K. K. Saini

Using Nano-Arrayed Structures in Sol-Gel Derived Mn2+ Doped Tio2 for High Sensitivity Urea Biosensor

Ordered and self-organized nano-array structures have been developed by Mn 2+ doping in TiO 2 thin fi lms deposition on conducting substrates by dip coating technique. Mn doped TiO 2 thin fi lms exhibits better bioactivity for enzyme immobilization and cyclic voltammetry measurement has been used for qualitative characterization of electrochemical induction of oxidation-reduction process in TiO 2 and Mn doped TiO 2 fi lms. Due to presence of Mn 2+ ions at fi lm surface, current voltage characteristic of Mn doped TiO 2 matrix was enhanced by a factor of ten and it had also reduced the crystallite size and promoted transformation of anatase to rutile phase of TiO 2 . Urea concentration in the electrolyte was determined by observing chronoamperometry response on urease immobilized working electrodes. The urea detection sensitivity of the Mn doped TiO 2 thin fi lms base platform was 2.3 μ A mM − 1 cm − 2 which is about 15 times higher from only TiO 2 base platforms. Such kind of enzyme–TiO 2 /Mn nano-array electrode could contribute a potential prospect in low cost biomedical diagnosis.

Studies on e-beam deposited transparent conductive films of In2O3:Sn at moderate substrate temperatures

An electron beam evaporation method is used to prepare In2O3 films with and without Sn doping. It is shown that highly transparent and conducting films can be prepared at substrate temperature as low as 200 degrees C. The characteristic feature of such films is their high carrier density and high infrared reflectivity. The lowest resistivity is found to be 2.4*10-4 Omega cm with a carrier concentration of 8*1020 cm-3 and mobility of about 30 cm2 V-1 s-1 at the doping level of 4 mol.% SnO2. These polycrystalline films show a highly preferred orientation. On the basis of Hall measurements and structural data, sources of scattering in these films are suggested.

Mycotoxin detection on antibody-immobilized conducting polymer-supported electrochemically polymerized acacia gum.

Electrochemical polymerization of acacia gum (AG) was initiated by electroactive polyaniline (PANI) monomers by radical cation formation and their coupling reactions with AG molecules. R(CT) values obtained from electrochemical impedance spectroscopy analysis at various AG concentrations with PANI were drastically decreased, confirming formation of conducting AG complexes with PANI. Quantitative analysis of ochratoxin-A (OTA) detection in electrolyte was carried out on rabbit antibody-immobilized PANI and PANI-AG matrices. The observed sensitivities of 50, 150, and 250 mg AG-added PANI matrix-based platforms were 3.3 ± 0.5, 10.0 ± 0.5, and 12.7 ± 0.5 μA/ng/ml, respectively. The sensitivity of only PANI electrodes was 2.6 ± 0.3 μA/ng/ml, which was relatively lower than AG-added PANI. This increase was due to the presence of glycan functional groups in AG molecules that supported the retention of activity of antibodies. In addition, enhanced electron transportation at AG-PANI film surface was observed due to formation of an electroactive polymer film of two different electroactive functions to contribute toward enhancement in the detection sensitivity.

Strategies to prepare TiO2 thin films, doped with transition metal ions, that exhibit specific physicochemical properties to support osteoblast cell adhesion and proliferation.

Metal ion doped titanium oxide (TiO2) thin films, as bioactive coatings on metal or other implantable materials, can be used as surfaces for studying the cell biological properties of osteogenic and other cell types. Bulk crystallite phase distribution and surface carbon-oxygen constitution of thin films, play an important role in determining the biological responses of cells that come in their contact. Here we present a strategy to control the polarity of atomic interactions between the dopant metal and TiO2 molecules and obtain surfaces with smaller crystallite phases and optimal surface carbon-oxygen composition to support the maximum proliferation and adhesion of osteoblast cells. Our results suggest that surfaces, in which atomic interactions between the dopant metals and TiO2 were less polar, could support better adhesion, spreading and proliferation of cells.

One-pot synthesis of three bismuth oxyhalides (BiOCl, BiOBr, BiOI) and their photocatalytic properties in three different exposure conditions

Abstract BiOCl, BiOBr, and BiOI have been synthesized by wet chemical route using bismuth nitrate (Bi(NO3)3.5H2O) and potassium halides, KCl, KBr, and KI, using a mixture of de-ionized water and ethanol as the solvent. Synthesized samples were characterized by X-ray diffraction and high-resolution SEM to observe the crystalline phase and crystallite size. Effective surface areas of the synthesized samples were estimated by Brunauer–Emmett–Teller studies. Photoactive properties of these samples were studied under three types of light exposure conditions viz. UV light from mercury vapour lamp, natural sunlight, and visible radiations from a 100-W incandescent tungsten filament. Degradation of methyl orange (MO) in aqueous media was estimated spectrophotometerically in visible range from the area under the curve with a peak at 464 nm. Kinetic constant for degradation reaction was calculated assuming the pseudo-first-order degradation mechanism. It was revealed that all the three samples show excellent degradation of MO in UV exposure with BiOCl as the most efficient photocatalyst in these radiations. BiOBr shows highest photodegradation performance among the three samples under natural sunlight exposure. Overall performance of the three photocatalyst samples is much better than the popular titanium dioxide photocatalyst.

Growth, differentiation, and migration of osteoblasts on transparent Ni doped TiO2 thin films deposited on borosilicate glass†

A simple and cost effective dip coating method was used to deposit thin films of amorphous (AM) or anatase (AN) titanium dioxide (TiO(2)) on borosilicate glass substrates, either with or without prior doping of TiO(2) with nickel (Ni) cations by a specially designed sol gel technique. The objective of the study was to compare the physicochemical and biological properties of these films and assess their use in orthopedic implants or for in vitro cell biological studies. Analytical techniques such as XRD and XPS, in combination with ATR-FTIR and SEM revealed that only AN films, prepared by controlled heating up to 450°C, irrespective of prior doping with Ni, contained significant crystalline structures of variable morphologies. This observation could be linked to the carbon and oxygen contents and the availability of functional groups in the films. Cell biological studies revealed that Ni doping of TiO(2) in both AM and AN films improved the adhesion, spreading, proliferation, differentiation, and migration of MC3T3 cells. Our studies provide a new approach to prepare optically transparent metal surfaces, with tunable physicochemical properties, which could be suitable for eliciting optimal osteoinductive cell responses and permit the detailed in vitro cell biological studies of osteoblasts.

Dielectric properties of Fe-doped TiO2 nanoparticles synthesised by sol–gel route

Fe-doped nanocrystalline samples of titanium oxide have been synthesised by sol–gel route and conventional sintering process at 450°C under atmospheric conditions. These samples are characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and dielectric property measurement. Samples with Fe content more than 4 mole% crystallises in rutile phase and those with less than 4 mole% crystallises in anatase phase. Nanocrystallite size has been controlled by Fe doping. Crystallite size was found to decrease with Fe concentration in the anatase phase samples whereas reverse happens in rutile phase samples of titanium oxide. There is a slight variation in numerical values of crystallite sizes measured by the two techniques: TEM and XRD peak broadening. The highest crystallite size was 86 nm in 10 mole% Fe-doped samples and the lowest 20 nm in 4 mole% Fe-doped sample. Large dispersions and anomalous values of the dielectric constant, εr were observed at low frequency in anatase phase samples. Rutile phase samples exhibit little dispersion over the measurement frequency range of 20 Hz to 10 MHz. The dielectric constant value of all the samples stabilises to a constant value at higher frequencies. This value is dependent on the final crystalline phase but independent of the crystallite size. The anomalous dielectric behaviour of anatase samples at low frequencies is assigned to the adsorbed –OH ions on the sample surface.

Characterization of the Photocatalytic Activity of Bismuth Oxychloride Nanostructures

ABSTRACT Bismuth oxychloride materials were synthesized by a one-step procedure with high purity precursors with variation of the pH from 1 to 6. The materials were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer Emmett Teller measurements, and photoluminescence. Photocatalytic properties were characterized by the degradation of methylene blue with visible light from a 100 W lamp and natural sunlight. All samples contained the tetragonal phase with platelet structures. The thickness of the platelets was sensitive to pH during synthesis and increased from 97 to 227 nm with an increase in pH. The photoactivity of the sample decreased with an increase in pH. The highest photocatalytic activity of 0.00295 min−1 for the 100 W electric lamp and 0.00316 min−1 for sunlight was observed for the material prepared at pH 1. The photocatalytic activity values of these materials were approximately one order or magnitude higher than titanium dioxide in the visible region. Photoluminescence studies confirmed the presence of mid-band gap states that enabled the material to absorb light in the 400 to 450 nm region.

Dielectric and structural properties of iron doped titanate nano-composites

TiO2 has been used for gas sensing devices (Mohammadi et al., 2007) photo catalytic devices (Litter and Navio, 1996) and photoelectric devices (Levy, 1997). Recently the dielectric properties of TiO2 have been of great interest for applications in the telecommunications industry due to its unusual high dielectric constant and low dielectric loss. The use of layers of high dielectric constant materials in small scale metal insulator semiconductor devices has been considered in numerous recent publications these materials unable to maintain the same capacitance density as SiO2 films but provide a smaller leakage current density. Examples of such materials include tantalum and yttrium oxides (Moon et al., 1999) and titanium dioxide which has the largest dielectric constant value varying in the range of 25-100 (Tang et al, 1997).

Effect of thallium concentration on Tl-2201 superconducting phase by flash sintering process

Abstract Samples with nominal composition TlxBa2Cu2O6 where x = 0.5, 1.0, 1.5, 1.75, 2.0, 2.5 and 3.0 were calcined at 890°C for 10 h and sintered at various temperatures for 3 1 2 min. X-ray powder diffraction patterns of all the samples show the characteristics of the 2201 phase which suggests the transformation of all the nominal compositions to 2201 phase. In some cases extra peaks due to BaCuO2 and Tl2O3 are also present. The samples having Tl contents 1.5, 1.75 and 2.0 are monophase material with unit cell parameters a = 3.86 A , c = 23.20±0.02 A . The overall symmetry is tetragonal. All the lines are indexible on the I4/mmm space group. Samples with Tl content 1.5-2.0, sintered at 930–950°C, show the best superconducting properties. The highest Tc is obtained in Tl2.0 and the highest Meissner fraction in Tl1.5. Chemical analysis indicates Tl deficiency in all the samples, which suggests substitution of Tl3+ by Cu1+ or Cu2+ and oxidation of copper to Cu3+, which increases monotonically with Tc. Tl contents in optimum samples lie in the range 1.14-1.82 and oxygen content varies from 5.6-6.1