Coarse and fine-tuning of lasing transverse electromagnetic modes in coupled all-inorganic perovskite quantum dots

Inorganic perovskite lasers are of particular interest,with much recent work focusing on Fabry-P6rot cavity-forming nanowires.We demonstrate the direct observation of lasing from transverse electromagnetic(TEM)modes with a long coherence time-9.5ps in coupled CsPbBr₃ quantum dots,which dispense with an external cavity resonator and show how the wavelength of the modes can be controlled via two independent tuning-mechanisms.Controlling the pump power allowed us tofine-tune the TEM mode structure to the emission wavelength,thus providing a degree of control over the properties of the lasing signal.The temperature-tuning provided an additional degree of control over the wavelength of the lasing peak,importantly,maintained a constant full width at half maximum(FWHM)over the entire tuning range without mode-hopping.     

Rapid room-temperature synthesis of a porphyrinic MOF for encapsulating metal nanoparticles

While metal nanoparticles(NPs)have shown great promising applications as heterogeneous catalysts,their agglomeration caused by thermodynamic instability is detrimental to the catalytic performance.To tackle this hurdle,we successfully prepared a functional and stable porphyrinic metal-organic framework(MOF),PCN-224-RT,as a host for encapsulating metal nanoparticles by direct stirring at room temperature.As a result,Pt@PCN-224-RT composites with well-dispersed Pt NPs can be constructed by introducing pre-synthesized Pt NPs into the precursor solution of PCN-224-RT.Of note,the rapid and simple stirring method in this work is more in line with the requirements of environmental friendly and industrialization compared with traditional solvothermal methods.     

Geometrical quasi-ballistic effects on thermal transport in nanostructured devices

We employ thermoreflectance thermal imaging to directly measure the steady-state two-dimensional(2D)temperature field generated by nanostructured heat sources deposited on silicon substrate with different geometrical configurations and characteristic sizes down to 400nm.The analysis of the results using Fourier's law not only breaks down as size scales down,but it alsofails to capture the impact of the geometry of the heat source.The substrate effective Fourier thermal conductivities fitted to wire-shaped and circular-shaped structures with identical characteristic lengths are found to display up to 40%mismatch.Remarkably,a hydrcxjynamic heat transport model reproduces the observed temperature fields for all device sizes and shapes using just intrinsic Si parameters,i.e.,a geometry and size-independent thermal conductivity and nonlocal length scale.The hydrodynamic model provides insight into the observed thermal response and of the contradictory Fourier predictions.We discuss the substantial Silicon hydrodynamic behavior at room temperature and contrast it to InGaAs,which shows less hydrodynamic effects due to dominant phonon-impurity scattering.     

Two-dimensional polymer nanosheets for efficient energy storage and conversion

As a promising graphene analogue, two-dimensional (2D) polymer nanosheets with unique 2D features, diversified topological structures and as well as tunable electronic properties, have received extensive attention in recent years. Here in this review, we summarized the recent research progress in the preparation methods of 2D polymer nanosheets, mainly including interfacial polymerization and solution polymerization. We also discussed the recent research advancements of 2D polymer nanosheets in the fields of energy storage and conversion applications, such as batteries, supercapacitors, electrocatalysis and photocatalysis. Finally, on the basis of their current development, we put forward the existing challenges and some personal perspectives.

     

Corrosion formation and phase transformation of nickel-iron hydroxide nanosheets array for efficient water oxidation

Designing earth-abundant electrocatalysts with high performance towards water oxidation is highly decisive for the sustainable energy technologies. This study develops a facile natural corrosion approach to fabricate nickel-iron hydroxides for water oxidation. The resulted electrode demonstrates an outstanding activity and stability with an overpotential of 275 mV to deliver 10 mA·cm⁻². Experimental and theoretical results suggest the corrosion-induced formation of hydroxides and their transformation to oxyhydroxides would account for this excellent performance. This work not only provides an interesting corrosion approach for the fabrication of excellent water oxidation electrode, but also bridges traditional corrosion engineering and novel materials fabrication, which would offer some insights in the innovative principles for nanomaterials and energy technologies.

     

Colloidal lead-free Cs2AgBiBr6 double perovskite nanocrystals: Synthesis,uniform thin-film fabrication,and application in solution-processed solar cells

Recently developed lead-free double perovskite nanocrystals(NCs)have been proposed for the possible application in solutionprocessed optoelectronic devices.However,the optoelectronic applications of double perovskite NCs have been hampered due to the structural and chemical instability in the presence of polar molecules.Here,we report a facile strategy for the synthesis and purification of Cs₂AgBiBr₆double perovskite NCs that remained stable even after washing with polar solvent.This is realized with our efficient colloidal route to synthesize Cs₂AgBiBr₆NCs that involve stable and strongly coordinated precursor such as silvertrioctyl phosphine complex together with bismuth neodecanoate,which leads to a significantly improved chemical and colloidal stability.Using layer-by-layer solid-state ligand exchange technique,a compact and crack-free thin film of Cs₂AgBiBr₆NCs were fabricated.Finally,perovskite solar cells consisting of Cs₂AgBiBr₆as an absorber layer were fabricated and tested.     

Two-dimensional oxide derived from high-temperature liquid metals via bubble templating

Two-dimensional (2D) oxide can be continuously produced by bubbling oxygen into liquid metals and the harvesting of these oxide relies on the proper choice of dispersion solvents. The mass-production of ligand-free 2D materials from high melting-point metals will not be possible if the limited stability of the traditional dispersion solvents is not circumvented. Herein, liquid tin was used for the first time in the bubbling protocol and 2D tin oxide was obtained in molten salts. The nanosheets were studied with combined microscopic and spectroscopic techniques, and high-density grain boundaries was identified between the sub-5-nm nano-crystallites in the nanosheets. It gives rise to the high performance in electrocatalytic CO₂ reduction reaction. Density-functional-theory based calculation was applied to achieve a deeper understanding of the relationship between the activity, selectivity, and the grain-boundary features. The molten-salt based protocol could be explored for the synthesis of a library of functional 2D oxides.

     

High power and stable P-doped yolk-shell structured Si@C anode simultaneously enhancing conductivity and Li+ diffusion kinetics

Silicon is a low price and high capacity ancxje material for lithium-ion batteries.The yolk-shell structure can effectively accommodate Si expansion to improve stability.However,the limited rate performance of Si anodes can't meet people's growing demand for high power density.Herein,the phosphorus-doped yolk-shell Si@C materials(P-doped Si@C)were prepared through carbon coating on P-doped Si/SiO_xmatrix to obtain high power and stable devices.Therefore,the as-prepared P-doped Si@C electrodes delivered a rapid increase in Coulombic efficiency from 74.4%to 99.6%after only 6 cycles,high capacity retention of-95%over 800 cycles at 4 A·g^-1,and great rate capability(510 mAh·g^-1at 35 A·g^-1).As a result,P-doped Si@C anodes paired with commercial activated carbon and LiFePO₄cathode to assemble lithium-ion capacitor(high power density of?61,080 W·kg^-1at 20 A·g^-1)and lithium-ion full cell(good rate performance with 68.3 mAh·g^-1at 5 C),respectively.This work can provide an effective way tofurther improve power density and stability for energy storage devices.     

Pulsed laser reshaping and fragmentation of upconversion nanoparticles — from hexagonal prisms to 1D nanorods through “Medusa”-like structures

One dimensional (1D) nanostructures attract considerable attention, enabling a broad application owing to their unique properties. However, the precise mechanism of 1D morphology attainment remains a matter of debate. In this study, ultrafast picosecond (ps) laser-induced treatment on upconversion nanoparticles (UCNPs) is offered as a tool for 1D-nanostructures formation. Fragmentation, reshaping through recrystallization process and bioadaptation of initially hydrophobic (β-Na_1.5Y_1.5F₆: Yb³⁺, Tm³⁺/β-Na_1.5Y_1.5F₆) core/shell nanoparticles by means of one-step laser treatment in water are demonstrated. “True” 1D nanostructures through “Medusa”-like structures can be obtained, maintaining anti-Stokes luminescence functionalities. A matter of the one-dimensional UCNPs based on direction of energy migration processes is debated. The proposed laser treatment approach is suitable for fast UCNP surface modification and nano-to-nano transformation, that open unique opportunities to expand UCNP applications in industry and biomedicine.

     

Recent advances in anode materials for potassium-ion batteries: A review

Potassium-ion batteries (PIBs) are appealing alternatives to conventional lithium-ion batteries (LIBs) because of their wide potential window, fast ionic conductivity in the electrolyte, and reduced cost. However, PIBs suffer from sluggish K⁺ reaction kinetics in electrode materials, large volume expansion of electroactive materials, and the unstable solid electrolyte interphase. Various strategies, especially in terms of electrode design, have been proposed to address these issues. In this review, the recent progress on advanced anode materials of PIBs is systematically discussed, ranging from the design principles, and nanoscale fabrication and engineering to the structure-performance relationship. Finally, the remaining limitations, potential solutions, and possible research directions for the development of PIBs towards practical applications are presented. This review will provide new insights into the lab development and real-world applications of PIBs.

     

Unprecedently low thermal conductivity of unique tellurium nanoribbons

Tellurene, probably one of the most promising two-dimensional (2D) system in the thermoelectric materials, displays ultra-low thermal conductivity. However, a linear thickness-dependent thermal conductivity of unique tellurium nanoribbons in this study reveals that unprecedently low thermal conductivity can be achieved via well-defined nanostructures of low-dimensional tellurium instead of pursuing dimension-reduced 2D tellurene. For thinnest tellurium nanoribbon with thickness of 144 nm, the thermal conductivity is only ∼1.88 ± 0.22 W·m⁻¹·K⁻¹ at room temperature. It’s a dramatic decrease (45%), compared with the well-annealed high-purity bulk tellurium. To be more specific, an expected thermal conductivity of tellurium nanoribbons is even lower than that of 2D tellurene, as a result of strong phonon-surface scattering. We have faith in low-dimensional tellurium in which the thermoelectric performance could realize further breakthrough.

     

Polymersome formation by solvent annealing-induced structural reengineering under 3D soft confinement

A solvent annealing-induced structural reengineering approach is exploited to fabricate polymersomes from block copolymers that are hard to form vesicles through the traditional solution self-assembly route. More specifically, polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) particles with sphere-within-sphere structure (SS particles) are prepared by three-dimensional (3D) soft-confined assembly through emulsion-solvent evaporation, followed by 3D soft-confined solvent annealing upon the SS particles in aqueous dispersions for structural engineering. A water-miscible solvent (e.g., THF) is employed for annealing, which results in dramatic transitions of the assemblies, e.g., from SS particles to polymersomes. This approach works for PS-b-P4VP in a wide range of block ratios. Moreover, this method enables effective encapsulation/loading of cargoes such as fluorescent dyes and metal nanoparticles, which offers a new route to prepare polymersomes that could be applied for cargo release, diagnostic imaging, and nanoreactor, etc.

     

Spontaneous migration induced Co nanokarstcave encapsulated in N-doped carbon hybrids for efficient oxygen electrocatalyst

Despite the extensive application of porous nanostructures as oxygen electrocatalysts, it is challenging to synthesize single-metal state materials with porous structures, especially the ultrasmall ones due to the uniform diffusion of the same metal. Herein, we pioneer demonstrate a new size effect-based controllable synthesis strategy for the homogeneous Co nanokarstcaves assisted by Co-CN hybrids (CCHs). The preferential migration of cobalt atoms on the surface of small size zeolitic imidazolate framework (ZIF) with high surface energy during pyrolysis is the key factor for the formation of nanokarstcave structure. Furthermore, graphene can act as a diffusion barrier to prevent the agglomeration of nanoparticles in the synthesis process, which also plays an important role in the formation of porous nanostructures. In alkali media, CCHs achieve overpotential of 287 mV (@10 mA·cm⁻²) for oxygen evolution reaction (OER) and a half wave potential of 0.86 V (vs. RHE) for oxygen reduction reaction (ORR).

     

Single copper sites dispersed on hierarchically porous carbon for improving oxygen reduction reaction towards zinc-air battery

The demand for high-performance non-precious-metal electrocatalysts to replace the noble metal-based catalysts for oxygen reduction reaction(ORR)is intensively increasing.Herein,single-atomic copper sites supported on N-doped three-dimensional hierarchically porous carbon catalyst(Cu₁/NC)was prepared by coordination pyrolysis strategy.Remarkably,the Cu₁/NC-900 catalyst not only exhibits excellent ORR performance with a half-wave potential of 0.894 V(vs.RHE)in alkaline media,outperforming those of commercial Pt/C(0.851 V)and Cu nanoparticles anchored on N-doped porous carbon(CuNPs/NC-900),but also demonstrates high stability and methanol tolerance.Moreover,the Cu₁/NC-900 based Zn-air battery exhibits higher power density,rechargeability and cyclic stability than the one based on Pt/C.Both experimental and theoretical investigations demonstrated that the excellent performance of the as-obtained Cu₁/NC-900 could be attributed to the synergistic effect between copper coordinated by three N atoms active sites and the neighbouring carbon defect,resulting in elevated Cu d-band centers of Cu atoms and facilitating intermediate desorption for ORR process.This study may lead towards the development of highly efficient non-noble metal catalysts for applications in electrochemical energy conversion.     

Chemically exfoliated WS2 nanosheets efficiently inhibit amyloid β-peptide aggregation and can be used for photothermal treatment of Alzheimer’s disease

Polymerization of amyloid-β peptide (Aβ) into amyloid fibrils is a critical step in the pathogenesis of Alzheimer’s disease (AD). Inhibition of Aβ aggregation and destabilization of preformed Aβ fibrils have promising effects against AD and have been used in clinic trials. Herein, we demonstrate, for the first time, the application of WS₂ nanosheets, to not only effectively inhibit Aβ aggregation, but also dissociate preformed Aβ aggregates upon near infrared (NIR) irradiation. Additionally, the biocompatible WS₂ nanosheets possess the ability to cross the blood-brain barrier (BBB) to overcome the limitations of most previously reported Aβ inhibitors. Through van der Waals and electrostatic interactions between Aβ40 and WS₂, Aβ40 monomers can be selectively adsorbed on the surface of the nanosheet to inhibit the Aβ40 aggregation process. Intriguingly, the unique high NIR absorption property of WS₂ enables amyloid aggregates to be dissolved upon NIR irradiation. These results will promote biological applications of WS₂ and provide new insight into the design of multifunctional nanomaterials for AD treatment.

     

Recent progress about 2D metal dichalcogenides: Synthesis and application in photodetectors

In recent years, two-dimensional (2D) layered metal dichalcogenides (MDCs) have received enormous attention on account of their excellent optoelectronic properties. Especially, various MDCs can be constructed into vertical/lateral heterostructures with many novel optical and electrical properties, exhibiting great potential for the application in photodetectors. Therefore, the batch production of 2D MDCs and their heterostructures is crucial for the practical application. Recently, the vapour phase methods have been proved to be dependable for growing large-scale MDCs and related heterostructures with high quality. In this paper, we summarize the latest progress about the synthesis of 2D MDCs and their heterostructures by vapour phase methods. Particular focus is paid to the control of influence factors during the vapour phase growth process. Furthermore, the application of MDCs and their heterostructures in photodetectors with outstanding performance is also outlined. Finally, the challenges and prospects for the future application are presented.

     

Atomic-resolution characterization on the structure of strontium doped barium titanate nanoparticles

Ferroelectric barium titanate nanoparticles (BTO NPs) may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors. While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade, the majority of the investigation was carried out in thin-film materials; therefore, the doping effect on nanoparticles remains unclear. Especially, doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled. In this work, we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), integrated differential phase contrast (iDPC)-STEM, and energy dispersive X-ray spectroscopy (EDX) mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles. Powder X-ray diffraction (PXRD) results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase, but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles. Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.

     

Synthesis of magnetic two-dimensional materials by chemical vapor deposition

The development of magnetic two-dimensional (2D) materials in its infancy has generated an enormous amount of attention as it offers an ideal platform for the exploration of magnetic properties down to the 2D limit, paving the way for spintronic devices. Due to the nonnegligible advantages including time efficiency and simplified process, the facile bottom-up chemical vapor deposition (CVD) is regarded as a robust method to fabricate ultrathin magnetic nanosheets. Recently, some ultrathin magnets possessing fascinating properties have been successfully synthesized via CVD. Here, the recent researches toward magnetic 2D materials grown by CVD are systematically summarized with special emphasis on the fabrication methods. Then, heteroatoms doping and phase transition induced in CVD growth to bring or tune the magnetic properties in 2D materials are discussed. Characterizations and applications of these magnetic materials are also discussed and reviewed. Finally, some perspectives in need of urgent attention regarding the development of CVD-grown magnetic 2D materials are proposed.

     

Graphene: A promising candidate for charge regulation in high-performance lithium-ion batteries

The development of rechargeable lithium-ion batteries (LIBs) is being driven by the ever-increasing demand for high energy density and excellent rate performance. Charge transfer kinetics and polarization theory, considered as basic principles for charge regulation in the LIBs, indicate that the rapid transfer of both electrons and ions is vital to the electrochemical reaction process. Graphene, a promising candidate for charge regulation in high-performance LIBs, has received extensive investigations due to its excellent carrier mobility, large specific surface area and structure tunability, etc. Recent progresses on the structural design and interfacial modification of graphene to regulate the charge transport in LIBs have been summarized. Besides, the structure-performance relationships between the structure of the graphene and its dedicated applications for LIBs have also been clarified in detail. Taking graphene as a typical example to explore the mechanism of charge regulation will outline ways to further understand and improve carbon-based nanomaterials towards the next generation of electrochemical energy storage devices.

     

Revealing the effect of anion-tuning in bimetallic chalcogenides on electrocatalytic overall water splitting

Enhancing electrocatalytic water splitting performance by modulating the intrinsic electronic structure is of great importance. Here, porous bimetallic oxide and chalcogenide nanosheets grown on carbon paper denoted as NiCo₂X₄/CP (X = O, S, and Se) are prepared to demonstrate how the anion components affect the electronic structures and thereby disclose the correlation between their intermediates interaction and catalytic activities. The experimental characterization and theoretical calculation demonstrate that Se and S substitution can promote the ratio of Co³⁺/Co²⁺ and thereby modulate the electronic structure accompanied with the upshift of d band centers, which not only enhance the inner conductivity but also regulate the interaction between the catalyst surface and intermediates, especially for the adsorption of absorbed H and hydroperoxy intermediates towards respective hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As a result, a full alkaline electrolyzer using NiCo₂Se₄/CP and NiCo₂S₄/CP as cathode and anode delivers a low voltage of 1.51 V at 10 mA·cm⁻², which is comparable even superior to most transition metal-based electrolyzers.