The strong interaction of electromagnetic fields with plasmonic nanomaterials offers opportunities in various technologies that take advantage of photophysical processes amplified by this light-matter interaction. Recently, it has been shown that in addition to photophysical processes, optically excited plasmonic nanoparticles can also activate chemical transformations directly on their surfaces. This potentially offers a number of opportunities in the field of selective chemical synthesis. In this Review we summarize recent progress in the field of photochemical catalysis on plasmonic metallic nanostructures. We discuss the underlying physical mechanisms responsible for the observed chemical activity, and the issues that must be better understood to see progress in the field of plasmon-mediated photocatalysis.

Plasmonic metal nanoparticles enhance chemical reactions on their surface when illuminated with light of particular frequencies. It has been shown that these processes are driven by excitation of localized surface plasmon resonance (LSPR). The interaction of LSPR with adsorbate orbitals can lead to the injection of energized charge carriers into the adsorbate, which can result in chemical transformations. The mechanism of the charge injection process (and role of LSPR) is not well understood. Here we shed light on the specifics of this mechanism by coupling optical characterization methods, mainly wavelength-dependent Stokes and anti-Stokes SERS, with kinetic analysis of photocatalytic reactions in an Ag nanocube–methylene blue plasmonic system. We propose that localized LSPR-induced electric fields result in a direct charge transfer within the molecule–adsorbate system. These observations provide a foundation for the development of plasmonic catalysts that can selectively activate targeted chemical bonds, since the mechanism allows for tuning plasmonic nanomaterials in such a way that illumination can selectively enhance desired chemical pathways.

Conductive organic and composite films represent the critical component of many areas of technology. This study demonstrates that highly conductive coatings can be made by layer-by-layer (LBL) assembly of single-walled carbon nanotubes (SWNTs). These films reveal electrical conductivities of 10 2 to ∼10 3 S/m at room temperature without doping with nanotube loading as low as ∼10%. This is indicative of efficient utilization of SWNT in percolation pathways. Low SWNT loading also makes the coatings quite transparent with transmission as high as 97% for visible light. Thicker delaminated LBL films displayed conductivities of 4.15 × 10 4 S/m. The free-standing films were highly flexible and possessed 160 MPa of tensile strength, which makes them the strongest organic conductor. The high strength and conductivities are attributed to the unique homogeneity of the LBL assembled composites, which opens the way to future optimization of electrical, mechanical, and optical properties and to fit the needs of specific applications, which may be exemplified by transparent flexible electronics, light emitting diodes, smart windows, solar cells, sensors, structural materials, and biomedical devices.

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Electro-chemical and thermo-chemical processes occurring at multi-phase interfaces are the basis of many devices facilitating conversion between forms of energy including solar, electrical, and chemical in a number of devices from fuel cells to batteries. Large electric fields, high potential bias and inherent inaccessibility of these interfaces to many conventional experimental probes contribute to an absence of fundamental insight into mechanistic behavior of chemical species and interfacial environment. Modern first-principles tools including Density Functional Theory (DFT) can be used to study these interfaces from a first-principles approach and provide insight for molecular transformations. In our studies we also coarse-grain DFT calculations with the Cluster Expansion (CE) and extend quantum-mechanical ab-initio information to larger systems and include environmental factors such as temperature, partial pressure of oxygen, and surface morphology (undercoordinated step and edge sites). We investigate two case studies: recharge cycle of lithium/oxygen batteries and oxygen on a metal surface in ethylene epoxidation.