K. Chidambaram

Eco-Friendly Synthesis of Graphene Oxide Reinforced Hydroxypropyl Methylcellulose/Polyvinyl Alcohol Blend Nanocomposites Filled with Zinc Oxide Nanoparticles for High-k Capacitor Applications

ABSTRACT Polymer/inorganic nanocomposites comprising of hydroxypropyl methylcellulose and polyvinyl alcohol as a polymer matrix and unique combination of graphene oxide and zinc oxide nanoparticles as fillers have been prepared using colloidal processing technique and characterized using various analytical methods. The dielectric properties of the nanocomposites are investigated using impedance analyzer. The nanocomposites show improvement in the dielectric properties compared to hydroxypropyl methylcellulose/polyvinyl alcohol (50/50) blends, which results from the homogeneous dispersion of fillers into the polymer matrix. The results indicate that these nanocomposites have a potential to meet the technological demands of high-k dielectrics and/or embedded capacitors. GRAPHICAL ABSTRACT

Watermelon rind-mediated green synthesis of noble palladium nanoparticles: catalytic application

The present study reports the feasibility of synthesis of palladium nanoparticles (Pd NPs) by watermelon rind. The aqueous extract prepared from watermelon rind, an agro waste, was evaluated as capping and reducing agent for biosynthesis of palladium nanoparticles. The formation of Pd NPs was visually monitored with change in color from pale yellow to dark brown and later monitored with UV–Vis spectroscopy. The synthesized Pd NPs were further characterized by XRD, FTIR, DLS, AFM and TEM techniques. The synthesized Pd NPs were employed in Suzuki coupling reaction as catalyst. The results reveal that watermelon rind, an agro waste, is capable of synthesizing spherical-shaped Pd NPs with catalytic activity.

Modified PVA moiety with PbO as humidity sensor

Polyvinyl alcohol (PVA)-composed lead oxide (PbO) films were prepared by solution casting method. Proposed composite moiety reveals the presence of orthorhombic and monoclinic multiphase structural modification due to loading of PbO which was demonstrated by X-ray diffraction. The electronic transition due to oxide impurity decreases the transmission intensity and shift of wavelength confirmed by ultraviolet tool. The magnitude of dielectric polarization is directly proportional to the loaded PbO% and is based on the Debye model. The composite morphology demonstrates the presence of inorganic filler with a cross linked network of polymer PVA confirmed by AFM. The synthetic film loaded with PbO sensing for varying RH% with linearity (decreasing) in resistance may apply as humidity sensor.

One-step, low-temperature fabrication of CdS quantum dots by watermelon rind: a green approach

We investigated the one-step synthesis of CdS nanoparticles via green synthesis that used aqueous extract of watermelon rind as a capping and stabilizing agent. Preliminary phytochemical analysis depicted the presence of carbohydrates which can act as capping and stabilizing agents. Synthesized CdS nanoparticles were characterized using UV-visible, Fourier transform infrared spectroscopy, X-ray diffraction, EDX, dynamic light scattering, transmission electron microscopy, and atomic force microscopy techniques. The CdS nanoparticles were found to be size- and shape-controlled and were stable even after 3 months of synthesis. The results suggest that watermelon rind, an agro-waste, can be used for synthesis of CdS nanoparticles without any addition of stabilizing and capping agents.

Optical Analysis of Iron-Doped Lead Sulfide Thin Films for Opto-Electronic Applications

Iron-doped lead sulfide thin films were deposited on glass substrates using successive ionic layer adsorption and reaction method (SILAR) at room temperature. The X-ray diffraction pattern of the film shows a well formed crystalline thin film with face-centered cubic structure along the preferential orientation (1 1 1). The lattice constant is determined using Nelson Riley plots. Using X-ray broadening, the crystallite size is determined by Scherrer formula. Morphology of the thin film was studied using a scanning electron microscope. The optical properties of the film were investigated using a UV–vis spectrophotometer. We observed an increase in the optical band gap from 2.45 to 3.03eV after doping iron in the lead sulfide thin film. The cutoff wavelength lies in the visible region, and hence the grown thin films can be used for optoelectronic and sensor applications. The results from the photoluminescence study show the emission at 500–720nm. The vibrating sample magnetometer measurements confirmed that the lead sulfide thin film becomes weakly ferromagnetic material after doping with iron.

Biopolymer Composites With High Dielectric Performance: Interface Engineering

In recent years, there is a growing interest in studying the dielectric behavior of biopolymer composites due to their potential application as a dielectric material in various electronic devices such as microchips, transformers, and circuit boards. Conducting electroactive polymer composites have also been investigated for various potential applications which include biological, biomedical, flexible electrodes, display devices, biosensors, and cells for tissue engineering. In this chapter, the preparation and dielectric behavior of various biopolymer composites is presented. These biopolymer composites generally consist of nanoscale metal nanoparticles and carbon-based nanofillers such as carbon nanotubes, graphene, graphene oxide (GO), etc., dispersed into the polymer matrix. The physical and chemical properties of these fillers and their interactions with polymers have a significant effect on the microstructure and the final properties of nanocomposites. The biopolymer composites with excellent dielectric properties show great promise as an energy storage dielectric layer in high-performance capacitor applications such as embedded capacitors. This chapter highlights some of the examples of such biopolymer composites; their processing and dielectric behavior will be discussed in detail.

Recent Advances in Poly (Amide-B-Ethylene) Based Membranes for Carbon Dioxide (CO2) Capture: A Review

ABSTRACT Polyamide-b-ethylene (Pebax) is a promising material for membrane-based gas separation application with excellent CO2 capturing potential. Pebax is a rubbery elastomer which offers good mechanical support with its hard crystalline phase and excellent gas transport through its amorphous polyether phase. This review article includes recent advances in Pebax based membrane synthesis, solvent selection for membrane synthesis, compatible fillers with Pebax matrix and the improved gas separation performance of the prepared membranes. The literature review shows that Pebax based membranes are a good candidate for separation of CO2 from flue gases and can be used for commercial applications. GRAPHICAL ABSTRACT

Studies on the Electrical Properties of Graphene Oxide-Reinforced Poly (4-Styrene Sulfonic Acid) and Polyvinyl Alcohol Blend Composites

In the present study, graphene oxide (GO)-reinforced poly (4-styrenesulfonic acid) (PSSA)/polyvinyl alcohol (PVA) blend composite films were prepared using colloidal blending technique at various concentrations of GO (0–3wt.%). The morphological investigations of the prepared composites were carried out using polarized optical microscopy and scanning electron microscopy. The electrical properties of composites were evaluated using an impedance analyzer in the frequency range 50Hz to 20MHz and temperature in the range 40–150∘C. Morphological studies infer that GO was homogeneously dispersed in the PSSA/PVA blend matrix. Investigations of electrical property indicate that the incorporation of GO into PSSA/PVA blend matrix resulted in the enhancement of the impedance (Z) and the quality factor (Q-factor) values. A maximum impedance of about 4.32×106Ω was observed at 50Hz and 90∘C for PSSA/PVA/GO composites with 3wt.% GO loading. The Q-factor also increased from 8.37 for PSSA/PVA blend to 59.8 for PSSA/PVA/GO...

Chapter 10 – Dielectric Spectroscopy

In this chapter, an attempt has been made to review dielectric spectroscopy (DS) as a technique for the characterization of nanomaterials. DS involves the study of the response of a material to an electric field, which furnishes structural information, i.e., molecular structure, physical arrangement, and behavior of the molecules within the structure. DS is a well-established technique in the fields of physics, polymers, and colloidal science and also in pharmaceutics. It is used to measure the dielectric and electric properties of a medium as a function of frequency. Nanomaterials have been known by the term nanodielectric, mainly because of their gradual evolution as excellent functional materials for dielectric and electrical insulation applications. DS has been validated as a powerful technique for appraising the structural and molecular dynamics of nanomaterials. DS in nanomaterial systems is specifically used to probe structure–property relationships, which helps to optimize composition and synthesis/processing conditions, which is useful in the design of new functional materials with envisioned properties. General perspectives such as the principle of DS, dielectric mechanisms such as polarization and relaxation, and dielectric formalisms such as permittivity, electrical modulus, and impedance are described in this chapter.

Synthesis, Characterization and Optical Properties of Nano Structure Lead Oxide

Nanocrystalline lead oxide was prepared by solvo-thermal technique at a temperature of 75 °C. X-ray diffraction studies show the formation of stable β - PbO at 75 °C and heat treated from 200 to 500 °C for 2 h. Scanning electron micrograph images reveal the change in morphology of PbO particles from spherical to rhombus shape at higher temperatures. The band gap of the material was estimated by Diffused Reflectance Spectroscopy (DRS) found to be 2.67 eV. Photoluminescence spectrum of all the samples exhibits several band peaks due to radiative transitions from defect levels and recombination process.