Synthesis of Lead Zirconate Titanate Stannate Antiferroelectric Thick Films by Sol-Gel Processing

The effects of different sintering procedures on the preparation of antiferroelectric thick films and the structure–property relations in these films were studied. An acetic acid-based sol–gel processing with multistep annealing and suitable lead oxide overcoat layers was developed to fabricate both niobium-doped and lanthanum-doped lead zirconate titanate stannate antiferroelectric thick films. The 5-μm-thick Pb_0.99Nb_0.02(Zr_0.85Sn_0.13Ti_0.02)_0.98O₃ films demonstrate typical square hysteresis loops with a maximum polarization of 40 μC/cm², zero remanent polarization, an antiferroelectric-to-ferroelectric phase transition field of 153 kV/cm, and a ferroelectric-to-antiferroelectric phase transition field of 97 kV/cm. The dielectric constant and dielectric loss are 283 and 1.7%, respectively. The 5-μm-thick Pb_0.97La_0.02(Zr_0.65Sn_0.31Ti_0.04)O₃ films display typical slanted hysteresis loops with very small hysteresis, a maximum polarization of 35.0 μC/cm², and zero remanent polarization. The dielectric constant and dielectric loss are 434 and 2.0%, respectively.     

Amino acid-assisted synthesis of strontium hydroxyapatite bone cement by a soft solution freezing method

Among many cations that can substitute for calcium in the structure of hydroxyapatite, strontium provokes an increasing interest because of its beneficial effect on bone formation and prevention of bone resorption. Strontium-incorporated calcium phosphates show potential in biomedical application, particularly the doped strontium may help in new bone formation. We have synthesized strontium hydroxyapatite powders at 2 °C by a soft solution freezing method using glycine as the template. The structural and morphological characterizations were carried out on the as obtained powders using Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy techniques. Strontium was quantitatively incorporated into hydroxyapatite where its substitution for calcium provoked a linear shift of the infrared absorption bands of the hydroxyl and phosphate groups. The strontium substituted bone cement has potential for use in orthopaedic surgeries. The present study shows that the addition of glycine plays an important role in reducing the particle size of strontium hydroxyapatite which could be used for biomedical applications.     

Photovoltaic properties of nanocrystalline CdS films deposited by SILAR and CBD techniques—a comparative study

CdS films were fabricated using Successive Ionic Layer Adsorption and Reaction (SILAR) technique from starting solutions having S:Cd ratio 1:1, 3:1, 5:1 and 7:1 and their structural, surface morphological and optical properties were investigated and compared with that of their chemical bath deposited counterparts. The X-ray diffraction profiles showed that the films have cubic crystal structure with preferential orientation along the (111) plane and the intensity of the (111) plane increases for both the techniques as the S:Cd ratio increases. The energy dispersive X-ray analysis revealed that for SILAR deposited films, the S/Cd ratio in the sample increases from 0.8308 (for S:Cd 1:1) to 1.04 (for S:Cd 7:1) as the molar concentration of sulphur in the starting solution increases. But for CBD films, the S/Cd is only ~0.80 for all concentrations of sulphur in the starting solution. The optical band gap increases with the increase in S:Cd ratio in the starting solution in both the techniques.     

Conductivity enhancement of ZnO:F thin films by the deposition of SnO2:F over layers for optoelectronic applications

Fluorine doped tin oxide (SnO₂:F – FTO) layer is deposited over fluorine doped zinc oxide layer (ZnO:F – FZO) so as to get FTO/FZO bilayers with varying thickness proportions of the two layers using a simplified spray pyrolysis technique. In order to analyse the possible enhancement in the transparent conducting properties of these bilayered films, two separate sets of single layered FTO and FZO films are prepared with similar thickness values and their electrical, optical, photoluminescence and structural characteristics are compared with their bilayered counterparts. The electrical studies revealed that the double-layered films with the lesser thickness of FTO exhibit higher sheet resistance (R_sh) and the R_sh value decreases with the increase in the thickness of FTO over layer. The FTO/FZO bilayer with thickness proportions of FTO:FZO nearly equal to 450 nm:300 nm (3:2) is found to have good figure of merit (quality factor) when compared with FZO films. Even though the optical transmittance (T) in the visible range of FTO/FZO bilayer is lesser (80%) than that of FZO (90%) and FTO (85%) films, the electro-optical properties are reasonably good for the bilayered films making them suitable candidates for opto-electronic applications. The photoluminescence studies support the results obtained in the electrical and structural studies.     

Fabrication of a novel SnO2:Al/ZnO:F bi-layer for opto-electronic applications

Single layered aluminium doped tin oxide (ATO), fluorine doped zinc oxide (FZO) and bi-layered ATO/FZO thin films were deposited onto preheated glass substrates (T_s = 340 ± 5 °C) using a low-cost and simplified spray pyrolysis technique. The structural, optical, electrical and surface morphological properties of the bi-layered ATO/FZO thin films were studied and compared with that of the single layered films. The average optical transmittance of the bi-layer film in the visible range was found to be around 80 %. The bi-layered ATO/FZO films possessed both better transmittance in the visible range and sharp absorption edge, the unique desirable features of ATO and FZO films, respectively. The optical band gap (E_g) value of the bi-layer coating (3.22 eV) was found to lie between the E_g values of single layered ATO (3.71 eV) and FZO (3.20 eV) films. Sheet resistance values of ATO and FZO single layer films were 3.47 and 11.2 kΩ/sq., respectively. The bi-layered ATO/FZO thin films exhibited a sheet resistance of 4.42 kΩ/sq. which was very much close to that of ATO films and three times less than that of FZO film. The AFM images showed the good packing density and homogeneity of the surface of the bi-layer films. The annealing studies clearly showed that the ATO over layer remarkably improved the thermal stability of the bi-layered film.     

Click chemistry approach for fabricating PVA/gelatin nanofibers for the differentiation of ADSCs to keratinocytes

Every year, millions of people suffer from dermal wounds caused by heat, fire, chemicals, electricity, ultraviolet radiation or disease. Tissue engineering and nanotechnology have enabled the engineering of nanostructured materials to meet the current challenges in skin treatments owing to such rising occurrences of accidental damages, skin diseases and defects. The abundance and accessibility of adipose derived stem cells (ADSCs) may prove to be novel cell therapeutics for skin regeneration. The nanofibrous PVA/gelatin/azide scaffolds were then fabricated by electrospinning using water as solvent and allowed to undergo click reaction. The scaffolds were characterized by SEM, contact angle and FTIR. The cell–scaffold interactions were analyzed by cell proliferation and the results observed that the rate of cell proliferation was significantly increased (P ≤ 0.05) on PVA/gelatin/azide scaffolds compared to PVA/gelatin nanofibers. In the present study, manipulating the biochemical cues by the addition of an induction medium, in combination with environmental and physical factors of the culture substrate by functionalizing with click moieties, we were able to drive ADSCs into epidermal lineage with the development of epidermis-like structures, was further confirmed by the expression of early and intermediate epidermal differentiation markers like keratin and filaggrin. This study not only provides an insight into the design of a site-specific niche-like microenvironment for stem cell lineage commitment, but also sheds light on the therapeutic application of an alternative cell source—ADSCs, for wound healing and skin tissue reconstitution.     

Identification of growth mechanism of CBD CIAS thin films from SEM analysis

Near stoichiometric and stoichiometric CuIn_(1?x)Al_(x)Se₂ (CIAS) thin films have been prepared by chemical bath deposition (CBD) technique. X-ray diffraction (XRD) and energy dispersive x-ray analysis (EDAX) spectra have been employed to confirm the structure and composition of the prepared films. SEM analysis of near-stoichiometric and stoichiometric CIAS thin films enabled us to estimate the grain size, to identify the growth mechanism and also to visualize the surface morphology. Transmittance spectra have been employed to determine the type of transition and other optical parameters such as absorption coefficient, extinction coefficient, dielectric constant, refractive index, Sellmeier parameters and bandgap which are reported in this paper in detail.     

Applications of calcium and its supplement derived from marine organisms

Calcium, being an essential mineral with many important and diversified functions, plays an important role in the health and well being of the human. Marine organisms serve as an alternate source for calcium. Calcium has to be solubilized in the body in order to have the maximum benefits. The increased solubility of calcium from diet contributes to calcium absorption and bioavailability in the body. In this paper, we report various marine sources of calcium, solubilizing the calcium to improve the bioavailability and the applications of calcium as an important mineral in controlling different diseases.