TY - JOUR
T1 - In-situ ellipsometric study of the optical properties of LTL-doped thin film sensors for copper(II) ion detection
AU - Cody, Dervil
AU - Babeva, Tsvetanka
AU - Madjarova, Violeta
AU - Kharchenko, Anastasia
AU - Sabad-E-gul,
AU - Mintova, Svetlana
AU - Barrett, Christopher J.
AU - Naydenova, Izabela
N1 - Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. T.
PY - 2020/4
Y1 - 2020/4
N2 - Optical sensors fabricated in zeolite nanoparticle composite films rely on changes in their optical properties (refractive index, n, and thickness, d) to produce a measurable response in the presence of a target analyte. Here, ellipsometry is used to characterize the changes in optical properties of Linde Type L (LTL) zeolite thin films in the presence of Cu2+ ions in solution, with a view to improving the design of optical sensors that involve the change of n and/or d due to the adsorption of Cu2+ ions. The suitability of two different ellipsometry techniques (single wavelength and spectroscopic) for the evaluation of changes in n and d of both undoped and zeolite-doped films during exposure to water and Cu2+-containing solutions was investigated. The influence of pre-immersion thermal treatment conditions on sensor response was also studied. Due to the high temporal resolution, single wavelength ellipsometry facilitated the identification of a Cu2+ concentration response immediately after Cu2+ introduction, indicating that the single wavelength technique is suitable for dynamic studies of sensor–analyte interactions over short time scales. In comparison, spectroscopic ellipsometry produced a robust analysis of absolute changes in film n and d, as well as yielding insight into the net influence of competing and simultaneous changes in n and d inside the zeolite-doped films arising due to water adsorption and the ion exchange of potassium (K+) cations by copper (Cu2+).
AB - Optical sensors fabricated in zeolite nanoparticle composite films rely on changes in their optical properties (refractive index, n, and thickness, d) to produce a measurable response in the presence of a target analyte. Here, ellipsometry is used to characterize the changes in optical properties of Linde Type L (LTL) zeolite thin films in the presence of Cu2+ ions in solution, with a view to improving the design of optical sensors that involve the change of n and/or d due to the adsorption of Cu2+ ions. The suitability of two different ellipsometry techniques (single wavelength and spectroscopic) for the evaluation of changes in n and d of both undoped and zeolite-doped films during exposure to water and Cu2+-containing solutions was investigated. The influence of pre-immersion thermal treatment conditions on sensor response was also studied. Due to the high temporal resolution, single wavelength ellipsometry facilitated the identification of a Cu2+ concentration response immediately after Cu2+ introduction, indicating that the single wavelength technique is suitable for dynamic studies of sensor–analyte interactions over short time scales. In comparison, spectroscopic ellipsometry produced a robust analysis of absolute changes in film n and d, as well as yielding insight into the net influence of competing and simultaneous changes in n and d inside the zeolite-doped films arising due to water adsorption and the ion exchange of potassium (K+) cations by copper (Cu2+).
KW - Ellipsometry
KW - Optical materials
KW - Optical sensors
KW - Single wavelength ellipsometry
KW - Spectroscopic ellipsometry
KW - Zeolites
UR - http://www.scopus.com/inward/record.url?scp=85091262156&partnerID=8YFLogxK
U2 - 10.3390/coatings10040423
DO - 10.3390/coatings10040423
M3 - Article
AN - SCOPUS:85091262156
SN - 2079-6412
VL - 10
SP - 1
EP - 12
JO - Coatings
JF - Coatings
IS - 4
M1 - 423
ER -