Fluorescence Spectral Properties Research Articles

Fluorescence Study of the Interactions Between Insulin Amyloid Fibrils and Proteins

Self-assembly of proteins and peptides into amyloid fibrils is the subject of intense research due to association of this process with multiple human disorders. Despite considerable progress in understanding the nature of amyloid cytotoxicity, the role of cellular components, in particular proteins, in the cytotoxic action of amyloid aggregates is still poorly investigated. The present study was focused on exploring the fibril-protein interactions between the insulin amyloid fibrils and several proteins differing in their structure and physicochemical properties. To this end, the fluorescence spectral properties of the amyloid-sensitive fluorescent phosphonium dye TDV have been measured in the insulin fibrils (InsF) and their mixtures with serum albumin (SA) in its native solution state, lysozyme (Lz) and insulin (Ins) partially unfolded at low pH. It was found that the binding of TDV to the insulin amyloid fibrils is followed by considerable increase of the fluorescence intensity. In the system (InsF + TDV) the TDV fluorescence spectra were decomposed into three spectral components centered at ~ 572 nm, 608 nm and 649 nm. The addition of SA, Lz or Ins to the mixture (InsF + TDV) resulted in the changes of the fluorescence intensity, the maximum position and relative contributions (f1,3) of the first and third spectral components into the overall spectra. The Förster resonance energy transfer between the TDV as a donor and a squaraine dye SQ1 as an acceptor was used to gain further insights into the interaction between the insulin amyloid fibrils and proteins. It was found that the presence of SA do not change the FRET efficiency compared with control system (InsF + chromophores), while the addition of Lz and Ins resulted in the FRET efficiency decrease. The changes in the TDV fluorescence response in the protein-fibril systems were attributed to the probe redistribution between the binding sites located at InsF, the non-fibrillized Ins, SA or Lz and protein-protein interface

Interactions of Novel Phosphonium Dye with Lipid Bilayers: A Fluorescence Study

The phosphonium-based optical probes attract ever growing interest due to their excellent chemical and photophysical stability, high aqueous solubility, long wavelength absorption and emission, large extinction coefficient, high fluorescence quantum yield, low cytotoxicity, etc. The present study was focused on assessing the ability of the novel phosphonium dye TDV to monitor the changes in physicochemical properties of the model lipid membranes. To this end, the fluorescence spectral properties of TDV have been explored in lipid bilayers composed of zwitterionic lipid phosphatidylcholine (PC) and its mixtures with cholesterol (Chol) or/and anionic phospholipid cardiolipin (CL). It was observed that in the buffer solution TDV possesses one well-defined fluorescence peak with the emission maximum at 533 nm. The dye transfer from the aqueous to lipid phase was followed by the enhancement of the fluorescence intensity coupled with a red shift of the emission maximum up to 67 nm, depending on the liposome composition. The quantitative information about the dye partitioning into lipid phase of the model membranes was obtained through approximating the experimental dependencies of the fluorescence intensity increase vs lipid concentration by the partition model. Analysis of the partition coefficients showed that TDV has a rather high lipid-associating ability and displays sensitivity to the changes in physicochemical properties of the model lipid membranes. The addition of CL, Chol or both lipids to the PC bilayer gives rise to the increase of the TDV partition coefficients compared to the neat PC membranes. The enhancement of the phosphonium dye partitioning in the CL and Chol-containing lipid bilayers has been attributed to the cardiolopin- and cholesterol-induced changes in the structure and physicochemical characteristics of the polar membrane region.

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions.

A novel hemicucurbituril-based macrocycle, alternately consisting of amidobenzene and 2-imidazolidione moieties was designed and synthesized. Based on the fragment coupling strategy, nitrobenzene-containing hemicucurbituril was firstly prepared facilely under alkaline environment, and reduction of the nitro groups produced the desired amidobenzene-containing hemicucurbituril. As an original fluorescent chemosensor, it exhibited strong interactions with Fe3+ over other metal cations. The experimental evidence of fluorescence spectra suggested that a 1:1 complex was formed between this macrocycle and Fe3+ with an association constant up to (2.1 ± 0.3) × 104 M−1. Meanwhile, this macrocycle showed no obvious or only slight enhancement of the fluorescence intensity with selected anions.

Changes in Spectral Fluorescence Properties of a Near-Infrared Photosensitizer in a Nanoform as a Coating of an Optical Fiber Neuroport

In this work, we tested a new approach to assess the presence of inflammatory process in the implant area using spectral methods and the technique of fiber fluorescence analysis of photosensitizers in nanoform. First of all, the spectral characteristics of the photosensitizer when interacting with the porous surface of the implant, based on hydroxyapatite under in vitro and in vivo conditions, were determined. Thus, it was shown that spectral characteristics of photosensitizers can be used for judgement on the process of inflammation in the implant area and thus on the local presence of the immunocompetent cells. The analysis was performed at a sufficient depth in the biotissue by using the near-infrared spectral region, as well as two different methods: fiber-based laser spectroscopy and fiber-optic neuroscopy, which served to monitor the process and regular fluorescence diagnosis of the studied area. Fluorescence spectroscopic analysis was performed on experimental animals in vivo, i.e., under conditions of active immune system intervention, as well as on cell cultures in vitro in order to judge the role of the immune system in the interaction with the implant in comparison. Thus, the aim of the study was to determine the relationship between the fluorescence signal of nanophotosensitizers in the near infrared spectral region and its parameters with the level of inflammation and the type of surface with which the photosensitizer interacts in the implant area. Thus, fiber-optic control opens up new approaches for further diagnosis and therapy in the implant area, making immune cells a prime target for advanced therapies.

Spectral and Nonlinear Properties of Coconut Oil

In this research, the spectral properties of Absorption and Fluorescence of synthetic coconut oil (Local made) have been studied. It was found that the efficiency of coconut oil equal to (3.276%). In addition, non-linear optical properties represented by the refractive index (n2) and absorption coefficient(β) have been calculatal using three –dimensioual scanning technigue (z-scan and Helium Neom laser. Refractive inex (n2=4.231×10-7 cm2/mW) and absorption coefficient (β= 0.72373 cm/mW) have been measured from Closed-aperture part and Open-aperture part, respectively. Coconut oil has non-linear properties, where it can be utilize in nonlinear spectral applications, especially in the study the living tissue through its application and its treatment with laser.

Fluorescence and Photoacoustic Spectroscopy-Based Assessment of Mitochondrial Dysfunction in Oral Cancer Together with Machine Learning: A Pilot Study.

The current study reports an integrated approach of machine learning and tryptophan fluorescence and photoacoustic spectral properties to assess the mitochondrial status under oral pathological conditions. The mitochondria in the study were isolated from oral cancer tissues and adjacent normal counterparts, and the corresponding fluorescence and photoacoustic spectra of tryptophan were recorded at 281 nm pulsed laser excitations. A set of features were selected from the pre-processed spectra and were used to classify the data using support vector machine (SVM) learning in the MATLAB platform. SVM analysis demonstrated clear differentiation between mitochondria isolated from normal and cancer tissues for fluorescence (sensitivity, 86.6%; specificity, 90%) and photoacoustic (sensitivity, 86.6%; specificity, 96.6%) measurements. Further investigation into the influence of change in protein conformation on the nature of tryptophan spectral properties was evaluated by 8-anilino-1-naphthalene sulfonic acid (ANS) fluorescence assay. The impact of protein structural changes on the mitochondrial functions was also estimated by mitochondrial membrane potential (MMP), reactive oxygen species (ROS), and cytochrome c oxidase (COX) assays, suggesting an altered mitochondrial function. The findings indicate that tryptophan fluorescence and photoacoustic spectral properties together with machine learning algorithms may delineate the mitochondrial functional status in vitro, indicating its translational potential.

Enhancement of fluorescence of single quantum dots by encasing in semiconductor and metal nanoparticles

Quantum dots (QDs) are widely investigated in the field of optoelectronics due to their various unique spectral and excellent fluorescence properties. However, QDs suffer from intermittent fluorescence, also known as blinking, that limits their use in optoelectronic devices. The blinking mechanism can be suppressed by numerous processes, and one such process includes the interaction of the QDs with semiconductor nanoparticles (NPs) such as indium tin oxide (ITO) and titanium dioxide (TiO2). By encapsulating the QDs in these NPs, the blinking rate is significantly reduced due to the electron transfer pathway between them. The interaction of QDs with metal NPs such as silver (Ag) and gold (Au) also greatly enhances the fluorescence behavior due to energy transfer and plasmonic effects. This work deals with the electron transfer model that analyzes the effect of radiative recombination, non-radiative recombination, and electron transfer between QDs and the NPs. An analysis of the on and off states for QDs under the influence of considered NPs has also been done. The on and off time for QDs have also been studied, which provide a comprehensive framework of the performance of the QDs interfaced with these NPs. A comparison between the QDs interacting with glass and other semiconductor and metal NPs is also drawn to compare the efficacy of QDs under the influence of different NPs. This analysis postulates the physical mechanism for blinking and ways to curb these mechanisms using the semiconductor and metal NPs. The theoretical study demonstrates the quantitative insights and prerequisites for designing QD-based optoelectronic devices.

Optical Properties of Water for Prediction of Wastewater Contamination, Human-Associated Bacteria, and Fecal Indicator Bacteria in Surface Water at Three Watershed Scales.

Relations between spectral absorbance and fluorescence properties of water and human-associated and fecal indicator bacteria were developed for facilitating field sensor applications to estimate wastewater contamination in waterways. Leaking wastewater conveyance infrastructure commonly contaminates receiving waters. Methods to quantify such contamination can be time consuming, expensive, and often nonspecific. Human-associated bacteria are wastewater specific but require discrete sampling and laboratory analyses, introducing latency. Human sewage has fluorescence and absorbance properties different than those of natural waters. To assist real-time field sensor development, this study investigated optical properties for use as surrogates for human-associated bacteria to estimate wastewater prevalence in environmental waters. Three spatial scales were studied: Eight watershed-scale sites, five subwatershed-scale sites, and 213 storm sewers and open channels within three small watersheds (small-scale sites) were sampled (996 total samples) for optical properties, human-associated bacteria, fecal indicator bacteria, and, for selected samples, human viruses. Regression analysis indicated that bacteria concentrations could be estimated by optical properties used in existing field sensors for watershed and subwatershed scales. Human virus occurrence increased with modeled human-associated bacteria concentration, providing confidence in these regressions as surrogates for wastewater contamination. Adequate regressions were not found for small-scale sites to reliably estimate bacteria concentrations likely due to inconsistent local sanitary sewer inputs.

Influence of progressive halogenation of Zn(II)-tetraarylporphyrins and their free bases on the structure and spectral-fluorescence properties of tetrapyrrolic macrocycle

Zn(II)-2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetra-(2,6-difluorophenyl)porphyrin was synthesized by the interaction of Zn(II)-5,10,15,20-tetra-(2,6-difluorophenyl)porphyrin with N-bromosuccinimide in a mixture of chloroform-methanol, chloroform-dimethylformamide and in dimethylformamide. Zn(II)-2,3,7,8,12,13,17,18-octachloro-5,10,15,20-tetra-(2,6-difluorophenyl)porphyrin was formed by the reaction of 2,6-difluoro-substituted Zn(II)-porphyrin with N-chlorosuccinimide in the chloroform-methanol mixture and dimethylformamide. Zn(II)-2,3,7,8,12,13,17,18-octachloro-5,10,15,20-tetra-(2,3,4,5,6-pentafluorophenyl) porphyrin was synthesized from Zn(II)-5,10,15,20-tetra-(2,3,4,5,6-pentafluorophenyl)porphyrin with an excess of N-chlorosuccinimide via chlorination in dimethylformamide. The corresponding porphyrin-ligands were obtained by treating halogen-substituted zinc porphyrins with trifluoroacetic acid. The synthesized compounds were characterized by UV–Vis, fluorescence, 1H NMR spectroscopy and mass spectrometry methods. The structures of halogen-substituted porphyrins and their Zn(II) complexes were calculated by the DFT method. The effect of the β-pyrrole halogenation on fluorescence quantum yields of the synthesized compounds was estimated. These halogenated products can be employed for covalent functionalization of the macrocycle pyrrole fragments with the aim of imparting practically important optical, electrochemical and red-ox properties to them.

Two-photon excitation fluorescent spectral and decay properties of retrograde neuronal tracer Fluoro-Gold

Fluoro-Gold is a fluorescent neuronal tracer suitable for targeted deep imaging of the nervous system. Widefield fluorescence microscopy enables visualization of Fluoro-Gold, but lacks depth discrimination. Though scanning laser confocal microscopy yields volumetric data, imaging depth is limited, and optimal single-photon excitation of Fluoro-Gold requires an unconventional ultraviolet excitation line. Two-photon excitation microscopy employs ultrafast pulsed infrared lasers to image fluorophores at high-resolution at unparalleled depths in opaque tissue. Deep imaging of Fluoro-Gold-labeled neurons carries potential to advance understanding of the central and peripheral nervous systems, yet its two-photon spectral and temporal properties remain uncharacterized. Herein, we report the two-photon excitation spectrum of Fluoro-Gold between 720 and 990 nm, and its fluorescence decay rate in aqueous solution and murine brainstem tissue. We demonstrate unprecedented imaging depth of whole-mounted murine brainstem via two-photon excitation microscopy of Fluoro-Gold labeled facial motor nuclei. Optimal two-photon excitation of Fluoro-Gold within microscope tuning range occurred at 720 nm, while maximum lifetime contrast was observed at 760 nm with mean fluorescence lifetime of 1.4 ns. Whole-mount brainstem explants were readily imaged to depths in excess of 450 µm via immersion in refractive-index matching solution.

Fluorescence Spectral Properties of Methyl Orange in Homogeneous Media.

The methyl orange [C14H14N3SO3Na], an azo dye exhibited strong emission and large Stokes shift in various solvents, and the largest shift (Δλ = 125.51nm or Δν = 9297cm-1) was obtained in the water. The UV-visible spectra of the dye showed the absorption in the range (33,333 - 20,000) cm-1. We found that solvent effects on the absorption wavelength are consistent. The bathochromic shift in water and the hypsochromic shift in methanol observed in the absorption (43 nm) as well as in the fluorescence (42 nm) spectra predict the strong solute-solvent interaction. The fluorescence quantum yield (ɸf) was decreased from 24% in DMSO to 5% in water. The fluorescent properties of this dye are strongly solvent dependent, the wavelength of minimum fluorescence emission (λem = 435.51nm) shifts to the red. The maximum and minimum calculated oscillator strength is 32% with (Ɛmax = 29011 M-1cm-1) and 11% (Ɛmax = 6682 M-1cm-1) in methanol and DMSO, respectively. Protonated solvents without exception give a shorter lifetime and lower quantum yield. The average excited-state lifetime of the dye was found maximum (τav = 5.36 ns) in DMSO. Also, fluorescence lifetime was combined to deduce the radiative and non-radiative decay rate.

Synthesis, solvatochromism and dipole moment in the ground and excited states of substitute phenol derivative fluorescent Schiff base compounds

Three new fluorescent o-hydroxyaryl Schiff base derivatives are synthesized and their structures are characterized by NMR and FTIR spectroscopies. In this study, the solvent effect on the absorption and fluorescence spectral properties, Catalán and Taft-Kamlet solvatochromism models, and electric dipole moments in the ground and excited states, are investigated for synthesized compounds. Specific and non-specific solute–solvent interactions are investigated using Catalán and Taft-Kamlet solvatochromism models in various solvents with different polarities. Taft-Kamlet and Catalán solvatochromism models derived for absorption spectra indicate that solvent dipolarity/polarizability (π*) and solvent polarity (SP) are dominant in controlling absorption spectral shifts. As a result of solute–solvent interactions, absorption spectra exhibit positive solvatochromism, while fluorescence spectra show negative solvatochromism with the increase of solvent polarity. The ground state dipole moment is determined using the Bilot–Kawski method, and the excited state dipole moment is calculated using the Bilot–Kawski, Lippert–Mataga, Bakhshiev, modified Bilot-Kawski and Reichardt correlation methods. The dipole moments estimated in both ground and excited states confirm that Schiff base compounds are more polar in the excited state. The frontier molecular orbitals (HOMO and LUMO), molecular electrostatic potential (MEP), density of states (DOS) and solvent accessibility surfaces (SAS) of these compounds have been calculated using the DFT/B3LYP/6-311++G(d,p) level of theory.

Photonics of meso-substituted carbocyanine dyes in solutions and in complexes with DNA

Spectral-fluorescent and photochemical properties (photoisomerization and generation of the triplet state) of meso-substituted cationic carbocyanine dyes, 3,3′-di-(β-hydroxyethyl)-5,5′-dimethoxy-9-ethylthiacarbocyanine iodide (K1) and 3,3′-di-(β-hydroxyethyl)-9-methylthiacarbocyanine iodide (K2), have been studied in solutions and in the presence of DNA. In solutions, on passing from acetonitrile to dioxane, a growth of fluorescence of the dyes is observed due to a shift of the equilibrium of cis/trans isomers toward the fluorescent trans-isomer. Upon flash photolysis of dye solutions in dioxane, the formation and subsequent decay of the cis-photoisomers of the dyes are observed.In aqueous solutions, the interaction with DNA leads to the formation of noncovalent complexes of K1 and K2 with DNA, which is accompanied by a significant increase in the fluorescence intensity. The results of the molecular docking experiments showed the possibility of several types of binding, which was confirmed by the data obtained from other experiments. The effects of temperature and additions of NaCl on the stability of the dye–DNA complexes were studied. The spectral-fluorescent data were used to estimate the binding constants of the dyes with DNA and other characteristics of the dyes that are important for their use as probes.Upon flash photolysis of the dyes in complexes with DNA, photoisomerization is not observed, but the quantum yield of intersystem crossing to the triplet state increases. The decay of the triplet states occurs by a two-exponential law. The rate constants for quenching of the triplet states of the dyes complexed with DNA by oxygen were found to be lower than the expected values for diffusion-controlled quenching (taking into account the spin statistical factor 1/9), which is explained by the steric factor of complexation.

A comparative investigation of the interaction and pharmacokinetics of hemoglobin with berberine and its oxymetabolite

Berberine (BBR), isolated from Coptis chinensis, is one type of isoquinoline alkaloids. BBR exerts numerous of bioactivities but the plasma concentration is really low. In our previous study, a new oxymetabolite (OBB) has been discovered and showed superior anti-inflammatory effect comparing with BBR. The aim of this study is to investigate the interaction, metabolite and pharmacokinetics of BBR with hemoglobin. Sprague-Dawley rats were used to carry out the interaction, metabolite and pharmacokinetics of BBR and OBB in vivo. Fluorescence spectra were used to analyse the interaction in vitro. Results showed that OBB could be generated after intravenous injection or incubating with BBR in vitro and in vivo; Both BBR and OBB exerted much stronger binding interaction with hemoglobin than plasma and affect the conformation of bovine hemoglobin and change the fluorescence spectral properties; BBR and OBB were mainly presented and transported in the proteins-bound form. These results provide a new insight to understand the dynamic equilibrium of BBR and OBB within body from the perspective of new metabolic pathways.

A Selective Ratiometric Receptor 2-((E)-(3-(prop-1-en-2-yl)phenylimino)methyl)-4-nitrophenol for the Detection of Cu2+ions Supported By DFT Studies.

A Schiff-base 2-((E)-(3-(prop-1-en-2-yl)phenylimino)methyl)-4-nitrophenol (Receptor 1) colorimetric probe was synthesized and its UV-visible and fluorescence spectral properties for the sensing of Cu+ 2 ions inCH3OH/H2O (60:40,v/v) solvent system was explored. The Receptor 1 showed the discriminating spectral behavior with the addition of Cu2+ ions solution. The other metal ions showed no significant effect towards Receptor 1. Moreover, the addition of Cu2+ions to the Receptor 1 demonstrated the shift in the peak towards longer wavelength of 405 nm due to the ligand to metal charge transfer (LMCT) effect. The red-shift and new peak at 405nm are due to the deprotonation of the -OH group and formation of complex and O-Cu covalent bond,respectively. A slight increase in the Cu2+ion concentration exhibited strong absorption and fluorescence properties, leading to the spontaneous change in color from pale yellow to orange. Additionally, Density Functional Theory (DFT) studies were performed to investigate the interaction of Cu2+ ions with Receptor 1. The decrease in the energies (3.59062 kcal/mol to 0.36028 kcal/mol) of Cu2+-Receptor-1 complex compared to Receptor 1 confirms the strong interaction with high stability. The association constant (Ka) ofCu2+-Receptor-1 complex was found as 175000M- 1.The limit of detection (LOD) was calculated and noted as 179 nM.

Hydrophilic meso-substituted cyanine dyes in solution and in complexes with serum albumins: spectral properties and molecular docking study

The absorption and fluorescence spectral properties of three meso-substituted hydrophilic thiacarbocyanine dyes were studied in solutions and in noncovalent complexes with human and bovine serum albumins (HSA and BSA, respectively). The presence of alkyl substituents at the meso-position of the polymethine chain of the dyes determines the occurrence of a cis–trans equilibrium. Dyes form aggregates in aqueous media; the effect of electrolyte (NaCl) on aggregation has been studied. The interaction of the dyes with albumins leads to the decomposition of the aggregates and is accompanied by a shift in the isomeric equilibrium. Complexation with HSA leads to accumulation of dye monomers in the trans-form. However, in the case of BSA the cis-to-trans isomeric shift is incomplete. Using the fluorescence data, the effective binding constants of the trans-isomers with albumins (Ka) and the detection limits of albumin molecules (LD and LQ) were determined. The data obtained are indicative of high selectivity of some dyes to HSA compared to BSA. The results of molecular docking experiments correspond to the data obtained from the spectra. The influence of the dyes on intrinsic fluorescence of HSA and BSA was also studied, and fluorescence quenching, static in nature, was detected.

Detection and identification of polyaromatic hydrocarbons (PAHs) contamination in soil using intrinsic fluorescence.

Polyaromatic hydrocarbons (PAHs), such as pyrene, benzo[a]pyrene, phenanthrene, and anthracene induce toxic, carcinogenic, and mutagenic effects on living organisms and are considered as primary pollutants. Traditional methods for their identification are often laborious and time-consuming and do not account for the heterogeneous nature of their distribution. Here we present confocal microscopy as a rapid and accurate technique for direct analysis of PAHs in soil samples without the complexity of sample pre-processing which might delay results for several days. The method uses the intrinsic fluorescence of PAHs for detection and their emission spectra for the identification of different PAHs. A clear difference was observed in the fluorescence spectral properties of phenanthrene, pyrene and naphthalene in real-time environmental samples. The post-processing of confocal scans obtained in the detection stage of PAHs was completed through the application of ImageJ software. Intrinsic fluorescence-based detections of PAHs may open new avenues in terms of rapid detection and identification of PAHs in heterogeneous complex soil samples.

Effect of donor and acceptor end-groups on electronic structure and spectral-fluorescent properties of merocyanines in frozen ethanol

UV–vis absorption and fluorescence spectra of a series of merocyanines with varying heterocyclic donor and carbonyl-comprising acceptor groups have been studied in frozen ethanol at 77 K. Due to a greater polarity of a frozen solvent matrix in comparison with the liquid solvent, the electronic structure of donor–π–acceptor molecules in the former becomes much more dipolar. The resulting spectral effects depend on the donor–acceptor abilities of the terminal groups. In the case of positively solvatochromic indole-based dyes comprising the 1,3-indandione or barbituric acceptors, going from 293 to 77 K results in a narrowing and bathochromic shifts of absorption bands. Vice versa, for more dipolar reversely and negatively solvatochromic merocyanines comprising the thiobarbituric acceptor-group, the solvent freezing leads to a broadening and hypsochromic shifts of the absorption bands, which is very unique, taking into account that the solute vibrations/rotations should decrease in a frozen solvent. In all cases, the fluorescence bands are shifted hypsochromically at cryo-temperature and are closely mirror-like to the absorption ones, which, along with the smaller Stokes shifts, has been explained by the inhibited solvent rearrangement in the frozen matrix, resulting in a greater similarity of the ground state S0 and the fluorescent excited state S1. The deductions about the electronic structure of the studied dyes in the ground and excited states and its dependence on the donor–acceptor properties of the end-groups correlate well with the results of the PCM/(TD)-DFT calculations performed within the four-level diagram of electronic transitions.

3D spectral fluorescence signature of cerium(III)-melamine coordination polymer: A novel sensing material for explosive detection.

Hidden or buried explosives are the most common scenario by terrorist attacks; therefore explosive vapour detection is a vital demand. Explosives are electron deficient materials; the vicinity of explosives to fluorescent material can encounter electron migration. This study reports on facile synthesis of cerium (III)-melamine coordination polymer (CeM-CP) with exclusive optical properties. CeM-CP demonstrated novel spectral fluorescence properties over visible and infrared bands when stimulated with UVA LED source at 385nm of 100mW power. Stimulated CeM-CP demonstrated unique spectral fluorescence signal at 400, 700, and 785nm. These fluorescent signals were correlated to cerium coordination with four nitrogen atoms; vacant orbital will be available for electron excitation migration. Spectral fluorescent signals were quenched as CeM-CP was subjected to TNT vapours. Hyperspectral imaging offered 3D plot of fluorescence signature. The main outcome is that complete fluorescence signal attenuation was achieved at 785nm. CeM-CP could act as as a novel sensing element for explosive vapour detection.

Multicolor conjugated polymers containing thiophene/indole moieties and the influence of structures on their photophysical properties

A series of new monomers (M1~M6) containing both thiophene and indole structures and carrying different substituents with varied electronic effects on the 2,3-position of indole have been designed and synthesized. The corresponding conjugated polymers (P1~P6) obtained via oxidative polymerization presented different spectral phenomena and fluorescence properties as well as fluorescence lifetime due to the synergistic influence of varied electronic effects, the interaction between polymer chains and π-π stacking of indole moieties. By adjusting the properties of substituents and their position in indole ring, these as-prepared conjugated polymers can emit fluorescence with varied colors such as blue-green, yellow, orange-red, brown red, light red and red, and show the changes of fluorescence intensity in different degrees with the increase of 365 nm UV irradiation time. Among them, P3 and P5 show much stronger fluorescence than other species, which is very desirable for application.