pKa determination of graphene-like materials: Validating chemical functionalization

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Graphene-based materials like graphene oxide (GO) and graphene nanoribbons (GNR) possess diverse functional groups.
• Accurate quantification of these functional groups is crucial for tailoring material properties and applications.
• Existing methods for functional group quantification can be complex and time-consuming.

Purpose of the Study:

• To introduce a novel and simplified computational method for determining the pKa values of various functional groups on graphene-like materials.
• To quantify the composition and degree of functionalization for different graphene derivatives.
• To validate the method's efficacy compared to traditional techniques.

Main Methods:

• Utilized the BEST7 computational program to analyze titration curves of graphene oxide (GO), reduced GO (rGO), graphene nanoribbons (GNR), oxidized GNR (GONR), and their functionalized derivatives (GOSH, GOIMZ, GONRSH).
• Discriminated pKa values for carboxylic acid and alcohol groups, and quantified their composition.
• Identified and quantified thiol and imidazole functional groups after modification of GO and GONR samples.

Main Results:

• Successfully determined pKa values for carboxylic acids (pKa1≈4.0, pKa2≈6.0) and alcohols (pKa4≈10.0) in graphene materials.
• Identified pKa values for thiol (pKa≈6.7) and imidazole (pKa≈6.6) moieties on functionalized graphene derivatives.
• Quantified the degree of functionalization, revealing thiol content of 48% (GOSH) and 36% (GONRSH), and imidazole content of 29% (GOIMZ).

Conclusions:

• The developed computational method offers a simpler and innovative approach for pKa determination and functional group quantification in graphene-based materials.
• This method provides accurate insights into the chemical composition and functionalization degree of GO, rGO, GNR, and their derivatives.
• The findings facilitate a better understanding and control over the chemical properties of graphene materials for advanced applications.