A smartphone-based photometric and fluorescence sensing for accurate estimation of zinc ion in water

This paper demonstrates the development of a smartphone-based analytical system to determine zinc ion (Zn2+) concentration in water. The proposed system has been designed for simultaneous sensing in photometric and fluorescence mode on a single platform. Two inbuilt sensors of the phone, namely, the ambient light sensor (ALS) and the rear camera, have been utilized to develop the proposed sensing system. For photometric-based sensing, the ALS receives the transmitted modulated signal from the sample, while the rear camera records the fluorescence signal emitted from the sample at right angle to the direction of the excitation signal. The holder for the proposed sensing system has been fabricated in a 3D printer. A custom-designed android application has been developed to convert the proposed platform into a standalone tool. Using the designed sensor, Zn2+ ion concentration of field-collected water samples has been estimated successfully. Responses of the designed platform have been compared with the standard laboratory counterparts. The limit of detection and the percentage recovery of the proposed sensor are found to be 0.1 ppm and 103.10% respectively.