No abstract

Binary polymeric beads of sodium alginate and starch were prepared and characterized by IR spectral and scanning electron microscopy (SEM) techniques. The beads were examined for water uptake potential, and he influence of various factors, including chemical composition of the macromolecular matrix, pH, ionic strength, and temperature of the swelling medium, were investigated on the degree of water sorption. The prepared beads were loaded with KNO 3 , as a model agrochemical, and the release kinetics of KNO 3 were studied under varying experimental conditions, as mentioned previously. The release data were analyzed by Fick's equation, and the mechanism of KNO 3 release was worked out at different experimental conditions.

Highly water absorbing and homogeneous binary biopolymeric blends in bead form were prepared of calcium alginate and carboxymethyl cellulose by solution cast method. The prepared blends were evaluated for controlled delivery of KNO 3 taking it as a model agrochemical. The beads characterized by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) were used to investigate the molecular structure and morphology of beads. The swelling experiments were performed for different compositions of beads and at varying pH and temperature of the aqueous media. The release experiments were performed under static and varying experimental conditions and the release data obtained were conductometrically fitted to Ficks equation to evaluate diffusion coefficients of released KNO 3 . The release results were further analyzed by Ficks power law equation, and the possible mechanisms of KNO 3 release were explored at different experimental conditions.

The structural, optical, and electrical properties of ZnO are intimately intertwined. In the present work, the structural and transport properties of 100 nm thick polycrystalline ZnO films obtained by atomic layer deposition (ALD) at a growth temperature (Tg) of 100–300 °C were investigated. The electrical properties of the films showed a dependence on the substrate (a-Al2O3 or Si (100)) and a high sensitivity to Tg, related to the deviation of the film stoichiometry as demonstrated by the RT-Hall effect. The average crystallite size increased from 20–30 nm for as grown samples to 80–100 nm after rapid thermal annealing, which affects carrier scattering. The ZnO layers deposited on silicon showed lower strain and dislocation density than on sapphire at the same Tg. The calculated half crystallite size (D/2) was higher than the Debye length (LD) for all as grown and annealed ZnO films, except for annealed ZnO/Si films grown within the ALD window (100–200 °C), indicating different homogeneity of charge carrier distribution for annealed ZnO/Si and ZnO/a-Al2O3 layers. For as grown films the hydrogen impurity concentration detected via secondary ion mass spectrometry (SIMS) was 1021 cm−3 and was decreased by two orders of magnitude after annealing, accompanied by a decrease in Urbach energy in the ZnO/a-Al2O3 layers.

Optical properties of thin (≈100 nm) ZnO films in comparison with thick (≈1 μm) layers deposited on sapphire substrates by atomic layer deposition (ALD) at temperatures from 100 to 300 °C are investigated by optical transmittance and luminescence. It is found that growth temperature, the thickness of the layers, and post‐grown annealing influence the measured optical bandgap values and low‐temperature photoluminescence. However, the values of the bandgaps corrected according to the Burstein–Moss effect do not depend on layer thickness, whereas an increase in growth temperature leads to a decrease in the energy gap. On the other hand, post‐growth annealing of the layers results in increasing the value of the energy gap and decreasing Urbach energy. It is observed that thicker and annealed samples show more intensive and narrower PL bands, which are assigned to donor and acceptor bound excitons, free electrons to acceptors, and donor–acceptor pair transitions. Their energy position and relative intensity depend on the growth temperature applied.