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Journal ArticleDOI

Pd2+ doped ZnO nanostructures: Structural, luminescence and gas sensing properties

TL;DR: In this paper, the synthesis of Pd-doping of ZnO-nanostructures and its role on the gas sensing properties of NH3 and H2S were investigated.
About: This article is published in Materials Letters.The article was published on 2015-12-01. It has received 45 citations till now. The article focuses on the topics: Wurtzite crystal structure & Photoluminescence.
Citations
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Journal ArticleDOI
01 Nov 2019-Talanta
TL;DR: The fundamental working principles of the ammonia detection techniques relying on electronics, electrochemistry, tunable diode laser spectroscopy, surface acoustic wave, and field effect transistors are briefly described first, in conjunction with various sensing materials.

291 citations

Journal ArticleDOI
TL;DR: Results verify that hydrothermally grown MoO3 nanoribbons are a promising sensing material for enhanced NH3 gas monitoring and represent a remarkable limit of detection of 280 ppt.
Abstract: A highly-sensitive ammonia (NH3) gas sensor based on molybdenum trioxide nanoribbons was developed in this study. α-MoO3 nanoribbons (MoO3 NRs) were successfully synthesized via a hydrothermal method and systematically characterized using various advanced technologies. Following a simple drop-cast process, a high-performance chemiresistive NH3 sensor was fabricated through the deposition of a MoO3 NR sensing film onto Au interdigitated electrodes. At an optimal operation temperature of 450 °C, the MoO3 nanoribbon-based sensor exhibited an excellent sensitivity (0.72) at NH3 concentration as low as 50 ppb, a fast response time of 21 s, good stability and reproducibility, and impressive selectivity against the interfering gases such as H2, NO2, and O2. More importantly, the sensor represents a remarkable limit of detection of 280 ppt (calculated based on a signal-to-noise ratio of 3), which makes the as-prepared MoO3 NR sensor the most sensitive NH3 sensor in the literature. Moreover, density functional theory (DFT) simulations were employed to understand the adsorption energetics and electronic structures and thus shed light on the fundamentals of sensing performance. The enhanced sensitivity for NH3 is explicitly discussed and explained by the remarkable band structure modification because of the NH3 adsorption at the oxygen vacancy site on α-MoO3 nanoribbons. These results verify that hydrothermally grown MoO3 nanoribbons are a promising sensing material for enhanced NH3 gas monitoring.

153 citations

Journal ArticleDOI
TL;DR: In this article, a low-temperature and high-performance NO2 sensor based on Pd-functionalized ZnO nanowires (Pd-ZNWs) prepared by a facile one-pot hydrothermal method was reported.
Abstract: The application of NO2 sensor based on metal oxide semiconductor is limited due to high operating temperature and poor selectivity. In this work, a low-temperature and high-performance NO2 sensor based on Pd-functionalized ZnO nanowires (Pd-ZNWs) prepared by a facile one-pot hydrothermal method was reported. The Pd was formed and self-assembled onto the surface of ZnO nanowires (ZNWs) during this one-pot hydrothermal process. Microstructure characterization of Pd-ZNWs indicated that the obtained ZNWs with diameter of 100–250 nm and length of 2–10 μm had a single crystal hexagonal structure, and Pd/PdO nanoparticles of approximately 2–5 nm in diameter were distributed on their surface. Gas sensing measurement showed that Pd-ZNWs exhibited higher response, lower optimal operating temperature, and faster response/recovery speeds towards NO2 than those of pure ZNWs. The maximum responses of 1 mol%, 2 mol%, and 5 mol% Pd-ZNWs towards 1 ppm NO2 were 13.5, 9.4, and 9.4, respectively, which were obtained at a low operating temperature of 100 °C and 30% RH. Pd-ZNWs also showed a significant improvement in sensing selectivity towards NO2. At a high RH condition of 60%, the sensors based on pure and Pd-ZNWs still exhibited noticeable responses, fast response/recovery speeds, and good long-term stability to NO2 gas. The sensing mechanism of Pd-ZNWs towards NO2 was discussed by the combination of electronic and chemical sensitization.

148 citations

Journal ArticleDOI
TL;DR: It was confirmed that Au form nanoparticles loaded on the surface of ZnO, and it was demonstrated that Au/ZnO based sensors were highly selective to NH3 gas at room temperature.

108 citations

Journal ArticleDOI
TL;DR: In this paper, an ultrasensitive self-powered ammonia (NH3) sensing system based on a vertical contact-separate mode triboelectric nanogenerator (TENG) has been proposed for room temperature detection of NH3 concentrations both in the ambient environment and in human exhaled gases.

93 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the effects of grain size on gas sensitivity were investigated by using porous sintered SnO2 elements fabricated with pure and impurity-doped SnO 2 elements.
Abstract: Effects of grain size on gas sensitivity (S) are investigated by using porous sintered SnO2 elements fabricated with pure SnO2, foreign oxide-stabilized SnO2, or impurity-doped SnO2. When the SnO2 crystallite size (D) is controlled to a size in the range 5–32 nm, S for H2, CO and i-C4H10 is found to increase steeply as D decreases to be comparable with or less than 2L (≈ 6 nm) is both pure and stabilized elements, where L is the depth of the space-charge layer. However, S for ethyl alcohol gas is found to be also affected by surface acid-base properties, being greatly promoted by basic oxides. It is found that the control of L by doping impurities (Al3+ or Sb5+) into the SnO2 lattice results in great changes in S even when D is the same. Thus Al-doped SnO2 shows high sensitivity with increasing L even at D above 20 nm, while Sb-doped SnO2 is insensitive in the whole D region. A model for the grain-size effects is proposed, in which the transducer function is operated by a mechanism of grain control, neck control or grain-boundary control, depending on D.

1,275 citations

Journal ArticleDOI
27 Feb 2012-Sensors
TL;DR: The gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article and the effect of doping is summarized and the perspectives ofMetal oxide gas sensor are given.
Abstract: Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion Besides, doping is also an effective method to decrease particle size and improve gas sensing properties Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given

915 citations

Journal ArticleDOI
TL;DR: In this article, the authors focus on the sensors based on zinc oxide (ZnO) nanostructures, which have fascinating properties including large specific surface area, good biocompatibility, high electron mobility and piezoelectricity.
Abstract: This review focuses on the sensors based on zinc oxide (ZnO) nanostructures, which have fascinating properties including large specific surface area, good biocompatibility, high electron mobility and piezoelectricity. Due to these versatile characteristics, ZnO nanostructures can be based upon to construct gas sensors, chemical sensors, biosensors, UV sensors, pH sensors and other sensors with different sensing mechanisms. The main structures of the sensors and factors influencing the sensitivity are also discussed.

365 citations

Journal ArticleDOI
TL;DR: In this article, nanoporous ZnO films consisting of nanostructural beads were prepared by pyrolytic decomposition of an aqueous zinc nitrate solution and their liquid petroleum gas (LPG) sensing properties were studied.
Abstract: The nanoporous ZnO films consisting of nanostructural beads were prepared by pyrolytic decomposition of an aqueous zinc nitrate solution and their liquid petroleum gas (LPG) sensing properties were studied. The response of the ZnO nanobeads towards LPG was enhanced significantly by palladium (Pd) sensitization which was deposited onto the ZnO nanobeads by a sequential dipping and drying method. The LPG sensing properties of the ZnO nanobeads and Pd-sensitized ZnO were investigated at different operating temperatures and different gas concentrations ranging from 0.1 to 0.4 vol%. The unsensitized ZnO nanobeads exhibited the maximum response of 31% at 673 K upon exposure to 0.2 vol% LPG which was improved up to 63% at the optimum temperature of 548 K by Pd sensitization. Additionally, the Pd-sensitized ZnO was able to respond very quickly to the exposure of LPG.

135 citations

Journal ArticleDOI
Ning Han1, Peng Hu1, Ahui Zuo1, Dangwen Zhang1, Yajun Tian1, Yunfa Chen1 
TL;DR: In this article, the gas sensing property of ZnO nanorods prepared by plasmaenhanced chemical vapor deposition (CVD) method is studied using formaldehyde as the probe gas, and the intrinsic defects are investigated by photoluminescence (PL).
Abstract: Gas sensing property of ZnO nanorods prepared by plasma-enhanced chemical vapor deposition (CVD) method is studied using formaldehyde as the probe gas, and the intrinsic defects are investigated by photoluminescence (PL). The results show that high ratio of visible to ultra-violet luminescence cannot account for high gas response. The PL spectra are Gaussian decomposed to subpeaks according to their origination, which are separated into donor-(DL) and acceptor-related (AL) ones. A conclusion is derived that where the content of DL is high and that of AL is low, the gas response is high. This conclusion is further confirmed by tuning the PL spectra and gas sensing property through annealing in different atmospheres. (C) 2009 Elsevier B.V. All rights reserved.

128 citations