3D nanoporous plasmonic chips for extremely sensitive NO2 detection

Encapsulation of 3D plasmonic nanostructures with ultrathin hydrogel skin for rapid and direct detection of toxic small molecules in complex fluids

Nanogap-rich 3D plasmonic nanostructures provide enhanced molecular Raman fingerprints in a nondestructive and label-free manner. However, the molecular detection of small target molecules in complex fluids is challenging due to nonspecific protein adsorption, which prevents access of the target molecules. Therefore, the molecular detection for complex mixtures usually requires a tedious and time-consuming pretreatment of samples. Herein, we report the encapsulation of 3D plasmonic nanostructures with an ultrathin hydrogel skin for the rapid and direct detection of small molecules in complex mixtures. To demonstrate the proof of concept, we directly detect pesticide dissolved in milk without pretreatment. This detection is enabled by the selective permeation of target molecules into the 3D mesh of the hydrogel skin and the adsorption onto plasmonic hotspots, accompanied by the rejection of large adhesive proteins and colloids. The high sensitivity of nanogap-rich plasmonic nanostructures in a conjunction with the molecular selection of the hydrogel skin enables the fast and reliable detection of tricyclazole in whole milk with a limit of detection as low as 10 ppb within 1 h. We believe that this plasmonic platform is highly adaptable for in situ and on-site detection of small molecules in various complex mixtures including foods, biological fluids, and environmental fluids.

Ethanol Sensors Based on Porous In2O3 Nanosheet-Assembled Micro-Flowers

By controlling the hydrothermal time, porous In₂O₃ nanosheet-assembled micro-flowers were successfully synthesized by a one-step method. The crystal structure, microstructure, and internal structure of the prepared samples were represented by an x-ray structure diffractometry, scanning electron microscopy, and transmission electron microscopy, respectively. The characterization results showed that when the hydrothermal time was 8 h, the In₂O₃ nano materials presented a flower-like structure assembled by In₂O₃ porous nanosheets. After successfully preparing the In₂O₃ gas sensor, the gas sensing was fully studied. The results show that the In₂O₃ gas sensor had an excellent gas sensing response to ethanol, and the material prepared under 8 h hydrothermal conditions had the best gas sensing property. At the optimum working temperature of 270 °C, the highest response value could reach 66, with a response time of 12.4 s and recovery time of 10.4 s, respectively. In addition, the prepared In₂O₃ gas sensor had a wide detection range for ethanol concentration, and still had obvious response for 500 ppb ethanol. Furthermore, the gas sensing mechanism of In₂O₃ micro-flowers was also studied in detail.