Atomically dispersed Ag implanted zeolitic imidazolate Frameworks-8 for Visible-Light enhanced plasmonic opto-chemical sensor

A reliable and highly sensitive gas sensor is regarded as an indispensable approach for monitoring and ensuring human health and safety. Herein, a wet-chemical synthesis strategy is developed to fabricate a Agx/ZIF-8 heterostructure, in which Ag is encapsulated in porous zeolitic imidazolate frameworks-8 (ZIF-8). The size of Ag is highly tunable and precisely controllable in the range of single atom to 50 nm. Agx/ZIF-8 samples are found to be particularly useful in gas sensors for triethylamine (TEA) detection, and their sensing performance can be further enhanced via downsizing the Ag nanoparticle (NPs) into the atomical level, thus realizing the maximum utilization of Ag element as well as achieving the most outstanding sensing performance. As a result, the optimal sample Ag(SAs-1mL)/ZIF-8 with the atomic Ag, shows relatively lower operating temperature (290 °C), high response (142), superior detection limits (0.41 ppm), and ultra-fast response/recovery time (4/15 s), which are significantly better than the sample Ag(0.5nm-0.25mL)/ZIF-8 with Ag nanoclusters (ca. 0.5–1 nm in size) and other Agx/ZIF-8 samples with larger Ag nanoparticles (range from ca. 2 nm to 50 nm in diameter). Moreover, benefiting from the localized surface plasmon resonance (LSPR) effect, the response of Ag(SAs-1mL)/ZIF-8 sensor is greatly increased by as much as 440 % when it illuminated with the 405 nm LED, where the light wavelength resonates with the plasmon frequency of Ag. This work highlights the crucial role of size effect of noble metal, proves the LSPR effect of atomic level Ag, and offering an attractive strategy to improve sensitivity and stability of gas sensors based on single atoms.