Nanoparticle Multilayer Films Research Articles

Photoelectric Characteristics of Reduced Graphene Oxide/Silver Nanoparticles Multilayer Films via Spin-Coating and Self-Assembly

Photoelectric Characteristics of Reduced Graphene Oxide/Silver Nanoparticles Multilayer Films via Spin-Coating and Self-Assembly

Rapid and In Situ Synthesis of Gold Nanoparticles in Redox Multilayer Film for Biosensor Applications

AbstractFerrocene‐grafted poly(ethyleneimine)/poly(acrylic acid) (PEI‐Fc/PAA) multilayer films were constructed via layer‐by‐layer assembly. When the PEI‐Fc/PAA films were immersed in HAuCl4 solution, Fc and the AuIII were converted to Fc+ and Au0, respectively, via the redox reaction of Fc and HAuCl4, and the PEI‐Fc/PAA@Au nanoparticles (NPs) multilayer films were rapidly fabricated. SEM and TEM results showed Au NPs were distributed homogeneously throughout the thickness of the whole film. The electron transfer behavior of PEI‐Fc/PAA@Au NPs multilayer films was investigated by cyclic voltammetry and AC impedance. The results indicated that the Au NPs greatly improve the conductivity of multilayer films and thus enhance the electrochemical properties of films. The PEI‐Fc/PAA@Au NPs films were further used for the fabrication of a hydrogen peroxide (H2O2) sensor, which showed good catalytic ability for the reduction of H2O2. This approach is expected to expand the routes towards rapid fabrication of Au NPs into multilayer films.

Electrostatically assisted fabrication of silver–dielectric core/shell nanoparticles thin film capacitor with uniform metal nanoparticle distribution and controlled spacing

An electrostatically-assisted strategy for fabrication of thin film composite capacitors with controllable dielectric constant (k) has been developed. The capacitor is composed of metal–dielectric core/shell nanoparticle (silver/silica, Ag@SiO2) multilayer films, and a backfilling polymer. Compared with the simple metal particle-polymer mixtures where the metal nanoparticles (NP) are randomly dispersed in the polymer matrix, the metal volume fraction in our capacitor was significantly increased, owing to the densely packed NP multilayers formed by the electrostatically assisted assembly process. Moreover, the insulating layer of silica shell provides a potential barrier that reduces the tunneling current between neighboring Ag cores, endowing the core/shell nanocomposites with a stable and relatively high dielectric constant (k) and low dielectric loss (D). Our work also shows that the thickness of the SiO2 shell plays a dominant role in controlling the dielectric properties of the nanocomposites. Control over metal NP separation distance was realized not only by variation the shell thickness of the core/shell NPs but also by introducing a high k nanoparticle, barium strontium titanate (BST) of relatively smaller size (∼8nm) compared to 80–160nm of the core/shell Ag@SiO2 NPs. The BST assemble between the Ag@SiO2 and fill the void space between the closely packed core/shell NPs leading to significant enhancement of the dielectric constant. This electrostatically assisted assembly method is promising for generating multilayer films of a large variety of NPs over large areas at low cost.

A new and facile way to fabricate catalytically active block copolymer/Au nanoparticle multilayer thin films at the air/liquid interface

A catalytically active multilayer film of PB-b-P2VP doped with Au nanoparticles was fabricated through liquid/liquid interfacial mass transfer, self-assembly in an aqueous phase and adsorption at the air/liquid interface.

Heat-induced coarsening of layer-by-layer assembled mixed Au and Pd nanoparticles.

This article shows the coarsening behavior of nanoparticle multilayers during heat treatments which produce larger metallic nanostructures with varying shapes and sizes on glass slides. Nanoparticle multilayer films are initially constructed via the layer-by-layer self-assembly of small and monodispersed gold and/or palladium nanoparticles with different compositions (gold only, palladium only, or both gold and palladium) and assembly orders (compounding layers of gold layers over palladium layers or vice versa). Upon heating the slides at 600°C, the surface nanoparticles undergo coalescence becoming larger nanostructured metallic films. UV-Vis results show a clear reliance of the layering sequence on the optical properties of these metal films, which demonstrates an importance of the outmost (top) layers in each nanoparticle multilayer films. Topographic surface features show that the heat treatments of nanoparticle multilayer films result in the nucleation of nanoparticles and the formation of metallic cluster structures. The results confirm that different composition and layering sequence of nanoparticle multilayer films clearly affect the coalescence behavior of nanoparticles during heat treatments.

Preparation of ZnO Nanoparticles Under Ultrasonic Irradiation and Photocatalytic Performance of ZnO Nanoparticles Multilayer Films

Preparation of ZnO Nanoparticles Under Ultrasonic Irradiation and Photocatalytic Performance of ZnO Nanoparticles Multilayer Films

SPR Biosensors Based on Gold and Silver Nanoparticle Multilayer Films

Gold and silver nanoparticle multilayer films were used for the development of a plasmonic sensor, applied to detect surface binding of organic and/or biological molecules. The sensitivity to binding events is related to energetic shifts of the surface plasmon resonance on the film. When applied as a bulk sensor (sensitivity to changes on refractive index of the medium in contact with the metal surface), the sensitivity was found to be ca. 220 ± 33 nm RIU-1 for gold and ca. 140 ± 10 nm RIU-1 for silver nanoparticles. The systems were also found efficient as surface biosensors (sensitivity to changes on the effective refractive index due to adsorptions on the metal surface) detecting the surface binding of biotin-streptavidin protein system. The main advantage of the plasmonic biosensor developed in this work is the use of a very simple and low cost methodology when compared to fancier approaches, such as the ones using focused ion beam and surface relief gratings, although presenting similar sensitivity, and allowing, as for these cases, real-time measurements.

Layer-by-layer assembled multilayer films of reduced graphene oxide/gold nanoparticles for the electrochemical detection of dopamine

Graphene/gold nanoparticle multilayer films composed of polysodium 4-styrenesulfonate (PSS) functionalized reduced graphene oxide (RGO) and polyamidoamine (PAMAM) dendrimer stabilized gold nanoparticles (AuNPs) were built up using the electrostatic layer-by-layer (LBL) self-assembly technique on a glassy carbon electrode (GCE) modified with a first layer of poly(diallyldimethylammonium chloride) (PDDA). The film assembly, the electrochemical property as well as the electrocatalytic activity toward the oxidation of dopamine were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Electrochemical studies exhibit that the LBL assembled RGO/AuNPs films possess an excellent sensing performance for the detection of dopamine with a linear range from 1μM to 60μM and a limit of detection (LOD) as low as 0.02μM based on S/N=3. In addition, this electrochemical sensor was applied to the simultaneous detection of dopamine and uric acid by using DPV with high sensitivity and selectivity. The good analytical performance and long-term stability of the proposed sensor can be attributed to the combination of the reduced graphene oxide and gold nanoparticles in the LBL assembly films and the synergistic effect on the electrochemical oxidation of dopamine.

Characterization of localized surface plasmon resonance transducers produced from Au25 nanoparticle multilayers

This article reports the preparation of gold plasmonic transducers using a nanoparticle self-assembly/heating method and the characterization of the films using scattering-type scanning near-field optical microscopy (s-SNOM). Nanoparticle-polymer multilayer films were prepared by the layer-by-layer assembly on glass slides by alternating exposures to monodisperse Au25 nanoparticles and ionic polymer linkers. Thermal evaporation of organic matters from the nanoparticle-polymer multilayer films at 600°C allowed the nanoparticles to coalescence and form nanostructured films. Characterization of the nanostructured films generated from Au25 nanoparticles using atomic force microscopy (AFM) showed that the films have rounded, small, island-like morphologies (d: 30–50nm) with a pit in the center of many islands. However, further characterizations with s-SNOM revealed that the produced nanoislands contain a single gold cluster in a pit surrounded by donut-shaped dielectric species. Formation of such a structure is thought to be resulted from the embedding of gold clusters under the reorganized polysiloxane binder coatings and glass surfaces during heat treatment of the Au25 nanoparticle multilayer films. The nanostructured films displayed strong surface plasmon resonance bands in UV–vis spectra with a peak absorbance occurring at ∼545–550nm. The optical sensing capability of the films was examined using d-glucose-functionalized gold island films with the interaction of Concanavalin A (ConA). The result showed that the adsorption of ConA on island films causes a large change in the LSPR band intensity.

Linker-free layer-by-layer self-assembly of gold nanoparticle multilayer films for direct electron transfer of horseradish peroxidase and H 2O 2 detection

Au nanoparticle (AuNP) multilayer films were fabricated by combining interfacial assembly and layer-by-layer assembly. The key point is that the procedure does not require assistance of organic linker molecules, thus providing a suitable platform for the modification of biological molecules. Direct electron transfer can easily take place between a glassy carbon electrode and horseradish peroxidase (HRP) molecules adsorbed on AuNP films. The current density of direct electron transfer was closely related to the layer number, m, and reached a maximum value for m = 4. The optimized HRP/AuNP multilayer film had a relatively rapid response and satisfactory selectivity for H 2O 2 detection. The linear range and the detection limit were 9.8 × 10 −6 to 6 × 10 −3 mol/L and ∼4.9 × 10 −6 mol/L ( S/ N = 3), respectively.

Stability and Morphology of Gold Nanoisland Arrays Generated from Layer-by-Layer Assembled Nanoparticle Multilayer Films: Effects of Heating Temperature and Particle Size

This article reports the effects of heating temperature and composition of nanoparticle multilayer films on the morphology, stability, and optical property of gold nanoisland films prepared by nanoparticle self-assembly/heating method. First, nanoparticle-polymer multilayer films are prepared by the layer-by-layer assembly. Nanoparticle multilayer films are then heated at temperature ranging from 500 °C to 625 °C in air to induce an evaporation of organic matters from the films. During the heating process, the nanoparticles on the solid surface undergo coalescence, resulting in the formation of nanostructured gold island arrays. Characterization of nanoisland films using atomic force microscopy and UV-vis spectroscopy suggests that the morphology and stability of gold island films change when different heating temperatures are applied. Stable gold nanoisland thin film arrays can only be obtained after heat treatments at or above 575 °C. In addition, the results show that the use of nanoparticles with different sizes produces nanoisland films with different morphologies. Multilayer films containing smaller gold nanoparticles tend to produce more monodisperse and smaller island nanostructures. Other variables such as capping ligands around nanoparticles and molecular weight of polymer linkers are found to have only minimal effects on the structure of island films. The adsorption of streptavidin on the biotin-functionalized nanoisland films is studied for examining the biosensing capability of nanoisland arrays.

Bifunctional composite prepared using layer-by-layer assembly of polyelectrolyte–gold nanoparticle films on Fe3O4–silica core–shell microspheres

Layer-by-layer assembly of polyelectrolyte–gold nanoparticles (NPs) multilayer films on Fe3O4–silica core–shell microspheres provides a convenient method to design a bifunctional hybrid composite combining the catalytic and magnetic performance together. The Au NPs are effectively immobilized in the polyelectrolyte layer without blocking the catalytic sites. The obtained hybrid magnetic microspheres exhibit high catalytic performance in both organic and inorganic reduction reactions. The use of magnetic support for the immobilization of Au NPs guarantees facile, clean, fast and efficient separation of the catalyst at the end of the reaction cycle.

Preparation of Self-Assembled Zinc Oxide Nanoparticles Multilayer Films Under Ultrasonic Irradiation

Zinc oxide nanoparticles were synthesized and self-assembled on the reactive surface of a glass slide functionalized with (3-mercaptopropyl)-trimethoxysilane under ultrasonic irradiation. The structure, morphology, and optical property of the zinc oxide nanoparticles were investigated by TEM, XRD, and UV-vis spectroscopy. The functionalized glass slide was soaked in an aqueous solution which dispersed zinc oxide nanoparticles under ultrasonic irradiation. Zinc oxide multilayer films grew up to several layers (up to 5 layers) depending on the immersion time. The self-assembled zinc oxide nanoparticles multilayer films were characterized using UV-vis spectroscopy and SEM. Ultrasonic irradiation was an efficient method to make multilayer films on the functionalized glass slide with zinc oxide nanoparticles.

Electrochromic properties of self-assembled nanoparticle multilayer films

Hexagonal tungsten bronze (HTB) nanocrystal and TiO 2 nanoparticles were assembled into thin films by layer-by-layer self-assembly method. HTB nanocrystals were synthesized by hydrothermal route at 155 °C. UV–Vis spectra showed that the HTB/TiO 2 films exhibit a linear increase in film thickness with assembly exposure steps. The electrochromic property of the film was carefully investigated. Cyclic voltammetry indicated that the redox peak was around −0.5 V. The electrochromic contrast, coloration efficiency, switching speed, stability and optical memory were carefully investigated. The films vary from white to blue and finally dark brown. The electrochromic contrast is 63.9% at 633 nm. The coloration efficiency of the films is relatively high. The response time is less than 3 s.

Preparation of Gold Nanoisland Arrays from Layer-by-Layer Assembled Nanoparticle Multilayer Films

o C in air to evaporate organic matters from the films. During the annealing process, the nano- particles on the solid surface undergo nucleation and coalescence, resulting in the formation of nanostructured gold island arrays. By controlling the overall thickness (number of layers) of nanoparticle multilayer films, nanoisland films with various island density and different average sizes are obtained. The surface property of gold nanoisland films is further controlled by the self-assembly of alkanethiols, which results in an increased surface hydrophobicity of the films. The structure and characteristics of these nanoisland film arrays are found to be quite comparable to those of nano- island films prepared by vacuum evaporation method. However, this self-assembly/annealing protocol is simple and requires only common laboratory supplies and equipment for the entire preparation process.

Layer-by-Layer Self-Assembly for Constructing a Graphene/Platinum Nanoparticle Three-Dimensional Hybrid Nanostructure Using Ionic Liquid as a Linker

In this report, we succeed in constructing a hybrid three-dimensional (3D) nanocomposite film by alternatively assembling the graphene nanosheets modified by ionic liquid (IL) and Pt nanoparticles (Pt NPs). In this strategy, an imidazolium salt-based ionic liquid (IS-IL)-functionalized graphene was synthesized by covalently binding 1-(3-aminopropyl)-3-methylimidazolium bromide onto graphene nanosheets. The introduction of IS-IL on the surface of graphene nanosheets can obtain dispersed graphene nanosheets with positive charge. Also, the desired functionalization of graphene can form the building blocks for constructing hybrid 3D nanocomposite film. Then, the positively charged IS-IL-functionalized graphene nanosheets are strong enough to drive the formation of the 3D nanomaterials with negatively charged citrate-stabilized Pt NPs through electrostatic interaction. As far as we know, the reports on the layer-by-layer (LBL) self-assembly of G-IS-IL and nanoparticle multilayer films are few at the moment. UV-visible-near-infrared (UV-vis-NIR) absorption spectroscopy, atomic force microscopy (AFM) and cyclic voltammetry (CV) were used to characterize the uniform growth of the multilayer film. The newly prepared 3D nanomaterials containing G-IS-IL and Pt NPs show high electrocatalytic activity toward oxygen reduction. Furthermore, the electrocatalytic activity of the films could be further tailored by simply choosing different cycles in the LBL process. This demonstration offers a new route to assemble graphene/nanoparticle multilayer films and opens up the possibility of building more complex multicomponent nanostructures, which are believed to be useful for electrochemical nanodevices.

Sonochemical Synthesis of Closed [5,6]-bridged Aziridino[70]fullerene Derivative and Self-assembled Multilayer Films

This cycloaddition of [70]fullerene with methyl azidoacetate in benzene under ultrasonic irradiated condition afforded the closed [5,6]-bridged aziridino[70]fullerene derivative, which was unusual product of cycloaddition to the 5,6-junction of fullerene. Its structure was determined by FAB-MS, UV-vis, <TEX>$^1H-$</TEX> and <TEX>$^{13}C$</TEX>-NMR spectral data. The closed [5,6]-bridged aziridino[70]fullerene-functionalized gold nanoparticle films were self-assembled using the layer-by-layer method on the reactive of glass slides functionalized with 3-mercaptopropyl trimethoxysilane. The functionalized glass slides were alternately soaked in the solution containing closed the [5,6]-bridged aziridino[70]fullerene and 4-aminothiophenoxide/hexanethiolate-protected gold nanoparticles. The closed [5,6]-bridged aziridino[70]fullerene-functionalized gold nanoparticle films have grown up to 5 layers depending on the immersion time. The self-assembled nanoparticle multilayer films were characterized using UV-vis spectroscopy showed that the surface plasmon band of gold at 527 nm gradually became more evident as successive layers were added to the films.

Synthesis of Gold Nanoparticle with Aqueous Carbon Nano Colloid under Ultrasonication and Self-Assembled Carbon-Gold Nanoparticle Multilayer Films

The preparation of gold nanoparticle showed in carbon nano colloid under ultrasonic irradiation. The products of gold nanoparticle were well dispersed in carbon nano colloid investigated by UV-vis., SEM, TEM, EDX, and XRD spectra. Carbon nano colloid – gold nanoparticle films were self-assembled on the reactive surface of glass slides functionalized with 3-aminopropyltrimethoxysilane. Also, the self-assembled nanoparticle films were characterized using UV-vis. spectra.

Carbon nanotube/chitosan/gold nanoparticles-based glucose biosensor prepared by a layer-by-layer technique

A new amperometric glucose biosensor was constructed, based on the immobilization of glucose oxidase (GOx) with cross-linking in the matrix of chitosan on a glassy carbon electrode, which was modified by layer-by-layer assembled carbon nanotube (CNT)/chitosan (CHIT)/gold nanoparticles (GNp) multilayer films. With the increasing of CNT/CHIT/GNp layers, the response current to H 2O 2 was changed regularly and the response current reached a maximum value when the number of CNT/CHIT/GNp layers was 8. The assembling process of multilayer films was simple to operate. With GOx as an enzyme model, a new glucose biosensor was fabricated. The excellent electocatalytic activity and special structure of the enzyme electrode resulted in good characteristics. The linear range was 6 × 10 − 6 ∼ 5 × 10 − 3 M, with a detection limit of 3 × 10 − 6 M estimated at a signal-to-noise ratio of 3, fast response time (less than 6 s). Moreover, it exhibited good reproducibility and stability.

Self-assembly of multilayer films containing gold nanoparticles via hydrogen bonding

Polymer/Au nanoparticle multilayer ultrathin films are fabricated via hydrogen-bonding interaction by a layer-by-layer technique. The Au nanoparticles surface-modified with pyridine groups of poly(4-vinylpyridine) (PVP) are prepared in dimethyl formamide (DMF). Transmission electron microscopy (TEM) image shows that uniform nanoparticles are dispersed in the PVP chains. Poly(3-thiophene acetic acid) (PTAA) and poly(acrylic acid) (PAA) are utilized to form hydrogen bonds with PVP, respectively. Considering the pH-sensitive dissociation behavior of PTAA and PAA, we investigate the release behavior of the Au-containing multilayers at different pH values in this work. UV–vis spectroscopy and atomic force microscopy (AFM) are employed to monitor the buildup and the release of the multilayers. The results indicate that in the films assembled with gold nanoparticles, the polymers are difficult to be removed from the substrate. The interaction between the gold particles and the neighboring PVP chains is responsible for the phenomenon. Gold particles act as physical cross-link points in the multilayers. Due to the additional interaction caused by the gold nanoparticles in the films except the hydrogen-bonding interaction between PTAA (or PAA) and PVP, the stability of the Au-containing multilayer film is ensured even though the changes in pH values may result in the break of the hydrogen bonds.