Universiteit Leiden

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Lecture

This Week’s Discoveries | 31 January 2017

Date
31 January 2017
Time
Explanation
This Week's Discoveries
Address
Oort Building
Niels Bohrweg 2
2333 CA Leiden
Room
De Sitterzaal

First Lecture

Title
Gold nanoparticles as nano-thermometers

Speaker

Aquiles Carattino (LION) is a PhD student in the Single-molecule Optics group at LION.

Abstract
Nano-thermometry is a challenging field that can open the door to very intriguing results ranging from biology and medicine to material sciences. Gold nanoparticles are excellent candidates to act as nanoprobes because they are reasonably bright emitters upon excitation with a monochromatic source. Moreover, gold nanoparticles are already used in photothermal therapy as efficient transducers of electromagnetic radiation into heat. In this work we show that the emission spectrum of gold nanorods can be used to measure the absolute temperature of the nanoparticles. The procedure does not require any previous calibration and can be easily implemented in any microscope capable of acquiring emission spectra.

Second Lecture

Title
How oxides catalyse water splitting

Speaker
Marc Koper (LIC) is professor of fundamental surface science at LIC. His research focuses on electrocatalysis and electrochemical surface science for sustainable energy and chemistry. Reactions of interest are the redox reactions of the oxygen/hydrogen cycle (water oxidation, hydrogen evolution), the carbon cycle (reduction of carbon dioxide, oxidation of small organic molecules) and the nitrogen cycle (oxidation of ammonia, reduction of nitrate).

Abstract
The generation of molecular hydrogen and molecular oxygen by water electrolysis (or “water splitting”) is a promising way to store renewable energy in a sustainable fuel, i.e. hydrogen, making use of only water and electricity generated for instance by solar and wind. The efficiency bottleneck (and cost bottleneck) of this catalytic process is the electrochemical oxygen evolution reaction taking place at the anode. This reaction occurs on oxide electrodes, but the exact mechanism through which these oxides catalyze the reaction has remained elusive. In a recent paper in Nature Chemistry, the groups of Yang Shao-Horn at MIT and Marc Koper at Leiden have collaborated to generate new insights into how a series of Cobalt-based perovskites catalyze the oxygen evolution reaction. The work elucidates the important effect of the electronic structure of the oxide on the reactivity and the redox chemistry of oxygen in the oxide, with important impacts on the pH dependence of the overall reactivity and the mechanism through which molecular oxygen is formed. These insights may help in developing cheaper and more efficient anodes for sustainable energy conversion.