Attachment Of Gold Nanoparticles Research Articles

Plasmonic modulation of the upconversion fluorescence in NaYF4 :Yb/Tm hexaplate nanocrystals using gold nanoparticles or nanoshells.

Automatic upgrade: attachment of gold nanoparticles (NPs) onto upconversion nanocrystals (NCs) results in plasmonic interactions that lead to a significant enhancement of upconversion emission of more than 2.5. Conversely, formation of a gold shell greatly suppresses the NC emission because of considerable scattering of excitation irradiation (see picture; a=NC before seed attachment; b, c=NC with attached Au NPs; c=NC with Au shell; scale bar=50 nm).

나이트로벤젠다이아조늄 양이온의 화학 및 전기화학 반응을 이용한 실리콘 표면상으로의 단백질 고정

The immobilization of proteins on silicon surfaces using electrochemical reaction has been studied. Chemical deposition of nitrobenzendiazonium (NiBD) cations is employed to modify silicon surfaces. Electrochemical reduction of nitro-group to primary amine-group have been conducted on the modified surfaces to activate silicon surfaces for the protein immobilization. Attachment of gold nanoparticles was used to prove the reduction. The current method was applied to selective activation of a silicon nanowire and immobilize proteins on the selected nanowire. It has been demonstrated that the use of chemical and electrochemical reaction NiBD is efficient for the selective immobilization of proteins on silicon nanowire surfaces.

Preparation of Amino‐functionalized Multiwall Carbon Nanotube/Gold Nanoparticle Composites

AbstractMultiwall carbon nanotubes (MWNT) were modified orderly with carboxyl groups and amino groups. The MWNT/gold nanoparticle composites were formed when the amino‐functionalized MWNT was interacted with gold colloids. The functionalized MWNT was characterized using Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The amino‐functionalized MWNT allows further attaching gold nanoparticles through electrostatic interaction between the negatively charged gold nanoparticles and amino groups on the surface of the MWNT. The composite of gold nanoprticles and amino‐functionalized MWNT was characterized by transmission electron microscopy. This method decorating carbon nanotubes can be used to identify the location of functional groups, i.e. defect sites on carbon nanotubes.

Ink-jetable patterning of metal-catalysts for regioselective growth of nanowires

Nanosized (20-30 nm) colloidal gold, silver and their alloys were obtained by reductive transformation of corresponding metal salts. Dispersions of metal nanoparticles (σ < 4%) in aqueous solutions were obtained by appropriate surface functionalization which led to inorganic inks with solid fraction ranging from 0.01-4%. Judicious choice of a polymer additive (polyethylene glycol or carboxymethyl cellulose) was found to be crucial to avoid the agglomeration of nanocrystals in the ink-jetted structures upon solvent evaporation. The versatility of the nanoparticle-based printing technology was demonstrated by fabrication of dot-matrices and circuitry patterns on different substrates. Characterization of printed structures showed a homogeneous topography (AFM) and uniform distribution of metallic nanoparticles (SEM/TEM) within the ink-jetted microdrops. The site-specific patterning on silicon (001) substrates with nanoparticle (mono)layers could also be achieved by printing the linker molecule, aminopropyltriethoxysilane, followed by selective attachment of gold nanoparticles. Positionally ordered and chemically bonded gold catalyst patterns were used for the chemical vapour deposition (CVD) of nanowires, which led to site-specific growth of nanowires via the vapour-liquid-solid (VLS) mechanism and unlike in the case of spin-coated metal colloids no significant lateral diffusion of metal nanoparticles was observed, in chemically anchored Au nanoparticles. Nanoparticle containing inks allow a user-defined dilution to vary the density of CVD grown nanowires, which was utilized to show the differences in catalytic activities of silver and gold catalysts in the VLS growth.

Modeling of Nanoparticle-Mediated Electric Field Enhancement Inside Biological Cells Exposed to AC Electric Fields

We present in this article the effect of alternating electric field at kilohertz (kHz) and megahertz (MHz) frequencies on the biological cells in presence and absence of nanoparticles. The induced electric field strength distribution in the region around cell membrane and nucleus envelope display different behavior at kHz and MHz frequencies. The attachment of gold nanoparticles (GNPs), especially gold nanowires around the surface of nucleus induce enhanced electric field strengths. The induced field strengths are dependent on the length of nanowire and create varying field regions when the length of nanowire is increased from 2 to 4 µm. The varying nanowire length increased the induced field strengths inside nucleoplasm and region adjacent to the nucleus in the cytoplasm. We investigated a process of electrostatic disruption of nucleus membrane when the induced electric field strength across the nucleus exceeds its tensile strength.

Formation of Efficient Electron Transfer Pathways by Adsorbing Gold Nanoparticles to Self-Assembled Monolayer Modified Electrodes

The influence of the length of a self-assembled monolayer (SAM) linker on the electrochemical performance of electrode-linker-gold nanoparticle molecular constructs is investigated. Electrodes were first modified with amino-1-alkanethiols of four different lengths (C=2, 6, 8, and 11). The SAM showed progressively greater blocking ability to ruthenium hexamine as the length of the alkyl chain increased to the point where no significant Faradaic peak was observed for the amino-1-undecanethiol SAM. Upon the attachment of gold nanoparticles, distinct Faradaic electrochemistry of the ruthenium hexamine was observed for all four length SAMs with the electrochemistry being similar to that observed on a bare electrode. The charge transfer resistance to this Faradaic process was observed to be insensitive to the length of the intervening SAM, indicating it is electron transfer between the redox species and the nanoparticles, rather than tunneling across the SAM, which is the rate-limiting step. Some comments on the mechanism of charge transfer are provided. When forming multilayers of the linker-nanoparticle constructs, fabricated in a stepwise manner, whenever the distal species was the SAM the Faradaic process was blocked and whenever it was the nanoparticle a distinct Faradaic process was observed. With up to five layers of linker-nanoparticles, there was little increase in charge transfer resistance and again the charge transfer resistance was insensitive to the length of the linker.

Engineering the Spatial Selectivity of Surfaces at the Nanoscale Using Particle Lithography Combined with Vapor Deposition of Organosilanes

Particle lithography is a practical approach to generate millions of organosilane nanostructures on various surfaces, without the need for vacuum environments or expensive instrumentation. This report describes a stepwise chemistry route to prepare organosilane nanostructures and then apply the patterns as a spatially selective foundation to attach gold nanoparticles. Sites with thiol terminal groups were sufficiently small to localize the attachment of clusters of 2-5 nanoparticles. Basic steps such as centrifuging, drying, heating, and rinsing were used to generate arrays of regular nanopatterns. Close-packed films of monodisperse latex spheres can be used as an evaporative mask to spatially direct the placement of nanoscopic amounts of water on surfaces. Vapor phase organosilanes deposit selectively at areas of the surface containing water residues to generate nanostructures with regular thickness, geometry, and periodicity as revealed in atomic force microscopy images. The area of contact underneath the mesospheres is effectively masked for later synthetic steps, providing exquisite control of surface coverage and local chemistry. By judicious selection in designing the terminal groups of organosilanes, surface sites can be engineered at the nanoscale for building more complex structures. The density of the nanopatterns and surface coverage scale predictably with the diameter of the mesoparticle masks. The examples presented definitively illustrate the capabilities of using the chemistry of molecularly thin films of organosilanes to spatially define the selectivity of surfaces at very small size scales.

Functionalization of gold and carbon nanostructured materials using gamma-ray irradiation

Gold nanoparticles were successfully attached to the surface sites of carbon nanotubes (CNT). Both nanostructured materials were functionalized by λ-ray irradiation without chemical treatments for creating active sites. UV–visible absorption spectra of the un-irradiated and gamma ray-irradiated nanomaterials are also studied. The absorption spectrum of the irradiated CNT shows a new strong peak located at 700 nm, which might act as the active site on the surface of CNT, the result being an attachment of gold nanoparticles. This approach provides an efficient method to attach other nanostructures to carbon nanotubes for using them in different applications such as medicine and synthesis of catalytic materials.

Selective Attachment of Gold Nanoparticles to Ionic Liquids Adsorbed Multiwalled Carbon Nanotubes

Room temperature ionic liquids were adsorbed on the surface of the multiwalled carbon nanotubes (MWCNTs) by electrostatic interaction between carboxyl groups on the chemically oxidized MWCNTs surface and room temperature ionic liquids. The cations of ionic liquids and carboxyl groups on the carbon nanotube surface are put into a one-to-one correspondence by the electrostatic interaction. Negatively charged 15 nm gold nanoparticles are subsequently anchored to the surface of the MWCNTs through the electrostatic interaction between the ionic liquids and the gold nanoparticles. Gold nanoparticles are selectively attached to chemically functionalized surface sites of carbon nanotubes. This approach provides an efficient method to attach other nanostructures to carbon nanotubes and can be used as an illustrative detection of the functional groups on carbon nanotube surfaces.

Photostimulated Reversible Attachment of Gold Nanoparticles on Multiwalled Carbon Nanotubes

In this study, a hybrid system of gold nanoparticles and multiwalled carbon nanotubes (MWNTs) with a switching function was successfully realized through photocontrolled host−guest interaction based on α-cyclodextrin (α-CD) and azobenzene derivatives. First, the azobenzene derivative was covalently bonded onto the surface of MWNTs by a simple and effective reaction, leading to highly water-soluble MWNTs. Then, narrowly distributed gold nanoparticles were prepared using thiolated α-CD as a capping agent. Because of the photochemically controlled inclusion−exclusion interaction between the azobenzene moiety and α-CD, the reversible attachment of gold nanoparticles onto the MWNT surface was realized. TEM observation traced and testified to this reversible process, and at the same time Raman spectra provided convincing proof of the photoisomerization process.

Surface Observation for Seed-mediated Growth Attachment of Gold Nanoparticles on a Glassy Carbon Substrate

A seed-mediated growth method for surface modification was applied to the attachment of gold nanoparticles (AuNPs) to glassy carbon (GC) surfaces. By simply immersing a GC plate at first into a seed solution containing 4 nm Au nano-seed particles and then into a growth solution containing HAuCl(4), ascorbic acid and cetyltrimethyammonium bromide, AuNPs could be successfully attached to the GC surface via the growth of nanoparticles. A possible control of the size and density of AuNPs on GC was examined by observing surface images with a field-emission scanning electron microscope (FE-SEM) after several preparations with different immersion times. Compared with previous results on the growth of AuNPs on indium tin oxide (ITO) surfaces, it was characteristic that the AuNPs attached to GC surfaces exhibited smaller size and higher density as well as a flatter and non-crystal-like morphology. In addition, for performing the dense attachment of regular nano-sized AuNPs on GC surfaces, immersion for 2 h into the growth solution was sufficient. Longer immersion for 24 h caused an irregular growth of bold Au micro-crystals, while 24 h was necessary in the case of AuNPs on ITO surfaces. Shorter seeding and growth times were found to be effective for a sparse attachment of smaller Au nanoparticles whose size was ca. 20 nm. It was clarified that the seed-mediated growth method for surface modification was valid for fabricating a nanointerface composed of AuNPs on GC surfaces.

Effects of linker molecules on the attachment and growth of gold nanoparticles on indium tin oxide surfaces

As a linker molecule to attach gold nanoparticles (AuNPs) on indium tin oxide (ITO) surfaces, cysteamine was examined together with well-known 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane (APTMS). Systematic comparisons of AuNPs’ nanostructures formed on ITO were carried out after the room temperature treatment in an ethanol solution of linker molecules followed by the attachment of AuNPs using (i) one-step immersion into the 20-nm Au colloidal solution or (ii) two-step immersion, i.e., a seed-mediated growth treatment. Consequently, in case (i), it was found that APTMS was most effective for denser and homogeneous attachment of AuNPs on ITO surfaces with keeping the dispersion. With the MPTMS or cysteamine linkers in case (i), AuNPs aggregated on the ITO surfaces, and the attached amount of AuNPs were larger with the MPTMS linker. In contrast, in case (ii), nanostructural growth of AuNPs was possible with MPTMS or cysteamine using the seed-mediated growth, while the growth of AuNPs was significantly suppressed with the APTMS linker. Because quite different results were obtained between APTMS and cysteamine, it was found that the attachment and nanostructural growth of AuNPs on the organic linker layers cannot be simply governed by the functional groups, –NH 2, on the outer surfaces.

Controlled attachment of gold nanoparticles on ordered titania nanotube arrays

Download options Please wait... Supplementary files Solution temperature variation with soaking time; goldloading variation with soaking time PDF (366K) Article information DOI https://doi.org/10.1039/B903197A Article type Communication Submitted 16 Feb 2009 Accepted 04 Apr 2009 First published 27 May 2009 Download Citation J. Mater. Chem., 2009,19, 4483-4487 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Controlled attachment of gold nanoparticles on ordered titania nanotube arrays M. A. Elmoula, E. Panaitescu, M. Phan, D. Yin, C. Richter, L. H. Lewis and L. Menon, J. Mater. Chem., 2009, 19, 4483 DOI: 10.1039/B903197A To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Mohamed Abd Elmoula Eugen Panaitescu Minh Phan David Yin Christiaan Richter Laura H. Lewis Latika Menon

Easy decoration of carbon nanotubes with well dispersed gold nanoparticles and the use of the material as an electrocatalyst

A simple method has been developed to directly attach gold nanoparticles (Au-NPs) on carbon nanotubes (CNTs) with high dispersivity by using a small amount of ethanol to reduce the interfacial tension between CNTs and aqueous solution and impart solubility for CNTs in the solution containing Au-NPs. Both SEM and TEM characterization showed that Au-NPs distributed uniformly on the walls of CNTs. UV–vis spectra of the solution before and after attachment revealed that Au-NPs in the original solution were completely loaded on the CNTs without loss of Au source. The content of Au-NPs on CNTs could be controlled readily by adjusting the weight ratio between Au particles and CNTs. The electrochemical catalytic properties of the so-produced composites were characterized, and the samples showed a catalytic activity for the oxygen reduction reaction that is higher than those reported in the literature.

High-density attachment of gold nanoparticles on functionalized multiwalled carbon nanotubes using ion exchange

The attachment of gold nanoparticles (NPs) onto chemically functionalized multiwalled carbon nanotubes (MWCNTs) by ion pairing interaction is reported. The structure and composition of the resulting gold NP/MWCNT hybrids were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. A high-density of gold NPs was homogeneously dispersed on the modified MWCNTs. The hybrids show characteristic plasmon absorption of gold NPs in the UV–visible spectrum and good electrochemical properties.

Ultrasensitive detection of testosterone using conjugate linker technology in a nanoparticle-enhanced surface plasmon resonance biosensor

A rationally designed oligoethylene glycol linker conjugate to testosterone was synthesised and covalently immobilized on a surface plasmon resonance (SPR) biosensor surface. The sensing surface was stable for more than 330 binding and regeneration cycles allowing a high degree of re-use. This surface was then used in the development of an ultrasensitive immunobiosensor system for testosterone in buffer utilizing both secondary antibody and gold nanoparticle signal enhancement. The mechanism for the increased sensitivity results from increased binding mass and a gold plasmon coupling effect. The addition of a secondary antibody with an attached gold nanoparticle increased the signal sensitivity of the assay 12.5-fold compared with primary antibody alone. In the enhanced format the assay had limits of detection (LOD) of 3.7pgml−1 with standard in running buffer, and 15.4pgml−1 in a stripped human saliva matrix. This immunobiosensor system has sufficient sensitivity to measure testosterone across the broad physiologically relevant range in male saliva (29–290pgml−1) in under 13min allowing monitoring of testosterone in near real-time.

An improved DNA biosensor built by layer-by-layer covalent attachment of multi-walled carbon nanotubes and gold nanoparticles

In this work, we synthesized a type of compound, MWCNTs–CONH–(CH 2) 2–SH, via carboxylation, and investigated a thickness-tunable multilayer films DNA biosensor built by layer-by-layer (LBL) covalent attachment of gold nanoparticles (GNPs) and multi-walled carbon nanotubes (MWCNTs) on an Au electrode. Fourier transform infrared (FT-IR) spectra were used to identify the products formed in the step of carboxylation; scanning electron microscopy (SEM) and cyclic voltammetry (CV) were used to study the film assembly process. The hybridization events were monitored through measurement the signal of intercalated doxorubicin by differential pulse voltammetry (DPV), and the oxidation peak currents show a good linear relationship with the logarithm of the concentration of target DNA from 5.0 × 10 −10 to 1.0 × 10 −11 M with a detection limit of 6.2 pM. The improved DNA biosensor has a good stability and reproducibility.

Microarray-Based Study of Carbohydrate−Protein Binding by Gold Nanoparticle Probes

In order to develop a novel high-throughput tool for monitoring carbohydrate-protein interactions, we prepared carbohydrate or glycoprotein microarrays by immobilizing amino modified carbohydrates on aldehyde-derivatized glass slides or glycoprotein on epoxide-derivatized glass slides and carried out lectin binding experiments by using these microarrays, respectively. The interaction events are marked by attachment of gold nanoparticles followed by silver deposition for signal enhancement. The attachment of the gold nanoparticles is achieved by standard avidin-biotin chemistry. The detection principle is resonance light scattering (RLS). The well-defined recognition systems, namely, three monosaccharides (Man-alpha, Glc-beta and Gal-beta) or three glycoproteins (Asf, RNase A and RNase B) with two lectins (ConA and RCA120), were chosen here to establish the RLS assay, respectively. Highly selective recognition of carbohydrate-protein down to 25.6 pg/mL for RCA120 in solution and 8 microM for Gal-beta and 32 ng/mL for Asf on the microarray spots is demonstrated.

Enhancement of Radiation Cytotoxicity in Breast‐Cancer Cells by Localized Attachment of Gold Nanoparticles

Gold nanoparticles (GNPs) and modified GNPs having two kinds of functional molecules, cysteamine (AET) and thioglucose (Glu), are synthesized. Cell uptake and radiation cytotoxicity enhancement in a breast-cancer cell line (MCF-7) versus a nonmalignant breast-cell line (MCF-10A) are studied. Transmission electron microscopy (TEM) results show that cancer cells take up functional Glu-GNPs significantly more than naked GNPs. The TEM results also indicate that AET-capped GNPs are mostly bound to the MCF-7 cell membrane, while Glu-GNPs enter the cells and are distributed in the cytoplasm. After MCF-7 cell uptake of Glu-GNPs, or binding of AET-GNPs, the in vitro cytotoxicity effects are observed at 24, 48, and 72 hours. The results show that these functional GNPs have little or no toxicity to these cells. To validate the enhanced killing effect on cancer cells, various forms of radiation are applied such as 200 kVp X-rays and gamma-rays, to the cells, both with and without functional GNPs. By comparison with irradiation alone, the results show that GNPs significantly enhance cancer killing.

Seed-mediated shape evolution of gold nanomaterials: from spherical nanoparticles to polycrystalline nanochains and single-crystalline nanowires

We studied the kinetics of the reduction of a gold precursor (HAuCl4) and the effect of the molar ratio (R) of sodium citrate, which was introduced from a seed solution, and the gold precursor on the shape evolution of gold nanomaterials in the presence of preformed 13 nm gold nanoparticles as seeds. The reduction of the gold precursor by sodium citrate was accelerated due to the presence of gold seeds. Nearly single-crystalline gold nanowires were formed at a very low R value (R = 0.16) in the presence of the seeds as a result of the oriented attachment of the growing gold nanoparticles. At a higher R value (R = 0.33), gold nanochains were formed due to the non-oriented attachment of gold nanoparticles. At a much higher R value (R = 1.32), only larger spherical gold nanoparticles grown from the seeds were found. In the absence of gold seeds, no single-crystalline nanowires were formed at the same R value. Our results indicate that the formation of the 1D nanostructures (nanochains and nanowires) at low R values is due to the attachment of gold nanoparticles along one direction, which is driven by the surface energy reduction, nanoparticle attraction, and dipole–dipole interaction between adjacent nanoparticles.