Near-infrared Rhodols-based fluorescent probe with large Stokes shift for tracking of H2S in food spoilage and living cells

Hydrogen sulfide (H2S), as a biomarker signaling gas, is not only susceptible to food spoilage, but also plays a key function in many biological processes. In this work, an activated near infrared (NIR) H2S fluorescent probe was designed and synthesized with quinoline-conjugated Rhodols dye as fluorophore skeleton and a dinitrophenyl group as the responsive moiety. Due to the quenching effect of dinitrophenyl group and the closed-loop structure of Rhodols fluorophore, probe itself has a very weak absorption and fluorescence background signal. After the H2S-induced thiolysis reaction, the probe exhibits a remarkable colormetric change and NIR fluorescent enhancement response at 716 nm with large Stokes shift (116 nm), and possesses high sensing selectivity and sensitivity with a low detection limits of 330 nM. The response mechanism is systematically characterized by 1H NMR, MS and DFT calculations. The colorimetric change allows the probe to be used as a test strips to detect H2S in food spoilage, while NIR fluorescent response helps the probe monitor intracellular H2S.

Synchronous spectrofluorimetry and chemometric modeling: A synergistic approach for analyzing simeprevir and daclatasvir, with application to pharmacokinetics evaluation

Simeprevir and daclatasvir represent a cornerstone in the management of Hepatitis C Virus infection, a global health concern that affects millions of people worldwide. In this study, we propose a synergistic approach combining synchronous spectrofluorimetry and chemometric modeling i.e. Partial Least Squares (PLS-1) for the analysis of simeprevir and daclatasvir in different matrices. Moreover, the study employs firefly algorithms to further optimize the chemometric models via selecting the most informative features thus improving the accuracy and robustness of the calibration models. The firefly algorithm was able to reduce the number of selected wavelengths to 47-44% for simeprevir and daclatasvir, respectively offering a fast and sensitive technique for the determination of simeprevir and daclatasvir. Validation results underscore the models' effectiveness, as evidenced by recovery rates close to 100% with relative root mean square error of prediction (RRMSEP) of 2.253 and 2.1381 for simeprevir and daclatasvir, respectively. Moreover, the proposed models have been applied to determine the pharmacokinetics of simeprevir and daclatasvir, providing valuable insights into their distribution and elimination patterns. Overall, the study demonstrates the effectiveness of synchronous spectrofluorimetry coupled with multivariate calibration optimized by firefly algorithms in accurately determining and quantifying simeprevir and daclatasvir in HCV antiviral treatment, offering potential applications in pharmaceutical formulation analysis and pharmacokinetic studies for these drugs.

Aggregation-induced-emission red carbon dots for ratiometric sensing of norfloxacin and anti-counterfeiting

The detection of trace antibiotic residues holds significant importance because it's related to food safety and human health. In this study, we developed a new high-yield red-emitting carbon dots (R-CDs) with aggregation-induced emission properties for ratiometric sensing of norfloxacin. R-CDs were prepared in 30 min using an economical and efficient microwave-assisted method with tartaric acid and o-phenylenediamine as precursors, achieving a high yield of 34.4 %. R-CDs showed concentration-dependent fluorescence and aggregation-induced-emission properties. A ratiometric fluorescent probe for detecting the norfloxacin was developed. In the range of 0-40 μM, the intensity ratio of two emission peaks (I445 nm/I395 nm) towards norfloxacin show good linear relationship with its concentrations and a low detection limit was obtained (36.78 nM). In addition, complex patterns were developed for anti-counterfeiting based on different emission phenomenon at different concentrations. In summary, this study designed a novel ratiometric fluorescent probe for detection of norfloxacin, which greatly shortens the detection time and improves efficiency compared with high-performance liquid chromatography and other methods. The study will promote the application of carbon dots in anti-counterfeiting and other related fields, laying the foundation for the preparation of low-cost photosensitive anti-counterfeiting materials.

Smartphone-based dual inverse signal MOFs fluorescence sensing for intelligent on-site visual detection of malachite green

The development of intelligent, sensitive, and visual methods for the rapid detection of veterinary drug residues is essential to ensure food quality and safety. Here, a smartphone-based dual inverse signal MOFs fluorescence sensing system was proposed for intelligent in-site visual detection of malachite green (MG). A UiO-66-NH2@RhB-dual-emission fluorescent probe was successfully synthesized in one step using a simple one-pot method. The inner filter effect (IFE) quenches the red fluorescence, while hydrogen bonding interaction enhances the blue fluorescence, enabling highly sensitive, accurate, and visual detection of MG dual inverse signals through fluorescence analysis. The probe showed great linearity over a wide range of 0.1-100 μmol/L, with a limit of detection (LOD) of 20 nmol/L. By integrating smartphone photography and RGB (red, green, and blue) analysis, accurate quantitative analysis of MG in water and actual fish samples can be achieved within 5 min. This developed platform holds great promise for the on-site detection of MG in practical applications, with the advantages of simplicity, cost-effectiveness, and rapidity. Consequently, it may open up a new pathway for on-site evaluation of food safety and environmental health.

UIO66 low background signal and fluorescence synergism strategy for highly sensitive detection of Salmonella typhimurium

Successful construction of a detection method for Salmonella typhimurium (S. typhimurium) based on the synergy of hybridization chain reaction (HCR) and fluorescence was realized in this paper. First, the aptamer modified with the quenching group Black Hole Quencher-1 acid (BHQ1) was immobilized on the magnetic beads in combination with the complementary chain of the aptamer modified with 6-carboxyfluorescein (6-FAM). Second, S. typhimurium and cDNA-6-FAM immobilized on magnetic beads competitively bound to the aptamer. Finally, the cDNA-6-FAM was released after magnetic separation acted as a promoter to trigger HCR amplification when the target presented. The fluorescence signal could be significantly improved by the combination of green SYBR Green I (SGI) and HCR long double-stranded DNA and the fluorescent synergy of 6-FAM and SGI. Because of the separation of target and its aptamer, the trigger strand was abstracted by magnetic separation. There was no HCR to generate long double-stranded DNA, and the fluorescence of excess hairpin/SGI could be adsorbed through UIO66 so that only a very low background signal was detected. This fluorescent sensor was capable of monitoring S. typhimurium in the range of 10-3.2 × 107 CFU mL-1 with a limit of detection as low as 1.5 CFU mL-1. Because of the excellent properties of the aptasensor and the validity of SGI fluorescence synergy, this HCR enzyme-free amplification strategy could be generalized to other areas.

Natural flavonols as probes for direct determination of borax: From conventional fluorescence analysis to paper-based smartphone sensing

Borax is strictly regulated in the food processing and pharmaceutical industry due to its physiological toxicity, and the development of a direct analytical method is essential for effectively monitoring the borax abuse. In this work, the fluorescence properties of flavonoids, including flavones, isoflavones and flavonols, were systematically investigated from aqueous to borax solutions, and it was found that the weak intrinsic fluorescence of flavonols could be pervasively sensitized by borax. A natural flavonol, morin, was subsequently chosen as a representative probe to develop a turn-on fluorescence sensing method for borax analysis, which achieved a linear response spanning four orders of magnitude with a detection limit of 1.07 μM (0.22 μg mL-1 in terms of Na2B4O7 content). Furthermore, a smartphone-assisted paper-based test device was designed and constructed by 3D printing technology. Using morin-impregnated test strips as the carrier, the borax could be visually detected by the RGB signals of the captured images, with a detection limit of 0.13 mM (27.05 μg mL-1 for Na2B4O7). Combining ion exchange treatment for food samples and sodium periodate oxidation for drug samples, the developed methods were successfully applied for the direct analysis of borax in various products with the recoveries of 86.9-106.3% for traditional fluorescence analysis and 82.7-108.8% for smartphone-assisted fluorescence sensing. The fluorescence property of the morin-borax system was studied using time-dependent density functional theory, and the sensing mechanism was discussed in conjunction with experimental research.

Enhancement of intrinsic guanine fluorescence by protonation in DNA of various structures

Understanding the diversity of DNA structure and functions in biology requires tools to study this biomolecule selectively and thoroughly. Fluorescence methods are powerful technique for non-invasive research. Due to the low quantum yield, the intrinsic fluorescence of nucleotides has not been considered for use in the detection and differentiation of nucleic acid bases. Here, we have studied the influence of protonation of nucleotides on their fluorescence properties. We show that protonation of ATP and GTP leads to enhanced intrinsic fluorescence. Fluorescence enhancement at acidic pH has been observed for double-stranded DNA and single-stranded oligonucleotides. The formation of G4 secondary structures apparently protected certain nucleotides from protonation, resulting in less pronounced fluorescence enhancement. Furthermore, acid-induced depurination under protonation was less noticeable in G4 structures than in double-stranded and single-stranded DNA. We show that changes in the intrinsic fluorescence of guanine can be used as a sensitive sensor for changes in the structure of the DNA and for the protonation of specific nucleotides.

CdTe based water-soluble fluorescent probe for rapid detection of zilpaterol in swine urine and pork

Zilpaterol hydrochloride (zilpaterol) is used in animal feed as it can increase the lean meat mass. However, consuming zilpaterol-containing animal products may damage human health. Therefore, rapid detection of zilpaterol is attracting increasing research attention. This study aimed to developed a fast, accurate, and ultrasensitive fluorescence immunoassay based on CdTe quantum dots (QDs). A CdTe QD fluorescence sensor was synthesized from thioglycolic acid using a simple hydrothermal method. The morphology and structure of the CdTe QDs were characterized using transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The detection limits of our method in swine urine and pork samples were 0.5 μg/L and 1.2 μg/kg, respectively. A wide linear range of 0.1-10000 μg/L (R2 = 0.996) was achieved. Both within-run precision (CVw) and between-run precision (CVb) were ≤ 10 %. The method was then successfully applied for the analysis of zilpaterol contents in swine urine and pork samples.

Joint forces of mass spectrometric techniques (ICP-MS and MALDI-TOF-MS) and fluorescence spectrometry in the study of platinum-based cytostatic drugs interactions with metallothionein MT2 and MT3

Herby, the interaction of metallothioneins with commonly used Pt-based anticancer drugs - cisplatin, carboplatin, and oxaliplatin - was investigated using the combined power of elemental (i.e. LA-ICP-MS, CE-ICP-MS) and molecular (i.e. MALDI-TOF-MS) analytical techniques providing not only required information about the interaction, but also the benefit of low sample consumption. The amount of Cd and Pt incorporated within the protein was determined for protein monomers and dimer/oligomers formed by non-oxidative dimerization. Moreover, fluorescence spectrometry using Zn2+-selective fluorescent indicator - FluoZin3 - was employed to monitor the ability of Pt drugs to release natively occurring Zn from the protein molecule. The investigation was carried out using two protein isoforms (i.e. MT2, MT3), and significant differences in behaviour of these two isoforms were observed. The main attention was paid to elucidating whether the protein dimerization/oligomerization may be the reason for the potential failure of the anticancer therapy based on these drugs. Based on the results, it was demonstrated that the interaction of MT2 (both monomers and dimers) interacted with Pt drugs significantly less compared to MT3 (both monomers and dimers). Also, a significant difference between monomeric and dimeric forms (both MT2 and MT3) was not observed. This may suggest that dimer formation is not the key factor leading to the inactivation of Pt drugs.

Ratio-fluorescence detection of tert-butylhydroquinone based on non-conjugated polymer dots and gold nanoclusters

A novel ratiometric fluorescent probe based on non-conjugated polymer dots (NCPDs) and gold nanocluster (AuNCs) was constructed to determine tert-butylhydroquinone (TBHQ). The probe exhibited dual emission peaks at 480 nm and 630 nm under 370 nm excitation. The fluorescence of AuNCs was quenched by TBHQ due to strong electrostatic interactions, whereas the emission of NCPDs increased. The ratio of fluorescence intensity at 480 nm to 630 nm (F480 / F630) was monitored as analytical signal response. The probe have been utilized for the detection of TBHQ with good linear relationship in the range of 0.2 to 60 μg/mL. The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.048 μg/mL and 0.159 μg/L, respectively. Three levels of spiked-in TBHQ concentrations were obtained with recovery rates from 80 % to 102 %. The present study provided an effective ratiometric fluorescence method for selective screening of TBHQ in food samples.

A novel fluorescence platform for specific detection of tetracycline antibiotics based on [MQDA-Eu3+] system

Tetracycline antibiotics (TCs) are extensively used in clinical medicine, animal husbandry, and aquaculture because of their cost-effectiveness and high antibacterial efficacy. However, the presence of TCs residues in the environment poses risks to humans. In this study, an inner filter effect (IFE) fluorescent probe, 2,2'-(ethane-1,2-diylbis((2-((2-methylquinolin-8-yl)amino)-2-oxoethyl)azanediyl))diacetic acid (MQDA), was developed for the rapid detection of Eu3+ within 30 s. And its complex [MQDA-Eu3+] was successfully used for the detection of TCs. Upon coordination of a carboxyl of MQDA with Eu3+ to form a [MQDA-Eu3+] complex, the carboxyl served as an antenna ligand for the effective detection of Eu3+ to intensify the emission intensity of MQDA via "antenna effect", the process was the energy absorbed by TCs via UV excitation was effectively transferred to Eu3+. Fluorescence quenching of the [MQDA-Eu3+] complex was caused by the IFE in multicolor fluorescence systems. The limits of detection of [MQDA-Eu3+] for oxytetracycline, chlorotetracycline hydrochloride, and tetracycline were 0.80, 0.93, and 1.7 μM in DMSO/HEPES (7:3, v/v, pH = 7.0), respectively. [MQDA-Eu3+] demonstrated sensitive detection of TCs in environmental and food samples with satisfactory recoveries and exhibited excellent imaging capabilities for TCs in living cells and zebrafish with low cytotoxicity. The proposed approach demonstrated considerable potential for the quantitative detection of TCs.

Biomass-derived carbon dots as emerging visual platforms for fluorescent sensing

Biomass-derived carbon dots (CDs) are non-toxic and fluorescently stable, making them suitable for extensive application in fluorescence sensing. The use of cheap and renewable materials not only improves the utilization rate of waste resources, but it is also drawing increasing attention to and interest in the production of biomass-derived CDs. Visual fluorescence detection based on CDs is the focus of current research. This method offers high sensitivity and accuracy and can be used for rapid and accurate determination under complex conditions. This paper describes the biomass precursors of CDs, including plants, animal remains and microorganisms. The factors affecting the use of CDs as fluorescent probes are also discussed, and a brief overview of enhancements made to the preparation process of CDs is provided. In addition, the application prospects and challenges related to biomass-derived CDs are demonstrated.

A quadratic isothermal amplification fluorescent biosensor without intermediate purification for ultrasensitive detection of circulating tumor DNA

Circulating tumor DNA (ctDNA) is an auspicious tumor biomarker released into the bloodstream by tumor cells, offering abundant information concerning cancer genes. It plays a crucial role in the early diagnosis of cancer. However, due to extremely low levels in body fluids, achieving a simple, sensitive, and highly specific detection of ctDNA remains challenging. Here, we constructed a purification-free fluorescence biosensor based on quadratic amplification of ctDNA by combining nicking enzyme mediated amplification (NEMA) and catalytic hairpin assembly (CHA) reactions. After double isothermal amplification, this biosensor achieved an impressive signal amplification of nearly 107-fold, enabling it to detect ctDNA with ultra-sensitivity. And the detection limit of this biosensor is as low as 2 aM. In addition, we explored the influence of human serum on the performance of the biosensor and found that it showed favorable sensitivity in the presence of serum. This biosensor eliminates the need for an intermediate purification step, resulting in enhanced sensitivity and convenience. Thus, our purification-free fluorescent biosensor exhibits ultra-high sensitivity when compared to other biosensors and has the potential to serve as an effective diagnostic tool for early detection of cancer.

Selective and sensitive CQD-based sensing platform for Cu2+ detection in Wilson's disease

Excessive Cu2+ intake can cause neurological disorders (e.g. Wilson's disease) and adversely affect the gastrointestinal, liver, and kidney organs. The presence of Cu2+ is strongly linked to the emergence and progression of Wilson's disease (WD), and accurately measuring the amount of copper is a crucial step in diagnosing WD at an early stage in a clinical setting. In this work, CQDs were fabricated through a facile technique as a novel fluorescence-based sensing platform for detecting Cu(II) in aqueous solutions, and in the serum samples of healthy and affected individuals by WD. The CQDs interact with Cu(II) ions to produce Turn-on and Turn-off states at nano-molar and micro-molar levels, respectively, with LODs of 0.001 µM and 1 µM. In fact, the Cu2+ ions can act like a bridge between two CQDs by which the charge and electron transfer between the CQDs may increase, possibly can have significant effects on the spectroscopic features of the CQDs. To the best of our knowledge, this is the first reported research that can detect Cu(II) at low levels using two different complexation states, with promising results in testing serum. The potential of the sensor to detect Cu(II) was tested on serum samples from healthy and affected individuals by WD, and compared to results obtained by ICP-OES. Astonishingly, the results showed an excellent correlation between the measured Cu(II) levels using the proposed technique and ICP-OES, indicating the high potential of the fluorimetric CQD-based probe for Cu(II) detection. The accuracy, sensitivity, selectivity, high precision, accuracy, and applicability of the probe toward Cu(II) ions make it a potential diagnostic tool for Wilson's disease in a clinical setting.

A combined experimental and theoretical approach for doxycycline sensing using simple fluorescent probe with distinct fluorescence change in wide range of interferences

Overuse of doxycycline (DOXY) can cause serious problems to human health, environment and food quality. So, it is essential to develop a new sensing methodology that is both sensitive and selective for the quantitative detection of DOXY. In our current research, we synthesized a simple fluorescent probe 4,4'-bis(benzyloxy)-1,1'-biphenyl (BBP) for the highly selective detection of doxycycline by through fluorescence spectroscopy. The probe BBP displayed ultra-sensitivity towards doxycycline due to Forster resonance energy transfer (FRET). Fluorescence spectroscopy, density functional theory (DFT), 1H NMR titration, UV-Vis, and Job's plot were used to confirm the sensing mechanism. The charge transfer between the probe and analyte was further examined qualitatively by electron density differences (EDD) and quantitively by natural bond orbital (NBO) analyses. Whereas the non-covalent nature of probe BBP towards DOXY was verified by theoretical non-covalent interaction (NCI) analysis as along with Bader's quantum theory of atoms in molecules (QTAIM) analysis. Furthermore, probe BBP was also practically employed for the detection of doxycycline in fish samples, pharmaceutical wastewater and blood samples.

Ratiometric luminescent simultaneous sensing of aristolochic acids (I-IV) by a novel metal-organic framework and its nanowire

Aristolochic acids (AAs), which are a group of nitrophenanthrene carboxylic acids formed by Aristolochia plant, have become an increasing serious threat to humans due to their nephrotoxicity and carcinogenicity. Fast and accurate approaches capable of simultaneous sensing of aristolochic acids (I-IV) are vital to avoid intake of such compounds. In this research, the novel ratiometric fluorescence zinc metal-organic framework and its nanowire have been prepared. The two different coordination modes (tetrahedral configuration and twisted triangular bipyramidal configuration) within zinc metal-organic framework lead to the significant double emissions. The ratiometric fluorescence approach based on nanowire provides a broader concentration range (3.00 × 10-7~1.00 × 10-4 M) and lower limit of detection (3.70 × 10-8 M) than that based on zinc metal-organic framework (1.00 × 10-6~1.00 × 10-4 M, 5.91 × 10-7 M). The RSDs of the results are in the range 1.4-3.5% (nanowire). The density functional theory calculations and UV-Vis absorption verify that the sensing mechanism is due to charge transfer and energy transfer. Excellent spiked recoveries for AAs(I-IV) in soil and water support that nanowire is competent to simultaneously detect these targets in real samples, and the proposed approach has potential as a fluorescence sensing platform for the simultaneous detection of AAs (I-IV) in complex systems.

Biophysical characterization and design of a minimal version of the Hoechst RNA aptamer

RNA aptamers are oligonucleotides, selected through Systematic Evolution of Ligands by EXponential Enrichment (SELEX), that can bind to specific target molecules with high affinity. One such molecule is the RNA aptamer that binds to a blue-fluorescent Hoechst dye that was modified with bulky t-Bu groups to prevent non-specific binding to DNA. This aptamer has potential for biosensor applications; however, limited information is available regarding its conformation, molecular interactions with the ligand, and binding mechanism. The study presented here aims to biophysically characterize the Hoechst RNA aptamer when complexed with the t-Bu Hoechst dye and to further optimize the RNA sequence by designing and synthesizing new sequence variants. Each variant aptamer-t-Bu Hoechst complex was evaluated through a combination of fluorescence emission, native polyacrylamide gel electrophoresis, fluorescence titration, and isothermal titration calorimetry experiments. The results were used to design a minimal version of the aptamer consisting of only 21 nucleotides. The performed study also describes a more efficient method for synthesizing the t-Bu Hoechst dye derivative. Understanding the biophysical properties of the t-Bu Hoechst dye-RNA complex lays the foundation for nuclear magnetic resonance spectroscopy studies and its potential development as a building block for an aptamer-based biosensor that can be used in medical, environmental or laboratory settings.

Development of a high throughput oxidation profiling strategy for monoclonal antibody products

Oxidation is one of the most common degradation pathways of biopharmaceutics, potentially leading to altered product stability, pharmacokinetics, reduced biological activity and/or an increased immunogenicity. However, it is often insufficiently assessed in early development stages, leaving potential molecule liabilities undiscovered. Aim of the present work was the development of a high throughput oxidation profiling strategy, applicable throughout various stages of biopharmaceutical development. The study demonstrates that the combination of multiple stress assays, including peroxide-based, visible light, and metal-catalyzed oxidation (MCO), enables a comprehensive understanding of a mAb's oxidation susceptibility. The most effective parameters to evaluate oxidation in a high-throughput screening workflow are aggregation, tryptophan oxidation and changes in the hydrophobicity profile of the Fc and Fab subunit measured via Size Exclusion Chromatography, Intrinsic Tryptophan Fluorescence Emission spectroscopy and Reversed-Phase Chromatography subunit analysis, respectively. This oxidation profiling approach is valuable tool to systematically characterize the oxidation susceptibility under relevant conditions, time effective and with minimal sample consumption.

Quinoline-quinoline schiff-base as an effective chromogenic, fluorogenic, and smartphone assisted RGB detection of Pb2+ ion in near aqueous medium

A novel multimode colorimetric and fluorescent chemosensor was developed using an 8-hydroxy quinoline carbaldehyde Schiff base with a quinoline hydrazide probe (E)-2-((2-(quinolin-2-yl)hydrazineylidene)methyl)quinolin-8-ol (L). NMR (1H & 13C), FTIR, and HR-mass spectral characterization techniques confirmed the probe L structural conformation. As Probe L contacts Pb2+ ions, a color change and turn-off emission can be visually detected in EtOH:H2O (1:1, v/v, pH = 7.21) medium. The probe displays a good emission at 440 nm due to the combined ESIPT and ICT process. The Pb2+ ion interacts with the probe and selectively quenches fluorescence by inhibiting ESIPT and >CN- isomerization. As per Job's plot, L-Pb2+ complex formation occurred in a 1:1 stoichiometric ratio, with association constant (Ka) and quenching constant (Ksv) estimated at 1.52 × 105 M-1 and 4.12 × 105 M, respectively. The detection limits of Pb2+ by spectrophotometric and spectrofluorometric were 1.99 μM (41 ppb) and 23.4 nM (485 ppt), respectively. Additionally, the test paper kit and RGB tool were used to monitor the color changes of L with Pb2+ and the LOD was found to be 5.99 μM (125 ppb). Its recognition mechanism has been verified by 1H NMR, ESI-mass, and theoretical studies.

Ultraviolet-fluorescence detection of E. Coli using threshold-comparison electronics

We describe an optical system that detects the presence of E. coli bacteria, making use of the bacteria's natural fluorescence properties. The system provides an excitation signal at 365 nm and detects the emission signal, from the bacteria, at approximately 445 nm. The system also allows the intensity of the emitted signal to be compared with a user-programmable threshold. This allows rapid testing of many samples in a laboratory setting. Complete setup and performance details are provided, enabling the experimentalist to tailor the system parameters to other species of microorganisms, which may have fluorescence properties at other wavelengths.

Machine learning-assisted chromium speciation using a single-well ratiometric fluorescent nanoprobe

Chromium is widely recognized as a significant pollutant discharged into the environment by various industrial activities. The toxicity of this element is dependent on its oxidation state, making speciation analysis crucial for monitoring the quality of environmental water and assessing the potential risks associated with industrial waste. This study introduces a single-well fluorometric sensor that utilizes orange emissive thioglycolic acid stabilized CdTe quantum dots (TGA-QDs) and blue emissive carbon dots (CDs) to detect and differentiate between various chromium species, such as Cr (III) and Cr (VI) (i.e., CrO42- and Cr2O72-). The variations of fluorescence spectra of the proposed probe upon chromium species addition were analyzed using machine learning techniques such as linear discriminant analysis and partial least squares regression as a classification and multivariate calibration technique, respectively. Linear discriminant analysis (LDA) demonstrated exceptional accuracy in differentiating single-component and bicomponent samples. Additionally, the findings from the partial least squares regression (PLSR) showed that the sensor created has strong linearity within the 1.0-100.0, 1.0-100.0, and 0.1-15 μM range for Cr2O72-, CrO42-, and Cr3+, respectively. Furthermore, appropriate detection limits were successfully achieved, which were 2.6, 2.9, and 0.7 μM for Cr2O72-, CrO42-, and Cr3+, respectively. Ultimately, the successful capability of the sensing platform in the identification and quantification of chromium species in environmental water samples provides innovative insights into general speciation analytics.

Rapid and specific detection of thiabendazole: enzymatic digestion-enabled fluorescent aptasensor

Thiabendazole, a widely used broad-spectrum fungicide in agriculture, poses risks to human health. To monitor its presence in water, we propose a fluorescent aptasensor utilizing Escherichia coli exonuclease I (Exo I). The findings demonstrate a linear correlation between thiabendazole concentrations and digestion percentage, with a detection limit (LOD) exceeding 1 µM and a determination coefficient (R2) of 0.959. This aptamer-based fluorescence spectroscopy detection system holds promise for a rapid, specific, and sensitive analysis of thiabendazole in environmental waters and food matrices.

A new carbazole based fluorescent probe with AIE characteristic for detecting and imaging hydrazine in living cells, mungbean sprouts, Arabidopsis thaliana, and practical samples

In this study, we report a new carbazole-malononitrile fluorescent probe CBC with an interesting aggregation-induced emission (AIE) characteristic. Probe CBC could rapidly and selectively detect hydrazine (N2H4) in ～100% aqueous media, and also exhibit an exceedingly low detection limit of 6.3 nM for sensitively detecting N2H4. The sensing mechanism of CBC towards N2H4 has been well demonstrated through the spectra of 1H NMR, HRMS and FTIR. Interestingly, probe CBC was applied to visualize and detect gaseous and aqueous N2H4 with sensitive color changes. Importantly, probe CBC was applied to effectively detect N2H4 in practical samples such as soil, human serum, human urine, plants, foods and beverages, as well as sensitively sense and image N2H4 in biological systems including living mungbean sprouts, Arabidopsis thaliana, and HeLa cells.

Unveiling large charge transfer character of PSII in an iron-deficient cyanobacterial membrane: A Stark fluorescence spectroscopy study

In this work, we applied Stark fluorescence spectroscopy to an iron-stressed cyanobacterial membrane to reveal key insights about the electronic structures and excited state dynamics of the two important pigment-protein complexes, IsiA and PSII, both of which prevail simultaneously within the membrane during iron deficiency and whose fluorescence spectra are highly overlapped and hence often hardly resolved by conventional fluorescence spectroscopy. Thanks to the ability of Stark fluorescence spectroscopy, the fluorescence signatures of the two complexes could be plausibly recognized and disentangled. The systematic analysis of the SF spectra, carried out by employing standard Liptay formalism with a realistic spectral deconvolution protocol, revealed that the IsiA in an intact membrane retains almost identical excited state electronic structures and dynamics as compared to the isolated IsiA we reported in our earlier study. Moreover, the analysis uncovered that the excited state of the PSII subunit of the intact membrane possesses a significantly large CT character. The observed notably large magnitude of the excited state CT character may signify the supplementary role of PSII in regulative energy dissipation during iron deficiency.

Fluorescence in depth: integration of spectroscopy and imaging with Raman, IR, and CD for advanced research

Fluorescence spectroscopy serves as a vital technique for studying the interaction between light and fluorescent molecules. It encompasses a range of methods, each presenting unique advantages and applications. This technique finds utility in various chemical studies. This review discusses Fluorescence spectroscopy, its branches such as Time-Resolved Fluorescence Spectroscopy (TRFS) and Fluorescence Lifetime Imaging Microscopy (FLIM), and their integration with other spectroscopic methods, including Raman, Infrared (IR), and Circular Dichroism (CD) spectroscopies. By delving into these methods, we aim to provide a comprehensive understanding of the capabilities and significance of fluorescence spectroscopy in scientific research, highlighting its diverse applications and the enhanced understanding it brings when combined with other spectroscopic methods. This review looks at each technique's unique features and applications. It discusses the prospects of their combined use in advancing scientific understanding and applications across various domains.