Particle-impact analysis of the degree of cluster formation of rutile nanoparticles in aqueous solution

Abstract

Cluster formation can profoundly influence the bioavailability and (bio)geochemical activity of nanoparticles in natural aquatic systems. While colloidal properties of nanoparticles are commonly investigated using light-scattering techniques, the requirement to dilute samples can affect the fundamental nature and extent of the cluster size. Hence, an alternative in situ approach that can cover a much higher and wider concentration range of particles is desirable. In this study, particle impact chronoamperometry is employed to probe the degree of cluster formation of Alizarin Red S modified rutile nanoparticles of diameter ca. 167 nm in conditions approximating those existing in the environment. Random collisions of individual clusters of the modified rutile particles with a stationary electrode result in transient current signals during a chronoamperometric measurement, indicative of the reduction of the adsorbed Alizarin Red S dye molecules. The results from the particle-impact analysis reveal that the nanoparticles are heavily clustered with an average 91 monomeric particles per cluster. As the spherical equivalent size of the clusters (ca. 754 nm in diameter) is considerably larger than that from nanoparticle tracking analysis (ca. 117 nm), the present work highlights the impact of the dilution on the fundamental nature of the colloidal suspension and introduces the electrochemical determination of the size distribution of inert mineral nanoparticles in highly concentrated media.

Platinum Nanoparticle Impacts at a Liquid|Liquid Interface

“…The histograms of current spike amplitude are plotted in Figures A–C. Even if the presence of NP aggregates is suspected, the smaller current region of each histogram has been fitted using a log‐normal distribution to establish average spike amplitudes—taken from the log‐normal peak—of 10, 40, and 46 pA for the 5, 30, and 50 nm NPs, respectively.…”

Semiconducting Nanoparticles: Single Entity Electrochemistry and Photoelectrochemistry

“…Furthermore, the potentials at which the current spikes onset are clearly related to the chemical identity of the nanoparticles and recent work has shown that it is able to measure the states of agglomeration/aggregation of the particles ( Tschulik et al, 2014 ) and the porosity of the particles ( Jiao et al, 2017 ). Currently, the direct nano-impact studies on MOS mainly focus on the redox behavior of the MOS themselves Fe 3 O 4 ( Tschulik and Compton, 2014 ), Fe 2 O 3 ( Shimizu et al, 2016a ; Shimizu et al, 2016b ), ZnO ( Perera et al, 2015 ; Karunathilake et al, 2020 ; Ma et al, 2018 ) and CuO ( Zampardi et al, 2018 ) and the MOS surface-bound with electroactive species CeO 2 ( Karimi et al, 2019 ), TiO 2 ( Shimizu et al, 2017 ) and Al 2 O 3 ( Lin and Compton 2015 , 2017 ).…”

“…The motivation for studies of semiconducting (SC) NPs starts from the interest in investigating photoelectrochemical currents for energy conversion in SC nanostructures. Since then, single entity studies on the semiconducting materials such as metal oxides and some quantum dots materials have been performed ( Sardesai et al, 2013 ; Tschulik, et al, 2013 ; Perera et al, 2015 ; Fernando et al, 2015 ; Shimizu et al, 2017 ; Alshalfouh et al, 2019 ; Karunathilake et al, 2020 ; Wang et al, 2021 ). The overarching goal of studying single SC (photo) electrochemistry is to understand the net (photo) electrochemistry catalytic process at single particle level and to establish their instinct activity-structure relationship.…”

Platinum Nanoparticle Impacts at a Liquid|Liquid Interface

“…Even if the presence of NP aggregates is suspected, [17] the smaller current region of each histogram has been fitted using a log-normal distribution to establish average spike amplitudestaken from the log-normal peakof 10, 40, and 46pA for the 5, 30 and 50 nm particles, respectively.…”