Heterogeneous metal nano catalysts have recently emerged as attractive catalysts for variety of couplings (e.g., C-C, C-N, C-S, C-O, etc.). However, the characterization of catalytic pathway remains challenging. By exploiting localized surface plasmon resonance (LSPR) of catalytically relevant gold (Au) nanostructure, we show 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 tracking stability of nano catalysts and characterizing the catalytic pathway in a range of coupling reactions. Furthermore, By exploiting localized surface plasmon resonance of catalytically relevant nanostructures, such as monometallic (Pd, Pt, Ni, Rh, Au, and Cu) nanoparticles and bimetallic core-shell (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 nano catalysts 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.

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 of applications, including nanoscale optics, solar energy harvesting and photocatalysis. However, there are inherent problems associated with plasmonic metals, such as high Ohmic losses, and poorer compatibility with the conventional complementary metal-oxide-semiconductor (CMOS) microfabrication processes. These limitations inhibit the broader use of PMNs in practical applications. Herein, we report submicron cuprous oxide and cupric oxide particles can exhibit strong electric and magnetic Mie resonances with extinction/scattering cross sections comparable to or slightly exceeding those of Ag particles. Using size- and shape-controlling particle synthesis techniques, optical spectroscopy, and finite-difference-time-domain simulations, we show that the Mie resonance wavelengths are size- and shape-dependent and tunable in the visible to near-infrared regions. Therefore, submicron copper oxide particles may potentially emerge as high-performance alternatives to PMNs in a wide range of applications