Reagent-Free Synthesis and Plasmonic Antioxidation of Unique Nanostructured Metal-Metal Oxide Core-Shell Microfibers

Scalable fluid-spinning nanowire-based inorganic semiconductor yarns for electrochromic actuators

Semiconductor yarns with unique functional characteristics have great potential applications in next-generation electronic devices. However, scalable inorganic semiconductor yarns with excellent mechanical and electrical properties, and environmental stability have not been discovered. In this study, we explored a unique fluid-spinning strategy to obtain a series of scalable inorganic semiconductor yarns including neat and hybrid semiconductor yarns. Different from the conventional yarn spinning strategy through a mechanical motor, we utilized the fluid force from the triple-phase interface to assemble and twist inorganic nanofiber building blocks simultaneously, and eventually obtained highly oriented inorganic nanowire-based semiconductor yarns. The obtained semiconductor yarns showed an excellent flexibility (curvature exceeding 2 cm^-1) and mechanical strength (tensile strength of 443 MPa) because of their highly oriented hierarchical nanostructures, which make them coiling able with highly twisted insertion. Additionally, coiled yarns were obtained by combining the host core material and functional guest sheath in a fluid-spinning process, which are flexible in deep cryogenic temperature owing to the pure inorganic building blocks (26.28% tensile strain in liquid nitrogen). In particular, inorganic yarn-based electrochromic actuators can obtain as high as 15.3% tensile stroke and 0.82 J g^-1 work capacity by electrochemical charge injection-associated multicolor switching.

Construction of Core-Shell Nanowire Arrays in a Cu-Cu2O Film Electrode for High Efficiency in Heat Dissipation

Thermal engineering dramatically impacts the efficiency of microelectronics, but the corresponding technology lags far behind the need. For energy-efficient thermal management, a Cu-Cu₂O film with highly ordered core-shell nanowire arrays and a good self-protection property was successfully fabricated using the magnetron sputtering method. The dense arrangement of nanowires in the films enhances the electronic transport property (220 mΩ sq^-1), while the modified stable Cu₂O layer maintained its perfect heat dissipation property, along with long-term thermal stability. The core-shell and nanogaps structure imparted an anisotropic thermal conductivity, where the out-plane electronic thermal conductivity (321 ± 16 W m^-1 K^-1) was 33.6 times higher than the in-plane value. To study the role of anisotropic properties in heat dissipation, a boiling experiment and thermal simulation were undertaken. The Cu-Cu₂O core-shell electrode was beneficial to elevate the heat transfer coefficient, which would cause a fast directional transport and reduction of interfacial superheating. We demonstrated that an advancement of microelectronics could be achieved by integrating Cu electrodes with an ordered architecture.

Microfluidic spinning of editable polychromatic fibers

Chromatic fibers that change color in response to external stimuli are expected to be widely used in various applications such as anti-counterfeiting, military camouflage, and wearable displays. Advanced chromatic fibers with polychromatic and editable color properties behavior are strongly desired for practical applications but have not yet been realized using existing spinning technologies. Here, we present the low-cost, continuous microfluidic spinning of editable polychromatic polylactide (PLA) fibers. The structure and performance of the polychromatic PLA fibers were precisely controlled by adjusting the parameters used in microfluidic spinning. The structure of the as-spun products evolved through three different stages based on the editable encapsulation of functional materials into the PLA matrix. Fibers with versatile performance were achieved. A beaded polychromatic PLA fiber showed the possibility to delivery coded information through its editable chromatic behavior. A core-shell polychromatic PLA fiber showed good mechanical properties and knittability, which make it promising to fabricate smart color-changing textiles.

Oriented attachment growth of monocrystalline cuprous oxide nanowires in pure water

As a crucial mechanism of non-classical crystallization, the oriented attachment (OA) growth of nanocrystals is of great interest in nanoscience and materials science. The OA process occurring in aqueous solution with chemical reagents has been reported many times, but there are limited studies reporting the OA growth in pure water. In this work, we report the temperature-dependent OA growth of cuprous oxide (Cu₂O) nanowires in pure water through a reagent-free electrophoretic method. Our experiments demonstrate that Cu₂O quantum dots randomly coalesced to form polycrystalline nanowires at room temperature, while they form monocrystalline nanowires at higher temperatures by the OA mechanism. DFT modeling and computations indicate that the water coverage on the Cu₂O nanoparticles could affect the particle attachment mechanisms. This study sheds light on the understanding of the effects of water molecules on the OA mechanism and shows new approaches for better controllable non-classical crystallization in pure water.

Synthesis of core–shell N-TiO2@CuOx with enhanced visible light photocatalytic performance

In this paper, a core–shell N-TiO₂@CuO_x nanomaterial with increased visible light photocatalytic activity was successfully synthesized using a simple method. By synthesizing ammonium titanyl oxalate as a precursor, N-doped TiO₂ can be prepared, then the core–shell structure of N-TiO₂@CuO_x with a catalyst loading of Cu on its surface was prepared using a precipitation method. It was characterized in detail using XRD, TEM, BET, XPS and H₂-TPR, while its photocatalytic activity was evaluated using the probe reaction of the degradation of methyl orange. We found that the core–shell N-TiO₂@CuO_x nanomaterial can lessen the TiO₂ energy band-gap width due to the N-doping, as well as remarkably improving the photo-degradation activity due to a certain loading of Cu on the surfaces of N-TiO₂ supports. Therefore, a preparation method for a novel N, Cu co-doped TiO₂ photocatalyst with a core–shell structure and efficient photocatalytic performance has been provided.

In this paper, a core–shell N-TiO₂@CuO_x nanomaterial with increased visible light photocatalytic activity was successfully synthesized using a simple method.

Gas-generating reactions for point-of-care testing

Gas generation-based measurement is an attractive alternative approach for POC (Point-of-care) testing, which relies on the amount of generated gas to detect the corresponding target concentrations.

Ultralight, Flexible, and Semi-Transparent Metal Oxide Papers for Photoelectrochemical Water Splitting

Thanks to their versatile functionality, metal oxides (MOs) constitute one of the key family materials in a variety of current demands for sensor, catalysis, energy storage and conversion, optical electronics, and piezoelectric mechanics. Much effort has focused on engineering specific nanostructure and macroscopic morphology of MOs that aims to enhance their performances, but the design and controlled synthesis of ultrafine nanostructured MOs in a cost-effective and facile way remains a challenge. In this work, we have exploited the advantages of intrinsic structures of graphene oxide (GO) papers, serving as a sacrificial template, to design and synthesize two-dimensional (2D) layered and free-standing MO papers with ultrafine nanostructures. Physicochemical characterizations showed that these MO materials are nanostructured, porous, flexible, and ultralight. The as-synthesized materials were tested for their potential application in photoelectrochemical (PEC) energy conversion. In terms of PEC water splitting, copper oxide papers were used as an example and exhibited excellent performances with an extremely high photocurrent-to-weight ratio of 3 A cm^-2 g^-1. We have also shown that the synthesis method is generally valid for many earth-abundant transition metals including copper, nickel, iron, cobalt, and manganese.