posted on 2024-01-16, 22:30authored byAyesha Kousar, Ulviyya Quliyeva, Ishan Pande, Jani Sainio, Jaakko Julin, Timo Sajavaara, Hua Jiang, Tomi Laurila
There
is a significant lack of literature addressing changes in
the microstructure of different interfacial metal layer combinations
employed in fabricating electrochemical sensors based on carbon nanomaterials.
This research gap extends to analyzing their influence on the electrochemical
performance, which, in turn, impacts the understanding of the properties
of materials incorporating these layers. In this study, microstructural
variations and electrochemical activity of chromium and titanium adhesion
layers, in combination with nickel catalyst layers (designated as
TiNi and CrNi), on silicon wafers were analyzed post annealing. Interestingly,
during a brief annealing period of 5 min, TiNi developed a surface
layer comprising graphitic carbon, alongside the formation of TiO2, TiC, and NiSi, and exhibited electrochemical activity toward
both dopamine (DA) and ascorbic acid (AA). Conversely, CrNi annealed
for 5 min did not show the presence of such a carbon layer and displayed
no discernible electrochemical activity toward the target molecules.
Only after an extended annealing time of 20 min, signs of a carbon
layer appear on CrNi, displaying a moderate electrochemical activity
toward DA and AA. The formation of a carbon layer on CrNi is delayed
due to the presence of Ni near the surface, which disrupts the local
equilibrium. Consequently, the formation of the Cr2O3 barrier layer is delayed, which in turn permits carbon diffusion
into the underlying Cr layer. Conversely, Ni stabilizes the β-Ti
form and markedly decreases the solubility of carbon and oxygen within
the TiNi system. By providing a comprehensive analysis of microstructural
changes and their impact on the surface chemistry and electrochemical
responses of commonly used interfacial metal layers, this paper offers
invaluable insights in selecting suitable adhesion and catalyst layer
combinations for carbon nanomaterial fabrication.