Oligonucleotides-based biosensors with high sensitivity and selectivity for mercury using electrochemical impedance spectroscopy

A novel electrochemical biosensor with high sensitivity and selectivity for mercuric ion detection, based on DNA self-assembly electrode, is designed. Thiol functionalized poly-T oligonucleotides were used as gold electrode modifier through formation of Au–S bond between DNA and gold electrode. In presence of Hg²⁺ ions, the specific coordination between Hg²⁺ and thymine bases can change parallel ss-DNA from linear to hairpin structures, which can cause the release of partial DNA molecules from the surface of the electrode. The density of DNA on the surface of electrode correlated with the concentration of mercury in the solution and can be monitored by electrochemical impedance spectroscopy. The limit of detection of this method is pM level of mercuric ions which is far below the upper limit of Hg²⁺ mandated by United States Environmental Protection Agency (EPA), 2 ppb (10 nM). In addition, this method showed excellent selectivity. A series of divalent metal ions, including Ni²⁺, Co²⁺, Mg²⁺, Zn²⁺, Ba²⁺ and Cd²⁺, have little interference with the detection of Hg²⁺.     

Electrochemical Detection of Epinephrine Based on a Screen-printed Electrode Modified with NiO−ERGO Nanocomposite Film

This study presents a new electrochemical sensor (NiO−ERGO/SPE) for sensitive and selective detection of epinephrine (EPI) on the screen-printed electrode (SPE) which is modified with a nanocomposite film consisting of electrochemically reduced graphene oxide and NiO nanoparticles. After surface functionalization, structural and electrochemical characterization of NiO−ERGO film, DPV signals of NiO−ERGO/SPE towards the oxidation of EPI exhibited a linear correlation in the concentration range of 0.025 μM to 175 μM with a detection limit of 0.015 μM, which reveals NiO−ERGO film is manifested a good electrocatalytic activity for EPI detection compared with the previous reports. The selectivity of NiO−ERGO film was also tested on a very wide scale of possible interferents (ascorbic acid, uric acid, dopamine, lactic acid, phenylalanine, tyrosine, tryptophan, Li⁺, Na⁺, K⁺, Ca²⁺, and Zn²⁺). Moreover, to evaluate the applicability of the proposed sensor for real sample analysis, NiO−ERGO/SPE was successfully utilized for the determination of EPI in pharmaceutical samples.     

An Electrochemical Robotic System for Routine Cathodic Adsorptive Stripping Analysis of Ni2+ Ion Release from Corroding NiTi Shape Memory Alloys

Cathodic adsorptive stripping voltammetry (AdSV) as highly sensitive and selective method for quantifying trace amounts of dissolved Ni²⁺‐ions has been integrated into an electrochemical robotic device using the wells of microtiter plates as low‐volume electrochemical cells. A three‐electrode assembly integrating a Bismuth film‐modified glassy carbon electrode as working electrode and a glass capillary for delivering Ni²⁺ standard solution in conjunction with an adapted software allowed multiple AdSV measuring cycles to be performed one after the other in the individual compartments of a 24‐well microtiter plate. Of advantage for the automation was the possibility of an in‐well electrochemical removal of used and a replating of fresh Bi films in between distinct measuring cycles. With optimized parameters for the accumulation of the complex between Ni²⁺‐ions and dimethylglyoxime onto the surface of the Bi film electrode and the subsequent stripping procedure, automated adsorptive stripping voltammetry in the established system offered a linear dynamic range of up to 170 nM, a sensitivity of 12 nA/nM Ni²⁺ and a limit of of detection of 2.1 nM (N=16) for the detection of trace levels of Ni²⁺‐ions. Automated AdSV certainly is of convenience for studying larger number of samples due to the high‐throughput capability of the robotic apparatus. As example, the automatic quantification of Ni²⁺‐ion release from electropolished surfaces of NiTi shape memory alloys during corrosion in NaCl solutions is described.     

Non-conductive nanomaterial enhanced electrochemical response in stripping voltammetry: The use of nanostructured magnesium silicate hollow spheres for heavy metal ions detection

Nanostructured magnesium silicate hollow spheres, one kind of non-conductive nanomaterials, were used in heavy metal ions (HMIs) detection with enhanced performance for the first time. The detailed study of the enhancing electrochemical response in stripping voltammetry for simultaneous detection of ultratrace Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ was described. Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. The anodic stripping voltammetric performance toward HMIs was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detection limits achieved (0.186 nM, 0.247 nM, 0.169 nM and 0.375 nM for Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺) are much lower than the guideline values in drinking water given by the World Health Organization (WHO). In addition, the interference and stability of the modified electrode were also investigated under the optimized conditions. An interesting phenomenon of mutual interference between different metal ions was observed. Most importantly, the sensitivity of Pb²⁺ increased in the presence of certain concentrations of other metal ions, such as Cd²⁺, Cu²⁺ and Hg²⁺ both individually and simultaneously. The proposed electrochemical sensing method is thus expected to open new opportunities to broaden the use of SWASV in analysis for detecting HMIs in the environment.     

Surface Modification of Gold by Quercetin Monolayer for the Electrochemical Determination of Copper(II)

A quercetin monolayer has been prepared on top of the self‐assembled 3‐mercaptopropionic acid (MPA) layer for the copper ion determination. Cu²⁺ ions are readily accumulated on this modified electrode through the complex formation and electrochemically detected. With a quercetin layer, the redox process of Cu²⁺ became more reversible than at the MPA‐modified electrode. Complexation sites in MPA and quercetin were occupied within five min when the electrode was immersed in 10 μM Cu²⁺ solution. The MPA and quercetin layers were stable enough to allow repeated EDTA treatment to remove adsorbed Cu²⁺ for the surface regeneration. Only 7% decrease was found after ten times regeneration and use. Linear current response was found over the concentration range of 1 nM and 10 μM with detection limit of 0.1 nM. Common interfering ions such as Cd²⁺, Zn²⁺, and Fe^2+/3+ did not show any electrochemical response in the potential range of Cu²⁺ determination.     

Synthesis and characterisation of a novel bi-nuclear copper2+ complex and its application as electrode-modifying agent for simultaneous voltammetric determination of dopamine and ascorbic acid

A new binuclear complex of copper²⁺, [LCu²⁺(CH₃COO)₂Cu²⁺L](CH₃COO)₂ where L is N,N-bis(phthalimide)ethylenediamine, was synthesised and characterised. The complex ion [LCu²⁺ (CH₃COO)₂Cu²⁺L]²⁺ was encapsulated into ZSM-5 zeolite and used to modify the surface of the glassy carbon electrode. This modified electrode, in a phosphate buffer solution at pH 7.0, exhibited an oxidation potential for dopamine (DA) and ascorbic acid (AA) at electrode potentials of 0.230 V and ?0.090 V vs. Ag/AgCl respectively, a separation of 0.320 V. The electro-oxidation of DA or AA on the modified electrode is independent of each other. No interference was observed from Na⁺, K⁺, Cl^?, SO ₄ ^2? , Mg²⁺, Ca²⁺, Zn²⁺, Fe²⁺, and glucose. The detection limits obtained were 2.91 × 10^?7 M for DA and 3.5 × 10^?7 M for AA.     

Ordered Mesoporous Carbon and Thiolated Polyaniline Modified Electrode for Simultaneous Determination of Cadmium(II) and Lead(II) by Anodic Stripping Voltammetry

The fabrication and evaluation of a glassy carbon electrode (GCE) modified with ordered mesoporous carbon (OMC), 2‐mercaptoethanesulfonate (MES)‐tethered polyaniline (PANI) and bismuth for simultaneous determination of trace Cd²⁺ and Pb²⁺ by differential pulse anodic stripping voltammetry (DPASV) are presented here. The morphology and electrochemical properties of the fabricated electrode were respectively characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Experimental parameters such as PANI disposition, preconcentration potential, preconcentration time and bismuth concentration were optimized. Under optimum conditions, the fabricated electrode exhibited linear calibration curves ranged from 1 to 120 nM for Cd²⁺ and Pb²⁺. The limits of detection (LOD) were 0.26 nM for Cd²⁺ and 0.16 nM for Pb²⁺ (S/N=3), respectively. Additionally, repeatability, reproducibility, interference and application were also investigated, and the proposed electrode exhibited excellent performance. The proposed method could be extended for the development of other new sensors for heavy metal determination.     

Highly sensitive and selective amperometric sensors for nanomolar detection of iodate and periodate based on glassy carbon electrode modified with iridium oxide nanoparticles

Iridium oxide nanoparticles are grown on a glassy carbon electrode by electrodepositing method. The electrochemical behavior and electrocatalytic activity of modified electrode towards reduction of iodate and periodate are studied. The reductions of both ions occur at the unusual positive peak potential of 0.7 V vs. reference electrode. The modified electrode is employed successfully for iodate and periodates detection using cyclic voltammetry, hydrodynamic amperometry and flow injection analysis (FIA). In the performed experiments, flow injection amperometric determination of iodate and periodate yielded calibration curves with the following characteristics: linear dynamic range up to 100 and 80 μM, sensitivity of 140.9 and 150.6 nA μM⁻¹ and detection limits of 5 and 36 nM, respectively. The repeatability of the modified electrode for 21 injections of 1.5 μM of iodate solution is 1.5%. The interference effects of NO₂⁻, NO₃⁻, ClO₃⁻, BrO₃⁻, ClO₄⁻, SO₄²⁻, Cu²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Cd²⁺, Ca²⁺, Na⁺, K⁺, NH₄⁺ and K⁺, CH₃COO⁻ and glucose were negligible at the concentration ratio of more than 1000. The obtained attractive analytical performance together with high selectivity and simplicity of the proposed method provide an effective and e novel modified electrode to develop an iodate and periodate sensor. Sensitivity, selectivity, the liner concentration range and the detection limit of the developed sensor are all much better than all known similar sensors in the literature for iodate and periodate determination.     

Electrochemical sensor using graphene/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanosheets functionalized with garlic extract for the detection of lead ion

Based on the modulated electronic properties of Fe₃O₄-graphene (Fe₃O₄/GN composite) as well as the outstanding complexation between Pb²⁺ and natural substances garlic extract (GE), a novel electrochemical sensor for the determination of Pb²⁺ in wastewater was prepared by immobilization of Fe₃O₄/GN composite integrated with GE onto the surface of glassy carbon electrode (GCE). Fe₃O₄/GN composite was employed as an electrochemical active probe for enhancing electrical response by facilitating charge transfer while GE was used to improve the selectivity and sensitivity of the proposed sensor to Pb²⁺ assay. The electrochemical sensing performance toward Pb²⁺ was appraised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV). Under the optimized condition, the sensor exhibited two dynamic linear ranges (LDR) including 0.001 to 0.5 nM and 0.5 to 1000 nM with excellent low detection limit (LOD) of 0.0123 pM (S/N =?3) and quantification limit (LOQ) of 0.41 pM (S/N =?10). Meanwhile, it displayed remarkable stability, reproducibility (RSD of 3.61%, n =?3), and selectivity toward the assay for the 100-fold higher concentration of other heavy metal ions. Furthermore, the novel sensor has been successfully employed to detect Pb²⁺ from real water samples with satisfactory results.     

Electrochemical Determination of Cd2+ and Pb2+ Using NSAID‐mefenamic Acid Functionalized Mesoporous Carbon Microspheres Modified Glassy Carbon Electrode

This paper describes the electrochemical behaviors of Cd²⁺ and Pb²⁺ on the proposed mesoporous carbon microspheres/mefenamic acid/nafion modified glassy carbon electrode (MC/MA/Nafion/GC) studied by square wave anodic stripping voltammetry (SWASV). The prepared material is characterized by XRD, SEM, FTIR, RAMAN and BET analysis. Experimental parameters, such as the deposition potential and time, the pH value of buffer solution were optimized. Under the optimized conditions, the electrode responded linearly to Cd²⁺ and Pb²⁺ in the concentration range from 50 to 300 nM, and the detection limits were 24.2 and 11.26 nM respectively. The sensitivity determined was 0.0623 μA/nM (Cd²⁺) and 0.192 μA/nM (Pb²⁺). Multiple metal ion detection with clear demarcation of peaks was produced by the electrode. Moreover, the modified electrode has possessed good selectivity and reproducibility of Cd²⁺ and Pb²⁺ detection. We also investigated the interference of various anions and surfactants for the detection of Cd²⁺ and Pb²⁺ ions. Finally the modified electrode was used to detect the presence of metal ions in practical samples and the results obtained are comparatively good with respect to AAS.     

Picomolar Detection of Hydrogen Peroxide at Glassy Carbon Electrode Modified with NAD+ and Single Walled Carbon Nanotubes

Potential cycling was used for oxidation of NAD⁺ and producing an electroactive redox couple which strongly adsorbed on the electrode surface modified with single walled carbon nanotubes (SWCNTs). Modified electrode shows a pair of well defined and nearly reversible redox peaks at pH range 1–13 and the response showed a surface‐controlled electrode process. The surface coverage and heterogeneous electron transfer rate constant (k_s) of adsorbed redox couple onto CNTs films were about 6.32×10^?10 mol cm^?2 and 2.0 (±0.20) s^?1, respectively, indicating the high loading ability of CNTs toward the oxidation product of NAD⁺ (2,8‐dihydroxy adenine dinucleotide) and great facilitation of the electron transfer between redox couple and CNTs immobilized onto electrode surface. The modified electrode exhibited excellent electrocatalytic activity for H₂O₂ reduction at reduced overpotential. The catalytic rate constant for H₂O₂ reduction was found to be 2.22(±0.20)×10⁴ M^?1 s^?1. The catalytic reduction current allows the amperometric detection of H₂O₂ at an applied potential of ?0.25 V vs. Ag/AgCl with a detection limit of 10 pM and linear response up to 100 nM and resulting analytical sensitivity 747.6 nA/pM. The remarkably low detection limit (10 pM) is the lowest value ever reported for direct H₂O₂ determination on the electrodes at pH 7. The modified electrode can be used for monitoring H₂O₂ without the need for an enzyme or enzyme mimic. The proposed method for rapid amperometric detection of H₂O₂ is low cost and high throughput. Furthermore, the sensor can be used to any detection scheme that uses enzymatically generated H₂O₂ as a reactive product in biological systems.     

A ratiometric electrochemical biosensor for sensitive detection of Hg based on thymine–Hg–thymine structure

In this paper, a simple, selective and reusable electrochemical biosensor for the sensitive detection of mercury ions (Hg²⁺) has been developed based on thymine (T)-rich stem–loop (hairpin) DNA probe and a dual-signaling electrochemical ratiometric strategy. The assay strategy includes both “signal-on” and “signal-off” elements. The thiolated methylene blue (MB)-modified T-rich hairpin DNA capture probe (MB-P) firstly self-assembled on the gold electrode surface via Au–S bond. In the presence of Hg²⁺, the ferrocene (Fc)-labeled T-rich DNA probe (Fc-P) hybridized with MB-P via the Hg²⁺-mediated coordination of T–Hg²⁺–T base pairs. As a result, the hairpin MB-P was opened, the MB tags were away from the gold electrode surface and the Fc tags closed to the gold electrode surface. These conformation changes led to the decrease of the oxidation peak current of MB (I_MB), accompanied with the increase of that of Fc (I_Fc). The logarithmic value of I_Fc/I_MB is linear with the logarithm of Hg²⁺ concentration in the range from 0.5 nM to 5000 nM, and the detection limit of 0.08 nM is much lower than 10 nM (the US Environmental Protection Agency (EPA) limit of Hg²⁺ in drinking water). What is more, the developed DNA-based electrochemical biosensor could be regenerated by adding cysteine and Mg²⁺. This strategy provides a simple and rapid approach for the detection of Hg²⁺, and has promising application in the detection of Hg²⁺ in real environmental samples.     

The Ag+-G interaction inhibits the electrocatalytic oxidation of guanine--a novel mechanism for Ag+ detection

The heavy metal ions-nucleobases interaction is an important research topic in environmental and biochemical analysis. The presence of the silver ion (Ag⁺) may influence the formation of oxidation intermediate and the electrocatalytic oxidation activity of guanine (G), since Ag⁺ can interact with guanine at the binding sites which are involved in the electrocatalytic oxidation reaction of guanine. According to this principle, a new electrochemical sensor for indirectly detecting Ag⁺ based on the interaction of Ag⁺ with isolated guanine base using differential pulse voltammetry (DPV) was constructed. Among the heavy metal ions examined, only Ag⁺ showed the strongest inhibitory effect on the electrocatalytic oxidation of guanine at the multi-walled carbon nanotubes modified glassy carbon electrode (CNTs/GC). And the quantitative study of Ag⁺ based on Ag⁺-G sensing system gave a linear range from 100 nM to 2.5 μM with a detection limit of 30 nM. In addition, this modified electrode had very good reproducibility and stability. The developed electrochemical method is an ideal tool for Ag⁺ detection with some merits including remarkable simplicity, low-cost, and no requirement for probe preparation.     

Highly sensitive determination of hydroxylamine using fused gold nanoparticles immobilized on sol-gel film modified gold electrode

We are reporting the highly sensitive determination of hydroxylamine (HA) using 2-mercapto-4-methyl-5-thiazoleacetic acid (TAA) capped fused spherical gold nanoparticles (AuNPs) modified Au electrode. The fused TAA-AuNPs were immobilized on (3-mercaptopropyl)-trimethoxysilane (MPTS) sol-gel film, which was pre-assembled on Au electrode. The immobilization of fused TAA-AuNPs on MPTS sol-gel film was confirmed by UV-vis absorption spectroscopy and atomic force microscopy (AFM). The AFM image showed that the AuNPs retained the fused spherical morphology after immobilized on sol-gel film. The fused TAA-AuNPs on MPTS modified Au electrode were used for the determination of HA in phosphate buffer (PB) solution (pH = 7.2). When compared to bare Au electrode, the fused AuNPs modified electrode not only shifted the oxidation potential of HA towards less positive potential but also enhanced its oxidation peak current. Further, the oxidation of HA was highly stable at fused AuNPs modified electrode. Using amperometric method, determination of 17.5 nM HA was achieved for the first time. Further, the current response of HA increases linearly while increasing its concentration from 17.5 nM to 22 mM and a detection limit was found to be 0.39 nM (S/N = 3). The present modified electrode was also successfully used for the determination of 17.5 nM HA in the presence of 200-fold excess of common interferents such as urea, NO₂⁻, NH₄⁺, oxalate, Mn²⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺ and Cu²⁺. The practical application of the present modified electrode was demonstrated by measuring the concentration of HA in ground water samples.     

A Novel Highly Sensitive Zeolite-Based Conductometric Microsensor for Ammonium Determination

Natural zeolite clinoptilolite was successfully applied in the sensing technology for electrochemical detection of ammonium. A novel ammonium-selective sensor was developed based on clinoptilolite, possessing intrinsic ammonium-sieving and ion exchange capacity. The sensor design allowed measurements in both differential mode and requiring no classical reference electrode. The sensor selectivity towards Na⁺, K⁺, Ca²⁺, Mg²⁺, and Al³⁺ was studied. The limit of detection and the dynamic range of the ammonium-selective conductometric microsensor, determined in the phosphate buffer solution, were 1.0 × 10^?8 M and 0–8 mM, respectively. The ammonium sensor presented high operational and storage stability.     

Coulomb explosion dynamics of N2O in intense laser-field: Identification of new two-body and three-body fragmentation pathways

The Coulomb explosion process of N₂O in an intense laser-field (∼5 PW/cm²) has been investigated by the high-resolution time-of-flight (TOF) spectroscopy. Six two-body explosion pathways involving the NO⁺, NO²⁺, N₂ ⁺ molecular ions have been securely identified from the momentum-scaled TOF spectra of the fragment ions. Assuming a linear geometry, three-body explosion pathways were investigated by sequential and concerted explosion models. When the concerted model is adopted, the observed momentum distributions of six atomic ion channels; N⁺, N²⁺, N³⁺, O⁺, O²⁺ and O³⁺, were well fitted using the Gaussian momentum distribution with the optimized bond elongation factor of 2.2(3). From the yields of individual Coulomb explosion pathways determined by the fit, the abundance of the parent ions, N₂O^z+ (z=2–8), prior to the two- body and three-body explosion processes was found to have a smooth distribution with a maximum at z∼3.     

Ion-Selective Electrodes Based on Bilayer Film Coating

The electrode characteristics of ion-selective electrodes (ISEs) for K⁺, Na⁺, NH₄ ⁺, and Ca²⁺ based on bilayer film coatings, where the inner layer films are electroactive electropolymerized ones and the outer layer films are composed of conventional ion-sensitive materials, have been examined. These ISEs of the coated-wire electrode type have no conventional internal reference solution and reference electrode, but the inner films may be considered to function as the “internal standard solution.” The ion selectivity coefficients and the activity range showing Nernstian response were almost comparable to those of conventional liquid-membrane electrodes. The bilayer-coated ISEs showed insensitivity to O₂ and CO₂, long-term stability, and little drift. It was also found that the electrode performance is practically unchanged after sterilization in an autoclave. The results demonstrate that the bilayer-coated ISEs examined are promising for the determination of K⁺, Na⁺, NH₄ ⁺, or Ca²⁺ activity in biological and environmental systems.     

An Electrochemical Sensor for the Detection of Cu2+ Based on Gold Nanoflowers‐modifed Electrode and DNAzyme Functionalized Au@MIL‐101 (Fe)

In this study, we developed an electrochemical sensor for sensitive detection of Cu²⁺ based on gold nanoflowers (AuNFs)‐modified electrode and DNAzyme functionalized Au@MIL‐101(Fe) (MIL: Materials of Institute Lavoisier). The AuNFs‐modified indium tin oxide modified conductive glass electrode(AuNFs/ITO) prepared via electrodeposition showed improved electronic transport properties and provided more active sites to adsorb large amounts of oligonucleotide substrate (DNA1) via thiol‐gold bonds. The stable Au@MIL‐101(Fe) could guarantee the sensitivity because of its intrinsic peroxidase mimic property, while the Cu²⁺‐dependent DNA‐cleaving DNAzyme linked to Au@MIL‐101(Fe) achieved the selectivity toward Cu²⁺. After the DNAzyme substrate strand (DNA2) was cleaved into two parts due to the presence of Cu²⁺, the oligonucleotide fragment linked to MIL‐101(Fe) was able to hybridize with DNA1 adsorbed onto the surface of AuNFs/ITO. Due to the peroxidase‐like catalytic activity of MIL‐101(Fe) and the affinity recognition property of DNAzyme toward Cu²⁺, the electrochemical biosensor showed a sensitive detection range from 0.001 to 100 μM, a detection limit of 0.457 nM and a high selectivity, demonstrating its potential for Cu²⁺ detection in real environmental samples.     

A Novel Electroactive Polymer for pH‐independent Oxygen Sensing

Methylene blue (MB⁺) and pyrrole were copolymerised to electrodeposit a novel electroactive polymer on a Au electrode which was assessed for O₂ sensing. The electroactive polymer exhibits diffusion‐limited behaviour and an electrochemical, followed by catalytic (EC′) mechanism in the presence of dissolved O₂. Notably, it is pH‐insensitive in both N₂‐purged and air‐equilibrated phosphate buffered saline (PBS) from pH 4 to 8. It is stable over 18 days, possesses a good sensitivity of 256.335 µA mM^?1 cm^?2, wide linear range of 15 µM to 285 µM and detection limit of 1.47 µM (S/N=3) for dissolved O₂. It is highly promising for use in biological investigations where pH fluctuations are expected.     

A Unique,Porous C3N4 Nanotube for Electrochemiluminescence with High Emission Intensity and Long-Term Stability: The Role of Calcination Atmosphere

Developing excellent strategies to optimize the electrochemiluminescence (ECL) performance of C₃N₄ materials remains a challenge due to the electrode passivation, causing weak and unstable light emission. A strategy of controlling the calcination atmosphere was proposed to improve the ECL performance of C₃N₄ nanotubes. Interestingly, we found that calcination atmosphere played a key role in specific surface area, pore-size and crystallinity of C₃N₄ nanotubes. The C₃N₄ nanotubes prepared in the Air atmosphere (C₃N₄ NT-Air) possess a larger specific surface area, smaller pore-size and better crystallinity, which is crucial to improve ECL properties. Therefore, more C₃N₄^•− excitons could be produced on C₃N₄ NT-Air, reacting with the SO₄^•− during the electrochemical reaction, which can greatly increase the ECL signal. Furthermore, when C₃N₄ nanotube/K₂S₂O₈ system is proposed as a sensing platform, it offers a high sensitivity, and good selectivity for the detection of Cu²⁺, with a wide linear range of 0.25 nM~1000 nM and a low detection limit of 0.08 nM.