A Solid‐State Electrochemiluminescence Immunosensor Based on MWCNTs‐Nafion and Ru(bpy)32+/Nano‐Pt Nanocomposites for Detection of α‐Fetoprotein

A approach was successfully employed for constructing a solid‐state electrochemiluminescence (ECL) immunosensor by layer‐by‐layer self‐assembly of multiwall carbon nanotubes (MWCNTs)‐Nafion composite film, Ru(bpy)₃²⁺/nano‐Pt aggregates (Ru‐PtNPs) and Pt nanoparticles (PtNPs). The influence of Pt nanoparticles on the ECL intensity was quantitatively evaluated by calculating the electroactive surface area of different electrodes with or without PtNPs to immobilize Ru(bpy)₃²⁺. The principle of ECL detection for target α‐fetoprotein antigen (AFP) was based on the increment of resistance after immunoreaction, which led to a decrease in ECL intensity. The linear response range was 0.01–10 ng mL^?1 with the detection limit of 3.3 pg mL^?1. The immunosensor exhibited advantages of simple preparation and operation, high sensitivity and good selectivity.     

A facile one-pot interfacial synthesis of Pt nanoparticles/polypyrrole composites and their application for non-enzymatic sensing hydrogen peroxide

Pt nanoparticles (PtNPs)/polypyrole (PPy) composites were successfully prepared through a facile one-pot interfacial polymerization of pyrrole by using H₂PtCl₆ as the oxidant for the first time. The as-prepared PPy was granular particles with particle size within a few hundred nanometers, on which PtNPs (1.7–3.5) nm were homogeneously dispersed. The PtNPs/PPy composites displayed excellent electrocatalytic activity toward redox of H₂O₂. The non-enzyme sensor constructed with PtNPs/PPy composites displayed good sensing ability toward H₂O₂ at ?0.1 V with a significantly high sensitivity of 6056 μAmM^?1cm^?2 and a low detection limit of 1.8 μM (S/N = 3).     

Size-tunable green synthesis of platinum nanoparticles using chlorogenic acid

A facile green synthesis of platinum nanoparticles (PtNPs) using chlorogenic acid (CGA) as a reducing agent and stabilizing agent has been reported here for the first time to the knowledge of the authors. Well-dispersed PtNPs are synthesized in spherical shapes and are tuned in size by simply changing the molar ratio of H₂PtCl₆ to CGA, with the same salt, temperature and solvent. The average sizes of the particles were 16.9 ± 4.7, 13.3 ± 4.0, 10.8 ± 3.4, and 7.5 ± 2.3 nm, respectively, corresponding to molar ratios of the initial H₂PtCl₆/CGA of 1:1, 1:2, 1:3 and 1:4 and decreased with an increase in CGA concentration. Transmission electron microscope; energy-dispersive spectrometer; UV–visible absorption spectra (UV–Vis); and Fourier transmission infrared spectra were used to characterize the PtNPs. Additionally, the advantage of CGA for possible synergistic biological activity was studied through the in vitro antioxidant activity of PtNPs by CGA for capture of free radicals. Our results indicate that CGA is an excellent reducing and stabilizing agent in green synthesis of PtNPs, and these size-tunable PtNPs can provide potential applications in the field of biomedicines.

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A Novel Hydrogen Peroxide Biosensor Based on the Synergistic Effect of Gold‐Platinum Alloy Nanoparticles/Polyaniline Nanotube/Chitosan Nanocomposite Membrane

Based on the immobilization of horseradish peroxidase (HRP) in chitosan(CS) on a glassy carbon electrode (GCE) modified with the Au‐Pt alloy nanoparticles (NPs) / polyaniline nanotube (nanoPAN) nanocomposite film, a novel hydrogen peroxide biosensor was constructed. The modified processes of GCE were monitored by cyclic voltammetry and electrochemical impedance spectroscopy. Au‐PtNPs/nanoPAN/CS had a better synergistic electrochemical effect than did AuNPs/nanoPAN/CS or PtNPs/nanoPAN/CS. The amperometric response of the biosensor towards H₂O₂ was investigated by successively adding aliquots of H₂O₂ to a continuous stirring phosphate buffer solution under the optimized conditions. Because Au‐PtNPs have unique catalytic properties and good biocompatibility, and especially Au‐PtNPs and nanoPAN have synergistic augmentation for facilitating electron‐transfer, the biosensor displayed a fast response time (<2 s) and broad linear response to H₂O₂ in the range from 1.0 to 2200 μmol L^?1 with a relatively low detection limit of 0.5 μmol L^?1 at 3 times the background noise. Moreover, the biosensor can be applied in practical analysis and exhibited high sensitivity, good reproducibility, and long‐term stability.     

Electrochemiluminescence Immunosensor Based on Functionalized Graphene/Fe3O4‐Au Magnetic Capture Probes for Ultrasensitive Detection of Tetrodotoxin

An ultrasensitive electrochemiluminescence (ECL) immunosensor for the detection of tetrodotoxin (TTX) is proposed, which are composed of the branched poly‐(ethylenimine) (BPEI) functionalized graphene (BGNs)/Fe₃O₄‐Au magnetic capture probes and luminol‐capped gold nanocomposites (luminol‐AuNPs) as the signal tag. Herein, a typical sandwich immunecomplex was constructed on the glassy carbon electrode. The BGNs/Fe₃O₄‐Au hybrids could efficiently conjugate primary antibody via the Au−S chemical bonds or Au−N chemical bonds and rapidly separate under external magnetic field. The introduction of BPEI to GO could enhance the luminol‐ECL intensity. Meanwhile, the multifunctional nanocomposites have been proved with good water‐solubility, excellent electron transfer, outstanding stability, etc. The luminescent luminol‐AuNPs, a high efficient electrochemiluminescence marker, can be assembled on the second antibody, which can produce the ECL signal to achieve the determination of TTX. This proposed ECL immunosensor with a linear range from 0.01–100 ng/mL can be applied in the detection of TTX in real samples with satisfactory results.     

Amplified electrochemiluminescent aptasensor using mimicking bi-enzyme nanocomplexes as signal enhancement

In this work, a sandwich-type electrochemiluminescence (ECL) aptasensor for ultrasensitive detection of thrombin (TB) was designed based on mimicking bi-enzyme cascade catalysis to in situ generate coreactant of dissolved oxygen (O₂) for signal amplification. We utilized hollow Au nanoparticles (HAuNPs) as carriers to immobilize glucose oxidase nanoparticles (GOxNPs) and Pt nanoparticles (PtNPs) by electrostatic adsorption. Then, the detection aptamer of thrombin (TBA 2) was immobilized on the PtNPs/GOxNPs/HAuNPs nanocomplexes. Finally, hemin was intercalated into the TBA 2 to obtain the hemin/G-quadruplex structure. The hemin/G-quadruplex was an interesting DNAzyme that commonly mimiced horseradish peroxidase (HRP). Herein, GOxNPs, hemin/G-quadruplex and PtNPs could form mimicking bi-enzyme cascade catalysis system to in situ generate dissolved O₂ as coreactant in peroxydisulfate solution when the testing buffer contained proper amounts of glucose. This method had successfully overcome the disadvantage of difficulty to label the dissolved O₂ and realized the ECL signal amplification. The experiment proved that the aptasensor had good linear relationship on low concentration of TB. The linear range was 1 × 10⁻⁶–10 nM, with a detection limit of 0.3 fM.     

Facile synthesis of PbSe hollow nanostructure assemblies via a solid/liquid-phase chemical route and their electrogenerated chemiluminescence properties

Spherical PbSe hollow nanostructure assemblies (HNSAs) were synthesized by a simple one‐pot solid/liquid‐phase reaction in which solid KPbI₃ ? 2 H₂O and SeO₂ are heated in oleic acid/dodecylamine/1‐octadecene at 250 °C for 30 min. XRD analysis shows that the obtained product is cubic‐phase PbSe and well crystallized. FESEM and TEM images reveal that the obtained spherical PbSe assemblies are made up of small, irregular, and fused hollow nanostructure building blocks. On the basis of temperature‐ and time‐dependent investigations as well as control experiments, molten‐salt corrosion of solid PbSe nanocrystal aggregates formed in situ during the high‐temperature ripening stage is suggested to explain the formation of such novel assemblies. Moreover, when the reaction temperature is further increased to 280 or 320 °C with other conditions unchanged, cubic and orthorhombic mixed‐phase PbSe HNSAs is generated. The obtained PbSe HNSAs exhibit excellent electrogenerated chemiluminescence (ECL) performance. Two strong and stable emission peaks at about ?1.4 and +1.5 V (vs. Ag/AgCl) are observed. In particular, the ECL intensity is influenced by the crystal phase of PbSe.     

A Sandwich‐type Electrochemiluminescence Aptasensor for Thrombin Based on Functional Co‐polymer Electrode Using Ru(bpy)32+ Doped Nanocomposites as Signal‐amplifying Tags

Herein, a signal‐on sandwich‐type electrochemiluminescence (ECL) aptasensor for the detection of thrombin (TB) was proposed. The graphene (GR) doped thionine (TH) was electropolymerized synchronously on the bare glassy carbon electrode (GCE) to form co‐polymer (PTG) electrode. The gold nanoparticles (AuNPs) were decorated on the surface of the PTG by in‐situ electrodeposition, and the functional co‐polymer (PTG‐AuNPs) electrode was utilized as sensing interface. Then, TB binding aptamer I (TBA I) as capture probes were modified on the PTG‐AuNPs electrode to capture TB, and Ru(bpy)₃²⁺/silver nanoparticles doped silica core‐shell nanocomposites‐labeled TB binding aptamer II (RuAg/SiO₂NPs@TBA II) were used as signal probes to further bind TB, resulting in a sandwich structure. With the assistant of silica shell and AgNPs, the enrichment and luminous efficiency of Ru(bpy)₃²⁺ were significantly improved. Under the synergy of PTG‐AuNPs and RuAg/SiO₂NPs, the ECL signal was dramatically increased. The proposed ECL aptasensor displayed a wide linear range from 2 fM to 2 pM with the detection limit of 1 fM, which is comparable or better than that in reported ECL aptasensors for TB using Ru(bpy)₃²⁺ and its derivatives as the luminescent substance. The excellent sensitivity makes the proposed aptasensor a promising potential in pharmaceutical and clinical analysis.     

The Sensitized Solid‐Phase Electrochemiluminescence of Electrodeposited Poly‐Luminol/Aniline on AuAg/TiO2 Nanohybrid Functionalized Electrode for Flow Injection Analysis

In this study, a copolymer of luminol with aniline is electrochemically deposited onto the AuAg/TiO₂ nanohybrid functionalized indium tin oxide coated glass. It is used as a reagentless electrochemiluminescent (ECL) electrode for flow‐injection‐analysis (FIA). The properties of this solid phase ECL electrode are characterized by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy etc. It has stronger ECL emission, sensitive response for target analytes and excellent stability. The so‐prepared ECL electrode shows sensitive response to reactive oxygen species thereafter to be applied for determination of hydrogen peroxide with FIA mode. Under optimized conditions, a mass detection limit of 0.822 pg of hydrogen peroxide was obtained. Thus the hydrogen peroxide residues in samples were detected with satisfactory result.     

Amperometric Glucose Biosensor Based on Platinum Nanoparticles Combined Aligned Carbon Nanotubes Electrode

A sensitive amperometric glucose biosensor based on platinum nanoparticles (PtNPs) combined aligned carbon nanotubes (ACNTs) electrode was investigated. PtNPs which can enhance the electrocatalytic activity of the electrode for electrooxidating hydrogen peroxide by enzymatic reaction were electrocrystallized on 4‐aminobenzene monolayer‐grafted ACNTs electrode by potential‐step method. These PtNPs combined ACNTs' (PtNPs/ACNTs) surfaces were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The highly dispersed PtNPs on ACNTs can be obtained. The enzyme electrode exhibits excellent response performance to glucose with linear range from 1×10^?5–7×10^?3 mol L^?1 and fast response time within 5 s. Furthermore, this glucose biosensor also has good reproducibility. It is demonstrated that the PtNPs/ACNTs electrode with high electrocatalytic activity is a suitable basic electrode for preparing enzyme electrodes.     

High‐Performance Amperometric Sensors Using Catalytic Platinum Nanoparticles‐Thionine‐Multiwalled Carbon Nanotubes Nanocomposite

Thionine (TH) adsorbed on multiwalled carbon nanotubes (MWCNTs) increases the load and dispersion of platinum nanoparticles (PtNPs) generated by chemical reduction of H₂PtCl₆ with NaBH₄. Under the optimum conditions, the PtNPs‐TH‐MWCNTs/Au electrode electrocatalyzed the reduction and oxidation of H₂O₂ with high sensitivity, and after glucose oxidase (GOx) adsorption it responded to glucose concentration with a sensitivity of 0.14 A M^?1 cm^?2. The cyclic voltammetric cathodic peak current for NO₂^? reduction on PtNPs‐TH‐MWCNTs/Au responded linearly to NO₂^? concentration from 0.5 to 150 µM, with a sensitivity of 5.52 A M^?1 cm^?2 and a detection limit of 0.2 µM.     

Synthesis of PtNPs/AQ/Ru(bpy)3(2+) colloid and its application as a sensitive solid-state electrochemiluminescence sensor material

The facile synthesis of the novel platinum nanoparticles/Eastman AQ55D/ruthenium(II) tris(bipyridine) (PtNPs/AQ/Ru(bpy)3(2+)) colloidal material for ultrasensitive ECL solid-state sensors was reported for the first time. The cation ion-exchanger AQ was used not only to immobilize ECL active species Ru(bpy)3(2+) but also as the dispersant of PtNPs. Colloidal characterization was accomplished by transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), and UV-vis spectroscopy. Directly coating the as-prepared colloid on the surface of a glassy carbon electrode produces an electrochemiluminescence (ECL) sensor. The electronic conductivity and electroactivity of PtNPs in composite film made the sensor exhibit faster electron transfer, higher ECL intensity of Ru(bpy)3(2+), and a shorter equilibration time than Ru(bpy)3(2+) immobilized in pure AQ film. Furthermore, it was demonstrated that the combination of PtNPs and permselective cation exchanger made the sensor exhibite excellent ECL behavior and stability and a very low limit of detection (1 x 10(-15) M) of tripropylamine with application prospects in bioanalysis. This method was very simple, effective, and low cost.     

Laser‐induced Graphene‐based Non‐enzymatic Sensor for Detection of Hydrogen Peroxide

In this study, a laser‐induced graphene (LIG) loaded platinum nanoparticles (PtNPs) was prepared for precise, rapid and non‐enzymatic electrochemical detection of hydrogen peroxide (H₂O₂). The commercial PI films were used as the substrate of LIG. In order to improve the electrochemical performance of LIG, a layer of PtNPs catalyst was fabricated through a magnetron sputtering process on the surface of LIG (PtLIG). Under optimized conditions, a linear relationship between H₂O₂ reduction current and H₂O₂ concentration was recorded, the correlation coefficient R² is 0.9919 with the detection limit of 0.1 μM (S/N=3) and the sensitivity of 248.4 μA mM^?1cm^?2. Moreover, the PtLIG exhibits excellent selectivity, reproducibility and repeatability. Because of these remarkable advantages, we believe that PtLIG will provide a wider range of applications in biosensors and bioelectronic devices.     

Chemiluminescence of Electrochemically Oxidized 9‐(Phenylthiophosphoryloxymethylidene)‐10‐methylacridan Derivatives

The electrochemistry and electrochemiluminescence (ECL) properties of acridan phosphate ester are reported. Electrochemical oxidation of 9‐(phenylthiophosphoryloxymethylidene)‐10‐methylacridan disodium salt (Compound 1) yields the corresponding acridinium ester. The latter undergoes a fast reaction with hydrogen peroxide forming an intermediate, which produces electronically excited 9‐methyl acridone and emits blue light after relaxation to the ground state. The electrochemical oxidation of this compound appears to occur in two one‐electron steps and light emission is observed for both steps. The chemiluminescence reaction could also be triggered by electrochemical oxidation of Compound 1 in the absence of H₂O₂ when the solution was saturated with O₂. Mechanisms for these reactions based on ECL, voltammetry and in situ UV‐vis identification of the oxidation products are proposed. Due to the low electrode potential required to achieve ECL emission and the occurrence of light emission in the absence of hydrogen peroxide, this compound is proposed as a label for rapid and sensitive determination of biomolecules in automated analysis.     

Preparation of Nanoparticles of Bipyridineruthenium and Silicotungstate and Application as Electrochemiluminescence Sensor

The novel nanoparticles, [Ru(bpy)₃]₂SiW₁₂O₄₀?2 H₂O, were firstly synthesized and characterized by elemental analysis, IR, and TEM. The nanoparticles were used to fabricate a chemically modified carbon paste electrode (CPE) by dispersing nanoparticles and graphite powder in silicone grease. Thus‐prepared CPE shows bifunctional electrocatalytic activities towards the reduction of nitrite and the oxidation of oxalate, and exhibits sensitive electrochemiluminescence (ECL). The modified CPE has high stability and excellent repeatability owing to the insolubility and homogeneous disperses of the nanoparticles. The nanoparticles modified CPE may open a way to be used as solid electrochemical sensor for both ECL and electrocatalysis in practical applications.     

Electrochemiluminescence of Supramolecular Nanorods and Their Application in the “On–Off–On” Detection of Copper Ions

In this work, an “on–off–on” switch system has been successfully applied through the construction of an electrochemiluminscent biosensor for copper ion (Cu²⁺) detection based on a new electrochemiluminescence (ECL) emitter of supramolecular nanorods, which was achieved through supramolecular interactions between 3,4,9,10‐perylenetetracarboxylic acid (PTCA) and aniline. The initial “signal‐on” state with strong and stable ECL emission was obtained by use of the supramolecular nanorods with a new signal amplification strategy involving a co‐reaction accelerator. In addition, ECL quencher probes (Fc‐NH₂/Cu‐Sub/nano‐Au) were fabricated by immobilizing aminoferrocene (Fc‐NH₂) on Cu‐substrate strand modified Au nanoparticles. The quencher probes were hybridized with the immobilized Cu‐enzyme strand to form Cu²⁺‐specific DNAzyme. Similarly, the “signal‐off” state was obtained by the high quenching effect of Fc‐NH₂ on the ECL of the excited‐state PTCA (¹PTCA*). As expected, the second “switch‐on” state could achieved by incubating with the target Cu²⁺, owing to the Cu²⁺‐specific DNAzyme, which was irreversibly cleaved, resulting in the release of the quencher probes from the sensor interface. Herein, on the basis of the ECL intensity changes (ΔI_ECL) before and after incubating with the target Cu²⁺, the prepared Cu²⁺‐specific DNAzyme‐based biosensor was used for the determination of Cu²⁺ concentrations with high sensitivity, excellent selectivity, and good regeneration.     

A Novel Electrogenerated Chemiluminescence Reaction Scheme Using Core-Shell LuminoI-Based SiO2 Nanoparticles as a Regulator and Its Analytical Application

A novel core-shell luminol-based SiO2 nanoparticle While these nanoparticles were used as electrogenerated was synthesized by two step micro-emulsion method. chemiluminescence （ECL） reagent, the electrochemical （EC） reaction as well as the subsequent chemiluminescence （CL） reaction not only could be separated spatially, but also presented high efficiency for analytical purpose. In this case, the core-shell luminol-based SiO2 nanoparticles offered more potential to avoid the contradiction between the EC and the CL reaction conditions. A new ECL method based on the nanoparticle was developed, and isoniazid was selected as a model analyte to illustrate the characteristics of this new ECL method. Under the selected conditions, the proposed ECL response to isoniazid concentration was linear in the range of 1.0 ×10^-10 to 1.0 × 10^-6 g/mL with 2 × 10^-11g/mL detection limit.     

Electrogenerated Chemiluminescence of Lucigenin in Ethanol Solution at a Polycrystalline Gold Electrode

The electrogenerated chemiluminescence (ECL) behavior of lucigenin in ethanol solution at a polycrystalline gold electrode was studied under conventional cyclic voltammetric conditions. Compared with the ECL of lucigenin in aqueous solution, one cathodic ECL peak (ECL‐1 at ?0.98 V versus SCE) with a shoulder (S₁ at ?0.42 V) and three new anodic ECL peaks (ECL‐2 at ?0.53 V, ECL‐3 at 0.20 V, and ECL‐4 at 0.51 V) were observed, respectively, on the curve of ECL intensity versus potential. The effects of initial potential scan direction, the presence of O₂ or N₂, potential scan ranges, supporting electrolyte and the concentration of lucigenin on these ECL peaks were examined. The electrochemistry of lucigenin in ethanol solution was also studied. The emitter of all ECL peaks was identified as N‐methylacridone (NMA) by analyzing the ECL spectra. The mechanism for these ECL peaks is proposed to be due to the reactions of lucigenin and its redox products such as Luc and DBA with dissolved oxygen or O₂ electrogenerated by the dissolved oxygen at different potentials. The formation of new anodic ECL peaks in ethanol solution is due to longer lifetime of superoxide ions and easier electro‐oxidation of DBA in nonaqueous solution, revealing that the solvent plays an important role in the lucigenin ECL reactions.     

Explaining the Size Dependence in Platinum‐Nanoparticle‐Catalyzed Hydrogenation Reactions

Hydrogenation reactions are industrially important reactions that typically require unfavorably high H₂ pressure and temperature for many functional groups. Herein we reveal surprisingly strong size‐dependent activity of Pt nanoparticles (PtNPs) in catalyzing this reaction. Based on unambiguous spectral analyses, the size effect has been rationalized by the size‐dependent d‐band electron structure of the PtNPs. This understanding enables production of a catalyst with size of 1.2 nm, which shows a sixfold increase in turnover frequency and 28‐fold increase in mass activity in the regioselective hydrogenation of quinoline, compared with PtNPs of 5.3 nm, allowing the reaction to proceed under ambient conditions with unprecedentedly high reaction rates. The size effect and the synthesis strategy developed herein may provide a general methodology in the design of metal‐nanoparticle‐based catalysts for a broad range of organic syntheses.     

Formation of Surface Traps on Quantum Dots by Bidentate Chelation and Their Application in Low‐Potential Electrochemiluminescent Biosensing

Bidentate chelation, meso‐2,3‐dimercaptosuccinic acid (DMSA), was used as a stabilizer for the synthesis of CdTe quantum dots (QDs). The bidentate chelate QDs, characterized with FT‐IR, PL, and UV/Vis spectroscopy; element analysis; and high‐resolution transmission electron microscope, exhibited surface traps due to the large surface/volume ratio of QD particle and the steric hindrance of the DMSA molecule. The unpassivated surface of the QDs produced a narrower band gap than the core and electrochemiluminescent (ECL) emission at relatively low cathodic potential. In air‐saturated pH 7.0 buffer, the QDs immobilized on electrode surface showed an intense ECL emission peak at ?0.85 V (vs. Ag/AgCl). H₂O₂ produced from electrochemical reduction of dissolved oxygen was demonstrated to be the co‐reactant, which avoided the need of strong oxidant as the co‐reactant and produced a sensitive analytical method for peroxidase‐related analytes. Using hydroquinone/horseradish peroxidase/H₂O₂ as a model system, a new, reagentless, phenolic, ECL biosensor for hydroquinone was constructed, based on the quenching effect of ECL emission of QDs by consumption of co‐reactant H₂O₂. The biosensor showed a linear range of 0.2–10 μM with acceptable stability and reproducibility. This work opens new avenues in the search for new ECL emitters with excellent analytical performance and makes QDs a more attractive alternative in biosensing.