Single-layer transition metal dichalcogenides (TMDs), such as WS2, offer promising catalytic performance and good electron mobility, making them attractive cocatalysts for photo- and electrocatalysis. However, their structural instability under reaction conditions often leads to formation of inactive bulk metal oxides and contamination of final products, limiting long-term performance and industrial applicability. Herein, we demonstrate that this instability can instead be harnessed as a constructive transformation pathway. Under mild aqueous conditions, exfoliated WS2 monolayers undergo spontaneous transformation at the interface with anatase TiO2, resulting in the formation of highly dispersed tungsten species anchored on the oxide surface and accompanied by the generation of abundant oxygen vacancies. Comprehensive structural, spectroscopic, and theoretical analyses reveal that strong interfacial interactions direct the oxidation pathway away from bulk oxide formation and toward stabilized, atomically dispersed active sites with modified local electronic structures. The resulting catalyst exhibits enhanced charge separation, improved conductivity, and markedly improved stability and performance under photocatalytic conditions. These serendipitous findings reframe TMD degradation as a beneficial process and establish a strategy for repurposing unstable metal sulfide monolayers into functional components of robust photocatalytic systems.

Graphene nanoribbons (GNRs) combine the remarkable optical and electronic properties of graphene with the presence of a tunable band gap, making them promising for optoelectronic applications. Here, we investigate the excitonic properties of individual cove-edge GNRs through microphotoluminescence (micro-PL) spectroscopy. We observe ultranarrow emission lines with full width at half-maximum as low as 24 μeV, demonstrating a reduction of inhomogeneous broadening by 3 orders of magnitude compared to GNR ensembles. Temperature-dependent PL reveals phonon-mediated broadening mechanisms, with electron-phonon coupling parameters in agreement with ensemble studies but with dramatically reduced line widths. Time-resolved PL suggests long-lived excitonic states, while spectral diffusion analysis demonstrates stable emission energies, highlighting the exceptional quality of these GNRs as single-photon emitters. The absence of intensity blinking and low Mandel parameters further support the robustness of the emission properties. Our findings establish cove-edge GNRs as promising candidates for quantum light sources and nanoscale optoelectronic applications.

Lead-halide perovskite nanocrystals (NCs) have gained attention for optoelectronics, but careful selection of the antisolvent used for purification is essential to achieve high monodispersity and yield while minimizing surface damage. Current understanding indicates that this requires lowering the relative polarity of the antisolvent, yet high-polarity antisolvents are widely used for purification, as we confirm through data mining. We show that polarity alone is insufficient for antisolvent selection by comparing ethyl acetate and acetonitrile for CsPbI3 NC purification. Despite its higher polarity, acetonitrile yields improved colloidal stability compared to ethyl acetate. Using 1H NMR, FTIR, and XPS measurements, alongside DFT calculations, we demonstrate that acetonitrile acts as a stronger Lewis base, binding to and passivating the NC surface. Coordination of acetonitrile to the perovskite NC surface enhances stability and improves their performance in light-emitting diodes. These findings establish a mechanistic framework for antisolvent selection to realize bright and stable halide perovskite NCs.

ABSTRACT CsPbCl 3 perovskite nanocrystals (NCs) are promising violet emitters owing to their narrow emission and high color purity, but their low defect tolerance demands careful passivation to achieve high photoluminescence quantum yield (PLQY), and typically only for fresh CsPbCl 3 NCs. Here, we report a delayed dual‐passivation pathway in CsPbCl 3 NCs induced by the halide‐rich molecular reagent phosphorus oxychloride (POCl 3 ), which unexpectedly yields a strong time‐dependent PLQY enhancement instead of the rapid degradation usually observed. POCl 3 gradually decomposes into P‐ and Cl‐containing species, enabling a controlled release of excess halides that autonomously passivates halide vacancies in a self‐regulated manner. This dynamic self‐healing process boosts the PLQY of colloidal CsPbCl 3 NCs by over 40‐fold relative to pristine samples and sustains high violet emission efficiencies for more than 2 months of storage under ambient conditions. Spectroscopic measurements and calculations indicate that both liberated Cl − and in situ—formed phosphonic species passivate halide vacancies and Pb 2 + dangling bonds, suppressing mid‐gap defect states. The resulting self‐passivated NCs deliver a luminance of 409 cd m − 2 , the highest reported for CsPbCl 3 ‐based violet emitters. These results establish halide‐rich dual passivators such as POCl 3 as powerful tools for long‐term defect control in chloride perovskite NCs and for robust, bright violet‐LEDs.

All-organic circularly polarized luminescence (CPL) emitters acting as intrinsic liquid polarizers provide a promising route to reduce optical crosstalk and enhance spatial resolution in displays by directly emitting circularly polarized light, thereby eliminating external polarizers and minimizing energy loss. Herein, we report a highly efficient, all-organic CPL-active liquid polarizer based on chiral organic binary composites (COBCs), in which camphorquinone-derived chiral inducers are integrated with polymeric carbon quantum dots (PCQDs), opening a previously unexplored pathway toward chiral organic-quantum dot composites. The composites exhibit intense blue emission with a photoluminescence quantum yield (PL QY) of 64%, and strong enantioselective CPL with luminescence dissymmetry factors (glum ≈ ±10-2). Circular dichroism spectroscopy reveals multiple Cotton effects with high absorption anisotropy (gabs = 1.2 × 10-2), while time-resolved photoluminescence and electrochemical analyses indicate that hydrogen-bonded chiral networks promote charge transfer and generate intrinsic chiral fields enabling selective CPL emission. A prototype device based on COBCs achieves a spatial resolution of 4 lp mm-1, nearly double that of achiral analogues, while effectively suppressing glare and enhancing image contrast. Our findings establish a design strategy for transforming achiral CQDs into CPL-active materials, opening pathways toward next-generation, energy-efficient photonic and display technologies.

The temperature-dependent photoluminescence of CsPbBr3/SiO2 and CsPbI3/SiO2 nanocrystals was investigated to understand the thermal stability of SiO2 encapsulation. At increased temperature, intensity quenching, linewidth broadening, energy level shift, and decay dynamics were evaluated as quantified parameters. Comprehensive analysis of these parameters supports that CsPbI3/SiO2 nanocrystals show a stronger interaction with phonons compared with CsPbBr3/SiO2 nanocrystals. Despite SiO2 encapsulation, we conclude that trapping states are still present and the degree of localization can be characterized in terms of short-lived decay time and thermal activation energy.

Graphene quantum dots (GQDs) exhibit complex photoluminescence (PL) originating from intrinsic sp2 carbon domains, surface functional groups, and structural defects. Yet the spectral overlap among these emissive channels hinders clear identification of their recombination pathways. Here, we investigate multichannel PL dynamics of commercial GQDs using time-resolved and cryogenic PL spectroscopy. PL spectra reveal three distinct peaks: Peak I (443 nm) from π-π* transitions, Peak II (520 nm) from surface-dominated contribution functional states, and Peak III (583 nm) from pyrrolic N-related defects. Time-correlated single-photon counting detects only a 460 nm emission linked to graphitic N traps, indicating that Peaks I-III decay faster than the nanosecond window. Ultrafast optical Kerr-gate measurements further resolve distinct lifetimes for hydroxyl (<5 ps), carboxyl (5-10 ps), amine (20-30 ps), and carbonyl (40-80 ps) groups. The transient evolution displays cascade relaxation from deep to shallow traps, evidenced by a progressive blue-shift of Peak II. Cryogenic PL shows stable emission of Peak I, whereas Peak III red-shifts and broadens with temperature, revealing strong electron-phonon coupling and deep-level trapping. These results clarify the multichannel emission mechanisms of GQDs and provide design principles for tuning their optical properties.

Conventional machine vision systems based on RGB cameras struggle to distinguish materials that appear visually identical, such as plastics of the same color and shape. To address this limitation, we present a spectrometer-free time-division multiplexed (TDM) near-infrared (NIR) time-of-flight (ToF) vision system that enables simultaneous acquisition of spectral and geometric information using dual-detector architecture composed of an avalanche photodiode (APD) for multispectral reflectance detection and a single-photon avalanche diode (SPAD) for ToF ranging. By extending TDM to multispectral NIR imaging, the proposed system temporally separates nanosecond laser pulses at 980 nm, 1450 nm, and 1650 nm for material discrimination, while an additional 905 nm channel provides high-precision ToF depth mapping. This architecture eliminates bulky spectrometers and dispersive optics, minimizing optical loss while maintaining compactness and scalability. The system successfully recognizes 12 visually similar materials, including six white plastics, three green rubbers, and three silver metals, based on their unique NIR reflectance fingerprints encoded into false-color RGB images. A convolutional neural network (CNN) trained on these images achieves near-perfect classification accuracy. Furthermore, a dual-domain experiment with a mannequin and a human subject demonstrates simultaneous reconstruction of surface geometry and material differentiation under realistic conditions. This spectrometer-free multispectral ToF vision approach establishes a compact and efficient sensing platform for high-precision robotic perception, intelligent manufacturing, and physical artificial intelligence systems requiring both spectral and spatial awareness.

The optical properties of graphene (Gr)-covered CsPbBr3 quantum dots (QDs) were investigated using micro-photoluminescence spectroscopy, revealing a remarkable three orders of magnitude enhancement in photoluminescence (PL) intensity compared to bare CsPbBr3 QDs. To elucidate the underlying mechanisms, we combined experimental techniques with density functional theory (DFT) calculations. DFT simulations showed that the graphene layer generates interfacial electrostatic potential barriers when in contact with the CsPbBr3 surface, impeding carrier leakage from perovskite to graphene and enhancing radiative recombination. Additionally, graphene passivates CsPbBr3 surface defect states, suppressing nonradiative recombination of photo-generated carriers. Our study also revealed that graphene becomes n-doped upon contact with CsPbBr3 QDs, activating its plasmon mode. This mode resonantly couples with photo-generated excitons in the perovskite. The momentum mismatch between graphene plasmons and free-space photons is resolved through plasmon scattering at Gr/CsPbBr3 interface corrugations, facilitating the observed super-bright emission. These findings highlight the critical role of graphene as a top contact in dramatically enhancing CsPbBr3 QDs’ PL. Our work advances the understanding of graphene-perovskite interfaces and opens new avenues for designing high-efficiency optoelectronic devices. The multifaceted enhancement mechanisms uncovered provide valuable insights for future research in nanophotonics and materials science, potentially leading to breakthroughs in light-emitting technologies.

Weakly bonded native ligands severely degrade the performance of perovskite quantum dot (PeQD) light-emitting diodes (LEDs). While conventional approaches can be used to strengthen ligand binding, they fail to achieve complete ligand exchange, leaving residual ligands that promote degradation. Herein, we present a dual-functional fluorinated benzyl phosphonic acid (F-BPA) ligand that modulates the acidity and enhances the binding affinity between the phosphonate groups of F-BPA and the perovskite surface compared to BPA due to a significant redistribution of the electrostatic potential of the molecule induced by fluorination. The F-BPA treatment facilitates effective ligand exchange and obtains well-passivated CsPbI3 PeQDs with improved stability under thermal, light, and polar solvent stress. Red-emissive LEDs achieved a maximum external quantum efficiency of 24.0% with improved device stability (half-lifetime of 1,020 min at 100 cd m-2). This study demonstrates a dual-functional ligand strategy and opens a new pathway toward PeQDs for next-generation display technologies.

The main challenges in the optical and morphological tuning of highly stable orange-emitting Mn-doped perovskite include achieving uniform dopant distribution, maintaining structural integrity under varying environmental conditions, and optimizing luminescent efficiency while minimizing non-radiative recombination pathways. This study presents a novel, one-step, water-induced ultrafast synthesis strategy for obtaining Mndoped mixed-halide perovskites at room temperature. This technique offers morphological control by varying the amount of water-based precursor, allowing the tuning of resulting nanostructures to produce nanoplatelets, nanocubes, or nanowires. In the growth mechanism, Mn2+ dopants affect the crystal structure by promoting stable growth and uniform doping at higher concentrations, while water improves ion dispersion, reaction kinetics, and passivation, facilitating optimal crystal growth and the formation of desired nanostructure morphologies. The synthesized Mn:CsPbBr3_xClx NCs form a highly stable colloidal solution with approximately 100 % emission stability for up to one year under ambient conditions and retain 98.9 % of its photoluminescence after aging at 85 degrees C for 200 h. We also explore the PL mechanism in Mn:CsPbBr3-xClx NCs, where temperature- dependent PL analysis reveals energy transfer from CsPbBr3-xClx exciton states to Mn2+-doped levels, enhancing PL intensity, with both exciton and Mn2+ emissions exhibiting a blue shift as the temperature increased from 6 K to 300 K, attributed to lattice expansion and electron-phonon interactions. A warm white light emission is achieved with excellent stability and an exceptionally wide color gamut coverage. The proposed strategy has the potential to enable large-scale synthesis and fabrication of highly stable perovskite devices for high-quality display and lighting applications.

Lead halide perovskite nanocrystals exhibit excellent optoelectronic properties, yet simultaneous observation of bright singlet and triplet exciton emissions under identical conditions has remained elusive. This limitation hinders optimization of quantum efficiency in light-emitting devices. Here, we provide the direct spectroscopic evidence for coexisting bright singlet and triplet excitons in CsPbBr3 nanocrystals, overcoming the conventional 25 % spin-statistical efficiency ceiling. Using polarization-resolved, spatially resolved, and time-resolved micro-photoluminescence at 7 K, we resolve three sharp triplet fine-structure components (T1, T2, T3) with energy separations of 1-3 meV and linear polarization >85 %, coexisting with broad singlet emission. The triplet emissions display distinct polarization axes, nonlinear intensity scaling, and nanosecond lifetimes, confirming their assignment as Rashba-split bright triplet states. Spatial mapping reveals that these emissions arise from structurally pristine domains with exciton diffusion lengths exceeding 9 mu m. Time-resolved measurements show concurrent fast and slow decay components, consistent with singlet-to-triplet intersystem crossing followed by radiative triplet recombination. Our findings establish a comprehensive picture of exciton spin dynamics in perovskite nanocrystals and open new avenues for spin-engineered photonic devices. This work lays the foundation for next-generation LEDs, lasers, and quantum light sources that leverage both singlet and triplet radiative channels to exceed traditional efficiency limits. While these findings are demonstrated at cryogenic temperatures, they highlight essential spin-related mechanisms that could be harnessed for room-temperature operation through enhanced Rashba coupling, dielectric engineering, or compositional tuning.

We have estimated the intrinsic complex refractive index spectrum of a CsPbBr3 nanocrystal. With various dilute solutions of CsPbBr3 nanocrystals dissolved in toluene, effective refractive indices were measured at two different wavelengths using Michelson interferometry. Given the effective absorption spectrum of the solution, a full spectrum of the effective refractive index was also obtained through the Kramers–Krönig relations. Based on the Maxwell–Garnett model in the effective medium approximation, the real and imaginary spectrum of the complex refractive index was estimated for the CsPbBr3 nanocrystal, and the dominant inaccuracy was attributed to the size inhomogeneity.

Two-dimensional layered perovskite oxides have emerged as promising photocatalysts for solar-driven hydrogen evolution. Although doping has been widely employed to enhance photocatalytic performance, its role in modulating the electronic structure and the local chemical environment of these materials remains poorly understood. Here in this study, we investigate the codoping of Rh and La into exfoliated nanosheets of the Dion-Jacobson perovskite KCa2Nb3O10 to enhance photocatalytic hydrogen evolution reaction (HER) activity. A substantial increase in H2 evolution rate, from 12.3 to 69.0 μmol h-1, was achieved at an optimal doping level of 0.2 wt % Rh and 1.3 wt % La. Comprehensive structural and spectroscopic analyses, including synchrotron techniques and high-resolution microscopy, revealed that Rh3+ substitutes Nb5+ to introduce shallow 4d acceptor states that mediate charge separation, while La3+ substitutes Ca2+, compensates for aliovalent charge imbalance, and modulates local lattice distortions and oxygen vacancy formation. This codoping strategy enhances charge carrier lifetime and separation efficiency through a trap-mediated mechanism. The observed volcano-shaped activity trend highlights a narrow compositional window, where electronic and structural factors are optimally balanced. These findings establish a mechanistic foundation for defect engineering in layered perovskites and offer a pathway for the rational design of photocatalysts.

Room‐temperature collective quantum emission (RT‐CQE), enabled by many‐body interactions and phase‐synchronized dipole oscillations, offers a promising path for scalable quantum photonics. Here, superfluorescence (SF) is demonstrated in CsPbBr3 perovskite nanowires (NWs), facilitated by Wannier–Mott excitons with spatially delocalized wavefunctions and strong dipole–dipole interactions. The intrinsic quasi‐1D geometry and occasional bundling promote preferential dipole alignment along the NW axis, enabling long‐range phase coherence. Key experimental signatures, photon bunching with g2(0) ≈2, femtosecond‐scale coherence time (≈88 fs), and ultralow excitation threshold (≈210 nJ−1 cm2), confirm the onset of SF at ambient conditions. Ultrafast spectroscopy reveals bandgap renormalization, state filling, and exciton‐phonon coupling, consistent with collective excitonic behavior mediated by delocalized states. Unlike other RT‐SF mechanisms based on polarons or electron–hole liquids, the system exploits directional dipole alignment and exciton delocalization in quasi‐1D NWs, allowing coherent emission without the need for high excitation densities or complex structural ordering. These findings demonstrate that CsPbBr3 NWs can sustain RT‐SF driven by exciton delocalization and directional dipole coupling, providing a new physical platform for coherent light generation under ambient conditions.

1D and 2D integrations provide significant promise for machine vision by enabling compact, power‐efficient optoelectronic devices. However, the potential of 1D materials in mixed‐dimensional structures for convolutional image processing remains largely unexplored. Here, high‐quality 1D‐Nb 2 Pd 3 Se 8 is synthesized and integrated with 2D‐WSe 2 to form self‐powered photodetectors, exhibiting gate‐tunable bi‐directional photoresponse for image processing. Utilizing the narrow band gap and favorable work function of 1D‐Nb 2 Pd 3 Se 8 , a type‐I junction and 1D van der Waals interface are established with transition metal dichalcogenides. The gate tunable built‐in electric field enables switching between n‐p and n‐n + configurations, allowing the drift photocurrent direction to be reversed, achieving both negative and positive photocurrent. Furthermore, efficient conversion of high‐energy photons along one dimension enhances sensitivity at 375 nm. The device achieves a responsivity of 232 mA W −1 , external quantum efficiency of 77% at 375 nm illumination, rapid response time of ~3 µs, detectivity of 6.35 × 10 10 Jones, and broadband photodetection from ultraviolet to near‐infrared. The demonstrated gate‐controllable, bi‐directional photoresponse with linear power dependence in a 1D heterojunction offers a promising platform for in‐sensor convolutional processing with high integration and portability.

High-resolution spectroscopy unveils the fundamental physics of quantum states, molecular dynamics, and energy transfers. Ideally, a higher spectral resolution over a broader bandwidth is the prerequisite, but traditional spectroscopic techniques can only partially fulfill this requirement even with a bulky system. Here we report that a multi-frequency acousto-optic phase modulation at a chip-scale of soft polydimethylsiloxane can readily support a 200-times higher 0.5-MHz spectral resolution for the frequency-comb-based spectroscopy, while co-located plasmonic nanostructures mediate the strong light-matter interaction. These results suggest the potential of polydimethylsiloxane acousto-optic phase modulation for cost-effective, compact, multifunctional chip-scale tools in diverse applications such as quantum spectroscopy, high-finesse cavity analysis, and surface plasmonic spectroscopy.

We have successfully produced an ultrathin freely suspended GO film, which is a biomimetic structure inspired by the transparent dragonfly wing structure. Based on a colloidal self-assembly process over a large area, solvent evaporation was applied within a limited opening geometry. The free-standing GO film shows a significant enhancement of the nonlinear optical absorption, where saturable absorption and photoinduced absorption were observed at dramatically decreased excitation fluence compared with other work on GO films dispersed on substrates. Surprisingly, we also found that free-standing GO films are beneficial for compressing femtosecond pulses around 800 nm. Using a frequency-resolved optical gating as well as an open aperture Z-scan method, the origin was found to be associated with two effects. While the pulse shortening results from saturable absorption, the chirp effect is also suppressed due to the presence of an inflection point around 800 nm in the refractive index spectrum of free-standing GO film.

Achieving stable and efficient circularly polarized luminescence (CPL) from achiral perovskite nanocrystals (PNCs) remains a major challenge in the development of advanced chiroptical materials. Herein, the syntheses of a total of nine compounds, including full-color colloidal polymer-capped PNC composites are reported based on organic-inorganic hybrid perovskites and inorganic 2D nanosheets (NSs) using phenacyl halide as a single organic source of halide precursor. While the initial PNCs exhibit low photoluminescence quantum yield (PL QY) and poor stability, a previously unexplored surface absorption/ion exchange strategy employing 2D-ZrH2P2O8 NSs significantly enhances both optical properties and long-term stability, e.g., the FAPbBr3@ZrH2P2O8 (FA = formamidinium) composite exhibits a significantly enhanced PL QY of 88.57%, compared to 30.9% for the pristine counterparts, owing to the protective effect of the robust 2D ZrH2P2O8 network that enhances stability under ambient conditions. Crucially, embedding these stabilized PNCs into a chiral polymer matrix induces distinct mirror-image strong CPL signals both in solution and solid-state. This rare dual-phase CPL activity arises from the conformational adaptability of the chiral polymer, which imparts chirality to the achiral PNCs via both covalent and non-covalent interactions. These findings present a versatile strategy for producing robust, CPL-active stable perovskite materials across the visible spectrum for next-generation chiroptoelectronic devices.

We demonstrate a novel defect-mediated, thermally-activated emission mechanism in [(CH3)(3)NPh](2)MnBr4 single crystals, driven by the coexistence of temperature-sensitive shallow traps and temperature-independent deep traps introduced by Br vacancies. Through comprehensive temperature-dependent photoluminescence (PL) and time-resolved PL measurements, combined with first-principles calculations, we reveal that the material exhibits exceptional thermal stability, retaining 67 % of its relative PL quantum yield at room temperature and achieving an absolute quantum yield of similar to 38.9 % under optimal excitation conditions. The dual-component PL decay dynamics consist of a fast decay (similar to hundreds of ps) governed by shallow traps and a long decay (similar to 350 mu s) dominated by deep traps, creating an energy cascade that efficiently promotes radiative recombination while minimizing non-radiative losses. Our findings provide critical insights into defect-mediated, thermally-sensitive delayed emission mechanisms and establish [(CH3)(3)NPh](2)MnBr4 as a lead-free, thermally stable material with high efficiency, making it an excellent candidate for next-generation optoelectronic applications, including solidstate lighting and temperature-sensitive devices.