Exploring alkyl-diamine chain length effects on electrochemical behavior of AuNPs fabricated electrodes: Influence of linkers on the sensitive detection of hydrazine

Abstract

In this electrochemical exploration, we scrutinized the influence of alkyl-diamine (AD) chain length as crucial linkers between glassy carbon electrodes (GCE) and citrate-capped gold nanoparticles (Cit-AuNPs), focusing on their conductive behavior and sensing proficiency, particularly in hydrazine detection. Meticulous examination of self-assembled monolayers (SAMs) formed by three distinct ADs, namely 1,6-hexanediamine (HDA), 1,8-octanediamine (ODA) and 1,10-decanediamine (DDA) unfolded over GC surfaces revealed a precise adherence to Langmuir adsorption kinetics during the SAM formation process. Utilizing cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the electrochemical activity of the [Ru(NH₃)₆]³⁺/²⁺ redox pair at electrodes modified with ADs was investigated. The proposed mechanism involves a Michael-like nucleophilic addition process at the GC surface/diamine solution interface during the SAM formation. Analysis across various techniques underscored the compact nature of the DDA-formed SAM in comparison to HDA and ODA. Exploiting the free amine functional groups on the SAMs, the as-synthesized Cit-AuNPs were attached on the electrode surface and investigated comprehensively through CV, EIS, attenuated total reflection Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Remarkably, Cit-AuNPs attached DDA-SAM/GC electrode offered superior electro active surface area, establishing an advanced electrochemical platform for carcinogenic hydrazine determination. The DDA/Cit-AuNPs electrode demonstrated a linear determination range of 0.003–1 mM, limits of detection at 11 nM, and sensitivity of 1080 µA mM−1 cm−2. This study gives a complete picture of how AD chain lengths, SAM formation, Cit-AuNPs attachment, and electrocatalytic performance work together to make an advanced electrochemical sensing scaffold for environmental pollutants determination.