Optical and thermal characterization of dye intercalated montmorillonites and rare earth doped materials Lyjo K. Joseph International School of Photonics Cochin University of Science and Technology Kochi- 682022, Kerala, India Ph. D. Thesis submitted to Cochin University of Science and Technology in partial fulfillment of the requirements for the Degree of Doctor of Philosophy November 2009 Optical and thermal characterization of dye intercalated montmorillonites and rare earth doped materials Ph. D. Thesis in the field of Photonics Author: Lyjo K. Joseph Research Fellow, International School of Photonics Cochin University of Science and Technology Kochi — 682 022, India Email: [email protected], [email protected] Research Advisors: Dr. P Radhakrishnan Professor, lntemational School of Photonics Cochin University of Science and Technology Kochi — 682 022, India Email: [email protected] Dr. V P N Nampoori Professor, lntemational School of Photonics Cochin University of Science and Technology Kochi — 682 022, India Email: [email protected] International School of Photonics. Cochin University of Science and Technology Kochi — 682 022, India URL:www.photonics.cusat.edu November 2009. Cover design: Manu Balakrishnan CERTIFICATE Certified that the work presented in the thesis entitled “Optical and thermal characterization of dye intercalated montmorillonites and rare earth doped materials” is based on the original work done by Mr. Lyjo K Joseph under my guidance and supervision at the International School of Photonics, Cochin University of Science and Technology, Kochi-22, India and has not been included in any other thesis submitted previously for the award of any degree. \.I . Kochi — 682022 Prof. P. Radlfakrishnant/-«M 20"‘ November 2009. (Supervising Guide) DECLARATION Certified that the work presented in the thesis entitled “Optical and thermal characterization of dye intercalated montmorillonites and rare earth doped materials” is based on the original work done by me under the guidance of Dr. P Radhakrishnan, Professor, International School of Photonics, Cochin University of Science and Technology, Kochi—22, India and the co—guidance of Dr. V P N Nampoori, Professor, International School of Photonics, Cochin University of Science and Technology, Kochi—22, India and it has not been included in any other thesis submitted previously for the award of any degree. Kochi — 682 022 20"" November 2009. Lyjo K Joseph Contents Acknowledgements xix General remarks regarding the thesis xx Preface xxi List of publications xxv List of abbreviations xxix Chapter 1: Materials, Methods and Measurements- An Overview Abstract 1.1. Section I—Materials 1.1.1. Part A: Clay minerals Al. Introduction A2. Clay mineral properties A3. Structures and mineralogy of clay minerals A3. 1. Tetrahedral sheet A3.2. Octahedral sheet A3.3. Subdivision of layer lattice silicates A4. Montmorillonite A5. Clay-water interactions --\D\1C\LllLIIUJUJL»JUJ 1.1.2. Part B: Dyes Bl. Introduction B2. Methylene blue B3. Malachite green B4. Rhodamine B B5. Auramine 0 B6. Concluding remarks 1.1.3. Part C: Dye intercalated clay minerals Cl. Introduction C2. Organisation of molecules at clay mineral surfaces C3. Dye aggregation in clay dispersions 1.1.4. Part D: Rare earth doped materials Contents D l. Rare earth elements D2. Optical properties of rare earth ions D3. General properties of lanthanides D3. 1. Lanthanide contraction D3.2. Radiative transitions in rare earth ions D3.3. Magnetism of lanthanides D3.4. Non-radiative transitions in rare earth ions D4. Applications of rare earth elements D5. Rare earth titanates D6. Rare earth doped glasses 1.2. Section II —Methods 26 1.2.1. Part A: Self propagated high temperature synthesis (SHS) 26 El. Introduction 26 E2. Advanced ceramics 26 E3. Basics of reactions 27 E4. Advantages 29 E5. Features 30 E6. Drawback 3 l E7. Applications 3 1 1.2.2. Part B: Sol gel 3| F l . Introduction 31 F2. Sol and gel 32 F3. The silicon alkoxide sol gel process 32 F4. Advantages of sol gel synthesis 32 F5. Limitations of sol gel synthesis 33 F6. Silica sol gels- Reaction mechanisms and chemical control of reactions 34 F6. 1. Hydrolysis- Acid and base catalysis 34 F6.2. Condensation 35 F6.3. Gelation 36 F6.4. Ageing 36 F6.4. l. Significance of ageing 37 F6.5. Drying 38 F6.5. I. Consequences of drying 38 F6.5.2. Avoiding cracks 38 viii Optical and thermal characterization. .. F66. Densification 38 F7. Additives for structuring and processing 39 F7. 1. Drying and control additives 39 F8. Entrapment of functional materials— Efficiency of entrapment 40 F9. The characterization of sol gel materials 40 F10. Application of sol gel silicates 40 1.2.3.G1. Part C: Introduction Photothermal phenomena 42 42 G2. Photothermal detection and applications 44 H.HI. Photoacoustics Introduction 45 H2. Photothermal spectroscopy 46 H2. 1. Photoacoustic spectroscopy 47 H3.H2.2. Historical Principle of photoacoustic perspective spectroscopy 49 47 H4. InstrumentationH4. 1. The aspects light of photoacoustics source 50 50 H4.2.H4.3. Modulation Detection techniquesschemes 5]50 H4.4. Signal processing 51 H5. Advantages of photoacoustics 5| H6. Limitations of photoacoustics 53 H7. Applications of photoacoustics 53 I. Rosencwaig-Il. Introduction Gersho (RG) theory 54 54 12. The thermal diffusion equations 55 13. Temperature distribution in the cell 57 14. Production of the acoustic signal 58 I6.15. Importance Special of RGcases theory 59 61 J. Photothermal deflection (PTD) 61 J1.J2. IntroductionLimitations 6261 Contents J3. Advantages 62 K. Thermal property determination by photothermal techniques 62 Kl. Introduction 62 K2. Thermal diffusivity (TD) 63 K3. Thermal effusivity (TE) 64 l.2.4. Part D: Fluorescence and absorption 65 Ll. Introduction 65 L2. Absorption spectroscopy 65 L3. Fluorescence 65 L4. Fluorescence excitation spectroscopy 66 L5. Laser induced fluorescence (LIF) 66 1.3. Section III —Measurements 67 l.3.l. Part A: Light sources 67 Ml. Argon ion laser 67 M2. Pulsed Nd: YAG laser 67 M3. Xenon arc lamp 67 M4. Mode-locked Ti: sapphire laser 67 M5. Diode pumped solid state (DPSS) laser 68 M6. He- Ne laser 68 1.3.2. Part B: Photoacoustic cell (PAC) 68 N1. Introduction 68 N2. Standard photoacoustic cell 68 N3. Designing aspects of photoacoustic cell 68 N4. Photoacoustic cell design 69 1.3.3. Part C: Measuring instruments 71 0 l . Spectrophotometer 7l Ol . l Specifications 7] 01 .2. Reflectance measurement 71 O2. Fluorescence spectrophotometer 7] O3. Monochromator 72 O4. Monochromator CCD assembly 72 05. Chopper 72 Optical and thermal characterization. O6. Locl<- in amplifier 73 O8.O7. PreamplifierMicrometer 7373 l.4.1.5. Scope References of the thesis 74 73 Chapter 2: Thermal and optical characterization of Abstractdye intercalated montmorillonites 93 93 2.2.2. l. Sample Prologue details 95 96 2.2.1. Commercial clay samples: KSF and K-10 96 2.2.2. Sample preparation- Dye adsorption from solution 96 2.3. Dye2.3.1. molecular aggregates The —Molecularexciton exciton model coupling theory 97 96 2.3.2. Angle of slippage (Cl) 98 2.3.3. H and J aggregates 98 2.4. Section I - Thermal characterization of dye intercalated 2.4.montmorillonites l. Preamble using photoacoustics l0l 101 2.4.2. Thermal diffusivity measurement - photoacoustic theory 102 2.4.3.2.4.4. Experimental Sample details setup 103 l03 2.4.5. Part A: Thermal diffusivity dependence on host montmorillonite 104 A2.A I. Materials Introduction and methods 104 104 A2.1. Sample details 104 A2.2. Reflectance spectra measurement I04 A2.3.A2.4. Specific TG/DTA surface area andmeasurement porosity measurement 105 105 A3. Results and discussions 105 A3. 1. Optical reflectance study I05 A3.2. Photoacoustic study 106 Contents A3.3. Effect of pore volume on thermal diffusivity I08 A3.4. Effect of repeated adsorption on K-IO I09 A3.5. Poreadsorbed volume effect on the thermal KSFdiffusivity of dye I I0 A3.6. Effect of repeated adsorption on KSF I I0 A3.7. Thermal diffusivity of methylene blue A4. Conclusionsadsorbed K-IO and KSF — A comparison I 1 I I I 2.4.6. PartBI. B: Thermal Introduction diffusivity dependence on sintering temperature 11 11I I B2. Experimental details I I2 B4.B3. Results Sample and discussiondetails 112 I 12 B4. 1. Samples sintered at 300 °C I 12 B4.2. TGA analysis of methylene blue intercalated K-IO 1 13 B5.B4.3. Conclusions Samples sintered at 500 1°C I41 I3 2.4.7.Cl. Part C: ThermalIntroduction diffusivity dependence onI dye14 I14 C2. Experimental setup I 14 C3.C4. Results Sample and discussionsdetails 1 115 I4 C4.2.C4. 1. Absorption Photoacoustic studies on dye intercalated study samples I I7I I5 C4.3. AnomalousMG-X behaviour of samplerepeatedly adsorbed I I9 C4.4. Thermal diffusivity of rhodamine B intercalatecl K-IO samples I20 C4.5. Ultrasonicated dye adsorbed sample I20 C4.5.I. Sample preparation I20 C5.C4.5.2. Conclusions Thermal diffusivity of the sample l2l I2l xii Optical and thermal characterization. 2.5. Section II - Spectroscopic studies of dye intercalated 2.5.1.K-10 montmorillonite Preamble aqueous dispersions 122 122 2.5.2. Dispersions of dye intercalated montmorillonite 123 2.5.3. Optical characterization 123 2.5.4.D1. Part A: RhodamineIntroduction B intercalated K-l()123 123 D2. Experimenta|- Materials and methods 124 D2.l. Dye adsorption from solution 124 D3.D2.2. UltrasonicatedResults dye adsorption 124 124 D3. 1. Optical absorption studies 124 D4.D3.2. Discussions Fluorescence studies 128 125 D4.]. Optical absorption studies 128 D5.D4.2. Conclusions Fluorescence studies 130 129 2.5.5.El. Part B: Introduction Malachite green intercalated K-10131 131 E2.E3. Dispersions of Resultsmalachite green intercalated K-10 montmorillonite 131 131 E3. 1. Optical absorption studies 131 E3.2. Fluorescence studies 132 E4.E5. ConclusionsDiscussions 133134 2.5.6.