Common Medieval Pigments

This paper discusses the pigments used in medieval manuscripts. Specific types of pigments that are examined are earths, minerals, manufactured, and organics. It also focuses on both destructive and non-destructive methods for identifying medieval pigments

Macroscale multimodal imaging reveals ancient painting production technology and the vogue in Greco-Roman Egypt.

Macroscale multimodal chemical imaging combining hyperspectral diffuse reflectance (400-2500 nm), luminescence (400-1000 nm), and X-ray fluorescence (XRF, 2 to 25 keV) data, is uniquely equipped for noninvasive characterization of heterogeneous complex systems such as paintings. Here we present the first application of multimodal chemical imaging to analyze the production technology of an 1,800-year-old painting and one of the oldest surviving encaustic ("burned in") paintings in the world. Co-registration of the data cubes from these three hyperspectral imaging modalities enabled the comparison of reflectance, luminescence, and XRF spectra at each pixel in the image for the entire painting. By comparing the molecular and elemental spectral signatures at each pixel, this fusion of the data allowed for a more thorough identification and mapping of the painting's constituent organic and inorganic materials, revealing key information on the selection of raw materials, production sequence and the fashion aesthetics and chemical arts practiced in Egypt in the second century AD

Facile synthesis of metal-free organic dyes featuring a thienylethynyl spacer for dye sensitized solar cells

In this article, we report the facile synthesis of metal-free dyes 6 and 7, their solution-based optical and redox properties and their use as sensitizers in dye-sensitized solar cells (DSSCs). Our studies indicate that the addition of the second thiophene unit in dye 7, decreases the oxidation and reduction potential and consequently the band gap of the molecule compared to 6. Furthermore, increasing the length of the conjugated spacer also affects on the properties of the DSSCs, with dye 7 providing a higher power conversion efficiency compared to 6 (η = 4.49 versus 3.23%)

Spectral signatures of photosynthesis I: Review of Earth organisms

Why do plants reflect in the green and have a 'red edge' in the red, and should extrasolar photosynthesis be the same? We provide: 1) a brief review of how photosynthesis works; 2) an overview of the diversity of photosynthetic organisms, their light harvesting systems, and environmental ranges; 3) a synthesis of photosynthetic surface spectral signatures; 4) evolutionary rationales for photosynthetic surface reflectance spectra with regard to utilization of photon energy and the planetary light environment. Given the surface incident photon flux density spectrum and resonance transfer in light harvesting, we propose some rules with regard to where photosynthetic pigments will peak in absorbance: a) the wavelength of peak incident photon flux; b) the longest available wavelength for core antenna or reaction center pigments; and c) the shortest wavelengths within an atmospheric window for accessory pigments. That plants absorb less green light may not be an inefficient legacy of evolutionary history, but may actually satisfy the above criteria.Comment: 69 pages, 7 figures, forthcoming in Astrobiology March 200

Studies on Bile Pigments II. Seperation of Natural Direct Bilirubins

Separation of both forms of the direct bilirubin were carried out from the dog's gallbladder bile, and further isolations of them were also done. 1. The natural salt-form bilirubin was isolated after separation on the column of aluminium oxide with a n-propanolic aqueous solution. 2. The natural salt-form bilirubin was obtained in amorphous yellow powders which were strongly hygroscopic and easily soluble in water and methanol but not in chloroform or carbon tetrachloride. An aqueous solution of these powders showed both the direct diazo and Gmelin reaction, but neither Ehrlich's aldehyde nor Schlesinger reaction. The salt-form bilirubin was transferred into chloroform only when some quantities of hydrochloric acid were added to a mixture of chloroform and an aqueous solution of it. 3. The absorption maxima of the natural salt-form bilirubin existed at 420 to 430 m&#956; in a methanolic solution and at 425 or 435m&#956; in 50% or 10% n-propanol. 4. The natural ester-form bilirubin was isolated after separating on the column of silica gel with a chloroformethanolic mixture. 5. The natural ester-form bilirubin was obtained in amorphous greenish yellow powders. It was further hygroscopic and easily soluble in water and methanol but not in chloroform or carbon tetrachloride. An aqueous solution of it showed the direct diazo and Gmelin reaction, but neither Ehrlich's aldehyde nor Schlesinger's reaction. No pigment was transferred into chloroform even if some quantities of hydrochloric acid were added to a mixture of chloroform and an aqueous solution of it, but did by saponification with 5% methanolic potash. 6. The absorption maxima of the natural ester-form bilirubin existed at 415 m&#956; in both methanolic and aqueous solutions.</p