Nano-optical imaging of bacteria on 2D materials

Bacteria cause hazards via biofouling and develop resistance to antibiotic treatments. However, due to their small size, spectroscopic imaging and analyzing bacteria using conventional optical microscopy is challenging. Moreover, atomically thin 2D materials, especially transition metal dichalcogenides, with their wide range of applications in optoelectronics, have also shown promising biological applications. In this work, we developed a novel nanoscale imaging approach to characterize bacteria-substrate interactions. Untreated and antibiotic-treated bacteria were deposited on the junction of monolayer MoS₂-WS₂ materials on top of a Si substrate. The optical characterization with 532 nm laser excitation provided far-field photoluminescence (PL) and near-field tip-enhanced photoluminescence (TEPL) measurements. When the bacteria were placed on the 2D materials, a higher PL signal was observed compared to the pure material. The enhancement and the red shift of the PL signal can be accounted as strain caused by the bacteria on the 2D materials. These observations show promising results to prompt further studies to analyze interactions of different bacteria with TMDs.