Red-shifted Fluorescence Research Articles

Photonics of High-Entropy Polymers Revealing Molecular Dispersion via Polymer Mixing.

Blending multiple polymers together to form the so-called "high-entropy polymers (HEPs)" can generate the effects of molecular dispersion in addition to suppressing polymer phase separation. We embedded a semiconducting polymer (conjugated polymers, CPs) in an optically inert matrix composed of n polymer species and found that a molecule-level dispersion is attained in HEPs defined as n ≥ 5. In the regime of dilute CP concentrations, the photonic properties vary widely in the n = 1 matrices owing to diverse solubility parameters, but the distribution narrows with n, and the CP starts to exhibit behaviors of molecule-level dispersion at n ≥ 5, where the matrix polymers compete with each other to exert direct influences on the embedded CP. Specifically, for MEH-PPV, increasing n reduces the fluorescence redshift and spectral width from diminishing aggregation. For the rigid PFO molecules, increasing n creates a dilution effect facilitating formation of the low-energy planar β-phase. For the flexible regioregular P3HT-rr, HEPs offer well-dispersed amorphous chains highly susceptible to chain environments, thus influencing ηR's in the quasi-fixed amorphous-crystalline energy transfer landscape. The HEP effects continue for greater CP concentrations, consistent with the matrix dispersing behaviors in the dilute regime. This work demonstrates a molecular-level dispersion by HEPs, offering a method of molecular tailoring for polymer research and applications via simple mixing.

Permeability-Controlled Probe for Ratiometric Detection of Plasma Membrane Integrity and Late Apoptosis.

The destruction of plasma membrane integrity is closely related to immune response, neuronal injury, cell apoptosis, and other pathological events. However, the construction of ratiometric fluorescent probes capable of detecting plasma membrane integrity remains a significant challenge, hindering in-depth studies on related biomedical areas. Herein, a polarity-responsive fluorescent probe was constructed for the ratiometric detection of cell membrane integrity for the first time. The probe targeted intact plasma membranes in healthy cells and relocated into the cytoplasm to give significantly red-shifted fluorescence after plasma membrane damage. Molecular simulations revealed that the high transmembrane barrier and amphipathic nature of the probe were responsible for its targeting ability. With the probe, the ratiometric detection of late apoptosis stage was realized for the first time, and the membrane damage of tumor cells induced by UV irradiation, toxins, and antitumor drugs was visualized. The effect of formaldehyde on membrane integrity was evaluated using a probe, and cysteine was proved to be a potential detoxifier to counteract the toxicity of formaldehyde.

C3-symmetric triarylboron building blocks: Synthesis, structures, and photophysical properties

Synthesis of C3-symmetric triarylboranes, tris(4-bromo-2,6-dimethylphenyl)-borane (1), N,N',N''-(boranetriyltris(3,5-diisopropyl-3′,5′-dimethyl-[1,1′-biphenyl]-4′,4-diyl))tris(1,1-diphenylmethanimine) (2), N,N',N''-(boranetriyltris(3′,5′-dimethyl-[1,1′-biphenyl]-4′,4-diyl))tris-(1,1-diphenylmethanimine) (3), 4′,4′'',4′''''-boranetriyltris(3′,5′-dimethyl-[1,1′-biphenyl]-4-carbaldehyde) (4), 4,4′,4′'-boranetriyltris(3,5-dimethylaniline) (5), 4′,4′'',4′''''-borane-triyltris(3′,5′-dimethyl-[1,1′-biphenyl]-4-carbonitrile) (6), 4′,4′'',4′''''-boranetriyltris(3′,5′-dimethyl-[1,1′-biphenyl]-4-amine) (7), and 4,4′,4′'-boranetriyltris(3,5-dimethylbenzaldehyde) (8) has been accomplished using well-known synthetic methodologies. These new potential building blocks have been characterized by various spectroscopic and analytical techniques and their photophysical properties have been examined. It is observed that photophysical properties of these compounds are enhanced with π conjugation expansions along the branches when donor moieties such as -NH2 groups are present at the para-position of the aryl rings. The highest quantum yield of 0.293 is observed for 4′,4′'',4′''''-boranetriyltris(3′,5′-dimethyl-[1,1′-biphenyl]-4-amine) (7). Interestingly, red-shifted fluorescence spectra follow the same trend as absorption spectra. The fluorescence lifetime increases with the number of donor moieties. The present findings demonstrate the possible use of these C3-symmetric boron-containing building blocks in developing new polymeric materials with improved photophysical properties for various applications.

Aryl/fluoroaryl-substituted triphenylene discotic liquid crystals: Synthesis, mesomorphism, and photophysical properties

Fluorine aromatic hydrocarbons are ubiquitous optoelectronic functional materials and their efficient synthetic methods are still the subject of rapid, ongoing development. Here, several aryl- and fluoroaryl-substituted triphenylenes (Ar-TP/FAr-TP) were synthesized via either Suzuki-Miyaura cross-coupling or aromatic nucleophilic substitution (SNAr) of perfluoroarenes, respectively, starting indifferently from 2-bromo-3,6,7,10,11-pentakis(hexyloxy)triphenylene (Br-TP). These compounds possess very high thermal stability with initial decomposition temperature over 300 °C, as measured by thermal gravimetric analysis (TGA). Differential scanning calorimetry (DSC), polarized optical microscopy (POM), and small/wide angle X-ray scattering (S/WAXS) revealed that they all self-organize into hexagonal columnar (Colhex) mesophase over broad temperature ranges, occurring at room temperature for some of them, with higher stability than the archetypical 2,3,6,7,10,11-hexakis(hexyloxy)triphenylene parent compound. Under the combined influence of the conjugated π-system and core-side arm distortion, the clearing temperatures and mesophase ranges increase from phenyl- (P-TP), naphthyl- (N-TP), to biphenyl-triphenylene (BP-TP). The number of fluorine atoms on the side fluoroaryl group also impacts the columnar mesomorphism: the more fluorine atoms, the higher the clearing temperatures and the wider the Colhex phase ranges, concomitantly with increasing arene-fluorarene intermolecular interactions. In addition, these compounds show blue-violet photoluminescence in solution: the largest fluorescent absolute quantum yield is measured for BP-TP (45 %), while the smallest is for 7FN-TP (10 %). Perfluoroaryls tend to lower the LUMO, which results in fluorescence red-shift. The arene-perfluoroarene polar-π interactions improve the physical properties of these FAr-TP discotic liquid crystals.

Energetic Landscape and Terminal Emitters of Phycobilisome Cores from Quantum Chemical Modeling.

Phycobilisomes (PBs) are giant antenna supercomplexes of cyanobacteria that use phycobilin pigments to capture sunlight and transfer the collected energy to membrane-bound photosystems. In the PB core, phycobilins are bound to particular allophycocyanin (APC) proteins. Some phycobilins are thought to be terminal emitters (TEs) with red-shifted fluorescence. However, the precise identification of TEs is still under debate. In this work, we employ multiscale quantum-mechanical calculations to disentangle the excitation energy landscape of PB cores. Using the recent atomistic PB structures from Synechoccoccus PCC 7002 and Synechocystis PCC 6803, we compute the spectral properties of different APC trimers and assign the low-energy pigments. We show that the excitation energy of APC phycobilins is determined by geometric and electrostatic factors and is tuned by the specific protein-protein interactions within the core. Our findings challenge the simple picture of a few red-shifted bilins in the PB core and instead suggest that the red-shifts are established by the entire TE-containing APC trimers. Our work provides a theoretical microscopic basis for the interpretation of energy migration and time-resolved spectroscopy in phycobilisomes.

An Acid-Responsive Fluorescent Molecule for Erasable Anti-Counterfeiting.

A tetraphenylethylene (TPE) derivative, TPEPhDAT, modified by diaminotriazine (DAT), was prepared by successive Suzuki-Miyaura coupling and ring-closing reactions. This compound exhibits aggregation-induced emission enhancement (AIEE) properties in the DMSO/MeOH system, with a fluorescence emission intensity in the aggregated state that is 5-fold higher than that of its counterpart in a dilute solution. Moreover, the DAT structure of the molecule is a good acceptor of protons; thus, the TPEPhDAT molecule exhibits acid-responsive fluorescence. TPEPhDAT was protonated by trifluoroacetic acid (TFA), leading to fluorescence quenching, which was reversibly restored by treatment with ammonia (on-off switch). Time-dependent density functional theory (TDDFT) computational studies have shown that protonation enhances the electron-withdrawing capacity of the triazine nucleus and reduces the bandgap. The protonated TPEPhDAT conformation became more distorted, and the fluorescence lifetime was attenuated, which may have produced a twisted intramolecular charge transfer (TICT) effect, leading to fluorescence redshift and quenching. MeOH can easily remove the protonated TPEPhDAT, and this acid-induced discoloration and erasable property can be applied in anti-counterfeiting.

Methyl- and fluoro-substituted triphenylamine core toward fast-switching visible and near-infrared electrochromic polymers

Herein, two monomers MTPA and FTPA, and their corresponding polymers (PMTPA and PFTPA) based on a methyl-and fluoro-substituted triphenylamine were synthesized by Stille reaction and electropolymerization. MTPA exhibited the red-shift absorption and fluorescence emission spectra, and lower Eonset (0.53 V) compared with FTPA (0.57 V), which is beneficial to achieve high-quality polymers. The polymer films exhibited reversible color transition from yellow green to deep blue for PMPTA and from dark brown to light blue for PFTPA, respectively. In addition, both PMTPA and PFTPA films exhibited good optical contrasts of 36 % and 40 % at 1100 nm, respectively. The coloration efficiency and response times at 1100 nm are 196.4 C−1 cm2 with 0.6 s for PMTPA, and 160.9 C−1 cm2 with 1.4 s for PFTPA, respectively. These polymer films demonstrated excellent electrochemical property and electrochromic performance. These results will also provide a new strategy to rationally design the excellent electrochromic polymers based on the triphenylamine core.

Aminophenylboronic acid-modified nitrogen-doped graphene quantum dots and their applications in lysine sensing based on interplaying fluorescent mechanisms.

Using nitrogen-doped graphene quantum dots (N-GQDs) and 3-aminophenylboronic acid (APBA), a novel fluorescence nanosensorwas developed. This nanosensor exhibits high selectivity and sensitivity for lysine detection. Its sensing mechanism involves the suppression of electron transfer from APBA to the N-GQDs unit, thereby inhibiting photoinduced electron transfer and initiating internal charge transfer. At an optimal pH of 7, the protonated α-amine and ε-amine groups of lysine interact with the amide and boronic acid moieties, respectively. This interaction results in a redshift of fluorescence, substantially enhancing the response signal. A linear response was observed within a concentration range 0.40-3.01μM, with the detection limit being 0.005μM. A similar linear range was also achieved for the determination of lysine in human serum. Density functional theory calculations correlating molecular orbits and geometries support UV-vis and fluorescence findings. Additionally, the nanosensor wassuccessfully applied to detect lysine in living cells and real samples, including milk and honey. For practical application, we construct a lysine-specific sensing platform using a commercial chip (TCS34725) that collects red, blue, and green signals, thereby facilitating the convenient use of the nanosensor. Overall, this study offers new perspectives on the development and application of fluorescent nanosensors for detecting individual amino acids.

Enhanced Quantum Efficiency of Near-IR Perovskite Light Emitting Diodes Via Dual Interfacial Modification

Near-infrared (NIR) light-emitting diodes play a crucial role in a wide range of applications, including sensors, night vision displays, security systems, medicine, spectroscopy, and military applications. The potential for high-performance NIR perovskite light-emitting diodes (NIR-PeLEDs) has been highlighted with the impressive advancement of fluorescent perovskite thin films. These PeLEDs exhibit promising features such as a tunable band gap, high color purity, and low non-radiative recombination rates. Despite these advantages, the current state-of-the-art NIR-PeLEDs faces challenges primarily related to poor film quality and increased defect states, leading to limitations in external quantum efficiency (EQE) and operational stability. In addressing these issues, we present a novel dual interfacial modification approach involving the incorporation of fluorinated phenethylammonium iodide (F-PEAI), a bulky organic cation, at both the bottom and top interfaces of perovskite emitting films. The modified interfaces result in perovskite films with a smoother surface morphology, complete coverage, and high crystallinity, leading to a red-shifted fluorescence band extending toward 800 nm. Furthermore, the introduction of F-PEAI facilitates the formation of compact and fine grains in perovskite films, contributing to an enhanced photoluminescence quantum yield (PLQY). Consequently, NIR-PeLEDs modified with F-PEAI demonstrate improved EQE values coupled with enhanced operational stability. The combination of electrical, optical, and physical analyses of both films and devices underscores the effectiveness of the dual interface modification in developing efficient NIR perovskite LEDs suitable for practical applications.

Environment-dependent chlorophyll-chlorophyll charge transfer states in Lhca4 pigment-protein complex.

Photosystem I (PSI) light-harvesting antenna complexes LHCI contain spectral forms that absorb and emit photons of lower energy than that of its primary electron donor, P700. The most red-shifted fluorescence is associated with the Lhca4 complex. It has been suggested that this red emission is related to the inter-chlorophyll charge transfer (CT) states. In this work we present a systematic quantum-chemical study of the CT states in Lhca4, accounting for the influence of the protein environment by estimating the electrostatic interactions. We show that significant energy shifts result from these interactions and propose that the emission of the Lhca4 complex is related not only to the previously proposed a603+-a608- state, but also to the a602+-a603- state. We also investigate how different protonation patterns of protein amino acids affect the energetics of the CT states.

Structure of the red-shifted Fittonia albivenis photosystem I

Photosystem I (PSI) from Fittonia albivenis, an Acanthaceae ornamental plant, is notable among green plants for its red-shifted emission spectrum. Here, we solved the structure of a PSI–light harvesting complex I (LHCI) supercomplex from F. albivenis at 2.46-Å resolution using cryo-electron microscopy. The supercomplex contains a core complex of 14 subunits and an LHCI belt with four antenna subunits (Lhca1–4) similar to previously reported angiosperm PSI–LHCI structures; however, Lhca3 differs in three regions surrounding a dimer of low-energy chlorophylls (Chls) termed red Chls, which absorb far-red beyond visible light. The unique amino acid sequences within these regions are exclusively shared by plants with strongly red-shifted fluorescence emission, suggesting candidate structural elements for regulating the energy state of red Chls. These results provide a structural basis for unraveling the mechanisms of light harvest and transfer in PSI–LHCI of under canopy plants and for designing Lhc to harness longer-wavelength light in the far-red spectral range.

Coordination Synergistic-Induced J-Aggregation Enhanced Fluorescent Performance of HBT-Excimers and Imaging Applications.

Developing a novel strategy to improve the optical performances of fluorescent probes is a vital factor in elevating its practical application; viz., novel biocompatible fluorescent probes with excellent multifunctions exhibited unparalleled advantages in probing functions of intracellular molecules to elucidate intracellular events in living systems. Herein, we have successfully constructed a new strategy that aggregation and coordination synergistically induce (2-hydroxylphenyl-benzothiazole) HBT derivatives to form excimers with large red-shifted fluorescence and application for insight into stress-response zinc fluctuations in living systems. We have synthesized four HBT-based derivatives and deeply investigated the response mechanism by fluorescent spectral studies, demonstrating that probes 3 and 4 showcased large red shifts in emission wavelength due to J-aggregation. More interestingly, the fluorescence of probe 4 was significantly enhanced in the presence of a zinc ion, suggesting that zinc coordination synergistically induced J-aggregation. Probe 4 was successfully applied to image zinc fluctuations in different models of living systems, proving that this probe is a powerful tool to unveil the relationship between invasive stress and diseases by monitoring endogenous zinc fluctuations.

A Ratiometric Fast-Response Fluorescent Probe Based on Dicyanoisophorone for Monitoring HClO in Paper Test Strips and Living Mice.

A new dicyanoisophorone-based ratiometric fluorescent probe NOSA was synthesized and characterized. It showed a fast fluorescence response to HClO with the emission color change from dark green to bright red. NMR, IR, and HRMS suggested that the detection of NOSA to HClO may originate from the hydroxyl deprotection reaction by HClO on the molecule NOSA, which caused a red-shift of fluorescence. The probe NOSA displayed high selectivity and excellent anti-interference performance with a limit of detection at 3.835 × 10-7M. The convenient paper test strips were successfully obtained and applied to the detection of HClO based on fluorescence color change with the varied NaClO concentration. Moreover, spiked recovery experiments in real water samples indicated that the probe NSOA could quantitatively detect HClO, and the fluorescence bio-imagings in vivo were carried out, and HClO detection in biosystems using NOSA was realized.

Design and synthesis of fluorescent BODIPY derivatives with D-A structure for cancer cell imaging

Boron-dipyrromethene (BODIPY) as a traditional fluorescent dye has received increasing attention because of its high molar extinction coefficient, easy modification, and good light stability. In this work, three BODIPY compounds (BDP-1, BDP-2 and BDP-3) were designed and synthesized by introducing PEG chains and a naphthalimide (NI) group onto the parent structure of BODIPY. Due to the electron-withdrawing properties of NI, the compounds of BDP-2 and BDP-3 formed a typical donor (D)-acceptor (A) structure, which led to the red-shifted absorption and fluorescence spectrum. The synthesized BODIPY exhibited intense green emission, with fluorescence quantum yield of 0.66, 0.29, and 0.19 for BDP-1, BDP-2 and BDP-3 respectively. The decrease in fluorescence of BDP-2 and BDP-3 was probably ascribed to the enhanced intramolecular charge transfer because of the introduction of the NI group. The good biocompatibility and low cytotoxicity of the synthesized BODIPY compounds were verified by the CCK-8 assay. The subcellular localization of the three compounds was further evaluated through a confocal laser scanning microscope. The results showed that these BODIPY derivatives were mainly localized in the lysosomes of cancer cells. Thus, the synthesized BODIPY fluorescent dyes show promising applications in tumor imaging benefiting from their good biocompatibility and strong fluorescence.

Solid-State Red Carbon Dots Based on Biomass Furan Derivatives.

In the preparation of carbon dots (CDs), precursors are crucial, and abundant precursors endow CDs with various structures and fluorescence characteristics. Furan (FU) and its derivatives are considered excellent carbonization materials due to their π conjugated structures and active functional groups, such as hydroxyl and aldehyde groups. Herein, we prepare FU-derivative-based CDs by a solvothermal method and investigate the influences of the precursor structure on the fluorescence characteristics. Surprisingly, CDs prepared from 5-hydroxymethylfurfural (HMF) with both aldehyde and hydroxyl groups exhibit red-shifted fluorescence characteristics in the solid state. We postulate that this solid-state fluorescence characteristic is due to the enhancement of supramolecular cross-linking fluorescence between CDs. The unique precursor structure leads to carboxyl groups on the surface of HMF-CDs that are conducive to the hydrogen bond formation. As the concentration of CDs increases, the hydrogen bonding effect increases, leading to a red-shift in the fluorescence wavelength. Therefore, basically full-color CDs/poly(vinyl alcohol) (PVA) phosphor-based light-emitting diodes can be achieved by controlling the degree of supramolecular cross-linking of CDs in PVA. This research provides a new approach for the preparation of solid-state luminescent CDs.

Bis-Ortho-Donor-Modification of Boracyclic π-Electron Systems beyond Steric Protection to Produce Thermally Activated Delayed Fluorescence Materials.

Polycyclic π-conjugated compounds that contain tricoordinate boron atoms at their periphery represent an attractive class of materials with electron-accepting character. Their molecular design generally requires the introduction of a bulky aryl group onto the boron atom, where it provides predominantly kinetic stabilization. The addition of extra functionality to the aryl group on the boron atom can be expected to further expand the potential utility of this class of materials. Herein, we report the synthesis of a series of boracyclic π-conjugated molecules with firm ortho B⋅⋅⋅N nonbonding interactions by introducing N-containing electron-donors at the ortho-positions of the aryl group on the boron atom. X-ray crystallographic analysis revealed that the combination of a planar boracyclic π-skeleton with only sp2 carbons and a strong electron-donating phenothiazine moiety results in a particularly short B⋅⋅⋅N distance. Theoretical study provided insights into the inherent nature of the B⋅⋅⋅N interaction. Owing to their donor-acceptor (D-A) structures, these molecules exhibit substantially red-shifted fluorescence in solution, albeit that the fluorescence quantum yields (ΦF) are low. In contrast, when incorporated into films, these compounds exhibit thermally activated delayed fluorescence (TADF) with improved ΦF values. Organic light-emitting diodes (OLEDs) fabricated using the ortho-donor-substituted derivatives exhibit orange-red electroluminescence.

Light Induced Proton Coupled Charge Transfer Triggers Counterion Directional Translocation.

We demonstrate directed translocation of ClO4 - anions from cationic to neutral binding site along the synthetized BPym-OH dye molecule that exhibits coupled excited-state intramolecular proton-transfer (ESIPT) and charge-transfer (CT) reaction (PCCT). The results of steady-state and time-resolved spectroscopy together with computer simulation and modeling show that in low polar toluene the excited-state redistribution of electronic charge enhanced by ESIPT generates the driving force, which is much stronger than by CT reaction itself and provides more informative gigantic shifts of fluorescence spectra signaling on ultrafast ion motion. The associated with ion translocation red-shifted fluorescence band (at 750 nm, extending to near-IR region) appears at the time ~83 ps as a result of electrochromic modulation of PCCT reaction. It occurs at substantial delay to PCCT that displayed fluorescence band at 640 nm and risetime of <200 fs. Thus, it becomes possible to visualize the manifestations of light-triggered ion translocation and of its driving force by fluorescence techniques and to separate them in time and energy domains.

The influence of the interaction between whey protein and erythritol on protein conformation, interfacial properties and stability

This study investigated the impact of erythritol (ERY) on structural and functional properties of whey protein isolate (WPI). FTIR and CD revealed that WPI underwent structural changes, including formation of β‐folds and random coils, upon interaction with 20 mg/mL ERY. SEM showed increased surface roughness of WPI, indicating enhanced protein exposure. Moreover, binding rate exceeded 85%, accompanied by increased surface hydrophobicity. Fluorescence spectroscopy indicated a red shift in fluorescence of WPI and tyrosine (Tyr) residues, altering polarity of Tyr environment due to ERY coordination. Additionally, ERY presence enhanced the functional properties of WPI, including foaming, freeze–thaw stability, rheology and antioxidant activity.

Meta-Analysis of Optical Surrogates for the Characterization of Dissolved Organic Matter.

Optical surrogates, derived from absorbance and fluorescence spectra, are widely used to infer dissolved organic matter (DOM) composition (molecular weight, aromaticity) and genesis (autochthonous vs allochthonous). Despite the broad adoption of optical surrogates, several limitations exist, such as context- and sample-specific factors. These limitations create uncertainty about how compositional interpretations based on optical surrogates are generalized across contexts, specifically if there is duplicative or contradictory information in those interpretations. To explore these limitations, we performed a meta-analysis of optical surrogates for DOM from diverse sources, both from natural systems and after water treatment processes (n = 762). Prior to analysis, data were screened using a newly developed, standardized methodology that applies systematic quality control criteria before reporting surrogates. There was substantial overlap in surrogate values from natural and treated samples, suggesting that the gradients governing the surrogate variability can be generated in both contexts. This overlap provides justification for using optical surrogates originally developed in the context of natural systems to describe DOM changes in engineered systems, although the interpretations may change. Absorbance-based surrogates that describe the amount of spectral tailing (e.g., E2:E3 and S275-295) had a high frequency of strong correlations with one another but not to specific absorbance (SUVA254) or absorbance slope ratio (SR). The fluorescence index (FI) and biological index (β/α) were strongly correlated with one another and to the peak emission wavelength but not to the humification index (HIX). Although SUVA254 and FI have both been correlated to DOM aromaticity in prior research, there was a lack of reciprocity between these optical surrogates across this data set. Additionally, there were patterns of deviations in the wastewater subset, suggesting that effluent organic matter may not follow conventional interpretations, urging caution in the use of optical surrogates to track DOM in water reuse applications. Finally, the meta-analysis highlights that three aspects should be captured when optical spectra are used for DOM interpretation: specific absorbance, absorbance tailing, and the extent of red-shifted fluorescence. We recommend that SUVA254, E2:E3, and FI or β/α be prioritized in future DOM studies to capture these aspects, respectively.

Excimer Fluorescence of Acriflavine Dye in Glycerol and Ethylene Glycol.

This research investigates the excimerisation of acriflavine dye in ethylene glycol and glycerol solvents. Acriflavine, a member of the acridine dye family, exhibits unique fluorescence properties with applications in various fields, including cellular nucleus observation, nucleic acid analysis, and dye laser active media etc. The study explores the impact of solvent and concentration on acriflavine's emission properties, with a focus on excimer formation, which can influence its suitability as a dye laser active medium. UV-Visible absorption spectroscopy reveals concentration-dependent absorption profiles, with distinctive monomer bands. Steady-state fluorescence studies demonstrate the emergence of red-shifted excimer fluorescence bands as concentrations increase in both solvents. Temperature-dependent fluorescence studies reveal the dynamics of excimer formation, suggesting dynamic diffusion as the excimerisation mechanism. Time-resolved fluorescence spectroscopy confirms the singlet character of both monomer and excimer states, providing insights into the excimerisation process. Critical concentration values are determined, representing the equilibrium between monomeric and excimeric forms. The study also explores pH-induced spectral shifts, highlighting the influence of acidity on fluorescence properties. Overall, this research deepens our understanding of acriflavine's excimerisation in ethylene glycol and glycerol, offering insights that can enhance its diverse applications, especially in laser technologies.