Synthesis of Platinum Cubes, Polypods, Cuboctahedrons, and Raspberries Assisted by Cobalt Nanocrystals

Abstract

The introduction of metallic traces into the synthesis of platinum nanocrystals (Pt NCs) has been investigated as a surfactant-independent means of controlling shape. Various nanocrystal morphologies have been produced without modification of the reaction conditions, composition, and concentration other than the presence of cobalt traces (<5%). In the presence of metallic cobalt (a strong reducer for Pt cations) cubic Pt NCs are obtained, while cobalt ions or gold NCs have no effect on the synthesis, and as a result, polypods are obtained. Intermediate shapes such as cemented cubes or cuboctahedron NCs are also obtained under similar conditions. Thus, various NC shapes can be obtained with subtle changes, which illustrates the high susceptibility and mutability of the NC shape to modification of the reaction kinetics during the early reduction process. Our studies help progress toward a general mechanism for nanocrystal shape control.

Small Adsorbate‐Assisted Shape Control of Pd and Pt Nanocrystals

“…Pt nanocubes were also prepared in the presence of trace Co 2 (CO) 8 . [84] No formation of Pt nanocubes was observed when Co 2 (CO) 8 was replaced by other Co sources. Although the zero-valent metal in the metal carbonyls was considered to play an essential role in the synthesis, possible role of CO decomposed from the carbonyls during the reaction was entirely ignored.…”

Understanding of the major reactions in solution synthesis of functional nanomaterials

“…Without going through a zero-valent state, the precursor compounds can be directly convered into dimers and trimers. Reduction Single-crystals Perfect/truncated cube Pd [208,240], Ag [43,64,241], Au [242,243], Pt [244,245], Cu [246], Rh [247], Fe [248] Concave cube Pd [219] Perfect/truncated octahedron Pd [193,194], Ag [43,64], Au [242,243], Pt [244,245] Perfect/truncated tetrahedron Ag [241],Au [243,249], Pt [45,244] Rectangular bar Pd [186] Multipods Au [250], Pt [244,245,251], Rh [247] Singly twinned Right bipyramid Pd [252], Ag [253] Multiply twinned Decahedron Pd [193], Ag [254], Au [243,249] Icosahedrons Pd [193], Au [249] Five-fold twinned pentagonal rod/wire Pd [255], Ag [256], Au [257], Cu [255] Triangular/hexagonal plate Pd …”

Exploring New Synthetic Strategies for the Production of Advanced Complex Inorganic Nanocrystals

“…This implies both, high difficulty in reproducibility and extreme versatility in morphology, which is translated into the fact that minute modifications of the original recipes leads to very different NC's morphologies and therefore properties [86,87]. Since then, the kinetic control of the synthesis of NCs has been evolving and developing, leading to more and more complex and artificial nanostructures.…”

“…Due to their high surface-to-volume ratio NCs are especially reactive and by its dissolution one may provide electrons and ions suitable for the synthesis of secondary NCs in a suitable form. The strategy, similar to the use of sacrificial templates for the synthesis of hollow NCs, contains sophisticated differences such as the introduction of metallic traces in the form of Co NCs (used as electron and ion providers) into the synthesis of Pt NCs as an effective surfactant-independent mean of controlling Pt shapes [86,87,108]. It also illustrates the high susceptibility and mutability of the NC's shape to modification of the reaction kinetics during the early reduction process, and help progress toward a general mechanism for NC's shape control.…”

“…By the use of different reducers at substoichiometric concentrations the nucleation and growth, and therefore the number and size of NCs in the reaction vessel, can be adjusted providing effective means for the control of the reaction kinetics [108]. Recently reported examples are the production of citrate-stabilized Ag NCs by the combined use of sodium citrate and tannic acid [91] and Au NRs through the use of salicylic acid and ascorbic acid [109].…”