Researchers at Karolinska Institutet in Sweden have developed a tiny sensor for detecting pesticides on fruit in just a few minutes. The technique, described as a proof-of-concept in a paper in the journal Advanced Science, uses flame-sprayed nanoparticles made from silver to increase the signal of chemicals.    While still at an early stage, the researchers hope these nano-sensors could help uncover food pesticides before consumption.   “Reports show that up to half of all fruits sold in th...