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It is critically important to develop actuator systems for diverse needs ranging from robots and sensors to memory chips. The advancement of mechanical actuators depends on the development of new materials and rational structure design. In this study, we have developed a novel graphene electrochemical actuator based on a rationally designed monolithic graphene film with asymmetrically modified surfaces. Hexane and O(2) plasma treatment were applied to the opposite sides of graphene film to induce the asymmetrical surface properties and hence asymmetrical electrochemical responses, responsible for actuation behaviors. The newly designed graphene actuator demonstrated here opens a new way for actuator fabrication and shows the potential of graphene film for applications in various electromechanical systems.

As a member of the lead-halide perovskite family, inorganic perovskite CsPbBr3 exhibits excellent optical and electrical properties with higher stability to the environment. However, former efforts to obtain large-size CsPbBr3 single crystals with satisfactory quality using low temperature solution methods reached limited results. In this work, we have studied the growth of CsPbBr3 crystals using the antisolvent vapor-assisted crystallization (AVC) method. By adjusting the mole ratio of PbBr2 and CsBr, the phase diagram of the final products is acquired. Five regions are identified, including the Cs4PbBr6 single phase region, Cs4PbBr6 and CsPbBr3 two phases region, CsPbBr3 single phase region, CsPbBr3 and PbBr2­·2­[(CH3)2SO] metastable two phases region, and CsPbBr3 and PbBr2­·2­[(CH3)2SO] two phases region. Three methods are adopted to improve the size and crystalline quality of CsPbBr3. The growth rate is effectively tailored by diluting the antisolvent MeOH solution using DMSO to reduce the MeOH vapor pressure. Centimeter-size bright CsPbBr3 crystals have been obtained. The room temperature bandgap of CsPbBr3 is estimated at ∼2.29 eV by the transmission spectra. The photoluminescence spectra show two strong emission peaks, located at 530 and 555 nm, respectively, which are related to the free and bond excitons. The resistivity is as large as 2.1 × 109 Ω·cm. Hall effect measurements demonstrate the CsPbBr3 is p-type conductivity with a hole carrier concentration of 4.55 × 107 cm–3 and the mobility of 143 cm2 V–1 s–1. The resulting Au/CsPbBr3/Au device exhibits strong photoresponse to optical light, with an on–off ratio of two orders under a light emitting diode (∼1 mW/cm2) with a wavelength of 365–420 nm. Our research would shed more light on the growth and the photoresponse properties of CsPbBr3 crystals.

The hydrogen bond represents a fundamental interaction widely existing in nature, which plays a key role in chemical, physical and biochemical processes. However, hydrogen bond dynamics at the molecular level are extremely difficult to directly investigate. Here, in this work we address direct electrical measurements of hydrogen bond dynamics at the single-molecule and single-event level on the basis of the platform of molecular nanocircuits, where a quadrupolar hydrogen bonding system is covalently incorporated into graphene point contacts to build stable supramolecule-assembled single-molecule junctions. The dynamics of individual hydrogen bonds in different solvents at different temperatures are studied in combination with density functional theory. Both experimental and theoretical results consistently show a multimodal distribution, stemming from the stochastic rearrangement of the hydrogen bond structure mainly through intermolecular proton transfer and lactam–lactim tautomerism. This work demonstrates an approach of probing hydrogen bond dynamics with single-bond resolution, making an important contribution to broad fields beyond supramolecular chemistry.

Centimeter-sized single-crystalline graphene is obtained by an oxidative-etching-assisted chemical vapor deposition (CVD) method. Gaseous oxidants are found to be highly responsible for graphene etching. By diminishing the uncertain amount of H2 O vapor in commercial H2 and precisely introducing additional O2 , the graphene nucleation density can be well controlled.

Co3O4 nanosheets are straightforwardly fabricated through an in situ dealloying and oxidation process of etching CoAl alloy in alkaline solutions. X‐ray diffraction and electron spectroscopy characterizations demonstrate the formation of a Co3O4 nanostructure with an intricate hierarchical nanosheet morphology comprising interconnected nanoslices with the diameter as small as 6 nm. Upon calcination in O2 atmosphere, these novel Co3O4 nanosheets exhibit excellent catalytic activity toward CO oxidation in normal feed gas at ambient temperature. Catalytic tests reveal the strong influence of calcination temperature on the resultant catalytic activities, whereby 300 °C is found to be preferable possibly due to an optimum balance between the surface area and the amount of active species as compared with 200 and 450 °C. Moreover, Co3O4 nanosheets showed good time‐on‐stream catalytic stability; CO conversion at T50 (the temperature for 50 % CO conversion) reduced to 37 % after 20 h, and at T100 (the temperature for full CO conversion) the conversion only decreased to about 90 % after 15 h.

The rational assembly of quantum dots (QDs) in a geometrically well-defined fashion opens up the possibility of accessing the full potential of the material and allows new functions of the assembled QDs to be achieved. In this work, well-confined two-dimensional (2D) and 3D carbon quantum dot (CQD) honeycomb structures have been assembled by electrodeposition of oxygen-rich functional CQDs within the interstitial voids of assemblies of SiO(2) nanospheres, followed by extraction of the SiO(2) cores with HF treatment. Although made from quantum sized carbon dots, the CQD assemblies present a solid porous framework, which can be further used as a sacrificial template for the fabrication of new nanostructures made from other functional materials. Based on the unique honeycomb architecture of the CQDs, which allows the more efficient adsorption of molecules, the formed Au nanoparticles on the CQD honeycomb exhibit 8-11 times stronger surface enhanced Raman scattering (SERS) effect than the widely used Au nanoparticle SERS substrate for the highly sensitive detection of target molecules. This work provides a new approach for the design and fabrication of ultrasensitive SERS platforms for various applications.

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