As fruit and vegetables ripen, ethylene gas is released. Ethylene also influences the speed at which they ripen. Chemist Tom van Dijkman (Leiden University) studied how small and inexpensive sensors that measure ethylene concentrations during transportation can be made. His research was done within NanoNextNL, within the programme Food process monitoring and product quality assessment. He worked in partnership with Wageningen UR and the companies Nanosens and EMS.
A lot of fruit, vegetables and flowers perish during transportation, partly due to the fact that the current sensors for ethylene are too big and too expensive. Small, inexpensive sensors are needed that can be placed in the containers transporting fruit and vegetables to measure the ethylene concentrations.
Van Dijkman, under the supervision of Professor Lies Bouweman, discovered that the chemical properties of a number of copper compounds can be modified for air sensitivity, melting point, solubility and bonding characteristics with ethylene gas. His research also showed that when such compounds are placed on graphene, extremely large concentrations of ethylene and ethanol in the air can be measured.
“I tested a lot of copper compounds using a broad range of analytical methods. The copper compounds were then put onto graphene. The minute amount of material that ‘sticks’ to the graphene forms a thin layer that has high reactivity with gases in the air,” Tom van Dijkman explained. “By first analysing the chemical properties of the copper compounds, it was possible to understand the chemical reactions on the surface of the graphene sensors. The measurements give a clear picture of these reactions. By looking at the same reaction to different gases, it was possible to show that the proposed reaction mechanism works for different gases and that the differences in the various measurements could be both predicted and explained.”
The compounds were tested, placed on a chip and developed into actual sensors, all within the context of the NanoNextNL research programme Food process monitoring and product quality assessment, in partnerhsip with Wageningen UR and the companies Nanosens and EMS.
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