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Recently, the observations of spontaneous out-of-plane electric polarization and ferroelectric switching in WTe2 related devices with semimetal property a have generated considerable attentions. The polar structure of WTe2 was proposed to be vital, however there is still no consensus about the physical origin, which deserves detailed surface analysis. Here, by using angle-dependent X-ray photoelectron spectroscopy (ADXPS), we observed an obvious downward band bending in WTe2 after slightly surface oxidation, which can't be observed on the freshly cleaved WTe2. And it will disappear after fully oxidation, demonstrating strong correlation between band bending and surface oxidation. Our study suggests surface oxidation and resulted band bending in WTe2 should be taken into account in the WTe2-related devices, such as ferroelectric.

A monolayer 1T′-WTe2 film is grown on SrTiO3(001) with in-plane tensile strain. A height of ∼0.7 nm, obvious charge transfer, and incommensurate charge fluctuations in 1T′-WTe2 suggest strong coupling to the STO substrate. Scanning tunneling spectroscopy on the surface reveals that a large energy gap opens at the Fermi level with nearly zero conductance. The opened energy gap decreases with the increase in the WTe2 island size. The lack of the metallic edge state on monolayer 1T′-WTe2/SrTiO3(001) indicates the absence of the quantum spin Hall (QSH) state. Our study here demonstrates that the energy gap of monolayer 1T′-WTe2 can be tuned by lattice strain and illustrates the importance of interface coupling to realize the metallic edge state and QSH in monolayer 1T′-WTe2.

The development of high-performance catalysts for CO2 reduction to hydrocarbons is of great importance for addressing the energy crisis issue. In this work, the Cu@porphyrin-COFs nanorods materials were first designed and synthesized by solvothermal method followed by the electrodeposition of Cu nanowires to the free-base porphyrin-COFs on the carbon fibers. The structure of the free-base porphyrin-COFs were well characterized experimentally and simulatively calculated by DFT method. The Cu@porphyrin-COFs nanorods show high catalytic activity for CO2 reduction under photoelectrocatalytic (PEC) conditions, giving C1–C3 chemicals such as methanol (CH3OH), ethanol (CH3CH2OH), ethane-1,1-diol (CH3CH(OH)2) and acetone (CH3COCH3) with an extremely apparent Faradaic efficiency (AFE) of total carbon-based products of 452.75% due to the efficient adsorption of protons onto the surfaces of Cu crystals and excellent absorption of solar light. The 13CO2 labeling experiments verified that the carbon-based products are derived from CO2. On the other hand, combining with simulation, we show that the hydroxyl groups in free-base porphyrins COFs play a vital role in photoelectrocatalytic reduction of CO2.

Chemical exfoliation method was applied to transform bulky assemblies of Au(I)–3-mercaptopropionate (MPA) coordination polymer (CP) to nanosheets and nanostrings using sodium citrate as an exfoliator. The exfoliation process and the structural characteristics of the Au(I)–MPA nanosheets and nanostrings were fully investigated by transmission electron microscopy, atomic force microscopy, UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy and so on. As the structural rigidity and stability of the obtained Au(I)–MPA nanosheets, they are ideal precursors for fabrication of water soluble gold nanoparticle assemblies through progressive pyrolysis. This work provides a significant strategy toward the morphology regulation of CP nanostructures and will inspire further development of this research area.

We report a simple method for the fabrication of biomimetic antireflective hierarchical arrays based on the combination of self-assembled polymer spheres and nanoimprint lithography (NIL). The hierarchical structures are fabricated by creating nanopillars on the microscale round protrusion arrays, which are similar to natural mosquito eyes consisting of combined micro- and nanostructures. The hierarchical arrays dramatically suppress the surface reflection from visible to near-infrared regions with an angle of incidence of up to 70°.

In this paper, a simple method is demonstrated for patterning conducting polymers based on the combination of the "rabbit ear" effect, which is an unconventional nanoimprint lithography (NIL) method, and isotropic plasma etching (IPE). By integrating these two techniques, complex conducting polymer patterns are fabricated by employing simple stamps. Especially, nanopatterns are created with microscale stamps, which can not be achieved by traditional NIL. The generated feature width can be as small as 12% of the original one. Furthermore, this method can be easily extended to other polymers.

Therefore,oneoftheimportantchallengesinfabricatingmetallicmicrostructures is to find an easy, repeatable, and controllablemethod to meet the increasing demands in optoelectronics andplasmonics.In this communication, we report a new template-assistedelectrochemical approach to fabricate arrays of metallic nano-wires. Unlike conventional template-assisted growth, where thegenerated wires are confined by the size of template, in ourcase the width of the metallic wires can be tuned by changing thecontrol parameters of electrodeposition. By imprinting polymerstripes ona silicon surface, the concave corner of polymerstripesandsiliconsubstrateprovidesapreferentialnucleationsitefortheformation of metal nanowires. The width of wires can be tunedfrom 25nm to a few hundred nanometers. Further, wedemonstrate that this method can be applied for fabricatingmore complicated structures rather than straight lines only.In our experiments, the metallic nanowires are electrodepo-sited with the help of polymer stripes embossed on siliconsurfaces. To form the patterned substrate, a thin film ofpoly(methylmethacrylate) (PMMA) (mr-I 7030E M

A simple approach to wafer-scale self-cleaning antireflective hierarchical silicon structures is demonstrated. By employing the KOH etching and silver catalytic etching, pyramidal hierarchical structures were generated on the crystalline silicon wafer, which exhibit strong antireflection and superhydrophobic properties after fluorination. Furthermore, a flexible superhydrophobic substrate was fabricated by transferring the hierarchical Si structure to the NOA 63 film with UV-assisted imprint lithography. This method is of potential application in optical, optoelectronic, and wettability control devices.

In this work, we present a method for fabricating high-resolution metal arrays based on the topography-mediated electrochemical deposition (ECD) process. By this approach, silver arrays of 200nm feature size can be obtained with the mediation of microscale patterns on silicon wafer. It should be possible to extend this method to other materials and substrates, which may have applications in sensors, optical and optoelectronic devices.

It is demonstrated that silver nanoparticle (SNP) arrays fabricated by combining nanoimprint lithography and electrochemical deposition methods can be used as substrates for metal-enhanced fluorescence, which is widely used in optics, sensitive detection, and bioimaging. The method presented here is simple and efficient at controlling the nanoparticle density and interparticle distance within one array. Furthermore, it is found that the fluorescence intensity can be tuned by engineering the feature size of the SNP arrays. This is due to the different coupling efficiency between the emission of the fluorophores and surface plasmon resonance band of the metallic nanostructures.

We present a simple solvent-assisted soft lithography method to fabricate titania (TiO(2)) patterns. The dimensions of the TiO(2) features can be controlled by adjusting the concentration of the solution, the solvent evaporation duration, and temperature. This method may provide a facile route for fabricating large area patterns of metal oxide.

Conducting polymer (CP) patterns with feature sizes of submicrometer to nanometer dimensions have attracted considerable attention due to their applications in light-emitting diodes (OLEDs), organic field effect transistors (OFETs), polymeric electrochromic devices, sensors, and biotechnology. In the last decade, the integration of two or more functional materials together is of increasing interest because materials with multiple components may exhibit integrative properties that single component materials do not possess. For example, CPs have been integrated with doping agent molecules or nanoparticles in order to improve properties or achieve multiplex character. Efforts to prepare conducting polymer patterns have mainly focused on photochemical patterning, microcontact printing (mCP), scanning probe lithography (SPL), electron-beam lithography (EBL), and dip-pen nanolithography. However, most of the techniques are incapable of integrating high resolution with high throughput. Nanoimprint lithography (NIL), which has gained significant attention due to its low cost and high throughput, is based on the mechanical deformation of the resist polymer by heating above the glass transition temperature (Tg) or by UVcrosslinking. By taking the CP or its mixture as resist layers and a subsequent reactive ion etching process, CPs have been patterned using NIL. However, NIL can only be applied on polymers that have a Tg or are UV-crosslinkable.

We present a new approach to fabricate arrays of silver nanoparticles (SNPs) on predefined positions by means of electrochemical deposition (ECD) combined with nanoimprint lithography (NIL). The SNPs arrangement, especially the density can be tuned by varying the pattern design and the preparation conditions. By this approach, various arrays of SNPs with feature size down to submicrometer can be fabricated over several square centimeters on one substrate. The SNPs arrays can be readily extended to other conductive substrates, which have potential applications in detecting and sensing fields, such as surface-enhanced raman scatter.

A bio-inspired antireflective hetero-nanojunction structure has been fabricated by the hydrothermal growth of ZnO nanorods on silicon micro-pyramids. It has been shown that this structure suppresses light reflection more effectively resulting in a high photocurrent response and good charge separation simultaneously. The strategy provides a means to enhance solar energy conversion.