Journal of Fluorescence最新文献

Fluorescence spectroscopy is a potential diagnostic tool for the characterization and differentiation of microbial species. This research article explores the potential of Fluorescence spectroscopy to differentiate Methicillin Resistant Staphylococcus aureus (MRSA) from Methicillin Sensitive Staphylococcus aureus (MSSA) based on their unique spectral features. MRSA infections are more challenging to treat so their rapid and accurate identification can ensure timely administration of required antibiotics, thus countering the growing threat of antimicrobial resistance. In this study 101 clinical isolates of MRSA and MSSA were used to validate fluorescence emission spectral fingerprints. Fluorescence spectra for each of these isolates were obtained by excitation of bacterial colony at 405 nm. The emission spectra of both phenotypes were clearly differentiated by their emission bands at 510 and 550 nm. Furthermore, Principal component analysis (PCA) was applied to further highlight spectral variations, which showed a good reproducibility among the emission spectra of same bacterial strains. In conclusion, Fluorescence spectroscopy has proved to be a reproducible and effective tool for up to 100% accurate differentiation of MRSA and MSSA isolates, offering a rapid, simple and convenient approach that would reduce the time as well as cost for detection of methicillin resistance in Staphylococcus species.

This study aimed to develop a time-resolved fluoroimmunoassay (TRFIA) for the quantitative detection of soluble terminal complement complex (sC5b-9) and to evaluate the clinical significance of urinary sC5b-9 in patients with lupus nephritis (LN). The sC5b-9-TRFIA was established using a 96-well microplate coated with anti-sC5b-9 monoclonal antibody, anti-sC5b-9 polyclonal antibody, and Eu³⁺-labeled goat anti-rabbit IgG. Urinary sC5b-9 levels were determined in 42 patients with LN and 18 healthy controls to further assess its diagnostic potential in LN. The assay demonstrated a detection limit of 1.38 ng/mL and a linear measurement range of 6.25-1000 ng/mL. The intra-assay and inter-assay coefficients of variation ranged from 4.84% to 7.91% and from 7.06% to 9.11%, respectively, indicating good precision. The sC5b-9-TRFIA showed strong agreement with commercially available enzyme-linked immunosorbent assay (ELISA) kits within the same detection range (P < 0.0001). Urinary sC5b-9 concentrations were significantly elevated in LN patients (157.45 ± 127 ng/mL) compared with healthy controls (38.87 ± 30.11 ng/mL, P < 0.0001). In summary, a wide-range sC5b-9 TRFIA based on europium (Eu³⁺) chelate labeling was successfully developed, providing a sensitive and reliable method for assessing the clinical condition of LN.

A series of Sm³⁺- doped NaCaBi₂(PO₄)₃ (NCBP: xSm³⁺, x = 0.02-0.14 mol) phosphors were synthesized via a conventional solid-state method. Phase purity, morphology and elemental composition were confirmed through PXRD data, FESEM images and EDAX analysis respectively. The Rietveld refinement analysis was performed and crystal structure was modelled using VESTA software. The optical energy band gap values were estimated from DRS measurements. Photoluminescence studies under 403 nm excitation revealed characteristic Sm³⁺ emissions at 563, 600, 647, and 707 nm (⁴G_5/2 → ⁶H_J).The emission intensity increased with Sm³⁺ concentration up to x = 0.08 mol, beyond which concentration quenching occurred due to non-radiative energy transfer predominantly through dipole-dipole interactions among Sm³⁺ ions. Lifetime measurements for the 600 nm emission revealed a systematic decrease in decay lifetime with increasing Sm³⁺ doping, supporting the observed quenching mechanism.The optimized composition (x = 0.08 mol) exhibited good thermal stability. The temperature dependent luminescence lifetime of the NCBP:0.08Sm³⁺ phosphor was measured under excitation at 403 nm and emission at 600 nm showed that the relative sensitivity is increasing from 0.21% °C^- 1 at 30 °C to 0.35% °C^- 1 at 210 °C. The CIE coordinates (0.590, 0.408) and low CCT (1647 K) confirmed efficient orange-red emission of the prepared sample. The internal quantum efficiency of the optimum phosphor was measured to be 33.32%. The calculated Judd-Ofelt intensity parameters confirm the low local symmetry and high covalency of the environment within the lattice, resulting in efficient radiative transitions. These results highlight the potential of NCBP: Sm³⁺ as a multifunctional phosphor for warm white solid-state lighting and temperature-sensing applications.

The escalating trend of industrial cyanide consumption emphasises the critical need for reliable cyanide sensors to ensure the safety of human health and the ecosystem. Thereby, a highly selective and sensitive chemodosimeter (R) was designed, synthesised and characterised as a cyanide sensor. Notably, the non-fluorescent, bright blue-coloured solution of R faded to colourless and then fluoresced bright blue upon interaction with CN^-. The UV-Vis and fluorescence spectral titration profiles confirmed the strong binding affinity of R towards CN^- (10⁴ M^- 1), and the Job's plot revealed the 1:1 binding mode of R + CN^- adduct formation. Mechanistic insights collected from ^IH and ^I3C NMR and mass spectral findings revealed that the interacting CN^- underwent nucleophilic addition at the electropositive carbon atom of the activated olefinic bond, disrupting the conjugation within R. Moreover, the theoretical findings evidenced the interplay of electrons in manipulating the colour and fluorescence emission of R, and highlighted that nucleophilic addition of CN^- terminated the ICT process within R and increased the energy gap between the ground and excited states, thus explaining the changes in the optical properties of R in the presence of CN^-. Further, the lowest limit of detection of R was calculated to be 0.38 µM, which is 5 times lower than the WHO publicised allowable limit of CN^- in drinking water and 52.6 times lower than the lethal level of CN^- estimated in fire victims, highlighting its practical applicability. Since the receptor R selectively distinguishes CN^- without the interference of other competing anions with a very high sensitivity, it was successfully employed as a portable test kit suitable for the on-site detection of CN^-.

Carbon quantum dots (CQDs), a novel class of zero-dimensional carbon-based nanomaterials, have attracted widespread interest due to their remarkable optical, electronic, and chemical properties, such as tunable photoluminescence, excellent biocompatibility, high surface area, and environmental friendliness. In this study, we report a facile, efficient, and scalable synthesis route for CQDs via a one-pot hot injection technique. This method involves the controlled thermal decomposition of an organic carbon precursor in the presence of a high-boiling point solvent and a surface passivation agent, enabling the formation of well-dispersed, highly luminescent CQDs with uniform particle size distribution. The synthesized CQDs exhibit strong and stable photoluminescence emission, which can be attributed to their quantum confinement effect and abundant surface functional groups introduced during synthesis. To explore their potential in environmental applications, the photocatalytic activity of the CQDs was evaluated by monitoring the degradation of Indigo Carmine (IC), a commonly used but environmentally persistent dye, under ultraviolet (UV) irradiation. The CQDs demonstrated outstanding photocatalytic performance, achieving significant degradation efficiency within a short irradiation period. The enhanced photocatalytic behavior is attributed to their efficient light-harvesting capability, rapid charge separation, and generation of reactive oxygen species. Radical scavenging studies were also carried out to understand the mechanism behind photocatalytic degradation of IC dye using carbon dots. This study not only introduces a straightforward and reproducible method for synthesizing high-performance CQDs but also highlights their effectiveness as a standalone photocatalyst for dye degradation. The findings pave the way for the development of sustainable nanomaterials for advanced environmental remediation technologies.

This research presents the development of an innovative, environmentally sustainable, economical fluorimetric method for the detection of Ticagrelor (TICA) using oxygen rich carbon quantum dots (O-CQDs) prepared via a green pyrolysis technique from gallic acid, urea, and sodium edetate. The resulting O-CQDs exhibited a blue shifted maximum excitation (λ_ex/λ_em of 290/417 nm) high quantum yield of 27.85 ± 0.89%, excellent photostability, and strong fluorescence emission, making them ideal candidates for analytical applications. Characterization of the synthesized O-CQDs was conducted with different techniques; high resolution transmission electron microscopy (HRTEM) coupled with energy-dispersive X-ray spectroscopy (EDX), Dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR). The fluorescent probe showed a linear response for TICA over a concentration range of 0.50-16.00 µg/mL, and LOD of 0.21 µg/mL. The quenching mechanism was investigated and attributed primarily to the inner filter effect (IFE) and dynamic quenching. The method was successfully applied to commercial pill formulations with high accuracy and precision. Additionally, the greenness and applicability of the proposed method were successfully examined using the AGREE and BAGI tools, proving the method's consistency with green chemistry concepts and real-world applicability.

Enhancing fluorescence image brightness is critical for improving the detection sensitivity in analytical applications. In this study, we evaluated the respective contributions of (i) the overlap between the photonic stop band (PSB) wavelength (λ_PSB) of a hydrogel-based inverse opal photonic crystal (IOPC) and the emission wavelength (λ_emi) of a fluorescent dye, and (ii) the pore diameter (d) of the IOPC, which governs the fluorophore loading capacity, to the overall fluorescence intensity. The overlap was selected by employing a consistent d and a specific dye, Alexa Fluor™ 488 (A488). Meanwhile, the variation in fluorescence intensity (I_fluor.) with respect to d was normalized, revealing that although d reached 90% of the value at which wavelength overlap occurred (d_overl.), I_fluor. increased to only 59%. However, when d increased to 110% and 125% of d_overl., I_fluor reached only 75.6% and 77.1%, respectively. This suggested that the overlap effect was the key factor contributing to the enhancement of the I_fluor. compared with the contribution from an increase in d. In addition, this result highlighted the potential application of the IOPC with an overlap between λ_PSB and λ_emi for the detection of Escherichia coli (E. coli). Although IOPC samples with d value reached 110% and 125% of d_overl were used, I_fluor. only reached 71.6% and 78.4%, respectively, of the value at which the overlap occurred. The limit of detection (LOD) and linear range were 10 cfu/mL and 10 ÷ 10⁵ cfu/mL (R² = 0.91), respectively. This indicated the potential application of the hydrogel IOPC exhibiting the overlap effect for analytical detection based on fluorescence imaging.

This paper describes a new approach to the synthesis and design of mono-6-deoxy-(m-acetophenonethio)-β-cyclodextrin, a novel thio-functionalized β-cyclodextrin-based ligand. The ligand effectively complexed with Cu(II) and Co(II) ions to produce two complexes that were soluble in water. Through structural characterization using FT-IR, UV-visible spectroscopy, ¹H NMR, and MS, it was discovered to have a 1:1 stoichiometry of metal to ligand and a tetra-coordinated geometry. Further investigation of the complexes' electronic structure, stability, and optimized geometries was carried out using Density Functional Theory (DFT) calculations, which showed that the electronic characteristics agreed with experimental results. The in vitro anti-microbial activity of the free ligand and its metal complexes was assessed against various Gram-positive and Gram-negative bacterial strains. Additional evidence for the reported biological activity came from molecular docking simulations that revealed advantageous interactions with significant bacterial proteins that suggested possible mechanisms of action. This work opens the door for the creation of bioactive cyclodextrin-metal complexes by tying coordination chemistry/ coordination, and theoretical investigations to supramolecular ligand design principles.