Determination of formic acid vapour using piezoelectric crystals with 4-ethyl-3-thiosemicarbazide and 2,6-diacetylpyridine coatings

Phenyl-Modified Carbon Nitride Quantum Nanoflakes for Ultra-Highly Selective Sensing of Formic Acid: A Combined Experimental by QCM and Density Functional Theory Study

“…The lower detection limit of colloidal Ph-g-C 3 N 4 -nanoflake-coated QCM for HCOOH vapor was found to be 80 ppb (Table S4), which is substantially lower than the human olfactory threshold limit in the workplace of 5.0 ppm set by the Occupational Safety and Health Administration (OSHA), which is the level at which vapor-phase HCOOH becomes irritating to the eyes, nose, and throat of the most sensitive individuals. 66 Our colloidal Ph-g-C 3 N 4 quantum nanoflakes show a superior sensing response toward HCOOH compared to previously reported materials including various carbon nitrides, metal−organic frameworks (MOFs), and polymeric-material-based QCM sensors, [27][28][29]32 chemiresistors, 63 impedance-based sensors, 19,20 and amperometric biosensors 21 (Table S5). This work establishes Ph-g-C 3 N 4 -based QCM sensor discrimination of HCOOH, HCHO, and CH 3 COOH in the vapor phase by Ph-g-C 3 N 4 quantum nanoflakes using the QCM sensor technique (Figure 5a).…”

“…Chemiresistors based on metal oxides and nitrides, or carbon nanotubes (CNTs), have been studied, showing encouraging results. , The detection of HCOOH vapor using piezoelectric sensors has also been investigated. For this purpose, the quartz crystal microbalance (QCM) was selected for its ease of use, cost-effectiveness, low-power consumption, and room-temperature operation with several active coating materials available, for example, carbon nitride, polyaniline (PANI), and other polymeric materials, , and carbon-based nanostructures are attractive platforms for the development of gas sensors. Although strong acids have been reported to p-dope or protonate carbon nanostructures, such as graphene and CNT-based chemiresistors and field-effect transistors (FETs), − there has been little attention paid to QCM sensors of carboxylic acids based on carbon materials. , FET and chemiresistor devices are based on difficult-to-manufacture interdigitated electrodes, which require the use of photolithography and have significant operating complexities.…”