Nanostructured Ag₄O₄films with enhanced antibacterial activity

Abstract

Ag(4)O(4) (i.e. silver(I)-silver(III) oxide) thin films with tailored structure and morphology at the nanoscale have been grown by reactive pulsed laser deposition (PLD) in an oxygen-containing atmosphere and they are shown to exhibit a very strong antibacterial activity towards Gram-negative bacteria (E. coli) and to completely inhibit the growth of Gram-positive bacteria (S. aureus). The formation of this particular high-valence silver oxide is explained in terms of the reactions occurring during the expansion of the ablated species in the reactive atmosphere, leading to the formation of low-stability Ag-O dimers and atomic oxygen, providing reactive species at the substrate where the film grows. PLD is shown to allow control of the structure (i.e. crystallinity and grain size) and of the morphology of the films, from compact and columnar to foam-like, thus allowing the deposition of nanocrystalline films with increased porosity and surface area. The antibacterial action towards E. coli is demonstrated and is shown to be superior to that of nanostructured Ag-based medical products. This can be related to the release of Ag ions with high oxidation number, which are known to be very reactive towards bacteria, and to the peculiar morphology at the nanoscale resulting in a large effective surface area.

Self-Assembled Hierarchical Nanostructures for High-Efficiency Porous Photonic Crystals

“…Conversely, high pressures favor the growth of hierarchical nanostructures and hence of a porous film. As demonstrated in previous publications, 31,32,[38][39][40] chemical and morphological parameters of complex hierarchical nanostructures can be finely controlled. Moreover, high specific surface areas, as measured by the Brunauer-EmmettTeller (BET) method, in the range of 100-300 m 2 /g and high pore volume density are obtained for 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 An important aspect to take into account for a precise control of the RI modulation is the influence of each layer on the following during growth (see details in Supporting Information and Figure SI 3).…”

Electronic structures of silver oxides

“…Both Ag 2 O and AgO have uses in battery technologies [16][17][18][19] and antibacterial applications. [20][21][22] Ag 2 O is also used in molecular sensor technologies, 23 for example, as an enzymeless glucose sensor with Cu, 23,24 water splitting, 25 optical memories, 26 and organic catalysis, for example, in transmetalation 27 and the oxidation of aldehydes by molecular oxygen. 28 Additionally, Ag 2 O is used as a component of a range of fast-ion conducting glasses of the form AgIAg 2 Ag 2 O has been the most widely studied of the different silver oxides, with investigations mainly focusing on the electronic structure of the material [33][34][35][36] and the interaction and bonding between the silver and oxygen atoms (primarily concerning the degree of covalency).…”

Electronic structure of mixed-valence silver oxide AgO from hybrid density-functional theory

“…[1][2][3] It has also gained interest for possessing bacteriostatic properties, 4,5 and has been tested for applications in the treatment and cure of dermatological skin conditions. 6 Although not as widely studied as Ag 2 O, several structural and spectroscopic studies have been carried out on AgO in an effort to elucidate the geometry and electronic structure of the material.…”