Simultaneous color sensing of O2 and pH using a smartphone

Using a smartphone with camera function, simultaneous color sensing of oxygen and pH could be realized. In the sensing film, chitosan was selected as a matrix, and platinum tetrakis pentafluorophenyl porphin, a sensitive dye towards oxygen with red color emission, was immobilized in this matrix. A sensitive pH sensing dye, fluorescein isothiocyanate with green fluorescence emission, was selected and covalently bonded to chitosan. In addition, the doped 4,40-bis(2-benzoxazolyl) stilbene with blue color emission in the matrix played the role of reference. In the red-green-blue (RGB) sensor, the emission color of the oxygen dye matched the red channel of the smartphone, while the emission of the pH indicator matched its green channel. The reference dye was emitted in the blue channel. All the dyes were excited using a 385 nm ultraviolet lamp. The sensor allowed simultaneous sensing of both pH and oxygen in a single RGB digital photo and showed quite good stability.