The preparation of silver quantum clusters embedded in organic-templated-boehmite-nanoarchitecture (OTBN) and its use as a sensor for quantity of water flow measured by change of color in visible light upon flow of contaminated water have been provided. Silver quantum clusters-embedded OTBN are highly luminescent. Since the quantum clusters are embedded in the matrix, they are highly stable over a long period of time. The composition described here is utilized in the form of a device for ‘visible/ultraviolet light color change-based detection’ upon passage of water through a water purification device. Upon interaction with ions present in water, luminescent silver clusters undergo chemical transformation to Ag2S nanoparticles. The transformation is reflected in the form of visible color change (from pink to black) and luminescence quenching (from red emission to negligible luminescence).