Gold Nanoclusters@Ru(bpy)₃²⁺-Layered Double Hydroxide Ultrathin Film as a Cathodic Electrochemiluminescence Resonance Energy Transfer Probe

Herein, it is the first report that a cathodic electrochemiluminescence (ECL) resonance energy transfer (ERET) system is fabricated by layer-by-layer (LBL) electrostatic assembly of CoAl layered double hydroxide (LDH) nanosheets with a mixture of blue BSA–gold nanoclusters (AuNCs) and Ru­(bpy)₃²⁺ (denoted as AuNCs@Ru) on an Au electrode. The possible ECL mechanism indicates that the appearance of CoAl–LDH nanosheets generates a long-range stacking order of the AuNCs@Ru on an Au electrode, facilitating the occurrence of the ERET between BSA–AuNC donors and Ru­(bpy)₃²⁺ acceptors on the as-prepared AuNCs@Ru–LDH ultrathin films (UTFs). Furthermore, it is observed that the cathodic ECL intensity can be quenched efficiently in the presence of 6-mercaptopurine (6-MP) in a linear range of 2.5–100 nM with a detection limit of 1.0 nM. On the basis of these interesting phenomena, a facile cathodic ECL sensor has successfully distinguished 6-MP from other thiol-containing compounds (e.g., cysteine and glutathione) in human serum and urine samples. The proposed sensing scheme opens a way for employing the layered UTFs as a platform for the cathodic ECL of Ru­(bpy)₃²⁺

Electroless Deposition of Palladium Nanoparticles on Graphdiyne Boosts Electrochemiluminescence

Modulating the electronic structure of metal nanoparticles via metal–support interaction has attracted intense interest in the field of catalytic science. However, the roles of supporting substrates in regulating the catalytic properties of electrochemiluminescence (ECL) remain elusive. Here, we find that the use of graphdiyne (GDY) as the substrate for electroless deposition of Pd nanoparticles (Pd/GDY) produces the most pronounced anodic signal enhancement in luminol–dissolved oxygen (O2) ECL system as co-reactant accelerator over other carbon-based Pd composite nanomaterials. Pd/GDY exhibits electrocatalytic activity for the reduction of O2 through a four-electron pathway at approximately −0.059 V (vs Ag/AgCl) in neutral solution forming reactive oxygen species (ROS) as intermediates. The study shows that the interaction of Pd and GDY increases the amount and stability of ROS on the Pd/GDY electrode surface and promotes the reaction of ROS and luminol anion radical to generate excited luminol, which significantly boosts the luminol anodic ECL emission. Based on quenching of luminol ECL through the consumption of ROS by antioxidants, we develop a platform for the detection of intracellular antioxidants. This study provides an avenue for the development of efficient luminol ECL systems in neutral media and expands the biological application of ECL systems

Quenching of the Electrochemiluminescence of Tris(2,2′-bipyridine)ruthenium(II)/Tri‑<i>n</i>‑propylamine by Pristine Carbon Nanotube and Its Application to Quantitative Detection of DNA

In this study, we describe the quenching of electrochemiluminescence (ECL) of tris­(2,2′-bipyridine)-ruthenium­(II)­(Ru­(bpy)₃²⁺)/tri-<i>n</i>-propylamine­(TPA) at pristine multiwall carbon nanotube (MWNT) modified glassy carbon (GC) electrode. Even though the faradic current of the Ru­(bpy)₃²⁺/TPA system and the oxidation of TPA obtained at pristine MWNT-modified GC electrode is enhanced compared with those at the bare GC electrode, the intensity of ECL produced at MWNT electrode is smaller than that at GC electrode. For testing the possible reason of quenching, a comparison of ECL behavior of Ru­(bpy)₃²⁺/TPA at pristine MWNT and acid-treated, heat-treated, and polyethylene glycol (PEG)-wrapped MWNT-modified GC electrode is studied. The results demonstrate that the oxygen-containing groups at the surface of MWNT and the intrinsic electron properties of MWNT are considered to be the major reason for the suppression of ECL. The comparison also demonstrates that this quenching is related to the distance between MWNT and Ru­(bpy)₃²⁺/TPA. Utilizing this essential quenching mechanism, a new signal-on DNA hybridization assay is proposed on the basis of the MWNT modified electrode, where single-stranded DNA (ssDNA) labeled with Ru­(bpy)₃²⁺ derivatives probe (Ru-ssDNA) at the distal end is covalently attached onto the MWNT electrode. ECL signal is quenched where Ru-ssDNA is self-organized on the surface of MWNT electrode; however, the quenched ECL signal returns in case of the presence of complementary ssDNA. The developed approach for sequence-specific DNA detection has good selectivity, sensitivity, and signal-to-background ratio. Therefore, the quenching of the ECL of Ru­(bpy)₃²⁺/TPA system by the pristine MWNT can be an excellent platform for nucleic acid studies and molecular sensing

Noncovalent Immobilization of a Pyrene-Modified Cobalt Corrole on Carbon Supports for Enhanced Electrocatalytic Oxygen Reduction and Oxygen Evolution in Aqueous Solutions

Efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are the determinants of the realization of a hydrogen-based society, as sluggish OER and ORR are the bottlenecks for the production and utilization of H₂, respectively. A Co complex of 5,15-bis­(pentafluorophenyl)-10-(4)-(1-pyrenyl)­phenylcorrole (<b>1</b>) bearing a pyrene substituent was synthesized. When it was immobilized on multiwalled carbon nanotubes (MWCNTs), the <b>1</b>/MWCNT composite displayed very high electrocatalytic activity and durability for both OER and ORR in aqueous solutions: it catalyzed a direct four-electron reduction of O₂ to H₂O in 0.5 M H₂SO₄ with an onset potential of 0.75 V vs normal hydrogen electrode (NHE), and it catalyzed the oxidation of water to O₂ in neutral aqueous solution with an onset potential of 1.15 V (vs NHE, η = 330 mV). Control studies using a Co complex of 5,10,15-tris­(pentafluorophenyl)­corrole (<b>2</b>) demonstrated that the enhanced catalytic performance of <b>1</b> was due to the strong noncovalent π–π interactions between its pyrene moiety and MWCNTs, which were considered to facilitate the fast electron transfer from the electrode to <b>1</b> and also to increase the adhesion of <b>1</b> on carbon supports. The noncovalent immobilization of molecular complexes on carbon supports through strong π–π interactions appears to be a simple and straightforward strategy to prepare highly efficient electrocatalytic materials

Charge-Pattern Indicated Relaxation Dynamics and Glass Transition of Polymer Thin Films Studied by Atomic Force Microscopy

Polymers are widely used as dielectrics in microelectronics. As the thickness of polymer films decreases to the submicrometer or nanometer scale, abnormal relaxation deviations from the bulk matrix are expected. Evaluation of the relaxation dynamics in an efficient and quantitative manner is highly desired. Utilizing this patterned charge as an indicator, we demonstrate here that the polymer relaxation dynamics and glass transition temperature (<i>T</i>_g) of thin polymer films can be investigated by monitoring the charge decay behaviors. This approach of charge patterning combined with atomic force microscopy is more facile to evaluate polymer relaxation behavior with direct contrast between charged and electrically neutral domains versus conventional polymer <i>T</i>_g and relaxation dynamic measurements. This study also illuminates the coexisting processes of polymer relaxation and trapped charge decay in thin polymer film. This sheds light on the microscopic mechanism of charge storage and relaxation properties in the polymer