Studies on Isolation and Characterization of Starch from Rajgeera Grains (Amaranthus paniculatus Lin.)

Isolation and some of the important physicochemical properties of starch from rajgeera grains have been investigated. The yield of starch was about 61.2%, on whole grain basis. The results on physicochemical properties revealed that it exhibited moderate swelling and higher solubility (55.5%) in water, as compared to other millet starches. An extensive solubility in dimethylsulphoxid (72.5%) of the starch indicated easy penetration of solvent in a granular matrix, may be due to labile and heterogenous bonding forces within the granules. Brabender viscoamylographic data on pasting characteristics revealed that it yielded low viscosity (448 B. U.) at concentration of 10% (w/v) and showed very little tendency to retrograde during cooling of the starch paste. The amylopectin content was 88.5% indicating the starch of rajgeera is probably waxy in nature. Amylolytic digestibility of native and gelatinized starch of rajgeera by human salivary α-amylase and glucoamylase was investigated.     

Functionalization of Graphene Oxide Films with Au and MoOx Nanoparticles as Efficient p‐Contact Electrodes for Inverted Planar Perovskite Solar Cells

A graphene oxide (GO) film is functionalized with metal (Au) and metal‐oxide (MoO_x) nanoparticles (NPs) as a hole‐extraction layer for high‐performance inverted planar‐heterojunction perovskite solar cells (PSCs). These NPs can increase the work function of GO, which is confirmed with X‐ray photoelectron spectra, Kelvin probe force microscopy, and ultraviolet photoelectron spectra measurements. The down‐shifts of work functions lead to a decreased level of potential energy and hence increased V_oc of the PSC devices. Although the GO‐AuNP film shows rapid hole extraction and increased V_oc, a J_sc improvement is not observed because of localization of the extracted holes inside the AuNP that leads to rapid charge recombination, which is confirmed with transient photoelectric measurements. The power conversion efficiency (PCE) of the GO‐AuNP device attains 14.6%, which is comparable with that of the GO‐based device (14.4%). In contrast, the rapid hole extraction from perovskite to the GO‐MoO_x layer does not cause trapping of holes and delocalization of holes in the GO film accelerates rapid charge transfer to the indium tin oxide substrate; charge recombination in the perovskite/GO‐MoO_x interface is hence significantly retarded. The GO‐MoO_x device consequently shows significantly enhanced V_oc and J_sc, for which its device performance attains PCE of 16.7% with great reproducibility and enduring stability.     

Physical properties of sprayed antimony doped tin oxide thin films:The role of thickness

Transparent conducting antimony doped tin oxide（Sb:SnO₂） thin films have been deposited onto preheated glass substrates using a spray pyrolysis technique by varying the quantity of spraying solution.The structural, morphological,X-ray photoelectron spectroscopy,optical,photoluminescence and electrical properties of these films have been studied.It is found that the films are polycrystalline in nature with a tetragonal crystal structure having orientation along the（211） and（112） planes.Polyhedrons like grains appear in the FE-SEM images. The average grain size increases with increasing spraying quantity.The compositional analysis and electronic behaviour of Sb:SnO₂ thin films were studied using X-ray photoelectron spectroscopy.The binding energy of Sn3d_5/2 for all samples shows the Sn⁴⁺ bonding state from SnO₂.An intensive violet luminescence peak near 395 nm is observed at room temperature due to oxygen vacancies or donor levels formed by Sb⁵⁺ ions.The film deposited with 20 cc solution shows 70%transmittance at 550 nm leading to the highest figure of merit(2.11×10^-3Ω^-1). The resistivity and carrier concentration vary over 1.22×10^-3 to 0.89×10^-3Ω·cm and 5.19×10²⁰ to 8.52×10²⁰ cm^-3,respectively.     

(Photo) electrochemical investigations on spray deposited n-CdIn 2Se4 thin film/polysulphide/c photoelectrochemical solar cell1

Cadmium indium selenide (n-CdIn ₂Se₄) thin films have been synthesized by spraying the mixture of an equimolar solutions of cadmium chloride [CdCl₂], indium trichloride [InCl₃] and selenourea [(NH₂)₂CSe] in aqueous media onto preheated fluorine doped tin oxide (FTO) coated glass substrates at optimized parameters of substrate temperature and solution concentration. The photoelectrochemical (PEC) cell configuration of n-CdIn₂Se/(l MNaOH + 1 MNa₂S + 1 M S)/C has been used for investigating the current—voltage (I–V) characteristics under dark and white light illumination, photovoltaic output, spectral response, photovoltaic rise and decay characteristics. The PEC study reveals the thin film of CdIn₂Se₄ exhibits n-type conductivity. The junction quality factor in dark (n _d) and light (n _l), series and shunt resistance (R _s and R _sh), fill factor (FF) and efficiency (η) for the cell have been estimated. The observed efficiency and FF of PEC solar cell is found to be 1.95 and 0.37% respectively. Mott-Schottky plot shows the flat-band potential (V _fb) of n-CdIn₂Se₄/(l M NaOH + 1 M Na₂S + 1 M S)/C cell to be—0.655 V/SCE.     

Studies on morphological and electrical properties of Al incorporated combusted iron oxide

The aluminium incorporated iron oxide samples were prepared by combustion route using aluminium nitrate and ferric trichloride as precursors. The samples were characterized for their morphological, dielectrical, impedance and thermal conductivity properties as a function of temperature. A strong low frequency dielectric dispersion is found to exist in these samples; this is ascribed to the presence of the ionized space charge carriers such as oxygen ion vacancies and interfacial polarization. The room temperature dielectric constant and the loss tangent (tan δ) at 1 kHz are 315 and 0.0855 for optimized 10 at.% Al:Fe₂O₃ sample, respectively. The frequency analysis of dielectric and ac conduction properties of these samples suggests the conduction process in these samples to be via oxygen ion vacancy motion through various defect sites. Impedance spectroscopy is used to characterize the electrical behavior. Results indicate that the relaxation mechanism of the material is temperature and frequency dependent and has dominant bulk contribution in different temperature ranges.     

Sensitized monomer fluorescence and excitation energy transfer in perylene-doped phenanthrene in crystalline and in polymer matrix

Sensitized monomer fluorescence and excitation energy transfer in crystalline and spin cast polymer films was investigated at room temperature. The fluorescence spectra of perylene doped phenanthrene reveals the characteristic monomeric emission of perylene and partial quenching of phenanthrene emission. The excimer formation of perylene is not observed in mixed crystalline luminophors and in spin cast films of the phenanthrene luminophors. The observed quenching of phenanthrene emission indicates the excitation energy transfer from phenanthrene to perylene in crystalline as well as in polymer matrix. Energy transfer is not observed in the experiments when phenanthrene and perylene were physically mixed where the components exist separately. The overlap between the excitation spectrum of perylene and emission spectrum of the phenanthrene supports the fact that the perylene molecules accept the excitation energy from phenanthrene. The energy transfer was found to depend upon the perylene concentration.     

Novel hybrid solar cells based on α-copper phthalocyanine–cadmium sulfide planar heterojunction

Cadmium sulfide (CdS) has been employed as an alternative acceptor for planar heterojunction solar cell based on copper phthalocyanine (CuPc). Spin-coated poly-3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) on indium tin oxide (ITO)-coated glass substrates was used for the vacuum deposition of CuPc and CdS planar heterojunction. In the present study, we have fabricated two different architectures of CuPc/CdS devices: (1) ITO/PEDOT:PSS/CuPc/CdS/Al and (2) ITO/PEDOT:PSS/CuPc/CdS/LiF/Al. Our results indicate that the CdS could effectively facilitate charge transport in the nanostructured network, and be a good acceptor. The fabricated bare CuPc/CdS device shows 0.13 % conversion efficiency while incorporation of LiF layer between CuPc/CdS and Al contact facilitates low-recombination rate results ~43 % enhancement in efficiency. The ITO/PEDOT:PSS/CuPc/CdS/LiF/Al device shows 0.30 % power conversion efficiency.     

Novel synthesis of interconnected nanocubic PbS thin films by facile aqueous chemical route

In the present investigation, we have successfully synthesized lead sulfide (PbS) thin films by using simple, cost effective and facile aqueous chemical route. The effect of deposition time on optical, structural and morphological properties of PbS thin films were investigated by using UV–Vis–NIR absorption spectroscopy, X-ray diffraction (XRD), photoluminescence, field emission scanning electron microscopy (FESEM), high-resolution-transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The optical band gap energy was varied in the range of 0.96–1.56 eV. The XRD patterns revealed the formation of pure cubic crystal structure. FESEM micrographs demonstrated the conversion of morphology from pyramidal to interconnected nanocubic. HRTEM and selected area electron diffraction (SAED) pattern illustrated that nanoparticles are compact, well interconnected and single crystalline in nature. EDS spectrum confirms that deposited PbS thin films are in good stoichiometry.