MSGID: 1:317/3 6413ecf0   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Nano cut-and-sew: New method for chemically tailoring layered   
   nanomaterials could open pathways to designing 2D materials on demand    
      
     Date:   
         March 16, 2023   
     Source:   
         Drexel University   
     Summary:   
         A new process that lets scientists chemically cut apart and stitch   
         together nanoscopic layers of two-dimensional materials -- like a   
         tailor altering a suit -- could be just the tool for designing   
         the technology of a sustainable energy future. Researchers   
         have developed a method for structurally splitting, editing and   
         reconstituting layered materials, called MAX phases and MXenes,   
         with the potential of producing new materials with very unusual   
         compositions and exceptional properties.   
      
      
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   FULL STORY   
   ==========================================================================   
   A new process that lets scientists chemically cut apart and stitch   
   together nanoscopic layers of two-dimensional materials -- like a tailor   
   altering a suit -- could be just the tool for designing the technology   
   of a sustainable energy future. Researchers from Drexel University,   
   China and Sweden, have developed a method for structurally splitting,   
   editing and reconstituting layered materials, called MAX phases and   
   MXenes, with the potential of producing new materials with very unusual   
   compositions and exceptional properties.   
      
      
   ==========================================================================   
   A "chemical scissor" is a chemical designed to react with a specific   
   compound to break a chemical bond. The original set of chemical scissors,   
   designed to break carbon-hydrogen bonds in organic molecules, was reported   
   more than a decade ago. In a paper recently published in Science, the   
   international team reported on a method to sharpen the scissors so that   
   they can cut through extremely strong and stable layered nanomaterials   
   in a way that breaks atomic bonds within a single atomic plane, then   
   substitutes new elements - - fundamentally altering the material's   
   composition in a single chemical "snip."  "This research opens a new era   
   of materials science, enabling atomistic engineering of two-dimensional   
   and layered materials," said Yury Gogotsi, PhD, Distinguished University   
   professor and Bach chair in Drexel's College of Engineering, who was an   
   author of the research. "We are showing a way to assemble and disassemble   
   these materials like LEGO blocks, which will lead to the development of   
   exciting new materials that have not even been predicted to be able to   
   exist until now."  Gogotsi and his collaborators at Drexel have been   
   studying the properties of a family of layered nanomaterials called   
   MXenes, that they discovered in 2011.   
      
   MXenes begin as a precursor material called a MAX phase; "MAX" is a   
   chemical portmanteau signifying the three layers of the material: M, A,   
   and X. Applying a strong acid to the MAX phase chemically etches away   
   the A layer, creating a more porously layered material -- with an A-less   
   moniker: MXene.   
      
   The discovery came on the heels of worldwide excitement about a   
   two-dimensional nanomaterial called graphene, posited to be the strongest   
   material in existence when the team of researchers who discovered it   
   won the Nobel prize in 2010.   
      
   Graphene's discovery expanded the search for other atomically thin   
   materials with extraordinary properties -- like MXenes.   
      
   Drexel's team has been assiduously exploring the properties of MXene   
   materials, leading to discoveries about its exceptional electrical   
   conductivity, durability and ability to attract and filter chemical   
   compounds, among others.   
      
   But in some ways, the potential for MXenes has been capped from their   
   inception by the way they're produced and the limited set of MAX phases   
   and etchants that can be used to create them.   
      
   "Previously we could only produce new MXenes by adjusting the chemistry   
   of the MAX phase or the acid used to etch it," Gogotsi said. "While this   
   allowed us to create dozens of MXenes, and predict that many dozen more   
   could be created, the process did not allow for a great deal of control   
   or precision."  By contrast, the process that the team -- led by Gogotsi   
   and Qing Huang, PhD, a professor at the Chinese Academy of Sciences --   
   reported in its Sciencepaper explains that, "chemical scissor-mediated   
   structural editing of layered transition metal carbides," is more like   
   performing surgery, according to Gogotsi.   
      
   The first step is using a Lewis acidic molten salt (LAMS) etching protocol   
   that removes the A layer, as usual, but is also able to replace it with   
   another element, such as chlorine. This is significant because it puts   
   the material in a chemical state such that its layers can be sliced apart   
   using a second set of chemical scissors, composed of a metal, such as   
   zinc. These layers are the raw materials of MAX phases, which means the   
   addition of a bit of chemical "mortar" -- a process called intercalation   
   -- lets the team build their own MAX phases, which can then be used to   
   create new MXenes, tailored to enhance specific properties.   
      
   "This process is like making a surgical cut of the MAX structure, peeling   
   apart the layers and then reconstructing it with new and different metal   
   layers," Gogotsi said. "In addition to being able to produce new and   
   unusual chemistries, which is interesting fundamentally, we can also   
   make new and different MAX phases and use them to produce MXenes that   
   are tailored to optimize various properties."  In addition to building   
   new MAX phases, the team also reported on using the method to create   
   MXenes that can host new "guest atoms" that it previously would not have   
   been chemically able to accommodate -- further expanding the family of   
   MXene materials.   
      
   "We expect this work to lead to a major expansion of the already very   
   large space of layered and two-dimensional materials," Gogotsi said. "New   
   MXenes that could not be produced from conventional MAX precursors are   
   becoming possible.   
      
   Of course, new materials with unusual structure and properties are   
   expected to enable new technologies."  The next step for this research,   
   according to Gogotsi, is the delamination of two- and three-dimensional   
   layered carbides, as well as metal intercalated two- dimensional carbides,   
   into single- and few-layer nanosheets. This will allow the researchers to   
   characterize their fundamental properties to optimize the new materials   
   for use in energy storage, electronics and other applications.   
      
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   ==========================================================================   
   Story Source: Materials provided by Drexel_University. Note: Content   
   may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Haoming Ding, Youbing Li, Mian Li, Ke Chen, Kun Liang, Guoxin   
      Chen, Jun   
         Lu, Justinas Palisaitis, Per O. AA. Persson, Per Eklund, Lars   
         Hultman, Shiyu Du, Zhifang Chai, Yury Gogotsi, Qing Huang. Chemical   
         scissor- mediated structural editing of layered transition metal   
         carbides.   
      
         Science, 2023; 379 (6637): 1130 DOI: 10.1126/science.add5901   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/03/230316140936.htm   
      
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