Cun Zhou

Synthesis and Imidization of Polyamic Acid

Polyamic acids (PAA) were synthesized by solution polycondensation of aromatic diamine with dianhydride and PAA were readily soluble in polar organic solvents (N-methylpyrrolidinone, N, N-dimethylacetamide and DMF). It was found that the most appropriated reaction conditions of synthesis of PAA solution were the ratio of dianhydride with diamine being 1.02:1and 3h reaction time at ambient temperature in both N-methylpyrrolidinone and N, N-dimethylacetamide polar organic solvents. PAA thin films were prepared by PAA solution spread on the glass plate and PI thin films were obtained by the casted thin films which underwent a special high-temperature (300°C, 2h) heat curing. The structures of PAA and PI films were characterized by FT-IR spectra and degree of imidization of PAA solution was indicated from IR spectra. The thermal stability was studied by thermogravimetric analysis (TGA) and the thermal behaviors were investigated by differential scanning calorimetry (DSC) in this paper. It was shown that PAA solution were imidization at 200°C mostly and PI had higher thermal stability.

DNA Electrochemical Biosensor Based on Chitosan and Core-Shell Au@SiO2 Nanoparticles

In this paper, an efficient process for preparing monodisperse gold nanoparticles coated with silica shells (Au@SiO2) was reported, and a novel DNA electrochemical biosensor based on layer-by-layer self-assembled technology as well as Au@SiO2 nanoparticles was presented. Chitosan was immobilized on gold electrode by good film-forming property and lots of amino because of strong electrostatic adsorption effect between amino and gold atom, Au@SiO2 nanoparticles were also immobilized to the electrode in that it kept the excellent features of gold nanoparticles, therefore, thoil group modified DNA (SH-ssDNA) probe sequence can self-assembled on Au@SiO2 nanoparticles modified electrode with the purpose of realize quantitative detection of complementary DNA. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were applied to investigate the electrochemical behavior of different modified electrodes with methylene blue as hybrid indicator. The results in optimization experiment condition show that: the peak current difference value pre and post hybridization was linearly related to the logatithmic value of the target DNA concentration ranging from 10-10~10-6mol/L. A detection limit of 4.02×10-11mol/L can be estimated.

Detection of toxoplasma gondii with a DNA molecular beacon probe

Toxoplasma gondii is a kind of microscopic parasite that may infect humans, and there are increasing concerns on the early detection of latent Toxoplasma gondii infection in recent years. This research highlights a new type of molecular beacon (MB) fluorescent probe for Toxoplasma DNA testing. We combined high-efficiency fluorescent inorganic core-shell quantum dots-CdTe/ZnS (as fluorescent energy donor) and BHQ-2 (energy acceptor) to the single-strand DNA of Toxoplasma Gondii, and a molecular beacon sensing system based on fluorescence resonance energy transfer (FRET) was achieved. Core-shell quantum dots CdTe/ZnS was firstly prepared in aqueous solution, and the influencing factor of its fluorescent properties, including CdTe/Na2S/Zn(CH3COO)2 (v/v), dependence of reaction time, temperature, and pH, is investigated systematically. The synthesized quantum dots and molecular beacon were characterized by transmission electron microscopy (TEM), ultraviolet-visible spectrophotometer (UV-vis), fluorescent spectrophotometer (FS), respectively. The TEM results showed that CdTe/ZnS core-shell quantum dots is ~11nm in size, and the quantum dots is water-soluble well. The sensing ability of target DNA of assembled MB was investigated, and results showed that the target Toxoplasma Gonddi DNA can be successfully detected by measuring the change of fluorescence intensity. The results showed that the current sensing probe will be a useful and convenient tool in Toxoplasma gondii early detection.

Highly Hydrophobic Conductive Polyester Fabric Based on Homogeneous Coating Surface Treatment

ABSTRACT A highly hydrophobic conductive polyester (PET-HE) fabric was prepared by a simple two-steps method. Firstly, homogeneous coating (the mixture of PET and carbon black (CB)) was uniformly coated on the PET fabric, which through curing in water coagulation bath and electrically conductive (PET-E) fabric was prepared. Then the solvent-induced crystallization process was adopted to PET-E fabric to endow the hydrophobic property. Investigations showed that PET-HE treated fabrics exhibited better hydrophobic and conductivity when the content of PET is 9wt% and the content of CB is the range of 8wt%-10wt%. The prepared polyester fabric proved to have such features as WCA was about 145°and surface resistance was about 300 Ω.GRAPHICAL ABSTRACT Graphical Abstract

Preparation of Polyurethane-Modified Epoxy

Polyurethane (PU) prepolymer with the isocyanine-based were synthesized by toluene -2, 4-diisocyanate (TDI), polyethylene glycol (PEG-400) and polyethylene glycol (PEG-1000) with N-methylpyrrolidone as the solvent. The effects of temperature and time on the synthesis of polyurethane prepolymer were examined in this paper. The structures of PU, unmodified epoxy resin and modified epoxy resin were identified by FI-IR spectra. It was shown that polyurethane prepolymer was synthesized at 70°C for 5 hours and modified epoxy resin was synthesized successfully.

Synthesis and Characterization of Polyimide/Silica Nanocomposites

Two kind of polyimide/silica nanocomposites which were recorded poly(amic acid)/ silica(PAA/SiO2) and SiO2 in poly(amic acid) ammonium salt(PAS/SiO2) respectively, have been prepared for different methods. The size of SiO2 in PAA/SiO2 and PAS/SiO2 are measured by Particle size analysis and the average particle size are 377nm and 53.7nm. Transmission electron microscopy(TEM) images of PAS/ SiO2 confirm that the size of particles are ranged from 40 to 80nm. The stuctures of samples have been characterized by FT-IR spectra. The thermal stability of PAA/SiO2 and PAS/SiO2 are studied by thermogravimetric analysis (TGA) and the thermal behaviors were investigated by differential scanning calorimetry (DSC) in this paper. It is shown that PAA/SiO2 have slightly better thermal properties than that of PAS/SiO2. The results obtained from Instron universal strength tester present the water-solube PAS/SiO2 own the excellent mechanical prperties as same as PAA/SiO2.

Structures and Properties of Modification Copolyester Fiber

This study investigated the structures and properties of cationic dyeable poly(ethylene terephthalate) (CDP) and easy cationic dyeable poly(ethylene terephthalate) (ECDP) by FTIR, X-ray diffraction, mechanical test, and DSC. The results showed that the FTIR spectrums of CDP and ester-type ECDP fibers were similar to the that of PET. It suggested that the adding of the third monomer and the fourth monomer had good compatible with the original structure unit of PET. the position of X-ray diffraction peak of CDP and ester-type ECDP were the same as which of PET, the third monomer and the fourth monomer did not pack into the original polyester unit cell but concentrated at the polyester crystalline surface and the amorphous regions.With adding the third monmome and the fourth monmomer, the initial modulus of the CDP and ester-type ECDP fibers became inferior. But the breaking elongation of them increased. The DSC suggested that The melting range of CDP and ECDP finished fiber were wider than that of PET fiber, but the melting point and crystallinity were less than them of PET fiber.

Electrochemical DNA Biosensor for the Detection of Short DNA Species by Using Compound Co(phen)32

The application of electrochemical techniques for DNA detection is motivated by their potential to detect hybridization events in a more rapid, simplistic and cost-effective manner compared to conventional methods. Here, we present an electrochemical DNA biosensor for the specific and quantitative detection of single-stranded DNA (ssDNA). Probe oligonucleotides were immobilized onto gold electrodes by a 5′ end thiol-group linker. Following hybridization with the complementary DNA, the cobalt complex was electrochemically accumulated on the double-stranded DNA layer and the differential pulse voltammogram (DPV) for this electrode gave an electrochemical signal due to the redox reaction of [Co(phen)3]2+/3+ that was bound to the double-stranded DNA on the electrode, and it can sense single base-pair mismatche within the sequence of the hybridized double-stranded DNA (dsDNA).

DNA Electrochemical Biosensor Based on Chitosan and Gold Nanoparticles Using Methylene Blue as Electrochemical Indicator

In this paper, a novel DNA electrochemical biosensor based on layer-by-layer self-assembled technology was reported. Gold nanoparticles were firstly immobilized on chitosan modified gold electrode by large amino of chitosan because of strong electrostatic adsorption effect between amino and gold atom, and thoil group modified DNA (SH-ssDNA) probe sequence was then self-assembled onto the electrode. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were applied to investigate the electrochemical behavior of different modified electrodes with methylene blue as hybrid indicator. The results in optimization experiment condition show that: The peak current difference value pre and post hybridization was linearly related to the logatithmic value of the target DNA concentration ranging from 10-8~10-5mol/L.A detection limit of 3.55×10-9mol/L can be estimated.

Preparation and Property of Epoxy Based Nano-SiO2/TiO2/Polyimide Hybrid Enhanced Sizing

Abstract: An epoxy based nano-SiO2/TiO2/polyimide hybrid enhanced sizing for carbon fiber was prepared by modified SiO2/TiO2 precursor in PAA collosol with silane couple agent(WD-50) and eligibility surfactant via sol-gel reaction, and both ultrasonic cavitation and multi-complex technology were used during the process. The properties of PAA-SiO2-TiO2 hybrid sizing and micro-morphology of carbon fiber surface were analyzed by FTIR, DSC, Particle Size Analyzer and STM. The results indicated that nanoscale SiO2•TiO2 particles dispersed in the hybrid sizing film homogeneously, and a layer with nano particles was formed on carbon fiber surface after treated by the hybrid enhanceing sizing. The roughness was increased and interface properties of carbon fiber would be improved. At the same time both tensile strength and the interlaminar shear strength were increased obviously.