Rutherford Backscattering Spectrometry for Evaluating the Transfer of MoS2 Films into Printed Electrodes

Printed electrodes are promising platforms for electrochemical biosensors due to their low cost
and portability [1]; however, characterizing their surface heterogeneity and thin-film uniformity
remains a major challenge affecting device reproducibility [2]. This study evaluates the potential
of Rutherford backscattering spectrometry (RBS) as a primary tool to characterize screen-printed
carbon electrodes (SPCEs) modified with molybdenum disulfide (MoS2) films, correlating the
results with complementary micro-PIXE and Raman spectroscopy analyses.
MoS2 thin films were initially deposited on SiO2/Si substrates via sputtering, followed by a
thermal synthesis process to promote phase formation and crystallization [3]. To transfer the 2D
material onto the SPCEs, a temporary naphthalene/paraffin support layer was drop-cast on the
surface. Structural detachment was achieved via interfacial electrostatic repulsion by immersing
the samples in an aqueous ammonium hydroxide (NH4OH) solution [4]. The resulting
free-standing film was transferred onto the SPCE working region, heated at 50 °C to promote
adhesion, and the organic support was subsequently dissolved using hexane.
While the close kinematic factors of sulfur and chlorine (from the conductive ink) challenge
direct sulfur resolution via RBS, the isolated molybdenum signal serves as a reliable proxy to
quantify MoS2 coverage and homogeneity across the heterogeneous electrode surface.
Complementary micro-PIXE chemical mapping provided spatial-resolution visualization of the
conductive ink constituents and verified the uniformity of the element distribution. Crucially,
Raman spectroscopy resolved the characteristic E2g1 and A1g vibrational modes, unambiguously
confirming the structural identity and preservation of the MoS2 phase after transfer. Together,
this multi-technique approach demonstrates that RBS, alongside micro-PIXE and Raman,
constitutes a robust framework for optimizing reliable and reproducible 2D-material-based
electrochemical platforms for biosensing applications.