Delocalized excitons govern the optoelectronic properties of molecular materials, yet the real-space reconstruction of their wave functions-the spatial distribution of amplitude and phase-has remained a long-standing scientific goal. Here, we demonstrate that scanning tunneling microscopy-induced luminescence enables real-space reconstruction of amplitude and phase of delocalized excitonic states in molecular chains. Through subnanometer-resolved photon imaging of linear molecular chains, coherent purely excitonic (0-0) emission patterns reveal the wave function's relative phases, while incoherent vibronic (0-1) emission maps the squared wave function amplitudes. This near-field technique enables the reconstruction of wave functions for both bright superradiant states and optically dark subradiant states inaccessible by conventional far-field optics. Furthermore, the submolecular resolution of the vibronic maps allows for the contributions of different vibrational symmetries, namely, Franck-Condon and Herzberg-Teller modes, to be distinguished. Our findings establish a unique approach for the excitonic wave function reconstruction and open a route for exploring exciton dynamics and interactions in molecular systems.

Electric field-induced chemistry at the solid/vacuum interface has distinct advantages over enzyme- and electrocatalysis because chemical reactivity is solely governed by external electrical fields (EEFs), while other factors such as solvent and ion effects are ruled out. Intense EEFs on the order of 109 V m-1 are generated between the metal tip of a scanning tunneling microscope (STM) and a single-crystalline metal surface. Reactive centers can be aligned along the direction of the EEF, that is, orthogonal to the metal surface, for experiencing the maximum field. Here, a strategy is introduced to achieve this: a terminal alkyne as a reactive center is connected to the sp3-hybridized core of a triphenylmethane-based rigid molecular tripod chemisorbed on Au(111), while its upright configuration is probed experimentally by low-temperature (LT) ultrahigh-vacuum (UHV) single-molecule STM and STM-based tip-enhanced Raman scattering (TERS) in conjunction with density functional theory (DFT). The orientation of the alkyne moiety relative to the surface normal is inferred from STM height profiles and particularly the Raman intensity of the dominant C≡C stretching peak. The upright configuration and stability of the alkyne reactive center in the presence of intense EEFs paves the way for future E-field-induced chemistry monitored in situ by TERS.

Manipulating the electroluminescence of organic molecules is important for the development of advanced organic light-emitting diodes (OLEDs). Here, we demonstrate a single-molecule sensitization strategy to brighten an otherwise-weak molecular emitter by using the scanning tunneling microscope induced luminescence (STML) technique. We show that while the free-base phthalocyanine (H2Pc) molecule is a bright emitter, the molecule upon double deprotonation ([Pc]2−) exhibits electroluminescence that is suppressed by three orders of magnitude. The extremely weak emission of [Pc]2− is traced to a misalignment of its frontier orbitals with the substrate, which fundamentally shifts the excitation from an efficient carrier-injection mechanism in H2Pc to an inefficient inelastic electron scattering process in [Pc]2−. However, by bringing a zinc-phthalocyanine (ZnPc) molecule close to it to form a donor–acceptor dimer (ZnPc–[Pc]2−), we introduce an intermolecular energy transfer pathway that enhances the luminescence of [Pc]2− by approximately 135-fold. Furthermore, combined with theoretical calculations, the dependence of STML spectra on the intermolecular distances (d) indicates that the energy-transfer mechanism is dominated by Förster resonance energy transfer. Our findings demonstrate a viable strategy for overcoming molecular-level charge-injection limitations and provide actionable guidelines for designing OLED architectures with enhanced luminescence efficiency.

Determining the chemical structure for a single molecule on surface from spectroscopic data represents a challenging high-dimensional inverse problem. Tip-enhanced Raman spectroscopy (TERS) enables chemically specific imaging of single molecules with sub-nanometer spatial resolution, yet reconstructing complete molecular structures from TERS maps remains difficult owing to the ambiguous vibrational signatures and reliance on expert interpretation. Here, we introduce TERS-ABNet, a deep-learning framework that formulates single-molecule structure determination from spectroscopic images as an image-to-graph inference task. Using a "two-track" architecture, the model jointly predicts probabilistic atom and bond maps, enabling direct construction of explicit atom-bond graphs without relying on predefined chemical rules. Trained on simulated datasets, TERS-ABNet achieves about 94

Host-guest doping has emerged as a facile and efficient strategy for the fabrication of organic room-temperature phosphorescence (RTP) materials. Nonetheless, how the chemical structures of dopants and matrices systematically influence the triplet exciton dynamics of solid-state materials remains elusive. While investigations have been focusing on electronic structures and energy levels, here we show that doped phenothiazine model systems largely follow the well-known principle of “like dissolves like” and exhibit phase-separation-controlled photophysical state switching between RTP and triplet-triplet annihilation delayed fluorescence (TTA-DF), evidenced by scanning electron microscopy, confocal microscopy, and micro-region spectrometry. In the structurally similar host-guest combination, the miscible solid solution exhibits strong guest RTP emission; in the thermodynamically favored microphase-separated state, the RTP is severely outcompeted by TTA-DF of the guest aggregate, which has significantly faster decay kinetics. Microscopy results show that simple mechanical force by gentle grinding is sufficient to partially amorphize the nanophase-separated crystalline sample and promote intense host-sensitized guest RTP. This work demonstrates that, in addition to quantum mechanical considerations, thermodynamic rules provide the crucial missing link to predictably govern structural morphology and macroscopic luminescence in doped organic crystals, laying a more complete foundation for the design of dynamically tunable, stimuli-responsive RTP materials.

We report the development of a cryogen-free, low-temperature optical-coupled scanning probe microscope (LT-OC-SPM) designed for high-resolution multimodal imaging and spectroscopy. To mitigate the mechanical vibrations from the cryocooler cold head, we implement a remote liquefaction scheme that effectively decouples the noise from the tunneling junction. The system achieves a stable base operation temperature below 3K and a tunneling current noise level under 20 fA/Hz1/2, comparable to the performance of the conventional SPM systems employing bath cryostats. Moreover, our system features a customized rigid scanner integrated with in-vacuo piezo-driven high-numerical aperture lenses, facilitating simultaneous topographic and spectroscopic measurements. Multimodal characterization of silver phthalocyanine (AgPc) molecules on Ag(110) demonstrates ångström scale probing of intramolecular structure and localized vibrational modes, highlighting the versatility of our system in high-resolution surface characterization. Consequently, this remote liquefaction architecture provides a sustainable, high-performance cryogen-free platform for ångström-resolved spectroscopic imaging, establishing a robust foundation for future multifunctional near-field optical spectroscopy.

Exciton coherence is a phenomenon involving collective electronic transition dipole moments of molecular aggregates with interesting photophysical behaviors such as superradiance and subradiance in J- and H-type aggregates, respectively. Although singlet aggregate excitons have been extensively studied, the understanding of triplet exciton coherence in terms of specific conditions is still lacking due to limited experimental observations. Here, by synthesizing model organic compounds of fluorene monomer, dimer, trimer, and polymer, we systematically studied their photoluminescence in both solution and aggregation states. Strong triplet exciton coherence is present in polyfluorene aggregates, including nanoparticles, microparticles, and thin films, and is manifested either as HJ-aggregate phosphorescence or delayed fluorescence depending on the size of these aggregates. Notably, in the phosphorescence state, the polyfluorene polymer exhibits an unusually sharp atomic-spectrum-like emission band with a narrow full width at half maximum (FWHM) of only 0.05 eV (14 nm) and the longest lifetime of 0.63 s. This study shows that the size of organic aggregates is essential in dictating organic exciton dynamics in the solid state and holds importance for the development of advanced optoelectronic technologies.

Natural photosynthesis inspires the design of artificial cyclic light-harvesting architectures, yet probing their excitonic behaviors-particularly optically dark states-remains challenging for far-field optics due to diffraction limits and dipole selection rules. Here, combining scanning tunneling microscope manipulation with tip-enhanced photoluminescence, we visualize discrete excitonic states in constructed cyclic zinc-phthalocyanine architectures with sub-nanometer resolution. By controlling intermolecular distances, we map excitonic evolution across weak, intermediate, and strong coupling regimes. We uncover a transition dipole rotation phenomenon arising from the molecules' orthogonal, degenerate dipoles, which facilitates coherent intermolecular coupling. Furthermore, by comparing hollow and solid architectures, we demonstrate that the molecular architectures determine the nature of the lowest-lying excitonic state: a hollow ring possesses an optically dark lowest-lying state, whereas a solid architecture features a bright one, highlighting a possible structural physical advantage of hollow cyclic architectures for suppressing radiative losses. These findings provide guidelines for designing organic architectures with high energy transfer efficiencies.

The functions of biomolecules such as DNA are not only determined by their sequences but also strongly dependent on their stereostructures and geometric configurations of constituent units. However, most DNA sequencing techniques developed to date heavily rely on fluorescent labeling and extensive replication, and the DNA chains might thus be unwound and even modified during these treatments, resulting in the loss of structural information. Recent development of single-molecule tip-enhanced Raman spectroscopy (TERS) offers a label-free approach to identifying individual nucleobases with both high spatial resolution and chemical sensitivity but amounts to mainly proof-of-principle demonstrations of very short single-stranded DNA molecules. Here, we propose an algorithm-assisted strategy for determining the structures of long-chain DNA molecules based on TERS imaging in real space. We first develop a matching algorithm to rapidly simulate the TERS spectra and mapping images for long-chain DNA containing tens of thousands of atoms, circumventing the huge computational cost of the quantum chemistry simulation of large molecules. After validating the accuracy and efficiency of this algorithm in various DNA molecular systems, we further combine it with the Bayesian algorithm to determine the experimental molecular structures with single-nucleobase precision from the TERS measurements on two long-chain ssDNA model systems on surfaces, showing a general agreement between theories and experiments. Our approach will promote the machine-learning assisted TERS technique as a generic tool to identify the sequence and configuration of complicated biomolecular systems, including long DNA/RNA chains, proteins, and even glyco-peptide complexes.

RNA modifications play critical roles in epitranscriptomic processes such as RNA stability, localization, translation efficiency, and splicing by altering RNA structures and interactions. Identifying these modifications at single-base resolution is highly desirable for understanding their functions and mechanisms. However, traditional sequencing-based methods (such as antibody enrichment or chemical derivatization) suffer from indirect labeling and bulk analysis limitations, whereas the nanopore sequencing method lacks spatial resolution for distinguishing adjacent modified nucleotides. Tip-enhanced Raman spectroscopy (TERS) offers a promising solution to this end by combining high spatial resolution with sensitive chemical specificity. Unlike sequencing-based methods, TERS can directly probe the intrinsic vibrational fingerprint of RNA molecules without chemical labeling, enabling real-space imaging of modification sites in their native configurations. Recent advancements in TERS have demonstrated its ability to spectrally resolve nucleobases in single-stranded DNA, but direct real-space identification of RNA modifications with single-base resolution still remains out of reach experimentally. Here, we explore the capability of TERS to identify the modification sites of pseudouridine (Psi) in two exemplified RNA molecules that are artificially synthesized. By measuring the TERS spectra of unmodified uracil (U) and modified Psi, their structural differences can be distinguished through respective vibrational fingerprints, particularly the characteristic vibrational modes associated with the splitting of C=O stretching peaks. Spatially resolved TERS spectra further enable both the identification of Psi and its localization in a long RNA sequence. Our results demonstrate the potential of TERS as a tool for identifying different types of RNA modifications.

Photocatalytic seawater splitting is an attractive way for producing green hydrogen.Significant progresses have been made recently in catalytic efficien-cies,but the activity of catalysts can only maintain stable for about 10 h.Here,we develop a vacancy-engineered Ag3PO4/CdS porous microreactor chip photocatalyst,operating in seawater with a performance stability exceeding 300 h.This is achieved by the establishment of both catalytic selectivity for impurity ions and tailored interac-tions between vacancies and sulfur species.Efficient transport of carriers with strong redox ability is ensured by forming a heterojunction within a space charge region,where the visualization of potential distribution confirms the key design concept of our chip.Moreover,the separation of oxidation and reduction reactions in space inhibits the reverse recombination,making the chip capable of working at atmos-pheric pressure.Consequently,in the presence of Pt co-catalysts,a high solar-to-hydrogen efficiency of 0.81％can be achieved in the whole durability test.When using a fully solar-driven 256 cm2 hydrogen production prototype,a H2 evolution rate of 68.01 mmol h-1 m-2 can be achieved under outdoor insolation.Our findings provide a novel approach to achieve high selectivity,and demonstrate an efficient and scalable prototype suitable for practical solar H2 production.

Surface-enhanced Raman spectroscopy (SERS) has evolved significantly over fifty years into a powerful analytical technique. This review aims to achieve five main goals. (1) Providing a comprehensive history of SERS's discovery, its experimental and theoretical foundations, its connections to advances in nanoscience and plasmonics, and highlighting collective contributions of key pioneers. (2) Classifying four pivotal phases from the view of innovative methodologies in the fifty-year progression: initial development (mid-1970s to mid-1980s), downturn (mid-1980s to mid-1990s), nano-driven transformation (mid-1990s to mid-2010s), and recent boom (mid-2010s onwards). (3) Illuminating the entire journey and framework of SERS and its family members such as tip-enhanced Raman spectroscopy (TERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and highlighting the trajectory. (4) Emphasizing the importance of innovative methods to overcome developmental bottlenecks, thereby expanding the material, morphology, and molecule generalities to leverage SERS as a versatile technique for broad applications. (5) Extracting the invaluable spirit of groundbreaking discovery and perseverant innovations from the pioneers and trailblazers. These key inspirations include proactively embracing and leveraging emerging scientific technologies, fostering interdisciplinary cooperation to transform the impossible into reality, and persistently searching to break bottlenecks even during low-tide periods, as luck is what happens when preparation meets opportunity.

Surface with well-defined components and structures possesses unique electronic, magnetic, optical and chemical properties. As a result, surface chemistry research plays a crucial role in various fields such as catalysis, energy, materials, quantum, and microelectronics. Surface science mainly investigates the correspondence between surface property and functionality. Scanning probe microscopy (SPM) techniques are important tools to characterize surface properties because of the capability of atomic-scale imaging, spectroscopy and manipulation at the single-atom level. In this review, we summarize recent advances in surface electronic, magnetic and optical properties characterized mainly by SPM-based methods. We focus on elucidating the π-magnetism in graphene-based nanostructures, construction of spin qubits on surfaces, topology properties of surface organic structures, STM-based light emission, tip-enhanced Raman spectroscopy and integration of machine learning in SPM studies.

Since the electronic and optical properties of two-dimensional (2D) transition-metal dichalcogenides (TMDs) are highly susceptible to mechanical deformations, it is very important to understand how the geometries, band structures, and excitonic dynamics are influenced under different strain conditions in TMDs, especially for nanowrinkles and nanobubbles with complex inhomogeneities in real space. Here, we proposed a general model to explore the influence of local strains on both the electronic and phononic band structures for various nanostructures. We demonstrate that the electronic bandgaps in nanotubes and nanowrinkles can be accurately predicted from the monolayer results by considering both the effects of tensile strain and curvature-induced flexoelectricity. The frequency shifts of intrinsic vibrational modes can be adopted as the indicator of local strains, while the newly emerged radial-breathing-like mode, originated from the out-of-plane acoustic phonons in a monolayer, is quite sensitive to the magnitude of curvature. This model is further generalized to the nanobubble structure, exhibiting smaller electronic bandgaps and lower vibrational frequencies in general, except for the radial-breathing-like mode, which shows the largest vibrational frequency at the center, consistent with the spatial distributions of local strains and curvatures in the nanobubble. Our findings establish a framework for predicting strain-induced spectral changes in complex nanostructures, guiding the design of strain-engineered optoelectronic devices based on 2D materials.

Probing quantum coherence in excitonic energy transfer (EET) is critical for understanding and designing advanced organic optoelectronic materials and devices. However, direct experimental evidence for coherent EET under ambient conditions remains elusive due to the complexity and losses inherent in molecular solids. Here, we demonstrate a straightforward steady-state photoluminescence spectroscopic approach that selectively probe coherent exciton populations in engineered organic doping systems. Using pyrene or anthracene derivatives as dopants (guest) within the crystal of a naphthalene derivative (host), the type of EET from the host to the guest is highly selective, governed by quantum coherence. Specifically, the coherent aggregate exciton population of the host is almost entirely depleted, whereas the host monomer emission largely persists in the presence of the guest dopant, despite the guest absorption being better matched to the host monomer emission. By chemically modifying the energy donor naphthalene, the populations of aggregate and monomer excitons of the host can be systematically tuned, which directly correlates with the sensitivity of the guest photoluminescence in doped host crystals. These findings have important implications for understanding exciton dynamics in optoelectronic devices.

Raman optical activity (ROA) spectroscopy is a powerful technique for chiral discrimination of enantiomeric compounds. Nevertheless, conventional ROA measurements always face fundamental limitations in sensitivities due to inherently weak chiroptical signals, making it very difficult to study the ROA properties of the single chiral molecules. Here, we propose a theoretical model to study the tip-enhanced ROA (TEROA), simulating the chiroptical responses of single molecules through differential detection of tip-enhanced Raman intensities under right-versus left-circularly polarized excitation. Due to the synergistic combination of plasmonic near-field enhancement and amplified optical chirality generation near the tip apex, the TEROA signal of a single chiral molecule can be enhanced by more than 8 orders of magnitude compared to conventional ROA configurations, enabling single-molecule TEROA detection sensitivity. Furthermore, the simulated TEROA mapping images exhibit similar spatial distributions to the optical chirality enhancement, confirming the critical role of plasmon-mediated superchiral nearfields in this enhancement mechanism. This fundamental understanding of the synergistic interplay between electromagnetic field enhancement and chirality density amplification in TEROA provides a transformative framework for next-generation ultrasensitive chiral spectroscopic analysis.

The chemical reactivity of molecules can be controlled by a variety of effects, ranging from chemical reagents to purely physical stimuli. Metal tips employed in scanning probe microscopy are an elegant tool to manipulate reactive centers in single molecules. However, to achieve excellent control over distance and orientation, it is crucial to immobilize the reactive center and align it along the direction of the tip. Here, we aligned a reactive alkyne center via a rigid triphenylmethane-based tripod for upright adsorption on Au(111) for inducing bond weakening in the alkyne moiety by approaching a silver tip. Single-molecule ultrahigh vacuum low-temperature tip-enhanced Raman scattering was employed for probing tip-induced bond weakening in the gap distance range from 550 to 250 pm. Both the equivalent to C-H stretching at similar to 3330 cm(-1) and the dominant -C equivalent to C- stretching peak at similar to 2130 cm(-1) exhibit a shift to smaller wavenumbers due to tip-induced bond weakening and an exponential increase in Raman intensity originating from the increased local electric field in the nanogap. To rationalize the underlying physical contributions and chemical effects of tip-induced bond weakening, density functional theory calculations for gap distances in the range 800 to 100 pm were performed. The computational results confirmed the presence of different gap distance regimes including the onset of Pauli repulsion for short distances; for the latter, the calculations additionally predict structural distortions of the terminal alkyne induced by the nearby metal tip. These findings allow us to set a lower limit for the tip-tripod gap distance in studies requiring an intact upright configuration of the alkyne-tripod, for example, electric field-induced chemistry.

Resolving the sequence and structure of flexible biomolecules such as DNA is crucial to understanding their biological mechanisms and functions. Traditional structural biology methods remain challenging for the analysis of small and disordered biomolecules, especially those that are difficult to label or crystallize. Recent development of single-molecule tip-enhanced Raman spectroscopy (TERS) offers a label-free approach to identifying nucleobases in a single DNA chain. However, a clear demonstration of sequencing both spatially and spectrally at single-base resolution is still elusive due to the challenges caused by weak Raman signals and the flexibility of DNA molecules. Here, we report a proof-of-principle demonstration to this end, spectrally resolving in real space individual nucleobases and their sequence structures within a short, single-stranded DNA molecule artificially designed. This breakthrough is achieved through the development of subnanometer-resolved low-temperature TERS methodology for such thermally unstable flexible biomolecules. Further TERS mapping over individual nucleobases provides additional structural information about the molecular configurations and even the locations of functional groups, offering a way to track modification types and binding sites in biomolecules.