CAS: Dual-Mode Operando Nanothermometry and Reaction Monitoring for Probing Photochemical and Photothermal Transformations

在化学系化学测量与成像（CMI）项目的支持下，罗切斯特大学的Andrea Pickel正在开发一种结合纳米尺度测温和化学反应监测的技术，以研究热对等离子体增强光催化的贡献。在等离子体驱动的光催化中，自由电子的集体振荡驱动金属纳米结构表面的化学反应，但非热等离子体效应与表面加热对观察到的增强的相对贡献存在争议。Pickel团队将开发一种光谱技术，利用单个上转换纳米颗粒的温度依赖性发光进行测温，同时通过增强反应分子的拉曼散射来监测化学反应。他们的发现可以让我们更好地理解加热是否在催化等离子体增强反应中起重要作用。Pickel博士还将开发一门基于发光测温的本科实验课程，并为当地小学生开展一项以等离子体传感为重点的教育活动。目前分离等离子体光催化的热贡献的方法是通过与监测化学反应相同的表面增强拉曼散射光谱来测量温度。然而，这些光谱依赖于局部的化学和电磁效应，这些效应会随着测量而变化，这使得等离子体加热的解释难以分离。为了在等离子体光催化过程中提供高保真的操作温度测量，将使用单个激光来激发上转换纳米粒子（UCNP）温度计和光催化化学反应。由于UCNP发光存在较大的反斯托克斯位移，测温信号和反应监测信号在光谱域中自然分离。将研究几个目标，包括了解不同的等离子体环境如何影响温度依赖的UCNP发光，制造具有不同热性质但几乎相同的等离子体性质的衬底，以及使用纳米操作将具有不同光谱发射的UCNP温度计放置在等离子体纳米结构的战略位置上。这些研究有可能阐明热对等离子体光催化的重要性，并且在化学系统中具有广泛的应用，其中UCNP发射和源自分析物或生物分子的拉曼光谱的固有光谱分离同样有利。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, Andrea Pickel of the University of Rochester is developing a combined nanoscale thermometry and chemical reaction monitoring technique to study thermal contributions to plasmon-enhanced photocatalysis. In plasmon-driven photocatalysis, the collective oscillation of free electrons drives chemical reactions on the surfaces of metal nanostructures, but the relative contributions of non-thermal plasmonic effects versus surface heating to the observed enhancement are debated. The Pickel group will develop a spectroscopic technique that employs the temperature-dependent luminescence of individual upconverting nanoparticles for thermometry while simultaneously monitoring the chemical reaction via enhanced Raman scattering from the reacting molecules. Their discoveries could lead to a better understanding of whether heating plays an important role in catalyzing plasmon-enhanced reactions. Dr. Pickel will also develop an undergraduate lab course based on luminescence thermometry and an educational activity focused on plasmonic sensing for local elementary school students. Current approaches for isolating thermal contributions to plasmonic photocatalysis measure temperature via the same surface-enhanced Raman scattering spectra used to monitor the chemical reactions. These spectra, however, depend on local chemical and electromagnetic effects that can vary through a measurement, which makes elucidation of plasmonic heating difficult to separate. To provide high-fidelity operando thermometry during plasmonic photocatalysis, a single laser will be used to both excite upconverting nanoparticle (UCNP) thermometers and photocatalyze a chemical reaction. The thermometry and reaction monitoring signals naturally separate in the spectral domain due to the large anti-Stokes shift of the UCNP luminescence. Several objectives will be investigated including understanding how different the plasmonic environment affects the temperature-dependent UCNP luminescence, fabricating substrates with different thermal properties yet near-identical plasmonic properties, and using nanomanipulation to place UCNP thermometers with spectrally distinct emission at strategic locations on plasmonic nanostructures. These studies have the potential to elucidate the importance of thermal contributions to plasmonic photocatalysis as well as have broad applications in chemistry for systems in which the intrinsic spectral separation of the UCNP emission and Raman spectra originating from analytes or biomolecules is likewise advantageous.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.