Electron Mobility and Trapping in Ferrihydrite Nanoparticles - Research paper on electron transfer and recombination mechanisms

Sep 21, 2026

Uploaded by Aurora

Iron is abundant in Earth’s crust, and iron oxide minerals strongly influence environmental redox reactions, yet the precise electron-transfer mechanisms remain incomplete. This work links electron mobility to interfacial electron transfer in ferrihydrite nanoparticles. A coarse-grained lattice Monte Carlo model simulates mobilities and photoinjected electron lifetimes, while pump-probe spectroscopy tests predicted trends across particle size and solution conditions, using cryogenic TEM to assess aggregation. Biphasic recombination kinetics span picoseconds to microseconds, with slow processes dominated by deep traps.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages12

Reading Time30 min

AccessFree to download

Abstract

Keywords

Introduction

Environmental roles of iron oxides and ferrihydrite

Mechanistic background: electron transfer and small polaron model

UC Berkeley UC Berkeley Previously Published Works Title Electron Mobility and Trapping in Ferrihydrite Nanoparticles Permalink [https://escholarship.org/uc/item/537967ff](https://escholarship.org/uc/item/537967ff) Journal ACS Earth and Space Chemistry, 1(4) ISSN 2472-3452 Authors Soltis, Jennifer ASchwartzberg, Adam M Zarzycki, Piotr et al. Publication Date 2017-06-15 DOI 10.1021/acsearthspacechem.7b00030 Peer reviewed [eScholarship.org](eScholarship.org) Powered by the California Digital Library University of California Article [http://pubs.acs.org/journal/aesccq](http://pubs.acs.org/journal/aesccq) Electron Mobility and Trapping in Ferrihydrite Nanoparticles Jennifer A. Soltis,†,‡ Adam M. Schwartzberg, § Piotr Zarzycki,⊥, ∥ R. Lee Penn,† Kevin M. Rosso,*,‡ and Benjamin Gilbert*,⊥ †Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States ‡Physical Sciences Division, Paciﬁc Northwest National Laboratory, Richland, Washington 99354, United States §Molecular Foundry and ⊥Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States ∥Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland ABSTRACT: Iron is the most abundant transition metal in the Earth’s crust, and naturally occurring iron oxide minerals play a commanding role in environmental redox reactions. Although iron oxide redox reactions are well-studied, their precise mechanisms are not fully understood. Recent work has shown that these involve electron transfer pathways within the solid, suggesting that overall reaction rates could be dependent upon electron mobility. Initial ultrafast spectroscopy studies of iron oxide nanoparticles sensitized by ﬂuorescein derivatives supported a model for electron mobility based on polaronic hopping of electron charge carriers between iron sites, but the constitutive relationships between hopping mobilities and interfacial charge transfer processes has remained obscured. We developed a coarse-grained lattice Monte Carlo model to simulate the collective mobilities and lifetimes of these photoinjected electrons with respect to recombination with adsorbed dye molecules for essential nanophase ferrihydrite and tested predictions made by the simulations using pump−probe spectroscopy. We acquired optical transient absorption spectra as a function of the particle size and under a variety of solution conditions and used cryogenic transmission electron microscopy to determine the aggregation state of the nanoparticles. We observed biphasic electron recombination kinetics over time scales that spanned from picoseconds to microseconds, the slower regime of which was ﬁt with a stretched exponential decay function. The recombination rates were weakly aﬀected by the nanoparticle size and aggregation state, suspension pH, and injection of multiple electrons per nanoparticle. We conclude that electron mobility indeed limits the rate of interfacial electron transfer in these systems, with the slowest processes relating to escape from deep traps, the presence of which outweighs the inﬂuence of environmental factors, such as pH-dependent surface charge. KEYWORDS: iron, redox, electron transfer, ferrihydrite, charge separation ■ INTRODUCTION Iron oxide, hydroxide, and oxyhydroxide minerals (collectively referred to as iron oxides) are abundant in soils, groundwater, and marine environments. 1−4 They play important roles in biogeochemical cycling of many elements due, in part, to their redox reactivity. Ferrihydrite, a nanophase and poorly crystalline Fe(III) oxyhydroxide, plays an especially important role in controlling contaminant and nutrient availability.1,2,4,5 Arsenic, aluminum, and heavy metals can be adsorbed to or incorporated into ferrihydrite, sequestering them from the water supply.6−11 However, iron oxides readily undergo reductive transformations under appropriate conditio

FAQs

What scientific question does the study address about iron oxide systems?

It examines how electron mobility controls the rate of interfacial electron transfer in ferrihydrite nanoparticles and how this relates to electron hopping and trapping processes.

How were electron mobility and trapping investigated?

The study used a coarse-grained lattice Monte Carlo model to simulate collective mobilities and lifetimes of photoinjected electrons, then tested predictions with pump–probe spectroscopy.

What did the researchers observe about electron recombination over time?

They observed biphasic electron recombination kinetics, with a faster regime and a slower regime spanning picoseconds to microseconds, where the slower part was fit by a stretched exponential decay.

Sep 21, 2026

Uploaded by Aurora