Multispectral investigation of natural resins.

Resins have been used as remedies since ancient times and various embalming resins have been identified in recent years. In Europe, Mumia vera aegyptiaca, a resinous substance from ancient Egyptian mummies, was even sold in pharmacies as a tonic until the early 20th century. It is difficult to examine the composition of these archeological samples in detail as the well-established analytical techniques, that is, gas chromatography-mass spectrometry or liquid chromatography coupled with tandem mass spectrometry, are destructive and therefore do not allow the analysis of valuable archeological samples.

External Control of GaN Band Bending Using Phosphonate Self-Assembled Monolayers.

We report on the optoelectronic properties of GaN(0001) and (11̅00) surfaces after their functionalization with phosphonic acid derivatives. To analyze the possible correlation between the acid's electronegativity and the GaN surface band bending, two types of phosphonic acids, n-octylphosphonic acid (OPA) and 1,1,2,2-perfluorooctanephosphonic acid (PFOPA), are grafted on oxidized GaN(0001) and GaN(11̅00) layers as well as on GaN nanowires. The resulting hybrid inorganic/organic heterostructures are investigated by X-ray photoemission and photoluminescence spectroscopy.