Nanoscale Horizons最新文献

Transition-metal nitride thin-film electrodes are potential electrode materials for all-solid-state thin-film lithium-ion batteries. In this study, orthorhombic Hf₃N₄ thin-film electrodes applied in lithium-ion batteries were fabricated by the magnetron sputtering deposition of Hf followed by N₂ plasma immersion and post-annealing for the first time. This electrode material without additives such as binders and conductive agents exhibited a high specific capacity, high cycling stability, and excellent rate performance. At a current density of 0.1 A g⁻¹, the initial discharge capacity was 583.2 mA h g⁻¹ and the stable Coulombic efficiency was 96.6%. At a high current density of 2 A g⁻¹, the Hf₃N₄ thin-film electrodes could still provide a stable discharge capacity of about 260 mA h g⁻¹ and Coulombic efficiency close to 100%. By analyzing the cyclic voltammetry curves at different scan rates, it was found that the Li⁺ storage in Hf₃N₄ thin-film electrodes was mainly contributed by a pseudo-capacitance mechanism.

Creating tin-alloyed silicon nanocrystals with tailored bandgap values is a significant challenge, primarily because a substantial concentration of tin is essential to observe useful changes in the electronic structure. However, high concentration of Sn leads to instability of the silicon–tin nanocrystals. This work introduces a completely new approach to doping and the modification of the electronic structure of nanoparticles by incorporating few-atom clusters in nanocrystals, deviating from isolated atom doping or attempting alloying. This approach is exemplified via a combined theoretical and experimental study on tin (Sn) ‘cluster-doping’ of silicon (Si) nanocrystals, motivated by the opportunities offered by the Si–Sn system with tailored band energy. First-principles modelling predicts two noteworthy outcomes: a considerably smaller bandgap of these nanocrystals even with a modest concentration of tin compared to an equivalent-sized pure silicon nanocrystal and an unexpected decrease in the bandgap of nanocrystals as the diameter of nanocrystals increases, contrary to the typical quantum confined behaviour. Experimental verification using atmospheric pressure microplasma synthesis confirms the stability of these nanocrystals under ambient conditions. The plasma-synthesised nanocrystals exhibited the predicted atypical size-dependent behaviour of the bandgap, which ranged from 1.6 eV for 1.4 nm mean diameter particles to 2.4 eV for 2.2 nm mean diameter particles.

In order to achieve a therapeutic effect, many drugs have to reach specific cellular compartments. Nanoscale drug delivery systems extend the circulation time, reduce adverse effects and thus improve tolerability compared to systemic administration. We have developed two types of albumin-coated nanocarriers equipped with built-in dyes to track their cellular uptake and intracellular enzymatic opening. Using the approved antiprotozoal drug and STAT3 inhibitor Atovaquone (Ato) as prototype for a hydrophobic small molecule, we show that Ato-loaded ovalbumin-coated nanocapsules (Ato-nCap) preferentially enter human myeloid cells. In contrast, Ato nanocrystals coated with human serum albumin (Ato-nCry) distribute their cargo in all different immune cell types, including T and B cells. By measuring the effect of Ato nanocarriers on induced STAT3 phosphorylation in IL-10-primed human dendritic cells and constitutive STAT3 phosphorylation in human melanoma cells, we demonstrate that the intracellular Ato release is particularly effective from Ato nanocrystals and less toxic than equal doses of free drug. These new nanocarriers thus represent effective systems for intracellular drug delivery.

Marine biofouling severely limits the development of the marine economy, and reactive oxygen species (ROS) produced by electrocatalytic antifouling techniques could inactivate marine microorganisms and inhibit the formation of marine biofouling. Compared with an electro-Fenton reaction, a three-electron oxygen reduction reaction (3e⁻ ORR) could generate a hydroxyl radical (˙OH) in situ without the limitation of pH and iron mud pollutants. Herein, O_v-rich γ-MnO₂ is designed to enhance the 3e⁻ ORR performance in neutral media and exhibits excellent sterilization performance for typical marine bacteria. DFT calculation reveals that O_v is beneficial to the “end-on” adsorption and activation of O₂, and the Mn site could accept the electrons from *OOH and promote its further reduction to form ˙OH; O_v and Mn sites together guarantee the high 3e⁻ ORR efficiency. In addition, liquid chromatography–tandem mass spectrometry (LC–MS/MS) proves the vast formation of ˙OH in the primary reaction stage, which is the key to sterilization. This work explores the reaction mechanism of the 3e⁻ ORR in neutral media and provides the possibility for the application of electrocatalysis technology in the treatment of marine biofouling pollution.

Gold nanoclusters (AuNCs) are a type of rising-star fluorescence nanomaterials, but their properties and applications are hindered by the multi-step synthesis and purification routes, as well as the lack of desired supporting substrates. To enhance optical performance and working efficiency, the synthesis and applications of AuNCs are suggested to be merged with emerging substrates. Herein, glutathione-modified hydrophilic rice papers are incubated in chloroauric acid aqueous solutions, and the oxidation–reduction reaction between glutathione and Au ions enables the in situ formation of fluorescent AuNCs on the solid fibres of rice papers. The in situ growth of fluorescent AuNCs on rice papers resulted in eye-catching fluorescence tracks, similar to traditional Chinese conventional calligraphy; thus, this fluoresence calligraphy is defined in this work. The entire process, including synthesis and signal responses, is extremely simple, rapid, and repeatable. Moreover, the diversity of additive chemical reagents in the studied rice papers resulted in responsive fluorescence calligraphy, and the as-synthesized AuNC materials exhibited high reliability and optical stability. Significantly, with the integration of synchronous formation and application of Au nanoclusters on hydrophilic paper substrates, high-performance logical gates and information encryption systems were constructed, remarkably facilitating the progress of molecular sensing and important information transmission.

Plasmonic nanoparticles (NPs) have played a significant role in the evolution of modern nanoscience and nanotechnology in terms of colloidal synthesis, general understanding of nanocrystal growth mechanisms, and their impact in a wide range of applications. They exhibit strong visible colors due to localized surface plasmon resonance (LSPR) that depends on their size, shape, composition, and the surrounding dielectric environment. Under resonant excitation, the LSPR of plasmonic NPs leads to a strong field enhancement near their surfaces and thus enhances various light–matter interactions. These unique optical properties of plasmonic NPs have been used to design chemical and biological sensors. Over the last few decades, colloidal plasmonic NPs have been greatly exploited in sensing applications through LSPR shifts (colorimetry), surface-enhanced Raman scattering, surface-enhanced fluorescence, and chiroptical activity. Although colloidal plasmonic NPs have emerged at the forefront of nanobiosensors, there are still several important challenges to be addressed for the realization of plasmonic NP-based sensor kits for routine use in daily life. In this comprehensive review, researchers of different disciplines (colloidal and analytical chemistry, biology, physics, and medicine) have joined together to summarize the past, present, and future of plasmonic NP-based sensors in terms of different sensing platforms, understanding of the sensing mechanisms, different chemical and biological analytes, and the expected future technologies. This review is expected to guide the researchers currently working in this field and inspire future generations of scientists to join this compelling research field and its branches.

The magnesiothermic reduction of SiO₂ is an important reaction as it is a bulk method that produces porous Si for a wide range of applications directly from SiO₂. While its main advantage is potential tunability, the reaction behavior and final product properties are heavily dependent on many parameters including feedstock type. However, a complete understanding of the reaction pathway has not yet been achieved. Here, using in situ X-ray diffraction analysis, for the first time, various pathways through which the magnesiothermic reduction reaction proceeds were mapped. Further, the key parameters and conditions that determine which pathways are favored were determined. It was discovered that the reaction onset temperatures can be as low as 348 ± 7 °C, which is significantly lower when compared to previously reported values. The onset temperature is dependent on the size of Mg particles used in the reaction. Further, Mg₂Si was identified as a key intermediate rather than a reaction byproduct during the reduction process. Its rate of consumption is determined by the reaction temperature which needs to be >561 °C. These findings can enable process and product optimization of the magnesiothermic reduction process to manufacture and tune porous Si for a range of applications.

Valleytronics, i.e., use of the valley degree of freedom in semiconductors as an information carrier, is a promising alternative to conventional approaches for information processing. Transition metal dichalcogenides with degenerate K/K′ valleys have received attention as prototype 2D/layered semiconductors for valleytronics, but these systems rely on exotic effects such as the valley-Hall effect for electrical readout of the valley occupancy. Non-traditional valleytronic systems hosting sets of addressable non-degenerate valleys could overcome this limitation. In the van der Waals semiconductor Sn(II) sulfide (SnS), for instance, different bandgaps and band edges may allow manipulating the population of the X- and Y-valleys via charge transfer across interfaces to other layered semiconductors. Here, we establish this concept by comparing SnS flakes and SnS-based heterostructures. Cathodoluminescence spectroscopy shows a striking reversal of the luminescence intensity of the two valleys in SnS–GeS van der Waals stacks, which stems from a selective electron transfer from the Y-valley into GeS while X-valley electrons remain confined to SnS. Our results suggest that non-traditional systems, embodied here by SnS-based van der Waals heterostructures, open avenues for valley-selective readout relying on design parameters such as heterostructure band offsets that are among the core concepts of semiconductor technology.

Metamaterials have demonstrated significant potential for enhancing nonlinear processes at the nanoscale. The presence of narrowband hot-spots and highly inhomogeneous mode-field distributions often limit the enhancement of nonlinear interactions over larger spatial scales. This has posed a formidable challenge in achieving simultaneous enhancement across a broadband spectral range, significantly constraining the potential of photonic nanostructures in enhancing nonlinear frequency conversion. Here, we propose a broadband resonant mode matching method through near-field examinations that supports the multipole modes and enables the development of an ultrabroadband-enhanced 3–5 μm mid-infrared frequency upconversion technique utilizing a hyperbolic triangular pyramidal metasurface. The gap-plasma mode of the hyperbolic metamaterial multilayer system excites narrowly high-order resonances at near-infrared pump light wavelengths, while the slow-light effect generated by the dipoles achieves ultrabroadband near-field enhancement at mid-infrared wavelengths. The symmetry breaking of the triangular structure localizes these resonant modes at the tips, enabling mode-matched modulation at different wavelengths, and thus boosting the nonlinear frequency conversion process. Our approach provides a promising platform for metasurface-based frequency conversion techniques.

Spin waves (magnons) can enable neuromorphic computing by which one aims at overcoming limitations inherent to conventional electronics and the von Neumann architecture. Encoding magnon signal by reversing magnetization of a nanomagnetic memory bit is pivotal to realize such novel computing schemes efficiently. A magnonic neural network was recently proposed consisting of differently configured nanomagnets that control nonlinear magnon interference in an underlying yttrium iron garnet (YIG) film [Papp et al., Nat. Commun., 2021, 12, 6422]. In this study, we explore the nonvolatile encoding of magnon signals by switching the magnetization of periodic and aperiodic arrays (gratings) of Ni₈₁Fe₁₉ (Py) nanostripes with widths w between 50 nm and 200 nm. Integrating 50-nm-wide nanostripes with a coplanar waveguide, we excited magnons having a wavelength λ of ≈100 nm. At a small spin-precessional power of 11 nW, these ultrashort magnons switch the magnetization of 50-nm-wide Py nanostripes after they have propagated over 25 μm in YIG in an applied field. We also demonstrate the magnetization reversal of nanostripes patterned in an aperiodic sequence. We thereby show that the magnon-induced reversal happens regardless of the width and periodicity of the nanostripe gratings. Our study enlarges substantially the parameter regime for magnon-induced nanomagnet reversal on YIG and is important for realizing in-memory computing paradigms making use of magnons with ultrashort wavelengths at low power consumption.