Gold nanorods were synthesized by the colloidal seed-mediated, surfactant-assisted approach Gou et al., Chem. Mater. 2005, 17, 3668−3672 using CTAB (hexadecylcetyltrimethylammonium bromide) obtained ...from ten different suppliers. The yield of gold nanorods depended strongly on the CTAB used: with the same recipe, three of the CTABs did not yield nanorods and produced only spherical gold particles, whereas the other CTABs yielded nanorods with nearly 100% yield. These results suggest that an impurity in the CTAB is very important for nanorod formation.
We demonstrate the use of gold nanorods as bright contrast agents for two-photon luminescence (TPL) imaging of cancer cells in a three-dimensional tissue phantom down to 75 μm deep. The TPL intensity ...from gold-nanorod-labeled cancer cells is 3 orders of magnitude brighter than the two-photon autofluorescence (TPAF) emission intensity from unlabeled cancer cells at 760 nm excitation light. Their strong signal, resistance to photobleaching, chemical stability, ease of synthesis, simplicity of conjugation chemistry, and biocompatibility make gold nanorods an attractive contrast agent for two-photon imaging of epithelial cancer.
Background. New hepatitis C virus (HCV) treatments deliver higher cure rates with fewer contraindications, increasing demand for treatment and healthcare costs. The cost-effectiveness of new ...treatments is unknown. Methods. We conducted a microsimulation of guideline testing followed by alternative treatment regimens for HCV among the US population aged 20 and older to estimate cases identified, treated, sustained viral response, deaths, medical costs, quality-adjusted life-years (QALYs), and the incremental cost-effectiveness ratio (ICER) of different treatment options expressed as discounted lifetime costs and benefits from the healthcare perspective. Results. Compared to treatment with pegylated interferon and ribavirin (PR), and a protease inhibitor for HCV genotype (G) 1 and PR alone for G2/3, treatment with PR and Sofosbuvir (PRS) for G1/4 and treatment with Sofosbuvir and ribavirin (SR) for G2/3 increased QALYs by 555 226, reduced deaths by 80 682, and increased costs by $26.2 billion at an ICER of $47 304 per QALY gained. As compared to PRS/SR, treating with an all oral regimen of Sofosbuvir and Simeprevir (SS) for G1/4 and SR for G2/3, increased QALYs by 1 110 451 and reduced deaths by an additional 164 540 at an incremental cost of $80.1 billion and an ICER of $72 169. In sensitivity analysis, where treatment with SS effectiveness was set to the list price of Viekira Pak and then Harvoni, treatment cost $24 921 and $25 405 per QALY gained as compared to PRS/SR. Conclusions. New treatments are cost-effectiveness per person treated, but pent-up demand for treatment may create challenges for financing.
The gold nanocrystal seed-mediated approach using cetyltrimethylammonium bromide (CTAB) as a stabilizing surfactant is commonly used to make large quantities of monodisperse gold nanorods. This ...method, however, has been at times difficult to reproduce in different laboratories. We recently showed Smith, D. K.; Korgel, B. A. Langmuir 2008, 24, 644−649 that a very low concentration impurity in CTAB obtained from some suppliers prevents nanorod growth but were not able to identify the impurity. Here, we report that the impurity is iodide. Inductively coupled plasma mass spectroscopy (ICP-MS) revealed that iodide concentrations vary in CTAB from different suppliers, from less than 2.75 ppm up to 840 ppm. When CTAB with iodide concentrations greater than 50 ppm is used, nanorods do not form and the product consists entirely of spherical nanocrystals. Iodide slows the reduction of Au(III) to Au0. Iodide adsorption on Au {111} surfaces inhibits nanorod growth.
We have synthesized alkylselenide reagents to replace the native oleate ligand on PbSe quantum dots (QDs) in order to investigate the effect of surface modification on their stoichiometry, ...photophysics, and air stability. The alkylselenide reagent removes all of the oleate on the QD surface and results in Se addition; however, complete Se enrichment does not occur, achieving a 53% decrease in the amount of excess Pb for 2 nm diameter QDs and a 23% decrease for 10 nm QDs. Our analysis suggests that the Se ligand preferentially binds to the {111} faces, which are more prevalent in smaller QDs. We find that attachment of the alkylselenide ligand to the QD surface enhances oxidative resistance, likely resulting from a more stable bond between surface Pb atoms and the alkylselenide ligand compared to Pb-oleate. However, binding of the alkylselenide ligand produces a separate nonradiative relaxation route that partially quenches PL, suggesting the formation of a dark hole-trap.
We report the synthesis and characterization of composition-tunable ternary lead chalcogenide alloys PbSe x Te1-x , PbS x Te1-x , and PbS x Se1-x . This work explores the relative reaction rates of ...chalcogenide precursors to produce alloyed quantum dots (QDs), and we find the highly reactive bis(trimethylsilyl) (TMS2)-based precursors allow for the homogeneous incorporation of anions. By varying the Pb to oleic acid ratio, we demonstrate size control of similar composition alloys. We find the resulting QDs are Pb-rich but the Pb/anion ratio is size- and composition-dependent in all alloyed QD as well as in PbSe, PbTe, and PbS QDs and is consistent with the reaction rates of the anion precursors. A more reactive anion precursor results in a lower Pb/anion ratio.
Binary superlattices (BSLs) of sterically stabilized, hydrophobic, large (A; 11.5 nm diameter) Fe(2)O(3) and small (B; 6.1 nm diameter) Au nanocrystals were assembled by slow evaporation of colloidal ...dispersions on tilted substrates. A detailed analysis of the BSL structure was carried out using transmission and scanning electron microscopy (TEM and SEM) and grazing incidence small-angle X-ray scattering (GISAXS). The BSLs were simple hexagonal (sh) AB(2) superlattices (isostructural with the compound AlB(2); space group 191, P6/mmm) of large nanocrystals occupying a simple hexagonal lattice with small nanocrystals in the interstitial spaces. SEM and GISAXS confirmed long-range order of the BSLs and GISAXS revealed that the superlattice is slightly contracted (8-12%) perpendicular to the substrate as a result of solvent drying in the deposition process. When the sh-AB(2) superlattice deposits on a (100) plane, this shrinkage occurs in the 210 direction and changes the lattice symmetry to centered orthorhombic. Additionally, nearly periodic superlattice dislocations consisting of inserted half-planes of gold nanocrystals were observed by SEM in some BSLs.
Gold nanoshells (dielectric silica core/gold shell) are a novel class of hybrid metal nanoparticles whose unique optical properties have spawned new applications including more sensitive molecular ...assays and cancer therapy. We report a new photo-physical property of nanoshells (NS) whereby these particles glow brightly when excited by near-infrared light. We characterized the luminescence brightness of NS, comparing to that of gold nanorods (NR) and fluorescent beads (FB). We find that NS are as bright as NR and 140 times brighter than FB. To demonstrate the potential application of this bright two-photon-induced photoluminescence (TPIP) signal for biological imaging, we imaged the 3D distribution of gold nanoshells targeted to murine tumors.
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