Photocatalytic Degradation Of Methyl Orange Research Articles

Robust Photocatalytic MICROSCAFS® with Interconnected Macropores for Sustainable Solar-Driven Water Purification.

Advanced oxidation processes, including photocatalysis, have been proven effective at organic dye degradation. Tailored porous materials with regulated pore size, shape, and morphology offer a sustainable solution to the water pollution problem by acting as support materials to grafted photocatalytic nanoparticles (NPs). This research investigated the influence of pore and particle sizes of photocatalytic MICROSCAFS® on the degradation of methyl orange (MO) in aqueous solution (10 mg/L). Photocatalytic MICROSCAFS® are made of binder-less supported P25 TiO2 NPs within MICROSCAFS®, which are silica-titania microspheres with a controlled size and interconnected macroporosity, synthesized by an adapted sol-gel method that involves a polymerization-induced phase separation process. Photocatalytic experiments were performed both in batch and flow reactors, with this latter one targeting a proof of concept for continuous transformation processes and real-life conditions. Photocatalytic degradation of 87% in 2 h (batch) was achieved, using a calibrated solar light simulator (1 sun) and a photocatalyst/pollutant mass ratio of 23. This study introduces a novel flow kinetic model which provides the modeling and simulation of the photocatalytic MICROSCAFS® performance. A scavenger study was performed, enabling an in-depth mechanistic understanding. Finally, the transformation products resulting from the MO photocatalytic degradation were elucidated by high-resolution mass spectrometry experiments and subjected to an in silico toxicity assessment.

Ag-Incorporated Cr-Doped BaTiO3 Aerogel toward Enhanced Photocatalytic Degradation of Methyl Orange.

A novel Cr-doped BaTiO3 aerogel was successfully synthesized using a co-gelation technique that involves two metallic alkoxides and a supercritical drying method. This freshly prepared aerogel has a high specific surface area of over 100 m2/g and exhibits improved responsiveness to the simulated sunlight spectrum. Methyl orange (MO) was chosen as the simulated pollutant, and the results reveal that the Cr-doped BaTiO3 aerogel, when modified with the noble metal silver (Ag), achieves a pollutant removal rate approximately 3.2 times higher than that of the commercially available P25, reaching up to 92% within 60 min. The excellent photocatalytic performance of the Ag-modified Cr-doped BaTiO3 aerogel can be primarily attributed to its extensive specific surface area and three-dimensional porous architecture. Furthermore, the incorporation of Ag nanoparticles effectively suppresses the recombination of photo-generated electrons and holes. Stability and reusability tests have confirmed the reliability of the Ag-modified Cr-doped BaTiO3 aerogel. Therefore, this material emerges as a highly promising candidate for the treatment of textile wastewater.

The Synthesis of Ag/TiO2 via the DC Magnetron Sputtering Method and Its Application in the Photocatalytic Degradation of Methyl Orange in Na2SO4 Solution

TiO2 and TiO2 films modified with Ag (Ag/TiO2) were prepared via the DC magnetron sputtering method and the degree of modification was controlled via the sputtering power and time of Ag. The microstructures and properties of these films were characterized using field emission scanning electron microscopy, X-ray diffractometry, ultraviolet–visible diffuse reflectance spectrometry, atomic force microscopy, and X-ray photoelectron spectroscopy (XPS). The results show that the prepared films have an anatase structure. Compared with pure TiO2, Ag deposition can improve the utilization of light. The three-dimensional images of Ag/TiO2 clearly show that with the increase in Ag sputtering power and sputtering time, Ag particles on the surface of the film gradually increase, and the structure of the film is relatively dense. The photocatalytic effect of Ag/TiO2 films is the best when the Ag sputtering power is 5 W and the sputtering time is 50 s. Under high-pressure mercury lamp irradiation, the photocatalytic degradation rate of methyl orange (MO) in pure MO solution with Ag/TiO2-5 W-50 s can reach 100% within 55 min, whereas that in MO-Na2SO4 mixed solution can reach 99.55% within 65 min. The results suggest that the presence of Na2SO4 in MO solution can inhibit the degradation of MO using Ag/TiO2, the result of XPS suggests that Na2SO4 accelerates the oxidation of Ag, which may lead to an increase in the recombination rate of photogenerated electron–hole pairs and a decrease in the degradation rate. During the process of recycling photocatalysts, the degradation rate of MO was apparently reduced. A possible reason is that the Ag particles have been oxidized and products of photocatalytic degradation are on the surface of the photocatalyst. The photocatalytic degradation mechanism was studied.

Synthesis, Characterization, and Photocatalytic Activity of Cu-Doped MgO Nanoparticles on Degradation of Methyl Orange (MO)

The purpose of this study is to synthesize Cu-doped MgO nanoparticles and test the performance of photocatalytic degradation of methyl orange (MO). Mg(NO3)2, CuCl2, NaOH, and fresh Calotropis procera leaf extract were used as precursors. The prepared nanoparticles were characterized by using FT-IR, XRD, SEM, and UV-Vis spectrometer to study the functional group, crystal structure, surface morphology, and absorption edge, respectively. The wide band above 3000 cm−1 from the FT-IR spectrum corresponds to the stretching vibrations of flavonoids and phenolic compounds of Calotropis procera leaf extract. Furthermore, the Mg-O bonding of undoped MgO and Cu-doped MgO NPs is represented by new peaks which appeared at 831 and 835 cm−1, respectively. The crystal size of undoped MgO and Cu-doped MgO nanoparticles is 13.04 nm and 12.08 nm, respectively. The SEM microstructure of pure MgO showed higher agglomeration than the Cu-doped MgO nanoparticles. The degradation efficiency of the Cu-doped MgO NPs was compared with that of the MgO NPs, and the photocatalytic activity of these NPs was evaluated using the photocatalytic degradation rates of MO dye. Cu-doped MgO NPs showed higher degradation efficiency than pure MgO NPs. The insertion of Cu in the MgO structure improved the photocatalytic efficiency of the MgO NPs under optimal conditions. Therefore, Cu-doped MgO exhibits high photocatalytic activity compared with undoped MgO nanoparticles under sunlight irradiation.

Preparation of Novel Layered High Entropy Bismuth-Based Materials and their Photocatalytic Degradation Mechanism.

We prepared BiOCl, BiO(ClBr), BiO(ClBrI), and BiO[ClBrI(CO3)0.5] materials using a simple coprecipitation method. It was found that adjusting the number of anions in the anion layer was conducive to adjusting the band structure of BiOX and could effectively promote the migration and separation of photogenerated carriers, thus improving the photocatalytic activity. We first selected methyl orange (MO) as the study pollutant and compared it with BiOCl, BiO(ClBr), and BiO(ClBrI). The first-order kinetic constants of MO degradation by BiO[ClBrI(CO3)0.5] increased by 90.3, 33.9, and 3.1 times, respectively. The photocatalytic degradation rate of methylene blue by BiO[ClBrI(CO3)0.5] was 89.5%, indicating the excellent photocatalytic performance of BiO[ClBrI(CO3)0.5]. The stability of BiO[ClBrI(CO3)0.5] was demonstrated through cyclic experiments and XRD analysis before and after the reaction. The photocatalytic degradation of MO by BiO[ClBrI(CO3)0.5] showed that h+ and 1O2 were the main active oxidizing species and •O2- was the secondary active substance. Overall, our work provides new ideas for the synthesis and degradation of organic pollutants by using two-dimensional anionic high-entropy materials.

Efficient Catalytic Degradation of Methyl Orange by Various ZnO-Doped Lignin-Based Carbons.

Herein, a series of ZnO-doped lignin-based carbons (LC/ZnO) were successfully prepared from different types of lignin and used for methyl orange (MO) photocatalytic degradation. The apparent morphology, internal structure, and photoelectric properties of prepared LC/ZnO composites and their effects on subsequent MO photocatalytic degradation were investigated by various characterization techniques. The results showed that the LC/ZnO composites that were prepared in this work mainly consisted of highly dispersed ZnO nanoparticles and lignin-based carbon nano-sheets, which were beneficial for subsequent photogenerated electrons and holes formation, dispersion, and migration. The MO could be significantly degraded with various ZnO-doped lignin-based carbons, especially over the LCSL/ZnO, and the maximum degradation rate was 96.9% within 30 min under the simulated 300w sunlight exposure. The experiments of free radical elimination showed that the photocatalytic degradation of MO over LC/ZnO were a result of the co-action of multiple free radicals, and h+ might play the predominant roles in MO degradation. In addition, the pH of the solution had little effect on MO degradation, and the MO could be effectively degraded even in an alkaline solution of pH = 12.0. The cycling experiments showed that the prepared LC/ZnO had a good stability for MO photodegradation, especially for LCSL/ZnO, even after 5 times recycling, and the degradation rate of MO only dropped from 97.0% to 93.0%. The research not only provided a fundamental theory for the efficient photocatalytic degradation of MO by LC/ZnO composites, but also offered a new insight into lignin valorization.

Photocatalytic Degradation and Anticancer Activity of Green Synthesized Molybdenum Nanoparticles for Inhibiting the Cervical Cancer Cells

This work reports the synthesis of molybdenum nanoparticles (Mo NPs) through green routes using horse gram seed extracts and characterized by GC-MS, electronic (UV-visible) spectroscopy, IR, XRD and SEM techniques. Their potent applications as in vitro anticancer agent against HeLa cell lines and photocatalytic degradation of methyl orange (MO) and methyl violet (MV) dyes were also evaluated. The anti-malignant properties of Schiff base ligands [2-fluorobenzaldehyde semicarbazone (L1H) and 2-fluorobenzaldehyde thiosemicarbazone (L2H) with molybdenum metal precursor [dioxobis(2,4-pentanedionato)molybdenum] were also explored and their Mo complexes after conversion into nano form as both ligands, L1H and L2H approve their binding property based on molecular docking studies.

Photocatalytic degradation of methyl orange using CuO/Al2O3 nanocomposite obtained by microwave-assisted thermal decomposition route

Aluminum oxide (Al2O3) and copper oxide (CuO) are known to exhibit very exceptional properties including high thermal and chemical properties that promise a wide area of applications. In this paper, we report the microwave-assisted thermal decomposition route to CuO/Al2O3 nanocomposite and its application as a photocatalyst for methyl orange (MO) degradation. Al2O3 was first prepared at different temperatures of 900, 1000, and 1100 °C, denoted as Al2O3(1), Al2O3(2), and Al2O3(3). Subsequently, the best temperature (1000 °C) was selected for the synthesis of CuO/Al2O3 nanocomposite. XRD analysis confirmed the hexagonal crystal structure for all the Al2O3 and the monoclinic phase for the CuO within the composite. The crystallite sizes of the alumina increased with temperature and a similar growth pattern occurred in the entire samples. Scanning electron microscopy and transmission electron microscopy (SEM and TEM) show clear spherical morphology for all the samples with obvious agglomeration as temperature increases. Optical characterization displayed decreasing band gap energies with increasing temperature, implying size increase due to particle interaction, boundary energy reduction, and grain boundary migration. The photocatalytic performance of the CuO/Al2O3 under visible light was evaluated on methyl orange (MO), and the degradation was studied with some process parameters such as the effect of catalysts dosage and initial concentration of MO. Results showed that the CuO/Al2O3 exhibited about 94.2 % efficiency within 3 h using an optimum dose of 2.0 g/L and an initial MO concentration of 20 mg/L. However, the use of CuO/Al2O3 nanocomposites to remove other organic pollutants could confirm the robustness of this catalyst.

Photocatalytic degradation of methyl orange in water using oyster shell-derived calcium oxide nanoparticles

In response to the Philippine-textile-industry goal of adapting sustainable waste management practices, oyster shells as abundant waste, can be valorized for photocatalytic wastewater treatment. Moreover, aeration and water quality as lesser-known parameters were assessed. Here, a nano-sized calcium oxide (CaO NP) photocatalyst from oyster shells was prepared with a 57 % CaO yield. Instrumental characterization confirmed its nanoparticle size, elemental composition, and narrow bandgap, which favor adsorption-photodegradation. The optimum photocatalyst dose achieved 93.7 % removal efficiency and was significantly maximized to 98.5 % under aerated conditions. CaO NP is reusable with stable performance and has first-order dye degradation kinetics. Aerated photocatalytic treatment of simulated wastewater showed a significant reduction in color and chemical oxygen demand with acceptable final pH. Furthermore, the treated wastewater is dischargeable to Class C waters by Philippine environmental standards, proving its successful remediation and application as a dispersible and recyclable photocatalyst for removing methyl orange in water.

Au9 clusters deposited as co-catalysts on S-modified mesoporous TiO2 for photocatalytic degradation of methyl orange

Au9 nanoclusters (Au9 NCs) were deposited onto S-functionalized mesoporous TiO2 (SMTiO2) to produce efficient photocatalysts for Methyl Orange (MO) dye degradation with UV light. The morphology, the surface composition and the size of the deposited Au9 NCs of the catalyst was analysed. SMTiO2 could adsorb more clusters with lesser Au9 cluster agglomeration than unmodified MTiO2. This finding is attributed to the capability of the thiol groups to form strong bonds with the Au9 clusters. To study Au9 NCs effect on dye degradation activity, the MO degradation reaction constants under UV-light irradiation for SMTiO2 nanoparticles (NPs) and Au9 NCs decorated SMTiO2 photocatalysts were studied, which were 0.07 min−1 and 0.149 min−1, respectively. Hence, it takes almost half the time to completely degrade MO using Au9 NCs decorated SMTiO2 photocatalysts compared to SMTiO2 substrate. Results were analysed using the response surface methodology (RSM) to study the interaction between the reaction parameters.

Research Progress on Photocatalytic Degradation of Methyl Orange Dye Wastewater by Light‐assisted Composite‐modified Ag3PO4

AbstractA new type of modified catalyst was prepared by a silver ammonia‐assisted precipitation method through a custom‐built electrochemical reactor, and the catalytic degradation of the azo dye methyl orange was studied under the synergistic effect of visible light. The optimum doping ratio for the loading of graphene oxide (GO) is 1.0 %. Under the optimum conditions, the degradation rate of Ag3PO4/GO/NiFe2O4 to methyl orange is 97.56 % when the light reaction time is 50 min. After three cycles, the degradation rate of methyl orange by Ag3PO4/GO/NiFe2O4 is 94.47 %. Through the free radical capture experiment, it is known that the contribution degree of the main active substances in the photocatalytic degradation of methyl orange is h + >⋅O2− >⋅OH. By forming a Z‐type heterojunction between Ag3PO4 and NiFe2O4, the recombination probability of photogenerated carriers is greatly reduced, and the stability of Ag3PO4 is improved.

Photocatalytic degradation of methyl orange via supramolecular self-assembly of cucurbit[6]uril and phosphotungstic acid

Photocatalytic degradation of methyl orange via supramolecular self-assembly of cucurbit[6]uril and phosphotungstic acid

Eco-Friendly TiO2 and ZnO Biocar Nanocomposites: Transforming Water Decontamination and Bacteria Inactivation

Water pollution ranging from harmful chemical substances to pathogenic bacteria is a growing problem from industry to society as a whole[1-2].There is a need to find new, cost-effective sustainable materials with high efficacy to clean up water and to protect the environment. Biocarbon (BC), a material with high specific surface area and large porosity, has some potential for removing water pollutants, but it also has many limitations. However, biocarbon-based composites can be tailored and may have a greater potential for removing contaminants in water. ZnO biochar and TiO2 biochar nanocomposites have been shown to effectively remove harmful chemical substances, such as industrial dyes, and additionally kill potential pathogenic bacteria[2–8].In this project, we combined TiO2 and ZnO with biochar to create an active nanocomposite surface to see if this could be a cost-effective method to deactivate bacteria and degrade specific dyes. We present the fabrication and examination of TiO2/biochar (BC) and ZnO/BC composite photocatalysts, synthesized via hydrolysis technique. These catalysts were designed for the purpose of methyl orange (MO) degradation and bacterial strain inactivation. A comprehensive assessment of these catalysts was carried out using a number of sophisticated methods, including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis spectrophotometry for evaluation of degradation. Moreover, the direct contact method was used for antibacterial analysis. Our findings underline the exceptional properties of these composites for water decontamination and antibacterial efficacy. The nanocomposites showed remarkable photocatalytic performance in MO removal from wastewater, achieving a superior removal efficiency of 92%, as shown in Figure 1. This can be attributed to their outstanding electron transfer efficacy. In addition, the TiO2/BC and ZnO/BC nanocomposites manifested robust antibacterial properties, and they showed an antibacterial effectiveness of 85% against Escherichia coli (E. coli) (Table 1). This research highlights the promising potential of TiO2/BC and ZnO/BC nanocomposites as eco-friendly and multifaceted materials, suggesting a wide range of potential applications in water purification and antibacterial activity. Acknowledgments: The authors acknowledge the research grants from project # 6000237-13 Figure: Figure 1. Photocatalytic degradation of MO (initial concentration; 20 mg/L) under solar light irradiation, a) Pure BC and TiO2, and composite TiO2/BC catalysts, b) Pure BC and ZnO, and ZnO/BC catalysts. Table: Table 1. Antimicrobial efficiency of 5 different catalysts against E. coli.

Nano-island-like heterojunction of nitrogen-doped carbon quantum dots anchoring on titanium oxide nano sheets@Cu2O for enhancing visible light-driving photocatalytic degradation of methyl orange

Cu2O and TiO2 are promising for photocatalysis owing to their lower cost and excellent performance. Unfortunately, the efficiency of light utilization by Cu2O and TiO2 is still low. Herein, the nano-island-like heterojunction of nitrogen-doped carbon quantum dots anchoring on titanium oxide nano sheets@Cu2O (NCQDs/TNSs@Cu2O) was synthesized through the hydrothermal and chemical precipitation process and its photocatalytic performance was systematically characterized. Benefiting from the unique heterojunction, NCQDs/TNSs@Cu2O exhibited a superior photocatalytic performance. High-resolution transmission electron microscopy showed that NCQDs/TNSs nanoclusters were decorated on Cu2O nanoparticle surface and formed heterojunctions. The UV–Vis-DRS spectra indicated that NCQDs/TNSs@Cu2O exhibited the strong adsorption peaks between 400 and 650 nm. Under simulated sunlight irradiation, NCQDs/TNSs@Cu2O exhibited excellent photocatalytic degradation performance on methyl orange. For example, the degradation was completed within 20 min and the photo-degradation capacity of NCQDs/TNSs@Cu2O remained 90.1 % after four recycling cycles. Furthermore, the potential mechanism for the photo-induced degradation was proposed based on the active substances identified through the electron spin resonance. Conclusively, this study provides a novel perspective on the role of NCQDs and prepares the way for the design of the biomass-based photocatalyst.

Structural and magnetic properties of sol-gel autocombustion and microwave synthesized nickel ferrite nanoparticles and their photocatalytic and anti-microbial applications

Nickel Ferrite was synthesized from its nitrate precursors via sol–gel auto combustion method and microwave synthesis with ethylene glycol as fuel. The phase identification was carried out by XRD and the crystalline size was calculated. The Williamson- Hall plot was drawn and lattice strain and crystallite size was determined. The spinel structure of ferrite was confirmed using FTIR spectra. The morphology of samples were studied from HR-TEM. The UV–Visible spectra of samples were obtained and the band gap was determined from Tauc plot. The magnetic properties of samples were studied using VSM. The antibacterial activity of samples on Escherichia coli and Staphylococcus aureus was studied by well diffusion method. Their photocatalytic degradation of Methyl Orange under UV light was carried out and studied using UV–Visible Spectrophotometry.

3DOM BiOI/TiO2 composites modified by metal Ag with broad spectrum response for photocatalytic degradation and water splitting

In order to improve the photocatalytic performance of TiO2 and expand its absorption range in the visible light region, depositing noble metals, constructing the p-n heterojunction and controlling the morphology were used to modify TiO2. First, the TiO2 photocatalyst with a three-dimensional ordered macroporous structure was prepared by vacuum impregnation combined with calcination, and then the 3DOM Ag/BiOI/TiO2 composites were successfully prepared by the in-situ deposition and photoreduction. The characterization results show that the composites present a large number of open and transparent pore structures. The pore wall is formed by stacking TiO2 nanoparticles, with BiOI and Ag nanoparticles evenly distributed on the surface of the pore wall and in the macroporous framework, which expands the specific surface area of 3DOM TiO2 and provides more active sites for the reaction. The introduction of BiOI and Ag expands the visible light response range and improves the light utilization efficiency. Furthermore, the formation of the Schottky barrier and the internal electric field formed by the p–n heterojunction effectively promotes the interfacial electron transfer and suppress the electron–hole recombination, thereby generating more active species during the photocatalytic process. The experimental results of multi-mode photocatalytic degradation of methyl orange (MO) also show that 3DOM Ag/BiOI/TiO2 photocatalyst has the best photocatalytic degradation activity. In addition, different samples were tested for hydrogen production by photolysis of water under simulated sunlight conditions, and the results show that 3DOM Ag/BiOI/TiO2 has the best hydrogen production ability of photolysis of water. The excellent performance of multi-modal photocatalytic degradation of organic pollution and high photohydrogen production activity in 3DOM Ag/BiOI/TiO2 composites is attributed to the synergistic effect between the introduction of metallic Ag, the unique 3DOM structure, and the p–n heterojunction.

Saccharide-Derived Zinc Oxide Nanoparticles with High Photocatalytic Activity for Water Decontamination and Sanitation

Zinc oxide nanoparticles (ZnO NPs) with a high photocatalytic performance were prepared by using the aerobic combustion of saccharides such as glucose, fructose, dextrin, and starch with zinc nitrate. The ZnO NPs were characterized by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray scattering spectroscopy (EDX), X-ray powder diffraction (XRPD), and UV-vis spectroscopy. The TEM images revealed that the ZnO NPs have sizes ranging from ~20 to 35 nm with a bandgap of ~3.32 eV. The XRPD pattern revealed the hexagonal wurtzite crystalline structure of the ZnO NPs. The photocatalytic properties of the ZnO NPs were studied by the photocatalytic degradation of methyl orange (MO) in deionized water (DIW) and simulated fresh drinking water (FDW) under ultraviolet light (UV-B) and sunlight illumination. The terephthalic acid photoluminescence technique was also used to study the generation of a hydroxyl radical (•OH) by ZnO NPs. The saccharide-derived ZnO NPs exhibited higher photocatalytic activity than the nonsaccharide-derived ZnO NPs. Varying the type of saccharides used during the calcination had some effect on the degree of the catalytic enhancement.

Novel magnetic nanocomposites BiFeO3/Cu(BDC) for efficient dye removal

In this study, bismuth ferrite nanoparticles and metal-organic framework, Cu(BDC), were prepared by microwave-assisted combustion in solid state and ultrasound-assisted method, respectively. To enhance the properties of bismuth ferrite nanoparticles and Cu(BDC), we form them as their composite through microwave and ultrasonic probe strategies. Various analyses, including FT-IR, XRD, SEM, DRS, VSM, and so on, were applied to verify the synthesis accuracy. Then, the catalytic performances of the nanoparticles and the as-prepared nanocomposites were evaluated through photocatalytic degradation of methyl orange. Furthermore, the adsorption capacity of the as-synthesized materials was assessed toward the Congo red removal from wastewater. All the results prove that the proposed nanocomposite can be an acceptable candidate for eliminating contaminants from wastewater. The electrochemical properties of bismuth ferrite, BiFeO3/Cu(BDC) nanocomposite 1, and BiFeO3/Cu(BDC) nanocomposite 2 have been studied by cyclic voltammetry.

Effect of oxygen vacancy modification of ZnO on photocatalytic degradation of methyl orange: A kinetic study

This study investigated a novel kinetic model of the adsorption and photocatalytic degradation of methyl orange, an anionic dye, using a commercial ZnO and reduced commercial ZnO photocatalysts. The results were compared and discussed with our previous study on methylene blue, a cationic dye, providing new insights into the interaction of the catalyst with molecules with different charges. The kinetic model was applied to describe adsorption in the dark, followed by photocatalytic degradation under simulated sunlight. In addition, the predicted pKa values of methyl orange were estimated using the kinetic model, which were found to be 4.40 and 9.34. The effect of ZnO oxygen vacancies (created through hydrogen reduction at 500 °C) on the adsorption and photocatalytic degradation of methyl orange was investigated. The existence and effects of oxygen vacancies on ZnO were analyzed using TPR, PL, XPS, XRD, FE-SEM, EDS, BET, Tauc plot, Mott-Schottky, and cyclic Voltammetry. The appearance of oxygen vacancies was clearly observed by the characterization results, while the morphology of the nanoparticles was found to be unchanged. Additionally, the band gap of ZnO was decreased from 3.22 to 3.07 eV, and the maximum valence band of the catalyst was increased from 2.43 to 2.67 eV due to the reduction pretreatment. The findings suggest that the photocatalytic degradation rate of the reduced ZnO substantially increased. However, the adsorption removal of the anionic dye declined, which could be attributed to the more negative zeta potential of ZnO after hydrogen reduction. Finally, the quantum yield of photocatalytic process was calculated and compared with the results of methylene blue.

One-Pot Synthesis of Green-Emitting Nitrogen-Doped Carbon Dots from Xylose

Carbon dots (CDs) are interesting carbon nanomaterials that exhibit great photoluminescent features, low cytotoxicity, and excellent water stability and solubility. For these reasons, many fields are starting to integrate their use for a variety of purposes. The catalytic performance of VOPO4 has been evaluated in the synthesis of nitrogen-doped carbon dots (N-CDs). The synthesis reaction was carried out at 180 °C using VOPO4 as a heterogeneous catalyst for 2 to 4 h of reaction time. After reaction, the N-CDs were purified using a novel method for the protection of the functional groups over the surfaces of the N-CDs. The morphological, superficial, and photoelectronic properties of the N-CDs were thoroughly studied by means of TEM, HRTEM, XPS, and photoluminescence measurements. The conversion of the carbon precursor was followed by HPLC. After three catalytic runs, the catalyst was still active while ensuring the quality of the N-CDs obtained. After the third cycle, the catalyst was regenerated, and it recovered its full activity. The obtained N-CDs showed a great degree of oxidized groups in their surfaces that translated into high photoluminescence when irradiated under different lasers. Due to the observed photoelectronic properties, they were then assayed in the photocatalytic degradation of methyl orange.