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Penicilloic acid (PA) is a degraded byproduct of penicillin and often causes fatal allergies to humans, but its rapid detection in penicillin drugs remains a challenge due to its similarity to the mother structure of penicillin. Here, we reported a ligand-replaced molecularly imprinted monolayer strategy on a surface-enhanced Raman scattering (SERS) substrate for the specific recognition and rapid detection of Raman-inactive PA in penicillin. The bis(phenylenediamine)-Cu(2+)-PA complex was first synthesized and stabilized onto the surface of silver nanoparticle film that was fabricated by a bromide ion-added silver mirror reaction. A molecularly imprinted monolayer was formed by the further modification of alkanethiol around the stabilized complex on the Ag film substrate, and the imprinted recognition site was then created by the replacement of the complex template with Raman-active probe molecule p-aminothiophenol. When PA rebound into the imprinted site in the alkanethiol monolayer, the SERS signal of p-aminothiophenol exhibited remarkable enhancement with a detection limit of 0.10 nM. The imprinted monolayer can efficiently exclude the interference of penicillin and thus provides a selective determination of 0.10‰ (w/w) PA in penicillin, which is about 1 order of magnitude lower than the prescribed residual amount of 1.0‰. The strategy reported here is simple, rapid and inexpensive compared to the traditional chromatography-based methods.

This paper reports the finding of an investigation of a surface molecular self-assembly strategy for molecular imprinting of polymer nanowires/nanotubes. It has been demonstrated that 2,4,6-trinitrotoluene (TNT) templates were spontaneously assembled onto aminopropyl group-modified alumina pore walls by a strong charge-transfer complexing interaction between amino groups and electron-deficient nitroaromatics, forming a novel basis of surface molecular imprinting. While an additional amount of TNT templates was further replenished into a precursor mixture, a stepwise progressive polymerization was designed toward the controllable preparation of TNT-imprinted polymer nanowire/nanotube arrays in an alumina membrane. The imprinted nanowires/nanotubes with a high density of surface-imprinted sites and regular interior sites exhibit the high capacity of binding TNT molecules, which is nearly 2.5-3.0-fold that of normal imprinted particles. Moreover, the imprinted nanotubes and nanowires have ~6- and 4-fold increase in the rate of binding TNT molecules, respectively. The combination of surface molecular assembly with nanostructures in the imprinting technique can create more effective recognition sites than the only use of porogens in traditional approaches. This novel, facile strategy reported herein can be further expected to fabricate various molecular recognition nanoarrays for sensing or analytic applications. [ABSTRACT FROM AUTHOR]