Pranayee Datta

Fiber‐Optic pH Sensor Based on SPR of Silver Nanostructured Film

Surface Plasmon Resonance (SPR) nanosensor has become an increasingly exploited technology for detection and analysis of chemical and biological compounds. Silver (Ag) nanostructured film fabricated by thermolysis method is shown to exhibit a strong Localized Surface Plasmon Resonance (LSPR) at wavelength around 400 nm. The spectral position of LSPR is sensitive to its local environment and also the nanoparticle size and shape. In this paper, we will demonstrate optical sensing of pH using nanosilver coated fiber optic technique based on the principle of LSPR.

Fabrication of Ag/PVA nanocomposites and their potential applicability as dielectric layer in thin film capacitor

Over the past decade, polymer–metal nanocomposites have drawn a great deal of attention due to their extensive application in organic flexible devices. Here, we describe the synthesis and characterisation of silver–polyvinyl alcohol nanocomposite thin films and investigates the possibility of application of these composite films as dielectric layer in efficient capacitors. The material characterisation is done through UV–vis absorption, scanning electron microscopy and atomic force microscope. The dielectric property of the nanocomposite material is investigated with a LCR meter. The different fabricating parameters for generating homogeneous thin films are optimised in this investigation. The composite material thin films exhibit high capacitance density and low dielectric loss and hence they may be suitable ingredients for high capacitance capacitors.

Possible Applications of PVA/PbS Nanocomposites

This paper reports synthesis of PVA/PbS and PVA/PbS:Zn nanocomposites adopting chemical route. The fabricated samples are characterized by PL, UV‐Vis, XRD, TEM, EDS etc. Observed characteristics confirm nano formation with strong confinement. The I‐V characteristics of the samples are investigated for possible applications as ‘Memristor’. The characteristics are studied for increasing and decreasing voltage in the forward as well as in reverse direction. I‐V characterization of the prepared samples are studied for different materials of connecting wires also and significant changes are observed. This may lead to other possible applications. Works are in progress.

Synthesis, Characterization and Application of CdS Quantum Dot

Wide band gap semiconductor quantum dots (for example CdS) need extensive studies as they are capable of showing excitonic absorption even at room temperature. This paper reports chemical synthesis of CdS quantum dots and their characterization by XRD, TEM, UV‐VIS, PL and EDS. Possible applications of the fabricated samples in the field of electronics are also investigated.

Cobalt chloride doped polymer film for relative humidity measurement

We report a simple approach to measure relative humidity with high dynamic range and fast response time using Cobalt chloride (CoCl2) doped polymer thin film. Anhydrous Cobalt chloride exhibits high absorption at low humidity level in the wavelength range 550-700 nm while possess very low absorption at high humidity level present in the environment. Thin CoCl2 doped polymer films of different thickness were fabricated on thin cover slides using dip coating technique. Expanded light from a diode laser source (680 nm) was allowed to transmit through the sensing film of the slide. The variation in intensity of the transmitted light with the moisture level present in the environment was monitored using silicon photodiode and finally the detector signal was taken through a computer. As large area of the sensing region is exposed to the environment, high sensitivity of the sensor is achieved. Further, sensor response was investigated in terms of chemically synthesized film thickness on the slides. A high dynamic range of the sensor is obtained with fully reversible and repeatable behavior. The advantage of the system is its simplicity and is a very low cost technique to monitor relative humidity present in environment.

Modeling of absorption and scattering properties of core -shell nanoparticles for application as nanoantenna in optical domain

The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications.

Synthesis, Characterization, and Possible Applications of ZnO Nanocrystals

ZnO nanocrystals are synthesized using the quenching method. The properties of the grown nanocrystals are studied using ultraviolet-vis spectroscopy, x-ray diffraction, photoluminescence, electron diffraction, energy dispersive x-ray spectroscopy, and high resolution transmission electron microscopy. Current-voltage characteristics of the prepared samples are studied for investigating the possible application of the samples as switch and memristor.

Luminescence of CdS and CdS: Cu Quantum Dots Embedded in PVA Matrix

We report the synthesis of cadmium sulphide embedded in poly vinyl alcohol (PVA/CdS) and cadmium sulphide doped with copper embedded in poly vinyl alcohol (PVA/CdS: Cu) nanocomposites by chemical route. Characterizations are done by X‐Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM), Selected Area Electron Diffraction (SEAD), UV‐Visible (UV‐VIS), Photoluminescence (PL) and Energy Dispersive Spectroscopy (EDS). Sizes of the fabricated nanoparticles obtained from XRD are in good agreement with those from TEM and confinement is found to be strong in some samples. The PL spectra show luminescence from band edge emission as well as from trap levels caused by sulpher vacancies. The PL spectra without as well as with applied DC bias are also studied using platinum electrodes. Results indicate that peak position remains same in the two cases and intensity is an increasing function of excitation voltage. Encouraged by the results obta...

Synthesis, Characterization and Application Of PbS Quantum Dots

Lead Chalcogenides (PbS, PbSe, PbTe) quantum dots (QDs) are ideal for fundamental studies of strongly quantum confined systems with possible technological applications. Tunable electronic transitions at near—infrared wavelengths can be obtained with these QDs. Applications of lead chalcogenides encompass quite a good number of important field viz. the fields of telecommunications, medical electronics, optoelectronics etc. Very recently, it has been proposed that ‘memristor’ (Memory resistor) can be realized in nanoscale systems with coupled ionic and electronic transports. The hystersis characteristics of ‘memristor’ are observed in many nanoscale electronic devices including semiconductor quantum dot devices. This paper reports synthesis of PbS QDs by chemical route. The fabricated samples are characterized by UV‐Vis, XRD, SEM, TEM, EDS, etc. Observed characteristics confirm nano formation. I‐V characteristics of the sample are studied for investigating their applications as ‘memristor’.

Optical and Structural Studies of Chemically Synthesized ZnO Nanocrystals

ZnO nanocrystals were synthesized by adopting quenching method with Poly-vinyl alcohol as the matrix. X-ray diffraction, UV-vis spectroscopy, Photoluminescence, scanning electron microscopy, energy dispersive x-ray spectroscopy and transmission electron microscopy has been used to study the prepared samples. The size of the nanocrystals is in the range of 6.9 nm to 12.5 nm. We have successfully varied the size of the nanocrystals by varying the weight ratio of poly-vinyl alcohol and ZnO. The conductivity of the samples has been tested in atmospheric pressure as well as in vacuum.