NEWS OF THE WEEK
SEMICONDUCTOR SOLUTION A thiol and amine mixture at room temperature dissolves at least nine semiconductors, a finding that could lower processing costs for thin-film applications.
MATERIALS: Uncommon solvent
system may lead to low-cost liquid-phase processing
J. AM. CHEM. SOC.
EMICONDUCTORS, thanks to their controllable
S
and highly customizable electronic properties, function as control centers in most of today’s high-tech devices. Typically, these devices are manufactured via expensive and energy-consuming vacuum deposition methods. Solution-phase processing—simply and inexpensively spraying a thin film of semiconductors, for instance, instead of using a complex vacuum-based process to deposit them—would be a major improvement. But nearly all solvents are ineffective at dissolving semiconductors. The most effective one, hydrazine, is toxic and highly explosive. That obstacle has been overcome. University of Southern California chemists David H. Webber and Richard L. Brutchey now report that a largely unexplored, “relatively nonhazardous” two-component solvent readily dissolves a family of semiconduc-
INDIA AS WORLD’S DRUGSTORE PHARMACEUTICALS: Country sets ambitious medicine export targets at CPhI meeting NDIA HOPES TO EXPORT $25 billion worth of phar-
I
maceuticals in 2016, an increase of more than $10 billion from current levels. Government officials announced the export target last week at CPhI, the world’s largest pharmaceutical ingredients trade fair. India aims to achieve the much higher drug sales despite challenges to its patent regime by Western countries and at a time when the image of its pharmaceutical industry is tarnished by quality problems at prominent firms. The country’s optimism is buoyed by its recent performance. Over the past four years, exports have risen on average by 24% annually, according to the India Brand Equity Foundation, a government-sponsored B RA N D I N D I A
A poster from India’s drug export campaign.
CEN.ACS.ORG
8
tors (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja4084336). Specifically, the team finds that at room temperature and under ambient pressure, a mixture of 1,2-ethylenediamine and 1,2-ethanedithiol can rapidly dissolve bulk samples of nine metal chalcogenides—binary semiconductors with the general formula V2VI3, where V represents arsenic, antimony, or bismuth and VI represents sulfur, selenium, or tellurium. Webber and Brutchey found that the mixed solvent could be used to make highly concentrated (21–32% by weight) solutions of several metal chalcogenides, including As2S3, As2Se3, As2Te3, Sb2S3, Sb2Se3, and Sb2Te3. The solution concentrations of the other compounds they studied, Bi2S3, Bi2Se3, and Bi2Te3, fell in the roughly 1–10-wt% range. In an initial test of the solvent’s usefulness for processing semiconductors, the team prepared thin films of Sb2Se3 and Bi2S3 by spin coating the liquids on a support material and rapidly heating to evaporate the solvent. On the basis of X-ray, microscopy, and spectroscopy analyses, the group reports that the method yields high-quality, contaminant-free crystalline films. “These are exciting results in thin-film formation for a number of important semiconductors,” especially because the method does not use hydrazine, says University of California, Davis, chemist Susan M. Kauzlarich. These findings, she adds, may be useful for other semiconductors.—MITCH JACOBY
group. Claiming that India is already the world’s largest exporter of generic pharmaceuticals, IBEF says it wants to position India as the “pharmacy of the world.” “Thanks to our expertise, quality standards, and costeffective manufacturing techniques, we have been able to lower the cost of vital medicines in the developing world,” said Sudhanshu Pandey, joint secretary in the Indian Ministry of Commerce & Industry, in a statement issued before CPhI. But India will face a number of challenges. The country’s pharmaceutical industry is striving to clean up its image after reports that it does not abide by environmental and quality standards. For example, Swedish researchers found in 2007 that water near pharmaceutical plants in Patancheru, an industrial district near Hyderabad, was heavily contaminated by antibiotics. And in recent years, U.S. and European regulators have banned pharmaceuticals from leading Indian firms including Wockhardt, Aurobindo, and Ranbaxy Laboratories for poor quality. The U.S. Department of Justice slapped Ranbaxy with a fine of $500 million—the largest ever for a generics producer—after FDA found numerous breaches of manufacturing protocols at its plants. India’s export goals may also come up against pressure from the U.S. and Europe for the country to tighten its patent laws. Western drugmakers complain that many of the drugs India exports are patented in the West but not in India or the developing countries where they are sold.—JEAN-FRANÇOIS TREMBLAY
OCTOBER 28, 2013
