MCM-41 functionalized with YVO4 : Eu3+: a novel drug delivery system

Luminescence functionalization of ordered mesoporous MCM-41 silica was realized by depositing a YVO4:Eu3+ phosphor layer on its surface via the Pechini sol-gel process. This material, which combines the mesoporous structure of MCM-41 and the strong red luminescence property of YVO4: Eu3+, has been studied as a host carrier for drug delivery/release systems. The structure, morphology, texture and optical properties of the materials were well characterized by x-ray diffraction ( XRD), Fourier infrared spectroscopy ( FT-IR), transmission electron microscopy ( TEM), N-2 adsorption and photoluminescence ( PL) spectra. The results indicated that the specific surface area and pore volume of MCM-41, which were directly correlated to the drug-loading amount and ibuprofen ( IBU) release rate, decreased in sequence after deposition of YVO4:Eu3+ and loading of IBU as expected. The IBU-loaded YVO4:Eu3+@ MCM-41 system still showed red luminescence under UV irradiation ( 365 nm) and a controlled release property for IBU. In addition, the emission intensity of Eu3+ increases with an increase in the cumulative released amount of IBU, making the extent of drug release easily identified, tracked and monitored by the change of luminescence, which demonstrates its potential application in drug delivery/release systems.

Alternate assemblies of polyelectrolyte functionalized carbon nanotubes and platinum nanoparticles as tunable electrocatalysts for dioxygen reduction

A novel method based on electrostatic layer-by-layer self-assembly (LBL) technique for alternate assemblies of polyelectrolyte functionalized multi-walled carbon nanotubes (MWNTs) and platinum nanoparticles (PtNPs) is proposed. The shortened MWNTs can be functionalized with positively charged poly(diallyldimethylammonium chloride) (PDDA) based on electrostatic interaction. Through electrostatic layer-by-layer assembly, the positively charged PDDA functionalized MWNTs (PDWNTs) and negatively charged citrate-stabilized PtNPs were alternately assembled on a 3-mercaptopropanesulfonic sodium (NIPS) modified gold electrode and also on other negatively charged surface, e.g. quartz slide and indium-tin-oxide (ITO) plate, directly forming the three-dimensional (3D) nanostructured materials. This is a very general and powerful technique for the assembling three-dimensional nanostructured materials containing carbon nanotubes (CNTs) and nanoparticles. Thus prepared multilayer films were characterized by ultraviolet-visiblenear-infrared spectroscopy (UV-vis-NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). Regular growth of the mutilayer films is monitored by UV-vis-NIR.

Sensitive biomimetic sensor based on molecular imprinting at functionalized indium tin oxide electrodes

We initially report an electrochemical sensing platform based on molecularly imprinted polymers (MIPs) at functionalized Indium Tin Oxide Electrodes (ITO). In this research, aminopropyl-derivatized organosilane aminopropyltriethoxysilane (APTES), which plays the role of functional monomers for template recognition, was firstly self-assembled on an ITO electrode and then dopamine-imprinted sol was spin-coated on the modified surface. APTES which can interact with template dopamine (DA) through hydrogen bonds brought more binding sites located closely to the surface of the ITO electrode, thus made the prepared sensor more sensitive for DA detection. Potential scanning is presented to extract DA from the modified film, thus DA can rapidly and completely leach out. The affinity and selectivity of the resulting biomimetic sensor were characterized using cyclic voltammetry (CV). It exhibited an increased affinity for DA over that of structurally related molecules, the anodic current for DA oxidation depended on the concentration of DA in the linear range from 2 x 10(-6) M to 0.8 x 10(-3) M with a correlation coefficient of 0.9927.In contrast, DA-templated film prepared under identical conditions on a bare ITO showed obviously lower response toward dopamine in solution.

Synthesis of the first rare earth metal bis(alkyl)s bearing an indenyl functionalized N-heterocyclic carbene

Treatment of indenyl-modified imidazolium bromide [C9H7CH2CH2(NCHCHN(C6H2Me3-2,4,6)CH)Br] ((IndH-NHC-H)Br) with rare earth metal tetra(alkyl) lithium (Ln(CH2SiMe3)(4)Li(THF)(4)) or with (trimethylsilylmethyl)lithium (LiCH2SiMe3) and rare earth metal tris(alkyl)s (Ln(CH2SiMe3)(3)(THF)(2)) sequentially afforded the first NHC-stabilized monomeric rare earth metal bis(alkyl) complexes (Ind-NHC)Ln(CH2SiMe3)(2) (1, Ln = Y; 2, Ln = Lu; 3, Ln = Sc) via double-deprotonation reactions. Complexes 1-3 are THF-free isostructural monomers. The monoanionic Ind-NHC species bond to the central metal ion in a eta(5):kappa(1) constrained geometry configuration (CGC) mode, which combine with the two cis-located alkyl moieties to form a tetrahedron ligand core, leading to the chirality of the complexes. Under the presence of activators AlEt3 and [Ph3C][B(C6F5)(4)], complex 2 showed catalytic activity toward the polymerization of isoprene to afford 3,4-regulated polyisoprene (91%).

Polyelectrolyte-functionalized ionic liquid for electrochemistry in supporting electrolyte-free aqueous solutions and application in amperometric flow injection analysis

As a green process, electrochemistry in aqueous solution without a supporting electrolyte has been described based on a simple polyelectrolyte-functionalized ionic liquid (PFIL)-modified electrode. The studied PFIL material combines features of ionic liquids and traditional polyelectrolytes. The ionic liquid part provides a high ionic conductivity and affinity to many different compounds. The polyelectrolyte part has a good stability in aqueous solution and a capability of being immobilized on different substrates. The electrochemical properties of such a PFIL-modified electrode assembly in a supporting electrolyte-free solution have been investigated by using an electrically neutral electroactive species, hydroquinone ( HQ) as the model compound. The partition coefficient and diffusion coefficient of HQ in the PFIL film were calculated to be 0.346 and 4.74 X 10(-6) cm(2) s(-1), respectively. Electrochemistry in PFIL is similar to electrochemistry in a solution of traditional supporting electrolytes, except that the electrochemical reaction takes place in a thin film on the surface of the electrode. PFILs are easily immobilized on solid substrates, are inexpensive and electrochemically stable. A PFIL-modified electrode assembly is successfully used in the flow analysis of HQ by amperometric detection in solution without a supporting electrolyte.

Enhanced response induced by polyelectrolyte-functionalized ionic liquid in glucose biosensor based on sol-gel organic-inorganic hybrid material

In this work, a polyelectrolyte-functionalized ionic liquid (PFIL) was firstly incorporated into a sol-gel organic-inorganic hybrid material (PFIL/sol-gel). This new composite material was used to immobilize glucose oxidase on a glassy carbon electrode. An enhanced current response towards glucose was obtained, relative to a control case without PFIL. In addition, chronoamperometry showed that electroactive mediators diffused at a rate 10 times higher in the apparent diffusion coefficient in PFIL-containing matrices. These findings suggest a potential application in bioelectroanalytical chemistry.

Simultaneous determination of dopamine and ascorbic acid at an in-site functionalized self-assembled monolayer on gold electrode

The in-site functionalization of 4-aminothiophenol (4-ATP) self-assembled monolayer on gold electrode at physiological pH yields a redox active monolayer of 4'-mercapto-N-phenylquinone diimine (MNPD). The functionalized electrode exhibits excellent electrocatalytic responses towards dopamine (DA) and ascorbic acid (AA), reducing the overpotentials by about 0.22 V and 0.34 V, respectively, with greatly enhanced current responses. Due to its different catalytic activities toward DA and AA, the modified electrode resolves the overlapping voltammetric responses of DA and AA into two well-defined voltammetric peaks by differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly related to DA and AA concentration in the ranges of 5.0 x 10-6 - 1.25 x 10-4 M and 8.0 x 10-6 - 1.3 x 10-4 M with correlation coefficient of 0.999 and 0.998, respectively. The detective limits (3sigma) for DA and AA were found to be 1.2 x 10-6 M and 2.4 x 10-6 M, respectively.

A novel method to construct a third-generation biosensor: self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres

A novel method for fabrication of horseradish peroxidase (HRP) biosensor has been developed by self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanospheres. At first, a cleaned gold electrode was immersed in thiol-functionalized poly(St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization of St with AA and function with dithioglycol to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups. Finally, horseradish peroxi- dase was immobilized on the surface of the gold nanoparticles. The sensor displayed an excellent electrocatalytical response to reduction of H2O2 without the aid of an electron mediator. The sensor was highly sensitive to hydrogen peroxide with a detection limit of 4.0 mumol l(-1), and the linear range was from 10.0 mumol l(-1) to 7.0 mmol l(-1). The biosensor retained more than 97.8% of its original activity after 60 days of use. Moreover, the Studied biosensor exhibited good current repeatability and good fabrication reproducibility.

Radical co-polymerization of diiminedibromidenickel(II)-functionalized olefin with styrene: synthesis of polymer-incorporated nickel(II) alpha-diimine catalysts for ethylene polymerization

alpha-Diimine nickel catalyst hearing two allyl groups [ArN=C](2)C10H6NiBr2 (Ar = 4-allyl-2,6-(i-Pr)(2)C6H2)] (Cat-I) has been synthesized and characterized. The corresponding polymer-incorporated nickel catalysts PC and the SiO2-supported shell-core structure catalyst SC-1 were obtained by the co-polymerization of the olefin groups of Cat-1 with styrene in the presence of a radical initiator. Radical co-polymerizations with styrene in Solution were investigated in detail, and the compositions and molecular weight of the copolymers were determined. All three types of catalysts (Cat-1, PC and SC-1) have been investigated for ethylene polymerization. These catalysts were found to exhibit high activity in the presence of modified methylaluminoxane (MMAO) as a co-catalyst. Among them, the polymer-incorporated PC and SiO2 shell-core catalyst SC-1 displayed very high activity (similar to2.62 and similar to1.11 kg (mmol Ni)(-1) h(-1), respectively) with product molecular weights (M,) in the range 26 x 10(4) to 47 x 10(4) under 0.1 MPa ethylene pressure. The particle morphology of polyethylene produced by the shell-core structure catalyst SC-1 was improved.

Synthesis and characterization of functionalized mesoporous silica by aerosol-assisted self-assembly

An efficient, productive, and low-cost aerosol-assisted self-assembly process has been developed to produce organically modified mesoporous silica particles via a direct co-condensation of silicate species and organosilicates that contain nonhydrolyzable functional groups in the presence of templating surfactant molecules. Different surfactants including cetyltrimethylammonium bromide, nonionic surfactant Brij-56, and triblock copolymer P123 have been used as the structure-directing agents. The organosilanes used in this study include tridecafluoro-1, 1,2,2-tetrahydrooctyltriethoxysilane, methytriethoxysilane, vinyltrimethoxysilane, and 3-(trimethoxysilyl)propyl methacrylate. X-ray diffraction and transmission electron microscopy studies indicate the formation of particles with various mesostructures. Fourier transform infrared and solid-state nuclear magnetic resonance spectra confirm the organic ligands are covalently bound to the surface of the silica framework. The porosity, pore size, and surface area of the particles were characterized using nitrogen adsorption and desorption measurements.

Covalent linking of near-infrared luminescent ternary lanthanide (Er3+, Nd3+, Yb3+) complexes on functionalized mesoporous MCM-41 and SBA-15

The near-infrared (NIR) luminescent lanthanide ions, such as Er(III), Nd(III), and Yb(III), have been paid much attention for the potential use in the optical communications or laser systems. For the first time, the NIR-luminescent Ln(dbm)(3)phen complexes have been covalently bonded to the ordered mesoporous materials MCM-41 and SBA-15 via a functionalized phen group phen-Si (phen-Si = 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline; dbm = dibenzoylmethanate; Ln = Er, Nd, Yb). The synthesis parameters X = 12 and Y = 6 h (X denotes Ln(dbM)(3)(H2O)(2)/phen-MCM-41 molar ratio or Ln(dbM)(3)(H2O)(2)/phenSBA-15 molar ratio and Y is the reaction time for the ligand exchange reaction; phen-MCM-41 and phenSBA-15 are phen-functionalized MCM-41 and SBA-15 mesoporous materials, respectively) were selected through a systematic and comparative study. The derivative materials, denoted as Ln(dbM)(3)phen-MCM-41 and Ln(dbm)(3)phen-SBA-15 (Ln = Er, Nd, Yb), were characterized by powder X-ray diffraction, nitrogen adsorption/desorption, Fourier transform infrared (FT-IR), elemental analysis, and fluorescence spectra. Upon excitation of the ligands absorption bands, all these materials show the characteristic NIR luminescence of the corresponding lanthanide ions through the intramolecular energy transfer from the ligands to the lanthanide ions.

Self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres for fabrication of a mediatorless biosensor

A novel strategy to construct a sensitive mediatorless sensor of H2O2 was described. At first, a cleaned gold electrode was immersed in thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization St with AA and function with dithioglycol to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups and formed monolayers on the surface of poly(St-co-AA) nanospheres. Finally, horseradish peroxidase (HRP) was immobilized on the surface of the gold nanoparticles. The sensor displayed an excellent electrocatalytical response to reduction of H2O2 without the aid of an electron mediator. The biosensor showed a linear range of 8.0 mu mol L-1-7.0 mmol L-1 with a detection limit of 4.0 mu mol L-1. The biosensor retained more than 97.8% of its original activity after 60 days' storage. Moreover, the studied biosensor exhibited good current reproducibility and good fabrication reproducibility.

Hydrazide-functionalized hollow porous poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) spheres for immobilization of enzyme

Hollow porous poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate)(HEMA-co-EDMA) spheres were prepared by emulsifier-free emulsion polymerization, swelling, seed emulsion polymerization and extraction. Then the spheres activated with 2,4,6-trichloro-1,3,5-triazine were functioned with adipohydrazide (AH). After periodate oxidation of its carbohydrate moieties, horseradish peroxidase was immobilized on the hydrazide-functionalized hollow porous poly(HEMA-co-EDMA) spheres. The amount of immobilized enzyme was up to 43.4 mu g of enzyme/g of support. Moreover, the immobilized horseradish peroxidase exhibited high activity and good stability.