Latest ArticlesAcetone is an important industrial raw material as well as biomarker in medical diagnosis. The detection of acetone has great significance for safety and health. However, high selectivity and low concentration (ppb level) detection remain challenges for semiconductor gas sensor. Herein, we present a novel sensitive material with bimetallic PtCu nanocrystal modified on WO3·H2O hollow spheres (HS), which shows high sensitivity, excellent selectivity, fast response/recovery speed and low limit of detection (LOD) to acetone detection. Noteworthy, the response (Ra/Rg) of WO3·H2O HS sensor increased by 9.5 times after modification with 0.02% bimetallic PtCu nanocrystals. The response of PtCu/WO3·H2O HS to 50 ppm acetone is as high as 204.9 with short response/recovery times (3.4 s/7.5 s). Finally, the gassensitivity mechanism was discussed based on gas sensitivity test results. This research will offer a new route for high efficient acetone detection.
Ethylene (C2H4), as a plant hormone, its emission can be served as an indicator to measure fruit quality. Due to the limited physiochemical reactivity of C2H4, it is a challenge to develop high performance C2H4 sensors for fruit detection. Herein, this paper presents a resistive-type C2H4 sensor based on Pd-loaded tin oxide (SnO2). The C2H4 sensing performance of proposed sensor are tested at optimum operating temperature (250 ℃) with ambient relative humidity (51.9% RH). The results show that the response of Pd-loaded SnO2 sensor (11.1, Ra/Rg) is about 3 times higher than that of pristine SnO2 (3.5) for 100 ppm C2H4. The response time is also significantly shortened from 7 s to 1 s compared with pristine SnO2. Especially, the Pd-loaded SnO2 sensor possesses good sensitivity (0.58 ppm-1) at low concentration (0.05-1 ppm) with excellent linearity (R2=0.9963) and low detection limit (50 ppb). The high sensing performance of Pd-loaded SnO2 are attributed to the excellent adsorption and catalysis effects of Pd nanoparticle. Meaningfully, the potential applications of C2H4 sensor are performed for monitoring the maturity and freshness of fruits, which presents a promising prospect in fruit quality evaluation.
This paper reports a high-performance H2S gas sensing material that is made of ZnO nanowires (NWs) modified by an optimal amount of ZnS to form nano-heterojunctions. Compared with the intrinsic ZnONWs, the three differently modified nano-heterostructure material ZnO-ZnS-x (x=5, 10, 15) shows significant improvement in sensing performance to H2S at the working temperatures of 100 400 ℃, especially in the low temperature range (< 300 ℃). The chemiresistive sensor with ZnO-ZnS-10 sensingmaterial exhibits the largest response signal to H2S among all the other ZnO-ZnS-x (x=5, 10, 15, 20) sensors. Its response signal to 5 ppm H2S at 150 ℃ is about 2.7 times to that of the ZnO-NWs sensor. Besides, the ZnO-ZnS-10 sensor also features satisfactory selectivity and repeatability at 150 ℃. With the technical advantage attributed to the reduction of the redesigned band gap at the interface between ZnO and ZnS, the ZnO-ZnS heterostructure sensor rather than the traditional ZnO-NWs sensor can be used for high-sensitivity application at low working temperature.
Tin dioxide is important gas sensor material and has wide applications in the detection of toxic gases and volatile organic compounds. Here, we synthesized a 3D laminated structural CuO/SnO2 material possessing p-n heterostructures. The morphology and structure were characterized by XRD, SEM, TEM and XPS techniques and the sensing properties were investigated for the detection of triethylamine (TEA). The results indicate that 3D laminated CuO/SnO2 material, assembled by lamellae consisting of ordered nanoparticles, exhibit an enhanced sensing performance compared with SnO2, and notably, CuO/SnO2 with size less than 1 μm has obvious high selectivity in the detection of 100 ppm TEA. Particularly, it has a high response and stability to 1 and 5 ppm TEA (S is 8 and 33), and that is higher than SnO2 material, suggesting 3D laminated CuO/SnO2 is an effective candidate material served as sensor platform to detect low-concentration amines.
A homogeneous porous Co3O4-ZnO nanomaterial (Zn-CoOx) was successfully fabricated by precipitationannealing route. The as-prepared Zn-CoOx exhibited good response, reliable reversibility and good selectivity towards alcohols, which attributed to the porous structure and p-n heterojunction formed between Co3O4 and ZnO. In particular, the different Fermi levels of Co3O4 and ZnO leaded to a further increase the depth of the space charge layer, which improved the gas sensitivity of the material from 10% to 480%. Besides, the continuous Co3O4 leaded to a relatively lower operating temperature and resistance. This material preparation method and bimetallic oxides could be widely used in the research and development of metal oxide gas sensitive materials and sensors.
Graphene quantum dots (GQDs) have both the properties of graphene and semiconductor quantum dots, and exhibit stronger quantum confinement effect and boundary effect than graphene. In addition, the band gap of GQDs will transform to non-zero from 0 eV of graphene by surface functionalization, which can be dispersed in common solvents and compounded with solid materials. In this work, the SnO2 nanosheets were prepared by hydrothermal method. As the sensitizer, nitrogen-doped graphene quantum dots (N-GQDs) were prepared and composited with SnO2 nanosheets. Sensing performance of pristine SnO2 and N-GQDs/SnO2 were investigated with HCHO as the target gas. The response (Ra/Rg) of 0.1% N-GQDs/SnO2 was 256 for 100 ppm HCHO at 60 ℃, which was about 2.2 times higher than pristine SnO2 nanosheet. In addition, the material also had excellent selectivity and low operation temperature. The high sensitivity of N-GQDs/SnO2 was attributed to the increase of active sites on materials surface and the electrical regulation of N-GQDs. This research is helpful to develop new HCHO gas sensor and expand the application field of GQDs.
Metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted great attention for room-temperature gas sensing applications. The development of novel sensing materials is the key issue for the effective detection of ammoniagas at room temperature. In the present work, the novel reduced graphene oxide (rGO)-In2O3 nanocubes hybrid materials have been prepared via a simple electrostatic self-assembly strategy. Characterization results exhibit that the intimate interfacial contact between In2O3 nanocubes and the rGO sheets are achieved. Particularly, the as-prepared rGO/In2O3 nanocomposites displayed high sensitivity, fast response and excellent selectivity towards ammonia (NH3) at room-temperature, which clearly uncovers the merit of structural design and rational integration with rGO sheets. The superior gas sensing performance of the rGO/In2O3 nanocomposites can be attributed to the synergetic effects of rGO sheets and porous In2O3 nanocubes. The reported synthesis offers a general approach to rGO/MOS-based semiconductor composites for room-temperature gas sensing applications.
Semiconducting metal oxides have been considered as effective approach for designing high-performance chemical sensing materials. In this paper, a kind of metal-organic frameworks ZIF-8 was used as sacrificed template to prepare porous ZnO hollow nanocubes for the application in gas sensing. It is found that changing calcination temperature and solvent can greatly influence the morphology of the material, which finally affects the gas sensing performance. Acetylene-sensing properties of the sensors were investigated in detail. It can be clearly seen that the material used methanol as reaction solvent with the decomposition at 350 ℃ for 2 h (ZnO-350-M) showed the optimal formaldehyde-sensing behaviors compared with other materials prepared in this experiment. The dynamic transients of the ZnO-350-M-based sensors demonstrated a high response value (about 10), fast response and recovery rate (4 s and 4 s, respectively) and good selectivity towards 100 ppm (part per million) formaldehyde as well as a low detectable limit (1 ppm). As exemplified for the sensing investigation towards formaldehyde, the porous ZnO hollow nanocubes showed a significantly improved chemical sensitivity due to the highly synergistic effects from the well exposed surfaces, defect states and the robust ZnO.
The morphological and structural design provides an efficient protocol to optimize the performance of gas sensing materials. In this work, a gas sensor with high sensitivity for triethylamine (TEA) detection is developed based on p-type NiCo2O4 hierarchical microspheres. The NiCo2O4 microspheres, synthesized by a hydrothermal route, have a three-dimensional (3D) urchin-like structure assembled by nanorod building blocks. The structure-property correlation has been investigated by powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscope, scanning electron microscope, N2 adsorption-desorption tests and comprehensive gas sensing experiments. The influence of calcination temperature on the morphological structure and sensing performances has been investigated. Results reveal that the material annealed at 300 ℃ has a very large specific surface area of 125.27 m2/g, thereby demonstrating the best TEA sensing properties including high response and low limit of detection (145 ppb), good selectivity and stability. The further increase of the calcination temperature leads to the collapse of the 3D hierarchical structure with significantly decreased surface area, which is found to decline the sensing performances. This work indicates the promise of ternary p-type metal oxide nanostructures for application in highly sensitive gas sensors.
Using SnSO4, D-glucose, urea and water, hierarchical shell-core SnO2 microspheres were successfully synthesized via a simple hydrothermal method. The characterization results showed that the sizes of asprepared SnO2 microspheres were 0.6-1 μm, with shell thicknesses of 40-60 nm. The shell and large core of the SnO2 microspheres were all comprised of the same basic rice-like nanoparticles with diameters of 16-25 nm and lengths of 16-45 nm. Further investigaton showed that the glucose and urea served as structural guiding agents, and urea facilitated the formation of the hierarchical structure. The as-prepared SnO2 nanomaterials were used to fabricate a gas sensor with an electrode blade used for the gas sensitivity tests. The hierarchical shell-core SnO2 microspheres exhibited high sensitivity and selectivity toward ethanol, with a responsivity of 63.8 for 50 ppm ethanol at 250 ℃, while the response and recovery time were 7 s and 28 s, respectively. Moreover, the responsivity of the materials showed good linearity at ethanol concentrations from 500 ppb to 10 ppm. The simple synthetic method, environmentally-friendly raw materials, and excellent gas sensitivity demonstrate that the as-prepared SnO2 nanomaterial has great potential applications for the sensing of ethanol gas.
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