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The fabrication of unique taper-ended GaN-Nanotowers structure based highly efficient ultraviolet photodetector is demonstrated. Hexagonally stacked, single crystalline GaN nanocolumnar structure (nanotowers) grown on AlN buffer layer exhibits higher photocurrent generation due to high quality nanotowers morphology and increased surface/volume ratio which significantly enhances its responsivity upon ultraviolet exposure leading to outstanding performance from the developed detection device. The fabricated detector display low dark current (~ 12 nA), high ILight/IDark ratio (> 104), fast time-correlated transient response (~ 433 µs) upon ultraviolet (325 nm) illumination. A high photoresponsivity of 2.47 A/W is achieved in self-powered mode of operation. The reason behind such high performance could be attributed to built-in electric field developed from a difference in Schottky barrier heights will be discussed in detail. While in photoconductive mode, the responsivity is observed to be 35.4 A/W @ − 3 V along with very high external quantum efficiency (~ 104%), lower noise equivalent power (~ 10–13 WHz−1/2) and excellent UV–Vis selectivity. Nanotower structure with lower strain and dislocations as well as reduced trap states cumulatively contributed to augmented performance from the device. The utilization of these GaN-Nanotower structures can potentially be useful towards the fabrication of energy-efficient ultraviolet photodetectors.

Maqusood Ahamed,1 Mohd Javed Akhtar,1 MA Majeed Khan,1 Hisham A Alhadlaq1,2 1King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi Arabia; 2Department of Physics and Astronomy, College of Science, King Saud University, Riyadh 11451, Saudi ArabiaCorrespondence: Maqusood AhamedKing Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi ArabiaEmail mahamed@ksu.edu.saBackground: Therapeutic selectivity and drug resistance are critical issues in cancer therapy. Currently, zinc oxide nanoparticles (ZnO NPs) hold considerable promise to tackle this problem due to their tunable physicochemical properties. This work was designed to prepare SnO2-doped ZnO NPs/reduced graphene oxide nanocomposites (SnO2-ZnO/rGO NCs) with enhanced anticancer activity and better biocompatibility than those of pure ZnO NPs.Materials and Methods: Pure ZnO NPs, SnO2-doped ZnO (SnO2-ZnO) NPs, and SnO2-ZnO/rGO NCs were prepared via a facile hydrothermal method. Prepared samples were characterized by field emission transmission electron microscopy (FETEM), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), ultraviolet-visible (UV-VIS) spectrometer, and dynamic light scattering (DLS) techniques. Selectivity and anticancer activity of prepared samples were assessed in human breast cancer (MCF-7) and human normal breast epithelial (MCF10A) cells. Possible mechanisms of anticancer activity of prepared samples were explored through oxidative stress pathway.Results: XRD spectra of SnO2-ZnO/rGO NCs confirmed the formation of single-phase of hexagonal wurtzite ZnO. High resolution TEM and SEM mapping showed homogenous distribution of SnO2 and rGO in ZnO NPs with high quality lattice fringes without any distortion. Band gap energy of SnO2-ZnO/rGO NCs was lower compared to SnO2-ZnO NPs and pure ZnO NPs. The SnO2-ZnO/rGO NCs exhibited significantly higher anticancer activity against MCF-7 cancer cells than those of SnO2-ZnO NPs and ZnO NPs. The SnO2-ZnO/rGO NCs induced apoptotic response through the upregulation of caspase-3 gene and depletion of mitochondrial membrane potential. Mechanistic study indicated that SnO2-ZnO/rGO NCs kill cancer cells through oxidative stress pathway. Moreover, biocompatibility of SnO2-ZnO/rGO NCs was also higher against normal breast epithelial (MCF10A cells) in comparison to SnO2-ZnO NPs and ZnO NPs.Conclusion: SnO2-ZnO/rGO NCs showed enhanced anticancer activity and better biocompatibility than SnO2-ZnO NPs and pure ZnO NPs. This work suggested a new approach to improve the selectivity and anticancer activity of ZnO NPs. Studies on antitumor activity of SnO2-ZnO/rGO NCs in animal models are further warranted.Keywords: ZnO nanocomposites, improved anticancer activity, better selectivity, reactive oxygen species, caspase-3, breast cancer

Double perovskite La2MnNiO6 nanoparticles (approximately 30 nm in diameter) were synthesized using a modified sol-gel method followed by a firing process and used as promising electrode materials for oxygen evolution reactions (OERs). The phase purity of the nanoparticles was verified using X-ray diffraction and Raman spectroscopy measurements. La2MnNiO6 nanoparticles crystallize in a monoclinic structure (P21/n space group) with refined lattice parameters of a = 5.461(5) A, b = 5.512(3) A, c = 7.760(5) A, and β = 90.10(2)°. The elemental composition, particle size, size distribution, and surface area of the La2MnNiO6 nanoparticles were also investigated. La2MnNiO6 nanoparticles are ferromagnetic in nature and exhibit hysteresis with a saturation magnetization value of approximately 9 emu/g. La2MnNiO6 nanoparticles exhibit highly efficient electro-catalytic activity for OERs with a low onset over-potential (approximately 65 mV) and low Tafel slope values (120 mV/dec) in alkaline media. The over-potential of La2MnNiO6 nanoparticles at a current density of 10 mA/cm2 is in good agreement with the reported over-potential (ƞ10) of double perovskites, commercial Pt/C and IrO2 electro-catalysts for promoting OERs.

Delafossite AgFeO2 nanoparticles were synthesized by the modified hydrothermal procedure for excellent photochemical performances for the removal of organic dye from neutral and alkaline aqueous medium. The structure, morphology, and elemental studies of the delafossite AgFeO2 nanoparticles were done by analytical methods. AgFeO2 nanoparticles show the refined lattice parameters of “a” = 3.033(2) A and “c” = 18.591(3) A of R3m phase. The excellent photocatalytic performance of delafossite AgFeO2 nanoparticles was observed under the full sunlight irradiations, which resulted ~92% degradation of methylene blue (MB) dye in 40 min using alkaline medium. The kinetic studies confirm the pseudo-first-order reactions of MB dye degradation in presence of photocatalysts. The fragmentations of organic dye molecules in presence of delafossite AgFeO2 photocatalysts under sunlight irradiations were also studied using the GC–MS technique. The delafossite AgFeO2 nanoparticles show excellent photocatalytic regeneration efficiency.

In this work, undoped and iron doped titania nanoparticles (Fe:TiO2 NPs) were successfully prepared by sol-gel route with two different Fe concentration (5 and 10 mol.%). The effects of Fe doping into TiO2 were thoroughly investigated by XRD, TEM, HRTEM, XPS, FTIR, Raman, UV–Visible spectroscopy and VSM. The obtained nanoparticles have narrow size distribution 41–49 nm and were recognized as anatase TiO2 structure with no signature of Fe cluster or iron oxides as analyzed by X-ray diffraction and Raman. The optical band gap of undoped and iron doped TiO2 NPs is red shifted with respect to the incorporation of iron content. Room temperature M-H loops revealed that all the samples showed a significant paramagnetic behaviour. The enhanced photocatalytic performance was observed for iron doped titania nanoparticles compared with pure TiO2 NPs in respect of methylene blue dye degradation in aqueous suspension under visible light illumination.

In the present work, we have investigated the structural, optical, photocatalytic activity, electrical transport and magnetic properties of Fe3O4 nanoparticles and its composite with reduced graphene oxide (Fe3O4/RGO) by varying the ratio of reduced graphene oxide (RGO: 2% and 4%). Fe3O4 nanoparticles and RGO were synthesized by the modified sol-gel and Hummers methods respectively. The as-prepared samples were examined by various analytical techniques to investigate their functional properties and possible applications. Rietveld refinement analysis of the XRD data reveals face-centered cubic (fcc) structure of the Fe3O4 nanoparticles and confirms the characteristic planes of magnetite phase. The average crystallite size of the Fe3O4, Fe3O4/RGO (2%) and Fe3O4/RGO (4%) samples was estimated using Scherrer's equation and found to be ∼10, 15 and 19 nm respectively. TEM/HRTEM micrographs establish spherical shapes of the magnetite nanoparticles with an average diameter of ∼12 nm for Fe3O4, while 17 and 20 nm in the nanocomposites respectively. The low temperature resistivity measurements exhibit semiconducting nature of all the samples and follow variable range hopping (VRH) mechanism. The magnetic measurements demonstrate typical superparamagnetic behavior of the samples at room temperature. The photocatalytic performance of the samples has been investigated for the decolorization of methylene blue (MB) organic dye under visible light irradiation. The Fe3O4/RGO nanocomposites display better adsorption behaviour and excellent photocatalytic activity than RGO and Fe3O4 nanoparticles. This may be due to strong interactions between Fe3O4 nanoparticles and graphene sheets.

The PdS/p-Si heterojunction was fabricated by preparation of PdS thin films on the p-type Si (10 0) substrates using versatile SILAR method. The alteration of nanostructural, morphological, optical and I–V characterization of CuxPd1−xS/p-Si (x = 0–0.1) heterojunction was examined at the different Cu-doping level to inspect the doping effects on the properties of heterojunction. The X-ray diffraction investigated that the crystallinity of prepared thin films enhanced as a function of Cu concentration. The morphological analysis presented that the PdS thin films was smooth, homogeneous and closed packed spherical grains. Electron dispersive X-ray (EDX) analysis confirmed the stoichiometric composition of PdS thin films. The diffuse reflectance spectroscopy in the prepared PbS/p-Si heterojunction was reduced and the band edge showed the blue shift in the visible range. Photoluminescence (PL) spectra revealed that the PbS/p-Si heterojunction recombination rate is decreased with Cu-doping. The effects of Cu-doping level on the electrical parameters of heterojunction such as ideality factor (n), saturation current (IS), barrier height (Φb) and series resistance (Rs) were computed by the execution of current–voltage (I–V) properties. Electrical properties indicated that behavior of the PdS/p-Si heterojunction were precisely controlled by doping level.

Single‐atom catalysts (SACs) are highly enviable to exploit the utmost utilization of metallic catalysts; their efficiency by utilizing nearly all atoms to often exhibit high catalytic performances. To architect the isolated single atom on an ideal solid support with strong coordination has remained a crucial trial. Herein, graphene functionalized with nitrile groups (cyanographene) as an ideal support to immobilize isolated copper atoms G(CN)‐Cu with strong coordination is reported. The precisely designed mixed‐valence single atom copper (G(CN)‐Cu) catalysts deliver exceptional conversions for electrochemical methanol oxidation (MOR) and CO2reduction (CO2RR) targeting a “closed carbon cycle.” An onset of MOR and CO2RR are obtained to be ≈0.4V and ≈−0.7 versus Ag/AgCl, respectively, with single active sites located in an unsaturated coordination environment, it being the most active Cu sites for both studied reactions. Moreover, G(CN)‐Cu exhibited significantly lower resistivity and higher current density toward MOR and CO2RR than observed for reference catalysts.

Based on 1-phenylpyrrolidine (PT) dye, six new metal-free organic molecules S1–S6, containing PT as donor (D) connected through different linkages (π) and cyanoacrylic acid as acceptor (A), were designed and studied for dye sensitised solar cells (DSSCs). In this paper, D-π-A system of S1–S6 dye molecules was investigated by quantum chemical calculations to inspect the optical absorption properties and photovoltaic (PV) parameters. In particular, there are applied three long-range corrected (LC) functionals, such as B3PW91, CAM-B3LYP and ωB97XD with the time-dependent DFT (TD-DFT) calculation to systematically investigate the absorption peak in PT dye. From the calculated results, CAM-B3LYP functional was a good match with the PT dye. Therefore, the S1–S6 molecules’ optical absorption spectra have been computed by using the CAM-B3LYP/6-31+G(d) theory. The conductor-like polarisable continuum model (C-PCM) results show that the precise absorption spectra have attained solvent effect included in the excited state geometries. The frontier molecular orbitals (FMOs) of the HOMOs and LUMOs energies of S1–S6 derivatives confirm positive results on the dye regeneration and electron injection processes. The outcomes display that the benzo[c][1,2,5]thiadizole (S4) and benzo[c][1,2,5]oxadizole (S5) molecules are the most suitable spacers for D to A, owing to longer absorption peaks and revealing red-shifted optical absorption.

Barium titanate (BaTiO3) nanoparticles (BT NPs) have shown exceptional characteristics such as high dielectric constant and suitable ferro-, piezo-, and pyro-electric properties. Thus, BT NPs have shown potential to be applied in various fields including electro-optical devices and biomedicine. However, very limited knowledge is available on the interaction of BT NPs with human cells. This work was planned to study the interaction of BT NPs with human lung carcinoma (A549) cells. Results showed that BT NPs decreased cell viability in a dose- and time-dependent manner. Depletion of mitochondrial membrane potential and induction of caspase-3 and -9 enzyme activity were also observed following BT NP exposure. BT NPs further induced oxidative stress indicated by induction of pro-oxidants (reactive oxygen species and hydrogen peroxide) and reduction of antioxidants (glutathione and several antioxidant enzymes). Moreover, BT NP-induced cytotoxicity and oxidative stress were effectively abrogated by N-acetyl-cysteine (an ROS scavenger), suggesting that BT NP-induced cytotoxicity was mediated through oxidative stress. Intriguingly, the underlying mechanism of cytotoxicity of BT NPs was similar to the mode of action of ZnO NPs. At the end, we found that BT NPs did not affect the non-cancerous human lung fibroblasts (IMR-90). Altogether, BT NPs selectively induced cytotoxicity in A549 cells via oxidative stress. This work warrants further research on selective cytotoxicity mechanisms of BT NPs in different types of cancer cells and their normal counterparts.

Combined exposure of single-walled carbon nanotubes (SWCNTs) and trace metal lead (Pb) in ambient air is unavoidable. Most of the previous studies on the toxicity of SWCNTs and Pb have been conducted individually. There is a scarcity of information on the combined toxicity of SWCNTs and Pb in human cells. This work was designed to explore the combined effects of SWCNTs and Pb in human lung epithelial (A549) cells. SWCNTs were prepared through the plasma-enhanced vapor deposition technique. Prepared SWCNTs were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and dynamic light scattering. We observed that SWCNTs up to a concentration of 100 &micro, g/mL was safe, while Pb induced dose-dependent (5&ndash, 100 &micro, g/mL) cytotoxicity in A549 cells. Importantly, cytotoxicity, cell cycle arrest, mitochondrial membrane potential depletion, lipid peroxidation, and induction of caspase-3 and -9 enzymes following Pb exposure (50 &micro, g/mL for 24 h) were efficiently attenuated by the co-exposure of SWCNTs (10 &micro, g/mL for 24 h). Furthermore, generation of Pb-induced pro-oxidants (reactive oxygen species and hydrogen peroxide) and the reduction of antioxidants (antioxidant enzymes and glutathione) were also mitigated by the co-exposure of SWCNTs. Inductively coupled plasma-mass spectrometry results suggest that the adsorption of Pb on the surface of SWCNTs could attenuate the bioavailability and toxicity of Pb in A549 cells. Our data warrant further research on the combined effects of SWCNTs and Pb in animal models.

Magnetic Fe3O4 nanostructures for electrochemical water splitting and supercapacitor applications were synthesized by low temperature simple wet-chemical route. The crystal structure and morphology of as-acquired nanostructures were examined by powder X-ray diffraction and transmission electron microscopy. Magnetic measurements indicate that the as-synthesized Fe3O4 nanostructures are ferromagnetic at room temperature. The synthesized nanostructures have a high-specific surface area of 268 m2/g, which affects the electrocatalytic activity of the electrode materials. The purity of the as-synthesized nanostructures was affirmed by Raman and X-ray Photoelectron studies. The electrochemical activity of the magnetic iron oxide nanoparticles (MIONPs) for the hydrogen evolution reaction (HER) and supercapacitors were investigated in alkaline medium (0.5 M KOH) versus Ag/AgCl at room temperature. The electrocatalysts show low onset potential (~0.18 V) and Tafel slope (~440 mV/dec) for HER. Additionally, the specific capacitance of MIONPs was investigated, which is to be ~135 &plusmn, 5 F/g at 5 mV/s in 1 M KOH.

Nanostructure titanium dioxide (TiO2) thin films were grown by atomic layer deposition on florin-doped tin oxide (FTO) substrates at 200 °C of thickness 100 nm. The TiO2 films were annealed at 300–500 °C in air for a period of 1 h. The prepared thin films have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–Vis spectroscopy, photoluminescence (PL) spectroscopy and current–voltage (I–V) properties. From X-ray diffraction patterns, as-deposited TiO2 thin films have a mixed anatase and rutile phases with FTO peaks. When the films were annealed the phase transformed to single anatase phase of the TiO2 films. The optical transmittance of as-deposited thin films is more than 58% and decreased with the increase in annealing temperatures. The energy band gap value was found to change with annealing temperature. The room-temperature PL spectra of TiO2 thin films show the band gap and defect peak at 409 nm and 420 nm with excitation at 325 nm. An enhancement of luminescence intensity is found due to change in the crystalline environment and reduction in oxygen amount with temperature. The value of ideality factor of prepared heterojunction is more than one, while the calculated values of saturation current, series resistance and barrier height altered with annealing because of defect-induced carrier capturing on interface between TiO2 and FTO.

Iron oxide&ndash, reduced graphene oxide (Fe3O4-RGO) nanocomposites have attracted enormous interest in the biomedical field. However, studies on biological response of Fe3O4-RGO nanocomposites at the cellular and molecular level are scarce. This study was designed to synthesize, characterize, and explore the cytotoxicity of Fe3O4-RGO nanocomposites in human liver (HepG2) cells. Potential mechanisms of cytotoxicity of Fe3O4-RGO nanocomposites were further explored through oxidative stress. Prepared samples were characterized by UV-visible spectrophotometer, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The results demonstrated that RGO induce dose-dependent cytotoxicity in HepG2 cells. However, Fe3O4-RGO nanocomposites were not toxic. We further noted that RGO induce apoptosis in HepG2 cells, as evidenced by mitochondrial membrane potential loss, higher caspase-3 enzyme activity, and cell cycle arrest. On the other hand, Fe3O4-RGO nanocomposites did not alter these apoptotic parameters. Moreover, we observed that RGO increases intracellular reactive oxygen species and hydrogen peroxide while decrease antioxidant glutathione. Again, Fe3O4-RGO nanocomposites did not exert oxidative stress. Altogether, we found that RGO significantly induced cytotoxicity, apoptosis and oxidative stress. However, Fe3O4-RGO nanocomposites showed good biocompatibility to HepG2 cells. This study warrants further research to investigate the biological response of Fe3O4-RGO nanocomposites at the gene and molecular level.

Due to unique optical and electronic properties tin oxide nanoparticles (SnO2 NPs) have shown potential for various applications including solar cell, catalyst, and biomedicine. However, there is limited information concerning the interaction of SnO2 NPs with human cells. In this study, we explored the potential mechanisms of cytotoxicity of SnO2 NPs in human breast cancer (MCF-7) cells. Results demonstrated that SnO2 NPs induce cell viability reduction, lactate dehydrogenase leakage, rounded cell morphology, cell cycle arrest and low mitochondrial membrane potential in dose- and time-dependent manner. SnO2 NPs were also found to provoke oxidative stress evident by generation of reactive oxygen species (ROS), hydrogen peroxide (H2O2) and lipid peroxidation, while depletion of glutathione (GSH) level and lower activity of several antioxidant enzymes. Remarkably, we observed that ROS generation, GSH depletion, and cytotoxicity induced by SnO2 NPs were effectively abrogated by antioxidant N-acetylcycteine. Our data have shown that SnO2 NPs induce toxicity in MCF-7 cells via oxidative stress. This study warrants further research to explore the genotoxicity of SnO2 NPs in different types of cancer cells.

Present work focuses on the growth of single-walled carbon nanotubes (SWCNTs) using nickel as a catalyst onto the silicon substrate through plasma enhanced chemical vapour deposition (PECVD) method. As synthesised SWCNTs have been characterized by employing various analytical techniques like XRD, SEM, HR-TEM/EDS and UV-visible absorption spectroscopy. The HRTEM micrographs revealed that the SWCNTs were mostly entangled bundles with diameters of about 2 nm. The optical absorption data were used to estimate energy bandgap of the SWCNTs and found to be 2.67 eV. The photocatalytic performance of the nanotubes was examined by the deterioration of an organic dye methylene blue (MB) under visible light irradiation. The observed results exhibit excellent photocatalytic activity of the nanotubes that may be due to the large surface defects, surface area and small energy bandgap characteristics of the nanotubes.

In this article, pure and silver (Ag) loaded tungsten oxide (WO3) nanoparticles have been produced by a simple and cost effective hydrothermal method. The crystal morphology and structure properties of the fabricated pure WO3 and Ag (4 and 8 wt%) loaded WO3 nanoparticles have been determined by X-ray diffraction, transmission electron microscopy, micro-Raman spectroscopy and Fourier transform infrared spectroscopy. Both crystallographic (X-ray diffraction and Raman spectra) data indicated the monoclinic structure of prepared samples. Transmission electron microscopic analysis showed that pure and silver loaded tungsten oxide nanoparticles have spherically shaped morphology with average size 25–35 nm which found to be in fair agreement with the average crystallite sizes 28–34 nm as estimated from Scherrer's equation. UV–visible absorption spectra revealed that the optical energy band gap of Ag loaded WO3 nanoparticles decreased with increasing the Ag content. The photocatalytic activity of WO3 with different Ag concentration was evaluated by the photocatalytic degradation of methylene blue under irradiation with visible light; and it exhibited significant enhancement in photocatalytic activity of Ag loaded WO3 as compared to pure WO3. In this way, it acts as a very efficient photocatalyst employable for degradation of toxic dyes and chemicals usually present in textile effluents. In addition, the diffusion coefficient of WO3 increases considerably with Ag loading, which is favourable for its application in energy storage devices.

Pure titania and zirconium titanate composites have been synthesized using sol-gel technique and annealed at 650, 875 and 1100 °C for 4 h. Acetylacetone was used to control the rate of hydrolysis of precursors. The Rietveld refinement, micro-structural, optical and thermal parameters of prepared composites was investigated. Effect of annealing and concentration of Zr and Ti in composites on their crystal structure, morphology, PL emission wavelength and band gap have been studied. X-ray diffraction and Rietveld analysis exhibit that all prepared samples of composites have orthorhombic single phase of zirconium titanate with space group pbcn. The lower values of profile parameters such as R p , R wp , R B , R F , χ 2 indicated that the calculated diffraction pattern is in fair agreement with observed pattern. The increase in zirconia concentration decreases the degree of crystallization of ZrTiO 4 . The photoluminescence spectra show the blue shifting of emission peak at 420 nm as the zirconia concentration increases. The optical band gap of zirconium titanate composites also blue shifted (3.24–3.64 eV) with decrease in crystallite size of composites.

Halide perovskites have swiftly been elevated to a subject worthy of serious and extensive research. They are unequivocally an unprecedented class of semiconductors with a broad range of optoelectronic applications. These materials display outstanding properties, which are the results of their direct and tunable band gap, high electron/hole mobility, strong light-absorption coefficient, and high defect tolerance coupled with low non-radiative recombination rates. Their preparation is also extremely easy and compatible with room-temperature deposition processes. Nonetheless, the toxic nature of lead (Pb and its ions) and the poor stability against moisture, limit their mass production and commercialization. This article thoroughly reviews the recent investigations undertaken to solve these thorny problems by focusing mainly on the structural development and the photoluminescence tuning ability of lead-free perovskite nanocrystals (NCs). In the light of the principles related to crystal chemistry, we present the development of perovskite NCs from mineral prototypes, which leads to a variety of multi component Pb2+-free perovskite type compounds. Then, assuming that the ultimate goal is the production of a single-component white-light emission device, we shed light on the development of broadly tunable Pb2+-free perovskite NCs with intrinsic emission as well as extrinsic emission achieved by doping with various ions, and on the corresponding energy transfer (ET) mechanism, which governs the color and the photoluminescence emission tuning ability. The present review aims to assist the research which deals with the discovery of new highly stable, nontoxic perovskite NCs, following a strategy associated with excitonic luminescence enhancement, in conjunction with a comprehensive understanding of the role of energy transfer phenomenon, whereby efficient tuning ability is achieved by various dopants

In the present work, we report on the role of the methanol medium and ball-milling time in the substitution of carbon in carbon nanotube CNT-MgB2 superconductors. In our samples, we find that the CNTs are intact and well dispersed. However, the liquid medium (methanol) used for dispersion of the constituent materials is also acting as a source of C for substitution. However, the substitution of C from methanol is not direct; rather, B2O3, which had been considered as just an impurity, plays a positive role in binding the methanol molecules to the surface of B. The detailed mechanism of methanol absorption and the role of B2O3 and ball-milling time are presented here. In addition, we present the J C(H, T) data, which show that approximately 3% of C substitution provides the best critical current density at 20 K.

The demand for semiconductor indium oxide (In2O3) nanocrystals is increasing because of their diverse applications, including in biomedicine. However, there is a scarcity of studies on the biological interaction of indium oxide nanocrystals. Here, we explored the underlying mechanisms of toxicity induced by indium oxide nanocubes in human lung epithelial (A549) cells. Prepared indium oxide nanocubes were crystalline with an average size of 21 nm. Biointeraction studies have shown that indium oxide nanocubes induce cell viability reduction and cell membrane damage in a dose- and time-dependent manner. Indium oxide nanocubes were also found to induce reactive oxygen species (ROS) generation, glutathione depletion and lower activity of superoxide oxide dismutase. Further, indium oxide nanocubes induced a mitochondrial membrane potential loss and altered the mRNA expression levels of apoptotic genes (p53, bax, bcl-2, CASP3 & CASP9). The activities of apoptotic enzymes (caspase-3 and −9) were also higher in indium oxide nanocube-treated cells. Finally, we observed that the cytotoxicity and apoptosis induction of indium oxide nanocubes were efficiently prevented by N-acetyl-cysteine. We believe that this is the first report suggesting that indium oxide nanocubes induce toxicity in lung cells via ROS generation and oxidative stress. This study warrants future research on the toxicity mechanisms of indium oxide nanoparticles in animal models.

Graphene-based nanocomposites have attracted enormous interest in nanomedicine and environmental remediation, owing to their unique characteristics. The increased production and widespread application of these nanocomposites might raise concern about their adverse health effects. In this study, for the first time, we examine the cytotoxicity and oxidative stress response of a relatively new nanocomposite of cerium oxide-reduced graphene oxide (CeO2-RGO) in human lung epithelial (A549) cells. CeO2-RGO nanocomposites and RGO were prepared by a simple hydrothermal method and characterized by relevant analytical techniques. Cytotoxicity data have shown that RGO significantly induces toxicity in A549 cells, evident by cell viability reduction, membrane damage, cell cycle arrest, and mitochondrial membrane potential loss. However, CeO2-RGO nanocomposites did not cause statistically significant toxicity as compared to a control. We further observed that RGO significantly induces reactive oxygen species generation and reduces glutathione levels. However, CeO2-RGO nanocomposites did not induce oxidative stress in A549 cells. Interestingly, we observed that CeO2 nanoparticles (NPs) alone significantly increase glutathione (GSH) levels in A549 cells as compared to a control. The GSH replenishing potential of CeO2 nanoparticles could be one of the possible reasons for the biocompatible nature of CeO2-RGO nanocomposites. Our data warrant further and more advanced research to explore the biocompatibility/safety mechanisms of CeO2-RGO nanocomposites in different cell lines and animal models.

Cerium (Ce) doped SnO2/g-C3N4 composites were synthesized by a facile hydrothermal method. The obtained Ce doped SnO2/g-C3N4 composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–Vis), scanning electron microscope (SEM), energy dispersive spectra (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS). An electrode made of Ce doped SnO2/g-C3N4 exhibited a maximum specific capacitance of 274 F/g at 1 A/g current density. The supercapacitor device fabricated by using Ce-SnO2/g-C3N4//Activated Carbon as electrodes has showed an energy and power densities of 39.3 W h kg−1 and 7425 W kg−1. The asymmetric device gives the retention of 84.2% after completing 5000 cycles. When the same, Ce-SnO2/g-C3N4, composite is used as a photo-catalyst for reduction of methylene blue dye under visible light irradiation, exhibits a higher degradation efficiency of 98% which is higher efficiency compared to all other synthesized samples.

In this work, we report enhanced specific capactance and cycle stability of Fe-SnO2@CeO2 electrode for supercapacitor applications. The Fe-SnO2@CeO2 nanocomposite was synthesized through a simple chemical co-precipitation method. The electrochemical performances of the Fe-SnO2@CeO2 nanocomposite electrode are assessed by using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy techniques. In three electrode system, the Fe-SnO2@CeO2 nanocomposite electrode is exhibited a maximum specific capacitance of 348 F/g at a current density of 1 A/g. Further, the asymmetric supercapacitor (ASC) device performance has been evaluated and the ASC device produces a specific energy and specific power of 32.2 W h kg−1 and 747 W kg−1 at a current density of 1A/g, respectively. The device exhibited the capacitance retention of 85.05 % over 5000 cycles of operation. This study confirms that the Fe-SnO2@CeO2 is an alternative electrode material for high energy storage supercapacitor applications.

In present study, we report hydrothermal synthesis of reduced graphene oxide (RGO) supported NiMoO4-nanorods (NRs) nanocomposites (NiMoO4-NRs@RGO nanocomposites) for electro-catalysis of water to oxygen evolution and reduction reactions (OER/ORR). The prepared nanocomposites were characterized by x-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), energy dispersive and x-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performances of NiMoO4-NRs@RGO nanocomposites were examined in 0.5 M KOH (alkaline electrolyte) using cyclic voltammetry (CV), linear sweep voltammetry (LSV), Tafel and chronoamperometry (CA) electrochemical techniques at room temperature. The onset over-potentials of NiMoO4-NRs@RGO nanocomposite for ORR and OER were found to be of ~75 and ~185 mV, respectively, while the Tafel slopes for OER and ORR were observed to be ~54 and ~245 mV/dec respectively. The involved electrons (i.e. 4e−) in redox reactions were calculated using rotating disc electrode experiments. Based on admirable electro-catalytic performance of NiMoO4-NRs@RGO nanocomposites with low energy loss, suggesting it as cost effective and efficient OER/ORR electro-catalysts compared to noble metal electro-catalysts.

Zinc molybdenum oxide (ZnMoO4) sub-micron plates were efficaciously synthesized by hydrothermal method for electro-catalytic energy conversion applications. Electron microscopic studies show plate like morphology of the synthesized materials. The electrochemical experiments were conducted to investigate the catalytic performance of ZnMoO4 for hydrogen evolution reactions (HER) in acidic medium using 0.5 M H2SO4 electrolyte. The onset over potential, over-potential at 10 mA/cm2, and Tafel of ZnMoO4 sub-micron plates for HER were found to be of ~45 mV, ~140 mV, and ~230 mV/dec respectively.

In this article, Bio-treatment of α-Fe2O3 nanostructure using Phyllanthus niruri and Moringa stenopetala leaf extract as an effective reducing agent is carried out. The preparation of the rhombohedral α-Fe2O3 nanostructure is confirmed using X-ray diffraction analysis. The adsorption of biomolecules on the surface of the α-Fe2O3 nanostructure is confirmed using FT-IR. The chemical state analysis of green treated α-Fe2O3 nanoparticles was carried out using XPS techniques and it confirms the existence of Fe-2p and O-1s elements. The surface area of Moringa stenopetala leaf extract treated α-Fe2O3 nanoparticles were identified using BET analysis and it is found to be 58 m2/g. The formation of spherical shaped α-Fe2O3 nanoparticles was identified using HR-TEM analysis and EDX reveals the absence of any other impurities. The reactive species trapping experiment confirms the rapid production of O2•- and •OH radicals during photocatalytic process. The degradation efficiency of PNFO and MSFO against MB after 180 min was estimated to be 92% and 96%, respectively. The degradation efficiency of PNFO and MSFO against phenol after 240 min was estimated to be 90% and 92%, respectively.

In this paper, an investigation on microstructure, optical, dielectric, photocatalytic and electrochemical properties of monodispersed Ag-doped BaTiO3 nanosized particles modified with different contents of silver (1, 3, 5 mol %) prepared by viable sol-gel technique has been carried out. The obtained samples exhibit tetragonal phase as confirmed by X-ray diffraction and Raman spectra. Using XRD data, the crystallite size of undoped and Ag-doped BaTiO3 nanoparticles (NPs) was found to be in the range of 46–54 nm, and have interplanar spacing of 0.283 nm as confirmed by HRTEM images. The characteristic peaks occurred at 309, 511 and 717 cm−1 in Raman spectra predicted the formation of tetragonal phase of barium titanate. The calculated band gap energy of BaTiO3 NPs was reduced from 3.87 to 3.47 eV by incorporating the silver ions (5% Ag). Intensity of photoluminescent peaks decrease with increasing Ag content indicating that recombination of electrons-holes was effectively restrained. Dielectric permittivity as well as loss of prepared nanosized particles have been decreased sharply in low frequency region and remained almost constant with low value in high frequency region. Photo-assisted-catalytic property of Ag-doped BaTiO3 NPs towards degradation of hazardous rhodamine B (RhB) dye under visible irradiation (λ ≥ 400 nm) was thoroughly investigated, and a remarkable photocatalytic activity of Ag (5%)-doped BaTiO3 NPs was observed as 79%. On this account, it is promoted as an excellent nanophotocatalyst for the degradation of organic pollutants. C–V analysis depicted that the diffusion coefficient of BaTiO3 NPs increases considerably with Ag incorporation, which is favourable for large–scale energy storage applications. BET analysis supported the claim of presently prepared materials to be an efficient photocatalyst as well as a potential material for efficient energy storage devices.

In this paper, we report significant recycled efficiency of nickel molybdenum oxide (NMO) nanorods for multi-functional catalytic activities in photo-catalysis, electrochemical glucose sensing and asymmetric supercapacitors. Initially, we have used NMO nanorods as the photo-catalysts for organic dye degradation reactions using visible light source. The NMO nanorods show momentous photocatalytic activity in degradation of organic dye (~90% in 160 min) and also exhibit excellent regeneration efficiency. Consequently, the photo-catalysts were recovered via batch experiments for further use in other applications including electrochemical glucose sensing and asymmetric supercapacitors. Powder X-ray diffraction (XRD) and electron microscopic experiments were conducted before and after photo-catalysis for the materials stability. The recovered NMO nanorods show significant electrochemical detection of glucose in 0.1 M KOH. Moreover, the recovered NMO nanorods show promising nature for supercapacitors. The specific capacitance of recovered NMO nanorods was found to be ~660 F/g at 2 mV/s in 5 M KOH. Charge-discharge and stability of the electrodes were also studied for the commercial purpose.

Cobalt iron oxide (CoFe2O4) nanoparticles (CIO NPs) have been one of the most widely explored magnetic NPs because of their excellent chemical stability, mechanical hardness and heat generating potential. However, there is limited information concerning the interaction of CIO NPs with biological systems. In this study, we investigated the reactive oxygen species (ROS) mediated cytotoxicity and apoptotic response of CIO NPs in human liver cells (HepG2). Diameter of crystalline CIO NPs was found to be 23nm with a band gap of 1.97eV. CIO NPs induced cell viability reduction and membrane damage, and degree of induction was dose- and time-dependent. CIO NPs were also found to induce oxidative stress revealed by induction of ROS, depletion of glutathione and lower activity of superoxide dismutase enzyme. Real-time PCR data has shown that mRNA level of tumor suppressor gene p53 and apoptotic genes (bax, CASP3 and CASP9) were higher, while the expression level of anti-apoptotic gene bcl-2 was lower in cells following exposure to CIO NPs. Activity of caspase-3 and caspase-9 enzymes was also higher in CIO NPs exposed cells. Furthermore, co-exposure of N-acetyl-cysteine (ROS scavenger) efficiently abrogated the modulation of apoptotic genes along with the prevention of cytotoxicity caused by CIO NPs. Overall, we observed that CIO NPs induced cytotoxicity and apoptosis in HepG2 cells through ROS via p53 pathway. This study suggests that toxicity mechanisms of CIO NPs should be further investigated in animal models.

In this work, nanostructured In2O3 thin films with thickness in the range of 40–160 nm were deposited on glass substrates by the chemical spray pyrolysis technique. The microstructural, surface morphology and optical properties were investigated as a function of film thickness through x-ray diffraction, scanning electron microscopy equipped with energy dispersive spectroscopy, atomic force microscopy, Raman spectroscopy, UV–visible spectroscopy and photoluminescence measurements. The x-ray diffraction analysis showed that the deposited films were polycrystalline in nature with a cubic structure having (222) as preferred orientation. The morphological analyses of the samples exhibited uniform and smooth surface of the films with systematical increments in the surface roughness with increasing film thickness. The grain size increased from 9 nm to 13 nm with increasing film thickness. Raman spectroscopy has been employed to study the crystalline quality and the structural disorder of the films. A blue-shift in the energy band gap (E g) from 3.74 eV to 3.98 eV was observed with the increase of film thickness. Moreover, photoluminescence peaks of the In2O3 films appeared at 443 nm and 527 nm for all films. The thickness had a substantial influence on the microstructural and optical properties as well as on the luminescence intensity of the films. The strategy presented here indicates that the prepared films could be suitable candidates for optoelectronic device applications.

In this paper, we present a study of the structural and optical properties of organic-inorganic halide-based perovskite semiconductors with band gaps varying from NIR to visible at room temperature. Thin films of nanocrystalline CH3NH3PbI3 with different concentrations of methylammonium iodide (MAI) have been successfully deposited onto glass substrates using single step spin-coating technique. The prepared films have been characterized by X-ray diffraction, optical absorption spectroscopy and photoluminescence measurements. X-ray diffraction scans revealed that even for stoichiometric atomic cOncentrations of MA:Pb:I of 1:1:3, the PbI2 phase was also present. The PbI2 phase showed a highly textured along the (001) direction in all the prepared films, with a crystallite size in the range of approximately 30-40 nm. The optical absorbance edge of CH3NH3PbI3 thin films is described in terms of direct transition model proposed by Tauc in the strong absorption region. The band gap of the pure PbI2 film was calculated to be 2.40 eV, whereas the band gap of the pervoskite film with stoichiometric ionic ratio of 1:1 PhI2 and CH3NH3I was calculated to be 1.46 eV, while absorption coefficient is similar to 10(5) cm(-1). Photoluminescence measurements showed a red shift in the perovskite emission with increasing the MAI concentration, confirming the correct placement of the MA ions in the perovskite crystalline structure showing the PbI2 octahedra. Our results confirm the existence of PbI2 phase in the highly efficient perovskite solar cells, as demonstrated in the recent publication. (C) 2015 Elsevier B.V. All rights reserved.

In this communication, indium oxide (In2O3) and Zn-doped In2O3 nanoparticles with different zinc percentage (0–5%) have been prepared by a facile chemical process. A variety of analytical tools such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-Visible, photoluminescence spectroscopy, photocatalytic measurements and impedance spectroscopy were employed to assess the characteristics of prepared nanoparticles (NPs). From XRD analysis it is observed that all samples exhibit pure cubic phase with highly crystalline nature. XPS spectra revealed the composition and chemical state of Zn-doped In2O3 NPs. The estimated optical band gap was found to decrease with increase of Zn concentration. Magnetic hysteresis exhibited that pure and Zn-doped In2O3 NPs possess ferromagnetic behavior at room temperature. Dielectric constant ( e ' ) as well as dielectric loss ( e '' ) decreases exponentially in lower frequency range, but remains almost constant in higher frequency range. Moreover, Zn(5%)-doped In2O3 nanoparticles showed much higher photocatalytic activity as compared with pure In2O3 nanoparticles towards degradation of hazardous methylene blue dye. The results of present study demonstrated that synthesized nanoparticles may be employed efficiently as environmentally convenient photocatalyst for industrial effluent treatment.

In the present study, undoped and Mn-doped ZnO nanoparticles with different Mn concentrations (4 and 6 at.%) have been prepared by polymeric precursor method. The effects of Mn content on the structural, optical, and magnetic properties of these nanoparticles were investigated in detail. Room temperature X-ray diffraction (XRD) data revealed hexagonal wurtzite structure of the samples and no other secondary phase has been noticed. The microstructural analysis confirms that the particles of Mn:ZnO are spherical in shape with size ranging between 32 and 45 nm as calculated by Scherrer’s equation and transmission electron microscopy (TEM) images. UV–visible absorption spectroscopy measurements affirm a blue-shift in the band gap with increasing Mn doping in ZnO. The hysteresis loops (M–H) exhibit ferromagnetic behaviour of all samples at room temperature. Temperature-dependent resistivity measurements show semiconducting nature of the samples and reduction in the resistivity on Mn substitution.

Because of unique optical behavior gold nanorods (GNRs) have attracted attention for the application in biomedical field such as bio-sensing, bio-imaging and hyperthermia. However, toxicological response of GNRs is controversial due to their different surface coating. Therefore, a comprehensive knowledge about toxicological profile of GNRs is necessary before their biomedical applications. First time, we investigated the toxic response of GNRs coated with platinum (GNRs-Pt) in human breast carci- noma (MCF-7) cells. Platinum coating further improves the optical and catalytic properties of GNRs. Assays such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT), neutral red uptake (NRU) and lactate dehydroganase (LDH) assays have shown that GNRs-Pt induced cytotoxicity at very low exposure levels (0.1-0.8 l gm L 21 ). Accumulation of cells in SubG1 phase and low mitochondrial membrane potential (JC-1 probe) in treated cells suggest that GNRs-Pt induced cell death via apoptotic pathway. Quantitative real-time PCR data demonstrated that mRNA expression of apoptotic genes (bax, caspase-3 and caspase-9) were up-regulated while anti-apoptotic gene bcl-2 was down-regulated in cells exposed to GNRs-Pt. We further observed the higher activity of caspase-3 and caspase-9 enzymes in GNRs-Pt treated cells supporting mRNA data. Moreover, N-acetyl cysteine (NAC) significantly attenu- ated the ROS generation and cytotoxicity induced by GNRs-Pt in MCF-7 cells suggesting that ROS might plays a crucial role in GNRs-Pt induced toxicity. This study warns of possible toxicity of GNRs even at very low exposure levels. Further investigations needed to explore potential mechanisms of this low dose

We investigated the anticancer potential of Ag-doped (0.5–5%) anatase TiO2 NPs. Characterization study showed that dopant Ag was well-distributed on the surface of host TiO2 NPs. Size (15 nm to 9 nm) and band gap energy (3.32 eV to 3.15 eV) of TiO2 NPs were decreases with increasing the concentration of Ag dopant. Biological studies demonstrated that Ag-doped TiO2 NP-induced cytotoxicity and apoptosis in human liver cancer (HepG2) cells. The toxic intensity of TiO2 NPs was increases with increasing the amount of Ag-doping. The Ag-doped TiO2 NPs further found to provoke reactive oxygen species (ROS) generation and antioxidants depletion. Toxicity induced by Ag-doped TiO2 NPs in HepG2 cells was efficiently abrogated by antioxidant N-acetyl-cysteine (ROS scavenger). We also found that Ag-doped TiO2 NPs induced cytotoxicity and oxidative stress in human lung (A549) and breast (MCF-7) cancer cells. Interestingly, Ag-doped TiO2 NPs did not cause much toxicity to normal cells such as primary rat hepatocytes and human lung fibroblasts. Overall, we found that Ag-doped TiO2 NPs have potential to selectively kill cancer cells while sparing normal cells. This study warranted further research on anticancer potential of Ag-doped TiO2 NPs in various types of cancer cells and in vivo models.

The microstructural, optical and photocatalytic properties of undoped and 5% Zn doped CeO2 nanocrystals (NCs) have been explored through various analytical techniques, viz. powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-visible, Raman and photoluminescence (PL) spectroscopy. XRD data analysis revealed face centred cubic (FCC) crystal symmetry of the samples with average crystallite size in the range of 19–24 nm. XPS results confirmed that the Zn ions exist in +2 states and successfully incorporated into the CeO2 matrix. Internal structure and morphology observed by TEM exhibited almost uniform cubical shape of the particles of average size ~20–26 nm. The enegy bandgap of undoped and Zn doped CeO2 NCs had a direct transition of 3.46 eV and 3.57 eV respectively as estimated by the optical absorption data. The increase in the bandgap revealed blue shift of absorption edge due to the quantum confinement effects. The NCs exhibited an inherent luminescence emission peak at ~408 nm in PL spectra. Improvement in the photocatalytic activity was observed for Zn incorporated sample attributed to the enhanced light absorption or/and fall in charge recombination rate between CeO2 and Zn.

In this report, a parametric study was carried out on the single walled carbon nanotubes (SWCNTs) based Cu2O/SWCNTs nanocomposite. The SWCNTs were synthesized via plasma enhanced chemical vapour deposition (PECVD) process and nanocomposite through RF sputtering technique. The prepared samples have been characterized through Fourier transform infrared (FTIR) spectroscopy, x-ray diffractometry (XRD), electron microscopy (SEM/HRTEM), energy dispersive x-ray (EDX) spectroscopy, x-ray photoelectron spectroscopy (XPS) and Raman scattering techniques for the detailed structural information. The analysis of XRD data affirms the amorphous nature of the nanotubes and crystalline phase of the Cu2O sample. HRTEM micrographs reveal dispersion of Cu2O nanoparticles of an average size of ∼3.2 nm onto the surface of SWCNTs. The optical properties were studied through UV–vis spectroscopy. Using Tauc’s relation, band gap was estimated and found to be 2.7 and 2.51 eV for Cu2O and Cu2O/SWCNTs nanocomposite respectively. The photocatalytic activity of the nanoparticles and nanocomposite was explored by the photodegradation of methylene blue solution under visible light irradiation. Field dependent magnetization exhibits ferromagnetic nature of both the samples at room temperature that opens a new window for the future electronic devices based on carbon nanotubes.

We investigated the effect of Zn-doping on structural and optical properties as well as cellular response of TiO2 nanoparticles (NPs) in human breast cancer MCF-7 cells. A library of Zn-doped (1–10 at wt%) TiO2 NPs was prepared. Characterization data indicated that dopant Zn was incorporated into the lattice of host TiO2. The average particle size of TiO2 NPs was decreases (38 to 28 nm) while the band gap energy was increases (3.35 eV–3.85 eV) with increasing the amount of Zn-doping. Cellular data demonstrated that Zn-doped TiO2 NPs induced cytotoxicity (cell viability reduction, membrane damage and cell cycle arrest) and oxidative stress (reactive oxygen species generation & glutathione depletion) in MCF-7 cells and toxic intensity was increases with increasing the concentration of Zn-doping. Molecular data revealed that Zn-doped TiO2 NPs induced the down-regulation of super oxide dismutase gene while the up-regulation of heme oxygenase-1 gene in MCF-7 cells. Cytotoxicity induced by Zn-doped TiO2 NPs was efficiently prevented by N-acetyl-cysteine suggesting that oxidative stress might be the primarily cause of toxicity. In conclusion, our data indicated that Zn-doping decreases the particle size and increases the band gap energy as well the oxidative stress-mediated toxicity of TiO2 NPs in MCF-7 cells.

Cadmium sulfide (CdS) quantum dots (QDs) with cubic phase were prepared using simple precursors by chemical precipitation technique, and their thin films were grown on glass substrates by chemical bath deposition. The obtained quantum dots were characterized for their structural, morphological, optical, thermal and electrical properties using X-ray diffraction (XRD), field emission transmission electron microscopy, UV–visible absorption spectroscopy, Raman spectroscopy, photoluminescence, thermogravimetric analysis/differential thermal analysis and low-temperature electrical transport measurements, respectively. XRD pattern reveals that the prepared CdS QDs are highly pure and crystalline in nature with cubic phase. The average particle size, estimated to be ~2 nm, is almost in agreement with the values calculated by Brusis formula. Selected area electron diffraction also recognizes the cubic structure of CdS quantum dots. The UV–visible spectra exhibit a blueshift with respect to that of bulk sample which is attributed to the quantum size effect of electrons and holes. The band gap of CdS QDs is calculated from absorption data using Tauc plot and found to be 2.84 eV. Energy-dispersive X-ray analysis reveals the presence of Cd and S in almost stoichiometric ratio in the prepared CdS QDs. Micro-Raman spectroscopic studies also yield convincing evidence for the transformation of structure. The emission spectra of CdS QDs show peak centered at 541 nm, which is attributed to the presence of cadmium vacancies in the lattice. The DC resistivity data at low temperatures are qualitatively consistent with the variable-range hopping model, and the density of states at the Fermi level is determined.