Fabrication and spectroscopic broadening properties for 1.5 mu m amplification of Er3+-doped BaF2 nanoparticles

We show the potential application of Er3+-doped BaF2 nanoparticles prepared from microemulsion technology for 1.5 mu m amplification in telecommunication. Nanoparticles with different sizes of about 8, 10, and 20.5 nm were prepared. The XRD patterns showed the excursion of diffraction peaks. When the particle size is smaller or the diffraction angle is larger, this kind of excursion will be more serious.

Electrochemical and electrochemiluminescence study of Ru(bpy)(3)(2+)-doped silica nanoparticles with covalently grafted biomacromolecules

Spherical Ru(bpy)(3)(2+)-doped silica (RuSi) nanoparticles were prepared via a water-in-oil microemulsion approach. The electrochemical and electrochemiluminescent properties of the RuSi nanoparticles immobilized on an indium tin oxide (ITO) electrode were investigated. Further, electrochemiluminescence (ECL) of the RuSi nanoparticles with covalently coated biomacromolecules was studied. By covalent cross-linking with glutaraldehyde, gamma-(aminopropyl) triethoxysilane (APTES)-pretreated RuSi nanoparticles were coupled with different concentrations of bovine serum albumin (BSA), hemoglobin, and myoglobin, respectively.

Formation of reversible shell cross-linked micelles from the biodegradable amphiphilic diblock copolymer poly(L-cysteine)-block-poly(L-lactide)

A novel biodegradable diblock copolymer, poly(L-cysteine)-b-Poly(L-lactide) (PLC-b-PLLA), was synthesized by ring-opening polymerization (ROP) of N-carboxyanhydride of beta-benzyloxycarbonyl-L-Cysteine (ZLC-NCA) with amino-terminated Poly(L-lactide) (NH2-PLLA) as a macroinitiator in a convenient way. The diblock copolymer and its precursor were characterized by H-1 NMR, Fourier transform infrared (FT-IR), gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS) measurements. The length of each block polymer could be tailored by molecular design and the ratios of feeding monomers.

Electroactive Aniline Pentamer Cross-Linking Chitosan for Stimulation Growth of Electrically Sensitive Cells

A new kind of electroactive polymers was synthesized by using aniline pentamer (AP) cross-linking chitosan (CS) in acetic acid/DMSO/DMF solution. UV-vis and CV confirmed the electroactivity of polymers in acidic aqueous solution. The amphiphilic polymers self-assembled into 200-300 nm micelles by dialysis against deionized water from the acetic acid buffer solution. Three samples with different weight percentages of AP were used to identify the relationship between the content of AP and the differentiation of rat neuronal pheochromocytoma PC-12 cells without external stimulation.

Immobilization of dipyridyl complex to magnetic nanoparticle via click chemistry as a recyclable catalyst for Suzuki cross-coupling reactions

A magnetic nanoparticle (MNP)-supported di(2-pyridyl)methanol palladium dichloride complex was prepared via click chemistry. The MNP-supported catalyst was evaluated in Suzuki coupling reaction in term of activity and recyclability in DMF. It was found to be highly efficient for Suzuki coupling reaction using aryl bromides as substrates and could be easily separated by an external magnet and reused in five consecutive runs without obvious loss of activity.

Preparation of Hollow Carbon and Silicon Carbide Fibers with Different Cross-Sections by using Electrospun Fibers as Templates

Hollow carbon nanofibers with circular and rectangular opening were prepared by using electrospun silica fibers as templates. Silica fibers were synthesized by electrospinning, and they were coated with a carbon layer formed by thermal decomposition and carbonization of polystyrene under a nitrogen atmosphere. Hollow carbon nanofibers with circular and rectangular openings were then obtained after the silica core was etched by hydrofluoric acid. The carbon nanofibers with different morphologies also could be used as templates to fabricate silicon carbide fibers. The silicon carbide fibers with circular and rectangular openings could be obtained by using hollow carbon nanofibers and carbon belts as templates, respectively.

Macrocycle-Terminated Core-Cross-Linked Star Polymers: Synthesis and Characterization

We have synthesized macrocyclic polystyrene- (PS-) terminated PS star polymers via a core-cross-linking approach in this work. A tadpole-shaped macrocyclic PS-linear-PS copolymer was synthesized at first via click chemistry and ATRP polymerization method. The "living" ATRP initiating chain-ends of the tadpole-shaped copolymers were linked together via ATRP polymerization with divinylbenzene to form a core-cross-linked macrocyclic star polymer. The number of arms attached to the macrocyclic star polymers was measured with NMR. and absolute molecular weights with gel permeation chromatography (GPC) with multiangle laser light scattering detector. These macrocyclic star polymers had a highly cross-linked core and many radiating arms. The shorter tadpole-shaped precursors caused core-cross-linked star polymers with higher molecular weights and more arm numbers. The macrocycle-terminated core-cross-linked star polymers showed two glass transition temperatures, one arising from the linear branches and another from the macrocycles.

[Ru(bpy)(2)(dcbpy)NHS] Labeling/Aptamer-Based Biosensor for the Detection of Lysozyme by Increasing Sensitivity with Gold Nanoparticle Amplification

A novel [Ru(bpy)(2) (dcbpy)NHS] labeling/aptamer-based biosensor combined with gold nanoparticle amplification for the determination of lysozyme with an electrochemiluminescence (ECL) method is presented. In this work, an aptamer, an ECL probe, gold nanoparticle amplification, and competition assay are the main protocols employed in ECL detection. With all the protocols used, an original biosensor coupled with an aptamer and [Ru(bpy)(2)(dcbpy)NHS] has been prepared. Its high selectivity and sensitivity are the main advantages over other traditional [Ru(bpy)(3)](2+) biosensors. The electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) characterization illustrate that this biosensor is fabricated successfully. Finally, the biosensor was applied to a displacement assay in different concentrations of lysozyme solution, and an ultrasensitive ECL signal was obtained. The ECL intensity decreased proportionally to the lysozyme concentration over the range 1.0 x 10-(13)-1.0 x 10(-8) mol L-1 with a detection limit of 1.0 x 10(-13) mol L-1.

Guanidine/Pd(OAc)(2)-catalyzed room temperature Suzuki cross-coupling reaction in aqueous media under aerobic conditions

A highly efficient Pd(OAc)(2)/guanidine aqueous system for the room temperature Suzuki cross-coupling reaction has been developed. The new water-soluble and air-stable catalyst Pd(OAc)(2)(.)(1f)(2) from Pd(OAc)(2) and 1,1,3,3-tetramethyl-2-n-butylguanidine (1f) was synthesized and characterized by X-ray crystallography. In the presence of Pd(OAc)(2)(.)(1f)(2), coupling of arylboronic acids with a wide range of aryl halides, including aryl iodides, aryl bromides, even activated aryl chlorides, was carried out smoothly in aqueous solvent to afford the cross-coupling products in good to excellent yields and high turnover numbers (TONs) (TONs up to 850 000 for the reaction of 1-iodo-4-nitrobenzene and phenylboronic acid). Furthermore, this mild protocol could tolerate a broad range of functional groups.

Monooxychlorophosphine as a novel and efficient ligand for palladium-catalyzed suzuki-miyaura cross-coupling of aryl chlorides

A new sterically hindered monooxychlorophosphine was synthesized and the complex generated in situ from its reaction with Pd-2(dba)(3) promoted the Suzuki-Miyaura reactions of arylboronic acids with aryl chlorides in good yields.

Synthesis and characterization of photo-cross-linked hydrogels based on biodegradable polyphosphoesters and poly(ethylene glycol) copolymers

Novel biodegradable hydrogels by photo-cross-linking macromers based on polyphosphoesters and poly(ethylene glycol) (PEG) are reported. Photo-cross-linkable macromers were synthesized by ring-opening polymerization of the cyclic phosphoester monomer 2-(2-oxo-1,3,2-dioxaphospholoyloxy) ethyl methacrylate (OPEMA) using PEG as the initiator and stannous octoate as the catalyst. The macrorners were characterized by H-1 NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography measurements. The content of polyphosphoester in the macromer was controlled by varying the feed ratio of OPEMA to PEG. Hydrogels were fabricated by exposing aqueous solutions of macromers with 0.05% (w/w) photoinitiator to UV light irradiation, and their swelling kinetics as well as degradation behaviors were evaluated. The results demonstrated that cross-linking density and pH values strongly affected the degradation rates. The macromers was compatible to osteoblast cells, not exhibiting significant cytotoxicity up to 0.5 mg/mL. "Live/dead" cell staining assay also demonstrated that a large majority of the osteoblast cells remained viable after encapsulation into the hydrogel constructs, showing their potential as tissue engineering scaffolds.

The critical lowest molecular weight for PEG to crystallize in cross-linked networks

Poly(ethylene glycol) (PEG) networks were synthesized by gamma-irradiation. The crystalline behavior of PEG was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). It was shown that the crystallinity of PEG is dramatically lower in the cross-linked, networks than in pure PEG. When the molecular weight of PEG in the networks decreased to 1000, it could not crystallize at all. Moreover, we also found that the melting temperature of PEG is greatly affected by the presence of a cross-linked network.

Preparation of fully cross-linked CNBR/PP-g-GMA and CNBR/PP/PP-g-GMA thermoplastic elastomers and their morphology, structure and properties

Binary CNBR/PP-g-GMA and ternary CNBR/PP/PP-g-GMA thermoplastic elastomers were prepared by reactive blending carboxy nitrile rubber (CNBR) powder with nanometer dimension and polypropylene functionalized with glycidyl methacrylate (PP-g-GMA). Morphology observation by using an atomic force microscope (AFM) and TEM revealed that the size of CNBR dispersed phase in CNBR/PP-g-GMA binary blends was much smaller than that of the corresponding CNBR/PP binary blends. Thermal behavior of CNBR/PP-g-GMA and CNBR/PP blends was studied by DSC. Comparing with the plain PP-g-GMA, T, of PP-g-GMA in CNBR/PP-g-GMA blends increased about 10degreesC. Both thermodynamic and kinetic effects would influence the crystallization behavior of PP-g-GMA in CNBR/PP-g-GMA blends. At a fixed content of CNBR, the apparent viscosity of the blending system increased with increasing the content of PP-g-GMA. FTIR spectrum verified that the improvement of miscibility of CNBR and PP-g-GMA was originated from the reaction between carboxy end groups of CNBR and epoxy groups of GMA grafted onto PP molecular chains. Comparing with CNBR/PP blends, the tensile strength, stress at 100% strain, and elongation at break of CNBR/PP-g-GMA blends were greatly improved.

Immunosensors based on layer-by-layer self-assembled Au colloidal electrode for the electrochemical detection of antigen

Colloidal Au particles have been deposited on the gold electrode through layer-by-layer self-assembly using cysteamine as cross-linkers. Self-assembly of colloidal Au on the gold electrode resulted in ail easier attachment of antibody, larger electrode surface and ideal electrode behavior. The redox reactions of [Fe(CN)(6)]-/[Fe(CN)(6)](3-) on the gold surface were blocked due to antibody immobilization, which were investigated by cyclic voltammetry and impedance spectroscopy. The interaction of antigen with grafted antibody recognition layers was carried out by soaking the modified electrode into a phosphate buffer at pH 7.0 with various concentrations of antigen at 37degreesC for 30 min. Further, an amplification strategy to use biotin conjugated antibody was introduced for improving the sensitivity of impedance measurements. Thus, the sensor based oil this immobilization method exhibits a large linear dynamic range, from 5 - 400 mug/L for detection of Human IgG. The detection limit is about 0.5 mug/L.

Synthesis of fluorene-based oligomeric organoboron reagents via Kumada, Heck, and stille cross-coupling reactions

Boronic pinacol ester group is not reactive in Kumada, Heck and Stille coupling reaction conditions. Fluorene-based sophisticated organoboron compounds were synthesized by means of Palladium catalyzed Kumada, Heck and Stille cross-coupling reactions from halofluorenyl boronic esters.