Specific Area Research Articles

Traditional and Novel Organophosphate Esters in Plastic Greenhouse: Occurrence, Multimedia Migration, and Exposure Risk via Vegetable Consumption.

The migration and risk of organophosphate esters (OPEs) in agricultural air-soil-plant multimedia systems due to plastic film application remain unclear. This study investigates the multimedia distribution of traditional OPEs (TOPEs), novel OPEs (NOPEs), and their transformation products (POPEs) in plastic and solar greenhouses. The total concentration of OPE-associated contaminants in air and airborne particles ranged from 594 to 1560 pg/m3 and 443 to 15600 ng/g, respectively. Significant correlations between air OPE concentrations and those in polyolefin film (P < 0.01) indicate plastic film as the primary source. Contaminants were also found in soils (96.8-9630 ng/g) and vegetables (197-7540 ng/g). The primary migration pathway for NOPEs was particle dry deposition onto the soil and leaf, followed by plant accumulation. Leaf absorption was the main uptake pathway for TOPEs and POPEs, influenced by vegetable specific leaf surface area. Moreover, total exposure to OPE-associated contaminants via vegetable intake was assessed at 2250 ng/kg bw/day for adults and 2900 ng/kg bw/day for children, with an acceptable hazard index. However, a high ecological risk was identified for NOPE compounds (median risk quotient, 975). This study provides the first evidence of the multimedia distribution and potential threat posed by OPE-associated contaminants in agricultural greenhouses.

A sustainable and economical solution for CO2 capture with biobased carbon materials derived from palm kernel shells.

This study investigates the synthesize of activated carbon for carbon dioxide adsorption using palm kernel shell (PKS), a by-product of oil palm industry. The adsorbent synthesis involved a simple two-step carbonization method. Firstly, PKS was activated with potassium oxide (KOH), followed by functionalization with magnesium oxide (MgO). Surface analysis revealed that KOH activated PKS has resulted in a high specific surface area of 1086 m2/g compared to untreated PKS (435 m2/g). However, impregnation of MgO resulted in the reduction of surface area due to blockage of pores by MgO. Thermogravimetric analysis (TGA) demonstrated that PKS-based adsorbents exhibited minimal weight loss of less than 30% up to 500 °C, indicating their suitability for high-temperature applications. CO2 adsorption experiments revealed that PKS-AC-MgO has achieved a higher adsorption capacity of 155.35 mg/g compared to PKS-AC (149.63 mg/g) at 25 °C and 5 bars. The adsorption behaviour of PKS-AC-MgO was well fitted by both the Sips and Langmuir isotherms, suggesting a combination of both heterogeneous and homogeneous adsorption and indicating a chemical reaction between MgO and CO2. Thermodynamic analysis indicated a spontaneous and thermodynamically favourable process for CO2 capture by PKS-AC-MgO, with negative change in enthalpy (- 0.21 kJ/mol), positive change in entropy (2.44 kJ/mol), and negative change in Gibbs free energy (- 729.61 J/mol, - 790.79 J/mol, and - 851.98 J/mol) across tested temperature. Economic assessment revealed that the cost of PKS-AC-MgO is 21% lower than the current market price of commercial activated carbon, indicating its potential for industrial application. Environmental assessment shows a significant reduction in greenhouse gas emissions (381.9 tCO2) through the utilization of PKS-AC-MgO, underscoring its environmental benefits. In summary, the use of activated carbon produced from PKS and functionalised with MgO shows great potential for absorbing CO2. This aligns with the ideas of a circular economy and sustainable development.

Simultaneous determination of lead and cadmium in water by metal oxide framework complex-modified glassy carbon electrodes

Lead (Pb) and cadmium (Cd) are pervasive environmental pollutants known for their significant biological toxicity. The traditional methods for detecting these ions often necessitate large-scale instruments and complex procedures. In contrast, electrochemical detection methods offer advantages such as rapidity, portability, and sensitivity, making them suitable for the simultaneous detection of heavy metals. Metal-organic frameworks (MOFs), characterized by their exceptional adsorption and enrichment capabilities for heavy metal ions, have shown promise in this regard. Nevertheless, the poor conductivity of most MOFs has limited their electrochemical applications. In this study, glassy carbon electrodes (GCEs) were modified using the MOF ZIF-8, in combination with a bismuth complex and carboxylated multi-walled carbon nanotubes, resulting in the fabrication of Bi@ZIF-8/CMWCNTs/GCE electrochemical sensors. Leveraging the porous nature and large specific surface area of ZIF-8, the lead and cadmium ion adsorption by bismuth akin to mercury, and the conductivity of carboxylated multi-walled carbon nanotubes, the sensor developed in this study exhibits excellent capability for simultaneous detection of lead and cadmium ions in water. Under optimized conditions, Pb2+ and Cd2+ showed good linear relationships with the peak current in the concentration range of 2.0–50.0 μg/L. In the concentration range studied, the regression equations for Pb2+ and Cd2+ were determined as follows: y = 0.2982x + 0.4553 (r = 0.9962) for Pb2+ and y = 0.3631x + 0.1242 (r = 0.9949) for Cd2+. The detection limits for Pb2+ and Cd2+ were 0.76 μg/L and 0.87 μg/L, respectively. The relative standard deviations (RSDs) for 50 μg/L mixed standard solution of Pb and Cd were 1.89 % and 1.23 %, respectively. Furthermore, the RSDs for the same modified electrode tested with 50 μg/L Pb2+ and Cd2+ mixed standard solution over seven consecutive days were 2.27 % and 1.42 %, respectively, under identical conditions. In practice, the lead and cadmium concentrations of a lake were found to range from 4.42 μg/L to 5.60 μg/L, while the lead and cadmium concentrations of effluent from a wastewater plant ranged from 11.83 μg/L to 14.49 μg/L. This research not only describes a new electrochemical platform for the simultaneous determination of lead and cadmium in water but also provides a new method for the simultaneous determination of lead and cadmium in water. This research is valuable for promoting the application of MOFs in the field of electrochemistry.

Unveiling drastic influence of cross-interactions in hydrothermal carbonization of spirulina with cellulose, lignin or poplar on nature of hydrochar and activated carbon

Spirulina platensis contains abundant nitrogen-containing organics, which might react with derivatives of cellulose/lignin during hydrothermal carbonization (HTC), probably affecting yield, property of hydrochar, and pore development in activation of hydrochar. This was investigated herein by conducting co-HTC of spirulina platensis with cellulose, lignin, and sawdust at 260 °C and subsequent activation of the resulting hydrochars with K2C2O4 at 800 °C. The results showed that cross-condensation of spirulina platensis-derived proteins with cellulose/lignin-derived ketones and phenolics did take place in the co-HTC, forming more π-conjugated heavier organics, retaining more nitrogen species in hydrochar, reducing yields of hydrochar, making the hydrochar more aromatic and increasing the thermal stability and resistivity towards activation. This enhanced the yield of activated carbon (AC) by 7 %–20 % and significantly increased specific surface area of the AC from activation of hydrochar of spirulina platensis + lignin to 2074.5 m2/g (859.3 m2/g from spirulina platensis only and 1170.1 m2/g from lignin only). Furthermore, more mesopores from activation of hydrochar of spirulina platensis + cellulose (47 %) and more micropores from activation of hydrochar of spirulina + sawdust (93 %) was generated. The AC from spirulina platensis + lignin with the developed pore structures generated sufficient sites for adsorption of tetracycline from aqueous phase and minimized steric hindrance for mass transfer with the abundant mesopores (43 %).

Synthesis of ZnO@Fe2O3 microflowers with enhanced performance in volatile organic compound detection

Metal-oxide semiconductor is widely applied in gas sensor for volatile organic compound detection. However, these sensors usually exhibit poor selectivity and inferior sensitivity. Here, ZnO@Fe2O3 microflowers were synthesized using FeOOH microflowers as precursors via a simple solution reaction route, followed by heat treatment. The ZnO@Fe2O3 microflowers were characterized using a series of techniques, and their sensing responses to volatile organic compounds (VOCs) were evaluated in comparison with those of pristine Fe2O3. The ZnO@Fe2O3 microflower sensor exhibited better responses to several gases, especially acetone, with a response of 74.3 towards 100 ppm acetone, which is 2.85 times higher than that of the Fe2O3 microflower sensor. The sensor also presented high selectivity, reproducibility, and stability in sensing different VOCs. The large specific surface area, heterostructure, favorable hierarchical flower-like nanostructure assembled by the nanosheets, and high porosity of the ZnO@Fe2O3 microflowers contributed to its enhanced gas-sensing responses. Overall, this synthetic strategy for fabricating flower-like ZnO@Fe2O3 nanostructures can be widely applied.

Effects of Cation Exchange in Rhodamine B Photocatalytic Degradation Using Peroxo-Titanate Nanotubes.

Lepidocrocite-type layered sodium titanate (NaxH2-xTi2O5) is widely used in environmental remediation because of its large specific surface area, formed by anisotropic crystal growth, and its ability to store and exchange cations between layers. Additionally, peroxo-titanate nanotubes (PTNTs), which are tubular titanates with peroxy groups, exhibit visible-light absorption capabilities, rendering them suitable for photocatalytic applications under visible light irradiation. However, because of cation exchange reactions, the Na+ concentration and pH of the solution can fluctuate under aqueous conditions, affecting the photocatalytic performance of the PTNTs. Herein, we evaluated the impact of cation exchange reactions on the photocatalytic degradation of Rhodamine B (Rh B) by PTNTs at controlled Na+ ratios. The observed pH of Rh B solutions increases due to the cation exchange reaction with Na+ and H3O+, leading to the formation of zwitter-ionic Rh B molecules, eventually weakening their adsorption and photodegradation performance. Moreover, the results indicate that inhibiting the pH increase of the Rh B solution can prevent the weakening of both the adsorption and photodegradation performance of PTNTs. This study highlights the significance of regulating the sodium ion content in layered titanate materials, emphasizing their importance in optimizing these materials' photocatalytic efficacy for environmental purification applications.

Preparation of biomass-derived porous biochar for efficient removal of iodized X-ray contrast media in water: Adsorption performance and underlying mechanism

Hydrophilic Iodized X-ray contrast medias (ICM) are difficult to separate from water. Here, a novel porous biochar (MBC) with a high specific surface area (1435.1 m2 g−1) was prepared by one-step pyrolysis, which showed excellent adsorption capacity for Iodized X-ray contrast media, including diatrizoic acid (95.1 mg g-1), iohexol (297.8 mg g-1), and iopamidol (298.9 mg g-1). The optimal pyrolysis temperature for MBC was 700 ℃, and the ratio of sodium hydroxide to sodium carbonate was 1:3. Adsorption kinetic was well fitted by the pseudo-second-order model. Adsorption isotherm was best fitted to the Freundlich model. Adsorption thermodynamics suggested that ICM adsorption was spontaneous and endothermic. Material characterizations demonstrated that good adsorption performance of MBC for ICM mainly depended on pore filling, π-π interaction. The density functional theory (DFT) showed that H-bonding between oxygen-containing functional groups on MBC and ICM further promoted adsorption. Recycling experiments showed that MBC had good reusability. The study indicated that one-step pyrolysis synthesis of alkaline substance pretreatment biochar could be a promising adsorbent for water purification.

Poly (hydroxyethylmethacrylate-co-methacryloyl glutamic acid) nanocarrier system for controlled release of levothyroxine

The deterioration in the structure of thyroid hormones causes many thyroid-related disorders, which leads to a negative effect on the quality of life, as well as the change in metabolic rate. For the treatment of thyroid disorders, daily use of levothyroxine-based medication is essential. In the study, it is aimed to develop a polymeric nanocarrier that can provide controlled drug release of levothyroxine. In this respect, the p(HEMA-MAGA) nanopolymer was synthesized and then characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Zeta size analysis. The specific surface area of the nanopolymer was calculated as 587.68 m2/g. The pH, temperature, concentration, and time parameters were determined for levothyroxine binding to p(HEMA-MAGA) and optimum binding was determined as pH 7.4, 25 °C, 25 µg/mL concentration, and 30 min adsorption time. As a result of the release performed at pH 7.4, a release profile was observed which increased for the first 3 days and continued for 14 days. According to the results of MTT cell viability analysis, it was determined that the p(HEMA-MAGA) nanopolymeric carrier system had no cytotoxic effect. This developed polymer-based nanocarrier system is suitable for long-term and controlled release of levothyroxine. This is a unique and novel study in terms of developing poly hydroxyethylmethacrylate-co-methacryloyl glutamic acid-based polymeric nanoparticles for levothyroxine release.

Removal of hypertoxic Cr(VI) from water by polyaniline-coated ZIF-67-derived nitrogen-doped magnetic carbon.

Heavy metals are highly toxic and nonbiodegradable, posing a serious threat to the water environment and human beings. Therefore, it is crucial to develop a highly efficient adsorbent that is easy to recover and separate for the removal of heavy metals. In this paper, nitrogen-doped magnetic carbon (NC-67) was prepared by carbonization and hydrochloric acid treatment using cobalt-containing MOF (ZIF-67) as precursor. Then, polyaniline (PANI) was grown directly on NC-67 with high specific surface area by in situ polymerization to prepare polyaniline-coated nitrogen-doped magnetic carbon (NC-67@PANI), which was characterized by XRD, SEM, TEM and VSM, etc. and used for the removal of Cr(VI)from wastewater. The experimental results showed that the adsorption process of Cr(VI) by NC-67@PANI was spontaneous and endothermic, which conformed to the pseudo-second-order model and Freundlich adsorption isotherm model. Due to the synergistic effect of adsorption and reduction, the experimental adsorption capacity of NC-67@PANI for Cr(VI) was 410.2 mg/g. NC-67@PANI maintained a removal efficiency of 65.8% for Cr(VI) after five cycles. In addition, NC-67@PANI had good magnetism and was easy to separate under external magnetic field. The excellent adsorption capacity and easy separation characteristics of NC-67@PANI indicate that it is a promising adsorbent for Cr(VI) removal from wastewater.

Fabrication of sea urchin shaped polyaniline-modified magnetic microporous organic network for efficient extraction of non-steroidal anti-inflammatory drugs from animal-derived food samples

In this work, a novel polyaniline-modified magnetic microporous organic network (MMON-PANI) composite was fabricated for effective magnetic solid phase extraction (MSPE) of five typical nonsteroidal anti-inflammatory drugs (NSAIDs) from animal-derived food samples before high performance liquid chromatography (HPLC) detection. The core-shell sea urchin shaped MMON-PANI integrates the merits of Fe3O4, MON, and PANI, exhibiting large specific surface area, rapid magnetic responsiveness, good stability, and multiple binding sites to NSAIDs. Convenient and effective extraction of trace NSAIDs from chicken, beef and pork samples is realized on MMON-PANI via the synergetic π-π, hydrogen bonding, hydrophobic, and electrostatic interactions. Under optimal conditions, the MMON-PANI-MSPE-HPLC-UV method exhibits wide linear ranges (0.2–1000 μg L−1), low limits of detection (0.07–1.7 μg L−1), good precisions (intraday and inter-day RSDs < 5.4 %, n = 3), large enrichment factors (98.6–99.9), and less adsorbent consumption (3 mg). The extraction mechanism and selectivity of MMON-PANI are also evaluated in detail. This work proves the incorporation of PANI onto MMON is an efficient way to promote NSAIDs enrichment and provides a new strategy to synthesize multifunctional MON-based composites in sample pretreatment.

Superior Anodic Lithium Storage in Core–Shell Heterostructures Composed of Carbon Nanotubes and Schiff‐Base Covalent Organic Frameworks

Covalent organic frameworks (COFs) after undergoing the superlithiation process promise high‐capacity anodes while suffering from sluggish reaction kinetics and low electrochemical utilization of redox‐active sites. Herein, integrating carbon nanotubes (CNTs) with imine‐linked covalent organic frameworks (COFs) was rationally executed by in‐situ Schiff‐base condensation between 1,1′‐biphenyl]‐3,3′,5,5′‐tetracarbaldehyde and 1,4‐diaminobenzene in the presence of CNTs to produce core–shell heterostructured composites (CNT@COF). Accordingly, the redox‐active shell of COF nanoparticles around one‐dimensional conductive CNTs synergistically creates robust three‐dimensional hybrid architectures with high specific surface area, thus promoting electron transport and affording abundant active functional groups accessible for electrochemical utilization throughout the whole electrode. Remarkably, upon the full activation with a superlithiation process, the as‐fabricated CNT@COF anode achieves a specific capacity of 2324 mAh g−1, which is the highest specific capacity among organic electrode materials reported so far. Meanwhile, the superior rate capability and excellent cycling stability are also obtained. The redox reaction mechanisms for the COF moiety were further revealed by Fourier‐transform infrared spectroscopy in conjunction with X‐ray photoelectron spectroscopy, involving the reversible redox reactions between lithium ions and C=N groups and gradual electrochemical activation of the unsaturated C=C bonds within COFs.

Ultra-Large Two-Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation.

Despite the great research interest in two-dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow-based approach is developed, enabling the facile preparation of large-scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg-1) among current unsupported catalysts, which is 103.5 times higher than Pt-black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

2D MXene Biomaterials for Catalytic Medical Applications.

In recent years, two-dimensional transition metal carbides, nitrides, and carbonitrides, termed as MXenes, have been widely applied in energy storage, photocatalysis and biomedicine owing to their unique physicochemical properties of large specific surface area, high electrical conductivity, excellent optical performance, good stability, etc. Moreover, due to their strong light absorption capacity in the first and second near-infrared bio-window, and their ability of being simply functionalized with multiple organic/inorganic materials, MXene biomaterials have shown great potential in the field of catalytic therapy. This review will summarize the common catalytic mechanism of MXene biomaterials and their latest applications in catalytic medicine such as tumor therapy, antibacterial and anti-inflammatory, and present the current challenges and opportunities in clinical translation for future development to promote the advancement of MXene biomaterials in the field of catalytic medicine.

Ultra‐Large Two‐Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation

AbstractDespite the great research interest in two‐dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow‐based approach is developed, enabling the facile preparation of large‐scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg−1) among current unsupported catalysts, which is 103.5 times higher than Pt‐black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

PH-responsive chitosan-mediated spherical mesoporous silica microspheres for high loading and controlled delivery of 5-Fluorouracil

The objective of this study is to develop a drug carrier to overcome the inherent drawbacks of 5-Fluorouracil (5-Fu), including low bioavailability, short half-life, and systemic toxicity. In the present work, mesoporous silica nanoparticles (MSNs) capped by chitosan (CS) to encapsulate 5-Fu (5-Fu MSNs/CS) were fabricated by the sol-gel process, ultrasonic impregnation, and emulsion cross-linking. The 5-Fu MSNs/CS microspheres exhibit pH-responsive drug release and remarkable drug encapsulation capacity, as well as perfect sphericity, high specific surface area (680.62 cm2/g), and uniform particle size (2.64 ± 0.05 μm). The drug-loading content and encapsulation efficiency are 14.12 ± 0.53 % and 82.21 ± 2.13 %, respectively. The cumulative release of 5-Fu from MSNs/CS microspheres is fast and sustained at pH 5.0 (89.56 ± 0.97 %) compared to that at pH 7.4 (57.88 ± 0.91 %) in 96 h, and it is Fickian diffusion controlled. In conclusion, the MSNs/CS microspheres prepared in this study could be potential carriers for 5-Fu delivery.

Synthesis of Mesoporous Silica Sol with Low Refractive Properties for Increasing Transmittance.

Currently, coating with anti-reflective materials is an attractive approach to improve the quality of screen-based displays. In this study, mesoporous silica particles were systematically synthesized as a function of surfactant (i.e., CTAC-cetyltrimethylammonium chloride) concentration to serve as main coating fillers possessing low refractive indices. Precisely changing the amount of the CTAC surfactant, silica sol with an average diameter of 50 nm exhibits distinctively different specific surface areas, pore size, and pore volume. Prior to the preparation of final coating solutions containing these silica particle fillers, the percentage of solid content was optimized on a glass slide. The use of 50 wt% solid content exhibited the highest transmittance of light. Among various content levels of silica sol, the use of 3.5 wt% of silica particles in the solid content displayed the highest transmittance (i.e., best anti-reflectiveness). Under the almost identical coating layers prepared with the fixed amount of silica particles possessing different surface areas, pore size, and pore volume, it appears that the largest pore volume played the most important role in improving the anti-reflective properties. Experimentally understanding the key feature of low-refractive filler materials under the optimized conditions could provide a clear view to develop highly effective anti-reflective materials for various display applications.

Magnetic response of Ho3+ doped Ni0.4Cu0.6HoyFe2-yO4 spinel ferrites and their correlation with crystallite size

This study investigates the magnetic response of Ho3+ doped Ni0.4Cu0.6HoyFe2-yO4 (y = 0.0, 0.02, 0.04, 0.06, and 0.08) spinel ferrites (SFs) and their correlation with crystallite size. The synthesis was achieved using a sol-gel auto-combustion (SGAC) route and performed different characterizations, including X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray (EDX), Inductively coupled plasma atomic emission spectroscopy (ICP-AES), and vibrating sample magnetometer (VSM) analysis. The cubic spinel phase was verified via XRD in pure NCF and Ho3+ doped NCF samples. The lattice constant (a) was improved from 8.344 Å to 8.378 Å. The substitution of Ho3+ ions led to a decrease in porosity from 42.22 % to 39.54 %. The introduction of Ho3+ ions also reduced the crystallite size (D) from 37.05 nm to 27.72 nm. The specific surface area (S) was increased from 27.44 g/cm2 to 36.14 g/cm2 with the doping of Ho3+. The average particle size (DS) was decreased from 54 nm to 35 nm. The EDX and ICP-AES analyses confirmed the good agreement with the theoretical composition. The VSM measurements provided insights into their magnetic properties. Furthermore, the doping of Ho3+ ions enhanced coercivity (HC), while reducing saturation magnetization (MS) from 64.35 emu/g to 16.22 emu/g. The decrease in crystalline anisotropy (K) observed at higher concentrations of Ho3+ may result from the increase in coercivity, potentially attributable to the smaller crystallite size of the single-domain SFs particles. The single-phase matrix and their magnetic behaviour showed that the Ho3+ doped Ni–Cu SFs samples are suitable for high-frequency applications.

Improved photocatalytic degradation of malachite green, crystal violet and antibacterial activity of mesoporous Zn1-xCoxO nanoflakes

ABSTRACT The photocatalytic ability of the Zinc Oxide nanoparticles can be significantly enhanced through transition metal doping. In this work, Zn1-xCoxO nanoparticles were synthesised by a chemical coprecipitation method at room temperature. XRD studies indicated non-monotonic decrease in the Scherrer’s crystalline size from 19.79 nm for the pristine ZnO NPs to 14.81 nm for 2.5% Co2+ doped ZnO nanocrystals. The morphology of the nanoparticles was revealed by FESEM to resemble nanoflakes, and the existence of Co, Zn and O elements was verified by EDS findings. Tauc plots demonstrated a shrinkage of the optical band gap from 3.15 eV to 2.98 eV. The mesoporous nature and noteworthy increase in specific surface area (from 22.198 m2/gm to 54.159 m2/gm) were revealed by BET analysis of the N2 adsorption of the nanoflakes. Further, the degradation experiments of cationic dyes Malachite Green (MG) and Crystal Violet (CV) were carried out in the presence of synthesised catalysts under a high-pressure mercury vapour (450W-UV) lamp. Among the doped ZnO nanocatalysts, 2.5% Co2+ doped ZnO nanoflakes showed the most efficient photocatalytic degradation against MG (97.87%) and CV (93.27%) in 20 minutes. Furthermore, antibacterial activity was investigated against pathogenic bacteria Staphylococcus aureus, Bacillus subtilis and Escherichia coli which revealed improved bactericidal effects of 2.5% Co2+ doped ZnO nanoflakes. Hence, the current finding explored 2.5% Co2+ doped ZnO nanoflakes can serve as dual role efficient and potential candidate for eradication of organic as well as microbial contaminants from wastewater.

Advanced design of sol-gel derived multilayered cerium titanate films: structural, surface, photoelectrochemical and photocatalytic properties

Crystallization of Ce2Ti2O7 in the mixture of TiO2 and CeO2 was achieved by the three-layered coating of cerium − titanium mixed sol of the 1 : 1 metals molar ratio on a glass substrate at certain temperature regime in air as proven by XRD, SAED and Raman spectroscopy. Anatase and Ce2Ti2O7 crystallization with XRD undetectable crystallites brought to the increase of the specific surface area of the films. The formation of Ti–O–Ce bonds on the surface of the films was proven by the noticeable shift of Ti2p and O1s XPS maxima compared to TiO2 ones. The additional peaks in Ti2p, O1s and Ce3d XPS spectra belonging to the common bonds between the metals ions were identified for the first time. The bandgap energy and band-edge positions of Ce2Ti2O7 were firstly determined by photoelectrochemical measurements. The inactivity of the films in photocatalytic reductive and oxidative processes was caused by the unfavorable position of the valence band of Ce2Ti2O7 causing the recombination of the photo-formed electron−hole pair.

Fabrication of Zn-doped Cu2O for auxiliary graphdiyne to enhance photocatalytic H2 evolution performance

Graphdiyne (GDY) is widely used in photocatalysis due to its large specific surface area, high porosity and good stability. In this study, GDY was prepared by ball-milling-assisted alkyne-negative method, and GDY/Zn-Cu2O S-scheme heterojunction catalysts were constructed by introducing Zn-doped Cu2O into it through low-temperature mixing. The modified composite catalysts showed hydrogen evolution performance reached 213.65 μmol after 5 h of visible light irradiation, which was 142.4, 82.2 and 8.1 times than that of Cu2O, Zn-Cu2O and GDY, respectively. The large specific surface area of GDY provided abundant active sites to promote surface kinetics. Zinc doping adjusted the energy band structure of Cu2O and improved the light absorption efficiency of the catalysts. The S-scheme heterojunction established between Zn-Cu2O and GDY greatly facilitated the separation and transport of photogenerated carriers, which was the dominant factor for the improvement of hydrogen evolution performance. A possible mechanism is proposed and analyzed by combining ultraviolet photoelectron spectroscopy (UPS), valence band XPS (VB-XPS), in-situ irradiated X-ray photoelectron spectroscopy (In-situ XPS) and density functional theory (DFT) results. This work provides a new insight into the doping and construction strategies of GDY-based S-scheme heterojunction.