Final Report Summary - 1MOLECULENEARPLASMON (Single-molecule spectroscopy in the near field of plasmonic metal nanoparticles)
The project aimed at observing modification in coupling of a plasmonic antenna to single molecules in a solid at cryogenic temperatures. This is a difficult experiment that has not been achieved yet because it requires control of the nano-environment of the antenna in a cryostat at liquid-helium temperature. The unique advantages of this experiments, though are:
1. the coupling of the molecule can be evaluated precisely and quantitatively by measurements of linewidth (or lifetime), saturation intensity, and rate of emission at saturation. These measurements are much more difficult and less precise at room temperature because of the limited stability of molecules in these conditions.
2. because of spectral selectivity at low temperature, a large number of molecules can be coupled to the same nanoantenna, allowing comparison of the antenna effect on molecules at different positions. This is impossible at room temperature because each antenna can interact with at most one molecule at a time.
3. photobleaching and photoblinking are much reduced or suppressed at low temperature, which allows very precise determination of the optical properties. At room temperature, molecule fluctuate in position and orientation and eventually bleach.
In the frame of the two-year project, the fellow has built up a new setup for cryogenic single-molecule microscopy. He had identified a promising host-guest system (dibenzoterrylene in anthracene or in para-dichlorobenzene) and a promising nano-antenna (a gold nanorod with dimensions 40 nm width and 84 nm length) to try the experiment. He has performed the preliminary spectroscopic experiments on this host-guest system to prepare the experiment. Unfortunately, his stay has not been long enough to write the publication of the latter part, nor to try the actual experiment. This will be attempted in the coming months by a PhD student succeeding the fellow.
1. the coupling of the molecule can be evaluated precisely and quantitatively by measurements of linewidth (or lifetime), saturation intensity, and rate of emission at saturation. These measurements are much more difficult and less precise at room temperature because of the limited stability of molecules in these conditions.
2. because of spectral selectivity at low temperature, a large number of molecules can be coupled to the same nanoantenna, allowing comparison of the antenna effect on molecules at different positions. This is impossible at room temperature because each antenna can interact with at most one molecule at a time.
3. photobleaching and photoblinking are much reduced or suppressed at low temperature, which allows very precise determination of the optical properties. At room temperature, molecule fluctuate in position and orientation and eventually bleach.
In the frame of the two-year project, the fellow has built up a new setup for cryogenic single-molecule microscopy. He had identified a promising host-guest system (dibenzoterrylene in anthracene or in para-dichlorobenzene) and a promising nano-antenna (a gold nanorod with dimensions 40 nm width and 84 nm length) to try the experiment. He has performed the preliminary spectroscopic experiments on this host-guest system to prepare the experiment. Unfortunately, his stay has not been long enough to write the publication of the latter part, nor to try the actual experiment. This will be attempted in the coming months by a PhD student succeeding the fellow.
