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The development of graphene-based room temperature gas sensors has drawn massive attention due to their unique advantage of gas sensing at room temperature. In this paper, in pursuit of developing high-performance graphene-based gas sensors, a NO 2 gas sensor has been successfully fabricated using sulfonated reduced graphene oxide (S-rGO) anchoring with SnO 2 nanoparticles as sensing materials. The SnO 2 nanoparticles modified S-rGO (SnO 2 /S-rGO) hybrids were prepared by deposition of SnO 2 nanoparticles on the surface of S-rGO through hydrothermal synthesis method. The combined characterizations of X-ray diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive spectroscopy, as well as N 2 sorption isotherm indicate the successful preparation of SnO 2 /S-rGO hybrids with porous structure. Most importantly, SnO 2 /S-rGO hybrids exhibit good sensing performances for detection of NO 2 at room temperature, such as high response, fast response and recovery rate, and good selectivity. The sensor based on SnO 2 /S-rGO hybrids exhibits better sensing performances than the previously reported rGO-based gas sensors. Furthermore, the excellent sensing performances of sensor based on SnO 2 /S-rGO also render it suitable for development of high performance gas sensors operated at room temperature. [ABSTRACT FROM AUTHOR]

Lithium chloride (LiCl)-loaded 3D cubic mesoporous silica KIT-6 (LiCl-KIT-6) composites were prepared as resistance-type humidity-sensitive materials. The structures of the resultant composites were characterized by X-ray diffraction, N 2 adsorption–desorption, and transmission electron microscopy. The humidity sensors based on LiCl-KIT-6 composites were fabricated and the sensing properties were investigated. Results indicate the uniform pore distribution of KIT-6 contributes to the rapid hydrone transport in mesoporous channels. The impedance of optimized 3 wt% LiCl-KIT-6 sensor changed by more than three orders of magnitude over the relative humidity range of 11–95%. The response and recovery times of the sensor were 15 s and 28 s, respectively. Finally, the complex impedance method was used to analyze the humidity sensing mechanism of the sensor based on LiCl-KIT-6. [ABSTRACT FROM AUTHOR]

A facile and effective strategy has been successfully developed to synthesize reduced graphene oxide-multiwalled carbon nanotubes-tin oxide nanoparticles (rGO-CNT-SnO 2 ) hybrids by hydrothermal method. The combined characterizations of X-ray diffraction, Raman spectrum and Transmission electron microscopy were used to characterize the samples thus obtained, indicating the successful preparation of rGO-CNT-SnO 2 hybrids. A room temperature NO 2 sensor was fabricated by dropping the dispersion of rGO-CNT-SnO 2 hybrids on the surface of ceramic substrate previously printed Au electrodes. Most importantly, the sensor based on rGO-CNT-SnO 2 hybrids shows high response, fast response and recovery rate, high selectivity and good stability, which are much better than NO 2 sensors based on pure rGO and rGO-SnO 2 hybrids. [ABSTRACT FROM AUTHOR]

Highly sensitive and selective toluene sensors based on ordered mesoporous Co3O4 have been successfully developed. The combined characterizations of X-ray diffraction (XRD) patterns, nitrogen adsorption–desorption isothermal, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) indicate that mesoporous Co3O4 with ordered mesoporous structure and high surface area has been successfully prepared by the nanocasting method using mesoporous silica (SBA-15) as hard template and Co(NO3)2·6H2O as cobalt source. It is also found that mesoporous Co3O4 thus obtained shows good response toward toluene with the concentrations ranging from 1ppm to 1000ppm. Furthermore, mesoporous Co3O4 also exhibits high selectivity for detection of toluene, compared to other interferences, such as ethanol, formaldehyde, ethanol, acetone, methanol and ammonia. Most importantly, mesoporous Co3O4 exhibits better sensing performance than that of non-porous Co3O4 obtained by direct calcination of Co(NO3)2·6H2O in the absence of any templates, which can be attributed to unique properties of mesopotous Co3O4, such as high surface area, open mesoporous structure as well as relatively small crystal size. [ABSTRACT FROM AUTHOR]

Ag nanoparticles/graphene nanosheet (AgNPs/GN) composites have been rapidly prepared by a one-pot microwave-assisted reduction method, carried out by microwave irradiation of a N, N-dimethylformamide (DMF) solution of graphene oxide (GO) and AgNO. Several analytical techniques including UV-vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) have been used to characterize the resulting AgNPs/GN composites. It suggests that such composites exhibit good catalytic activity toward reduction of hydrogen peroxide (HO), leading to a HO sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 0.1 to 100 mM ( r = 0 .999), and the detection limit is estimated to be 0.5 μM at a signal-to-noise ratio of 3. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Polymer-free Pt/graphene nanosheet (GN) composites have been rapidly prepared by a one-step microwave-assisted reduction method, carried out by ethylene glycol reduction of HPtCl in a graphene oxide suspension. Several analytic techniques including UV-vis spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy have been used to characterize the resulting Pt/GN composites. It suggests that such composites exhibit good catalytic activity toward methanol oxidation. [ABSTRACT FROM AUTHOR]

Abstract: Ordered hexagonal mesoporous silica materials with additional disordered large-mesopore networks (DL-SBA-15s) have been prepared by one-pot process using urea as a producer of gas. Combined characterizations of XRD, SEM, and TEM techniques show that DL-SBA-15s not only have ordered 2D hexagonal mesopores (about 10nm) similar to SBA-15, but also have another disordered large-mesopore network (about 20nm) interconnected with hexagonal mesoporous channels, which are confirmed by nitrogen isotherms. The ordered hexagonal mesopores are templated by polymer surfactant micelle, and disordered large-mesopores are formed by gaseous expansion due to the decomposition of urea added in the silica gel. 29Si MAS NMR and FT-IR spectra show DL-SBA-15s have high degree of silica condensation and low silanols on the surface, compared with SBA-15. Furthermore, we have compared the adsorption capacity of myoglobin over conventional SBA-15 and DL-SBA-15 samples, and the results show that DL-SBA-15s exhibit much higher adsorption rate than conventional SBA-15 due to the presence of additional disordered large-mesopore networks and larger pore volume, which is potentially important for immobilization of enzymes on ordered mesoporous materials. [ABSTRACT FROM AUTHOR]

A mesostructured sulfated tin oxide with large surface area (172 m2/g) has been successfully prepared using a block copolymer as structure-directing agent, which is extensively characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption, and Thermogravimetric analysis (TG) techniques. The results indicate that the mesostructured sulfated tin oxide was tetragonal crystalline, and catalytic tests show that the mesostructured sulfated tin oxide is much more active than conventional one for esterification and Friedel–Crafts acylation. [ABSTRACT FROM AUTHOR]

Abstract: A series of mesoporous aluminophosphates (MAP) and Fe-aluminophosphates (Fe-MAP) with highly thermal stability and large surface area have been successfully synthesized by the use of semi-fluorinated surfactant, which were characterized by XRD, TEM, N2 adsorption, NMR, UV–Vis, and ESR techniques. These results show these samples are thermally stable up to 600°C. More importantly, these samples give large surface area (BET, ca. 430–580m2/g), which has an advantage for the use of catalysts or catalyst supports. In contrast, mesoporous aluminophosphates templated from copolymer surfactants such as F127 show relatively low surface area (<260m2/g). Furthermore, UV–Vis and ESR spectra suggest that Fe species in Fe-MAP are mainly in tetrahedral coordination. Finally, the tests of hydroxylation of phenol with hydrogen peroxide show that Fe-MAPs are catalytically active. [Copyright &y& Elsevier]

Graphical abstract Highlights • In this work, the obtained Zn 2 SnO 4 -RGO hybrids exhibited outstanding sensing performance for detecting oxidizing gases (NO 2 and O 3) with very low cross sensitivities to reducing gases, such as C 2 H 5 OH, CH 3 COCH 3 and CO. • The Zn 2 SnO 4 -RGO based sensors exhibited high response values of up to 3.50 for 500 ppb NO 2 , which is higher than that for detection of 500 ppb O 3 (1.78) at 30 °C under 50% relative humidity (RH). • The surface reaction between Zn 2 SnO 4 -RGO hybrids and NO 2 can be concluded from Operando diffuse reflectance infrared Fourier transformed spectroscopy (Operando DRIFT). Abstract Highly selective oxidizing gas sensors are of great importance for environmental pollution monitoring. In this work, a hybrid material containing Zn 2 SnO 4 nanoparticles (NPs) and immobilized reduced graphene oxide (Zn 2 SnO 4 -RGO) was developed as a high performance gas sensing material for the detection of ppb-levels of oxidizing gases (NO 2 and O 3). The structural, morphological and compositional properties of the Zn 2 SnO 4 -RGO hybrids were systematically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), which demonstrated the successful anchoring of Zn 2 SnO 4 NPs on RGO nanosheets. The obtained Zn 2 SnO 4 -RGO hybrids exhibited outstanding sensing performance for detecting oxidizing gases (NO 2 and O 3) with very low cross sensitivities to reducing gases, such as C 2 H 5 OH, CH 3 COCH 3 and CO. The Zn 2 SnO 4 -RGO based sensors exhibited high response values of up to 3.50 for 500 ppb NO 2 , which is higher than that for detection of 500 ppb O 3 (1.78) at 30 °C under 50% relative humidity (RH). Moreover, the NO 2 sensing performances of Zn 2 SnO 4 -RGO-based sensors were investigated under various RH. In all cases, the sensors based on RGO and Zn 2 SnO 4 -RGO hybrids presented p-type behavior. The sensors based on Zn 2 SnO 4 -RGO hybrids also exhibited high response values of up to 3.62 for 1 ppm NO 2 at 50 °C in 80% RH, which is much higher than that of pure RGO (1.31). The excellent sensing performances are mainly ascribed to the synergetic effect of Zn 2 SnO 4 NPs and RGO. Furthermore, the surface reaction between Zn 2 SnO 4 -RGO hybrids and NO 2 can be concluded from Operando diffuse reflectance infrared Fourier transformed spectroscopy (Operando DRIFT). [ABSTRACT FROM AUTHOR]

Abstract: A hierarchical mesoporous ZSM-5 zeolite has been synthesized by using starch-derived bread as a meso-template. The obtained mesoporous ZSM-5 was characterized with X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric (TG)/differential thermal analysis (DTA) techniques. Hydrothermal treatments revealed that the mesoporosity in hierarchical mesoporous ZSM-5 exhibited excellent hydrothermal stability. Catalytic tests showed that hierarchical mesoporous ZSM-5 was more active than conventional zeolite of ZSM-5 in catalytic cracking of 1,3,5-tri-isopropylbenzene. Hydrogen adsorption measurements showed hierarchical mesoporous ZSM-5 had a higher storage capacity than the conventional ZSM-5. [Copyright &y& Elsevier]