A novel approach for amine derivatization of MoS2 nanosheets and their application toward label-free immunosensor.

The application of molybdenum disulfide (MoS2) nanosheets has assumed great significance in the design of next-generation biosensors. The immobilization of biomolecules on MoS2 nanosheets has generally been achieved via hydrophobic interactions or through other complicated surface modifications. In this work, we report a novel strategy for electrochemically assisted amine derivatization of MoS2 nanosheets. This newly proposed approach helped to immobilize the MoS2 nanosheets with antibodies via facile EDC/NHS {N-(3-dimethylaminopropyl)-N-(ethylcarbodiimide/N-hydroxysuccinimide)} cross-linking chemistry. The MoS2 nanosheets were first exfoliated and then electrochemically modified with 2-aminobenzylamine. Through a subsequent bioconjugation of the above amine-derivatized MoS2 nanosheets with anti-prostate-specific antigen (PSA) antibodies, an immunosensing device was realized for the detection of the 'prostate specific antigen'. The application of the proposed immunosensor was characterized with a low detection limit (10-3 ng/mL) over a very wide quantitation range (10-3 to 200 ng/mL).

A comprehensive review on nano-molybdenum disulfide/DNA interfaces as emerging biosensing platforms.

The development of nucleic acid-based portable platforms for the real-time analysis of diseases has attracted considerable scientific and commercial interest. Recently, 2D layered molybdenum sulfide (2D MoS2 from here on) nanosheets have shown great potential for the development of next-generation platforms for efficient signal transduction. Through combination with DNA as a biorecognition medium, MoS2 nanostructures have opened new opportunities to design and construct highly sensitive, specific, and commercially viable sensing devices. The use of specific short ssDNA sequences like aptamers has been proven to bind well with the unique transduction properties of 2D MoS2 nanosheets to realize aptasensing devices. Such sensors can be operated on the principles of fluorescence, electro-cheumuluminescence, and electrochemistry with many advantageous features (e.g., robust biointerfacing through various conjugation chemistries, facile sensor assembly, high stability with regard to temperature/pH, and high affinity to target). This review encompasses the state of the art information on various design tactics and working principles of MoS2/DNA sensor technology which is emerging as one of the most sought-after and valuable fields with the advent of nucleic acid inspired devices. To help achieve a new milestone in biosensing applications, great potential of this emerging technique is described further with regard to sensitivity, specificity, operational convenience, and versatility.

Green synthesis of highly stable carbon nanodots and their photocatalytic performance.

The present study reports a novel, facile, biosynthesis route for the synthesis of carbon nanodots (CDs) with an approximate quantum yield of 38.5%, using Musk melon extract as a naturally derived-precursor material. The synthesis of CDs was established by using ultraviolet-visible (UV-vis) spectroscopy, Dynamic light scattering, photoluminescence spectroscopy, X-ray diffraction, transmission electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The as-prepared CDs possess an eminent fluorescence under UV-light (λex = 365 nm). The size range of CDs was found to be in the range of 5-10 nm. The authors further explored the use of such biosynthesised CDs as a photocatalyst material for removal of industrial dye. Degradation of methylene blue dye was performed in a photocatalytic reactor and monitored using UV-vis spectroscopy. The CDs show excellent dye degradation capability of 37.08% in 60 min and reaction rate of 0.0032 min-1. This study shows that synthesised CDs are highly stable in nature, and possess potential application in wastewater treatment.

Fungal biomolecules assisted biosynthesis of Au-Ag alloy nanoparticles and evaluation of their catalytic property.

The catalytic reduction of methylene blue was studied using biosynthesised gold-silver (Au-Ag) alloy nanoparticles (NPs). The fungal biomass of Trichoderma harzianum was used as a reducing and stabilising agent in the synthesis of Au-Ag alloy NPs. The synthesised NPs were well characterised by UV-vis spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The plausible synthesis mechanism involved in the formation of Au-Ag alloy NPs was also discussed with diagrammatic representation. A series of experiments was performed to investigate the catalytic activity of the as-prepared Au-Ag alloy NPs and found that the alloy NPs show excellent catalytic activity.

ZnO nanoflowers: novel biogenic synthesis and enhanced photocatalytic activity.

We demonstrate a novel, unprecedented and eco-friendly mode for the biosynthesis of zinc oxide (ZnO) nanoflowers at ambient room temperature using Bacillus licheniformis MTCC 9555 and assessed their photocatalytic activity. The photocatalytic degradation of methylene blue (MB) dye was analyzed under UV-irradiation. An enhanced photocatalytic activity of ZnO nanoflowers was obtained compared to the earlier reports on ZnO nanostructures and other photocatalytic materials. The mechanism behind the enhanced photocatalytic activity was illustrated with diagrammatic representation. It is assumed that due to larger content of oxygen vacancy ZnO nanoflowers shows enhanced photocatalytic activity. Photostability of ZnO nanoflowers was analyzed for consecutive 3 cycles. The size and morphology of ZnO nanoflowers have been characterized by SEM, TEM and found to be in the size range of 250 nm to 1 µm with flower like morphology. It was found that ZnO nanoflowers was formed by agglomeration of ZnO nanorods. Further the EDX established the presence of the elemental signal of the Zn and O. XRD spectrum of ZnO nanoflowers confirmed 2θ values analogous to the ZnO nanocrystal. FTIR analysis was carried to determine the probable biomolecules responsible for stabilization of ZnO nanoflowers. The plausible mechanism behind the synthesis of ZnO nanoflowers by Bacillus licheniformis MTCC 9555 was also discussed with diagram representation.