Photoinduced Hydrophilicity of Surfaces of Thin Films

Rudakova, Aida V.; Emeline, Alexei V.

doi:10.1134/s1061933x21010105

Cited by 16 publications

(18 citation statements)

References 120 publications

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“…10, left side), photogenerated electrons and holes can react with lattice metal centers and bridging O surface species, respectively. As reported for TiO 2 and ZnO, 23,24,106,108 this behaviour results in the formation of reduced metal defective sites and O vacancies, which play an important role in the subsequent events. In fact, water exposure induces the formation of hydroxyl groups chemically bonded to the material surface, rendering it hydrophilic, with important practical outcomes.…”

Section: Anti-fogging and Self-cleaning Platforms: Smart Light-respon...mentioning

confidence: 57%

“…Various studies have examined the process theoretical background, 23,106,108,110,113 and it has been demonstrated that wetting properties are directly connected with the system nano-texture, 25,26,113,114 whose tailoring is a powerful tool to control and modulate such features by design. As for De-NO x photocatalysts, the most investigated material is TiO 2 , 24,106,112,113 but an attractive alternative is offered by nanostructures of ZnO, either as such or combined with suitable semiconductors/metals. 26,77,108,109 An interesting example is provided by the work of Wei et al on ZnO NR arrays coated with gold NPs under different conditions.…”

Section: Anti-fogging and Self-cleaning Platforms: Smart Light-respon...mentioning

confidence: 99%

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Nanoarchitectonics of metal oxide materials for sustainable technologies and environmental applications

Barreca

Maccato

2023

CrystEngComm

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Section: Anti-fogging and Self-cleaning Platforms: Smart Light-respon...mentioning

confidence: 57%

Section: Anti-fogging and Self-cleaning Platforms: Smart Light-respon...mentioning

confidence: 99%

Nanoarchitectonics of metal oxide materials for sustainable technologies and environmental applications

Barreca

Maccato

2023

CrystEngComm

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“…Type II heterostructures are also of greatest interest in the mechanistic study of photoinduced changes in the surface hydrophilicity of "layer-by-layer" films composed of photoactive materials, since effective charge separation leads to the purposeful alteration in the ratio between electron and hole concentrations compared to that of an individual semiconductor. According to the previously proposed mechanism [9,10] of photostimulated alteration of the surface hydrophilicity, this ratio between electron and hole concentrations at the surface is responsible for the direction and efficiency of the effect.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Type of Heterostructures on Photostimulated Alteration of the Surface Hydrophilicity: TiO2/BiVO4 vs. ZnO/BiVO4 Planar Heterostructured Coatings

et al. 2021

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Here, we report the results of comparative studies of the photostimulated hydrophilic behavior of heterostructured TiO2/BiVO4 and ZnO/BiVO4, and monocomponent TiO2 and ZnO nanocoating surfaces. The chemical composition and morphology of the synthesized nanocoatings were characterized by XPS, SEM, and AFM methods. The electronic energy structure of the heterostructure components (band gap, top of the valence band, bottom of the conduction band, and Fermi level position) was determined on the basis of experimental results obtained by XPS, UV-V absorption spectroscopy and Kelvin probe methods. According to their electronic energy structure, the ZnO/BiVO4 and TiO2/BiVO4 heterostructures correspond to type I and type II heterostructures, respectively. The difference in the type of heterostructures causes the difference in the charge transfer behavior at heterojunctions: the type II TiO2/BiVO4 heterostructure favors and the type I ZnO/BiVO4 heterostructure prevents the photogenerated hole transfer from BiVO4 to the outer layer of the corresponding metal oxide. The results of the comparative studies show that the interaction of the photogenerated holes with surface hydroxy-hydrated multilayers is responsible for the superhydrophilic surface conversion accompanying the increase of the surface free energy and work function. The formation of the type II heterostructure leads to the spectral sensitization of the photostimulated surface superhydrophilic conversion.

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“…[3]. A wettability switch can be triggered by various external stimuli, including electricity (based on electrowetting or the doping of conducting polymers) [4], temperature (based on thermoresponsive polymers) [5,6], light (based on photosensitive metal-oxide semiconductors and photo-responsive organic compounds) [7], pH (based on protonation and deprotonation of pH-responsive surfaces) [8,9], mechanical strain (based on extending and unloading elastic films) [10,11], etc. Materials on which switching wettability has been demonstrated include polymers [2], metal oxides [12], silica [13], and magnetic nanoparticles [14], among others.…”

Section: Introductionmentioning

confidence: 99%

Hierarchical ‘rose-petal’ ZnO/Si surfaces with reversible wettability reaching complete water repellence without chemical modification

et al. 2023

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Smart surfaces with externally controlled wettability patterns are ubiquitous building blocks for micro-/nanofluidic and lab-on-chip devices, among others. We develop hierarchical surfaces of ZnO nanorods grown on laser-microstructured silicon with reversible photo-induced and heat-induced wettability. The as-prepared surfaces are superhydrophilic, with very low water contact angles (~ 10°), and transition to a wetting state with high water contact angles (~ 150°) when annealed in vacuum. As the annealing temperature increases to 400 °C, the surfaces become completely water-repellent. Even though the annealed surfaces present high water contact angles, at the same time, they are very adhesive for water droplets, which do not roll off even when tilted at 90° or 180o (rose-petal effect), unlike standard hydrophobic surfaces which typically combine high water contact angles with low roll-off angles. The surfaces return to the superhydrophilic state when irradiated with UV light, which indicates a reversible wettability with external stimuli. Based on this transition, we demonstrate local modification of the wetting state of the surfaces by UV irradiation through a mask, which results in directed liquid motion, useful for microfluidic applications. The high contact angles obtained in this work are usually obtained only after chemical modification of the ZnO surface with organic coatings, which was not necessary for the hierarchical surfaces developed here, reducing the cost and processing steps of the fabrication route. These rose-petal surfaces can be used as “mechanical hands” in several applications, such as no-loss transport of small liquid volumes, precision coatings, spectroscopy, and others. Furthermore, the completely water-repellent surfaces, rarely reported elsewhere, may find important applications in frictionless liquid transport for microfluidic and other devices.

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Photoinduced Hydrophilicity of Surfaces of Thin Films

Cited by 16 publications

References 120 publications

Nanoarchitectonics of metal oxide materials for sustainable technologies and environmental applications

Nanoarchitectonics of metal oxide materials for sustainable technologies and environmental applications

Effect of the Type of Heterostructures on Photostimulated Alteration of the Surface Hydrophilicity: TiO2/BiVO4 vs. ZnO/BiVO4 Planar Heterostructured Coatings

Hierarchical ‘rose-petal’ ZnO/Si surfaces with reversible wettability reaching complete water repellence without chemical modification

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