Nanomaterials for solar thermoplasmonics: classes, optical properties and applications

Solar thermoplasmonics has evolved from a niche of nonradiative plasmon relaxation into a materials platform for controlling how sunlight is absorbed, dissipated and spatially deployed as heat. Yet the field is often presented through isolated material examples or application-specific case studies, without elucidating the broader design logic required for realistic applications. Here, recent progress across solar thermoplasmonic nanomaterials is discussed with a multiscale approach that links ultrafast carrier relaxation, mesoscale thermal accumulation and, ultimately, device-level performance. First, the fundamentals of thermoplasmonics are introduced, including plasmon excitation and relaxation dynamics, localized heating, thermal boundary conductance, and radiative losses. Low-flux, steady-state and broadband solar light illumination is specifically addressed, in contrast to single-wavelength or pulsed laser-irradiation processes usually considered in the general context of plasmonics. Then, the relevant classes of thermoplasmonic nanomaterials are described and benchmarked according to how carrier density, damping, spectral bandwidth and interfacial architecture govern heat generation. These classes span noble metals, earth-abundant alloys, heavily doped semiconductors, refractory nitrides and carbides, and hybrid nanostructures, organized as dispersions, films, mesostructures, or metamaterials. The meta-analysis of literature data on thermoplasmonic nanomaterials further provides an overview of emerging trends. Finally, the translation of thermoplasmonic properties into applications such as solar steam generation, thermocatalysis, solar energy generation, environmental remediation and sanitation, is treated. Overall, this review identifies relevant performance descriptors and structural design criteria which represent the foundation for future advances in solar thermoplasmonics.