# Rapid and Efficient Polymer/Contaminant Removal from Single-Layer Graphene via Aqueous Sodium Nitrite Rinsing for Enhanced Electronic Applications

## TL;DR

A new method using sodium nitrite solution rapidly removes contaminants from single-layer graphene, preserving its electronic properties for advanced devices.

## Contribution

A novel and efficient aqueous sodium nitrite rinsing method is introduced for rapid removal of polymer and ionic contaminants from single-layer graphene.

## Key findings

- The sodium nitrite rinse effectively removes PMMA polymers and Cl− ions in less than 10 minutes.
- The treatment restores the work function of graphene to near-pristine levels (~4.79 eV).
- The method improves structural integrity and reduces doping effects, as confirmed by Raman spectroscopy.

## Abstract

The removal of surface residues from single-layer graphene (SLG), including poly(methyl methacrylate) (PMMA) polymers and Cl− ions, during the transfer process remains a significant challenge with regard to preserving the intrinsic properties of SLG, with the process often leading to unintended doping and reduced electronic performance capabilities. This study presents a rapid and efficient surface treatment method that relies on an aqueous sodium nitrite (NaNO2) solution to remove such contaminants effectively. The NaNO2 solution rinse leverages reactive nitric oxide (NO) species to neutralize ionic contaminants (e.g., Cl−) and partially oxidize polymer residues in less than 10 min, thereby facilitating a more thorough final cleaning while preserving the intrinsic properties of graphene. Characterization techniques, including atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM), and X-ray photoelectron spectroscopy (XPS), demonstrated substantial reductions in the levels of surface residues. The treatment restored the work function of the SLG to approximately 4.79 eV, close to that of pristine graphene (~4.5–4.8 eV), compared to the value of nearly 5.09 eV for conventional SLG samples treated with deionized (DI) water. Raman spectroscopy confirmed the reduced doping effects and improved structural integrity of the rinsed SLG. This effective rinsing process enhances the reproducibility and performance of SLG, enabling its integration into advanced electronic devices such as organic light-emitting diodes (OLEDs), photovoltaic (PV) cells, and transistors. Furthermore, the technique is broadly applicable to other two-dimensional (2D) materials, paving the way for next-generation (opto)electronic technologies.