Qian Guodong

Synthesis in situ of 2,2′-dipyridyl-Tb(iii) complexes in silica gel

Abstracts are not published in this journal

Structural evolution and fluorescence properties of Tb3+-doped silica xerogels in the gel to glass conversion

The Tb3+-doped silica glasses were prepared by a sol-gel process with appropriate heat treatment. The structural changes during the gel to glass transition of Tb3+-doped silica xerogels and the effect on fluorescence properties of Tb3+ were studied in this paper. The results show that the doped silica glasses may be obtained after the xerogels are heat-treated at 800 °C for 24 h. During heat treatment at 400 °C, the residual organic molecules and most of the absorbed water molecules in silica xerogels are removed, and the SiO4 tetrahedral structural network forms and strengthens gradually with decreasing number of silanol (SiOH) groups. The fluorescence intensity of Tb3+ ions increases remarkably when the doped xerogel is heat-treated in the range 300–500 °C, and increases slowly above 500 °C(up to 800 °C). This observation leads to a conclusion that the radiative transitions of Tb3+ ion in the aqueous gels are quenched strongly by the high-frequency vibrations of OH groups from the coordinated water rather than physically absorbed water. The inhomogeneity in the site state of Tb3+ ions increases with rise in temperature of heat treatment, which broadens the emission bands of Tb3+ ions doped in silica glasses. Moreover, there will also be an additional interaction owing to the influence of the ligand field of the glasses, which makes the emission bands shift to red and produces Stark splitting of the Tb3+ ion energy levels.

Preparation and fluorescence properties of nanocomposites of amorphous silica glasses doped with lanthanide(III) benzoates

Abstract Lanthanide(III) benzoate complexes are decomposed by a few drops of HCl and, thus, cannot be doped in amorphous silica glasses prepared by the acidic (HCl) hydrolysis of tetraethoxysilane (TEOS). This work presents a novel technique of homogeneous doping these complexes in silica gel glasses. Eu(III) (or Tb(III)) and benzoic acid are co-introduced in sol-gel precursor solutions with suitable pH. The nano-scale Eu(III) (or Tb(III)) benzoate complexes are confirmed to form in amorphous silica glass through controlled gelation and drying. The fluorescence spectra of Eu(III) (or Tb(III)) in nanocomposites and the energy transfer efficiencies between Eu(III) (or Tb(III)) and benzoate are studied.

In situ synthesis and fluorescence characterization of 2,2′-dipyridyl-Eu(III) complex in silica xerogel prepared by the sol-gel process

Abstract The complex of Eu(III) with 2,2′-dipyridyl is decomposed by water, and thus cannot be doped in gel glasses prepared by the sol-gel process. This paper presents a novel technique of homogeneous doping of the 2,2′-dipyridyl-Eu(III) complex in silica gel glass. By codoping of 2,2′-dipyridyl and Eu(III) in silica xerogel, an in situ complex of Eu(III) with 2,2′-dipyridyl is synthesized in the transparent monolithic gel glass by suitable heat treatment. Compared with a sample undergoing no heat treatment, the fluorescence intensity of Eu(III) in the xenogel heated at 100°C for 24 h increases by a factor of about ten due to the formation of the in situ 2,2′-dipyridyl-Eu(III) complex. From the fluorescence spectrum, it is suggested that the in situ complex may be Eu(C 10 H 8 N 2 )Cl 3 ·4H 2 O.

The influence of the matrix on the fluorescence properties of pyrene

The fluorescence properties of pyrene doped in silica xerogels by a sol-gel process and dissolved in ethanol in various concentrations were studied comparatively. With increasing gelation time the fluorescence spectra of pyrene doped in silica gels change greatly. Pyrene monomer excitation bands arise gradually with decreasing intensity of pyrene excimer excitation bands, which increases the intensity of the monomer emission and decreases that of the excimer emission. Compared with dissolving pyrene in ethanol, doping with pyrene in silica xerogels can increase the quenching concentration of pyrene enormously and thus increase the monomer fluorescence intensity of pyrene by a factor of approximately 20 with respect to that in ethanol solution. These changes can be explained by the modification of the pyrene surroundings. The pyrene molecules are isolated and absorbed in the tiny pores of the silica network steadily to avoid aggregate formation in silica xerogels.

Structural characteristics of surface-functionalized nitrogen-doped diamond-like carbon films and effective adjustment to cell attachment*

Nitrogen-doped diamond-like carbon (DLC:N) films prepared by the filtered cathodic vacuum arc technology are functionalized with various chemical molecules including dopamine (DA), 3-Aminobenzeneboronic acid (APBA), and adenosine triphosphate (ATP), and the impacts of surface functionalities on the surface morphologies, compositions, microstructures, and cell compatibility of the DLC:N films are systematically investigated. We demonstrate that the surface groups of DLC:N have a significant effect on the surface and structural properties of the film. The activity of PC12 cells depends on the particular type of surface functional groups of DLC:N films regardless of surface roughness and wettability. Our research offers a novel way for designing functionalized carbon films as tailorable substrates for biosensors and biomedical engineering applications.