{"577931":{"#nid":"577931","#data":{"type":"news","title":"Uniform \u201cHairy\u201d Nanorods Have Potential Energy, Biomedical Applications","body":[{"value":"\u003Cp\u003EMaterials scientists have developed a new strategy for crafting one-dimensional nanorods from a wide range of precursor materials. Based on a cellulose backbone, the system relies on the growth of block copolymer \u201carms\u201d that help create a compartment to serve as a nanometer-scale chemical reactor. The outer blocks of the arms prevent aggregation of the nanorods.\u003C\/p\u003E\u003Cp\u003EThe produced structures resemble tiny bottlebrushes with polymer \u201chairs\u201d on the nanorod surface. The nanorods range in size from a few hundred nanometers to a few micrometers in length, and a few tens of nanometers in diameter. This new technique enables tight control over diameter, length and surface properties of the nanorods, whose optical, electrical, magnetic and catalytic properties depend on the precursor materials used and the dimensions of the nanorods.\u003C\/p\u003E\u003Cp\u003EThe nanorods could have applications in such areas as electronics, sensory devices, energy conversion and storage, drug delivery, and cancer treatment. Using their technique, the researchers have so far fabricated uniform metallic, ferroelectric, upconversion, semiconducting and thermoelectric nanocrystals, as well as combinations thereof. The research, supported by Air Force Office of Scientific Research, was reported in the September 16 issue of the journal \u003Cem\u003EScience\u003C\/em\u003E.\u003C\/p\u003E\u003Cp\u003E\u201cWe have developed a very general and robust strategy to craft a rich variety of nanorods with precisely-controlled dimensions, compositions, architectures and surface chemistries,\u201d said \u003Ca href=\u0022http:\/\/www.mse.gatech.edu\/faculty\/lin\u0022\u003EZhiqun Lin\u003C\/a\u003E, a professor in the \u003Ca href=\u0022http:\/\/www.mse.gatech.edu\/\u0022\u003ESchool of Materials Science and Engineering\u003C\/a\u003E at the Georgia Institute of Technology. \u201cTo create these structures, we used nonlinear bottlebrush-like block copolymers as tiny reactors to template the growth of an exciting variety of inorganic nanorods.\u201d\u003C\/p\u003E\u003Cp\u003ENanorod structures aren\u2019t new, but the technique used by Lin\u2019s lab produces nanorods of uniform sizes \u2013 such as barium titanate and iron oxide, which have not yet been demonstrated via wet-chemistry approaches in the literature \u2013 and highly-uniform core-shell nanorods made by combining two dissimilar materials. Lin and former postdoctoral research associate Xinchang Pang say the precursor materials applicable to the technique are virtually limitless.\u003C\/p\u003E\u003Cp\u003E\u201cThere are many precursors of different materials available that can be used with this robust system,\u201d Lin said. \u201cBy choosing a different outer block in the bottlebrush-like block copolymers, our nanorods can be dissolved and uniformly dispersed in organic solvents such as toluene or chloroform, or in water.\u201d\u003C\/p\u003E\u003Cp\u003EFabrication of the nanorods begins with the functionalization of individual lengths of cellulose, an inexpensive long-chain biopolymer harvested from trees. Each unit of cellulose has three hydroxyl groups, which are chemically modified with a bromine atom. The brominated cellulose then serves as macroinitiator for the growth of the block copolymer arms with well-controlled lengths using the atom transfer radical polymerization (ATRP) process, with, for example, poly(acrylic acid)-block-polystyrene (PAA-b-PS) yielding cellulose densely grafted with PAA-b-PS (i.e., cellulose-g-[PAA-b-PS]) that give the bottlebrush appearance.\u003C\/p\u003E\u003Cp\u003EThe next step involves the preferential partitioning of precursors in the inner PAA compartment that serves as a nanoreactor to initiate the nucleation and growth of nanorods. The densely grafted block copolymer arms, together with the rigid cellulose backbone, give researchers the ability to not only prevent aggregation of the resulting nanorods, but also to keep them from bending.\u003C\/p\u003E\u003Cp\u003E\u201cThe polymers are like long spaghetti and they want to coil up,\u201d Lin explained. \u201cBut they cannot do this in the complex macromolecules we make because with so many block copolymer arms formed, there is no space. This leads to the stretching of the arms, forming a very rigid structure.\u201d\u003C\/p\u003E\u003Cp\u003EBy varying the chemistry and the number of blocks in the arms of the bottlebrush-like block copolymers, Lin and coworkers produced an array of oil-soluble and water-soluble plain nanorods, core-shell nanorods, and hollow nanorods \u2013 nanotubes \u2013 of different dimensions and compositions.\u003C\/p\u003E\u003Cp\u003EFor example, by using bottlebrush-like triblock copolymers containing densely grafted amphiphilic triblock copolymer arms, the core-shell nanorods can be formed from two different materials. In most cases, a large lattice mismatch between core and shell materials would prevent the formation of high-quality core-shell structures, but the technique overcomes that limitation.\u003C\/p\u003E\u003Cp\u003E\u201cBy using this approach, we can grow the core and shell materials independently in their respective nanoreactors,\u201d Lin said. \u201cThis allows us to bypass the requirement for matching the crystal lattices and permits fabrication of a large variety of core-shell structures with different combinations that would otherwise be very challenging to obtain.\u201d\u003C\/p\u003E\u003Cp\u003ELin sees many potential applications for the nanorods.\u003C\/p\u003E\u003Cp\u003E\u201cWith a broad range of physical properties \u2013 optical, electrical, optoelectronic, catalytic, magnetic, and sensing \u2013 that are dependent sensitively on their size and shape as well as their assemblies, the produced nanorods are of both fundamental and practical interest,\u201d Lin said. \u201cPotential applications include optics, electronics, photonics, magnetic technologies, sensory materials and devices, lightweight structural materials, catalysis, drug delivery, and bio-nanotechnology.\u201d\u003C\/p\u003E\u003Cp\u003EFor example, plain gold nanorods of different lengths may allow effective plasmonic absorption in the near-infrared range for use in solar energy conversion with improved harvesting of solar spectrum. The upconversion nanorods can preferentially harvest the IR solar photons, followed by the absorption of emitted high-energy photons to generate extra photocurrent in solar cells. They can also be used for biological labeling because of their low toxicity, chemical stability, and intense luminescence when excited by near-IR radiation, which can penetrate tissue much better than higher energy radiation such as ultraviolet, as is often required with quantum dot labels.\u003C\/p\u003E\u003Cp\u003EThe gold-iron oxide core-shell nanorods may be useful in cancer therapy, with MRI imaging enabled by the iron oxide shell, and local heating created by the photothermal effect on the gold nanorod core killing cancer cells.\u003C\/p\u003E\u003Cp\u003EIn addition to the researchers already mentioned, co-authors included graduate research assistant Yanjie He and postdoctoral researcher Jaehan Jung in Georgia Tech\u2019s School of Materials Science and Engineering.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the Air Force Office of Scientific Research under grant FA9550-16-1-0187. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Xinchang Pang, Yanjie He, Jaehan Jung, Zhiqun Lin, \u201c1D nanocrystals with precisely controlled dimensions, compositions, and architectures,\u201d (Science 2016). \u003Ca href=\u0022http:\/\/science.sciencemag.org\/cgi\/doi\/10.1126\/science.aad8279\u0022\u003Ehttp:\/\/science.sciencemag.org\/cgi\/doi\/10.1126\/science.aad8279\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, GA 30332-0181 USA\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986) (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Ben Brumfield (404-385-1933) (\u003Ca href=\u0022mailto:ben.brumfield@comm.gatech.edu\u0022\u003Eben.brumfield@comm.gatech.edu\u003C\/a\u003E).\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EMaterials scientists have developed a new strategy for crafting one-dimensional nanorods from a wide range of precursor materials. Based on a cellulose backbone, the system relies on the growth of block copolymer \u201carms\u201d that help create a compartment to serve as a nanometer-scale chemical reactor. The outer blocks of the arms prevent aggregation of the nanorods.\u0026nbsp;\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Materials scientists have developed a new strategy for crafting one-dimensional nanorods from a wide range of precursor materials."}],"uid":"27303","created_gmt":"2016-09-15 13:19:24","changed_gmt":"2022-05-26 17:09:36","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2016-09-15T00:00:00-04:00","iso_date":"2016-09-15T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"577791":{"id":"577791","type":"image","title":"Gold nanorods","body":null,"created":"1473958972","gmt_created":"2016-09-15 17:02:52","changed":"1475895388","gmt_changed":"2016-10-08 02:56:28","alt":"Gold 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