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In-situ TEM Probing of Nanomaterials
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.ORCID iD: 0000-0001-9137-3440
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanomaterials because of their small size, may have special properties unlikely to be seen in ordinary types of materials. Nanomaterials like nanotubes,nanowires and nanoparticles are best studied at the nanoscale, vital but also problematic. In this thesis we use a transmission electron microscope (TEM)combined with a scanning tunneling microscope probe. This system allows TEM images to be captured and recorded into a movie together with recordedelectrical data for real time analysis. Using this method we found that the electrical conductivity of molybdenumbased nanowires Mo6S3I6 can be improved by current induced transformation. This might be a general method of improving nanowires which is of high valueif the wires are to be used in electrical circuits or field emission devices. The bending modulus for these nanowires were also determined, by an electromechanical resonance method, to 4.9 GPa. The sintering phase of silver nanoparticles, used in electrical conductive ink for printing electrical circuits, were studied by the in-situ TEM probing method. We observed that percolation path ways are formed and that the dispersive agent of the particles can be pyrolysed into a net of carbon with characteristics similar to graphite. We also developed a method for decorating nanowires and nanotubes with gold nanoparticles. Nanowire particle composites are often used in assembling more complex devices (electronic circuits) or for linking to organic molecules (biosensor applications) and existing particle decoration methods are either difficult or with low yield. By in situ TEM probing we found that carbon nanocages can be grown onto these gold nanoparticles. The size of the gold nanoparticles is controllable an thus the size of the nanocages. These nanocages may be used in medicine- or hydrogen storage-applications.

Abstract [sv]

Nanomaterial har givits stort intresse under det senaste årtiondet, detta på grund av deras unika egenskaper som gör att de i många hänseenden överträffar traditionella material. Egenskaperna beror till största del på storlek och därför är det nödvändigt att studera dessa material på nanonivå, något som är problematiskt. För sådana studier krävs ett instrument med tillräckligt hög upplösning på nanonivå samt ett system med en prob som möjligör selektion och karakterisering utav individuella byggstenar. I denna avhandling används ett transmissionselektronmikroskop (TEM) tillsammans med ett sveptunnelmikroskop (STM) där det senare används som prob. Systemet medger studier på nanonivå och karakterisering av enskilda byggstenar under realtids avbildning (in situ). Metoden medger en bättre överblick och hanterbarhet vid nanomanipulering än vad till exempel atomkraftmikroskopi medger. Piezodrivna probar kan även användas i svepelektronmikroskop men dessa medger inte samma upplösning som transmissionselektronmikroskopet. Nanotrådar av Mo6S3I6 är ett alternativt material till kolnanorör och överträffar dessa i form av löslighet i båda organiska såväl som polära lösningsmedel. De är enkla att syntetisera men deras elektriska konduktivitet är låg. Mo6S3I6 nanotrådar studerades med in situ TEM probing. Vi fann att genom att driva en tillräckligt hög elektrisk ström genom nanotråden så resulterade detta i en omvandling till en solid metallisk molybden nanotråd med en konduktivitet nära värdet för bulkmaterialet. Resultat är intressant då nanotrådar kan användas i t.ex. fältemission, men resultatet visar också på att det kan vara en generell metod för att förbättra nanotrådar överlag. På dessa nanotrådar har även en elektromekanisk resonans studie utförts där böjmodulen för materialet bestämdes till 4.9 GPa. Med in situ-TEM-probing metoden har även silvernanobläck studerats under en sintringsprocess. Studien visade att vid sintringen så bildas perkulativa vägar genom bläckets silvernanopartiklar samt att vid hög sinteringstemperatur förkolnades det lösningsmedel som silvernanopartiklarna är lösta i. Förkolningen av lösningsmedlet resulterade i ett kolnät med liknande egenskaper som för grafit. Förståelse utav sinteringsprocessen är nödvändig eftersom vid tryckning av elektriskt ledande banor på papper används sintring för att höja ledningsförmågan. Genom att växa nanopartiklar på nanotrådar förändras deras egenskaper och tillämpningar. Existerande metoder är endera komplicerade eller ger dåligt ut- byte. Ett enkelt recept för att växa guldnanopartiklar på kolnanorör och Mo6S3I6 nanotrådar har därför tagits fram. Dessa kolnanorör och nanotrådar har sedan studerats med in-situ-TEM-probing metoden som visade att utanpå dessa guldnanopartiklar kan burar av kol skapas. Eftersom partiklarnas storlek kan kontrolleras kan även kolnanoburarnas storlek kontrolleras. Burarna har användningsområden t.ex. inom medicin och vid lagring av vätgas.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2009. , 76 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 69
Keyword [en]
nanotechnology, in situ, TEM, probing, nanowires, nanoparticles, ink
National Category
Other Engineering and Technologies not elsewhere specified Other Engineering and Technologies not elsewhere specified Condensed Matter Physics
Identifiers
URN: urn:nbn:se:miun:diva-8998ISBN: 978-91-86073-34-3 (print)OAI: oai:DiVA.org:miun-8998DiVA: diva2:219550
Public defence
2009-06-05, O102, Holmgatan 10, Sundsvall, 13:15 (English)
Opponent
Supervisors
Note
The thesis covers six scientific papersAvailable from: 2009-06-03 Created: 2009-05-27 Last updated: 2010-02-25Bibliographically approved
List of papers
1. Nanowire Transformation and Annealing by Joule Heating
Open this publication in new window or tab >>Nanowire Transformation and Annealing by Joule Heating
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2010 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 16, 165704-165704 p.Article in journal (Refereed) Published
Abstract [en]

Joule heating of bundles of Mo6S3I6 nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo6S3I6 into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m(-1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

Keyword
GRAIN-GROWTH; MO6S3I6 NANOWIRES; TEM-STM; KINETICS; METALS; WIRES; SIZE
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-9049 (URN)10.1088/0957-4484/21/16/165704 (DOI)000276111200023 ()20351407 (PubMedID)2-s2.0-77950486292 (Scopus ID)
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2013-08-23Bibliographically approved
2. Bending Modulus of Mo6S3I6 Nanowires Studied by Electromechanical Resonances
Open this publication in new window or tab >>Bending Modulus of Mo6S3I6 Nanowires Studied by Electromechanical Resonances
(English)Manuscript (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-9050 (URN)
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2013-08-23Bibliographically approved
3. Electrical Sintering of Silver Nanoparticle Ink Studied by In-Situ TEM Probing
Open this publication in new window or tab >>Electrical Sintering of Silver Nanoparticle Ink Studied by In-Situ TEM Probing
2011 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 2, Art. no. e17209- p.Article in journal (Refereed) Published
Abstract [en]

Metallic nanoparticle inks are used for printed electronics, but to reach acceptable conductivity the structures need to be sintered, usually using a furnace. Recently, sintering by direct resistive heating has been demonstrated. For a microscopic understanding of this Joule heating sintering method, we studied the entire process in real time inside a transmission electron microscope equipped with a movable electrical probe. We found an onset of Joule heating induced sintering and coalescence of nanoparticles at power levels of 0.1-10 mW/mu m(3). In addition, a carbonization of the organic shells that stabilize the nanoparticles were found, with a conductivity of 4 10(5) Sm-1

Keyword
GOLD NANOPARTICLES; METAL NANOPARTICLES; ROOM-TEMPERATURE; COALESCENCE; FABRICATION; MICROSCOPE; PARTICLES; NANOWIRES; SUBSTRATE; TRACKS
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-9051 (URN)10.1371/journal.pone.0017209 (DOI)000287761700035 ()2-s2.0-79952095106 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2016-10-26Bibliographically approved
4. Simple and efficient gold nanoparticles deposition on carbon nanotubes with controllable particle sizes
Open this publication in new window or tab >>Simple and efficient gold nanoparticles deposition on carbon nanotubes with controllable particle sizes
2009 (English)In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 158, no 1-3, 48-52 p.Article in journal (Refereed) Published
Abstract [en]

There are important applications of multiwalled carbon nanotubes (MWCNT) with deposited nanoparticles and several methods exist for synthesizing these nanocomposites. However, a simpler and more efficient method is desired in many cases. Here, we introduce a method where MWCNT were pre-mixed with sodium citrate, and using ultrasonication, shells of sodium citrate were formed on the nanotubes. These functionalized MWCNTs served as substrates for gold nanoparticle growth. When HAuCl4 was added to the reaction system, Au3+ was directly reduced at the surface of the MWCNT and gold nanoparticles were assembled along the MWCNT. Transmission electron microscopy (TEM) demonstrated that the density of the gold nanoparticle coating process depended on the amount of the carbon nanotubes when the sodium citrate concentration was keep unchanged. In addition, by controlling the concentration of sodium citrate and HAuCl4, the size of gold nanoparticles could be controlled. Scanning electron microscope (SEM), energy dispersive X-ray (EDX), and UV–vis were also used to characterize the MWCNT–Au nanocomposites. Compared with other methods, the procedure described here required only water solutions and there are no needs for high temperature steps, surfactants or organic solvents, resulting in a simple and fast method for efficient gold nanoparticle decoration of carbon nanotubes.

National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-8786 (URN)10.1016/j.mseb.2008.12.038 (DOI)000265051500009 ()2-s2.0-61649088793 (Scopus ID)
Available from: 2009-04-15 Created: 2009-04-15 Last updated: 2016-09-26Bibliographically approved
5. Carbon nanocages grown by gold templating
Open this publication in new window or tab >>Carbon nanocages grown by gold templating
2010 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 48, no 2, 424-430 p.Article in journal (Refereed) Published
Abstract [en]

A method for growing carbon cages using gold nanoparticles as templates is reported. Gold nanoparticles were deposited on carbon nanotubes (CNTs). The nanocages were grown on the gold particles by electrical Joule heating of the CNT. The gold was subsequently evaporated, leaving the cages intact. A special in-situ TEM-holder equipped with a small scanning tunneling microscope was used as an electrical probe to drive current through the CNT, while the TEM was used for imaging of the entire growth process. The method might provide a general way for making carbon structures limited only by the shapes allowed by the fabrication methods of the gold nanostructures.

National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-9052 (URN)10.1016/j.carbon.2009.09.056 (DOI)000272764300014 ()2-s2.0-70449527722 (Scopus ID)
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2013-08-23Bibliographically approved
6. Mo6S3I6-Au composites: Synthesis, Conductance, and Applications
Open this publication in new window or tab >>Mo6S3I6-Au composites: Synthesis, Conductance, and Applications
Show others...
2010 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 348, no 2, 299-302 p.Article in journal (Refereed) Published
Abstract [en]

A single-step, premixing method was used to directly deposit gold nanoparticles on Mo6S3I6 (MSI) molecular wire bundles. Gold nanoparticles with different sizes and densities were coated on the MSI by changing the concentration of the gold containing salt, HAuCl4. TEM, SEM, and EDX characterization showed deposition of gold nanoparticles on the MSI nanowire surface. The electrical resistance of these MSI-Au composites was more than 100 times lower than that for pure MSI, and was mainly dependent on the density of the deposited gold nanoparticles. Furthermore, we immobilized thiol group-labeled oligonucleotide on the composites and then hybridized with a fully matched sequence. The resistance of the MSI-Au composites increased during the thiol step, while it decreased by hybridizing, due to the conductance difference between single- and double-stranded DNA chains. These results indicate that this new kind of MSI-Au composite could be used as a platform for different applications, including biosensors.

Keyword
DNA sensing; Gold nanoparticles; Mo6S3I6 nanowire; Nanocomposites; Synthesis
National Category
Computer Science
Identifiers
urn:nbn:se:miun:diva-9054 (URN)10.1016/j.jcis.2010.04.047 (DOI)000279968700001 ()20494366 (PubMedID)2-s2.0-77953916258 (Scopus ID)
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2016-09-22Bibliographically approved

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