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•V2O5 nanorods/g-C3N4 nanosheet (VONRs/CNNs) composites were constructed by an impregnation method.•4 wt% VONRs/CNNs exhibited high photodegradation of Congo Red and photoreduction of ...Cr (VI) under sunlight irradiation.•The enhanced photocatalytic activity was mainly due to the synergistic effect of heterojunctions.•VONRs/CNNs composites exhibited excellent stability and reusability.•A Z-scheme photocatalytic mechanism was proposed for VONRs/CNNs composites.
Photocatalytic materials for environmental remediation of organic pollutants and heavy metals require not only a strong visible light response and high photocatalytic performance, but also the regeneration and reuse of catalysts. In this work, 1D/2D V2O5 nanorods/g-C3N4 nanosheets (VONRs/CNNs) composites were prepared by a facile impregnation method and employed in the degradation of a Congo red (CR) and reduction of Cr (VI) under sunlight irradiation. The as-prepared samples were studied by several characterization techniques including XRD, SEM, TEM, EDS, XPS, FTIR, UV–vis DRS and PL. Results revealed that the interface interaction between VONRs and CNNs was recognized via V2O5 nanorods loading on the surface of g-C3N4 nanosheets, improving the separation and transfer of photogenerated electron-hole pairs and restraining the recombination rate of charge carriers. As a result, the photocatalytic activity of the composites was enhanced in comparison with pure CNNs and VONRs. The photocatalytic efficiency of optimal composite (4-VONRs/CNNs) for the removal of CR (Cr (VI)) was about 9.33 (4.22) and 73.52 (19.2) times higher than that of pure CNNs and VONRs, respectively. Meanwhile, the 4-VONRs/CNNs exhibited good photocatalytic stability in recycling experiments. Such enormous enhancement in photocatalytic performance was predominantly ascribed to the efficient separation and transfer of photogenerated electron-hole pairs at the VONRs/CNNs interface imparted through the direct Z-scheme charge carrier migration mechanism. Moreover, the energy band structure and the quenching effects of different scavengers demonstrated that the electrons of CNNs and holes of VONRs with higher oxidizability and reducibility are the real participants in photocatalytic reactions.
Electrochemical water splitting in alkaline solution plays a growing role in alternative energy devices due to the need for clean and sustainable energy. However, catalysts that are active for both ...hydrogen evolution and oxygen evolution reactions are rare. Herein, we demonstrate that cobalt phosphide (CoP), which was synthesized via the hydrothermal route and has been shown to have hydrogen evolution activity, is highly active for oxygen evolution. A current density of 10 mA cm–2 was generated at an overpotential of only 320 mV in 1 M KOH for a CoP nanorod-based electrode (CoP NR/C), which was competitive with commercial IrO2. The Tafel slope for CoP NR/C was only 71 mV dec–1, and the catalyst maintained high stability during a 12 h test. This high activity was attributed to the formation of a thin layer of ultrafine crystalline cobalt oxide on the CoP surface.
•A novel and simple DNA optical biosensor based on unmodified gold nanorods and hybridization chain reaction was developed.•This new colorimetric biosensor exhibits wide linear range, high ...sensitivity and selectivity for DNA detection.•This method is label-free, modification-free, and enzyme-free, which hold great promise for routine sensing application.
A novel and simple colorimetric biosensor was developed by combining the unique optical properties of unmodified gold nanorods (AuNRs) with the amplification strategy of hybridization chain reaction (HCR), which was capable of detecting DNA sensitively and selectively. The detection mechanism is based on the dispersion/aggregation of AuNRs under the high concentration of salt. When target DNA introduces, the hybridization of hairpin DNA is triggered and a nicked double-helix DNA as HCR product forms which sticks tightly with AuNRs through a strong electrostatic adsorption and protects AuNRs from aggregation in high salt concentration condition. When no target DNA appears, AuNRs undergo aggregation due to the weak protection of hairpin DNA. The approach is able to detect target DNA in a range of 0–60 nM with a detection limit of 1.47 nM and exhibits high selectivity to distinguish fully matched and single-base mismatched DNA. Results demonstrate this method is label-free, modification-free, and enzyme-free, which holds great promise for routine sensing applications.
In this paper, sulfur and nitrogen co-doped graphene quantum dots (S,N-GQDs) were compounded with titanium dioxide (TiO2) nanorods by chemical surface modification. S,N-GQDs in diameter of 5 nm are ...uniformly distributed on the surface of TiO2 nanorod arrays. The presence of CS bonds in S,N-GQDs not only broaden the absorption of visible light by GQDs, but also enhanced the visible light absorption of S,N-GQDs/TiO2 composites. The photocurrent densities of S,N-GQDs/TiO2 were 3.66 times that of unmodified TiO2. The calculation results of density functional theory (DFT) showed that the band gap of S,N-GQDs is significantly reduced compared to GQDs, indicating that electrons are more likely to transit to higher energy levels and form more activation sites. Moreover, compared with TiO2, the DFT calculation results of band gap, density of states and charge density difference of S,N-GQDs/TiO2 showed that S,N-GQDs/TiO2 had a wide wavelength of visible light absorption and better electron-hole separation ability, resulting in the superior photoelectrocatalytic property. This research provides favorable analytical value for the development of photocatalysts based on heterostructures.
S,N-GQDs/TiO2 nanocomposites with excellent photocatalytic activity were prepared by simple surface modification. N–H, C–N, CS functional groups of S,N doped GQDs is conducive to the absorption of visible light and the enhancement of catalytic activity. Both theoretical and experimental results confirmed the extension of optical absorption into the visible range and the frequent charge transfer from S,N-GQDs to the TiO2 surface, facilitating electron-hole separation and reducing charge recombination rate. Display omitted
•S,N-GQDs/TiO2 prepared by chemical surface modification present good electron-hole separation ability.•S,N-GQDs broaden the visible light absorption range and promote the separation of electron-hole pairs of TiO2.•The band gap, density of states and charge differential density of nanocomposites were studied by DFT.
Two-dimensional carbon-coated molybdenum disulfide (MoS2@C) hollow nanorods are combined with nucleic acid signal amplification strategies and DNA hexahedral nanoframework to construct a novel ...self-powered biosensing platform for ultra-sensitive dual-mode detection of tumor suppressor microRNA-199a. The nanomaterial is applied on carbon cloth and then modified with glucose oxidase or using as bioanode. A large number of double helix DNA chains are produced on bicathode by nucleic acid technologies including 3D DNA walker, hybrid chain reaction and DNA hexahedral nanoframework to adsorb methylene blue, producing high EOCV signal. Methylene blue also is reduced and an increased RGB Blue value is observed. For microRNA-199a detection, the assay shows a extensive linear range of 0.0001–100 pM with a low detection limit of 4.94 amol/L (S/N = 3). The method has been applied to the detection of actual serum samples, providing a novel method for the accurate and sensitive detection of tumor markers.
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•The 2D MoS2@C hollow nanorods with good conductivity are prepared.•A smart self-powered sensor with quadruple-signal amplification is fabricated.•A dual-mode strategy with high reliability is developed for miRNA-199a detection.
For the first time, colloidal gold (Au)–ZnSe hybrid nanorods (NRs) with controlled size and location of Au domains are synthesized and used for hydrogen production by photocatalytic water splitting. ...Au tips are found to grow on the apices of ZnSe NRs nonepitaxially to form an interface with no preference of orientation between Au(111) and ZnSe(001). Density functional theory calculations reveal that the Au tips on ZnSe hybrid NRs gain enhanced adsorption of H compared to pristine Au, which favors the hydrogen evolution reaction. Photocatalytic tests reveal that the Au tips on ZnSe NRs effectively enhance the photocatalytic performance in hydrogen generation, in which the single Au‐tipped ZnSe hybrid NRs show the highest photocatalytic hydrogen production rate of 437.8 µmol h−1 g−1 in comparison with a rate of 51.5 µmol h−1 g−1 for pristine ZnSe NRs. An apparent quantum efficiency of 1.3% for hydrogen evolution reaction for single Au‐tipped ZnSe hybrid NRs is obtained, showing the potential application of this type of cadmium (Cd)‐free metal–semiconductor hybrid nanoparticles (NPs) in solar hydrogen production. This work opens an avenue toward Cd‐free hybrid NP‐based photocatalysis for clean fuel production.
Au–ZnSe hybrid nanorods with controlled size and location of Au domains are synthesized and tested for hydrogen production by photocatalytic water splitting for the first time. The nonepitaxial growth of Au tips on ZnSe NRs is studied experimentally and theoretically. This new Cd‐free hybrid system may provide a platform for hybrid nanoparticle‐based photocatalysis toward clean fuel production.
This study successfully developed a semiconductor metal oxide-based ammonia gas sensor that was powered by an Ultraviolet–Visible-near-IR optical light source. However, optical fibre gas sensors ...using single metal oxide nanomaterial are limited. To address this situation, a h-MoO3 nanorod was grown on a tapered region of optical fibre glass using a simple chemical bath deposition to form a unique sensing element. An additional annealing treatment was then performed to modify the oxidation state of h-MoO3. The property changes of the samples were characterised using different techniques, such as FESEM, TEM, XRD, XPS, TGA and UV–Vis. Overall, the annealing treatment improved the sensitivity performance, response and recovery time of the sensor towards NH3. h-MoO3 that was annealed at 150 °C in air showed stable room temperature absorbance responses of 0.05, 0.18, 0.22, 0.28 and 0.35, a fast response time of 210 s towards 500 ppm of NH3 and strong stability and repeatability. The optical NH3 gas-sensing behaviour was significantly correlated with the non-stoichiometric Mo5+ content. The chemisorbed oxygen species and physiosorbed NH3 altered the refractive index and its absorption coefficient on the nanorod, which manipulated the optical signal and acts as a sensing mechanism. These results verify that a chemical bath deposition growth of the h-MoO3 nanorod exhibits a promising optical sensing characteristic, which paves a path for emerging gas-sensing technology.
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•Simple fabrication of fast response optical fiber ammonia gas sensor using chemical bath deposition is reported in this work.•Annealed h-MoO3 at 150 °C in air shows superior ammonia gas sensing due to the non-stoichiometric Mo5+.•Experimental result demonstrates a fast response time of 210s towards 500ppm of NH3 in room temperature.•Sensor shows a relatively high selectivity towards NH3 comparing with H2 and CH4.
The light photoresponse, the separation of photogenerated charge carriers and the specific surface area are of great importance for the development of semiconductor‐based photocatalysts. We report ...the anchorage of small‐sized ZnO nanorods with a length of ca. 38 nm at the surface of graphitic carbon nitride (gCN) sheets. The gCN loading in the ZnO/gCN composites was varied and the materials characterized by TEM, XRD, XPS, BET and UV‐vis diffuse reflectance spectroscopy. The ZnO/gCN (10 %) composite exhibits a high photocatalytic activity for the degradation of dyes (Orange II, Resazurin and Reactive Black 5) under visible light irradiation of low intensity (2.5 mW/cm2) and for salicylic acid under simulated sunlight irradiation (5 mW/cm2). These results are supported by photoluminescence, photocurrent and electrochemical impedance spectroscopy measurements. The photocatalytic activity originates from synergistic effects in ZnO/gCN composites including a high specific surface area (60.4 m2/g), an enhanced visible light absorption capacity and the charge carriers separation. The ZnO/gCN photocatalyst exhibits a high stability and could be reused up to ten times with no loss of efficiency. A mechanism is proposed for the degradation of dyes using the ZnO/gCN composites.
Synergy. The growth of ZnO rods at the surface of graphitic carbon nitride sheets affords photocatalysts with high activity under visible light irradiation due to the improvement of separation efficiency of photogenerated electron‐hole pairs and to the increase of specific surface area.
The Cover Feature shows the bilayer TiO2/α‐Fe2O3 nanorod arrays modified with Cu:NiOx hole transfer layer and Co‐Pi co‐catalyst as a photoanode for efficient solar water splitting. The advantages for ...the combination of bottom‐up engineering of electron–hole transport channels and OER cocatalyst modification are demonstrated. A remarkably enhanced photocurrent density of 2.43 mA cm−2 at 1.23 VRHE under 1 sun illumination and almost no activity attenuation after long‐time operation are achieved. More information can be found in the Full Paper by H. Li et al.
Cancer poses a significant threat to human health, and monotherapy frequently fails to achieve optimal therapeutic outcomes. Based on this premise, porphyran (PHP), a marine polysaccharide with ...immunomodulatory function, was used as a framework to coat gold nanorods and construct a novel nanomedicine (PHP-MPBA-GNRs) combining photothermal therapy and immunotherapy. In this design, PHP not only maintained the dispersion stability and photothermal stability of gold nanorods but also could be released under weakly acidic conditions to activate anti-tumor immunity. In vivo studies have shown that PHP-MPBA-GNRs can effectively inhibit tumor cell proliferation and reduce metastasis under near-infrared (NIR) light irradiation. Preliminary mechanistic investigation revealed that PHP-MPBA-GNRs could increase reactive oxygen species (ROS) and induce apoptosis in cancer cells. The PHP in PHP-MPBA-GNRs can also activate dendritic cells and up-regulate the expression of co-stimulatory molecules and antigen-presenting complexes. All biological experiments, including in vivo tests, demonstrated that PHP-MPBA-GNRs achieved a combination of photothermal therapy and immunotherapy for tumors.
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