it's actually rather surprising, and important, that they were able to get 90 percent solar absorptivity combined with 30 percent infrared emissivity. this is difficult because absorptivity is the same thing as emissivity, but of course you can have different emissivities at different wavelengths; that's why things are different colors. but the vast majority of opaque solid materials have rather pastel colors, which is to say that their absorptivity (and thus emissivity) varies slowly with wavelength. this is undesirable for concentrating solar power, because it makes it hard to transfer the heat energy from the sunlight to the coolant rather than reradiating it as infrared. all the materials you named with albedos of under .1 are also great absorbers of infrared, which means they're also great emitters of infrared, so they wouldn't work very well for this application. (you also happened to pick three that won't withstand kilokelvin temperatures.)
there are a number of 'spectrally selective coatings' already in existence with this unusual combination of emissivities, but they are all very expensive to produce.
the longer lifetime is useful too, but not so useful they bothered to mention it in the abstract of their paper.
the small particles mentioned are made of a silicon-germanium blend, although they claim you can use different semiconductors for this. they picked that blend because its bandgap is about a volt, so it absorbs photons of more than about an electron volt.