Spatially resolved indiffusion behavior of Cu²⁺ and Ni²⁺ in polypropylene

Abstract

Microplastics and their effects on the environment and food chain have become increasingly important in recent years. These polymer particles, which are only few millimeters in size or smaller, accumulate in the environment and can enter the human food chain via animals that ingest them. Moreover, they can accumulate impurities such as heavy metals. Therefore, this study focuses on the indiffusion behavior of metal ions into semicrystalline polypropylene (PP) applying time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) at cryo‐conditions. Diffusion coefficients of Cu2+ and Ni2+ in PP are determined by classical SIMS depth profiling in frozen state (T <−130°C) and subsequent data analysis according to Fick's second law of diffusion. The results show that diffusion of Cu2+ ions in dry PP (DPP,Cu = [2.21 ± 0.15]·10−12 cm2/s) is faster compared to Ni2+ ion diffusion of dry PP (DPP,Ni = [4.43 ± 0.55]·10−13 cm2/s). Interestingly, the diffusion of Cu2+ ions in water‐saturated PP (DPP,H2O,Cu = [1.91 ± 0.28]·10−13 cm2/s) is slower compared to Cu2+ ion diffusion in dry PP. Furthermore, high‐lateral resolution ToF‐SIMS analysis shows that metal ions only diffuse in certain areas of PP, which are most likely amorphous.

Protective Coating for the Lithium Metal Anode Prepared by Plasma Polymerization

“…However, the surface roughness of the polymer layer (200 nm) can also induce this effect due to earlier probing of the lithium signal in thinner coating regions. Kern et al also showed that the metal ion diffusion in polymers is faster in amorphous regions than in crystalline regions . Therefore, the interphase layer shown in Figure c is probably on average thinner and the polymer layer thicker than indicated by the depth profile.…”

“…Kern et al also showed that the metal ion diffusion in polymers is faster in amorphous regions than in crystalline regions. 30 Therefore, the interphase layer shown in Figure 3c is probably on average thinner and the polymer layer thicker than indicated by the depth profile. Analyses at different regions of interest showed a decrease of the probable interphase layer of about 50% in areas where the lithium signal is probed later (not shown).…”

“…All data were calibrated in relation to the signal of adventitious carbon at 284.8 eV. A Shirley-type background and Gauss-Lorentz [GL (30)] line shapes were applied for data evaluation.…”

Determination of Sr2+ mobility in viscous bovine bone marrow by cryo‐time‐of‐flight secondary ion mass spectrometry

“… $$$$ \frac{\delta c}{\delta t}=\frac{\delta }{\delta x}\left[D\frac{\delta c}{\delta x}\right]. $$$$ For Sr 2+ diffusion in bovine bone marrow, we assumed diffusion from an exhaustless source into semi‐infinite space as boundary conditions for solving Fick's second law of diffusion (Equation []), as previously described 26,27,53,54 . Following assumptions had to be made 55 : Because species concentration c is proportional to secondary ion intensity I in SIMS, the fit can be carried out with the obtained Sr + ion signal intensities. The measured ion intensity I is considered as a linear function of the real Sr 2+ intensity ( I bg ). Strontium diffusion occurs from an infinite reservoir of Sr 2+ with an intensity I 0 at the initial position x 0 . There are no reactions of Sr 2+ (diffusing species) with the bone marrow matrix. …”

“…For Sr 2+ diffusion in bovine bone marrow, we assumed diffusion from an exhaustless source into semi-infinite space as boundary conditions for solving Fick's second law of diffusion (Equation [2]), as previously described. 26,27,53,54 Following assumptions had to be d. There are no reactions of Sr 2+ (diffusing species) with the bone marrow matrix.…”