Novel functional 2D-materials based on nanoporous alumina lattices

• Applicant: Dr. Mikhail Pashchanka
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 348124222

• Final Report Year: 2021

Final Report Abstract

During the implementation of the project, a number of new scientific results that demonstrate important relationships between the aluminium anodizing conditions, morphologies of the nanostructured anodic materials and impacts on their valuable functional properties have been achieved. Many of these accomplishments can qualify as novel preliminary works for proposals for future research. To summarize, the main achievements from the project can be listed as follows: For the first time, the effect of the coherent domain size (i.e. the average size of a hexagonally ordered array of nanopores which act as “hotspots”) in Ag-sputtered PAA-based substrates on the SERS enhancement was reported. Upon the increase of the coherent domain size, a substantial SERS signal enhancement for Rhodamine B which was used as model analyte in our investigation has been observed. Prior to this research, barrier-type anodic alumina (BAA) was never considered for SERS applications because of the absence of porosity and the anticipation of low SERS sensitivity. During the work on the project, it was found that nonporous BAA obtained through electrolysis using the novel HIO3 and HIO4 electrolytes followed by Ag-coating exhibits higher SERS enhancement than that of Ag-coated PAA (the measured enhancement factors were increased by a factor of 2.6). One-step spontaneous formation of hierarchical honeycomb-like textures on anodized aluminium with unprecedented scalability of pores (from 50-60 nm to 0.45-0.90 mm, i.e. approximately by a factor of 104) has been reported for the first time. Such self-organized hierarchical textures on Al monoliths are very promising for fabrication of the next generation supports for heterogeneous catalysis. A new low-temperature in situ method for controllable reduction of anionic contamination in PAA laminas has been pioneered. The unwanted admixture content can be reduced by 40- 50% irrespective of its chemical nature. The new method is especially helpful if the contaminants are extremely thermally stable and cannot be reduced by the traditional annealing procedure. The PAA laminas purified by the new invented method also retain planarity (flatness), optical transparency and degradability in acidic or alkaline media. A conceptually new way of thinking about the light-absorbing mechanism in pigment-free black PAA layers obtained via “aluminium burning” anodizing regime has been provided. The novel structurally colored black coatings can find application in construction of optical devices and in the aerospace technology. The spectroscopic properties of new PAA-based metamaterials impregnated with dye molecules which exhibit unique response to electromagnetic waves have been studied.

Publications

• “Strong coupling in the novel dye / alumina membrane metamaterial”, in Proceedings of Conference on Lasers and Electro-Optics, 2017
  C. On, K. E. Tanyi, M. Pashchanka, V. Peters, J. R. Skuza, M. Noginov
  
• “Spectroscopic studies of dye-doped porous alumina membranes”, Journal of the Optical Society of America B, 2018, 8 (35), 1785-1790
  C. On, E. K. Tanyi, M. Pashchanka, J. R. Skuza, V. N. Peters, and M. A. Noginov
  
• “Controllable Reduction of Anionic Contamination in Degradable Amorphous Anodic Alumina Nanoporous Membranes”, ACS Applied Nano Materials, 2020, 3, 10531 – 10542
  M. Pashchanka
  
• “Long-Range Hexagonal Pore Ordering as the Key to Controlling SERS Efficiency in Substrates Based on Porous Alumina” , The Journal of Physical Chemistry C, 2020, 124 (47), 25931 – 25943
  M. Pashchanka, S. Okeil and J. J. Schneider
  
• “Multilevel self-organization on anodized aluminium: discovering hierarchical honeycomb structures from nanometre to sub-millimetre scale”, Physical Chemistry Chemical Physics, 2020, 22, 15867 – 15875
  M. Pashchanka
  
• „Synergistic Physical and Chemical Enhancement Effects Observed on SERS Substrates of Silver Coated Barrier-Type Anodic Alumina“, Journal of Physical Chemistry C, 2020, 124 (24), 13316–13328
  S. Okeil, M. Pashchanka and J. J. Schneider
  
• A Strategy towards Light-Absorbing Coatings Based on Optically Black Nanoporous Alumina with Tailored Disorder”, Materials, 2021, 14 (19), 5827
  M. Pashchanka, G. Cherkashinin
  
• “Conceptual Progress for Explaining and Predicting Self-Organization on Anodized Aluminum Surfaces”, Nanomaterials, 2021, 11 (9), 2271
  M. Pashchanka