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A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 1 8 1 4 NANOTECHNOLOGY MOTHER-OF-PEARL INSPIRES SUPER STRONG CARBON SHEETS A team of researchers from Bei- hang University, China, and The Uni- versity of Texas at Dallas recently de- veloped high strength, super-tough carbon sheets that can be inexpensive- ly fabricated at low temperatures. The team made the sheets by chemically stitching together platelets of graphit- ic carbon. The fabrication process re- sults in a material whose mechanical properties exceed those of carbon fi- ber composites currently used in com- mercial products. Today’s carbon fi- ber composites are expensive in part because the fibers are produced at ex- tremely high temperatures, which can exceed 2500°C. “In contrast, our process can use graphite that is cheaply dug from the ground and processed at temperatures below 45°C,” says chemistry professor Qunfeng Cheng of Beihang Universi- ty. “The strengths of these sheets in all in-plane directions match that of plied carbon fiber composites, and they can absorb much higher mechanical en- ergy before failing than carbon fiber composites.” The researchers found inspiration in natural nacre, also known as moth- er-of-pearl, which gives some seashells their strength and toughness. Nacre is composed of parallel platelets that are bound together by thin layers of organ- ic material. “Instead of mechanically stacking large-area graphene sheets, we oxidize micron-size graphite plate- lets so that they can be dispersed in water, and then filter this dispersion to inexpensively make sheets of oriented graphene oxide,” says Ray Baughman, director of the NanoTech Institute at UT Dallas. “This process is akin to hand- making sheets of paper by filtering a slurry of fibers.” Sheets that incorporate the bridg- ing agents are 4.5 times stronger and 7.9 times tougher than agent-free sheets, say researchers. utdallas.edu. NEW 2D MATERIAL MAY BE EFFICIENT PHOTOCATALYST An international research team led by scientists from Rice University, Houston, has created another 2D ma- terial that researchers say could be a game changer for solar fuel generation. Materials scientist Pulickel Ajayan and colleagues extracted 3-atom-thick he- matene from common iron ore. Hema- tene may be an efficient photocata- lyst, especially for splitting water into hydrogen and oxygen, and could also serve as an ultrathin magnetic material for spintronic-based devices, according to the team. “2D magnetism is becoming a very exciting field with recent advances in synthesizing such materials, but the synthesis techniques are complex and the materials’ stability is limited,” says Ajayan. “Here, we have a simple, scal- able method, and the hematene struc- ture should be environmentally stable.” Ajayan’s lab worked with research- ers at the University of Houston and in India, Brazil, Germany, and elsewhere to exfoliate the material from natural- ly occurring hematite using a combina- tion of sonication, centrifugation, and vacuum-assisted filtration. rice.edu . BRIEF Researchers at the University of Tokyo developed a new method to build large areas of a semiconductive material that is just two molecules thick and 4.4 nm tall. The material functions as a thin film transistor and has potential for use in flexible electronics or chemical detectors. These transistors are the first examples of semiconductive single molecular bilayers created with liquid solution processing, a standard and cost-effective manufacturing process. www.u-tokyo.ac.jp/en. Atomic arrangement of iron (blue) and oxygen (white) atoms in hematene, a 2Dmaterial exfoliated from hematite. Courtesy of Cristiano Woellner and Douglas Galvao. False-color, scanning electron micro- scope image shows fractured surface of a sequentially bonded graphene sheet developed at UT Dallas and Beihang University.