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Preparation of Novel Nano-Sized Ion Imprinted Polymers for the Selective Determination of Some Transition and Alkali Metal Ions & Synthesis, Characterizations and Applications of Nano-Sized ZnS Quantum Dots: Interaction Study with BSA, Determination of Hazardous Anions, and Removal of Pollutant Dyes

Name: Preparation of Novel Nano-Sized Ion Imprinted Polymers for the Selective Determination of Some Transition and Alkali Metal Ions &amp; Synthesis, Characterizations and Applications of Nano-Sized ZnS Quantum Dots: Interaction Study with BSA, Determination of Hazardous Anions, and Removal of Pollutant Dyes
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Ph.D Thesis

Preparation of Novel Nano-Sized Ion Imprinted Polymers for the Selective Determination of Some Transition and Alkali Metal Ions

&

Synthesis, Characterizations and Applications of Nano-Sized ZnS Quantum Dots: Interaction Study with BSA, Determination of Hazardous Anions, and Removal of Pollutant Dyes

Part A

New Zn²⁺ion-imprinted polymeric nanobeads were prepared by dissolving stoichiometric amounts of zinc nitrate and selected chelating ligands, Morin (3,5,7,20,40-pentahydroxyflavone), in 15 mL ethanol-acetonitrile (2:1; v/v) mixture as porogen solvent in the presence of ethyleneglycol-dimethacrylate (EGDMA) as cross-linking, and methacrylic acid (MAA) as monomer, via thermally polymerization method, using 2,2-azobisisobutyronitrile (AIBN) as initiator. The synthesized ion imprinted polymers with an average size of 70–90 nm in diameter, were characterized using FTIR, SEM, and thermal analysis techniques. Optimum pH range for rebinding of Zn²⁺ ion on the IIP (7.5) and equilibrium binding time were studied. Maximum adsorbent capacity and enrichment factor for Zn²⁺ion were obtained as 45.3 mg.g^-1 and 150, respectively, using flame atomic absorption spectrometry (FAAS).

Novel ion imprinted polymeric nanoparticles were synthesized via precipitation polymerization for recognition and determination of Hg²⁺ ions in aqueous solutions. The Hg-IIP nanoparticles were prepared by copolymerizing of mercury chloride and 5,10,15,20-tetrakis (3-hydroxyphenyl)-porphyrin, as a suitable chelating ligand in 25 mL of acetonitrile-dimethylsulfoxide (4:1; v/v) mixture as porogen solvent, in the presence of EGDMA, MAA, and AIBN. The adsorbed mercury was easily eluted by 5.0 mL 1.0 M HNO₃and mercury contents of the leach samples have been determined by cold vapor atomic adsorption spectrometry (CVAAS). The results demonstrated that the Hg(II) imprinted copolymers had a large adsorption capacity of 248.9 mg.g^-1 for dry copolymer. The relative standard deviation and detection limit (3σ) of the method were evaluated as 2.2% and 0.15 µg.L^-1, respectively. The prepared mercury imprinted copolymers can be used at least 30 times without any significant decrease in the polymer binding affinities.

In addition, the prepared Hg²⁺ ion imprinted polymer was used as solid phase sorbent for preconcentration and on-line photometric determination of Hg²⁺ ions by using flow injection technique. The experimental parameters including pH of sample solution, preconcentration and elution times, nature, volume, concentration of eluent, flow rate of loading and leaching solutions were investigated and optimized. The Hg²⁺ ions retained by the polymeric nanoparticles were eluted quickly with 5.0 mL of HNO₃1.0 M. The amounts of adsorbed Hg²⁺ions on the IIPs were determined photometrically at 485 nm using alcoholic diphenylthiocarbazone as a suitable reagent after elution in the setupped flow injection system. The relative standard deviation and detection limit (3σ) of the method for eight replicate at optimum pH of 7.0, were evaluated as 4.2% and 0.0036 ng.mL^-1, respectively.

The first application of the ion imprinting technology was reported for the determination of potassium ion by precipitation polymerization method. Ion imprinted polymeric (IIP) nanoparticles were prepared by using dicyclohexyl-18C6 (DC18C6) as a selective ligand for K⁺ ion, in the AN/DMSO (3:1; v/v) mixture as porogen solvent in the presence of EGDMA, MAA, and AIBN. The SEM results showed IIP nanoparticles of 60–90 nm in diameter and slightly irregular in shape. The maximum adsorption capacity and preconcentration factor of the ion-imprinted polymers (IIPs) for K⁺ion were 33.5 mg.g^-1, 60, and at pH 9.0, respectively. The relative standard deviation (RSD %) and detection limit (DL) (3σ) of the method were evaluated as 1.7% and 3.8 ng.mL^-1, respectively. The relative selectivity coefficient values of the imprinted adsorbent for, K⁺/Li⁺, K⁺/Na⁺, K⁺/Rb⁺, K⁺/Cs⁺, K⁺/Mg²⁺, K⁺/Ca²⁺, and K⁺/Sr²⁺ were found to be as 24.8, 24.0, 20.4, 17.4, 19.4, 14.6 and 18.1 times greater than those for non-imprinted matrix, respectively.

Also, the first research on the preparation of a cesium ion imprinted polymer was carried out by a precipitation polymerization strategy for the uptake of cesium ion from aqueous solutions. Ion imprinted polymeric (IIP) nanoparticles were prepared by using dibenzo-24-crown-8 (DB24C8) as a Cs⁺ ion selective crown ether. The scanning electron micrographs showed the preparation of nanoparticles of 50–80 nm. The prepared cesium IIP nanoparticles showed highly selective recognition of Cs⁺ ion, with rapid adsorption and desorption processes. The RSD % and DL (3σ) of the method were evaluated as 0.9% and 0.7 ng.mL^-1, respectively. The relative selectivity coefficient values of the imprinted adsorbent for Cs⁺ ion related to Li⁺, Na⁺, K⁺, Rb⁺, Ag⁺, NH₄⁺, Mg²⁺, Ca²⁺, and Sr²⁺ were obtained to be 43.1, 37.5, 47.3, 23.5, 25.3, 23.4, 32.9, 41.2 and 23.2 times greater than non-imprinted matrix, respectively.

Part B

Ultra small zinc sulfide and iron doped zinc sulfide quantum dots (QDs) was synthesized in aqueous media, in the presence of 2-mercaptoethanol as a capping agent, at room temperature. The effect of Fe³⁺ion concentration as dopant on the optical properties of ZnS was studied. The size of quantum dots was determined to be about 1 nm, using scanning tunneling microscopy (STM) technique. The X-ray diffraction (XRD) analysis indicated that the iron doped nanoparticles are crystalline, with cubic zinc blend structure, having particle diameters of 17±2 Å. Finally, the interaction of the prepared QDs with bovine serum albumin was investigated at pH of 7.2, by using UV-Vis absorption and fluorescence spectroscopic methods at different temperature. In the steady-state fluorescence studies, the interaction parameters including binding constants (K_a), number of binding sites (n), quenching constants (K’_SV), and bimolecular quenching rate constant (k_q) were determined at three different temperatures and the results were then used to evaluate the corresponding thermodynamic parameters ΔH, ΔS and ΔG.

A novel, rapid and simple method for selective and sensitive determination of hazardous cyanide ion in aqueous solution was developed. The zinc sulfide (ZnS) nanoparticles exhibited a strong fluorescent emission at about 421 nm. Luminescent surface-modified QDs, with particle size below 5 nm, have been applied for spectrofluorometric determination of cyanide ions. Under the optimum conditions, the decrease in fluorescence intensity of ZnS QDs was linearly proportional to the cyanide ion concentration in the range of 2.4×10⁻⁶ to 2.6×10⁻⁵M with a detection limit of 1.7×10^-7 M. The relative standard deviation for six replicate measurements was obtained to be 2.6%. There is no significant wavelength shift on the fluorescence-quenched signals in the presence of cyanide ion at the pH of 11. In addition, the designed fluorescent sensor revealed remarkable selectivity for cyanide ion over other anions such as Cl⁻, Br⁻, F⁻, I⁻, IO₃⁻, ClO₄⁻, BrO₃⁻, CO₃²⁻, NO₂⁻, NO₃⁻, SO₄²⁻, S₂O₄²⁻, C₂O₄²⁻, SCN⁻, N₃⁻, citrate, and tartarate. Negligible influences were observed on cyanide detection by the coexistence of other anions.

A simple spectrofluorimetric method for the selective and sensitive determination of sulfide ion in aqueous solution was suggested. The ultra small zinc sulfide doped with manganese (ZnS:Mn) QDs were synthesized by using a safe and efficient procedure based on the co-precipitation of nanoparticles in aqueous solution in the presence of 2-mercaptoethanol (ME) at room temperature. The ZnS:Mn nanoparticles have exhibited two strong fluorescent emission at about 423.9 and 594.0 nm. Under the optimum conditions, the decreased fluorescence intensity of ZnS:Mn QDs is linearly proportional to the sulfide ion concentration in the range of 1.2×10^-6 to 2.6×10^-5M with a detection limit of 2.3×10^-7 M. The RSD for five replicate measurements (for 5.0×10^-6M of sulfide solution) was obtained 3.4%. There was no significant wavelength shift on the fluorescence-quenched signals in the presence of sulfide ion at the pH of 10. In addition, the designed fluorescent sensor possesses remarkable selectivity for sulfide over other anions.

In the last part, pure ZnS and iron doped ZnS quantum dots capped with 2-mercaptoethanol were used for decolorization of three color pollutants. Comparative photocatalytic degradations of the cationic dyes, including malachite green (MG) methyl violet (MV) and victoria blue 4R (VB), were performed to study the photoactivity behaviors of the prepared QDs, under UV light irradiation. The effect of operational parameters including; dosage of nanophotocatalyst, irradiation time, and pH of sample solutions on the decolorization efficiency of the organic dyes were studied. It was founded that the maximum degradation of the dyes was obtained at 80 mg.L^-1 of photocatacyst as an optimum value for the dosage of it in alkaline pH under UV light intensity of 40 W.m^-2. Also, the reproducibility of nanoparticles behavior, as photocatalyst showed at least three cycles of photodegradation processes. Finally, kinetic and degradation mechanisms of the dyes were discussed.

دسته: زبان خارجه, زبان خارجه برچسب: and Removal of Pollutant Dyes, Characterizations and Applications of Nano-Sized ZnS Quantum Dots: Interaction Study with BSA, Determination of Hazardous Anions, Preparation of Novel Nano-Sized Ion Imprinted Polymers for the Selective Determination of Some Transition and Alkali Metal Ions, Synthesis

توضیحات

TABLE OF CONTENTS PAGE

PART A

Imprinted Polymeric Materials

Section I

Introduction and Literature Review

1.1. Introduction 3

1.2. What is molecular imprinting 4

1.3. Molecular imprinting technology 5

1.4. Category of imprinted polymers 7

1.4.1. Covalent approach 9

1.4.2. Non-covalent approach 10

1.5. Ion imprinted polymers 11

1.6. Effecting of special target recognition 12

1.7. Optimization of the polymer structure 13

1.7.1. Template 13

1.7.2. Monomers 14

1.7.3. Cross-linkers 15

1.7.4. Porogenic solvents 17

1.7.5. Initiators 18

1.8. Preparation methods 20

1.8.1. Bulk polymerization 20

1.8.2. Multi-step swelling polymerization 22

1.8.3. Suspension polymerization 22

1.8.4. Precipitation polymerization 23

1.8.5. Surface imprinting polymerization 24

1.8.6. Monolithic imprinted polymerization 25

1.9. Overview of the synthesis of metal ion selective polymers 25

1.9.1. Monomer selection and preparation 26

1.9.2. Preparation of complexes 26

1.9.3. Preparation of polymers 27

1.10. Testing for selectivity 28

TABLE OF CONTENTS PAGE

1.11. Polymer characterization 29

1.11.1. Chemical characterization 29

1.11.2. Morphological characterization 29

1.12. Applications of imprinted polymers in analytical chemistry 30

1.12.1. Separation 30

1.12.1.1. Chromatography 30

1.12.1.2. Capillary electrochromatography 31

1.12.1.3. Solid phase extraction 32

1.12.2. Sensors 33

1.12.2.1. Selectrodes 34

1.12.2.2. Optrodes 34

1.12.2.3. Miscellaneous 35

1.12.3. Membrane separations 35

1.12.4. Flow injection analysis 36

Section II

Preparation of Novel Nano–Sized Ion Imprinted Polymers for the Selective Determination of Some Transition and Alkali Metal Ions:

Chapter One

Synthesis, characterization and development of a novel ion imprinted polymeric nanobeads for selective separation and sensitive determination of Zn(II) ions

2.1. Introduction 40

2.2. Experimental 41

2.2.1. Materials and Apparatus 41

2.2.2. Preparation of Zn–IIP and NIP nanoparticles 42

2.2.3 Sorption/desorption procedure 43

2.2.4. Pretreatment and analysis of real samples 44

2.3. Results and discussion 45

2.3.1. Preliminary complexation studies 45

TABLE OF CONTENTS PAGE

2.3.2. Characterization studies 46

2.3.2.1. FT–IR spectra 46

2.3.2.2. SEM Studies 49

2.3.2.3 Thermal analysis 49

2.3.3. Sorption/desorption studies 51

2.3.3.1. Choice of Eluent 51

2.3.3.2. Effect of pH 51

2.3.3.3. Adsorption capacity 52

2.3.3.4. Effect of other experimental parameters 54

2.3.4. Analytical performance 54

2.3.5. Repeated use 55

2.3.6. Selectivity study 56

2.3.7. Determination of Zn(II) ions in real samples 58

2.4. Conclusion 58

Chapter Two

An efficient and selective ion imprinted polymeric nanoparticles based on 5,10,15,20–tetrakis(3–hydroxyphenyl) porphyrin as a novel sorbent for fast determination of mercury ions

3.1. Introduction 61

3.2. Experimental 62

3.2.1. Materials and Apparatus 62

3.2.2. Preparation of Hg(II)–imprinted polymeric nanoparticles 63

3.2.3 Sorption/desorption procedure 64

3.2.4. Analysis of water samples 64

3.3. Results and discussion 64

3.3.1. Characterization of synthesized IIP nanobeads 65

3.3.1.1. SEM image 65

3.3.1.2. FT–IR Spectra 66

3.3.2. Sorption/desorption studies 67

TABLE OF CONTENTS PAGE

3.3.2.1 Effect of pH 67

3.3.2.2 Choice of Eluent 68

3.3.2.3 Adsorption and desorption times 69

3.3.2.4 Adsorption capacity 71

3.3.2.5. Maximum sample volume and weight of IIP 71

3.3.2.6. Stability and repeated use 72

3.3.3. Analytical performance 74

3.3.4. Selectivity study 74

3.3.5. Analytical applications 75

3.4. Conclusion 76

Chapter Three

Application of flow injection analysis for highly selective solid phase extraction and on-line photometric determination of mercury ions based on ion imprinted polymeric nanobeads

4.1. Introduction 79

4.2. Experimental 80

4.2.1. Materials and Apparatus 80

4.2.2. Procedure 81

4.2.3. Analysis of water and human hair samples 82

4.3. Results and discussion 83

4.3.1. Sorption/desorption studies 83

4.3.2. Choice of Eluent 83

4.3.3. Effect of pH 86

4.3.4. Effect of the loading and leaching flow rates 86

4.3.5. Selectivity study 88

4.3.6. Analytical performance 89

4.3.7. Determination of Hg²⁺ ions in real samples 91

4.4. Conclusion 93

TABLE OF CONTENTS PAGE

Chapter Four

Preparation of a novel potassium ion imprinted polymeric nanoparticles based on dicyclohexyl 18C6 for selective determination of K⁺ ion in different water samples

5.1. Introduction 95

5.2. Experimental 97

5.2.1. Materials and Apparatus 97

5.2.2. Preparation of K⁺–ion imprinted polymeric nanoparticles 98

5.2.3. Sorption/desorption procedure 98

5.3. Results and discussion 98

5.3.1. Characterization studies 98

5.3.1.1. SEM 98

5.3.1.2. FT–IR Spectra 99

5.3.2. Sorption/desorption experiments 100

5.3.2.1. Effect of pH 100

5.3.2.2. Choice of Eluent 102

5.3.2.3. Adsorption and desorption times 103

5.3.2.4. Adsorption capacity 103

5.3.2.5. Preconcentration factor and amount of sorbent 105

5.3.2.6. Reusability and stability 106

5.3.2.7. Analytical performance 107

5.3.2.8. Selectivity study 107

5.3.2.9. Analytical applications 109

5.4. Conclusion 110

Chapter Five

Highly selective recognition and sensitive determination of cesium ion by imprinting of Cs–Dibenzo24crown8 complex as template in the polymeric nanobeads assisted by precipitation polymerization

6.1. Introduction 112

6.2. Experimental 113

TABLE OF CONTENTS PAGE

6.2.1. Materials and Apparatus 113

6.2.2. Preparation of Cs⁺–ion imprinted polymeric nanoparticles 114

6.2.3. Sorption/desorption procedure 114

6.3. Results and discussion 115

6.3.1. Characterization studies 115

6.3.2. Sorption/desorption experiments 116

6.3.2.1 Choice of Eluent 116

6.3.2.2. Effect of pH 117

6.3.2.3. Adsorption and desorption times 118

6.3.2.4. Adsorption capacity 119

6.3.2.5. Preconcentration factor and amount of sorbent 120

6.3.2.6. Reusability and stability 121

6.3.2.7. Analytical performance 122

6.3.2.8. Selectivity 122

6.3.2.9. Analytical applications 124

6.4. Conclusion 125

PART B

Quantum Dots

Section I

Introduction and Literature Review

7.1. Introduction 127

7.2. Semiconductor quantum dots 128

7.3. Quantum size confinement 129

7.4. Properties of QDs 132

7.4.1. Electronic properties of QDs 132

7.4.2. Optical properties of QDs 133

7.4.2.1. Absorption 134

7.4.2.2. Photoluminescence 134

7.5. Quantum dots vs. Organic fluorophores 136

7.6. Types of QDs 139

7.7. Toxicity of QDs 139

7.8. Zinc sulfide 141

7.9. Synthesis methods of semiconductor nanocrystals 141

7.9.1. Water-based synthesis approaches to QDs 142

7.9.2. Organometallic synthesis of QDs: The hot-injection approach 142

7.9.3. Versatility of the hot-injection approach 144

7.9.4. Greener hot-injection syntheses 144

7.9.5. Organometallic syntheses of QDs not based on the hot-injection approach 145

7.9.6. The liquid-solid-solution approach for the synthesis of QDs 145

7.9.7. Hydrothermal method/Microwave-assisted method 147

7.10. Doped nanocrystals 147

7.10.1. Why dope semiconductor nanocrystals? 147

7.10.2. Synthesis and characterization of doped NCs 148

7.10.3. Theoretical models 149

7.11. Application of QDs 150

7.11.1. Biological applications 151

7.11.1.1. Fluorescence/bioluminescence resonance energy transfer analysis 151

7.11.1.2. Cell labeling 152

7.11.1.3. Gene technology 153

7.11.1.4. In vivo imaging 153

7.11.2. Analytical applications 154

7.11.2.1. Chemiluminescence and Electrogenerated chemiluminescence reactions 154

7.11.2.2. Surface plasmon resonance applications 155

7.11.2.3. Fluorescence–based sensors 155

7.11.2.4. QD–based pH probes 157

7.11.2.5. Electrochemical –based sensors 157

7.11.2.6. Chip detection 158

7.11.2.7. Capillary Electrophoresis 158

TABLE OF CONTENTS PAGE

Section II

Synthesis, Characterizations and Applications of Nano–Sized ZnS Quantum Dots: Interaction Study with BSA, Determination of Hazardous Anions, and Removal of Pollutant Dyes

Chapter One

Synthesis and characterizations of ultra–small ZnS and Zn_(1-x)Fe_xS quantum dots in aqueous media and spectroscopic study of their interactions with bovine serum albumin

8.1. Introduction 161

8.2. Experimental 162

8.2.1. Materials and apparatus 162

8.2.2. Synthesis of pure and doped ZnS QDs 163

8.2.3. Spectroscopic studies of QD–BSA interactions 163

8.3. Results and discussion 164

8.3.1. Characterization and optical properties of Zn_(1-x)Fe_xS QDs 164

8.3.1.1. STM of QDs 164

8.3.1.2. UV–Vis studies of QDs 165

8.3.1.3. X–ray diffraction characterization 169

8.3.2. Spectroscopic studies of BSA–QDs interactions 169

8.3.2.1. Absorption characteristic of BSA–QD systems 169

8.3.2.2. Steady-state fluorescence measurements 171

8.3.2.3. Binding constant and number of binding sites for BSA–QDs 173

8.3.2.4. Determination of thermodynamic parameters and nature of forces involved

in BSA–QDs interactions 174

4. Conclusion 176

Chapter Two

Zinc sulfide quantum dot as a novel luminescent probe for highly selective determination of hazardous cyanide ion

9.1. Introduction 178

9.2. Experimental 179

TABLE OF CONTENTS PAGE

9.2.1. Apparatus and materials 179

9.2.2. Fluorescent detection of CN^–179

9.3. Results and discussion 180

9.3.1. Characterization of the synthesized ZnS QDs 180

9.3.1.1. TEM images of the QDs 180

9.3.1.2. X–ray diffraction 180

9.3.1.3. Optical characteristics of ZnS QDs 181

9.3.2. Effect of pH 184

9.3.3. Effect of the QDs concentration 185

9.3.4. Fluorescence detection of cyanide ion by the quenching emission of ME–capped

ZnS QDs 186

9.3.5. Interference study of foreign anions 187

9.3.6. Determination of cyanide in water samples 188

9.3.7. Proposed mechanism 189

9.4. Conclusion 190

Chapter Three

Selective spectrofluorimetric determination of sulfide ion using manganese doped ZnS quantum dots as luminescent probe

10.1. Introduction 193

10.2. Experimental 194

10.2.1. Apparatus and materials 194

10.2.2 Preparation of ZnS:Mn QDs 195

10.2.3. Fluorescent detection of sulfide 195

10.3. Results and discussion 195

10.3.1. Characterization of the synthesized ZnS:Mn QDs 195

10.3.1.1 TEM images of the QDs 195

10.3.1.2. X–ray diffraction 196

10.3.1.3. Optical characteristics of ZnS:Mn nanoparticles 197

10.3.2. Effect of pH 199

TABLE OF CONTENTS PAGE

10.3.3. Effect of the QDs concentration 199

10.3.4. Effect of reaction time 200

10.3.5. Spectrofluorimetric determination of sulfide ion by ZnS:Mn QDs 201

10.3.6. Interference study 204

10.3.7. Determination of sulfide in water samples 204

10.3.8. Proposed mechanism 204

10.4. Conclusion 205

Chapter Four

Comparative investigation of photoactivity behavior of ZnS and Zn_(1-x)Fe_(x)S quantum dots as new class of nanophotocatalysts for removal of cationic dyes

11.1. Introduction 208

11.2. Experimental 209

11.2.1. Materials and apparatus 209

11.2.3. UV/ Zn_(1-x)Fe_xS QDs process 210

11.3. Results and discussion 211

11.3.1. Characterization of nanophotocatalysts 211

11.3.1.1. TEM image of QDs 211

11.3.1.2. X–ray diffraction 211

11.3.2. Decolorization efficiency of UV/ZnS process 212

11.3.2.1. The effect of pH 214

11.3.2.2 Dosage of Nanoparticles 216

11.3.2.3. Effect of initial dye concentration 216

11.3.3. Decolorization efficiency of UV/Zn_(1-x)Fe_xS process 217

11.3.4. Influence of initial dye concentration 217

11.3.5. Kinetic model and mechanism of degradation 223

11.3.5.1. Kinetic Study 223

11.3.5.2. Mechanism of degradation 223

11.3.6. Reproducibility of the photocatalysts 229

11.4. Conclusion 229

LIST OF FIGURES PAGE

Fig. 1.1. Principle of Molecular Imprinting inspired… 5

Fig. 1.2. Schematic representation of covalent and non-covalent… 8

Fig. 1.3. Common functional monomers used in non-covalent… 15

Fig. 1.4. Chemical structure of common cross-linkers used… 16

Fig.1.5. Chemical structure of common initiators used… 19

Fig.1.6. Schematical representation of the synthetic steps… 22

Fig. 1.7. The three significant methods of metal ion… 28

Fig. 2.1. Schematic representation of the syntheses of Zn(II) … 43

Fig. 2.2. (A) UV–Vis spectra for titration of morin… 46

Fig. 2.3. The FT–IR spectra of unleached and leached… 48

Fig. 2.4. Scanning electron micrograph (SEM) of Zn–IIP… 48

Fig. 2.5. TG/DTA curves for thermal decomposition… 50

Fig. 2.6. Effect of pH on sorption of Zn²⁺ ion on imprinted… 52

Fig. 2.7. The effect of Zn²⁺ ion initial concentration… 53

Fig. 2.8. Effect of 22 adsorption–desorption cycles… 56

Fig. 3.1. Schematic representation of the synthesis of Hg(II) … 63

Fig. 3.2. Scanning electron micrograph of Hg–IIP… 65

Fig. 3.3. The FT–IR spectra of unleached (A) and leached… 66

Fig. 3.4. Effect of sample pH on the extraction percent… 68

Fig. 3.5. Influence of HNO₃ concentration… 69

Fig. 3.6. Effect of adsorption (A), and leaching (B) time… 70

Fig. 3.7. Effect of initial concentration of mercury ion… 71

Fig. 3.8. Influence of IIP weight on the elution… 73

Fig. 3.9. Effect of 12 adsorption–desorption cycles… 73

Fig. 4.1. Schematic diagram of the IIP–FIA manifold… 82

Fig.4.2. The typical recording of photometric response… 84

Fig. 4.3. Influence of HNO₃ concentration on the elution… 85

Fig. 4.4. Effect of sample pH on the adsorption of Hg²⁺… 85

Fig. 4.5. Effect of loading flow rate on the elution of Hg²⁺… 87

LIST OF FIGURES PAGE

Fig. 4.6. Effect of eluent flow rate on the elution of Hg²⁺… 87

Fig. 4.7. (A) Photometric responses of eluted mercury ion… 90

Fig. 4.8. Precision of the proposed method for eight… 91

Fig. 5.1. Schematic representation of the syntheses … 97

Fig. 5.2. Scanning electron micrograph of K⁺ ion–imprinted… 99

Fig 5.3. The FT–IR spectra of unleached (A) and leached… 100

Fig. 5.4. Effect of sample pH on the adsorption of K⁺ ion… 101

Fig. 5.5. Influence of HNO₃ concentration on the elution of K⁺… 102

Fig. 5.6. Effect of adsorption and desorption time on the percent… 104

Fig. 5.7. Effect of initial concentration of potassium ion… 104

Fig. 5.8. Influence of IIP weight on the elution… 105

Fig. 5.9. Effect of 15 adsorption–desorption cycles… 106

Fig. 6.1. Schematic representation of the syntheses… 114

Fig. 6.2. Scanning electron micrograph (SEM) of Cs⁺… 115

Fig. 6.3. Influence of HNO₃ concentration… 117

Fig. 6.4. Effect of sample pH on the extraction… 117

Fig. 6.5. Effect of adsorption and leaching time… 119

Fig. 6.6. Effect of initial concentration of cesium ion… 120

Fig. 6.7. Influence of IIP weight on the elution… 121

Fig. 6.8. Effect of 15 adsorption–desorption cycles… 122

Fig. 7.1. A schematic of bulk, quantum well … 131

Fig. 7.2. Spatial electronic state diagram for bulk… 133

Fig. 7.3. Absorption and normalized photoluminescence… 133

Fig. 7.4. Fluorescence in a bulk semiconductor… 135

Fig. 7.5. Schematic representation of the exciton states… 136

Fig. 7.6. Size-tunable fluorescence spectra of CdSe… 137

Fig. 7.7. Excitation (a) and emission (b) profiles… 138

Fig. 7.8. (Left) Schematic standard setup for a hot-injection… 143

Fig. 7.9. Sketch highlighting the various processes involved… 146

Fig. 7.10. Schematic and characteristics of three models used… 149

LIST OF FIGURES PAGE

Fig. 7.11. Quantum dot–based (ECL) reaction mechanism… 154

Fig. 8.1. 2D STM images of an individual (A) and a typical… 164

Fig. 8.2. UV–Vis absorption spectra of ZnS quantum dots… 166

Fig. 8.3. UV–Vis spectra of Zn_(1-x)Fe_xS QDs at constant… 167

Fig. 8.4. UV–Vis absorption spectra of QDs… 168

Fig. 8.5. X–ray diffraction pattern of Zn_0.98Fe_0.02S… 169

Fig. 8.6. UV–Vis absorption spectra of BSA… 170

Fig. 8.7. Fluorescence emission spectra of BSA… 172

Fig. 8.8. Unmodified (at 298 K) and modified… 173

Fig. 9.1. Typical TEM image of the 2–mercaptoethanol capped ZnS… 181

Fig. 9.2. XRD pattern of the prepared ZnS nanocrystal… 181

Fig. 9.3. UV–Vis absorption (A) and fluorescence (B) spectra… 182

Fig. 9.4. The plot of (ahv)² vs. (hv) of 2–mercaptoethanol… 183

Fig. 9.5. (A) Effect of pH on the fluorescence intensity… 184

Fig. 9.6. Effect of the concentration of ME capped ZnS QDs… 185

Fig. 9.7. Effect of the cyanide concentration (0.00–2.59×10^-5mol.L^-1) … 186