Improved adsorption and photocatalytic removal of methylene blue by MoO3 thin films: Role of the sputtering power, film thickness, and sputtering working pressure

Sputtering thin films: Materials, applications, challenges and future directions

Sputtering is an effective technique for producing ultrathin films with diverse applications. The review begins by providing an in-depth overview of the background, introducing the early development of sputtering and its principles. Consequently, progress in advancements made in recent decades highlights the renaissance of sputtering as a powerful technology for creating thin films with varied compositions, structures, and properties. For the first time, we have discussed a thorough overview of several sputtered thin film materials based on metal and metal oxide, metal nitride, alloys, carbon, and ceramic-based thin film along with their properties and their applicability in various fields. We further delve into the applications of sputter-coated thin films, specifically emphasizing their relevance in environmental sustainability, energy and electronics, and biomedical fields. We critically examine the recent advancements in developing sputter-coated catalysts for eliminating water pollutants andhydrogen generation. Additionally, the review sheds light on advantages, shortcomings, and future directions for developing sputter-coated thin films utilized in biodegradable metals and alloys with enhanced corrosion resistance and biocompatibility. This review is a comprehensive integration of recent literature, covering diverse sputtering thin film applications. We delve deeply into various material types and emphasize critical analysis of recent advancements, particularly in environmental, energy, and biomedical fields. By offering insights into both advancements and limitations, the review provides a nuanced understanding essential for practical utilization.

Tunable structure of TiO2 deposited by DC magnetron sputtering to adsorb Cr (VI) and Fe (III) from water

TiO2 thin films with mixtures of the anatase, rutile, and brookite phases were deposited on glass substrates via magnetron sputtering. Based on XRD and Raman results, the TiO2-0.47 and TiO2-3.47 films principally contained the brookite phase, while the TiO2-1.27 and TiO2-2.13 films were primarily anatase. The capacities of the TiO2 films to adsorb heavy metals were tested with Cr(VI) and Fe(III) solutions, and the maximum Cr(VI) and Fe(III) adsorption capacities were realized with the TiO2-0.47 film (334.5 mg/g) and TiO2-3.47 film (271.3 mg/g), respectively. SEM‒EDS results revealed the presence of Cr and Fe on the surfaces of the films, thus corroborating the ability of the TiO2 films to adsorb and remove heavy metals. They are strong candidates for use in wastewater treatment plants.

Enhanced pollutant photodegradation over nanoporous titanium-vanadium oxides with improved interfacial interactions

This study addressed the separation problem of colloidal catalytic powder from its solution and pore blockage of traditional metallic oxides by fabricating nanoporous composites of titanium (Ti)-vanadium (V) oxide via magnetron sputtering, electrochemical anodization, and annealing processes. The effect of V-deposited loading on the composite semiconductors was investigated by varying V sputtering power (20-250 W) to correlate their physicochemical properties to the photodegradation performance of methylene blue. The obtained semiconductors revealed circular and elliptical pores (14-23 nm) and formed different metallic and metallic oxide crystalline phases. Within the nanoporous composite layer, V ions substituted Ti⁴⁺, leading to Ti³⁺ formation accompanied by decreased band gap values and higher visible-light absorption. Thus, the band gap of TiO₂ was 3.15 eV, while that of Ti-V oxide with the maximum V content (at 250 W) was 2.47 eV. The interfacial separators between clusters in the mentioned composite created traps disrupting the charge carrier movements between crystallites, thereby decreasing the photoactivity. In contrast, the composite prepared with the minimum V content showed approximately 90% degradation efficiency under solar-simulated irradiation resulting from the homogeneous V dispersion and the lower recombination possibility, owing to its p-n heterojunction constituent. The nanoporous photocatalyst layers with their novel synthesis approach and outstanding performance can be applied in other environmental remediation applications.

Leidenfrost green synthesis method for MoO3 and WO3 nanorods preparation: characterization and methylene blue adsorption ability

Environmental pollution is a critical issue due to its impact on humans and other organisms. An important demand nowadays is the need for a green method to synthesize nanoparticles to remove pollutants. Therefore, this study focuses for the first time on synthesizing the MoO₃ and WO₃ nanorods using the green and self-assembled Leidenfrost method. The XRD, SEM, BET and FTIR analyses were used to characterize the yield powder. The XRD results emphasize the formation of WO₃ and MoO₃ in nanoscale with crystallite sizes 46.28 and 53.05 nm and surface area 2.67 and 24.72 m² g^-1, respectively. A comparative study uses synthetic nanorods as adsorbents to adsorb methylene blue (MB) in aqueous solutions. A batch adsorption experiment was performed to investigate the effects of adsorbent doses, shaking time, solution pH and dye concentration to remove MB dye. The results demonstrate that the optimal removal was achieved at pH 2 and 10 with 99% for WO₃ and MoO₃, respectively. The experimental isothermal data follow Langmuir for both adsorbents with a maximum adsorption capacity of 102.37 and 151.41 mg g^-1 for WO₃ and MoO₃.

Removal of Methylene Blue from a synthetic effluent by ionic flocculation

Methylene Blue (MB) is a dye widely used in the industrial sector and in human and veterinary pharmacology. This dye, if improperly disposed of, can cause a significant environmental impact due to its low biodegradability, as it is a stable and complex substance. Additionally, it may affect human health and generate highly toxic byproducts. Hence, the purpose of this work is to assess the removal efficiency of MB from a synthetic effluent using a ionic flocculation process. Such a process consists of the dissolution of a biodegradable anionic surfactant (obtained from soybean oil used for frying food) in the synthetic effluent and the subsequent addition of calcium to the system. The addition of Ca leads to the formation of insoluble surfactant flocs with a high capacity to adsorb organic pollutants. The FTIR testing showed the presence of OH⁻ and C=O groups in the surfactant flocs, which favor the removal of MB by an adsorption process. The maximum adsorption capacity of MB was 101.38 mg g⁻¹. The process is in fact a chemisorption and has an exothermic nature. Desorption studies showed a desorption efficiency of up to 47.81% using an ethanol 1:2 solution. An MB removal efficiency of up to 93.71% was attained in just 0.5 min for an initial MB concentration of 100 mg L⁻¹, showing that ionic flocculation is a very fast and effective process for the treatment of effluents.

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Ionic flocculation is a simple, inexpensive and highly efficient process.

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Biodegradable and sustainable surfactant.

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Fast and high removal of Methylene Blue (0.5 min–93.71%).

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Process of exothermic nature.

Synthesis and Characterization of Highly Photocatalytic Active Ce and Cu Co-Doped Novel Spray Pyrolysis Developed MoO3 Films for Photocatalytic Degradation of Eosin-Y Dye

The current work deals with the fabrication of novel MoO3 nanostructured films with Ce and Cu co-doping through the spray pyrolysis route on a glass substrate maintained at 460 °C for the first time. The phase of developed films was approved by an X-ray diffraction study, and the crystallite size was determined between 82 and 92 nm. The optical transmission of the developed films was noticed to be reduced with doping and found between 45 and 90% for all films, and the absorption edge shifted to a higher wavelength with doping. The optical energy gap of the fabricated films was found to be reduced from 3.85 to 3.28 eV with doping. The developed films were used to degrade the harmful Eosin-Y dye under UV light. The system with 2% Ce and 1% Cu-doped MoO3 turned out to be the most effective catalyst for photodegradation of the dye in a period of 3H and almost degrade it. Hence, the MoO3 films prepared with 2% Ce and 1% Cu will be highly applicable as photocatalysts for the removal of hazardous dye from wastewater.

Facile Synthesis of g-C3N4/MoO3 Nanohybrid for Efficient Removal of Aqueous Diclofenac Sodium

Graphitic carbon nitride modified by molybdenum trioxide (g-C₃N_4/MoO₃) as a nanohybrid was synthesized by co-precipitation method. Here, g-C₃N₄/MoO₃ nanohybrid was used for the first time as an adsorbent for the pharmaceutical drug, diclofenac, (an aqueous micropollutant) from water to mitigate its possible environmental toxic effects. Compared to pristine components, the nanohybrid exhibited better adsorptive removal of diclofenac. Adsorption was enhanced with increment in MoO₃ content from 1 to 3 wt %; however further increment in MoO₃ content resulted in lower adsorption capacity due to agglomeration of MoO₃ particles over g-C₃N₄. 162 mg g⁻¹ adsorption capacity was achieved for 300 mg L⁻¹ diclofenac in solution with 1 g L⁻¹ adsorbent at pH = 6. Adsorption of diclofenac over g-C₃N₄ /MoO₃ followed pseudo 2nd order kinetics. Temkin, Langmuir, Dubinin Radushkevich and Freundlich isotherm models were applied on the experimental results concluding that diclofenac adsorption over g-C₃N₄/MoO₃ followed the Langmuir isotherm. The adsorption mechanism could be explained by the π–π interaction between aromatic rings of diclofenac and g-C₃N₄/MoO₃ (3%) nanohybrid, which is also evident by the FTIR results. This study presents the facile fabrication of a 2nd generation adsorbent for the treatment of diclofenac contaminated water that may as well help achieve the removal of other micropollutants form water.

Effective medium theory to the description of plasmonic resonances: Role of Au and Ti nanoparticles embedded in MoO3 thin films

The growing interest in functional transition metal oxides for efficient energy consumption or in the bio-sensing process; indicates that is necessary to develop a new theoretical method that describes experiments. This article presents a new theoretical methodology to characterize molybdenum trioxide (MoO₃) thin films doped with resonant gold – nanoparticles (Au – NPs) and non-resonant titanium – nanoparticles (Ti – NPs). The modulation of surface plasmon resonance (SPR) and the implications in the MoO₃ transmittance spectrum is described by applying an effective medium theory. The transmittance modulation was modified by variating three parameters, the radius of the NPs, the concentration of the NPs as well as the variation of the MoO₃ thin films thickness. It was found that the nanoparticles concentration is the most important parameter in the transmittance modulation. Additionally, the orthorhombic and monoclinic structure of MoO₃ was studied, from which it was obtained that the monoclinic structure of the MoO₃ doped with Au – NPs favors the reduction in the transmittance values in the visible region which is associated with the increase of the SPR signal. Similar analyses are performed for non-resonant nanoparticles such as Ti, where it was found that optical modulation is not as marked as the case of gold nanoparticles.