Electron-Phonon Coupling Mediated Self-Trapped-Exciton Emission and Internal Quantum Confinement in Highly Luminescent Zero-Dimensional (Guanidinium)6Mn3X12 (X = Cl and Br).

We report a large Stokes shift and broad emission band in a Mn-based organic-inorganic hybrid halide, (Guanidinium)6Mn3Br12 [GuMBr], consisting of trimeric units of distorted MnBr6 octahedra representing a zero-dimensional compound with a liquid like crystalline lattice. Analysis of the photoluminescence (PL) line width and Raman spectra reveals the effects of electron-phonon coupling, suggestive of the formation of Frenkel-like bound excitons. These bound excitons, regarded as the self-trapped excitons (STEs), account for the large Stokes shift and broad emission band. The excited-state dynamics was studied using femtosecond transient absorption spectroscopy, which confirms the STE emission. Further, this compound is highly emissive with a PL quantum yield of ∼50%. With chloride ion incorporation, we observe enhancement of the emissive properties and attribute it to the effects of intrinsic quantum confinement. Localized electronic states in flat bands lining the gap and their strong coupling with phonons are confirmed with first-principles calculations.

Graphene oxide based electrochemical immunosensor for rapid detection of groundnut bud necrosis orthotospovirus in agricultural crops.

Groundnut bud necrosis orthotospovirus (GBNV) is one of the causative plant viruses responsible for the outbreak of many viral epidemics in food crops across India and other south-Asian countries. Its management is a major challenge due to fast vector transmission, and the non-availability of appropriate agrochemical treatment. The timely detection of GBNV becomes indispensable for the effective management of viral infection and the periodic monitoring of plant health. We report the fabrication of graphene oxide (GO) based electrochemical immunosensor for the rapid and sensitive detection of GBNV. The immunoelectrode is prepared by depositing GO onto indium-tin oxide (ITO) coated glass substrates and functionalized by anti-GBNV antibodies using N-ethyl-N'-(3- dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide (EDC-NHS) conjugation chemistry. The response measurements of the immunoelectrodes revealed a sensitivity of 221 ± 1 µA µg-1 mL-1(n = 3) and limit of detection (LOD) of 5.7 ± 0.7 ng mL-1(n = 3) for the standard concentrations of GBNV antigen. Further, the GBNV detection was carried out in infected leaf extracts of three different host plants i.e., Tomato, Cowpea, and N. benthamiana, and the results have been compared with the conventionally used direct antigen coated enzyme-linked immunosorbent assay (DAC-ELISA) technique. The comparable results obtained for the detection of GBNV in infected plants using electrochemical immunosensing and DAC-ELISA techniques advocated the immense potential of GO based immunosensor as a point-of-care sensing device that is poised to overcome the limitations of the traditional methods of virus detection in field conditions and may transform the diagnostics in agriculture.

Chitosan-Fe-Al-Mn metal oxyhydroxides composite as highly efficient fluoride scavenger for aqueous medium.

Nano-particles are highly efficient fluoride adsorbents, but agglomerate easily due to their high surface activity and are difficult to separate from aqueous medium after use. Mixed-metals oxyhydroxides nano-particles were prepared into a natural polymeric matrix of chitosan to overcome these problems. Hydrous mixed-metal oxyhydroxides, loaded chitosan composite (Fe-Al-Mn@chitosan) was prepared using abundantly available laterite clay and waste from steel industry via co-precipitation method. Fluoride removal using Fe-Al-Mn@chitosan composite followed Freundlich isotherm model which revealed multilayer adsorption on heterogeneous surface sites. Fe-Al-Mn@chitosan exhibited maximum adsorption capacity of 40±0.5 mg/g, while if only the inorganic mass fraction of composite was considered; the value reached 55±0.5 mg/g. Fluoride adsorption on Fe-Al-Mn@chitosan followed the pseudo-second order kinetics with rapid adsorption. No significant effect of other competitive ions was observed on F- adsorption using Fe-Al-Mn@chitosan composite. The composite adsorbent is found to be effective to produce drinking water from fluoride contaminated groundwater.