Zinc-doping enhanced cadmium sulfide electrochemiluminescence behavior based on Au-Cu alloy nanocrystals quenching...

Novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated for insulin detection. Au-ZnCd₁₄S combined nitrogen doping mesoporous carbons (Au-ZnCd₁₄S/NH₂-NMCs) acted as sensing platform and Au-Cu alloy nanocrystals were employed as labels to quench the ECL of Au-ZnCd₁₄S/NH₂-NMCs. Zinc-doping promoted the ECL behavior of CdS nanocrystals, with the best ECL emission obtained when the molar ratio of Zn/Cd was 1:14. Simultaneously, the modification of gold nanoparticles (Au NPs) and combination with NH₂-NMC further enhanced the ECL emission of ZnCd₁₄S due to its excellent conductivity and large specific surface area, which is desirable for the immunosensor construction. Au-Cu alloy nanocrystals were employed in the ECL system of ZnCd₁₄S/K₂S₂O₈ triggering ECL quenching effects. The ECL spectra of ZnCd₁₄S, acting as the energy donor, exhibited well overlaps with the absorption band of Au-Cu alloy nanocrystals which acted as the energy acceptor, leading to an effective ECL resonance energy transfer (ECL-RET). On the basis of the ECL quenching effects, a sensitive ECL immunosensor for insulin detection was successfully constructed with a linear response range of insulin concentration from 0.1pg/mL to 30ng/mL and the limit of detection was calculated to be 0.03pg/mL (S/N = 3).