Fabrication of Inert Silver Nanoparticles with a Thin Silica Coating

Abstract

The role of Lorentz invariance as a fundamental symmetry of nature has been lately reconsidered in different approaches to quantum gravity. It is thus natural to study whether other puzzles of physics may be solved within these proposals. This may be the case for the cosmological constant problem. Indeed, it has been shown that breaking Lorentz invariance provides Lagrangians that can drive the current acceleration of the universe without experiencing large corrections from ultraviolet physics. In this work, we focus on the simplest model of this type, called ΘCDM, and study its cosmological implications in detail. At the background level, this model cannot be distinguished from ΛCDM. The differences appear at the level of perturbations. We show that in ΘCDM, the spectrum of CMB anisotropies and matter fluctuations may be affected by a rescaling of the gravitational constant in the Poisson equation, by the presence of extra contributions to the anisotropic stress, and finally by the existence of extra clustering degrees of freedom. To explore these modifications accurately, we modify the Boltzmann code class. We then use the parameter inference code Monte Python to confront ΘCDM with data from WMAP-7, SPT and WiggleZ. We obtain strong bounds on the parameters accounting for deviations from ΛCDM. In particular, we find that the discrepancy between the gravitational constants appearing in the Poisson and Friedmann equations is constrained at the level of 1.8%.

Fast and facile synthesis of silica coated silver nanoparticles by microwave irradiation

“…Ag@SiO 2 nanoparticle with silica layer (3-5 nm), smaller than that of the core size, enhances the electric field around Ag nanoparticles. These nanoparticles can be used as UV lasing materials in the near UV region [45]. Additional advantages of MW method include reduction of reaction time from few hours or a day to 2 min, formation of monodispersed Ag@SiO 2 nanoparticles with uniform silica shell thickness and without core-free silica or silica shell free core nanoparticles, wide range of tuning of silica thickness (3-80 nm).…”

Optimally designed nanolayered metal-dielectric particles as probes for massively multiplexed and ultrasensitive molecular assays

“…Thicker metal shells result in higher fields (larger EE) but smaller dielectric volumes (lower reporter loading) and higher metal absorption losses. The ultimate constraints on shell sizes, further, are determined by common fabrication limits of nanostructures (39,40). The problem of determining enhancement for any LAMP structure is, thus, bounded.…”

Sculpting the Analytical Volume in and around Nanoparticle Sensors Using a Multilayer Geometry

“…The details of the GA-based approach for optimization of enhancements are discussed earlier . The constraints on the thickness are imposed according to the recent experimental implementations of such geometries. − A minimal thickness constraint of 1 nm is imposed for the silica layers, and a minimal thickness constraint of 2 nm is imposed for the metal layers according to the current fabrication limits. , Similarly a size constraint of 10 nm is imposed for metal and silica cores. These values reflect commonly encountered limits of fabrication.…”

“…39−41 A minimal thickness constraint of 1 nm is imposed for the silica layers, and a minimal thickness constraint of 2 nm is imposed for the metal layers according to the current fabrication limits. 42,43 Similarly a size constraint of 10 nm is imposed for metal and silica cores. These values reflect commonly encountered limits of fabrication.…”