Photodegradation Properties Research Articles

Synergistic impact of lanthanum and cerium co-doping ZnO for improved photocatalytic rhodamine B degradation efficiency under UV light

In this study, the influence of different La and Ce co-doping amounts on the structural, morphological, optical, and photodegradation properties of ZnO nanostructures was evaluated. Zn1–2xLaxCexO nanoparticles (NPs) were prepared using sol-gel auto-ignition process, where x = 0.00 (pure ZnO), 0.01 (LC1), 0.03 (LC3), and 0.05 (LC5). The X-ray diffraction (XRD) and Raman results revealed that the prepared ZnO NPs crystallize in the hexagonal wurtzite structure. The size of crystallites is affected by the increment of La and Ce and it decreased from 24.29 nm to 10.40 nm with the increase in the concentration of La and Ce. Transmission electron microscopy (TEM) showed that the samples exhibit an irregular distribution of NPs with a dominant spherical shape morphology. The simultaneous incorporation of La and Ce in ZnO NPs led to a slight variation in the absorption edge and a slight shift in the values of the band gap energy from 3.20 to 3.24 eV. Furthermore, a reduction in the recombination rate of photogenerated charge carriers and the creation of fewer additional defects upon the appropriate insertion of Ce and La ions are highlighted by the analysis of photoluminescence spectra, Nyquist plots, and transient photocurrent measurements. The photocatalytic activity of samples was evaluated against rhodamine B organic dye under UV light irradiation. The analysis showed that LC1 sample exhibited superior photocatalytic performance with 99.1 % degradation efficiency and a degradation rate constant of 0.0762 min-1. This enhancement has been ascribed to the surface defects and the optimized crystallite size achieved, which help to generate reactive entities such as •OH and O2•− in addition to the great role of holes (h+) and impede the recombination of charge carriers e-/h+.

WO3/g-C3N4 synergistic photocatalysts for degradation and H2 production

WO3/g-C3N4 composite samples were prepared using hydrothermal method. The photocatalytic activity was assessed by photocatalytic degradation and H2 production experiments. The experimental findings suggested that WO3/g-C3N4 (1:1) degraded 95 % of the MB in 50 min and produced H2 at a rate of 712.38 μmol⸱g−1⸱h−1, which was 10 times the H2 production rate of g-C3N4. The improved photodegradation and H2 production properties could be due to the increased specific surface area, improved photogenerated carrier separation efficiency, broadened visible light absorption range, increased photocurrent density, and reduced charge transfer resistance. Meanwhile, the synergistic effect of WO3 and g-C3N4 realizes the bifunctionality of degradation and H2 production. In addition, possible reaction mechanisms of WO3/g-C3N4 composite samples in photodegradation and H2 production were proposed.

Construction S-scheme Bi4O5Br2/BiOI composite for accelerated charge separation and enhanced photocatalytic degradation and antibacterial performance

Photocatalytic technology is an effective solution to environmental pollution problems. The development of efficient photocatalysts is of great practical significance for environmental remediation. In this study, Bi4O5Br2/BiOI S-scheme heterojunction was successfully prepared by solvothermal and facile room-temperature deposition methods. The optimum sample 30 % Bi4O5Br2/BiOI (BrI-30) could degrade 90.5 % methyl orange (MO) in 60 min and 71.6 % tetracycline (TC) in 90 min under LED light irradiation, and it could completely inactivate Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in 30 min. Bi4O5Br2/BiOI composites exhibited efficient degradation and antimicrobial activities, which were principally ascribed to the formation of the heterojunction interface between Bi4O5Br2 and BiOI facilitating the migration of photo-generated carriers. The effects of different factors on the photo-degradation properties were systematically investigated. In addition, mass spectrometry (MS) has been accustomed to detecting the intermediates formed when TC degraded and possible pathways for TC degradation were proposed. Eventually, based on energy-band analysis, the mechanism of removing pollutants and inactivating bacteria in Bi4O5Br2/BiOI composites was proposed. This study provides a novel solution for treating organic pollutants and bacteria in water bodies, which has practical applications in environmental remediation.

Giant Photodegradation Rate Enabled by Vertically Grown 1T/2H MoS2 Catalyst on Top of Silver Nanoparticles

The exaltation of the photodegradation performance of dichalcogenide MoS2 grown on top of silver nanoparticles (Ag‐NPs) is reported on. The fabricated MoS2 nanosheets nucleate vertically from Ag‐NPs seeds, enabling the growth of both metallic and semiconductor phases 1T/2H‐MoS2. Findings reveal remarkable enhancement of the Raman scattering and an exceptional broadband optical absorption attributed to plasmonic effects induced by the presence of both metallic 1T‐MoS2 and Ag‐NPS at 2H‐MoS2 interfaces. To leverage this effect, photodegradation tests are conducted to remove methyl orange pollutant. Notably, results reveal a significant increase in photodegradation efficiency and rate constant, reaching up to 120% and 550% over pristine 2H‐MoS2, respectively. This finding underscores the role of Ag‐NPs and 1T‐MoS2 tandem to unlock the superior photodegradation properties of vertically aligned 2H‐MoS2 toward methyl orange, paving the way for the development of dichalcogenide‐based hybrid photocatalyst for wastewater treatment and environmental remediation.

HYDROTHERMALLY DEVELOPED TITANIUM DIOXIDE AND EUROPIUM-DOPED COMPOSITE MATERIALS FOR PHOTODEGRADATION APPLICATIONS

Metal oxide nanocomposites are a critical element in nanoscale technology. Because of their many uses, a great deal of study has involved photocatalytic materials. These photocatalytic degradation characteristics also included applications like solar-cell applications. Waste­water management was included in the photodegradation property. The following study explored the development of europium tungstate nanocomposites with titanium dioxide and how they can be used in photocatalytic applications. The synthesis was conducted using the hydrothermal method and is characterized by Fourier-transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy. Application experiments were conducted using four distinct dyes, namely methyl orange, methylene blue, congo red and methyl red. The photodegradation experiments were conducted using visible light emitted by a tungsten-filament lamp. Methylene blue and methyl orange degraded to 20 % and 35 % after 1 hour respectively. After 90 min, the degradation of methylene blue went down to 15 % and congo red degraded down to 9 %. With the experiment conducted, the sample showed that it had a relatively higher photodegradation property with the dyes used. The results show that the compound had better reaction with these dyes, with a degradation down to 10 %.

Insight into the photodegradation of methylisothiazolinone and benzoisothiazolinone in aquatic environments

Methylisothiazolinone (MIT) and Benzisothiazolinone (BIT) are two widely used non-oxidizing biocides of isothiazolinones. Their production and usage volume have sharply increased since the pandemic of COVID-19, inevitably leading to more release into water environment. However, their photochemical behaviors in water environment are still unclear. Therefore, this study investigated photodegradation properties of MIT and BIT in natural water under simulated sunlight. The results demonstrated that direct photolysis was mainly responsible for their photodegradation which occurred through their excited singlet states rather than triplet states. The quantum yields of MIT and BIT photodegradation were 11 - 13.6 × 10−4 and 2.43 - 5.79 × 10−4, respectively. pH had almost no effect on the photodegradation of MIT, while the photodegradation of BIT was significantly promoted under alkaline condition due to abundance of BIT in its deprotonated form (BIT-N−). Cl−, NO3− and dissolved organic matter (DOM) in natural water inhibited the photodegradation of both MIT and BIT, with the light screening effect of DOM being the most significantly inhibitory factor. The addition of other isothiazolinones, which possibly coexisted with MIT and BIT in actual condition, slightly inhibited the photodegradation of MIT and BIT. The estimated half-life under natural sunlight at a 30°N latitude was estimated to be approximately 1.1 days. The photodegradation pathways of MIT and BIT are similar, primarily initiated from the ring-opening at the N-S bond, with Frontier electron densities (FED) calculations suggesting the likelihood of oxidation and ·OH addition reactions at the O, N, and S sites. While the photodegradation products exhibited significantly reduced acute toxicity compared to their parent compounds, they nonetheless posed substantial chronic toxicity. These insights are vital for assessing the ecological impacts of MIT and BIT in aquatic environments.

High performance metal halide Cu–Ag–I–Cl alloys for photodegradation

Ag-based semiconductors have stimulated great interest as promising photocatalysts due to their high optical absorption. While exhibiting excellent photocatalytic activity, they suffer from poor stability. On the other hand, CuI is an air-stable material with excellent optical absorption and bandgap of 3 eV, and can be an alternative to the photosensitive and expensive Ag halides for photocatalytic applications. In this study, alloying strategy was used to prepare Cu–Ag–I–Cl alloys with wide compositions Cu1-xAgxI1-xClx (0 ≤ x ≤ 1), and their structural, optical and photodegradation properties were evaluated. X-ray diffractionmeasurements revealed the single-phase solid solution formation with systematic phase transition, from γ-phase to β-phase upon alloying of AgCl into CuI, infer the coordination effects associated with atomic size. The optical band gap has shown significant modifications with alloying, with minima of 2.65 eV at x = 0.25. The Malachite green dye photodegradation under UV-light exposure was evaluated for various Cu1-xAgxI1-xClx alloy samples at different solution pH. Compared to pure CuI, alloying of AgCl into CuI has significantly enhanced photodegradation, with the highest degradation efficiency of 88 % at 40 minutes and pH of 3 for x = 0.25. Further, the Cu1-xAgxI1-xClx alloy has demonstrated significant photodegradation (54 % at 100 minutes) of ofloxacin, indicating that they can be potential for other stubborn organic pollutants removal from wastewater. Through quenching experiments, the O2•− reactive oxygen species were identified as primarily responsible for the photodegradation in this system. The origin of high photodegradation performance in Cu–Ag–I–Cl alloy system is attributed to the configurational entropy and surface plasmon resonance of nonstoichiometric Ag on the surface. The significant efficiency achieved with an alloying strategy involving functional halides could open a novel path to develop photocatalysts alternative to complex heterogeneous and multicomponent methods.

Synthesis, crystal structure, photoelectric and photocatalytic properties of (C4H14N2)0.5Cu2SbSe3 with a two-dimensional layered structure

A selenoantimonate (C4H14N2)0.5Cu2SbSe3 (1) (C4H12N2 = 1, 4-butanediamine) was synthesized by solvothermal synthesis using 1, 4-butanediamine as solvent. By single-crystal X-ray diffraction, compound 1 has a two-dimensional (2-D) layered structure composed of a protonated organic amine [(C4H14N2)0.5]+ and an anionic layer [Cu2SbSe3]- containing the 6-membered rings (6-MR) Cu2SbSe3 and the 10-membered rings (10-MR) Cu3Sb2Se5. Solid-state UV-diffuse reflectance analysis showed that 1 has a band gap value of 1.85 eV, indicating its potential semiconducting properties. This paper studied the photodegradation properties of selenoantimonate containing the transition metal Cu for the first time, and found that its degradation rate methylene blue (MB) was 68.5 %. In addition, a series of characterizations were also performed.

Revolutionizing photocatalysis: Synergistic enhancement of structural, optical, and photodegradation properties in Be-doped V2O5 nanoparticles for efficient methylene blue removal

This study focuses on the investigation of beryllium (Be) doping in V2O5 nanoparticles and the coordinated effects it has on the structural, optical, and photocatalytic characteristics of the material. XRD analysis reveals modifications in the orthorhombic structure upon Be doping, decreasing crystallite size (68.7–46.6 nm), and increased dislocation line density. Optimizing charge carrier mobility and separation is crucial for improving photocatalytic activity, and this is achieved via these adjustments. Raman spectra indicated increased crystallinity with Be doping. The optical analysis demonstrated an adjustable band gap (2.47–2.60 eV) and reduced refractive index (2.49–2.45), that enhance light absorption efficiency. More importantly, the study shows that Be-doped V2O5 nanoparticles have better photocatalytic activity for the breakdown of methylene blue, indicating its potential for environmentally friendly remediation. The present work contributes to the advancement of customized doping approaches for maximizing V2O5 functioning across a range of applications by clarifying the complex impacts of Be doping.

Nanoarchitectonics of high-performance TiO2/C composites from Ti4+-coordination crosslinked Pickering emulsion gel

TiO2/C composites have been developed from polysaccharide-Ti4+ complex to photodegrade methylene blue (MB) but with low BET surface area. The present study aimed to obtain TiO2/C composite materials with improved BET surface area by Ti4+-coordination crosslinked Pickering emulsion gel. FT-IR, UV–vis, XRD, XPS, UV–vis DRS, TG-DTA, PEC, N2 adsorption-desorption, SEM-EDS, and TEM were used to characterize the morphology and structure of the as-prepared composite materials. The composites showed enhanced BET surface area with uniform particle size, in which the TiO2 was distributed uniformly. Carbon is mainly present on the surface, which facilitates the separation of charge carriers. The photodegradation properties of the obtained composite materials were investigated. TiO2/C composite prepared at 500 °C has excellent adsorption and photodegradation performance, and 98.91 % of MB was removed within 40 min. In addition, the composite material has good cycling stability. Overall, a simple and efficient method for TiO2/C preparation was proposed, which can be promoted to other polysaccharides.

Synthesis of carboxylated cellulose nanocrystal/ZnO nanohybrids using Oxytenanthera abyssinica cellulose and zinc nitrate hexahydrate for radical scavenging, photocatalytic, and antibacterial activities

The extremely low antioxidant, photocatalytic, and antibacterial properties of cellulose limit its application in the biomedical and environmental sectors. To improve these properties, nanohybrides were prepared by mixing carboxylated cellulose nanocrystals (CCNCs) and zinc nitrate hexahydrate. Data from FTIR, XRD, DLS, and SEM spectra showed that, ZnO nanoparticles, with a size ranging from 94 to 351 nm and the smallest nanoparticle size of 164.18 nm, were loaded onto CCNCs. CCNCs/ZnO1 nanohybrids demonstrated superior antibacterial, photocatalytic, and antioxidant performance. More considerable antibacterial activity was shown with a zone of inhibition ranging from 26.00 ± 1.00 to 40.33 ± 2.08 mm and from 31.66 ± 3.51 to 41.33 ± 1.15 mm against Gram-positive and Gram-negative bacteria, respectively. Regarding photodegradation properties, the maximum value (∼91.52 %) of photocatalytic methylene blue degradation was observed after 75 min exposure to a UV lamp. At a concentration of 125.00 μm/ml of the CCNC/ZnO1 nanohybrids sample, 53.15 ± 1.03 % DPPH scavenging activity was obtained with an IC50 value of 117.66 μm/ml. A facile, cost-effective, one-step synthesis technique was applied to fabricate CCNCs/ZnO nanohybrids at mild temperature using Oxytenanthera abyssinica carboxylated cellulose nanocrystals as biotemplate. The result showed that CCNCs/ZnO nanohybrids possess potential applications in developing advanced functional materials for dye removal and antibacterial and antioxidant applications.

Constructing a Titanium Silicon Molecular Sieve-Based Z-Scheme Heterojunction with Enhanced Photocatalytic Activity.

Titanium silicon molecular sieve (TS-1) is an oxidation catalyst that possesses a long lifetime of charge transfer excited state, high Ti utilization efficiency, large specific surface area, and good adsorption property; therefore, TS-1 acts as a Ti-based photocatalyst candidate. In this work, TS-1 coupled Bi2MoO6 (TS-1/BMO) photocatalysts were fabricated via a facile hydrothermal route. Interestingly, the optimized TS-1/BMO-1.0 catalyst exhibited a decent photodegradation property toward tetracycline hydrochloride (85.49% in 120 min) under the irradiation of full spectrum light, which were 4.38 and 1.76 times compared to TS-1 and BMO, respectively. The enhanced photodegradation property of the TS-1/BMO-1.0 catalyst could be attributed to the reinforced light-harvesting capacity of the photocatalyst, high charge mobility, and suitable band structure for tetracycline hydrochloride degradation. In addition, the mechanism of photocatalytic degradation of tetracycline hydrochloride by the TS-1/BMO-1.0 catalyst was reasonably proposed based on the band structure, trapping, and ESR tests. This research provided feasible ideas for the design and construction of high-efficiency photocatalysts for contaminant degradation.

Tailored synthesis of SnSe/SnO2@rGO composites with synergistic properties for photodegradation

SnSe/SnO2@rGO composite photocatalyst was prepared using a simple in-situ selenization method. The structure, morphology, and properties of the material were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller method. Moreover, the photocatalytic efficiency of the catalyst was evaluated on the aqueous solution of methylene blue under simulated natural light irradiation (wavelength >300 nm). After 120 min of degradation, the photocatalytic activity of SnSe/SnO2@rGO exceeded 90%. These results indicate that the heterojunction structure of SnSe/SnO2@rGO effectively promoted interfacial electron transfer and reduced the self-radiative recombination of charges, thereby improving the performance of the photocatalyst. Hence, the synthesized SnSe/SnO2@rGO possesses potential applications in the photocatalytic degradation of wastewater.

Efficient photocatalytic degradation of ciprofloxacin by doped Bi4O5I2 with Gd3+ as an electron trap: Gd3+ substitutes Bi3+ in the lattice

Gd3+-doped Bi4O5I2 with a flower-like structure has been successfully prepared for the first time using a one-step hydrothermal method. The effect of different doping amounts on the photodegradation properties has been investigated. The total removal of ciprofloxacin (CIP) by 3 % Gd–Bi4O5I2 (molar atomic ratio of Gd to Bi = 0.03:1) under visible light irradiation was 94.50 % (within 120 min). The reaction rate constant was 6.3 times higher than that of pure Bi4O5I2. In complex water containing humic acid (HA) and various anions, 3 % Gd–Bi4O5I2 maintained a high total removal rate for CIP. UV–Vis diffuse reflectance spectroscopy and electrochemical tests have shown that doping Gd3+ not only extends the photoresponse range, but also reduces the photonic band gap width. Gd3+ ions act as electron traps to trap excited electrons and promote the separation and migration efficiency of photogenerated electron-hole pairs, improving the performance of Gd–Bi4O5I2 composites for the photocatalytic degradation of CIP.

Design of functional coating with superior liquid repellency, self-cleaning, photodegradation and thermal insulation properties for building protection

A super-hydrophobic multifunctional coating (SMC) was designed and fabricated by combining commercial TiO2 with polydimethylsiloxane and perfluorodecyltrichlorosilane. The main objective of this research is to enhance the feasibility and effectiveness of SMC coating for building protection. After optimization, the comprehensive performance was significantly improved. The SMC not only significantly improves the water repellency of concrete (decreasing the capillary water absorption by 92.91 %), but also endows concrete with great self-cleaning and photodegradation properties. Additionally, ultraviolet–simulated (90 d) and practical environment (150 d) irradiation tests demonstrate the superior radiative cooling properties of SMC. COMSOL finite element simulation indicates about 20 % of ultraviolet light absorbance and 80 % of visible and near-infrared light reflectance on the SMC. The multifunctional SMC coating not only enhances the water repellency and self-cleaning properties of concrete, but also demonstrates excellent radiative cooling capabilities. These findings highlight the potential of the SMC coating as a promising material for sustainable and energy-efficient building applications.

New 3,5-bis(3,4-dicarboxyphenoxy)benzoic acid-appended Mn(ii) coordination polymers: synthesis, characterization and antibiotic photodegradation properties

Four new 3,5-bis(3,4-dicarboxyphenoxy)benzoic acid-appended Mn(ii) coordination polymers were synthesized and used as photocatalysts for the photodegradation of antibiotics.

Assembling Ag@CuO/UiO-66-NH2 nanocomposites for efficient photocatalytic degradation of xylene.

Achieving efficient and stable photocatalytic degradation of xylene hinges on the advancement of photocatalytic materials with outstanding visible light activity. This low-carbon strategy serves as a promising solution to combat air pollution effectively. In this study, we synthesized a Z-scheme heterojunction Ag@CuO/UiO-66-NH2 nanocomposite by hydrothermal method to investigate its photodegradation properties for xylene gas under visible light conditions. XRD, XPS, SEM, FTIR, and UV-vis analyses were employed to confirm the presence of the Z-scheme heterojunction. The CuO/UiO-66-NH2 (CuU-2) composite has high photocatalytic activity, which is 2.37 times that of the original UiO-66-NH2. The incorporation of Z-scheme heterojunction facilitates efficient charge transfer and separation, leading to a substantial enhancement in photocatalytic activity. The Ag@CuO/UiO-66-NH2 (Ag-1@CuU) composite has the highest photocatalytic activity with a degradation efficiency of 84.12%, which is 3.36 times and 1.41 times that of UiO-66-NH2 and CuO/UiO-66-NH2, respectively. The silver cocatalyst improves the absorption capacity of the composite material to visible light, makes the ultraviolet visible absorption edge redshift, and significantly improves the photocatalytic performance. This study introduces a novel approach for xylene gas degradation and offers a versatile strategy for designing and synthesizing metal-organic framework (MOF)-based photocatalysts with exceptional performance.

Study of amur cork tree bark extract-dyed paper under artificial UVA irradiation

Some ancient Chinese paper artifacts dyed with amur cork tree bark extracts are currently preserved to different extents in museums and libraries worldwide. As traditional natural plant dyes, the long-term performance of the amur cork tree bark extract-dyed handmade paper has been questioned under a preserved environment. The photodegradation process of the extract-dyed papers was examined under accelerating artificial UVA irradiation conditions according to China national standard-paper and board- accelerated aging (exposure to light). Changes during aging were analyzed by optical observation and scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), pH, and tensile strength and folding endurance tests. The results showed that the main components from extracted dyes played an important role in affecting the photodegradation properties of dyed paper. The changes in surface color, pH, morphology and mechanical properties after the artificial UVA accelerated degradation tests revealed that a suitable concentration of the extract dyes for maintaining the long-term irradiation stability of the paper is important.

A3B type asymmetric metallo phthalocyanines bearing carboxylic acid and tert-butyl groups: Photophysical, photochemical and aggregation properties

In this study, A3B type asymmetric magnesium(II), zinc(II) and indium(III)chloro phthalocyanine derivatives bearing carboxylic acid and tert-butyl groups were synthesized and their photochemical, photophysical and aggregation properties for photodynamic therapy (PDT) application were investigated. In the first part of the study; phthalonitriles, which are the starting materials, were synthesized and then different phthalocyanine compounds were obtained from the synthesized phthalonitriles in the second part. The synthesized compounds were characterized using different techniques. At the same time, the photophysical and photochemical properties of the synthesized compounds were also investigated. The calculated singlet oxygen quantum values in DMSO are 0.30 for MgPc, 0.72 for ZnPc, and 0.62 for InPc in and these values in DMF are 0.25 for MgPc, 0.68 for ZnPc, and 0.60 for InPc after photochemical studies. The obtained results proved that the contribution of the substituents increased the therapeutic efficacy. Finally, our results show that all Pc derivatives have displayed desirable singlet oxygen, photodegradation, fluorescence and aggregation properties for PDT studies.

Eco-friendly and multifunctional superhydrophilic and underwater superoleophobic materials with adsorption, photodegradation and oil-water separation properties

The frequent water pollution problems have caused serious harm to the ecological environment and human health, among which, a large number of waste water contains heavy metal ions, organic dyes, oil-water emulsion and other pollutants. Therefore, it is particularly important to prepare multifunctional materials that can separate these pollutants and purify wastewater. In this paper, ovalbumin (OVA), phytic acid (PA) and egg shell powder (ESP) and TiO2 particles were used to construct a composite system, which was loaded on fabric, cotton and PVDF membrane by impregnation method. The preparation of OVA-ESP-TiO2-PA modified materials which can efficiently separate various oil-water mixtures and oil-water emulsions were successfully achieved. The modified material could achieve high flux (up to13458 L m−2h−1) and separation efficiency (＞99 %) for various mixtures of oil and water by gravity-driven. Typically, it shows good stability and durability under strong acid and alkali (pH=1–12) and different temperatures (T = 10–60 ℃), and can be reused. What's more, the modified materials can effectively adsorb organic dyes (＞92 %) and heavy metal ions (up to 85 %) and can degrade organic dyes by ultraviolet light. It provides a new idea for the separation of oil-water mixture and the purification of waste liquid containing organic dyes and heavy metal ions, which has a good application prospect in the treatment of industrial wastewater and domestic wastewater.