• Monika

Articles written in Bulletin of Materials Science

• Preparation and characterization of nanostructured ZnO thin films for photoelectrochemical splitting of water

Nanostructured zinc oxide thin films (ZnO) were prepared on conducting glass support (SnO2: F overlayer) via sol–gel starting from colloidal solution of zinc acetate 2-hydrate in ethanol and 2-methoxy ethanol. Films were obtained by spin coating at 1500 rpm under room conditions (temperature, 28–35°C) and were subsequently sintered in air at three different temperatures (400, 500 and 600°C). The evolution of oxide coatings under thermal treatment was studied by glancing incidence X-ray diffraction and scanning electron microscopy. Average particle size, resistivity and bandgap energy were also determined. Photoelectrochemical properties of thin films and their suitability for splitting of water were investigated. Study suggests that thin films of ZnO, sintered at 600°C are better for photoconversion than the films sintered at 400 or 500°C. Plausible explanations have been provided.

• Thromboresistance of functionalized poly(methylmethacrylate): the effect of surface polarity

An implant material when comes in contact with blood fluids (e.g., blood and lymph), adsorb proteins spontaneously on its surface. Notably, blood coagulation is influenced by many factors, including mainly chemical structure and polarity (charge) of the material. The present study describes the methodology to improve the blood compatibility of poly(methylmethacrylate) (PMMA) by incorporating ionic groups with varying polarities. PMMA has been functionalized with different groups containing positive, negative and neutral polarity by the free radical polymerization technique and suchmodification were further confirmed through Fourier transform infrared (FTIR) spectroscopy. The level of thrombogenicity was found three times lower with negatively charged PMMA in comparison to those of positively charged and neutral PMMA. Platelet adhesion was noted almost negligible in all samples after 10 s of blood exposure. High adsorption of fibrinogen from the blood was noticed in the test sample containing a group with positive polarity (thiouronium chloride) while there was no platelet adhesion observed even after 120 s of blood exposure in the test samples containing negatively charged (sulphate) and neutral (hydroxyl group) functional groups.

• Green synthesis of silver nanoparticles and biopolymer nanocomposites: a comparative study on physico-chemical, antimicrobial and anticancer activity

The current report was intended towards comparative study of green-synthesized biogenic Rhubarb silver nanoparticles (RS-AgNPs) and chitosan crosslinked silver nanocomposites (CSHD-AgNCs). The physico-chemical characterization was done by UV–visible, FTIR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), EDX, TGA, XRD and zeta potential ($\zeta$). The analysis and spectroscopic characterization was done by SEM and TEM and their results reveal that the nanoparticles are spherical in shape, with average size ranges from 5 to 50 nm, and was gatheredby face centered cubic (FCC) structure throughout the polymer matrix and stable without any protecting or capping reagents over 450 days. The antimicrobial property of RS-AgNPs and CSHD-AgNCs ($\zeta = +29.6$ and $+$32.8 mV) was evaluated against E. coli and S. aureus and showed an effective inhibitory property. The RS-AgNPs and CSHD-AgNCs were assessedfor their anticancer activity against HeLa cell line by MTT method, and it reveals a dose–response activity, time and cell line-dependent cytotoxicity. Based on the results obtained, the RS-AgNPs exhibited higher toxicity over CSHD-AgNCsafter 24 h incubation of HeLa cells with different concentrations and is negligible for the aqueous Rhubarb extract. It was concluded that the changes in anticancer activity towards HeLa cells due to biological activity of silver nanoparticles depend on their method of biosynthesis and their physico-chemical nature.

• Structure of ice confined in carbon and silica nanopores

In this work, water confined in silica and carbon nanopores has been examined. The purpose of this study is to describe the melting behaviour and structure of ice confined in silica nanopores, KIT-6 and ordered carbon nanopores, CMK-3, having pore diameters of 5.9 and 5.2 nm, respectively. To determine the melting temperature of ice inside the nanopores, we performed differential scanning calorimetry measurements of the systems studied.We found that the melting temperature of confined ice is reduced relative to the bulk melting point and this shift is 16 K for water confined in KIT-6 and 21 K for water confined in CMK-3. The structural properties of water at the interfaces were analysed by using the neutron diffraction method (ND). The ND measurements for all the systems studied, showed the features of both hexagonal ice, $I_h$,and cubic ice, $I_c$. However, we show that the ice confined in nanopores does not have a structure corresponding to the typical hexagonal form or the metastable cubic form. The ice confined in nanopores has a structure made up of cubic sequences interlaced with hexagonal sequences, which produce the stacking disordered ice (ice $I_{\rm sd}$).

• Mesoporous $x$[Cu(II)O] nanoclusters dispersed and immobilized on $y$[SiO$_2$] matrix: structure and effective controlled biocidal activity against Pseudomonas aeruginosa and Bacillus subtilis

Herein we report the synthesis of mesoporous nanostructures comprising copper (II) oxide {$x$[Cu(II)O]} immobilized on silica $y$[SiO$_2$] template for release of copper ions by precipitation via sol–gel technique. Three different specimens with increasing amount of Cu in the matrix with amount of Si being the same in all the samples, viz. ‘6Cu:5Si’, ‘4.5Cu:5Si’ and ‘3Cu:5Si’ where the numbers refer to the respective molar ratios of their respective domains, were prepared. Increase of crystallinity in the mesoporous material with increase in incorporation of copper domains consisting of CuO in SiO$_2$ matrix has been established. The average size of the CuO nanoparticle (NP) (domain) is 20–30 nm. The BET surface area has been found to be 276–390 m$^2$ g$^{−1}$ and Langmuir surface area has been found to be 422–605.9 m2 g−1 for the samples5Si:3Cu–5Si:6Cu, respectively, having pore size of 4–6.5 nm. The cytotoxicity data show that the NPs are less toxic below concentration of 125 $\mu$g ml$^{−1}$. A steady increase in percentage of bacterial-‘Escherichia coli’, ‘Pseudomonas aeruginosa’ and ‘Bacillus subtilis’ cell death (indicated by decrease in optical density) due to increase in concentrations of NPs after incubation for 14 h, showing sensitivity even at very low concentrations (5–20 $\mu$g), has been observed. A comparative antibacterial activity test among the three prepared specimens has been reported, which shows better antibacterial activity with the lowest copper concentration. Better antibacterial sensitivity when compared with equivalent amount of commercial CuO is established.

• # Bulletin of Materials Science

Volume 43, 2020
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020