A Designed ZnO@ZIF‐8 Core–Shell Nanorod Film as a Gas Sensor with Excellent Selectivity for H₂ over CO

Abstract

Abstract:The development of H 2 gas sensors is important for H 2 production as af uel. In this work, aZ nO@ZIF-8c oreshell nanorod film is designed and synthesized as ag as sensor through af acile solutiond eposition process. This film shows an excellent selective response for H 2 over CO. By fine-tuning the reaction conditions, aZ nO@ZIF-8 core-shell structure with at hin, fine-grain, porousZ IF-8 shell is obtained. Owing to the facile H 2 penetration through the ZIF-8 thin shell ( % 110nm) and the increased oxygen vacancies for the complex film, the ZnO@ZIF-8 nanorod film shows ah igher H 2 sensitivity than ar aw ZnO nanorod film. More importantly,t he ZnO@ZIF-8 nanorod film shows no response for CO at 200 8C. Because of the fine-grain confinemento f the porous ZIF-8 shell (< 140 nm), the molecular sieving effect is strengthened, which allows the effective separation of H 2 over CO. This work providesapromising strategy for the design of high-performance H 2 sensors.

ZnO Nanorods for Gas Sensors

“…6.1 ZnO@ZIF-8 core-shell nanorod film Figure 14 shows ZnO@ZIF-8 (zeolitic imidazolate framework-8) core-shell nanorod film was designed and synthesized through a facile solution deposition method for H 2 gas sensor. The ZnO@ZIF-8 core-shell nanorod film with a thin, fine-grain, porous ZIF-8 shell realized the selective response for H 2 over CO and enhances the H 2 sensitivity [35]. The 2-methylimidazolate (HmIM) concentration plays a crucial role in forming the core-shell structure and controlling the ZIF-8 grain size.…”

Metal–Organic Framework-Based Sensors for Environmental Contaminant Sensing

“…As for the practical applications of gas sensors, MOF-based films have attracted considerable attention owing to their relatively large exposure area to gas and their high stability in the target gas flow [ 109 ]. In a recent study, a ZnO@ZIF-8 core–shell nanorod film (thickness of 100 nm) was synthesized to detect H 2 over CO 2 through a facile solution deposition process [ 110 ]. The ZnO nanorod film was grown on a KMnO 4 -activated glass substrate to form a nanorod structure and ensure direct contact between the film and substrate.…”

“…The ZnO nanorod film was grown on a KMnO 4 -activated glass substrate to form a nanorod structure and ensure direct contact between the film and substrate. The ZIF-8 material had huge cavities of 11.6 Å diameter as well as short pore apertures of 3.4 Å, which exhibited effective separation of H 2 (2.9 Å) from CO (3.7 Å) owing to the molecular sieving effect [ 110 , 111 ]. Thus, thin ZnO nanorod film is favorable for H 2 diffusion owing to its open structure, while ZIF-8 enhances the selectivity of H 2 sensing over other gases.…”

“…e Concentration-dependent H 2 response curves of two sensors at 250 °C. Reprinted with permission from [ 110 ]. Copyright (2017) John Wiley & Sons, Inc. …”

Encapsulation of live cells by metal-organic frameworks for viability protection

“…Among the chosen materials reported, metal-organic frameworks (MOFs) [16][17][18], a type of crystalline material constructed with metal ions or metal clusters and organic ligands, have attracted the most attention because of their porous structures, diversity of precursors, and convenient synthesis [19][20][21]. Several materials [22][23][24] and semiconductors [25][26][27] of different sizes and shapes have been coated with MOFs to form composite materials. In addition, some biological macromolecules, such as proteins [28][29][30], enzymes [31][32][33][34][35][36], and cells [37,38], have been coated with MOFs under mild conditions, which is critical for the maintenance of their biological activity.…”