Origin of observed narrow bandgap of mica nanosheets

Abstract

Mica nanosheets possess peculiar feature of narrowed bandgap with the decrease of thickness but a conclusive theoretical understanding of the narrowing mechanisms is still under development. In this report, first-principles calculations were carried out to investigate the electronic band structure of mica nanosheets with the deposition of K2CO3. Bulk mica shows an indirect bandgap of 4.90 eV. Mica nanosheets show similar electronic structures to bulk mica with a gradually increased bandgap of 4.44 eV, 4.52 eV and 4.67 eV for 1-layer, 2-layers and 3-layers nanosheets, respectively, which is attributed to the lattice relaxation. K2CO3 is found to have strong affinity towards mica nanosheets. The K2CO3 deposited mica nanosheets showed an increased bandgap with the increase of thickness, consistent with experimental observations. The calculated bandgap of K2CO3 deposited mica for 2-layers and 3-layers nanosheets are 2.60 eV and 2.75 eV, respectively, which are comparable with the corresponding experimental values of 2.5 eV and 3.0 eV. Our theoretical findings support the experimental evidence of surface contamination of mica by K2CO3, and provide new insight into the structure and properties of 2D mica.

Mica nanosheets synthesized via liquid Ga embrittlement: demonstrating enhanced CO2 capture

“…The formation of K 2 CO 3 on the mica surface has been previously reported in experiments, 33 and further insights have been gained through first-principles calculations conducted by our research group. 34 Our study demonstrated that the calculated binding energy between few-layered mica and K 2 CO 3 is negative, indicating a favorable interaction. Additionally, we found that K 2 CO 3 had a greater affinity for mica nanosheets than for bulk mica.…”

“…Additionally, we found that K 2 CO 3 had a greater affinity for mica nanosheets than for bulk mica. 34 This K 2 CO 3 layer enhances electron transfer to CO 2 and facilitates further CO 2 adsorption through physisorption. 7 Moreover, the efficiency of many CO 2 capture systems can be affected by contaminants like water vapor or other organic substances.…”

Efficient Synthesis of 2D Mica Nanosheets by Solvothermal and Microwave-Assisted Techniques for CO2 Capture Applications

“…However, it is known that preparing mica surfaces that are truly clean is not easy, since mica has a high-energy surface that readily adsorbs water, organic contaminants, and gases from the atmosphere. Previous experimental and theoretical studies suggest the deposition of potassium carbonate (K 2 CO 3 ) crystals on the mica surface, [ 27 , 51 , 52 , 53 ] which can be attributed to the reaction of ambient water and CO 2 with surface K + ions. Considering that our eMica nanosheets are prepared and maintained in an open environment rather than under an ultrahigh vacuum, it is relatively impossible to avoid deposition of K 2 CO 3 on the high-energy mica monolayer surface, which is in agreement with the presence of C=O in XPS analysis of eMica nanosheets ( Figure 6 c).…”

“…The stable supercell structure of mica, mica monolayer and K 2 CO 3 -deposited mica monolayer obtained in our previous work [ 27 ] was adopted to investigate their CO 2 adsorption behavior. Mica surface was obtained by cleaving the bulk in the (001) direction.…”

A new multifunctional energy harvester based on mica nanosheet-dispersed PVDF nanofabrics featuring piezo-capacitive, piezoelectric and triboelectric effects

“…39 Mica consists of two tetrahedral (aluminium, silicon, oxygen) units and an octahedral unit (aluminium, oxygen, hydrogen), and an interlayer cation (potassium). 40 The presence of hydroxyl and oxygen groups on the surface of MNS could facilitates its interaction with PVDF chains, enhancing the β-phase content of the latter. Also, MNS could enhance the dielectric properties of PVDF.…”