We use the natural zeolite clinoptilolite as the sensitive element in a plasticized PVC membrane: High Electron Mobility Transistor Research Paper, UM, Malaysia

We use the natural zeolite clinoptilolite as the sensitive element in a plasticized PVC membrane. Separated, a sample pool and a reference pool in a water-gated SnO2 thin-film transistor (SnO2 WGTFT) with such a membrane leads to membrane potential, and thus transistor threshold shift in response to the common drinking water pollutants Pb2þ or Cu2þ in the sample pool. Threshold shift with ion concentration, c, follows a Langmuir–Freundlich (LF) characteristic.

As the LF characteristic shows the steepest slope in the limit c → 0, this opens a window to limits-of-detection (LoDs) far below the ‘action levels’ of the ‘lead-and-copper rule’ for drinking water: Pb2þ: LoD 0.9 nM vs 72 nM action level, Cu2þ: LoD 14 nM vs 20.5 μM action level. LoDs are far lower than for membranes using organic macrocycles as their sensitive elements.

Threshold shifts at the lead and copper action levels are more significant than shifts in response to variations in the concentration of non-toxic co-cations, and we discuss in detail how to moderate interference. The selective response to lead and copper qualifies clinoptilolite-sensitized WGTFTs as a low-footprint sensor technology for monitoring the lead-and-copper rule and confirming the effectiveness of attempts to extract lead and copper from
water.

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