Amorphous B-doped graphitic carbon nitride quantum dots with high photoluminescence quantum yield of near 90% and their sensitive detection of Fe2+/Cd2+

Abstract

Graphitic carbon nitride quantum dots (CNQDs) are emerging as attractive photoluminescent (PL) materials with excellent application potential in fluorescence imaging and heavy-metal ion detection. However, three limitations, namely, low quantum yields (QYs), self-quenching, and excitation-dependent PL emission behaviors, severely impede the commercial applications of crystalline CNQDs. Here we address these three challenges by synthesizing borondoped amorphous CNQDs via a hydrothermal process followed by the top-down cutting approach. Structural disorder endows the amorphous boron-doped CNQDs (B-CNQDs) with superior elastic strain performance over a wide range of pH values, thus effectively promoting mass transport and reducing exciton quenching. Boron as a dopant could fine-tune the electronic structure and emission properties of the PL material to achieve excitation-independent emission via the formation of uniform boron states. As a result, the amorphous B-CNQDs show unprecedented fluorescent stability (i.e., no obvious fading after two years) and a high QY of 87.4%; these values indicate that the quantum dots obtained are very promising fluorescent materials. Moreover, the B-CNQDs show bright-blue fluorescence under ultraviolet excitation when applied as ink on commercially available paper and are capable of the selective and sensitive detection of Fe 2+ and Cd 2+ in the parts-per-billion range. This work presents a novel avenue and scientific insights on amorphous carbon-based fluorescent materials for photoelectrical devices and sensors.

Recent Progress of Amorphous Nanomaterials

“…Recently, they went one step further by modeling the enamel from the nanoscale to the macroscale. A layer of amorphous ZrO 2 was evenly grown on the surface of the hydroxyapatite column and then assembled in an orderly manner to form an enamel-like composite, which is the closest enamel-like composite to tooth enamel so far, as shown in Figure c . Similarly, the storage modulus and damping coefficient of the artificial tooth enamel (ATE) tested by nanoindentation technology had a record high value compared with traditional engineering materials.…”

“…Amorphous structure provides a new opportunity to resolve the above problems, and as reported by Huang et al, the distorted structure leads to the superior elastic strain performance of amorphous boron-doped CNQDs (B-CNQDs) in a wide pH range. This will promote the mass transport and reduce exciton quenching effectively . The synthesis of stable red-emitting carbon spots is a challenge, so it is important to explore the pressure sensitivity of amorphous carbon spots. , Lu et al reported the pressure sensitivity of amorphous carbon dots, whose red-emissive amorphous carbon dots presented pressure-triggered aggregation-induced emission enhancement and reversible piezochromic luminescence, as shown in Figure d–f.…”

Emerging Trends of Carbon‐Based Quantum Dots: Nanoarchitectonics and Applications

“…[151] The latter is usually formed by sp 2 hybridization of nitrogen and carbon in π-conjugated graphitic planes, with both crystalline and amorphous structures. [152,153] Their bandgaps can be flexibly modified thanks to the quantum confinement effect. Graphene has a zero bandgap electronic structure, which can badly hinder its applications in catalysis and optoelectronics.…”

Donor–Acceptor Modification of Carbon Nitride for Enhanced Photocatalytic Hydrogen Evolution

“…Among the various as‐developed photocatalysts, polymeric carbon nitride (CN) has inspired intense concerns of researchers for its appropriate band structure, facile preparation, low cost, and superior chemical stability. [ 7–9 ] However, the photocatalytic activity of pristine CN was severely restricted due to the poor optical absorption and rapid recombination of photogenerated electron–hole pairs. Then a variety of strategies have been applied to improve the optical utilization and migration efficiency of charge carriers, such as morphological control, [ 10–12 ] elemental doping, [ 13,14 ] molecular engineering, [ 15,16 ] and heterostructure construction.…”