Synthesis and characterization of multifunctional carbon dots for fluorescent applications
- Abstract
- The carbon dots (CDs) are zero-dimensional carbon nanomaterials which are several nanometers in diameter. The CDs have been researched in the past decade because of their excellent optical properties compared with semiconductor quantum dots.
In this study, the CDs were synthesized from acetone, masks, paper and toner powder using hydrothermal and solvothermal methods. The prepared CDs showed various structural, chemical bonding and optical properties due to the variation of their synthesis method and conditions. The light blocking film, light emitting diode (LED), anti-counterfeiting, and metal sensing application of the CDs were developed. These results suggest that CDs derived from organic materials are promising candidates as a luminescent material.
Firstly, human eyes are regularly exposed to ultraviolet (UV) and blue light from LED-based devices. However, blue light is known to cause eye diseases such as macular degeneration, eye strain, optic nerve crush and increases reactive oxygen species. UV light is also harmful effect on human health. It induces photokeratitis, cataract, and ocular surface squamous neoplasia. Here, we show the CD films with different CD contents, prepared by a simple method. The films exhibit strong UV and blue light absorption. The transmittance of CD films is >70% in the visible region (>500 nm). The UV light blocking ratio of commercial blue blocking filter and CD film using UV LED chips is 94.1% and 95.9% (40 wt%), respectively. The blue light blocking ratio of commercial blue blocking filter and CD film using blue LED chips is 10.2% and 82.3% (40 wt%), respectively. These results indicate that the prepared CD films have a UV blocking rate similar to that of commercial blue blocking filters and a much better blue blocking rate than commercial blue blocking filters. Therefore, they can be effectively used as UV and blue blocking films in various applications.
Secondly, the currently commercial white LEDs (WLEDs) including the YAG:Ce3+ phosphor has been used. However, the commercial WLEDs has a disadvantage such as high correlated color temperature (CCT, CCT>6000 K) due to the shortage of red region. To solve these problems, we aim to synthesize the CDs that exhibit a red shifted central wavelength compared to YAG:Ce3+ phosphor. we synthesized the white CDs (W-CDs) with using printer toner powder by a simple solvothermal method. The WLED are successfully fabricated with using polyvinylpyrrolidone (PVP) and W-CDs coated with ultraviolet (UV) LED chip. Commission Internationale de l'Eclairage (CIE) coordinates of the fabricated W-CDs LED is (0.323, 0.327) and commercial WLED is (0.299, 0.352). The CCT value of the fabricated CDs-WLED and commercial WLED is 5969 K and 6967 K. Therefore, the fabricated W-CDs is relatively warm. This work provides the new development of low cost, eco-friendly and high-performance CD based warm WLEDs.
Thirdly, these days, counterfeiting of valuable items such as medicine, currency, confidential documents and jewelry has become a global problem because it badly affects social economy. Therefore, the development of anti-counterfeiting technique is needed. Up till now, several methods for preventing the counterfeiting include luminescent labels with using luminescent materials. Therefore, we synthesize the CDs from paper by different solvents by a conventional hydrothermal and solvothermal method. The CDs synthesized with papers have several advantages such as low toxicity, low cost and eco-friendly. The prepared CDs have main emission peak from 440 to 540 nm under 340~480 nm excitation. The prepared CDs can be applied to easily prepare anti-counterfeiting ink and fluorescent flexible film because of their unique optical property and excellent chemical and photostability.
At last, Iron is a heavy metal which affects water pollution and human body. Iron ion is an important role in organisms such as cellular metabolism, oxygen carrier, blood production. But, iron excess or deficiency is not good to human body. It results in various diseases such as kidney damages, cancer, anemia, Alzheimer’s. Then, it is very important to check the amount of iron ions. Therefore, we synthesize the CDs with using parts (non-woven, melt-blown and non-woven/melt-blown) of disposable masks without mask residues. The prepared CDs have a size about 3.5~4.0 nm and blue region emission. As a result of fluorescence data, the CDs mixed with Fe3+ ion display quenching effect due to several oxygen groups. Thus, the CDs can be applied to several fields (metal sensing and anti-counterfeiting).
- Issued Date
- 2025
- Awarded Date
- 2025-08
- Type
- Dissertation
- Publisher
- 국립부경대학교 대학원
- Alternative Author(s)
- Park Sung Jun
- Affiliation
- 국립부경대학교 대학원
- Department
- 대학원 인공지능융합학과
- Advisor
- Hyun Kyoung Yang
- Table Of Contents
- 1. Introduction 1
2. Theoretical backgrounds 5
2. 1 Carbon dots 5
2. 1. 1 History 5
2. 1. 2 Luminescence mechanism 8
2. 1. 2. 1 Quantum confinement effect 8
2. 1. 2. 2 Surface defect state 10
2. 1. 2. 3 Luminophores or luminescent molecules 12
2. 1. 2. 4 Heteroatoms or other atoms doping 16
2. 2 Synthesis approaches of carbon dots 24
2. 2. 1 Pyrolysis 26
2. 2. 2 Acidic oxidation 27
2. 2. 3 Hydrothermal and solvothermal method 28
2. 2. 4 Microwave- and sonication-assisted method 29
2. 2. 5 Electrochemical method 30
2. 2. 6 Laser ablation 32
2. 3 Precursor 33
2. 3. 1 Organic molecules 33
2. 3. 2 Natural source 36
2. 3. 3 Carbon based source 40
2. 4 Application 44
2. 4. 1 LED 44
2. 4. 2 Anti-counterfeiting 49
2. 4. 3 Bio-imaging 52
2. 4. 4 Photocatalysis 55
2. 4. 5 Solar concentrator 57
2. 4. 6 Solar cell 61
2. 4. 7 Sensing 64
2. 4. 8 Latent fingerprint detection 67
2. 5 Measurement 72
2. 5. 1 Transmission electron microscope 72
2. 5. 2 Scanning electron microscope 74
2. 5. 3 X-ray diffraction 76
2. 5. 4 Raman spectroscopy 79
2. 5. 5 X-ray photoelectron spectroscopy 82
2. 5. 6 Fourier transform infrared spectroscopy 84
2. 5. 7 Ultraviolet-visible spectroscopy 87
2. 5. 8 Photoluminescence spectroscopy 90
2. 5. 9 Fouriertransform nuclear magnetic resonance spectrometer 92
3. Results 95
Chapter 1. Ultraviolet to blue blocking film using carbon dots deri ved from acetone 95
3. 1. 1 Introduction 95
3. 1. 2 Synthesis 97
3. 1. 3 Results 99
3. 1. 4 Conclusion 117
Chapter 2. White LED application using carbon dots derived from toner powders 119
3. 2. 1 Introduction 119
3. 2. 2 Synthesis 120
3. 2. 3 Results 122
3. 2. 4 Conclusion 131
Chapter 3. Anti-counterfeiting application using carbon dots derive d from paper 132
3. 3. 1 Introduction 132
3. 3. 2 Synthesis 134
3. 3. 3 Results 137
3. 3. 4 Conclusion 148
Chapter 4. Metal sensing application using carbon dots derived from mask 149
3. 4. 1 Introduction 149
3. 4. 2 Synthesis 150
3. 4. 3 Results 152
3. 4. 4 Conclusion 162
4. Summary 163
References 167
- Degree
- Doctor
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