Naked Science Forum

General Science => General Science => Topic started by: katieHaylor on 28/07/2017 15:18:57

Title: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: katieHaylor on 28/07/2017 15:18:57
Mark asks:

As sheets of Graphene are only one atom thick, if you turned a sheet of it edge on, would it vanish? Also, would that edge be sharp? Or too flimsy?

What do you think?
Title: Re: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: Kryptid on 28/07/2017 21:51:10
Indeed, a single atom of thickness is much too thin to see with the naked eye. A single sheet of graphene might be too thin to see at all, even when viewed from the broad side. Technically, you could say that the edge is sharp, but the sheet would be very flexible. That wouldn't make it good at cutting other things.
Title: Re: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: evan_au on 29/07/2017 02:37:12
Quote from: Mark
if you turned a sheet of it edge on, would it vanish?
A graphene sheet is much thinner (37 nm) than the wavelength of visible light (700 nm for green).

An object does not affect a wave very much if it is less than a quarter wavelength.
- So I would say that a flat single sheet would be invisible to the human eye, edge-on.
- But humans have two eyes, so then you aren't viewing it edge-on...

Quote from: Kryptid
A single sheet of graphene might be too thin to see at all, even when viewed from the broad side.
A single layer of graphene absorbs about 2% of the light passing through it.
So this would be just visible, if you had a side-by-side comparison of graphene/no graphene; it would be more visible with 4 or more layers.

Quote from: Mark
would that edge be sharp? Or too flimsy?
I understand that there are major challenges in handling graphene.
As soon as you peel it off the production substrate, the graphene quickly scrunches itself into a multi-layer mess - a bit like trying to handle a long stretch of sticky-tape in a stiff breeze with one hand!

See: https://en.wikipedia.org/wiki/Graphene#Optical
Title: Re: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: Bored chemist on 29/07/2017 11:06:17
You can see a single atom- as long as it's well enough lit.
You can't tell where it is to better precision than (roughly) the wavelength of the light you are using- but you can see it.
Title: Re: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: puppypower on 29/07/2017 11:40:07
Say you had the single layer of graphene on top of another substrate, which we can see. Could the absorption and reflection difference, due to the single layer of graphene, show up as a tonal difference than can be seen? The analogy would be like a thin layer of oil on water can cause a rainbow pattern.

Title: Re: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: Bored chemist on 29/07/2017 13:33:00
Say you had the single layer of graphene on top of another substrate, which we can see. Could the absorption and reflection difference, due to the single layer of graphene, show up as a tonal difference than can be seen? The analogy would be like a thin layer of oil on water can cause a rainbow pattern.
Probabaly
"it was the strong optical absorption
of single-layer graphene (with its absorbance of 2.3% [17], as
discussed below) that permitted the initial discovery of exfoliated
monolayers by visual inspection under an optical microscope [8].
"
from
http://heinz.phys.columbia.edu/publications/Pub193.pdf
Title: Re: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: evan_au on 30/07/2017 00:24:27
Quote from: puppypower
a tonal difference than can be seen...like a thin layer of oil on water can cause a rainbow pattern
Graphene absorbs light over a wide range of visible and infra-red wavelengths, so it appears as a grey color.

If you put a lot of layers together, it becomes black - graphite is contains many layers of graphene stacked on top of each other.
Title: Re: Edge on, would a one-atom-thick graphene sheet be visible to the naked eye?
Post by: chris on 30/07/2017 11:10:05
A propos what @evan_au has said above, it's nanotubes rather than graphene, but this interview with Pulickel Ajayan about the blackest substance (https://www.thenakedscientists.com/articles/interviews/blackest-black) yet made, makes some interesting points.

(https://www.thenakedscientists.com/sites/default/files/media/xBlackest_Black_01.jpg.pagespeed.ic.aF4dJAlVoX.webp)