The control of heat at the nanoscale via the excitation of localized surface plasmons in nanoparticles (NPs) irradiated with light holds great potential in several fields (cancer therapy, catalysis, desalination). To date, most thermoplasmonic applications are based on Ag and Au NPs, whose cost of raw materials inevitably limits the scalability for industrial applications requiring large amounts of photothermal NPs, as in the case of desalination plants. On the other hand, alternative nanomaterials proposed so far exhibit severe restrictions associated with the insufficient photothermal efficacy in the visible, the poor chemical stability, and the challenging scalability. Here, it is demonstrated the outstanding potential of NiSe and CoSe topological nodal‐line semimetals for thermoplasmonics. The anisotropic dielectric properties of NiSe and CoSe activate additional plasmonic resonances. Specifically, NiSe and CoSe NPs support multiple localized surface plasmons in the optical range, resulting in a broadband matching with sunlight radiation spectrum. Finally, it is validated the proposed NiSe and CoSe‐based thermoplasmonic platform by implementing solar‐driven membrane distillation by adopting NiSe and CoSe nanofillers embedded in a polymeric membrane for seawater desalination. Remarkably, replacing Ag with NiSe and CoSe for solar membrane distillation increases the transmembrane flux by 330% and 690%, respectively. Correspondingly, costs of raw materials are also reduced by 24 and 11 times, respectively. The results pave the way for the advent of NiSe and CoSe for efficient and sustainable thermoplasmonics and related applications exploiting sunlight within the paradigm of the circular blue economy.

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Several bulk transition-metal dichalcogenides exhibit a strong optical anisotropy, high refractive index, and even a natural hyperbolic response, which are enabling ingredients in a variety of nanophotonic scenarios of great interest. Here, we investigate the electromagnetic response of NiTe 2 , a type-II Dirac semimetal, whose infrared/optical properties have been hitherto largely unexplored. Through density-functional-theory-based ab initio modeling, along with electron energy loss spectroscopy experiments, we show that NiTe 2 exhibits a varied, extremely anisotropic response within the infrared and visible ranges. We also demonstrate the high tunability of its optical properties and illustrate the key role played by Dirac fermions. Our results pave the way for realizing nanophotonic devices for efficient light manipulation at subwavelength scales.

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