Ultrasensitive Surface-Enhanced Raman Scattering Sensor of Gaseous Aldehydes as Biomarkers of Lung Cancer on Dendritic Ag Nanocrystals.

Surface-enhanced Raman scattering (SERS) is expected as a technique that even theoretically detected chemicals at the single molecule level by surface plasmon phenomena of noble metal nanostructures. Insensitivity of detecting Raman weak-intensity molecules and low adsorptivity of gaseous molecules on solid substrates are two main factors hindering the application of SERS in gas detectors. In this manuscript, we demonstrated an operational SERS strategy to detect gaseous Raman weak-intensity aldehydes that have been considered as a biomarker of lung cancer for abnormal content was measured in volatile organic compounds (VOCs) of lung cancer patients. To enhance the adsorption of gaseous molecules, dendritic Ag nanocrystals mimicking the structural feature (dendritic) of moth's antennae were formed, wherein the existence of numerous cavity traps in Ag dendritic nanocrystals prolonged reaction time of the gaseous molecules on the surface of solid surface through the "cavity-vortex" effect. By the nucleophilic addition reaction with the Raman-active probe molecule p-aminothiophenol (4-ATP) pregrafted on dendritic Ag nanocrystals, the gaseous aldehyde molecules were sensitively captured to detect at the ppb (parts per billion) level. Additionally, the sensitivity of this operational SERS strategy to detection of lung cancer biomarkers was not affected by the humidity, which represented a great potential in fast, easy, cost-effective, and noninvasive recognition of lung malignancies.