Novel photoelectrochemical sensor for cholesterol based on CH₃NH₃PbBr₃ perovskite /TiO₂ inverse opal heterojunction coated with molecularly imprinted polymers

Developing cost-effective, ease-to-use and sensitive cholesterol sensors is of great importance. Photoelectrochemical (PEC) sensor has exhibited their potential with low cost, simple instrumentation, easy miniaturization, and high sensitivity. Organometal lead halide perovskites (MAPbX₃) with exceptional opto-electronic properties have been appealing materials for optoelectronic devices. Whereas the extreme sensitivity of MAPbX₃ towards even moisture has always restricted their application in biological use. Here we report a novel MAPbX₃ photoelectrochemical cholesterol sensor with water stability. The titanium dioxide inverse opal (TiO₂ IOPCs) and CH₃NH₃PbBr₃ quantum dot heterojunction on ITO glass exhibited a remarkably increased photoelectric current density of approximately 40 μA/cm². The further encapsulation within the imprinted polymer presented high selectivity towards cholesterol and significantly improved the stability of perovskites as well. Linear detection of cholesterol in buffer was achieved with the detection limit of 2.51 × 10^-10 mol/L, lower than that of the reported cholesterol PEC sensor in aqueous buffer. Recovery rates in serum were also obtained with the cholesterol concentration lower than the reported imprinted polymer based (photo)electrochemical sensor. Additionally, the photocurrent intensity under continuous emission was maintained at 80% after immersing this sensor in an aqueous solution for 500 s. The storage stability was more than 20 days. Here we present the first MAPbX3 perovskite-based sensor applicable in aqueous samples with super sensitivity and selectivity, which promote the perovskite nanomaterial-mediated sensing of biologically important species.