Figure 1
a) Digital photographs of the AuCl4
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(aq) solution and aqueous suspensions containing Au NPs 15 ± 2.2, 26 ± 2.4, and 34 ± 3.0 nm in diameter (shown from left to right, respectively). b) UV-VIS extinction spectra recorded for the AuCl4
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(aq) solution and aqueous suspensions containing Au NPs 15 ± 2.2, 26 ± 2.4, and 34 ± 3.0 nm in diameter (blue, black, red, and green traces, respectively). Adapted with permission from ref. (da Silva et al. 2014) Copyright 2014 Scielo Brazil.
Figure 2
Maximum current densities for formic acid oxidation employing Pd nanocrystals displaying controlled shapes as electrocatalysts. Adapted with permission from ref.(Jin et al. 2012JIN M, ZHANG H, XIE Z AND XIA Y. 2012. Palladium nanocrystals enclosed by {100} and {111} facets in controlled proportions and their catalytic activities for formic acid oxidation. Energy Environ Sci 5: 6352-6357.) Copyright 2012 Royal Society of Chemistry.
Figure 3
Atomic arrangements and surface energy values for {100}, {110}, and {111} surface facets (from left to right, respectively).
Figure 4
Top-down and bottom-up approaches for producing controlled nanomaterials.
Figure 5
Different shapes that have been enabled for a range of metals nanocrystals by solution- phase synthesis.
Figure 6
Variations in the atomic concentration of growth species in solution as a function of time during the generation of atoms, nucleation, and growth stages. Adapted with permission from ref (Xia et al. 2009XIA Y, XIONG Y, LIM B AND SKRABALAK SE. 2009. Shape-Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics? Angew Chem Int Ed 48: 60-103.) Copyright 2009 Wiley-VCH.
Figure 7
Main stages of controlled synthesis of metal nanomaterials with face-centered cubic (fcc) structure: (i) nucleation (in the center); (ii) growth of nuclei into seeds (in the middle ring); and (iii) evolution of the seeds into the final nanocrystal (in the outer ring). The shape assumed by the nanocrystal depends on the structure of its corresponding seed and the relative binding affinities of capping agents to its distinct surface facets. The red lines indicate the twin defects or stacking faults in a seed or nanocrystal while the yellow, green and purple colors correspond to the {111}, {100}, and {110} facets, respectively. When there is a change in the background color, symmetry breaking is involved during the growth. Adapted with permission from ref (Gilroy et al. 2017GILROY KD, PENG HC, YANG X, RUDITSKIY A AND XIA Y. 2017. Symmetry breaking during nanocrystal growth. Chem Commun 53: 4530-4541.) Copyright 2017 Royal Society of Chemistry.
Figure 8
Thermodynamic and kinetic approaches to controlling the internal structure of seeds. a) Phase diagram of Au seeds as a function of temperature and nanoparticle size; b) Population of Pd nanocrystals as a function of the initial reduction rate, displaying plates with stacking faults (orange), multiply twinned icosahedra (purple), and single-crystal cuboctahedra (blue). Adapted with permission from refs (Barnard et al. 2009, Wang et al. 2015WANG Y, PENG HC, LIU J, HUANG CZ AND XIA Y. 2015. Use of Reduction Rate as a Quantitative Knob for Controlling the Twin Structure and Shape of Palladium Nanocrystals. Nano Lett 15: 1445-1450.) Copyright 2009 and 2015 American Chemical Society, respectively.
Figure 9
a-i) SEM and TEM images for a variety of shapes that have been successfully reported by the solution phase synthesis. a) spheres; b) cubes; c) tetrahedrons; d) hexagonal plates; e) wires; f) octahedra; g) triangular plates; h) rods and, i) truncated cubes. Adapted with permission from: a, c and i) ref. (Wiley et al. 2007WILEY B, SUN Y AND XIA Y. 2007. Synthesis of silver nanostructures with controlled shapes and properties. Acc Chem Res 40: 1067-1076.) Copyright 2007 American Chemical Society, b) ref. (Zhang et al. 2010ZHANG Q, LI W, MORAN C, ZENG J, CHEN J, WEN LP AND XIA Y. 2010. Seed-Mediated Synthesis of Ag Nanocubes with Controllable Edge Lengths in the Range of 30−200 nm and Comparison of Their Optical Properties. J Am Chem Soc 132: 11372-11378.) Copyright 2010 American Chemical Society; d) ref. (Wiley et al. 2007) Copyright 2007 American Chemical Society; e) ref.(Rodrigues et al. 2017RODRIGUES TS, DA SILVA AGM, DE MOURA ABL, GEONMONOND RS AND CAMARGO PHC. 2017. AgAu Nanotubes: Investigating the Effect of Surface Morphologies and Optical Properties over Applications in Catalysis and Photocatalysis. J Braz Chem Soc 28: 1630-1638. ) Copyright 2017 Scielo Brazil; f) ref. (Lohse et al. 2014LOHSE SE, BURROWS ND, SCARABELLI L, LIZ-MARZÁN LM AND MURPHY CJ. 2014. Anisotropic Noble Metal Nanocrystal Growth: The Role of Halides. Chem Mater 26: 34-43.) Copyright 2014 American Chemical Society; (G) ref. (Chen et al. 2014CHEN L, JI F, XU Y, HE L, MI Y, BAO F, SUN B, ZHANG X AND ZHANG Q. 2014. High-Yield Seedless Synthesis of Triangular Gold Nanoplates through Oxidative Etching. Nano Lett 14: 7201-7206.) Copyright 2014 American Chemical Society, and h) ref. (Nikoobakht and El-Sayed 2003NIKOOBAKHT B AND EL-SAYED MA. 2003. Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method. Chem Mater 15: 1957-1962.) Copyright 2003 American Chemical Society.
Figure 10
Schematic illustration of the morphological and structural changes at different stages of the galvanic replacement reaction between a Ag nanoparticle and HAuCl4 in an aqueous solution. Adapted with permission from ref. (Xia et al. 2013XIA X, WANG Y, RUDITSKIY A AND XIA Y. 2013. 25th Anniversary Article: Galvanic Replacement: A Simple and Versatile Route to Hollow Nanostructures with Tunable and Well-Controlled Properties. Adv Mater 25: 6313-6333.) Copyright 2013 Wiley-VCH.
Figure 11
a-d) TEM images of a) AgPd bimetallic nanoshells, b) AgAu nanoboxes, c) AgAu triangular nanoframes, and d) SEM image of AgAu pentagonal nanotubes. Adapted with permission from: a) ref. (Rodrigues et al. 2015RODRIGUES T, DA SILVA AM, MACEDO A, FARINI B, ALVES R AND CAMARGO PC. 2015. Probing the catalytic activity of bimetallic versus trimetallic nanoshells. J Mater Sci 50: 5620-5629.) Copyright 2015 Springer Publishing Company, b) ref. (Lu et al. 2007LU X, AU L, MCLELLAN J, LI Z-Y, MARQUEZ M AND XIA Y. 2007. Fabrication of Cubic Nanocages and Nanoframes by Dealloying Au/Ag Alloy Nanoboxes with an Aqueous Etchant Based on Fe(NO3)3 or NH4OH. Nano Lett 7: 1764-1769.) Copyright 2007 American Chemical Society; c) ref. (Métraux et al. 2003MÉTRAUX GS, CAO YC, RONGCHAO JIN AND MIRKIN CA. 2003. Triangular Nanoframes Made of Gold and Silver. Nano Lett 3: 519-522.) Copyright 2013 American Chemical Society. d) ref. (Rodrigues et al. 2017) Copyright 2017 Scielo Brazil.
Figure 12
TEM images of Au nanospheres with a) 15, b) 26 and c) 34 nm, respectively. d) Plot of ln(C/C0) and e) UV-Vis spectra recorded as a function of time at room temperature for Au nanospheres with 34 nm in diameter. f) Calculated TOFs as a function of time for the 15, 26 and 34 nm Au nanospheres (red, black and blue traces, respectively). Adapted with permission from ref. (da Silva et al. 2014) Copyright 2014 Scielo Brazil.
Figure 13
SEM images of a) Au octahedra, b) Au nanocubes, and c) Au rhombic dodecahedra. Scale bars are equal to 100 nm. d) Time-dependent UV-vis absorption spectra for the borohydride reduction of 4-aminophenol (4-NA) at 25 °C and e) ln(4-NA) versus time plots using gold nanocubes, octahedra, and rhombic dodecahedra as catalysts (green, red and black points, respectively). Adapted with permission from ref. (Chiu et al. 2012CHIU CY, CHUNG PJ, LAO KU, LIAO CW AND HUANG MH. 2012. Facet-Dependent Catalytic Activity of Gold Nanocubes, Octahedra, and Rhombic Dodecahedra toward 4-Nitroaniline Reduction. J Phys Chem C 116: 23757-23763.) Copyright 2012 American Chemical Society.
Figure 14
a-c) SEM images of TiO2-Au colloidal spheres that were obtained after the first a), second b), and third c) reduction steps employing 3 mL of 1 mM AuCl4
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(aq) as the precursor solution. The scale bars in the insets correspond to 100 nm. d) UV-vis extinction spectra recorded for the TiO2 (black trace) and TiO2-Au (red, blue ang green traces correspond to samples showed in a, b, and c, respectively). The inset depicts a photograph of TiO2, and samples a, b and c, aqueous suspensions (from left to right, respectively). Adapted with permission from ref. (Damato et al. 2013DAMATO TC, DE OLIVEIRA CCS, ANDO RA AND CAMARGO PHC. 2013. A Facile Approach to TiO2 Colloidal Spheres Decorated with Au Nanoparticles Displaying Well-Defined Sizes and Uniform Dispersion. Langmuir 29: 1642-1649.) Copyright 2013 American Chemical Society.
Figure 15
a) Strategy for the synthesis of MnO2 nanowires decorated with ultrasmall Au NPs. b-e) HRTEM images of MnO2-Au NPs depicting the ultrasmall and monodisperse Au NPs size as well as their uniform distribution over the MnO2 surface. The lattice fringe orientations in the phase-contrast HRTEM images (d and e) show that both the MnO2 nanowires and Au NPs were single crystalline. Adapted with permission from ref. (da Silva et al. 2016) Copyright 2016 Elsevier.
Figure 16
SEM images of AgAu nanodendrites with controlled surface morphologies supported on commercial SiO2 (AgAu/SiO2) by wet impregnation. The average sizes of the AgAu nanodendrites corresponded to: (a and b) 148 ± 6 nm, (c and d) 96 ± 5 nm, (e and f) 66 ± 4 nm, and (g and h) 45 ± 3 nm. Adapted with permission from ref. (da Silva et al. 2015a) Copyright 2015 American Chemical Society.
Figure 17
Main mechanisms involved in plasmonic catalysis: a) photo-induced temperature increase provides heat to an adjacent reactant; b) the enhancement of the optical near field at the vicinity of the NP increases the photon rate seen by an adjacent reactant; c) a photoinduced hot electron is transferred to a nearby reactant; d) the electron-hole (e−-h+) generation rate in a photocatalyst is enhanced by heat generated by the NP; e) the electron-hole generation rate in a photocatalyst is enhanced by the strong optical near-field of the plasmonic NP; and f) the photocatalyst adjacent to the NP is activated by hot electron transfer from the plasmonic NP. Adapted with permission from ref. (Baffou and Quidant 2014BAFFOU G AND QUIDANT R. 2014. Nanoplasmonics for chemistry. Chem Soc Rev 43: 3898-3907.) Copyright 2014 Royal Society of Chemistry.
Figure 18
a) Scheme showing the SPR-mediated oxidation of PATP to DMAB by 3O2 employing AgAu nanoparticles as catalysts; b) UV-Vis extinction spectra and c) SPR peak positions as a function of the Au content (Au mole fraction) in the AgAu nanoparticles; d) SERS spectra as a function of composition (Au mole fraction) employing Ag, AgAu and Au nanoparticles functionalized with PATP; e) Obtained DMAB/PATP 1433/1593 cm-1 intensity ratios as a function of the Au content in the nanoparticles. Adapted with permission from ref. (Wang et al. 2014WANG JL, ANDO RA AND CAMARGO PHC. 2014. Investigating the plasmon-mediated catalytic activity of agau nanoparticles as a function of composition: Are two metals better than one? ACS Catalysis 4: 3815-3819.) Copyright 2014 American Chemical Society.
