ABSTRACT
Self-assembled monolayers (SAMs) bearing pendant carbohydrate functionality are frequently employed to tailor glycan-specific bioactivity onto gold substrates. The resulting glycoSAMs are valuable for interrogating glycan-mediated biological interactions via surface analytical techniques, microarrays, and label-free biosensors. GlycoSAM composition can be readily modified during assembly by using mixed solutions containing thiolated species, including carbohydrates, oligo(ethylene glycol) (OEG), and other inert moieties. This intrinsic tunability of the self-assembled system is frequently used to optimize bioavailability and antibiofouling properties of the resulting SAM. However, until now, our nanoscale understanding of the behavior of these mixed glycoSAMs has lacked detail. In this study, we examined the time-dependent clustering of mixed sugar + OEG glycoSAMs on ultraflat gold substrates. Composition and surface morphologic changes in the monolayers were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. We provide evidence that the observed clustering is consistent with a phase separation process in which surface-bound glycans self-associate to form dense glycoclusters within the monolayer. These observations have significant implications for the construction of mixed glycoSAMs for use in biosensing and glycomics applications.
Subject(s)
Gold/chemistry , Nanotechnology/methods , Polysaccharides/chemistry , Sulfhydryl Compounds/chemistry , Biosensing Techniques , Carbohydrate Conformation , Models, Molecular , Polyethylene Glycols/chemistry , Surface PropertiesABSTRACT
Diffractive light trapping in 1.5 µm thick crystal silicon films is studied experimentally through hemispherical reflection measurements and theoretically through rigorous coupled-wave analysis modeling. The gratings were fabricated by nanoimprinting of dielectric precursor films. The model data, which match the experimental results well without the use of any fitting parameters, are used to extract the light trapping efficiency. Diffractive light trapping is studied as a function of incidence angle, and an enhancement of light absorption is found for incidence angles up to 50° for both TE and TM polarizations.
ABSTRACT
Nanostructured ferroelectric patterns are promising for a wide range of applications, including sensing and actuation, data storage, photonics, spintronics, and energy conversion and storage. In this work, a rapid nanoimprinting technique is developed to pattern ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers in just 3 min, which exhibit excellent ferroelectricity and piezoresponse without any post-imprinting annealing. The effects of imprinting conditions have been thoroughly investigated, and the optimal imprinting parameters for excellent pattern transfer have been identified. The application of the imprinted polymeric patterns as a ferroelectric nonvolatile memory for data storage has also been demonstrated and discussed.
