Lead-Free Double Perovskite Cs₂AgInCl₆ Nanocrystals Supported on Graphene for Photoelectrochemical Biosensing of 8-Hydroxy-2′-deoxyguanosine

Suitable photoactive materials play an important role in the construction of photoelectrochemical (PEC) sensors. In this work, a novel photoactive material, lead-free double perovskite Cs 2 AgInCl 6 nanocrystals supported on graphene (Cs 2 AgInCl 6 /G), with superior phototo-electric conversion efficiency was prepared by a simple thermal injection method. The morphology, structure, and PEC properties were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and PEC methods. The results show that the obtained Cs 2 AgInCl 6 /G reveals better PEC performance than pure Cs 2 AgInCl 6 in aqueous media with dissolved oxygen and the DNA oxidative stress damage biomarker of 8-hydroxy-2′-deoxyguanosine (8-OH-dG), which inspired us to develop an electron donor–acceptor codriven PEC sensing platform for highly sensitive biosensing of 8-OH-dG. 8-OH-dG and dissolved oxygen can be used as an electron donor and acceptor to efficiently reduce electron–hole pair recombination and thus enhance the cathodic photocurrent response. The resulting PEC sensing platform presents efficient PEC performance for 8-OH-dG with a detection limit down to 3.3 nM and a broad linear range from 0.005 to 1000 μM. Moreover, the designed PEC sensor has been successfully applied to measure the amount of 8-OH-dG in a biological matrix such as urine samples with satisfactory results. The wonderful cooperation of Cs 2 AgInCl 6 /G with the electron donor–acceptor synergy concept for simple and accurate PEC sensing of 8-OH-dG provides a new perspective to design and develop advanced PEC sensing strategies.