Discerning Site Selectivity on Graphene Nanoflakes Using Conceptual Density Functional Theory Based Reactivity Descriptors

Abstract

Graphene nanoflakes (GNFs) have more configurational degrees of freedom as compared to Graphene nanoribbons (GNRs) and are viable candidates for future nanodevices. GNFs can be devised with disparate geometries, and their electronic properties can be fine-tuned by genuine chemical functionalization. Hence, it is vital to know specific sites on GNFs where reaction is most feasible for chemical functionalization with donor–acceptor functional groups (nucleophiles/electrophiles). Here, we present spin-polarized and dispersion-corrected density functional theory based relative reactivity descriptor calculations to shed light on the reactivity pattern in small-sized GNFs. To have a clear understanding on the structure–property relationship, we consider GNFs with 24, 42, and 54 carbon atoms having various edges, namely, fully armchair, armchair/zigzag (arm-zig), and fully zigzag. All the edge atoms are saturated by hydrogen atoms. On the basis of the symmetry of the GNFs, susceptibility of assorted reactive sites pertinent to nucleophilic and electrophilic attacks is anticipated using relative reactivity descriptors. Further, we validate these relative reactivity descriptors for nucleophilic attack on armchair-C24H14 and zigzag-C24H12 by explicit adsorption of OH–, NH2–, and H2O molecules. Our study reveals that the reactivity pattern varies in small-sized GNFs as a function of shape. Importantly, few specific structural isomers have alternate Lewis acid–base pairs. It also manifests how the reactivity of peripheral and interior carbon atoms differ with shape and size of GNFs. With a discernment on site selectivity, GNFs can be functionalized by proper donor–acceptor groups at specific sites and hence can be used as potential candidates for molecular- and nanoelectronics.