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Advancement in molecularly imprinted biomimetics has aided in developing robust artificial recognition-based materials, which can be customized for bio/chemo-sensing of distinct molecules. The present study reports a simple one-step synthesis and analysis of protein-imprinted polymer thin films as a recognition element directly onto a solid support. Dopamine has been explored as a versatile functional monomer for a molecularly imprinted polymer (MIP) matrix to fabricate polydopamine (PDA) thin films with bovine hemoglobin as a template protein molecule. A detailed molecular-level insight into the recognition of the template molecule at each step has been investigated using vibrational sum frequency generation (VSFG) spectroscopy. A suitable PDA-coated thin film is selected based on the extent of polymerized intermediates formed after non-imprinted polymer fabrication at different time durations. An optimally prepared film of MIP is specified by observing the spectral signature of the methyl groups from protein molecules at the air–polymer interface. The template removal from MIP films after the washing procedure and subsequent re-binding of the protein molecules were evaluated by VSFG spectroscopy. The insightful molecular-level findings from SFG spectroscopy demonstrate the fabrication of an imprinted matrix as a label-free chemical sensor. [ABSTRACT FROM AUTHOR]

Quantitative measurements in nonlinear surface vibrational spectroscopy enable the investigation of the orientation of molecules through analysis of the observed bands in resonance with specific chemical functional groups. Thin polymer films are commonly used to create a specific chemical environment or degree of hydrophobicity. We illustrate the effect of multiple beam interference in the thin films on the structural analysis of free-surface molecules, even in the case where the overlaying molecules are the only source term in the nonlinear polarization. Our findings illustrate that neglect of the modulation of the local field due to interference results in a substantial error in the determination of the molecular tilt angle. In cases where the phase of the response is of interest, the results are substantially influenced as well. In both cases, the effects are more pronounced as the refractive index of the solid support increases. We further demonstrate that the insensitivity of these effects to the experimental geometry provides a straightforward route to the treatment of these interference effects. [ABSTRACT FROM AUTHOR]

We demonstrate that the thickness of a polymer film may be determined by a simple analysis of the interference fringes observed in a transparent region of its transmission spectrum. By measuring the transmission spectrum of the uncoated substrate in the same wavelength region, we can determine the dispersion of the refractive index for the substrate and film and the thickness of the film, without prior knowledge of the optical constants of any of the materials. The results of our approach agree with measurements obtained by a direct contact method. This analysis provides a fast, simple, and nondestructive method of thickness measurement using equipment available in many teaching laboratories. The method enables students to make routine thickness measurements while introducing them to refractive index dispersion, Fresnel coefficients, thin film interference, and regression analysis. [ABSTRACT FROM AUTHOR]