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Thin films of conducting molecularly imprinted polymers (MIPs) were prepared for simultaneous chronoamperometry (CA) and piezoelectric microgravimetry (PM) determination of several explosive nitroaromatic compounds (NTs) including 2,4,6-trinitrophenol (TNP), 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), and 2,4-dinitrotoluene (DNT). For that, the bis(2,2–-bithienyl)-(4-aminophenyl)methane 1 functional monomer allowing for π-π stacking recognition of the NTs was designed and synthesized. Both theoretical DFT calculations at the M062X/3-21G* level and experimental fluorescence titrations indicated the 1:1 stoichiometry of the 1 and NT prepolymerization complexes formed in solutions. The NT-templated MIP (MIP-NT) films were deposited by potentiodynamic electropolymerization on the Au-coated quartz crystal resonators (Au-QCRs) from solutions of 1 and each of the NT templates at the 1-to-NT mole ratio of 1:1. For sensing application, the NTs were extracted from the MIP-NT films. Completeness of the extraction was confirmed by the presence and absence before and after extraction, respectively, of both the XPS peak of the N 1s electrons of the NT nitro groups and the DPV peak of electroreduction of the NTs for the MIP-NT. Ultimately, the recognition signal was transduced to the analytical signal of simultaneous changes of CA cathodic current and PM resonant frequency. The limit of detection (LOD) for NTs was in the range of hundreds and tens micromolar for CA and PM, respectively. Moreover, selectivity with respect to common interferences of the chemosensors was in the range 2.1-4.8, as determined by molecular cross-imprinting. [ABSTRACT FROM AUTHOR]

A 6-aminopurine (adenine) derivative of bis(2,2′-bithienyl)methane, vis., 4-[2-(6-amino-9H-purin-9-yl)ethoxy]phenyl-4-[bis(2,2′-bithienyl)methane] or Ade-BTM, was designed and synthesized for recognition of 5-fluorouracil (FU), an antitumor chemotherapy agent, by RNA-type (nucleobase pairing)-driven molecular imprinting. The prepolymerization complex stoichiometry involved one FU molecule and two molecules of the Ade-BTM functional monomer. Molecular structure of this complex was thermodynamically optimized via density functional theory at the B3LYP/3-21G* level. The stability constant of the FU-Ade-BTM complex of 1:2 stoichiometry was K = 2.17(±0.07) × 107 M-2, as determined by titration with quenching of fluorescence of the bis(2,2′-bithienyl)methane moiety of Ade-BTM by the FU titrant, in benzonitrile, at 352 nm excitation. Next, (5-fluorouracil)-templated molecularly imprinted polymer (MIP-FU) films were deposited on indium-tin oxide (ITO) or Au film-coated glass slides, Pt disk electrodes, or 10-MHz quartz crystal resonators by potentiodynamic electropolymerization from solution of FU, Ade-BTM, and tris([2,2′-bithiophen]-5-yl)methane (TTM) cross-linking monomer at FU:Ade-BTM:TTM = 1:2:3 mol ratio. Then UV-visible and Fourier transform infrared (FT-IR) spectra of the MIP-FU films were recorded to confirm the FU template presence in the MIP-FU film and its subsequent release by extraction with methanol from this film. For determination of the stability constant of the complex of the MIP cavity and FU, piezoelectric microgravimetry (PM) under both batch- and flow-injection analysis conditions was used. For sensing application, three different transduction platforms [differential pulse voltammetry (DPV), capacitive impedimetry (CI), and PM] were integrated with the MIP-FU recognition unit. The limit of detection (LOD) was 56 nM, 75 nM, and 0.26 mM, for these chemosensors, respectively, indicating suitability of the former two for FU determination in blood plasma or serum (500 nM). Moreover, the CI chemosensor was appreciably more sensitive to FU than to their common interferences. [ABSTRACT FROM AUTHOR]