•This structure incorporates gas sensing and LED light functions to form a 3D-like heterogeneous device with an integrated structure.•In this study, ITO is used for the electrodes and the micro ...heater. The thermal image shows that the micro heater provides a heat source.•To allow highly sensitive gas sensing, the ZnO NWs are integrated directly on the electrodes and a suspension layer using a hydrothermal method.•The blue light increases the carrier concentration in the ZnO NWs. The response value to 50 ppb NO gas is increased from 48% to 86%.
This sturdy constructs a 3D-like heterogeneous device integrated structure using a transparent ZnO nanowire MEMS gas sensor and a blue LED. For the transparent gas sensor, ITO is used for the electrodes and the micro heater. The thermal image shows that the micro heater provides a heat source. The sensors exhibit a higher sensitivity to NO than other gases (C2H5OH, HCHO, H2S) at the optimal operating temperature of 200 ℃. For the MEMS gas sensor with blue light illumination from the bottom of the sensors, the results show that the blue light increases the carrier concentration in the ZnO nanowires. The response value to 50 ppb NO gas is increased from 48.13% to 86.17%.
•This study produces Co3O4 nanoparticles (NPs) using ultrasonic wave grinding technology.•For a 100-ppb NO2 gas concentration, an Au/Co3O4-NPs/MEMS gas sensor has the greatest sensor response.•The ...Au/Co3O4-NPs/MEMS gas sensor has a higher sensitivity to NO2 than other gases (SO2, NH3, CO, tingCO2).•The average diameter of Co3O4-NPs and Au-NPs are about 6 nm and 1 nm.
This study produces Co3O4 nanoparticles (NPs) using ultrasonic wave grinding technology. The experimental results show that the average diameter of Co3O4-NPs is about 6 nm. Au nanoparticles are adsorbed onto the surface of Co3O4-NPs and integrated with a MEMS structure to form a Au/Co3O4-NPs/MEMS NO2 gas sensor. The diameter of Au nanoparticle is approximately 1 nm. For a 100-ppb NO2 gas concentration, an Au/Co3O4-NPs/MEMS gas sensor has the greatest sensor response and has a higher sensitivity to NO2 than other gases (SO2, NH3, CO, CO2) when NO2 gas is introduced at 10 ppm and at the optimal operating temperature of 136 ℃.
•High density p-type Na-doped ZnO nanowires were uniformly synthesized on glass substrate via the hydrothermal method.•The p-type characteristic of the nanowires was verified through Hall and ...humidity measurements.•2∼6 nm Au nanoparticles were sputtered on nanowires to fabricate a room temperature sensor and strengthen p-type property.•The p-type gas sensor has a high response, sensitivity and selectivity under UV illumination at room temperature.
High density p-type Na-doped ZnO nanowires were uniformly grown on glass substrate via the hydrothermal method, and then examined by SEM, XRD, PL, XPS, and TEM analysis. The p-type characteristic of the nanowires was verified through Hall and humidity measurements. 2∼6 nm Au nanoparticles were sputtered on the nanowires to fabricate a room temperature sensor and strengthen its p-type property, which was enhanced by the Schottky barrier at Au NPs/ZnO interface. The p-type gas sensor has a high response, sensitivity and selectivity under UV illumination at room temperature.
High density CuO/Cu2O composite nanowires were synthesized on simpler Cu through-silicon via by heated oxidation. XRD spectrum analysis and HR-TEM revealed that these nanowires had Cu2O cubic ...crystalline and CuO monoclinic structures. The sensing current of the CuO/Cu2O composite nanowires decreased as the ethanol concentration increased due to their p-type material property. The relative humidity response of the nanowires increased along with the relative humidity. The UV photoresponse of the CuO/Cu2O composite nanowires also increased with the relative humidity, due to the photocatalytic layer that formed on the nanowire surface.
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•ZnO nanowires were hydrothermally synthesized on a silicone layer of UV-LED.•The ZnO nanowires/LED combination device can perform humidity sensing, gas sensing, and UV ...detection.•Under various LED illumination, humidity and ethanol gas response of device showed its unique physical characteristics.•The ethanol gas response characteristics of the device were enhanced when the input power was increased.
ZnO nanowires were hydrothermally synthesized on a silicone layer of an ultraviolet (UV) light-emitting diode (LED). The ZnO nanowires/LED combination was used to fabricate a device that can perform humidity sensing, gas sensing, and UV detection. Under UV, blue, and green LED illumination, the humidity and ethanol gas response of the device showed its unique physical characteristics. The ethanol gas response characteristics of the device were enhanced when the input power was increased.
Bilayer graphene was synthesized by chemical vapor deposition, for which the optical transmission is ~95%-96%. XPS detected that a few oxygen molecules were absorbed on the surface of graphene. The ...Raman and optical transmission spectra verified that the graphene sample is bilayer. The responses of the bilayer graphene sample increased with increased relative humidity.
In this letter, a WO 3 nanoparticle gas sensor was fabricated using an ICP-assisted hot wire system. The results of experiments indicated that the sensitivity became smaller when the measured ...temperature increased. It was also found that the WO 3 nanoparticle gas sensor prepared at an annealing temperature of 400°C had the greatest sensitivity. The measured sensitivity for a micro-electromechanical system type WO 3 nanoparticle gas sensor was found to be around 3.22, 3.91, 5.02, 7.52, 11.68, and 15.93 when the operating temperature of the micro-heater was 150°C and the concentration of injected NO gas was 100, 150, 200, 250, 300, and 350 ppb, respectively.
This investigation studies the feasibility of synthesizing high-density transparent p-type ZnO nanoparticles and n-type ZnO nanowires on a glass substrate at 650°C using the self-catalyzed ...vapor–liquid–solid method. The doping impurity is Sb, which reduces the concentration of electrons in n-type nanowires and increases the concentration of holes in p-type nanoparticles. XRD spectra clearly include a strong peak that is associated with the wurtzite structure and very weak peaks that are associated with Sb2O3. All XRD peaks of the ZnO sample shift by a small angle upon doping by Sb. The Hall effect indicates that ZnO nanowires and ZnO:Sb nanoparticles are n-type and p-type, respectively. The Sb atoms produce the Moiré pattern and cause stacked faults to form nanoparticles as determined by HRTEM. The reaction between ethanol and ionic oxygen species yield electrons, which increase the conductivity of the n-type nanowires and reduce the conductivity of the p-type nanoparticles. The responses of p-type ZnO nanoparticles/n-type ZnO nanowires to gas are dominated by those of p-type sensors at 25°C and n-type sensors above 200°C.
This study produces cupric oxide (CuO) nanowires (NWs) using RF sputtering, and integrated CuO NWs in a micro electron mechanical systems (MEMS) structure to form a CuO-NWS/MEMS gas sensor. The XRD ...pattern shows a preferred (002) orientation of the CuO NWs. The CuO-NWS grows vertically on the MEMS structure and a competitive growth model is illustrated. It is found that the CuO-NWs/MEMS gas sensor has a higher selectivity to NO2 compared with CO, CO2, NH3 and SO2. In long term measurement, the average sensor response is about 50.1% with an inaccuracy of 3% at the temperature of 119 ℃ and the NO2 concentration of 500 ppb. These results show that the CuO-NWs/MEMS sensor with sputtering method is stable and reproducible in NO2 gas sensing.
•This study uses RF magnetron sputtering to grow vertical CuO nanowires on a MEMS structure to form a NO2 gas sensor.•SEM and TEM, results show that CuO nanowires grow vertically on the SiO2/Si and MEMS structure.•The CuO-NWS grows vertically on the MEMS structure and a competitive growth model is illustrated.•In long term measurement, the average sensor response is about 50.1% (±3%) at 119℃ and the NO2 of 500 ppb.
