X-ray Induced Formation of Metal Nanoparticles from Interpolyelectrolyte Complexes with Copper and Silver Ions: The Radiation-Chemical Contrast

Abstract

Tuning the size and spatial distribution of metal nanoparticles is a key issue for obtaining metal−polymer nanocomposites with desirable properties. It was shown that the action of white X-ray radiation (bremsstrahlung, E max ∼ 30 keV) on swollen films of interpolyelectrolyte complexes with copper and silver ions in an aqueousalcoholic environment resulted in the formation of a specific type of metal nanostructures characterized by transmission electron microscopy (TEM). The structure pattern was explained by autocatalytic enhancement of the rate of chemical transformations in the vicinity of preformed metal nanoparticles. The effect was attributed to increasing absorption of X-ray photons by compact metal nanoparticles leading to local sensitization described as the radiation-chemical contrast. The nanostructure pattern exhibited a remarkable evolution with increasing irradiation dose. In particular, at a certain stage, the big primary nanoparticles induce formation of "clouds" of ultrasmall secondary particles due to local distribution of the secondary electrons. The scale of the radiation-induced events is determined by the photon energy and electronic properties of absorbers. In the case of copper ions, major interaction occurs with K-electrons, whereas the interactions with both K-and L-electrons are significant for silver ions, which results in bimodal distribution of nanoparticle size.

Unwanted effects of X-rays in surface grafted copper(ii) organometallics and copper exchanged zeolites, how they manifest, and what can be done about them

“…The fact that X-rays, along with other probes, such as electrons and lasers, carry with them a potential for affecting the apparent behavior of materials, either through thermal effects, or through the effects of the secondary production of electrons, resulting from their application, is well known. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Furthermore, a propensity for Cu II to be reduced to Cu I under the influence of X-ray beams has been demonstrated previously, and found to be a function of the nature of counter ions present in homogeneous (aqueous) systems. 13,19 However, and in spite of many previous X-ray spectroscopic studies of the behaviour of copper containing zeolites for the direct conversion of methane to methanol, 26,27,29,31,35,41,42,[45][46][47][48][49][50][51][52] we are unaware of any previous consideration that the results may have been influenced by the application of the X-ray probe.…”

“…[7][8][9][10][11] In other important areas, such as material chemistry and heterogeneous catalysis, which largely occupy themselves with materials that are inorganic, rather than predominantly organic and biological in nature, such systematic studies of the radiation tolerances of materials are much less common. That said, studies do exist, [11][12][13][14][15][16][17][18][19] that have reported, and to varying degrees examined, X-ray induced damage in a variety of systems, including those based upon Cu II in solution. 13,19 The two types of copper-based material we consider are, to varying degrees, and amongst many other types inorganic materials, investigated to understand how to achieve speciation and process environment required for the efficient and selective conversion of methane to methanol.…”

“…That said, studies do exist, [11][12][13][14][15][16][17][18][19] that have reported, and to varying degrees examined, X-ray induced damage in a variety of systems, including those based upon Cu II in solution. 13,19 The two types of copper-based material we consider are, to varying degrees, and amongst many other types inorganic materials, investigated to understand how to achieve speciation and process environment required for the efficient and selective conversion of methane to methanol. The desirability of achieving such a direct conversion is matched by the extreme challenge that this conversion poses to materials synthesis and process design.…”

Unexpected effects in non crystalline materials exposed to X-ray radiation

“…The interaction of intense beams of synchrotron radiation based X-rays with a variety of materials has been found to alter the state of the materials. Damage is not only sustained to samples in static experiments but there is also evidence that X-ray interactions can change the dynamics [1], or even induce, structure forming processes [2][3][4][5], or influence the reaction rate of catalytic processes [6].…”

Green Synthesis of Stable Nanocomposites Containing Copper Nanoparticles Incorporated in Poly-N-vinylimidazole

“…(natural compounds) [ 27 , 28 ], as well as poly-N-vinylpyrrolidone, polyacrylamide, poly-N-vinyl-1,2,4-triazole, etc. (synthetic compounds) are used as effective stabilizers of copper nanoparticles [ 29 , 30 , 31 , 32 ].…”