Browsing by Subject "Metal Nanoparticles"
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Item Open Access Connecting the nanodots: programmable nanofabrication of fused metal shapes on DNA templates.(Nano letters, 2011-08) Pilo-Pais, M; Goldberg, S; Samano, E; Labean, TH; Finkelstein, GWe present a novel method for producing complex metallic nanostructures of programmable design. DNA origami templates, modified to have DNA binding sites with a uniquely coded sequence, were adsorbed onto silicon dioxide substrates. Gold nanoparticles functionalized with the cDNA sequence were then attached. These seed nanoparticles were later enlarged, and even fused, by electroless deposition of silver. Using this method, we constructed a variety of metallic structures, including rings, pairs of bars, and H shapes.Item Open Access Deposition of silver nanoparticles in geochemically heterogeneous porous media: predicting affinity from surface composition analysis.(2011) Lin, ShihongThe transport of uncoated silver nanoparticles (AgNPs) in a porous medium composed of silica glass beads modified with a partial coverage of iron oxide (hematite) was studied and compared to that in a porous medium composed of unmodified glass beads (GB). At a pH lower than the point of zero charge (PZC) of hematite, the affinity of AgNPs for a hematite-coated glass bead (FeO-GB) surface was significantly higher than that for an uncoated surface. There was a linear correlation between the average nanoparticle affinity for media composed of mixtures of FeO-GB and GB collectors and the relative composition of those media as quantified by the attachment efficiency over a range of mixing mass ratios of the two types of collectors, so that the average AgNPs affinity for these media is readily predicted from the mass (or surface) weighted average of affinities for each of the surface types. X-ray photoelectron spectroscopy (XPS) was used to quantify the composition of the collector surface as a basis for predicting the affinity between the nanoparticles for a heterogeneous collector surface. A correlation was also observed between the local abundances of AgNPs and FeO on the collector surface.Item Open Access Emerging contaminant or an old toxin in disguise? Silver nanoparticle impacts on ecosystems.(Environ Sci Technol, 2014-05-06) Colman, Benjamin P; Espinasse, Benjamin; Richardson, Curtis J; Matson, Cole W; Lowry, Gregory V; Hunt, Dana E; Wiesner, Mark R; Bernhardt, Emily SThe use of antimicrobial silver nanoparticles (AgNPs) in consumer-products is rising. Much of these AgNPs are expected to enter the wastewater stream, with up to 10% of that eventually released as effluent into aquatic ecosystems with unknown ecological consequences. We examined AgNP impacts on aquatic ecosystems by comparing the effects of two AgNP sizes (12 and 49 nm) to ionic silver (Ag(+); added as AgNO3), a historically problematic contaminant with known impacts. Using 19 wetland mesocosms, we added Ag to the 360 L aquatic compartment to reach 2.5 mg Ag L(-1). Silver treatments and two coating controls were done in triplicate, and compared to four replicate controls. All three silver treatments were toxic to aquatic plants, leading to a significant release of dissolved organic carbon and chloride following exposure. Simultaneously, dissolved methane concentrations increased forty-fold relative to controls in all three Ag treatments. Despite dramatic toxicity differences observed in lab studies for these three forms of Ag, our results show surprising convergence in the direction, magnitude, and duration of ecosystem-scale impacts for all Ag treatments. Our results suggest that all forms of Ag changed solute chemistry driving transformations of Ag which then altered Ag impacts.Item Open Access Gold nanoparticles on polarizable surfaces as Raman scattering antennas.(ACS Nano, 2010-11-23) Chen, Shiuan-Yeh; Mock, Jack J; Hill, Ryan T; Chilkoti, Ashutosh; Smith, David R; Lazarides, Anne ASurface plasmons supported by metal nanoparticles are perturbed by coupling to a surface that is polarizable. Coupling results in enhancement of near fields and may increase the scattering efficiency of radiative modes. In this study, we investigate the Rayleigh and Raman scattering properties of gold nanoparticles functionalized with cyanine deposited on silicon and quartz wafers and on gold thin films. Dark-field scattering images display red shifting of the gold nanoparticle plasmon resonance and doughnut-shaped scattering patterns when particles are deposited on silicon or on a gold film. The imaged radiation patterns and individual particle spectra reveal that the polarizable substrates control both the orientation and brightness of the radiative modes. Comparison with simulation indicates that, in a particle-surface system with a fixed junction width, plasmon band shifts are controlled quantitatively by the permittivity of the wafer or the film. Surface-enhanced resonance Raman scattering (SERRS) spectra and images are collected from cyanine on particles on gold films. SERRS images of the particles on gold films are doughnut-shaped as are their Rayleigh images, indicating that the SERRS is controlled by the polarization of plasmons in the antenna nanostructures. Near-field enhancement and radiative efficiency of the antenna are sufficient to enable Raman scattering cyanines to function as gap field probes. Through collective interpretation of individual particle Rayleigh spectra and spectral simulations, the geometric basis for small observed variations in the wavelength and intensity of plasmon resonant scattering from individual antenna on the three surfaces is explained.Item Open Access Inkless microcontact printing on SAMs of Boc- and TBS-protected thiols.(Nano Lett, 2010-01) Shestopalov, Alexander A; Clark, Robert L; Toone, Eric JWe report a new inkless catalytic muCP technique that achieves accurate, fast, and complete pattern reproduction on SAMs of Boc- and TBS-protected thiols immobilized on gold using a polyurethane-acrylate stamp functionalized with covalently bound sulfonic acids. Pattern transfer is complete at room temperature just after one minute of contact and renders sub-200 nm size structures of chemically differentiated SAMs.Item Open Access Low concentrations of silver nanoparticles in biosolids cause adverse ecosystem responses under realistic field scenario.(PLoS One, 2013) Colman, Benjamin P; Arnaout, Christina L; Anciaux, Sarah; Gunsch, Claudia K; Hochella, Michael F; Kim, Bojeong; Lowry, Gregory V; McGill, Bonnie M; Reinsch, Brian C; Richardson, Curtis J; Unrine, Jason M; Wright, Justin P; Yin, Liyan; Bernhardt, Emily SA large fraction of engineered nanomaterials in consumer and commercial products will reach natural ecosystems. To date, research on the biological impacts of environmental nanomaterial exposures has largely focused on high-concentration exposures in mechanistic lab studies with single strains of model organisms. These results are difficult to extrapolate to ecosystems, where exposures will likely be at low-concentrations and which are inhabited by a diversity of organisms. Here we show adverse responses of plants and microorganisms in a replicated long-term terrestrial mesocosm field experiment following a single low dose of silver nanoparticles (0.14 mg Ag kg(-1) soil) applied via a likely route of exposure, sewage biosolid application. While total aboveground plant biomass did not differ between treatments receiving biosolids, one plant species, Microstegium vimeneum, had 32 % less biomass in the Slurry+AgNP treatment relative to the Slurry only treatment. Microorganisms were also affected by AgNP treatment, which gave a significantly different community composition of bacteria in the Slurry+AgNPs as opposed to the Slurry treatment one day after addition as analyzed by T-RFLP analysis of 16S-rRNA genes. After eight days, N2O flux was 4.5 fold higher in the Slurry+AgNPs treatment than the Slurry treatment. After fifty days, community composition and N2O flux of the Slurry+AgNPs treatment converged with the Slurry. However, the soil microbial extracellular enzymes leucine amino peptidase and phosphatase had 52 and 27% lower activities, respectively, while microbial biomass was 35% lower than the Slurry. We also show that the magnitude of these responses was in all cases as large as or larger than the positive control, AgNO3, added at 4-fold the Ag concentration of the silver nanoparticles.Item Open Access Metallic Nanoislands on Graphene as Highly Sensitive Transducers of Mechanical, Biological, and Optical Signals.(Nano Lett, 2016-02-10) Zaretski, Aliaksandr V; Root, Samuel E; Savchenko, Alex; Molokanova, Elena; Printz, Adam D; Jibril, Liban; Arya, Gaurav; Mercola, Mark; Lipomi, Darren JThis article describes an effect based on the wetting transparency of graphene; the morphology of a metallic film (≤20 nm) when deposited on graphene by evaporation depends strongly on the identity of the substrate supporting the graphene. This control permits the formation of a range of geometries, such as tightly packed nanospheres, nanocrystals, and island-like formations with controllable gaps down to 3 nm. These graphene-supported structures can be transferred to any surface and function as ultrasensitive mechanical signal transducers with high sensitivity and range (at least 4 orders of magnitude of strain) for applications in structural health monitoring, electronic skin, measurement of the contractions of cardiomyocytes, and substrates for surface-enhanced Raman scattering (SERS, including on the tips of optical fibers). These composite films can thus be treated as a platform technology for multimodal sensing. Moreover, they are low profile, mechanically robust, semitransparent and have the potential for reproducible manufacturing over large areas.Item Open Access Plasmonic Nanoparticles: Factors Controlling Refractive Index Sensitivity(2007-05-10T15:23:09Z) Miller, Molly McBainPlasmonic nanoparticles support surface plasmon resonances that are sensitive to the environment. Factors contributing to the refractive index sensitivity are explored systematically through simulation, theory, and experiment. Particles small with respect to the wavelength of light and with size parameters much less than 1 have optical properties accurately predicted by quasi-electrostatic theory while particles with larger size parameters necessitate electrodynamics. A theory is developed that captures the effects of geometry on the refractive index sensitivity with a single factor, plasmon band location, and, although based on electrostatic theory, well predicts the sensitivity of particles whose properties are beyond the electrostatic limit. This theory is validated by high quality simulations for compact particles with shape parameters approaching 1 and, therefore, electrodynamic in nature, as well as higher aspect ratio particles that are electrostatic. Experimentally observed optical spectra for nanorods immobilized on glass and subjected to changes in n of the medium are used to calculate the sensitivity of the particles, found to be well matched by a variation on the homogeneous plasmon band theory. The separate electrostatic and electrodynamic components of plasmon band width, are explored and the overall width is found to affect the observability of the aforementioned sensitivity similarly within each particle class. The extent of the sensing volume around a spherical particle is explored and found to vary with particle size for small particles. Through simulation of oriented dielectric layers, it is shown particles are most sensitive to material located in regions of highest field enhancement. Variations on seed-mediated growth of gold nanorods results in spectra exhibiting a middle peak, intermediate to the generally accepted longitudinal and transverse modes. Simulated optical properties and calculated field enhancement illustrates the correlation between geometry and optical properties and allows for identification of the middle peak.Item Open Access Probing the ultimate limits of plasmonic enhancement.(Science, 2012-08-31) Ciracì, C; Hill, RT; Mock, JJ; Urzhumov, Y; Fernández-Domínguez, AI; Maier, SA; Pendry, JB; Chilkoti, A; Smith, DRMetals support surface plasmons at optical wavelengths and have the ability to localize light to subwavelength regions. The field enhancements that occur in these regions set the ultimate limitations on a wide range of nonlinear and quantum optical phenomena. We found that the dominant limiting factor is not the resistive loss of the metal, but rather the intrinsic nonlocality of its dielectric response. A semiclassical model of the electronic response of a metal places strict bounds on the ultimate field enhancement. To demonstrate the accuracy of this model, we studied optical scattering from gold nanoparticles spaced a few angstroms from a gold film. The bounds derived from the models and experiments impose limitations on all nanophotonic systems.Item Open Access Sensitive detection of H2S using gold nanoparticle decorated single-walled carbon nanotubes.(Anal Chem, 2010-01-01) Mubeen, Syed; Zhang, Ting; Chartuprayoon, Nicha; Rheem, Youngwoo; Mulchandani, Ashok; Myung, Nosang V; Deshusses, Marc AHerein, we demonstrate that highly sensitive conductometric gas nanosensors for H(2)S can be synthesized by electrodepositing gold nanoparticles on single-walled carbon nanotube (SWNT) networks. Adjusting the electrodeposition conditions allowed for tuning of the size and number of gold nanoparticles deposited. The best H(2)S sensing performance was obtained with discrete gold nanodeposits rather than continuous nanowires. The gas nanosensors could sense H(2)S in air at room temperature with a 3 ppb limit of detection. The sensors were reversible, and increasing the bias voltage reduced the sensor recovery time, probably by local Joule heating. The sensing mechanism is believed to be based on the modulation of the conduction path across the nanotubes emanating from the modulation of electron exchange between the gold and carbon nanotube defect sites when exposed to H(2)S.Item Open Access Simultaneous Detection of Multiple Tumor-targeted Gold Nanoparticles in HER2-Positive Breast Tumors Using Optoacoustic Imaging.(Radiology. Imaging cancer, 2023-05) Samykutty, Abhilash; Thomas, Karl N; McNally, Molly; Hagood, Jordan; Chiba, Akiko; Thomas, Alexandra; McWilliams, Libby; Behkam, Bahareh; Zhan, Ying; Council-Troche, McAlister; Claros-Sorto, Juan C; Henson, Christina; Garwe, Tabitha; Sarwar, Zoona; Grizzle, William E; McNally, Lacey RPurpose To develop optoacoustic, spectrally distinct, actively targeted gold nanoparticle-based near-infrared probes (trastuzumab [TRA], TRA-Aurelia-1, and TRA-Aurelia-2) that can be individually identifiable at multispectral optoacoustic tomography (MSOT) of human epidermal growth factor receptor 2 (HER2)-positive breast tumors. Materials and Methods Gold nanoparticle-based near-infrared probes (Aurelia-1 and 2) that are optoacoustically active and spectrally distinct for simultaneous MSOT imaging were synthesized and conjugated to TRA to produce TRA-Aurelia-1 and 2. Freshly resected human HER2-positive (n = 6) and HER2-negative (n = 6) triple-negative breast cancer tumors were treated with TRA-Aurelia-1 and TRA-Aurelia-2 for 2 hours and imaged with MSOT. HER2-expressing DY36T2Q cells and HER2-negative MDA-MB-231 cells were implanted orthotopically into mice (n = 5). MSOT imaging was performed 6 hours following the injection, and the Friedman test was used for analysis. Results TRA-Aurelia-1 (absorption peak, 780 nm) and TRA-Aurelia-2 (absorption peak, 720 nm) were spectrally distinct. HER2-positive human breast tumors exhibited a significant increase in optoacoustic signal following TRA-Aurelia-1 (28.8-fold) or 2 (29.5-fold) (P = .002) treatment relative to HER2-negative tumors. Treatment with TRA-Aurelia-1 and 2 increased optoacoustic signals in DY36T2Q tumors relative to those in MDA-MB-231 controls (14.8-fold, P < .001; 20.8-fold, P < .001, respectively). Conclusion The study demonstrates that TRA-Aurelia 1 and 2 nanoparticles operate as a spectrally distinct HER2 breast tumor-targeted in vivo optoacoustic agent. Keywords: Molecular Imaging, Nanoparticles, Photoacoustic Imaging, Breast Cancer Supplemental material is available for this article. © RSNA, 2023.Item Open Access Surface-enhanced Raman scattering plasmonic enhancement using DNA origami-based complex metallic nanostructures.(Nano letters, 2014-01) Pilo-Pais, M; Watson, A; Demers, S; LaBean, TH; Finkelstein, GDNA origami is a novel self-assembly technique allowing one to form various two-dimensional shapes and position matter with nanometer accuracy. We use DNA origami templates to engineer surface-enhanced Raman scattering substrates. Specifically, gold nanoparticles were selectively placed on the corners of rectangular origami and subsequently enlarged via solution-based metal deposition. The resulting assemblies exhibit "hot spots" of enhanced electromagnetic field between the nanoparticles. We observed a significant Raman signal enhancement from molecules covalently attached to the assemblies, as compared to control nanoparticle samples that lack interparticle hot spots. Furthermore, Raman molecules are used to map out the hot spots' distribution, as they are burned when experiencing a threshold electric field. Our method opens up the prospects of using DNA origami to rationally engineer and assemble plasmonic structures for molecular spectroscopy.