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Toxic acetone gas emissions and leakage are a potential threat to the environment and human health. Gas sensors founded on metal oxide semiconductors (MOS) have become an effective strategy for toxic gas detection with their mature process. In the present work, an efficient acetone gas sensor based on Au-modified ZnO porous nanofoam (Au/ZnO) is synthesized by polyvinylpyrrolidone-blowing followed by a calcination method. XRD and XPS spectra were utilized to investigate its structure, while SEM and TEM characterized its morphology. The gas sensitivity of the Au/ZnO sensors was investigated in a static test system. The results reveal that the gas-sensitive performance of porous ZnO toward the acetone can be enhanced by adjusting the loading ratio of noble Au nanoparticles. Specifically, the Au/ZnO sensor prepared by the Au loading ratio of 3.0% (Au/ZnO-3.0%) achieved a 100 ppm acetone gas response of 20.02 at the optimum working temperature of 275 °C. Additionally, a portable electronic device used a STM32 primary control chip to integrate the Au/ZnO-3.0% gas sensor with other modules to achieve the function of detecting and alarming toxic acetone gas. This work is of great significance for efficiently detecting and reducing acetone emissions. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) with one-dimensional nanostructure are an ideal support for oxygen reduction reaction (ORR) catalysts thanks to their intrinsic outstanding electrical conductivity and high specific surface area. Iron and nitrogen doping could alter the local electronic structure and therefore enhance the ORR activity of MWCNTs, but the preparation process always includes complicated growth conditions and post-treatment. Herein, an iron and nitrogen co-modified multi-walled carbon nanotubes (Fe–N-MWCNTs) with hierarchical nanostructure is engineered and synthesized via a simple two-step pyrolysis approach. Large specific surface area, low resistivity, and intensified charge density near the Fermi level synergistically endow the Fe–N-MWCNTs with outstanding ORR activity. The optimal Fe–N-MWCNTs exhibit a higher onset potential value of 0.92 V (versus RHE) and half-wave potential (E 1/2) of 0.85 V (versus RHE) in 0.1 M KOH medium, which exceeds the benchmark Pt/C electrocatalyst (E 1/2 = 0.84 V). This strategy of modifying MWCNTs support by a simple calcination process provides a feasible method to prepare cost-efficient ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Developing efficient drug-detecting technologies is critical to the fight against their related abuse and trafficking crimes. In the present work, a novel morphine detection device based on metal-oxide-semiconductor (MOS) gas sensors with low-cost, highly sensitive, and portable is designed and fabricated. The exclusive sensitive material, ZnO nanoparticles self-assembly porous networks (ZnO-N) with ample oxygen vacancies (O V) defects prepared by PVP-chelated precipitation followed by a chemical blowing calcination method, is decisive to morphine drug identification. O V defects can modulate the intrinsic electronic structure and endow ZnO-N with more suitable band structures for enhancing oxygen species adsorption and morphine molecules oxidation. The optimal ZnO-N-2 sensor exhibits positive linear relationship response values of 1.1–8.8 in the concentrations of 2–200 ppm toward the standard morphine drug sample at the optimal operating temperature of 250°C. More importantly, the homemade portable device equipped with the ZnO-N-2 sensor can accurately identify the morphine drug and perform early warning. This work innovatively demonstrates the feasibility of MOS gas sensors for the detection of stashing morphine drugs in methanol, which is of great significance for effectively combating global drug-related crimes. [Display omitted] • Designed a novel morphine drug detection device based on the MOS gas sensor. • The portable device can perform early warning when detecting morphine drug. • The exclusive ZnO-sensitive material is decisive to morphine drug identification. • The ZnO presents porous networks nanostructure with ample oxygen vacancies defects. • Defects modulate the intrinsic electronic structure of ZnO. [ABSTRACT FROM AUTHOR]

A novel porous bimetallic cobalt-iron phosphide nanofoam is designed to enhance the performance of oxygen evolution reaction (OER). Its surface undergoes a reconstruction process and forms new high active (Co x Fe 1− x)OOH. Bimetal Co and Fe optimized the d -band centers and thus balanced the adsorption–desorption capacities for OER intermediates, which contributes to lowering the overpotential (258 mV@10 mA cm−2) and enhancing the long-term stability (70 h@100 mA cm−2). [Display omitted] Developing oxygen evolution reaction (OER) catalysts with high activity and long-term stability is critical to achieving efficient hydrogen production from water electrolysis. Herein, a porous bimetallic cobalt-iron phosphide (CoFe-P) nanofoam is synthesized via a novel one-pot glucose-blowing followed by oxidization and then phosphidization process. The CoFe-P nanofoam presents a porous nanostructure which contributes to contact with electrolytes and release of generated gas during electrocatalytic reactions. As OER catalysts in alkaline, the bimetallic porous CoFe-P nanofoam exhibit a lower overpotential (258 mV@10 mA cm−2) as well as outstanding stability (70 h@100 mA cm−2), which surpasses the RuO 2 and is comparable to many high-performance Co and Fe-based catalysts. It is demonstrated that the surface of CoFe-P undergo a reconstruction process and form new high active (Co x Fe 1−x)OOH. Density functional theory (DFT) calculations reveal that the elevated activity is caused by the bimetal Co and Fe optimizing the d -band center (E d) energy levels and thus balancing the adsorption–desorption capacities for OER intermediates. This work through constructing porous bimetallic nanofoam offers a feasible strategy to facilitate the reaction activity and prolong the long-term stability of OER. [ABSTRACT FROM AUTHOR]

A novel ultrasonic-assisted Fenton reaction inducing surface reconstruction strategy enables the low-spin states of Ni2+ (t 2 g 6 e g 2) and Fe2+ (t 2 g 4 e g 2) on the NiFe-LDH surface to partially transform into high-spin states of Ni3+ (t 2 g 6 e g 1) and Fe3+ (t 2 g 3 e g 2) and formation of the highly active species of NiFeOOH. The as-prepared electrode not only shows superior activity for water oxidation but also for various organics electrooxidation. [Display omitted] Nickel/iron-layered double hydroxide (NiFe-LDH) tends to undergo an electrochemically induced surface reconstruction during the water oxidation in alkaline, which will consume excess electric energy to overcome the reconstruction thermodynamic barrier. In the present work, a novel ultrasonic wave-assisted Fenton reaction strategy is employed to synthesize the surface reconstructed NiFe-LDH nanosheets cultivated directly on Ni foam (NiFe-LDH/NF-W). Morphological and structural characterizations reveal that the low-spin states of Ni2+ (t 2 g 6 e g 2) and Fe2+ (t 2 g 4 e g 2) on the NiFe-LDH surface partially transform into high-spin states of Ni3+ (t 2 g 6 e g 1) and Fe3+ (t 2 g 3 e g 2) and formation of the highly active species of NiFeOOH. A lower surface reconstruction thermodynamic barrier advantages the electrochemical process and enables the NiFe-LDH/NF-W electrode to exhibit superior electrocatalytic water oxidation activity, which delivers 10 mA cm−2 merely needing an overpotential of 235 mV. Besides, surface reconstruction endows NiFe-LDH/NF-W with outstanding electrooxidation activities for organic molecules of methanol, ethanol, glycerol, ethylene glycol, glucose, and urea. Ultrasonic-assisted Fenton reaction inducing surface reconstruction strategy will further advance the utilization of NiFe-LDH catalyst in water and organics electrooxidation. [ABSTRACT FROM AUTHOR]

A novel crystalline carbon modified hierarchical porous iron and nitrogen co-doped carbon (Fe-N/C) electrocatalyst with enhanced electronic conductivity is designed and prepared. The crystalline carbon provides a faster channel for electron transport in the oxygen reduction reaction, thereby enhancing the electrocatalytic activity. [Display omitted] Hierarchical porous iron and nitrogen co-doped carbon (Fe-N/C) materials have been considered as an appealing non-noble metal-based catalyst in oxygen reduction reactions (ORR). However, the conductivity loss caused by the scattering of electrons on pores and defects markedly limits their catalytic activity, which attracted seldom attention in this area. Herein, a novel crystalline carbon modified hierarchical porous Fe-N/C electrocatalyst with enhanced electronic conductivity is designed and prepared via a two-step calcination-catalysis process. The resistivity of hierarchical porous Fe-N/C is decreased from 2.123 Ω cm to 0.479 Ω cm after crystalline carbon introduction. The electrocatalyst annealed at 800 °C (Fe-N/C-800) exhibits a superior activity with the half-wave potential (E 1/2) of 0.89 V, which outperforms the commercial carbon-supported platinum (Pt/C) catalyst (0.85 V). The strategy of crystalline carbon modification provides a fresh approach to improve the electronic conductivity of porous carbon-based materials. [ABSTRACT FROM AUTHOR]

A novel porous nanoscale NiO/NiCo 2 O 4 heterostructure with abundant interfaces is designed to enhance the performance of oxygen evolution reaction (OER). The NiO/NiCo 2 O 4 heterostructure exhibits superior OER activity with a low overpotential (264 mV @10 mA cm−2) and small Tafel slope (44.2 mV dec−1). It also showcases excellent electrochemical stability which can remain stable over 24 h at 100 mA cm−2. • Nanoscale NiO/NiCo 2 O 4 heterostructure is fabricated by two-stage calcination approach. • The electrocatalyst possesses abundant pores and heterostructure interfaces. • Porous nanostructure exposes more active sites. • Ni3+ species endow the catalyst with superior intrinsic activity. • Interfaces promote the chemisorption of oxygen-containing intermediates. Developing highly active and inexpensive electrocatalysts for oxygen evolution reaction (OER) is critical to large-scale applications of electrochemical water splitting. In the present work, a novel porous NiO/NiCo 2 O 4 heterostructure is constructed by two-stage calcination of nickel-cobalt bimetallic hydroxide precursors prepared using a microwave-assisted hydrothermal method, in which abundant interfaces are constituted. The NiO phase stabilized in NiCo 2 O 4 matrix is the nanometer scale (ca. 13 nm). The porous nanoscale NiO/NiCo 2 O 4 heterostructure shows a 10 mA cm−2 current density under the overpotential of 264 mV which outperforms the noble catalyst RuO 2. It is demonstrated that the highly active Ni3+ species generated by the oxidation of nanometer scale NiO surface are responsible for enhanced OER. Additionally, DFT calculations certify that the heterostructure interfaces promote the chemisorption of OH intermediates. This strategy of increasing the intrinsic activity and improving the chemisorption abilities for oxygen-containing intermediates by constructing nanoscale heterostructure electrocatalysts provides a feasible method to accelerate the reaction rate of OER. [ABSTRACT FROM AUTHOR]

A series of silver nanoparticle-modified graphitic carbon nitride/N-doped TiO hybrids (Ag/g-CN/N-TiO or ACTs) were prepared by one-step in situ calcination process at 550 °C for 3 h in air atmosphere. The morphology, structure, and optical properties of ACTs with different Ag contents were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra, and UV-vis diffuse reflectance spectroscopy. Ag nanoparticles with grain size of about 5 nm are anchored on the surface of ACTs. In UV-vis absorption test, a red-shift of light absorption edge and more visible light absorption (compared to N-TiO and g-CN/N-TiO) are observed for ACTs. Moreover, the dependence of photocatalytic activity on Ag contents was investigated, and ACTs-3 presents the highest photocatalytic activity as the optimal Ag content under visible light irradiation. Remarkably enhanced UV-visible light photoelectrochemical response was also confirmed for ACTs compared with TiO, N-TiO, and g-CN/N-TiO. Ag-decorated g-CN/N-TiO composites result in enhanced light absorption capacity and improved transfer of charge carriers, which prominently contribute to the improvement of photoactivity. This work demonstrates that Ag/g-CN/N-TiO is a promising photocatalytic material for organic pollutant degradation under visible light irradiation. [ABSTRACT FROM AUTHOR]

A facile in situ self-catalysis and subsequent chemical transformation route were developed to encapsulated ultrafine FeSe 2 nanoparticles into bamboo-like 3D N-doped carbon nanotubes networks. Realizing excellent lithium and sodium ion storage performances. The Li+/Na+ storage mechanisms were investigated via in situ characterization tests and density functional theory (DFT) calculations. [Display omitted] • A facile in situ self-catalysis and subsequent chemical transformation route has been explored to FeSe 2 @CNTs composite. • The ultrafine FeSe 2 nanoparticles were encapsulated within the bamboo-like N-doped carbon nanotubes. • The in situ electroanalytical techniques and DFT calculations reveal the energy storage mechanism. • The FeSe 2 @CNTs composite exhibits ultratable cycling performance and ultrahigh rate capability. Encapsulating the multifunctional nanostructures within a lightweight nanocarbon network is considered to be a promising strategy for developing state-of-the-art electrodes for alkali metal-ion batteries (AMIBs). Herein, the ultrafine FeSe 2 nanoparticles (NPs) were encapsulated within the bamboo-like N-doped carbon nanotubes (FeSe 2 @CNTs) via a rationally in situ self-catalysis and subsequent chemical transformation, realizing a workable capacity and stable architecture. The 3D interactive CNT network provides a fast electron/ion conducting path, and constructs a solid electronic link between the CNTs and FeSe 2 NPs. The ultrafine dimension of FeSe 2 NPs ensures small volume change and short Li+/Na+ diffusion distance during charge and discharge. Profiting from the fast transport capability of both electrons and ions, the unique FeSe 2 @CNTs exhibits outstanding host potential for Li+ storage with a capability of 397 mA h g−1 at 10 A g−1. Serving as anode for Na+ storage, the optimized electrode possesses excellent rate capability of 329 mA h g−1 at 8 A g−1. Additionally, the Li+/Na+ storage mechanisms are further revealed by in situ electrochemical techniques and density functional theory (DFT) calculations. The present work inspired a new window for developing high-performance hybrids towards various electrochemical energy applications. [ABSTRACT FROM AUTHOR]

Abstract Graphene promoted triphasic N/Ti3+-TiO 2 (GNTT) heterostructures with different weight addition ratios of graphene have been assembled by a facile in-situ hydrothermal treatment of TiN and graphene oxide. The obtained GNTT photocatalysts are characterized by a collection of techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and photoluminescence (PL), etc. It is demonstrated that graphene modified N/Ti3+ codoped TiO 2 with ternary phases mixture of brookite, anatase and rutile can be obtained. Furthermore, the GNTT heterostructure photocatalysts exhibit an enhanced photoactivity for photocatalytic degradation of methyl blue, levofloxacin, and rhodamine B as compared with TiO 2 , N-doped TiO 2 , and N/Ti3+ codoped TiO 2 (NTT). The reason for the improved photoactivity can be listed as follows: i) N and Ti3+ doping can severally form N2p impurity level above valance band (VB) and local states below the conduction band (CB) of TiO 2 , which contribute to the visible light response of TiO 2 ; ii) the ternary heterophase junction can efficiently transfer and separate photogenerated electron-hole pairs; iii) graphene acts as an electron reservoir to trap and transport the electrons photogenerated from TiO 2. The synergistic effect of these factors accounts for the photoactivity advancement of GNTT photocatalysts. This study develops a novel approach to improve the visible light utilization of TiO 2 and facilitates their applications in the environment and energy issues. Graphical abstract Image 1 Highlights • One step hydrothermal synthesis of graphene promoted triphasic N/Ti3+-TiO 2 composites. • N and Ti3+ codoping contributes to the improvement of visible light response of TiO 2. • Heterophase junction and heterojunction promotes the separation of electron-hole pairs. • Enhanced photocatalytic degradation of organic pollutants was demonstrated. [ABSTRACT FROM AUTHOR]

The all-trans conformation (β -phase) possesses a significant impact on the piezoelectric polymer polyvinylidene fluoride (PVDF). Inducing more molecular chain [−CH2−CF2−] n to form all-trans conformation is one of the biggest obstacles for manufacturing high-performance piezoelectric sensing devices. Herein, the continuous vacuum technology is used to modulate the polarity of binary solvents by the proportion of the lower solvent. The regulated solvent forms a high dipole moment, an interaction between the dipole of β -phase and the dipole moment makes the phase reversal in PVDF. Fourier transform infrared spectroscopy, piezoelectric constant test and other characterization results show that when the weakly polar acetone and the strongly polar solvent DMF reach a ratio of 4:6, the pure PVDF film possesses high piezoelectricity (d 33 ∼ −44.8 pC N−1) and strong self-polarization. Additionally, the A4D6 device exhibits high sensitivity (S 1 = 0.182 V/N, 0.5 N ∼ 30 N), driven capability (0.49 mW m−2), and reliability during the electrical tests as a pressure device. This work provides an effective and cost-effective route of optimizing the solvent's polarity to improve the piezoelectric characteristics of the polymer. [ABSTRACT FROM AUTHOR]

For real-time and in-situ NO x monitoring in an online vehicle diagnosis (OBD) system, yttria-stabilized zirconia (YSZ) based high-performance NO 2 mixed potential sensor was successfully fabricated with an MMn 2 O 4 (M = Co, Cd and Zn) sensing electrode(SE). Compared to CdMn 2 O 4 and CoMn 2 O 4 , the ZnMn 2 O 4 sensing electrode had the smallest interface resistance to 100 ppm NO 2 , and the sensor based on ZnMn 2 O 4 -SE exhibited the highest response. To further improve the sensing performance of the device, the effect of the sintering temperature was studied and the sensor based on ZnMn 2 O 4 sintered at 1000 °C has the highest response of 23 mV to 10 ppm NO 2. Moreover, the present NO 2 sensor has a wide detection range of 1–1000 ppm, with sensitivities of 18 mV/decade for 1–10 ppm NO 2 and 64 mV/decade for 10–1000 ppm NO 2. In addition, the device also performs excellent repeatability, terrific selectivity, acceptable O 2 resistance and marvelous long-term stability during continuous measurements over 10 days. Overall, based on its excellent sensing performance, the developed sensor has marvelous application prospects for in-situ NO x monitoring in online vehicle diagnosis (OBD) systems. [ABSTRACT FROM AUTHOR]

Chemically bonded graphene/TiO 2 nanorod hybrid composites with superior dispersity were synthesized by a one-step in situ hydrothermal method using graphene oxide (GO) and TiO 2 (P25) as the starting materials. The as-prepared samples were characterized by XRD, XPS, TEM, FE-SEM, EDX, Raman, N 2 adsorption, and UV–vis DRS techniques. Enhanced light absorption and a red shift of absorption edge were observed for the composites in the ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). Their effective photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light irradiation. An enhancement of photocatalytic performance was observed over graphene/TiO 2 nanorod hybrid composite photocatalysts, as 3.7 times larger than that of pristine TiO 2 nanorods. This work demonstrated that the synthesis of TiO 2 nanorods and simultaneous conversion of GO to graphene “without using reducing agents” had shown to be a rapid, direct and clean approach to fabricate chemically bonded graphene/TiO 2 nanorod hybrid composites with enhanced photocatalytic performance. [ABSTRACT FROM AUTHOR]

The acetone concentration in exhaled breath can be utilized for the noninvasive diagnosis of diabetes. In this study, to fulfil the requirements of breath analysis for diabetes diagnosis, high-performance mixed-potential acetone sensors based on yttria-stabilized zirconia were successfully developed by employing a novel sensitive electrode (SE) material, namely, LaBaCo 2 O 5+δ. Electrochemical measurement results revealed that the LaBaCo 2 O 5+δ SE, sintered at 1000 ℃, exhibited outstanding electrochemical catalytic activity toward acetone. The device incorporating this SE demonstrated a peak response of −46 mV to 100 ppm acetone at 655 ℃. Sensitive performance assessments indicated the capability of the sensor to detect acetone concentrations ranging from 200 ppb to 100 ppm. Based on the mixed-potential model, the sensitivities of the current device were quantified as −1.3 and −53.7 mV/decade within the acetone concentration ranges of 0.2−5 and 10−100 ppm, respectively. Furthermore, the fabricated sensor exhibited exceptional selectivity, repeatability, humidity resistance, and long-term stability. In addition, simulated expiratory experiments showed that the developed sensor has substantial potential for application in breath analysis for diabetes diagnosis and noninvasive monitoring of a patient's physical status. ● Varying the sintering temperature of a material to tune its micro- and nanostructure. ● The sensor with LaBaCo 2 O 5 -1000-SE shows a low detection limit of 200 ppb for acetone. ● The potential for noninvasive testing is verified by simulated exhaling experiments. [ABSTRACT FROM AUTHOR]

For hazardous gas monitoring and non-invasive diagnosis of diabetes using breath analysis, porous foams assembled by Co 3 O 4 nanoparticles were designed as sensing electrode materials to fabricate efficient yttria-stabilized zirconia (YSZ)-based acetone sensors. The sensitivity of the sensors was improved by varying the sintering temperature to regulate the morphology. Compared to other materials sintered at different temperatures, the porous Co 3 O 4 nanofoams sintered at 800 °C exhibited the highest electrochemical catalytic activity during the electrochemical test. The response of the corresponding Co 3 O 4 -based sensor to 10 ppm acetone was –77.2 mV and it exhibited fast response and recovery times. Moreover, the fabricated sensor achieved a low detection limit of 0.05 ppm and a high sensitivity of –56 mV/decade in the acetone concentration range of 1–20 ppm. The sensor also exhibited excellent repeatability, acceptable selectivity, good O 2 /humidity resistance, and long-term stability during continuous measurements for over 30 days. Moreover, the fabricated sensor was used to determine the acetone concentration in the exhaled breaths of patients with diabetic ketosis. The results indicated that it could distinguish between healthy individuals and patients with diabetic ketosis, thereby proving its abilities to diagnose and monitor diabetic ketosis. Based on its excellent sensitivity and exhaled breath measurement results, the developed sensor has broad application prospects. [Display omitted] • Porous Co 3 O 4 nanofoams were first designed to fabricate YSZ-based acetone sensor. • An efficient, stable, and inexpensive method has been proposed. • Low detection limit was 50 ppb with high sensitivity and excellent stability. • The sensor can distinguish healthy people from diabetic ketosis patients. • Fabricated sensor has broad application prospects in actual environment test. [ABSTRACT FROM AUTHOR]

In this paper, for the detection of hazardous gas hydrogen sulfide (H 2 S), new type YSZ (yttria stabilized-zirconia)-based mixed potential gas sensor is developed and K 2 NiF 4 type oxides Nd 2 AO 4 (A=Cu, Ba and Ni) are successfully synthesized as sensing electrode (SE). XRD results shows the materials have pure phase K 2 NiF 4 -type oxides. Compared with other sensors, the sensor based on Nd 2 NiO 4 sensing electrode has the highest response value to 1 ppm H 2 S. Polarization curve results show that the reason for the highest response value is that it has the strongest electrochemical catalytic activity to H 2 S. Moreover, the response of the sensor based on Nd 2 NiO 4 -SE to 1 ppm H 2 S is − 28 mV with fast response/recovery time (70 s/135 s). The low detection range is 0.05 ppm, meeting the requirement of security monitoring field. The sensitivities of the sensor to 0.05–0.2 ppm and 0.2–10 ppm H 2 S are − 5 mV/decade and − 63 mV/decade respectively. Besides, the present device also performs good repeatability, excellent selectivity and acceptable stability during 30 days continuous measurement, which demonstrated that the sensor we fabricated has a good application prospect for the field of real-time and in-situ security monitoring of hydrogen sulfide. • Mixed potential sensor based on YSZ and new type sensing material Nd 2 AO 4 (A=Cu, Ba and Ni) was designed for H 2 S detection. • The device utilizing Nd 2 NiO 4 -SE performed the largest response of − 28 mV to 1 ppm H 2 S. • The low detection limit of the sensor was 50 ppb with fast respone and recovery. • The sensor has acceptable long-term stability, which meet the requirement of the in-situ security monitoring [ABSTRACT FROM AUTHOR]

[Display omitted] • In situ growth of Co 3 O 4 nanorods and nanosheets arrays with exposing different crystal facets. • Co 3 O 4 nanorods with exposed (1 1 0) facet demonstrates the highest sensing characteristics in ethanol. • The synergistic adsorption effect between the -OH and the surface of Co and low coordination O atom on the surface of Co 3 O 4 (1 1 0). • The exist of synergistic adsorption sites promotes the gas sensing property of Co 3 O 4 -NR. A deep understanding of the relationship between the properties and structure of transition metal oxide semiconductor gas sensors is essential for optimizing sensor design. Comparing and analyzing the sensing properties of nanomaterials with different morphologies and crystal facets by combining the experiment analysis and the density functional theory (DFT) calculations could identify and understand the corresponding mechanisms at the atomic or ionic level. Here, grown Co 3 O 4 nanosheet (Co 3 O 4 -NS) with exposed (1 1 1) facets, and Co 3 O 4 nanorods (Co 3 O 4 -NR) with exposed (1 1 0) facets on alumina ceramic tubes were prepared and studied in sensing ethanol. The adsorption characteristics of ethanol on the sensor surface were analyzed by DFT calculation. The results demonstrated that the sensing performance of Co 3 O 4 -NR was superior to Co 3 O 4 -NS. The adsorption of hydroxyl groups in ethanol was better than the methyl groups on the surface. The oxygen and hydrogen atoms from the hydroxyl groups in ethanol had the lowest adsorption energies (E ads = −3.44 eV) when they interact with the Co atom and the indirectly adjacent low-coordinate oxygen atoms on the (1 1 0) surface, respectively. The synergistic adsorption of target gases by exposed surface atoms induced superior sensing properties of the material. [ABSTRACT FROM AUTHOR]

MoS 2 /CdS/TiO 2 nanocomposites were synthesized via one-step in situ solvothermal method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron micrograph, X-ray photoelectron spectroscopy, photoluminescence spectra, Ultraviolet–Visible diffuse reflectance spectroscopy, and photocatalytic measurement. Enhanced visible light photoresponse, higher efficiency of charge carriers separation, and improved photocatalytic degradation of methylene blue were confirmed for MoS 2 /CdS/TiO 2 nanocomposites. It was observed that the highest degradation ratio was achieved for MoS 2 /CdS/TiO 2 nanoparticles (72%) prepared at 180 °C when exposed to visible light illumination for 160 min relative to CdS/TiO 2 (59%) and TiO 2 (29%). Furthermore, the improved photocatalytic performance of MoS 2 /CdS/TiO 2 nanoparticles was also demonstrated by the degradation of colorless resorcinol under UV–vis light irradiation. This work demonstrates that synergetic effect of MoS 2 and CdS in which it proves to be a good choice for improving the utilization of visible light of TiO 2 -based materials. [ABSTRACT FROM AUTHOR]

Herein, we report the successful formation of graphitic carbon nitride coated titanium oxide nanotube array thin films (g-C3N4/TiO2) via the facile thermal treatment of anodized Ti sheets over melamine. The proportion of C3N4 and TiO2 in the composite can be adjusted by changing the initial addition mass of melamine. The as-prepared samples are characterized by several techniques in order to understand the morphological, structural, compositional and optical properties. UV-vis absorption studies exhibit a remarkable red shift for the g-C3N4/TiO2 thin films as compared to the pristine TiO2 nanotubes. Importantly, the prepared composites exhibit an enhanced photocurrent and photo-potential under both UV-vis and visible light irradiation. Moreover, the observed maximum photo-conversion efficiency of the prepared composites is 1.59 times higher than that of the pristine TiO2 nanotubes. The optical and electrochemical impedance spectra analysis reveals that the better photo-electrochemical performance of the g-C3N4/TiO2 nanotubes is mainly due to the wider light absorption and reduced impedance compared to the bare TiO2 nanotube electrode. The presented work demonstrates a facile and simple method to fabricate g-C3N4/TiO2 nanotubes and clearly revealed that the introduction of g-C3N4 is a new and innovative approach to improve the photocurrent and photo-potential efficiencies of TiO2. [ABSTRACT FROM AUTHOR]

Pt-doped α -Fe 2 O 3 mesoporous microspheres for acetone detection with high sensitivity and selectivity. [Display omitted] • A simple solvothermal method was used to synthesize Pt-doped α -Fe 2 O 3 mesoporous microspheres. • The sensor based on Pt-doped α -Fe 2 O 3 presents superior sensing properties to 100 ppm of acetone with response of 105 at a low operating temperature of 175 °C. • The gas sensor manifests satisfied humidity resistance, stability and low detection limit as low as 20 ppb toward acetone. • A simulated detection of human breath components was carried out, and the sensor achieved effective identification of acetone gas. In this study, Pt-doped α -Fe 2 O 3 mesoporous microspheres were prepared by a simple solvothermal method and used for the detection of acetone. XRD, SEM, TEM, Raman, FT-IR, XPS, UV–vis and O 2 -TPD were utilized to characterize the structure and chemical properties of the samples. Different components were prepared by controlling the amount of the amount of Pt, and the corresponding sensing performance detection was carried out. The excellent sensing performance was obtained in the sample of 2 at% Pt-doped α -Fe 2 O 3 (Pt 2% -Fe). At a lower operating temperature (175 °C), the Pt 2% -Fe sensor response of 100 ppm acetone reaches 105, which is 2.5 times of pure α -Fe 2 O 3. Even the concentration reduces to 20 ppb acetone, the response can still reach 1.24 at 175 °C. Meanwhile, the favorable sensing performance can still be maintained under high humidity (90 % RH). The addition of Pt increases the specific surface area and reduces the band gap of the sensitive material. The excellent acetone sensing performance indicated that doping Pt effectively increases the adsorption capacity (catalytic properties) of the surface for the sensitive material and the sensitivity to the target gas (alter in the depletion layer). Hence, this high response, low detection limit and good moisture resistance sensor has a significant potential in the detection of acetone in human breath. [ABSTRACT FROM AUTHOR]

Carbon-incorporated TiO 2 microspheres (CTMs), produced by a flame assisted hydrolysis method, were successfully decorated with Cu 2 O nanoparticles via a chemical bath deposition process. A red shift of absorption edge and enhanced visible light absorption were observed for the resulted Cu 2 O/CTMs composites compared with bare TiO 2 and CTMs. Their effective visible-light-driven photocatalytic activity and the effect of deposition amount of Cu 2 O on the photocatalytic properties were determined by the degradation of methylene blue. The highest degradation rate was achieved for Cu 2 O/CTMs composite (29.2%) compared to CTMs (18.5%) and bare TiO 2 (7.3%) under visible light illumination for 80 min. The improved photoactivity can be ascribed to the integrative synergistic effect of carbon and Cu 2 O on TiO 2 . This work develops a rapid and facile approach for the fabrication of Cu 2 O decorated carbon-incorporated TiO 2 microspheres composites and demonstrates it is an efficient route to improve the photocatalytic activity of TiO 2 . [ABSTRACT FROM AUTHOR]

CdS photocatalysts loaded with AgS and MoS as dual co-catalysts were prepared via a one-step in situ hydrothermal method using CdCl·2.5HO, HMoO, AgNO·9HO, and CS(NH) as the raw materials. The as-prepared photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron micrograph, X-ray photoelectron spectroscopy, photoluminescence spectra, and Ultraviolet-Visible diffuse reflectance spectroscopy (UV-Vis DRS). The highest photocatalytic degradation rate was achieved for AgS/MoS/CdS composites (87 %) compared to MoS/CdS composites (66 %) and CdS (62 %) under visible light illumination for 60 min. The recycled photocatalytic experiments showed that the photocatalytic stability of CdS was improved with the introduction of AgS and MoS. The improved photocatalytic performance of AgS/MoS/CdS composites can be ascribed to the red shift of absorption edge, enhanced light absorption intensity, and the increased separation of the photoinduced electron-hole pairs, which was attributed to the synergetic effect of MoS and AgS on CdS. It was proven that AgS and MoS can act as effective dual co-catalysts to enhance the photocatalytic degradation activity of CdS. [ABSTRACT FROM AUTHOR]

A ternary composite of Cu 2 O, graphene and rutile TiO 2 nanorods was prepared using Cu(CH 3 COO) 2 ·H 2 O, graphene oxide and TiCl 4 as the starting materials and its enhanced photocatalytic performance was demonstrated. Graphene/TiO 2 nanorod composites (GT) were obtained by a simple hydrothermal method and then, Cu 2 O was coupled onto the surface of graphene/rutile TiO 2 to form Cu 2 O/graphene/rutile TiO 2 nanorod (CGT) composites via a chemical bath deposition process. The as-prepared sample was characterized by X-ray diffraction (XRD), emission field scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), specific surface area analyzer (BET), Raman spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). It is found that the introduction of graphene and Cu 2 O has little effect on the morphology of TiO 2 nanorods with average dimensions of 140 nm (length) × 30 nm (diameter) (L/D ratio ≈5). A red shift of light absorption edge and more absorption in the visible light region were observed for the resulted ternary samples compared with TiO 2 and graphene/TiO 2 composites. The photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light irradiation, which showed 2.8 times corresponding enhancement of the degradation efficiency for the ternary composites compared with TiO 2 . This work provides a new strategy to improve the visible light response of TiO 2 and facilitate its application in environmental remediation. [ABSTRACT FROM AUTHOR]