Visible light boosting hydrophobic ZnO/(Sr0.6Bi0.305)2Bi2O7 chemiresistor toward ambient trimethylamine

Fig. 1. SEM images of (a) SBO, (b) ZnO and (c) ZnO/SBO composite, the insets show the contact angle image of the water drops on the surfaces of (a) ZnO, (b) SBO and (c) ZnO/SBO chemiresistors. (d) TEM and HRTEM images of ZnO/SBO. (e) XRD pattern, (f) EDS pattern, HAADF-STEM image and EDS elemental mapping. it is detected by XRD, SEM ,TEM and HAADF-STEM.Fig. 2. TMA (50 ppm) response of SBO, ZnO and ZnO/SBO under (a) 365 nm, (the inset depicts a schematic image of device measurement configuration), (b) 455 nm and (c) 530 nm light irradiation with different light intensity at room temperature. TMA (50 ppm) transient resistance response of ZnO, SBO and ZnO/SBO under (d) 365 nm (0.7 mW/cm2), (e) 455 nm (11.3mW/cm2) and (f) 530 nm (7.1 mW/cm2) light irradiation at room temperature. it is detected by gas sensitive test system.Fig. 3. (a–c) Photo response characteristics of three devices under 530, 455 and 365 nm light irradiation with an identical light intensity of 17.3 mW/cm2 at room temperature. (d–f) On/off current ratio of three devices under 530, 455 and 365 nm with different light intensity with a bias of 1 V at room temperature. it is displayed by semiconductor test system 4200.Fig. 4. PL spectra of ZnO (a) without pre-treatment, (b) pre-treatment under 365 nm, (c) pre-treatment under 455 nm and ZnO/SBO (d) without pre-treatment, (e) pre-treatment under 365 nm, (f) pre-treatment under 455 nm irradiation for 30 min. it is detected by PL。Fig. 5. (a) ESR spectra of SBO, ZnO and ZnO/SBO under the 0, 10 and 20 min 455 nm light irradiation. (b) Intensity of the ESR signal at g = 2.004 due to the electrons trapped on the oxygen vacancy as a function of the irradiation time at 455 nm light irradiation. (c) Light enhanced sensing mechanisms in ZnO/SBO n-n heterojunction-based optoelectronic TMA gas chemiresistor.it is detected by ESR.Fig. 6. Sensing characteristics under visible 455 nm illumination (11.3 mW/cm2) at room temperature. (a) Response curves of SBO, ZnO and ZnO/SBO chemiresistors upon exposure to 0.01–50 ppm TMA. (b) TMA concentration dependent sensitivity curves of ZnO/SBO and ZnO chemiresistor. Repeatability of (c) ZnO/SBO and (d) ZnO chemiresistor to 10 ppm TMA for 8 cycles at a bias of 1 V. (e) Response time and recovery time fitting of the ZnO and ZnO/SBO chemiresistors to 50 ppm TMA. (f) Long-term stability of ZnO and ZnO/SBO chemiresistors to 10 ppm TMA at a bias of 1 V. (g) Selectivity and (h) PCA analysis for 9 kinds of vapors (colored online) of ZnO/SBO gas chemiresistor. it is displayed by semiconductor test system 4200 and gas sensitive test system.Fig. 7. Response of ZnO/SBO heterojunction chemiresistor to 50 ppm TMA gas at different relative humidity under 365 and 455 nm light irradiation. it is displayed by gas sensitive test system with different relative humidity.Fig. 8. Measured WCA and WCA/WCA0 change over time on (a, d) ZnO, (b, e) SBO and (c, f) ZnO/SBO irradiated with 365 nm and 455 nm irradiation. Inset pictures are captured images of water droplet on the surface of sample, before and after the light illumination (the interval time is 5 min). it is displayed by water contact angle system..Fig. 9. DMPO spin-trapping ESR spectra recorded at ambient temperature in aqueous ZnO/SBO dispersion for DMPO-•OH under 455 nm, the inset is schematic illustration of heterostructural ZnO/SBO surface at low/high RH. it is displayed by ESR.