Near-infrared Electrochemiluminescence Research Articles

The carbon dots with near-infrared electrochemiluminescence emission and low excitation potential for ultrasensitive analysis of microRNA-222

In this work, nitrogen and sulfur codoped near-infrared emission carbon dots (N,S-NIR-CDs) were used as neoteric electrochemiluminescence (ECL) emitters with high efficiency to construct a biosensor for ultrasensitive analysis of microRNA-222 (miRNA-222), which has been regarded as prospective biomarkers for early cancer diagnosis. Impressively, compared to conventional CDs with short ECL wavelength and large excitation voltage, N,S-NIR-CDs possessed wide sp2 domains and narrow band gap, leading to the near-infrared ECL emission at 680 nm and low excitation potential from −1.0 to 0 V, which not only decreased the photochemical damage for biomolecules but also reduced the side reaction. Moreover, an improved T7 Exonuclease induced cascade amplification (EICA) strategy was designed to transform trace miRNA-222 into plentiful output DNA in dual-cycle for greatly improving the target conversion efficiency. Therefore, by combining the N,S-NIR-CDs as neoteric ECL emitters and EICA strategy as signal amplifier, the constructed ECL biosensor could realize the ultrasensitive analysis of miRNA-222 with a identification limit of 5.65 aM and successfully employed in miRNA-222 analysis from liver cancer cell (HCCLM3 and MHCC-97L) lysate. This strategy developed a kind of neoteric CDs with NIR ECL emission and low excitation potential to establish a highly efficient biosensor for biomarker analysis, which prepared a road for early diseases diagnosis and lied a foundation for biological ECL imaging.

Effect of surface ligand density on near-infrared electrochemiluminescence of glutathione-stabilized Au nanoclusters

Here, we report the crucial role of surface ligand density in electrochemiluminescence (ECL) of water-soluble Au NCs stabilized with glutathione ligands. The Au NCs, having four distinct surface ligand densities, displayed unique ECL features that were dependent on the surface ligand density of the NCs, similar to their fluorescence properties. The Au NCs displayed dual-wavelength ECL emissions at ∼620 nm and ∼820 nm. The ECL properties were significantly affected by the surface ligand density of the NCs, with lower densities resulting in enhanced ECL emission, particularly in the near-infrared region. This enhancement surpassed the near-infrared ECL emissions observed in other known ECL-active Au NCs, resulting in approximately a 9-fold improvement compared to well-established Au NCs stabilized with bovine serum albumin (BSA). In addition, the dual-emission features of the Au NCs stabilized with glutathione were attributed to the presence of two Au-S emission motifs related to different Au-S bonding environments resulting from varied surface ligand densities. These findings revealed the critical role of the surface ligand density in modulating not only the fluorescence of the Au NCs but also the ECL of NCs.

Spectroscopy and absolute quantum efficiency of near-infrared electrochemiluminescence for a macrocyclic palladium complex

Electrochemiluminescence (ECL) is widely applied as a reliable tool in clinical diagnosis, including immunoassays, cancer biomarker detection, etc. Metal complexes with emission in the near-infrared (NIR) range possess distinct features such as high transmission and minimal tissue auto-absorption, making them versatile for applications in biosensing and other fields. Through ECL spectral studies of an O-linked nonaromatic benzitripyrrin (C^N^N^N) macrocyclic palladium complex (Pd1) with multiple pyrrole structures, we observed emission peaks from the Qx(0,0) and its vibronic Qx(0,1) bands during both photoluminescence (PL) and ECL. Notably, the emission from the Qx(0,1) band was significantly enhanced in the ECL spectrum, demonstrating higher selectivity for near-infrared light at 743 nm. In the ECL annihilation pathway, the appearance of ECL signals showed a strong correlation with the redox processes of the tri-pyrrin structure, revealing a cyclic tri-pyrrin ligand-centered nature with contributions from the metal center. Upon the introduction of tripropylamine (TPrA) and benzoyl peroxide (BPO) coreactants, the ECL signals exhibited enhancements ranging from several hundred to tens of times. Various reaction routes within different coreactant systems are extensively discussed. Additionally, the absolute quantum efficiencies of the Pd1/TPrA coreactant system were determined, showing efficiencies of 0.0032% ± 0.0005% and 0.000074% ± 0.000016% during pulsing and CV scan processes, respectively. This work addresses gaps in the study of palladacycle complexes in ECL and provides insights into the design of NIR luminescent structures that contribute to the fast screening and deep tissue penetration bioimaging techniques.

Near-infrared electrochemiluminescence biosensors facilitated by thermally activated delayed fluorescence (TADF) emitters for ctDNA analysis

The near-infrared electrochemiluminescence technique (NIR ECL) has gained significant attention as a powerful analytical tool in biomedicine and clinical diagnosis due to its inherent advantages. In this work, we successfully synthesized a novel NIR ECL emitter of TPA-DCPP nanoparticles (NPs) with a D-π-A-π-D configuration. By utilizing the thermally activated delayed fluorescence (TADF) property, we achieved enhanced electrochemiluminescence (ECL) emission through complete exciton harvesting for radiative decay. Specifically, when BDEA was used as a co-reactant, the TPA-DCPP NPs exhibited strong bandgap ECL emission. Additionally, they demonstrated an exceptionally higher ECL efficiency compared to conventional near-infrared fluorescence organic nanomaterials (BSeT-BT NPs). By integrating the efficient anodic ECL performance of TPA-DCPP NPs with Exo III-assisted polymerase enzyme reaction cascade amplification, a highly efficient ECL resonance energy transfer (ECL-RET) platform was developed for ultrasensitive detection of circulating tumor DNA (ctDNA). The established biosensor demonstrated an exceptional linear dynamic range and achieved attomolar-level detection limit. This study highlights the immense potential of TADF emitters in enhancing ECL efficiency and extends the emission wavelength of organic nanomaterials to the NIR region, thereby expanding their applications in biological analysis.

Co-Reactive Ligand In Situ Engineered Gold Nanoclusters with Ultra-Bright Near-Infrared Electrochemiluminescence for Ultrasensitive and Label-Free Detection of Carboxylesterase Activity.

Ultrasensitive and accurate monitoring of carboxylesterase (CE) activity is extremely crucial for the early diagnosis of hepatocellular carcinoma (HCC), which is still a considerable challenge. Herein, using a co-reactive ligand engineering strategy, ultra-bright near-infrared (λmax = 830 nm) and self-enhanced electrochemiluminescence (ECL) Au nanoclusters (NCs) were in situ prepared with 2-(diethylamino) ethanethiol (DEAET) as a co-reactive ligand. Remarkably, the co-reactive ligand not only acts as a stabilizer like traditional ligands but also plays a crucial role as a co-reactant to ensure a confinement effect to shorten the charge transfer distance and increase the local concentration, significantly improving the collision efficiency between the electrogenerated free radicals. Consequently, the DEAET Au NCs exhibited a record and stable anodal ECL without the addition of an exogenous co-reactant, dramatically superior to classical Au NCs and Ru(bpy)32+ with a certain amount of the co-reactant. As a proof of concept, a convenient and label-free CE biosensor was innovatively constructed using 1-naphthyl acetate as a selective substrate, achieving ultrasensitive detection for CE activity with a low limit of detection of 9.1 × 10-7 U/L. Therefore, this work not only paves a co-reactive ligand engineering strategy for in situ preparation of high-efficiency metal NCs but also provides an ultrasensitive and convenient platform for the early diagnosis of HCC.

Near-infrared electrochemiluminescence of defect-rich molybdenum disulfide quantum dots for sensitive bioanalysis

Developing high-efficiency near-infrared (NIR) electrochemiluminescence (ECL) active transition metal dichalcogenides quantum dots (TMDs QDs) for spectroscopic multiplex analysis and biological imaging poses a significant challenge in versatile bioanalysis. In this work, we report a facile one-step hydrothermal method for the synthesis of defect-rich molybdenum disulfide quantum dots (MoS2 QDs). Because of the defect effect on the nanocrystalline surface, the MoS2 QDs exhibit enhanced fluorescence (quantum yield is 7.7%) in comparison with those from top-down physical approaches. Moreover, the defect-rich MoS2 QDs exhibit remarkable ECL performance using K2S2O8 as a coreactant, with a maximum emission at ∼810 nm. The ECL mechanisms of potential-dependent emission from MoS2 QDs were elucidated based on electrochemistry, photoluminescence, and spooling ECL spectroscopy. Leveraging the good biocompatibility and defect-induced ECL enhancement of MoS2 QDs, a sandwich ECL immunosensor was developed for carcinoembryonic antigen (CEA) detection. Without any signal amplification techniques, the proposed biosensor demonstrated a detection limit of 0.005 ng/mL CEA with a linear range from 0.005 ng/mL to 400 ng/mL, and a good selectivity and potential for real human serum analysis. The defect engineering of MoS2 QDs in this study provides guidance for regulating their optical properties and exploring new bioanalysis applications.

Potential-controlled visible and near-infrared electrochemiluminescence from a BODIPY-DO3A macrocycle conjugate

A multicolour ECL system consisting of a conjugate composed of BODIPY (boron-dipyrromethene) core coupled via an amide linkage to DOTA (1,4,7,10-Tetraazacyclododecane-1,4,7-tris(t‑butyl acetate)) was studied. When a lanthanide ion was bound to the DOTA ligand, it was found that energy transfer could be initiated by optical but not electrochemical excitation. However, ECL experiments on the conjugate in the absence of lanthanide ions, revealed an interesting dual wavelength ECL behaviour at 549 and 730 nm in both annihilation and co-reactant pathways, which could be modulated by controlling the potential. Using the 3D ECL technique to probe the potential and concentration dependence of the ECL emission, it was possible to characterise the various mechanisms giving rise to annihilation and co-reactant ECL emissions in the visible and near-infrared. Analysis of the energetics of each reaction showed that aggregation following radical ion electrogeneration explained the long wavelength emission, facilitated by the incorporation of tBu-DO3A into the BODIPY structure. This system offers interesting new insights into BODIPY-based ECL systems.

Near-infrared electrochemiluminescence of carbon nitride quantum dots for ultrasensitive microRNA assay

Herein, carbon nitride quantum dots (CNQDs) with efficient near-infrared electrochemiluminescence (NIR-ECL) and excellent biocompatibility were prepared as an emitter to construct an ultrasensitive regenerative biosensing platform for detection of microRNA-222 (miRNA-222). Impressively, the introduction of electron-rich pyrimidine effectively increased the conjugation effect of electrons on triazine ring in CNQDs to result in red shift of ECL emission wavelength from 483 nm to 690 nm with the increase of pyrimidine. Meanwhile, an improved circular DNA walker was assembled by the catalytic ligation of T4 DNA ligase instead of traditional base complementary pairing, which enhanced the stability of circular DNA walker to increase walking efficiency. Based on CNQDs as emitter and circular DNA walker as signal amplifier, a regenerative biosensor platform was prepared to achieve the ultrasensitive detection of miRNA-222 with the limit of detection of 2.39 aM and it was successfully applied for sensitive detection of miRNA-222 in the lysate of cancer cells. This work opened a promising road for synthesizing efficient NIR-ECL CNQDs to reduce damage to organisms and achieve deeper tissue penetration and provided a new method for biomarker detection and disease diagnosis.

Novel inner filter effect-based near-infrared electrochemiluminescence sensor mediated by well-matched AgBr-nitrogen-doped Ti3C2 MXene and nonmetallic plasmon WO3•H2O

The development of innovative and efficient strategy is of paramount importance for near-infrared (NIR) electrochemiluminescence (ECL) sensing, which can substantially promote ECL detection in a wide range of situations. Herein, the inner filter effect (IFE) strategy was designed to construct an ultrasensitive NIR ECL biosensor based on the well-matched AgBr nanocrystals (NCs) decorated nitrogen-doped Ti3C2 MXene nanocomposites (AgBr–N–Ti3C2) and hydrated defective tungsten oxide nanosheets (dWO3•H2O). Specifically, the AgBr–N–Ti3C2 nanocomposites displayed extremely effective NIR ECL emission because N-doping could accelerate electron transfer and boost the red-shift of the ECL spectrum. The nonmetallic plasmon dWO3•H2O was used as an absorber due to its facile tuning of the spectra overlap and higher molar extinction coefficients. Time-resolved emission decay curves proved that the decreased ECL intensity was ascribed to the IFE-based steady quenching mechanism. With the support of tetracycline (TC) aptamer and the complementary DNA chain, the fabricated NIR ECL-IFE biosensor performed a wide linear range of 100 nM ∼ 10 fM with a low detection limit of 2.2 fM (S/N = 3), and it exhibited excellent stability, sensitivity, and reproducibility, so as to be applied to real samples. This strategy opens a new avenue to constructing an efficient NIR ECL-IFE system and shows excellent practical potential in actual sample analysis.

Energy Level Engineering in Gold Nanoclusters for Exceptionally Bright NIR Electrochemiluminescence at a Low Trigger Potential.

Electrochemiluminescence (ECL) is a widely used light output mechanism from electrochemical excitation. Understanding the intrinsic essence for ideal ECL generation remains a fundamental challenge. Here, based on the molecular orbital theory, we reported an energy level engineering strategy to regulate the ECL performance by using ligand-protected gold nanoclusters (AuNCs) as luminophores and N,N-diisopropylethylamine (DIPEA) as a coreactant. The energy level matching between the AuNCs and DIPEA effectively promoted their electron transfer reactions, thus improving the excitation efficiency and reducing the trigger potential. Simultaneously, the narrow band gap of the AuNCs further enabled enhanced emission efficiency. Using the energy level engineering theory developed here, a dual-enhanced strategy was proposed, and β-CD-AuNCs were designed to further verify this mechanism. The β-CD-AuNCs/DIPEA system resulted in highly stable near-infrared ECL with an unprecedented ECL efficiency (145-fold higher than that of the classic Ru(bpy)32+/tetra-n-butylammonium perchlorate system) and a low trigger potential of 0.48 V. A visual NIR-ECL based on this ECL system was successfully realized by an infrared camera. This work provides an original mechanistic understanding for designing efficient ECL systems, which promises to be a harbinger for broad applicability of this strategy for other ECL systems and ECL sensing platforms.

AgAuS Quantum Dots as a Highly Efficient Near-Infrared Electrochemiluminescence Emitter for the Ultrasensitive Detection of MicroRNA.

Herein, the novel alloyed silver gold sulfur quantum dots (AgAuS QDs) with highly efficient near-infrared (NIR) electrochemiluminescence (ECL) emission at 707 nm were successfully prepared to construct a biosensing platform for ultrasensitive detection of microRNA-222 (miRNA-222). Interestingly, AgAuS QDs revealed excellent ECL efficiency (34.91%) compared to that of Ag2S QDs (10.30%), versus the standard [Ru(bpy)3]2+/S2O82- system, which benefited from the advantages of abundant surface defects and narrow bandgaps by Au incorporation. Additionally, an improved localized catalytic hairpin self-assembly (L-CHA) system was developed to display an increased reaction speed by improving the local concentration of DNA strands, which addressed the obstacles of time-consuming traditional CHA systems. As a proof of concept, based on AgAuS QDs as an ECL emitter and improved localized CHA systems as a signal amplification strategy, a "signal on-off" ECL biosensor was developed to exhibit a superior reaction rate and excellent sensitivity with a detection limit of 10.5 aM for the target miRNA-222, which was further employed for the analysis of miRNA-222 from cancer cell (MHCC-97L) lysate. This work advances the exploration of highly efficient NIR ECL emitters to construct an ultrasensitive biosensor for the detection of biomolecules in disease diagnosis and NIR biological imaging.

S–CdIn2S4: A novel near-infrared emitter triggered by low potential for constructing a dual-mode immunosensing platform

CdIn2S4 is an interesting ternary metal sulfide whose narrow band gap and tunable optical properties offer new opportunities for the development of novel ECL emitters. Here, we use a simple hydrothermal synthesis to obtain hollow spindle CdIn2S4 (S–CIS), which exhibits strong near-infrared electrochemiluminescence (ECL) emission with K2S2O8 as a coreactant at a low excitation potential (−1.3 V), which is encouraging. The lower excitation potential of S–CIS is probably due to the low band gap energy, which makes the excitation potential positively shift. This lower excitation potential reduces the side-reactions caused by high voltages, effectively avoiding irreversible damage to biomolecules, and protecting the biological activity of antigens and antibodides. In this work, new features of S–CIS in ECL studies are also presented, demonstrating that the ECL emission mechanism of S–CIS is generated by surface state transitions and that S–CIS exhibits excellent near-infrared (NIR) characteristics. Importantly, we introduced S–CIS into electrochemical impedance spectroscopy (EIS) and ECL to the construct a dual-mode sensing platform to achieve AFP detection. The two models with intrinsic reference calibration and high accuracy showed outstanding analytical performance in AFP detection. The detection limits were 0.862 pg mL−1 and 16.8 fg mL−1, respectively. This study demonstrates the key role and great application potential of S–CIS as a novel NIR emitter with easy preparation, low cost and great performance in the development of a simple, efficient and ultrasensitive dual-mode response sensing platform for early clinical use.

Highly efficient near-infrared electrochemiluminescence resonance energy transfer system for biosensing: Nonmetallic plasmon Mediated well-matched energy donor-acceptor pair

Herein, a well-matched energy donor-acceptor pair strategy was designed to construct highly efficient NIR ECL-RET system. In detail, an ECL amplification system consisting of SnS2 quantum dots decorated Ti3C2 MXene nanocomposites (SnS2 QDs-Ti3C2) as the energy donor were developed via a one-pot method, and the nanocomposites exhibited highly efficient NIR ECL emission due to the surface-defect effect generated by the oxygen-containing functional groups in MXene. Nonmetallic plasmon hydrated defective tungsten oxide nanosheets (dWO3•H2O) were utilized as energy acceptors because of its strong surface plasmon resonance effect in Vis-NIR absorption range. Compared with non-defective tungsten oxide hydrate nanosheets (WO3•H2O), the overlapping area between ECL spectrum of SnS2 QDs-Ti3C2 and UV–vis spectrum of dWO3•H2O was increased by 2.1 times, and the results showed that more efficient quenching effect was obtained. As a proof of concept, tetracycline (TCN) aptamer and its complementary chain were served as a bridge to connect the energy donor and acceptor, achieving the successful construction of NIR ECL-RET aptasensor. The as-fabricated ECL sensing platform exhibited a low detection limit of 6.2 fM (S/N = 3) within a wide linear range from 10 fM to 10 μM. Besides, the NIR ECL-RET aptasensor also showed excellent stability, reproducibility and selectivity, providing a promising tool to detect TCN in real samples. This strategy offered a universal and effective method in constructing highly efficient NIR ECL-RET system for developing rapid, sensitive and accurate biological detection platform.

Ligand-Based Shielding Effect Induced Efficient Near-Infrared Electrochemiluminescence of Gold Nanoclusters and Its Sensing Application

Preparing high-efficiency ECL gold nanoclusters (Au NCs) still faces a serious challenge due to the poor stability of co-reactant radicals in aqueous media. Herein, we report a ligand-based shielding effect induced record near-infrared (λmax = 786 nm) ECL efficiency of β-cyclodextrin-protected Au NCs (β-CD-Au NCs) with triethylamine (TEA) as co-reactant. The ligand of β-CD-Au NCs with a matched hydrophobic cavity could encapsulate TEA driven by host-guest chemistry, which not only allows the generation of TEA• in the cavity to diminish environmental exposure, thus reducing the quenching by dissolved oxygen, water, etc., but also shortens the charge transfer pathway without extensive chemical modification. Density functional theory, 1H NMR spectra, electron paramagnetic resonance, and differential pulse voltammetry studies revealed that the β-CD ligand-based shielding effect significantly increased the reactivity efficiency of TEA. More importantly, in stark contrast to those of traditional ligand-protected Au NCs, the ECL efficiency of β-CD-Au NCs enhanced 321-fold versus BSA-Au NCs, 153-fold versus ATT-Au NCs, and 19-fold versus GSH-Au NCs with 1 mM TEA. Therefore, this work provides an in-depth understanding of the crucial role of ligands in enhancing the active co-reactant radical stability for high-efficiency ECL metal NCs to immensely stimulate their promising applications. Using the β-CD-Au NCs as emitters, a "signal off" ECL sensing platform was constructed to detect noradrenaline as a model target with a lower detection limit of 0.91 nM.

Coreactant-free and Near-Infrared Electrochemiluminescence Immunoassay with n-Type Au Nanocrystals as Luminophores.

The electrochemiluminescence (ECL) bioassay is prominently carried out with the involvement of the coreactant. To remove the detrimental effects of the coreactant on the ECL of luminophores, herein, a promising ECL immunoassay strategy with biocompatible nanoparticles as the luminophore is proposed, which involves directly and electrochemically oxidizing the luminophore methionine-capped Au (Met@Au) nanocrystals (NCs) without the participation of any coreactant. Met@Au NCs are a kind of n-type nanoparticles, and they can be electrochemically injected with valence band (VB) holes around +0.80 and +1.10 V (vs Ag/AgCl). The electrochemically injected exogenous VB hole can recombine with the endogenous conduction band electron of Met@Au NCs and eventually bring out two coreactant-free and near-infrared ECL processes around 0.80 V (ECL-1) and 1.10 V (ECL-2). The intensity of coreactant-free ECL is primarily determined by the electrochemical oxidation-induced hole-injection process. ECL-2 is considerably stronger than ECL-1 and can be exploited for determining the carcinoembryonic antigen (CEA) in a sandwich immunoassay procedure with a linear range from 0.1 to 50 pg/mL as well as a limit of detection of 0.03 pg/mL (S/N = 3).

Kinetics-Based Ratiometric Electrochemiluminescence Analysis for Signal Specificity: Case Studies of Piperazine Drug Discrimination with Au Nanoclusters.

A multi-parameter calibration and analysis strategy has been developed based on the kinetics of charge transfer reactions. Absolute and ratiometric electrochemiluminescence signals are elucidated from single measurements for the detection of hydroxyzine and cetirizine as prototype drugs which greatly enhance the near-infrared electrochemiluminescence from atomically precise Au22 nanoclusters stabilized with lipoic acid ligands on ITO electrodes. The signal-on sensing mechanism eliminates the need for recognition elements and highly excess co-reactants in conventional electrochemiluminescence practice. The rates of sequential charge transfer reactions render specificity in electrochemiluminescence intensity and kinetics toward the target molecular/electronic structures and are conveniently controlled/optimized by operation parameters. Signal kinetic profiles, in stark contrast to steady-state or single-point recordings, not only improve the signal/noise ratio but also offer greater resolving power to differentiate analogue species and nonspecific interference. The fundamental kinetics-based ratiometric concept/strategy is not limited to a specific luminophore or a co-reactant and is thus generalizable. The case studies successfully detect and discriminate drug compounds at sub-nanomolar physiological ranges, with efficacy validated using synthetic urine toward point-of-care applications in therapeutic/abuse drug monitoring.

Enhanced near-infrared electrochemiluminescence of Au nanoclusters treated with piperidine

Au nanoclusters (NCs) are considered a promising electrochemiluminescence (ECL) luminophore with biocompatibility and stability that make it suitable for use in bioelectrochemical investigations. The near-infrared (near-IR) ECL of Au NCs is of particular interest for biological applications. In this study, we report the significantly enhanced near-IR ECL of water-soluble Au NCs stabilized with glutathione, which was induced by treating the Au NCs with piperidine. The piperidine treatment of Au NCs enabled a 16-fold enhancement in the near-IR ECL of the NCs in the presence of triethylamine coreactants in water. Compared to the well-known near-IR ECL of Au NCs stabilized with bovine serum albumin (BSA) as a control, the near-IR ECL emission of the piperidine-treated Au NCs (p-Au NCs) was 8 times that of the BSA-stabilized Au NCs. Detailed control experiments suggested that the enhanced near-IR ECL of p-Au NCs could be attributed not to environmental effects (e.g., pH and chemical interference) and the surface ligand effect, but to the reduction of Au(I)-glutathione to Au(0)-glutathione in the NCs. Importantly, the piperidine treatment was also shown to be applicable to different types of Au NCs, such as well-established Au22(SG)18, for improving the ECL emission of the NCs in the near-IR region.

A simple and sensitive electrochemiluminescence spectrum measurement platform and spectrum-resolved ratiometric sensor for miroRNA-141 determination

The electrochemiluminescence (ECL) spectral information is useful in ECL mechanism investigations, ratiometric ECL sensors and multi-analyte determinations. To overcome the shortcomings of low sensitivity in charge coupled devices (CCD) ECL spectrometer and low time efficiency for spectrum discrimination by using single band-pass filter (BPF) in one potential scan, a simple and sensitive ECL spectrum measurement platform is developed by placing a portable BPF array turntable device (with eleven measurement channels and one indicator channel) between the working electrode and photomultiplier in a conventional ECL analyzer. The systematic error due to the time dependent ECL intensity, which is the main obstacle for ECL spectrum measurement in wavelength scan mode, is neutralized by using the accumulated intensity for each channel in a group of spectrum measurement cycles. In a spectrum-resolved ratiometric ECL sensor for miroRNA-141 determination, near-infrared ECL emitter of methionine-stabilized Au nanoclusters (Met-Au NCs) is used as the tag and blue ECL emitter of g-C3N4 as the reference. The ratio of the total ECL intensity in near-infrared wavelength region (from Met-Au NCs) to that in blue wavelength region (from g-C3N4) is in linear correlation with the logarithmic concentration of microRNA-141 from 1 fM to 10 pM, with the limit of detection of 0.22 fM.

Hollow Double-Shell CuCo2O4@Cu2O Heterostructures as a Highly Efficient Coreaction Accelerator for Amplifying NIR Electrochemiluminescence of Gold Nanoclusters in Immunoassay.

The evolution of electrochemiluminescence (ECL) emission amplified by coreaction accelerator in near-infrared (NIR) area has been overwhelmingly anticipated for ultrasensitive detection of disease biomarkers. Herein, the hollow double-shell CuCo2O4@Cu2O (HDS-CuCo2O4@Cu2O) heterostructures were conveniently prepared and utilized as an attractive coreaction accelerator to improve the NIR ECL performance of gold nanoclusters (AuNCs) for the first time. Benefiting from perfect-matched lattice spacing, unique Cu2O nanoparticles (NPs) were formed in situ on the layered-hollow CuCo2O4 nanospheres (NSs) to obtain HDS-CuCo2O4@Cu2O heterostructures. The formed heterojunctions supplied shorter charge transfer distance and better interfacial charge transfer efficiency as well as more effective separation performance. Consequently, HDS-CuCo2O4@Cu2O heterostructures as an admirable electroactive substrate could significantly promote the formation of sufficient coreactant intermediate radicals to react with AuNCs cationic radicals, realizing about 3-folds stronger NIR ECL response than that of individual AuNCs. In addition, the AuNCs templated by l-methionine (l-Met) exhibited NIR ECL emission around 830 nm, which could decrease the photochemical damage to even realize a nondestructive detection with improved susceptibility and circumambient adaptability. Subsequently, a well site-oriented fixation strategy utilizing HWRGWVC heptapeptide as the specific antibody immobilizer was introduced to further preserve the bioactivity of antibody on the HDS-CuCo2O4@Cu2O and AuNCs surface along with enhancing the incubation performance markedly. In view of the progressive sensing mechanism, a NIR immunosensor was obtained for the ultrasensitive analysis of CYFRA21-1, which achieved a broad linear ranging from 2 fg/mL to 50 ng/mL and a low limit of detection (LOD) of 0.67 fg/mL (S/N = 3).

A signal amplification of near-infrared electrochemiluminescence immunosensor for SFTSV determination based on SiO2 photonic crystals nanomembrane

In this work, a novel near-infrared electrochemiluminescence signal amplification strategy was fabricated based on SiO2 photonic crystals nanomembrane as the ECL electrodes for sensitive and specific detection of SFTSV. The photonic crystal structure of the SiO2 nanomembrane has an excellent light scattering effect, which significantly increases the photon flux in the luminescent molecule and improves the excitation of the ECL molecule (CdTe@CdS QDs) by the re-radiation dipole electromagnetic field. In addition, the increase of the effective electroactive area of the photonic crystals modified electrode also prominently contributes to the ECL intensity. The results manifested that the SiO2 photonic crystals nanomembrane modified electrode constructed in this work can effectively improve the ECL intensity by about 7 times. Subsequently, a sandwich-type SFTSV immunosensor with a very low limit of detection of 0.0014 fg/mL was constructed. Due to the low cost and easy preparation of SiO2 photonic crystal solid-state electrodes, this work can not only effectively detect the SFTSV virus, but also provides an effective ECL signal amplification strategy.