Tuning the Emission Color of Hydrothermally Synthesized Carbon Quantum Dots by Precursor Engineering

Abstract

Water-soluble, biocompatible, and highly luminescence carbon quantum dots (CQDs) have synthesized successfully from a citric acid (CA) and ethylenediamine (EDA) by using different approaches. Although the emission quantum yield of CQDs could be as high as 80% their emission spectrum is usually dominated by surface fluorophore groups and maximized at about 450 nm. Herein, we examined the effects of acid and amine precursors on the photoluminescence (PL) of resulting CQDs by systematic comparison the optical properties of CQDs obtained from CA, PA (phthalic acid) and EDA, ANL (aniline). UV-vis and PL spectroscopic studies revealed that the absorption onset varied from 325 nm to 400 nm while PL maximum changed from 390 nm to 450 nm by engineering acid and amine precursors. The emission quantum yield was also changed from 9 to 70%, depending on the used acid-amine precursors. 
 Keywords
 Carbon quantum dots, hydrothermal synthesis, color tuning, photoluminescence, acid, amine
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Excitation‐Independent Emission of Carbon Quantum Dot Solids

“…e effects of excitation on the emission of CQDs in the solution and solid state are summarized in Figure 3. Clearly, CQDs in the solution exhibited common excitation dependence, e.g., emission spectrum is red-shifted when the excitation wavelength increases [6,9,11,25]. On the contrary, PL spectra of CQD films exhibited similar features, with the exception of PL intensity, when varying the excitation wavelength.…”

Smartphone Platform for Low-Cost Point-of-Care Quantitative Detection of Vitamin B12 Utilizing a Biodegradable Bioplastic Nanocomposite-Based Fluorescence Nanosensor

“…The FRET energy transfer efficiency was estimated to be 49.19% at pH 2.05, 60.86% at pH 7.10, and 87.23% at pH 12.15. Others have demonstrated comparable fluorescence quenching via nonradiative energy transfer . Electrostatic interactions are more likely to be involved in energy transfer under basic conditions than under neutral and acidic conditions because vitamin B 12 contains a cobalt­(II) ion that is coordinated by four corrin ring nitrogen atoms and a fifth nitrogen atom of the imidazole group.…”

“…Others have demonstrated comparable fluorescence quenching via nonradiative energy transfer. 45 Electrostatic interactions are more likely to be involved in energy transfer under basic conditions than under neutral and acidic conditions because vitamin B 12 contains a cobalt(II) ion that is coordinated by four corrin ring nitrogen atoms and a fifth nitrogen atom of the imidazole group. This is because the zeta potential under basic conditions is more negative than under neutral and acidic conditions (−35.35 mV for pH: 12.15, −3.85 mV for pH: 2.05, and −25.786 for pH: 7.10).…”