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.

Ultrafast laser-induced decomposition for selective activation of GaAs

The manipulation of micro/nanostructures to customise their inherent material characteristics has garnered considerable attention.In this study,we present the selective activation of gallium arsenide(GaAs)via ultrafast laser-induced decomposition,which correlates with the emergence of ripples on the surface.This instigated a pronounced enrichment in the arsenic(As)concentration around the surface while inducing a depletion of gallium(Ga)at the structural depth.Theoretical simulations based on first principles exhibited a robust inclination towards the phase separation of GaAs,with the gasification of As-As pairs proving more facile than that of Ga-Ga pairs,particularly above the melting point of GaAs.As an illustrative application,a metal-semiconductor hybrid surface was confirmed,showing surface chemical bonding and surface-enhanced Raman scattering(SERS)through the reduction of silver ions on the laser-activated pattern.This laser-induced selective activation holds promise for broader applications,including the controlled growth of Pd and the development of Au/Ag alloy-based platforms,and thereby opens innovative avenues for advancements in semiconductors,solar cell technologies,precision sensing,and detection methodologies.

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.