High quantum yield carbon quantum dots synthesized via three different routes for anti-counterfeiting inkjet inks application

doi:10.21203/rs.3.rs-2241183/v1

Download PDF

Article

High quantum yield carbon quantum dots synthesized via three different routes for anti-counterfeiting inkjet inks application

https://doi.org/10.21203/rs.3.rs-2241183/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

Fluorescent inks based on carbon quantum dots (CQDs) can be used in different applications, such as militaries for anti-counterfeiting messages, banks, money, worthy documents, and cheques. On the other hand, CQDs can be used for biological and imaging purposes like flow cytometry, DNA mutation, drug delivery, drug releasing, and bioimaging. In this study, CQDs were synthesized utilizing a one-step procedure using citric acid, ethylene diamine, and aniline in different ratios using different synthesis methods like hydrothermal, microwave, and simple heating. UV-Visible, Photoluminescence, Energy Dispersive Spectroscopy, Field Emission Scanning Electron Microscopes, Transmission electron microscopy, and water contact angle were carried out to investigate the synthesized carbon quantum dots. The best CQDs were selected as a functional dye to fabricate fluorescent ink and were printed on paper. By analyzing the visual effects of printed papers under UV light and daylight, it was shown that all printings were successfully done, and all samples had noticeable fluorescence emission. Water contact angle measurements were done on both printed area and unprinted paper for further investigations. The results showed that the contact angle decreased after printing on the paper, which was related to the penetration of ink into the substrate’s pores.

Physical sciences/Materials science/Nanoscale materials

Physical sciences/Engineering/Chemical engineering

Physical sciences/Nanoscience and technology/Nanoscale materials/Quantum dots

Carbon Quantom Dots

Anti-counterfeiting

Inkjet

Quantom Yield

Photoluminescence

Luminescence is the emission of light from any substance and occurs from electrochemically excited states. Luminescence is divided into fluorescence and phosphorescence, depending on the excitation of the electrons. Fluorescence is related to the state that excited electron in the orbital that is paired with the electron in the ground state and has an emission lifetime of nearly 10 ns. On the other hand, in phosphorescent materials, the emission of light occurs from triplet excited states, in which the electron in the excited states have the same spin orientation as the ground state. Transition to the ground state is forbidden, and the emission rates are slow, so the lifetime of phosphorescent materials is in the range of milliseconds to seconds ¹.

A fluorophore is a molecule with fluorescence properties. Fluorophores absorb the photons and emit them with lower energy in return. Fluorophores typically contain multiple bonded aromatic groups, or planar or cyclic molecules with multiple π bonds. These materials can be used alone as tracers in liquids, as dyes to stain specific structures, as substrates for enzymes, or as probes or indicators (where fluorescence is affected by environmental conditions such as polarity and ions). ^2,3. More commonly, they may be used by covalently attachment to macromolecules that act as markers (dyes, tags, reporters) for affinity or bioactive reagents (antibodies, peptides, nucleic acids). Fluorophores are used among other materials to stain tissues, cells or materials in a variety of analytical methods. i.e. fluorescence imaging and spectroscopy. In this regard, quantum dots have been nominated as promising nanomaterials for fluorescent applications. Based on their physical and chemical properties, quantum dot-based fluorescent nanomaterials can be divided into inorganic quantum dots, carbon quantum dots (CQDs), and graphene quantum dots (GQDs) ⁴. In past decades, Cadmium Selenide (CdSe) and Cadmium Telluride (CdTe) have gotten so much attention because of their perfect light-emitting properties ⁵. These inorganic quantum dots are harmful to humans and can cause cancer, so they only get used as sensors. Researchers have been developing a new green, organic way to solve these problems by decreasing pollution and making non-toxic materials. Carbon quantum dots are one of these materials that can be used in several applications like white LEDs (WLEDs) ⁶, solar cells ^7,8, drug delivery systems ^9,10, biosensors ¹¹, bio-imaging ¹² and so on. Carbon quantum dots are mainly derived from active carbon and coal ¹³.

Carbon dots can be synthesized with two different routes; the top-down approach and the bottom-up approach. The top-down approach refers to breaking down large carbon particles via discharge, electrochemical oxidation, sonication, and chemical oxidation to smaller particles; however, these methods require expensive equipment and a long reaction time ¹⁴. On the other hand, the bottom-up approach refers to converting carbon atoms to carbon quantum dots in the desired particle size. Bottom-up approach can be conducted via hydrothermal treatment, thermal decomposition, pyrolysis, carbonization, microwave-assisted synthesis, and solvothermal methods. CQDs have a size in the range of 1–10 nm ^5,15, and they can be doped by different atoms like nitrogen ^16,17, boron ^18,19, phosphorous ^20,21, and sulfur ²².

Ming Zhang and coworkers studied nitrogen and sulfur co-doped carbon quantum dots, which led to evaluating the anticounterfeiting inks for spraying on paper²³. Mohini Sain et al. synthesized Nitrogen-doped CQDs by using Trans Aconitic acid as a carbon precursor and diethylenetriamine as a doping agent. The synthesized CQDs showed a high quantum yield (81%) that was utilized for switch sensing and imaging ²⁴. Josue Carinhana et al. worked on synthesizing nitrogen and phosphorous co-doped carbon quantum dots using phytic acid and L-arginine as precursors. The synthesized N-CQD and P-CQD were used to determine Cr (VI) ion in water and soil samples ²⁵. Wei Dong and co-workers studied the synthesizing fluorine-doped carbon quantum dots using 4,5-difluorobenzene-1,2-diamine, which led to yellow emitting F-CQD and was used as red cell imaging and sensitive intracellular Ag⁺ ion detection²⁶. James Joseph et al. synthesized phosphorus-doped carbon quantum dots using trisodium citrate as a precursor and phosphoric acid as an F-doping agent ²⁷. The synthesized material was used as a fluorometric probe for iron detection.

The amorphous region around the core of CQDs can affect the optical properties, which are directly related to reaction temperature. On the other hand, the high reaction temperature leads to fully carbonization of the amorphous surface. The large size of the carbon core can cause a shift in the photoluminescence emission toward a longer wavelength. As mentioned by Plinio Innocenzi et al., an increase in temperature leads to the growth of the carbonic core and a decrease in the amorphous area over the core. At low temperatures, it is difficult to form a carbonaceous core. The highest quantum yield was obtained at an intermediate temperature where the core and the shell coexist ²⁸.

It is necessary to point out that there is no clear temperature to control the coexistence of core and amorphous shell; however, a temperature between 150–200 with a synthesis time of 8–12 hours can result in premium quantum yields.

As mentioned, doping agents, reaction temperature, and synthesis routes can totally affect the properties of synthesized CQDs. Therefore, in this study, we used three different synthesis routes with different reaction temperatures and doping agents to have a comprehensive understanding on the effect of above-mentioned parameters on the properties of CQDs. The synthesized CQDs exhibited a significant fluorescent emission, good quantum yield, and super printability properties.

2.1. Materials and reagents

Aniline and 1,2- ethylene diamine were purchased from Merck Co., Germany. Aniline was purified by a two-component distillation method just before use. Citric acid was purchased from Dr. Mojallali Co, Iran, and was used without any further purification. N-methyl-2-pyrrolidone was purchased from Sigma-Aldrich Co., and Glycerin and Polyethylene glycol (PEG) were purchased from Dr. Mojallali Co.

2.2. Synthesis of Nitrogen Dopes CQDs (N-CQDs) and un-doped CQD

N-CQDs were synthesized using hydrothermal, microwave-assisted, and simple heating methods by two different doping agents, 1, 2- ethylene diamine and Aniline. To synthesize N-CQDs with 1, 2- ethylene diamine doing agent (N-E-CQD), 1 g citric acid, 0.3 mL of ethylene diamine, and 50 mL of double distilled water were totally mixed together. To synthesize the N-CQDs with Aniline doing agent (N-A-CQD), 1 g of citric acid, 0.3 mL of distilled aniline, and 50 mL of double distilled water were used. Un-doped CQD (CQD) was synthesized with the addition of 1g of citric acid and 50 mL of double-distilled water to the reaction mixture. All the concentrations to synthesize the N-E-CQD, N-A-CQD and CQD were the same for different synthesis routes.

2.2.1. Hydrothermal synthesis method

In the hydrothermal method, citric acid was dissolved in water for 30 minutes at 60℃, followed by cooling to room temperature and addition of nitrogen doping agent. The reaction mixture was transferred into a Teflon-lined autoclave and kept at 200℃ for 12 hours. After reaction completion, the synthesized carbon quantum dots were filtered via a 220 nm Polytetrafluoroethylene (PTFE) syringe filter and then freeze-dried and kept under nitrogen atmosphere in a desiccator for further use. Figure 1a shows a schematic illustration of this synthesis procedure.

2.2.2. Microwave-assisted synthesis method

As seen in Fig. 1b, microwave oven was used for the microwave-assisted synthesis method. First, 1g citric acid was dissolved in 50 mL of double distilled water at 60℃ for 30 minutes, followed by cooling down to room temperature and addition of nitrogen doping agent. Then all the components were transferred into a beaker and, microwave oven working at 800 watts for 10 minutes was used to complete the reaction. In the next step, 20 mL of double distilled water was added to the beaker. The film was dispersed in water for another 2 hours. The synthesized carbon quantum dots were filtered via a 220 nm PTFE syringe filter followed by freeze-drying. The obtained materials were kept under nitrogen atmosphere in a desiccator for further investigation.

2.2.3. Simple heating synthesis method

A reflux system was used for the simple heating synthesis method, and the procedure is shown in Fig. 1c. 1 g of citric acid was dissolved in 50 mL of double-distilled water at 60℃ for 30 minutes, followed by cooling down to room temperature and addition of nitrogen doping agent. Then considering to the used doping agent, the aniline or EDA was used, and the reflux system was set to 180℃, with nitrogen purge. After 20 hours of reaction, the setup was separated, and the obtained material was filtered via a 220 nm PTFE filter and freeze-dried. Then the produced samples were kept in a desiccator under nitrogen atmosphere for further investigation.

2.3. Instruments and apparatus

Ultraviolet-Visible absorption spectra were obtained on an Onlab-EU-2200R spectrometer (ONLAB Co., China) in the wavelength range of 200–800 nm. Photoluminescence spectra (PL) measured by FP-750 fluorometer (Jasco, Japan). Dynamic light scattering method (DLS) was used to measure the particle size of CQD particles by using Zetasizer Nano ZS90 (Malvern, France). Scanning Electron Microscopy images were obtained from Field Emission Scanning Electron Microscope (FE-SEM) Mira3 (TEscan, Czech republic). Water contact angle and surface tension were measured by CAG-10 (Jikan, Islamic Republic of Iran), and the T50 (Epson, Japan) printer was used to print fluorescent inks on paper. Quantum yield \({\phi }_{s}\)was calculated using Eq. 1²⁹. In this equation, \({\phi }_{r}\) is the quantum yield of standard Rhodamine 6G as the reference, m_s and m_r are the slope of the linear fit for the integrated fluorescence intensity of CQDs as a function of concentration for the sample and reference Rhodamine 6G, respectively. In this equation, \({\eta }_{r}\) is the refractive index of the standard solution, and \({\eta }_{s}\) is the refractive index of the studied fluorescent material ³⁰.

\({\phi }_{s}={\phi }_{r}\frac{{\text{m}}_{\text{s}}}{{m}_{r}} {\left(\frac{{\eta }_{s}}{{\eta }_{r}}\right)}^{2}\)

Eq. 1

3.1. Optical Characterization of Carbon Quantum Dots

The CQDs’ maximum absorbance wavelength (λ_max) were set to be used as the reference excitation wavelength in photoluminescence analysis. Figure 2 shows UV-Vis spectra of the un-doped and N-doped CQDs with three different synthesis routes. As shown in Fig. 2a, un-doped CQDs in all three synthesizing methods showed a low intensity absorbance peak, and the λ_max was measured as 278 nm. As shown in Fig. 2b, hydrothermal synthesized N-A-CQD showed the highest intensity absorbance peak. The two other nanomaterials, synthesized by microwave-assisted and simple heating methods, showed a low absorbance level, and their maximum absorbance peak was measured to be located at 320 nm. The N-E-CQD sample, as it is shown in Fig. 2c, showed high absorbance intensity in all three synthesized methods, while the microwave-assisted synthesized sample showed higher absorbance intensity in comparison to the other methods. The N-E-CQD samples showed an absorbance peak at the wavelength of 340 nm.

Photoluminescence analyses were done to evaluate the emission spectra of synthesized samples. The excitation range was set ± 20 nm of the maximum absorbance obtained from UV-Vis spectroscopy. The PL emission spectra of a dilute solution of un-doped CQD in DI water (0.3 mg mL^− 1) obtained from hydrothermal, microwave-assisted, and simple heating synthesis methods exhibited a maximum emission intensity at 550 nm in which the excitation wavelength was 278 nm (Fig. 3a, b and c). Diluted solution of N-A-CQD in water (0.3 mg.mL^− 1) obtained from hydrothermal synthesis method showed a maximum intensity at 406 nm where the excitation wavelengths were set in the range of 290 to 330 nm (Fig. 3d). The diluted solution of N-A-CQD synthesized via microwave-assisted and simple heating synthesis routes showed lower intensity of fluorescence emission, where the excitation wavelength of both samples were set in the range of 310 to 350 nm and maximum emission intensity were 450 and 455 nm for microwave-assisted and simple heating synthesis routes, respectively (Fig. 3e, f). As shown in Fig. 3g, h and i, diluted solution of N-E-CQD obtained via hydrothermal, microwave-assisted and simple heating routes had a maximum emission intensity at 470 nm, where the excitation wavelength of all types of N-E-CQD was set at the range of 310 to 360 nm. In this case, microwave-assisted synthesis method exhibited more emission intensity compared to other two routes. Due to the reported data, hydrothermal synthesized CQD and N-A-CQD and microwave-assisted synthesized N-E-CQD samples were selected as optimum nanomaterial for further investigations.

The quantum yield of the optimum carbon quantum dots were calculated by using Eq. 1. The results were ~ 100% for N-E-CQD, 20% for N-A-CQD, and 14% for CQD, which showed a high quantum yield obtained for nitrogen doped carbon quantum dots via microwave assisted synthesis route.

3.2. Morphological characterization of synthesized quantum dots

Morphology and size distribution of optimum N-CQDs and CQD were characterized using DLS, FE-SEM, and TEM analysis. The size distribution of synthesized quantum dots was in the range of 6.5 nm to 9.8 nm. DLS analysis gave size distribution of 6, 9.5, and 7 nm for un-doped CQD, N-A-CQD and N-E-CQD, respectively.

FE-SEM analysis was conducted on both N-CQDs to study the morphology and size of the synthesized samples. In this case, 4 mL of N-CQDs were first injected on a laboratory slide and dried for 24 hours at room temperature. Size distribution of 7.5 nm and 8.5 nm of each carbon quantum dot was achieved using image processing by ImageJ software. Figure 4a) shows the FE-SEM analysis for N-E-CQD in which the size of the particles measured were in range of 7.5 ± 2nm, and Fig. 4b) shows the FE-SEM of N-A-CQD in which the size of the particles were figured out to be in a range of 8.5 ± 2 nm.

3.2.1. TEM analysis

The morphology and size distribution of the optimum N-E-CQD was investigated by TEM analysis. As shown in Fig. 5, the size distribution of N-E-CQD sample was in good accordance with SEM and DLS results. To have further investigation and verify the successful formation of both N-A- CQD, and N-E-CQD, EDS (EDAX) analysis was done and the results are reported.

3.3. Chemical Characterization of N-CQDs

EDS analysis (Energy Dispersive X-Ray Analysis) was done for the chemical characterization of synthesized N-CQDs. 4 mL of N-E-CQD and N-A-CQD were injected on the surface of a laboratory slide and then dried for 24 hours at room temperature. The results showed that the doping agent were successfully incorporated in the quantum dots. As we can see in Table 1 the N-E-CQD has 67% wt. of Carbon, 24% wt. of Oxygen, and 8% wt. of Nitrogen atom which shows incorporation of Nitrogen atom in the structure of quantum dots. In N-A-CQD sample, 30% wt. of Carbon, 68% wt. of Oxygen atom, and 2% wt. of Nitrogen was reported.

As the EDS results showed, N-E-CQD has more Nitrogen in its structure that can be related to the nature of used doping agent (ethylene diamine) which has more amine groups in its structure than the aniline which was used as doping agent in N-A-CQD sample.

Table 1

EDS analysis of N-E-CQD and N-A-CQD
	N-E-CQD		N-A-CQD
Atom	Weight %	Atomic %	Molecular %	Atomic %
C	66.94	72.23	30.47	36.76
N	8.58	7.94	1.94	2.03
O	24.47	19.82	67.57	61.20
Total	100	100	100	100

3.4. Visual properties of synthesized quantum dots

To visualize the optimum quantum dots, a UVA Lamp was used in a black box, as shown in Fig. 6. The left side of the figure shows the synthesized CQDs under illuminant A (Tangenstane Light Source), the middle shows the visual properties of CQDs under UV irradiation which shows blue and blue-greenish appereance, and the right side shows the synthesized CQDs under illuminant D65 (white LED light source). As seen in Fig. 6, N-E-CQD has the most fluorescent emission compared to others which was in good accordance with the calculated quantum yield values. Figure 6a, b, c, indicates the optimum CQD and N-A-CQD, synthesized via hydrothermal method and N-E-CQD, synthesized via microwave-assisted method respectively. N-E-CQD was selected as the best synthesised carbon quantum dot and was used in fabrication of inks for inkjet printers.

3.5. Printing properties of N-E-CQD

N-E-CQD was selected to study the printing properties of synthesized CQDs in ink formulation because of its excellent optical and chemical properties as mentioned above. For ink preparation, dye loading level was adjusted to 1 wt.%, and other ink components like solvents and cosolvents were adjusted up to 99 wt.% of the remained total ink formulation. The printer used to investigate printing inks was an Epson stylus photo T-50, and the results of the printed papers are shown in Fig. 7. The left side of the figure shows the printed page under daylight, and the right side shows these printed pages under UV irradiation. Prepared inks were printed with 1,5,10, and 15 times of repetitions on paper. As it can be seen in Fig. 7, one-time printing can be selected as the premium number of repetitions because it doesn’t load any footprints of inks under daylight and can be chosen for anti-counterfeiting purposes, and it was selected for further research. Water contact angle analysis was used to validate the ink's absorbance into the papers. As demonstrated in Fig. 8, the part of the paper with no printing has a higher water contact angle (79º) than the printed piece of paper (42º), which shows that the ink has been successfully penetrated into the printed area and the surface properties are altered.

In this research, the blue and blue-greenish N-CQDs and CQD were derived from citric acid as carbon precursor and ethylene diamine and aniline as doping agent in three different synthesis routes. The synthesis routes were simple one-pot hydrothermal method, microwave-assisted method, and simple heating synthesis method. Un-doped CQD had an emission at 550 nm and N-A-CQD, showed fluorescence emission at 480 nm which showed a greenish-blue color under UV irradiation. Moreover, N-E-CQD synthesized by three different routes showed an excellent fluorescent emission at the range of 450–460 nm. the best value was for the microwave-assisted synthesis method at excitation range of 330 nm and emission of 460 nm. All these materials were characterized and studied for their optical and chemical properties. Microwave-assisted synthesized N-E-CQD was selected as the best-synthesized CQD, and its printability was studied using an Epson inkjet printer. The result of this study led to anti-counterfeiting inks that showed an excellent fluorescence emission under UV light, and left no footprints on papers under daylight.

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

Albrecht, C. Joseph R. Lakowicz: Principles of fluorescence spectroscopy, 3rd Edition. Analytical and Bioanalytical Chemistry 390, 1223-1224, doi:10.1007/s00216-007-1822-x (2008).
Godbey, W. T. in Biotechnology and its Applications (Second Edition) (ed W T Godbey) 187-201 (Academic Press, 2022).
Wang, F. & Liu, X. in Comprehensive Nanoscience and Nanotechnology (Second Edition) (eds David L. Andrews, Robert H. Lipson, & Thomas Nann) 359-384 (Academic Press, 2011).
Saleh Mohammadnia, M. et al. Fluorescent cellulosic composites based on carbon dots: Recent advances, developments, and applications. Carbohydrate Polymers 294, 119768, doi:https://doi.org/10.1016/j.carbpol.2022.119768 (2022).
Zhou, Y., Sharma, S. K., Peng, Z. & Leblanc, R. M. Polymers in Carbon Dots: A Review. Polymers (Basel) 9, doi:10.3390/polym9020067 (2017).
He, P. et al. Recent advances in white light-emitting diodes of carbon quantum dots. Nanoscale 12, 4826-4832, doi:10.1039/C9NR10958G (2020).
Chandra, S. et al. Luminescent S-doped carbon dots: an emergent architecture for multimodal applications. J Mater Chem B 1, 2375-2382, doi:10.1039/c3tb00583f (2013).
Matsoso, B. J. et al. Single-step synthesis of crystalline h-BN quantum- and nanodots embedded in boron carbon nitride films. Nanotechnology 28, 105602, doi:10.1088/1361-6528/aa56df (2017).
Wang, Y. & Hu, A. Carbon quantum dots: synthesis, properties and applications. Journal of Materials Chemistry C 2, 6921, doi:10.1039/c4tc00988f (2014).
Zheng, M. et al. Integrating Oxaliplatin with Highly Luminescent Carbon Dots: An Unprecedented Theranostic Agent for Personalized Medicine. Advanced Materials 26, 3554-3560, doi:https://doi.org/10.1002/adma.201306192 (2014).
Li, H., Zhang, Y., Wang, L., Tian, J. & Sun, X. Nucleic acid detection using carbon nanoparticles as a fluorescent sensing platform. Chemical Communications 47, 961-963, doi:10.1039/C0CC04326E (2011).
Song, Y., Zhu, S. & Yang, B. Bioimaging based on fluorescent carbon dots. RSC Advances 4, 27184-27200, doi:10.1039/C3RA47994C (2014).
Khairol Anuar, N. K., Tan, H. L., Lim, Y. P., So’aib, M. S. & Abu Bakar, N. F. A Review on Multifunctional Carbon-Dots Synthesized From Biomass Waste: Design/ Fabrication, Characterization and Applications. Frontiers in Energy Research 9, doi:10.3389/fenrg.2021.626549 (2021).
Mirlou Miavagh, F., Rezvani Moghaddam, A. & Roghani-Mamaqani, H. Fluorescent Pigments Based on Carbon Quantum Dots: Synthesis methods and Applications. Journal of Studies in Color World 12, 159-169 (2022).
Sharma, A. & Das, J. Small molecules derived carbon dots: synthesis and applications in sensing, catalysis, imaging, and biomedicine. J Nanobiotechnology 17, 92, doi:10.1186/s12951-019-0525-8 (2019).
Chen, X. et al. Facile one-pot synthesis of self-assembled nitrogen-doped carbon dots/cellulose nanofibril hydrogel with enhanced fluorescence and mechanical properties. Green Chemistry 22, 3296-3308, doi:10.1039/d0gc00845a (2020).
Niu, W.-J. et al. Ethylenediamine-assisted hydrothermal synthesis of nitrogen-doped carbon quantum dots as fluorescent probes for sensitive biosensing and bioimaging. Sensors and Actuators B: Chemical 218, 229-236, doi:10.1016/j.snb.2015.05.006 (2015).
Liu, Y. et al. Hydrothermal synthesis of nitrogen and boron co-doped carbon quantum dots for application in acetone and dopamine sensors and multicolor cellular imaging. Sensors and Actuators B: Chemical 281, 34-43, doi:10.1016/j.snb.2018.10.075 (2019).
Mohapatra, S. & Das, R. K. Dopamine integrated B, N, S doped CQD nanoprobe for rapid and selective detection of fluoride ion. Anal Chim Acta 1058, 146-154, doi:10.1016/j.aca.2019.01.021 (2019).
Algarra, M. et al. P-doped carbon nano-powders for fingerprint imaging. Talanta 194, 150-157, doi:10.1016/j.talanta.2018.10.033 (2019).
Shi, D. et al. P-doped carbon dots act as a nanosensor for trace 2,4,6-trinitrophenol detection and a fluorescent reagent for biological imaging. RSC Advances 5, 98492-98499, doi:10.1039/c5ra18800h (2015).
Yang, G., Wan, X., Su, Y., Zeng, X. & Tang, J. Acidophilic S-doped carbon quantum dots derived from cellulose fibers and their fluorescence sensing performance for metal ions in an extremely strong acid environment. Journal of Materials Chemistry A 4, 12841-12849, doi:10.1039/c6ta05943k (2016).
Gao, J. P. et al. Blue luminescent N,S-doped carbon dots encapsulated in red emissive Eu-MOF to form dually emissive composite for reversible anti-counterfeit ink. Dalton Trans 50, 1690-1696, doi:10.1039/d0dt03048a (2021).
Yi, Z. et al. High quantum yield photoluminescent N-doped carbon dots for switch sensing and imaging. Talanta 222, 121663, doi:10.1016/j.talanta.2020.121663 (2021).
Tall, A. et al. Green emitting N, P-doped carbon dots as efficient fluorescent nanoprobes for determination of Cr(VI) in water and soil samples. Microchemical Journal 166, 106219, doi:10.1016/j.microc.2021.106219 (2021).
Zuo, G. et al. Large Emission Red-Shift of Carbon Dots by Fluorine Doping and Their Applications for Red Cell Imaging and Sensitive Intracellular Ag+ Detection. The Journal of Physical Chemistry C 121, 26558-26565, doi:10.1021/acs.jpcc.7b10179 (2017).
Kalaiyarasan, G., Joseph, J. & Kumar, P. Phosphorus-Doped Carbon Quantum Dots as Fluorometric Probes for Iron Detection. ACS Omega 5, 22278-22288, doi:10.1021/acsomega.0c02627 (2020).
Ren, J., Malfatti, L. & Innocenzi, P. Citric Acid Derived Carbon Dots, the Challenge of Understanding the Synthesis-Structure Relationship. C 7, 2, doi:10.3390/c7010002 (2020).
Li, C. et al. A feasible and universal one-step method for functionalizing carbon dots efficiently via in-situ free radical polymerization. Journal of Luminescence 238, 118246, doi:10.1016/j.jlumin.2021.118246 (2021).
Latief, U., Ul Islam, S., Khan, Z. & Khan, M. S. A facile green synthesis of functionalized carbon quantum dots as fluorescent probes for a highly selective and sensitive detection of Fe(3+) ions. Spectrochim Acta A Mol Biomol Spectrosc 262, 120132, doi:10.1016/j.saa.2021.120132 (2021).

No competing interests reported.

GA.png
Graphical abstract

Download PDF

Version 1

posted

You are reading this latest preprint version

High quantum yield carbon quantum dots synthesized via three different routes for anti-counterfeiting inkjet inks application

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental Section

2.1. Materials and reagents

2.2. Synthesis of Nitrogen Dopes CQDs (N-CQDs) and un-doped CQD

2.2.1. Hydrothermal synthesis method

2.2.2. Microwave-assisted synthesis method

2.2.3. Simple heating synthesis method

2.3. Instruments and apparatus

3. Results And Discussion

3.1. Optical Characterization of Carbon Quantum Dots

3.2. Morphological characterization of synthesized quantum dots

3.2.1. TEM analysis

3.3. Chemical Characterization of N-CQDs

3.4. Visual properties of synthesized quantum dots

3.5. Printing properties of N-E-CQD

4. Conclusions

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1