Liheng Feng

Synthesis and photophysics of novel 8-hydroxyquinoline aluminum metal dye with hole transfer groups

A novel luminescent dye metal complex, (CZHQ)3Al, with 8-hydroxyquinoline aluminum and hole-transporting carbazole units was designed and synthesized. The (CZHQ)3Al optical properties were carefully investigated by UV-vis absorption and fluorescence spectra in diluent solution. The results showed that the luminescent quantum yield of (CZHQ)3Al was 0.62 in DMSO and it emitted red-light with the band gap of 2.89 eV estimated from the onset absorption. In addition, the light-emission of (CZHQ)3Al can be quenched by electron acceptor (dimethylterephalate), where the process followed the Stern-Volmer equation. However, the fluorescent intensities of (CZHQ)3Al were slowly increased with the addition of electron donor (N,N-dimethylaniline). Furthermore, the molecular interactions of (CZHQ)3Al with fullerene (C60) and carbon nanotubes (CNTs) were also respectively investigated, which indicated the metal dye can be used as new fluorescent probe.

Biological Functionalization of Conjugated Polymer Nanoparticles for Targeted Imaging and Photodynamic Killing of Tumor Cells

Conjugated polymer nanoparticles composed of PFT/PS as a core and PEG-COOH on the surface were prepared by a reprecipitating method. The CPNs diaplay excellet properties such as good photostability, low cytotoxicity, and strong brightness, etc. The average diamater of CPNs is 30 nm with a spherical morphology. To realize specific imaging in different parts of tumor cells, the bare CPNs with the carboxyls on the surface were conjugated with antibody or peptide by a covalent mode. Studies display that CPNs modified with anti-EpCAM can recognize MCF-7 tumor cells and locate on the membrane, while CPNs conjugated with transcriptional activator protein (Tat) specifically locate in the cytoplasm of MCF-7 cells. On the basis of the ability of CPNs for producing reactive oxygen species (ROS) under light irradiation, photodynamic therapy for tumor cells was investigated. Due to the long distance and wide diffusion range, MCF-7 tumor cells with CPNs/anti-EpCAM have no obvious change with or without white light irradiation. However, CPNs/Tat exhibits higher killing ability for MCF-7 cells. Noticeably, multifunctional CPNs linked with anti-EpCAM and Tat simultaneously not only can specifically target MCF-7 tumor cells, but also may inhibit and kill these cells. This work develops a potential application platform for multifunctional CPNs in locating imaging, photodynamic therapy, and other aspects.

A highly selective and colorimetric naked-eye chemosensor for Cu2+

A sample and practical colorimetric naked-eye chemosensor 3-nitro-4-ethylenediamido-nitrobenzene (2) for metal cations was designed and synthesized. It displays high selectivity and sensitivity for Cu2+ by the UV absorption which appeared a new peak at 525 nm and color change from yellow to red by naked-eye in CH3OH/H2O pH 7.6.

Synthesis and photophysics of novel 8-hydroxyquinoline aluminum metal complex with 1,3,4-oxadiazole units.

A novel luminescent metal complex, (OXHQ)3Al, with 8-hydroxyquinoline aluminum and electron-transporting 1,3,4-oxadiazole unit was designed and synthesized. The photophysical processes were investigated by UV-vis absorption and fluorescence emission spectra in diluent solution. The results showed that the luminescence quantum yield of (OXHQ)3Al was 0.67 in DMSO and it emitted blue light with the band gap of 3.13 eV estimated from the onset absorption. In addition, the light-emitting of (OXHQ)3Al can be quenched by electron acceptor (dimethylterephalate), where the processes followed the Stern-Volmer equation. However, with the addition of electron donor (N,N-dimethylaniline) fluorescent intensity of (OXHQ)3Al was increased and emission peak was lightly blue-shift. Furthermore, the molecular interactions of (OXHQ)3Al with fullerene (C60) or carbon nanotubes (CNTs) were also carefully investigated.

Preparation, regulation and biological application of a Schiff base fluorescence probe

A facile fluorescence switch with Schiff base units was designed and achieved by nucleophilic addition and dehydration reaction. The fluorescence of the probe can be regulated by metal ions (Al(3+) and Cu(2+)). The whole process shows that the weak fluorescence of the probe enhances with the addition of Al(3+), and then the strong fluorescence of the probe/Al(3+) ensemble reduces by introducing Cu(2+). Meanwhile, the solution color changes of the probe with metal ions can be observed under 365 nm UV-vis light from weak light, pale green, green, pale green to weak light. Noticeably, the photo regulation processes of the probe by metal ions can be realized in the biological system and applied in cells imaging. The work provides a new strategy for designing facile regulation probe and develops a new application for Schiff base derivatives.

Synthesis and photophysical processes of an anthracene derivative containing hole transfer groups.

A novel luminescent compound 9,10-di-(N-carbazovinylene)anthracene (DCVA) was synthesized by Heck reaction of 9,10-dibromoanthracene and N-vinylcarbazole. The structure was characterized by MS, 1H NMR and Elemental analysis. The photoluminescent properties of DCVA have been carefully investigated by UV-vis absorption and fluorescence emission spectra. The results showed that the luminescent quantum yield of DCVA was 0.73 in THF and it emitted blue-light with the band gap of 3.60 eV estimated from the onset absorption. In addition, the light-emission of DCVA can be quenched by electron acceptor (dimethyl terephthalate), however, the fluorescent intensities of DCVA were slowly increased with the addition of electron donor (N,N-dimethylaniline). Furthermore, the molecular interactions of DCVA with fullerene (C60) and carbon nanotubes (CNTs) were also investigated, which indicated the organic luminescent compound can be used as new fluorescent probe.

A facile Al(III)-specific fluorescence probe and its application in biological systems

A facile fluorescence receptor was easily synthesized by an one-step reaction of 3,4-dihydroxybenzaldehyde and hydrazinecarbothioamide. The receptor as a fluorescence probe was used to recognize metal ions by UV-vis and fluorescence techniques. The data of UV-vis and fluorescence spectra display the high sensitivity and selectivity of the receptor for Al(III) ions. When introducing Al(III) ions, the fluorescence of the probe exhibits an obvious enhancement because of inhibiting the photoinduced electron transfer (PET) process. The certain bonding mode of the receptor with Al(III) was verified by 1H NMR, HRMS-ESI and Job-plot data. The prospective fluorescence “Off–On” signal for Al(III) ions including the color change of the receptor solution was observed. The detection limit of the receptor for Al(III) may reach 10−7 mol L−1. Noticeably, the probe as a fluorescence “Off–On” switch can detect the trace level of Al(III) in living cells and mouse organs. The work provides a strategy for design simple fluorescence probes for Al(III) and applications in biological systems.

A facile strategy for achieving high selective Zn(II) fluorescence probe by regulating the solvent polarity

A simple Schiff base comprised of tris(2-aminoethyl)amine and salicylaldehyde was designed and synthesized by one-step reaction. Although this compound has poor selectivity for metal ions in acetonitrile, it shows high selectivity and sensitivity detection for Zn(II) ions through adjusting the solvent polarity (the volume ratio of CH3CN/H2O). In other words, this work provides a facile way to realize a transformation from poor to excellent feature for fluorescent probes. The bonding mode of this probe with Zn(II) ions was verified by 1H NMR and MS assays. The stoichiometric ratio of the probe with Zn(II) is 1:1 (mole), which matches with the Job-plot assay. The detection limitation of the probe for Zn(II) is up to 1 × 10-8 mol/L. The electrochemical property of the probe combined with Zn(II) was investigated by cyclic voltammetry method, and the result agreed with the theoretical calculation by the Gaussian 09 software. The probe for Zn(II) could be applied in practical samples and biological systems. The main contribution of this work lies in providing a very simple method to realize the selectivity transformation for poor selective probes. The providing way is a simple, easy and low-cost method for obtaining high selectively fluorescence probes.

A high brightness probe of polymer nanoparticles for biological imaging

Conjugated polymer nanoparticles (CPNs) with high brightness in long wavelength region were prepared by the nano-precipitation method. Based on fluorescence resonance energy transfer (FRET) mechanism, the high brightness property of the CPNs was realized by four different emission polymers. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) displayed that the CPNs possessed a spherical structure and an average diameter of ~75nm. Analysis assays showed that the CPNs had excellent biocompatibility, good photostability and low cytotoxicity. The CPNs were bio-modified with a cell penetrating peptide (Tat, a targeted element) through covalent link. Based on the entire wave fluorescence emission, the functionalized CPNs1-4 can meet multichannel and high throughput assays in cell and organ imaging. The contribution of the work lies in not only providing a new way to obtain a high brightness imaging probe in long wavelength region, but also using targeted cell and organ imaging.

A novel polymer probe for Zn(II) detection with ratiometric fluorescence signal

A conjugated polymer probe comprised of fluorene, quinolone and benzothiazole units was designed and synthesized by the Suzuki coupling reaction. Through the studies of photophysical and thermal properties, the polymer displays blue-emitting feature and good thermal stability. A ratiometric fluorescence signal of the probe for Zn(II) was observed in ethanol with a new emission peak at 555 nm. The probe possesses a high selectivity and sensitivity for Zn(II) during familiar metal ions in ethanol. The detection limit of the probe for Zn (II) is up to 10-8 mol/L. The electron distributions of the polymer before and after bonding with Zn (II) were investigated by the Gaussian 09 software, which agreed with the experimental results. Noticeably, based on the color property of the probe with Zn(II), a series of color test paper were developed for visual detecting Zn(II) ions. This work helps to provide a platform or pattern for the development of polymer fluorescence probe in the chemosensor field.