HAADF‐STEM characterization and simulation of nanoparticle distributions in an inhomogeneous matrix

Abstract

Measuring with a high accuracy the size distribution of small metallic nanoparticles loaded in a mesoporous metal oxide matrix is of particular interest for many studies related to new generations of interesting metamaterials. Transmission electron microscopy (TEM) is a powerful tool to determine the nature and morphology of very small particles, but their reliable and automatic identification in an inhomogeneous environment where the nanoparticle/background contrast locally varies is not straightforward. Here, we present how a quantitative analysis of high-angle annular dark field scanning TEM (HAADF STEM) images, accounting for the chemical sensitivity of the technique, can improve the accuracy of semiautomatic segmentation methods based on morphological processing to calculate size histograms. The paper also provides an estimate of the reliability of this method through the analysis of numerically synthesized images. The latter are based on the simulation of HAADF STEM projections of a volume filled with titania, pores and silver particles, whose morphological features, such as dimensions, shapes and densities are evaluated from experimental measurements of real samples. The results obtained with synthesized images prove the performances of the quantitative analysis to suppress nonsilver nanoparticles from the statistics and allow to infer empirical rules to determine imaging parameters that ensure a good reliability of histograms.

Deep learning detection of nanoparticles and multiple object tracking of their dynamic evolution during in situ ETEM studies

“…file (sections SI-D and E). Interestingly, the consistency of both simulated and experimental images is well demonstrated using the method developed by Treacy and Rice 67 , 68 , see Fig. 6 c,d.…”

“…In addition, Fig. 6 illustrates that the routine measuring the integrated intensity of NPs after a local background subtraction works reasonably well since the expected linear variation of the Treacy-Rice relation = f(D) (where D is the projected diameter of any NP belonging to a chemically homogeneous population 67 , 68 ) is properly verified at each frame (only the first and last frames of the sequence are reported here). It is seen that NP intensities retrieved during the tracking step f) and h) are almost perfectly identical to the ones input in the simulation e) and g).…”

Microstructuring of Mesoporous Titania Films Loaded with Silver Salts to Enhance the Photocatalytic Degradation of Methyl Blue under Visible Light

“…The first was a homogeneous UV illumination for 30 min with two lamps emitting at 254 nm and each delivering a power of 15 W. This illumination allowed the silver salts to be reduced and a homogenous distribution of silver NPs in the uppermost 80–100 nm layer of the film to be produced ( Figure 1 a,d and Figure 2 b). Silver NP growth inside the mesoporous TiO 2 matrix [ 9 ] leads to a certain diameter distribution of the silver NPs, which has been estimated by image processing [ 10 ] to be in the range of 1 to 12 nm in diameter with a maximum particle size distribution of around 5 nm in diameter ( Figure 1 g). Before illumination, the films were transparent and the spectroscopic measurement (PerkinElmer Lambda 900) showed no absorption bands in the UV or visible range, but after illumination, a large absorption band centered around 460 nm appeared ( Figure 3 a).…”

Tailoring metal-dielectric nanocomposite materials with ultrashort laser pulses for dichroic color control

“…The films were elaborated on these substrates by sol-gel process consisting of titanium tetraisopropoxide (TTIP, Aldrich; 97%), acetylacetone (AcAc, Aldrich; 99%), hydrochloric acid (HCl, Roth; 37%), ethanol (EtOH, Carlo Erba; absolute), Pluronic P123 ((PEO) 20 (PPO) 70 (PEO) 20 (Aldrich; MW: 5000), and ultrapure water (H 2 O) with specific molar ratios at: TTIP : P123 : EtOH : HCl : H 2 O : AcAc :: 1 : 0.025 : 28.5 : 0.015 : 29.97 : 0.5, as published previously in our articles. 48 The films were annealed at 340°C, to obtain mesoporous amorphous titania thin films with a thickness of 200 ± 30 nm.…”