(Luận văn) fabrication of photocatalytic thin films containing tio2 nanoparticles and poly(l dopa) by layer by layer self assembly

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY DUONG CUONG THINH lu an va FABRICATION OF PHOTOCATALYTIC THIN FILMS CONTAINING n gh tn to TIO2 NANOPARTICLES AND POLY(L-DOPA) BY LAYER-BY-LAYER p ie SELF-ASSEMBLY nl w d oa BACHELOR THESIS an lu : Full- time Major Faculty : Bachelor in Environmental Science and Management : International Training and Development Center Batch : 2011-1016 nf va Study Mode z at nh oi lm ul z m co l gm @ Thai Nguyen, 15/09/2016 an Lu n va ac th si 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 Prof Wu Chien-Hou PhD Nguyen HuuTho lu Abstract: The photocatalytic thin films containing TiO2 nanoparticles and poly(L- an n va Dopa) were fabricated by layer-by-layer self-assembly The thin films were to characterized by dynamic light scattering (DLS), Fourier transform infrared gh tn spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force p ie w microscopy (AFM) The photocatalytic activity was evaluated through the degradation d oa nl of sulforhodamine B (SRB) in aqueous solution Nano-structured thin films under an lu different conditions and their photocatalytic activities were investigated and studied nf va Poly(acrylic acid) (PAA) was used to verify the role of poly(L-Dopa).The results show lm ul that layer-by-layer self-assembly was a simple and useful method to fabricate Nano- z at nh oi 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- z Dopa) with negatively charge at wide range of pH values made it a good substitute gm @ among commercially available polyelectrolytes P25 and poly(L-Dopa) were recorded l m co as an optimal charge with high zeta-potential and small particle size, contributing for an Lu high colloidal stability and low sedimentation at pH The obtained multilayer films n va ac th i si 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 20.5.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 lu an Supervisor’s signature n va p ie gh tn to d oa nl w nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th ii si 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 my thesis oversea I had a precious opportunity to take part in the internship in Department of Biomedical Engineering and Environmental lu an Sciences in National Tsing Hua University (NTHU), Taiwan n va tn to First of all, I want to thank my supervisors Assoc Prof Wu Chien-Hou from ie gh Biomedical Engineering & Environmental Science Department, National Tsing Hua p University and PhD Nguyen Huu Tho from Thai Nguyen University of Agriculture oa nl w and Forestry Their priceless advices are not only valuable to my research in order to d gain successful results, but also contribute to my future career orientation an lu nf va Secondly, I am grateful to Mr Weichang Yuan, MS student and my friends in lm ul the laboratory, who facilitated and provided the information and data necessary for my z at nh oi implementation process and helped me finish this thesis Last but not least, thanks to my parents and good friends who always encourage z l gm @ me and offer support and love Sincerely, m co an Lu Duong CuongThinh n va ac th iii si TABLE OF CONTENT ACKNOWLEDGEMENT iii TABLE OF CONTENT iv LIST OF FIGURES LIST OF TABLES lu LIST OF ABBREVIATIONS an va PART I INTRODUCTION n Research rationale Research’s objectives 1.2 p ie gh tn to 1.1 Research questions and hypotheses 1.4 Limitations d oa nl w 1.3 an lu nf va PART II LITERATURE REVIEW lm ul 2.1 Overview of Titanium dioxide z at nh oi 2.1.1 Titanium oxidation structures and properties 2.1.2 The photocatalytic activity of TiO2 z @ l gm 2.2 Layer-by-layer self-assembly 10 m co 2.3 Overview of Poly(L-Dopa) 12 an Lu PART III METHODS 13 n va 3.1 Material 13 ac th iv si 3.1.1 Chemicals .13 3.1.2 Equipment 14 3.2 Methods 14 3.2.1 General principle 14 3.2.2 Fabrication of photocatalytic thin [TiO2/ Polymer]n films by the layer-bylayer self-assembly 15 3.2.2 Characterization .17 lu an 3.2.3 Photodegradation performance 19 n va PART IV RESULT .20 tn to p ie gh 4.1 Optical Photo 20 nl w 4.1.1 Optical photos of P25/PDopa films .20 d oa 4.1.2 Optical photos of multiple films 20 nf va an lu 4.2 Characterization of P25/Pdopa 21 4.2.1 Dynamic Light Scattering (DLS) 21 lm ul 4.2.2 FTIR .23 z at nh oi 4.2.3 SEM images of P25/Pdopa 24 z 4.2.4 AFM .26 gm @ 4.3 Photodegradation performance 30 co l 4.3.1 Calibration .30 m an Lu 4.3.2 Photodegradation activities of PDopa films 31 n va ac th v si 4.3.2 Photodegradation performance of TiO2 34 4.4 P25/PDoPa films band gap 36 PART V DISCUSSION AND CONCLUSION 38 5.1 Discussion 38 5.2 Conclusion .40 REFERENCES 41 lu an n va p ie gh tn to d oa nl w nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th vi si LIST OF FIGURES Figure 1Crystal structures of rutile, anatase and brookite titanium dioxide Figure Schematic diagram illustrating the principle of TiO2 photocatalysis with the presence of water pollutant (RH) .10 Figure The principle of Layer-by-layer self-assembling method .11 Figure Poly(L-DOPA) 12 lu an Figure Chemicals: a) PDopa, b) SRB 10 uM, DIW c) pH=3, d) PAA 13 n va tn to Figure Equipment: a) UV-Visible Spectrophotometer, b) Photochemical reactor, c) ie gh pH adjustment, d) Magnetic stirrer, e) Ultrasonic, f) DLS 14 p Figure Experimental process 15 oa nl w Figure Photos of P25/PDopa film .20 d Figure 5.5 bilayer thin films' images: a) St-01, b) St-21, c) P25 20 lu nf va an 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 lm ul Figure 12 P25 size varied from pH 22 z at nh oi Figure 13 FT-IR spectra of Degussa P25, L-Dopa, PDopa, P25/PDopa, PAA, P25/PAA .23 z @ l gm Figure 14 SEM images of (a) 0.5 bilayers, (b) 1.5 bilayers, (c) 2.5 bilayers, (d) 5.5 bilayers, (e) 10.5 bilayers, (f) 15.5 bilayers, (g) 20.5 bilayers 26 co m Figure 15 AFM images of thin films prepared with the coating sequence of an Lu (P25/PDopa)n: a) 0.5 bilayers, b) 2.5 bilayers, c) 5.5 bilayers before photodegradation n va ac th si 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 lu an of SRB using (P25/PDopa)n thin films at wavelength 562 nm, 33 n va Figure 19 (a) SRB degradation profiles of (TiO2/PDopa)n thin films at wavelength 562 tn to nm, (b) the first-order kinetic plot of ln(C/C0) and time(minutes) for photodegradation gh p ie of SRB using diffirent kinds of TiO2 .34 nl w Figure 20 (a) Absorbance of P25/PDoPa films, (b) Absorbance at 300 nm of d oa P25/PDoPa, (c) band gap of P25/PDopa .36 nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th si LIST OF TABLES Table Numbers of layers 17 Table Roughness of P25/PDopa films with different numbers of bilayer 29 lu an n va p ie gh tn to d oa nl w nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th si 4.3 Photodegradation performance 4.3.1 Calibration 2.0 0.5 uM uM uM uM 10 uM 20 uM Absorbance 1.5 1.0 0.5 0.0 lu 400 450 500 550 600 650 700 750 an Wavelength (nm) va n a) tn to 2.0 ie gh 1.0 d oa nl w Absorbance at 562nm p 1.5 y = 0.0928x - 0.005 R² = 0.9999 0.0 nf va an lu 0.5 lm ul 10 15 20 Concentration (uM) z at nh oi b) z Figure 16 Absorbance of SRB: a) in range from 400nm to 750nm, b) at 562nm @ l gm The upper figure exhibits a straight-line calibration data set where X = concentration and Y = Absorbance at 562 nm (Y = 0.0928x -0.005) The black dots are co m data points For this set of data, the measured slope is 0.928 and the intercept is 0.005 an Lu The true value of the slope is exactly 7, which included blank The quality of fit n va ac th 30 si (standard deviation) is 0.9999, which shows high quality of this method in concentration range from 0.5 uM to 20 uM 4.3.2 Photodegradation activities of PDopa films a) 2.5 Bilayers 5.5 Bilayers 10.5 Bilayers 15.5 Bilayers 20.5 Bilayers 1.0 0.8 C/C0 0.6 0.4 0.2 lu an 0.0 va n 10 20 30 40 50 60 p ie gh tn to Time (min) b) 0.5 w 2.5 Bilayers 5.5 Bilayers 10.5 Bilayers 15.5 Bilayers 20.5 Bilayers oa nl 0.0 -0.5 d an lu -1.0 -2.0 R² = 0.996 y = -0.037x + 0.0602 R² = 0.9957 y = -0.0488x + 0.1525 lm ul -2.5 y = -0.0316x + 0.0495 nf va ln(C/C0) -1.5 -3.0 -4.0 10 z at nh oi -3.5 R² = 0.9864 y = -0.0523x + 0.1732 20 30 40 R² = 0.9845 y = -0.0643x + 0.2285 R² = 0.9823 50 60 70 80 Time (min) z @ l gm Figure 17 (a) SRB photodegradation profiles of (P25/PAA)nthin films at wavelength 562 nm, (b) the first-order kinetic plot of ln(C/C0) and time(minutes) m co for photodegradation of SRB using (P25/PAA)n thin films at wavelength 562 nm an Lu n va ac th 31 si Figure 17(a) shows the efficiencies of the photocatalytic degradation under UVvis irradiation, C is the concentration of SRB at the irradiation time t and C0 is the concentration in the absorption equilibrium of photocatalysts before irradiation As shown in this figure, in term of P25/PAA bilayers films, about 98% of SRB solutions were degraded after h irradiation for 20.5 bilayers films whereas 85% for 2.5 bilayers films made by dip-coating, which reveals that the photocatalytic activity has been extremely improved due to the layer by layer structure Figure 17(b) shows the relationship of time versus ln(C/C0) for all photocatalysts According to the results, it lu an is of great importance to note that the photocatalytic efficiency of P25/PAA layer by n va layer composite 20.5 bilayers is two times that of 2.5 bilayers film p ie gh tn to d oa nl w nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th 32 si a) 2.5 Bilayers 5.5 Bilayers 10.5 Bilayers 15.5 Bilayers 20.5 Bilayers 1.0 0.8 C/C0 0.6 0.4 0.2 0.0 10 20 30 40 50 60 Time (min) b) lu 0.5 an 0.0 va -0.5 n -1.0 to -1.5 p ie gh ln (C/C0) tn -2.0 y = -0.0364x + 0.0551 -2.5 y = -0.0427x + 0.11 R² = 0.9963 R² = 0.9913 y = -0.0541x + 0.1605 2.5 Bilayers 5.5 Bilayers 10.5 Bilayers 15.5 Bilayers 20.5 Bilayers -3.0 -3.5 w -4.0 R² = 0.9896 y = -0.0599x + 0.2305 R² = 0.9802 y = -0.0749x + 0.2933 oa nl -4.5 -5.0 R² = 0.9786 d an lu Time (min) nf va Figure 18 (a) SRB degradation profiles of (P25/PDopa)n thin films at wavelength lm ul 562 nm, (b) the first-order kinetic plot of ln(C/C0) and time(minutes) for z at nh oi photodegradation of SRB using (P25/PDopa)n thin films at wavelength 562 nm, z m co l gm @ an Lu n va ac th 33 si By comparison, the multilayer films containing Poly(L-Dopa) were recorded at higher of photodegradation efficiency It is about almost 99% of SRB solutions were degraded after h irradiation for 20.5 bilayers films whereas 89% for 2.5 bilayers films made by dip-coating 4.3.3 Photodegradation performance of TiO2 a) P25 St-01 St-21 1.0 0.8 lu 0.6 n va C/C0 an 0.4 tn to 0.2 ie gh 0.0 10 20 30 40 50 60 p nl w Time (minutes) 0.0 d oa b) lu an y = -0.0061x - 0.0055 -0.5 R² = 0.9993 nf va y = -0.0144x + 0.0055 -1.5 P25 St-01 St-21 -2.5 z at nh oi -2.0 y = -0.0427x + 0.11 R² = 0.9913 z 10 20 30 40 @ -3.0 R² = 0.9997 lm ul ln(C/C0) -1.0 50 60 70 80 l gm Time (minutes) m co Figure 19 (a) SRB degradation profiles of (TiO2/PDopa)n thin films at an Lu wavelength 562 nm, (b) the first-order kinetic plot of ln(C/C0) and time(minutes) n va for photodegradation of SRB using diffirent kinds of TiO2 ac th 34 si SRB degradation profiles of the multilayer films containing different kinds of TiO2 and the first-order kinetic plot of ln(C/C0) and time (minutes) for photodegradation of SRB using diffirent kinds of TiO2 were graphed as in figure 19 The photodegradation efficiency of the multilayer films containing P25 was recorded as three times as that of St-21 and six times as that of St-01 lu an n va p ie gh tn to d oa nl w nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th 35 si 4.4 P25/PDoPa films band gap a) 2.5 Bilayers 5.5 Bilayers 10.5 Bilayers 15.5 Bilayers 20.5 Bilayer Absorbance 200 300 400 500 600 Wavelength (nm) b) lu 3.0 an va 2.5 p ie gh tn to Absorbance at 300 nm n 2.0 1.5 1.0 w oa nl 0.5 10 12 14 16 18 20 22 No P25/PDopa bilayers d lu c) an 3.5 1/2 2.0 z at nh oi 1.5 1/2 (ahv) /(eV.m) lm ul 2.5 nf va 3.0 1.0 0.5 Photo energy/(eV) co l gm @ -0.5 z 0.0 m Figure 20 (a) Absorbance of P25/PDoPa films, (b) Absorbance at 300 nm of an Lu P25/PDoPa, (c) band gap of P25/PDopa n va ac th 36 si It is quite obvious in figure 20(a) that the P25/Pdopa bilayer films cannot absorb any visible light due to the fact that its absorption edge is 400 nm As the data shown in figure 20 (b), at 300 nm wavelength, as the increase of bilayers, the absorbance of the films is increasing According to the Kubelka-Munkequation : αhυ=const(hυ−Eg)2 where α=(1−R)2/2R, R=10−A, and A is an optical absorption Band gap of photocatalyst can be calculated from the equation Figure 20(c) plots the relationship lu of (αhυ)1/2 versus photon energy, showing that the band gap of P25/PDoPa films is an n va around 3.2 eV p ie gh tn to d oa nl w nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th 37 si PART V DISCUSSION AND CONCLUSION 5.1 Discussion In general, based on photodegradation data, fabrication of photocatalytic thin films by the layer-by-layer self-assembling method containing P25 and poly(L-Dopa) contributed to be a promising method for efficiency improvement in contaminant degradation because of its advantage of it materials as well as the method Compared to St-01 and St-21, DLS shows that P25 has the highest zeta- lu an potential and the smallest particle size at pH 3.At pH 3, the highest zeta-potential va contributes to a high colloidal stability rate in P25 (Greenwood & Kendall, n to gh tn 1999;Hanaor, Michelazzi, Leonelli, & Sorrell, 2012) whereas with smallest particle p ie size, P25 has low sedimentation rate (Kammermeyer, K., Binder, J 1941) In addition nl w to this, the photodegradation efficiency of the multilayer films containing P25 was d oa recorded as much higher than that of St-21 and that of St-01 As a result, at pH 3, P25 an lu solution is suitable for fabrication of multilayer films due to its high colloidal stability nf va and low sedimentation rate lm ul Additionally, in case of pH values, Poly(L-Dopa) domains negative charge at z at nh oi wide range of pH values from to (Zeta-potential < -30 mV) while P25 gets high positive charge from pH to (Zeta-potential >40 mV) and small size from pH to z gm @ According to “Zeta Potential for measurement of stability of nanoparticles “by co l Anirbandeep Bose, at range of Zeta-potential is around +-30 to +-60, stability behavior m of the colloids is moderate and good stable Therefore, P25 and Poly(L-Dopa) an Lu solutions at pH to are good selection n va ac th 38 si In comparison between Poly(L-Dopa) and PAA, the multilayer films containing Poly(L-Dopa) were recorded at higher of photodegradation efficiency This contributes to former researches by using Poly(L-Dopa) instead of PAA in fabrication of multilayer films Moreover, FTIR figure shows the inheritance of functional group as well as the properties of bare P25 and PDopa in the multilayer films It is clear that the multilayer films have similar peaks to P25 and PDopa, which means that they have the same lu functional groups an n va Furthermore, SEM and AFM images present the growth of thickness of the to gh tn multilayer films as results of increment of both P25 and PDopa layers This result p ie shows that layer-by-layer self-assembly method works effectively in improvement of nl w the thickness of the films The record indicated that the growth of films thickness is d oa not an ideal one layer after another deposition.TiO2 nanoparticles fill into the pores nf va an lu and stack to achieve thickness growth simultaneously In addition, the photodegradation performance shows the effectiveness of P25 lm ul and PDopa in presence of themselves As the result of the increment of bilayers, the z at nh oi photodegradation rate increases Besides, the multilayer films were recorded with band gap 3.2 and the disability of visible light absorption It is the same with the band gap z gm @ of bare P25 (Amtout & Leonelli, 1995; Asahi, Taga, Mannstadt, & Freeman, 2000; m co l Koelsch, Cassaignon, Minh, Guillemoles, & Jolivet, 2004; Pelaez et al., 2012) However, there are various unanswered questions and limitations here Firstly, an Lu the highest number of bilayers in the study is 20.5, so what is the maximum number of n va ac th 39 si bilayers in reality that is possible to fabricate for the most effective? Secondly, this study evaluated only the photodegradation performance of the multilayer films in SRB Thus, it is quite limited to conclude that P25/PDopa performs good result in pollution degradation This could be interesting to focus on for future researchers 5.2 Conclusion In this study, it is clear that particle size and colloidal stability of TiO2 aqueous suspension play an important part in achievement of high photocatalytic performance lu Poly(L-Dopa) was negatively charge at wide range of pH values, which contributes it a an n va good substitution for the current commercially available polyelectrolyte At pH 3, P25 tn to Degussa and Poly(L-Dopa) were recorded as an optimal charge with high zeta- ie gh potential and low particle size, contributing for high colloidal stability and low p sedimentation Furthermore, the results show that the layer-by-layer self-assembling w oa nl method was simple and useful to fabricate the thin films of nano-structured thin film d containing P25 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Society 19(4), 479–488 Hanaor, D.A.H., Michelazzi, M., Leonelli, C.; Sorrell, C.C (2012) The effects of carboxylic acids on the aqueous dispersion and electrophoretic deposition of ZrO2 Journal of the European Ceramic Society 32(1), 235–244 lu Anirbandeep Bose Zeta Potential for measurement of stability an n va nanoparticles.Pharmainfo.net.Retrieved of from physicochemical-characterization-nanoparticles/zeta(accessed on 12/09/2016) p ie gh tn to http://www.pharmainfo.net/book/emerging-trends-nanotechnology-pharmacy- d oa nl w nf va an lu z at nh oi lm ul z m co l gm @ an Lu n va ac th 44 si