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The infrared (IR) gas sensing technique is excellent for CO 2 gas detection systems that require high accuracy and safety standard; however, there is a significant barrier to its application due to its high cost and difficulty in miniaturization. CO 2 sensors that are functional within near- or short-wavelength IR have the potential to reduce this barrier. In this work, a highly sensitive plasmonic material based on nanostructured covellite copper sulfide (CuS), which exhibits desired localized surface plasmon resonance for surface-enhanced IR absorption (SEIRA) throughout near- and mid-IR ranges, was investigated. We prepared CuS thin films facilely in an additive manner based on a spatial successive ionic layer adsorption and reaction process at room temperature. The resulting CuS thin film possesses a structure consisting of hexagonal nanoflakes, and demonstrates significant SEIRA for 100 ppm CO 2 with an enhancement factor of 10 4 . 

Nanostructured gold has attracted significant interest from materials science, chemistry, optics and photonics, and biology due to their extraordinary potential for manipulating visible and near‐infrared light through the excitation of plasmon resonances. However, gold nanostructures are rarely measured experimentally in their plasmonic properties and hardly used for high‐temperature applications because of the inherent instability in mass and shape due to the high surface energy at elevated temperatures. In this work, the first direct observation of thermally excited surface plasmons in gold nanorods at 1100 K is demonstrated. By coupling with an optical fiber in the near‐field, the thermally excited surface plasmons from gold nanorods can be converted into the propagating modes in the optical fiber and experimentally characterized in a remote manner. This fiber‐coupled technique can effectively characterize the near‐field thermoplasmonic emission from gold nanorods. A direct simulation scheme is also developed to quantitively understand the thermal emission from the array of gold nanorods. The experimental work in conjunction with the direct simulation results paves the way of using gold nanostructures as high‐temperature plasmonic nanomaterials, which has important implications in thermal energy conversion, thermal emission control, and chemical sensing.

 

Metal nanomeshes are demonstrated as flexible transparent conductors with performance comparable to indium tin oxide. However, it is not known what the performance limits of these structures are in terms of transparency and sheet resistance. More importantly, the haze, which describes how much incident light is scattered by these structures, has not been studied. In this paper, the transmission, sheet resistance, and haze of metal nanomeshes are comprehensively studied to determine their fundamental performance limits as transparent conductors through simulations and experiments. Numerical simulations and analytical calculations are used to evaluate the tradeoffs and correlations between these three figures of merit. A strong correlation is found between haze and transmission, where structures with high transmission tend to have low haze and vice versa. Structures with a pitch above 1000 nm are beneficial for achieving transmission over 80% and larger thickness is favorable in reducing sheet resistance without significantly affecting transmission. Furthermore, metal nanomeshes are fabricated to verify simulation results. The haze may be primarily explained by Fraunhofer diffraction, but the spectral dependence of haze requires analysis with Mie scattering theory. The results should apply to all metal grid or grating‐like structures. The fundamental performance limits evaluated here are helpful for guiding engineering design and research prioritization.