The diffraction barrier responsible for a finite focal spot size and limited resolution in far-field fluorescence microscopy has been fundamentally broken. This is accomplished by quenching excited organic molecules at the rim of through stimulated emission. Along optic axis, was reduced up to 6 times beyond barrier. simultaneous 2-fold improvement radial direction rendered nearly spherical with diameter 90–110 nm. volume down 0.67 attoliters 18 smaller than that confocal microscopy, thus...

The radiative and nonradiative decay rates of lissamine dye molecules, chemically attached to differently sized gold nanoparticles, are investigated by means time-resolved fluorescence experiments. A pronounced quenching is observed already for the smallest nanoparticles $1\text{ }\text{ }\mathrm{n}\mathrm{m}$ radius. caused not only an increased rate but, equally important, a drastic decrease in dye's rate. Assuming resonant energy transfer be responsible channel, we compare our...

We overcame the resolution limit of scanning far-field fluorescence microscopy by disabling from outer part focal spot. Whereas a near-UV pulse generates diffraction-limited distribution excited molecules, spatially offset quenches molecules focus through stimulated emission. This results in subdiffraction-sized effective point-spread function. For 1.4 aperture and 388-nm excitation wavelength spatial is increased 150 +/- 8 nm to 106 with single beam. Superior lateral demonstrated separation...

Using a near-field optical antenna effect, we measure the homogeneous line shape of surface-plasmon resonance in single gold nanoparticles. The dephasing times extracted from spectra individual particles vary around 8 fs. This mean value agrees with calculations based on Mie theory, which neglect surface effects. Deviations this are interpreted as being due to variations local nanoenvironment. We also observe double-peaked shapes caused by electromagnetic coupling between close-lying particles.

The fluorescence quantum yield of Cy5 molecules attached to gold nanoparticles via ssDNA spacers is measured for Cy5-nanoparticle distances between 2 and 16 nm. Different numbers per nanoparticle allow fine-tune the distance. change radiative nonradiative molecular decay rates with distance determined using time-resolved photoluminescence spectroscopy. Remarkably, dependent efficiency almost exclusively governed by rate.

We report on the state-of-the art synthesis and improved luminescence properties of thiol-capped CdTe nanocrystals (NCs) synthesized in water. The optimized pH (12) molar ratio thiol to Cd ions (1.3:1) increases room-temperature photoluminescence quantum efficiency as-synthesized NCs capped by thioglycolic acid (TGA) values 40−60%. By employing mercaptopropionic (MPA) as a stabilizer, we have large (up 6.0 nm diameter) so that spectral range NCs' emission currently available within this...

A method for biomolecular recognition is reported using light scattering of a single gold nanoparticle functionalized with biotin. Addition streptavidin and subsequent specific binding events alter the dielectric environment nanoparticle, resulting in spectral shift particle plasmon resonance. As we use nanoparticles showing homogeneous spectrum, shifts as small 2 meV can be detected.

We show that plasmonic nanoresonators composed of two gold nanoparticles change not only the intensity but also spectral shape emission fluorescent molecules. The resonance frequency can be tuned by varying distance between nanoparticles, which allows us to selectively favor transitions a molecule specific vibrational ground state. Experimental data from correlated scattering and fluorescence microscopy agree well with calculations in framework generalized Mie theory. Our results widely used...

Light emission at the particle plasmon frequency is observed in optically excited spherical gold nanoparticles. We find a photoluminescence efficiency of ${10}^{\ensuremath{-}6}$, which essentially independent size and four orders magnitude higher than efficiencies determined from metal films. Our experimental findings are explained with process $d$-band holes recombine nonradiatively $\mathit{sp}$ electrons, emitting plasmons. These plasmons subsequently radiate, giving rise to experiment....

Gold nanostars provide high sensitivity for single nanoparticle label-free biosensing. The present multiple plasmon resonances of which the lower energy ones, corresponding to nanostar tips and core−tip interactions, are most sensitive environmental changes. Streptavidin molecules detected upon binding individual, biotin-modified gold by spectral shifts in resonances. Concentrations as low 0.1 nM produce a shift tip related about 2.3 nm (5.3 meV).

We observe an enhancement of fluorescence from a single fluorescent sphere, which is sandwiched between two individual gold nanoparticles, forming hot spot strong field enhancement. The enhancing custom-designed by the deliberate assembly nanoparticles with atomic force microscope cantilever. intensity monitored while separation reduced gradually pushing closer to sphere. maximal when distance smallest, excitation polarization parallel axis sandwich, and sphere positioned exactly on...

We propose a cascaded energy transfer structure made of semiconductor nanocrystals. Funnel-like band gap profiles are realized applying layer-by-layer assembly to CdTe nanocrystals distinct sizes. Optical excitations efficiently along the gradient and finally captured by largest The photoluminescence yield from center layer is surprisingly high. stepwise passing on excitation avoids hot carriers, funnel recycles otherwise trapped lost electron−hole pairs.

We report on the generation of various hole-centered beams in focal region a lens and investigate their effectiveness to break diffraction barrier fluorescence microscopy by stimulated emission. Patterning phase stimulating beam across entrance pupil objective produces point-spread-functions with twofold, fourfold, circular symmetry, which narrow down spot 65-100 nm. Comparison high-resolution confocal images exhibits resolution much beyond barrier. Particles that are only 65-nm apart...

Molecular sensors based on scattering spectroscopy of single gold nanoparticles can be improved three-fold by the use nanoshells instead solid nanoparticles. The particle plasmon resonance responds more sensitively to changes in environment, biological spectral window is accessible, and spectra show sharper resonances. In particular, we focus our discussion narrow homogeneous line width only 180 meV.

The synthesis and characterization of two bright white-light-emitting semiconductor nanocrystal (NC)-based systems is reported. CdS NCs emit white light because the presence surface states over entire range visible spectrum, whereas CdSe/ZnS/CdSe/ZnS core/shell/shell/shell are designed to as a result combination blue orange emissions from shell core, respectively (see figure).

Förster (or fluorescence) resonant energy transfer (FRET) is a powerful spectroscopic technique to study interactions, conformational and distance changes, in hybrid nanosystems. Semiconductor nanocrystals, also known as colloidal quantum dots, are highly efficient fluorophores with strong band-gap luminescence tuneable by size result of the confinement effect. Starting from short summary on FRET formalism basic properties semiconductor this Feature Article provides an overview major classes...

We report the first homogeneous sandwich immunoassay with gold nanoparticles (AuNPs) as fluorescence quenchers. The assay is designed for detection of protein cardiac troponin T (cTnT) by its simultaneous interaction two different antibodies, one attached to AuNPs and other labeled fluorescent dyes. demonstrate working principle using time-resolved spectroscopy, we determine quenching efficiency nanoparticles. In spite relatively large separation distance between dye molecules AuNPs, ranging...

Different types of Binary Nanoparticle Superlattices (BNSLs) have been self-assembled from monodisperse 8.7 nm CdSe and 5.5 Au nanocrystals. Fluorescence spectroscopy studies AlB2-type BNSL nanocrystals revealed considerably decreased fluorescence a shortened lifetime the NCs in BNSLs compared to CdSe-only sample.

A concept to electrically control the scattering of light is introduced. The idea embed noble metal nanoparticles in an electro-optical material such as a liquid crystal order induce spectral shift particle plasmon resonance by applying electric field. Light experiments on single gold show that spherically shaped become optically spheroidal when covered anisotropic crystal. two resonances can be spectrally shifted up 50 meV fields more than 10 kV/cm are applied.

Two-photon direct laser writing (DLW) lithography is limited in the achievable structure size as well resolution. Adding stimulated emission depletion (STED) to DLW allowed overcoming both restrictions. We now push new limits. Using visible light for two-photon (780 nm) and STED (532 nm), we obtain lateral sizes of 55 nm, a Sparrow limit around 100 nm present two clearly separated lines spaced only 120 apart. The photo-resist used these experiments mixture tri- tetra-acrylates...

In traditional DNA melting assays, the temperature of DNA-containing solution is slowly ramped up. contrast, we use 300 ns laser pulses to rapidly heat bound gold nanoparticle aggregates. We show that double-stranded melts on a microsecond time scale leads disintegration aggregates millisecond scale. A perfectly matching and point-mutated sequence can be clearly distinguished in less than one even 1:1 mixture both targets.

We report on efficient resonant energy transfer in bilayers of water-soluble CdTe quantum dots. The nanocrystals two different sizes capped by short-chain thiols were formed layer-by-layer assembly. Temporally and spectrally resolved fluorescence spectroscopy reveals spectral diffusion the signal for dots within one layer as well rapid (254 ps) from layers small to larger dots, which is fast nanocrystal pairs. Subspecies inhomogeneous distribution donor even show rates (134 ps)−1 due a large...

The race toward engineering metamaterials comprising of negative refractive indexes in the optical range started with realization negative-index materials for gigahertz frequencies six years ago. Sheer miniaturization resonant structures is one approach. Alternative designs make use localized plasmon metal nanoparticles or nanoholes films. Following this approach, a index has been realized very recently. We review these recent results and summarize how to unambiguously retrieve effective...