Microwave-assisted Hydrothermal Method Research Articles

Study on the properties of biomass carbon quantum dots modified with diamine compounds and their application in iron ion detection

Diamine compounds are widely used as surface modifiers in the functionalization of carbon quantum dots, yet the effects of different diamines on the properties of carbon quantum dots remain unclear. In this study, carbon dots (P-CDs) were synthesized from peanut shell powder via a simple one-step microwave-assisted hydrothermal method. The surface of these carbon dots was modified through co-heating with ethylenediamine (EDA), o-phenylenediamine (OPD), m-phenylenediamine (MPD), and p-phenylenediamine (PPD). The effects of different diamines on the morphology and optical properties of P-CDs were systematically analyzed. The diamine-modified P-CDs exhibited varying sizes and similar crystal structures, with significantly enhanced fluorescence and quantum yields, reaching 35.2% for EDA-CDs. EDA-CDs and OPD-CDs demonstrated excitation-dependent emission behavior, while MPD-CDs and PPD-CDs did not. Based on EDA-CDs, a probe with high sensitivity for Fe3+ was developed, showing a good linear response within the Fe3+ concentration range of 20–100 μM and a detection limit of 2.768 μM. Additionally, the ion probe exhibited a recovery rate of 100.85% in both deionized and tap water, indicating good practical applicability. This study provides essential guidance for the nitrogen surface modification of biomass-derived carbon quantum dots and presents a promising Fe3+ probe with potential applications.

Valorisation of citrus waste for sustainable synthesis of carbon-supported copper nanoparticles active in CO2 electroreduction

A microwave-assisted hydrothermal method is used to synthesise carbon-supported Cu2O/Cu electrocatalysts for CO2 conversion using citrus peels as the source of both the carbon support and the Cu cations reducing agent.

A novel chitosan/quercetin-based film enables non-enzymatic detection of glucose: Electrochemical and fluorescent behavior

In this study, a novel functional hydrogel film was synthesized using natural polymer chitosan and quercetin as raw materials. Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) analysis indicate that phenylboronic acid modified carbon nanodots (PBA-CDs) were successfully prepared via a simple microwave-assisted hydrothermal method. The experimental results demonstrate that a dual electrochemical and fluorescence detection of glucose can be realized based on the boronate ester bonding between chitosan/quercetin (Chit0/Quer) films and PBA-CDs. The addition of PBA-CDs hinders the electron transfer between the phenolic hydroxyl groups of quercetin and the redox mediators, and inhibits the intramolecular rotation of quercetin, which leads to a decreased electrical signal and enhanced fluorescence intensity. After the addition of glucose, the peak redox current of the Chit0/Quer hydrogel film is restored due to the competitive binding of glucose to the boronate ester, resulting in a dual-input logic circuit for the qualitative detection of glucose. In addition, the fluorescence intensity of the hydrogel decreases with increasing glucose concentration, and the concentration of glucose can be quantitatively detected by detecting the change in fluorescence intensity. Besides, the sensor has better stability and selectivity for biomarkers. Finally, we demonstrate that the electrochemical and fluorescence sensing strategies can be used for the detection of glucose in real beverage samples. In conclusion, based on the redox activity of quercetin and the competitive binding of boronate ester bonds, we explored a new strategy for enzyme-free electrochemical and fluorescence sensing for the detection of glucose, which is expected to be applied in biomedicine, food industry and other fields.

Insight into the Modification of the Low-Pt Electrocatalysts By the Defective Metal Oxide Additives: The Effect on the Oxygen Reduction Reaction in Acid Media

The global rise in energy consumption combined with severe environmental issues and climate change has promoted the development of green alternative technologies such as low-temperature proton exchange membrane fuel cells (PEMFCs). However, the performance and operational cost of PEMFC largely depend on the application of highly expensive state-of-the-art Pt-based systems, which are so far the most effective catalysts for the oxygen reduction reaction (ORR) at the fuel cell’s cathode. The widespread commercialization of the PEMFC technology has also been complicated by the limited lifetime of catalytic systems due to the instability of carbon supports as well as Pt catalytic centers. Due to these facts, it is of great significance to gain an in-depth insight into the ORR mechanism to optimize the activity of the ORR catalytic centers and their more efficient utilization while minimizing the Pt content without loss of performance and durability, which are essential features to ensure wider use of the low-temperature hydrogen-oxygen fuel cell systems. One of the reasonable strategies for ameliorating stability, and selectivity of carbon-supported low Pt content electrocatalysts for the ORR in acid media is their functionalization by selected nanostructured non-noble metal oxides (MOx)1. The strong mutual interactions between all components in such hybrid material (Pt, C, MOx) are capable of tuning the Pt electronic structure at the electrocatalytic interface, thus promoting centers for the adsorption of oxygen and the cleavage of O=O bonds as well as the durability of the carbon carriers can be improved under highly aggressive acidic conditions. Additionally, the application of metal oxide co-catalysts which are capable of inducing the decomposition of hydrogen peroxide and/or scavenging of free radicals can make a significant contribution to improving the durability and overall efficiency of fuel cells.Due to the unique structure, redox ability, oxygen vacancies, and other features resulting from the 4f electronic configuration of cerium, in the present studies, we synthesis the reduced CeOx nanostructured and investigate the influence of such additive on the stability and selectivity of low-Pt content electrocatalysts in the oxygen reduction reaction (ORR) in acidic media. The stable oxide phases with the tailored redox properties and the presence of oxygen vacancies were obtained by controlling their morphology and composition. Preparation of small ceria nanoparticles by microwave-assisted hydrothermal method and introduction of various dopants (e.g. Pr, Nb, Cu) into these oxide structures improve its reducibility and non-stoichiometry phase content, optimizing important parameters for catalytic activity. The received results revealed that the CeOx/M-CeOx additive is allowed to obtain a lower amount of undesirable H2O2 produced during the ORR and improve the Pt/C stability. It is assumed that the improved durability and the better selectivity towards 4e– reduction of oxygen of the modified catalyst result from the defective cerium oxide properties and strong interactions between all components. Acknowledgments: This research was funded by the National Science Center (Poland) under Sonatina Project (2022/44/C/ST5/00077) and under the auspices of the European Union EIT Raw Materials ALPE 19247 Project (Specific Grant Agreement No. EIT/RAW MATERIALS/SGA2020/1).

Enhanced Cyanide Oxidation to Cyanate via Photocatalytic Ozonation: Comparing Sol–Gel and Hydrothermal Synthesis of BiVO4 Catalysts

Bismuth vanadate has been reported as a promising active semiconductor for visible light harvesting. However, the rapid recombination of charge carriers has limited its photocatalytic properties. As an alternative route to treat contaminated water containing cyanide ions, photoactivated BiVO4 in combination with ozone has been investigated. BiVO4 photocatalysts were synthesized by microwave-assisted hydrothermal method, as well as by sol–gel, obtaining the monoclinic crystalline structure and a band gap of ~ 2.5 eV by XRD and UV–Vis DRS. The morphological analysis, elemental chemical composition, BET surface area, stability, and photoluminescence characteristics were carried out for both samples. Although the majority composition belongs to BiVO4, the presence of secondary phases was confirmed by XPS. The BiVO4 obtained by sol–gel (sol–gel BVO) exhibited superior photocatalytic performance with a lower reaction time (15 min) to oxidize free cyanide under visible-light radiation in combination with ozone. The degradation kinetics is described by pseudo-zero-order kinetics, and the rate constant (k0) of BiVO4 synthesized by microwave-assisted hydrothermal method was found to be the lower of the two. The high efficiency of the photocatalytic ozonation for the removal of free cyanide can be ascribed to a combination of two oxidation systems and the synergy of both processes.

Magnesium-Doped Hydroxyapatite Nanofibers for Medicine Applications: Characterization, Antimicrobial Activity, and Cytotoxicity Study.

Magnesium-doped hydroxyapatite (HAp-Mg) nanofibers show promise for medical applications due to their structural similarity to bone minerals and enhanced biological properties, such as improved biocompatibility and antimicrobial activity. This study synthesized HAp-Mg nanofibers using a microwave-assisted hydrothermal method (MAHM) to evaluate their cytotoxicity, biocompatibility, and antimicrobial efficacy compared to commercial hydroxyapatite (HAp). Characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR) confirmed the successful incorporation of magnesium, producing high-purity, crystalline nanofibers with hexagonal morphology. Rietveld refinement showed slight lattice parameter shortening, indicating Mg2+ ion integration. Cell viability assays (MTT and AlamarBlue) revealed a significant increase in fibroblast proliferation with 2% and 5% HAp-Mg concentrations compared to controls (p < 0.05), demonstrating non-cytotoxicity and enhanced biocompatibility. Antimicrobial tests (disk diffusion method, 100 µg/mL) showed that HAp-Mg had strong antibacterial effects against Gram-positive and Gram-negative bacteria and moderate antifungal activity against Candida albicans. In contrast, commercial HAp showed no antimicrobial effects. These results suggest HAp-Mg nanofibers have significant advantages as biomaterials for medical applications, particularly in preventing implant-related infections and supporting further clinical development.

Rapid synthesis of cobalt manganese phosphate by microwave-assisted hydrothermal method and application as positrode material in supercapatteries

Electrochemical energy storage devices with high specific capacity are of utmost important for the next-generation electronic devices. Supercapatteries (SCs) are highly demanded energy storage devices nowadays as these bridge the low energy supercapacitors and low power batteries. Herein, we report a rapid synthesis of cobalt manganese phosphate (COMAP) by microwave-assisted hydrothermal method and facile fabrication of SCs using electrodes comprising of COMAP as positrode material. The effect of precursor concentration on the microstructure and surface morphology of the COMAP samples are examined initially. Further, the electrochemical performance of COMAP electrodes is studied systematically in 3 M KOH (aqueous) electrolyte. COMAP exhibits excellent charge storage capabilities where type of charge storage mechanism is found to be battery-type based on the calculation obtained from Dunn’s method. The SC electrode fabricated with COMAP synthesized using cobalt: manganese precursor ratio as 80:20 exhibits a highest specific capacity of 191.4 C/g at a scan rate of 1 mV/s. An asymmetric SC (ASC) cell fabricated with COMAP as positrode and activated carbon (AC) as negatrode exhibits a specific capacity of 165.5 C/g at a current density of 1.8 A/g. The COMAP//AC ASC cell exhibits an energy density of 34.1 Wh/kg at a corresponding power density of 1875 W/kg at a current density of 1.8 A/g.

Microwave-hydrothermal synthesis, near ultraviolet/infrared-excited green fluorescence and ratiometric thermometry of Er3+-activated iodate phosphors

Fluorescence intensity ratio (FIR) technique has been a promising non-contact thermometry method owing to the characteristics of rapid response and exceptional resolution. In this study, a new iodate phosphor NaYI4O12:Er3+ (NYIO:Er3+) is synthesized via a microwave-assisted hydrothermal method. It exhibits bright green emission under 380 and 980 nm excitations. The power-dependent upconversion and Er3+ content-dependent downshifting performances are investigated. Excited by 380 nm, the temperature-dependent FIR originating from thermally coupled levels of Er3+ are discussed in detail. The resulting material displays outstanding temperature sensing properties across the temperature range of 298–523 K. The absolute and relative sensitivities can reach the maximum values of 0.51 × 10−2 K−1 and 1.3 % K−1, separately. Meanwhile, the reliability and repeatability of the temperature sensing characteristics are verified. The result demonstrates that the Er3+-activated iodate phosphor NaYI4O12:Er3+ is a promising candidate in non-contact optical thermometry domain.

Cu-doped NaNbO3 nanorods: Enhanced photocatalytic activity for RhB dye removal and antibacterial activity against E. coli

Sodium niobate (NaNbO3) nanorods with Cu (0.00, 0.01, 0.02 and 0.04 mmol) insertion were prepared by the microwave-assisted hydrothermal method and the photocatalytic and antibacterial activity was explored for the first time. X-ray diffraction confirms the coexistence of two orthorhombic phases (P21ma and Pbma) for all samples, with the percentage of each phase being strongly influenced by doping. The micrographs reveal that doping did not alter the shape or size of the grains (nanorods, with a diameter of ∼200 nm and a length of tens micrometers). The samples of pure NaNbO3 and those with 0.01 and 0.02 mmol of Cu showed an average band gap value of 3.08 eV. However, the sample containing 0.04 mmol of Cu exhibited a slight redshift. The photocatalytic activity of the samples was assessed by the removal of Rhodamine B dye (RhB), under ultraviolet light. All doped samples exhibited superior performance, with the sample containing 0.02 mmol of Cu showing the best photocatalytic activity, achieving 100 % RhB removal in 50 min. This was attributed to a lower rate of recombination of photogenerated charges, as evaluated through photoluminescence analysis. Additionally, the photocatalyst demonstrated excellent recyclability over three cycles. Pure NaNbO3 nanorods showed no antibacterial activity, but doping with 0.04 mmol of Cu reduced the growth of Escherichia coli.

Competent CuS QDs@Fe MIL101 heterojunction for Sunlight-driven degradation of pharmaceutical contaminants from wastewater

In this study, we introduce an advanced photocatalyst developed by integrating copper sulfide quantum dots (CuS QDs) with an iron-based metal–organic framework (MOF), specifically Fe MIL101. The resulting CuS QDs@Fe MIL101 photocatalyst is engineered to efficiently degrade meloxicam (MLX) under simulated sunlight. The heterojunctions were generated by incorporating different concentrations of CuS QDs (5 %, 10 %, 15 %, 20 %, and 50 %) into the Fe MIL101 MOF matrix using the microwave-assisted hydrothermal method. The results of the XRD and the TEM studies confirmed the formation of the heterojunctions, which maintain the structural integrity of both CuS QDs and Fe MIL101. The BET measurements indicated a decrease in surface area upon CuS QDs incorporation, attributed to porés blockage and structural modifications. UV–Vis diffuse reflectance spectroscopy (DRS) revealed a redshift in absorption edges as CuS QDs content increased, enhancing visible light absorption. Photoluminescence (PL) investigations revealed that the 15 % CuS QDs@Fe MIL101 heterojunction had an effective charge separation and low recombination rates. The zeta potential analysis revealed a negative surface charge, indicating an overall electronegative characteristic. The photocatalytic performance, assessed through the degradation of MLX, demonstrated that the 15 % CuS QDs@Fe MIL101 heterojunction achieved the maximum degradation efficiency, reaching 96 % after 45 min of irradiation at a dosage of 0.1 g/L. This exceptional performance is attributed to potent charge separation, improving visible light absorption, high surface area and adsorption capacity. Various scavengers were used to investigate the roles of different reactive species, revealing holes as the predominant active species in the photocatalytic degradation process. These results highlight the potential of 15 % CuS QDs@Fe MIL101 heterojunctions as efficient photocatalyst for environmental remediation from pharmaceutical pollutants under simulated sunlight. These findings highlight the potential for application of CuS QDs@Fe MIL101 in real-world wastewater treatment systems, particularly in addressing pharmaceutical contaminants like meloxicam in industrial effluents.

Microwave-assisted hydrothermal synthesis of highly dispersed cerium–zirconium solid solution on Ti3C2Tx nanosheets as an efficient decontamination towards sulfur mustard simulants

The microwave-assisted hydrothermal method has facilitated the straightforward and efficient production of nanoscale CexZr1−xO2/Ti3C2Tx composites. This technique has greatly shortened the synthesis time several hours required by conventional hydrothermal method to merely 10 min. Due to the unique mechanism of microwave-hydrothermal synthesis, composites with excellent crystallinity, uniform particle size, and superior degradation capabilities can be obtained without calcination. Our investigation systematically explores the influence of various factors including mineralizer concentration, dispersant types, synthesis duration, cerium-to-zirconium ratio, as well as MXene content on the material properties. Optimal degradation of 2-chloroethyl ethyl sulfide (2-CEES), sulfur mustard simulants, is achieved using PEG1000 as the dispersant, a cerium-to-zirconium ratio of 1:2, along with 15 mL of MXene, resulting in a remarkably short half-life of only 6.5 min. Furthermore, it is confirmed that the incorporation of cerium atoms into ZrO2 lattice, forming a solid solution that is deposited onto the interlayer and surface of Ti3C2Tx nanosheets, with the composite particles measuring approximately 5.01 nm. The reduced size and increased specific surface area, coupled with the synergistic effects of oxygen vacancies and acid-base sites, ultimately contribute to the hydrolysis and elimination reactions occurring on 2-CEES. This research offers fresh perspectives on the development of novel materials for the degradation of chemical warfare agents.

Novel synthesis and application of zeolite-Y from waste clay for efficient CO2 capture and water purification

In the present study, the microwave-assisted hydrothermal method using sodium hydroxide (NaOH) has been used to synthesise zeolite-Y from three different waste clays (WC) from Teesside, Northeast of England, UK. The effects of microwave time intervals and WC type were investigated to produce crystalline zeolite-Y. All WCs and synthesised zeolites were characterised by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller surface area measurement (BET). The characterisation results showed that the zeolite-Y samples synthesised at 6 min intervals exhibited larger total pore volumes, higher surface areas, and higher crystallinity compared to the samples synthesised at 4 min intervals. Especially, the synthesised zeolite-Y from Clay 1 displayed high CO2 adsorption capacity, achieving 5.23 mmol/g at 298 K and 1 bar, with a maximum methylene blue removal of 94.3 %. This sample showed a surface area of 485 m²/g and a pore volume of 0.24 cm³/g, alongside an Si/Al ratio of 3.7, highlighting its excellent thermal stability at elevated temperatures. The high CO2 adsorption capacity combined with the high methylene blue removal efficacy makes the synthesised zeolite-Y from WC an excellent candidate for efficient CO2 capture and removal of methylene blue from contaminated water. Additionally, this study illustrates the potential for waste valorisation through the conversion of low-value WC into high-performance, value-added materials. This transformation not only mitigates waste disposal issues but also contributes to sustainable resource management and environmental protection by offering a practical solution for treating industrial effluents and gas emissions.

Effect of polyethylene glycol on the synthesis of hydroxyapatite obtained via microwave-assisted hydrothermal method

Effect of polyethylene glycol on the synthesis of hydroxyapatite obtained via microwave-assisted hydrothermal method

BaZrO3 and its application as a photocatalyst for Rhodamine B removal

In this investigation, Barium zirconate (BaZrO3 or BZO) showcasing high photocatalytic efficacy was synthesized by the microwave-assisted hydrothermal method. Photocatalytic activity was investigated through the removal of the Rhodamine B (RhB) dye. Although it has a high band gap (∼5 eV), BZO showed the capacity to remove ∼ 56 % of RhB. Defects, hydroxyl radicals adsorbed on its surface and favorable electronic structure were factors that promoted photocatalytic activity. Furthermore, the BZO exhibited exceptional recyclability, underscoring its potential as a photocatalyst for environmental remediation applications.

Hierarchically porous MgO/biochar composites for efficient CO2 capture: Structure, performance and mechanism

For enhancing the CO2 uptake performance of MgO-based materials, hierarchically porous MgO/biochar composites were prepared using a microwave-assisted hydrothermal method. The CO2 adsorption properties was investigated in detail and the adsorption mechanism was revealed by considering structure − function relationships and performing density functional theory calculations. The MgO/biochar-1 had hierarchical pore structure and high specific surface area (1453 m2·g−1) with abundant narrow micropores (<1.0 nm), facilitating the adsorption of CO2. The results demonstrated that MgO/biochar-1 exhibited the highest CO2 capture capacity of 6.65 mol⋅kg−1 (273 K, 1 bar) and excellent selectivity for CO2/N2 (96.70 at CO2/N2 = 15:85, v/v). After 3 cycles, the adsorption capacity of MgO/biochar-1 still remained at 5.70 mol⋅kg−1 (273 K, 1 bar), suggesting the well cycling performance. The results of density functional theory calculation indicated that the oxygen-containing functional groups and MgO particles substantially enhanced the CO2 capture performance due to the enhanced interactions between MgO/biochar and CO2. This study provides novel insights for the construction of efficient and cheap solid adsorbents for CO2 capture.

Enhanced antimicrobial activity of Cu-decorated graphene nanoplatelets and carbon nanotubes

New materials with antimicrobial properties are necessary to combat the proliferation and transmission of pathogenic microorganisms. In this work, graphene nanoplatelets (GPN) and multi-walled carbon nanotubes (CNT) decorated with Cu nanoparticles (Cu NPs) were synthetized by microwave-assisted hydrothermal method, varying the Cu content from 1 to 10 wt.%. These materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, and scanning and transmission electron microscopy (SEM and TEM) and their antimicrobial activity against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) were evaluated. The sample with 10 wt.% Cu at CNTs is more effective compared to GPNs. Then, brass coatings with pure and Cu-decorated (10 wt.%) CNTs and GPNs were prepared by spin coating to evaluate the antimicrobial activity of these surfaces. It was observed that coatings with the carbon matrices reduced microbial growth by 2 logs, whereas decoration with Cu NPs amplified this value, especially for the Cu/CNT coating, achieving up to a 6-log reduction after 24 h of contact. The stability of the antimicrobial activity of these coatings was evaluated over 5 successive 24-h cycles, demonstrating high stability. DFT calculations on a simplified model, based on a Cu atom adsorbed on GPN and CNT, reveal a thermodynamically favorable pathway to explain the antibacterial activity. The results show a mechanism that could promote the formation of the precursors of hydroxyl (⦁OH), superoxide (⦁O2−), and hydroperoxyl (⦁OOH) radicals, which are adsorbed strongly on GPN and CNT surfaces. This study highlighted the critical role of Cu NPs-loaded on carbon materials, GPN and CNT, in enhancing the antibacterial activity.

Microwave-assisted hydrothermal synthesis of Ag/Bi2MoO6/ZnO heterojunction with nano Ag as electronic accelerator pump for high-efficienty photocatalytic degradation of levofloxacin

The fluoroquinolone antibiotics, as a category of emerging refractory organic pollutants, have triggered intensive attention due to their persistent ecotoxicology for aquatic environments. Herein, a novel Ag/Bi2MoO6/ZnO (Ag/BMO/ZnO) heterojunction was prepared using a two-step microwave-assisted hydrothermal method for photocatalytic degradation of levofloxacin (LFX). The optimal Ag/BMO/ZnO delivers higher photocatalytic degradation efficiency toward LFX reaching 86.4 %, which is 3 times and 7 times higher than those of neat Bi2MoO6 and ZnO, respectively. This can mainly be attributed that the existence of heterojunction between Bi2MoO6 and ZnO promotes the transmission of photogenerated charges (e−/h+). Furthermore, the introduction of Ag nanoparticles serves as an electron accelerator pump, which can also effectively accelerate the transport and separation of the photogenerated e−/h+. Both of these indirectly retard the recombination of e−/h+. The radical capture assays demonstrate that 1O2, OH, h+ and O2– are responsible for the the degradation of LFX and the 1O2 is the primary reactive oxygen species (ROS). Moreover, based on the identification of degradation intermediates via the liquid-chromatography-mass spectrometry (LC-MS) technique, the possible degradation routes of LFX were plausibly inferred. In conclusion, this work provides a new perspective toward antibiotics removal by developing novel heterojunction photocatalysts anchored with precious nanoparticles.

New insights into non-linear optical properties, photocatalytic activity, and applications of ZnSe:Cu nanoparticles prepared by microwave-assisted hydrothermal method

In the present work, semiconducting ZnSe:Cu (0, 0.1, 0.75, 1.5, 2.25 and 3 mol%) nanoparticles (NPs) were prepared by microwave-assisted hydrothermal (MAH) method at the fixed pH of 11.2. XRD patterns certified the formation of nanocrystals with the size of about 2.04–2.21 nm. Also, FESEM and TEM images confirmed the formation of round-shape NPs. UV–Vis spectra showed that the energy gap of nanoparticles decreased from 3.615 to 3.342 eV by the increment in copper impurity content. The exact value of the energy gap of NPs was determined by the absorption spectrum fitting derivative method (DASF). Results revealed that these NPs have a high potential in optical and optoelectronic applications; specially, the samples owing 1.5 and 2.25 mol% of Cu-impurity, as the best candidates for optical fiber applications, showed the highest third order non-linear optical susceptibility (χ(3)). Also, for all synthesized NPs, the optical characteristics such as the optical transition index (m), Urbach energy (Etail), dielectric constant (ε) and the refractive index (n) at the absorption edge were determined. Moreover, the amount of metallization factor was also calculated, which decreases with the increase of impurity and microwave irradiation, indicating the increase of metal affinity of the samples. Photoluminescence (PL) spectra of ZnSe NPs demonstrated a general reduction in the intensity upon the introduction of Cu. This anticipated quenching further supports their heightened photocatalytic activity. The results of photocatalytic tests indicate that the sample containing 2.25 mol% of Cu exhibits the highest rate constant value (0.0255 min−1) and achieves the maximum efficiency (75.7 % after 60 min) for degrading the DB71, establishing it as the prime candidate for photocatalytic applications.

Visible-light-driven Bi2WO6/biochar composite photocatalyst efficiently degrades 17α-ethinylestradiol (EE2) and 17β-estradiol (E2) under persulfate synergy

Biochar (BC) composite photocatalysts have attracted much attention by virtue of their high efficiency in removing endocrine disruptors (EDCs). However, there has been a lack of systematic research on the mechanism and constitutive relationship of BC on photocatalysts, which has seriously impeded the development process in this field. In this study, Bi2WO6–BC2% composite photocatalysts were prepared by microwave-assisted hydrothermal method and used for degradation of 17α-ethinylestradiol (EE2) and 17β-estradiol (E2) in conjunction with persulfate synergy (PS). The removal rate of EE2 and E2 by Bi2WO6–BC2% was as high as 99.41 % (12 min) and 97.84 % (15 min), respectively. Systematic studies have shown that BC enhances the catalytic activity mainly through the following ways, increasing the specific surface area of the photocatalytic system, enriching the types of functional groups, enhancing the separation ability of photogenerated electron–hole pairs, and promoting the concentration of active free radicals. The results of the phytotoxicity experiments showed that compared to the EE2 or E2 pollutant solutions, the stem and root lengths of V. radiata increased by 93.63 % and 389.58 % in EE2 metabolites, and by 117.35 % and 160.38 % in E2 metabolites. Similarly, the stem and root lengths of P. vulgaris increased by 80.08 % and 174.91 % in EE2 metabolites, and by 188.92 % and 345.75 % in E2 metabolites. This work not only fills the gap in the study of the mechanism of action of BC, but also provides a green catalyst with very excellent photocatalytic efficiency and detoxification properties.

Tunable multi-peak emission solid-state fluorescent carbon dots: Luminescence regulation mechanism and application in single-component-based LEDs

The design of solid-state fluorescent carbon dots (CDs) with multi-peak emission has become an urgent challenge to be solved with the in-depth research of CDs in LEDs. Here, one- and two-component solid-state white light CDs are synthesized by microwave-assisted hydrothermal method using the biological pollutant cyanobacteria, respectively. The solid-state fluorescence quantum yield of the one-component CDs was as high as 41.8 %, and the solid-state fluorescence mechanism of CDs is discussed to be mainly attributed to the self-quenching-resistant feature of “core-shell” structure and the reabsorption/RET-induced long-wavelength red light emission, and attenuation of the short emission wavelength. For two-component white light CDs, blue- and red-light CDs are obtained by simple dialysis separation, realizing the fluorescence tunability. The different origins of their multi-peak emission are discussed: core, edge and surface states. The synthesis yields of CDs are up to 62 %, enabling stable gram-scale production. The white- and red-light CDs are used as phosphors to fabricate fluorescent films and cold, pure, and warm white- and red-light LEDs with good resistance to photobleaching and temperature stability and CRI of 84.4, 85.7 and 61.5.