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Optimal optical absorption properties are imperative for the utilization of nanofluids in solar energy applications. Excellent optical absorption facilitates the augmentation of solar energy utilization efficiency. The base fluid contributes significantly to the optical properties of the nanofluid. However, the effect of base fluid on the nanofluid optical properties has yet to be explored. This work investigates the effect of three base fluids, deionized water, ethylene glycol, and 1,2-propanediol, on the optical absorption properties of titanium nitride (TiN) nanofluids. The results show differences in the optical properties of the TiN nanofluids prepared for different sonication times. With the absence of surfactant addition, the stability of TiN nanofluids based on ethylene glycol-based and 1,2-Propanediol-based surpasses that of deionized water-based TiN nanofluids. However, in comparison to ethylene glycol-based and 1,2-Propanediol-based, deionized water-based TiN nanofluids exhibit commendable light absorption capacity. Finally, the photothermal conversion efficiency is calculated for different base fluids. The photothermal conversion efficiency of the deionized water-based TiN nanofluid is 50.82%, which is 13.91% and 15.98% higher than that of the ethylene glycol-based and 1,2-propanediol-based TiN nanofluids under the same conditions, respectively. Thus, deionized water-based TiN shows excellent optical absorption properties, essential for enhanced solar energy thermal utilization. This work will help guide the application of TiN nanofluids. [ABSTRACT FROM AUTHOR]

• The effect of slotting on the optical properties of silver nanopillars is studied. • Slotting can enhance the resonance absorption peaks of silver nanopillars. • The best slotting method offers a 13 % improvement compared to nanopillars. • This work shows slotting has a promising prospect in solar thermal utilization. Metal nanoparticles (MNPs) have attracted enormous research interest due to their excellent plasma properties. However, in the thermal utilization of solar energy, the narrowband absorption of MNPs limits their application. The investigation of MNP absorption through adjustment in the broadband spectrum holds significant scientific and practical implications. In this work, we study the effect of slotting on the light absorption and photothermal properties of silver nanopillars. The results show that the increase in the number of slots is beneficial to reduce scattering and improving the resonance absorption of silver nanopillar. Through the calculation of photothermal conversion efficiency, it is found that different slotting methods have different levels of improvement compared with silver nanopillars. The utilization of a combination of transverse and longitudinal slotting techniques leads to a 13 % enhancement in the photothermal conversion efficiency of silver nanopillars. The electric field distribution and temperature distribution at resonant wavelengths shows that the excellent light absorption ability of the slot nanopillars is caused by the "lightning rod" effect at the tip of the slit and the excitation of multiple plasmon resonances. The existence of slots is beneficial to compensate for the photothermal response of silver nanopillars in the near-infrared region. Our study proves that slotting helps enhance the application of silver nanopillars in solar thermal utilization. [ABSTRACT FROM AUTHOR]

MXene has received a lot of attention from researchers in the fields of photothermal and photovoltaic due to its excellent optical properties. However, research on MXene-based solar absorbers has rarely been carried out. In this work, we proposed a MXene-based solar absorber with absorption broadband, wide-angle, and polarization insensitive. The absorber has excellent light capture capability, with its average absorption in the solar band as high as 97.8 % and an energy absorption ratio of 98.9 % in the AM1.5 solar radiation spectrum. The electric and magnetic field distributions indicate that the unique hierarchical nanohole design can effectively excite multiple resonance couplings of surface plasmon resonance, cavity resonance, and guided mode resonance. The proposed absorber can still maintain the broadband absorption characteristics within a certain manufacturing tolerances. Moreover, the absorber is insensitive to polarization and has a high light absorption under a large incident angle. We believe that this work holds great promise for solar thermal conversion and heat utilization. [ABSTRACT FROM AUTHOR]

Novel nanofluids (NFs) based on bio-nanotechnology have enormous potential for solar thermal utilization. The biomimetic nanoparticles (NPs) nanostructures provide new ideas for the design of solar collector medium. Inspired by the biological properties of waxberry, we proposed waxberry-shaped biomimetic nanoparticles (WSBNPs) for solar thermal conversion in this work. Numerical results show TiN WSBNPs exhibit good optical absorption properties compared to Ag- and Au-based WSBNPs. When the volume fraction f v = 5 × 10−6 and the depth h = 15 mm, the photothermal conversion efficiency η abs can reach 93.9%. The mechanistic analysis shows that the high absorption performance of WSBNPs can be attributed to the presence of the "lightning rod" effect on the surface of NPs and the mutual coupling of surface plasmon resonance. The η abs of TiN WSBNPs can reach 90% at a lower penetration h = 11 mm and f v = 5 × 10−6. Meanwhile, the η abs of WSBNPs is proportional to the number of protrusions on the exterior surface. It has been shown that TiN WSBNPs with a raised exterior surface have excellent potential for efficient solar energy utilization. [ABSTRACT FROM AUTHOR]