Abstract
In this paper, metal–insulator–metal (MIM) nanostructures, which were designed to exhibit two absorption peaks within 500–1100 nm wavelength range, were fabricated using magnesium difluoride (MgF2) as the insulator layer. Since the MIM nanostructures have two plasmon modes corresponding to the absorption peaks, they independently responded to the changes in two phases: the surrounding medium and the inside insulator layer, the structure is expected to obtain multiple information from sample solution: refractive index (RI) and molecular interaction between solution components and the insulator layer. The fabricated MIM nanostructure had a diameter of 139.6 ± 2.8 nm and a slope of 70°, and exhibited absorption peaks derived from individual plasmon modes at the 719 and 907 nm wavelengths. The evaluation of the response to surrounding solution component of the MIM nanostructures revealed a linear response of one plasmon mode toward the RI of the surrounding medium and a large blue shift of the other plasmon mode under conditions where glycerol was present at high concentration. From optical simulation and the evaluation of the MgF2 fabricated by deposition, the blue shift was expected to be due to the swelling of MgF2 interacting with the hydroxyl groups abundantly included in the glycerol molecules. The results indicated the individual responses of two plasmon modes in MIM nanostructures toward medium components, and brought the prospect for the simultaneous measurement of multiple elements using two or more plasmon modes.
Highlights
Au-MgF2 -Au and Its Potential in Responding to Two Different Factors in Sample Solutions Using Individual
Metal nanostructures have been studied for highly efficient optical materials and biochemical sensor applications because of the unique optical characteristics derived from the collective oscillation of free electrons on their surfaces, i.e., the localized surface plasmon (LSP) [1,2,3,4,5,6]
MIM nanostructures which have absorption peaks at 715 and 920 nm wavelength were successfully designed by setting its their parameters as follows: 30 nm Au layer thickness; 20 nm MgF2 layer thickness; and 140 nm diameter
Summary
Au-MgF2 -Au and Its Potential in Responding to Two Different Factors in Sample Solutions Using Individual. Since the MIM nanostructures have two plasmon modes corresponding to the absorption peaks, they independently responded to the changes in two phases: the surrounding medium and the inside insulator layer, the structure is expected to obtain multiple information from sample solution: refractive index (RI) and molecular interaction between solution components and the insulator layer. Metal nanostructures have been studied for highly efficient optical materials and biochemical sensor applications because of the unique optical characteristics derived from the collective oscillation of free electrons on their surfaces, i.e., the localized surface plasmon (LSP) [1,2,3,4,5,6]. Metal nanostructures have been studied for their applications in highly sensitive, label-free sensors that detect surrounding RI changes caused by adsorption or molecule interaction on metal nanostructure surfaces [10,11]. In the field of RI sensing technology, through improvements in fabrication [15,16,17], numerous studies on the label-free and real-time detection of several targets such as cells [18,19,20], DNA [21,22,23], antigens [24,25,26], and ions [27,28] have been reported
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