Enhanced Electrochemiluminescence Intensity Research Articles

Ultrasensitive detection of microRNA-21 based on plasmon-coupling-induced electrochemiluminescence enhancement

Noble metal nanoparticles possess excellent optical and electrical properties, and have been widely used in the construction of biosensors and in surface-enhanced spectroscopy. Herein, we describe an enzyme-assisted ultra-sensitive biosensor with gold nanoparticle (GNP) dimers, based on a localized surface plasmon resonance (LSPR)-enhanced electrochemiluminescence (ECL) mechanism. CdS nanocrystals (NCs) acted as ECL emitters, and the GNP dimers were constructed by hybridization of DNA strands on the surface of an electrode modified with CdS NCs after an enzyme-assisted cyclic amplification process. The plasmon-coupling-induced electromagnetic field enhancement effects of the GNP dimers resulted in an increase in ECL intensity of as much as 6.3-fold under optimized conditions. Based on this LSPR-ECL sensor platform, the detection limit for microRNA-21 is as low as 3.6 fM with a wide linear range from 10 fM to 20 pM with good sensitivity and selectivity.

MoS2 quantum dots-combined zirconium-metalloporphyrin frameworks: Synergistic effect on electron transfer and application for bioassay

In this study, 2D-MoS2 quantum dots (MQDs) were combined with the zirconium based porphyrinic metal-organic framework (MOF-545-Zn) through simple ultrasonic method for the purpose of the enhanced electrochemiluminescence (ECL). In addition, electrochemiluminescence (ECL), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to investigate the synergistic effect on electron transfer of the composite. MQD loading with confined orientation on the surface of MOF-545-Zn was confirmed by morphology and spectroscopy. Moreover, from hybrids material, the higher ECL intensity was received. MOF-545-Zn@MQDs was functionalized by alpha lipoic acid (LA) and was further applied to develop a novel ECL immunosensors for carcinoembryonic antigen (CEA).

A novel amplified electrochemiluminescence biosensor based on Au NPs@PDA@CuInZnS QDs nanocomposites for ultrasensitive detection of p53 gene

In this work, a novel surface plasmon resonance (SPR) enhanced electrochemiluminescence (ECL) biosensing model was first designed based on Au NPs@polydopamine (PDA)@CuInZnS QDs nanocomposite. Au NPs were coated with the PDA layer via the electrostatic force. CuInZnS QDs were bound on the surface of Au NPs@PDA nanocomposite. CuInZnS QDs worked as ECL luminophore in the sensing application. PDA shell not only controlled the separation length between Au NPs and QDs to induce SPR enhanced ECL response, but also limited the potential charge transfer and ECL quenching effect. As a result, the nanocomposite ECL intensity was twice that of QDs with K2S2O8. The tumor suppressor p53 gene was detected in the amplified ECL sensing system. The sensing method has a linear response in the range of 0.1 nmol/L to 15 nmol/L with a detection limit of 0.03 nmol/L. The DNA biosensor based on the nanocomposite showed excellent sensitivity, selectivity, reproducibility and stability and was applied in spiked human serum samples with satisfactory results.

Aggregation-Induced Enhanced Electrochemiluminescence from Organic Nanoparticles of Donor-Acceptor Based Coumarin Derivatives.

Organic nanoparticles (NPs) from donor-acceptor based coumarin derivatives, 6-[4-(N,N-diphenylamino)phenyl]-3-ethoxycarbonyl coumarin (DPA-CM), with an average size of 5.82 nm, were synthesized by a facile reprecipitation method using water as a poor solvent and tetrahydrofuran as a good solvent. Red-shifted absorption, blue-shifted photoluminescence emission, and aggregation-induced enhanced electrochemiluminescence (ECL) emission were observed for the DPA-CM NPs in aqueous solution compared with the original DPA-CM in organic solution. The aggregation-induced enhanced ECL emission is ascribed to the combined effects of the small size of the DPA-CM NPs, the restricted conformational relaxation in the NPs, and the good stability of the cationic radical of DPA-CM. A strong and stable ECL emission is obtained at the DPA-CM NPs modified glassy carbon electrode in the presence of tri-n-propylamine, and the ECL intensity of the DPA-CM NPs modified electrode is quenched linearly in the range of 0.05-50 μM with detection limit of 0.04, 0.2, and 0.4 μM for ascorbic acid, uric acid, and dopamine, respectively. This work shows an example of donor-acceptor based organic NPs as ECL emitters and their analytical applications to monitor biomolecules.

Ultrasensitive determination of 2,4,6-trinitrotoluene by exploiting the strongly enhanced electrochemiluminescence of an assembly between CdSe and graphene quantum dots and its quenching by TNT

The authors describe an electrochemiluminescence (ECL) assay for the determination of 2,4,6-trinitrotoluene (TNT) in soil. It is based on the finding that graphene quantum dots (GQDs) strongly enhance the ECL of CdSe quantum dots (CdSe QDs), and ECL is strongly quenched by TNT. In order to assemble the GQDs and CdSe QDs, the latter were functionalized with carboxy groups and then coupled to amino-functionalized GQDs (afGQDs). The resulting CdSe-GQDs conjugation was placed as a thin film on a glassy carbon electrode (GCE). The modified electrode displays an about 8-fold enhanced ECL intensity compared to an GCE with CdSe QDs only, and the onset potential of the ECL reaction is positively shifted by 140 mV. In the presence of TNT, the ECL is quenched due to the formation of the TNT-amine complex. The decrease in ECL intensity is related to the logarithm of the TNT concentration in the range from 0.01 to 100 ppb, with a detection limit as low as 3 ppt. The results of TNT assays in (spiked) soil samples showed recoveries between 99.2 and 105.0 % and relative standard deviations between 3.0 and 8.2 %. This strategy offers a new perspective for developing ECL assays based on the use of semiconductor nanoparticles and graphene-based nanomaterials.

A triple-amplification SPR electrochemiluminescence assay for chloramphenicol based on polymer enzyme-linked nanotracers and exonuclease-assisted target recycling

The present study aimed to explore a novel triple-amplification electrochemiluminescence (ECL) assay for detecting of chloramphenicol (CAP). This strategy was based on single-stranded DNA-binding protein (SSB) and horseradish peroxidase (HRP) enzyme-linked polymer (EnVision reagent, EV) labeled on Au nanoparticles (EV–Au–SSB) as nanotracer and exonuclease-assisted target recycling. The composite probes were prepared via immunoreactions between the CdS nanocrystal (CdS NC)-functionalized partial complementary DNA and aptamer (CdSNCs/Apt-ssDNA1) as capture probes, and EV–Au–SSB as nanotracer. When the composite probe solution co-existed with CAP and Exo I, the aptamer on the capture probes preferentially combined with CAP, and then CAP–Apt and nanotracer complex were released into the solution. Subsequently, Exo I in the solution could further digest the CAP–Apt from the 3′-end of the aptamer and release CAP, which could participate in further reaction with the probes. It was worth mentioning that EV contained a large number of HRPs on its dendritic chain. In the EV–Au–SSB, Au could enhance ECL intensity of CdS NCs by surface plasmon resonance. What's more, HRPs on EV could catalyze the reaction of H2O2, which could obviously enhance ECL intensity of CdS NCs. This study demonstrated excellent performance of the triple-amplification ECL assay, which makes this aptasensor system suitable and promising for the practical application of CAP residues in fish samples. Moreover, the assay might provide a promising avenue to develop efficient aptasensors to determine small-molecule harmful substances in environmental monitoring and food safety.

Label-free electrochemiluminescence biosensor for ultrasensitive detection of telomerase activity in HeLa cells based on extension reaction and intercalation of Ru(phen)3 (2.).

Telomerase is one of the most common markers of human malignant tumors, such as uterine, stomach, esophageal, breast, colorectal, laryngeal squamous cell, thyroid, bladder, and so on. It is necessary to develop some sensitive but convenient detection methods for telomerase activity determination. In this study, a label-free and ultrasensitive electrochemiluminescence (ECL) biosensor has been fabricated to detect the activity of telomerase extracted from HeLa cells. Thiolated telomerase substrate (TS) primer was immobilized on the gold electrode surface through gold-sulfur (Au-S) interaction and then elongated by telomerase specifically. Then, it was hybridized with complementary DNA to form double-stranded DNA (dsDNA) fragments on the electrode surface, and Ru(phen)3 (2+) has been intercalated into the dsDNA grooves to act as the ECL probe. The enhanced ECL intensity has a linear relationship with the number of HeLa cells in the range of 5∼5000 and with a detection limit of 2 HeLa cells. The proposed ECL biosensor has high specificity to telomerase in the presence of common interferents. The relative standard deviations (RSDs) were <5% at 100 HeLa cells. The proposed method provides a convenient approach for telomerase-related cancer screening or diagnosis.

Ultrasensitive Cytosensor Based on Self-Enhanced Electrochemiluminescent Ruthenium-Silica Composite Nanoparticles for Efficient Drug Screening with Cell Apoptosis Monitoring.

The self-enhanced electrochemiluminescence (ECL) with high sensitivity could be an effective method for anticancer drug screening with cell apoptosis monitoring. Here we reported an ultrasensitive ECL cytosensor for cell apoptosis monitoring by using self-enhanced electrochemiluminescent ruthenium-silica composite nanoparticles (Ru-N-SiNPs) labeled annexin V as signal probes. The Ru-N-SiNPs were first synthesized through simple hydrolysis of a novel precursor containing luminescent and intracoreactant groups in one molecule, which presented higher emission efficiency and enhanced ECL intensity due to the shorter electron-transfer path and less energy loss. Moreover, the as-proposed ECL cytosensor was successfully used to investigate efficiency of paclitaxel toward MDA-MB-231 breast cancer cell in the range from 1 nM to 200 nM with a detection limit of 0.3 nM and a correlation coefficient of 0.9917. The improved accuracy and excellent dynamic range revealed the potential applications in biomolecules diagnostics and cells detections, especially in living and complex systems.

One-step preparation of disposable multi-functionalized g-C3N4 based electrochemiluminescence immunosensor for the detection of CA125

A novel, disposable and label-free electrochemiluminescence (ECL) immunosensor, based on multi-functionalized graphitic carbon nitride (g-C3N4) coated on the one-off screen-printed carbon electrodes (SPCEs), for the detection of tumor marker carbohydrate antigen 125 (CA125) was developed. The multi-functionalized g-C3N4 was prepared with amino-coated Fe3O4 nanoparticles and CA125 antibody (anti-CA125) chemically bound to the surface of carboxylated g-C3N4 simultaneously. The Fe3O4 nanoparticles ensured the presence of multi-functionalized g-C3N4 in the outer Helmholtz plane (OHP) of the ECL immunosensor and even becoming part of the electrode surface. This assembly promoted the electron transfer between g-C3N4 and the electrode resulting in greatly enhanced ECL intensity. The CA125 was selectively captured by anti-CA125 leading to effective inhibition of the ECL signal. Under optimal conditions, this disposable ECL immunosensor exhibited a wide dynamic linear detection range for CA125 (0.001–5U/mL) with a lower detection limit of 0.4mU/mL, providing high sensitivity. In addition, the immunosensor also exhibited high specificity, good reproducibility and long-term stability. All these properties offer great promise for rapid, simple, selective and effective detection of CA125 in clinical applications.

An experimental study and multi-compartmental modelling of the distribution in, and elimination from the body of iron oxide nanoparticles deposited in the lower airways during long-term repeated inhalation exposures of rats

A new electrochemiluminescence (ECL) sensor was constructed for the ultrasensitive detection of diphenhydramine hydrochloride (DPH) based on l-cysteine-functionalized multiwalled carbon nanotubes/gold nanoparticles (MWCNTs-Cys-AuNPs) nanocomposites. In this work, the nanocomposites were facilely synthesized by using l-cysteine as linking agent which could covalently conjugate to MWCNTs and AuNPs via amide bond and AuS bond. Herein, the prepared MWCNTs-Cys-AuNPs were used as matrix material and fixed by Nafion to adsorb Ru(bpy)32+ on glassy carbon electrode (GCE) to provide a new ECL sensor for DPH. Then the electrochemical and ECL behaviors of the sensor were investigated. Approximate 9-fold enhancement in ECL intensity was observed after addition of DPH. By optimizing the experimental conditions, the proposed ECL sensor exhibited excellent assay performances in determination of DPH with a wide linear range (2 × 10−8–7.5 × 10−4 M), low detection limit (6.7 × 10−9 M), good reproducibility and acceptable stability. Furthermore, the constructed ECL sensor was used to analyze the DPH in real sample with a satisfactory result, which holds a great potential in the field of pharmaceutical analysis.

Enhanced Electrochemiluminescence of N-(aminobutyl)-N-(ethylisoluminol) Functionalized Gold Nanoparticles by Graphene Oxide Nanoribbons

The mechanism of electrochemiluminescence (ECL) of an N-(aminobutyl)-N-(ethylisoluminol) -functionalized gold nanoparticle (ABEI-AuNP) hybrid with graphene oxide nanoribbons (GONRs) as a functional supporting matrix on a modified screen-printed electrode (SPE) was studied under alkaline conditions. In our catalytic system, ABEI-AuNPs supported by GONRs were profoundly superior to the unsupported ABEI-AuNP/SPE, and exhibited greatly enhanced ECL intensity (≈30.0%). This difference is attributed not only to an 80.2% increase in the total surface area of the ABEI-AuNP-GONR/SPE, but also to enhancements of the ABEI-AuNP catalytic activity resulting from metal-oxygen bonding between the functional groups on the GONRs and the Au active sites. This improved catalytic activity of ABEI-AuNP facilitates both oxidative radical generation and fast reaction kinetics of the ABEI oxidation process. To further elucidate the mechanism of the counter-peak phenomenon in the ABEI ECL under cyclic voltammetry (CV) conditions, the effects of various factors, including pH of buffer solution, existence of dissolved oxygen, and concentration of hydrogen peroxide, on the ECL of ABEI were investigated. The mechanisms of liquid-phase ABEI on bare SPE and GONR/SPE were also compared to that of solid-phase ABEI-AuNP to validate the proposed mechanism for ABEI-AuNP-GONR/SPE.

A glassy carbon electrode modified with in-situ generated chromium-loaded CdS nanoprobes and heparin for ultrasensitive electrochemiluminescent determination of thrombin

We describe the in-situ electrochemical synthesis of a chromium-loaded CdS nanoprobe (CdS-Cr) for use in ultrasensitive electrochemiluminescence (ECL) detection of thrombin. A glassy carbon electrode was covered with (a) a film of electro-polymerized polyaniline nanofibers (PANI-NF), (b) the in-situ synthesized CdS-Cr nanoprobe, (c) heparin, and (d) a coating of BSA to prevent unspecific adsorption. Atomic force microscopy and scanning electron microscopy images showed the size of nanoprobe to have increased to an average size of 50 ± 5 nm, which was larger than pure CdS nanocrystals (NCs) with their typical size of 10 ± 2 nm. The modified glassy carbon electrode was electrochemically characterized by cyclic voltammetry and impedance spectroscopy. The thrombin-heparin interaction served as a new recognition tool for thrombin and represented an attractive alternative to respective aptamers. About 6-fold enhancement of ECL intensity (compared to pure CdS NCs) was observed in presence of persulfate. This ECL assay has a wide dynamic range (from 10 fM to 100 pM concentrations of thrombin), and a lower detection limit of 6.8 fM at 3σ. The technique for in-situ electrochemical preparation of the nanoprobe is simple, facile, and yields a sensor surface with favorable space structure, positive charge and stability.

Two orders-of-magnitude enhancement in the electrochemiluminescence of [formula omitted] by vertically ordered silica mesochannels

In this paper, we report significantly enhanced electrochemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) at indium tin oxide (ITO) electrodes modified with a thin film consisting of vertically aligned silica mesochannels (SMCs). The perpendicular SMCs allow for the effective mass transport of Ru(bpy)32+ and its co-reactants from the solution to the underlying ITO electrode surface. Moreover, due to the ultrasmall diameter (namely 2–3 nm) and the negatively charged surface, SMCs exerted a strong electrostatic attraction to the positively charged Ru(bpy)32+ to accelerate its mass transport, resulting in a remarkably increased ECL signal. As a model system, when using tri-n-propylamine (TPrA) as the co-reactant, the intensity of ECL generated at the SMCs-modified ITO electrode was stronger than that at a bare ITO electrode by more than two orders of magnitude (i.e., ∼107-fold increase). In this case, the amount of Ru(bpy)32+ required for ECL-based analysis can be considerably reduced. A very low concentration of Ru(bpy)32+, namely 9 μM, was demonstrated to be enough for achieving the sensitive detection of TPrA, nicotine and atropine. Both photomultiplier (PMT) and charge coupled device (CCD) were used to measure the luminescence from the ECL reaction. The obtained detection limits were 0.17 nM for TPrA on the basis of the ECL intensity measurement, 72 nM for nicotine and 38 nM for atropine based on the gray value analysis of captured ECL images.

Electrochemiluminescence biosensor for ultrasensitive determination of ochratoxin A in corn samples based on aptamer and hyperbranched rolling circle amplification.

Determination of ochratoxin A (OTA) is highly important for food safety control. In this study, a signal-on electrochemiluminescence (ECL) biosensor which combined the characteristics of high efficiency of hyperbranched rolling circle amplification (HRCA) and high selectivity of aptamer was developed for OTA determination. The capture probe DNA (CDNA) was firstly immobilized on the gold electrode surface through Au-S interaction, then the OTA aptamer was modified on the electrode surface through hybridization with CDNA. Since OTA can competitively bind with the aptamer due to their high affinity, which would induce the releasing of aptamer from the electrode surface. Subsequently, the free CDNA on the electrode surface can hybridize with the padlock probe and induce HRCA reaction subsequently. Thus, the HRCA products which contained large amount of double-stranded DNA (dsDNA) fragments can be accumulated on the electrode surface. Since Ru(phen)3(2+) can intercalate into the groove of dsDNA and acts as ECL indicator, high ECL intensity can be detected from the electrode surface. The enhanced ECL intensity has a linear relationship with OTA in the range of 0.05-500 pg/mL with a correlation coefficient of 0.9957, and the limit of detection (LOD) was 0.02 pg/mL. The developed biosensor has been applied to determine OTA concentration in the corn samples with satisfied results.

Tunable electrochemiluminescence of CdSe@ZnSe quantum dots by adjusting ZnSe shell thickness

Abstract CdSe quantum dots as cores capped with ZnSe shell (CdSe@ZnSe QDs) via a facile and eco-friendly strategy have been synthesized in aqueous solution for the first time. The electrochemiluminescence (ECL) of CdSe@ZnSe QDs was greatly enhanced compared to that of CdSe QDs. In particular, the ECL properties of the resulting CdSe@ZnSe QDs were found to be controllable by adjusting the thickness of ZnSe shells. Benefiting from the enhanced ECL intensity, the sensor based on CdSe@ZnSe QDs could accurately quantify dopamine from 10.0 nM to 3.0 μM with a detection limit of 3.6 nM.

An ultrasensitive electrochemiluminescence sensor for detecting diphenhydramine hydrochloride based on l-cysteine-functionalized multiwalled carbon nanotubes/gold nanoparticles nanocomposites

A new electrochemiluminescence (ECL) sensor was constructed for the ultrasensitive detection of diphenhydramine hydrochloride (DPH) based on l-cysteine-functionalized multiwalled carbon nanotubes/gold nanoparticles (MWCNTs-Cys-AuNPs) nanocomposites. In this work, the nanocomposites were facilely synthesized by using l-cysteine as linking agent which could covalently conjugate to MWCNTs and AuNPs via amide bond and AuS bond. Herein, the prepared MWCNTs-Cys-AuNPs were used as matrix material and fixed by Nafion to adsorb Ru(bpy)32+ on glassy carbon electrode (GCE) to provide a new ECL sensor for DPH. Then the electrochemical and ECL behaviors of the sensor were investigated. Approximate 9-fold enhancement in ECL intensity was observed after addition of DPH. By optimizing the experimental conditions, the proposed ECL sensor exhibited excellent assay performances in determination of DPH with a wide linear range (2×10−8–7.5×10−4M), low detection limit (6.7×10−9M), good reproducibility and acceptable stability. Furthermore, the constructed ECL sensor was used to analyze the DPH in real sample with a satisfactory result, which holds a great potential in the field of pharmaceutical analysis.

Self-enhanced electrogenerated chemiluminescence of ruthenium(II) complexes conjugated with Schiff bases.

In this work, we obtain two ruthenium(ii) complexes with Schiff base cavities that exhibit significantly enhanced electrochemiluminescence (ECL) intensity and quantum efficiency due to Ru(bpy)3(2+) in aqueous solution, without the addition of tri-n-propylamine (TPrA). The great increase in ECL intensity is confirmed to be due to the electrochemical oxidation of phenolic hydroxyl groups and the resonant structure of imino radicals. Thus, the electrons are transferred intramolecularly to the Ru(iii) center, leading to efficient generation of the excited state of Ru(ii)*. Subsequently, we find that Co(2+) bonding with the salen cavity can selectively and quickly quench the ECL signal. Furthermore, we study the mechanism of the process by which Co(2+) hinders the oxidation of phenolic groups and blocks the electron transfer from imino radicals to the Ru center. Thus, a highly sensitive and selective ECL probe for the recognition of Co(2+) was developed with a stable response over a concentration range of 0.9 μM to 6.3 μM and a detection limit as low as 21 nM.

Synthesis and electrochemiluminescence properties of a new ternary terbium complex and its application for the determination of norfloxacin

A new ternary terbium complex with 2,6-pyridinedicarboxylic acid (DPA) and 2,2′-bipyridyl (bipy) as ligand was synthesized and characterized by EDTA titration, elemental analysis and FTIR. The complex showed strong and stable electrochemiluminescence (ECL) property in NaBO4–NaOH buffer solution (pH=10.0) with the coreactant of potassium peroxydisulfate. The possible mechanism for the ECL behavior of terbium complex was discussed. Base on the ECL of the complex, a simple and ultrasensitive detection method for norfloxacin (NFX) was thus established. Under the optimized conditions, the enhanced ECL intensity versus the concentration of norfloxacin was in a good linear relationship over a concentration range from 1.0×10−9 to 4.0×10−7mol/L. The detection limit was found to be 6.9×10−10mol/L. The mechanism of ECL enhancement of NFX was also studied. The results obtained by the proposed ECL system, in terms of sensitivity, were much better than those obtained previously reported methods. In addition, the method was applied successfully to determine the total residuals of the norfloxacin in urine samples, the recoveries obtained were from 98.0% to 101.0%.

Electrochemiluminescence biosensor for folate receptor based on terminal protection of small-molecule-linked DNA

Owning to the characteristics such as high sensitivity and simplicity of apparatus, electrochemiluminescence (ECL) has become a powerful analytical technique and has been widely used. Ru(phen)32+ can be intercalated into the grooves of dsDNA and act as an ECL probe efficiently, which has been applied to develop a sensitive ECL biosensor for folate receptor in this study. One ssDNA with a thiol group at its 3′ termini had been modified on the Au electrode first, and the other ssDNA with folic acid at its 3′ termini hybridized with the former one being modified on the electrode surface to form a dsDNA. In the absence of folate receptor, the 3′-terminus in the dsDNA region can be specificity hydrolyzed into mononucleotides by ExoIII and on dsDNA presents on the electrode surface, leading to the lower of ECL intensity detected. However, in the presence of the target (folate receptor), ExoIII failed to hydrolyze the dsDNA since the one 3′-terminus had been protected by the target and the other protected by the Au electrode, resulting in the enhancement of ECL intensity. The enhanced ECL intensity has a linear relationship with the logarithm of folate receptor concentration in the range of 0.66nmol/L and 26.31nmol/L with a detection limit of 0.1204nmol/L. The proposed biosensor had been applied to detect HeLa cells concentration with satisfied results.

Photoluminescence, chemiluminescence and anodic electrochemiluminescence of hydrazide-modified graphene quantum dots.

Single-layer graphene quantum dots (SGQDs) were refluxed with hydrazine (N2H4) to prepare hydrazide-modified SGQDs (HM-SGQDs). Compared with SGQDs, partial oxygen-containing groups have been removed from HM-SGQDs. At the same time, a lot of hydrazide groups have been introduced into HM-SGQDs. The introduced hydrazide groups provide HM-SGQDs with a new kind of surface state, and give HM-SGQDs unique photoluminescence (PL) properties such as blue-shifted PL emission and a relatively high PL quantum yield. More importantly, the hydrazide-modification made HM-SGQDs have abundant luminol-like units. Accordingly, HM-SGQDs exhibit unique and excellent chemiluminescence (CL) and anodic electrochemiluminescence (ECL). The hydrazide groups of HM-SGQDs can be chemically oxidized by the dissolved oxygen (O2) in alkaline solutions, producing a strong CL signal. The CL intensity is mainly dependent on the pH value and the concentration of O2, implying the potential applications of HM-SGQDs in pH and O2 sensors. The hydrazide groups of HM-SGQDs can also be electrochemically oxidized in alkaline solutions, producing a strong anodic ECL signal. The ECL intensity can be enhanced sensitively by hydrogen peroxide (H2O2). The enhanced ECL intensity is proportional to the concentration of H2O2 in a wide range of 3 μM to 500 μM. The detection limit of H2O2 was calculated to be about 0.7 μM. The results suggest the great potential applications of HM-SGQDs in the sensors of H2O2 and bio-molecules that are able to produce H2O2 in the presence of enzymes.