Chirality of Metal Nanoparticles in Chiral Mesoporous Silica

Abstract

Chiroptical properties of pure inorganic material have been achieved by dispersing small amounts of achiral Ag nanoparticles into highly ordered chiral mesoporous silica. There are three types of chirality in chiral mesoporous silica: i) the helical hexagonal surface, ii) the helical pore orientation, and iii) the helical arrangement of aminopropyl groups on the surface of the mesopores, all of which impart plasmonic circular dichroism and have been investigated by introducing Ag nanoparticles into the as‐made, calcined and extracted chiral mesoporous silica, respectively. The three types of optical response originate from asymmetric plasmon‐plasmon interactions of achiral Ag nanoparticles in three types of chiral environments. Among the three sources of chirality, the helical pore orientation was considered to be predominantly responsible for the optical response owing to the high efficiency of nanoscale chirality. Interestingly, large Ag nanoparticles aggregation as a result of calcination still resulted in a strong optical activity, even the chiral mesostructure was destroyed completely. Rather than the pitch length, the length of helical channel was more effective for increasing the intensity of plasmonic circular dichroism due to longitudinal propagation of Ag nanoparticles along helical channel. Such novel chiral inorganic material will bring new opportunities in non‐linear optics, biosensors and chiral recognition.

Twisted and tubular silica structures by anionic surfactant fibers encapsulation

“…Bringing chirality to plasmonic nanomaterials is on demand for potential applications in nanotechnology and metamaterials [43][44][45][46][47]. We used the fabricated silica structures as a scaffold for gold nanoparticles assemblies by applying different strategies.…”

Optically active chiral Ag nanowires

“…Recently, we have obtained chiral arrangement of Ag NPs and nanowire arrays in chiral mesoporous silica by hard template method [36,37], which resulted in the OA in surface plasmon resonance based on chiral superstructure of assembled NPs. However, the origin of the chiral OA by hard template method is so complicated that more efforts are needed to reveal the mechanism.…”

Functional helical silica nanofibers with coaxial mixed mesostructures for the fabrication of PtCo nanowires that display unique geometry-dependent magnetism

“…These helical silicas are also promising hard templates for the preparation of helical nanowires composed of metals [12][13][14][15] or other compositions that may possess unique optical, 16,17 electromagnetic 9,18 or other properties. Efforts to understand the formation mechanism of these helical nanostructures provide additional insights into the interplay of the thermodynamics and kinetics of the assembly of structure-directing surfactants and inorganic silicate species 1,2,19,20 and may also lead to the design and synthesis of additional novel selfassembled nanomaterials with controllable mesostructures and morphologies, allowing for innovative applications.…”