A researcher performing a picloram detection experiment with a nanoengineered sensor chip. Credit: Daphika S Dkhar
A highly sensitive sensor can detect minute traces of picloram, a herbicide used to kill broad-leaved weeds in land used for grazing and cultivation1. The sensor rapidly identifies the chemical in rice water and soil samples from agricultural fields.
The sensor can be used to monitor picloram in groundwater and a wide variety of crops, says a team at the Indian Institute of Technology (BHU) in Varanasi.
Picloram can seep through soil, damage crops and contaminate water. It is potentially harmful to humans and existing methods to detect it are expensive and time-consuming.
To find an inexpensive sensor, scientists, led by Pranjal Chandra synthesised a nanohybrid by mixing chemically unzipped, multiwalled carbon nanotubes with reduced graphene oxide. They then modified a glassy carbon electrode with gold nanoparticles and coated it with the nanohybrid to produce the sensor.
The team, which included researchers Daphika S. Dkhar and Rohini Kumari, exposed the sensor to different concentrations of picloram – an increased concentration enhanced the current flow.
The sensor was able to detect picloram within 0.2 seconds and retained sensitivity for more than 10 weeks. The highly conducting and electrocatalytic nanohybrid contributed to its rapid response, which is much faster than bioreceptor-based sensors.
The sensor identified picloram even in the presence of interfering agents such as mercury, lead, arsenic, chromium and bisphenol A, which are commonly found in soil and surface water. The interfering molecules displayed no current response, demonstrating the sensor’s selectivity towards picloram.
