Development of a Piezoelectric Crystal Sorption Detector for Monitoring of Total Organic Compounds in Air

Abstract

A light and portable organic vapours monitor has been developed using piezoelectric (P/Z) quartz crystal to determine Volatile Organic Compounds (VOCs) commonly found in workplace air. Out of the eight coating material studied, High Vacuum Grease (HVG) was found to be the best for determining commonly encountered organic vapours such as 1,1,1-Trichloroethane, Chloroform, Benzene and Toluene in room air. The optimised coating weight was 23 μg HVG at a flow rate of 200 mL/min. Moisture was found to interfere and the use of a Nafion gas dryer was found to reduce the relative humidity to a constant 37 % for room air with 43–81 % relative humidity. Under optimised conditions, a mean sensitivity of 1.9 × 1^?2 Hz/ppm was obtained for total VOCs with 17.2% RSD variation towards different VOCs. Excellent linear working ranges were obtained from 40 to 2400 ppm (v/v), with response time and recovery time within one minute up to 500 ppm (v/v) of analyte. High and relatively constant response factors were obtained for different VOCs. The reliability of the mcthod has been established by parallel method comparison using established GC-FID method. The P/Z detector developed could also be used to monitor individual VOCs.     

Asymmetric ZnO Panel‐Like Hierarchical Architectures with Highly Interconnected Pathways for Free‐Electron Transport and Photovoltaic Improvements

Through a rapid and template‐free precipitation approach, we synthesized an asymmetric panel‐like ZnO hierarchical architecture (PHA) for photoanodes of dye‐sensitized solar cells (DSCs). The two sides of the PHA are constructed differently using densely interconnected, mono‐crystalline and ultrathin ZnO nanosheets. By mixing these PHAs with ZnO nanoparticles (NPs), we developed an effective and feasible strategy to improve the electrical transport and photovoltaic performance of the composite photoanodes of DSCs. The highly crystallized and interconnected ZnO nanosheets largely minimized the total grain boundaries within the composite photoanodes and thus served as direct pathways for the transport and effective collection of free electrons. Through low‐temperature (200 °C) annealing, these novel composite photoanodes achieved high conversion efficiencies of up to 5.59 % for ZnO‐based quasi‐solid DSCs.