With the rapid development of portable devices and Internet of Things, the need for integration of sensors has accelerated the research of multifunctional sensing platforms. Multifunctional sensors that can detect light radiation, biological activities, stress, and gases in order to monitor environmental changes have great potential applications.

High-precision guidance, all-weather early warning, and dual-band detection technology in complex environments based on ultraviolet/infrared dual-band detectors will surely become the main functional units in the field of photodetection in the future. Tracking environmental conditions, including concentration of harmful gas, ambient temperature, UV radiation, etc., provided valuable information for human activity monitoring and personal telemedicine care.

In a study published in ACS Applied Materials & Interfaces, a research group led by LI Shaojuan from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed a multifunctional sensing device based on Sn-doped In₂O₃ nanocrystal (ITO NC) achieving visible-blind dual-band photodetection in UV and IR regimes and light-activated NO₂ gas detection at room temperature.

The development and synthesis of multifunctional materials was a prerequisite for the construction of multifunctional devices. Although important progress has been made in the research of optoelectronic devices based on ITO NC, the currently developed devices usually have a single target function and cannot meet the needs of multifunctional sensing platforms.

In this study, LI’s team prepared ITO NCs with tunable Sn doping concentration via a low-temperature esterification reaction strategy. The effects of different surface ligands and annealing process of ITO NCs on their photodetection performance were investigated.

The ITO NCs capped with 1,2-ethanedithiol (EDT) can obtain a significant photoresponse in the 2200 nm with a maximum responsivity of 177.7 mAW^-1 and a normalized detectivity of 1×10⁹ Jones. In the 375 nm with a normalized detectivity of 1.3×10¹⁰ Jones. Under UV irradiation, the gas sensor based on ITO NCs exhibited significantly higher response to NO₂, shorter response/recovery speeds, and lower limit of detection (219 ppb) compared with in the dark.

This multifunctional sensing system provided a new platform for emerging miniaturized and integrated sensors that hold potential applications in fire rescue, monitoring of lung inflammation, and prevention of skin damage caused by UV light.