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Cellular glutathione plays critical roles in protecting neuronal cells against dopamine induced oxidative stress and electrophilic cellular damage; inspired by above mentioned properties of glutathione, we used glutathione as a polymerization inhibitor to develop a dopamine biosensor which can be used in alkaline environment. The detection of dopamine in alkaline environment has been challenged by its polymerization for many years, glutathione as a kind of thiol can be used to prevent the polymerization of dopamine in alkaline environment by eliminating the electrophilic quinone molecules needed during the polymerization. In order to enhance the electrochemical performance of electrode, Ag 2 Se/MoSe 2 composite with large exposed surface areas was synthesized, which improved the sensitivity and stability for dopamine detection. The low oxidation peak potential for dopamine, 0.04 V vs. SCE, indicats that glutathione can realize the electrooxidation of dopamine at lower potential in alkaline environment. In this study, by introducing glutathione to inhibit the dopamine polymerization, sensitive and stable detection of dopamine can be achieved at pH 8.5 based on the Ag 2 Se/MoSe 2 /GCE. [ABSTRACT FROM AUTHOR]

Hydrogen sensors with high sensitivity, rapid response and low cost are urgently demanded in today’s industry. In this work, we reported our research on the fabrication process and the relevant sensing mechanisms of a TiO 2 film based hydrogen sensor which showed an excellent performance at room temperature in air. The sensor, prepared by hydrothermal methods with a seed layer being introduced during the growth of the thin films, exhibited the concentration detection limit as low as 1 ppm and the response time as short as 9 s. Structural analysis revealed that the introduction of the seed layer resulted in a significant improvement in the quality of the TiO 2 thin film, which was intimately related to the sensing properties. The dynamical response process was studied and the corresponding sensing mechanisms were analyzed in detail. It was found that, in addition to the generally accepted Schottky barrier mechanism, the adsorption of H 2 molecules at (002) surface of the TiO 2 thin film played a key role in achieving such a low detection limit and a short response time for the sensor. [ABSTRACT FROM AUTHOR]

Abstract: A convenient and low-cost synthesis approach is proposed for the development of a simple and novel electrochemical sensor for the determination of tryptophan (Try). In this synthesis process, graphene-like molybdenum sulfide was successfully obtained, and silver nanoflakes (AgNFs) were directly synthesized on the surface of molybdenum sulfide (MoS2) films, in this process chitosan (CS) and ascorbic acid (AA) acted as the stabilizer and reducing agent, respectively. This nanocomposite was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to evaluate the electrochemical property of Ag-MoS2/CS toward the oxidation of tryptophan. Under the optimized experimental conditions, the oxidation peak currents are proportional to the concentrations of tryptophan over the range of 0.5μM to 120μM, and the detection limit is 0.05μM (S/N=3). Moreover, the proposed method is free of interference from other amino acid to other coexisting species. [Copyright &y& Elsevier]

Abstract: Self-aligned titania thin films of either the rutile or the anatase phase were successfully grown on FTO (F-doped SnO2) substrates with hydrothermal methods. The selection of the targeted phase, either rutile or anatase, in the thin films was controlled by adjusting the content and type of acidic anions such as Cl− and SO4 2−. The growth kinetics depended on the synthesis temperature and the types of alcohol in the solvent. The self-alignment in both the anatase and rutile thin films was attributed to the minimization of surface energies during growth. The hydrogen sensing characteristics of dense films of both rutile and anatase phases were investigated and there was remarkable improvement of sensitivity response over reported data. It was found that rutile films had higher sensitivity while anatase films had faster response. [Copyright &y& Elsevier]

Metal oxide semiconductor heterojunctions and homojunctions are considered to have better performance than single phase material for room temperature hydrogen gas sensing. In this work, TiO 2 facet homojunction (TiO 2 -FH) thin films were prepared by a two-step hydrothermal method. The TiO 2 -FH thin films were decorated with Pt nanoparticles using a green photodeposition method and then evaluated for H 2 sensing. Non-noble metal Al was used as finger electrodes instead of noble metal Pt. Compared with the TiO 2 -FH sensor, the H 2 detection limits of the platinum loaded TiO 2 -FH@Pt sensors are remarkably decreased from 8000 ppm to 1 ppm at room temperature. The optimized sensor achieves an excellent sensing performance of S = 1.21 and fast response / recovery times of about 42 s / 30 s when exposed to 1 ppm H 2 concentration. The synergy between the Schottky barrier at the Pt/TiO 2 interface and the barrier between the (110) and (001) facets of TiO 2 is the key to the improvement of the sensing performance. Replacement of noble metal Pt with Al and C electrodes greatly help to clarify the mechanism of the junctions in the thin film sensors, especially the function of the Pt/TiO 2 junction and the (110)/(001) TiO 2 junction. The simple and green fabrication method and cheap Al interdigitated electrodes are advantageous for practical applications. • Noble metal electrodes of gas sensors were substituted by non-noble metal Al and C. • Trace Pt decorated TiO 2 homojunction was designed for hydrogen sensing. • The sensors maintain the wide detection range and high response. • The Schottky barrier at Pt/TiO 2 interface is the main factor for the sensing performance. • The function of the barrier between the (110) and (001) facets of TiO 2 is clarified. [ABSTRACT FROM AUTHOR]

• Nb doped rutile/anatase TiO 2 heterophase junction thin film was synthesized through one-step hydrothermal self-adjusted Nb doping. • The heterophase junction sensors show remarkably extended detection range and significantly enhanced response for H 2 detecting. • The Schottky junction at Pt/TiO 2 and the heterophase junction at anatase/rutile TiO 2 enhances the sensing response in low H 2 concentration. • The results provides experimental verification of inverse dependence of detectivity on H 2 concentration in high concentration range. Hydrogen sensors combining wide detection range and high response, that can operate at room temperature, are urgently demanded for monitoring different concentrations of hydrogen on a single device. Here, a novel one-step hydrothermal method is reported to construct Nb doped rutile/anatase TiO 2 heterophase junctions for a highly sensitive H 2 sensor. The Nb concentration in the solvent plays an important role for the heterophase juncton self-assemble, and the reaction time determines the surface morphology giving either a rutile TiO 2 nanorod decorated anatase form, or a Nb doped rutile/anatase TiO 2 bi-layer structure. An inverse dependence of the detectivity on H 2 concentration is obtained as theoretically predicted but previously not experimentally verified for the high concentration region at low temperatures. The H 2 concentration detection range is remarkably expanded, extending from 1 ppm to 12000 ppm for nanorod decorated film. The H 2 response at 1 ppm is significantly enhanced to 22.5%, and reaches 98.9% in 8000 ppm H 2 for the bilayer structure. The remarkablely extended detection range is the result of the massive accumulation of reactive pre-absorbed O 2 − on the surface due to the Nb doping, and the significantly enhanced response at room temperature results from the joint contributions of pre-absorbed O 2 − , film compactness and the heterophase junction. Moreover, Nb doped rutile/anatase TiO 2 heterophase juncton films show high stability and humidity resistance for hydrogen sensing. [ABSTRACT FROM AUTHOR]

Electrochemical immunosensors are widely used in the detection of biomarkers. In order to further improve the detection sensitivity and accuracy, we constructed a dual-signal electrochemical immunosensor with CoTe 2 @CeO 2 nanocomposites (CoTe 2 @CeO 2 NCs) as an electrocatalytic label and successfully applied it to the detection of prostate-specific antigen (PSA). It was discovered that the CoTe 2 @CeO 2 NCs obtained by two-step hydrothermal process with outstanding oxygen evolution reaction (OER) activity and the Te- oxidation during OER, it produces a strong OER signal and a huge oxidation peak signal in neutral solution. Based on this, we propose an ingenious and simple dual-signal strategy that requires only one label, using CoTe 2 @CeO 2 NCs as an electrochemical immunosensor electrocatalytic label. Experimental results show that the developed dual-signal electrochemical immunosensor with a broad linear response (0.002 ∼ 200 ng mL−1) and very low detection limits (I peak : 8.26 fg mL−1, I OER : 448 fg mL−1) for PSA. It was successfully used for the detection of real samples with good detection and self-calibration capability. Furthermore, this constructed dual-signal immunosensor may also be used to detect other biomarkers by altering the recognition components. In conclusion, the construction strategy of this novel immunosensor is very meaningful for the early detection and treatment of diseases. [Display omitted] ● CoTe 2 @CeO 2 NCs generates both peak and OER signals in neutral environment. ● A dual-signal immunosensor was constructed using CoTe 2 @CeO 2 NCs as the label. ● This electrochemical immunosensor with excellent detection performance for PSA. ● Dual signal inter-validation and self-calibration for more reliable assay results. [ABSTRACT FROM AUTHOR]

Constructing a heterojunction is an effective way to improve the gas sensing properties of metal oxide semiconductors. In this work, a hydrogen sensor containing hierarchical and porous NiO/TiO 2 heterojunction bilayer structure was designed. The top layer is formed by the NiO nanowalls grown along the [220] direction with exposed (111) facets, and the bottom layer is formed by the [002] oriented TiO 2 nanorod arrays. The exposed high energy crystal surfaces of NiO and TiO 2 , together with the adapted surface depletion region, induced by the formation of the heterojunction, enable the hydrogen sensor to have both a wide detection range and a much higher response to hydrogen than single layer materials. With the optimized size of the pores existing between the walls, the hydrogen sensor shows excellent prevention to interference from CO. Both the gas diffusion regulated by the porous structure and the surface interaction between H 2 /CO and O 2 - controlled by the heterojunction barrier contribute to the distinctive detection of H 2 and CO at room temperature (25 ℃ ± 2 ℃). • A (111)NiO/(002)TiO 2 hierarchical heterojunction was designed for hydrogen sensing. • The sensor has wide detection range and high response than single layer materials. • The hydrogen sensor shows excellent performance to prevent interference from CO. • The hierarchical diffusion and the interface adsorption reaction are the key factors. [ABSTRACT FROM AUTHOR]

Development of advanced hydrogen sensors with high sensitivity, fast response speed, and long term stability is essential for safe utilization of hydrogen energy. In this work, a gas sensor with TiO 2 hierarchical trunk/branch structure as the sensing material is prepared by hydrothermal and immersion method. The experimental results show that facet homojunctions are formed by the facet contacts at the trunk/branch interfaces. The optimized sensor works at room temperature with an excellent sensing performance of S = 31.6% when exposed to 1 ppm H 2 concentration and a fast response and recovery time of about 10 s. The sensor also shows long-term stability, high sensing gas selectivity and high humidity resistance. It is found that the facet homojunction in the hierarchical structure of TiO 2 results in a significantly increased density of the charged oxygen ions absorbed on the surface and an enhanced effective barrier height, which are responsible for the much promoted sensing performance. This work provides a new way for designing gas sensors with highly commercial competitiveness. • TiO 2 hierarchical trunk/branch structure are fabricated. • Facet homojunctions are formed at the trunk/branch interfaces. • The hydrogen sensing performance is comprehensively enhanced. [ABSTRACT FROM AUTHOR]