Abstract
Dual-fluorescence carbon dots have great potential as nanosensors in life and materials sciences. Such carbon dots can be obtained via a solvothermal synthesis route with glutathione and formamide. In this work, we show that the dual-fluorescence emission of the synthesis products does not originate from a single carbon dot emitter, but rather from a mixture of physically separate compounds. We characterized the synthesis products with UV–vis, Raman, infrared, and fluorescence spectroscopy, and identified blue-emissive carbon dots and red-emissive porphyrin. We demonstrate an easy way to separate the two compounds without the need for time-consuming dialysis. Understanding the nature of the system, we can now steer the synthesis toward the desired product, which paves the way for a cheap and environmentally friendly synthesis route toward carbon dots, water-soluble porphyrin, and mixed systems.
Highlights
We have observed that the synthesis products after dialysis have two distinct emission bands, which were ascribed by Macairan et al to dual emissive Carbon dots (CDs) (Figure 1b).[28]
Our findings show that these emissive states originate from a blue-emitting CD and a red-emitting molecular fluorophore called porphyrin (400 nm excitation, Figure 1a−b), revealing that the two states are not just physically distinct but rather physically separated
We find low intensity PL around 400−600 nm in the porphyrin fraction, which disappears after further purification with THF, indicating that this signal stems from residual molecular fluorophores
Summary
Carbon dots (CDs) are fluorescent carbon-based nanoparticles with tunable and functional photoluminescence.[1,2] Since their serendipitous discovery during carbon nanotube purification in 2004,3 they have gained significant interest for application as a new generation light source,[4−6] solution-based chemo-sensors for detecting chemicals and metal cations,[2,7−11] and nanoprobes for mapping biological systems.[2,7−11] they have shown great potential to be applied directly or in hybrid materials for photocatalytic and electrocatalytic applications.[12−16] CDs are generally regarded as environmentally friendly, nontoxic material because the synthesis precursors are relatively abundant, harmless, and environmentally friendly and the synthesis does not involve extreme reaction conditions nor produces harmful waste.[17−21] This motivates their use outside the academic research lab in industrial and consumer applications An example being their use as sensors for the detection of dangerous chemicals, for the detection of reaction products in high-throughput catalyst testing, or even to map the heterogeneity in the chemical composition of porous materials. The carbon structures contain primarily oxygen and nitrogen heteroatoms and the exact composition is heavily dependent on the synthesis precursor and synthesis conditions.[23]
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