Browsing by Author "Zhang, Yanyan"
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Item Controlled synthesis of highly-branched plasmonic gold nanoparticles through peptoid engineering(2018) Yan, Feng; Liu, Lili (TTU); Walsh, Tiffany R.; Gong, Yu; El-Khoury, Patrick Z.; Zhang, Yanyan; Zhu, Zihua; De Yoreo, James J.; Engelhard, Mark H.; Zhang, Xin; Chen, Chun LongIn nature, specific biomolecules interacting with mineral precursors are responsible for the precise production of nanostructured inorganic materials that exhibit complex morphologies and superior performance. Despite advances in developing biomimetic approaches, the design rules for creating sequence-defined molecules that lead to the synthesis of inorganic nanomaterials with predictable complex morphologies are unknown. Herein we report the design of sequence-defined peptoids for controlled synthesis of highly branched plasmonic gold particles. By engineering peptoid sequences and investigating the resulting particle formation mechanisms, we develop a rule of thumb for designing peptoids that predictively enabled the morphological evolution from spherical to coral-shaped nanoparticles. Through a combination of hyperspectral UV-Vis extinction microscopy and three-photon photoemission electron microscopy, we demonstrate that the individual coral-shaped gold nanoparticles exhibit a plasmonic enhancement as high as 105-fold. This research significantly advances our ultimate vision of predictive bio-inspired materials synthesis using sequence-defined synthetic molecules that mimic proteins and peptides.Item Structural phase transition and photoluminescence properties of wurtzite CdS:Eu3+ nanoparticles under high pressure(2017) Zhao, Rui; Yang, Tianye; Luo, Yang; Chuai, Mingyan; Wu, Xiaoxin; Zhang, Yanyan; Ma, Yanzhang (TTU); Zhang, MingzheHigh-pressure behaviors of wurtzite CdS and CdS:Eu3+ nanoparticles (8–10 nm) were investigated by synchrotron radiation X-ray diffraction, Raman spectroscopy, and photoluminescence under high pressure at ambient temperature. The doping of Eu ions increases the phase transition pressure from wurtzite structure to rocksalt structure (CdS = 4.76 GPa and CdS:Eu = 5.22 GPa) and so does the bulk modulus (B0) of the initial and high pressure phases. This phenomenon can be attributed to the great impact on tensile strain along the c-axis of CdS nanoparticles, which is identified by the relationship of lattice contraction and the pressure obtained from Raman 1LO. The phase transitions of all samples are partly reversible. The Eu3+ ions luminescence from 5D0 → 7FJ (J = 1, 2) transition in CdS:Eu nanoparticles emerges obviously and changes during the phase transformation, which indicate the variation of the local symmetry of the Eu3+ ions. The new peak of 5D0 → 7F3 emerges at 7.26 GPa, persisting until the end of the whole experiment. The obtained CdS nanoparticles will hold promising potential in the fabrication of effective biological sensors and photodetectors for practical application under high pressure.