Pyrene-imprinted polythiophene sensors for detection of polycyclic aromatic hydrocarbons

A pyrene-imprinted polythiophene nanofilm is prepared by electrochemical deposition and used for highly sensitive detection of pyrene and its analogues. Using a molecular imprinting technique, pyrene-specific recognition sites are formed throughout the oligo/polythiophene film deposited onto a gold surface. These pyrene "imprints" possess complimentary geometric features to the analyte and are capable of forming π-donor and hydrogen bonding interactions with pyrene. Upon exposure to pyrene, the functionalized nanosurface produces specific fluorescence emission whose response is linearly proportional to its concentration range between 0.01 and 1.0 μM with good stability and reproducibility (relative standard deviation <5.6%). The nanofilm sensor can also discriminate pyrene from its structural analogues in ultra-trace levels by shifting the fluorescence detection. Based on theoretical modeling studies, the strong polar hydrogen (Hp)-π interaction between the polythiophene film and pyrene, which generate fluorescent emission, was determined to be within -15 to -25 kJ/mol, a range close or even larger than common hydrogen bonds. The -SH groups of the thiophene moities act as the Hp-π interaction donors while the aromatic ring of pyrene functions as an Hp-π acceptor. These interactions as combined with the size and shape of the pyrene binding sites lead to a highly sensitive and specific detection of pyrene. The nanofilm MIP sensor may have advantages in environmental monitoring of pyrene and other polycyclic aromatic hydrocarbons (PAHs) in aquatic, marine and air samples.