Controllable Formation of Luminescent Carbon Quantum Dots Mediated by the Fano Resonances Formed in Oligomers of Gold Nanoparticles

Abstract

Carbonicnanomaterials such as nanodiamonds, fullerenes, carbon nanotubes, graphene sheets, and carbon quantum dots (CQDs) have attracted extensive research efforts because of their unique properties and great potential for a wide variety of applications. [1][2][3][4][5][6][7] The accidental discovery of CQDs during the separation and purification of single-walled carbon nanotubes triggered subsequent studies to exploit the fluorescence properties of CQDs which comprise discrete nanoparticles with diameters below 10 nm and contain considerable amounts of carboxyl moieties at their surfaces. [8] Fluorescent CQDs are considered as the most promising candidates for replacing semiconductor quantum dots containing heavy metals in bioimaging because of their low toxicity, biocompatibility, low cost, and chemical inertness. [9][10][11][12][13][14] In addition, the large amounts of carboxyl moieties on the surfaces of CQDs impart excellent water solubility and suitable chemically reactive groups for surface passivation and functionalization. Moreover, the interesting photoinduced electron transfer properties of CQDs would offer exciting opportunities for light energy conversion, photovoltaic devices, and related applications. [1,[15][16][17] Basically, CQDs can be synthesized by either the top-down route or the bottom-up one. [18][19][20][21] So far, the production of CQDs via laser ablation of a carbon target has become a very important method and the synthesis of fluorescent CQDs by laser irradiation of a suspension of carbon materials in organic solvent has been demonstrated. [22][23][24] By properly selecting organic solvents, the surface states of CQDs could be modified to achieve tunable light emission and the origin of the luminescence was attributed to the surface states related to the ligands on the surfaces of CQDs. A review of the fabrication methods for CQDs, however, reveals some common limitations such as the long production time and the low controllability of the formed CQDs because only colloid CQDs are obtained. From the viewpoint of many practical applications, including but not limited to optical data storage, optical displays, and biosensing, the rapid and controllable formation of CQDs and especially CQD arrays is highly desirable. Rapid and controllable formation of fluorescent carbon quantum dots (CQDs) is highly desirable in the fields of nanophotonics and biophotonics.Here, a novel strategy for creating CQDs, which emit white light efficiently under the excitation of either laser light or a mercury lamp, is proposed and demonstrated. The luminescent CQDs are generated by irradiating a poly(vinyl alcohol) (PVA) film doped with dense gold nanoparticles (AuNPs) with femtosecond laser pulses. The creation of CQDs from PVA is a twostep dehydration process mediated by AuNPs which act not only as heat sources but also as catalytic agents. The formation of CC, CC, and CO bonds is confirmed by infrared Fourier transformation spectroscopy and X-ray photoelectron spectroscopy. It is revealed both numerica...

Deciphering Limitations to Meet Highly Stable Bio‐Hybrid Light‐Emitting Diodes

“…HLEDs aim to replace IPs with low‐price, highly luminescent organic molecules as color down‐converting packaging or organic phosphors (OPs) without losing the high efficiency and brightness of ILEDs. To date, a myriad of OPs based on polymers, carbon quantum dots, coordination complexes, laser dyes, transition metal complexes, pure organic biomarkers, and fluorescent proteins (FPs) are under development . While excellent color characteristics (color rendering index (CRI) superior to 90 and efficiencies over 100 lm W −1 ) have been achieved, their low stability is still a major drawback .…”

In Situ Femtosecond-Laser-Induced Fluorophores on Surface of Polyvinyl Alcohol for H2O/Co2+ Sensing and Data Security

“…The fitting peak area results indicate that after laser irradiation the relative content of the C-C/C=C bonds increased by 13%. Such changes in chemical bonds signify the carbonization of PVA [24][25][26]. Meanwhile, dehydration of the PVA chain is expected to occur owing to laser-induced thermal effects.…”

“…However, the existence form of fluorophores remains to be investigated. Transmission electron microscopy (TEM) characterization of in situ generated fluorophores remains challenging [26]. The chemical changes in the PVA samples were characterized using X-ray photoelectron spectroscopy (XPS).…”

“…However, the existence form of fluorophores remains to be investigated. Transmission electron microscopy (TEM) characterization of in situ generated fluorophores remains challenging [26].…”

Optically‐Controlled Quantum Size Effect in a Hybrid Nanocavity Composed of a Perovskite Nanoparticle and a Thin Gold Film

“…Previously, spatially‐localized temperature distribution was successfully achieved by exploiting the Fano resonance formed in an oligomer of gold (Au) nanoparticles. [ 42 ] It was used to produce carbon quantum dots with small diameters, which emit efficient luminescence in the visible light spectrum. As mentioned above, the strongly‐localized electric field achieved in the gap region between a dielectric nanoparticle and a thin metal film has been exploited to construct nanoscale photonic devices with different functionalities.…”