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2022 - 20232
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Author: Neha × Start date: 2021 × Type: Thesis ×
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    Properties of Metal Telluride Thin Films Embedded In Polyvinyl Alcohol Matrix
    (Punjab Agricultural University, Ludhiana, 2023) Neha; Rajeev Kumar
    The present research work describes the preparation of Cadmium Telluride nanocomposite embedded in Polyvinyl Alcohol matrix by using heat induced chemical methodology. PVA/CdTe nanocomposite thin films were further casted on glass substrates using Chemical Bath Deposition technique. The structural phase analysis and morphological study of PVA/CdTe nanocomposite was carried out by using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), respectively. It was confirmed that PVA/CdTe nanocomposite possesses a cubic zinc blend structure having nanocrystalline nature with average particle size of 6.4 nm. Fourier Transform Infrared (FTIR) spectroscopy was carried out for the identification of various chemical functional groups possessed by the PVA/CdTe nanocomposite. Various optical properties such as optical absorbance, transmittance, optical band gap, Urbach energy, refractive index, extinction coefficient, dispersion energy, single oscillator energy, dielectric properties and optical conductivity of PVA/CdTe nanocrystalline thin films casted at bath temperatures of 303 K, 313 K, 323 K, 333 K and 343 K were evaluated using UVVisible spectrophotometer. It was also revealed that energy band gap of the thin films showed a red shift as temperature increases for direct transitions of electrons. For the measurement of the optoelectronic characteristics of material, photoluminescence (PL) spectroscopy was carried out at bath temperature of 303 K in wavelength region from 300 nm to 600 nm., and observed a single narrow intensity peak at a wavelength around 445 nm. Different acoustical properties like adiabatic compressibility, acoustic impedance, intermolecular free length, relaxation time, attenuation coefficient and surface tension were studied for deep understanding of behavioural changes in particle-fluid interactions with change in bath temperature of PVA/CdTe nanocomposite. The properties of PVA/CdTe were found to be highly interdependent and influenced with change in temperature. Temperature dependent as well as frequency dependent capacitance-voltage characterisation was carried out for PVA/CdTe nanocomposite. Temperature dependent C-V parameters computed under reverse bias voltage such as barrier height, built in voltage and depletion width were found to decrease whereas carrier concentration increased with temperature. Interfacial state density for PVA/CdTe nanocomposite was evaluated using frequency dependent C-V profiling and it was found to decrease with increasing forward biasing.
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    ThesisItemOpen Access
    Microbial degradation of paddy straw by solid state fermentation
    (Punjab Agricultural University, Ludhiana, 2022) Neha; Katyal, Priya
    Paddy straw is the most abundant yet unmanaged agricultural waste, leading to resource wastage and generation of environment pollution. The action of microbes could help to restraint the waste and evolve it to useful products. The present study was conduct to evaluate the lignocellulolytic efficency of microbes for the degradation of paddy straw under solidstate fermentation. Six bacterial cultures, one actinomycete culture and one fungal culture were isolated, purified and screened qualitatively and quantitatively for lignocellulose degrading ability. Three standard lignolytic cultures (Delftia sp. PP4_S3, Bacillus sp., and Pseudomonas sp.) were used as positive control. A consortium of the isolated and standard culture was used to decompose untreated paddy straw resulting in maximum enzyme activities of endoglucanase (2.70 U/ml), exoglucanase (7.54 U/ml), β-glucosidase (18.32 U/ml), xylanase (77.73 U/ml) and manganese peroxidase (6.20 U/ml) after 28 days of incubation along with maximum laccase activity (5.40 U/ml) after 21 days of incubation. Consortium when used along with 5% urea pretreated straw under solid state fermentation reported maximum enzyme activities for endoglucanase (2.50 U/ml), exoglucanase (7.47 U/ml), β-glucosidase (7.32 U/ml), xylanase (44.59 U/ml), manganese peroxidase (3.60 U/ml) and laccasse (3.20 U/ml) after 14 days of incubation. Scanning electron microscope (SEM) micrographs revealed sufficient sloughing off of cellulose and hemicellulose with profuse growth of microbes without any silica degradation. The proximate change in untreated paddy straw was found to be 27.81% reduction in cellulose, 41.28% in hemicellulose and 30.9% in lignin whereas, in pretreated paddy straw decrease in cellulose content was 37.73%, 38.88% in hemicellulose and 25% in lignin content. Biochemical components in untreated paddy straw after fermentation of 28 days was found to be 78.60% total solids, 14.60% ash, 85.39% volatile solids and 47.44% total organic carbon. Similarly, biochemical components found in pretreated paddy straw were 77.26% total solids, 15.77% ash, 84.23% volatile solids and 46.79% total organic carbon content.