Current Lifetime of Single-Nanoparticle Electrochemical Collision for In Situ Monitoring Nanoparticles Agglomeration and Aggregation

Abstract

In situ monitoring of the agglomeration/aggregation process of nanoparticles (NPs) is crucial because it seriously affects cell entry, biosafety, catalytic performance of NPs, and so on. Nevertheless, it remains hard to monitor the solution phase agglomeration/aggregation of NPs via conventional techniques such as electron microscopy, which requires sample pretreatment and cannot represent native state NPs in solution. Considering that single-nanoparticle electrochemical collision (SNEC) is powerful to detect NPs in solution at the single-particle level, and the current lifetime, which refers to the time that current intensity decays to 1/e of the original value, is skilled in distinguishing different sized NPs, herein, a current lifetime-based SNEC has been developed to distinguish a single Au NP (d = 18 nm) from its agglomeration/aggregation. Based on this, the agglomeration/aggregation process of small-sized NPs and the discrimination of agglomeration vs aggregation have been carefully investigated at the single-particle level. Results showed that the agglomeration/ aggregation of Au NPs (d = 18 nm) in 0.8 mM HClO 4 climbed from 19% to 69% over two hours, whereas there was no visible granular sediment, and Au NPs tended to agglomerate rather than aggregate irreversibly under normal conditions. Hence, the proposed current lifetime-based SNEC could serve as a complementary method to in situ monitor the agglomeration/aggregation of small-sized NPs in solution at the single-particle level and provide effective guidance for the practical application of NPs.

Centrifugal Field-Flow Fractionation Enables Detection of Slight Aggregation of Nanoparticles That Impacts Their Biomedical Applications

“…Although the detailed mechanism needs to be further examined, our results suggest that the centrifugal force in the purification process could induce a slight aggregation. In addition to the centrifugation examined in this study, other factors in conventionally used Ab modification processes, such as the equivalent ratio of Ab and agitation, salt concentration, dispersion methods using ultrasonication after purification, 45 etc., may also cause slight aggregation of NPs. Therefore, this study proposes that the bioconjugation methods of NPs, considered to be established in the field of NP-based biomedical applications, need to be revisited by accurate aggregation analysis.…”

Single‐nanoparticle electrochemical collision for study of the size‐dependent activity of Au nanoparticles during hydrogen evolution reaction

“…Considering that the current intensity measured before and after Au NPs dispersing in 0.8 mM HClO 4 for 30 min had essentially the same distributions (Figure S6), which indicate that Au NPs can basically exist stably under this condition, all collision experiments were performed in 0.8 mM HClO 4 within 30 min to avoid agglomerate effects [13]. To ensure that the HER reaction is controlled by mass transfer, the average current intensity and collision frequency of Au NPs under different potentials were compared.…”

Impact electrochemistry for biosensing: advances and future directions

“…In addition to the impact frequency, the current lifetime in the collision events can also serve as signal output mode for target analysis. 34 Leveraging differences in the current rise time resulting from the collisions of PtNPs of various sizes on an ultramicroelectrode (UME), Zhang et al developed a size-resolved strategy for multiple microRNA detection assays using two sizes of PtNPs (5 and 15 nm) as detection probes (Fig. 1b).…”

“…These are categorized as transient "spikes" or "staircases", depending on the process occurring between the colliding particles and the electrode surface. 23,24 Impact electrochemistry originally served as a powerful electroanalytical tool for the analysis and characterization of rigid inorganic nanoparticles, encompassing the acquisition of the physicochemical properties, 7,[25][26][27][28][29][30][31][32][33][34][35][36][37] reaction kinetics, [38][39][40][41][42] and reaction mechanisms. 43 Recently, impact electrochemistry has also been increasingly used for nanoparticle synthesis and screening purposes, [44][45][46][47] as well as for studying entity-to-entity interactions 48 and the transient electrochemical process at a confined interface.…”