Kishor Kumar Sadasivuni

Transparent and Flexible Cellulose Nanocrystal/Reduced Graphene Oxide Film for Proximity Sensing

The rapid development of touch screens as well as photoelectric sensors has stimulated the fabrication of reliable, convenient, and human-friendly devices. Other than sensors that detect physical touch or are based on pressure sensing, proximity sensors offer controlled sensibility without physical contact. In this work we present a transparent and eco-friendly sensor made through layer-by-layer spraying of modified graphene oxide filled cellulose nanocrystals on lithographic patterns of interdigitated electrodes on polymer substrates, which help to realize the precise location of approaching objects. Stable and reproducible signals generated by keeping the finger in close proximity to the sensor can be controlled by humidity, temperature, and the distance and number of sprayed layers. The chemical modification and reduction of the graphene oxide/cellulose crystal composite and its excellent nanostructure enable the development of proximity sensors with faster response and higher sensitivity, the integration of which resolves nearly all of the technological issues imposed on optoelectronic sensing devices.

Carbon nanotube based elastomer composites – an approach towards multifunctional materials

The current study focuses on giving a basic understanding of tubular graphene sheets or carbon nanotubes (CNTs) and points towards their role in fabricating elastomer composites. Since the properties and the performance of CNT reinforced elastomer composites predominantly depend on the rate of dispersion of fillers in the matrix, the physical and chemical interaction of polymer chains with the nanotubes, crosslinking chemistry of rubbers and the orientation of the tubes within the matrix, here, a thorough study of these topics is carried out. For this, various techniques of composite manufacturing such as pulverization, heterocoagulation, freeze drying, etc. are discussed by emphasizing the dispersion and alignment of CNTs in elastomers. The importance of the functionalization technique as well as the confinement effect of nanotubes in elastomer media is derived. In a word, this article is aimed exclusively at addressing the prevailing problems related to the CNT dispersion in various rubber matrices, the solutions to produce advanced high-performance elastomeric composites and various fields of applications of such composites, especially electronics. Special attention has also been given to the non-linear viscoelasticity effects of elastomers such as the Payne effect, Mullins effect and hysteresis in regulating the composite properties. Moreover, the current challenges and opportunities for efficiently translating the extraordinary electrical properties of CNTs to rubbery matrices are also dealt with.

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

Oleic acid-grafted chitosan/graphene oxide composite coating for corrosion protection of carbon steel

An anticorrosion coating film based on the formation of nanocomposite coating is reported in this study. The composite consisted of chitosan (green matrix), oleic acid, and graphene oxide (nano filler). The nanocomposite coating was arranged on the surface of carbon steel, and the corrosion resistance was monitored using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP). Compared to the pure chitosan (CS) coating, the corrosion resistance of oleic acid-modified chitosan/graphene oxide film (CS/GO-OA) is increased by 100 folds. Since the well-dispersed smart grafted nanolayers delayed the penetration rate of corrosive species and thus maintained long term anticorrosive stability which is correlated with hydrophobicity and permeability.

Heterogeneous growth mechanism of ZnO nanostructures and the effects of their morphology on optical and photocatalytic properties

Zinc oxide (ZnO) nanoflowers have huge potential for various applications. However, the growth mechanism of ZnO nanoflowers is still under debate despite various growth mechanisms having been proposed. The aim of this study is to investigate the growth mechanism of different morphologies in a single sample; hopefully, this might help to understand the exact growth mechanism of ZnO nanoflowers. Herein, two models are proposed: (I) the growth mechanism of different morphologies (shapes) in a single sample; and (II) the growth mechanism of different sized ZnO flowers in a single sample. The present work also investigates the mechanism for how morphology assists in tuning the properties of nanomaterials, which is still unclear to date. New insight into the relationship between morphology and native defects has been introduced in this work. XPS, photoluminescence, and FT-IR analyses reveal the presence of oxygen vacancy defects in the structures of the materials prepared, with respect to their morphology. These defects act as self-dopants. Therefore, a change in their concentration results in tuning the band gap and thereby the photocatalytic activity.

Poly-carboxylic acids functionalized chitosan nanocarriers for controlled and targeted anti-cancer drug delivery.

The present study evaluates the in-vitro cisplatin (CDDP) release from four different poly oxalates cross-linked chitosan (CS) nanocomposites. The poly oxalates were synthesized from the reaction of four different dicarboxylic acids with ethylene glycol (EG). The encapsulation of CDDP on CS cross-linked with Oxalic acid-EG, Succinic acid-EG, Citric acid-EG and tartaric acid-EG carriers were carried out by the ionic gelation technique. The poly-oxalate nanocarriers were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction studies and zeta potential analysis. The stability of poly-oxalates was calculated by the density functional theory (DFT) using Gaussview 05. Excellent drug release kinetics and good biocompatibility of nanocomposites were observed for the in-vitro analysis. The unloaded poly oxalate nanocomposites perform to have a low inherent cytotoxicity, whereas the loaded nanocomposites were as active as free CDDP in the MCF-7 cancer cell line. The tumor growth inhibitions of CDDP-loaded nanocomposites are more or equal to that of free CDDP. Taken together, these two poly oxalate nanocomposites are established as promising drug carriers for the delivery of CDDP.

Targeted delivery of rifampicin to tuberculosis-infected macrophages: design, in-vitro , and in-vivo performance of rifampicin-loaded poly(ester amide)s nanocarriers

We have developed a nano drug delivery system for the treatment of tuberculosis (TB) using rifampicin (RF) encapsulated in poly(ester amide)s nanoparticles (PEA-RF-NPs), which are biocompatible polymers. In this study, biodegradable amino acid based poly(ester amide)s (PEAs) were synthesized by the poly condensation reaction and RF-loaded NPs were fabricated by the dialysis method. The surface morphology and in-vitro drug release efficiency were examined. The effect of time and temperature on the cellular uptake of PEA-RF-NPs in NR8383 cells was evaluated. Fluorescence microscopic results of PEA-RF-NPs from NR8383 cell lines suggest its potential application in treating TB. The antibacterial activity of RF against Mycobacterium smegmatis was also evaluated. Based on these results, this approach provides a new means for controlled and efficient release of RF using the PEA-NPs delivery system and is promising for the treatment of TB.

Flexible and stretchable electronic composites

Natural Polyisoprene Composites and its Electronic Applications.- Electronic Applications of Polymer Electrolytes of Epoxidized Natural Rubber and its Composites.- Electronic Applications of Ethylene Vinyl Acetate and its Composites.- Electronic Applications of Polyurethane and its Composites.- Electronic Applications of Polyamide Elastomers and its Composites.- Electronic Applications of Polyacrylic Rubber and its Composites.-Electronic Applications of Polydimethylsiloxane and its Composites.- Chlorosulfonated Polyethylene and its Composites for Electronics Applications.- Electronic Applications of Styrene-Butadiene Rubber and its Composites.- Electronic Applications of Chloroprene Rubber and its Composites.- Electronic Applications of Ethylene Propylene Diene Monomer Rubber and its Composites.- Poly(Isobutylene-co-isoprene) Composites for Flexible Electronic Applications.-Nanomaterials Embedded Liquid Crystal Elastomers in Electronics Devices application.

Reduced graphene oxide filled poly(dimethyl siloxane) based transparent stretchable, and touch-responsive sensors

The ongoing revolution in touch panel technology and electronics demands the need for thin films, which are flexible, stretchable, conductive, and highly touch responsive. In this regard, conductive elastomer nanocomposites offer potential solutions for these stipulations; however, viability is limited to the poor dispersion of conductive nanomaterials such as graphene into the matrix. Here, we fabricated a reduced graphene oxide (rGO) and poly(dimethylsiloxane) (PDMS) elastomer based transparent and flexible conductive touch responsive film by dispersing rGO honeycombs uniformly into PDMS elastomer through an ionic liquid (IL) modification. Pursuing a simple, scalable, and safe method of solution casting, this provides a versatile and creative design of a transparent and stretchable rGO/IL-PDMS capacitive touch responsive, where rGO acts as a sensing element. This transparent film with ∼70% transmittance exhibits approximately a five times faster response in comparison to rGO/PDMS film, with negligible degradation over time. The performance of this touch screen film is expected to have applications in the emerging field of foldable electronics.

Flexible cellulose acetate/graphene blueprints for vibrotactile actuator

Tactile devices containing many actuators within are being sutured using electroactive polymers. This innovation forms the basis of hand-like tactile feedback in emerging smart robotic manipulation. Here, we introduce low power consuming modified reduced graphene oxide embedded cellulose acetate composite of high flexibility and conformability to surfaces made by simple and low cost synthesis methods, which thus points towards simple read-out electronics. The material performance was evaluated based on various actuation conditions in terms of electrical potential, bias voltage, temperature and frequency. The actuator vibrating at various frequencies with faster response time illustrates a range of haptic feedbacks to users, which can be used in braille display devices. Excellent repeatability of the haptic actuation process was also noticed.