Sun Capture

The Sun's spectrum peaks at about $5.99584916e14\,Hz$.  From the post "Photons With Kinetic Energy?" dated 5 Dec 2017,

$f=\sqrt{\cfrac{c^3}{8\pi}*{density}*{Z}*3.4354}$

The best material to absorb this frequency is,

${density}*{Z}=f^2\cfrac{8\pi}{c^3}*\cfrac{1}{3.4354}=(5.99584916e14)^2*\cfrac{8\pi}{c^3}*\cfrac{1}{3.4354}$

${density}*{Z}=97611.69$

where $density$ is in $kgm^{-3}$ and $Z$ is the atomic number or the sum of all atomic numbers in a molecule.

At this high value, water ($Z=10$) cannot act as a good absorber because of its low density $1000\,kgm^{-3}$

Titanium $Z=22$ and density $4506\,kgm^{-3}$, on the other hand,

${density}*{Z}=22*4506=99132$

comes close to this value,  so a suspension of $Ti$ or $TiO_2$ ($Z=22+2*8=38$, density $4230\,kgm^{-3}$ (Rutile) and $3780\,kgm^{-3}$ (Anatase)) in a suitable fluid such that its adjusted density is,

$suspension\,density=\cfrac{97611.69}{Z}$

will absorb at the Sun's peak frequency.

For the case of $Ti$,  by weight, a portion,

$\cfrac{97611.69}{99132}=0.98466$

of the suspension is $Ti$ and the rest by weight is fluid.  Given the high density of $Ti$, it might still be possible for a good suspension that flow with low viscosity.

For the case of $TiO_2$, Anatase, in a suspension of,

$\cfrac{97611.69}{38*3780}=0.67956$

portion $TiO_2$ by weight.  A light weight fluid will hold this material in suspension that flows well.

It is best that the suspension flows to prevent settlements.

But what is captured from the Sun's spectrum?