Color-changing Paper Sensor Detects Hazardous Gases in Minutes

A compact optoelectronic array identifies chemical threats with high accuracy

A low-cost, durable sensor made from adhesive paper and dye-coated silica microparticles can identify and quantify a range of toxic gases, including highly dangerous compounds such as chlorosarin. Researchers have demonstrated that the sensor changes color in specific patterns in response to chemical vapors, producing accurate results within five minutes.

Optoelectronic noses, or e-noses, detect airborne chemical threats without the need for complex electronics. Instead, they use materials that undergo visible changes when exposed to certain chemicals. In a new study published in ACS Sensors, researchers developed an embossed sensor array that captures these changes across a grid of tiny color-coded spots, allowing for rapid detection and analysis of multiple gases.

An array built from colorimetric silica microparticles

Each element of the sensor is a paper square embedded with silica microparticles. These particles are soaked in one of 36 dye solutions that respond to different chemical stimuli. After drying, the dyed particles are placed in a 12×3 grid within a microwell plate, then transferred onto the paper using adhesive backing. A thin metal sheet adds structural support, helping the array maintain its shape during testing.

The researchers tested the sensor by exposing it to 12 hazardous gases, each at two concentrations. Before and after images of the sensor were used to track changes in color intensity and hue. The pattern of changes across the grid acted as a chemical fingerprint, identifying both the type and concentration of the gas.

Rapid and accurate detection

The sensor demonstrated strong performance across repeated trials, achieving 99% accuracy for identifying specific gases and 96% accuracy for determining their concentration. The sensor’s performance was not affected by humidity, suggesting it could be used reliably in outdoor or variable environments.

With an estimated production cost of 20 cents (USD) per array, the sensor offers a scalable and economical tool for monitoring air quality or detecting hazardous releases. The team plans to develop a hand-held prototype for further testing in real-world settings.

Reference: Shrivas R, Nagpal H, Agarwal S, et al. Simple and cost-effective fabrication of embossed colorimetric sensor array for an optoelectronic nose via integration of a self-adhesive paper and mesoporous colorimetric silica microparticles. ACS Sensors. 2025. doi: 10.1021/acssensors.5c01026

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