Fabrication of biomimetic tio2 fdtscotton fabric with special wettability for effective self cleaning application

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN THI HONG NHUNG FABRICATION OF BIOMIMETIC TiO2-FDTS@COTTON FABRIC WITH SPECIAL WETTABILITY FOR EFFECTIVE SELF-CLEANING APPLICATION MASTER'S THESIS VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN THI HONG NHUNG FABRICATION OF BIOMIMETIC TiO2-FDTS@COTTON FABRIC WITH SPECIAL WETTABILITY FOR EFFECTIVE SELF-CLEANING APPLICATION MAJOR: ENVIRONMENTAL ENGINEERING CODE: 8520320.01 RESEARCH SUPERVISOR: Dr TRAN THI VIET HA Hanoi, 2021 ACKNOWWLEDGMENTS First of all, I wish to express my deepest gratitude to Dr Tran Thi Viet Ha who is a kindness, esteemed supervisor and other Professors/Lecturers of Master’s Program in Environment Engineering for their tutelage I also want to say thank to VNU Vietnam Japan University (VJU), Hanoi National University – Hanoi University of Science (HUS); VNU Key Laboratory of Advanced Materials Applied in Green Development and Laboratory of Master’s Program in Nanotechnology to recognize the invaluable assistance that you all provided during my study In particular, I acknowledge VJU's JICA research fund (period 2021-2023) Principal Investigator Dr Tran Thi Viet Ha - for financially supporting my thesis research With this generous support, my research was favorably conducted on schedule without any discontinuation Finally, I would like to extend my sincere thanks to my classmates and colleagues who have always been by my side for spiritual support Specially, I cannot leave La Thi Ngoc Mai - 4th intake student at Master’s Program in Nanotechnology - without mentioning, who has spent a lot of time supporting me unconditionally through the analysis stage Hanoi, 2021 Nguyen Thi Hong Nhung TABLE OF CONTENTS LIST OF TABLES i LIST OF FIGURES ii LIST OF ABBREVIATIONS iv CHAPER INTRODUCTION CHAPER LITERATURE REVIEW .3 2.1 Theoretical basis 2.2 Methods to fabricate the superhydrophobic surface 2.3 Applications of the superhydrophobic material 2.4 Analysis methodologies 11 2.4.1 SEM 11 2.4.2 FTIR 15 2.4.3 XRD 16 2.4.4 WCA 16 2.5 Superhydrophobic material studies in Viet Nam 17 2.6 Oil pollution situation in Vietnam in recent years and treatment methods 18 CHAPTER MATERIALS AND METHODOLOGIES .20 3.1 Materials 20 3.2 Methodologies 20 3.2.1 Fabrication produce 20 3.2.2 Material characterization 22 3.2.3 Applications of fabricated superhydrophobic fabric 26 3.2.4 Durability test for fabricated superhydrophobic fabric 27 CHAPER RESULTS AND DISCUSSION 29 4.1 Results 29 4.1.1 Optimization condition for fabrication of superhydrophobic fabric 29 4.1.2 Material characterization results 32 4.1.3 Applications of fabricated superhydrophobic fabric 36 4.1.4 Durability of fabricated superhydrophobic cotton fabric 40 4.2 Discussion 42 CONCLUSIONS 44 REFERENCES 45 LIST OF TABLES Table 2.1 The values of the WCA correspond to the solid surface states Table 4.1 WCA of TiO2-FDTS@cotton samples with different number TiO2 coating 31 Table 4.2 Optimal conditions in the first layer coating with TiO2 32 Table 4.3 Oil recover efficiency 39 i LIST OF FIGURES Figure 2.1 Young theory (Young, 1805) Where, γsv, γsl, γlv are the interfacial tensions of the solid-vapor, solid-liquid and the liquid-vapor interface, respectively Figure 2.2 Wenzel and Cassie-Baxter models (Wenzel, 1936),(B D Cassie and Baxter, n.d.) Figure 2.3 Wetting state and static water contact angle of the solid surfaces Figure 2.4 Shedding angle Figure 2.5 Electron beam and the different types of signals which are generated (T F Scientific, n.d.) 12 Figure 2.6 Magnetic lens schematic (T F Scientific, n.d.) 12 Figure 2.7 Electron beam deflector (a) and lector-static lens (b) (T F Scientific, n.d.) 13 Figure 2.8 Magnetic lens (T F Scientific, n.d.) 13 Figure 2.9 Different kinds of electrostatic lenses: single-aperture positive and negative lenses (a, b), two-aperture lens (c) and three aperture Einzel lens (d) (T F Scientific, n.d.) 14 Figure 2.10 Michelson interferometer in configured for FTIR (Petergans, 2017) 15 Figure 2.11 Contact angle measurement (image cut from video) (B Scientific, n.d.)17 Figure 3.1 Cellulose, TiO2 and FDTS structures 20 Figure 3.2 Experiment process 21 Figure 3.3 SEM device 23 Figure 3.4 FTIR device 23 Figure 3.5 XRD device 24 Figure 3.6 WCA measurement device (Femtobiomed, 2021) 25 Figure 3.7 Shedding angle test 25 Figure 3.8 Self-cleaning test 26 Figure 3.9 Oil-water mixture 27 Figure 3.10 Preparation for oil-water separation by glass filter holder 27 Figure 4.1 SEM images of TiO2 coated samples (a) pH = 2~3; (b) pH = 3~4; (c) pH = 4~5; (d) pH= ~6; (e) pH= 6~7; (f) pH = 7~8; (g) pH = 8~9; (h) pH = 9~10; (i) pH = 10~11 29 Figure 4.2 SEM images of TiO2 coated samples (a) T =100oC; (b) T =120oC; (c) T =140oC; (d) T =160oC 30 Figure 4.3 SEM images of TiO2 coated samples (a) t =2h; (b) t=3h; (c) t=4h; (d) t=5h; (e) t=6h 31 Figure 4.4 WCA of TiO2-FDTS@cotton 32 Figure 4.5 WCA 33 Figure 4.6 SEM images, EDS spectrum of the cotton (a1, b1) raw cotton, (b1, b2) TiO2@cotton and (c1, c2) TiO2-FTDS@cotton 34 Figure 4.7 FTIR spectra of the cotton samples 35 ii Figure 4.8 XRD spectra of TiO2-FTDS@cotton 36 Figure 4.9 The water droplets carry dirt (Shrimp sell powder) and roll off the cotton fabric surface with shedding angle = 7o 36 Figure 4.10 The water droplets carry dirt (Sand) and roll off the cotton fabric surface with shedding angle = 7o 37 Figure 4.11 Organic solvents removal test Time sequence of (a-c) toluene dyed red on water surface, and (d-f) underwater chloroform dyed red with superhydrophobic cotton pad 38 Figure 4.12 Oil-water separation test 39 Figure 4.13 Separation efficiency vs no of cycles representing the durability of superhydrophobic cotton after several uses 40 Figure 4.14 Water drop on cotton surface after 10 laundering cycles 41 Figure 4.15 Water dropt on cotton surface (a) before and (b) after one month in room condition 41 Figure 4.16 Water dropt on cotton fabric (a) only TiO2 coated, (b) TiO2-FDTS coated, (c) only FTDS coated 42 Figure 4.17 Mechanism of the attachment TiO2 and FTDS on cotton fiber 43 iii LIST OF ABBREVIATIONS BSE: Backscattered electrons COD: Crystallography open database EDS: Energy-Dispersive X-Ray Spectrometry FTDS: 1H,1H,2H,2H-Perfluorodecyltrimethoxysilane FTIR: Fourier-transform infrared spectroscopy SA: Shedding angle SE: Secondary electrons SEM: Scanning Electron Microscopy WCA: Water contact angle XRD: X-Ray Diffraction iv CHAPER INTRODUCTION The self-cleaning materials has been explored and be consider as the materials of the future in 21st century since the theory was first revealed from 1805 after Thomas Young's report on the wettability of materials The natural phenomenon of lotus leaves is a typical example, inspiring surface studies by its exceptional wetting properties Until now, thousands of self-cleaning-material-articles have been published, and these materials are popularity usage around the world They are not only for the purpose of researches, but also have diversity applications in real life, beyond the self-cleaning feature, and have great contribution to the advance of science and technology Although there are several techniques which were reported to develop selfcleaning surface, the consideration of the properties of the substrates and the purposes of the study make the chosen of appropriate fabrication techniques become extremely necessary A substrate can be fabricated by different methods For instance, on glass, Haiyan Hi et al.(Ji et al., 2013) was performed the hydrothermal process, while Satish A Mahadik et al making repellent surface by sol-gel route (Mahadik et al., 2010) Recently, Yi Lin et al.(Lin et al., 2018) Huynh H Nguyen et al.(Nguyen et al., 2021) was carried out the laser processing to hydrophobize the surface and have been successfully obtained the repellent property A method can be applied on many different substrate Thus, each substrate has its own set of optimal conditions One of the most popular techniques is sol-gel  which applies to most substrates – has been show the versatility on several representative are fabric (Yang et al., 2018) copper (Raimondo et al., 2017), glass (Mahadik et al., 2010), ceramic (Jamalludin et al., 2020), wood (Jia et al., 2018), paper (Dimitrakellis et al., 2017), etc Further, the combination of multiple methods in one study has also is a flexible research plan (Li et al., 2015) Self-cleaning feature has been successfully built on different substrates However, even in recent studies, there are still some limitations such as using toxic solvents (toluene) or technique that require high energy consumption (plasma etching) On the other hand, the research and application on this material has not been widely developed in Vietnam Superhydrophobic material is one of the economically, a1 a2 b1 b2 c1 c2 Figure 4.6 SEM images, EDS spectrum of the cotton (a1, b1) raw cotton, (b1, b2) TiO2@cotton and (c1, c2) TiO2-FTDS@cotton (iii) FTIR Figure 4.7 shows the FTIR spectra of raw cotton (blue line) and TiO2- FDTS@cotton (red line) in the wavenumber range of 400  4000 cm-1 Initial cotton has 3381 cm-1 position represented for hydroxyl group (OH); 1070 cm-1 is the C-O present; While the red line of superhydrophobic cotton has the wavenumber of 532 cm-1 presenting for Ti-O-Ti bonding; 1622 - 1725 cm-1 is where Ti-OH vibration; Si-O is 34 represented by the 1396 cm-1; 1199 cm-1 correspond to C-F functional groups This results was demonstrated that both two layers successfully prepared on cotton fibers Figure 4.7 FTIR spectra of the cotton samples (iv) XRD In figure 4.8, the raw sample X-ray diffraction (black line) has the peaks 15.3598o; 23.0695o; 28.2344o and 29.2894o which represented for cellulose fiber Compared with the X-ray diffraction result of TiO2-FDTS@cotton fabric (red line), the red line has 32.3385o; 34.2591o and 49.1235o are the peaks of TiO2 indicated the presense of TiO2 particles Besides, the lightly decrease of the peak at position 23.0695o was explained the binding of TiO2 to the -OH group in cellulose fibers Thus, this results has proven the successful coating of TiO2 micro-particles and on cotton fabric surface 35 Figure 4.8 XRD spectra of TiO2-FTDS@cotton 4.1.3 Applications of fabricated superhydrophobic fabric (i) Self-cleaning Figure 4.9 The water droplets carry dirt (Shrimp sell powder) and roll off the cotton fabric surface with shedding angle = 7o The result of self-cleaning experiment with Shrimp sell powder showed that dust on the superhydrophobic cotton surface is washed away by water and stay dried Water drips down naturally without any force, easily removing dirt, leaving the surface of the cotton fabric as clean as initial The weight of the cotton fabric was unchanged before 36 and after the test, indicating that the cotton surface is capable of completely self-cleaning from solid dust The second experiment used sand to be sprinkled on the surface of superhydrophobic cotton pad that had been glued to a flat transparent sheet slide in SA = 7o leans against on a round dish (Figure 4.10) Water droplets carrying sand fall off the surface Due to the mass of the sand particles, the water particles need to apply a spray force to wash away completely Finally, the fabric surface is completely cleaned Figure 4.10 The water droplets carry dirt (Sand) and roll off the cotton fabric surface with shedding angle = 7o (ii) Organic solvents removal The superhydrophobicity of TiO2-FDTS@cotton is both applicable in underwater and in the water surface for organic solvents-water separation Superhydrophobic fabric selectively absorbed red-dyed-toluene drops on the surface of water (Figure 4.11 a-c) Similarly, it also instantly removed chloroform drops lying underwater (Figure 4.11 df), leaved absolute clean water as initial Toluene and Chloroform droplets can be taken by absorbed cotton from water immediately Nevertheless, due to the poor space capacity of cotton fabric, the application of this superhydrophobic cotton for the absorption of oil from water might be restricted 37 a b c d e f Figure 4.11 Organic solvents removal test Time sequence of (a-c) toluene dyed red on water surface, and (d-f) underwater chloroform dyed red with superhydrophobic cotton pad (iii) Oil-water separation TiO2-FTDS@cotton fabric selectively collected oil from oil-water mixtures efficiently when the mixture of kerosene-water (50% v/v) were poured slowly into the glass filter holder as Figure 4.12 Only the red dyed oil goes throw into the flask while the water remains on the cotton fabric due to its anti-wet property Filtration occurs naturally without a pump; thus a small amount of oil is absorbed inside the cotton fabric 38 Figure 4.12 Oil-water separation test Table 4.3 Oil recover efficiency Water (ml) Oil (ml) Recovered oil (ml) 20 20 20 20 20 20 18 18.5 18 Oil recover efficiency (%) 90 92.5 90 Oil recover efficiency in average (%) 90.8 Superhydrophobic cotton fabric has proven its ability of recover oil with efficiency is over 90% This result suggests that the cotton fabric has ability of separate oil−water mixtures by a simple filtering process 39 4.1.4 Durability of fabricated superhydrophobic cotton fabric The durability of the superhydrophobic cotton fabric was evaluated via oil filtration cycles The experiment as Figure 4.12 was repeatedly carried out for several times The results show good behavior during 10 filter cycles However, the wettability has slight changed at the 10th filtration (Figure 4.13) Figure 4.13 Separation efficiency vs no of cycles representing the durability of superhydrophobic cotton after several uses As the Figure 4.13 displays, the filtration process was repeatedly performed more than 20 times, and it shows 92% oil recovery in the first 10 cycles After 10 cycles, the filtration efficiency has light decreasing started from the 11th cycle, the filtration efficiency was recorded of 80% from 18th cycle 40 Figure 4.14 Water drop on cotton surface after 10 laundering cycles After 10 times of oil filtration and washing with absolute ethanol in each cycle, the water droplet has only slight change compared to the cotton fabric before filtration (Figure 4.14) A sample is left in room air for one month in order to examine the wettability The results show that there no change (Figure 4.15) after one month when the fabric is still remaining the self-cleaning property a b Figure 4.15 Water dropt on cotton surface (a) before and (b) after one month in room condition 41 4.2 Discussion Figure 4.16 Water dropt on cotton fabric (a) only TiO2 coated, (b) TiO2-FDTS coated, (c) only FTDS coated The test proves that the combination of two coatings in order is important, only TiO2 or FTDS layer is not changes the wettability significantly Wenzel theory experiment has demonstrated WCA is effected by the pattern of surface If the hydrophilic surface is rougher, it even more hydrophilic While a hydrophobic surface is rougher, it even more hydrophobic Therefore, cotton has hydrophilicity, when cotton being coated on, it became more hydrophilic On the other hand, FDTS gives the hydrophobic functional group This is explained the order of the coating layers cannot be reversed and both modification techniques were both necessary for superhydrophobicity Based on the characterization analysis data, the mechanism of forming superhydrophobic surface can be proposed as following (Figure 4.17) Cotton fiber has hydroxyl groups in composition, during hydrothermal reaction period a hydrogen element will be replaced by TiO2 particles by high temperature and pressure in furnace TiO2@cotton will be further coated followed the process in second step While TiO2@cotton immersed in a coating solution containing FTDS in ethanol, a less stable bond in the double bond between Ti and O is broken and be replaced by the functional group from FTDS in a CH3 position 42 Figure 4.17 Mechanism of the attachment TiO2 and FTDS on cotton fiber 43 CONCLUSIONS Two simple techniques are hydrothermal and dip-coating was applied with low temperature and easy to performance These methods have remarkable advantages and are the optimal choice for developing superhydrophobic materials without consuming energy or requiring high technical equipment The set of optimal conditions has been found Reaction temperature of the first layer of TiO2 is 120oC for hours consecutively with solution pH in the range of  5, this process needs to be repeated at least three times before coating the second layer with FTDS in immersed temperature is 60oC for hours TiO2-FDTS@cotton fabric achieved superhydrophobic state with WCA = 152.9o  1o and shedding angle is 7o The SEM image shows a crystalline structure growing over on the surface of the fabric The FTIR and XRD spectra demonstrate the structure of the surface coated with TiO2 and the superhydrophobic functional group Besides, self-cleaning property was successfully tested, promising outcomes in stay dried when water successfully washed the surface Additionally, superhydrophobic cotton fabric shows a reliable oil-water effectively, organic solvent-water separation both in surface water and under water 44 REFERENCES Ahuja, D., Dhiman, S., Rattan, G., Monga, S., Singhal, S., Kaushik, A., 2021 Superhydrophobic modification of 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(d) t=5h; (e) t=6h (iv) Effect of number of coating on the first coating of TiO2 Minimum number of TiO2 coatings to achieve superhydrophobic state upon completion of fabrication as demonstrated