Preparation method of carbon quantum dot ink for inkjet printing
Carbon quantum dot inks prepared by surface adsorption of metal ions and optimized dispersion methods have solved the problems of insufficient stability and electrochemical performance in inkjet printing, achieving high-precision inkjet printing and excellent electrochemical performance, making them suitable for micro energy storage devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANCHANG HANGKONG UNIVERSITY
- Filing Date
- 2024-09-03
- Publication Date
- 2026-05-29
AI Technical Summary
Existing carbon quantum dot inks suffer from poor stability and insufficient electrochemical performance in inkjet printing of micro energy storage devices, and it is difficult to achieve high-precision inkjet printing, especially for printheads with nozzle diameters of less than 50 μm.
By modifying carbon quantum dots with surface adsorption of metal ions, and combining optimized dispersants and dispersion methods, a carbon quantum dot ink with high stability and excellent electrochemical performance was prepared. Ultrasonic dispersion treatment and surfactants were used to adjust the surface tension and viscosity of the ink, making it suitable for printheads with nozzle diameters of less than 50 μm.
It achieves high stability and high precision inkjet printing with excellent printing performance, no "coffee ring" phenomenon, and good electrochemical performance, making it suitable for micro energy storage devices.
Smart Images
Figure CN118978830B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing carbon quantum dot ink for inkjet printing, specifically belonging to the field of inkjet printing technology. Background Technology
[0002] With the rapid development of modern science and technology, the application of electronic products is also moving towards intelligence, flexibility, and miniaturization, making the development of micro energy storage devices extremely urgent. Currently, micro energy storage devices mainly consist of micro batteries and micro supercapacitors. Compared to micro batteries, micro supercapacitors have advantages such as longer lifespan and higher power density. Inkjet printing technology is currently one of the most popular fabrication technologies in the field of micro energy storage, possessing wide applicability and numerous advantages such as rapid mass production, controllable morphology, and high precision.
[0003] The key to inkjet printing is the preparation of inks with appropriate flowability and high stability. Inks mainly contain active materials, dispersants, solvents, and defoamers (Applied Physics Reviews, 2021, 8: 021319). In the literature (Journal of Materials Chemistry C, 2019, 7: 8771-8795), inks currently used for inkjet printing to prepare micro supercapacitors mostly employ nozzle diameters ≥50 μm. To further achieve finer inkjet printing, further optimization of the particle size and stability of the active materials in the ink is crucial.
[0004] Carbon quantum dots (CQDs) are zero-dimensional carbon nanomaterials with a particle size of 2-30 nm (FlatChem, 2020, 22:100171). The surface of carbon quantum dots possesses abundant functional groups, allowing for uniform dispersion in water, making them an excellent active material for high-precision inkjet printing. Furthermore, carbon quantum dots are environmentally friendly, easy to prepare, low in cost, and readily modifiable. Therefore, carbon quantum dot inks have been widely used in inkjet printing (CN106634218A, CN107057463A, CN108975309A, CN109504376A, CN109593524A, CN112391086A, CN114752257A, CN117050576A, CN117384513A, CN117757304A). In the aforementioned disclosed patents, the carbon quantum dot inks are all prepared based on the good dispersibility of carbon quantum dots themselves and are used in the field of fluorescence. To date, no carbon quantum dot ink has been found that can be used for inkjet printing of microcapacitors.
[0005] Carbon quantum dots possess electrochemical activity and show promising application potential in capacitors. However, pure carbon quantum dots exhibit low specific capacitance. Athika et al. (Materials Letter, 2019, 241: 156-159) reported that milk-derived carbon quantum dots had a specific capacitance of only 95 F / g in a 1 M H₂SO₄ electrolyte at a current density of 0.12 A / g. Zhu et al. (Energy & Environmental Science, 2013, 6: 3665.) found that carbon quantum dots prepared by the chemical oxidation of nanographite had a specific capacitance of only 53 F / g in a 1 M Na₂SO₄ electrolyte at a current density of 2 A / g. Furthermore, unmodified pure carbon quantum dots have good water solubility. When used to construct microelectrodes via inkjet printing after forming ink, the carbon quantum dots are easily dispersed by aqueous electrolytes during subsequent electrochemical testing, causing them to detach from the substrate surface and affecting the stability of the micro-energy storage device. Therefore, to date, there is no literature on the use of carbon quantum dot inks for inkjet printing to prepare micro energy storage devices.
[0006] Therefore, this invention modifies the water solubility and electrochemical activity of carbon quantum dots by adsorbing metal ions on their surface, and by optimizing the dispersant and dispersion method, it has invented a carbon quantum dot inkjet printing ink with stable dispersion and excellent electrochemical performance. This ink has advantages such as high stability, excellent printing performance, absence of the "coffee ring" phenomenon, and good electrochemical performance. Summary of the Invention
[0007] To address the aforementioned issues, this invention proposes a method for preparing carbon quantum dot ink for inkjet printing. The method for preparing carbon quantum dot ink for inkjet printing according to this invention includes the following steps:
[0008] Step 1: Preparation of carbon quantum dots with surface adsorption of metal ions
[0009] An aqueous solution of citric acid and thiourea was subjected to a hydrothermal reaction and then cooled to room temperature. After centrifugation, the supernatant was collected to obtain a sulfur-doped carbon quantum dot solution (S-CQDs). A metal salt solution was added to the sulfur-doped carbon quantum dot solution and stirred to obtain a carbon quantum dot solution with adsorbed metal ions. After freeze-drying, carbon quantum dots with adsorbed metal ions on the surface were obtained.
[0010] Step 2: Preparation of carbon quantum dot dispersion
[0011] Carbon quantum dots with adsorbed metal ions on their surface were dispersed in deionized water by ultrasonic dispersion to prepare a carbon quantum dot dispersion.
[0012] Step 3: Preparation of carbon quantum dot ink
[0013] The surfactant was added to the carbon quantum dot dispersion in step 2, and ultrasonic dispersion was used to obtain carbon quantum dot ink for inkjet printing with a surface tension of 26~38 mN / m and a viscosity of 4~12 mPa / s.
[0014] The amount of metal ions adsorbed on the surface of the carbon quantum dots is 10wt%-30wt%.
[0015] The metal ions adsorbed on the surface of the carbon quantum dots are one or both of nickel and cobalt ions.
[0016] The process parameters for the ultrasonic dispersion treatment are: power 270~900 W, on for 2~10 s, off for 2~10 s, and time 5~20 min.
[0017] The surfactant content in the inkjet printing carbon quantum dot ink is 0.5wt%~10wt%, and the concentration of carbon quantum dots is 15~40 mg / mL.
[0018] The surfactant is one of Triton X-100, CTAB (hexadecyltrimethylammonium bromide), and SDS (sodium dodecyl sulfate).
[0019] The carbon quantum dot ink for inkjet printing uses parameters such as a waveform voltage amplitude of 10~40 V, a piezoelectric waveform period of 25.6 μs, an inkjet frequency of 2000~5000 Hz, and a printhead diameter of 30 μm to prepare microcapacitors.
[0020] The beneficial effects of the present invention are: (1) The carbon quantum dot ink of the present invention has high stability, small particle size and uniform distribution, and can be used for inkjet printing with a nozzle diameter of less than 50 μm. The preparation method is simple.
[0021] (2) The carbon quantum dot ink of the present invention has excellent printing performance. It can not only achieve patterning, but also print patterns without obvious coffee rings.
[0022] (3) The carbon quantum dot ink of the present invention has excellent electrochemical properties and can be applied to inkjet printing of micro energy storage devices. Attached Figure Description
[0023] Figure 1 This is a transmission electron microscope image of the carbon quantum dots in Example 1 of the present invention;
[0024] Figure 2 This is a transmission electron microscope image of carbon quantum dots in Example 2 of the present invention;
[0025] Figure 3 This is a transmission electron microscope image of the carbon quantum dots in Example 3 of the present invention;
[0026] Figure 4 Image of the carbon quantum dot ink prepared in Example 1 of this invention;
[0027] Figure 5 Image of the interdigitated pattern of the miniature supercapacitor prepared in Comparative Example 1 of this invention;
[0028] Figure 6 Cyclic voltammetry curves of the micro supercapacitor at different scan rates in Embodiment 1 of the present invention;
[0029] Figure 7 Cyclic voltammetry curves of the micro supercapacitor at different scan rates in Embodiment 2 of the present invention;
[0030] Figure 8 Cyclic voltammetry curves of the micro supercapacitor at different scan rates in Embodiment 3 of the present invention. Detailed Implementation
[0031] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.
[0032] Example 1
[0033] The preparation method of carbon quantum dot ink for inkjet printing is as follows:
[0034] Step 1: Preparation of carbon quantum dots with surface adsorption of cobalt ions
[0035] 6 g of citric acid and 3 g of thiourea were added to 60 mL of aqueous solution and stirred until completely dissolved. The solution was then transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and kept at 200 °C for 10 h for hydrothermal reaction. After cooling to room temperature, the solution was centrifuged at 8000 rpm for 30 min and the supernatant was collected to obtain sulfur-doped carbon quantum dot solution (S-CQDs).
[0036] 0.04 g Co(NO3)2·6H2O was dissolved in 10 mL of deionized water and stirred at room temperature for 0.5 hours. Then it was slowly added dropwise to 10 mL of S-CQD solution. After the reaction was completed, the resulting cobalt ion-containing carbon quantum dot solution (Co-CQD) was freeze-dried to obtain carbon quantum dots with cobalt ions adsorbed on the surface.
[0037] Step 2: Carbon quantum dot dispersion
[0038] 200 mg of carbon quantum dots (Co-CQD) with surface adsorbed cobalt ions were added to 10 mL of deionized water and ultrasonically dispersed to obtain a carbon quantum dot dispersion. The ultrasonic dispersion process parameters were: power 60% (900 W) and ultrasonic time 15 min.
[0039] Step 3: Carbon quantum dot ink
[0040] A 10 wt% surfactant Triton X100 was added to a carbon quantum dot dispersion and ultrasonically dispersed to obtain a carbon quantum dot ink for inkjet printing with a viscosity of 6.47 mPa / s and a surface tension of 31.98 mN / m.
[0041] Step 4: Fabrication of the miniature supercapacitor:
[0042] Using inkjet printing technology, 35 layers were printed with a waveform voltage amplitude of 25 V, a piezoelectric waveform period of 25.6 μs, an inkjet frequency of 4000 Hz, a printhead diameter of 30 μm, an ink droplet spacing of 10 μm, and a post-processing temperature of 40℃ for 10 min. Carbon quantum dot ink was printed into interdigitated electrode patterns on a substrate, dried, and then electrolyte was added to prepare a micro supercapacitor.
[0043] The microstructure of the electrode material prepared in Example 1 is as follows: Figure 1 As shown, the electrode material exhibits a small and uniform particle size distribution, with no obvious agglomeration, proving that the carbon quantum dots electrode material are suitable for use in inkjet printing inks. The electrode material ink prepared in Example 1 is as follows... Figure 4 As shown. The cyclic voltammetry curves of the micro supercapacitor prepared in Example 1 at different scan rates are shown in Figure 1. Figure 6 As shown, the rectangular curve indicates that the device exhibits good capacitive behavior, with 22.9 mF / cm² at a scan rate of 50 mV / s. 2 The surface capacitance indicates that the prepared micro supercapacitor has good electrochemical performance.
[0044] Example 2
[0045] Step 1: Preparation of carbon quantum dots with nickel ion adsorbed on the surface
[0046] 6 g of citric acid and 3 g of thiourea were added to 60 mL of aqueous solution and stirred until completely dissolved. The solution was then transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and kept at 200 °C for 10 h for hydrothermal reaction. After cooling to room temperature, the solution was centrifuged at 8000 rpm for 30 min and the supernatant was collected to obtain sulfur-doped carbon quantum dot solution (S-CQDs).
[0047] 0.04 g Ni(NO3)2·6H2O was dissolved in 10 mL of deionized water and stirred at room temperature for 0.5 hours. Then it was slowly added dropwise to 10 mL of S-CQD solution. After the reaction was completed, the resulting aqueous solution of carbon quantum dots containing nickel ions (Ni-CQD) was freeze-dried to obtain carbon quantum dots with nickel ions adsorbed on the surface.
[0048] Step 2: Carbon quantum dot dispersion
[0049] 200 mg of carbon quantum dots with nickel ions adsorbed on the surface of Ni-CQD were added to 10 mL of deionized water and ultrasonically dispersed to obtain a carbon quantum dot dispersion. The ultrasonic dispersion process parameters were: power 30% (900W) and ultrasonic time 5 min.
[0050] Step 3: Carbon quantum dot ink
[0051] A carbon quantum dot ink for inkjet printing with a viscosity of 7.35 mPa / s and a surface tension of 30.46 mN / m was prepared by adding 0.1 M of the surfactant cetyltrimethylammonium bromide to a carbon quantum dot dispersion and then dispersing it by ultrasonication.
[0052] Step 4: Fabrication of miniature supercapacitors
[0053] Using inkjet printing technology, the printing layers are 35, the waveform voltage amplitude is 40 V, the piezoelectric waveform period is 25.6 μs, the inkjet frequency is 2000 Hz, the printhead diameter is 30 μm, the droplet spacing is 15 μm, the post-processing temperature is 40 ℃, and the time is 10 min.
[0054] Electrode material was printed into an interdigitated electrode pattern on a substrate, dried, and then electrolyte was added to prepare a micro supercapacitor. The microstructure of the electrode material prepared in Example 2 is as follows. Figure 2 As shown, the electrode material has a small and uniform particle size distribution.
[0055] The cyclic voltammetry curves of the micro supercapacitor prepared in Example 2 at different scan rates are shown below. Figure 7 As shown in the figure, even at high scan rates, the curve shape remains unchanged, maintaining a roughly rectangular shape. At a scan rate of 50 mV / s, the surface capacitance is 28.9 mF / cm². 2 This indicates that the prepared micro supercapacitor has good electrochemical performance.
[0056] Comparative Example 1
[0057] The carbon quantum dot ink used as the electrode material in Example 1 was printed on photographic paper using inkjet printing technology. The printing layer consisted of 15 layers, and the pattern was an interdigitated electrode design. The printing method described in Example 1 was used to obtain the electrode material layers. The interdigitated electrode prepared in Comparative Example 1 is shown below. Figure 5 As shown, the printed pattern shows no obvious "coffee ring" phenomenon, and the electrode material is deposited evenly and concentratedly, proving that the carbon quantum dot ink of the electrode material has good printability.
[0058] Example 3
[0059] Step 1: Preparation of carbon quantum dots with surface adsorption of nickel-cobalt ions
[0060] 6 g of citric acid and 3 g of thiourea were added to 60 mL of aqueous solution and stirred until completely dissolved. The solution was then transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and kept at 200 °C for 10 h for hydrothermal reaction. After cooling to room temperature, the solution was centrifuged at 8000 rpm for 30 min and the supernatant was collected to obtain sulfur-doped carbon quantum dot solution (S-CQDs).
[0061] 0.02 g Ni(NO3)2·6H2O and 0.02 g Co(NO3)2·6H2O were dissolved in 10 mL of deionized water and stirred at room temperature for 0.5 hours. Then, the mixture was slowly added dropwise to 10 mL of S-CQD solution. After the reaction was completed, the resulting aqueous solution of carbon quantum dots containing nickel and cobalt ions (NiCo-CQD) was freeze-dried to obtain carbon quantum dots with nickel and cobalt ions adsorbed on the surface.
[0062] Step 2: Carbon quantum dot dispersion
[0063] 200 mg of carbon quantum dots with adsorbed nickel and cobalt ions on the surface of NiCo-CQD were added to 10 mL of deionized water and ultrasonically dispersed to obtain a carbon quantum dot dispersion. The ultrasonic dispersion process parameters were: power 70% (900 W) and ultrasonic time 20 min.
[0064] Step 3: Carbon quantum dot ink
[0065] A carbon quantum dot ink for inkjet printing with a viscosity of 5.92 mPa / s and a surface tension of 33.28 mN / m was prepared by adding 0.05 M of the surfactant cetyltrimethylammonium bromide to a carbon quantum dot dispersion and then dispersing it by ultrasonication.
[0066] Step 4: Fabrication of miniature supercapacitors
[0067] Using inkjet printing technology, the printing layers are 35, the waveform voltage amplitude is 20 V, the piezoelectric waveform period is 25.6 μs, the inkjet frequency is 5000 Hz, the printhead diameter is 30 μm, the ink droplet spacing is 10 μm, the post-processing temperature is 40℃, and the time is 10 min.
[0068] Electrode materials are printed into interdigitated electrode patterns on a substrate, dried, and then electrolyte is added to prepare a micro supercapacitor.
[0069] The microstructure of the electrode material prepared in Example 3 is as follows: Figure 3 As shown, the electrode material has a small and uniform particle size distribution. The cyclic voltammetry curves of the micro supercapacitor prepared in Example 3 at different scan rates are shown below. Figure 8 As shown in the figure, even at high scan rates, the curve shape remains unchanged, maintaining a near-rectangular shape. At a scan rate of 50 mV / s, the surface capacitance is 29.6 mF / cm². 2 This indicates that the prepared micro supercapacitor has good electrochemical performance.
Claims
1. A method for preparing carbon quantum dot ink for inkjet printing, characterized in that: The preparation method includes the following steps: Step 1: Preparation of carbon quantum dots with surface adsorption of metal ions An aqueous solution of citric acid and thiourea was subjected to a hydrothermal reaction and then cooled to room temperature. After centrifugation, the supernatant was collected to obtain a sulfur-doped carbon quantum dot solution. A metal salt solution was added to the sulfur-doped carbon quantum dot solution and stirred to obtain a carbon quantum dot solution with adsorbed metal ions. After freeze-drying, carbon quantum dots with adsorbed metal ions on the surface were obtained. Step 2: Preparation of carbon quantum dot dispersion Carbon quantum dots with adsorbed metal ions on their surface were dispersed in deionized water by ultrasonic dispersion to prepare a carbon quantum dot dispersion. Step 3: Preparation of carbon quantum dot ink The surfactant was added to the carbon quantum dot dispersion in step 2, and ultrasonic dispersion was used to obtain carbon quantum dot ink for inkjet printing with a surface tension of 26~38 mN / m and a viscosity of 4~12 mPa / s.
2. The method for preparing carbon quantum dot ink for inkjet printing according to claim 1, characterized in that: The amount of metal ions adsorbed on the surface of the carbon quantum dots is 10wt%-30wt%.
3. The method for preparing carbon quantum dot ink for inkjet printing according to claim 1, characterized in that: The metal ions adsorbed on the surface of the carbon quantum dots are one or both of nickel and cobalt ions.
4. The method for preparing carbon quantum dot ink for inkjet printing according to claim 1, characterized in that: The process parameters for the ultrasonic dispersion treatment are: power 270~900 W, on for 2~10 s, off for 2~10 s, time 5~20 min.
5. The method for preparing carbon quantum dot ink for inkjet printing according to claim 1, characterized in that, The surfactant content in the inkjet printing carbon quantum dot ink is 0.5wt%~10wt%, and the concentration of carbon quantum dots is 15~40 mg / mL.
6. The method for preparing carbon quantum dot ink for inkjet printing according to claim 1, characterized in that, The surfactant is one of Triton X100, CTAB, and SDS.