Comparative studies on zirconia and graphene composites obtained by one-step and stepwise electrodeposition for deoxyribonucleic acid sensing Original Research Article

In this paper, the comparison of two kinds of electrochemically reduced graphene oxide (ERGNO) and zirconia composites, obtained by one-step (ZrO2–ERGNO) and stepwise (ZrO2/ERGNO) electrodeposition for DNA sensing, is systematically studied. The resulting composites were characterized by scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. The results indicated that the ZrO2–ERGNO presented fine globular nanostructure. However, ZrO2/ERGNO presented agglomerate massive microstructure due to the absence of the oxygen-containing groups of graphene oxide, confirming the oxygen-containing groups provided a better affinity for the deposition of ZrO2. Due to the strong binding of the phosphate groups of DNA with the zirconia film, DNA probes were attached on the ZrO2-based composites. ZrO2–ERGNO/Au owning fine nanostructure presented larger surface area than microstructured ZrO2/ERGNO/Au. Moreover, compared with microstructured ZrO2/ERGNO, the nanostructured ZrO2–ERGNO provided more accessible space for immobilized DNA probe hybridization with target sequence, which consequently resulted in higher hybridization efficiency. Therefore, the ZrO2–ERGNO was chosen for fabricating DNA sensor with a limit of detection 1.21 × 10−14 mol L−1.