Combining gravimetric with electrical transduction methods for the detection of volatile organic compounds (VOCs) by Langmuir-Blodgett films from fluorescently labeled phospholipids.

Abstract Volatile organic compounds (VOCs) are organic chemical compounds found in various products that easily vaporize and reach in the environment under normal conditions. They adversely affect the environment and human health. Hence, portable in-field chemical sensors with the possibility for continuous monitoring of VOCs are in great demand. Such sensors should have a smooth, thin sensing layer for fast detection. After this layer captures the studied VOC, the signal has to be transduced into a proper electrical signal for further manipulation and display. The best method for producing the sensing layer is the Langmuir and Blodgett (LB) method for layer-after-layer deposition. We use LB monolayers from a fluorescently head-labeled phospholipid DPPE-NBD. It forms stable 3D aggregates thus highly increasing the surface-to-volume ratio even when a monolayer is deposited. Therefore, a fast and very sensitive sensor is prepared. We measured VOCs with LB films from lipids with gravimetric detection using a 434 MHz two-port Surface Acoustic Wave (SAW) resonator with gold electrodes. We also used the SAW resonators’ interdigitated electrodes to enhance the signal in the Electrical Impedance Spectroscopy (EIS) detection method. Combining the two complementary transduction techniques – gravimetry and electrical methods on a single device gives additional selectivity to the chemical sensor. So a highly sensitive chemical sensor for VOCs can be prepared with the suggested approach.