Temperature Determination of Resonantly Excited Plasmonic Branched Gold Nanoparticles by X-ray Absorption Spectroscopy

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2011-09, Vol.7 (17), p.2498-2506
• Main Authors: Van de Broek, Bieke, Grandjean, Didier, Trekker, Jesse, Ye, Jian, Verstreken, Kris, Maes, Guido, Borghs, Gustaaf, Nikitenko, Sergey, Lagae, Liesbet, Bartic, Carmen, Temst, Kristiaan, Van Bael, Margriet J.
• Format: Article
• Language: English
• Subjects: Branched; EXAFS spectroscopy; Gold; Gold - chemistry; Gold - radiation effects; Hot Temperature; Humans; Illumination; Laser Therapy; Lasers; Metal Nanoparticles - chemistry; Metal Nanoparticles - radiation effects; Metal Nanoparticles - ultrastructure; Nanomaterials; Nanomedicine; Nanoparticles; Nanostructure; Nanotechnology; Plasmonics; Surface Plasmon Resonance; thermo-optical properties; thermometry; Thermometry - methods; X-Ray Absorption Spectroscopy - methods
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.201100089

The fields of bioscience and nanomedicine demand precise thermometry for nanoparticle heat characterization down to the nanoscale regime. Since current methods often use indirect and less accurate techniques to determine the nanoparticle temperature, there is a pressing need for a direct and reliable element‐specific method. In‐situ extended X‐ray absorption fine structure (EXAFS) spectroscopy is used to determine the thermo‐optical properties of plasmonic branched gold nanoparticles upon resonant laser illumination. With EXAFS, the direct determination of the nanoparticle temperature increase upon laser illumination is possible via the thermal influence on the gold lattice parameters. More specifically, using the change of the Debye–Waller term representing the lattice disorder, the temperature increase is selectively measured within the plasmonic branched nanoparticles upon resonant laser illumination. In addition, the signal intensity shows that the nanoparticle concentration in the beam more than doubles during laser illumination, thereby demonstrating that photothermal heating is a dynamic process. A comparable temperature increase is measured in the nanoparticle suspension using a thermocouple. This good correspondence between the temperature at the level of the nanoparticle and at the level of the suspension points to an efficient heat transfer between the nanoparticle and the surrounding medium, thus confirming the potential of branched gold nanoparticles for hyperthermia applications. This work demonstrates that X‐ray absorption spectroscopy‐based nanothermometry could be a valuable tool in the fast‐growing number of applications of plasmonic nanoparticles, particularly in life sciences and medicine. The temperature increase of branched gold nanoparticles upon laser illumination is experimentally determined using two techniques. With the extended X‐ray absorption fine structure (EXAFS) method the temperature increase at the nanoparticle level is measured via the thermal influence on the lattice parameters, while a thermocouple is used to measure the temperature increase in the nanoparticle suspension.