Fengshou Wu

Phosphorescent Cu(I) complexes based on bis(pyrazol-1-yl-methyl)-pyridine derivatives for organic light-emitting diodes†

Mononuclear Cu(I) complexes based on bis(pyrazol-1-yl-methyl)-pyridine derivatives and ancillary triphenylphosphine have been prepared and characterized by 1H NMR, mass spectroscopy and single-crystal X-ray analysis. The thermogravimetric analysis shows that the complexes exhibit high thermal stability. The electronic absorption spectra display two features in the regions of 230–260 and 290–350 nm attributable to mixed ligand-to-ligand (LLCT) and metal-to-ligand-charge-transfer (MLCT) excited states, which is supported by the results of density functional theory (DFT) and time-dependent DFT (TDDFT) calculations on these Cu(I) complexes. These complexes are strongly emissive in the solid state at ambient temperature. Intense blue or green emission in the poly(methyl methacrylate) film is observed in the region of 475–518 nm for these complexes with the emission lifetimes in the microsecond time scale (12–20 μs), indicating that the emission may be phosphorescence emission. Increasing the steric hindrance of the substituents on the pyrazole unit results in a blue-shift of the emission bands and enhanced emission quantum efficiency in PMMA films. The two most emissive complexes have been used for the fabrication of phosphorescent organic light-emitting diodes (POLEDs).

Near-infrared emissive lanthanide hybridized carbon quantum dots for bioimaging applications

Lanthanide hybridized carbon quantum dots (Ln-CQDs) were synthesized by a facile one-pot hydrothermal method using citric acid as a carbon precursor and Yb3+ or Nd3+ as a doping ion. The morphology and chemical structures of Ln-CQDs were investigated by TEM, XRD, XPS, and FTIR spectroscopy. The obtained Ln-CQDs are spherical and well dispersed in water, and their aqueous solutions emit strong blue emission under UV excitation. The Ln-CQDs exhibit excitation-dependent PL behavior with the emission maximum ranging from 443 to 552 nm under 300-520 nm excitation. Moreover, the carbon quantum dots can not only act as visible imaging agents, but also as antennae for photoluminescence (PL) of lanthanide ions. Hence, CQDs hybridized with Yb3+ or Nd3+ ions exhibit the characteristic emission in the near-infrared region with the emission maximum centered at about 998 and 1068 nm, respectively. The MTT assay against HeLa cells verified the low cytotoxicity of Ln-CQDs. They have been used as excellent optical probes for multicolor cell-imaging, demonstrating their great potential for both visible/NIR bioimaging and biomedical applications in vivo.

Facile synthesis of N-rich carbon quantum dots from porphyrins as efficient probes for bioimaging and biosensing in living cells

N-rich metal-free and metal-doped carbon quantum dots (CQDs) have been prepared through one-step hydrothermal method using tetraphenylporphyrin or its transition metal (Pd or Pt) complex as precursor. The structures and morphology of the as-prepared nanoparticles were analyzed by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra. Three kinds of nanocomposites show similar structures except for the presence of metal ions in Pd-CQDs and Pt-CQDs indicated by X-ray photoelectron spectroscopy. All of them display bright blue emission upon exposure to ultraviolet irradiation. The CQDs exhibit typical excitation-dependent emission behavior, with the emission quantum yield of 10.1%, 17.8%, and 15.2% for CQDs, Pd-CQDs, and Pt-CQDs, respectively. Moreover, the CQDs, Pd-CQDs, and Pt-CQDs could serve as fluorescent probes for the specific and sensitive detection of Fe3+ ions in aqueous solution. The low cytotoxicity of CQDs is demonstrated by MTT assay against HeLa cells. Therefore, the CQDs can be used as efficient probes for cellular multicolor imaging and fluorescence sensors for the detection of Fe3+ ions due to their low toxicity, excellent biocompatibility, and low detection limits. This work provides a new route to synthesize highly luminescent N-rich metal-free or metal-doped CQDs for multifunctional applications.

Cetuximab-conjugated iodine doped carbon dots as a dual fluorescent/CT probe for targeted imaging of lung cancer cells

Iodine doped carbon quantum dots (I-CQDs) have been synthesized by a facile one-pot hydrothermal method using citric acid and iohexol as precursors. The morphology and chemical structures of I-CQDs are investigated by TEM, XRD, XPS, and FTIR spectroscopy. The as-prepared I-CQDs exhibit excitation-dependent PL behavior with the emission quantum yield of 18%. The presence of iodine ions in I-CQDs is confirmed by XPS spectrum, which endows the composite with CT imaging performance. Thus, they could be used as efficient probes for fluorescence/CT bimodal imaging. To realize a precise diagnosis of tumor lesions, the surface of I-CQDs is conjugated with a targeting molecular (cetuximab) to afford I-CQDs-C225. The MTT assay against three kinds of human cell lines verifies the low cytotoxicity of I-CQDs-C225. The targeting ability of I-CQDs-C225 are evaluated in vitro using HCC827 cells (lung cancer cell line, over-expression of EGFR), H23 (lung cancer cell line, low expression of EGFR) and HLF cells (lung normal cell line, low expression of EGFR) via a confocal laser scanning microscope. The results show that HCC827 cells exhibited strong fluorescence, indicating the cetuximab-conjugated I-CQDs could target specifically the cancer cells with over-expression of EGFR via EGFR mediated endocytosis.