Sensing behaviour of some nanocomposite systems

Silver nanoparticles of diameters 3.4 to 13.2 nm grown at the interfaces between silicate glass and some oxide crystallites exhibited about six orders of magnitude reduction in resistivity for a relative humidity change from 25% to 80%. Sn-SnO2 nano core-shell structure prepared within a gel-derived silica glass film by electrodeposition technique followed by heat treatment showed large change in resistivity as a function of humidity. The resistivity also changed due to gas flow of CO2, C2H5OH and NO2, respectively. The latter arose because of reduction/oxidation of Sn4+/Sn2+ species present at the shell layer of the nanostructures. Nickel nanosheets of thickness ~0.6 nm grown within the interlayer spaces of Na-4 mica crystallites showed a change of dielectric permittivity (5%) for an applied magnetic field of 1.2 Tesla. An inhomogeneous model was used to explain this behavior. Two dimensional CuO phase was grown within the channels of diameter ~5 nm of mesoporous SiO2 structure. A magnetodielectric (MD) parameter M.D. of 4.4% was obtained in this case. BaTiO3 nanoparticles of diameter ~25 nm having pores with diameter 10 nm showed multiferroic behavior which arose due to the presence of oxygen vacancies as a result of large surface area present. An M.D. parameter of 11% was found. Similarly mesoporous LiNbO3 of 10 nm diameter showed an M.D. parameter of ~4.5% at a magnetic field 1 Tesla. A giant magnetocapacitance effect with a value of 44% at 1.5 T was observed in nickel zinc ferrite (NZF) impregnated mesoporous silica. A magnetocapacitance of 51% at magnetic field 1.7 T was found in the case of nanocomposites comprising of iron ion containing silica based nanoglass and mesoporous silica. In the last two examples the behavior was explained on the basis of Catalan model of space-charge polarization with extracted values of magnetoresistance of the NZF and nanoglass phases being 58%

Synthesis of two-dimensional metallic silver using sodium beta-alumina crystal channels

Sodium beta-alumina (β-NaAl<SUB>11</SUB>0<SUB>17</SUB>) crystals were grown within a gel containing Na<SUB>2</SUB>O and Al<SUB>2</SUB>O<SUB>3</SUB>. The glass-crystal composite was put through a Na<SUP>+</SUP> ↔ Ag<SUP>+</SUP> ion-exchange reaction. The ion-exchanged glass-crystal was then subjected to an electrodeposition process. Nanosheets of metallic silver were found to have grown within the β-NaAl<SUB>11</SUB>0<SUB>17</SUB> channels which usually contain the mobile sodium ions. The DC electrical resistance of the composites was caused due to charge transport in the two-dimensional crystal planes. The average silver layer thickness was ~0.6 nm and the interlayer separation ~1.13 nm

Availability of Village Health and Nutrition Day services in Uttarakhand, India

Background: Village Health and Nutrition Day (VHND) was identified to provide primary care services (health, nutrition and sanitation) at village level under National Rural Health Mission. Aim: The study aimed to assess availability of health, nutrition and sanitation services, required instruments/equipment and medicines at VHND with client satisfaction from the VHND services. Materials and Methods: A cross-sectional study was conducted in three districts of Uttarakhand at Nainital, Tehri-Garhwal and Chamoli involving 24 villages in six blocks using multistage stratified sampling using predesigned pretested observation checklists (quantitative data). All the concerned functionaries of health, Integrated Child Development Services and Panchayati Raj Institution were interviewed (qualitative data) to understand the gap in services and remediation. Results: Of the 24 VHNDs observed, blood pressure measurement was done at 11 (45.83%) and weight at 13 (54.17%) sites in ante-natal care services; non-availability of blood pressure instrument and adult weighing machine were 45.83% and 41.66% sites, respectively. Immunization for children was provided at 22 sites; however, availability of other services were poor-vitamin A (three), growth monitoring of children (seven); supplementary nutrition (five); identification of households for construction of toilet (eight). Yet, one-third of clients provided three and four for satisfaction from VHND services on the scale score of 1-5. Conclusion: It was noted that none of the VHND site was providing all the stipulated services, though immunization was provided mostly. Anganwadi centers were lacking availability of various essential instruments and equipment. So regular orientation of village functionaries for ensuring all the VHND services with the availability of required logistic is recommended

Solution-processed hybrid p-n junction vertical diode

Solution-processed n-ZnO/p-poly(3,3′′′-didodecylquaterthiophene) (PQT-12) vertical p–n junction diodes were prepared on ITO-coated glass. A continuous film of ZnO nanoparticles was grown on the ITO glass by dip-coating and subsequent heat treatment of a zinc acetate film. PQT-12 was then spin-coated to form the ZnO/PQT-12 diode. Gold was chosen as the top electrode to complement ITO for this diode. The microstructures of ZnO films are studied by atomic force microscopy (AFM) and show a continuous, dense layer of ZnO nanoparticles. The current–voltage (I–V) measurement shows that the maximum current density for this p–n junction diode is 400 A/cm2, which is much higher than previously reported polymer diodes. Capacitance–voltage (C–V) data also provide evidence of formation of the p–n junction. The rectification was characterized by observation of full input-half output waves. Data indicate that these devices can operate up to frequencies of 14 MHz under ambient environment conditions. This rectification frequency is higher than other reported polymer Schottky diodes under these conditions. Turnon voltages of this diode are also much lower than for the reported polymer diodes

Ingenious Fabrication of Ag-Filled Porous Anodic Alumina Films as Powerful SERS Substrates for Efficient Detection of Biological and Organic Molecules

Surface-enhanced Raman scattering (SERS) has been widely used to effectively detect various biological and organic molecules. This detection method needs analytes adsorbed onto a specific metal nanostructure, e.g., Ag-nanoparticles. A substrate containing such a structure (called SERS substrate) is user-friendly for people implementing the adsorption and subsequent SERS detection. Here, we report on powerful SERS substrates based on efficient fabrication of Ag-filled anodic aluminum oxide (AAO) films. The films contain many nanopores with small as-grown inter-pore gap of 15 nm. The substrates are created by electrochemically depositing silver into nanopores without an additional pore widening process, which is usually needed for conventional two-step AAO fabrication. The created substrates contain well-separated Ag-nanoparticles with quite a small inter-particle gap and a high number density (2.5 × 1010 cm−2). We use one-step anodization together with omitting additional pore widening to improve the throughput of substrate fabrication. Such substrates provide a low concentration detection limit of 10−11 M and high SERS enhancement factor of 1 × 106 for rhodamine 6G (R6G). The effective detection of biological and organic molecules by the substrate is demonstrated with analytes of adenine, glucose, R6G, eosin Y, and methylene blue. These results allow us to take one step further toward the successful commercialization of AAO-based SERS substrates