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[Display omitted] • IrCo 0.13 nanoalloy is prepared by chemical reduction and electrochemical treatment. • Abundant Co vacancies and atomic heterostructure facilitate OER and HER. • Strong interaction of Ir and Co contributes to remarkable stability and activity. • IrCo 0.13 exhibits an overpotential of 238 (OER) and 18.6 mV (HER)@10 mA cm−2, respectively. • Bifunctional IrCo 0.13 as both anode and cathode displays 1.68 V@1 A cm−2 in PEMWE. Exploring the electrocatalysts with high intrinsic activity and stability for both anode and cathode to tolerate the extremely acidic condition in proton exchange membrane water electrolyzer (PEMWE) is crucial for widespread industrial application. Herein, we constructed the bifunctional IrCo x nanoalloys with abundant metal vacancies via the combination of chemical reduction and electrochemical treatment for overall water splitting. The developed IrCo 0.13 exhibits ultra-low overpotentials of 238 mV for OER and 18.6 mV for HER at 10 mA cm−2 in 0.1 M HClO 4 , and achieves the exceptional stability of 1000 h for OER and 100 h for HER at 10 mA cm−2. Further, the cell voltage is only 1.68 V to reach a high current density of 1 A cm−2 in PEMWE with IrCo 0.13 as the both cathode and anode catalytic layer, and it shows excellent corrosion resistance in acidic environment, evidenced by 415 h stable operation at 1 A cm−2. The strong electronic interactions in the Ir-Co atomic heterostructure and the in-situ generation of Co vacancies by electrochemical oxidation synergistically contribute to the enhanced activity and stability via optimizing the electronic structure of adjacent Ir active sites, enhancing the conductivity and electrochemical active surface area of the catalyst, accelerating charge transfer and kinetics. This work provides a new perspective for designing bifunctional catalysts for practical application in PEMWE. [ABSTRACT FROM AUTHOR]

[Display omitted] Production of C 2 chemicals (such as C 2 H 4 , C 2 H 5 OH, etc.) from CO 2 electroreduction reaction (CO 2 ER) has been regarded as a promising route to solve the environmental problems and energy crisis. In this work, mesoporous Cu 2 O microspheres of ca. 700 nm diameter size with low crystallinity were fabricated to enable efficient conversion of CO 2 to C 2 chemicals by electrocatalytic reduction. It is revealed that compared with bulk Cu 2 O, the obtained mesoporous Cu 2 O microspheres have larger surface area, more grain boundaries and defects (unsaturated coordination sites), which facilitate the adsorption and stabilization of the important intermediates, such as *CO, on the route to C 2 chemicals formation. As a result, the Faraday efficiency (FE) of C 2 products reaches as high as 82.6 % and 78.5 % in an H-cell and a flow cell, respectively. In situ Raman and FT-IR spectra reveal that during CO 2 ER test there exists abundant *CO on the mesoporous Cu 2 O surface, thus increasing the opportunity of C C coupling. And the high coverage of *CO on catalyst surface during CO 2 ER protects and stabilizes the oxidation state of Cu species. This work demonstrates an effective strategy to introduce mesoporous structures and decreased crystallinity for improving the performance of CO 2 ER to C 2 products. [ABSTRACT FROM AUTHOR]

A Cs 3 Bi 2 Br 9 @Nb 2 O 5 S-scheme photocatalyst is constructed by embedding Cs 3 Bi 2 Br 9 perovskite quantum dots into mesoporous Nb 2 O 5. Profiting from the boosted charge separation, as well as the enhanced CO 2 adsorption contributed by mesoporous Nb 2 O 5 , the Cs 3 Bi 2 Br 9 @Nb 2 O 5 nanocomposite exhibits excellent CO 2 photoreduction performance. [Display omitted] Solar-energy-powered CO 2 reduction into valuable chemical fuels represents a highly promising strategy to address the currently energy and environmental issues. Owing to the nontoxicity and robust reduction capability, lead-free Cs 3 Bi 2 Br 9 perovskite quantum dots (PQDs) are regarded as an attractive material for CO 2 photoreduction. Nevertheless, the potential of their applications in this field has been restricted by the severe charge recombination, resulting in unsatisfactory photocatalytic performance. Herein, a step-scheme-based Cs 3 Bi 2 Br 9 @Nb 2 O 5 (CBB@Nb 2 O 5) nanocomposite was fabricated by embedding the CBB PQDs into mesoporous Nb 2 O 5. Experimental studies, along with theoretical calculations, revealed that the charge migration route in the CBB@Nb 2 O 5 nanocomposite conformed to the step-scheme (S-scheme) mode, enabling effective charge separation and strong redox ability preservation. Profiting from the promoted charge separation, as well as the improved CO 2 adsorption contributed by mesoporous Nb 2 O 5 , the CBB@Nb 2 O 5 nanocomposite unveiled superior CO 2 photoreduction performance, with CO evolution rate reaching 143.63 μmol g−1h−1. The present study provides a potential strategy to manufacture highly-efficient perovskite-based photocatalysts for achieving carbon neutrality. [ABSTRACT FROM AUTHOR]

[Display omitted] Although solar steam generation is promising for seawater desalination, it is less effective in purifying wastewater with both salt/heavy metal ions and organic contaminants. It is thus imperative to develop multifunctional integrated solar-driven water purification systems with high solar-thermal evaporation and photocatalytic degradation efficiencies. Herein, a lamellar reduced graphene oxide (L-RGO) foam with the vertical lamellar structure is fabricated by bidirectional-freezing, lyophilization, and slight chemical reduction for water purification. The unique vertical lamellar structure not only accelerates upward transport of water for facilitating water evaporation but also endows the L-RGO foam with superb high elasticity for tuning the interlayer distance and varying interactions between the oxygen-containing groups and water molecules to adjust water energy state. As a result, the L-RGO foam achieves a superb water evaporation rate of 2.40 kg m−2 h−1 along with an energy efficiency of 95.3 % under the compressive strain of 44.7 % under 1-sun irradiation. Equally importantly, the decoration of L-RGO foam with polypyrrole is capable of efficiently degrading organic pollutants while retaining high solar steam generation performances, exhibiting great potential in the comprehensive treatment of various water sources for relieving freshwater crisis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The carbonized recycled melamine sponge obtained excellent low-cost porous matrix. • FeNi@NCS shows lower reaction potential and higher electron transfer ability on UOR. • Successfully assembled the DBHPFC using urine as fuel. • DUHPFC presents excellent open circuit voltage. The direct urea fuel cell (DUFC) is a power generation equipment with urea-rich wastewater or urine as fuel source. It has the unique ability to purify sewage while simultaneously generating electricity, making it a highly efficient and environmentally friendly option. In this paper, pomegranate seed-like Ni nano-blocks and Fe nanosheets were synthesized by electrodeposition and chemical reduction and attached to the carbonized melamine sponge matrix. The N -doped carbon sponge (NCS) provided a large number of polyhedral holes, which allowed for efficient gas escape through channels. The combination of Fe reduces the initial urea oxidation potential, reaction activation energy and reaction resistance. The synthesized FeNi supported on N -doped carbon sponge composite (FeNi@NCS) has a catalytic current density of 625 mA cm−2 and a Tafel slope of 42.51 mV dec−1 for urea electrooxidation reaction (UOR). Assembling the direct urine-hydrogen peroxide fuel cell (DUrHPFC) resulted in the highest performance output. The open circuit voltage (OCV) was 0.98 V, and the peak power density reached 9.61 mW cm−2. The results show that the prepared catalyst provides an opportunity to solve the problems that hinder the development of urea green cycle at present. [ABSTRACT FROM AUTHOR]

[Display omitted] • Expanded vermiculite is integrated with a photoactive COF polymer. • Total Cr removal is realized by combining Cr(VI) reduction with Cr(III) exchange. • The spent catalyst is recycled for efficient ciprofloxacin and NO photooxidation. Design and fabrication of feasible remediation composites for total Cr (Cr(T)) removal is still challenging but urgently required. Herein, eco-friendly expanded vermiculite (VE) is integrated with a photoactive covalent organic framework (COF) polymer, in which photoinduced electrons of surface anchored COF can freely transfer to Cr(VI) for chemical reduction, and layered expanded VE allows ion exchange between resultant Cr(III) cations and interlayered K+, Ca2+, Mg2+, Na+, etc. The Cr(T) removal capacities of the surface-modified VE with important parameters (solution pH value, initial Cr(VI) concentration, etc.) are discussed extensively to understand how to select the best conditions for optimum Cr(T) removal performance. More interestingly, from a circular economy view point, spent Cr-loading VE-based waste can serve as a photocatalyst towards oxidation conversion of ciprofloxacin and NO gas subsequently. Explanations for different effects on physicochemical properties as well as catalytic activities of the reused Cr-loading waste are given. This strategy could provide valuable and promising contribution towards the development of sustainable low-cost mineral materials for Cr(T) removal. These findings also shed new light on the research of recycling spent photocatalyst for resource and reutilization. [ABSTRACT FROM AUTHOR]

The OVs-rich BiOBr-(0 0 1)/Bi 2 SiO 5 /Bi S-scheme hybrid photocatalyst with efficient electron/hole separation and highly active for CO 2 reduction was designed and synthesized by the facile solvothermal strategy for high-efficient photocatalytic CO 2 reduction activity and stability to CO under simulated sunlight irradiation. [Display omitted] Photocatalysis CO 2 reduction into high-value-added chemical feedstocks is desirable for simultaneously addressing the solar energy storage, CO 2 excess and energy shortage issues. In this work, a kind of original S-scheme BiOBr-(0 0 1)/Bi 2 SiO 5 /Bi (OSB) heterostructure photocatalyst with rich oxygen vacancies is in-situ synthesized, which significantly promotes the photocatalytic CO 2 reduction performance. Interestingly, the lower formation energy of oxygen vacancy exhibits the easy feasibility on the BiOBr-(0 0 1) surface via the assistant of ultrasound. There exists the highest photocatalytic CO 2 reduction activity to CO of 234.05 μmol g-1h−1 for OSB-20 sample (ultrasound time: 20 min), higher 3.3 times than OSB-0 sample (without ultrasound). Combined with experimental and calculated results, the significative formation mechanism, widened light-response range, highly-efficient separation/transfer paths and improved redox-reduction abilities of photogenerated electron-hole pairs for S-scheme OSB-20 heterostructure are investigated and proposed. Our findings provide new insights for the construction and synthesis of the S-scheme Bi-based heterojunction photocatalyst system. [ABSTRACT FROM AUTHOR]

[Display omitted] Solar-energy-driven CO 2 reduction for chemical reagents production, such as CH 3 OH, CH 4 and CO, has tremendous potential for carbon neutrality in the energy industries. However, the low reduction efficiency limits its applicability. Herein, W 18 O 49 /MnWO 4 (WMn) heterojunctions were prepared via one-step in-situ solvothermal process. Through this method, W 18 O 49 tightly combined with the surface of MnWO 4 nanofibers to form nanoflower heterojunction. It was found that under full spectrum light irradiation for 4 h, the yields of photoreduction of CO 2 to CO, CH 4 and CH 3 OH by 3–1 WMn heterojunction were 61.74, 71.30 and 18.98 μmol/g, respectively, which were 2.4, 1.8 and 1.1 times that of pristine W 18 O 49 , and ca.20 times that of pristine MnWO 4 towards CO production. Furthermore, even in the air atmosphere, the WMn heterojunction still performed excellent photocatalytic performance. Systematic investigations demonstrated that the catalytic performance of WMn heterojunction was improved by superior light utilization and more efficient photo-generated carrier separation and migration as compared with W 18 O 49 and MnWO 4. Meanwhile, the intermediate products of the photocatalytic CO 2 reduction process were also studied in detail by in-situ FTIR. Therefore, this study provides a new way for designing high efficiency of heterojunction for CO 2 reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] Two-dimension (2D) MXene materials have increasingly attracted attentions in improving the photocatalytic conversion of solar-to-chemical energy over graphitic carbon nitride (g-C 3 N 4). In this work, Pt nanoparticles modified few-layer Ti 3 C 2 MXene sheet (MXene@Pt) was successfully prepared by chemical reduction, which was used as efficient co-catalysts to enhance the photocatalytic hydrogen evolution over porous g-C 3 N 4 (PCN). The high work function of MXene@Pt and the tight 2D/2D interfacial contact between MXene@Pt and PCN significantly promoted the transfer and separation of photogenerated electron-hole. Besides, the MXene@Pt could enhance the light-harvesting of PCN and provide plentiful active sites for hydrogen evolution reaction. The hydrogen evolution activity of optimum 2D/2D MXene@Pt modified PCN (PCN/MPt-5) composite was dramatically enhanced, even higher than that of equal Pt mass modified PCN. Besides, overall water splitting was realized via a two-electron pathway with H 2 O 2 and H 2 generation. This work may provide the fabrication strategy for developing MXene-based co-catalyst in photocatalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, pristine and NaBH 4 etched CeO 2 nanorods supported ruthenium (Ru) catalysts were synthesized and employed to investigate the effects of chemical etching and reduction activation treatment on CO oxidation. With 1 wt% Ru loading, the CeO 2 nanorods supported catalyst samples, after 6 wt% NaBH 4 etching treatment, showed significantly promoted H 2 consumption under 100 °C and low apparent activation energy (i.e., E a ∼ 31.2 kJ/mol) for CO oxidation. In - situ CO-DRIFTS profiles revealed that, for the reduced sample, the observed CO adsorption at ∼ 2020 cm−1 at 40 °C may be related to a strong RuO x -CeO 2 interaction induced by the NaBH 4 etching treatment, which was supported by the oxygen vacancy analysis results of X-ray photoelectron spectroscopy and CO-temperature programmed desorption. The enriched surface defects on CeO 2 support due to the chemical etching and reduction treatments are believed to promote the interaction between RuO x species and CeO 2 , which is responsible for the enhanced activity of CO oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Plasmonic Cu 6 Sn 5 bimetal was prepared using chemical reduction method. • Photocatalytic activity was enhanced for Cu 6 Sn 5 after combined with polyaniline. • A mechanism of plasmon-driven photocatalytic water splitting was proposed. A plasmonic Cu 6 Sn 5 /polyaniline (Cu 6 Sn 5 /PANI) nanocomposite was synthesized by chemical reduction and hydrothermal methods. The best photocatalytic overall water splitting performance was achieved by the Cu 6 Sn 5 /PANI 3wt% composite, which contains 3 wt% PANI, which is approximately three times more than that of pure Cu 6 Sn 5. Meanwhile, Cu 6 Sn 5 /PANI 3wt% exhibited excellent photocatalytic stability for water splitting during the stability investigation. The dramatic promotion of the photocatalytic activity performance can be ascribed to the cocatalyst PANI. The existence of PANI can remarkably promote the separation and transfer efficiency of the photoinduced electron-hole pairs, and therefore enhance the photocatalytic activity. Our results also verify that the photogenerated charge comes from plasmonic Cu 6 Sn 5 with the surface plasmon resonance (SPR) effect, which is different from traditional semiconductor-based photocatalysts. This work sheds some light on plasmonic photocatalyst development and provides an alternative pathway for photocatalytic reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] Nickel oxyhydroxide (NiOOH) is regarded as one of the promising cocatalysts to enhance the catalytic performance of photoanodes but suffers from serious interfacial charge-carrier recombination at the photoanode||NiOOH interface. In this work, surface-engineered BiVO 4 photoanodes are fabricated by sandwiching an oxygen vacancy (O vac) interlayer between BiVO 4 and NiOOH. The surface O vac interlayer is introduced on BiVO 4 by a chemical reduction treatment using a mild reducing agent, sodium hypophosphite. The induced O vac can alleviate the interfacial charge-carrier recombination at the BiVO4||NiOOH junction, resulting in efficient charge separation and transfer efficiencies, while an outer NiOOH layer is coated to prevent the O vac layer from degradation. As a result, the as-prepared NiOOH-P-BiVO 4 photoanode exhibits a high photocurrent density of 3.2 mA cm−2 at 1.23 V vs. RHE under the irradiation of 100 mW/cm2 AM 1.5G simulated sunlight, in comparison to those of bare BiVO 4 , P-BiVO 4, and NiOOH-BiVO 4 photoanodes (1.1, 2.1 and 2.3 mA cm−2, respectively). In addition to the superior photoactivity, the 5-h amperometric measurements illustrate improved stability of the surface-engineered NiOOH-P-BiVO 4 photoanode. Our work showcases the feasibility of combining cocatalysts with O vac , for improved photoactivity and stability of photoelectrodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • OMNs Pt-Ru-Ir catalyst shows improved oxygen bifunctional electrocatalysis. • Superior ORR activity (0.21 mA/µg & 0.33 mA/cm2) with extended durability was found. • Excellent OER activity with low Tafel slope and enhanced durability obtained for Pt 70 Ru 25 Ir 5. • Synergistic and mesoporous morphology with trace Ir boosting the bifunctional oxygen kinetics. An efficient oxygen bifunctional catalyst Pt-Ru-Ir with ordered mesoporous nanostructures (OMNs) was successfully synthesized by chemical reduction using KIT-6 mesoporous silica as a template. The crystallographic behavior, electronic effects, and microstructure of the catalysts were investigated by XRD, XPS, SEM, and TEM analysis. The influence of OMNs and the effect of Ir content in Pt-Ru-Ir catalyst on both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated. The synergistic and electronic effects play an important role in electrocatalytic performance through the electronic coupling between Pt, Ru and Ir followed by the alloy formation with different lattice strain percentages. Amongst, the OMNs Pt 70 Ru 25 Ir 5 catalyst exhibits the highest mass activity of 0.21 mA µg−1 and specific activity of 0.33 mA cm−2 for ORR, which are nearly 5-fold greater than those for benchmark Pt/C catalyst. Furthermore, the Pt 70 Ru 25 Ir 5 demonstrated enhanced OER activity with an overpotential of 470 mV at 10 mA cm−2, an onset potential of 1.70 V, and a Tafel slope of 118 mV dec-1, outperforming commercial IrO 2. In addition, the durability of the Pt 70 Ru 25 Ir 5 catalyst for ORR and OER are found to be extended in comparison with that of other catalysts reported in this work after 6000 cycles. These results demonstrate that the ordered OMNs Pt-Ru-Ir with low Ir content (∼5 wt%) could be a promising oxygen bifunctional catalyst for electrochemical energy conversion and storage applications. [ABSTRACT FROM AUTHOR]

• The Pd/DPHE-GS was fabricated by the facile strategies. • The Pd/DPHE-GS displays impressive electrochemical MOR and EOR performance. • The exciting MOR and EOR behavior is owing to the metal-organic interface interaction. • This work presents an effective interface engineering to enhance electrocatalytic property. Adjusting the surface structures and electronic structures of metal nanocrystals (NCs) by the metal-organic interface interaction is an emerging strategy to enhance their electrocatalytic behavior. In this work, the d -phenylalanine-functionalized graphene (DPHE-GS) anchoring Pd NCs (denoted as Pd/DPHE-GS) was fabricated via the diazo-reaction followed by a simple chemical reduction. Owing to the metal-organic interface interaction between Pd NCs and DPHE, the size, distribution and electronic structures of Pd NCs on the surface of DPHE-GS can be adjusted. Therefore, the Pd/DPHE-GS shows the highest electrocatalytic activity and the most robust long-term durability and stability towards methanol and ethanol oxidation reaction (MOR and EOR) compared to the commercial Pd/C and other counterparts. This work presents an effective interface engineering strategy to enhance electrocatalytic property. [ABSTRACT FROM AUTHOR]

In this study, we investigate the interactions between the cellulose surface and Ag nanoparticles (AgNPs) for the purpose of manufacturing hybrid nanomaterials using bacterial cellulose nanocrystals (BCNs) as a model substrate. We focus on the role of the BCN surface chemistry on the AgNP nucleation obtained by chemical reduction of Ag+ ions. Homogeneous hybrid suspensions of BCN/AgNP are produced, regardless of whether the BCNs are quasi-neutral, negatively (TBCNs) or positively charged (ABCNs). The characterization of BCN/AgNP hybrids identifies the –OH surface groups as nucleation points for AgNPs, of about 20 nm revealing that surface charges only improve the accessibility to OH groups. X-ray Absorption technics (XANES and EXAFS) revealed a high metallic Ag 0 content ranging from 88% to 97%. Moreover, the grafting of hydrophobic molecules on a BCN surface (HBCNs) does not prevent AgNP nucleation, illustrating the versatility of our method and the possibility to obtain bifunctional NPs. A H 2 O 2 redox post-treatment on the hybrid induces an increase in AgNPs size, up to 90 nm as well as a shape variation (i.e., triangular). In contrast, H 2 O 2 induces no size/shape variation for aggregated hybrids, emphasizing that the accessibility to –OH groups ensures the nucleation of bigger Ag nano-objects. [ABSTRACT FROM AUTHOR]

Polymer additives such as Polyvinylpyrrolidone (PVP) are ubiquitously used in wet chemical reduction methods to tune nanoparticle sizes and shapes. However, all polymers retain some traces of their synthetic history through their end-groups and impurities. These impurities may thus impact redox and interfacial processes occurring during the formation of nanocolloids. We report a systematic comparison of four representative silver nanoparticle syntheses in the presence of either commercial PVP or its purified version, obtained through dialysis or filtration. We characterized the resulting nanoparticle dispersions through UV–visible spectroscopy, electron microscopy, X-ray scattering and Raman spectroscopy. For all syntheses and methods, the simple removal of PVP molecular impurities drastically modifies nanoparticle size, shape and formation kinetic. Impurities from additives thus play a pivotal role in nanoparticle syntheses and must be systematically evaluated for relevant mechanistic investigations and robust process engineering. [ABSTRACT FROM AUTHOR]

A novel three-dimensional graphene aerogel composite Nb 2 O 5 -g-C 3 N 4 /rGA was prepared, with a composition of nanorods-nanosheets Nb 2 O 5 -g-C 3 N 4 (NbNR-CN) heterojunction and graphene aerogel (rGA). The 1D-2D NbNR-CN heterojunction was first prepared by a simple grinding and calcination method. Afterwards, different amounts of NbNR-CN (30%, 60%, 90%) were loaded onto graphene nanosheets by chemical reduction self-assembly method to obtain the 3D composites Nb 2 O 5 -g-C 3 N 4 /rGA (NbNR-CN/rGA). The compositions, morphologies, and optical properties of all materials were characterized. The results showed that the obtained 1D-2D heterojunctions were uniformly loaded onto rGA and the NbNR-CN/rGA composites had good visible light response. Compared with g-C 3 N 4 , NbNR and NbNR-CN, NbNR-CN/rGA showed the lowest charge transfer resistance and the highest photocurrent density. Photodegradation experiments indicated that the NbNR-CN/rGA composites exhibited remarkably enhanced visible-light photocatalytic activity for degradation of Rhodamine B (RhB). The removal rate for the 60%NbNR-CN/rGA composite was 94.8% within 100 min. The enhanced photoactivity could be explained by prolonged lifetime of photogenerated carriers due to the formation of heterojunction as well as the good electron transfer ability of rGA. Our research demonstrated that the NbNR-CN/rGA composite is a promising candidate for visible-light photocatalyst. [ABSTRACT FROM AUTHOR]

The introduction of oxygen vacancies into electrode materials has been proven to be a valid way to enhance the electrochemical performance. However, the traditional methods to introduce oxygen vacancies require severe conditions that may be harmful to hydroxides. Herein, the oxygen vacancy-rich nickel-cobalt (NiCo) layered double hydroxide (denoted as V o -NiCo LDH) nanowire array electrode is synthesized using the chemical reduction method. Owing to the reduction of NaBH 4 solution, we can create oxygen vacancies under milder conditions, thus avoiding any damage to the hydroxide. The as-synthesized electrode shows a specific capacitance of 1563.1 F g−1 at 1 A g−1, which is much higher than that of the pristine electrode (995.4 F g−1 at 1 A g−1). Moreover, the cycling performance and rate performance are also enhanced. The as-fabricated asymmetric supercapacitor (V o -NiCo LDH//Fe 2 O 3) is able to deliver a maximum energy density of 56.2 W h kg−1 at a power density of 800 W kg−1 with a voltage window of 1.6 V. [ABSTRACT FROM AUTHOR]

The rGO-wrapped nanocomposites can be regarded as promising candidates for the development of advanced microwave absorbing materials. In this work, hierarchical rGO-wrapped CNFs were prepared via a two-step strategy, including a classical modified Hummers method and a green reduction reaction. Accompany with the chemical treatments, graphene oxide appears on the outer walls of carbon nanofibers. By modulating the addition amount of ascorbic acid, the outer graphene oxide can be controllably reduced. Moreover, the CNFs/rGO with proper reduction degree exhibits desirable microwave absorption performance, whose minimum RL and effective bandwidth are −38.1 dB (3.85 GHz, d = 5.0 mm) and 4.1 GHz (5.08–9.18 GHz, d = 3.5 mm). The superior microwave attenuation performance is attributed to the synergistic effects between the CNFs and rGO. While the nanofibers provide the obtained sample with an extremely long conductive network, rGO introduces a moderate amount of lattice defects and functional groups, resulting in desirable conductivity loss and multiple polarizations. The existence of rGO also endows CNFs/rGO with suitable dielectric values so that the absorber achieves well impedance matching. Considering the excellent microwave absorption performance, this research provides a new facile route to fabricate rGO-wrapped carbonaceous materials with proper oxygen-containing groups for MAMs. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pt NPs were deposited on TiO 2 NTs by photo-deposition and chemical reduction methods. • Particle size of Pt by CR and PD methods are 1.3–2.3 nm and 4–10 nm, respectively. • Photo-deposited catalyst has Pt⁰, while the chemical-reduction has Pt2+ and Pt4+. • CR method is more effective in decolourization of dye compared to PD method. Abstract Direct conversion of solar energy into clean fuels is emerging as an efficient way for the future energy generation and solving environmental issues. Especially, photocatalytic splitting of water into H 2 under solar light irradiation is one of the best techniques for clean energy production. Also, decomposition of organic pollutants using solar light is an urgent need to protect the environment. Hence, in the present study, we studied Pt-TiO 2 nanotubes based composites for H 2 generation and methyl orange dye degradation under solar light irradiation and compared the effect of deposition methods namely photo-deposition and chemical reduction methods. We have achieved the highest rate of H 2 generation activity compared to other Pt-TiO 2 based composite photocatalysts reported previously, and it is ≈173 mmol·h−1·g−1 cat for both photo-deposited and chemically reduced Pt/TiO 2 nanotubes. This is about 46.8 folds higher than the pristine TiO 2 nanotubes at the same experimental conditions. The selected catalysts were tested for degradation of methyl orange dye, where the catalyst prepared by chemical reduction method showed improved activity (94% degradation in 30 min) compared to the one which is prepared by photo-deposition method (50.5% degradation in 30 min). XPS analysis revealed that the photo-deposited catalyst consist only metallic Pt⁰, while the chemical-reduction yielded Pt with multiple oxidation states, Pt⁰, Pt2+ and Pt4+. [ABSTRACT FROM AUTHOR]

Graphical abstract Ti3+ dual-doping single-crystalline SrTiO 3−x /TiO 2−x (B) heterojunction photocatalysts are fabricated via two-step hydrothermal process, followed by in-situ solid-state chemical reduction, and exhibit high visible-light-driven photocatalytic performance, which is ascribed to synergistic effect of the special nanoarchitecture, heterojunctions, oxygen vacancy and Ti3+ dual-doping favoring visible light absorption and spatial separation of photogenerated charge carriers. Abstract Ti3+ self-doped single-crystalline SrTiO 3−x nanocubes acting as molecular bricks are successfully assembled onto Ti3+ self-doping single-crystalline TiO 2−x (B) nanorods through an effortless two-step hydrothermal process coupled with an in situ solid-state chemical reduction method. SrTiO 3−x nanocubes act as molecular bricks, which are uniformly assembled onto the surface of TiO 2−x (B) nanorods due to lattice matching. The band gap of the resultant SrTiO 3−x /TiO 2−x (B) sample is ∼2.97 eV, which exhibits excellent photocatalytic performance for the reduction of Cr(VI) and hydrogen production under visible light. The apparent rate constant k value for the photocatalytic reaction of SrTiO 3−x /TiO 2−x (B) for Cr(VI) reduction is ∼8 times higher than that of white TiO 2 (B). The photocatalytic hydrogen production rate for SrTiO 3−x /TiO 2−x (B) is ∼160.2 μmol g−1 h−1, which is ∼5 times higher than that of white TiO 2 (B). The enhanced photocatalytic activity can be considered to be caused by a synergetic effect of heterojunction formation and the introduction of Ti3+ self-doping, which can not only facilitate the separation of photogenerated charge carriers between TiO 2−x (B) and SrTiO 3−x , but also broaden the photoresponse from the UV to visible-light region. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract In this paper, the photocatalytic degradation of organic pollutants was investigated using Ag/ZnS nanoparticles at different noble metal loadings. The photocatalysts were prepared at room temperature by two different methods: photodeposition and chemical reduction. The obtained samples were characterized by Specific surface area measurement, X-ray photoelectron spectroscopy, X-ray Powder diffraction, ultraviolet–visible diffuse reflectance and Raman spectroscopy. The X-ray photoelectron spectroscopy spectra showed that Ag is present on ZnS surface as intermediate state between nanostructured Ag0 and Ag 2 O. Moreover, the addition of silver caused a significant change of the absorption spectrum of bare ZnS, resulting in higher absorbance in the visible region, due to the Ag surface plasmon band. Methylene blue (MB) was used to evaluate the photocatalytic activity of the prepared samples. The best photocatalytic activity was observed using the sample at 0.1 wt% Ag loading prepared by chemical reduction method. In particular, the almost complete MB degradation was achieved using UV-LEDs as light sources and 6 g L−1 of catalyst dosage. Finally, the optimized photocatalyst was also effective in the degradation of phenol in aqueous solution under UV irradiation. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Graphitic carbon nitride with nitrogen defects (g-C 3 N 4-x) is prepared by a facile and effective solid-state chemical reduction technique at mild temperature conditions. The cyano groups and nitrogen vacancies, as evidenced by electron paramagnetic resonance (EPR), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectra (FTIR) and Solid-state 13C MAS NMR spectra, are controllable via adjusting chemical reduction temperature. Comparing to the pristine g-C 3 N 4 , the as-prepared g-C 3 N 4-x shows much enhanced photocatalytic H 2 evolution activity under visible-light irradiation. The maximum H 2 evolution rate of 3068 μmol·g−1·h−1 is achieved with g-C 3 N 4-x after chemical reduction treatment at 400 °C for 1 h, which is 4.85 times that of the pristine g-C 3 N 4. Moreover, excellent reusability and storage stability have been shown by this photocatalyst as well. It is discovered that nitrogen defects can result in both the up-shift of the valance band and the down-shift of the conduction band, which benefit the absorption of longer wavelength photons and trapping of the photoinduced electrons, therefore reducing the recombination losses of the generated carriers. It is because of this improved visible-light absorption and charge carrier separation, g-C 3 N 4-x displays better visible-light photocatalytic activity compared to the pristine g-C 3 N 4. It is then concluded that the synthetic strategy presented here represents a straightforward and efficient way to synergistically optimize the chemical composition, optical response, and photocatalytic characteristics of g-C 3 N 4 -based photocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Bio-MOF-1-derived highly graphitized N-doped porous carbon catalyst which exhibited superior ORR activity to that of commercial 20 wt% Pt/C. Abstract Nitrogen-doped carbon materials are promising oxygen reduction reaction (ORR) electrocatalysts owing to high performance and stability. Herein, a three-dimensional porous bio-MOF-1, Zn 8 (Ad) 4 (Bpdc) 6 O·2Me 2 NH 2 (Ad = adeninate; Bpdc = biphenyldicarboxylate), was used as precursor to fabricate N-doped porous carbon materials (NPC-1000-ts, where 1000 stands for the carbonization temperature and t represents the carbonization time, t = 2, 3 and 4 h) by simple carbonization under Ar atmosphere. The porous carbon materials had different contents of graphitic N and graphitization degrees of carbon. The catalytic activities of NPCs as metal-free ORR electrocatalysts were studied. The obtained NPC-1000-4 (pyrolysis under 1000 °C for 4 h) displayed outstanding ORR performance, with a positive onset potential (−0.012 V), a higher half-wave potential (E 1/2) (−0.13 V) and a larger limiting current density (−5.76 mA/cm2) at −0.8 V (vs. Ag/AgCl) in KOH solution (0.1 M) than those of commercial Pt/C (20 wt%) catalyst (E onset = −0.014 V, E 1/2 = −0.14 V and −5.08 mA/cm2 at −0.8 V vs. Ag/AgCl). Obviously, the onset potential of NPC-1000-4 surpassed that of Pt/C, which was rare among currently available studies on metal-free nitrogen-doped porous carbon materials. Graphitic N significantly affected ORR catalytic performance besides graphitization degree of carbon. Meanwhile, NPC-1000-4 allowed an effective 4e−-dominant ORR process, and most importantly, coupled with much higher long-term stability (89.5%) than that of commercial Pt/C (20 wt%, 65.8%) catalyst and higher resistance to methanol poisoning. The remarkable ORR activity of NPC-1000-4 can be ascribed to large surface area, considerable hierarchical porosity, high graphitization degree and synergism between enriched active sites and high portion of graphitic N. Overall, the findings guide the development of MOF-derived metal-free N-doped carbon materials as high-activity non-precious electrocatalysts for ORR. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract In this study, we successfully demonstrate an efficient, metal-free nitrogen, fluoride-codoped carbon (NFC) oxygen reduction reaction (ORR) electrocatalyst, which is produced by directly pyrolyzing melamine hydrogen fluoride salt (using as a single N and F precursor for the first time) mixed with carbon black BP2000 in a N 2 atmosphere. The ORR electrocatalytic performances are evaluated by rotating ring disk electrode experiments in 0.1 M KOH. The NFC electrocatalyst prepared at the optimized temperature of 1000 °C (NFC1000) demonstrates a high ORR electrocatalytic activity with a peak potential of 0.82 V (vs. RHE), half-wave potential of 0.82 V (vs. RHE), predominant direct 4-electron reaction pathway, and good durability and methanol tolerance. Transmission electron microscopy equipped with mapping, X-ray diffraction and X-ray photoelectron spectroscopy results indicate that NFC1000 possesses an amorphous carbon structure with a homogenous codoped distribution of N and F at 2.25 at% and 1.52 at%, respectively. N 2 adsorption-desorption analysis reveals that the as-prepared NFC1000 has a high surface area of 1169 m2 g−1. This study provides a feasible approach to synthesize low-cost and highly efficient metal-free heteroatom-doped carbon-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Efficient reduction of nitroaromatics by PDA-g-C 3 N 4 /Au catalyst. Abstract A green synthesized gold-catalyst (PDA-g-C 3 N 4 /Au) for highly efficient reduction of nitroaromatics by NaBH 4 was proposed. Polydopamine (PDA) served as the reductant and stabilizer for AuNPs reduction, avoiding the use of chemical reductant and stabilizer that may result in secondary contamination. g-C 3 N 4 not only acted as the support but also provided compatibility for AuNPs deposition, enhancing the stability and deposition of AuNPs, which improved the catalytic activity. Different experimental parameters including the amount of Au loading, concentration of NaBH 4 , and dosage of catalyst were studied. Results showed that PDA-g-C 3 N 4 /Au (3) revealed higher catalytic activity with a rate constant of 0.0514 s−1 and TOF of 545.60 h−1 for 4-NP reduction. In addition, the catalyst was highly efficient in reduction of other nitroaromatics and the reduction rates of these compounds were found as the sequence: methyl orange > 2-nitrophenol > 2, 4-dinitrophenol > Erichrome Black T > Congo red. Moreover, the PDA-g-C 3 N 4 /Au (3) catalyst kept high stability and excellent conversion efficiency over ten reduction cycles. The practical application on different real water samples suggests that this Au catalyst has promising application in environmental water purification. The simple and green synthetic Au catalyst expands the range of application and provides potential application on environmental remediation. [ABSTRACT FROM AUTHOR]

Graphical abstract The hierarchical Zn 3 V 3 O 8 @C/rGO composite with a unique lychee-like architecture was fabricated by a simple one-pot ethanol thermal reduction strategy. When used as an anode material for lithium-ion batteries, it exhibited high reversible capacities (1012 mAh g−1 at 0.1 A g−1 after 200 cycles) and high rate stability (448 mAh g−1 at 4 A g−1 after 1000 cycles). Abstract In the present work, the hierarchical Zn 3 V 3 O 8 @C/rGO composite with a unique lychee-like architecture was fabricated by a simple one-pot ethanol thermal reduction strategy. When used as an anode material, it exhibited outstanding electrochemical performance for lithium-ion batteries (LIBs). For instance, the Zn 3 V 3 O 8 @C/rGO composite delivers high reversible capacities (1012 mAh g−1 at 0.1 A g−1 after 200 cycles) and high rate stability (448 mAh g−1 at 4 A g−1 after 1000 cycles). This outstanding performance can be attributed to the synergistic effect of the diverse structural virtues, effective interface and dual-spatially hybrid carbon network. Significantly, this one-pot simple strategy can be extended to fabricating highly stable and high rate performance of vanadates or other anode materials for LIBs. [ABSTRACT FROM AUTHOR]

Graphical abstract The mechanism of Cr(VI) removal enhanced by Pb and for silicon rich biochar supported nanoscale zero-valent iron. Abstract The potential of silicon-rich biochar and Pd were evaluated for the enhanced removal of Cr(VI) in solution by nanoscale zero-valent iron (nZVI) composites. The composition and structures of the nZVI, RS700-supported nZVI, and Pd-doped samples were analyzed by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy before and after reaction with Cr(VI). The amount of Cr(VI) removed by nZVI-RS700-Pd was considerably greater than the removal by nZVI, nZVI-Pd, or nZVI-RS700. This was mainly due to the enhanced reduction and adsorption of Cr(VI) by silicon-rich biochar and Pd. Silicon and Pd promoted the reduction of Cr(VI) due to the Fe0 crystallinity in the nZVI structures. The significantly decreased removal of Cr(VI) by the silicon-removed sample (nZVI-RS700 (-Si)) further confirmed that silicon played a significant role in the removal of Cr(VI). Cr(VI) adsorption was enhanced by the dispersion and adsorption of RS700. Following the reaction of RS700-supported nZVI with Cr(VI), ferrous chromite (FeCr 2 O 4) was observed on the nZVI-RS700 composite surface. The formation of FeCr 2 O 4 can be attributed to the reduction of Cr(VI) by the nZVI and coprecipitation of chromium oxide with iron on the RS700 surface. Therefore, nZVI-RS700-Pd is a potential remediation reagent that can be used to effectively treat Cr(VI)-contaminated groundwater. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A series of small-sized (about 2.0 nm) gold nanoparticles (AuNPs) with apparent lattice fringes are synthesized by NaBH 4 reduction of HAuCl 4 in the presence of stabilizing linear or dendronized 1,2,3-triazolyl-containing ferrocenyl polymers. These AuNPs show high catalytic activity for biphasic 4-nitrophenol (4-NP) reduction to 4-aminophenol (4-AP) by NaBH 4. The lower generation G1 dendronized polymers (DPs) is a more efficient stabilizer for AuNP catalytic activity in the reduction of 4-NP than linear G0 polymers or bulky G2 DPs. The G1 DP-stabilized AuNPs are robust and easily recyclable, and the catalyst is recovered and reused at least twenty times with progressive smooth AuNP size increase along with some decrease of catalytic activity. [ABSTRACT FROM AUTHOR]

The aim of this work is the fabrication of very efficient visible-light-driven photocatalysts through anchoring carbon dots and BiOBr over nanosheets of graphitic carbon nitride. Hence, a series of g-C 3 N 4 nanosheets/Carbon dots/BiOBr (denoted as CNNS/CDs/BiOBr) nanocomposites with different amounts of BiOBr were synthesized by refluxing route. The resultant photocatalysts were characterized by XRD, EDX, SEM, TEM, HRTEM, AFM, XPS, FT-IR, UV–vis DRS, TGA, BET, and PL instruments. Among the photocatalysts, the CNNS/CDs/BiOBr (20%) nanocomposite exhibited the highest photocatalytic performance for degradations of RhB, MB, and MO under visible light, which is about 129, 29.8, and 20.5 times as superior as the CN powder, respectively. Also, photoreduction of Cr(VI) to Cr(III) over the ternary nanocomposite with 20% of BiOBr showed high photoactivity, which was 21.7-folds higher than that of the pristine CN. Reactive species trapping experiments revealed that superoxide anion radicals and hydroxyl radicals played significant role in degradation reaction of RhB. The utilized photocatalyst was recycled with negligible loss in the activity, which is important in photocatalytic processes. Finally, by studying the electrochemical behavior, the band alignments of the semiconductors were obtained and the preliminary mechanism was suggested as a direct Z‐scheme system for the enhanced interfacial charge separation and transfer, which leads to the exceptional photocatalytic performance. [ABSTRACT FROM AUTHOR]

We analyzed the role of hydrodynamic interactions in a microfluidic channel flow containing a dilute suspension of micron-scale colloidal spheres (0.03%, 0.1%, 0.3% volume fraction) engineered to adhere onto a collector patch on the channel wall at wall shear rates of 9.3–930 s −1 . Particle-wall adhesion was mediated by single-stranded DNA oligomers grafted onto the spheres and the glass channel wall, producing well-defined interactions via DNA strand base pairing. Particle positions in the flow were evolved using Brownian dynamics simulations in which hydrodynamic interactions between moving particles and the channel walls and/or adhered particles were computed off-line using a series of local simulations that explicitly resolve the fluid flow at the particle scale. By systematically varying the nature of hydrodynamic interactions captured in the Brownian dynamics simulations, we find that the interactions between moving and adhered particles represents the single most important physical element in such models. Once captured sufficiently accurately, the resulting models are able to predict coarse variables such as the overall particle coverage evolution, as well as more subtle characteristics, such as the microstructural distribution of the adhered particles. [ABSTRACT FROM AUTHOR]

The objective of our work is to improve low-temperature fuel cell catalysts by increasing the surface area to augment the efficiency of catalytic reactions. Reduced graphene oxide (rGO) supports were prepared by adding N-containing derivatives of polydopamine (PDA) and loading of Pt and Pt-based metal alloy nanoparticles were accomplished for catalyst preparation. To study the effects of surface modification on catalyst activity, the GO surfaces modified by addition of PDA (PDA-rGO) were richer in oxygen- and nitrogen-containing functional groups, which reduced the number of graphene defects. Reduction of metals (M = Pt, Pd, Pt x Pd y where x and y = 1–3) by NaBH 4 produced M/GO (metal on GO) and M/PDA-rGO (metal on PDA-rGO) catalysts. Examination of morphology and chemical composition confirmed that the existence of particle size on M/PDA-rGO catalysts was smaller than that on M/GO catalysts in agreement with calculated electrochemically active surface areas (ECSA). Electrochemical analysis was conducted to evaluate the catalyst activity and stability. The prepared catalysts had significantly greater surface areas as a result of association between the metal nanoparticles and the oxygen and nitrogen functional groups on the rGO supports. The catalysts also exhibited lower onset potentials and greater current intensities, I f /I b values, and long-term stabilities for methanol and ethanol oxidation compared with those of commercial PtRu/C. Moreover, the diameter of the Nyquist plot of the catalysts on PDA-rGO were smaller than that of the catalysts M/GO. The results suggest that variation of the Pt x Pd y atomic ratio on carbon nanocomposites is an encouraging means of enhancing electrocatalytic performance in direct alcohol fuel cell applications. [ABSTRACT FROM AUTHOR]

Hexavalent chromium is one of the most chronic and harmful to human beings, animals, and environmental well-being, and hence needs a high attention to detoxify it. For this purpose, bimetallic (In,Ga) 2 (O,S) 3 oxy-sulfide nanoflower catalyst with different Ga contents was successfully synthesized at a low temperature of 150 °C via a facile method. It was systematically characterized and the visible light-driven photocatalytic reduction of toxic Cr(VI) was 100% completed at 4 min. The Cr(VI) reduction reaction rate constant was 13.8 fold higher than that of Ga-free In 2 (O,S) 3 catalyst. It also showed lower recombination of photogenerated charge carriers, faster interfacial reaction rate, and higher electrical conductivity. The photoexcited electrons and H + ions played crucial roles in the reduction of Cr(VI). The Cr(III) composition was 12.0% of the total atomic composition. The as-synthesized catalyst showed a tremendously fast Cr(VI) reduction activity and hence, it is promising for detoxification of hazardous Cr(VI). [ABSTRACT FROM AUTHOR]

This paper reports a facile solvothermal method for the synthesis of Bi 2 S 3 flower-like nanostructures grown in situ on a nitrogen-doped reduced graphene oxide (Bi 2 S 3 @N-G) surface. Thiourea was used as the nitrogen source and reducing agent for graphene oxide. The surface morphology of the as-prepared Bi 2 S 3 @N-G composites was analyzed by field emission scanning electron microscopy and transmission electron microscopy. The crystalline structure and surface chemical states were examined by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The as-prepared Bi 2 S 3 @N-G composite was deposited on a glassy carbon (GC) electrode, and the modified electrode was employed for the electrocatalytic detection of H 2 O 2 . The calculated diffusion coefficient and catalytic rate constant of the Bi 2 S 3 @N-G modified electrode were 4.9 × 10 −6  cm 2  s −1 and 5671 M −1  s −1 , respectively. The Bi 2 S 3 @N-G/GC electrode demonstrated a wide concentration range for H 2 O 2 , from 10 to 42,960 μM, with a sensitivity of 0.1535 μA μM −1 and an obtained limit of detection of 1.9 μM. [ABSTRACT FROM AUTHOR]

In the present work, a facile and environment-friendly route is illustrated for the efficient fabrication of highly dispersed PdCo nanoparticles (NPs) by modified cotton-derived carbon fibers (PdCo/CCF). Firstly, commercial cotton was impregnated with CoCl 2 , followed by pyrolysis under high calcination temperature to obtain the Co NPs modified CCF sample (Co/CCF). Secondly, Co/CCF was treated with Pd(AcO) 2 aqueous solution, wherein, through a spontaneous replacement reaction process, Pd 2+ is reduced to metallic Pd and mostly covered on the surface of the Co NPs. Thus, the PdCo/CCF catalyst was obtained avoiding the use of toxic reductants like NaBH 4 , NH 2 NH 2 and HCHO. The PdCo/CCF catalyst exhibits excellent catalytic activity and recyclability for the reduction of 4-nitrophenol and other nitroarenes compared with Pd/CCF, PdCo NPs and many other noble metals based catalysts. The reasons could be attributed to the uniformly dispersed and accessible PdCo NPs on the surface of the CCF, and the Pd atoms deposited on the Co NPs surface that makes the Pd active sites available for optimum use. The PdCo/CCF catalyst also exhibits potential application for catalytic reduction of nitroarenes in a fixed bed reactor under mild reaction conditions. Furthermore, the PdCo/CCF catalyst can be magnetically recycled and reused for at least ten cycles without either losing catalytic activity or leaching of Pd active sites, thereby confirming its superior stability. [ABSTRACT FROM AUTHOR]

Molybdenum sulfide/reduced graphene oxide (MoS 2 /RGO) porous film was in-situ deposited on fluorine-doped tin oxide (FTO) substrates via a one-pot hydrothermal method. Due to the oxygen-containing groups distributing on graphene oxide (GO) surface, the MoS 2 sheets could nucleate and grow taking GO as substrates and the MoS 2 /RGO film can be strongly linked to the FTO. Based on the electrochemical investigations, the enhanced cell performance could be ascribed to the improved electrical conductivity, catalytic active sites and electrolyte diffusion rate, which finally contribute to the high catalytic performance on the reduction of I − /I 3 − couples in the electrolyte. Therefore, the cell adopting as-prepared MoS 2 /RGO as counter electrode demonstrated high power conversion efficiencies (PCE) of 7.63%, which indicates ∼14% enhancement compared with the MoS 2 -based (6.68%) device. [ABSTRACT FROM AUTHOR]

To address the pollution problem of organic dyes, monodispersed anionic silver nanoparticles (AgNPs) with an average size of 6 nm were prepared in water media via chemical reduction method from oleic acid and n -butyl amine. The aqueous solution of the resultant AgNPs was utilized as a photocatalyst to investigate the adsorption and photodegradation behaviors of organic dyes under different light irradiation. The morphology and surface characteristics of the synthesized AgNPs were probed using TEM, XRD, FTIR and zeta potential analysis. The adsorption and degradation process of organic dyes on the AgNPs were characterized in details by UV–Vis spectrophotometer. The results showed that the AgNPs exhibited a characteristic charge- and size-selective adsorption of dyes owing to the profoundly negative charged surface, which enables the AgNPs to possess high selective degradation of Methylene Blue. More still, due to the surface plasmon resonance (SPR) effect of AgNPs, the obtained AgNPs presented a higher photocatalytic activity to Methylene Blue under UV light, visible light, and solar light compared with commercial photocatalysts. The 5 cyclic reactions revealed its high stability and reusability. In a nutshell, the proposed mechanism systematically combined the selective adsorption and the SPR effect to explain the detailed photocatalytic process of the obtained AgNPs. [ABSTRACT FROM AUTHOR]

Plasmon Ag decorated 3D urchinlike N-TiO 2−x photocatalysts are successfully synthesized by a facile hydrothermal treatment (180 °C) and combined with a photo-deposition approach, followed by a reduction treatment. The results show that the resultant Ag/N-TiO 2−x sample possesses a three-dimensional (3D) urchinlike nanostructure with high crystallinity of anatase. Meanwhile, it exhibits the narrow optical band gap (Eg ∼ 2.61 eV) and the excellent visible-light-driven photocatalytic performance. Moreover, the hydrogen generation rate and photocatalytic degradation rate of phenol are up to 186.2 μmol h −1  g −1 and 97.7% under visible light irradiation, which are about 4.2 and 5.4 folds greater than that of N-TiO 2 . The mechanism of photocatalytic process is also proposed, and the enhanced photocatalytic property is mainly due to the synergistic reaction of the Ti 3+ and N codoping, which narrows the band gap and favors the utilization of visible light, and the plasmon effect of Ag nanoparticles and unique 3D urchinlike architecture, which are propitious to the separation and transmission of photogenerated carriers. [ABSTRACT FROM AUTHOR]

The SnS 2 nanoflowers anchored on three dimensional porous graphene were easily constructed with nickel foam (NF) as supported backbone through the dip-coating method followed by one-step controllable hydrothermal growth and mild reduction. The interconnected SnS 2 nanoflowers with cross-linking nanosheets and rich pores assembled to form one layer of continuous network structure, which tightly adhered on the surface of graphene. The porous graphene supported by NF built a conductively integral highway that is preferable for the charge transfer kinetics, while the hierarchical pores from the SnS 2 nanoflowers and NF are particularly beneficial for mitigating the volume expansion and promoting electrolyte penetration. The as-constructed Ni foam/reduced graphene oxide/SnS 2 (NF/RGO/SnS 2 ) composite exhibited dramatically enhanced reversible capacity, remarkable rate capability, and long-term cycling stabilities without the use of any binders and conductive additives. Especially, NF/RGO/SnS 2 composite remained the specific capacity as high as 561.9 mA h g −1 at the current densities of 1000 mA g −1 after continuous tests for 160 cycles, which is much higher than conventional SnS 2 /RGO composite. With the advantages of unique architecture and excellent sodium storage performances, the NF/RGO/SnS 2 composite shows promising application potential in the sodium ion batteries. [ABSTRACT FROM AUTHOR]

To realize the efficient and complete removal of organic pollutants in waste water, it is highly urgent for scalable synthesis of either self-supported bimetallic nanocatalysts or anchored on carbon-based materials. In this study, a simple one-pot coreduction method was developed for preparing well-dispersed AgPd alloyed nanoclusters uniformly dispersed on reduced graphene oxide (AgPd NCs/rGO) at room temperature by utilizing 5-azacytosine as the capping agent. The nanocomposites were characterized by a set of physical characterizations. The formation mechanism and catalytic mechanism were discussed in some details. Moreover, the prepared AgPd NCs/rGO exhibited dramatically increased catalytic properties towards the reduction of 4-nitrophenol (4-NP) in the presence of NaBH 4 when compared to commercial Pd/C (20  wt .%). [ABSTRACT FROM AUTHOR]

Chemical reduction of graphene oxide (GO) is a simple and inexpensive method for the large-scale production of graphene-based materials. A suitable reducing agent, especially a green reductant, is in high demand for the production of reduced GO (RGO). Vancomycin, a glycopeptide antibiotic used to treat a variety of Gram-positive bacterial infections, was used to chemically reduce GO at a weak alkaline pH. As far as we know, this is the first report of reduction of GO by a glycopeptide antibiotic. The resulting vancomycin-decorated RGO (RGO-Van) was characterized by UV–visible adsorption and Raman spectroscopies, X-ray diffraction pattern and atomic force microscopy (AFM). The antibacterial effect of the RGO-Van suspension was investigated by the bacterial growth curves. The RGO-Van sheet can be fabricated into paper-like film through vacuum filtration. The antibacterial property of the as-obtained RGO-Van film was assessed by the inhibition zone test, and the bacterial adhesion assay. The antibacterial efficacy of the RGO-Van film was also verified by treatment of wound infection caused by Staphylococcus aureus ( S. aureus ) in a rat infection model. [ABSTRACT FROM AUTHOR]

Herein, we developed a facile one-pot co-reduction method to fabricate highly dentritic platinum-palladium/palladium core-shell nanocrystals on reduced graphene oxide (PtPd@Pd NCs/rGO), where poly- l -lysine (PLL) worked as the eco-friendly structure director and stabilizer. The nanocomposite was mainly characterized by microscopic analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), along with the discussion of the formation mechanism. The synthesized PtPd@Pd NCs/rGO have the enlarged electrochemically active surface area (ECSA) of 51.65 m 2  g −1 , showing 1.3 folds enhancement in the peak current density relative to commercial Pt/C (50 wt%) for glycerol oxidation reaction (GOR), coupled with the small Tafel slope of 28 mV dec −1 for hydrogen evolution reaction (HER). [ABSTRACT FROM AUTHOR]

In this study Pt and Pd-based nanostructured thin films have been successfully fabricated by room temperature self-assembly of metal nanoparticles (NPs) at the interface between toluene and water without/with using stabilizers such as graphene oxide (GO) or aminoclay (AC). Successful formation of these thin films is investigated by transmission electron microscopy (TEM), energy dispersive analysis of X-ray (EDAX) and X-ray diffraction (XRD). Catalytic hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was investigated using thin film nanocatalysts. The as synthesized nanostructured thin films exhibit high catalytic activity toward hydrogenation reaction of 4-NP. This study highlights the value of nano alloy thin films and their ability as catalyst in catalytic hydrogenation reaction. [ABSTRACT FROM AUTHOR]

We investigate the aggregation and collapse of water soluble amphiphilic polymer, poly(N-isopropylacrylamide) (PNIPAM), in aqueous solution containing variable amount of trehalose, sucrose and sorbitol. The effect of these osmolytes on the coil to globular transition of the PNIPAM is studied by the use of comprehensive biophysical techniques like UV–visible spectroscopy, fluorescence spectroscopy, dynamic light scattering and Fourier transform infrared spectroscopy (FTIR). The polarization induced by these additives promotes the collapsed state of PNIPAM at much lower temperature as compared to the pure PNIPAM in aqueous solution. The decrease in the lower critical solution temperature (LCST) of the polymer with increase in the concentration of osmolyte is due to the significant changes in the interactions among polymer, osmolyte and water. The high affinity of these additives toward water destabilize the hydrated macromolecular structure via preferential interactions. To investigate the molecular mechanism behind the decrease in the LCST of the polymer in presence of the osmolytes, a molecular dynamics (MD) study was performed. The MD simulation has clearly shown the reduction in hydration shell of the polymer after interacting with the osmolyte. MD study revealed significant changes in polymer conformation because of osmolyte interaction and strongly supports the experimental observation of polymer phase transition at temperature lower than typical LCST. The driving force for concomitant sharp configurational transition has been attributed to the rupture of hydrogen bonds between water and polymer and to the hydrophobic association of the polymer. The results of the present study can be used in the bioresponsive smart PNIPAM-based devices as its LCST is close to body temperature. This study provides an alternative method to tune the LCST of the widely accepted model PNIPAM polymer. [ABSTRACT FROM AUTHOR]

In this work, we described gas sensors based on the materials composed of hierarchical flower-likeIn 2 O 3 and reduced graphene oxide (rGO), which were fabricated by a facile one-step hydrothermal method. The rGO-In 2 O 3 composites exhibited enhanced sensing performance towards NO 2 through comparison with the pure In 2 O 3 sample. The operating temperature can be tuned by the percentage of rGO in the composites. The sensor based on 5 wt% rGO-In 2 O 3 could work at room temperature with a high response value to 1 ppm NO 2 . 3 wt% rGO-In 2 O 3 composite was adopted for the ultra-sensitivity gas sensor owing to its extremely low limit of detection of 10 ppb with rapid response time to NO 2 . The sensor also exhibited excellent selectivity and stability. The ultra-sensitivity of rGO-In 2 O 3 should be related to synergistic effect of the hierarchical structure of In 2 O 3 and the presence of rGO in the composites, which provided enhanced surface area and local p-n heterojunctions in rGO/In 2 O 3 composites. [ABSTRACT FROM AUTHOR]

Amphiphilic compounds consisting of polycations and lipid segments are well established as building blocks for the construction of siRNA carriers. They are capable of forming nanoparticles with high-affinity positive charges for siRNA in aqueous media due to their intra- and/or intermolecular hydrophobic and electrostatic interactions. Unfortunately, safety and efficiency of lipid-modified polycations as the two great challenges to the clinical application need to be improved. Beyond that, the role of the hydrophobic segment in the process of siRNA delivery is elusive. Herein, in this study, branched polyethylenimine with a molecular weight of 600 (bPEI 600 ) was grafted with reducible lipids via Michael addition reaction between amines and alkyl acrylates. Reducible amphiphilic polyethylenimines (PEIs) were able to condense siRNA into nanoparticles and disassemble under the reductive environment. Investigations with these materials in vitro revealed that the polymers with higher grafting degree provided high luciferase knockdown efficacies even at lower N/P ratios and the polymers with longer lipid chain displayed greater cellular uptake rate. Interestingly, the polymers with lower grafting degree had efficient cellular uptake than native bPEI 600 , although their in luciferase knockdown assays were most likely inefficient. The inconsistency between the cellular uptake profile and silencing efficacy proved that the intracellular trafficking of siRNA was a bottleneck for siRNA delivery with some polymers prepared in this study. As expected, reducible lipid-modified PEIs were equally efficient and much less toxic compared to non-reducible counterparts and might provide broader therapeutic windows. These findings showed the feasibility of reducible lipid-modified PEIs as carriers for therapeutic siRNA. [ABSTRACT FROM AUTHOR]

Here, we demonstrate a novel reversible addition-fragmentation chain transfer agent (RAFT-CTA)-modified reduced graphene oxide nanosheets (CTA-rGONSs) by crosslinking rGONSs with a RAFT-CTA via esterification reaction. These nano CTA-rGONSs were used to polymerize a hydrophobic amino acid-based methacrylamide (N-acryloyl- l -phenylalanine methyl ester) monomer with different monomer/initiator ratios. Thermogravimetric analysis showed that the polymer-graphene composites were thermally more stable than GO itself. M n of the polymers increased with increasing monomer/initiator ratio, while the polydispersity index decreased, indicating controlled polymerization. The composites were stable in DMF even after two months. [ABSTRACT FROM AUTHOR]

The preparation of nanocomposites of reduced graphene oxide with loaded TiO 2 nanoparticles (TRGO) by a facile one-step hydrothermal treatment is reported. We have successfully increased the contact area of TiO 2 and RGO to enhance polarization point, which is in favor of strengthening interfacial polarization. The interfaregioncial polarization has been regarded as an important role on the attenuation of high-frequency electromagnetic waves. Therefore, a good absorber is prepared by inserting the polarization point on the graphene aerogel, which shows excellent electromagnetic wave absorbing properties. In detail, the minimum reflection loss value at 2.1 mm is up to −27.2 dB for the TRGO-1.5 composite and the frequency bandwidth of 5.2 GHz can be obtained. Thus, it demonstrates that the adjustment of interface polarization would play a key role in the microwave-absorbing ability. [ABSTRACT FROM AUTHOR]

Formation of positively charged gold nanoparticle monolayers on the Si/SiO 2 was studied under in situ conditions using quartz microbalance (QCM). The gold nanoparticles were synthesized in a chemical reduction method using sodium borohydride as reducing agent. Cysteamine hydrochloride was applied to generate a positive surface charge of nanoparticles. The micrographs obtained from transmission electron microscopy (TEM) revealed that the average size of nanoparticles was equal to 12 ± 3 nm. The stability of nanoparticle suspensions under controlled pH and ionic strength was determined by dynamic light scattering (DLS). The electrophoretic mobility measurements showed that the zeta potential of nanoparticles was positive, decreasing with ionic strength and pH from 56 mV at pH 4.2 and I = 10 −4 M to 22 mV at pH 8.3 and I = 3 × 10 −3 M. The surface enhanced Raman spectroscopy (SERS) confirmed chemisorption of cysteamine on nanoparticles and the contribution of amine moieties in the generation of nanoparticle charge. The influence of suspension concentration, ionic strength and flow rate on the kinetics of nanoparticle deposition on the sensors was quantitatively determined. It was confirmed that the deposition for the low coverage regime is governed by the bulk mass transfer that results in a linear increase of the coverage with time. The significant increase in the maximum coverage of gold monolayers with ionic strength was interpreted as due to the decreasing range of the electrostatic interactions among deposited particles. Moreover, the hydratation of formed monolayers, their structure and the stability were determined by the comparison of the QCM results with those obtained by AFM and SEM. The experimental data were adequately interpreted in terms of the extended random sequential adsorption (eRSA) model that considers the bulk and surface transfer steps in a rigorous way. The obtained results are useful for a facile fabrication of gold nanoparticle-based biosensors capable to bind target molecules via available amine moieties. [ABSTRACT FROM AUTHOR]

In this study, Cr(VI) removal by Zn-substituted magnetite coupled with aqueous Fe(II) through adsorption and reduction was investigated. A series of Zn-substituted magnetites (Fe 3− x Zn x O 4 , x = 0, 0.25, 0.49, 0.74 and 0.99) were synthesized by a coprecipitation method, followed by systematic characterization, e.g., X-ray diffraction (XRD), thermogravimetry (TG), specific surface area and surface acid/base titration. The characterization results show that all samples had a spinel structure without an obvious alternation by Zn substitution. The BET surface area and surface site density gradually increased with Zn substitution. During Cr removal under neutral pH value, Cr(VI) was first adsorbed on the magnetite surface and then reduced to Cr(III) by Fe 3− x Zn x O 4 and adsorbed Fe(II); finally, it was immobilized on the Fe 3− x Zn x O 4 surface, which was verified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES) analyses and desorption experiment. With the increase in the Zn content in magnetite, the Cr removal efficiency initially decreased; then, it improved, which was ascribed to the decreasing Cr(VI) reduction and increasing Cr(VI) adsorption. This variation in activity by Zn substitution was discussed in terms of the reaction mechanism as well as the cationic microstructure and surface properties of Fe 3− x Zn x O 4 . [ABSTRACT FROM AUTHOR]