Stimulus-responsive water soluble synthetic nanographene

Nanographenes (NGs) are exceptionally hydrophobic. They are insoluble in water, preventing the exploration and utilization of their photophysical properties under aqueous conditions. This work discloses an atomically precise water-soluble synthetic NG 1, featuring a 2 nm sp² carbon skeleton appended with 12 branched triethylene glycol chains. It synergistically combines low critical solution temperature (LCST) behavior and a photothermal effect to create the first thermo- and photo-responsive atomically precise NG functioning in an aqueous solution. The LCST behavior can be attributed to a delicate balance of hydrophobic-hydrophilic interactions, providing a sensitive thermal response to changes over a temperature range of physiological interest (close to 37 °C). Moreover, 1 has considerable photothermal conversion capability, with irradiation of 1 in water by red or near infrared light increasing the solutions temperature to above the clouding point within seconds, leading to a reversible clear-to-turbid transition over many cycles without evident fatigue. [Figure not available: see fulltext.]