The present investigation details our interesting findings and insights into the evolution of exotic hierarchical superstructures of In(OH)3 under solvothermal conditions. Controlled variation of reaction parameters such as, reactant concentration, solvent system, crystal structure modifiers, water content along with temperature and time, yielded remarkable architectures. Diverse morphologies achieved for the first time includes (i) raspberry-like hollow spheres, (ii) nanosheet-assembled spheres, (iii) nanoparticle-assembled spheres, (iv) nanocube-assembled hollow spheres, (v) yolk-like spheres, (vi) solid spheres, (vii) nanosheets/flakes, and (viii) ultrafine nanosheets. A plausible mechanism is proposed based on the evidence gathered from a comprehensive analysis aided by electron microscopy and X-ray diffraction studies. Key stages of morphological evolution could be discerned and rationally correlated with nucleation, growth, oriented attachment, and Ostwald ripening mediated by dissolution-redeposition mechanism coupled with solid evacuation. Remarkably phase-pure bcc-In2O3 with retention of precursor morphology could be realized postcalcination at 400 °C, which underlines the advantage of this strategy. Two typical hierarchical structures (raspberry-like hollow spheres and nanoparticles assembled spheres) were investigated for their gas sensing and photocatalytic performances to highlight the advantages offered by nanostructuring. An impressive sensor response, Smax ≈ 7340 and 4055, respectively for the two structures along with appreciably fast response/recovery times over a wide concentration range and as low as 1 ppm exhibits the superior sensitivity toward carbon monoxide (CO). When compared to commercial In2O3, estimated rate constant indicates ∼3-4 times enhancement in photocatalytic activity of the substrates toward Rhodamine-B.
Summary
Nanofibrous CoMn2O4 materials are prepared by a simple and most adoptable sol‐gel process. To create the nanofabric morphology, small pieces of tissue paper are utilized as a template form. The prepared CoMn2O4 material was characterized by X‐ray diffraction, field‐emission scanning electron microscopy, Fourier‐transform infrared spectroscopy, Brunauer‐Emmett‐Teller, X‐ray photoelectron spectroscopy, and transmission electron microscopy techniques. Supercapacitive performance of the CoMn2O4 nanofibers was observed in an aqueous potassium hydroxide electrolyte, and a specific capacity of 134 mAh g−1 at 1 A g−1 was obtained. On the basis of the high energy storage performance of this material, an aqueous asymmetric supercapacitor (ASC) was assembled. The high power and energy density values of 0.725 kW kg−1 and 30 W h kg−1, respectively at 1 A g−1 were achieved. The ASCs can light up eleven light‐emitting diodes. Furthermore, a kitchen timer and a toy motor were also powered by the fabricated ASCs.
NiMn 2 O 4 (NMO) nanomaterials were prepared via a facile sol-gel process and small pieces of tissue paper were used as a template to obtain one-dimensional (1D) nanofabric shape. Connectivity of the nanoparticles in fabric shape was observed by field-emission scanning electron microscope and transmission electron microscope images. X-ray diffraction pattern was analyzed to confirm the pure phase and crystallinity of the end product. Energy dispersive X-ray spectroscopy was done to check the homogeneous distribution of the Ni, Mn and O elements. The 1D nanofabric NMO was further employed as an electrode material for supercapacitors (SCs). The cyclic voltammetry, galvanostatic charging/discharging and electrochemical impedance spectroscopy techniques were used to determine the supercapacitive properties of electrode materials. The high specific capacitance of 303 F g −1 was obtained at the current density of 0.5 A g −1 . Almost stable specific capacitance was obtained till 5000 cycles. The high specific capacitance and stability of the electrode material may be attributed to the fabric shape and connectivity of the particles where voids/gaps in between particles provide more accommodation for the ions. Asymmetric SC (ASC) device was also fabricated and its electrochemical performance was checked. Two yellow color light-emitting diodes and a motor fan were powered from series-connected two ASCs.
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