scispace - formally typeset
Search or ask a question
Author

Mengjun Wang

Bio: Mengjun Wang is an academic researcher from Hebei University of Technology. The author has contributed to research in topics: Antenna (radio) & Finite-difference time-domain method. The author has an hindex of 11, co-authored 78 publications receiving 475 citations.

Papers published on a yearly basis

Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, a flexible dual-band antenna with a metamaterial structure (MS) is presented, which makes the antenna thin and bendable, is used as the substrate for the antenna.
Abstract: A flexible dual-band antenna with a metamaterial structure (MS) is presented. Polyimide substance, which makes the antenna thin and bendable, is used as the substrate for the antenna. When the MS is placed between the antenna and the human’s forearm, the antenna gain is increased by 9.3 and 5.37 dB, and the radiation efficiency is increased by 48.4% and 35.7%, at 2.45 and 5.8 GHz, respectively. In addition, the specific absorption rate is decreased by more than 70%, considering the limitations imposed by Federal Communications Commission and the regulation of International Commission on Non-Ionizing Radiation Protection (ICNIRP) for the frequencies cited above. The fabricated prototype of the antenna with the integrated MS was investigated by placing it on different places of human body, as also on different human bodies. The obtained results show that the proposed antenna is safe and suitable for use, in terms of the ICNIRP standards of World Health Organization.

118 citations

Journal ArticleDOI
TL;DR: In this article, the surface of WO3 nanoparticles was modified by Ru through a modified impregnation method based on an electronic adsorption mechanism, which significantly enhanced the activity of surface lattice oxygens.
Abstract: In this paper, WO3 nanoparticles in a lamellar-structured were fabricated via an acidification method and the surface of nanoparticles were catalytically modified by Ru through a modified impregnation method based on an electronic adsorption mechanism. Gas sensors based on neat and Ru-loaded WO3 nanoparticles were fabricated based on screen printing and sensor responses of acetone were evaluated under a dry and humid ambient, respectively. Experimental results clearly indicated that most of Ru was removed from the WO3 during the washing process, however, a strong sensitization effect of Ru was achieved with a very few loading amount. Accordingly, the basic sensitization mechanism of Ru was investigated based on TPR results and oxygen adsorption behaviors. It is revealed that Ru is loaded on the surface with an oxidized state contributing to an electronic sensitization effect. In addition, Ru on the surface of WO3 as a catalyst significantly enhanced the activity of surface lattice oxygens. As a consequence, surface lattice oxygens could also react with acetone and reduce sensor resistance leading to a sensitization effect. However, we do not expect that reactions of lattice oxygens dominate the sensing process.

71 citations

Journal ArticleDOI
TL;DR: In this article, the power-law response of nanosized metal oxide semiconductor gas sensors was theoretically investigated using the previously proposed concept of reduced transducer and receptor functions in their previous paper.
Abstract: The power-law response of nanosized metal oxide semiconductor gas sensors were theoretically investigated using the previously proposed concept of reduced transducer and receptor functions in our previous paper. The size and shape effects on the power-law response are theoretically revealed through derivations of the power-law exponents for gas sensors consisting of large and nanosized grains, respectively. It is found that the ratio of grain size to depletion width modulates the transducing mechanism and in turn the power-law response of gas sensors. At grain sizes equal to or less than the depletion width, the power-law exponent is inversely proportional with the grain size and linearly proportional with the surface to volume ratio of the grain. The power-law response is also experimentally characterized and found to be well consistent with our theoretical results.

56 citations

Journal ArticleDOI
TL;DR: In this article, a simple, effective and low-cost hydrothermal synthesis route was used to obtain tin (II) sulfide (SnS) and the morphology, phase structure and chemical composition of the obtained SnS were characterized.

53 citations

Journal ArticleDOI
TL;DR: In this paper, the selectivity of sensors based on Pd-WO3 can be significantly tailored towards specific target gases by adding a printed zeolite film to improve selectivity.
Abstract: In the present study, gas sensors based on Pd-loaded WO3 sensor layers were prepared and coated with zeolite films to improve the selectivity. The sensing behavior of such sensors was characterized using different single gases and mixtures to assess their selectivity. We observed that the selectivity of sensors based on Pd-WO3 can be significantly tailored towards specific target gases by adding a printed zeolite film. The use of an HZSM-5 zeolite film made the Pd-loaded WO3 sensor highly sensitive to CO, with a response of around 10 at 100 ppm CO. When Pt-modified HZSM-5 zeolite film was used, same sensor became sensitive to methanol, with a detection limit of 0.5 ppm even in the presence of high concentration of CO. Interestingly, the Pt-modified HZSM-5 film caused the catalytic conversion of CO, which resulted in a p-type response to CO. In addition, in the presence of methanol such a p-type response to CO was also observed in pure WO3 sensor. Based on the power-law response to oxygen, it is proposed that the resistive responses of all tested sensors were highly dependent on the oxygen content, indicating that oxygen adsorbates on the surface were involved in the fundamental sensing mechanism, which is the same process as conventional gas sensors. The present study showed that the configuration of Pd-WO3 sensing layers coated with zeolite films is viable for tailoring the selectivity of gas sensors.

50 citations


Cited by
More filters
20 Oct 1988
TL;DR: In this paper, the electronic interaction of SnO2 with Ag and Pd particles dispersed on its surface was examined by means of X-ray photoelectron spectroscopy (XPS).
Abstract: The electronic interaction of SnO2 with Ag and Pd particles dispersed on its surface was examined by means of X-ray photoelectron spectroscopy (XPS). The binding energies (BE) of Sn3d and O1s of Ag(1.5 wt%)-SnO2 and Pd(3.0 wt%)-SnO2, which were lower by 0.5–0.7 eV than those of pure SnO2 in the as-prepared state, shifted reversibly by reduction and oxidation treatments. These shifts in BE are shown to reflect the shifts of Fermi energy of SnO2 which are interacting electronically with the metal additives. The electronic interaction depended on the metal loading, being strongest at 1.5 wt% and 3.0 wt% loadings of Ag and Pb, respectively. The implication is that the electronic interaction is of primary importance to the inflammable gas detection by Ag-SnO2 sensors.

261 citations

Journal ArticleDOI
TL;DR: In this article, the 1D/2D W18O49/Ti3C2Tx Mxene composites were constructed using a facile solvothermal process.
Abstract: The development of gas sensor that is capable of detecting ppb-level detection of acetone and possesses high response toward low-concentration acetone remains a great challenge. Herein, we present the construction of the W18O49/Ti3C2Tx composites based on the in situ grown of the 1D W18O49 nanorods (NRs) on the surfaces of the 2D Ti3C2Tx Mxene sheets via a facile solvothermal process. The W18O49/Ti3C2Tx composites exhibit high response to low concentration acetone (11.6 to 20 ppm acetone), ideal selectivity, long-term stability, very low limit of detection of 170 ppb acetone, and fast response and recover rates (5.6/6 s to 170 ppb acetone). Compared to the W18O49 NRs and Ti3C2Tx sheets, the W18O49/Ti3C2Tx composites show significant improvement on the acetone-sensing performance, which can be ascribed to the homogeneous distribution of the W18O49 NRs on the Ti3C2Tx surface, the removal of the fluorine-containing groups from the Ti3C2Tx after the solvothermal process, and the synergistic interfacial interactions between the W18O49 NRs and the Ti3C2Tx sheets. The synthesis of the 1D/2D W18O49/Ti3C2Tx Mxene composites provides a new avenue to develop other promising hybrids for acetone sensing.

161 citations

Journal ArticleDOI
TL;DR: In this paper, a Pt-Fe2O3 nanocomposite sensor was proposed for low-cost, low-temperature, low temperature sensor for detecting acetone gas.
Abstract: Nanosized Pt-loaded Fe2O3 nanocubes are prepared through, successively, a simple hydrothermal reaction, two-step annealing process and finally reduction with NaBH4 of H2PtCl4. The resultant Pt decorated Fe2O3 nanocubes, made up of Fe2O3 nanoplatelets, are hierarchical, hollow and porous, with an average edge length of 200–300 nm. The sensor based on Pt decorated Fe2O3 nanocomposites exhibits higher response (Rair/Rgas = 25.7) to 100 ppm of acetone gas at lower temperature (139 °C), with a short response-recovery time (3 s/22 s), compared with pure Fe2O3 nanocubes sensor. The Pt-Fe2O3 nanocomposite sensor shows excellent potential to act as a low cost, low temperature sensor for acetone gas, with high acetone selectivity under high humidity conditions and with the interference of other gases. Under various environmental conditions designed to mimic exhaled air, the sensor is able to detect ppb amounts of acetone, with high repeatability and stability, making it suitable for applications such as oral diabetic sensors. The attractive chemical and electronic sensitizations of partially oxidized Pt nanoparticles are responsible for the enhancement of acetone sensing performance. Based on the high acetone selectivity, high stability and fast dynamic response, the Pt enhanced Fe2O3 nanocubes sensor is an exceptionally suitable candidate for a low cost acetone sensor, and the proposed approach provides a route to develop gas sensors that can operate at low temperatures for a wide variety of applications.

155 citations

Journal ArticleDOI
TL;DR: ZnO-based gas sensors have been widely used due to fast response, low detection limit, high selectivity, reliable performance and low manufacturing cost as discussed by the authors, however, their sensitivity and selectivity are low.

149 citations