Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source
Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized in a one-step hydrothermal technique utilizing L-lactic acid as that of the source of carbon and ethylenediamine as that of the source of nitrogen, and were characterized using dynamic light scattering, X-ray photoelectron spectroscopy ult...
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2022-01-01
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| author | Kaixin Chang Qianjin Zhu Liyan Qi Mingwei Guo Woming Gao Qinwei Gao |
| author_facet | Kaixin Chang Qianjin Zhu Liyan Qi Mingwei Guo Woming Gao Qinwei Gao |
| author_sort | Kaixin Chang |
| collection | DOAJ |
| description | Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized in a one-step hydrothermal technique utilizing L-lactic acid as that of the source of carbon and ethylenediamine as that of the source of nitrogen, and were characterized using dynamic light scattering, X-ray photoelectron spectroscopy ultraviolet-visible spectrum, Fourier-transformed infrared spectrum, high-resolution transmission electron microscopy, and fluorescence spectrum. The generated N-CQDs have a spherical structure and overall diameters ranging from 1–4 nm, and their surface comprises specific functional groups such as amino, carboxyl, and hydroxyl, resulting in greater water solubility and fluorescence. The quantum yield of N-CQDs (being 46%) is significantly higher than that of the CQDs synthesized from other biomass in literatures. Its fluorescence intensity is dependent on the excitation wavelength, and N-CQDs release blue light at 365 nm under ultraviolet light. The pH values may impact the protonation of N-CQDs surface functional groups and lead to significant fluorescence quenching of N-CQDs. Therefore, the fluorescence intensity of N-CQDs is the highest at pH 7.0, but it decreases with pH as pH values being either more than or less than pH 7.0. The N-CQDs exhibit high sensitivity to Fe<sup>3+</sup> ions, for Fe<sup>3+</sup> ions would decrease the fluorescence intensity of N-CQDs by 99.6%, and the influence of Fe<sup>3+</sup> ions on N-CQDs fluorescence quenching is slightly affected by other metal ions. Moreover, the fluorescence quenching efficiency of Fe<sup>3+</sup> ions displays an obvious linear relationship to Fe<sup>3+</sup> concentrations in a wide range of concentrations (up to 200 µM) and with a detection limit of 1.89 µM. Therefore, the generated N-CQDs may be utilized as a robust fluorescence sensor for detecting pH and Fe<sup>3+</sup> ions. |
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| language | English |
| last_indexed | 2024-03-10T01:04:15Z |
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| spelling | doaj.art-242a044dcb9940ff9d0050c516c6d4412023-11-23T14:29:34ZengMDPI AGMaterials1996-19442022-01-0115246610.3390/ma15020466Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon SourceKaixin Chang0Qianjin Zhu1Liyan Qi2Mingwei Guo3Woming Gao4Qinwei Gao5College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, ChinaNitrogen-doped carbon quantum dots (N-CQDs) were synthesized in a one-step hydrothermal technique utilizing L-lactic acid as that of the source of carbon and ethylenediamine as that of the source of nitrogen, and were characterized using dynamic light scattering, X-ray photoelectron spectroscopy ultraviolet-visible spectrum, Fourier-transformed infrared spectrum, high-resolution transmission electron microscopy, and fluorescence spectrum. The generated N-CQDs have a spherical structure and overall diameters ranging from 1–4 nm, and their surface comprises specific functional groups such as amino, carboxyl, and hydroxyl, resulting in greater water solubility and fluorescence. The quantum yield of N-CQDs (being 46%) is significantly higher than that of the CQDs synthesized from other biomass in literatures. Its fluorescence intensity is dependent on the excitation wavelength, and N-CQDs release blue light at 365 nm under ultraviolet light. The pH values may impact the protonation of N-CQDs surface functional groups and lead to significant fluorescence quenching of N-CQDs. Therefore, the fluorescence intensity of N-CQDs is the highest at pH 7.0, but it decreases with pH as pH values being either more than or less than pH 7.0. The N-CQDs exhibit high sensitivity to Fe<sup>3+</sup> ions, for Fe<sup>3+</sup> ions would decrease the fluorescence intensity of N-CQDs by 99.6%, and the influence of Fe<sup>3+</sup> ions on N-CQDs fluorescence quenching is slightly affected by other metal ions. Moreover, the fluorescence quenching efficiency of Fe<sup>3+</sup> ions displays an obvious linear relationship to Fe<sup>3+</sup> concentrations in a wide range of concentrations (up to 200 µM) and with a detection limit of 1.89 µM. Therefore, the generated N-CQDs may be utilized as a robust fluorescence sensor for detecting pH and Fe<sup>3+</sup> ions.https://www.mdpi.com/1996-1944/15/2/466nitrogen-doped carbon quantum dotsfluorescencepH valueFe<sup>3+</sup> ionlactic acid |
| spellingShingle | Kaixin Chang Qianjin Zhu Liyan Qi Mingwei Guo Woming Gao Qinwei Gao Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source Materials nitrogen-doped carbon quantum dots fluorescence pH value Fe<sup>3+</sup> ion lactic acid |
| title | Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source |
| title_full | Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source |
| title_fullStr | Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source |
| title_full_unstemmed | Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source |
| title_short | Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source |
| title_sort | synthesis and properties of nitrogen doped carbon quantum dots using lactic acid as carbon source |
| topic | nitrogen-doped carbon quantum dots fluorescence pH value Fe<sup>3+</sup> ion lactic acid |
| url | https://www.mdpi.com/1996-1944/15/2/466 |
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