pH-regulated reversible photoluminescence and localized surface plasmon resonances arising from molybdenum oxide quantum dot

•A facile strategy was developed to simultaneously tune photoluminescence and visible LSPR of MoOx QDs.•As prepared quantum dot acted as an effective dual-modal extreme acidity indicator.•The dual-modal sensing platform achieved a high selectivity and excellent reversibility.•High feasibility of this probe was confirmed in E. coli cells without influence of background signal.