Although graphite phase carbon nitride
quantum dots (GCN QDs) showed
some advantages in the electrochemiluminescence (ECL) analytical research,
the low ECL efficiency limited the potential sensing application.
Herein, we synthesized sulfur-doped graphite phase carbon nitride
quantum dots (S-GCN QDs) to fabricate a sandwich sensor based on amplified
surface plasmon coupling ECL (SPC-ECL) mode. Sulfur doping can change
the surface states of QDs effectively and produced new element vacancy.
As a result, the ECL efficiency of S-GCN QDs was 2.5× over GCN
QDs. Furthermore, compared with the big gap between the ECL peak of
GCN QDs (620 nm) and the absorption peak of Au NPs, the doped sulfur
elements in S-GCN QDs generated new ECL emission peaks at 555 nm,
which was closed to the absorption peak of Au NPs at 530 nm. Due to
the wavelength-dependent surface plasmon coupling effect, the ECL
peak of S-GCN QDs at 555 nm had greater amplitude of enhancement in
the sensing system. The proposed biosensor can quantify the K-RAS
gene from 50 fM to 1 nM with a limit of detection (LOD) of 16 fM.
We were the first to provide insight into the role of wavelength-dependent
surface plasmon coupling in enhancing the sensitivity of ECL biosensor.
Because boron nitride
quantum dots (BN QDs) have a wider gap (5.0–6.0
eV) than other QDs, the edge configurations, chemical functionalities,
and heteroatom dopants can decrease and regulate the band gap of BN
QDs, thereby ameliorating the QDs’ properties. Now, the precise
control and regulation of BN QDs are still at an early stage and is
a challenging task. Therefore, we used thiourea and l-cysteine
as different sulfur precursors to regulate the BN QDs’ optoelectronic
properties in this study. It is interesting that two kinds of S-regulated
BN QDs present significantly different electrochemiluminescence (ECL)
properties and electro-optical activity. Furthermore, a ratiometric
and enzyme-free ECL sensing mode is constructed with the amplified
surface plasmon coupled-ECL (SPC-ECL) strategy. The proposed DNA sensor
can quantify the BRAF gene from 1 pmol/L to 1.5 nmol/L with a limit
of detection (LOD) of 0.3 pmol/L. The change of BN QDs’ ECL
signal was easily observed with a smartphone camera. This work for
the first time provides insight into the role of sulfur regulation
in enhancing ECL efficiency and the electro-optical activity of BN
QDs.
A novel multiplex electrochemiluminescence (ECL) polarization assay was developed to detect breast cancer-related genes BRCA1 and BRCA2 simultaneously based on the polarization characteristics of surface plasmon-coupled electrochemiluminescence (SPC-ECL). In this work, boron nitride quantum dots (BN QDs) were used as ECL emitters, and gold nanoparticles (Au NPs) and gold-coated silver nanoparticles (Ag@Au NPs) were employed as surface plasmon materials. The surface plasmon coupling resonance of different metal NPs not only enhanced the ECL intensity but also converted the isotropic emission into directional emission. This study revealed the relation between the structure of metal nanomaterials and SPC-ECL, and a high polarization-resolved sensing system was designed to detect multitarget DNA from 100 aM to 1 nM simultaneously. Polarizationbased multiple ECL analysis has broad prospects in related cancer diagnosis and treatment evaluation.
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