Gownolla Malegowd Raghavendra

Nano zinc oxide-sodium alginate antibacterial cellulose fibres

Abstract In the present study, antibacterial cellulose fibres were successfully fabricated by a simple and cost-effective procedure by utilizing nano zinc oxide. The possible nano zinc oxide was successfully synthesized by precipitation technique and then impregnated effectively over cellulose fibres through sodium alginate matrix. XRD analysis revealed the ‘rod-like’ shape alignment of zinc oxide with an interplanar d-spacing of 0.246nm corresponding to the (101) planes of the hexagonal wurtzite structure. TEM analysis confirmed the nano dimension of the synthesized zinc oxide nanoparticles. The presence of nano zinc oxide over cellulose fibres was evident from the SEM–EDS experiments. FTIR and TGA studies exhibited their effective bonding interaction. The tensile stress–strain curves data indicated the feasibility of the fabricated fibres for longer duration utility without any significant damage or breakage. The antibacterial studies against Escherichia coli revealed the excellent bacterial devastation property. Further, it was observed that when all the parameters remained constant, the variation of sodium alginate concentration showed impact in devastating the E. coli. In overall, the fabricated nano zinc oxide–sodium alginate cellulose fibres can be effectively utilized as antibacterial fibres for biomedical applications.

A mini review on hydrogels classification and recent developments in miscellaneous applications

Hydrogels are composed of three-dimensional smart and/or hungry networks, which do not dissolve in water but swell considerably in an aqueous medium, demonstrating an extraordinary ability to absorb water into the reticulated structure. Such inherent feature is a subject of considerable scientific research interest which leads to a dominating path in extending their potential in hi-tech applications. Over the past decades, significant progress has been made in the field of hydrogels. Further, explorations are continuously being made in all directions at an accelerated pace for their extensive usage. In view of this, the present review discusses the subject on the miscellaneous hydrogels with regard to their raw materials, methods of fabrication and applications. In addition, this article summarizes the classification of hydrogels, based on their cross-linking and physical states. Lately, a brief outlook on the future prospects of hydrogels is also presented.

Step-reduced synthesis of starch-silver nanoparticles

In the present process, silver nanoparticles were directly synthesized in a single step by microwave irradiation of a mixture of starch, silver nitrate, and deionized water. This is different from the commonly adopted procedure for starch-silver nanoparticle synthesis in which silver nanoparticles are synthesized by preparing a starch solution as a reaction medium first. Thus, the additional step associated with the preparation of the starch solution was eliminated. In addition, no additional reducing agent was utilized. The adopted method was facile and straight forward, affording spherical silver nanoparticles with diameter below 10nm that exhibited good antibacterial activity. Further, influence of starch on the size of the silver nanoparticles was noticed.

Microwave assisted antibacterial chitosan-silver nanocomposite films.

In the current approach, antibacterial chitosan-silver nanocomposite films were fabricated through microwave irradiation. During the process, by utilizing chitosan as reducing agent, silver nanoparticles were synthesized within 11 min by microwave irradiation. Further, films were fabricated within 90 min. It involved an energy consumption of just 0.146 kWh to synthesize silver nanoparticles. This is many times less than the energy consumed during conventional methods. The silver nanoparticles were examined through UV-vis spectrum and transmission electron microscopy (TEM). The fabricated films were characterized by using scanning electron microscopy coupled with an energy dispersive spectrometer (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and contact angle (CA) measurements. The films exhibited antibacterial properties against both Gram-negative micro-organisms (Escherichia coli; E. coli) and Gram-positive micro-organisms (Staphylococcus aureus; S. aureus). In overall, the procedure adopted for fabricating these antibacterial films is environmental friendly, time-saving and energy-saving.

Development of biodegradable metaloxide/polymer nanocomposite films based on poly-ε-caprolactone and terephthalic acid

The present investigation describes the development of metal-oxide polymer nanocomposite films from biodegradable poly-ε-caprolactone, disposed poly(ethylene terephthalate) oil bottles monomer and zinc oxide-copper oxide nanoparticles. The terephthalic acid and zinc oxide-copper oxide nanoparticles were synthesized by using a temperature-dependent precipitation technique and double precipitation method, respectively. The terephthalic acid synthesized was confirmed by FTIR analysis and furthermore, it was characterized by thermal analysis. The as-prepared CuO-ZnO nanoparticles structure was confirmed by XRD analysis and its morphology was analyzed by SEM/EDS and TEM. Furthermore, the metal-oxide polymer nanocomposite films have excellent mechanical properties, with tensile strength and modulus better than pure films. The metal-oxide polymer nanocomposite films that were successfully developed show a relatively brighter colour when compared to CuO film. These new metal-oxide polymer nanocomposite films can replace many non-degradable plastics. The new metal-oxide polymer nanocomposite films developed are envisaged to be suitable for use in industrial and domestic packaging applications.

One-step synthesis of starch-silver nanoparticle solution and its application to antibacterial paper coating

Antibacterial starch-silver nanoparticles (ST-AgNPs) for use as coating solutions were prepared in a single step by ultrasonicating a mixture of starch, silver nitrate, and distilled water. The starch was used as an eco-friendly and inexpensive reducing agent. UV-vis spectra and transmission electron microscopy indicated that our single-step process was effective for synthesizing starch-based coating solution with AgNPs. Further, the as-prepared coating solution with AgNPs was applied to expand the application of paper for antibacterial packaging. The starch-coated paper with AgNPs showed not only highly enhanced oil resistance, but also excellent antibacterial activity, making our biodegradable starch-coated paper with AgNPs highly feasible for packaging applications.

Chitosan-mediated synthesis of flowery-CuO, and its antibacterial and catalytic properties

In the current investigation, CuO with a flower-like morphology has been successfully synthesized in situ in a chitosan medium (0.0015gmL-1) from copper nitrate (Cu(NO3)2·3H2O) and ammonia solution via a facile microwave-induced method. The as-prepared CuO was characterized by SEM, TEM, EDX, XRD, FTIR and TGA. The antibacterial activity of the flower-CuO against Escherichia coli was examined by analyzing colony forming units, and it was proved that the flower-CuO was able to kill >99% bacteria. Further, the flower-CuO exhibited excellent catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The reaction kinetics followed a pseudo-first-order rate law with a rate constant of 0.183min-1. To the best of our knowledge, this is the first time that copper oxide with the flower-like morphology has been synthesized by using a chitosan solution.

Improving properties of Hanji by coating chitosan–silver nanoparticle solution

A chitosan-silver nanoparticle solution (CSNS) was applied as a coating material to Hanji (Korean traditional paper), and the properties of the coated paper were investigated as a function of the dilution ratio. The required CSNS was first prepared from AgNO3 (30mmol) by utilizing chitosan as a reducing and stabilizing agent via ultrasonication. The as-prepared CSNS was diluted to various ratios (undiluted, 1/10, 1/100, and 1/1000) and applied to Hanji by a dip-coating method. The tensile, burst, oil resistance, and antibacterial properties of the coated Hanji against Escherichia coli were evaluated. Among the various dilution ratios, the maximum level of dilution that can positively influence the tensile, burst, oil resistance, and antibacterial properties of Hanji was identified as 1/10, 1/100, 1/10 and 1/1000 of the pure CSNS, respectively. These findings are significant because a specific property of Hanji can be economically improved by changing the dilution ratio.