Visible Photocatalytic Properties Research Articles

Visible light-induced photocatalytic and antibacterial adhesion properties of superhydrophilic TiO2 nanoparticles

Bacterial infections triggered by patient or healthcare worker contact with surfaces are a major cause of medically acquired infections. By controlling the kinetics of tetrabutyl titanate hydrolysis and condensation during the sol–gel process, it is possible to regulate the content of Ti3+ and oxygen vacancies (OVs) in TiO2, and adjust the associated visible light-induced photocatalytic performance and anti-bacterial adhesion properties. The results have shown that the Ti3+ content in TiO2 was 9.87% at the calcination temperature of the reaction system was 300 °C and pH was 1.0, corresponding to optimal photocatalytic and hydrophilic properties. The formation of a hydrated layer on the superhydrophilic surface provided resistance to bacterial adhesion, preventing cross-contamination on high-touch surfaces. The excellent photocatalytic self-cleaning performance and anti-bacterial adhesion properties can be attributed to synergistic effects associated with the high specific surface area of TiO2 nanoparticles, the mesoporous structure, and the presence of Ti3+ and OVs. The formation of superhydrophilic self-cleaning surfaces under visible light can serve as the basis for the development of a new class of anti-bacterial adhesion materials.

Visible-light-driven 2D π-conjugated polyimide/ZnO efficiently removes tetracycline

Heterojunction organic-inorganic composites are promising for wastewater treatment due to their excellent physical and chemical properties. ZnO was immobilized on the PI surface using the hydrothermal technique to prepare PI/ZnO n-n heterojunctions with outstanding visible photocatalytic properties. The photocatalytic performance of different ratios of PI/ZnO composites was significantly improved in comparison to pure PI and ZnO, among which 40% PI/ZnO showed the most outstanding results. The 40% PI/ZnO can adsorption remove around 40% of tetracycline (TC) in 20 min in entirely shaded conditions and can attain up to 90% of the TC removal efficiency in 40 min under visible light exposure. The formation of a PI/ZnO heterojunction enhances the efficiency of charge separation and reduces the recombination of photogenerated electron-hole pairs, resulting in improved photocatalytic performance. Meanwhile, the 40% PI/ZnO composites showed a substantial increase in specific surface area (205.22 m2/g) compared to pure PI and ZnO, which was 103 and 25 times that of PI and ZnO, respectively. The increase in surface area provided a larger number of adsorption sites, thereby increasing the contact area between the pollutants and the photocatalysts, which led to a significant improvement of the PI/ZnO composites in the adsorption and photocatalytic properties. In this study, the heterojunction was formed by the composite of conjugated polymer and metal oxide, so that the composites could remove the organic matter more efficiently by adsorption and then photocatalysis, which will provide some ideas for the development of more efficient conjugated polymer materials.

Self-grown Ag2O nanoparticles on Ag-NASICON material for efficient visible light photocatalysis

Ag-containing semiconductors have gained great attention due to their outstanding visible light-responsive photocatalytic properties. In the current work, silver oxide (Ag2O) nanoparticles were in situ self-grown on the surface of AgZr2(PO4)3 NASICON-type material using sodium hydroxide-assisted precipitation to form an Ag2O/Ag1-xNaxZr2(PO4)3 nanocomposite. The crystalline structures, morphological observations, elemental composition, and optical properties of the prepared product were carried out using various characterization methods. The photocatalytic performance of Ag2O/Ag1-xNaxZr2(PO4)3 has then been explored in the decomposition of methyl orange (MO) wastewater pollutant under visible light. The obtained photocatalyst exhibited excellent decomposition efficiency (95.08 %, k = 0.0303 min−1) for MO removal within 60 min. In addition, the prepared nanocomposite exhibited proper reusability even after five successive cycles without any significant loss in photocatalytic activities. Furthermore, a simple catalyst regeneration strategy based on hydrogen peroxide (H2O2) was adopted, revealing that the spent photocatalyst can achieve nearly total self-regeneration to the initial AgZr2(PO4)3 material.

Synthesis of hierarchical FePc-ZS-1 zeolites and its rapid photocatalytic degradation of MB under visible light and H2O2

This manuscript details the successful production of hierarchical FePc-ZS-1 zeolite with rapid visible photocatalytic properties through an impregnation method utilizing reactive dyes as a sensitizing agent. The impact of the dye species on the visible photocatalytic properties of the resulting products was thoroughly examined in a Fenton reaction system created by combining H2O2 and the synthesized materials. The synthesized materials were subjected to characterization through various methods including XPS, XRD, FTIR, SEM, and N2 adsorption-desorption isotherm.The synthetized FePc-ZS-1 zeolite is an ellipsoid with smooth surface, highly ordered pore structure, and characteristic peaks in the visible region of 400–800 nm. The final results indicate that the phthalocyanine dye-sensitized zeolite had the most significant impact on the visible light degradation efficiency of methylene blue dye solution. The degradation efficiency of FePc-ZS-1 zeolite on MB solution reached an amazing 99.96 % in just 30 min. After examining the photocatalytic activity and kinetics model, it was determined that the photocatalytic activity is consistent with the apparent first-order kinetic model. Furthermore, through radical capture experiments and ESR characterization, the hypothesized mechanism of the photocatalytic reaction and the MB degradation pathways were thoroughly addressed. Finally, the samples were subjected to reuse experiments, and the results showed that the degradation rate was still above 90 % after 5 times of reuse, with good recyclability. The above results indicate that the visible photocatalytic material prepared in this study is a promising source of green energy, which is worthy of further application.

Nano‐SH‐MOF@Self‐Assembling Hollow Spherical g‐C3N4 Heterojunction for Visible‐Light Photocatalytic Nitrogen Fixation

AbstractMetal‐organic frameworks (MOFs)@g‐C3N4 heterojunctions are widely investigated as one of the most potential photocatalysts for N2 fixation owing to the visible absorption and effective photocatalytic properties. It is still a huge challenge to synthesize hollow spherical C3N4 coated with Nano‐MOF layers towards efficient visible photocatalytic activity on N2 fixation. In this work, the paramagnetic hollow spherical C3N4 (H‐C3N4) are coated with free radical MOF with sulfhydryl ligand (Nano‐SH‐MOF)[Zn2(DSBDC)] by self‐assemble method. The C8 M2 samples (the mass ratio of H‐C3N4 to Nano‐SH‐MOF is 8 : 2) exhibited an improved photocatalytic activity, which is almost 5.4 times higher than the pure H‐C3N4. The improved photocatalytic activity is also discussed in this work. It can be imagined that this work may be helpful for the hollow spherical C3N4 based heterojunction and MOF‐based heterojunction photocatalysts with effective photocatalytic nitrogen fixation.

Obvious enhancement of visible photocatalytic performance of Cu2O modified with TiO2-g-C3N4: A strategy to achieve synergistic effect of p-n junction and Z-scheme

The Cu2O–TiO2-g-C3N4 (C-TCN) composite photocatalysts which have excellent photocatalytic properties was synthesized via facile calcination and hydrothermal technique. The composition, morphology and structure of the synthetic materials were investigated by a series of characterizations. The results exhibited that TiO2-g-C3N4 (TCN) modified Cu2O ternary composites were successfully prepared. The photo-degradation rate of methyl orange (MO) dye and tetracycline hydrochloride (TC) were 95.08% and 93.28% in the presence of the C-TCN photocatalysts under visible-light. The dramatically increase of photocatalytic properties of ternary composites was assumed to g-C3N4 functioned as the ladder and relay station between TiO2 and Cu2O, which could simultaneously create p-n conjunction between Cu2O and g-C3N4 and Z-scheme between Cu2O and TiO2. The free radical quenching experiment and ESR detection verified that •O2− and •OH were the core redox species in the visible photocatalysis process. This paper demonstrate a feasible idea for synthesizing Cu2O based multi-component composites with dramatically improved visible photocatalytic properties.

Fabrication of an organic-based PI/ZnO composite with high visible photocatalytic properties toward tetracycline

Fabrication of an organic-based PI/ZnO composite with high visible photocatalytic properties toward tetracycline

In-situ oxidation selective deposition of tetrahedral Ag3PO4{111} on monoclinic BiVO4{040} with highly efficient visible light-driven photocatalysis and long recycling

Photocatalytic technology utilizing solar energy to eliminate organic pollutants is considered to be a promising and sustainable method. Adopting light-driven and in-situ oxidation methods, tetrahedral Ag3PO4{111} (t-Ag3PO4) was selectively grown on monoclinic BiVO4{040} (m-BiVO4), and then m-BiVO4@t-Ag3PO4 with excellent visible light-driven photocatalytic properties and long recycling was obtained. When the catalyst dosage is 0.50 g/L, the m-BiVO4@t-Ag3PO4 heterojunction photocatalyst could remove 99.9 % of rhodamine B within 30 min under visible light irradiation, and the degradation efficiency after 11 cycles remains 97.2 %. The morphology details and photocatalytic properties were confirmed by SEM, TEM, DSR, PL, PC and EIS. Active species capturing experiments and electron spin resonce measurements show that the superoxide radical (·O2-) and hydroxyl radical (·OH) are the main active species during the photocatalysis process. This work provides a promising method for constructing heterojunction photocatalysts with controllable morphology and visible light persistent catalysis. m-BiVO4@t-Ag3PO4 heterojunction photocatalyst has the advantage of price in the market and good features for application in organic wastewater treatment.

Visible photocatalytic properties of Ag–Ag2O/ITO NWs fabricated by mechanical injection-discharge-oxidation method

In the present study, anodic aluminum oxide (AAO) plates with a pore size of 40 nm were used as templates to fabricate indium-tin (In9Sn1) alloy nanowires (NWs) by vacuum mechanical injection method, and then Ag nanoparticles were coated onto the surface of the In9Sn1 NWs by means of the “in-situ discharge reduction” method. Finally, the composites were exposed in air for heat treatment to synthesize Ag–Ag2O/indium-tin oxide (ITO) NWs. The morphology, composition, and structure of the obtained samples were identified using scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction analysis. The results show that the length of the In9Sn1 NWs is 69.6 μm and Ag nanoparticles with 5–10 nm are uniformly coated on the surface of the In9Sn1 NWs, after calcination in air, Ag/In9Sn1 NWs are oxidized to Ag–Ag2O/ITO NWs. Additionally, the photocatalytic property of Ag–Ag2O/ITO NWs is tested, and it reveals the good photocatalytic activity thereof for the degradation of methylene blue under visible light irradiation.

A novel bentonite–cobalt doped bismuth ferrite nanoparticles with boosted visible light induced photodegradation of methyl orange: synthesis, characterization and analysis of physiochemical changes

ABSTRACT In this work, pure and bentonite-Co-doped multiferroic Bi1- x BentxFe1- y Co y O3 (x = 0.00 – 0.03, y = 0.00 – 0.15) bismuth ferrite (BFO) nanoparticles (NPs) were synthesised using a cost-effective solvothermal process without using any mineraliser. A meticulous investigation has been made on the structural, magnetic, electric and visible light-driven photocatalytic properties of bentonite–cobalt-doped BFO NPs. The XRD patterns showed a well-arranged rhombohedral crystalline structure with space group R3c. The structural phase transformation has been observed from R3c to orthorhombic with the pnma group for Bi1- x Bent x Fe1- y CoyO3 samples. The SEM analysis confirmed the presence of components with villiform aggregates and new dense nanometric spots with an average crystal size of about 14 nm. The values of the dielectric constant of BFO NPs have been increased with bentonite–Co doping and are maximum (340 at 1 kHz) for x = 0.03 and y = 0.05 at 100 Hz. The saturation magnetisation value of 0.47 emu/g for BFO increases with bentonite-Co-doped BFO NPs to a maximum value of 1.79 emu/g for the Bi0.97Bent0.03Fe0.85Co0.15O3 sample. The energy band gap value of Eg = 2.99 eV for BFO decreases with bentonite–Co doping, and minimum value, Eg = 2.59 eV for the x = 0.03, y = 0.15 sample. The percentage degradation efficiency of undoped BFO NPs (64%) increased after bentonite–Co doping to 92% for the removal of methyl orange. The improved ferroelectric, magnetic and photocatalytic properties of bentonite–Co-doped BFO NPs offer new application in multiferroic-based energy storage devices as well as the removal of toxic dyes (methyl orange) from water.

Visible light-driven photocatalytic and enzyme-like properties of novel AgBr/Ag2MoO4 for degradation of pollutants and improved antibacterial application

The manufacture of multiple catalytic materials is an important matter to solve environmental pollution and bacterial infection. AgBr/Ag2MoO4 nanoparticles with different molar ratios were prepared by a simple one-step precipitation method. The morphology and component of AgBr/Ag2MoO4 were analyzed by several characterizations means including XRD, XPS, and SEM et al., which showed that the loaded content of AgBr was different in different molar ratios. 1:1AgBr/Ag2MoO4 displayed better enzyme-like activity than that of the pure AgBr and Ag2MoO4. It can depict that 1:1AgBr/Ag2MoO4 possessed excellent photocatalytic activity with a 100% degradation rate of rhodamine B, and nearly 80% degradation rate of tetracycline hydrochloride. ∙O2– can be produced from the enzyme reaction system and the photocatalytic system, and ∙OH can be generated under visible light, which can successfully kill Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The sterilization rate of AgBr/Ag2MoO4 with visible light and H2O2 achieved 100% in a short time toward E. coli and S. aureus. The AgBr/Ag2MoO4 composite, as the bactericidal catalyst, with dual catalytic activities is a promising material in the field of environmental pollution and bacterial infection.

Visible Photocatalytic Properties of Ag-Ag2o/Ito Nws Fabricated by Mechanical Injection-Discharge-Oxidation Method

Visible Photocatalytic Properties of Ag-Ag2o/Ito Nws Fabricated by Mechanical Injection-Discharge-Oxidation Method

Preparation and Visible Photocatalytic Properties of N-Doped TiO2/Muscovite Nanocomposites

AbstractAs a photocatalyst with good prospects, TiO2 has the shortcomings of easy agglomeration and no catalytic performance under visible light. The purpose of the present study was to help solve these problems by employing muscovite as a carrier for N-doped TiO2 in a nanocomposite. The nanocomposites were prepared by a liquid precipitation-grinding method using muscovite as the matrix and urea as the nitrogen source. The crystal structures, chemical bonding, and micromorphology of the nanocomposites were analyzed by X-ray diffraction, infrared absorption spectrometry, and field emission scanning electron microscopy, respectively. Visible and ultraviolet (UV-Vis) light absorption of the nanocomposites was analyzed by solid ultraviolet diffuse reflectance spectroscopy. The photocatalytic effect of the nanocomposites was studied based on the degradation of rhodamine B (RhB) solution. The photocatalytic degradation product of RhB was detected by high-performance liquid chromatography-mass spectrometry, revealing that N-doping inhibits the growth of TiO2 nanoparticles. The photocatalytic performance of N-TiO2/muscovite composite nanomaterials decreased with increasing heat-treatment temperature. N-doped TiO2/muscovite nanocomposites that were heated at 400°C showed the best photocatalytic performance under visible-light illumination with an RhB degradation of 97%.

Band Gap Narrowing in Silane-Grafted ZnO Nanocrystals. A Comprehensive Study by Wide-Angle X-ray Total Scattering Methods

Zinc oxide (ZnO) is a largely investigated semiconducting nanomaterial for photocatalytic applications and is an excellent active layer candidate in photovoltaics. Among native defects, having a primary role in ZnO optoelectronic properties, the influence of nearly ubiquitous planar faults of wurtzite sequences in ultrasmall (≤5 nm) nanocrystals (NCs) remains poorly understood. Here, we present a thorough study of ZnO NCs prepared under morphological control of covalently grafted vinyltrimethoxysilane (VTMS) and exhibiting either narrowing or widening of the band gap upon NCs downsizing, depending on the NC growth rate. By using synchrotron X-ray total scattering data, atomistic models and the Debye Scattering Equation (DSE) method, complemented by spectroscopic (FTIR and UV–vis) investigations, we provide a comprehensive quantitative picture in which effects from planar defects are disentangled from those due to NC size, morphology, and lattice strain (here controlled by preferential binding of VTMS on the ZnO basal faces). When faults occur in high concentration (linear density up to 1.6 × 10⁶ cm–¹), NCs exhibit optical band gap narrowing (3.27 eV vs 3.37 eV in bulk ZnO), whereas gap widening (3.52 eV) is observed at a lower density (0.8 × 10⁶ cm–¹), at which quantum-size confinement effects prevail. Supported by photoluminescence and photodegradation experiments, surface defect passivation by VTMS, affecting visible emissions and photocatalytic properties of ZnO, is also discussed in relation to silane coating and fault-driven bandgap. This work sheds light on the complex interplay among planar defects, quantum size effect, and surface modifications in ultrasmall ZnO NCs and on the importance of advanced X-ray total scattering methods toward atomically precise control of defects in nanostructures.

Facial synthesis of K0·3WO3/Ag nanocomposites for self-cleaning energy efficient window coatings

Ag nanoparticles were uniformly attached to the surface of K0·3WO3 nanorods by the chemical reduction method. The photocatalytic performance and NIR shielding property of the nanocomposites could be regulated by changing the mass ratio of Ag to K0·3WO3. The NIR shielding ability of the nanocomposites was as high as 49.8%. The prepared K0·3WO3/Ag nanocomposites exhibited improved visible photocatalytic performance, resulting in an enhanced self-cleaning property of K0·3WO3/Ag films. The improvement in visible photocatalytic activity of the K0·3WO3/Ag nanocomposites could be attributed to the improved separation efficiency of photo-generated carriers. Furthermore, K0·3WO3/Ag coated glass can reduce the interior temperature of the heat box by 2.4 °C. Therefore, the integration of good visible light transmittance, superior visible photocatalytic self-cleaning property, and strong NIR shielding performance make K0·3WO3/Ag nanocomposites good candidates for smart window coatings.

Electrophoresis-Deposited Mesoporous Graphitic Carbon Nitride Surfaces with Efficient Bactericidal Properties

With the rise of bacterial infections and antimicrobial resistance, it is important to develop environmentally friendly functional materials and surfaces with efficient bactericidal activity. In this work, nanostructured graphitic carbon nitride (g-C3N4) surfaces were fabricated by electrophoresis deposition of mesoporous g-C3N4 materials. Efficient bactericidal performance was achieved through the synergistic biophysical interaction of bacterial cells with the nanotopographies and visible light active photocatalytic properties. The nanotopographies of g-C3N4 surfaces demonstrated a "contact-killing" efficiency of >90% against Pseudomonas aeruginosa and >80% against Staphylococcus aureus cells. The number of surviving bacteria on the surfaces further decreased remarkably upon illumination using visible light generated by a light-emitting diode lamp with an irradiation intensity of 12.4 mW cm-2. In total, the number of viable bacteria was reduced by approximately 3 orders of magnitude for P. aeruginosa and 2 orders of magnitude for S. aureus. Our experimental findings provide potential prospects for developing highly efficient photocatalytic bactericidal surfaces.

Visible light-driven photocatalytic properties of BiOI-based photocatalyst prepared by different solvents

Visible light-driven photocatalytic properties of BiOI-based photocatalyst prepared by different solvents

Visible light driven photocatalytic activity of palladium nanoparticles assisted potassium niobate microrods

KNbO3 nano/micro materials possess unique structure with fascinating multifunctional properties. Particularly, it acts as promising catalytic materials in the UV region. In order to improve the visible light catalytic activity, noble metals addition is widely employed. In this work, we report on the structural, morphological, optical and visible light active photocatalytic properties of potassium niobate (KNbO3) and 0.5 and 1.0 wt% palladium nanoparticles (Pd NPs) assisted KNbO3 microrods. X-ray diffraction and Raman spectra confirmed the formation of orthorhombic structure of KNbO3. The grain growth orientation, interplanar spacing and crystalline nature of the Pd NPs, KNbO3 and Pd NPs (1.0 wt%) assisted KNbO3 were confirmed by transmission electron microscopy. The UV–visible diffuse reflectance spectra revealed variation in the absorption edge (390–420 nm) and band gap values (3.28–3.24 eV). The photoluminescence spectra of the prepared KNbO3 samples showed visible light emission (485–544 nm) at room temperature. In the present study, a high photocatalytic dye degradation efficiency (2 times greater than that of KNbO3) and high reaction rate constant (~15 times that of KNbO3) for Pd NPs (1.0 wt%) assisted KNbO3 microrods were obtained. It is concluded that the Pd NPs (1.0 wt%) assisted KNbO3 microrods with high BET surface area (11.78 m2 g−1) leads to efficient electron-hole pair separation which enhances photocatalytic degradation of RhB dye aqueous solution under visible light region.

Formula omitted] composites: Synthesis, structural characterization, magnetic and UV–visible photocatalytic properties

In this work a series of Bi25FeO40−Fe3O4−Fe2O3 composite samples were prepared directly through the solid state reaction process using bismuth and iron based minerals. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible spectroscopy. A series of samples was prepared, varying the calcination temperature between 550∘C and 750∘C. XRD results show the formation of composites, consisting of the phases Bi25FeO40, magnetite (Fe3O4) and hematite (Fe2O3). The percentage of the Bi25FeO40 phase in the samples ranged from 60% to 85% according to the calcination temperature. SEM micrographs show that the particles making up these materials have lamellar, spherical and cylindrical structures. Magnetic measurements show that the saturation magnetization decreases with the percentage of magnetite. The coercive field (HC = 210 Oe) remains constant for all samples calcined in the temperature range between 550−700∘C. The sample calcined at 750∘C presents an atypical behavior, with an increase of 3× in the value of the coercive field and a low saturation magnetization value, Ms = 0.40 emu/g. UV–visible spectroscopy results show that samples calcined between 550−750∘C show absorption of ultraviolet and visible light. These results indicate that the powders of the composite Bi25FeO40−Fe3O4−Fe2O3 have photocatalytic properties which can be easily recycled by magnetic separation.

Cu(ii)/Ni(ii)-organic frameworks constructed from the homometallic clusters by 5-(2-carboxyphenoxy)isophthalic acid and N-ligand: synthesis, structures and visible light-driven photocatalytic properties.

Four new complexes, namely, Cu2(O-cpia)(btb)0.5·(OH) (1), Cu3(O-cpia)2(bpy)2 (2), [Ni2(O-cpia)(phen)·(OH)·H2O]·2H2O (3) and [Ni3(O-cpia)2(bpy)3·2H2O]·2H2O (4) (O-cpia = 5-(2-carboxyphenoxy)isophthalic acid, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, bpy = 4,4′-bipyridine) were successfully isolated under hydrothermal conditions. The four complexes exhibit different architectures constructed from different homometallic clusters varying from mononuclear, binuclear to tetranuclear metal(ii) polyhedra as Second Building Blocks (SBUs). 1 features a 3D framework constructed from the tetranuclear clusters [Cu4(μ3-OH)2] as SBUs, linked with Cu(1)O4N and Cu(2)O5 polyhedra by O-cpia/btb mixed linkers. 2 also exhibits a 3D structure based on trinuclear clusters [Cu3(COO)4] SBUs, bridged with Cu(1)O3N2 and Cu(2)O4 polyhedra via O-cpia/bpy mixed ligands. 3 shows a 2D network consisting of tetranuclear clusters [Ni4(μ3-OH)2] SBUs, which are bridged with Ni(1)O4N2 and Ni(2)O6 through O-cpia ligands. It is worth noting that 4, with a 3D structure, is generated from the binuclear clusters [Ni2(COO)4] (Ni(1)O4N) and mononuclear metal Ni(2) cores (Ni(2)O4N2) as SBUs, and bridged by O-cpia/bpy mixed ligands. Meanwhile, the degradation of dyes (RhB) by the complexes under visible light irradiation was studied. 1–4 are semiconducting in nature, with Eg of 1.30 eV (1), 1.78 eV (2), 2.85 eV (3) and 2.14 eV (4). Cu(ii) complexes 1 and 2 are highly efficient photocatalysts for the degradation of RhB under visible light irradiation.