High-speed, miniaturized, portable chemical sensors have a wide range of application in environmental monitoring, homeland security, food safety, and health screening. Specifically, metal nanoparticles with self-assembled organic-functional monolayers (SAM) have provided the ability to detect volatile organic compounds with fast responses. As rapid-developing sensing elements, organo-functionalized metal-nanoparticles (NP’s) transduce vapor sorption in SAM layers into measurable electrical signals. To achieve good selectivity and sensitivity toward various analytes, diverse metal-ligand pairs are essential to construct high-order chemiresistive sensor arrays. These multichannel sensing materials are often called electronic noses because they have broad resolution against many different types of molecules. It is important to incorporate different ligand functionality into single chip sensors to understand the affinity of sensing materials toward different analytes. This work presents a detailed study on how the construction of metal-ligand nanoparticles affects electrical properties and sensitivity for analyte detection.  In this study, we present the integration of metal-nanoparticle sensing elements into a 36-device array of micro and nanostructures to detect 6 common laboratory organic vapors. Controlled assemblies of amine-functionalized gold and palladium nanoparticles were achieved by drop-casting and dielectrophoresis (DEP) into 4-μm and 50-nm electrode gaps fabricated using electron-beam lithography and photolithography. Simultaneous measurement of real time sensitivity, expressed as ΔR/R, were performed for 8 different devices integrated on the same chip, using a switch matrix and source measurement unit. In DEP experiments, the trapping density of nanoparticles around the sensing region can be tuned by changing applied frequency, peak-to-peak voltage, and processing time that will lead to a variation in device baseline resistances. Working sensors with 1-10% ΔR/R were achieved with a baseline resistance between 100 and 10000 Ω. Sensing performance is supported by principal component analysis (PCA) that illustrates unique fingerprints for each analyte. In addition, sensitivity response trends scale with baseline resistance. These results provide insights into selection of the most ideal metal-ligands to sense analytes in open environments.

Nanoscale chemical sensors for fast and reversible detection of organic vapors

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.