Nanocomposites of genipin-crosslinked chitosan/silver nanoparticles--structural reinforcement and antimicrobial properties

This study investigates the feasibility of a novel nanocomposite (GC/Ag) of a genipin-crosslinked chitosan (GC) film in which was embedded various amounts of Ag nanoparticles for wound-dressing applications. In situ UV-vis results revealed that adding chitosan solution did not affect the characteristics of Ag nanoparticles. The water uptake ratios and surface hydrophilicity of the GC/Ag nanocomposite were better and the degradation rates slightly lower than those of the pure GC film. The presence of Ag nanoparticles enhanced L929 cell attachment and growth. Its function as an anti-microbial agent in a GC/Ag nanocomposite was assessed for Ag contents of over 100 ppm. In conclusion, silver ions had dual functions--structural reinforcement and provision of antimicrobial properties to a biocompatible polymer.     

Photo induced silver on nano titanium dioxide as an enhanced antimicrobial agent for wool

In this study an effective nanocomposite antimicrobial agent for wool fabric was introduced. The silver loaded nano TiO(2) as a nanocomposite was prepared through UV irradiation in an ultrasonic bath. The nanocomposite was stabilized on the wool fabric surface by using citric acid as a friendly cross-linking agent. The treated wool fabrics indicated an antimicrobial activity against both Staphylococcus aureus and Escherichia coli bacteria. Increasing the concentration of Ag/TiO(2) nanocomposite led to an improvement in antibacterial activities of the treated fabrics. Also increasing the amount of citric acid improved the adsorption of Ag/TiO(2) on the wool fabric surface leading to enhance antibacterial activity. The EDS spectrum, SEM images, and XRD patterns was studied to confirm the presence of existence of nanocomposite on the fabric surface. The role of both cross-linking agent and nanocomposite concentrations on the results was investigated using response surface methodology (RSM).     

Polyacrylamide/reduced graphene oxide-Ag nanocomposite as highly efficient antibacterial transparent film

In this study, preparation and characterization of polyacrylamide/reduced graphene oxide-Ag (PAM/rGO-Ag) nanocomposites as a new nanocomposite film were investigated. First, PAM/GO nanocomposite was synthesized by in situ polymerization strategy. Afterward, highly stable and uniformly distributed silver nanoparticles (Ag NPs) have been obtained with PAM/GO nanocomposite as nanoreactors via in situ reduction of silver nitrate (AgNO₃) using sodium borohydride (NaBH₄) as reducing agent. In addition, the prepared PAM/rGO-Ag nanocomposite was thermally annealed in order to achieve high-performance nanocomposite film with antimicrobial activities. The prepared nanocomposite was characterized by XRD, FT-IR, SEM, TEM and TGA. The obtained results demonstrate that the silver nanoparticles were well decorated and dispersed on the graphene oxide nanosheets. In fact, the GO nanosheets and polyacrylamide chains act as a support and stabilize the Ag nanoparticles. Moreover, antimicrobial activities of the films were also examined, and the films containing well-dispersed and stabilized Ag nanoparticles showed outstanding antibacterial activity.     

Electroless synthesis of multibranched gold nanostructures encapsulated by poly(o-phenylenediamine) in Nafion

Multibranched gold (Au) nanocomposite materials encapsulated by poly(o-phenylenediamine) (PoPD) (Au@PoPD) were synthesized in a Nafion polymer film through the electroless synthetic route. The micro-heterogeneous structured Nafion film acted as a reaction vessel and as the template for the formation of Au@PoPD nanocomposite materials leading to the formation of highly uniform distribution of high density of the polymer-gold nanocomposite material. The formation of Au@PoPD nanomaterials at the GP/Nf surface was scrutinized by recording in situ absorption spectra and was characterized. The formation of the (111) plane of gold was dominant at the Au@PoPD nanocomposite. The ratio of the benzenoid and quinoid units of the PoPD (ca. 1.65) observed for the Au@PoPD confirmed that the micro-heterogeneous structure of Nf film acted as a reaction vessel and as template for the formation of Au@PoPD nanocomposite material. Both PoPD and Au at the Au@PoPD nanocomposite showed electrochemical activities at the GC/Nf-Au@PoPD modified electrode. The electrocatalytic activity of the GC/Nf-Au@PoPD modified electrode was studied for oxygen reduction reaction (ORR).     

Facile method for fabrication of nanocomposite films with an ordered porous surface

This paper presents a novel and facile method for the fabrication of nanocomposite films with ordered porous surface structures. In this approach, a water-borne poly(styrene-co-butyl acrylate-co-acrylic acid)/silica nanocomposite dispersion was synthesized in situ by surfactant-free emulsion polymerization by using 3-allyloxy-2-hydroxy-1-propanesulfonate as a polymerizable surfactant. When this dispersion was dried to form a film at a certain temperature, an ordered porous structure could be directly obtained on the surface of the nanocomposite film. SEM, TEM, and AFM were employed to observe the morphology, and XPS and particle analyzer were used to analyze the surface composition of the ordered porous nanocomposite film and the particle size, respectively.     

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.     

Direct Electrochemistry and Electrocatalysis of Myoglobin Immobilized on Graphene‐CTAB‐Ionic Liquid Nanocomposite Film

This paper describes the direct electrochemistry and electrocatalysis of myoglobin immobilized on graphene‐cetylramethylammonium bromide (CTAB)‐ionic liquid nanocomposite film on a glassy carbon electrode. The nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and electrochemistry. It was found that the high surface area of graphene was helpful for immobilizing more proteins and the nanocomposite film could provide a favorable microenvironment for MB to retain its native structure and activity and to achieve reversible direct electron transfer reaction at an electrode. The ionic liquid may play dual roles here: it keeps the protein's activity and improves stability of the nanocomposite film; it also serves as a binder between protein and electrode, therefore, enhancing the electron transfer between the protein and the electrode. The nanocomposite films also exhibit good stability and catalytic activities for the electrocatalytic reduction of H₂O₂.     

Apatite-forming ability of titanium compound nanotube thin films formed on a titanium metal plate in a simulated body fluid

We compared the apatite-forming ability of a sodium titanate nanotube thin film, an anatase-type titanium dioxide nanotube thin film, and a silver nanoparticle/silver titanate nanotube nanocomposite thin film, in simulated body fluid. The ability of the silver nanoparticle/silver titanate nanotube nanocomposite thin film is slightly higher than that of the anatase-type titanium dioxide nanotube thin film and significantly higher than that of the sodium titanate nanotube thin film. The high ability of the silver nanoparticle/silver titanate nanotube nanocomposite thin film is a newly observed phenomenon, which is probably due to the crystal structure of silver titanate – specifically, to the surface atomic arrangement, the large amount of Ti–OH formed on the nanotube surface, or both. The anatase-type titanium dioxide nanotube thin film and the silver nanoparticle/silver titanate nanotube nanocomposite thin film may have bright prospects for future use in implant materials such as artificial joints. The silver nanoparticle/silver titanate nanotube nanocomposite thin film is particularly promising for its antibacterial properties.     

核壳型Fe_3O_4/Au粒子的制备及其在表面等离子体子共振传感器中的应用

合成了核壳型Fe3O4/Au复合粒子,并对其形貌、光学性质进行了表征.通过外加磁场将Fe3O4/Au复合粒子与兔抗人IgG的偶联体固定于表面等离子体子共振(SPR)传感器的金基底膜上,形成了Fe3O4/Au/抗IgG敏感膜.与传统的通过巯基丙酸连接蛋白的方式相比,磁场作用固定的Fe3O4/Au/抗IgG敏感膜制备简单,易洗脱,具有良好的再生性,且在一定程度上提高了传感器的灵敏度.并对人IgG进行了测定,结果表明,传感器对于浓度范围在1.25～20.00μg·mL-1的人IgG有良好的信号响应.     

Morphological investigation of hybrid Langmuir-Blodgett films of arachidic acid with a hydrotalcite/dendrimer nanocomposite

A hydrotalcite clay/dendrimer nanocomposite prepared by the ionic exchange process was adsorbed from suspension of the nanocomposite on a Langmuir monolayer of arachidic acid at the air/water interface, followed by compressing and transferring onto an arachidic acid monolayer Langmuir-Blodgett (LB) film on mica. For comparison, the hydrotalcite-adsorbed hybrid film was also prepared. The morphology of hydrotalcite and the nanocomposite studied by transmission electron microscopy indicated the layered structures with respectively 1.2 +/- 0.3 and 3.2 +/- 0.5 nm repeating distances. The hybrid Langmuir films displayed the occupied surface area of 0.24 nm2 for both hydrotalcite and the nanocomposite. The formation of hybrid Langmuir films was confirmed by Brewster angle microscopy. Atomic force microscopic images of hybrid LB films revealed the formation of plateau domains with the height difference of 6 nm for hydrotalcite and 12 nm for the nanocomposite and the presence of dendrimers adsorbed on the clay surface of the nanocomposite.     

Ag/WO3纳米复合膜的制备及其电致变色性质和器件的研究

通过真空镀膜方法制备的纳米Ag薄膜均匀致密, 表面光滑. 然后通过电化学方法在Ag纳米薄膜上沉积一层三氧化钨(WO3), 制备纳米Ag/WO3复合膜. 并在此基础上构筑五层式玻璃/ITO/纳米Ag-WO3复合膜/固态电解质/聚(3-甲基噻吩)/ITO/玻璃电致变色器件. 实验结果表明, 与传统的WO3膜相比, 纳米Ag/WO3复合膜具有更好的电化学活性、更高的对比度、更短的响应时间, 以及更好的稳定性. 由该复合膜组装的电致变色器件工艺简单, 电致变色性能良好.     

A Sensitive and Selective Nitrite Detection in Water Using Graphene/Platinum Nanocomposite

A glassy carbon electrode modified with reduced graphene oxide and platinum nanocomposite film was developed simply by electrochemical method for the sensitive and selective detection of nitrite in water. The electrochemical reduction of graphene oxide (GO) efficiently eliminates oxygen‐containing functional groups. Pt nanoparticles were electrochemically and homogeneously deposited on the ErGO surface. Field emission scanning electron microscopy (FE‐SEM), Raman spectroscopy, attenuated total reflectance‐fourier transform infrared spectroscopy (ATR‐FTIR), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were used to examine the surface morphology and electrocatalytic properties of the Pt‐ErGO nanocomposite film‐modified electrode surface. The fabricated nitrite sensor showed good electrochemical performance with two linear ranges; one from 5 to 100 µM (R²=0.9995) and the other from 100 to 1000 µM (R²=0.9972) and a detection limit of 0.22 µM. The proposed sensor was successfully applied for the detection of nitrite in tap water samples which proves performance of the Pt‐ErGO nanocomposite films.     

Direct electrochemistry and electrocatalysis of reduced glutathione on CNFs-PDDA/PB nanocomposite film modified ITO electrode for biosensors

The electrochemical oxidation of reduced glutathione (GSH) catalyzed by electro generated Berlin green at carbon nanofibers-poly(diallyldimethylammonium chloride)/Prussian blue (CNFs-PDDA/PB) nanocomposite film modified ITO electrode has been studied. The CNFs-PDDA/PB nanocomposite film were fabricated by casting the composite CNFs enfolded PDDA on ITO electrode followed by electrochemical deposition of PB on the CNFs-PDDA matrix using cyclic voltammetry (CV). Electron microscopy (TEM, AFM), and Fourier transform infrared spectroscopy (FT-IR) studies were used to characterize the morphology and structure of the nanocomposite. The fabricated CNFs-PDDA/PB/ITO nanocomposite film electrode shows significant improvement of redox activity of PB due to the excellent electron transfer ability of CNFs. It was also found to possess prominent electrocatalytic activity toward the oxidation of glutathione with high sensitivity as high as 2.07 μA dm(3) mol(-1) cm(-2). A nontoxic, stable and convenient method for the detection of GSH in the concentration range of 6.0×10(-6) to 1.74×10(-5) M has been developed and it showed improved sensor performance compared to the unmodified PB electrode. The high sensitivity, wider linear range, good reproducibility, and the minimal surface fouling make this CNFs/PDDA/PB nanocomposite film a promising candidate for GSH sensors.     

Spectrum Activity and Lauric Acid Release Behaviour of Antimicrobial Starch-based Film

This study aimed at the development of antimicrobial (AM) packaging based on wheat starch incorporated with chitosan and lauric acid as antimicrobial agents. A series of blends with different ratio of starch, chitosan and lauric acid (S:C:LA) were prepared by casting method. Effects of incorporation of antimicrobial agents into starch-based film were investigated in order to improve the spectrum activity based on measured distributions of inhibitory results. The diffusivity equation approach for describing the antimicrobial effects was also extended to include information about the molecular size of particles in the formed matrices. The Agar Disc Diffusion Assay and Liquid Culture Test measure the distributions of inhibitory effect towards type of bacterial contamination in terms of Gram-positive, Gram-negative and their combination of wider spectrum activity in the blend films. For the first time, the inhibition size distribution resulting from rationing of base polymers and lauric acid as filler in the starch-base film itself was quantified. Spectrum activity of different Gram-stained bacteria as measured by the bacterial growth inhibition, gave surprisingly consistent pattern on rationing of compositions in the film. This indicates that the spectrum activity produced by the antimicrobial components can be related directly to the ratio on blending during film preparation. This phenomenon is proven by dominating of chitosan (S:C:LA ratio 1:9:0.08 to 3:7:0.24) for 48% increase of effective E. coli inhibition (Gram-negative bacteria). More positively, however, it signifies that the affinity of lauric acid towards starch as reported by previous researches indicates relatively unambiguously the ratio required to achieve a constant degree of B. subtilis (Gram-positive) bacterial inhibition from starch/lauric acid dominating of S:C:LA ratio at 4:6:0.32 to 7:3:0.56. Furthermore, S:C:LA ratio 8:2:0.64 and 9:1:0.72 showed good synergic inhibition of 54% higher relative to sole chitosan towards both bacteria. Further studies of antimicrobial effects investigated the mode of release from the base film. The release of lauric acid in fatty acid food stimulant was satisfactorily expressed by Fickian-diffusion mechanism described by zero order kinetics which indicated that lauric acid released from the film matrix remains constant over time.     

Application of polyaniline/bacterial extracellular polysaccharide nanocomposite for removal and detoxification of Cr(VI)

Polyaniline/bacterial extracellular polysaccharide (Pn/EPS) nanocomposite was prepared by in situ polymerization of aniline using ammonium peroxydisulfate as oxidant. Transmission electron micrograph showed that the surface of the nanocomposite was rough, providing good possibility for adsorption of Cr(VI). Under optimized conditions, the nanocomposite removed 97.3 % (25 mg L^?1) of Cr(VI) from aqueous solution. The Freundlich isotherm model and pseudo-first order rate expression better described the adsorption equilibrium of Pn/EPS nanocomposite. X-ray diffractogram peak for Cr₂O₃ (2θ = 24.5) in the nanocomposite confirmed the reduction of Cr(VI). Fourier transform infrared spectroscopy pattern of the nanocomposite confirmed the ionic interaction between Cr species and surface functional groups. The results of the study indicate that Pn/EPS nanocomposite could be used for the removal and detoxification of Cr(VI) from aqueous solution.     

One step electrochemically deposited nanocomposite film of chitosan-carbon nanotubes-gold nanoparticles for carcinoembryonic antigen immunosensor application

A simple and controllable one-step electrodeposition method for the preparation of a chitosan-carbon nanotubes-gold nanoparticles (CS-CNTs-GNPs) nanocomposite film was used to fabricate an immunosensor for detection of carcinoembryonic antigen (CEA). The porous three-dimensional CS-CNTs-GNPs nanocomposite film, which offered a large specific surface area for immobilization of antibodies, exhibited improved conductivity, high stability and good biocompatibility. The morphology of the formed nanocomposite film was investigated by scanning electron microscopy (SEM), and the electrochemical behaviors of the immunosensor were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Under the optimal conditions, the proposed immunosensor could detect CEA in two linear ranges from 0.1 to 2.0 ng mL⁻¹ and from 2.0 to 200.0 ng mL⁻¹, with a detection limit of 0.04 ng mL⁻¹. The immunosensor based on CS-CNTs-GNPs nanocomposite film as the antibody immobilization matrix could exhibit good sensitivity, stability, and reproducibility for the determination of CEA.     

Electrochemical study of methylene blue/titanate nanotubes nanocomposite and its layer-by-layer assembly multilayer films

Titanate nanotubes (TNT) were proven to be efficient support for the immobilization of methylene blue (MB). UV–vis absorption and Fourier transform infrared spectra showed that the effect of MB absorbed on TNT was better than nanocrystalline anatase TiO₂ (TNP). The quantity of MB absorbed onto TNT was found to be greater than that of TNP and the electrode modified with the MB–TNT film was more stable due to the strong interaction between TNT and MB as well. The absorption of MB on TNT was impacted by the pH value of the reaction solution for the change of surface charge. Electrochemical oxidation of dopamine (DA) at different electrodes was studied. The result showed that the MB–TNT composite film exhibited excellent catalytic activities to DA compared to those of pure TNT, which is a result of the great promotion of the electron-transfer rate between DA and the electrode surface by the MB–TNT film. Furthermore, the layer-by-layer self-assembly behavior of the electrochemically functional MB–TNT nanocomposite was also discussed after obtaining the stable colloid suspension of MB–TNT. The excellent electrochemical ability and the easy fabrication of layered nanocomposite make the MB–TNT nanocomposite very promising in electrochemistry study and new nanotube-based devices.     

Synthesis of Chitosan-La2O3 Nanocomposite and Its Utility as a Powerful Catalyst in the Synthesis of Pyridines and Pyrazoles

Recently, the development of nanocatalysts based on naturally occurring polysaccharides has received a lot of attention. Chitosan (CS), as a biodegradable and biocompatible polysaccharide, is considered to be an excellent template for the design of a hybrid biopolymer-based metal oxide nanocomposite. In this case, lanthanum oxide nanoparticles doped with chitosan at different weight percentages (5, 10, 15, and 20 wt% CS/La₂O₃) were prepared via a simple solution casting method. The prepared CS/La₂O₃ nanocomposite solutions were cast in a Petri dish in order to produce the developed catalyst, which was shaped as a thin film. The structural features of the hybrid nanocomposite film were studied by FTIR, SEM, and XRD analytical tools. FTIR spectra confirmed the presence of the major characteristic peaks of chitosan, which were modified by interaction with La₂O₃ nanoparticles. Additionally, SEM graphs showed dramatic morphological changes on the surface of chitosan, which is attributed to surface adsorption with La₂O₃ molecules. The prepared CS/La₂O₃ nanocomposite film (15% by weight) was investigated as an effective, recyclable, and heterogeneous base catalyst in the synthesis of pyridines and pyrazoles. The nanocomposite used was sufficiently stable and was collected and reused more than three times without loss of catalytic activity.     

The role of conditioning film formation and surface chemical changes on Xylella fastidiosa adhesion and biofilm evolution

Biofilms are complex microbial communities with important biological functions including enhanced resistance against external factors like antimicrobial agents. The formation of a biofilm is known to be strongly dependent on substrate properties including hydrophobicity/hydrophilicity, structure, and roughness. The adsorption of (macro)molecules on the substrate, also known as conditioning film, changes the physicochemical properties of the surface and affects the bacterial adhesion. In this study, we investigate the physicochemical changes caused by Periwinkle wilt (PW) culture medium conditioning film formation on different surfaces (glass and silicon) and their effect on X. fastidiosa biofilm formation. Contact angle measurements have shown that the film formation decreases the surface hydrophilicity degree of both glass and silicon after few hours. Atomic force microscopy (AFM) images show the glass surface roughness is drastically reduced with conditioning film formation. First-layer X. fastidiosa biofilm on glass was observed in the AFM liquid cell after a period of time similar to that determined for the hydrophilicity changes. In addition, attenuation total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy supports the AFM observation, since the PW absorption spectra increases with time showing a stronger contribution from the phosphate groups. Although hydrophobic and rough surfaces are commonly considered to increase bacteria cell attachment, our results suggest that these properties are not as important as the surface functional groups resulting from PW conditioning film formation for X. fastidiosa adhesion and biofilm development.