{"217271":{"#nid":"217271","#data":{"type":"news","title":"Polymer Structures Serve as \u201cNanoreactors\u201d for Nanocrystals with Uniform Sizes and Shapes","body":[{"value":"\u003Cp\u003EUsing star-shaped block co-polymer structures as tiny reaction vessels, researchers have developed an improved technique for producing nanocrystals with consistent sizes, compositions and architectures \u2013 including metallic, ferroelectric, magnetic, semiconductor and luminescent nanocrystals. The technique relies on the length of polymer molecules and the ratio of two solvents to control the size and uniformity of colloidal nanocrystals.\u003C\/p\u003E\u003Cp\u003EThe technique could facilitate the use of nanoparticles for optical, electrical, optoelectronic, magnetic, catalysis and other applications in which tight control over size and structure is essential to obtaining desirable properties. The technique produces plain, core-shell and hollow nanoparticles that can be made soluble either in water or in organic solvents.\u003C\/p\u003E\u003Cp\u003E\u201cWe have developed a general strategy for making a large variety of nanoparticles in different size ranges, compositions and architectures,\u201d said \u003Ca href=\u0022http:\/\/www.mse.gatech.edu\/faculty-staff\/faculty\/zhiqun-lin\u0022\u003EZhiqun Lin\u003C\/a\u003E, an associate 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. \u201cThis very robust technique allows us to craft a wide range of nanoparticles that cannot be easily produced with any other approaches.\u201d\u003C\/p\u003E\u003Cp\u003EThe technique was described in the June issue of the journal \u003Cem\u003ENature Nanotechnology\u003C\/em\u003E. The research was supported by the Air Force Office of Scientific Research.\u003C\/p\u003E\u003Cp\u003EThe star-shaped block co-polymer structures consist of a central beta-cyclodextrin core to which multiple \u201carms\u201d \u2013 as many as 21 linear block co-polymers \u2013 are covalently bonded. The star-shaped block co-polymers form the unimolecular micelles that serve as a reaction vessel and template for the formation of the nanocrystals.\u003C\/p\u003E\u003Cp\u003EThe inner blocks of unimolecular micelles are poly(acrylic) acid (PAA), which is hydrophilic, which allows metal ions to enter them. Once inside the tiny reaction vessels made of PAA, the ions react with the PAA to form nanocrystals, which range in size from a few nanometers up to a few tens of nanometers. The size of the nanoparticles is determined by the length of the PAA chain.\u003C\/p\u003E\u003Cp\u003EThe block co-polymer structures can be made with hydrophilic inner blocks and hydrophobic outer blocks \u2013 amphiphilic block co-polymers, with which the resulting nanoparticles can be dissolved in organic solvents. However, if both inner and outer blocks are hydrophilic \u2013 all hydrophilic block co-polymers \u2013 the resulting nanoparticles will be water-soluble, making them suitable for biomedical applications.\u003C\/p\u003E\u003Cp\u003ELin and collaborators Xinchang Pang, Lei Zhao, Wei Han and Xukai Xin found that they could control the uniformity of the nanoparticles by varying the volume ratio of two solvents \u2013 dimethlformamide and benzyl alcohol \u2013 in which the nanoparticles are formed. For ferroelectric lead titanate (PbTiO\u003Csub\u003E3\u003C\/sub\u003E) nanoparticles, for instance, a 9-to-1 solvent ratio produces the most uniform nanoparticles.\u003C\/p\u003E\u003Cp\u003EThe researchers have also made iron oxide, zinc oxide, titanium oxide, cuprous oxide, cadmium selenide, barium titanate, gold, platinum and silver nanocrystals. The technique could be applicable to nearly all transition or main-group metal ions and organometallic ions, Lin said.\u003C\/p\u003E\u003Cp\u003E\u201cThe crystallinity of the nanoparticles we are able to create is the key to a lot of applications,\u201d he added. \u201cWe need to make them with good crystalline structures so they will exhibit good physical properties.\u201d\u003C\/p\u003E\u003Cp\u003EEarlier techniques for producing polymeric micelles with linear block co-polymers have been limited by the stability of the structures and by the consistency of the nanocrystals they produce, Lin said. Current fabrication techniques include organic solution-phase synthesis, thermolysis of organometallic precursors, sol-gel processes, hydrothermal reactions and biomimetic or dendrimer templating. These existing techniques often require stringent conditions, are difficult to generalize, include a complex series of steps, and can\u2019t withstand changes in the environment around them.\u003C\/p\u003E\u003Cp\u003EBy contrast, nanoparticle production technique developed by the Georgia Tech researchers is general and robust. The nanoparticles remain stable and homogeneous for long periods of time \u2013 as much as two years so far \u2013 with no precipitation. Such flexibility and stability could allow a range of practical applications, Lin said.\u003C\/p\u003E\u003Cp\u003E\u201cOur star-like block co-polymers can overcome the thermodynamic instabilities of conventional linear block co-polymers,\u201d he said. \u201cThe chain length of the inner PAA blocks dictates the size of the nanoparticles, and the uniformity of the nanoparticles is influenced by the solvents used in the system.\u201d\u003C\/p\u003E\u003Cp\u003EThe researchers have used a variety of star-like di-block and tri-block co-polymers as nanoreactors. Among them are poly(acrylic acid)-block-polystyrene (PAA-b-PS) and poly(acrylic acid)-blockpoly(ethylene oxide) (PAA-b-PEO) diblock co-polymers, and poly(4-vinylpyridine)-block-poly(tert-butyl acrylate)-block-polystyrene (P4VP-b-PtBA-b-PS), poly(4-vinylpyridine)-block-poly (tert-butyl acrylate)-block-poly(ethylene oxide) (P4VP-b-PtBA-b-PEO), polystyrene-block-poly(acrylic acid)-block-polystyrene (PS-b-PAA-b-PS) and polystyrene-block-poly(acrylic acid)-block-poly(ethylene oxide) (PS-b-PAA-b-PEO) tri-block co-polymers.\u003C\/p\u003E\u003Cp\u003EFor the future, Lin envisions more complex nanocrystals with multifunctional shells and additional shapes, including nanorods and so-called \u201cJanus\u201d nanoparticles that are composed of biphasic geometry of two dissimilar materials.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the Air Force Office of Scientific Research (AFOSR) under awards FA9550-09-1-0388 and FA9550-13-1-0101. The conclusions expressed in this news releases are those of the principal investigator and do not necessarily represent the official views of the AFOSR.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Xinchang Pang, Lei Zhao, Wei Han, Xukai Xin and Zhiqun Lin, \u201cA general and robust strategy for the synthesis of nearly monodisperse colloidal nanocrystals,\u201d (Nature Nanotechnology, 8, 426, 2013). \u003Ca href=\u0022http:\/\/dx.doi.org\/10.1038\/nnano.2013.85\u0022 title=\u0022http:\/\/dx.doi.org\/10.1038\/nnano.2013.85\u0022\u003Ehttp:\/\/dx.doi.org\/10.1038\/nnano.2013.85\u003C\/a\u003E.\u003Cbr \/\u003E\u003Cbr \/\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, Georgia\u0026nbsp; 30332-0181\u0026nbsp; USA\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E)(404-894-6986).\u003Cbr \/\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EUsing star-shaped block co-polymer structures as tiny reaction vessels, researchers have developed an improved technique for producing nanocrystals with consistent sizes, compositions and architectures \u2013 including metallic, ferroelectric, magnetic, semiconductor and luminescent nanocrystals. The technique relies on the length of polymer molecules and the ratio of two solvents to control the size and uniformity of colloidal nanocrystals.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers are using star-shaped block co-polymer structures as tiny reaction vessels."}],"uid":"27303","created_gmt":"2013-06-11 13:35:24","changed_gmt":"2016-10-08 03:14:23","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2013-06-11T00:00:00-04:00","iso_date":"2013-06-11T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"217231":{"id":"217231","type":"image","title":"Nanocrystal nanoreactors2","body":null,"created":"1449180130","gmt_created":"2015-12-03 22:02:10","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Nanocrystal nanoreactors2","file":{"fid":"197151","name":"nanocrystals182.jpg","image_path":"\/sites\/default\/files\/images\/nanocrystals182_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/nanocrystals182_0.jpg","mime":"image\/jpeg","size":1029446,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/nanocrystals182_0.jpg?itok=7H2iubBt"}},"217221":{"id":"217221","type":"image","title":"Nanocrystal nanoreactors","body":null,"created":"1449180130","gmt_created":"2015-12-03 22:02:10","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Nanocrystal nanoreactors","file":{"fid":"197150","name":"nanocrystals96.jpg","image_path":"\/sites\/default\/files\/images\/nanocrystals96_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/nanocrystals96_0.jpg","mime":"image\/jpeg","size":926631,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/nanocrystals96_0.jpg?itok=XsDHi_-5"}},"217261":{"id":"217261","type":"image","title":"Nanocrystal nanoreactors5","body":null,"created":"1449180130","gmt_created":"2015-12-03 22:02:10","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Nanocrystal nanoreactors5","file":{"fid":"197154","name":"nanocrystals328.jpg","image_path":"\/sites\/default\/files\/images\/nanocrystals328_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/nanocrystals328_0.jpg","mime":"image\/jpeg","size":1058749,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/nanocrystals328_0.jpg?itok=yjp0DC_Q"}},"217241":{"id":"217241","type":"image","title":"Nanocrystal nanoreactors3","body":null,"created":"1449180130","gmt_created":"2015-12-03 22:02:10","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Nanocrystal nanoreactors3","file":{"fid":"197152","name":"nanocrystals251.jpg","image_path":"\/sites\/default\/files\/images\/nanocrystals251_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/nanocrystals251_0.jpg","mime":"image\/jpeg","size":883481,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/nanocrystals251_0.jpg?itok=yPuWvEaz"}},"217251":{"id":"217251","type":"image","title":"Nanocrystal nanoreactors4","body":null,"created":"1449180130","gmt_created":"2015-12-03 22:02:10","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Nanocrystal nanoreactors4","file":{"fid":"197153","name":"nanocrystals275.jpg","image_path":"\/sites\/default\/files\/images\/nanocrystals275_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/nanocrystals275_0.jpg","mime":"image\/jpeg","size":1189843,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/nanocrystals275_0.jpg?itok=fuSCaYQX"}}},"media_ids":["217231","217221","217261","217241","217251"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"141","name":"Chemistry and Chemical Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"}],"keywords":[{"id":"7562","name":"nanocrystal"},{"id":"2054","name":"nanoparticle"},{"id":"107","name":"Nanotechnology"},{"id":"167535","name":"School of Materials Science and Engineering"},{"id":"67921","name":"Zhiqun Lin"}],"core_research_areas":[{"id":"39451","name":"Electronics and Nanotechnology"},{"id":"39471","name":"Materials"}],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}