Photodegradation Properties Research Articles

Increasing the photocatalytic and fungicide activities of Ag3PO4 microcrystals under visible-light irradiation

The present study reports for the first time the performance of silver phosphate (Ag3PO4) microcrystals as photocatalyst (degradation of Rodamine B-RhB) and antifungal agent (against Candida albicans–C. albicans) under visible-light irradiation (455 nm). Ag3PO4 microcrystals were synthesized by a simple co-precipitation (CP) method at room temperature. The structural and electronic properties of the as-synthetized Ag3PO4 have been investigated before and after 4 cycles of RhB degradation under visible light using X-ray diffraction (XRD), micro-Raman spectroscopy, UV–Vis spectrophotometer and field emission scanning electron microscopy (FE-SEM) images. The antifungal activity was analyzed in planktonic cells and 48h-biofilm of C. albicans by colony forming units (CFU) counting, confocal laser and FE-SE microscopies. Statistical analysis was carried out using SPSS software. Morphological and structural modifications of Ag3PO4 were observed upon recycling. After 4 recycles, the material maintained its photodegradation property; an eightfold increase in the efficiency of Ag3PO4 was observed in planktonic cells and a two fold increase in biofilm when irradiated under visible light. Thus, higher antifungal effectiveness against C. albicans was obtained when associated with visible-light irradiation.

Comparison in UV-induced photodegradation properties of dissolved organic matters with different origins

Dissolved organic matter (DOM) is ubiquitous in aquatic environments, whose behaviors and fate are highly related to the chemical compositions and size distribution. In this study, the UV-induced photodegradation properties of DOMs with different origins (i.e., macrophyte- and algae-derived) were investigated using absorption and fluorescence spectroscopy as well as flow field-flow fractionation (FlFFF). Results showed that, irrespective of DOM origins, the chromophoric components could be more effectively photo-degraded than the non-chromophoric ones. Though the two DOMs were characterized with similar fluorophores, the photodegradation properties showed obvious heterogeneities in DOM origins and molecular weights (MWs). Compared to macrophyte-derived DOM (MDOM), the algae-derived DOM (ADOM) exhibited a higher degradation rate and efficiency due to the abundance of labile components like newborn protein-like substances. The FlFFF results revealed a high photo-preferability of 100 kDa-0.45 μm protein-like MDOM and same photo-sensitivity of the size-fractionated humic-like moieties, testifying the reduction of molecular sizes during the photodegradation. However, the increase in relative percentage for 100 kDa-0.45 μm protein-like components and 5–15 kDa humic-like moieties implied a possible enhancement of molecular sizes for ADOM during the early period (i.e., the first hour) of photodegradation. This study provides new insights into the origin-related heterogeneities in compositions and size distribution for DOM transformation.

Synthesis And CharacterizationOf Eu2wo6 By Hydrothermal Method

Metal oxide nanocomposites play an important role in nanoworld. Materials with photo catalytic properties are widely studied because of their numerous applications. These applications include solar cell application and other photodegradation properties too. This photodegradation property include the waste water management too. This paper reports the synthesis and characterization of europium tungstate nanocomposites and explain their photocatalytic applications. The synthesis is carried out with hydrothermal method. XRD, FTIR, SEM and PL studies have been used to study the structural and morphological and optical studies. From these characterizations the sample is studied and further studied for its future uses.

Fly Ash Waste Recycling by Pt/TiO2 Incorporation for Industrial Dye Removal.

New materials are obtained by transforming fly ash wastes into a valuable composite, with tandem adsorption and photodegradation properties. Mild hydrothermal synthesis, from titanium dioxide, platinum nanoparticles and zeolite materials obtained from a waste, fly ash, as support, was involved in the composite preparation. The platinum nanoparticles extended the photocatalytic activity of the composite in visible range (Eg = 2.1 eV). The efficiency of tandem adsorption and photocatalytic activity of the new composite were determined to be 25% for Bemacid Blau and 43.89% for Bemacid Rot after 360 min, the irradiation time. The addition of H2O2 improves the process efficiency up to 80.70% and 93.43%, respectively. The Pt nanoparticle (PtNP) contribution led to the band gap energy change to Vis light (400 nm), thus suggesting the possibility of photocatalysis under the action of a fraction of natural light.

Two new hybrids built upon Wells-Dawson polyoxoanions and copper–ethylendiamine coordination cations

Two new organic-inorganic hybrid copper-substituted supramolecular polyoxotungstates, namely H[Cu(en)2(H2O)]2[Cu(en)2][P2W18O62]Cl·7H2O (1) and H3[Cu(en)2(H2O)]2[Cu(en)2]1.5[CuP2W17O62]·39H2O (2) (en = 1,2-ethylenediamine), have been prepared via a simple one-pot hydrothermal synthesis method and characterized by elemental analyses, IR spectra, XRD, thermogravimetric (TG) analyses and X-ray single-crystal diffraction. X-ray structural analysis reveals that both of them are containing Wells-Dawson polyoxoanions and copper-en cations. With the rare connection modes of WOCu and WOW linkers, compound 1 further displays an organic-inorganic hybrid 1D ladder-like mono-chain whereas 2 is in a stable configuration of an interesting double-chain. Subsequently, the intriguing 2D double-layer for 1 and 3D supramolecular architecture for 2 were fabricated through hydrogen bonding among the [P2W18O62]6− fragments and the copper counter-cations, respectively. It is worthy to note that the connection modes and the packing networks of the title hybrid complexes are rare. In addition, the photodegradation properties of the title complexes for methylene blue under UV irradiation have been investigated in detail. This work guides us to design and synthesize more attractive hybrid materials for extensively potential applications.

Enhanced photocatalytic properties of ZnO/Al2O3 nanorod heterostructure

The separation and transfer of the photoinduced charge carriers are essential for the high-efficient photocatalytic materials. Heterostructures which compose of several semiconductors can take advantage of energy level difference to improve photocatalytic properties. However, the fabrication of the related heterostructures normally adopts the physical vapor deposition method, such as atomic layer deposition, hindering the mass production of photocatalytic materials. In this work, ZnO nanorod arrays and ZnO/Al2O3 heterostructure were prepared on Si (100) substrates by a cost-efficient method which combines the hydrothermal and photochemical techniques. Microstructure and surface composition analysis on the heterostructure confirm the synthesis of the ZnO/Al2O3 core–shell heterostructure. According to the ultraviolet (UV)–visible diffuse reflectance spectroscopy, the band gap of the ZnO/Al2O3 heterostructure can be estimated to be 3.25 eV, which is larger than that of pure ZnO nanorod arrays. Moreover, the heterostructure exhibits an obviously enhanced photocatalytic property for photodegradation of methyl orange under UV-irradiation. The energy band diagram of heterostructure shows that the improvement of photocatalytic property can be ascribed to the increase in the electron-hole pair separation rate. This work provides a simple method to fabricate nanoscale semiconductor heterostructures for photocatalytic applications.

Solid-state synthesis and photodegradation property of anatase TiO2 micro-nanopowder by sodium replacement

To investigate the effect of the doping of alkali metal on the band structure and photocatalytic property of titanium oxide crystals, the mesoporous sodium doped titanium dioxide (Na–TiO2) micro-nano powder was synthesized by the solid-state reaction (SSR) method, and characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectrum (UV–Vis), scanning electron microscopy/energy dispersive spectroscopy, X-ray photoelectron spectroscopy (XPS), N2 desorption-adsorption. Meanwhile, the UV-degradation properties of Na–TiO2 and P25–TiO2 powder materials for hydroquinone (HQ) were studied. The results show that sodium ions with the low charge density entered into the (004) crystal place of anatase TiO2, producing the dislocation defects of TiO2 crystal structure. The spherical-like morphology micro-nanopowder with a size of 50–500 nm, sodium content of 3.36(wt%), the bandgap width of 3.08 eV, BET surface area of 111.52 m2/g, the pore size distribution center of 4.72 nm, the pore volume of 0.32 cm3/g are obtained, respectively. Within 60min and 25 °C, the UV-degradation rate (97.32%) of mesoporous Na–TiO2 powders for hydroquinone is 2.62 times for that (37.08%) of P25–TiO2 powder. It is mainly derived from the increase of dislocation density of Na–TiO2 powder, and the results of the synergistic photocatalystic degradation of hydroxyl radicals and superoxide radicals. And the photocatalytic efficiency is associated with pH value, photocatalyst dosage, concentration of HQ, irradiation time and stability.

Application of superhydrophobic ZnO rod composites with environmentally-friendly and photodegradation properties in water environment treatment

The treatment of water pollution is faced with a severe postgraduate examination, which shows that pollutants of different properties, such as water-soluble and non-water-soluble pollutants, exist at the same time. In this paper, superhydrophobic S-ZnO/BiOBr cotton (SH cotton) is designed, which has the ability to degrade water-soluble pollutants through light response and the performance of selective removal of organic solvents. The water contact angle of droplets on the surface of the material reached 162°, on which toluene spread rapidly. When applied to an environment with water-soluble pollutants, the material showed an excellent cyclic degradation ability, and the degradation efficiency of 5 cycles’ was higher than 98.4%. Importantly, the 3 cycles of outdoor degradation efficiency was higher than 92.1% under the actual working conditions. The VB positions of the S-ZnO and BiOBr were calculated to be 2.89 eV and 2.96 eV, respectively. The CB positions of the S-ZnO and BiOBr were calculated to be −0.31 eV and 0.38 eV, respectively.

Enhanced photocatalytic activity of Ce-doped β-Ga2O3 nanofiber fabricated by electrospinning method

Herein, β-Ga2O3 photocatalyst was designed to improve the photocatalytic activity. Therefore, two strategies were employed: chemical modification by Ce doping and morphological control by formation of nanofibers. Therefore, Ce-doped β-Ga2O3 nanofibers were successfully synthesized using a sol–gel derived electrospinning. These synthesized nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis spectroscopy. The SEM and XRD results indicated that Ce doping slightly influence on the morphology and crystal structure of nanofibers. In addition, the UV–vis transmittance spectra result indicates that the bandgap energy of Ce-doped β-Ga2O3 nanofibers was significantly reduced from 4.92 eV to 4.54 eV. In specific, the 0.7 mol % Ce-doped β-Ga2O3 nanofibers exhibits the lowest optical band gap energy as 4.54 eV. Moreover, the photodegradation properties of β-Ga2O3 nanofibers were evaluated by using the Methylene Blue (MB) under UV light. Interestingly, the β-Ga2O3 nanofibers doped by 0.7 mol% cerium atom exhibited the highest photocatalytic activity than other synthesized nanofibers. Consequently, from the overall characterizations, it was found that improved activity of photocatalytic degradation will be attributed to the narrow optical bandgap energy and reduced recombination rate arising from the cerium doping.

Synthesis of SiO2/CoFe2O4 Nanoparticles Doped CMC: Exploring the Morphology and Optical Characteristics for Photodegradation of Organic Dyes

The present work deals with enhanced structural and optical studies of silicon oxide (SiO2)–cobalt ferrite (CoFe2O4) nanoparticles doped carboxymethyl cellulose (CMC) to use in a photo-degradation of organic dyes pollutants for first time with low cost and excellent activity. The structural characteristics included of FTIR analysis and images microscope. The optical characteristics were measured using a VU spectrophotometer which included absorption spectra recording then optical parameters calculations. The optical characteristics results indicated to the absorbance of CMC increased about 93.1% when reached the SiO2–CoFe2O4 NPs content to 4.5 wt% at λ = 500 nm. The energy band gap of polymer decreased from 5.2 to 4.8 eV. The optical parameters of CMC enhanced with rising of the SiO2-CoFe2O4NPs ratio. The photo-degradation property was investigated under solar light for methyl orange (MO). The results showed that the photo-degradation of CMC was enhanced from 13.99 to 45.73% by adding of SiO2–CoFe2O4 NPs. Finally, the results indicated that the CMC/SiO2–CoFe2O4 nanocomposites have good photo-degradation for organic pollutants with low concentration of nanoparticles, short irradiation time and inexpensive.

Construction of porous-hydrangea BiOBr/BiOI n-n heterojunction with enhanced photodegradation of tetracycline hydrochloride under visible light

Porous-hydrangea x%BiOBr/BiOI n-n heterojunction with ordered morphology was successfully prepared through a simple solvothermal process using Bi(NO3)3·5H2O, KBr, BiOI, and ethylene glycol as the precursors. The prepared x%BiOBr/BiOI (x = 2, 5, 10, 15 mol ratio) n-n heterojunctions exhibit enhanced photodegradation properties during treatment of tetracycline hydrochloride (TC-HCl) under visible light irradiation. The highest efficiency at optimized x = 5 is 1.3-, 1.7- and 1.3-fold higher than that of the pristine BiOI, BiOBr, and commercial titanium dioxide (P25), respectively. The improved photocatalytic performance was assigned to the optimized charge-separation properties of n-n heterojunction. However, over-loading of BiOBr upon BiOI may restrain the access of light to BiOI, which could limit the light absorption. The active species have been investigated by trapping experiments and it was found that holes (h+) and superoxide radicals (∙O2-) were mainly responsible for the photodegradation of TC-HCl. Additionally, the structure and activity relationship were systemically investigated, and the formation of n-n heterojunction is discussed accordingly. The photodegradation of TC-HCl is proved to be a complete mineralization process and the reaction mechanism is also proposed.

A Co(II) coordination polymer derived from pentaerythritol as an efficient photocatalyst for the degradation of organic dyes

In this work, a one-dimensional (1-D) cobalt(II)-based coordination polymer, [Co(SCN)2(peol)]n (H4peol = pentaerythritol and NCS− = thiocyanate), was synthesized under solvothermal conditions. Elemental, FTIR, UV–Visible, PXRD, TGA, magnetic and single-crystal X-ray diffraction analyses characterized the polymer (Co-CP). Further, scanning electron microscopy (SEM) was employed to understand the outer morphology ofCo-CP. The material importance of Co-CP was investigated by studying its magnetic and photodegradation properties. Variable temperature magnetic data of Co-CPunveiled the existence of strong antiferromagnetic interactions coupled with anisotropy in the system, with parameters C = 2.71 cm3 K mol−1 and θ = −6.43 K. Furthermore, Co-CPhas been effectively used as a photocatalyst for the degradation of organic pollutants methylene blue (MB) and rhodamine-B (Rh-B) in the aqueous phase, with good recyclability. Co-CPexhibits unusual photocatalytic activity toward the degradation of the solid organic dyes. Based on a scavenging investigation, a plausible mechanism for the photocatalytic activity has also been proposed.

One–pot synthesis of Bi4V2O11/BiVO4 heterostructure with enhanced photocatalytic activity for dye degradation

Photocatalytic technology is one promise strategy for organic pollutant elimination from aqueous environment. In this work, a novel and facile one–pot hydrothermal method was developed to fabricate type II Bi4V2O11/BiVO4 heterostructure basing on the adjusting of ethylene glycol (EG) usage. In hydrothermal procedure, the addition of EG promoted the formation of Bi–O–Bi structure for nucleation of Bi4V2O11 and m–BiVO4. And m–BiVO4 took the lead in growing, subsequently Bi4V2O11 bred on (112) m–BiVO4 to form intimate contract between these two semiconductors. In comparison with pure BiVO4, Bi4V2O11/BiVO4 exhibited more excellent photocatalytic activity toward RhB. And a total of 91.1% RhB was photodegraded by optimal Bi4V2O11/BiVO4 within 90 min. The enhanced photocatalytic performance of Bi4V2O11/BiVO4 was mainly ascribed to the efficient spatial transfer of charge carrier in heterostructure. Besides, the formation mechanisms of heterostructure and photodegradation reaction for RhB were proposed based on the morphology observation and quenching experiment, respectively. Furthermore, it found that the photodegradation property of Bi4V2O11/BiVO4 toward RhB was influenced by the syntheticaction of crystal facet, overlapping extent of atomic orbitals, content of Bi4V2O11 and specific surface area.

Self-assembly and boosted photodegradation properties of perylene diimide via different solvents

Through different solvents, the self-assembly process of monomer PDI was studied. The rapid separation and transfer of the photogenerated carriers and π–π interaction between self-assembled PDI together boost the photocatalytic degradation reaction.

Photodegradation Properties of Earlywood and Latewood Spruce Timber Surfaces

Spruce (Picea abies Karst.) samples were irradiated using an ultraviolet light emitter mercury vapour lamp. The examined specimen surfaces contained earlywood or latewood to determine the photodegradation properties of these two tissue types. The generated chemical changes were monitored by diffuse reflectance Fourier transformed infrared spectroscopy. The difference spectrum method was used to present absorption changes. The earlywood suffered considerably greater degradation than the latewood during the UV irradiation. Most of the lignin molecules in the examined surface layer degraded during the first 11 days of UV irradiation for both earlywood and latewood. Results demonstrated that two types of unconjugated carbonyls absorbing at 1705 and 1764 cm–1 wavenumbers were created during the photodegradation. Time dependence of the absorption changes showed correlation between the guaiacyl lignin degradation and the generation of unconjugated carbonyl group absorbing at 1764 cm–1 wavenumber.

TiO2 grafted activated carbon elaboration by milling: Composition effect on sorption and photocatalytic properties

Activated-Carbon/Titania composites (AC/TiO2) is a relevant option to gather the dual adsorption/photodegradation property within a single material. This work aimed to investigate the composition influence on the adsorption and photodegradation properties of AC/TiO2 composites against caffeine. TiO2 grafted AC powders covering the whole composition scale were synthesized by a one-step mechanical milling process. This original simple elaboration route led to the obtention of powders which particles size and composition were homogeneous and well controlled. When the adsorbent mass ratio varied in the range 0.01−0.75, the adsorption properties, i.e. apparent kinetic and maximum adsorption capacity of the composites increased respectively by 1 and 2-log. At the opposite, the photo-oxidation rate decreased significantly when the adsorbent ratio increased. The simple elaboration route explored produces flexible AC/TiO2 composites with adjustable properties that can easily be managed to meet the requirements of different target applications.

Robust ferromagnetic and fast sunlight photocatalytic properties of nanocrystalline SnO2: Co/Cu codoping

Spintronics technology and organic pollutants removing have pushed the researchers to explore strong ferromagnetic and sunlight photocatalytic properties in oxide semiconductors. Herein, the role of Co monodoping and Co/Cu codoping on room temperature ferromagnetism and sunlight photodegradation properties of SnO2 nanoparticles was investigated. Series compositions composed of SnO2, Sn0.97Co0.03O2, Sn0.94Co0.03Cu0.03O2 and Sn0.91Co0.03Cu0.06O2 nanopowders were synthesized by coprecipitation method. The synthesized powders showed a single phase nature of tetragonal rutile structure with no sign for any impurities or secondary phases. SEM images demonstrate that the grains of the pure SnO2 consist of large aggregates which are transformed to fine particles due to Co/Cu codoping. The UV band gap of SnO2 was strongly engineered to visible light responses due to incorporation of Co/Cu ions. Integration between Co (magnetic) and Cu (nonmagnetic) ions induces clear room temperature ferromagnetism in SnO2. The exchange interactions between localized spins of Co3+-Co3+ Co3+-Cu2+ and Cu2+-Cu2+ via high-density doping-induced defects (oxygen vacancies) lead to strong ferromagnetic ordering. Sn0.94Co0.03Cu0.03O2 and Sn0.91Co0.03Cu0.06O2 nanopowders revealed a fast sunlight photocatalytic performance (~100%) for Congo red (CR), malachite green (MG) and methylene blue (MB) dyes. The partial substitution of Sn4+ by Co3+ and Cu2+ are found to augment the wavelengths absorbed, amount of oxygen vacancies and life time of the photo-generated electron hole pairs, resulting in better photocatalytic activity of Sn0.94Co0.03Cu0.03O2 and Sn0.91Co0.03Cu0.06O2 nanopowders in comparison with undoped and Co monodoped SnO2.

Introducing of a novel polyoxometalate-based organic–inorganic hybrid: Insights into electochemical property-photoactivity relationship

Herein a new visible photocatalyst by TiO2 and nanosized polyoxometalate-based inorganic–organic hybrid material, NaH8[PDA]3[PW9Co3O37]·13H2O (PDA = p-phenylenediamine) (PDA-Co3W9), were successfully synthesized by an new straight forward method. Prepared powder was characterized by, FT-IR, PL, XRD, UV–Vis, DRS, and FE-SEM techniques. The FE-SEM images of the nanocomposite showed spherical-like nanoparticles with the mean size particle of 20–30 nm. The resulting materials were evaluated in the photodegradation of dye, using different light illuminations. Under optimized conditions, 100% dye removal was obtained. Tauc plots showed different bandgaps for different PDA-Co3W9 weight percentages on TiO2 (PDA-Co3W9/TiO2). The amplified photodegradation properties would be owing to the synergetic effect of PDA, Co3W9 and TiO2 as components. Optimization of conditions were studied by response surface methodology. Also, relationship between effective factors and electrochemical properties of photocatalyst was investigated by Mott-Schotcky, Nyqist, and Bode plots. Vfb, ND, and lifetimes of photogenerated electron–hole separation were calculated and compared with each other according to the photoactivity of different kinds of the catalysts. Specific capacitance of the best photocatalyst was calculated. Mechanism of photodegradation and reusability of the catalyst were also investigated.

Rapid synthesis of triple-layered cylindrical ZnO@SiO2@Ag core-shell nanostructures for photocatalytic applications

Core-shell nanocomposites are promising materials in the degradation of harmful chemicals released from industries/factories. In this work, ZnO@SiO2@Ag triple–layered core-shell nanocomposites synthesized by a facile chemical precipitation route at 400 °C using as-prepared ZnO@SiO2 samples as a precursor were investigated for photocatalytic application. The synthesized ZnO@SiO2 and ZnO@SiO2@Ag samples were characterized using XRD, SEM, TEM, XPS, and UV-Vis spectrometer. The XRD studies showed that both nanocomposites possess the hexagonal wurtzite crystalline phase of the core ZnO. Moreover, the average crystallite sizes of ZnO@SiO2@Ag composites determined from the XRD spectra were found to be 27.98 nm and 30.56 nm for reaction times of 4 h and 12 h, respectively. The SEM and TEM analyses indicate that the morphologies of the samples were rod-shaped. The UV-Vis spectroscopy showed that the ZnO@SiO2@Ag nanoparticles exhibited maximum absorbance peak at 363 nm with a calculated band gap energy of 3.13 eV. In addition, the photocatalytic activity and stability were analyzed by a photoreduction method using the photodegradation property of organic methylene blue under UV-Vis light irradiation. Compared with the “bare” ZnO@SiO2 samples, the stability and photocatalytic performance of the Ag coated ZnO@SiO2@Ag nanocomposites were highly enhanced, and the reasons for the enhancement are discussed.

Enhanced Photocatalytic Degradation of Organic Pollutants and Anticorrosion of Mild Steel by Vanadium Modified Titanate Nanotubes (X%V‐TiNTs)

AbstractThe present work aims to study the anticorrosion and the photodegradation properties of titanate nanotubes (TiNTs) and vanadium doped‐titanate nanotubes (V‐TiNTs). Moreover, this article seeks to investigate the effect of doping TiNTs by vanadium species at different amount (2, 5 and 10 wt %). The raw materials (i.e:TiO2 and V2O5‐TiO2) are obtained by a sol gel process, while the hydrothermal treatment is chosen to achieve the hollow structure. The structural evolutions and morphological characteristics of materials have performed using various techniques such as: Scanning Electron Microscopy and Energy Dispersive X‐ray (MEB/EDS), X‐ray diffraction (XRD), UV‐Visible in Reflection Diffuse spectroscopy (RD/UV‐Vis) and Fourier Transform InfraRed spectroscopy (FTIR) analysis. However, the anticorrosion properties of the synthesized nanotubes are evaluated on mild steel corrosion in 1 N HCl using a weight loss method. All materials showed a potential inhibitor effect (up to 90 %) depending on the vanadium percentage and the inhibitor concentration. The photodegradation activity of the prepared materials is evaluated in the photodegradation of two organic pollutants: Methylene Blue (MB) and Malachite Green (MG) under UV‐Visible irradiation. The obtained results underlined the improvement of photocatalytic activity of TiNTs by vanadium species. A conversion rate up to 96 % is achieved at reduced time. Therefore, the prepared materials could be suitable for the anticorrosion of mild steel and the photodegradation of organic pollutants.