NEWS OF TH E WEEK
MINNESOTA BANS TRICLOSAN LEGISLATION: State is halting retail sales of soaps containing antibacterial chemical INNESOTA IS POISED to become the first
state in the nation to ban the sale of soaps and cleaning products that contain the antibacterial compound triclosan. A new law, signed by Gov. Mark Dayton (D) in mid-May, will prohibit retailers in the state from selling soaps and cleaners with triclosan as of Jan. 1, 2017. Despite opposition from the American Cleaning Institute, a trade association of soap and detergent makers, the legislation garnered broad support in the Minnesota State Legislature. It passed the House of Representatives 110-19 and the Senate 58-0. One of the bill’s sponsors, state Sen. John Marty (D), predicts other states and the federal government are likely to follow Minnesota’s lead. “While this is an effort to ban triclosan from one of the 50 states, I think it will have a greater impact than that,” Marty says. In fact, the New York State Legislature is consider-
CHERY L HOGUE/C&EN
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RETHINKING PHOTOCATALYSIS CATALYSIS: Study questions conventionally ascribed role of metal particles on semiconductors ITANIUM DIOXIDE’S knack for mediating
sunlight-driven chemical reactions has made it the material of choice for a host of applications, including self-cleaning glass, antifogging coatings, and splitting water to make hydrogen. Researchers have known for years that modifying the semiconductor with metal nanoparticles increases its photocatalytic activity. But the conventional explanation for that enhancement has been called into question by a new study that challenges the mechanistic role of the metal nanoparticles. The study may deepen understanding of photochemical processes and may lead to lower-cost catalysts. Shining light on TiO2 or other semiconductors promotes electrons to an excited state from which they can stimulate chemical reactions. Much of the time, the electrons shed their excess energy far too quickly for reactions to commence. But if TiO2 is doped with platinum or other metal nanoparticles, excited electrons can quickly hop onto the metals and get trapped before they
ADAPTED FROM PROC. NATL. ACAD. SCI. USA
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ing bills that would ban the sale of products containing triclosan. Support for such action stems from growing concerns about possible health effects associated with antibacterial ingredients and their potential to lead to antibiotic resistance. The American Cleaning Institute says Minnesota’s ban will take safe, effective, and beneficial products off the shelves. But a number of leading manufacturers, including Procter & Gamble and Johnson & Johnson, are reformulating consumer products to eliminate triclosan in response to demands from consumers and major retailers including Walmart and Target. Minnesota’s new law builds on a procurement policy that Dayton’s administration implemented last year. That policy allows state agencies to purchase only soaps and detergents that are free of triclosan. However, it does allow purchase of soaps containing the chemical for use in health care settings. The federal Food & Drug Administration, meanwhile, is taking aim at triclosan and a related chemical, triclocarban. A December 2013 proposal by FDA would require makers of antibacterial soaps to demonstrate that their products are safe for everyday use and are more effective at preventing the spread of germs than ordinary soap.—CHERYL HOGUE & BRITT ERICKSON
Triclosan is an ingredient in some soaps and dishwashing liquids.
can cool down, according to the common explanation. In the case of water splitting, that model indicates that the metals serve as tiny islands on the semiconductor surface on which hydrogen ions can congregate, undergo reduction with trapped electrons, and form H2. A team led by University of California, Riverside, chemistry professor Francisco Zaera now proposes that electron transfer from the semiconductor to the metal may not play a UNCONVENTIONAL Metal particles on TiO2 are significant role in phocommonly regarded as electron-transfer sites active tocatalysis. The team came to that conclusion in production of H2 (left). A study suggests that the metals may be uninvolved in electron transfer (right). by using transientabsorption and timeLight Light H2 H2 resolved-fluorescence H+ spectroscopy methods H• H+ to probe the photo• Gold Gold H physics and energytransfer processes in a e– e– TiO2 TiO2 series of custom-made nanoparticles, including Au/TiO2 and Pt/TiO2 (Proc. Natl. Acad. Sci. USA 2014, DOI: 10.1073/pnas.1405365111). The Riverside team proposes that in contrast to the electron-trap model, excited electrons stimulate H+ reduction on the surface of the semiconductor, not the metal. Hydrogen atoms then migrate from the semiconductor to the metal, which combines them catalytically to form H2.—MITCH JACOBY
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MAY 26, 2014
