On‐site Colorimetric Forensic Sensor (I): Quantitative Detection of Toxic H2S and NH3 Gases Using Metal‐Ion‐modified Silica Powders

Abstract

A highly sensitive on‐site colorimetric forensic sensor has been developed for the quantitative detection of hydrogen sulfide and ammonia gases. The sensor consists of metal‐ion‐modified silica‐gel powders placed in a glass tube. The powder color changes upon reaction with toxic hydrogen sulfide and ammonia gases. It is capable of easily detecting toxic gases in the concentration range between 100 ppm, which is considered as immediately dangerous to life and health, and 3000 ppm, which may cause death, by using a glass tube with an inner diameter of 3 mm. As the sensor reported here is insensitive to environmental conditions such as temperature or humidity, and is featured by simplicity, fast response, high sensitivity, and easily understandable results based on absolute affirmative/negative response, it is expected to be effectively used for on‐site applications such as testing the existence of toxic gases in confined working and industrial spaces.