Subsurface synthesis and characterization of Ag nanoparticles embedded in MgO

Abstract

Metal nanoparticles exhibit a localized surface plasmon resonance (LSPR) which is very sensitive to the size and shape of the nanoparticle and the surrounding dielectric medium. The coupling between the electromagnetic radiation and the localized surface plasmon in metallic nanoparticles results in a sizable enhancement of the incident fields, making them possible candidates for plasmonic applications. In particular, partially exposed metallic nanoparticles distributed in a dielectric matrix can provide prime locations for LSPR spectroscopy and sensing. We report the synthesis and characterization of a plasmonic substrate consisting of Ag nanoparticles partially buried in MgO. Ag nanoparticles of different shapes and size distributions were synthesized below the surface of MgO by implanting 200 keV Ag(+) ions followed by annealing at 1000 °C for 10 and 30 h. A detailed optical and structural characterization was carried out to understand the evolution of the Ag nanoparticle and size distribution inside the MgO matrix. Micro x-ray diffraction (Micro-XRD) was employed to investigate the structural properties and estimate the crystallite size. The nanoparticles evolved from a spherical to a faceted morphology with annealing time, assuming an octahedral shape truncated at the (001) planes, as visualized from aberration-corrected transmission electron microscopy (TEM) images. The nanoparticles embedded in MgO were shown to be pure metallic Ag using atom probe tomography (APT). The nanoparticles were partially exposed to the surface by employing plasma etch techniques to remove the overlaying MgO. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to study the surface morphology and obtain a height distribution for the partially exposed nanoparticles.

Kinetics modeling of precipitation with characteristic shape during post-implantation annealing

“…Figure 1 illustrates distinctly the whole process of the nucleation and growth of faceted precipitates during post-implantation annealing, which provides a lot of useful information to comprehend the mechanism of the precipitation. Similar experimental observations about the formation and evolution of precipitates with characteristic shape in the literatures 5,6,24 confirm the availability of our simulation results. In order to explore the influence of ion dose on the kinetics of nucleation and growth of precipitates, different ion doses of implantation are calculated by changing the values of c i in Eq.…”

Behavior of molecules and molecular ions near a field emitter

“…Building upon this work, Cerezo et al [10], followed by Blavette et al [11], and finally Kelly et al [12] developed a technique currently known as atom probe tomography (APT). APT provides analytical, three-dimensional mapping of a range of solid materials [11,[13][14][15][16][17][18][19][20][21][22][23][24][25] with near-atomic resolution.…”

Discerning the Location and Nature of Coke Deposition from Surface to Bulk of Spent Zeolite Catalysts

“…Even though such studies have investigated the nature of coke formed during ethanol conversion reactions at a bulk average level or at a macroscopic level, nanoscale imaging of the carbonaceous molecules present in spent catalyst materials using depth profiling is lacking in the literature. Recently, a relatively new characterization capability called atom probe tomography (APT) has been increasingly used to perform 3D quantitative analysis of element distribution in catalyst materials with sub-nanometer–scale spatial resolution and high mass sensitivity up to the few parts per million level of concentration of elements in materials2627282930313233. It has also been demonstrated that APT can be used to quantitatively image the Al distribution in zeolite materials, and evidence for changes in Al distribution can be obtained by comparing results before and after severe steam treatment of HZSM-5 at 700 °C34.…”