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Silver (Ag) is a widely used heavy metal, and its oxidation state (Ag+) causes serious harm to organisms after bioaccumulation and biomagnification, posing urgent demand for the rapid, efficient, and simply operated Ag+ detection techniques. In this work, a fast, portable, and label-free Ag+ detection sensor based on a Ti3C2Tx MXene field-effect transistor (FET) is reported. The Ti3C2Tx MXene works as the sensing element in the FET sensor, which shows excellent sensing performance, i.e., fast response (few seconds) and good sensitivity and selectivity to Ag+ without any detection label or probe. Utilizing the visual photograph, transmission electron microscopy image, and Ag elemental mapping analysis, the sensing mechanism of the label-free Ti3C2Tx MXene FET sensor is demonstrated to be the in situ reduction of Ag+ and the formation of Ag nanoparticles (AgNPs). Moreover, Ag+ detection in real samples shows that the proposed FET devices have satisfactory sensing capability for Ag+ in tap water and river water. This study puts forward a novel FET strategy for Ag+ detection in aqueous systems, which is of essential and inspiring meaning for motivating the potential applications of MXene-based sensor devices in analytical applications and the realization of on-site environmental monitoring.

Objectives The coronavirus (COVID-19) global pandemic has increased psychological distress among the general population. The objective of this study is to evaluate a mindfulness-based intervention for psychological distress among Chinese residents during COVID-19. Methods This study used a switching replications design to test the feasibility and efficacy of a brief online mindfulness-based intervention for Chinese residents’ psychological distress. Fifty-one residents in the Hubei province were randomly allocated to two groups (experimental group and waitlist control group) with three waves of measurement at time 1, time 2, and time 3 for changes in mindfulness and psychological distress. Results In addition to significant within-group improvements over time for both groups, OLS linear regression with full information likelihood estimation revealed statistically significant between-group treatment effects across outcome domains, including mindfulness awareness, b = 2.84, p < 0.001, g = 6.92, psychological distress, b = −21.33, p < 0.001, g = 6.62, somatic symptoms, b = −6.22, p < 0.001, g = 4.42, depressive symptoms, b = −7.16, p < 0.001, g = 5.07, and anxiety symptoms, b = −8.09, p < 0.001, g = 6.84. Conclusions Results suggest that a brief online mindfulness-based intervention can be a feasible and promising intervention for improving mindfulness and decreasing psychological distress among Chinese residents staying at home during the COVID-19 outbreak. The study used a small convenience sample which led to a concern of external generalizability and with limited evaluation of long-term change.

A simple, efficient, and environmentally friendly electro-Fenton (EF) process is highly demanded for EF practical application. Herein, a highly practical double-cathode EF system has been developed...

Field-effect transistors (FETs) receive growing attention for gas detection owing to their superior sensing performance over traditional techniques. The sensitivity and selectivity of FET sensors can be enhanced by tuning the structure of channel materials via doping, surface functionalization, hybridization, etc. However, the intrinsic semiconductor characteristics of the channel material and its gas adsorption capacity largely determine the sensing performance. In this work, we compared the room-temperature sensing performance of FET sensors with few-layer graphene, black phosphorous (BP), and MoS2 with mixed polymorphic phases (metallic 1T phase and semiconducting 2H phase), and 2H-MoS2 as a channel material for formaldehyde. The sensing results indicate that 1T/2H-MoS2 exhibits the best sensitivity, response time as well as selectivity for formaldehyde detection. The theoretical calculation demonstrates that 1T/2H-MoS2 yields the optimum semiconducting properties and gas adsorption capability for formaldehyde over other 2D channels. Moreover, by investigating the sensing performance under humid conditions, it was discovered that high humidity enhances the sensing response. This study demonstrates that the regulation of the intrinsic electronic structures of the 2D semiconducting channel directly affects the gas detection performance.

Monolayer MoS2 (ML-MoS2) with various polymorphic phases attracts growing interests for device applications in recent years. Herein, a field-effect transistor (FET) gas sensor is developed on the basis of monolayer MoS2 with a heterophase of a 1T metallic phase and a 2H semiconducting phase. Lithium-exfoliated MoS2 nanosheets own a monolayer structure with rich active sites for gas adsorption. With thermal annealing from 50 to 300 °C, the initial lithium-exfoliated 1T-phase MoS2 gradually transforms into the 2H phase, during which the 1T and 2H heterophases can be modulated. The 1T/2H heterophase MoS2 shows p-type semiconducting properties and prominent adsorption capability for NO2 molecules. The highest response is observed for 100 °C annealed MoS2 of a 40% 1T phase and a 60% 2H phase, which shows a sensitivity up to 25% toward 2 ppm NO2 at room temperature in a very short time (10 s) and a lower limit of detection down to 25 ppb. This study demonstrates that the gas detection capability of ML-MoS2 could be boosted with the heterophase construction, which brings new insights into transition-metal dichalcogenide gas sensors.

MXenes, a group of emerging two-dimensional (2D) transition metal carbides or nitrides, have attracted wide interest due to their unique structures and properties. Their stability and applicability in different media especially in an alkaline environment are directly associated with their potential applications and are not yet explored. Herein, a field-effect transistor (FET) is fabricated with single/double-layer Ti3C2Tx MXene. The Ti3C2Tx FET indicator shows a fast (∼1 s), sensitive, and selective response to alkali. Moreover, the device can work even in a high-salinity (2 M NaCl) environment, suggesting its high anti-interference ability for alkali in a high-ionic-strength environment. Using an in situ morphological image evolution study, it is demonstrated that the response signal results from alkali-induced denaturation of Ti3C2Tx nanosheets. The Ti3C2Tx-based alkali FET indicator and systematic evaluation on alkali-induced structure evolution of Ti3C2Tx provide essential insights into MXene-based FETs and future applications of MXene in alkaline environments.

Article Highlights Recent advances of two-dimensional (2D) transition-metal dichalcogenide (TMDC)-based field-effect transistor (FET) sensors for environmental analysis are summarized.Representative TMDC FET sensors in gaseous and aqueous media analysis are introduced.Challenges and future research directions of 2D TMDC FET sensors are discussed., Field-effect transistors (FETs) present highly sensitive, rapid, and in situ detection capability in chemical and biological analysis. Recently, two-dimensional (2D) transition-metal dichalcogenides (TMDCs) attract significant attention as FET channel due to their unique structures and outstanding properties. With the booming of studies on TMDC FETs, we aim to give a timely review on TMDC-based FET sensors for environmental analysis in different media. First, theoretical basics on TMDC and FET sensor are introduced. Then, recent advances of TMDC FET sensor for pollutant detection in gaseous and aqueous media are, respectively, discussed. At last, future perspectives and challenges in practical application and commercialization are given for TMDC FET sensors. This article provides an overview on TMDC sensors for a wide variety of analytes with an emphasize on the increasing demand of advanced sensing technologies in environmental analysis.

Objective: The study aimed to review evidence on the efficacy of submucosal (SM) administration vs. intravenous (IV) or intramuscular (IM) route of injections of dexamethasone for improving outcomes after mandibular third molar surgery.Methods: PubMed, Embase, CENTRAL, and Google Scholar were searched for randomized controlled trials (RCTs) up to 20th May 2021. Early (2–3 days) and late (7 days) outcomes were compared between SM vs. IV or IM dexamethasone. Quality of evidence was assessed based on GRADE.Results: Thirteen trials were included in the systematic review and 10 in the meta-analysis. Meta-analysis indicated a significant reduction in early pain with IV dexamethasone but no such difference for late pain compared to the SM group. There was no difference in early and late swelling scores between the SM and IV groups. Pooled analysis indicated no significant difference in early and late trismus between SM and IV groups. Comparing SM with IM dexamethasone, there was no significant difference in early and late pain scores. Swelling in the early and late postoperative periods was not significantly different between the two groups. There was no significant difference in early and late trismus between SM and IM groups. The quality of evidence was low for all outcomes.Conclusion: Low-quality evidence suggests that SM infiltration of dexamethasone results in similar outcomes as compared to IV or IM administration of the drug after third molar surgeries. Further high-quality RCTs are needed to corroborate the current conclusions.

Exciton polarization dissociation, charge transfer and surface electron density in photocatalysts are crucial for photocatalytic hydrogen evolution reactions (HERs). In this study, crystalline carbon nitride with cyanamide defect edges (crystalline CCN) was synthesized by one step polymerization of urea in the presence of KCl. The texture and electronic band structure of carbon nitrides could be facilely tailored by changing KCl dosage. The light absorption edge of crystalline CCN extended to 736 nm due to n→π* electron transition. The enhanced dielectric constants of crystalline carbon nitrides promoted exciton polarization dissociation. The small effective electron mass (me*) in crystalline CCN facilitated me* diffusion. The efficient separation of electrons and holes benefited the formation of internal electric field, showing an 8.56-fold promotion in electron transfer compared to pristine CN. Significantly, femtosecond time-resolved transient absorption demonstrated that the surface electron density on crystalline CCN was enhanced in the presence of salt ions (NaCl). As a result, crystalline CCN exhibited 14.9 times higher HER rate than pristine CN under visible light irradiation. The apparent quantum yield for H2 evolution on crystalline CCN reached to 42% at 420 nm and 9% at 500 nm. This study gets a comprehensive understanding of photocatalytic HERs using carbon nitride photocatalysts.

Mercury ions (Hg2+) are the dominant mercury species in water, and have severe toxic effects on human health and the ecosystem. Due to the limitations of traditional analytical methods for mercury determination, e.g., complex pretreatment, costly instruments, and being unsuitable for low-level online sensing, numerous efforts have been made to develop rapid, low-cost, and portable sensors for Hg2+ determination. The excellent characteristics of graphene, i.e., a unique two-dimensional structure, large surface area, high conductivity and carrier mobility, and good optical and electrochemical properties, lead to intense studies on graphene-based Hg2+ sensors with desirable performance and broad application prospects. The scope of this review is recent advances in graphene Hg2+ sensors with a special focus on optical, electrochemical, and electronic sensors. The working principles and advantages of representative graphene Hg2+ sensors are introduced and compared with traditional methods. Moreover, challenges as well as potential solutions and research directions of mercury sensors are discussed, which will guide future research of Hg2+ sensors in biomedical and environmental monitoring applications.

Heat dissipation is a critical issue in high-performance electronics, which needs to be solved, and an electronic paste is a good choice to solve this issue. In this paper, silver nanoparticles/multi-walled carbon nanotube (Ag-NPs/MWCNT) composites were prepared by the chemical process for the modification of electronic pastes. The micromorphology and spectral analysis of the as-prepared Ag-NPs/MWCNT composites indicated that Ag-NPs were uniformly distributed on the MWCNT surfaces with high distribution densities; the average size of Ag-NPs was estimated to be 8.29 nm. The as-obtained Ag-NPs/MWCNT composites were then added to a silver-epoxy paste. Field emission scanning electron microscopy (FESEM), thermogravimetry (TG) and thermal conductivity analyses suggested the incorporation of Ag-NPs/MWCNT composites in the silver-epoxy paste; Ag flakes were better connected by Ag-NPs/MWCNTs, which improved the thermal conductivity of the paste from 0.73 to 0.96 W m−1 K−1. However, more weight loss was observed when Ag-NPs/MWCNTs were incorporated in the silver-epoxy paste. Overall, the addition of Ag-NPs/MWCNTs into the silver-epoxy paste increased the thermal conductivity, which can be applied to high-performance electronics.

Photoinduced electron transfer and separation from its home atom to form spatial isolated electron/hole pairs is the most crucial factor in artificial photocatalysis field. The scalable production of nanoscale g-C3N4 with remarkable electron separation efficiency in one-step, green, economic and “bottom-up” approach is of great challenge. Herein, one-dimensional porous architectural g-C3N4 nanorods have been facilely prepared by direct calcination of hydrous melamine nanofibers precipitated from aqueous solution of melamine. Porous morphologies with increased interfacial area enhance light capture capacity and accelerate catalysis reaction. It is noted that oxygen atoms were simultaneously doped into g-C3N4 matrix, which broke the symmetry of pristine g-C3N4, resulting in more effective separation of electron/hole pairs. Thus, the oxygen-doped g-C3N4 nanorods loaded with Pt presented excellent visible-light photocatalytic hydrogen evolution in the triethanolamine solution (732 μmol g−1 h−1) and in overall water splitting (29.6 μmol g−1 h−1), and 2,4-dinitrophenol degradation for O-doped g-C3N4 nanorod (removal efficiency of 100% within 75 min). Subsequently, the visible-light photocatalytic H2 evolution (96 μmol g−1 h−1) with simultaneous 2,4-dinitrophenol degradation were achieved for Pt@g-C3N4 nanorod. The proposed synthesis strategy overcomes long-standing, stubborn and serious stacking/agglomeration for g-C3N4 synthesis, and paves the pathway for industrial scale-up production of high-performance g-C3N4 and application in practical energy and environment area.

A three-dimensional (3D) reduced graphene oxide–Mn3O4 nanosheet (Mn3O4@rGO) hybrid was achieved by simple electrodeposition technique. Small palladium nanoparticle were homogeneously anchored onto Mn3O4@rGO substrate through the reduction of palladium salt. The interpenetrating network architecture of Mn3O4@rGO greatly inhibited the aggregation of 2D sheets of Mn3O4 and rGO, and the open 3D orientation of the Mn3O4@rGO hybrid nanosheets on the electrode facilitated both mass transport and electron transfer as well as maximally exposed active sites. The introduction of Mn3O4 enhanced the structural and electrochemical stability of rGO. The as-synthesized Pd/Mn3O4@rGO hybrid was employed as an electrocatalyst for electrocatalytic hydrogen evolution reaction (HER). The electrocatalyst showed a low overpotential of 20 mV at 10 mA cm−2, a small Tafel slope of 48.2 mV dec−1, and a large exchange current density of 0.59 mA cm−2. Importantly, the catalyst possessed superior durability with 85.87% of catalytic activity after a long-time test (10 h). This work presents a simple and efficient stratagy to construct high-performance electrocatalysts for energy and environmental applications.

Simple, efficient, and durable electrodes are highly demanded for practical electro­chemical process. In this study, a reduced graphene oxide modified nickel foam electrode (GR‑Ni foam) was facilely prepared via one-step cyclic voltammetry electrodeposition of gra­phene oxide suspension onto the Ni foam. The electrochemical degradation of nitrofuran­zone (NFZ, a kind of typical antibiotics) was studied on the GR-Ni foam cathode. The cyclic voltammetry and electrochemical impedance spectra analysis confirmed that presence of GR loading accelerated the electron transfer from the cathode surface to NFZ. With the applied cathode potential of −1.25 V (vs. Ag/AgCl), the removal efficiency of NFZ (C0 = 20 mg L−1) at the GR-Ni foam electrode reached up to 99 % within 30 min, showing a higher reaction rate constant (0.1297 min−1) than 0.0870 min−1 at the Pd-Ni foam and 0.0186 min−1 at the Ni foam electrode. It was also found that the pH, dissolved oxygen and NFZ initial concentration have slight effect on NFZ degradation at the GR-Ni foam electrode. The reactions first occurred at nitro groups (-NO2), unsaturated C=N bonds and N-N bonds to generate furan ring-containing products, and then these products were transformed into linear diamine products. The direct reduction by electrons was mainly responsible for NFZ reduction at the GR-Ni foam electrode. Even after 18 cycles, the removal efficiency of NFZ still reached up to 98 % within 1 h. In addition, the cathodic degradation process could eliminate the antibacterial activity of NFZ. The GR-Ni foam electrode would have a great potential in electrochemical process for treating wastewater containing furan antibiotics.

Mercury is one of the leading chemicals of concern and receives much attention in environmental safety. It is of great necessity to develop advanced Hg2+ analysis method for rapid detection and monitoring. Field-effect transistor (FET) sensor, an emerging electronic sensor, has received great attention in environmental analysis since it has unique advantages in achieving rapid analysis of chemicals. Herein, an FET sensor is constructed with Ti3C2Tx MXene as the channel material to detect Hg2+ in water. The sensor displays rapid and selective response to Hg2+. Moreover, the sensor achieves satisfactory performance in Hg2+ detection in high salinity environment (1 M NaCl), which benefits its applications in real water analysis. Based on the investigation of sensing mechanism, the strong response of Ti3C2Tx MXene FET sensor to Hg2+ is due to the adsorption and reduction of Hg2+ to Hg+ on the Ti3C2Tx surface. This reported label-free Ti3C2Tx MXene platform can detect Hg2+ in high salinity environment with high specificity, which has significant application potential for on-site monitoring and risk assessment of Hg2+ in aqueous systems.

Biochar adsorbents for removing As(III) suffer from the problems of low adsorption capacity and ineffective removal. Herein, a granular MgO-embedded biochar (g-MgO-Bc) adsorbent is fabricated in the form of millimeter-sized particles through a simple gelation-calcination method using chitosan as biochar sources. High-density MgO nanoparticles are evenly dispersed throughout the biochar matrix and can be fully exposed to As(III) through the rich pores in g-MgO-Bc. These features endow the adsorbent with a high adsorption capacity of 249.1 mg/g for As(III). The g-MgO-Bc can efficiently remove As(III) over a wide pH of 3–10. The coexisting carbonate, nitrate, sulfate, silicate, and humic acid exert a negligible influence on As(III) removal. 300 μg/L of As(III) can be purified to far below 10 μg/L using only 0.3 g/L g-MgO-Bc. The spent g-MgO-Bc could be well regenerated by simple calcination. In fixed-bed column experiments, the effective treatment volume of As(III)-spiked groundwater achieves 1500 BV (30 L) (3 g of adsorbent, solution flow rate of 2.0 mL/min, C0 = 50 μg/L). The Mg(OH)2 generated in situ in g-MgO-Bc is responsible for the adsorption of As(III) through the inner-sphere complex mechanism. The work would extend the potential applicability of biochar adsorbent for As(III) removal to a great extent.

A highly stable and effective electrochemiluminescence (ECL) sensing system of cadmium sulfide nanowires/reduced graphene oxide (CdS NWS/rGO) hybrid is presented for supersensitive detection of pentachlorophenol (PCP). CdS nanowire is for the first time exploited in ECL sensing. The rGO served as both ECL signal amplifier and immobilization platform, can perfectly enhance the ECL intensity and stability of the sensing system. With S 2 O 8 2− as coreactant, the ECL signal can be significantly quenched by the addition of PCP. The established ECL sensing system presents a wider linear range from 1.0 × 10 −14 to 1.0 × 10 −8 M and a much low detection limit of 2 × 10 −15 M under the optimum test conditions (e.g., pH 7.0 and 100 mM S 2 O 8 2− ). Furthermore, the ECL sensing system displays a good selectivity for PCP detection. The practicability of the ECL sensing system in real water sample shows that this system could be promisingly applied in the analytical detection of PCP in real water environments.

The serious photocorrosion of silver phosphate (Ag 3 PO 4 ) has limited its practical applications. In this work, we propose a strategy to suppress its photocorrosion by the construction of a Z-Scheme photocatalytic system, which composed of reduced graphene oxide-enwrapped Ag 3 PO 4 (Ag 3 PO 4 @RGO) and La,Cr-codoped SrTiO 3 (La,Cr:SrTiO 3 ). Dramatically, this system shows superior anti-photocorrosion and photocatalytic performances in degradation of both RhB and 2,4-DNP. Especially for RhB, it can be completely degraded after only 5 min under intense sunlight irradiation. The improved photoactivity and anti-photocorrosion of Ag 3 PO 4 @RGO@La,Cr:SrTiO 3 can be attributed to the following: (i) The sufficient interfacial contact between Ag 3 PO 4 and RGO is favorable to transfer the carriers and lengthen the lifetime of it; (ii) the package of Ag 3 PO 4 with RGO could work as a sheltering layer to protect Ag 3 PO 4 from photocorrosion. (iii) The aggregation of photogenerated holes in the VB of Ag 3 PO 4 makes it a rich-hole region due to Z-Scheme electrons transport mechanism, which can protect Ag 3 PO 4 from the photo-reduction. This strategy provides a new thought of protecting photosensitive semiconductor from photocorrosion and could regard as an efficient application method for environmental cleaning under natural sunlight irradiation. Furthermore, it even could be extended to outdoor or indoor air cleaning in the future.

Exploiting highly efficient electrocatalysts through simple methods is very critical to the development of energy conversion technologies. Herein, we develop a hierarchical reduced graphene oxide supported dealloyed platinum–copper nanoparticle catalyst (Pt–Cu/RGO) by a facile one-step electrodeposition of graphene oxide in the presence of H2PtCl6 and copper ethylenediamine tetraacetate. The nanostructure and composition were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Meanwhile, the electrocatalytic performance was investigated by cyclic voltammetry and chronoamperometry, showing that the Pt–Cu/RGO catalyst not only equips with an outstanding electrocatalytic activity for the methanol oxidation reaction (2.3 times that of commercial Pt/C catalyst), but also shows a robust durability and superior tolerance to CO poisoning. The excellent electrocatalytic performance could be attributed to the three-dimensional hierarchical structure, porous dealloyed nanoparticles and synergistic effect between each component.

Transition metal phosphides (TMPs) have been one of the ideal candidates as low-cost and high-efficiency catalysts for hydrogen evolution reactions (HERs). We report herein a novel TMP architecture, Fe2P nanoparticles/reduced graphene oxide (rGO) nanosheets/Fe2P nanoparticles (Fe2P@rGO) sandwich-structured (Fe2P@rGO) nanowall arrays on a Ti plate. This nanostructure was easily prepared via one-step electrodeposition followed by a low-temperature phosphidation reaction. The Fe2P@rGO nanowall array film is featured with maximally exposed catalytic sites, fast electron and mass transport, and robust structure stability, and therefore it behaves as an excellent HER electrocatalyst. The Fe2P@rGO shows a low overpotential of 101 mV at a current density of 10 mA cm−2 and a small Tafel slope of 55.2 mV dec−1 with a large exchange current density of 0.146 mA cm−2. Furthermore, the catalyst exhibits superior durability evidenced by about 87% catalytic activity retention against about 55% for the commercial Pt/C catalyst after a 12 h test. The study presents a new nanoengineering strategy for high-performance TMP-based HER catalysts.

Photoelectrocatalytic (PEC) process is a rising approach to simultaneous removal of heavy metals and organic pollutants. However, electric field plays a dual role in the reduction of negatively charged metal species (e.g., Cr 2 O 7 2− ): Reduction driving force makes metal species move to cathode; electric field force pulls negatively charged species to anode. The reduction reaction of Cr(VI) (Cr 2 O 7 2− ) strongly depends on the concentration of both Cr 2 O 7 2− and H + on the surface of cathodes. The reduction of Cr(VI) in conventional PEC process must enhance proton concentration with a mass of strong acid or prolong reaction time. A highly effective PEC system was constructed with amino-modified carbon cloth as cathode and reduced graphene oxide functionalized TiO 2 nanotube arrays as photo-anode. The amino groups could concentrate protons to form quaternary ammonium cations which could adsorb Cr 2 O 7 2− ions through electrostatic interaction. The graphene functionalized anode greatly accelerated the mass transfer of organic pollutants onto photo-anode. Resultantly, Cr(VI) and 2,4-dichlorophenoxyacetic acid (2,4-D) could be removed faster at lower cell voltage compared with conventional PEC process and the electric energy consumption decreased by at least 50%. Furthermore, the proposed PEC process could be repeatedly utilized with highly stable working performance. This work would give a new insight into the development of cost-effective PEC process for treatment of Cr(VI)-containing wastewater.

Although Fe-based biochar adsorbents are attractive for removing arsenic from water due to their advantages of costing little and being producible at a large scale, the practical applications of these granular adsorbents are mainly limited by low Fe utilization and slow adsorption kinetics. In this study, iron oxide nanoneedle array-decorated biochar fibers (Fe-NN/BFs) adsorbents have been prepared through a simple hydrothermal reaction. The vertical growth of iron oxide nanoneedle arrays on the surface of biochar fibers maximizes Fe utilization and shortens As diffusion distance, thereby increasing As removal kinetics and capacity. Batch experiments show that the adsorption capacities of Fe-NN/BFs for As(V) and As(III) reach to 93.94 and 70.22 mg/g-Fe at pH 7.0, respectively. As(V) levels (275 μg/L) in groundwater are rapidly reduced (less than 5 min) to below 10 μg/L using Fe-NN/BFs (1 g/L) at pH 6.7. Similar As(III) levels can be reduced to below 10 μg/L within 30 min by Fe-NN/BFs (1.5 g/L). In fixed-bed experiments, the treatment volumes of As(V) and As(III) spiked groundwater reach to 2900 BV (26.2 L) and 2500 BV (22.6 L), respectively, using two columns packed with Fe-NN/BFs in tandem (C0 = 275 μg/L, 2 g of adsorbents in each column). When the As concentration in the influent is reduced to 50 μg/L (As(V): 25 μg/L + As(III): 25 μg/L), the treatment volume using one column reaches up to 11000 BV. The Fe-NN/BFs packed column can be easily regenerated and reused many times. After four regenerations, the treatment volume of As(V) and As(III) were reduced by 10.4% and 22.8%, respectively.

As charge storage occurs both on the surface and in the bulk of material, the dynamics of charge storage is a key issue in the practice of energy storage. Although the energy storage can be increased in the bulk of the material, it often suffers from a quite slow kinetics, which seriously hinders the rate capability. Keeping high surface-induced capacitive contribution is proposed to address this issue. Herein, a porous scaffold, TiO2 nanotube arrays grown in a Ti foil (TiO2 NTs/Ti) is selected as the current collector for electrodeposition of porous polyaniline/reduced graphene oxide (PANI/rGO) hybrid film. The capacitive contribution of PANI/rGO@TiO2/Ti is quantitatively evaluated, showing a high surface-induced capacitive contribution up to 58% at high rates (>25 mV s−1) and large electron transfer coefficient of 2. As a result, the electrode not only shows an ultrahigh specific capacity of 908 C g−1 at 1 mV s−1, but also delivers an outstanding rate capacity of 310 C g−1 at 500 mV s−1. PANI/rGO@TiO2/Ti also shows excellent cycling stability with 80% capacity retention after 10,000 cycles at a high current density of 25 A g−1.

A new hierarchical nanoarchitecture with integration of multiple active materials has been developed for highly efficient hydrogen evolution reaction (HER), by decorating a perpendicular hybrid of MoS2 and N-doped graphene nanosheets with CdS nanoparticles. The unique architecture promoted light trapping and absorption for highly efficient light harvesting and photocarrier generation, and offered an unblocked electron transport pathway for rapid charge separation/transport to suppress charge recombination. Its high surface area and high density of active sites result in highly efficient utilization of photogenerated carriers for productive HER. Significantly, without using noble metals as co-catalysts, the photocatalysts demonstrated rapid HER rates as high as 5.01 mmol h−1 g−1 under visible-light irradiation, which was approximately 25 times that of pure CdS. The hydrogen production remained stable after a continued test for 30 h, showing an exceedingly high performance and superior stability.

Anodic electrochemiluminescence (ECL) emission was for the first time observed from noble metal nanoparticles under coreactants. In this work, we present a novel ECL sensor based on Pt nanoclusters/graphene (Pt NCs/GR) hybrid with triethanolamine (TEA) as the coreactant for the trace detection of copper ion (Cu2 +). GR significantly enhanced the anode ECL signal, due to its superior electron conduction. The ECL intensity could be greatly weakened by addition of Cu2 +. The proposed protocol offered a highly sensitive, selective and recyclable method for detection of Cu2 + with a wide linear range from 1.0 × 10− 4 to 2.0 × 10− 1 mg/L and a low detection limit of 1.0 × 10− 4 mg/L. Furthermore, the practicability of the ECL sensor in real water sample was also tested, showing that the ECL sensor based on Pt NCs/GR could be a promising alternative method for the monitoring of the Cu2 + in real sample.

In this paper, g-C3N4/GR hybrid has been prepared by a novel one-step electrochemical reduction technology for the first time. GR not only serves as immobilization platform for g-C3N4, but also significantly enhances the electrochemiluminescence (ECL) signal of g-C3N4 (∼4.7 times); additionally, the ECL signal can be further enhanced in the presence of the self-produced coreactant from oxygen reduction. Moreover, due to the quenching effect of pentachlorophenol (PCP) on the ECL signal of g-C3N4/GR, an advanced ECL sensor based on g-C3N4/GR has been fabricated for the ultrasensitive and rapid detection of PCP with unprecedented sensitivity reaching 1.0 × 10−11 mol L−1 in a wide linear range from 1.0 × 10−11 to 1.0 × 10−7 mol L−1, and the possible ECL detection mechanism has been proposed in detail. The practicability of the sensing platform in real water sample shows ideal recovery rates. Moreover, we also find that the one-step electrodeposition technology might be a good and viable way to make the bulk g-C3N4 thinner. Our experiments display the powerful utility of GR to g-C3N4 ECL studies and will emerge eximious applications in analytical communities and environmental monitoring.

Highly efficient planar heterojunction perovskite solar cells (PHJ–PSCs) with a structure of ITO/PEDOT:PSS/CH3NH3PbI3–xClx/PCBM/C60/Ag was fabricated, in which the compact and pinhole-free CH3NH3PbI3–xClx perovskite thin film was obtained using a mixture of precursors containing lead iodide (PbI2), lead chloride (PbCl2), and methylammonium iodide (CH3NH3I) at an optimized ratio of 1:1:4. The morphology and formation process of CH3NH3PbI3–xClx thin film was closely related to the annealing temperature and time, which would result in the controllable performance for the PHJ–PSC devices. The morphology, crystallization process, and element analysis suggested that the chlorine gradually diffused and sublimated from the film surface while the iodine moved to the surface, together with the removal of the pinholes in the film. The PHJ–PSCs with the as-prepared CH3NH3PbI3–xClx thin film showed good performance and excellent repeatability. The power conversion efficiency (PCE) up to 14.03% was achieved without obv...

Interface is one of the most important factors to influence the device stability, which directly determines the commercialization of perovskite solar cells (PSCs). The research disclosed the degradation process and mechanism of planar heterojunction (PHJ) PSCs with a structure of ITO/PEDOT:PSS/CH 3 NH 3 PbI 3 /PCBM/Al using in-situ experiments. The degradation of PHJ-PSCs is mainly attributed to the interface decay of perovskite/cathode. Large amount of bubbles formed quickly at the interface and grew up as PHJ-PSCs exposed to air. The cathode electrode easily peeled off from the devices that led to lose the efficiency completely after only 1 h exposure to air. On the other hand, the degradation driven by intrinsic decomposition of perovskite itself under atmosphere (humidity ∼ 45 RH%) was not obvious and the power conversion efficiency ( PCE ) could retain almost the same when only the perovskite layer was exposed to air for 200 h. Furthermore, annealing-free TiO 2 nanocrystalline particles (TiO 2 NPs) as an interface modification layer was inserted into PHJ-PSCs and dramatically improved the stability, of which the PCEs retained over 75% of its initial values after exposure to air for 200 h. The results provide important information to understand the degradation of PSCs and the improvement of the stability, which may potentially accelerate the development and commercialization of PSCs.

Nitrogen-rich carbon material derived from carbon self-repairing g-C3N4 is self-assembled with graphene oxide (GO) to form a porous structure. Different from the pristine g-C3N4, which has scarcely been employed in supercapacitors because of its low charge mobility, the carbon self-repairing g-C3N4 (C-C3N4) shows an improved electrochemical activity. After carbon-repairing, a delocalized big π-bond can be formed by the homogeneous C-substitution for N atoms or the formation of new interstitial C–N bond. The extending π-conjugation planar layer of C-C3N4 possesses a closer contact with GO to form a three-dimensional (3D) pore structure, which ensures good mobility for electrons and quick access for electrolytes. Under the optimum C-repairing content of 5.99 at%, the C-C3N4@rGO exhibited high specific capacity of 379.7 F g−1 and energy density of 52.7 W h kg−1 at a current density of 0.25 A g−1. Moreover, the electrode kept 85% capacity retention after 10 000 cycles at a high constant current density of 10 A g−1. The active sites of pseudocapacitance can be confirmed in the oxygen-containing groups and the carbon atoms close to the nitrogen by the XPS results.

A highly stable and effective electrochemiluminescence (ECL) sensing platform of copper oxide nanowires coupled with reduced graphene oxide (CuO NWs/rGO) is presented for ultrasensitive detection of pentachlorophenol (PCP). The CuO NWs/rGO sensing system is prepared via an electrodeposition technique followed by chemical oxidation and annealing processes. The CuO nanowire is revealed to be electroluminescent for the first time, and the rGO greatly enhances the ECL signal. In the presence of the coreactant S 2 O 8 2− , the CuO NWs/rGO-based ECL sensor can sensitively and selectively detect PCP with a wide linear range from 1.0 × 10 −14 to 1.0 × 10 −9 mol L −1 and a very low detection limit of 0.7 × 10 −14 mol L −1 . The sensor shows excellent recyclability and outstanding durability evidenced by its nearly unchanged ECL signal after the sensing electrode being stored for 10 months in air at room temperature. The proposed ECL sensor could be a promising alternative method for the emergency and routine monitoring of the PCP in real environment.

We report a nearly vertical reduced graphene oxide (VrGO) nanosheet coupled with polyaniline (PANI) for supporting palladium (Pd) nanoparticles. The PANI-coupled VrGO (PANI@VrGO) nanosheet is prepared by a simple one-step electrodeposition technique ,and Pd nanoparticles are anchored on the support of PANI@VrGO through the spontaneous redox reaction of PANI with a palladium salt. The designed PANI@VrGO nanosheet efficiently exposes the surface of rGO sheets and stabilizes metal nanoparticles. Consequently, the Pd/PANI@VrGO electrocatalyst exhibits high catalytic activity and excellent durability for alcohol oxidation reaction. The proposed nanoarchitecture offers a new pathway to greatly promote the performances of rGO in various applications; moreover, this work provides a powerful and universal synthetic strategy for such an architecture.

Cathode materials with high activity, selectivity and stability are essential to efficient electrochemical H2O2 generation. Herein, nitrogen-doped porous carbon (NPC) is synthesized via direct calcination of nitrogen-containing metal organic framework. The N doping into porous carbon boosts H2O2 generation, thus enhancing electro-Fenton activity. The NPC cathode exhibits a highly selective reduction of O2 to H2O2 (96.4% at pH 1 and −0.1 V vs SCE) and H2O2 production rate reaches 52.3 mmol·L−1 h−1 (pH 1, −0.6 V vs SCE). Moreover, NPC achieves a high current efficiency of 87.7% for H2O2 production (pH 1, −0.5 V vs SCE). The removal efficiency of oxcarbazepine antibiotics achieves 100% in 10 min ([Fe2+] = 1.0 mmol L−1, C0 = 12.61 mg L−1 (50 μmol L−1), pH 1–5, −0.5 V vs SCE), and total organic carbon (TOC) removal efficiency reaches 90.7% in 60 min. Additionally, the removal efficiency of other antibiotics of prednisolone, chloramphenicol and thiamphenicol reaches 97.0–98.8% in 10 min and the TOC removal efficiency achieves 70.8–92.0% in 60 min. Moreover, NPC shows an excellent electrochemical stability. This work is valuable for designing electro-Fenton catalysts with high activity, selectivity and stability.

Photoelectrocatalytic (PEC) especially continuous flow PEC process for organic wastewater treatment greatly depends on both catalytic capacity and practical availability of electrode materials. In this study, g-C3N4 nanosheets are implanted into TiO2 nanotube arrays mesh (TCNs) through direct calcination of TiO2 nanotube array mesh loading melamine precursor. The TCNs photoelectrodes exhibit excellent PEC activity in organic pollutant degradation. Typically, almost 100% of tetracycline (TC, an emerging refractory antibiotic pollutant) is removed in 2 h and TOC removal reaches to 93% in 3 h under simulated solar irradiation at 1 V vs. Ag/AgCl. Theoretical calculations are performed to predict the primary reactive sites for radical species attack and the intermediates are identified. Meanwhile, the ecotoxicity of TC-containing wastewater greatly decrease after PEC treatment. Impressively, because of the mesh screen effect and high catalytic capacity of the photoelectrode, continuous flow PEC process keeps 80% removal efficiency of TC in real wastewater in the absence of additional background electrolyte. After prolonging 20 h, the level of treatment is highly stable. This work would set an example for potential large-scale treatment of organic wastewater using PEC process.

Lithium ion sieves (LIS) have gained great interest in lithium recovery. However, the synthesis of high stability, selectivity, and adsorption capacity of LIS is still a great challenge. Here, a general strategy combining electrospinning and calcination techniques is developed to fabricate a series of porous titanium-based LIS nanofibers. The porous structure created by calcination increases the exposure of the adsorption sites, which significantly accelerates the deintercalation and intercalation of Li+ from and into the vacancies in the framework. All of samples have good Li+ adsorption capacity and high selectivity for Li+. As a proof of concept, porous H4Ti5O12 nanofibers (P-HTO-NF) transformed from the electrospun porous Li4Ti5O12 nanofibers (P-LTO-NF) are systematically investigated in lithium recovery. P-HTO-NF possesses a superior adsorption capacity (59.1 mg/g), which is nearly close to the theoretical value (63.77 mg/g). The Freundlich isotherm model can well describe the adsorption isotherm data. The adsorption equilibrium can reach within 30 min (C0 = 300 mg/L, pH = 11, S/L = 60 mg/60 mL). The equilibrium distribution coefficient (Kd, mL/g) for Li + (232) is extremely higher than that for competing ions (1.41 for Na+, 1.17 for K+, 0.88 for Mg2+, 0.58 for Ca2+) (C0 = 40 mg/L for Li+, pH = 8), indicative of a highly selective recovery of lithium from brine water. The LIS show excellent stability with a low Ti dissolution and the adsorption capacity for Li+ remains 86.5% after 6 cycles. Our work provides a universal strategy for the synthesis of porous LIS.

Highly efficient and non-hysteresis organic/perovskite planar heterojunction solar cells was fabricated by low-temperature, solution-processed method with a structure of ITO/PEDOT:PSS/CH 3 NH 3 PbI 3 /PCBM/Al. The high-quality perovskite thin film was obtained using a solvent-induced-fast-crystallization deposition involving spin-coating the CH 3 NH 3 PbI 3 solution followed by top-dropping chlorobenzene with an accurate control to induce the crystallization, which results in highly crystalline, pinhole-free, and smooth perovskite thin film. Furthermore, it was found that the molar ratio of CH 3 NH 3 I to PbI 2 greatly influence the properties of CH 3 NH 3 PbI 3 film and the device performance. The equimolar or excess PbI 2 was facile to form a flat CH 3 NH 3 PbI 3 film and produced relatively uniform perovskite crystals. Perovskite solar cells (PSCs) with high-quality CH 3 NH 3 PbI 3 thin film showed good performance and excellent repeatability. The power conversion efficiency ( PCE ) up to 13.49% was achieved, which is one of the highest PCEs obtained for low-temperature, solution-processed planar perovskite solar cells based on the structure ITO/PEDOT:PSS/CH 3 NH 3 PbI 3 /PC 61 BM/Al. More importantly, PSCs fabricated using this method didn’t show obvious hysteresis under different scan direction and speed.

Here for the first time, we present a novel electrochemiluminescence (ECL) sensor based on graphitic carbon nitride/graphene oxide (g-C3N4/GO) hybrid for the ultrasensitive detection of Cu(2+), which is a common pollutant in environmental system. The g-C3N4/GO shows stable ECL signal in the presence of the self-produced coreactant from oxygen reduction, and the ECL signal could be effectively quenched by Cu(2+), the possible ECL detection mechanism has been proposed in detail. GO can not only significantly enhance the cathodic ECL signal of g-C3N4 (∼3.8 times), but also serve as immobilization platform for g-C3N4. After optimization of experimental conditions, the proposed protocol can offer an ultrasensitive, highly selective and recyclable method for the detection of Cu(2+) with a low detection limit of 1.0 × 10(-11) M and a wide linear range from 1.0 × 10(-11) to 1.0 × 10(-7) M. Moreover, the practicability of the ECL sensor in real wastewater samples is also tested, showing that the proposed ECL sensor could be a promising alternative method for the emergency and routine monitoring of Cu(2+) in real sample.

Reduced graphene oxide (rGO) is a promising support material for nanosized electrocatalysts. However, the conventional stacking arrangement of rGO sheets confines the electrocatalysts between rGO layers, which decreases the number of catalytic sites substantially. We report here a facile synthesis of vertically oriented reduced graphene oxide (VrGO) through cyclic voltammetric electrolysis of graphene oxide (GO) in the presence of Na2 PdCl4 . Experiments without Pd nanoparticles or with a low loading amount of Pd nanoparticles results in the deposition of rGO parallel to the electrodes. The vertical orientation of Pd/rGO nanoflakes causes a remarkable enhancement of the catalytic activity toward methanol electro-oxidation. The mass activity (620.1 A gPd (-1) ) of Pd/VrGO is 1.9 and 6.2 times that of Pd/flat-lying rGO (331.8 A gPd (-1) ) and commercial Pd/C (100.5 A gPd (-1) ), respectively. Furthermore, the Pd/VrGO catalyst shows excellent resistance to CO poisoning. This work provides a simple wet-chemical method for VrGO preparation.

Pentachlorophenol (PCP) is an environmental pollutant of serious concern due to its high toxicity and long persistence property. Fast and sensitive detection of PCP is therefore of great interest. Here, for the first time, a novel electrochemiluminescence (ECL) sensor based on Au nanoclusters/graphene (Au NCs/GR) hybrid has been constructed for the detection of PCP, with S 2 O 8 2− as coreactant. GR facilitates both Au − and SO 4 − production, and a high yield of the excited Au NCs (Au *+ ) produces due to the presence of Au – and SO 4 − . The interaction between PCP and the Au *+ results in a sensitive change in the ECL intensity, with an unprecedented sensitivity reaching 1.0 × 10 −14 M concentration in a wide linear range from 1.0 × 10 −14 M to 1.0 × 10 −10 M. Other compounds which cannot be oxidized by the Au *+ show little interference on the detection of PCP. The obtained ECL sensor is low toxicity and regenerable, furthermore, the practicability of the ECL sensor in real water sample is also tested, which shows satisfactory results.

Graphene is a promising support for nanosized electrocatalysts, however the conventional stacking arrangement of its graphene sheets substantially decreases the catalytic sites on the catalyst. We report here the fabrication of a graphene/Cu electrocatalyst by the simple cyclic voltammetric electrolysis of graphene oxide (GO) and copper ethylenediamine tetraacetate (Cu–EDTA), and find that the electrochemically reduced GO (RGO) and Cu nanoparticles can be sequentially self-assembled into layer-by-layer, 3D sandwich-type, and homogenous architectures as the concentration ratio of Cu–EDTA/GO increases. The 3D sandwich-type RGO/Cu composite (S-RGO/Cu) shows RGO sheets decorated with Cu nanoparticles which stand nearly perpendicular on the electrode, leading to a significant increase in the electrochemically accessible surface area (0.685 cm2) relative to those of the horizontal layer-by-layer RGO/Cu composite (0.147 cm2) and the homogenous RGO/Cu composite (0.265 cm2). Stemming from its high electrochemical surface area, the S-RGO/Cu composite exhibits a high electrocatalytic activity in hydrazine oxidation in terms of current density and overpotential. Mechanistic analysis of the electrode reactions reveals the reaction pathways of hydrazine on RGO/Cu are closely related to the electrochemical surface area of the RGO/Cu electrocatalyst. The correlation between the architectures and their performances in electrocatalysis presented here can guide the design of novel structures with enhanced properties.

Integral buckle arrestor, which consists of welded stiff rings, has proved to be very effective to arrest the propagating buckle and can be applied in sandwich pipe systems. This paper examines the propagating buckle experiments on small-scale sandwich pipes with integral arrestors under different interface bonding conditions. In addition, a numerical framework was developed to reproduce the phenomenon of buckling propagation and crossover under external pressure, and good consistency was observed between the measured and predicted results. Then, the crossover pressure was studied parametrically covering the interface bonding conditions, key material properties, as well as geometries. An empirical expression was established based upon extensive numerical analysis to predict the crossover pressure of integral arrestors for sandwich pipes. The analysis further demonstrated that its arresting performance can be reasonably evaluated with the established empirical expression and lower bound envelope line.

TiO2 nanotube array (TiO2 NT) was co-decorated by reduced graphene oxide (RGO) and CdTe nanoparticles (NPs) through a simple one-step electrodeposition process. RGO film was formed on the top surface of TiO2 NT and CdTe NPs homogeneously dispersed within the RGO sheets and on the inner/outer walls of TiO2 NT. Resulting from the synergetic effect of RGO and CdTe, the photocatalytic activity of the ternary RGO/CdTe–TiO2 NT photocatalyst far exceeded those of bare TiO2 NT, RGO-TiO2 NT, and CdTe–TiO2 NT photocatalysts in the degradation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated solar light or visible light irradiation. After 180-min UV–Vis (or visible light) irradiation, almost 100 % (or 96 %) 2,4-D removal efficiency was achieved on RGO/CdTe–TiO2 NT, much higher than 42 % (or 2 %) on bare TiO2 NT, 58 % (or 10 %) on RGO–TiO2 NT, and 52 % (or 41 %) on CdTe–TiO2 NT. This study will inspire better design of advanced photocatalysts with high visible-light photocatalytic activity.

Au nanoparticles and reduced graphene oxide co-loaded TiO 2 nanotube arrays (Au/RGO–TiO 2 NTs) were prepared through a simple one-step constant-potential electrolysis of chloroauric acid and graphene oxide on TiO 2 NTs. Compared with Au–TiO 2 NTs, RGO–TiO 2 NTs and un-modified TiO 2 NTs, the Au/RGO–TiO 2 NTs exhibited high efficiency in photocatalytic degradation of methyl orange (MO) under simulated solar light irradiation. The highly efficient photocatalytic activity is associated with broad absorption in the visible light region, increased photoinduced charge separation through transferring photogenerated electrons from TiO 2 NTs to both Au and RGO, as well as the strong adsorption ability of RGO to MO molecules. Moreover, the Au/RGO–TiO 2 NTs has an excellent stability. This work provides an insight into designing and synthesizing new TiO 2 NTs-based hybrid materials for effective visible light-activated photocatalysis.

We report on a highly sensitive and selective electrochemiluminescence (ECL) based method for the determination of pentachlorophenol (PCP). It is based on a new hybrid material composed of CdS quantum dots (QDs), graphene, and carbon nanotubes (CNTs), and uses peroxodisulfate as the coreactant. The use of this system results in a nearly 18-fold increase in ECL intensity. On interaction between PCP and the QDs, a decrease in ECL intensity is observed at PCP in a concentration as low as 1.0 pM and over a wide linear range (from 1.0 pM to 1.0 nM). The method is hardly affected by other chlorophenols and nitrophenols, and the electrode can be recycled.

Refractory herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) can be efficiently removed by photocatalytic degradation when using reduced graphene oxide (RGO) and CuInS2 nanoparticles (NPs) co-decorated TiO2 nanotube arrays (NTs) (RGO/CuInS2–TiO2 NTs) as a photocatalyst prepared by successive pulse electrodeposition of CuInS2 and RGO film onto the top surface of TiO2 NTs. The new catalyst exhibits significant photocatalytic activity and good removal efficiency of 2,4-D. The photodegradation rate toward 2,4-D over RGO/CuInS2–TiO2 NTs under simulated solar light (or visible light) irradiation is 96.2% (or 87.7%), much higher than 68.0% (or 58.4%) over CuInS2–TiO2 NTs, 50.1% (or 38.1%) over RGO–TiO2 NTs and 36.0% (or 26.3%) over bare TiO2 NTs, respectively, meaning that the photocatalytic performance of TiO2 NTs could be greatly enhanced by the synergetic effect of RGO and CuInS2. This work could provide new insights into the design and fabrication of advanced photocatalysts.

A simple one-step electrochemical deposition method was demonstrated to fabricate reduced graphene oxide/Ag nanoparticle co-decorated TiO2 nanotube arrays (RGO/Ag–TiO2NTs) photocatalyst in this study. The structures and properties of these photocatalysts were characterized using scanning electron microscope, X-ray diffraction, UV–Vis diffuse reflection spectra, and photoluminescence. By taking the advantages of TiO2, graphene, and Ag nanoparticles (AgNPs), RGO/Ag–TiO2NTs showed a greatly improved photocatalytic activity compared with the bare TiO2NTs, Ag–TiO2NTs or RGO–TiO2NTs. The deposited RGO and AgNPs not only reduce the recombination of photogenerated electrons and holes, but also increase the surface area of the catalyst. Both photocatalytic performance and adsorptivity of the catalyst have been improved. The ternary photocatalyst exhibited over 93 % removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated solar light irradiation with good stability and easy recovery, which justifies the photocatalytic system, a promising application for herbicide or other organic pollutant removal from water.

A new photocatalyst, magnetic TiO2-graphene, was designed and facilely produced by combining sol-gel and assembling processes. Taking advantages of graphene and TiO2, the catalyst exhibited strong light absorption in the visible region and high adsorption capacity to organic pollutants, resulting in almost 100% photocatalytic removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water under simulated solar light irradiation, far higher than 33% on commercial P25. Toxicity assessment indicates the total decomposition of the original substrate. Furthermore, the catalyst can be rapidly recovered with highly stable photocatalytic performance. After 8 successive cycles, the removal efficiency of 2,4-D maintained 97.7%, and particularly, 99.1% 2,4-D removal efficiency came back at the ninth recycle when the catalyst was re-treated by ultrasonication. Moreover, even after being laid aside for one year the catalyst still kept the 2,4-D removal efficiency as high as 95.6%. For practical application, the photocatalytic also demonstrated high removal efficiencies of herbicide 2,4-D. The photocatalyst is a promising platform for removing herbicide pollutants from water.

TiO 2 nanotube arrays (TiO 2 NTs) were simultaneously modified by reduced graphene oxide (RGO) and PbS nonoparticles (NPs) through a simple one-step electrodeposition process. RGO film is formed on the top surface of TiO 2 NTs and PbS NPs showing size less than 20 nm are intercalated within the RGO sheets and also dispersed inside/outside walls the TiO 2 NTs. Resulting from the synergetic effect of RGO and PbS, the photocatalytic activity of the ternary RGO/PbS-TiO 2 NTs photocatalyst far exceeds those of bare TiO 2 NTs, the binary RGO-TiO 2 NTs and PbS-TiO 2 NTs photocatalysts in the degradation of pentachlorophenol (PCP) under simulated solar light. After 120-min irradiation, almost 100% PCP removal is obtained on the RGO/PbS-TiO 2 NTs, compared to 61% on bare TiO 2 NTs, 76% on RGO-TiO 2 NTs, and 86% on PbS-TiO 2 NTs. Because the PbS NPs were covered by the RGO sheets, to a certain extent the photocorrosion of PbS was suppressed, and therefore the RGO/PbS-TiO 2 NTs photocatalyst shows a good stability relative to the PbS-TiO 2 NTs without RGO. This study will inspire better design of advanced photocatalysts with high visible-light photocatalytic activity, easy recovery, and good stability.

We have modified a glassy carbon electrode by single-step electrodeposition of graphene (GR), gold nanoparticles (AgNPs), and chitosan (CS) directly from a solution containing graphene oxide, tetrachloroauric acid, and chitosan. The surface and electrochemical properties of the film-modified electrode were investigated by SEM and TEM images. The AuNPs have a diameter of about 20 nm and are uniformly dispersed in the matrix. Combining the advantages of GR (i.e., high surface area and conductivity), of AuNPs (excellent electrical conductivity) and CS (excellent film-forming ability and good water permeability), the hybrid film effectively enhances electron-transfer and promotes the response to lead(II) ion. Under the optimum conditions, a linear relationship exists between electrical current and the concentration of lead (II) ion in the range between 0.5 to 100 μg L-1, with a detection limit of 1 ng L-1 (at an SNR of 3). The electrode was successfully applied to the detection of lead(II) in spiked samples of river water.