Multi-Functional Electrospun AgNO3/PVB and Its Ag NP/PVB Nanofiber Membrane

This study focuses on the fabrication of fiber membranes containing different concentrations of AgNO3 via the electrospinning technique. The AgNO3 present in the fibers is subsequently reduced to silver nanoparticles (Ag NPs) through UV irradiation. The resulting nanofiber film is characterized using scanning electron microscopy, X-ray diffraction, and evaluations of its anti-UV and anti-electromagnetic radiation properties. Experimental results demonstrate that increasing the AgNO3 content initially decreases and then increases the fiber diameter and fiber diameter deviation. Under UV light, the nanofibers fuse and bond, leading to an increase in the fiber diameter. AgNO3 is effectively reduced to Ag NPs after UV irradiation for more than 60 min, as confirmed by the characteristic diffraction peaks of Ag NPs in the XRD spectrum of the irradiated AgNO3/PVB fibers. The nanofiber film containing AgNO3 exhibits superior anti-UV performance compared to the film containing AgNO3-derived Ag NPs. The anti-electromagnetic radiation performances of the nanofiber films containing AgNO3 and AgNO3-derived Ag NPs are similar, but the nanofiber film containing AgNO3-derived Ag NPs exhibits higher performance at approximately 2.5 GHZ frequency. Additionally, at an AgNO3 concentration of less than 0.5 wt%, the anti-electromagnetic radiation performance is poor, and the shielding effect of the nanofiber film on medium- and low-frequency electromagnetic waves surpasses that on high-frequency waves. This study provides guidance for the preparation of polyvinyl butyral nanofibers, Ag NPs, and functional materials with anti-ultraviolet and anti-electromagnetic radiation properties.


Introduction
Affected by a new heatwave, many countries in the northern hemisphere, including Italy and Spain, continue to experience high temperatures. Scientists suggest that 2023 could be the hottest year on record. Textiles carry the consumers' aspirations for a better life, with the hope that they possess multifunctional properties, such as ultraviolet (UV) resistance and antibacterial features. Silver nitrates and their conversion to nanosilver have many excellent properties, making them one of the most investigated research materials. Given that absorbing UV light converts silver nitrate into nanosilver, its addition into fibers will enhance the UV shielding performance of existing materials. Polyvinyl butyral (PVB) is a thermoplastic encapsulant widely used in various applications, including safety glass laminates, building-integrated photovoltaics, and thin films with a glass-to-glass configuration [1,2]. PVB is frequently employed in electrospinning due to its adjustable molecular weight and excellent spinnability [3][4][5]. Electrospun PVB nanofibers have found applications in bioengineering fields, serving as antimicrobial agents, drug carriers, and tissue engineering materials, owing to their antimicrobial properties, biocompatibility, and non-cytotoxicity [6]. Furthermore, PVB fibers are used in the production of oil, thymol, structural integrity, and increased potential applications in biomedicine, sensors, filtration, and ultraviolet and electromagnetic radiation protection. The summer of 2023 has been the hottest on record in many places. Many new cars, such as Teslas, now have beautiful panoramic glass roofs. However, they have high UV transmission rates and do not provide adequate heat insulation, resulting in high temperatures inside the vehicles. The intense sunlight can make occupants feel uncomfortable. The findings of this study may provide valuable insights into improving the UV resistance of double-layer PVB glass.
Current academic research mainly focuses on the antibacterial properties of silver nitrate and nanosilver, with relatively fewer studies on their anti-ultraviolet functionalities. PVB itself has certain UV-resistance properties. As extreme weather becomes more frequent, the demand for UV resistance in textiles and glass products is increasing. Therefore, this paper introduces silver nitrate into PVB to enhance its multi-functional properties. We prepared fiber membranes with different concentrations of AgNO 3 via electrospinning and subsequently reduced the AgNO 3 to Ag NPs through UV irradiation. We investigated the anti-ultraviolet and electromagnetic radiation protection performances of nanofibers with silver nitrate and nanosilver incorporated into PVB. Figure 1 displays the SEM images of the nanofiber membranes prepared with different concentrations of AgNO 3 and subsequently UV-irradiated for 60 min. Figure 1(1b,2b,3b,4b,5b) shows the SEM images of the non-irradiated nanofiber membranes with corresponding AgNO 3 concentrations. The fiber diameters for the 0%, 0.5%, 1%, 1.5%, and 2.0% AgNO 3 samples were measured to be 0.26 ± 0.03; 0.22 ± 0.02; 0.20 ± 0.01; 0.19 ± 0.01; and 0.24 ± 0.02 µm, respectively. From Figure 2a, it can be seen that the concentration of AgNO 3 is less than 2.0% and that the fiber diameter does not change much. Fibers without AgNO 3 exhibited slightly greater thickness and occasional beading. Conversely, the electrospun fibers containing AgNO 3 appeared smooth, straight, and devoid of beading, with a highly uniform fiber diameter distribution. With an increasing AgNO 3 content, the fiber diameter and deviation initially decreased and then increased. The improved conductivity of the spinning solution due to AgNO 3 led to greater stretching of the jet under a stronger electric field force, resulting in smaller fiber diameters. However, this trend was not infinite, as there is a limit to how much repulsive charges can affect the viscoelastic force of the solution. Beyond this point, further increases in salt content did not lead to additional reductions in fiber diameter. Previous studies have reported an initial decrease in fiber diameter with the addition of AgNO 3 , followed by an increase as AgNO 3 content further increased in aqueous-based polymer solutions. Moreover, the quality of the fibers deteriorated with increased beading and variation in fiber diameter at higher AgNO 3 concentrations [32]. As Ke H et al. reported, the diameters of the obtained PAN/AgNP composite fibers decreased with an increase in the initial AgNO 3 concentration in the solutions [33].

Morphological Analysis
After UV irradiation, the fiber diameter decreased, and irregularities in diameter increased due to the reduction in material mass after decomposition. Under UV light, the PVB fibers experienced heating and fusion, resulting in an increase in fiber diameter, as shown in Figure 1. This fusion was attributed to the glass transition temperature of PVB, which ranges from 50 • C to 70 • C [34]. The UV-irradiated fibers without AgNO 3 exhibited the highest fusion degree, as depicted in Figure 1a, while the UV-irradiated fibers with 2.0 wt% AgNO 3 exhibited the lowest fusion degree. This study used a UV aging machine as a standard light source for UV irradiation, and all samples were stored in a specific enclosed space. After UV irradiation, the sample heating phenomenon occurred; hence, the fibers in the samples melted and stuck together, which is a distinctive event. In contrast, other papers used relatively lower UV irradiation intensities and different glass transition temperatures. In addition, their samples were placed in a more open space, where heat could disperse easily and not heat the fibers to their melting point, thus avoiding the melting and sticking phenomenon [33,35,36]. This indicates that the fusion degree decreased with increasing AgNO 3 concentration.
with increasing AgNO3 concentration.
The AgNO3 absorbed energy from the UV light and underwent a chemical reaction (Equation (1)), reducing the overall temperature of the nanofiber membrane and decreasing the number of fused PVB fibers [37]. The average fiber diameter after irradiation was larger than before irradiation due to fiber adhesion and irregularities caused by fusion. Additionally, AgNO3 in the PVB fibers absorbed UV light and converted to Ag NPs, contributing to a reduction in the overall temperature of the nanofiber membrane.  From Figure 2b, it can be seen that with the increase in radiation time, the diameter of the nanofiber membrane containing 1.5 wt% AgNO3 shows an upward trend. Figure 3 present SEM images of the nanofiber membrane containing 1.5 wt% AgNO3 and subjected to different UV irradiation times: 0, 60, 120, 180, and 240 min. As the UV irradiation time increased, a greater amount of AgNO3 underwent the reaction, leading to the formation of Ag NPs. Consequently, the temperature of the irradiated fibers naturally increased. At the glass transition temperature, a significant number of PVB fibers fused and adhered to each other, resulting in the observed structural changes. In addition, it was found that the surface color of the fiber membrane gradually changed from light yellow to dark brown. Similar to the report by Hong K H et al., all the colors of the electrospun AgNO3-containing PVA composite fiber webs changed from a white tone to a light yellow tone during ing and sticking phenomenon [33,35,36]. This indicates that the fusion degree decreased with increasing AgNO3 concentration.
The AgNO3 absorbed energy from the UV light and underwent a chemical reaction (Equation (1)), reducing the overall temperature of the nanofiber membrane and decreasing the number of fused PVB fibers [37]. The average fiber diameter after irradiation was larger than before irradiation due to fiber adhesion and irregularities caused by fusion. Additionally, AgNO3 in the PVB fibers absorbed UV light and converted to Ag NPs, contributing to a reduction in the overall temperature of the nanofiber membrane.  From Figure 2b, it can be seen that with the increase in radiation time, the diameter of the nanofiber membrane containing 1.5 wt% AgNO3 shows an upward trend. Figure 3 present SEM images of the nanofiber membrane containing 1.5 wt% AgNO3 and subjected to different UV irradiation times: 0, 60, 120, 180, and 240 min. As the UV irradiation time increased, a greater amount of AgNO3 underwent the reaction, leading to the formation of Ag NPs. Consequently, the temperature of the irradiated fibers naturally increased. At the glass transition temperature, a significant number of PVB fibers fused and adhered to each other, resulting in the observed structural changes. In addition, it was found that the surface color of the fiber membrane gradually changed from light yellow to dark brown. Similar to the report by Hong K H et al., all the colors of the electrospun AgNO3-containing PVA composite fiber webs changed from a white tone to a light yellow tone during The AgNO 3 absorbed energy from the UV light and underwent a chemical reaction (Equation (1)), reducing the overall temperature of the nanofiber membrane and decreasing the number of fused PVB fibers [37]. The average fiber diameter after irradiation was larger than before irradiation due to fiber adhesion and irregularities caused by fusion. Additionally, AgNO 3 in the PVB fibers absorbed UV light and converted to Ag NPs, contributing to a reduction in the overall temperature of the nanofiber membrane.
From Figure 2b, it can be seen that with the increase in radiation time, the diameter of the nanofiber membrane containing 1.5 wt% AgNO 3 shows an upward trend. Figure 3 present SEM images of the nanofiber membrane containing 1.5 wt% AgNO 3 and subjected to different UV irradiation times: 0, 60, 120, 180, and 240 min. As the UV irradiation time increased, a greater amount of AgNO 3 underwent the reaction, leading to the formation of Ag NPs. Consequently, the temperature of the irradiated fibers naturally increased. At the glass transition temperature, a significant number of PVB fibers fused and adhered to each other, resulting in the observed structural changes. In addition, it was found that the surface color of the fiber membrane gradually changed from light yellow to dark brown. Similar to the report by Hong K H et al., all the colors of the electrospun AgNO 3 -containing PVA composite fiber webs changed from a white tone to a light yellow tone during the preparation process. This indicates that in the electrospun AgNO 3 /PVA fibers, Agþ ions were reduced and aggregated into Ag nanoparticles [35].
Molecules 2023, 28, x FOR PEER REVIEW 5 of 13 the preparation process. This indicates that in the electrospun AgNO3/PVA fibers, Agþ ions were reduced and aggregated into Ag nanoparticles [35].

XRD Analysis
The X-ray diffraction (XRD) spectrum of the non-irradiated AgNO3/PVB fibers did not exhibit any diffraction peaks, as shown in Figure 4, indicating the absence of a crystal structure or Ag NPs within the fibers. Comparatively, the XRD patterns of the fibers irradiated for 60, 120, and 180 min displayed characteristic diffraction peaks associated with Ag NPs. The XRD patterns confirmed that the Ag NPs within the Ag/PVB fibers possessed a face-centered cubic structure. Notably, the XRD spectrum of the irradiated AgNO3/PVB fibers displayed distinct peaks at 2θ values of 38.04°, 44.28°, 64.46°, and 77.42°, corresponding to the 111, 200, 220, and 311 crystallographic planes of face-centered cubic Ag crystals, respectively. The distinct peaks were consistent with those shown in the paper of Hassanien A S et al. [38]. These results indicated that the Ag NPs formed were crystalline. Conversely, the XRD patterns of the non-irradiated AgNO3 samples revealed the presence of Ag as the main crystalline phase, without any additional phases or impurities (Ag XRD Ref. No. 01-087-0719) [39]. It can be concluded that AgNO3 was successfully transformed into Ag NPs after UV irradiation for more than 60 min. Pure nanosilver particles had no impurity X-ray diffraction (XRD) peaks [40]. The nanosilver particles in this study were encapsulated in PVB polymer, and similar to the report of Hong K H et al. on AgNO3/PVA, after crystallization, the impurity peaks (at around 2θ = 23°) of PVB could be observed [35]. The crystallinity of the PVB polymer was increased after UV treatment. This is in contrast to the paper of Hong K H et al., where the characteristic nanosilver peaks were not clearly visible. The reason was that the temperature they used for treating silver nitrate was only 155 °C, which had not reached the decomposition temperature of silver nitrate [41]. However, in this study, the silver nitrate decomposition was more thorough due to the relatively high UV light intensity, and the nanosilver characteristic peaks were clearly visible.
The average particle size of the Ag NPs was estimated using the Debye-Scherrer equation (Equation (2)) [42]: where D represents the average crystallite size of the Ag NPs, K is the Scherrer constant (with values ranging from 0.9 to 1, accounting for the shape factor), λ is the X-ray wavelength (1.5418 Å), β1/2 is the width of the XRD peak at half height, and θ is the Bragg

XRD Analysis
The X-ray diffraction (XRD) spectrum of the non-irradiated AgNO 3 /PVB fibers did not exhibit any diffraction peaks, as shown in Figure 4, indicating the absence of a crystal structure or Ag NPs within the fibers. Comparatively, the XRD patterns of the fibers irradiated for 60, 120, and 180 min displayed characteristic diffraction peaks associated with Ag NPs. The XRD patterns confirmed that the Ag NPs within the Ag/PVB fibers possessed a face-centered cubic structure. Notably, the XRD spectrum of the irradiated AgNO 3 /PVB fibers displayed distinct peaks at 2θ values of 38.04 • , 44.28 • , 64.46 • , and 77.42 • , corresponding to the 111, 200, 220, and 311 crystallographic planes of face-centered cubic Ag crystals, respectively. The distinct peaks were consistent with those shown in the paper of Hassanien A S et al. [38]. These results indicated that the Ag NPs formed were crystalline. Conversely, the XRD patterns of the non-irradiated AgNO 3 samples revealed the presence of Ag as the main crystalline phase, without any additional phases or impurities (Ag XRD Ref. No. 01-087-0719) [39]. It can be concluded that AgNO 3 was successfully transformed into Ag NPs after UV irradiation for more than 60 min. Pure nanosilver particles had no impurity X-ray diffraction (XRD) peaks [40]. The nanosilver particles in this study were encapsulated in PVB polymer, and similar to the report of Hong K H et al. on AgNO 3 /PVA, after crystallization, the impurity peaks (at around 2θ = 23 • ) of PVB could be observed [35]. The crystallinity of the PVB polymer was increased after UV treatment. This is in contrast to the paper of Hong K H et al., where the characteristic nanosilver peaks were not clearly visible. The reason was that the temperature they used for treating silver nitrate was only 155 • C, which had not reached the decomposition temperature of silver nitrate [41]. However, in this study, the silver nitrate decomposition was more thorough due to the relatively high UV light intensity, and the nanosilver characteristic peaks were clearly visible.
The average particle size of the Ag NPs was estimated using the Debye-Scherrer equation (Equation (2)) [42]: where D represents the average crystallite size of the Ag NPs, K is the Scherrer constant (with values ranging from 0.9 to 1, accounting for the shape factor), λ is the X-ray wavelength (1.5418 Å), β1/2 is the width of the XRD peak at half height, and θ is the Bragg angle. Based on the Scherrer equation, the average crystallite size of the Ag NPs was estimated to be approximately 10-20 nm, and the calculated average crystallite size aligned with the grain size range computed by other researchers [43,44]. angle. Based on the Scherrer equation, the average crystallite size of the Ag NPs was estimated to be approximately 10-20 nm, and the calculated average crystallite size aligned with the grain size range computed by other researchers [43,44].

Anti-UV Performance Test and Analysis
The ultraviolet protection factor (UPF) and ultraviolet transmittance of the nanofiber films were measured using an anti-UV performance tester according to the AS/NZS 4399:1996 test standard [45]. The anti-UV coefficient, which represents the ratio of the average amount of UV radiation absorbed on the unprotected skin to the amount absorbed on the tested textiles, was used to evaluate the effectiveness of the UV-irradiated textiles.
Due to the inherent anti-UV function of PVB fibers, the UPF value of the PVB fibers containing AgNO3 was already above 40, indicating excellent UV protection capability, as exhibited in Table 1, which reveals an enhancement in the anti-UV function of PVB materials with the addition of AgNO3 or Ag NPs. The nanofiber film containing AgNO3 at concentrations ranging from 0.5% to 1.5% exhibited better anti-ultraviolet performance than the nanofiber film containing Ag NPs. This result can be attributed to AgNO3 absorbing UV light and converting it into Ag NPs, thereby reducing the amount of UV radiation penetrating the nanofiber film. This effect was most pronounced at an AgNO3 concentration of 0.5%. The ultraviolet transmittance of the non-irradiated nanofiber membrane was significantly lower than that of the nanofiber membrane containing AgNO3-derived Ag NPs. Similarly, the UPF value of the non-irradiated nanofiber membrane was significantly higher than that of the membrane containing AgNO3-derived Ag NPs. This difference can be attributed to the smaller content of AgNO3-derived Ag NPs, which was insufficient to cover the entire nanofiber membrane [46]. At an AgNO3 concentration of 2%, the anti-UV performances of the irradiated nanofiber films containing AgNO3 and AgNO3-derived Ag NPs were similar. The nanofiber film containing AgNO3-derived Ag NPs exhibited a high UPF value, indicating the effective blocking of UV rays through reflection, scattering, and light absorption. In theory, the higher the AgNO3 concentration, the greater the anti-UV performance of the nanofiber membrane. Notably, UV protection factor (UPF) values exceeding 100 were displayed as 100+ due to the limitations of the testing instrument. The

Anti-UV Performance Test and Analysis
The ultraviolet protection factor (UPF) and ultraviolet transmittance of the nanofiber films were measured using an anti-UV performance tester according to the AS/NZS 4399:1996 test standard [45]. The anti-UV coefficient, which represents the ratio of the average amount of UV radiation absorbed on the unprotected skin to the amount absorbed on the tested textiles, was used to evaluate the effectiveness of the UV-irradiated textiles.
Due to the inherent anti-UV function of PVB fibers, the UPF value of the PVB fibers containing AgNO 3 was already above 40, indicating excellent UV protection capability, as exhibited in Table 1, which reveals an enhancement in the anti-UV function of PVB materials with the addition of AgNO 3 or Ag NPs. The nanofiber film containing AgNO 3 at concentrations ranging from 0.5% to 1.5% exhibited better anti-ultraviolet performance than the nanofiber film containing Ag NPs. This result can be attributed to AgNO 3 absorbing UV light and converting it into Ag NPs, thereby reducing the amount of UV radiation penetrating the nanofiber film. This effect was most pronounced at an AgNO 3 concentration of 0.5%. The ultraviolet transmittance of the non-irradiated nanofiber membrane was significantly lower than that of the nanofiber membrane containing AgNO 3 -derived Ag NPs. Similarly, the UPF value of the non-irradiated nanofiber membrane was significantly higher than that of the membrane containing AgNO 3 -derived Ag NPs. This difference can be attributed to the smaller content of AgNO 3 -derived Ag NPs, which was insufficient to cover the entire nanofiber membrane [46]. At an AgNO 3 concentration of 2%, the anti-UV performances of the irradiated nanofiber films containing AgNO 3 and AgNO 3 -derived Ag NPs were similar. The nanofiber film containing AgNO 3 -derived Ag NPs exhibited a high UPF value, indicating the effective blocking of UV rays through reflection, scattering, and light absorption. In theory, the higher the AgNO 3 concentration, the greater the anti-UV performance of the nanofiber membrane. Notably, UV protection factor (UPF) values exceeding 100 were displayed as 100+ due to the limitations of the testing instrument. The actual UPF values of the irradiated nanofiber films with higher AgNO 3 concentrations were much higher than 100. In existing studies on the UV resistance of Ag NP textiles, Ag NPs were attached to the fabric surface through a post-processing technique. For example, after loading nanosilver onto cotton textiles with poor UV protection, the UV protection factor (UPF) value was 148, and the transmittance rate for UVA was 1.11% [47]. Also, after depositing nanosilver onto the surface of leather textiles, which inherently had good UV protection, the UPF value (478 ± 3) was significantly higher than other samples [48]. However, these post-processing techniques did not typically have lasting functionality, and the functionality significantly decreased after washing [49]. The nanosilver in this study was added to the fibers during the electrospinning process, and silver nitrate itself could absorb UV rays. After conversion to nanosilver, its UV resistance was outstanding. Due to the range limitations of equipment, the UPF value was 100+, but the transmittance rate for UVA was just 0.03, and its UV protection far exceeded other samples. Additionally, this functionality was permanent and did not decrease after washings. This excellent UV-resistant functionality makes it particularly suitable for scenarios where high UV protection levels are required.

Electromagnetic Radiation Protection Performance Test and Analysis
The electromagnetic radiation protection performance of the nanofiber films was evaluated using a DR-913G fabric anti-electromagnetic radiation performance tester [50], and the data obtained were plotted on a broken line chart. Figure 5 illustrates the slight differences in the anti-electromagnetic radiation performance between the non-irradiated and irradiated nanofiber films, indicating slight variations in conductivity between the nanofiber films containing AgNO 3 and AgNO 3 -derived Ag NPs. However, the nanofiber film containing AgNO 3 -derived Ag NPs exhibited superior anti-electromagnetic radiation performance compared to the non-irradiated nanofiber film containing AgNO 3 , particularly around the frequency of 2.5 GHZ [51,52]. This finding suggests that the nanofiber film can be utilized for targeted electromagnetic radiation protection at specific frequencies. The comparison of transmittance among the fiber membranes with different AgNO 3 concentrations revealed poor anti-electromagnetic radiation performance at AgNO 3 concentrations below 0.5 wt%, indicating inadequate conductivity in these membranes. Conversely, AgNO 3 concentrations above 1 wt% yielded good anti-electromagnetic radiation performance, although the differences were not significant. Overall, the nanofiber membrane exhibited better shielding effects against medium and low-frequency electromagnetic waves compared to high-frequency waves [53]. Due to their simplicity and efficient results, the preferred techniques for incorporating silver nanoparticles were direct blending and ultraviolet irradiation methods [36].
netic interference (EMI) shielding efficiency (SE) increased to 15.5 dB after plating Cu NPs on the polyethylene terephthalate (PET) fabric. The ability to shield EM waves depended on forming an electrically conductive network on the fabric surface after plating Cu NPs [54]. The silver-nanoparticle-coated woven cotton fabric showed an EMI shielding effectiveness of −20 dB [55]. Compared to textiles coated with silver nanoparticles, the sample in this paper had the same excellent performance, making it a promising textile with many protective properties.

Materials
Anhydrous ethanol (AR grade) was obtained from Tianjin Hengxing Reagent Co., Ltd. (Tianjin, China). AR-grade PVB with a molecular weight of 80,000 was purchased from Shanghai Sinopharm Group Reagent Co., Ltd. (Shanghai, China). AR-grade AgNO3 was acquired from Tianjin Damao Chemical Reagent Factory (Tianjin, China). The highvoltage DC power source was purchased from Dongwen High-voltage Power Supply Current research on the electromagnetic shielding effect of metal nanoparticles on textiles primarily focuses on the loading of metal nanoparticles on the surface of the textiles; the ability to shield electromagnetic (EM) waves depends on the formation of an electrically conductive network on the fabric surface after plating NPs. The electromagnetic interference (EMI) shielding efficiency (SE) increased to 15.5 dB after plating Cu NPs on the polyethylene terephthalate (PET) fabric. The ability to shield EM waves depended on forming an electrically conductive network on the fabric surface after plating Cu NPs [54]. The silver-nanoparticle-coated woven cotton fabric showed an EMI shielding effectiveness of −20 dB [55]. Compared to textiles coated with silver nanoparticles, the sample in this paper had the same excellent performance, making it a promising textile with many protective properties.

Materials
Anhydrous ethanol (AR grade) was obtained from Tianjin Hengxing Reagent Co., Ltd.

Preparation
Solutions for electrospinning were prepared with different concentrations of AgNO 3 (0%, 0.5%, 1%, 1.5%, and 2.0% wt%) and 7.375% wt% PVB. Each solution was magnetically stirred for 18 h to ensure the complete dissolution of AgNO 3 and PVB, resulting in a transparent solution. The electrospinning process was conducted at an ambient temperature of approximately 25 • C and a relative humidity of 40-60%. The electrospinning parameters were set as follows: a collection distance of 12 cm; voltage of 22 kV; flow rate of 1.5 mL/h; and three 18 G needles, each with an inner diameter of 0.84 mm and arranged at 3 cm intervals. After 4 h of electrospinning, the electrospun AgNO 3 /PVB nanofiber membrane was collected. To induce the reduction of AgNO 3 to Ag NPs with UV light, the AgNO 3 /PVB nanofiber membrane was irradiated with UV light for 60 min at a temperature of 60 • C and a power of 0.89 W/m 2 using a QUV accelerated aging machine (Wenzhou Darong Textile Instrument Co., Ltd., Wenzhou, China) to prepare the Ag NP/PVB nanofiber membrane.

Characterization
The surface morphology of the nanofiber bundles was examined using a scanning electron microscope (SEM, JSM-6390, JEOL Co., Ltd., Tokyo, Japan). The XRD spectrum of the nanofiber was measured using an X-ray diffractometer (Rigaku D/max2550VB3, Rigaku Co., Ltd., Tokyo, Japan). The UV transmittance and anti-UV performance of the nanofiber films were assessed using a textile anti-UV performance tester (YG912E, Quanzhou Meibang Instrument Co., Ltd., Quanzhou, China). The anti-electromagnetic radiation performance of the films was evaluated using an anti-electromagnetic radiation performance tester (DR-913G, Wenzhou Darong Textile Instrument Co., Ltd.).
The preparation and characterization process of silver-nanoparticle PVB nanofibers are shown in Scheme 1. The AgNO 3 /PVB nanofiber membrane was prepared via electrospinning first. Then, the AgNO 3 /PVB nanofiber membrane was exposed to UV light to form an Ag NP/PVB nanofiber film, and finally, tests and analyses were performed.

Preparation
Solutions for electrospinning were prepared with different concentrations of AgNO3 (0%, 0.5%, 1%, 1.5%, and 2.0% wt%) and 7.375% wt% PVB. Each solution was magnetically stirred for 18 h to ensure the complete dissolution of AgNO3 and PVB, resulting in a transparent solution. The electrospinning process was conducted at an ambient temperature of approximately 25 °C and a relative humidity of 40-60%. The electrospinning parameters were set as follows: a collection distance of 12 cm; voltage of 22 kV; flow rate of 1.5 mL/h; and three 18 G needles, each with an inner diameter of 0.84 mm and arranged at 3 cm intervals. After 4 h of electrospinning, the electrospun AgNO3/PVB nanofiber membrane was collected. To induce the reduction of AgNO3 to Ag NPs with UV light, the AgNO3/PVB nanofiber membrane was irradiated with UV light for 60 min at a temperature of 60 °C and a power of 0.89 W/m 2 using a QUV accelerated aging machine (Wenzhou Darong Textile Instrument Co., Ltd., Wenzhou, China) to prepare the Ag NP/PVB nanofiber membrane.

Characterization
The surface morphology of the nanofiber bundles was examined using a scanning electron microscope (SEM, JSM-6390, JEOL Co., Ltd., Tokyo, Japan). The XRD spectrum of the nanofiber was measured using an X-ray diffractometer (Rigaku D/max2550VB3, Rigaku Co., Ltd., Tokyo, Japan ). The UV transmittance and anti-UV performance of the nanofiber films were assessed using a textile anti-UV performance tester (YG912E, Quanzhou Meibang Instrument Co., Ltd., Quanzhou, China). The anti-electromagnetic radiation performance of the films was evaluated using an anti-electromagnetic radiation performance tester (DR-913G, Wenzhou Darong Textile Instrument Co., Ltd.).
The preparation and characterization process of silver-nanoparticle PVB nanofibers are shown in Scheme 1. The AgNO3/PVB nanofiber membrane was prepared via electrospinning first. Then, the AgNO3/PVB nanofiber membrane was exposed to UV light to form an Ag NP/PVB nanofiber film, and finally, tests and analyses were performed.

Conclusions
With the increasing frequency of extreme weather events worldwide, the demand for multifunctional textiles is rising. In this study, we prepared AgNO3/PVB nanofiber membranes, which was transformed into Ag NP/PVB nanofiber membranes under UV radiation. Through testing, it was found that both AgNO3/PVB and Ag NP/PVB had UV re-Scheme 1. Preparation and characterization diagram of Ag NP PVB nanofibers.

Conclusions
With the increasing frequency of extreme weather events worldwide, the demand for multifunctional textiles is rising. In this study, we prepared AgNO 3 /PVB nanofiber membranes, which was transformed into Ag NP/PVB nanofiber membranes under UV radiation. Through testing, it was found that both AgNO 3 /PVB and Ag NP/PVB had UV resistance and electromagnetic shielding properties, with their UV resistance being particularly exceptional. This makes them suitable for use in scenarios with high UV protection requirements. According to the literature, Ag NP/PVB nanofiber membranes also possess excellent antibacterial properties, making the samples prepared in this study multifunctional.
Some interesting experimental phenomena were also observed during the research process. The addition of AgNO 3 improved the conductivity of the spinning solution, resulting in a reduction in fiber diameter due to enhanced stretching caused by a larger electric field force. Under UV light, the fusion and adhesion of PVB fibers led to an increase in fiber diameter and irregularity. Nevertheless, the presence of AgNO 3 in PVB fibers reduced the temperature increase rate of the nanofiber membranes by absorbing UV energy and undergoing a chemical reaction, thereby minimizing fiber fusion. Notably, a significant number of PVB fibers fused and adhered to each other upon reaching the glass transition temperature. The incorporation of AgNO 3 effectively alleviated the fiber adhesion issue, thereby stabilizing the temperature increase in the irradiated PVB fibers. The XRD patterns exhibited characteristic diffraction peaks corresponding to Ag NPs, indicating their crystalline nature. The anti-UV performance of the nanofiber membranes was enhanced by the addition of AgNO 3 or Ag NPs. The nanofiber film containing AgNO 3derived Ag NPs demonstrated better anti-UV performance compared to the non-irradiated nanofiber film containing AgNO 3 . The anti-electromagnetic radiation performance slightly differed between the nanofiber films containing AgNO 3 and AgNO 3 -derived Ag NPs, with superior performance observed at the frequency of 2.5 GHZ for the nanofiber film containing AgNO 3 -derived Ag NPs. The nanofiber membrane displayed superior shielding effects against medium-and low-frequency electromagnetic waves compared to highfrequency waves.
The experimental phenomena and pattern analysis in the study process provided useful references for preparing multifunctional materials containing Ag NPs, especially by proposing methods to enhance the anti-UV function of existing materials. However, due to the limitations of the laboratory conditions, tests for the mechanical properties of the samples, as well as transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) tests, could not be completed. Consequently, the UV radiation impact on the mechanical properties of the samples had not been analyzed. Moreover, further analysis by TEM and XPS had not been conducted to determine the distribution and existence of silver nanoparticles. In the future, the project team will improve experimental conditions, prepare samples based on actual usage requirements, and conduct more comprehensive sample testing. The focus will be on optimizing the sample preparation methods to achieve the best mechanical performance. To this end, we will be using more comprehensive tests, such as TEM and XPS, to analyze the distribution of functional nanoparticles and the pattern of their impact on performance. This will expand its applications in other fields, such as catalysis, new electrode materials for batteries, electrically conductive materials, and low-temperature thermally conductive materials, to meet the highest multifunctional requirements. The team also has a concept: many new energy vehicles now have glass sunroofs, like Tesla, but the sun is too intense in the summer. It is worth further exploration whether silver nitrate can be added when using PVB as a laminated glass to enhance the UV resistance of the glass.

Data Availability Statement:
The authors declare that the data supporting the findings of this study are available within the paper. Should any raw data files be needed in another format, they are available from the corresponding author [S. Cao] upon reasonable request.