Electrocrystallization of Copper 7,7,8,8-Tetracyanoquinodimethane Charge-Transfer Complex on Flexible Substrates for Real-Time Ammonia Gas Sensing

Abstract

Real-time monitoring of public safety, individual health, and environmental conditions relies on accurate continuous data collected by gas sensors, which provide users with cost-effective insights to support informed decision-making. This study presents an innovative approach that simplifies the manufacturing process of nanowire (NW)-based gas sensors by enabling direct electrodeposition of NW crystals on various substrates, such as silicon wafers and polyethylene terephthalate (PET). Copper 7,7,8,8-Tetracyanoquinodimethane (CuTCNQ), a charge-transfer complex, is electrodeposited directly onto photolithographically patterned interdigitated triangle-tip electrodes and functions as a chemiresistive gas sensor that responds to ammonia gas through charge interactions. The sensor's performance can be precisely controlled using electrochemical techniques, allowing for tailored sensitivity across different concentration ranges. To enhance the practical application of this technology, a flexible, near-field communication-based passive tag is developed by integrating the CuTCNQ gas sensor with a flexible printed circuit board. This device enables on-demand ammonia concentration analysis and operates battery-free and wireless through mobile phone scanning. This capability is crucial for wearable or industrial devices and aligns with the increasing demand for robust environmental monitoring solutions. This approach represents a significant step forward in improving both human health and environmental protection through accessible and efficient gas sensing technology.