Exogenous photothermal agents absorbing in the second near-infrared optical window (NIR-II, 1000−1700 nm) have received much attention due to their use in noninvasive photothermal therapy. A small quantity of organic NIR-II photothermal agents have been exploited, and the development of organic NIR-II photothermal materials is an urgent need for biological applications. In this study, we designed and synthesized three dithiolene nickel(II) complexes with different ligands bis(phenyl) dithiolene for NiBD-Ph, bis(fluorenyl) dithiolene for NiBD-Fl, and bis(carbazolyl) dithiolene for NiBD-Czand investigated their photophysical properties. These complexes exhibited ligand-dependent NIR absorption performance, centered at 854 nm for NiBD-Ph, 942 nm for NiBD-Fl, and 1010 nm for NiBD-Cz, respectively. NiBD-Cz is wrapped in ethylene oxide/propylene oxide block copolymer (F-127) through a hydrophilic− hydrophobic interaction to form water-soluble NiBD-Cz/F-127 nanoparticles (NiBD-Cz NPs), and the absorption peak of NiBD-Cz NPs are red-shifted to 1036 nm. NiBD-Cz NPs exhibit good dispersibility in water, robust photostability, and a high photothermal conversion efficiency (PCE) of 63.6% under 1064 nm laser irradiation, which is the highest PCE among metal bis(dithiolene) complexes up to now. The high PCE makes it possible to achieve better photothermal treatment effects even at low concentrations and under low-power laser irradiation.

The black-nickel film on the flat type radiometer chip was investigated, and a black-nickel film which can be applied in this chip was prepared using electroplating method. The analyses of absorption of radiometer chip indicated that the absorption rate of the chip is proportional to the surface roughness. The black-nickel film was prepared and tested, and surface morphology testing showed that this film has microstructures of the scale 50 nm—1.5 μm. Infrared absorption measurement indicated that the absorptivity of the film in the 1.4—8 μm range is higher than 0.989. This high absorptivity black-nickel film improves the performance of the chip.