Journal of Fluorescence最新文献

Carbon dots (CDs) are nanomaterials that have gained worldwide attention due to their unique properties. This study investigated the stability of polyethylene glycol (PEG) CDs over a period of 60 days. To our knowledge, the stability of microwave-synthesized PEG CDs has not been extensively investigated by previous research groups. Comprehensive characterization was conducted using spectroscopic techniques, including UV-Vis, and fluorescence and additional techniques like DLS and TEM. UV-Vis, fluorescence, and DLS analysis were performed at regular intervals (days 1, 15, 30, and 60) to monitor changes in optical properties, particle size, and dispersion. Quantum yield (QY) and lifetime measurements were conducted on day 1 and day 60 to assess the luminescence efficiency. The results demonstrated exceptional stability of the PEG CDs, evident from the consistent UV-Vis, fluorescence spectra, unchanged particle size, and preserved morphology. Moreover, the QY and lifetime values showed small changes, indicating the robustness of the CDs.

The current study focuses on the cytotoxicity assessment of 6,6'-substituted 2,2'-bipyridine derivatives containing functional groups, namely methyl (-CH₃, L1), acid (-COOH, L2), ester (-COOCH₃, L3), semicarbozone (-CONHNH₂, L4). The ligands exhibited high solubility in dimethyl sulfoxide (DMSO) and moderately soluble in dimethyl formamide (DMF), acetonitrile (ACN) and low solubility in water. The ligands display a significant π→π* transition in the region of 270 nm to 305 nm. The emission spectra of the ligands reveal a prominent band in the 300 nm to 450 nm range, with a Stokes shift of 120 cm^- 1. UV-VIS spectra analysis, the ligands (L1-L4, 1mM) demonstrated stability in various environmental like water, glutathione (GSH, 1mM), and MTT condition (10% DMSO). The interaction of ligands with DNA was assessed through calf thymus deoxyribonucleic acid (ctDNA) binding assay, viscosity studies, and ethidium bromide (EtBr) displacement assay, with L1 and L4 exhibiting the highest interaction. The MTT assay was conducted for 24 h and 48 h using ligands (L1-L4) and doxorubicin in MCF-7, HeLa, and L929 cell lines. Ligand L4 showed high potency IC₅₀ values after 48 h in MCF-7 (1.28 µM) and HeLa (1.81 µM), but its potency is lower than doxorubicin. Overall, for the first time these results suggest that L4 has high anticancer activity at lower concentrations against breast and cervical cancers.

Third-order nonlinear optical (NLO) properties of Acridine Orange (AO) dye were studied using Z-scan method under low power conditions and DFT method. The dye was completely dissolved in polar solvents, including ethanol, methanol, acetone, and 1-propanol. Significant optical nonlinearity was observed in polar liquids, with methanol showing the largest optical susceptibility for the AO dye. The open aperture (OA) Z-scan results indicate both positive and negative nonlinearities, attributed to saturable absorption (SA) and reverse saturable absorption (RSA). The closed aperture (CA) Z-scan results for the AO dye in all solvents demonstrated self-defocusing phenomena, as evidenced by a curve that displayed a peak followed by a valley in transmittance. The nonlinear absorption coefficient and nonlinear refractive index of the AO dye were measured to be the order of 10^-7cm²/W and 10^-2 cm/W, respectively. The third-order NLO susceptibility (χ³) of the AO dye was found to be the order of 10^-7 esu. The effect of solvents on the solute molecules were examined using Kamlet-Abboud-Taft multi-parameter scale, which quantified the contribution percentages of solvent spectral features. Additionally, the NLO properties of the AO dye were investigated using density functional theory (DFT) at the B3LYP/6-311 + + G(d,p) level. Analyses were performed on geometry optimization, Frontier Molecular Orbital (FMO), and Electrostatic Potential (ESP). Furthermore, linear polarizability (α), first-order hyperpolarizability (β), and second-order hyperpolarizability (γ) were computed in various solvents, revealing a solvent-dependent enhancement of NLO properties that aligns with the experimental data.

Melanoma, a highly aggressive cancer, is closely associated with an elevated tumor mutation burden (TMB) and an active tumor microenvironment (TME). Melanin synthesis, a key feature of melanoma progression, is primarily regulated by tyrosinase (TYR), the rate-limiting enzyme controlled by the microphthalmia-associated transcription factor (MITF). Resveratrol (Res), a natural polyphenol known for its antioxidant and anticancer properties, faces limitations including poor solubility, low bioavailability, and rapid metabolism. To overcome these challenges, a three-dimensional Co(II) coordination polymer {[Co(bpdado)(bpe)(H₂O)₂]·2DMF·2 H₂O}n (1) was synthesized and incorporated into a composite material, 1@CP1, for Res delivery (1@CP1@Res). The system exhibited enhanced solubility, pH-sensitive release, and improved biological activity. Fluorescence assays demonstrated significant quenching in the presence of Cu²⁺ ions, indicating a high sensitivity of 1@CP1@Res to metal ion interactions. The pH-responsive drug release profile was confirmed by in vitro studies showing accelerated release at lower pH values, mimicking the acidic tumor microenvironment. Cell viability assays revealed that 1@CP1@Res significantly inhibited the proliferation of murine B16-F10 melanoma cells, with cell survival rates of 72.4%, 58.2%, and 43.6% at 24, 48, and 72 h of incubation, respectively, at a concentration of 100 µM. Molecular docking studies further revealed multiple binding interactions between Res and the coordination polymer, suggesting a promising therapeutic strategy for melanoma treatment by integrating advanced materials with bioactive compounds.

Recent literature on biosensing and bioimaging has explored excited state intramolecular proton transfer (ESIPT) cyanide dyes. These classes of fluorescence dyes generally use the classical pyridinium or indolium cations acceptor units' styrene with the ESIPT core. This work studied the photophysical and ESIPT kinetics of novel flavylium cation as an acceptor unit styrene with an ESIPT core using DFT/TD-DFT calculations. Two new ESIPT cyanine dyes, namely (E)-4-(3-(benzo[d]thiazol-2-yl)-2-hydroxystyryl)-7-(dimethylamino)-2-phenyl chromenylium (PSS) and (E)-4-(3-(benzo[d]oxazol-2-yl)-2-hydroxystyryl)-7-(dimethylamino)-2-phenylchromenylium (PSO) were designed and fully studies. This is concerned with studying changes in intramolecular hydrogen bonds, molecular orbitals at the frontier of the ESIPT process, absorption and fluorescence spectra, and excited state energy barriers. As a result, both the systems considered here can undergo an ultrafast ESIPT reaction with PSS and then PSO. Furthermore, ESIPT is more accessible in the normal enol-form first excited singlet (S₁) state, with shorter hydrogen bonds. The intersystem crossing between the S₁ state and the triplet (T₁) state greatly influences the fluorescence efficiency of PSO and PSS. The potential energy curve and transition state energy profiles of PSS and PSO show that ultrafast ESIPT occurs in the state. Furthermore, the PSS shows less energy barriers, which leads to faster proton transfer than PSO. The current study will advance knowledge of the mechanism behind the ESIPT process and help enhance the qualities of the cyanine dye used in ESIPT.

The novel red phosphors Na₂SrSi₂O₆:xEu³⁺(x = 0.1 ~ 0.5) were successfully prepared using the high-temperature solid-state synthesis method. The phase morphology, luminescence properties, fluorescence quenching, thermal stability, fluorescence lifetime, quantum efficiency, and CIE chromaticity coordinates of the phosphors were characterized. Experimental results show that the Na₂SrSi₂O₆:Eu³⁺ phosphors are capable of emitting intense red light when illuminated by 393 nm excitation wavelength. By studying the fluorescence emission spectra at different doping concentrations, a doping concentration of x = 0.3 was determined. The concentration quenching mechanism of Na₂SrSi₂O₆:Eu³⁺ phosphor was identified as electric dipole-electric dipole (d-d) interactions. At temperatures of 313 K, 373 K, and 433 K, the emission intensity was maintained at 99.2%, 94.6%, and 90.8% of the room temperature value, respectively. Furthermore, the samples displayed high quantum efficiency, extended fluorescence lifetime, superior color purity, and low correlated color temperature. Consequently, the Na₂SrSi₂O₆:Eu³⁺ red phosphor shows significant potential for applications in the realm of white light LEDs.

Histamine is a naturally occurring alkaloid that is an important indicator of meat spoilage, and excessive levels in food can lead to food poisoning or trigger allergic reactions. Therefore, accurate detection of histamine in meat is crucial for evaluating freshness and ensuring meat quality. In this study, a fluorescence probe based on ionic covalent organic networks confined with molecularly imprinted polymers (iCON@MIPs) was developed for detecting histamine in aquatic products. The probe was utilized iCOFs as the light-emitting element to improve the selectivity of the system for histamine by ion attraction reaction, and its anti-interference ability enhanced through molecular imprinting technology. The maximum emission wavelength of iCON@MIPs was at 570 nm, giving it a bright yellow emission and endowing it with the ability for on-site detection. The detection limit of iCON@MIPs for histamine was 0.516 µg L^- 1, with a good recovery rate of 87.29-102.26% in fish samples. The fluorescence probe developed in this study provides an effective and rapid detection method for harmful substances in food, agriculture, environment and even medicine.

The review explores the pivotal role of cellulose in enhancing the sensing capabilities of fluorescent chemo-sensors, particularly carbon dots (CDs) and delineates cellulose's multifaceted contributions as both a precursor and stabilizing matrix, highlighting its structural adaptability across varied forms-hydrogels, aerogels, films-to bolster the stability, sensitivity, and selectivity of these sensors. Cellulose's structural versatility enables advanced functionalization, fostering a robust platform that amplifies the stability and functional efficiency of CDs across diverse sensing paradigms. The investigation encompasses utilization of cellulose as precursor for CDs, cellulose nanocrystals and matrix for the integration of CDs, elucidating their collective impact on advancing fluorescence-based detection technologies.

This study, we employed computer-aided design to develop 27 peptide aptamers, and initially screened 11 candidates with binding energies less than - 6.0 kcal/mol. Subsequently, three peptide aptamers with strong specificity were selected using a direct time-resolved fluorescence immunoassay (TRFIA). Peptide aptamer B3, in combination with monoclonal antibody R001, was used to construct a TRFIA-based sandwich assay system. The performance of this system was evaluated concerning sensitivity, specificity, and reproducibility, and was further tested using 20 simulated pharyngeal swab samples. The dominant peptide aptamer, B3(RGQGVPI), was identified as the most promising candidate. This peptide demonstrated high specificity for the SARS-CoV-2 nucleocapsid (N) protein, with the lowest detectable concentration of 203.78 pg/mL. Importantly, the peptide had no cross-reactions with other potential interferents, including RSV, Flu A, and MP, confirming its specificity. The assay also exhibited good reproducibility, with coefficients of variation of 11.33% and 8.00% at different concentrations in pharyngeal swab samples. Additionally, the LOB and LOD in clinical samples were 31.59 pg/mL and 243.70 pg/mL and the correlation coefficient R² was 0.9784, which indicated that the method had good resistance to clinical interference. In this study, we successfully developed a sandwich TRFIA method based on the peptide aptamer B3-R001, which can be used to quantitatively measure the SARS-CoV-2 N protein level in pharyngeal swabs. Compared to antibodies, peptide aptamers are easily synthesized, inexpensive, and show great potential for clinical applications. This method provides a novel approach for rapidly detecting viral pathogens, contributing to the advancement of diagnostic tools.

The photophysical properties of an anthraquinone based dye, Solvent Green 3 (SG3) were investigated in chloroform solution and stearic acid supported Langmuir-Blodgett films (SG-LB) by steady state and time-resolved spectroscopic techniques. Both steady state and time-resolved studies were performed for SG3 in chloroform solution (1 µM) whereas only steady-state measurements were performed for the SG-LB films. The studies revealed that the photodynamics of SG3 are guided by deexcitation of energetically separated conformers and aggregates of SG3, namely the closed form (CF) and open form (OF) in solution. However, in SG-LB, the OF dominates the photophysical properties. The current report sheds light on the effect of conformational confinement on the photophysical properties of organic dye molecules, thereby enabling better understanding of photo behaviour of small organic molecules.