Detect pesticides on fruit in minutes with this new nano sensor

A new nano sensor capable of detecting pesticides on fruit within minutes has been developed by researchers at Karolinska Institutet in Sweden.

The proof-of-concept nano sensor uses flame-sprayed nanoparticles made from silver to increase the signal of chemicals. Though the sensor is still in early stages of development, researchers are optimistic that these nano-sensors could help uncover food pesticides before consumption.

The new nano-sensors employ a 1970s discovery known as surface-enhanced Raman scattering, or SERS, a powerful sensing technique that can increase the diagnostic signals of biomolecules on metal surfaces by more than 1 million times. The technology has been used in several research fields, including chemical and environmental analysis as well as to detect biomarkers for various diseases. However, high production costs and limited batch-to-batch reproducibility have so far hindered widespread application in food safety diagnostics.

In the current study, the researchers created a SERS nano-sensor by using flame spray – a well-established and cost-effective technique for depositing metallic coating – to deliver small droplets of silver nanoparticles onto a glass surface.

The researchers then finetuned the distance between the individual silver nanoparticles to enhance their sensitivity. To test their substance-detecting ability, they applied a thin layer of tracer dye on top of the sensors and used a spectrometer to uncover their molecular fingerprints. The sensors reliably and uniformly detected the molecular signals and their performance remained intact when tested again after 2,5 months, which underscores their shelf life potential and feasibility for large-scale production, according to the researchers.

To test the sensors’ practical application, the researchers calibrated them to detect low concentrations of parathion-ethyl, a toxic agricultural insecticide that is banned or restricted in most countries. A small amount of parathion-ethyl was placed on part of an apple. The residues were later collected with a cotton swab that was immersed in a solution to dissolve the pesticide molecules. The solution was dropped on the sensor, which confirmed the presence of pesticides.

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