Poly(2-dimethylaminoethyl methacrylate) was grafted onto flat silicon substrates via atom transfer radical polymerization to form bottom layers. Two fabrication processes, very-large-scale integration and reactive ion etching, were applied in sequence to generate 400 nm-scale hole arrays of tethered poly(2dimethylaminoethyl methacrylate) layers as sub-wavelength hole array on the Si surfaces, followed by the immobilization of surface functionalized gold nanoparticles by means of physical interaction (electrostatic attraction, entanglement, and hydrogen bonding) to generate a metamaterial absorber.Hole dimensions of the metamaterial absorber shrank reversibly and significantly upon changing the pH from 10.7 and 3.3 due to swelling behavior, leading to a significant change in surface plasmon resonance. We found that the change in the surface plasmon resonance of the metamaterial absorber, related to the dimensions of its holes upon pH treatment, resulted in a color change from purple to orange, observable by the naked eye at a fixed angle of 10 . The maximum shift of the absorptive peak position was greater than 300 nm, and these shifts corresponded to the color changes in the solutions at various values of pH.

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In this study, we fabricated nanopillar arrays of silicon oxide for use as two-dimensional periodic relief gratings (2DPRGs) on Si surfaces. We deposited antibodies onto the pillar surfaces of 2DPRGs modified with protein G to obtain optical detectors that were specific for the targeted antigen; the antigen units that filled the spaces between the nanopillars of the 2DPRG lead to a dramatic change in the pillar scale. The effective refractive index (n eff) of the 2DPRGs was related to the pillar scale of the 2DPRG; after coupling of the antigen, a color change from pure green to orange was observable. V

In this study, nanopillar arrays of silicon oxide are fabricated through a process involving very‐large‐scale integration, for use as two‐dimensional periodic relief gratings (2DPRGs) on silicon surfaces. Oligonucleotides are successively immobilized on the pillar surface, allowing the system to be used as an optical detector specific for the targeted single‐stranded DNAs (ssDNAs). The surfaces of the oligonucleotides‐modified 2DPRGs undergo insignificant structural changes, but upon hybridizing with target ssDNA, the 2DPRGs undergo dramatic changes in terms of their pillar scale. Binding of the oligonucleotides to the 2DPRG occurs in a way that allows them to retain their function and selectively bind the target ssDNA. The performance of the sensor is evaluated by capturing the target ssDNA on the 2DPRGs and measuring the effective refractive index (neff). The binding of the target ssDNA species to the 2DPRGs results in a color change from pure blue to red, observable by the naked eye along an angle of 15–20°. Moreover, effective medium theory is used to calculate the filling factors inside the 2DPRGs and, thereby, examine the values of neff during the structural changes of the 2DPRGs. Accordingly, these new films have potential applications as label‐free optical biosensors.