Sensing of polycyclic aromatic hydrocarbons with cyclodextrin inclusion complexes on silver nanoparticles by surface-enhanced Raman scattering.

We have developed a new type of surface-enhanced Raman scattering (SERS) substrate that consists of per-6-deoxy-(6-thio)-beta-cyclodextrin (CD-SH) modified by silver nanoparticles (AgNPs) for sensing of polycyclic aromatic hydrocarbons (PAHs), a kind of environmental pollutant, with very low affinity to metallic surfaces. The designed system can induce some PAH molecules (anthracene and pyrene) to insert into the hydrophobic cavity of beta-CD, which enables one to detect SERS of PAHs because the analytes are very close to the AgNPs surface, which is the zone of electromagnetic enhancement. The measured spectra can easily distinguish the two kinds of PAH compounds in a mixture by their own characteristic peaks. In addition, we carried out selective detection of PAHs by SERS of the inclusion complexes with different concentrations in the presence of CD-SH functionalized AgNPs. Moreover, this sensing platform has been applied to quantitative detection of PAH in a mixture consisting of anthracene and pyrene. The CD molecule has the feature of high selectivity due to its size of cavity, significantly enhancing the sensitivity of the system after CD-SH adsorbs on AgNPs via the terminal thiol. This proposed method for the detection of PAHs holds great potential in environmental analytical chemistry.