Optimising electrogenerated chemiluminescence of quantum dots via co-reactant selection

Abstract

We demonstrate that for quantum dot (QD) based electrochemiluminescence (ECL), the commonly used co-reactant does not perform as effectively as potassium persulfate. By exploiting this small change in co-reactant, ECL intensity can be enhanced dramatically in a cathodic-based ECL system. However, TPA remains the preferential co-reactant-based system for anodic ECL. This phenomenon can be rationalised through the relative energy-level profiles of the QD to the co-reactant in conjunction with the applied potential range. This work highlights the importance of understanding the co-reactant pathway for optimising the application of ECL to bioanalytical analysis, in particular for near-infrared (NIR) QDs which can be utilised for analysis in blood. Graphical Abstract Optimising ECL Production Through Careful Selection of Co-Reactions Based on Energetics Involved.

Keywords: Electroanalytical methods; Electrochemiluminescence; Quantum dots.

Graphical Abstract

Optimising ECL Production Through Careful Selection of Co-Reactions Based on Energetics Involved

Fig. 1

ECL response of an 800 nm QD/chitosan film in 1 mM TPA (red) and 1 mM K₂S₂O₈ (black) at a scan rate of 100 mV s⁻¹ over the potential range –2 ≤ ν ≤ 2 V vs. Ag/AgCl

Fig. 2

Emission profiles of 800 nm QDs from optically induced (red) and ECL (black) processes

Fig. 3

Energy level diagram for 800 nm CdSeTe/ZnS QDs based on their reductive and oxidative ECL onset potentials and HOMO–LUMO energy gap

Fig. 4

ECL response of 800 nm QD/chitosan film in 0.1 M PBS (red) + 1 mM Na₂C₂O₄ (blue) and + 1 mM TPA (black) at a scan rate of 100 mV s⁻¹ over the potential range 0.5 ≤ ν ≤ 1.6 V vs. Ag/AgCl

Fig. 5

ECL response of 800 nm QD/chitosan film in 0.1 M PBS (black), 1 mM H₂O₂ (blue) and 1 mM K₂S₂O₈ (red) at a scan rate of 100 mV s⁻¹ over the potential range −2 ≤ ν ≤ 0 V vs. Ag/AgCl

Fig. 6

ECL response of 800 nm QD/chitosan film with 1 mM K₂S₂O₈ (red), 1 mM H₂O₂ (blue), 1 mM TPA (black) and 1 mM Na₂C₂O₄ (purple) at a scan rate of 100 mV s⁻¹ over the potential range −2 ≤ ν ≤ 1.6 V vs. Ag/AgCl

Fig. 7

Maximum ECL intensity of 800 nm QD/chitosan film in a selection of co-reactant systems. The inset shows the lower response of H₂O₂ and Na₂C₂O₄ for clarity with the averaged results also shown

Fig. 8

ECL response of 800 nm QD/chitosan film with 1 mM H₂O₂ (red), 1 mM TPA (blue) and 1 mM Na₂C₂O₄ (black) at a scan rate of 100 mV s⁻¹ over the potential range −2 ≤ ν ≤ 1.6 V vs. Ag/AgCl

Fig. 9

Significant energy-level interactions and resulting ECL process of 800 nm QDs with H₂O₂ and K₂S₂O₈ co-reactants

Fig. 10

Significant energy-level interactions and resulting ECL process of 800 nm QDs with TPA and Na₂C₂O₄ co-reactants