Engineering CuMOF in TiO₂ Nanochannels as Flexible Gas Sensor for High-Performance NO Detection at Room Temperature

Abstract

As a marker molecule in respiratory gases for the pulmonary disease asthma, nitric oxide (NO) has attracted much attention for real-time gas monitoring. However, low sensitivity, poor selectivity, and high operating temperature limit the practical applications of metal oxide semiconductor (MOS) based chemiresistor gas sensors. Herein, by deliberately introducing metal−organic frameworks (MOFs) in free-standing TiO 2 nanochannels (NCs), a chemiresistor gas sensor with excellent detection ability and outstanding selective traits is developed for sensing NO at room temperature (RT). The precisely engineered Cu(II)-based MOF Cu-TCA (H 3 TCA = tricarboxytriphenyl amine) induces more active surface in the NCs, causing the buildup of CuTCA/TiO 2 p−n heterojunctions that improve the sensing response at RT just via a simple UV irradiation (λ = 365 nm). Importantly, the specialized reductive reaction of Cu(II) by NO enables a remarkable selectivity toward NO analysis. Owing to the synergistic large active surface and chemical sensitization effects from Cu-TCA, the resulting Cu-TCA/TiO 2 NCs show outstanding sensing performance; i.e., the response ((R gas − R air )/R air ) reaches 124% at 50 ppm of NO with a detection limit of 140 ppb at RT. In addition, the response time decreases to 25.6% if the system is subjected to UV irradiation. The as-formed sensing membrane is also demonstrated to be practically effective for flexible and wearable sensing devices for quantitative NO analysis. This study facilitates the use of MOFs to achieve synergistically enhanced selectivity and sensitivity to develop high-performance gas sensors.

Nanometric Surface-Selective Regulation of Au/In2O3 Nanofibers as an Exhaled H2S Chemiresistor for Periodontitis Diagnosis

“…However, such approaches still hardly achieve satisfactory selectivity of SMO gas sensors for target gases, because main contribution of these strategies is to modulate the amount of absorbed oxygen spices. Recently, some fine-tuning strategies for selectivity enhancement have been devised, such as surface coating of gas molecular sieve filters with different porosity like metal–organic framework or porous graphene, − facile modification of biomolecules, and surface functional group or single-stranded DNA modification for specific molecular recognition. , The emergence of these strategies paves the way for tangible improvement to the selectivity of SMO devices.…”

Recent Advances in Photo−Activated Chemical Sensors

“…As another example, a p−n heterostructure was used to detect NO gas. He et al represented a UV−activated NO gas sensor operable at room temperature using Cu−TCA (H3TCA = tricarboxytriphenylamine) and TiO 2 nanochannels (TiNCs) as a p−n heterostructure [ 86 ]. The Cu−TCA porous structure, due to the metal−organic framework (MOF), allows only the NO gas contained in the mixed gas to be adsorbed, providing selectivity for NO gas.…”

“… ( a ) Response of the TiO 2 @NGQDs sensor under UV irradiated; ( b ) response and recovery times of TiO 2 @NGQD sensors with UV−on and UV−off; ( c ) selectivity characteristics of the TiO 2 @NGQDs sensor (adapted from [ 85 ] with permission from the American Chemical Society); ( d ) image of the flexible and wearable TiO 2 @NGQDs sensor with human arm and wrist; ( e ) response of the Cu−TCA/TiNCs sensor ppb with UV−on and UV−off; ( f ) response and recovery time of the Cu−TCA/TiNCs sensor (adapted from [ 86 ] with permission from the American Chemical Society). …”

An ultra-fast UV-electrochemical sensor based on Cu-MOF for highly sensitive and selective detection of ferric ions

“…The response of Cu-TCA/TiNC-20 to NO under UV irradiation was 4.6 times higher than that of the original Ti-NCs. 17…”