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In the transition from carbon to iron-gall inks, the two documents from the Egyptian Museum and Papyrus Collection in Berlin with shelfmarks P 13500 and P 13501 discussed in this work present an important case. Their inks appear brownish, although they date back to the fourth and third century BCE, when carbon inks are believed to have been commonly if not exclusively used. Using imaging micro-X-ray fluorescence and infrared reflectography, we discovered that the inks in both documents contain a significant amount of copper in addition to carbon. Comparing the extant recipes for black writing inks and the experimental evidence, we suggest that these inks are a transition between the pure carbon and the iron-gall inks. Such inks may have been quite common before the production of iron-gall ink was clearly understood and established.
The spectroscopic characterization by surface-enhanced Raman scattering (SERS) has shown great potential in studies of heterogeneous catalysis. We describe a plug-in multifunctional optofluidic platform that can be tailored to serve both as a variable catalyst material and for sensitive optical characterization of the respective reactions using SERS in microfluidic systems. The platform enables the characterization of reactions under a controlled gas atmosphere and does not present with limitations due to nanoparticle adsorption or memory effects. Spectra of the gold-catalyzed reduction of p-nitrothiophenol by sodium borohydride using the plug-in probe provide evidence that the borohydride is the direct source of hydrogen on the gold surface, and that a radical anion is formed as an intermediate. The in situ monitoring of the photoinduced dimerization of p-aminothiophenol indicates that the activation of oxygen is essential for the plasmon-catalyzed oxidation on gold nanoparticles and strongly supports the central role of metal oxide species.