Efficient Photocurrent Enhancement from Porphyrin Molecules on Plasmonic Copper Arrays: Beneficial Utilization of Copper Nanoanntenae on Plasmonic Photoelectric Conversion Systems

Abstract

We demonstrated the usefulness of Cu light-harvesting plasmonic nanoantennae for the development of inexpensive and efficient artificial organic photoelectric conversion systems. The systems consisted of the stacked structures of layers of porphyrin as a dye molecule, oxidation-suppressing layers, and plasmonic Cu arrayed electrodes. To accurately evaluate the effect of Cu nanoantenna on the porphyrin photocurrent, the production of CuO by the spontaneous oxidation of the electrode surfaces, which can act as a photoexcited species under visible light irradiation, was effectively suppressed by inserting the ultrathin linking layers consisting of 16-mercaptohexadecanoic acid, titanium oxide, and poly(vinyl alcohol) between the electrode surface and porphyrin molecules. The reflection spectra in an aqueous environment of the arrayed electrodes, which were prepared by thermally depositing Cu on two-dimensional colloidal crystals of silica with diameters of 160, 260, and 330 nm, showed clear reflection dips at 596, 703, and 762 nm, respectively, which are attributed to the excitation of localized surface plasmon resonance (LSPR). While the first dip lies within the wavelengths where the imaginary part of the Cu dielectric function is moderately large, the latter two dips lie within a region of a quite small imaginary part. Consequently, the LSPR excited at the red region provided a particularly large enhancement of porphyrin photocurrent at the Q-band (ca. 59-fold), compared to that on a Cu planar electrode. These results strongly suggest that the plasmonic Cu nanoantennae contribute to the substantial improvement of photoelectric conversion efficiency at the wavelengths, where the imaginary part of the dielectric function is small.

Plasmonic triangular nanoprism sensors

“…The chemical synthesis of Ag NPrs, which is faster and more favourable to mass production than photochemical synthesis, requires polymeric protective agents, which could limit the sensitivity. Sensors using Au and Ag have been mostly researched and reviewed herein but devices using cheaper earth-abundant alternative materials (e.g., Cu 23,24,108 ) are desirable. Use of other materials requires us to find clever workarounds to intrinsic inferior properties (e.g., prone to oxidation) or new perspectives.…”

“…21,22 Among these, Cu has been less explored as a sensor material because Cu has the largest imaginary part of permittivity and is most readily oxidized under ambient conditions. 23,24 We are not aware of copper-based plasmonic nanoprism sensors, although advances have been made in the fabrication and protection from oxidation of anisotropic Cu nanoparticles. [25][26][27][28] Therefore, we focus our attention to nanoprisms made of Au and Ag.…”

Review of porphyrin-based photodynamic therapy materials

“…Despite of the chemical functionalization of porphyrins, physical encapsulation is recognized as another commonly used strategy to enhance the water-solubility and biocompatibility of porphyrins. A large number of inorganic/organic nanoparticles have been constructed for the loading and delivery of genes and various hydrophobic drugs including porphyrins [64][65][66][67][68][69]. The nanoscale size of obtained nanoparticles leads to the significant EPR effect for their passive accumulation at tumor sites.…”

Review of Conjugated Porphyrin Systems

“…CNTs are 1-dimensional (1D) 46 cylindrical macromolecules with diameters in the nanoscale; single walled carbon nanotubes (SWCNTs) can have a diameter of 1-2 nm 47 and multiwalled carbon nanotubes (MWCNTs) which contain multiple numbers of carbon layers can have a diameter between 2 and 100 nm. 48 The walls of CNTs are made up of sp 2 hybridized 49 carbon atoms arranged in a hexagonal lattice.…”