Nanoreactor-confined synthesis and separation of yellow-luminescent graphene quantum dots with a recyclable SBA-15 template and their application for Fe(III) sensing

Graphene quantum dots (GQDs) have inspired growing research efforts. Although continuous progresses have been achieved in the syntheses of diverse GQDs, it is still a challenge in size-controllable and high-yield preparation of well dispersed GQDs via simple routes. Herein, we present a top-down synthesis of GQDs by using a SBA-15 template as a nanoreactor via a HNO3 vapor cutting strategy. With the recyclable ordered mesoporous SBA-15 template and a silica grid, a high-yield (48%) preparation as well as a facile separation of yellow-luminescent GQDs have been achieved. The obtained GQDs containing abundant oxygen-containing groups (ca. 30% for oxygen content) showed a narrow size distribution (2.5-5.2 nm), good water solubility, good photostability and high selectivity for Fe(III) sensing in tap water with satisfying recovery. Further experiments indicated that Cu(II), Co(II), Mn(II), Ni(II) could also quench the fluorescence of the as-prepared GQD after its surface states being adjusted, which might presage more possible applications of this material.