Nano-Micro Letters最新文献

Si is a promising anode material for Li ion batteries because of its high specific capacity, abundant reserve, and low cost. However, its rate performance and cycling stability are poor due to the severe particle pulverization during the lithiation/delithiation process. The high stress induced by the Li concentration gradient and anisotropic deformation is the main reason for the fracture of Si particles. Here we present a new stress mitigation strategy by uniformly distributing small amounts of Sn and Sb in Si micron-sized particles, which reduces the Li concentration gradient and realizes an isotropic lithiation/delithiation process. The Si_8.5Sn_0.5Sb microparticles (mean particle size: 8.22 μm) show over 6000-fold and tenfold improvements in electronic conductivity and Li diffusivity than Si particles, respectively. The discharge capacities of the Si_8.5Sn_0.5Sb microparticle anode after 100 cycles at 1.0 and 3.0 A g⁻¹ are 1.62 and 1.19 Ah g⁻¹, respectively, corresponding to a retention rate of 94.2% and 99.6%, respectively, relative to the capacity of the first cycle after activation. Multicomponent microparticle anodes containing Si, Sn, Sb, Ge and Ag prepared using the same method yields an ultra-low capacity decay rate of 0.02% per cycle for 1000 cycles at 1 A g⁻¹, corroborating the proposed mechanism. The stress regulation mechanism enabled by the industry-compatible fabrication methods opens up enormous opportunities for low-cost and high-energy–density Li-ion batteries.

Room temperature low threshold lasing of green GaN-based vertical cavity surface emitting laser (VCSEL) was demonstrated under continuous wave (CW) operation. By using self-formed InGaN quantum dots (QDs) as the active region, the VCSEL emitting at 524.0 nm has a threshold current density of 51.97 A cm⁻², the lowest ever reported. The QD epitaxial wafer featured with a high IQE of 69.94% and the δ-function-like density of states plays an important role in achieving low threshold current. Besides, a short cavity of the device (~ 4.0 λ) is vital to enhance the spontaneous emission coupling factor to 0.094, increase the gain coefficient factor, and decrease the optical loss. To improve heat dissipation, AlN layer was used as the current confinement layer and electroplated copper plate was used to replace metal bonding. The results provide important guidance to achieving high performance GaN-based VCSELs.

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Artificial cells are constructed from synthetic materials to imitate the biological functions of natural cells. By virtue of nanoengineering techniques, artificial cells with designed biomimetic functions provide alternatives to natural cells, showing vast potential for biomedical applications. Especially in cancer treatment, the deficiency of immunoactive macrophages results in tumor progression and immune resistance. To overcome the limitation, a BaSO₄@ZIF-8/transferrin (TRF) nanomacrophage (NMΦ) is herein constructed as an alternative to immunoactive macrophages. Alike to natural immunoactive macrophages, NMΦ is stably retained in tumors through the specific affinity of TRF to tumor cells. Zn²⁺ as an “artificial cytokine” is then released from the ZIF-8 layer of NMΦ under tumor microenvironment. Similar as proinflammatory cytokines, Zn²⁺ can trigger cell anoikis to expose tumor antigens, which are selectively captured by the BaSO₄ cavities. Therefore, the hierarchical nanostructure of NMΦs allows them to mediate immunogenic death of tumor cells and subsequent antigen capture for T cell activation to fabricate long-term antitumor immunity. As a proof-of-concept, the NMΦ mimics the biological functions of macrophage, including tumor residence, cytokine release, antigen capture and immune activation, which is hopeful to provide a paradigm for the design and biomedical applications of artificial cells.

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Hydrazine oxidation reaction (HzOR) assisted hydrogen evolution reaction (HER) offers a feasible path for low power consumption to hydrogen production. Unfortunately however, the total electrooxidation of hydrazine in anode and the dissociation kinetics of water in cathode are critically depend on the interaction between the reaction intermediates and surface of catalysts, which are still challenging due to the totally different catalytic mechanisms. Herein, the [W–O] group with strong adsorption capacity is introduced into CoP nanoflakes to fabricate bifunctional catalyst, which possesses excellent catalytic performances towards both HER (185.60 mV at 1000 mA cm⁻²) and HzOR (78.99 mV at 10,00 mA cm⁻²) with the overall electrolyzer potential of 1.634 V lower than that of the water splitting system at 100 mA cm⁻². The introduction of [W–O] groups, working as the adsorption sites for H₂O dissociation and N₂H₄ dehydrogenation, leads to the formation of porous structure on CoP nanoflakes and regulates the electronic structure of Co through the linked O in [W–O] group as well, resultantly boosting the hydrogen production and HzOR. Moreover, a proof-of-concept direct hydrazine fuel cell-powered H₂ production system has been assembled, realizing H₂ evolution at a rate of 3.53 mmol cm⁻² h⁻¹ at room temperature without external electricity supply.