Figure 1.1. Example of counterfeit product damage in newspaper, journal, and advertising 26

Figure 1.2. Anticounterfeit product a RFID, b fluorescence optical system, c hologram 27

Figure 1.3. Photochromism materials a Spiropyran derivative, b Diarylethene, c Oxazolidine 28

Figure 1.4. Photoluminsecence materials a Fluorescence dye, b Quantum dots, c Polymer dots, d... 28

Figure 1.5. Photonic crystal as structural color emission materials a colloidal nanocrystal clusters, b... 29

Figure 1.6. Metallic nanoparticles selectively absorb and scatter light of different wavelengths, which... 30

Figure 1.7. Printing technique a Direct printing, b Templated printing 31

Figure 2.1. The schematic of fabricating highly stacked PCDA-Co nanoplates, a, Synthesis of PCDA-... 36

Figure 2.2. SEM image of isolated PCDA-Co nanoplates. 39

Figure 2.3. a Color change observed in isolated PCDA-Co nanoplates (RPCDA/Co＝0.33) in solution upon...[이미지참조] 39

Figure 2.4. Rapid color changes observed for isolated PCDA-Co nanoplates in solution after treatment... 40

Figure 2.5. Color change observed in isolated PCDA-Co nanoplates (RPCDA/Co＝0.33) in solution, after...[이미지참조] 40

Figure 2.6. Change in UV-vis absorption intensities of isolated PCDA-Co nanoplates upon treatment... 41

Figure 2.7. Color changes observed for solution-phase isolated PCDA-Co nanoplates prepared using... 42

Figure 2.8. Color changes observed in solution for isolated PCDA-Co nanoplates fabricated using... 42

Figure 2.9. Bright-field microscopy images of a isolated PCDA-Co nanoplates and b agglomerated... 43

Figure 2.10. Color change observed in agglomerated PCDA-Co nanoplates (RPCDA/Co＝0.33) in solution...[이미지참조] 44

Figure 2.11. Changes in UV-vis absorption intensities of isolated PCDA-Co nanoplates in solution upon... 45

Figure 2.12. SEM images of isolated PCDA-Co nanoplates in solution based on various initial molar... 45

Figure 2.13. Color changes observed for highly stacked PCDA-Co nanoplates prepared using various... 46

Figure 2.14. Color change observed in highly stacked PCDA-Co nanoplates films upon treatment with... 46

Figure 2.15. Color changes observed for highly stacked PCDA-Co nanoplates prepared using various... 47

Figure 2.16. a XPS and b Raman spectra of highly stacked PCDA-Co nanoplates film before/after... 48

Figure 2.17. XRD spectra of a isolated PCDA-Co nanoplates, and b agglomerated PCDA-Co... 49

Figure 2.18. Changes observed in SEM images of a isolated PCDA-Co nanoplates, b agglomerated... 50

Figure 2.19. SEM image of UCNs incorporated into highly stacked PCDA-Co nanoplates. 51

Figure 2.20. a Color and luminescence changes of UCNs/PCDA-Co nanoplate composites film upon... 52

Figure 2.21. a Schematic of the portable detection system, b Selective detection of CN ions with the... 53

Figure 3.1. Scheme of the crystal phase transition of UCNs through an annealing process involving... 62

Figure 3.2. Luminescence image and XRD data of UCNs/metalloid oxide composite compared to those... 63

Figure 3.3. Schematic representation of the fabrication of UCNs-embedded microparticles with/without... 64

Figure 3.4. a Luminescence color image and b transmittance of UCNs in PUA. 64

Figure 3.5. Change in the luminescence color and efficiency of UCNs with/without SiO₂ NPs after the... 65

Figure 3.6. Luminance of UCNs with and without SiO₂ NPs after the annealing process at 900 ℃. Inset:... 66

Figure 3.7. Normalized luminescence spectra of the four types of UCNs with different reconversion... 68

Figure 3.8. Change in the crystal structure and morphology of UCNs with and without SiO₂E NPs in... 69

Figure 3.9. XRD, luminescence spectrum, and SEM analysis of UCNs with and without SiO₂ NPs.... 70

Figure 3.10. Fourier-transform infrared spectra of an UCNs- and SiO₂ NPs-embedded PUA film, a... 71

Figure 3.11. Variation in the XRD pattern according to the concentration of SiO₂ NPs. The UCNs- and... 72

Figure 3.12. XRD patterns revealing the crystal phase transition of UCNs. XRD pattern of a pristine... 73

Figure 3.13. Comparison of the luminescence spectra of cubic NaREF₄ and hexagonal apatite UCNs.... 74

Figure 3.14. Structural and electronic properties, and the proposed energy transfer mechanism of three... 75

Figure 3.15. Energy level diagrams of Er3+ doped in three crystal phases. Energy level diagrams of Er3+...[이미지참조] 76

Figure 3.16. Phonon density of states of Er3+ in three types of crystal phases. Phonon density of states...[이미지참조] 77

Figure 3.17. XRD patterns of Tm3+-doped UCNs without/with SiO₂ NPs after annealing at 900 ℃: a...[이미지참조] 79

Figure 3.18. Electronic properties and phonon density of states of Tm3+ in cubic NaREF₄ and hexagonal...[이미지참조] 79

Figure 3.19. Demonstration of multiple luminescence color changing high temperature labeling systems,... 81

Figure 4.1. Schematic illustration of computer controlled 3D hydrogel-based SERS platform fabrication... 89

Figure 4.2. Schematic illustration of the UV LED installed DMD lithography system. 90

Figure 4.3. The fabrication and characterization of the microposts array, a Bright-field optical... 91

Figure 4.4. a 365 nm UV-light intensity profile through 20x projection lens, b Z-stack image of... 92

Figure 4.5. a Bright-field optical micrographs of PEGDA hydrogel micro-post fabricated without AA... 93

Figure 4.6. Energy-dispersive X-ray spectroscopy (EDS) spectra of PEGDA/AA/Ag hydrogel micro-... 95

Figure 4.7. UV-Vis absorption spectra of the 1 µM R6G in PEGDA/AA and PEGDA/AAmide micro-... 96

Figure 4.8. a Bright-field optical micrograph and b UV-Vis absorption spectra of the micro-post array... 96

Figure 4.9. SERS detection of R6G using the micropost array, Bright-field optical micrograph of the... 97

Figure 4.10. The normal Raman spectrum of aqueous 10-1 M R6G molecules adsorbed on PEGDA...[이미지참조] 98

Figure 4.11. Calculated results of SERS enhancement factor of Ag NP systems, a Model system of Ag... 101

Figure 4.12. The reliability and reproducibility of measurements for R6G by the PEGDA/AA/Ag... 102

Figure 4.13. The reusability, continuous multitarget sensing capability, and a demonstration of the... 104

Figure 4.14. The effect of washing solvent on recovering the pristine state of the PEGDA/AA/Ag micro-... 105

Figure 4.15. SERS spectra of GHB (5.0 M) and 40% EtOH in PEGDA/AA/Ag micro-posts and Raman... 106

Figure 5.1. a Depending on immersion solvent, PDA organogels acting as volume phase holographic... 115

Figure 5.2. a Schematic showing fabrication of conjugated PDA organogels. Two-dimensionally... 116

Figure 5.3. a Bright-field microscopy images of crosslinked HD-DA microstructures according to 365... 116

Figure 5.4. Bright-field images of crosslinked HD-DA microstructures by changing 365 nm UV... 118

Figure 5.5. Bright-field microscope images of crosslinked a HD-DA and b HDDA microstructures... 118

Figure 5.6. Bright-field (left) and fluorescence (right) microscopy images show reversible volume and... 119

Figure 5.7. UV-Vis spectra a and fluorescence emission spectra b of PDA organogels immersed in ACN... 119

Figure 5.8. Comparison of an area of top region of PDA microstructure and their fluorescence intensity... 120

Figure 5.9. 3D simulation result (left) shows predicted deformed shape, and each cut plane of simulation... 121

Figure 5.10. Organogel crosslinked without dithering pattern into a disk shape and shrunk in MeOH... 122

Figure 5.11. Bright-field microscopy images of PDA organogel microstructure (left) composed of 2D... 122

Figure 5.12. Refractive indices of rod and matrix when exposed to a ACN and b water. 123

Figure 5.13. Confocal microscopy image of rod and matrix in conjugated PDA organogel microstructure,... 123

Figure 5.14. Structural color of the patterned PDA organogel. Structural color of the patterned PDA... 124

Figure 5.15. Schematic of the imaging setup for structural color of dithering mask patterned organogel... 124

Figure 5.16. a Schematic of the diffraction efficiency measuring system. Transmitted and diffracted... 124

Figure 5.17. Confocal microscopy images of dithering mask patterned conjugated PDA organogel... 126

Figure 5.18. When organogel contracted in water, a three-dimensional view (left) and a cross-sectional... 127

Figure 5.19. Bright-field (top row) and fluorescence microscopy images (bottom row) of dithering mask... 127

Figure 5.20. a Bright-field micrographs (top row), widefield fluorescence micrographs (middle row),... 128

Figure 5.21. FEA results showing that solvent exchange shrank the organogel patterned with a square... 129

Figure 5.22. Orthogonal confocal microscopy image (left) of square dithering mask patterned PDA... 129

Figure 5.23. Line profile of initial fluorescence intensity of uniform PDA organogel. Uniform... 129

Figure 5.24. Fluorescence expression predicted for the patterned organogel in FEA results after... 130

Figure 5.25. Bright-field and fluorescence microscopy images of dithering mask patterned PDA... 131

Figure 5.26. Bright-field and fluorescence microscopy images of PDA organogel microstructures upon... 131

Figure 5.27. Changing of signal shape with varying contraction level. Modeled fluorescence signals... 132

Figure 5.28. Light propagation simulations, a The 3D organogel structure was divided into N＝90 layers.... 133

Figure 5.29. a Expected fluorescence intensity based on fluorescence expression and illumination... 133

Figure 5.30. a Bright-field and b fluorescence microscopy images of hexagon patterned PDA organogel... 134

Figure 5.31. Bright-field and fluorescence microscopy image of dithering mask patterned fluorescein... 135

Figure 5.32. Fabrication process of shape morphing PDA organogel microstructure.. 135

Figure 5.33. a A dithering mask used for the organogel microstructure (a square dithering pattern for... 136

Figure 5.34. Microarray consisting of organogels patterned with horizontal lines on the right of the red... 137

Figure 5.35. a Horizontal lined dithering mask pattern image. Bright-field microscopy images of... 137

Figure 5.36. Dynamic flip-flop structural color systems displaying letter changes from T to E and T to... 138

Figure 5.37. a Fabrication of letter transition systems using four types of dithering masks. Hexagon... 138

Figure 5.38. Selective patterning of conjugated PDA organogel for structural color and 1,6-hexanediol... 139

Figure 5.39. Free-standing flexible films with embedded holographic lettering fabricated using... 139

Figure 5.40. a A schematic diagram of encryption process that generates a specific dithering pattern in... 140

Figure 5.41. Structural color displayed by encoded organogel matrices with varying matrix size. 0° and... 140

Figure 5.42. Encrypted information, structural color, bright-field image, and maginified bright-field images... 141

Figure 5.43. Structural colors displayed by 4x3 micro-array of 4x4 encoded organogel matrices. 141

Figure 5.44. Encrypted information (left) and structural color (right) of PDA organogel microstructures... 142

Figure 5.45. An array of structural color displayed by an imprinted flexible PDMS film. Scale bar is 200 ㎛. 142

Figure 5.46. Encoded organogel matrices in the form of free-floating microparticles. Scale bar is 200 ㎛. 142

Figure 5.47. A computer-assisted method to convert digital color images to structural color encrypted holograms. 143

Figure 5.48. Structural color encrypted PDA organogel micro-particles displaying The Starry Night,... 143

Figure 5.49. Selective structural color change of masterpiece encrypted microstructures by changing... 143

Figure 5.50. Structural color (top), bright-field (middle), and maginified bright-field (bottom) images of... 144

Figure 5.51. Transmittance of photo-crosslinked HD-DA film. 144

Figure 5.52. Structural color on-off PDA organogel microstructures patterned with two types of line... 145

Figure 5.53. Selective structural color changing of PDA organogels by rotating the portable imaging... 146

Figure 5.54. a A flexible free-standing PDMS film encoded with Van Gogh self-portrait hologram and... 146