Real-time humidity monitoring using copper nanorods-based portable testing strips

Simple, rapid and sensitive humidity monitoring is of great significance in our daily life, health care, agriculture and industrial manufacture. Here, a humidity-responsive material, aminated copper nanorods (CuNRs) with disassembly-induced polychromatic emission activity, is reported. The optical behavior of CuNRs, including luminescent wavelength and intensity, significantly vary with the humidity. Experimental results combined with theoretical calculations unlock that the humidity response may be driven by the reconstruction of hydrogen-bond network in CuNRs interface. External –OH group can destroy inherent N–H⋯N–H network of CuNRs interface through the anisotropic hydrogen-bond forces, and generate an N–H⋯O–H network, eventually resulting in the variation of luminescent behaviors. More importantly, a portable CuNRs-based test strip was prepared for moisture sensing through the naked eye but also via a smartphone, enabling convenient on-site monitoring and demonstrating similar results to a commercialized electronic devices. This work not only fabricates a facile and reliable platform for humidity sensing, but also enriches the extant armory of responsive material in humidity studies and beyond.