Beyond templates: exploring uncharted territory in anisotropic gold nanostructure-oligomer composites synthesis and electrocatalytic performance towards environmental pollutants

Abstract

The synthesis of polymer/oligomer-stabilized metal nanostructures (MNS) opens up a wide range of possibilities, from fundamental materials science to practical applications in domains such as medicine, catalysis, sensing, and energy. Because of the versatility of this synthetic approach, it is a dynamic and ever-changing field of study. These polymers/oligomers have precise control over the nucleation and growth kinetics, allowing the production of mono-disperse MNS with well-defined properties. The protective coating provided by polymers or oligomers increased the stability and colloidal dispersity of MNS in these oligomer-MNS composites. As a result, the current research reports the electrocatalytic reduction of nitrobenzene (NB) utilizing oligomeric aminomercaptotriazole (oligo AMTa) and oligo (AMTa-AuNS) modified glassy carbon (GC) electrodes developed via a wet chemical technique. UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), high resolution mass spectroscopy (HR-MS), and high-resolution transmission electron microscopy (HR-TEM) approaches were used to confirm the development of oligomer and AuNS. After that, the GC electrode was directly linked to the oligo AMTa and oligo AMTa-AuNS by dipping them in the appropriate solutions. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cycle voltammetry (CV) were all employed to confirm the fabrication of oligo AMTa and oligo AMTa-AuNS. Eventually, the electrochemical reduction of NB occurred using the fabricated electrodes. The catalytic activity of oligo AMTa-AuNS has been observed to be more than that of the other modified electrode. As an outcome, the film was employed to determine the sensitivity level of NB, and a limit of detection (LOD) of 2.8 nM was found. The straight-forward method's practical utility was proven by measuring NB in lake sample water.

Scheme 1. Synthetic strategy of (A) oligo AMTa and (B) oligo AMTa-AuNS by wet chemical method.

Fig. 1. UV-visible spectra of (A) AMTa, (B) oligo AMTa and (C) oligo AMTa-AuNS solutions.

Fig. 2. XPS spectra of powder oligo AMTa-AuNS: (a) C 1s, (b) N 1s, (c) O 1s, (d) S 2p and (e) Au 4f regions.

Fig. 3. TEM images of oligo AMTa (a–c) and oligo AMTa-AuNS (d–f).

Fig. 4. HR-TEM images for (a–c) controlled shapes of anisotropic oligo AMTa-AuNS synthesized by 500 μL AMTa addition at 80 °C reaction temperature and (d–i) HR-TEM images of magnified view of (d) triangle, (e) rod, (f) pyramid, (g) hexagonal (h) spherical and (i) boat shaped anisotropic oligo AMTa-AuNS.

Fig. 5. HR-TEM images uncontrolled growth of anisotropic oligo AMTa-AuNS synthesized by (a and b) 1 mL AMTa at 80 °C, (c and d) 2 mL AMTa at 80 °C, (e and f) 500 μL AMTa at 60 °C, (g and h) 500 μL AMTa at 100 °C and (i and j) pure AuNPs.

Fig. 6. HR-MS of (a) oligo AMTa and (b) oligo AMTa-AuNS.

Fig. 7. A Nyquist plot for (a) unmodified GC, (b) GC/oligo AMTa, and (c) GC/oligo AMTa-AuNS electrodes in 1 mM K₃[Fe(CN)₆]/K₄[Fe(CN)₆] containing 0.2 M PB solution (pH 7.2) at scanning frequencies from 0.01 to 100 000 Hz.

Fig. 8. CVs obtained for (a) GC/oligo AMTa-AuNS electrode in the absence of NB and (b) unmodified GC, (c) GC/oligo AMTa, (d) GC/AuNPs and (e) GC/oligo AMTa-AuNS electrodes (solid line: first cycle and dotted line: after five cycle) in the presence of 0.5 mM NB containing 0.2 M PB solution (pH 7.2) at a scan rate of 50 mV s⁻¹.

Fig. 9. DPVs obtained for each increment (curves b–o) of 100 nM NB at GC/oligo AMTa-AuNS electrode in 0.2 M PB solution (pH 7.2). (a) GC/oligo AMTa-AuNS electrode in the absence of NB. (Inset): Plot of current vs. concentration of NB.