Wide linear-range detecting high sensitivity cholesterol biosensors based on aspect-ratio controlled ZnO nanorods grown on silver electrodes

We have fabricated highly sensitive and wide linear-range detecting cholesterol biosensors based on zinc oxide nanorods (ZnO NRS). We report, for the first time, the use of aspect-ratio (AR) controlled ZnO NRs grown directly on silver (Ag) electrodes in solution at 90 °C for the fabrication of cholesterol biosensors. More immobilization of enzymes and faster electron conduction with larger AR ZnO NRs were obtained. The biosensor with AR = 60 ZnO NRs exhibits a high reproducible sensitivity of 74.10 μA/mM/cm2, a wide linear range up to 16.0 mM, and a fast response time less than 2 s, which is the best reported to date for cholesterol biosensors using ZnO nanostructures. Furthermore, the fabricated biosensors show an excellent anti-interference ability against electroactive species such as glucose, ascorbic acid, l-cysteine, and uric acid.