Fluorophore-Induced Plasmonic Current Generation from Aluminum Nanoparticle Films

Abstract

In this paper, we demonstrate fluorophore-induced plasmonic current (FIPC) from aluminum nanoparticle films. It has been previously shown that near-field excited fluorophores are able to plasmonically couple with metal nanoparticle films (MNFs) and induce surface plasmons, which in turn leads to a direct measurable electrical current through the MNF. These currents have been detected and quantified in noble metal MNFs; however, due to future envisioned cost considerations, there has been a push to adapt FIPC for use with less expensive metals. Subsequently, we observe that plasmonic aluminum films are able to produce these current changes when in close proximity to excited fluorophores, and the magnitude of the current changes is in accord with to the magnitude of the extinction coefficients of the fluorophores themselves. These findings also further support recent literature reports showing the inverse relationship between metal-enhanced fluorescence and FIPC.

Fluorophore-Induced Plasmonic Current Generation from Copper Nanoparticle Films

“…From Figure , we can see that there are two major regions where increased thickness leads to an increased absorbance: in the UV spectral range from 300 to 500 nm and in the red wavelength range from 700 to 700 nm and beyond with the largest absorbances seen in the 3.5 nm films as expected. This is to be expected as the increased density of nanoparticles leads to an increased absorption of light relative to the silane glass slide substrate support. , In Supporting Figure S1, we can see that as film thickness increases, we start to see a dramatic increase in the absorption of the thicker films (10 → 15 nm) in the regions above 600 nm, eventually losing the copper nanoparticle plasmon band and instead displaying mirror-like properties indicative of a solid metal continuous film. These thicker films were found to be continuous and not suitable for FIPC experiments due to a high background current, a reduced film resistance, and little interaction with the fluorophore upon excitation.…”

“…As FIPC conditions become more favorable, in this case, on the 2.5 nm copper film, a larger portion of energy that would be emitted through the fluorescence pathway is instead channeled through the film as plasmonic current. [15][16][17][18]24 For all of these experiments, the laser power was held constant. A concentration series experiment was also undertaken using fluorescein concentrations of 5, 10, 25, 50, and 100 μM and the experiment was performed in the same manner as the previous literature 24 (Figure 7).…”

“…response as compared to the S-oriented light, consistent with FIPC-polarized results observed for other metals. 24 3.4. Solution Conductance and Its Effect on Plasmonic Current Generation.…”

“…2−6 Recent work by our group has shown that under certain conditions, this coupling event is able to generate a novel phenomenon known as fluorophore-induced plasmonic current (FIPC), wherein instead of an enhanced fluorescence emission from the complex, a detectable current is now also observed across the nanoparticle film, upon the excitation of the fluorophore−nanoparticle complex. [15][16][17][18]24 This generated current has been experimentally linked to MEF emission, wherein MEF emission decreases as the magnitude of current generation increases, demonstrating a conservation of energy within the system. This current generation is believed to be due to nonradiative energy transfer from the excited-state fluorophore to an individual nanoparticle on the film.…”

Sensitive Aluminum SPR Sensors Prepared by Thermal Evaporation Deposition

“…LSPR provides a highly confined near-field with extremely high local intensity that is favorable to nonlinear processes. Al nanostructures have been applied in fundamental research, − polarization generation, modifying light phase and intensity in the visible range, color generation, − enhancing specific light–matter interactions, − biosensing, nonlinear optics, , and others. − The strong localized near-field can cause photon damage to the sensing analytes, especially for biological samples. Optical absorption from the metallic materials generates a local thermal spike that can cause thermal shock to the sensing analytes or melt the nanostructures.…”