Nanosphere Monolayer on a Transducer for Enhanced
Detection of Gaseous Heavy Metal
- Publication date
- 2015
- Publisher
Abstract
This study reports for the first
time that polystyrene monodispersed
nanosphere monolayer (PS-MNM) based Au (Au-MNM) and Ag (Ag-MNM) nanostructures
deposited on quartz crystal microbalance (QCM) transducers can be
used for nonoptical based chemical sensing with extremely high sensitivity
and selectivity. This was demonstrated by exposing the Au-MNM and
Ag-MNM based QCMs to low concentrations of Hg<sup>0</sup> vapor in
the presence interferent gas species (i.e., H<sub>2</sub>O, NH<sub>3</sub>, volatile organics, etc.) at operating temperatures of 30
and 75 °C. At 30 °C, the Au-MNM and Ag-MNM based QCMs showed
∼16 and ∼20 times higher response magnitude toward Hg<sup>0</sup> vapor concentration of 3.26 mg/m<sup>3</sup> (364 parts per
billion by volume (ppb<sub>v</sub>)) relative to their unmodified
control counterparts, respectively. The results indicated that the
extremely high sensitivity was not due to the increased surface area
(only 4.62 times increase) but due to their long-range interspatial
order and high number of surface defect formation which are selectively
active toward Hg<sup>0</sup> vapor sorption. The Au-MNM and Ag-MNM
also had more than an order of magnitude lower detection limits (<3
ppb<sub>v</sub>) toward Hg<sup>0</sup> vapor compared to their unmodified
control counterparts (>30 ppb<sub>v</sub>). When the operating
temperature
was increased from 30 to 75 °C, it was found that the sensors
exhibited lower drift, better accuracy, and better selectivity toward
Hg<sup>0</sup> vapor but at the compromise of higher detection limits.
The high repeatability (84%), accuracy (97%), and stability of Au-MNM
in particular make it practical to potentially be used as nonspectroscopic
based Hg<sup>0</sup> vapor sensor in many industries either as mercury
emission monitoring or as part of a mercury control feedback system