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Tenofovir (TFV) is the active form of the prodrugs tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF), both clinically prescribed as HIV reverse transcriptase inhibitors. The biophysical interactions between these compounds and human serum albumin (HSA), the primary carrier of exogenous compounds in the human bloodstream, have not yet been thoroughly characterized. Thus, the present study reports the interaction profile between HSA and TFV, TDF, and TAF via UV–Vis, steady-state, and time-resolved fluorescence techniques combined with isothermal titration calorimetry (ITC) and in silico calculations. A spontaneous interaction in the ground state, which does not perturb the microenvironment close to the Trp-214 residue, is classified as weak. In the case of HSA/TFV and HSA/TDF, the binding is both enthalpically and entropically driven, while for HSA/TAF, the binding is only entropically dominated. The binding constant (Ka) and thermodynamic parameters obtained via ITC assays agree with those obtained using steady-state fluorescence quenching measurements, reinforcing the reliability of the data. The small internal cavity known as site I is probably the main binding pocket for TFV due to the low steric volume of the drug. In contrast, most external sites (II and III) can better accommodate TAF due to the high steric volume of this prodrug. The cross-docking approach corroborated experimental drug-displacement assays, indicating that the binding affinity of TFV and TAF might be impacted by the presence of different compounds bound to albumin. Overall, the weak binding capacity of albumin to TFV, TDF, and TAF is one of the main factors for the low residence time of these antiretrovirals in the human bloodstream; however, positive cooperativity for TAF and TDF was detected in the presence of some drugs, which might improve their residence time (pharmacokinetic profile). [ABSTRACT FROM AUTHOR]

A new structurally simple fluorescent CP probe based on chromone was designed and synthesized, and its structure was fully characterized using various analytical techniques. The CP probe displays a high selectivity and sensitivity for sensing Fe3+ with a "turn-off" fluorescence response over other metal ions in a DMSO/H2O (4:1, v/v) solution. The experiment results show that the CP probe is stable over a wide pH range of 2.0–12.0. The detection limit for Fe3+ was calculated to be 0.044 μmol•L−1. The molar ratio method indicated that the binding mode between the CP probe and Fe3+ is a 1:1 complex formation. HR-MS and density functional theory (DFT) calculations were also performed to further confirm the recognition mechanism. Both fluorescence imaging experiments and the MTT assay demonstrated that the CP probe was suitable for detecting intracellular Fe3+ and no significant cytotoxicity in living cells. [ABSTRACT FROM AUTHOR]

In order to achieve effective removal of radioactive iodine, trace detection of dinitrophenol (DNP), here, we have synthesized two porous organic polymers (POPs, TMCHA and HMCHA) by nucleophilic substitution reactions with specific surface areas of 1730 and 1796 m2 g−1, respectively. The adsorption capacities of POPs in iodine vapor and cyclohexane and the fluorescence sensing performances for DNP are studied. The results show that the adsorption capacities of TMCHA and HMCHA in iodine vapor are as high as 3.77 and 2.74 g g−1, and the removal efficiencies of iodine in iodine-cyclohexane solution are 97% and 73%, respectively. The iodine adsorption mechanism of the MCHA-based POPs is the electron transfer mechanism. The Stern–Volmer quenching constants (Ksv) of TMCHA and HMCHA for fluorescence quenching of DNP are 4.04 × 103 and 4.42 × 103 L mol−1, respectively. The fluorescence quenching of TMCHA and HMCHA was caused by FRET and PET together. [ABSTRACT FROM AUTHOR]

Detecting the presence of explosives is important to protect human lives during military conflicts and peacetime. Gas-phase detection of explosives can make use of the change of material properties, which can be sensitive to environmental conditions such as temperature and humidity. This paper describes a remote-controlled automatic shutter method for the environmental impact assessment of photoluminescence (PL) sensors under near-open conditions. Utilizing the remote-sensing method, we obtained environmental effects without being exposed to sensing vapor molecules and explained how PL intensity was influenced by the temperature, humidity, and exposure time. We also developed a theoretical model including the effect of exciton diffusion for PL quenching, which worked well under limited molecular diffusions. Incomplete recovery of PL intensity or the degradation effect was considered as an additional factor in the model. [ABSTRACT FROM AUTHOR]

BACKGROUND: Several different factors underlie the molecular mechanisms of phenolic compound‐protein interactions. They include the environmental conditions. In the case of γ‐conglutin, pH conditions translate directly into the adoption of two distinct oligomeric assemblies, i.e. hexameric (pH 7.5) or monomeric (pH 4.5). This paper reports research on the pH‐dependent oligomerization of γ‐conglutin in terms of its ability to form complexes with a model flavonoid (vitexin). RESULTS: Fluorescence‐quenching thermodynamic measurements indicate that hydrogen bonds, electrostatic forces, and van der Waals interactions are the main driving forces involved in the complex formation. The interaction turned out to be a spontaneous and exothermic process. Assessment of structural composition (secondary structure changes and arrangement/dynamics of aromatic amino acids), molecular size, and the thermal stability of the different oligomeric forms showed that γ‐conglutin in a monomeric state was less affected by vitexin during the interaction. CONCLUSION: The data show precisely how environmental conditions might influence phenolic compound‐protein complex formation directly. This knowledge is essential for the preparation of food products containing γ‐conglutin. The results can contribute to a better understanding of the detailed fate of this unique health‐promoting lupin seed protein after its intake. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

A novel ZnII coordination polymer, namely, poly[{μ2-bis[4-(2-methyl-1Himidazol-1-yl)phenyl]methanone-κ² N³ :N³′ }(μ2-5-bromobenzene-1,3-dicarboxylato-κ² O¹ :O³ )zinc(II)], [Zn(C8H3BrO4)(C21H18N4O)]n or [Zn(Br-BDC)(MIPMO)]n, (I), has been synthesized by the solvothermal method using 5-bromoisophthalic acid (Br-H2BDC), bis[4-(2-methyl-1H-imidazol-1-yl)phenyl]methanone (MIPMO) and Zn(NO3)2·6H2O. Structure analysis showed that compound (I) displays twofold parallel interwoven sql nets. Fluorescence experiments confirmed that the compound can sensitively and selectively detect nitrofurantoin (NFT) in aqueous medium. In addition, the possible fluorescence quenching mechanisms of compound (I) toward NFT are investigated. [ABSTRACT FROM AUTHOR]

In this study, Eucheuma denticulatum marine algae were used as the raw material to prepare Eucheuma denticulatum-derived carbon quantum dots (E-CQDs) via a mild chemical oxidation method. The E-CQDs demonstrated good stability and water solubility owing to the presence of hydroxyl groups on the surface. The structure and chemical composition of the E-CQDs were characterized by three means, including transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The E-CQDs maintained exceptional stability under varying ion concentrations, pH levels, ultraviolet (UV) irradiation durations, and temperatures. The fluorescence quenching effect of tetracycline (TC) on the E-CQDs was utilized to establish a sensitive and selective TC fluorescence detection method. The mechanism of the TC quenching of the fluorescence of E-CQDs involved an internal filtration effect and dynamic quenching. At the TC concentration of 20–100 μM, the fluorescence intensity showed an excellent linear relationship (R2 = 0.997); the limit of detection and quantity was 0.47 μM and 1.57 μM, respectively. These results revealed that this method for TC detection offers good selectivity and immunity to interference. [ABSTRACT FROM AUTHOR]

First-principles calculations reveal that CZA aggregates and CZA/CD aggregates are responsible for blue emission and green emission, respectively. The J-type CZA aggregates in head-to-tail configuration are the most stable, while the H-type aggregates are prone to π-π stacking, resulting in fluorescence quenching. For CZA/CD aggregates, the bonding modes and sites have a significant impact on the photoluminescence properties of CDs. When the bonding sites belong to electron-donating groups, electron-withdrawing groups or sp2 domain, the luminescent intensities of CDs are significantly enhanced. [Display omitted] The effect of aggregation configuration of molecular fluorophore citrazinic acid (CZA) on the photoluminescence (PL) properties of carbon dots (CDs) has been investigated using first-principles method. The structural stability of all aggregates has been analyzed, and the results show that the most stable structures are J-type CZA aggregates with head-to-tail configurations and the CZA/CD aggregates are bonded by replacing H atoms on the CD edges with de-OH from the pyridine ring of CZA. The luminescent properties of CZA/CD aggregates are mainly affected by the binding modes and binding sites. When the sites belong to electron-donating groups, electron-withdrawing groups or sp2 domain, the PL spectra of CDs are shifted and the luminescent intensities are significantly enhanced. The results suggest that covalently bonded CZA/CD aggregates are responsible for the high fluorescence quantum yield of CD. Moreover, the distance between the centers of the two pyridine rings in H-type CZA dimers less than 3.5 Å is prone to π-π stacking, leading to fluorescence quenching of aggregates. The present work is helpful in understanding the effect of molecular fluorophores on the PL properties of CDs and provides theoretical guidance for the controllable synthesis of CDs. [ABSTRACT FROM AUTHOR]

Nanosized alginate-based particles (NAPs) were obtained in a one-pot solvent-free synthesis procedure, achieving the design of a biocompatible nanocarrier for the encapsulation of IbM6 antimicrobial peptide (IbM6). IbM6 is integrated in the nascent nanosized hydrogel self-assembly guided by electrostatic interactions and by weak interactions, typical of soft matter. The formation of the nanogel is a dynamic and complex process, which presents an interesting temporal evolution. In this work, we optimized the synthesis conditions of IbM6-NAPs based on small-angle X-ray scattering (SAXS) measurements and evaluated its time evolution over several weeks by sensing the IbM6 environment in IbM6-NAPs from photochemical experiments. Fluorescence deactivation experiments revealed that the accessibility of different quenchers to the IbM6 peptide embedded in NAPs is dependent on the aging time of the alginate network. Lifetimes measurements indicate that the deactivation paths of the excited state of the IbM6 in the nanoaggregates are reduced when compared with those exhibited by the peptide in aqueous solution, and are also dependent on the aging time of the nanosized alginate network. Finally, the entrapment of IbM6 in NAPs hinders the degradation of the peptide by trypsin, increasing its antimicrobial activity against Escherichia coli K-12 in simulated operation conditions. [ABSTRACT FROM AUTHOR]

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This study is to investigate the impact of thulium concentration on the performance of in-band pumped thulium-doped silica fiber amplifiers with considering ion–ion interactions. Due to the fluorescence quenching in silica glass, the fluorescence lifetimes are required to compute at every Tm concentration. The theoretical model of fluorescence decay curves at in-band pumped thulium-doped silica fiber is used to determine the fluorescence lifetimes of the 3F4 and 3H4 levels. The calculated lifetimes of the commercially available thulium-doped silica fiber are 650 µs for 3F4 level and 14 µs for 3H4 level and these results are consentient well with the experimental reported results. The theoretical evaluating of the amplifier performance shows that the gain amplifier reduces with concentration increase because of the impact of both fluorescence quenching and the reverse cross-relaxation process. Thus, in contrast to pumping wavelength at 790 nm, there are negative effects of the high doping concentration of Tm ions on the amplifier performance at the in-band pumping scheme. [ABSTRACT FROM AUTHOR]

This study uses an optical sensor utilizing a manganese metal–organic framework (Mn-MOF) to detect tetracycline in wastewater. tetracycline was directly detected through fluorescence quenching with the dispersion of Mn-MOF in an ethanol solution, enabling direct tetracycline detection. The sensor has a notable detection limit of 66.39 nM and can detect tetracycline in the linear detection range spanning from 0.0032 to 0.43 µM. It has been found that Mn-MOF demonstrated excellent selectivity for tetracycline in the presence of other antibiotics. This selectivity suggests promising applications for environmental monitoring, showing the sensor's potential in effectively quantifying tetracycline amidst complex matrices found in wastewater. This sensor emerges as a crucial advancement in remediation strategies and environmental monitoring by addressing the challenge of tetracycline contamination. Its selectivity, sensitivity, and ability to operate within complex environments marks a significant step forward in developing efficient and reliable detection methods for tetracycline detection in wastewater and environmental protection. [ABSTRACT FROM AUTHOR]

In order to achieve a wider range of ionizing radiations detection, novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer (PET) effect. Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized, and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry (HRMS), nuclear magnetic resonance hydrogen and carbon spectroscopy (¹H and 13C NMR). The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration. The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process. Despite the similarities in chemical structures, the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine. In the direct irradiation experiments of ionizing radiation, the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4, respectively. Furthermore, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 eV and 1.13 eV, respectively. A wider energy range has a stronger driving force on electrons, which is conducive to fluorescence quenching. Both femtosecond transient absorption spectroscopy (fs-TAS) and transient fluorescence spectroscopy (TFS) tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant. Although both isomers can significantly reduce LOD during PET process, PDI-B with aromatic amine has a wider detection range of 0.118e240 Gy due to its larger emission enhancement, which is a leap of three orders of magnitude. It breaks through the detection range of gamma radiation reported in existing studies, and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection. [ABSTRACT FROM AUTHOR]

A simple, rapid, and low‐cost technique was developed to allow reliable analysis of the anti‐hepatitis C drug sofosbuvir in bulk, tablet form, and spiked human plasma. This method depends on the ability of sofosbuvir to quench the fluorescence of the newly synthesized 2‐amino‐3‐cyano‐4,6‐dimethylpyridine (reagent 3). Elemental analysis and spectral data were used to validate the structure of the synthesized reagent. The newly synthesized reagent exhibited a satisfactory level of fluorescence emission at 365 nm after excitation at 247 nm. All experimental variables that might affect the quenching process were analyzed and optimized. Linearity, range, accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ) were all validated in accordance with the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines. The concentration range was shown to be linear between 0.1 and 1.5 μg/mL. The technique was effectively utilized for sofosbuvir analysis in both its tablet dosage form and spiked human plasma, with mean percentage recoveries of 100.13 ± 0.35 and 94.26 ± 1.69, respectively. [ABSTRACT FROM AUTHOR]

A fluorescent probe NS was successfully developed using triphenylamine aldehyde and 1‐hydroxy‐2‐naphthaldehyde. NS demonstrated selective recognition of Cu2+ in a DMSO/H2O solution, forming a stable 1 : 1 complex that led to fluorescence quenching. The addition of EDTA resulted in fluorescence recovery. The fluorescent intensity of NS showed a linear correlation with Cu2+ concentration within the range of 2~14 μmol ⋅ L−1, with a detection limit of 39 nmol ⋅ L−1 and a binding constant of 1.56×103 L mol−1. Additionally, the detection limit of the NS‐Cu2+ complex for EDTA was calculated to be 187 nmol ⋅ L−1. NS also displayed promising applications in the environmental and alcoholic drinks for detecting Cu2+ in water, wine, and Chinese Baijiu samples. [ABSTRACT FROM AUTHOR]

Titanium carbide quantum dots (Ti3C2 QDs) are derived from MXenes, an emerging layered two-dimensional material. Ti3C2 QDs exhibit better chemical stability, dispersibility, and photoluminescence than MXenes and have great application potential in biological imaging, environmental pollution, and food safety. Ascorbic acid (AA), a key coenzyme in human metabolic pathways, plays an important role in various physiological reactions. Herein, a fluorescent sensor to detect AA is designed by combining Ti3C2 QDs with cobalt oxy-hydroxide (CoOOH) nanosheets. CoOOH nanosheets, as effective fluorescence quenching agents, can considerably quench the fluorescence of Ti3C2 QDs. During the detection process, AA is oxidized to dehydroascorbic acid and CoOOH nanosheets are reduced to Co2+ and disintegrated, resulting in the recovery of the fluorescence intensity of Ti3C2 QDs. Therefore, AA is detected by monitoring the degree of recovery of the fluorescence intensity of Ti3C2 QDs. The fluorescent sensor exhibits a linear range of 0–100 μM and a detection limit of 0.19 μM for AA. Its recovery rates in commercial orange juice and watermelon juice are 97.12–103.95% and 94.46–107.32%, respectively, and it exhibits good detection reproducibility. This fluorescent sensor can be used to measure the AA concentration in fruits and beverages. [ABSTRACT FROM AUTHOR]

Au(III) bis(pyrrolide-imine) chelates are emerging as a class of versatile, efficacious metallodrug candidates. Here, we synthesised two enantiopure chiral ligands H2L1 and H2L2 (tetradentate cyclohexane-1,2-diamine-bridged bis(pyrrole-imine) derivatives). Metallation of the ligands with Au(III) afforded the chiral cationic complexes AuL1 and AuL2. The in vitro cytotoxicities of AuL1 and AuL2 determined in the NCI-60 single-dose drug screen were 56.5% and 89.1%, respectively. AuL1 was subsequently selected for a five-dose NCI-60 screen, attaining GI50, IC50, and LC50 values of 4.7, 9.3 and 39.8 μM, respectively. Hierarchical cluster analysis of the NCI-60 data indicated that the profile for AuL1 was similar to that of vinblastine sulfate, a microtubule-targeting vinca alkaloid. Reactions of AuL1 with glutathione (GSH) in vitro confirmed its susceptibility to reduction, Au(III) → Au(I), by intracellular thiols. Because human serum albumin (HSA) is responsible for transporting clinically deployed and investigational drugs, we studied the uptake of AuL1 and AuL2 by HSA to delineate how chirality impacts their protein-binding affinity. Steady-state fluorescence quenching data acquired on the native protein and data from site-specific probes showed that the compounds bind at sites close enough to Trp-214 (subdomain IIA) of HSA to quench the fluorophore. The bimolecular quenching rate constants, Kq, were ca. 102 times higher than the maximum diffusion-controlled collision constant of a biomolecule in water (1010 M−1 s−1), confirming that static fluorescence quenching was the dominant mechanism. The Stern–Volmer constants, KSV, were ∼104 M−1 at 37 °C, while the affinity constants, Ka (37 °C), measured ∼2.1 × 104 M−1 (AuL1) and ∼1.2 × 104 M−1 (AuL2) for enthalpy-driven ligand uptake targeting Sudlow's site I. Although far- and near-UV CD spectroscopy indicated that both complexes minimally perturb the secondary and tertiary structure of HSA, substantial shifts in the CD spectra were recorded for both protein-bound ligands. This study highlights the role of chirality in determining the cytotoxicity profiles and protein binding behaviour of enantiomeric Au(III) chelates. [ABSTRACT FROM AUTHOR]

Due to their hazard to biological systems, it is urgent to develop materials that can rapidly and sensitively detect the concentration of H2PO4− and OCN− ions. In this work, a new CdII-based luminescent metal–organic framework with the formula [Cd(BTDB)(2,6-BBIP)]n (JXUST-47, H2BTDB = (benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid, 2,6-BBIP = 2,6-bis(benzimidazol-1-yl)pyridine) and sql topology was successfully synthesized using a mixed-ligand strategy. JXUST-47 shows good chemical and thermal stability. It also exhibits weak quenching and fluorescence blue shift for H2PO4− and red shift for OCN−, with the detection limits of 0.106 and 0.128 mM, respectively. In addition, considering the demand for H2PO4− and OCN− ion detection, by combining this with the functions of a smartphone, the chroma of photographs have been used to realize the consecutive visual detection of the concentration of these ions. [ABSTRACT FROM AUTHOR]

Due to their hazard to biological systems, it is urgent to develop materials that can rapidly and sensitively detect the concentration of H2PO4− and OCN− ions. In this work, a new CdII-based luminescent metal–organic framework with the formula [Cd(BTDB)(2,6-BBIP)]n (JXUST-47, H2BTDB = (benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid, 2,6-BBIP = 2,6-bis(benzimidazol-1-yl)pyridine) and sql topology was successfully synthesized using a mixed-ligand strategy. JXUST-47 shows good chemical and thermal stability. It also exhibits weak quenching and fluorescence blue shift for H2PO4− and red shift for OCN−, with the detection limits of 0.106 and 0.128 mM, respectively. In addition, considering the demand for H2PO4− and OCN− ion detection, by combining this with the functions of a smartphone, the chroma of photographs have been used to realize the consecutive visual detection of the concentration of these ions. [ABSTRACT FROM AUTHOR]

Opioid use, particularly morphine, is linked to CNS-related disorders, comorbidities, and premature death. Morphine, a widely abused opioid, poses a significant global health threat and serves as a key metabolite in various opioids. Here, we present a turn-off fluorescent sensor capable of detecting morphine with exceptional sensitivity and speed in various samples. The fluorescent sensor was developed through the dimerization process of 7-methoxy-1-tetralone and subsequent demethylation to produce the final product. Despite morphine possessing inherent fluorophoric properties and emitting light in an approximately similar wavelength as the sensor's fluorescent blue light, the introduction of the target molecule (morphine) in the presence of the sensor caused a reduction in the sensor's fluorescence intensity, which is attributable to the formation of the sensor–morphine complex. By utilizing this fluorescence quenching sensor, the chemo-selective detection of morphine becomes highly feasible, encompassing a linear range from 0.008 to 40 ppm with an impressive limit of detection of 8 ppb. Consequently, this molecular probe demonstrates a successful application in determining trace amounts of morphine within urine, yielding satisfactory analytical results. The study also explores the effect of several variables on the sensor's response and optimizes the detection of morphine in urine using a response surface methodology with a central composite design. [ABSTRACT FROM AUTHOR]

BACKGROUND: The application of curcumin (Cur) in the food industry is usually limited by its low water solubility and poor stability. This study aimed to fabricate self‐assembled nanoparticles using pea vicilin (7S) through a pH‐shifting method (pH 7–pH 12–pH 7) to develop water‐soluble nanocarriers of Cur. RESULTS: Intrinsic fluorescence, far‐UV circular dichroism spectra and transmission electron microscopy analysis demonstrated that the structure of 7S could be unfolded at pH 12.0 and refolded when the pH shifted to 7.0. The assembled 7S–Cur exhibited a high loading ability of 81.63 μg mg−1 for Cur and homogeneous particle distribution. Cur was encapsulated in the 7S hydrophobic nucleus in an amorphous form and combined through hydrophobic interactions and hydrogen bonding, resulting in the static fluorescence quenching of 7S. Compared with free Cur, the retention rates of Cur in 7S–Cur were approximately 1.12 and 1.70 times higher under UV exposure at 365 nm or heating at 75 °C for 120 min, respectively, as well as 7S–Cur showing approximately 1.50 times higher antioxidant activity. During simulated gastrointestinal experiments, 7S–Cur exhibited a better sustained‐release property than free Cur. CONCLUSION: The self‐assembled 7S nanocarriers prepared using a pH‐shifting method effectively improved the antioxidant activity, environmental stability and sustained‐release property of Cur. Therefore, 7S isolated from pea protein could be used as potential nanocarriers for Cur. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Since the initial findings that food tannin/salivary protein interaction and subsequent precipitation is the main cause of the astringency development, numerous studies have concentrated on the supramolecular characterization of these bindings. Most of these works have focused on the low-molecular-weight salivary proteins, in particular proline-rich proteins, hardly considering the involvement of the high-molecular-weight salivary proteins (HMWSPs). Herein, different techniques such as fluorescence quenching, Isothermal Titration Calorimetry and HPLC-MS-DAD were employed to determine the occurrence of molecular interactions between three HMWSPs, namely, mucin, α-amylase and albumin, and a complex extract of tannins composed mainly of flavan-3-ols. The obtained results prove the capability of the three HMWSPs to effectively interact with the flavan-3-ol extract, involving different forces and action mechanisms. Flavan-3-ols are capable of interacting with mucins by a mechanism that includes the formation of stable ground-state complexes that led to approximately 90% flavan-3-ol precipitation, while for albumin and α-amylase, the interaction model of a "sphere of action" was established, which represented only 20% flavan-3-ol precipitation. These data highlight the relevance of including HMWSPs in astringency analyses, paying special heed to the role of mucins in the interaction and subsequent precipitation of dietary tannins. [ABSTRACT FROM AUTHOR]

The present study sought to develop a cardiac troponin I (cTnI) detection system based on background fluorescence quenching of internal filtration effect (IFE) and study the influence of IFE on the sensitivity of cTnI detection. Three nanogold materials were synthesized as fluorescence quenchers, and rhodamine 6 G (R6G) and Cy5 were used as fluorescence probes. Six experimental systems were established to detect cTnI in negative serum test solutions and clinical serum samples. The sensitivity of each system was compared to explore the contribution of IFE to the detection sensitivity of cTnI. When applied to negative serum test solutions, the R6G-nanogold material I system exhibited a superior detection effect for cTnI, with a limit of detection (LOD) of 0.15 ng ml−1. When applied to clinical serum samples, the Cy5-nanogold material Ⅲ system yielded a better detection effect for cTnI, with the lowest concentration of cTnI detected at 2 ng ml−1. The first and second internal filtering effects in the proposed system can be achieved simultaneously, effectively avoiding light absorption interference from clinical serum samples and enhancing the sensitivity of the background fluorescence quenching detection of cTnI. [ABSTRACT FROM AUTHOR]

Organic light‐emitting transistors (OLETs) are highly integrated and minimized optoelectronic devices with significant potential superiority in smart displays and optical communications. To realize these various applications, it is urgently needed for color‐tunable emission in OLETs, but remains a great challenge as a result of the difficulty for designing organic semiconductors simultaneously integrating high carrier mobility, strong solid‐state emission, and the ability for potential tunable colors. Herein, a high mobility emissive excimer organic semiconductor, 2,7‐di(2‐anthryl)‐9H‐fluorene (2,7‐DAF) was reasonably designed by introducing a rotatable carbon–carbon single bond connecting two anthracene groups at the 2,7‐sites of fluorene, and the small torsion angles simultaneously guarantee effective conjugation and suppress fluorescence quenching. Indeed, the unique stable dimer arrangement and herringbone packing mode of 2,7‐DAF single crystal enables its superior integrated optoelectronic properties with high carrier mobility of 2.16 cm2 ⋅ V−1 ⋅ s−1, and strong excimer emission with absolute photoluminescence quantum yield (PLQY) of 47.4 %. Furthermore, the voltage‐dependent electrically induced color‐tunable emission from orange to blue was also demonstrated for an individual 2,7‐DAF single crystal based OLETs for the first time. This work opens the door for a new class of high mobility emissive excimer organic semiconductors, and provides a good platform for the study of color‐tunable OLETs. [ABSTRACT FROM AUTHOR]

The quantitative detection and discrimination of glutathione (GSH) were achieved based on oxalyl dihydrazide (ODH) decorated sulfur nanodots. ODH resulted in the aggregation and fluorescence quenching of the sulfur nanodots, and GSH selectively triggered fluorescence recovery through forming stronger hydrogen bonds with ODH than other biological thiols. [ABSTRACT FROM AUTHOR]

A new π-conjugated bridging-type dicarboxylic acid with a functional alkynyl group, 4,4′-(ethynylimino)bis[benzoic acid] (H2L), was designed and synthesized to construct a Zn(II)-based coordination compound [ZnL(dpa)]n (dpa = 4,4′-dipyridylamine). Compound 1 has two-dimensional layers with alkynyl groups protruding on each side of the layer. The introduction of the ligand dpa ensured the existence of uncoordinated nitrogen atoms. Through Hg⋯C (alkynyl group) and Hg⋯N (amino group) coordination interactions, 1 can effectively detect Hg2+ ions (Ksv = 1.34 × 104 M−1 and LOD = 3.75 × 10−4 mM) by fluorescence quenching. Meanwhile, for Fe3+, in addition to the coordination interactions between Fe3+ ions and the uncoordinated amino groups, competitive absorption was the major contributor to the fluorescence quenching of compound 1. Competitive absorption prompted the sensitive sensing of Fe3+ (Ksv = 3.09 × 104 M−1 and LOD = 1.94 × 10−4 mM) and 4-nitrophenol (Ksv = 7.46 × 104 M−1 and LOD = 4.32 × 10−4 mM). [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of cuprous iodide (CuI) has drawn significant attention in the scientific community. In order to investigate the growth methods and environmental conditions on the fluorescence, we first prepared CuI via immersion of copper in hydroiodic acid. This method is beneficial for the growth of large grains (> 20 μm) with intensive red fluorescence emission at 708 nm. The fluorescence has a high quantum yield (34 %), and superior stability. Then we studied the fluorescence behaviors in water. We observed fluorescence quenching, which is due to the energy transfer. Additionally, we studied the effect of temperature on the fluorescence. We found that the fluorescence intensity increased initially then decreased as the temperature increased. The underlying mechanism was analyzed in terms of fluorescence quencher (water) removal and thermal quenching. By controlling heating, we successfully obtained intensive and pure red fluorescence. Finally, we explored the potential application of the red fluorescent of CuI in optical communication. The results demonstrate bit error rates within permissible range of forward error correction, highlighting the superior performance of CuI in optical communication systems. [ABSTRACT FROM AUTHOR]

Water molecules play an important role in the structure, function, and dynamics of (bio‐) materials. A direct access to the number of water molecules in nanoscopic volumes can thus give new molecular insights into materials and allow for fine‐tuning their properties in sophisticated applications. The determination of the local water content has become possible by the finding that H2O quenches the fluorescence of red‐emitting dyes. Since deuterated water, D2O, does not induce significant fluorescence quenching, fluorescence lifetime measurements performed in different H2O/D2O‐ratios yield the local water concentration. We combined this effect with the recently developed fluorescence lifetime single molecule localization microscopy imaging (FL‐SMLM) in order to nanoscopically determine the local water content in microgels, i.e. soft hydrogel particles consisting of a cross‐linked polymer swollen in water. The change in water content of thermo‐responsive microgels when changing from their swollen state at room temperature to a collapsed state at elevated temperature could be analyzed. A clear decrease in water content was found that was, to our surprise, rather uniform throughout the entire microgel volume. Only a slightly higher water content around the dye was found in the periphery with respect to the center of the swollen microgels. [ABSTRACT FROM AUTHOR]

A hybrid material, consisting of commercially available nitrocellulose (NC) membrane non-covalently modified with amino-polyethylene glycol functionalized reduced graphene oxide (NH2-PEG-rGO) nanoparticles, was successfully synthesized for oligonucleotide extraction. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the modification of the NC membrane, revealing characteristic peaks of both compounds, i.e., NC and NH2-PEG-rGO. Scanning Electron Microscopy (SEM) exhibited morphological changes in the NC/NH2-PEG-rGO hybrid membrane, marked by the introduction of NH2-PEG-rGO particles, resulting in a distinctly smothered surface compared to the porous surface of the NC control membrane. Wettability assays revealed hydrophobic behavior for the NC/NH2-PEG-rGO hybrid membrane, with a water contact angle exceeding 90°, contrasting with the hydrophilic behavior characterized by a 16.7° contact angle in the NC membrane. The performance of the NC/NH2-PEG-rGO hybrid membrane was evaluated for the extraction of ssDNA with fewer than 50 nucleotides from solutions containing various ionic species (MnCl2, MgCl2, and MnCl2/MgCl2). The NC/NH2-PEG-rGO hybrid membrane exhibited optimal performance when incubated in MgCl2, presenting the highest fluorescence emission at 525 relative fluorescence units (r.f.u.). This corresponds to the extraction of approximately 610 pg (≈13%) of the total oligo-DNA, underscoring the efficacy of the pristine material, which extracts 286 pg (≈6%) of oligo-DNA in complex solutions. [ABSTRACT FROM AUTHOR]

Mesotrione is a widely used post-emergence herbicide for maize. The toxicity of mesotrione to maize (especially sweet corn) has been widely reported, and some sweet corn varieties are highly sensitive to mesotrione, which affects subsequent plant growth periods. However, the molecular mechanisms responsible for the differences in susceptibility to mesotrione are not known. By comparing changes in the transcriptome of mesotrione-tolerant line 301 and mesotrione-sensitive line 276 after mesotrione treatment, we found that the genes coding light-harvesting chlorophyll protein complex were induced in 301, and the genes coding loosening cell walls were overrepresented in 276. The net photosynthetic rate, maximum photochemical efficiency of leaf PSII, photochemical quenching of chlorophyll fluorescence, and the electron transport rate were significantly higher in 301 than in 276 after mesotrione treatment, and these effects became more severe as time passed. In addition, oxidative balance was also affected by mesotrione. Compared with 301, SOD, POD, and CAT activities were significantly reduced with longer exposure time in 276. The results suggested that sweet corn can mitigate herbicide mesotrione toxicity by improving photosynthesis, ROS scavenging, and cell wall synthesis. [ABSTRACT FROM AUTHOR]

Transient receptor potential vanilloid 4 (TRPV4) is a widely expressed cation channel that plays an important role in many physiological and pathological processes. However, most TRPV4 drugs carry a risk of side effects. Moreover, existing screening methods are not suitable for the high-throughput screening (HTS) of drugs. In this study, a cell model and HTS method for targeting TRPV4 channel drugs were established based on a calcium-activated chloride channel protein 1 Anoctamin 1 (ANO1) and a double mutant (YFP-H148Q/I152L) of the yellow fluorescent protein (YFP). Patch-clamp experiments and fluorescence quenching kinetic experiments were used to verify that the model could sensitively detect changes in intracellular Ca2+ concentration. The functionality of the TRPV4 cell model was examined through temperature variations and different concentrations of TRPV4 modulators, and the performance of the model in HTS was also evaluated. The model was able to sensitively detect changes in the intracellular Ca2+ concentration and also excelled at screening TRPV4 drugs, and the model was more suitable for HTS. We successfully constructed a drug cell screening model targeting the TRPV4 channel, which provides a tool to study the pathophysiological functions of TRPV4 in vitro. [ABSTRACT FROM AUTHOR]

Biomacromolecular probes have been extensively employed in the detection of metal ions for their prominent biocompatibility, water solubility, high selectivity, and easy modification of fluorescent groups. In this study, a fluorescent probe FP was constructed. The probe FP exhibited high specificity recognition for Cu2+. With the combination of Cu2+, the probe was subjected to fluorescence quenching. The research suggested that the probe FP carried out the highly sensitive detection of Cu2+ with detection limits of 1.7 nM. The fluorescence quenching of fluorescamine was induced by Cu2+ perhaps due to the PET (photoinduced electron transfer) mechanism. The FP-Cu2+ complex shows weak fluorescence, which is likely due to the PET quenching effect from Cu2+ to fluorescamine fluorophore. Moreover, the probe FP can be employed for imaging Cu2+ in living cells. The new fluorescent probe developed in this study shows the advantages of good biocompatibility and low cytotoxicity. It can be adopted for the targeted detection of Cu2+ in cells, and it has promising applications in the mechanism research and diagnosis of Cu2+-associated diseases. [ABSTRACT FROM AUTHOR]

The high toxicity of arsenic (As) can cause irreversible harm to the environment and human health. In this study, the chlorin e6 (Ce6), which emits fluorescence in the infrared region, was introduced as the luminescence center, and the addition of copper ion (Cu2+) and As(V) provoked a regular change in fluorescence at 652 nm, whereas that of As(III) was 665 nm, which was used to optionally detect Cu2+, arsenic (As(III), and As(V)). The limit of detection (LOD) values were 0.212 μM, 0.089 ppm, and 1.375 ppb for Cu2+, As(III), and As(V), respectively. The developed method can be used to determine Cu2+ and arsenic in water and soil with good sensitivity and selectivity. The 1:1 stoichiometry of Ce6 with Cu2+ was obtained from the Job plot that was developed from UV–visible spectra. The binding constants for Cu2+ and As(V) were established to be 1.248 × 105 M−1 and 2.35 × 1012 M−2, respectively, using B–H (Benesi–Hildebrand) plots. Fluorescence lifetimes, B–H plots, FT–IR, and 1H-NMR were used to postulate the mechanism of Cu2+ fluorescence quenching and As(V) fluorescence restoration and the interactions of the two ions with the Ce6 molecule. [ABSTRACT FROM AUTHOR]

Sub-nanometer-sized gold nanoclusters (Au NCs) were prepared via the spontaneous reduction of [AuCl4]−- ions with a hydroxamate derivative of L-tryptophan (Trp) natural amino acid (TrpHA). The prepared TrpHA-Au NCs possess intense blue emission (λem = 470 nm; λex = 380 nm) with a 2.13% absolute quantum yield and 1.47 ns average lifetime. The Trp-stabilized noble metal NCs are excellent metal ion sensors for Fe3+, but in this work, we highlighted that the incorporation of the hydroxamate functional group with an excellent metal ion binding capability can tune the selectivity and sensitivity of these NCs, which is a promising way to design novel strategies for the detection of other metal ions as well. Moreover, their simultaneous identification can also be realized. By decreasing the sensitivity of our nano-sensor for Fe3+ (limit of detection (LOD) ~11 µM), it was clearly demonstrated that the selectivity for Cu2+-ions can be significantly increased (LOD = 3.16 µM) in an acidic (pH = 3–4) condition. The surface-bounded TrpHA molecules can coordinate the Cu2+ confirmed by thermodynamic data, which strongly generates the linking of the NCs via the Cu2+ ions in acidic pH, and a parallel fluorescence quenching occurs. In the case of Fe3+, the degree of quenching strongly depends on the metal ion concentration, and it only occurs when the NCs are not able to bind more Fe3+ (~10 µM) on the surface, causing the NCs' aggregation. [ABSTRACT FROM AUTHOR]

Carbon nanodots (CDs) are a new type of carbon‐based fluorescent nanomaterials, but they are limited in many applications due to the inherent fluorescence weakening and quenching problems suffered in solid state. Herein, ZIF‐8, a class of metal–organic framework (MOF) is employed as a matrix to immobilize fluorescent CDs, resulting in the strong luminescence of CDs achieved in solid state. The as‐synthesized CDs@ZIF‐8 fluorescent powders possess blue, green, and red emissions with the main emission at ≈495, 528, and 600 nm, and the corresponding photoluminescence quantum yields (PLQYs) are as high as 25.89%, 52.24%, and 15.42%, respectively. It is found that the encapsulation of ZIF‐8 with CDs will increase the excitation dependence of the product fluorescence, which may be attributed to the carrier effect of ZIF‐8 as a carrier of CDs and some surface defects or surface functional groups change of the CDs introduced by ZIF‐8. In addition, the encapsulation of CDs with ZIF‐8 may result in the charge transfer. Importantly, the prepared CDs@ZIF‐8 phosphors present a promising application in the fabrication of monochromatic light‐emitting diodes (LEDs). The synthesis design is expected to provide technical support for future solid‐state fluorescent CDs preparation and applications. [ABSTRACT FROM AUTHOR]

Glutathione (GSH)-switched fluorescent assays have received attention due to their rapid signal changes of fluorescent nanoprobes. Small polydopamine nanodots (PDs) exhibit remarkable photoluminescent properties. In this work, fluorescent PDs were synthesized through oxidation using dopamine as precursor. The prepared PDs had rich surface functionalities and exhibited good optical properties with maximum emission using 330 nm excitation. The fluorescence was quenched by Ag+ through the interaction with catechols in the PDs. After the addition of GSH, Ag was bound with sulfhydryl groups in GSH and the fluorescence of the PDs was restored. Therefore, a fluorescence turn on-off-on strategy was constructed for Ag+ and GSH using the synthesized PDs as the probe. The PDs showed good performance for Ag+ from 0.01 to 1 μM, with a limit of detection (LOD) equal to 2.82 nM. The system also exhibited a linear relationship for GSH from 0.01 to 0.5 μM with a LOD equal to 1.93 nM. GSH was determined in human serum to demonstrate a practical application of the assay. This work expands the application of PDs in biological analysis. [ABSTRACT FROM AUTHOR]

A novel fluorescence "off–on" probe was developed using a boron difluoride–modified zinc metal–organic framework (Zn-MOF3) for sensitive determination of tetracycline (TC) and Al3+. The Zn-MOF3 has excellent optical property and good applicability in aqueous phase. The fluorescence recorded at 436 nm was quenched at the excitation wavelength of 336 nm. Signal-off detection of tetracycline via fluorescence quenching of Zn-MOF3 is based on the inner filter effect. Fluorescence on–off-on detection of Al3+ occurs via the specific binding between tetracycline and Al3+. The limits of detection for TC and Al3+ were 28.4 nM and 106.7 nM, respectively. This probe exhibited high selectivity which was used for the determination of TC and Al3+ with satisfied recoveries (89.8 to 105.6% for TC, 90.0 to 110.4% for Al3+) and good precision (< 5%) in milk. The developed sensor represents the first "off–on" system for fluorescence detection of TC and Al3+ based on Zn-MOF3 with a better aspect of the innovation. [ABSTRACT FROM AUTHOR]

With the expansion of human activities, the consequent influx of mercury (Hg) into the food chain and the environment is seriously threatening human life. Herein, nitrogen and sulfur co-doped fluorescent carbon quantum dots (yCQDs) were prepared via a hydrothermal method using o-phenylenediamine (OPD) and taurine as precursors. The morphological characteristics as well as spectral features of yCQDs indicated that the photoluminescence mechanism should be the molecular state fluorophores of 2, 3-diaminophenothiazine (oxOPD), which is the oxide of OPD. The as-synthesized yCQDs exhibited sensitive recognition of Hg2+. According to the investigation in combination of UV-Vis absorption spectra, time-resolved fluorescence spectra and quantum chemical calculations, the abundant functional groups on the surface of yCQDs allowed Hg2+ to bind with yCQDs through various interactions, and the formed complexes significantly inhibited the absorption of excitation light, resulting in the static fluorescence quenching of yCQDs. The proposed yCQDs was utilized for Hg2+ sensing with the limit of detection calculated to be 4.50 × 10− 8 M. Furthermore, the recognition ability of yCQDs for Hg2+ was estimated in tap water, lake water and bottled water, and the results indicated that yCQDs have potential applications in monitoring Hg2+. [ABSTRACT FROM AUTHOR]

The accurate and effective identification of hydrogen sulfide holds great significance for environmental monitoring. Azide-binding fluorescent probes are powerful tools for hydrogen sulfide detection. We combined the 2'-Hydroxychalcone scaffold with azide moiety to construct probe Chal-N3, the electron-withdrawing azide moiety was utilized to block the ESIPT process of 2'-Hydroxychalcone and quenches the fluorescence. The fluorescent probe was triggered with the addition of hydrogen sulfide, accompanied by great fluorescence intensity enhancement with a large Stokes shift. With excellent fluorescence properties including high sensitivity, specificity selectivity, and wider pH range tolerance, the probe was successfully applied to natural water samples. [ABSTRACT FROM AUTHOR]

In this study, we report a new syringe aldehyde-derived hydrazinyl-imidazole based fluorescent sensor (L) for sensitive detection of different inorganic quenchers (halide ions, bicarbonate ion, sulphide ion and transition metal ions). The chromophore (L) was obtained in good yield by the 1:1 condensation reaction of 2-hydrazino-4,5-dihydroimidazole hydrobromide and 4-hydroxy-3,5-dimethoxy benzaldehyde. L exhibited strong fluorescence in the visible region (around 380 nm) and its interaction with different quenchers was studied in details via fluorescence technique. For the halide ions series, its sensitivity is higher for NaF (Climit = 4 × 10− 4 M) than for NaCl while the fluorescence quenching occurred mainly through a dynamic process. Similar considerations were observed for HCO3− and S2− quencher too, when static and dynamic quenching take place simultaneously. Regarding transition metal ions, at a fixed ion concentration (4 × 10− 6 M), best performance was achieved for Cu2+ and Fe2+ (fluorescence intensity was reduced by 79% and 84.9% respectively), while for other metal ions, the sensor performance was evaluated and found to be very less (< 40%). Thus, minimum detection limits (10− 6 – 10− 5 M range) recommended the use of such derivatives as highly sensitive sensors capable to monitor delicate changes in varied environments. [ABSTRACT FROM AUTHOR]

The chalcone compound DHPO was synthesized through a chemical reaction between 1-(2-hydroxyphenyl)-ethanone and 3,4-dimethoxy benzaldehyde under ultrasound irradiation. The interaction between the DHPO compound and several metal ions was studied using fluorescence behavior, revealing that the chalcone function as a "turn on and turn off" switch fluorescent sensor, for selectively and sensitively detecting Fe3+ ions. The process of fluorescence quenching and complexation of DHPO with Fe3+ ion was further studied using methods such as Benesi-Hildebrand, Stern-Volmer plot, and job plot. [ABSTRACT FROM AUTHOR]

Herein, we have prepared a 5,10,15,20-Tetrakis(4-hydroxyphenyl) porphyrin (P) which acts as a probe for selective and sensitive detection of Bi3+ ions. Probe P was obtained by reacting pyrrole with 4-hydroxyl benzaldehyde and characterized by NMR, IR, and ESI-MS. All photo-physical studies of P were tested in DMSO:H2O (8:2, v/v) media by spectrophotometry and spectrofluorometry respectively. The selectivity of P was tested with different metal ions in solution as well as in the solid phase, only Bi3+ showed red fluorescence quenching while with other metal ions, no such effect was observed. The Job's plot unveiled the 1:1 stoichiometric binding ratio of the probe with Bi3+ and anticipated association constant of 3.4 ×105 M-1, whereas the Stern-Volmer quenching constant was noticed to be 5.6 ×105 M-1. Probe P could detect Bi3+ down to 27 nM by spectrofluorometric. The binding mechanism of P with Bi3+ was well supported with NMR, mass, and DFT studies. Further, the P was applied for the quantitative determination of Bi3+ in various water samples and the biocompatibility of P was examined using neuro 2A (N2a) cells. Overall, probe P proves promising for the detection of Bi3+ in the semi-aqueous phase and it is the first report as a colorimetric and fluorogenic probe. [ABSTRACT FROM AUTHOR]

Green and economical self-doped nitrogen-containing fluorescent carbon quantum dots (N-CQDs) were synthesized using a one-pot hydrothermal treatment method. The optical and structural properties of the N-CQDs were investigated in detail by UV-vis and fluorescence spectroscopy, X-ray diffraction (XRD) techniques, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) spectroscopy, and elemental analysis illustrate the surface function and composition of N-CQDs. N-CQDs emit a broad fluorescence between365 ̴ 465 nm and fluoresce most strongly at the excitation wavelength of 415 nm. Meanwhile, Cr (VI) could significantly burst the fluorescence intensity of N-CQDs. N-CQDs showed an excellent sensitivity and selectivity to Cr (VI), which exhibited good linearity in the range of 0 ̴ 40 µmol/L with a detection limit of 0.16 µmol/L. In addition, the mechanism of Fluorescence quenching of N-CQDs by Cr (VI) was investigated. This work well provides a research idea for the preparation of green carbon quantum dots from biomass and their use for the detection of metal ions. [ABSTRACT FROM AUTHOR]

Organic fluorophores with dual-state emission (DSE) are rare or difficult to observe because most of them display either aggregation-induced emission (AIE) or aggregation-caused quenching (ACQ). Amazing works have been accomplished, yet most of the DSE compounds were excited by UV light which limits their wide application in bioimaging. In this work, we achieved a visible-light excited DSE fluorophore and realized its imaging in SKOV-3 cells and zebrafish. The naphtho[2',3':4,5]imidazo[1,2-a]pyridine (NIP) core ensures its emission in dilute solution. Meanwhile, the twisted phenyl ring blocks fluorescence quenching induced by the π-π stacking and leads to the emission of the solid. The fluorescence intensity is steady even after 6 h of continuous intense sunlight. More importantly, photostability of NIP in cells is much better than commercial dye (mitochondrial green). [ABSTRACT FROM AUTHOR]

The absorption of exciting light by an inner filter may be the cause of large errors in estimating the efficiency of fluorescence quenching. We performed fluorescence measurements of 5,10,15,20-tetraphenylporphyrin toluene solution in a wide concentration range. We have shown a Förster-free fluorescence quenching in a right-angle geometry experiment, caused by second order inner filter. We proposed to perform measurements in a front-surface geometry to investigate the nature of quenching not related to the inner filters. We have shown that concentration effects in tetraphenylporphyrin solutions in toluene are not accompanied by a decrease in the fluorescence intensity in a front-surface geometry at concentrations of 10− 3-10− 7 mol/l. It was possible to separate the phenomena of the internal filters from the processes occurring in a liquid medium. Our results are of great importance due to the widespread fundamental research of porphyrin-based dyes properties. Highlights: The Förster-free effect fluorescence is observed up to closed to the ultimate solubility concentrations in tetraphenylporphyrins toluene solution at concentrations of 10-3-10-7 mol/l. Förster radius was estimated for 5,10,15,20-tetraphenylporphyrin molecules. Concentration quenching of tetraphenylporphyrin solutions was studied in a wide range of concentrations. A correction experimental method is proposed conditions to minimize inner filter effects. [ABSTRACT FROM AUTHOR]

In this study, CdS quantum dots (QDs) capped with benzyl mercaptan (thiol) were prepared by microwave irradiation technique. The shape, size, morphology, and spectral properties of thiol-capped CdS QDs were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis absorption, and photoluminescence (PL) spectrometry. The photophysical properties of synthesized thiol-capped CdS QDs in the presence of different amounts of gold nanoparticles (AuNPs) have been investigated, exhibiting strong PL quenching. The amount of fluorescence quenching was found to be dependent on the concentration of metal nanoparticles. A Stern-Volmer kinetics model was used to analyze the observed quenching mechanism as a function of the quencher (AuNPs) concentration. The Stern-Volmer plot along with the absorption spectra of thiol-capped CdS QDs in the absence and presence of AuNPs suggest the dynamic (collision) nature of quenching and rule out the possibility of static quenching. The energy transfers from QDs to Au NPs, and hence the quenching of QDs emissions provides new insight into designing novel optical-based materials and the development of FRET-based bionanosensors and phototherapeutic applications. [ABSTRACT FROM AUTHOR]

Uranium, regarded as an important element in nuclear fission energy schemes, is harmful to public health owing to its high toxicity and radioactivity. Herein, a novel fluorescent probe (SC4A@Tb3+) was developed using a one-step liquid-phase method with 4-sulfocalix[4]arene (SC4A) and rare earth–metal ions (Tb3+) as precursors to realize the accurate monitoring of uranyl ion (UO22+) detection. Based on the dynamic quenching mechanism, the SC4A@Tb3+ fluorescence quenching sensor for UO22+ detection was in the linear range of 0–0.36 µM, with a detection limit of 20 µg·L−1, and successfully quantified UO22+ in water and human serum samples. These results suggest that SC4A@Tb3+ is a potential sensing material for UO22+ detection. [ABSTRACT FROM AUTHOR]

Walnut pellicle extracts (WPE) is rich in phenolic acids. The effects of WPE and its monomeric phenolics (ellagic acid (EA), (+)-catechin (CA), chlorogenic acid (CLA), and epigallocatechin gallate (EGCG)) on in vitro digestion of walnut protein isolate (WPI) were studied. The underlying mechanisms on WPI enzymatic digestion through WPE and pure phenolic compounds with digestive enzymes (pepsin and trypsin) therein using Michaelis-Menten kinetics, fluorescence quenching, molecules docking, and surface plasmon resonance (SPR). The in vitro digestibility of WPI decreased significantly by the addition of WPE. WPE had the strong inhibitory effect on WPI digestion and pepsin and trypsin activities. The effects of polyphenols on WPI digestibility were mainly manifested in the interaction between polyphenols and digestive enzymes. SPR as well as fluorescence quenching indicated that WPE bound to pepsin and trypsin was the strongest. Among the four phenolic compounds abundant in the tested WPE, EGCG inhibited pepsin and trypsin more strongly than the other three compounds. SPR showed that EGCG was bound more tightly to pepsin and trypsin than CLA, CA, and EA. In vitro WPI digestion was strongly inhibited by WPE, mainly due to its high content of EGCG, CLA, CA, and EA causing strong inhibition of pepsin and trypsin. The study investigated the influence of plant protein by phenolic acids in the human digestive system and providing a theoretical basis for the processing and manufacturing of polyphenolrich nut-based functional foods. [ABSTRACT FROM AUTHOR]

• Mesoporous silica-based heterogeneous chemosensor has been demonstrated. • The PI-MSNs show selective sensing of Fe3+ ions by visible color change and fluorescence quenching. • The PI-MSNs demonstrated efficient recyclability and reusability. The fabrication of red fluorescent hybrid mesoporous silica-based nanosensor materials has promised the bioimaging and selective detection of toxic pollutants in aqueous solutions. In this study, we present a hybrid mesoporous silica nanosensor in which the propidium iodide (PI) was used to conveniently integrate into the mesopore walls using bis(trimethoxysilylpropyl silane) precursors. Various characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared (FTIR), N 2 adsorption–desorption, zeta potential, particle size analysis, thermogravimetric, and UV–visible analysis were used to analyze the prepared materials. The prepared PI integrated mesoporous silica nanoparticles (PI-MSNs) selective metal ion sensing capabilities were tested with a variety of heavy metal ions (100 mM), including Ni2+, Cd2+, Co2+, Zn2+, Cr3+, Cu2+, Al3+, Mg2+, Hg2+ and Fe3+ ions. Among the investigated metal ions, the prepared PI-MSNs demonstrated selective monitoring of Fe3+ ions with a significant visible colorimetric pink color change into orange and quenching of pink fluorescence in an aqueous suspension. The selective sensing behavior of PI-MSNs might be due to the interaction of Fe3+ ions with the integrated PI functional fluorophore present in the mesopore walls. Therefore, we emphasize that the prepared PI-MSNs could be efficient for selective monitoring of Fe3+ ions in an aqueous solution and in the biological cellular microenvironment. [ABSTRACT FROM AUTHOR]

Autonomous underwater vehicles provide water column observations of phytoplankton biomass using chlorophyll a (Chl a) fluorometers. However, under high incident light, phytoplankton fluorescence yield decreases in a process known as non‐photochemical quenching, resulting in a reduced Chl a fluorescence signal. Methods have been developed to identify and remove the quenched signal from observations by autonomous underwater vehicles. These existing methods rely on assumptions of the homogeneity of the system, both in terms of time (i.e., between day and night observations) and space (i.e., within the water column or between neighboring profiles). These assumptions are not valid in shallow shelf seas or when sampling across different water masses. Thus, we evaluate six new quenching correction methods based on an existing ocean‐based method, but adapted for a continental shelf sea environment where the water mass changes between night and day observations. We have included two main changes to the existing method. First, we interpolate the unquenched, nighttime signal across the daytime observations and use this as a reference for correcting the quenched, daytime signal. Second, we explore the inclusion of a fluorescence quenching depth limit. By interpolating nighttime observations across daytime periods, the diel changes in non‐photochemical quenching were separated from the phytoplankton population changes. The proposed methods all show improved performance compared to existing approach. The methods presented here, and the approach used to evaluate them, are applicable in other shelf sea environments, enabling studies using autonomous Chl a fluorescence data across shelf sea ecosystems. [ABSTRACT FROM AUTHOR]