Effect of Al2O3 thickness on performance of Al2O3/CNTS in the electrochemical sensing of di- hydroxybenzene isomers

This study aimed at analyzing the effect of thickness of dielectric Al
₂
O
₃
coatings deposited onto the conductive stacked- cup carbon nanotubes (SCCNTs) on their electrochemical properties. Atomic layer deposition (ALD) technique was used to deposit well-controlled variable thicknesses of Al
₂
O
₃
on the SCCNTs substrates. Transmission electron microscopy (TEM)), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and the energy dispersive X-ray spectroscopy (EDX) elemental-mappings clearly demonstrated the successful conformal deposition of Al
₂
O
₃
with different thicknesses onto the inner and outer walls of the carbon nanotubes. The SCCNT/Al
₂
O
₃
(X) modified screen printed electrodes (SPEs) were used towards the simultaneous determination of di-hydroxybenzene isomers, hydroquinone (HQ) and catechol (CC). SCCNT/Al
₂
O
₃
nanostructures resulted highly active towards di-hydroxybenzene isomers and both sensitivity and selectivity of the developed electrochemical sensors are strongly dependent on the thickness of the Al
₂
O
₃
layer. The remarkable performance of the as-synthesized SCCNT/Al
₂
O
₃
heterostructures can be attributed to the conformal coating of the Al
₂
O
₃
shell layer, the optimized thickness of the Al
₂
O
₃
film and the CNT conductive substrate.