Considered one of the most promising materials for the technology of the future, from ultra-fast microchips to next-generation sensors, graphene owes its exceptional properties to its extraordinarily thin structure, consisting of a single layer of carbon atoms. However, although the material appears homogeneous under a conventional microscope, tiny local variations in its structure and electrical charges can radically alter its behaviour.

To identify these details, the study conducted by Sapienza University of Rome, together with the Politecnico of Turin and Graphenea, compared conventional analytical methods with advanced tools capable of observing graphene at the nanoscale, revealing defects and heterogeneities that had previously remained invisible. The research was carried out as part of the European CHALLENGES project (Real time nano CHAracterization reLatEd techNloGiEeS) and published in the journal ACS Omega. The image produced for the study was also selected for the cover of Volume 11, Issue 34, dated 1 September 2026, of the journal.

Raman spectroscopy has long been used to analyse graphene, an optical technique that makes it possible to study its structure and defects. However, this traditional method has a limitation: it measures a relatively large area of the material, effectively taking an “average” of its characteristics and concealing the smallest details. To overcome this limitation, the researchers used TERS (Tip-Enhanced Raman Spectroscopy). This advanced technology employs a tiny, highly precise probe that acts like a nanoscale magnifying glass, allowing the material to be explored at a considerably higher level of detail than with conventional analyses.

The combination of TERS measurements and mathematical data processing revealed what had previously only been hypothesised: seemingly uniform behaviour conceals a marked variety of nanoscale micro-environments. The researchers were therefore able to distinguish and map both the mechanical strain within the graphene structure (strain effects) and the concentrations of electrical charges (doping), providing an exceptionally precise picture of the material.

This result demonstrates the need to study advanced materials precisely at the infinitesimal scale at which the phenomena governing their behaviour occur. The analytical method developed by the team is not limited to graphene: it could be extended to an entire class of new two-dimensional and nanostructured materials, in which imperceptible local variations can make a significant difference to the final performance of devices and technologies.

References: Anacleto Proietti et al., Nanoscale Disentangling of Strain and Doping in Monolayer Graphene Grown on Cu-Based Growth Template and Transferred onto Si Substrate by Combining TERS, Raman Correlation Analysis, and PCA, ACS Omega (2026) DOI: 10.1021/acsomega.6c05883