Author: Jay W. HotchkissPublisher:
ISBN:
Category : Addition polymerization
Languages : en
Pages : 462
Book Description
Surface Modification of Gold Nanorods with Raft Polymers as Templates for the Oxidative Polymerization of Pyrrole, Thiophene, and Synthesis of Metallic Nanoparticles
Author: Jay W. HotchkissPublisher:
ISBN:
Category : Addition polymerization
Languages : en
Pages : 462
Book Description
Directed Self-assembly of Gold Nanorods Using Surface Modification
Author: David A. WalkerPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
ABSTRACT: Metallic nanoparticles are unique materials for optical, electronic, catalytic, and sensing applications. Due to the vast flexibility in controlling the surface chemistry of these particles through functionalization there is a great deal of interest in using metallic nanoparticles as building blocks in the development of more complex nanostructures through the use of a 'bottom-up' approach. Using self assembly techniques, one can exploit spontaneous chemical interactions to build complex constructs on the nanometer scale. Towards this end, gold nanorods have been synthesized and modified with various polymers, inorganic oxides and organic ligands to establish principles for self-assembly of these unique nanomaterials. Gold nanorods are of great interest due to their strong optical absorption in the visible and near infrared regions, which can be tuned through material preparation and modification of the surrounding environment. This thesis focuses on investigating approaches for both irreversible and reversible self-assembly of gold nanorods. Techniques such as dynamic light scattering (DLS), ultraviolet-visible (UV) spectroscopy, transmission electron microscopy (TEM), and polarization modulation infrared reflection absorbance spectroscopy (PM-IRRAS) were used to characterize the colloidal particles and gold surfaces. A novel contribution of this work is the successful demonstration of end-to-end linking of gold nanorods in a rapid and reversible manner using a pH responsive polypeptide.
Selective Surface Modification of Gold Nanorods with Functional Polymers for Tunable Self-assembly and Optical Properties
Author: Sjören SchweizerhofSurface Modification of Gold Nanorods
Author: Naresh C. DesaiSurface Modification Using Gold Nanoparticles
Author: Ann C. GaffeySynthesis, Characterization, and Self-Assembly of Gold Nanorods and Nanoprisms
Author: Kristina L. TranPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The unique properties of gold nanoparticles make them excellent candidates for applications in electronics, sensing, imaging, and photothermal therapy. Though abundant literature exists for isotropic gold nanoparticles, work on nanoparticles of different shapes has been gaining interest recently. Anisotropic gold nanoparticles, such as nanorods and nanoprisms, have tunable optical properties in the visible and near-infrared regions. Through synthesis and surface modification, the production of various shapes of these gold nanoparticles can be controlled to meet different applications. Two different types of gold nanorods were used in this thesis. The first type was stabilized with cetyltrimethylammonium bromide (CTAB) and had aspect ratios of 3-4 (defined as the nanorod length divided by the diameter). The second type was synthesized using CTAB and benzyldimethylhexadecylammonium chloride (BDAC) in a binary surfactant system which produced aspect ratios greater than 4. The nanorods were characterized with UV-Vis spectroscopy and transmission electron microscopy (TEM). Two types of bowl-shaped macrocyclic compounds called resorcinarenes were used to direct self-assembly of the nanorods. The first type of resorcinarene (R2S) consisted of thiol(SH)-terminated alkyl chains on both rims. The second type (R1S) contained thiol-terminated alkyl chains on only one rim. The monolayer formation of these resorcinarenes on planar gold surfaces was studied and characterized by FTIR spectroscopy. Resorcinarene-mediated assembly of gold nanorods was monitored with UV-Vis spectroscopy, dynamic light scattering (DLS), and TEM. In addition to gold nanorods, gold nanoprisms were synthesized through a kinetically-controlled reduction route in the presence of CTAB. The linking of nanoprisms using resorcinarenes was also explored.
Novel Synthetic Approaches for Fabrication of Polymer Brushes on Gold Surfaces Via Raft Polymerization: A New Era for Gold Modification
Author: Candan CatliPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Nanobiotechnology is an important branch of nanotechnology, which has been dramatically developed for creating functional nanoscale materials for various biomedical applications. The past few decades have witnessed significant advances in the development of various functionalized surfaces for applications in a wide range of fields such as chemistry, biology, pharmacy and physics. There has recently been extensive research to modify gold surfaces, thereby opening up opportunities to enhance breadth of their applicability. Recently developed methods have allowed the modification of gold nanop...
Molecular Engineering of Gold Nanorod Surfaces: Towards Improved Physical Properties and Understanding Nanoparticle-cell Interactions
Author: Alaaldin M. AlkilanyPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Gold nanorods have unique optical properties and various promising applications. Wet chemical synthesis of gold nanorods requires the use of cetyl trimethylammonium bromide (CTAB) as shape-directing surfactant, which form a bilayer on the surfaces of gold nanorods. CTAB bilayer stabilizes the nanorods against aggregation and has the ability to sequester organic molecules from aqueous bulk. CTAB molecules in the bilayer are held via weak hydrophobic forces and thus tend to desorb resulting in nanorods aggregation and toxicity to cultured cells. Herein, three surface-engineering approaches to enhance the colloidal physical stability and biocompatibility of gold nanorods have been examined: 1) electrostatic approach via overcoating with polyelectrolytes; 2) covalent approach via surfactant polymerization; 3) and hydrophobic approach via cholesterol insertion into the bilayer. Layer-by-layer coating has been used to overcoat CTAB-capped nanorods with both negatively and positively charged polyelectrolytes. Compared to CTAB-capped nanorods, polyelectrolyte-coated gold nanorods showed improved stability against aggregation in culture medium and enhanced biocompatibility to cultured cells. The toxicity of CTAB-capped gold nanorod solutions was assigned quantitatively to free CTAB molecules, where gold nanorods themselves were found not toxic. Similar biocompatibility profiles for both cationic and anionic coated-gold nanorods were observed due to spontaneous protein adsorption. In growth media, all examined nanorods were covered with protein corona and thus bear similar negative effective surface charge explaining their similar toxicity profiles. ! """! ! Our covalent approach to stabilize the surfactant bilayer on the surface of gold nanorods relies on synthesizing a polymerizable version of the CTAB, which we have used to prepare gold nanoparticles (both spheres and rods). Surfactant polymerization on the surface of gold nanoparticles was found to retard surfactant desorption and thus enhance both stability against aggregation and biocombatibility of these nanomaterials. The hydrophobic approach to stabilize the CTAB bilayer on gold nanorods relies on using a bilayer-condensing agent such as cholesterol to increase the total hydrophobic interactions. Cholesterol is known to consist of up to 50% of mammalian cell membrane0́9s total lipids, and thus have important effect on their stability and physical properties. Using cholesterol-rich growth medium, we have prepared gold nanorods with excellent size and shape distribution. The prepared gold nanorods in the presence of cholesterol have a significantly higher surface charge and exhibit superior stability against aggregation compared to the nanorods prepared without cholesterol. In addition to the enhanced aqueous stability and biocompatibility, stabilization the CTAB bilayer on the surface of gold nanorods have allowed for suspension gold nanorods in organic solvents without aggregation. Polyelectrolyte-coated gold nanorods showed remarkable stability in polar organic solvents against aggregation as compared to CTAB-capped nanorods. The suspendability of coated-gold nanorods in polar organic solvents facilitates the incorporation of these nanomaterials into hydrophobic polymers and thus fabrication of thin films that contain uniform gold nanorod dispersions (nanocomposites).
Surface Patterning of Polymer-functionalized Gold Nanoparticles
Author: Linye ChenPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Polymer patterning on nanoparticles has been recently achieved on polymer-grafted nanoparticles, opening doors to more advanced nanofabrication and self-assembly. However, patchy nanoparticles are mostly prepared using homopolymers under unfavorable solvent. Fabrication conditions and tendency to aggregate at high concentrations limit their throughput and potential utilization. This thesis aims to improve the long-term stability of patchy nanoparticles by using block copolymers as well as mixed polymer brushes. A block copolymer, polystyrene-b- poly(4-vinylbenzoic acid) (PS-b-P4VBA), was used to produce patchy nanocubes. It was that found not only could patchy nanocubes be obtained using PS-b-P4VBA, but also the aggregation of patchy nanoparticles was largely prevented by the P4VBA outer block. Alternatively, mixed polymer brushes of polystyrene and polyethylene glycol were employed to produce patchy nanorods. Due to their microphase separation, gold nanorods carrying helical patches were successfully obtained at certain grafting ratios between the two polymers, even in a good solvent environment.
Surface Engineering of Gold Nanoparticles and Their Applications
Author: Qiu DaiPublisher:
ISBN:
Category : Gold
Languages : en
Pages : 168
Book Description
Gold nanoparticles (AuNPs) with their unique sizes, shapes, and properties have generated much enthusiasm over the last two decades, and have been explored for many potential applications. The successful application of AuNPs depends critically on the ability to modify and functionalize their surface to provide stability, compatibility, and special chemical functionality. This dissertation is aimed at exploring the chemical synthesis and surface modification of AuNPs with the effort to (1) control the number of functional groups on the particle surface, and to (2) increase the colloidal stability at the physiological conditions. To control the functionality on the particle surface, a solid phase place exchange reaction strategy was developed to synthesize the 2 nm AuNPs with a single carboxylic acid group attached on the particle surface. Such monofunctional AuNPs can be treated and used as molecular nanobuilding blocks to form more complex nanomaterials with controllable structures. A "necklace"--Like AuNP/polymer assembly was obtained by conjugating covalently the monofunctional AuNPs with polylysine template, and exhibited an enhanced optical limiting property due to strong electromagnetic interaction between the nanoparticles in close proximity. To improve the colloidal stability in the psychological condition, biocompatible polymers, polyacrylic acid (PAA), and polyethylene glycol (PEG) were used to surface modify the 30 nm citrate-stabilized AuNPs. These polymer-modified AuNPs are able to disperse individually in the high ionic strength solution, and offer as the promising optical probes for bioassay applications. The Prostate specific antigen (PSA) and target DNA can be detected in the low pM range by taking advantages of the large scattering cross section of AuNPs and the high sensitivity of dynamic light scattering (DLS) measurement. In addition to the large scattering cross section, AuNPs can absorb strongly the photon energy at the surface plasmon resonance wavelength and then transform efficiently to the heat energy. The efficient photon-thermal energy conversion property of AuNPs has been used to thermal ablate the A[beta] peptide aggregates under laser irradiation toward Alzheimer's disease therapy.