Materials with Janus structures have attracted significant attention in recent years.

Although Janus films of different compositions have been commonly utilized to develop moisture actuators due to the different capabilities of swelling in materials, a sole material with a distinct structural design is also able to provide moisture-actuation. In this study, we simply used graphene oxide (GO) to fabricate a sole GO film with an asymmetric structure which consisted of a wavy layer and a smooth layer. Due to the asymmetric structure and excellent hygroscopicity of the GO material, the asymmetric graphene oxide (AGO) film (2.5 × 0.5 cm2) was responsive to moisture and showed a maximum bending angle change of ≈1800° as the relative humidity (RH) changed. Compared with other reports about moisture actuators, the AGO film exhibited a superior bending capability. Furthermore, we propose a novel mechanism for moisture actuation of the AGO film based on our detailed observations, and a wavy structure has been introduced for showing great potential in bending deformation. Finally, the AGO film was used as a grabber to grab a leaf and it exhibited good capability to twine around a plastic rod. This work provides a novel pathway for the development of moisture-responsive materials for potential applications in robotics, artificial muscles and switches.

In recent years, Janus materials have become a research hotspot in the field of materials science; however, fabricating inorganic Janus-like nanofibers (NFs) is still a challenge. Herein, we report novel ZnO/NiO Janus-like NFs with efficient photocatalytic performance via an electrospinning method followed by calcination treatment. The morphology, structure, chemical composition and crystallinity of ZnO/NiO Janus-like NFs were studied in detail via SEM, TEM, HRTEM, EDS, FT-IR, XPS and XRD, indicating that the NFs had a perfect Janus-like structure composed of ZnO and NiO. A series of photocatalytic experiments were carried out in aqueous organic dye solutions under 365 nm UV radiation for 1 h, with the degradation rate of malachite green able to reach 96%, proving that the NFs have great potential in the field of organic dye degradation. Furthermore, a reasonable catalytic mechanism for the ZnO/NiO Janus-like NFs was proposed, which was discussed from the view of electron-hole pairs and p-n junctions. In short, the method in our work is expected to become a new way of effectively preparing functional inorganic Janus-like NFs.

Magnetic-fluorescent bifunctional materials have received global attention owing to their potential in many fields. Herein, we reported a novel magnetic-fluorescent bifunctional Janus nanofiber membrane (NFM) by adding the as-prepared magnetic CoFeO nanoparticles into the polyacrylonitrile (PAN) side (m-PAN) and the fluorescent molecules of 1,8-naphthalene anhydride (1,8-NAD) into the polyvinylpyrrolidone (PVP) side (f-PVP) via electrospinning method. The obtained m-PAN/f-PVP Janus NFM exhibited excellent magnetic performance and high fluorescent properties due to the unique structure. Compared with the m-PAN/f-PVP composite NFM, the Janus NFM showed higher fluorescent performance because the fluorescent molecules were isolated from the magnetic nanoparticles. In addition, the Janus NFM not only maintain the good self-supporting state in water but also realize a directional movement attracted by a magnet. The unique structure of Janus nanofiber is of great importance and demonstrates great potential applications.

Genotypic data provide deep insights into the population history and medical genetics. The local ancestry inference (LAI) (also termed local ancestry deconvolution) method uses the hidden Markov model (HMM) to solve the mathematical problem of ancestry reconstruction based on genomic data. HMM is combined with other statistical models and machine learning techniques for particular genetic tasks in a series of computer tools. In this article, we surveyed the mathematical structure, application characteristics, historical development, and benchmark analysis of the LAI method in detail, which will help researchers better understand and further develop LAI methods. Firstly, we extensively explore the mathematical structure of each model and its characteristic applications. Next, we use bibliometrics to show detailed model application fields and list articles to elaborate on the historical development. LAI publications had experienced a peak period during 2006–2016 and had kept on moving in the following years. The efficiency, accuracy, and stability of the existing models were evaluated by the benchmark. We find that phased data had higher accuracy in comparison with unphased data. We summarize these models with their distinct advantages and disadvantages. The Loter model uses dynamic programming to obtain a globally optimal solution with its parameter-free advantage. Aligned bases can be used directly in the Seqmix model if the genotype is hard to call. This research may help model developers to realize current challenges, develop more advanced models, and enable scholars to select appropriate models according to given populations and datasets.

Carbon-based non-precious metal catalysts have been regarded as the most promising alternatives to the state-of-art Pt/C catalyst for the oxygen reduction reaction (ORR). However, there are still some unresolved challenges such as agglomeration of nanoparticles, complex preparation process and low production efficiency, which severely hamper the large-scale production of non-precious metal catalysts. Herein, a novel carbon-based non-precious metal catalyst, i.e. iron carbide nanoparticles embedded on carbon nanofibers (Fe 2 C/CNFs), prepared via the direct pyrolysis of carbon-and iron-containing Janus fibrous precursors obtained by electrospinning. The Fe 2 C/CNF catalyst shows uniform dispersion and narrow size distribution of Fe 2 C nanoparticles embedded on the CNFs. The obtained catalyst exhibits positive onset potential (0.87 V versus RHE), large kinetic current density (1.9 mA cm −2 ), and nearly follows the effective four-electron route, suggesting an outstanding electrocatalytic activity for the ORR in 0.1 M of KOH solution. Besides, its stability is better than that of the commercial Pt/C catalyst, due to the strong binding force between Fe 2 C particles and CNFs. This strategy opens new avenues for the design and efficient production of promising electrocatalysts for the ORR.

No abstract

No abstract