Ultrasensitive detection of local acoustic vibrations at room temperature by plasmon-enhanced single-molecule fluorescence.

Sensitive detection of local acoustic vibrations at the nanometer scale has promising potential applications involving miniaturized devices in many areas, such as geological exploration, military reconnaissance, and ultrasound imaging. However, sensitive detection of weak acoustic signals with high spatial resolution at room temperature has become a major challenge. Here, we report a nanometer-scale system for acoustic detection with a single molecule as a probe based on minute variations of its distance to the surface of a plasmonic gold nanorod.

Single-molecule fluorescence enhancement of a near-infrared dye by gold nanorods using DNA transient binding.

Fluorescence enhancement by plasmonic nanostructures enables the optical detection of single molecules with weak fluorescence, extending the scope of molecular fluorescence imaging to new materials and systems. In this work, we study single-molecule fluorescence enhancement by individual gold nanorods exploiting a DNA-based transient binding technique. Single molecules are attached to short DNA oligomers that can reversibly hybridize to their complementary docking DNA strands immobilized on the surface of gold nanorods or the glass substrate next to gold nanorods.

Intersystem crossing rates of single perylene molecules in ortho-dichlorobenzene.

Triplet states can be interesting for optical switching of molecular fluorescence as well as quantum experiments relying on the manipulation of spin states. However, the ground state of molecules is usually a singlet state. It is therefore interesting to study the intersystem crossing (ISC) rates between singlet and triplet states.

In situ tuning of gold nanorod plasmon through oxidative cyanide etching.

Single gold nanorods exhibit great opportunities for bio-sensing, enhanced spectroscopies and photothermal therapy. A key property of these particles is the surface plasmon resonance, that is strongly dependent on their shape. Methods for tuning this resonance after the synthesis of the particles are of great interest for many applications.

Spectroscopy of Single Dibenzoterrylene Molecules in para-Dichlorobenzene.

We study single dibenzoterrylene (DBT) molecules embedded in 1,4-dichlorobenzene (para-dichlorobenzene, pDCB) at 1.2 K. Due to the relatively low melting point of pDCB (53 °C), this host-guest system can be easily prepared from the molten phase.

Temperature-cycle microscopy reveals single-molecule conformational heterogeneity.

Our previous temperature-cycle study reported FRET transitions between different states on FRET-labeled polyprolines [Yuan et al., PCCP, 2011, 13, 1762]. The conformational origin of such transitions, however, was left open.

Enhanced-fluorescence correlation spectroscopy at micro-molar dye concentration around a single gold nanorod.

Fluorescence correlation spectroscopy (FCS) is a standard tool for studying diffusion of molecules in solution, but is limited to low analyte concentrations, in the range between 10 pM and 1 nM. Such concentration limitations can be overcome by using a plasmonic nanoantenna which confines the electric field of excitation light into a tiny volume near its surface and thereby reduces the effective excitation volume by several orders of magnitude. Here we demonstrate successful FCS measurements on a 1 μM solution of crystal violet (CV) dye in glycerol using a gold nanorod antenna.