Fixed Escherichia coli bacterial templates enable the production of sensitive SERS-based gold nanostructures

• Bacterial cells coated with gold and annealed at 550 °C generate gold nanoparticles.
• TEM grid is used for easy localization of bacterial templates on glass substrate.
• Sensitive SERS detection is reported for BPE molecule down to 10−12 M.

We show herein for the first time the ability to fabricate highly sensitive SERS substrates using fixed Escherichia coli bacterial cells, used as templates after glutaraldehyde fixing, whereupon stable gold nanostructures of a suitable size for SERS generation were found lying on top of bacteria after an evaporation deposition procedure, followed by high temperature annealing. Thanks to the template effect provided by the bacterial cells, gold nanoparticles had been produced forming controlled agglomerate patterns containing high density plasmonic “hot spots”, thereby contributing to a remarkable enhancement of Raman signals. Moreover, a TEM copper grid marker used during the gold evaporation process, enabled to precisely correlate the optical properties (including LSPR and SERS spectra) and SEM morphology of a pre-defined area of gold nanostructures. It was observed that modulating either gold film thickness or annealing temperature, enabled to influence the LSPR properties of the produced Au NPs, and this was demonstrated by obtaining a highly sensitive SERS detection of a model compound, trans-1,2-bis(4-pyridyl)ethylene (BPE), down to 10−12 M.

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