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Catherine J Murphy - One of the best experts on this subject based on the ideXlab platform.

  • oxidation state of capping agent affects spatial reactivity on Gold Nanorods
    Journal of the American Chemical Society, 2017
    Co-Authors: Joshua G. Hinman, Ji Li, Jonathan R Eller, Wayne Lin, Junheng Li, Catherine J Murphy
    Abstract:

    Despite enormous progress toward controlling the shapes and surface chemistry of colloidal nanoparticles, spatial control of nanoparticle surface chemistry remains a major challenge. In recent years, there have been tantalizing reports demonstrating anisotropic silica coating of Gold Nanorods in which silica is deposited only on the sides by functionalizing the Nanorods with poly(ethylene glycol) methyl ether thiol (PEG-thiol) prior to silica coating, but such results have been difficult to reproduce. We report that the oxidation state of PEG-thiol is key to anisotropic silica coating, with the disulfide, not the thiol, leading to side silica coating. PEG-disulfide appears to selectively functionalize the ends of Gold Nanorods, and robust methods are developed to reliably deposit side silica shells on PEG-disulfide functionalized Gold Nanorods.

  • Surface Chemistry of Gold Nanorods
    Langmuir, 2016
    Co-Authors: Nathan D. Burrows, Joshua G. Hinman, Jordan M. Dennison, Ariane M. Vartanian, Nardine S. Abadeer, Elissa M. Grzincic, Lisa M. Jacob, Ji Li, Catherine J Murphy
    Abstract:

    Gold Nanorods have garnered a great deal of scientific interest because of their unique optical properties, and they have the potential to greatly impact many areas of science and technology. Understanding the structure and chemical makeup of their surfaces as well as how to tailor them is of paramount importance in the development of their successful applications. This Feature Article reviews the current understanding of the surface chemistry of as-synthesized Gold Nanorods, methods of tailoring the surface chemistry of Gold Nanorods with various inorganic and organic coatings/ligands, and the techniques employed to characterize ligands on the surface of Gold Nanorods as well as the associated measurement challenges. Specifically, we address the challenges of determining how thick the ligand shell is, how many ligands per nanorod are present on the surface, and where the ligands are located in regiospecific and mixed-ligand systems. We conclude with an outlook on the development of the surface chemistry ...

  • The Many Faces of Gold Nanorods
    Journal of Physical Chemistry Letters, 2010
    Co-Authors: Catherine J Murphy, Lucas B. Thompson, Alaaldin M. Alkilany, Patrick N. Sisco, Stefano P. Boulos, Sean T. Sivapalan, Jie An Yang, Davin J. Chernak, Jingyu Huang
    Abstract:

    Gold Nanorods exhibit optical properties that are tunable with their shape, leading to sensing, imaging, and biomedical therapeutic applications. Colloidal preparations of Gold Nanorods impart surfactants or other species on the nanorod surfaces; a popular preparation leads to a surfactant bilayer on the surface. The specific chemistry at three distinct interfaces has roles to play in the growth and subsequent usage of these nanomaterials; these interfaces are the Gold−surfactant interface, the hydrophobic surfactant bilayer, and, finally, the surfactant interface with the aqueous bulk. Each one of these interfaces provides strategies for altering nanorod properties such as stability against aggregation, toxicity, and ease of assembly. It is the solvent-accessible interface that dictates nanorod interactions with other particles, macromolecules, and living cells.

  • quantitation of metal content in the silver assisted growth of Gold Nanorods
    Journal of Physical Chemistry B, 2006
    Co-Authors: Christopher J Orendorff, Catherine J Murphy
    Abstract:

    The seed-mediated approach to making Gold Nanorods in aqueous surfactant solutions has become tremendously popular in recent years. Unlike the use of strong chemical reductants to make spherical Gold nanoparticles, the growth of Gold Nanorods requires weak reducing conditions, leading to an unknown degree of Gold reduction. The metal content of Gold Nanorods, made in high yield in the presence of silver ion, is determined by inductively coupled plasma atomic emission spectroscopy. Through the use of the known Gold concentration in Nanorods, molar extinction coefficients are calculated for Nanorods of varying aspect ratios from 2.0 to 4.5. The extinction coefficients at the longitudinal plasmon band peak maxima for these Nanorods vary from 2.5 × 109 to 5.5 × 109 M-1 cm-1, respectively, on a per-particle basis. Many of the Gold ions present in the growth solution remain unreacted; insights into the growth mechanism of Gold Nanorods are discussed.

  • Biotin-streptavidin-induced aggregation of Gold Nanorods : Tuning rod-rod orientation
    Langmuir, 2005
    Co-Authors: Anand Gole, Catherine J Murphy
    Abstract:

    We report herein biotin−streptavidin-mediated aggregation studies of long Gold Nanorods. We have previously demonstrated end-to-end linkages of Gold Nanorods driven by the biotin−streptavidin interaction (Caswell et al. J. Am. Chem. Soc. 2003, 125, 13914). In that report, the specific binding of biotin disulfide to the Gold nanorod edges was achieved due to the preferred binding of thiol molecules to the Au{111} surface (Gold nanorod ends) as opposed to the Gold nanorod side faces. This led to the end−end linkage of Gold Nanorods upon subsequent addition of streptavidin. In this report we demonstrate a simple procedure to biotinylate the entire Gold nanorod surface and subsequently form a 3-D assembly by addition of streptavidin. Gold Nanorods were synthesized by the three-step seeding protocol documented in our previous articles. The surface of Gold Nanorods was further modified by a layer of a weak polyelectrolyte, poly(acrylic acid), PAA. A biotin molecule which has an amine group at one end (biotin−PE...

Ryan M. Richards - One of the best experts on this subject based on the ideXlab platform.

  • Size tunable Gold Nanorods evenly distributed in the channels of mesoporous silica.
    ACS Nano, 2008
    Co-Authors: Zhi Li, Christian Kübel, Vasile I. Pârvulescu, Ryan M. Richards
    Abstract:

    Uniformly distributed Gold Nanorods in mesoporous silica were synthesized in situ by performing a seed-mediated growth process in the channels of SBA-15 which functions as a hard-template to confine the diameter of Gold Nanorods. By changing the amount of Gold precursor, Gold Nanorods were prepared with a fixed diameter (6−7 nm) and tunable aspect ratios from 3 to 30. Transmission electron microscope and electron tomography were utilized to visualize the Gold Nanorods supported on one piece of SBA-15 segment and showed a fairly uniform 3-dimensional distribution of Gold Nanorods within the SBA-15 channels. The longitudinal plasmon resonances of the Gold Nanorods/SBA-15 composites analyzed by diffuse reflectance UV−vis spectra were found to be tunable depending on the length of Gold Nanorods. No significant decrease in surface area and/or pore size of the composite was found after growth, indicating the growth process did not disrupt the open mesoporous structure of SBA-15. The combination of the tunable s...

  • Size tunable Gold Nanorods evenly distributed in the channels of mesoporous silica.
    ACS nano, 2008
    Co-Authors: Christian Kübel, Vasile I. Pârvulescu, Ryan M. Richards
    Abstract:

    Uniformly distributed Gold Nanorods in mesoporous silica were synthesized in situ by performing a seed-mediated growth process in the channels of SBA-15 which functions as a hard-template to confine the diameter of Gold Nanorods. By changing the amount of Gold precursor, Gold Nanorods were prepared with a fixed diameter (6-7 nm) and tunable aspect ratios from 3 to 30. Transmission electron microscope and electron tomography were utilized to visualize the Gold Nanorods supported on one piece of SBA-15 segment and showed a fairly uniform 3-dimensional distribution of Gold Nanorods within the SBA-15 channels. The longitudinal plasmon resonances of the Gold Nanorods/SBA-15 composites analyzed by diffuse reflectance UV-vis spectra were found to be tunable depending on the length of Gold Nanorods. No significant decrease in surface area and/or pore size of the composite was found after growth, indicating the growth process did not disrupt the open mesoporous structure of SBA-15. The combination of the tunable size of the Nanorods and their 3-dimensional distribution within the open supporting matrix makes the Gold Nanorods/SBA-15 composites interesting candidates to systematically study the influence of the aspect ratio of Gold Nanorods on their properties and potential applications, i.e., catalyst, optical polarizer, and ultrasensitive medical imaging technique.

Yasuro Niidome - One of the best experts on this subject based on the ideXlab platform.

  • Assemblies of Gold Nanorods for efficient SALDI mass spectrometry
    Optical Materials Express, 2016
    Co-Authors: Masanori Fujii, Naotoshi Nakashima, Yasuro Niidome
    Abstract:

    Surface-assisted laser desorption/ionization (SALDI) mass spectrometry was performed using Gold Nanorods deposited on ITO plates. The degree of aggregation of the Nanorods was controlled on the plates, and the relationship between the SALDI signals and the longitudinal surface plasmon (SP) bands of the Gold Nanorods were examined. Highly efficient SALDI processes were obtained when the bandwidth of the SP bands was about 300 nm. Optical dark field and SEM observations showed that fusion and ablation of nanorod-assemblies consisting of 4–10 Gold Nanorods contributed to the efficient SALDI processes.

  • PEG-silica-modified Gold Nanorods that retain their optical properties in tumor tissues
    Journal of Biomaterials Science-polymer Edition, 2013
    Co-Authors: Yasuyuki Akiyama, Yasuro Niidome, Takeshi Mori, Yoshiki Katayama, Takuro Niidome
    Abstract:

    Gold Nanorods modified with polyethylene glycol (PEG) chains via Au–S bonds form aggregates, and their absorption spectra broaden in tumor tissues. In contrast, the Gold Nanorods modified here via the crosslinking of PEG chains on the silica shell on Gold Nanorods showed enhanced permeability and retention effects and retained the optical properties of the original Gold Nanorods in tumor tissues.

  • Theragnostic approaches using Gold Nanorods and near infrared light
    Yakugaku Zasshi-journal of The Pharmaceutical Society of Japan, 2010
    Co-Authors: Takuro Niidome, Atsushi Shiotani, Yasuyuki Akiyama, Akira Ohga, Keisuke Nose, Dakrong Pissuwan, Yasuro Niidome
    Abstract:

    Gold nanoparticles have unique optical properties such as surface-plasmon and photothermal effects. Such properties have resulted in Gold nanoparticles having several clinical applications. Gold Nanorods (which are rod-shaped Gold nanoparticles) show a surface plasmon band in the near-infrared region. They have therefore been proposed as contrast agents for bioimaging, or as heating devices for photothermal therapy. Polyethylene glycol-modified Gold Nanorods systemically administrated into mice can be detected with integrating sphere, and the stability of the Gold Nanorods in blood flow evaluated. After intravenous injection of Gold Nanorods followed by near-infrared laser irradiation, significant tumor damage triggered by the photothermal effect was observed. To deliver Gold Nanorods to the target tissue, thermosensitive polymer gel-coated Gold Nanorods were prepared. After intravenous injection of the gel-modified Gold Nanorods and irradiation of the tumor, a larger amount of Gold was detected in the irradiated tumor than in the non-irradiated tumor. This effect is due to the hydrophobic interaction between the cellular membrane or the extracellular matrix and the gel surfaces induced by the photothermal effect. Furthermore, the photothermal effect enhanced the permeability of the stratum corneum of the skin. As a result of treatment of the skin with ovalbumin and Gold Nanorods followed by near-infrared light irradiation, a significant amount of protein was detected in the skin. The Gold Nanorods therefore showed several functions as a photothermal nanodevice for bioimaging, thermal therapy, and a drug delivery system.

  • Controlled release of PEG chain from Gold Nanorods: Targeted delivery to tumor
    Bioorganic & Medicinal Chemistry, 2010
    Co-Authors: Takuro Niidome, Yasuyuki Akiyama, Akira Ohga, Yasuro Niidome, Takeshi Mori, Kazuto Watanabe, Yoshiki Katayama
    Abstract:

    Abstract Gold Nanorods exhibit strong absorbance of light in the near infrared region, which penetrates deeply into tissues. Since the absorbed light energy is converted into heat, Gold Nanorods are expected to act as a contrast agent for in vivo bioimaging and as a thermal converter for photothermal therapy. To construct a Gold nanorod targeted delivery system for tumor a peptide substrate for urokinase-type plasminogen activator (uPA), expressed specifically on malignant tumors, was inserted between the PEG chain and the surface of the Gold Nanorods. In other words, we constructed PEG–peptide-modified Gold Nanorods. After mixing the Gold Nanorods with uPA, the PEG chain was released from the surface of the Gold and subsequently nanorod aggregation took place. The formation of the aggregation was monitored as a decrease in light absorption at 900 nm. Tumor homogenate induced a significant decrease in this absorption. Larger amount of the PEG–peptide-modified Gold Nanorods bound to cells expressing uPA in vitro compared with control Gold Nanorods, which had scrambled sequence of the peptide. The PEG–peptide-modified Gold Nanorods showed higher accumulation in tumor than the control after they were injected intravenously into tumor-bearing mice, however, the density of the peptide on the surface of the Gold Nanorods was a key factor of their biodistributions. This targeted delivery system, which responds to uPA activity, is expected to be a powerful tool for tumor bioimaging and photothermal tumor therapy.

  • Poly(ethylene glycol)-Modified Gold Nanorods as a Photothermal Nanodevice for Hyperthermia
    Journal of biomaterials science. Polymer edition, 2009
    Co-Authors: Takuro Niidome, Yasuyuki Akiyama, Yasuro Niidome, Masato Yamagata, Takahito Kawano, Takeshi Mori, Yoshiki Katayama
    Abstract:

    Gold Nanorods, which have a strong surface plasmon band at the near-infrared region, absorb light energy which is then converted to heat. Since near-infrared light can penetrate deeply into tissue, Gold Nanorods are expected to be useful as photosensitizers for photothermal therapy. In this study, the length of the poly(ethylene glycol) (PEG) chain was optimized in order to stabilize the Gold Nanorods in the blood circulation after intravenous injection. PEG5000- and PEG10000-modified Gold Nanorods showed higher stability in the blood circulation compared with PEG2000- and PEG20000-modified Gold Nanorods. As a demonstration of photothermal tissue damage, PEG5000-modified Gold Nanorods were injected into the muscle in the hind limbs of a mouse, and then irradiated with near-infrared pulsed laser light. Significant tissue damage was observed only in the presence of Gold Nanorods and laser irradiation. We next injected the Gold Nanorods directly into subcutaneous tumors in mice, and then irradiated the tumor...

Anand Gole - One of the best experts on this subject based on the ideXlab platform.

  • Biotin-streptavidin-induced aggregation of Gold Nanorods : Tuning rod-rod orientation
    Langmuir, 2005
    Co-Authors: Anand Gole, Catherine J Murphy
    Abstract:

    We report herein biotin−streptavidin-mediated aggregation studies of long Gold Nanorods. We have previously demonstrated end-to-end linkages of Gold Nanorods driven by the biotin−streptavidin interaction (Caswell et al. J. Am. Chem. Soc. 2003, 125, 13914). In that report, the specific binding of biotin disulfide to the Gold nanorod edges was achieved due to the preferred binding of thiol molecules to the Au{111} surface (Gold nanorod ends) as opposed to the Gold nanorod side faces. This led to the end−end linkage of Gold Nanorods upon subsequent addition of streptavidin. In this report we demonstrate a simple procedure to biotinylate the entire Gold nanorod surface and subsequently form a 3-D assembly by addition of streptavidin. Gold Nanorods were synthesized by the three-step seeding protocol documented in our previous articles. The surface of Gold Nanorods was further modified by a layer of a weak polyelectrolyte, poly(acrylic acid), PAA. A biotin molecule which has an amine group at one end (biotin−PE...

  • Biotin-streptavidin-induced aggregation of Gold Nanorods: Tuning rod-rod orientation
    Langmuir : the ACS journal of surfaces and colloids, 2005
    Co-Authors: Anand Gole, Catherine J Murphy
    Abstract:

    We report herein biotin-streptavidin-mediated aggregation studies of long Gold Nanorods. We have previously demonstrated end-to-end linkages of Gold Nanorods driven by the biotin-streptavidin interaction (Caswell et al. J. Am. Chem. Soc. 2003, 125, 13914). In that report, the specific binding of biotin disulfide to the Gold nanorod edges was achieved due to the preferred binding of thiol molecules to the Au[111] surface (Gold nanorod ends) as opposed to the Gold nanorod side faces. This led to the end-end linkage of Gold Nanorods upon subsequent addition of streptavidin. In this report we demonstrate a simple procedure to biotinylate the entire Gold nanorod surface and subsequently form a 3-D assembly by addition of streptavidin. Gold Nanorods were synthesized by the three-step seeding protocol documented in our previous articles. The surface of Gold Nanorods was further modified by a layer of a weak polyelectrolyte, poly(acrylic acid), PAA. A biotin molecule which has an amine group at one end (biotin-PEO-amine) was anchored to the carboxylic acid group of the polyelectrolyte using the well-known carbodiimide chemistry. This process biotinylates the entire Gold nanorod surface. Addition of streptavidin further leads to aggregation of Gold Nanorods. A closer look at the aggregates reveals a preferential side-to-side assembly of Gold Nanorods. The Gold Nanorods were characterized at each stage by UV-vis spectroscopy, light scattering, and transmission electron microscopy (TEM) measurements.

  • Polyelectrolyte-Coated Gold Nanorods: Synthesis, Characterization and Immobilization
    Chemistry of Materials, 2005
    Co-Authors: Anand Gole, Catherine J Murphy
    Abstract:

    The versatile layer-by-layer (LbL) approach has been used for the synthesis of polyelectrolyte-coated Gold Nanorods. The simple process first involves the synthesis of Gold Nanorods by our previously published three-step seed-mediated protocol. The presence of a bilayer of the surfactant cetyltrimethylammonium bromide (CTAB) on the Gold nanorod surface imparts a net positive charge to the Nanorods. Alternate adsorption of anionic and cationic polyelectrolytes on these positively charged Gold Nanorods leads to the formation of polyelectrolyte multilayers around the Nanorods. These coated Gold Nanorods have been characterized by UV−vis spectroscopy, zeta potential measurements, and transmission electron microscopy (TEM). Depending on the surface chemical functionality of the coated Gold Nanorods, they have been selectively immobilized onto either cationic or anionic surfaces. Scanning electron microscopy (SEM) has been used to visualize the immobilized Nanorods and to determine the nanorod density on flat s...

Michel Orrit - One of the best experts on this subject based on the ideXlab platform.

  • Probing, Sensing, and Fluorescence Enhancement with Single Gold Nanorods.
    Journal of Physical Chemistry Letters, 2014
    Co-Authors: Saumyakanti Khatua, Michel Orrit
    Abstract:

    Gold Nanorods with dimensions around 10–100 nm present original optical properties. Their main advantages are the tunability from 600 to 1000 nm of their main absorption band, and its high intensity, stemming from the good conducting properties of Gold in this spectral range. Gold Nanorods have been applied to tracking, probing, sensing, and manipulation experiments. Here, we discuss experiments done with single Gold Nanorods with emphasis on recent results from our group.

  • luminescence quantum yield of single Gold Nanorods
    Nano Letters, 2012
    Co-Authors: Mustafa Yorulmaz, Saumyakanti Khatua, Peter Zijlstra, Alexander Gaiduk, Michel Orrit
    Abstract:

    We study the luminescence quantum yield (QY) of single Gold Nanorods with different aspect ratios and volumes. Compared to Gold nanospheres, we observe an increase of QY by about an order of magnitude for particles with a plasmon resonance >650 nm. The observed trend in QY is further confirmed by controlled reshaping of a single Gold nanorod to a spherelike shape. Moreover, we identify two spectral components, one around 500 nm originating from a combination of interband transitions and the transverse plasmon and one coinciding with the longitudinal plasmon band. These components are analyzed by correlating scattering and luminescence spectra of single Nanorods and performing polarization sensitive measurements. Our study contributes to the understanding of luminescence from Gold Nanorods. The enhanced QY we report can benefit applications in biological and soft matter studies.