SPECTROSCOPY
Baking soda washes pesticides from apples Alkaline solution wipes out residues on the fruits’ surface, study shows Rinsing produce with tap water removes germs and also significantly reduces pesticide residues. But some pesticides persist on produce after washing, raising health concerns about chronic, low-level exposure to the compounds. A new study finds that a baking soda (sodium bicarbonate) wash can completely remove the residues of two pesticides from the surface of apples (J. Agric. Food Chem. 2017, DOI: 10.1021/acs.jafc.7b03118). According to the U.S. Department of Agriculture, about 85% of the produce sampled in 2015 had pesticide residues, with apples sporting 16 different ones. Commercial processers wash their fruits and vegetables for two minutes after harvest with a bleach sanitizer to remove dirt and germs. Lili He, an analytical chemist
at the University of Massachusetts, Amherst, and her team wondered if the wash might also remove pesticide residues. The scientists compared the efficacy of the germicidal bleach to rinsing with tap water or a sodium bicarbonate solution, which is alkaline. “Most pesticides are not stable at an alkaline pH, which breaks down the compounds and helps to wash them away,” He explains. The researchers applied two common pesticides, thiabendazole and phosmet, to organic Gala apples at concentrations used by farmers. After the various washes, He and coworkers used surface-enhanced Raman scattering (SERS) to map pesticide residues on the surface of the apples and inside their skins. Immersing the apples in a sodium bi-
Rinsing with tap water doesn’t remove pesticides from the surface of apples as well as washing with a baking soda solution. carbonate solution for 15 minutes followed by a freshwater rinse removed all surface pesticide residues, whereas the tap water and bleach treatments removed some, but not all. SERS also uncovered some of the pesticides lurking inside the peel. “The study hit two classes of pesticides,” says Jason C. White, an analytical chemist at the Connecticut Agricultural Experiment Station, “but there are probably 50 insecticides labeled for use on apples, and they will be removed at different rates, so more testing is needed.”—JANET
PELLEY, special to C&EN
NANOMATERIALS
C R E D I T: S H U TT E RSTO CK ( A P P L ES ) ; CO U RT ESY O F B RO O K H AV EN N AT I O N AL L AB O RATO RY (G L ASS)
Making glass disappear Nanotexturing gives materials antireflective properties To reduce the annoying glare from the surfaces of cell phones and eyeglasses, manufacturers often coat them with antireflective films. Yet these coatings are limited because they reduce the reflection of light only at certain optimal wavelengths. Now, by directly changing the morphology of glass in a process called nanotexturing, researchers can fabricate glass that cuts down on reflection from light across wide swaths of visible and infrared wavelengths, making the material close to invisible. The new glass could be useful in devices such as laser systems and solar cells, in which light loss causes inefficient performance. The researchers, led by Charles Black, a materials scientist at Brookhaven National Laboratory, began by creating a patterned polystyrene-b-poly(methyl methacrylate) block copolymer template. When placed over top of glass, the template enables the transfer of its pattern to the material via plasma etching. In this process, which the team had previously developed for
silicon, gas runs over the template surface, gouging out trenches in the exposed substrate surface and creating a “forest” of nanocones (Appl. Phys. Lett. 2017, DOI: 10.1063/1.5000965). These nanocones—less than 10 nm in width on average—reduce the reflections from the front and back of materials to less than 0.2% for the whole visible and near-infrared spectrum (450-2,500 nm). Using this method, the team made nanotextured glass substrates up to about 10 cm in diameter. The researchers have not yet tested the materials’ durability, a property that will dictate what applications this approach is suitable for, Black says. In one experiment, the researchers evaluated the efficiency by which a solar cell converted light into electricity with an uncovered device, a device covered with the nanotextured glass, and a device covered with regular glass. They found that the uncovered and nanotextured glass devices were comparable and the regular
Nanotextured glass (top) compared to regular glass (bottom) greatly reduces the glare from lights overhead. glass device was about half a percent less efficient. The fabrication process is quite complex, which could make it difficult to scale, says Tolga Aytug, a materials researcher at Oak Ridge National Laboratory. Black acknowledges the limitations of the process but says the team hopes to find commercial partners to help scale up the technology.—TIEN NGUYEN NOVEMBER 6, 2017 | CEN.ACS.ORG | C&EN
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