Effect of Open Metal Sites in Cobalt-Based Bimetallic Metal–Organic Framework Nanoparticles-Coated Quartz Crystal Microbalance (QCM) for Humidity Detection

Abstract

As one of the most important environmental parameters, humidity always affects people’s life. It is still a challenge in attaining precise humidity sensors with a rapid and convenient method. Herein, cobalt-based bimetallic zeolitic imidazolate frameworks (ZIFs) nanomaterials were obtained by a facile solution precipitation method and applied for quartz crystal microbalance (QCM) sensors to measure relative humidity (RH) at room temperature. The characterization and sensing results show that ZIF-67 and ZIF-CoX (X = Ni, Cu, Zn) samples possess well-defined polyhedron, and the sensor based on ZIF-CoNi exhibits satisfactory sensitivity (6.10 Hz/%RH, at 97% RH), short response/recovery time (3/3 s, at 97% RH), and narrow hysteresis in the range 11%–97% RH compared with that of ZIF-67, while ZIF-CoCu and ZIF-CoZn have poor sensitivity. Finally, the humidity sensing mechanism was explored by wetting behaviors and FT-IR. Such a comprehensive research provides valuable information for the fast detection of humidity.

MIL-101(Cr)@QCM and MIL-101(Cr)@IDE as Sorbent-Based Humidity Sensors for Indoor Air Monitoring

“…Various types of humidity sensors have thus been developed, based on transducers that generate optical, , magnetic, , or electrical , signals upon water exposure. Among the humidity-sensing platforms, quartz crystal microbalance (QCM) , and interdigitated electrode (IDE) , devices have demonstrated great interest since they combine high sensitivity, fast response, miniaturization, and low cost. As an alternative electrical field is applied, QCM-based sensors rely on the electric resonance frequency shift induced by a change in mass, while IDE-based sensors result from the alteration of the dielectric/conductive properties of the system, i.e., capacitance/resistance or impedance.…”

Guar Gum/Ethyl Cellulose-Polyvinyl Pyrrolidone Composite-Based Quartz Crystal Microbalance Humidity Sensor for Human Respiration Monitoring

“…So far, a variety of hydrophilic materials have been used as humidity-sensitive materials, such as polymers, metal organic frameworks (MOFs), two-dimensional materials, , hydroxides, and biomaterials . Polymers derived from biomaterials have recently been popular to develop humidity sensors due to their extensive source and simple preparation.…”

Metal organic framework/polyelectrolyte composites for water vapor sorption applications

“…Until now, MOFs are being investigated as catalysts 2,4 and materials for storage and separation of gases, 5,6,10 humidity sorbents in harvesters of atmospheric water, air-conditioners, environmentally friendly heating and cooling technologies based on the sorption-desorption cycle of water vapor, 1,3,[11][12][13][14] and humidity sensors. 15 The devices based on MOF utilizing sorbents can effectively capture water at low (below 30%) atmospheric humidity and further use solar energy or other secondary heat sources to regenerate the sorbent. Model units operating in arid climates (10-30% humidity, dew point below zero) can produce 0.25 L of water per 1 kg of MOF in one daily cycle.…”