Smartphone coupled handheld array reader for real-time toxic gas detection

Smartphones and related accessories are rapidly expanding their applications in various fields. Herein we developed a smartphone coupled handheld array reader with the integration of complementary metal oxide (CMOS) image sensor for detecting various toxic gases by colorimetric monitoring approach. In this study, toxic gases such as hydrogen fluoride (HF), chlorine (Cl₂), ammonia (NH₃), and formaldehyde (CH₂O) were detected using titanium nanoparticles (TiO₂ NPs) blended poly (vinyl alcohol) (PVA) hydrogel test strips, which were patterned with chemically responsive dyes. The dye colors changed based on acid-base reactions, and the colorimetric reader monitored the array strips and mapped them in the form of chrominance data. The observed signals transferred to a smartphone that displays the detected toxic gases and their exposure levels with the aid of the smartphone app "Toxic Gas Detection". The colorimetric array reader was precisely constructed with an auto-calibration system to minimize potential errors. Various concentration of toxic gases (0.5-10 ppm) were analyzed and achieved the detection limit of 1 ppm for each gas. Also, various analytical performance including sensitivity, stability, selectivity, and reproducibility analysis proved the reliability and accuracy of the detection system. Additionally, the smartphone app can be installed on any type of tablet, laptop, or other portable device. This study proved that smartphone coupled colorimetric array reader is a suitable system for detecting various toxic gases, chemicals and biochemical analysis with real-time monitoring approach.