Hydrogen peroxide is a chemical used widely in household and healthcare products like hand sanitiser as a disinfectant, in rocket fuel as a propellant, and is also found in biological cells, IISc said in a statement.
The technique researchers used involved preparing a gel from a solution containing a specially designed molecule, treated with a liquid that has hydrogen peroxide and air-drying them on a thin paper disc about 0.45 cm in diameter. The paper disc emits green light when placed under a UV lamp, only in the presence of hydrogen peroxide. The intensity of the light was found to be directly proportional to the concentration of hydrogen peroxide.
Schematic depicting the process to detect hydrogen peroxide | Credit: IISc
“…You can actually visualise this green emission (photoluminescence) with the naked eye and don’t need sophisticated instruments. All you need is a simple UV light source,” Arnab Dutta, PhD student at IISc’s department of organic chemistry and the first author of the study published in ACS Sensors, explained.
The statement added that because the paper disc is low-cost, biodegradable and easy to use, it could serve as a powerful tool in low-resource settings, even for testing biological fluids like blood.
“Detecting hydrogen peroxide efficiently is also crucial in other fields: Peroxide-based explosives, for example, can be traced using hydrogen peroxide which is sometimes used as a starting material. When researchers used their technique to randomly test five different hand sanitiser brands, they found only three to contain the level of hydrogen peroxide mandated by the World Health Organisation (WHO) — 0.125%. The fourth appeared to have much lower than 0.125% and the fifth had almost zero hydrogen peroxide,” IISc said.
Prof Uday Maitra from the department of organic chemistry and senior author of the study said hydrogen peroxide can be detected on a larger scale using titration and other experiments, but those are cumbersome and require training.
“…This method is easy because of its simplicity,” Maitra, whose lab has been working on developing several ‘sensitiser’ molecules that turn on the photoluminescence of elements called lanthanides in the presence of specific chemicals or compounds, said.
His lab has previously developed paper-based sensors for detecting specific antioxidants in green tea — and thereby testing its quality — as well as sensors for various enzymes.
IISc added that the sensitiser molecule they designed in this study enables a metal called terbium to emit green light under a UV lamp. When the sensitiser is combined with a masking agent, the green light vanishes and when hydrogen peroxide is added to this combination, it unmasks the sensitiser molecule, making it glow green once again.
“The way we designed the mask, that is where the thinking process comes in…The molecule we have designed is very specifically unmasked by hydrogen peroxide,” says Maitra.
His team is currently working on cutting down the reaction time; it takes a bit longer if the concentration of hydrogen peroxide is lower, IISc said, while Maitra added that they are also working on developing a small portable device where the detection can be done in a more automated manner.
“We are in touch with a start-up in Chennai. We have a few prototypes made with UV LEDs and a camera, to generate the emission, take a photograph, and use an image processing app to quantify the amount of hydrogen peroxide,” he said.