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A Cu(II) coordinated metal–organic framework, {[Cu4(BTC)2(4-APy)2(μ3-OH)2]·[(CH3OH)0.5]2·(H2O)2}n(Cu-MOF), has been synthesized by the solvo-diffusion of Cu(NO3)2to an alcoholic solution of 4-aminopyridine (4-APy) and 1,3,5-benzenetricarboxylic acid (H3BTC) in equimolar proportion. A single-crystal X-ray structure determination suggests that the four-Cu(II)-connected motif ([CuII]4) via edge sharing of two Cu3–O cores and bridging by six acetato functions of the BTC3–connector generates two five-coordinated distorted-square-pyramidal CuO5units and two distorted-square-planar CuO4units; the Cu(II) knot in the latter one (CuO4) is coordinated by pyridyl-Nof 4-APy. The remaining donor centers of acetato-Oof BTC3–bind adjacent [CuII]4core to form an infinite 3D network structure. The coordination of CH3OH and H2O forms different hydrogen bonds to make a strong superstructure. A surface morphology determination shows a nanoflower pattern. The hybrid material Cu-MOF exhibits a very high specific capacitance, 547 F g–1, at a scan rate of 2 mV s–1with excellent recycling stability (retains 97.4% after 5000 cycles). The χMTvalue for Cu-MOF at 300 K is 1.735 cm3mol–1K for four copper(II) ions, which is as expected for four isolated copper(II) ions with g= 2.15. The χMTvalues are almost constant until ca. 55 K, and then χMTdecreases sharply, giving a minimum value of 0.753 cm3K mol–1at 2 K.

Propylammonium lead iodide, C3H7NH3PbI3, was synthesized by sol-gel method and incorporated in polyvinylidene difluoride (PVDF) to produce nanofibers by electrospinning technique. These nanofibers possess an improved degree of crystallinity with the successful conversion of non-polar phase to polar phase content. The tensile strength and thermal stability of nanofibers are also enhanced significantly with the addition of C3H7NH3PbI3.The fabricated lightweight, flexible, durable, cost-effective, self-powered piezoelectric nanogenerator is observed to generate 60 V open circuit voltage, 27.5 μA short circuit current, and 9.81 mW/m2power under periodic hammering with a free hand. Voltage generation of this nanogenerator scavenging mechanical energy from various sources is also detected. This device exhibits remarkable mechano-sensitivity (∼ 6.3 V/N in the low applied force region and 12.12 V/N in the higher applied force region) with superior energy conversion efficiency ∼ 42.03 %. The flexibility along with ultra-sensitivity of this power generator initiates its utility as wearable nano sensors. Moreover, the ultrafast capacitor charging ability of the nanogenerator assures its potential as a nano-tactile sensor. The optimal energy band gap and photoactive nature of the C3H7NH3PbI3@PVDF composite confirm its efficacy as a photodetector/diode. Therefore, the proposed C3H7NH3PbI3@PVDF composite enables to design a multifaceted device that can perform separately/simultaneously as mechanical energy and solar energy harvester.

Monoclinic amorphous Ni1-xMnxWO4(x = 0.00, 0.02) compounds have been successfully synthesized by hydrothermal technique for achieving better capacitive and conductive performances. Different characterization techniques like X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis) and photoluminescence (PL) spectroscopy have been employed to investigate their structural, microstructural, and optical properties. Mn-ion incorporation in the NiWO4lattice reduces the particle size of the sample to ∼4.5 nm, compared to the pure undoped NiWO4sample (∼18 nm), confirmed from the transmission electron microscopy image and Brunauer–Emmett–Teller analyses (BET). Tauc plot of Ni0.98Mn0.02WO4sample exhibits a significant increase in bandgap energy, compared to pure undoped NiWO4sample due to the quantum confinement effect. The electrochemical performance of electrodes made with these materials has been revealed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) properties and electrochemical impedance spectroscopy (EIS). Moreover, the addition of 2 % Mn in NiWO4causes an increase in specific surface area (117.390 m2/g) due to the reduced particle size of the material, resulting in excellent specific capacitance of 463 F g−1at 0.5 A g−1current density. The detailed charge storage mechanism for the improvement of conductivity and electrochemical performance of the Mn-doped NiWO4has been revealed in different studies. An asymmetric supercapacitor device (ASC) has been fabricated using Mn-doped NiWO4electrode material as positive electrode. The device shows superior cyclic stability upto 5000 cycles, can retain 88.4 % of its initial value.