Layered materials

Graphite, LDHs, RP-Oxides

Graphite:
LDH: Between the layers: Nitrate, H\(_2\)O anionic between the cationic layers, much stronger interlayer bonds(hydrogen bonds) than graphite.
RP: Ruddlesen-popper. Extremely high interlayer bonds, polarcovalent.

Delamination: Remove them somewhat from each other
Exfoliation: Completely remove the layers from each other
Reconstruction: The reverse process of the aforementioned: restacking layers
Graphite easy to delaminate, LDH harder and RP phases hard to delaminate.

Delamination:
- Weaken interlayer forces:
  - External force (shear; ultrasonication)
  - Soft chemistry: Solvents. Formamide easily delaminates nitrate LDH.
  - Stabilize nanoflakes in suspension: Good solvent needed, “likt løser likt”

h-BN has equal crystal structure to Graphite
All three can be exfoliated.
- Graphene: conducting properties, strong
- Songle Layer Boron Nitride: Coatings, dielectric
- MoS\(_2\): Lube(as bulk), quantum dots(since it is semiconductor)

Crystal structure: As Brucite - Mg(OH)\(_2\). Spacegroup: P3m1
Fill anions between the cation hydroxide layers to establish charge neutrality.
Other cations must have about the same size as magnesium.
Carbonate anions are most used in nature. Organics like amino acids can also be used.
Driving force of delamination:
- Ex: Formamide has equal oxygen to nitrate, which makes it easy to replace nitrate with formamide. The layers are expanded in the Z axis and the delamination is made much easier since the bond strength is lowered.
Reconstruction can be done by adding sodium carbonates since carbonates is so strongly bonded between brucite layers (also hard to exfoliate LDHs with carbonates)

Create LDH, manipulate the chemical structure of the LDH
Ni Al Mg homogenoeusley dispersed in the Brucite layers by wet chemistry synthesis (Can also be made by delamination of two LDH’s: one with MgAl and another with NiAl, which can be mixed and restacked by adding sodium carbonate.)
Heat treat it to remove carbonate and H\(_2\)O. Then you have MgNi(Al)O, but we need metallic Ni on the MgAlO!
Heat again (650C) with H\(_2\) gas. This reduces the ox state of Nickel, which diffuses to surface and crystallizes as metal blobs.
Ni-loading can be found by MP-AES(Microwave Plasma Atomic Emission Spectrometry)
But Ni(s)/Ni\(^{2+}\) can be found by paramagnetic momentum of metallic nickel.(by getting max saturation magnetization of sample.)

n = \(\infty\) -> only rocksalt phase. RP-1 -> n = 1 -> 0.5 rocksalt layer separates 1 berovskite block.
22% power conversion efficiency in the use of RP phase solar cells.
The higher the n, the higher the wavelength of absorption of light. Higher absorption energy -> smaller quantum dot (really layer thickness)
When doing monolayer RP phases, all absorption peaks are shifted only slightly to higher energies. Main takeaway: monolayers doesnt really affect it, which proves the quantum dot effect in the above point.