Contribution of Hydrogen-Bond Nanoarchitectonics to Switchable Photothermal-Mechanical Properties of Bioinorganic Fibers

Abstract

Open AccessCCS ChemistryRESEARCH ARTICLE21 Jun 2022Contribution of Hydrogen-Bond Nanoarchitectonics to Switchable Photothermal-Mechanical Properties of Bioinorganic Fibers Jing Sun†, Jinrui Zhang†, Lai Zhao†, Sikang Wan, Baiheng Wu, Chao Ma, Jingjing Li, Fan Wang, Xiwen Xing, Dong Chen, Hongjie Zhang and Kai Liu Jing Sun† Department of Chemistry, Tsinghua University, Beijing 100084 State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 Institute of Organic Chemistry, Ulm University, Ulm 89081 , Jinrui Zhang† State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 Department of Orthopedics, China-Japan Union Hospital of Jilin University, Changchun 130033 , Lai Zhao† State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 Department of Urology, China-Japan Union Hospital of Jilin University, Changchun 130033 , Sikang Wan State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 , Baiheng Wu College of Energy Engineering, Zhejiang University, Hangzhou 310027 , Chao Ma Department of Chemistry, Tsinghua University, Beijing 100084 , Jingjing Li State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 , Fan Wang State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 , Xiwen Xing *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Department of Biotechnology, College of Life Science and Technology, Jinan University, Guangzhou, Guangdong 510632 , Dong Chen *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] College of Energy Engineering, Zhejiang University, Hangzhou 310027 , Hongjie Zhang Department of Chemistry, Tsinghua University, Beijing 100084 State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 and Kai Liu *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Department of Chemistry, Tsinghua University, Beijing 100084 State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Changchun 130022 https://doi.org/10.31635/ccschem.022.202201946 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Stimuli-responsive materials hold great potential for the development of smart materials due to their specifically tailored characteristics. However, it is challenging to understand internal molecular dynamics when the macroscopic mechanics of materials change in response to specific applied stimuli. Herein, we present the biological composite fibers of which mechanical properties can be reversibly controlled on demand by photothermal effect of an alternating near-infrared light irradiation. In stark contrast to the weakening of the mechanical properties of conventional materials by heating, the mechanical performance of the obtained fibers are significantly enhanced, showing an increase of Young's modulus by a factor of four. The outstanding photothermal-mechanical behavior relies on the evolution of hydrogen bonds within the system. We envision that this type of fiber material will inspire a new strategy for the construction of smart devices. Download figure Download PowerPoint Introduction Stimuli-responsive materials can respond reversibly to an external stimulus where changes on the nanoscale will alter their macroscopic properties.1–8 As a result, various stimuli have been extensively explored to fabricate stimuli-responsive materials over the past few years.9–16 In particular, the ability to transform molecular movement into macroscopic work upon light irradiation is vitally important to design smart materials with tailored responsive features.17–22 On this basis, manipulating the molecular interactions within the materials on the microscopic scale is crucial for tuning their mechanical properties, especially for light-responsive materials. This makes it significant to explore the intrinsic relationship between macroscopic mechanical performance and microscopic change within the materials upon light irradiation on the molecular level.23–27 However, the heat generated by light irradiation often weakens the mechanical properties of the materials, resulting in decreased strength and stiffness.28 Currently, there is still a lack of appropriate systems in which mechanical performance can be manipulated through photothermal effect, especially to enhance the mechanical performance of bulk materials.29–32 Although various photothermal systems have been developed,33–36 the integration of biomolecules with a photothermal agent (PTA) to develop composite materials in which mechanical properties can be reversibly modulated by altering the internal molecular interactions via photothermal effect has not yet been reported. The pioneering exploration of this field can offer an alternative strategy to construct smart devices. In this regard, we fabricated a type of PTA-complexed biological composite fiber with outstanding photothermal-mechanical behavior. The biological fibers are composed of inorganic PTAs and alginate molecules, and their mechanical behavior can be reversibly manipulated upon near-infrared (NIR) light irradiation (808 nm). Interestingly, Young's modulus of these PTA-complexed fibers is enhanced significantly upon 808 nm light irradiation, which becomes more than four times stiffer than nonirradiated ones. Further investigation indicated that the interaction mechanism is based on the photothermally induced assembly and disassembly of hydrogen bonds within the system. Especially after the photoinduced high temperature, the formation of inter-/intramolecular hydrogen bonds between the biomolecules increased the cross-linking density effectively and enhanced the mechanical performance, resulting in a high stiffness. Experimental Methods Materials Calcium chloride and alginate (Mw = 4.3 × 105 g·mol−1) were purchased from Xilong Scientific Co. Ltd. (Guangzhou, Guangdong, China) and Alfa Aesar Chemical Co. Ltd. (Shanghai, China), respectively. Oleic acid (OA), sodium hydroxide (NaOH), sodium borohydride (NaBH4), and sodium oleate (NaOL) were purchased from Aladdin (Shanghai, China). Ethylene glycol (EG), hydrochloric acid (HCl, 37 wt % in water), hexadecyltrimethylammonium bromide (CTAB), tetrachloroauric (III) acid trihydrate (HAuCl4·3H2O), silver nitrate (AgNO3), ascorbic acid (AA), and ethanol were purchased from Sinopharm Chemical Reagent (Shanghai, China). Fabrication of alginate composite fibers The alginate (1 wt %) was dissolved in deionized water. Gold nanorods (GNRs), upconversion nanoparticles (UCNP), and Ag3AuS2 were kindly provided by our laboratory.37–39 The size of GNRs, UCNP, and Ag3AuS2 is 120.8 ± 12.9 nm, 32.4 ± 1.6 nm, and 12.5 ± 1.4 nm, respectively. PTAs were then mixed with alginate solution at a mass ratio of PTA∶alginate=1∶10. Alginate composite fibers were extruded from a syringe needle into a coagulation bath with calcium chloride (1 wt %) in water. The formed composite fibers were collected by a rotating cylinder and dried in air at room temperature for 3 h before the tensile test. Tensile test A tensile test was carried out on a FAVIMAT+ instrument (Textechno, Monchengladbach, North Rhine-Westphalia, Germany) using a speed of 2 mm·min−1 under ambient conditions. The gauge length was 10 mm. The fibers were alternately or continuously irradiated by an 808 nm laser during the tensile test. Moreover, the diameter of fibers was determined a Nikon inverted optical microscope (Tokyo, Japan). The obtained statistics were graphed and analyzed by Origin software. Polarized optical microscope analysis The orientation of alginate molecules was detected by a polarized optical microscope (POM; Nikon, Shanghai, China; ECLIPSE LV100N POL, 100–240 V, 1.2A, 50/60 Hz). Scanning electron microscope analysis and energy dispersive spectrometer analysis A scanning electron microscope (SEM, Hitachi S-4800, Portland, Oregon, United States) was utilized to observe the morphology of the fibers and analyze the distribution of Au elements in the composite fibers. Transmission electron microscopy Transmission electron microscopy (TEM) images were acquired by TECNAI G2 transmission electron microscope (FEI, Eindhoven, Noord-Brabant, the Netherlands) with an acceleration voltage of 200 kV. Small-angle X-ray scattering analysis Small-angle X-ray scattering (SAXS) analysis of the fibers was performed using synchrotron radiation at the BL19U2 station of the Shanghai Synchrotron Radiation Facility (SSRF). The X-ray wavelength (λ) was 0.923 nm, and the energy was 13.43 keV. The sample-to-detector distance was 2753 mm. The exposure time for each measurement was 5 s. The samples were mounted on a hollow specimen holder with double-sided adhesive tape. Fourier transform infrared spectra All the Fourier transform infrared (FT-IR) spectra of the samples were collected using a Nicolet Nexus 6700 FT-IR spectrometer (Madison, Wisconsin, United State) equipped with a deuterated triglycine sulfate detector. To gain an acceptable signal-to-noise ratio, 32 scans with a resolution of 4 cm−1 have been accumulated. During the test, the temperatures were controlled using an electronic cell holder, and the heating rate was maintained at 1 °C·min−1 from 30 to 120 °C in dry air. Two-dimensional correlation spectroscopy (2D COS) analysis of FT-IR spectra at different temperatures was conducted using software 2D Shige version 1.3 (Shigeaki Morita, Kwansei Gakuin University, Nishinomiya City, Hyogo Prefecture, Japan, 2004–2005). The final contour maps were plotted using Origin version 8.5, with red colors denoting positive intensities and blue colors denoting negative ones. Thermogravimetric analysis The thermogravimetric analysis (TGA) analysis was carried out using a TA Instrument (Shanghai, China) with a Q50 system under an air atmosphere and a heating/cooling rate of 10 °C·min−1. Results and Discussion The alginate/GNR composite fibers were fabricated using a wet-spinning strategy.40 To obtain Alg/GNR composite fibers, a mixture of GNRs and alginate was injected into an aqueous solution with Ca2+ ions. Each Ca2+ ion coordinated with two different carboxylic groups on the alginate backbones to form a cross-linking network (Figure 1a). After the dehydration process, the Alg/GNR composite fibers were prepared and collected by a rotating cylinder (Figure 1b). The integration of uniform GNRs ( Supporting Information Figure S1a) into the alginate matrix resulted in ordered composite fibers with significant birefringent properties (Figure 1c) and distinct fibrillary structural features (Figure 1d). In addition, the energy dispersive spectrometer analysis exhibited the uniform distribution of GNRs on the surface of the composite fibers ( Supporting Information Figure S1b). The SAXS analysis using synchrotron radiation demonstrated that the molecules are stacked in a well-ordered alignment along the fibers, as shown in Figure 1e, which is in good agreement with the POM analysis. Figure 1 | Fabrication and characterization of GNR-complexed alginate fibers. (a) GNR-complexed alginate fibers were fabricated by employing the wet-spinning method. The mixture of alginate and GNR solutions was extruded into the coagulation bath with Ca2+ ions. After the dehydration process, the composite fiber was formed and collected by a rotating cylinder. (b) Photograph of composite fibers on the collector. The diameter of the fibers is approximately 25 μm. (c) POM image of the composite fibers shows a strong birefringence, suggesting an ordered structure within composite fibers. (d) Surface morphology and cross section of composite fibers are characterized by SEM. The SEM images show that the fibers have a typical smooth, solid, and uniform fibrillary structure. (e) 2D SAXS pattern of the composite fiber was obtained by synchrotron radiation. Download figure Download PowerPoint The photothermal behavior of composite fibers was confirmed by recording the temperature changes via an infrared camera after the 808 nm laser irradiation (1 W). Of note, the 808 nm laser was chosen due to its low water absorption, avoiding undesired heating processes and loss of excitation efficiency. As shown in Figure 2a, the temperature of the area irradiated by laser was higher than that of nonirradiated areas. In contrast, the temperature changes of pristine alginate fibers were much smaller than that of Alg/GNR composite fibers ( Supporting Information Figure S1c). These results suggested that the energy conversion from light to heat was mainly achieved by introducing GNRs. Subsequently, the photothermal-mechanical behaviors of Alg/GNR composite fibers were investigated by tensile testing. Alternating on/off irradiation of 808 nm laser (1 W) was applied to the fibers during the tensile testing. Interestingly, the mechanical performance of the composite fibers can be manipulated reversibly by alternating 808 nm laser irradiation (Figure 2b). When the fibers were subjected to 808 nm laser irradiation, the slope of the stress–strain curve became steeper, indicating that Young's modulus of the fibers was significantly enhanced. In contrast, the composite fibers demonstrated a remarkable decrease in stress after switching off the 808 nm laser irradiation (Figure 2c). Notably, under the periodic on and off of the NIR light irradiation, the stress–strain curves exhibited a regular sawtooth shape with a generally increasing trend in stress as the strain increased. It should be noted that the photothermal behavior barely affects the mechanical properties of pristine alginate fibers under the same conditions ( Supporting Information Figure S2a). This phenomenon can be attributed to the photothermal effect of GNRs under NIR light irradiation, which can be ignored when compared to that of pristine alginate fibers. Figure 2 | Photothermal-mechanical behaviors of GNR-complexed alginate composite fibers. (a) Infrared image of GNR-complexed alginate composite fibers upon 808 nm irradiation (1 W). (b) Typical stress–strain curves of composite fibers (Alg∶GNR = 10∶1) under periodic switching between on and off of NIR light irradiation. The sawtooth-like variation curve observed under the periodic on/off irradiation suggests that the mechanical property of the fibers can be enhanced and reversibly manipulated by the photothermal-mechanical effect. (c) Variation of Young's modulus and stress difference between neighboring irradiation calculated from (b) after different on/off irradiation cycles. ΔM is calculated according to the equation ΔM = Mx−M1, in which the slope after yielding point is set as M1 and each slope after x round irradiation is set as Mx (slope of the pink area in Figure 2b). In addition, ΔS represents the stress difference after each irradiation (stress difference of the pink area in Figure 2b). Of note, the irradiation time is approximately the same for each round. (d) Influence of the GNR content on the mechanical performance of the composite fibers. *p = 0.035 (Alg vs Alg∶GNR = 10∶1) <0.05, **p = 0.0038 (Alg vs Alg∶GNR = 20∶1), and 0.0075 (Alg vs Alg∶GNR = 50∶1) <0.01, ns p = 0.436 (Alg vs Alg∶GNR = 100∶1). (e) Influence of different PTAs on the mechanical performance of the composite fibers. **p = 0.0060 (Alg/GNR vs Alg/UCNP), and 0.0036 (Alg/UCNP vs Alg/Ag3AuS2) <0.01. (f) Dependence of the mechanical performance on the power density of the NIR light irradiation, including 1, 3, and 4 W. A higher power density of the NIR light irradiation results in a larger Young's modulus. ***p = 0.0006 <0.001, ****p < 0.0001. Download figure Download PowerPoint To further explore the photothermal-mechanical behaviors induced by GNRs, the different mass ratios of alginate to GNR was investigated, including 10∶1, 20∶1, 50∶1, and 100∶1 ( Supporting Information Figure 2b–e). Under periodic switching between on and off of NIR light irradiation, the tensile strength of the composite fibers (Alg∶GNR = 10∶1) did not exhibit any noticeable increase when compared to that of pristine alginate fibers, as shown in Supporting Information Figure 2a,b. In contrast, the mechanical performance of the fibers was significantly enhanced when decreasing the GNR content (Alg:GNR = 20:1 and 50:1) ( Supporting Information Figure 2c,d). Similar tooth-like variation was observed in the stress–strain curves under periodic on/off irradiation while the ultimate tensile strength of the fibers increased to 76.1 ± 31.9 MPa for the samples with Alg∶GNR = 20∶1 and 96.4 ± 17.3 MPa for the samples with Alg∶GNR = 50∶1, which is much higher than that of pristine fibers, fibers with Alg∶GNR = 10∶1, and fibers with Alg∶GNR = 100∶1. However, the tensile strength of composite fibers decreased when further decreasing GNR content (Alg∶GNR = 100∶1) ( Supporting Information Figure S2e). The extremely low GNR content cannot generate enough heat to evaporate water within the fiber to improve the fiber's mechanics. It is noteworthy that similar mechanical performance of composite fibers was observed upon direct heating instead of NIR light irradiation ( Supporting Information Figure S3). Generally, GNRs will reduce the cross-linking density of the alginate matrix, thereby yielding lower tensile strength of the composite fibers without NIR light irradiation ( Supporting Information Figure S4). However, adequate content of GNRs can significantly enhance the fiber's Young's modulus and tensile strength under NIR light irradiation through the photothermal-mechanical behavior. To systematically investigate the system, we explored the influence of several other parameters on the photothermal-mechanical behavior of the composite fibers, including the irradiation method, type of PTAs, and irradiation power density. It was found that the Young's modulus of fibers increased under continuous NIR light irradiation (808 nm, 1 W) (Figure 2d and Supporting Information Figure S5). In particular, the composite fibers with a mass ratio of Alg∶GNR=10∶1, 20∶1, and 50∶1 exhibited a significant improvement in Young's modulus under this condition, showing a modulus difference (ΔM) of 110.7 ± 19.8 MPa, 113.1 ± 10.8 MPa, and 145.7 ± 22.4 MPa, respectively ( Supporting Information Table S1), which is larger than that of pristine alginate fibers. However, those values decreased to 64.1 ± 3.9 MPa when further decreasing the GNR content (Alg∶GNR=100∶1). In addition to GNRs, the influence of other types of PTAs on the fiber's mechanics was investigated by continuous 808 nm irradiation, such as UCNP and Ag3AuS2 (Figure 2e and Supporting Information Figure S6). It should be noted that the mass ratio of alginate to PTA is 50∶1 for the experiments. The results show that Young's modulus of Alg/UCNP fibers only increased to 51.2 ± 11.5 MPa after continuous NIR light irradiation (808 nm, 1 W). In sharp contrast, this value increased significantly to 169.6 ± 7.9 MPa (Alg/Ag3AuS2 fibers) and 145.7 ± 22.4 MPa (Alg/GNR fibers) under the same conditions ( Supporting Information Table S2). This difference can be attributed to the higher photothermal conversion efficiency of GNRs and Ag3AuS2 than UCNP in the alginate matrix.37–39,41,42 These results also indicate the universality of our strategy. The NIR-responsive behavior of Alg/GNR (Alg∶GNR = 20∶1) fibers was further investigated under 808 nm light irradiation of different power densities (Figure 2f and Supporting Information Figure S7). The power density's dependence on the fiber's mechanics was observed ( Supporting Information Table S3). Apparently, a higher power density of NIR light resulted in a higher heating density, which is beneficial for manipulating the fiber's mechanics. Notably, the variation of Young's modulus in the fibers was ∼426.5 ± 22.8 MPa when irradiated with 4 W 808 nm light, which is approximately four times higher than that of fibers irradiated with 1 W 808 nm light. Overall, these results demonstrate that the photothermal effect can be used to manipulate the mechanical properties of composite fibers. To gain more insight into Alg/GNR fibers, we performed FT-IR spectroscopy to investigate the structural changes during the heating from 30 to 120 °C. Three typical spectral regions, including 3700–2700, 1700–1540, and 1090–960 cm−1, were compared in detail ( Supporting Information Figure S8). It was found that the O–H stretching vibrations (3600–3000 cm−1) exhibited an obvious decrease in intensity due to the evaporation of water upon heating while C–H stretching vibrations (3000–2800 cm−1) were barely affected. Meanwhile, the COO− asymmetric stretching vibrations (1700–1540 cm−1) and C–O stretching vibrations (1090–940 cm−1) showed a blueshift and a redshift, respectively, which could be attributed to the variations of hydrogen bonding upon heating. To understand the molecular interactions within the alginate/GNR composite fibers, especially the dynamic evolution of hydrogen bonding, 2D COS was employed to explore subtle spectral changes under external perturbations, including temperature and concentration (Figure 3 and Supporting Information Figures S8–S10).43 The synchronous and asynchronous 2D correlation spectra of calcium alginate/GNR films in the spectral regions of and cm−1 are shown in Figures and to the spectral changes during heating can be as cm−1 cm−1 cm−1 cm−1 cm−1 The of the to the are in Table The spectral results that in water in in the It should be noted that the asymmetric stretching vibrations of COO− with calcium are also at cm−1, which is to change due to its higher energy when compared to hydrogen These results indicate that alginate hydrogen bonds with water before heating, and dehydration of alginate upon heating. Subsequently, and COO− form inter-/intramolecular hydrogen such as and in the The formation of inter-/intramolecular hydrogen bonds the cross-linking density effectively and the mechanical performance, yielding a high modulus. Figure 3 | 2D synchronous (a) and asynchronous (b) correlation spectra of calcium alginate/GNR during heating between 30 and 120 °C. In 2D synchronous positive are as red similar to temperature In contrast, negative cross are as blue to temperature Download figure Download PowerPoint Table 1 | of the Calcium in the 2D COS Results water in hydrogen in in the The observed photothermal-mechanical behavior of Alg/GNR composite fibers is different from conventional fibers. Generally, upon heating, the of molecules which the of stress within the matrix and to a decrease in mechanical However, in Alg/GNR composite fibers, an in the mechanical performance is observed upon heating, which is attributed to the change of molecular interactions within the matrix (Figure NIR irradiation, alginate molecules to form hydrogen bonds with water Under NIR irradiation, GNRs energy into energy and increase the temperature in the system, of the water molecules and the composite fibers. In the of water molecules, alginate molecules to form inter-/intramolecular hydrogen which effectively increase the cross-linking density and the fiber's modulus. After off the NIR light irradiation, the temperature to room temperature, and the fiber's mechanics are due to the of hydrogen bonding between water molecules and alginate through design of the system on the molecular the of NIR light irradiation to molecular interactions within the fibers can changes in the bulk mechanics on the macroscopic this point of our composite fibers can be applied in the of smart the of or laser by composite fibers is due to their photothermal behavior. However, the mechanical performance and mass of composite fiber to be Figure 4 | of the mechanism for the photothermal-mechanical behaviors of alginate/GNR composite fibers. NIR irradiation, water molecules to alginate molecules via hydrogen When water molecules are due to the photothermal effect of GNRs under NIR irradiation, hydrogen bonds alginate molecules, effectively to the cross-linking density within the alginate matrix, thereby the mechanical property of the system. Download figure Download PowerPoint We the design and of biological composite fibers with photothermal-mechanical Interestingly, the mechanical properties of biological composite fibers can be modulated by alternating NIR light irradiation. In particular, the Young's modulus of these biological composite fibers increased approximately four times upon NIR light irradiation. the mechanical properties of such fibers can be reversibly and effectively manipulated on demand by the photothermal effect. In the system, the dynamic evolution between disassembly and of inter-/intramolecular hydrogen bonding is for the photothermally induced mechanical this work represents a new strategy for the intrinsic mechanism between macroscopic mechanical performance and microscopic molecular The photothermal-mechanical properties of the composite biological fibers are for in which mechanical is Supporting Information Supporting Information is and and characterization of is of to Information This work is by the Science of and the Key of and and from Science of Guangdong and The are also for the at the BL19U2 of the Facility for Science Shanghai at for during of to with and Li Li Key for the of Organic and and for Li Wang Ma Liu Zhang Fibers with Properties by 3, Li Ma Wang W. Zhang Liu and of Zhang for and Zhang Ma Chen Liu and by Liu Zhang Li Chen Wang Zhang Liu and with and Wang Li Wu Ma Chen Zhang Liu with and Switchable in Wang Wang through Chemical for the of Liu Chen of in of from Wang Zhang Liu 1, Materials with Chen from of Liu with Switchable Li Chen for Energy to Li for Materials from to and at the of the of Materials a of Materials as a for in in and in the of the in A for W. of Wu as a for Wan Wu as and in Wang for Switchable of Wan Wu Chen Chen Fan Zhang Liu of of and on Li Liu Li Wang for In Liu Li Ma Liu Zhang Wang and with Chen Liu Fabrication by Zhang Chen Ma Zhang Au for of Wang Wang for in Wu the Hydrogen-Bond in Alginate through Infrared in Zhang Wang of and Alginate on a Information Chinese Chemical are also for the at the BL19U2 of the Facility for Science Shanghai at for during times

Topics & Concepts