Synthesis of Highly Fluorescent Nitrogen and Sulfur co-doped Carbon Quantum Dots using Microwave-assisted Hydrothermal Method
Main Article Content
Abstract
This study presents the synthesis of highly fluorescent nitrogen and sulfur co-doped carbon quantum dots (NS-CQDs) using a microwave-assisted hydrothermal method. Citric acid monohydrate and thiourea were used as precursors, and the synthesis was completed in just 7 minutes under microwave irradiation at 800W. The resulting NS-CQDs, with an average size of 5 to 8 nm, were characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and UV-Vis spectroscopy. These techniques confirmed the successful doping of nitrogen and sulfur into the carbon quantum dots, as well as the presence of various functional groups that enhance their hydrophilicity and chemical reactivity. The NS-CQDs exhibited strong absorption in the UV region and emitted bright blue fluorescence with a peak at 435 nm upon excitation at 365 nm, achieving a quantum yield of 26.9%. The fluorescence properties of NS-CQDs were found to be pH-sensitive, with maximum intensity observed at pH 7. Additionally, the NS-CQDs demonstrated excellent stability under UV irradiation and long-term storage. Due to their unique optical properties and stability, NS-CQDs hold significant potential for applications in biosensing, bioimaging, drug delivery, and optoelectronics.
Keywords:
Carbon quantum dots, Nitrogen and sulfur co-doping, Enhanced fluorescence properties, Biosensing applications
References
[1] H. Wang, S. Jiang, Z. Xu, L. Xu, A Novel Fluorescent Sensor Based on a Magnetic Covalent Organic Framework-Supported, Carbon Dot-Embedded Molecularly Imprinted Composite for the Specific Optosensing of Bisphenol a in Foods, Sensors and Actuators B: Chemical, Vol. 361, 2022, pp. 131729.
[2] Q. K. Nguyen, D. T. Nguyen, T. M. A. Pham, B. Pham, T. A. H. Nguyen, T. D. Pham et al., A Highly Sensitive Fluorescence Nanosensor for Determination of Amikacin Antibiotics Using Composites of Carbon Quantum Dots and Gold Nanoparticles, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Vol. 305, 2024, pp. 123466.
[3] F. Yuan, S. Li, Z. Fan, X. Meng, L. Fan, S. Yang, Shining Carbon Dots: Synthesis and Biomedical and Optoelectronic Applications, Nano Today, Vol. 11, No. 5, 2016, pp. 565-586.
[4] P. G. Luo, S. Sahu, S. T. Yang, S. K. Sonkar, J. Wang, H. Wang et al., Carbon “Quantum” Dots for Optical Bioimaging, Journal of Materials Chemistry B, Vol. 1, No. 16, 2013, pp. 2116-2127.
[5] L. Li, G. Wu, G. Yang, J. Peng, J. Zhao, J. J. Zhu, Focusing on Luminescent Graphene Quantum Dots: Current Status and Future Perspectives, Nanoscale, Vol. 5, No. 10, 2013, pp. 4015-4039.
[6] X. Kou, S. Jiang, S. J. Park, L. Y. Meng, A Review: Recent Advances in Preparations and Applications of Heteroatom-Doped Carbon Quantum Dots, Dalton Transactions, Vol. 49, No. 21, 2020, pp. 6915-6938.
[7] S. D. Dsouza, M. Buerkle, P. Brunet, C. Maddi, D. B. Padmanaban, A. Morelli et al., The Importance of Surface States in N-Doped Carbon Quantum Dots, Carbon, Vol. 183, 2021, pp. 1-11.
[8] H. Lu, C. Li, H. Wang, X. Wang, S. Xu, Biomass-Derived Sulfur, Nitrogen Co-Doped Carbon Dots for Colorimetric and Fluorescent Dual Mode Detection of Silver (I) and Cell Imaging, ACS Omega, Vol. 4, No. 25, 2019, pp. 21500-21508.
[9] Y. W. Zeng, D. K. Ma, W. Wang, J. J. Chen, L. Zhou, Y. Z. Zheng et al., N, S Co-Doped Carbon Dots with Orange Luminescence Synthesized through Polymerization and Carbonization Reaction of Amino Acids, Applied Surface Science, Vol. 342, 2015, pp. 136-143.
[10] S. Yang, X. Sun, Z. Wang, X. Wang, G. Guo, Q. Pu, Anomalous Enhancement of Fluorescence of Carbon Dots through Lanthanum Doping and Potential Application in Intracellular Imaging of Ferric Ion, Nano Research, Vol. 11, 2018, pp. 1369-1378.
[11] R. K. Das, S. Panda, C. S. Bhol, S. K. Bhutia, S. Mohapatra, N-Doped Carbon Quantum Dot (NCQD)-Deposited Carbon Capsules for Synergistic Fluorescence Imaging and Photothermal Therapy of Oral Cancer, Langmuir, Vol. 35, No. 47, 2019, pp. 15320-15329.
[12] H. Wu, C. Tong, Nitrogen- and Sulfur-Codoped Carbon Dots for Highly Selective and Sensitive Fluorescent Detection of Hg2+ Ions and Sulfide in Environmental Water Samples, Journal of Agricultural and Food Chemistry, Vol. 67, No. 10, 2019, pp. 2794-2800.
[13] Y. Li, Y. Hu, Y. Jia, X. Jiang, Z. Cheng, N, S Co-Doped Carbon Quantum Dots for the Selective and Sensitive Fluorescent Determination of N-Acetyl-L-Cysteine in Pharmaceutical Products and Urine, Analytical Letters, Vol. 52, No. 11, 2019, pp. 1711-1731.
[14] S. A. Shaik, S. Sengupta, R. S. Varma, M. B. Gawande, A. Goswami, Syntheses of N-Doped Carbon Quantum Dots (NCQDs) from Bioderived Precursors: A Timely Update, ACS Sustainable Chemistry & Engineering, Vol. 9, No. 1, 2020, pp. 3-49.
[15] J. Tang, J. Zhang, Y. Zhang, Y. Xiao, Y. Shi, Y. Chen et al., Influence of Group Modification at the Edges of Carbon Quantum Dots on Fluorescent Emission, Nanoscale Research Letters, Vol. 14, 2019, pp. 1-10.
[16] Y. Guo, W. Zhao, Hydrothermal Synthesis of Highly Fluorescent Nitrogen-Doped Carbon Quantum Dots with Good Biocompatibility and the Application for Sensing Ellagic Acid, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Vol. 240, 2020, pp. 118580.
[17] S. Chandra, D. Bano, P. Pradhan, V. K. Singh, P. K. Yadav, D. Sinha et al., Nitrogen/Sulfur-Co-Doped Carbon Quantum Dots: A Biocompatible Material for the Selective Detection of Picric Acid in Aqueous Solution and Living Cells, Analytical and Bioanalytical Chemistry, Vol. 412, 2020, pp. 3753-3763.
[18] K. W. Sung, K. Y. Ko, H. J. Ahn, Tailored Sulfur and Nitrogen Co-Doped Carbon Quantum Dot Interfacial Layer on Copper Foil for Highly Stable and Ultrafast Lithium-Ion Capacitors, Journal of Energy Storage, Vol. 72, 2023, pp. 108797.
[19] J. R. Adsetts, S. Hoesterey, C. Gao, D. A. Love, Z. Ding, Electrochemiluminescence and Photoluminescence of Carbon Quantum Dots Controlled by Aggregation-Induced Emission, Aggregation-Caused Quenching, and Interfacial Reactions, Langmuir, Vol. 36, No. 47, 2020, pp. 14432–14442.
[20] R. Wang, K. Q. Lu, Z. R. Tang, Y. J. Xu, Recent Progress in Carbon Quantum Dots: Synthesis, Properties and Applications in Photocatalysis, Journal of Materials Chemistry A, Vol. 5, No. 8, 2017, pp. 3717-3734.
[21] A. Mozdbar, A. Nouralishahi, S. Fatemi, G. Mirakhori, eds., The Effect of Precursor on the Optical Properties of Carbon Quantum Dots Synthesized by Hydrothermal/Solvothermal Method, AIP Conference Proceedings, AIP Publishing, 2018.
[22] Y. Pang, H. Gao, S. Wu, X. Li, Facile Synthesis the Nitrogen and Sulfur Co-Doped Carbon Dots for Selective Fluorescence Detection of Heavy Metal Ions, Materials Letters, Vol. 193, 2017, pp. 236-239.
[23] K. K. Chan, C. Yang, Y. H. Chien, N. Panwar, K. T. Yong, A Facile Synthesis of Label-Free Carbon Dots with Unique Selectivity-Tunable Characteristics for Ferric Ion Detection and Cellular Imaging Applications, New Journal of Chemistry, Vol. 43, No. 12, 2019, pp. 4734-4744.
[24] R. Tabaraki, N. Sadeghinejad, Microwave Assisted Synthesis of Doped Carbon Dots and Their Application as Green and Simple Turn Off–On Fluorescent Sensor for Mercury (II) and Iodide in Environmental Samples, Ecotoxicology and Environmental Safety, Vol. 153, 2018, pp. 101-106.
[25] M. P. Szmyt, B. Buszewski, R. G. Kopciuch, Sulphur and Nitrogen Doped Carbon Dots Synthesis by Microwave Assisted Method as Quantitative Analytical Nano-Tool for Mercury Ion Sensing, Materials Chemistry and Physics, Vol. 242, 2020, pp. 122484.
[26] Z. Qin, W. Wang, X. Zhan, X. Du, Q. Zhang, R. Zhang et al., One-Pot Synthesis of Dual Carbon Dots Using Only an N and S Co-Existed Dopant for Fluorescence Detection of Ag+, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Vol. 208, 2019, pp. 162-171.
[27] J. S. Boruah, K. Sankaranarayanan, D. Chowdhury, Insight into Carbon Quantum Dot–Vesicles Interactions: Role of Functional Groups, RSC Advances, Vol. 12, No. 7, 2022, pp. 4382-4394.
[28] G. Magdy, N. Said, R. A. E. Domany, F. Belal, Nitrogen and Sulfur-Doped Carbon Quantum Dots as Fluorescent Nanoprobes for Spectrofluorimetric Determination of Olanzapine and Diazepam in Biological Fluids and Dosage Forms: Application to Content Uniformity Testing, BMC Chemistry, Vol. 16, No. 1, 2022, pp. 98.
[29] S. R. Kamali, C. N. Chen, D. C. Agrawal, T. H. Wei, Sulfur-Doped Carbon Dots Synthesis under Microwave Irradiation as Turn-Off Fluorescent Sensor for Cr (III), Journal of Analytical Science and Technology, Vol. 12, 2021, pp. 1-11.
[30] Q. Li, B. Chen, B. Xing, Aggregation Kinetics and Self-Assembly Mechanisms of Graphene Quantum Dots in Aqueous Solutions: Cooperative Effects of pH and Electrolytes, Environmental Science & Technology, Vol. 51, No. 3, 2017, pp. 1364-1376.
[2] Q. K. Nguyen, D. T. Nguyen, T. M. A. Pham, B. Pham, T. A. H. Nguyen, T. D. Pham et al., A Highly Sensitive Fluorescence Nanosensor for Determination of Amikacin Antibiotics Using Composites of Carbon Quantum Dots and Gold Nanoparticles, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Vol. 305, 2024, pp. 123466.
[3] F. Yuan, S. Li, Z. Fan, X. Meng, L. Fan, S. Yang, Shining Carbon Dots: Synthesis and Biomedical and Optoelectronic Applications, Nano Today, Vol. 11, No. 5, 2016, pp. 565-586.
[4] P. G. Luo, S. Sahu, S. T. Yang, S. K. Sonkar, J. Wang, H. Wang et al., Carbon “Quantum” Dots for Optical Bioimaging, Journal of Materials Chemistry B, Vol. 1, No. 16, 2013, pp. 2116-2127.
[5] L. Li, G. Wu, G. Yang, J. Peng, J. Zhao, J. J. Zhu, Focusing on Luminescent Graphene Quantum Dots: Current Status and Future Perspectives, Nanoscale, Vol. 5, No. 10, 2013, pp. 4015-4039.
[6] X. Kou, S. Jiang, S. J. Park, L. Y. Meng, A Review: Recent Advances in Preparations and Applications of Heteroatom-Doped Carbon Quantum Dots, Dalton Transactions, Vol. 49, No. 21, 2020, pp. 6915-6938.
[7] S. D. Dsouza, M. Buerkle, P. Brunet, C. Maddi, D. B. Padmanaban, A. Morelli et al., The Importance of Surface States in N-Doped Carbon Quantum Dots, Carbon, Vol. 183, 2021, pp. 1-11.
[8] H. Lu, C. Li, H. Wang, X. Wang, S. Xu, Biomass-Derived Sulfur, Nitrogen Co-Doped Carbon Dots for Colorimetric and Fluorescent Dual Mode Detection of Silver (I) and Cell Imaging, ACS Omega, Vol. 4, No. 25, 2019, pp. 21500-21508.
[9] Y. W. Zeng, D. K. Ma, W. Wang, J. J. Chen, L. Zhou, Y. Z. Zheng et al., N, S Co-Doped Carbon Dots with Orange Luminescence Synthesized through Polymerization and Carbonization Reaction of Amino Acids, Applied Surface Science, Vol. 342, 2015, pp. 136-143.
[10] S. Yang, X. Sun, Z. Wang, X. Wang, G. Guo, Q. Pu, Anomalous Enhancement of Fluorescence of Carbon Dots through Lanthanum Doping and Potential Application in Intracellular Imaging of Ferric Ion, Nano Research, Vol. 11, 2018, pp. 1369-1378.
[11] R. K. Das, S. Panda, C. S. Bhol, S. K. Bhutia, S. Mohapatra, N-Doped Carbon Quantum Dot (NCQD)-Deposited Carbon Capsules for Synergistic Fluorescence Imaging and Photothermal Therapy of Oral Cancer, Langmuir, Vol. 35, No. 47, 2019, pp. 15320-15329.
[12] H. Wu, C. Tong, Nitrogen- and Sulfur-Codoped Carbon Dots for Highly Selective and Sensitive Fluorescent Detection of Hg2+ Ions and Sulfide in Environmental Water Samples, Journal of Agricultural and Food Chemistry, Vol. 67, No. 10, 2019, pp. 2794-2800.
[13] Y. Li, Y. Hu, Y. Jia, X. Jiang, Z. Cheng, N, S Co-Doped Carbon Quantum Dots for the Selective and Sensitive Fluorescent Determination of N-Acetyl-L-Cysteine in Pharmaceutical Products and Urine, Analytical Letters, Vol. 52, No. 11, 2019, pp. 1711-1731.
[14] S. A. Shaik, S. Sengupta, R. S. Varma, M. B. Gawande, A. Goswami, Syntheses of N-Doped Carbon Quantum Dots (NCQDs) from Bioderived Precursors: A Timely Update, ACS Sustainable Chemistry & Engineering, Vol. 9, No. 1, 2020, pp. 3-49.
[15] J. Tang, J. Zhang, Y. Zhang, Y. Xiao, Y. Shi, Y. Chen et al., Influence of Group Modification at the Edges of Carbon Quantum Dots on Fluorescent Emission, Nanoscale Research Letters, Vol. 14, 2019, pp. 1-10.
[16] Y. Guo, W. Zhao, Hydrothermal Synthesis of Highly Fluorescent Nitrogen-Doped Carbon Quantum Dots with Good Biocompatibility and the Application for Sensing Ellagic Acid, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Vol. 240, 2020, pp. 118580.
[17] S. Chandra, D. Bano, P. Pradhan, V. K. Singh, P. K. Yadav, D. Sinha et al., Nitrogen/Sulfur-Co-Doped Carbon Quantum Dots: A Biocompatible Material for the Selective Detection of Picric Acid in Aqueous Solution and Living Cells, Analytical and Bioanalytical Chemistry, Vol. 412, 2020, pp. 3753-3763.
[18] K. W. Sung, K. Y. Ko, H. J. Ahn, Tailored Sulfur and Nitrogen Co-Doped Carbon Quantum Dot Interfacial Layer on Copper Foil for Highly Stable and Ultrafast Lithium-Ion Capacitors, Journal of Energy Storage, Vol. 72, 2023, pp. 108797.
[19] J. R. Adsetts, S. Hoesterey, C. Gao, D. A. Love, Z. Ding, Electrochemiluminescence and Photoluminescence of Carbon Quantum Dots Controlled by Aggregation-Induced Emission, Aggregation-Caused Quenching, and Interfacial Reactions, Langmuir, Vol. 36, No. 47, 2020, pp. 14432–14442.
[20] R. Wang, K. Q. Lu, Z. R. Tang, Y. J. Xu, Recent Progress in Carbon Quantum Dots: Synthesis, Properties and Applications in Photocatalysis, Journal of Materials Chemistry A, Vol. 5, No. 8, 2017, pp. 3717-3734.
[21] A. Mozdbar, A. Nouralishahi, S. Fatemi, G. Mirakhori, eds., The Effect of Precursor on the Optical Properties of Carbon Quantum Dots Synthesized by Hydrothermal/Solvothermal Method, AIP Conference Proceedings, AIP Publishing, 2018.
[22] Y. Pang, H. Gao, S. Wu, X. Li, Facile Synthesis the Nitrogen and Sulfur Co-Doped Carbon Dots for Selective Fluorescence Detection of Heavy Metal Ions, Materials Letters, Vol. 193, 2017, pp. 236-239.
[23] K. K. Chan, C. Yang, Y. H. Chien, N. Panwar, K. T. Yong, A Facile Synthesis of Label-Free Carbon Dots with Unique Selectivity-Tunable Characteristics for Ferric Ion Detection and Cellular Imaging Applications, New Journal of Chemistry, Vol. 43, No. 12, 2019, pp. 4734-4744.
[24] R. Tabaraki, N. Sadeghinejad, Microwave Assisted Synthesis of Doped Carbon Dots and Their Application as Green and Simple Turn Off–On Fluorescent Sensor for Mercury (II) and Iodide in Environmental Samples, Ecotoxicology and Environmental Safety, Vol. 153, 2018, pp. 101-106.
[25] M. P. Szmyt, B. Buszewski, R. G. Kopciuch, Sulphur and Nitrogen Doped Carbon Dots Synthesis by Microwave Assisted Method as Quantitative Analytical Nano-Tool for Mercury Ion Sensing, Materials Chemistry and Physics, Vol. 242, 2020, pp. 122484.
[26] Z. Qin, W. Wang, X. Zhan, X. Du, Q. Zhang, R. Zhang et al., One-Pot Synthesis of Dual Carbon Dots Using Only an N and S Co-Existed Dopant for Fluorescence Detection of Ag+, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Vol. 208, 2019, pp. 162-171.
[27] J. S. Boruah, K. Sankaranarayanan, D. Chowdhury, Insight into Carbon Quantum Dot–Vesicles Interactions: Role of Functional Groups, RSC Advances, Vol. 12, No. 7, 2022, pp. 4382-4394.
[28] G. Magdy, N. Said, R. A. E. Domany, F. Belal, Nitrogen and Sulfur-Doped Carbon Quantum Dots as Fluorescent Nanoprobes for Spectrofluorimetric Determination of Olanzapine and Diazepam in Biological Fluids and Dosage Forms: Application to Content Uniformity Testing, BMC Chemistry, Vol. 16, No. 1, 2022, pp. 98.
[29] S. R. Kamali, C. N. Chen, D. C. Agrawal, T. H. Wei, Sulfur-Doped Carbon Dots Synthesis under Microwave Irradiation as Turn-Off Fluorescent Sensor for Cr (III), Journal of Analytical Science and Technology, Vol. 12, 2021, pp. 1-11.
[30] Q. Li, B. Chen, B. Xing, Aggregation Kinetics and Self-Assembly Mechanisms of Graphene Quantum Dots in Aqueous Solutions: Cooperative Effects of pH and Electrolytes, Environmental Science & Technology, Vol. 51, No. 3, 2017, pp. 1364-1376.