Fabrication and characterization of a ZnO quantum dots-based metal-semiconductor-metal sensor for hydrogen gas.
TL;DR: A high selectivity of the proposed sensor with respect to ammonia, sulfur dioxide and organic vapours such as acetone, methanol, chlorobenzene, and chloroform has also been achieved due to nanostructure ZnO film.
Abstract: This paper reports an interdigitated metal-semiconductor-metal (MSM) based hydrogen gas (H2) sensor using colloidal zinc oxide (ZnO) quantum dots (QDs) as the sensing material. The active layer is obtained by spin coating of as-synthesized colloidal ZnO QDs on a SiO2/Si substrate in which the SiO2 layer is grown by oxidation of the Si substrate. The surface morphology of a ZnO QDs -based active film is measured using scanning electron microscopy (SEM) and atomic force microscopy (AFM) support for enhanced gas response. The change in current is measured for different concentrations of H2 gas at 175 °C in an ambient air atmosphere. Reasonably good gas responses of ∼41% for 1% H2 gas and 83.2% for 4% H2 gas have been obtained in ambient air condition. A high selectivity of the proposed sensor with respect to ammonia, sulfur dioxide and organic vapours such as acetone, methanol, chlorobenzene, and chloroform has also been achieved due to nanostructure ZnO films.
Citations
More filters
TL;DR: In this article, an overview of the progress in the research of semiconductor quantum dots for application in chemical gas sensors is provided, along with the achievements and issues that are important for future studies.
61 citations
TL;DR: In this paper , the morphology and structure of these materials influence on the sensor response, and challenges and future perspectives for ZnO chemiresistive sensors are also discussed, focusing on how the morphology of the materials can influence on sensor response.
Abstract: Chemiresistive gas sensors have been widely applied to monitor analytes of environmental, food and health importance. Among the plethora of materials that can be used for designing chemiresistive sensors, ZnO is one of the most explored for gas sensing, as this material has a low-cost, is non-toxic and can be easily obtained through standard chemical synthesis. Adding to this, ZnO can form heterostructures capable to improve sensor performance regarding sensitivity, selectivity and stability. Moreover, ZnO heterostructures also contribute to lower operating temperature of gas sensors, since the synergistic effects contribute to amplify the sensor signal. In this review, we survey recent advances on different types of chemiresistive ZnO-based gas sensors, focusing on how the morphology and structure of these materials influence on the sensor response. Challenges and future perspectives for ZnO chemiresistive sensors are also discussed.
47 citations
TL;DR: In this paper, high quality fibrous Al-doped ZnO thin films with enhanced conductivity and optical response with controlled doping of Al are synthesized using low-cost sol-gel method.
Abstract: Ultraviolet (UV) detection properties of undoped ZnO and Al-doped ZnO (AZO) based interdigitated metal-semiconductor-metal (MSM) structure are investigated in this paper. High quality of fibrous Al-doped ZnO thin films with enhanced conductivity and optical response with controlled doping of Al are synthesized using low-cost sol-gel method. The surface morphology and absorption properties of the films have been investigated. The responsivity and detectivity characteristics of both the devices are compared over 300–700 nm wavelengths. The Al-doped ZnO based Ag/AZO/Ag MSM structure show the maximum responsivity and detectivity of ~5.63 A/W and $\sim 1.8\times 10 ^{12}$ cmHz1/2W−1 while the respective values for the Ag/undoped-ZnO/Ag photodetector are ~3.65 A/W and $\sim 1.3\times 10 ^{12}$ cmHz1/2W−1 at 365 nm and $34~\mu \text{W}$ /cm2 incident UV intensity. The proposed AZO based MSM photodetector has smaller rise time (~30 s) than that (~35 s) of the undoped ZnO based MSM photodetector. However, the AZO based device shows slightly poor spectrum selectivity over the undoped ZnO based device.
36 citations
Cites background from "Fabrication and characterization of..."
...[6]–[11], but the poor conductivity of the material restricts the electrical and optical performances of the undoped-ZnO based devices....
[...]
TL;DR: In this paper, the authors have focused on pure, rare-earth, and transition metal-doped ZnO QD properties, and various synthetic processes and applications, and the effect of quantum confinement has also been summarized.
Abstract: Currently, developments in the field of quantum dots (QDs) have attracted researchers worldwide. A large variety of QDs have been discovered in the few years, which have excellent optoelectronic, antibacterial, magnetic, and other properties. However, ZnO is the single known material that can exist in the quantum state and can hold all the above properties. There is a lot of work going on in this field and we will be shorthanded if we do not accommodate this treasure at one place. This manuscript will prove to be a milestone in this noble cause. Having a tremendous potential, there is a developing enthusiasm toward the application of ZnO QDs in diverse areas. Sol–gel method being the simplest is the widely-favored synthetic method. Synthesis via this method is largely affected by a number of factors such as the reaction temperature, duration of the reaction, type of solvent, pH of the solution, and the precipitating agent. Doping enhances the optical, magnetic, anti-bacterial, anti-microbial, and other properties of ZnO QDs. However, doping elements reside mostly on the surface of the QDs. The presence of doping elements inside the core is still a major challenge for doping techniques. In this review article, we have focused on pure, rare-earth, and transition metal-doped ZnO QD properties, and the various synthetic processes and applications. Quantum confinement effect is present in nearly every aspect of the QDs. The effect of quantum confinement has also been summarized in this manuscript. Furthermore, the doping of rare earth elements and transition metal, synthetic methods for different organic molecule-capped ZnO QDs, mechanisms for reactive oxygen species (ROS) generation, drug delivery system for cancer treatment, and many more application are discussed in this paper.
30 citations
TL;DR: In this article, the authors summarized some of the latest works on ALD for batteries, supercapacitors, and sensors, and demonstrate the benefits of ALD comprehensively.
Abstract: Nanostructures are considered to have great potential and are widely used in energy storage and sensing devices, and atomic layer deposition (ALD) is of great help for better nanostructure fabrications. ALD can help to preserve the original properties of materials, and, meanwhile, the excellent film quality, nanoscale precise thickness control, and high conformality also play important role in fabrication process. To enhance the performance of energy storage and sensor devices, ALD has been used in directly fabricating active nanostructures, depositing protective passivation layers, etc. ALD is a convenient technique which has been widely engaged in energy-related fields including electrochemical conversion and storage, as well as in sensor and biosensors. The related research interest is increasing significantly. In this review, we summarize some of the latest works on ALD for batteries, supercapacitors, and sensors, and demonstrate the benefits of ALD comprehensively. In these devices, different materials are deposited by ALD under different conditions to achieve better battery performance, higher supercapacitor capacitance, and higher sensitivity. This review fully presents the strengths of ALD and its application in energy storage and sensing devices and proposes the future prospects for this rapidly developing technology.
23 citations
References
More filters
1,260 citations
TL;DR: In this paper, the authors investigated the interaction of tin oxide surface with oxygen, water vapor, and hydrogen using temperature-programmed desorption (TPD) chromatograms of oxygen.
736 citations
TL;DR: In this paper, a C-axis vertically aligned ZnO nanorod arrays were synthesized using a simple hydrothermal route, with a diameter of 30-100nm and a length of about several hundred nanometres.
Abstract: C-axis vertically aligned ZnO nanorod arrays were synthesized on a ZnO thin film through a simple hydrothermal route. The nanorods have a diameter of 30–100 nm and a length of about several hundred nanometres. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to H2 from room temperature to a maximum sensitivity at 250 °C and a detection limit of 20 ppm. In addition, the ZnO gas sensor also exhibited excellent responses to NH3 and CO exposure. Our results demonstrate that the hydrothermally grown vertically aligned ZnO nanorod arrays are very promising for the fabrication of cost effective and high performance gas sensors.
662 citations
TL;DR: In this article, the relationship between electric conductivity and electron paramagnetic resonance (EPR) measurements was investigated and the relation between the two was shown to be linear in the number of electrons.
Abstract: Chemisorption of oxygen on tin oxide is studied. Correlations between electric conductivity and electron paramagnetic resonance (EPR) measurements are reported.
388 citations
TL;DR: In this article, a comparison of the sensitivities for detecting hydrogen with Pt-coated single ZnO nanorods and thin films of various thicknesses (20-350 nm) was made.
Abstract: A comparison is made of the sensitivities for detecting hydrogen with Pt-coated single ZnO nanorods and thin films of various thicknesses (20–350 nm). The Pt-coated single nanorods show a current response of approximately a factor of 3 larger at room temperature upon exposure to 500ppmH2 in N2 than the thin films of ZnO. The power consumption with both types of sensors can be very small (in the nW range) when using discontinuous coatings of Pt. Once the Pt coating becomes continuous, the current required to operate the sensors increases to the μW range. The optimum ZnO thin film thickness under our conditions was between 40–170 nm, with the hydrogen sensitivity falling off outside this range. The nanorod sensors show a slower recovery in air after hydrogen exposure than the thin films, but exhibit a faster response to hydrogen, consistent with the notion that the former adsorb relatively more hydrogen on their surface. Both ZnO thin and nanorods cannot detect oxygen.
275 citations