High-Efficient Electrochemiluminescence of Au Nanoclusters Induced by the Electrosensitizer Cu₂O: The Mechanism Insights from the Electrogenerated Process

Abstract

Herein, a novel Au nanoclusters/Cu 2 O (Au NCs/ Cu 2 O) heterostructure exhibited exceptionally strong electrochemiluminescence (ECL) emission, in which the p-type semiconductor Cu 2 O was defined as the electrosensitizer to provide the electrogenerated holes for rapidly transferring the electrogenerated hot electrons of Au NCs. Thus, the fast charge transfer of Au NCs/ Cu 2 O was achieved by the electrosensitizer compared to the sluggish one via intramolecular covalent bond charge transfer of traditional Au NCs, resulting in a greatly higher ECL efficiency (63.8%) than that of pure Au NCs (2.7%) versus the standard [Ru(bpy) 3 ] 2+ . It solved one main challenge of electrochemiluminophore-based metal NCs: high efficiency with energic charge-transport kinetics. As a proof of concept, Au NCs/Cu 2 O was successfully employed in an ultrasensitive ECL biosensing platform for determining the biological antioxidant glutathione with a limit of detection (LOD) as low as 6.3 pM. The heterostructure as an ECL emitter is a very promising start for guiding the rational design of efficient electrochemiluminophores in intense light-emitting devices and high-definition ECL imaging.

Cysteine Modification of Glutathione-Stabilized Au Nanoclusters to Red-Shift and Enhance the Electrochemiluminescence for Sensitive Bioanalysis

“…24,25 Moreover, their ECL emission wavebands and efficiency can be regulated by changing the stabilizer capped on their surface and accelerating the charge transfer among the electrochemical process with a electrosensitizer such as Cu 2 O. 26 By covalently binding N,N-diethylethylenediamine to lipoic acid-stabilized AuNCs 20 or preoxidizing Lmethionine (Met)-stabilized AuNCs (Met-AuNCs), 21 the ECL performance can be improved. A doping-in-growth way has also been proposed to enhance the ECL performance and regulate the emission waveband of AuNCs.…”

“…The ECL of luminol, Ru­(bpy) 3 2+ , and nanomaterials such as CdSe, g-C 3 N 4 , and polymer dots (P-dots) is primarily located in the visible region. Although some ECL luminophores with low emission potential or near-infrared (NIR) band , have been presented for decreasing the interference and photochemical damage in bioassay, their ECL efficiency is still limited owing to the depressed through-bond charge transfer in the electronic process and the enhanced nonradiative relaxation of excited states during the energy transition. , In recent years, some metal nanoclusters (NCs) with admirable physicochemical properties have been found to show good ECL performance. − Especially, AuNCs have been successfully proved to be a kind of biocompatible and eco-friendly NIR ECL luminophores. , Moreover, their ECL emission wavebands and efficiency can be regulated by changing the stabilizer capped on their surface and accelerating the charge transfer among the electrochemical process with a electrosensitizer such as Cu 2 O . By covalently binding N , N -diethylethylenediamine to lipoic acid-stabilized AuNCs or preoxidizing l -methionine (Met)-stabilized AuNCs (Met-AuNCs), the ECL performance can be improved.…”

Identifying Highly Photoelectrochemical Active Sites of Two Au21 Nanocluster Isomers toward Bright Near-Infrared Electrochemiluminescence

“…ECL can be produced via the reaction of cation and anion radicals electrogenerated from a luminophore, which is known as an ion-annihilation route. Alternatively, a secondary compound with its highly oxidative or reductive radical can be added to assist ECL generation, which is called a coreactant pathway. , So far, ECL of diverse types of materials including silicon nanocrystals, GNCs, − inorganic and organic materials, and their hybrids − has been investigated and found applications in imaging, , biodetection, and single-event studies …”

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

“…Electrochemiluminescence (ECL) involves the electrochemically triggered energy-relaxation phenomenon in which the luminophore can utilize electron-transfer to achieve excited states for emitting light. − ECL has been extensively identified to be a persuasive analytical technique with merits of intrinsically low background, high sensitivity, broad detection range, and admirable controllability. , Recently, Au nanoclusters (AuNCs) as one of the most burgeoning electrochemiluminophores have obtained remarkable attention owing to their distinctive chemical, electrical, and optical characteristics. − In particular, l -methionine ( l -Met) stabilized AuNCs with admirable biocompatibility not only act as a near-infrared (NIR) signal label with improved susceptibility and circumambient adaptability, but also function as a linker for the decoration of immunizing molecules via sufficient functional groups supplied by l -Met. , However, AuNCs usually undergo poor ECL efficiency due to the depressed charges transfer efficiency in the electrogenerated procedure and plentiful nonradiative transition of excited species in the energy relaxed process. − More recently, the biocompatible AuNCs with property of aggregation induced emission (AIE) have been exploited to promote the ECL efficiency via inhibiting the nonradiative transition. , However, the insufficient charge-transfer mechanism during electrochemical redox of AuNCs has not been systematically solved and still results in the inferior NIR ECL efficiency, which becomes primary factor that affects the widespread application and sensitive bioassay. Then, it is anticipated to implement considerable endeavors to explore appropriately supplementary methods for enhancing the charge transfer and facilitating the NIR ECL efficiency of AuNCs.…”