THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY DUONG CUONG THINH FABRICATION OF PHOTOCATALYTIC THIN FILMS CONTAINING TIO2 NANOPARTICLES AND POLY(L-DOPA) BY LAYER-BY-LAYER SELF-ASSEMBLY BACHELOR THESIS Study : Full- time Mode Major : Bachelor in Environmental Science and Management Faculty : International Training and Development Center Batch : 2011-1016 Thai Nguyen, 15/09/2016 1 n DOCUMENTATION PAGE WITH ABSTRACT Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor in Environmental Science and Management Student Name Duong Cuong Thinh Student ID DTN1153180221 Supervisor Assoc. Wu Chien-Hou PhD. Nguyen HuuTho Abstract: The photocatalytic thin films containing TiO2 nanoparticles and poly(L- Dopa) were fabricated by layer-by-layer self-assembly. The thin films were characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM).
The photocatalytic activity was evaluated through the degradation of sulforhodamine B (SRB) in aqueous solution. Nano-structured thin films under different conditions and their photocatalytic activities were investigated and studied.The results show that layer-by-layer self-assembly was a simple and useful method to fabricate Nano- structured thin films with low cost and high reusability. High transparency films using Degussa P25 was attributed to suitable particle size and colloidal stability. Poly(L- Dopa) with negatively charge at wide range of pH values made it a good substitute among commercially available polyelectrolytes.
P25 and poly(L-Dopa) were recorded as an optimal charge with high zeta-potential and small particle size, contributing for high colloidal stability and low sedimentation at pH 3. The obtained multilayer films i n retained the band gap of bare P25 at 3.2 eV and the properties of functional groups of poly(L-Dopa). The optimal number of P25/Poly(L-Dopa) bilayers was 20.The photocatalytic thin films containing P25 and poly(L-Dopa) are promising materials for environmental remediation. Keywords:Titanium dioxide, layer-by-layer self-assembly, P25, poly(L-Dopa) Number of page 51 Date of Submission 15/09/2016 Supervisor’s signature ii n ACKNOWLEDGEMENT To have completed this thesis, in addition to the ongoing efforts of myself, I would like to thank for teachers in faculty of International Training and Development as well as teachers in Thai Nguyen University of Agriculture and Forestry, who have dedicated teaching to me the valuable knowledge during study time in the university and given me a chance to do my thesis oversea.
I had a precious opportunity to take part in the internship in Department of Biomedical Engineering and Environmental Sciences in National Tsing Hua University (NTHU), Taiwan. First of all, I want to thank my supervisors Assoc. Wu Chien-Hou from Biomedical Engineering & Environmental Science Department, National Tsing Hua University and PhD. Nguyen Huu Tho from Thai Nguyen University of Agriculture and Forestry.
Their priceless advices are not only valuable to my research in order to gain successful results, but also contribute to my future career orientation. Secondly, I am grateful to Mr. Weichang Yuan, MS student and my friends in the laboratory, who facilitated and provided the information and data necessary for my implementation process and helped me finish this thesis. Last but not least, thanks to my parents and good friends who always encourage me and offer support and love.
Sincerely, Duong CuongThinh iii n TABLE OF CONTENT ACKNOWLEDGEMENT. iii TABLE OF CONTENT .iv LIST OF FIGURES .1 LIST OF TABLES .3 LIST OF ABBREVIATIONS. Research questions and hypotheses. Overview of Titanium dioxide.
Titanium oxidation structures and properties. The photocatalytic activity of TiO2. Layer-by-layer self-assembly. Overview of Poly(L-Dopa) .2 Fabrication of photocatalytic thin [TiO2/ Polymer]n films by the layer-by- layer self-assembly .1 Optical photos of P25/PDopa films .2 Optical photos of multiple films .2 Characterization of P25/Pdopa.1 Dynamic Light Scattering (DLS).
SEM images of P25/Pdopa .2 Photodegradation activities of PDopa films .2 Photodegradation performance of TiO2 .4 P25/PDoPa films band gap. DISCUSSION AND CONCLUSION .41 vi n LIST OF FIGURES Figure 1Crystal structures of rutile, anatase and brookite titanium dioxide .9 Figure 2 Schematic diagram illustrating the principle of TiO2 photocatalysis with the presence of water pollutant (RH).10 Figure 3 The principle of Layer-by-layer self-assembling method .12 Figure 5 Chemicals: a) PDopa, b) SRB 10 uM, DIW c) pH=3, d) PAA .13 Figure 6 Equipment: a) UV-Visible Spectrophotometer, b) Photochemical reactor, c) pH adjustment, d) Magnetic stirrer, e) Ultrasonic, f) DLS.14 Figure 7 Experimental process .15 Figure 8 Photos of P25/PDopa film.5 bilayer thin films' images: a) St-01, b) St-21, c) P25 .20 Figure 10 TiO2 size and zeta-potential at (pH=3, concentration = 1g/l) .21 Figure 11 PDopa zeta-potential and P25 zeta-potential varied from pH .22 Figure 12 P25 size varied from pH.22 Figure 13 FT-IR spectra of Degussa P25, L-Dopa, PDopa, P25/PDopa, PAA, P25/PAA .23 Figure 14 SEM images of (a) 0.26 Figure 15 AFM images of thin films prepared with the coating sequence of (P25/PDopa)n: a) 0.5 bilayers before photodegradation 1 n in UV light d) 5.5 bilayers after photodegradation in UV light, e) 5.5 bilayers after photodegradation .28 Figure 16 Absorbance of SRB: a) in range from 400nm to 750nm, b) at 562nm .30 Figure 17 (a) SRB photodegradation profiles of (P25/PAA)n thin films at wavelength 562 nm, (b) the first-order kinetic plot of ln(C/C0) and time(minutes) for photodegradation of SRB using (P25/PAA)n thin films at wavelength 562 nm .31 Figure 18 (a) SRB degradation profiles of (P25/PDopa)n thin films at wavelength 562 nm, (b) the first-order kinetic plot of ln(C/C0) and time(minutes) for photodegradation of SRB using (P25/PDopa)n thin films at wavelength 562 nm, .33 Figure 19 (a) SRB degradation profiles of (TiO2/PDopa)n thin films at wavelength 562 nm, (b) the first-order kinetic plot of ln(C/C0) and time(minutes) for photodegradation of SRB using diffirent kinds of TiO2 .34 Figure 20 (a) Absorbance of P25/PDoPa films, (b) Absorbance at 300 nm of P25/PDoPa, (c) band gap of P25/PDopa .36 2 n LIST OF TABLES Table 1 Numbers of layers .17 Table 2 Roughness of P25/PDopa films with different numbers of bilayer .29 3 n LIST OF ABBREVIATIONS Abbreviations Full text content Ultra-violet UV Visible Vis LBL-SA Layer-by-layer self-assembly PAA Poly(acrylic acid) P25 P25 Degussa Pdopa Poly(L-dopa) SEM Scanning Electron Microscopy AFM Atomic Force Microscopy FTIR Fourier Transform Infrared Spectroscopy DLS Dynamic Light Scattering 4 n PART I. Research rationale In the context of the current population explosion followed by the excessive demand of utilization of both natural and artificial resources in order to motivate the development of agricultural and industrial manufactures, our environment has been dramatically affected by inadequate access to these kinds of resources and the shortcomings of management. Water, soil and air resources have been polluted seriously, resulting in a sequence of negative consequences to human being and living organisms.
Environmental pollution has become one of the most enormous challenges of the world that humans need to face in the 21st century. Up to now, various processes have been proposed to constantly tackle and step-by-step take actions to prevent, mitigate environmental degradation in order to adapt the human demand. One of a few possible options can be seen in water reuse by wastewater treatment from agricultural and industrial activities. In view to suppress the worsening of clean water shortage, development of advanced techniques with low-cost and high efficiency to treat the wastewater is desirable.
Due to its more experts than other conventional water treatment methods, photo-degradation process of nanoparticles has increasingly gotten the attention of scientists these days. A method to mitigate low concentrations of organic contaminants from gaseous effluents by converting them into products that are in safety to the environment is known as Heterogeneous photocatalytic oxidation (PCO)(Blount, Kim, & Falconer, 2001). In that case, Nano-TiO2photocatalyst is well-known for its high efficiency, low cost, physical and chemical stability, 5 n widespread availability, and noncorrosive property(Carp, Huisman, & Reller, 2004; Dong et al., 2015; Herrmann et al. However, the practical applications of TiO 2 were prohibited due to its difficulty of separation and recovery from liquid phase (Dong et al.
In view of tackle the problem, several approaches have been studied. One of these approaches is to immobilize the TiO2 nanoparticles onto various supports. Although numerous techniques were introduced to be able to fabricate thin films having nanostructured TiO2, the processes are too complex and require expensive equipment to avoid the nanoparticle loss by agglomeration during fabrication(Kim & Sohn, 2002). From previous study, fabrication of thin films containing TiO 2 nanoparticles using layer- by-layer self-assembly is well-known as a promising technique (Dong et al.
In this study, the different films of various kinds of TiO2 and Poly (L-Dopa) using the layer-by-layer self-assembly were fabricated. The obtained films were tested by employing Uv-Vis spectrometer, and characterized by several techniques such as dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) in order to assess efficiency of them in practical application in case of approaches for the immobilization efficiency of TiO2 particles with low cost and high reusability. Sulforhodamine B (SRB) was used as a model to study the “photocatalytic activity”. Research’s objectives The research aims to prepare TiO2 films with high optical transparency through layer-by-layer self-assembly using commercial TiO2 and Poly(L-Dopa).
Research questions and hypotheses a) What is the procedure method of [TiO2/Poly(L-Dopa)]n films? b) What is roles of Poly(L-dopa) (Pdopa) in fabrication of photocatalytic multilayer thin films? c) How effective are P25 Degussa, St-01, and St-21 in term of fabrication of the films and their pollutant degradation? 1. Limitations Due to the shortcoming of time frame, the research could be limited and was not able to be expended into many as other experiments. Overview of Titanium dioxide 2. Titanium oxidation structures and properties Up to now, the n-type semiconductor Titanium dioxide (TiO2) has been widely utilized as a photocatalyst due to their potential applications in decomposition of environmental pollutants (Dong et al., 2015; Kim & Sohn, 2002; Wisitsmat, Tuantranont, Comini, Sberveglieri, & Modarski, 2009).
The nano-TiO2photocatalyst is well-known among the metal oxides for its high efficiency, low cost, biological inertness, physical and chemical stability, widespread availability, noncorrosive property and no risks for the environment or humans (Carp et al., 2004; Dong et al., 2015; Herrmann et al. There are three different polymorphs that Titanium dioxide (TiO2) exists asanatase, rutile and brookite(Nolan, Seery, & Pillai, 2009; Pelaez et al. Rutile is the primary source and the most stable form of TiO2(Pelaez et al., 2012) while Anatase phase is reported to be better photocatalytically active than the other major phases in Titania (Nolan et al. The band gap of anatase is 3.2 eV while that of rutile is 3.0 eV, and brookite is ∼3.2 eV (Amtout & Leonelli, 1995; Asahi, Taga, Mannstadt, & Freeman, 2000; Koelsch, Cassaignon, Minh, Guillemoles, & Jolivet, 2004; Pelaez et al.
It proves that Rutile can be excited by both visible and ultraviolet (UV) light (wavelengths smaller than 390 nanometers, Anatase is only excited by UV light, and Brookite is not excited by UV light. 8 n In all three forms, titanium (Ti4+) atoms are coordinated to six oxygen (O2−) atoms, forming TiO6 octahedral (Pelaez et al. The structures of the three phases are shown in the under figure with the titanium atoms are gray and the oxygen atoms are red. Anatase can be transformed into rutile at high temperatures (Floriano, Scalvi, Saeki, & Sambrano, 2014).
Brookite with its orthorhombic crystal system can be transformed into rutile with the application of heat(Kadam et al. Crystal structures of rutile, anatase and brookite titanium dioxide (Shannon, 2012; Woodley & Catlow, 2009) P25 (Degussa, Japan Aerosil) is made from titanium chloride at relatively high temperature while ST-01 and ST-21 (Ishihara Sangyo Co.) is anatase powder that is made from titanium sulfonate. P25 Degussa contains 80% anatase and 20% rutile. Meanwhile ST-01, and ST-21 contain 100% anatase (Zarei, Khataee, Ordikhani- Seyedlar, & Fathinia, 2010).
The photocatalytic activity of TiO2 When nano-TiO2 is irradiated with ultraviolet (UV) light, electrons are promoted from the valence band to the conduction band, resulting in the generation of energized “holes” in the former.