Preparation and application of chemical copper plating cellulose composite fiber

Abstract

The invention belongs to the field of new materials, and particularly relates to preparation and application of chemical copper plating cellulose composite fibers. The preparation method of the composite fiber comprises the following steps: (1) mixing absolute ethyl alcohol, ammonia water and water in proportion, adding cellulose fiber, heating, stirring and uniformly mixing, adding a dopamine hydrochloride solution, washing and drying to obtain a polydopamine coating / cellulose composite fiber; (2) adding the composite fiber prepared in the step (1) into an alkaline solution, adding a silver nitrate solution, stirring, washing and drying to obtain a polydopamine reduced nano-silver / cellulose composite fiber; and (3) adding the composite fiber obtained in the step (2) into a chemical plating solution containing copper ions for plating to obtain the chemical copper-plated cellulose composite fiber. The electroless copper-plated cellulose composite fiber shows outstanding electric heating and photo-thermal properties, can accurately capture electrocardiosignals of a human body before and after movement at the same time, and provides a new thought for development of wearable electronic fabrics and intelligent sensors.

Description

Technical Field

[0001] The present invention belongs to the field of new materials, and particularly relates to the preparation and application of electroless copper-plated cellulose composite fibers. Background Art

[0002] Due to their excellent conductivity and flexibility, conductive polymer-based cellulose conductive fiber materials show broad application potential in fields such as flexible electronics, sensors, and smart textiles. However, the conductivity of such materials is usually lower than that of metal materials, and their performance may decay in high humidity or extreme environments, which limits their development in high-performance applications. To solve this problem, researchers have begun to explore the combination of metal materials (such as silver, copper, gold, etc.) with cellulose to prepare metal-based cellulose conductive fiber materials. Such materials not only retain the renewability and biodegradability of cellulose but also possess the high conductivity, high stability, and excellent mechanical properties of metal materials, providing new possibilities for applications in fields such as flexible electronics and electromagnetic shielding.

[0003] In recent years, the application of functional nanomaterials combined with cellulose through surface modification technology has become more and more extensive in the fields of electronic devices, sensing, and catalysis. Among them, polydopamine (PDA) has been widely used to construct multifunctional coatings on the surface of cellulose due to its excellent adhesion, reducibility, and abundant functional groups (such as catechol and amino), and is further used to load metal nanoparticles to achieve catalytic, conductive, or antibacterial properties. In the metallization process, electroless copper plating has become an important means for preparing conductive composites due to its low cost, high conductivity, and good coverage. Traditional electroless copper plating relies on noble metal catalysts (such as palladium), but it has high costs, complex processes, and environmental pollution risks. Considering that catalyst silver nanoparticles (AgNPs) and others that play an important role in the electroless copper plating process can be loaded by biological methods, thus reducing traditional process steps, there have now been reports on the reduction of AgNPs by various bio-based substances, which may replace the synthesis steps of catalysts in the electroless plating process. Dopamine is an organic compound of catecholamines and can spontaneously polymerize into a very adhesive polydopamine coating under a weak base environment at room temperature. The polydopamine coating has high reactivity, and metal nanoparticles can be directly deposited on the polydopamine film without grafting the already synthesized metal nanoparticles onto the substrate. Therefore, this fact provides a reliable basis for catalysis and can be used for the chemical metallization of various materials.

[0004] Based on this, the present study proposes a novel "cellulose-PDA-AgNPs" composite system, in which AgNPs are in-situ generated on the surface of cellulose through the dual functions (adhesion and reduction) of the PDA coating, and further catalyze the electroless copper plating reaction. Summary of the Invention

[0005] In view of the problems and deficiencies existing in the prior art, the purpose of the present invention is to provide a preparation method and application of electroless copper-plated cellulose composite fibers.

[0006] To achieve the purpose of the invention, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present invention provides a preparation method of electroless copper-plated cellulose composite fibers, including the following steps:

[0008] (1) Mix anhydrous ethanol, ammonia water, and water in proportion to obtain a mixed solution; add cellulose fibers (CF) to the mixed solution, stir and mix evenly, then add a hydrochloric acid dopamine solution to the mixed solution, heat and stir to react. After the reaction is completed, take out the cellulose fibers, and the cellulose fibers are washed and dried to obtain polydopamine-coated / cellulose composite fibers (CP);

[0009] (2) Add the polydopamine-coated / cellulose composite fibers prepared in step (1) and a silver nitrate solution to an alkaline solution, heat and stir to react. After the reaction is completed, take out the polydopamine-coated / cellulose composite fibers, and the polydopamine-coated / cellulose composite fibers are washed and dried to obtain polydopamine-reduced silver nanoparticles / cellulose composite fibers (CPA);

[0010] (3) Add the polydopamine-reduced silver nanoparticles / cellulose composite fibers obtained in step (2) to an electroless plating solution containing copper ions for electroless plating treatment to obtain electroless copper-plated cellulose composite fibers (CPAC).

[0011] Preferably, in step (3), the electroless plating solution is prepared by mixing anhydrous copper sulfate, ethylenediaminetetraacetic acid, sodium potassium tartrate, ethanol, formaldehyde, and water; in the electroless plating solution, the mass concentration of anhydrous copper sulfate is 0.01 - 0.05 g / ml, the mass concentration of ethylenediaminetetraacetic acid is 0.01 - 0.05 g / ml, the mass concentration of sodium potassium tartrate is 0.01 - 0.02 g / ml, the volume fraction of ethanol is 0.5% - 1%, and the volume fraction of formaldehyde is 0.5% - 1%.

[0012] More preferably, in the electroless plating solution, the mass concentration of anhydrous copper sulfate is 0.025 g / ml, the mass concentration of ethylenediaminetetraacetic acid is 0.03 g / ml, the mass concentration of sodium potassium tartrate is 0.01 g / ml, the volume fraction of ethanol is 0.6%, and the volume fraction of formaldehyde is 0.8%.

[0013] Preferably, the mass ratio of the electroless plating solution to the polydopamine-reduced silver nanoparticles / cellulose composite fibers is 50 - 100:1; the pH of the electroless plating solution is 11 - 13.

[0014] More preferably, the mass ratio of the electroless plating solution to the polydopamine-reduced silver nano / cellulose composite fiber is 100:1; the pH of the electroless plating solution is 12.5.

[0015] Preferably, in step (1), the mass concentration of the dopamine hydrochloride solution is 0.01 - 0.1 g / ml; the volume ratio of water, absolute ethanol, and ammonia water in the mixed solution is 8 - 10:4:0.2; the mass ratio of the dopamine hydrochloride solution, the mixed solution, and the cellulose fiber is 50 - 100∶50 - 100∶1.

[0016] More preferably, the concentration of the dopamine hydrochloride is 0.05 g / ml; the volume ratio of water, absolute ethanol, and ammonia water in the mixed solution is 9∶4∶0.2; the mass ratio of the dopamine hydrochloride solution, the mixed solution, and the cellulose fiber is 100∶100∶1.

[0017] Preferably, in step (2), the mass concentration of the silver nitrate solution is 0.001 - 0.005 g / ml; the mass ratio of the silver nitrate solution to the polydopamine-coated / cellulose composite fiber is 10 - 20∶1.

[0018] More preferably, the concentration of the silver nitrate solution is 0.002 g / ml; the mass ratio of the silver nitrate solution to the polydopamine-coated / cellulose composite fiber is 20∶1.

[0019] Preferably, in step (1), the heating temperature is 20 - 40 °C, and the stirring time is 12 - 24 h; in step (2), the heating temperature is 20 - 40 °C, and the stirring time is 0.5 - 2 h.

[0020] More preferably, in step (1), the heating temperature is 40 °C, and the stirring reaction time is 24 h; in step (2), the heating temperature is 40 °C, and the stirring time is 2 h.

[0021] Preferably, in step (3), the plating treatment time is 3 - 9 min.

[0022] Preferably, in step (1), the preparation method of the cellulose fiber is as follows: Add ionic liquid to the washed and dried pulp, heat and stir until the cellulose is completely dissolved to obtain a cellulose solution; subject the cellulose solution to spinning treatment, the spinning solution is stretched and then regenerated into a hydrogel fiber in a coagulation bath, and then stretched, washed, and dried to obtain a cellulose fiber. After removing the ionic liquid in the fiber and drying, the cellulose fiber is obtained.

[0023] Preferably, the ionic liquid is 1-ethyl-3-methylimidazolium acetate.

[0024] In a second aspect, the present invention provides an electroless copper-plated cellulose composite fiber prepared by the method described in the first aspect.

[0025] In a third aspect, the present invention provides an application of the electroless copper-plated cellulose composite fiber described in the second aspect in a sensor. Preferably, the sensor is a sensor for collecting bioelectrical signals.

[0026] In a fourth aspect, the present invention provides an application of the electroless copper-plated cellulose composite fiber described in the second aspect in wearable electronic textiles.

[0027] Compared with the prior art, the positive and beneficial effects achieved by the present invention are as follows:

[0028] 1. The cellulose fiber is mixed with hydrochloric acid dopamine. Through the self-polymerization of hydrochloric acid dopamine on the fiber surface and hydrogen bond action, polydopamine can firmly adhere to the cellulose surface; the abundant phenolic hydroxyl groups on polydopamine have strong reducibility and can reduce AgNO3 to obtain AgNPs. Therefore, the polydopamine-reduced silver nanoparticles / cellulose composite fiber prepared by the present invention has good catalytic activity and can be used as a reducing agent for copper ions; in the electroless plating solution, under the dual action of ethylenediaminetetraacetic acid and sodium potassium tartrate, Cu 2+ forms a relatively stable complex. Under the catalytic action of AgNPs on the polydopamine-reduced silver nanoparticles / cellulose composite fiber, Cu 2+ is reduced to elemental Cu and firmly adheres to the surface of the cellulose fiber, and finally an electroless copper-plated cellulose composite fiber is obtained (the schematic diagram of the preparation process is as shown in Figure 1 ). Due to the ultra-high catalytic activity of AgNPs, Cu 2+ can be reduced within just a few minutes, greatly improving the plating efficiency and providing a basis for high-efficiency and large-scale production.

[0029] 2. During the electroless copper plating process, a more uniform conductive copper layer adheres to the surface of the CPAC fiber. Therefore, the fabric prepared with the CPAC fiber of the present invention can better fit the skin surface. Moreover, the interfacial state between the CPAC fabric electrode and the skin is relatively stable, the relative sliding between the electrode and the skin is small, and the quality of the collected electrocardiogram signal is also high. The CPAC fabric electrode can effectively monitor the electrocardiogram signal during static and dynamic states and can be applied to the construction of electrocardiogram signal wearable fabrics.

[0030] 3. The CPAC of the present invention is obtained by loading a nano - copper layer on the cellulose fabric. Therefore, the CPAC fabric has electro - heating and photothermal functions. The CPAC fabric shows excellent heating performance at a relatively low voltage (3V), and a high stable heating temperature (121 °C) is obtained within a short stable heating time (7s). Moreover, the temperature of the CPAC fabric can rise to 137.1 °C within 8s under near - infrared light irradiation, showing more excellent near - infrared heating performance. Brief Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the preparation process of the electroless copper - plated cellulose composite fiber of the present invention;

[0032] Figure 2 It is the infrared spectrum, XRD, and XPS spectra of the cellulose fiber (CF) prepared in Example 1 of the present invention, the polydopamine - coated / cellulose composite fiber (CP) prepared in Example 2, the polydopamine - reduced nano - silver / cellulose composite fiber (CPA) prepared in Example 3, and the electroless copper - plated cellulose composite fiber (CPAC9) prepared in Example 7. In the figure, CPAC represents CPAC9 prepared in Example 7, where (a - b) are the infrared spectra of CF, CP, CPA, and CPAC9; (c) is the XRD analysis of CF, CP, CPA, and CPAC9; (d) are the XPS spectra of CPAC9 and CF; (e) is the C1s spectrum of CF; (f) is the C1s spectrum of CPAC9; (g) is the N1s spectrum of CPAC9; (h) is the Ag3d spectrum of CPAC9; (i) is the Cu2p spectrum of CPAC9;

[0033] Figure 3 It is the SEM scanning electron micrograph of the cellulose fiber (CF) prepared in Example 1 of the present invention, the polydopamine - coated / cellulose composite fiber (CP) prepared in Example 2, the polydopamine - reduced nano - silver / cellulose composite fiber (CPA) prepared in Example 3, and the electroless copper - plated cellulose composite fiber (CPAC9) prepared in Example 7 (in the figure, CPAC represents CPAC9 prepared in Example 7) and the EDS elemental analysis diagram of the polydopamine - reduced nano - silver / cellulose composite fiber (CPA) prepared in Example 3. Among them, a is the SEM scanning electron micrograph of CF; b is the SEM scanning electron micrograph of CP; c is the SEM scanning electron micrograph of CPA; d is the SEM scanning electron micrograph of CPAC9; e, g, h, i are the EDS elemental analysis images of CPA; f is the particle size distribution diagram of AgNPs on the surface of CPA;

[0034] Figure 4Cross-sectional SEM images of the cellulose fibers (CF) and composite fibers (CP, CPA, CPAC3, CPAC5, CPAC7, CPAC9) prepared in Examples 1-7 of the present invention; among them, a1 and a2 are the cross-sectional SEM images of CF; b1 and b2 are the cross-sectional SEM images of CP; c1 and c2 are the cross-sectional SEM images of CPA; d1 and d2 are the cross-sectional SEM images of CPAC3; e1 and e2 are the cross-sectional SEM images of CPAC5; f1 and f2 are the cross-sectional SEM images of CPAC7; g1 and g2 are the cross-sectional SEM images of CPAC9;

[0035] Figure 5 EDS elemental analysis image of the cross-section of the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7 of the present invention;

[0036] Figure 6 Analysis diagrams of the conductivity and stability of the electroless copper-plated cellulose composite fibers (CPAC3, CPAC5, CPAC7, CPAC9) prepared in Examples 4-7 of the present invention, where (a) conductivity of CPAC3, CPAC5, CPAC7, CPAC9; (b) density and specific conductivity of CPAC3, CPAC5, CPAC7, CPAC9; (c) resistance change curve of CPAC9 after 30 simulated washings; (d) comparison of the conductivity of various conductive fibers (silver nanowire / silver nanoparticle / SBS composite fiber, silk fibroin / MXene composite fiber, single-walled carbon nanotube / multi-walled carbon nanotube / polyurethane composite yarn, silver nanowire / polyurethane composite fiber, copper-coordinated cellulose fiber, bacterial cellulose / carbon nanotube / polypyrrole composite fiber, MXene / liquid metal / SBS composite fiber) with the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7, where This work is CPAC9;

[0037] Figure 7Mechanical property analysis of cellulose fibers (CF) prepared in Examples 1 - 7 of the present invention, polydopamine-coated / cellulose composite fibers (CP) prepared in Example 2, polydopamine-reduced silver nanoparticles / cellulose composite fibers (CPA) prepared in Example 3, and electroless copper-plated cellulose composite fibers (CPAC3, CPAC5, CPAC7, CPAC9) prepared in Examples 4 - 7. Among them, (a) stress-strain curves of CF, CP, CPA, and CPAC3; (b) tensile strengths of CF, CP, CPA, and CPAC3; (c) elongation at break of CF, CP, CPA, and CPAC3; (d) stress-strain curves of CPAC3, CPAC5, CPAC7, and CPAC9; (e) tensile strengths of CPAC3, CPAC5, CPAC7, and CPAC9; (f) elongation at break of CPAC3, CPAC5, CPAC7, and CPAC9;

[0038] Figure 8 TG and DTG curves of cellulose fibers (CF) prepared in Example 1 of the present invention, polydopamine-coated / cellulose composite fibers (CP) prepared in Example 2, polydopamine-reduced silver nanoparticles / cellulose composite fibers (CPA) prepared in Example 3, and electroless copper-plated cellulose composite fibers (CPAC9) prepared in Example 7. In the figure, CPAC represents CPAC9 prepared in Example 7. Among them, (a) TG curves of CF, CP, CPA, and CPAC9; (b) DTG curves of CF, CP, CPA, and CPAC3;

[0039] Figure 9 Electrical heating temperature curve and infrared thermal imaging photos during the heating process of electroless copper-plated cellulose composite fibers (CPAC9) prepared in Example 7 of the present invention. In the figure, CPAC represents CPAC9 prepared in Example 7. Among them, (a) temperature change curves of CPAC9 at different voltages; (b) photothermal repeat curve of CPAC9 before washing; (c) photothermal repeat curve of CPAC9 after washing; (d) infrared photos of CPAC9 at different voltages;

[0040] Figure 10 Schematic diagram of photothermal conversion of cellulose fibers (CF) prepared in Example 1 of the present invention, polydopamine-coated / cellulose composite fibers (CP) prepared in Example 2, polydopamine-reduced silver nanoparticles / cellulose composite fibers (CPA) prepared in Example 3, and electroless copper-plated cellulose composite fibers (CPAC9) prepared in Example 7. In the figure, CPAC represents CPAC9 prepared in Example 7. Among them, (a) photothermal mechanism of CPAC9 fabric; (b) temperature change curves of CF, CP, CPA, and CPAC under near-infrared light irradiation; (c) photothermal repeat curve of CPAC9 before washing; (d) photothermal repeat curve of CPAC9 after washing;

[0041] Figure 11 This is a comparison chart of the electrothermal and photothermal properties of the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7 of the present invention as an ECG electrode for monitoring the changes in human heart potential and various composite fibers. In the figure, CPAC represents CPAC9 prepared in Example 7. Among them, (a) is a simulated picture of CPAC9 fabric as an ECG electrode; (b) is the ECG signal image of CPAC9 fabric electrode at rest; (c) is the ECG signal image of CPAC9 fabric electrode after exercise; (d) is a comparison of the electrothermal properties of various composite fibers (redox graphene / graphene composite film, polydimethylsiloxane / MXene / wood sponge, MXene / silver nanoparticle composite fabric, silver nanowire / poly(3,4-ethylenedioxythiophene)-graphene composite film, polydopamine / MXene / polydimethylsiloxane composite fabric, poly(3,4-ethylenedioxythiophene) / cotton composite fabric) and the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7. Among them, This work is CPAC9; (e) is a comparison of the photothermal properties of various composite fibers (alginate / chitosan derivative / copper sulfide@polydopamine composite fiber, carbon fiber / MXene composite fabric, gelatin / polycaprolactone composite fiber, cobalt iron layered double hydroxide / carbon fiber fabric, MXene / polyester composite fabric, MXene / iron oxide / polyimide composite fiber membrane, aramid nanofiber / MXene / poly(3,4-ethylenedioxythiophene) composite membrane, chitosan / copper sulfide nanoparticle composite fiber, poly(3,4-ethylenedioxythiophene) / cotton composite fabric) and the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7. Among them, This work is CPAC9. Detailed implementation mode

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0043] Example 1:

[0044] The pulp board was shredded and washed with deionized water to remove impurities, and then placed in a drying oven and dried at 50 °C for 12 h. Weigh 1.2 g of pulp particles into a beaker, add 18.8 g of ionic liquid (EmimOAc), heat in a water bath at 90 °C for 1 h, stir evenly to fully dissolve the cellulose. Pour the uniform cellulose solution into a dry spinning can (with a pore size of 0.5 mm), place the spinning can in a vacuum oven, set the temperature to 90 °C, and after reducing the pressure to -0.1 MPa, remove the air bubbles in the cellulose solution in the spinning can. After cleaning the coagulation bath, add a certain amount of deionized water to the bath to submerge the pulley. Install the spinning can on the spinning frame, turn on the oil-free silent air compressor, set the distance between the spinning can and the coagulation bath liquid level to 30 mm, and set the spinning temperature to 70 °C. Open the jet valve, adjust the spinning pressure to -0.1 MPa, and start spinning. The spinning solution is stretched through the air gap and then enters the deionized water coagulation bath to regenerate hydrogel fibers, and then enters a beaker filled with deionized water after being stretched by a drafting machine to further remove the ionic liquid in the fibers. Dry with a hot roller dryer (temperature of 100 °C) to obtain cellulose fibers (CF).

[0045] Example 2:

[0046] Mix anhydrous ethanol, ammonia water, and water in a volume ratio of 9:4:0.2 and stir for 0.5 h to obtain a mixed solution; add the cellulose fibers prepared in Example 1 to the mixed solution, mix well, and then add a hydrochloric acid dopamine solution with a mass concentration of 0.05 g / ml to the mixed solution. The mass ratio of the hydrochloric acid dopamine solution, the mixed solution, and the cellulose fibers is 100∶100∶1. Heat at 40 °C and stir for 24 h. After the reaction is completed, take out the composite fibers, wash the composite fibers with anhydrous ethanol and deionized water, and then dry them with a hot roller dryer to obtain polydopamine-coated / cellulose composite fibers (CP).

[0047] Example 3:

[0048] Add ammonia water and a silver nitrate solution with a mass concentration of 0.002 g / ml to the polydopamine-coated / cellulose composite fibers prepared in Example 2. The mass ratio of the silver nitrate solution to the polydopamine-coated / cellulose composite fibers is 20∶1. Stir and react at 40 °C for 2 h. After the reaction is completed, take out the polydopamine-coated / cellulose composite fibers. Wash the polydopamine-coated / cellulose composite fibers with anhydrous ethanol and deionized water, and then dry them with a hot roller dryer to obtain polydopamine-reduced silver nanoparticles / cellulose composite fibers (CPA).

[0049] Example 4:

[0050] The polydopamine-reduced silver nanowire / cellulose composite fiber obtained in Example 3 was added to a electroless plating solution containing copper ions and subjected to electroless plating treatment for 3 min to obtain an electroless copper-plated cellulose composite fiber (denoted as CPAC3); wherein, the electroless plating solution was prepared by mixing copper sulfate anhydrous, ethylenediaminetetraacetic acid, sodium potassium tartrate, ethanol, formaldehyde and water; in the electroless plating solution, the mass concentration of copper sulfate anhydrous was 0.025 g / ml, the mass concentration of ethylenediaminetetraacetic acid was 0.03 g / ml, the mass concentration of sodium potassium tartrate was 0.01 g / ml, the volume fraction of ethanol was 0.6%, the volume fraction of formaldehyde was 0.8%, and the mass ratio of the electroless plating solution to the polydopamine-reduced silver nanowire / cellulose composite fiber was 100:1.

[0051] Example 5:

[0052] The content of Example 5 was basically the same as that of Example 4, except that: the electroless plating treatment was carried out for 5 min, and the obtained electroless copper-plated cellulose composite fiber was denoted as CPAC5.

[0053] Example 6:

[0054] The content of Example 6 was basically the same as that of Example 4, except that the electroless plating treatment was carried out for 7 min, and the obtained electroless copper-plated cellulose composite fiber was denoted as CPAC7.

[0055] Example 7:

[0056] The content of Example 7 was basically the same as that of Example 4, except that the electroless plating treatment was carried out for 9 min, and the obtained electroless copper-plated cellulose composite fiber was denoted as CPAC9.

[0057] Example 8:

[0058] The content of Example 8 was basically the same as that of Example 2, except that: the mass concentration of the dopamine hydrochloride solution was 0.01 g / ml; the volume ratio of water, absolute ethanol and ammonia water in the mixed solution was 8:4:0.2; the mass ratio of the dopamine hydrochloride solution, the mixed solution and the cellulose fiber was 50:50:1; the heating temperature was 20 °C, and the stirring reaction time was 12 h, and the obtained polydopamine-coated / cellulose composite fiber was denoted as CP2.

[0059] Example 9:

[0060] The content of Example 9 is basically the same as that of Example 2, except that the mass concentration of the dopamine hydrochloride solution is 0.1 g / ml; the volume ratio of water, absolute ethanol and ammonia water in the mixed solution is 10:4:0.2; the mass ratio of the dopamine hydrochloride solution, the mixed solution and the cellulose fiber is 70∶70∶1; the heating temperature is 30 °C, and the stirring reaction time is 18 h. The obtained polydopamine-coated / cellulose composite fiber is denoted as CP3.

[0061] Example 10:

[0062] The content of Example 10 is basically the same as that of Example 3, except that the mass concentration of the silver nitrate solution is 0.001 g / ml; the mass ratio of the silver nitrate solution to the polydopamine-coated / cellulose composite fiber is 10∶1; the heating temperature is 20 °C, and the stirring time is 0.5 h. The obtained polydopamine-reduced silver nanoparticles / cellulose composite fiber is denoted as CPA2.

[0063] Example 11:

[0064] The content of Example 11 is basically the same as that of Example 3, except that the mass concentration of the silver nitrate solution is 0.005 g / ml; the mass ratio of the silver nitrate solution to the polydopamine-coated / cellulose composite fiber is 15∶1; the heating temperature is 30 °C, and the stirring time is 1 h. The obtained polydopamine-reduced silver nanoparticles / cellulose composite fiber is denoted as CPA3.

[0065] Example 12:

[0066] The content of Example 12 is basically the same as that of Example 4, except that the electroless plating solution is prepared by mixing anhydrous copper sulfate, ethylenediaminetetraacetic acid, sodium potassium tartrate, ethanol, formaldehyde and water; in the electroless plating solution, the mass concentration of anhydrous copper sulfate is 0.01 g / ml, the mass concentration of ethylenediaminetetraacetic acid is 0.01 g / ml, the mass concentration of sodium potassium tartrate is 0.015 g / ml, the volume fraction of ethanol is 0.5%, and the volume fraction of formaldehyde is 0.5%; the mass ratio of the electroless plating solution to the polydopamine-reduced silver nanoparticles / cellulose composite fiber is 50∶1; the pH of the electroless plating solution is 11. The obtained electroless copper-plated cellulose composite fiber is denoted as CPAC12.

[0067] Example 13:

[0068] The content of Example 13 is basically the same as that of Example 4, except that the electroless plating solution is prepared by mixing anhydrous copper sulfate, ethylenediaminetetraacetic acid, sodium potassium tartrate, ethanol, formaldehyde and water; in the electroless plating solution, the mass concentration of anhydrous copper sulfate is 0.05 g / ml, the mass concentration of ethylenediaminetetraacetic acid is 0.05 g / ml, the mass concentration of sodium potassium tartrate is 0.02 g / ml, the volume fraction of ethanol is 1%, and the volume fraction of formaldehyde is 1%; the mass ratio of the electroless plating solution to the polydopamine-reduced silver nanowire / cellulose composite fiber is 80:1; the pH of the electroless plating solution is 13, and the obtained electroless copper-plated cellulose composite fiber is denoted as CPAC13.

[0069] Characterization and performance testing of composite fibers

[0070] (1) Structure analysis of electroless copper-plated cellulose composite fibers

[0071] The infrared spectra of the cellulose fibers (CF) and composite fibers (CP, CPA, CPAC9) prepared in Examples 1 to 3 and Example 7 are as shown in Figure 2 a and 2b. As can be seen from Figure 2 a and 2b, characteristic peaks at 3451 cm -1 and 2925 cm -1 are observed in CF, which belong to the stretching vibrations of O-H and C-H, respectively. In CP, CPA and CPAC, the broad peak at 3100 - 3700 cm -1 represents the stretching vibrations of O-H and N-H, the absorption peak at 1596 cm -1 corresponds to the C═C stretching vibration and C═O stretching vibration (quinone structure) of the aromatic ring, and the absorption peak at 1380 cm -1 corresponds to the C-N stretching vibration. The presence of these peaks indicates that polydopamine has been successfully compounded onto the surface of cellulose fibers.

[0072] The composition of the cellulose fibers (CF) and composite fibers (CP, CPA, CPAC9) prepared in Examples 1 to 3 and Example 7 was analyzed by XRD, and the results are as shown in Figure 2 c. As can be seen from Figure 2 c, the two characteristic diffraction peaks at 12.3° and 20.1° in the XRD image of CPAC9 correspond to the and (110) crystal planes of cellulose type II, and the characteristic diffraction peaks at 37.9°, 64.3° and 77.3° correspond to the (111), (220) and (311) of Ag (JCPDS No. 04 - 0783), respectively. The diffraction peaks at 43.3°, 0.4° and 74.0° correspond to the (111), (200) and (220) crystal planes of Cu (JCDS No. 04 - 0836). These results all indicate that Ag+ and Cu 2+ have been successfully reduced to metal nanoparticles and loaded on the polydopamine-coated / cellulose composite fiber.

[0073] XPS can be used to analyze the types and valence states of elements in a substance. The XPS (full scan spectra) of the cellulose fiber (CF) and the composite fiber (CPAC9) prepared in Example 1 and Example 7 are as Figure 2 shown in Figure 2 d. As can be seen from

[0074] shown in Figure 2 e, with the C1s (C-C / C-H) at 284.8 eV as the reference for calibrating the original XPS data and performing deconvolution fitting, the C1s spectrum of the cellulose fiber (CF) prepared in Example 1 shows three peaks, corresponding to C-C (284.8 eV), C-O (286.4 eV), and O-C-O (288.2 eV) respectively. Figure 2 f shows the C1s spectrum of the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7. As Figure 2 shown in f, the characteristic peak at 285.7 eV is the C-N bond of polydopamine. Figure 2 g shows the N1s spectrum of CPAC9. As can be seen from Figure 2 g, the three characteristic peaks correspond to -N=, -NH-, and -NH2 in polydopamine respectively. Imine bonds will be generated in the indole group during the self-polymerization of dopamine, indicating the polymerization of dopamine. The Ag3d spectrum of CPAC9 is as Figure 2 shown in Figure 2 h. As can be seen from 5 / 2 h, the characteristic peaks at 368.2 and 374.2 eV correspond to Ag3d 3 / 2 and Ag3d 0 , representing the characteristic peaks of Ag Figure 2 The Cu2p spectrum of CPAC9 is as Figure 2 shown in i. As can be seen from 3 / 2 i, the binding energies of 932.6 (Cu2P 1 / 2 ) and 952.4 eV (Cu2P 0 ) are in line with Cu 2+ , and the appearance of other peaks is related to the oxidation of Cu on the surface of Cu exposed to humid air.

[0075] (2) Morphology and EDS elemental analysis of electroless copper-plated cellulose composite fiber

[0076] To verify the formation of AgNPs during electroless copper plating, scanning electron microscopy analysis was performed on the surfaces of the cellulose fibers (CF) and composite fibers (CP, CPA, CPAC9) prepared in Examples 1 to 7. From Figure 3 a - d, it can be seen that after the self - polymerization of dopamine, a uniform and smooth - surfaced polydopamine coating is formed on the surface of the cellulose fibers, and the uniform coating also provides a large number of sites for the reduction of AgNPs. From Figure 3 e, it is known that the polydopamine - coated / cellulose composite fiber (CP) prepared in Example 2 reduces Ag through the phenolic hydroxyl groups on the surface of polydopamine after soaking in AgNO3 and firmly attaches AgNPs to the surface through chelation. +

[0077] From Figure 3 f, it can be seen that most of the reduced AgNPs have a particle size of less than 100 nm, and metal particles at the nanoscale often have some special functions, such as catalytic action. That is, during copper plating, CuSO4 also firmly adheres to the fiber surface through the catalysis of AgNPs. Due to the relatively high concentration of the plating solution, CuNPs aggregate on the fiber surface ( Figure 3 d).

[0078] Figure 3 g - i are the EDS elemental analyses of the polydopamine - reduced silver nanoparticles / cellulose composite fiber (CPA) prepared in Example 3. It can be seen from the figure that CPA contains C, O, and Ag elements.

[0079] SEM detection was performed on the cross - sections of the cellulose fibers (CF) and composite fibers (CP, CPA, CPAC3, CPAC5, CPAC7, CPAC9) prepared in Examples 1 to 7, and the detection results are as Figure 4 shown. From Figure 4 it can be seen that the surface of the cellulose fiber (CF) prepared in Example 1 is relatively smooth and has no obvious edge structure ( Figure 4 a1 and Figure 4 a2). After the composite of polydopamine and Ag, it can be found that obvious layered structures appear on the fiber surface, and polydopamine can firmly adhere to the surface of the cellulose fiber ( Figure 4 b1, Figure 4 b2, Figure 4 c1, Figure 4 c2). After plating in the composite fiber electroless plating solution, it can be found that its surface becomes significantly rough, that is, metal nanoparticles aggregate on the fiber surface to form micro - and nano - structures of different sizes, and with the increase of the plating time, the thickness of the metal copper layer on the fiber surface also gradually increases ( Figure 4 d1 - Figure 4 g2).

[0080] Figure 5 ​It is the cross-sectional EDS elemental analysis diagram of the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7. From Figure 5 it can be seen that the Cu element is mainly distributed on the surface of the fiber to form a dense copper layer.

[0081] The element contents in the electroless copper-plated cellulose composite fibers (CPAC3, CPAC5, CPAC7, CPAC9) prepared in Examples 4 to 7 were detected, and the detection results are shown in Table 1. It can be seen from Table 1 that the content of the Ag element is relatively low, indicating that a low content of AgNPs can efficiently catalyze a large amount of Cu 2+ to be reduced, that is, the AgNPs reduced by polydopamine have high catalytic activity in catalyzing electroless copper plating.

[0082] Table 1 Element contents of electroless copper-plated cellulose composite fibers with different plating times

[0083]

[0084] (3) Conductivity measurement and stability analysis

[0085] Figure 6 It is the conductivity and stability analysis of the electroless copper-plated cellulose composite fibers (CPAC3, CPAC5, CPAC7, CPAC9) prepared in Examples 4 to 7. From Figure 6 a, it can be obtained that the conductivity of CPAC3 reached 2.3×10 4 S / m at the plating time of 3 min; as the plating time increases, the conductivity of the electroless copper-plated cellulose composite fiber increases sharply and then tends to be flat. This is because when the plating time is short, there are still some defects on the fiber surface, and increasing the plating time can make the conductive layer more perfect; when the defects are filled, the only factor affecting the conductivity is the thickness of the copper layer. At the plating time of 9 min, the conductivity of CPAC9 can reach 4.5×10 5 S / m, and the conductivity will increase slowly and finally approach the conductivity of the copper wire. At the same time, as the plating time increases, the density of the fiber is also gradually increasing, and the specific conductivity is also gradually increasing ( Figure 6 b). In order to determine the feasibility of the electroless copper-plated cellulose composite fiber as a wearable electronic fabric, the conductivity stability was simulated by using the deionized water stirring method. From Figure 6 c, it can be seen that the resistance of the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7 is relatively stable after 30 times of simulated washing, and it has the feasibility as an electronic textile and a conductive material. Figure 6 d shows the conductivity and the thickness of the conductive layer of various conductive fibers. It can be found that compared with these materials, the electroless copper-plated cellulose composite fiber has a higher conductivity and a smaller thickness of the conductive layer.

[0086] (4) Mechanical property analysis

[0087] Figure 7 are the test results of the mechanical properties of the cellulose fibers (CF) and composite fibers (CP, CPA, CPAC3, CPAC5, CPAC7, CPAC9) prepared in Examples 1 - 7. As can be seen from Figure 7 a - c, the cellulose fiber (CF) prepared in Example 1 has relatively high mechanical strength (246.6 MPa) and elongation at break (16.6%). After CPAC3 is treated with polydopamine, Ag, and a short - time copper bath, the tensile strength and elongation at break of the composite fiber do not change much. This is because a small amount of the coating simply adheres to the surface of the cellulose fiber and does not affect the fiber's own structure. As can be seen from Figure 7 d - f, the mechanical properties of the electroless copper - plated cellulose composite fiber change significantly after being plated in the plating solution for different times. There are two reasons: one is that soaking in the strongly alkaline plating solution for a long time will damage the structure of cellulose, resulting in a decrease in strength; the other is that after a long - time plating, a thick conductive copper layer will form on the fiber surface, and the compatibility between the metal and the polymer is poor, which will also damage the fiber's properties.

[0088] (5) Thermal analysis

[0089] The thermogravimetric analyzer is used to evaluate the thermal stability of the cellulose fibers (CF) and composite fibers (CP, CPA, CPAC9) prepared in Examples 1 - 3 and Example 7. The TG and DTG curves of the fiber specimens are as shown in Figure 8 As shown. As can be seen from Figure 8 a, in the temperature range from room temperature to 150 °C, the mass of several fibers decreases slightly due to the evaporation of moisture. As the temperature rises (244 °C), the crystal structure and chain structure of cellulose will be damaged, including the fracture of C - C and C - O and the decomposition of other groups. At this stage, the mass of the fiber changes significantly. In contrast, due to the protection of the coating, the decomposition temperature of the fiber increases, and the decomposition temperature of CPAC9 increases to 275 °C. As can be seen from Figure 8 b, due to the addition of copper, the residual mass of CPAC9 increases significantly. In summary, the composite of polydopamine and metal will improve the thermal stability of the fiber, which can meet the actual use scenarios of the composite fiber.

[0090] (6) Electro - thermal property analysis

[0091] To verify the feasibility of the electroless copper - plated cellulose fiber in wearable electronic devices and further evaluate the electro - heating performance of the composite fiber, the electroless copper - plated cellulose composite fiber (CPAC9) prepared in Example 7 is woven into a simple fabric, and an external battery pack is used to record the surface temperature of the fabric with an infrared camera. Figure 9a-c and d are respectively the electrothermal temperature curves of the electroless copper-plated cellulose composite fibers (CPAC9) prepared in Example 7 and the infrared thermal imaging photos during the heating process. As Figure 9 shown in a and d, at a voltage of 1.5 V, the temperature of the CPAC9 fabric reached 60.6 °C at 25 s. After increasing the voltage to 3 V, the temperature stabilized at 121 °C in a short time (7 s), indicating that the CPAC9 fabric has excellent electrothermal performance. To evaluate the stability of the electrothermal performance of CPAC9, the composite fabric was subjected to electrothermal cycling before washing ( Figure 9 b) and after washing ( Figure 9 c). The results showed that the electroheating ability of the CPAC9 fabric had good repeatability after washing. Therefore, this fabric is expected to be applied to the active heating device of wearable fabrics.

[0092] (7) Photothermal performance analysis

[0093] The cellulose fibers (CF) and composite fibers (CP, CPA, CPAC9) prepared in Examples 1-3 and Example 7 were woven into fabrics, and the temperature changes on the fabric surface under the irradiation of a 0.5 W near-infrared light source were recorded by an infrared camera. Figure 10 a is the schematic diagram of the photothermal conversion of CPAC9. The metal nanostructure has a local surface plasmon resonance (LSPR) effect, making it have excellent photothermal conversion ability. After the near-infrared light is absorbed, the electrons in the metal material transition from the valence band to the conduction band. At the same time, the ultra-low resistance in the metal can strengthen the rapid movement of free electrons, thereby increasing the heat conduction path. As Figure 10 shown in b, the temperature of CF increased slightly under the irradiation of near-infrared light, indicating that cellulose has less absorption of near-infrared light. After being coated with polydopamine, the surface temperature of the fabric increased significantly. The reason is that polydopamine has a high near-infrared light absorption ability in the near-infrared region. After absorbing photons, the electrons in polydopamine transition from the ground state to the excited state, and then the energy is converted into heat energy through the vibration of molecules, showing a high photothermal conversion ability. After the reduction of AgNPs, the photothermal performance of the composite fabric was further improved, and the temperature could reach 117.8 °C at 17 s under the irradiation of near-infrared light. The random and wide size distribution of AgNPs can generate a series of plasmon resonances at different optical wavelengths, and the plasmon near-field coupling effect can be excited from the gaps (less than 10 nm) between adjacent metal nanoparticles, thus showing an ultra-high absorption efficiency for near-infrared light. After the fabric was copper-plated, its photothermal performance was greatly improved again, and the temperature could rise to 137.1 °C within 8 s under the irradiation of near-infrared light, showing excellent photothermal performance. The main reason is the local surface plasmon resonance effect of copper nanoparticles and the synergistic effect of polydopamine and AgNPs.

[0094] To evaluate the photothermal properties of electroless copper-plated cellulose composite fiber fabrics before and after washing, deionized water stirring was used to simulate washing. As Figure 10 As shown in c and d, the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7 had good repeatability and thermal stability before washing. After washing, the heating-up time of CPAC9 did not change much and still had good repeatability, indicating that the electroless copper-plated cellulose composite fiber had very excellent photothermal stability.

[0095] Application and performance comparison of electroless copper-plated cellulose composite fiber

[0096] Figure 11 a - c show the electroless copper-plated cellulose composite fiber (CPAC9) prepared in Example 7 being used as an ECG electrode to monitor the changes in human heart potential. After using the fabric electrode, it can be monitored that the heart rate of the human body is about 87 beats per minute at rest. After simple exercise, the heart rate of the human body increases to about 125 beats per minute, and the typical P wave, QRS complex, and T wave of the electrocardiogram can be clearly identified in the figure.

[0097] As Figure 11 shown in d, the CPAC9 fabric showed excellent heating performance compared with other electrothermal fabrics at a lower voltage (3V), and a very high stable heating temperature (121 °C) was obtained within a short stable heating time (7 s). Figure 11 e shows the comparison of the near-infrared photothermal properties of the CPAC9 fabric and other fiber fabrics. As Figure 11 shown in e, the temperature of the CPAC9 fabric can rise to 137.1 °C within 8 s under near-infrared light irradiation. Compared with other composite fabrics, the CPAC fabric has more excellent near-infrared heating performance.

[0098] The above embodiments are specific implementation manners of the present invention, but the implementation manners of the present invention are not limited by the above embodiments. Any combination, change, modification, substitution, and simplification that does not exceed the design idea of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing electroless copper-plated cellulose composite fibers, characterized in that, It includes the following steps: (1) Mix absolute ethanol, ammonia water, and water in a certain proportion to obtain a mixed solution; add cellulose fibers to the mixed solution, stir and mix evenly, then add a hydrochloric acid dopamine solution to the mixed solution, heat and stir for reaction. After the reaction ends, take out the cellulose fibers, and the cellulose fibers are washed and dried to obtain polydopamine-coated / cellulose composite fibers; (2) Add the polydopamine-coated / cellulose composite fibers prepared in step (1) and a silver nitrate solution to an alkaline solution, heat and stir for reaction. After the reaction ends, take out the polydopamine-coated / cellulose composite fibers, and the polydopamine-coated / cellulose composite fibers are washed and dried to obtain polydopamine-reduced silver nanoparticles / cellulose composite fibers; (3) Add the polydopamine-reduced silver nanoparticles / cellulose composite fibers obtained in step (2) to a electroless plating solution containing copper ions for electroless plating treatment to obtain electroless copper-plated cellulose composite fibers.

2. The preparation method of the electroless copper-plated cellulose composite fiber according to claim 1, characterized in that, In step (3), the electroless plating solution is prepared by mixing copper sulfate anhydrous, ethylenediaminetetraacetic acid, sodium potassium tartrate, ethanol, formaldehyde, and water; in the electroless plating solution, the mass concentration of copper sulfate anhydrous is 0.01 - 0.05 g / ml, the mass concentration of ethylenediaminetetraacetic acid is 0.01 - 0.05 g / ml, the mass concentration of sodium potassium tartrate is 0.01 - 0.02 g / ml, the volume fraction of ethanol is 0.5% - 1%, and the volume fraction of formaldehyde is 0.5% - 1%.

3. The preparation method of the electroless copper-plated cellulose composite fiber according to claim 2, wherein, The mass ratio of the electroless plating solution to the polydopamine-reduced silver nanoparticles / cellulose composite fibers is 50 - 100∶1, and the pH of the electroless plating solution is 11 - 13.

4. The preparation method of the electroless copper-plated cellulose composite fiber according to claim 1, wherein, In step (1), the mass concentration of the hydrochloric acid dopamine solution is 0.01 - 0.1 g / ml; the volume ratio of water, absolute ethanol, and ammonia water in the mixed solution is 8 - 10:4:0.2; the mass ratio of the hydrochloric acid dopamine solution, the mixed solution, and the cellulose fibers is 50 - 100∶50 - 100∶1.

5. The preparation method of the electroless copper-plated cellulose composite fiber according to claim 1, wherein In step (2), the mass concentration of the silver nitrate solution is 0.001 - 0.005 g / ml; the mass ratio of the silver nitrate solution to the polydopamine-coated / cellulose composite fibers is 10 - 20∶1.

6. The preparation method of the electroless copper-plated cellulose composite fiber according to claim 1, wherein, In step (1), the heating temperature is 20 - 40 °C, and the stirring reaction time is 12 - 24 h; in step (2), the heating temperature is 20 - 40 °C, and the stirring time is 0.5 - 2 h.

7. The preparation method of the electroless copper-plated cellulose composite fiber according to any one of claims 1 to 6, characterized in that, In step (3), the electroless plating treatment time is 3 - 9 min.

8. An electroless copper-plated cellulose composite fiber prepared by using the method according to any one of claims 1 - 7.

9. The application of the electroless copper-plated cellulose composite fiber according to claim 8 in a sensor.

10. The application of the electroless copper-plated cellulose composite fiber according to claim 8 in wearable electronic textiles.

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