Use Of Au Nanoparticles Research Articles

Spherical gold nanoparticles and gold nanorods for the determination of gentamicin

Gentamicin is an antibiotic indicated to treat mastitis in dairy cattle and for the treatment of bacterial resistance in the context of hospital infections. The effect caused by gentamicin on the optical properties of gold nanoparticles aqueous dispersions were used to develop quantitative methods to determine this antibiotic. Two different aqueous dispersions, one containing spherical Au nanoparticles (AuNPs) and the other containing Au nanorods (AuNRs), had their conditions adjusted to enable a stable and sensitive response towards gentamicin. The use of AuNPs, with measurement at 681nm of the rising coupling plasmon band, enabled a limit of detection (LOD) of 0.4ngmL−1 (0.02ng absolute LOD), ten times lower than the one achieved by measuring the decreasing of the longitudinal surface plasmon resonance band (at 662nm). The linear analytical response of AuNPs measured at 681nm did not require rationing of signal values to correct for linearity. Stability of the analytical response resulted in intermediary precision below 2%. No significant interference was imposed by excipients traditionally present in injectable solutions for veterinary use. Percent recoveries obtained in such formulations were between 94.5 and 98.2% regardless the existence of any difference in the proportion of the compounds known as gentamicin (C1, C1a and C2) in standard and in the samples. The method requires no derivatization with toxic reagents as usually is required in other spectroscopic approaches.

Radiotherapy Improvements by Using Au Nanoparticles.

Au nanoparticles can be prepared inside biological solutions and incorporated in special molecules for their transport through blood, drugs and proteins up to the tumour sites or directly injected in their volume when it is possible. The Au nanoparticles are biocompatible and can be accepted locally in the organism also at relatively high concentrations. The use of Au nanoparticles injected in the tumour site enhances significantly the effective atomic number of the medium, depending on the used concentration, and consequently the proton and electron energy loss and the X-ray absorption coefficient determining an increment of the local absorbed dose during radiotherapy. Traditional radiotherapy using electrons, X-rays and gamma rays, and innovative protontherapy can benefit the increment of the effective atomic number of the tissue in the presence of Au-nanoparticles embedded in the tumour volume with an adaptive up-take procedure. This method decreases the dose released to the healthy tissues permitting a better cantering of the irradiated targets and shielding the healthy tissue placed behind the tumour. The presented theoretical study approach permits to evaluate an enhancement of the radiotherapy dose of the order of 1 % using 60 MeV protons, of the order of 10% using 6 MeV electrons and of the order of 100 % using 100 keV X-ray photons. Here, we also disccused for patents relaed to the topic.

Raman analysis of gold on WSe2 single crystal film

Synthesis and characterization of high-quality single-crystal tungsten diselenide (WSe2) films on a highly insulating substrate is presented. We demonstrate for the first time that the presence of gold (Au) nanoparticles in the basal plane of a WSe2 film can enhance its Raman scattering intensity. The experimentally observed enhancement ratio in the Raman signal correlates well with the simulated electric field intensity using both three-dimensional electromagnetic software and theoretical calculation considering layered medium coupled-dipole approximation (LM-CDA). This work serves as a guideline for the use of Au nanoparticles on WSe2 single-crystal thin films for surface enhanced Raman scattering (SERS) applications in the future.

Comparison of Au and TiO2 based catalysts for the synthesis of chalcogenide nanowires

We present a comparative study of TiO2-based and Au catalysts for the physical vapor deposition of (Bi1−xSbx)2Se3 topological insulator nanowires. The standard Au nanoparticle catalyst was compared to five TiO2 nanoparticle based catalysts (anatase, rutile, P-25, high surface area anatase, and TiO2 supported Au particles). The use of Au nanoparticles seriously harms the properties of nanowires, thereby limiting their application. In contrast, TiO2 based catalysts lead to the residue-free growth of nanowires with a higher degree of crystallinity. Homogeneous nanowire ensembles are achieved with the mixed phase P-25 catalyst, and a possible growth mechanism is proposed.

Size Matters: Gold Nanoparticles in Targeted Cancer Drug Delivery

Cancer is the current leading cause of death worldwide, responsible for approximately one quarter of all deaths in the USA and UK. Nanotechnologies provide tremendous opportunities for multimodal, site-specific drug delivery to these disease sites and Au nanoparticles further offer a particularly unique set of physical, chemical and photonic properties with which to do so. This review will highlight some recent advances, by our laboratory and others, in the use of Au nanoparticles for systemic drug delivery to these malignancies and will also provide insights into their rational design, synthesis, physiological properties and clinical/preclinical applications, as well as strategies and challenges toward the clinical implementation of these constructs moving forward.

Immobilization of barley oxalate oxidase onto gold–nanoparticle-porous CaCO3 microsphere hybrid for amperometric determination of oxalate in biological materials

The use of Au nanoparticles (AuNPs)-CaCO(3) porous microsphere hybrid as a matrix for enzyme immobilization to increase the performance of an amperometric biosensor. A method is described for construction of an amperometric oxalate biosensor by immobilizing a barley root oxalate oxidase (OxOx) onto AuNPs-CaCO(3) porous microsphere hybrid encapsulated in silica sol and deposited on Au electrode. The biosensor showed optimum response within 4s at pH 5.0 and 30°C, when polarized at +0.4V vs. Ag/agCl. The biosensor possesses high sensitivity and measures oxalate concentrations as low as 1.0 μmol/L. The working linear range was from 1.0 to 1000 μmol/L of oxalate. The biosensor measured urinary and plasma oxalate of normal persons and stone formers. The use of AuNPs-CaCO(3) porous microsphere hybrid as a support for immobilization of OxOx has resulted into an improved amperometric oxalate biosensor.

Enhanced electrocatalytic activity of a polyoxometalates-based film decorated by gold nanoparticles

A K 6P 2MoW 17O 62-based film decorated by gold nanoparticles was prepared by layer-by-layer self-assembly method. It was fabricated on quartz, silicon and ITO substrates in a progressive and uniform manner monitored by UV–vis spectroscopy, and characterized by atomic force microscopy (AFM), cyclic voltammograms (CVs) and electrochemical impedance spectra (EIS). A set of experimental results revealed that the incorporation of Au nanoparticles into K 6P 2MoW 17O 62-based film enhanced the conductivity of the film, leading to several or more than tenfold increase in electrocatalytic efficiency of this film for reduction of H 2O 2, IO 3 −, NO 2 − compared to the no use of Au nanoparticles. It also has been found that presence of Au nanoparticles endowed the film electrocatlytic activity towards oxidation of ascorbic acid and the photo-luminescence property arising from inter electron transitions between occupied 5d bands to 6sp conduction bands of AuNPs.

Au-catalyst-free epitaxy of InAs nanowires

Semiconducting nanowires have been intensively studied in order to exploit unique optical and electrical properties that develop at the nano-scale. Commonly, nanowires are produced using Au nanoparticles (∼50 nm diameter) as seed particles on the surface applied prior to epitaxy. The Au particle acts as a preferred nucleation site for nanowire growth. This report demonstrates InAs nanowire epitaxy on GaAs(1 0 0) and GaAs(1 1 1) substrates without the use of Au nanoparticles. InAs nanowires are formed by using in-situ generated metallic droplets via decomposition of the metalorganic source during OMVPE. The InAs nanowires grow preferentially in the [1 1 1] direction, although evidence of [1 0 0] growth is observed. InAs nanowires in excess of 0.5 μm in length have been observed on GaAs(1 0 0) substrates. The effect of OMVPE conditions such as substrate orientation, V/III ratio, and growth temperature on the InAs nanowire structure is described.

Enhanced Photocurrent in the RuL2(NCS)2/di-(3-aminopropyl)-viologen/Au Nanoparticles/ITO System: Use of Au Nanoparticles for Retardation of the Back Electron Transfer Reaction

This paper reports the use of Au nanoparticles (NPs) as electron transfer bridge layers to improve the photocurrent of viologen/Ru complex-based photoelectrochemical cells. The Ru complex/ viologen/Au NPs on electrodes were prepared using self-assembled monolayers. The cell system showed an excellent photocurrent of 25 nA/cm2 under the 1.5 air mass condition (I = 100 mW/cm2), which is five times greater than Au NPs due to the reduced recombination reaction.

Near-Ideal Photodiodes from Sintered Gold Nanoparticle Films on Methyl-Terminated Si(111) Surfaces

We report photocurrent-voltage data for improved n-Si/metal devices using CH3-terminated n-Si(111) and Au nanoparticles (NPs). CH3-terminated Si(111) surfaces maintain good electronic properties throughout device assembly, while the use of Au NPs as precursors to metal films circumvents the standard issues associated with interfacial reactivity of metals in Schottky barrier formation. Such devices demonstrate excellent photovoltaic properties, with photovoltages that approach the maximum values predicted for photodiodes that are limited by Si bulk diffusion/recombination processes rather than interfacial processes. These devices are compared to standard n-Si/Au devices made via thermally evaporated Au films which are well-known to be limited by junction-based recombination.

AFM and STM characterization of thiol and thiophene functionalized SWNTs: pitfalls in the use of chemical markers to determine the extent of sidewall functionalization in SWNTs

Thiol- and thiophene-functionalized SWNTs prepared via the reaction of a substituted amine with fluoronanotubes show similar levels of sidewall functionalization, however, the use of Au nanoparticles as chemical markers for AFM gives misleading results for substituent distribution since STM shows the thiol substituents grouped in bands while the thiophene substituents uniformly distributed along the SWNTs.