Structural and morphological peculiarities of hybrid Au/nanodiamond engineered nanostructures.

Roberto Matassa,Maria Cristina Cassani,Maria Letizia Terranova,Silvia Orlanducci,Giacomo Reina,Daniele Passeri,Marco Rossi

doi:10.1038/srep31163

Abstract

Nanostructured Au nano-platelets have been synthesized from an Au(III) complex by growth process triggered by nanodiamond (ND). An electroless synthetic route has been used to obtain 2D Au/ND architectures, where individual nanodiamond particles are intimately embedded into face-centered cubic Au platelets. The combined use of high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED), was able to reveal the unusual organization of these hybrid nanoparticles, ascertaining the existence of preferential crystallographic orientations for both nanocrystalline species and highlighting their mutual locations. Detailed information on the sample microstructure have been gathered by fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) of HR-TEM images, allowing us to figure out the role of Au defects, able to anchor ND crystallites and to provide specific sites for heteroepitaxial Au growth. Aggregates constituted by coupled ND and Au, represent interesting systems conjugating the best optoelectronics and plasmonics properties of the two different materials. In order to promote realistically the applications of such outstanding Au/ND materials, the cooperative mechanisms at the basis of material synthesis and their influence on the details of the hybrid nanostructures have to be deeply understood.

Highlights

Nowadays, hybrid nanocrystalline particles, at the basis of many advanced materials for frontier applications in several technological fields ranging from optoelectronics to nanocatalysis and to biomedicine, receive an increasing attention owing to their outstanding properties[1,2]
A full spectral analysis comprises the following components: a band positioned at 1520 cm−1 ascribed to G-bands of disordered sp[2] carbon species, the bands at 1180 and 1410 cm−1 attributed to transpolyacetilene forms[40] and spectral features at 1630 cm−1 assigned to surface OH groups[41], produced at the surface of detonation ND by the purification and dispersion process[42,43]
The lowering of the signal at 1630 cm−1 can be assigned to the OH groups, while the emergence of a band at 1070 cm−1 can be assigned to the stretching of the C-O bond

Summary

Results and Discussion

A preliminary morphological and structural analysis was carried out on the ND powder to assess nanoscale features before the reaction with Au, and in particular, to verify the efficiency of the adopted protocol in removing graphitic-carbon impurities and promoting the formation of hydroxyl (alcoholic and/or enolic) groups at the surface which represent the sites for Au+3 reduction. In order to highlight the nanodiamond structure, the contribution of the Au crystal to the FFT has been subtracted before performing the inverse FFT (IFFT), recovering so the image in the real space This procedure evidences the presence of two separate nanodiamond crystallites (Fig. 4e), having a structures with the same crystalline features already observed in region I (see Fig. 4b). Besides the hexagonal FFT pattern of the Au crystallite, two external spots belonging to a single ND crystallite (d = 0.126 nm, white arrows), and again we have two inner extra spots (denoted by yellows arrows) with interplanar distance d = 0.236 nm, that we estimated to be slightly larger than the highest one of standard Au. The IFFT performed on region IV (Fig. 5g) shows irregular lattice fringes overlapping the regular one. It is interesting to notice that nanodiamonds entrapped into the Au nanoplatelets or attached to the surface show the same crystallographic orientation corresponding to a [001] zone axis (Fig. 4g,h)

Conclusions

Author Contributions

Additional Information