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• SnO 2 samples with controllable oxygen vacancy concentration have been developed by organometallic chemistry-assisted strategy. • The SnO 2 samples with high oxygen vacancy concentration exhibit excellent sensing performances for detection of acetone. • This work paves a new avenue for fabricating metal oxides with controllable oxygen vacancies for various applications. Oxygen vacancies play a critical role in the sensing performances for metal oxides-based chemiresistor-type sensors. Developing facile and effective strategies for fabricating metal oxides with controllable oxygen vacancies is in great demand but remains paramount challenge. Herein, a novel organometallic chemistry-assisted method is reported to prepare SnO 2 samples containing controllable surface oxygen vacancies. This new approach combines modification of SnO 2 with dimethyltin dichloride, and subsequently thermal treatment in air atmosphere. Taking commercial SnO 2 as an example, it is found that the optimized SnO 2 sample possesses highest surface oxygen vacancy concentration of 37.13%. Owing to increased oxygen vacancy concentration, the resulting SnO 2 sample (SnO 2 -Sn-0.5) presents excellent sensing performances for detection of acetone, including high response, fast response and recovery rate, good selectivity, compared with pristine SnO 2 with low oxygen vacancy concentration (28.66%). This work paves a new avenue for fabricating metal oxides with controllable oxygen vacancies for various applications of sensing, energy storage, and so on. [ABSTRACT FROM AUTHOR]

Nanoparticles-assembled NiO nanosheets have been successfully prepared using graphene oxide (GO) film as template, where the Ni 2+ ion was firstly adsorbed in GO film, followed by calcination in N 2 to form NiO-based materials and calcination in air to remove carbon-based template. The morphology, structure, and electrochemical activities of these NiO nanosheets were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and electrochemical techniques, respectively. It is found that the NiO nanosheets thus obtained could electrochemically catalyze glucose oxidation in 0.1 M NaOH, leading to fabrication of non-enzymatic glucose sensor. The glucose sensor based on NiO nanosheets exhibits detection limit of 0.18 μM, and linear range from 1 μM to 0.4 mM with the sensitivity of 1138 μA mM −2 cm −2 . Furthermore, such glucose sensor also shows excellent selectivity for detection of glucose, compared to the commonly interfering species, such as ascorbic acid, dopamine, and uric acid. [ABSTRACT FROM AUTHOR]

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]

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]

Mesoporous SnO 2 has been successfully prepared by the solvent-free infiltration method using SiO 2 nanoparticles as template. The combined characterizations of X-ray diffraction pattern, nitrogen sorption isothermal, and transmission electron microscopy indicate the successful preparation of mesoporous SnO 2 . It is found that the mesoporous SnO 2 exhibits high response, good selectivity, fast response and recovery rate for detection of ethanol, which are much better than that of bulky SnO 2 prepared in the absence of SiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-doped carbon (N-carbon) materials have been prepared by low temperature (300°C) heat treatment of hexamethylenetetramine in air. The combined characterizations of X-ray diffraction pattern, scanning electron microscopy, and X-ray photoelectron spectroscopy indicate the successful preparation of N-carbon materials. Most importantly, the N-carbon exhibits catalytic activity toward electrochemical reduction of H2O2, leading to a novel metal-free non-enzymatic H2O2 sensor. The linear detection range is estimated to be from 0.1mM to 40mM (r =0.996), and the detection limit is estimated to be 90μM at a signal-to-noise ratio of 3. [Copyright &y& Elsevier]

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]

A novel NO 2 gas sensor has been constructed using Ag nanoparticles-SnO 2 nanoparticles-reduced graphene oxide (AgNPs-SnO 2 -rGO) hybrids as sensing materials. AgNPs-SnO 2 -rGO hybrids were prepared by a two-step wet-chemical method. Firstly, SnO 2 -rGO hybrids were synthesized by hydrothermal treatment of aqueous dispersion of GO in the presence of SnCl 4 . Then, AgNPs-SnO 2 -rGO hybrids were obtained by in situ reduction of AgNO 3 on the surface of SnO 2 -rGO hybrids. The combined characterizations of UV–vis spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectrometer (EDX), elemental mapping, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and Raman spectra were used to investigate the structure of AgNPs-SnO 2 -rGO hybrids. Most importantly, the sensor based on AgNPs-SnO 2 -rGO hybrids exhibits good sensing performance for NO 2 sensing operating at room temperature. For example, the response time and recovery time of the sensor based on AgNPs-SnO 2 -rGO hybrids for 5 ppm NO 2 are 49 s and 339 s, which are much shorter than that of SnO 2 -rGO hybrids (415 s and 740 s), indicating that the sensing performances for NO 2 sensing at room temperature have been tremendously enhanced by introduction of AgNPs into SnO 2 -rGO hybrids. [ABSTRACT FROM AUTHOR]

Three-dimensional reduced graphene oxide (3D-rGO) materials have been successfully prepared by a template-assisted self-assembly method using polystyrene spheres (PSs) as sacrificial templates. PSs-rGO hybrids were prepared by self-assembly of PSs and GO through the π–π interaction, followed by reduction of such hybrids using hydrazine as reducing agent. 3D-rGO materials were obtained after removal of PSs in PSs-rGO hybrids by toluene. The combined characterizations of field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) indicate the successful preparation of 3D-rGO materials. More importantly, 3D-rGO materials thus obtained exhibit good sensing performances for electrochemical detection of dopamine (DA), leading to a high-performance DA sensor. The DA sensor based on 3D-rGO materials has been evidenced to exhibit a better sensing performances than that of rGO and poly-(vinylpyrrolidone) (PVP)-stabilizing rGO. Furthermore, differential pulse voltammetry (DPV) indicates that the 3D-rGO-based DA sensor could be effectively used for DA sensing in the presence of ascorbic acid (AA) and uric acid (UA), indicating high selectivity of the DA sensor based on 3D-rGO materials. [ABSTRACT FROM AUTHOR]

Low humidity detection has been a great challenge in the field of humidity sensing. In recent years, polyelectrolytes have been proven to be promising materials for highly sensitive humidity sensors. In this work, cross-linked poly(ionic liquid)s (PILs) were prepared for low humidity detection. The strong hydrophilicity of PILs contributes to humidity sensing while the cross-linked structure guarantees the stability of the sensing film. The optimized sensor shows high response (48.0) in 5–35% RH, with short response/recovery time (1 s/10 s) and a small humidity hysteresis (0.2% RH). The possible sensing mechanism of the sensors was discussed. • Cross-linked poly(ionic liquid)s were used as low humidity sensitive materials. • The optimized sensor shows high response in 5–35% RH. • The optimized sensor has short recovery time and small humidity hysteresis. • The introduction of glycerol could reduce the impedance of the sensor. [ABSTRACT FROM AUTHOR]

Development of room-temperature gas sensors with excellent sensing performances for detection of dimethyl methylphosphonate (DMMP, a simulant of organophosphate) has aroused considerable attention. However, the weak adsorption ability of sensing materials toward DMMP molecules causes poor sensing performances. In this work, a multisite strategy for enhancing sensitivity was proposed by introduction of both N-doped carbon nanoparticles (N-CNPs) and copper ions onto the surface of rGO (designated as GNC). Impressively, optimal GNC-3 exhibits the response value of 10.2% toward 100 ppm DMMP, which is 5.3 times higher than that of pristine rGO. This mechanism for multisite-assisted enhanced DMMP sensing performances was investigated by combined characterizations of Fourier-transform infrared spectra, UV-Vis spectra, photoluminescence spectra and Mott-Schottky curves. Besides the construction of multisite, improvement of hydrogen bonding interactions between DMMP molecules and N-CNPs in hybrids assisted by copper ions, and decrease of conduction band potential by formation of ternary hybrids also contribute to enhance the sensitivity of DMMP sensors. These findings not only provided new insights into designing high-performance room-temperature gas sensors, but also promoted the fundamental research on sensing mechanism for room-temperature gas sensors. • A multisite strategy for enhancing sensitivity was proposed by constructing three kinds of DMMP adsorption active sites. • GNC hybrids demonstrate 5.3-fold improvement in response to 100 ppm DMMP compared to pristine rGO hybrids. • This mechanism for multisite-assisted enhanced DMMP sensing performances was confirmed by the spectroscopy. [ABSTRACT FROM AUTHOR]

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]

Highlights • A novel MCM-41/PPy (Polypyrrole) based humidity sensor was prepared. • An in-situ way of loading PPy into the channels of MCM-41 framework was used for quantity control. • The MCM-41/PPy (90) sensor shows a high sensitivity and wider humidity sensing range than MCM-41sensor or PPy sensor. • A proper mechanism about dielectric constant change was discussed to explain the sensing phenomenon. Abstract Inorganic zeolites, such as MCM (Mesoporous Crystalline Material), are widely used as skeleton to load humidity sensitive materials for constructing high-performance humidity sensor. In this work, an in-situ preparation method was developed to prepare MCM-41/polypyrrole (PPy) humidity sensors, by inducing the polymerization of pyrrole vapor inside MCM-41 film that was coated on the ceramics substrate with carbon interdigital electrodes. MCM-41/PPy sensors with different polymerization times were fabricated, and their capacitance humidity sensing properties demonstrate much better performance than individual MCM-41 sensor or PPy sensor, with high sensitivity and a wide humidity sensing range. The sensing properties of MCM-41/PPy sensors were further optimized by controlling the polymerization time. In addition, a humidity sensing mechanism explanation is discussed at the end of this paper. [ABSTRACT FROM AUTHOR]

In this paper, SnO 2 nanoparticles (NPs) decorated reduced graphene oxide hybrids with abundant vacancies (designated as SnO 2 -RGO-OVs) have been successfully prepared by a combined hydrothermal synthesis and chemical solution deposition method. It is found that high density SnO 2 NPs with the size of 3–5 nm are uniformly distributed on the surface of RGO nanosheets. Most importantly, SnO 2 -RGO-OVs hybrids exhibit excellent room-temperature NO 2 sensing properties with the low detection limit of 50 ppb. When SnO 2 -RGO-OVs-based sensor was exposed to 1 ppm NO 2 , the response is 3.80 and response time and recovery time are 14 s and 190 s, respectively. These sensing performances are superior to those of most reported room-temperature NO 2 sensors based on RGO-based materials and other materials. The excellent sensing performances of SnO 2 -RGO-OVs hybrids can be attributed to their specific structure, e.g., RGO that could facilitate transferring carriers during sensing progress, and abundant OVs that could facilitate adsorption of more NO 2 molecules onto SnO 2 NPs in SnO 2 -RGO-OVs hybrids. [ABSTRACT FROM AUTHOR]

Composites fabricated by mesoporous silica loading hydrophilic elements have been widely investigated as humidity sensitive materials. The physical mixing process for loading hydrophilic elements is difficult to guarantee the uniformity and structural stability of the composites. Furthermore, the poor dispersibility of the silica skeleton restricts its solution processability. Herein, solution processible organic-inorganic hybrid materials were synthesized via a thiol-ene click reaction between sulfhydryl functionalized microporous silica nanoparticles (MSNs) and hydrophilic alkenyl monomer. The optimal hybrid material could disperse in water stably with a concentration of 50 mg/mL owing to the small particle size (about 105 nm) and the hydrophilic characteristic. Humidity sensors were fabricated by solution process and the humidity sensing properties were investigated. The sensor exhibits high sensitivity (about three orders impedance modulus change), small hysteresis (∼2% RH) and rapid response (the response and recovery time are 5 and 40 s, respectively) in the humidity range of 11%–95% RH. [ABSTRACT FROM AUTHOR]

In this work, we have reported a novel NO 2 sensor using molybdenum disulfide nanoparticles (MoS 2 NPs) decorated RGO (MoS 2 -RGO) hybrids as sensing materials, where MoS 2 -RGO hybrids were prepared by a two-step wet-chemical method. Firstly, MoS 2 NPs prepared by modified liquid exfoliation method from bulky MoS 2 powder. Then, MoS 2 -RGO hybrids were obtained by self-assembly of MoS 2 NPs and GO nanosheets, followed by a facile hydrothermal treatment progress. The combined characterizations indicate that MoS 2 NPs with the size of 3–5 nm are uniformly dispersed on RGO nanosheets. Most importantly, the sensor based on MoS 2 -RGO hybrids could detect NO 2 at room temperature. To further improve sensing performances, especially response and recovery rate, sensing properties are further examined by increasing the operation temperature to 160 °C. It is notably seen that MoS 2 -RGO-based NO 2 sensor not only shows improved sensitivity to NO 2 compared to pure RGO-based sensor, but also exhibits fast response and recovery characteristics (response time and recovery time are 8 s and 20 s toward 3 ppm NO 2 ). This work paves a new way for application of MoS 2 and RGO in chemical sensors, providing an effective method for fabrication of NO 2 sensors with high sensitivity and fast response/recovery rate. [ABSTRACT FROM AUTHOR]

The micro-motion of the machine is essential and valuable in environment, biology and medicine research. Environment-propelled micromotion can exhibit driven non-equilibrium behaviors. The energy conversation of micromotors from fluid environment would be an important power supply method for the distributed sensor network. Here, we report a kind of rotating motion of microturbines as micromotors driven by hydrodynamic liquid flow. By using femtosecond laser direct writing technology, the microturbine was fabricated, containing a simple and controllable structure of a fixed central axis and movable blades. The rotation speed could be controlled by the speed of flow, the blade tilt angle, the blade length and the blade number, and the rotation direction of microturbine could be decided by the tilt direction of blades. A dual linkage system constituted two microturbines could be designed and achieved. The ability to harness and control the power of motions appears an important requirement for further development of hydrodynamic flow-driven mechanical systems. [ABSTRACT FROM AUTHOR]

A novel organic-inorganic hybrid material with the core-shell framework was prepared by modifying the poly(vinylsulfonic acid, sodium salt) (PSS) on vinyl functionalized silica nanoparticles (VSNs) via the free radical polymerization. SNs with different contents of PSS were prepared and the structures were carefully characterized. The hybrid material could enhance the durability of PSS under high humidity environment. Meanwhile, the SNs skeleton provides interstitial channels in the PSS@SNs films, which are available for water molecules transport. The PSS coated SNs (PSS@SNs) films were formed by drop-coating and their sensing properties were investigated. The impedance of the optimal humidity sensor changed more than four orders of magnitude over the relative humidity range of 33–95%, with good linearity under semi-logarithm scale (R 2 = 0.950) and a small humidity hysteresis of 2% RH. The obtained sensor also showed rapid response to humidity change (the response and recovery time were 2 and 65 s, respectively). Finally, the resultant sensor was explored for respiratory rate monitoring. [ABSTRACT FROM AUTHOR]

Mesoporous silicas loading hydrophilic materials composites were widely used in humidity sensors during the last decade. However, the physical mixing process used for loading the hydrophilic materials in the channel of mesoporous silicas is hard to guarantee their uniform dispersion, and there is no strong force to bind the host and guest materials together. To solve above problems, novel vinyl functionalized mesoporous silicas (SBA-15-vinyl) were chemically modified with hydrophilic sodium p -styrenesulfonate (SSS) with free radical polymerization. The chemical and porous structures of the obtained hybrid materials (SBA-15-PSSx) were characterized by fourier transform infrared spectroscopy (FT-IR), elemental analyses (EA), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and N 2 adsorption-desorption. The humidity sensing properties of the sensors based on SBA-15-vinyl and SBA-15-PSS indicate the introduction of PSS could effectively enhance the sensing properties of SBA-15-vinyl. The impedance of the optimized sensor changed by more than three orders of magnitude over the relative humidity (RH) range of 11%–95%, with rapid response to RH change. [ABSTRACT FROM AUTHOR]

Herein, a novel electrochemical hydrazine sensor has been successfully fabricated using N-doped carbon film-immobilized Au nanoparticles coated ZnO jungle on indium tin oxide (AuNPs@NC-ZnO/ITO) as working electrode. The AuNPs@NC-ZnO/ITO has been prepared by an in situ synthesis method through the following steps. Firstly, the ZnO jungle modified ITO was prepared by electrochemical deposition method. Then, zeolitic imidazolate framework-8 (ZIF-8) film was formed on the surface of ZnO jungle by wet-chemical method using ZnO jungle and 2-methylimidazole as Zn precursor and organic ligand, respectively. The loading AuNPs was performed by adsorption of Au 3+ into micropores of ZIF-8, followed by heat treatment under N 2 atmosphere, where the ZIF-8 converted into N-doped carbon and Au 3+ converted into AuNPs embedded in N-doped carbon film. Most importantly, such AuNPs@NC-ZnO/ITO exhibited good electrocatalytic activity for the oxidation of hydrazine. The hydrazine sensor based on AuNPs@NC-ZnO/ITO showed linear detection range from 0.05 to 10 μM and detection limit of 4.1 nM at a signal-to-noise ratio of 3. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (RGO)-based NO 2 sensors have attracted considerable attention due to their excellent advantages of low power consumption and manufacturability to facilitate massive deployment. However, it is still a great challenge to fabricate RGO-based room-temperatureNO 2 sensors with excellent sensing performances. Herein, we have demonstrated a combined surface modification and heteroatom doping approach to enhance the sensing performances of RGO-based room-temperature NO 2 sensors, where SnO 2 nanoparticles modified nitrogen-doped RGO (SnO 2 /N-RGO) hybrids had been used as sensing materials. The SnO 2 /N-RGO hybrids were prepared by hydrothermal synthesis method using SnCl 4 , GO and urea as precursors. The combined characterizations of X-ray diffraction (XRD), energy-dispersive X-ray spectrometer (EDS), elemental mapping, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), Raman spectra as well as N 2 sorption isotherm were used to characterize the materials thus obtained, indicating the successful preparation of SnO 2 /N-RGO hybrids. During the hydrothermal progress, SnCl 4 conversed into SnO 2 nanoparticles (NPs), and GO was reduced into RGO, while urea was decomposed into nitrogen-containing molecule and doped into RGO. It is found that SnO 2 NPs with the size of 3–5 nm are uniformly dispersed on N-RGO nanosheets. Most importantly, SnO 2 /N-RGO hybrids-based sensor exhibits superior sensing performances toward NO 2 operated at room temperature, which are better than those of pure RGO and SnO 2 /RGO hybrids. For example, SnO 2 /N-RGO hybrids show response of 1.38 to 5 ppm NO 2 with the response time and recovery time of 45 s and 168 s. The excellent sensing performances are attributed to incorporation of N atoms into RGO and the modification of RGO with SnO 2 NPs. This novel sensor based on SnO 2 /N-RGO hybrids promises to provide an essential sensing platform for the detection of NO 2 with excellent sensing performances at room temperature. [ABSTRACT FROM AUTHOR]

The development of metal oxides-based gas sensors for DMMP detection simultaneously possessing low operating temperature, low limit of detection and high sensitivity remains formidable challenges. In this work, a facile and efficient colloidal assembly approach is proposed to prepare Au modified SnO 2 hybrids (Au-SnO 2) with perfect metal-semiconductor interface and successfully used in DMMP detection application. After optimization, the best DMMP sensors based on Au-SnO 2 hybrids display outstanding sensing performances, including high response (1.88 to 680 ppb DMMP), low operating temperature (200 °C), extremely low limit of detection (34 ppb), as well as short response/recovery time (25 s/72 s). The sensing mechanism analysis reveals that the excellent sensing performances are mainly attributed to the synergy of chemical oxidation of DMMP catalyzed by Au-SnO 2 hybrids and physical adsorption of DMMP by hydrogen-bonding interactions. The present work not only provides an insight into the DMMP sensing mechanism, but also offers a promising general approach for development of high-performance gas sensors. [Display omitted] • A facile and efficient colloidal assembly approach waa proposed to synthesize Au modified SnO 2 hybrids. • The Au-SnO 2 -based sensor exhibits high response of 1.88 towards 680 ppb DMMP. • The limit of detection of the Au-SnO 2 -based sensor was 34 ppb. • An integrated chemical oxidation and hydrogen-bonding DMMP sensing mechanism model was first proposed. [ABSTRACT FROM AUTHOR]

Abstract: In2O3 micro/nanotubes (MNTs) with different diameters are successfully synthesized by an effective and template-free coaxial electrospinning method. The diameters of the MNTs can be simply tailored by controlling the ratio of reactants. The HCHO sensing tests of as-prepared MNTs reveal that the samples possess high response value, fast response and recovery rate, and favorable selectivity. Moreover, compared with the large diameter (∼1μm or ∼500nm) In2O3 MNTs, the small diameter (∼100nm) In2O3 MNTs exhibit highly enhanced sensing properties. The gas sensing mechanism of In2O3 MNTs has been discussed in detail. The promising HCHO-sensing properties enable In2O3 MNTs to be a competitive candidate for detecting poisonous HCHO in practice. The experiment also indicates that the coaxial electrospinning is an environmental friendly and easy method for constructing tubular structure of metal oxides with different diameters for various applications. [Copyright &y& Elsevier]

• Polypyrrole decorated-reduced graphene oxide (PPy-rGO) hybrids were successfully synthesized by a self-redox strategy. • The PPy-rGO-3-based sensor exhibits a higher response and fast response and recovery behavior to DMMP than pristine rGO. • The enhanced DMMP sensing properties were attributed to formation of hydrogen bonds between DMMP and PPy. The development of fast-response, high sensitivity and selectivity gas sensors for monitoring of organophosphorus is essential, where two dimensional graphene-based materials possessing exceptionsal carrier mobility are considered as promising candidates for room-temperature organophosphorus detection. However, it is challenging to fabrication of graphene-based gas sensors for detection of organophosphorus with excellent sensing performances. Herein, we develope a self-redox strategy to synthesize polypyrrole decorated-reduced graphene oxide hybrids (PPy-rGO) by redox reactions between pyrrole and GO during hydrothermal treatment process. This self-redox strategy results in the formation of perfact interfical strucutre between PPy and rGO through the π-π interactions without the impurity from the conventional oxidation/reducing agents. Most importantly, such PPy-rGO hybrids can be used as novel sensing materials for detection of dimethyl methylphosphonate (DMMP) at room temperature. Specially, the response of PPy-rGO-based sensor towards 100 ppm DMMP can reach 12.9 %, which is 3-fold higher than that pristine rGO-based sensor. Meanwhile, PPy-rGO-based sensor exhibits short response time/recovery time (43 s/75 s), low detection limit (5 ppm), excellent repeatability, and high selectivity. By combination of FT-IR and N 2 sorption isotherms, the enhanced DMMP sensing performances of PPy-rGO hybrids are concluded as following two aspects. Firstly, the formation of hydrogen bonds between PPy-rGO hybrids and DMMP molecules regulates the adsorption/desorption of DMMP. Secondly, increasing BET surface area by introduction of PPy into rGO matrix is beneficial to DMMP diffusion among the sensing materials. Our work would offer a new strategy for rational development of graphene-based materials for detection of organophosphorus at room temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Humidity sensors based on glycidyl trimethyl ammonium chloride (EPTAC) modified cellulose paper via a facile solution method were fabricated. • The paper is used for the purpose of the humidity sensing material and the sensor substrate. • The as-fabricated paper-based humidity sensor is provided with outstanding humidity sensing properties and good stability. • The humidity sensor was applied to multifunctional applications including human breath rate, non-contact switch and skin humidity. It is of great significance to exploit a simple, cost-effective and environmentally friendly preparation method of multifunctional humidity sensors. However, most humidity sensors need complex manufacturing processes, high cost and narrow usage range. Herein, humidity sensors based on glycidyl trimethyl ammonium chloride (EPTAC) modified cellulose paper via a facile solution method were fabricated, among which the paper is used for the purpose of the humidity sensing material and the sensor substrate. The sensitivity of the obtained sensor was improved by the modification of EPTAC, the response time was decreased to 25 s, which is equivalent to the first-rate paper-based humidity sensors. In addition, the paper-based humidity sensor is provided with well flexibility and biocompatibility, and it exhibits multifunctional applications in respiratory monitoring, non-contact switch and skin humidity monitoring. The low cost and facile preparation technique in this work could provide a useful strategy for developing multifunctional humidity sensor. [ABSTRACT FROM AUTHOR]

• The porous ionogel humidity sensitive material was successfully fabricated with the aid of PAA as the template and humidity sensing component. • The humidity sensor based on the porous ionogel shows rapid response (1.2/0.6 s) to humidity change. • Various molecular weights PAA were applied to investigate PAA's function in pore construction and humidity sensing. • The ultrafast-response humidity sensor can accurately record the human breath in real time, which is benefit for respiration data calculation. Electronic devices that can accurately record and monitor human respiration in real-time are of great interest for researchers. Ultrafast-response ionogel humidity sensors that can follow the human respiration were realized by an in-situ vinyl-thiol click reaction in this work. Polyacrylic acid (PAA) was utilized both as the template to construct porous films and for preparing humidity sensing component. The obtained optimal sensor owns a rapid response to humidity change (response and recovery time is 1.2 s and 0.6 s, respectively) and a small humidity hysteresis (∼2.2% RH). The water adsorption capability and sensing mechanism were investigated systematically. The ionogel humidity sensor with good stability and repeatability was applied in breath monitoring, which has a great potential application in diagnostic breath analysis. [ABSTRACT FROM AUTHOR]

• An ultrafast-response humidity sensor based on gel polymer electrolytes was fabricated. • The humidity sensors were in situ prepared facilely on the substrate by thiol-ene click chemistry reaction in batches. • The sensitive materials with the three-dimensional network structure guarantee the stability under high humidity. • A novel mechanism is proposed and studied in detail by QCM sensors and Cole-Cole plots. • The humidity sensor was successfully applied to human breath monitoring due to the particularly rapid response. Respiratory monitoring is crucial for the assessment of human health, and can be realized by detecting the humidity of exhaled gases. In this work, a facile method for the in situ fabrication of stable humidity sensors based on gel polymer electrolytes was developed. The obtained humidity sensors demonstrate ultrafast response/recovery times (0.19/0.30 s), which are very promising for monitoring respiration. Reliable signals for different respiratory states were obtained via humidity sensors. In addition, the ultrafast-response mechanism of the sensors was investigated using complex impedance spectroscopy and a quartz crystal microbalance (QCM). [ABSTRACT FROM AUTHOR]