The growth of highly crystalline LaB6 films with an excellent optical response and low loss is reported, which will be useful for high‐performance photothermal device applications when combined with their inherent refractory properties. Optimum growth parameters for realizing uniaxial and coherent LaB6 thin films, exhibiting an excellent plasmonic response for near‐ to mid‐infrared device applications, are established. Numerical electromagnetic simulations of the epitaxial LaB6 nanostructures revealed that the electromagnetic field at the LaB6 surface can be as high as that of the Au nanostructures. Furthermore, the LaB6 nanostructures show resonance in the visible (red) to mid‐infrared region comparable to those of Au with the added advantage of improved temperature stability that can withstand harsh photothermal device operations.

The growth of high-quality LaB6 thin films on Si(001), by using electron beam deposition, is reported. The films show (001) orientation as confirmed with X-ray diffraction and electron backscattered diffraction (EBSD). The sharp Kikuchi pattern from EBSD evidences a single-crystalline nature of the LaB6(001) films. To accommodate for the lattice mismatch, the LaB6 is azimuthally rotated by 45° with respect to the Si lattice (LaB6[100] ∣∣ Si[110]) and grows in a supercell structure. Early stages of the film growth were clarified using atomic force microscopy, with a unique “directional” and “island-to layer-by-layer” type of growth of this covalently bonded heterosystem.

Photo-excitation of hot carriers in metallic nanostructures have been applied to various photoelectric conversions to harvest low-energy photons. The relaxed hot carriers become heat where the heated areas are limited to the surrounding of the metallic nanostructures, leading to indirect local heating. In contrast to the research on photoelectric and photothermal conversions using metals, our recent works have shown that transition metal nitrides and transition meal carbides can be alternative to metals. These materials are cost-effective and out-perform gold that has been used in most of the past studies. In the current articles, we briefly review our current photoelectric and photothermal conversions using transition metal nitrides and transition meal carbides and discuss the future direction.

Black color is a typical choice to absorb sunlight. To realize black color, paints or coatings of organic or inorganic materials have been used. In contrast, here we show with analytical calculations as well as experiments that resonant nanoparticles can act as efficient sunlight absorbers even though their bulk materials are not black. The important role of nanoparticles is to excite either plasmon or Mie resonances, which are excited at metallic and dielectric materials, respectively. Among the materials we have considered, highly conductive titanium nitride nanoparticles exhibit strong and broad absorption which covers the majority of the solar spectrum. For Mie resonances, germanium nanoparticles exhibit strong but rather narrow absorption peaks. However, if these nanoparticles have size variations, they can still absorb broad spectrum as a whole. In experiment, we examine the photothermal effect of these nanoparticles dispersed in water and demonstrate that they are efficient in heating and vaporizing water under the illumination of sunlight. The nanoparticle concentration can be as small as 0.1 vol% to improve the water heating and vaporization by a factor of few. These resonant nanoparticles can be applied in solar water heating systems as well as in solar water distillation systems for the efficient usage of solar heat for a sustainable society.

In this work, we have fabricated lead selenide (PbSe) thin films by the pulsed laser deposition method on Si/SiO2 substrates and investigated the effect of oxygen annealing (sensitization) in these films. The oxygen-sensitized films show high responsivity in the visible (VIS) and the near-infrared (NIR) region at room temperature without cooling. We also demonstrate the effective surface oxidation of PbSe thin films during the oxygen annealing process without treated with commonly used halogens that leads to a better photoresponse in these PbSe films.

In this work, a promising strategy to increase the broadband solar light absorption was developed by synthesizing a composite of metal-free carbon nitride-carbon dots (C3N4-C dots) and plasmonic titanium nitride (TiN) nanoparticles (NPs) to improve the photoelectrochemical water-splitting performance under simulated solar radiation. Hot-electron injection from plasmonic TiN NPs to C3N4 played a role in photocatalysis, whereas C dots acted as catalysts for the decomposition of H2O2 to O2. The use of C dots also eliminated the need for a sacrificial reagent and prevented catalytic poisoning. By incorporating the TiN NPs and C dots, a sixfold improvement in the catalytic performance of C3N4 was observed. The proposed approach of combining TiN NPs and C dots with C3N4 proved effective in overcoming low optical absorption and charge recombination losses and also widens the spectral window, leading to improved photocatalytic activity.

Titanium nitride (TiN) nanostructure shows broad optical resonance that covers the majority of solar spectrum. By taking advantage of this resonance, i.e., surface plasmon resonance, we demonstrate that TiN nanostructures can efficiently harvest sunlight for internal photoemission and photothermal conversion. Some of the applications of TiN nanostructures include visible active photocatalysis and solar water evaporation. Since TiN has been used in industries, the use of TiN is practical, motiving the application oriented research for solar energy harvesting.

We report the fabrication of titanium nitride (TiN) films with the “best” plasmonic behavior reported so far by the pulsed laser deposition method. Even though the deposition is done at room temperature (∼25 °C) and grown on an amorphous native oxide of a silicon wafer, the plasmonic property of the TiN is comparable to that of gold, which is a conventional plasmonic material in the visible to near-infrared region. Because of the highly plasmonic nature of the TiN, the near field around the TiN nanostructure can be as high as that of a gold nanostructure. A room-temperature process without a strict requirement on the substrate allows depositing a TiN film even on a flexible polymer film without degrading its property. Our results pave the way for using TiN as a truly practical plasmonic material, replacing the use of noble metals.

Thin films of SrTiO3 (STO) and niobium-doped SrTiO3 (Nb-STO) were synthesized by sol gel method and loaded with gold nanoparticles. We investigated the effect of Nb doping and the associated defect formations, as well as plasmonic enhancement in photocurrent. Both pristine STO and Nb-STO films exhibited anodic photocurrent and enhancements in photocurrent were observed in the UV and visible region for Nb-STO films when subsequently increasing the annealing temperature. Further enhancement in UV and visible light catalytic activity was observed from the photocurrent action spectrum by loading gold nanoparticles on the Nb-STO.

Plasmonic metamaterials are used for the fabrication of spectrally selective narrow-band mid-infrared thermal emitters operating at high temperatures. Using refractory materials, molybdenum and aluminum oxide in this case, high temperature operation has been demonstrated in vacuum up to 1000 °C. Colloidal mask etching is adopted to realize large-scale and cost-effective fabrication. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

We have developed narrow-band mid-infrared thermal emitters based on refractory plasmonic perfect absorbers operative at very high temperature. Colloidal mask etching was adopted to Mo-Al2O3-Mo trilayers to realize large-scale and cost-effective fabrication of periodically arrayed disk resonators. Using molybdenum and aluminum oxide as refractory components, high temperature operation was demonstrated up to 1000°C or even higher while retaining the excellent thermal stability and narrow-band emission comparable to that of noble metal plasmonic emitters. The narrow-band emission peaks can be tuned flexibly from 3 to 8 μm which overlaps well with the spectral region of molecular fingerprints. The proposed wavelength-selective thermal emitters can be used for various applications such as energy-saving high-power infrared heaters as well as for light sources for active infrared sensor systems.

We demonstrate that lossy plasmonic resonances of nanoparticles are broad enough to cover the majority of the solar spectrum and highly efficient for absorbing sunlight. In analytical calculation, we choose a titanium nitride nanoparticle as a lossy plasmonic nanoresonator and present that sunlight absorption efficiency of a titanium nitride nanoparticle is higher than gold and even black carbon nanoparticles. The experiments demonstrate that titanium nitride nanoparticles dispersed in water have high efficiency to heat water and generate vapor than carbon nanoparticles by converting sunlight into heat. Our results open great possibilities for efficient solar heat applications with titanium nitride nanoparticles.