Hong-Guo Liu

Fabrication and fluorescence characterization of the LB films of luminous rare earth complexes Eu(TTA)3Phen and Sm(TTA)3Phen

Abstract High quality and intensely fluorescent Langmuir-Blodgett (LB) films of Eu(TTA) 3 Phen/AA (in molar ratio 1:1) (AA, arachidic acid) and Sm(TTA) 3 Phen/AA (1:1) were fabricated successfully by using the composite subphase that, here, denotes the aqueous solution saturated with Phen (1,10-phenanthroline), TTA ( α -thenoyltrifluoroacetone) and Eu(TTA) 3 Phen or Sm(TTA) 3 Phen. FTIR results indicate that hydrogen bonds form between -CF 3 of the title complexes and -COOH of AA in these LB films. Low-angle X-ray diffraction results show that these LB films all have a periodic layer structure. The vertical uniformity of these LB films has been demonstrated by UV-Vis spectra and fluorescence emission spectra. Both absorbance and relative fluorescence intensity increase linearly with the number of LB layers. The two LB films can give off strong fluorescence, even though only one layer of LB film gives off strong fluorescence on ultraviolet irradiation. Strong fluorescence emission can be detected from this LB film by using a fluorescence spectrophotometer. Bright fluorescence spots can also be observed within the view field of a fluorescence microscope. However, when comparing one with the other, the fluorescence intensity of Eu(TTA) 3 Phen LB films is stronger than that of Sm(TTA) 3 Phen LB films. The intensity of the former is nearly 25 times the intensity of the latter.

Synthesis and assembly of gold nanoparticle-doped polymer solid foam films at the liquid/liquid interface and their catalytic properties.

Gold nanoparticle-doped poly(2-vinylpyridine) (P2VP) microcapsules and foam films were synthesized and assembled at the P2VP chloroform solution/HAuCl(4) aqueous solution interface at 25 °C. It was found that Au nanoparticles with the average diameter of 2.1 nm were homogeneously embedded in and adsorbed on the walls of the capsules and foams, the nanoparticles were composed of Au(0) and Au(III) with the molar ratio of about 75/25, and the mass percent of Au elements was measured to be 19.65%. The formation of the nanostructures was attributed to the self-assembly of P2VP at the liquid/liquid interface, the simultaneous reduction of AuCl(4)(-) ions by a small amount of ethanol in the chloroform and adsorption of AuCl(4)(-) ions. After irradiated by UV-light for 1h, the average diameter of the nanoparticles was found to be 2.2 nm, and the AuCl(4)(-) ions were transformed to Au(0) completely. The catalytic performance of these composite nanostructures were evaluated by using the reduction of 4-nitrophenol (4-NP) by potassium borohydride in aqueous solutions. The catalytic activity was very high in the first cycle, decreased rapidly and slightly in the second and third cycles, respectively, due to the aggregation of some nanoparticles, and stabilized after the third cycle.

Influence of several compounds on the fluorescence of rare earth complexes Eu(TTA)3Phen and Sm(TTA)3Phen in LB films

Abstract Five different compounds, included here arachidic acid (AA), tri-n-octyl phosphine oxide (TOPO), a kind of long chain Schiff base (SB), 5,10,15,20-tetra-4-oxy (2-stearic acid) phenyl porphyrin (TPP(−COOH)), and a long chain ferrocene derivative (Fc), were introduced into Langmuir—Blodgett (LB) films containing luminous rare earth complex Eu(TTA)3Phen or Sm(TTA)3Phen alternating with arachidic acid (AA). The subphase used was a composite subphase: an aqueous solution saturated with 1,10-phenanthroline, 2-thenoyltrifluoroacetone, and the complex Eu(TTA)3Phen or Sm(TTA)3Phen. Low angle X-ray diffraction results show that all the LB films have a periodic layer structure. Vertical uniformity of these LB films has been demonstrated by UV—Vis and fluorescence emission spectra. Both absorbance and relative fluorescence intensity increase linearly with the number of LB layers. The results of fluorescence spectra also indicate that, TOPO and SB have a fluorescence enhancement effect on the complexes, while TPP(−COOH) and Fc have a strong fluorescence quenching effect. AA does not influence the fluorescence of the complexes.

Expression of P-Glycoprotein and Multidrug Resistance-Associated Protein is Associated with Multidrug Resistance in Gastric Cancer

This study evaluated the sensitivities of gastric cancer cells to various chemotherapy drugs, and investigated the relationship between the expression of P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) and multidrug resistance. Drug sensitivities were determined using a methyltetrazolium assay: expression levels of P-gp and MRP were measured using immunohistochemistry. On purification culture, gastric cancer cells were found to be most sensitive to cisplatin, mitomycin and adriamycin, moderately sensitive to etoposide and 5-fluorouracil, and less sensitive to homocamptothecin and methotrexate, with sensitivities of 76.7%, 70.0%, 66.7%, 60.0%, 56.7%, 43.3% and 30.0%, respectively. Positive expression for P-gp and MRP in gastric cancer tissues was 41.7% and 29.2%, respectively;co-expression of P-gp and MRP in cancer tissue was 23%. The drug-resistant groups had higher positive expression of P-gp and MRP compared with the drug-sensitive groups. In conclusion, expression of P-gp and MRP seems to be associated with multidrug resistance in gastric cancer.

Formation of Ag nanoparticle-doped foam-like polymer films at the liquid-liquid interface.

The composite poly(2-vinylpyridine) (P2VP)-Ag(+) foam-like thin films were prepared at the interface between AgNO(3) aqueous solution and polymer chloroform solution at 25 °C. An X-ray photoelectron spectroscopy (XPS) investigation indicated that Ag(+) ions in the composite films were partially transformed to Ag atoms after irradiated by UV-light and completely transformed to Ag atoms after being treated with KBH(4) aqueous solution. Ag nanoparticles with the average sizes of 2.71 ± 0.82 and 3.28 ± 1.20 nm were generated in these two transferred films with different treatments, respectively. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images showed clearly that the composite films were composed of microcapsules whose walls had multilayer structures, and the nanoparticles were incorporated in the walls. The formation of the composite films at the liquid-liquid interface was attributed to the adsorption of the polymer molecules at the interface, coordination between the pyridine groups and Ag(+) ions, and self-assembly of the composite molecules. Furthermore, the catalytic activity of the composite films was evaluated using the reduction of 4-nitrophenol (4-NP) by KBH(4). The results demonstrated that the composite thin films have high and durable catalytic activity.

Free-standing poly(2-vinylpyridine) foam films doped with silver nanoparticles formed at the planar liquid/liquid interface.

Free-standing films of poly(2-vinylpyridine) doped with Ag(+) ions were fabricated at the planar liquid/liquid interface of an aqueous solution of AgNO(3) and a chloroform solution of the polymer through adsorption of the polymer molecules, combination with Ag(+) ions, and self-assembly of the composite species. Transmission electron microscopic (TEM) investigations indicated that the films were composed of planar thin layers decorated with separated microcapsules and foam structures of conglutinated microcapsules, and no Ag nanoparticles formed in the pristine films. After UV-light irradiation and KBH(4) aqueous solution treatment, Ag nanoparticles with the average size of 3.2 nm appeared and incorporated in the polymer matrices. X-ray photoelectron spectra (XPS) and UV-vis spectra are consistent with the TEM observations. Thermogravimetric analysis (TGA) showed good thermal stability of the composite films. The silver content was estimated to be 24.0% from the TG curve, closing to the calculated value. The catalytic performance of the composite films was evaluated by using the reduction of nitro-compounds, including nitrobenzene, 4-nitrophenol, and 4-nitrobenzoic acid by KBH(4) in aqueous solutions. The results indicated that the composite films have high and durable catalytic activity. The apparent reaction constants are related to the size of the nitro-compounds, suggesting that the Ag nanoparticles were incorporated in the matrices, and the diffusion of the reactant molecules has a great influence on the catalytic reaction.

Honeycomb-like thin films of Polystyrene-block-poly(2-vinylpyridine) embedded with gold or silver nanoparticles formed at the planer liquid/liquid interface

Composite thin films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) decorated with Au or Ag nanoclusters and nanoparticles were fabricated at the interfaces of chloroform solution of PS-b-P2VP and aqueous solutions of HAuCl4 or AgNO3. Transmission electron microscopy (TEM) investigations indicated that large area of a single-layer honeycomb structure was formed, which is composed of polygons (most of them are hexagons) whose walls look like spindles with the length of several hundreds of nanometers. Large amount of Au or Ag nanoparticles are embedded in the walls and the undersides of the honeycomb structures. The formation of these novel composite structures was attributed to the adsorption of block copolymer molecules and inorganic species of AuCl4(-) and Ag(+) ions at the liquid-liquid interface, the combination of the polymer molecules and the inorganic ions, and the self-assembly of the composite molecules. After UV-light irradiation and KBH4 aqueous solution treatment, the inorganic species were reduced completely, as confirmed by UV-vis spectra and X-ray photoelectron spectra. These composite films exhibited high catalytic activities for the reduction of 4-nitrophenol (4-NP) by KBH4 in aqueous solutions.

Influences of hydrophilic and hydrophobic substituents on the organization of supramolecular assemblies of porphyrin derivatives formed at the air/water interface

Abstract Monolayers and Langmuir–Blodgett (LB) films of several kinds of porphyrin derivatives that have different substituted alkyl chain length, chain numbers and central metals were studied by π-A isotherms, UV–Vis, polarized UV–Vis and fluorescence spectroscopy and low angle X-ray diffractometry (LAXD). The orientation angles of porphyrin rings and alkyl chains were derived from the polarized UV–Vis spectra and LAXD patterns of the monolayers or LB films, respectively. The rings of the freebase porphyrins with different alkyl chain length or number have similar orientation angles in the films due to the same hydrophilic groups on the rings, and those of metal porphyrins have different orientation angles from each other. The orientation of the alkyl chains is related to the special positions of the chains on the rings and the orientation of the rings. The influences of the hydrophilicity of the hydrophilic groups and the alkyl chain number and length on the organization of the supramolecular assemblies of the porphyrin derivatives were discussed.

Central metal effect on the organization of porphyrin LB films

Monolayers and Langmuir–Blodgett (LB) films of 5,10,15,20-tetra-4-oxy (2-stearic acid) phenylporphyrin (TSPP) and its complexes TSPPCu(II) and TSPPMn(III)Cl have been studied. π–A isotherms show that the molecular areas of the three molecules are similar to one another, while the polarized UV-vis spectra of the transferred films show different tilt angles of macrocycles with respect to the substrates: TSPP, 31°; TSPPCu(II), 0°; TSPPMn(III)Cl, 52°. The UV-vis spectra show that the π–π interactions between porphyrin macrocycles in monolayers of these three porphyrins are different. The Brewster angle microscopy (BAM) observations suggest that the monolayer behavior is also dependent on the central metal ions. These results indicate that the central metal ions have great influence on the organization of the films.

Fluorescence Spectroscopy of Polymer Systems Doped with Rare-Earth Metal Ions and Their Complexes

Abstract There has been an increased attention to explore the possibility of using polymer materials with rare-earth (RE) metal ions and their complexes as potential optical materials due to their capability of exhibiting novel and unusual properties. The fluorescence characteristics of polymer systems doped with RE metal ions and/or their complexes were analyzed and the effects of the doping metal ion/metal complexes as well as nature of the material were discussed. Electron transitions of REs can be manipulated by efficient ligand designs and proper doping into the polymer matrix. Emphasis was especially focused on the accommodation of the metal ion/metal complex in polymer matrix as well as its role in fluorescence. The photochemistry of the fluorescent polymer matrices with RE complexes is expected to open up frontier fields that lie between photophysics and materials science. Recent developments on a new aspect of these technologies related to the fluorescence dynamics in polymer analysis will also be discussed in this present review.