Chemically-Controlled Ultrafast Photothermal Response in Plasmonic Nanostructured Assemblies

Abstract

Plasmonic nanoparticles are renowned as efficient heaters due to their capability to resonantly absorb and concentrate electromagnetic radiation, trigger excitation of highly energetic (hot) carriers, and locally convert their excess energy into heat via ultrafast nonradiative relaxation processes. Furthermore, in assembly configurations (i.e., suprastructures), collective effects can even enhance the heating performance. Here, we report on the dynamics of photothermal conversion and the related nonlinear optical response from water-soluble nanoeggs consisting of a Au nanocrystal assembly trapped in a water-soluble shell of ferrite nanocrystals (also called colloidosome) of ∼250–300 nm in size. This nanoegg configuration of the plasmonic assembly enables control of the size of the gold suprastructure core by changing the Au concentration in the chemical synthesis. Different metal concentrations are analyzed by means of ultrafast pump–probe spectroscopy and semiclassical modeling of photothermal dynamics from the onset of hot-carrier photogeneration (few picosecond time scale) to the heating of the matrix ligands in the suprastructure core (hundreds of nanoseconds). Results show the possibility to design and tailor the photothermal properties of the nanoeggs by acting on the core size and indicate superior performances (both in terms of peak temperatures and thermalization speed) compared to conventional (unstructured) nanoheaters of comparable size and chemical composition.

DNA-Condensed Plasmonic Supraballs Transparent to Molecules

“…86 The 5 nm AuNPs constituting the supraballs are intriguing since small AuNPs show fast hot-electron thermalization, making them attractive for photothermal applications. 56,57 The DNA matrices featuring alterable metal ions and nucleobases can be explored for their biological effects toward nanomedical pursuits. 87 In this regard, the supraballs' plasmonic properties and possible interactions with drug molecules would provide rich chances.…”

“…The existence of rich and tunable hotspots in the plasmonic supraballs along with their excellent colloidal and chemical stabilities promises their use as “homogeneous” SERS and fluorescence substrates workable in harsh environments. − The molecular permeability and nanoporosity of the metallic structures would be especially attractive to catalytic functions . The 5 nm AuNPs constituting the supraballs are intriguing since small AuNPs show fast hot-electron thermalization, making them attractive for photothermal applications. , The DNA matrices featuring alterable metal ions and nucleobases can be explored for their biological effects toward nanomedical pursuits . In this regard, the supraballs’ plasmonic properties and possible interactions with drug molecules would provide rich chances.…”

“…For example, ligand exchange by hydrophobic thiols was employed to obtain AuNP supraballs that behaved as a high-capacity adsorbent for guest objects . Apart from noncovalent interactions, molecular cross-linking and coordinative bonding can also be involved. , In general, an equilibrium between attractive and repulsive colloidal forces is critical to achieve self-limited supraparticles. , The resulting metaspheres have found innovative uses in theranostics and catalysis. − …”

Thermal dynamics of gold nanoshell dimers under femtosecond laser pulse irradiation: A numerical approach

“…In essence, TTM provides a powerful framework to simulate the rapid energy exchange between electron and lattice subsystems during and after the laser excitation process, thereby offering valuable insights into the ultrafast thermal dynamics in fs laser-irradiated materials. 51,52 In this context, the present work aims to add to the existing body of knowledge by using established photothermal models and numerical methods to examine a specific system that has not been thoroughly investigated so far, namely plasmonic nanoshell dimers. This application is novel and contributes to the field by providing new insights into the thermal response of such systems under fs laser pulse irradiation.…”

“…Therefore, the electrons and the lattice can be considered as separate subsystems with their own temperatures for a short period of time, allowing us to accurately model and study ultrafast thermal processes induced by fs laser pulses. In essence, TTM provides a powerful framework to simulate the rapid energy exchange between electron and lattice subsystems during and after the laser excitation process, thereby offering valuable insights into the ultrafast thermal dynamics in fs laser‐irradiated materials 51,52 …”