A signal-on photoelectrochemical aptasensor based on ferrocene labeled triple helix DNA molecular switch for detection of antibiotic amoxicillin.

• P-type CuInS 2 microflower recombined rGO modified ITO was used as photocathode. • Target was recognized by triple helix DNA switch in homogeneous solution. • Ferrocene labeled single stranded DNA was released as signal probe. • Energy level matching between ferrocene and CuInS 2 leaded an enhanced photocurrent. A sensitive signal-on photoelectrochemical aptasensor for antibiotic determination was constructed based on the energy level matching between ferrocene and CuInS 2. P-type CuInS 2 microflower was complexed with reduced graphene oxide (CuInS 2 /rGO) to get photocathode current with good photoelectric conversion efficiency and stability. Then, hairpin DNA (HP) was covalently bonded to the electrode surface. A triple helix DNA (THMS) was used as a molecular switch. After the specific recognition between target and THMS in homogeneous solution, ferrocene labeled probe (Fc-T2) was released. Finally, Fc-T2 was captured by the HP, which leaded the obvious increase of photocurrent for the energy level matching between ferrocene and CuInS 2. The increase of the photocurrent signal was proportional to the concentration of target amoxicillin (AMOX), the linear range was 100 fM-100 nM with detection limit of 19.57 fM. Meanwhile, the method has been successfully applied for milk and lake water samples analysis with satisfactory results. [ABSTRACT FROM AUTHOR]