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Top‐down fabricated nanoantenna architectures of both metallic and dielectric materials show powerful functionalities for Raman and fluorescence enhancement with relevance to single molecule sensing while inducing directionality of chromophore emission with implications for single photon sources. We synthesize the smallest bow‐tie nanoantenna by selective tip‐to‐tip fusion of two tetrahedral colloidal quantum dots (CQDs) forming a dimer. While the tetrahedral monomers emit non‐polarized light, the bow‐tie architecture manifests nanoantenna functionality of enhanced emission polarization along the bow‐tie axis, as predicted theoretically and revealed by single‐particle spectroscopy. Theory also predicts the formation of an electric‐field hotspot at the bow‐tie epicenter. This is utilized for selective light‐induced photocatalytic metal growth at that location, unlike growth on the free tips in dark conditions, thus demonstrating bow‐tie dimer functionality as a photochemical reaction center. [ABSTRACT FROM AUTHOR]

Zinc chalcogenides nanostructures are promising newly‐studied materials for photocatalytic reactions such as water reduction for hydrogen generation and photoinitiation of radical polymerization processes. Herein, we introduced a straightforward synthesis of thin ZnS shell on ZnSe nanorods and characterized the resulting core/shell ZnSe/ZnS nanorods by electron microscopy techniques and X‐ray photoelectron spectroscopy. Then, the photocatalytic activities of the nanorods were studied by gas chromatography for hydrogen generation and by Fourier transform infrared spectroscopy for the photoinitiation capability. While such core/shell systems may limit charge transfer to the solution due to the type‐I band alignment, we find that the photochemical stability and photocatalytic activity of this system is significantly enhanced over pristine ZnSe nanorods. ZnSe/ZnS nanorods with Ni(NO3)2 co‐catalyst are used for hydrogen generation and the effects of the nanorods' surface coating, pH conditions and type of hole scavenger are examined. The best performances were observed for nanorods after ligand stripping with Meerwein′s reagent using ascorbic acid as a hole acceptor at pH 4.5. All three parameters were found to affect the photocatalytic activity. Yet, the surface coating and pH dependence differ from previous reports on cadmium chalcogenides photocatalysts. The origin of their differences is discussed and attributed to the band alignment of the systems and the nature of the co‐catalyst. The stable heavy‐metal free ZnSe/ZnS nanorods system presented here holds promise for various photocatalytic applications. [ABSTRACT FROM AUTHOR]