Crystalline silica particle functionalized by PEG for its collision-enhanced detection at ultramicroelectrode

Xiaojun Liu; Xiaoyu Chen; Lei Zhang; Kwaku Junior Twum; Xia Wang; Yong Xu; Xiangqun Zeng

doi:10.1016/j.aca.2023.341178

Crystalline silica particle functionalized by PEG for its collision-enhanced detection at ultramicroelectrode

Anal Chim Acta. 2023 Jun 15:1260:341178. doi: 10.1016/j.aca.2023.341178. Epub 2023 Apr 10.

Authors

Xiaojun Liu¹, Xiaoyu Chen², Lei Zhang³, Kwaku Junior Twum¹, Xia Wang³, Yong Xu², Xiangqun Zeng⁴

Affiliations

¹ Department of Chemistry, Oakland University, Rochester Hills, MI, 48309, USA.
² College of Engineering, Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI, 48202, USA.
³ Department of Mechanical Engineering, Oakland University, Rochester Hills, MI, 48309, USA.
⁴ Department of Chemistry, Oakland University, Rochester Hills, MI, 48309, USA. Electronic address: zeng@oakland.edu.

PMID: 37121651
DOI: 10.1016/j.aca.2023.341178

Abstract

Detecting individual particulate matter is highly significant in many areas, such as mine safety, environment, and human health. The analytical method based on single entity electrochemistry (SEE) has shown great potential in detecting, counting, and measuring individual particles, especially conductive metals or carbon particles, based on their unique charge transfer reactions at an ultramicroelectrode (UME). In this study, we report an innovative SEE method for improving the sensitivity of the detection of electrochemical inert crystalline silica particles by functionalizing silica particles with polyethylene glycol (PEG) molecules. The PEG surface functionalization of the silica was characterized by Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The morphology of silica particles was characterized by a scanning electron microscope (SEM), and a transmission electron microscope (TEM) was employed to calibrate size distribution and determine the elemental composition of silica particles. The surface charges of silica particles were measured by dynamic light scattering techniques. The collision behaviors of crystalline silica particles with UME were investigated by cyclic voltammetric experiments, which are rarely reported in the literature. The crystalline silica particles were detected based on electrochemically blocking the flux of the redox mediator at the surface of UME, which showed significant signal amplification in the proposed method. Our method was demonstrated for detecting crystalline silica functionalized with or without PEG, acquiring the limit of quantification (LOQ) values of 0.391 μM (23.45 μg/L) and 0.824 μM (49.45 μg/L), respectively, which confirmed that a more than two times improvement in LOQ could be achieved over the PEG functionalized silica particles. We further presented a theoretical model using finite element simulations with COMSOL Multiphysics. We deduced a quantitative relation between the distribution of the current step size and the size distribution of silica particles. Therefore, the reported method here provides a paradigm for SEE-based detection of electrochemically inert crystalline silica particles, which extends the previous report substantially concerning particle detection.

Keywords: Collision event; Crystalline silica particle; Electrochemical blocking; Functionalization; Single entity electrochemistry; Ultramicroelectrode.