Transparent substrates comprising three-dimensional porous conductive graphene films and methods for making the same
Disclosed herein are graphene coatings characterized by a porous, three-dimensional, spherical structure having a hollow core, along with methods for forming such graphene coatings on glasses, glass-ceramics, ceramics, and crystalline materials. Such coatings can be further coated with organic or inorganic layers and are useful in chemical and electronic applications.
1. An article comprising:
a dense substrate comprising a glass, a glass ceramic, a ceramic, an inorganic crystalline or polycrystalline material, the dense substrate has a surface roughness (Ra) of 2 nm or less; and
a coating layer having a thickness from about 500 nm to about 800 μm adhered to the substrate, the coating layer comprising a porous, three-dimensional construction having an average surface area from about 200 m 2 /g to about 2200 m 2 /g, the porous, three-dimensional construction comprising a random network of a plurality of three-dimensional graphene structures having hollow cores,
wherein the three-dimensional graphene structure is spherical and has an average diameter from about 20 nm to about 500 nm.
2. The article of claim 1 , wherein the hollow core of the at least one three-dimensional graphene structure is substantially free of a metal or metal oxide.
3. The article of claim 1 , wherein the average diameter as measured by scanning electron microscope of the at least one three-dimensional graphene structure is from about 50 nm to about 500 nm.
4. The article of claim 1 , wherein the average surface area of the porous, three-dimensional construction is from about 500 to 1500 m 2 /g.
5. The article of claim 1 , wherein the porous, three-dimensional construction has a porosity of from about 90% to about 99.6% as measured by scanning electron microscope.
6. The article of claim 1 , wherein
the dense substrate is transparent; and
the adhesion of the coating layer to the dense substrate exhibits an effective adhesion energy at the interface of the coating layer and the substrate of from about 0.1 J/m 2 to about 4 J/m 2 .
7. The article of claim 1 , wherein the dense substrate comprises a transparent material and the optical transmission of the article, as measured by ultraviolet-visible spectroscopy, is greater than 60% at 550 nm.
8. The article of claim 1 , wherein the substrate comprises fused silica.
9. An article comprising:
a substrate that is dense and transparent, the substrate comprising a glass and a thickness of 0.1 mm to 2.5 mm, the substrate having a surface roughness (Ra) of 2 nm or less; and
a porous coating on the substrate, the porous coating comprising a random network of a plurality of spherical hollow graphene structures having an average diameter from about 20 nm to about 500 nm, wherein the porous coating has an average surface area from about 200 m 2 /g to about 2200 m 2 /g, and a thickness of 20 nm to 800 nm;
wherein the article has a transmittance of 40% to 80% at 550 nm, and the coating has a sheet resistance of 1.5 kQ/sq to 10 kQ/sq; and
wherein adhesion of the coating to the substrate exhibits an effective adhesion energy at an interface of the coating and the substrate of from about 0.1 J/m 2 to about 4 J/m 2 .
10. The article of claim 9 , wherein the substrate is fused silica.
11. The article of claim 9 , wherein the substrate further comprises copper, the amount of which decreases as a function of distance into the substrate from the interface.