Biology

Electrochemiluminescence

Biomedical engineering

Materials science

Chromatography

Biocompatible material

Infrared

Nanoclusters

Biochemistry

Immunoassay

Biosensor

Immunology

Combinatorial chemistry

Physics

Luminophore

Nanotechnology

Organic chemistry

Luminescent Measurements

Optics

Analyte

Luminescence

Analytical Chemistry (journal)

Triethanolamine

Medicine

Chemistry

Detection limit

Antibody

Optoelectronics

Analytical Chemistry

The design and development of novel electrochemiluminescence (ECL) systems with near-infrared (NIR) emission beyond 800 nm are promising for ECL evolution, especially for improving the throughput of the spectrum-resolved multiplexing ECL assay and biological imaging. Herein a biocompatible and environmentally friendly luminophore, that is, the methionine-stabilized Au nanoclusters (Met-Au NCs), are proposed to achieve efficient aqueous ECL of ∼835 nm with triethanolamine as coreactant. The Met-Au NCs not only demonstrate a 75 times enhanced ECL compared with the traditional Au NCs with bovine serum albumin as a capping agent but also can be employed as ECL tags to label proteins with a methionine linker and enable a highly sensitive NIR ECL bioassay. A sandwich-type NIR ECL immunosensor is constructed with the Met-Au NCs as tags and α-fetoprotein (AFP) as a model analyte and exhibits a wide linearity range from 3 fg·mL–1 to 0.1 ng·mL–1 with a limit of detection of 1 fg mL–1 (S/N = 3) as well as desired selectivity.

Near-Infrared Electrochemiluminescence Immunoassay with Biocompatible Au Nanoclusters as Tags