Preparation and Optimization of Fluorescent Thin Films of Rosamine-SiO2/TiO2 Composites for NO2 Sensing

Abstract

The incorporation of a prototypical rosamine fluorescent dye from organic solutions into transparent and microstructured columnar TiO2 and SiO2 (MO2) thin films, prepared by evaporation at glancing angles (GAPVD), was evaluated. The aggregation of the adsorbed molecules, the infiltration efficiency and the adsorption kinetics were studied by means of UV-Vis absorption and fluorescence spectroscopies. Specifically, the infiltration equilibrium as well as the kinetic of adsorption of the emitting dye has been described by a Langmuir type adsorption isotherm and a pseudosecond order kinetic model, respectively. The anchoring mechanism of the rosamine to the MO2 matrix has been revealed by specular reflectance Fourier transform infrared spectroscopy and infiltration from aqueous solutions at different pH values. Finally, the sensing performance towards NO2 gas of optimized films has been assessed by following the changes of its fluorescence intensity revealing that the so-selected device exhibited improved sensing response compared to similar hybrid films reported in the literature.

Fluorescent Rosamine/TiO2 Composite Films for the Optical Detection of NO2

“…When anchored to the TiO 2 , RosCOOH spectrum showed mainly its monomeric form, with a slight redshift (1 nm) with respect to its solution spectrum due to a minimal contribution of J-aggregates. The presence of H-aggregates already identified in the absorption spectrum would not induce shifts in fluorescence [28,33,34], hence the absence of further shifting in the fluorescence spectrum of this rosamine. On the other hand, RosNH 2 /TiO 2 film spectrum featured a redshift (7 nm) with respect to its solution spectrum, which was attributed to the presence of J-aggregates as they are characterized by a shifting towards higher wavelengths of 3 Journal of Sensors the bands in the fluorescence spectrum [28,33,34].…”

“…The different types of aggregation between rosamines once anchored to the TiO 2 molecules in the film and their implications on their respective spectra can be explained in terms of the type of interaction between rosamine and TiO 2 , taking into account that the transition dipole moments for both rosamines are located along the xanthene ring. The binding of RosCOOH to TiO 2 has been extensively discussed elsewhere [28]. Briefly, the molecular structure of RosCOOH allows its anchoring to TiO 2 by covalent bonding (through the carboxylic group) and by electrostatic interaction (through the ammonium group).…”

“…Here, we use transparent nanocrystalline TiO 2 films prepared by screen printing as substrates for the incorporation of two rosamine derivatives featuring a carboxylic acid and an amino group, respectively. The anchoring of carboxylic rosamines to inorganic substrates prepared by physical vapor deposition has been previously studied with promising gas sensing results [28]. Our main objectives are to compare the film formation capabilities of both rosamines regarding their different molecular structures and to analyze the gas sensing properties of the rosamine/TiO 2 composites towards NO 2 gas.…”

Effect of the Functionalization of Porous Silicon/WO3 Nanorods with Pd Nanoparticles and Their Enhanced NO2-Sensing Performance at Room Temperature

“…There is an urgent demand for developing high-quality gas-sensitive materials accordingly. Among the various gas-sensitive materials, resistive-type nanostructured metal oxide semiconductors (MOS), such as TiO 2 , In 2 O 3 , SnO 2 , ZnO, CuO, and WO 3 [ 4 , 5 , 6 , 7 , 8 , 9 ] have been most attractive in terms ofNO 2 detection because of their high sensitivity, simplicity, and low cost [ 10 ]. WO 3 , as a typical n-type semiconductor with stable physicochemical properties, is promising for the detection of NO 2 in recent years due to its excellent sensitivity and selectivity to NO 2 compared with other gases.…”

Fabrication of Nanosized Island-Like CdO Crystallites-Decorated TiO2 Rod Nanocomposites via a Combinational Methodology and Their Low-Concentration NO2 Gas-Sensing Behavior

“…Gas sensors based on oxide semiconductors, such as TiO 2 , have the potential to detect harmful and toxic gases with high sensitivity [ 1 , 2 , 3 , 4 ]. TiO 2 nanostructures have a large surface-to-volume ratio because of their one-dimensional structure, which is advantageous in providing high surface effects between the oxide surface and the detected gases.…”