Chiral artificial nanosystems constructed from inorganic nanoparticles brought about a paradigm shift in chiral sensing, enantioselective catalysis, chiral polarization engineering, and chiral emission due to their strong light–matter interaction and their precisely engineered properties. Especially bottom‐up approaches hold great potential for the inexpensive, scalable production of plasmonic, excitonic, and upconversion chiral materials. This perspective first reviews the state‐of‐the‐art fabrication schemes: chiral molecule‐induced chirality, chiral nanoparticle growth, and assembly of chiral superstructures from achiral building blocks. Next, the emerging field of dynamically tunable chiroptical materials, promising for adaptive thin‐film optics, display technologies, and information encoding, is explored. Here, the strength of chiral assemblies based on their rich tuning mechanisms and their ability for geometrical reconfiguration is highlighted. Finally, promising future directions and opportunities in the field of active chiroptical materials are discussed.

Applications based on metasurfaces are often hampered by the limited scalability and real‐time tunability of lithographically produced samples (top‐down). Bottom‐up approaches that start from nanoparticle building blocks relax these constraints. Here, a large‐area mechano‐tunable metasurface composed of a square array of silicon nanospheres (Si NSs) is introduced. The metasurface is produced by capillarity‐assisted self‐assembly of size‐purified colloidal Si NSs that have Mie resonances in the visible and near‐infrared range. The collective response of Si NSs in the metasurface exhibits reflectance peaks originating from electric (ED) and magnetic dipole (MD) resonances of individual Si NSs. The resonance wavelengths are sensitive to the lattice constant and thus can be modulated in a wide wavelength range (≈130 nm) by external mechanical strain. At a proper strain level, the ED and MD lattice resonances spectrally overlap, resulting in destructive interference of the backward scattering light (lattice Kerker effect), which strongly suppresses the reflectance. The reflectance modulation is at a maximum of 45.9% and is reversible over 100 stretching‐releasing cycles. This suggests that the produced flexible metasurface can be a mechano‐tunable flexible optical component.

Chiral molecules in nature usually show optical activity only in the deep ultraviolet, whereas artificial chiral plasmonic nanostructures can generate much stronger responses at visible and near-infrared wavelengths. An important challenge is whether the abundant biomolecular chirality in nature can be directly transferred to achiral plasmonic systems without elaborate three-dimensional nanofabrication. Here we show that the mechanical stretching of protein molecules anchored within achiral gold nanoparticle assemblies strongly enhances and reversibly modulates plasmon-coupled circular dichroism. Stretching amplifies the chiroptical response to an ellipticity of 1.18° and a dissymmetry factor of 0.2, far exceeding conventional hotspot-based strategies. Repeated stretching and relaxation further enable reversible switching over more than 100 cycles. Simulations and in situ spectroscopy indicate that the deformation of protein changes its conformation and dipole alignment, thereby strengthening the plasmonic chiral response. These findings establish a route to achieve dynamically controllable chiroptical activity in achiral plasmonic assemblies, revealing how small biomolecular deformations can strongly influence plasmonic responses of much larger nanostructures.

Yet while nature effortlessly creates chiral biomolecules, the fabrication of artificial chiral nanostructures is significantly more onerous. Therefore, investigating the chirality transfer from abundant biomolecules to simple nanostructures without sophisticated three-dimensional nanofabrication is convenient and meaningful. However, in the previous studies with this goal, the biomolecules mostly acted as structurally chiral templates to permanently break the mirror symmetry of nanostructures, whose chirality transfer was irreversible and thus lacking in flexibility in applications. Here we discovered an in-situ biomolecule-stretching strategy to realize the highly efficient (dissymmetry factor 0.2) and reversible chirality transfer from biomolecules to nanoparticles for the first time, based on a Coulombic “field effect” rather than a traditional “structural effect”. Due to this unique “field effect”, the mirror symmetry of nanostructures is well maintained. Thus, the chirality can be smartly reversed over 100 cycles to meet various requirements of modern chiral devices. Our results unravel how achiral plasmons acquire chirality from a biomolecule efficiently and reversibly, interpreting the intimate interaction between biomolecules and plasmonic fields.

The immobilization of gold nanoparticle (AuNP) linear surface assemblies on polycarbonate (PC) melt surface via molding is investigated. The order of the particle assemblies is preserved during the molding process. The assemblies on PC exhibit plasmonic coupling features and dichroic properties. The structure of the assemblies is quantified based on Scanning Electron Microscopy (SEM) and image analysis data using an orientational order parameter. The transfer process from mold to melt shows high structural fidelity. The order parameter of around 0.98 reflects the orientation of the lines and remains unaffected, independent of the injection direction of the melt relative to the particle lines. This is discussed in the frame of fountain flow during injection molding. The particles were permanently fixed and withstood the injection molding process, detachment of the substrate, and extraction in boiling ethanol. The plasmonic particles coupled strongly within the dense nanoparticle lines to produce anisotropic optical properties, as quantified by dichroic ratios of 0.28 and 0.52 using ultraviolet–visible–near-infrared (UV–Vis–NIR) spectroscopy. AuNP line assemblies on a polymer surface may be a basis for plasmonic devices like surface-enhanced Raman scattering (SERS) sensors or a precursor for nanowires. Their embedding via injection molding constitutes an important link between particle-self-assembly approaches for optically functional surfaces and polymer processing techniques.