Light-Directed Patchy Particle Fabrication and Assembly from Isotropic Silver Nanoparticles

We demonstrate the creation of anisotropic patchy silver nanospheroids (AgNSs) using linearly polarized UV light and a photo-uncaging <i>o</i>-nitrobenzyl-based ligand, which anchors to the AgNSs by two gold-sulfur bonds. Exposure to a 1 J/cm² dose of UV light induces a photo-uncaging reaction in the ligand that reveals a primary amine on the surface. By using linearly polarized UV light, we meter the exposure dose such that only the poles of the nanoparticle receive a full dose, limiting the photo-uncaging reaction primarily to the particle’s plasmonic hot spots. We reveal this anisotropy by preferentially adhering negatively charged gold nanospheres (AuNSs) to the AgNSs’ poles by using the electrostatic attraction between them and the positively charged primary amines generated by photo-uncaging. When the assembly is performed onto silver particles that are immobilized on a substrate, it results in nanoscale structures with a strong tendency to align with the polarization of the exposing light. This manifests in polarimetric spectroscopy as a linear dichroism aligned with the polarization direction

Chemo‑, Regio‑, and Stereoselective Copper(II)-Catalyzed Boron Addition to Acetylenic Esters and Amides in Aqueous Media

Aqueous conditions were developed for conducting an open-to-air, copper­(II)-catalyzed addition of pinBBdan to alkynoates and alkynamides. The simple and mild β-borylation protocol proceeds in a remarkably chemo-, regio-, and stereoselective fashion to afford 1,8-diamino­naphthalene protected (<i>Z</i>)-β-boryl enoates and primary, secondary, and tertiary enamides in good to excellent yields. These reactions demonstrate a high tolerance toward a variety of alkyl, aryl, and heteroatom functional groups and provide convenient access to a diverse range of vinylboronic acid derivatives

Plasmon-Induced Photoreaction of <i>o</i>‑Nitrobenzyl-Based Ligands under 550 nm Light

We have studied the plasmon-driven photoreaction of a dual thiol-anchored <i>o</i>-nitrobenzyl-based photouncaging ligand on silver nanoparticles. Previous results have shown that this compound strongly anchors to gold surfaces, and a 1 J/cm² dose of UV light induces the intended photoreaction, uncaging an amine on the surface. This allows for photopatterning and the selective adhesion of gold nanospheres (AuNSs) to a surface via electrostatic attraction between the positively charged amines and negatively charged AuNSs. Here, we report that when the ligand is adsorbed on a silver nanospheroid film (AgNS), an additional photoreaction induced by green light inhibits AuNSs adhesion in the UV exposed film. Our findings suggest that this is a result of the neutralization of the amine group’s ability to become charged, as opposed to the removal of the ligand from the surface of the silver nanospheroids. We hypothesize that this neutralization may be due to a form of hot-hole-induced photocatalysis, resulting in an NN double bond between two neighboring ligands. This reaction has been documented in similarly amine-terminated moieties. This neutralization allows for a more fine-tuned, plasmonically based control of the ligand’s photoreaction, as the green light exposure only affects the ligand if it has previously been cleaved by UV light, and makes it possible to perform reverse photopatterning on the surface