Baokang Jin

Enhanced electrochemiluminescence of CdSe quantum dots composited with graphene oxide and chitosan for sensitive sensor.

A novel strategy for the enhancement of electrochemiluminescence (ECL) was developed by combining CdSe quantum dots (QDs) with graphene oxide-chitosan (GO-CHIT). The ECL sensor fabricated with CdSe QDs/GO-CHIT composite exhibited high ECL intensity, good biocompatibility and long-term stability, and was used to detect of cytochrome C (Cyt C). The results show that the ECL sensor has high sensitivity for Cyt C with the linear range from 4.0 to 324 μM and the detection limit of 1.5 μM. Furthermore, the ECL sensor can selectively sense Cyt C from glucose and bovine serum albumin (BSA).

A sulfur-terminal Zn(II) complex and its two-photon microscopy biological imaging application.

A novel sulfur-terminal Zn(II) complex Zn(S)(2)L (L = N-hexyl-3-{2-[4-(2,2:6,2-terpyridin-4-yl)phenyl] ethenyl}carbazole) was obtained by a facile solvothermal process. The unique feature in this new reaction design is the use of ZnS nanocrystals as a precursor and bulky chromophoric L as an ancillary ligand. The versatility of the two terminal sulfur atoms is relevant to biological system. The resulting Zn(S)(2)L complex shows two-photon excited fluorescence (TPEF), which has been proven to be potentially useful for two-photon microscopy imaging in living cells. In addition, cytotoxicity tests showed that the low-micromolar concentrations of Zn(S)(2)L did not cause significant reduction in cell viability over a period of at least 24 h and should be safe for further biological studies.

Facile synthesis and systematic investigations of a series of novel bent-shaped two-photon absorption chromophores based on pyrimidine.

The synthesis, structure, and single- and two-photon spectroscopic properties of a series of pyrimidine-based (bent-shaped) molecules are reported. All these stable heterocyclic compounds are fully characterized, and exhibit intense single- and two-photon excited fluorescence (SPEF and TPEF) over a wide spectral range from blue to red, with the spectral peak position of the SPEF being basically the same as that of the TPEF. The well-conjugated pi-systems, observed from the crystal structure, indicate the charge transfer feature of the ground state. Meanwhile, the theoretical and experimental studies indicate that the charge transfer from donor to acceptor is greatly enhanced in the excited states and the different substituted donor groups on the pyrimidine have a large effect on the optical and electrochemical properties. Based on typical structure data and comprehensive spectral data, the following structure-property relationships can be determined: for such bent-shaped chromophores, the absorption and the fluorescence wavelength maximum of the SPEF and TPEF, and two-photon absorption cross sections show a similar trend with increasing electron-donating strength of the corresponding terminal group and the number of branches, while the average bond lengths of the pi-linkage and HOMO-LUMO energy levels show an inverse trend. Experimental data and theoretical calculation provide a coherent picture. With these findings, bent-shaped quadrupolar chromophores combining peak TPA cross sections (up to 2280 GM), broad TPA bands throughout the whole 700-900 nm range, and high fluorescence quantum yields could, thus, be obtained. Such compounds are of particular interest for TPEF microscopy, as well as optical data storage in the visible and NIR regions. A data recording experiment proved the potential application of these materials.

Synthesis, Crystal Structures, Photophysical Properties, and Bioimaging of Living Cells of Bis-β-Diketonate Phenothiazine Ligands and Its Cyclic Dinuclear Complexes

Two bis-β-diketones, RCOCH(2)CO-EPTZ-COCH(2)COR (EPTZ = 10-ethylphenothiazine; R = C(6)H(5) for H(2)L(1) and CF(3) for H(2)L(2)) and their cyclic dinuclear Zn(II), Cd(II), Ni(II), Mn(II), Cu(II), Co(II) complexes have been synthesized and fully characterized. Their crystal structures were determined by single crystal X-ray diffraction analysis. Their photophysical properties have been further investigated both experimentally and theoretically. The results revealed that significant enhancement of two-photon absorption cross section values were obtained for the cyclic dinuclear Zn(II) and Cd(II) complexes compared with their free ligands. Additionally, confocal microscopy and two-photon microscopy fluorescent imaging of MCF-7 cells labeled with two ligands and Zn(II) complexes reveal their potential applications as a biological fluorescent probe.

IR spectroelectrochemical cyclic voltabsorptometry and derivative cyclic voltabsorptometry.

In this paper, we report the IR (infrared) CVA (cyclic voltabsorptometry) and DCVA (derivative cyclic voltabsorptometry) spectroelectrochemical techniques to elucidate an electrochemical mechanism. First we set potassium ferrocyanide as an example to explain the validity of this method. Then the electrochemical redox of two compounds, 1,4-benzoquinone and 1,4-bis(2-ferrocenylvinyl)benzene, was selected to be examined with this method. 1,4-Benzoquinone exhibits two single-electron waves in the cyclic voltammetric (CV) experiment, whereas two electroactive groups (Fc) are contained in p-(Fc-CH=CH)(2)BZ, but only one redox wave is observed. IR CVA results show that three IR absorption peaks in 1,4-benzoquinone, 1232 cm(-1) (the absorption of final production), 1656 cm(-1) (the absorption of original reactant), and 1510 cm(-1) (the absorption of intermediate), and two IR absorption peaks in 1,4-bis(2-ferrocenylvinyl)benzene, 1620 cm(-1) (the absorption of final oxide production) and 1589 cm(-1) (the absorption of intermediate), can be used to track the electron transfer. On the basis of the IR absorbance at the appropriate monitored wavelength (mentioned above), we can analyze simultaneously the concentration change of the corresponding redox transition during CV scans. Also the combination of the DCVA spectroelectrochemical technique with theory analysis allows reconstructing the current-potential (i-E) curve for each step of electron transfer. The reconstructed i-E curve can help us to understand the electron-transfer process. We believe IR CVA and DCVA spectroelectrochemical techniques can be applicable to the study of a wide range of complex electrochemistry processes.

Tuning the optical properties of flurophore-hexylcarbazole organic nanoribbons with dispersed inorganic nanocrystals (AgNCs)

A carbazole derivative (3-(2,2-dicyanovinyl)-9-hexylcarbazole, abbreviated as L) has been designed, synthesized and used to prepare a novel organic–inorganic nanohybrid consisting of silver nanocrystals (Ag NCs) uniformly dispersed on the surface of L nanoribbons. Detailed characterizations have been performed. The results reveal that L couples with Ag NCs through a π-conjugated unit, which results in a significant red-shift of the fluorescence (FL), an obvious increase of FL lifetime and enhanced Raman scattering.

Electrochemical and in situ FTIR studies of biferrocene platinum(II) complex

Electron transfer mechanism during redox process of Pt(LSB)2, a derivative of S-benzyl-N-(ferrocenyl-1-methyl-metylidene)-dithiocarbazate (HLSB), is studied by cyclic voltammetry, differential pulse voltammetry, digitally simulation and in situ FTIR spectroelectrochemistry. Electrochemistry results indicated the redox process of Pt(LSB)2 involves two consecutive one-electron steps. Coordination of Pt to HLSB resulted in the increase of electron-withdrawing of the dithiocarbazate group, which is demonstrated by the positive shift of redox potentials of Pt(LSB)2 compared with those of HLSB. The peak–peak separation of 129 mV revealed a strong degree of electronic communication between the two-ferrocene moieties in Pt(LSB)2. The results of in situ FTIR indicated that electronic communication takes place through the skeleton chain of HLSB due to the extensive electron delocalization in the whole molecule.

Study on the spectroelectrochemical properties of S-benzyl-N-(ferrocenyl-1-methyl-metylidene)-dithio-carbazate nickel (II) complex

Mechanism of electron transfer of a bridge biferrocene complex, Ni(LSB)2, derived from the Schiff base ligand, HLSB, S-benzyl-N-(ferrocenyl-1-methyl-metylidene)-dithio-carbazate Ni(LSB)2, during redox processes is illuminated by in-situ Fourier transform infrared (FTIR) spectroelectrochemistry. The results indicated that two consecutive one-electron steps were involved which gives the corresponding mono- and di-ferricenium cations, respectively. This complex exhibits moderately strong degree of electronic communication between the two-ferrocene moieties, taking place through the skeleton chain of the ligand due to an extensive electron delocalization in the molecule. Possible pathways of electron transfer of Ni(LSB)2 during the redox processes are postulated.

Dual-functional analogous cis-platinum complex with high antitumor activities and two-photon bioimaging.

Here we have designed and synthesized a novel analogous cis-platinum complex (TDPt) with strong two-photon absorption properties and higher stability upon laser irradiation. Interestingly, a higher cytotoxicity against three types of cancer cells compared to that of commercial cis-platinum was observed. The initial confocal micrographs showed that lysosomes may be the biological targets of such TDPt, except the conventional presumed DNA. This hypothesis was further confirmed by the two-photon microscopy and transmission electron microscopy micrograph. These results form an important basis for future on-site observation of the anticancer mechanism of the Pt(II) complex.