Antioxidant efficacy of chitosan/graphene functionalized superparamagnetic iron oxide nanoparticles.

The antioxidant potential of superparamagnetic iron oxide nanoparticles functionalized with chitosan and graphene were examined in the present work. Coprecipitation technique was followed for the synthesis of iron oxide nanoparticles. Graphene-iron oxide nanocomposites were synthesized by mechanical mixing followed by the heat treatment at moderate temperature. The chitosan coated iron oxide nanoparticles were prepared by dispersing nanoparticles in chitosan solution. The nanoparticles/nanocomposites were characterized using XRD, SEM, TEM and HAADF-STEM for phase structure, morphology and elemental analysis. The superparamagnetic behavior of nanoparticles/nanocomposites were confirmed by magnetic measurements using vibrating sample magnetometry. Antioxidant efficacy of these nanoparticles/nanocomposites were investigated in terms of free radical scavenging and reducing potential using an array of in vitro assay system. Ferric reducing antioxidant power (FRAP) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) were used for the antioxidant capacity. The investigation suggests that the graphene improves the antiradical response of iron oxide nanoparticles at higher concentration which is almost comparable to the ascorbic acid used as standard.

ZrO2@chitosan composite for simultaneous photodegradation of three emerging contaminants and antibacterial application.

Emerging contaminants (ECs) are often detected in water bodies due to their prevalent use combined with inefficiency of the conventional wastewater treatment plants for their complete removal. Elimination of ECs using photocatalysis as a tertiary treatment can be a sustainable option for the reuse wastewater. Reported herewith is a photocatalyst, chitosan-based zirconia hybrid composite (ZrO2CTS-HC) for the individual/ simultaneous degradation of multiple ECs like Congo red (CR), Methyl orange (MO) and 4-hydroxybenzoic acid (4-HA) under visible light irradiation. Successfully synthesized ZrO2CTS-HC as confirmed by theoretical and various characterization techniques depicted photodegradation efficiency of 91.11, 69.11 and 78.40% for CR, MO and 4-HA respectively (SD 0.5-0.95; HPLC) aided by the reactive hydroxyl radical. Probable degradation mechanism supported by LC-MS/MS, COD and TOC along with reusability and antibacterial ability towards E.Coli & S.aureus is also reported. ZrO2CTS-HC can be a good option for elimination of residual ECs during tertiary treatment.

Alteration of the electronic structure and the optical properties of graphitic carbon nitride by metal ion doping.

The photoluminescence quenching of graphitic carbon nitride (GCN) was systematically investigated with the doping of transition metal ions. The photoluminescence spectra of metal doped and pristine GCN were monitored and the trend of quenching efficiency was found to be Cu2+ > Co2+ > Mn2+. Interestingly, with the increasing doping concentration of different metal ions simultaneous red shift and luminescence quenching was determined in the photoluminescence spectra as well as increased absorption tail in longer wavelength hence enhancement in the bandgap. The change in the optical properties could be mainly due to structural reconstruction and doping induced electronic redistribution is discussed.