Methods and Applications in Fluorescence

Lead halide perovskite nanocrystals (PNCs) have attracted intense attention due to their excellent optoelectronic properties. In this work, a series of water-stable CsPb(Br/I)3 PNCs fluorescent probes were prepared using an anion exchange method. It was found that the PNCs probes could be used to detect ascorbic acid (AA) in water, and interestingly, the selectivity for AA detection could be improved by adjusting the FL spectra of the PNCs probes by controlling the concentration of KI in anion exchange. The high sensitivity and selectivity characteristics make CsPb(Br/I)3 PNCs ideal materials for AA sensing...

The alignment of chromophores plays a crucial role in determining the optoelectronic properties of materials. Such alignment can make interpretation of fluorescence anisotropy microscopy (FAM) images somewhat ambiguous. The time-resolved emission behaviour can also influence the fluorescence anisotropy. This is particularly the case when probing excitation energy migration between chromophores in a condensed phase. Ideally information concerning the chromophoric alignment, emission decay kinetics and fluorescence anisotropy can be recorded and correlated...

Polycationic photosensitizers (PS) are not susceptible to aggregation in solutions, but their high local concentrations in Gram-negative bacteria can be sufficient for aggregation and reduced effectiveness of antibacterial photodynamic treatment. By measuring fluorescence spectra and kinetics we were able to evaluate the degree of aggregation of polycationic PS ZnPcChol8 in Gram‑negative bacteria E. coli K12 TG1. Binding of ZnPcChol8 to E. coli K12 TG1 leads to an appearance of groups of molecules with shorter PS fluorescence lifetime, a decrease in fluorescence intensity and a shift in the fluorescence spectral maximum...

This study evaluated the reliability of portable X-ray fluorescence (pXRF) in Pb2+ adsorption kinetics and isotherm experiments using soybean straw biochar. The research aimed to compare pXRF results with those obtained through traditional atomic absorption spectrometry (AAS). Soybean straw biochar, produced at 400 ºC, was employed as the adsorbent for Pb2+. The efficiency of adsorption was assessed using Langmuir and Freundlich models. The kinetics of Pb2+ adsorption was analysed through pseudo-first-order and pseudo-second-order models...

Lanthanide-doped fluoride nanocrystals (NCs) exhibit excellent optical features, including upconversion and downconversion luminescence (UCL and DCL), that can be utilized in a variety of applications. In this study, we have successfully demonstrated the photoluminescence behavior of triple-doped NaYF4: Yb3+, Er3+, Pr3+ NCs in the Vis-NIR region. Herein, highly monodisperse hexagonal phase NaYF4: Yb0.2, Er0.02, Prx nanocrystals in various Pr3+ (x = 0, 0.1, 0.5, and 1 mol %) concentration with ~ 22 nm diameter synthesized by thermal decomposition technique...

Absorption and fluorescence spectra of the nitrogen polycyclic aromatic hydrocarbon carbazole (CZL) were analyzed with native cyclodextrins (CD; α,β,γ); derivatized CD (hydroxypropyl-β-cyclodextrin, HPCD; methyl-β-cyclodextrin, MeCD) and p-sulfonated calixarenes (SCAn, with n= 6 and 8) macrocycles. The results showed a slight increase in the absorbance of CZL with CD, but the mixture of CZL with SCA showed lower absorption than the sum of the individual spectra. Also, changes in fluorescence were observed by adding the macrocycles, quenching with SCA, and significant increases with CD...

Here we apply the gSUPPOSe algorithm on images acquired using Stimulated Emission Depletion (STED) microscopy with the aim of improving the resolution limit achieved. We processed images of the nuclear pore complex (NPC) from cell lines in which the Nup96 nucleoporin was endogenously labeled. This reference protein forms a ring whose diameter is ∽107 nm with 8 corners ∽42 nm apart from each other. The stereotypic arrangement of proteins in the NPC has been used as reference structures to characterize the performance of a variety of microscopy techniques...

Forsythoside E is one secondary metabolite of Forsythia suspensa (Thunb.) Vahl. In the study, the interactions between forsythoside E and two types of cholinesterases, acetylcholinesterase and butyrylcholinesterase were investigated in the different conditions. Forsythoside E increased the fluorescence intensity of acetylcholinesterase but quenched the fluorescence of butyrylcholinesterase. Aβ25-35 used in the study may not form complexes with cholinesterases, and did not affect the interaction between forsythoside E and cholinesterases...

We here report the formation of a turbid-gel phase in acrylic cuvettes upon exposure to pure Dimethyl Sulfoxide (DMSO) at room temperature. The observed phenomenon occurred over a 10h to 14h incubation in the presence of environmental oxygen. After the turbid gel was removed from the cuvette, it became a white solid exhibiting unique emission behavior. The formation of the turbid-gel phase was accelerated upon exposure to UV 295 LED pulses of light from 6h to 8h. Surprisingly, subsequent exposure of the white solid to a few microliters of pure DMSO and vortexing resulted in its transformation into a transparent gel state in just a few minutes, eventually acquiring transparent and liquid properties...

Biofluorescence in echinoderms is largely unexplored and even though the green sea urchin Strongylocentrotus droebachiensis is a well-studied species, the presence and/or function of fluorescence remains very poorly understood. Hyperspectral imaging was conducted on mature sea urchins (N=380) while fluorospectrometric analysis was conducted on sea urchin coelomic fluid (N=30). Fluorescence was documented in both the spines and coelomic fluid of S. droebachiensis. Intact spines exhibited a low intensity green emission (~550-600 nm), while broken spines averaged a high emission peak in the green spectrum (~580 nm)...

Food contaminants pose a danger to human health, but rapid, sensitive and reliable food safety detection methods can offer a solution to this problem. In this study, an optical fiber ratiometric fluorescence sensing system based on carbon dots (CDs) and o-phenylenediamine (OPD) was constructed. The ratiometric fluorescence response of Cu2+ and thiram was carried out by the fluorescence resonance energy transfer (FRET) between CDs and 2,3-diaminophenazine (ox-OPD, oxidized state o-phenylenediamine). The oxidation of OPD by Cu2+ resulted in the formation of ox-OPD, which quenched the fluorescence of CDs and exhibited a new emission peak at 573 nm...

Dopamine (DA) is the most abundant catecholamine neurotransmitter in the brain and plays an extremely essential role in the physiological activities of the living organism. There is a critical need for accurately and efficiently detecting DA levels in organisms aiming to reflect physiological states. Carbon nitride quantum dots (C3N4), in recent years, used enormously as electrochemistry and fluorescence probes for metal ions, biomarkers and other environmental or food impurities due to their unique optical and electronic properties...

No abstract text is available yet for this article.

Many medical imaging modalities have benefited from recent advances in Machine Learning (ML), specifically in deep learning, such as neural networks.
Computers can be trained to investigate and enhance medical imaging methods without using valuable human resources.
In recent years, Fluorescence Lifetime Imaging (FLIm) has received increasing attention from the ML community. 
FLIm goes beyond conventional spectral imaging, providing additional lifetime information, and could lead to optical histopathology supporting real-time diagnostics...

Duvelisib (DUV) is a potent anticancer drug whereas Moxifloxacin (MOX) is an antimicrobial drug with anti-proliferative potency against cancerous cells, which is empirically administered in cancer treatment. DUV and MOX combination is commonly prescribed to combat infections in patients while they are under chemotherapy treatment. This study describes, for the first time, the development of a simple and green synchronous spectrofluorimetric (SSF) method for the simultaneous estimation of DUV and MOX in plasma...

Although the great importance of oral contraceptive agents in birth control, their existence in breast milk became a cause for concern, since infant exposure to these hormones is associated with many health problems. Consequentially, developing a sensitive bioanalytical method for monitoring their concentrations in breast milk is an urgent demand to examine the safety or the risk of these compounds on infants. Levonorgestrel [1] is one of the most common contraceptive hormones under concern. Despite the high sensitivity of the fluorometric methods, detection of LEV by them is confined because its structure does not exhibit any fluorescence...

In this study, QuEChERS extraction was combined with dispersive liquid-liquid microextraction (DLLME) to extract pesticides from tropical fruits for determination by a highly accurate and sensitive liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) system. The QuEChERS method served as a matrix clean-up tool and the DLLME method preconcentrated the analytes for their determination at trace levels. All parameter variables of the DLLME method were optimized to improve the extraction output and lower the limits of detection and quantification (LOD and LOQ) for all the analytes...

Detection and identification of body fluids are crucial aspects of forensic investigations, aiding in crime scene reconstructions and providing important leads. Although many methods have been developed for these purposes, no method is currently in use in the forensic field that allows rapid, non-contact detection and identification of vaginal fluids directly at the crime scene. The development of such technique is mainly challenged by the complex chemistry of the constituents, which can differ between donors and exhibits changes based on woman's menstrual cycle...

We studied the effect of annealing on the luminescence of Coumarin 106 (C106) in poly (vinyl alcohol) films (PVA films). The samples and reference polymer films were treated at temperatures between 100 °C and 150 °C (212 F and 302 F) for various times. After cooling and smoothing, the samples and references were measured at room temperature. We observed that the PVA polymer (reference films) changes its optical properties with annealing at higher temperatures, affecting the baselines in absorption and the backgrounds in emission measurements...

In this study, a test strip for fluorometric analysis of iron ion (Fe3+) was constructed based on nitrogen, zinc and copper codoped carbon dots (NZC-CDs) as fluorescence probes. NZC-CDs were synthesized by hydrothermal method. The optical properties, appearance, size, components and crystal state of NZC-CDs were characterized by ultraviolet (UV), fluorescence, infrared, TEM, XPS and XRD techniques. NZC-CDs exhibited bright blue fluorescence under UV lamp with a quantum yield at 17.4%. The fluorescence of NZC-CDs was quenched by Fe3+ in the presence of Fe3+ possibly due to the aggregation induced quenching...