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Additive manufacturing techniques have revolutionized the field of fabricating micro-supercapacitors (MSCs) with a high degree of pattern and geometry flexibility. However, traditional additive manufacturing processes are based on the functionality of microstructural modulation, which is essential for device performance. Herein, Ti3C2Tx MXene was chosen to report a convenient aerosol jet printing (AJP) process for the in situ curling and alignment of MXene nanosheets. The aerosol droplet provides a microscale regime for curling MXene monolayers while their alignment is performed by the as-generated directional stress derived from the quasi-conical fiber array (CFA)-guided parallel droplet flow. Interdigital microelectrodes were further developed with the curled MXene and a satisfying areal capacitance performance has been demonstrated. Importantly, the AJP technique holds promise for revolutionizing additive manufacturing techniques for fabricating future smart microelectronics and devices not only in the microscale but also in the nanoscale.

Researches on environmentally friendly semiconductor photocatalysts for efficient photocatalytic hydrogen evolution have important practical significance. Here, using first-principles calculations, the CeO2(111)/hBN heterojunction was conceived. The influence of the interface effect on the structural, electronic and optical properties of the heterojunction was investigated in detail. The band gap of the heterojunction is smaller than the two individual components and forms a type-II heterojunction, improving the photocatalytic activity. Furthermore, by doping two C atoms, the band gap of heterojunction was further narrowed. Both the oxidation and reduction potential of CeO2(111)/hBN heterojunction meet the requirements of water splitting and has certain advantages over other photocatalysts in the ability for photocatalytic hydrogen evolution. The study revealed the possible mechanism of CeO2(111) and hBN monolayers compositing to facilitate photocatalysis and hydrogen evolution ability, which may provide a possible reference direction for the practical design of more high-quality semiconductor photocatalysts.

In this study, Au nanoparticles modified novel nanosheet-branched TiO2 hollow spheres with high specific surface area (556.39 m2 g−1) are constructed as photocatalysts for adsorption and degradation of organic dyes under solar light irradiation. The adsorption and photocatalytic activities were evaluated by monitoring the concentration of R6G with or without simulated solar light irradiation. The results reveal that the adsorption capacity between R6G molecules and absorbents (TiO2 or Au/TiO2) is controlled by chemisorption, and the adsorption capacity of the pristine TiO2 (84.89 mg g−1) is higher than those of the Au/TiO2 nanocomposites. The highest photocatalytic activity (0.0896 min−1) can be found in 5 at.% Au/TiO2 hollow nanospheres. Considering both adsorption and photocatalytic performances, 5 at.% Au/TiO2 nanocomposites are optimized and chosen as a desired solar-light-driven photocatalyst for organic dye degradation. This study may offer a reference to design the novel nanostructure of TiO2-based photocatalysts for multi-energy and environmental applications.

Core–shell structure photocatalysts have attracted extensive attention in the field of wastewater treatment because of their desirable capacity of efficient charge separation. In this study, a novel Pt nanoparticles-modified WO3@TiO2 core–shell ternary structure was synthesized and its photocatalytic property was evaluated by degrading 30 ppm of tetracycline (TC) under simulated solar light. It was found that the optimal Pt-WO3@TiO2 ternary structures exhibit extremely superior performance in photocurrent response (30 times higher) and photocatalysis (10 times higher) compared to the pristine WO3 nanorods. The enhanced photocatalytic performance is attributed to the long lifetime of charge carriers and the increment of oxygen vacancies generated by introducing Pt nanoparticles. The radicals trapping experiments verified a two-step TC photodegradation process which can be ascribed to the existence of superoxide radicals ( $$\cdot {\text{O}}_{2}^{ - }$$ ) and holes (h+). This work may shed light on the design of novel ternary core–shell structure for efficient degradation of TC under solar light.

Developing high-performance non-noble metal bifunctional oxygen reduction and evolution reaction electrocatalysts is a critical factor for the commercialization of rechargeable Zn-air batteries. Herein, Co/Co-N/Co-O rooted on reduced graphene oxide (rGO) hybrid boron and nitrogen codoped carbon (BCN) nanotube arrays (BCN/rGO-Co) is prepared by facile low-temperature precross-linking and high-temperature pyrolysis treatment. Benefit from the synergistic effect of its B/N codoping, Co/Co-N/Co-O bifunctional active sites, 3D hybrid porous structure of BCN nanotubes, and highly conductive rGO sheets. The obtained BCN/rGO-Co exhibits superior bifunctional oxygen catalytic activity with a positive ORR half-wave potential (0.85 V) and a low OER potential (1.61 V) at 10 mA cm

Intelligent actuators offer a lot of potential for use in soft robots, artificial muscles, sensors since it can alter shape in response to external stimuli. However, the stiffness of the material and the constrained specific surface area brought on by the dense stacking of materials restrict the response of the conventional humidity-responsive actuators. Herein, optimal humidity-responsive actuators of MXene were developed by designing topologies of heterostructured membrane of stacked nanosheets and 3D wrinkled MXene (3D-MXene). In this configuration, the stacked MXene nanosheets sustain the device’s overall strength, while the 3D-MXene layer significantly improves the device’s moisture absorption and decreases its stiffness. Importantly, the actuators have been strengthened due to the van der Waals forces at the interface of the stacked nanosheets and 3D-MXene. The fabricated MXene/3D-MXene actuator has exhibited remarkable response speed and deformation ability, obviously superior to any previously reported humidity-responsive actuators. By combining excellent electrical conductivity, the developed actuators demonstrated rapid response for electrical switches. This work highlights the significant potential for developing high performance responsive actuators by designing heterostructured configurations for applications in intelligent switches, soft robotics and synthetic muscles.

This study demonstrates a novel one-dimensional core-shell structure based on the coating of silver nanowires (Ag NWs) with a layer of titanium oxide (TiO2) nanoparticles. This approach for generating core-shell structures is facile and straightforward, utilizing a sol-gel method followed by the crystallization of TiO2 using a simple open-air hydrothermal method. The Ag nanowires are ˜10 μm in length and have a diameter of 100 nm, and their TiO2 polycrystalline shell is 10–15 nm in thickness. These novel structures offer large surface area and high stability, which are qualities that favor gas sensing performance. Gas sensing tests have demonstrated that the generated Ag NWs@TiO2 core-shell nanocomposites exhibit better sensing properties (response, selectivity, optimized working temperature, minimum concentration, and response and recovery time) when compared to sensors containing pure TiO2 nanoparticles. The mechanism of sensing enhancement can be attributed to the Schottky barrier that exists at the interface between the Ag NWs and the TiO2. The Ag core has an excellent conductive property for electronic transfer and further accelerates the oxygen ionization and surface redox reactions. These results may shed light on the design and construction of TiO2-based nanocomposites for gas sensor applications.

Developing high-performance photocatalysts for H2 production via fabricating heterojunctions has attracted much attention. Herein, we design a simple strategy to prepare composites that consist of TaON/CdS hybrids via a hydrothermal process. The results show that the pristine CdS nanoparticles loaded with 20 wt% TaON (TC4) could maximize the photocatalytic hydrogen evolution rate to 19.29 mmol g−1 h−1 under visible light irradiation, which was 2.13 times higher than that of the pristine CdS (9.03 mmol g−1 h−1) under the same conditions. The apparent quantum yield (AQY) of the TC4 nanocomposites at 420 nm was calculated to be 18.23%. The outstanding photocatalytic performance of the composites can be ascribed to the formation of heterojunctions. The electrochemical measurements indicate that the decoration facilitates the generation of extra photo-electrons, prolonging the recombination rate of photogenerated charge carriers, offering adequate active sites and improving catalytic stability. This study sheds light on the construction strategy and the deep understanding of the novel CdS-based composites for high-performance photocatalytic H2 production.

Core-shell semiconductor nanostructures can be suitable for high-performance gas sensors due to their unique structural features. In this study, In2O3@ MoO3 core-shell hollow spheres were synthesized by a facile two-step solvo-thermal method, followed by post-heat treatment. The synthesis results in 20-nm thick MoO3 shells coated on In2O3 hollow spheres (200-nm diameter). The effects of the morphology and composition on gas sensing performance were systematically investigated by adjusting the molar ratio of In to Mo. The sensing tests suggest that the core-shell structure with the In to Mo molar ratio of 1:1 exhibits the highest sensing response (28.1) towards 100-ppm n-butylamine at the optimized working temperature of 300°C. This response is two times higher than that of the In2O3 & MoO3 binary mixture (11.1) and five times than that of the pristine In2O3 hollow spheres (4.8). The sensing performance is a result of the unique core-shell structures including both the catalytic reaction mechanism of MoO3 and the co-catalytic properties of the In2O3 hollow spheres. This study may shed light on the design of practical, high-performance amine gas sensors in the future.

This study reports various integration types of In2O3/ZnS composites as high-performance sensing materials to different volatile organic compounds. By adjusting the molar ratios of In2O3 to ZnS, two optimized structures were prepared via two-step hydrothermal methods, e.g., the ZnS nanoparticles (∼10 nm) modified In2O3 hollow spheres (at the molar ratio of 1:0.1) and the In2O3@ZnS core-shell hollow spheres (at the molar ratio of 1:1). These two kinds of structures exhibit different sensing responses towards n-butylamine and n-butanol respectively, in comparison with other target gases (e.g. ethanol, methanol, isopropanol, and formaldehyde). Specifically, the ZnS nanoparticles modified In2O3 hollow spheres show a good response (5.8) to n-butylamine at the optimized working temperature of 300 °C while the In2O3@ZnS core-shell structures exhibit a high response (8.6) towards n-butanol at 260 °C. DFT simulation was used to reveal the reason for the long recovery time by calculating the adsorption energies between ZnS (110) and the target molecules. The enhanced gas sensing property is attributed to the unique structure of the materials and the formation of heterojunction between In2O3 and ZnS. This research provides a reference for developing high-performance gas sensors from the perspective of composite selection and structure design.

In this work, pristine Cu2O and Au nanoparticle modified Cu2O (Au/Cu2O) spherical nanocomposites were prepared by a simple redox method at room temperature. The as-prepared Cu2O nanospheres with diameters of 150–200 nm show relatively large surface area. The dye removal abilities of the pure Cu2O and the Au/Cu2O nanocomposites were tested by evaluating their adsorption and photocatalytic activities towards different aromatic molecules (e.g., Congo red (CR), Methyl orange (MO), Methyl blue (MB), Rhodamine B (RhB)). The experimental results indicate that the Au/Cu2O nanocomposites exhibit much superior adsorption and photocatalytic properties to the pristine Cu2O nanospheres. Among the catalysts, 1 wt% Au/Cu2O nanocomposite shows the best removal abilities to various dyes. Besides, the removal abilities towards these dyes are quite different from each other. For deep understanding of the adsorption mechanism, molecular dynamics (MD) caculations were conducted to investigate the adsorption energy of the Cu2O spheres by simulating the porous structure and Au modification. The calculation results indicate that CR and MO are chemically adsorbed on the Cu2O materials while the adsorption of MB and RhB are physical adsorption, which are well consistent with the experimental results. This study demonstrates the porous Cu2O based nanocomposites are promising materials with high adsorption and solar light-photocatalytic performance. In the meanwhile, the underlying mechanism on the superior dye removal abilities of Au modified Cu2O nanospheres were systematically discussed.

This study demonstrates an ultra-sensitive material towards 1-butylamine. The material is composed of 4 wt% Au nanoparticles decorated on MoO3 nanobelts, which are prepared via the hydrothermal method and in-situ reduction. The related characterizations reveal that the nanobelts are highly crystallized layer structures with a width of ~ 200 nm, a thickness of 40 nm and a length of several micrometers. The Au/MoO3 composites exhibit ultra-high sensing response (~300) towards 100 ppm of 1-butylamine at the working temperature of 240 °C. Even without Au decoration, the pristine MoO3 nanobelts offer the response as high as ~ 90 toward the same concentration of 1-butylamine at the temperature of 340 °C, much higher than the existing materials. More importantly, the proposal materials have excellent selectivity towards 1-butylamine, which offers the possibility for practical use. The excellent sensing performance is attributed to the unique sensing mechanism of the layered MoO3 nanobelts via catalytic reaction between 1-butylamine and the lattice oxygen of MoO3. Besides, Au decoration enables to enhance the adsorption of 1-butylamine and facilitate the catalytic sensing process, resulting in further increase in sensing response and selectivity of 1-butylamine. This study may shield light on a promising high-performance gas sensing materials to detect amines in practical application.

A MD simulation of FeCuNi alloys was performed. The evolution of structural parameters (including CN, the common neighbor sub-cluster, the largest standard cluster, and the structural entropy (Sstr)) revealed that the alloys are transformed into glass and Tg increases with Ni-addition. The effect of Ni-addition on the liquid state is opposite to or the same as the solid state, depending on the structural parameters. Analysis of the opposite effect unveiled another critical temperature (where crystal structures stop growing). Sstr can effectively quantify the disordered degree of a system. These findings have profound significance for the characteristics of disordered systems.

Based on difference in work function, novel Au nanoparticle-decorated WO3@TiO2 ternary core–shell rod-like nanocomposites (Au-WO3@TiO2) are designed and constructed as solar-light-driven photocatalysts. The photocatalytic activities were evaluated by monitoring the concentration change of methylene blue (MB) under simulated solar light irradiation. The results show that the Au-WO3@TiO2 ternary core–shell nanocomposites exhibited higher photocatalytic performance than the pure WO3 nanorods, the Au decorated WO3 nanorods and the WO3@TiO2 core–shell nanorods. The highest photocatalytic activity was found in the 1 wt% Au-WO3@TiO2 ternary core–shell nanocomposites, whose degradation efficiency and apparent rate constant (k) are 94.5% in 240 min under simulated solar light irradiation and 0.0295 min−1, respectively. The high performance of the ternary composites can be attributed to high specific area by coating of TiO2, the high utilization of solar light achieved by the surface plasmon resonance (SPR) effect of Au nanoparticles, and the low recombination rate of electrons and holes caused by electron transfer from TiO2 to Au and WO3. This study may offer a demonstration to make use of WO3 based ternary structure to help suppress the recombination of photo-induced electrons and holes in TiO2 and ultimately improve the photocatalytic efficiencies for multiple energy and environmental application.

This study demonstrates a hollow structure constructed by Au nanoparticles decorated on the surface of the In2O3 hollow nanospheres. This structure is prepared via calcination of solid organic precursors and in-situ reduction of Au nanoparticles on the metal oxide surface. The In2O3 hollow nanospheres are with the diameter of ˜200 nm and the shell thickness of 30 nm, while the Au nanoparticles on the surface of In2O3 hollow spheres are with the size of ˜10 nm. XPS indicates that the Au modification can increase the deficient oxygen vacancy ratio, and the presence of the positive Au ions (Auδ+) in the composites helps to trap the electrons and further improve the sensing performance. The gas sensing tests indicate that the Au decorated In2O3 hollow nanocomposites show excellent sensitivity (26.3 of 100 ppm) and selectivity toward 1-butylamine at the optimized temperature of 340 °C. The decoration of Au nanoparticles can lower the optimized working temperature and shorten the response/recovery times. The enhanced sensing mechanism can be attributed to electronic and chemical sensitization. The decoration of Au nanoparticles on the In2O3 surface can cause the Schottky barrier at the interface. The existence of positive Au ions can boost the barrier by trapping extra electrons. These results tender the promising hollow structure for sensing organic amine vapor in field-based use.