title: Titanium oxide thin films obtained with physical and chemical vapour deposition methods for optical biosensing purposes.
abstract: This work discusses an application of titanium oxide (TiOx) thin films deposited using physical (reactive magnetron sputtering, RMS) and chemical (atomic layer deposition, ALD) vapour deposition methods as a functional coating for label-free optical biosensors. The films were applied as a coating for two types of sensors based on the localised surface plasmon resonance (LSPR) of gold nanoparticles deposited on a glass plate and on a long-period grating (LPG) induced in an optical fibre. Optical and structural properties of the TiOxthin films were investigated and discussed. It has been found that deposition method has a significant influence on optical properties and composition of the films, but negligible impact on TiOxsurface silanization effectiveness. A higher content of oxygen with lower Ti content in the ALD films leads to the formation of layers with higher refractive index and slightly higher extinction coefficient than for the RMS TiOx. Moreover, application of the TiOxfilm independently on deposition method enables not only for tuning of the spectral response of the investigated biosensors, but also in case of LSPR for enhancing the ability for biofunctionalization, i.e., TiOxfilm mechanically protects the nanoparticles and induces change in the biofunctionalization procedure to the one typical for oxides. TiOxcoated LSPR and LPG sensors with refractive index sensitivity of close to 30 and 3400nm/RIU, respectively, were investigated. The ability for molecular recognition was evaluated with the well-known complex formation between avidin and biotin as a model system. The shift in resonance wavelength reached 3 and 13.2nm in case of LSPR and LPG sensors, respectively. Any modification in TiOxproperties resulting from the biofunctionalization process can be also clearly detected.
authors.affiliation: Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa, 75, Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Dominik
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Leśniewski
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Janczuk
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Niedziółka-Jönsson
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Hołdyński
authors.affiliation: Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.
authors.forename: Ł
authors.initials: Ł
authors.lastname: Wachnicki
authors.affiliation: Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Godlewski
authors.affiliation: Centre de recherche en photonique, Université du Québec en Outaouais, 101 rue Saint-Jean-Bosco, Gatineau, QC, Canada J8X 3X7.
authors.forename: W J
authors.initials: WJ
authors.lastname: Bock
authors.affiliation: Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa, 75, Warsaw, Poland. Electronic address: M.Smietana@elka.pw.edu.pl.
authors.forename: M
authors.initials: M
authors.lastname: Śmietana
mesh_terms: D015374:Biosensing Techniques; D005898:Glass; D006046:Gold / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry; D020349:Surface Plasmon Resonance; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D010087:Oxides; C009495:titanium dioxide; D006046:Gold; D014025:Titanium
keywords: Atomic layer deposition; Biofunctionalization; Label-free sensing; Localised surface plasmon resonance; Long-period grating; Optical properties; Reactive magnetron sputtering; Titanium oxide