Ultrafast Thermal Imprinting of Plasmonic Hotspots

Plasmonic photochemistry is driven by a rich collection of near-field, hot charge carrier, energy transfer, and thermal effects, most often accomplished by continuous wave illumination. Heat generation is usually considered undesirable, because noble metal nanoparticles heat up isotropically, losing the extreme energy confinement of the optical resonance. Here it is demonstrated through optical and heat-transfer modelling that the judicious choice of nanoreactor geometry and material enables the direct thermal imprint of plasmonic optical absorption hotspots onto the lattice with high fidelity. Transition metal nitrides (TMNs, e.g., TiN/HfN) embody the ideal material requirements, where ultrafast electron–phonon coupling prevents fast electronic heat dissipation and low thermal conductivity prolongs the heat confinement. The extreme energy confinement leads to unprecedented peak temperatures and internal heat gradients (>10 K nm−1) that cannot be achieved using noble metals or any current heating method. TMN nanoreactors consequently yield up to ten thousand times more product in pulsed photothermal chemical conversion compared with noble metals (Ag, Au, Cu). These findings open up a completely unexplored realm of nano-photochemistry, where adjacent reaction centers experience substantially different temperatures for hundreds of picoseconds, long enough for bond breaking to occur

Upconverting nanovesicles for the activation of ruthenium anti-cancer prodrugs with red light

Ruthenium complexes are promising prodrugs in photoactivated chemotherapy (PACT): to prevent systemic therapeutic side-effects, a non-toxic version of the drug is introduced in the body and is only activated at the place of the tumor by means of visible light irradiation. However, most of these PACT compounds are only sensitive for UV or blue light, while this light does not permeate the body very well, in contrast to red or near-infrared light. To circumvent this problem, the principle of light-upconversion can be used to "upgrade" red light to blue light in a drug carrier such as a nanovesicle: the tumor is irradiated with red light, after which blue light is generated locally and used to activate the prodrug. Among the various methods of light-upconversion, triplet-triplet annihilation upconversion (TTA-UC) was selected as the most promising. In this thesis it is described that green-to-blue and red-to-blue upconverting nanovesicles were prepared. The red-to-blue upconverted light was successfully used to activate a ruthenium polypyridyl complex that was anchored to the same vesicle. Finally, the inherent oxygen-sensitivity of TTA-UC was greatly mitigated by the addition of water-soluble and biocompatible anti-oxidants. We expect that the results of this thesis will lead to exciting applications in PACT.NWO Vidi grantMetals in Catalysis, Biomimetics & Inorganic Material

Understanding the complexity of intelligence problems

The complexity of an intelligence problem determines to a great extent the certainty that can be provided by intelligence and security services. This article will argue this deductively and validate this claim using a set of intelligence reports produced by the Dutch Intelligence & Security Service (AIVD). A better understanding of how the level of complexity affects intelligence analysis is helpful for the further (academic) study of analysis methodologies, as well as for managing expectations of intelligence clients, and for informing the debates over legislation that affects intelligence and security services.Security and Global AffairsFGGA – Publicaties zonder aanstelling Universiteit Leide

Ultrafast Photoinduced Heat Generation by Plasmonic HfN Nanoparticles

There is great interest in the development of alternatives to noble metals for plasmonic nanostructures. Transition metal nitrides are promising due to their robust refractory properties. However, the photophysics of these nanostructures, particularly the hot carrier dynamics and photothermal response on ultrafast timescales, are not well understood. This limits their implementation in applications such as photothermal catalysis or solar thermophotovoltaics. In this study, the light-induced relaxation processes in water-dispersed HfN nanoparticles are, for the first time, elucidated by fs transient absorption, Lumerical FDTD and COMSOL Multiphysics simulations, and temperature-dependent ellipsometry. It is unequivocally demonstrated that HfN nanoparticles convert absorbed photons into heat within <100 fs; no signature of hot charge carriers is observed. Interestingly, under high photon energy or intense irradiation stimulated Raman scattering characteristic of oxynitride surface termination is observed. These findings suggest that transition metal nitrides could offer benefits over noble metals in the field of plasmonic photothermal catalysis

Imaging the lipid bilayer of giant unilamellar vesicles using red-to-blue light upconversion

Red-to-blue triplet–triplet annihilation upconversion was obtained in giant unilamellar vesicles. The upconverted light was homogeneously distributed across the membrane and could be utilized for the imaging of individual giant vesicles in three dimensions. These results show the great potential of TTA-UC for imaging applications under anoxic conditions

A novel coordination network of Tb(III) with 2-hydroxy-trimesic acid showing very intense photoluminescence

Metals in Catalysis, Biomimetics & Inorganic Material