Nano structured Hausmannite (Mn 3 O 4) has efficacious applications in numerous fields, such as catalytic, medical, biosensors, waste water remediation, energy storage devices etc. The potential application in wastewater treatment is due to its distinct structural features combined with fascinating physicochemical properties. Another area of interest is the oxidative properties imparted due to its reduction potential. Larger surface to volume ratio and high reactivity than the bulk form shows great progress as antimicrobial agent to control drug resistant microbial population. The distinct surface morphologies, crystalline forms, reaction conditions and synthetic methods exerts significant impact on the photo catalytic and bactericidal efficiency. Hence, the present paper focuses on a concise review of the multifarious study on synthetic methods of Mn 3 O 4 , growth mechanisms, structural forms, phase transformation and phase control, shape and dimensionality. The review also confers its applications towards photo catalytic and bactericidal studies.

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A B S T R A C TEthyl orange (EO) is a mono-azo dye, which is chiefly used as a dye in textile, food, and cosmetic industries. Removal of this dye from wastewater generated by these industries is a main concern in wastewater treatment. Hence, there is a need for a simple and inexpensive method to abolish this dye present in wastewater. A search through literature revealed that very few reports are available on the decolorization of EO dye and also no kinetic and mechanistic studies have been carried out about this dye. Consequently, an attempt is made to develop an oxidative decolorization method for EO dye with chloramine-T (CAT). The present study also aims to investigate the kinetics and mechanism of oxidative decolorization of EO dye with CAT in HClO 4 medium spectrophotometrically (λ max = 474 nm) at 303 K. The reaction exhibits a first-order dependence of rate on [EO] ], respectively. The dielectric effect is positive. Activation parameters have been deduced. Oxidation products were identified as N-(4-diethylamino-phenyl)-hydroxyamine and 4-nitroso-benzenesulfonic acid. Suitable mechanism and related rate law have been worked out. Importantly, the present decolorization method is definitely an advantageous alternative technique in treating the EO dye present in wastewater.

BiVO 4 have been proven to be one of the most promising photocatalyst for degradation of organic dyes and also exhibit good electrochemical performances in heavy metal detection. Herein, we have developed a simple, economic and low-cost combustion synthesis of BiVO 4 nanoparticles using bismuth nitrate as an oxidiser, lemon (Citrus Limon) juice as fuel. The prepared nanoparticles were characterized by Powder X-ray diffractometer (PXRD), Fourier Transform-Infrared spectroscopy (FTIR), Diffused Reflectance Spectroscopy (DRS), Photolumines-cence Spectroscopy (PL), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analytical techniques. Flower-like morphology BiVO 4 nanoparticles were observed for higher ratio of fuel (Citrus Limon). BiVO 4 nanoparticles showed an excellent photocatalytic activity towards degradation of Indigo Carmine dye in solution. Further, BiVO 4 modified electrode was examined for the detection of Hg (II) using electrochemical techniques.[a] Dr.