Green-emissive carbon quantum dots with high fluorescence quantum yield:Preparation and cell imaging

High fluorescence quantum yield(QY),excellent fluorescence stability,and low toxicity are essential for a good cellular imaging fluorescent probe.Green-emissive carbon quantum dots(CQDs)with many advantages,such as unique fluorescence properties,anti-photobleaching,low toxicity,fine biocompatibility and high penetration depth in tissues,have been considered as a potential candidate in cell imaging fluorescent probes.Herein,N,S-codoped green-emissive CQDs(QY=64.03%)were synthesized by the one-step hydrothermal method,with m-phenylenediamine as the carbon and nitrogen source,and L-cysteine as the nitrogen and sulfur dopant,under the optimum condition of 200℃ reaction for 2 h.Their luminescence was found to originate from the surface state.In light of the satisfactory photobleaching resistance and the low cytotoxicity,CQDs were used as a cell imaging probe for HeLa cell imaging.The results clearly indicate that cells can be labeled with CQDs,which can not only enter the cytoplasm,but also enter the nucleus through the nuclear pore,showing their broad application prospect in the field of cell imaging.

Measurement of the fluorescence quantum yield of bis-MSB

The fluorescence quantum yield of bis-MSB, a widely used liquid scintillator wavelength shifter, was measured to study the photon absorption and re-emission processes in a liquid scintillator. The re-emission process affects the photoelectron yield and distribution, especially in a large liquid scintillator detector, thus must be under- stood to optimize the liquid scintillator for good energy resolution and to precisely simulate the detector with Monte Carlo. In this study, solutions of different bis-MSB concentration were prepared for absorption and fluorescence emission measurements to cover a broad range of wavelengths. Harmane was used as a standard reference to obtain the absolution fluorescence quantum yield. For the first time we measured the fluorescence quantum yield of bis-MSB up to 430 nm as inputs required by Monte Carlo simulation, which is 0.926±0.053 at ;λex=350 nm.

Fluorescence quantum yield of Gd_(0.9-x)R_xEu_(0.1)OOH(R=Y, La) crystals

Gdo.9xRxEUo.lOOH （R=Y, La） crystals were synthesized by a flux method using a mixture of NaOH and KOH as the flux. X-ray diffraction data were well refined using the Rietveld method assuming that the crystals had a monoclinic structre belonging to the P21/m space group. The unit cell volumes of the Gdo.9 xLaxEuo.OOH crystals increased with increasing x, whereas those of Gdo.9-xYxEUo.lOOH decreased with increasing x. The Commission Internationale de IEclairage （CIE） chromaticity coordinates of Gdo.9 xRxEUo.lOOH （R=Y, La） crystals were located in the red region and were nearly constant over the range ofx values considered. The fluorescence quantum yield Dr monotonically decreased with increasing x regardless of the ionic radii of the substitute ions. The fact that the Dr value of Lao.9EuoAOOH was greater than that of Gdo.gEUo.lOOH indicated that the observed decrease in the values of the Gdo.9-,LaxEuo.1OOH crystals up to x=0.3 could not be attributed to an increase in the distance between Eu3＋ ions or to a decrease in the Gd3＋ content. The decrease might be due to an increase of killer centers introduced by elemental substitutions with the larger ion.

Absorption,quenching,and enhancement by tracer in acetone/toluene laser-induced fluorescence

To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of the two components.Appropriate excitation laser wavelength and filters are used to assess the influence of acetone and toluene on each other’s fluorescence signal at room temperature.Experimental results show that acetone has a strong absorption effect on toluene’s fluorescence signal,the effective absorption cross-section is 5.77×10-20 cm-2.Acetone has an obvious quenching effect on the toluene fluorescence signal,and the Stern–Volmer coefficient is 0.50 kPa-1.The collisions between the molecules of toluene and acetone will lead to the enhancement of the fluorescence signal of acetone,and the enhancement coefficient is exponential with the acetone’s concentration.The quantitative relationship between the fluorescence intensity and the concentrations of the two tracers is obtained by establishing the photophysical model of toluene and acetone’s fluorescence signals.

Synthesis and Photoelectrical Properties of D-A Type Carbazole-quinoline

The key issues concerning the design and synthesis of high fluorescent efficiency,good thermal stability of organic blue materials should be solved urgently in organic light emittingdiodes. In this article, three D-A type blue emitters based on carbazole and phenylquinoline withflexible chains were prepared through Friedlander condensation reaction in relatively high yield.The photoelectric properties of all compounds were studied by UV-vis absorption, emission spectraand cyclic voltammograms. Density functional theory calculations （DFT） were performed to obtaina better understanding of the electronic structures. Interestingly, compound a3 with the highestfluorescence quantum yield of 0.53 can be applied into blue light emission materials on account ofgood thermal performance. Furthermore, al-a3 with narrow band gap make them becomepotential candidates in the fields of OLED, solar cells and OFET.

Synthesis, Photophysical Properties and DNA-Photocleavage Activity of Silicon Phthalocyanine Derivatives

Silicon phthalocyanine derivatives 1a and 1b were synthesized and characterized by UV, 1H-NMR and MS. The photophysical properties of the compounds in DMSO were investigated. The maximum absorption peaks of compounds 1a and 1b at the Q-band are 681 nm. With ZnPc (ΦF = 0.20, ΦΔ = 0.67) as a reference, the fluorescence quantum yield (ΦF) of 1a and 1b are 0.20 and 0.31 respectively, and the singlet oxygen quantum yield (ΦΔ) are 0.66 and 0.59 respectively. The DNA-photocleavage activities of compounds 1a and 1b were studied by gel electrophoresis. Compounds 1a and 1b possess good photocleavage activity to pBR322 DNA. The results demonstrate that compounds 1a and 1b are potential photosensitizers for tumor therapy.

Fluorescent Quantum Yield of Pyrene Probe in Ultrathin Polymer Films

The fluorescently labelled polymers including pyrene-labelled polystyrene(PyPS) and pyrene-labelled poly(methyl methacrylate)(PyPMMA) with narrow molecular weight distributions were synthesized by the atom transfer radical copolymerization(ATRCP) of styrene or methyl methacrylate with 1-pyrenemethyl methacrylate(PyMMA). The ultrathin PyPS and PyPMMA films with the thickness ranging from 30 nm to 400 nm supported on the quartz slides were prepared by spin-coating. The fluorescent quantum yield(QY) of the pyrene probe in the ultrathin polymer films was investigated by the photoluminescence spectrometer using an integrating sphere detector. The QY decreased with the reduction of film thickness in the sub-200 nm range.

Theoretical Investigation for Unexpected Transition Metal-π Interaction Enhanced Fluorescence in Cu-π-diborene

Unexpected transition metal(TM)-π interaction enhanced fluorescence in Cu-π-diborene complexes is a novel phenomenon compared with other metal enhanced fluorescence. In order to discover the mechanism, theoretical investigation was carried out for Cu-π-diborene as well as diborene. Simulation results show the main decay method in diborene and Cu-π-diborene are internal conversion(IC) and fluorescence(FL), respectively. TM-π interaction leads to larger HOMO-LUMO gap of Cu-π-diborene than that of the free diborene, which results in lower IC rates and makes them smaller than the FL rates. At the same time, ISC rates are always smaller than IC and FL rates, which cause enhanced fluorescence of Cu-π-diborene. More interestingly, even though Cu-π-diborene shows enhanced fluorescence, intersystem crossing(ISC) in Cu-π-diborene is enhanced from diborene. The theoretical analysis shows the competition among IC, FL and ISC is the key factor for TM-π interactions enhanced fluorescence, which also shows that cation-π complexes have potential to be used as luminescent probes.

Novel seven-membered ring-fused naphthalimide derivatives with potentials for cancer theranostics

Naphthalimide derivatives have good planarity and large conjugated structure and therefore possess photophysical properties and biological activities. Previously, our group discovered seven-membered heterocyclic derivatives via modifying 4-and 5-positions of naphthalimide skeleton and found the derivatives had good water solubility and showed large stokes shift and strong fluorescence in water. In this article, we designed and synthesized more seven-membered ring-fused naphthalimide derivatives(Y1-Y16)by introducing different substitutions on the imide group. Among them, Y1, Y5, Y9 were found to show similar cytotoxic activities with Amonafide against A549 and HL60 cells, with IC50values at 10^(-6)mol/L.What is more, the asymmetry derivatives(Y1 and Y5) showed high fluorescent quantum yields in the aqueous phase(Ф = 0.47). Considering the great fluorescence quantum yields in water and the potent anti-tumor activities of the representative seven-membered ring-fused naphthalimides, they have potentials to be used as agents for cancer theranostics.

Study of absorption and re-emission processes in a ternary liquid scintillation system

Liquid scintillators are widely used as the neutrino target in neutrino experiments.The absorption and emission of different components of a ternary liquid scintillator （Linear Alkyl Benzene （LAB） as the solvent,2,5-diphenyloxazole （PPO） as the fluor and p-bis-（o-methylstyryl）-benzene （bis-MSB） as wavelength shifter） are studied.It is shown that the absorption of this liquid scintillator is dominant by LAB and PPO at wavelengths less than 349 nm,and the absorption by bis-MSB becomes prevalent at the wavelength larger than 349 nm.The fluorescence quantum yields,which are the key parameters to model the absorption and re-emission processes in large liquid scintillation detectors,are measured.

Simultaneous studies of pressure effect on charge transport and photophysical properties in organic semiconductors:A theoretical investigation

High-mobility and strong luminescent materials are essential as an important component of organic photodiodes,having received extensive attention in the field of organic optoelectronics.Beyond the conventional chemical synthesis of new molecules,pressure technology,as a flexible and efficient method,can tune the electronic and optical properties reversibly.However,the mechanism in organic materials has not been systematically revealed.Here,we theoretically predicted the pressure-depended luminescence and charge transport properties of high-performance organic optoelectronic semiconductors,2,6-diphenylanthracene(DPA),by first-principle and multi-scale theoretical calculation methods.The dispersion-corrected density functional theory(DFT-D)and hybrid quantum mechanics/molecular mechanics(QM/MM)method were used to get the electronic structures and vibration properties under pressure.Furthermore,the charge transport and luminescence properties were calculated with the quantum tunneling method and thermal vibration correlation function.We found that the pressure could significantly improve the charge transport performance of the DPA single crystal.When the applied pressure increased to 1.86 GPa,the hole mobility could be doubled.At the same time,due to the weak exciton coupling effect and the rigid flat structure,there is neither fluorescence quenching nor obvious emission enhancement phenomenon.The DPA single crystal possesses a slightly higher fluorescence quantum yield~0.47 under pressure.Our work systematically explored the pressure-dependence photoelectric properties and explained the inside mechanism.Also,we proposed that the exte rnal pressure would be an effective way to improve the photoelectric perfo rmance of organic semiconductors.

One-pot synthesis of nuclear targeting carbon dots with high photoluminescence

Carbon dots(CDs) are novel fluorescent nanomaterials with good water solubility, high resistance to photobleaching and low toxicity. While, there are few studies elaborate on the relationship among reaction conditions, properties and applications of CDs. In this study, a series of CDs are synthesized through a one-pot hydrothermal method, and different reaction conditions are carried out to study the influencing factors of CDs properties. As a result, with the increase of temperature and reaction time, the particle size and zeta potential of CDs increased, the maximum emission wavelength red-shifted and the fluorescence quantum yield(QY) improved. Among them, CD3006 has good water solubility and highest QY of 81.4%, which is beneficial for its applications in bioimaging and ion detection. CD3006 is almost nontoxic in cells at a concentration of 500 μg/m L. In addition, the positive charged CD3006 shows nuclear targeting potential because of its combination with DNA through electrostatic interaction in nucleus. The properties of CDs can be greatly enhanced by controlling reaction conditions, and it provides great application prospects.

Spontaneously bundled nanotubes exhibit greatly enhanced emission via inter-nanotube energy transfer

Spontaneously bundled nanotubes assembled from chiral perylene diimide molecules exhibit greatly enhanced emission via inter-nanotube excitation energy transfer. The formation of densely packed superstructures is an effective approach for high fluorescence quantum yield in assembled nanomaterials without compromising optoelectronic properties.

Synthesis and Spectral Properties of Novel Water-soluble Indocyanine Dyes as Fluorescent Dyes for Proteins Detection

Two novel water-soluble indocyanine dyes were synthesized. Their chemical structures were confirmed by 1H NMR, IR, MS and UV-vis techniques. The absorptions of the prepared dyes in different solvents were measured. Two dyes exhibited negative solvatochromism, with a blue shift of the absorption and an emission maximum in （bovine serum albumin） protonic solvent relative to non protonic solvent. The fluorescence properties of the dyes in both free state and BSA were investigated. Significant enhancement of the fluorescence intensity for the Dye2 was observed in the presence of BSA. Dye2 could be proposed as fluorescent dyes for BSA detection in aqueous solution.