Analyzing Near-Infrared Electrochemiluminescence of Graphene Quantum Dots in Aqueous Media

Abstract

Mechanisms of emissions, especially electrochemiluminescence (ECL), for graphene quantum dots (GQDs) are poorly understood, which makes near-infrared (NIR)-emitting GQDs difficult to create. To explore this poorly understood NIR ECL, two GQDs, nitrogen-doped GQDs (GQD-1) and nitrogenand sulfur-doped ones (GQD-2), were prepared by a simple onestep solvothermal reaction with similar core structures but different surface states. The GQDs were analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and highresolution transmission electron microscopy. Photoluminescence results, with a comparable quantum efficiency of 13% to strong luminophores in aqueous media, suggested a mechanism that the emission mainly depends on the core structure while slightly adjusted by the heteroatom doping. ECL of GQD-2 dispersed in aqueous media with K 2 S 2 O 8 as the coreactant was measured by means of ECL−voltage curves and ECL spectroscopy, demonstrating strong NIR emissions between 680 and 870 nm, with a high ECL efficiency of 13% relative to that of the Ru(bpy) 3 2+ /K 2 S 2 O 8 system. Interestingly, ECL is generated by surface excited states emitting light at a much longer wavelength in the NIR region. The easily prepared GQD-2 has several advantages such as low cost and quite strong NIR-ECL in aqueous media, with which wide applications in biodetection are anticipated.

Insights of Shadow Trapping States and Intramolecular Charge Transfer on Simultaneous Redshift and Efficiency Enhancement of Electrochemiluminescence in Carbon Dots

“…This unusual fine regulation of both ECL emission wavelength and efficiency was further explored by the kinetics studies and theoretical calculation. It was disclosed that P dopants in the form of P-C and P-O groups not only imported shadow trapping states as previously reported [22,33] but also promoted intramolecular charge transfer (ICT) in ECL. This work would provide new insight into the correlation between the elemental doping and ECL of nanocarbon, and open a new avenue for the desirable design of nanocarbon towards given applications.…”

“…Since surface functional groups play a critical role in ECL generation, 2-aminoterephthalic acid (ATA) was selected as a precursor for synthesizing CDs with ECL properties due to its amine and carboxyl groups (the as-obtained CDs were denoted as NCDs). [33,34] Given the sizeable atomic radius and high electron-donating ability of P, bis[tetrakis(hydroxymethyl)phosphonium] sulfate solution (THPS) was chosen as an additional precursor for P source to produce P-doped CDs (PNCDs). By adjusting the molar ratio of THPS (m) and ATA (n), different PNCDs-m-n were obtained (Table S1).…”

Closely Following Equivalent Circuit Changes during Operation of Graphene Dot Light‐Emitting Electrochemical Cells

“…PVK was employed as a matrix to facilitate the necessary ion rearrangement for the LEC to operate efficiently. GQDs also have two excitation modes: a surface and core state [6a,b,21] which have been characterized previously to be 2.70 eV and 3.87 eV respectively with resulting emissions of 660 nm and 440 nm [17] . The concentrations for the components of the light emitting layer were all optimized for a low turn‐on voltage and a high luminance.…”

Flow Injection Analysis-Based Electrochemiluminescence: An Overview of Experimental Design and Its Biosensing Applications

“…Nanomaterials such as quantum dots (QDs), metal clusters are frequently used as ECL reagents. 18,[41][42][43][44] Metal based QDs like cadmium selenide (CdSe), [45][46][47] cadmium sulfide (CdS), 48,49 cadmium telluride (CdTe), 41,46,48 CdSe/zink sulfide (ZnS), 46,47 and CdZnSe, 46 and carbon-based QDs such as carbon QDs (CQDs) 50 and graphene QDs (GQDs) 47,51,52 are the mostly used nanomaterials as luminophores. One of the major advantages of these nanomaterials is they can easily make covalent linkage with other molecules z E-mail: pgraju146@gmail.com; ssenthilmugam@gmail.com; ssenthilkumar@cecri.…”