Fabrication of a novel impedance cell sensor based on the polystyrene/polyaniline/Au nanocomposite

Gold nanoparticles (AuNPs) were assembled on the surface of polystyrene (PS) and polyaniline (PANI) core-shell nanocomposite (PS@PANI) for the immobilization of HL-60 leukemia cells to fabricate a cell electrochemical sensor. The immobilized cells exhibited irreversible voltammetric response and increased the electron transfer resistance with a good correlation to the logarithmic value of concentration ranging from 1.6 × 10³ to 1.6 × 10⁸ cells mL⁻¹ with a limit of detection of 7.3 × 10² cells mL⁻¹ at 10σ. This biosensor was simple, low cost and disposable, which implied that the PS@PANI/Au composites can regard as the potential applications for clinical applications.     

A highly sensitive dopamine sensor based on a polyaniline/reduced graphene oxide/Nafion nanocomposite

A nanocomposite of polyaniline/reduced graphene oxide (PANI-rGO) was synthesized using a hydrothermal method. The product was characterized by FT-IR, Raman spectra, XRD, SEM and TEM. Then the hybrid material of PANI-rGO and Nafion (PANI-rGO-NF) was prepared and used to modify glassy carbon electrode for the trace determination of dopamine (DA) employing differential pulse voltammetry (DPV). It was found that the hybrid material showed good catalytic activity toward the oxidation of DA, and no response to ascorbic acid (AA) and uric acid (UA) was observed, suggesting a high selectivity of the sensor toward DA. The peak currents were linearly correlated with the concentration of DA in the range from 0.05 μmol/L to 60.0 μmol/L (R=0.996) and 60.0 μmol/L to 180.0 μmol/L (R=0.996) with a detection limit of 0.024 μmol/L (S/N=3). The modified electrode also exhibited excellent repeatability and stability.     

Fabrication of glucose biosensor for whole blood based on Au/hyperbranched polyester nanoparticles multilayers by antibiofouling and self-assembly technique

Acknowledging the benefits of hyperbranched polymers and their nanoparticles, herein we report the design and synthesis of sulfonic acid group functionalized hydroxyl-terminated hyperbranched polyester (H30-SO₃H) nanoparticles and their biomedical application. The H30-SO₃H nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance spectroscopy (¹H NMR). The good hemocompatibility of H30-SO₃H nanoparticles was also investigated by coagulation tests, complement activation and platelet activation. The novel glucose biosensor was fabricated by immobilizing the positively charged Au nanoparticles, H30-SO₃H nanoparticles and glucose oxidase (GOx) onto the surface of glassy carbon electrode (GCE). It can be applied in whole blood directly, which was based on the good hemocompatibility and antibiofouling property of H30-SO₃H nanoparticles. The biosensor had good electrocatalytic activity toward glucose with a wide linear range (0.2–20 mM), a low detection limit 1.2 × 10⁻⁵ M in whole blood and good anti-interference property. The development of materials science will offer a novel platform for application to substance detection in whole blood.     

Fabrication of novel multihollow superparamagnetic magnetite/polystyrene nanocomposite microspheres via water-in-oil-in-water double emulsions

We herein present a novel and simple synthetic strategy for fabricating multihollow superparamagnetic magnetite/polystyrene nanocomposite microspheres via water-in-oil-in-water double emulsions. Amphipathic magnetite nanoparticles surface-modified with oleic acid act as an oil-soluble emulsifier and sodium dodecyl sulfate acts as a water-soluble surfactant in the system. The final products were thoroughly characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field-emission scanning electron microscopy, which showed the formation of multihollow magnetite/polystyrene nanocomposite microspheres. Preliminary results of magnetic properties of multihollow magnetite/polystyrene microspheres were reported. The effect of the content of amphipathic magnetite nanoparticles on the morphology of nanocomposite microspheres was studied. Furthermore, the mechanism of formation of multihollow magnetic nanocomposite microspheres was also discussed.     

Synthesis,characterization and antibacterial properties of a novel nanocomposite based on polyaniline/polyvinyl alcohol/Ag

In this study, a novel nanocomposite based on polyaniline/polyvinyl alcohol/Ag (PANI/PVA/Ag) has been successfully synthesized. The chemical reduction method was used to produce Ag nanoparticle colloidal solution from Ag⁺ ions. The polymerization of aniline occurred in situ for the preparation of polyaniline (PANI) in the presence of ammonium persulfate. With exposure to Ag nanoparticles on the PANI/PVA composite, a new nanocomposite was obtained. The morphology and particle size of the novel nanocomposite was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) analyses. According to XRD analysis, the size of nanoparticles was found to be in the range of 10–17 nm. SEM images showed the favored shape of nanoparticles as triangle which is a benign shape for antibacterial analysis. The antibacterial activity of the obtained nanocomposite was also evaluated against Gram positive bacteria Staphylococcus aureus (Staph. aureus) and Gram negative Escherichia coli (E. coli) using the paper disk diffusion method. The antibacterial study showed that the PANI/PVA composite did not have a very good antibacterial activity but PANI/PVA/Ag nanocomposites were found to be effective against two bacteria.     

Glucose biosensor based on immobilization of glucose oxidase in platinum nanoparticles/graphene/chitosan nanocomposite film

The bionanocomposite film consisting of glucose oxidase/Pt/functional graphene sheets/chitosan (GOD/Pt/FGS/chitosan) for glucose sensing is described. With the electrocatalytic synergy of FGS and Pt nanoparticles to hydrogen peroxide, a sensitive biosensor with a detection limit of 0.6 μM glucose was achieved. The biosensor also has good reproducibility, long-term stability and negligible interfering signals from ascorbic acid and uric acid comparing with the response to glucose. The large surface area and good electrical conductivity of graphene suggests that graphene is a potential candidate as a sensor material. The hybrid nanocomposite glucose sensor provides new opportunity for clinical diagnosis and point-of-care applications.     

Fabrication and characterization of core/shell structured TiO2/polyaniline nanocomposite

A novel core/shell structured TiO(2)/polyaniline nanocomposite was fabricated by grafting aniline on aminobenzoate monolayer that is chemically adsorbed on the TiO(2) nanocrystal surface. The formation and nanostructure of the nanocomposite were investigated by FT-IR and UV-Vis spectra, TEM, FE-SEM, and TG-DTA analysis. Adsorption of aminobenzoate on the TiO(2) surface is an effective method to obtain the uniform nanocomposite. The thickness of polyaniline layer coating on the TiO(2) nanocrystal surface can be controlled in a range of 2-5 nm by this method. A photoelectrochemical study was carried out on the TiO(2)/polyaniline nanocomposite, and found that polyaniline in the nanocomposite acted as a visible-light sensitizer in a photoelectrochemical reaction. The sensitization effect increased with increasing binding strength between polyaniline and TiO(2). A dye-sensitized solar cell with a short circuit current density of 0.19 mA/cm(2) and an open circuit voltage of 0.35 V was fabricated by using the TiO(2)/polyaniline nanocomposite film as a sensitized electrode.     

Fabrication of an amperometric tyramine biosensor based on immobilization of tyramine oxidase on AgNPs/l-Cys-modified Au electrode

An amperometric tyramine biosensor was constructed based on covalent immobilization of black gram tyramine oxidase onto citric acid-capped silver nanoparticles bound to surface of Au electrode through cysteine self-assembled monolayer. The enzyme electrode was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and cyclic voltametry. The biosensor showed optimum response within 8 s, when polarized at 0.25 V, pH 8.5, and 35 °C, with linearity from 0.017 to 0.25 mM and a detection limit of 0.01 mM. The biosensor was employed for measurement of tyramine in beer and sauce. The mean analytical recovery of added tyramine in beer at 0.36 and 0.72 mM were 97.2?±?2.7 and 95.8?±?4.1 %, respectively, and within and between batches coefficients of variation were 0.33–0.38 and 0.34–0.62 %, respectively. The enzyme electrode lost 35 % of its initial activity after its 100 uses, over a period of 2 months, when stored at 4 °C.     

Investigation of novel mediators for a glucose biosensor based on metal picolinate complexes

The metal complexes [Os(byp)(2)(pic)](+) and [Ru(byp)(2)(pic)](+) where byp is 2,2'-bipyridine and HPic is o-picolinic acid were synthesised and characterised using spectroscopic and electrochemical techniques. These complexes were then evaluated as mediators for a glucose oxidase (GOx)-based biosensor. Results demonstrate the electrocatalytic behaviour of both metal couples towards regeneration of the flavoprotein GOx (FADH(2)) group, when co-immobilised with glucose oxidase. Surface immobilisation was achieved by potential cycling in aqueous solutions of the metal complexes at a glucose oxidase (GOx)/Nafion modified electrode. This proved successful in terms of catalytic efficiency and stability of redox sites. Kinetic parameters associated with both enzymatic and mediator reactions were estimated and the stability/performance properties of the sensor were tested.     

A highly sensitive and rapid organophosphate biosensor based on enhancement of CdS-decorated graphene nanocomposite

Benzoyl peroxide (BPO) as a brightener is often added to wheat flour, and excessive use of this food additive is receiving increasing concern. Herein, a simple and fast method for fluorescence detection of BPO is proposed based on consecutive chemical reactions. In this approach, BPO first oxidizes Fe(2+) into Fe(3+) and the resulting Fe(3+) then induces the opening of the spirolactam ring of a new rhodamine derivative, N-methoxy rhodamine-6G spirolactam, switching on fluorescence of the detection system. More importantly, the fluorescence response of the reaction system to BPO is rather rapid and sensitive, with a detection limit of 6 mg kg(-1) (k=3), which makes it to be of great potential use in food safety analysis. The applicability of the proposed method has been successfully demonstrated on the determination of BPO in wheat flour samples.     

Controllable synthesis of novel sandwiched polyaniline/ZnO/polyaniline free‐standing nanocomposite films

Controllable synthesis of novel sandwiched polyaniline (PANI)/ZnO/PANI free‐standing nanocomposite films is reported via spin coating of ZnO quantum‐dot interlayer on PANI base layer and then PANI surface layer on the ZnO interlayer. The thickness of the ZnO interlayer and the PANI surface layer can be easily controlled by adjusting spin time and spin speed, respectively. The effects of the ZnO interlayer thickness and the PANI surface layer thickness are examined in detail on the photoluminescence (PL) property. It is worth noting that coverage of the PANI surface layer on the ZnO interlayer can not only lead to great enhancement in the PL property but also to a maximum PL intensity at a medium PANI surface layer thickness. This maximum PL property is caused by the combined ZnO/PANI carrier transportation and PANI shielding effects. In addition, the nanocomposite films show reasonably good conductivity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Fabrication,characterization of polyaniline intercalated NiO nanocomposites and application in the development of non-enzymatic glucose biosensor

Determination of glucose plays very important part in diagnostics and management of diabetes. Nowadays, determination of glucose is necessary in human health. In order to develop the glucose biosensor, polymer modified catalytic composites were fabricated and used to detect glucose molecules. In this work, NiO nanostructure metal oxide (NMO) was fabricated via thermal decomposition method and polyaniline (wt% = 2, 4 and 6) assisted nanocomposites (NiO/PANI) were also prepared. The morphology and structure of synthesized nanocomposites were characterized by UV–visible diffusion reflectance spectroscopy (UV–vis-DRS), Fourier transform- infra red spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption-desorption isotherm measurement. The modified NiO/6%PANI/GCE had higher catalytic activity toward the oxidation of glucose than NiO/GCE, PANI/GCE, NiO/2%PANI/GCE and NiO/4%PANI/GCE. This is due to the larger surface area of NiO/6%PANI nanocomposites provide a ploform for faster electron transfer to the detection of glucose. The constructed glucose biosensor have been exhibited a high sensitivity of 606.13 µA mM⁻¹ cm⁻², lowest detection limit of 0.19 µM, high selectivity, stability, simplicity and low cost for the quick detection of glucose in real sample as well.     

A novel electrochemiluminescence glucose biosensor based on platinum nanoflowers/graphene oxide/glucose oxidase modified glassy carbon electrode

A novel electrochemiluminescence (ECL) biosensor based on platinum nanoflowers (PtNFs)/graphene oxide (GO)/glucose oxidase (GODx) was discovered for glucose detection. PtNFs/GO was synthesized using a nontoxic, rapid, one-pot and template-free method and characterized by transmission electron microscopy (TEM) and high-resolution TEM techniques. The as-prepared PtNFs/GO with clean surface and multiporous structure was used to assemble GODx to form a glucose biosensor. Based on ECL results, the PtNFs/GO/GODx film-modified electrode displayed a high electrocatalytic activity towards the oxidation of glucose, which generated hydrogen peroxide (H₂O₂) to react with the luminol radicals thus enhanced the luminol ECL. Under the optimized conditions, two linear regions of ECL intensity to glucose concentration were valid in the range from 5 to 80 μmol/L (r?=?0.9957) and 80 to 1,000 μmol/L (r?=?0.9909) with a detection limit (S/N?=?3) of 2.8 μmol/L. In order to verify the reliability, the thus-fabricated biosensor was applied to determine the glucose concentration in glucose injection, glucose functional drink, and blood serum. The results indicated that the proposed biosensor presented good characteristics in terms of high sensitivity and good reproducibility for glucose determination, promising the applicability of this sensor in practical analysis.     

Study of a nanocomposite based on a conducting polymer: polyaniline

A simple way to obtain a conducting nanocomposite is described, and the conducting particles are characterized. Core-shell particles [polystyrene-polyaniline (PANI)] have been obtained by the dispersion process from three types of polystyrene latexes: a no-cross-linked core stabilized by a nonylphenolethoxylate (NP40) and two cross-linked cores stabilized by NP40 and a mixture NP40/Surfamid (a surfactant bearing an amide group). The surface of these particles has been extensively characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and scanning electron microscopy. A maximum coverage of 94% was obtained for the high PANI content as revealed by XPS analysis. A better coverage was obtained for the cross-linked polystyrene latex stabilized by the Surfamid. The amide group of this surfactant allows the H-bonding formation with the PANI backbone and, thus, improves the conductivity. It was shown that a uniform coverage of the core particles was not required to ensure a good conductivity.     

Nonenzymatic dopamine biosensor based on tannin nanocomposite

A dopamine (DA) biosensor was developed based on polypyrrole/tannin/cetyltrimethylammonium bromide (PPy/TA/CTAB) nanocomposite and central composite rotatable design (CCRD) was employed for the optimization of conditions. Chemical polymerization of the PPy/TA in the presence of a cationic surfactant, CTAB, reduced the particle size of composite and a rod-like structure with a lumpy surface and high porosity was observed for nanocomposite justifying the highest current response for the modified electrode. Amperometry and differential pulse voltammetry analyses were applied for all electrochemical measurements and DA detection in the range of 0.5–100 μM. The good adhesion of nanocomposite on the electrode surface, as well as porosity and high surface area of the modified electrode, enhanced the diffusion of DA molecules inside the matrix. Amperometry analysis of the Screen printed carbon electrode/PPy/TA/CTAB modified electrode displayed a good sensitivity of 0.039 μA (μM)⁻¹ toward DA with the limit of detection of 2.9 × 10^–7 M. The modified biosensor also excludes the interfering species of ascorbic acid and uric acid which makes this sensor appropriate for DA determination. The proposed biosensor showed an acceptable reproducibility and repeatability with low relative standard deviations of 4.8% and 4.4%, respectively.     

Preparation and structure of highly confined intercalated polystyrene/montmorillonite nanocomposite via a two-step method

A two-step approach with a combination of emulsion polymerization and melt intercalation with higher clay loading of 33 wt.% is disclosed to highly confine the polystyrene (PS) chains by montmorillonite. The product of the emulsion polymerization is an easily crushable fine powder. And the powder is readily processible by open mill to form a transparent sheet. In the melt intercalation process, further intercalation of polystyrene narrows the space among the tactoids and results a highly confined intercalated nanocomposite. The results of dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) showed that the cooperative motions of PS segments were substantially depressed, indicative of the highly intercalated structure formed in the nanocomposites. A structural model is proposed to explain the highly confined mesostruture of the PS/MMT nanocomposite.     

Fabrication of polystyrene/upconversion nanocrystals nanocomposite spheres through in situ dispersion polymerization

This paper presents a feasible and efficacious procedure to synthesize polystyrene/upconversion nanocrystals (PS/UCNCs) nanocomposite spheres with raspberry-like structure via an in situ dispersion polymerization technique. During this process, polyacrylic acid (PAA) as stabilizer plays the key role in adsorbing UCNCs, including NaYF(4):Yb(3+)-Er(3+), NaYF(4):Yb(3+)-Tm(3+) and NaYF(4):Yb(3+)-Ho(3+) onto the PS surfaces. TEM and SEM images confirmed the raspberry-like morphology of the obtained nanocomposite spheres. The effect of synthetic conditions, for instances, PAA amount, type and concentration of UCNCs on the structure and fluorescence of the PS/UCNCs nanocomposite spheres were studied in detail.     

A novel tyrosinase biosensor based on hydroxyapatite-chitosan nanocomposite for the detection of phenolic compounds

A novel tyrosinase biosensor based on hydroxyapatite nanoparticles (nano-HA)-chitosan nanocomposite has been developed for the detection of phenolic compounds. The uniform and size controlled nano-HA was synthesized by hydrothermal method, and its morphological characterization was examined by transmission electron microscope (TEM). Tyrosinase was then immobilized on a nano-HA-chitosan nanocomposite-modified gold electrode. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize the sensing film. The prepared biosensor was applied to determine phenolic compounds by monitoring the reduction signal of the biocatalytically produced quinone species at −0.2 V (vs. saturated calomel electrode). The effects of the pH, temperature and applied potential on the biosensor performance were investigated, and experimental conditions were optimized. The biosensor exhibited a linear response to catechol over a wide concentration range from 10 nM to 7 μM, with a high sensitivity of 2.11 × 10³ μA mM⁻¹ cm⁻², and a limit of detection down to 5 nM (based on S/N = 3). The apparent Michaelis-Menten constants of the enzyme electrode were estimated to be 3.16, 1.31 and 3.52 μM for catechol, phenol and m-cresol, respectively. Moreover, the stability and reproducibility of this biosensor were evaluated with satisfactory results.     

A novel amperometric biosensor based on NiO hollow nanospheres for biosensing glucose

NiO hollow nanospheres were synthesized by controlled precipitation of metal ions with urea using carbon microspheres as templates, which were for the first time adopted to construct a novel amperometric glucose biosensor. Glucose oxidase was immobilized on the surface of hollow nanospheres through chitosan-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of NiO hollow nanospheres, the constructed glucose biosensors exhibited a high sensitivity of 3.43 μA/mM. The low detection limit was estimated to be 47 μM (S/N = 3), and the Michaelis-Menten constant was found to be 7.76 mM, indicating the high affinity of enzyme on NiO hollow nanospheres to glucose. These results show that the NiO hollow nanospheres are a promising material to construct enzyme biosensors.     

Optimization of a glucose biosensor setup based on a Ni/Al HT matrix

An amperometric glucose biosensor was developed using an anionic clay matrix of hydrotalcitic nature (Ni/Al-NO₃ HT) as enzyme support, which was electrochemically synthesized at −0.90 V versus SCE, using a rotating disk Pt electrode to assure homogeneity of the electrodeposition suspension. The biorecognition element was glucose oxidase (GOx) immobilized on HT during the electrosynthesis, which was followed by cross-linking with glutaraldehyde vapours to avoid the enzyme release.The performances of the biosensor, in terms of sensitivity to glucose calculated from the slope of the calibration curve, are dependent on parameters related to the electrodeposition.An experimental design was applied to detect the optimal conditions of electrosynthesis in order to optimize the glucose biosensor performance. The factors taken into account were enzyme concentration and Ni/Al molar ratio. A full factorial design was performed to study linear interactions between factors and their quadratic effects and the optimal setup was evaluated by the isoresponse curves. The significant factors were enzyme concentration (linear and quadratic terms) and the interaction between enzyme concentration and Ni/Al molar ratio. Under the optimized electrodeposition conditions, the reproducibility of the biosensor fabrication was very good, being the RSD of the sensitivity about 5%.