Torres-Cavanillas Ramón, Sanchis-Gual Roger, Dugay Julien, Coronado-Puchau Marc, Giménez-Marqués Mónica, Coronado Eugenio
Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, c/Catedrático José Beltrán 2, Paterna, 46980, Spain.
Adv Mater. 2019 Jul;31(27):e1900039. doi: 10.1002/adma.201900039. Epub 2019 Apr 18.
A simple chemical protocol to prepare core-shell gold@spin-crossover (Au@SCO) nanoparticles (NPs) based on the 1D spin-crossover Fe(Htrz) (trz) coordination polymer is reported. The synthesis relies on a two-step approach consisting of a partial surface ligand substitution of the citrate-stabilized Au NPs followed by the controlled growth of a very thin layer of the SCO polymer. As a result, colloidally stable core@shell spherical NPs with a Au core of ca. 12 nm and a thin SCO shell 4 nm thick, are obtained, exhibiting a narrow distribution in sizes. Differential scanning calorimetry proves that a cooperative spin transition in the range 340-360 K is maintained in these Au@SCO NPs, in full agreement with the values reported for pristine 4 nm SCO NPs. Temperature-dependent charge-transport measurements of an electrical device based on assemblies of these Au@SCO NPs also support this spin transition. Thus, a large change in conductance upon spin state switching, as compared with other memory devices based on the pristine SCO NPs, is detected. This results in a large improvement in the sensitivity of the device to the spin transition, with values for the ON/OFF ratio which are an order of magnitude better than the best ones obtained in previous SCO devices.
报道了一种基于一维自旋交叉Fe(Htrz)(trz)配位聚合物制备核壳型金@自旋交叉（Au@SCO）纳米颗粒（NPs）的简单化学方法。该合成方法依赖于两步法，包括对柠檬酸盐稳定的金纳米颗粒进行部分表面配体取代，然后控制生长一层非常薄的SCO聚合物。结果，获得了胶体稳定的核@壳球形纳米颗粒，其金核直径约为12 nm，SCO壳层厚度为4 nm，尺寸分布狭窄。差示扫描量热法证明，这些Au@SCO纳米颗粒在340 - 360 K范围内保持协同自旋转变，这与原始4 nm SCO纳米颗粒报道的值完全一致。基于这些Au@SCO纳米颗粒组装的电子器件的温度依赖电荷传输测量也支持这种自旋转变。因此，与基于原始SCO纳米颗粒的其他存储器件相比，检测到自旋状态切换时电导有很大变化。这导致器件对自旋转变的灵敏度有很大提高，开/关比的值比之前SCO器件获得的最佳值好一个数量级。
