A General Route for Chemiluminescence of n-Type Au Nanocrystals

Abstract

The photoluminescence, electroluminescence, and electrochemiluminescence from nanocrystals (NCs) have been extensively exploited for both fundamental and applied investigation over two decades, while the understanding of chemiluminescence (CL) from NCs is still far from clear by now. Herein, a general route for triggering CL from NC luminophore is proposed by extensively exploiting the charge transfer between n-type NCs and oxidants. Oxidants, such as K2S2O8, H2O2, KMnO4, and NaClO, can chemically inject the hole onto the valence band (VB) of methionine-capped n-type AuNCs (Met@AuNCs) and enable the occurrence of efficient radiative-charge-recombination between the chemically injected exogenous VB hole and the pre-existed endogenous conduction band (CB) electron, which eventually results in single-color and defect-involved CL with the maximum emission wavelength around 824 nm. The CL of Met@AuNCs/oxidant is qualified for ultrasensitive CL immunoassay in a similar procedure to the biotin–avidin and magnetic separation involved commercial CL immunoassay and exhibits acceptable performance for linearly determining carcinoembryonic antigen from 50 pg/mL to 100 ng/mL with a limit of detection of 10 pg/mL (S/N = 3). This strategy provides a general route to develop nanoparticulate CL luminophores and might eventually enable CL multiplexing assay via extensively exploiting the CL of different wavebands.

Coreactant-free and Near-Infrared Electrochemiluminescence Immunoassay with n-Type Au Nanocrystals as Luminophores

“…The two PL peaks around 610 and 810 nm are related to band-gap-engineered and defect-induced PL, respectively . The optical nature of proposed Met@Au NCs is identical to previously reported Met@Au NCs obtained with a similar synthesis procedure . The HRTEM pattern indicates that Met@Au NCs are monodispersed with an average diameter around 3.5 nm (Figure B).…”

“…A linear relationship between the maximum coreactant-free ECL intensity and the logarithm of CEA concentration is obtained from 0.1 to 50 pg/mL ( R 2 = 0.993, inset of Figure A) with a limit of detection (LOD) of 0.03 pg/mL (S/N = 3). The LOD of coreactant-free ECL immunoassay is superior to that of CL immunoassay using the same Met@Au NCs as tags and other recently reported coreactant ECL biosensors. − …”

“…A linear relationship between the maximum coreactant-free ECL intensity and the logarithm of CEA concentration is obtained from 0.1 to 50 pg/mL (R 2 = 0.993, inset of Figure 5A) with a limit of detection (LOD) of 0.03 pg/mL (S/N = 3). The LOD of coreactant-free ECL immunoassay is superior to that of CL immunoassay using the same Met@Au NCs as tags 37 and other recently reported coreactant ECL biosensors. 48−50 According to Figure 5B, the existence of abundant interfering proteins in the CEA blank sample, such as 100 pg/mL AFP, 1 U/mL CA125, and 100 pg/mL PSA, fails to cause any obvious ECL response, while the sample containing both CEA and several coexisting interfering proteins can only cause a similar ECL response to the sample containing just CEA of the same concentration.…”

“…45 The optical nature of proposed Met@Au NCs is identical to previously reported Met@Au NCs obtained with a similar synthesis procedure. 37 The HRTEM pattern indicates that Met@Au NCs are monodispersed with an average diameter around 3.5 nm (Figure 1B). The Hall coefficient of Met@Au NCs is −38.36, indicating that the prepared Met@Au NCs are a kind of n-type NCs.…”

“…Recent investigation on the chemiluminescence (CL) of nanoparticles demonstrated that methionine-capped Au (Met@Au) NCs are a kind of n-type nanoparticles and can be chemically oxidized for direct CL . Inspired by the promising achievement on both CL and coreactant-free ECL from n-type nanoparticles, , herein, n-type Met@Au NCs are exploited as a kind of biocompatible luminophore for coreactant-free ECL beyond the eye-visible waveband, which are highly anticipated for spectrum-resolved ECL multiplexing with a more simplified operation procedure. , The coreactant-free ECL with the maximum emission wavelength around 824 nm and the maximum emission potential around +1.10 V (vs Ag/AgCl) of Met@Au NCs can be utilized for the ECL immunoassay, which exhibits improved performance than the CL immunoassay with the same Met@Au NCs as tags.…”