Final Report Summary - SINSLIM (Smart Inorganic Nanocrystals for Sub-diffraction Limited IMaging)
Over the last decades, there has been tremendous progress in the controlled fabrication of colloidal semiconductor nanocrystals. This enabled the production of core/shell materials and shaped particles. Nevertheless, practically all the available systems were composed of ‘isolated’ quantum dots (‘artificial atoms’). In our work we have fabricated the first colloidal nanocrystal which contains two separate quantum dots having strong electronic coupling between them (by analogy, this is like an artificial asymmetric diatomic molecule). In order to prove that such a system really is what we claim it to be, one needs to show that it is a two-color quantum emitter. In other words, it has to emit light at two different colors (each associated with a different emitting dot) but that a single particle cannot emit simultaneously at both colors due to coupling. We have shown that our system exhibits this phenomenon, which we termed two-color antibunching.
Once we had these two-color nanocrystals at hand, we have utilized them for a multitude of tasks. We have shown that in such a coupled system the dynamics of ‘blinking’, spontaneous transitions of the nanocrystal from a highly emissive state to a low-emission state, are dramatically modified due to charge transfer between the two dots. Thus, the ‘complex’ molecule can shed light on light-induced processes occurring in ‘simple’ dots which have long been under debate, by introducing a controlled perturbation to the simpler system.
We have also shown the utility of these nanocrystals as self-calibrated nanoscale electric field sensors. We are currently attempting to use these as optical sensors to detect dynamics of neural circuits, and are developing tools which will enable deep-tissue optical excitation and detection of these signals.
We have shown that such systems can exhibit incoherent luminescence upconversion – a process by which two low energy photons are converted into a single high energy photon. The ability to tune both the absorption and the emission wavelength independently via size control, enabled us to fabricate the first broadband infrared upconversion nanoparticles. Efficient upconversion is long sought after for photovoltaic applications as well as for low-light level nonlinear microscopy.
Finally, using semiconductor nanocrystals as quantum emitters, we have shown for the first time sub-diffraction limited imaging based on the quantum statistics of light, realizing a thought experiment by S.W. Hell and coworkers dating back two decades. This experiment paves the way towards the use of quantum phenomena in practical microscopy systems.
Once we had these two-color nanocrystals at hand, we have utilized them for a multitude of tasks. We have shown that in such a coupled system the dynamics of ‘blinking’, spontaneous transitions of the nanocrystal from a highly emissive state to a low-emission state, are dramatically modified due to charge transfer between the two dots. Thus, the ‘complex’ molecule can shed light on light-induced processes occurring in ‘simple’ dots which have long been under debate, by introducing a controlled perturbation to the simpler system.
We have also shown the utility of these nanocrystals as self-calibrated nanoscale electric field sensors. We are currently attempting to use these as optical sensors to detect dynamics of neural circuits, and are developing tools which will enable deep-tissue optical excitation and detection of these signals.
We have shown that such systems can exhibit incoherent luminescence upconversion – a process by which two low energy photons are converted into a single high energy photon. The ability to tune both the absorption and the emission wavelength independently via size control, enabled us to fabricate the first broadband infrared upconversion nanoparticles. Efficient upconversion is long sought after for photovoltaic applications as well as for low-light level nonlinear microscopy.
Finally, using semiconductor nanocrystals as quantum emitters, we have shown for the first time sub-diffraction limited imaging based on the quantum statistics of light, realizing a thought experiment by S.W. Hell and coworkers dating back two decades. This experiment paves the way towards the use of quantum phenomena in practical microscopy systems.