Journal of Fluorescence最新文献

Micelles are small spherical structures formed by one or a combination of amphiphilic structures known as surfactants. Surfactants are amphiphilic molecules with both hydrophilic and hydrophobic regions and can self-assemble into micelles above the critical micelle concentration, with the hydrophobic tails oriented inwards and hydrophilic head outwards. In this review article, critical micelle concentration determination using the fluorescence spectroscopy technique is described for both single and mixed micellar systems with the preparation of samples, working principle, and also about theoretical aspects. Fluorescence measurements using direct i.e. intrinsic fluorescence of surfactant molecule and indirect i.e. using extrinsic fluorescence probes have been discussed. Fluorescence spectroscopy offers a sensitive and valid approach for the characterization of surfactant behaviors in aqueous solutions. Various fluorescence parameters are measured at specific wavelengths with an increase in surfactant concentration and a plot is generated from which the critical micelle concentration is determined. Furthermore, the calculation of critical packing parameter is also described which gives an idea about the geometrical arrangement of the surfactant molecules in a micellar structure. This value also provides valuable insights into the micelle's shape and structure. In conclusion, the effectiveness of the fluorescence spectroscopy technique in determining the critical micelle concentration and the critical packing parameter is described in detail in this review article.

The polarity of an environment can modify molecular optical characteristics. In this study, the spectroscopy and DFT methods were applied to study environment effects. Multi-parameter models based on polarity factors were used. In addition, spectroscopic data were applied to determine the nonlinear optical properties of Indan-1-one compounds in different environments. The experimental results emphasize the importance of the dipolarity/polarizability parameter in hyperpolarizability of samples in similar behavior to their linear optical behavior. Hence, the studies on the nature of a solvent environment and its effects on the linear responses of Indan-1-one compounds provide an effective way to estimate the dominant solvent polarity effects on the nonlinear hyperpolarizability of the studied molecules. On the other hand, Indan-1-one compounds with their good nonlinear properties can be used in various optical phenomena.

The development of rapid and reliable techniques for detecting pathogenic bacterial strains is of utmost importance in ensuring food security and safeguarding public health. This study presents a novel approach to fabricating highly fluorescent Carbon dots (CDs) through a facile one-step thermal calcination method, utilizing disposable face masks as the exclusive carbon source. The developed CDs demonstrated excellent fluorescence stability, excitation-dependent emission and particle sizes ranging from 4 - 10 nm. The developed CDs demonstrated efficient fluorescence quenching upon interaction with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), attributed to the robust bonding between the bacterial species and the CD surface. This unique property positions the CDs as functional sensors for the detection of specific bacterial strains. The sensor displayed an impressive limit of detection, reaching as low as 8 CFU/ml for E. coli and 9 CFU/ml for S. aureus. Furthermore, the synthesized CDs were integrated into a polyvinyl alcohol (PVA) matrix to fabricate PVA@CDs films. These films inherited the distinctive optical characteristics of fluorescent CDs, resulting in intense cyan fluorescence emission, high visible transparency, and an exceptional approximately 100% ultraviolet (UV) rays-blocking ratio in the UV region. This multifaceted approach not only addresses the urgent need for effective pathogenic bacterial detection but also extends the application of CDs to UV-blocking films with potential implications for various fields, including healthcare and environmental safety.

A simple, sensitive and accurate spectrofluorimetric method was presented for the determination of citalopram hydrobromide (CTM) in tablets. The method was based on the quenching of bovine serum albumin (BSA) fluorescence with CTM at pH 7.4. The fluorescence intensities were measured at 342 nm after excitation at 279 nm. Various factors affecting the quenching of BSA fluorescence were optimized by response surface methodology (RSM) through Box-Behnken design (BBD. The plot of F₀/F versus CTM concentration was linear in the concentration range of 10-100 µg mL^-1. The limit of detection (LOD) and limit of quantitation (LOQ) were 2.08 and 6.30 µg mL^-1, respectively The molar combining ratio between CTM and BSA was 1:1. The complementary modified green analytical procedure index (ComplexMoGAPI) was 90%. The effect interference of common excipients found in tablets was investigated. Percent recoveries of CTM was ranged from 99.92 to 100.27% in tablets.

Single-pair Förster resonance energy transfer (spFRET) probes the dynamics of molecular structures with (sub-)nanometer accuracy. When combined with fluorescence correlation spectroscopy (FCS), diffusion times and conformation lifetimes can be obtained. Alternating excitation (ALEX) further complements spFRET measurements on freely diffusing molecules, allowing for burst analysis, which can be used to reduce background signal without significant changes to the experimental setup. ALEX is particularly useful for extracting conformational dynamics, but extracting small differences in FRET levels and/or diffusion times can still be difficult for multi-species samples with fast or slow transition rates. Though the combination of spFRET, FCS and ALEX can help to constrain the fits of correlation curves, a rigorous analysis of the range of lifetimes that can be probed with a combination of these methods is lacking. Here, we simulated spFRET-ALEX-FCS experiments of molecules with two conformations that differ both in FRET levels and in diffusion coefficients, representative of fully wrapped and partially unwrapped nucleosomes. We show that we can distinguish small changes in the diffusion coefficient and that burst selection yields accurate lifetimes ranging from 100 us to 100 ms. The simulations provide a framework that can be expanded for more complex systems having a larger number of conformational states, variable stoichiometries from binding interactions and/or other excitation schemes.

Prostate cancer is a major global health concern, ranking as the second most common malignancy in men and the fifth leading cause of cancer-related deaths. Although curcumin exhibits potent antioxidant, anti-inflammatory, and antitumor properties, its clinical application is limited by poor solubility, low bioavailability, and rapid metabolism. In this study, we developed a microorganism-metal-organic framework (MOF)-based carrier (1-CP1) by combining a novel Zn(II) coordination polymer, [Zn(Hbcb)(PYTPY)] (1), with CP1. The carrier, loaded with curcumin to form 1-CP1@Curcumin, significantly enhanced the solubility, bioavailability, and stability of curcumin. Fluorescence assays revealed that the composite demonstrated a fluorescence emission peak at 511 nm, with a strong response to Fe³⁺ ions, showing a quenching efficiency of over 95%. In vitro experiments on LNCaP prostate cancer cells showed that 1-CP1@Curcumin significantly inhibited cell viability, with a reduction of approximately 50% at 20 µM curcumin concentration after 48 h of treatment. Additionally, quantitative PCR analysis of apoptosis-related gene expression revealed a significant decrease in Bcl-2 mRNA levels, indicating that the composite induced apoptosis in prostate cancer cells. These results highlight that 1-CP1@Curcumin effectively overcomes curcumin's delivery limitations and offers strong antitumor efficacy, providing an innovative platform for potential clinical applications in prostate cancer therapy.

A series of four bright red Eu(III) complexes are reported here, with the general formula [Eu(L)₃.auxiliary] where L is 4,4,4-trifluoro-1-phenyl-1,3-butanedione (TPB) whereas auxiliary ligands are the N-donor heterocyclic aromatic systems. The solution precipitation method was used to synthesize these complexes, and Elemental analysis, EDAX, TEM, XRD, UV, FTIR, NMR, and SEM techniques were used for characterization. The results of investigations indicated that complexes between the metal ion, diketonic moiety, and auxiliary ligands had been successfully synthesized. The thermal stability of complexes is determined by TGA/DTA. The complexes showed excellent luminescence in both the solid and solution phases. Hypersensitive ⁵D₀ → ⁷F₂ transition is responsible for bright red color emitted by complexes on exposure to UV rays. J-O analysis asserted the asymmetrical coordination surrounding of Eu(III) ion in complexes. Various radiative properties (A_rad, A_NR, β_exp) and band gap values were also determined, which revealed the applicability of complexes in diverse optoelectronic domains. The complexes in the solid and solution phases show high color purity (> 90%). However, CCT value unveiled use of the complexes as a warm light source. All of the studies confirmed the complexes have exquisite luminosity, which makes them even more promising as a luminescent material for a variety of applications. All complexes show good antimicrobial properties.

A novel ratiometric fluorometric sensor has been developed utilizing dual-emission nitrogen and sulfur co-doped carbon dots (NS-CDs) for the sensitive determination of metformin. The sensing mechanism relies on a unique disaggregation phenomenon observed under acidic conditions, where electrostatic repulsion between positively charged NS-CDs and metformin molecules leads to enhanced fluorescence emission. Upon metformin addition, the NS-CDs exhibit differential enhancement of their characteristic emission peaks, with the 562 nm peak showing markedly greater amplification than the 365 nm peak. This distinctive response enabled the development of a ratiometric detection approach using the F₅₆₂/F₃₆₅ intensity ratio as an analytical signal, providing enhanced measurement reliability by minimizing biological matrix interferences. The sensor demonstrated excellent analytical performance with a linear response range of 0.05-0.9 µM and an impressive detection limit of 15 nM, surpassing the sensitivity of many previously reported methods. The method exhibited remarkable selectivity toward metformin in the presence of common interferents including co-administered drugs, biomolecules, and ionic species typically present in plasma samples. The practical utility of the sensor was validated through successful application in pharmacokinetic studies in rabbit plasma following oral metformin administration, demonstrating its potential for therapeutic drug monitoring and bioanalytical applications. This sensing platform combines high sensitivity, excellent selectivity, and rapid response time, making it a promising tool for metformin quantification in complex biological matrices.

Iron is an essential nutrient involved in various physiological processes, including oxygen transport, enzyme activity, and cellular metabolism. However, excessive iron accumulation in the body can disrupt this delicate balance, leading to adverse effects on growth and development. Maintaining optimal iron levels is crucial for pediatric health, as both deficiency and overload pose significant risks. Fluorometric and colorimetric sensing techniques play a vital role in accurately detecting Fe²⁺/Fe³⁺ levels in biological matrices, facilitating early diagnosis and intervention in cases of iron overload. This study explores the impact of excess iron on children growth parameters, offering insights that can inform public health policies and clinical strategies for promoting healthy development. Additionally, this review highlights recent advancements (2022-2024) in organic colorimetric and fluorometric probes, which exhibit high sensitivity and selectivity for Fe²⁺/Fe³⁺ detection at trace levels.

Multifunctional fluorescent C-dots from Pomelo wastes (peel/pomace) were produced using microwave and hydrothermal treatment. Surface of synthesized C-dots were modified to detect the pesticide in food samples. Synthesized C-dots and functionalized C-dots were characterized using FTIR; SEM; and UV spectroscopy. Microwave synthesized C-dots were of amorphous structure and particle size were in the range of 0.4 to 2.5 nm. The surface passivated C-dots were used as a nanoprobe for cost-effective detection of methyl parathion in food samples; however C-dots without surface passivation were utilized sucessfully for the development of pH paper for determination of pH (3.5-12.5). Fluorescent intensity of developed pH paper varied linearly with the change in the pH. Utilizing optical characteristics and a large number of surface functional groups, C-dots have a potential to be used as a fluorescence or fluorescent sensor to detect methyl parathion from food samples by following the "turn-on-off" mechanism. LOD and LOQ level of surface passivated C-dots were 0.12 and 0.46 mg/L respectively for parathion methyl pesticide.