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Organic chromophores such as the thionated derivatives of perylene diimides (PDIs) show prolonged triplet-excited state lifetimes in contrast to their pristine parent PDI molecule, which shows near unity fluorescence quantum yield. The excited state dynamics in the trans-dithionated PDI (S2-PDI) are studied here. Unlike PDI, the photo absorbing ππ* state of S2-PDI is in close proximity to quasi-degenerate nπ* states. The latter exhibits an interesting vibronic problem leading to the breaking of orbital symmetry mediated through non-totally symmetric vibrations. The time-dependent quantum dynamics are studied with a diabatic model Hamiltonian involving three singlet and three triplet states coupled via 22 vibrational modes. A combined effect of multiple internal-conversion and inter-system crossing (ISC) pathways leads to population transfer from the 1ππ* state to the 3ππ* state via the nπ* states, with an overall ISC rate of 0.70 ps that compares well with the experimental value. The calculated absorption spectra for PDI and S2-PDI reproduce the essential vibronic features in the observed experimental spectra. The dominant vibronic progressions are found to have significant contributions from the vinyl stretching modes of the PDI core. [ABSTRACT FROM AUTHOR]

Quantitative fluorescence quenching is a common analytical approach to studying the mechanism of chemical reactions. The Stern–Volmer (S–V) equation is the most common expression used to analyze the quenching behavior and can be used to extract kinetics in complex environments. However, the approximations underlying the S–V equation are incompatible with Förster Resonance Energy Transfer (FRET) acting as the primary quenching mechanism. The nonlinear distance dependence of FRET leads to significant departures from "standard" S–V quenching curves, both by modulating the interaction range of donor species and by increasing the effect of component diffusion. We demonstrate this inadequacy by probing the fluorescence quenching of long-lifetime lead sulfide quantum dots mixed with plasmonic covellite copper sulfide nanodisks (NDs), which serve as perfect fluorescent quenchers. By applying kinetic Monte Carlo methods, which consider particle distributions and diffusion, we are able to quantitatively reproduce experimental data, which show significant quenching at very small concentrations of NDs. The distribution of interparticle distances and diffusion are concluded to play important roles in fluorescence quenching, particularly in the shortwave infrared, where photoluminescent lifetimes are often long relative to diffusion time scales. [ABSTRACT FROM AUTHOR]

Nanoclusters for fluorescence detection are generally comprised of rare and expensive noble metals, and the nanoclusters based on more affordable transition metal have attracted increasing attention. This study designed a ratiometric fluorescent probe to detect dopamine (DA), an important neurotransmitter. With carbon dots encapsulated within silica (CDs@SiO2) as the reference, the emitted reference signal was almost unchanged due to the protection of inert silicon shell. Meanwhile, copper nanoclusters modified with 3-aminophenyl boronic acid (APBA-GSH-CuNCs) provided the sensing signal, in which the phenylboric acid could specifically recognize the cis-diol structure of DA, and caused the fluorescence quenching by photoinduced electron transfer. This dual emission ratiometric fluorescent probe exhibited high sensitivity and anti-interference, and was able to selectively responded to DA with a linear range of 0–1.4 mM, the detection limit of 5.6 nM, and the sensitivity of 815 mM−1. Furthermore, the probe successfully detected DA in human serum samples, yielding recoveries ranging from 92.5% to 102.7%. Overall, this study highlights the promising potential of this ratiometric probe for detecting DA. [ABSTRACT FROM AUTHOR]

Summary: Obesity is becoming a top global health problem. Inhibition of digestive enzymes is an effective approach in weight management due to the reduction of energy absorption. In this study, the inhibitory effects of luteolin on α‐glucosidase and pancreatic lipase were investigated in vitro and in vivo via enzyme kinetics, fluorescence quenching, molecular docking and rat experiments. The results showed that luteolin inhibited α‐glucosidase and pancreatic lipase in a mixed‐type and uncompetitive manner with IC50 values of 29.31 and 42.74 μg mL−1 respectively. The binding of luteolin with the two enzymes caused the quenching of intrinsic fluorescence of protein. Molecular docking simulation revealed that luteolin could be located in the active pocket of α‐glucosidase and interact with the key amino acid residues. Moreover, a hydrophobic interaction and a van der Waals force were formed between luteolin and the key amino acid residues of pancreatic lipase (His264 and Ser153). In vivo studies further confirmed that luteolin could significantly decrease the absorption of glucose and triacylglyceride in rats by inhibiting α‐glucosidase and pancreatic lipase. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Stability against oxygen is an important factor affecting the performance of organic semiconductor devices. Improving photooxidation stability can prolong the service life of the device and maintain the mechanical and photoelectric properties of the device. Generally, various encapsulation methods from molecular structure to macroscopic device level are used to improve photooxidation stability. Here, we adopted a crystallization strategy to allow 14H‐spiro[dibenzo[c,h]acridine‐7,9′‐fluorene] (SFDBA) to pack tightly to resist fluorescence decay caused by oxidation. In this case, the inert group of SFDBA acts as a "steric armor", protecting the photosensitive group from being attacked by oxygen. Therefore, compared with the fluorescence quenching of SFDBA powder under 2 h of sunlight, SFDBA crystal can maintain its fluorescence emission for more than 8 h under the same conditions. Furthermore, the photoluminescence quantum yields (PLQYs) of the crystalline film is 327% higher than that of the amorphous film. It shows that the crystallization strategy is an effective method to resist oxidation. [ABSTRACT FROM AUTHOR]

A fluorescent probe, 4-(di-phenylamino)-benzaldehyde oxime (DPBO), was developed comprising 4-(diphenylamino) benzaldehyde as the fluorophore and hydroxyl amine, where the resultant oxime group leads to the formation of a recognition site for the selective "on–off" fluorescence detection of lethal phosgene with the dimer formation of DPBO through carbonate linkage generated from phosgene. The probe DPBO also exhibits notable spectrofluorometric response in different solvents, as demonstrated by SEM analysis. The detection limit of the probe DPBO towards phosgene was calculated as 21.53 μM, with a fast reaction response time within 30 s and the fluorescence quenching efficiency of DPBO by phosgene was measured through the Stern–Volmer quenching constant (KSV) estimated at 1.03 × 104 M−1. Confirmation of the sensing mechanism was achieved through various spectroscopic techniques such as UV-vis, emission spectroscopy, mass spectrometry, and computational studies. For practical applications, the sensor DPBO can be utilized for the detection of phosgene in household bleach, soil analysis and dipstick method. [ABSTRACT FROM AUTHOR]

The rapid discrimination of bacteria is currently an emerging trend in the fields of food safety, medical detection, and environmental observation. Traditional methods often require lengthy culturing processes, specialized analytical equipment, and bacterial recognition receptors. In response to this need, we have developed a paper-based fluorescence sensor array platform for identifying different bacteria. The sensor array is based on three unique carbon quantum dots (CQDs) as sensing units, each modified with a different antibiotic (polymyxin B, ampicillin, and gentamicin). These antibiotic-modified CQDs can aggregate on the bacterial surface, triggering aggregation-induced fluorescence quenching. The sensor array exhibits varying fluorescent responses to different bacterial species. To achieve low-cost and portable detection, CQDs were formulated into fluorescent ink and used with an inkjet printer to manufacture paper-based sensor arrays. A smartphone was used to collect the responses generated by the bacteria and platform. Diverse machine learning algorithms were utilized to discriminate bacterial types. Our findings showcase the platform's remarkable capability to differentiate among five bacterial strains, within a detection range spanning from 1.0 × 103 CFU/mL to 1.0 × 107 CFU/mL. Its practicality is further validated through the accurate identification of blind bacterial samples. With its cost-effectiveness, ease of fabrication, and high degree of integration, this platform holds significant promise for on-site detection of diverse bacteria. [ABSTRACT FROM AUTHOR]

The interactions with calf thymus DNA (CT-DNA) of three Schiff bases formed by the condensation of hesperetin with benzohydrazide (HHSB or L1H3), isoniazid (HIN or L2H3), or thiosemicarbazide (HTSC or L3H3) and their CuII complexes (CuHHSB, CuHIN, and CuHTSC with the general formula [CuLnH2(AcO)]) were evaluated in aqueous solution both experimentally and theoretically. UV–Vis studies indicate that the ligands and complexes exhibit hypochromism, which suggests helical ordering in the DNA helix. The intrinsic binding constants (Kb) of the Cu compounds with CT-DNA, in the range (2.3–9.2) × 106, from CuHTSC to CuHHSB, were higher than other copper-based potential drugs, suggesting that π–π stacking interaction due to the presence of the aromatic rings favors the binding. Thiazole orange (TO) assays confirmed that ligands and Cu complexes displace TO from the DNA binding site, quenching the fluorescence emission. DFT calculations allow for an assessment of the equilibrium between [Cu(LnH2)(AcO)] and [Cu(LnH2)(H2O)]+, the tautomer that binds CuII, amido (am) and not imido (im), and the coordination mode of HTSC (O−, N, S), instead of (O−, N, NH2). The docking studies indicate that the intercalative is preferred over the minor groove binding to CT-DNA with the order [Cu(L1H2am)(AcO)] > [Cu(L2H2am)(AcO)] ≈ TO ≈ L1H3 > [Cu(L3H2am)(AcO)], in line with the experimental Kb constants, obtained from the UV–Vis spectroscopy. Moreover, dockings predict that the binding strength of [Cu(L1H2am)(AcO)] is larger than [Cu(L1H2am)(H2O)]+. Overall, the results suggest that when different enantiomers, tautomers, and donor sets are possible for a metal complex, a computational approach should be recommended to predict the type and strength of binding to DNA and, in general, to macromolecules. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are a type of carbon‐based nanoparticles that are typically smaller than 10 nanometres in size. In this study, L‐tryptophan‐mediated CQDs were synthesized using the hydrothermal carbonization (HTC) technique, which is known for its non‐toxic, environmentally friendly, and cost‐effective nature. The synthesized carbon quntum dot was successfully characterized. The HR‐TEM analysis clearly revealed the formation of specific aggregates with a size distribution ranging from 3.0 to 5.1 nm. These L‐tryptophan‐mediated CQDs exhibited remarkable emission behaviour, displaying strong and stable blue fluorescence. Moreover, they were utilized as a sensor for the sensitive detection of Fe3+ and Hg2+ ions in an aqueous solution, employing a fluorescence quenching mechanism. The limit of detection for Fe3+ sensing was determined to be 1.2×10−5 M, while for Hg2+ sensing, it was found to be 1.9×10−5 M. The sensing of Fe3+ and Hg2+ ions was also confirmed through visual eye detection, as a significant color change of the CQDs was observed. Additionally, a competitive study was conducted to verify the selectivity of the L‐tryptophan‐mediated CQDs towards Fe3+ and Hg2+ metal ions. [ABSTRACT FROM AUTHOR]

Film‐based fluorescence sensors are attractive for rapid and on‐site detection of illicit drugs, due to their potential for portability, high sensitivity and reusability. Three new bay‐substituted perylene diimide derivatives are synthesized , P1‐CH3 (1‐methyl), P1‐CF3 (1‐trifluoromethyl), and P1‐(CF3)2 (1,7‐di‐trifluoromethyl) that can be solution processed into thin films capable of detecting methamphetamine hydrochloride (MA•HCl) and cocaine•HCl via a luminescence quenching mechanism. The ionization potentials of the materials are sufficiently high to enable photoinduced hole transfer to occur, which led to the luminescence quenching. The trifluoromethyl‐substituted PDIs exhibit superior sensitivity and reversibility of the luminescence quenching process. In particular, P1‐(CF3)2 shows a limit of detection to MA•HCl of ≈100 ng after a 15‐second exposure, and its luminescence can be fully recovered either through mild heating or being placed in an air flow. Furthermore, by using the luminescence quenching and recovery responses of four PDI sensing materials it is possible to differentiate MA•HCl, cocaine•HCl, from aspirin, caffeine, sugar, and (sebum) skin oil in around a minute. [ABSTRACT FROM AUTHOR]

A novel dual-mode fluorometric and colorimetric sensing platform is reported for determining glutathione S-transferase (GST) by utilizing polyethyleneimine-capped silver nanoclusters (PEI-AgNCs) and cobalt-manganese oxide nanosheets (CoMn-ONSs) with oxidase-like activity. Abundant active oxygen species (O2•−) can be produced through the CoMn-ONSs interacting with dissolved oxygen. Afterward, the pink oxDPD was generated through the oxidation of colorless N,N-diethyl-p-phenylenediamine (DPD) by O2•−, and two absorption peaks at 510 and 551 nm could be observed. Simultaneously, oxDPD could quench the fluorescence of PEI-AgNCs at 504 nm via the inner filter effect (IFE). However, in the presence of glutathione (GSH), GSH prevents the oxidation of DPD due to the reducibility of GSH, leading to the absorbance decrease at 510 and 551 nm. Furthermore, the fluorescence at 504 nm was restored due to the quenching effect of oxDPD on decreased PEI-AgNCs. Under the catalysis of GST, GSH and1-chloro-2,4-dinitrobenzo (CDNB) conjugate to generate an adduct, initiating the occurrence of the oxidation of the chromogenic substrate DPD, thereby inducing a distinct colorimetric response again and the significant quenching of PEI-AgNCs. The detection limits for GST determination were 0.04 and 0.21 U/L for fluorometric and colorimetric modes, respectively. The sensing platform illustrated reliable applicability in detecting GST in real samples. [ABSTRACT FROM AUTHOR]

A dual-mode (colorimetric/fluorescence) nanoenzyme-linked immunosorbent assay (NLISA) was developed based on Au-Cu nanocubes generating Prussian blue nanoparticles (PBNPs). It is expected that this method can be used to detect the residues of sulfonamides in the field, and solve the problem of long analysis time and high cost of the traditional method. Sulfadimethoxine (SDM) was selected as the proof-of-concept target analyte. The Au-Cu nanocubes were linked to the aptamer by amide interaction, and the Au-Cu nanocubes, SDM and antibody were immobilized on a 96-well plate using the sandwich method. The assay generates PBNPs by oxidising the Cu shells on the Au-Cu nanocubes in the presence of hydrochloric acid, Fe3+ and K3[Fe (CN)6]. In this process, the copper shell undergoes oxidation to Cu2+ and subsequently Cu2 + further quenches the fluorescence of the carbon point. PBNPs exhibit peroxidase-like activity, oxidising 3,3',5,5'-tetramethylbenzidine (TMB) to OX-TMB in the presence of H2O2, which alters the colorimetric signal. The dual-mode signals are directly proportional to the sulfadimethoxine concentration within the range 10− 3~10− 7 mg/mL. The limit of detection (LOD) of the assay is 0.023 ng/mL and 0.071 ng/mL for the fluorescent signal and the colorimetric signal, respectively. Moreover, the assay was successfully applied to determine sulfadimethoxine in silver carp, shrimp, and lamb samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Chlorophyll a fluorescence parameters related to PSII photochemistry, photoprotection and photoinhibition were investigated in four C3 plant species growing in their natural habitat: Prosopis juliflora; Abutilon indicum; Salvadora persica; and Phragmites karka. This study compared the light reaction responses of P. juliflora, an invasive species, with three native co-existing species, which adapt to varying water deficit and high salt stress. Chlorophyll a fluorescence quenching analyses revealed that P. juliflora had the highest photochemical quantum efficiency and yield, regulated by higher fraction of open reaction centres and reduced photoprotective energy dissipation without compromising the integrity of photosynthetic apparatus due to photoinhibition. Moreover, the elevated values of parameters obtained through polyphasic chlorophyll a fluorescence induction kinetics, which characterise the photochemistry of PSII and electron transport, highlighted the superior performance index of energy conservation in the transition from excitation to the reduction of intersystem electron carriers for P. juliflora compared to other species. Enhanced pigment contents and their stoichiometry in P. juliflora apparently contributed to upregulating fluxes and yields of energy absorbance, trapping and transport. This enhanced photochemistry, along with reduced non-photochemical processes, could explain the proclivity for invasion advantage in P. juliflora across diverse stress conditions. [ABSTRACT FROM AUTHOR]

Macrocyclic arenes show conformational adaptability, which allows host–guest complexations with the size‐matched guest molecules. However, their emission properties are often poor in the solid states due to the self‐absorption. Herein, we newly synthesized pillar[6]arene derivatives having alternate methylene and nitrogen bridging structures. Solvatochromic study reveals that the nitrogen‐embedding into the cyclic structures can strengthen the intramolecular charge transfer (CT) nature compared to that of the linear nitrogen‐bridged precursor. Owing to the large Stokes shift in the solid state, one of the nitrogen‐embedded pillar[6]arenes shows high absolute photoluminescence quantum yield (ΦPL=0.36). Furthermore, it displays a turn‐off sensing ability toward nitrobenzene (NB) vapor; a fluorescence quenching is observed when exposed to the NB vapor. From the structural analysis before and after the exposure of NB vapor, the amorphous nitrogen‐embedded pillar[6]arene efficiently co‐crystallize with NB and formed non‐emissive intermolecular CT complexes with NB. [ABSTRACT FROM AUTHOR]

Inorganic perovskite quantum dots (QDs) have garnered significant attention due to their outstanding optical properties. However, perovskite quantum dot light‐emitting diodes (Pe‐QLEDs) still face challenges related to their fluorescence efficiency and electron injection. First, the electron transport layer (ETL) leads to severe non‐radiative recombination due to fluorescence quenching in CsPbI3 QDs. Second, there is an electron injection imbalance resulting from low electron injection efficiency, leading to reduced non‐radiative recombination and external quantum efficiency. To address these issues, this study introduces two interface layer materials with different electron affinities, 1,3,5‐Tris(3‐pyridyl‐3‐phenyl)benzene (TmPyPB) and 2,4,6‐Tris(3′‐(pyridine‐3‐yl)biphenyl‐3‐yl)‐1,3,5‐triazine (TmPPPyTz). These materials not only passivated defects on the surface of CsPbI3 QDs films but also effectively prevented the fluorescence quenching of CsPbI3 QDs by the PO‐T2T (ETL). TmPPPyTz, with a relatively lower LUMO energy level, further improved energy level matching, significantly enhancing electron injection efficiency. Ultimately, using interface engineering with the TmPPPyTz interface layer, the devices achieved an outstanding 25.80% champion‐level external quantum efficiency (EQE) for Pe‐QLEDs with only a sub‐bandgap voltage of 1.7 V and half‐life (T50) is 17.99 h at 100 nits. This research provided an effective method to enhance the performance of CsPbI3 Pe‐QLEDs, addressing long‐standing issues inhibiting their efficiency. [ABSTRACT FROM AUTHOR]

Candida albicans and C. glabrata express exporters of the ATP-binding cassette (ABC) superfamily and address them to their plasma membrane to expel azole antifungals, which cancels out their action and allows the yeast to become multidrug resistant (MDR). In a way to understand this mechanism of defense, we describe the purification and characterization of Cdr1, the membrane ABC exporter mainly responsible for such phenotype in both species. Cdr1 proteins were functionally expressed in the baker yeast, tagged at their C-terminal end with either a His-tag for the glabrata version, cg Cdr1-His, or a green fluorescent protein (GFP) preceded by a proteolytic cleavage site for the albicans version, ca Cdr1-P-GFP. A membrane Cdr1-enriched fraction was then prepared to assay several detergents and stabilizers, probing their level of extraction and the ATPase activity of the proteins as a functional marker. Immobilized metal-affinity and size-exclusion chromatographies (IMAC, SEC) were then carried out to isolate homogenous samples. Overall, our data show that although topologically and phylogenetically close, both proteins display quite distinct behaviors during the extraction and purification steps, and qualify cg Cdr1 as a good candidate to characterize this type of proteins for developing future inhibitors of their azole antifungal efflux activity. • This paper describes the purification of a clinically relevant drug transporter of pathogenic fungi • It includes a detailed methodology on working with membrane proteins, including detergent screening, purification and characterization • The use of fluorescence quenching allows to measure the affinity of the protein for its ligands • NanoDifferential Scanning Fluorimetry showed a differential stabilization of the protein, thus making it an interesting tool to screen for future inhibitors • The purification of an ATPase active protein paves the way for structural studies of these transporters. [ABSTRACT FROM AUTHOR]

The water‐soluble compound [Ru3O(CH3COO)6(4‐ampy)3]Cl (1, 4‐ampy=4‐aminopyridine) was evaluated in terms of its biologically relevant properties. Compound 1 participates in a hydrogen bonding network which includes the NH2 substituents of the ancillary ligands, methanol molecules, the Cl− counter‐ion, and a non‐conventional hydrogen bond with the neighboring 4‐ampy molecules′ π‐cloud, as determined by X‐ray measurements. One protonation equilibrium was observed at pH values below 2.3. Additionally, the compound exhibited a partition coefficient value of −0.86 (±0.07), indicating that it is highly hydrophilic. At 37 0C and pH=7.4 (phosphate buffer), compound 1 shows moderate (Ksv=2.4 104 M−1) and spontaneous (ΔG=−26.4 kJ mol−1) binding to human serum albumin (HSA) through ground‐state association, which involves formation of hydrogen bonds (ΔH=−35.7 kJ mol−1 and, ΔS=−29.8 J mol−1 K−1). Molecular docking calculations support the formation of hydrogen bonds between 1 and HSA, and suggest subdomain IIA (site I), which contains the Trp‐214 residue, as the primary interactive pocket, in agreement with the experimental static fluorescence quenching mechanism. Furthermore, a preliminary assay reveals that 1 has low cytotoxicity towards human glioblastoma U87‐MG cells. [ABSTRACT FROM AUTHOR]

The establishment of a convenient and effective detection method for doxycycline (DC) holds significant importance in drug monitoring and drug residue assessment. In this work, carbon quantum dots (CQDs) with excellent and stable luminescence performance (the quantum yield of CQDs was 21.8%) were synthesized by the melting method and employed as probes to monitor the fluorescence intensity variations before and after the introduction of DC. A fluorescence analytical method based on the internal filtration effect (IFE) was developed for DC determination. The mechanism of DC quenching CQDs was verified using fluorescence lifetime tests, absorption spectroscopy, and evaluation of internal filtration parameters. After optimizing experimental conditions, it was found that the DC concentration (CDC) exhibited a good linear relationship with the fluorescence quenching efficiency ((F0-F)/F0) of CQDs in the range of 5–30 µM. The fitted linear equation was Y = 0.01249*CDC+0.03625, R2 = 0.9987, and the detection limit was 2.343 µM (n = 8). This developed method has been successfully applied to accurately determine DC concentrations in both doxycycline hydrochloride tablets and human serum samples. It stands out for its simplicity, rapidity, and acceptable detection performance. Due to its advantages, this method holds great promise for application in the biomedical field for monitoring DC drug concentrations and ensuring quality control. [ABSTRACT FROM AUTHOR]

We present the synthesis of a new oxacalix[4]arene system, DMANSOC, wherein two 5-(dimethylamino)-1-naphthalene sulfonamide subunits are attached to the lower rims of the basic oxacalix[4]arene platform. Extensive spectrophotometric studies were conducted to investigate the selectivity and sensitivity of DMANSOC towards nitroaromatic explosives. Detailed analysis of spectrophotometric data, utilizing techniques such as Stern-Volmer, Benesi-Hildebrand, Job's plot, and interference study, unequivocally demonstrated the effectiveness of DMANSOC as a highly efficient fluorescent sensor for 2,4,6-trinitrophenol explosive (TNP) detection in an aqueous medium. The sensor exhibited a linear concentration range of 7.5 μM to 50 μM, with a low detection limit of 4.64 μM and a high binding affinity of 2.45 × 104 M towards TNP. Furthermore, the efficiency of the sensor in environmental samples contaminated with TNP was evaluated, yielding excellent recovery rates. Complementary DFT calculations and molecular dynamics simulations were performed to elucidate the mechanism behind the selective fluorescence quenching of DMANSOC in the presence of TNP. [ABSTRACT FROM AUTHOR]

In this study, a citalopram optical nano-sensor was developed. Citalopram is a well-known antidepressant drug that reduces the reuptake of serotonin in neurons as a result, serotonin neurotransmission, the primary response to antidepressant treatments, increases in many parts of the brain. This study introduces a carbon quantum dots (CQDs)-based optical nanosensor for rapid detection of citalopram. This fluorescent nanosensor was made through the polymerization of tetraethyl orthosilicate in the presence of CQDs as the fluorescent materials and citalopram as the template molecule. Following the polymerization, the templated molecules were washed and removed from the structure, and the matrix of the polymer was left with some cavities that resembled citalopram in terms of size and shape. The final structure which is used as a chemical nanosensor, is named carbon quantum dots embedded silica molecularly imprinted polymer (CQDs-SMIP). The materials used in designing nano-sensors were characterized using FTIR, UV/Vis, and fluorescence spectroscopy, as well as high-resolution transmission electron microscopy (HR-TEM), and field emission scanning electron microscopy (FESEM). CQDs-SMIP showed a strong fluorescence emission at 420 nm in the absence of the template molecule. The fluorescence intensity of the nanosensor decreased in the presence of citalopram. The correlation between the extent of the fluorescence quenching and the concentration of citalopram provided the nano-sensor signal. The nano-sensor was used to measure citalopram in complex matrices such as human plasma and urine samples with remarkable selectivity and sensitivity. The detection limit of 10.3 µg.L-1 over a linear range of 100 to 700 µg.L-1, and RSD of 3.15% was obtained. This nano-sensor was applied to analyze of citalopram in plasma and human urine samples with remarkable results. [ABSTRACT FROM AUTHOR]

The usage of food-derived polyphenols with different polarities has been limited by their instability and incompatibility. Therefore, a biocarrier was developed by co-assembly of whey protein isolate (WPI) and hydrophilic proanthocyanidin (PC) for loading hydrophobic pterostilbene (PTE). Such biocarrier has superior affinity for PTE than WPI alone, as determined by encapsulation efficiency and loading capacity assay, fluorescence quenching analysis, and molecular docking, whereas the assembly process was characterized by particle size and zeta potential, 3-dimensional fluorescence, and scanning electron microscopy. Circular dichroism and Fourier transform infrared spectroscopy spectra confirmed the α-helix to β-sheet and random coil transition of proteins during the formation of nanocomplexes. Whey protein isolate acted as a mediator through altering the binding mode of PC and PTE, allowing them to perform significant synergistic effects in enhancing 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging and reducing H 2 O 2 -induced cell damage. This research may serve to develop new protein/polyphenol co-loading systems and offer a reliable nutritional fortification. [ABSTRACT FROM AUTHOR]

BACKGROUND: Flaxseed orbitides have health‐promoting properties, particularly potent anti‐cancer activity. However, flaxseed orbitides containing a methionine structure, such as [1‐9‐NαC]‐linusorb B2 (CLB), are easily oxidized to sulfoxide ([1‐9‐NαC],[1‐Rs,Ss‐MetO]‐linusorb‐B2 (CLC)) and sulfone ([1–9‐NαC], [1‐MetO]‐linusorb B2 (CLK)), with CLC having less anti‐cancer ability than CLB. It is unclear why oxidized flaxseed orbitides are less effective against cancer than non‐oxidized flaxseed orbitide. RESULTS: Non‐oxidized ([1‐9‐NαC]‐linusorb‐B3 (CLA) and CLB) and oxidized (CLC and CLK) flaxseed orbitides were found to significantly upregulate the levels of pro‐apoptotic proteins, including Bax/Bcl‐2, CytoC, caspase‐3, and caspase‐8, in a dose‐dependent manner, with non‐oxidized flaxseed orbitides being more effective than oxidized flaxseed orbitides. Mechanically, the cellular absorption of non‐oxidized flaxseed orbitides was higher than that of oxidized flaxseed orbitides. Moreover, the significant fluorescence quenching of DR4 protein by flaxseed orbitides (especially non‐oxidized orbitides) indicated the formation of a DR4–orbitide complex. Molecular docking demonstrated that non‐oxidized orbitides could easily dock into the active cavity of DR4 protein. Further blocking DR4 significantly reduced the ability of non‐oxidized flaxseed orbitides to stimulate caspase‐3 expression, whereas oxidized flaxseed orbitides retained this ability. CONCLUSION: Non‐oxidized flaxseed orbitides are more effective against cancer than oxidized flaxseed orbitides due to higher cellular uptake and activation of the DR4‐mediated death receptor signaling pathway. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • We developed chiral quasi-two-dimensional perovskites for H 2 S detection and E. coli antibacterial. • Bio(R/S-PEA) 2 CsPb 2 Br 7 as probes exhibit fast and sensitive responses to H 2 S. • Bio(R/S-PEA) 2 CsPb 2 Br 7 have a significant effect as antibacterial agents in inhibiting the growth of E. coli. • This work provides ideas for biological applications of aqueous-phase dual-functional perovskite materials. Perovskite nanocrystals (PNCs) have attracted extensive attention for their potential applications in biology. However, only a handful of PNCs have been scrutinized in the biological domain due to issues such as instability, poor dispersion, and size inhomogeneity in polar solvents. The development of dual-functional perovskite nanomaterials with hydrogen sulfide (H 2 S) sensing and antibacterial capabilities is particularly intriguing. In this study, we prepared chiral quasi-two-dimensional (quasi-2D) perovskite nanomaterials, Bio(S-PEA) 2 CsPb 2 Br 7 and Bio(R-PEA) 2 CsPb 2 Br 7 , that were uniformly dispersed in aqueous media. The effective encapsulation of methoxypolyethylene glycol amine (mPEG-NH 2) improved water stability and uniformity of particle size. Circular dichroism (CD) signals were created by the successful insertion of chiral cations. These perovskites as probes showed a rapid and sensitive fluorescence quenching response to H 2 S, and the effect of imaging detection was observed at the Escherichia coli (E. coli) level. As antibacterial agents, their pronounced positive charge properties facilitated membrane lysis and subsequent E. coli death, indicating a significant antibacterial effect. This work has preliminary explored the application of chiral perovskites in biology and provides insight into the development of bifunctional perovskite nanomaterials for biological applications. [ABSTRACT FROM AUTHOR]

Organophosphorus are typically hazardous chemicals used in the pharmaceutical, agricultural, and other industries. They pose a serious risk to human life and can be fatal upon direct exposure. Hence, studying the interaction between such compounds with proteins is crucial for environmental, health, and food safety. In this study, we investigated the interaction mechanism between azinphos‐methyl (AZM) and β‐lactoglobulin (BLG) at pH 7.4 using a combination of biophysical techniques. Intrinsic fluorescence investigations revealed that BLG fluorescence was quenched in the presence of increasing AZM concentrations. The quenching mechanism was identified as static, as evidenced by a decrease in the fluorescence quenching constant (1.25 × 104, 1.18 × 104, and 0.86 × 104 M−1) with an increase in temperatures. Thermodynamic calculations (ΔH > 0; ΔS > 0) affirmed the formation of a complex between AZM and BLG through hydrophobic interactions. The BLG's secondary structure was found to be increased due to AZM interaction. Ultraviolet –visible spectroscopy data showed alterations in BLG conformation in the presence of AZM. Molecular docking highlighted the significant role of hydrophobic interactions involving residues such as Val43, Ile56, Ile71, Val92, Phe105, and Met107 in the binding between BLG and AZM. A docking energy of −6.9 kcal mol−1, and binding affinity of 1.15 × 105 M−1 suggest spontaneous interaction between AZM and BLG with moderate to high affinity. These findings underscore the potential health risks associated with the entry of AZM into the food chain, emphasizing the need for further consideration of its impact on human health. [ABSTRACT FROM AUTHOR]

Many diseases are due to bacterial infections, which are treated by penicillin. Existing methods for penicillin detection have relatively high requirements for sample storage and processing, personnel professionalism, and instruments. Herein, water-soluble N–C quantum dots (QDs) from wheat straw were synthesized in a green way by using an efficient and simple method. The N–C QDs were modified with an imprinted layer by a gel–sol method. Penicillin selectively quenched the fluorescence emission of N–C QDs@MIP, and a linear relationship was obtained in the concentration range of 1.0 × 10−6–15.2 × 10−6 mol L−1. The reliability of the sensor in real sample analysis was satisfactory with results in the range of 93.6%–100%, and the sensor showed good reproducibility and long-term stability. The study provides a simple strategy to fabricate N–C QDs@MIP with a highly selective recognition ability and opens an avenue to develop highly efficient sensing probes for the detection of antibiotics in biological applications. [ABSTRACT FROM AUTHOR]

This article introduces distance-based paper analytical devices (dPADs) integrated with molecularly imprinted polymers (MIPs) and carbon dots (CDs) for simultaneous quantification of cytokine biomarkers, namely C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-a), and interleukin-6 (IL-6) in human biological samples for diagnosis of cytokine syndrome. Using fluorescent CDs and MIP technology, the dPAD exhibits high selectivity and sensitivity. Detection is based on fluorescence quenching of CDs achieved through the interaction of the target analytes with the MIP layer on the paper substrate. Quantitative analysis is easily accomplished by measuring the distance length of quenched fluorescence with a traditional ruler and naked eye readout enabling rapid diagnosis of cytokine syndrome and the underlying infection. Our sensor demonstrated linear ranges of 2.50-24.0 pg mL-1 (R2 = 0.9974), 0.25-3.20 pg mL-1 (R2 = 0.9985), and 1.50-16.0 pg mL-1 (R2 = 0.9966) with detection limits (LODs) of 2.50, 0.25, and 1.50 pg mL-1 for CRP, TNF-a, and IL-6, respectively. This sensor also demonstrated remarkable selectivity compared to a sensor employing a non-imprinted polymer (NIP), and precision with the highest relative standard deviation (RSD) of 5.14%. The sensor is more accessible compared to prior methods relying on expensive reagents and instruments and complex fabrication methods. Furthermore, the assay provided notable accuracy for monitoring these biomarkers in various human samples with recovery percentages ranging between 99.22% and 103.58%. By integrating microfluidic systems, nanosensing, and MIPs technology, our developed dPADs hold significant potential as a cost-effective and user-friendly analytical method for point-of-care diagnostics (POC) of cytokine-related disorders. This concept can be further extended to developing diagnostic devices for other biomarkers. [ABSTRACT FROM AUTHOR]

A new method utilizing fluorescent ratiometry is proposed for detecting putrescine and spermidine. The method involves the use of a fluorescent probe comprising a 2D halide perovskite synthesized from octadecylamine-iodine and PbI2via a grinding-sonicating technique, along with a Eu3+-complex. Upon excitation at 290 nm, the probe fluoresces at two distinguishable wavelengths. The addition of putrescine and spermidine significantly decreases the emission of the 2D halide perovskite at 496 nm, while the emission of the Eu3+-complex at 618 nm remains stable. The color changes of the probe depend on the concentration of putrescine and spermidine, and the assay offers linearity over a wide concentration range (30–4000 ng mL−1), a low detection limit (4 ng mL−1 for putrescine, and 7 ng mL−1 for spermidine), and a quick response time. Furthermore, a portable device based on a smartphone can be used to record the color change of the paper test strip using the prepared fluorescent materials. The fluorescence quenching mechanism of the probe is explained as dynamic quenching. [ABSTRACT FROM AUTHOR]

Fluorescent carbon dots (CDs) are a new type of photoluminescent nanomaterial. Solid-state CDs usually undergo fluorescence quenching due to direct π-π* interactions and superabundant energy resonance transfer. Therefore, the preparation of solid-state fluorescent CDs is a challenge, especially the preparation of long wavelength solid-state CDs. In this research, long wavelength emission CDs were successfully synthesized by solvothermal methods, and the prepared CDs showed good hydrophobicity. The composite solid-state CDs/PVP (Polyvinyl pyrrolidone) can emit strong red fluorescence, and the quantum yield (QY) of the CDs/PVP powder reaches 18.9%. The prepared CDs/PVP solid-state powder was successfully applied to latent fingerprint detection. The results indicate that the latent fingerprints developed by CDs/PVP powder have a fine definition and high contrast visualization effect, which proves that the prepared CDs/PVP has great application potential in latent fingerprint detection. This study may provide inspiration and ideas for the design of new hydrophobic CDs. [ABSTRACT FROM AUTHOR]

Multifunctional nanocomposites from an equimolar As4S4/Fe3O4 cut section have been successfully fabricated from coarse-grained bulky counterparts, employing two-step mechanochemical processing in a high-energy mill operational in dry- and wet-milling modes (in an aqueous solution of Poloxamer 407 acting as a surfactant). As was inferred from the X-ray diffraction analysis, these surfactant-free and surfactant-capped nanocomposites are β-As4S4-bearing nanocrystalline–amorphous substances supplemented by an iso-compositional amorphous phase (a-AsS), both principal constituents (monoclinic β-As4S4 and cubic Fe3O4) being core–shell structured and enriched after wet milling by contamination products (such as nanocrystalline–amorphous zirconia), suppressing their nanocrystalline behavior. The fluorescence and magnetic properties of these nanocomposites are intricate, being tuned by the sizes of the nanoparticles and their interfaces, dependent on storage after nanocomposite fabrication. A specific core–shell arrangement consisted of inner and outer shell interfaces around quantum-confined nm-sized β-As4S4 crystallites hosting a-AsS, and the capping agent is responsible for the blue-cyan fluorescence in as-fabricated Poloxamer capped nanocomposites peaking at ~417 nm and ~442 nm, while fluorescence quenching in one-year-aged nanocomposites is explained in terms of their destroyed core–shell architectures. The magnetic co-functionalization of these nanocomposites is defined by size-extended heterogeneous shells around homogeneous nanocrystalline Fe3O4 cores, composed by an admixture of amorphous phase (a-AsS), nanocrystalline–amorphous zirconia as products of contamination in the wet-milling mode, and surfactant. [ABSTRACT FROM AUTHOR]

Ascorbic acid (AA) is a biomarker of some nervous system diseases, whose detection is of significance in many fields. The hydrothermal reaction of naphthalene‐2,6‐dicarboxylic acid (H2NDBC) with Eu3+ produced a europium MOF, Eu‐NDBC. Eu‐NDBC emits the combined emissions from the intraligand charge transfer (ILCT) of NDBC2− ligand and 5D0→7Fj (j=1–4) transfers of Eu(III). The factors of MOF dosage, pH and fluorescence response time are optimized as 0.6 mg, 7.35, and 5 min respectively. The sensitivity test shows a linear fitting equation of I0/I=0.00239 ⋅ CAA+1.03774 (CAA=AA concentration), with its limit of detection calculated as 4.53 μM in a wide linear range of 0–900 μM. The linear fitting of Stern‐Volmer equation gives KSV=2.46×103 M−1 and Kq=4.96×106 M−1 S−1, suggesting Eu‐NDBC sensing AA is a dynamic fluorescence quenching process. Nine control amino acids can't affect Eu‐NDBC sensing AA and the emission intensity stay stable in five fluorescence quenching‐recovery cycles. The returned CAA closed to the set CAA and the recoveries around 100 % support the accurate AA detection by Eu‐NDBC in human serum. Totally, Eu‐NDBC can be regarded as a quantitative turn‐off fluorescence sensor to AA with high sensitivity and selectivity, rapid response and durability. [ABSTRACT FROM AUTHOR]

L‐3,4‐dihydroxyphenylalanine (levodopa or L–DOPA) a precursor of neurotransmitter dopamine, has been universally prescribed as a gold standard for treatment of Parkinson's Disease (PD). However, direct administration of L–DOPA has risky adverse effects which makes it challenging in the treatment of PD. Hence developing simple detection platform for sensing of L–DOPA is significant. In this work, we have developed cysteine stabilized copper nanocluster quenched with Fe2+ (Fe2+@cys@CuNC) and used as both fluorescent and colorimetric probe for detection of L–DOPA. L–DOPA attributed a fluorescence quenching effect on developed probe. Fe2+@cys@CuNC detected L–DOPA within a linear range from 0.06 mM to 1.31 mM with a low limit of detection (LoD) of 6.57 nM. The probe also exhibited high selectivity for L–DOPA over other biomolecules and neurotransmitters. Furthermore, the capability of this probe was validated by sensing L–DOPA from human serum with excellent recovery rates of 85.75 % to 115.07 %. A low‐cost paper strip‐based portable detection platform was also developed for visual detection of L–DOPA. [ABSTRACT FROM AUTHOR]

This work investigates the impact of pressure on the structural, optical properties, and electronic structure of CsPbBr3 quantum dots (QDs) using steady‐state photoluminescence, steady‐state absorption, and femtosecond transient absorption spectroscopy, reaching a maximum pressure of 3.38 GPa. The experimental results indicate that CsPbBr3 QDs undergo electronic state (ES) transitions from ES‐I to ES‐II and ES‐II to ES‐III at 0.38 and 1.08 GPa, respectively. Intriguingly, a mixed state of ES‐II and ES‐III is observed within the pressure range of 1.08–1.68 GPa. The pressure‐induced fluorescence quenching in ES‐II is attributed to enhanced defect trapping and reduced radiative recombination. Above 1.68 GPa, fluorescence vanishes entirely, attributed to the complete phase transformation from ES‐II to ES‐III in which radiative recombination becomes non‐existent. Notably, owing to stronger quantum confinement effects, CsPbBr3 QDs exhibit an impressive bandgap tuning range of 0.497 eV from 0 to 2.08 GPa, outperforming nanocrystals by 1.4 times and bulk counterparts by 11.3 times. Furthermore, this work analyzes various carrier dynamics processes in the pressure‐induced bandgap evolution and electron state transitions, and systematically studies the microphysical mechanisms of optical properties in CsPbBr3 QDs under pressure, offering insights for optimizing optical properties and designing novel materials. [ABSTRACT FROM AUTHOR]

The heavy-atom effect usually quenches fluorescence, but scarcely enhances it. Herein, fluorescence turn-on sensors without or with a bromine atom for F- detection are presented, achieving fast response time within 1 min, and the LODs of 1.9 × 10-7 and 8.5 × 10-8 M, reflecting that halogen atom introduction is beneficial for F- detection ability improvement. The sensing mechanism of -OH unit deprotonation is confirmed based on the results of a 1: 2 stoichiometric ratio, ¹H NMR titration and TD-DFT calculation. The water environment F- detection and spiked recovery experiments demonstrate their potential for real sample detection. [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]

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 work, a fluorescent complex [Zn(NTD)2(DTP)2(H2O)2]·(H2O)0.8 (Complex Zn), (H2NTD = 1,4-naphthalenedicarboxylic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine) was synthesized. The fluorescent complex was characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and thermogravimetric, elemental, infrared spectroscopy, and fluorescence analyses. In the fluorescence sensing tests, Complex Zn exhibited excellent fluorescence quenching efficiency towards Fe3+, MnO4−, Cr2O72−, nitrofurantoin, and imidacloprid in aqueous media. A mechanism investigation suggested that the fluorescence quenching caused by the quenchers toward the sensor was due to the inner filter effect and the fluorescence resonance energy transfer effect in the fluorescent sensing process. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

The contamination of water by hazardous industrial discharges and harmful bacteria has evolved into a pressing concern, inflicting considerable harm on both the environment and human well-being. It is imperative that decisive measures are taken to mitigate and eradicate industrial wastewater pollution. In this study, we applied (phosphorus) P-doped carbon quantum dots simultaneously for metal ion sensing and photocatalytic without any post-treatment. P-doped carbon quantum dots (CQDs) were prepared from a green precursor microwave irradiation method. Our investigation delved into the structural, morphological, chemical, and elemental composition through various techniques. The P-CQD presented abundant functional groups on the surface with about 5 nm size. The P dopant and P–O–P bonds confirm the presence of P on CQDs. We investigated the influence of P-doping on the absorption, adsorption, and fluorescence characteristics in detail using UV–visible and photoluminescence (PL) spectroscopy. Our findings revealed that the PL emission in blue region is intricately linked to the excitation and pH levels. A noticeable 33% PL quantum yield was found. PL phenomenon attributed to the functional groups presents on the surface of the CQDs. Further, the potential of P-CQDs for the detection of metal ions specifically Fe3+ and Hg2+ in an aqueous environment was investigated, by employing a fluorescence quenching mechanism. The main factors driving quenching are the energy transfer interaction between carbon dots and metal ions facilitated by a certain interaction involving functional groups and surface traps. Impressively, P-CQDs exhibited a low detection limit of 51 nM for Fe3+ and 81 nM for Hg2+. It is worth noting that the P-CQDs exhibited superior quenching efficiency when exposed to Fe3+ and Hg2+ ions compared to other cations. Additionally, it displayed the ability to degrade methyl orange dye, achieving 70% degradation efficiency within a mere 240 min under ordinary visible light without any further integration with other materials. Thus, our study on P-CQDs demonstrates immense dual potential and efficiency for environmental applications. [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]

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]

[Display omitted] In this study, nitrogen-doped carbon dots (N -CDs) were facilely fabricated by one-pot hydrothermal method with levulinic acid and triethanolamine. A fluorescent sensor array was established for identifying azo compounds including Sudan Orange G (SOG), p-diaminoazobenzene, p-aminoazobenzene, azobenzene and quantitative detection of SOG. Experimental results revealed that azo compounds could quench the fluorescent intensity of N -CDs. Owing to various azo compounds showing different affinities to N -CDs, the sensor array exhibited different fluorescence quenching changes, which were further analyzed with principal component analysis to discriminate azo compounds. The sensor array was able to differentiate and recognize diverse concentrations of azo compounds from 0.25 to 2 mg/L. Simultaneously, a variety of factors affecting the detection of SOG were optimized. Under the optimized conditions, the sensor showed excellent stability and sensitivity. The sensor possessed marvelous linearity in the range of 0.1–1 mg/L and 1–4 mg/L and the detection limit was 27.82 μg/L. Spiked recoveries of 90.8–98.2 % were attained at spiked levels of 0.2 mg/L and 1 mg/L, demonstrating that the constructed fluorescence sensor was dependable and feasible for sensing SOG in environmental water samples. [ABSTRACT FROM AUTHOR]

Extracytoplasmic Ni(II)‐binding proteins (NiBPs) are molecular shuttles involved in cellular nickel uptake. Here, we determined the crystal structure of apo CcNikZ‐II at 2.38 Å, which revealed a Ni(II)‐binding site comprised of the double His (HH‐)prong (His511, His512) and a short variable (v‐)loop nearby (Thr59‐Thr64, TEDKYT). Mutagenesis of the site identified Glu60 and His511 as critical for high affinity Ni(II)‐binding. Phylogenetic analysis showed 15 protein clusters with two groups containing the HH‐prong. Metal‐binding assays with 11 purified NiBPs containing this feature yielded higher Ni(II)‐binding affinities. Replacement of the wild type v‐loop with those from other NiBPs improved the affinity by up to an order of magnitude. This work provides molecular insights into the determinants for Ni(II) affinity and paves way for NiBP engineering. [ABSTRACT FROM AUTHOR]

A novel tellurium (Te) containing fluorophore, 1 and its nickel (2) and copper (3) containing metal organic complex (MOC) have been synthesized to exploit their structural and optical properties and to deploy these molecules as fluorescent probes for the selective and sensitive detection of picric acid (PA) over other commonly available nitro‐explosives. Furthermore, density functional theory (DFT) and single crystal X‐ray diffraction (SCXRD) techniques revealed the inclusion of “soft” Tellurium (Te) and “hard” Nitrogen (N), Oxygen (O) atoms in the molecular frameworks. Owing to the presence of electron rich “N” and “O” atoms along with “Te” in the molecular framework, 1 could efficiently and selectively sense PA with more than 80 % fluorescence quenching efficiency in organic medium and having detection limit of 4.60 μM. The selective detection of PA compared to other nitro‐explosives follows a multi‐mechanism based “turn‐off” sensing which includes photo‐induced electron transfer (PET), electrostatic (π‐π stacking and π‐anion/cation) interaction, intermolecular hydrogen bonding and inner filter effect (IFE). The test strip study also establishes the sensitivity of 1 for detection of PA. [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]

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]