High-Sensitivity Electrochemiluminescence Biosensor Based on Silver-Carbon Nitride for the Detection of Dopamine utilizing Enhancement Effects

TiO2 nanoparticles modified graphitic carbon nitride with potential-resolved multicolor electrochemiluminescence and application for sensitive sensing of rutin

Recently, nanocomposites with potential-resolved multicolor electrochemiluminescence (ECL) property have attracted new research interests. Herein, TiO₂ nanoparticles modified graphitic carbon nitride (TiO₂-NPs/g-C₃N₄) with inherent potential-resolved multicolor ECL emission was prepared via a simple synthesis method. The morphology and chemical composition of the synthesized TiO₂-NPs/g-C₃N₄ were characterized. The obtained TiO₂-NPs/g-C₃N₄ exhibited dual-peak multicolor ECL emission under cyclic voltammetry scanning by using K₂S₂O₈ as co-reagent. The first ECL peak (ECL-1) is composed of turquoise blue ECL emission (471 nm) located at -1.3 V and olive green ECL emission (490 nm) ranging from -1.4 to -2.0 V. The second ECL peak (ECL-2) is composed of navy blue ECL emission (458 nm) located at -3.0 V. The ECL mechanism for the potential-resolved multicolor ECL emission was proposed. Furthermore, the first ECL imaging sensing method was fabricated for the sensitive quantitative detection of rutin based on the effective quenching effect of rutin on the ECL of TiO₂-NPs/g-C₃N₄. The linear response range is 0.005-400 µM with detection limit as low as 2 nM. This work presents a simple way to prepare g-C₃N₄-based nanocomposites with potential-resolved multicolor ECL, which broadens the potential applications of g-C₃N₄-based nanocomposites for ECL imaging sensing and light-emitting devices.

A dual-recognition MIP-ECL sensor based on boric acid functional carbon dots for detection of dopamine

We report a molecularly imprinted polymer electrochemiluminescence (MIP-ECL) sensor with dual recognition effects on dopamine (DA). Boric-acid-functionalized carbon dots (B-CDs) with good ECL performance at - 2.0 V (vs. Ag/AgCl) were prepared and immobilized on a glassy carbon electrode (GCE). The MIP was then introduced via electropolymerization using o-phenylenediamine (OPD) as a functional monomer and DA as a template molecule to fabricate the MIP-ECL sensor. The cavities in the MIP after elution were used to capture the target molecular DA. The affinity of boric acid of B-CDs to the cis-diol of DA, as well as the special recognition of MIP, provides dual recognition effects on DA. The selective readsorption of DA onto the sensor leads to the ECL quenching of B-CDs. The quenching effect was used to detect DA from 1.0 × 10^-9 to 1.0 × 10^-5 mol·L^-1 with a detection limit of 2.1 × 10^-10 mol·L^-1. The dual recognition caused the MIP-ECL sensor exhibiting excellent selectivity and sensitivity toward  DA. The sensor was successfully used to determine DA in real samples.

O-Fluorobenzoic Acid-Mediated Construction of Porous Graphitic Carbon Nitride with Nitrogen Defects for Multicolor Electrochemiluminescence Imaging Sensing

Graphitic carbon nitride (g-CN) is an attractive electrochemiluminescence (ECL) luminophore. However, g-CN with wavelength-tunable ECL emission is still limited, which limits its application in multicolor ECL sensing and imaging analysis. In this study, porous g-CN (PCN) with nitrogen defects was synthesized through the condensation of melamine by using o-fluorobenzoic acid (o-FBA) as an effective regulation reagent. A series of PCNs, including PCN-5%, PCN-10%, and PCN-30%, were obtained by changing the mass ratio of o-FBA and melamine. The porous structure and tunable chemical composition change of the PCNs were carefully characterized. The nitrogen defects and porous structure of the synthesized PCNs can enlarge the specific surface area, facilitate electron transfer, and generate various surface states with gradually changed energy bands, leading to wavelength-tunable multicolor ECL emissions. Accordingly, g-CN, PCN-5%, PCN-10%, and PCN-30% can generate navy blue, turquoise blue, turquoise green, and olive green ECL emissions, respectively, with the peak ECL wavelength varied from 465 to 550 nm. Then, a multicolor ECL sensing array was proposed for the discrimination of polyphenols based on the prepared g-CN and PCNs by using a smartphone as a portable detector for the first time. Five polyphenol substances including vitamin P, resveratrol, phloretin, phlorizin, and caffeic acid were discriminated by using principal component analysis and hierarchical cluster analysis. The present work provides a simple strategy to adjust the ECL wavelength of g-CN and presents a simple way to fabricate multicolor ECL sensing array, which has great application potential for multiplexed analysis and multicolor ECL imaging sensing.

Single-step microwave synthesis of a novel ternary nanocomposite as an efficient luminophore and boron nitride quantum dots as a new coreactant for a cathodic ECL monitoring of chlorpyrifos

In this study, a novel and innovative enzyme-free electrochemiluminescence (ECL) pesticide probe based on a ternary nanocomposite, CuS/CQDs/g-C₃N₄NS, was demonstrated for the accurate monitoring of chlorpyrifos. Boron nitride quantum dots were introduced as a new and effective coreactant in comparison with other coreactants, such as hydrogen peroxide, peroxydisulfate, and tripropylamine, in the negative potential range for the first time. The nanocomposite as a promoted luminophore was synthesized by a one-pot microwave route. Carbon quantum dots and copper sulfide nanostructures were truly incorporated on the porous graphitized carbon nitride, which displayed a good cooperative effect on the signal improvement. CuS as a co-reaction accelerator and CQDs with a superior luminescence effect produced more radical species, and thus, the ECL signal was amplified. Upon increasing the appropriate concentration of this coreactant in electrolyte media, the signal intensity of the nanocomposite increases. A low detection limit of 3.0 × 10^-16 M and a wide range from 2.0 × 10^-15 to 7.0 × 10^-9 M were gained. Also, the fabricated pesticide sensor presented excellent repeatability for 20 consecutive optical signals, with a RSD of about 1.4%. Owing to its high proficiency, the developed sensor was applied as a new probe for chlorpyrifos analysis in water and fruit samples.