Deposition Of Gold Nanoparticles Research Articles

Electrochemical nitric oxide detection using gold deposited cobalt oxide nanostructures

Hydrothermal synthesis of cobalt oxide (CoO) nanostructures were grown on fluorine doped tin oxide (FTO) substrates for electrochemical NO detection. The NO sensing performance of the electrodes has been improved by depositing gold nanoparticles using photoreduction method. The electrochemical NO sensing was performed using amperometric i-t measurements. The optimized Au decorated CoO electrode demonstrated sensitivity 1.37 mM−1 μA cm−2 with wide linear range 10 μM−1.4 mM. The determination of dissolved NO in tap water and tube well water have been studied using such Au-CoO electrodes.

A flexible immunosensor based on the electrochemically rGO with Au SAM using half-antibody for collagen type I sensing

For an efficient diagnostic, modern biosensing systems require miniaturization of portable electronic devices, should be high sensitivity to achieve detection at a low level, high specificity to the targeted molecule, and ease of operation. To address some of such tasks, this research demonstrates the fabrication of an electrochemically reduced graphene oxide (ERGO) on the surface of flexible, polymer-coated (polyethylene terephthalate, PET) covered with indium tin oxide (ITO) for biosensing application. Such fabricated ERGO film exhibited high electrical properties and a considerable amount of the oxide groups followed by thiol functionalization (tERGO). High stability and the immobilization of antibody receptors were achieved by covalent interactions between deposited gold nanoparticles (AuNPs) and reduced half-IgG collagen type I antibodies. Our biosensing immunosensor revealed a remarkable response to the complementary detected analyte collagen type I in the range of 10 pg/mL to 100 pg/mL. The performed immunosensor had a relatively low detection limit (LOD = 6 pg/mL) in comparison to the currently applied systems that are used for the detection of collagen. Therefore, it is presented an innovative attempt involving ideas for future pliable collagen immunosensors with high sensitivity and selectivity properties, which due to user-friendly handling and low cost of its production, and enabling for future application in the wearable sensors.

Atomic Layer Deposition of Gold Nanoparticles with Controlled Size and Distribution on Titania Support

AbstractNano‐sized gold particles have shown unique merits in the field of catalysis, sensing and imaging, whereas their controllable synthesis with sub‐nanometer size and narrow distribution on a support still remains a challenge. Herein, we developed a facile and controllable process of atomic layer deposition (ALD) using dimethyl(acetylacetonate)gold (Me2Au(acac)) and ozone as the precursor reactants to directly synthesize ultrafine Au nanoparticles on titania support. The size of Au nanoparticles could be precisely controlled via the modulation of depositing temperature and the counter reactant. Additionally, the dispersion of Au nanoparticles on the support is decreased by pre‐calcining TiO2 in air, which is due to the decreased surface hydroxyls concentration on support, leading to less adsorption sites of gold precursor. Moreover, we demonstrated that Au nanoparticles prepared by this method on TiO2 could function as an effective co‐catalyst for photocatalytic hydrogen evolution reaction.

Facile Gold-Nanoparticle Boosted Graphene Sensor Fabrication Enhanced Biochemical Signal Detection.

Graphene has been considered as an excellent biochemical sensors’ substrate material because of its excellent physical and chemical properties. Most of these sensors have employed enzymes, antibodies, antigens, and other biomolecules with corresponding recognition ability as recognition elements, to convert chemical signals into electrical signals. However, oxidoreductase enzymes that grow on graphene surfaces are affected significantly by the environment and are easily inactivated, which hinders the further improvement of detection sensitivity and robusticity. A gold-boosted graphene sensor was fabricated by the in situ electrochemical deposition of inorganic gold nanoparticles on vertical graphene nanosheets. This approach solves the instability of biological enzymes and improves the detection performance of graphene-based sensors. The uric acid sensitivity of the gold-boosted electrode was 6230 µA mM−1 cm−2, which is 6 times higher than the original graphene electrode. A 7 h GNSs/CC electrode showed an impressive detection performance for ascorbic acid, dopamine, and uric acid, simultaneously. Moreover, it exhibited a reliable detection performance in human serum in terms of uric acid. The possible reason could be that the vertical aliened graphene nanosheet acts as a reaction active spot. This 3D graphene-nanosheet-based doping approach can be applied to a wide variety of inorganic catalytic materials to enhance their performance and improve their durability in aspects such as single-atom catalysis and integration of multiple catalytic properties.

Effect of poly(N-vinylpyrrolidone) ligand on catalytic activities of Au nanoparticles supported on Nb2O5 for CO oxidation and furfural oxidation

The development of green preparation methods for acidic metal oxide supported gold catalysts is of great importance for the extensive use of gold catalysts as well as for a comprehensive understanding of gold catalysts. In this study, poly(N-vinylpyrrolidone) (PVP) was used as the stabilizer of gold colloids to deposit gold nanoparticles on an acidic metal oxide, Nb2O5. The effects of the PVP ligand on the preparation of Au(-PVP)/Nb2O5 and on the catalytic activities for gas-phase CO oxidation and liquid-phase furfural oxidation were investigated. As removing more ligand PVP of Au(-PVP)/Nb2O5, the catalytic activities for both CO oxidation and furfural oxidation increased. The optimal calcination temperature for Au(-PVP)/Nb2O5 was determined to be 400 °C, and calcination at that temperature gave gold nanoparticles with an average size of 6.4 ± 2.5 nm and of the support of Nb2O5 remained as the original crystalline structure. The temperature for 50% CO conversion (T50%) of Au(-PVP)/Nb2O5 (calcined at 400 °C) was 81 °C. In addition, Au(-PVP)/Nb2O5 (calcined at 400 °C) presented 43% furfural conversion with 100% selectivity of furoic acid under a mild conditions (0.5 MPa O2, 40 °C) in the batch system. These results suggested that Au(-PVP)/Nb2O5 is a good catalyst for both gas-phase and liquid-phase reactions.

Detection of Amyloid-β(1-42) Aggregation With a Nanostructured Electrochemical Sandwich Immunoassay Biosensor.

Amyloid-β(1–42) [Aβ(1–42)] oligomer accumulations are associated with physiologic alterations in the brains of individuals with Alzheimer’s disease. In this study, we demonstrate that a nanostructured gold electrode with deposited gold nanoparticles, induced via electrochemical impedance spectroscopy (EIS), may be used as an Aβ(1–42) conformation biosensor for the detection of Alzheimer’s disease. Monoclonal antibodies (12F4) were immobilized on self-assembled monolayers of the electrochemical sandwich immunoassay biosensor to capture Aβ(1–42) monomers and oligomers. Western blot and fluorescence microscopy analyses were performed to confirm the presence of Aβ(1–42) monomers and oligomers. EIS analysis with an equivalent circuit model was used to determine the concentrations of different Aβ(1–42) conformations in this study. We identified conformations of Aβ(1–42) monomers and Aβ(1–42) oligomers using probe antibodies (12F4) by employing EIS. indicates the sum resistance of impedance measured during Aβ(1–42) immobilization. refers to the concentration of probe antibody (12F4) binding with Aβ(1–42). The concentration of Aβ(1–42) oligomer was defined as the percentage of Aβ(1–42) aggregation . The experimental results show that the biosensor has high selectivity to differentiate Aβ(1–40) and Aβ(1–42) monomers and Aβ(1–42) oligomers and that it can detect Aβ(1–42) oligomer accurately. The linear detection range for Aβ(1–42) oligomers was between 10 pg/ml and 100 ng/ml. The limit of detection was estimated to be 113 fg/ml.

Surface-Enhanced Raman Scattering from Dye Molecules in Silicon Nanowire Structures Decorated by Gold Nanoparticles.

Silicon nanowires (SiNWs) prepared by metal-assisted chemical etching of crystalline silicon wafers followed by deposition of plasmonic gold (Au) nanoparticles (NPs) were explored as templates for surface-enhanced Raman scattering (SERS) from probe molecules of Methylene blue and Rhodamine B. The filling factor by pores (porosity) of SiNW arrays was found to control the SERS efficiency, and the maximal enhancement was observed for the samples with porosity of 55%, which corresponded to dense arrays of SiNWs. The obtained results are discussed in terms of the electromagnetic enhancement of SERS related to the localized surface plasmon resonances in Au-NPs on SiNW’s surfaces accompanied with light scattering in the SiNW arrays. The observed SERS effect combined with the high stability of Au-NPs, scalability, and relatively simple preparation method are promising for the application of SiNW:Au-NP hybrid nanostructures as templates in molecular sensorics.

Aerosol Dry Printing for SERS and Photoluminescence-Active Gold Nanostructures Preparation for Detection of Traces in Dye Mixtures.

We proposed a novel method of nanostructure preparation for observation of surface-enhanced Raman spectroscopy (SERS) and metal-enhanced fluorescence (MEF) based on the deposition of gold nanoparticles (GNPs) above the thin dye film by dry aerosol printing. We detected various enhanced SERS and MEF signals of films of malachite green (MG) and rhodamine B (RhB) mixtures, depending on the surface packing density of Au NPs on the strip, and found the optimum one to achieve the 3.5 × 105 SERS enhancement. It was shown that statistical methods of chemometrics such as projection on latent structures provided the opportunity to distinguish SERS of MG from 100 ppm RhB in a mixture, whereas separation of MEF signals are feasible even for a mixture of MG and 1 ppm RhB due to two-photon excitation.

Investigating the thermal transport in gold decorated graphene by opto-thermal Raman technique

We report a systematic study on the thermal transport properties of gold nanoparticles (Au NPs) decorated single-layer graphene on a SiO2/Si substrate by the opto-thermal Raman technique. Our results, with moderate Au NPs coverage (<10%), demonstrate an enhancement in the thermal conductivity of graphene by ∼55% from its pristine value and a decrement in the interface conductance by a factor of 1.5. A detailed analysis of our results shows the importance of the photo-thermal conversion efficiency of Au NPs, plasmon–phonon coupling and lattice modifications in the graphene developed after gold nanoparticles deposition in enhancing the thermal conductivity and reducing the interface thermal conductance of the system. Our study paves way for a better understanding of the thermal management in such hybrid systems, which are envisioned as excellent candidates for optoelectronics and photonics applications.

Bifunctional monomer oligomers-based composite molecularly imprinted membranes for the electrochemical monitoring of Sudan I.

Herein, we developed a highly sensitive electrochemical sensor for the trace detection of Sudan I (SDI) dye based on composite molecularly imprinted membranes (MIMs). The pentenyl (lipoic acyl)-isoleucyl-chitosan oligosaccharide (P(L)ICO) and pentenyl-asparaginyl-chitosan oligosaccharide (PASCO) served as bifunctional monomer oligomers. After deposition of gold nanoparticles on a glassy carbon electrode (GCE) surface, a P(L)ICO layer successfully self-assembled on the surface. Subsequently, the primary MIM was polymerised on the electrode surface by using SDI as a template, PASCO as a functional monomer oligomer, and ethylene glycol dimethacrylate as a cross-linking agent. Electrochemical polymerisation was then conducted in an N,N'-methylenebisacrylamide solution. After eluting the SDI molecules from the composite MIMs, the fabricated SDI-MIM(PM)/Fn-Au/GCE demonstrated specific adsorption of SDI. Under optimal conditions, the constructed sensor exhibited a linear relationship between decreasing peak current and SDI concentration from 0.02 to 3.5 μM with a low detection limit of 4 nM (S/N = 3). As a proof of concept, SDI-MIM(PM)/Fn-Au/GCE was also applied to detect SDI in chili powder samples, with recoveries ranging from 96.8 to 106.6%.

Chemical Detection by Analyte-Induced Change in Electrophoretic Deposition of Gold Nanoparticles

The electrophoretic deposition (EPD) of citrate-stabilized Au nanoparticles (cit-Au NPs) occurs on indium tin oxide (ITO)-coated glass electrodes upon electrochemical oxidation of hydroquinone (HQ) due to the release of hydronium ions. Anodic stripping voltammetry (ASV) for Au oxidation allows the determination of the amount of Au NP deposition under a specific EPD potential and time. The binding of Cr3+ to the cit-Au NPs inhibits the EPD by inducing aggregation and/or reducing the negative charge, which could lower the effective NP concentration of the cit-Au NPs and/or lower the electrophoretic mobility. This lowers the Au oxidation charge in the ASV, which acts as an indirect signal for Cr3+. The binding of melamine to cit-Au NPs similarly leads to aggregation and/or lowers the negative charge, also resulting in reduction of the ASV Au oxidation peak. The decrease in Au oxidation charge measured by ASV increases linearly with increasing Cr3+ and melamine concentration. The limit of detection (LOD) for Cr3+ is 21.1 ppb and 16.0 ppb for 15.1 and 4.1 nm diameter cit-Au NPs, respectively. Improving the sensing conditions allows for as low as 1 ppb detection of Cr3+. The LOD for melamine is 45.7 ppb for 4.1 nm Au NPs.

The Effect of Laser Heating and Overcasting Deposition on the Efficiency of Plasmonic Solar Cell with Noble Metallic Nanostructures

Surface plasmon resonance could increase the efficiency of solar cells , when light is trapped by the noble metallic nanoparticles arrangement at and into the silicon solar cell (SSC) surface. Pure noble metal (silver and gold) nanoparticles (NPs) have been synthesized as colloids in de-ionized water (DW) by pulsed laser ablation (PLA) process at optimum laser fluence. Silicon solar cell with low efficiency was converted to plasmonic silicon solar cell by overcasting deposition method of silver nanoparticles on the front side of the SSC. The performance of plasmonic solar cell (PSC) was increased due to light trapping. Two mechanisms were involved : inserting silver nanoparticles (Ag NPs) inside the silicon layer by the heating effect of pulsed laser and depositing gold nanoparticles (Au NPs) on the surface of the SSC by overcasting method. The optical properties of silver and gold colloidal solutions were studied with UV- Visible spectrophotometer with a range from 190 nm to 1100 nm. The absorption spectra showed single absorption peak located at about the characteristic value for silver and gold nanoparticles due to the surface plasmon resonance. Atomic Force Microscope (AFM) images were studied , the ablated noble NPs by pulsed laser have an average diameter less than 100 nm. AFM images showed the morphology of SSC surface without and with nanoparticles before and after overcasting and heating by laser methods. Electrical measurements for SSC namely current – voltage ( I-V )characteristics and responsivity (Rλ) displayed higher efficiency after these procedures. The efficiency rise to(5.2%) due to the localized surface plasmons excitation of (Ag NPs) that were embedded into the silicon layer by the heating effect of pulsed laser. The deposition of AuNPs on the silicon surface of the plasmonic SC additionally increased the efficiency to (7.28%), due to light trapping by scattering from Au NPs towards the plasmonic solar cell depth .

Laser-Induced Chemical Liquid-Phase Deposition Plasmonic Gold Nanoparticles on Porous TiO2 Film with Great Photoelectrochemical Performance

This paper considers the photoelectrochemical characteristics of a composite porous TiO2 thin film with deposited plasmonic gold nanoparticles. The deposition of gold nanoparticles was carried out by the laser-induced chemical liquid-phase deposition (LCLD) method. The structural characteristics of the composite have been studied; it has been shown that the porous TiO2 film has a lattice related to the tetragonal system and is in the anatase phase. Gold nanoparticles form on the surface of a porous TiO2 film. A complex of photoelectrochemical measurements was carried out. It was shown that the deposition of plasmonic gold nanoparticles led to a significant increase in the photocurrent density by ~820%. The proposed concept is aimed at testing the method of forming a uniform layer of plasmonic gold nanoparticles on a porous TiO2 film, studying their photocatalytic properties for further scaling, and obtaining large area Au/TiO2/FTO photoelectrodes, including in the roll-to-roll process.

Surface plasmon resonance biosensor for exosome detection based on reformative tyramine signal amplification activated by molecular aptamer beacon

Human epidermal growth factor receptor 2 (HER2)-positive exosomes play an extremely important role in the diagnosis and treatment options of breast cancers. Herein, based on the reformative tyramine signal amplification (TSA) enabled by molecular aptamer beacon (MAB) conversion, a label-free surface plasmon resonance (SPR) biosensor was proposed for highly sensitive and specific detection of HER2-positive exosomes. The exosomes were captured by the HER2 aptamer region of MAB immobilized on the chip surface, which enabled the exposure of the G-quadruplex DNA (G4 DNA) that could form peroxidase-like G4-hemin. In turn, the formed G4-hemin catalyzed the deposition of plentiful tyramine-coated gold nanoparticles (AuNPs-Ty) on the exosome membrane with the help of H2O2, generating a significantly enhanced SPR signal. In the reformative TSA system, the horseradish peroxidase (HRP) as a major component was replaced with nonenzymic G4-hemin, bypassing the defects of natural enzymes. Moreover, the dual-recognition of the surface proteins and lipid membrane of the desired exosomes endowed the sensing strategy with high specificity without the interruption of free proteins. As a result, this developed SPR biosensor exhibited a wide linear range from 1.0 × 104 to 1.0 × 107 particles/mL. Importantly, this strategy was able to accurately distinguish HER2-positive breast cancer patients from healthy individuals, exhibiting great potential clinical application.Graphical

Facile fabrication of ultrahigh-sensitivity surface-enhanced Raman scattering sensor using porous silicon photonic crystals prepared on backside silicon wafer

Photonic crystals (PhCs) with rough surfaces can considerably enhance the formation of electromagnetic hotspots, which significantly promote surface-enhanced Raman scattering (SERS) activity. In this study, porous silicon PhCs with rough surfaces were synthesized. Deposition of gold nanoparticles on the substrate yielded a SERS substrate with good activity and reproducibility, consequently achieving the ultratrace detection of Rhodamine 6 G (R6G), with a minimum concentration of 10−15 M. The SERS activity of this substrate was simulated via finite element modeling. The experimental and theoretical results confirmed that the optical characteristics of the “black silicon,” created by inducing a rough surface, and the enhancement of the effective Raman susceptibility, or the time period of the light–matter interaction owing to photonic crystals, played an important role in the enhancement of the overall SERS activity. Furthermore, we demonstrated that the rough-surface porous silicon SERS substrate could be employed to selectively detect ultratrace military explosives containing picric acid (PA) with increased sensitivity. Accordingly, the detection limits of PA and the probe molecule R6G in the Raman spectra were 0.79 nM and 0.24 fM, respectively. This study suggests that the porous silicon PhCs with rough surfaces are promising candidates for ultratrace chemical sensing.

Uncapped Gold Nanoparticles for the Metallization of Organic Monolayers

AbstractDeposition of the top‐contact electrode to create large‐area electrode | monolayer | electrode junctions represents a contemporary challenge to the integration of molecular electronic phenomena into device structures. Here, a top contact electrode is formed on top of an organic monolayer over a large area (cm2) by two simple, sequential self‐assembly steps. Initial self‐assembly of 4,4′‐(1,4‐phenylenebis(ethyne‐2,1‐diyl))dianiline onto gold‐on‐glass substrates gives high‐quality monolayers. The exposed amine functionality is subsequently used to anchor uncapped gold nanoparticles deposited in a second self‐assembly step. These uncapped gold nanoparticles are prepared by thermolysis of lipoic acid stabilized gold nanoclusters and contain gold oxide (≈9%) that provides stability in the absence of an organic capping ligand. This two‐step procedure results in full coverage of the monolayer by the densely packed gold nanoparticles, which spontaneously condense to give a semi‐continuous film. The electrical properties of these junctions are determined from I–V curves, revealing uniform electrical response and absence of metallic short‐circuits or evidence of damage to the underlying molecular monolayer. These promising electrical characteristics suggest that the deposition of uncapped gold nanoparticles on suitably functionalized molecular monolayers provides a path for the fabrication of molecular electronic devices using simple methodologies.

Electrochemical Detection of Anti-anxiety Drug Clonazepam Using Electrophoretically Deposited Gold Nanoparticles

Electrochemical Detection of Anti-anxiety Drug Clonazepam Using Electrophoretically Deposited Gold Nanoparticles

Reducing Efficiency of Fucoxanthin in Diatom Mediated Biofabrication of Gold Nanoparticles.

In the present investigation, fucoxanthin—one of the major pigments in diatoms—has been extracted from Nanofrustulum shiloi SZCZM1342, and its reducing efficiency in the biogenesis of gold nanoparticles (GNPs) was checked. Fucoxanthin extracted from golden-brown cells of N. shiloi was compared to the healthy, growing biomass of N. shiloi and standard fucoxanthin after separate exposure to 25 mg L−1 aqueous hydrogen tetrachloroaurate solutions at room temperature. Isolated and standard fucoxanthin were found to be able to reduce gold ions within 12 h whereas, the whole biomass turned pink in color after 72 h of reaction. The synthesized particles were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV–vis spectroscopy of purple-colored suspensions showed the absorption band at approximately 520–545 nm, indicating a strong positive signal for GNP synthesis. The SEM study revealed the deposition of GNPs on siliceous frustules of metal-treated diatom cells. The TEM analysis confirmed the GNPs synthesized by whole biomass are triangular, spherical and hexagonal in nature, whereas the particles produced by extracted and standard fucoxanthin are all spherical in nature. This study demonstrates the involvement of fucoxanthin in the reduction of gold ions and subsequent production of gold nanospheres.

Exposure-time-dependent subcellular staging of gold nanoparticles deposition and vesicle destruction in mice livers

Several advances in nanomedicine have been accompanied by rising concerns about the bioaccumulation and toxicity of gold nanoparticles (AuNPs). Here, we assessed the in vivo fate of diversely sized AuNPs that were injected into mice as a computed tomography contrast agent and examined with multi-scale analyses across the organ, tissue, cell, and subcellular levels. After focusing on the strong detected accumulation in livers, our data revealed a set of three clear, exposure-time-dependent patterns based on i) AuNPs deposit morphology and ii) readily identifiable phenotypes for AuNP-impacted subcellular vesicles. Importantly, we detected no obvious differences in liver function, liver cell apoptosis, or autophagy upon exposure to AuNPs. Thus, our study illustrates an accessible experimental and high-resolution data interpretation framework for quickly obtaining and contextualizing informative trends about any AuNP-triggered patterns of subcellular damage in nanomedicine studies; these can help guide cytotoxity and safety testing of diagnostic nanomedical technologies.

Multifunctional and Sensitivity Enhancement of Hybrid Acoustoplasmonic Sensors Fabricated on 36XY-LiTaO3 with Gold Nanoparticles for the Detection of Permittivity, Conductivity, and the Refractive Index.

Integration of high-sensitivity sensors with multiple sensing performance for the environmental detection of permittivity (εr), conductivity (σ), and the refractive index (n) is required to support Societies 5.0. However, there are still many sensors with low sensitivity that stand alone. A shear-horizontal surface acoustic wave (SH-SAW) sensor is usually used because of its high-sensitivity performance in detecting electrical properties. Moreover, localized surface plasmon resonance (LSPR) sensors show remarkable optical side capability. Here, we have successfully combined these advantages with an additional benefit of sensitivity enhancement. We propose a hybrid acoustoplasmonic sensor generated by integrating SH-SAW and LSPR devices to simultaneously detect εr, σ, and n. The SH-SAW sensor was fabricated on a 36XY-LiTaO3 substrate using a developed interdigital transducer. Then, the LSPR sensor was implemented by the deposition of gold nanoparticles (AuNPs) on the propagation surfaces of the SH-SAW sensor. Fascinatingly, the AuNPs not only generate the LSPR effect but also enhance the SH-SAW sensor sensitivity. Comprehensive investigations were performed with atomic force microscopy imaging, CST software used for plasmonic E-field simulation, and hybrid sensing evaluation. Moreover, the SH-SAW sensitivity enhancement achieved using AuNPs was verified by frequency-domain and time-domain measurements. Thus, the SH-SAW sensor with AuNPs has a wide εr detection range (25-85), sensing capabilities for ultrasmall σ (0.00528-0.02504 S/m), and high sensitivity for n detection (45.5-201.9 nm/RIU). The cross-sectional effects were also evaluated. The effect of the LSPR device on the SH-SAW device was examined by turning the light OFF or ON (hereafter OFF/ON). The impact of the SH-SAW device on the LSPR device was investigated by turning the sine signal OFF/ON. We found that the SH-SAW sensor was not impacted by light. Interestingly, the presence of the SH-SAW sensor affects the positions of the AuNPs, which consistently generates a small blueshift in the LSPR effect. However, insignificant variation was noted in independent performances. In general, the SH-SAW sensor with AuNPs shows multifunctional independent characteristics and high-sensitivity performance, making it suitable for a chemical environment, with the possibility of integration with a wireless network.