Gold Sunflower Microelectrode Arrays with Dendritic Nanostructures on the Lateral Surfaces for Antireflection and Surface-Enhanced Raman Scattering

Abstract

A facile method is presented for uniform electrochemical growth of dendritic gold nanostructures selectively at the lateral surfaces of conductor–dielectric disc arrays to obtain gold sunflower microelectrode arrays (SMA). The electrical anisotropicity of Au–SiO2 disc arrays is leveraged to restrain the electrochemical growth to the lateral surfaces, while the enhanced electric field on the lateral surfaces due to the fringe effect facilitates growth of highly dendritic nanostructures in unprecedented growth regimes. Electrochemical growth of gold dendrites is performed on 200 nm thick gold lateral surfaces of Au–SiO2 disc arrays with a disc diameter of 5 μm, a 50 nm SiO2 thickness, and dendrite sizes controlled from 150 to 1400 nm in length. The fabricated SMA exhibit broadband antireflection characteristics for visible radiation, tunable photonic–plasmonic hybrid modes in the near-infrared region, strong electromagnetic (EM) field enhancements, and a high density of EM hotspots useful for surface-enhanced Raman scattering (SERS). The efficacy of developed gold SMA is demonstrated for SERS-based detection of an important Raman label 4-aminothiophenol (4-ATP), which is widely used for binding and detection of different biomarkers. The optimized SERS substrate exhibits an impressive limit of detection of 0.5 nM for 4-ATP with a relative standard deviation of only 6.74% and could be reused multiple times following the surface regeneration process.

Single-Step Fabrication of Longtail Glasswing Butterfly-Inspired Omnidirectional Antireflective Structures

“…Unanticipatedly, the PET substrate turns blue after coating with 180 nm silica colloidal crystals. The blue color is derived from considerable light scattering, which is more effective at short wavelengths, in all directions by the 180 nm silica protuberances [ 31 ].…”

Smart Nanozymes for Cancer Therapy: The Next Frontier in Oncology

“…Similarly, conductive metals like copper, silver, gold, and platinum are ideal for photothermal and photodynamic therapy because these metals support plasmon excita-tion by light irradiation, exhibit tuneable plasmonic response and are also known to be biocompatible. [67] Figure 3 depicts the important characteristics of nanozymes. The composition can be considered a primary characteristic because it governs the basic framework upon which other tumor remediation functionalities are added.…”

Readily tunable surface plasmon resonances in gold nanoring arrays fabricated using lateral electrodeposition

“…In our previous study, we had shown that the growth direction and morphology of dendritic nanostructures on electrically anisotropic disc arrays was greatly impacted by the spatial distributions of electric field and current density. 20 In these studies, an enhanced but asymmetrical growth was observed at the edge of the arrays whereas the central regions of the array experienced highly symmetrical growth of nanostructures. For a disc located in the centre of the array, finite element method (FEM) simulations showed that the electric field lines originated perpendicular to the conducting lateral surfaces, bent upwards towards the counter electrode and curled inwards towards the centre of the disc beyond a certain height as shown in Fig.…”

“…S4. † 20 We posit that the reduction of gold ions on the lateral surfaces and growth of gold rings follows the electric field lines. Such growth dynamics allowed us to obtain nanorings with an inner diameter of 1243 nm for GNR5 which is nearly 1.6 folds smaller than the diameter of the parent Ni-SiO 2 discs (1928 nm).…”

“…For a disc located in the centre of the array, finite element method (FEM) simulations showed that the electric field lines originated perpendicular to the conducting lateral surfaces, bent upwards towards the counter electrode and curled inwards towards the centre of the disc beyond a certain height as shown in Fig. S4 † 20 . We posit that the reduction of gold ions on the lateral surfaces and growth of gold rings follows the electric field lines.…”