Odor Sensors Based on Silicon Nanowires With a Modified Surface for Electronic Nose Application

In this letter, an odor sensor based on silicon nanowires (SіNWs) with a modified surface was fabricated. The SiNW array was obtained by a two-stage metal-assisted chemical etching. Two approaches were used to modify the SiNW array. Surface structure modification was carried out using an additional treatment in an acid etchant. Surface chemical modification was carried out by immersing the SiNW array in a solution of dispersed multiwalled carbon nanotubes. The surface morphology of the obtained structures was studied by scanning electron microscopy and energy dispersive X-ray spectroscopy. In this letter, the sensors were tested for odors in essential oils, food, and beverages. Sensor performance was evaluated based on the following parameters: response, selectivity, speed, and reversibility. Especially, it was shown that the selectivity, i.e., the difference in the device response to different types of essential oils, reached 14 times, while for the group of spirits, this value was 3 times, and for food products, it was 2.7 times. The device speed (duration of one measurement cycle for the certain odor, response, and recovery) was 20–30 s. The obtained sensors can be used to develop an electronic nose that enables to determine the freshness of food and prevent counterfeiting of alcoholic beverages and essential oils.