In Situ Photothermal Response of Single Gold Nanoparticles through Hyperspectral Imaging Anti-Stokes Thermometry

Abstract

Several fields of applications require a reliable characterization of the photothermal response and heat dissipation of nanoscopic systems, which remains a challenging task for both modeling and experimental measurements. Here, we present an implementation of anti-Stokes thermometry that enables the in situ photothermal characterization of individual nanoparticles (NPs) from a single hyperspectral photoluminescence confocal image. The method is label-free, potentially applicable to any NP with detectable anti-Stokes emission, and does not require any prior information about the NP itself or the surrounding media. With it, we first studied the photothermal response of spherical gold NPs of different sizes on glass substrates, immersed in water, and found that heat dissipation is mainly dominated by the water for NPs larger than 50 nm. Then, the role of the substrate was studied by comparing the photothermal response of 80 nm gold NPs on glass with sapphire and graphene, two materials with high thermal conductivity. For a given irradiance level, the NPs reach temperatures 18% lower on sapphire and 24% higher on graphene than on bare glass. The fact that the presence of a highly conductive material such as graphene leads to a poorer thermal dissipation demonstrates that interfacial thermal resistances play a very significant role in nanoscopic systems and emphasize the need for in situ experimental thermometry techniques. The developed method will allow addressing several open questions about the role of temperature in plasmon-assisted applications, especially ones where NPs of arbitrary shapes are present in complex matrixes and environments.

Hyperspectral Mapping for the Detection of SARS-CoV-2 Using Nanomolecular Probes with Yoctomole Sensitivity

“… 23 , 26 , 27 This capability offers the ability to discriminate, with precision, different nanomaterials and differentiate them from biological materials. 28 , 29 Nanoparticles are an excellent candidate for sensor construction due to their photophysical properties. 23 , 30 Our current sensor platform relies on one such important parameter, in which the aggregation among nanoparticles will induce a change in their light scattering.…”

Anti-Stokes Thermometry in Nanoplasmonics

“…The authors used the initial normalization procedure of Xie and Cahill, 30 but noticed that the nanoparticle temperature increase Δ𝑇 = 𝑇 − 𝑇 : should be proportional to the laser intensity 𝐼 exc : δ𝑇 = β𝐼 exc . 5 This simple, additional mathematical constraint enabled the authors to achieve temperature measurements without pre-calibration or use of another laser, making their approach more direct and simpler than current methods. In addition, the authors acquired hyperspectral images (Figures 3d,e) by raster scanning the laser beam over the nanoparticle of interest (2 s of integration time per pixel), eliminating the need for precise laser alignment with respect to the nanoparticle.…”

“…The study by Barella et al published in the February issue of ACS Nano stresses once more the particular interest in anti-Stokes thermometry. 5 This approach lifts most of the limitations encountered by fluorescence thermometry: namely, it is labelfree, it is more reliable due to its decreased sensitivity to other physical parameters, and it gives access to the temperature of the nanoparticles directly.…”

Plasmonic metal nanostructures: concepts, challenges and opportunities in photo-mediated chemical transformations

“…Cortes et al. developed a method to in situ characterize the photothermal effects of single NPs by exploiting anti-Stokes thermometry, which is label-free, applicable to any NPs with detectable anti-Stokes emission, and does not require any prior information about the NP or the surrounding media ( Barella et al., 2020 ). In addition, the development of temperature calculation will also be of paramount importance for understanding the temperature evolution as well.…”