Nanocomposites of Metallic Silver with Octamolybdate Amine Complexes of Nickel(II) and Copper(II)

Abstract

It was shown that interaction of photoreduced octamolybdate amine complexes of nickel(II) and copper (II) with silver(I) nitrate in aqueous solutions leads to formation of nanocomposite materials containing metallic silver nanoparticles. The nature of the 3d metal was established to affect the average size and dispersion of the silver nanoparticles, which are significantly greater in the composite based on the nickel complex. The photoluminescent properties of the materials obtained have been studied.The inherent ability of polyoxometallates (POMs) to undergo stepwise multiple-electron transformations while retaining structural integrity [1] opens up possibilities for using them in various areas, in particular for designing new materials with useful redox, catalytic, optical, magnetic, and other characteristics [2, 3].One way to use POMs is employment of their water-soluble forms as reducing agents to obtain nanoparticles of noble metals (Ag, Au, Pd, Pt, Rh, Ru) [4,5]. Such an approach allows to obtain metallic nanoparticles without using energy-intensive technologies, but a disadvantage of the approach is the need to separate the metallic nanoparticles formed from the liquid phase, followed by deposition on the required support. Considering this, one-step synthesis of composites containing (along with the metallic nanoparticles) another component acting as a support and having its own useful properties (in particular, POMs) is a logical step in development of this direction. Recently published papers have demonstrated the fruitfulness of such an approach for obtaining nanocomposite materials with promising catalytic [6], electrocatalytic [7], photocatalytic [8], and electrophysical [9] properties.We showed previously that interaction between aqueous solutions of AgNO 3 or H[AuCl 4 ] and crystalline complex compounds formed by partially reduced Keggin POM anions [EM 12 O 40 ] n-(M = Mo or W, E = P V or Si IV ) leads to formation of composites in which the metallic nanoparticles are localized on the surface of POM crystallites, and ways to control the composition and structure of the materials formed have been suggested [10][11][12].The aim of this work was to determine the possibilities for using Anderson octamolybdate complexes [Mo 8 O 26 ] 4-for one-step synthesis of nanocomposites Ag@POM, and to establish the effect of the nature of the metal ion of the cationic component on the size and dispersion of the metallic silver nanoparticles formed. We have also studied the photoluminescent characteristics of the nanocomposites obtained, which can be considered as potential systems for creating new luminescent materials.As the objects of investigation, we selected compounds formed by cationic amine complexes of copper(II) and nickel(II) [M(L)] 2+ (L = 1,9-diamino-3,7-diazanonane) and the octamolybdate anion, and specifically [Ni(L)] 2 [Mo 8 O 26 ]·4H 2 O (1) and (NH 4 ) 2 [Cu(L)] 3 [Mo 8 O 26 ] 2 (2). 62 0040-5760/15/5101-0062