RESUMEN
For gas sensing applications, most of the reported two-dimensional (2D) materials are suffering from relatively low sensitivity and high limit of detection (LOD) at room temperature. In this work, we selected rhenium disulfide (ReS2) nanosheets to fabricate ReS2 transistor-based gas sensors (RTGSs) with ultrahigh sensitivity and low LOD toward nitrogen dioxide (NO2). The ReS2 nanosheets with different thicknesses were prepared via mechanical exfoliation and all-dry transfer method. Under 405 nm light illumination at room temperature (25 °C), the fabricated gas sensors showed a significant enhancement of the response with full reversibility toward ppb level NO2 (response of 9.07 at 500 ppb, a LOD of 50 ppb). In particular, the total response and recovery time of the RTGS was revealed to be less than 4 minutes (55 and 180 s, respectively), which is one of the top three shortest response and recovery times toward ppb level NO2 of the reported 2D material-based room-temperature gas sensors so far. Via Raman spectrometry, Kelvin probe force microscopy (KPFM), and X-ray photoelectron spectrometry (XPS), the structure and gas sensing mechanism of the materials were systematically investigated. It was confirmed that the electrons transfer from the ReS2 surface to NO2 molecules, inducing the hole doping of ReS2, which consequently increased the sensor resistance. Moreover, the concentration of the photogenerated carriers in ReS2 would accordingly be promoted by light illumination, which accounts for the substantial light enhancement of the gas sensing performance of RTGSs.
Asunto(s)
Iluminación , Dióxido de Nitrógeno , Luz , Límite de Detección , TemperaturaRESUMEN
A smart surface with converse temperature-dependent (CTD) wettability was fabricated from an upper critical solution temperature-type (UCST-type) poly(acrylamide-co-acrylonitrile) (P(AAm-co-AN)) copolymer. The obtained surface exhibits a remarkable and reversible hydrophobic-hydrophilic transition depending on temperature with a high response rate. The static water contact angle of the surface decreases from 103° ± 2° to 60° ± 1° as the temperature increases from 30 °C to 80 °C. Further, the wettability of the UCST-type surface shows a positive linear relationship between wettability and temperature. This study for the first time provides an UCST-type smart surface with wettability that decreases by over 35° as the temperature increases by only 20 °C.
RESUMEN
In this study, a graphene-based composite 4HQ-rGO/Cu2+ was prepared via the supramolecular assembly of graphene nanosheets with 4-hydroxyquinoline (4HQ) and copper(ii) ions. The as-prepared supramolecular assembly exhibited an excellent and enhanced sensing performance towards acetic acid at room-temperature, which was due to the fact that the D-π-A molecules, i.e. 4HQ, were able to accelerate the charge transfer between the graphene nanosheets and 4HQ molecules when acetic acid was attached. In addition, at room temperature, the copper(ii) ions also played a critical role as the main active site for gas adsorption, and thus the as-fabricated sensor exhibited a high response, outstanding selectivity, and ultra-fast response/recovery time. To examine the selectivity of the Cu2+ ions for the supramolecular assembly, various other transition metal ions such as Mn2+, Fe3+, Co2+, Ni2+, Cu2+, and Cd2+ were attached to the 4HQ-rGO assembly, and their acetic sensing performance was determined. Interestingly, the supramolecular assembly with the Cu2+ ions (4HQ-rGO/Cu2+) exhibited the best sensing performance compared to other metal ion-based 4HQ-rGO materials. Compared with the typical acetic acid gas sensors reported in the literature, it is noteworthy to mention that the as-prepared 4HQ-rGO/Cu2+ supramolecular assembly exhibited the shortest gas response time (within 5 s) at room temperature. The presented study demonstrates that the as-prepared supramolecular assembly is a promising material as a room temperature acetic acid gas sensor in practical applications.