Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection
Blue emissive N-doped carbon quantum dots (N-CQDs) were prepared through a convenient and sustainable microwave synthesis method using citric acid monohydrate (CA) and urea as carbon and nitrogen sources, respectively, with an optimum molar ratio of 1:3 (CA:Urea). The surface functional groups, morp...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Penerbit Universiti Kebangsaan Malaysia
2022
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| Online Access: | http://journalarticle.ukm.my/19282/ http://journalarticle.ukm.my/19282/1/20.pdf |
| _version_ | 1848814798082408448 |
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| author | Melissa Asha Larsson, Pravena Ramachandran, Purim Jarujamrus, Lee, Hooi Ling |
| author_facet | Melissa Asha Larsson, Pravena Ramachandran, Purim Jarujamrus, Lee, Hooi Ling |
| author_sort | Melissa Asha Larsson, |
| building | UKM Institutional Repository |
| collection | Online Access |
| description | Blue emissive N-doped carbon quantum dots (N-CQDs) were prepared through a convenient and sustainable microwave synthesis method using citric acid monohydrate (CA) and urea as carbon and nitrogen sources, respectively, with an optimum molar ratio of 1:3 (CA:Urea). The surface functional groups, morphology, and hydrodynamic characteristics of N-CQDs were analysed with Fourier-transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS), respectively. The as-synthesised N-CQDs with a quantum yield of 14.8%, exhibited excitation-independent fluorescence emission at 443 nm due to surface-state-induced fluorescence, with an optimum excitation wavelength at 360 nm. The N-CQDs were spherical, with an average particle size of 7.29 ± 3.91 nm based on HRTEM analysis. However, DLS analysis showed that the hydrodynamic size (293.0 ± 110.8 nm) was larger than the average particle size due to the presence of hydrophilic polymer chains and abundant surface groups on the N-CQDs. The free chorine-induced fluorescence quenching of N-CQDs at pH 9 denotes the sensitivity of N-CQDs towards detection of free chlorine in the form of hypochlorite (ClO-) ion, providing the limit of detection (LOD) of 0.4 mM and limit of quantification (LOQ) of 1.2 mM. The fluorescence quenching effect in the N-CQDs caused by the quencher (ClO-) is attributed to the dynamic quenching mechanism, via an intersystem crossing. The low selectivity of N-CQDs towards various ions justified N-CQDs’ selectivity as a free chlorine fluorescent probe that can be used for wastewater testing due to its high range sensitivity. |
| first_indexed | 2025-11-15T00:39:48Z |
| format | Article |
| id | oai:generic.eprints.org:19282 |
| institution | Universiti Kebangasaan Malaysia |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-15T00:39:48Z |
| publishDate | 2022 |
| publisher | Penerbit Universiti Kebangsaan Malaysia |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | oai:generic.eprints.org:192822022-08-08T06:45:06Z http://journalarticle.ukm.my/19282/ Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection Melissa Asha Larsson, Pravena Ramachandran, Purim Jarujamrus, Lee, Hooi Ling Blue emissive N-doped carbon quantum dots (N-CQDs) were prepared through a convenient and sustainable microwave synthesis method using citric acid monohydrate (CA) and urea as carbon and nitrogen sources, respectively, with an optimum molar ratio of 1:3 (CA:Urea). The surface functional groups, morphology, and hydrodynamic characteristics of N-CQDs were analysed with Fourier-transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS), respectively. The as-synthesised N-CQDs with a quantum yield of 14.8%, exhibited excitation-independent fluorescence emission at 443 nm due to surface-state-induced fluorescence, with an optimum excitation wavelength at 360 nm. The N-CQDs were spherical, with an average particle size of 7.29 ± 3.91 nm based on HRTEM analysis. However, DLS analysis showed that the hydrodynamic size (293.0 ± 110.8 nm) was larger than the average particle size due to the presence of hydrophilic polymer chains and abundant surface groups on the N-CQDs. The free chorine-induced fluorescence quenching of N-CQDs at pH 9 denotes the sensitivity of N-CQDs towards detection of free chlorine in the form of hypochlorite (ClO-) ion, providing the limit of detection (LOD) of 0.4 mM and limit of quantification (LOQ) of 1.2 mM. The fluorescence quenching effect in the N-CQDs caused by the quencher (ClO-) is attributed to the dynamic quenching mechanism, via an intersystem crossing. The low selectivity of N-CQDs towards various ions justified N-CQDs’ selectivity as a free chlorine fluorescent probe that can be used for wastewater testing due to its high range sensitivity. Penerbit Universiti Kebangsaan Malaysia 2022-04 Article PeerReviewed application/pdf en http://journalarticle.ukm.my/19282/1/20.pdf Melissa Asha Larsson, and Pravena Ramachandran, and Purim Jarujamrus, and Lee, Hooi Ling (2022) Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection. Sains Malaysiana, 51 (4). pp. 1197-1212. ISSN 0126-6039 https://www.ukm.my/jsm/malay_journals/jilid51bil4_2022/KandunganJilid51Bil4_2022.html |
| spellingShingle | Melissa Asha Larsson, Pravena Ramachandran, Purim Jarujamrus, Lee, Hooi Ling Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection |
| title | Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection |
| title_full | Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection |
| title_fullStr | Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection |
| title_full_unstemmed | Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection |
| title_short | Microwave synthesis of blue emissive N-doped carbon quantum dots as a fluorescent probe for free chlorine detection |
| title_sort | microwave synthesis of blue emissive n-doped carbon quantum dots as a fluorescent probe for free chlorine detection |
| url | http://journalarticle.ukm.my/19282/ http://journalarticle.ukm.my/19282/ http://journalarticle.ukm.my/19282/1/20.pdf |