Discriminative Detection of Volatile Sulfur Compound Mixtures with a Plasma-Polymerized Film-Based Sensor Array Installed in a Humidity-Control System

Abstract

We demonstrated the discrimination of volatile sulfur compound mixtures with different mixing ratios by using an array of the plasma-polymerized film (PPF)-coated quartz crystal resonators. The PPF sensor array, which contains PPFs prepared from amino acids and synthetic polymers, exhibited different response patterns to mono or mixed volatile sulfur compounds (VSCs) (hydrogen sulfide and methanethiol) under a dry environment. The sensor array was installed in a desktop-size relative humidity controller. The relative humidity and temperature conditions of the sample flow to the sensor cell were equalized to those of the inner atmosphere of the sensor cell based on the concept of the two-separate-temperatures method. In this way, the baseline drift of PPF sensor response caused by the introduction of a highly humid sample was successfully suppressed. We compared the sensor array responses under the controlled humidity conditions. Presorption of water molecules by PPFs caused a decrease of sensor sensitivity, but the films still had the ability to discriminate sub-ppmv VSC mixtures having 6:1, 1:1, and 1:6 mixture ratios of hydrogen sulfide and methanethiol.

Facile Plasma‐Enhanced Deposition of Ultrathin Crosslinked Amino Acid Films for Conformal Biometallization

“…The method of in situ polymerization of tyrosine coatings proposed herein focuses on the utilization of plasma‐enhanced chemical vapor deposition (PECVD) as a potential method to polymerize the tyrosine monomer in the plasma stream and directly deposit the polytyrosine on the substrate. This type of plasma polymerization reaction has been demonstrated previously with various organic molecules and amino acids to form thin films that can also be easily patterned through the use of a mask secured on the substrate 33–39…”

Application of Low-Cost Electrochemical Sensors to Aqueous Systems to Allow Automated Determination of NH3 and H2S in Water

“…Another alternative technique, which has been successfully applied to both high humidity gases and aqueous systems, is to measure the change of mass using a Quartz crystal microbalance (QCM). By coating the surface of the QCM, specific sensors for ammonia/ammonium ions [27,28] or hydrogen sulfide [29,30] have been developed. While QCMs are easily available, the measurement of specific species is only possible if the users are able to apply the specific coating to the surface of the QCM themselves.…”

Silver Ion Polyelectrolyte Container as a Sensitive Quartz Crystal Microbalance Gas Detector

“…A sensing film coated on the QCM electrode selectively interacts with a target gas, and the selectivity for target gases changes depending on the sensing film. − In a previous study, we used a poly­(ethylenimine) coating on an Al 2 O 3 porous film in a QCM sensor for methylmercaptan gas with a detection limit of 100 ppb . Moreover, Seyama et al reported a QCM sensor with polyethylene, d -phenylalanine, or d -histidine with a detection limit of 84 ppb for methylmercaptan gas . As these sensitivities are lower than the olfactory threshold (<1 ppb), it is necessary to develop methylmercaptan gas detectors with higher sensitivity.…”

“…It is well-known that gas chromatography, − semiconductor sensors, − biosensors, optical sensors, , quartz crystal microbalance (QCM) sensors, , and their combinations , can be used to detect mercaptan. Gas chromatography has the advantages of high sensitivity and selectivity but the disadvantage of relatively high power consumption and cost as well as large equipment size.…”

“…16 Moreover, Seyama et al reported a QCM sensor with polyethylene, D-phenylalanine, or D-histidine with a detection limit of 84 ppb for methylmercaptan gas. 15 As these sensitivities are lower than the olfactory threshold (<1 ppb), it is necessary to develop methylmercaptan gas detectors with higher sensitivity.…”