Laser‐Directed Asymmetric Growth of Plasmonic Chiral Ensembles

Abstract

Chiral plasmonic system due to its enhanced chiroptic activity in the visible region has attracted numerous interests in the last decade. Although various strategies have been developed for the fabrication of chiral plasmonic nanostructures, the limitations of cost-effectiveness and controllability have been the main obstacle for their practical applications. Here, continuous wave laser is used to direct the growth of chiral ensembles of gold nanoparticles (AuNPs). These AuNPs are grown from the Au-doped titanium dioxide (TiO 2 ) films in a ring-shaped arrangement under photoreduction, which can then evolve into nanotetramers, nanotrimers, and nanodimers at different irradiation time, showing good controllability and reproducibility. Especially, the nanodimers and nanotrimers show circular differential scattering (CDS) over 20%. The optical chirality of the nanotrimers presents a prominent superchiral field, which is demonstrated for the optical sensing of chiral molecules (approximately × 10 −3 m) with large spectral dissymmetric factors. Such an unprecedented growth strategy via laser direct writing is facile, tailorable, location-selective, and ligand-free, which presents significant implications for on-chip integration of chiral nano-optic devices and surface-enhanced Raman optical activity (SEROA).

Chiral nanomaterials in tissue engineering

“…3-iv), which were characterised by spatial gradients in thickness spanning several microns across substrate lengths measuring tens of centimetres. 102 To address the high cost of GLAD, a novel technique involving the light-induced solid-state growth of chiral gold ensembles was devised by Wang and Ding, 103 with a resolution of several hundred nanometres. This system enabled the customisable fabrication of plasmonic chiral assemblies (Fig.…”

Bottom‐Up Assembly of Inorganic Particle‐Based Chiroptical Materials

“…Wang et al grew ring-shaped Au NP oligomers by irradiating Au-doped titanium dioxide with a continuous-wave laser. [100] Independently of the laser polarization, the seed particles grow and fuse randomly into asymmetric clusters that show CD in the single-particle scattering signal. However, the handedness of the particles cannot be controlled by this method.…”

Trace-Amount Detection of Chiral Molecules Based on Plasmonic Racemic Arrays Fabricated via Direct Laser Writing

“…The conventional method of chiral detection via circular dichroism (CD) typically has a detection limit of ∼0.1 mM, which is mainly active in the ultraviolet band. Plasmonic nanostructures, due to their highly concentrated electromagnetic near field, can significantly enhance chiral light–matter interactions and convert the CD signals of chiral molecules into the visible band via plasmon resonances, , which has shown promising sensing capability for a few chiral molecules. , Furthermore, the intrinsic chirality of chiral plasmonic nanostructures exhibits high optical chirality due to the formation of superchiral fields, significantly improving the detection sensitivity of chiral molecules to less than hundreds. − However, the fabrication of chiral plasmonic nanostructures is complicated and expensive, and the chiral sensing performance cannot reveal the intrinsic nature of the chiral molecules as it is largely based on the dissymmetry of the spectral shift. − Although achiral photonic and plasmonic structures can also present a superchiral field for enhanced chiroptic sensing, − their density of optical chirality is small (∼50), which shows limited sensing performance.…”