Design of Photocatalytic Functional Coatings Based on the Immobilization of Metal Oxide Particles by the Combination of Electrospinning and Layer-by-Layer Deposition Techniques

Abstract

This work reports the design and characterization of functional photocatalytic coatings based on the combination of two different deposition techniques. In a first step, a poly(acrylic acid) + β-Cyclodextrin (denoted as PAA+ β-CD) electrospun fiber mat was deposited by using the electrospinning technique followed by a thermal treatment in order to provide an enhancement in the resultant adhesion and mechanical resistance. In a second step, a layer-by-layer (LbL) assembly process was performed in order to immobilize the metal oxide particles onto the previously electrospun fiber mat. In this context, titanium dioxide (TiO2) was used as the main photocatalytic element, acting as the cationic element in the multilayer LbL structure. In addition, two different metal oxides, such as tungsten oxide (WO3) and iron oxide (Fe2O3), were added into PAA anionic polyelectrolyte solution with the objective of optimizing the photocatalytic efficiency of the coating. All of the coatings were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images, showing an increase in the original fiber diameter and a decrease in roughness of the mats because of the LbL second step. The variation in the wettability properties from a superhydrophilic surface to a less wettable surface as a function of the incorporation of the metal oxides was also observed by means of water contact angle (WCA) measurements. With the aim of analyzing the photocatalytic efficiency of the samples, degradation of methyl blue (MB) azo-dye was studied, showing an almost complete discoloration of the dye in the irradiated area. This study reports a novel combination method of two deposition techniques in order to obtain a functional, homogeneous and efficient photocatalytic coating.

A Comparative Study in the Design of TiO2 Assisted Photocatalytic Coatings Monitored by Controlling Hydrophilic Behavior and Rhodamine B Degradation

“…Another methodology to characterize the photocatalytic response of coatings is studying the photodegradation of a dye by employing the previously described optical fiber setup [ 70 , 73 ]. Typical peaks of this colorant are shown in Figure 8 , with a lower peak centered at 525 nm and the main peak centered at 570 nm.…”

“…The other methodology to measure the photocatalytic efficiency of samples is employing an optical fiber setup, which has been described in previous works [ 70 ]. In order to conduct this assay, samples were immersed in a Rhodamine B dye solution, inking the samples with a pink-purple color, and dried for 24 h at room temperature.…”

An Alternative Methodology for the Evaluation of Photocatalytic Activity of Polymeric Coatings by Monitoring Dye Degradation

“…For the photocatalytic efficiency determination, the optical transmission setup used in previous works has been employed [2,40]. More specifically, both UV (maximum spectra at λ = 365 nm) and visible light sources have been connected to a bifurcated optical fibre, which is in charge of guiding both light irradiation to the holder where the functional coatings with the immobilized dyes (samples) are perfectly placed.…”

“…In this work, the water contact angle measurements have increased from 1.6 • ± 0.5 • in the case of REF, 25.3 ± 2.3 for S0 up to a value of 66.9 ± 1.2 in the case of S01 (see Figure 5a). In terms of fibre diameter, after performing the layer-by-layer assembly, the alternate deposition of oppositely charged polyelectrolytes has produced an increase in the resultant diameter (see Figure 5b), this effect being more notorious in the sample composed of the photocatalytic metal oxides than in the functional matrix [40]. The corresponding fibre diameter has been from 2.2 ± 0.3 µm (REF), 3.1 ± 0.4 µm (S0) up to 5.1 ± 0.6 µm (S01).…”

Novel Design of Superhydrophobic and Anticorrosive PTFE and PAA + β − CD Composite Coating Deposited by Electrospinning, Spin Coating and Electrospraying Techniques

“…In order to maximize the hydrophobic properties and improve the coating adhesion, a three-step process combining electrospinning, electrospraying, and spin-coating techniques has been used. In the first one, a PAA + β-CD electrosprayed fiber membrane is deposited onto the substrates to take advantage of its adhesive properties [ 39 , 40 , 41 ]. In the second one, a PTFE spin-coated layer is deposited, thus obtaining a uniform particle distribution embedded in the porous PAA + β-CD network that leads to WCA values similar to those reported in literature for PTFE fibers [ 42 , 43 , 44 , 45 ].…”