Resumen de Engineering of photonic structures based on nanoporous anodic alumina as an optical sensing platform
Nanoporous Anodic Alumina Photonic Structures (NAA-PS) demonstrate considerable ability as advanced and useful optical sensing platforms due to their exceptional physical, chemical, and optical properties.
The geometric properties of nanopores in NAA-PSs can be precisely engineered by different anodization approaches to selectively filter molecules by size-exclusion and increase the available binding functional sites due to the high specific surface area to volume ratio of these nanoporous PSs. Furthermore, the surface chemistry of NAA-PSs can be adjusted with different functional molecules. NAA-PSs are active optical platforms that confine, guide, reflect, emit, and transmit incident light, generating stable optical signals for optical sensing based on different spectral shifts upon exposure to analyte molecules such as reflectivity, photoluminescence, transmittance, waveguiding, absorbance, or color changes. Different forms of NAA-PSs can be integrated with various optical techniques such as reflectometric interference spectroscopy (RIfS), reflection and transmission spectroscopy, and photoluminescence spectroscopy (PL).
Recent advances in anodization technology has focused on structural engineering of NAA-PSs by distinct forms of pulse-like anodization approaches. In contrast to pioneering pulse-like anodization combining hybrid pulses between mild and hard anodization regimes, pulse anodization performed under mild conditions moderate electrolyte temperature and anodizing voltage/current density– provide superior controllability over the anodic oxide growth rate and its porosity. Despite these advances, nowadays a limited number of pulse shapes have been implemented into anodization approaches to engineering distinct forms of NAA-PSs including sinusoidal, symmetric and asymmetric stepwise, and sawtooth. Although these strategies have successfully realized the engineering of NAA–PSs with outstanding optical properties, further developments of anodization technology will be needed to tailor-engineer the structure of NAA–PSs with versatility for harnessing specific forms of light–matter interactions and spreading the applicability of these unique photonic structures across light-based technologies.
Motivated by the previous works and the potential of these photonic structures of several applications like sensing, optical encoding, photonics, and photovoltaics. For this reason, this thesis is focused on the fabrication, characterization of Photonic Structures based in nanoporous anodic alumina using different anodization approaches. The obtained Photonic structures were tested as an optical sensing platform.
The main objectives of this doctoral tesis are:
1. To improve and develop different nanoporous anodic alumina photonic structures.
2. To fabricate nanoporous anodic alumina photonic structures with sinusoidal anodization profile.
3. To fabricate new and advanced nanoporous anodic alumina photonic structures using several anodization approaches.
4. To apply these nanoporous photonic structures as an optical sensor.
The methodology used during the elaboration of this doctoral thesis was thefabrication of optical structures of variable refractive index (photonic structures) of porous alumina with different anodization profiles (sinusoidal and Gaussian) in simple, stacked configuration. Furthemore the fabrication of optical microcavities and theri application as an optical sensor.
These photonic structures was applied as an optical sensor by modifying the surface of the structures through different functionalizations (silanization) for the detection of different biomolecules or chemical substances: mainly D-glucose, alcoholes and NaCl ions by means of RIfS (reflective interferometric spectroscopy). The results obtained was analyzed and the limit of detection (LOD), linearity, sensor sensitivity, was calculated. Geometric properties such as the effect of pore size will also be analyzed. Different methods are used for characterization such as UV-VIS-NIR spectroscopy, FTIR, Fluorimetry, SEM, ESEM, fiber optic spectroscopy, flow cells.
For the developmento of the thesis i follow differente tasksin order to achieve the main objectives of the thesis.
Task 1. Design and manufacture of photonic structures in nanoporous alumina• Design and manufacture of photonic structures in nanoporous alumina• Characterization and measurement of structures• Functionalization of the structures (modification of the surface)• Application of the structures as an optical sensor• Detection of biomolecules Task 2. Design and manufacture of photonic structures in stacked and superimposed configuration• Design and manufacture of photonic structures in stacked and superimposed configuration • Characterization and measurement of structures • Functionalization of the structures (modification of the surface) • Application of the samples as an optical sensor • Detection of biomolecules Task 3. Design and manufacture of photonic structures with different anodizing profile (gaussian profile) • Manufacture of photonic structures samples with different anodization profile (gaussian profile) • Characterization and measurement of samples • Functionalization of the structures (modification of the surface) • Application of the samples as an optical sensor Task 4. Design and Manufacture of advanced photonic structures (optical microcavities) as sensing platforms.
• Manufacture and design of structures • Characterization of the different structures • Characterization and measurement of samples • Application as a sensing platform • Detection of biomolecules In this thesis we fabricated succesfully different photonic structures with tunable photonic stop bands across of the different spectral regions such as UV-UV-Vis-NIR. The effect of the anodization parameters was evaluated as well as their opticcal properties . different anodization approaches was implemented. All of these structures was assessed as an optical sensor using different concentrations of D-glucose, alcoholes, NaCl. Nanoporous anodic alumina is a very suitable material for the formation of these photonic structures due to its optical properties that allow use it as a sensing platform. Furthemore, we demonstrated the structural tuning of intrinsic photoluminescence emissions from nanoporous anodic alumina photonic crystals.
In summary, all the data and work presented in this thesis demonstrated the ability of the Photonic structures based on Nanoporous Anodic Alumina as a potential platform for develop optical sensors.
