Decoration Of Au Nanoparticles Research Articles

Platinum-based nanocomposite as oxygen reduction catalyst for efficient signal amplification: Toward building of high-performance photocathodic immunoassay

Photocathodic bioassays have shown great potential to apply in real bio-sample detection owning to their intrinsic abilities against interference from reductive species. However, the pursuit of photocathodic bioassays with excellent detection performance is still in the infancy. Herein, an advanced signal amplifier of platinum-based nanocatalyst with efficient oxygen reduction capability was explored to build a high-performance photocathodic immunoassay. The target model of carbohydrate antigen 19-9 (CA19-9, Ag) was used for describing the sensing platform. Specifically, the nontoxic Au/CuBi2O4 photocathode was first prepared by decorating Au nanoparticles on CuBi2O4 nanofilm and was used as the matrix to anchor capture CA19-9 antibody (Ab1). Platinum (Pt) nanoparticles were loaded on graphene (GR) nanosheet to form Pt/GR nanocomposite, which was utilized as signal amplifier conjugating with signal CA19-9 antibody (Ab2). When specific sandwich immunoreaction happened, the Pt/GR played the role of an efficient nanocatalyst to accelerate the reduction reaction of electron acceptor of oxygen in the electrolyte, causing evidently enhanced cathodic photocurrent signal. By incorporating this superior signal amplification strategy into the anti-interference photocathodic immunoassay, highly sensitive and specific detection of target Ag was realized. This work pioneers a new perspective for the design of advanced photocathodic bioanalysis for various targets of interest.

Plasmon expedited response time and enhanced response in gold nanoparticles-decorated zinc oxide nanowire-based nitrogen dioxide gas sensor at room temperature

A highly sensitive and rapidly responsive nitrogen dioxide (NO2) gas sensor based on gold (Au) nanoparticles (NPs)-decorated zinc oxide (ZnO) nanowires (NWs) is presented. The Au NPs decoration was conducted onto ZnO NWs with and without a (3-aminopropyl)triethoxysilane (APTES) layer on their surface by using the electrostatic force. The samples without the APTES layer exhibited high NO2 gas sensitivity (i.e. expedited response time and enhanced gas response) due to localized surface plasmon resonance (LSPR) of the Au NPs; in particular, the NO2 gas response and the response time were increased by three times and shortened by 86%, respectively, compared with the undecorated ZnO NWs. The presence of the APTES layer improved the Au NPs attachment, but hindering the gas adsorption on the ZnO NWs surface, as proven by the observed photocurrent and gas response. Our findings imply that the response time of semiconductor gas sensors can be remarkably expedited by the LSPR effect, which is useful for developing practical gas sensors.

Light harvesting enhancement by hierarchical Au/TiO2 microspheres consisted with nanorod units for dye sensitized solar cells

In this work, we developed the light harvesting enhancement with hierarchical Au/TiO2 microspheres (AuTMS) embedded into photoanode for efficient dye sensitized solar cells (DSSCs). The light scattering capability caused by the large size of AuTMS and plasmonic effect provided by the decoration of Au nanoparticles dually improve the light harvesting of photoanode. The conversion efficiency of 9.60% has been achieved relative to 5.71% for P25, resulting in a 68.13% improvement in photovoltaic performance. The excellent photovoltaic performance could mainly ascribe to the enhancement of JSC, which results from the accelerated light harvesting and more generated charge carriers in DSSCs. Meanwhile, the nanorod units in AuTMS can act as electron transfer paths, which ensure fast electron transfer and inhibited charge recombination. The light harvesting enhancement through hierarchical Au/TiO2 spheres is supposed to contribute to efficient solar devices.

Preparation and Catalytic Property of Au-decorated Titanium Dioxide Dendritic Nanofibers

To remove organic pollutants from industrial wastewater, the Au-decorated titanium dioxide dendritic nanofibers (Au-Ti DNFs) were synthesized through in situ decoration of gold (Au) nanoparticles on the titanium dioxide dendritic nanofibers (Ti DNFs). The electrospun Ti NFs were firstly prepared by sol-gel method combined with electrospinning technology, then in situ converted to Ti DNFs in the NaOH solution via a hydrothermal route, and finally treated in the solution of HAuCl4.4H2O to produce Au-DTi NFs. SEM and TEM analyses showed that the Au-Ti DNFs had the dendritic and fibrous morphology and consisted of a large number of Au-Ti nanowires. 4-Nitrophenol was used as the model organic material to test the catalytic performance of Au-Ti DNFs. The results showed that Au-Ti DNFs catalytically reduced 4-nitrphenol to 4-amonphenol and their catalytic performance was higher than that of Ti DNFs due to the decoration of Au nanoparticles.

Construction of novel ternary Au/LaFeO3/Cu2O composite photocatalysts for RhB degradation via photo-Fenton catalysis

ABSTRACT By immobilising LaFeO3 and Au nanoparticles on the surface of Cu2O polyhedral microspheres, we have prepared novel binary LaFeO3/Cu2O and ternary Au/LaFeO3/Cu2O composite photocatalysts. The as-fabricated composites were systematically investigated by using various characterisation techniques. Photocurrent response and EIS measurements suggest that the composite photocatalysts exhibit an electron/hole pair separation more efficient than bare LaFeO3 and Cu2O. The photocatalysis and photo-Fenton degradation experiments were carried out by removing RhB from water under simulated sunlight irradiation. The composite photocatalysts are demonstrated to have superior photocatalysis/photo-Fenton degradation performances to bare LaFeO3 and Cu2O. 20%LaFeO3/Cu2O is determined to be the optimal binary composite photocatalyst. Moreover, the decoration of Au nanoparticles onto the 20%LaFeO3/Cu2O composite can further improve the photocatalysis/photo-Fenton degradation performance. The enhanced photocatalysis and photo-Fenton decomposition mechanisms for the ternary Au/LaFeO3/Cu2O composites were investigated and discussed on the based of the Z-scheme electron transfer process, LSPR of Au nanoparticles and photo-Fenton synergistic effect.

Engineering nanotubular titania with gold nanoparticles for antibiofilm enhancement and soft tissue healing promotion

The success rate of titanium dental implants were challenged from peri-implant infections. However, pure titanium surfaces possess no antibacterial properties and are bio-inert for soft tissue healing delay. In the present study, the anodized titania nanotubes (TiO2-NTs) on Ti substrate were fabricated following by Au nanoparticle (AuNPs) deposition. The AuNPs incorporation into hierarchical TiO2-NTs would not only exhibit photocatalytic activity by visible-light irradiation, but also generate more quantum yield of reactive oxygen species, due to the prevention of electron-hole recombination and the surface plasmon resonance of Au, thus resulting in an enhanced antibacterial effect against multispecies biofilm. Antibacterial efficacy of AuNPs/TiO2-NTs was positively corelated with Au nanoparticle amount in TiO2-NTs samples. Besides, AuNPs decoration would also exert favorable functions on cell attachment, proliferation and migration of fibroblast. Experiments in animal model also indicated a superior soft tissue healing promotion for AuNPs/TiO2-NTs. Therefore, this designed AuNPs/TiO2-NTs is beneficial and applicable to dental implant surfaces to inhibit pathogens, promote soft tissue healing and combat periodontitis.

Enhancing visible-light-driven water splitting of ZnO nanorods by dual synergistic effects of plasmonic Au nanoparticles and Cu dopants

Converting solar energy into chemical fuels is important to develop renewable energy. Here, Cu-doped ZnO nanorods (NRs) decorated with Au nanoparticles (NPs) are used as an efficient semiconductor catalyst for visible-light-driven water splitting. Doping Cu into ZnO NRs narrows the bandgap and shifts the absorbance toward red light; decorating Au NPs onto the ZnO:Cu NRs enhances the absorbance in the visible region and improves the solar energy conversion. The band gap of the ZnO:Cu NRs is optimized at 3% Cu doping, which presents a minimum value of 3.09 eV. Furthermore, the surface plasmon resonance effect, which is caused by decorating 10-nm Au NPs on the Cu-doped ZnO NRs, enhances the optical absorption and improves the photoelectrochemical water splitting performance. The presence of Au NPs on the surface of the NRs also reduces charge recombination, increasing the photocurrent. Under visible illumination (λ > 420 nm), the considerable photocurrent density of this device reaches 10.2 μA cm−2 at 0.581 V, which is about 7.3 times higher than that of a pure ZnO NRs sample. The simple and cost-effective fabrication process of this design provides an innovative approach for water splitting and future optoelectronic devices.

Au Decorated WO3-X Nanoflake Arrays Used As Photoelectrochemical Detection and Surface Enhanced Raman Scattering

The increasing of environment organic pollution in water body is calling for the development of high efficient sensors for fast and stable monitoring. Herein, a new Au decorated WO3-x nanoflake arrays sensor combined photoelectrochemical detection with surface enhanced Raman scattering (SERS) was proposed, in which self-doped tungsten trioxide (WO3-x) nanoflake arrays were synthesized by dealloying of Fe-W amorphous alloy and thermal treatment, following by surface decoration of sputtering Au nanoparticles. The effect of size and distribution of gold particles on the photocatalytic degradation of WO3-x was investigated. It was found that the annealing temperature plays an important role in the growth of gold particles, the optimal size is about 10nm (annealing temperature was 400 ℃); photoelectrochemical test revealed that the current density was positively correlated with the pollutant concentration with the detect limit of 10-9 mol/L; at the same time, these functional nanoflake arrays showed high sensitivity for R6G (10-8mol/L) in Raman spectrum detection. We believe that this technique will have a great prospect for qualitative and quantitative analysis of environmental pollutants.

Three-dimensional flexible Au nanoparticles-decorated TiO2 nanotube arrays for photoelectrochemical biosensing

Controlling the charge transfer and thus enhancing the excitons’ lifetime are the key to the realization of efficient photoelectrochemical (PEC) devices. Moreover, fabrication of flexible and collapsible sensors can greatly facilitate the implementation of smart PEC sensing devices into practical applications. Herein, we sagely designed and successfully fabricated three-dimensional flexible Au nanoparticles-decorated TiO2 nanotube arrays (Au@TiO2) for the efficient PEC biosensing of glucose. The Schottky barrier derived from the Au@TiO2 heterostructure efficiently separates the charge carriers at the junction interfaces, thus greatly increasing the concentration and lifetime of holes left in the valence band of TiO2. The separated holes further evidently generate the active hydroxyl radicals, which can specifically recognize and oxidize glucose. As a result, Au@TiO2 exhibits excellent photoelectric activity and selectivity, far superior to TiO2 without decorated Au nanoparticles. In addition, such asymmetric Au@TiO2 system has been proved to feature the intrinsic flexibility nature, since its PEC biosensing performance is almost unaffected under indirect light irradiation and serious tensile strain.

Decoration of Cube‐Like Ceria Crystals by Well‐Dispersed Au Nanoparticles: Surface Influence

AbstractIn this paper, the run of the decorating process of the active support, like CeO2, by the gold nanoparticles via deposition‐precipitation method has been studied. Two types of the Au/CeO2 systems with different mean particle size (but the same morphology) of the support have been investigated. It was noted that the decoration process proceeds easily only for large crystals with average size about 67 nm. Three hypotheses were tested in order to explain unsuccessful initial Au nanoparticles decoration of the cube‐like CeO2 crystals with average size about 14 nm as a support. The tests have shown that the ratio of the molar content of the chloroauric acid to the total surface area of the support (MAu/SCeO2) has a significant impact on the decorating process of CeO2 by nano‐Au. If the above ratio is too small, the thin layer of gold instead of the Au nanoparticles is formed on the support surface. In this paper, the calculations of the real surface area (from TEM/HRTEM data) were used to adjust the optimum the MAu/SCeO2 to obtain the Au/CeO2 system with the desired properties.

Enhanced Optical and Photocatalytic Properties of Au/Ag Nanoparticle-decorated ZnO Films

Plasmonic Au- and Ag-decorated ZnO films on a glass substrate were obtained by a plasma electrolyte oxidation method with high-voltage discharge, followed by the decoration of Au nanoparticles (NPs) on their surface. With the increasing concentration of the Ag precursor, the thickness of the Ag-ZnO films decreased and the width of the bandgap increased, causing an enhancement in the near band-edge ultraviolet (UV) emission. With the decoration of the Au NPs, the photoluminescence of the Ag-ZnO films exhibited quenching of the band-edge UV emission, accompanied by the suppression of the visible emission in the photoluminescence spectra, and a significant enhancement in the photocatalytic efficiency for the photodegradation of Rhodamine B under solar simulator irradiation.

Enhanced self-powered UV sensing performance of ZnO/Au/Al2O3 photodetector with the decoration of Au nanoparticles

In this work, self-powered ZnO/Au/Al2O3 photodetectors (PDs) with enhanced UV sensing performance were successfully fabricated. The effects of Au nanoparticles on optical and photodetect ability of ZnO/Au/Al2O3 nanorods were studied in detail. The results showed that the ZnO nanorods exhibited enhanced UV emission and reduced visible emission after the Au decoration. The best UV sensing performance was achieved from the ZnO/Au/Al2O3-based PD, of which the size of the Au nanoparticles and the thickness of the Al2O3 were 3–4 nm and 6 nm, respectively. The on/off ratio, UV sensing responsibility, and detectivity were 805, 6.8 mA/W, and 1.7 × 109 Jones, respectively, which were 8.5, 8.6, and 8.5 times to that of ZnO/Al2O3-based PD without Au nanoparticle decoration (@ light intensity of 0.6 mW/cm2; 0 bias). It was believed that the surface plasmonic effect, carrier confinement, and the surface passivation co-contributed to the enhanced UV photodetect ability. The work may provide an insight into the design and synthesis of 1D nano-material-based self-powered UV detectors for next-generation low cost, large area, and energy-efficient optoelectronic devices.

Efficient Ce–Co composite oxide decorated Au nanoparticles for catalytic oxidation of CO in the simulated atmosphere of a CO2 laser

Gold nanoparticles have a high activity for CO oxidation, making them suitable to be used in a CO2 laser which maintains its efficiency and stability via the recombination of CO and O2 produced by the CO2 decomposition. However, the high concentration of CO2 in the working environment greatly reduces the activity of the catalyst and makes the already unstable gold nanoparticles even more so. A novel Au/Ce-Co-Ox/Al2O3 gold catalyst, prepared by a deposition precipitation method in this study, displays high activity and good stability for CO oxidation in a simulated atmosphere of a CO2 laser with the feed gases containing a high concentration of CO2 up to 60 vol% but a low concentration of O2 for the stoichiometric reaction with CO. An excellent performance for CO oxidation under CO2-rich conditions could be achieved by decorating the surface of the Al2O3 support with Ce–Co composite oxides. The strong interaction between gold and the composite support, accompanied by the increase of labile lattice oxygen species and the decrease of surface basicity, led to a high CO oxidation rate and resistance towards CO2 poisoning.

Boosting field emission performance of TiO2 nanoarrays with designed architectures

As the “heart” of vacuum electronic device, the low turn-on field (Eto) of field emitters plays a crucial role for their practical application. In current work, we reported the designed fabrication of TiO2 field emitters with boosted field emission (FE) behaviors, by growing sharp branches and decorating Au nanoparticles (Au NPs) around the surfaces of preformed TiO2 nanorod arrays. It was found that the obtained nanoarrays with designed architectures could make a balance between the increased emission sites and limited field screening effect. The field enhancement factor (β) of as-fabricated TiO2 emitters was ~2 times to that the bare emitters. Moreover, their turn-on field and current density could be of 1.61 V/μm and ~4.95 mA/cm2, respectively, both of which were state-of-the-art ones among the TiO2 field emitters ever reported.

Fabrication of Au-CuO hybrid plasmonic nanostructured thin films with enhanced photocatalytic activity

Thin films of Au-CuO plasmonic nanohybrids were fabricated by simple thermal evaporation. SEM and XRD investigations unveiled the impact of annealing on the structural properties and morphology of the synthesized Au-CuO hybrid thin film. Au nanoparticle decoration onto CuO thin film significantly altered the photocatalytic activity, structural and optical properties of CuO thin film. The as-prepared Au-CuO nanostructured hybrid plasmonic thin film showed improved photocatalytic efficiency for decomposition of MG and MB than pristine CuO and annealed Au-CuO thin film samples. The improved photocatalytic efficiency of Au-CuO hybrid nanostructured thin film is attributed to reduction in the recombination of charge carriers in CuO nanostructures and improvement in light utilization capability due to attachment of Au nanoparticles on nanostructured CuO thin film. Cracks in Au-CuO nanohybrid thin film facilitated enhanced adsorption of dye molecules and played an essential role in improving the photocatalytic efficiency.

CdS quantum dots/Au nanoparticles/ZnO nanowire array for self-powered photoelectrochemical detection of Escherichia coli O157:H7

In this paper, the hydrothermally grown ZnO nanowire array (NWs) was modified by Au nanoparticles (NPs) and CdS quantum dots (QDs) to construct a high-performance photoelectrochemical (PEC) electrode. The aligned ZnO NWs, which decorated Au NPs and CdS QDs have the effective light absorption range from UV to visible region. This hybrid structure provided a self-powered PEC electrode with a favorable energy-band configuration for fast charge separation and transportation. Meanwhile, the Au NPs and CdS QDs also made increase of the surface area to improve the immobilization of the analytes. After assembling aptamer as recognition element, this composite nanoarray was further developed as a self-powered PEC biosensor by synergizing above multiple enhancement factors. The PEC aptasensor exhibited a rapid response in a wide linear range of 10–107 CFU/mL with the detection limit as low as 1.125 CFU/mL to Escherichia coli O157:H7 (E. coli O157:H7). This approach would offer an alternative PEC transduction for fast environment monitoring and clinical diagnosis related to pathogenic bacteria.

Bulk/Surface Defects Engineered TiO2 Nanotube Photonic Crystals Coupled with Plasmonic Gold Nanoparticles for Effective in Vivo Near-Infrared Light Photoelectrochemical Detection.

Photoelectrochemical (PEC) techniques are of fundamental and practical importance, and they have been widely used for solar energy conversion and experimental protection. Besides these important applications, an emerging and fast developing PEC application of PEC bioanalysis is receiving more attention from both academic and clinic communities. However, the typical PEC biosensing is still limited under illumination of ultraviolet and visible (UV/vis) light, which hampers its in vivo detection in deep tissues. Expanding the optical absorption wavelength of photoelectrodes from the UV/vis light region into the near-infrared (NIR) light region is highly desirable due to its deep tissue penetrability and minimal invasiveness for organisms, but the exploration of a facile strategy to implement efficient NIR absorption with biocompatible materials is still a big challenge. Herein, under the guidance of theorical calculations, we propose a strategy through modulation of bulk/surface defects and decoration of Au nanoparticles on TiO2 nanotube photonic crystals to implement efficient NIR response and thus successfully realize sensitive and selective PEC detection of antibiotics in real bio- and experimental-samples under NIR illumination. In addition, we first implement the in vivo PEC detection under illumination of NIR light. We have faith that this new NIR photoelectric responsive strategy will provide a broad platform for detection of life-related biomolecules in deep tissues or even in vivo for real-time measurement and shed light on the intrinsic connections between biomarkers and clinical diseases.

Plasmon-enhanced photoluminescence from SnO2 nanostructures decorated with Au nanoparticles

We report significantly enhanced photoluminescence from hybrid nanostructured Au/SnO2 thin films due to surface plasmons excited in Au nanoparticles decorating SnO2 nanostructured thin film. Nanostructured thin films with Au nanoparticles decorated SnO2 nanostructures were prepared by sputter deposition of ultrathin Au films following thermal evaporation of SnO2 film. The effects of deposition of ultrathin film of Au nanoparticles on the morphology, structure and optical response of nanostructured SnO2 film were investigated. Nanocrystalline SnO2, Au, Sn and Au-Sn alloy were revealed by XRD analysis. PL studies revealed that Au nanoparticle decoration of nanostructured SnO2 film led to highly enhanced UV emission. The mechanism of strong enhancement of PL from nanostructured SnO2 film is tentatively proposed. The coupling of excitonic emission from SnO2 nanostructures and excited surface plasmons in Au nanoparticles led to the observed strong PL enhancement. The hybrid nanostructured Au/SnO2 thin films with strong UV emission are promising for designing efficient optical and photoelectrical devices.

Ensemble Effect in Bimetallic Electrocatalysts for CO2 Reduction.

Alloying is an important strategy for the design of catalytic materials beyond pure metals. The conventional alloy catalysts however lack precise control over the local atomic structures of active sites. Here we report on an investigation of the active-site ensemble effect in bimetallic Pd-Au electrocatalysts for CO2 reduction. A series of Pd@Au electrocatalysts are synthesized by decorating Au nanoparticles with Pd of controlled doses, giving rise to bimetallic surfaces containing Pd ensembles of various sizes. Their catalytic activity for electroreduction of CO2 to CO exhibits a nonlinear behavior in dependence of the Pd content, which is attributed to the variation of Pd ensemble size and the corresponding tuning of adsorption properties. Density functional theory calculations reveal that the Pd@Au electrocatalysts with atomically dispersed Pd sites possess lower energy barriers for activation of CO2 than pure Au and are also less poisoned by strongly binding *CO intermediates than pure Pd, with an intermediate ensemble size of active sites, such as Pd dimers, giving rise to the balance between these two rate-limiting factors and achieving the highest activity for CO2 reduction.

Bifunctional Au–TiO2 thin films with enhanced photocatalytic activity and SERS based multiplexed detection of organic pollutant

In the current study, Au–TiO2 thin films were prepared on glass substrates through the combined approach of spin-coating thermal evaporation method. The decoration of Au nanoparticles on to TiO2 surface has been achieved by the thermal annealing process under Ar atmosphere. Au–TiO2 thin films with improved optical absorption and effective bandgap narrowing exhibits outstanding photodegradation activity and ultra-sensitivity towards surface-enhanced Raman spectroscopy (SERS) based detection of the organic molecules. The existence of Au nanoparticles on TiO2 nanostructures efficiently controls the rate of recombination consequently Au–TiO2 thin films show significantly improved sun-light induced photodegradation efficiency for methylene blue (MB) dye. Au–TiO2 thin films decomposed 5 µM MB dye solution in 40 min under sun light exposure (850 W/cm2). Au–TiO2 thin films also exhibit efficient detection capabilities for the two organic molecules rhodamine 6G (R6G) and methylene blue (MB) with the Raman intensity enhancement factors of the order of ~ 107. The observed excellent SERS sensitivity of Au–TiO2 thin films towards the pollutant molecules are ascribed to the contribution of charge transfer mechanism among TiO2 and dye molecules. Furthermore, the fabricated Au–TiO2 thin films were also evaluated for the multiplexed detection by simultaneously detecting the two analytes (MB and R6G) from their mixture with superior sensitivity. Au–TiO2 nanohybrids thin films with these tremendous applications can be further employed for different applications like solar cell, gas sensing, energy production, and water splitting.