How can a thin, transparent, single-atomic layer be observed? A team of researchers has found a rather unique solution. A very thin anti-reflective absorbent layer is deposited on transparent glass. By illuminating this layer on the side of the glass and not the air, the reflection can be completely switched off. When placed on the antireflection layer, a material of nanometric thickness modifies the extinction conditions and appears with good contrast.

This technique, named Backside Absorbing Layer Microscopy or BALM, works in the air and in a solvent. For example, chemists were able to easily follow the absorption kinetics of small molecules on monolayer graphene oxide in a solvent and in real time, while this proves very delicate with other techniques. BALM can also be combined with other techniques for the analysis or modification of nanomaterials, including electrochemistry.

This work was carried out in collaboration with CNRS researchers from Le Mans, the Fresnel Institute in Marseille and the Lebanese University in Beirut.