Bulk preparation of free-standing single-iron-atom catalysts directly as the air electrodes for high-performance zinc-air batteries

The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction(ORR)at the cathode.Herein,we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube(FeSAC/PCMT)sponge.Benefiting from its unique structure that greatly facilitates the catalytic kinetics,mass transport,and electron transfer,our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at^(-3) mA cm^(-2).When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries,high peak power densities of 183.1 and 58.0 mW cm^(-2) were respectively achieved,better than its powdery counterpart and commercial Pt/C catalyst.Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N_(5) species in FeSAC/PCMT.This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes,provides a significant new insight into the catalytic mechanisms,and helps to realize significant advances in energy devices.

Iron-Imprinted Single-Atomic Site Catalyst-Based Nanoprobe for Detection of Hydrogen Peroxide in Living Cells

Fe-based single-atomic site catalysts(SASCs),with the natural metalloproteases-like active site structure,have attracted widespread attention in biocatalysis and biosensing.Precisely,controlling the isolated single-atom Fe-N-C active site structure is crucial to improve the SASCs’performance.In this work,we use a facile ion-imprinting method(IIM)to synthesize isolated Fe-N-C single-atomic site catalysts(IIM-Fe-SASC).With this method,the ion-imprinting process can precisely control ion at the atomic level and form numerous well-defined single-atomic Fe-N-C sites.The IIM-Fe-SASC shows better peroxidase-like activities than that of non-imprinted references.Due to its excellent properties,IIM-Fe-SASC is an ideal nanoprobe used in the colorimetric biosensing of hydrogen peroxide(H_(2)O_(2)).Using IIM-Fe-SASC as the nanoprobe,in situ detection of H_(2)O_(2)generated from MDA-MB-231 cells has been successfully demonstrated with satisfactory sensitivity and specificity.This work opens a novel and easy route in designing advanced SASC and provides a sensitive tool for intracellular H_(2)O_(2)detection.

磷化蛋白phospho-p53^(15)的电化学免疫传感器

p53蛋白是调控人体内细胞生长和监控细胞分裂时DNA的复制最重要的分子．它是一种重要的肿瘤抑制基因，能防止癌变．还能帮助细胞基因修复缺陷。但当人体受到紫外光照射或化学致癌物的作用时，p53不能执行上述功能时，对细胞的增殖失去控制，往往就会导致细胞发生癌变。据报道超过一半的人体癌细胞中．

A peroxidase-like single-atom Fe-N_(5)active site for effective killing human lung adenocarcinoma cells

Single-atom catalyst(SAC)is one of the newest catalysts,and attracts people’s wide attention in cancer therapy based on their characteristics of maximum specific catalytic activity and high stability.We designed and synthesized a Fe-N decorated graphene nanosheet(Fe-N5/GN SAC)with the coordination number of five.Through enzymology and theoretical calculations,the Fe-N5/GN SAC has outstanding intrinsic peroxidase-like catalytic activity due to single-atom Fe site with five-N-coordination structure.We explored its potential on lung cancer therapy,and found that it could kill human lung adenocarcinoma cells(A549)by decomposing hydrogen peroxide(H_(2)O_(2))into toxic reactive oxygen species(ROS)under acidic microenvironment in threedimensional(3D)lung cancer cell model.Our study demonstrates a promising application of SAC with highly efficient single-atom catalytic sites for cancer treatment.

Zeptomole Imaging of Cytosolic MicroRNA Cancer Biomarkers with A Light-Controlled Nanoantenna

Detecting and quantifying intracellular microRNAs(miRNAs)are a critical step in resolving a cancer diagnostic and resolving the ensemble of gene products that orchestrate the living state of cells.However,the nanoprobe for detecting low abundance miRNAs in cell cytosol is restricted by either the"one-to-one"signaltrigger model or di culty for cytosol delivery.To address these challenges,we designed a lightharvesting nanoantenna-based nanoprobe,which directs excitation energy to a single molecule to sensitively detect cytosolic miRNA.With light irradiation,the light-harvesting nanoantenna e ectively disrupted lysosomal structures by generationof reactive oxygen species,substantially achieved cytosol delivery.The nanoantenna containing>4000 donor dyes can e ciently transfer excitation energy to one or two acceptors with 99%e ciency,leading to unprecedented signal amplification and biosensing sensitivity.The designed nanoantenna can quantify cytosolic miR-210 at zeptomolar level.The fluorescence lifetime of the donor exhibited good relationship with miR-210 concentration in the range of 0.032 to 2.97 amol/ngRNA.The zeptomole sensitivity of nanoantenna provides accurate bioimaging of miR-210 both in multiple cell lines and in vivo assay,which creates a pathway for the creation of miRNA toolbox for quantitative epigenetics and personalized medicine.

Assembly of highly efficient aqueous light-harvesting system from sequence-defined peptoids for cytosolic microRNA detection

Precisely controlled spatial distributions of artificial light-harvesting systems in aqueous media are of significant importance for mimicking natural light-harvesting systems;however,they are often restrained by the solubility and the aggregation-caused quenching effect of the hydrophobic chromophores.Herein,we report one highly efficient artificial light-harvesting system based on peptoid nanotubes that mimic the hierarchical cylindrical structure of natural systems.The high crystallinity of these nanotubes enabled the organization of arrays of donor chromophores with precisely controlled spatial distributions,favoring an efficient Förster resonance energy transfer(FRET)process in aqueous media.This FRET system exhibits an extremely high efficiency of 98.6%with a fluorescence quantum yield of 40%and an antenna effect of 29.9.We further demonstrated the use of this artificial light-harvesting system for quantifying miR-210 within cancer cells.The fluorescence intensity ratio of donor to acceptor is linearly related to the concentration of intercellular miR-210 in the range of 3.3–156 copies/cell.Such high sensitivity in intracellular detection of miR-210 using this artificial light-harvesting system offers a great opportunity and pathways for biological imaging and detection,and for the further creation of microRNA(miRNA)toolbox for quantitative epigenetics and personalized medicine.

Single-Atom Nanozymes Linked Immunosorbent Assay for Sensitive Detection of Aβ1-40:A Biomarker of Alzheimer’s Disease

Single-atom nanozymes(SANs)possess unique features of maximum atomic utilization and present highly assembled enzyme-like structure and remarkable enzyme-like activity.By introducing SANs into immunoassay,limitations of ELISA such as low stability of horseradish peroxidase(HRP)can be well addressed,thereby improving the performance of the immunoassays.In this work,we have developed novel Fe-N-C single-atom nanozymes(Fe-N_(x)SANs)derived from Fe-doped polypyrrole(PPy)nanotube and substituted the enzymes in ELISA kit for enhancing the detection sensitivity of amyloid beta 1-40.Results indicate that the Fe-N_(x)SANs contain high density of single-atom active sites and comparable enzyme-like properties as HRP,owing to the maximized utilization of Fe atoms and their abundant active sites,which could mimic natural metalloproteases structures.Further designed SAN-linked immunosorbent assay(SAN-LISA)demonstrates the ultralow limit of detection(LOD)of 0.88 pg/mL,much more sensitive than that of commercial ELISA(9.98 pg/mL).The results confirm that the Fe-N_(x)SANs can serve as a satisfactory replacement of enzyme labels,which show great potential as an ultrasensitive colorimetric immunoassay.

Recent advances in carbon-supported non-precious metal singleatom catalysts for energy conversion electrocatalysis

Non-precious metal single-atom catalysts(NPM-SACs)with unique electronic structures and coordination environments have gained much attention in electrocatalysis owing to their low cost,high atomic utilization,and high performance.NPM-SACs on carbon support(NPM-SACs/CS)are promising because of the carbon substrate with a large surface area,excellent electrical conductivity,and high chemical stability.This review provides an overview of recent developments in NPM-SACs/CS for the electrocatalytic field.First,the state-of-the-art synthesis methods and advanced characterization techniques of NPM-SACs/CS are discussed in detail.Then,the structural adjustment strategy of NPM-SACs/CS for optimizing electrocatalytic performance is introduced concisely.Furthermore,we provide a comprehensive summary of recent advances in developing NPM-SACs/CS for important electrochemical reactions,including carbon dioxide reduction reaction,hydrogen evolution reaction,oxygen evolution reaction,oxygen reduction reaction,and nitrogen reduction reaction.In the end,the existing challenges and future opportunities of NPM-SACs/CS in the electrocatalytic field are highlighted.

Single-Atomic Site Catalyst Enhanced Lateral Flow Immunoassay for Point-of-Care Detection of Herbicide

Point-of-care(POC)detection of herbicides is of great importance due to their impact on the environment and potential risks to human health.Here,we design a single-atomic site catalyst(SASC)with excellent peroxidase-like(POD-like)catalytic activity,which enhances the detection performance of corresponding lateral flow immunoassay(LFIA).The iron single-atomic site catalyst(Fe-SASC)is synthesized from hemin-doped ZIF-8,creating active sites that mimic the Fe active center coordination environment of natural enzyme and their functions.Due to its atomically dispersed iron active sites that result in maximum utilization of active metal atoms,the Fe-SASC exhibits superior POD-like activity,which has great potential to replace its natural counterparts.Also,the catalytic mechanism of Fe-SASC is systematically investigated.Utilizing its outstanding catalytic activity,the Fe-SASC is used as label to construct LFIA(Fe-SASC-LFIA)for herbicide detection.The 2,4-dichlorophenoxyacetic acid(2,4-D)is selected as a target here,since it is a commonly used herbicide as well as a biomarker for herbicide exposure evaluation.A linear detection range of 1-250 ng/mL with a low limit of detection(LOD)of 0.82 ng/mL has been achieved.Meanwhile,excellent specificity and selectivity towards 2,4-D have been obtained.The outstanding detection performance of the Fe-SASC-LFIA has also been demonstrated in the detection of human urine samples,indicating the practicability of this POC detection platform for analyzing the 2,4-D exposure level of a person.We believe this proposed Fe-SASC-LFIA has potential as a portable,rapid,and high-sensitive POC detection strategy for pesticide exposure evaluation.

Boosting the activity of Fe–N_x moieties in Fe–N–C electrocatalysts via phosphorus doping for oxygen reduction reaction

The Fe–N–C material is a promising non-noblemetal electrocatalyst for oxygen reduction reaction(ORR).Further improvement on the ORR activity is highly desired in order to replace Pt/C in acidic media.Herein,we developed a new-type of single-atom Fe–N–C electrocatalyst,in which Fe–Nxactive sites were modified by P atoms.The half-wave potential of the optimized material reached 0.858 V,which is 23 mV higher than that of the pristine one in a 0.1 mol L-1 HClO4 solution.Density functional theory(DFT)calculations revealed that P-doping can reduce the thermodynamic overpotential of the rate determining step and consequently improve the ORR activity.

SciFinder-guided rational design of fluorescent carbon dots for ratiometric monitoring intracellular pH fluctuations under heat shock

Intracellular pH plays a significant role in various biological processes, including cell proliferation,apoptosis, metabolism, enzyme activity and homeostasis. In this work, a novel design strategy for the preparation of pH responsive carbon dots(CDs-pH) for ratiometric intracellular imaging was reported. By using SciFinder database, fluorescent CDs-pH with the required p Kavalue of 6.84 were rationally designed, which is vital important for precise sensing of intracellular pH. As a result, the synthesized CDspH demonstrated robust ability to test pH fluctuations within the physiological range of 5.4-7.4. The CDspH was further utilized for fluorescent ratiometric imaging of pH in living HeLa cells, effectively avoided the influence of autofluorescence from native cellular species. Moreover, real-time monitoring of intracellular pH fluctuation under heat shock was successfully realized. This SciFinder-guided design strategy is simple and flexible, which has a great potential to be used for the development of other types of CDs for various applications.

Nanozyme Enhanced Colorimetric Immunoassay for Naked-Eye Detection of Salmonella Enteritidis

Salmonella Enteritidis is a major public health threat of global proportions,while it is still a serious challenge to develop point-of-care detection assay.In this study,nanozymes(Fe-MOF nanoparticles)were successfully synthesized and applied as signal in a colorimetric immunoassay for naked-eye detection of Salmonella Enteritidis.After optimization,the proposed assay was able to detect Salmonella Enteritidis with a detection limit of 34 CFU/mL.The coefficients of variation(CV)of the test were less than 7.0%after 30 days storage at 4°C.The estimated recoveries in milk samples of the colorimetric immu-noassay range from 94.68 to 124%,which indicated the developed method is capable of detecting Salmonella Enteritidis in real samples.This method provides a potential platform for Salmonella detection with naked eyes,which has a significant application value for foodborne pathogen analysis at the point-of-care.

Template-directed synthesis of nitrogen- and sulfur- codoped carbon nanowire aerogels with enhanced electrocatalytic performance for oxygen reduction

Heteroatom doping, precise composition control and rational morphology design are efficient strategies for producing novel nanocatalysts for the oxygen reduction reaction （ORR） in fuel cells. Herein, a cost-effective approach to synthesize nitrogen- and sulfur-codoped carbon nanowire aerogels using a hard templating method is proposed. The aerogels prepared using a combination of hydrothermal treatment and carbonization exhibit good catalytic activity for the ORR in alkaline solution. At the optimal annealing temperature and mass ratio between the nitrogen and sulfur precursors, the resultant aerogels show comparable electrocatalytic activity to that of a commercial Pt/C catalyst for the ORR. Importantly, the optimized catalyst shows much better long-term stability and satisfactory tolerance for the methanol crossover effect. These codoped aerogels are expected to have potential applications in fuel cells.

Multifunctional SnO2/3D graphene hybrid materials for sodium-ion and lithium-ion batteries with excellent rate capability and long cycle life

SnO2 is a promising material for both Li-ion and Na-ion batteries owing to its high theoretical capacities. Unfortunately, the electrochemical performance of SnO2 is unsatisfactory because of the large volume change that occurs during cycling, low electronic conductivity of inactive oxide matrix, and poor kinetics, which are particularly severe in Na-ion batteries. Herein, ultra-fine SnO2 nanocrystals anchored on a unique three-dimensional （3D） porous reduced graphene oxide （rGO） matrix are described as promising bifunctional electrodes for Li-ion and Na-ion batteries with excellent rate capability and long cycle life. Ultra-fine SnO2 nanocrystals of size -6 nm are well-coordinated to the graphene sheets that comprise the 3D macro-porous structure. Notably, superior rate capability was obtained up to 3 C （1In C is a measure of the rate that allows the cell to be charged/discharged in n h） for both batteries. In situ X-ray diffractometry measurements during lithiation （or sodiation） and delithiation （or desodiation） were combined with various electrochemical techniques to reveal the real-time phase evolution. This critical information was linked with the internal resistance, ion diffusivity （DLi＋ and DNa＋）, and the unique structure of the composite electrode materials to explain their excellent electrochemical performance. The improved capacity and superior rate capabilities demonstrated in this work can be ascribed to the enhanced transport kinetics of both electrons and ions within the electrode structure because of the well-interconnected, 3D macro-porous rGO matrix. The porous rGO matrix appears to play a more important role in sodium-ion batteries （SIBs）, where the larger mass/radius of Na-ions are marked concerns.

Mesoporous PtPd nanoparticles for ligand-mediated and imaging-guided chemo-photothermal therapy of breast cancer

The synergistic therapy of chemotherapy and photothermal therapy(PTT)has been reported as a promising antitumor strategy.To achieve effective combination therapy,developing more suitable candidate nanomaterials with optimal photothermal property and high chemical drug loading capacity is very necessary.Herein,a bimetallic PtPd nanoparticle was synthesized with the merits of excellent photothermal effect and mesoporous structure for doxorubicin(DOX)loading.We further designed PtPd-ethylene glycol(PEG)-folic acid(FA)-doxorubicin(DOX)nanoparticle for chemo-photothermal therapy of MCF-7 tumor with folic acid engineering to achieve active targeting.Moreover,excellent photoacoustic(PA)imaging of PtPd-PEG-FA-DOX nanoparticles facilitated the precise in vivo tracking and further evaluation of nanoparticles’targeting effect.The in vitro and in vivo results both demonstrated PtPd-PEG-FA-DOX nanoparticles serve as a safe and promising system for effective treatment of MCF-7 tumor.

Sequence-Defined Nanotubes Assembled from IR780-Conjugated Peptoids for Chemophototherapy of Malignant Glioma

Near-infrared(NIR)laser-induced phototherapy through NIR agents has demonstrated the great potential for cancer therapy.However,insufficient tumor killing due to the nonuniform heat or cytotoxic singlet oxygen(1 O2)distribution over tumors from phototherapy results in tumor recurrence and inferior outcomes.To achieve high tumor killing efficacy,one of the solutions is to employ the combinational treatment of phototherapy with other modalities,especially with chemotherapeutic agents.In this paper,a simple and effective multimodal therapeutic system was designed via combining chemotherapy,photothermal therapy(PTT),and photodynamic therapy(PDT)to achieve the polytherapy of malignant glioma which is one of the most aggressive tumors in the brain.IR-780(IR780)dye-labeled tube-forming peptoids(PepIR)were synthesized and self-assembled into crystalline nanotubes(PepIR nanotubes).These PepIR nanotubes showed an excellent efficacy for PDT/PTT because the IR780 photosensitizers were effectively packed and separated from each other within crystalline nanotubes by tuning IR780 density;thus,a self-quenching of these IR780 molecules was significantly reduced.Moreover,the efficient DOX loading achieved due to the nanotube large surface area contributed to an efficient and synergistic chemotherapy against glioma cells.Given the unique properties of peptoids and peptoid nanotubes,we believe that the developed multimodal DOX-loaded PepIR nanotubes in this work offer great promises for future glioma therapy in clinic.

Recent progress on rational design of catalysts for fermentative hydrogen production

The increasingly severe energy crisis has strengthened the determination to develop environmentally friendly energy.And hydrogen has emerged as a candi-date for clean energy.Among many hydrogen generation methods,biohydrogen stands out due to its environmental sustainability,simple operating environ-ment,and cost advantages.This review focuses on the rational design of catalysts for fermentative hydrogen production.The principles of microbial dark fermen-tation and photo-fermentation are elucidated exhaustively.Various strategies to increase the efficiency of fermentative hydrogen production are summa-rized,and some recent representative works from microbial dark fermentation and photo-fermentation are described.Meanwhile,perspectives and discussions on the rational design of catalysts for fermentative hydrogen production are provided.