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Abstract

Surface-enhanced infrared absorption (SEIRA) spectra of manganese (III) tetraphenylporphine chloride (Mn(TPP)Cl) on metal island films were measured in transmission mode. Dependences of the enhancement factor of SEIRA on both the sample quantity and the type of evaporated metal were investigated by subsequently increasing the amount of Mn(TPP)Cl on gold and silver substrates. The enhancement increases nonlinearly with the amount of sample and varies slightly with the thickness of metal islands. In particular, the SEIRA transmission method presents an anomalous spectral enhancement by a factor of 579, with substantial spectral shifts, observed only for the physisorbed Mn(TPP)Cl that remained on a 3-nm-thick gold film after immersion of the substrates into acetone. A charge-transfer (CT) interaction between the porphyrinic Mn and gold islands is therefore proposed as an additional factor in the SEIRA mechanism of the porphyrin system. The number of remaining porphyrin molecules was estimated by calibration-based fluorescence spectroscopy to be 2.36×1013 molecules (i.e., ~2.910 -11 mol/cm 2 ) for a 3-nm-thick gold film, suggesting that the physisorbed molecules distributed very loosely on the metal island surface as a result of the weak van der Waals interactions. Fluorescence microscopy revealed the formation of microcrystalline porphyrin aggregates during the consecutive increase in sample solution. However, the immersion likely redistributed the porphyrin to be directly attached on the gold surface, as evidenced by an absence of porphyrinic microcrystals and the observed SEIRA enhancement. The distinctive red shift in the UV-visible spectra and the SEIRA-enhanced peaks indicate the presence of a preferred orientation in the form of the porphyrin ring inclined with respect to the gold surface.

Electroless Gold Island Thin Films: Photoluminescence and Thermal Transformation to Nanoparticle Ensembles

“…Annealing at higher temperature (450 °C) increased pore diameters in composite Au films for 10 initial hours and then decreased pore diameters in five subsequent hours . We are currently evaluating laser irradiation to replace thermal annealing as a method to coalesce island film structures by way of diffusion-limited cluster−cluster aggregation to form aggregate chains. , Previous work with sputtered and evaporated films suggests adjustments in film thickness, deposition rate, and annealing conditions that affect EL island film morphology would impact enhancement factors in SERS, ,, distance-dependent sensitivity of transmission-SPR spectroscopy to analyte/Au-bound receptor interactions . Whereas EL deposition directly onto Si−H yields domes with a significant (220) orientation, our method yields Au islands with predominantly (111) orientation and relatively small (220) orientation after annealing.…”

“…Au thin films are applied in gateable electronic transistors , and conductors, optically induced thermoplasmonic gratings for nanomanipulation of picoliter droplets, surface plasmon resonance (SPR) sensors (45−60-nm thickness), and SERS-active substrates , excited by visible (red), near-IR, and IR light. Au island films are substrates for SERS, attenuated total reflection surface-enhanced IR absorption (SEIRA) microspectroscopy, and transmission localized surface plasmon sensors − and identify nanoscale structures in near-field scanning optical microscopy (NSOM) , nanoactuation, immunoassays, porphyrin-conjugated nano-wires, surface-enhanced Raman (SER) scattering for single-molecule spectroscopy, , and SER nanosensors …”

Protein-Mediated Sandwich Strategy for Surface-Enhanced Raman Scattering: Application to Versatile Protein Detection

“…On one hand, the first Au layer was prepared by electrostatic interaction between PDDA and negatively charged Au nanoparticles, which is a self-assembled process, so it is cheaper and more accessible. On the other hand, the size of Au nanoparticles used in this study is more homogeneous than that of the common Au substrate, 24 and thus, it enables more homogeneous properties in SERS spectra and makes easier analysis of the results.…”

Cellular Localization of Selected Porphyrins and Their Effect on the In Vitro Motility of Human Colon Tumors and Normal Cells

“…This phenomenon can be explained in several ways. Mn-porphyrin molecules did not show bright fluorescence emission at any excitation wavelength [ 22 , 23 ]. Coordinated metal ions increase the probability of non-radiative decay of the excited state of porphyrin [ 18 ]; therefore, fluorescence spectroscopy could not be employed for determining the localization of Mn-porphyrin molecules.…”