Synthesis of Ag/Polypyrrole Core-Shell Nanospheres by a Seeding Method

Ag/polypyrrole (PPy) core‐shell nanospheres were fabricated through the redox reaction between pyrrole monomer and silver nitrate in the presence of polyvinylpyrrolidone (PVP) and by using the Ag colloidal nanoparticles acting as the seedings. The prepared nanospheres with a shell thickness of 10–12 nm and a core diameter of 20–40 nm are uniform in size and well dispersed. The morphologies, compositions, and electrochemical activities of Ag/PPy composites were characterized by TEM, XRD, FTIR, TGA and CV. The synthetic route employed here is gentle and can be extended to prepare other conducting polymer/inorganic nanocomposites.     

Preparation and evaluation of a macroporous molecularly imprinted hybrid silica monolithic column for recognition of proteins by high performance liquid chromatography

A novel type of macroporous molecularly imprinted hybrid silica monolithic column was first developed for recognition of proteins. The macroporous silica-based monolithic skeleton was synthesized in a 4.6 mm i.d. stainless steel column by a mild sol–gel process with methyltrimethoxysilane (MTMS) as a sole precursor, and then vinyl groups were introduced onto the surface of the silica skeleton by chemical modification of γ-methacryloxypropyltrimethoxysilane (γ-MAPS). Subsequently, the molecularly imprinted polymer (MIP) coating was copolymerized and anchored onto the surface of the silica monolith. Bovine serum albumin (BSA) and lysozyme (Lyz), which differ greatly in molecular size, isoelectric point, and charge, were representatively selected for imprinted templates to evaluate recognition property of the hybrid silica-based MIP monolith. Some important factors, such as template–monomer molar ratio, total monomer concentration and crosslinking density, were systematically investigated. Under the optimum conditions, the obtained hybrid silica-based MIP monolith showed higher binding affinity for template than its corresponding non-imprinted (NIP) monolith. The imprinted factor (IF) for BSA and Lyz reached 9.07 and 6.52, respectively. Moreover, the hybrid silica-based MIP monolith displayed favorable binding characteristics for template over competitive protein. Compared with the imprinted silica beads for stationary phase and in situ organic polymer-based hydrogel MIP monolith, the hybrid silica MIP monolith exhibited higher recognition, stability and lifetime.     

Frame difference families and resolvable balanced incomplete block designs

Frame difference families, which can be obtained via a careful use of cyclotomic conditions attached to strong difference families, play an important role in direct constructions for resolvable balanced incomplete block designs. We establish asymptotic existences for several classes of frame difference families. As corollaries new infinite families of 1-rotational \((pq+1,p+1,1)\)-RBIBDs over \({\mathbb {F}}_{p}^+ \times {\mathbb {F}}_{q}^+\) are derived, and the existence of \((125q+1,6,1)\)-RBIBDs is discussed. We construct (v, 8, 1)-RBIBDs for \(v\in \{624,\) \(1576,2976,5720,5776,10200,14176,24480\}\), whose existence were previously in doubt. As applications, we establish asymptotic existences for an infinite family of optimal constant composition codes and an infinite family of strictly optimal frequency hopping sequences.     

Synthesis of SERS active Au nanowires in different noncoordinating solvents

Au nanowires with length up to micrometers were synthesized through a simple and one-pot solution growth method. HAuCl₄ was reduced in a micellar structure formed by 1-octadecylamine and oleic acid in hexane, heptane, toluene and chloroform, respectively. As the non-polarity of noncoordinating solvents can affect the nucleation and growth rates of Au nanostructures, Au nanowires with different diameters could be obtained by changing the noncoordinating solvents in the synthetic process. The influences of the solvents on the morphology of Au nanowires were systematically studied. When using hexane as reaction solvent, the product turned to be high portion of Au nanowires with more uniform size than the others. Furthermore, surface-enhanced Raman scattering (SERS) spectrum of 2-thionaphthol was obtained on the Au nanowire-modified substrate, indicating that the as-synthesized Au nanowires have potential for highly sensitive optical detection application.     

Further results on (v,4,1)-perfect difference families

In this paper, it is shown that an ASP$(2r+1,3)$ exists for $2\le r\le 100$ and $r\ne 4,5$. The existence of a $(v,4,1)$-PDF is investigated by taking advantage of the relationship between ASPs and perfect difference families (PDFs). It is proved that a $(12t+1,4,1)$-PDF exists for $t\le 100$ and $t\ne 2,3$. Several recursive constructions for ASPs and PDFs are also presented. As a consequence, the existence results of an optimal $(v,4,1)$-OOC is updated.     

Electronic structure of oligoaniline doped by inorganic and organic acids

The electronic structure of doped‐oligoaniline with various dopants is investigated by means of DFT method. After doping by hydrochloric acid (HCl) and camphorsulfonic acid (HCSA), the alternation of bond‐lengths is decreased and the co‐planarity of adjacent aromatic rings is increased. The π‐conjugating effect is increased in the electronic nature of Ph‐N system because the electrons can be delocalized along the backbone of oligoaniline where the hydrogen bonds as a bridge transfer the electrons. The electronic structure of polaron and bipolaron conformation and their relative stability is discussed, indicating that the preferable conformation is dependant on various dopants. The calculation results reveal that there is a relatively stronger interaction between the organic dopant of HCSA and N atoms of PANI, and more charge transfer between PANI and HCSA is a reason for the fact that the conductivity of HCSA‐doped PANI is higher than that of HCl‐doped PANI. The doping mechanism is proposed based on the calculation results. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

New i‐Perfect Cycle Decompositions via Vertex Colorings of Graphs

Generalizing a result by Buratti et al.[M. Buratti, F. Rania, and F. Zuanni, Some constructions for cyclic perfect cycle systems, Discrete Math 299 (2005), 33–48], we present a construction for i‐perfect k‐cycle decompositions of the complete m‐partite graph with parts of size k. These decompositions are sharply vertex‐transitive under the additive group of with R a suitable ring of order m. The construction works whenever a suitable i‐perfect map exists. We show that for determining the set of all triples for which such a map exists, it is crucial to calculate the chromatic numbers of some auxiliary graphs. We completely determine this set except for one special case where is the product of two distinct primes, is even, and . This result allows us to obtain a plethora of new i‐perfect k‐cycle decompositions of the complete graph of order (mod 2k) with k odd. In particular, if k is a prime, such a decomposition exists for any possible i provided that .     

A selective dopamine biosensor based on AgCl@polyaniline core-shell nanocomposites

Silver chloride@polyaniline (PANI) core-shell (AgCl@PANI) nanocomposites were synthesized in the presence of polyvinylpyrrolidone (PVP). The obtained AgCl@PANI nanocomposites could be easily dispersed in aqueous media, which overcame the processible issues of PANI. Moreover, the nanocomposites showed excellent electrochemical behavior at pH neutral environment, and had inhibitive effect on oxidation of ascorbic acid. Fourier transform infrared spectrophotometry (FTIR) confirmed the existence of PVP in the nanocomposites. The C=O group of PVP is easy to form hydrogen bonding with the hydroxyl group of ascorbic acid, which can prevent ascorbic acid from oxidization. A selective dopamine biosensor was constructed based on the particular characteristic of the AgCl@PANI nanocomposites by the simple drop-coating. The biosensor could detect dopamine at its very low concentration in the presence of 5000 time concentration of ascorbic acid at neutral environment.     

MnO2/Graphene Nanocomposites for Nonenzymatic Electrochemical Detection of Hydrogen Peroxide

MnO₂/graphene nanocomposites with different morphologies were synthesized and the petal‐shaped nanosheet MnO₂/graphene composite was developed as an electrode material for nonenzymatic hydrogen peroxide (H₂O₂) sensor. The morphology, structure, composition, and hydrophilicity of the resulting products were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and the contact angle tests. In addition, the fabricated MnO₂/graphene composites could be used as catalysts for the electrochemical oxidation of H₂O₂. Cyclic voltammogram (CV) experiments indicated that MnO₂/graphene‐modified electrode showed good electrocatalytic activity towards both the oxidation and reduction of H₂O₂ in a neutral environment. Amperometric response results illustrated that this nonenzymatic sensor had excellent anti‐interference ability and displayed two linear ranges from 10 to 90 µM and from 0.2 to 0.9 mM with a detection limit of 2 µM.     

Fabrication of a label-free electrochemical immunosensor of low-density lipoprotein

The silver chloride@polyaniline (PANI) core-shell nanocomposites (AgCl@PANI) combined with Au nanoparticles (AuNPs) were used to prepare the AuNPs-AgCl@PANI hybrid material. A novel sensitive label-free low-density lipoprotein (LDL) electrochemical biosensor was fabricated by adsorption of antibody to apolipoprotein B-100 (aopB-100) on an AuNPs-AgCl@PANI-modified glassy carbon (GC) electrode. The hybrid material could provide surface for high antibody loading due to its large surface-to-volume ratio. Since each LDL has an apoB-100 on its phospholipids coat, they could be bonded to the electrode surface through the specific antibody-antigen reaction. Electrochemical impedance spectroscopy (EIS) was used to characterize the recognition of LDL. The negative charges carried by LDL phospholipids coat would block the electron transfer of the [Fe(CN)6]3-/4- redox couple severely. In addition, the conductivity of LDL is very poor, so small amounts of LDL on the electrode could result in great change in the electron-transfer resistance (Ret). The biosensor exhibited a highly sensitive response to LDL with a detection limit of 0.34 pg/mL, and some factors that would affect the performance of the biosensor were studied, such as incubation time and temperature.