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During the last few decades, substantial attention has been devoted to copper and copper oxide nanocatalysts, due to copper's natural abundance, low cost and lower toxicity in comparison to precious metal-based nanoparticles. Cuprous oxide (Cu2O) nanoparticles show versatility in catalyzing and mediating carbon–carbon (C–C) and carbon–heteroatom (e.g., C–N, C–O, C–S and C–Se) bond-forming reactions. Here, we demonstrate Cu2O nanoparticle-mediated oxidative C–C homocoupling reactions for the synthesis of polyphenylenediethynylenes under ligandless conditions, mild base and atmospheric air as the oxidant, with reasonable yields and moderate number-average molecular weights. Also, we demonstrate that, during the reaction, Cu2O nanoparticles undergo substrate-induced leaching to form homogeneous copper catalytic species. The leaching of catalytic species and in situ formation of copper complexes are characterized by electrospray ionization mass spectrometry, ultraviolet-visible extinction spectroscopy, transmission electron microscopy and reactor study. The results confirm the contribution of a homogeneous catalytic pathway for the oxidative C–C homocoupling reactions under the reaction conditions used.

The ability of plasmonic metal nanostructures (PMNs), such as silver and gold nanoparticles, to manipulate and concentrate electromagnetic fields at the nanoscale is the foundation for wide range o...

Heterogeneous metal nanocatalysts have recently emerged as attractive catalysts for a variety of couplings (e.g., C–C, C–N, C–S, C–O, etc.). However, the characterization of the catalytic pathway remains challenging. By exploiting localized surface plasmon resonance (LSPR) of the catalytically relevant gold (Au) nanostructure, we show that UV–vis spectroscopy can be used to confirm the homogeneous catalytic pathway. Specifically, we have demonstrated that Au nanoparticles under C–C coupling conditions undergo substrate-induced leaching to form homogeneous Au catalytic species. The LSPR spectroscopic approach opens a new door to track stability of nanocatalysts and characterize the catalytic pathway in a range of coupling reactions.

Copper based nanocatalysts have recently emerged as attractive catalysts for a diversity of bond formations, such as C–C, C–N, C–O, C–S, and C–Se. However, the identification of truly heterogeneous versus homogeneous catalytic conditions remains an ongoing challenge within the field. Herein, we report that in cuprous oxide (Cu2O) nanoparticle-mediated C–C homo-coupling and cross-coupling reactions, the presence of a base facilitates the copper complex mediated homogeneous catalytic pathway. Whereas in the absence of a base, the reaction can proceed heterogeneously on the surface of Cu2O nanoparticles. We distinguished the homogenous versus heterogeneous pathways using a combination of reactor study, ultraviolet-visible extinction spectroscopy, electrospray ionization mass spectrometry, flame atomic absorption spectroscopy, transmission electron microscopy, and density-functional theory calculations. Our findings indicate that Cu2O nanoparticles can catalyze C–C coupling reactions under lingandless and base-free conditions via a truly heterogeneous pathway paving the way for the development of highly efficient, robust and sustainable processes.

Metal nanoparticle-catalyzed reactions such as hydrogenation, cross-coupling, carbonylation, and hydroformylation reactions are the most widely used reactions in the pharmaceutical and fine chemical industries. However, there is no operando spectroscopic technique that exists to monitor the size of functioning nanocatalyst. By exploiting localized surface plasmon resonance of catalytically relevant nanostructures, such as monometallic (e.g., Pd, Pt, Ni, Rh, Au, and Cu) nanoparticles and bimetallic core–shell (e.g., Ag-Pd) nanoparticles, we show UV–Vis spectroscopy can be used to determine the size of functioning nanocatalyst. Based on our finite-difference time-domain simulations, it is possible to detect leaching of even a monolayer of atoms from the surface of widely used metal nanocatalysts with a conventional UV–Vis spectrometer. This sensitive, inexpensive and robust spectroscopic approach can be potentially used as in-line process analytical technology (PAT) in pharmaceutical development and manufacturing.

Over the years plasmonic materials have received wide attention for their ability to convert solar into chemical energy. Plasmonic nanoparticles (NPs) exhibit strong electromagnetic-field (EMF) enhancement for the incident light because of the Localized Surface Plasmon Resonance (LSPR). This property has been shown to enhance the photocatalytic performance of nearby semiconductors in the composite, and hybrid photocatalysts build on plasmonic metal nanoparticle and semiconductor. In this presentation, we will focus on copper based hybrid plasmonic nanostructures and optically resonant high dielectric nanostructures for efficient conversion of solar into chemical energy. Our FDTD simulation results predict that the EMF enhancement observed over high dielectric NPs are 2-3 orders of magnitude higher than the plasmonic NPs. This new family of non-plasmonic metal oxide nanostructures is dielectric in nature with high refractive index (> 2). Our simulation results predict that the Mie resonance over these high-dielectric nanostructures can be tuned anywhere from UV-Vis to the near-IR region by controlling the geometry of the nanostructures. We will also show experimental results that validate the simulation results. We utilized size and shape-controlled synthesis techniques to design optically resonant nanostructures with tunable Mie resonance. The optoelectronic properties of these nanostructures are confirmed using a number of spectroscopic techniques. Also, we will show the visible-light enhanced photocatalytic performance of the high dielectric nanostructures for carbon-carbon (C-C) coupling reactions. The design rules developed for the optically resonant nanostructures in our study will potentially have a wide range of applications including the use of these nanostructures for solar-light driven photocatalysis and thin-film solar cell applications.