Publications (8)30.63 Total impact
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Article: Metallic Nanoantennae and their Use in Organic-Polymer Photovoltaics
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ABSTRACT: The potential of gold nanorods to act as “antennae” in organic photovoltaic devices and improve performance by enhancing the The potential of gold nanorods to act as “antennae” in organic photovoltaic devices and improve performance by enhancing the optical field within the device has been examined. Gold nanorods were blended into the buffer layer of standard poly (3-hexothiopene) optical field within the device has been examined. Gold nanorods were blended into the buffer layer of standard poly (3-hexothiopene) (P3HT): 6, 6-phenyl C61-butyric acid methyl ester (PCBM) photovoltaic cells. Increases in both the broad spectrum absorption (P3HT): 6, 6-phenyl C61-butyric acid methyl ester (PCBM) photovoltaic cells. Increases in both the broad spectrum absorption and device fill factors (as compared to solar cells without nanorods) were observed. A comparison of the internal resistance and device fill factors (as compared to solar cells without nanorods) were observed. A comparison of the internal resistance and absorption allows estimation of what part in the change in performance can be attributed to greater absorption and increases and absorption allows estimation of what part in the change in performance can be attributed to greater absorption and increases in buffer layer conductivity. in buffer layer conductivity. KeywordsOrganic photovoltaics–Gold nanorods–Optical antenna–Light absorption KeywordsOrganic photovoltaics–Gold nanorods–Optical antenna–Light absorptionJournal of Cluster Science 04/2012; 22(1):59-64. · 0.92 Impact Factor -
Article: Polyelectrolyte-coated gold nanorods and their interactions with type I collagen.
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ABSTRACT: Gold nanorods (AuNRs) have unique optical properties for numerous biomedical applications, but the interactions between AuNRs and proteins, particularly those of the extracellular matrix (ECM), are poorly understood. Here the effects of AuNRs on the self-assembly, mechanics, and remodeling of type I collagen gels were examined in vitro. AuNRs were modified with polyelectrolyte multilayers (PEMs) to minimize cytotoxicity, and AuNRs with different terminal polymer chemistries were examined for their interactions with collagen by turbidity assays, rheological tests, and microscopy. Gel contraction assays were used to examine the effects of the PEM-coated AuNRs on cell-mediated collagen remodeling. Polyanion-terminated AuNRs significantly reduced the lag (nucleation) phase of collagen self-assembly and significantly increased the dynamic shear modulus of the polymerized gels, whereas polycation-terminated AuNRs had no effect on the mechanical properties of the collagen. Both polyanion- and polycation-terminated AuNRs significantly inhibited collagen gel contraction by cardiac fibroblasts, and the nanoparticles were localized in intra-, peri-, and extracellular compartments, suggesting that PEM-coated AuNRs influence cell behavior via multiple mechanisms. These results demonstrate the significance of nanoparticle-ECM interactions in determining the bioactivity of nanoparticles.Biomaterials 08/2009; 30(29):5639-48. · 7.40 Impact Factor -
Article: Surface-coverage dependence of surface-enhanced raman scattering from gold nanocubes on self-assembled monolayers of analyte.
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ABSTRACT: Surface enhanced Raman scattering (SERS) spectra of 4-mercaptobenzoic acid (4-MBA) self-assembled monolayers (SAMs) on gold substrates are presented for SAMs onto which gold nanocubes have been electrostaticaly immobilized. In the absence of nanocubes, no SERS signals from 4-MBA SAMs are observed. Upon addition of the gold nanocubes to the SAM, a sandwich architecture is formed, allowing for coupling between the localized surface plasmon of the nanocubes and the surface plasmon of the gold substrate. This creates a large electromagnetic field in the area where the 4-MBA molecules reside, causing the characteristic vibrational modes of 4-MBA to appear. SERS intensities increase linearly with increasing nanocube coverage up to a factor of 7 in the best case studied here, with enhancement factors of up to 10(13).The Journal of Physical Chemistry A 04/2009; 113(16):3973-8. · 2.95 Impact Factor -
Article: Chemical sensing and imaging with metallic nanorods.
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ABSTRACT: In this Feature Article, we examine recent advances in chemical analyte detection and optical imaging applications using gold and silver nanoparticles, with a primary focus on our own work. Noble metal nanoparticles have exciting physical and chemical properties that are entirely different from the bulk. For chemical sensing and imaging, the optical properties of metallic nanoparticles provide a wide range of opportunities, all of which ultimately arise from the collective oscillations of conduction band electrons ("plasmons") in response to external electromagnetic radiation. Nanorods have multiple plasmon bands compared to nanospheres. We identify four optical sensing and imaging modalities for metallic nanoparticles: (1) aggregation-dependent shifts in plasmon frequency; (2) local refractive index-dependent shifts in plasmon frequency; (3) inelastic (surface-enhanced Raman) light scattering; and (4) elastic (Rayleigh) light scattering. The surface chemistry of the nanoparticles must be tunable to create chemical specificity, and is a key requirement for successful sensing and imaging platforms.Chemical Communications 03/2008; · 6.17 Impact Factor -
Article: Using gold nanorods to probe cell-induced collagen deformation.
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ABSTRACT: In biological tissue, complex mechanisms of cellular response are closely linked to the mechanical environment that cells experience. The key to understanding these mechanisms may lie in measurement of local mechanical fields near living cells and between cells. We have developed a novel optical measurement technique which combines the light elastically scattered from gold nanorods with digital image analysis to track local deformations that occur in vitro between cells, in real time, under darkfield optical microscopy. We find that measurable tension and compression exist in the intercellular matrix at the length scale of micrometers, as the cells assess, adapt, and rearrange their environment.Nano Letters 02/2007; 7(1):116-9. · 13.20 Impact Factor -
Article: Glycosaminoglycan-functionalized gold nanorods: interactions with cardiac cells and type I collagen
19(35):6332-6340. -
Article: Gold nanorods: Applications in chemical sensing, biological imaging and effects on 3-dimensional tissue culture
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ABSTRACT: Gold nanoparticles have attracted great interest in the last decade for applications in biochemical detection, imaging, and therapeutics, due to their useful optoelectronic properties. Interest in this area has recently focused on engineering the surface of the nanoparticles, because of the ease in which the charge, functionality, and reactivity of the surface can be altered. This dissertation will focus on the applications of surface-engineered gold nanoparticles in chemical detection and biomedical imaging, and look at the effects surface modified gold nanorods have on the behavior of cardiac fibroblasts in tissue culture. As an alternative to solution-based techniques in Raman spectroscopy, we have found that a sandwich architecture in which a surface assembled monolayer (SAM) of 4-mercaptobenzoic acid (4-MBA) is sandwiched between a 100 nm thick gold substrate and electrostaticaly immobilized gold nanocubes allows for more reproducible data as well as enhancement factors up to 1013. The sandwich architecture creates a large electromagnetic field in the area where the 4-MBA molecules reside causing the characteristic vibrational modes of 4-MBA to appear. We have also moved out of the realm of chemical sensing and have used our gold nanorods as point sensors to monitor the mechanical properties associated with mechanotransduction. Cell behavior in the presence of nanomaterials is typically explored through simple viability assays, but there is mounting evidence that nanomaterials can have more subtle effects on a variety of cell functions. Numerous studies have documented the cellular uptake and cytotoxicity of gold nanoparticles in different cell types, but very little is known about how nanoparticles affect cellular function. We have shown that gold nanorods in a collagen thin film can be used to measure the local mechanical fields near and between living cells as they assess, adapt, and rearrange their environment. We have also found that gold nanorods in 3-D tissue culture interfere with the cardiac fibroblast-mediated remodeling of a collagen tissue construct. We have found several factors associated with the dose dependent decrease in cell-mediated collagen remodeling including the alteration of fibroblast phenotype, adsorption of cellular proteins needed for cell mediated remodeling, as well as a change in the mechanical properties of the tissue construct. The following chapters will detail the use of our gold nanomaterials as both biochemical and imaging agents, and discuss cell behavior in the presence of surface modified gold nanorods. -
Article: Glycosaminoglycan-functionalized gold nanorods: interactions with cardiac cells and type I collagen
Journal of Materials Chemistry. 19(35):6332-6340.
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Institutions
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2007
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University of South Carolina
- Chemistry and Biochemistry
Columbia, SC, USA
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