Dye Degradation Test Research Articles

Silver doped barium titanate nanoparticles for enhanced visible light photocatalytic degradation of dyes

Due to the rapid growth of global population, new, fast and reliable methods must be developed to purify contaminated water. Various photocatalysts have been developed to remove organic dyes from water. Herein, Ag doped BaTiO3 has been synthesized using a facile solvothermal method and its excellent photocatalytic activities were demonstrated in degradation of both anionic and cationic dyes under visible light illumination. Ag doped BaTiO3 nanoparticles showed greater efficacy in the degradation of methylene blue (MB) and eosin yellow (EY) than undoped BaTiO3 nanoparticles, which makes them a better candidate for photocatalysis. 1.0 AgBT sample showed the highest photocatalytic activity for MB (99.1 % in 100 min) and EY (99.3 % in 60 min) dye degradation compared with those of other samples. Further, the trapping experiments revealed that hydroxyl radicals and holes are the active species in the photocatalytic process of MB and EY dye degradation and recycle test showed excellent stability of the synthesized material.

Effect of adding silver on photocatalytic properties of ZnAl2O4 nanopowder synthesized using microemulsion and polyacrylamide gel methods for recycled water

In recent decades, water purification and removal of organic pollutants such as organic dyes have been among the most important issues. Photocatalyst is one of the most effective methods for recycled water to eliminate organic pollutants and break them down into safe compounds. One of the most significant factors for determining the efficiency of photocatalyst nanoparticles is the utilization of new synthesis methods. Microemulsion and polyacrylamide gel methods are the two methods that were used for the synthesis of zinc aluminate nanoparticles for this study. The powders obtained from these two synthesis methods were characterized using the X-ray diffraction (XRD) technique, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and ultraviolet–visible spectroscopy (UV–Vis) which were utilized as photocatalysts in the photocatalytic degradation reaction of methylene blue (MB). The results demonstrated that the nanoparticles synthesized in both methods were of single-phase zinc aluminate with a spinel structure. The crystallite size obtained for zinc aluminate synthesized using the microemulsion method was 21.7 nm, whereas, in the polyacrylamide gel method, it was 26.3 nm. Microscopic images represented smaller and more uniform particle sizes in the nanoparticles obtained by the microemulsion method. The band gap energy of zinc aluminate nanoparticles obtained using microemulsion and polyacrylamide gel methods was 4.15 and 3.82 eV, respectively. Similarly, the results of MB removal showed that zinc aluminate nanoparticles synthesized using the microemulsion method and polyacrylamide gel, respectively, were 100% and 71% after 120 min. In the second phase of this study, silver nanoparticles were added to zinc aluminate nanoparticles during the synthesis process. X-ray diffraction showed that silver nanoparticles are formed metallically next to zinc aluminate. Moreover, the addition of silver decreased the crystallite size and slightly increased the band gap energy of zinc aluminate. The results of MB dye degradation tests in the presence of ZnAl2O4–Ag nanocomposites showed that the kinetics of dye degradation increased when the silver increased up to 5 wt%. Finally, the mechanism studied on dye degradation using scavenger agents showed that the main agents of dye degradation are the superoxide radical and the holes created in the valence band. It was consistently confirmed by examining the valence and conduction band potentials and also by comparing these potentials with those responsible for producing superoxide and hydroxyl radicals.

(Poster Award - 3rd Place) Photocatalysis of TiO2 Nanosheets Prepared by the Cellulose Nanofiber Template

Two-dimensional material inspired tremendous research interest by its unique structure and specific property different from bulk material, which could benefit various applications such as optics, electronics, and chemistry. However, most documented processes for 2D materials are complicated with a lengthy process. We introduced the cellulose nanofiber (CNF) extracted from agricultural waste rice straws, which inherently possesses many functional groups, e.g., hydroxyl group, and carboxylate group, making it a terrific template method candidate. Besides, aerogel composed of cellulose nanofiber provides many surface and layered structures that facilitate the adhesion of titanium isopropoxide to form a uniform coating layer, which hydrolyzed to TiO2. The cellulose nanofiber serves as a template and could be removed entirely in an easy thermal process by thermogravimetric analysis; meanwhile, we can transform the original amorphous TiO2 nanosheet into an anatase phase which is flavored in the photocatalyst field. Atomic force microscopy (AFM) results spotted a stacked ultrathin TiO2 nanosheet with a thickness of less than 5 nm for each layer, and the lateral size could reach micron size. For the RhB dye degradation test, TiO2 nanosheets could decompose the 10 ppm RhB solution within 30 mins with a reaction rate of 0.065 min-1. In conclusion, we combine the CNF template and hydrolysis process, proposing a simple 2D TiO2 nanosheets

Piezo-Flexocatalysis of Single-Atom Pt-Loaded Graphitic Carbon Nitride.

This study develops a single-atom Pt-loaded graphitic carbon nitride (SA-Pt/CN) and evaluates its piezo-flexocatalytic properties by conducting a hydrogen evolution reaction (HER) and Rhodamine B (RB) dye degradation test under ultrasonic vibration in the dark. SA-Pt/CN has a hydrogen gas yield of 1283.8µmolg-1h-1, which is 23.3 times higher than that of pristine g-C3N4. Moreover, SA-Pt/CN enhances the dye degradation reaction rate by ≈2.3 times compared with the pristine sample. SA-Pt/CN exhibits lattice distortion and strain gradient enlargement caused by the single atom Pt at the N sites of g-C3N4, which disrupts the symmetric structure and contributes to the enhancement of piezoelectric and flexoelectric polarization. As far as it is known, this is the first study to investigate the piezo-flexocatalytic reaction of SA-Pt/CN without light irradiation and provides new insights into single-atom piezocatalysts.

CO2 Photoreduction Activity Enhancement and Unexpected Observation of Carbon Monoxide Adsorbates on the Surface of TiO2 Nanotube Arrays Synthesized in Formamide Electrolytes.

TiO2 nanotube arrays grown through electrochemical anodization in a formamide-based electrolyte (TNTA-FA) exhibited a whole host of unusual properties compared to nanotubes grown in the conventional ethylene glycol-based electrolyte (TNTA-EG). TNTA-FA exhibited shorter phonon lifetimes, lower lattice strain, more visible light absorption, lower work function, and a highly unusual adsorbate structure consisting of physisorbed and chemisorbed CO along with linearly adsorbed CO2 and various monodentate and bidentate carbonate species. The observation of adsorbed CO in the dark is highly unusual and indicates spontaneous deoxygenation of CO2 on the surface of TNTA-FA. The significance of this finding is that the formation of CO2•- is no longer the rate-limiting bottleneck for the reduction of CO2 on TNTA-FA surfaces as it is for all TiO2 surfaces. TNTA-FA samples are strongly colored (inclusive of a fluorescent green color) and consist of rounded, vertically oriented hollow cylinders as opposed to the honeycomb-like morphology of TNTA-EG arranged in an approximate triangular lattice. The photocatalytic activity was tested through the CO2 photoreduction and dye degradation tests. Formamide-based nanotubes outperformed the EG-based nanotubes by almost 1.7 and 2 times, respectively, in CO2 reduction and dye degradation tests done on methylene blue, brilliant green, and rhodamine B dyes. These results are attributed to stronger surface band bending in TNTA-FA which facilitates more efficient separation of photogenerated electron-hole pairs.

Cobalt Ferrite (CoFe2O4) Spinel as a New Efficient Magnetic Heterogeneous Fenton-like Catalyst for Wastewater Treatment

For the first time, cobalt ferrite spinel (CoFe2O4) was used as a catalyst in the Fenton process for Remazol Red RR dye degradation in water. CoFe2O4 was synthesized via gel combustion using tris(hydroxymethyl)aminomethane as an alternative fuel in one step with a ratio of Ψ = 0.8. Its structural, surface optics, magnetic properties, and the optimal conditions of the Fenton reagents for dye degradation were evaluated. The saturation magnetization and remanence (Ms and Mr, respectively) for the as-prepared powder were 65.7 emu/g and 30.4 emu/g, respectively, and the coercivity (Hc) was 1243 Oe, indicating its ferromagnetic nature and suitability as a magnetic catalyst. Red Remazol RR dye degradation tests were performed using the Fenton process to evaluate the influence of the catalyst dosage and H2O2 concentration. The tests were performed in a batch reactor in the dark with constant agitation for 24 h. The best result was obtained using 1 g/L of catalyst with a dye degradation of 80.6%. The optimal concentration of H2O2 (1.0 M) resulted in 96.5% dye degradation. Nanoparticle recyclability testing indicated that the material could be satisfactorily reused as a catalyst for at least three cycles. The potential use of the CoFe2O4 synthesized in this study as a catalyst for dye degradation by the Fenton process was demonstrated.

Silver Nanoparticles’ Biogenic Synthesis Using Caralluma subulata Aqueous Extract and Application for Dye Degradation and Antimicrobials Activities

The issue of organic contaminants in water resulting from industrial, agricultural, and home activities makes it necessary to effectively address the problems of water scarcity. Using modern technologies that can effectively remove pollutants from wastewater is the way to address this key problem. The use of nanoparticles (NPs) has been advocated due to their unique physical and chemical characteristics and advantageous applications. NPs’ surface stability and synthesis routes are core concerns for environmental remediation and biological applications. In this work, we demonstrated the biogenic synthesis of silver NPs (Ag-CS NPs) by using Caralluma subulata (CS) aqueous extract as a reducing and capping/template agent. The synthesized Ag-CS NPs were characterized by UV-visible absorbance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, powdered X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and Zeta potential. The performance of Ag-CS NPs was evaluated on methylene blue (MB) dye degradation and antibacterial activity tests against bacterial and fungal isolates. The results showed that Ag-CS NPs (0.05%, 20.0 μL) reduced MB by 95.52% within 28 min in the presence of NaBH4 (10.0 mM, 0.980 μL). The degradation of MB followed pseudo zero-order chemical kinetics (R2 = 0.9380), with the reaction rate constant 0.0508 mol L−1 min−1. In addition, Ag-CS NPs were applied as antibacterial agents against 19 bacterial isolates. Ag-CS NPs showed inhibition in both Gram-positive and Gram-negative bacterial, as well as fungal isolates. As a greener ecofriendly approach, multifunctional Ag-CS NPs make a promising candidate for the remediation of contaminated water, as well as for important bioapplications.

Combined Structural and Plasmonic Enhancement of Nanometer-Thin Film Photocatalysis for Solar-Driven Wastewater Treatment.

Titanium dioxide (TiO2) thin films are commonly used as photocatalytic materials. Here, we enhance the photocatalytic activity of devices based on titanium dioxide (TiO2) by combining nanostructured glass substrates with metallic plasmonic nanostructures. We achieve a three-fold increase of the catalyst's surface area through nanoscale, three-dimensional patterning of periodic, conical grids, which creates a broadband optical absorber. The addition of aluminum and gold activates the structures plasmonically and increases the optical absorption in the TiO2 films to above 70% in the visible and NIR spectral range. We demonstrate the resulting enhancement of the photocatalytic activity with organic dye degradation tests under different light sources. Furthermore, the pharmaceutical drug Carbamazepine, a common water pollutant, is reduced in the aqueous solution by up to 48% in 360 min. Our approach is scalable and potentially enables future solar-driven wastewater treatment.

Visible light driven photocatalytic and competent antioxidant properties of phyto-fabricated zinc oxide nanoparticles (ZnO-NPs) from Borreria hispida

Zinc oxide nanoparticles (ZnO-NPs) have gained considerable interest in biological and photocatalytic applications due to their distinctive physico-chemical characteristics. The study aimed to synthesize ZnO-NPs using the leaf extract of Borreria hispida, a medicinally important plant for its antioxidant and photocatalytic efficacy. The B. hispida mediated ZnO-NPs (Bh-ZnO-NPs) illustrated a characteristic peak at 304 nm with 3.45 eV bandgap energy during the spectral analysis. The Bh-ZnO-NPs XRD studies revealed stiff and narrow peaks with ∼21.87 nm in size. The SEM analysis revealed that the obtained Bh-ZnO-NPs were agglomerated and ZnO elemental purity of 98.23% was confirmed through EDS. The spectral results of Bh-ZnO-NPs obtained by the FT-IR affirmed that phyto-constituents participated in the reduction, capping and stabilization of the particles during the synthesis of nanoparticles. The BET surface area analysis of the Bh-ZnO-NPs confirmed that the particles exhibit a similar Type – IV isotherm curve as per IUPAC classification with 11.681 m2g-1 and a surface roughness (Ra) value of 6.25 nm. The Bh-ZnO-NPs offered significant (p ≤ 0.05) radical scavenging activity, which was dose-dependent with IC50 value falling between 0.6 to 0.8 mg mL−1 among the evaluated test methods. Methyl red (MR) dye degradation tests employing phyto-fabricated Bh-ZnO-NPs resulted in dye degradation up to 94.22% after 40 min of solar irradiation and the decolorization of MR dye followed pseudo-first-order kinetics. In addition to those mentioned above, the fifth cycle of the photocatalyst's stability and reusability studies showed 84.8% dye degradation ability. The findings demonstrate that the phyto-fabricated ZnO-NPs from B. hispida have potent antioxidant and dye-degrading properties that can be investigated at an industrial scale.

Simple two-step development of TiO2/Fe2O3 nanocomposite for oxygen evolution reaction (OER) and photo-bio active applications

The simultaneous incorporation of iron (III) oxide (Fe2O3) and titanium oxide (TiO2) forms a noteworthy composite for oxygen evolution reactions, photocatalytic, and antimicrobial applications. TiO2/Fe2O3 nanocomposite was deposited utilizing a patented, single-step altered pseudo-successive ionic layer adsorption and reaction (p-SILAR) process for the deposition of oxides, which was employed in this study to form Fe2O3 for the first time. The developed nanocomposite exhibits improved electrocatalytic water splitting, photocatalytic activity, and antimicrobial performance. Controlled deposition and heat treatment enable the formation of Fe2O3 and TiO2, as verified by SEM, EAM, and XPS analysis. Incorporation of Fe2O3 significantly enhances the photocatalytic activity of P25 TiO2 nanoparticles, demonstrated by the visible light dye degradation test. The nanocomposite degrades 58% of the Rhodamine B dye in 100 min, while pure TiO2 degrades only 26%. The NC also shows higher antibacterial activity against E. coli and S. aureus compared to pure TiO2. Water splitting performance is evaluated using Electro Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV), and Tafel Slopes. The results show that TiO2/Fe2O3 NCs exhibit improved oxygen evolution reaction compared to pure TiO2.

2D-3D metal oxide heterojunction nanostructures for catalytic applications

A simple template-free method was used to fabricate unique undoped, Cr-doped, and S-doped mesoporous 2D-3D ceria (CeO2-x) nanostructures by using triethanolamine (TEA) to exfoliate electrodeposited cerium coordination polymer (Ce-CP), followed by heat treatment at 450 °C. For undoped CeO2-x fabrication, varying the amount of TEA impacted the exfoliation extent and the resultant microstructural and defect characteristics, with the optimal Ce-CP to TEA ratio determined to be 30 mg:0.35 mL. For doped CeO2-x, the introduction of dopants (substitutionally and/or interstitially) and heterojunction formation resulted in the creation of defects from charge compensation (ionic, electronic, and redox) which influenced charge carrier concentrations for reactions. The precipitation of excess dopants on the surface to create heterojunctions allowed for reduced crystallite sizes, lowering of the optical band gaps, and increased charge carrier separation, which in turn minimised charge carrier diffusion distance, ultimately increasing photocatalytic efficiency. Dye degradation tests showed that 10 mol% Cr-doped CeO2-x revealed superior photocatalytic performance with a reaction rate of 15.88 × 10−3 min−1 (87% degradation after 160 min) compared to both 2.5 mol% S-doped CeO2-x and undoped CeO2-x (68% and 57% after 160 min, respectively). With sulphur addition, although the defect concentration increased and the crystallite sizes and band gaps were lowered, the degradation performance declined with increasing dopant amount owing to the reduced porosity from liquid-phase microstructural densification. Thus, the positive changes to the electronic and microstructural features from dopant-related heterojunction formations were observed to be the most critical factors impacting the photocatalytic performance of these unique nanostructures.

Efficient Solar Light Photocatalyst Made of Ag3PO4 Coated TiO2-SiO2 Microspheres.

Solar light active photocatalyst was prepared as silver phosphate (Ag3PO4) coating on titania-silica (TiO2-SiO2) microspheres. Titania-silica microsphere was obtained by spray drying TiO2-SiO2 colloidal solutions, whereas Ag3PO4 was applied by wet impregnation. XRD on the granules and SEM analysis show that the silver phosphate particles cover the surface of the titania-silica microspheres, and UV-visible diffuse reflectance analysis highlights that Ag3PO4/TiO2-SiO2 composites can absorb the entire visible light spectrum. BET measurements show higher specific surface area of the composite samples compared to bare Ag3PO4. Photocatalytic activity was evaluated by dye degradation tests under solar light irradiation. The prepared catalysts follow a pseudo-first-order rate law for dye degradation tests under solar light irradiation. The composite catalysts with an Ag3PO4/TiO2-SiO2 ratio of 1:1.6 wt% show better catalytic activity towards both rhodamine B and methylene blue degradation and compared with the results with uncoated TiO2-SiO2 microspheres and the benchmark commercial TiO2 (Evonik-P25) as a reference. The composite photocatalyst showed exceptional efficiency compared to its pristine counterparts and reference material. This is explained as having a higher surface area with optimum light absorption capacity.

Enhanced electron transfer due to rGO makes Ag–CaTiO3@rGO a promising plasmonic photocatalyst

Herein, the synthesis of a new ternary nanocomposite, Ag–CaTiO 3 @rGO, exhibiting high photocatalytic dye degradation efficiency is reported. The photocatalytic activity of Ag–CaTiO 3 @rGO was studied under natural sunlight with a model dye pollutant sulforhodamine B. This photocatalyst's high degradation efficiency is attributed to the synergistic effect of plasmon-induced visible light-harvesting due to Ag and enhanced adsorption and electron–transport properties due to rGO. It is found that the Ag-induced surface plasmon characteristics of the nanocomposites are sensitive to rGO concentration. Absorption spectra of the nanocomposites indicated that Ag and rGO enhance and extend the absorbance in the visible region, which is beneficial for creating photo-carriers during the photocatalytic reaction under sunlight. In the X-ray photoelectron spectra, ∼0.7–0.8 eV positive binding energy shift is observed in Ca 2p, Ti 2p, and O 1s peaks of typical Ag–CaTiO 3 @rGO compared to Ag–CaTiO 3 and CaTiO 3 , indicating that electrons are transferred to the electron acceptor, rGO. The reusability of this photocatalyst Ag–CaTiO 3 @rGO was analyzed by conducting repeated dye degradation tests. The adsorption characteristics of the designed catalyst followed the Langmuir isotherm model. A model for the plausible mechanism of enhanced sunlight-driven photocatalysis by Ag–CaTiO 3 @rGO with 7.5 wt% GO is also proposed.

Application of pulsed chemical vapor deposition on the SiO2-coated TiO2 production within a rotary reactor at room temperature

Pulsed chemical vapor deposition (P-CVD) is a promising technology for the surface modification of TiO 2 particles. For the scale-up application of P-CVD, a custom-designed rotary reactor and corresponding coating process at room temperature was developed in the present work. The obtained SiO 2 -coated TiO 2 particles were characterized by various measures including high-resolution transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, etc . The results illustrated that the SiO 2 films with a thickness of (3.7 ± 0.7) nm were successfully deposited onto the surface of TiO 2 particles. According to the dye degradation tests and acid solubility measurement, the deposited film can effectively inhibit the photocatalytic activity and enhance the weatherability of the TiO 2 particles. Zeta potential measurements showed that the SiO 2 -coated TiO 2 is possible to be stably dispersed in the pH range of 6.9–11.6. The coating process made the whiteness of TiO 2 particles decreased slightly but still sufficient (97.3 ± 0.1) for application. Furthermore, the properties of the TiO 2 particles coated by P-CVD were compared with the particles coated by traditional wet chemical deposition. It is shown that the P-CVD can produce thinner but denser films with better photoactivity suppression performance. The developed coating process within the rotary reactor was proved practically feasible and convenient for the scale-up production of SiO 2 -coated TiO 2 via P-CVD.

Synthesis of a novel solid mediator Z-scheme heterojunction photocatalysis CuFe2O4/Cu/UiO-66-NH2 for oxidation of dye in water

Metal mediator Z-scheme photocatalyst comprises three elements: two semiconductors and a sandwiched metal mediator, so the catalyst can effectively degrade pollutants using visible lights. Proper design and synthesis of Z-scheme with targeted performance has not been systematically proposed. This work proposed the protocol to design and synthesize a Z-scheme photocatalyst with targeted performance. A novel metal mediator Z-scheme photocatalyst CuFe2O4/Cu/UiO-66-NH2 was used to implement the design proposal. After determining synthesis protocol from the theory, the concentrations of three reagents – glucose, l-cysteine, and precursor of UiO-66-NH2 for synthesizing Z-scheme photocatalyst were revised to achieve successful photocatalyst. Dropwise photocatalytic tests were performed to confirm the activities of the synthesized catalysts using 0.112 mmol/mL UiO-66-NH2 precursor, 10 mmol/mL glucose, and 1 mmol/mL l-cysteine yielded effective photocatalyst to degrade rhodamine 6G. The dye degradation tests and EPR tests confirmed the successful synthesis of the designed Z-scheme photocatalyst.

A Convenient Procedure for Preparing BiOX-TiO2 Photoelectrocatalytic Electrodes from a Titanium-Oxo Compound-Modified Carbon Fiber Cloth.

Photoelectrocatalysis (PEC) has shown great advantages in sustainable organic synthesis and wastewater treatment because the PEC process can minimize electron-hole recombination, thereby improving the photocatalytic performance. Here, we report a convenient procedure for preparing immobilized BiOX-TiO2 photoelectrocatalytic electrodes from a titanium-oxo compound (TOC)-modified carbon fiber cloth (CFC). Crystalline TOCs composed of Ti12 cations and bismuth halide anions, [Ti12O14(OiPr)18][Bi3Br11(THF)2] (1) and [Ti12O14(OiPr)18][Bi4I14(THF)2] (2), were grown on CFC. Taking advantage of the easy hydrolysis of the titanium-oxo cation and bismuth halide anion, we could easily transform these CFC-immobilized crystals into BiOX-TiO2/CFC (X = Br or I) photocatalysts, which facilitates recycling of the catalysts. The photocatalytic dye degradation test showed that the efficiency did not decrease obviously after 10 photocatalytic cycles. Using BiOX-TiO2-modified CFC as electrodes, electrocatalysis (EC), photocatalysis (PC), and PEC were examined. PEC showed an attractive synergistic effect of EC and PC. These TOC-modified CFCs would be potential candidates for catalytic electrodes for sustainable wastewater purification.

Investigating the viability of sulfur polymers for the fabrication of photoactive, antimicrobial, water repellent coatings.

Elemental sulfur (S8), a by-product of the petroleum refining industries, possesses many favourable properties including photocatalytic activity and antibacterial activity, in addition to being intrinsically hydrophobic. Despite this, there is a relative lack of research employing elemental sulfur and/or sulfur copolymers within superhydrophobic materials design. In this work, we present the use of sulfur copolymers to produce superhydrophobic materials with advanced functionalities. Using inverse vulcanization and the use of a natural organic crosslinker, perillyl alcohol (PER), stable S8-PER copolymers were synthesised and later combined with silica (SiO2) nanoparticles, to achieve highly water repellent composites that displayed both antimicrobial and photocatalytic properties, in the absence of carcinogenic and/or expensive materials. Here, we investigated the antibacterial performance of coatings against the Staphylococcus aureus bacterial strain, where coatings displayed great promise for use in antifouling applications, as they were found to limit surface adhesion by more than 99%, when compared to uncoated glass samples. Furthermore, UV dye degradation tests were performed, utilizing the commercially available dye resazurin, and it was shown that coatings had the potential to simultaneously exhibit surface hydrophobicity and photoactivity, demonstrating a great advancement in the field of superhydrophobic materials.

Photocatalytic degradation of contaminants of emerging concern using a low-cost and efficient black bismuth titanate-based water treatment reactor

Photocatalysis is recognized as a sustainable technology for wastewater treatment, but it is limited by its scalability and efficiency. Here, we report the fabrication of a bespoke photocatalytic reactor, made from readily available consumer market components. The reactor was loaded with glass rods coated with a bismuth titanate photocatalyst deposited by reactive pulsed DC magnetron sputtering. Bismuth titanate is a remarkable material, which has shown the property of increasing its photocatalytic capabilities over repeated usage due to photoinduced oxygen vacancies, forming oxygen-vacancy rich “black” bismuth titanate. The reactor was tested with different rod configurations and photocatalytic material was cycled over 25 times, equivalent to 125 h of consecutive use, against methylene blue dye under UV light. Orange II dye degradation tests carried out in the presence of scavengers revealed that photocatalytic reactions were driven by superoxide (O2∙−) and holes (h+), when using pristine bismuth titanate and by superoxide (O2∙−), electrons (e−) and holes (h+), when using “black” bismuth titanate. Finally, the reactor was used to successfully degrade levofloxacin, a typical antibiotic, which was verified by UV–Vis (ultraviolet-visible) spectroscopy and inhibition zone tests in the presence of three different pathogens (E. coli, S. aureus and A. baumannii).

Photocatalytic Activity of Ag-ZnO Nanocomposites Integrated Essential Ginger Oil Fabricated by Green Synthesis Method

Facile and eco-friendly green synthesis route was used to fabricate pure ZnO nanoparticles (NPs) and silver doped ZnO nanocomposites (Ag-ZnO NCPs) using essential ginger oil (EGO) as reduction agent. These Ag-ZnO NCPs were determined and characterized via various analytical tools such as X-ray diffraction, FESEM, and UV-Vis spectrophotometer. X-ray diffraction patterns confirmed the crystallinity of single ZnO that showed a hexagonal wurtizite (HW) structure with preferential orientation in the (100) direction and the Ag NPs verified face center cubic (FCC) structure with preferred orientation in the (111) direction. The FESEM images exposed uniformly distributed triangle cages of ZnO NPs and nanowires shape of Ag-ZnO NCPs. The UV-Vis absorption band of as-synthesized Ag-ZnO NCPs showed sharp and minor peaks at 395 nm and 550 nm. Photocatalytic activity of Ag-ZnO NCPs was obtained through methylene orange (MO) dye degradation tests, which exhibited remarkable photodegradation efficiency around ≈ 90% after 150 min under UV light. In contrast, single ZnO revealed photodegradation efficiency ≈ 84% at 150 min UV light exposure. These Ag-ZnO NCPs can offer a great potential for large demands of semiconductor applications.

Durability of self-cleaning cement-based materials

The use of self-cleaning materials as building materials is gaining more and more interest, but their performance characterization over time has been poorly investigated. For this purpose, accelerated durability tests were carried out on different self-cleaning materials, either based on photocatalytic principles (i.e. containing TiO2) or on the lotus effect, which were subjected to UV radiation, rain, freeze-thaw and thermal cycles variations. The accelerated ageing tests program involved different commercial materials and was aimed at a second step of characterization of their photocatalytic activity and self-cleaning ability, in order to investigate their durability and the retention of such functionality over time. With this aim, rhodamine B (Rh-B) dye degradation tests were performed. The experimental campaign proved the actual self-cleaning behaviour of these materials in their freshly produced state, but it also demonstrated the detrimental effect of ageing on their performances. Moreover, issues related to the test method emerged with special reference to the evaluation of materials durability.