Self-assembled monolayer of 3-mercaptopropionic acid on electrospun polystyrene membranes for Cu2+ detection

A highly sensitive coating comprising 3-mercaptopropionic acid (MPA) monolayer modified electrospun polystyrene (PS) membranes was constructed on the electrode of quartz crystal microbalance (QCM) for Cu2+ detection. The three-dimensional fibrous PS membranes with high specific surface area (SSA) were deposited on the electrode of QCM via electrospinning. The PS membranes were sputter coated with gold, then modified with self-assembled monolayer of MPA. The PS-MPA sensors showed fast response (2–3 s) to Cu2+ and a detection limit down to 100 ppb. Additionally, sensor sensitivity increased concurrently with both increasing PS loading and SSA on QCM electrodes. The response of the PS-MPA sensors with a PS membrane loading of 978 Hz and SSA of 43.31 m2/g was 40 times larger than that without membranes when exposed to 1 ppm of Cu2+. The sensor responses were reproducible toward Cu2+ in the 100–5 ppm concentration range, whereas a linear response was found in the 100–1 ppm concentration range. The sensor response to Cu2+ showed a linear relationship with an increase in pH from 2 to 7. Moreover, the sensors also exhibited chelation selectivity for other transition metal ions in the descending order Cu2+ > Ni2+ > Zn2+ > Fe2+ at concentration between 1 and 5 ppm.