Preparation Of Zinc Oxide-based Micro-/Nano-materials And Their Application In Biosensors

Biosensors have great potential applications in many areas, such as medicine, food control, and environmental protection. Among them, enzyme-based electrochemical biosensors have attracted much attention of researchers due to their good selectivity, high sensitivity, low detection limit, easy fabrication, robustness, etc. Because of the features of enzymes, immobilization method and materials play a vital part in the fabrication of biosensors. ZnO has attracted considerable interest in the application of biosensors due to many advantages, such as non-toxicity, bio-safety, excellent biological compatibility, high electron-transfer ability, high isoelectric point (IEP～9.5), and easy preparation. All these advantageous properties render ZnO suitable for immobilization of biomolecules. On the other hand, considerable attention has been paid to develop non-enzymatic biosensors in order to overcome the disadvantages of the enzymatic electrodes, such as instability, high cost of enzymes and complicated immobilization procedure, harsh environment requirements during storage and use. CuO is a kind of attractive material and has excellent electro-catalytic ability towards glucose.Given the above considerations, in this article, ZnO with novel micro-/nano-structures were fabricated to immobilize enzymes; and ZnO-CuO composite porous core-shell spheres were applied in non-enzymatic glucose biosensor. The main contents and results are as follows:(1) Micro/nano-porous ZnO films were synthesized through a simple biotemplate-directed method using mango core inner shell membrane as template. The products are ideal platforms for the immobilization of enzymes. The fabricated glucose biosensor based on the porous ZnO films exhibits good selective detection ability of the analyte with high sensitivity, good stability and wide linear range.(2) ZnO micro-pompons were fabricated by a controlled synthesis route via a soft template-directed wet chemical method followed by a subsequent calcination in air. The enzymatic electrode fabricated with Horseradish peroxidase (HRP) immobilized on ZnO micro-pompons exhibits excellent response for detecting H2O2, with a wide linear range of0.2-3.4mM and a high sensitivity of1395.64μA/mMcm2, indicating a great potential in fabricating electrochemical biosensors.(3) Sponge-like porous ZnO was fabricated via solution combustion synthesis followed by a subsequent calcination in air. The enzymatic electrode base on the synthesized material shows excellent detection behavior towards H2O2with a sensitivity of1405.36μA/mMcm2, illustrating that the porous ZnO bulk material is an good platform for the immobilization of biomolecules.(4) ZnO-CuO composite porous spheres with core-shell structure were synthesized through a simple top-down route to take advantage of the excellent features of these two materials. The obtained sample with a core surrounded by a porous shell has a large surface area. Non-enzymatic glucose sensors based on ZnO-CuO composite porous spheres show good performance with a wide linear range of0.02-4.86mM, a high sensitivity of845.41μA cm-2mM-1, and a low detection limit of1.677μM, indicating a good detection behavior of glucose.