Fluorescence Band Research Articles

Unraveling environmental effects in the absorption and fluorescence spectra of p-methoxyphenylpiperazine derivatives

The p-methoxyphenylpiperazine motif can be found in many biologically active molecules, including approved drugs. It is characterized by a relatively weak fluorescence, which can be employed in different types of studies involving molecules with this motif. In this work, a thorough analysis of the absorption, excitation and emission spectra of the diphenyl(aminomethyl)phosphine and tris(aminomethyl)phosphine derivatives of p-methoxyphenylpiperazine, supported by the DFT calculations (ωB97XD/6-311++G(d,p)) with NBO and QTAIM analysis also for different model molecules (e.g. 1-(4-methoxyphenyl)-4-methylpiperazine) enabled determination of the mechanisms underlying beneath the electronic transitions and allowed to rationalize mixed solvent effects observed in electronic spectra of the studied compounds. Electronic transition from the ground state to the first excited state can be regarded as the n,π → π* transition with no solvatochromic effects, however the hydrogen bonds between the HBD solvent molecules and the nitrogen atom bound directly to the aromatic ring (N(4)) are shifting strongly the 1st absorption or excitation band maxima to the higher energies. Fluorescence band, as a result of the electron transition from the equilibrated 1st excited state to the ground state, can be described as the π*→π with positive solvatochromism. N(4) in the excited states adopts a sp2 hybridization and is no longer able to form HBs. On the other hand, increased electron density on the aromatic ring makes the emission processes vulnerable to its direct environment.

Corrosion analysis of unearthed jade from Daye Zhen Tomb of Northern Zhou Dynasty

X-ray fluorescence spectroscopy, scanning electron microscopy energy spectrum, excitation-emission matrix spectroscopy, and Fourier transform infrared spectroscopy was applied to the unearthed jade with multilayered corrosion, to reveal the microstructure, composition structure, and distribution of organic matters. Our results showed that the interior of the jade was mainly composed of layered serpentine with a regular structure, while the white layer structure on the surface is scattered and irregular, and the content of calcite formed by elements Ca and C increases significantly; between the green matrix and the white layer on the surface, there are brown corrosion zones with obvious fluorescence effect and mainly composed of humic acid, which continuously extends inward along the corrosion cracks for accelerating the internal corrosion. This article, for the first time, argued for the corrosive and fluorescent humic acid bands that appear inside serpentine jade and cautions its role in investigating the corrosion of jade.

A smart fluorescent colorimetric dual-response sensing for the determination of tetracycline antibiotics

This work synthesized the ethylenediamine-doped puffer fish skin carbon dots using biomass as a green precursor. Three tetracycline antibiotics (TCs) were detected fluorescence and colorimetrically using carbon dots as probes; on this basis, hydrogels were used to carry out visual identification and quantification. In the presence of TCs, the nitrogen-doped carbon dots (N-CDs) displayed a quenching impact on fluorescence because of fluorescence resonance energy transfer (FRET), dynamic quenching, and band gap transition. As a result, it was possible to identify the precise concentrations of tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC). The assay has great biocompatibility, which was supported by cytotoxicity, a wide linear range (0.5–500 M), a low detection limit (0.15 M), and outstanding selectivity. With a high recovery rate, the approach has been successfully used to identify TCs in food and water samples such milk, honey, and tap water.

Detection of Karenia brevis red tides on the West Florida Shelf using VIIRS observations: Accounting for spatial coherence with artificial intelligence

Harmful algal blooms (HABs) of the toxic dinoflagellate Karenia brevis (K. brevis) occur annually on the West Florida Shelf (WFS). Detection of these blooms using satellite observations often suffers from two problems: lack of accurate algorithms to identify phytoplankton blooms in optically complex waters and patchiness (i.e., heterogeneity) of K. brevis during blooms. Here, using data collected by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) between 2017 and 2019, we develop a practical approach to overcome these difficulties despite the lack of a chlorophyll-a fluorescence band on VIIRS. The approach is based on artificial intelligence (specifically, a deep-learning (DL) convolutional neural network model), which uses spatial coherence of bloom patches to account for the patchiness of K. brevis concentrations. After proper training, the overall performance (i.e., F1 score) of the deep learning model is 89%. Extracted K. brevis patches were consistent with those derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, which has a fluorescence band. Furthermore, the wider swath of VIIRS over MODIS (3040-km versus 2330-km) led to more valid observations of bloom extent, enabling improved near-real-time applications. The results not only demonstrate the capacity of VIIRS in HABs monitoring, but also show the value of the DL model in extracting K. brevis bloom patches for both near real-time applications and retrospective analysis.

Origin of Low-Lying Red States in the Lhca4 Light-Harvesting Complex of Photosystem I.

The antenna complexes of Photosystem I present low-lying states visible as red-shifted and broadened absorption and fluorescence bands. Among these, Lhca4 has the most evident features of these "red" states, with a fluorescence band shifted by more than 25 nm from typical LHC emission. This signal arises from a mixing of exciton and charge-transfer (CT) states within the excitonically coupled a603-a609 chlorophyll (Chl) dimer. Here we combine molecular dynamics, multiscale quantum chemical calculations, and spectral simulations to uncover the molecular mechanism for the formation and tuning of exciton-CT interactions in Lhca4. We show that the coupling between exciton and CT states is extremely sensitive to tiny variations in the Chl dimer arrangement, explaining both the red-shifted bands and the switch between conformations with blue and red emission observed in single-molecule spectroscopy. Finally, we show that mutating the axial ligand of a603 diminishes the exciton-CT coupling, removing any red-state fingerprint.

The Solvent Effect on Nanomaterials Composed of Liquid Crystals and Nanoparticles: uv-vis Absorbance and Fluorescence Spectra

We have been investigated in different solvent medium to interactions between 4-Ethoxybenzoic acid (4EOBA), 4-Pentylbenzoic acid (4PentBA), and 4-Pentylphenyl 4-Methylbenzoate (4PP4MetB) liquid crystals with CdS, CdSe and ZnS nanoparticles. For this, the new materials composed from LC compound including the solvent and nanoparticle were investigated by use absorbance and fluorescence spectra. Electronic transitions and differences in absorbance and fluorescence spectra were interpreted. The fluorescence of liquid crystals has been defined in the shifts between wavelengths of the fluorescence of nanomaterials. It can be said that it has occurred blue shift at the maximum fluorescence wavelengths of the 4EOBA-CdS-DMSO and 4EOBA-CdSe-DMSO compared to 4EOBA-DMSO. On the other hand, we can say that in the 4EOBA-ZnS-DMSO solution occurs red shift in the fluorescence band, while the peaks seen in the fluorescence band occur in result of interaction of liquid crystals and nanoparticles.

Janus-Type ESIPT Chromophores with Distinctive Intramolecular Hydrogen-bonding Selectivity.

Excited-state intramolecular proton transfer (ESIPT)-based solid luminescent materials with multiple hydrogen bond acceptors (HBAs) remain unexplored. Herein, we introduced a family of Janus-type ESIPT chromophores featuring distinctive hydrogen bond (H-bond) selectivity between competitive HBAs in a single molecule. Our investigations showed that the central hydroxyl group preferentially forms intramolecular H-bonds with imines in imine-modified 2-hydroxyphenyl benzothiazole (HBT) chromophores but tethers the benzothiazole moiety in hydrazone-modified HBT chromophores. Imine-derived HBTs generally exhibit higher fluorescence efficiency, while hydrazone-derived HBTs show a reduced overlap between the absorption and fluorescence bands. Quantum chemical calculations unveiled the molecular origins of the biased intramolecular H-bonds and their impact on the ESIPT process. This Janus-type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.

Janus‐Type ESIPT Chromophores with Distinctive Intramolecular Hydrogen‐bonding Selectivity

AbstractExcited‐state intramolecular proton transfer (ESIPT)‐based solid luminescent materials with multiple hydrogen bond acceptors (HBAs) remain unexplored. Herein, we introduced a family of Janus‐type ESIPT chromophores featuring distinctive hydrogen bond (H‐bond) selectivity between competitive HBAs in a single molecule. Our investigations showed that the central hydroxyl group preferentially forms intramolecular H‐bonds with imines in imine‐modified 2‐hydroxyphenyl benzothiazole (HBT) chromophores but tethers the benzothiazole moiety in hydrazone‐modified HBT chromophores. Imine‐derived HBTs generally exhibit higher fluorescence efficiency, while hydrazone‐derived HBTs show a reduced overlap between the absorption and fluorescence bands. Quantum chemical calculations unveiled the molecular origins of the biased intramolecular H‐bonds and their impact on the ESIPT process. This Janus‐type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.

Rhodamine 6G based molecular ion-active switches of optical and fluorescent properties

A series of rhodamine 6G derivatives with o -hydroxyarylime substituents was synthesized. The obtained compounds in acetonitrile are capable of H+ induced transformation of the spirolactam form into open form. The process is accompanied by the formation of new long-wave absorption maxima at 527-529 nm and fluorescence bands at 557-560 nm. The compound containing 2-hydroxy-4-dimethylaminophenyl substituent in the presence of Zn2+ cations displays switching of emission at 429 nm. This fluorescence is quenched selectively by the CN- anion. Copper(II) cations cause the transformation of the spirostructure of rhodamine with a 2-hydroxy-3- tert -butylbenzofuran group into an open form. Isomerization occurs with a chromogenic naked-eye effect - a change in the color of the solution from pale yellow to pink and the appearance of fluorescence at 556 nm. The observed ion-induced spectral transformations can be used in design of optical and fluorescent chemosensors.

Application of steady-state and time-resolved fluorescence spectroscopy in identification of cold-pressed vegetal oils

Monitoring the quality of food products is very important, due to the fact that substances potentially harmful to consumers may be formed during production and storage. In addition, vegetal oils are subject to falsification, which is based mainly on mixing and adding other, usually cheaper equivalents or providing false data on the composition and origin. In this way, the path from a very healthy product to a product that has a negative impact on the human body is very short. In this study fluorescence spectra and fluorescence decay kinetics of selected cold-pressed oils were characterized and the origin of the observed fluorescence bands was discussed. The obtained fluorescence characteristics were found to be the unique fingerprints of the individual oils and showed evident differences which arise from specific qualitative and quantitative compositions of the oils. The most apparent differences in the shape of fluorescence bands were observed in the emission spectrum at excitation wavelength 350 nm and in the excitation spectrum recorded at emission wavelength 500 nm. The obtained results show the utility of the applied steady-state and time –resolved fluorescence measurements in the identification of the tested vegetal oils.

Time gated Fourier transform spectroscopy as a technique for disentangling short- and long-lived luminescence

Overlapping short- and long-lived luminescence signals are often encountered and are not trivial to disentangle in a single measurement. Here, we demonstrate for a broad range of emitters that time gated Fourier transform spectroscopy can be used as a technique to simultaneously capture and temporally disentangle overlapping spectral features of luminescence signals. This allows us to concurrently measure the fluorescence and phosphorescence bands of an organic fluorophore, retrieve the emission of a quantum dot that is overshadowed by an autofluorescent serum solution, and for removing residual laser scatter and ambient room light in an optical filter free configuration. Time gated Fourier transform spectroscopy only requires the introduction of a common-path interferometer to the emission path of a standard time-correlated single photon counting setup; it can function as a technique to both discriminate signals as well as characterize properties of new materials.

Alternative boronic acids in the detection of Mycolactone A/B using the thin layer chromatography (f-TLC) method for diagnosis of Buruli ulcer

BackgroundMycobacterium ulcerans is the causative agent of Buruli ulcer. The pathology of M. ulcerans disease has been attributed to the secretion of a potent macrolide cytotoxin known as mycolactone which plays an important role in the virulence of the disease. Mycolactone is a biomarker for the diagnosis of BU that can be detected using the fluorescent-thin layer chromatography (f-TLC) technique. The technique relies on the chemical derivatization of mycolactone A/B with 2-naphthylboronic acid (BA) which acts as a fluorogenic chemosensor. However, background interferences due to co-extracted human tissue lipids, especially with clinical samples coupled with the subjectivity of the method call for an investigation to find an alternative to BA.MethodsTwenty-six commercially available arylboronic acids were initially screened as alternatives to BA using the f-TLC experiment. UV–vis measurements were also conducted to determine the absorption maximum spectra of mycolactone A/B and myco-boronic acid adducts followed by an investigation of the fluorescence-enhancing ability of the boronate ester formation between mycolactone A/B and our three most promising boronic acids (BA15, BA18, and BA21). LC–MS technique was employed to confirm the adduct formation between mycolactone and boronic acids. Furthermore, a comparative study was conducted between BA18 and BA using 6 Polymerase Chain Reaction (PCR) confirmed BU patient samples.ResultsThree of the boronic acids (BA15, BA18, and BA21) produced fluorescent band intensities superior to BA. Complexation studies conducted on thin layer chromatography (TLC) using 0.1 M solution of the three boronic acids and various volumes of 10 ng/µL of synthetic mycolactone ranging from 1 µL – 9 µL corresponding to 10 ng – 90 ng gave similar results with myco-BA18 adduct emerging with the most visibly intense fluorescence bands. UV–vis absorption maxima (λmax) for the free mycolactone A/B was observed at 362 nm, and the values for the adducts myco-BA15, myco-BA18, and myco-BA21 were at 272 nm, 270 nm, and 286 nm respectively. The comparable experimental λmax of 362 nm for mycolactone A/B to the calculated Woodward-Fieser value of 367 nm for the fatty acid side chain of mycolactone A/B demonstrate that even though 2 cyclic boronates were formed, only the boronate of the southern side chain with the chromophore was excited by irradiation at 365 nm. Fluorescence experiments have demonstrated that coupling BA18 to mycolactone A/B along the 1,3-diols remarkably enhanced the fluorescence intensity at 537 nm. High-Resolution Mass Spectrometer (HR-MS) was used to confirm the formation of the myco-BA15 adduct. Finally, f-TLC analysis of patient samples with BA18 gave improved BA18-adduct intensities compared to the original BA-adduct.ConclusionTwenty-six commercially available boronic acids were investigated as alternatives to BA, used in the f-TLC analysis for the diagnosis of BU. Three (3) of them BA15, BA18, and BA21 gave superior fluorescence band intensity profiles. They gave profiles that were easier to interpret after the myco-boronic acid adduct formation and in experiments with clinical samples from patients with BA18 the best. BA18, therefore, has been identified as a potential alternative to BA and could provide a solution to the challenge of background interference of co-extracted human tissue lipids from clinical samples currently associated with the use of BA.

Enhancement of Monacolin K Production by Intergeneric Hybridization between Monascus purpureus (Arg-) and Monascus ruber (Thi-, Met-) Auxotrophs

This study aims to reconcile industrially suitable strains of higher red pigment producing Monascus purpureus MPA5 and higher Monacolin K producing Monascus ruber MRA7, were tried to fuse for development of increased efficacy of targeted secondary metabolites production. The optimum concentration of protoplast mixture was standardized, before the fusion experiment. The effective fusion was observed with the solution of 30 % PEG 6000, CaCl2.2H2O (0.01 M) and glycine (0.05 M). Colonies of the fusants were segregated using complete medium. The fusants were irradiated under UV- light in LD50 dose. On the basis of non-segregation of colony appearance after repeated subculturing in complete medium, 8 colonies were selected. Finally, one of the stable fusant MF11 grew more rapidly than one of the parental strain M. purpureus MPA5, but not as fast as M. ruber MRA7, were selected and grown on low grade rice as solid substrate for production of metabolites. Production of red pigments, alpha-amylase and acid protease were at intermediate stage between two parental strains but enhancement of Monacolin K was observed. High performance liquid chromatography (HPLC) analysis was revealed that Monacolin K content was increased as much as two and half times than the parents. No fluorescent yellow band was detected in TLC plate, indicating of citrinin negativity of the fusant MF11. It is the first report of enhanced Monacolin K production by a stable fusant of Monascus sp.

Deuterated PET: The new verification target of the Raman spectrometer for the MMX mission to explore Phobos

AbstractJAXA's upcoming MMX (Martian Moons eXploration) mission will deliver a small rover to Phobos, to explore its surface complementary to the MMX orbiter and the sample return lander. On board this rover is a Raman spectrometer, the RAX Instrument (RAman Spectrometer for MMX), a payload to science. RAX has been designed for being capable to analyze the mineral composition of the Phobos' surface, in order to help reveal the nature and distribution of materials on the surface and ultimately the origin and evolution of the moon. Attached to MMX spacecraft, with direct view from the RAX instrument, a polyethylene terephthalate (PET) target will be placed for on‐ground and during cruise, spectral instrument performances verification, before the MMX rover is released and dropped to the Phobos surface for developing its scientific tasks. A novel deuterated PET material was proposed as verification target (VT) to check the spectral instrument performances. INTA‐CAB developed, manufactured and qualified for the MMX‐RAX space mission, 13 mm diameter and 2‐mm thick pellets of this material, which incorporates two relevant improvement characteristics: reduction in fluorescence and additional Raman bands with regard to ordinary PET used with this purpose. The material was selected as RAX VT and delivered to DLR for performance tests and later integration into the MMX rover together with the RAX flight model. The RAX VT will be critical to check the instrument performances during the several months cruise phase after launch and just before its landing on Phobos surface. This paper reports the development and characterization of the deuterated PET.

The role of photobehaviour in sponge larval dispersal and settlement.

Deciphering the behavioural ecology of adult (sessile) sponges is challenging. However, their motile larval stages afford opportunities to investigate how behaviour contributes to dispersal and selection of habitat. Light is a fundamental cue contributing to larval sponge dispersal where photoreceptive cells contribute to this process. But how universal is light as a cue to sponge larval dispersal and settlement? Behavioural choice experiments were used to test the effect of light on dispersal and settlement behaviours. Larvae of the tropical sponge species Coscinoderma mathewsi, Luffariella variabilis, Ircinia microconnulosa, and Haliclona sp., from deep (12-15 m) and shallower-water habitats (2-5 m), were used in experiments. Dispersal experiments provided a light-gradient-choice where light represented light attenuation with depth. Light treatments included white light and the spectral components of red and blue light. Settlement experiments comprised a choice between illuminated and shaded treatments. Fluorescence microscopy was used to establish the presence of fluorescent proteins associated with posterior locomotory cilia. Deeper-water species, C. mathewsi and I. microconnulosa discriminate light spectral signatures. Both species changed dispersal behaviour to light spectra as larvae aged. For C. mathewsi positive phototaxis to blue light changed to photophobic responses (all light treatments) after six hours and behaviours in I. microconnulosa changed from positive to negative phototaxis (white light) after six hours. L. variabilis, also a deeper-water species, was negatively phototactic to all light treatments. Larvae from the shallow-water species, Haliclona sp., moved towards all light wavelengths tested. There was no effect of light on settlement of the shallow-water Haliclona sp., but larvae in all three deeper-water species showed significantly higher settlement in shaded treatments. Fluorescence microscopy showed discrete fluorescent bands contiguous to posterior tufted cilia in all four species. These fluorescent bands may play a contributory role in larval photobehaviour.

Cytogenetic screening of a Canadian swine breeding nucleus using a newly developed karyotyping method named oligo-banding

BackgroundThe frequency of chromosomal rearrangements in Canadian breeding boars has been estimated at 0.91 to 1.64%. These abnormalities are widely recognized as a potential cause of subfertility in livestock production. Since artificial insemination is practiced in almost all intensive pig production systems, the use of elite boars carrying cytogenetic defects that have an impact on fertility can lead to major economic losses. To avoid keeping subfertile boars in artificial insemination centres and spreading chromosomal defects within populations, cytogenetic screening of boars is crucial. Different techniques are used for this purpose, but several issues are frequently encountered, i.e. environmental factors can influence the quality of results, the lack of genomic information outputted by these techniques, and the need for prior cytogenetic skills. The aim of this study was to develop a new pig karyotyping method based on fluorescent banding patterns.ResultsThe use of 207,847 specific oligonucleotides generated 96 fluorescent bands that are distributed across the 18 autosomes and the sex chromosomes. Tested alongside conventional G-banding, this oligo-banding method allowed us to identify four chromosomal translocations and a rare unbalanced chromosomal rearrangement that was not detected by conventional banding. In addition, this method allowed us to investigate chromosomal imbalance in spermatozoa.ConclusionsThe use of oligo-banding was found to be appropriate for detecting chromosomal aberrations in a Canadian pig nucleus and its convenient design and use make it an interesting tool for livestock karyotyping and cytogenetic studies.

Excited-state properties of 6-methoxyflavone in the presence of halide ions in aqueous media

The present work investigated the influence of different halides on the excited state dynamics of 6-methoxyflavone (6MF) in an aqueous solution with steady-state and time-resolved techniques. On successive addition of I− and Br− ions, the fluorescence of 6MF quenched significantly, whereas the respective ions do not change the maximum fluorescence band. Fluorescence of 6MF was quenched 66% by I− ions and 34% by Br− ions. In a pure aqueous medium, both the H-bonded: CT and protonated species of 6MF participate in the quenching of fluorescence. The quenching process was categorized by Stern–Volmer (S–V) and Lehrer equations. Quenching parameters such as KSV, KSV-L and kq were higher for I− ions than Br− ions. The decrease in fluorescence intensity and a reduction in fluorescence lifetime suggested the dynamic nature of quenching by I− ions following the electron transfer mechanism. Fluorescence quenching of 6MF has also been observed in the acidic medium in the presence of different halides. Thus, the study reveals that 6MF is responsive towards I− ions in a wide range of pH, specifically in a purely aqueous environment (pH∼7), hence important for sensing/detection applications.

Comparative Cytogenetics and Fluorescent Chromosome Banding in Five Indian Species of Dipcadi Medik

The genus Dipcadi Medik. (Subfamily: Scilloideae) has a narrow distribution in India and several overlapping morphological traits make the genus taxonomically challenging at the species level. Cytogenetic characterization can provide additional taxonomic data and can be used to evaluate genetic diversity at the species level. We have accomplished comparative karyotype analysis and fluorescence banding patterns using 4′-6-Diamidino-2-phenylindole (DAPI) and Chromomycin A3 (CMA) in five Indian species for the first time. The karyotypes of D. concanense and D. goaense exhibited similar fluorochrome banding profiles. However, D. montanum, D. ursulae and D. erythraeum differ distinctly in their karyotypes. In all taxa, CMA+ve/DAPI−ve or DAPI0 (GC-rich) constitutive heterochromatin was located at the constriction region or terminal satellite of the nucleolar chromosome. DAPI+ve/CMA−ve or CMA0 (AT-rich) heterochromatin dominates in D. montanum, D. ursulae and D. erythraeum. However, D. erythraeum shows a distinct variation in fluorochrome banding pattern from all other species. The distribution of CMA and DAPI bands is a reflection of heterochromatin composition and variations acquired by different species. This characterization can be used to assess phylogenetic relationships in the understudied genus Dipcadi and may serve as a basis for other genomic analyses and evolutionary studies.

Aminoquinolines: Fluorescent sensors to DNA – A minor groove probe. Experimental and in silico studies

An aminoquinoline (AQ4) was developed and proven to be a new and efficient DNA minor groove fluorescent probe. The specificity for DNA minor groove was attested by comparing it with well-established DNA probes such as Hoechst stain, acridine orange, and ethidium bromide. AQ4 was similar to the Hoechst stain, a classic minor groove probe, and opposite to acridine orange and ethidium bromide, the typical intercalating probes. An advantage of AQ4 to the Hoechst stain was the higher fluorescent signal-to-noise ratio (+DNA/-DNA). The interaction with DNA leads to an exclusive fluorescent band centered at 590 nm. The red-shifted fluorescent band is associated with a new absorption band (490 nm), revealing a ground-state complex formation. The complexation was also evidenced by circular dichroism, anisotropy, and fluorescence lifetime. The complex AQ4-DNA was pH dependent, being favored in an acidic medium. This feature was related to the preferential interaction with a protonated form of AQ4, i.e., AQ4(H+), revealing the role of electrostatic forces, which was corroborated by the strong dependence on the ionic strength of the medium and, particularly, on magnesium ions. The complexes were studied by docking and molecular dynamics and confirmed the stability of AQ4(H+). Additionally, 500 ns simulations were performed by adding salts. The presence of the salts leads to the loss of the binding of AQ4(H+) after 52 ns (NaCl) and 142 ns (MgCl2). Experimental and in silico outcomes showed the advantages of the aminoquinoline over the commercial DNA minor groove stain, the Hoechst dye. Hence, we propose its further application in cell-based assays.

Benzophenoxazine-based colorimetric and fluorescent probe for highly sensitive detection of amines and food freshness

In this work, we reported a chromogenic and near infrared (NIR) region fluorogenic dual-channel probe NRB, which could visually detect gaseous amines with high sensitivity (eg. 50 and 17 ppt for methylamine (MeNH2) via naked eyes and fluorescence spectrometer respectively). It exhibited a wide fluorescent emission band extending to the NIR region with a peak at 615 nm when stimulated by the MeNH2 solution. The plausible sensing mechanism was proved by mass spectrometry, where the reaction process was based on a nucleophilic substitution between the probe and amines rather than the ester group hydrolysis. Furthermore, NRB was successfully applied to monitor the food freshness (seafood and meat food), because of its low cytotoxicity and excellent photophysical properties. It was worth mentioning that real time monitoring for food quality can be realized visually by using a 365 nm UV lamp. In addition, the probe was stable during the quality guarantee period for perishable packaged food. It was believed that the applied experiments have demonstrated the value of this probe in the practical applications for food safety.