Plasmonics can be used to enhance the emission properties of single quantum nano-objects and use them as bright ultrafast single photon sources. However, plasmonic trapping single quantum objects has remained highly challenging so far.
In a recent Nano Letters publication, we introduce a dedicated plasmonic nanoantenna design to trap single colloidal quantum dots and enhance their single photon emission. The nano-optical trapping automatically locates the quantum emitter at the nanoantenna hotspot where the emission enhancement is maximum.
Novelty and Impact:
- Enhanced single photon brightness is demonstrated from a trapped single quantum dot, together with strongly reduced blinking and accelerated lifetime. This provides a significant advance over previous reports lacking a clear demonstration of antibunching.
- Our novel nanoantenna design achieves the highest trap stiffness reported so far for individual quantum dots, allowing to reduce the trapping intensity and mitigate the thermal effects.
Preprint also freely available on ArXiv 2108.06508
Ultraviolet plasmonics has attracted recently a growing attention owing to the possibility to take advantage of increased light-matter interaction in the UV range. However, the core question of demonstrating the capacity of UV plasmonic structures to enhance the radiative emission rate of proteins has remained unproven yet.
In a recent article published in J . Phys D Appl. Phys, we report the first complete demonstration of the Purcell radiative rate enhancement for label-free proteins in plasmonic aluminum nanoapertures. Regardless of the complexity of protein structure and its low intrinsic emission quantum yield, we can clearly show that the aluminum plasmonic nanoapertures can significantly enhance the spontaneous UV emission rate of proteins. Our results show that concepts developed for single quantum sources in the visible can still be applied on complex proteins containing thousands of aminoacids.
Open access paper also freely available on arXiv 2107.06357
What happens when you shine a UV laser onto a single aluminum nanohole filled with water? See the video below of the experiment, accelerated 5x. Holes get brighter once exposed to the laser: this is laser-induced corrosion of the aluminum film by water molecules. It is not direct laser damage (we use a power of 60 µW, 3x below the direct photodamage threshold). This photocorrosion is very general once aluminum, water and UV laser are present, which correspond to 99% of the biosensing applications of UV plasmonics.
In a recent publication in ACS Applied Nano Materials, we use various metal oxides layers deposited by atomic layer deposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD) on top of the aluminum to protect against UV photocorrosion. We discuss the best material choice, and report the influence of different experimental conditions. Choosing the optimum protection and conditions significantly extends the corrosion resistance by more than 20x.
This approach is the key to extend plasmonics into the UV range in water-based environments. We apply it to demonstrate the label-free UV detection of streptavidin proteins. Alternatively, the ALD/PECVD approach also improves the long-term corrosion resistance of Al structures in corrosive chloride solutions.
Preprint freely available on arXiv 2106.09392.
Our team-member Aleksandr Barulin recently got awarded the thesis prize of the Doctoral School "Physics and Sciences of the Matter" for his PhD work. Congratulations Aleksandr for this well-deserved prize!