Transformation of Freestanding Carbon-Containing Gold Nanosheets into Au Nanoparticles Encapsulated within Amorphous Carbon: Implications for Surface Modification of Complex-Shaped Materials and Structures

Abstract

Freestanding metallic nanosheets (or 2D metals) have been attracting tremendous research interest because of their potential applications in numerous important fields, such as green energy, biomedical imaging, and nanodevices. However, thermal stability of 2D metals received much less attention and remains as an open issue to resolve. Here, we report the first synthesis of large-area freestanding carbon-containing gold nanosheets by polymer surface buckling-enabled exfoliation (PSBEE). Through a systematic study based on flash differential scanning calorimetry, we find that such 2D nanosheets tend to fragment upon heating, which are eventually transformed into nanoparticles of different sizes. Inspired by this interesting finding, we develop a facile method that enables scalable production of crystalline Au nanoparticles encapsulated with amorphous C by isothermally annealing the carbon-containing gold nanosheets. Compared to the traditional methods for the synthesis and deployment of nanoparticles, our nanosheet-based fabrication method is flexible and highly efficient, which can simultaneously synthesize and deploy nanoparticles on different materials regardless of their surface topologies, therefore appealing to various surface-related applications, especially the surface modification of complex-shaped electrodes and biosensors.

Strong, Ductile, and Tough Nanocrystal-Assembled Freestanding Gold Nanosheets

“…Figure b shows the transmission electron microscopy (TEM) image of an 18 nm thick gold nanosheet, which clearly reveals clustering of individual gold NPs within amorphous carbon (Figure c–e). The presence of amorphous carbon was due to the carbonization of the hydrogel during ion beam sputtering and subsequent metal film exfoliation, as confirmed by the Raman spectrum of the gold nanosheets (Figure g). As the thickness ( t Au ) of the gold nanosheets increases, we note that the atomic ratio of carbon to gold decreases from ∼4.5:1 for t Au = 11 nm to ∼1:5 for t Au = 100 nm (Figure S2g).…”

“…Following the method we recently developed, − we fabricated gold nanosheets with an aspect ratio as large as 10 6 (see the Methods in the Supporting Information and Supplementary Movies 1 and 2), which had thicknesses ranging from 11 to 100 nm (Figure S1). According to X-ray diffraction (XRD) and selected-area electron diffraction, the gold nanosheets exhibit face-centered cubic (FCC) symmetry (Figure S2).…”

In Situ Monitoring of Scale Effects on Phase Selection and Plasmonic Shifts during the Growth of AgCu Alloy Nanostructures for Anticounterfeiting Applications

“…The kinetics of the formation of single-component clusters on surfaces and their physical properties has extensively been investigated, both by theory and experiments. ,− Besides such single-component clusters, presently alloys or multicomponent-supported clusters receive increasing attention. Prominent supported cluster synthesis methods include chemical methods and vacuum deposition. − Hence, already much effort has been undertaken to synthesize such multicomponent and metallic clusters using different methods such as pyrolysis, sol–gel synthesis, templating, aggregation sources, , and sputter deposition. ,, The nucleation and growth of silver and copper clusters during magnetron sputtering was observed very successfully by X-ray scattering. , Applications of supported clusters range from heterogeneous catalysis and photocatalysis to information technology and solar cells as well as anticounterfeiting. − Here, nanoscale heterostructures and alloying allow for the facile tuning of chemical and optoelectronic properties. , Sputter deposition allows for alloying and high cluster density layers, enabling, for example, an organic shell-free cluster incorporated in layer-by-layer printing processes …”

“…10,15−18 Besides such single-component clusters, presently alloys or multicomponent-supported clusters receive increasing attention. Prominent supported cluster synthesis methods include chemical methods 19 and vacuum deposition. 20−22 Hence, already much effort has been undertaken to synthesize such multicomponent and metallic clusters using different methods such as pyrolysis, 23 sol−gel synthesis, 24 templating, 25 aggregation sources, 26,27 and sputter deposition.…”

Polymer-Based Fabrication of 2D Metallic and Ceramic Nanomaterials

“…19 Furthermore, we can also synthesize 0D nanomaterials (e.g., nanoparticles) through thermal annealing of 2D and 1D nanomaterials in ambient conditions. 20 In this Account, we aim to delve into the fundamental aspects of PSBEE, provide an overview of the structural and functional properties exhibited by 2D nanomaterials fabricated by this method, and discuss the potential applications of these materials. By examining these key aspects, we hope to shed light on the immense potential of PSBEE as a versatile fabrication technique and highlight the exciting opportunities it presents for advancing the field of nanomaterials.…”