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| 008 | 201217b2015 a|||f mb|| 00| 0 eng d | ||
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_aeng _beng _bara |
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_aOmnia Mahmoud Abdel Ghaney _9208 |
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| 245 | 1 |
_aImproving Nanosized -Anatase Photocatase photocatalytic Activity for Dental Bleaching Application _cOmnia Mahmoud Abdel Ghaney |
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| 260 | _c2015 | ||
| 300 |
_a p. _bill. _c21 cm. |
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| 500 | _3Supervisor: Mostafa El Ashry | ||
| 502 | _aThesis (M.A.)—Nile University, Egypt, 2015 . | ||
| 504 | _a"Includes bibliographical references" | ||
| 505 | 0 | _aContents: CHAPTER II: Background and Literature Review ....................................................... 5 1. Teeth discoloration.............................................................................................. 5 1.1 Intrinsic discoloration .................................................................................. 5 1.2 Internalized discoloration ............................................................................ 5 1.3 Extrinsic discoloration ................................................................................. 5 1.3.1 Direct stains ............................................................................................. 6 1.3.2 Indirect stains ........................................................................................... 6 2. Historical background ......................................................................................... 6 3. Mechanisms of peroxide dental bleaching .......................................................... 8 4. Types of dental bleaching ................................................................................. 12 5. In-Office dental bleaching ................................................................................ 12 Efficacy ................................................................................................................ 13 Side effects ........................................................................................................... 14 6. Assisted dental bleaching .................................................................................. 15 6.1 Heat-activated ............................................................................................ 15 6.2 Light-activated ........................................................................................... 16 6.3 Photo-catalyst activated ................................................................................. 17 7. Titania as a photo-catalyst ................................................................................ 18 7.1 Methods of synthesis ................................................................................. 20 7.2 Mechanism of Titania photo-catalysis ....................................................... 21 8. Modifications of Titania ................................................................................... 24 8.1 Non-metal Modification of Titania............................................................ 24 8.2 Heterojunctions .......................................................................................... 26 8.3 Metallic modification of Titania ................................................................ 26 8.4 Modification with Noble metal nano-particles .......................................... 27 8.4.1 Silver addition ........................................................................................ 29 8.4.2 Gold addition ......................................................................................... 31 CHAPTER III: METHODOLOGY ............................................................................. 33 1. Preparation ........................................................................................................ 34 1.1 Fabrication ................................................................................................. 34 ix The Chemicals ..................................................................................................... 35 1.1.1. Nanosized-anatase preparation (T) ........................................................ 35 1.1.2. Method 1 (M1) noble metal addition (TS, TG preparation) .................. 36 1.1.3. Method 2 (M2) noble metal addition (TSnp, TGnp Preparation) .......... 36 Silver nano-particles preparation (Snp) ............................................................... 37 Gold nano-particles preparation (Gnp) ................................................................ 37 1.2. Characterization ......................................................................................... 37 1.2.1. X-Ray Diffraction (XRD) ...................................................................... 38 1.2.2. Transmission Electron Microscope (TEM) ........................................... 39 1.2.3. UV-Vis Spectrophotometer ................................................................... 40 2. Testing............................................................................................................... 41 2.1. Experimental Solutions preparation .......................................................... 42 2.2. Glassware................................................................................................... 43 2.3. Equipment .................................................................................................. 44 2.3.1. Activating light ...................................................................................... 44 2.3.2. Vis-NIR Spectrophotometer .................................................................. 45 2.4. Experimental set-up ................................................................................... 46 2.5. The experiment .......................................................................................... 47 CHAPTER IV: RESULTS AND DISCUSSION ........................................................ 48 1. Results of the preparation phase ....................................................................... 48 1.1. Titania ........................................................................................................ 48 Transmission electron microscope (TEM)........................................................... 48 UV-Vis spectrophotometer .................................................................................. 49 X-ray diffraction (XRD) ...................................................................................... 50 1.2. Method 1 (M1) noble metal addition ......................................................... 51 1.2.1. Titania silver (TSO) ............................................................................... 51 TEM ..................................................................................................................... 51 UV-Vis spectrophotometer .................................................................................. 52 XRD ..................................................................................................................... 52 1.2.2. Titania gold (TG) ................................................................................... 53 TEM ..................................................................................................................... 53 UV-Vis spectrophotometer .................................................................................. 53 XRD ..................................................................................................................... 54 1.3. Method 2 noble metal addition .................................................................. 55 Silver nano-particles (Snp) .................................................................................. 55 Gold nano-particles (Gnp) ................................................................................... 55 1.3.1. Titania + Silver nano-particles (TSnp) .................................................. 56 TEM ..................................................................................................................... 56 UV-Vis spectroscope ........................................................................................... 57 1.3.2. Titania + gold nano-particles (TGnp) .................................................... 57 TEM ..................................................................................................................... 57 UV-Vis spectroscope ........................................................................................... 58 2. Results of the testing phase ............................................................................... 59 2.1. Pilot study: Effect of Titania photocatalyst on the bleaching process of MB dye (T vs controls) ............................................................................................... 59 UV group ............................................................................................................. 60 Vis light group ..................................................................................................... 61 UV vs Vis ............................................................................................................. 63 2.2. Effect of noble metal addition Method 1(T vs M1) ................................... 64 UV group ............................................................................................................. 64 x Vis group .............................................................................................................. 66 UV vs Vis ............................................................................................................. 67 2.3. Effect of noble metal addition Method 2 (T vs M2) .................................. 68 UV group ............................................................................................................. 68 Vis group .............................................................................................................. 70 UV vs Vis ............................................................................................................. 71 3. Data analysis ..................................................................................................... 72 3.1. Effect of photocatalyst addition ................................................................. 72 3.2. The effect of addition method on the photosensitivity and photocatalytic activity of Titania (M1 vs M2)............................................................................. 73 3.2.1 M1 vs M2 with Silver ............................................................................ 74 3.2.2 M1 vs M2 with Gold .............................................................................. 75 3.3. Best performance ....................................................................................... 76 CHAPTER V: CONCLUSION.................................................................................... 78 REFERENCES ............................................................................................................ 80 Appendix A .................................................................................................................. | |
| 520 | 3 | _aAbstract: In-office dental bleaching is a popular treatment for restoring and improving teeth color. In-office bleaching products contain high concentrations of hydrogen peroxide (up to 40%), which can be damaging to teeth. Nanosized-anatase photocatalysts (T) were used to enhance the activity of bleaching products using lower concentrations of hydrogen peroxide (H). However, T requires activation by ultraviolet (UV) radiation, which can be harmful to patients. In the present study, we aimed to improve the photocatalytic activity and photosensitivity (to Vis light) of T used for dental bleaching by gold and silver addition. Improvement was evaluated via the photo-degradation of methylene blue dye (MB) in H solution of 3.5% under UV radiation and under Vis light source. T was prepared using sol-gel method and a pilot study was done to assess its activity in both UV and Vis light. T modification with gold (G) and silver (S) was done using two methods (M1, and M2). M1: was done by adding gold and silver precursors to T during preparation making (TS, and TG). M2: was done by preparing gold and silver nanoparticles (Gnp, and Snp) separately and mix them with T freshly in the experimental solution forming (TGnp, and TSnp). The experiment was done by exposing the experimental solutions to activating light for 10 min and measuring the photo-degradation\min of MB using Vis-NIR spectrophotometer. The results showed an improvement in photocatalytic activity and photosensitivity of all samples especially with TSnp, which yielded the best performance in Vis light. We concluded that G and S addition did improve both the photocatalytic activity and photosensitivity of T highlighting the TSnp as a strong candidate for Vis light assisted in-office dental bleaching. | |
| 546 | _aText in English, abstracts in English and Arabic | ||
| 650 | 4 |
_aNano- Science & Technology _9199 |
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| 655 | 7 |
_2NULIB _aDissertation, Academic _9187 |
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_aNano- Science & Technology _9199 |
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_2ddc _cTH |
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_c8747 _d8747 |
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