Browsing by Author "Singh, Jaydeep"

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    Colorimetric detection of hydrogen peroxide and cholesterol using Fe3O4-brominated graphene nanocomposite
    (Springer Science and Business Media Deutschland GmbH, 2022) Singh, Jaydeep; Singh, Rajshree; Singh, Shikha; Mitra, Kheyanath; Mondal, Sourov; Vishwakarma, Sambhav; Ray, Biswajit
    Fe3O4-brominated graphene (Fe3O4-GBR) nanocomposites were synthesized via an in situ method using the precursors FeSO4.7H2O and GBR in different (1:1, 1:2, 2:1, 1:5, 1:10, 1:20, and 5:1) weight ratios at pH�11.5. The Fe3O4-GBR (1:5) nanocomposite in combination with H2O2 and 3,3?,5,5?-tetramethylbenzidine (TMB) showed swift and superior intrinsic peroxidase mimetic enzyme activity compared with the other Fe3O4-GBR composites, GBR and Fe3O4, as observed by colorimetry. It was characterized using high-resolution scanning electron microscopy (HRSEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Its catalytic activity was optimized by varying different parameters, and the optimum conditions for peroxidase mimetic activity were observed using 100�?L Fe3O4-GBR (1�mg/mL), 50�?L TMB (1�mg/mL), and 200�?L H2O2(1�mM) in 400�?L of acetate buffer of pH�2.3 at 30��C temperature. Kinetic analysis has revealed the Michaelis�Menten kinetic behavior of peroxidase activity with Michaelis�Menten constants (Km) and maximum initial velocities (Vmax) of 0.082�mM and 14.1 nMs?1 respectively, for H2O2 and 0.086�mM and 5.1 nMs?1, respectively for TMB. The limit of detection and linear range were found to be 49.6�?M and 100�880�?M, respectively, for H2O2 and 41.9�?M and 47.6�952.3�?M, respectively, for cholesterol. On this basis, a simple, swift, sensitive, selective, and reproducible colorimetric assay to detect cholesterol levels in blood serum samples using Fe3O4-GBR nanocomposite has been developed. Thus, Fe3O4-GBR composite as compared to Fe3O4 and GBR has shown better peroxidase mimicking activity for biosensing. Graphical abstract: [Figure not available: see fulltext.] � 2022, Springer-Verlag GmbH Germany, part of Springer Nature.