Photophysical Mechanism Research Articles

Photo-physical mechanism of near-IR femtosecond laser-induced refractive-index change in PMMA

Micromodification in bulk undoped polymethylmethacrylate (PMMA) by single focused (numerical aperture (NA) = 0.25), 1030-nm 250-fs laser pump pulses was explored by pump self-transmittance; optical, 3D-scanning confocal photoluminescence (PL); Raman micro-spectroscopy; and optical polarimetric and interferometric microscopy. Starting from the threshold pulse energy Eth = 0.4 ± 0.1 μJ (peak laser intensity Ith ≈ 8 TW/cm2), visible bright micro-voxels emerged inside PMMA at the 100 ÷ 300-μm depth, with their PL-acquired dimensions increasing versus pulse energy. Optical phase change was interferometrically measured in the voxels at the 532-nm wavelength, exhibiting versus the pulse energy the isotropic refractive index increase Δn = +(4 ÷ 10) × 10−4, and a new 1640-cm−1 peak of C=C vibrations emerged in the Raman spectra. Pump self-transmittance measurements demonstrated the predominating eight-photon absorption (excited energy level ≈ 9.7 eV, coefficient β8 ≈ 3 × 10−5 cm13/TW7) at the sub-threshold I < Ith, implying photoionization of the PMMA chains (the ionization potential of MMA molecule ≈ 9.7 eV). At higher peak intensities I > Ith, inverse brems-strahlung absorption (coefficient ∼103cm−1) of near-critical micro-plasma (density >5 × 1020 cm−3) predominates over the multi-photon PMMA absorption, providing the bulk energy density >6 × 102 J/cm3 and the temperature rise ΔT > 2.2 × 102 K, which are sufficient for PMMA (de)polymerization near the equilibrium bulk temperature TP ≈ 220°C. These results uncover the quantitative mechanism of fs-laser modification of PMMA, justifying the previous qualitative findings and enabling controllable energy deposition during fs-laser PMMA micromachining of diverse functional applications.

The Photophysics of Perovskite Emitters: from Ensemble to Single Particle.

Halide perovskite emitters are a groundbreaking class of optoelectronic materials possessing remarkable photophysical properties for diverse applications. In perovskite light emitting devices, they have achieved external quantum efficiencies exceeding 28%, showcasing their potential for next-generation solid-state lighting and ultra high definition displays. Furthermore, the demonstration of room temperature continuous-wave perovskite lasing underscores their potential for integrated optoelectronics. Of late, perovskite emitters are also found to exhibit desirable single-photon emission characteristics as well as superfluorescence or superradiance phenomena for quantum optics. With progressive advances in synthesis, surface engineering, and encapsulation, halide perovskite emitters are poised to become key components in quantum optical technologies. Understanding the underpinning photophysical mechanisms is crucial for engineering these novel emergent quantum materials. This review aims to provide a condensed overview of the current state of halide perovskite emitter research covering both established and fledging applications, distill the underlying mechanisms, and offer insights into future directions for this rapidly evolving field.

Non-adiabatic Couplings in Surface Hopping with Tight Binding Density Functional Theory: The Case of Molecular Motors.

Nonadiabatic molecular dynamics (NAMD) has become an essential computational technique for studying the photophysical relaxation of molecular systems after light absorption. These phenomena require approximations that go beyond the Born-Oppenheimer approximation, and the accuracy of the results heavily depends on the electronic structure theory employed. Sophisticated electronic methods, however, make these techniques computationally expensive, even for medium size systems. Consequently, simulations are often performed on simplified models to interpret the experimental results. In this context, a variety of techniques have been developed to perform NAMD using approximate methods, particularly density functional tight binding (DFTB). Despite the use of these techniques on large systems, where ab initio methods are computationally prohibitive, a comprehensive validation has been lacking. In this work, we present a new implementation of trajectory surface hopping combined with DFTB, utilizing nonadiabatic coupling vectors. We selected the methaniminium cation and furan systems for validation, providing an exhaustive comparison with the higher-level electronic structure methods. As a case study, we simulated a system from the class of molecular motors, which has been extensively studied experimentally but remains challenging to simulate with ab initio methods due to its inherent complexity. Our approach effectively captures the key photophysical mechanism of dihedral rotation after the absorption of light. Additionally, we successfully reproduced the transition from the bright to dark states observed in the time-dependent fluorescence experiments, providing valuable insights into this critical part of the photophysical behavior in molecular motors.

Recent Advances in Thermally Activated Delayed Fluorescence-Based Organic Afterglow Materials.

Thermally activated delayed fluorescence (TADF)-based materials are attracting widespread attention for different applications owing to their ability of harvesting both singlet and triplet excitons without noble metals in their structures. As compared to the conventional fluorescence and room-temperature phosphorescence pathways, TADF originates from the reverse intersystem crossing process from the excited triplet state (T1) to the singlet state (S1). Therefore, TADF emitters enabling activated and long lifetime T1 excitons are potential candidates for generating long-lived afterglow emission, an effect that can still be observed for a while by the naked eye after the removal of the excitation light source. Recently, TADF-based organic afterglow materials featuring high photoluminescence quantum yields and long lifetimes above 100 ms under ambient conditions, have emerged for advanced information security, high-contrast biological imaging, optoelectronic devices, and intelligent sensors, whereas the related systematic review is still lacking. Herein, the recent progress in TADF-based organic afterglow materials is summarized and an overview of the photophysical mechanism, design strategies, and the performances for relevant applications is given. In addition, the challenge and perspective of this area are given at the end of the review.

2D Material Sensors with Light Excitation

Abstract2D materials are highly regarded for their exceptional sensing application prospects, stemming from their distinctive atomic layer structure and exceptionally sensitive surfaces. Over the past decade, numerous high‐performance 2D material sensors are extensively developed; however, challenges related to sensitivity, selectivity, and stability continue to impede their industrial advancement. The interaction between light and 2D materials has introduced unique properties, including absorption and emission characteristics, photoelectric effects, nonlinear optical effects, surface‐enhanced Raman scattering, and light response enhancement. Consequently, exciting and adjusting the electronic structure and carrier concentration of 2D materials through light with specific wavelength ranges is an effective strategy for enhancing sensing performance. This strategy has yielded remarkable breakthroughs in applications such as photodetectors, semiconductor gas sensors, and fiber optic sensors. Moreover, it demonstrates extraordinary potential in emerging applications such as image sensors, flexible electronics, and biomedical sensors. However, the sensing mechanism, device structure design, and specific applications of 2D materials under light excitation remain unclear. This perspective endeavors to elucidate the intrinsic photophysical mechanisms between light‐excited 2D materials and their target sensing analytes. Furthermore, it aims to explain the evolutionary pattern of sensing applications and provide novel insights and inspiration to advance this burgeoning field.

Tunable multimode emissions of Yb3+/Er3+-doped rare-earth-based Cs2NaYCl6 double perovskite crystals for versatile applications

Lead-free halide double perovskite materials are gaining recognition because of their excellent optoelectronic performance. However, achieving multimode luminescence with tunable emission colors in single-component double perovskites remains a significant challenge. Understanding the mechanism of trivalent lanthanide-ion doping could provide a valuable solution. Herein, we report the synthesis of rare-earth-based Cs2NaYCl6 double perovskites using a hydrothermal method. Efficient visible to near-infrared down-shifting (DS) photoluminescence and green up-conversion (UC) emissions were realized by incorporating Er3+ ions with abundant energy levels into the hosts. Notably, the DS and UC emission colors could both be adjusted by further introducing Yb3+ ions that acted as sensitizers, and the photoluminescence was significantly enhanced due to the strong absorption at 980 nm. Spectral analysis revealed that the high compatibility of lanthanide ions with the rare-earth-based double perovskites and cross-relaxation processes played a key role in achieving modulated emission and multiple excitation modes. This study aimed to understand the photophysical mechanism of lanthanide-ion-doped double perovskites, as well as to highlight their ability to modulate emissions. Furthermore, this study expands the versatile applications of lanthanide-ion-doped double perovskites in the fields of high-security anti-counterfeiting, tissue imaging, and night-vision systems.

Identifying Organic-Inorganic Interaction Sites Toward Emission Enhancement in Non-Hydrogen-Bonded Hybrid Perovskite via Pressure Engineering.

The interaction between organic and inorganic components in metal hybrid perovskites fundamentally determines the intrinsic optoelectronic performance. However, the underlying interaction sites have still remained elusive, especially for those non-hydrogen-bonded hybrid perovskites, thus largely impeding materials precise design with targeted properties. Herein, high pressure is utilized to elucidate the interaction mechanism between organic and inorganic components in the as-synthesized one-dimensional hybrid metal halide (DBU)PbBr3 (DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene). The interaction sites are identified to be the N from DBU and the Br from inorganic framework by the indicative of enhanced Raman mode under high pressure. The change in interaction strength is indeed derived from the pressure modulation on both distance and spatial arrangement of the nearest Br and N, rather than traditional hydrogen-bonding effect. Furthermore, the enhanced interaction increased charge transfer, resulting in a cyan emission with photoluminescence quantum yields (PLQYs) of 86.6%. The enhanced cyan emission is particularly important for underwater communication due to the much less attenuation in water than at other wavelength emissions. This study provides deep insights into the underlying photophysical mechanism of non-hydrogen-bonded hybrid metal halides and is expected to impart innovative construction with superior performance.

Green Preparation of S, N Co-Doped Low-Dimensional C Nanoribbon/C Dot Composites and Their Optoelectronic Response Properties in the Visible and NIR Regions.

The green production of nanocomposites holds great potential for the development of new materials. Graphene is an important class of carbon-based materials. Despite its high carrier mobility, it has low light absorption and is a zero-bandgap material. In order to tune the bandgap and improve the light absorption, S, N co-doped low-dimensional C/C nanocomposites with polymer and graphene oxide nanoribbons (the graphene oxide nanoribbons were prepared by open zipping of carbon nanotubes in a previous study) were synthesized by one-pot carbonization through dimensional-interface and phase-interface tailoring of nanocomposites in this paper. The resulting C/C nanocomposites were coated on untreated A4 printing paper and the optoelectronic properties were investigated. The results showed that the S, N co-doped C/C nanoribbon/carbon dot hybrid exhibited enhanced photocurrent signals of the typical 650, 808, 980, and 1064 nm light sources and rapid interfacial charge transfer compared to the N-doped counterpart. These results can be attributed to the introduction of lone electron pairs of S, N elements, resulting in more transition energy and the defect passivation of carbon materials. In addition, the nanocomposite also exhibited some electrical switching response to the applied strain. The photophysical and doping mechanisms are discussed. This study provides a facile and green chemical approach to prepare hybrid materials with external stimuli response and multifunctionality. It provides some valuable information for the design of C/C functional nanocomposites through dimensional-interface and phase-interface tailoring and the interdisciplinary applications.

Pressure-Induced Changes in the Phase Distribution and Carrier Dynamics of Quasi-Two-Dimensional Ruddlesden-Popper Perovskites.

Quasi-two-dimensional (quasi-2D) perovskites hold significant potential for diverse design strategies due to their tunable structures, exceptional optical properties, and environmental stability. Due to the complexity of the structure and carrier dynamics, characterization methods such as photoluminescence and absorption spectroscopy can observe but cannot precisely distinguish or identify the phase distribution within quasi-2D perovskite films or correlate phases with carrier dynamics. In this study, we used pressure to modulate the intralayer and interlayer structures of (PEA)2Csn-1PbnBr3n+1 quasi-2D perovskite films, investigating charge carrier dynamics. Steady-state spectroscopy revealed phase transitions at 1.62, 3, and 8 GPa, with free excitons transforming into self-trapped excitons after 8 GPa. Transient absorption spectroscopy elucidated the structural evolution, energy transfer, and pressure-induced transition mechanisms. The results demonstrate that combining pressure and spectroscopy enables the precise identification of phase distribution and pressure response ranges and reveals photophysical mechanisms, providing new insights for optimizing optoelectronic materials.

Polymer-Gel-Derived PbS/C Composite Nanosheets and Their Photoelectronic Response Properties Studies in the NIR

Non-conjugated polymer-derived functional nanocomposites are one of the important ways to develop multifunctional hybrids. By increasing the degree of crosslinking, their photophysical properties can be improved. PbS is a class of narrow bandgap infrared active materials. To avoid aggregation and passivation of the surface defects of PbS nanomaterials, a large number of organic and inorganic ligands are usually used. In this study, PbS/C composite nanosheets were synthesized with Pb2+ ion-crosslinked sodium alginate gel by one-pot carbonization. The resulting nanosheets were coated on untreated A4 printing paper, and the electrodes were the graphite electrodes with 5B pencil drawings. The photocurrent signals of the products were measured using typical 650, 808, 980, and 1064 nm light sources. The results showed that the photocurrent switching signals were effectively extracted in the visible and near-infrared regions, which was attributed to the mutual passivation of defects during the in situ preparation of PbS and carbon nanomaterials. At the same time, the resulting nanocomposite exhibited electrical switching responses to the applied strain to a certain extent. The photophysical and defect passivation mechanisms were discussed based on the aggregation state of the carbon hybrid and the interfacial electron interaction. This material would have potential applications in broadband flexible photodetectors, tentacle sensors, or light harvesting interdisciplinary areas. This study provided a facile approach to prepare a low-cost hybrid with external stimulus response and multifunctionality. These results show that the interfacial charge transfer is the direct experimental evidence of interfacial interaction, and the regulation of interfacial interaction can improve the physical and chemical properties of nanocomposites, which can meet the interdisciplinary application. The interdisciplinary and application of more non-conjugated polymer systems in some frontier areas will be expanded upon.

Atomic‐Thin 2D Copper Sulfide Nanocrystals with over 94% Photothermal Conversion Efficiency as Superior NIR‐II Photoacoustic Agents

AbstractExploring photothermal nanomaterials is essential for new energy and biomedical applications; however, preparing materials with intense absorption, highly efficient light‐to‐heat conversion, and enhanced photostability still faces the enduring challenge. Herein, the study synthesizes atomic‐thin (≈1.6 nm) 2D copper sulfide (AT‐CuS) plasmonic nanocrystals and find its extraordinary photothermal conversion efficiency (PCE) reaching up to 94.3% at the second near‐infrared (NIR‐II) window. Photophysical mechanism studies reveal that the strong localized surface plasmon resonance (LSPR) and out‐of‐plane size effect of AT‐CuS induce strong optical absorption and non‐equilibrium carrier scattering, resulting in a significant carrier‐phonon coupling (7.18 × 1017 J K−1 s−1 m−3), ultimately enhancing the heat generation. Such a photothermal nanomaterial demonstrates at leastmes stronger NIR‐II photoacoustic (PA) signal intensity than that of most commonly used miniature gold nanorods, together with greater biocompatibility and photo‐/thermal‐stability, enabling noninvasive PA imaging of brain microvascular in living animals. This work provides an insight into the rational exploration of superb NIR‐II photothermal and photoacoustic agents for future practical utilizations.

Unraveling the Photocatalytic Mechanism of N2 Fixation on Single Ruthenium Sites.

Photocatalytic N2 fixation offers promise for ammonia synthesis, yet traditional photocatalysts encounter challenges such as low efficiency and short carrier lifetimes. Atomically precise ligand-metal nanoclusters emerge as a solution to address these issues, but the photophysical mechanism remains elusive. Inspired by the synthesis of Au4Ru2 NCs, we investigate the mechanism behind N2 activation on Au4Ru2, focusing on photoactivity and carrier dynamics. Our results reveal that vibration of the Ru-N bond in the low-frequency domain suppresses the deactivation process leading to a long lifetime of the excited N2. By the strategy of isoelectronic substitution, we identify the single Ru sites as the active sites for N2 activation. Furthermore, these ligand-protected M4Ru2 (M = Au, Ag, Cu) NCs show robust thermal stability in explicit solvation and decent photochemical activity for N2 activation and NH3 production. These findings have significant implications for the optimization of catalysts for sustainable ammonia synthesis.

Building New Structural Distortion Descriptors through Pressure Engineering toward Enhanced Violet Emission in 2D Hybrid Perovskite

AbstractBuilding an explicit structure‐property relationship for two‐dimensional (2D) hybrid perovskites is critical to guide the synthesis of highly luminescent materials. However, traditional studies are limited to the deviation of individual intra‐octahedron, which fails to well reflect collective lattice distortion. Here, a set of new structural distortion descriptors associated with inter‐octahedra is introduced for 2D perovskite (C7H10N)2PbBr4, that is,(PMA)2PbBr4 through pressure engineering. An experimental conclusion is reached that adjacent Pb displacement, as the inter‐octahedron distortion, is an effective parameter in determining the structural distortion and emission behavior of (PMA)2PbBr4 under high pressure. Under high pressure, 2D perovskite (PMA)2PbBr4 exhibits two emission behaviors, free excitons (FEs) emission and self‐trapped excitons (STEs) emission. Different types of four‐Pb‐shaped quadrilateral correspond to different emissions: square‐type (only FEs emission), parallelogram‐type (coexistence of FEs emission and STEs emission), kite‐type (only STEs emission). Moreover, an enhanced violet emission at ≈431 nm is achieved under a mild pressure of 1.0 GPa, which is a crucial light source of medical sterilization. The underlying structure‐property relationship is clarified fundamentally deepens the photophysical mechanism of (PMA)2PbBr4, thus facilitating the design of high‐efficiency perovskite luminophores.

Theoretical study the photophysical mechanism of fluorescent probe on detecting mitochondria-targeted hydrogen peroxide

The photophysical mechanism and dynamics behaviors of (E)-4-(2-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)vinyl)-1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)pyridin-1-ium (Compound 1) on detecting hydrogen peroxide (H2O2) has been theoretically studied. The boron ester in Compound 1 is cleaved when H2O2 is added to the solution, resulting in the formation of (E)-7-(diethylamino)-3-(2-(pyridin-4-yl)vinyl)-2H-chromen-2-one (Compound 2). Theoretical calculations show that the fluorescence spectra of the compounds exhibit a significant blue shift from 616 nm of Compound 1 to 542 nm of Compound 2 before and after the reaction, which are in good agreement with the experimental results (640 nm → 535 nm). The calculated electron–hole transfer distance of Compound 1 (5.986 Å) is larger than that of Compound 2 (3.544 Å), and Compound 1 is demonstrated to be charge transfer excitation while the Compound 2 is localized excitation, which results in a blue shift of the fluorescence spectra. The analysis of molecular electrostatic potential demonstrates that compound 1 has the highest electrostatic potential (4.60 eV) at the pyridine position and the lowest (−0.30 eV) at the oxygen atom of the coumarin moiety, suggesting that compound 1 undergoes fragmentation at this position. This study provides a theoretical explanation for the reaction mechanism of molecular probes.

Photophysical mechanism study of photophysical properties of new red BODIPY chromophores with or without methyl substitution

The relationship between the photophysical properties and structure of BODIPY derivatives always has attracted much attention. Two new BODIPY derivative chromophores with phenyl group substitutions at meso-/6- positions, with or without methyl substitutions at 1/3/5/7 positions were investigated by ways of combination of multiple experimental techniques and theoretical methods. The chromophore without methyl substitutions has a larger Stokes shift and better viscosity sensitivity compared to the other one. The intrinsic reason is that considerable charge transfer between the BODIPY core and the 6- position group is achieved in chromophore. However, this charge transfer process is severely weakened, if 1-/3-/5-/7- methyl substitutions existing, via restricting rotation between the core and side groups. At the same time, the non-radiative process is amplified significantly in chromophore without methyl substitution and the fluorescence efficiency decrease from 51.7% (with methyl substitutions) to 1.84% (without methyl substitutions) in DMSO. Quantum calculations indicate the presence or absence of methyl substitution can change both the shape and height of the torsional potential energy curve of the side groups, thereby affecting the fluorescence quantum yield and viscosity response performance of chromophores. Our work can provide foundation and ideas for designing and optimizing BODIPY derivatives with objective photophysical properties.

Recent Advances in Fast-Decaying Metal Halide Perovskites Scintillators.

Fast-decaying scintillators show subnanoseconds or nanoseconds lifetime and high time resolution, making them important in nuclear physics, medical diagnostics, scientific research, and other fields. Metal halide perovskites (MHPs) show great potential for scintillator applications owing to their easy synthesis procedure and attractive optical properties. However, MHPs scintillators still need further improvement in decay lifetime. To optimize the decay lifetime, great progress has been achieved recently. In this Perspective, we first summarize the structural characteristics of MHPs in various dimensions, which brings different exciton behaviors. Then, recent advances in designing fast-decaying MHPs according to different exciton behaviors have been concluded, focusing on the photophysical mechanisms to achieve fast-decaying lifetimes. These advancements in decay lifetimes could facilitate the MHPs scintillators in advanced applications, such as time-of-flight positron emission tomography (TOF-PET), photon-counting computed tomography (PCCT), etc. Finally, the challenges and future opportunities are discussed to provide a roadmap for designing novel fast-decaying MHPs scintillators.

Thermal Enhanced Energy Transfer and High Thermal Sensitivity of Sb3+ Doped Cs2KYbCl6 Rare Earth Double Perovskites

AbstractRare‐earth based double perovskites (DPs) have attracted much attention due to stable, efficient, and unique luminescence, and wide applications in many optoelectronic fields. However, their weak near‐infrared (NIR) emission and poor anti‐thermal quenching severely limit the further applications. Herein, Sb3+‐doped Cs2KYbCl6 DP with cyan self‐trapped exciton (STE) and NIR emission is prepared by a solvothermal method, and the separate photoluminescence quantum yields from STE and NIR emission reached ≈26.1% and 43.8%, respectively. More importantly, Sb3+ not only contributes to the absorption and energy transfer but also helps to establish an effective thermally enhanced energy transfer channel through self‐trapping state, resulting in the NIR emission with superior anti‐thermal quenching resistance. The thermal sensitivity of luminescence intensity ratio (LIR) of I1010 nm/I505 nm (I is the intensity of PL) and time‐resolved temperature sensor reach 21.4 and 13.6% K−1, respectively, which are ahead of most temperature sensing materials. Furthermore, it is found that the material exhibited advanced multifunctional applications in LED lighting, flexible luminescent thin film, and NIR imaging. This work provides in‐depth understanding on photophysical mechanisms of rare‐earth luminescent materials and references for designing high‐performance materials.

Exploiting in-plane anisotropy in Ta2NiSe5 spanning near to mid-infrared photodetection

Miniaturized and stabilized polarization-sensitive mid-Infrared photodetectors at room temperature are indispensable in fields ranging from medical diagnostics to military surveillance in the next-generation on-chip polarimeters. Emerging two-dimensional materials offer a promising avenue to fulfill these requirements, facilitated by their ease of integration onto complex structures, inherent in-plane anisotropic crystal structures that enhance polarization sensitivity, and robust quantum confinement effects that enable superior photodetection performance at room temperature. Here, we report the systematic investigation of polarization-dependent infrared photoresponse based on Ta2NiSe5, revealing significant anisotropy photocurrent with excellent stability at room temperature. Significantly, a large anisotropic ratio of Ta2NiSe5 ensures the polarization sensitivity achieves a ratio of 1.23 at 1550 nm. Moreover, at 4.6 μm, the device exhibits a peak photocurrent response of 1.16 A/W along the armchair orientation, with an anisotropy ratio of approximately 3.3. These findings not only enhance our understanding of the photophysical mechanisms in two-dimensional materials but also guide the optimization of photodetector design for enhanced performance.

Improved Exciton Diffusion through Modulating Förster Resonance Energy Transfer for Efficient Organic Solar Cells

Förster resonance energy transfer (FRET) is commonly utilized in organic solar cells (OSCs) to enhance the power conversion efficiency (PCE) by promoting molecular interactions. The PCE is greatly affected by the number of photo‐generated excitons that effectively reach interfaces between the donor and acceptor materials of OSCs. However, the correlation between FRET and exciton diffusion has received limited attention. Therefore, it is crucial to understand and manipulate FRET process for investigating exciton dynamics in OSCs. Herein, BTA3 and its derivatives are chosen as the third components and energy donors to elucidate the intrinsic photophysical mechanism of FRET in OSCs by manipulating their efficiency. The results unambiguously demonstrate that the addition of guest F‐BTA3 exhibits the highest FRET efficiency, leading to a significant enhancement in the PCE of both PM6:Y6 and PM6:PY‐IT host systems. By correlating FRET process and exciton dynamics, this enhancement to remarkable increment in exciton diffusion length is attributed. Experimental results and theoretical simulations indicate high FRET efficiency arises from strong dipole–dipole interaction, and exhibits a positive correlation with exciton diffusion length. This study showcases the effective regulation of exciton diffusion in OSCs through modulation of FRET, offering a novel perspective for optimizing the performance of organic photovoltaic devices.

Deepening insights of AIE plus TICT activated fluorescent sensor mechanism in probe molecule DPA-CI

The DPA-CI molecule is a novel fluorescent sensing probe synthesized with TICT and AIE properties. It can detect phosgene, generating DPA-CI-PS. We investigated their photophysical mechanisms in THF solvent using DFT and TD-DFT methods. Large torsion angles and noticeable charge separation confirmed that the TICT occurs in DPA-CI. Due to the formation of a robust cyclic structure, the TICT is inhibited in DPA-CI-PS. Besides, based on NBO analysis, we demonstrated that DPA-CI-PS exhibits significant AIE characters. This work clearly illuminates the detection mechanism, which offers theoretical insights valuable for developing efficient fluorescent sensing probes.