Fluorescence Enhancement Research Articles

A portable fluorescence sensing system for timely onsite perfluorooctane sulfonate detection based on an aggregate induced emission fluorescence sensor.

Perfluorooctane sulfonate (PFOS), a ubiquitous persistent organic pollutant, has aroused growing concern due to its adverse effects on human health. Timely onsite monitoring of PFOS in heavily contaminated areas is crucial for effective pollution management and prevention of its spread. However, relevant PFOS detection methods have rarely been reported. Herein, we developed a fluorescence sensing system capable of achieving timely onsite detection of PFOS under outdoor conditions. First, aggregate induced emission (AIE) fluorescence sensors, TPE-PAs, were synthesized. The optimized sensor could selectively interact with PFOS through electrostatic attraction and hydrogen bonding and exhibited prominent fluorescence enhancement after treating with PFOS. There was a good linear relationship between the fluorescence enhancement and PFOS concentration in the range of 0.05-30 ppm, and the limit of detection was measured to be 0.047 ppm. In addition, owing to the AIE fluorescence mechanism and high concentration of TPE-PAs in the sensing medium, the sensor demonstrated excellent anti-interference performance. Second, we developed a portable fluorometer, by modifying the power supply and sample cell of a tiny fluorometer, and further integrated this modified fluorometer, the prepared fluorescence sensor, standard PFOS solutions and other consumables into a portable test system. This test system showed good detection accuracy and reliability and successfully achieved timely onsite PFOS detection in real water samples.

Long-range enhancement for fluorescence and Raman spectroscopy using Ag nanoislands protected with column-structured silica overlayer

We demonstrate long-range enhancement of fluorescence and Raman scattering using a dense random array of Ag nanoislands (AgNIs) coated with column-structured silica (CSS) overlayer of over 100 nm thickness, namely, remote plasmonic-like enhancement (RPE). The CSS layer provides physical and chemical protection, reducing the impact between analyte molecules and metal nanostructures. RPE plates are fabricated with high productivity using sputtering and chemical immersion in gold(I)/halide solution. The RPE plate significantly enhances Raman scattering and fluorescence, even without proximity between analyte molecules and metal nanostructures. The maximum enhancement factors are 107-fold for Raman scattering and 102-fold for fluorescence. RPE is successfully applied to enhance fluorescence biosensing of intracellular signalling dynamics in HeLa cells and Raman histological imaging of oesophagus tissues. Our findings present an interesting deviation from the conventional near-field enhancement theory, as they cannot be readily explained within its framework. However, based on the phenomenological aspects we have demonstrated, the observed enhancement is likely associated with the remote resonant coupling between the localised surface plasmon of AgNIs and the molecular transition dipole of the analyte, facilitated through the CSS structure. Although further investigation is warranted to fully understand the underlying mechanisms, the RPE plate offers practical advantages, such as high productivity and biocompatibility, making it a valuable tool for biosensing and biomolecular analysis in chemistry, biology, and medicine. We anticipate that RPE will advance as a versatile analytical tool for enhanced biosensing using Raman and fluorescence analysis in various biological contexts.

Uncovering Integrated Dual-State ESIPT-Conductivity, Redox-Capacity, and Opto-Electronic Responses Toward Hg(II)/ Cr(III) of Aliphatic Fluorescent Polymers.

Excited-state intramolecular proton transfer (ESIPT)-associated dual-state emissive aliphatic dual-light emitting conducting polymers (DLECPs) having oxidation-reduction capacities are prepared polymerizing 2-acrylamido-2-methylpropane-1-sulfonic acid, methacrylic acid, and 2-methyl-3-(N-(2-methyl-1-sulfopropan-2-yl)acrylamido)propanoic acid monomers. Of as-synthesized DLECPs, nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies, fluorescent enhancements (I/I0), and computational investigation indicate intriguing photophysical features in DLECP3 (optimum composition). In DLECP3, ─CONH─, ─CON<, and ─COOH subluminophores are recognized by density-functional theory (DFT)/time-dependent-DFT calculations and experimental investigations. ESIPT-associated dual-state emission/conductivity, aggregation-enhanced emissions, selective opto-electronic responses toward Hg(II)/Cr(III) at 437/574nm, and redox properties of DLECP3 are supported by solid-state/solution spectroscopies, time-correlated single photon counting (TCSPC) measurements, dual-state excitation dependent emissions, microscopic images, electrochemical measurements, and DFT calculations. Here, preferential interaction of Hg(II)/Cr(III) with DLECP3 (amide)/DLECP3 (imidol) and reduction/oxidation of Hg(II)/Cr(III) to Hg(I)/Cr(VI) are substantiated by UV-vis, FTIR, and X-ray photoelectron spectroscopies; TCSPC measurements; NMR-titration; electrochemical studies; alongside computational calculations. The proton-electrical conductivities of DLECP3, Hg(II/I)-DLECP3, and Cr(III/VI)-DLECP3 in solids/solutions are 15.27 × 10-5/6.16 × 10-5, 19.60 × 10-5/25.52 × 10-5, and 26.69 × 10-5/27.60 × 10-5 S cm-1, respectively.

Synergistically Activated Aggregation-Induced Emission Probe for Precise In Situ Staining of Lipids in Atherosclerotic Plaques.

Visualizing the localization and distribution of lipids within arteries is crucial for studying atherosclerosis. However, existing lipid-specific probes face challenges such as strong hydrophobicity and nonspecific staining of lipophilic organelles or tissues, making them impractical for the precise identification of atherosclerotic plaques. To address this issue, we design a synergistically activated probe, Cbz-Lys-Lys-TPEB, which responds to cathepsin B (CTB) and H2O2 for the in situ generation of aggregation-induced emission luminogens (AIEgens). This enables specific staining of lipids within arteries and precise imaging of atherosclerotic plaques. The probe combines a tetraphenylethene building block with a hydrophilic peptide sequence (Cbz-Lys-Lys) and phenylboric acid module, providing excellent water solubility and fluorescence quenching in a molecular dispersion state. Upon interaction with H2O2 and CTB within plaques, the hydrophilic Cbz-Lys-Lys-TPEB probe is specifically cleaved and converted into hydrophobic AIEgens, leading to rapid aggregation and significant fluorescence enhancement. Interestingly, the in situ-liberated AIEgens display distinct lipid binding ability, effectively tracking the location and distribution of lipids in plaques. This synergistic target-activated AIEgen liberation strategy demonstrates significant feasibility for the reliable and accurate identification of atherosclerotic plaques, holding tremendous potential for clinical diagnosis and risk stratification of atherosclerosis.

Early Diagnosis of Liver Injury and Real-Time Evaluation of Photothermal Therapy Efficacy with a Viscosity-Responsive NIR-II Smart Molecule.

The early diagnosis of liver injury and in situ real-time monitoring of tumor therapy efficacy are important for the enhancement of personalized precision therapy but remain challenging due to the lack of reliable in vivo visualization tools with integrated diagnostic, therapeutic, and efficacy monitoring functions. Herein, a smart second near-infrared window (NIR-II) molecule (BITX-OH) is rationally designed for diagnosis and therapy by vinyl-bridging hydroxyl diphenyl xanthine unit and benzo[cd]indolium skeleton. BITX-OH exhibits high selectivity and sensitivity toward viscosity, exhibiting a significant enhancement (1167-fold) in NIR-II fluorescence at 962nm. With the assistance of BITX-OH and NIR-II fluorescence imaging, early diagnosis and therapeutic evaluation of non-alcoholic fatty liver (NAFL), as well as in-site real-time monitoring of hepatic fibrosis (HF) in live mice have been successfully achieved, which is at least several hours earlier than the typical clinical test. Notably, BITX-OH displays excellent photothermal conversion efficiency when exposed to an 808nm laser, which can induce tumor ablation and increase viscosity, thereby enhancing NIR-II fluorescence for the real-time evaluation of photothermal therapy (PTT). This viscosity-based "self-monitoring" strategy provides a convenient and reliable platform for timely obtaining therapeutic feedback to avoid over- or under-treatment, thus enabling personalized precision therapy.

Turn-off fluorescent nanoprobe based on carbon dots synthesised by UV/H2O2 advanced oxidation for the detection of bisphenol A in canned foods.

Anovel assay was developedbased on a turn-off fluorescent probe using the in situ generation of carbon dots (CDs) by means of UV/H2O2 advanced oxidation of carbohydrates for the detection of bisphenol A (BPA) in food. Different parameters involved in the synthesis of CDs for the direct recognition of BPA have been optimised and a sensing mechanism is outlined. The presence of H2O2 during CD synthesis causes a fluorescence enhancement due to the action of highly oxidant HO· radicals formed throughout the photochemical reaction. Phenolic compounds such as BPA can be easily degraded by the UV/H2O2 oxidation process, acting as a HO· free radical scavengers. This results in a decrease in the fluorescence that can be related to the BPA concentration. Under optimal conditions, a detection limit of 15µg/kg of BPA and a quantification limit of 46µg/kg of BPA in food sampleswere obtained. The repeatability and reproducibility, expressed as relative standard deviation and obtained for two concentration levels (30µg/kg and 200µg/kg, n = 5), were less than 2.0% and 6.4%, respectively. The proposed procedure was applied to the analysis of five samples of canned foods (sweet corn, peas, mushrooms, cockles and natural tuna), obtaining concentrations in the range 29.8-49.9µg/kg of sample. Recovery studies were conducted at two concentration levels (100and 400µgBPA/kg of sample), resulting in recoveries in the range 99-101%. Method validation against two certified reference materials was also successfully performed. The experimental results demonstrate that the novel approach is suitable for the detection and quantification of BPA in canned foods.

Evaluating the Accuracy of the COMSOL-Based Finite-Element Method for Simulating Plasmon-Modified Fluorescence.

Accurately modeling plasmon-modified fluorescence is important for understanding and guiding the design of experimental nanostructures that reliably enhance fluorescence. They are of particular interest due to their potential to allow localized "hot spots" of high fluorescence enhancement in a reproducible manner. Given the increasingly prevalent use of the COMSOL Multiphysics software package for simulating these phenomena, we investigate its accuracy using an analytically tractable model consisting of a gold nanosphere interacting with either a plane wave or a radiating point dipole. COMSOL simulation results were compared with a formally exact analytical theory. It was found that simulation parameters commonly used for plane-wave scattering do not necessarily produce accurate results for the nanoparticle-plasmon-coupled dipole emission case. Instead, user-input adaptive meshing parameters were found to be helpful in achieving quantitative agreements between COMSOL and analytical theory results for plasmon-modified fluorescence. Our studies suggest convergence to analytically calculated values when a minimum of two additional user-input mesh elements separate the point-dipole position and the nanoparticle surface. This practical insight is expected to aid in the application of COMSOL simulations to planning and interpreting fluorescence modification experiments.

The First N,O-Chelated Diphenylboron-Based Fluorescent Probe for Peroxynitrite and Its Bioimaging Applications

Peroxynitrite (ONOO−) is a reactive oxygen species (ROS) that takes part in the oxidation-reduction homeostasis while at the same time being responsible for activating numerous pathological pathways. Accordingly, monitoring the dynamic changes in ONOO− concentration has attracted a great deal of attention, undoubtedly prompting the development of appropriate fluorescent chemosensors. Herein, we developed a novel N,O-chelated diphenylboron-based fluorescent probe (DPB) for ONOO− featuring high selectivity, a quick response time (2.0 min), and a low detection limit (55 nM). DPB incorporates tetra-coordinated boron in the center of the fluorogenic core and a three-coordinated boron from the pinacolphenylboronate fragment, which acts as the recognition site for ONOO−. As confirmed by HR-MS and 1H NMR, the interaction of DPB with ONOO− led to an oxidative cleavage of pinacolphenylboronate moiety to produce strongly emissive derivative DPB-OH. The fluorescence enhancement is likely a result of a substantial deactivation of non-radiative decay due to the replacement of the bulky pinacolphenylboronate moiety with a compact hydroxyl group. Importantly, DPB probe exhibits negligible cytotoxicity and favorable biocompatibility allowing for an efficient tracking of ONOO− in living cells and zebrafish. Overall, the current study does not only represents the first N,O-chelated diphenylboron-based fluorescent probe for a specific analyte, but also serves as a guideline for designing more potent fluorescent probes based on the chemistry of boron chelates.

Fabrication of a novel mixed-valent copper-based coordination polymer as a fluorescent sensor for selective and efficient detection of multiple analytes

A novel three-dimensional fluorescent mixed-valent copper-based coordination polymer (CP), namely {[CuICuII4(triazol)6(bpta)2]Cl}n (Cu-CP), was synthesized hydrothermally in the presence of Cu(II) ion, 2,4,6-tri(1H-1,2,4-triazol-1-yl)-1,3,5-triazine (TTT), and 2,2′,4,4′-biphenyltetracarboxylic acid (H4bpta). The structure of the Cu-CP was studied using single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD). Interestingly, the crystallographic data revealed that a part of Cu(II) ions were reduced in situ to Cu(I) ions as well as the nitrogen-containing ligand TTT was converted to triazol, which possessed excellent fluorescence characteristics as a transition metal ion with a d10 electronic configuration, prompting further investigation into the fluorescence sensing properties of Cu-CP. The results confirmed that Cu-CP exhibited excellent fluorescence performance which an outstanding candidate as a fluorescence sensor for Fe3+, Cr2O72−, CrO42−, MnO4− and nitrobenzene (NB), with a low limit of detection. For ethylene glycol (EG) detection, Cu-CP showed high-efficiency fluorescence enhancement across a range of temperatures. The underlying mechanism of fluorescence enhancement was investigated through comprehensive experimental studies.

Core‐Fluorinated BODIPYs – a New Family of Highly Efficient Luminophores

AbstractA modular synthesis of novel series of 1,7‐difluorinated BODIPYs has been elaborated. First, the acid‐catalyzed condensation of ethyl 3‐aryl‐4‐fluoro‐1H‐pyrrole‐2‐carboxylates with aromatic aldehydes gives the corresponding dipyrromethane‐1,9‐dicarboxylates. The latter are subjected to the exhaustive reduction with lithium aluminum hydride to transform the ester moieties into methyl groups. The subsequent oxidation of the resulting 1,9‐dimethylated dipyrromethanes followed by the boron difluoride complexation afforded a family of novel core‐fluorinated BODIPYs in up to 74 % yield. Photophysical properties of the resulting BODIPYs were tuned by varying of the starting fluoropyrroles and aromatic aldehydes and were studied by UV‐visible and fluorescence spectroscopy. As a result, the fluorescence quantum yields of the obtained compounds reached up to 99 %. In addition, their ability to generate singlet oxygen and electrochemical properties were also evaluated. As a result, a new promising family of fluorophores with a good combination of the fluorescence and photosensitizing properties was obtained. It was found that conversion of ester groups into methyl ones at the 3,5‐positions of the BODIPY core is a crucial step toward fluorescence enhancement. In addition, DFT calculations were performed to elucidate a relationship between electronic structure, geometry and photophysical properties of these BODIPYs.

A multifunctional metal–organic complex fluorescent probe for highly sensitive detection of lysine, CrO42-/Cr2O72-, Fe3+ and nitro-aromatic compounds

Water contamination caused by organic and inorganic compounds represents an urgent global issue. It is meaningful to detect these compounds. A metal–organic complex (Zn-HTBA) was investigated as a multifunctional fluorescent probe which showed exceptional fluorescence characteristics. The Zn- HTBA can specifically detect lysine in water through fluorescence enhancement, and the detection limit was 0.17 μM. The Zn-HTBA also selectively detect CrO42-/Cr2O72- and Fe3+ with the detection limits of 0.014/0.022 and 0.12 μM through fluorescence quenching. In addition, the Zn-HTBA was found to sensitively detect nitroaromatic compounds in ethanol through fluorescence quenching. The possible detection mechanisms were studied in detail through UV–Vis, PXRD, XPS, etc. The mechanism of Zn-HTBA to detect CrO42-/Cr2O72-, Fe3+ and 2-nitrotoluene was energy competition, and the mechanism of Zn-HTBA to detect lysine was the formation of hydrogen bonds.

Determination of sudan III using nitrogen and sulfur co-doped carbon quantum dots with fluorescence enhancement effect

Sudan III, a synthetic azo dye, is commonly used for coloring oils, waxes, and various plastics. However, its unauthorized presence in food and food products poses serious health hazards, including potential carcinogenic effects. In this study, we investigated the application of nitrogen and sulfur co-doped carbon quantum dots (N,S-CQDs) as a fluorescence sensor to detect trace amounts of sudan III. When exposed to trace amounts of sudan III, the fluorescence signal of N,S-CQDs was significantly enhanced. Under optimal conditions (pH 5.0 and an incubation time of 4 minutes), the fluorescence enhancement of N,S-CQDs showed a linear relationship with sudan III concentration in the range of 7.5 x 10-10 to 1.0 x 10-8 M, with a limit of detection of 2.0 x 10-10 M (equivalent to 0.07 ppb). The method demonstrated high accuracy (recovery from 91.5% to 103.5%), good reproducibility (RSD &amp;lt; 3.86%), and excellent selectivity for sudan III over other azo dyes. We successfully applied this developed method to analyze sudan III in chili sauce and chili powder samples, cross-checking differences between results less than 10% with LC-MS/MS analysis.

Enhanced detection of glyphosate with a Co-MOF integrated opto-electrochemical sensor

Abstract This study presents a new method for detecting the organophosphorus pesticide glyphosate using advanced scanning electrodes (SPE) and enhanced fluorescence. Metal-organic frameworks from cobalt ions were synthesized using a solvothermal method. It is characterized using Raman spectroscopy, FT-IR, and X-ray diffraction techniques. The electrocatalytic behavior of the materials was studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) examined the positive response of plants to glyphosate over a concentration range of 0.55–5.95 mM with a detection limit of 0.334 mM. The fluorescence enhancement ranges from 0.07 mM to 0.67 mM, and the detection limit is 0.0998 mM. Additionally, the selectivity of the proposed opto-electrochemical sensor was evaluated. This selection demonstrates the sensor's ability to detect glyphosate in complex wastewater matrices. This has important implications for environmental monitoring. By addressing glyphosate contamination, the sensor could significantly advance ecological remediation and monitoring strategies. The selectivity, sensitivity, and ability to operate under harsh conditions represent a significant advance in the development of efficient and reliable glyphosate technology for wastewater treatment and environmental protection. In real-sample matrices, the suggested sensor showed a good recovery of the pesticide that had been spiked.

Restricted Intramolecular Rotation: A Dual Fluorescence Response to Hg2+ Quenching and Ag+ Enhancement in Live Rhizoctonia Solani Cells.

A novel imidazo[1,2-a]pyridine derivative probe (R) was designed, synthesized, and characterized via various characterization techniques, such as ESI-MS, 1H NMR, 13C NMR, and Dept-135 NMR. The data obtained from single-crystal XRD reveal that probe R has a coplanar configuration and is part of the monoclinic crystal system, designated the P2(1)/n space group. The fluorescence of (R) is further enhanced by silver (I) ions. On the other hand, Hg2+ significantly quenches the fluorescence of probe R. The presence of other common metal ions does not influence the fluorescence of probe R in the CH3CN: H2O (1:1) mixture, as they neither increase nor quench it. From the fluorescence enhancement data, the low detection limit (LOD) for Ag + ions was determined to be 1.24 × 10- 8 M, whereas the quenching caused by Hg2+ resulted in an LOD of 5.69 × 10- 9 M. The complex of probe R with Ag+/Hg2+ exhibited a 1:1 stoichiometry, as confirmed by mass spectrometry and a Job plot. Single-crystal XRD analysis of R and its complex with Hg2+ revealed a loss of coplanarity, which confirmed their nonfluorescent behavior. We present a promising application of probe R in visualizing living Rhizoctonia oryzae cells exposed to silver (I) and mercury (II) ions.

Benzo-Fused BOPAM Fluorophores: Synthesis, Post-functionalization, Photophysical Properties and Acid sensing Applications.

A novel category of asymmetric boron chromophores with the attachment of two BF2 moieties denoted as BOPAM has been successfully synthesized via a one-pot three-step reaction starting from N-phenylbenzothioamide. This synthetic route results in the production of [a] and [b]benzo-fused BOPAMs along with post-functionalization of the [a]benzo-fused BOPAMs. The photophysical properties of these compounds have been systematically investigated through steady-state absorption and fluorescence emission measurements in solvents at both ambient and cryogenic temperatures, as well as in the solid state. Computational methods have been employed to elucidate the emissive characteristics of the benzo-fused BOPAMs, revealing distinctive photophysical attributes, including solvent-dependent fluorescence intensity. Remarkably, certain BOPAM derivatives exhibit noteworthy photophysical phenomena, such as the induction of off-on fluorescence emission under specific solvent conditions and the manifestation of intermolecular charge transfer states in solid-state matrices. Through post-functionalization strategies involving the introduction of electron-donating groups onto the [a]benzo-fused BOPAM scaffold, an intramolecular charge transfer (ICT) pathway is activated, leading to substantial fluorescence quenching via non-radiative decay processes. Notably, one [a]benzo-fused BOPAM variant exhibits a pronounced fluorescence enhancement upon exposure to acidic conditions, thereby underscoring its potential utility in pH-sensing applications.

Thermo-controlled Water Microenvironment Inducing Fluorescence Enhancement of Chalcone Nanohydrogels for Mitochondrial Temperature Sensing.

Developing aggregation-induced emission (AIE)-based hydrogels that exhibit fluorescence enhancement as to thermal properties is an interesting and challenging task. In this work, we employed the fluorophore 2'-hydroxychalcone (HC), fluorescence properties of which are easily influenced by the excited-state intramolecular proton transfer and twisted intramolecular charge transfer (TICT) effects, to develop a novel type of temperature-sensitive polymers, hydroxychalcone-based polymers (HCPs). By controlling the temperature-dependent water microenvironments in HCPs, the intramolecular hydrogen bonds between water and HCPs can be regulated, thereby influencing the TICT process and leading to thermo-induced fluorescence enhancement, which shows a contrary tendency compared to typical AIEgens that always exhibit fluorescence attenuation as the thermal energy accelerates the molecular motion. Following the decoration with triphenylphosphine, the resulting polymer P-HCP assembled into nanohydrogels and served as a fluorescent probe for intracellular mitochondrial temperature sensing.

Surface Defects‐Induced Photoactivation of Carbon Dots‐NiFe2O4 Nanocomposite: Synthesis, Mechanism and Applications

AbstractThe optical properties of quantum dots are significantly influenced by photoactivation. However, the progress in the development of photoactivation carbon dot (CDs) is still stagnant. Herein, a method for preparing photoactivated CDs/NiFe2O4 by introducing affluent defects onto the surface of CDs through modification with NiFe2O4, extremely filling the gap of photoactivated CDs is proposed. Interestingly, a fantastic fluorescence detection strategy in a unique “OFF‐ON‐OFF” mode, combined with Ag+‐assisted fluorescence enhancement, to establish a dual‐channel regulation mechanism for ultra‐sensitive detection of Hg2+ is first proposed. By increasing surface traps and non‐radiative recombination, defect‐induced manipulation on the surface of CDs creates favorable conditions for enhancing photoactivation capacity. Unexpectedly, the CDs/NiFe2O4 shows a 25‐fold enhancement in fluorescence intensity after exposure to UV‐lamp. Compared to CDs/NiFe2O4, Ag+‐assisted photoactivation CDs/NiFe2O4 exhibits superior selectivity and sensitivity for Hg2+ detection, with low detection limits of 0.7 nM. Moreover, TiO2@CDs/NiFe2O4 catalyst is successfully prepared by anchoring CDs/NiFe2O4 onto the surface of TiO2, which demonstrates efficient degradation of tetracycline within 90 min under visible light irradiation, with a degradation rate of 98.3%. This work first provides a novel defects modification strategy for developing highly active photoactivated CDs technology that is significant for future environmentally sensitive applications.

Aggregation induced emission “Turn on” ultra-low detection of anti-inflammatory drug flufenamic acid in human urine samples by carbon dots derived from bamboo stem waste

Carbon dot-based fluorescence sensors have attracted research interest for the selective determination of anti-inflammatory drugs in biological fluids and environments. The overdose and accumulation of anti-inflammatory drugs in tissues can cause chronic side effects including abdominal pain, and renal damage. Herein, we report a new fluorescent probe, bamboo stem waste-derived carbon dots (BS-CDs) for highly sensitive detection of Flufenamic acid (FA), a hazardous anti-inflammatory drug. The UV–vis absorption spectra of BS-CDs show a redshifted absorption peak at 283 nm upon the addition of FA suggesting strong binding interaction between BS-CDs and FA molecule. The BS-CDs showed a fluorescence enhancement (∼2-fold) detection for FA (400 μM) in the linear concentration range (0.40 → 0.65 μM) with a limit of detection (LoD; 17 nM) and binding constant (Ka = 1.33 × 10−3 M−1). The time-resolved fluorescence decay analysis showed that the average lifetime of BS-CDs has slightly changed (4.42 → 4.67 ns) by the interaction with FA through the aggregation-induced emission (AIE) process. The interference, pH, and effect of time results suggest that BS-CDs are highly selective probes for FA detection and do not show any interference involvement during FA detection. The confirmation of the structure and morphology changes of BS-CDs after interaction with FA was carried out by XRD, FESEM, HRTEM, FTIR, and Raman spectroscopy. The practicability of the BS-CDs probe was proved by the detection of FA in human urine samples with recovery of 103–109 %. This suggests that the proposed BS-CDs-based ‘turn-on’ sensor could be used to determine the FA in biological fluids.

Co-Assembled Nanosystems Exhibiting Intrinsic Fluorescence by Complexation of Amino Terpolymer and Its Quaternized Analog with Aggregation-Induced Emission (AIE) Dye.

Aggregation-induced emission dyes (AIEs) have gained significant interest due to their unique optical properties. Upon aggregation, AIEs can exhibit remarkable fluorescence enhancement. These systems are ideal candidates for applications in bioimaging, such as image-guided drug delivery or surgery. Encapsulation of AIEs in polymeric nanocarriers can result in biocompatible and efficient nanosystems. Herein, we report the fabrication of novel nanoaggregates formulated by amino terpolymer and tetraphenylethylene (TPE) AIE in aqueous media. Poly(di(ethylene glycol) methyl ether methacrylate-co-2-(dimethylamino)ethylmethacrylate-co-oligoethylene glycol methyl ether methacrylate), P(DEGMA-co-DMAEMA-co-OEGMA) hydrophilic terpolymer was utilized for the complexation of the sodium tetraphenylethylene 4,4',4″,4‴-tetrasulfonate AIE dye. Fluorescence spectroscopy, physicochemical studies, and self-assembly in aqueous and fetal bovine serum media were carried out. The finely dispersed nanoparticles exhibited enhanced fluorescence compared to the pure dye. To investigate the role of tertiary amino groups in the aggregation phenomenon, the polymer was quaternized, and quaternized polymer nanocarriers were fabricated. The increase in fluorescence intensity indicated stronger interaction between the cationic polymer analog and the dye. A stronger interaction between the nanoparticles and fetal bovine serum was observed in the case of the quaternized polymer. Thus, P(DEGMA-co-DMAEMA-co-OEGMA) formulations are better candidates for bioimaging applications than the quaternized ones, presenting both aggregation-induced emission and less interaction with fetal bovine serum.

TDDFT elucidating the PET-Inhibition Mediated fluorescence enhancement in a Cysteine probe

TDDFT has been used to confirm the cysteine-sensing mechanism of a reported fluorescent probe (Talanta, 2020, 220, 12136). Frontier molecular orbital analysis showed that the probe underwent a PET process from quinazolinone to acryloyl, which made the fluorescence quenched together with nonplanar structure. Cysteine removed the acryloyl moiety and inhibited the PET process. The planar geometry of the probe-cysteine product enlarged the conjugated system and enhanced the green fluorescence of the fluorophore. Moreover, the charge redistribution also led to the excited-state proton transfer process, ultimately enhanced the fluorescence intensity and a notable Stocks shift.