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Multi-shelled upconversion nanostructures with enhanced photoluminescence intensity <i>via</i> successive epitaxial layer-by-layer formation (SELF) strategy for high-level anticounterfeiting
摘要： Owing to the ability to convert near-infrared (NIR) incident light into high-energy ultraviolet or visible light photons, lanthanide-doped upconversion nanoparticles (UCNPs) have attracted great attention in anticounterfeiting applications as appealing and unparalleled agents. To facilitate the efficient energy transfer and overcome the bottleneck of low upconverted photoluminescence, we report a one-pot successive epitaxial layer-by-layer formation (SELF) strategy based on ion layer adsorption and Oswald ripening to synthesize a series of high-quality monodispersed multi-shelled UCNPs with narrow size distribution (coefficient of variation less than 5 %). Up to 30 layers of uniform shell are successfully deposited by successive introduction of the shell precursor solutions, which results in fold change of 300 and 200 in upconverted emission intensities for Er3+ and Tm3+-doped multi-shelled UCNPs, respectively. Using as-prepared multi-shelled UCNPs via SELF approach in conjunction with fabricated downconversion nanoparticles (DCNPs), we develop a facile and cost-effective strategy based on dual-modal manipulation of luminescence in anticounterfeiting to provide extra high-level security protection. The genuine pattern with true information is easier to visualize with the naked eye under excitation of 980 nm near-infrared (NIR) laser, while the false information could be readily read out when exposed to ultraviolet (UV) light. Meanwhile, latent fingerprint recognition with low background interference and distinguishable details in ridge patterns is achieved taking advantage of the significantly improved brightness in multi-shelled UCNPs.
关键词： anticounterfeiting,Upconversion,enhanced photoluminescence,multi-shell,latent fingerprint
更新于2025-11-19 16:46:39
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Learning compact q-space representations for multi-shell diffusion-weighted MRI
摘要： Diffusion-weighted MRI measures the direction and scale of the local diffusion process in every voxel through its spectrum in q-space, typically acquired in one or more shells. Recent developments in microstructure imaging and multi-tissue decomposition have sparked renewed attention in the radial b-value dependence of the signal. Applications in motion correction and outlier rejection therefore require a compact linear signal representation that extends over the radial as well as angular domain. Here, we introduce SHARD, a data-driven representation of the q-space signal based on spherical harmonics and a radial decomposition into orthonormal components. This representation provides a complete, orthogonal signal basis, tailored to the spherical geometry of q-space and calibrated to the data at hand. We demonstrate that the rank-reduced decomposition outperforms model-based alternatives in human brain data, whilst faithfully capturing the micro- and meso-structural information in the signal. Furthermore, we validate the potential of joint radial-spherical as compared to single-shell representations. As such, SHARD is optimally suited for applications that require low-rank signal predictions, such as motion correction and outlier rejection. Finally, we illustrate its application for the latter using outlier robust regression.
关键词： Diffusion-weighted imaging,Blind source separation,Multi-shell HARDI,Dimensionality reduction
更新于2025-09-23 15:23:52
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Polychromatic emission in a wide energy range from InP-InAs-InP multi-shell nanowires
摘要： InP-InAs-InP multi-shell nanowires (NWs) were grown in the wurtzite or zincblende crystal phase and their photoluminescence (PL) properties were investigated at low temperature (≈6K) for different measurement geometries. PL emissions from the NWs were carefully studied in a wide energy range from 0.7 eV to 1.6 eV. The different features observed in the PL spectra for increasing energies are attributed to four distinct emitting domains of these nano-heterostructures: the InAs island (axially grown), the thin InAs capping shell (radially grown), the crystal-phase quantum disks arising from the coexistence of InP zincblende and wurtzite segments in the same NW, and the InP portions of the NW. These results provide a useful frame for the rational implementation of InP-InAs-InP multi-shell NWs containing various quantum confined domains as polychromatic optically active components in nanodevices for quantum information and communication technologies.
关键词： photoluminescence,multi-shell nanowire,InP-InAs-InP heterostructure
更新于2025-09-23 15:22:29
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Synergistic enhancements in the performances of dye-sensitized solar cells by the scattering and plasmon resonance of Au-nanoparticle multi-shell hollow nanospheres
摘要： Novel multi-shell hollow SiO2@Au@TiO2 (HSAT) nanospheres are synthesized by multi-step method. Composite photoanodes and Dye-sensitized solar cells (DSSCs) with different amount of HSAT nanospheres are studied. The study indicates that the HSAT nanospheres have enhanced the scattering and absorption of incident light in the photoanode, reduced the interface transmission resistance, increased the electron lifetime, and thus significantly improved performance of DSSCs. The maximal Jsc and photoelectric conversion efficiency (PCE) obtained in the optimal DSSC doped with HSAT of 3.0% are 15.83 mA cm?2 and 7.21%, greatly enhanced by 21.0% and 20.4%, respectively, compared with those of the pure TiO2-based DSSC. These remarkable enhancements in DSSCs performance can be attributed to the synergistic and complementary effects of the localized surface plasmon resonance and strong light scattering of HSAT nanospheres, which has significantly improved the absorption and utilization on incident light and thus the PCE of the DSSCs. Such synergistic and complementary effects of the different functions are also likely expected to play roles in the performance improvements in other solar cells.
关键词： scattering enhancement,localized surface plasmon resonance,composite photoanodes,dye-sensitized solar cells,multi-shell hollow structure
更新于2025-09-19 17:13:59