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Few-atom-thick two-dimensional (2D) molybdenum disulfide (MoS2) monolayers possess numerous crucial applications in energy storage. Usually, the strategy of activating interfacial electron transfer was employed to promote their performance. Herein, we reshape the structure of materials to excite their subinterfacial and interfacial electron transfer for superior metal-ion batteries. As an example, we rationally design and reconfigure the structure of 2D MoS2 and propose a new stable structure, B-MoS2, which has an S–Mo–S sandwich structure with a buckled square lattice. The B-MoS2 monolayer is a promising anode material for magnesium-ion batteries (MgIBs) with a high capacity (921.3 mA h g−1) and a low averaged open circuit voltage (0.154 V). Multiscale underlying mechanisms for the storage of Mg and Li ions in MoS2 are provided. Based on the electronic level, the high capacity is ascribed to the occurrence of interfacial and subinterfacial electron transfer between metal ions and B-MoS2. Based on the atomic level, the insertion-adsorption mechanism or adsorption-insertion mechanism is determined for different ion storage at B-MoS2. The intrinsic metallic property of B-MoS2 and the enhanced electronic conductivity of Mg/B-MoS2 systems as well as low migration barriers (∼0.604 eV) of Mg ions at MoS2 suggest that the B-MoS2 anode has fast charge/discharge rates. This work offers novel concepts (i.e. subinterfacial electron transfer and its activation) for superior energy storage materials, and proposes new multiscale underlying mechanisms for ion storage in the MoS2 family.

Light-harvesting capacity and photoexcited charge carrier separation ability are two crucial requirements for high-efficiency semiconductor photocatalysis. Here, we report a plasmonic Z-scheme nanohybrid by hydrothermally in-situ growing two-dimensional (2D) oxygen-deficient molybdenum oxide (MoO3-x) nanoplates onto 2D graphitic carbon nitride (g-C3N4) nanosheets. The resultant 2D/2D MoO3-x/g-C3N4 nanohybrids not only construct a unique Z-scheme heterojunction, which improves the photogenerated charge carrier separation efficiency, but also possess numerous oxygen vacancies on the surface of MoO3-x, which could excite its plasmon resonance for extending spectrum adsorption. Importantly, the plasmon resonance can be readily designed by tailoring the oxygen vacancy concentration via an annealing in air. Benefiting from the synergetic effect of interfacial Z-scheme heterojunction and the tunable plasmon resonance of MoO3-x, the as-obtained nanohybrids achieve a remarkably improved photocatalytic H2 evolution efficiency. The optimal Z-scheme heterostructure presents 2.6 and 1.7 times higher of H2 evolution rate as compared to pure g-C3N4 and the annealing nanohybrid under visible light irradiation. Even under light irradiation with wavelength longer than 590 nm, the hybrid photocatalyst displays a H2 generation rate as high as 22.8 µmol h−1 due to the plasmonic sensitization effect. The result in our work can provide an alternative for fabricating Z-scheme heterostructures that take advantages of Z-scheme-induced charge carrier separation, accompanied with plasmon-enhanced light harvesting of semiconductor to advance the solar energy conversion efficiency in photocatalysis.

An ultrasensitive sandwich-type electrochemical immunosensor based on AuBP@Pt nanostructures and AuPd-PDA nanozyme was developed for the detection of apolipoprotein E4 (APOE4) which was an important risk factor for Alzheimer's disease (AD). In this work, gold nanobipyramid coated Pt (AuBP@Pt) nanostructures were prepared and applied to electrochemical immunosensors as a substrate material. AuBP@Pt nanostructures have advantages of electrical conductivity and large electroactive area, which could greatly increase electron transfer rate. In previous work, we designed AuPd alloy modified polydopamine (AuPd-PDA) nanozyme which catalyzed the decomposition of hydrogen peroxide (H2O2). AuPd-PDA nanozyme was used to label detection antibody due to excellent catalytic capability and stability in this new paper. And the concentration of APOE4 could be detected quantitatively by variation for transient current. As a result, the electrochemical immunosensor based on AuBP@Pt and AuPd-PDA exhibited a wide linear range from 0.05 to 2000 ng mL−1 and low detection limit of 15.4 pg mL−1 (S/N = 3). Furthermore, the designed biosensor displayed good selectivity in phosphate buffer saline (PBS) buffer solution or commercial goat serum, which provided a promising tool for early diagnosis of AD.

We develop pH-responsive GOD@CaCO3-Fe3O4 particles as catalytic nanomedicine for chemodynamic therapy through ultrasound-assisted Fenton reaction. By loading glucose oxidase (GOD) in the interior of the particles, GOD can be well protected and effectively delivered to catalyze glucose in cancer cells. A considerable amount of H2O2 is then generated for Fenton reaction by reacting with Fe3O4 nanoparticles. The introduction of ultrasound irradiation can significantly improve Fenton reaction efficiency in tumors owing to ultrasonic cavitation. Highly toxic hydroxyl radicals are then generated in abundance to kill cancer cells. Good cancer therapeutic effect was realized both in vitro and in vivo via this ultrasound-chemodynamic strategy based on the designed particles, providing a novel strategy for efficient cancer therapy.

Poplar catkins are an environmental pollutant because they can trigger sneezing, shortness of breath, skin allergy and even cause forest fire. It is very attractive to discover ways for reducing the threats of poplar catkins to the environment and human health and even to convert poplar catkins into useful materials. Herein we report on a facile and cost-efficient strategy for the synthesis of hierarchical porous carbon microtubes using poplar catkins as the carbon source. The synthesis involves pre-carbonization and subsequent ZnCl2 activation. The resultant materials not only inherit the natural tubular morphology of poplar catkins, but also develop a hierarchical porous structure, with nitrogen from the biomass being self-doped in the resultant carbon skeleton. The hierarchical porosity, especially the microporosity with the pore size from 0.5 to 1 nm, surface structure, tube wall thickness and nitrogen content can be readily controlled by adjusting the activation temperature and the ZnCl2-to-precursor mass ratio. The produced materials exhibit an excellent CO2 capture capacity. The optimal sample activated at 800 °C with a ZnCl2-to-precursor mass ratio of 4:1 shows an extraordinarily high CO2 adsorption capacity of 6.22 and 4.05 mmol g−1 at 273 and 298 K, respectively, at 1 bar of CO2. Furthermore, the material also displays an excellent recyclability and CO2/N2 selectivity. Our approach not only relieves the environmental pollution of poplar catkins but also leads to the production of a high-performance CO2 adsorbent, which is promising for industrial CO2 capture and separation. It therefore demonstrates an example of trash-to-treasure transformation.

The highly efficient detection method for hydrogen peroxide (H2O2) has been attracting significant attention. In this study, AuPd alloy-modified polydopamine (AuPd-PDA) nanotubes were prepared, and an electrochemical nonenzymatic sensor based on the AuPd-PDA nanotubes was developed. A single AuPd alloy on the surface of PDA nanotubes consisted of many smaller nanoparticles of size ranging several nanometers, which greatly enhanced the catalytic activity. In addition, PDA nanotubes, as carriers of AuPd alloys, were used to amplify the signal and improve the sensitivity of H2O2 sensors. Owing to its synergistic effect and structural advantage, the H2O2 sensor based on AuPd-PDA nanotubes exhibited good sensing performances, including a high sensitivity of 314.2 μA mM−1 cm−2, a wide linear range from 1.0 μM to 11.22 mM and a low detection limit of 0.26 μM (S/N, 3 : 1). Moreover, the detection of H2O2 in HeLa and Raw 264.7 cells was also achieved, which indicated that the sensors based on AuPd-PDA nanotubes could be used for real-time monitoring of H2O2 in physiological and pathological processes in a clinic.

Crab shells derived from discarded seafood bio-waste, are a naturally abundant and sustainable resource, but their difficult solubility limits their processing and applications, resulting in severe environmental pollution. It is very attractive to discover approaches for reducing the threats of crab shells to the environment and even to convert crab shells into useful materials. Herein, we attempted to convert crab shells into three-dimensional (3D) honeycomb-like graphitized hierarchically porous carbons (GHPCs) by a convenient one-step carbonization process simultaneously combining catalytic graphitization and chemical activation routes. The removal of abundant inorganics from crab shells resulted in a unique honeycomb-like structure, and meanwhile a high doping concentration of N element was inherited in the framework of GHPCs. Furthermore, the simultaneous activation/graphitization treatment developed interconnected hierarchical porosity with a large accessible surface area and highly graphitized skeleton. Benefiting from these unique structural characteristics, GHPCs exhibited a remarkable capacitive performance as supercapacitor electrodes. The GHPC electrode delivered a high gravimetric capacitance of 367.4 F g−1 at 1 A g−1 in 6 M KOH electrolyte. More importantly, the electrode showed satisfactory rate capability where an extremely high current density of 100 A g−1 for charge–discharge operation was available in both KOH and Na2SO4 electrolytes. Furthermore, the assembled symmetric flexible all-solid-state capacitor exhibited a high energy density of 11.1 W h kg−1 and a power density of 100.5 W kg−1, as well as a good cycling stability of 90.8% capacitance retention after 10 000 cycles in a PVA/KOH gel electrolyte. Our approach not only relieved the environmental pollution caused by crab shells but also achieved the production of a high-performance supercapacitor electrode, which was promising for industrial energy conversion and storage. It therefore demonstrated an example of trash-to-treasure transformation.

Current chemodynamic therapy (CDT) has been restricted by the requirement of strongly acidic conditions, insufficient endogenous H2O2 and upregulated cellular antioxidant defense. To overcome these obstacles, the carrier-free Fe(III)-ART nanoparticle is developed via coordination driven self-assembly of Fe3+ and hydrolyzed ART and evaluated as a redox-triggered C-centered free radicals nanogenerator for self-enhanced magnetic resonance imaging and chemodynamic therapy. The carrier-free Fe(III)-ART NPs can be triggered by intracellular GSH to release ART and Fe3+, which is further reduced to Fe2+ that catalyzed the endoperoxide of ART to generate C-centered free radicals. Notably, unlike current CDT, such a free radical generation process is without reliance on pH or endogenous H2O2. Meanwhile, the concurrent GSH depletion can diminish the antioxidation of tumors and enhance CDT. The C-centered free radicals-mediated apoptosis and GSH depletion-induced ferrotosis act in synergy, leading to potent tumor growth inhibition and superior anticancer efficacy in vitro and in vivo. Moreover, Fe(III)-ART NPs exhibit redox-triggered T2 relaxivity and contribute to activatable MRI-guided CDT. The development of biodegradable Fe(III)-ART NPs with superior anticancer efficacy, favorable pharmacokinetics and good biocompatibility provides a promising strategy to break through the bottlenecks of traditional CDT and greatly promotes the development of next-generation cancer theranostics.

An increasing energy storage property with high rate capability during fast charging at the high current density has been a long-standing challenge for supercapacitors. In this work, a novel nitrogen-enriched graphitized hierarchical porous carbon (NGHPC) was synthesized by a convenient one-step carbonization process from melamine(M)-resorcinol(R)-formaldehyde(F) co-polymeric microspheres using nano γ-Fe2O3 as template, graphitized catalyst precursor and activation promoting agent coupled with ZnCl2 activation. The nano-sized γ-Fe2O3 was reduced to Fe metal and other Fe-containing species in the carbonization process, and Fe served as catalyst to generate perfectly graphitized carbon skeleton, and other nanoparticles acted as the template of macropores. Meanwhile, CO2 which generated from the oxidation reactions of CO and γ-Fe2O3 reacted with carbon to bring the in situ CO2 physical activation, resulting in the promotive tailoring in microporosity. Interestingly, the morphology of the obtaining NGHPC materials could be controlled from spherical aspect to the structure of sphere coated by thin sheet by varying the M/R mass ratio. As supercapacitor electrodes materials, the optimal material achieved an outstanding specific capacitance of 417.5 F g−1 at 0.5 A g−1 in 6 M KOH electrolyte. More importantly, a superb rate capability was also exhibited, and a capacitance of 296.4 F g−1 was still retained at an ultrahigh current density of 100 A g−1. Besides, the assembled symmetric supercapacitor with the optimal material displayed a high integrated energy density of 33.9 Wh kg−1 at a power density of 809.9 W kg−1 within a voltage range of 0–1.8 V in 0.5 M Na2SO4 natural electrolyte and an approximate 84.8% capacitance retention after consecutive 10,000 cycles at 5 A g−1.

With the development of clean and renewable energy, hydrogen produced via photoelectrochemical (PEC) water splitting has attracted considerable attention. However, to develop the photoanodes with stable and excellent PEC ability is still a big challenge. In our work, TiO2 nanorods decorated with boron doped g-C3N4 (BCN/TiO2) is fabricated via thermal polymerization method to improve the PEC performance. The BCN/TiO2 displays 4-fold increase of the photocurrent density (1.01 mA cm−2) at 1.23 V vs. RHE under irradiation (100 mW cm−2, AM 1.5 G). And the onset potential of BCN/TiO2 exhibits a negative shift with 100 mV. Attributed to the broad light absorption of BCN and hetero-junction forming between BCN and TiO2, the IPCE value is increased to 87.8% in 380 nm, and the charge separation and transfer efficiency are both increased. Doping metal-free inorganic material with heteroatoms is a simple and efficient strategy to increase the light absorption within visible light and charge transfer efficiency in PEC and photocatalytic applications.

Cross-linked microporous carbon beads (MCBs) were successfully synthesized via a green, convenient, and cost-efficient strategy derived from a renewable sugar source. Such an approach avoids the time-consuming procedure and the use of corrosive chemical activating agents and toxic solvents and only involves a simple carbonization process, which makes it to be applicable for rapid and large-scale industrial production of MCB materials. The obtained MCBs possessed well-defined microporous structure, narrow pore size, and high surface area. Particularly, the microporosity of the resultant MCBs could be easily tailored to arise primary pores of size 0.5–0.9 nm by adjusting the carbonization temperature and reaction time, which remarkably favor the CO2 capture. The optimal sample of MCBs-9-5 carbonized at 900 °C for 5 h was characterized by high microporosity (80% of the surface area from micropores), especially ultrahigh narrow microporosity (53% of pore volume from micropores of size

The catalytic activity of metal nanocrystals is mainly tuned through the control of their shapes and sizes. However, the shapes and sizes of many metal nanocrystals are difficult to control and therefore their catalytic activity is hard to tune. Here, we demonstrate another approach, using differently charged surfactants, for tuning the catalytic activity of metal nanocrystals. Au and Pd nanocrystals capped with cationic cetyltrimethylammonium bromide (CTAB) and anionic citrate are chosen to study the effect of surfactant charges on the catalytic activity. The oxidation of o-phenylenediamine to 2,3-diaminophenazine by H2O2 is selected as a model reaction. The prepared Au and Pd nanocrystals are initially capped with CTAB, which is changed to citrate through surfactant exchange. Owing to the relatively weak electrostatic interaction of CTAB with the nanocrystals, the surfactant exchange does not induce observable changes in nanocrystal shapes and sizes. In contrast, the catalytic activity is greatly improved by the surfactant exchange. XPS analysis and theoretical calculations indicate that the adsorption of anionic citrate enriches the electrons of the nanocrystal surfaces, while the adsorption of CTAB depletes the electrons of the nanocrystal surfaces. The different catalytic activities of CTAB and citrate-capped nanocrystals arise from the different behaviors of electron transfer between the surfactants and the nanocrystal surface. Since the surfacants that electrostatically bind to the metal nanocrystals are facile to exchange into other surfactants, our findings provide an effective way to tuning the catalytic activity of metal nanocrystals.

As an emerging technique for rapid detection, Surface-enhanced Raman scattering (SERS) has received much practical attention. Here, we report a uniformly distributed silver nanoparticles on well-defined tungsten oxide nanoflakes hierarchical nanostructures (Ag/WO3-x) as flexible solid SERS substrate. The vertically aligned Ag/WO3-x nanoflakes were prepared by in situ redox reaction without reductant additives, ensuring the clean surface and free of extra interferences with good signal-to-noise ratio. Using rhodamine 6G (R6G) as probe molecule, the enhancement factor of developed Ag/WO3-x nanoflakes SERS substrate was found to be high as 2.41 × 107 with an ultrasensitive detection concentration of 10-12 M. Additionally, Ag/WO3-x nanoflakes SERS substrate exhibited good reproducibility and long-time stability. Meanwhile, the pesticide thiram with a 1.3 pM limit of detection (LOD) can be readily determined via developed SERS substrate. To illustrate the potential practical value of the prepared substrates, 2.4 ppb spiked thiram on apple peel surface were both successfully detected. Notably, the developed SERS substrates could be cut into small pieces for detecting trace chemical or biological molecules and the flexible utilization of substrates would be improved dramatically. As a result, vertically aligned Ag/WO3-x nanoflakes with well-defined shape and hierarchical structure have great potential as solid SERS substrate in the field of fast detection and trace analysis.

Herein, considering the great potential of nitrogen-doped hierarchical porous carbons in energy storage and CO2 capture, we designed a convenient and easily large-scale production strategy for preparing nitrogen-doped hierarchical porous carbon sphere (NHPCS) materials. In this synthesis route, spherical resorcinol-formaldehyde (RF) resins were selected as carbon precursor, and then the ZnCl2-impregnated RF resin spheres were carbonized in a NH3 atmosphere at a temperature range of 600–800 °C. During the one-step heat-treatment process, nitrogen atom could be efficiently incorporated into the carbon skeleton, and the interconnected and hierarchical pore structure with different micro/mesopore proportion could be generated and tuned by adjusting the activating agent ZnCl2 dosage and carbonization temperature. The resultant nitrogen-doped hierarchical porous carbon sphere materials exhibited a satisfactory charge storage capacity, and the optimal sample of NHPCS-2-8 with a high mesopore proportion obtained at 800 °C with a ZnCl2/RF mass ratio of 2:1 presented a specific capacitance of 273.8 F g−1 at a current density of 0.5 A g−1. More importantly, the assembled NHPCS-2-8-based symmetric capacitor displayed a high energy density of 17.2 Wh kg−1 at a power density of 178.9 W kg−1 within a voltage window of 0 ∼ 1.8 V in 0.5 M Na2SO4 aqueous electrolyte. In addition, the CO2 capture application of these NHPCS materials was also explored, and the optimal sample of NHPCS-0-8 with a large micropore proportion prepared at 800 °C exhibited an exceptional CO2 uptake capacity at ambient pressures of up to 4.23 mmol g−1 at 0 °C.

Herein, we proposed a cost-efficient strategy to prepare nitrogen-doped porous graphitized carbon nanosheets, i.e. urea-assisted chemical blowing via foaming starch into the bubble networks of starch-derived polymers combining catalytic graphitization and subsequent KOH activation. In this synthesis route, starch acts as carbon precursor and foaming agent to build a bubble network of polymer, urea acts as nitrogen source and blowing agent to further blow bubble to form N-doped sheet-like carbons with ultrathin structure, γ-Fe 2 O 3 serves as a graphitization catalyst precursor to generate highly graphitized framework. Importantly, the thickness of sheets, the nitrogen content and the graphitization degree can be simply tuned by adjusting the mass ratio of urea/γ-Fe 2 O 3 /KOH. The optimal sample exhibited uniform sheet-like morphology with a thickness of ∼80 nm, a high surface area of 2129.8 m 2 g −1 , and a large pore volume of 0.97 cm 3 g −1 . Acting as an electrode for supercapacitor in 6 M KOH electrolyte, it presented a high specific capacitance of 337.6 F g −1 at 0.5 A g −1 . Moreover, the two-electrode symmetric cell was assembled in 1 M TEABF 4 /AN, and displayed a high energy density of 27.5 Wh kg −1 as well as an excellent cycling stability with 87.6% retention after 5000 cycles.

Many novel two-dimensional (2D) allotropes of carbon have been predicted to be (meta)stable at 0 K, however, their thermal stability and mechanical properties at finite temperatures remain unclear. In this study, the mechanical properties and fracture behaviors of five newly predicted monatomic thick carbon sheets (C 31 , C 33 , δ-graphyne (GY), γ-GY, C 63 , and graphene) are investigated using molecular simulations. The δ-GY, γ-GY, and graphene show brittle fractures in uniaxial tension testing at temperatures from 1 to 1200 K. The first signs of fracture in these brittle carbon sheets indicate that the C C bonds linking the benzene rings and linear acetylenic carbons break with strong directional preference, whereby the direction of the breaking C C bonds is parallel to the direction of tensile stress. A brittle-to-ductile transition is identified in the C 31 , C 33 , and C 63 sheets at high temperatures, which corresponds to the breakages of the C C bonds in the triangular carbon rings. Global and local order-order structural transitions as well as order-disorder transitions are obtained in different ductile carbon sheets, and are found in the same carbon sheet under tensile stress along different directions. These results suggest a strong correlation between the structure and the failure mechanism in 2D carbon sheets, which is of great importance in the future design, synthesis and application of novel 2D materials.

The development of efficient nanomedicines to improve anticancer therapeutic effects is highly attractive. In this work, we firstly report titania-coated Au nanoplate (Au NPL@TiO2) heterostructures, which play dual roles as nanoagents for synergistic photothermal/sonodynamic therapy in the second near-infrared (NIR) window. On the one hand, because the controlled TiO2 shells endow the Au NPL@TiO2 nanostructures with a red shift to the NIR II region, the as-prepared Au NPL@TiO2 nanostructures possess a high photothermal conversion efficiency of 42.05% when irradiated by a 1064 nm laser and are anticipated to be very promising candidates as photothermal agents. On the other hand, the Au nanoplates (Au NPLs), as electron traps, vastly improve the generation of reactive oxygen species (ROS) by the Au NPL@TiO2 nanostructures in contrast with pure TiO2 shell nanoparticles upon activation by ultrasound (US) via a sonodynamic process. Moreover, the toxicity and therapeutic effect of the Au NPL@TiO2 nanostructures were relatively systemically evaluated in vitro. The Au NPL@TiO2 nanostructures generate a large amount of intracellular ROS and exhibit laser power density-dependent toxicity, which eventually induces apoptosis of cancer cells. Furthermore, a synergistic therapeutic effect, with a cell viability of only 20.3% upon both photothermal and sonodynamic activation, was achieved at low concentrations of the Au NPL@TiO2 nanostructures. Experiments on mice also demonstrate the superiority of the combination of PTT and SDT, with the total elimination of tumors. This work provides a way of applying two-dimensional (2D) gold nanoplate core/TiO2 shell nanostructures as novel nanoagents for advanced multifunctional anticancer therapies in the second NIR window.

Utilization of solar energy to split water via photoelectrochemical (PEC) technique is a desirable technology to address the development of sustainable carbon-free energy source. The key challenge of this advanced technique is to design a photoelectrode with both high solar to chemical efficiency and fast charge transfer and separation efficiency. Herein, the core-shell heterostructure of TiO2@PCN (P doped g-C3N4) decorating with Au nanoparticles (Au NPs) photoanode (Au/TiO2@PCN) is successfully fabricated for high-efficiency PEC water splitting. The resulting integrated Au/TiO2@PCN photoanode exhibits significantly enhanced PEC activities both in UV and visible light region with AM 1.5 G irradiation (100 mW cm−2). Each component of Au/TiO2@PCN plays a vital role in promoting the PEC performance. The TiO2@PCN core-shell heterostructure could remarkably facilitate the charge transfer and separation efficiency with the effect of an internal built-in electric field. The introduction of Au NPs could further enhance the charge transfer efficiency and improve the PEC activity of TiO2@PCN in visible light, which is attributed to the localized surface plasmon resonance (LSPR) effect. Accordingly, the Au/TiO2@PCN presents pronounced photocurrent density of 2.03 mA cm−2 (1.23 V vs. RHE), which is four-fold higher than that of TiO2 NRs (0.51 mA cm−2). This work supports a new approach to combine the advantages of the core-shell heterostructure and the LSPR effect of noble metal for high-performance PEC water oxidation.

Sulfated titania loaded mesoporous silica solid acid catalyst was successfully obtained by a facile ammonia/water vapor-induced internal hydrolysis route. Ti(SO4)2 used as titania precursor and the supplier of SO4 2− ions. By controlling the hydrolysis rate of precursor under ammonia/water vapor ambience, a thin titania layer formed and coated on the pore internal surface of SBA-15. The solid acid catalyst was characterized by powder X-ray diffraction, N2 adsorption–desorption and transmission electron microscopy, and the results showed that such catalyst retained the ordered mesoporous structure, relatively high surface area, connected and open pore channel without pore blocking. Fourier transform infrared spectroscopy and energy dispersive spectrum analysis results indicated that the resultant catalyst possessed higher connect of sulfate groups and more catalytically active sites than those of unloaded sulfated titania and sulfated titania loaded SBA-15 hydrolyzed by ammonia aqueous solution. Meanwhile, the catalyzing results suggested such solid acid catalyst exhibited improved catalytic property for esterification of oleic acid with methanol compared to conventional sulfated titania solid acid. In addition, the experimental parameters including reaction time, reaction temperature and the molar ratio of reactants were optimized, and ca. 85 % of catalytic activity were remained after three consecutive cycles.

A facile one-step microwave irradiation method is developed to synthesize a composite of graphene and zinc oxide, which is quick and environmentally friendly. The obtained nanostructured hybrid material was utilized for the fabrication of a supercapacitor electrode and the electrochemical performance was investigated intensively. The electrode with the as-prepared graphene/zinc oxide composite displayed a specific capacitance as high as 201 F g−1 in 1 M Na2SO4 at a current density of 1 A g−1, which is much higher than those of pure microwave reduction graphene oxide (77 F g−1) and zinc oxide (5 F g−1) at the same current density. In addition, the specific capacitance of the MRGO/ZnO electrode presented an outstanding cycling stability with capacitance retention of 93% even after 3000 cycles. This research provides a feasible method for low-cost manufacture of other graphene-based materials with high-performance applications in energy-storage.

Graphene-based conductive organic composites are a class of electrode materials with great potential for next-generation energy storage devices due to their good flexibility, high conductivity and abundant redox sites. Herein, a series of novel 7-aminoindole/rGO composites are successfully synthesized by a universal solvothermal method. With rGO as supporting framework, the morphology, structure and conductivity of the composites are optimized by the synergistic effect of 7-aminoindole and rGO to comprehensively enhance the electrochemical performance of the electrode. The obtained optimal electrode delivers a high specific capacitance of 391.88 F g−1 at 0.5 A g−1. Simultaneously, the assembled symmetric device also exhibits an energy density of 11.97 Wh kg−1 at a power density of 325 W kg−1 and a super-long cycling stability (97.62%) after 25,000 cycles at a current density of 5 A g−1. Such measurement results strongly demonstrate that the synthesized novel composite electrodes have a great potential for application in new energy storage devices such as flexible electronics and wearable devices.

Silicon-based two-dimensional (2D) materials have unique properties and extraordinary engineering applications. However, penta-silicene is unstable. Herein, by employing first-principles calculations, we provide a facile surface chemistry method, i.e. functionalization, to acquire and reconfigure stable penta-silicene for use in flexible lithium-ion batteries. Our results of density functional theory calculations showed that the reconfigured penta-silicene nanosheets possess a broad range of properties, including semiconductors with an indirect bandgap, semiconductors with a direct bandgap, semimetals and metals. For fluorinated penta-silicene, a fluorine-concentration-induced transition from a semiconductor to a metal is found. For fully fluorinated penta-silicene, a mechanically induced transition from a semiconductor with an indirect bandgap to a semiconductor with a direct bandgap is obtained. Our calculation results showed the reconfigured penta-silicene is a high-performance anode for use in flexible lithium (Li)-ion batteries. A transition from a semiconductor to a metal with adsorption of Li atoms indicates a high electrical conductivity. It possesses low Li diffusion barriers (0.08–0.28 eV), demonstrating a high mobility of Li ions. The metallic feature and low Li diffusion barriers reveal that it has an ultrafast charge/discharge rate. This work suggests that surface chemistry reconfiguration provides new stable materials with excellent mechanical properties and tunable electronic properties for their promising applications in flexible metal-ion batteries and solar batteries as well as nanoelectronics devices.

Auxetic materials have numerous promising engineering applications such as fracture resistance and energy storage due to their negative Poisson's ratios (NPRs). However, compared to materials possessing positive Poisson's ratios (PPRs), auxetic materials are rare. In this paper, by employing first principles calculations, we found a high NPR two-dimensional (2D) material, tungsten carbide (W2C), in the transition metal carbides (MXenes). Our results of the relatively moderate Young's modulus and fracture strength as well as the critical strain showed that the 2D monolayer W2C is an extraordinary flexible material. Our DFT results also demonstrated that W2C possesses high NPRs while Hf2C and Ta2C have PPRs. Furthermore, the mechanically induced deformation mechanism and the NPR formation mechanism of W2C have been proposed. Such an intrinsic NPR in W2C is attributed to the strong coupling between the C-p and W-d orbitals in the pyramid structural unit. The mechanically induced deformation mechanism and the PPR formation mechanism of Hf2C have also been determined. The intrinsic NPR for W2C transforms to PPR upon the surface functionalization induced. The behavior occurs due to the W-C interaction weakening. The excellent NPR in the 2D MXene material combined with other outstanding properties such as the metallic state would bring about its promising engineering prospects, ranging from the metal-ion battery, to automobiles and aircraft.

Integration of semiconductors with noble metals to form heteronanostructures can give rise to many interesting plasmonic and electronic properties. A number of such heteronanostructures have been demonstrated comprising noble metals and n-type semiconductors, such as TiO2 , ZnO, SnO2 , Fe3 O4 , and CuO. In contrast, reports on heteronanostructures made of noble metals and p-type semiconductors are scarce. Cu2 O is an unintentional p-type semiconductor with unique properties. Here, the uniform coating of Cu2 O on two types of Au nanorods and systematic studies of the plasmonic properties of the resultant core-shell heteronanostructures are reported. One type of Au nanorods is prepared by seed-mediated growth, and the other is obtained by oxidation of the as-prepared Au nanorods. The (Au nanorod)@Cu2 O nanostructures produced from the as-prepared nanorods exhibit two transverse plasmon peaks, whereas those derived from the oxidized nanorods display only one transverse plasmon peak. Through electrodynamic simulations the additional transverse plasmon peak is found to originate from a discontinuous gap formed at the side of the as-prepared nanorods. The existence of the gap is verified and its formation mechanism is unraveled with additional experiments. The results will be useful for designing metal-semiconductor heteronanostructures with desired plasmonic properties and therefore also for exploring plasmon-enhanced applications in photocatalysis, solar-energy harvesting, and biotechnologies.