水热法制备MoO3-GQDs的三甲胺气敏性能

采用水热法制备了一系列具有不同碳量子点(GQDs)含量的MoO3?GQDs纳米复合材料,利用X射线衍射、扫描电子显微镜、透射电子显微镜、FTIR等对MoO3?GQDs复合材料进行了表征,研究了其气敏性能。结果表明,复合材料中GQDs的含量对MoO3?GQDs复合材料的气敏响应和选择性有显著影响。MoO3?GQDs纳米复合材料(S?6,GQDs悬浮液的含量为6 mL)传感器在230℃时对三甲胺(TMA)表现出高的气敏响应和好的气敏选择性;该传感器对1000μL·L^-1 TMA的响应为74.08;对1000μL·L^-1 TMA的响应时间和恢复时间分别为73和34 s;S?6复合材料气敏传感器在230℃时可以检测到1μL·L^-1的TMA。     

基于半导体纳米SnO_2构建的气敏传感器的应用研究进展

SnO2是传统的气敏材料,由于其具有间隙锡离子和氧空位的特性,使得气体更容易吸附在材料表面,从而显示出更好的气敏性质.通过把SnO2进行贵金属附载掺杂和多种气敏性半导体氧化物的复合,探讨了一系列性能良好的气敏传感器,阐述了SnO2气敏传感的最新进展.     

Fabrication of a New Electrochemiluminescent Sensing Interface Based on Zinc Oxide Nanorod

A new electrochemiluminescence (ECL) sensing interface was established based on the zinc oxide nanorod in this paper. Firstly, the zinc oxide (ZnO) nanorod was prepared on an indium tin oxide (ITO) electrode surface by the method of constant current cathodic electrodeposition, on which the Nafion film was then modified, and finally ruthenium(II) tris(bipyridine) (Ru(bpy)₃²⁺) was immobilized at the ZnO nanorod/Nafion composite‐modified electrode. The sensing interface shows well ECL behaviors and perfect stability after being constant temperature treatment at 80 °C. The composite electrode was characterized by EIS, SEM and XRD. The results showed that the good stability maybe related to the water content of Nafion film.     

Study of the nonenzymatic glucose sensor based on highly dispersed Pt nanoparticles supported on carbon nanotubes

An amperometric biosensor for sensitive and selective detection of glucose has been constructed by using highly dispersed Pt nanoparticles supported on carbon nanotubes (Pt-MWCNTs) as sensing interface. The Pt-MWCNTs were synthesized by using the two-step pyrolysis method. This composite shows good electrocatalytic activity towards the oxidation of glucose in alkaline and thus can be used to selectively detect glucose. We found that detection potential and Nafion amount covered on the Pt-MWCNTs modified glassy carbon electrode had considerable influence on the selectivity for amperometric detection of glucose. Under optimal detection conditions (detection potential of 0.0 V versus SCE and 10 μL 1.5% Nafion), selective detection of glucose in the glucose concentration range of 1.0-26.5 mM (correlation coefficient, >0.999) can be performed. The results demonstrate that the Pt-MWCNTs composite is promising for the fabrication of nonenzymatic glucose sensors.     

金属氧化物异质结气体传感器气敏增强机理

金属氧化物异质结由于费米能级效应、不同组分之间的协同作用,常被用来提高电阻型金属氧化物半导体气体传感器的气敏特性。本文简述了近年来国内外金属氧化物异质结材料的类别,主要分为混合氧化物结构、层状结构、第二相粒子修饰结构、一维纳米结构和核-壳结构;重点综述了金属氧化物异质结的气敏增强机理,包括异质结效应、协同效应、催化溢流效应、响应反型、载流子分离及微结构调控六大机理;分析了当前异质结气体传感器面临的瓶颈。最后对纳米异质结气体传感器的发展进行了展望,今后金属氧化物异质结气体传感器可以从明确异质结界面机理展开,这将为自下而上地设计出符合实际需要的气体传感器提供一定参考。     

Applications of metal nanoparticles/metal-organic frameworks composites in sensing field

Metal nanoparticles (MNPs) possess size-dependent desirable electronic and optical properties while metal-organic frameworks (MOFs) have an edge over extremely large specific surface areas, homogeneous structure, high porosity and remarkable chemical stability. Their combination (MNPs/MOFs) is a novel nanomaterial with broad application prospect in sensing field. To improve performance in sensing applications, we have paid great attention to synergistic effects between the two compositions above. Because of the synergistic effects between MNPs and MOFs, sensors on the basis of MNPs/MOFs composites show significant sensing enhancement with respect to stability, selectivity and sensitivity. In this review, various applications for MNPs/MOFs composites in electrochemical sensing, fluorescent sensing, colorimetric sensing, surface-enhanced Raman scattering sensing and chemiluminescence/electrochemiluminescence sensing are focused and summarized. Besides, the synergistic interactions between MNPs and MOFs was investigated. Finally, based on theoretical information from the reports as well as experimental experience, this review offers the challenges and opportunities for future research on MNPs/MOFs composites.     

Tris(2,2′‐bipyridyl)ruthenium(II) Electrogenerated Chemiluminescence Sensor Based on Platinized Carbon Nanotube–Zirconia–Nafion Composite Films

Mesoporous films of platinized carbon nanotube–zirconia–Nafion composite have been used for the immobilization of tris(2,2′‐bipyridyl)ruthenium (II) (Ru(bpy)₃²⁺) on an electrode surface to yield a solid‐state electrogenerated chemiluminescence (ECL) sensor. The composite films of Pt–CNT–zirconia–Nafion exhibit much larger pore diameter (3.55 nm) than that of Nafion (2.82 nm) and thus leading to much larger ECL response for tripropylamine (TPA) because of the fast diffusion of the analyte within the films. Due to the conducting and electrocatalytic features of CNTs and Pt nanoparticles, their incorporation into the zirconia–Nafion composite films resulted in the decreased electron transfer resistance within the films. The present ECL sensor based on the Pt–CNT–zirconia–Nafion gave a linear response (R²=0.999) for TPA concentration from 3.0 nM to 1.0 mM with a remarkable detection limit (S/N=3) of 1.0 nM, which is much lower compared to those obtained with the ECL sensors based on other types of sol‐gel ceramic–Nafion composite films such as silica–Nafion and titania–Nafion.     

Studies on QCM-type NO2 Gas Sensor Based on Graphene Composites at Room Temperature

Synthetic graphene composite was modified on a transducer of quartz crystal microbalance(QCM) to fabricate a gas sensor for low concentration nitrogen dioxide(NO₂) detection. The gas sensing properties of the QCM coated with SnO₂-rGO and AgNPs-SnO₂-rGO composites were investigated when exposing QCM to low NO₂ con-centration(2.05-20.5 mg/m³) atmosphere at room temperature. The sensing performances of the QCM with AgNPs-SnO₂-rGO composites were enhanced by the introduction of Ag nanoparticles, and the QCM modified with AgNPs-SnO₂-rGO composites could detect NO₂ at room temperature.     

Carbon nanotubes-Nafion composites as Pt-Ru catalyst support for methanol electro-oxidation in acid media

Carbon nanotubes-Nafion (CNTs-Nafion) composites were prepared by impregnated CNTs with Nafion in ethanol solution and characterized by FT-IR. Pt-Ru catalysts supported on CNTs-Nafion composites were synthesized by microwave-assisted polyol process. The physical and electrochemical properties of the catalysts were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), CO stripping voltammetry, cyclic voltammetry (CV) and chronoamperometry (CA). The results showed that the Nafion incorporation in CNTs-Nafion composites did not significantly alter the oxygen-containing groups on the CNTs surface. The Pt-Ru catalyst supported on CNTs-Nafion composites with 2 wt% Nafion showed good dispersion and the best CO oxidation and methanol electro-oxidation activities.     

Polymer‐coated Boron Doped Diamond Optically Transparent Electrodes for Spectroelectrochemical Sensors

Spectroelectrochemical sensors combine electrochemistry, spectroscopy, and partitioning into a film to provide improved selectivity for the target analyte. The sensor usually consists of an optically transparent electrode (OTE) coated with a charge selective polymer film. The polymer film is chosen to pre‐concentrate analyte at the OTE surface to improve the sensitivity and provide selectivity against like charged interferences. OTEs such as Indium Tin Oxide (ITO) have been used extensively for spectroelectrochemical sensors, but little is known about the applicability of such sensors using other OTE materials, such as Boron Doped Diamond (BDD). One distinct advantage of BDD OTEs over ITO OTEs is their significant increase in sensitivity for organic compounds, such as 4‐aminophenol and hydroquinone. We have developed absorption and fluorescence‐based sensing methods with a BDD OTE coated with a sulfonated ionomer film, Nafion. This is demonstrated with tris(2,2′‐bipyridyl)ruthenium(II) ion [Ru(bpy)₃²⁺] using an attenuated total reflectance (ATR) flow cell setup for both absorption and fluorescence. With a Nafion coated BDD optically transparent thin layer electrode (OTTLE), we developed a fluorescence based sensor for a common polyaromatic hydrocarbon (PAH), 1‐hydroxypyrene (1‐pyOH), achieving a detection limit of 80 nM (17 ppb). This work manifests new sensing applications while broadening the use of spectroelectrochemistry, OTEs, and BDD as an electrode material.     

Electrodeposition of chitosan enables synthesis of copper/carbon composites for H2O2 sensing

This work presents a novel approach in synthesizing copper (Cu)/carbon composite materials by electrodeposition of the biopolymer chitosan, a renewable carbon precursor, on a copper anode, followed by pyrolysis of the electrodeposited chitosan gel. The amount of copper in the Cu/carbon composite material can be controlled by modifying the pH of the chitosan solution from which the electrodeposition is performed. This further influences the physical properties of the composite material. Here we show a 14 fold increase in electrical conductivity of the Cu/carbon composite, when compared to the material without copper inclusions. Metal/carbon composite materials have a wide range of applications already reported in the literature. As a proof of concept, we demonstrate the electrochemical sensing capability of this Cu/carbon material for non-enzymatic detection of hydrogen peroxide, achieving a sensitivity of 58.9 μA/mM cm², which is comparable to state of the art non-enzymatic hydrogen peroxide sensors. The anodic electrodeposition of chitosan proves to be a simple and straightforward medium for synthesis of Cu/carbon composites. We speculate that this method can be extended to obtain other metal/carbon composites as a low-cost alternative for the fabrication of functional composite electrodes.     

Tris(2,2′‐bipyridyl)ruthenium(II) Electrogenerated Chemiluminescence Sensor Based on Sol–Gel‐Derived V2O5/Nafion Composite Films

Mesoporous V₂O₅/Nafion composite films have been used for the immobilization of tris(2,2′‐bipyridyl)ruthenium (II) (Ru(bpy) ) on an electrode surface to yield a solid‐state electrogenerated chemiluminescence (ECL) sensor. The electrochemical and ECL behavior of Ru(bpy) ion‐exchanged into the composite films has been characterized as a function of the amount of Nafion incorporated into the V₂O₅/Nafion composite. The composite film with 80% Nafion content has the largest pore diameter (4.19 nm) and yields the maximum ECL response for tripropylamine (TPA) because of the fast diffusion of analyte into the film with large pores. Due to the enlarged pore size and enhanced conductivity of the V₂O₅/Nafion composite, the present ECL sensor based on the composite films exhibited around 2 orders of magnitude higher ECL response and one order of magnitude lower detection limit for TPA (10 nM) compared to those obtained with the ECL sensors based on other types of sol–gel ceramic/Nafion composite films such as SiO₂/Nafion and TiO₂/Nafion.     

Designing State-of-the-Art Gas Sensors: From Fundamentals to Applications

Gas sensors are crucial in environmental monitoring, industrial safety, and medical diagnostics. Due to the rising demand for precise and reliable gas detection, there is a rising demand for cutting-edge gas sensors that possess exceptional sensitivity, selectivity, and stability. Due to their tunable electrical properties, high-density surface-active sites, and significant surface-to-volume ratio, nanomaterials have been extensively investigated in this regard. The traditional gas sensors utilize homogeneous material for sensing where the adsorbed surface oxygen species play a vital role in their sensing activity. However, their performance for selective gas sensing is still unsatisfactory because the employed high temperature leads to the poor stability. The heterostructures nanomaterials can easily tune sensing performance and their different energy band structures, work functions, charge carrier concentration and polarity, and interfacial band alignments can be precisely designed for high-performance selective gas sensing at low temperature. In this review article, we discuss in detail the fundamentals of semiconductor gas sensing along with their mechanisms. Further, we highlight the existed challenges in semiconductor gas sensing. In addition, we review the recent advancements in semiconductor gas sensor design for applications from different perspective. Finally, the conclusion and future perspectives for improvement of the gas sensing performance are discussed.     

Carbon nanotube-based fluorescence sensors

The one-dimensional π-conjugated structure endows carbon nanotube (CNT) with large specific surface area and excellent photophysical properties, thus providing a unique platform for the development of chemo- and biosensors based on optical signal output. Although CNT acts as an optical signal transducer, it does not own any intrinsic ability for the selective binding and recognition of analytes. Thus, hybridization of CNTs with functional components that specifically recognize various chemical and biomolecular analytes is often necessary in the preparation of CNT-based sensors. In this review, we summarize preparation and photophysical properties of CNT-based composites, and then highlight on fluorescence sensors based on CNT-composites. These composite sensors integrate the signal transduction property of CNT and the recognition properties of the hybridized functional components. The functional components selectively bind with the target analytes, whereas, CNTs transform the binding events into output signals detectable using spectrofluorometer. Particularly, we highlight on recent progress in the chemical and bimolecular sensors based on near-infrared fluorescence of semiconducting single-walled CNT (SWCNT) and the excellent fluorescence quenching ability of CNTs over conventional organic quenchers.     

Protein Templated Au-CuO Bimetallic Nanoclusters toward Neutral Glucose Sensing

In this study, the application of bovine serum albumin (BSA) as a carrier to glucose-sensitive materials for the detection of glucose was proposed. Au-CuO bimetallic nanoclusters (Au-CuO/BSA) were prepared using BSA as a template, the new sensing material (Au-CuO/BSA/MWCNTs) was synthesized by mixing with multi-walled carbon nanotubes (MWCNT) and applied to non-enzymatic electrochemical sensors to detect glucose stably and effectively under neutral condition. The scanning electron microscopy was used to investigate the morphology of the synthesized nanocomposite. The electrochemical properties of the sensor were studied by cyclic voltammetry. Glucose detection experiments show that Au-CuO/BSA/MWCNTs/Au electrode has good glucose detection ability, stability, accuracy, repeatability, and high selectivity in neutral environment. Unlike existing glucose-sensitive materials, due to the use of BSA, the composite material is firmly fixed to the electrode surface without a Nafion solution, which reduces the current blocking effect on the modified electrode. The composite materials can be effectively preserved for extremely long periods, higher than 80% activity is maintained at room temperature in a closed environment for 3 to 4 months, due to the special effects of BSA. In addition, the feasibility of using BSA in glucose-sensitive materials is confirmed.     

Electric field processing to control the structure of poly(vinylidene fluoride) composite proton conducting membranes

A novel method is reported for controlling the structure of poly(vinylidene fluoride) (PVdF) composite proton conducting membranes. When proton conducting Nafion or zirconium phosphate sulfophenylenphosphonate (ZrPSPP) particles are dispersed in a mixed colloidal suspension with PVdF particles, the proton conducting particles selectively respond to an applied electric field. Under appropriate conditions, the proton conducting particles are induced to assemble into chains that rapidly grow to span the gap between electrodes as the electric field is applied. By removing the solvent and melting the PVdF phase while applying the electric field, composite membranes were formed that have field-induced structure. In comparison to randomly structured composites, the electric field-processed Nafion/PVdF or ZrPSPP/PVdF composite membranes showed improved proton conductivity, water sorption, selectivity for protons over methanol, and controlled surface area changes upon swelling with water. The transport and mechanical properties of the electric field-processed composite membranes suggest the potential for improved performance in direct methanol fuel cells.     

Influence of polyfurfuryl alcohol (PFA) loading on the properties of Nafion composite membranes

Composite membranes based on Nafion (N115) loaded with furfuryl alcohol (FA) were prepared by in situ acid-catalyzed polymerization technique, with the aim to improve the ionic conductivity of Nafion membranes. The functionalization, thermal stability, electrical properties and mechanical strength of N115-PFA composites was analyzed by means of Fourier transform infrared (FT-IR) attenuated total reflection (ATR) spectroscopy, small- and wide-angle X-ray scattering (SAXS/WAXS), thermogravimetric analysis (TGA), electrical impedance spectroscopy, dynamic vapor sorption (DVS) and dynamic mechanical analyser (DMA). The FA loading in the resultant composites had a positive correlation with the water uptake (W_u), water vapor uptake (W_vu), ionic conductivity and thermo-mechanical stability. At low polyfurfuryl alcohol (PFA) loading, these membranes displayed higher W_u and improved ionic and electrical properties. Further, the thermo-mechanical stability also gradually increased with the PFA loading. All the composites showed a well-defined glass transition temperature in DMA, which shifted to higher temperature with repeated PFA loading. Overall, the results indicate that the developed composite membrane are promising for low temperature polymer electrolyte membrane (PEM) fuel cells.     

Surface engineering of one-dimensional tin oxide nanostructures for chemical sensors

Nanostructured materials are promising candidates for chemical sensors due to their fascinating physicochemical properties. Among various candidates, tin oxide (SnO₂) has been widely explored in gas sensing elements due to its excellent chemical stability, low cost, ease of fabrication and remarkable reproducibility. We are presenting an overview on recent investigations on 1-dimensional (1D) SnO₂ nanostructures for chemical sensing. In particular, we focus on the performance of devices based on surface engineered SnO₂ nanostructures, and on aspects of morphology, size, and functionality. The synthesis and sensing mechanism of highly selective, sensitive and stable 1D nanostructures for use in chemical sensing are discussed first. This is followed by a discussion of the relationship between the surface properties of the SnO₂ layer and the sensor performance from a thermodynamic point of view. Then, the opportunities and recent progress of chemical sensors fabricated from 1D SnO₂ heterogeneous nanostructures are discussed. Finally, we summarize current challenges in terms of improving the performance of chemical (gas) sensors using such nanostructures and suggest potential applications. Contains 101 references.