Poly(L-lysine)-graft-chitosan copolymers: Synthesis, characterization, and gene transfection effect

Polypeptide/polysaccharide graft copolymers poly(L-lysine)-graft-chitosan (PLL-g-Chi) were prepared by ring-opening polymerization (ROP) of epsilon-benzoxycarbonyl L-lysine N-carboxyanhydrides (Z-L-lysine NCA) in the presence of 6-O-triphenylmethyl chitosan. The PLL-g-Chi copolymers were thoroughly characterized by H-1 NMR, C-13 NMR, Fourier transform infrared (FT-IR), and gel permeation chromatography (GPC). The number-average degree of polymerization of PLL grafted onto the chitosan backbone could be adjusted by controlling the feed ratio of NCA to 6-O-triphenylmethyl chitosan. The particle size of the complexes formed from the copolymer and calf thymus DNA was measured by dynamic light scattering (DLS). It was found in the range of 120 similar to 340 nm. The gel retardation electrophoresis showed that the PLL-g-Chi copolymers possessed better plasmid DNA-binding ability than chitosan. The gene transfection effect in HEK 293T cells of the copolymers was evaluated, and the results showed that the gene transfection ability of the copolymer was better than that of chitosan and was dependent on the PLL grafting ratio. The PLL-g-Chi copolymers could be used as effective gene delivery vectors.

A biodegradable triblock copolymer poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-lysine): Synthesis, self-assembly and RGD peptide modification

A novel biodegradable triblock copolymer poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-lysine) (PEG-PLA-PLL) was synthesized by acidolysis of poly(ethylene glycol)-b-poly(L-lactide)-b-poly(F-benzyloxycarbonyl-L-lysine) (PEG-PLA-PZLL) obtained by the ring-opening polymerization (ROP) of epsilon-benzyloxycarbonyl-L-lysine N-carboxyanhydride (ZLys NCA) with amino-terminated PEG-PLA-NH2 as a macro-initiator, and the pendant amino groups of the lysine residues were modified with a peptide known to modulate cellular functions, Gly-Arg-Gly-Asp-Ser-Tyr (GRGDSY, abbreviated as RGD) in the presence of 1,1'-carbonyldiimidazole (CDI). The structures of PEG-PLA-PLL/RGD and its precursors were confirmed by H-1 NMR, FT-IR, amino acid analysis and XPS analysis. The cell adhesion and cell spread on the PEG-PLA-PLL/RGD film were enhanced compared to those on pure PLA film. Therefore, the novel RGD-grafted triblock copolymer is promising for cell or tissue engineering applications. Both copolymers PEG-PLA-PZLL and PEG-PLA-PLL showed an amphiphilic nature and could self-assemble into micelles of homogeneous spherical morphology. The micelles were determined by fluorescence technique, dynamic light scattering (DLS), and field emission scanning electron microscopy (ESEM) and could be expected to find application in drug and gene delivery systems.

新型杂化浆料的合成及其对碳纤维/异构聚酰亚胺复合材料性能的影响

通过合成新型改性剂——(γ-苯乙炔亚胺基)丙基三乙氧基硅烷(PEIPTES)实现对SiO2前驱体的原位改性,制备新型异构聚酰亚胺/SiO2杂化浆料,利用元素分析、FT-IR、热重分析等对PEIPTES的结构和性能以及新型杂化浆料的结构进行表征与分析。结果表明,杂化浆料中有机相与无机相之间形成化学键。利用该杂化浆料对碳纤维表面进行改性。AFM分析表明,改性后碳纤维表面覆盖一层有纳米级颗粒状突起的物质,增加表面粗糙度,有利于改善复合材料界面性能。复合材料力学性能研究表明,杂化浆料可提高碳纤维/异构聚酰亚胺复合材料的层间剪切强度,当SiO2含量为5wt%时层间剪切强度达到最大值,此时冲击性能和界面耐热性能均有显著提高。

Thionine-interlinked multi-walled carbon nanotube/gold nanoparticle composites

Multi-walled carbon nanotube (MWCNT)/thionine/gold nanoparticle composites were prepared by binding gold nanoparticles to the surfaces of thionine-coated carbon nanotubes. TEM images show gold nanoparticles distributed uniformly on nanotube walls and ends. UV-Vis, Raman, FT-IR, and zeta potential measurements were used to examine the properties of the resulting products. The composites demonstrate significant electrocatalytic activity for oxygen reduction. Although only gold nanoparticles were investigated here, the method could be easily extended to attach other metallic nanoparticles to the sidewalls of carbon nanotubes.

Fabrication and characterization of self-doped poly (aniline-co-anthranilic acid) nanorods in bundles

Poly (aniline-co-anthranilic acid) (PANANA) nanorods in bundles was prepared successfully in an alcohol/aqueous media without assistance of an), other kinds of acids. Anthranilic acid played all roles of monomer, acid-media provider, and dopant in the reaction system, and ammonium persulfate (APS) served as the oxidant. The morphologies of PANANA nanorods in bundles were investigated by scanning electron microscopy (SEM). Influences of the monomer molar ratio on the resulting morphology were investigated. Moreover the formation mechanism of the nanostructured copolymer was proposed. FT-IR. UV-vis and X-ray diffraction (XRD) measurements were used to confirm the molecular and electrical structure of the self-doped PANANA. The intrinsic properties, such as conductivity, electrochemical redox activity and room-temperature solubility of the resulting copolymer were explored.

Study of the mechanism of nanocrystalline Pb(Zr0.52Ti0.48)O-3 prepared by accelerated sol-gel process

Nanocrystalline Pb(Zr0.52Ti0.48)O-3 was prepared from lead acetate, zirconium oxynitrate and titanium tetra-n-butoxide by a sol-gel method. It is found that both the crystallization temperature of precursor PZT and PZT product size were increased with increase of V(C3H8O2)/V(H2O) ratio in solution used. At V(C3H8O2)/V(H2O) = 4.47 the gel was formed moderately quick, and the nanocrystalline PZT with uniform granularity and low crystallizing temperature could be obtained. The diameter of the final nanocrystalline was ranged 60similar to70 nm as measured by atomic force microscopy (AFM). The crystallizing temperature of the precursor PZT was 443degreesC and the crystallization reaction was completed at 500degreesC by DTA and TG. The sol-gel reaction process was monitored by FT-IR and XRD.

Sol-ogel deposition and luminescence properties of lanthanide ion-doped Y2(1-x)Gd2xSiWO8 (0 <= x <= 1) phosphor films

Y2(1-x) Gd2xSiWO8 : A ( 0 <= x <= 1; A= Eu3+, Dy3+, Sm3+, Er3+) phosphor films have been prepared on silica glass substrates through the sol - gel dip-coating process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscope (AFM), scanning electron microscopy (SEM) and photoluminescence spectra as well as lifetimes were used to characterize the resulting films. The results of the XRD indicated that the films began to crystallize at 800 degrees C and crystallized completely at 1000 degrees C. The AFM and SEM study revealed that the phosphor films, which mainly consisted of closely packed grains with an average size of 90 - 120 nm with a thickness of 660 nm, were uniform and crack free. Owing to an efficient energy transfer from the WO42- groups to the activators, the doped lanthanide ion ( A) showed its characteristic f - f transition emissions in crystalline Y2(1-x) Gd2xSiWO8 (0 <= x <= 1) films. The optimum concentrations for Eu3+, Dy3+, Sm3+, Er3+ were determined to be 21, 5, 3 and 7 mol% of Y3+ in Y2SiWO8 films, respectively.

Fabrication and luminescent properties of rare earths-doped Gd-2(WO4)(3) thin film phosphors by Pechini sol-gel process

Rare earth ions (Eu3+ and Dy3+)-doped Gd-2(WO4)(3) phosphor films were prepared by a Pechini sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting powders and films. The results of XRD indicate that the films begin to crystallize at 600degreesC and the crystallinity increases with the elevation of annealing temperatures. The film is uniform and crack-free, WO(4)(2-)mainly consists of closely packed fine particles with an average grain size of 80 nm. Owing to an energy transfer from 4 groups, the rare earth ions show their characteristic emissions in crystalline Gd-2(WO4)(3) phosphor films, i.e., D-5(J) -F-7(J), (J = 0, 1, 2, 3; J' = 0 1, 2, 3, 4, not in all cases) transitions for Eu3+ and F-4(9/2)-H-6(J) (J = 13/2, 15/2) transitions for D Y3+, with the hypersensitive transitions D-5(0)-F-7(2) (Eu3+) and F-4(9/2) - H-6(13/2) (Dy3+) being the most prominent groups, respectively.

Fabrication, patterning and luminescence properties of X-2-Y2SiO5 : A (A = Eu3+, Tb3+, Ce3+) phosphor films via sol-gel soft lithography

X-2-y(2)SiO(5):A (A = Eu3+, Tb3+, Ce3+) phosphor films and their patterning were fabricated by a sol-gel process combined with a soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy (SEM) optical microscopy and photoluminescence (PL) were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 900 degreesC with X-1-Y2SiO5, which transformed completely to X-2-Y2SiO5 at 1250 degreesC. Patterned thin films with different band widths (5 pin spaced by 5 pm and 16 pm spaced by 24 pm) were obtained by a soft lithography technique (micromoulding in capillaries, MIMIC). The SEM and AFM study revealed that the nonpattemed phosphor films were uniform and crack free, and the films mainly consisted of closely packed grains with an average size of 350 run. The doped rare earth ions (A) showed their characteristic emissions in X-2-Y2SiO5 phosphor films, i.e., D-5(0)-F-7(J) (J = 0, 1, 2,3,4) for Eu3+, D-5(3), (4)-F-7(J) (J = 6, 5, 4, 3) for Tb3+ and 5d (D-2)-4f (F-2(2/5),(2/7)) for Ce3+, respectively. The optimum doping concentrations for EU3+, Tb3+ were determined to be 13 and 8 mol% of Y3+ in X-2-Y2SiO5 films, respectively.

Citrate-gel synthesis and luminescent properties of alpha-Zn-3(PO4)(2) doped with Eu3+

By using inorganic salts as raw materials and citric acid as complexing agent, alpha-Zn-3(PO4)(2) and Eu3+ doped alpha-Zn-3(PO4)(2) phosphor powders were prepared by a citrate-gel process. X-ray diffraction, (XRD), TG - DTA, FT - IR and luminescence excitation and emission spectra were used to characterize the resulting products. The results of XRD reveal that the powders begin to crystallize at 500 degreesC and pure alpha-Zn-3(PO4)(2) phase is obtained at 800 degreesC. And the results of XRD reveal that Eu3+ exists Lis EoPO(4) ill the powder. In the phosphor powders, the Eu3+ shows its characteristic red-orange (592 nm, D-5(0) - F-7(1)) emission and has no quenching concentration.

Grafting polymerization of L-lactide on the surface of hydroxyapatite nano-crystals

A novel method of grafting ring-opening polymerization of L-lactide (LLA) onto the surface of hydroxyapatite nano-particles (n-HAP) was developed. PLLA was directly connected onto the HAP surface through a chemical linkage. The PLLA-g-HAP particles could be stably dispersed in organic solvent such as chloroform for several weeks. The n-HAP particles still retained the original dimension and shape after the grafting of PLLA. Compared with the P-31 MAS-NMR spectrum of pure HAP powders, there appeared a downfield displacement of 1.2 ppm in the spectrum of PLLA-g-HAP. Fourier transformation infrared (FT-IR) spectra further confirmed the existence of PLLA on the surface of PLLA-g-HAP. The amount of grafted polymer determined by thermal gravimetric analysis (TGA) was about 6% in weight. The tensile strength and elongation at break of the PLLA/PLLA-g-HAP composite containing 8 wt% of PLLA-g-HAP were 55 MPa and about 10-13%, respectively, while those of the PLLA/n-HAP composites were 40 MPa and 3-5%, respectively.

Synthesis of a novel structural triblock copolymer of poly(gamma-benzyl-L-glutamic acid)-b-poly(ethylene oxide)-b-poly(epsilon-caprolactone)

A novel structural triblock copolymer of poly(gamma-benzyl-L-glutamic acid)-b-poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PBLG-PEO-PCL) was synthesized by a new approach in the following three steps: (1) sequential anionic ring opening polymerization (ROP) of ethylene oxide and epsilon-caprolactone with an acetonitrile/potassium naphthalene initiator system to obtain a diblock copolymer CN-PEO-PCL with a cyano end-group; (2) conversion of the CN end-group into NH2 end-group by hydrogenation to obtain NH2-PEO-PCL; (3) ROP of gamma-benzyl-L-glutamate-N-carboxyanhydrides (Bz-L-GluNCA) with NH2-PEO-PCL as macroinitiator to obtain the target triblock copolymer. The structures from CN-PEO precursor to the triblock copolymers were confirmed by FT-IR and H-1 NMR spectroscopy, and their molecular weights were measured by gel permeation chromatography. The monomer of Bz-L-GluNCA can react almost quantitatively with the amino end-groups of NH2-PEO-PCL macroinitiator by ROP.

Preparation and luminescence properties of in situ formed lanthanide complexes covalently grafted to a silica network

Lanthanide-doped sol-gel-derived materials are an attractive type of luminescent materials that can be processed at ambient temperatures. However, the solubility of the lanthanide complexes in the matrix is a problem and it is difficult to obtain a uniform distribution of the complexes. Fortunately, these problems can be solved by covalently linking the lanthanide complex to the sol-gel-derived matrix. In this study, luminescent Eu3+ and Tb3+ bipyridine complexes were immobilized on sol-gel-derived silica. FT-IR, DTA-TG and luminescence spectra, as well as luminescence decay analysis, were used to characterize the obtained hybrid materials. The organic groups from the bipyridine-Si moiety were mostly destroyed between 220 and 600 degreesC. The luminescence properties of lanthanide bipyridine complexes anchored to the backbone of the silica network and the corresponding pure complexes were comparatively investigated, which indicates that the lanthanide bipyridine complex was formed during the hydrolysis and co-condensation of TEOS and modified bipyridine. Excitation at the ligand absorption wavelength (336 nm for the hybrid materials and 350 nm for the pure complexes) resulted in strong emission of the lanthanide ions: Eu3+ D-5(0)-F-7(J) (J = 0, 1, 2, 3, 4) and Tb3+ D-5(4)-F-7(J) (J = 6, 5, 4, 3) emission lines due to efficient energy transfer from the ligands to the lanthanide ions.

Novel soluble N-phenyl-carbazole-containing PPVs for light-emitting devices: Synthesis, electrochemical, optical, and electroluminescent properties

Novel PPV derivatives (PCA8-PV and PCA8-MEHPV) containing N-phenyl-carbazole units on the back-bone were successfully synthesized by the Wittig polycondensation of 3,6-bisformyl-N-(4-octyloxy-phenyl)carbazole with the corresponding tributyl phosphonium salts in good yields. The newly formed and dominant trans vinylene double bonds were confirmed by FT-IR and NMR spectroscopy. The polymers (with (M) over bar (w) of 6289 for PCA8-PV and 7387 for PCA8-MEHPV) were soluble in common organic solvents and displayed high thermal stability (T(g)s are 110.7 degreesC for PCA8-PV and 92.2 degreesC for PCA8-MEHPV, respectively) because of the incorporation of the N-phenyl-carbazole units. Cyclic voltammetry investigations (onsets: 0.8 V for PCA8-PV and 0.7 V for PCA8-MEHPV) suggested that the polymers possess enhanced hole injection/transport properties, which can be also attributed to the N-phenyl-carbazole units on the backbone. Both the single-layer and the double-layer light-emitting diodes (LEDs) that used the polymers as the active layer emitted a greenish-blue or bluish-green light (the maximum emissions located 494 nm for PCA8-PV and 507 nm for PCA8-MEHPV, respectively).

beta-cyclodextrin controlled assembling nanostructures from gold nanoparticles to gold nanowires

In this Letter, P-cyclodextrin (P-CD) was employed as stabilizer in the synthesis of gold nanoparticles. Gold nanoparticles were synthesized by the reduction of HAuCl4 by NaBH4 in the presence of P-CD. Varying the ratio of P-Cl) to HAuCl4, isolated gold nanoparticles could be assembled into nanowires. The nanoparticles and nanowires were characterized by transmission electron microscopy, UV/visible spectroscopy, infrared spectroscopy and X-ray photoelectron spectroscopy. The decreased relative intensity of skeletal and ring vibration in FT-IR spectra and the negative shift of the Au4f(7/2) binding energy in XPS spectra confirmed that beta-CD was chemisorped on An nanoparticles via hydroxyl group.