Advances of Electrochemical and Electrochemiluminescent Sensors Based on Covalent Organic Frameworks

Covalent organic frameworks(COFs),a rapidly developing category of crystalline conjugated organic polymers,possess highly ordered structures,large specific surface areas,stable chemical properties,and tunable pore microenvironments.Since the first report of boroxine/boronate ester-linked COFs in 2005,COFs have rapidly gained popularity,showing important application prospects in various fields,such as sensing,catalysis,separation,and energy storage.Among them,COFs-based electrochemical(EC)sensors with upgraded analytical performance are arousing extensive interest.In this review,therefore,we summarize the basic properties and the general synthesis methods of COFs used in the field of electroanalytical chemistry,with special emphasis on their usages in the fabrication of chemical sensors,ions sensors,immunosensors,and aptasensors.Notably,the emerged COFs in the electrochemiluminescence(ECL)realm are thoroughly covered along with their preliminary applications.Additionally,final conclusions on state-of-the-art COFs are provided in terms of EC and ECL sensors,as well as challenges and prospects for extending and improving the research and applications of COFs in electroanalytical chemistry.

Overcoming the biofilm barrier by cell-like microbubbles for the treatment of biofilm-associated implant infections

Although the advent of antibiotics has significantly improved the quality of life of infected patients,bacterial infections continue to pose a serious threat to public health[1,2].According to a recent report,within the next 30 years,bacterial infections are projected to surpass cancer in terms of lethality rates,resulting in an alarming 10 million deaths annually by 2050 due to the development of bacterial resistance[3].Moreover,the formation of bacterial biofilms hampers the penetration of antibacterial agents and inhibits the host immune response,making biofilm infections extremely challenging to treat[4-7].Hence,the development of innovative antimicrobial biofilm therapeutics is imperative.

Advanced development of grain boundaries in TMDs from fundamentals to hydrogen evolution application

Grain boundary(GB),as a kind of lattice defect,widely exists in two-dimensional transition metal dichalcogenides(2D TMDs),which has complex and diverse influences on the physical/chemical properties of 2D TMDs.GBs are universally considered to be a double-edged sword,although some electrical and mechanical properties of 2D TMDs would be adversely affected leading to the reduced overall quality,certain structure-oriented applications could be realized based on its unique properties.In this review,we first detailed the atomic structure characteristics of GBs and the corresponding techniques,then we systematically summarized the methods of introducing GBs into 2D TMDs.Next,we expounded unique electrical,mechanical,and chemical properties of the GBs in 2D TMDs and clarified its internal relationship with the atomic structure.Moreover,the application of GB structure in hydrogen evolution reaction(HER)is also discussed.In the end,we make a conclusion and put forward outlooks,hoping to further promote the basic research of GB and boost the wide application of 2D TMDs.

Recent Advances in Tumor Microenvironment Hydrogen Peroxide-Responsive Materials for Cancer Photodynamic Therapy

Photodynamic therapy(PDT),as one of the noninvasive clinical cancer phototherapies,suffers from the key drawback associated with hypoxia at the tumor microenvironment(TME),which plays an important role in protecting tumor cells from damage caused by common treatments.High concentration of hydrogen peroxide(H2O2),one of the hallmarks of TME,has been recognized as a double-edged sword,posing both challenges,and opportunities for cancer therapy.The promising perspectives,strategies,and approaches for enhanced tumor therapies,including PDT,have been developed based on the fast advances in H2O2-enabled theranostic nanomedicine.In this review,we outline the latest advances in H2O2-responsive materials,including organic and inorganic materials for enhanced PDT.Finally,the challenges and opportunities for further research on H2O2-responsive anticancer agents are envisioned.

Lead‑Free Perovskite Materials for Solar Cells

The toxicity issue of lead hinders large-scale commercial production and photovoltaic field application of lead halide perovskites.Some novel non-or low-toxic perovskite materials have been explored for development of environmentally friendly lead-free perovskite solar cells(PSCs).This review studies the substitution of equivalent/heterovalent metals for Pb based on first-principles calculation,summarizes the theoretical basis of lead-free perovskites,and screens out some promising lead-free candidates with suitable bandgap,optical,and electrical properties.Then,it reports notable achievements for the experimental studies of lead-free perovskites to date,including the crystal structure and material bandgap for all of lead-free materials and photovoltaic performance and stability for corresponding devices.The review finally discusses challenges facing the successful development and commercialization of lead-free PSCs and predicts the prospect of lead-free PSCs in the future.

Controllable synthesis of grain boundary-enriched Pt nanoworms decorated on graphitic carbon nanosheets for ultrahigh methanol oxidation catalytic activity

Although one-dimensional Pt nanocrystals have long been regarded as ideal electrode catalysts for fuel cells,the synthetic techniques commonly involve the use of various complicated templates or surfactants,which have largely hampered their large-scale industrial application.Herein,we present a convenient and cost-effective approach to the stereoassembly of quasi-one-dimensional grain boundary-enriched Pt nanoworms on nitrogen-doped low-defect graphitic carbon nanosheets(Pt NWs/NL-CNS).Benefiting from its numerous catalytically active grain boundaries as well as optimized electronic structure,the as-derived Pt NWs/NL-CNS catalyst possesses exceptionally good electrocatalytic properties for methanol oxidation,including an ultrahigh mass activity of 1949.5 mA mg^(-1), reliable long-term durability,and strong poison tolerance,affording one of the most active Pt-based electrocatalysts for methanol oxidation reaction.Density functional theory calculation further reveals that the formation of worm-shape Pt morphology is attributed to the modified electronic structure as well as controllable defect density of the carbon matrix,which could also weaken the adsorption ability of Pt towards CO molecule and meanwhile synergistically promotes the catalytic reaction kinetics.

A MXene-functionalized paper-based electrochemical immunosensor for label-free detection of cardiac troponin I

Convenient,rapid,and accurate detection of cardiac troponin I(cTnI)is crucial in early diagnosis of acute myocardial infarction(AMI).A paper-based electrochemical immunosensor is a promising choice in this field,because of the flexibility,porosity,and cost-efficacy of the paper.However,paper is poor in electronic conductivity and surface functionality.Herein,we report a paper-based electrochemical immunosensor for the label-free detection of cTnI with the working electrode modified by MXene(Ti_(3)C_(2))nanosheets.In order to immobilize the bio-receptor(anti-cTnI)on the MXene-modified working electrode,the MXene nanosheets were functionalized by aminosilane,and the functionalized MXene was immobilized onto the surface of the working electrode through Nafion.The large surface area of the MXene nanosheets facilitates the immobilization of antibodies,and the excellent conductivity facilitates the electron transfer between the electrochemical species and the underlying electrode surface.As a result,the paper-based immunosensor could detect cTnI within a wide range of 5-100 ng/mL with a detection limit of 0.58 ng/mL.The immunosensor also shows outstanding selectivity and good repeatability.Our MXene-modified paper-based electrochemical immunosensor enables fast and sensitive detection of cTnI,which may be used in real-time and cost-efficient monitoring of AMI diseases in clinics.

Metallic vanadium trioxide intercalated with phase transformation for advanced aqueous zinc-ion batteries

Aqueous zinc-ion batteries have broad application prospects due to the eco-friendliness,cost-economy and high safety.However,the scarcity of high-performance cathodes with outstanding rate capability and long lifespan has affected their development.Herein,we report a metallic vanadium trioxide material intercalated with phase transformation as cathode applied in aqueous zinc-ion batteries.It offers satisfactory electrochemical performances with a high specific capacity(435 mAh g^(-1) at 0.5 A g^(-1)),decent power density(5.23 kW kg^(-1))and desired energy density(331 Wh kg^(-1)),as well as good cyclability.The superior performance originates from the stable structure and fast Zn^(2+)diffusion,enabled by the pre-intercalation of Zn^(2+)and water molecules.

Recent advances in two-dimensional nanomaterials-based electrochemical sensors for environmental analysis

With the rapidly increased concerns in environmental pollution, there have been urgent needs to develop fast, sensitive, low-cost and multiplexed sensing devices for the detection of environmental pollutants. Two-dimensional(2D) nanomaterials hold great promise due to their unique chemical and physical properties, which have been extensively employed to monitor the environmental pollutants combined with different detection techniques. In this review, we summarize recent advances in 2D nanomaterials-based electrochemical sensors for detecting heavy metal ions, organic compounds, pesticides, antibiotics and bacteria. We also discuss perspectives and challenges of 2D nanomaterials in environmental monitoring.

Perovskite LEDs: World Record of External Quantum Efficiency That ApproachThose of the Best-performing Organic LEDs

Light-emitting diodes (LEDs), which convert electricity to light, are widely used in modern society,for example, in lighting, flat-panel displays, medical devices and many other situations. Ge- nerally, the efficiency of LEDs is limited by nonradiative recombination (whereby charge carriers recombine without releasing photons) and light trapping [1]. In planar LEDs, such as organic LEDs, around 70% to 80% of the light generated from the emitters is trapped in the device [2], leaving considerable opportunity for improvements in efficiency. Many methods, including the use of diffraction gratings, low-index grids and buckling patterns, have been used to extract the light trapped in LEDs [3]. However, these methods usually involve complicated fabrication processes and can distort the light-output spectrum and directionality [3].

Triple-phase interfaces of graphene-like carbon clusters on antimony trisulfide nanowires enable high-loading and long-lasting liquid Li_(2)S_(6)-based lithium-sulfur batteries

High performance of lithium-sulfur batteries have been dragged down by their shuttling behavior which is complicated multiphase transition-based 16-electron redox reactions of the S8/Li2 S.In this article,the triple-phase interfaces of graphene-like carbon clusters on antimony trisulfide(C-Sb_(2)S_(3))nanowires are tailored to design a multifunctional polysulfide host which can inhibit migration of polysulfides and accelerate conversion kinetics of redox electrochemical reactions.Benefiting from the triple-interface design of polysulfides/Sb_(2)S_(3)/carbon clusters,the C-Sb_(2)S_(3) electrode not only anchors polysulfide migration by the synergistic effect of Sb,S,and C atoms as interfacial active sites,but also the graphene-like carbon clusters shorten the diffusion paths to further favor redox electron/ion transport through the liquid(electrolyte/polysulfide)and solid(Li2 S/S8,carbon clusters,and Sb_(2)S_(3))-based triple-phases.Therefore,these Li_(2)S_(6)-based C-Sb_(2)S_(3) cells possess high sulfur loading,excellent cycling stability,impressive specific capacity,and great rate capability.This work of interfacial engineering reveals insight for powering reaction kinetics in the complicated multistep catalysis reaction with multiphase evolution-based chargetransfer/non-transfer processes.

Purification of rectangle DNA origami by rate-zonal centrifugation

DNA origami technique, a breakthrough in DNA nanotechnology, has been widely used to prepare complex DNA nanostructures with nanoscale addressability. However, the purity and yield are generally the bottleneck to application of DNA nanostructures, and current methods for purifying DNA origami nanostructures in large quantities are time-consuming and laborious. This study aims to develop a scalable, cost-effective and contamination-free method of purifying DNA origami nanostructures. We employ an effective and convenient purification approach to purify planar rectangle DNA origami structures through rate-zonal centrifugation. By subjecting DNA origami samples to high centrifugal force in a density gradient media of glycerol, well-folded nanostructures and by-products are separated successfully, which are confirmed by agarose gel electrophoresis and atomic force microscopy(AFM). This method will aid the production of pure rectangle DNA origami nanostructures in large quantity.

DNA origami-templated assembly of plasmonic nanostructures with enhanced Raman scattering

DNA origami have been established as versatile templates to fabricate plasmonic nanostructures in predefined shapes and multiple dimensions. Limited to the size of DNA origami, which are approximate to 100 nm, it is hard to assemble more intricate plasmonic nanostructures in large scale. Herein, we used rectangular DNA origami as the template to anchor two 30-nm gold nanoparticles(Au NPs) which induced dimers nanostructures. Transmission electron microscopy(TEM) images showed the assembly of Au NPs with high yields. Using the linkers to organize the DNA origami templates into nanoribbons,chains of Au NPs were obtained, which was validated bythe TEM images. Furthermore, we observed a significant Raman signal enhancement from molecules covalently attached to the Au NP-dimers and Au NP-chains. Our method opens up the prospects of high-ordered plasmonic nanostructures with tailored optical properties.

The enhancement of 21.2%-power conversion efficiency in polymer photovoltaic cells by using mixed Au nanoparticles with a wide absorption spectrum of 400 nm–1000 nm

Au nanoparticles （NPs） mixed with a majority of bone-like, rod, and cube shapes and a minority of irregu- lar spheres, which can generate a wide absorption spectrum of 400 nm-1000 nm and three localized surface plas- mon resonance peaks, respectively, at 525, 575, and 775 nrn, are introduced into the hole extraction layer poly（3,4- ethylenedioxythiophene）：poly（4-styrenesulfonate） （PEDOT：PSS） to improve optical-to-electrical conversion performances in polymer photovoltaic ceils. With the doping concentration of Au NPs optimized, the cell performance is significantly improved： the short-circuit current density and power conversion efficiency of the poly（3-hexylthiophene）： [6,6]-phenyl- C60-butyric acid methyl ester cell are increased by 20.54% and 21.2%, reaching 11.15 mA.cm-2 and 4.23%. The variations of optical, electrical, and morphology with the incorporation of Au NPs in the cells are analyzed in detail, and our results demonstrate that the cell performance improvement can be attributed to a synergistic reaction, including： 1） both the local- ized surface plasmon resonanceand scattering-induced absorption enhancement of the active layer, 2） Au doping-induced hole transport/extraction ability enhancement, and 3） large interface roughness-induced efficient exciton dissociation and hole collection.

Protein-mimicking nanoparticle(Protmin)-based nanosensor for intracellular analysis of metal ions

In this study, we designed and applied proteinmimicking nanoparticles(Protmin) as an intracellular nanosensor for in vivo detection of lead ions(Pb^(2+)).Monodispersed gold nanoparticles(Au NPs) of 13 nm in diameter were modified using poly-adenine-tailed Pb^(2+)-specific 8–17 DNAzyme to form a spherical and functional Protmin. Substrate strands modified with a fluorophore at the 50 end and a quencher at the 30 end were bound to DNAzyme. Pb^(2+) facilitated cleavage of DNAzyme to release the fluorophore-modified short strands to generate fluorescence. We observed rapid kinetics of the Protmin nanosensor, for which the typical assay time was 10 min.Further, we demonstrated the Protmin nanosensor could readily enter living cells and respond to Pb^(2+) in the intracellular environment. The broad of range of Protmindesigns will be useful for advancing biological and medical applications.

Crystallographic and magnetic properties of van der Waals layered FePS_3 crystal

The crystallographic and magnetic properties are presented for van der Waals antiferromagnetic FePS_3. High-quality single crystals of millimeter size have been successfully synthesized through the chemical vapor transport method. The layered structure and cleavability of the compound are apparent, which are beneficial for a potential exploration of the interesting low dimensional magnetism, as well as for incorporation of FePS_3 into van der Waals heterostructures. For the sake of completeness, we have measured both direct current(dc) and alternating current(ac) magnetic susceptibility.The paramagnetic to antiferromagnetic transition occurs at approximately T_N 115 K. The effective moment is larger than the spin-only effective moment, suggesting that an orbital contribution to the total angular momentum of the Fe^(2+) could be present. The ac susceptibility is independent of frequency, which means that the spin freezing effect is excluded.Strong anisotropy of out-of-plane and in-plane susceptibility has been shown, demonstrating the Ising-type magnetic order in FePS_3 system.

Utilization of triplet excited states in organic semiconductors

Organic optoelectronics is an emerging research field, which has attracted extensive interests in the last few decades owing to its practical applications, like organic light-emitting diodes (OLEDs), organic memory devices, organic photovoltaic (OPV), sensors, and organic field-effect transistors[1, 2]. Organic semiconductors play a crucial role in this field. Compared to the traditional inorganic semiconductors, organic semiconductors open a fascinating research direction because of some unique advantages, such as flexible design, low cost, and rich optical and electronic properties. In organic optoelectronics, the excited states greatly determine the photoelectronic properties and application areas as shown in Fig. 1. Based on the electron spin in the molecule, the excited states of organic semiconductors include singlet and triplet states. As we know, the radiative transitions of singlet and triplet excited states are always accompanied by fluorescence and phosphorescence emission, respectively.

Spectroscopic properties of Yb^(3+)-doped TeO_2–BaO–BaF_2–Nb_2O_5-based oxyfluoride tellurite glasses

A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5, （15 mol%-x） BaO, x BaF2 （x =0 mol%, 5 mol%, 10 mol%, 15 mol%） doped with Yb2O3 were prepared by the melt-quenching method. Their emission cross-sections, fluorescence lifetimes, and gain properties were investigated by using the absorption spectra and the fluorescence decay curves. The results show that by substituting BaF2 for BaO, the emission cross-section decreases from 1.37 pm^2 to 1.21 pm^2, and the fluorescence lifetime increases from 0.71 ms to 0.96 ms. These properties indicate that this oxyfluoride tellurite glass may have potential uses as the Yb2O3-doped gain medium in a solid laser.

SYNTHESIS,CHARACTERIZATION AND QUENCHING BEHAVIOR OF A CATIONIC POLY(p-PHENYLENEVINYLENE) RELATED COPOLYMER

A cationic poly(p-phenylene vinylene) related copolymer without bulky phenylene substitutents attached to the conjugated backbone was prepared through Wittig reaction.The molecular structure and optical properties were highly investigated through ~1H-NMR,UV and PL spectroscopy.The quenching behavior was also investigated,and the results demonstrate that incomplete quenching exists,which is consistent with the cationic poly(p-phenylene vinylene) related copolymer containing bulky phenylene substitutents,prob...

Fluorine substitution position effects on spiro(fluorene-9,9’-xanthene) cored hole transporting materials for high-performance planar perovskite solar cells

Fluorine substitution in molecular design has become an effective strategy for improving the overall performance of organic photovoltaics.In this study,three low-cost small molecules of spiro-linked hole transporting materials(SFX-O-2 F,SFX-m-2 F,and SFX-p-2 F) endowed with two-armed t rip he ny la mine moieties were synthesized via tuning of the fluorine substitution position,and they were employed for use in highly efficient perovskite solar cells(PSCs).Despite the fluorine substitution position playing a negligible role in the optical and electrochemical properties of the resulting small molecules,the photovoltaic performance thereof was observed to vary significantly.The planar n-i-p PSCs based on SFX-m-2 F demonstrated superior performance(18.86%) when compared to that of the corresponding SFX-o-2 F(9.7%) and SFX-p-2 F(16.33%) under 100 mW cm^(-2) AM1.5 G solar illumination,which is competitive with the performance of the benchmark spiro-OMeTAD-based device(18.98%).Moreover,the SFX-m-2 Fbased PSCs were observed to be more stable than the spiro-OMeTAD-based devices under ambient conditions.The improved performance of SFX-m-2 F is primarily associated with improved morphology,more efficient hole transport,and extraction characteristics at the perovskite/HTM interface.This work demonstrated the application of fluorination engineering to the tuning of material film morphology and charge transfer properties,showing the promising potential of fluorinated SM-HTMs for the construction of low-cost,high-efficiency PSCs.