The study utilizes surface sensitive techniques in order to quantitatively characterize the nature of organization and bonding of alkanethiol adsorbates on GaP (100) surfaces. The evaluation was performed using water contact angle, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The hydrophobicity and consistency of surface roughness were studied via water contact angle and AFM. The FT-IR experimental protocol permitted the identification of characteristic functional groups on the surface and enabled insight into the organization within the adlayers on the GaP surface. XPS data showed evidence for the formation of a covalent bond between the sulfur and the surface and was used to calculate the adlayer thicknesses, tilt angles, and molecular coverages for different adsorbates. The thickness and tilt angles values were comparable to other modified semiconductor materials. High coverages were observed for all alkanethiols on GaP (100). The quantitative XPS protocol reported can be applied to the evaluation of other adsorbates on semiconductor materials.

No abstract

No abstract

No abstract

We report the use of microcantilevers (MCs) for the detection of three retinoid isomers: 9-cis-retinal, 13-cis-retinal and all-trans-retinal. Detection of synthetic and natural retinoids in topical cosmetic products is important, and their presence can be used to predict reactions with the skin surface. In this study the MC surfaces were functionalized in order to promote the formation of covalent bonds with the chromophores. The lowest mass shift we detected with the functionalized MCs was 1.2 ppt, which is in the range needed by the cosmetics industry. Our results indicate that properly designed and functionalized microcantilevers can be used to construct economical, fast, and sensitive sensors for quality control in cosmetics.