A handy imaging sensor array based on the phase transformation from CsPbBr₃ to CsPb₂Br₅: highly sensitive and rapid detection of water content in ethanol

Detection of the water content in ethanol has become very important in many fields; however, well-established methods usually require complex strategies and devices. Herein, a simple and non-instrument methodology was developed for the determination of the water content in ethanol. In this work, a CsPbBr3@PVA imaging array sensor was constructed based on the fluorescence on/off mechanism and applied to the detection of water content for the first time. When preparing CsPbBr3@PVA, the photoluminescence of CsPbBr3 was quenched by water in PVA due to the decomposition of CsPbBr3. By employing ethanol with fast volatilization to remove water, the decomposed composition recrystallized and formed luminescent CsPb2Br5. When the water content in ethanol was increased, the degree of the recovered fluorescence drastically reduced. To develop a portable and easily-operated methodology, the pictures of the sensor array were captured using a smartphone and quickly analyzed with ImageJ to read the gray-level values for each sample. The latter displayed a good linear relationship (R-2 = 0.995) with the water content increasing from 0% to 7% in ethanol, and a low limit of detection of 0.006% was achieved. Moreover, the sensor array showed advantages like a fast response speed (5 s), strong selectivity and application potential in real samples. This method does not require expensive spectrometers and professional personnel to operate, having the virtues of low cost, fast detection and high sensitivity.