Damping of Acoustic Vibrations of Single Gold Nanoparticles Optically Trapped in Water
2012; 12 (2): 1063-1069
Brownian Fluctuations and Heating of an Optically Aligned Gold Nanorod
PHYSICAL REVIEW LETTERS
2011; 107 (3)
We combine ultrafast pump-probe spectroscopy with optical trapping to study homogeneous damping of the acoustic vibrations of single gold nanospheres (80 nm diameter) and nanorods (25 nm diameter by 60 nm length) in water. We find a significant particle-to-particle variation in damping times. Our results indicate that vibrational damping occurs not only by dissipation into the liquid, but also by damping mechanisms intrinsic to the particle. Our experiment opens the study of mechanisms of intrinsic mechanical dissipation in metals at frequencies 1-1000 GHz, a range that has been difficult to access thus far.
View details for DOI 10.1021/nl204311q
View details for Web of Science ID 000299967800090
View details for PubMedID 22251064
Making gold nanoparticles fluorescent for simultaneous absorption and fluorescence detection on the single particle level
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2011; 13 (1): 149-153
We present the first quantitative measurements of the torque exerted on a single gold nanorod in a polarized three-dimensional optical trap. We determined the torque both by observing the time-averaged orientation distribution and by measuring the dynamics of the rotational brownian fluctuations. The measurements are in good agreement with calculations, where the temperature profile around the hot nanorod gives rise to a reduced, effective viscosity. The maximum torque on a 60??nm×25??nm nanorod was 100??pN·nm, large enough to address single-molecule processes in soft and biological matter.
View details for DOI 10.1103/PhysRevLett.107.037401
View details for Web of Science ID 000292597400024
View details for PubMedID 21838403
Room-Temperature Detection of a Single Molecule's Absorption by Photothermal Contrast
2010; 330 (6002): 353-356
We demonstrate a simple way of making individual 20 nm gold nanoparticles fluorescent (with a fluorescence quantum yield of about 10(-6)) in glycerol. Gold NPs prepared in such a way have bright fluorescence for a long time under moderate excitation, and their fluorescence remains when the solvent is exchanged to water. We propose to use these nanoparticles as a calibration standard for simultaneous detection of fluorescence and absorption (by means of photothermal detection), and experimentally demonstrate the theoretically predicted shift in axial positions of these signals. Simultaneous absorption and fluorescence detection of such stable labels makes them attractive for multidimensional tracking and screening applications.
View details for DOI 10.1039/c0cp01389g
View details for Web of Science ID 000285099800017
View details for PubMedID 21042602
Spontaneous emission of a nanoscopic emitter in a strongly scattering disordered medium
2010; 18 (6): 6360-6365
So far, single-molecule imaging has predominantly relied on fluorescence detection. We imaged single nonfluorescent azo dye molecules in room-temperature glycerol by the refractive effect of the heat that they release in their environment upon intense illumination. This photothermal technique provides contrast for the absorbing objects only, irrespective of scattering by defects or roughness, with a signal-to-noise ratio of ~10 for a single molecule in an integration time of 300 milliseconds. In the absence of oxygen, virtually no bleaching event was observed, even after more than 10 minutes of illumination. In a solution saturated with oxygen, the average bleaching time was of the order of 1 minute. No blinking was observed in the absorption signal. On the basis of bleaching steps, we obtained an average absorption cross section of 4 angstroms(2) for a single chromophore.
View details for DOI 10.1126/science.1195475
View details for Web of Science ID 000282986700036
View details for PubMedID 20947760
Acoustic and Optical Modes of Single Dumbbells of Gold Nanoparticles
2009; 10 (1): 111-114
Fluorescence lifetimes of nitrogen-vacancy color centers in individual diamond nanocrystals were measured at the interface between a glass substrate and a strongly scattering medium. Comparison of the results with values recorded from the same nanocrystals at the glass-air interface revealed fluctuations of fluorescence lifetimes in the scattering medium. After discussing a range of possible systematic effects, we attribute the observed lengthening of the lifetimes to the reduction of the local density of states. Our approach is very promising for exploring the strong threedimensional localization of light directly on the microscopic scale.
View details for Web of Science ID 000276002500109
View details for PubMedID 20389659