Fluorescence Band Research Articles

The Origin of Dual-Emission in PLICT Compounds - an Empirical Approach.

Fluorescence spectroscopy proves to be a powerful and versatile tool in scientific research, demanding ongoing advancements of fluorescence probes to cater to a broad range of applications. The particular interest lies in the development of fluorophores with multiplexing capability, emitting from more than one excited state depending on the polarity and viscosity of the surrounding medium. Here, we present a variety of novel dual planarized intramolecular charge transfer (PLICT) emitters based on cyano-1-aminoindole structures. We have chosen a combination of experimental studies, theoretical calculations and the creation of a unique fluorophore cataloging map. This map serves as a useful tool for empirically determining the origin of both fluorescence bands.

Spectroscopic and 1.5–1.6 μm laser properties of Er:Yb:GdSr3(PO4)3 crystal

An Er:Yb:GdSr3(PO4)3 crystal was grown by the Czochralski method, and its spectroscopic properties were investigated at room temperature. The peak absorption cross section is 1.12 × 10−20 cm2 at 975 nm and the full width at half maximum of the absorption band is 5.8 nm. The peak emission cross section is 0.74 × 10−20 cm2 at 1535 nm and the full width at half maximum of the fluorescence band is 41 nm. Fluorescence lifetime of the 4I13/2 multiplet of Er3+ and Yb3+→Er3+ energy transfer efficiency in the crystal are 7.97 ms and 91.8 %, respectively. End-pumped by a 975 nm diode laser, a 1563 nm continuous-wave laser with a maximum output power of 60 mW and a slope efficiency of 16.1 % was realized in an Er:Yb:GdSr3(PO4)3 crystal at an absorbed pump power of 413 mW. Using a SiO2 birefringent filter as a wavelength tuning element, a continuously tunable 1.5–1.6 μm laser with a range of 45 nm and a maximum output power of 30 mW at 1541 nm was obtained at the same pump power.

Cu-Catalyzed Azide-Alkyne-Thiol Reaction Forms Ubiquitous Background in Chemical Proteomic Studies.

We report here a Cu-catalyzed azide-alkyne-thiol reaction forming thiotriazoles as the major byproduct under widely used bio-orthogonal protein labeling "click" conditions. The development of Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) had a tremendous impact on many biological discoveries. However, the considered chemoselectivity of CuAAC is hampered by the high reactivity of cysteine free thiols, yielding thiotriazole protein conjugates. The reaction byproducts generate false-positive protein hits in functional proteomic studies. The reported detail investigation of conjugates between chemical probes containing terminal alkynes, azide tags, and cell lysates reveals the formation of thiotriazoles, which can be readily detected by in-gel fluorescence scanning or after peptide and protein enrichment by mass spectrometry-based proteomics. In protein level identification and quantification experiments, the produced fluorescent bands or enriched proteins may not result from the important enzymatically driven reaction and can be falsely assigned as hits. This study provides a complete list of the most common background proteins. The knowledge of this previously overlooked reactivity now leads to the introduction of modified CuAAC conditions, which avoids the undesired product formation, diminishes the background, and hence improves the signal-to-noise ratio.

A red fluorescent carbon dots with good water solubility for rapid detection of Al3+ in actual samples.

We developed a facile strategy for the fabrication of red fluorescent carbon nanodots (R-CDs) and demonstrated their applications for Al3+ sensing. Red-emission carbon dots (CDs) were synthesized using a simple hydrothermal treatment with citric acid and urea as precursors, manifesting intriguing red-emission behaviour at 610 nm. With increasing Al3+ concentration, the fluorescence band at 610 nm decreased gradually. Monitoring the intrinsic fluorescence variation (I610nm ), as-prepared CDs were developed as an effective platform for fluorescent Al3+ sensing, with a linear range of 0.5-60.0 μM and a detection limit of 3.0 nM. More importantly, R-CDs have been applied successfully to the analysis of Al3+ in actual samples with satisfactory recoveries in the range 97.12-102.05%, which indicated that obtained CDs could be implemented as an effective tool for the identification and detection of Al3+ in actual samples.

An Unprecedented Reaction of BOPHY: Fluorimetric Chemosensing of Amines by Tetrabrominated BOPHY

AbstractIn this study, we present an unprecedented reaction of BOPHY. Although tetrabrominated BOPHY (BrBPH) is known to give a substitution reaction with amines, we found that this reaction proceeds through an addition mechanism in the dilute medium. Upon this reaction, the absorption and fluorescence bands of BrBPH decrease dramatically. We used this newly presented reaction for the fluorimetric detection and quantification of amines. BrBPH‐adsorbed TLC plates were also utilized for the determination of food spoilage.

Regioisomers containing triarylboron-based motifs as multi-functional photoluminescent materials: from dual-mode delayed emission to pH-switchable room-temperature phosphorescence.

Triarylboron compounds have been established as promising candidates in optoelectronic applications. However, realizing multi-functional properties in triaryl boron-based materials remains challenging. Herein, we present two regioisomers, 1 and 2, designed judiciously by connecting a dimethylamino donor and a dimesitylboryl acceptor at 1,4 and 2,6-positions of the naphthalene spacer, respectively. Both compounds 1 and 2 display simultaneous, delayed fluorescence and persistent room-temperature phosphorescence (580 nm, τ av = 168 ms, Φ = 76% for 1; 550 nm, τ av = 129 ms, Φ = 88% for 2 in 1 wt% PMMA), with the delayed fluorescence bands being sensitive to doping concentration (in PMMA). Notably, compound 1 in 1 wt% PMMA films demonstrates a reversibly switchable single-molecule phosphorescence from orange (580 nm) to green (λ Ph = 550 nm, τ av = 42 ms) in response to pH, which can be utilized for anti-counterfeiting applications. These results were further corroborated by studying the respective cationic salts 1-OTF and 2-OTF. Moreover, 1 and 2 exhibited blue-shifted fluorescence in response to mechanical pressure. Compound 2 also showed three-photon (σ3P) absorption properties which were better compared to those of compound 1.

Selective identification of p-nitroaniline by bromine-mediated polarization of carbon dots.

A fluorometric method based on boron, bromide-codoped carbon dots (BBCNs) was developed for the first time for the highly selective detection of p-nitroaniline (PNA) in wastewater samples. It should be noted that the introduction of bromine greatly increases the molecular polarizability of the probe, which can regulate the energy level matching between the probe and PNA, resulting in the interaction between BBCNs and PNA. In the presence of PNA, the fluorescence of BBCNs is obviously quenched and accompanied by a red shift of the fluorescence band, which might be attributed to the formation of aggregates caused by the polar adsorption of BBCNs and PNA. It is beneficial for constructing a highly selective sensing platform for PNA determination compared to its isomers (o-nitroaniline and m-nitroaniline) through atomic bromine-mediated polarization of the BBCNs. With the help of this mechanism, an excellent linear range of 0.5-300 μM with a low detection limit of 0.24 μM toward PNA was obtained. This work further confirms that there is a significant relationship between the nature of doping elements and the optical and physicochemical properties of fluorescent materials.

Excited-state dynamics of 4-hydroxyisoindoline-1,3-dione and its derivative as fluorescent probes.

Fluorescent probes have become promising tools for monitoring the concentration of peroxynitrite, which is linked to many diseases. However, despite focusing on developing numerous peroxynitrite based fluorescent probes, limited emphasis is placed on their sensing mechanism. Here, we investigated the sensing mechanism of a peroxynitrite fluorescent probe, named BHID-Bpin, with a focus on the relevant excited state dynamics. The photoexcited BHID-Bpin relaxes to its ground state via an efficient nonradiative process (∼300 ps) due to the presence of a minimum energy conical intersection between its first excited state and ground state. However, upon reacting with peroxynitrite, the Bpin moiety is cleaved from BHID-Bpin and BHID is formed. The formed BHID exhibits strong dual band fluorescence which is caused by an ultrafast excited-state intramolecular proton transfer process (∼1 ps).

Cytogenetical studies of some Convolvulaceae members from the Western Ghats, India reveal uniformity in karyotypes

Karyotypes of six Ipomoea and one Merremia species were studied. Chromosome counts of 2n = 30 for I. corymbosa, I. kotschyana, I. marginata f. candida and M. rhyncorhiza) and 2n = 60 for I. ochracea were observed for the first time. Meiotic course of five Ipomoea species was also examined for the first time and two counts, i.e. n = 15 and n = 30 were recorded. Meiosis was found normal. Karyotypes of the studied species exhibited uniformity. All the species had chromosomes with median region centromeres and karyotypes were symmetrical (Stebbins’ 4A category). I. marginata f. candida had the shortest chromosomes with mean length of 0.99 ± 0.02 µm. I. ochracea and I. corymbosa had the longest chromosomes with mean length of 1.22 ± 0.05 µm and 1.22 ± 0.01 µm, respectively. As chromosomes were small and exhibited uniform morphology, fluorescent banding or fluorescent in-situ hybridization can be useful to differentiate the karyotypes and understand species interrelationships.

Karyotype profile of holarrhena antidysenterica (Roxb. Ex fleming) wall

The karyomorphological features of Holarrhena antidysenterica (Roxb. ex Fleming) Wall. through the application of differential staining techniques (using orcein, CMA, and DAPI) were studied. After applying orcein staining, the interphase nuclei of this species exhibited a ‘simple chromocenter type’ with numerous small heterochromatin blocks and the prophase chromosomes were ‘interstitial type’. The karyotype analysis revealed that this species possesses diploid chromosome number of 2n = 22, with all metacentric chromosomes. The total length of the chromosome complement in the diploid set was 29.91 μm. A total of four CMA-positive bands were observed in this species whereas seven bands were found after DAPI-staining. Heteromorphicity was observed in the DAPI stained metaphase stage indicating the probable occurrences of chromosomal aberrations such as deletion and inversion. The karyotype profile of H. antidysenterica obtained from orcein and fluorescent banding was determined for the first time in Bangladesh. Bangladesh J. Bot. 52(4): 1085-1089, 2023 (December)

Silicon distyryl-BODIPY hybrid photodiode: moving a step ahead from organic interface layer to type II band alignment

Organic-inorganic heterojunctions are becoming an attractive topic of research for their applications in hybrid photodetectors, solar cells, resistive switching memory devices etc. The easy chemical synthesis and low-cost fabrication for organic thin films come with the benefit of high light absorptivity, high fluorescence quantum yield and band gap tunability along with high charge carrier lifetime that could be combined with the existing silicon-based technology. In this aspect, various organic dyes utilised as an interfacial layer with silicon Schottky junction are reported earlier. However, the photo responses are quite limited. Here, in this report, a Type II Silicon/Distyryl-BODIPY p-n junction has been proposed as an organic-inorganic hybrid photodetector which has not been explored extensively yet. The transformation from a mere organic interfacial layer to band aligned junction enhances the charge carrier separation providing higher photo-responsive behaviour. With the simple spin-coating technique, the Distyryl-BODIPY derivative with phenolic functionalities is coated to fabricate the p-n junction diode. To further improve the performance, pyramidal surface texturization on silicon is deployed using wet chemical etching that supplements the light absorption with internal reflections. Both the devices have been investigated for their photo-response characteristic where a high photo-responsivity of 4353 A W−1 is attained for the textured device as compared to 118 A W−1 for the planar silicon device at a − 3 V bias with an ultra-high specific detectivity of 1012 Jones and 1010 Jones respectively. The behaviours of interfacial states have been demonstrated using the capacitance (C), conductance (G) and series resistance (RS) vs voltage (V) curves at different frequencies. Further calculations of interfacial state density revealed the existence of 1000 times higher interfacial states in planar device leading to lower performance as compared to pyramidal device. The findings in this report suggest that dye-based organic-inorganic heterostructures find potential applications in photodetectors and other optoelectronic devices.

Excited-state proton transfer based fluorescence in Kaempferol powder and solutions with different concentrations

Kaempferol (KMP) is one of the most common flavonoids, currently being extensively studied for its numerous beneficial health effects. Here we study the fluorescence (FL) emission of KMP powder and of its solutions prepared using different types of solvents (polar and non-polar). In the spectra of KMP powder and KMP solutions with high concentration, the same FL peak with maximum at 1.9 eV is observed. Another FL peak, at higher energy of 2.45 eV, emerges in solutions, its relative intensity increases with decreasing solution concentration. The FL emission of solutions with lowest concentration displays only that peak. To calculate characteristic energies of absorption and emission of KMP molecule in vacuum and in solutions we use time-dependent density functional theory. Comparing the results of computations with measured FL spectra, we associate the FL band at 1.9 eV with the emission due to excited state intramolecular transfer of the proton of –OH5 hydroxyl group. The FL emission at 2.45 eV is related to the –OH3 proton transfer. We measure the FL spectra of KMP powder using two different excitation energies, 3.06 eV and 2.33 eV, and find that its FL spectrum depends on the excitation energy. To understand that dependence, we compare the FL spectra of KMP and Q monohydrate powders. We consider the excited state intermolecular transfer of the proton from –OH3′ hydroxyl group to a neighboring molecule in Q crystal and calculate the energy corresponding to the emission of the resulted anion of Q molecule. The spectral feature at 1.69 eV observed only in the FL spectrum of Q hydrate is attributed to the Q anion FL emission.

Unraveling the dual sensing mechanism of hydrogen peroxide probe: Photoinduced electron transfer and unusual local excited state intramolecular proton transfer

An understanding of hydrogen peroxide's (H2O2) sensing process is crucial for the development of effective fluorescent probes. In this investigation, we unraveled the sensing mechanism of the H2O2 fluorescent probe (BBD) derived from phthalimide-borate. The fluorescence of probe BBD is quenching and our findings establish this phenomenon can be attributed to a nonclassical photoinduced electron transfer (PET) process, wherein a crossing of energy curves between the local excited and charge transfer states is observed. The reaction between BBD and H2O2 causes the phenylboronic acid ester to oxidize and release a hydroxyl group, which turns off the PET process and causes the product HMD to enhance the fluorescence significantly. In addition, the results show that the generated HMD-N likewise undergoes fluorescence quenching, and the fluorescence band seen in the experiment originates from the HMD-T created by the unusual local excited state intramolecular proton transfer (ESIPT) process. In conclusion, our theoretical findings provide a comprehensive explanation for the fluorescence characteristics exhibited by BBD and HMD with an unusual local ESIPT combined PET process.

Lysozyme binding with amikacin and levofloxacin studied by tritium probe, fluorescence spectroscopy and molecular docking

Lysozyme complexes with amikacin and levofloxacin were studied by spectroscopy approaches as well as using a tritium probe. Tritium was used as a labeling agent to trace labeled compound concentration in a system of two immiscible liquids and in the atomic form to determine the possible position of the binding site. Co-adsorption of protein and drug at the liquid-liquid interface was analyzed by scintillation phase method that allowed us to directly determine the amount of protein and drug in the mixed adsorption layer. Also, tensiometric measuring of the interfacial tension was used for calculation of binding parameters accordingly to Fainerman model. The treatment of complexes with atomic tritium followed by trypsinolysis and analysis of tritium distribution in the lysozyme peptides reveals the binding sites, binding energies in which were analyzed using molecular docking. Formation of complexes with amikacin and levofloxacin preserves secondar structure of protein. However, the formation of complex with amikacin leads to the almost total loss of the enzymatic activity of lysozyme and the redshift of the maximum on the lysozyme fluorescence band. A slight decrease in the distribution coefficient of lysozyme in the presence of amikacin assumes that the complex has higher hydrophilicity in comparison to lysozyme without additives. The most favorable for binding were the positions of the active centers that included amino acids Asp52 and Glu35, as well as in the vicinity of peptide His15-Arg21, with the participation of amino acids Tyr20, Arg14. In the case of levofloxacin, the formation of lysozyme-ligand complex in aqueous solution is possible without changing the microenvironment of the active center of the protein. Binding of levofloxacin to the active center of the enzyme was the most favorable, but Asp52 and Glu35 that are responsible for the enzymatic activity of lysozyme, were not affected.

Application of Sonotriboluminescence to Determine Arene Molecules in Hydrocarbons

The sonotriboluminescence of suspensions of terbium(III) and europium(III) sulfates in decane without and in the presence of benzene, toluene and p-xylene was studied. The choice of crystals of these lanthanides is due to the fact that they have intense luminescence during mechanical action, and also do not dissolve in hydrocarbon solvents. During ultrasonic exposure to suspensions in pure alkanes, bands of Ln3+ ions and N2 in the UV region are recorded in the luminescence spectrum. When aromatic hydrocarbon molecules are added, bands of benzene, toluene and p-xylene molecules, coinciding with their photoluminescence spectra, are recorded in the sonotriboluminescence spectra in the UV region. The high sensitivity of the luminescence of suspensions to arene additives made it possible to obtain the dependence of the characteristic fluorescence of arene molecules in the sonotriboluminescence spectra on their concentration in suspensions. The limits of detection of benzene, toluene and p-xylene in the composition of this suspension were established. The lower limits of detection from the sonotriboluminescence spectra for xylene, toluene and benzene are 0.1, 3 and 50 ppmv, respectively. Fluorescence bands of these molecules were also recorded in the sonotriboluminescence spectra of suspensions in commercial dodecane and heptane with additives of commercial gasoline (up to 1%). The results obtained can be used for luminescent detection of aromatic compounds in saturated hydrocarbons.

Synthesis, spectroscopy, band gap energy and electrical conductivity of poly(dopamine–co–aniline) copolymer

Copolymerization is used to improve the solubility and processability of polymers and copolymers includes the individual properties of homopolymer. In this study, the poly(dopamine-co-aniline) (poly(DA-co-ANI) copolymer was synthesized and the UV–vis. absorption, optical band gap energy, fluorescence, FT-IR, SEM-EDS, MALDI-TOF-MS, XRD and electrical conductivity have been investigated. The obtained results for the poly(DA-co-ANI) copolymer were compared with the PDA and PANI homopolymers. It was observed that the poly(DA-co-ANI copolymer is soluble easily in NMP and DMF solvents. The optical band gap energy of the poly(DA-co-ANI) copolymer film were calculated. as 1.00 eV with favorable indirect transition. The poly(DA-co-ANI) copolymer showed the FL emission maximum bands at 390 and 533 nm wavelengths. It was observed from the SEM images that the poly(DA-co-ANI) has 0–1500 nm crystalline rectangular particles prepared in acidic media and 0–600 nm amorphous particles prepared in basic media. The electrical conductivity of the poly(DA-co-ANI) was 1.35 × 10−6 S/cm. In the MALDI-TOF-MS measurements, the number-average molecular weight of the copolymer was found as 2628 Da with a distribution up to 5500 Da. The poly(DA-co-ANI) copolymer, soluble in NMP and DMF solvents and with a low optical band gap energy can be utilized as optical, fluorescent, and semi-conductive material in biomedical applications.

A new bodipy/pillar[5]arene functionalized magnetic sporopollenin for the detection of Cu(II) and Hg(II) ions in aqueous solution

In this study, a new bodipy/pillar[5]arene functionalized magnetic MS-Sp-P[5]-bodipy microcapsule sensor was prepared based on the use of environmentally friendly for the selective and sensitive detection of Cu(II) and Hg(II) ions in aqueous media. SEM results used in the characterization process of the materials synthesized at each stage confirmed the structural and morphological changes in the pore structure, while other characterization results (FT-IR and XRD) elucidated the role of pillar[5]arene compound and bodipy dye in the synthesis of magnetic microcapsule sensors. The colloidal solution of MS-Sp-P[5]-bodipy (water/ethanol)) showed two fluorescence bands centered at 402 and 540 nm. The detection limits of MS-Sp-P[5]-bodipy for Hg(II) and Cu(II) were calculated to be 0.06 µM and 2.27 µM, respectively (at 540 nm). The linear range of the magnetic sensor for Hg(II) and Cu(II) was found to be in the range of 1–150 µM and 10–150 µM, respectively. The experimental results (response time, pH, temperature, sensitivity and selectivity) demonstrated the applicability and potential of the prepared magnetic microcapsule sensor for the detection of Cu(II) and Hg(II) in water and tap water samples containing heavy metal ions.

Study of the behavior of the 4-DASPI dye in samples of silicate hydrogel by fluorescence spectroscopy and quantum chemistry

The behavior of the 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (4-DASPI) dye in samples of silicate hydrogel obtained from tetrakis(2-hydroxyethyl) orthosilicate with the dye added at the synthesis stage or adsorbed on a previously synthesized hydrogel substrate is studied by luminescence spectroscopy and molecular dynamics and quantum chemistry calculations. Small hypsochromic shifts of the fluorescence spectra of the dye upon its interaction with silica are observed. Energies of adsorption of 4-DASPI in the ground and excited state on two types of amorphous silica are calculated and contributions of Coulomb and dispersion interactions are estimated. A transition of the 4-DASP+ cation to the TICT state upon its excitation in water and methanol solutions is proved by TD DFT calculations. Partial twisting of the 4-DASP+ cation on silica, both in the pore and on the surface, is proposed based on the results of calculations and experimental measurements. The main difference between the samples synthesized with the introduction of 4-DASPI into the reaction mixture and by the gel synthesis followed by the adsorption of 4-DASPI seems to be capturing of the dye molecule in a pore in hydrogel with freezing molecular vibrations and rotations and, consequently, the growth of fluorescence intensity in the first case and the adsorption of the dye on the silica surface with relatively easy molecular vibrations and hindered rotations in the second case. This explains a strong difference in the intensities of fluorescence bands in the spectra of the studied samples.

Volumetric Temperature Mapping Using Light-Sheet Microscopy and Upconversion Fluorescence from Micro- and Nano-Rare Earth Composites.

We present a combination of light-sheet excitation and two-dimensional fluorescence intensity ratio (FIR) measurements as a simple and promising technique for three-dimensional temperature mapping. The feasibility of this approach is demonstrated with samples fabricated with sodium yttrium fluoride nanoparticles co-doped with rare-earth ytterbium and erbium ions (NaYF4:Yb3+/Er3+) incorporated into polydimethylsiloxane (PDMS) as a host material. In addition, we also evaluate the technique using lipid-coated NaYF4:Yb3+/Er3+ nanoparticles immersed in agar. The composite materials show upconverted (UC) fluorescence bands when excited by a 980 nm near-infrared laser light-sheet. Using a single CMOS camera and a pair of interferometric optical filters to specifically image the two thermally-coupled bands (at 525 and 550 nm), the two-dimensional FIR and, hence, the temperature map can be readily obtained. The proposed method can take optically sectioned (confocal-like) images with good optical resolution over relatively large samples (up to the millimetric scale) for further 3D temperature reconstruction.

Establishment of Thin Layer Chromatographic Fingerprints for the Quality Control of Chanthalila Preparation, A Thai Traditional Antipyretic Medicine

Objective: This study aimed to develop thin layer chromatographic (TLC) fingerprints to control the quality of Chanthalila preparation (CP).Material and Methods: Twelve batches of reference CP were prepared from various sources and used as reference batches (CP1 to CP12). Artemisinin, atractylodin, eurycomanone, imperatorin and loureirin A were used as markers. The common and characteristic bands were assigned using the reference TLC fingerprints and applied to assess the qualitative parameters used in the identification and chemical profiling of eight commercial CPs.Results: The reference TLC fingerprints were established on a silica gel GF254 plate with two mobile phase systems, System A and System B. In System A, atractylodin, imperatorin, and loureirin A were assigned as characteristic bands along with 10-12 common bands under Ultraviolet (UV) 254 nm, UV 366 nanometer (nm), and derivatization. In System B, 6 common bands were observed under UV 254 nm, while 11 fluorescent bands were detected under UV 366 nm. Eurycomanone and artemisinin were not found in any reference CP batches, which revealed the TLC method had poor sensitivity. The TLC patterns of commercial CPs were markedly different from those of the reference fingerprints. Most commercial products failed to meet the specification criteria because only imperatorin appeared in the chromatogram.Conclusion: TLC fingerprinting is a fast and efficient method that can be employed in the quality control of CP. It enables the revelation of the quality of the raw materials in the chromatograms, which can be useful to manufacturers to evaluate their supplier sources. However, the sensitivity of this method for determining some markers was quite low.