Single-electron transport in H_(2)O@C_(60) single-molecule transistors

Single-molecule transistors(SMTs) based on fullerenes and their derivatives have been recognized as a long-sought platform for studying the single-electron transport properties.H_(2)O@C_(60) is a combination of fullerene and H_(2)O,a typical light molecule.Here we use the 'molecular surgery' technique to synthesize the H_(2)O@C_(60) molecule and then construct the H_(2)O@C_(60) SMTs,together with the C_(60) SMTs.Evidences for single-electron transport have been obtained in our measurements,including explicit Coulomb blockade and Coulomb oscillations.We then calculate the detailed parameters of the H_(2)O@C_(60) and C_(60) SMTs using a capacitance model derived from the Coulomb diamond feature,which gives a capacitance ratio of 1:5.05:8.52 for the H_(2)O@C_(60) SMT and 1:29.5:74.8 for the C_(60) SMT.Moreover,the gate efficiency factor a turns out to be 0.0686 in the H_(2)O@C_(60) SMT,about ten times larger than that in the C_(60) SMT.We propose that the enhanced gate efficiency in H_(2)O@C_(60) SMT may be induced by the closer attachment of molecular orbital electron clouds to the gate substrate due to polarization effects of H_(2)O.

Fe-substituted cobalt-phosphate polyoxometalates as enhanced oxygen evolution catalysts in acidic media

All-inorganic and earth-abundant bi-/trimetallic hydr(oxy)oxides are widely used as oxygen evolution electrocatalysts owing to their remarkable performance.However,their atomically precise structures remain undefined,complicating their optimization and limiting the understanding of their enhanced performance.Here,the underlying structure-property correlation is explored by using a well-defined cobalt-phosphate polyoxometalate cluster [{(Co4)(OH)3(PO4)}4(SiW9 O34)4]^32-(1),which may serve as a molecular model of multimetal hydr(oxy)oxides.The catalytic activity is enhanced upon replacing Co by Fe in 1,resulting in a reduced overpotential(385 mV) for oxygen evolution(by 66 mV) compared to that of the parent 1 at 10 mA cm^-2 in an acidic medium;this overpotential is comparable to that for the IrO2 catalyst These abundant-metal-based polyoxometalates exhibit high stability,with no evidence of degradation even after 24 h of operation.

Dynamic Variation of Excitonic Coupling in Excited Bilayer Graphene Quantum Dots

The intermolecular interaction determines the photophysical properties of the organic aggregates,which are critical to the performance of organic photovoltaics.Here,excitonic coupling,an important intermolecular interaction in organic aggregates,between theπ-stacking graphene quantum dots is studied by using transient absorption spectroscopy.We find that the spectral evolution of the ground state bleach arises from the dynamic variation of the excitonic coupling in the excitedπ-stacks.According to the spectral simulations,we demonstrate that the kinetics of the vibronic peak can be exploited as a probe to measure the dynamics of excitonic coupling in the excitedπ-stacks.

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.

Electrochemical hydrogen-storage capacity of graphene can achieve a carbon-hydrogen atomic ratio of 1:1

As a promising hydrogen-storage material,graphene is expected to have a theoretical capacity of 7.7 wt%,which means a carbon-hydrogen atomic ratio of 1:1.However,it has not been demonstrated yet by experiment,and the aim of the U.S.Department of Energy is to achieve 5.5 wt%in 2025.We designed a spatially-confined electrochemical system and found that the storage capacity of hydrogen adatoms on single layer graphene(SLG)is as high as 7.3 wt%,which indicates a carbon-hydrogen atomic ratio of 1:1 by considering the sp^(3) defects of SLG.First,SLG was deposited on a large-area polycrystalline platinum(Pt)foil by chemical vapor deposition(CVD);then,a micropipette with reference electrode,counter electrode and electrolyte solution inside was impacted on the SLG/Pt foil(the working electrode)to construct the spatially-confined electrochemical system.The SLG-uncovered Pt atoms act as the catalytic sites to convert protons(H^(+))to hydrogen adatoms(H_(ad)),which then spill over and are chemically adsorbed on SLG through surface diffusion during the cathodic scan.Because the electrode processes are reversible,the H_(ad) amount can be measured by the anodic stripping charge.This is the first experimental evidence for the theoretically expected hydrogen-storage capacity on graphene at ambient environment,especially by using H+rather than hydrogen gas(H_(2))as the hydrogen source,which is of significance for the practical utilization of hydrogen energy.

Isolation of a carbon nanohoop with Mobius topology

Carbon nanohoop,a class of constrained molecular architecture consisting of linked arene units,has attracted considerable interest from both experimental and theoretical chemists due to its synthetic challenge and aesthetic architectures.Another fascinating and synthetically challenging species,the Mobius-type molecule,has been attracting the scientific community with its elegant structure and aromaticity.Thus,combining two things together,synthesizing a carbon nanohoop with Mobius topology remains more challenging to date.Here we report a cyclophenylene featuring Mobius strip characterized by X-ray crystallography.Theoretical calculations reveal that such type of nanohoop is fully conjugated systems with electrons delocalized both inπsextets and the bridging carbon–carbon bonds.This work highlights that the manipulation of phenylene connection in a carbon nanohoop can help obtain more delicate and aesthetic molecular architectures.

Three-dimensional conjugated macrocycle with large polyaromatic blocks constructed by post-π-extension

Generally,the conjugated homo-macrocycles(CHMs)are synthesized by covalently linking the repeating subunits.However,large subunits are often difficult to conjugate together due to severe stereo-hindrance.Meanwhile,large polyaromatic blocks can not only incorporate its appealing electronic and optical properties into CHMs but also distort the CHMs from planar to three-dimensional(3D)molecular structure.Here we synthesized the 3D CHM composed of large polyaromatic units by post-π-extension.Specifically,cyclo-m-phenylenes,as the cyclic precursor,wereπ-extended by C-C coupling and then subjected to dehydrocyclization,affording cyclo-1,3-dibenzo[e,l]pyrenylenes(CMDP).The structures of CMDPs were unambiguously characterized by single crystal X-ray diffraction,showing a congested and strained 3D conformation,which was also confirmed by theoretical calculations.Compared with the monomer,CMDPs showed redshifted absorption and emission,as well as a ten-fold enhancement in photoluminescence quantum yield,which could be attributed to their 3D conformation.