Ag-Au cellulose composite photothermal film and preparation method thereof

Abstract

This invention proposes an Ag-Au cellulose composite photothermal film and its preparation method. The Ag-Au cellulose composite photothermal film is formed by growing Au metal on the surface of a Ag / fiber membrane as a substrate. The Ag / fiber membrane is deposited with nano-Ag through metal reduction. The resulting Ag-Au / cellulose composite photothermal film exhibits high solar evaporation efficiency and water evaporation rate, and exhibits high stability in a variety of water samples, including acidic water, alkaline water, dye-containing water, and seawater.

Description

Technical Field

[0001] The present invention relates to the field of photothermal films, and in particular to an Ag-Au cellulose composite photothermal film and a preparation method thereof. Background Art

[0002] Solar energy is the cleanest, most abundant, and renewable natural resource. Solar thermal-driven water distillation, powered by abundant renewable solar energy, is one of the most promising solutions for sustainable clean water production, enabling energy-efficient and CO2-free freshwater production. Efficiently harnessing solar energy to produce clean water has become a new research hotspot. Conventional solar water evaporators, with evaporation efficiencies of only 30-45%, are clearly far from meeting practical needs. In recent years, solar-driven interfacial water evaporation has emerged to reduce surface heat loss and minimize heat dissipation into the bulk water. Interfacial evaporation selectively heats the evaporating portion of the water, concentrating heat at the surface and limiting heat loss from the bulk water, thereby improving system thermal efficiency. This solar-driven interfacial evaporation avoids volumetric heating, minimizes the amount of photothermal materials used, and provides additional means to dynamically adjust evaporation performance, including vapor flux and vapor temperature. Photothermal materials that efficiently absorb solar radiation and convert it into heat are key to efficient air-water interfacial evaporation. The rational design of nanoscale photothermal materials remains a hot research topic in interfacial evaporation. However, the bactericidal properties of air-water interface evaporation systems in desalination and sewage purification are often overlooked, which may lead to potential water safety hazards. Therefore, the development of new nanomaterials with excellent photothermal performance, low energy consumption, environmental protection and antibacterial properties is a top priority.

[0003] In the design of efficient interfacial solar steam generators, photothermal films are crucial, and the choice of substrate for supporting the photothermal material is particularly important. Traditional synthetic polymer and metal substrates are not only expensive but also non-biodegradable, making them difficult to commercialize and apply, and therefore impractical.

[0004] Various types of cellulose are widely used in evaporator design, including bacterial nanocellulose, wood cellulose, wood, and cellulose paper. Cellulose paper, due to its excellent hydrophilicity, high mechanical strength, flexibility, and low cost, is widely used as a photothermal carrier. Wang et al. loaded Au nanoparticles onto cellulose paper via vacuum filtration to create a highly flexible and reusable plasma membrane. This membrane achieved interfacial heating to promote water vapor generation, achieving an energy efficiency of 85% under 10-sun illumination (Wang et al., 2017). For example, Wang et al. reported a 3D origami solar steam generator device with graphene oxide and carbon nanotubes as photothermal elements, achieving nearly 100% energy efficiency under 1-sun illumination (Hong, 2018). Chen et al. reported a cellulose paper-based solar evaporator that achieves both efficient water evaporation and salt tolerance. However, in the design of these metallocellulose-based evaporators, high photothermal conversion performance and antibacterial properties cannot be achieved simultaneously, and their performance needs to be improved. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an Ag-Au cellulose composite photothermal film and a preparation method thereof to solve the above problems.

[0006] The technical solution of the present invention is achieved as follows:

[0007] On the one hand, the present invention provides an Ag-Au cellulose composite photothermal film, which is obtained by using Ag / fiber membrane as a substrate and Au metal growing on the surface of the Ag / fiber membrane; the Ag / fiber membrane is obtained by depositing nano-Ag on the fiber membrane through metal reduction.

[0008] Preferably, the Ag / fiber membrane is formed by 2+ First bind to the fiber membrane, and then bind Sn 2+ The fiber membrane was transferred to Ag + In solution, Ag + Reduction is performed to deposit nanosilver on the fiber membrane; the Sn 2+ When first binding to the fiber membrane, it also includes adding hydrochloric acid solution;

[0009] The Ag-Au cellulose composite photothermal film is obtained by using Ag / fiber film as a substrate and immersing it in an Au growth solution. The Au growth solution includes chloroauric acid, sodium chloride, tartaric acid, sodium hydroxide and ethanol.

[0010] In one aspect, a Ag-Au cellulose composite photothermal film is provided, wherein the XPS spectrum of Ag 3d of the Ag-Au cellulose composite photothermal film has two characteristic peaks at binding energies of 367-368 eV and 373-374 eV, the XPS spectrum of Au 4f thereof has two peaks at 83-84 eV and 87-88 eV, the XPS spectrum of O1s thereof has two peaks at 531-532 eV and 534-535 eV, and the XPS spectrum of C1s thereof has three peaks at 284-285 eV, 286-287 eV, and 287.5-288 eV;

[0011] The XRD spectrum of the Ag-Au cellulose composite photothermal film has characteristic peaks at 2θ of 15.0°, 16.0-16.5°, 22.5-23.0°, 34-34.5° and 38-38.6°.

[0012] On the other hand, the present invention provides a method for preparing the above-mentioned Ag-Au / cellulose composite photothermal film, comprising the following preparation steps:

[0013] Preparation of S1 Ag / cellulose membrane: Place the cellulose membrane in a mixed solution of stannous chloride and hydrochloric acid, stir, and then let it stand to soak. Wash it with deionized water and ethanol respectively. Then transfer it to a silver nitrate solution, stir the cellulose membrane until the color of the cellulose membrane changes, and wash it with ethanol and deionized water respectively to obtain an Ag / cellulose membrane.

[0014] S2 Preparation of Ag-Au cellulose membrane: The Ag / cellulose membrane prepared in step S1 is transferred to an Au growth solution and immersed to obtain an Ag-Au cellulose membrane; the Au growth solution comprises chloroauric acid, sodium chloride, tartaric acid, sodium hydroxide and ethanol.

[0015] Preferably, the concentration ratio of stannous chloride to hydrochloric acid is 1:1-2; the stirring is continued for 10-20 minutes and then allowed to stand and soak for 40-50 minutes; and the concentration of silver nitrate is 8-12 mM.

[0016] Stannous ions in aqueous solution can be adsorbed onto the surface of cellulose membranes through electrostatic interactions and reduce silver ions, which is the principle behind the preparation of Ag / cellulose membranes. However, since stannous ions undergo reversible hydrolysis in aqueous solution, forming hydroxides, which is not conducive to the reduction reaction, hydrochloric acid is added to inhibit the hydrolysis of the stannous ions. The amount of stannous chloride corresponds to the amount of hydrochloric acid. At this ratio, the hydrochloric acid is just enough to inhibit the hydrolysis of the stannous ions. The amount of hydrochloric acid used should be greater than or equal to the amount of stannous ions to avoid incomplete inhibition of the hydrolysis reaction of the stannous ions, which in turn affects the adsorption of the stannous ions and the growth of Ag and Au metals.

[0017] Preferably, the Au growth solution comprises: adding 0.2-0.3 g of chloroauric acid, 0.1-0.2 g of sodium chloride, 0.05-0.15 g of tartaric acid, 1.2-1.5 g of sodium hydroxide and 0.4-0.6 mL of ethanol to every 45-55 mL of deionized water.

[0018] Preferably, in step S1, the stirring time of the cellulose membrane is 1 to 3 minutes; and in step S2, the soaking time is 2 to 20 minutes.

[0019] Preferably, in step S1, the stirring time of the cellulose membrane is 2 minutes; and in step S2, the soaking time is 10 minutes.

[0020] On the other hand, the present invention also provides an application of the Ag-Au cellulose composite photothermal film in at least one of wastewater purification, seawater desalination or water disinfection.

[0021] Preferably, the application in wastewater purification is the decolorization of wastewater contaminated by organic dyes; the application in seawater desalination is to reduce the Ca 2+ , K + Mg 2+ 、Na + or B 3+ Application of ion concentration; the application in water disinfection is the application of inhibiting Escherichia coli and Staphylococcus aureus.

[0022] This invention, for the first time, uses cellulose membrane as a substrate and successfully constructs an Ag-Au / cellulose composite photothermal film with Au and Ag nanoparticles by utilizing in-situ reduction of metal ions and immersion growth in a metal growth solution. Furthermore, the invention designs an "air-water interface" interfacial evaporator. This evaporator utilizes the Ag-Au / cellulose composite membrane as the photothermal conversion layer, a 3D-printed polylactic acid framework as the support layer, and the cellulose membrane as the water transport channel. The rough surface and porous structure of the cellulose paper improve the absorption of incident light through multiple scattering and an extended optical path. Furthermore, the localized surface plasmon resonance coupling between adjacent Au and Ag nanoparticles of varying sizes significantly increases the density of optical modes, thereby broadening the absorption wavelength and enhancing the absorption intensity. This results in a wider extended absorption compared to Ag / cellulose membranes, further enhancing the composite's absorption performance across the entire spectral range. Notably, the facile synthesis method, the ability to react in aqueous solution at room temperature, and the cellulose substrate amenable to large-scale production suggest great potential for industrial applications.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention designs a simple preparation method for Ag-Au / cellulose membrane, which realizes the simple and controllable synthesis of Ag-Au / cellulose membrane through impregnation with reduced metal ions and seed-mediated growth method, and is used for simultaneous high-efficiency water evaporation and water disinfection.

[0025] (2) The present invention prepares Ag / cellulose membrane by metal in situ growth method and uses it as a seed substrate, then prepares Ag-Au / cellulose membrane by seed-mediated growth method and optimizes the light absorption performance of Ag-Au / cellulose membrane by controlling the growth time of Au. In analyzing the mechanism of its photothermal behavior, a possible photothermal mechanism is proposed based on the absorbance and other characterization data of the hybrid membrane. That is, due to the synergistic effect of plasmonic Au nanoparticles with high photothermal conversion performance and Ag nanoparticles in light response, the localized surface plasmon resonance coupling between adjacent particles of Au and Ag of different sizes increases the density of the light mode, thereby broadening the absorption wavelength, so that the Ag-Au / cellulose membrane has an energy utilization efficiency of 81.3% and a relative absorption capacity of 1.58 kg m-2 under the entire solar spectrum. -2 h -1 water evaporation rate.

[0026] (3) The Ag-Au / cellulose membrane prepared in the present invention also maintains excellent purification ability and high evaporation efficiency when using a variety of water samples such as acidic water, alkaline water, dye water and seawater, showing highly competitive and attractive application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart for the preparation of the Ag-Au / cellulose membrane of the present invention.

[0028] Figure 2 These are the SEM images and EDS images of the cellulose membrane material used in the present invention, wherein ae is the SEM image of the original cellulose membrane, and f is the EDS analysis image of the original cellulose membrane.

[0029] Figure 3 The following are Fourier transform infrared spectra (FTIR) of the cellulose membrane material and microcrystalline cellulose used in the present invention.

[0030] Figure 4 1 is an SEM image of the Ag / cellulose membrane prepared in Example 1 of the present invention, and an element mapping diagram corresponding to the SEM image, wherein a and b are SEM images of the Ag / cellulose membrane, and cf are corresponding element mapping diagrams.

[0031] Figure 5 TEM images of nanofibers in the Ag / cellulose membrane and lattice images of Ag nanoparticles prepared in Example 1 of the present invention, wherein a is the TEM image of nanofibers in the Ag / cellulose membrane, and b is the lattice image of Ag nanoparticles.

[0032] Figure 6 This is the SEM image of the Ag-Au / cellulose membrane prepared in Example 1 of the present invention.

[0033] Figure 7 1 is an SEM image of the Ag / cellulose membrane prepared in Example 1 of the present invention, and an element mapping image corresponding to the SEM image, wherein a is the SEM image of the Ag / cellulose membrane, and bf are the corresponding element mapping images.

[0034] Figure 8 This is a structural information diagram of the Ag-Au / cellulose membrane prepared in Example 1 of the present invention, wherein a is the XPS measurement spectrum, be is the XPS spectra of Ag 3d, Au 4f, C1s and O1s, and f is the X-ray diffraction (XRD) spectrum of cellulose membrane, Ag / cellulose membrane, and Ag-Au / cellulose membrane.

[0035] Figure 9 a is Au in Comparative Example 1 of the present invention 2min / fiber membrane, Ag in Comparative Example 2 2min / cellulose film and Ag with different Au growth times 2min -UV-vis-NIR absorbance of Au / cellulose membrane, b and c are Au 2min / Fiber membrane, Ag 2min / cellulose film and Ag with different Au growth times 2min -Optical reflection and transmission images of Au / cellulose films.

[0036] Figure 10 a is the infrared thermal imaging photograph of the Ag-Au / cellulose membrane surface in dry and wet states according to Example 1 of the present invention; b is the temperature change of the bulk water and the photothermal membrane during water evaporation; c is the temperature change of the test sample; d is a schematic diagram of the synergistic effect between Ag nanoparticles and Au nanoparticles; e is a schematic diagram of blank water, Ag nanoparticles, and Au nanoparticles. 2min -Au 5min / cellulose membrane and Ag 2min -Au 10min / Comparison of water mass changes during evaporation of cellulose membrane, f is the actual picture of water evaporation device, g is Ag 2min -Au 10min / cellulose membrane (sample 1 is Example 1) and Ag 2min -Au 5min / cellulose film (sample 2 is Example 2) solar water evaporation rate and energy utilization efficiency, h is Ag 2min -Au 10min / Long-term stability test of cellulose membrane.

[0037] Figure 11 The application effect diagram of the Ag-Au / cellulose membrane prepared in Example 1 of the present invention, wherein a and b are the purification effects of the photothermal membrane on dye water (MB and RhB solutions), c is the comparison of the changes in the concentrations of the five main ions before and after seawater desalination, and d is the Ag 2min -Au 10min / Evaporation rate of cellulose membrane under different water environment conditions, e is the comparison of pH values ​​before and after acid and alkaline water purification.

[0038] Figure 12 The antibacterial performance diagram of the Ag-Au / cellulose membrane prepared in the present invention, wherein a is a photo of the inhibition zone test of Staphylococcus aureus culture medium, b is a photo of the inhibition zone test of Escherichia coli culture medium, and sample 1 is the Ag in Example 1. 2min -Au 10min / cellulose film, sample 2 is the Ag of Example 2 2min -Au 5min / cellulose film, sample 3 is the Ag of Example 3 2min -Au 16min / cellulose film. DETAILED DESCRIPTION

[0039] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0040] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0041] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0042] Example 1 - Preparation method of Ag-Au cellulose composite photothermal film

[0043] A method for preparing an Ag-Au cellulose composite photothermal film is as follows:

[0044] (1) Preparation of Ag / cellulose membrane: The cellulose membrane was placed in a stannous chloride aqueous solution (0.044 mol / L SnCl2; 0.04 mol / L concentrated hydrochloric acid) and stirred for 15 min, then allowed to stand and soak for 45 min to remove Sn. 2+ The Sn adsorbed on the cellulose fibers was removed by washing with deionized water and ethanol for 30 seconds. 2+ions, and then transferred to a 10mM AgNO3 solution. In order to uniformly reduce the silver ions, the cellulose paper was stirred for 2 minutes. The color of the cellulose membrane changed, and the silver nanoparticles were successfully deposited on the surface of the cellulose paper. The Ag / cellulose membrane was then washed with ethanol and deionized water to remove excess silver ions on the membrane surface. 2min / cellulose film.

[0045] (2) Preparation of Ag-Au / cellulose membrane: First, prepare the Au growth solution. Deionized water (50.0 mL), chloroauric acid (0.25 g), sodium chloride (0.15 g), tartaric acid (0.10 g), sodium hydroxide (1.30 g) and ethanol (0.5 mL) form the Au growth solution; transfer the Ag / cellulose membrane prepared in step (1) to the Au growth solution and soak for 10 min to obtain Ag. 2min -Au 10min / cellulose film.

[0046] The preparation flow chart of Ag-Au / cellulose membrane is as follows Figure 1 shown.

[0047] Example 2 - Preparation method of Ag-Au cellulose composite photothermal film

[0048] The difference between the preparation method of the Ag-Au / cellulose composite photothermal film of this embodiment and that of Example 1 is that in step (2), the immersion time is 5 minutes, and the steps are as follows:

[0049] (1) Preparation of Ag / cellulose membrane: The cellulose membrane was placed in a stannous chloride aqueous solution (0.044 mol / L SnCl2; 0.04 mol / L concentrated hydrochloric acid) and stirred for 15 min. The membrane was then allowed to stand and soak for 45 min. The membrane was washed with deionized water and ethanol for 30 s in sequence. The membrane was then transferred to a 10 mM AgNO3 solution. The cellulose paper was stirred for 2 min. The Ag / cellulose membrane was then washed with ethanol and deionized water to obtain Ag. 2min / cellulose film.

[0050] (2) Preparation of Ag-Au / cellulose membrane: First, prepare the Au growth solution. Deionized water (50.0 mL), chloroauric acid (0.25 g), sodium chloride (0.15 g), tartaric acid (0.10 g), sodium hydroxide (1.30 g) and ethanol (0.5 mL) form the Au growth solution; transfer the Ag / cellulose membrane prepared in step (1) to the Au growth solution and soak for 5 min to obtain Ag. 2min -Au 5min / cellulose film.

[0051] Example 3 - Preparation method of Ag-Au cellulose composite photothermal film

[0052] The difference between the preparation method of the Ag-Au / cellulose composite photothermal film of this embodiment and that of Example 1 is that in step (2), the immersion time is 16 minutes, and the steps are as follows:

[0053] (1) Preparation of Ag / cellulose membrane: The cellulose membrane was placed in a stannous chloride aqueous solution (0.044 mol / L SnCl2; 0.04 mol / L concentrated hydrochloric acid) and stirred for 15 min. The membrane was then allowed to stand and soak for 45 min. The membrane was washed with deionized water and ethanol for 30 s in sequence. The membrane was then transferred to a 10 mM AgNO3 solution. The cellulose paper was stirred for 2 min. The Ag / cellulose membrane was then washed with ethanol and deionized water to obtain Ag. 2min / cellulose film.

[0054] (2) Preparation of Ag-Au / cellulose membrane: First, prepare the Au growth solution. Deionized water (50.0 mL), chloroauric acid (0.25 g), sodium chloride (0.15 g), tartaric acid (0.10 g), sodium hydroxide (1.30 g) and ethanol (0.5 mL) form the Au growth solution; transfer the Ag / cellulose membrane prepared in step (1) to the Au growth solution and soak for 16 min to obtain Ag. 2min -Au 16min / cellulose film.

[0055] Comparative Example 1-Au 2min Preparation of cellulose membrane

[0056] Au 2min Preparation of Sn / cellulose membranes 2+ The ion treatment process of the cellulose membrane is the same as that of the Ag / cellulose membrane in Example 1. 2+ The cellulose membrane with ions was transferred to 0.1wt% chloroauric acid solution and stirred for 2min to obtain Au 2min / cellulose film.

[0057] Comparative Example 2-Ag 2min Preparation of cellulose membrane

[0058] Ag 2min Preparation of Ag / cellulose membrane: Preparation of Ag / cellulose membrane: The cellulose membrane was placed in a stannous chloride aqueous solution (0.044 mol / L SnCl2; 0.04 mol / L concentrated hydrochloric acid) and stirred for 15 min, then allowed to soak for 45 min, washed with deionized water and ethanol for 30 s in sequence, and then transferred to a 10 mM AgNO3 solution. The cellulose paper was stirred for 2 min, and then the Ag / cellulose membrane was washed with ethanol and deionized water to obtain Ag. 2min / cellulose film.

[0059] Comparative Example 3

[0060] (1) Preparation of Ag / cellulose membrane: The cellulose membrane was placed in a stannous chloride aqueous solution (0.046 mol / L SnCl2; 0.04 mol / L concentrated hydrochloric acid) and stirred for 15 min. The membrane was then allowed to stand and soak for 45 min. The membrane was washed with deionized water and ethanol for 30 s in sequence. The membrane was then transferred to a 10 mM AgNO3 solution. The cellulose paper was stirred for 2 min. The Ag / cellulose membrane was then washed with ethanol and deionized water to obtain Ag. 2min / cellulose film.

[0061] (2) Preparation of Ag-Au / cellulose membrane: First, prepare the Au growth solution. Deionized water (50.0 mL), chloroauric acid (0.55 g), sodium chloride (0.55 g), tartaric acid (0.30 g), sodium hydroxide (1.30 g) and ethanol (0.5 mL) form the Au growth solution; transfer the Ag / cellulose membrane prepared in step (1) to the Au growth solution and soak for 10 min to obtain Ag. 2min -Au 10min / cellulose film.

[0062] The test showed that the amount of silver nanoparticles attached to the cellulose membrane was reduced.

[0063] Example 4 - Composition of Ag-Au / cellulose composite photothermal film

[0064] The present invention uses lens cleaning paper as a source of cellulose substrate, which is composed of disordered cellulose microfibrils. Figure 2 Figures ae and c show SEM images of the original cellulose membrane, showing that each microfiber is approximately 40 μm wide and several hundred microns long, stacked on top of each other. Large gaps (≈3 μm) exist between the microfibers, and numerous nanogaps (≈10 nm) exist between the crystalline nanofibers. These gaps not only provide nanoscale enclosed spaces for particle growth but also provide channels for water transport. Furthermore, the hierarchical structure of the microfiber surface promotes the diffusion of ions within the cellulose microfibers, facilitating the rapid growth of dense metal nanoparticles. Figure 2 f shows the energy dispersive X-ray spectroscopy (EDS) analysis of the original fiber membrane. It can be seen that only C and O elements were detected in the original membrane.

[0065] The original cellulose and microcrystalline cellulose were analyzed by Fourier transform infrared spectroscopy (FTIR) ( Figure 3 ), the FTIR spectrum of the pristine cellulose membrane showed an absorption peak similar to that of microcrystalline cellulose, and the pristine cellulose membrane had almost no other vibration modes, indicating that the pristine cellulose membrane was composed of almost pure cellulose.

[0066] Example 5 - Structure of Ag-Au / cellulose composite photothermal film

[0067] The microstructure, crystal morphology and element valence state of the Ag-Au / cellulose composite photothermal film material prepared in Example 1 were characterized by SEM (Verios G4 UC), TEM (Talos F200X G2) and X-ray electron spectrometer (AxisSupra).

[0068] During the preparation of the Ag-Au / cellulose composite photothermal film, it can be seen that the original white cellulose paper has turned into dark brown ( Figure 5 a) The dark brown color presented optically is due to the plasmon resonance absorption of silver nanoparticles, a characteristic of silver nanoparticles, indicating that silver ions have been successfully reduced in situ to form elemental silver. To ensure uniform reduction of silver ions, the present invention controls the reduction time to 2 minutes. Figure 4 a, b show the SEM images of Ag / cellulose membranes. It can be seen that clear metal particles of different sizes grow on the membrane surface. The element mapping corresponding to the scanning electron microscopy (SEM) image 5c of the Ag- / cellulose membrane ( Figure 4 cf) show that Ag nanoparticles are distributed on the surface of cellulose membrane.

[0069] Figure 5 a shows a TEM image of the end of a cellulose fiber or its nanofibers, from which it can be seen that silver nanoparticles have been successfully and uniformly embedded in the cellulose nanofibers. In the high-resolution transmission electron microscopy (HRTEM) image ( Figure 5 In b), the lattice fringes of Ag nanoparticles can be clearly observed, and the lattice plane spacing is 0.23 nm, which is consistent with the (111) lattice of face-centered cubic Ag, proving that the Ag / cellulose substrate was successfully synthesized.

[0070] Based on the successful synthesis of the Ag / fiber membrane substrate, the Ag / fiber membrane was placed in an Au growth solution and stirred at an appropriate rate to allow Au metal particles to grow rapidly on the microfiber surface. During this process, the color of the Ag / cellulose membrane gradually changed from dark brown to black gray, preliminarily indicating the successful growth of Au element. For the Ag-Au / cellulose membrane, its SEM image ( Figure 6 ad) shows a rougher cellulose surface. It can be seen that compared with the fiber surface of the Ag / cellulose membrane, the fiber surface after the growth of Au has more particles distributed, which indicates that a large number of Au particles are deposited.

[0071] In order to confirm the distribution of nano-Ag and nano-Au on the surface of Ag-Au / cellulose membrane, element mapping was performed on its scanning image. Figure 7 a is the SEM image of a fiber surface, and its corresponding element mapping is as follows Figure 7As shown in bf, it can be seen that a large number of Au and Ag particles of different sizes are evenly distributed on the fiber surface.

[0072] Example 6 - Structural information of Ag-Au / cellulose composite photothermal film

[0073] XPS and XRD characterizations provide detailed structural information of the Ag-Au / cellulose composite photothermal film prepared in Example 1. First, X-ray photoelectron spectroscopy was used to further analyze the surface composition of the Ag-Au / cellulose film. Figure 8 a shows the full spectrum scan of the Ag-Au / cellulose membrane. The spectrum clearly and intuitively shows that the sample contains elements such as O, Ag, and Au. Further, a fine spectrum of the elements is obtained through narrow area scanning to analyze the valence state of the elements.

[0074] Figure 8 b is the XPS spectrum of Ag 3d in Ag-Au / cellulose film. Ag has two strong characteristic peaks with binding energies of 367.8 and 373.8 eV, respectively, and the difference between the two peaks is 6.0 eV, which can be attributed to Ag 0 Ag 3d 5 / 2 and Ag 3d 3 / 2 state, which agrees well with the silver metal value, indicating that Ag + The ions are effectively converted to their metallic state.

[0075] Figure 8 The Au 4f spectrum shown in c clearly shows the presence of Au in the Ag-Au / cellulose film. 0 Nanoparticles. The strong doublet at 83.8eV and 87.5eV corresponds to Au 0 Au 4f 7 / 2 and Au 4f 5 / 2 state.

[0076] The XPS spectrum of O1s is as follows Figure 8 As shown in Figure d, there is a binding energy peak at 531.5 eV related to the metal oxygen bond, which may be the peak at 532.8 eV. It is usually from the oxygen of the OH- group. There is also a small peak at 534.0 eV, which is related to the absorption of O2 and the OC=O bond.

[0077] At the same time, the XPS spectrum of the Ag / cellulose membrane showed a C1s peak, and the C1s spectrum of the sample was fitted ( Figure 8 e) revealed three peaks corresponding to carbon in different chemical environments. The main peak at 286.4 eV is attributed to C-OH and C-O bonds, characteristic of carbon-oxygen bonds in cellulose macromolecules. The peak at 284.7 eV is formed by C-C and C-H bonds, while the smaller peak at 287.9 ​​eV is due to the double bond C=O formed by the carbon atom and oxygen.

[0078] The XRD spectra of original cellulose film, Ag / cellulose film and Ag-Au / cellulose composite film are shown in Figure 2. Figure 8 As shown in Fig. 5(f), the typical peaks at 15.0°, 16.2°, 22.6° and 34.3° are attributed to the (101), (100), (002) and (040) crystal planes of cellulose, respectively (Liu Zhigang, 2014). A new peak appeared at 38.4° in the Ag-Au / cellulose film, which is attributed to the (111) crystal plane of Au.

[0079] These characterization results indicate that the synthesis route of the Ag-Au / cellulose nanohybrid material designed in the present invention is feasible and controllable.

[0080] Example 7 - Light absorption properties of Ag-Au / cellulose composite photothermal film

[0081] The light absorption properties of the samples were studied using a UV-visible-near-infrared spectrophotometer (UV-vis-NIR) (PerkinElmer Lambda 750s) with an integrating sphere to collect reflected light.

[0082] In photothermal materials, the quality of photothermal performance is closely related to the ability of the photothermal material to absorb sunlight. The light absorption performance of the photothermal film is divided into two stages. In the first stage, with the loading of Au nanoparticles, its light absorption capacity gradually increases until it reaches a peak. This can be attributed to the synergistic effect of the localized plasma resonance absorption of Au and Ag, which improves the light absorption of the photothermal film in the full spectrum band. In the second stage, after reaching the peak, the light absorption capacity gradually decreases. This can be attributed to the aggregation of nanoparticles on the surface of cellulose microfibers to form a continuous metal film, resulting in strong metal reflection, which in turn leads to a decrease in light absorption performance.

[0083] Figure 9 Describes Au 2min / Fiber membrane, Ag 2min / cellulose film and Ag with different Au growth times 2min -Optical properties of Au / cellulose films. Figure 9 a shows the UV-visible-near-infrared (UV-vis-NIR) absorbance of the above materials, Au 2min / Fiber membrane and Ag 2min The spectrum of the Ag / cellulose film exhibits broad bands at 550 nm and 480 nm, which are caused by the surface plasmon resonance absorption of gold and silver nanoparticles, respectively. 2minThe spectrum of the Au / cellulose composite film shows a broader extended absorption peak at 540-800 nm, which may be due to the localized surface plasmon resonance coupling between adjacent particles of Au and Ag with different sizes, which greatly increases the density of the optical mode. It can be seen that with the extension of the Au growth time, the Ag 2min The absorbance of the -Au / cellulose membrane showed a trend of first increasing and then decreasing.

[0084] The corresponding Figure 9 The optical reflectivity shown in b also has the same trend. It can be seen that the three groups of Ag 2min -The reflectivity of Au / cellulose film is significantly lower than that of Au 2min / Fiber membrane and Ag 2min / cellulose membrane, and Ag 2min -Au 10min / cellulose film has the lowest reflectivity. 2min -Au 5min / cellulose membrane and Ag 2min -Au 10min / The reflectivity of the cellulose film can correspond to the previous stage. In the previous stage, the Au particles are growing rapidly. With the increase of Au content, its light absorption capacity is gradually enhanced, and the diffuse reflectivity of light is gradually reduced. 2min -Au 16min The increase in the reflectivity of the cellulose film corresponds to the latter stage because the nanoparticles aggregate on the surface of the cellulose microfibers to form a continuous metal film, resulting in strong metallic reflection.

[0085] It is worth noting that Figure 9 Ag shown in c 2min The transmittance of the Ag-Au / cellulose film decreases with increasing Au growth time, which is related to the continuous loading of Au particles. Furthermore, the composite film has the lowest transmittance in the ultraviolet region, which is related to the strong absorption of the Ag-Au / cellulose film in the ultraviolet region. In summary, the Ag-Au / cellulose film has optimal light absorption.

[0086] Through the study of the optical properties of Ag-Au / cellulose membranes, it can be seen that the loading of Au particles can not only broaden the light absorption range, but also improve the light absorption rate of the entire solar spectrum band. The growth time of Au also has a very intuitive effect on the light absorption performance of the composite membrane. This shows that the reasonable regulation of the growth time of Au during the material synthesis process can obtain Ag-Au / cellulose membranes with optimal photothermal performance.

[0087] Example 8 - Photothermal conversion performance and water evaporation performance of Ag-Au / cellulose composite photothermal film

[0088] Thermal infrared images were captured using a combination of a thermal infrared imager (FLIR E6) and a mobile phone. The thermal infrared imager (FLIR E6) recorded the temperature changes of the samples. The concentrations of various ions in the seawater, as well as those before and after desalination, were analyzed using inductively coupled plasma spectroscopy (ICP-MS, Agilent 7700). The characteristic absorption peaks of the dyes were measured using a UV-vis absorption spectrometer (UV3600Plus, SHIMADZU). A xenon lamp (CEL-HXF300) was used as a simulated sunlight source for the solar evaporation experiments.

[0089] Evaporation performance test: indoor water evaporation test

[0090] In indoor experiments, the photothermal film was separated from a large amount of water, and a simple interface evaporation system was developed. In this work, a 3D-printed polylactic acid frame was placed on the mouth of a plastic cup, and non-woven fabric was used as a water transfer material and a photothermal film support layer. The photothermal film was placed on the top layer of the non-woven fabric, which can transport water into the sample film, avoiding heat transfer between the photothermal interface and the bulk water. The plastic cup containing the sample film, non-woven fabric, frame and deionized water was placed on an electronic analytical balance to record its weight change. The radiation power was 1000W / m 2 A xenon lamp (1 sun) was used to simulate sunlight, and the light intensity was measured using a densitometer. All experiments were performed in a closed room under the same experimental conditions (room temperature 25 ± 1 ° C, humidity: 40 ± 5%, no wind).

[0091] The solar evaporation rate of the sample can be calculated as:

[0092]

[0093] Where m is the mass of evaporated water, S is the sample membrane area, and t is the evaporation time.

[0094] According to previous reports, the solar evaporation efficiency of the sample can be calculated as:

[0095]

[0096] Where η is the evaporation efficiency, is the evaporation rate (kg m -2 h -1 ), h LV is the total liquid-vapor phase change enthalpy (2267 J g -1 ), P is the incident laser power density (kW m -2 ). The value is obtained by subtracting the water evaporation rate under 1 sun from the water evaporation rate under non-xenon lighting. When there is no xenon lamp lighting, the average evaporation rate of the photothermal film is about 0.3 kg m -2 h-1 .

[0097] Before testing the photothermal response ability of the photothermal material, the present invention built a simple temperature rise test platform. In order to more accurately test the temperature rise of the material, two wooden strips of the same height and wrapped with reflective tape were used as supports, and then a glass block was placed on top of the wooden block, and the sample was placed on top of the glass block (the sample was separated from the desktop, which was conducive to the normal heat dissipation of the material). Taking into account that the cellulose film will bend when heated, a frame printed with polylactic acid material was placed on the film. The size was slightly larger than the photothermal film, which can ensure that the surface remains flat during the heating process of the photothermal film. An infrared camera was used to monitor the surface temperature of the Ag-Au / cellulose photothermal film under simulated sunlight in real time. The temperature rise experiments were all tested at 1000W / m 2 (1 sun) of light power.

[0098] Figure 10 a is the temperature change of the Ag-Au / cellulose film with optimal light absorption in the dry state (upper row) and the wet film surface during water evaporation recorded by thermal infrared imaging, showing the surface temperature of the photothermal film at several time points. In the dry state, the temperature of the photothermal film surface quickly rose to 46.0°C within 60s, and within 5 minutes, the surface temperature rose to nearly 50°C. Subsequently, the surface temperature of the material stabilized and stabilized at around 53.0°C. In the wet state, the temperature of the photothermal film surface rose to around 30.0°C within 600s and remained stable, while the temperature of the water under the substrate always remained near the initial temperature ( Figure 10 b), which indicates that the interface evaporator has a good effect on the conduction of heat to the bulk water. The photothermal film shows a rapid photothermal response under sunlight, which indicates that the Ag-Au / cellulose photothermal film has excellent solar-thermal conversion performance. As a control, the temperature changes of the remaining samples are as follows Figure 10 c. The average interface temperature of the Ag-Au / cellulose photothermal film is significantly higher than that of the Ag / cellulose film and the Au / cellulose film. 2min -Au 10min The average interface temperature of the Ag / cellulose membrane is lower than that of the Ag 2min -Au 10min / cellulose film. It can be seen that the obvious temperature increase behavior of the Ag-Au / cellulose film is related to the successful loading of Au nanoparticles, and with the extension of Au growth time, that is, the increase of Au loading amount, the surface temperature of the photothermal film shows a trend of gradual increase. The obvious temperature increase behavior of the Ag-Au / cellulose photothermal film may be attributed to the synergistic effect of Au nanoparticles with high photothermal conversion performance and Ag nanoparticles ( Figure 10d) Au and Ag have excellent photothermal conversion performance due to their excellent localized surface plasmon resonance (LSPR) absorption. Their dense distribution may also lead to LSPR coupling, enhancing light absorption. Therefore, when the Ag-Au / cellulose film is exposed to sunlight, the Ag and Au nanoparticles, which have high photothermal conversion performance, heat up rapidly. Although the heating rates are slightly different, the uniform distribution of Ag and Ag metal particles on the cellulose film surface allows the heat generated by the Au and Ag nanoparticles to be quickly exchanged with each other, ensuring a fast photothermal response for the entire photothermal film.

[0099] like Figure 10 As shown in f, an interface evaporation system was built during the test to test the water evaporation performance of the sample. A polylactic acid support was used as a substrate under the photothermal film to avoid heat conduction to the water body, and non-woven fabric was used as a water transmission channel.

[0100] Figure 10 e shows Ag 2min –Au 5min / cellulose film, Ag 2min –Au 10min The results show that the change of water mass with time under 1 sun irradiation on Ag-Au / cellulose membrane and blank water showed a linear increase with the extension of irradiation time in all samples. 2min –Au 5min / cellulose membrane and Ag 2min –Au 10min The water evaporation of the cellulose membranes was 1.58 kg m -2 , 1.48kg·m -2 , which is much higher than the water evaporation of the blank water sample. The evaporation rate of sample 2 is slightly lower than that of sample 1, which corresponds to the previous temperature difference.

[0101] According to the mass change curve, the evaporation rate corresponding to different samples was calculated, and the solar evaporation efficiency of each sample was calculated to further evaluate the solar energy utilization efficiency, such as Figure 10 As shown in Figure g, the optimal water evaporation rate of the Ag–Au cellulose membrane is 1.58 kg·m -2 ·h -1 The water evaporation rate of the control sample was slightly lower, at 1.48 kg·m -2 ·h -1 At the same time, Ag-Au / cellulose photothermal film has good evaporation efficiency under one sun. 2min –Au 5min / cellulose membrane and Ag 2min –Au 10minThe water evaporation efficiencies of the Ag-Au / cellulose membranes are 81.3% and 75.0% respectively. Obviously, the longer growth time of Au nanoparticles will result in a higher evaporation rate and efficiency of the photothermal membrane. It is worth noting that the large micron-scale voids between the disordered lignocellulose microfibers and the large number of nanogaps (≈10nm) between the hydrophilic crystal nanofibers enable the water molecules to be rapidly transported along the channels to the surface of the photothermal membrane during the water evaporation process of the cellulose membrane, ensuring the efficient water evaporation rate and efficiency of the Ag-Au / cellulose membrane. Due to the commercial scalability and low price of cellulose membranes, it is entirely possible to produce 1m 2 The ultra-large photothermal film can produce enough water per hour to meet the water needs of an adult in real life, which clearly proves the high solar energy utilization efficiency of the Ag-Au / cellulose membrane.

[0102] The long-term stability of the Ag-Au / cellulose photothermal film was evaluated through continuous experiments. Figure 10 h shows the evaporation rate of the Ag-Au / cellulose photothermal film for 40 h during the test of solar water evaporation stability. It can be seen that the evaporation rate remains almost unchanged and at a good level (1.58 kg·m -2 ·h -1 ), indicating that the photothermal film has excellent long-term stability and practicality.

[0103] Example 9 - Water Evaporation Application of Ag-Au / Cellulose Composite Photothermal Film

[0104] In addition, Ag-Au / cellulose photothermal membrane can be used as a feasible solar evaporator for wastewater purification. The evaporation performance of Ag-Au / cellulose photothermal membrane in various water qualities was comprehensively and systematically studied.

[0105] First, the decolorization ability of Ag-Au / cellulose photothermal film during solar evaporation was tested ( Figure 11 a, b), organic dye wastewater including rhodamine B (10 mg / L) and methylene blue (20 mg / L). UV-visible absorption spectra show strong characteristic peaks at 553 nm and 663 nm for the rhodamine B solution and the methylene blue solution, respectively. No obvious signal was observed by testing evaporated water, which is consistent with the colorless solution collected from the wastewater evaporation process (inset), indicating that the Ag-Au / cellulose photothermal film has a good decolorization effect on organic dye water.

[0106] The desalination performance of Ag-Au / cellulose photothermal membrane was evaluated using real seawater from the South China Sea. Five major ions (Ca 2+ , K + Mg 2+ 、Na +and B 3+ ) were 452.8 mg / L, 756.2 mg / L, 1393.5 mg / L, 11523.3 mg / L, and 3.473 mg / L, respectively. The five main ions Ca in the condensate collected after 10 h of solar desalination were then determined. 2+ , K + Mg 2+ 、Na + and B 3+ ) are 0.03555 mg / L, 0.1671 mg / L, 0.01996 mg / L, 0.6961 mg / L, and 0.001170 mg / L, respectively, which are three orders of magnitude lower than the concentration in the original seawater. Plot the logarithm of the concentration, as shown in the following figure: Figure 11 As shown in Figure c, the removal efficiency of these five ions in evaporated water is greater than 99.9%, which is far below the World Health Organization's drinking water guideline value (total dissolved solids <600 mg / L for good palatability).

[0107] In addition, the water evaporation rate of Ag-Au / cellulose photothermal film in alkaline water, acidic water, organic dye water (rhodamine B, methylene blue) and natural seawater was tested (test time more than 2h). Figure 11 As shown in Figure d, although the water evaporation efficiency has decreased, it still remains at 1.530 kg·m -2 ·h -1 , 1.500kg·m -2 ·h -1 , 1.557kg·m -2 ·h -1 , 1.560kg·m -2 ·h -1 and 1.570 kg·m -2 ·h -1 In addition, the condensed water after evaporation of acidic and alkaline water was collected and the pH test paper showed that it was neutral (pH ≈ 7) ( Figure 11 e) The Ag-Au / cellulose photothermal membrane achieved a very high ion retention effect, successfully verifying that the Ag-Au / cellulose photothermal membrane still has good water purification performance under acidic and alkaline conditions.

[0108] Example 10 - Bactericidal performance of Ag-Au / cellulose composite photothermal film

[0109] The present invention evaluated the antibacterial properties of Ag-Au / cellulose membranes with different Au growth times. First, a nutrient solution required for bacterial growth was prepared using a certain amount of deionized water, sodium chloride, beef extract, and peptone. After the nutrient solution was sterilized at high temperature and high pressure, the bacteria were added and grown on a shaker overnight. A nutrient agar medium was also prepared with the same nutrient content as the nutrient solution, and an estimated amount of agar powder was added. On a clean bench, the two bacterial solutions were evenly applied to the surface of the agar solid culture medium, and the material was placed in the center of the culture medium and cultured at a constant temperature overnight.

[0110] The experiments used Escherichia coli and Staphylococcus aureus, the most common and representative Gram-negative and Gram-positive bacteria, respectively, as the study subjects. The antibacterial properties of the Ag-Au / cellulose membrane were evaluated using the diffusion inhibition ring test. All laboratory supplies were sterilized under high temperature and high pressure prior to the experiments. All experiments were conducted under sterile conditions, with three replicates per sample to ensure the accuracy of the results.

[0111] During photothermal interfacial evaporation, bacterial fouling, which reduces evaporation rates, is one of the most troubling issues. In this study, Ag-Au / cellulose membranes demonstrated excellent antibacterial properties. These membranes were tested against representative Gram-negative and Gram-positive bacteria, Escherichia coli and Staphylococcus aureus, cultured on agar plates. Diffusion inhibition rings were used to evaluate the intrinsic antibacterial properties of the samples. Figure 12 a and Figure 12 b shows the growth of Staphylococcus aureus and Escherichia coli treated with Ag-Au / cellulose photothermal film. The results show that the width of the inhibition zone of samples 1, 2, and 3 are 4.66, 3.88, and 2.18 mm, respectively. Figure 12 a), the widths of the inhibition zones of samples 1, 2, and 3 were 2.89, 2.64, and 1.40 mm, respectively ( Figure 12 b). This indicates that the antibacterial properties are related to the presence of Ag NPs. Furthermore, the inhibitory effect of reduced Ag on bacterial growth on the membrane surface was significantly prolonged, resulting in the Ag-Au / cellulose membrane exhibiting highly effective and long-term antibacterial properties.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An Ag-Au cellulose composite photothermal film, characterized in that: The Ag-Au cellulose composite photothermal film is based on an Ag / fiber film, with Au metal growing on the surface of the Ag / fiber film; the Ag / fiber film is obtained by depositing nano-Ag on the fiber film through metal reduction; The preparation method of the Ag-Au cellulose composite photothermal film comprises the following preparation steps: Preparation of S1 Ag / cellulose membrane: Place the cellulose membrane in a mixed solution of stannous chloride and hydrochloric acid, stir, and then let it stand to soak. Wash it with deionized water and ethanol, respectively. Then transfer it to a silver nitrate solution, stir the cellulose membrane until the color of the cellulose membrane changes, and wash it with ethanol and deionized water, respectively, to obtain an Ag / cellulose membrane. S2 Preparation of Ag-Au cellulose membrane: Transferring the Ag / cellulose membrane prepared in step S1 to an Au growth solution and soaking it to obtain an Ag-Au cellulose membrane; the Au growth solution comprises chloroauric acid, sodium chloride, tartaric acid, sodium hydroxide, and ethanol; The concentration ratio of stannous chloride to hydrochloric acid is 1:1-2; the stirring is continued for 10-20 minutes and then allowed to soak for 40-50 minutes; the concentration of silver nitrate is 8-12 mM; The Au growth solution comprises: adding 0.2-0.3 g of chloroauric acid, 0.1-0.2 g of sodium chloride, 0.05-0.15 g of tartaric acid, 1.2-1.5 g of sodium hydroxide and 0.4-0.6 mL of ethanol to every 45-55 mL of deionized water; In step S2, the soaking time is 2 to 20 minutes.

2. An Ag-Au cellulose composite photothermal film according to claim 1, characterized in that: The XPS spectrum of Ag 3d of the Ag-Au cellulose composite photothermal film has two characteristic peaks at binding energies of 367-368 eV and 373-374 eV, the XPS spectrum of Au 4f has two peaks at 83-84 eV and 87-88 eV, the XPS spectrum of O 1s has two peaks at 531-532 eV and 534-535 eV, and the XPS spectrum of C1s has three peaks at 284-285 eV, 286-287 eV, and 287.5-288 eV. In the XRD spectrum of the Ag-Au cellulose composite photothermal film, at 2θ of 15.0 o , 16.0~16.5 o , 22.5~23.0 o , 34~34.5 o and 38~38.6 o There is a characteristic peak.

3. The Ag-Au cellulose composite photothermal film according to claim 1, characterized in that: In step S1, the cellulose membrane is stirred for 1 to 3 minutes.

4. The Ag-Au cellulose composite photothermal film according to claim 3, characterized in that: In step S1, the stirring time of the cellulose membrane is 2 minutes; in step S2, the soaking time is 10 minutes.

5. An application of the Ag-Au cellulose composite photothermal film according to any one of claims 1 to 4, characterized in that: The Ag-Au cellulose composite photothermal film is used in at least one of wastewater purification, seawater desalination or water disinfection.

6. The use of the Ag-Au cellulose composite photothermal film according to claim 5, characterized in that: The application of the invention in wastewater purification is to decolorize wastewater contaminated by organic dyes; the application of the invention in desalination of seawater is to reduce the Ca content in seawater. 2+ , K + Mg 2+ 、Na + or B 3+ Application of ion concentration; the application in water disinfection is the application of inhibiting Escherichia coli and Staphylococcus aureus.

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