Highly active sites of NiVB nanoparticles dispersed onto graphene nanosheets towards efficient and pH-universal overall water splitting

Production of hydrogen(H2) and oxygen(O2) through electrocatalytic water splitting is one of the sustainable,green and pivotal ways to accomplish the ever-increasing demands for renewable energy sources,but remains a big challenge because of the uphill reaction during overall water splitting.Herein,we develop high-performance non-noble metal electrocatalysts for pH-universal water splitting,based on nickel/vanadium boride(NiVB) nanoparticles/reduced graphene oxide(rGO) hybrid(NiVB/rGO)through a facile chemical reduction approach under ambient condition.By virtue of more exposure to surface active sites,superior electron transfer capability and strong electronic coupling,the asprepared NiVB/rGO heterostructure needs pretty low overpotentials of 267 and 151 mV to deliver a current density of 10 mA cm^(-2) for oxygen evolution reaction(OER) and hydrogen evolution reaction(HER)respectively,with the corresponding Tafel slope of 44 and 88 mV dec^(-1) in 1.0 M KOH.Moreover,the NiVB/rGO electrocatalysts display a promising performance in a wide-pH conditions that require low overpotential of 310,353 and 489 mV to drive a current density of 10 mA cm^(-2) for OER under 0.5 M KOH,0.05 M H2SO4 and 1.0 M phosphate buffer solution(PBS) respectively,confirming the excellent electrocata lytic performance among state-of-the-art Ni-based electrocatalysts for overall water splitting.Therefore,the interfacial tuning based on incorporation of active heterostructure may pave a new route to develop bifunctional,cost-effective and efficient electrocatalyst systems for water splitting and H2 production.

One-dimensional molecular co-crystal alloys capable of full-color emission for low-loss optical waveguide and optical logic gate

The luminescence color of molecule-based photoactive materials is the key to the applications in lighting and optical communication.Realizing continuous regulation of emission color in molecular systems is highly desirable but still remains a challenge due to the individual emission band of purely organic molecules.Herein,a novel alloy strategy based on molecular co-crystals is reported.By adjusting the molar ratio of pyrene(Py)and fluorathene(Flu),three types of molecular co-crystal alloys(MCAs)assemblies are prepared involving Py-Flu-OFN-x%,Py-Flu-TFP-x%,Py-Flu-TCNB-x%.Multiple energy level structure and Förster resonance energy transfer(FRET)process endow materials with tunable full-spectra emission color in visible region.Impressively,these MCAs and co-crystals can be successfully applied to low optical loss waveguide and optical logic gate by virtue of all-color luminescence from blue across green to red,together with smooth surface of onedimensional microrods,which show promising applications as continuous light emitters for advance photonics applications.

Gold complex showing chiral persistent luminescence

Long-persistent luminescence(LPL)has received significant focus due to its exceptional applications in high-contrast molecular imaging,photodynamic therapy,data encryption and information storage,and among many others^([1]).Ultralong room-temperature phosphorescence(RTP),as a form of LPL.

Dynamic multi-color long-afterglow and cold-warm white light through phosphorescence resonance energy transfer in host-guest metal-organic frameworks

Dynamic tuning of single-color and multi-color(including white-light) luminescence has attracted much attention for applications in various fields;however, effective systems are still scarcity to date. Herein, we report the construction of host-guest metal-organic frameworks(MOFs) serves as an effective strategy to achieve the excitation-and time-dependent long afterglow and white light emitting, simultaneously. The guest-induced structural distortion modulates the single-triplet state intersystem crossing, promotes ligand-to-ligand charge transfer(LLCT) in layer-column MOFs, and further boosts multiple exciton generation of triplet states for multi-color ultralong phosphorescence, as indicated by both experiment and density functional theory(DFT) calculation. By further doping of dyes into MOFs, white-light emitting with tunable color temperature can be facilely obtained, which has been further fabricated into white-light light-emitting diode(LED) with color rendering index of 88.4,higher than that of most as-reported pure inorganics and inorganic-organic hybrid systems. Therefore, this work not only describes a host-guest energy transfer route for dynamic tailoring wide range of color-tunable long-afterglow, but also explores the application prospect of new white-light materials with high color rendering and low blue light for promising display and lighting applications.

Colorful ultralong room-temperature phosphorescence in dual-ligand metal-organic framework

Long afterglow organic-inorganic hybrid materials have attracted much attention in recent years and are widely used in information security, biological imaging and many other fields. Since up-conversion long-persistence materials are promising for bio-optical imaging due to their high penetration depth and elimination of autofluorescence background, it is highly desirable to combine down-conversion and up-conversion pathways to obtain smart materials with excitation-dependent tunable room-temperature phosphorescence properties. In this work, a metal-organic framework(Zn-DCPS-BIMB), consisting of divalent zinc ions, o-bis(imidazol-1-ylmethyl)benzene and 4,4-dicarboxydiphenylsulfone, is designed to stabilize triplet excitons, coordinate the emission of different ligands, and endow materials with tunable emission color and up-conversion properties via heavy atoms effects promoting single-triplet orbital coupling and intersystem crossing.

Brightening room-temperature phosphorescence in solution

The strategies including noncovalent macrocycle-confined supramolecular assembly and construction of rigid hydrogen-bond network have been verified as effective routes to brighten aqueous-phase room temperature phosphorescence.Molecule-based room-temperature phosphorescence(RTP)has attracted widespread attention in the fields of chemical sensors,optical anti-counterfeiting,information encoding and so on,due to unique characteristics of long excited-state lifetimes,large Stokes shifts and high signal-tonoise ratios[1,2].Currently,to obtain RTP with considerable efficiency and long lifetime,two brilliant strategies have been developed:one is the introduction of heavy atoms,which facilitates the spin-orbital coupling and intersystem crossing(ISC)from singlet to triplet states。

聚集诱导发光

聚集诱导发光(AIE)是唐本忠院士于2001年提出的一个科学概念,是指一类在溶液中不发光或者发光微弱的分子聚集后发光显著增强的现象。高效固态发光的AIE材料有望从根本上解决有机发光材料面临的聚集导致发光猝灭难题,具有重大的实际应用价值。从分子内旋转受限到分子内运动受限,从聚集诱导发光到聚集体科学,AIE领域已经取得了许多原创性的成果。在本综述中,我们从AIE材料的分类、机理、概念衍生、性能、应用和挑战等方面讨论了AIE领域最近取得的显著进展。希望本综述能激发更多关于分子聚集体的研究,并推动材料、化学和生物医学等学科的进一步交叉融合和更大发展。

Layer-by-layer assembly of long-afterglow self-supporting thin films with dual-stimuli-responsive phosphorescence and antiforgery applications

The assembly of thin films （TFs） having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors, anti-counterfeiting materials, and information-encryption systems. However, such films are limited compared with their powder and solution counterparts. In this study, by exploiting the self-organization of phosphors in the two-dimensional （2D） galleries between clay nanosheets, we developed a method for the ordered assembly of long-afterglow TFs by utilizing a hydrogen-bonding layer-by-layer （LBL） process. Compared with the pristine powder, the TFs exhibit high polarization and up-conversion room-temperature phosphorescence （RTP）, as well as enhanced quantum yields and luminescence lifetimes, allowing them to be used as room-temperature phosphorescent sensors for humidity and oxygen. Moreover, modified clay-based hybrids with multicolor RTP can serve as anti-counterfeiting marks and triple-mode 2D barcode displays. We anticipate that the LBL assembly process can be extended to the fabrication of other inorganic--organic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforgery applications.

Recent advances in photofunctional polymorphs of molecular materials

Recently,molecule-based luminescent materials have been drawing extensive attention due to their desirable properties and promising applications in the fields of sensors,lighting display and cell imaging.Crystalline polymorph is an intriguing phenomenon that the presence of multiple packing and aggregate architectures of the same molecular system.The studies on polymorphs for molecule-based fluorophores provide the opportunities to adjust the mode of molecular packing and photophysical properties,which will help to illustrate the structure-property relationship.In this review,we focus on the recent progress in various feasible methods of molecule-based crystalline polymorphism growth and their adjustable photofunctional properties,which will open up possibilities of variant optical applications.Firstly,several effective ways to prepare and screen polymorphs are sorted out.And then,we discuss the discrepant properties and multifunctional applications(such as sensors,laser and OFET).Finally,the development trends and future prospects of these polymorphs are also briefly introduced.

Multi-dimensional, light-controlled switch of fluorescence resonance energy transfer based on orderly assembly of 0D dye@micro-micelles and 2D ultrathin-layered nanosheets

Fluorescence resonance energy transfer （FRET） systems have broad applications in visual detection, intelligent materials, and biological imaging, all of which favor the transmission of light through multiple dimensions and in diverse directions. Herein, we have demonstrated multi-dimensional （0D and 2D） FRET within a multi-layer ultrathin film （UTF） by employing a layer-by-layer （LBL） assembly technique. The anionic block copolymer micelle poly（tert-butyl acrylate- co-ethyl acrylate-co-methacrylic acid） （PTBEM） is chosen as a molecular carrier for the incorporation of bis（8-hydroxyquinolate） zinc （Znq2） and open-ring merocyanine （MC） （denoted as （Znq2/MC）@PTBEM）. Alternatively, electrostatic assembly is performed with cationic layered double hydroxide （LDH） nanosheets （denoted as [（Znq2/MC）@PTBEM/LDH]n）. This [（Znq2/MC）@PTBEM/ LDH]n system offers a multi-dimensional propagation medium and ensures that the FRET donor and acceptor are located within their F6rster radii in each direction. The system demonstrates a FRET process that can be switched via alternating ultraviolet/visible （UV/vis） irradiation, with tunable blue-green/red fluorescence, resulting in a FRET efficiency as high as 81.7%. It is expected that this assembly method, which uses 0D micelles on a 2D layered material, can be extended to other systems for further development of multi-dimensional FRET.

Intercalation assembly of kojic acid into Zn-Ti layered double hydroxide with antibacterial and whitening performances

A melanin synthesis inhibitor and bacteriostatic agent, kojic acid(KA) has been intercalated into Zn-Ti layered double hydroxide(LDH) by an anion-exchange reaction. The structure and the thermal stability of the samples were characterized by XRD, FT-IR, TG-DTA and SEM. The study of KA release from ZnTi-KALDH in phosphate buffered solution(pH 5) implies that ZnTi-KA-LDH is a better controlled release system than pure KA. Meanwhile, the mechanisms of slow release were assessed by using four commonly kinetic models. The antimicrobial activity of ZnTi-KA-LDH was tested against three kinds of bacteria. The inhibition of L-dopa oxidation was tested to verify its skin whitening effect. The studies suggest that the kojic acid intercalated LDHs has the potential application as a safely functional composite in cosmetic.

A reversible acid-base fluorescent switch based on molecular cocrystal of 4-[2-4-quinolinyl)vinyl]phenol and tetrafluoroterephthalic acid

Photoactive cocrystal materials have received growing research interest in construction of photofunctional systems owing to the crucial roles in modifying the photo-related properties of molecular solids, based on the non-bonding interactions between self-assembly units. Herein, we report tunable luminescence and acid-base stimuli-responsive properties of a cocrystal assembled by 4-[2-(4-quinolinyl)vinyl]phenol (qv) and tetrafluoroterephthalic acid (a). The luminescent properties (such as wavelength, quantum yield and fluorescence lifetime) of qv.a changed obviously relative to the pristine qv, due to the proton transfer and the alternation of molecular arrangement within two-component crystalline material. The photoemission intensity of qv.a underwent from weak to strong upon HCl gas fuming, and the corresponding wavelength changed from 517 nm to 597 nm, which can be reversibly transferred after exposed in NH3. Such luminescent switching behavior may provide an effective way to develop new types of photoactive stimuli-responsive materials and optical sensors.

White-light emission and tunable room temperature phosphorescence of dibenzothiophene

Molecular materials exhibiting room temperature phosphorescence(RTP) have received much attention during last few years. It has been known that different stacking fashions(e.g., formation of polymorph) and aggregation/crystal states could largely influence the RTP efficiency. However, whether the crystal morphology or shape could play a key role in modulation of the RTP has not been detected yet. In this work, we report that the dibenzothiophene(DBT) with the same molecular stacking fashion but different crystal morphologies can present alternated RTP performances. By modulation of the fluorescence and phosphorescence dual emission, a direct warm-white color light-emitting has also been successfully achieved. Moreover, the RTP emission can be further tuned through hybridization with β-cyclodextrin in different ratios, with the longest lifetime of 0.43 s.

New flame retardant epoxy resins based on cyclophosphazene-derived curing agents

To obtain high-efficiency flame retardancy of epoxy resins,a cyclophosphazene derivative tri-(ohenylenediamino)cyclotriphosphazene(3 ACP)was successfully synthesized and used as a curing agent for the thermosetting of an epoxy resin system.The flame retardant properties,thermal stability,and pyrolysis mechanism of the resultant thermosets were investigated in detail.The experiments indicated that the synthesized thermoset achieved a UL-94 V-0 rate under a vertical burning test as well as a limiting oxygen index(LOI)of 29.2%,which was able to reach V-0 even when a small amount of 3 ACP was incorporated.Scanning electronic microscopic observation demonstrated that the char residue of the thermosets was extremely expanded after the vertical flame test.Thermal analysis showed that the samples had a lower initial decomposition temperature when 3 ACP was introduced into the epoxy resin systems.This indicates that the carbonization ability of the thermosets was significantly improved at elevated temperatures.In addition,the incorporation of 3 ACP can effectively suppress the release of combustible gases during the pyrolysis process,and the decomposition of E-44/DDS-3 ACP curing systems also promotes the formation of polyphosphoramides charred layer in the condensed phase.The investigation on the chemical structures of both the gaseous and condensed phase pyrolysis process confirmed the flame-retardant mechanism of the 3 ACP-cured epoxy resins.Therefore,the nonflammable halogen-free epoxy resin developed in this study has potential applications in electric and electronic fields for environment protection and human health.

An Effective Asphalt UV Blocking Material Based on Host-Guest Schiff Base/Layered Double Hydroxides

The development of asphalt-based UV blocking materials is important to extend the alphalt lifespan in road construction. In this work, we put forward that the fabrication of host-guest system can be an effective way to obtain UV blocking materials. Firstly, a new anionic Schiff base, N,N＇bis（salicylidine）-4,4＇-diaminostilbene-2,2＇-disulfonic acid （SDSD）, has been synthesized, which was intercalated into Zn-Al-LDH by anion-exchange method. FT-IR and XRD illustrate the layered organic-inorganic composite, Zn-Al-SDSD-LDH, has been successfully synthesized with high crystallinity. Laser particle size analyzer, SEM and TEM show that particle size distributions of Zn-Al-SDSD-LDH is in the range 100--500 nm. UV-vis absorption spectra show that Zn-Al-SDSD-LDH has better UV absorption than the pristine Zn-Al-LDH and SDSD. Furthermore, the mixture of asphalt and 3 wt% Zn-Al-SDSD-LDH presents enhanced UV blocking property relative to the pristine asphalt after irradiating by UV spray accelerated weathering test. Therefore, this work not only develops a new type of host-guest Zn-Al-SDSD- LDH, but also confirms it can be an effective asphalt UV blocking material for practical application.

Promoting electrochemical conversion of CO2 to formate with rich oxygen vacancies in nanoporous tin oxides

Defect engineering,especially oxygen vacancies(O-vacancies) introduction into metal oxide materials has been proved to be an effective strategy to manipulate their surface electron exchange processes.However,quantitative investigation of O-vacancies on CO2 electroreduction still remains rather ambiguous.Herein,a series of nanoporous tin oxide(SnOx) materials have been prepared by thermal treatment at various temperatures and reaction conditions.The annealing temperature dependent Ovacancies property of the SnOx was revealed and attributed to the balance tunning of the desorption of oxygen species and the continous oxidation of SnOx.The as-prepared nanoporous SnOx with 300℃treatment was found to be highest O-vacant material and showed an impressive CO2 RR activity and selectivity towards the conversion of CO2 into formic acid(up to 88.6%),and superior HCOOH incomplete current density to other samples.The ideal performance of the O-vacancies rich SnOx-300 material can be ascribed to the high delocalized electron density inducing much enhanced adsorption of CO2 with O binding and benefiting the subsequent reduction with high selectively forming of formic acid.

Room-Temperature Phosphorescent Organic-Doped Inorganic Frameworks Showing Wide-Range and Multicolor LongPersistent Luminescence

Long-persistent luminescence based on purely inorganic and/or organic compounds has recently attracted much attention in a wide variety of fields including illumination,biological imaging,and information safety.However,simultaneously tuning the static and dynamic afterglow performance still presents a challenge.In this work,we put forward a new route of organic-doped inorganic framework to achieve wide-range and multicolor ultralong room-temperature phosphorescence(RTP).Through a facile hydrothermal method,phosphor(tetrafluoroterephthalic acid(TFTPA))into the CdCO_(3)(or Zn_(_(2))(OH)_(2)CO_(3))host matrix exhibits an excitation-dependent colorful RTP due to the formation of diverse molecular aggregations with multicentral luminescence.The RTP lifetime of the doped organic/inorganic hybrids is greatly enhanced(313 times)compared to the pristine TFTPA.The high RTP quantum yield(43.9%)and good stability guarantee their easy visualization in both ambient and extreme conditions(such as acidic/basic solutions and an oxygen environment).Further codoped inorganic ions(Mn_(2)+and Pb_(2)+)afford the hybrid materials with a novel time-resolved tunable afterglow emission,and the excitation-dependent RTP color is highly adjustable from dark blue to red,covering nearly the whole visible spectrum and outperforming the current stateof-the-art RTP materials.Therefore,this work not only describes a combined codoping and multicentral strategy to obtain statically and dynamically tunable long-persistent luminescence but also provides great opportunity for the use of organicinorganic hybrid materials in multilevel anticounterfeiting and multicolor display applications.

Fast formation of single-unit-cell-thick and defect-rich layered double hydroxide nanosheets with highly enhanced oxygen evolution reaction for water splitting

The development of high-efficiency electrocatalysts for oxygen evolution reactions （OERs） plays an important role in the water-splitting process. Herein, we report a facile way to obtain two-dimensional （2D） single-unit-cell-thick layered double hydroxide （LDH） nanosheets （NSs, - 1.3 nm） within only 5 min. These nanosheets presented significantly enhanced OER performance compared to bulk LDH systems fabricated using the conventional co-precipitation method. The current strategy further allowed control over the chemical compositions and electrochemical activities of the LDH NSs. For example, CoFe-LDH NSs presented the lowest overpotential of 0.28 V at 10 mA/cm2, and the NiFe-LDHs NSs showed Tafel slopes of 33.4 mV/decade and nearly 100% faradaic efficiency, thus outperforming state-of-the-art IrO2 water electrolysis catalysts. Moreover, positron annihilation lifetime spectroscopy and high-resolution transmission electron microscopy observations confirmed that rich defects and distorted lattices occurred within the 2D LDH NSs, which could supply abundant electrochemically active OER sites. Periodic calculations based on density functional theory （DFT） further showed that the CoFe- and NiFe-LDHs presented very low energy gaps and obvious spin-polarization behavior, which facilitated high electron mobility during the OER process. Therefore, this work presents a combined experimental and theoretical study on 2D single-unit-cell-thick LDH NSs with high OER activities, which have potential application in water splitting for renewable energy.

In situ localization of BiVO_(4) onto two-dimensional MXene promoting photoelectrochemical nitrogen reduction to ammonia

The existing industrial ammonia synthesis usually adopts the Haber-Bosch process,which requires harsh conditions of high temperature and high pressure,and consumes high energy.Under this circumstance,photoelectrochemical(PEC)catalysis is regarded as a promising method for N_(2) reduction reaction(NRR),but bears problems of low efficiency and yield.Thus,exploring active catalysts remains highly desirable.In this work,BiVO_(4)@MXene hybrids have been facilely synthesized by a hydrothermal route.The heterojunctions by the in situ growth of BiVO_(4) onto two-dimensional(2D)MXene greatly increase the NRR efficiency:under photoelectric conditions,the optimized NH_(3) yield is 27.25µg h^(-1) cm^(-2),and the Faraday efficiency achieves 17.54% at−0.8 V relative to the reversible hydrogen electrode(RHE),which are higher than most state-of-the-art NRR(photo)electrocatalysts.The mechanism speculation shows the enhanced light absorption range and the heterojunction formation largely promote the separation and the transfer efficiency of photogenerated carriers,thereby improving the PEC catalytic ability.Therefore,this work provides a hybrid route to combine the advantages of photo and electric catalysis for effective artificial nitrogen fixation.

Stimuli-responsive organic phosphorescence through energy transfer

Organic room-temperature phosphorescence(RTP)has attracted much academic and engineering interest in the fields of bioimaging,light-emitting devices,and anti-counterfeiting.It is documented that the triplet excitons for generating RTP in molecular systems are highly sensitive to external quenchers(such as oxygen and water).