BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69d255aab3e71 DTSTART:20231213T090000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:ICFO Auditorium SUMMARY:ICFO | JANA OCKOVA CLASS:PUBLIC DESCRIPTION:Light is a powerful non invasive tool for probing matter down t o its fundamental molecular properties. The past three decades saw advent of metallic nanoantennas engineered to concentrate light into sub diffract ion limited hotspots and enhance optical properties of nearby emitters by many orders of magnitude. This boosted optical microscopy\, allowing it to interrogate even extremely dim systems at their most fundamental single m olecule level. The enhancement and local confinement also unlocked sensing applications down to zeptomolar concentrations\, which can revolutionise environmental monitoring\, clinical diagnosis and personalised medicine. B eyond sensing\, metallic nanoparticles can improve the efficiency of photo voltaic devices and next generation green catalysts. The current challenge for large scale practical implementations is lack of understanding and co ntrol of the underlying nanoscale processes. Here\, we use optical microsc opy and metallic nanoantennas to perform single molecule and single partic le experiments to shed light on fundamental mechanism of photosynthesis\, nanoscale parameters crucial for sensing and underlying photochemistry in nanoantenna hotspots relevant for catalysis.\nFirstly\, we employ gold nan orods and cryomicroscopy to study excitation energy transfer in the Fenna Matthews Olson photosynthetic complex. By probing one complex at a time at room temperature and 77 K\, we uncover energy transfer between its subuni ts\, where both experimental approaches constitute the first of their kind for this extremely dim system. Furthermore\, we show that maximising the nanorod enhancement likely yields more efficient energy transfer to the na norod than between the subunits of the complex\, making them operate as ef fectively independent. Our results shed new light on the role of excitatio n transfer and annihilation in the regulation of photosynthesis.\nNext\, w e evaluate Raman scattering enhancement of a library of ten nanoparticles using a home built automated Raman microscope. By recording a statisticall y significant dataset of spectral traces from discrete nanoscale spots\, w e can distinguish Raman enhancement performance of different types of nano particles that would otherwise appear identical in classical bulk measurem ents. Furthermore\, adding a dark field scattering detection allows us to classify the measurements between single and multiple nanoparticles and di rectly probe the variability of single particle enhancements. This is a cr ucial parameter for sensing applications and the detailed nanoscale insigh t provided by our measurement platform can be used to accelerate the ratio nal design of new nanoparticles for quantitative sensing.\nFinally\, we em ploy the automated Raman microscope to study light induced chemical reacti ons in metallic nanocavities. Specifically\, we record surface enhanced Ra man scattering of a few methylene blue molecules sandwiched between a gold mirror and a gold nanoparticle. We develop a new sample assembly compatib le with oil immersion that yields a 150 fold increase in the molecular sig nal than previously published air coupling schemes. We use a pulsed laser to induce a chemical transformation of the methylene blue molecules. By in terpreting the results in the context of plasmonic properties of the gold nanojunction obtained from dark field measurements and simulations\, we we re able to rule out lattice heating and narrow down the underlying mechani sm to a plasmon induced sub picosecond process. Furthermore\, we propose t hat spontaneous picosecond Raman spectroscopy is suitable to study reactio ns at metallic surfaces which lie at the heart of heterogeneous catalysis. \n \;\nThesis Director: Prof Dr. Niek F. van Hulst DTSTAMP:20260405T122930Z END:VEVENT END:VCALENDAR