Surface Modification of γ-Al2O3 Nanoparticles Using Conductive Polyaniline Doped by Dodecylbenzene Sulfonic Acid.

In this study, electrically conductive PANDB/γ-Al2O3 core-shell nanocomposites were synthesized by surface modification of γ-Al2O3 nanoparticles using polyaniline doped with dodecylbenzene sulfonic acid. The PANDB/γ-Al2O3 core-shell nanocomposites were synthesized by in situ polymerization. Pure PANDB and the PANDB/γ-Al2O3 core-shell nanocomposites were characterized using Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, transmission electron microscopy, field emission scanning electron microscopy, and measurement of a four-point probe. The conductivity of the PANDB/γ-Al2O3 core-shell nanocomposite was about 0.72 S/cm when the weight ratio of aniline/γ-Al2O3 was 3/1. The results showed that the conductivity of the PANDB/γ-Al2O3 core-shell nanocomposite decreased with increasing amounts of γ-Al2O3 nanoparticles. The transmission electron microscopy results indicated that the γ-Al2O3 nanoparticles were thoroughly coated with PANDB to form a core-shell structure. Transmission electron microscopy and field emission scanning electron microscopy images of the conductive PANDB/γ-Al2O3 core-shell nanocomposites also showed that the thickness of the PANDB layer decreased as the amount of γ-Al2O3 was increased.

Synthesis and Characterization of Conducting PANDB/χ-Al2O3 Core-Shell Nanocomposites by In Situ Polymerization.

Polyaniline doped with dodecylbenzenesulfonic acid/χ-aluminum oxide (PANDB/χ-Al2O3) conducting core-shell nanocomposites was synthesized via an in situ polymerization method in this study. PANDB was synthesized in the presence of dodecylbenzenesulfonic acid (DBSA), which functioned as a dopant and surfactant. The electrical conductivity of the conducting PANDB/χ-Al2O3 core-shell nanocomposite was approximately 1.7 × 10-1 S/cm when the aniline/χ-Al2O3 (AN/χ-Al2O3) weight ratio was 1.5. The transmission electron microscopy (TEM) results indicated that the χ-Al2O3 nanoflakes were thoroughly coated by PANDB to form the core-shell (χ-Al2O3-PANDB) structure. The TEM and field-emission scanning electron microscopy (FE-SEM) images of the conducting PANDB/χ-Al2O3 core-shell nanocomposites also indicated that the thickness of the PANDB layer (shell) could be increased as the weight ratio of AN/χ-Al2O3 was increased. In this study, the optimum weight ratio of AN/χ-Al2O3 was identified as 1.5. The conducting PANDB/χ-Al2O3 core-shell nanocomposite was then blended with water-based polyurethane (WPU) to form a conducting WPU/PANDB/χ-Al2O3 blend film. The resulting blend film has promising antistatic and electrostatic discharge (ESD) properties.

Conductive Polyaniline Doped with Dodecyl Benzene Sulfonic Acid: Synthesis, Characterization, and Antistatic Application.

A novel method was conducted to synthesize conductive polyaniline (PANI) doped with dodecyl benzene sulfonic acid (DBSA) (PANDB) in xylene by using chemical oxidative polymerization at 25 °C. Meanwhile, the synthesis process was photographed. Results showed as the reaction time was increased, and the color of the product was gradually turned into dark green. The influence of different synthesis time on properties of synthesized PANDB was then examined by a Fourier transform infrared (FTIR) spectrometer, an ultraviolet-visible spectrophotometer (UV-vis), a four-point measurement method, and a Field-emittance scanning electron microscope (FE-SEM). The result indicated that the optimum reaction time was 24 h with conductivity at around 2.03 S/cm. FE-SEM images and the conductivity testing showed that the more needle-like shapes in resulted PANDB, the higher the conductivity. The synthesized PANDB solution was blended with UV curable coating firstly and then coated on polyethylene terephthalate (PET) sheet. The UV coating/PANDB conductive composite films displayed an impressive translucency along with an adequate flexibility at room temperature. The UV coating/PANDB conductive composite film on PET sheet was flexible, transparent, and with antistatic function.

Studies of chitosan: II. Preparation and characterization of chitosan/poly(vinyl alcohol)/gelatin ternary blend films.

Chitosan/poly(vinyl alcohol)/gelatin (CS/PVA/GA) ternary blend films were prepared by solution blending method in this study. The thermal properties of the CS/PVA/GA ternary blend films were examined by differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The melting point of the CS/PVA/GA ternary blend film was increased when the amount of GA in the blend film was increased based upon the DSC thermal analysis. Results of X-ray diffraction (XRD) analyses indicated that the intensity of diffraction peak at 19 degrees of PVA became lower and broader with increasing the amount of GA in the CS/PVA/GA ternary blend film. Although CS, PVA, and GA are hydrophilic biodegradable polymers, the results of water contact angle measurements are still as high as 83 degrees, 68 degrees, and 66 degrees, respectively. A minimum water contact angle (56 degrees) was observed when the ternary blend film contains 50 wt.% GA (i.e. GA5). This behavior is primarily due to the reorientation of polar functional groups toward to the top surface of CS/PVA/GA ternary blend films.

Paper-based immunosensor utilizing dielectrophoretic trapping of microprobes for quantitative and label free detection using electrochemical impedance spectroscopy.

In this study, we have developed a novel paper based immunoassay for the quantitative detection of immunoreactions using electrochemical impedance spectroscopy. Paper provides an attractive platform for fabrication of simple, low cost, and portable diagnostic devices as it allows passive liquid transport, is biocompatible, and has tunable properties such as hydrophilicity, flexibility, permeability, and reactivity. We have used screen-printing to fabricate interdigitated electrodes (finger width and gap of 200 µm) on the paper substrate, while UV-lithography enables patterning of the paper into hydrophobic/hydrophilic regions. As a proof of concept, we have used this immunosensor to detect the immune response of Human Serum Albumin (HSA) antibody-antigen complex formation. To enable efficient immobilization of HSA antibodies, we have utilized dielectrophoresis to trap microprobes (MPs) on the electrode surface. The microprobes consist of an alumina nanoparticle core with a well-adhered polyaniline outer coating to which the HSA antibodies are conjugated in an oriented manner via covalent chemistry. The efficacy of the impedance-based immunosensor is compared when MPs are immobilized specifically on the electrode surface using dielectrophoresis (DEP) as opposed to being dropped and immobilized via physical absorption on the entire sensing area. Results show that a more reproducible and sensitive response is observed when DEP is utilized to trap the microprobes. Furthermore, the normalized impedance variation during immunosensing shows a linear dependence on the concentration of HSA with an observed limit of detection of 50 µg/ml, which is lower than conventionally used paper based urine dipsticks used for urinary protein detection. Thus, we have developed a low cost paper based immunoassay platform that can be used for the quantitative point of care detection of a wide range of immunoreactions.

A kinetic model of the gelation of konjac glucomannan induced by deacetylation.

The gelation of konjac glucomannan (KGM) often involves an induction period featured by an initial drop in modulus. The gelation kinetics recorded as a time-dependent modulus change is composed of an initial drop followed by a steady increase in modulus until an equilibrium stage is reached. In this work, the time-dependent modulus curve is described by a kinetic model which incorporates the cascade theory with the kinetic equations consisting of sequential reactions of deacetylation and cross-link formation. The proposed model is capable of predicting the presence of the induction period and the kinetic parameters can be extracted from the concentration dependence of the initial drop. A rheological experiment of KGM gelation using sodium carbonate as deacetylation agent was conducted to illustrate the feasibility of the proposed fitting approach, which yields kinetic curves agreeing satisfactorily with the experimental results.

Immunosensor for the ultrasensitive and quantitative detection of bladder cancer in point of care testing.

An ultrasensitive and real-time impedance based immunosensor has been fabricated for the quantitative detection of Galectin-1 (Gal-1) protein, a biomarker for the onset of multiple oncological conditions, especially bladder cancer. The chip consists of a gold annular interdigitated microelectrode array (3×3 format with a sensing area of 200µm) patterned using standard microfabrication processes, with the ability to electrically address each electrode individually. To improve sensitivity and immobilization efficiency, we have utilized nanoprobes (Gal-1 antibodies conjugated to alumina nanoparticles through silane modification) that are trapped on the microelectrode surface using programmable dielectrophoretic manipulations. The limit of detection of the immunosensor for Gal-1 protein is 0.0078mg/ml of T24 (Grade III) cell lysate in phosphate buffered saline, artificial urine and human urine samples. The normalized impedance variations show a linear dependence on the concentration of cell lysate present while specificity is demonstrated by comparing the immunosensor response for two different grades of bladder cancer cell lysates. We have also designed a portable impedance analyzing device to connect the immunosensor for regular checkup in point of care testing with the ability to transfer data over the internet using a personal computer. We believe that this diagnostic system would allow for improved public health monitoring and aid in early cancer diagnosis.

Facile synthesis of stable cubic mesoporous silica SBA-1 over a broad temperature range with the aid of D-fructose.

A highly ordered cubic mesoporous silica SBA-1 with enhanced stability towards washing with water has been synthesized simply by adding D-fructose as an auxiliary agent during the synthesis.

Lab on a chip for multiplexed immunoassays to detect bladder cancer using multifunctional dielectrophoretic manipulations.

A multiplexed immunosensor has been developed for the detection of specific biomarkers Galectin-1 (Gal-1) and Lactate Dehydrogenase B (LDH-B) present in different grades of bladder cancer cell lysates. In order to immobilize nanoprobes with different antibodies on a single chip we employed three-step programmable dielectrophoretic manipulations for focusing, guiding and trapping to enhance the fluorescent response and reduce the interference between the two antibody arrays. The chip consisted of a patterned indium tin oxide (ITO) electrode for sensing and a middle fish bone shaped gold electrode for focusing and guiding. Using ITO electrodes for the sensing area can effectively eliminate the background noise of fluorescence response as compared to metal electrodes. It was also observed that the three step manipulation increased fluorescence response after immunosensing by about 4.6 times as compared to utilizing DEP for just trapping the nanoprobes. Two different-grade bladder cancer cell lysates (grade I: RT4 and grade III: T24) were individually analyzed for detecting the protein expression levels of Gal-1 and LDH-B. The fluorescence intensity observed for Gal-1 is higher than that of LDH-B in the T24 cell lysate; however the response observed in RT4 is higher for LDH-B as compared to Gal-1. Thus we can effectively identify the different grades of bladder cancer cells. In addition, the platform for DEP manipulation developed in this study can enable real time detection of multiple analytes on a single chip and provide more practical benefits for clinical diagnosis.

Enhancing of intensity of fluorescence by DEP manipulations of polyaniline-coated Al2O3 nanoparticles for immunosensing.

A novel modification of low-cost Al2O3 nanoparticles (Al2O3 NPs) for antibody-protein immunosensing is proposed. The modified NPs are utilized to enhance the intensity of fluorescence in a dielectrophoretic (DEP) chip with a microelectrode array. The surface of the Al2O3 NPs is modified by ionic polyaniline (PANDB) rather than the conventional silane (3-aminopropyltrimethoxysilane) to conjugate the antibody on the outer shell. After the PANDB-Al2O3 NPs is functionalized to form probes, a DEP chip with a vertical non-uniform electric field that is produced by top and bottom electrodes condenses and immobilizes the nanoprobes on the surface of the electrodes by positive DEP force for immunosensing of the fluorescent protein. Additionally, each microelectrode array can be individually controlled with/without DEP manipulation using a computer program. Experimental results indicate that PANDB-based nanoprobes provide more rapid and sensitive immunosensing than those having undergone conventional silane modification. During immunosensing, fluorescence intensity can be doubled by the application of extra DEP force. The individual control of NPs on the microelectrode array has great potential for applications in multi-antibody arrays in a single chip for immunosensing.

On the interaction between konjac glucomannan and xanthan in mixed gels: an analysis based on the cascade model.

The rheological properties and critical behavior of konjac glucomannan (KGM)/xanthan (XG) mixed gels were investigated and analyzed using a two-component cascade model. The fitting results show that the optimal functionality value for KGM (fKGM) is 3, whereas the possible functionality value for XG (fXG) is 100-1000 obtained from the modulus data, or 25 obtained from the critical data. The van't Hoff analysis of the critical data shows that the binding of KGM with XG has a high enthalpy/entropy ratio (ΔH/300ΔS=5.52), which can be explained by the gain in the hydrational entropy due to the release of water molecules during the binding reaction. From these results, we proposed that the binding of KGM with XG takes place on the consecutive glucose residues of KGM with six or more units.