• SHAMIMA HUSSAIN

Articles written in Bulletin of Materials Science

• Studies on interfacial interactions of TiO2 nanoparticles with bacterial cells under light and dark conditions

The probable underlying mechanism(s) of bacterial cell–TiO2 nanoparticles (TiO2 NPs) interaction in the absence of photo-irradiation has been less studied since most of the prior cytotoxicity studies focused on irradiated TiO2. The present study draws attention to the possible role of cell surface–TiO2 NP interactions under dark conditions, through an array of spectroscopic and microscopic investigations. A dominant freshwater bacterial isolate, Bacillus licheniformis, which interacted with environmentally relevant concentrations of TiO2 NPs (1 𝜇g/mL), was analysed and compared under both light and dark conditions. Aggregation of cells upon NP interaction and adsorption of NPs onto the cell membrane was evident from the scanning electron micrographs under both light and dark conditions. The FT–IR and FT–Raman spectra suggested stress response of bacterial cells by elevated protein and polysaccharide content in the cell–NP interaction. The X-ray photoelectron spectroscopic data substantiated the reduction of titanium from Ti(IV) to Ti(III) species which might have contributed to the redox interactions on the cell surface under light as well as dark conditions. The internalization of NPs in the cytoplasm were obvious from the transmission electron micrographs. The consequent cell death/damage was confirmed through fluorescence spectroscopy and microscopy. To conclude, the current study established the substantial role of interfacial interactions in cytotoxicity of the TiO2 NPs irrespective of the irradiation conditions.

• Growth of brownmillerite Ca$_2$Fe$_2$O$_5$ single crystals under air, oxygen and argon atmospheres using optical floating zone technique: a comparative study

To the best of our knowledge, we report for the first time the growth of brownmillerite Ca$_2$Fe$_2$O$_5$ (CFO) single crystals under Argon (Ar) only ambience by optical floating zone (OFZ) technique and compare its structural andspectroscopic properties with CFO single crystals grown by OFZ method under air and oxygen (O$_2$) atmospheres. Singlecrystal X-ray diffraction confirms growth of Ca$_2$Fe$_2$O$_5$ single crystals in all the atmospheres. Crystals grown in air andoxygen (O$_2$) atmospheres show both metallic Fe$^0$ and Fe$^{3+}$states, whereas in Ar-grown crystals only Fe$^{3+}$ oxidation state is observed. An enhancement in oxygen vacancies is also observed in Ar-grown crystals. Growth ambience is found tohave a strong influence on cationic environment and binding energy of constituent elements, as is evident from the X-ray photoelectron spectroscopy of the Ca$_2$Fe$_2$O$_5$ crystals.

• # Bulletin of Materials Science

Volume 46, 2023
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