We can precisely control the diameter of nanoparticles and the gap distance by changing the plasma etching time. In this study, we arranged the interparticle distance at 80 nm for the reason that it is essential to keep substantial spacing

to attach the BSA protein molecule selleck compound on the surface of nanoshells. Figure 2 SEM images of the (a) PS nanoparticle monolayer and (b) 240-nm Au CX-5461 cell line nanoshell arrays. The scale bars in (a) and (b) are 2 μm. Figure 3a illustrates the normalized extinction spectra of Au, Ag, and Cu nanoshell arrays of similar size and geometry with 200 nm of core diameter and 20 nm of shell thickness. Each LSPR peak has a well-defined shape, and in the case of Au and Cu, it shows a broad shoulder around 600 nm originating from the interband transitions of bulk materials. Therefore, the interband transitions do not significantly affect the LSPR properties of Au and Cu nanoshell arrays. The LSPR λ max of Au, Ag, and Cu were measured to be 830, 744, and 914 nm, respectively, and the full width at half maximum of the LSPR were ca. 300, 280, and 390 nm, respectively. These peaks were not so sharp compared to expected results in nanoshells. This is because the fabricated samples consist of nanoshell particles and a glass substrate with GSK872 price a metal thin film exhibiting high extinction in the NIR region as shown in Figure 3b.

We anticipate that without the metal film on the glass substrate, a sharper optical peak in the NIR region can be achieved with selectively laminated metal nanoshells fabricated by plating techniques. The LSPR λ max of Au and Cu are at longer wavelengths than that of Ag nanoshell arrays of similar structural parameters. In other research, the trend was revealed from the discrete dipole approximation method where the LSPR λ max of Au > Cu > Ag for nanostructures of the same geometry [17]. Also, it was described that the LSPR peak of Cu nanostructures significantly red-shifted and broadened as the thickness of the oxide layer increased. In fact, our Cu nanoshell arrays included an oxide layer, and LSPR peaks might shift from their primary position. The discrepancy of the Cu LSPR λ max between experiment and theory can be attributed to

the difficulty in quantitative and ultratrace measurement. From the comparison of the LSPR of Au, Ag, and Cu nanoshell arrays with the objective of application to biosensing devices using NIR Selleck Neratinib light, we conclude that Au nanoshell arrays display suitable properties that are comparable to those of Ag and Cu. Figure 3 Normalized LSPR spectra of (a) nanoshell arrays and (b) metal films on glass substrates. Shell thickness was controlled to 20 nm. All spectra were collected in the air. We have fundamentally investigated Au nanoshells on glass substrates as potential label-free optical transduction elements in a nanoscale biosensor. In this experiment, the initial extinction properties of nanoshells are measured after UV-O3 surface cleaning for 20 min.