Plasmonic nanocrystals and multi-component nanocrystals for activation of chemical reactions using ultra-short temperature pulses

点击翻译按钮获取中文摘要

Within this project we will investigate how ultra-fast heated plasmonic nanoparticles in colloidal solution affect their environment, and in particular how they affect chemical reactions which take place in their vicinity.Plasmonic nanoparticles can be heated by ultra-short (nanosecond or picosecond) laser pulses extremely fast and extremely strong. Plasmonic nanoparticles possess unique characteristics when being heated by short laser pulses: their extinction coefficients are extremely high, and even under the most intense laser irradiation bleaching hardly occurs during the laser pulse in comparison to other materials. In addition, the spectral position of the plasmon resonance can be adjusted freely by choice of material, size and shape of the particles. As a consequence plasmonic nanoparticles can be heated even by individual picosecond laser pulses by about 1000 K or more; initially without their environment being heated.In this project the impact of such extremely short and extremely localized temperature peaks on chemical reactions of reactants which are also located in the colloidal solutions of such nanoparticles are studied. Therefore, first suitable plasmonic nanoparticles are produced. In addition to traditional noble metal nanoparticles also degenerately doped semiconductor particles are synthesized with plasmon resonances in the near infrared spectral range. Also, multi-component nanoparticles are produced, which consist of a plasmonic part for rapid heating under laser irradiation, and a further part of a catalytically active material. The heat generated by the laser pulse in the plasmonic particles is transferred to the catalytically active part, and at its surface a chemical reaction takes place.Various simple chemical reactions, which occur either directly on the surface of the fast heated nanoparticles or in their immediate vicinity in solution are examined. The conditions are chosen so that macroscopically practically no heating of the solution occurs and only extreme short and highly localized temperature peaks occur. The results of these studies will help to draw conclusions on how the heat conduction takes place in solutions on extremely short time scales and over very short distances. Here also such scenarios are of special interest, in which the particle temperature right after the temperature pulse is well above the boiling point of the solvent, because such scenarios cannot be realized on a macroscopic size scale.