Three-dimensional shapes and structures of lamellar-twinned fcc nanoparticles using ADF STEM

Gontard, Lionel C.; Dunin-Borkowski, Rafal E.; Gass, Mhairi; Bleloch, Andrew; Özkaya, Doğan

doi:10.1093/jmicro/dfp003

Cited by 24 publications

(20 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Additionally, the SAED analysis also seems to indicate that the Au@Ag particle is a single crystal, even though faint forbidden spots and splitted spots ( Figure 2 b and 2 d) or a "grid-like" pattern containing streaks ( Figure 2 f and Figure S5c in the Supporting Information) are present in the diffraction patterns. The origin of all of these effects is likely due to the presence the lamellar twins, [29,30] which can be clearly identified at the boundaries of the particle oriented in the [110] zone axis ( Figure 2 e and Figure S5 in the Supporting Information), in the form of asymmetric contrast distributions. Besides, high-resolution TEM (HRTEM) analysis revealed (see Figure S5 in the Supporting Information) the twinning plane as {111} and the twinning axis as < 110 > .…”

mentioning

confidence: 99%

Rapid Epitaxial Growth of Ag on Au Nanoparticles: From Au Nanorods to Core–Shell Au@Ag Octahedrons

Sánchez‐Iglesias

Carbó‐Argibay

Glaria

et al. 2010

Chemistry A European J

View full text Add to dashboard Cite

The strongly shape-dependent optical properties of metal nanoparticles have motivated the rapid development of new and efficient strategies toward morphology control. [1][2][3] However, a highly efficient control over shape and size has been mainly achieved for gold. Therefore, an interesting route toward the production of other metal nanoparticles with tailored morphology would be the use of pre-formed gold nanocrystals as templates, on which other metals could be grown. This would allow not only a tight control over the growth, and morphology of the nanocrystals, but also an interesting enhancement of the functionality of such nanomaterials, [4][5][6][7][8] the properties of which would differ from those found in similar nanostructures made of the individual constituent metals. [4][5][6][7][8][9][10][11] In particular, various approaches have been developed to fabricate Au@Ag core-shell nanoparticles by the epitaxial growth of Ag on preformed Au nanoparticles, which were in general based on either chemical or photoinduced reduction processes. [5,9,10,12] The former often make use of a weak reducing agent, such as ascorbic acid or hydroxylamine, so that the reduction takes place exclusively on the surface of the metallic seed particles, which act as catalysts. [9,[13][14][15][16]34] However, this can only be achieved within a narrow pH range so that homogeneous nucleation of Ag nanoparticles in solution is avoided.Herein, we describe a simple and rapid method to grow silver on single-crystal Au nanorods, resulting in single-crystal core-shell Au@Ag nanoparticles with tailored morphology, ranging from nanorods all the way to spheres, through octahedrons, and thereby giving rise to a remarkable control over the optical response spanning the whole visible range and into the near IR.The growth method is based on the use of hydroquinone as reducing agent. Although the preparation of silver nanoparticles using hydroquinone has been previously reported, this typically resulted in a rather poor control over shape and size. [17,18] Additionally, hydroquinone has also been used to grow thin silver shells on gold nanoparticles as a means to amplify their scattering properties, but this was restricted to very thin shells on small spherical particles. [19,20] However, we demonstrate here that these processes can be utilized in a much more controlled manner, thus allowing exquisite morphology control. Based on our previous experience on the reshaping of single-crystal gold nanorods into octahedrons, [21] we decided to explore the coating of the same type of nanorods with silver, so as to tune the morphology of the resulting core-shell particles. Interestingly, we found that silver grows preferentially on the lateral facets of the Au nanorods, so that, indeed complete reshaping of the initial rods into Au@Ag octahedrons and even spheres was achieved, which might be related to the prior capping agent exchange from cetyltrimethylammonium bromide (CTAB) to methoxy-poly(ethylene glycol)-thiol (mPEG-SH). Detailed analysis of the op...

show abstract

mentioning

confidence: 99%

Rapid Epitaxial Growth of Ag on Au Nanoparticles: From Au Nanorods to Core–Shell Au@Ag Octahedrons

Sánchez‐Iglesias

Carbó‐Argibay

Glaria

et al. 2010

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Fig. 5a shows a BF TEM image acquired at 0°tilt of a powder of Vulcan XC-72R, a commercial carbon black that find applications in heterogeneous catalysis and that lacks long-range order [19,20,42]. For tomographic reconstruction, the intensities of the tilt series were inverted (I x,y -À I x,y ), as shown in Fig.…”

Section: Bf Tem Tomography: Improvement Of Resolutionmentioning

confidence: 99%

“…In transmission electron microscopy (TEM), usually 'single-axis tilting' is used, in which the specimen is tilted about the eucentric axis of the specimen holder rod. After accurate alignment of the tomographic tilt series, reconstruction, segmentation, and visualisation of the 3D volume or tomogram are the steps necessary to extract quantitative morphological information from the 3D tomograms [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Removing the effects of the “dark matter” in tomography

Gontard

2015

Ultramicroscopy

View full text Add to dashboard Cite

a b s t r a c tElectron tomography (ET) using different imaging modes has been progressively consolidating its position as a key tool in materials science. The fidelity of a tomographic reconstruction, or tomogram, is affected by several experimental factors. Most often, an unrealistic cloud of intensity that does not correspond to a real material phase of the specimen ("dark matter") blurs the tomograms and enhances artefacts arising from the missing wedge (MW). Here we show that by simple preprocessing of the background level of any tomographic tilt series, it is possible to minimise the negative effects of that "dark matter". Iterative reconstruction algorithms converge better, leading to tomograms with fewer streaking artefacts from the MW, more contrast, and increased accuracy. The conclusions are valid irrespective of the imaging mode used, and the methodology improves the segmentation and visualisation of tomograms of both crystalline and amorphous materials. We show examples of HAADF STEM and BF TEM tomography.

show abstract

“…We also study the formation of bimetallic PtPd particles on γ-Al 2 O 3 and use high-angle annular dark-field (HAADF) scanning TEM (STEM) (Gontard et al, 2008(Gontard et al, , 2009) to obtain threedimensional information about the porosity of the support after successive heat treatments.…”

Section: Introductionmentioning

confidence: 99%

Tomographic Heating Holder forIn SituTEM: Study of Pt/C and PtPd/Al₂O₃Catalysts as a Function of Temperature

et al. 2014

View full text Add to dashboard Cite

A tomographic heating holder for transmission electron microscopy that can be used to study supported catalysts at temperatures of up to~1,500°C is described. The specimen is placed in direct thermal contact with a tungsten filament that is oriented perpendicular to the axis of the holder without using a support film, allowing tomographic image acquisition at high specimen tilt angles with minimum optical shadowing. We use the holder to illustrate the evolution of the active phases of Pt nanoparticles on carbon black and PtPd nanoparticles on γ-alumina with temperature. Particle size distributions and changes in active surface area are quantified from tilt series of images acquired after subjecting the specimens to increasing temperatures. The porosity of the alumina support and the sintering mechanisms of the catalysts are shown to depend on distance from the heating filament.

show abstract

Three-dimensional shapes and structures of lamellar-twinned fcc nanoparticles using ADF STEM

Cited by 24 publications

References 40 publications

Rapid Epitaxial Growth of Ag on Au Nanoparticles: From Au Nanorods to Core–Shell Au@Ag Octahedrons

Rapid Epitaxial Growth of Ag on Au Nanoparticles: From Au Nanorods to Core–Shell Au@Ag Octahedrons

Removing the effects of the “dark matter” in tomography

Tomographic Heating Holder forIn SituTEM: Study of Pt/C and PtPd/Al₂O₃Catalysts as a Function of Temperature

Contact Info

Product

Resources

About

Three-dimensional shapes and structures of lamellar-twinned fcc nanoparticles using ADF STEM

Cited by 24 publications

References 40 publications

Rapid Epitaxial Growth of Ag on Au Nanoparticles: From Au Nanorods to Core–Shell Au@Ag Octahedrons

Rapid Epitaxial Growth of Ag on Au Nanoparticles: From Au Nanorods to Core–Shell Au@Ag Octahedrons

Removing the effects of the “dark matter” in tomography

Tomographic Heating Holder forIn SituTEM: Study of Pt/C and PtPd/Al2O3Catalysts as a Function of Temperature

Contact Info

Product

Resources

About

Tomographic Heating Holder forIn SituTEM: Study of Pt/C and PtPd/Al₂O₃Catalysts as a Function of Temperature