Abstract
Nanoporous SnO2 thin films were elaborated to serve as sensing electrodes for label-free DNA detection using electrochemical impedance spectroscopy (EIS). Films were deposited by an electrodeposition process (EDP). Then the non-Faradic EIS behaviour was thoroughly investigated during some different steps of functionalization up to DNA hybridization. The results have shown a systematic decrease of the impedance upon DNA hybridization. The impedance decrease is attributed to an enhanced penetration of ionic species within the film volume. Besides, the comparison of impedance variations upon DNA hybridization between the liquid and vapour phase processes for organosilane (APTES) grafting on the nanoporous SnO2 films showed that vapour-phase method is more efficient. This is due to the fact that the vapour is more effective than the solution in penetrating the nanopores of the films. As a result, the DNA sensors built from vapour-treated silane layer exhibit a higher sensitivity than those produced from liquid-treated silane, in the range of tested target DNA concentration going to 10 nM. Finally, the impedance and fluorescence response signals strongly depend on the types of target DNA molecules, demonstrating a high selectivity of the process on nanoporous SnO2 films.
Highlights
Over the last decades, development of genosensors has increased significantly, as demonstrated by the large number of scientific publications on this topic [1]
We have studied the label free DNA detection using electrochemical impedance spectroscopy (EIS) on 0D nanoporous SnO2 films that have been deposited by an electrodeposition process
The results have shown a systematic decrease of the impedance upon DNA
Summary
Development of genosensors has increased significantly, as demonstrated by the large number of scientific publications on this topic [1]. Different kinds of sensitive materials for non-Faradic EIS DNA detection have been reported, including metals [17,18], conductive polymers [19,20,21] and semiconductors [22,23,24,25,26,27,28,29] The latter can be divided into two categories including CMOS heterostructures [22,23,24] and single working electrodes [25,26,27,28,29]. The idea is to reduce more the dimensionality of the electrode material down to 0D by elaborating nanoporous SnO2 films constituted of SnO2 nanoparticles and to investigate the resulting effect on the impedance signal upon. The obtained results help us to have a more complete view and understanding on the effect of the SnO2 sensing electrode morphology and dimensionality on the response signals to non-faradic DNA detection
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