"Nature" and "Science" Week (09.26-10.02) Frontiers of Materials Science

1. Biomechanical energy continuously supplies power to wearable electronic products
(Sustainably powering wearable electronics sole by biomechanical energy) Obtaining biomechanical energy is an important solution for powering wearable electronic products, but the current method is still battery powered, so it needs to be frequently recharged or replaced. The research team led by Professor Wang Zhonglin demonstrated a way to continuously supply power to wearable devices through human motion, that is, using nano-friction generators (TENG) that are optimized and structurally designed to supply power. This power plant is made of a spiral internal electrode and an elastic material and has desirable properties including flexibility, ductility, isotropy, manufacturability, water resistance and high surface charge density of 250 μC/m 2 . With the nano-friction generator built into the sole and the tester extracts energy by walking or jogging, the wearable electronic devices such as electronic watches and fitness trackers can be charged immediately and sustainably. (Nature Communications DOI: 10.1038/ncomms12744)

2. Multi-process 3D printing lifting component function
(Multiprocess 3D printing for increasing component functionality) Layer-by-layer deposition of material processing components, also known as three-dimensional (3D) printing or laminate manufacturing. In the past few years, 3D printing has been booming as a manufacturing process and can now be used to make complex geometries used as models, assembly firmware and molds. More and more people are paying attention to this technology for the direct production of parts. However, current 3D printing is still generally limited to manufacturing with a single material, which limits the end use and functionality of the product. Next-generation 3D printing requires not only the integration of different kinds of materials, but also the implementation of active components for achieving specific functions. MacDonald et al. reviewed the current multi-process 3D printing field, and they believe that the combination of tradition and innovation will advance the future of manufacturing. (Science DOI: 10.1126/science.aaf2093)

3. Perovskite light-emitting diodes based on solution treatment of self-organizing multiple quantum wells
(Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells) The organometallic halide perovskite is treated by a low temperature solution to form a crystalline direct band gap semiconductor having good photoelectric properties. However, the electroluminescence efficiency of such semiconductors is often limited by non-radiative recombination due to defects and leakage currents caused by incomplete surface coverage. The research team led by Academician Huang Wei of Nanjing University of Technology proposed a solution for the treatment of perovskite light-emitting diodes (LEDs) based on good thin-film morphology self-assembled multiple quantum wells (MQW). The MQW-based LED exhibits an external quantum efficiency of up to 11.7%, good stability, and exhibits high power performance with an energy conversion efficiency of 5.5% at a current density of 100 mA/cm2. A perovskite multiple quantum well with a higher energy gap effectively encloses the lower band gap region where electroluminescence is produced, thereby resulting in very efficient radiation decay, resulting in superior performance. Surprisingly, there is no evidence that large interfacial regions between different bandgap regions can cause luminescence quenching. (Nature Photonics DOI: 10.1038/NPHOTON.2016.185)

4. Use iron oxide nanoparticles to inhibit tumor growth
(Iron oxide nanoparticles inhibit tumour growth by inducing pro-inflammatory macrophage polarization in tumour tissues) Recently, the US Food and Drug Administration has approved iron oxide nanoparticles such as ferumoxytol (superparamagnetic iron oxide nanoinjection) for the treatment of iron deficiency, as a drug carrier and magnetic resonance imaging contrast agent. Zanganeh et al. demonstrated the intrinsic therapeutic effect exhibited by ferumoxytol for early breast cancer growth and liver lung cancer metastasis. Co-culture of adenocarcinoma cells, ferumoxytol and macrophages in vitro showed that ferumoxytol has an enhanced effect on caspase-3 activity. After macrophages are exposed to it, the correlation between mRNA and pro-inflammatory Th1-type response is enhanced. In vivo experiments, ferumoxytol significantly inhibited the growth of subcutaneous adenocarcinoma in mice. In addition, intravenous injection of ferumoxytol before venous tumor cells are stimulated can prevent liver tumor metastasis. Flow cytometric analysis (FACS) and histopathological studies have shown that inhibition of tumor cell growth is accompanied by an increase in proinflammatory M1 macrophages in tumor tissues. The results indicate that ferumoxytol can be used as an unconventional drug for the prevention of liver tumor metastasis and the regulation of cancer immunotherapy for enhancing macrophages. (Nature Nanotechnology DOI: 10.1038/NNANO.2016.168)

5. Preparation of highly stable sub-nanoplatinum
(Generation of subnanometric platinum with high stability during transformation of a 2D zeolite into 3D) Single metal atoms and metal clusters have attracted great research interest due to their unique heterogeneous catalytic advantages. However, the preparation of stable monoatoms and clusters on solid supports remains a significant challenge. Recently, Liu et al. reported a new strategy for synthesizing monoatomic Pt and Pt clusters with high thermal stability. They used MCM-22 zeolite to convert Pt atoms or clusters from two-dimensional to three-dimensional, and remained stable even after heating to 540 °C. Moreover, these stable Pt atoms or clusters confined within the framework cavity exhibit dimensional selectivity for catalyzing the hydrogenation of olefins. The high temperature redox treatment results in the growth of Pt atoms or clusters as small particles of 1-2 nm. This Pt catalyst also has good catalytic activity and stability for the dehydrogenation of propane to propylene. (Nature Materials DOI: 10.1038/NMAT4757)

6. Partial mismatched quasicrystal superlattice
(Quasicrystalline nanocrystal superlattice with partial matching rules) Expanding the self-assembled superlattice sample library is important for understanding the behavior of atomic crystals and supporting the development of mesoscale ordered materials. A soft quasicrystal of Ye et al. found a quasi-crystal binary superlattice that exhibits partial matching criteria. They determined the three-dimensional structural model by electron tomography and surface topography. This model breaks the 12-fold rotational symmetry of the quasicrystal, forming a quadrilateral and random stacking of large and small triangles with 6-fold symmetry. Their experimental-theoretical joint study demonstrates the ability of nanocrystalline superlattice to regulate and further narrows the gap between the crystal structure and the soft matter assembly. (Nature Materials DOI: 10.1038/NMAT4759)

7. Using hydrogenated twin crystals and NiSx photocatalytic hydrogen production
(Photocatalytic hydrogen production using twinned nanocrystals and an unanchored NiSx co-catalyst) Accelerating charge separation and surface redox reactions are considered to be the core to improve semiconductor-catalyzed solar hydrogen production. In order to achieve this, photocatalysts consisting of intimately contacted photosorbents and cocatalysts have attracted the attention of researchers. Liu et al. reported the use of a Cd0.5Zn0.5S nano-bright photocatalyst in combination with a NiSx cocatalyst for photocatalytic hydrogen production. They found that the internal quantum efficiency of photocatalytic hydrogen production tends to be 100% by using Na2S/Na2SO3 as a de-porating agent under 425 nm illumination. These results indicate that the NiSx co-catalyst is not attached to the main catalyst CZS, but exists as a sub-nano cluster in the reaction solution. They believe that the collision of electrons is achieved by the collision of CZS and NiSx clusters, which assists the charge separation and suppresses the reverse reaction and improves the water reduction rate. (Nature Energy DOI: 10.1038/NENERGY.2016.151)

8. Same-chiral polymerization drives the growth of graphene nanoribbons
(Homochiral polymerization-driven selective growth of graphene nanoribbons) Surface-assisted bottom-up synthesis of graphene nanoribbons (GNRs) has attracted the attention of many researchers. Although these reactions on the metal surface are generally considered to be due to the action of metal catalysis, in fact, this mechanism is not clear. Sakaguchi et al. demonstrated "conformal controlled surface catalysis": a two-zone vapor deposition of a "Z-link" precursor. They used this method to synthesize "acene type" graphene nanoribbons with a width of 1.45 nm. These precursors exhibit good flexibility, allowing them to accommodate highly asymmetric chiral conformations of the Au (111) plane. This method is conceptually similar to enzyme catalysis and can be applied to the synthesis of new carbon materials.
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