyl pyrrolidone (PVP)-capped Sb2S3 nanoparticles (NPs) synthesized successfully at 190 °C by facile polyol method. Raman modes further confirms their stoichiometric formation. Ratio of Sb to S was found to be a little deviated from 2:3 corresponding to Sb2S3 due to volatile nature of S. A striking effect on the surface charge of Sb2S3 NPs with and without PVP as surfactant was found in zeta potential (ξ) data collected using deionized water (DIW) for pH values in the range of 3 to 10.5. This reveals that anearly constant ξ of –51.64 mV is found in pH = 6.5 to 8.5 for the PVP-capped Sb2S3 NPs indicating their high stability in DIW compared to that of unstable nature (ξ = −23.45 mV or less) for pure Sb2S3 NPs. The isoelectronic point is found at pH = 4.2 for PVP-capped Sb2S3, not for pure sample. This information is likely to be useful for many applications like in cosmetics, for waste water treatment, ceramics, pharmaceuticals and in medicine. [ABSTRACT FROM AUTHOR]

Here we report the synthesis and characterisation of polyvinylpyrrolidone (PVP) capped Bi2S3 nanoparticles via one step catalyst-free polyol method. Raman spectroscopy, dynamic light scattering and zeta potential analysis were performed on it. Rietveld refinement of powder XRD of PVP capped samples confirmed the formation of single phase orthorhombic Bi2S3 for all PVP capped samples. The presence of eight obvious Raman modes further confirmed the formation of stoichiometric Bi2S3. Dynamic light scattering (DLS) studies show a clear increase in hydrodynamic diameter for samples made with increasing PVP concentration. Particle size obtained from DLS and XRD (using Scherrer’s formula) combine with change in full width half maxima of Raman modes collectively suggest overall improvement in crystallinity and quality of product on introducing PVP. In zeta potential (ζ) measurement, steric hindrance of carbon chains plays very crucial role and a systematic reduction of ζ value is observed for samples made with decreasing PVP concentration. An isoelectric point is obtained for sample made with low PVP (1g). Present results are likely to open a window for its medical and catalytic applications. [ABSTRACT FROM AUTHOR]

Cu7Te4 nanoparticles (NPs) have been successfully synthesized indiethylene glycol. X-ray powder diffraction (XRD) andfield emission scanning electron microscopy (FESEM) are employed to characterize the products. The average size of the particles about 35 nm using Scherrer formulais smaller than that~50 nm disc-type particles from FESEM. Both the electrical conductivity and Seebeck coefficient data exhibit metallic nature showing possible energy filtering at the grain boundaries, enhanced electronic density of states, hole-type conduction and degenerate semiconductor behavior. Finally, the power factor found at 300 K is encouragingly large. [ABSTRACT FROM AUTHOR]

This is the report on successful synthesis of Ag doped CuS nanostructures by modified polyol method. The resulting samples were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and dynamic light scattering (DLS). Particle size of pure CuS nanoparticles (NPs) was 17 nm, 38 nm and 97 nm as determined from Scherrer formula, AFM and DLS, respectively. Introduction of Ag led to formation of CuS/Ag2S composites. A transition at 55 K in thermopower is ascribed to structural transformation from hexagonal to orthorhombic structure. Further, their thermoelectric properties exhibit remarkable change owing to Ag doping in CuS nanostructures. The power factor improves with increasing Ag content. They reveal that CuS/Ag2S nanocomposites are some of the potential candidates for generation of thermoelectricity in future. [ABSTRACT FROM AUTHOR]

Silver sulfide (Ag2S) nanoparticles (NPs) were prepared successfully for the first time using diethylene glycol (DEG) as a surfactant. X-ray diffraction (XRD) data revealed single phase nature of the compound and energydispersive X-ray (EDX) confirmed its nominal composition. Their sizes were 43 nm from XRD, 50 nm from atomic force microscopy (AFM) and 19 nm & 213 nm from dynamic light scattering (DLS); their differences have been discussed. Autotitration study of zeta potential of these NPs in deionized water by DLS at different pH values confirmed an isoelectric point at pH = 5.14 and their very unstable nature in deionized water. [ABSTRACT FROM AUTHOR]