Evaluation of methods for measuring graphene in air

Purpose and goal:

The aim was to generate and evaluate different techniques for measuring graphene in air. The project was carried out at a laboratory in Germany.

The experiments were carried out according to plan. We generated an aerosol from 11 different graphene materials (graphene, graphene oxide, reduced graphene oxide, graphene nanoplatelets) from different manufacturers. We measured the aerosol with several different direct-reading techniques that measure particles in different size ranges (SMPS, OPC, AAC, microaethelometer) and collected generated samples for analysis with SEM.

Expected results and effects:

We generated a stable aerosol for some of the materials (mainly for graphene oxide) but for some of the others (graphene and graphene nanoplatelets) we saw that the materials agglomerated into large particles which could not reach the exposure chamber.

For graphene oxide, we were able to generate a stable monodispersive aerosol. There we could clearly see that different instrument types (detection methods) gave different results for the size of the same material.

The experiments have helped us interpret measurement data in actual work environments, which was the goal of the project. Approach and implementation:

The setup worked well when we had access to many well-characterized materials from the graphene family. The generation in the laboratory worked well for graphene oxide, but not as good for the other materials as they quickly agglomerated. The results from the instruments were supported by the subsequent SEM analyses.

By the successful graphene oxide generation, we learned that the "flat" structure of the graphene effects the signals from the direct-reading instruments . Thus, despite limited experimental time, we were able to draw important conclusions.