Various Configurations of Au@Pt Nanostructures on Modified Electrochemical Sensors for H2O2 Detection

Abstract

Hydrogen peroxide (H₂O₂) is a vital metabolite involved in numerous biological processes, with physiological concentrations in humans ranging from 1 to 50 μM. Its rapid production, utilization, and decomposition make accurate low-concentration detection challenging. Although precious metals such as gold and platinum are effective for H₂O₂ detection, their high cost and limited availability necessitate alternative strategies. Nanostructuring these materials into core-shell nanorods (their size ∼ 40 nm in length) offers a sustainable, efficient solution by reducing material usage while enhancing performance. In this study, we modified glassy carbon electrodes with two types of Au@Pt nanorods (NR) for H₂O₂'s cyclic voltammetric and chronoamperometric detection: plain-surfaced (Smooth) and appendaged-surfaced (Hairy). Both sensors exhibit rapid stabilization, achieving reliable measurements within 5 s, suitable for capturing the volatile nature of H₂O₂. The Hairy NRs demonstrate superior performance, attributed to the increased presence of catalytically active Pt(0) compared to the less active Pt-(II) in Smooth NRs. This difference in oxidation states, combined with the enhanced surface geometry of Hairy NRs, results in faster kinetics, a wider linear detection range (500 nM-50 μM vs 1-50 μM), lower detection limit (189 nM vs 370 nM), and nearly double sensitivity. To simulate physiological conditions, we assessed oxygen interference and evaluated performance in biologically relevant environments. Cell viability tests were conducted to determine the nanoparticles' toxicity toward neuroblastic cells. These findings support further development of modified Au@Pt nanorod electrodes for in vivo and in vitro applications. With rapid response times, favorable detection limits, and high sensitivity, these sensors are promising for biomedical diagnostics, environmental monitoring, and studying neurotransmitters like glutamate.

Keywords: Au@Pt nanorods; Pt oxidation state; cell toxicity assay; electrochemical sensor; hydrogen peroxide (H2O2); nanoparticle fabrication; surface chemistry.

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Au@Pt core–shell nanorods fabrication procedure (Created in BioRender. Mostafiz, B. (2025)).

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Bright field TEM images of (a) Au NRs, (b) Smooth Au@Pt NRs, and (c) Hairy Au@Pt NRs. HR-TEM images of (d) Au NRs, (e) Smooth Au@Pt NRs, and (f) Hairy Au@Pt NRs with the clearly observed lattice planes indexed.

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(a) UV–vis absorption spectra of Au particles (black), Au NRs (dark gray), Au@Ag NRs (light gray), Smooth Au@Pt NRs (blue), and Hairy Au@Pt NRs (pink). (b) Comparing XPS narrow scan spectra of Pt 4f and Br 3d for Smooth and Hairy Au@Pt NRs.

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Cyclic voltammogram of (a) the potential window obtained in PBS, (b) the OSR probe obtained in Ru­(NH₃)₆ ^3+/2+ 1 mM/KCl 1 M, (c) ISR probe obtained in Fe­(CN)₆ ^3–/4– 2 mM/KCl 0.1 M, all at the scan rate of 50 mV·s^–1, and (d) EIS Nyquist plot obtained in Fe­(CN)₆ ^3–/4– 2 mM/KCl 0.1 M, at a frequency range of 1 Hz to 1 MHz on the unmodified (cream), Smooth Au@Pt NRs (blue), and Hairy Au@Pt NR-modified (pink) electrodes.

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Cyclic voltammograms of (a) comparison peaks of the Smooth Au@Pt (light and dark blue) and Hairy Au@Pt (light and dark pink) electrode vs PBS and 50 μM of H₂O₂/PBS with a scan rate of 50 mV·s^–1. Effect of scan rates between 2 to 200 mV·s^–1 for (b) Smooth Au@Pt and (c) Hairy Au@Pt NR-modified electrode vs 50 μM of H₂O₂/PBS. (d) The logarithm of peak current is vs the logarithm of the scan rate for Smooth Au@Pt (blue) and Hairy Au@Pt NRs (pink) modified electrode.

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Cyclic voltammograms of 50 μM H₂O₂/ PBS on Smooth and Hairy Au@Pt NRs in the absence (solid lines) and presence (dashed lines) of O₂ bubbling, scan rate = 50 mV·s^–1.

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Amperometric response of (a) Smooth Au@pt NRs and (b) Hairy Au@Pt NRs in PBS (dashed lines), in concentrations between 1–50 μM and 500 nm–50 μM H₂O₂/PBS, respectively, potential step = 200 to 500 mV. Calibration curves of (c) Smooth (Blue) and Hairy (Pink) Au@Pt NRs according to the amperometric data.

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Viability of cells in the presence of Smooth and Hairy Au@Pt NRs (blue and pink) and surfactant solution (yellow).