Ionisensori

Ionisensori, or ion sensors, are devices designed to detect and quantify specific ions in liquids or gases. They translate the activity of target ions into measurable signals, typically electrical or optical.

The most common type is the ion-selective electrode (ISE), which uses an ion-selective membrane to generate a potential proportional to the target ion's activity. ISEs are paired with a reference electrode to form a potentiometric sensor, with response described by the Nernst equation. For monovalent ions at 25 C, the ideal slope is about 59 mV per decade of activity. Key challenges include interference from other ions, membrane fouling, drift, and the need for calibration.

Another major modality is the ion-sensitive field-effect transistor (ISFET), where the gate potential is modulated by ion activity in the solution through a sensing membrane interfacing with a semiconductor channel. ISFETs enable microfabrication, on-chip sensor arrays, and portable devices.

Optical ion sensors employ chromogenic or fluorogenic indicators that respond to specific ions with color change or luminescence, allowing detection by simple spectroscopic readout or imaging.

Applications span clinical electrolyte monitoring, environmental water quality (nitrates, chlorides, fluorides), agriculture and soil testing, food and beverage processing, and industrial control. Recent advances focus on solid-contact ISEs with improved stability, nanostructured membranes, molecularly imprinted polymers for selectivity, and multiplexed sensor arrays integrated with microfluidics and wireless data transmission.

Historically, ion sensing evolved from glass electrodes in the early to mid-20th century to modern solid-state and nanoengineered sensors, expanding from laboratory analysis to field-ready and wearable platforms.