研究目的
To develop and engineer stacked nanoporous anodic alumina gradient-index filters with tunable multi-spectral photonic stopbands for sensing applications, and to assess their sensitivity to changes in the effective medium.
研究成果
The study successfully fabricated stacked NAA-GIFs with tunable multi-spectral photonic stopbands, demonstrating precise control over band positions and high sensitivity to refractive index changes. The method overcomes amplitude limitations of previous approaches, enabling high-intensity bands. These structures show promise for advanced optical sensing platforms, with sensitivity increasing with pore diameter. Future work could explore functionalization for specific analytes and further optimization of the fabrication process.
研究不足
The fabrication method may have limitations in scalability or reproducibility for very complex waveforms. The sensitivity assessment is limited to D-glucose solutions and may not generalize to other analytes without surface functionalization. The pore widening treatment affects optical properties non-uniformly, potentially limiting control.
1：Experimental Design and Method Selection:
The study uses an electrochemical anodization process with sinusoidal current density profiles to fabricate NAA-GIFs. The method involves sequential application of sinusoidal anodization periods to create stacked photonic crystals. Optical characterization is performed using spectrophotometry and real-time monitoring with a flow cell.
2：Sample Selection and Data Sources:
High purity aluminum discs are used as substrates. Analytical solutions of D-glucose at various concentrations (
3：025–1 M) are used for sensitivity assessment. List of Experimental Equipment and Materials:
Aluminum discs (Goodfellow Cambridge Ltd), acetone, ethanol, perchloric acid, oxalic acid, hydrochloric acid, copper chloride, D-glucose (Sigma-Aldrich), Perkin Elmer UV-Visible-NIR Lambda 950 spectrophotometer, ESEM FEI Quanta 600, flow cell, halogen light source, spectrometer, Canon EOS 700D digital camera.
4：Experimental Procedures and Operational Workflow:
Aluminum substrates are cleaned, electropolished, and anodized in oxalic acid with specific current density waveforms. Pore widening is done with H3PO
5：Reflection spectra are measured, and real-time infiltration with glucose solutions is performed in a flow cell. Structural characterization is done with ESEM. Data Analysis Methods:
Reflectance spectra are analyzed for spectral shifts. Sensitivity and limit of detection are calculated from linear fits. Modelling uses effective medium approximation and transfer matrix method with MatLab.
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