Electrochemically engineered anodic alumina nanotubes: physico-chemical properties and applications
- Autores: Jakub Tomasz Domagalski
- Directores de la Tesis: Elisabet Xifré Pérez (dir. tes.), Lluís F. Marsal Garví (dir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: Josep Pallarès Marzal (presid.), Francisco J. Meseguer (secret.), Abel Santos Alejandro (voc.)
- Programa de doctorado: Programa de Doctorado en Tecnologías para Nanosistemas, Bioingeniería y Energía por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Justification and needs for the research Biomaterials [1], sensors [2], membranes [3], energy storage and conversion [4]: these are just examples of applications that have a great potential to improve our comfort and guide us towards better future. Nanotechnology is a branch of technology that is rapidly getting on popularity in the recent years. It is believed, that at least some of our struggles will be solved in the future with nanostructured materials or nanoparticles. The topic was also involved amongst the Key Enabling Technologies strategy proposed by the European Committee as a mean to secure strategic position and competitiveness of the European Union in thefuture [5].
Amongst many, the structures made of anodic alumina features properties promising in many fields involving nanotechnology.
The fabrication is an established procedure known for almost a century in the industry, and many decades in research. Currently,aluminum the most frequently anodized metal. With regards to nanotechnology the material offers fabrication simplicity, tailor-engineering versatility and the unprecedented self-ordered regularity as compared to other nanoporous materials. [6,7].
The material can be tuned in a broad range of geometrical features and properties, but also used to fabricate nanoparticles [8].
Specific combination of anodization parameters combined with the post-processing enable to produce highly regular nanotubes made of aluminum oxide [9]. There are already reports of their properties, compatibility studies and application proposals. They were demonstrated as biologically inert, non-biodegradable drug delivery container capable of infiltrating model cancer cells [10-12]. However, nanotubes fabrication through pulse anodization is a relatively new discovery that still needs improvements.
Additionally, there are few functionalization approaches reported for the material.
Aim of this thesis was to contribute to the research on the material: increase the understanding of the process, refine the manufacturing procedure and investigate new functionalization alternatives. The thesis contains detailed introduction to nanoporous anodic alumina in general, and may serve as a guidance when starting the work with the material. Equipment that constitute for fabrication setup and set of measurement techniques are described in detail. Further, formation mechanism and role of every fabrication parameters for creation of nanotubes is explained, providing a step-forward in the manufacturing technique. At last, novel functionalization methods and application of nanotubes are presented.
References:
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Recent Advances and Perspective. Advanced Materials Interfaces. 2020, 7, 1-17, DOI: 10.1002/admi.202001133.
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[5] E. Van de Velde, P. Debergh, C. Rammer, P. Schliessler, B. Gehrke, P. Wassmann, M. de Heide, M. Butter, S. Wydra, O. Som and N. Weidner. 2015. Key Enabling Technologies (KETs) Observatory. Methodology Report. Available online:
https://ec.europa.eu/growth/tools-databases/kets-tools/sites/default/files/documents/data_use_methodology_phase_i_final_report_kets_observatory_en.pdf (accessed on 22 November 2020).
[6] W. Lee and S. J. Park. Porous anodic aluminum oxide: Anodization and templated synthesis of functional nanostructures. Chem. Rev. 2014, 114, 7487-7556, DOI: 10.1021/cr500002z.
[7] C. S. Law, S. Y. Lim, A. D. Abell, N. H. Voelcker, and A. Santos. Nanoporous Anodic Alumina Photonic Crystals for Optical Chemo- and Biosensing: Fundamentals, Advances, and Perspectives. Nanomaterials. 2018, 8, 788, DOI: 10.3390/nano8100788.
[8] E. Xifre-Perez, S. Guaita-Esteruelas, M. Baranowska, J. Pallares, L. Masana, and L. F. Marsal. In Vitro Biocompatibility of Surface-Modified Porous Alumina Particles for HepG2 Tumor Cells: Toward Early Diagnosis and Targeted Treatment. ACS Appl. Mater. Interfaces. 2015, 7, 18600-18608, DOI: 10.1021/acsami.5b05016.
[9] W. Lee, R. Scholz, and U. Gösele. A continuous process for structurally well-defined Al2O 3 nanotubes based on pulse anodization of aluminum. Nano Lett. 2008, 8, 2155-2160, DOI: 10.1021/nl080280x.
[10] Y. Wang, G. Kaur, A. Zysk, V. Liapis, S. Hay, A. Santos, D. Losic, A. Evdokiou. Systematic invitro nanotoxicity study on anodic alumina nanotubes with engineered aspect ratio: Understanding nanotoxicity by a nanomaterial model. Biomaterials. 2015, 46, 117-130, DOI: 10.1016/j.biomaterials.2014.12.008.
[11] Y. Wang, I. Zinonos, A. Zysk, V. Panagopoulos, G. Kaur, A. Santos, D. Losic and A. Evdokiou. In vivo toxicological assessment of electrochemically engineered anodic alumina nanotubes: a study of biodistribution, subcutaneous implantation and intravenous injection. J. Mater. Chem. B. 2017, 5, 2511-2523, DOI: 10.1039/C7TB00222J.
[12] Y. Wang, G. Kaur, Y. Chen, A. Santos, D. Losic, and A. Evdokiou. Bioinert Anodic Alumina Nanotubes for Targeting of Endoplasmic Reticulum Stress and Autophagic Signaling: A Combinatorial Nanotube-Based Drug Delivery System for Enhancing Cancer Therapy. ACS Appl. Mater. Interfaces. 2015, 7, 49, 27140-27151, DOI: 10.1021/acsami.5b07557.
Methodology:
The base material is created and formed during anodization of aluminum. When aluminum substrates are sufficiently prepared,two anodization steps are performed. First produces standard nanoporous anodic alumina layer under potentiostatic process at the self-ordering voltage input. This layer is meant to provide mechanical integrity of the substrate for further processing, template for regular growth during the second step and to provide appropriate conditions for pore separation phenomenon to occur. Second step is pulse anodization interlacing pulses of high and low density pulses and the process is conducted in galvanostatic mode. Aim of this step is to produce vertical periodic modulations of the pores and structure with weaker connection between the pores. Removal of aluminum film followed by additional immersing in CuCl2/HCl mixture further weakens the structure, enabling to yield nanotubes when structure is introduced to water and sonicated.
Obtained nanotubes can be tailor-engineered adjusting process conditions, resulting in different geometrical features and properties. The latter can be additionally affected with different methods such as annealing. The material features surface charge and chemical surface that can be grafted with silanes, encouraging functionalization approaches such as electrostatic self-assembly or silanization.
Characterization techniques utilized during this work were:
- Environmental Scanning Electron Microscopy (ESEM) - Transmission Electron Microscopy (TEM) - Confocal Microscopy - Dynamic Light Scattering (DLS) and ζ-potential - Fourier Transform Infrared Spectroscopy (FT-IR) - Spectrophotometry - X-ray Diffraction (XRD) The most important conclusions:
- Current density during high density pulse was found to affect geometry and properties of the obtained nanotubes: higher current values resulted in longer (LAANT = 2.9 ± 0.5 nm mA-1 cm-2), more narrow nanotubes with thinner walls (dout = -0.32 ± 0.05 and din = -0.11 ± 0.02 nm mA-1 cm-2) and lower surface charge. (ζ = -0.20 ± 0.01 mV mA-1 cm-2).
- Length of AANTs is linearly dependent on the duration of high density pulse (LAANT = 268 ± 3 nm/s). Optimization of the process enabled to yield the shortest nanotubes obtained with the method so far: 424 nm ± 92 nm.
- Sonication parameters were evaluated and optimized. Cold sonication (10-15°C) resulted in superior separation and good stability of the structure. However, longer sonication time (> 1 h) result in slowly progressing degradation. The decay is further accelerated at higher temperatures and can lead to complete collapse of the nanotubular morphology.
- Annealing of the template prior to separation into nanotubes can be used to affect crystalline structure and surface properties of liberated nanotubes. Temperature increase leads to higher crystalline fraction and decrease their sulfur content.
- Surface charge of nanotubes is sufficient to perform electrostatic decoration of nanotubes with nanoparticles of the opposite charge.
- Maghemite nanoparticles – alumina nanotube composite features magnetic properties: its motion can be initiated with magnetic field.
- Nanotubes can be effectively modified on their inner walls, performing silanization prior to separation procedure. Layer of APTES does not impact ability to break the structure into nanotubes after acid etching and sonication.
- Designed maghemite nanoparticles-decorated fluorescein isothiocyanate-functionalized nanotubes were demonstrated to effectively detect presence of cathepsin B in the aqueous suspension demonstrating potential use of the structure as a detection system.
