N. Vigneshwaran

Functional behaviour of polypropylene/ZnO–soluble starch nanocomposites

ZnO-polypropylene nanocomposites (nano-PP) were prepared using nanoparticles of ZnO stabilized by soluble starch (nano-ZnO) as filler in PP by the melt mixing process. X-ray diffraction (XRD) and other spectroscopic analysis—ultraviolet–visible (UV–vis), Fourier transform infrared (FTIR) and photoluminescence—revealed the presence and characteristics of nano-ZnO in the composites. The presence of ZnO imparts whiteness, while starch increased the yellowing of polymers. The nanocomposites were analyzed for changes in optical, mechanical, electrical and rheological properties, as influenced by the increasing concentration of nano-ZnO. The mechanical properties were marginally increased and the dielectric strength of the nano-PP increased to a notable level. By monitoring the evolution of the carbonyl absorption bands from FTIR analysis, the efficacy of nano-ZnO in the reduction of photo-degradation due to UV irradiation was demonstrated. The excellent antibacterial activity exhibited by nano-ZnO impregnated PP against two human pathogenic bacteria, Staphylococcus aureus and Klebsiella pneumoniae, makes it a suitable candidate for food packaging applications.

A novel process for synthesis of spherical nanocellulose by controlled hydrolysis of microcrystalline cellulose using anaerobic microbial consortium.

Degradation of cellulose by anaerobic microbial consortium is brought about either by an exocellular process or by secretion of extracellular enzymes. In this work, a novel route for synthesis of nanocellulose is described where in an anaerobic microbial consortium enriched for cellulase producers is used for hydrolysis. Microcrystalline cellulose derived from cotton fibers was subjected to controlled hydrolysis by the anaerobic microbial consortium and the resultant nanocellulose was purified by differential centrifugation technique. The nanocellulose had a bimodal size distribution (43±13 and 119±9 nm) as revealed by atomic force microscopy. A maximum nanocellulose yield of 12.3% was achieved in a span of 7 days. While the conventional process of nanocellulose preparation using 63.5% (w/w) sulfuric acid resulted in the formation of whisker shaped nanocellulose with surface modified by sulfation, controlled hydrolysis by anaerobic microbial consortium yielded spherical nanocellulose also referred to as nano crystalline cellulose (NCC) without any surface modification as evidenced from Fourier transform infrared spectroscopy. Also, it scores over chemo-mechanical production of nanofibrillated cellulose by consuming less energy due to enzyme (cellulase) assisted catalysis. This implies the scope for use of microbial prepared nanocellulose in drug delivery and bio-medical applications requiring bio-compatibility.

Preparation of nano cellulose fibers and its application in kappa-carrageenan based film

Bio-based nanocomposite films were successfully developed using nanofibrillated cellulose (NFC) as the reinforcing phase and kappa-carrageenan (KCRG) as the matrix. NFC was successfully synthesis from short stable cotton fibers by chemo-mechanical process. The bionanocomposites were prepared by incorporating 0.1, 0.2, 0.3, 0.4, 0.5, and 1wt% of the NFC into a KCRG matrix using a solution casting method there characterization was done in terms of thermal properties (DSC), morphology (SEM), water vapor transmission rate (WVTR), oxygen transmission rate (OTR), X-ray diffractograms (XRD), and tensile properties. The main conclusion arising from the analysis of the result is that the bionanocomposites containing 0.4wt% of NFC exhibited the highest enhancement in tensile strength it is almost 44% improvement. WVTR and OTR results showed improvement of all nanocomposite film compare to control KCRG film.

Effect of Fenton's pretreatment on cotton cellulosic substrates to enhance its enzymatic hydrolysis response.

Fentons reagent that generates reactive hydroxyl radical species was evaluated for its effectiveness as a pretreatment agent on cotton cellulosic substrates to increase its susceptibility to cellulase enzyme. Response surface methodology was used to optimize four different process variables viz., time of reaction; substrate size and concentrations of Fe2+ and H2O2. Overall, the cellulose substrates treated at 0.5 mM concentration of Fe2+, 2% concentration of H2O2 for a reaction period of 48 h gave the highest enzyme activity as determined using the response surface methodology. Cellulose substrates with high aspect ratio recorded better enzyme response than that with low aspect ratio which is supported by copper number estimation. The cellulosic substrate prepared using a combination of optimized Fentons pretreatment conditions and/or enzyme hydrolysis were studied and characterized by atomic force microscopy and scanning electron microscopy. Additionally, degree of polymerization analysis gives further insight into the degradation during Fentons reaction.

Nanocellulose-Polymer Composites for Applications in Food Packaging: Current Status, Future Prospects and Challenges

ABSTRACT Nanocellulose has potential applications across the several industrial sectors and addresses a lot of issues related to environmental concern. As biodegradable filler in composite manufacturing, coating, and self-standing thin films, it offers novel and promising properties. Very few available reviews report on nanocellulose-impregnated composite materials for food packaging. Nanocellulose reinforcement is found to be promising for mechanical and barrier properties of composite for biopolymer and synthetic polymer. In this paper, we provide a thorough review of recent advances of nanocellulose synthesis and its application as a filler material for production of nanocomposites to be used for food packaging. GRAPHICAL ABSTRACT

Nanocellulose Production Using Cellulose Degrading Fungi

Nanocellulose, a novel material derived from cellulosic biomass, consists of cellulose having at least one dimension in the nano-size (<100 nm). Very high surface area to volume ratio (50–200 m2/g), high tensile strength (1–10 GPa) and low density (1.45 g/cc) make nanocellulose an attractive material as reinforcement agents in high performance composites. Earlier, nanocellulose was produced by concentrated sulphuric acid hydrolysis that removed the amorphous region leaving behind highly crystalline nanocellulose whiskers. Though they are stable due to sulfation on surface, scaling up could not be achieved due to reasons related to handling of concentrated (64 %) sulphuric acid and effluent disposal. Recently, research effort is towards mechanical preparation of nanocellulose by high pressure homogenization process that could circumvent the effluent problem. But, here the bottleneck is very high energy consumption (30,000 kWh/tonne) for nanocellulose production and frequent clogging of the production system. Various pre-treatments methodologies are evolved to reduce energy consumption and to avoid clogging in homogenizer. One among them, cellulase enzyme pre-treatment, is very popular and highly researched due to eco-friendliness and efficacy. Apart from cellulase enzyme the cellulase secreting fungi as such are being used for ease of handling and to reduce the cost of enzyme processing. Well studied fungi include Trichoderma sp. and Aspergillus sp. for pre-treatment of cellulosic biomass before homogenization process for production of nanocellulose. Lately, controlled hydrolysis by fungi itself evolved for production of nanocellulose thereby bypassing the homogenization process step. This makes fungi a versatile organism for production of nanocellulose.

Modification of textile surfaces using nanoparticles

Abstract: The application of nanotechnology on textile materials could lead to the addition of several functional properties to the base substrate. Those functional properties are of the highest importance, giving noticeable improvements in the wear comfort and care. This chapter discusses various functional properties – for example, anti-microbial, easy-care, ultraviolet-protecting and flame-retardant finishes that could be achieved by the application of metal and metal oxide nanoparticles. In addition, novel applications of textile materials using nanotechnology in biological detection, decomposition of toxic gases, self-decontamination and military protection gear are discussed.

Biomolecules–Nanoparticles: Interaction in Nanoscale

Even though the production of nanoparticles of silver and gold dates back many centuries, characterization and manipulation at nanoscale has initiated a new era for nanotechnology. Spreading its wings beyond physics and materials science, its scope of application in molecular biology, biochemistry, and medicine is only recently being appreciated. This necessitated a need for the interaction between nanoparticles and biomolecules. The importance of this field can be supported by the dedication of fifth issue of JACS Select that contains 22 communications and articles related to chemistry at the Nano–Bio Interface. The designing of various nanoparticles for biological applications has been enabled by advances in synthesis of functionalized nanoparticles that makes them compatible with biomolecules. In wet-chemical process the nanoparticles preparation is carried out in the presence of biomolecules like glucose, soluble starch, or chitosan that leads to stabilization of nanoparticles. Another approach is based on linker where the biomolecules like DNA, proteins are immobilized on nanoparticles through linkers like citrate, streptavidin, etc. Many of the free aminoacids were also used to stabilize fluorescence nanoparticles like cadmium sulfide and zinc sulfide. The recognition capability of biomolecules also helped in directed synthesis of nanoparticles with desired morphology and arrangement. In addition, biomolecules support in biotemplating and biomimetic synthesis of nanomaterials. Both the biomolecules and nanoparticles meet at the same nanometer scale that makes their interaction very interesting and promising in various applications. This chapter covers the major processes/products where biomolecules meet nanoparticles and their chemical interaction.