Nigoghossian K, Ouellet S, Plain J, Messaddeq Y, Boudreau D, Ribeiro S J L
Laboratory of Photonic Materials, Institute of Chemistry, São Paulo State University, UNESP, CP 355, Araraquara, São Paulo 14801-970, Brazil.
J Mater Chem B. 2017 Sep 14;5(34):7109-7117. doi: 10.1039/c7tb01621b. Epub 2017 Aug 17.
The present work involves the design of a multifunctional system based on gold nanoshells (AuNSs) decorated with lanthanide-based upconversion nanoparticles (UCNPs) intended as an optical heater and a temperature probe at the nanoscale. The synthesis of NaGdF UCNPs doped with ions Yb:Er was performed via thermal decomposition of lanthanide fluoride precursors at high temperatures (>300 °C) in the presence of a coordinating ligand (oleic acid). UCNPs were synthesized at three different temperatures (310, 315 and 320 °C) and characterized in terms of morphological, structural and emission properties. In view of the intended biological applications, the surface of hydrophobic oleate-capped UCNPs was modified using a silica coating to achieve sufficient water dispersibility, through a modified Stöber process using a reverse micro-emulsion method. Monodisperse NaGdF:Yb:Er upconversion nanocrystals (∼25 nm dia.) were obtained in cubic (at 310, 315 °C) and hexagonal (at 320 °C) phases. The UCNPs in the hexagonal phase were shown to be more suitable as temperature sensors, due to their lower red-to-green emission ratios and higher thermal sensitivities. The emission spectrum of NaGdF:Yb:Er (oleate- or silica-coated) UCNPs was recorded at different temperatures in the vicinity of the physiological range (20-70 °C) and presented suitable properties for application as temperature sensors, such as excellent linearity (r > 0.99) and sensitivity (>3 × 10 K). The heating capacity of AuNSs@UCNPs was verified by monitoring the Er emission, showing their potential for application as a hyperthermia agent controlled using a nanothermometer function.
本工作涉及基于金纳米壳（AuNSs）设计的多功能系统，该金纳米壳装饰有镧系元素上转换纳米粒子（UCNPs），旨在作为纳米级的光学加热器和温度探针。通过在高温（>300°C）下，在配位配体（油酸）存在下热分解镧系氟化物前驱体，合成了掺杂Yb:Er离子的NaGdF UCNPs。UCNPs在三个不同温度（310、315和320°C）下合成，并对其形态、结构和发光特性进行了表征。考虑到预期的生物应用，通过使用反向微乳液法的改进的斯托伯（Stöber）工艺，用二氧化硅涂层修饰疏水性油酸包覆的UCNPs表面，以实现足够的水分散性。获得了立方相（在310、315°C）和六方相（在320°C）的单分散NaGdF:Yb:Er上转换纳米晶体（直径约25 nm）。六方相的UCNPs由于其较低的红到绿发光比率和较高的热灵敏度，被证明更适合作为温度传感器。在生理范围（20 - 70°C）附近的不同温度下记录了NaGdF:Yb:Er（油酸包覆或二氧化硅包覆）UCNPs的发射光谱，其呈现出适合作为温度传感器应用的特性，如出色的线性度（r > 0.99）和灵敏度（>3×10 K）。通过监测Er发射验证了AuNSs@UCNPs的加热能力，表明它们具有作为使用纳米温度计功能控制的热疗剂的应用潜力。
