Tuning the miscibility of gold nanoparticles dispersed in liquid crystals via the thiol-for-DMAP reaction
作者:Jonathan Milette、Violeta Toader、Linda Reven、R. Bruce Lennox
DOI:10.1039/c1jm10553a
日期:——
Ligand exchange reactions using 4–5 nm 4-(N,N-dimethylamino)pyridine (DxMAP)-capped gold nanoparticles (AuNPs) formed the basis for synthesizing a family of liquid crystal (LC)-capped NPs for a rationalized miscibility in liquid crystal matrices. NPs with ligand capping layers composed of CH3(CH2)mSH (m = 5, 11) or 4′-(n-mercaptoalkyloxy)biphenyl-4-carbonitriles (CBO(CH2)nSH, n = 8, 12, 16) and their binary mixtures were prepared. The miscibility of the NPs in liquid crystals is found to be sensitive to the ligand chain length and the density of the LC ligands within the capping layers. Polarized optical microscopy and UV-vis data show that the NPs with only CH3(CH2)mSH ligands are either immiscible or only partially disperse in the isotropic phases of 4-n-pentyl-4′-cyanobiphenyl (5CB) and 4-n-octyl-4′-cyanobiphenyl (8CB). NPs with CBO(CH2)nSH (n = 8, 12, 16) ligands or mixed CH3(CH2)5SH/CBO(CH2)12SH ligand shells containing 28% or 70% CBO(CH2)12SH ligand content partly disperse. However, NPs with a 1 : 1 CH3(CH2)5SH/CBO(CH2)12SH ratio are completely miscible in isotropic 5CB up to at least 25 wt% Au. In general, the derivatization methodology developed here for mesogenic ligands provides in a complementary approach to thiol-for-thiol exchange for designing bifunctional AuNPs, offering the advantages of high reproducibility, access to a wide composition range and no need for large excesses of valuable functionalized ligand.
使用4-5 nm 4-(N,N-二甲氨基)吡啶(DxMAP)封端的金纳米颗粒(AuNPs)进行的配体交换反应,作为合成一系列液晶(LC)封端纳米颗粒的基础,以实现液晶基质中的合理混溶性。制备了配体封端层由CH3(CH2)mSH(m = 5, 11)或4′-(n-巯基烷氧基)联苯-4-碳腈(CBO(CH2)nSH, n = 8, 12, 16)及其二元混合物构成的纳米颗粒。研究发现,纳米颗粒在液晶中的混溶性对配体链长和封端层中液晶配体的密度非常敏感。偏振光学显微镜和紫外可见光数据表明,仅有CH3(CH2)mSH配体的纳米颗粒在4-n-戊基-4′-氰基联苯(5CB)和4-n-辛基-4′-氰基联苯(8CB)的各向同性相中要么不相溶,要么仅部分分散。含有CBO(CH2)nSH(n = 8, 12, 16)配体的纳米颗粒或包含28%或70% CBO(CH2)12SH配体的混合CH3(CH2)5SH/CBO(CH2)12SH配体壳的纳米颗粒部分分散。然而,配比为1:1的CH3(CH2)5SH/CBO(CH2)12SH纳米颗粒在各向同性5CB中可完全混溶,高达至少25 wt%的金。总的来说,这里开发的用于介晶配体的衍生化方法论为设计双功能金纳米颗粒提供了一种互补的方法,相较于硫醇对硫醇的交换,具有高重复性、广泛的成分范围,且无需大量过量的宝贵功能化配体的优点。