An impedance sensor for the detection of formaldehyde vapor using ZnO nanoparticles
- PDF / 446,571 Bytes
- 10 Pages / 584.957 x 782.986 pts Page_size
- 73 Downloads / 176 Views
Ramiah Saraswathia) Department of Materials Science, School of Chemistry, Madurai Kamaraj University, Madurai 625021, Tamil Nadu, India (Received 18 February 2017; accepted 11 April 2017)
A highly sensitive impedance sensor operating at room temperature has been developed for the quantitative determination of formaldehyde vapor. Nanostructured zinc oxide (ZnO) was synthesized by chemical reduction and used, in the form of a pellet, as the sensing material. Its performance was compared to that of the pellet made from commercial ZnO. Both samples were characterized by X-ray diffraction, Fourier transform infra-red spectroscopy, ultraviolet–visible spectroscopy, and atomic force microscopy techniques. Changes in impedance caused by formaldehyde in the concentration range from 100 to 800 ppm were measured and Nyquist plots revealed a systematic variation in impedance. The sensor response and formaldehyde concentration are exponentially correlated for both the laboratory synthesized and commercial ZnO samples. However, the lab-synthesized sample displays a better performance in terms of sensitivity, response, recovery, and stability. In addition, the response of the lab-synthesized sample is less sensitive to interferences by reducing gases such as ammonia, ethanol, methanol, and propanol. I. INTRODUCTION
Formaldehyde, a volatile organic vapor, is considered to be a toxic air pollutant present in both indoor and outdoor atmospheres.1 The release of formaldehyde into the environment from industrial and consumer products like building materials, wood furniture coating, textiles, cleaning products, disinfectants, preservatives, photoprocessing chemicals, and cosmetics is well-known. The outdoor sources arise from combustion of wood, marine environment, and plant physiological and plant atmospheric exchange processes. The permissible long-term exposure is limited to 0.08 parts per million (ppm) for 0.5 h.2 Considering these factors, it is very important to monitor the concentration of formaldehyde in both indoor and outdoor atmospheres. Nanostructured materials including metal oxides, conducting polymers, carbon nanotubes, graphene, and nanocomposites based on carbon nanomaterials are being extensively used in gas and vapor sensing applications.3–7 Owing to their high surface area, nanomaterials can enhance the adsorption of gas molecules and promote
Contributing Editor: Gary L. Messing a) Address all correspondence to this author. e-mail: [email protected], [email protected] DOI: 10.1557/jmr.2017.172
the kinetics of the surface processes relevant for gas and vapor sensing. In addition, the ability to control the microstructure of the nanomaterials makes them very attractive for the development of sensors with high sensitivity and fast response time. Semiconducting metal oxides have attracted wide attention in gas and vapor sensing applications due to their high surface to volume ratio, low cost, simple fabrication, high sensitivity and stability, and broad detection range with fast response.8 Some of the nano
Data Loading...
