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Mn-doped ZnO nanostructures were synthesized with three different estimated Mn concentration (atoms/cm3) using sol-gel technique. As synthesized nanostructures were analyzed using X-ray diffraction spectroscopy (XRD), Fourier-transform-infrared spectroscopy (FTIR), and field-emission secondary electron microscopy (FE-SEM). XRD pattern reveals of doped ZnO nanostructures reveal a peak related to Zn2Mn3O8 phase along with peaks related to pure ZnO. Average particle size, estimated using Scherer formula, increases with Mn-doping. FE-SEM reveals morphological change from spherical particles (~15-20 nm) to nano-rods then nano-belt like 2 D super lattice structure after doping. Optical band gap obtain from Tauc's plot is 3.82, 2.05, 2.1 and 2.47 eV for pure-ZnO and Mn-doped samples with 13×1017, 20×1017 and 32×1017 Mn atoms/cm3, respectively. Presence of vibration band from 665 to 680 cm-1 in FTIR spectra endorses metal oxide formation. Nanomaterials were screen printed over working electrode of pre-fabricated three terminal electrode. This was used for electrochemical detection of myoglobin (Mb); a biomarker for acute myocardial infarction and were tested for Mb concentrations from 0-15 nM using cyclic voltammetry and electrochemical impedance spectroscopy. Redox current and charge transfer resistance varied linearly with Mb concentration. 7-fold increased sensitivity towards Mb in Mn-doped ZnO sensors is attributed to doping induced stress in nanostructures. Maximum sensitivity of 95μA-cm-2 nM-1 with LOD of 0.35 nM is observed for ZnO with 13 × 1017 Mn atomic/cm3. Response time of ~10 ms is observed. Interference carried out with 7 nM Cytochrome c and 5 mM HSA reveal different oxidation potential and current value for Mb.

In a quest for developing new material with performance of dye sensitized solar cells (DSSC) a non-metallic doping i.e., of nitrogen was carried out to commercial TiO2 nanoparticle using simple, facile and sustainable mechanochemistry method. Melamine was used as source of nitrogen and different weight percentages (10, 30, 50, 70 and 90%), mixed with TiO2 mechanically in a ball mill for 12 h at an speed of 500 rotations per minute followed by annealing at 550 °C for 2 h under constant N2 flow. The post nitrogen doping structural analysis indicated anatase phase of TiO2.The morphological observations by transmission electron microscopy did not show change due to melamine and particle size remains less than 30 nm. N-doping resulted in an increased wavelength of peak absorption from 334 nm to about 350 nm and shifting of absorption edge from UV (~ 400 nm) to visible region (~ 500 nm) resulting in the reduction of the band gap from 3.14 to 2.43 eV which is supported by XPS and Tauc plot analysis. The functional analysis reveals amide bond at higher melamine concentration. The DSSC characteristics were measured with source-meter coupled with simulated light source which shows a significant increase of cell efficiency from 26 with 10% of melamine to that of 86 with 90% melamine. The increase in efficiency was linear with increasing nitrogen doping concentration. The study suggested that melamine can be used as a suitable N-dopant source for improved photoconversion properties that can help engineer to develop a device with enhanced performance.

Here we report a simple and effective method in tailoring the optoelectronic properties of semi-conducting metal oxide for suitable device application. Sol-gel synthesis was used to synthesize manganese doped TiO2 nanopowder and commercially available TiO2 nanopowder was used as reference material. Thick films of these powder were screen printed on FTO coated glass and annealed at 450 degrees C in ambient air. Separately, 60 μL of neodymium chloride prepared from neodymium oxide, 60 μL of ruthenium based commercial dye (N719) and 60 μL of extracts of calendula orange and dog flower were used as sensitizer to improve the photoconductance properties. Elemental analysis confirmed synthesis of composite material of Mn and TiO2. Morphological observation showed a uniform particles of 25 to 50 nm diameter. Optoelectronic properties were studied by using thick films of these powders as working electrode as a function of wavelength from 430 to 750 nm and the cyclic voltammogram were obtained by scanning potential from -1.5 V to +1.5 V at the illumination intensity of 1000 Wm(-2). Sensitization resulted in additional absorption and functional bands. Oxidation peak current was found decreasing with increasing wavelength. Sensitization with flower extract resulted in increased oxidation current at higher wavelength indicating the improved photoconduction in comparison with N719 and neodymium.

Extensive efforts are being made in enhancing the photoconversion efficiency of TiO2 based dye sensi- tized solar cells (DSSC) using different approaches. In this work, the Sn-doped TiO2 nanopowder was sensitized with flower extracts of Dahlia Violet (DV), Rabbit flower (RF) and their mixed extract separately other than the com- mercial N719 dye and DSSC characteristics were studied. Hydrothermal method was used to synthesize Sn-doped TiO2 for 48 h at 150 C. X-ray diffraction, UV-Vis, FTIR and Raman scattering were used to characterize the syn- thesized powder. DSSCs of the synthesized powder was fabricated using conventional sandwich type technique sealed with Surlyn polymer film. The photocurrent-volt- age characteristics were measured under solar simulated light using source-meter. It is interesting to note that the flower extract resulted in comparable photoconversion ef- ficiency as that of N719 dye. When the powder was sen- sitized with N719, 1.66 % efficiency was achieved while mixed extract resulted in 1.28 %, DV in 0.99 % and RF in 0.52 % efficiency. The results of various analysis tech- niques and cell characteristics are correlated.

With an increasing focus on applied research, series of single/composite materials are being investigated for device development to detect several hazardous, dangerous, and toxic molecules. Here, we report a preliminary attempt of an electrochemical sensor fabricated using pristine Ni and Cr–doped nano tin oxide material (SnO2) as a tool to detect agro-hazardous material, i.e. Organophosphate (OP, chlorpyrifos). The nanomaterial was synthesized using the solution method. Nickel and chromium were used as dopant during synthesis. The synthesized material was calcined at 1000 °C and characterized for morphological, structural, and elemental analysis that showed the formation of agglomerated nanosized particles of crystalline nature. Screen-printed films of powder obtained were used as a matrix for working electrodes in a cyclic voltammogram (CV) at various concentrations of organophosphates (0.01 to 100 ppm). The CV curves were obtained before and after the immobilization of acetylcholinesterase (AChE) on the nanomaterial matrix. An interference study was also conducted with hydroquinone to ascertain the selectivity. The preliminary study indicated that such material can be used as suitable matrix for a device that can easily detect OP to a level of 10 ppb and thus contributes to progress in terms of desired device technology for the food and agricultural-industries.