Latest ArticlesOrganic amines are important solvent and raw material in laboratory and industry, as well as releasing from cigarette smoke. It is significant to detect low-concentration amines for environment and public health. Here we reported that as-synthesized zinc oxide is an effective electrode material of electrochemical sensor for the detection of amines. The characterization results reveal that the ZnO morphologies experienced a change from hexagonal bowl-like microparticles, cones, prisms to nanoparticles by adjusting the reaction time, temperature, solvents and additives. Interestingly, ZnO material possessing hexagonal shapes and different sizes exhibits distinct electrochemical response in various amines solution, suggesting that there is a better dependent relationship between different morphological ZnO and amines detection. Particularly, regular hexagonal ZnO nanotablets exhibit a detectable electrochemical response and selectivity to ammonia, implying it can be serve as electrode material for highly effective detection of organic amines.
To develop a novel food preservation technology for efficiently enhance bactericidal activity in a long term, hollow mesoporous silica spheres (HMSS) with regular nanostructures were applied to encapsulate natural organic antimicrobial agents. The chemical structures, morphologies and thermal stabilities of linalool, HMSS and linalool-functionalized hollow mesoporous silica spheres (L-HMSS) nanoparticles were evaluated by polarimeter, field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), fourier transform infrared (FT-IR), thermal gravimetric analyzer (TGA), nitrogen adsorption-desorption, zeta potential and small angle X-ray diffraction (SXRD). The results show that the linalool was successfully introduced into the cavities of HMSS, and the inorganic host exhibited a high loading capacity of about 1500 mg/g. In addition, after 48 h of incubation, the minimum bactericidal concentrations (MBC) of L-HMSS against Escherichia coli (E. coli), Salmonella enterica (S. enterica) and Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes) were decreased to be 4 (< 5) mg/mL and 8 (< 10) mg/mL, respectively. These results revealed linaloolfunctionalized hollow mesoporous spheres could efficiently improve the bactericidal activities of the organic component. Furthermore, SEM images clearly showed that L-HMSS indeed had an extremely inhibitory effect against gram-negative (E. coli) and gram-positive (S. aureus) by breaking the structure of the cell membrane. This research is of great significance in the application of linalool in nano-delivery system as well as food industry.
Detection of trace-level hydrogen sulfide (H2S) gas is of great importance whether in industrial production or disease diagnosis. This research presents a novel H2S gas sensor based on integrated resonant dual-microcantilevers which can identify and detect trace-level H2S in real-time. The sensor consists of two integrated resonant microcantilever sensors with different functions. One cantilever sensor can identify H2S by outputting positive frequency shift signals, while the other cantilever sensor will detect H2S as a normally used cantilever sensor with negative frequency shifts. Combined the two cantilever sensors, the proposed gas sensor can distinguish H2S from a variety of common gases, and the detection limit to H2S of the sensor is as sensitive as below 1 ppb.
An optical fiber dual Fabry-Pérot interferometric carbon monoxide gas sensor based on PANI/Co3O4/GO (PCG) sensing membrane coated on the end face of the optical fiber is proposed and fabricated. One end face of photonic crystal fiber (PCF) without cut-off wavelength is fused with a single-mode fiber (SMF), and the other end face of the PCF is coated with PCG sensing membrane. The collapsed layer formed during the air hole fusion of PCF is used as the first reflector, the interface between PCF and sensing membrane is used as the second reflector, and the interface between the sensing membrane and the air is used as the third reflector, thus the dual Fabry-Pérot structure sensor is formed. The results show that the sensor has excellent sensitivity and selectivity to carbon monoxide. With the increasing concentration of carbon monoxide gas in the range of 0-60 ppm, the intensity of interference spectrum decreases. The sensitivity of the sensor is 0.3473 dB m/ppm, and its linearity is good. The response time and recovery time are 68 s and 106 s, respectively. The sensor has the advantages of the compact size, low cost, high sensitivity, strong selectivity and simple structure. It is suitable for the sensing detection of low concentration carbon monoxide gas.
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.
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.
In order to improve the convenience and sensitivity of amphetamines drug testing and reduce the threat of drugs to humans, we have designed a QCM gas sensor to detect amine-containing drugs. The sensing material is designed based on the chemical nature of amine drugs. The sensing mechanism is derived from a reversible Schiff base interaction between the amino group of the drug and the carbonyl group of the novel calix[6]arene derivatives as well as the hydrogen bond interaction between amino group and hydroxyl. The new composite material was well characterized by different analytical techniques including 1H nuclear magnetic resonance (1H-NMR), fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), transmission electron microscope (TEM), Raman spectra, powder X-ray diffraction, etc. The sensing experiments were conducted by coating the composite onto quartz crystal microbalance (QCM) transducers. The experimental results indicated that the novel calixarene derivatives and their GO complexes based on the design have excellent selectivity, high sensitivity and repeatability to β-phenylethylamine.
Ag- and Pt-doped WO3·0.33H2O nanorods with high response and selectivity to NH3 were synthesized from a tungsten-containing mineral of scheelite concentrate by a simple combined process, namely by a high pressure leaching method to obtain tungstate ions-containing leaching solution and followed by a hydrothermal method to prepare corresponding nanorods. The microstructure and NH3 sensing performance of the final products were investigated systematically. The microstructure characterization showed that the as-prepared WO3·0.33H2O nanorods had a hexagonal crystal structure, and Ag and Pt nanoparticles were uniformly distributed in the WO3·0.33H2O nanorods. Gas sensing measurements indicated that Ag and Pt nanoparticles not only could obviously enhance NH3 sensing properties in terms of response, selectivity as well as response/recovery time, but also could reduce the optimal operating temperature at which the highest response was achieved. The highest responses of 22.4 and 47.6 for Ag- and Pt-doped WO3·0.33H2O nanorods to 1000 ppm NH3 were obtained at 225 and 175 ℃, respectively, which were about four and eight folds higher than that of pure one at 250 ℃. The superior NH3 sensing properties are mainly ascribed to the catalytic activities of noble metals and the different work functions between noble metals and WO3·0.33H2O.
It is known that exposed surface determines materialos performance. WO3 is widely used in gas sensing and its working surface is proposed to control its sensitivity. However, the working surface, or most exposed surface with detailed surface structure remain unclear. In this paper, DFT calculation confirmed that oxygen vacancy O-terminated surface is the most exposed hexagonal WO3 (001) surface, judging from competitive adsorption of CO and O2, working surface determination for CO sensing and comparison of oxygen vacancy formation energies on different h-WO3 (001) surfaces. It is found that DFT can be a useful alternate for exposed surface determination. Our results provide new perspectives and performance explanations for material research.
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