Atomically Precise Imprinting π-Magnetism in Nanographenes via Probe Chemistry

The precise generation and harnessing of carbon magnetism at the single-molecule level have been captivating areas of research in chemistry and nanotechnology.However,the realization of magnetic nanographenes,also known as single-moleculeπ-magnets,through solution-based synthesis has proven challenging because of their high reactivity and insolubility tendency.Recent advancements in on-surface chemistry and scanning probe techniques have significantly propelled the fabrication of carbon-based magnetic nanostructures to offer a rich platform to probe quantumπ-magnetism at the single-molecule level.Atomic manipulation,also referred to as probe chemistry,stands as an exciting and essential approach in the toolbox of on-surface chemistry.This approach enables site-selective chemical reactions,thereby allowing for the atomically precise imprinting and tailoringπ-magnetism in a variety of nanographenes.This review highlights the recent achievements in the precise synthesis of single-moleculeπ-magnets using atomic manipulation.Furthermore,we also provide an outlook on the future of probe chemistry in the fabrication of this intriguing class of magnetic nanographenes,featuring designer quantum magnetism.

NBN-doped nanographene embedded with five-and seven-membered rings on Au(111)surface

Nanographenes(NGs)can be embedded with predesigned dopants or nonhexagonal rings to tailor the electronic properties and provide ideal platforms to study the unique physical and chemical properties.Here,we report the on-surface synthesis of NBN-doped NG embedded with five-and seven-membered rings(NBN-575-NG)on Au(111)from a oligophenylene precursor preinstalled with a NBN unit and a heptagonal ring.Scanning tunneling microscopy and non-contact atomic force microscopy images elucidate the intramolecular cyclodehydrogenation and the existence of the five-and seven-membered rings.Scanning tunneling spectroscopy spectra reveal that the NBN-575-NG is a semiconductor,which agrees with the density functional theory calculation results on a freestanding NBN-575-NG with the same structure.This work provides a feasible approach for the on-surface synthesis of novel NGs containing non-hexagonal rings.

Immobilization of GO_(X) on PEG/fluoresence functionalized nanographene oxide to describe fluctuation of glucose level

Enzyme,produced and worked in all living things,could work as macromolecular biological catalysts in diverse biochemical processes with particular specificity,like glucose oxidase(GOX).The efficient use of enzyme properties has great importance in pharmaceutics and therapeutics.In this work,we could fabricate naive and effective electrochemical biosensors in the determination of glucose levels via utilizing GOX.Graphene oxide,as a water-soluble derivative of graphene,has shown great promise in a variety of biomedical applications including biosensors.Thus,we established a new-type special platform for GOX immobilization to perform its prosperities,in which nanographene oxide(nGO)was employed as an ideal base and poly(ethylene glycol)(PEG)was conjugated on the edge of nGO sheets to enhance its biocompatibility.Additionally,preferable functional dyes(Rhodamine B/fluorescein isothiocyanate)were also introduced to the platform.Enzyme-nanocomposites were then provided by locating GOX on the platform,i.e.,GOX@nGO-PEG-RhB and GOX@nGO-PEG-FITC.The microstructure and composite of platforms and enzyme-nanocomposites were confirmed by diverse characterizations.Finally,on account of corresponding cyclic voltammetric and typical ready-state amperometric curves,it was informed that GOX@nGO-PEG-RhB and GOX@nGO-PEG-FITC could effectively respond to the fluctuation of glucose level as electrochemical biosensor.The present work presents special platforms for the immobilization of enzymes like GOX and provides new-type biosensors in the detection of glucose levels.

A fan-shaped synthetic chiral nanographene

We report the synthesis and characterization of a fan-shaped chiral nanographene 1,which is composed of 6 hexabenzocoronene subunits with 216 conjugated carbon atoms.In the dehydrocyclization reaction,38 C–C bonds are formed simultaneously.1 exhibits strong panchromatic absorption from the ultraviolet to the near-infrared,with an absorption coefficient of 209,000 L mol^(-1)cm^(-1)at 564 nm.Optically pure samples,obtained via chiral HPLC,show distinct ECD signals(|Δε|=704 L mol^(-1)cm^(-1)at 405 nm).Upon excitation,1 emits near-infrared fluorescence at 820 nm with a quantum yield of 5.5%.These photophysical properties of 1 were analyzed with the assistance of DFT calculations.

Magnetism engineering of nanographene:An enrichment strategy by co-depositing diverse precursors on Au(111)

The magnetism of nanographene is dominated by the structure of its carbon skeleton.However,the magnetism engineering of nanographene is hindered due to finite precursors.Here,we demonstrate an ingenious synthetic strategy to engineer the magnetism of nanographene through hetero-coupling two precursors on Au(111)surface.Bond-resolved scanning tunneling microscopy and spectroscopy results show that two homo-coupled products host a closed-shell structure,while the products with five membered ring defects perform as an open-shell one with the total spin number of 1/2,confirmed by spin-polarized density functional theory calculations.While two hetero precursors on Au(111)substrate,the heterocoupled products both perform as the magnetic structure with total spin quantum numbers of 1/2 and 1,resulting from carbon skeleton transformations.Our work provides an effective way to engineer the magnetism of nanographene by enriching the magnetic products simultaneous,which could be extended into other controllable magnetic nanographene instruction.

D^(6h)Symmetric Radical Donor-Acceptor Nanographene Modulated Interfacial Carrier Transfer for High-Performance Perovskite Solar Cells

Imbalanced charge-carrier extraction remains an issue aggravating interfacial charge accumulation and recombination.More hopping transport channels could accelerate the extraction of charge.Here,we demonstrated an effective“bridging interface”strategy between the perovskite/2,2′,7,7′-tetrakis(N,N-di-pmethoxyphenylamine)-9,9′-spirobifluorene(spiro-OMeTAD)that modulates interfacial charge transfer and improves hole mobility using radical-containing donor-acceptor nanographenes(D-A NGs)possessing electron-deficient perchlorinated NGs and electron-rich aniline derivatives.The fully delocalized backbone of nanographene formed a conjugated bridge for intermolecular charge transfer and generated stable radical cations,verified by electron spin resonance.Lamellar andπ-πstacking orientation of D-A NGs also provided advantageous hopping transport channels.Besides favorable charge transfer within D-A NGs,systematic explorations indicated a strong interface coupling and noticeable charge transfer across the D-A NGs and perovskite interface,where electrons would flow from D-A NGs to perovskite,and holes would flow from perovskite to D-A NGs.Moreover,the hole mobility of spiro-OMeTAD was also enhanced because the D-A NGs would diffuse into the spiro-OMeTAD layer.As a result,planar n-i-p perovskite solar cellsmodified byD-ANG-OMe/D-ANG-tBudeliveredchampion power conversion efficiencies(PCEs)of 23.25%and 23.51%,respectively.

Merging a Negatively Curved Nanographene and a Carbon Nanoring

Two molecular nanocarbons result from merging a negatively curved nanographene and a carbon nanoring in two constitutional isomers of D2 and C2v symmetry,respectively.They were synthesized by attachment o f C-shaped paraphenylene precurso rsto 2,11,18,27-tetrabromooctabenzo[8]circulene and the subsequent intramolecular Yamamoto coupling and reductive aromatization reactions.The flexible nature of octabenzo[8]circulene enabled two different ways of connection in the Yamamoto coupling reactions,leading to the two constitutional isomers.The D2 isomer is shaped like a figure eight,as revealed by X-ray crystallography,and is resolved into two enantiomers by chiral HPLC.The synthesis of the C2v isomer is regarded as a further step toward precision synthesis of carbon schwarzites through a bottom-up approach.

Polycyclic aromatic hydrocarbons in the graphene era

Polycyclic aromatic hydrocarbons(PAHs) have been the subject of interdisciplinary research in the fields of chemistry, physics,materials science, and biology. Notably, PAHs have drawn increasing attention since the discovery of graphene, which has been regarded as the "wonder" material in the 21 st century. Different from semimetallic graphene, nanoscale graphenes, such as graphene nanoribbons and graphene quantum dots, exhibit finite band gaps owing to the quantum confinement, making them attractive semiconductors for next-generation electronic applications. Researches based on PAHs and graphenes have expanded rapidly over the past decade, thereby posing a challenge in conducting a comprehensive review. This study aims to interconnect the fields of PAHs and graphenes, which have mainly been discussed separately. In particular, by selecting representative examples, we explain how these two domains can stimulate each other. We hope that this integrated approach can offer new opportunities and further promote synergistic developments in these fields.

Electrochemically derived nanographene oxide activates endothelial tip cells and promotes angiogenesis by binding endogenous lysophosphatidic acid

Graphene oxide(GO)exhibits good mechanical and physicochemical characteristics and has extensive application prospects in bone tissue engineering.However,its effect on angiogenesis is unclear,and its potential toxic effects are heavily disputed.Herein,we found that nanographene oxide(NGO)synthesized by one-step water electrolytic oxidation is smaller and shows superior biocompatibility.Moreover,NGO significantly enhanced angiogenesis in calvarial bone defect areas in vivo,providing a good microenvironment for bone regeneration.Endothelial tip cell differentiation is an important step in the initiation of angiogenesis.We verified that NGO activates endothelial tip cells by coupling with lysophosphatidic acid(LPA)in serum via strong hydrogen bonding interactions,which has not been reported.In addition,the mechanism by which NGO promotes angiogenesis was systematically studied.NGO-coupled LPA activates LPAR6 and facilitates the formation of migratory tip cells via Hippo/Yes-associated protein(YAP)independent of reactive oxygen species(ROS)stimulation or additional complex modifications.These results provide an effective strategy for the application of electrochemically derived NGO and more insight into NGO-mediated angiogenesis.

Three-dimensional spongy nanographene-functionalized silicon anodes for lithium ion batteries with superior cycling stability

An innovative spongy nanographene （SG） shell for a silicon substrate was prepared by low-temperature chemical vapor deposition on a hierarchical nickel nanotemplate. The SG-functionalized silicon （Si@SG） composite shows outstanding properties, which may be helpful to overcome issues affecting current silicon anodes used in lithium ion batteries such as poor conductivity, large volume expansion and high mass transfer resistance. The hierarchical nanographene shell exhibits elastic, sponge-like features that allow it to self-adaptively change its volume to accommodate the volume expansion of silicon. In addition, the porous, spongy framework containing randomly stacked graphene nanosheets presents low diffusion barriers and provides sufficiently free and short-haul channel segments to allow the fast migration of Li and electrolyte ions. The unique properties of the present silicon anode result in excellent electrochemical performances in terms of long-term cycling stability （95% capacity retention after 510 cycles）, rate performance, and cycling behavior for high mass loadings at different current densities.

Stimulus-responsive water soluble synthetic nanographene

Nanographenes(NGs)are exceptionally hydrophobic.They are insoluble in water,preventing the exploration and utilization of their photophysical properties under aqueous conditions.This work discloses an atomically precise water-soluble synthetic NG1,featuring a 2 nm sp^(2) carbon skeleton appended with 12 branched triethylene glycol chains.It synergistically combines low critical solution temperature(LCST)behavior and a photothermal effect to create the first thermo-and photo-responsive atomically precise NG functioning in an aqueous solution.The LCST behavior can be attributed to a delicate balance of hydrophobic-hydrophilic interactions,providing a sensitive thermal response to changes over a temperature range of physiological interest(close to 37℃).Moreover,1 has considerable photothermal conversion capability,with irradiation of 1 in water by red or near infrared light increasing the solutions temperature to above the clouding point within seconds,leading to a reversible clear-to-turbid transition over many cycles without evident fatigue.

On-Surface Stereochemical Characterization of a Highly Curved Chiral Nanographene by Noncontact Atomic Force Microscopy and Scanning Tunneling Microscopy

A highly distorted chiral nanographene structure composed of triple corannulene-fused[5]helicenes is prepared with the help of the Heck reaction and oxidative photocyclization with an overall isolated yield of 28%.The complex three-dimensional(3D)structure of the bowl-helix hybrid nanostructure is studied by a combination of noncontact atomic force microscopy(AFM)and scanning tunneling microscopy(STM)on the Cu(111)surface,density functional theory calculations,AFM/STM simulations,and high-performance liquid chromatography-electronic circular dichroism analysis.This examination reveals a molecular structure in which the three bowl-shaped corannulene bladesd position themselves in a C3-symmetric fashion around a highly twisted triphenylene core.The molecule appears to be shaped like a propeller in which the concave side of the bowls face away from the connected[5]helicene motif.The chirality of the nanostructure is confirmed by the direct visualization of both MMM and PPP enantiomers at the single-molecule level by scanning probe microscopies.These results underline that submolecular resolution imaging by AFM/STM is a powerful real-space tool for the stereochemical characterization of 3D curved chiral nanographene structures.