Nanovilli electrode boosts hydrogen evolution: A surface with superaerophobicity and superhydrophilicity

Although tremendous efforts have been paid on electrocatalysts toward efficient electrochemical hydrogen generation,breakthrough is still highly needed in the design and synthesis of wonderful non-precious-metal electrocatalyst.Herein,a nanovilli Ni2P electrode,which with superaerophobic and superhydropholic can significantly facilitate the mass and electron transfer was constructed via a facial morphology control strategy.Meanwhile,the substitution of sluggish oxygen evolution with urea oxidation,lowering the two-electrode cell voltage to only 1.48 volts to achieve a current density of 10 mA·cm^-2.Thus,the as-constructed electrode achieves the operation of hydrogen generation by an AA battery.This work sheds new light on the exploration of other high-efficient electrocatalysts for hydrogen generation by using intermittent clean energy.     

Layer-by-layer assembled dual-ligand conductive MOF nano-films with modulated chemiresistive sensitivity and selectivity

In this paper,a dual-ligand design strategy is demonstrated to modulate the performance of the electronically conductive metalorganic frameworks(EC-MOFs)thin film with a spray layer-by-layer assembly method.The thin film not only can be precisely prepared in nanometer scale(20-70 nm),but also shows the pin-hole-free smooth surface.The high quality nano-film of 2,3,6,7,10,11-hexaiminotriphenylene(HITP)doped Cu-HHTP enables the precise modulation of the chemiresistive sensitivity and selectivity.Selectivity improvement over 220%were realized for benzene vs.NH3>as well as enhanced response and recovery properties.In addition,the selectivity of the EC-MOF thin film sensors toward other gases(e.g.triethylamine,methane,ethylbenzene,hydrogen,butanone,and acetone)vs.NH3 at room temperature is also discussed.     

Highly effective H2/D2 separation in a stable Cu-based metal-organic framework

A three-dimensional copper metal-organic framework with the rare chabazite(CHA)topology namely FJI-Y11 has been constructed with flexibly carboxylic ligand 5,5'-[(1,4-phenylenebis(methylene))bis(oxy)]diisophthalic acid(H₄L).FJI-Y11 exhibits high water stability with the pH range from 2 to 12 at temperature as high as 373 K.Importantly,FJI-Y11 also shows high efficiency of hydrogen isotope separation using dynamic column breakthrough experiments under atmospheric pressure at 77 K.Attributed to its excellent structural stability,FJI-Y11 possesses good regenerated performance and maintains high separation efficiency after three cycles of breakthrough experiments.     

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.

     

Recent advances in engineered nanomaterials for acute kidney injury theranostics

Acute kidney injury(AKI),has become the focus of increasing attention due to its high risk of death.The early diagnosis and treatment of AKI significantly reduce the risk of renal tissue damage and kidney dysfunction.However,the efficient early diagnosis and treatment approach for AKI remains a challenge.AKI screening via precise nanomaterial theranostics is a new alternative approach.This study summarizes the recent advances in functional nanomaterials in the early detection and treatment of AKI.The challenges and problems in the use of nanomaterials for AKI in clinical applications are also discussed.It is anticipated that highlighting these new advances will lay the foundation for further translational research on the promising application of nanomaterials for AKI.     

Integrated hetero-nanoelectrodes for plasmon-enhanced electrocatalysis of hydrogen evolution

Hetero-nanostructures of plasmonic metals and semiconductors have attracted increasing attention in the field of photocatalysis.However,most of the hetero-nanostructured catalysts are randomly arranged and therefore require comprehensive structural design for optimizing their properties.Herein,we report the robust construction of hierarchical hetero-nanostructures where gold(Au)nanorods and molybdenum disulfide(Mo S₂)quantum sheets(QSs)are integrated in highly ordered arrays.Such construction is achieved through porous anodic alumina(PAA)template-assisted electrodeposition.The as-fabricated hetero-nanostructures demonstrate exciting electrocatalysis towards hydrogen evolution reaction(HER).Both plasmon-induced hot-electron injection and plasmonic scattering/reabsorption mechanisms are determinative to the enhanced electrocatalytic performances.Notably,broadband photoresponses of HER activity in the visible range are observed,indicating their superiority compared with random systems.Such integrated hetero-nanoelectrodes could provide a powerful platform for conversion and utilization of solar energy,meanwhile would greatly prompt the production and exploration of ordered nanoelectrodes.     

Ambipolar two-dimensional bismuth nanostructures in junction with bismuth oxychloride

Despite the unique properties of bismuth(Bi),there is a lack of two-dimensional(2D)heterostructures between Bi and other functional 2D materials.Here,a coherent strategy is reported to simultaneously synthesize rhombohedral phase Bi nanoflakes and bismuth oxychloride(BiOCI)nanosheets.The delicate balance between several reactions is mediated mainly for the reduction and chlorination in the chemical vapor transport(CVT)process.The Bi-BiOCI lateral heterostructures have been constructed via the coalescence of the two different 2D nanostructures.The characteristics of ambipolar conducting Bi and insulator-like BiOCI are elaborated by scanning microwave impedance microscopy(sMIM).This work demonstrates a way to construct a 2D Bi nanostructure in junction with its oxyhalide.     

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.     

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.     

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.     

How defects influence the photoluminescence of TMDCs

Two-dimensional(2D)transition metal dichalcogenide(TMDC)monolayers,a class of ultrathin materials with a direct bandgap and high exciton binding energies,provide an ideal platform to study the photoluminescence(PL)of light-emitting devices.Atomically thin TMDCs usually contain various defects,which enrich the lattice structure and give rise to many intriguing properties.As the influences of defects can be either detrimental or beneficial,a comprehensive understanding of the internal mechanisms underlying defect behaviour is required for PL tailoring.Herein,recent advances in the defect influences on PL emission are summarized and discussed.Fundamental mechanisms are the focus of this review,such as radiative/nonradiative recombination kinetics and band structure modification.Both challenges and opportunities are present in the field of defect manipulation,and the exploration of mechanisms is expected tofacilitate the applications of 2D TMDCs in the future.     

Highly efficient multi-metal catalysts for carbon dioxide reduction prepared from atomically sequenced metal organic frameworks

The precise control on the combination of multiple metal atoms in the structure of metal-organic frameworks(MOFs)endowed by reticular chemistry,allows the obtaining of materials with compositions that are programmed for achieving enhanced reactivity.The present work illustrates how through the transformation of MOFs with desired arrangements of metal cations,multi-metal spinel oxides with precise compositions can be obtained,and used as catalyst precursor for the reverse water-gas shift reaction.The differences in the spinel initial composition and structure,determined by neutron powder diffraction,influence the overall catalytic activity with changes in the process of in s itu formation of active,metal-oxide supported metal nanoparticles,which have been monitored and characterized with in situ X-ray diffraction and photoelectron spectroscopy studies.     

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.

     

Discovery of Zr-based metal-organic polygon: Unveiling new design opportunities in reticular chemistry

Metal-based secondary building unit and the shape of organic ligands are the two crucial factors for determining the final topology of metal-organic materials.A careful choice of organic and inorganic structural building units occasionally produces unexpected structures,facilitating deeper fundamental understanding of coordination-driven self-assembly behind metal-organic materials.Here,we have synthesized a triangular metal-organic polygon(MOT-1),assembled from bulky tetramethyl terephthalate and Zr-based secondary building unit.Surprisingly,the Zr-based secondary building unit serves as an unusual ditopic Zr-connector,toform metal-organic polygon MOT-1,proven to be a good candidate for water adsorption with recyclability.This study highlights the interplay of the geometrically frustrated ligand and secondary building unit in controlling the connectivity of metal-organic polygon.Such a strategy can be further used to unveil a new class of metal-organic materials.     

Synthesis of graphene quantum dots for their supramolecular polymorphic architectures

How to regulate the supramolecular structures in the assembly of graphene quantum dots(GQDs)is still a great challenge to be overcome.Herein,the GQDs of 1-3 layers with high quality are synthesized from the new precursor m-trihydroxybenzene in a green method.More importantly,a strategy for designing the supramolecular structures of GQDs is demonstrated,and the novel supramolecular morphologies of GQDs have been constructed for the first time.Moreover,the supramolecular morphologies of GQDs can be well controlled by regulating the preparation conditions,and the formation mechanism of the branch-like supramolecular structure has been explained by the the diffusion-limited aggregation(DLA)model.This work not only develops a new precoursor to synthesize GQDs,but also opens up an effective route toform the polymorphic supermolecules,thus greatly facilitating their potential applications.     

Opto-valleytronics in the 2D van der Waals heterostructure

The development of information processing devices with minimum carbon emission is crucial in this information age. One of the approaches to tackle this challenge is by using valleys (local extremum points in the momentum space) to encode the information instead of charges. The valley information in some material such as monolayer transition metal dichalcogenide (TMD) can be controlled by using circularly polarized light. This opens a new field called opto-valleytronics. In this article, we first review the valley physics in monolayer TMD and two-dimensional (2D) heterostructure composed of monolayer TMD and other materials. Such 2D heterostructure has been shown to exhibit interesting phenomena such as interlayer exciton, magnetic proximity effect, and spin-orbit proximity effect, which is beneficial for opto-valleytronics application. We then review some of the optical valley control methods that have been used in the monolayer TMD and the 2D heterostructure. Finally, a summary and outlook of the 2D heterostructure opto-valleytronics are given.

     

Robust enhanced hydrogen production at acidic conditions over molybdenum oxides-stabilized ultrafine palladium electrocatalysts

Electrochemical water splitting is quite seductive for eco-friendly hydrogen fuel energy production,however,the attainment of highly efficient,durable,and cheap catalysts for the hydrogen evolution reaction(HER)remains challenging.In this study,molybdenum oxides stabilized palladium nanoparticle catalysts(MoO_x-Pd)are in situ prepared on commercial carbon cloth(CC)by the facile two-step method of dip-coating and electrochemical reduction.As a self-supported Pd-based catalyst electrode,the MoO_x-Pd/CC presents a competitive Tafel slope of 45.75 mV·dec^-1,an ultralow overpotential of 25 mV,and extremely long cycling durability(one week)in 0.5M H₂S0₄electrolyte,superior to unmodified Pd catalysts and comparable to commercial Pt mesh electrode.On the one hand,the introduction of MoO_xcan inhibit the growth of Pd particles to obtain ultrafine Pd nanoparticles,thus exposing more available active sites.On the other hand,density functional theory(DFT)calculation revealed that MoO_xon the surface of Pd metal can regulate the electronic structure of Pd metal and enhance its intrinsic catalytic activity of HER.This work suggests that transitional metal nanoparticles stabilized by molybdenum oxides are hopeful approaches for obtaining fruitful hydrogen-producing electrocatalysts.     

Effects of connecting sequences of building blocks on reticular synthesis of covalent organic frameworks

The principle of reticular chemistry has been widely used to guide the design of crystalline porous materials such as metal organic frameworks(MOFs)and covalent organic frameworks(COFs).While in the early strategies only the symmetries of the building blocks were considered for reticular synthesis of COFs,recently a few researches on COFs with hierarchical porosities indicate that connecting sequence of building blocks also plays a crucial role in determining crystalline structures of COFs.However,this important phenomenon has not been systematically investigated yet.In this article,a model system has been established to demonstrate how different connecting sequences of two C_2v-symmetric building blocks lead to the formation of four two-dimensional(2D)COFs with distinct framework structures.To verify this concept,target synthesis was conducted to produce three COFs,whose structures were confirmed by powder X-ray diffraction and pore size distribution analysis.     

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.

     

Breakdown of Raman selection rules by Fröhlich interaction in few-layer WS2

The polarization selection rule of Raman scattering is crucial in symmetry analysis of elementary excitations in semiconductors and correlated electron systems. Here we reported the observation of breakdown of Raman selection rules in few-layer WS₂ by using resonant Raman spectroscopy. When the excitation energy is close to the dark A exciton state, we observed some infrared active modes and backscattering forbidden modes. Importantly, we found that all observed phonon modes follow the same paralleled-polarization behavior. According to the electron-phonon coupling near the band edge in WS₂, we proposed a theoretical model based on the intraband Fröhlich interaction. In this case, the polarization response of the scattering signal is no longer determined by the original Raman tensor of scattered phonons. Instead, it is determined by a new isotropic Raman tensor that generated from this intraband Fröhlich interaction between dark A exciton and phonons. We found that this theoretical model is in excellent agreement with the observed results. The breakdown of Raman selection rules can violate the conventional limitations of the optical response and provide an effective method to control the polarization of Raman scattering signals in two-dimensional materials.