A label-free electrochemiluminescence immunosensor based on KNbO3–Au nanoparticles@Bi2S3 for the detection of prostate specific antigen

A high sensitive label-free electrochemiluminescence (ECL) immunosensor was fabricated for the detection of prostate specific antigen (PSA) based on potassium niobate-Au nanoparticles@bismuth sulfide (KNbO 3 –Au NPs@Bi 2 S 3 ) modified glassy carbon electrode (GCE). The prepared Bi 2 S 3 nanosheets exhibited strong and stable cathodic ECL activity. The synthesized KNbO 3 –Au NPs was firstly used to fabricate ECL modified electrodes and Bi 2 S 3 nanosheets worked as luminophores for the first time in ECL sensors. Au NPs were used to combine with Bi 2 S 3 and anti-PSA via the Au–S covalent bond and Au–NH 2 covalent bond without the usage of crosslinking agents respectively, further enhancing the sensitivity and stability of immunosensor. Under the optimum experimental conditions, the ECL signal of KNbO 3 –Au NPs@Bi 2 S 3 linearly decreased with the increase of PSA concentration in the range of 0.005–5   ng/mL with a detection limit of 3   pg/mL. The preparated label-free ECL immunosensor exhibited high sensitivity and selectivity, good repeatability and long-term stability. The applicability of the proposed ECL immunosensor was also evaluated by detecting PSA in real samples.