Solid-state Electrochemiluminescence Research Articles

Mineralization of Dandelion as an Enzyme-like Nanoelectrode for Ultrasensitive Monitoring of H2O2 at a Single-Cell Level

Cellular heterogeneity is one of the major challenges in understanding cell-to-cell differences in therapeutics. A sensitive electrode with a micro/nanoscale diameter is urgently needed for sensing molecules at a single-cell level. A dandelion seed has a bristly fiber structure and measures roughly 14 mm. Inspired by this, a solid-state electrochemiluminescence (ECL) nanoelectrode based on a dandelion seed is developed for the ultrasensitive analysis of H2O2. A layer of gold nanoparticles is electroless-plated on the dandelion seeds to enable the bio-fibers to work as conductive electrodes. Because ECL is a surface-confined process, a layer of MIL-100(Fe) (MIL = Materials of Institut Lavoisier) film is coated on the fiber electrode as the carrier of a luminophore. Benefitting from the peroxidase-like activity of an iron(III) metal-organic framework (FeMOF), H2O2 is decomposed into •OH radicals, which in situ serve as the coreactants for the ECL emission. The design of this luminophore-in-MOF coater not only shortens the distance between the detection interface and the coreactant molecules but also effectively enriches the excited-state luminophore in a localized thin film. As a proof of concept, the nanosized filament tips are employed to sense the H2O2 released from different living cells at a single-cell level and demonstrate excellent feasibility in probing the cell heterogeneity. As a biomass electrode, the superiority of a dandelion nanoelectrode is that it is inexpensive, scalable, assessable, and environmentally friendly. This study not only advanced plant fibers as conductive nanoelectrodes but also, more importantly, offered access to the development of solid-state ECL nanoelectrodes with single-cell sensitivity.

Solid-state electrochemiluminescence sensor based on zeolitic imidazolate framework-67 electrospinning nanofibers for chlorpyrifos detection.

A novel solid-state electrochemiluminescence (ECL) sensor for chlorpyrifos (CPF) detection was constructed based on zeolitic imidazolate framework-67 electrospinning nanofibers (ZIF-67 NFs). Silver nanoparticles (Ag NPs), ZIF-67 NFs, tris(2,2'-bipyridyl) ruthenium(II) [Ru(bpy)32+], and Nafion were successively deposited on the surface of the electrode. Ag NPs played a role in promoting electron transfer, and ZIF-67 NFs played a role in fixing Ru(bpy)32+ and promoting electron transfer due to its large specific surface area and porosity. Nafion formed a film on the outermost layer of the electrode to further improve the stability of the system. Therefore, the modified electrode showed stable and obvious ECL signal in PBS solution containing 10 μL 0.01M TprA (pH 8.0). CPF quenched the ECL signal of the system, and the quenching value was linear with the logarithm of CPF concentration in the range 1.0 × 10-13 to 1.0 × 10-6M. The detection limit was 3.3 × 10-14M (S/N = 3). In this study, ZIF-67 NFs were used as an ECL promoter for the first time, broadening the application range of ZIF-67 NFs.

Bipolar silica nanochannel array confined electrochemiluminescence for ultrasensitive detection of SARS-CoV-2 antibody

Ultrasensitive, specific, and early identification of Coronavirus Disease (2019) (COVID-19) infection is critical to control virus spread and remains a global public health problem. Herein, we present a novel solid-state electrochemiluminescence (ECL) platform targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody with rapidity and ultrahigh sensitivity, in which a bipolar silica nanochannel array (bp-SNA) is fabricated on indium tin oxide (ITO) electrode for the first time to stably confine the ECL probe of tris(2,2′-bipyridyl) ruthenium (Ru(bpy)32+) under dual electrostatic force. The bp-SNA consists of tightly packed bilayer silica nanochannel array (SNA) with asymmetric surface charges, namely an inner negatively charged SNA (n-SNA) and an outer positively charged SNA (p-SNA), serving as an “electrostatic lock” to enrich and stabilize the cationic Ru(bpy)32+ probe without leakage from the electrode surface. The detection of SARS-CoV-2 IgG antibody could be realized via immobilization of SARS-CoV-2 spike protein on the utmost of Ru(bpy)32+-confined solid-state ECL platform (Ru@bp-SNA). Upon the capture of target SARS-CoV-2 IgG by immune recognition, the formed immunocomplex will block the nanochannel, leading to the hindered diffusion of the co-reactant (tri-n-propylamine, TPrA) and further producing a decreased ECL signal. The developed solid-stated ECL immunosensor is able to determine SARS-CoV-2 IgG with a wide linear range (5 pg mL−1 to 1 μg mL−1), a low limit-of-detection (2.9 pg mL−1), and a short incubation time (30 min). Furthermore, accurate analysis of SARS-CoV-2 IgG in real serum samples is also obtained by the sensor.

Water Washable and Flexible Light-Emitting Fibers Based on Electrochemiluminescent Gels.

Herein, a new concept of device architecture to fabricate fibrous light-emitting devices is demonstrated based on an electrochemiluminescence (ECL) material for an electronic textile system. A unique feature of this work is that instead of conventional semiconductor materials, such as organics, perovskites, and quantum dots for fibrous light emitting devices, a solid-state ECL electrolyte gel is employed as a light-emitting layer. The solid-state ECL gel is prepared from a precursor solution composed of matrix polymer, ionic liquid, and ECL luminophore. From this, we successfully realize light-emitting fibers through a simple and cost-effective single-step dip-coating method in ambient air, without complicated multistep vacuum processes. The resulting fiber devices reliably operated under applied AC bias of ±2.5 V and showed luminance of 47 cd m-2. More importantly, the light-emitting fibers exhibited outstanding water resistance without any passivation layers, owing to the water immiscible and hydrophobic nature of the ECL gel. In addition, because of their simple structure, the fiber devices can be easily deformed and woven together with commercial knitwear by hand. Therefore, these results suggest a promising strategy for the development of practical fiber displays and contribute to progress in electronic textile technology.

Novel cloth-based closed bipolar solid-state electrochemiluminescence (CBP-SS-ECL) aptasensor for detecting carcinoembryonic antigen

This study involved the construction of a novel cloth-based CBP-SS-ECL aptasensor by introducing proximity hybridisation (PH) and solid-state electrochemiluminescence (SS-ECL) into a closed bipolar (CBP) electrochemistry system. Screen-printing was used to fabricate the cloth-based aptasensors, and PH and aptamers provided good selectivity for the sensor. Furthermore, the CBP-SS-ECL sensing interface was produced by immobilising of Ru(bpy)32+- doped silica nanoparticles (Ru–Si-NPs) on the anode of closed bipolar electrode (C-BPE). PH product (PP) was formed due to the target (carcinoembryonic antigen, CEA), and then the PP opened the Au NP-labelled capture probe (Au-CP) on the C-BPE anode (CBA), allowing ferrocene carboxylic acid (FcA) close to the CBA surface and Au NPs away from the surface. The corresponding quenching and enhancement of ECL signal by FcA and Au NPs, respectively, markedly enhanced ECL signal. This aptasensor successfully achieved quantitative detection of CEA, with a linear detection range of 5–100000 pg mL−1 and a detection limit of 1.6 pg mL−1. The described aptasensor showed an acceptable sensitivity, selectivity, stability, and ability to detect CEA levels in complex human serum samples. In particular, this aptasensor showed satisfactory versatility, indicating its potential for simultaneous detection of CEA and K-ras gene.

Rational design of effective solid-state electrochemiluminescence platform of Gold@Polyluminol nanocomposite as an ultrasensitive immuno-probe for selective detection of prostate specific antigen

An electrodeposited gold@poly-luminol nanocomposite on glassy carbon electrode (Au@PL-NC/GCE) has been developed and demonstrated as solid-state electrochemiluminescence (ECL) immunosensor platform for prostate specific antigen (PSA) sensing. In-situ electro-generated reactive oxygen species (ROS) from oxygen reduction reaction in oxygen saturated PBS (pH 7.4) acts as sole co-reactant augmenting the signal transduction. Protein-G bio-affinity layer interfaced with Au@PL-NC/GCE (Protein-G/Au@PL-NC/GCE) to support the effective localization of Fc region of the monoclonal antibodies of PSA (mAb-PSA). As-developed ECL probe exhibit selective recognition of target analyte, PSA, enabling wide linearity of 1 fg mL−1 to 10 μg mL−1 with a calculated limit of detection (LOD) and limit of quantification (LOQ) of 0.45 fg mL−1 and 1.37 fg mL−1, respectively. The selectivity and specificity of the ECL probe was tested using human serum albumin, immunoglobulin G and mixtures of the same with target analyte. Fabricated ECL probe not only exhibit high sensitivity and specificity against commercial PSA samples but also enable clinical detection in real human serum and urine samples with acceptable recovery range from 97% to 103%. Our results suggest that the fabricated reagent-less solid-state ECL platform holds promising application in the field of prostate oncological screening and its point-of-care applications.

Disposable biosensor based on novel ternary Ru-PEI@PCN-333(Al) self-enhanced electrochemiluminescence system for on-site determination of caspase-3 activity

The number of death due to cancer-related diseases each year is at the alarming level and is constantly growing. Tools that can effectively and conveniently detect cancer cell apoptosis can play a significant role in cancer research, cancer therapy, and other related industries. Herein, we fabricated, for the first time, an ultrasensitive, disposable, self-enhanced off-on electrochemiluminescence (ECL) biosensor based on ternary Ru-PEI@PCN-333(Al) system to determine caspase-3 activity, the biomarker of apoptosis. The biosensor had a low detection limit of 0.017 pg/mL and was able to enhance the ECL emission and stability. A solid-state (SS) ECL strategy was adopted to overcome the relatively weak ECL emission due to the long distance between electrochemiluminophore and electrode surface. The analysis requires only one incubation step, which can significantly reduce the operational complexity and time. The biosensor had higher sensitivity, and the off-on ECL mode was achieved using caspase-3 as a switch. The on-site and rapid detection capability of the biosensor was achieved by the introduction of disposable screen-printed electrodes (SPEs). This study lays a foundation for the development of more advanced, ingenious, portable and reliable ECL devices for biosensing not only caspase-3, but also other bioanalytes.

Highly Active Electrochemiluminescence of Ruthenium Complex Co-assembled Chalcogenide Nanoclusters and the Application for Label-Free Detection of Alkaline Phosphatase.

Rational design of electrochemiluminescence (ECL) reagents is essential for the development of ECL biosensors with superior performances. In this work, the assembly of tris(1,10-phenanthroline)ruthenium(II) [Ru(phen)32+] and tetrahedral chalcogenide nanoclusters of [Cd32S14(SC6H5)38]2- in the formation of complex nanoclusters (CdS-Ru) was developed, in which Ru(phen)32+ was uniformly encapsulated and dispersed at a molecular level in the chalcogenide nanocluster via multiple noncovalent interactions. It was observed that the promoted ECL emission was realized by the charge transfer between the tetrahedral CdS nanocluster and Ru(phen)32+ by the formation of the assembly complex, which was elucidated by cyclic voltammetry curves, ECL-potential curves, and in situ dynamic ECL spectra. Taking advantages of the facile charge transfer in the open framework CdS-Ru, a high ECL efficiency has been achieved with remarkable stability. Moreover, a solid-state ECL sensor based on the CdS-Ru modified electrode was fabricated for label-free detection of alkaline phosphatase (ALP) activity with a detection limit as low as 0.35 U/L and superior reproducibility. This solid-state ECL sensor also displayed favorable selectivity among various interferences and was applied for ALP activity analysis in human serum samples. These results implicated the potential applications of CdS-Ru for sensitive ECL analysis in complicated reaction systems and enlightened the rational design for self-enhanced and highly efficient ECL materials.

Enhanced electrochemiluminescence bioassay triggered by intracellular leakage for detection of Escherichia coli

An intracellular leakage-trigged signal-on solid-state electrochemiluminescent (ECL) assay is developed for the detection of Escherichia coli (E. coli). A self-assembled multilayer ensemble of N, S co-doped carbon dots -poly dimethyl diallylammonium chloride grafted carbon nanospheres is used as ECL luminophores with peroxydisulfate (PS) ions as coreactants. The incorporation of molecularly imprinted electrospun nanofibers with the multilayer ensemble enables a robust, highly selective solid-state ECL probe without using any expensive and fragile biological receptor. Upon the imprinted E. coli exposed to the assay, under bactericidal effects of PS ions by destroying the integrity of E. coli cell membrane, intracellular leakage K+-triggered ECL enhancement is first disclosed via prompting the involved 1O2-mediated ECL process. Benefiting from the ECL enhancement upon increasing the concentration of E. coli, a unique intracellular leakage-trigged signal-on ECL system is created for sensing E. coli. Such a assay is proved to be highly specific and sensitive for sensing E. coli in the concentration range from 5 to 107 cfu mL−1, achieving a detection limit of 1 cfu mL−1 (S/N = 3). This label-free, simple and facile assay provides a promising point-of-care diagnostic tool for pathogen detection.

Encapsulating Ru(bpy)32+ in an infinite coordination polymer network: Towards a solid-state electrochemiluminescence sensing platform for histamine to evaluate fish product quality

In this work, we demonstrate a novel solid-state electrochemiluminescence (ECL) sensor based on the Ru(bpy)32+@terbium-guanosine monophosphate infinite coordination polymer network ((Ru(bpy)32+@Tb-GMP ICPn). Comparing with the traditional luminescence of Ru(bpy)32+ observed in a liquid system, the proposed method of encapsulating Ru(bpy)32+ into ICPn for immobilization greatly improves the ECL signal and efficiency, which is attributed to the unique porous structure and large specific surface area of ICPn. Moreover, the solid-state Ru(bpy)32+ ECL sensor has good biocompatibility and low toxicity. Taking histamine (HA) as a detection model, a good linear relationship between ECL intensity and logarithm of HA concentration was obtained with a low detection limit of 17 nM, and satisfactory results were obtained for detecting HA levels in fish samples as well. The proposed solid-state Ru(bpy)32+ ECL sensor has great application prospects in the safety of food.

Deployment of MIL-88B(Fe)/TiO2 Nanotube-Supported Ti Wires as Reusable Electrochemiluminescence Microelectrodes for Noninvasive Sensing of H2O2 from Single Cancer Cells.

As one of the significant intracellular signaling molecules, hydrogen peroxide (H2O2) regulates some vital biological processes. However, it remains a challenge to develop noninvasive electrodes that can be used for sensing trace H2O2 at the cellular level. Here, we evaluated a high-performance solid-state electrochemiluminescence (ECL) H2O2 sensor based on MIL-88B(Fe) nanocrystal-anchored Ti microwires. Semiconducting TiO2 nanotubes (TiNTs) vertically grown around a Ti wire via an anodization technique act as an intrinsic ECL luminophore. By integrating with MIL-88B(Fe), the synergistic effect of the TiO2 luminophore and the remarkable peroxidase-like activity of MIL-88B(Fe) enable the resulting H2O2 sensor an ultrahigh sensitivity featuring a minimum detection limit of 0.1 nM (S/N = 3), long-term stability, high durativity, and wide-range linear response to a concentration of up to 10 mM. To demonstrate the concept of a MIL-88B(Fe)@TiO2 microelectrode for single-cell sensing, the electrode was used to detect intracellular H2O2 in a single cell. Moreover, benefiting from the heterojunction of MIL-88B(Fe)/TiO2, the microelectrode was found to exhibit excellent photocatalytic activity in the visible-light range, that is, the sensor surface can be self-cleaning after a short visible-light treatment. These advanced sensor characteristics involving easy reusability reveal that the MIL-88B(Fe)@TiO2 microelectrode is a new platform for cytosensing. This study provides a new strategy to design semiconductor materials with arbitrary shape and size, allowing for profound applications in biomedical and clinical analysis.

Atom-Anchoring Strategy with Metal-Organic Frameworks for Highly Efficient Solid-State Electrochemiluminescence.

A chemical fixation strategy originating from single-atom-anchoring with metal-organic frameworks as a carrying matrix was proposed for solid-state electrochemiluminescence (ECL). Herein, UiO-67(N) with the exposure of 2,2'-bipyridine (bpy) ligands could coordinate with Ru2+ to form a local structure of [Ru(bpy)3]2+ (Ru-UiO). The influence of the steric effect induced with different Ru sources was discussed. The as-obtained Ru-UiO exhibits high ECL intensity and outstanding stability in the presence of a coreactant at low concentrations. The proposed synthesis strategy may hold great potential for the synthesis of solid-state ECL materials and their further utilization in ECL analysis.

Co-reactant-free self-enhanced solid-state electrochemiluminescence platform based on polyluminol-gold nanocomposite for signal-on detection of mercury ion

Development of a self-enhanced solid-state ECL platform creates a straightforward experimental design for the fabrication of point-of-care applications. Herein, we develop a promising method for self-enhanced solid-state ECL platform of polyluminol gold nanocomposite on glassy carbon electrode [(PL-Au)nano/GCE] via simple one-step electrochemical deposition process without involving any additional co-reactants. The presence of gold nanoparticles (AuNPs) augments the electron transfer kinetics of PL (polyluminol) and enhances the solid-state ECL intensity and promotes label-free, excellent sensitivity, and selectivity to detect Hg2+ in physiological pH through signal-on mode. Unlike pristine PL/GCE, electrochemically co-deposited AuNPs in the (PL-Au)nano/GCE composite, enable the co-reactant accelerator by improving the catalytic activity of PL towards oxygen reduction reaction (ORR) yielding in-situ ROS (co-reactant) generation. Further, the ECL intensity of (PL-Au)nano/GCE composite, gradually increases with each addition of Hg2+ ion. This is because of the formation of an amalgamation of Au-Hg on (PL-Au)nano/GCE composite surface which further accelerates the yield of in-situ ROS and enhances the intensity of ECL. Whereas no ECL signals changes were observed for PL/GCE composite. The proposed self-enhanced solid-state ECL platform is selectively sensing the Hg2+ ion in the linear range of 0.3–200 nM with a detection limit of 0.1 nM. The demonstrated (PL-Au)nano/GCE platform might pave new avenues for further studies in the solid-state ECL platform which could be more useful in on-site monitoring of clinical bioassay and immunosensors.

Polymer Electrochemiluminescence Featuring Thermally Activated Delayed Fluorescence.

Electrochemiluminescence (ECL) based on conjugated polymers or oligomers is persistently being pursued owing to its huge application scope ranging from ultra-sensitive bioanalysis to ultra-resolution imaging and spectroscopy. Because of the theoretical limit in radiative exciton generation yield (typically ∼25 %) of those polymers or oligomers, the corresponding ECL efficiency is still limited, which hampers its ECL performance and its related applications. Herein, we report ECL based on a thermally activated delayed fluorescence (TADF) polymer scaffold, which is characteristic of all-exciton harvesting in the ECL process, and thus potentially capable of achieving ∼100 % ECL efficiency. These desired properties of the TADF polymer ECL is attributed to a fast and efficient up-conversion process from non-radiative triplet to radiative singlet states under thermal activation, which is absent in conventional fluorescent polymers/oligomers, such as F8BT. In this study, various ECL modes, including annihilation or co-reactant mode using TPrA or S2 O82- as co-reactant, are confirmed for our model TADF polymer ECL system, which was different from fluorescent polymer ECL counterpart. Furthermore, solid-state ECL sensing on L-cysteine (an important marker of disease) is also evaluated by using the model TADF polymer. Ultralow detection limit in combination with high sensitivity and good specificity are achieved for this model system, indicative of a high potential of the TADF polymer scaffold for applications in the broad field of ECL.

Direct-laser-writing of electrochemiluminescent electrode on glassy carbon for iodide sensing in aqueous solution

Abstract Simple and scalable construction of high-efficient solid-state electrochemiluminescence (ECL) electrode has attracted a lot of attention. Herein, using CdS as a model ECL emitter, one-step laser-scribing technique was successfully explored as an in situ and straightforward solid-phase-transition approach for the facile construction of binder-free ECL electrode. The suitable laser-scanning of Cd2+-doped polyethersulfone film on glassy carbon (GC) leads to the synchronous generation of laser-induced graphene (LIG) and laser-induced CdS (LI-CdS) hybrids anchored on GC surface (LI-CdS-G@GC). The cathodic ECL properties of LI-CdS-G@GC electrodes before and after an ultrasonication process (LI-CdS-G@GCUS) were investigated using peroxodisulfate as co-reactant. Notably, 60-fold higher ECL emission with excellent stability and reproducibility was obtained from the resultant LI-CdS-G@GCUS as compared to untreated LI-CdS-G@GC due to the ultrasonication-assisted removal of blackbody effect of LIG. Ultimately, the as-prepared LI-CdS-G@GCUS electrode with rapid and reliable ECL response was employed to construct an ECL sensor for the detection of iodide ions, showing a wide linear range of 10.0 nM–2500 nM and a low detection limit of 4.0 nM with acceptable selectivity. This work not only expands the application range of LIG but also provides a guideline for the facile design and scalable fabrication of sensitive ECL sensing interface.

Electrochemiluminescent Transistors: A New Strategy toward Light-Emitting Switching Devices.

Light-emitting transistors (LETs) have attracted a significant amount of interest as multifunctional building blocks for next-generation electronics and optoelectronic devices. However, it is challenging to obtain LETs with a high carrier mobility and uniform light-emission because the semiconductor channel should provide both the electrical charge transport and optical light-emission, and typical emissive semiconductors have low, imbalanced carrier mobilities. In this work, a novel device platform that adapts the electrochemiluminescence (ECL) principle in LETs, referred to as an ECL transistor (ECLT) is proposed. ECL is a light-emission phenomenon from electrochemically excited luminophores generated by redox reactions. A solid-state ECL electrolyte consisting of a network-forming polymer, ionic liquid, luminophore, and co-reactant is employed as the light-emitting gate insulator of the ECLT. Based on this construction, high-performance LETs that make use of various conventional non-emissive semiconductors (e.g., poly(3-hexylthiophene), zinc oxide, and reduced graphene oxide) are successfully demonstrated. All the devices exhibit a high mobility (0.9-10 cm2 V-1 s-1 ) and a uniform light-emission. This innovative approach demonstrates a novel LET platform and provides a promising pathway to achieve significant breakthroughs to develop electronic circuits and optoelectronic applications.

Unraveling the reaction mechanism of co-reactant free in-situ cathodic solid state ECL of Ru(bpy)32+ molecule immobilized on Nafion coated nanoporous gold electrode

The electrochemiluminescence (ECL) of Ru(bpy)32+ molecule which is immobilized on Nafion coated nanoporous gold electrode (Ru(bpy)32+/Nafion/NPG) is investigated without involving any additional co-reactant in 0.1 M phosphate buffer solution (PBS) at pH 7.4 and the observed results are compared with Ru(bpy)32+ molecule immobilized on Nafion coated polycrystalline gold (Ru(bpy)32+/Nafion/pc-Au). Because of high surface area volume ratio and more active sites on NPG, the obtained co-reactant free unusual cathodic ECL signal at less cathodic potentials (0.1 V vs Ag/AgCl) showed 40 times higher intensity on Ru(bpy)32+/Nafion/NPG when compared with Ru(bpy)32+/Nafion/pc-Au in PBS (pH 7.4). Interestingly, this kind of ECL signal is not observed in the case of Ru(bpy)32+ molecule which is immobilized on Nafion coated glassy carbon (GC) and polycrystalline platinum (pc-Pt) electrodes. Based on the detailed experiments on effect of different pH, various direction of scanning potential and in-situ spectroelectrochemical studies, we proposed a new reaction mechanism for the unusual cathodic ECL on Ru(bpy)32+/Nafion/NPG. Upon electrochemical oxidation on Ru(bpy)32+/Nafion/NPG at higher potential, the stored Ru(bpy)32+ is converted into Ru(bpy)33+ at the same time generated reactive intermediate species like OH radical from the conversion of Au(OH)3 to Au0 during the reduction process leads energetic electron transfer reaction to proceed the excited state of Ru(bpy)32+ and then emits light. Unlike the conventional ECL system, this kind of co-reactant free in-situ generated solid state ECL approach offers to the scope in various bio analytical applications.

A sensitive signal-on electrochemiluminescence sensor based on a nanocomposite of polypyrrole-Gd2O3 for the determination of L-cysteine in biological fluids.

A sensitive solid-state electrochemiluminescence (ECL) electrode for L-cysteine was developed based on depositing layers of a hybrid nanocomposite of polypyrrole-dodecyl benzene sulfate-sodium perchlorate-sodium carbonate-gadolinium (PPy-Gd2O3) on a platinum substrate. The presence of the Gd2O3 nanoparticle layer improved the ECL signal, and under optimum conditions, a linear relationship was observed between the signal and the logarithm of L-cysteine concentration from 1.0 × 10-13 to 1.0 × 10-6M (R2 = 0.9937). At the emission wavelengtharound 425 nm, at which the analytical signal was measured, the electrode showed an RSD of less than 4% and a low detection limit of 4.2 × 10-14M. The results proved to be reproducible and stable, and the electrode was applicable in the determination of L-cysteine in biological fluids with recoveries from 94.0-107%. Graphical abstract The results of this research indicated that the weak ECL of luminol is greatly improved by traces of L-cysteine on a solid-state platinum electrode coated with polypyrrole and gadolinium oxide nanoparticles (NPs) and have hence been effectively used in the analysis of L-cysteine in plasma and saliva.

Metal-organic gel and metal-organic framework based switchable electrochemiluminescence RNA sensing platform for Zika virus

In this work, an ultrasensitive switchable electrochemiluminescence (ECL) RNA sensing platform was established based on metal-organic gel (MOG) and metal-organic framework (MOF) as electrode matrix and nanotag, respectively. The former was prepared via the in-situ loading of graphite-like carbon nitride (g-C3N4) and post-assembly of Au nanoparticles (AuNPs) within Zr-based MOG (AuNPs&g-C3N4@Zr-MOG), exhibiting highly efficient solid-state ECL. Fe-MIL-88 MOFs not only act as an ECL acceptor in ECL resonance energy transfer system but also have metal active centers to consume co-reactant, initiating double quenching effect on the ECL of AuNPs&g-C3N4@Zr-MOG. Then, DNA probe containing an apurinic/ apyrimidinic (AP) site connected the both, resulting in a turn-off signal. In the presence of the target RNA, the ECL was turned on because the AP site of DNA probe was activated to be circularly cleaved by endonuclease IV. Using Zika virus (ZIKV) RNA as a model analyte, the ECL platform showed a wide detection range from 0.3 nM to 3 μM with a detection limit as low as 0.1 nM. Besides, the sensor exhibited excellent specificity and stability, as well as acceptable real sample detection capability, illustrating the feasibility of clinical measurement in the future.

A novel label-free solid-state electrochemiluminescence sensor based on the resonance energy transfer from Ru(bpy)32+ to GO for DNA hybridization detection

Based on electrochemiluminescence resonance energy transfer (ERET) from Ru(bpy)32+ to graphene oxide (GO), a novel label-free solid-state ECL sensor for sensitive detection of DNA was proposed. First, Ru(bpy)32+/AuNPs was successfully prepared by using a simple and green method and characterized by transmission electron microscopy (TEM), Energy Dispersive X-ray (EDX), and UV–vis spectroscopy. Then, the Ru(bpy)32+/AuNPs colloid was assembled on the gold electrode surface for solid-state ECL film which also later could be used to immobilize thiol-derivatized, single-stranded DNA (HS-ssDNA) via Au–S interactions. The stepwise modification procedure was characterized by cyclic voltammetry(CV), electrochemical impedance spectroscopy (EIS), probe approach curves (PAC) and ECL, respectively. The resulting modified electrode was tested as ECL biosensor for DNA detection. Upon addition of GO, the strong noncovalent interaction between HS-ssDNA and GO led to ECL quenching because of ERET. When in the presence of target ssDNA (t-ssDNA), the distance between the HS-ssDNA and GO increased, which significantly hindered the ERET and, thus, resulted in the restoration of ECL. The ECL intensity of the biosensor increased linearly with t-ssDNA concentration in the range of 50–1000pM, and the detection limit is 20pM. To the best of our knowledge, this is the first application of solid-state ERET from Ru(bpy)32+ to GO and opens new opportunities for sensitive detection of biorecognition events.