Bai Mingjun, Liu Xiaohe, Sasaki Takayoshi, Ma Renzhi
School of Materials Science and Engineering, Central South University, Hunan 410083, P.R. China.
International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan.
Nanoscale. 2021 Mar 4;13(8):4551-4561. doi: 10.1039/d0nr08824b.
Europium and terbium doped layered gadolinium hydroxides were prepared by microwave assisted hydrothermal precipitation. They were subsequently exfoliated into nanosheets by sonication treatment in formamide. The thickness of the nanosheets (LGdH:Eu and LGdH:Tb) was found to be approximately 1 nm, exemplifying a single-layer feature. Multilayer and superlattice films were prepared through layer-by-layer (LbL) deposition of exfoliated hydroxide nanosheets with a polyanionic electrolyte (polystyrene sulfonate, PSS) and heteroassembly with semiconducting oxide nanosheets (Ti0.87O20.52- and TaO3-), respectively. Compared to the multilayers of (LGdH:Eu/PSS)n and (LGdH:Tb/PSS)n, the superlattices of (LGdH:Eu/Ti0.87O20.52-)n and (LGdH:Tb/TaO3-)n exhibited significantly enhanced photoluminescence intensity, ∼14 times and ∼5 times, respectively. The photoenergy absorbed by the semiconducting nanosheets can be transferred to the excited states of rare-earth hydroxide nanosheets for enhanced photoluminescence emission. Further investigation on the stacking sequence of the nanosheets revealed that direct neighboring and energy level matching with semiconducting nanosheets was essential for realizing efficient energy transfer across the nanosheet interface. Annealing at 600 °C could further enhance the emission intensity of the superlattice structured films. The current work demonstrates an important strategy for hetero-assembling nanosheets at the molecular level with a carefully designed interface for tunable and enhanced functionalities.
通过微波辅助水热沉淀法制备了铕和铽掺杂的层状氢氧化钆。随后，通过在甲酰胺中进行超声处理将它们剥离成纳米片。发现纳米片（LGdH:Eu和LGdH:Tb）的厚度约为1 nm，体现出单层特征。分别通过将剥离的氢氧化物纳米片与聚阴离子电解质（聚苯乙烯磺酸盐，PSS）进行逐层（LbL）沉积以及与半导体氧化物纳米片（Ti0.87O20.52-和TaO3-）进行异质组装，制备了多层膜和超晶格膜。与（LGdH:Eu/PSS）n和（LGdH:Tb/PSS）n的多层膜相比，（LGdH:Eu/Ti0.87O20.52-）n和（LGdH:Tb/TaO3-）n的超晶格表现出显著增强的光致发光强度，分别约为14倍和5倍。半导体纳米片吸收的光能可以转移到稀土氢氧化物纳米片的激发态，以增强光致发光发射。对纳米片堆叠顺序的进一步研究表明，与半导体纳米片直接相邻且能级匹配对于实现跨纳米片界面的有效能量转移至关重要。在600℃退火可以进一步提高超晶格结构薄膜 的发射强度。目前的工作展示了一种在分子水平上异质组装纳米片的重要策略，该策略具有精心设计的界面，可实现功能的可调谐和增强。
