Highly Sensitive Hybrid Nanostructures for Dimethyl Methyl Phosphonate Detection

Nanostructured materials synthesized by the hydrothermal and thermal reduction process were tested to detect the dimethyl methylphosphonate (DMMP) as a simulant for chemical warfare agents. Manganese oxide nitrogen-doped graphene oxide with polypyrrole (MnO2@NGO/PPy) exhibited the sensitivity of 51 Hz for 25 ppm of DMMP and showed the selectivity of 1.26 Hz/ppm. Nitrogen-doped multi-walled carbon nanotube (N-MWCNT) demonstrated good linearity with a correlation coefficient of 0.997. A comparison between a surface acoustic wave and quartz crystal microbalance sensor exhibited more than 100-times higher sensitivity of SAW sensor than QCM sensor.

A highly sensitive quartz crystal microbalance sensor assisted with ZnO nanosheets for nerve agent detection

ZnO is known as a promising material for surface acoustic wave (SAW) sensor devices because of its piezoelectric property. Recently, quartz crystal microbalances (QCMs) have been promising as a sensor platform due to their high sensitivity and ease of measurement. In particular, the alignment of ZnO nanosheets (NSs) into ordered nanoarrays is expected to improve the device sensitivity and stability due to large specific surface area, which allows the captured significant quantities of gas molecules. In this study, we fabricated a quartz crystal microbalance sensor with ZnO NSs structures using polyvinylidene fluoride as a receptor for nerve agent detection. We synthesized two-dimensional NSs by chemical bath deposition (CBD) via the potassium hydroxide etching method. CBD is an excellent method that can easily form uniform structures at low cost. We fabricated ZnO NSs modified with polyvinylidene fluoride and used it for detection of dimethyl methylphosphonate (DMMP) gas. The NSs structure indicated that, when a similar functional group material is coated, the specific surface area increased compared to the nanorods (NRs) structure. As a result, the sensitivity of the quartz crystal microbalance sensor to DMMP gas was improved.

Low-fouling CNT-PEG-hydrogel coated quartz crystal microbalance sensor for saliva glucose detection

We successfully achieved the direct detection of saliva glucose by a CNT-PEG-hydrogel. The top CNT-PEG layer provides channels for transporting glucose molecules and filters macromolecular impurities and the bottom base PBA-hydrogel film provides the glucose binding sites.