Adjustable Electrochemiluminescence from Highly Passivated CdTe/CdS Nanocrystals by Simple Surface Decoration with Counterions

Sulfur vacancy defects mediated CdZnTeS@BC heterojunction: Artificial intelligence-assisted self-enhanced electrochemiluminescence molecularly imprinted sensing of CTC

Environmental pollution caused by tetracycline antibiotics is a major concern of global public health. Here, a novel and portable molecularly imprinted electrochemiluminescence (MIECL) sensor based on smartphones for highly sensitive detection of chlortetracycline (CTC) has been successfully established. The high-performance ECL emitter of biomass carbon (BC) encapsulated CdZnTeS (CdZnTeS@BC) was successfully synthesized by hydrothermal. The enhanced ECL performance was ascribed to the introduction of the BC and increased the overall electrical conductivity of the nanoemitter, as well as increased the number of sulfur vacancies and doping on the surface of the emitter based on density functional theory calculations. An aniline-CTC molecular imprinted polymer was synthesized on the surface of the CdZnTeS@BC modified electrode by in-situ electropolymerization. The decrease in MIECL signal was attributed to the increase in impedance effect. The MIECL nanoplatform enabled a wide linear relationship in the range of 0.05-100 μmol/L with a detection limit of 0.029 μmol/L for spectrometer sensors. Interestingly, the light emitted during the MIECL reaction can be captured by a smartphone. Thus, machine learning was used to screen the photos that were taken, and color analysis was carried out on the screened photos by self-developed software, thus achieving a portable, convenient, and intelligent sensing mode. Finally, the sensor obtains satisfactory results in the detection of actual samples, with no significant differences from those of liquid chromatography.

Accurate Capture and Identification of Exosomes: Nanoarchitecture of the MXene Heterostructure/Engineered Lipid Layer

Recently, exosome detection has become an important breakthrough in clinical diagnosis. However, the effective capture and accurate identification of cancer exosomes in a complex biomatrix are still a tough task. Especially, the large size and non-conductivity of exosomes are not conducive to highly sensitive electrochemical or electrochemiluminescence (ECL) detection. Therefore, we have developed a Ti₃C₂T_x-Bi₂S_3-x heterostructure/engineered lipid layer-based nanoarchitecture to overcome the limitations. The engineered lipid layer not only specifically captured and efficiently fused CD63 positive exosomes but also showed excellent antifouling property in the biological matrix. Moreover, the MUC1 aptamer-modified Ti₃C₂T_x-Bi₂S_3-x heterostructure further identified and covered the gastric cancer exosomes that have been trapped in the engineered lipid layer. In the self-luminous Faraday cage-type sensing system, the Ti₃C₂T_x-Bi₂S_3-x heterostructure with sulfur vacancies extended the outer Helmholtz plane and amplified the ECL signal. Therefore, this sensor can be used to detect tumor exosomes in ascites of cancer patients without additional purification. It provides a new pathway to detect exosomes and other large-sized vesicles with high sensitivity.

An electrochemiluminescence aptasensor based on highly luminescent silver-based MOF and biotin-streptavidin system for mercury ion detection

In this study, for the first time, a silver-based metal-organic framework (Ag-MOF) was synthesized and used as the electrochemiluminescence (ECL) emitter for building an ECL sensor. After modification with chitosan (CS) and gold nanoparticles (Au NPs), the ECL stability of Ag-MOF was improved. To detect mercury ions, a biosensor was constructed using the mercury ion aptamer and steric effect of streptavidin. First, the capture strand (cDNA) with terminal-modified sulfhydryl group was attached to the electrode surface by the Au-S bond. Then, the mercury-ion aptamer (Apt-Hg) modified with biotin was anchored to the electrode by complementary pairing with cDNA. Streptavidin (SA) could be fixed on the electrode by linking with biotin, thereby reducing the ECL signal. However, in the presence of mercury ions, the aptamer was removed and streptavidin could not be immobilized on the electrode. Hence, the ECL signal of the sensor increased with the concentration of mercury ions, which was linear in the range from 1 μM to 300 fM. The detection limit could reach 66 fM (S/N = 3). The sensor provided a new method for the detection of mercury ions.

Highly Efficient Electrochemiluminescence of MnS:CdS@ZnS Core-Shell Quantum Dots for Ultrasensitive Detection of MicroRNA

In this work, a novel electrochemiluminescence (ECL) biosensor was developed for ultrasensitive detection of microRNA let-7a (miRNA let-7a) based on MnS:CdS@ZnS core-shell quantum dots (QDs) as ECL luminophores with high ECL efficiency. Impressively, compared to the CdS:Mn@ZnS QDs prepared by ionic doping with ECL efficiency of 0.87%, MnS:CdS@ZnS QDs synthesized by bimetallic clusters (Cd₂Mn₂O₄) doping exhibited high ECL efficiency of up to 15.84% with S₂O₈^2- as cathodic coreactant due to the elimination of the dopants size mismatch and "self-purification" effect, which could achieve the surface defect passivation of MnS:CdS@ZnS QDs for effectively improving the ECL emission. Furthermore, with the help of strand displacement amplification (SDA), the trace target miRNA let-7a was able to be converted to a number of output DNA labeled with ferrocene (Fc) to construct an ultrasensitive ECL biosensor. The well-designed ECL biosensor for miRNA let-7a exhibited high stability and excellent sensitivity of a concentration variation from 10 aM to 1 nM and a low detection limit of 4.1 aM, which was further applied to the analysis of miRNA let-7a from cancer cell (MCF-7) lysate. Thus, this strategy provides a novel method to prepare high-efficient ECL emitters for the construction of ECL biosensing platforms in biological fields and clinical diagnosis.

Polarization-Resolved Electrochemiluminescence Sensor Based on the Surface Plasmon Coupling Effect of a Au Nanotriangle-Patterned Structure

This work focused on the construction of a nanomaterial-patterned structure for high-resolved ECL signal modulation. Due to the surface coupling effect, the different shapes and distribution states of surface plasmonic nanomaterials not only affect the luminescence intensity enhancement but also decide the electrochemiluminescence (ECL) polarization characteristics. Herein, tin disulfide quantum dots were synthesized via a solvothermal method as ECL emitters. Compared with other nanostructures, Au nanotriangle (Au NT) displayed both the localized surface plasmon resonance electromagnetic enhancement effect and the tip amplification effect, which had significant hot spot regions at three sharp tips. Therefore, self-assembled Au NT-based patterned structures with high density and uniform hot spots were constructed as ideal surface plasmonic materials. More importantly, the distribution states of the hot spots affect the polarization characteristics of ECL, resulting in directional ECL emission at different angles. As a result, a polarization-resolved ECL biosensor was designed to detect miRNA 221. Moreover, this polarization-resolved biosensor achieved good quantitative detection in the linear range of 1 fM to 1 nM and showed satisfactory results in the analysis of the triple-negative breast cancer patients' serum.

Recent Progress of Novel Electrochemiluminescence Nanoprobes and Their Analytical Applications

High-performance nanomaterials have been seen as a new generation of electrochemiluminescence (ECL) probes or emitters for their finely tunable structure and concomitant remarkable properties, guaranteeing the prospective applications in the analysis and diagnosis devices with superior performances. The structure-activity relationships of ECL nanoprobes in nanoscale are presenting milestone in understanding of the ECL microscopic behaviors and mechanisms, and guide the exploitation of novel ECL probes. In this mini-review, we summarized the recent development of novel ECL probes based on the nanomaterials. The mechanism and relationships between their structure as well as the active sites and functionality were revealed. In addition, the design and regulation of the ECL nanoprobes were emphasized for the biosensing and imaging application. Finally, the potential prospect of the ECL nanoprobes, design, and their applications were discussed.

Electrochemically Lighting Up Luminophores at Similar Low Triggering Potentials with Mechanistic Insights

Electrochemiluminescence (ECL) with high electrode compatibility and less electrochemical interference has conventionally been envisioned by lowering the oxidative potential of luminophores and/or screening luminophores with a low oxidative potential. Herein, an alternative was developed by employing the environmental-friendly carbohydrazide as a coreactant, which enabled serial luminophores with oxidative-reduction ECL at one similar low triggering potential around 0.55 V versus Ag/AgCl, including Ru(bpy)₃²⁺ as well as CdTe, CdSe, CuInS₂/ZnS, and Au nanocrystals. Because the eight-electron releasing process of carbohydrazide was electrochemically triggered at ∼0.25 V versus Ag/AgCl, the radicals generated via electrochemical oxidation of carbohydrazide could reduce the luminophores at a much lower potential than those of traditional coreactants. All the luminophore/carbohydrazide systems exhibited one ECL process around 0.55 V, which was about 0.65 V lower than that of a traditional Ru(bpy)₃²⁺/tri-n-propylamine system (typically around +1.2 V), and even lower than the oxidative potential of some luminophores. The ECL of the luminophore/carbohydrazide system was spectrally close to that of the corresponding luminophore/tri-n-propylamine system; the maximum emission wavelength of the low triggering potential ECL could shift from 540 to 783 nm via the selection of luminophores in this case. The coreactant screening strategy would be a favorable addition to the expected luminophore screening strategy for achieving enhanced ECL performance. This work created an avenue toward a deeper understanding of the ECL mechanism.

Novel Ru(bpy)2(cpaphen)2+/TPrA/TiO2 Ternary ECL System: An Efficient Platform for the Detection of Glutathione with Mn2+ as Substitute Target

A sensitive electrochemiluminescence (ECL) biosensor was developed for glutathione (GSH) detection based on a novel Ru(bpy)₂(cpaphen)²⁺/TPrA/TiO₂ ternary ECL system with Mn²⁺ as substitute target for signal amplification. Specifically, the TiO₂ nanoneedles (TiO₂ NNs) were used as the coreaction accelerator for the first time to promote the oxidation process of coreactant tripropylamine (TPrA) in the anode and significantly increase the ECL signal of Ru(bpy)₂(cpaphen)²⁺ for an amplified initial signal. Meanwhile, a novel target conversion strategy for GSH was developed by reducing MnO₂ nanosheets to Mn²⁺ as a substitute target, which played the role of a coenzyme factor for cleaving DNA double strands intercalated with Ru(bpy)₂(cpaphen)²⁺ to markedly weaken initial signal. As a result, the novel "on-off" biosensor achieved a sensitive detection of GSH range from 5 μM to 215 μM with a detection limit of 0.33 μM. Importantly, the proposed strategy enriched the application of Ru complex and TPrA ECL system in bioanalytical applications, and provided a new signal amplification strategy for bioactive small molecules.

Tunable Electron-Injection Channels of Heterostructured ZnSe@CdTe Nanocrystals for Surface-Chemistry-Involved Electrochemiluminescence

Tunable charge transfer in and out of nanocrystals (NCs) is crucial to their profound light-emitting applications. Herein a convenient strategy toward tunable electron-injection channels of NCs was achieved by partially coating highly passivated CdTe NCs with unperfected ZnSe shell. Potential- and spectrum-resolved electrochemiluminescence (ECL) characterizations proved that radiative charge recombination for ECL of the heterostructured ZnSe@CdTe NCs only occurred within CdTe core, whereas configurational ions in ECL solution could electrostatically or chemically change the surface states of both the ZnSe shell and the uncoated CdTe core, resulting in tunable electron-injection channels for ECL of ZnSe@CdTe NCs. S^2- anion postponed the electron-injection channel for ECL of ZnSe@CdTe NCs from -1.44 to -1.58 V, Zn²⁺ cation presented two electron-injection channels for ECL at -1.53 and -1.22 V, respectively, whereas Cd²⁺ cation enabled three electron-injection channels for ECL at -1.53, -1.18, and -0.95 V, respectively. The "valve"-like role of configurational ions on the electron-injection channels of ZnSe@CdTe NCs is promising to design novel electrochemiluminophores.