Fluorescence Emission Features Research Articles

Determination of metanil yellow dye in turmeric powder using a unique fluorescence Europium doped carbon dots

Turmeric, a spice known for its therapeutic benefits, is a major source of curcumin which is a polyphenol with anti-inflammatory properties. It aids in treating arthritis, anxiety, metabolic syndrome, liver disease, hyperlipidemia, and inflammatory diseases. In this study, a novel fluorescence probe was designed to detect the adulteration of curcumin by metanil yellow (a harmful artificial dye). The probe was synthesized from the carbonization and conversion of the Tannic acid-Eu3+ complex to bright fluorescence Eu-carbon dots in the presence of orthophosphoric acid. The size, morphological, and optical features of the formed Eu-carbon dots were characterized by UV, SEM, TEM, and FTIR techniques. Furthermore, the formed Eu-carbon dots possess unique fluorescence excitation and emission features at 307.5 nm and 340.6 nm, respectively. These fluorescence features can be successfully quenched upon the addition of metanil yellow dye. The value of quenching in the fluorescence intensity of the Eu-C-dots was directly proportional to the dye's concentration. The LOD value for the proposed method was 0.390 µg/mL with a linear range of 1.0–15.0 µg/mL. Furthermore, the methodology exhibited good recovery values for determining the studied dye without any interference from the presence of curcumin.

Three-Pronged Attack by Hybrid Nanoplatform Involving MXenes, Upconversion Nanoparticle and Aggregation-Induced Emission Photosensitizer for Potent Cancer Theranostics.

Inspired by the excellent photothermal conversion ability and inherent nanomedicine platform property of MXenes, efficient reactive oxygen species production and prominent fluorescence emission feature of aggregation-induced emission (AIE)-active photosensitizers (PSs), as well as the extending excitation wavelength capability of upconversion nanoparticles (UCNPs), a versatile nanoplatform comprised of Ti3 C2 nanosheets (NSs), AIE-active PSs and UCNPs is intelligently fabricated. This three-pronged strategy takes advantages of each component simultaneously, and realizes fluorescence imaging/photoacoustic imaging/photothermal imaging triple-modal imaging-guided photothermal/photodynamic synergetic therapy under 808nm laser irradiation. The introduction of UCNPs actualizes the long wavelength-activation of AIE-active PSs, which significantly increases the tissue penetration depth. Spatially isolation of AIE-active PSs and Ti3 C2 NSs is beneficial for suppressing the fluorescence quenching effect of Ti3 C2 NSs, bringing about ultimately brilliant fluorescence. The covalently bonded polymer surface endows the nanoplatform with excellent physiological stability and efficient tumor accumulation. These outputs reveal a win-win cooperation of multiple inorganic/organic nanocomposites for phototheranostics, and present great potential for future clinical translations.

Acclimation of the photosynthetic apparatus to low light in a thermophilic Synechococcus sp. strain.

Depending upon their growth responses to high and low irradiance, respectively, thermophilic Synechococcus sp. isolates from microbial mats associated with the effluent channels of Mushroom Spring, an alkaline siliceous hot spring in Yellowstone National Park, can be described as either high-light (HL) or low-light (LL) ecotypes. Strains isolated from the bottom of the photic zone grow more rapidly at low irradiance compared to strains isolated from the uppermost layer of the mat, which conversely grow better at high irradiance. The LL-ecotypes develop far-red absorbance and fluorescence emission features after growth in LL. These isolates have a unique gene cluster that encodes a putative cyanobacteriochrome denoted LcyA, a putative sensor histidine kinase; an allophycocyanin (FRL-AP; ApcD4-ApcB3) that absorbs far-red light; and a putative chlorophyll a-binding protein, denoted IsiX, which is homologous to IsiA. The emergence of FRL absorbance in LL-adapted cells of Synechococcus sp. strain A1463 was analyzed in cultures responding to differences in light intensity. The far-red absorbance phenotype arises from expression of a novel antenna complex containing the FRL-AP, ApcD4-ApcB3, which is produced when cells were grown at very low irradiance. Additionally, the two GAF domains of LcyA were shown to bind phycocyanobilin and a [4Fe-4S] cluster, respectively. These ligands potentially enable this photoreceptor to respond to a variety of environmental factors including irradiance, redox potential, and/or oxygen concentration. The products of the gene clusters specific to LL-ecotypes likely facilitate growth in low-light environments through a process called Low-Light Photoacclimation.

Speckle patterning of a pumping laser light as a limiting factor for stimulated fluorescence emission in dense random media.

The features of fluorescence emission in a dye-doped dense multiple scattered medium under pulsed laser pumping are considered in terms of confined excitation in small zones associated with laser speckles occurring in a pumped medium. The results of numerical modeling of the fluorescence emission kinetics are compared to the experimental data obtained using the rhodamine 6G-doped layers of the densely packed TiO2 (anatase) particles pumped at 532 nm by 10 ns laser pulses. The intensity of pump radiation during the action of laser pulses was varied from 1·105 W/cm2 to 5·107 W/cm2. In the recovery of the ratios of stimulated to a spontaneous emission, the spectra of the stimulated component were fitted using the spectral function derived by R. Dicke. In the framework of the considered concept, saturation of the ratio of the stimulated to a spontaneous emission and linear growth of an integrated fluorescence output with a practically unchangeable half-width of the emission spectra at high pump intensities are interpreted.

Fluid inclusion studies to determine the paleotemperature and hydrocarbon quality in petroliferous basins

Hydrocarbon bearing fluid inclusions (HCFIs) along with the coeval aqueous inclusions could be utilized in petroleum exploration industry for determining the paleotemperature and American Petroleum Institute's (API) gravity of oils in a basin. These parameters can indirectly yield a quick assessment on the hydrocarbon quality in a basin. Here we use fluid inclusion data as a tool to study the paleotemperature and hydrocarbon quality of two offshore basins in India (dry wells from a proven basin and non-proven basin). Towards this objective, temperature of homogenization (Th) of coeval aqueous fluid inclusion, assemblages seen associated with HCFIs and fluorescence emission features of oils in HCFIs were studied. Depthwise comparison of two basins studied are accorded with the microthermometrically obtained Th data and spectroscopically determined (fluorescence) API gravity values that gives an estimation of the paleotemperature and hydrocarbon quality. The Th and, fluorescence emission features of oils in HCFIs (leads to API gravity) presented allow us to make a qualitative assessment of oils in these basins. This study brings out the potential information stored in HCFIs/adjacent brine fluid inclusions, as a tool for determining the paleotemperature and API gravity of oils in petroliferous basins.

Macromolecular Dyes by Chromophore-Initiated Ring Opening Polymerization of L-Lactide.

End functionalized polylactides are prepared by ring opening polymerization of L-lactide in the presence of stannous octoate (Sn(Oct)2). Three chromophores, 9H-carbazol-ethanol (CA), 9-fluorenyl-methanol (FM), and 2-(4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino)ethanol (Disperse Red 13, DR), are for the first time used as co-initiators in the polymerization process. The polymerization reaction is initiated by conventional thermal treatment, but in the case of FM, microwave-assisted polymerization is also carried out. CA and FM absorb and emit in the UV portion of the electromagnetic spectrum, whereas DR absorbs in the visible part. The obtained end-capped polylactides derivatives show the same photophysical properties as the initiator, so they are “macromolecular dyes” (MDs) that can be used “as synthesized” or can be blended with commercial poly(lactic acid) (PLA). The blends of PLA with MDs have ultraviolet-visible (UV-Vis) absorption and fluorescence emission features similar to that of MDs and thermal properties typical of PLA. Finally, migration tests, carried out onto the blends of PLA with MDs and PLA with free chromophores, show that MDs are less released than free chromophores both in solution and in the solid phase.

Molecular Engineering of Thermally Activated Delayed Fluorescence Emitters with Aggregation-Induced Emission via Introducing Intramolecular Hydrogen-Bonding Interactions for Efficient Solution-Processed Nondoped OLEDs.

Purely organic luminescent materials concurrently exhibiting thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) features are in great demand due to their high efficiency in aggregation-state toward efficient nondoped OLEDs. Herein, a class of TADF emitters adopting phenyl(pyridyl)methanone as electron-accepting segments and di(tert-butyl)carbazole and 9,9-dimethyl-9,10-dihydroacridine (or phenoxazine) as electron-donating groups are designed and synthesized. The existence of intramolecular hydrogen bonding is conducive to minish the energy difference between a singlet and a triplet (ΔEst), suppress nonradiative decay, and increase the luminescence efficiency. By using 3CPyM-DMAC as the emitter, the nondoped device via a solution process realize a high current efficiency (CE) and external quantum efficiency (EQE) of 35.4 cd A-1 and 11.4%, respectively, which is superior to that of CBM-DMAC with a CE and EQE of 14.3 cd A-1 and 6.7%. This work demonstrates a promising tactic to the establishment of TADF emitters with AIE features via introducing intramolecular hydrogen bonding.

Fluorescence Turn-On, Specific Detection of Cystine in Human Blood Plasma and Urine Samples by Nitrogen-Doped Carbon Quantum Dots.

Determination of cystine in blood and urine is very important to monitor and maintain the bio metabolism, immune systems, and prevent the tissue/DNA damage from free radicals, diagnosis of cystinuria disease, cancer, and related autoimmune diseases. Among the various detection methods, fluorometric detection is simple, rapid, and sensitive to cystine using nontoxic, inexpensive, highly fluorescent, stable carbon quantum dots (CQDs). The CQDs are prepared from p-phenylenediamine by the hydrothermal method to get the inherent optical features of pH-dependent and excitation wavelength-independent fluorescence emission along with high aqueous stability due to pre-eminent nitrogen content. The red emission of CQDs originates from the intrinsic core that is associated with photoinduced electron transfer (PET). The turn-on fluorescence observed in presence of cystine is due to decrease in the PET by oxidation of CQDs. On the basis of this observation, we have developed an assay for the determination of cystine with a concentration range of 10 nM to 10 μM and the limit of detection is 0.4 nM. Additionally, our assay shows good recoveries (93–105%) for the spiked blood plasma and urine samples using the standard addition method.

Probing hemoglobin glyco-products by fluorescence spectroscopy.

Maillard reaction products (MRPs) participate in reactions of carbohydrate intermediates with proteins, resulting in the formation of advanced glycation end-products (AGEs). Dietary Maillard reaction products are recognized as potential chemical modifiers of human proteins. We have investigated the reaction of isolated MRPs from an asparagine–glucose model system with hemoglobin (Hb) to elucidate the binding effect of the MRPs in hemoglobin by fluorescence spectrophotometry. The tryptophan-specific fluorescence obtained for glycated hemoglobin exhibited a Stokes effect since the wavelength of the emission peak was shifted to a higher wavelength than that of native Hb. The formation of new fluorescence emission features indicates the formation of modified hemoglobin species. Fluorescence spectroscopic studies provide evidence that the conformational changes in the β-Trp 37 moiety induce motion of the distal His 64 (E7) in the heme binding pocket. This results in the formation of inactive hemichrome forms of hemoglobin which are related to blood disorders.

Photoinduced electron and energy transfer in an amphiphilic perylenetetracarboxylic diimide derivative/CdS self-assembled hybrid film

An amphiphilic perylenetetracarboxylic diimide derivative with four 4-tert-butylphenoxy substituents at the bay positions (named as TPDI) has been used as not only the functional organic materials but also the organic template for growth of CdS nanoparticles. The highly ordered TPDI/CdS hybrid film was obtained where the petals-like CdS nanocrystals with a uniform size (about 50 nm) grown on the surface of TPDI film successfully. The crystalline regions for CdS were identified to be hexagonal wurtzite. Examination by spectroscopic methods revealed TPDI molecules in both pure film and hybrid film all adopt a typical J-aggregation mode with a slight declining orientation angle with respect to the substrate from 24.8° to 21.9° after incorporation of CdS nanoparticles into the TPDI matrix. In particular, energy transfer from CdS to TPDI is established by both increased fluorescence emission intensity and fluorescence quantum yield of TPDI in the hybrid film. Furthermore, the enhanced conductivity and electron mobility are obtained for the hybrid film relative to those of the pure film based on current-voltage (I-V), field-effect transistor (FET) and photocurrent measurements. Unexpectedly, photo-induced electron-transfer from TPDI molecules to CdS nanocrystals is revealed through much more enhanced conductivity and electron mobility for the TPDI/CdS hybrid film relative to pure TPDI film upon 365 nm UV light irradiation. In only one TPDI/CdS hybrid system, the energy band alignment of TPDI and CdS nanoparticles makes evident possibility for electron transfer, while their electronic absorption and fluorescence emission features provide reasonability for both electron and energy transfer.

A super-sensitive ratiometric fluorescent probe for monitoring intracellular subtle pH fluctuation

A new type of xanthene-based fluorescent probe capable of intracellular subtle pH fluctuation sensing was developed. The probe underwent reversible deprotonation-protontation processes and therefore generated two states with distinct contrast in fluorescence emission features. In the physiological range (pH 7.0–8.0), the probe markedly presented 31.2% fluorescence signal change upon pH fluctuation of 0.1 pH unit, enabling sensitivity infinitely superior to previous fluorescent pH probes. The preliminary biological experiments revealed the large dynamic range of the probe for intracellular pH sensing within the range of pH 6.0–8.0. Owing to its sensitive responses to pH fluctuation in the physiological pH range, the probe definitely demonstrated its ability for “distinguishing” tumor from normal cells based on the difference in microenvironment pH level between the former and the latter. The figure of merits of the probe, including pKa (7.45) in the physiological pH range, excellent photostability, extraordinary large dynamic range for pH sensing, as well as the preliminary bioimaging results regarding differentiating tumor from normal cells are indicative of its potential for providing the microenvironment information regarding the interfacial features at the perimeter of tumor tissues by presenting high-contrast fluorescence images.

Fabrication of AIE-active fluorescent organic nanoparticles through one-pot supramolecular polymerization and their biological imaging

Supramolecular interactions between individual molecules are universal forces in living organisms and have been extensively investigated and utilized for fabrication of multifunctional materials over the past few decades. In this work, we reported a rather facile strategy to fabricate the fluorescent organic nanoparticles (FONs) with red fluorescence and aggregation-induced emission (AIE) feature through the supramolecular interactions between the β cyclodextrin (β-CD) and adamantine terminating AIE dye. The structures of prepared Ph-Ad/β-CD FONs were characterized by 1H nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy(FTIR) spectroscopy. The size and morphology of the final self-assemblies (named as Ph-Ad/β-CD FONs) was characterized by transmission electronic microscopy (TEM). Results demonstrated that these AIE-active FONs can self-assemble into nanoparticles with excellent dispersity and strong fluorescence due to their AIE feature. Biological evaluation demonstrated that Ph-Ad/β-CD FONs has superior biocompatibility and imaging performance. These features endow the Ph-Ad/β-CD FONs good performance in biomedical fields.

Main photophysical properties of oxyblepharismin

Oxyblepharismin is the photo-oxidized form of blepharismin, the chromophore responsible for the photophobic response of heterotrich ciliate Blepharisma japonicum, and represents a nice model for the study of photo-transduction. In this work, we focused on the photophysical characterization of OxyBP, in view of highlighting the main features related to excitation and emission. By a combined experimental and computational approach we identified the main features of absorption and fluorescence emission of the molecule in solvents of different properties, identifying the nature of transitions as well as the possible heterogeneity at ground/excited state. The thorough photophysical characterization of OxyBP is meant to provide the starting point for the elucidation of the photo-transduction pathway in vivo.

A Colorimetric Fluorescent Probe for SO2 Derivatives-Bisulfite and Sulfite at Nanomolar Level.

A colorimetric fluorescent probe with fluorescence emission feature sensitive to SO2 derivatives, i.e. bisulfite (HSO3-) and sulfite (SO32-), was developed based on the HSO3-/SO32--mediated nucleophilic addition reaction of the probe that. This probe exhibited SO32- sensing ability with detection limit down to 46nM and desired selectivity over other reference anions and redox species. The preliminary fluorescence bioimaging experiments have validated the practicability of the as-prepared probe for SO2 derivatives sensing in living cells.

Potential Application of Fluorescence Imaging for Assessing Fecal Contamination of Soil and Compost Maturity

Pathogenic microorganisms can lead to serious outbreaks of foodborne illnesses, particularly if fresh produce becomes contaminated and then happens to be inappropriately handled in a manner that can incubate pathogens. Pathogenic microbial contamination of produce can occur through a variety of pathways, such as from the excrement of domesticated and wild animals, biological soil amendment, agricultural water, worker health and hygiene, and field tools used during growth and harvest. The use of mature manure compost and preventative control of fecal contamination from wildlife and livestock are subject to safety standards to minimize the risk of foodborne illness associated with produce. However, in a field production environment, neither traces of animal feces nor the degree of maturity of manure compost can be identified by the naked eye. In this study, we investigated hyperspectral fluorescence imaging techniques to characterize fecal samples from bovine, swine, poultry, and sheep species, and to determine feasibilities for both detecting the presence of animal feces as well as identifying the species origin of the feces in mixtures of soil and feces. In addition, the imaging techniques were evaluated for assessing the maturity of manure compost. The animal feces exhibited dynamic and unique fluorescence emission features that allowed for the detection of the presence of feces and showed that identification of the species origin of fecal matter present in soil-feces mixtures is feasible. Furthermore, the results indicate that using simple single-band fluorescence imaging at the fluorescence emission maximum for animal feces, simpler than full-spectrum hyperspectral fluorescence imaging, can be used to assess the maturity of manure compost.

Expanded Porphyrin-Anion Supramolecular Assemblies: Environmentally Responsive Sensors for Organic Solvents and Anions.

Porphyrins have been used frequently to construct supramolecular assemblies. In contrast, noncovalent ensembles derived from expanded porphyrins, larger congeners of naturally occurring tetrapyrrole macrocycles, are all but unknown. Here we report a series of expanded porphyrin-anion supramolecular assemblies. These systems display unique environmentally responsive behavior. Addition of polar organic solvents or common anions to the ensembles leads to either a visible color change, a change in the fluorescence emission features, or differences in solubility. The actual response, which could be followed easily by the naked eye, was found to depend on the specifics of the assembly, as well as the choice of analyte. Using the ensembles of this study, it proved possible to differentiate between common solvents, such as diethyl ether, THF, ethyl acetate, acetone, alcohol, acetonitrile, DMF, and DMSO, identify complex solvent systems, as well as distinguish between the fluoride, chloride, bromide, nitrate, and sulfate anions.

Dual-functional probes for sequential thiol and redox homeostasis sensing in live cells.

A new type of resorufin-based dual-functional fluorescent probe whose fluorescence emission features are sensitive to thiol compounds and redox homeostasis was developed. Thiols-triggered nucleophilic substitution of the probes converts the nonfluorescent probe to the highly fluorescent resorufin moiety; the released resorufin not only enables fluorescence signaling specific for thiol compounds but functions as a redox indicator with sensitive colorimetric and fluorescence emission change upon redox variation. Preliminary fluorescence imaging experiments have revealed the biocompatibility of the as-prepared probes and validated their practicability for thiol sensing and redox homeostasis mapping in living cells.

Hybrid fluorescent nanoparticles fabricated from pyridine-functionalized polyfluorene-based conjugated polymer as reversible pH probes over a broad range of acidity-alkalinity

Conjugated polymer nanoparticles (CPNs) were developed based on a polyfluorene-based conjugated polymer with thiophene units carrying pyridyl moieties incorporated in the backbone of polymer chains (PFPyT). Hybrid CPNs fabricated from PFPyT and an amphiphilic polymer (NP1) displayed pH-sensitive fluorescence emission features in the range from pH 4.8 to 13, which makes them an attractive nanomaterial for wide range optical sensing of pH values. The fluorescence of hybrid CPNs based on chemically close polyfluorene derivatives without pyridyl moieties (NP3), in contrast, remains virtually unperturbed by pH values in the same range. The fluorescence emission features of NP1 underwent fully reversible changes upon alternating acidification/basification of aqueous dispersions of the CPNs and also displayed excellent repeatability. The observed pH sensing properties of NP1 are attributed to protonation/deprotonation of the nitrogen atoms of the pyridine moieties. This, in turn, leads to the redistribution of electron density of pyridine moieties and their participation in the π-conjugation within the polymer main chains. The optically transparent amphiphilic polymers also exerted significant influence on the pH sensing features of the CPNs, likely by acting as proton sponge and/or acid chaperone.

Conjugated Polymer Nanoparticles with Ag+‐Sensitive Fluorescence Emission: A New Insight into the Cooperative Recognition Mechanism

Hybrid fluorescent nanoparticles (NPs) were developed on the basis of a series of chemically close polyfluorene‐based conjugated polymers and an amphiphilic polymer. NPs constructed from polyfluorene with 2,1,3‐benzothiadiazole units incorporated in the backbone of polymer chains displayed Ag+‐sensitive fluorescence emission features with high selectivity, which was demonstrated to be attributable to Ag+‐induced aggregation and fluorescence quenching. The negatively charged sulfonic acid groups of amphiphilic polymer components located on the surfaces of the hybrid NPs and therefore provided binding sites for metal ions, which was found indispensable for the observed silver ion sensing features of the as‐prepared hybrid NPs. Additionally, it was demonstrated that the benzothiadiazole‐containing conjugated polymer components not only acted as the fluorescence signaling source but also participated in the metal binding/recognition processes. Thus, a mechanism of cooperative recognition‐based aggregation‐induced fluorescence static quenching and Ag+‐triggered fluorescence dynamic quenching responsible for the observed Ag+ sensing results was confirmed.

The influence of counter ion and ligandmethyl substitution on the solid-state structures and photophysical properties of mercury(ii) complexes with (E)-N-(pyridin-2-ylmethylidene)arylamines

Ten neutral monomeric, dimeric and polymeric mercury(II) complexes of compositions HgX(2)L (3, 8), [HgX(2)L](2) (1, 2, 4-6 and 7), [Hg(NO(3))(2)L](n) (9) and {[Hg(N(3))(2)L](2)}(n) (10) where X = chloride, bromide, iodide, nitrate and azide, and L = (E)-N-(pyridin-2-ylmethylidene)arylamine, are described. Compounds 1-10 were characterized by elemental analyses, and IR and (1)H NMR spectroscopic studies. The solution-state photophysical properties of the complexes are highly dependent on the anions as seen in the fluorescence emission features. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Iodide gives discrete monomeric complexes, chloride and bromide generate binuclear complexes formed through Hg-X-Hg bridges, while nitrate and azide lead to 1D coordination polymers. The significant differences in the observed aggregation patterns of the compounds indicate that the anions exert a substantial influence on the formation of the compounds. A further influence upon supramolecular aggregation is the presence of methyl substituents in L(3) and L(4), which generally enhances the probability of forming supramolecular ππ interactions involving the five-membered C(2)N(2)Hg chelate rings in their crystal structures.