Up-converting $$\hbox {NaYF}_{4}$$:Yb,Er nanoparticles were obtained by polymer-assisted solvothermal synthesis using a common solution of hydrated RE nitrates in ethanol or ethylene glycol. It was shown that polymer choice (polyacrylic acid—PAA, polyvinylpyrrolidone—PVP and chitosan—CS) controls the size and shape of $$\hbox {NaYF}_{4}$$:Yb,Er nanoparticles, while the solvent type and pH value affect their crystallinity. Consequently, the spherical nanoparticles of a cubic ($$\upalpha $$) phase, the average size of which ranged from 60 to 140 nm, were obtained either when PVP/ethanol or PVP/ethylene glycol were used solely during synthesis, whereas NaOH addition induced hexagonal ($$\upbeta $$) phase nucleation. The formation of the hierarchically organized spherical aggregates and nanofoils was observed when CS and PAA were used during synthesis, respectively. The average crystallite size, microstrain, doping level, lattice parameters, as well as, the presence of the certain ligands on the particle surface were determined and correlated with the intensity of visible-light emission observed under 980 nm laser-diode excitation.

中文翻译：

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不同聚合物和溶剂对$$\hbox {NaYF}_{4}$$NaYF4:Yb/Er 相结晶的影响

上转换 $$\hbox {NaYF}_{4}$$:Yb,Er 纳米粒子是通过聚合物辅助溶剂热合成获得的，使用水合硝酸稀土在乙醇或乙二醇中的常见溶液。结果表明，聚合物的选择（聚丙烯酸-PAA、聚乙烯吡咯烷酮-PVP 和壳聚糖-CS）控制着$$\hbox {NaYF}_{4}$$:Yb,Er 纳米颗粒的尺寸和形状，而溶剂类型和pH值影响其结晶度。因此，当在合成过程中单独使用 PVP/乙醇或 PVP/乙二醇时，获得了立方 ($\upalpha $$) 相的球形纳米粒子，其平均尺寸范围为 60 到 140 nm，而 NaOH加成诱导六边形 ($$\upbeta $$) 相成核。当在合成过程中使用 CS 和 PAA 时，观察到分层组织的球形聚集体和纳米箔的形成，分别。确定了平均微晶尺寸、微应变、掺杂水平、晶格参数以及颗粒表面某些配体的存在，并将其与在 980 nm 激光二极管激发下观察到的可见光发射强度相关联。