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Manipulating the propagation of mid-infrared (mid-IR) light is crucial for optical imaging, biosensing, photocatalysis, and guiding photonic circuits. Artificially engineered metamaterials were introduced to comprehensively control optical waves. However, fabrication challenges and optical losses have impeded the progress. Fortunately, two-dimensional van der Waals (vdW) materials are alternatives because of their inherent optical properties, such as hyperbolic behavior, high confinement, low loss, and atomic-scale thickness. In this research, we conducted theoretical and numerical investigations on the α-phase molybdenum trioxide, a biaxial vdW material, with patterned graphene to assess the potential of the tunable focusing of mid-IR light. Our proposed method directly alters the path of excited light to focus mid-IR light by negative refraction. Further, the patterned graphene in our design offers enhanced focusing characteristics, featuring a significantly reduced waist diameter with 1/92 of the free-space wavelength, an enhanced beam quality without pronounced field ripples, and a fivefold increase in field intensity. Moreover, our approach significantly preserves the waist diameter of the focused beam while facilitating directional steering. Thus, the focused beam can propagate in a canalized manner toward the desired direction. These advancements lay the foundation for promising applications in planar photonics.

Concentrating solar power is the ideal way to solve the conflicts between energy and environment. Heat transfer and heat storage are the key links in solar thermal power generation, while molten salt is an excellent heat transfer and heat storage medium. Most of the solar thermal power stations operating at home and abroad use binary nitrates (solar salt) and ternary nitrates (Hitec). However, their low heat transfer and heat storage performance will affect the efficiency of solar energy utilization. The unique spatial structure of nanomaterials enables it to have excellent thermal conductivity and good stability. Introducing nanomaterials as additives into the nitrate molten salt system is expected to improve the thermal properties of the material such as heat transfer and heat storage, thereby improving the efficiency of solar thermal utilization and reducing the cost of power generation. In this paper, the related studies of nano metal particles, nano metal oxides, carbon nanomaterials, and other inorganic nanomaterials as doping additives in nitrate molten salt systems were reviewed. The changes in the thermal properties of molten salts after modification were discussed and the mechanism of action was explored, which can provide references for preparation of energy storage molten salt with excellent thermal properties. In the future research, the measurement of thermophysical properties, mechanism of heat transfer, quantitative structure-activity relationship and industrial pilot will be focused on, so that nitrate molten salt with excellent heat transfer and heat storage performance can be applied in the field of solar thermal power generation, which will play a more important role in the development and utilization of clean energy.