# Hybrid 1D Plasmonic/Photonic Crystals are Responsive to Escherichia Coli

## TL;DR

This paper introduces a hybrid plasmonic/photonic biosensor responsive to Escherichia coli, utilizing a silver layer on a photonic crystal to detect bacterial contamination through dielectric property changes, enabling low-cost, portable detection.

## Contribution

The work presents a novel hybrid plasmonic/photonic device that detects E. coli via dielectric modifications, combining plasmonic and photonic features for biosensing.

## Key findings

- Blue-shift in photonic response upon bacterial detection
- Silver layer's dielectric change correlates with bacterial presence
- Device offers a low-cost, portable detection platform

## Abstract

Photonic crystal-based biosensors hold great promise as valid and low-cost devices for real-time monitoring of a variety of biotargets. Given the high processability and easiness of read-out even for unskilled operators, these systems can be highly appealing for the detection of bacterial contaminants in food and water. Here, we propose a novel hybrid plasmonic/photonic device that is responsive to Escherichia coli, which is one of the most hazardous pathogenic bacterium. Our system consists of a thin layer of silver, a metal that exhibits both a plasmonic behavior and a well-known biocidal activity, on top of a solution processed 1D photonic crystal. We attribute the bio-responsivity to the modification of the dielectric properties of the silver film upon bacterial contamination, an effect that likely stems from the formation of polarization charges at the Ag/bacterium interface within a sort of bio-doping mechanism. Interestingly, this triggers a blue-shift in the photonic response. This work demonstrates that our hybrid plasmonic/photonic device can be a low-cost and portable platform for the detection of common contaminants in food and water.

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Source: https://tomesphere.com/paper/1905.02251