Study on formaldehyde gas-sensing of In2O3-sensitized ZnO nanoflowers under visible light irradiation at room temperature

Abstract

In 2 O 3 -sensitized flowerlike ZnO with visible light photoelectric response properties were synthesized by a facile two-step process, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), EDAX, HRTEM and UV-vis diffuse reflectance spectroscopy. The results revealed that In 2 O 3 nanoparticles have grown and eventually coalesced on the surface of the flowerlike ZnO successfully, and the samples exhibited significant response to visible light. The photoelectric gas-sensing of the In 2 O 3 -sensitized ZnO was also studied to formaldehyde (HCHO) under 460 nm light irradiation at room temperature with the help of surface photocurrent technique. It was found that ZnO sensitized with In 2 O 3 could enhance the gas response to HCHO under the visible light illumination. This may be due to the fact that the composite structure of In 2 O 3 -ZnO extends the photo absorbing range to visible light area, inhibits the recombination of photo-generated electrons and holes, and thus increases the utilization of photo-generated carriers in photoelectric gas detection, resulting in the higher sensing response in some extent. The gas response to 5 ppm and 100 ppm formaldehyde can reach to 19% and 419% under visible light irradiation at room temperature, respectively. These results should be valuable for designing a new type of visible-light assisted gas sensor at room temperature.

ZIF-8 membranes with improved reproducibility fabricated from sputter-coated ZnO/alumina supports

“…Initially, ZnO×3/support clearly exhibits an absorption edge at around 403 nm, while α-alumina support does not show any absorption between 300~800 nm. This result indicates that the successful deposition of ZnO particles on the support (Han et al, 2012). In view of no absorption between 300~800 nm on pure ZIF-8 materials (Esken et al, 2011), the absorption edge blue shift to 392 nm on ZIF-8 seed/support can be considered as the increase of the band gap in correlation to the intimate interfacial interaction between…”

Hierarchically porous indium oxide nanolamellas with ten-parts-per-billion-level formaldehyde-sensing performance

“…Fig S4 illustrates that the response and recover procedures of the HCHO sensing. The response and recovery times are 5 s and 1.3 s respectively, which were really short compared to that reported before [4,5,7,13,[30][31][32][33][34]. The HCHO detection limit, response time and recovery time of Sample 1 and those value reported before are listed in table S1, which have suggested that the Sample 1 was sensitivity to HCHO molecules and the adsorption and desorption of the HCHO molecules on the surfaces of Sample 1 were both rapid.…”

“…The curve describes changes in the electrical signal from Sample 1, which were caused by the reactions between the surfaces of Sample 1 and the HCHO molecules [2][3][4][5][6][7][19][20][21]. The changes indicate that the HCHO detection limit of Sample 1 is 80 ppb, lower than those (≥0.5 ppm) of the reported semiconductor-based sensors [4,5,7,13] and the health standard limitation (100 ppb) [1], and so meets the requirement of practical applications. Moreover, the HCHO sensing of Sample 1 is repeatable, as both the first peak and the third peak are all contain 100 ppb HCHO and the response of these two peaks are same, show in Fig.…”

“…But this method requires users to collect some indoor air and then to analyze the air specimen in a stationary and expensive instrument of gas chromatography for the HCHO concentration, and so it is time-consuming and of high cost [2]. In contrast, semiconductor-based gas sensors can give real-time readings of the HCHO concentration when they are placed in an indoor environment, and they are small, portable and of low cost [3][4][5][6][7]. Semiconductor nanoparticles including the In 2 O 3 ones are promising for detecting extremely dilute HCHO in air, because their surfaces contain sites active to react with target gas molecules [3][4][5][6][7] and the morphology of their porous assembly is easily diversified for high specific surface area (SSA) by many methods, such as layer-by-layer assembly [3], template method [6], structural replication [8][9][10][11], and hydrothermal synthesis [7][8][9][10][11][12].…”

Harvesting piezoelectric potential from zinc oxide nanoflowers grown on textile fabric substrate

“…Among the large family of ZnO nanostructures, NFs have several advantages such as high surface area‐to‐volume ratio and a short conduction path for electrons to transport. Therefore different researchers have used NF‐like structures for the fabrication of different devices such as solar cells, sensors, bio‐devices and display applications 22–26. Nevertheless, there is no report published on harvesting piezoelectric potential from ZnO NF‐like nanostructures.…”