Formation of Ag nanoparticles under electron beam irradiation: Atomistic origins from first‐principles calculations

Abstract

The formation of Ag nanoparticles is currently a topic subject to a great deal of research because they are excellent materials with many technological applications. Recently, the formation of Ag nanoparticles on a-Ag 2 WO 4 semiconductors induced by electron irradiation has been reported, but the mechanism underlying the transformations remains elusive. The aim of this article is to describe the mechanisms of electron beam irradiation on a-Ag 2 WO 4 and its transformation to form Ag nanoparticles in vacuum conditions. To this end, a combined study involving experiments and multiscale computational approaches (density functional theory calculations and molecular dynamics simulations) is presented. With the increasing interplay between experimental and computational approaches at multiple length scales, we will also discuss how these combined data can be used to provide a deep insight into the rationalization of electron beam-induced transformations. This phenomenon is likely to be promoted by electron charge redistribution in these materials due to electronic excitations combined with the formation of silver vacancies under electron beam irradiation. As this mechanism should be relevant to other Ag-based materials, our results provide pointers for the further development and optimization of electron beammediated engineering of the atomic structure and electronic properties at the atomic resolution. K E Y W O R D Sa-Ag 2 WO 4 , Ag nanoparticles, electron beam irradiation, first-principles calculations, plasmons | I N TR ODU C TI ONIn recent years, a strong continuous effort has been made in the synthesis of Ag nanoparticles (NPs) due to their remarkable properties and exciting applications in areas such as photonics, electronics, photocatalysis, sensing, and biomedicine. [1][2][3][4][5][6][7][8][9][10][11][12] The possibility of building new materials byThis article is dedicated to our colleague and friend, Prof. Nino Russo, as a tribute on the occasion of his 70th birthday. We hereby take this opportunity to convey our most heartfelt congratulations to an excellent person and a great researcher who possesses a privileged vision of interpersonal relations, teachinglearning processes, and technical-scientific innovations. combining metallic Ag with a semiconductor gives rise to a broad spectrum of synergistic and complementary properties that enable new applications to be developed, and many studies have revealed that the deposition of Ag on semiconductors enhances their photocatalytic activity due to the particular properties of Ag-based photocatalysts. [13,14] This phenomenon is related to the surface plasmon resonance, which improves the separation of the electron-hole pair. [15][16][17][18][19][20][21][22][23][24] The controlled combination of these two different materials is an interesting challenge, in which Ag NPs on the contact interface trigger structural and electronic variations that affect the photocatalytic performance of the semiconductor by increasing the electron-hole separation and then th...

Proof‐of‐Concept Studies Directed toward the Formation of Metallic Ag Nanostructures from Ag3PO4 Induced by Electron Beam and Femtosecond Laser

“…For fs laser irradiation, the sample can reach a pressure of around 1010 Pa and a temperature of 1000 K, thus causing the formation of a large number of confined photons in a small area. Moreover, when irradiated with fs pulses, the sample is in the steady state, that is, it does not present vibrational and rotational movements, since these occur in the second peak scale, which makes it difficult to follow the dynamic process of particle nucleation …”

“…Our research group, using a joint combination of experimental and theoretical studies, has conducted studies for understanding the formation mechanism of Ag nanoparticles (NPs) provoked by the exposure to electron beams of an electronic microscope on the surfaces of several Ag‐based materials such as α‐Ag 2 WO 4 , β‐Ag 2 WO 4 , γ‐Ag 2 WO 4 , β‐Ag 2 MoO 4 , Ag 2 CrO 4 , AgVO 3 , Ag 2 V 2 O 7 , and Ag 3 PO 4 crystals . Furthermore, we have reported four new phenomena provoked by fs laser irradiation: i) the scale‐up of the formation of Ag NPs on α‐Ag 2 WO 4 with bactericidal properties; ii) the synthesis of metallic Bi NPs with coexisting crystallographic structures (rhombohedral, monoclinic, and cubic) on NaBiO 3 ; iii) the formation of In NPs on InP; and iv) the synthesis of Ag–Bi nanoalloys from inorganic oxide Ag 2 WO 4 and NaBiO 3 targets .…”

Ag Nanoparticles/AgX (X=Cl, Br and I) Composites with Enhanced Photocatalytic Activity and Low Toxicological Effects

“…Electron beam irradiation in the transmission electron microscopy (TEM) can be used to produce and manipulate nanostructures . Our research group has presented an in situ method used to obtain Ag nanoparticles on the surface of a semiconductor, providing first‐principles calculations in conjunction with experiments and advanced characterization to gain a deep insight into the formation of Ag nanoparticles and the nature of the mechanisms provoked by electron beam irradiation . The formation process for Ag particles on AgCl crystals induced by electron beam irradiation has been previously reported, while Formo et al.…”

Evidence for the formation of metallic In after laser irradiation of InP

“…Our research endeavors are devoted to studying the interaction between electron beams and laser irradiation with matter via the joint use of theoretical calculations and advanced experimental techniques to obtain and develop novel systems with technological applications. [13][14][15] We have reported four new phenomena caused by femtosecond laser irradiation, enabling the fabrication of new complex nanoensembles, such as (i) the scale-up of the formation of Ag nanoparticles on α-Ag2WO4 with bactericidal properties by femtosecond laser irradiation; 16,17 (ii) the formation of nanoparticles of In from the laser irradiation of InP; 18 (iii) the synthesis of stable and metastable phases of Bi nanoparticles; 19 (iv) the synthesis of Ag-Bi nanoalloys with high antibacterial activity by femtosecond laser irradiations, which is interesting for potential antimicrobial applications; 20 and (v) the laser and electron beam-induced formation of Ag/Cr structures on Ag 2 CrO 4 . 21 In addition, we have analyzed the nature of chemical interactions by developing a new protocol based on the chemical pressure approach to point out the connection between some topological features of the electron density and structural stability of InP, thus providing an efficient tool to predict the breaking and formation of chemical bonds provoked by electron irradiation.…”