Synthesis of New Near-infrared Fluorescent Dyes

A new near-infrared fluorescent dye, 9-N-(2-hydroxyethyl)-N-methylamino-6-carbethoxy-5H-benzo[a]phenoxazin-5-one 1, was prepared from the reaction of N-(2-hydroxyethyl)-N-methyl-4-nitrosoaniline hydrochloride and ethyl 1,3-dihydroxynaphthoate. Five more fluorescent compounds were synthesized by the reaction of the resulting dye 1 with appropriate amino acid or carboxylic acids.

Syntheses of Some Organic Fluorescent Dyes for Security Tickers

Five organic fluorescence dyes were synthesized by two- or three-step reactions. These synthetic methods have an advantage of the simple processes, low costs and high yields. The compositions of the five compounds are characterized by IR, 1H NMR, elemental analyses and fluorescence spectroscopies. The quantum yields of fluorescence were measured.

Novel Water Soluble Fluorescent Trimethine Indocyanines Containing N-ρ-Carboxybenzyl Group

Two fluorescent indocyanine dyes containing at least one p-carboxybenzyl group on the nitrogen atoms in the heterocyclic rings were designed and synthesized. Their absorption maxima were 549 nm and 551 nm in water respectively. They had good water solubility and photostability.

Enhancement of electroluminescent properties of organic optoelectronic integrated device by doping phosphorescent dye

Organic optoelectronic integrated devices（OIDs） with ultraviolet（UV） photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence（TADF） material 4, 5-bis（carbazol-9-yl）-1, 2-dicyanobenzene（2 CzPN） as host. The OIDs doping with typical red phosphorescent dye [tris（1-phenylisoquinoline）iridium（Ⅲ）, Ir（piq）3], orange phosphorescent dye {bis[2-（4-tertbutylphenyl）benzothiazolato-N,C-（2＇）]iridium（acetylacetonate）,（tbt）2 Ir（acac）}, and blue phosphorescent dye [bis（2, 4-di-fluorophenylpyridinato）-tetrakis（1-pyrazolyl）borate iridium（Ⅲ）, FIr6] were investigated and compared. The（tbt）2 Ir（acac）-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the（tbt）2 Ir（acac）-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m^2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10^11 Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.

SUPPRESSION OF SIDELOBES IN SINGLE-PHOTON 4PI CONFOCAL MICROSCOPY BY FORSTER RESONANT ENERGY TRANSFER

Recently,we theoretically demonstrate that utilization of silica nanobeads co-doped with Cy3 and Cy5 molecules instead of single dye molecules asfluorescent labels can enable optical resolutions far beyond the diffraction-limit.Here,we show that by combining the 4Pi microscopy and the novelfluorescent label,it is possible to completely suppress the sidelobes in 4Pi focal spot and significantly enhance the optical resolution in the axial direction.

Green Light-Emitting Organic Electroluminescent Device with a New Fluorescent Dye Dispersed in Poly(N-vinylcarbazole) Emitter Layer

Double-layer organic electroluminescent devices have been constructed. A new fluorescent dye, 9,10-bis(phenylethynyl)anthracence, was chosen as the dopant which was molecularly dispersed in the polymer film, and green light was observed from the device with luminance of 130cd/m(2) at 17V.

What have we known so far for fluorescence staining and quantification of microplastics:A tutorial review

Understanding the fate and toxicity of microplastics(MPs,<5 mm plastic particles)is limited by quantification methods.This paper summarizes the methods in use and presents new ones.First,sampling and pretreatment processes ofMPs,including sample collection,digestion,density separation,and quality control are reviewed.Then the promising and convenient staining procedures and quantification methods for MPs using fluorescence dyes are reviewed.The factors that influence the staining of MPs,including their physicochemical properties,are summarized to provide an optimal operation procedure.In general,the digestion step is crucial to eliminate natural organic matter(NOM)to avoid interference in quantification.Chloroform was reported to be the most appropriate solvent,and 10–20μg/mL are recommended as optimal dye concentrations.In addition,a heating and cooling procedure is recommended to maintain the fluorescence intensity of MPs for two months.After staining,a fluorescence microscope is usually used to characterize the morphology,mass,or number of MPs,but compositional analysis cannot be determined with it.These fluorescence staining methods have been implemented to study MP abundance,transport,and toxicity and have been combined with other chemical characterization techniques,such as Fourier transform infrared spectroscopy and Raman spectroscopy.More studies are needed to focus on the synthesis of novel dyes to avoid NOM’s interference.They need to be combined with other spectroscopic techniques to characterize plastic composition and to develop image-analysis methods.The stability of stained MPs needs to be improved.

Upconversion nanoparticles for differential imaging of plant cells and detection of fluorescent dyes

Upconversion NaLuF4 nanoparticles were synthesized by the solvothermal method which could emit multicolor visible light under the excitation of 980 nm near-infrared (NIR) photons. These upconversion nanoparticles (UCNPs) with an acidic ligand could rapidly capture the basic rhodamine-B (RB) in plant cells to generate a close UCNPs@RB system. RB could efficiently absorb the green fluorescence from NaLuF4:18 mol.%Yb3+,2 mol.%Er3+ UCNPs and then emitted red light in the UCNPs@RB system by a robust luminescence resonance energy transfer (LRET) from UCNPs to RB. The detection limit of RB with these upconversion fluo-rescent nanoprobes could reach 0.25μg/cm3 in plant cell even under an ultra low excitation power source of 0.2 W/mm2. This LRET phenomenon was also extended to NaLuF4:18 mol.%Yb3+,0.5 mol.%Tm3+@Sodium fluorescein (SF) system. In addition, the differ-ential imaging could be achieved by successively incubating plant cells with fluorescent dyes and UCNPs. The fluorescent dyes ag-gregated in cell wall while UCNPs with surface modification distributed both in cell wall and cytoplasm, so that UCNPs@Dyes formed in cell walls which could emit multicolor light by LRET which was different from the emission in cytoplasm with only UCNPs.

Better understanding of the activated sludge process combining fluorescence-based methods and flow cytometry:A case study

This study aims to demonstrate the validity of fluorescence-based methods,together with flow cytometry,as a complementary tool to conventional physicochemical analyses carried out in wastewater treatment plants(WWTPs),for the control of the currently largely unknown activated sludge process.Staining with SYTO 9,propidium iodide and 5-(and 6)-carboxy-2’,7’-difluorodihydrofluorescein diacetate(carboxy-H2 DFFDA)was used for cell viability and oxidative stress monitoring of the bacterial population forming the activated sludge of a WWTP.Throughout the period of research,several unstable periods were detected,where the non-viable bacteria exceeded the 75%of the total bacterial population in the activated sludge,but only in one case the cells with oxidative stress grew to 9%,exceeding the typical values of2%-5%of this plant.These periods coincided in two cases with high values of total suspended solids(SST)and chemical oxygen demand(COD)in the effluent,and with an excess of ammonia in other case.A correlation between flow cytometric and physicochemical data was found,which enabled to clarify the possible origin of each case of instability in the biological system.This experience supports the application of bacterial fluorescence staining,together with flow cytometric analysis,as a simple,rapid and reliable tool for the control and better understanding of the bacteria dynamics in a biological wastewater treatment process.

Synthesis, properties and application of novel 5,6,5,6-tetracyclic pyrazine/pyrrole-fused unsymmetric bis（BF2） fluorescent dyes:BOPYPYs

Novel 5,6,5,6-tetracyclic pyrazine/pyrrole-fused unsymmetric bis(BF2) fluorescent dyes(BOPYPYs) were obtained by reaction of pyrrole-2-carboxaldehyde with 1-(pyrazin-2-yl)hydrazine in the presence of Et3 N-BF3·Et2 O for the first time.The absorption maxima of pyrazine-fused BOPYPY are obviously bathochromic shifts,in contrast to those of the reported BOPPY,indicating that the discrepant substitute groups between pyridine and pyrazine result in the remarkable wavelength difference.The new series of BO PYPYs possess high molar extinction coefficients,high fluorescence quantum yields,and larger Stokes shifts.A Knoevenagel reaction of BOPYPY with 4-dimethylaminobenzaldehyde smoothly produced the dye with the extension of π-conjugation.Dimethylamino-containing BOPYPY as a pH-responsive fluorescent sensor could detect pH value.

Synthesis and application of Vis/NIR dialkylaminophenylbuta-1,3-dienyl borondipyrromethene dyes

Mono- and bis-dialkylaminophenylbuta-l,3-dienyl boron-dipyrromethenes （BODIPYs） 1-12 were synthesized in 36%-42% yields by a Knoevenagel-type condensation. The absorption and emission maxima （λabs = 614-739 rim; ,λem = 655-776 nm in CHCI3） of 1-12 covered from the visible to the near- infrared region. Probe I was ratiometric Vis pH probes. Such probe was almost non-fluorescent. Upon the protonation of the tertiary amine function of 1, the strong fluorescence （φf =0.97） was released and the florescence intensity was dramatically increased by one thousand folds. The sharp isosbestic points were discovered at 590 nm, which was a ratiometric pH probe.

Monitoring Xylem Transport in the Stem of Lilium lancifolium Using Fluorescent Dye 5(6)-Carboxyfluorescein Diacetate

The xylem undergoes physiological changes in response to various environmental conditions during the process of plant growth.To understand these physiological changes,it is extremely important to observe the transport of xylem.In this study,the distribution and structure of vascular bundle in Lilium lancifolium were observed using the method of semithin section.Methods for introducing a fluorescent tracer into the xylem of the stems were evaluated.Then,the transport rule of 5(6)-Carboxyfluorescein diacetate(CFDA)in the xylem of the stem of L.lancifolium was studied by fluorescence dye in live cells tracer technology.The results showed that the vascular bundles of L.lancifolium were scattered in the basic tissue,the peripheral vascular bundles were smaller and densely distributed,and the closer to the center,the larger the volume of vascular bundles and the more sparsely distributed.The vascular bundles of L.lancifolium are limited external tenacity vascular bundles,which are composed of phloem and xylem.The most suitable method for CFDA labeling the xylem of isolated stem segments of L.lancifolium was solution soaking for 24 h.The running speed of CF in the isolated stem was 0.3 cm/h,which was consistent with the running speed of the material in the field.CF could be transported between the xylem and parenchyma cells,indicating that the material transport in the xylem could be through the symplastic pathway.The above results laid a foundation for the study of the xylem transport mechanism and the xylem pathogen disease of lily.

Synthesis, Photophysical Properties and TD-DFT Calculation of Fluorescent Dyes Based on Pyrenylthiazoles

Pyrene is one of significant fluorescent material and its fluorescence properties are excellent.It has been widely used for such as OLEDs,DSCs,LMOGs and so on[1-5].What＇s more,pyrene has been successfully applied to signaling the presence of metal ions,nucleic acids,proteins and so on[6-9].Thus,the development of the fluorescent dyes based on pyrene has been a research focus[10-12].However,the synthesis of many pyrene derivatives needed the high-cost coupling reaction such as Heck reaction and Suzuki reaction[1-3,10-12].

Immobilization of GO_(X) on PEG/fluoresence functionalized nanographene oxide to describe fluctuation of glucose level

Enzyme,produced and worked in all living things,could work as macromolecular biological catalysts in diverse biochemical processes with particular specificity,like glucose oxidase(GOX).The efficient use of enzyme properties has great importance in pharmaceutics and therapeutics.In this work,we could fabricate naive and effective electrochemical biosensors in the determination of glucose levels via utilizing GOX.Graphene oxide,as a water-soluble derivative of graphene,has shown great promise in a variety of biomedical applications including biosensors.Thus,we established a new-type special platform for GOX immobilization to perform its prosperities,in which nanographene oxide(nGO)was employed as an ideal base and poly(ethylene glycol)(PEG)was conjugated on the edge of nGO sheets to enhance its biocompatibility.Additionally,preferable functional dyes(Rhodamine B/fluorescein isothiocyanate)were also introduced to the platform.Enzyme-nanocomposites were then provided by locating GOX on the platform,i.e.,GOX@nGO-PEG-RhB and GOX@nGO-PEG-FITC.The microstructure and composite of platforms and enzyme-nanocomposites were confirmed by diverse characterizations.Finally,on account of corresponding cyclic voltammetric and typical ready-state amperometric curves,it was informed that GOX@nGO-PEG-RhB and GOX@nGO-PEG-FITC could effectively respond to the fluctuation of glucose level as electrochemical biosensor.The present work presents special platforms for the immobilization of enzymes like GOX and provides new-type biosensors in the detection of glucose levels.

Coumarin-based two-photon AIE fluorophores: Photophysical properties and biological application

Based on the coumarin skeleton, we deliberately designed two groups of fluorophores, termed as CoumR and Naph-Coum-R, using the diphenylamino group as the electron donor, which displayed longwavelength emissions(red spectral region), large Stokes shift(up to 204 nm), superior AIE performance,and large two-photon absorbance cross-sections(as high as 365 GM). The electron-withdrawing substituents at the 3-position of these dyes could induce a significant red-shift in their emission spectra.Preliminary imaging experiments demonstrated the capability of these dyes as two-photon fluorophores for specifically staining lipid droplets in living cells.

Rationally designed meso-benzimidazole-pyronin with emission wavelength beyond 700 nm enabling in vivo visualization of acute-liver-injury-induced peroxynitrite

Fluorescent dyes with fluorescence emission above 700 nm are favorable for bio-imaging due to the higher tissue transparency and lower background fluorescence. In this study, we present a mesobenzimidazole-pyronin platform(Si BMs) with fluorescence emission maxima above 700 nm, which possess good cell permeability, photostability, and lysosomal localization. The great photophysical properties of the Si BMs encouraged us to further exploit their application toward bio-imaging. We synthesized the reduced ‘dihydro’ derivative HSi BM3 for sensing ONOO^(-), with high selectivity and sensitivity and a fast fluorescence “off-on” response(within 2 s). Then, we confirmed the potential of HSi BM3 for visualizing exogenous and endogenous ONOO-in cells and mice. More importantly, HSi BM3 was successfully employed for visualizing acute-liver-injury-induced peroxynitrite.

Split-HaloTag imaging assay for sophisticated microscopy of protein–protein interactions in planta

An ever-increasing number of intracellular multi-protein networks have been identified in plant cells.Split-GFP-based protein–protein interaction assays combine the advantages of in vivo interaction studies in a native environment with additional visualization of protein complex localization.Because of their simple protocols,they have become some of the most frequently used methods.However,standard fluorescent proteins present several drawbacks for sophisticated microscopy.With the HaloTag system,these drawbacks can be overcome,as this reporter forms covalent irreversible bonds with synthetic photostable fluorescent ligands.Dyes can be used in adjustable concentrations and are suitable for advanced microscopy methods.Therefore,we have established the Split-HaloTag imaging assay in plants,which is based on the reconstitution of a functional HaloTag protein upon protein–protein interaction and the subsequent covalent binding of an added fluorescent ligand.Its suitability and robustness were demonstrated using a well-characterized interaction as an example of protein–protein interaction at cellular structures:the anchoring of the molybdenumcofactor biosynthesis complex to filamentous actin.In addition,a specific interactionwas visualized in a more distinctivemannerwith subdiffractional polarizationmicroscopy,Airyscan,and structured illumination microscopy to provide examples of sophisticated imaging.Split-GFPand Split-HaloTag can complement one another,as Split-HaloTag represents an alternative option and an addition to the large toolbox of in vivo methods.Therefore,this promising new Split-HaloTag imaging assay provides a unique and sensitive approach formore detailed characterization of protein–protein interactions using specific microscopy techniques,such as 3D imaging,single-molecule tracking,and super-resolution microscopy.

Development of aryl-containing dipyrrolyldiketone difluoroboron complexes(BONEPYs):Tune the hydrogen bond o-C—H…F for fluoride recognition

Dipyrrolyldiketone difluoroboron complexes(BONEPYs)were synthesized by condensation of the corresponding pyrroles and malonyl chloride followed by treatment with BF3·OEt2.The aryl-substituted pyrrole is introduced to form a cyclic system in order to investigate anion binding studies.In BONEPYs 1-3 the o-H of the aryl group forms hydrogen bonding with F to give a more table complex.In contrast,the intramolecular hydrogen-bonded BONEPY endo-4 is more stable than its exo isomer.While adding F,the hydrogen bonds must be broken first to give 4·(3)F.Owing to the electron-rich group(-OMe),the o-H of the phenyl group can hardly interact with F via hydrogen bonding to give the less stable complex4-(5)F.The energy diffe rences between the different conformations were calculated using DFT methods,which is consistent to the experimental observations.

Ratiometric Fluorescent Probe Based on Novel Red-emission BODIPY for Determination of Bovine Serum Albumin

A novel red-emission boron-dipyrromethene（BODIPY） dye with a pyrrole ring was synthesized simply via one-pot reaction. The spectral properties of it were investigated under the conditions of different solvents. The results show that the as-prepared BODIPY dye is extremely sensitive to solvent polarity, and the fluorescent emission enhances with the decrease of solvent polarity. In aqueous buffer, the addition of bovine serum albumin leads to a ratiometric change in absorption spectra with an association constant of 1.16×10^6 L/mol. Meanwhile, the fluorescence emission increases greatly at 622 nm but changes slightly at 575 nm. The response time is very short（less than 3 min）, and the changes of color can be noticed by naked eyes. Bovine serum albumin can be detected by this ratiometric fluorescence probe, but other proteins or enzymes cannot be detected by this method, which indicates that this novel dye has high selectivity towards bovine serum albumin. The reason is that bovine serum albumin has suitable hydro- phobic cavities for binding with the dye. In addition, the dye molecule can penetrate cell membrane easily and make a fast fluorescent stain, which makes it a potential probe for living-cell fluorescence imaging.