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• The novel porous Co 3 O 4 /N-RGO nanocomposite as gas-sensing materials derived from MOFs/RGO as templates and precursor. • Porous Co 3 O 4 concave cubes were distributed on the surface of nitrogen-doped RGO sheets to form Co 3 O 4 /N-RGO nanocomposite owned highly porous structures and large specific areas. • The synergistic effect or coupling effect between porous Co 3 O 4 and N-RGO enhance greatly the sensing performance towards ethanol vapor. • Compare with Co 3 O 4 and Co 3 O 4 /RGO, the Co 3 O 4 /N-RGO-0.5 nanocomposites as ethanol sensing materials showed lower working temperature (200 °C), higher response and shorter response-recover time. Co 3 O 4 /N-doped reduced graphene oxide (N-RGO) nanocomposite with mesoporous structure was fabricated by using metal organic frameworks (MOFs) as both template and precursor growing on RGO sheets. Porous Co 3 O 4 cubes were assembled and grown on the surface of N-RGO layers, while N was doped into RGO to form N-RGO in situ synthesis route. The effect of RGO initial concentration on structure, component and gas-sensing properties of Co 3 O 4 /N-RGO nanocomposite was studied. The gas-sensing result demonstrated that the sensor based-on Co 3 O 4 /N-RGO-0.5 (the mass of RGO was 0.5 mg) nanocomposite possessed better gas-sensing performances to ethanol, such as higher response, faster response-recovery time and lower working temperature than that of other samples. The enhanced gas-sensing properties of sensor based-on Co 3 O 4 /N-RGO-0.5 nanocomposite to ethanol could be attributed to increasing of specific surface area, coupling effect between Co 3 O 4 and nitrogen doped RGO as well as the existence of N-doping RGO which improved electron transferring of material in sensing process. Co 3 O 4 /N-RGO-0.5 nanocomposite has been proved to be a promising gas-sensing material for detecting ethanol at a low temperature. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The mesoporous Ni x Co 1-x Fe 2 O 4 nanostructured microspheres with tunable composite were synthesized by a solvothermal method. • The Ni-doping into CoFe 2 O 4 could lead to an increase in the concentration of oxygen vacancies and specific surface area. • The gas-sensing tests to toluene showed that the Ni 0.33 Co 0.67 Fe 2 O 4 microspheres showed highest gas-sensing sensitivity. • The suitable Ni-doping was good for the sensing properties of Ni x Co 1-x Fe 2 O 4 , which were suppressed with the more Ni doping. Abstract The mesoporous Ni x Co 1-x Fe 2 O 4 (x = 0, 0.33, 0.50, 0.67) nanostructured microspheres with tunable composite were successfully controllable synthesized by a simple solvothermal method. The results of XRD, XPS and FT-IR demonstrated that the Ni, taking the place of Co, were successfully doped into CoFe 2 O 4. The gas sensing results demonstrated that the Ni 0.33 Co 0.67 Fe 2 O 4 nanostructured microspheres showed higher gas-sensing response and better selectivity to harmful toluene than that of other samples. Moreover, the influences of Ni-doping amount on the structure, morphology and gas-sensing property of Ni x Co 1-x Fe 2 O 4 were investigated. The enhanced gas-sensing properties of gas sensor based on Ni 0.33 Co 0.67 Fe 2 O 4 to toluene may be due to appropriate Ni-doping into cobalt ferrite which resulted in the increased concentration of oxygen vacancies, large specific surface area (77.2 m2 g−1) and suitable catalytic activity. Therefore, the Ni x Co 1-x Fe 2 O 4 will be a promising candidate for gas-sensing material for detecting toluene. [ABSTRACT FROM AUTHOR]

Chestnut-like CoFe 2 O 4 @SiO 2 @In 2 O 3 nanocomposite microspheres with hierarchical structures were successfully synthesized by an in situ hydrothermal growth of In 2 O 3 nanowires covering on the CoFe 2 O 4 @SiO 2 microspheres. The resultant nanocomposite microspheres possessed an average size of 480 nm, while the In 2 O 3 nanowires exhibited a relatively small diameter of 5 nm. Especially, the unique hierarchical structures showed a large pore size of about 18 nm and large specific surface area of 54 m 2 g −1 . The gas sensing results demonstrated that the chestnut-like CoFe 2 O 4 @SiO 2 @In 2 O 3 nanocomposite microspheres exhibited superior sensitivity and fast response speed to low-ppm-level acetone. That superior property might be attributed to the unique hierarchical structure of chestnut-like CoFe 2 O 4 @SiO 2 @In 2 O 3 nanocomposite microspheres, which could be promising gas-sensing materials. [ABSTRACT FROM AUTHOR]

A novel non-enzymatic glucose sensor has been successfully fabricated based on Ni(OH) 2 /NiO nanosheet with unique defect-rich structure synthesized via a high-power, microwave-assisted hydrothermal method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were applied to characterize the composition and morphology of the materials. High-resolution transmission electron microscopy and Raman spectroscopy results verified that the Ni(OH) 2 /NiO nanosheets had abundant surface defects and additional active edge sites. Moreover, the glucose electrocatalytic properties of the defect-rich Ni(OH) 2 /NiO nanosheet were investigated through electrochemical methods, indicating that the fabricated biosensor had a high sensitivity of 2931.4 μA mM −1 cm −2 , a wide linear range from 0.09 mM to 3.62 mM, and a low detection limit of 5.0 μM ( S / N = 3). The excellent glucose-sensing properties can be attributed to the synergic effect of Ni(OH) 2 and NiO, as well as the unique defect-rich structure of the active materials that produces opulent exposed active sites for glucose oxidation. The successful application of defect engineering to glucose sensing will pave a new way for the development of more efficacious catalyst. [ABSTRACT FROM AUTHOR]

Ultrafine α-Fe 2 O 3 nanoparticles with an average size of ∼3 nm were successfully prepared by a facile reverse micro-emulsion method. As-prepared α-Fe 2 O 3 nanoparticles exhibited excellent gas sensing activity due to its size and surface effect. These ultrafine and highly monodisepersive α-Fe 2 O 3 nanoparticles (UHFN) showed fast response, high selectivity and good stability to acetone vapor. This kind of material is expected to be a prospecting candidate for the application in acetone sensors. [ABSTRACT FROM AUTHOR]

Highly sensitive and selective detection of toxic and harmful gases especially at low-ppb (part per billion) level is of great significance to human health and air quality, although it remains a great challenge in gas sensor applications. Herein, for the first time, we present an ordered mesoporous ZnCr 2 O 4 with both large mesopore of 11 nm and ultrathin crystalline framework of 3–5 nm for highly sensitive and selective detection of p -xylene at low ppb levels. The resultant ordered large-pore mesoporous ZnCr 2 O 4 with ultrathin framework exhibits a higher specific surface area of up to 168 m2 g−1 than those for its mesoporous counterpart with thick framework (60 m2 g−1) and bulk ZnCr 2 O 4 particle (48 m2 g−1), which also exhibits the highest response value (R gas / R air −1 = 26.8) toward 1 ppm of p -xylene at 270 °C and is nearly 8 and 10 times higher than those for its mesoporous counterpart with thick framework (3.32) and bulk ZnCr 2 O 4 particle (2.65) respectively. Notably, the ordered mesoporous ZnCr 2 O 4 also has a rather low limit of detection (<2 ppb) as well as good selectivity and would be potential in gas sensors. • Highly sensitive and selective p -xylene sensor using ordered large-pore (11 nm) mesoporous ZnCr 2 O 4. • Unprecedentedly large specific surface area (168 m2 g−1) and ultrathin framework (3–5 nm). • Ultralow detection limit (LOD<2 ppb) for p -xylene. [ABSTRACT FROM AUTHOR]

Abstract: SBA-15, SBA-16 and crystal like-SBA-16 were synthesized by a simple chemical method, and the copolymer template was removed by calcination or microwave digestion (MWD) method. They were investigated as humidity sensing materials at room temperature within the relative humidity range of 11–95%RH. It was found that after MWD treatment, the humidity sensitive property of mesoporous silica have been greatly improved, and the impedance of MWD-crystal like SBA-16 changed by more than three orders of magnitude over the whole humidity range. Further testing proved that it is a promising humidity sensing material and can be widely used. A possible mechanism was also proposed to explain the correlation between material and property. [Copyright &y& Elsevier]

Abstract: Li-doped 3D periodic mesoporous silica SBA-16 has been successfully prepared and investigated as humidity sensor material. After doping of 10% (wt) lithium chloride, mesoporous silica SBA-16 showed significant change in impedance of more than three orders of magnitude over almost the whole humidity range (11–95%RH), with fast response time (about 25s), and relatively low hysteresis (about 4%). The comprehensive affections of the 3D mesoporous structure, highly dispersed uniform morphology, hydrophilic behavior of triblock copolymer surfactant F108, and the doped Li+ maybe make a great contribution to the improvement in the humidity sensitive property. A possible mechanism was also provided to explain the humidity sensitive properties. [Copyright &y& Elsevier]

[Display omitted] • Fern-like mesoporous In 2 O 3 /ZnO nanocomposite was prepared by template method using MOFs as template. • In 2 O 3 /ZnO nanocomposite exhibited excellent gas sensing performance to triethylamine at only 100 °C. • Its enhanced gas-sensing properties was due to fern-like mesoporous heterojunction with nanowires. Fern-like In 2 O 3 /ZnO nanocomposite with mesoporous structure was derived from MIL-68/ZIF-8 via a simple template method. Abundant nanowires grew on the surface of microrods to form novel fern-like structure. The effect of MIL-68 concentration on component, structure, morphology and gas-sensing properties of In 2 O 3 /ZnO nanocomposite were studied. The results of gas tests exhibited that the sensor based on In 2 O 3 /ZnO (the mass of MIL-68 is 0.3 g) showed excellent sensing properties to TEA, which included superior response (44.6), ultralow work temperature (100 °C) and fast response-recovery time. The enhanced gas sensing properties of fern-like In 2 O 3 /ZnO nanocomposites were due to mesoporous structure, a large specific surface area, the specific structure of abundant nanowires growing on microrods and the n-n heterojunction formed at the interface of In 2 O 3 and ZnO, which all accelerated the gas sensing reaction between TEA molecules and adsorbed oxygen on the surface of materials. The fern-like In 2 O 3 /ZnO composite with mesoporous structure was an ideal gas sensing material for the detection of TEA. [ABSTRACT FROM AUTHOR]