Nanographite Synthesized from Acidified Sucrose Microemulsions under Ambient Conditions

Abstract

We show here that nanographite can be synthesized at room temperature and pressure through a simple process of acidifying sucrose microemulsions. This is in contrast to conventional wisdom, which stipulates that graphite can only be produced using high temperatures. Natural graphite arises via progressive metamorphisms of carbonaceous material subjected to temperatures above ∼600 K and pressures >2 kbar. Synthetic pyrolytic graphite requires temperatures >2500 K, and even nanographite formation from amorphous carbons requires temperatures >850 K. Our synthesis route utilizes the dehydration of sucrose by concentrated sulfuric acid, a variant of the well-known carbon black snake experiment, which produces an amorphous carbonaceous product. Crucially, though, we conduct the reaction in nanometer-sized microemulsion droplets to exert control over the reaction and sheet stacking process. This ensures that only sufficiently pristine graphene nanosheets can stack, thereby producing nanographite in a simple one-step synthesis under ambient conditions. The primary nanographitic particles of size ∼3-30 nm stack in crystallographic registry to form larger 250 nm- to μm-sized nanographitic aggregates. The amount of nanographite produced from the microemulsions is limited, however, because the sucrose concentration must be kept very low to slow the reaction kinetics. Hence, this is not a viable method for commercially producing nanographite.