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We report the synthesis of ZnV2O4 spinel oxide novel nanosheets via a template free route to explore its potential hydrogen storage properties for the first time. 2D layered nanostructures are excellent candidates for storage applications. This attracted our interest to synthesize novel spinel oxide nanosheets (NSNs) of ZnV2O4. The maximum value for hydrogen absorption in ZnV2O4 nanosheets at 473 K is 1.36 wt.% and 1.74 wt.% at 573 K, respectively. Our hydrogen storage measurements along ZnV2O4 reveal its superiority over previous reports on hydrogen absorption values concerning oxides, nitrides and chalcogenides. To understand the rate-limiting mechanism, various kinetics models are applied. The calculations show that kinetics is governed by 3D growth with constant interface velocity. The measurements point to ZnV2O4 spinel oxide as a promising hydrogen storage material. PL measurements demonstrate the potential for violet/blue optoelectronic devices.

The electronic, elastic, acoustic and optical properties of cubic phases TiO2 fluorite and pyrite are investigated using the first principles calculations. We have employed five different exchange–correlation functions within the local density and generalized gradient approximations using the ultrasoft plane wave pseudopotential method. The calculated band structures of cubic-TiO2 elucidate that the TiO2 fluorite and pyrite are direct and indirect semiconductors in contrast to the previous findings. From our studied properties such as bulk and shear moduli, elastic constants C44 and Debye temperature for TiO2 fluorite and pyrite, we infer that both the cubic phases are not superhard materials and the pyrite phase is harder than fluorite. The longitudinal and transversal acoustic wave speeds for both phases in the directions [100], [110] and [111] are determined using the pre-calculated elastic constants. In addition, we also calculate the optical properties such as dielectric function, absorption spectrum, refractive index and energy loss function using the pre-optimized structure. On the observation of optical properties TiO2 fluorite phase turn out to be more photocatalytic than pyrite. & 2013 Published by Elsevier B.V.

Fabrication of SnO2 nanobelts has been carried out by employing vapour liquid solid (VLS) and vapour solid (VS) mechanism. Nanobelts obtained by VLS mechanism were fabricated at relatively low temperature using Fe powders as a catalyst by means of chemical vapour deposition (CVD) technique. Direct thermal evaporation of SnO2 nanobelts was carried out at 1350°C in the atmosphere of Argon gas via VS mechanism. In both cases, ramp rate was adjusted to 10°C/min. The structural, compositional and morphological characterisations of synthesised SnO2 nanobelts were conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X‑ray spectroscopy (EDS). Magnetic behaviour of the nanobelts was studied by vibrating sample magnetometer (VSM). Cathodoluminescence (CL) spectra were studied using Renishaw Raman spectroscopy system. The growth of nanobelts is found to be homogeneous and dense. The nanobelts formed by VLS mechanism show ferromagnetic behaviour along with some other exciting...

In this work we propose a novel idea of using thermoelectric material in lithium ion batteries. The reason behind this idea is to improve the efficiency of batteries especially when heat dissipation and exothermic reaction of cathode and anode with the electrolyte at higher temperatures restricts their continuous operation due to thermal runaway. In order to execute this idea we develop a new synthetic technique for fabrication of Bi 2 Se 3 (thermoelectric material) and also compare it's efficiency by preparing this material by existing synthetic technique. Charge/discharge comparison of both the samples indicate that the synthesis technique has a profound effect on electrochemical performance. Bismuth selenide (Bi 2 Se 3 ) is intentionally selected for this purpose. Bi 2 Se 3 rectangular nanosheets (BRNS) with thicknesses of 200–500 nm are synthesized by a simple thermochemical method in which we use bismuth and selenium powders as precursors. Self assembled nanosheets (SANS) in spherical shape are prepared by conventional hydrothermal technique. Charge discharge experiments show that BRNS synthesized with this technique have reasonable performance as compared to nanosheets synthesized by conventional hydrothermal technique. It shows that first discharge capacity is up to 725.6 mAh g −1 for BRNS and 419.6 mAh g −1 for SANS.

Here we report the synthesis of highly pure single crystalline tin selenide (SnSe) nanospheres by pretreatment of precursors with aqueous ammonia. In this work we have demonstrated that aqueous ammonia not only controls the preferred growth orientation but also controls the morphology of SnSe. Chemical vapor deposition technique was used for the growth of SnSe nanostructures. The optical properties were studied using UV–vis–NIR spectroscopy and Photoluminescence (PL) spectrum.

The ultrasoft pseudopotential technique is used to explore the elastic, electronic and optical properties of cotunnite TiO2 using LDA and GGA proposed by Perdew Wang (PW91), Perdew–Burke–Ernzerhof (PBE) functional as defined by Wu and Cohen (PBEWC) and PBE functional for solids (PBESOL). The calculated elastic constants bulk modulus, shear modulus and Young’s modulus are in agreement with the previous theoretical reports. From our investigated shear anisotropy factors (A1 ,A 2, and A3), we infer that cotunnite TiO2 is strong anisotropy in case of A1 and A2 and less anisotropy in case of A3. The value of mean sound speed and Debye temperature are calculated using the obtained values of elastic moduli. The calculated structural parameters are in accord with the reported experiment and theoretical results. Our obtained values of direct bandgaps show an improvement over the other previous theoretical reports. The values of the dielectric constant (e1(o)) of cotunnite TiO2 calculated within LDA and GGA approximations are 7.655 (LDA (CA-PZ)), 7.578 (GGA (PW91)), 7.685 (GGA (WC)) and 7.655 (GGA (PBESOL)), which are slightly higher than the experimental values of rutile (6.69) and anatase (6.55) polymorphs. The obtained values of the refractive index are consistent with rutile TiO2 and higher than anatase phase. The investigated imaginary part of dielectric constant and absorption spectrum reflect that the cotunnite TiO2 is a weak photocatalytic material as compared to anatase and similar to rutile phases.

Monodispersed mesoporous hollow spheres of polymer-silica and carbon-silica nanocomposites with an "interpenetration twin" nanostructure have been successfully synthesized by a co-sol-emulsion-gel method. The obtained mesoporous hollow carbon spheres (MHCSs) exhibited an open interconnected mesoporous shell that is endowed with high specific surface area (SBET, 2106-2225 m(2) g(-1)) and large pore volume (1.95-2.53 cm(3) g(-1)). Interestingly, the diameter of the uniform MHCSs could be precisely tuned on demand, as an effective electrode material in supercapacitors, MHCSs with a diameter of 90 nm deliver the shortest time constant (τ0 = 0.75 s), which is highly beneficial for rate capacitance (180 F g(-1) at 100 A g(-1), a full charge-discharge within 0.9 s) and cyclic retainability (3% loss after 20,000 cycles). The newly developed synthesis route leads to unique interconnected mesoporous hollow carbonaceous spheres with open-framework structures, providing a new material platform in energy storage.

To explore the effect of morphology on catalytic properties of graphitic carbon nitride (GCN), we have studied oxygen reduction reaction (ORR) performance of two different morphologies of GCN in alkaline media. Among both, tubular GCN react with dissolved oxygen in the ORR with an onset potential close to commercial Pt/C. Furthermore, the higher stability and excellent methanol tolerance of tubular GCN compared to Pt/C emphasizes its suitability for fuel cells.

Controlled micro/mesopores interconnected structures of three-dimensional (3D) carbon with high specific surface areas (SSA) are successfully prepared by carbonization and activation of biomass (raw rice brans) through KOH. The highest SSA of 2475 m(2) g(-1) with optimized pore volume of 1.21 cm(3) g(-1) (40% for mesopores) is achieved for KOH/RBC = 4 mass ratio, than others. The as-prepared 3D porous carbon-based electrode materials for supercapacitors exhibit high specific capacitance specifically at large current densities of 10 A g(-1) and 100 A g(-1) i.e., 265 F g(-1) and 182 F g(-1) in 6 M KOH electrolyte, respectively. Moreover, a high power density ca. 1223 W kg(-1) (550 W L(-1)) and energy density 70 W h kg(-1) (32 W h L(-1)) are achieved on the base of active material loading (~10 mg cm(2)) in the ionic liquid. The findings can open a new avenue to use abundant agricultural by-products as ideal materials with promising applications in high-performance energy-storage devices.

Hierarchical nanostructures (Hs) have recently garnered enormous attention due to their remarkable performances in catalysis, electronic devices, energy storage and conversion. Considering the advantage of hierarchical nanostructures, we have formulated a facile and template free method to synthesize novel hierarchical nanospheres (NHNs) of ZnV2O4. Both zinc and vanadium are earth abundant, relatively economical and can offer several oxidation states, which can render a broad range of redox reactions favorable for electrochemical energy storage applications. Keeping these points in mind, we investigated for the first time the electrochemical supercapacitor performance of NHNs. The electrochemical measurements were performed in 2 M KOH solution. The measured specific capacitance of ZnV2O4 electrode is 360 F/g at 1 A/g with good stability and retention capacity of 89% after 1000 cycles. Moreover, the hydrogen storage properties of NHNs were measured at 473, 573, and 623 K with an absorption of 1.76, 2.03, and 2.49 wt %. respectively. These studies pave the way to consider ZnV2O4 as prospective material for energy storage applications.

We have developed a facile, scale up, and efficient method for the preparation of graphitic-C3N4 nanofibers (GCNNFs) as electrodes for supercapacitors and photocatalysts. The as-synthesized GCNNFs have 1D structure with higher concentration of nitrogen that is favorable for higher conductivity and electrochemical performance. Secondly, the high surface area of GCNNF provides a large electrode-electrolyte contact area, sufficient light harvesting and mass transfer, as well as increased redox potential. Thus, the GCNNF supercapacitor electrode shows high capacitance of 263.75 F g(-1) and excellent cyclic stability in 0.1 M Na2SO4 aqueous electrolyte with the capacitance retention of 93.6% after 2000 cycles at 1 A g(-1) current density. GCNNFs exhibit high capacitance of 208 F g(-1) even at 10 A g(-1), with the appreciable capacitance retention of 89.5%, which proves its better rate capability. Moreover, the GCNNF shows enhanced photocatalytic activity in the photodegradation of RhB in comparison to the bulk graphitic-C3N4 (GCN). The degradation rate constant of GCNNF photocatalyst is almost 4 times higher than GCN. The enhanced photocatalytic activity of GCNNF is mainly due to the higher surface area, appropriate bandgap, and fewer defects in GCNNF as compared to GCN. As an economical precursor (melamine) and harmless, facile, and template-free synthesis method with excellent performance both in supercapacitors and in photodegradation, GCNNF is a strong candidate for energy storage and environment protection applications.

We firstly present a simple thermochemical method to fabricate high-quality Bi2Se3 nanoplatelets with enhanced figure of merit using elemental bismuth and selenium powders as precursors. The crystal structure of as synthesized products is characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) measurements. Morphological and chemical synthetic parameters are investigated through a series of experiments; thickness and composition of the platelets are well controlled in large scale production. Subsequently spark plasma sintering (SPS) is performed to fabricate n-type nanostructured bulk thermoelectric materials. Raman Spectroscopy of the two selected samples with approximately of 50 and 100 nm thicknesses shows three vibrational modes. The lower thickness sample exhibits the maximum red shift of about 2.17 cm-1 and maximum broadening of about 10 cm-1 by in-plane vibrational mode E2g. The enhanced value of figure of merit ∼0.41 is obtained for pure phase bismuth selenide to the best of our knowledge. We observe metallic conduction behavior while semiconducting behavior for nanostructured bismuth selenide is reported elsewhere which could be due to different synthetic techniques adopted. These results clearly suggest that our adopted synthetic technique has profound effect on the electronic and thermoelectric transport properties of this material.

For the first time, high quality SnSe nanowires were synthesized via chemical vapour deposition (CVD). The synthesized SnSe nanowires are single crystalline. The length of the nanowires is in tens of microns with an average diameter of about 30–40 nm. Further, the optical and electrical properties reveal the potential of SnSe nanowires for photovoltaic and optical devices. These studies will enable significant advancements of the next generation photodetection and solar cell applications.

An easy, scalable and environmentally benign chemical method has been developed to synthesize micro strings of graphitic-C3N4 (msg-C3N4) through pre-treatment of melamine with HNO3 in alkaline solvent at low temperature. This methodology results in a unique string type morphology of msg-C3N4 with higher surface area. These msg-C3N4 micro strings were used as a photocatalyst under visible light for photodegradation of rhodamine B, methyl blue and methyl orange. The msg-C3N4 shows enhanced photodegradation efficiency due to its high surface area and favourable bandgap. The first order rate constant for msg-C3N4 was measured which confirms the higher performance of msg-C3N4 in comparison to other reported materials such as g-C3N4, Fe2O3/g-C3N4 and TiO2 nanotubes. Thus, the method developed here is favourable for the synthesis of materials with higher surface area and unique morphology, which are favourable for high photodegradation activity.

Well controlled nanosheets-based hierarchical microspheres (NSHMS) of pure covellite phase CuS were synthesized using a facile PVP assisted solvothermal process. The reaction conditions were optimized using various amounts of PVP to develop unique hierarchical structured hollow microspheres. CuS hollow structures have a bandgap of ~1.97 eV. These mesoporous structures exhibit excellent photocatalytic activity in degradation of organic dyes (Methylene Blue) under natural light in comparison to other structures of copper sulphide. These photocatalysts show extraordinary reusability with over 96.5% degradation of organic dye after 6th cycle. A “bottom-up” assembly was successfully developed to synthesize hollow microspheres with unique and well defined architectures at large scale, which offer a good opportunity to understand the fundamental significance of unusual and complex hierarchical structures for their potential applications.

We report here on investigations of electrical and optical properties of single zigzag SnO2 nanobelts. Large scale zigzag nanobelts were obtained on a silicon substrate by a Chemical Vapor Deposition (CVD) approach. The average value of carrier concentrations (Nd) and electron mobility (μ) were calculated to be 1.39 × 1018 cm−3 and 70.76 cm2 V−1 s−1, respectively. Room temperature PL exhibits a broad emission peak centred at 600 nm. Three Raman active modes at 474.8, 633.8, 775.8 cm−1 were observed. Electron paramagnetic resonance measurements suggest the presence of many singly ionized states.

Novel nanoflowers (NNF) of Nb3O7F have been synthesized by a facile template free route without using any surfactant. The evolution of these NNF have been studied by varying different reaction parameters. Using the UV-Vis spectra absorption peak the calculated bandgap was 2.9 eV. Organic dye rhodamine B (RhB) was degraded with average photodegradation efficiency of 87.8%, 94.23% and 99.7% with higher rate constant k = 1.1559, 1.9011 and 3.8862 for 0.005 g, 0.01 g and 0.1 g respectively. The rate constant for 0.1 g was found to be larger than for Nb2O5, commercial TiO2 Degussa P25, carbon modified Nb2O5/TiO2, g-C3N4, Fe2O3/g-C3N4 composites and SnNb2O6.

We have established a facile and scaleable approach to fabricate tubular graphitic-C3N4 using melamine. The construction of the unique tubular morphology is a result of the pre-treatment of melamine with HNO3. Herein, for the first time, we have explored the electrochemical properties of g-C3N4 as an electrode material for supercapacitors. Tubular g-C3N4 has significant advantages due to its distinctive morphology, high surface area (182.61 m2 g−1) and combination of carbon with nitrogen. Therefore, tubular g-C3N4 demonstrated a good specific capacitance of 233 F g−1 at a current density of 0.2 A g−1 in 6 M KOH electrolyte. Furthermore, tubular g-C3N4 maintained a high capacitance retention capability (90%) after 1000 cycles. The photocatalytic activity of tubular g-C3N4 was evaluated using the organic dyes such as Methylene Blue (MB) and Methylene Orange (MO) under visible light. Tubular g-C3N4 demonstrated good photocatalytic activity and enhanced stability compared to bulk g-C3N4. The enhanced performance is because of the high surface area, which contains more active sites for reaction. The encouraging performance of tubular g-C3N4 in supercapacitors and as a photocatalyst points toward it being a prospective material for energy storage that is environmentally clean.