다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This review paper encompasses a detailed study of semiconductor metal oxide (SMO) gas sensors. It provides for a detailed comparison of SMO gas sensors with other gas sensors, especially for ammonia gas sensing. Different parameters which affect the performance (sensitivity, selectivity and stability) of SMO gas sensors are discussed here under. This paper also gives an insight about the dopant or impurity induced variations in the SMO materials used for gas sensing. It is concluded that dopants enhance the properties of SMOs for gas sensing applications by changing their microstructure and morphology, activation energy, electronic structure or band gap of the metal oxides. In some cases, dopants create defects in SMOs by generating oxygen vacancy or by forming solid solutions. These defects enhance the gas sensing properties. Different nanostructures (nanowires, nanotubes, heterojunctions), other than nanopowders have also been studied in this review. At the end, examples of SMOs are given to illustrate the potential use of different SMO materials for gas sensing.

Semiconductor metal oxide gas sensors: A review

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.

Electronic Interaction between Metal Additives and Tin Dioxide in Tin Dioxide-Based Gas Sensors : Surfaces, Interfaces and Films

The alarming rise of indoor pollution and the need to combat the associated negative effects have promoted increasing attention in modernizing the chemical sensing technologies by newly designed materials with rich and tunable functionalities at atomic or molecular levels. With the appealing physical, chemical, optical, and electronic properties for various potential applications, the state-of-art gas-sensing nanomaterials and their future perspectives are well-documented and summarized in this paper. Specifically, the key performance attributes are addressed in detail such as the sensitivity, selectivity, reversibility, operating temperature, response time, and detection limit. As such, this review provides both critical insights in exploring and understanding various gas sensing nanomaterials and points out limitations and opportunities for further developments, such as morphology control, doping and surface alteration, atomic-scale characterization, and applications in different fields. Finally, the challenges and outlooks are discussed on the basis of the current developments.

Functional gas sensing nanomaterials: A panoramic view

Nanoporous network metal oxides are potential candidates for various applications such as filtration, biomaterials devices, and sensing materials. The present work focused on the simple and scalable fabrication of the α - Fe 2 O 3 nanoporous network for ethanol gas sensor using Fe 3 O 4 /reduced graphene oxide (rGO) as a precursor. The analyzed morphology and crystal structure indicated that the α - Fe 2 O 3 nanoporous network was formed due to some factors during thermal procedures such as the phase transformation from magnetite to hematite, nanoparticle agglomeration, and combustion of rGO. The ethanol gas-sensing properties of the α - Fe 2 O 3 nanoporous network were investigated. The response to 100 ppm ethanol gas was as high as 9.5, while the cross-gas responses to 100 ppm NH 3 , H 2 , and CO gases were all lower than 2.0. These values indicated a good selectivity of the sensors. Furthermore, the 90% response times to ethanol gas were less than 5 s at 400°–450 °C. The proposed strategy has potential in the preparation of other porous network metal oxides to achieve high-performance gas sensors.

Fe2O3 nanoporous network fabricated from Fe3O4/reduced graphene oxide for high-performance ethanol gas sensor

SnO2 porous nanofibers (NFs) were deposited on-chip by using a facile electrospinning method followed by heat treatment at 600 °C and used to detect H2S concentrations at sub-parts per million level. Morphological, compositional, crystal, and atomic structural properties of the as-spun and calcined SnO2 NFs were investigated by field emission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy, respectively. SnO2 porous NFs with an average diameter of 150 nm and consisting of many nanograins were successfully fabricated by on-chip electrospinning. The NFs were crystallized as the tetragonal structure of SnO2 with an average crystallite size and dislocation density of approximately 13.5 nm and 5.615 × 1015 lines/m2, respectively. The sensing characteristics of the SnO2 NF sensors were tested with 0.1–1 ppm H2S from 150 °C to 450 °C. The sensor achieved the optimal performance at 350 °C and exhibited gas response of 15.2 with fast response/recovery times of 15 s/230 s. The H2S gas sensing mechanisms of the SnO2 porous NF sensors were due to the modulation of the resistance along the surface depletion layer and the grain boundaries. The fabricated sensor also indicated a good selectivity to H2S, short-term stability, and the low detection limit of 1.6 ppb. The influence of humidity on the sensor’s performance in a low temperature range is also discussed.

One-step fabrication of SnO2 porous nanofiber gas sensors for sub-ppm H2S detection

Facile on-chip electrospinning of ZnFe2O4 nanofiber sensors with excellent sensing performance to H2S down ppb level.

On-chip growth of semiconductor metal oxide nanowires for gas sensors: A review

The synthesis and integration of a compact, highly sensitive, and inexpensive gas sensor for breath analysis have attracted considerable attention because of painless application, non-invasiveness, and ability to diagnose diseases during early stages. In this study, we introduced the on-chip growth of SnO 2 nanowire (NW)-based gas sensor to analyze the low concentration of H 2 gas for exhaled breath applications. We decorated the Pd catalyst on the surface of SnO 2 NWs to enhance gas-sensing performance. Comparative results revealed that Pd decoration enhanced the H 2 gas response at low operating temperature range (250–300 °C). Moreover, the Pd-decorated SnO 2 NW sensor exhibited good response to H 2 gas at considerably low temperature of 150 °C, whereas the bare SnO 2 NWs cannot respond. Finally, the packaged sensor was tested at different supplied powers to various H 2 concentrations ranging from 10 to 100 ppm. Gas selectivity toward CO 2 and ethanol gases was examined. Results demonstrated that the prepared gas sensor package is suitable for breath gas analysis.

Chu Manh Hung

Papers

Fe2O3 nanoporous network fabricated from Fe3O4/reduced graphene oxide for high-performance ethanol gas sensor

One-step fabrication of SnO2 porous nanofiber gas sensors for sub-ppm H2S detection

Facile on-chip electrospinning of ZnFe2O4 nanofiber sensors with excellent sensing performance to H2S down ppb level.

On-chip growth of semiconductor metal oxide nanowires for gas sensors: A review

Low-temperature prototype hydrogen sensors using Pd-decorated SnO2 nanowires for exhaled breath applications