Papers by Keyword: Visible Light

Abstract: Anatase-type TiO₂ films synthesised on quartz glass demonstrated cell adhesion control when illuminated from the backside with a 150 W Xe lamp emitting white light. The UV component was fully absorbed by the TiO₂ film, preventing cell exposure to it. By selectively applying localised light, non-contact control of cell adhesion areas was achieved. If non-toxic films responsive to conventional LED panels could be used, this would enable precise and easy control of cell adhesion areas. The purpose of this study was to synthesise inorganic semiconductor films with a narrower bandgap than TiO₂, responding to visible light from LED, and to investigate their photo-responsive properties. α-Fe₂O₃ films were deposited on borosilicate glass or ITO-coated quartz glass using RF sputtering with the corresponding metallic targets under an Ar or Ar/O₂ mixed atmosphere. XRD analysis showed sharp diffraction peaks, confirming the successful synthesis of the films. The absorption edges of the oxides shifted to longer wavelengths compared to that of TiO₂, corresponding to their bandgap differences. When a tablet device (HUAWEI MediaPad M3 Lite 10wp) displaying a white image was used as a light source, the oxide films showed a noticeable photocurrent. In the photocurrent profile during the on/off cycle of the light, a phenomenon of current flowing in the reverse direction when the light was turned off was observed. Moreover, this current reversal was more pronounced when the grains were fine. This suggests that the grain boundaries acted like a capacitor and induced polarisation behaviour.

Abstract: The textile industry in Indonesia is currently rapidly growing. However, this increase harms the environment because dyes from textile production are generally released into the environment without prior processing. Photocatalysis is one effort that can be used to overcome this problem. TiO₂ has been proven to be highly efficient in its work as a photocatalyst material. This study aims to investigate the effectiveness of methylene blue (MB) photodegradation using TiO₂ with steady pre-treatment optimizations. The pre-treatment was carried out by leaving the mixture of TiO₂ and methylene blue in various conditions under dark and room light conditions, resulting in ⁓37% and ⁓50% degradation efficiencies, respectively. Higher total percent MB degradation efficiencies (%Eff) were reached after visible light irradiation using mercury lamp in the post-treatment of more than 75%, concluding that the pre-treatment both in dark and room light storage optimized the MB degradation process. Therefore, these pre-treatment methods are potentially suitable for industrial wastewater treatment before the photocatalysis process to lower the waste management cost.

Abstract: This study involves the photocatalytic degradation of methylene blue (MB) under visible light using reticulated stainless steel that is coated with copper-doped TiO₂. Steel meshes of three different grades are used in the experiment: 50 mesh, 120 mesh and 400 mesh. The coating process coats an average of 0.3 mg/cm² of Cu–TiO₂ on the 50 mesh and the 120 mesh and 0.2 mg/cm² on the 400 mesh. SEM and XRD characterization show that the roughness of the mesh wire surface increases as the amount of coating is increased. All three types of mesh remove approximately 50% of MB, when coated with 1 mg/cm² of CuO-TiO₂. When the amount of coating is increased to 2.5 mg/cm², the order for the photocatalytic degradation of MB for the three meshes is 120 mesh (93%) > 400 mesh (91%) > 50 mesh (86%). However, when the amount of coating is further increased to 2.5 mg/cm², there is no significant difference between the three mesh groups, in terms of MB residue. The study demonstrates that the photocatalytic efficiency is affected by the surface area and thickness of the membrane that forms over the mesh openings.

Abstract: This research has prepared Fe₃O₄/SiO₂/TiO₂-S composite materials as magnetic photocatalysts. Detailed characterization of the composite materials was undertaken using FTIR, XRD, TEM, VSM and DRUV. The photocatalytic activity of composite materials was conducted through salicylic acid degradation under visible light illumination. The result based on the infrared spectra and XRD diffractogram revealed the appearance of the characteristic peak of Fe₃O₄, SiO₂, and S-TiO₂. The sulfur doping causes an absorption edge shifts toward a higher wavelength. Fe₃O₄/SiO₂/TiO₂-S 3% composite material had the narrowest band gap energy of 2.77 eV and presented good photocatalytic activity with a percentage degradation of 91.6% under visible light during 60 minutes of illumination time. The composite exhibited recoverable efficiency due to its magnetic properties.

Abstract: Synthesis of magnetic photocatalyst, Fe₃O₄/TiO₂-Ag, with characterization and photoactivity examination have been investigated. The synthesis was initiated by preparation of Fe₃O₄ particles using coprecipitation method. The Fe₃O₄ particles were then coated with TiO₂-Ag, weight ratios of concentrations Silver dopant were varied from 1 to 3, 5 and 7 wt%. The Fe₃O₄/TiO₂-Ag was characterized by FTIR, XRD, TEM, SEM-EDX, DR UV-visible and VSM methods. The degradation of metanil yellow solution was performed under exposure to UV, visible light and dark condition at optimum condition. The Fe₃O₄ and anatase diffraction peaks were presence on the X-ray diffractogram. The Fe₃O₄/TiO₂-Ag was responsive to visible light, according to DR UV-Vis spectra. The Fe₃O₄/TiO₂-Ag band gap energy was 2.49, 2.30, 2.00, and 2.46 eV, respectively, with dopant concentrations of 1; 3; 5; and 7%. Metanil yellow solution can be photodegraded for 180 minutes at a pH of 2.3. The Fe₃O₄/TiO₂-Ag has the highest ability to metanil yellow photodegradation with dopant concentration of 5% gave degradation yield of 82.18% and 72.53% under UV and visible irradiation, respectively. With K values of 0.52 g mg^-1 min^-1 under visible light and 0.5255 g mg^-1 min^-1 under UV light, the degradation kinetics of methanyl yellow dye followed Ho and McKay's kinetic model. The Fe₃O₄/TiO₂-Ag material exhibited magnetic characteristics that could be applied under visible light and reused.

Abstract: The synthesis of sulfur-doped titania magnetite composite and its activity as a photocatalyst in the degradation of metanil yellow have been investigated. The variations of sulfur dopan concentration studied were 1%, 3%, 5%, and 7%. The synthesized Fe₃O₄/TiO₂-S composite was characterized using FTIR, XRD, TEM, SEM-EDX, DR-UV, and VSM. The results showed that the Fe₃O₄/TiO₂-S photocatalyst is visible light responsive with magnetic properties. Sulfur dopan concentrations of 1, 3, 5, and 7 (%) had band gap energies of 2.83, 2.81, 2.76, and 2.84 (eV), respectively. The photodegradation results showed that Fe₃O₄/TiO₂-S 5% composite material could degrade metanil yellow in acidic pH at 180 min under visible light irradiation (73.44). The structural stability was observed after three times of photocatalyst reuse. The degradation kinetics of metanil yellow dye followed the pseudo-second order of Ho and McKay's kinetic model, with K values of 0.52 g mg^-1min^-1 under visible light. This composite has good photodegradation activity for metanil yellow can be applied under visible light and can be reused after use.

Abstract: Water is a valuable source that directly impact human life. The expansions of globalization as well industrialization led to water pollution, thus became worsen over the time. The issue of degradation of organic and inorganic pollutants become very serious from ecological point of view, especially organic pollutants in industrial effluents due to difficult to be remove by means of conventional technologies. Phenol compound in wastewater effluents can threatens the human and public health, water supplies, and has negative impacts on the ecosystems. In addition, the TiO₂ semiconductor metal oxide provides a great interest among researchers to overcome this problem via photocatalytic reaction under advanced oxidation processes (AOPs). The AOPs mainly used the hydroxyl radicals to attack and destroy a wide range of harmful dyes into non-toxic products, CO₂ and water at ambient temperature. Therefore, in this study, the synthesized TiO₂ catalyst gave the remarkable degradation of phenol up to 96.3%, meanwhile the commercial TiO₂ only show 80.3%, in respectively under similar optimum conditions of 10 mg/L at pH 5 with dosage of 1.25 g/L within 90 mins time reaction under light irradiation.

Abstract: Photochemistry to prepare platinum nanoparticles (Pt NPs) is an essential way to control Pt NPs catalyst size distribution. This article reports a series of morphologically controlled syntheses of Pt NPs loaded on modified carbon nanotube (Pt-CNTs). In the synthesis, Polyethylene glycol (PEG) participates in reactions both as a reducing agent and a stabilizer. Visible light irradiation was adopted as a kinetic controlling approach. Typical 4-nitrophenol (4-NP) reduction was adopted to probe the catalytic performances. Characterizations prove that visible light irradiation is an effective way to control the reaction process. In the optimized reaction conditions, i.e., when the ratio PEG:H₂O is 1:9, and the pH is 10, the as-prepared Pt NPs are consequently in a very narrow sized distribution with an average diameter of 1.29 nm. The Pt-CNTs present a high reaction rate constant of 0.624 min^-1 in the catalytic reduction of 4-NP. All the research results are beneficial for exploring more green chemistry and facile photochemical approaches in the controlled preparation of Pt nanocatalysts.

Abstract: Synthesis of Fe₃O₄/ZnO-Cu nanocomposite photocatalyst has been conducted. The synthesis was carried out using the co-precipitation method with the variation of Cu concentration and modification by Fe₃O₄ magnetic material. As synthesized photocatalysts were characterized using FTIR, XRD, TEM, and SR UV-Visible. Photocatalytic activities of samples were evaluated through Rhodamine B degradation under visible light irradiation. The results showed that a sample with Fe₃O₄/ZnO-Cu 1% has smaller band gap energy of 2.90 eV and the highest photocatalytic activity than pure ZnO or Fe₃O₄-modified ZnO (Fe₃O₄/ZnO-Cu 0%) under visible light. The percentage of Rhodamine B degradation was approximately 89.41% during 120 min of visible light illumination. Moreover, the photocatalyst materials could be easily separated after photocatalysis which is due to the magnetic property of Fe₃O₄ material. Therefore, Cu-doped ZnO with Fe₃O₄ modification has been an efficient and effective visible-light-induced photocatalyst in removing non-biodegradable Rhodamine B dyes.

Abstract: Ag nanoparticles and GO co-modified Co-g-C₃N₄ composites were prepared successfully. The visible-light adsorption of the optimized GO-Ag@Co-g-C₃N₄ was improved significantly by the SPR effect of Ag nanoparticles, and the separation efficiency of photo-induced electron-hole pairs of g-C₃N₄ was accelerated to a large extent by the heterojunction structure of the composite and the superior conductivity of GO. The optimized GO-Ag@CoCN showed promising degradation efficiency for RhB (10 mg/L) under visible light illumination (λ>420 nm) for 160 min, which was 130% and 16.5% higher than the performance using bare g-C₃N₄ and optimized Ag@Co-g-C₃N₄, respectively. This work provided a novel way for improving the optical property and photocatalytic activity of g-C₃N₄.