Geetha R. Balakrishna

N-heterocyclic carbene metal complexes as bio-organometallic antimicrobial and anticancer drugs

Late transition metal complexes that bear N-heterocyclic carbene (NHC) ligands have seen a speedy growth in their use as both, metal-based drug candidates and potentially active homogeneous catalysts in a plethora of C-C and C-N bond forming reactions. This review article focuses on the recent developments and advances in preparation and characterization of NHC-metal complexes (metal: silver, gold, copper, palladium, nickel and ruthenium) and their biomedical applications. Their design, syntheses and characterization have been reviewed and correlated to their antimicrobial and anticancer efficacies. All these initial discoveries help validate the great potential of NHC-metal derivatives as a class of effective antimicrobial and anticancer agents.

Enhanced photocatalytic hydrogen production from Y2O3/TiO2 nano-composites: a comparative study on hydrothermal synthesis with and without an ionic liquid

Hetero-junction Y2O3/TiO2 nano-composite (NC) photocatalysts were synthesized using a conventional hydrothermal method (Y2O3/TiO2 NC(HM)) and an ionic liquid assisted hydrothermal method (Y2O3/TiO2 NC(ILAHM)). The composite nature and physico-chemical properties of the photocatalysts prepared through both routes as a function of thermal treatment were investigated via thorough characterization. A comparison of the photocatalytic hydrogen production via water splitting is provided. It was found that the concentration of Y2O3 in the TiO2 matrix and the post thermal treatment have obvious effects on the hydrogen production activity, and they were fine-tuned for enhancement of the hydrogen production. The required synergy between Y2O3 and TiO2 was found to occur at an optimum concentration of 25 wt% Y2O3 in the TiO2 matrix, with the sample prepared at 400 °C for 1 h. The optimized NC i.e. 25 wt% Y2O3/TiO2 NC(ILAHM) produced a promising hydrogen evolution of 1380 μmol g−1 that was almost 2-fold the production from 25 wt% Y2O3/TiO2 NC(HM). The enhancement was attributed to the porous surface morphology, higher surface area and quantum yield of the NC prepared using the ionic liquid assisted hydrothermal method.

Excellent hydrogen evolution by a multi approach via structure–property tailoring of titania

Photocatalytic water splitting by solar energy is an ideal economic method for hydrogen generation. An attempt has been made to overcome the main barriers of photocatalytic hydrogen evolution (these being rapid recombination of electron–hole pairs, the process of back reaction and poor activation of titania by visible light) by the usage of Fe-induced titania. The method facilitates a cage like mesoporous structure and an effective surface level doping. The induction of dopants and formation of coupled semiconductor oxides of well matched band energy contribute favorably to the rise of mid bands and the perfect alignment of their energy levels, leading to a shallow trapping and detrapping of electrons, necessary for efficient charge separation and transfer. Decrease in the band gap energy to ∼2.0 eV and hence the extended light absorption in modified titania, together with a shift in band edge potentials (caused by pH variation), results in an activated titania, desirable for enhanced visible light hydrogen evolution. The modified nanostructure shows an excellent hydrogen evolution of 255 mmol g−1 h−1, one of the highest reported so far. Sodium acetate acts as a good sacrificial agent in preventing the back reaction. Characterization techniques like spectroscopy (XRD, UV, reflectance, EDX, XPS and PL) and microscopy (FESEM and HRTEM) have been used to evidence the presence of Fe as dopant/as oxide and to study the structure–property tailoring that occurs during chemical modification.

La activated high surface area titania float for the adsorption of Pb(II) from aqueous media

Currently, the world faces alarming challenges of heavy metal contamination, which are hazardous to humans and the environment because of their toxicity even in trace concentrations. Lead is one of the harmful heavy metal contaminants and has poisonous effects on human health. The present research investigation describes the adsorption of toxic Pb(II) on an immobilized adsorbent with a highly smaller crystallite size along with enhanced surface area and pore volume of La doped TiO2 synthesized from a simple co-precipitation method. Induction of dopant La3+ was confirmed by XPS with a smaller particle size of 25 nm as compared to TiO2 of 80 nm. The La doped TiO2 shows an enhanced surface area of 97.246 m2 g−1 compared to TiO2 of 17.2 m2 g−1 due to the introduction of oxygen vacancies leading to increased surface roughness and thus shows significant improvement in the adsorption of Pb(II) in comparison with TiO2 at basic pH due to the negative charge on La doped TiO2. A suitable optimized pH was examined and the Pb(II) adsorption study was measured using atomic absorption spectroscopy.