Introduction
Photonic crystals can also serve as a substrate to provide structural color properties and increase the security level of the fluorescent anti-counterfeit tags created by fluorescent nanoparticles. The SPR effect of AgNPs has been used to enhance fluorescent dyes modified on their surface, enabling fluorescence intensity-based encryption; meanwhile, the unique geographic fingerprint of the randomly deposited AgNPs can be read out and recorded by a dark field. It should be emphasized that none of the optical responses of the metallic nanoparticles, including absorption spectrum and SPR, can be read with the naked eye.
One of the main challenges in the industrial development of anti-counterfeiting products is their printing technology. These include surface treatments of the synthesized organic molecules and nanocomposites to become compatible with the ink cartridge15 or ligand exchange processes to transfer the nanocomposites to the aqueous phase16. They are generally divided into direct printing and stencil printing, and each of the methods has different resolutions and print speeds.
The choice of printing method depends on the constraints of cost, complexity and desired resolution and the nature of the products to be protected. Otherwise, screen printing, one of the stencil printing, is a well-established method of transferring nanocomposite ink to a substrate via a stenciled mesh.
Highly Stable Upconverting Nanocrystal−Polydiacetylenes Nanoplates for
Multi-Color Luminescence Transition of Upconversion Nanocrystals via Crystal
The XRD pattern of the above metalloid oxides resulted in different crystalline phases compared with the hexagonal apatite crystalline phase of UCNs/SiO2 after the annealing process. Normalized spectral change (top) and luminescence images (bottom) of UCNs-embedded microparticles during the annealing process: a without SiO2 NPs, b with SiO2 NPs, and c when changing the concentration of SiO2 NPs. Note that the luminescence spectra with and without SiO2 NPs were normalized based on red luminescence intensities (660 nm wavelength).
Inset: Luminescence images of UCNs-embedded microparticles with (green)/without (red) SiO2 NPs after the annealing process. Inset: Luminescence images of UCNs-embedded microparticles with (light blue)/without (dark blue) SiO2 NPs after the annealing process at 900 °C. Note that the signal from the Si-O-Si bond at 900 cm-1 is more evident after the annealing process.
Each colored box indicates the position of the energy level of the Er3+ ion in each crystal phase. Each colored box indicates the position of the energy level of the Tm3+ ion in each crystal phase.
Facile Microfluidic Fabrication of 3D Hydrogel SERS Substrate with High
Phonon density of states of Er3+ in Er3+ doped hexagonal NaREF4, cubic NaREF4 and hexagonal apatite phases. Note that although the imaginary frequency (negative frequency), which indicates structural instability, appeared in the cubic NaREF4 and hexagonal apatite phases, the contribution to the instability of the whole structure was marginal because the intensity was very weak. Electronic properties and phonon density of states of Tm3+ in cubic NaREF4 and hexagonal apatite phases.
Here, 2p states were analyzed for F− and O2− ions coordinated with the Tm3+ ion to calculate the lowest energy level of the Tm3+ ion. The location of the lowest unfilled energy level of Tm3+ ion was estimated by the energy difference between the maximum of Tm3+ 4f states near the maximum of the valence band (VBM) and the maximum of 2p state of F− or O2− in the valence band. The HR-TEM images of the micropost with Ag NPs were formed after the UV exposure for d 1 min and e 5 min prior to the leaching of smaller Ag NPs.
Scale bars are 100 µm. d UV–vis absorption spectra and E) Raman spectra of the 1 × 10−6 M R6G aqueous solution and the PEGDA, PEGDA/AA, and PEGDA/AA/Ag micropost arrays immersed in the same solution. The Raman signals were measured at nine different spots in each of the microstations selected from three individual microfluidic devices, i.e. at a total of 27 spots.
Dynamic Multimodal Holograms of Conjugated Organogels via Dithering mask
The initial luminescent green color of the UCNs changes to red when the blue PCDA-Co supramolecules turn red upon reaction with the target CN ions (Figure 2.1f). The fluorescence intensity of the isolated PCDA-Co nanoplate solution also increased upon exposure to CN ions (Figure 2.3c). As hypothesized in phase 1 of Figure 2.1, these isolated PCDA-Co nanoplates in solution did not exhibit a blue-to-red color transition when exposed to organic solvents (Figures 2.5a and 2.6a).
Interestingly, the resulting highly aggregated PCDA-Co nanoplates exhibited a blue-to-red color transition when treated with CN ions (Figure 2.14d). Isolated PCDA-Co nanoplates lost their planar characteristic and transformed into dissociated aggregates upon exposure to CN ions (Figure 2.18a). As shown in the SEM image, the UCNs were homogeneously incorporated into the highly aggregated PCDA-Co nanoplates (Figure 2.19).
As shown in Figure 2.21b, our portable device selectively detected the luminescence change of the UCNs/PCDA-Co composite system when exposed to 15 mM CN ions. Upon annealing at 300 °C, the luminescence color of the UCNs-embedded microparticles with/without SiO2 NPs changed to orange (Figure 3.5a, b).
Summary
오랫동안 우리와 함께 해주신 모든 분들께 감사드립니다. 먼저 지도교수이신 이지석 교수님에게 진심으로 감사의 말씀을 전하고 싶습니다. 또한 오랜 연구 기간 동안 도움을 준 연구실 직원들에게도 감사의 말씀을 전하고 싶습니다.
그리고 연구실에서 못생긴 선배들을 상대하느라 고생한 조교 다혜, 혜리에게도 감사하다. 그리고 가장 먼저 졸업하신 연구실 마스터들에게도 감사의 말씀을 전하고 싶습니다. 특히 저의 첫 대리이신 윤경이님께 감사의 말씀을 전하고 싶습니다.
다들 각자의 자리에서 잘 지내길 바랍니다. 상균이에게 무한한 감사의 마음을 전하고 싶습니다. 그리고 어렸을 때부터 함께 해준 친구들, 그리고 학부 시절 친하게 지낸 선후배들에게도 감사하다는 말씀 전하고 싶습니다.
전주에서 늘 함께해준 연탁, 기환, 정빈, 원기에게 감사하고 앞으로도 계속 함께 하길 바란다. 그리고 고등학교 때부터 함께해준 상혁이, 찬송이, 호진이에게도 감사 인사를 전하고 싶습니다. 곧 결혼하는 주혁이, 곧 의사가 될 종혁이와 함께한 것이 많은 도움이 되었다고 말씀드리고 싶습니다.
그리고 각자의 자리에서 열심히 일하고 있는 후배 혜성, 경애, 진수, 진우에게도 감사드립니다. 오랫동안 공부하는 아들을 늘 응원하고 믿어주셔서 감사합니다. 더 열심히 해서 자랑스러운 아들, 형이 되도록 하겠습니다.
