Electrospun Nanobelt-Shaped Polymer Membranes for Fast and High

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Applications of Polymer, Composite, and Coating Materials

Electrospun Nanobelt-Shaped Polymer Membranes for Fast and High Sensitivity Detection of Metal Ions Yiqun Qiao, Cuiping Shi, Xiaolin Wang, Panpan Wang, Yichi Zhang, Daoyuan Wang, Ruirui Qiao, Xichang Wang, and Jian Zhong ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b19839 • Publication Date (Web): 10 Jan 2019 Downloaded from http://pubs.acs.org on January 15, 2019

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ACS Applied Materials & Interfaces

Electrospun Nanobelt-Shaped Polymer Membranes for Fast and High Sensitivity Detection of Metal Ions Yiqun Qiao,†,§ Cuiping Shi,†,§ Xiaolin Wang,† Panpan Wang,† Yichi Zhang,† Daoyuan Wang,† Ruirui Qiao, ‡ Xichang Wang, † Jian Zhong*,†,⊥ †Integrated

Scientific Research Base on Comprehensive Utilization Technology for By-Products

of Aquatic Product Processing, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Laboratory of Quality and Safety Risk Assessment for Aquatic Products on Storage and Preservation (Shanghai), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Shanghai Engineering Research Center of Aquatic-Product Processing and Preservation, College of Food Science & Technology, Shanghai Ocean University, Shanghai 201306, China. ‡ARC

Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute

of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia ⊥ State

Key Laboratory of Molecular Engineering of Polymers (Fudan University), Shanghai

200438, China.

KEYWORDS: electrospinning, iron ion, nanobelt, nanofiber, sensor, zein

1 Environment ACS Paragon Plus

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ABSTRACT: Until now, no polymer nanobelt-shaped materials have been developed as electrochemical, optical, and mass sensors. In this work, we firstly develop polymer nanobeltshaped membranes for fast and high sensitivity detection of metal ions, which is fabricated by a new nanobelt-based processing method with simultaneous zein matrix crosslinking and curcumin crosslinking. Their morphologies, optimal detection pH, ion selectivity, and ion detection sensitivity are systematically analyzed. The limits of detection of electrospun curcumin-loaded zein membranes with a detection time of 0.5 h are: crosslinked nanobelt-shaped membranes (0.3 mg/L) < uncrosslinked nanobelt-shaped membranes (1 mg/L) ≈ crosslinked nanofibrous membranes (1 mg/L) < uncrosslinked nanofibrous membranes (3 mg/L). The crosslinked nanobelt-shaped membranes are also applied to detect Fe3+ in drinking water and environmental water. Finally, the mechanisms of Fe3+ detection by these membranes are studied and discussed. The results demonstrate that the difference of limit of detection is depended on if curcumin sensor is crosslinked or not and the membrane nanostructures (nanobelts or nanofibers). Crosslinking produces stable sensor molecules on the surface and therefore induces low limits of detection. Compared with nanofibers, nanobelts have a higher surface-to-volume ratio, and can have more sensor molecules on their surfaces and therefore have lower limits of detection. In addition, the as-prepared membranes had good membrane storage stability (at least three months at room temperature). All these results suggest that crosslinked electrospun nanobelt-shaped membranes by a new nanobelt-based processing method are ideal platforms for sensing. We believe it will attract increasing attentions in scientific and engineering fields such as materials, environmental, and food science.


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1. INTRODUCTION Inorganic (e.g. tin dioxide,1-6 Bi2O3-core/ZnO-shell,7 SnO2-core/In2O3-shell,8 Vanadium Pentoxide,9 and zinc sulfide.10) nanobelt-shaped sensors have been explored as electrochemical sensors for gas sensing,1-5, 7-9 nerve agent detection,6 ultraviolet-light sensing,10 etc. Cordination polymer single molecular layer-like nanobelts have been developed as optical biosensors for the detection of nucleic acids 11, 12 and antibacterial agents.13 However, to the best of our knowledge, no non-cordination polymer nanobelt-shaped materials have been developed as electrochemical, optical, and mass sensors. Electrospinning technique has been widely used to fabricate polymer nanofiber and has attracted increasing attention in recent decades due to its versatility and potential for application in many scientific and technical fields.14-18 The fabricated electrospun nanofibrous membranes have been widely applied in many notable application fields such as tissue engineering,19-21 drug delivery,22 enzyme immobilization,23,

24

sensors,25 and filtration,26 and energy research.27

Electrospun nanofibrous membrane-immobilized chemosensors are effective for detecting analytes because of the advantages such as easy fabrication and functionalization, low cost, easy detection operation, controllability, high porosity, environmental friendly to the detection solution and easy post-treatment after the detection process. Compared with conventional bulk materials, electrospun nanofibrous membranes can immobilize more chemosensors or receptors due to their high surface-to-volume ratio, and therefore, electrospun nanofirous membraneimmobilized chemosensors/receptors had lower detection limits. More and more scientists in the field of sensors have started to explore the application of electrospun nanofibrous membraneimmobilized chemosensors/receptors.14 Magnetic-fluorescence bifunctional polymer coaxial nanobelts have been successfully prepared by a modified coaxial spinneret electrospinning



technique.28-30 However, to the best of our knowledge, polymer nanobelt-shaped materials have not been successfully fabricated by single-spinneret electrospinning technique. Zein is an ethanol-soluble and edible natural organic polymer and has a variety of use in food, medical, and chemical industries. Electrospun nanofibrous zein membranes have been explored in the field of biomedical engineering and sensors. Especially, crosslinking agents such as glyoxal

31

and citric acid

32, 33

were applied to improve the mechanical properties and water

stability of electrospun nanofibrous zein membranes. Fe3+ ion plays an important role in biological and environmental systems. It is a cofactor in many in vivo biological processes such as oxygen transport, electron transport, and enzymatic reactions. A deficiency of Fe3+ ions limits the normal functions of cells and tissues, resulting in fatigue, poor work performance, and decreased immunity.34 Conversely, excess amounts of Fe3+ ion induce function deterioration of some organs such as heart, pancreas and lungs, and even to some types of cancers.35 Thus, it is important to develop a simple and easy observation method with a low limit of detection for daily detection of drinking water, aquaculture water, environmental water, etc. Many simple and easy determination methods of Fe3+ ions in a liquid medium have been developed based on fluorescence methods,36 ultraviolet methods,37 and visible light methods.38 In visible light methods, the presence of metal ions can induce the visible color change, which can be seen by naked eye, digital cameras, and visible spectroscopy. Conversely, large-scale instruments such as fluorescence and ultraviolet lamp/microscopy/spectrometry are required for fluorescence and ultraviolet methods, respectively. Therefore, visible light methods are more suitable for simple detection of metal ions in a family and an aquaculture farm. Curcumin is a yellow extract from the root of the plant Curcuma longa linn. Many studies


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have already demonstrated that curcumin could chelate with metal ions to form complexes to decrease heavy metal damages for human being.39, 40 Its chelating ability with some ions can be potentially applied in the sensor field. Until now, curcumin has been applied as sensors for the detection of Yttrium,41 fluoride ions,42 and cyanide.43 Our previous work also proved the curcumin-loaded electrospun nanofibrous cellulose acetate

2. RESULTS 2.1.

Preparation and Characterization of Electrospun Nanobelt-Shaped Membranes In this work, electrospinning technique was applied to prepare electrospun nanobelt-shaped

curcumin-loaded zein membranes using pure ethanol as a solvent. The same zein/citric acid/curcumin (1:0.09:0.05) mass ratio and different zein concentrations (25%, 30%, 35%, 40%, w/v) was applied to fabricate nanobelts. The obtained curcumin-loaded zein membranes were collected on a cover glass and were observed by optical microscopy, as shown in Figure S1. Some short nanobelts and microparticles were fabricated using 25% (w/v) zein solution (Figure S1A). A large number of long nanobelts and few microparticles were fabricated using 30% (w/v) zein solution (Figure S1B). A large number of long nanobelts and almost no microparticles were fabricated using 35% (w/v) zein solution (Figure S1C). In addition, 40% zein solution was too thick to be applied to fabricate nanobelts (Data not shown). Therefore, 35% zein solution was chosen for the preparation of electrospun curcumin-loaded zein membranes in further studies. The unheated and heated (150 ℃, 2.5 h) electrospun curcumin-loaded zein and pure zein membranes using 35% (w/v) zein solution were taken off from the stainless-steel rod and then were cut into round membrane patches with a diameter of 8 mm, as shown in Figure 1. The weight loss after the heating was 9.0%±0.1% by weighing the round membrane patches before



and after heating. Unheated pure zein membranes, heated pure zein membranes, unheated curcumin-loaded zein membranes, and heated curcumin-loaded zein membranes showed the colors of white, grey white, yellow, and dark yellow, respectively (Figure 1C). SEM results (Figure 1D-G) confirmed the successful fabrication of a large number of zein nanobelts. AFM results (Figure 1I-M) showed the widths were larger than the heights according to the sectional analyses, which further confirmed that these membranes were consisted of nanobelts, not nanofibers. Therefore, Electrospun nanobelt-shaped curcumin-loaded zein membranes were successfully fabricated using ethanol as a solvent. The characteristic peaks of zein, citric acid, and curcumin and their changes in the electrospun curcumin-loaded zein membranes were analyzed by ATR-FTIR spectroscopy. ATRFTIR spectra of these four types of curcumin-loaded zein membranes are shown in Figure 1H. FTIR spectra of pure and mixture chemical powers using a KBr pellet method are shown in Figure S2, which showed their characteristic peaks and also suggested that characteristic peak intensity was related with composite mass ratio of the mixture powders. According to FTIR spectra of zein, curcumin, and citric acid (Figure S2) and their chemical structures (Figure S3), the characteristic peaks of zein in the electrospun nanobelt-shaped curcumin-loaded zein membranes (Figure 1H) were observed at 3290 (m, broad) and 3069 (w) cm-1 assigned to N-H stretching of amide I band, 1641 (s) cm-1 assigned to C=O stretching of amide I band, and 1530 (m) cm-1 assigned to N-H bending of amide II band. Compared with the characteristic peaks of zein, the characteristic peak of citric acid was observed at 1722 (w) cm-1 assigned to C=O stretching of the carboxyl group in Figure 1H. Compared with the characteristic peaks of zein and citric acid in Figure 1H and the characteristic peaks of curcumin powder in Figure S2, the characteristic peak of curcumin was observed at 1031 (w) cm-1 assigned to C-O stretching of


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ether in Figure 1H. The intensity of characteristic peak 1722 (w) cm-1 of citric acid was decreased after the heating treatment process (150 ℃ for 2.5 h), which suggested the carboxyl group of citric acid was activated. 2.2.

Fe3+ Detection Using Electrospun Nanobelt-Shaped Membranes The unheated and heated electrospun nanobelt-shaped curcumin-loaded zein membranes

was applied for metal ion detection. The optimal pH of Fe3+ ion detection by unheated and heated electrospun nanobelt-shaped curcumin-loaded zein membranes was studied, as shown in Figure 2. Both unheated (Figure 2A) and heated (Figure 2C) electrospun nanobelt-shaped curcumin-loaded zein membranes showed slight and obvious color change after incubating with 1 and 10 mg/L Fe3+ solution, respectively, for 30 min at pH 2. Especially, unheated and heated membranes showed clear color change from yellow and dark yellow to dark brown and brown, respectively, after incubating with 10 mg/L Fe3+ solution at pH 2. Moreover, unheated membranes showed more color changes compared with heated membranes at this concentration. The nanobelt-shaped curcumin-loaded zein membranes had no obvious color change after incubating with ultrapure water at pH 2. Moreover, both unheated and heated electrospun nanobelt-shaped pure zein membranes had no obvious color change after incubating with 10 mg/L Fe3+ solution at pH 2 (Figure 2E). Therefore, the color change is resulted from the chelation of Fe3+ by curcumin in these membranes. The diameter of both unheated and heated electrospun nanobelt-shaped curcumin-loaded zein membranes was decreased from 8 mm to 4.7 ± 0.1 mm and 6.5 ± 0.2 mm after incubating with Fe3+ solution. The shrinkage amount (41.2%) of unheated electrospun nanobelt-shaped curcumin-loaded zein membranes was more than that (18.2%) of heated electrospun nanobelt-shaped curcumin-loaded zein membranes. SEM images showed that unheated nanobelts (Figure 2B) interblended and had larger width than heated



nanobelts (Figure 2D). It was consistent with our previous work that nanofibers would interblend after water immersion.19 The different behaviours of heated nanobelt-shaped membranes to unheated membranes might be resulted from zein matrix crosslinking during the heating process. During the ion detection process (membranes were immersed in the aqueous solution), unheated nanobelts shrinked in length and expanded in width, whereas heated nanobelts only showed less shrinkage and less expansion. Therefore, the shrinkage amount of the unheated membranes was significantly larger than that of the heated membranes, which suggested zein matrix crosslinked during the heating process. The significant shrinkage of unheated membranes also induced significant color change at 10 mg/L Fe3+ solution compared with heated membranes because of less surface area. ATR-FTIR spectra of unheated and heated curcumin-loaded zein membranes after incubating with 10 mg/L Fe3+ solution at pH 2 are shown in Figure 2F. Compared with the curcumin-loaded membranes before incubation (Figure 1H), no obvious changes were observed in the ATR-FTIR spectra. The possible reason might be that only 5% curcumin was present in the membranes and the ATR-FTIR spectra signals of Fe3+-curcumin interaction were masked. The ion selectivity of unheated and heated electrospun nanobelt-shaped curcumin-loaded zein membranes for many types of metal ions was studied. The results were observed by naked eye and digital camera, as shown in Figure 3A and 3B. Both unheated and heated electrospun nanobelt-shaped curcumin-loaded zein membranes showed obvious color change from yellow and dark yellow to dark brown and brown, respectively, after incubating with 10 mg/L Fe3+ solution and a little bit color change after incubating with 10 mg/L Fe2+ solution. It further demonstrated that curcumin in zein membranes could chelate Fe3+ and Fe2+ ions to induce the membrane color change. It was consistent with previous conclusion that curcumin can chelate


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with Fe3+ and Fe2+ ions and the chelate binding is more specific for Fe3+ than Fe2+.44 In order to analyze the effect of heating process, the unheated and heated membranes (Label 16 in both Figure 3A and 3B) were used as control, which confirmed that unheated curcumin-loaded zein membranes had more obvious color change than heated curcumin-loaded zein membranes, which was consistent with above results (Figure 2). The shrinkage amount of nanobelt-shaped membranes was also consistent with above results (Figure 2). These results further confirmed the above analyses according to Figure 2. The sensitivity of unheated and heated electrospun nanobelt-shaped curcumin-loaded zein membranes for Fe3+ was studied. The results were observed by naked eye and digital camera, as shown in Figure 3C. The results demonstrated that the limits of detection of unheated and heated nanobelt-shaped curcumin-loaded zein membranes were 1 mg/L and 0.3 mg/L compared with the membranes in ultrapure water, respectively. According to the drinking water standards of the World Health Organization (Guidelines for Drinking-water Quality, Fourth Edition) and Standardization Administration of the People's Republic of China (GB 5749-2006), the permissible limit of Fe3+ in water is 0.3 mg/L. Therefore, the heated nanobelt-shaped curcuminloaded zein membrane could be applied to check the Fe3+ amount in drinking waters and to judge if the water satisfy the water standard. In addition, the Fe3+ solutions after the incubation were also observed by naked eye and digital camera, as shown in Figure 3D. Curcumin molecules in unheated membranes dissolved/suspended into the Fe3+ solutions during the incubation process, whereas curcumin molecules in heated membranes could not dissolve/suspend into the Fe3+ solutions during the incubation process. It suggested that curcumin molecules were crosslinked with zein matrix during the heating process.



The effect of detection temperatures of 7 mg/mL Fe3+ solution (4℃, room temperature, 37℃, and 60℃) on the Fe3+ fast detection of heated nanobelt-shaped membrane patches were studied, as shown in Figure S4. The results demonstrated color deepened with the increase of detection temperature, which suggested the detection temperature had an obvious effect on the Fe3+ fast detection. In addition, membrane storage stability was also studied. Four types of nanobeltshaped zein membrane patches were stored at room temperature for three months. Then the membrane patches were applied for Fe3+ detection (Figure S5). These membrane patches showed similar color changes to the membrane patches that were stored at room temperature in two weeks, which suggested the nanobelt-shaped curcumin-loaded zein membranes had good membrane storage stability (at least three months at room temperature). The heated electrospun nanobelt-shaped curcumin-loaded zein membranes were applied to detect commercial drinking water, as shown in Figure 3E. All the heated membranes in the original drinking water without color except Coca-Cola showed similar color to that in ultrapure water, which confirmed that the five kinds of commercial drinking water (Nongfu Spring water, Nestle Packaged Drinking water, Uni-president Shuiquduo lactobacillus fermented beverage, Suntory peach water, Master Kong rock candy snow pear juice) had no excessive Fe3+. The membrane in brown Coca-Cola showed significant color change to brown. Compared with the membrane in ultrapure water, the membranes in the drinking waters spiked with 0.3 mg/L Fe3+ except Coco-Cola showed slight color differences. Considering that all the commercial drinking water definitely have no excessive Fe3+, the electrospun curcumin-loaded zein membranes could not be applied to detect drinking water with color such as Coco-Cola, but to be applied to detect drinking water without color such as Nongfu Spring water and Uni-president Shuiquduo


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lactobacillus fermented beverage. It is because the electrospun curcumin-loaded zein membranes could adsorb coloring matters and could disturb the color change from Fe3+ adsorption. Further, the heated electrospun nanobelt-shaped curcumin-loaded zein membranes were applied to detect different environmental water, as shown in Figure S6. Compared with ultrapure water, the membranes showed four types of water had excessive Fe3+: Pond water@SHOU > Tap water@SHOU > Water of Dishui Lake ≈ Water of East Ocean > 0.3 mg/L. It demonstrated that the heated electrospun nanobelt-shaped curcumin-loaded zein membranes could be applied to detect Fe3+ in environmental water. 2.3.

Fe3+ Detection Using Electrospun Nanofibrous Membranes Electrospinning technique was applied to prepare electrospun nanofibrous curcumin-loaded

zein membranes using ethanol/water (7:3, v:v) solution as a solvent. The obtained curcuminloaded zein membranes were collected on a cover glass and were observed by optical microscopy. Similar zein/citric acid/curcumin (1:0.09:0.05) mass ratio to nanobelt fabrication (Figure 1) was applied to prepare the electrospinning solution. 30%, 35%, and 40% (w/v) zein in ethanol/water (7:3, v:v) solutions were too thick to be applied to fabricate nanobelts/nanofibers (Data not shown). 25% zein in ethanol/water (7:3, v:v) solutions can be applied to fabricate nanofibers, as shown in Figure 4A-D. Optical microscopy image (Figure 4A) and SEM image (Figure 4B) showed the successful fabrication of a large number of long nanofiber. AFM result (Figure 4D) showed the width was similar to the height according to the sectional analyses, which were obviously different to the AFM results of electrospun nanobelts (Figure 1I-M). It confirmed that they are nanofibers, not nanobelts. After that, the unheated and heated electrospun nanofibrous curcumin-loaded zein membranes were applied to detected Fe3+ solution with



different concentrations (Figure 4E). The results demonstrated that the limits of detection of unheated and heated nanofibrous curcumin-loaded zein membranes were 3 mg/L and 1 mg/L compared with the membranes in ultrapure water, respectively. They were higher than those of unheated and heated nanobelt-shaped curcumin-loaded zein membranes (Figure 3C). Moreover, the color changes of all the samples were significantly less than those of nanobelt-shaped membranes (Figure 3C). According to the drinking water standards of the World Health Organization (Guidelines for Drinking-water Quality, Fourth Edition) and Standardization Administration of the People's Republic of China (GB 5749-2006), the heated nanofibrous curcumin-loaded zein membrane could not be applied to detect Fe3+ in drinking water. The diameter of both unheated and heated electrospun nanofibrous curcumin-loaded zein membranes was decreased from 8 mm to 3.4 ± 0.2 mm and 6.0 ± 0.2 mm after incubating with Fe3+ solution. The shrinkage amount of curcumin-loaded zein membranes were: unheated nanofibrous membrane (57.5%) > unheated nanobelt-shaped membrane (41.2%) > heated nanofibrous membrane (25.0%) > heated nanobelt-shaped membrane (18.2%). In addition, the Fe3+ solutions after the incubation were also observed by naked eye and digital camera, as shown in Figure S7. Curcumin molecules in unheated membranes dissolved/suspended into the Fe3+ solutions during the incubation process, whereas curcumin molecules in heated membranes could not dissolve/suspend into the Fe3+ solutions during the incubation process. It was consistent with the results of nanobelt-shaped curcumin-loaded zein membranes (Figure 3D) and further suggested that curcumin molecules were crosslinked with zein matrix during the heating process. 3. DISCUSSION


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In this work, unheated and heated (150 ℃ for 2.5 h) electrospun nanobelt-shaped and nanofibrous polymer membranes were successfully fabricated and applied for fast detection of Fe3+ in ultrapure water, drinking waters, and environmental waters. The results demonstrated heated electrospun nanobelt-shaped curcumin-loaded zein membranes had the lowest limit of detection (0.3 mg/L), which suggested the as-prepared membranes could be applied to check the Fe3+ amount in drinking waters and environmental waters and to judge if the water satisfy the water standard of WHO. Moreover, the as-prepared membranes had good membrane storage stability (at least three months at room temperature). During Fe3+ detection using electrospun nanobelt-shaped membranes (Figure 2), unheated nanobelts shrinked in length and expanded in width, whereas heated nanobelts only showed less shrinkage and less expansion. The shrinkage amount of curcumin-loaded zein membranes were (Figure 2 and 4): unheated nanofibrous membrane (57.5%) > unheated nanobelt-shaped membrane (41.2%) > heated nanofibrous membrane (25.0%) > heated nanobelt-shaped membrane (18.2%). This suggested zein matrix crosslinked during the heating process. Further, the sensitivity detection of unheated and heated electrospun nanobelt-shaped (Figure 3D) and nanfibrous (Figure S7) curcumin-loaded zein membranes for Fe3+ demonstrated curcumin molecules in unheated membranes suspended into the Fe3+ solutions during the incubation process, whereas curcumin molecules in heated membranes could not suspend into the Fe3+ solutions. It suggested that curcumin molecules were crosslinked with zein matrix during the heating process. Therefore, simultaneous zein matrix crosslinking and curcumin crosslinking occurred during the heating process. We can name the unheated membranes as uncrosslinked membranes and heated membranes as crosslinked membranes.



Chemical crosslinking is an important method and has been widely applied for the stability enhancement of proteins and enzymes,45 the mechanical improvement of materials,46 synthesis of new polymers,47 protein immobilization,48 etc. In order to analyze the mechanisms of zein matrix crosslinking and curcumin sensor crosslinking, ATR-FTIR spectroscopy was applied to characterize the functional group changes of zein, citric acid, and curcumin during the heating process (150 ℃ for 2.5 h). The effects of the heating treatment process on single component pure powders and deposited films (the single component solutions were adjusted to pH 4.9 before deposition) were studied by ATR-FTIR spectroscopy, as shown in Figure S8-S9. The results showed heating had no obvious effect on zein powder and film. Compared with unheated (uncrosslinked) curcumin powder and film, heated (crosslinked) curcumin power and film (Figure S8 and S9) showed the intensity of characteristic peak 3512 (m, sharp) cm-1 for O-H stretching of hydroxyl group and 1626 (s, sharp) for C=O stretching of carbonyl group were decreased, which suggested the phenolic hydroxyl group and the C=O group were decreased or activated after the heating process. In addition, the appearance of characteristic peak 3363 (m, broad) cm-1 demonstrated hydrogen bond formation among curcumin molecules. The characteristic peak 1602 (m) cm-1 for C=C stretching band of alkene was moved to characteristic peak 1577 cm-1, which significantly increased. Therefore, β-diketo structure of curcumin was changed to enol form (Figure S13A) and then hydrogen bonds were formed between hydroxyl groups of two close curcumin molecules. Compared with unheated citric acid powder and film, heated citric acid power and film (Figure S8 and S9) showed the intensity of the characteristic peak 1728 (s) cm-1 (powder) or 1708 (m) cm-1 (film) for C=O stretching of the carboxyl group were decreased. In addition, the


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appearance of characteristic peak 3602 (m, sharp) cm-1 demonstrated the presence of free carboxylic acid. Therefore, the carboxyl group was activated after the heating process. The effects of the heating process (150 ℃ for 2.5 h) on two-component films (the solutions were adjusted to pH 4.9 before deposition) among pure zein, citric acid, and curcumin were studied by ATR-FTIR spectroscopy, as shown in Figure S10-S12. Firstly, the effect of heating on zein/citric acid films with different mass ratios was studied by ATR-FTIR spectroscopy (Figure S10). The intensity of the characteristic peak 1719 (w) cm-1 for C=O stretching of the carboxyl group and 1224 (m) cm-1 for C-O stretching of the carboxyl group were decreased, which suggested the carboxyl group was decreased or activated. The intensity of the characteristic peak 1387 (m) cm-1 for C-N stretching of amide group was increased, which suggested amide group was formed during the heating process. Therefore, zein molecules were amide-crosslinked via amidation reaction between the carboxyl group of citric acid and the amino group of zein (Figure S13B). The zein matrix crosslinking could occur during the heating process and the mechanism was proposed as shown in Figure 5A. Secondly, the effect of heating on curcumin/citric acid film with a mass ratio of 50:50 was studied by ATR-FTIR spectroscopy (Figure S11). The appearance of characteristic peak 3350 (m, broad) cm-1, which was consistent with the result to pure curcumin film after heating treatment (Figure S9), demonstrated hydrogen bonds were formed among curcumin molecules. The characteristic peak 1583 (m) cm-1 for C=C stretching band of alkene was moved to characteristic peak 1570 cm-1, which significantly increased. Therefore, β-diketo structure of curcumin was changed to enol form and then hydrogen bonds were formed between hydroxyl groups of two close curcumin molecules, which was consistent with the heating effect on pure curcumin powder and film, as discussed above (Figure S9). The intensity of the characteristic peak 1717 (s) cm-1 for C=O stretching of the



carboxyl group was decreased. In addition, the intensity of the characteristic 1023 (w) cm-1 for C-O stretching of ether was decreased, which suggested that the ether bond was broken to form phenolic hydroxyl group during the heating process. Considering the sensor crosslinking occurred during the heating process. The most possible crosslinking reaction occurred between the carboxyl group of citric acid and the phenolic hydroxyl group of curcumin after the ether bond break (Figure S13C). Therefore, the curcumin sensor crosslinking could occur during the heating process and the mechanism was proposed as shown in Figure 5B. In the presence of citric acid, curcumin molecule was crosslinked to zein matrix via a citric acid arm. Concerning on unheated and heated deposited zein/curcumin films with different mass ratios, no significant peak changes were shown (Figure S12), which suggested that zein molecules could not react with curcumin molecules during the heating treatment process. Curcumin molecule has two possible sites to interact with metal: the phenolic hydroxyl group and the β-diketo moiety. Both sites have been recognized as important groups for the biological activity of curcumin.49 ATR-FTIR spectra of the curcumin-Fe3+ interaction films (Figure S14) showed all characteristic peaks had no obvious changes except the appearance of characteristic peak 3285 (m, broad) cm-1, which suggested the formation of hydrogen-bonded enol form of the β-diketo moiety. Previous work showed four major and other minor forms of metal interaction with the βdiketo moiety are known by keto-enol tautomerism, as shown in Figure S15.39 Type A indicates metal chelation with an ionic enolic form. Its FTIR spectrum generally has two strong bands between 1570 and 1525 cm-1 and two bands between 1400 and 1280 cm-1, associated with the coupled C=O and C=C stretching, respectively. Type B indicates metal chelation with a neutral ketonic form. Its FTIR spectrum generally has higher wavelengths of the carbonyls found


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between 1700 and 1650 cm-1. Type C indicates metal chelation with a neutral enolic form with only monodentate corordination to the metal. Its FTIR spectrum generally has two carbonyl bands at 1630 and 1560 cm-1. Type D indicates metal binding to the central γ-carbon of the ionic ketonic form. Its FTIR spectrum generally has a band between 1650 and 1600 cm-1 and a band between 1350 and 1200 cm-1, associated with two C=O stretching and two C=C stretching, respectively. The ATR-FTIR spectra in Figure S14 suggested type C was the main interaction way between Fe3+ and zein-immobilized curcumin molecule in our case (Figure 5C). According to above analysis (Figure S14), hydrogen-bonded enol form of the β-diketo moiety was formed during the Fe3+ detection process, which also confirmed that type C was the main interaction way between Fe3+ and zein-immobilized curcumin in our case (Figure 5C). This is also consistent with previous result that Fe3+ only can form one species of metal-curcumin complex in a 1:1 ratio. 39, 50 The uncrosslinked and crosslinked electrospun nanobelt-shaped curcumin-loaded zein membranes had limits of detection of 1 mg/L and 0.3 mg/L (Figure 3C), respectively, for Fe3+ detection. The uncrosslinked and crosslinked electrospun nanofibrous curcumin-loaded zein membranes had limits of detection of 3 mg/L and 1 mg/L (Figure 4E), respectively, for Fe3+ detection. Therefore, nanobelt-shaped membranes had lower limits of detection than nanofibrous membranes. Moreover, the color changes of nanobelt-shaped membranes (Figure 3C) were significantly higher than those of nanofibrous membranes (Figure 4E). Considering other parameters (mass ratio, fabrication conditions except the solvents) were the same, their surfaceto-volume ratios might be the reason for these differences, which could affect that they had different curcumin molecule amounts on the surfaces for Fe3+ detection. Recently, many works have already developed several chemical sensors for Fe3+ detection (Table 1). Compared to



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these chemical sensors, our crosslinked nanobelt-shaped membranes had a limit of detection of 0.3 mg/L after incubating for 0.5 h. These membranes had ideal limit of detection, fast detection time, simple detection method (no need to use complex detection instrument such as fluorescence spectroscopy), and no obvious secondary pollution (the membranes can be easily taken out after the detection of pollution substances in solution, and therefore, no obvious secondary pollution is introduced into the solution).14 Therefore, the crosslinked nanobelt-shaped membranes will have promising application in the field of environmental and food fast detection. Theoretical calculation was applied to compare the surface-to-volume ratios of a long nanobelt and a long nanofiber with same length and same sectional area (Figure 5D). The sectional surface area of a long nanobelt, 𝑆𝑆𝑛𝑏, is 𝑆𝑆𝑛𝑏 = ℎ𝑤

Eq. (1)

where h is the height of the sectional surface area of a long nanobelt. w is the width of the sectional surface area of a long nanobelt. They were designated to be consistent with previous discussions in Figure 1I-M (the width is larger than the height). Furthermore, if we define the width-to-height ratio,𝑘, as 𝑘 = 𝑤/ℎ

Eq. (2)

Where w≥h, and therefore 𝑘≥1. Combining Eq. (1) with Eq. (2), we can get the below equation (3): 𝑆𝑆𝑛𝑏 = 𝑘ℎ2 The sectional surface area of a long nanofiber, 𝑆𝑆𝑛𝑓, is


Eq. (3)

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1

𝑆𝑆𝑛𝑓 = 4𝜋𝑑2

Eq. (4)

where 𝑑 is the diameter of the sectional surface area of a long nanofiber. For the fabricated nanobelt and nanofiber with the same length, 𝑙, and the same sectional surface area, by combining Eq. (3) with Eq. (4), we can get the below equation (5): 1

𝑘ℎ2 = 𝑆𝑆𝑛𝑏 = 𝑆𝑆𝑛𝑓 = 4𝜋𝑑2

Eq. (5)

Then, we can get below equation (6): ℎ =

𝜋 4𝑘𝑑

Eq. (6)

The surface area of a long nanobelt, 𝑆𝑛𝑏, is 𝑆𝑛𝑏 = 𝑆𝑆𝑛𝑏 + 𝐿𝑆𝑛𝑏

Eq. (7)

Where 𝐿𝑆𝑛𝑏 is the lateral surface area of a long nanobelt and is 𝐿𝑆𝑛𝑏 = 𝑙 ∗ 2(ℎ + 𝑤) = 2𝑙(ℎ + 𝑘ℎ) = 2(𝑘 + 1)𝑙ℎ

Eq. (8)

Compared with 𝐿𝑆𝑛𝑏, 𝑆𝑆𝑛𝑏 can be negligible, and then we can get the below approximate equation: 𝑆𝑛𝑏 = 𝑆𝑆𝑛𝑏 + 𝐿𝑆𝑛𝑏 ≈ 𝐿𝑆𝑛𝑏

Eg. (9)

Combining Eqs. (7-9), we can get below equation: 𝑆𝑛𝑏 ≈ 2(𝑘 + 1)𝑙ℎ


Eq. (10)


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According similar calculation and approximate treatment to Eqs.(5)-(10), The surface area of a long nanofiber, 𝑆𝑛𝑓, is Eq. (11)

𝑆𝑛𝑓 = 𝑆𝑆𝑛𝑓 + 𝐿𝑆𝑛𝑓 ≈ 𝐿𝑆𝑛𝑓 = 𝑙 ∗ 𝜋𝑑 = 𝜋𝑙𝑑 Where 𝐿𝑆𝑛𝑓 is the lateral surface area of a long nanofiber. Mathematical deduction can be applied to compare 𝑆𝑛𝑏 with 𝑆𝑛𝑓 as below.

𝑆𝑛𝑏 𝑆𝑛𝑓

Further,

𝑘+1 𝜋𝑘

=

≈

(𝑘 + 1)2 𝜋𝑘

2(𝑘 + 1)𝑙ℎ 𝜋𝑙𝑑

=

=

2(𝑘 + 1)𝑙 ×

(𝑘 ― 1)2 + 4𝑥 𝜋𝑘

𝜋 4𝑘𝑑

𝜋𝑙𝑑

=

=

𝑘+1 𝜋𝑘

(𝑘 ― 1)2 + 4𝑘 𝜋𝑘

≥

Eq. (12) 4𝑘 𝜋𝑘

=

4 𝜋

>1

Eq. (13)

So, we can get below result: 𝑆𝑛𝑏 > 𝑆𝑛𝑓

Eq. (14)

𝑆𝑛𝑏

In addition, according to Eq. (12), the 𝑆𝑛𝑓 ratio as a function of 𝑘 can be produced, as shown in Fig. S16. The curve also confirmed that sectional surface area of a long nanobelt is larger than that of a long nanofiber, as analyzed by Eqs. (13) and (14). Therefore, compared with an ideal regular nanofiber with same length and same sectional surface area, an ideal regular nanobelt had a higher surface-to-volume ratio. SEM results (Figure 1F and Figure 4B) and AFM results (Figure 1L and Figure 4D) showed the sizes of nanobelts and nanofibers had no significant differences. Though the electrospun nanobelts (Figure 1) and nanofibers (Figure 4) were not as ideal as the ideal regular schematics (Figure 5D), we can reasonably speculate that electrospun nanobelts had a higher surface-to-volume ratio compared with electrospun nanofibers with same length and same sectional surface area. Compared with


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nanofibrous membranes, nanobelt-shaped membranes might have higher surface-to-volume ratio and have more curcumin sensors on their surfaces. Therefore, they have lower limits of detection for Fe3+ ions. According to our recent review work,14 preparation methods for electrospun nanofibrous membrane-immobilized chemosensors can be classified into four types: polymer-based chemical synthesis methods; polymer-based physical blending methods; nanofiber-based chemical treatment methods; and nanofiber-based physical adsorption methods. They all have their advantages and disadvantages. The first two methods have a simple and easy preparation process, but they have severe disadvantage: the sensor molecules can be dissolved into the solution during the detection, which potentially increase their limit of detection and increase the pollution risk to the solution. The last two methods had lower limits of detection and lower pollution risk, but they have several disadvantages such as the complicated chemical synthesis, low product efficacy, and high cost. Therefore, it’s necessary to develop new preparation methods for electrospun nanofibrous or nanobelt-shaped membrane-immobilized chemosensors. In this work, a new type preparation method was developed, which could be named as “nanofiber/nanobelt-based processing method”. In this method, appropriate polymer and original chemosensors/receptors were physically blended and were used to fabricate electrospun nanofibrous/nanobelt-shaped membranes. Then the membranes were processed (such as heating in this work) to crosslink original chemosensors/receptors to polymer matrix. This method has the advantages of four previous methods (simple and easy preparation, lower limit of detection, and lower pollution risk) and overcome the disadvantages (sensor molecule dissolution, complicated chemical synthesis, low product efficacy, and high cost) of four previous methods.



Overall, this nanofiber/nanobelt-based processing method had significant advantages compared with four previous methods and would attract increasing attention in the sensor fields. According to above analyses, simultaneous matrix crosslinking and sensor crosslinking of electrospun nanobelt-shaped/nanofibrous polymer membranes for the detection of Fe3+ could be illustrated, as shown in Figure 5D. (i) For crosslinked nanobelt-shaped membranes, zein, curcumin, and citric acid were mixed in ethanol (pH4.9), and then was applied to fabricate nanobelt-shaped membranes by electrospinning technique. The fabricated nanobelt-shaped membranes were heated (150 ℃ for 2.5 h) to achieve simultaneous zein matrix crosslinking and curcumin senor functionalization. Finally, the crosslinked nanobelt-shaped curcumin-loaded zein membranes were applied to detect Fe3+ in solution. During this process, curcumin could not dissolve/suspend into the solution. (ii) For uncrosslinked nanobelt-shaped membranes, zein, curcumin, and citric acid were mixed in ethanol (pH4.9), and then were applied to fabricate nanobelt-shaped membranes by electrospinning technique. The fabricated nanobelt-shaped curcumin-loaded zein membranes were directly applied to detect Fe3+ in solution. During this process, curcumin could dissolve/suspend into the solution. (iii) For crosslinked nanofibrous membranes, zein, curcumin, and citric acid were mixed in ethanol/water (pH4.9), and then was applied to fabricate nanofibrous membranes by electrospinning technique. The fabricated nanofibrous membranes were heated (150 ℃ for 2.5 h) to achieve simultaneous zein matrix crosslinking and curcumin senor functionalization. Finally, the crosslinked nanofibrous curcumin-loaded zein membranes were applied to detect Fe3+ in solution. During this process, curcumin could not dissolve/suspend into the solution.

(iv) For uncrosslinked nanofibrous

membranes, zein, curcumin, and citric acid were mixed in ethanol (pH 4.9), and then was applied to fabricate nanofibrous membranes by electrospinning technique. The fabricated nanofibrous


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curcumin-loaded zein membranes were directly applied to detect Fe3+ in solution. During this process, curcumin could dissolve/suspend into the solution. Depending on if curcumin sensor was immobilized or not and the membrane nanostructures (nanobelts or nanofibers), the limits of detection of electrospun curcumin-loaded zein membranes were: crosslinked nanobelt-shaped membranes (0.3 mg/L) < uncrosslinked nanobelt-shaped membranes (1 mg/L) ≈ crosslinked nanofibrous membranes (1 mg/L) < unclosslinked nanofibrous membranes (3 mg/L). In conclusion, we firstly developed electrospun nanobelt-shaped polymer membranes to provide higher sensitivity for metal ion detection with a fast detection time of 0.5 h compared with nanofibrous membranes. Our data suggest that simultaneous matrix crosslinking and sensor crosslinking was achieved in the new fabrication method “nanobelt-based processing method”. The limits of detection of electrospun curcumin-loaded zein membranes with a detection time of 0.5 h were: crosslinked nanobelt-shaped membranes < uncrosslinked nanobelt-shaped membranes ≈ crosslinked nanofibrous membranes < uncrosslinked nanofibrous membranes. The differences were depended on if curcumin sensor is crosslinked or not and the membrane nanostructures (nanobelts or nanofibers). Crosslinking produced stable sensor molecules on the surface and therefore induced low limits of detection. Compared with nanofibers, nanobelts had a higher surface-to-volume ratio, and could have more sensor molecules on their surfaces and therefore had lower limits of detection. The as-prepared membranes had good membrane storage stability (at least three months at room temperature). The application of polymer nanobelts and nanobelt-based processing method will attract increasing attentions in this field of materials, environmental, and food science. It should be noted that the detection temperature had an obvious effect on the Fe3+ fast detection of nanobelt-shaped membranes (Figure S4). Therefore, standard color changes as a function of Fe3+ concentrations at different detection temperatures



were required to be obtained prior to Fe3+ fast detection at different detection temperatures. In addition, it should be also noted that the optimal pH for the fast detection of Fe3+ is 2 in this work. The strong acidic condition (pH 2 used in this work) might limit the practical implementation for heavy metal detection because the user should adjust the sample pH to 2 prior to detection. Further work is necessary to develop nanobelt-based sensors that can work at natural conditions. 4. EXPERIMENTAL SECTION 4.1. Materials. Zein was purchased from Sigma-Aldrich Inc. (Milwaukee, WI, USA). Curcumin was purchased from Sigma-Aldrich Inc. (St. Louis, MO, USA). Other chemicals such citric acid and metal chemicals were of analytical reagent grade and were purchased from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). All the solutions were prepared by using ultrapure water and were used out in three days. 4.2. Preparation of electrospun nanobelt-shaped membranes. Electrospun nanobelt-shaped curcumin-loaded zein membranes were fabricated by a custom-designed electrospinning instrument. Briefly, zein (25%, 30%, 35%, and 40%, w/v) and citric acid were dissolved into ethanol, the solution pH was adjusted to 4.9, and then the solution was magnetically stirred (120 rpm) for 48 h. After that, curcumin was added into the solution and the solution was magnetically stirred (550 rpm) for 8 h. All the solutions had the same zein/citric acid/curcumin (1:0.09:0.05) mass ratio. The curcumin/citric acid/zein solution was loaded in a 5 mL syringe that was fitted with a needle (inner diameter of 0.41 mm) and placed on a syringe pump. An applied voltage of 15-18 kV was produced using a high voltage power supply (Tianjin Dongwen High Voltage Power Supply Co., Ltd, Tianjin, China). The feeding rate was 0.9 mL/h. A grounded stainless-steel rotating rod (200 mm in length and 10 mm in diameter) attached to a


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laboratory mixer motor with a rotation speed of 50-120 rpm was applied as a collector for electrospun nanobelts. The distance between the syringe needle and the collector (round stainless-steel rod) was 15-20 cm. The thickness of the electrospun nanobelt-shaped membranes was controlled by adjusting the feeding rate and the collecting time. Heating process was achieved by putting the obtained membranes on the stainless-steel rod in an oven at 150 ℃ for 2.5 h. The obtained unheated/heated nanobelt-shaped membranes were taken from the stainlesssteel rod and were cut off into round membrane patches with a diameter of 8 mm and a mass of 4.0-5.0 mg (unheated membranes) or 3.5-4.5 mg (heated membranes) for this study. The unheated/heated electrospun nanobelt-shaped pure zein membranes were prepared as controls. In this work, all the electrospun nanobelt-shaped membranes were stored at room temperature for up to 10 days except the membrane storage stability experiment (Figure S5). 4.3. Preparation of electrospun nanofibrous membranes. Electrospun nanofibrous curcuminloaded zein membranes were fabricated by a custom-designed electrospinning instrument. Briefly, zein (2.08g) and citric acid (0.1872g) were dissolved into 4 mL ethanol/water (7:3, v:v) solution, the solution pH was adjusted to 4.9, and then the solution was stored for 48 h without magnetically stirring the solution. After that, curcumin (0.104g) and 4 mL ethanol/water (7:3, v:v) solution were added into the solution and the solution was magnetically stirred (550 rpm) for 8 h. Then, electrospun nanofibrous membranes were fabricated by electrospinning technique under same operational conditions to electrospun nanobelt-shaped membranes. The thickness of the electrospun nanofibrous membranes was controlled by adjusting the feeding rate and the collecting time. Heating process was achieved by putting the obtained membranes on the stainless-steel rod in an oven at 150 ℃ for 2.5 h. The obtained unheated/heated nanofibrous membranes were taken from the stainless-steel rod and were cut off into round membrane



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patches with a diameter of 8 mm and a mass of 4.0-5.0 mg (unheated membranes) or 3.5-4.5 mg (heated membranes) for this study. In this work, all the electrospun nanofibrous membranes were stored at room temperature for up to 10 days. 4.4. Weight loss measurements after heating. The unheated membranes were taken from the stainless-steel rod and were cut off into round membrane patches with a diameter of 8 mm. These membranes were weighed, were heated (150 ℃ for 2.5 h) , and then weighed. The weight loss after heating could be calculated through the following Equation (S1): Weight loss (%)=(Mbefore-Mafter)/Mbefore× 100%

(S1)

Where Mbefore and Mafter were the measured mass of round membrane patches before and after heating, respectively. Three experiments were performed for each sample. 4.5. Morphology measurements. The morphology of nanobelts and nanofibers was observed by inverted optical microscope (MS500W, Shanghai Minz Precision Instruments Co. Ltd., Shanghai, China), scanning electron microscope (SEM) (S-3400, Hitachi, Tokyo, Japan) at an accelerated voltage of 4.00 kV, and SEM (S-4800, Hitachi, Tokyo, Japan) at an accelerated voltage of 10.00 kV. 4.6. FTIR measurements. The functional groups of chemicals were analyzed by an attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrometer (Nicolet iS5, Thermo Scientific, USA) in a wavenumber range of 650-4000 cm-1. Chemical powders were analyzed by a KBr pellet method. Briefly, chemicals with KBr was pressed into self-supported discs (13 mm in diameter) and then was analyzed by the FTIR spectrometer with the subtraction of KBr background. Electrospun membrane patches were directly analyzed by the ATR-FTIR spectrometer. Deposited films on mica were directly analyzed by the ATR-FTIR spectrometer 26 Environment ACS Paragon Plus

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with the subtraction of mica background. The untreated deposited zein/curcumin, curcumin/citric acid, and zein/citric acid films were prepared by a two-step method: solution preparation and solution deposition. Firstly, zein/curcumin, curcumin/citric acid, and zein/citric acid solutions were successfully prepared by adding the chemicals or not during the solution preparation step: zein and citric acid were dissolved into ethanol, the solution pH was adjusted to 4.9, and then the solution was magnetically stirred (12 rpm) for 48 h. After that, curcumin was added into the solution and the solution was magnetically stirred (120 rpm) for 8 h. Then, during the solution deposition step, 5 μL prepared solution was added onto freshly cleaved muscovite mica and was allowed to dry in ambient air for 20 min. The heated deposited zein/curcumin, curcumin/citric acid, and zein/citric acid films were obtained by putting the obtained deposited films in an oven at 150 ℃ for 2.5 h. In order to analyze the curcumin-Fe3+ interaction, curcumin film was formed onto a freshly cleaved mica by depositing curcumin ethanol solution (pH 4.9) in ethanol for 1 h, Fe3+ water solutions with different concentrations were added onto the curcumin film, the solutions were blow-dried after 30 min. Then the samples were characterized by ATR-FTIR spectrometer 4.7. AFM measurements. Nanobelts or nanofibers were collected by freshly cleaved muscovite mica during the electrospinning process. Then AFM images of these samples were captured by ScanAsyst mode on a BioScope Resolve atomic force microscope (Buker Corporation, USA) under ambient condition. Bruker's Sharp Nitride Lever Probe with a nominal spring constant of 0.35 N/m was used. The nominal AFM tip radius is 2 nm and the maximized tip radius is 12 nm. The tip height is 2.5-8.0 μm. AFM scan rate was 1.0 Hz and imaging resolution was 256×256 pixel. All images were treated with “flatten” function using Nanoscaope Analysis software (version 1.80r2, Bruker Corporation, USA) prior to analysis. The sectional surfaces and height



Page 28 of 40

differences of nanobelts and nanofibers were analyzed using the “section” function in the software. 4.8. Metal ion detection of electrospun nanobelt-shaped membranes. Metal ion solutions (KCl, NaCl, AgNO3, MgCl2, FeCl2, CuCl2, ZnCl2, Cd(NO3)2, Hg(NO3)2, PbCl2, AlCl3, CrCl3, FeCl3, SnCl4, and SnCl4.) were prepared by dissolving them into ultrapure water. The solution pH was adjusted by adding NaOH or HCl. The round membrane patches were dipped into 1 mL metal solutions for 30 min and then were taken out to observe the color change by both the naked eye and digital cameras. The diameter of round membrane patches before and after the immersion was determined by a digital caliper. The shrinkage amount (diameter decrease amount) after the immersion could be calculated through the following Equation (16): Shrinkage amount (%)=(Dbefore-Dafter)/Dbefore× 100%

(16)

Where Dbefore and Dafter were the measured diameter of round membrane patches before and after the immersion, respectively. Three experiments were performed for each sample. 4.9. Application to real drinking and environmental water samples. Untrapure water, Nongfu Spring water (Hangzhou, Zhejiang Province, China), Nestle Packaged Drinking water (Shanghai, China), Uni-president Shuiquduo lactobacillus fermented beverage (Hefei, Anhui Province, China), Suntory peach water (Suqian, Jiangsu Province, China), Master Kong rock candy snow pear juice (Suzhou, Jiangsu Province, China), Coca-Cola (Shanghai, China), tap water, pond water, water of Dishui Lake, and water of East Ocean were used as real samples for the assessment of the developed sensor. The real samples were directly adjusted to pH 2. In addition, 0.3 mg/L Fe3+ (FeCl3) was spiked in the real water samples (pH). Then, all the real samples (1 mL) were examined using the membrane sensor.


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Table 1. Comparisons of Fe3+ detection methods in this work and previous representitative works in last five years. Number

Sensor form

Limit of detection

Detection methods

Advantages

1

crosslinked nanobeltshaped membranes

0.3 mg/L after incubating for 0.5 h

Naked eye

Ideal limit of detection Fast detection time Simple detection method No obvious secondary pollution

/

uncrosslinked nanobeltshaped membranes

1 mg/L after incubating for 0.5 h

Fast detection time Simple detection method No obvious secondary pollution

Unideal limit of detection

crosslinked nanofibrous membranes




unclosslinked nanofibrous membranes




2

Nanofibrous membranes

0.4mg/L after incubating for 3 h

Naked eye

Simple detection method No obvious secondary pollution

Unideal limit of detection Slow detection time

33

3

Rhodamine B-based sensor molecules

0.396 μM (≈0.02mg/L)

fluorescence emission spectra

Low limit of detection Fast detection time

Complex detection instrument Cannot be observed by naked eye Secondary pollution

36

4

Graphitic carbon quantum dots

2 nM

Photoluminescence spectra



51

5

fluorescent carbon dots

0.02 μM

Fluorescence emission spectra



52

6

On-off-on fluorescent nanosensor

16 nM




53

7

Polydopamine nanodots

10 μM (≈0.56mg/L)


Fast detection time

Unideal limit of detection Complex detection instrument Cannot be observed by naked eye Secondary pollution

54

8

Multi heteroatoms (nitrogen and phosphorus) codoped carbon nanodots

1.8 nM




55


Limitations

References This work


Figures

Figure 1. Electrospun nanobelt-shaped membrane patches. (A): Electrospun nanobelt-shaped curcumin-loaded zein membranes on stainless steel rod. (B): Electrospun nanobelt-shaped pure zein membranes on stainless steel rod. (C): Electrospun nanobelt-shaped membrane patches. Three patches in the left-upper part: unheated pure zein membranes. Three patches in the rightupper part: heated pure zein membranes. Three patches in the left-lower part: unheated curcumin-loaded zein membranes. Three patches in the right-upper part: heated curcumin-loaded zein membranes. (D-G): SEM images of unheated pure zein membranes, heated pure zein membranes, unheated curcumin-loaded zein membranes, and heated curcumin-loaded zein membranes, respectively. (H): ATR-FTIR spectra of unheated pure zein membranes, heated pure zein membranes, unheated curcumin-loaded zein membranes, and heated curcumin-loaded zein membranes (from top to bottom). (I-M): AFM height images and section analyses to the 30 Environment ACS Paragon Plus

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corresponding white lines in the height images of unheated pure zein membranes, heated pure zein membranes, unheated curcumin-loaded zein membranes, and heated curcumin-loaded zein membranes, respectively. Scan size: 5×5μm. Z scales are 1.2μm.

Figure 2. Electrospun nanobelt-shaped curcumin-loaded zein membrane patches after incubating with Fe3+ solution with different solution pH (1, 2, 3, 4, and 5) and different ion concentrations (0, 1, and 10 mg/L) for 30 min. (A): digital camera image of unheated membrane patches. (B): SEM image of unheated membrane patches after incubating with 10 mg/L Fe3+ solution. (C): digital camera image of heated membrane patches. (D): heated membrane patches after incubating with 10 mg/L Fe3+ solution. (E): digital camera image of unheated (left) and heated (right) electrospun nanobelt-shaped pure zein membrane patches after incubating with 10 mg/L Fe3+ solution for 30 min. (F): ATR-FTIR spectra (from top to bottom) corresponding to (B) and (D).



Figure 3. Selectivity and sensitivity measurements of electrospun nanobelt-shaped curcuminloaded zein membrane patches. (A) and (B): Digital camera images of untreated (A) and heated (B) membrane patches after incubating with different metal solution with a concentration of 10 mg/L. Label 1: KCl. Label 2: NaCl. Label 3: AgNO3. Label 4: MgCl2. Label 5: FeCl2. Label 6: CuCl2. Label 7: ZnCl2. Label 8: Cd(NO3)2. Label 9: Hg(NO3)2. Label 10: PbCl2. Label 11: AlCl3. Label 12: CrCl3. Label 13: FeCl3. Label 14: SnCl4. Label 15: (NH4)2Ce(NO3)6. Label 17: ultrapure water. Label 16 in (A): heated membrane patch after incubating with FeCl3 solution. Label 16 in (B): unheated membrane patch after incubating with FeCl3 solution. (C): Digital camera images of unheated (-) and heated (+) membrane patches after incubating with FeCl3 solution with different concentrations (0, 0.3, 0.5, 1, 3, 5, and 7 mg/L). (D): FeCl3 solution with different concentrations (0, 0.3, 0.5, 1, 3, 5, and 7 mg/L) after incubation with unheated (-) and heated (+) membrane patches in (C). (E): Digital camera images of heated membrane patches after incubation with real water samples without (Label 1-7) or with spiked Fe3+ (Label 8-14, 0.3 mg/mL). Label 1 and 8: Ultrapure water. Label 2 and 9: Nongfu Spring water. Label 3 and 10: Nestle Packaged Drinking water. Label 4 and 11: Uni-president Shuiquduo lactobacillus fermented beverage. Label 5 and 12: Suntory peach water. Label 6 and 13: Master Kong rock candy snow pear juice. Label 7 and 14: Coca-Cola.


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Figure 4. Electrospun nanfiber-shaped curcumin-loaded zein membranes and their application for Fe3+ detection. (A) Optical microscopy image of unheated electrospun curcumin-loaded zein nanofibers. (B) SEM image of heated curcumin-loaded zein membrane. (C): AFM height image and section analysis to the corresponding white lines in the height image of unheated electrospun curcumin-loaded zein nanofibers Scan size: 5×5μm. Z scales are 1.2μm. (D) Digital camera images of unheated (-) and heated (+) membrane patches after incubating with FeCl3 solution with different concentrations (0, 0.3, 0.5, 1, 3, 5, and 7 mg/L).



Figure 5.Schematic of nanobelt and nanofiber for Fe3+ sensing. (A): Schematic of chemical crosslinking of zein molecules via citric acid. (B): Schematic of chemical crosslinking of curcumin molecule on zein molecule via citric acid. (D): Schematic of the interaction between Fe3+ and zein-crosslinked curcumin. (D): Schematic of ideal regular nanbelt and nanofiber with the same length and sectional surface area. It should be noted that the real electrospun nanobelts and nanofibers were not as ideal as these schematics. The width (w) and height (h) were designated to be consistent with previous discussions in Figure 1I-M (the width is larger than the height). (E): Schematic of preparation and Fe3+ sensing of nanobelt and nanofiber.


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ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: . Supporting Figures: S1 to S16 (PDF)

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (J. Z.) ORCID Jian Zhong: 0000-0002-2475-3221 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. §These authors contributed equally. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This research has been supported by research grants from the National Key R&D Program (2016YFD0400202-8) and Shanghai Municipal Education Commission—Gaoyuan Discipline of Food Science & Technology Grant Support (Shanghai Ocean University). REFERENCES



1. Comini, E.; Faglia, G.; Sberveglieri, G.; Pan, Z.; Wang, Z. L., Stable and Highly Sensitive Gas Sensors Based on Semiconducting Oxide Nanobelts. Appl. Phys. Lett. 2002, 81, 1869-1871. 2. Kolmakov, A.; Klenov, D. O.; Lilach, Y.; Stemmer, S.; Moskovits, M., Enhanced Gas Sensing by Individual SnO2 Nanowires and Nanobelts Functionalized with Pd Catalyst Particles. Nano Lett. 2005, 5, 667-673. 3. Jin, C.; Kim, H.; Park, S.; Kim, H. W.; Lee, S.; Lee, C., Enhanced Ethanol Gas Sensing Properties of SnO2 Nanobelts Functionalized with Au. Ceram. Int. 2012, 38, 6585-6590. 4. Fields, L. L.; Zheng, J. P.; Cheng, Y.; Xiong, P., Room-Temperature Low-Power Hydrogen Sensor Based on a Single Tin Dioxide Nanobelt. Appl. Phys. Lett. 2006, 88, 263102. 5. Li, M.; Qiao, L. J.; Chu, W. Y.; Volinsky, A. A., Water Pre-Adsorption Effect on Room Temperature SnO2 Nanobelt Ethanol Sensitivity in Oxygen-Deficient Conditions. Sensor. Actuat. B: Chem. 2011, 158, 340-344. 6. Yu, C.; Hao, Q.; Saha, S.; Shi, L.; Kong, X.; Wang, Z. L., Integration of Metal Oxide Nanobelts with Microsystems for Nerve Agent Detection. Appl. Phys. Lett. 2005, 86, 063101. 7. Park, S.; Ko, H.; Lee, S.; Kim, H.; Lee, C., Light-Activated Gas Sensing of Bi2O3Core/ZnO-Shell Nanobelt Gas Sensors. Thin Solid Films 2014, 570, 298-302. 8. Kim, H.; An, S.; Jin, C.; Lee, C., Structure and NO2 Gas Sensing Properties of SnO2Core/In2O3-Shell Nanobelts. Curr. Appl. Phys. 2012, 12, 1125-1130. 9. J., L.; X., W.; Q., P.; Y., L., Vanadium Pentoxide Nanobelts: Highly Selective and Stable Ethanol Sensor Materials. Adv. Mater. 2005, 17, 764-767. 10. Xiaosheng, F.; Yoshio, B.; Meiyong, L.; K., G. U.; Chunyi, Z.; Benjamin, D.; Baodan, L.; Tianyou, Z.; Takashi, S.; Yasuo, K.; Dmitri, G., Single‐Crystalline ZnS Nanobelts as Ultraviolet‐Light Sensors. Adv. Mater. 2009, 21, 2034-2039. 11. Yonglan, L.; Fang, L.; Wenbo, L.; Guohui, C.; Xuping, S., Coordination Polymer Nanobelts for Nucleic Acid Detection. Nanotechnology 2011, 22, 195502. 12. Wang, L.; Zhang, Y.; Tian, J.; Li, H.; Sun, X., Conjugation Polymer Nanobelts: a Novel Fluorescent Sensing Platform for Nucleic Acid Detection. Nucl. Acids Res. 2011, 39, e37-e37. 13. Song, K.-M.; Jeong, E.; Jeon, W.; Jo, H.; Ban, C., A Coordination Polymer Nanobelt (CPNB)-Based Aptasensor for Sulfadimethoxine. Biosens. Bioelectron. 2012, 33, 113-119. 14. Zhang, N.; Qiao, R.; Su, J.; Yan, J.; Xie, Z.; Qiao, Y.; Wang, X.; Zhong, J., Recent Advances of Electrospun Nanofibrous Membranes in the Development of Chemosensors for Heavy Metal Detection. Small 2017, 13, 1604293. 15. Jiang, S.; Duan, G.; Kuhn, U.; Mörl, M.; Altstädt, V.; Yarin, A. L.; Greiner, A., Spongy Gels by a Top-Down Approach from Polymer Fibrous Sponges. Angew. Chem. Int. Ed. 2017, 129, 3333-3336. 16. Jiang, S.; Agarwal, S.; Greiner, A., Low-Density Open Cellular Sponges as Functional Materials. Angew. Chem. Int. Ed. 2017, 56, 15520-15538. 17. Jiang, S.; Chen, Y.; Duan, G.; Mei, C.; Greiner, A.; Agarwal, S., Electrospun Nanofiber Reinforced Composites: a Review. Polymer Chemistry 2018, 9, 2685-2720. 18. Suo, H.; Wang, Z.; Dai, G.; Fu, J.; Yin, J.; Chang, L., Polyacrylonitrile Nerve Conduits With Inner Longitudinal Grooved Textures to Enhance Neuron Directional Outgrowth. J. Microelectromech. Sys. 2018, 27, 457-463. 19. Liu, X.; Wei, D.; Zhong, J.; Ma, M.; Zhou, J.; Peng, X.; Ye, Y.; Sun, G.; He, D., Electrospun Nanofibrous P(DLLA–CL) Nalloons as Calcium Phosphate Cement Filled


Page 36 of 40

Page 37 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Containers for Bone Repair: In Vitro and In Vivo Studies. ACS Appl. Mater. Interfaces 2015, 7, 18540-18552. 20. Sun, G.; Wei, D.; Liu, X.; Chen, Y.; Li, M.; He, D.; Zhong, J., Novel Biodegradable Electrospun Nanofibrous P(DLLA-CL) Balloons for the Treatment of Vertebral Compression Fractures. Nanomed. Nanotechnol. Biol. Med. 2013, 9, 829-838. 21. Zhong, J.; Zhang, H.; Yan, J.; Gong, X., Effect of Nnanofiber Orientation of Electrospun Nanofibrous Scaffolds on Cell Growth and Elastin Expression of Muscle Cells. Colloids Surf. B Biointerfaces 2015, 136, 772-778. 22. Yoo, H. S.; Kim, T. G.; Park, T. G., Surface-Functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery. Adv. Drug Del. Rev. 2009, 61, 1033-1042. 23. Zhen‐Gang, W.; Zhi‐Kang, X.; Ling‐Shu, W.; Jian, W.; Christophe, I.; Patrick, S., Nanofibrous Membranes Containing Carbon Nanotubes: Electrospun for Redox Enzyme Immobilization. Macromol. Rapid Commun. 2006, 27, 516-521. 24. Ma, J.; Wang, X.; Fu, Q.; Si, Y.; Yu, J.; Ding, B., Highly Carbonylated Cellulose Nanofibrous Membranes Utilizing Maleic Anhydride Grafting for Efficient Lysozyme Adsorption. ACS Appl. Mater. Interfaces 2015, 7, 15658-15666. 25. Yu, G.-F.; Yan, X.; Yu, M.; Jia, M.-Y.; Pan, W.; He, X.-X.; Han, W.-P.; Zhang, Z.-M.; Yu, L.-M.; Long, Y.-Z., Patterned, Highly Stretchable and Conductive Nanofibrous Pani/PVDF Strain Sensors Based on Electrospinning and In Situ Polymerization. Nanoscale 2016, 8, 29442950. 26. Ma, W.; Zhang, Q.; Samal, S. K.; Wang, F.; Gao, B.; Pan, H.; Xu, H.; Yao, J.; Zhan, X.; De Smedt, S. C.; Huang, C., Core-Sheath Structured Electrospun Nanofibrous Membranes for Oil-Water Separation. RSC Adv. 2016, 6, 41861-41870. 27. Li, Z.; Shen, J.; Abdalla, I.; Yu, J.; Ding, B., Nanofibrous Membrane Constructed Wearable Triboelectric Nanogenerator for High Performance Biomechanical Energy Harvesting. Nano Energy 2017, 36, 341-348. 28. Ma, Q.; Wang, J.; Dong, X.; Yu, W.; Liu, G., Fabrication of Magnetic–Fluorescent Bifunctional Flexible Coaxial Nanobelts by Electrospinning Using a Modified Coaxial Spinneret. ChemPlusChem 2014, 79, 290-297. 29. Sheng, S.; Ma, Q.; Dong, X.; Lv, N.; Wang, J.; Yu, W.; Liu, G., A Single Nanobelt to Achieve Simultaneous Photoluminescence–Electricity–Magnetism Trifunction. J. Mater. Sci.: Mater. Electron. 2014, 25, 2279-2286. 30. Xi, X.; Yu, W.; Ma, Q.; Li, D.; Dong, X.; Wang, J.; Liu, G., Using Special Janus Nanobelt as Constitutional Unit to Construct Anisotropic Conductive Array Membrane for Concurrently Affording Color-Tunable Luminescence and Superparamagnetism. RSC Adv. 2018, 8, 31608-31617. 31. Suwantong, O.; Pavasant, P.; Supaphol, P., Electrospun Zein Fibrous Membranes Using Glyoxal as Cross-Linking Agent: Preparation, Characterization and Potential for Use in Biomedical Applications. Chiang Mai J. Sci. 2011, 38, 56-70. 32. Jiang, Q.; Reddy, N.; Yang, Y., Cytocompatible Cross-Linking of Electrospun Zein Fibers for The Development of Water-Stable Tissue Engineering Scaffolds. Acta Biomater. 2010, 6, 4042-4051. 33. Saithongdee, A.; Praphairaksit, N.; Imyim, A., Electrospun Curcumin-Loaded Zein Membrane for Iron(III) Ions Sensing. Sens. Actuators, B: Chem. 2014, 202, 935-940.



34. Wang, L.; Fang, G.; Cao, D., A Novel Phenol-Based BODIPY Chemosensor for Selective Detection Fe3+ with Colorimetric and Fluorometric Dual-Mode. Sens. Actuators, B: Chem. 2015, 207, 849-857. 35. Bozkurt, E.; Arık, M.; Onganer, Y., A Novel System for Fe3+ Ion Detection Based on Fluorescence Resonance Energy Transfer. Sens. Actuators, B: Chem. 2015, 221, 136-147. 36. Bao, X.; Cao, X.; Nie, X.; Xu, Y.; Guo, W.; Zhou, B.; Zhang, L.; Liao, H.; Pang, T., A New Selective Fluorescent Chemical Sensor for Fe3+ Based on Rhodamine B and a 1,4,7,10Tetraoxa-13-Azacyclopentadecane Conjugate and its Imaging in Living Cells. Sens. Actuators, B: Chem. 2015, 208, 54-66. 37. Wang, D.; Wang, L.; Dong, X.; Shi, Z.; Jin, J., Chemically Tailoring Graphene Oxides into Fluorescent Nanosheets for Fe3+ Ion Detection. Carbon 2012, 50, 2147-2154. 38. Wu, S.-P.; Chen, Y.-P.; Sung, Y.-M., Colorimetric Detection of Fe3+ Ions Using Pyrophosphate Functionalized Gold Nanoparticles. Analyst 2011, 136, 1887-1891. 39. Daniel, S.; Limson, J. L.; Dairam, A.; Watkins, G. M.; Daya, S., Through Metal Binding, Curcumin Protects Against Lead- and Cadmium-Induced Lipid Peroxidation in Rat Brain Homogenates and Against Lead-Induced Tissue Damage in Rat Brain. J. Inorg. Biochem. 2004, 98, 266-275. 40. García-Niño, W. R.; Pedraza-Chaverrí, J., Protective Effect of Curcumin Against Heavy Metals-Induced Liver Damage. Food Chem. Toxicol. 2014, 69, 182-201. 41. Wang, F.; Huang, W.; Wang, Y., Fluorescence Enhancement Effect for the Determination of Curcumin with Yttrium(III)-Curcumin-Sodium Dodecyl Benzene Sulfonate System. J. Lumin. 2008, 128, 110-116. 42. Wu, F.-Y.; Sun, M.-Z.; Xiang, Y.-L.; Wu, Y.-M.; Tong, D.-Q., Curcumin as a Colorimetric and Fluorescent Chemosensor for Selective Recognition of Fluoride Ion. J. Lumin. 2010, 130, 304-308. 43. Chaicham, A.; Kulchat, S.; Tumcharern, G.; Tuntulani, T.; Tomapatanaget, B., Synthesis, Photophysical Properties, and Cyanide Detection in Aqueous Solution of BF2-Curcumin Dyes. Tetrahedron 2010, 66, 6217-6223. 44. Srichairatanakool, S.; Thephinlap, C.; Phisalaphong, C.; Porter, J. B.; Fucharoen, S., Curcumin Contributes to In Vitro Removal of Non-Transferrin Bound Iron by Deferiprone and Desferrioxamine in Thalassemic Plasma. Med. Chem. 2007, 3, 469-474. 45. Wong, S. S.; Wong, L.-J. C., Chemical Crosslinking and the Stabilization of Proteins and Enzymes. Enz. Microb. Technol. 1992, 14, 866-874. 46. Satti, A.; Larpent, P.; Gun’ko, Y., Improvement of Mechanical Properties of Graphene Oxide/Poly(Allylamine) Composites by Chemical Crosslinking. Carbon 2010, 48, 3376-3381. 47. Reddy, N.; Reddy, R.; Jiang, Q., Crosslinking Biopolymers for Biomedical Applications. Trends Biotechnol. 2015, 33, 362-369. 48. Martines, E.; Zhong, J.; Muzard, J.; Lee, A. C.; Akhremitchev, B. B.; Suter, D. M.; Lee, G. U., Single-Molecule Force Spectroscopy of the Aplysia Cell Adhesion Molecule Reveals Two Homophilic Bonds. Biophys. J. 2012, 103, 649-657. 49. Tc̵nnesen, H. H.; Greenhill, J. V., Studies on Curcumin and Curcuminoids. XXII: Curcumin as a Reducing Agent and as a Radical Scavenger. Int. J. Pharm. 1992, 87, 79-87. 50. Borsari, M.; Ferrari, E.; Grandi, R.; Saladini, M., Curcuminoids as Potential New IronChelating Agents: Spectroscopic, Polarographic and Potentiometric Study on their Fe(III) Complexing Ability. Inorg. Chim. Acta 2002, 328, 61-68.


Page 38 of 40

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51. Zhang, Y.-L.; Wang, L.; Zhang, H.-C.; Liu, Y.; Wang, H.-Y.; Kang, Z.-H.; Lee, S.-T., Graphitic Carbon Quantum Dots as a Fluorescent Sensing Platform for Highly Efficient Detection of Fe3+ Ions. RSC Adv. 2013, 3, 3733-3738. 52. Liu, W.; Diao, H.; Chang, H.; Wang, H.; Li, T.; Wei, W., Green Synthesis Of Carbon Dots from Rose-Heart Radish and Application for Fe3+ Detection and Cell Imaging. Sens. Actuators, B: Chem. 2017, 241, 190-198. 53. Gao, G.; Jiang, Y.-W.; Jia, H.-R.; Yang, J.; Wu, F.-G., On-Off-On Fluorescent Nanosensor for Fe3+ Detection and Cancer/Normal Cell Differentiation via Silicon-Doped Carbon Quantum Dots. Carbon 2018, 134, 232-243. 54. Qi, P.; Zhang, D.; Wan, Y., Morphology-Tunable Polydopamine Nanoparticles and Their Application in Fe3+ detection. Talanta 2017, 170, 173-179. 55. Shi, B.; Su, Y.; Zhang, L.; Huang, M.; Liu, R.; Zhao, S., Nitrogen and Phosphorus CoDoped Carbon Nanodots as a Novel Fluorescent Probe for Highly Sensitive Detection of Fe3+ in Human Serum and Living Cells. ACS Appl. Mater. Interfaces 2016, 8, 10717-10725.



Polymer nanobelt-shaped membranes for high sensitivity detection of metal ions were fabricated by a nanobelt-based processing method with simultaneous zein matrix crosslinking and curcumin sensor crosslinking. Compared with nanofibrous membranes, the fabricated nanobelt-shaped membranes had ideal limit of detection for Fe3+. This will promote the application of polymer nanobelts in scientific and engineering fields. 168x152mm (150 x 150 DPI)

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Electrospun Nanobelt-Shaped Polymer Membranes for Fast and High

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