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

在这个项目中，我们将研究胶体溶液中超快加热的等离子体纳米粒子如何影响其环境，特别是它们如何影响其附近发生的化学反应。等离子体纳米粒子可以通过极快且极强的超短（纳秒或皮秒）激光脉冲加热。等离子体纳米粒子在短激光脉冲加热时具有独特的特性：它们的消光系数极高，即使在最强烈的激光照射下，与其他材料相比，在激光脉冲期间也几乎不会发生漂白。此外，等离子共振的光谱位置可以通过选择材料、颗粒尺寸和形状来自由调节。因此，等离子体纳米颗粒甚至可以通过单独的皮秒激光脉冲加热约 1000 K 或更高；在该项目中，研究了这种极短且极其局部的温度峰值对也位于此类纳米粒子的胶体溶液中的反应物的化学反应的影响。因此，首先产生合适的等离子体纳米粒子。除了传统的贵金属纳米颗粒之外，还利用近红外光谱范围内的等离子共振合成了简并掺杂的半导体颗粒。此外，还产生了多组分纳米粒子，其由用于在激光照射下快速加热的等离子体部分和催化活性材料的另一部分组成。激光脉冲在等离子体颗粒中产生的热量被转移到催化活性部分，并在其表面发生化学反应。研究了直接发生在快速加热的纳米颗粒表面或溶液中紧邻纳米颗粒的各种简单化学反应。选择条件使得宏观上实际上不会发生溶液加热，并且仅发生极短且高度局部化的温度峰值。这些研究的结果将有助于得出关于热传导如何在极短的时间尺度和极短的距离内在溶液中发生的结论。这里这种情况也特别令人感兴趣，其中温度脉冲之后的颗粒温度远高于溶剂的沸点，因为这种情况无法在宏观尺寸尺度上实现。

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.