Interfacial coupling governs the emergent functionality of two-dimensional (2D) organic-inorganic heterostructures, underpinning advances in linear optoelectronics such as photovoltaics. However, extending this control to the nonlinear optical regime remains elusive, as it requires driving the coherent nonlinear polarization of the inorganic lattice using molecular states, which is distinct from the incoherent charge transfer exploited in linear devices. Here we report a giant second-harmonic generation (SHG) response driven purely by interfacial near-field dipole coupling in an α‑perylene organic crystal (α‑Pe)/WS2 heterostructure. We show that the specific crystalline anisotropy of the organic layer creates a polarization-tunable antenna, where anisotropic dipole-dipole coupling efficiently channels excitation energy into the WS2 layer to drive the nonlinear process. This mechanism yields a spatially uniform, giant effective second-order susceptibility χ eff ( 2 ) approaching ~ 20 nm V-1 in monolayers and, notably, induces interfacial symmetry breaking to activate robust SHG in nominally centrosymmetric bilayer WS2. Our results establish organic-inorganic interfacial coupling as a generalizable lever for engineering nonlinear optical responses; given the vast abundance of molecular crystals with distinct dipolar symmetries, this strategy offers a scalable route to compact, chemically designable on-chip nonlinear photonic systems.

Aqueous zinc-iodine batteries are promising candidates for grid scale energy storage due to high energy density, good safety and cost-effectiveness. Nevertheless, polyiodide shuttle effect and susceptibility of I+ to hydrolysis severely impede their practical applications. In this work, conjugation effect is coupled into iodine conversion reaction via anion-π interaction to simultaneously immobilize polyiodides/ICl2- anions and modulate I-/I0/I+ conversion kinetics. Experimental results combined with theoretical calculations reveal that methylene blue (MB) cation with π-acidic conjugated system tightly binds to polyiodide and ICl2- anion via strong anion-π interaction, which effectively suppresses polyiodides shuttle effect and I+ hydrolysis, hence ensuring reversibility of I-/I0/I+ conversion reaction. Moreover, the conjugated MB cation with highly mobile and homogeneous delocalized electron can serve as redox mediator to accelerate the iodine conversion with the aid of anion-π interaction, thus improving electrochemical kinetics. As a consequence, the batteries exhibit a specific capacity of 365.5 mAh g-1 at 2 A g-1 (based on the mass of iodine) and achieve ultralong cycling life of 0.10 million cycles with 65.2% capacity retention at a high rate of 40 A g-1. This study provides valuable insights into the conjugation effect-mediated iodine conversion for high-performance aqueous zinc-iodine batteries.

A gated integrating laser-combined scanning tunneling microscope has been developed for high-fidelity investigation of photophysical processes at the atomic scale. This instrument integrates a low-repetition-rate, high-pulse-energy laser with a synchronized gated-integration scheme, enabling selective extraction of the laser-induced tunneling current. To demonstrate its performance, atomically resolved topography and surface photovoltage mapping were simultaneously obtained on the Si(111)-(7 × 7) surface. The surface photovoltage distribution is found to be strongly correlated with the underlying atomic structure. In addition, a highly localized enhancement of the laser-induced tunneling current is observed at a specific single-atom defect site. Detailed analysis, supported by local density of states measurements, reveals that this defect possesses an unusually high density of deep valence-band states. This distinctive electronic structure likely promotes Auger recombination between photogenerated holes accumulated under positive sample bias and electrons tunneling from the tip, thereby giving rise to the observed increase in the local tunneling current.

A polarization rotator is designed and fabricated to rotate the polarization direction of an electromagnetic wave to an arbitrary angle. The device employs a mirror-symmetric, paired periscopic architecture composed entirely of reflective elements, which enables operation over a broad wavelength range. Linearly polarized lasers spanning the visible, near-infrared, and mid-infrared regions are used to validate its broadband compatibility and high orientational accuracy. Extinction-ratio measurements confirm effective preservation of polarization, meeting the requirements of most optical applications.

Vibrationally promoted electronic resonance offers a powerful strategy for modulating the electronic properties of molecular systems through vibrational-electronic (vibronic) coupling. A detailed understanding of the underlying coupling dynamics is essential for elucidating excited-state relaxation pathways. In this study, we investigate the influence of vibrational excitation on the electronic response of coumarin 6 using mode-selective mid-infrared (IR) pre-excitation fluorescence spectroscopy, complemented by IR/visible (IR/Vis) and IR/IR transient absorption techniques. Significant enhancements in both absorption and fluorescence are observed, particularly on the red edge of the electronic transition. Two distinct mechanisms contribute to these enhancements: (1) a nonlinear multi-photon absorption process, which dominates at low visible photon energies and when IR and visible pulses are temporally overlapped; and (2) a vibrationally excited population effect, which prevails at shorter visible wavelengths and persists over picosecond timescales, strongly influencing electronic excitation efficiency. Notably, the maximum enhancement in visible photon absorption arising from the vibrational population effect is orders of magnitude greater than that produced by nonlinear optical contributions. The interplay of these mechanisms yields several key observations: (1) a delay-dependent peak shift in the visible absorption enhancement; (2) a maximum fluorescence enhancement of approximately 10 times at a visible excitation wavelength of 515 nm; and (3) the appearance of two temporally distinct enhancement peaks in both absorption and fluorescence upon IR excitation at 1620 cm-1. The close correlation between IR-induced changes in visible absorption and fluorescence indicates that fluorescence can serve as a sensitive proxy for transient absorption dynamics. This work provides fundamental insight into vibrationally mediated modulation of electronic transitions and demonstrates the potential for controlling fluorescence through dual-mode excitation. These findings advance our understanding of vibronic coupling dynamics and open new avenues for applications in molecular sensing, photochemical control, and bond-selective fluorescence imaging.

Singlet-triplet intersystem crossing (ISC) underlies key processes in photovoltaics, photocatalysis, and photochemistry and is conventionally attributed to spin-orbit coupling (SOC) treated as a purely electronic interaction. In reality, strong coupling among electronic, spin, and vibrational motions can allow nuclear dynamics to modulate SOC, usually called vibronic SOC. Despite the fact that a considerable number of synthesized materials have demonstrated that vibronic SOC plays a key role in enhancing ISC, experimental approaches for direct manipulating such vibrationally mediated SOC have been lacking. Here, we report a direct experimental approach that proved vibrational excitation can enhance SOC and accelerate singlet-triplet intersystem crossing. Using a BODIPY sensitizer in a triplet-triplet annihilation upconversion system, selective mid-infrared excitation of skeletal modes increases upconversion emission by 156%, driven by the acceleration of ISC. Time-resolved mid-infrared spectroscopy and density functional theory reveal that these gains arise from vibrationally strengthened SOC, establishing a clear mechanistic link between specific nuclear motions and spin dynamics.

Rational design of electrode-electrolyte interfaces is central to achieving an efficient oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells. Here we demonstrate that 7-alkyltheophyllines are a group of bifunctional molecular additives capable of enhancing ORR activity on Pt(111) in the presence of strongly binding anions, for example, sulfonate in Nafion and phosphate, by enhancing intrinsic ORR kinetics and suppressing the specific adsorption of anions. Single-crystal voltammetric analysis and computational investigations reveal that the enhanced intrinsic ORR kinetics by adsorbed 7-alkyltheophyllines stems from facilitating the reduction of *O to *OH, which is a kinetically important step in the ORR on Pt surfaces. Mechanistic insights regarding the molecular additives gained on Pt(111) are shown to be valid on polycrystalline Pt. Finally, the practical relevance of this discovery is demonstrated by substantial performance enhancements in proton-exchange membrane fuel cells with Pt/C catalysts modified by 7-ethyltheophylline, highlighting the transferability of fundamental insights.

Crystallization from solution is commonly described in terms of direct nucleation from dispersed monomeric species, yet this picture becomes inadequate when strong coordination or solvation suppresses free-particle formation. Here we resolve the growth pathway of Pt nanoparticles formed by CO-mediated reduction of Pt precursors using real-time mass spectrometry, infrared and UV-vis spectroscopy, ultrafast chemical exchange measurements, and theory. We show that classical monomer-based nucleation is bypassed: strong Pt-CO coordination stabilizes metastable multinuclear clusters, with [Pt3(CO)6]n2- (n = 4) emerging as a dominant intermediate. Rather than acting as seeds, these clusters undergo a collapse-reassembly process upon oxidation, in which partial ligand loss generates locally concentrated, coordinatively unsaturated Pt fragments that rapidly reorganize into crystalline nanoparticles, enabling growth without the entropic penalty of stochastic atom aggregation. This mechanism may be broadly relevant to nanoparticle formation under strong coordination and redox-active conditions, and may also extend to crystallization processes in strongly solvated systems like ions in aqueous solutions, where transient, non-equilibrium clusters mediate the transition from molecular precursors to extended crystalline matter.

Carotenoid (Car) in photosynthesis plays an essential role in photoprotection by quenching chlorophyll triplet excitation (3Chl*) via a Chl-to-Car triplet energy transfer (TET). However, mechanistic studies on the Car triplet photoprotection (CTP) have been complicated by the involvement of the O2 quenching and the complexity of the thylakoid membrane. To clarify the interplay of the TET with the effects of O2 and lipid-protein interaction, we prepared nanodiscoidal lipid-protein assemblies of the light-harvesting complexes of photosystem II (LHCII) of Bryopsis corticulans and spinach and examined their triplet excitation dynamics in a broad temporal regime of 1-105 ns. For both kinds of LHCII complexes, besides the well-known ultrafast TET at both L1 and L2 sites, an O2 insensitive, slow TET reaction at the L1 (but not L2) site proceeding with a time constant of 11-25 ns was verified. Lipid membranes can substantially accelerate the slow TET reaction and prolong the 3Car* lifetime. On the other hand, both kinds of LHCII complexes bear a minor fraction of Car-unquenchable 3Chl*, i.e., 2.2% and 4.6% (1.5% and 2.2%) for Bry. corticulans (spinach) LHCII complexes in lipid and aqueous phases, respectively, which can be fully quenched by O2. In addition, the lipid membrane promotes the O2 accessibility of LHCII proteins and, compared to L2, the L1 site is (30-130)% more permissive to O2 access. The heterogeneous 3Chl* deactivation pathways and CTP potency of Bry. corticulans and spinach are compared.

Metal-to-ligand charge transfer (MLCT) emission is prevalent in metal complexes. Compared with the famous singlet and triplet MLCT emissions, doublet MLCT (2MLCT) emission is rarely reported and remains uncertain. Herein, trivalent cerium (Ce(III)) is chosen as the protagonist, and we demonstrate a well-designed Ce(III) complex showing unambiguous 2MLCT emission. With gradual lowering of the energy level of dithio-imidodiphosphinate ligands, three Ce(III) complexes Ce-S2ipR (R = Cy, CyPh, and Ph) display luminescent mechanism switching from conventional 5d-4f transition to 2MLCT emission. The 2MLCT emitter Ce-S2ipPh exhibits a broad emission band and solvent-polarity-dependent emission maxima, being different from the 5d-4f emitters Ce-S2ipCy and Ce-S2ipCyPh. Besides experimental proof, time-dependent density functional theory (TD-DFT) calculations were also conducted to validate the 2MLCT essence. The demonstration of the Ce(III) complex with a new luminescence mechanism may provide the possibility of designing highly efficient lanthanide 2MLCT emitters and give new insight into both doublet and MLCT emission materials.

Bryopsis (Bry.) corticulans is a marine green alga thriving in the intertidal zone. To utilize the underwater blue-green light, its major light-harvesting antenna LHCII adopts a high composition of chlorophyll (Chl) b and the keto-carotenoid (Car), siphonin (Spn), and siphonaxanhin (Spx). This work is intended to examine the intracomplex, ultrafast excitation transfer dynamics under blue-light excitation, emphasizing on the influence from the biomimicking lipid environment. From BryLHCII solubilized in aqueous phase to that embedded in a lipid-membrane nanodisc (mnd-BryLHCII), the overall singlet excitation transfer (SET) efficiency drops for (5∼13)% over 400-550 nm. Femtosecond time-resolved absorption spectroscopy and comprehensive spectral analysis reveal highly heterogeneous excitation relaxation pathways in terms of pigments and their binding sites in both LHCII preparations. With reference to BryLHCII, mnd-BryLHCII switches off the Spx521 S1 and the neoxanthin S1 pathways of Car-to-Chl a SET, whereas it keeps the S1 pathways of Spn520 and Spx522 active and even accelerated. Thus, the functionality of Spn520 at L1 and Spx521 at L2 is oriented toward light harvesting and triplet photoprotection, respectively. In addition, a minor portion of Chl b in mnd-BryLHCII fails to transfer the Qy excitation to the lowest-energy cluster of Chls, i.e., the terminal emitter. The inactivated or deficient SET pathways account for the observed decline in SET efficiency. Our findings demonstrate the role of the lipid environment in optimizing the light-harvesting and photoprotective functions of the pigment cofactors of the algal LHCII complex, shedding light on deeper understanding of the underlying molecular mechanisms.

Chlorophyll (Chl) is the most abundant light-harvesting pigment of oxygenic photosynthetic organisms; however, the Q-band energetics and relaxation dynamics remain unclear. In this work, we have applied femtosecond time-resolved (fs-TA) absorption spectroscopy in 430-1,700 nm to Chls a and b in diluted pyridine solutions under selective optical excitation within their Q-bands. The results revealed distinct near-infrared absorption features of the Bx,y <- Q y and Bx,y <- Q x transitions in 930-1,700 nm, which together with the steady-state absorption in 400-700 nm unveiled the Qx(0,0)-state energy that lies 1,000 +/- 400 and 600 +/- 400 cm-1 above the Qy(0,0)-state for Chls a and b, respectively. In addition, the Q x -to-Q y internal conversion time constants are estimated to be less than 80 fs for Chls a and b. These findings may shed light on understanding the roles of the Chls in the primary excitation energy transfer reactions of photosynthesis.

The light-harvesting complex of photosystem II (LHCII) plays the dual roles of photosynthetic energy capture and dissipation, where the excitation energy in excess is dissipated safely via non-photochemical quenching (NPQ) to avoid photodamage. Chlorophyll excimer was recently reported to be an intrinsic photophysical intermediate in LHCII, which may serve as an efficient quencher of Chl singlet excitation (1Chl*). We have employed ultrafast transient absorption and broadband two-dimensional electronic spectroscopy to investigate the mechanism of 1Chl* deactivation in quenched and non-quenched LHCII preparations, referred to as Q-F730 and U-F680, respectively. It is found that the photoproduction of carotenoid (Car) triplet excitation in Q-F730 is substantially lower than that in U-F680, implying that intersystem crossing is unlikely to be the major deactivation channel of 1Chl*. In addition to the Chl-to-Car singlet excitation transfer pathway, our data are consistent with 1Chl deactivation via the formation of a Chl excimer and subsequent population of a Chl charge transfer state. Our spectroscopic results provide direct evidence linking the excimer to the Chl singlet excitation in LHCII, shedding light on the mechanistic basis of NPQ.

Oxygenic photosynthetic organisms employ multiple photoprotection mechanisms. The major light-harvesting complex of photosystem II of Bryopsis corticulans (B-LHCII) and that of spinach (S-LHCII) are structurally analogous but differ in their pigment compositions. We have attempted to compare, by evaluating the rate of chlorophyll (Chl)-to-carotenoid (Car) triplet excitation transfer (TET), the photoprotection of B- and S-LHCII in light-harvesting and energy-quenched states and observed a fast and a slow TET pathway for the LHCIIs irrespective of the functional states. The fast one in a sub-nanosecond time scale is attributed to the TET from Chl a612 (a603) to L1-Car (L2-Car), whereas the slow one in ∼10 ns is assigned to the TET from Chl a613 to L1-Car. Ongoing from the light-harvesting to the quenched state, the slow TET is accelerated from (14.0 ns)-1 to (4.7 ns)-1 for S-LHCII and from (25.0 ns)-1 to (17.0 ns)-1 for B-LHCII, becoming dominant for photoprotection at the L1 site. Thus, the TET enhancement and energy-quenching reactivity constitute the synergistic photoprotection of the LHCIIs.

Semilogarithmic plot of the BChl-to-Car triplet excitation transfer (TET) rate constant ( k TET = τ TET −1 , s −1 ) for bacterial LHs as a function of the nearest edge-to-edge distance ( R ) between the conjugated backbones of BChl and Car.

To address the issue of the slow oxygen reduction reaction (ORR) kinetics in high-temperature proton exchange membrane fuel cells (HT-PEMFCs), 0.2 wt% Pt/CeO2 nanoparticles with oxygen vacancies are synthesized and incorporated into the cathode catalyst layer to enhance performance. Tests with 25 cm2 single-cells reveal a significant enhancement in HT-PEMFCs performance with the addition of Pt/CeO2, reaching a peak power density of 432 mW/cm2 at 160 degrees C, compared to 352 mW/cm2 without the particles. Electrochemical impedance spectroscopy (EIS) analyses show a reduction in charge transfer resistance, suggesting improved O2 activation. Additionally, oxygen diffusion is identified as a limiting factor in membrane electrode assembly (MEA) performance. To further enhance performance, ammonium oxalate is introduced as a pore-forming agent in the catalyst layer, increasing gas diffusion and reducing concentration polarization. Combining 10 % Pt/CeO2 with 20 % ammonium oxalate increases the maximum power density to 467 mW/cm2, a 33 % improvement over pure catalysts. Structural analyses reveal that the pore-forming agent effectively alters the pore size distribution. This research highlights the potential of Pt/CeO2 in accelerating ORR kinetics, enhancing HT-PEMFCs performance, and providing valuable insights for the design of catalyst layer additives in HT-PEMFCs.

The behaviors of solid-liquid interfacial electron spillovers under negative potentials are crucial for understanding heterogeneous reactions and catalysts. The missing experimental details at the angstrom scale leave the current understanding of interfacial electron spillovers largely conceptual. Herein, we demonstrated interfacial electron spillover at electrode-electrolyte interfaces by combining in situ electrochemical plasmon-enhanced Raman spectroscopy (PERS) with a plasmonic molecular ruler strategy. Using a series of molecules adsorbed on or proximate to metallic electrodes (Pt, Pd, Au, and Ag) as molecular rulers, the electron spillover from electrodes to electrolytes was experimentally and theoretically correlated to the PERS bands of the functional groups of rulers, which provided a spatial resolution down to the angstrom scale. The electron spillover length was highly dependent on the potentials, metals, and electrolytes. An electron spillover with a length of up to 4 Å was observed at the Ag electrode-organic electrolyte interface. These results provide quantitative measurements of the fundamental details of electronic behaviors in metal-liquid interfaces, which may guide efforts to tailor the physical and chemical properties of metals under electrochemical polarization and prospectively enable active control of quantum plasmonics for angstrom-scale interfacial sensing.

In this study, the impact of mimic reformate of formic acid decomposition on the anode polarization of HT-PEMFC is investigated under various operating conditions of the anode, including different concentrations of CO2, N-2, CO, and humidification. Polarization curve and EIS measurements indicate that there is no significant difference (less than 5 mV when i < 0.4A/cm(2)) between the same concentrations of CO2 and N-2 up to 75 vol%. No significant poisoning of the anode by CO2 (up to 75 vol%) has been observed, suggesting that the addition of concentrated CO2 acts more as a diluent than a poison. Upon separating the polarization effects, it is found that the oxygen reduction reaction (ORR) is a crucial step limiting the fuel cell performance, with cathodic activation losses reaching as high as 70 % at 0.8A/cm(2). However, with 1 vol% CO in a H-2/CO2 1/1 mixture, a significant poisoning effect on the fuel cell is observed. DRT (distribution of relaxation times) analyses reveal two peaks related to CO in high-frequency regions above 100 Hz associated with the anode polarization, with the peak integration being five times larger than in pure hydrogen. Humidification doesn't improve the voltage or mitigate CO poisoning. A one-dimensional flux model that includes the anode polarization is developed to analyze the polarizations for both cathode and anode under different concentrations of diluents, well describing the experimental results. When i < 0.8 A/cm(2), the predicted values from the model closely match the measured values (within 5-10 mV). Calculations suggest that the anode polarization cannot be ignored, especially when the anode is fed with diluted gases.

It is widely believed that the relaxation-induced bleaching signals at nanoseconds observed in ultrafast infrared spectroscopic measurements are due to the local heat effect resulting from the thermalization of the infrared excitations. In this work, combining ultrafast IR pump/probe, 2D-IR, visible pump/IR probe, and ultrafast visible/IR double resonant fluorescence experiments, the vibrational hot ground states of fluorescein dianion in methanol solutions are found to be unexpectedly long, at the time scale of nanoseconds. This result indicates that the long-standing bleaching signal observed in the nonlinear IR experiments must have significant contributions from these hot ground states for the initial couple of ns. It is likely that a similar mechanism can also hold for other molecular systems. The hot ground states can last much longer than conventionally expected, which can potentially be applied to modify chemical reactions.