Chemistry colors our world

Celebrating Chemistry Week, 18-24 October 2015

To mark National Chemistry Week, we are providing free access to ten chemistry articles published in 2015 that brighten up the world. Read more about these specially selected articles below:


New approach to metal finishing makes colors ‘greener’

The metal finishing industry has a big environmental impact, so researchers are keen to find ‘greener’ approaches. A new technique published in Electrochimica Acta aims to overcome some of the environmental issues associated with metal finishing. A team of researchers from The University of Adelaide, Nanjing Agricultural University in China and Nanjing Agricultural University in China made biomimetic photonic films to color aluminum. The team compared the differences between films produced in high purity and technical grade aluminum – their color, appearance, electrochemical behavior and internal nanoporous structure – to determine the best way to manufacture the material. With galvanostatic pulse anodization, they could produce a palette of colors for both types of aluminum.

On The Generation of Interferometric Colors in High Purity and Technical Grade Aluminum: An Alternative Green Process for Metal Finishing Industry,” Electrochimica Acta, Volume 174, 20 August 2015, Pages 672–681


Making pure color Perspex for optical fibers

PMMA – Poly(methyl methacrylate), more commonly known as Perspex or Plexiglas – is used in optoelectronic materials. It is low cost, has low optical absorbance and good mechanical peroperties, making it an ideal candidate for this use. A study published in Inorganic Chemistry Communications describes a metallopolymer based on Perspex. The researchers, from Northwest University in China, Hong Kong Baptist University in Hong Kong and The University of Texas at Austin in the United States, obtained dual-nodal PMMA-supported Eu3 +-containing metallopolymer with high color-purity red luminescence from the copolymerization of [Eu(TTA)3(4-vinyl-Py)2] with two active vinyl groups and MMA. The resulting material is an “interesting candidate” for use as polymeric optical fibers, say the authors.

Dual-nodal PMMA-supported Eu3 +-containing metallopolymer with high color-purity red luminescence,” Inorganic Chemistry Communications, Volume 60, October 2015, Pages 51–53


Heating fades wine – but the reason is complex

The color intensity and pH of red wine changes when it’s heated, but the cause is not a simple one. Research published in Tetrahedron shows that heating a Hungarian red wine decreased its color intensity and pH, caused by the dissociation of several phenolic OH groups. But adding hydrogen chloride – even when additional potassium ions were present – increased color intensity. According to the researchers, from the University of Pécs and János Szentágothai Research Center in Hungary, and State Research Institute for Viticulture and Pomiculture in Germany, this means the additional potassium ions change the pH dependence, and added calcium ions lead to a change in the dependence of color intensity on pH.

The effect of temperature, pH, and ionic strength on color stability of red wine,” Tetrahedron, Volume 71, Issue 20, 20 May 2015, Pages 3027–3031


Taking the color out of beet molasses

Beet molasses is used in the fermentation process to make ethanol and bioethanol products, and as a supplement for livestock feed. It is highly viscous and dark brown – there is big profit potential in removing the dark color compounds to avoid changes in the color and composition of beet molasses during use and storage. Research published in Chemical Engineering Journal examines the feasibility of decoloring beet molasses using an activated charcoal/ultrafiltration process. Researchers from the University of Burgos in Spain tested Norit powdered activated charcoal (NPAC) as a color adsorbent. NPAC reduced the color of beet molasses by over 98%, and the NPAC could be regenerated and reused.

Colour removal from beet molasses by ultrafiltration with activated charcoal,” Chemical Engineering Journal, Volume 283, 1 January 2016, Pages 313–322


Investigating the pigment in natural yellow silk

Some wild silkworms, including A. pernyi, A. yamamai and Saturniidae, produce silk that is naturally colored. Similarly, some mutants of the domestic silkworm, B. mori, can spin cocoons in different colors – pink, flesh, salmon, yellow, yellow-green and green. Their naturally colored silks are potentially valuable, if they can be processed without damage and fading. A study published in Dyes and Pigments categorizes the yellow pigment in one naturally occurring silk to understand better how the silk could best be processed. The research team, from Zhejiang Sci-Tech University and Zhejiang Entry-Exit Inspection and Quarantine Bureau in China, analyzed the fibers using NMR and found that the dominant pigment composition was all-trans-lutein, with five other components.

Characterization of the pigment in naturally yellow-colored domestic silk,” Dyes and Pigments, Volume 124, January 2016, Pages 6–11


Color analysis to test powder quality

In powder industries, the analysis of mixture quality or homogeneity is important to establish whether a product meets certain standards. Industries prefer methods that are reliable and easy to use, so research published in Powder Technology examined a new approach to this analysis. Researchers from the SP Technical Research Institute of Sweden, University College Cork in Ireland, and Tetra Pak Processing Systems and Santa Maria AB in Sweden, used a digital color imaging method (DCI) to study the quality of food powder mixtures. They then compared it to a more traditional salt conductivity method. The two methods produced similar results for mixtures in which there was a high color difference between the powders, such as in a paprika-salt mixture.

Evaluation of a digital colour imaging system for assessing the mixture quality of spice powder mixes by comparison with a salt conductivity method,” Powder Technology, Volume 286, December 2015, Pages 48–54


Analyzing the clay in paintings helps identify artists

Art galleries all over Europe have collections of paintings they don’t show publicly because of their doubtful attribution and dating. A study published in Applied Clay Science shows that analyzing the minerals in paintings can help identify their origin. A team of researchers from the Institute of Inorganic Chemistry of the Czech Academy of Sciences and the Academy of Fine Arts in Prague, Czech Republic, used X-ray powder micro-diffraction to analyze and categorize the earthy ground layers of paintings. By looking at the presence of clay-based materials they could distinguish paintings from Italy and central Europe.

Differentiation between anonymous paintings of the 17th and the early 18th century by composition of clay-based grounds,” Applied Clay Science, Volume 118, December 2015, Pages 8–20


Meteorite may explain how Mars is covered in red dust

The surface of Mars is red because it is covered in a thin layer of oxidized dust. Although researchers have studied the absorption of the dust for several decades, its attribution, geological and climatic implications are still a matter of debate. Research published in Earth and Planetary Science Letters reveals a prominent role of hydroxylated ferric minerals. A team led by researchers at Univ. Grenoble Alpes in France examined and characterized the Martian meteorite NWA 7533. Using infrared spectroscopy, Fe-XANES and petrography they identified the mineral hosts of hydrogen in the meteorite and compared them to information about the surface of Mars and results of laboratory experiments. They found its spectra are consistent with the Martian surface, suggesting similar lithologies “might play a role in the dust production mechanism.”

A Noachian source region for the “Black Beauty” meteorite, and a source lithology for Mars surface hydrated dust?Earth and Planetary Science Letters, Volume 427, 1 October 2015, Pages 104–111


What affects the oxidization of green rust?

Green rusts can be found in paddy soils, ground-water, sediments and iron corrosion products; they are found in suboxic environments, where they affect redox processes. Where green rusts are found in soil, they turn an ochre color on exposure to air, due to Fe(II) oxidation. Evidence suggests that phosphate and silicate can inhibit the oxidation of green rust, but little was known about how. A study published in Geochimica et Cosmochimica Acta by researchers from Huazhong Agricultural University in China, University of Wyoming in the United States and Wageningen University in the Netherlands shows that the oxidation of green rust to various crystalline iron oxyhydroxides depends on the presence of co-existing anions.

Effects of phosphate and silicate on the transformation of hydroxycarbonate green rust to ferric oxyhydroxides,” Geochimica et Cosmochimica Acta, Volume 171, 15 December 2015, Pages 1–14


Color glaze cools off tiles

Human activity can lead to towns and cities being significantly warmer than surrounding areas. To tackle these ‘urban heat islands’, cool roofs can be installed to reduce the temperature. The majority of today’s cool roofs are made of a polymeric product, which can reflect light and heat but are not very durable. New research published in Ceramics International by a team at Università di Modena e Reggio Emilia in Italy presents a new generation of colored glazes, on a traditionally engobed porcelain stoneware tile. Such glazes have the potential to perform better than existing materials; the results showed “promising values in solar reflectance.”

Design of a cool color glaze for solar reflective tile application,” Ceramics International, Volume 41, Issue 9, Part A, November 2015, Pages 11106–11116


Fabricating diamond material for electrical applications

Diamond has unique physical, mechanical electrical properties. Because of this, it has attracted attention for a number of different applications. However, its impurities and defects can make it less effective in various settings, altering its hardness and morphology, for example. Research published in the International Journal of Refractory Metals and Hard Materials investigated a way of fabricating a low-resistivity n-type and p-type material by doping diamond with donor and acceptor impurities, respectively. The researchers, from Jilin University, the Center for High Pressure Science & Technology Advanced Research and Tianjin University of Technology in China found that the color of diamond becomes deep green with the P3N5 additive.

The effect of phosphorus and nitrogen co-doped on the synthesis of diamond at high pressure and high temperature,” International Journal of Refractory Metals and Hard Materials, Volume 54, January 2016, Pages 309–314


Solving the problems of green ink

Market demand, legislation and resource scarcity have led ink manufacturers to develop more environmentally friendly and sustainable printing ink. Water-based inks have started to replace solvent-based inks and UV-curing systems are increasingly popular. This switch has led to a reduction in the volatile organic compounds (VOCs) released during printing. In a review published in Progress in Organic Coatings, Tobias Robert, from Fraunhofer-Institute for Wood Research – Wilhelm-Klauditz-Institut WKI in Germany, examines the changes in the printing industry towards more sustainable ink and looks at the advantages and disadvantages of the new systems, addressing unsolved problems.

Green ink in all colors – Printing ink from renewable resources,” Progress in Organic Coatings, Volume 78, January 2015, Pages 287–292