Layer-by-layer growth of Cu(HHTP) films on Cu(OH) nanowire arrays for high performance ascorbic acid sensing.

Growing three-dimensional (3D) metal organic frameworks (MOFs) via heterogeneous epitaxial growth on metal hydroxide arrays are effective for constructing electrochemical sensor. However, the growth of MOFs is difficult to control, resulting in thick and irregular morphologies and even damage the metal hydroxide template. In this work, Cu(HHTP) (HHTP = 2, 3, 6, 7, 10, 11-hexahydroxytriphenylene) films with controllable thickness and morphology were successfully prepared on Cu(OH) nanowire arrays (NWAs) through layer-by-layer (LBL) growth method. We have discovered that the LBL cycle and the reaction solvent composition are crucial for growing homogenous MOF thin films. The Cu(HHTP) based ascorbic acid (AA) sensor, fabricated in ethanol within 10 LBL cycles, generated an ultrahigh sensitivity of 821.64 μA mM cm in the range of 6-981.41 μM, a low detection limit of 60 nM as well as the great selectivity, stability and reproducibility. Moreover, the relative deviation for AA detection in two fruit juices were 3.22 % and 3.71 %, and the test result for human sweat fall within the normal AA concentration range, verifying the feasibility of as-prepared sensor for practical application.