Plasmonic heating has been utilized in many applications, including photocatalysis, photothermal therapy, and photocuring. However, the heat dissipation process of plasmonic nanoparticles (NPs) and the surrounding matrix is complex. How high the temperature of the matrix that surrounds the plasmonic NPs, such as the catalyst and substrate, can reach is unclear. Herein, we study the dissipation of plasmonic heat generated by resonantly excited gold (Au) NPs dispersed on a P25 TiO2 NP porous film in air. Under resonant 532 nm continuous wave (CW) laser irradiation at the surface of Au-TiO2, the surface evaporation and the aggregation of Au NPs were observed at moderate laser power. This process is accompanied by the phase transition of TiO2. More importantly, the TiO2 NP film melted, forming melt pools and a molten TiO2 matrix. This indicates that the temperature of TiO2 reached as high as its melting point of 1830 °C. When Au/TiO2 was irradiated with an off-resonance laser at 638 nm, no phase transformation or melting of TiO2 was observed. The temperature calculation showed that the heating generated by Au NPs is not localized. The collective heating from an ensemble of Au NPs in the irradiated area produced a global temperature increase that melted TiO2. Our results suggest that the photothermal effect could be a significant mechanism in the plasmon-assisted photocatalytic reactions.
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Catalytic Enhancement of Inductively Heated Fe 3 O 4 Nanoparticles by Removal of Surface Ligands
Heat management in catalysis is limited by each material's heat transfer efficiencies, resulting in energy losses despite current thermal engineering strategies. In contrast, induction heating of magnetic nanoparticles (NPs) generates heat at the surface of the catalyst where the reaction occurs, reducing waste heat via dissipation. However, the synthesis of magnetic NPs with optimal heat generation requires interfacial ligands, such as oleic acid, which act as heat sinks. Surface treatments using tetramethylammonium hydroxide (TMAOH) or pyridine are used to remove these ligands before applications in hydrophilic media. In this study, Fe3O4 NPs are surface treated to study the effect of induction heating on the catalytic oxidation of 1‐octanol. Whereas TMAOH was unsuccessful in removing oleic acid, pyridine treatment resulted in a roughly 2.5‐fold increase in heat generation and product yield. Therefore, efficient surfactant removal has profound implications in induction heating catalysis by increasing the heat transfer and available surface sites.
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- Award ID(s):
- 1805785
- PAR ID:
- 10210414
- Date Published:
- Journal Name:
- ChemSusChem
- ISSN:
- 1864-5631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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