19-Oct-2020 - American Chemical Society (ACS)

Gold- and bronze-like paints that don't contain metal

Researchers have developed organic-only dyes that can form films resembling gold or bronze, without the need for metals

Lustrous metallic paints are used to enhance the beauty of many products, such as home decorations, cars and artwork. But most of these pigments owe their sheen to flakes of aluminum, copper, zinc or other metals, which have drawbacks. Now, researchers reporting in ACS Omega have developed organic-only dyes that can form films resembling gold or bronze, without the need for metals.

In paints, metal flakes tend to settle to the bottom of the can, requiring regular stirring during use and storage. Multiple coats of metallic paint are often needed to provide good coverage, which adds weight to the object being painted. Also, when used in ink-jet printers, metallic pigments can clog ink nozzles. For these and other reasons, researchers are trying to develop nonmetallic, organic paints with metal-like luster. But so far, few candidates have displayed all of the desired qualities of solubility in solvents, good film-forming properties and excellent stability over time. Katsuyoshi Hoshino and colleagues from Chiba University in Japan recently introduced a perchlorate-doped 3-methoxythiophene oligomer that checked all of these boxes, but it had to be dissolved in solvents that are considered unsafe for painters. To develop an industrially acceptable metal-effect dye, the researchers wanted to make and test chloride-doped 3-methoxythiophene oligomers.

The team made two different versions of the chloride-doped oligomers, which, unlike their previously reported perchlorate-doped counterpart, dissolved in water. They coated glass plates with solutions of the new dyes and allowed them to dry. The two chloride-doped oligomers produced lustrous gold- or bronze-like films, respectively, but they each had a non-glossy dark stain, which resembled a coffee ring stain, near the center. Although more research is needed to determine how to prevent this stain from forming, both films had higher reflectance than the one made by the perchlorate-doped oligomer. The paints are soluble in water but can be made water-resistant by dehydration, which makes their industrial implementation feasible. The new dyes could be used in commercial ink-jet printers, and they also might someday be implemented in organic electronic systems, the researchers say.

Facts, background information, dossiers
More about American Chemical Society
  • News

    Luminescent wood could light up homes of the future

    The right indoor lighting can help set the mood, from a soft romantic glow to bright, stimulating colors. But some materials used for lighting, such as plastics, are not eco-friendly. Now, researchers reporting in ACS Nano have developed a bio-based, luminescent, water-resistant wood film t ... more

    Digitizing chemistry with a smart stir bar

    Miniaturized computer systems and wireless technology are offering scientists new ways to keep tabs on reactions without the need for larger, cumbersome equipment. In a proof-of-concept study in ACS Sensors, researchers describe an inexpensive new device that functions like a conventional m ... more

    Levitating droplets allows to perform 'touchless' chemical reactions

    Levitation has long been a staple of magic tricks and movies. But in the lab, it's no trick. Scientists can levitate droplets of liquid, though mixing them and observing the reactions has been challenging. The pay-off, however, could be big as it would allow researchers to conduct contact-f ... more

  • Videos

    What Makes Rubber Rubbery?

    Reactions is looking at sports science today. Sports balls owe their reliability to an unusual polymer. Learn about the chemistry of rubber the all-star’s best friend! more

    Dragon's Blood Could Save Your Life

    This week Reactions is looking at chemistry in bizarre places that could save your life. The science within the blood of the Komodo dragon or in a horseshoe crab can help with antibiotic resistance. But it doesn't end there, so we're taking a closer look at other wild places in nature that ... more

    Why is Olive Oil Awesome?

    Whether you sop it up with bread or use it to boost your cooking, olive oil is awesome. But a lot of chemistry goes on in that bottle that can make or break a product. Take the “extra virgin” standard: Chemistry tells us that a higher free-fatty-acid content leads to a lower grade, less tas ... more

More about Chiba University
  • News

    Tunneling out of the surface

    A research team comprising scientists from Tohoku University, RIKEN, the University of Tokyo, Chiba University and University College London have discovered a new chemical reaction pathway on titanium dioxide (TiO2), an important photocatalytic material. The reaction mechanism, reported in ... more

    Transition to sustainable catalysis

    Yasumasa Hamada and colleagues at Chiba University used a combination of nickel acetate and a commercially available phosphine ligand to catalyse the asymmetric hydrogenation of an alpha-amino-beta-keto ester hydrochloride. Although others have reported similar reactions, Hamada says this i ... more