Decoration Of Au Nanoparticles Research Articles

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.

Boron nitride nanosheets decorated with Au, Au-Ni, Au-Cu, or Au-Co nanoparticles as efficient electrocatalysts for hydrogen evolution reaction

Following our previous reports that 1. both oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) at gold electrode are accelerated by the surface modification with boron nitride nanosheet (BNNS), insulator, and 2. the ORR overpotential is further reduced by Au nanoparticles (Au NPs) decoration of BNNS, here we investigated the effect of Au, Au-Ni, Au-Cu, and Au-Co NPs decoration on HER at BNNS modified Au. HER rate was enhanced in all the cases. The lowest overpotential, only 30 mV more than that at a Pt electrode at −15 mA/cm2, was observed at Au electrode modified by BNNS decorated with Au-Ni NP. To confirm the importance of BNNS, the HER rates at Au electrode modified by rGO decorated with Au and Au-Ni NPs were also examined. Although the reduction of overpotential was observed even using rGO as a support, the effect was less than that using BNNS as a support by ca. 80 mV, showing the importance of BNNS for enhanced HER activity.

Plasmonic enhanced Au decorated TiO2 nanotube arrays as a visible light active catalyst towards photocatalytic CO2 conversion to CH4

To boost up the plasmonic metal-nanotube junction effect under visible light irradiation, a simplistic electrochemical deposition synthesis method has been employed to decorate the Au nanoparticles in the nanotubes (TNTs). A photocatalytic experiment for the conversion of CO2 has been conducted to justify the visible light effectivity of the Au-TNTs. The decoration of Au nanoparticles into the TNTs was explored by the morphological analysis which revealed well-arranged, well-ordered and stable Au modified nanotubes. The prepared Au-TNTs light harvesting properties investigated through UV–vis absorption spectra which reveals its visible light absorption capability owing to its LSPR behaviour. Improved charge carrier separation of plasmonic Au loaded TNTs was explored through PL analysis. Hence, the photocatalytic activity of TNTs and Au-TNTs obtained through CO2 conversion to CH4 and the total amount of CH4 production are 8.26% and 14.67%, respectively. Therefore, this study provides a simple path to modify the TNTs with Au with a trouble-free and controllable deposition method in order to increase visible light active catalytic properties. Moreover, the one-dimensional nanotube arrays semiconductor with the integration of plasmonic metal was attained a further visible light enhanced activity towards photocatalytic CO2 conversion.

Au decorated In2O3 hollow nanospheres: A novel sensing material toward amine

This study demonstrates a hollow structure constructed by Au nanoparticles decorated on the surface of the In2O3 hollow nanospheres. This structure is prepared via calcination of solid organic precursors and in-situ reduction of Au nanoparticles on the metal oxide surface. The In2O3 hollow nanospheres are with the diameter of ˜200 nm and the shell thickness of 30 nm, while the Au nanoparticles on the surface of In2O3 hollow spheres are with the size of ˜10 nm. XPS indicates that the Au modification can increase the deficient oxygen vacancy ratio, and the presence of the positive Au ions (Auδ+) in the composites helps to trap the electrons and further improve the sensing performance. The gas sensing tests indicate that the Au decorated In2O3 hollow nanocomposites show excellent sensitivity (26.3 of 100 ppm) and selectivity toward 1-butylamine at the optimized temperature of 340 °C. The decoration of Au nanoparticles can lower the optimized working temperature and shorten the response/recovery times. The enhanced sensing mechanism can be attributed to electronic and chemical sensitization. The decoration of Au nanoparticles on the In2O3 surface can cause the Schottky barrier at the interface. The existence of positive Au ions can boost the barrier by trapping extra electrons. These results tender the promising hollow structure for sensing organic amine vapor in field-based use.

Self-reduction combined with photo-deposition decorating Au nanoparticles on urchin-like WO2.72 for enhancement of trimethylamine-sensing performance

Hierarchical urchin-like WO2.72 microspheres decorated by uniform Au nanoparticles were synthesized via a two-step deposition process. The two-step deposition process, including weak reduction deposition and photo-deposition, ensures uniform size and well-dispersed Au nanoparticles. The gas-sensing properties of WO2.72 and Au/WO2.72 for trimethylamine (TMA) were investigated. The results show that Au/WO2.72 has more outstanding gas-sensing performances, especially 3 wt% Au-loaded WO2.72 (A3/WO2.72). A3/WO2.72 not only has superior selectivity and response for TMA gas but also exhibits fast response and recovery time. The response of A3/WO2.72–100 ppm of TMA at 260 °C can attain 87.3, which is approximately 6.1 times of pure WO2.72. Besides, the good long-term effectiveness of A3/WO2.72-based sensor also can be observed. The mechanism of enhanced gas-sensing performances derived from the synergy of morphology, composition, and the sensitization effect of Au nanoparticles is proposed, which will facilitate the design and development of sensors decorated by noble metal.

Enhanced dielectric permittivity and microwave absorbing properties of Au-decorated SiC nanowires

We report that SiC nanowires with enhanced dielectric and electromagnetic wave absorbing properties were prepared by the surface decoration of Au nanoparticles. The Au nanoparticles with a size of 5–10 nm were decorated via the simple and fast magnetic sputtering, which improved the conductance loss and polarization loss of SiC nanowires. By optimizing the sputtering time, the dielectric and electromagnetic wave absorbing properties were significantly enhanced. Au-decorated SiC nanowires show a minimum reflection loss of −50.6 dB and an effective absorption (RL<−10 dB) bandwidth of 7.2 GHz at the sputtering time of 30 s and filling ratio of 10 wt%.

Surface plasmon assisted laser ablation of stainless steel

Colloidal Au nanoparticles (NPs) were decorated on stainless steel for surface plasmon enhanced laser ablation. A comparative study of the laser ablation efficiency was carried out on stainless steel samples with and without the Au NPs decoration at a variable pulsed laser fluence and laser pulse number. Higher ablation efficiency was clearly demonstrated in the former as illustrated from the larger diameter, maximum depth and the cross-sectional area of the crater generated by the laser ablation under the same conditions. Additionally, both the maximum depth and efficiency enhancement were found to depend on the laser fluence and pulse number. The maximum enhanced ablation efficiency of 36% based on the cross-sectional area of the crater was obtained at 1 pulse number of laser fluence 1.53 J cm−2. The efficiency enhancement of laser ablation is attributed to the highly enhanced surface plasmon field at the interface between Au NPs and stainless steel.

Three-dimensional plasmonic photoanode of Co3O4 nanosheets coated onto TiO2 nanorod arrays for visible-light-driven water splitting

In this work, we report for the first time a plasmonic photoanode by decorating Au nanoparticles (NPs) onto two-dimensional (2D) Co3O4 nanosheets (NSs)/one-dimensional (1D) TiO2 nanorod arrays (NRAs) (Au/Co3O4/TiO2-NRAs) for enhanced visible-light photoelectrochemical (PEC) water splitting. In this plasmonic photoanode, TiO2 NRAs act as an electron acceptor, plasmonic Au NPs and hierarchical Co3O4 NSs serve as visible-light harvesters. Light absorption shows that Au/Co3O4/TiO2-NRAs heterojunction architectures exhibit greatly improved ability to harvest visible light due to the surface plasmon resonance (SPR) absorption of Au NPs and visible light harvesting ability of Co3O4 NSs. Spectroscopic measurements demonstrate that a type II band alignment is formed between Co3O4 and TiO2. Benefiting from the SPR effect, type II band alignment and novel hierarchical architecture, plasmonic Au/Co3O4/TiO2-NRAs photoanode shows remarkably enhanced visible-light PEC water splitting activity compared with Co3O4/TiO2-NRAs and pristine TiO2-NRAs photoanodes. Photocurrent density achieved by plasmonic photoanode is 37 and 1.2 times higher than those of TiO2-NRAs and Co3O4/TiO2-NRAs photoanodes, respectively. This work provides a promising strategy to highly enhance visible-light PEC water splitting activity of wide band-gap semiconductor-based photoelectrode materials.

Enhanced photocurrent performance of partially decorated Au nanoparticles on ZnO nanorods based UV photodetector

The surface modification is essentially required to develop a variety of hybrid zinc oxide (ZnO) nanostructures for fabricating optoelectronic devices. A facile solution method was proposed to prepare the relatively low and high aspect ratio ZnO nanorods (NRs) and subsequently decorated with gold nanoparticles (Au NPs) partially on the surface of ZnO NRs. The Au-ZnO NRs exhibited an enhanced band-edge emission due to the surface plasmon resonance quenching of deep level defect emission, as compared to bare ZnO NRs. The UV photodetector with the relatively low aspect ratio Au-ZnO NRs showed a lower photocurrent in dark. However, after UV light illumination, a remarkable enhancement in photocurrent owing to the Au modification was observed, which leads a strong absorption and an improved interfacial charge separation process. Hence, the relatively low aspect ratio Au-ZnO NRs provides a channel for fabricating a high performance UV photodetector, in the near future.

Enhanced properties of hierarchically-nanostructured undoped acceptor-rich ZnO single-crystal microtube irradiated by UV laser

Here a variety of hierarchic nanostructures on the undoped acceptor-rich ZnO (A-ZnO) single-crystal microtube are fabricated by KrF excimer laser irradiation. The effects of process parameters, i.e. laser fluence and number of pulse (NOP), on nanostructure morphology of the A-ZnO microtube are investigated, by which the controllable hierarchic nanostructures are achieved. The mechanism of the nanostructure formation is attributed to self-assembled growth by decomposition and re-nucleation owing to rapid heating and cooling down during laser irradiation near Zn-vacancy-related point defects. The Raman and photoluminescence spectra confirm that the nanostructures possess massive surface defects, e.g. oxygen vacancies (VO) and zinc interstitials (Zni). The electrical resistivity of the nanostructured A-ZnO microtube is down to ∼10−3 Ω cm, about one order of magnitude lower than that of the as-grown A-ZnO microtube. The great ratio of surface area to volume of the nanostructures realizes the improved UV detection and photodegradation performance. The optimal photoresponsivity can be up to 27.08 A/W using the process parameters of 200 mJ/cm2 and 100 pulses. The catalytic degradation rate of the A-ZnO microtube irradiated by 150 mJ/cm2 and 200 pulses with 6-nm Au nanoparticles decoration for methylene blue solution is ∼3.4 times higher than the commercial nanoparticles. The present work paves a new way to design and fabricate a variety of hierarchic nanostructures on undoped A-ZnO microtube for enhanced electrical and photocatalytic performance.

Reduced Graphene Oxide Decorated Au Nanoparticles as an Efficient Electrode for the Determination of Hydroquinone

Reduced Graphene Oxide Decorated Au Nanoparticles as an Efficient Electrode for the Determination of Hydroquinone

Reduced Graphene Oxide Decorated Au Nanoparticles as an Efficient Electrode for the Determination of Hydroquinone

Reduced Graphene Oxide Decorated Au Nanoparticles as an Efficient Electrode for the Determination of Hydroquinone

Photoelectrocatalytic Oxidation of Methane into Methanol over ZnO Nanowire Arrays Decorated with Plasmonic Au Nanoparticles

The pursuit for efficient conversion of methane under ambient conditions remains a challenge. Here, we reported photoelectrocatalytic oxidation of methane into methanol over ZnO nanowire arrays (NWAs) decorated with Au nanoparticles (NPs) under simulated sunlight illumination with ambient conditions. The photoelectrochemical (PEC) performances of the ZnO and ZnO/Au photoanodes were investigated to analyze the behavior and intensity of the reaction process of methane oxidation. The Faradaic efficiency of ZnO/Au was calculated to be 32.11%, nearly three times of 11.69% for ZnO. The above results show that ZnO NWAs exhibited exceptional activity as photoanode for photoelelctrocatalytic methane oxidation, and the decoration of Au NPs further enhanced the photo-activity via the surface plasmon resonance expanding its absorption spectra to visible region. On the other hand, as a co-catalyst, Au can promote the oxidation of methane by providing the trapping sites and active sites to facilitate the separation and also suppress the recombination of photogenerated charges and the existence of Au can boost the reaction by lowering the activation energy. This research demonstrates that ZnO NWAs decorated with Au NPs hold great promise for photoelectrocatalytic methane oxidation.

Enhanced photocatalytic activity of β-Ga2O3 nanowires by Au nanoparticles decoration

Combining plasmonic noble metals with semiconductor materials has been considered to be an effective way to improve catalyst performance. In the present paper, Au nanoparticles (NPs) were decorated onto CVD-grown β-Ga2O3 nanowires (NWs) through a chemical reduction method. Different quantity of HAuCl4 solution was used to control the size and density of Au NPs. The photocatalytic activity of the Au–Ga2O3 NWs is evaluated by degrading rhodamine B (Rh B) under UV and visible light irradiation. It is found that the size and density of the Au NPs had a great influence on the photocatalytic efficiency of β-Ga2O3 NWs. And Ga2O3 NWs with Au NPs of ~ 5.7 nm size and ~ 420/μm2 density shows the best catalytic efficiency. Moreover, Au NPs attachment on the Ga2O3 could extend its photocatalytic activity towards the visible light irradiation, which is significant to efficient utilization more solar light. A jointly effect of both the interfacial Schottky potential field between Au NPs and β-Ga2O3 NWs and local surface plasma resonance excitation is proposed to contribute the enhancement effects.

Electrical Conductivity, Selective Adhesion, and Biocompatibility in Bacteria-Inspired Peptide-Metal Self-Supporting Nanocomposites.

Bacterial type IV pili (T4P) are polymeric protein nanofibers that have diverse biological roles. Their unique physicochemical properties mark them as a candidate biomaterial for various applications, yet difficulties in producing native T4P hinder their utilization. Recent effort to mimic the T4P of the metal-reducing Geobacter sulfurreducens bacterium led to the design of synthetic peptide building blocks, which self-assemble into T4P-like nanofibers. Here, it is reported that the T4P-like peptide nanofibers efficiently bind metal oxide particles and reduce Au ions analogously to their native counterparts, and thus give rise to versatile and multifunctional peptide-metal nanocomposites. Focusing on the interaction with Au ions, a combination of experimental and computational methods provides mechanistic insight into the formation of an exceptionally dense Au nanoparticle (AuNP) decoration of the nanofibers. Characterization of the thus-formed peptide-AuNPs nanocomposite reveals enhanced thermal stability, electrical conductivity from the single-fiber level up, and substrate-selective adhesion. Exploring its potential applications, it is demonstrated that the peptide-AuNPs nanocomposite can act as a reusable catalytic coating or form self-supporting immersible films of desired shapes. The films scaffold the assembly of cardiac cells into synchronized patches, and present static charge detection capabilities at the macroscale. The study presents a novel T4P-inspired biometallic material.

Plasmonic Au Nanopraticles Modified Nanopyramid-Arrays BiVO4 with Enhanced Photoelectrochemical Activity

Gold nanoparticles (∼24 nm) were successfully loaded on the surface of BiVO4 nanopyramidal arrays by simple electrostatic self-assembly approach. By decorating gold nanoparticles on the surface of BiVO4 films, The photocurrent of as-prepared Au/BiVO4 photoanode increased from around 0.42 mA/cm2 for pristine BiVO4 to nearly 0.93 mA/cm2 at 1.23 vs. RHE under AM 1.5 illumination. The improved photoresponse of the Au/BiVO4 was found as a result from higher carrier generation and enhanced charge separation with the decoration of Au nanoparticles. The successful deposition provide a new route for desigining plasmonic photoanode and offers better understanding the photochemistry of noble metal-complex oxide heterostructures for photoelectrichemical water splitting.

Synthesis of Au-decorated three-phase-mixed TiO2/phosphate modified active carbon nanocomposites as easily-recycled efficient photocatalysts for degrading high-concentration 2,4-DCP.

It is of great significance to fabricate easily-recycled TiO2 photocatalysts with high activity. Herein, dominant-anatase three-phase (anatase/rutile/brookite)-mixed nanosized TiO2 with high photocatalytic activity for degrading a high-concentration of 2,4-DCP has been synthesized via a hydrothermal process with HCl as a phase-directing agent, and interestingly the apparent photoactivity could be greatly improved by decorating Au nanoparticles and then coupling phosphate-treated active carbon. The amount-optimized nanocomposite displays ∼12-fold enhancement in degradation rate constant (k) compared to anatase TiO2. Based on the steady-state surface photovoltage spectra, fluorescence spectra related to the produced ·OH amount, temperature-programmed desorption and O2 electrochemical reduction curves, it is confirmed that the exceptional photoactivity is mainly attributed to the greatly-enhanced charge separation from the phase-mixed composition, and from the decorated Au as electron acceptors and its promotion effects on O2 activation. Moreover, the use of phosphate-modified AC as a support is also positive for efficient photocatalytic reactions by accepting electrons and concentrating the pollutants, with recyclable features. This work provides a feasible strategy to fabricate TiO2-based nano-photocatalysts for degrading high-concentration pollutants to remediate the environment.

Intrinsic Au-decoration on anodic TiO2 nanotubes grown from metastable Ti–Au sputtered alloys—High density co-catalyst decoration enhances the photocatalytic H2 evolution

Recent work demonstrated that intrinsic Au nanoparticle decoration of TiO2 nanotube arrays (NTs) can be achieved by electrochemical anodization of Ti–Au alloy substrates. However, for a Ti–Au cast alloy produced by melt-alloying, the Au concentration cannot exceed the solubility limit of Au in Ti of 0.2at.% – this sets constraints on the intrinsic Au nanoparticle loading on anodic TiO2 NTs. Here we explore “metastable” Ti–Au metal substrates that are produced by Ti and Au cosputtering and we establish Au concentrations that far exceed the solubility limit in cast Ti–Au alloys. We show the use of these “metastable” Ti–Au sputtered layers for the anodic formation of TiO2 NTs with a much higher density of Au nanoparticle loading than using classic alloys. Under optimized conditions (Au nanoparticle density) photocatalytic H2 production from such Au@TiO2 platforms provides a 15 times higher photocatalytic H2 evolution rate than the best rates achieved with conventional alloys.

Au decorated hollow ZnO@ZnS heterostructure for enhanced photocatalytic hydrogen evolution: The insight into the roles of hollow channel and Au nanoparticles

A new type of Au nanoparticles (NPs) decorated hollow flower-like ZnO@ZnS (HZOS) heterostructure (HS) is elaborately designed as efficient photocatalyst for water splitting application. The optimal Au decorated HZOS exhibits a high hydrogen generation rate of 569.81 μmol/h (10 mg of catalyst), which is 345, 374 and 11 times higher than that of pristine ZnO (1.65 μmol/h), ZnS (1.52 μmol/h) and ZnO@ZnS (51.7 μmol/h), respectively. Furthermore, its apparent quantum efficiency reaches to 25.47% at the wavelength of 365 nm. The significantly enhanced H2 evolution can be attributed to the synergistic effects from the hollow channel structure and the deposited Au NPs. The hollow channel creates a new migration pathway where charge carriers can transfer towards the hollow channel in addition to the outer surface of the photocatalyst, thus significantly reducing the migration distance of charge carriers, suppressing the recombination of photogenerated electrons and holes, and reducing their transfer resistance. The decoration of Au NPs at the interface between ZnO and ZnS not only facilitates the directional migration of charge carriers because of the formation of Schottky barrier, but also works as electron shuttles to form a Z-scheme transfer process, effectively promoting the separation and migration of charge carriers.

Ultrasensitive label- and amplification-free photoelectric protocols based on sandwiched layer-by-layer plasmonic nanocomposite films for the detection of alpha-fetoprotein

A label- and amplification-free photoelectric immunosensor based on well-defined layer-by-layer sandwich-structured AuNP/TNW/AuNP composite is proposed for direct and ultrasensitive detection of α-fetoprotein (AFP). The AuNP/TNW/AuNP composite is produced by assembling an Au nanoparticle underlayer and anatase TiO2 nanowires (TNW) onto the FTO substrate, followed by decorating Au nanoparticles onto the TNW surface, through a simple sputtering and hydrothermal process. The resulting AuNP/TNW/AuNP electrode exhibits a 14-fold and 2-fold enhancement in photocurrent density under simulated sunlight compared with that of bare TNW and AuNP/TNW, respectively, which benefits from the SPR-induced photoabsorption increment and charge separation improvement in Au nanoparticle and interfacial charge transfer promotion at the TiO2/substrate interface in the Au underlayer. As a proof of concept, the AFP antigen can be quantitatively detected by the proposed AuNP/TNW/AuNP coupled with anti-AFP through the analysis of the photocurrent change. This novel AFP photoelectric immunosensor exhibited sensitive detection of AFP with an ultrahigh sensitivity of 0.001 ng mL−1 and good specific selectivity. Moreover, the practical determination of AFP in human serum is also investigated, demonstrating its applicability and potential attraction for clinical tests and disease diagnosis.