In this contribution, we outline the efficiency of shape-controlled electroless silver plating for the realization of functional nanomaterials. First, we demonstrate the simplicity and flexibility of the technique, followed by a discussion of strategies for application-oriented synthesis optimization. We then show how the obtained materials can be derivatized to introduce new functionalities.
By adding an iron-tartrate complex to a silver plating bath, we achieve selective two-dimensional growth without templates. Using this reaction, homogeneous films of high aspect ratio silver nanoplatelets can be deposited on various substrate materials in a short time. Moreover, recessed and curved substrates can be coated, such as the interior of glass microcapillaries (Fig. 1 a, b). Also, the nucleation behavior of the reaction can be tuned: Homogeneous nucleation and bath decomposition can be either enforced to obtain powders of sand-rose shaped silver particles (Fig. 1 c), which can be used to formulate catalyst inks or composites, or suppressed to achieve selective heterogeneous deposition of platelet films.
When sufficiently developed, the films possess continuous conduction paths. Together with the large, easily accessible and well-defined surface of the platelets, this renders them particularly interesting for electrochemical applications. The films can be used as supporting, nanostructured electrodes, or employed directly as electrocatalyst. As an example for the latter case, we used different silver structures for amperometric detection of hydrogen peroxide, in which a strong, selective and fast response to the analyte could be achieved. The sensitivity of the silver catalyst could be enhanced by tuning the deposit morphology, such as in the case of porous platelets of high aspect ratio and surface area (Fig. 1 d).
Electrolessly plated nanomaterials can be conveniently derivatized  using reactions such as thermal oxidation, galvanic replacement or chemical bath deposition. Several modification options for the silver nanoplatelet films will be presented. For example, by using the silver structures as substrate for subsequent cuprite plating, they can be decorated with Cu2O nanoparticles (Fig. 1 e, f).
Due to the wide functionality range of silver nanostructures and the shape-sensitivity of many of their properties , the approach described here provides a highly productive route toward materials for heterogeneous catalysis, sensing, plasmonics and (photo)electrochemistry, especially considering miniaturized designs such as microreactors and lab-on-a-chip sensors.
F. M. acknowledges funding by a Research Fellowship of the German Research Foundation (MU 4125/1-1).
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