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: Chiral inorganic nanostructures strongly interact with photons changing their polarization state. The resulting circularly polarized light emission (CPLE) has cross-disciplinary importance for a variety of chemical/biological processes and is essential for development of chiral photonics. However, the polarization effects are often complex and could be misinterpreted. CPLE in nanostructured media has multiple origins and several optical effects are typically convoluted into a single output. Analysing CPLE data obtained for nanoclusters, NPs, nanoassemblies, and nanocomposites from metals, chalcogenides, perovskite, and other nanostructures, we show that there are several distinct groups of nanomaterials for which CPLE is dominated either by circularly polarized luminescence (CPL) or circularly polarized scattering (CPS); there are also many nanomaterials for which they are comparable. We also show that (1) CPL and CPS contributions involve light-matter interactions at different structural levels; (2) contribution from CPS is especially strong for nanostructured microparticles, nanoassemblies and composites; and (3) engineering of materials with strongly polarized light emission requires synergistic implementation of CPL and CPS effects. These findings are expected to guide development of CPLE materials in a variety of technological fields, including 3D displays, information storage, biosensors, optical spintronics, and biological probes. 

Inorganic particles are effective photocatalysts for the liquid-state production of organic precursors and monomers at ambient conditions. However, poor colloidal stability of inorganic micro- and nanoparticles in low-polarity solvents limits their utilization as heterogeneous catalysts and coating them with surfactants drastically reduces their catalytic activity. Here we show that effective photo-oxidation of liquid cyclohexane (CH) is possible using spiky particles from metal oxides with hierarchical structure combining micro- and nanoscale structural features engineered for enhanced dispersibility in CH. Nanoscale ZnO spikes are assembled radially on α-Fe₂O₃microcube cores to produce complex ‘hedgehog’ particles (HPs). The ‘halo’ of stiff spikes reduces van der Waals attraction, preventing aggregation of the catalytic particles. Photocatalysis in Pickering emulsions formed by HPs with hydrogen peroxide provides a viable pathway to energy-efficient alkane oxidation in the liquid state. Additionally, HPs enable a direct chemical pathway from alkanes to epoxides at ambient conditions, specifically to cyclohexene oxide, indicating that the structure of HPs has a direct effect on the recombination of ion-radicals during the hydrocarbon oxidation. These findings demonstrate the potential of inorganic photocatalysts with complex architecture for ‘green’ catalysis.

 

Chiral nanostructures is one of the most rapidly developing research fields encompassing chemistry, physics, and biology. The rise to academic prominence of chiral nanostructures was fueled by their giant optical activity and the fundamental structural parallels between biotic and abiotic structures with mirror asymmetry. Our introduction and the themed collection provide both a timely snapshot and comprehensive overview of concepts being developed by a diverse spectrum of scientists around the world working in in chiral nanostructures from metals, semiconductors and ceramics. Many fundamental discoveries in this area are expected that are likely to encompass multiscale chirality transfer, chiral surfaces, biological signaling, and circularly polarized emitters. Technological applications being pursued along the way of fundamental studies include biosensing, healthcare, chiral photonics, and sustainable catalysis. 

Circularly polarized light interacts preferentially with the biomolecules to generate spectral fingerprints reflecting their primary and secondary structure in the ultraviolet region of the electromagnetic spectrum. The spectral features can be transferred to the visible and near‐infrared regions by coupling the biomolecules with plasmonic assemblies made of noble metals. Nanoscale gold tetrahelices were used to detect the presence of chiral objects that are 40 times smaller in size by using plane‐polarized light of 550 nm wavelength. The emergence of chiral hotspots in the gaps between 80 nm long tetrahelices differentiate between weakly scattering S‐ vs R‐molecules with optical constants similar to that of organic solvents. Simulations map the spatial distribution of the scattered field to reveal enantiomeric discrimination with selectivity up to 0.54.