Sulfonate-modified fullerenes mimicking tentacle structures for humidity sensors

In this work, a straightforward method for synthesizing fullerene derivatives with tentacle structures has been explored for monitoring environmental humidity, which involves introducing sulfonate onto the fullerenes. The structure and number of polar groups in three fullerene derivatives determined by a series of structural tests greatly affect their hydrophilicity and morphology, resulting in changes in humidity sensitive properties. In particular, the hysteresis and response time of the sensors display a great correlation with hydrophilicity. C₆₀-Ho, the best performing derivative of this work, has exhibited high response values (∼3500 times), good linearity (R² = 97.3 %), and rapid response/recovery times (0.3/4.4 s), making it suitable for various applications such as non-contact detection of respiration, finger distance, and soil humidity.