A photochromic UVI indication card and the colorimetric analysis system built on smartphones

Abstract

The present study offers a simple and real-time method to measure the ultraviolet index (UVI) via a photochromic UVI indication card and a colorimetric analysis system built on the smartphone. A photochromic Ormosil (Organically Modified Silicates) coating doped by the spirooxazine dye (SO-G) was prepared. The coating, with the broad absorption at 450–650nm, exhibited as a grey tone on its appearance under ultraviolet irradiation. The spectrokinetics of the SO-G doped Ormosil coating was investigated by monitoring the changes of absorption values at 495nm with time. During its photochromic process, the equilibrium time for both photostationary states were less than 20s. Tests of photochromic reversibility showed the reproducibility of at least 90 cycles. The UVI indication card was fabricated using the photochromic Ormosil coating and a printed standard depth scale was used for the UVI sensing strip to evaluate the instantaneous ultraviolet index. The relationship between the relative grayscales (Gy*) and the ultraviolet index was studied, and the linearity was obtained. The colorimetric analysis system including acquisition and processing of the image for colorimetric analysis was then built on the smartphone. By applying the UVI indication card as well as the Android application developed which brought the user experiences of visualization, convenience and participation, users can monitor fluctuating of the ultraviolet indexes all day long. This method is advantageous for application in smartphones used by nonprofessional consumers and is valuable to be investigated in-depth for the commercial importance.