One of the most rapidly growing areas of physics and nanotechnology focuses on plasmonic effects on the nanometre scale, with possible applications ranging from sensing and biomedicine to imaging and information technology. However, the full development of nanoplasmonics is hindered by the lack of devices that can generate coherent plasmonic fields. It has been proposed that in the same way as a laser generates stimulated emission of coherent photons, a 'spaser' could generate stimulated emission of surface plasmons (oscillations of free electrons in metallic nanostructures) in resonating metallic nanostructures adjacent to a gain medium. But attempts to realize a spaser face the challenge of absorption loss in metal, which is particularly strong at optical frequencies. The suggestion to compensate loss by optical gain in localized and propagating surface plasmons has been implemented recently and even allowed the amplification of propagating surface plasmons in open paths. Still, these experiments and the reported enhancement of the stimulated emission of dye molecules in the presence of metallic nanoparticles lack the feedback mechanism present in a spaser. Here we show that 44-nm-diameter nanoparticles with a gold core and dye-doped silica shell allow us to completely overcome the loss of localized surface plasmons by gain and realize a spaser. And in accord with the notion that only surface plasmon resonances are capable of squeezing optical frequency oscillations into a nanoscopic cavity to enable a true nanolaser, we show that outcoupling of surface plasmon oscillations to photonic modes at a wavelength of 531 nm makes our system the smallest nanolaser reported to date-and to our knowledge the first operating at visible wavelengths. We anticipate that now it has been realized experimentally, the spaser will advance our fundamental understanding of nanoplasmonics and the development of practical applications.

We present an investigation into incorporating core-shell Au-SiO(2) nanoparticles into dye-sensitized solar cells. We demonstrate plasmon-enhanced light absorption, photocurrent, and efficiency for both iodide/triiodide electrolyte based and solid-state dye-sensitized solar cells. Our spectroscopic investigation indicates that plasmon-enhanced photocarrier generation competes well with plasmons oscillation damping with in the first tens of femtoseconds following light absorption.

Mesoporous nanomaterials have attracted widespread interest because of their structural versatility for applications including catalysis, separation, and nanomedicine. We report a one-pot synthesis method for a class of mesoporous silica nanoparticles (MSNs) containing both cubic and hexagonally structured compartments within one particle. These multicompartment MSNs (mc-MSNs) consist of a core with cage-like cubic mesoporous morphology and up to four branches with hexagonally packed cylindrical mesopores epitaxially growing out of the cubic core vertices. The extent of cylindrical mesostructure growth can be controlled via a single additive in the synthesis. Results suggest a path toward high levels of architectural complexity in locally amorphous, mesostructured nanoparticles, which could enable tuning of different pore environments of the same particle for specific chemistries in catalysis or drug delivery.

Mesoporous silica with cubic symmetry has attracted interest from researchers for some times. Here we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, e.g. for co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously uptaken by cells as demonstrated by fluorescence microscopy.Significant research efforts in recent years have been devoted to the development of nanoparticles for applications in biomedical imaging, sensing and drug delivery.1 -4 Nanoparticle architecture and composition are key to the achievable property profiles. Silica is one of the most studied nanoparticle matrix materials due to low toxicity, versatile bulk and surface chemistry and biocompatibility.5 -9 Ordered mesoporous silica in particular has attracted considerable interest due to its ability to reversibly load other compounds. It provides high surface area and large pore volume, necessary in sorption and catalysis applications, while maintaining the intrinsic properties of silica.10 , 11 Mesoporous siliceous materials with three-dimensional pore systems, such as MCM-48, provide advantages in diffusion and transport over one-dimensional channel systems such as in MCM-41-type materials.6 , 11 , 12Among several three-dimensional mesoporous structures reported, mesoporous silica with cubic Pm3n symmetry and possessing a cage-type structure that is three-dimensionally interconnected with small open windows is a promising material, e.g. as carrier for biologically active molecules.12 , 13 Compared to cubic MCM-48 materials only a few studies report on Pm3n -type silica.14 -18 Recently, amine functionalized Pm3n mesoporous ubw1@cornell.edu. Supporting Information Available: Detailed experimental methods, characterizations, and fluorescent imaging procedure. This method is available free of charge via the Internet at http://pubs.acs.org. Herein, we report the room temperature synthesis of discrete, faceted Pm3n highly aminated mesoporous silica nanoparticles (NH 2 -MSNs), from 54 mol % APTES. To our surprise, the synthesis protocol is quite robust allowing the co-condensation of other functional moieties in the same synthesis, e.g. organic dyes, without appreciable loss of structure control. We further demonstrate that the addition of pore expander 1,3,5-trimethylbenzene (TMB) to the synthesis increases pore size from 2.7 to 5 nm while decreasing overall particle size. Rendering these highly aminated, pore-expanded particles fluorescent by co-condensing organic dyes into the particles reduces particle size even further, down to about 100 nm, th...