Highly photoactive SnO2 nanostructures engineered by electrochemically active biofilmElectronic supplementary information (ESI) available: a schematic representation of the modification process, SEAD patterns, HAADF FE-TEM images, images, EDX, DRS spectra, XPS survey spectra of the p-SnO2 and m-SnO2 nanostructures, kinetic fit spectra and rate constant table of 4-NP and MB degradation, adsorption-desorption equilibrium spectra, dark reaction (with catalyst) spectra, light reaction (without catal

This paper reports the defect-induced band gap narrowing of pure SnO 2 nanostructures (p-SnO 2 ) using an electrochemically active biofilm (EAB). The proposed approach is biogenic, simple and green. The systematic characterization of the modified SnO 2 nanostructures (m-SnO 2 ) revealed EAB-mediated defects in the pure SnO 2 nanostructures (p-SnO 2 ). The modified SnO 2 (m-SnO 2 ) nanostructures in visible light showed the enhanced photocatalytic degradation of p -nitrophenol and methylene blue compared to the p-SnO 2 nanostructures. The photoelectrochemical studies, such as the electrochemical impedance spectroscopy and linear scan voltammetry, also revealed a significant increase in the visible light response of the m-SnO 2 compared to the p-SnO 2 nanostructures. The enhanced activities of the m-SnO 2 in visible light was attributed to the high separation efficiency of the photoinduced electron-hole pairs due to surface defects mediated by an EAB, resulting in a band gap narrowing of the m-SnO 2 nanostructures. The tuned band gap of the m-SnO 2 nanostructures enables the harvesting of visible light to exploit the properties of the metal oxide towards photodegradation, which can in turn be used for environmental remediation applications. This paper reports the defect-induced band gap narrowing of pure SnO 2 nanostructures (p-SnO 2 ) using an electrochemically active biofilm (EAB).