Adsorption Thermodynamic Analysis of a Quartz Tuning Fork Based Sensor for Volatile Organic Compounds Detection

Abstract

A volatile organic compounds (VOC) sensor based on molecularly imprinted polymer (MIP) modified quartz tuning fork (QTF) has been developed. In this paper, the stability of the modified sensor as a function of the MIP composition, and the temperature effect of the analyte adsorption on the sensing transduction mechanism are evaluated. By mixing MIP and PS together, the stability was improved. A target analyte, o-xylene, was chosen as the VOC model to study the sensor response in a temperature range of 6-40 °C. Langmuir model fitted adsorption isotherms were used for thermodynamic analysis. The changes in the sensitivity of the QTF sensor to temperature rendered different behaviors. For a freshly modified QTF sensor, the adsorption response increased with increasing temperature, while for an aged QTF sensor, the adsorption response decreased with increasing temperature. The results indicated that the enthalpy change of the MIP and PS composition sensing material changes from positive to negative over the course of aging. The characterization of the reaction enabled the definition of sensor calibration conditions and stable sensor performance in field testing conditions.

Tracking Personal Health-Environment Interaction with Novel Mobile Sensing Devices

“…A mobile low-cost VOCs sensing device for free-living conditions has been reported before by our group [ 28 , 29 , 30 , 31 ]. The sensing device works with a frequency-based sensing mechanism, which utilizes a mass sensitive piezoelectric resonator with a selective polymer (molecularly imprinted polymer) modified quartz tuning fork.…”

“…The mobile VOCs sensing device connects wirelessly to an Android smart phone via Bluetooth ® . The validation tests of the VOC monitor were reported in our previous publications [ 28 , 29 , 30 , 31 ]. A total of 18 participants out of the 36 participants were randomly selected to have their VOCs exposure measured throughout the day.…”

Prospects and Challenges of Volatile Organic Compound Sensors in Human Healthcare

“…Different approaches were considered to improve the stability. Deng et al demonstrated improvements in stability of thermodynamic properties of known unstable sensing materials (molecularly imprinted polymer, MIP) for a quartz tuning fork (QTF) sensor . This has been reported through modification of MIP by mixing polystyrene.…”

Experimental and Modeling Study of Organic Chloride Compounds Removal from Naphtha Fraction of Contaminated Crude Oil Using Sintered γ-Al2O3 Nanoparticles: Equilibrium, Kinetic, and Thermodynamic Analysis

“…The relationship between other thermodynamic parameters including enthalpy change (Δ H 0 ) and entropy change (Δ S 0 ) with Gibbs free energy change (Δ G 0 ) can be described as the following equation ,, and this equation can be rewritten as ,,, On the basis of eq , Δ S 0 and Δ H 0 can be obtained from the intercept and the slope of the linear fitting line of ln K e plot versus 1/ T , respectively.…”