Chemically driven carbon-nanotube-guided thermopower waves

Choi, Wonjoon,Hong, Seunghyun,Abrahamson, Joel T.,Han, Jae-Hee,Song, Changsik,Nair, Nitish,Baik, Seunghyun,Strano, Michael S. Nature Publishing Group 2010 NATURE MATERIALS Vol.9 No.5

Theoretical calculations predict that by coupling an exothermic chemical reaction with a nanotube or nanowire possessing a high axial thermal conductivity, a self-propagating reactive wave can be driven along its length. Herein, such waves are realized using a 7-nm cyclotrimethylene trinitramine annular shell around a multiwalled carbon nanotube and are amplified by more than 10<SUP>4</SUP> times the bulk value, propagating faster than 2 m s<SUP>−1</SUP>, with an effective thermal conductivity of 1.28±0.2 kW m<SUP>−1</SUP> K<SUP>−1</SUP> at 2,860 K. This wave produces a concomitant electrical pulse of disproportionately high specific power, as large as 7 kW kg<SUP>−1</SUP>, which we identify as a thermopower wave. Thermally excited carriers flow in the direction of the propagating reaction with a specific power that scales inversely with system size. The reaction also evolves an anisotropic pressure wave of high total impulse per mass (300 N s kg<SUP>−1</SUP>). Such waves of high power density may find uses as unique energy sources.

A Compositional Window of Kinetic Stability for Amphiphilic Polymers and Colloidal Nanorods

Jeng, Esther S.,Shih, Chih-Jen,Barone, Paul W.,Jones, Naomi,Baik, Joon Hyun,Abrahamson, Joel T.,Strano, Michael S. American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.15

<P>Amphiphilic polymers are often used to disperse nanoparticles in aqueous solution. Polymer adsorption theory predicts that there exists a narrow compositional range of hydrophobic groups on the polymer chain that allows for kinetic stabilization. Too few groups limit polymer adsorption, while too many allow aggregation of polymer-coated nanoparticles for lack of entropic repulsion. We experimentally validate and mathematically describe the existence of this compositional range, and the resulting stability “window” for the first time using a phenoxy-dextran polymer to disperse single-walled carbon nanotubes. The results should provide a theoretical basis for the design of nanoparticle dispersants.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-15/jp109032h/production/images/medium/jp-2010-09032h_0001.gif'></P>

Catalytic synthesis of few-layer graphene on titania nanowires

Kudo, Akira,Jung, Sung Mi,Strano, Michael S.,Kong, Jing,Wardle, Brian L. Royal Society of Chemistry 2018 Nanoscale Vol.10 No.3

<P>Growth mechanisms of graphitic nanostructures on metal oxides by chemical vapor deposition (CVD) are observed at 750 °C, using titania nanowire aerogel (NWAG) as a three-dimensional substrate and without metal catalysts. We temporally observed catalytic transformation of amorphous carbon into few-layer graphene on the surface of 5-10 nm diameter titania nanowires. The graphitization spontaneously terminates when the titania nanowires are encapsulated by a shell of approximately three graphene layers. Extended CVD time beyond the termination point (>1125 seconds) yields only additional amorphous carbon deposits on top of the few-layer graphene. Furthermore, it was discovered that the islands of amorphous carbon do not graphitize unless they catalytically grow beyond a threshold size of 5-7 nm along the nanowire length, even after an extended thermal treatment. The electrical conductivity of the NWAG increased by four orders of magnitude, indicating that the graphene shell mediated by titania nanowires yielded a network of graphene throughout the three-dimensional nanostructure of the aerogel. Our results help us understand the growth mechanisms of few-layer graphene on nanostructured metal oxides, and inspire facile and controllable processing of metal oxide-nanocarbon fiber-shell composites.</P>

나노튜브/화학연료의 동축 구조에서 생성되는 열동력 파도를 이용한 전기 에너지 생성

최원준(Wonjoon Choi),마이클 스트라노(Michael S. Strano) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.6

이전 연구에서 우리는 나노구조와 화학연료의 동축 구조를 제작하여 이를 점화시켰을 때, 축방향으로 매우 빠르게 화학 반응이 전파되며, 이와 동시에 높은 비출력을 가지는 화학-전기 에너지를 생성할 수 있음을 증명하였으며, 이러한 현상을 열동력 파도로 명명하였다. 본 연구에서는 열동력 파도와 관련된 여러가지 물리적인 현상을 심도있게 다루려 한다. 나노구조의 다른 배열 상태에 따라 반응 전파속도, 에너지 생성 정도가 어떻게 달라지는지, 그리고 이와 동시에 발생하는 전기 신호와는 어떤 연관 관계가 있는 지를 연구하였다. 또한 이론적으로 온도 변화에 따라 달라지는 나노튜브와 화학연료의 성질, 대류와 복사에 의한 영향을 고려했을 때 열동력 파도의 전파 양상이 어떻게 달라지는 지를 규명하였다. There is considerable interest in developing energy sources capable of larger power densities. In our previous works, we proved that by coupling an exothermic chemical reaction with 1D nanostructures, a self-propagating reactive wave can be driven along its length with a concomitant electrical pulse of high specific power, which we identified as a thermopower wave. Herein, we discuss details about many different aspects of a thermopower wave. Different alignment degree in vertically aligned CNT films is evaluated in the reactive wave speed and correlated with its thermal reaction that affects the change in the magnitude of energy generation. The effects of the temperature-dependent properties of chemical fuels and CNTs are evaluated. Furthermore, we explore the convection and radiation portions in this thermal wave as well as the synchronization between the thermal reaction transfer and the oscillation of the electrical signal.

단일벽 탄소나노튜브 엑시톤 안테나 제조와 상온 양자전송특성

한재희(J. H. Han),김홍석(H. S. Kim),김대윤(D. Kim),정다운(D. Jung),Michael S. Strano 한국생산제조학회 2016 한국생산제조시스템학회 학술발표대회 논문집 Vol.2016 No.04

Highly efficient exfoliation of individual single-walled carbon nanotubes by biocompatible phenoxylated dextran.

Kwon, Taeyun,Lee, Gyudo,Choi, Hyerim,Strano, Michael S,Kim, Woo-Jae RSC Pub 2013 Nanoscale Vol.5 No.15

<P>Highly efficient exfoliation of individual single-walled carbon nanotubes (SWNTs) was successfully demonstrated by utilizing biocompatible phenoxylated dextran, a kind of polysaccharide, as a SWNT dispersion agent. Phenoxylated dextran shows greater ability in producing individual SWNTs from raw materials than any other dispersing agent, including anionic surfactants and another polysaccharide. Furthermore, with this novel polymer, SWNT bundles or impurities present in raw materials are removed under much milder processing conditions compared to those of ultra-centrifugation procedures. There exists an optimal composition of phenoxy groups (13.6 wt%) that leads to the production of high-quality SWNT suspensions, as confirmed by UV-vis-nIR absorption and nIR fluorescence spectroscopy. Furthermore, phenoxylated dextran strongly adsorbs onto SWNTs, enabling SWNT fluorescence even in solid-state films in which metallic SWNTs co-exist. By bypassing ultra-centrifugation, this low-energy dispersion scheme can potentially be scaled up to industrial production levels.</P>

DNA Aptamer-Passivated Nanocrystal Synthesis: A Facile Approach for Nanoparticle-Based Cancer Cell Growth Inhibition

Choi, Jong Hyun,Chen, Kok Hao,Han, Jae-Hee,Chaffee, Amanda M.,Strano, Michael S. WILEY-VCH Verlag 2009 Small Vol.5 No.6

<B>Graphic Abstract</B> <P>A class of DNA aptamers, recognizing and therapeutically targeting cancer cells, remains functional while forming stable colloidal PbS and Fe<SUB>3</SUB>O<SUB>4</SUB> nanocrystals. The aptamer-passivated nanocrystals (see image) are non-cytotoxic to normal cells, whereas MCF-7 human breast cancer cells incorporated with these particles have significantly reduced proliferation. The nanoparticle-aptamer systems provide a platform for novel nanoparticle therapeutics. <img src='wiley_img/16136810-2009-5-6-SMLL200801821-content.gif' alt='wiley_img/16136810-2009-5-6-SMLL200801821-content'> </P>

길이가 긴 탄소나노튜브의 향상된 마이크로웨이브 흡수

윤종주(Jongju Yun),전원재(Wonjae Jeon),Lee W. Drahushuk,백승현(Seunghyun Baik),Michael S. Strano 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

Extraordinary High Microwave Absorption Cross Section of Ultralong Carbon Nanotubes

Yun, Jongju,Jeon, Wonjae,Drahushuk, Lee W.,Baik, Seunghyun,Strano, Michael S. American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.25

<P>The microwave-induced heating of nanoparticles has been actively studied in pursuit of more efficient microwave absorbers. Here we systematically investigated the microwave absorption cross section of conductive particles (Al), magnetic particles (Fe<SUB>3</SUB>O<SUB>4</SUB>), and carbon nanotubes with different lengths. The particles were suspended in silicone oil and irradiated with a microwave at 2.45 GHz using a single-mode microwave reactor. The experimentally measured heating rate was analytically modeled based on the modified Lambert–Beer law to obtain the microwave absorption cross section per mass. The microwave-induced heating rate was primarily dependent on optical absorbance, which is proportional to the mass concentration of suspended particles. Under the similar optical absorbance, longer nanotubes provided greater microwave absorption cross section which could be described by the short dipole antenna theory. The microwave absorption cross section of 5 mm long multiwalled carbon nanotubes was ∼4080 times greater than that of Al particles. One-dimensional ultralong carbon nanotubes provide a unique opportunity as super microwave absorbers which may be useful in chemical, biomedical, and process applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-25/jp500831c/production/images/medium/jp-2014-00831c_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp500831c'>ACS Electronic Supporting Info</A></P>

Anomalously Large Reactivity of Single Graphene Layers and Edges toward Electron Transfer Chemistries

Sharma, Richa,Baik, Joon Hyun,Perera, Chrisantha J.,Strano, Michael S. American Chemical Society 2010 NANO LETTERS Vol.10 No.2

<P>The reactivity of graphene and its various multilayers toward electron transfer chemistries with 4-nitrobenzene diazonium tetrafluoroborate is probed by Raman spectroscopy after reaction on-chip. Single graphene sheets are found to be almost 10 times more reactive than bi- or multilayers of graphene according to the relative disorder (<I>D</I>) peak in the Raman spectrum examined before and after chemical reaction in water. A model whereby electron puddles that shift the Dirac point locally to values below the Fermi level is consistent with the reactivity difference. Because the chemistry at the graphene edge is important for controlling its electronic properties, particularly in ribbon form, we have developed a spectroscopic test to examine the relative reactivity of graphene edges versus the bulk. We show, for the first time, that the reactivity of edges is at least two times higher than the reactivity of the bulk single graphene sheet, as supported by electron transfer theory. These differences in electron transfer rates may be important for selecting and manipulating graphitic materials on-chip.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-2/nl902741x/production/images/medium/nl-2009-02741x_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl902741x'>ACS Electronic Supporting Info</A></P>