Photomodulated Self-Assembly of Hydrophobic Thiol Monolayer-Protected Gold Nanorods and Their Alignment in Thermotropic Liquid Crystal

Abstract

Three terminal thiols possessing azobenzene and perylene diimide (PDI) segments covalently linked by alkylene spacers of different lengths (P n SH, n = 4, 6, and 8) were synthesized to stabilize and functionalize gold nanorods (GNRs) via strong covalent Au–S bonds onto the gold surface. The resulting hydrophobic thiol monolayer-protected GNRs (P n GNRs) were stable in both organic solvent and the solid state and exhibited fascinating photoresponsive self-assembly behavior. The PDI moieties provided π–π interactions to promote GNR self-assemblies while the photoresponsive azobenzene moieties offered a way to phototune the assemblies in a reversible manner. Interestingly, when P n GNRs were mixed with a structurally similar room-temperature thermotropic liquid-crystal perylene diimide (LCP), the UV-irradiated P n GNRs showed more compatibility with the LCP host than their corresponding unirradiated ones. Furthermore, the P n GNRs with varied alkylene chain lengths showed different dispersion abilities in LCP. The UV-irradiated P4GNRs did not disperse well in LCP, whereas the UV-irradiated P6GNRs and P8GNRs dispersed well in LCP and were further aligned upon mechanical shearing. In addition, preliminary molecular simulation was performed to explain this interesting photomodulated self-assembly of the GNRs.

Induced growth of dendrite gold nanostructure by controlling self-assembly aggregation dynamics

“…Understanding the dynamics of nanoparticles aggregation is important for the applied research of functional materials. Many interface processes such as solid-liquid, liquid-liquid, and vaporliquid result in self-assembly [5][6][7][8][9] of the nanoparticles, in which lowering the interfacial potential leads to special spatial arrangement of the nanoparticles. Moreover the spatial arrangement has different patterns that depends on the kinetics of the nanoparticles involved [10][11][12][13].…”

Anisotropic Gold Nanoparticles: Preparation, Properties, and Applications

“…Lyotropic LC hosts that form nematic and hexagonal phases can be quite advantageous in aligning a high loading of AuNRs which are functionalized with micelles on surface [194]. Recently, organo-soluble thermotropic LCs were also used for such purpose [195]. In solid medium, polymer engineering is an attractive strategy to assemble AuNRs.…”

Liquid Crystal-Gold Nanoparticle Hybrid Materials

“…a 21 coated GNRs; b-e 20 coated GNRs, n = Zn, Cu, Mg, 2H, respectively [97,98]. [97] Copyright from ACS 2012; [98] Copyright from Elsevier 2013 Scheme 4.10 Chemical structure of photoresponsive perylene capping agents 22 self-assemblies can be further modulated by photoresponsive azobenzene group, based on the perylene-azo binary structure 22 [107]. Additionally, when mixing in perylene LC, the GNRs with weaker interaction after photo stimuli could disperse and further be aligned (Fig.…”