Electron Paramagnetic Resonance Characterization Research Articles

Reduction of c-type cytochromes by Fe(II)-ligand under oxic conditions: Roles of Fe(II)-heme complexation and reactive oxygen species

Microbial Fe(II) oxidation is mainly mediated by the outer-membrane proteins that contain c-type cytochromes (c-Cyts), and the widespread Fe(II)-oxidizing bacteria are usually subjected to fluctuations between oxic and anoxic conditions. However, it remains unclear how oxygen affects the redox dynamics of c-Cyts by Fe(II), particularly in the presence of organic ligands that are widely distributed in the environment. Here, the reduction of a model heme-containing c-Cyts by Fe(II) was investigated in the absence and presence of organic ligands (i.e., citrate and acetate) at pH 5.5 under anoxic and oxic conditions. The kinetic results showed that c-Cyts reduction was enhanced by citrate and acetate under anoxic conditions, and the enhancement by citrate was more pronounced than that by acetate. The speciation calculation and cyclic voltammetry results suggested that the proportions of Fe(II)-Citrate complexes were much higher than those of Fe(II)-Acetate complex, but the addition of acetate and citrate caused minor changes in redox potential of Fe(II)/Fe(III) species. Further analysis using quantum chemical computation demonstrated that the formation of Fe(II)-Heme complexes via lateral binding to the carboxyl group of c-Cyts was more stable than those via replacing the S-linked axial ligand of heme, with the recombination energy with Heme ranking as Fe(II)-Citrate < Fe(II)-Acetate < Fe(II). Therefore, the stronger complexation of Fe(II)-Citrate and its lower recombination energy with c-Cyts drive the enhanced c-Cyts reduction under anoxic conditions. By contrast, the c-Cyts reduction by Fe(II) and Fe(II)-ligand was inhibited under oxic conditions. The electron spin resonance characterization indicated that both O2−• and OH• radicals were produced in the system of c-Cyts with Fe(II) or Fe(II)-ligand under oxic conditions and the signals were higher with Fe(II)-ligand than those with Fe(II). These reactive oxygen species were proposed to enable a re-oxidation of the c-Cyts that was reduced by Fe(II) or Fe(II)-ligand, causing an inhibitory effect on the observed c-Cyts reduction and forming more reactive oxygen species. Our findings shed light on the important roles of Fe(II)-ligand-heme complexation and reactive oxygen species in the interaction between Fe(II) and c-Cyts, which deepen the understanding of microbial/enzymatic Fe(II) oxidation under oxic conditions at the molecular level.

Realizing golden ultraviolet C emission of 265 nm by oxygen vacancies engineering for 100 % sterilization efficiency

Ultraviolet C (UVC) light has a great promising application in the field of sterilization. However, how to obtain efficient UVC emission with peak maximum at 265 nm that is called ‘golden sterilization wavelength’ remains a great challenge. Herein, we propose a defect-engineering strategy to obtain enhanced UVC emission at the golden sterilization wavelength of 265 nm through introducing oxygen vacancies into Pr3+ doped Ba2MgSi2O7 melilite phosphors. Combined with X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and thermoluminescence (TL) characterizations, it is confirmed that the calcination of Ba2MgSi2O7:Pr3+ in an inert atmosphere could efficiently increase oxygen vacancy concentration, promoting the efficient energy transfer from the melilite host to Pr3+ ions. It could lead to a significant enhancement of the luminescence intensity to 2.43 times of the initial one with less oxygen vacancies. The optimized Ba2MgSi2O7:0.4%Pr3+ phosphor could effectively inactivate 100 % of Staphylococcus aureus within 8 min, showing higher efficiency than commercially available mercury lamp. This work provides an effective solution for the design and preparation of UVC phosphors using defect engineering to achieve golden UVC emission.

Rapid degradation of high-concentration antibiotic via heterogeneous photocatalysis coupling Fenton-like oxidation with MIL-53(Fe) under visible light irradiation

The photocatalytic technology based on Metal-Organic Frameworks (MOFs) has shown promising applications in the field of antibiotic pollution control. However, it still faces challenges in efficiently removing high-concentration antibiotic wastewater. A typical Fe-containing MOF, MIL-53(Fe), was successfully synthesized and demonstrated efficient photocatalytic activity under visible light irradiation for high-concentrations of tetracycline hydrochloride (TCH). However, the bare MIL-53(Fe) exhibited unsatisfactory photocatalytic performance. To overcome the low degradation efficiency resulting from the rapid recombination of light-induced electron-hole pairs, H2O2 was introduced as an external electron acceptor to establish a synergistic Fenton-like system to couple with the photocatalysis process. The results showed that in the MIL-53(Fe)/H2O2/Vis system, 99% of 1 g/L TCH was degraded within 80 min, while the degradation efficiency of the MIL-53(Fe)/Vis process was only 4.89% under identical conditions. The degradation mechanism of the coupling system was performed by radical scavenging experiments and Electron Spin Resonance characterization. The results indicated that ·OH was the dominant radical in the coupled reaction, and ·O2- and h+ also played a role in this system. The significant improvement in TCH degradation efficiency during the coupling process was attributed to the following three factors: (1) In the coupling reaction process, photo-generated electrons can stimulate H2O2 to form ·OH radicals, inhibiting the recombination of photo-generated electrons and holes, improving the efficiency of the photocatalytic reaction. (2) FeIII in MIL-53(Fe) can be excited by photo-generated electrons and converted to FeII, which then stimulates H2O2 to form ·OH radicals. (3) FeIII in MIL-53(Fe) can convert with FeII, stimulate H2O2 to form ·OH radicals, and participate in the degradation reaction. In addition, the reusability and stability of the MIL-53(Fe) photocatalyst in the coupled system, as well as the impact of operational parameters, were systematically studied. This work demonstrates a feasible strategy for environmental remediation by enhancing the efficiency of MIL-53(Fe) in photocatalytic Fenton-like systems, thereby providing a viable approach for the treatment of high-concentration antibiotic wastewater.

Bi-Doped and Bi Nanoparticles Loaded CeO2 Derived from Ce-MOF for Photocatalytic Degradation of Formaldehyde Gas and Tetracycline Hydrochloride.

Bi/CeO2 (BC-x) photocatalysts are successfully prepared by solvothermal loading Bi nanoparticles and Bi-doped CeO2 derived by Ce-MOF (Ce-BTC). Formaldehyde gas (HCHO) and tetracycline hydrochloride (HTC) are used to evaluate the photocatalytic activity of the synthesized Bi/CeO2. For BC-1000 photocatalyst, the degradation of HTC by 420nm < λ < 780nm light reaches 91.89% for 90min, and HCHO by 350nm < λ < 780nm light reaches 94.66% for 120min. The photocatalytic cycle experiments prove that BC-1000 has good cyclic stability and repeatability. The results of photoluminescence spectra, fluorescence lifetime, photocurrent response, and electrochemical impedance spectroscopy showed that the SPR (Surface Plasmon Resonance) effect of Bi nanoparticles acted as a bridge and promoted electron transfer and enhanced the response-ability of Bi/CeO2 to visible light. Bi-doping produced more oxygen vacancies to provide adsorption sites for adsorbing oxygen and generated more ·O2 - thus promoting photocatalytic reactions. The mechanism of photocatalytic degradation is analyzed in detail utilizing active free radical capture experiments and electron paramagnetic resonance (EPR) characterization. The experimental results indicate that ·O2 - and h+ active free radicals significantly promote the degradation of pollutants.

S-type heterojunction enhance the photocatalytic activity of TiO2/AgBr/Ag using loofah sponge as template towards ciprofloxacin degradation

Photocatalyst TiO2/AgBr/Ag (TBA) composites using loofah sponge as a template were successfully prepared for the first time. The photocatalytic activities of the TBA composites were evaluated by removing ciprofloxacin (CIP) under visible light. The PDOS shows that the valence band edge of TBA-30 is primarily composed of Ti 3d atom states, with small contributions from O 2p atom states. The conduction band edge is dominated by Ag 4d and O 2p atom states, with minor contributions from Br 4p atom states. TBA-30 composites demonstrate outstanding photocatalytic performance, degrading 87% of the target within 180 min. The degradation rate of CIP decreased to 70.19% after five runs, Furthermore, the TOC removal efficiency of CIP reached 84.2% in the end. CIP intermediates and degradation pathway were determined by GC-MS. Three-dimensional excitation-emission matrix fluorescence spectra (3D EEM) were used to study the degradation of CIP molecules. Trapping experiments and electron paramagnetic resonance (EPR) characterisation identified superoxide (·O2-) and photogenerated holes (h+) as the primary active radicals. Furthermore, formed S-type heterojunction and Ag as the electron capture site enhanced the separation efficiency of photoinduced electron-hole pairs. The DFT calculation was used to study the electron transport performance of TBA-30 by calculating the charge density difference.

Oxygen vacancy-rich CoMoO4/Carbon nitride S-scheme heterojunction for boosted photocatalytic H2 production: Microstructure regulation and charge transfer mechanism

Developing highly efficient S-scheme photocatalysts is a subject of immense interest for harnessing solar energy towards sustainable hydrogen production. Herein, a novel S-scheme heterojunction of oxygen vacancy-rich CoMoO4/CN (CMO/CN) photocatalyst was rationally constructed through loading CoMoO4 nanorods on carbon nitride (CN) nanosheets via a direct one-pot calcination method. The CMO/CN S-scheme heterojunction exhibited enhanced surface area, fine CN dispersion, rich oxygen vacancies, and accelerated charge separation/transfer efficiency, which were conducive to improving photocatalytic H2 evolution performance. Of note, the optimal 3 %CMO/CN sample displayed the highest H2 production rate of 8.35 mmol g−1 h−1, which is 4.6 folds that of pristine CN. In situ irradiated X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) characterizations confirmed the S-scheme charge transfer path between CN and CMO, which greatly promoted spatial charge separation. Density functional theory (DFT) calculations together with contact angle tests revealed the reduced activation energies for H2O dissociation and enhanced hydrophilicity of the CMO/CN. The CMO/CN photocatalysts also presented high stability and fine reusability. This work may provide insights into the combination of defect engineering and heterojunction designing for high-efficiency solar-to-chemical energy conversion.

Construction of Monoatomic-Modified Defective Ti4+αTi3+1-αO2-δ Nanofibers for Photocatalytic Oxidation of HMF to Valuable Chemicals.

Efficiently upgrading 5-hydroxymethylfurfural (HMF) into high-value-added products, such as 2,5-diformylfuran (DFF) and 2,5-furan dicarboxylic acid (FDCA), through a photocatalytic process by using solar energy has been incessantly pursued worldwide. Herein, a series of transition-metal (TM = Ni, Fe, Co, Cu) single atoms were supported on Ti4+αTi3+1-αO2-δ nanofibers (NFs) with certain defects (Ov), denoted as TM SAC-Ti4+αTi3+1-αO2-δ NFs (TM = Ni, Fe, Co, Cu), aiming to enhance the photocatalytic conversion of HMF. A super HMF conversion rate of 57% and a total yield of 1718.66 μmol g-1 h-1 (DFF and FDCA) surpassing that of the Ti4+αTi3+1-αO2-δ NFs by 1.6 and 2.1 times, respectively, are realized when TM is Co (Co SAC-Ti4+αTi3+1-αO2-δ NFs). Experiments combined with density functional theory calculation (DFT) demonstrate that the TM single atoms occupy the Ti site of Ti4+αTi3+1-αO2-δ NFs, which plays a dominant role in the photo-oxidation of HMF. Raman, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) characterizations confirm the strong electron local exchange interaction in TM SAC-Ti4+αTi3+1-αO2-δ NFs and demonstrate the substitution of Ti by the TM SACs. The projected density of states and charge density difference reveal that the strong interaction between metal-3d and O-2p orbitals forms Ti-O-TM bonds. The bonds are identified as the adsorption site, where TM single atoms on the surface of Ti4+αTi3+1-αO2-δ NFs reduce HMF molecule adsorption energy (Eads). Furthermore, the TM single atom modulates the electronic structure of TM SAC-Ti4+αTi3+1-αO2-δ NFs through electron transfer, leading to narrow band gaps of the photocatalysts and enhancing their photocatalytic performance. This study has uncovered a newer strategy for enhancing the photocatalytic attributes of semiconducting materials.

Investigating Iron-Sulfur Proteins in Infectious Diseases: A Review of Characterization Techniques

Iron-sulfur [Fe-S] clusters, comprising coordinated iron and sulfur atoms arranged in diverse configurations, play a pivotal role in redox reactions and various biological processes. Diverse structural variants of [Fe-S] clusters exist, each possessing distinct attributes and functions. Recent discovery of [Fe-S] clusters in infectious pathogens, such as Mycobacterium tuberculosis, and in viruses, such as rotavirus, polyomavirus, hepatitis virus, mimivirus, and coronavirus, have sparked interest in them being a potential therapeutics target. Recent findings have associated these [Fe-S] cluster proteins playing a critical role in structural and host protein activity. However, for a very long time, metalloenzymes containing iron-sulfur clusters have been prone to destabilization in the presence of oxygen, which led to a delayed understanding of [Fe-S] proteins compared to other non-heme iron-containing proteins. Consequently, working with [Fe-S] proteins require specialized equipment, such as anaerobic chambers to maintain cofactor integrity, and tools like ultraviolet visible (UV-Vis) spectroscopy, mass spectrometry, X-ray crystallography, nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), Mössbauer spectroscopy and electrochemical characterization. Many of these [Fe-S] cluster proteins have been misannotated as Zinc-binding proteins when purified aerobically. Moreover, the assembly of these iron-sulfur cluster cofactors have not been fully understood since it is a multi-step assembly process. Additionally, disruptions in this assembly process have been linked to human diseases. With rapid advancements in anaerobic gloveboxes and spectroscopic techniques, characterization of these [Fe-S] cluster-containing proteins that are essential for the pathogens can open up new avenues for diagnostics and therapeutics.

Improving the hydrothermal stability of Al-rich Cu-SSZ-13 zeolite via Pr-ion modification.

Al-rich (Si/Al = 4-6) Cu-SSZ-13 has been recognized as one of the potential catalysts to replace the commercial Cu-SSZ-13 (Si/Al = 10-12) towards ammonia-assisted selective catalytic reduction (NH3-SCR). However, poor hydrothermal stability is a great obstacle for Al-rich zeolites to meet the catalytic applications containing water vapor. Herein, we demonstrate that the hydrothermal stability of Al-rich Cu-SSZ-13 can be dramatically enhanced via Pr-ion modification. Particularly, after high-temperature hydrothermal aging (HTA), CuPr1.2-SSZ-13-HTA with an optimal Pr content of 1.2 wt% exhibits a T80 (temperature window of NO conversion above 80%) window of 225-550 °C and a T90 window of 250-350 °C. These values are superior to those of Cu-SSZ-13-HTA (225-450 °C for T80 and no T90 window). The results of X-ray diffraction Rietveld refinement, electron paramagnetic resonance (EPR) and spectral characterization reveal that Pr ions mainly located in the eight-membered rings (8MRs) in SSZ-13 zeolite can inhibit the generation of inactive CuOx during hydrothermal aging. This finding is further supported by density functional theory (DFT) calculations, which suggest that the presence of Pr ions restrains the transformation from Cu2+ ions in 6MRs into CuOx, resulting in enhanced hydrothermal stability. It is also noted that an excessive amount of Pr ions in Cu-SSZ-13 would result in the production of CuOx that causes the decline of catalytic performance. The present work provides a promising strategy for creating a hydrothermally stable Cu-SSZ-13 zeolite catalyst by adding secondary metal ions.

Utilizing EPR spectroscopy to investigate the liquid adsorption properties of bimetallic MIL-53(Al/Cr) MOF.

The flexibility of the MIL-53(M) metal-organic framework (MOF) has been elucidated through various characterization methodologies, particularly in gas and liquid adsorption processes. However, to the best of our knowledge, there has been no prior electron paramagnetic resonance (EPR) characterization of liquid-phase adsorption in the MOF MIL-53(M), which offers insights into local geometric changes at the oxygen octahedron containing the metal ions of the framework. In this study, we investigate, for the first time, the pore transformations within the MIL-53(Al0.99Cr0.01) framework during liquid-phase adsorption using EPR spectroscopy. Our investigation concentrates explicitly on the adsorption of pure solvents, including water, methanol, ethanol, isopropanol, pyridine, and mixed water/methanol phases. The EPR spectroscopy on the (Al0.99Cr0.01) MOF has allowed us to witness and comprehend the transitions between the narrow pore and large pore phases by examining changes in the zero-field splitting parameters of the S = 3/2 Cr(iii) species. Of all the solvents examined, a robust and distinct spectral feature observed during methanol adsorption unequivocally indicates the pore opening.

2D/1D BiOBr/TiO2 flexible nanofibrous film heterojunction photocatalyst for tetracycline degradation

Semiconductor photocatalysis is an ideal and sustainable solution to effectively remove Tetracycline (TC). Herein, a hierarchical flexible nanofibrous film (NF) heterojunction photocatalyst of BiOBr/TiO2 was fabricated via a combination of electrospinning and solvothermal method, obtaining the two-dimensional (2D) BiOBr nanosheets uniformly anchored on the surface of one-dimensional (1D) TiO2 nanofiber, and the amount of BiOBr significantly influences the physicochemical properties of the heterojunction photocatalyst, the optimal sample of BT-2 manifests large pore size and high surface area, prominent visible light response ability and narrow band gap as well as outstanding charge separation efficiency, thus achieves significantly enhanced photocatalysis activity for TC degradation, which is about twice higher than that of the pristine TiO2 NF. More importantly, the BT-2 sample also displays high reusability and stability over a 10-cycle period and can be easy to recover. Meanwhile, the radical scavenging experiments and electron spin resonance characterization reveal that ·O2– and h+ occupy an irreplaceable role in degrading TC. Moreover, regarding the analysis of intermediates and density functional theory calculations, the TC photodegradation mechanism and pathways are proposed. Our finding offers a prospective solution for designing BiOBr/TiO2 heterojunction recyclable photocatalysts for efficient TC photodegradation.

P1 Center Electron Spin Clusters Are Prevalent in Type Ib Diamonds.

Understanding the spatial distribution of the P1 centers is crucial for diamond-based sensors and quantum devices. P1 centers serve as polarization sources for dynamic nuclear polarization (DNP) quantum sensing and play a significant role in the relaxation of nitrogen vacancy (NV) centers. Additionally, the distribution of NV centers correlates with the distribution of P1 centers, as NV centers are formed through the conversion of P1 centers. We utilized DNP and pulsed electron paramagnetic resonance (EPR) techniques that revealed strong clustering of a significant population of P1 centers that exhibit exchange coupling and produce asymmetric line shapes. The 13C DNP frequency profile at a high magnetic field revealed a pattern that requires an asymmetric EPR line shape of the P1 clusters with electron-electron (e-e) coupling strengths exceeding the 13C nuclear Larmor frequency. EPR and DNP characterization at high magnetic fields was necessary to resolve energy contributions from different e-e couplings. We employed a two-frequency pump-probe pulsed electron double resonance technique to show cross-talk between the isolated and clustered P1 centers. This finding implies that the clustered P1 centers affect all of the P1 populations. Direct observation of clustered P1 centers and their asymmetric line shape offers a novel and crucial insight into understanding magnetic noise sources for quantum information applications of diamonds and for designing diamond-based polarizing agents with optimized DNP efficiency for 13C and other nuclear spins of analytes. We propose that room temperature 13C DNP at a high field, achievable through straightforward modifications to existing solution-state NMR systems, is a potent tool for evaluating and controlling diamond defects.

Copper Complexes in Verdigris Painting Mixtures: An Electron Paramagnetic Resonance Characterization

Abstract Copper complexes, also called “copper soaps” when referred to carboxylate compounds, have become a concern in the conservation of historical artefacts. These complexes are suspected to play a significant role in degradation processes such as darkening and cracking of painting layers. Here we propose the Continuous Wave Electron Paramagnetic Resonance spectroscopy (CW-EPR) as a tool for the identification of these species. EPR spectroscopy is a micro-invasive and non-destructive technique that is highly sensitive to paramagnetic species, including radicals, crystal defects, and transition metal ions, e.g., Cu(II) and Fe(III). We have selected the verdigris (copper acetate) pigment combined with many organic binders, e.g., egg tempera and gum Arabic, as mock-up systems because of the known degradation tendency of the copper-based pigment. We would like to demonstrate that a precise analysis of the experimental spectra assisted with the calculus of the main magnetic quantities could lead to a good characterization of the copper complexes (or “soaps”).

Nitrogen-doped hollow carbon spheres as efficient metal-free peroxymonosulfate activator for degradation of organic pollutant

Developing effective metal-free catalytic materials via constructing copious surface-exposed active sites to promote peroxymonosulfate (PMS) activating for degradation of hazardous organics is highly desirable toward practical application. In this study, we report the utilization of N-functionalized hollow carbon spheres (N-HCS) as efficient PMS activator for Rhodamine B (RhB) degradation. Results indicate that N-doping of hollow carbon spheres can introduce an abundance of pyridinic N and CO sites, which serve as catalytically active sites for PMS activation toward RhB degradation. The fabricated catalyst exhibits excellent performances with a degradation efficiency of 100 % and a rate constant of 0.0566 min−1 for RhB degradation under optimal conditions. Besides, the developed N-HCS catalyst displays a good reusability, maintaining a high degradation efficiency after the 5th run. Quenching tests and electron spin resonance characterization results reveal the coexistence of radical and non-radical degradation pathways, and SO4− and 1O2 are demonstrated as the dominant reactive oxygen species. This architecture integrated surface microenvironment engineering strategy can be extended to regulate the degradation performance of carbon-based materials for PMS activation toward removing other organic pollutants.

Novel Z-scheme Nb2O5/C3N5 photocatalyst for boosted degradation of tetracycline antibiotics by visible light-assisted activation of persulfate system

Photocatalytic-assisted activation of persulfate (PDS) is regarded as a promising method for the rapid and efficient degradation of refractory pollutants in the water environment. In this study, a novel Nb2O5/C3N5 (NOCN) p-n heterojunctions composite was created by loading n-type Nb2O5 onto p-type C3N5 via an in-situ facile one-step calcination method. The NOCN/PDS system exhibited excellent performance in degrading tetracycline (TC) antibiotics under visible light and had great cyclic stability. The degradation efficiency of the coupled system reached 95 %, surpassing the pure C3N5 and PDS systems by 3.5 times and 2.4 times, respectively. The degradation rate of target pollutants was improved by the coupled system with the photocatalytic activation of PDS. The photogenerated electrons (e-) in NOCN were able to activate PDS effectively, which facilitated the creation of more reactive species. The Photoluminescence (PL) and other photoelectrochemical data demonstrated that the interfacial charge separation and photoresponsivity were remarkably enhanced in the coupled system. According to Mott-Schooky and electron spin resonance (ESR) characterization, it was confirmed that the reaction mechanism was the Z-scheme charge transfer mechanism based on p-n heterojunctions in the NOCN/PDS system. In addition, LC-MS analyses, TOC monitoring and biotoxicity analyses detected that the target pollutants were degraded to weakly bio-toxic micromolecules. In conclusion, this work provides valuable insights into the application of visible light-activated PDS technology in the degradation of organic pollutants, highlighting its potential for practical implementation.

In-situ self-assembled flower-like ZnIn2S4/CdIn2S4 composites with enhanced interfacial charge transfer and photocatalytic degradation of atrazine

In heterostructure photocatalysts, interface charge transfer is a crucial step in the photocatalytic process, so it is crucial to construct photocatalysts with high interface charge transfer efficiency. Here we report an in-situ self-assembled flower-like ZnIn2S4/CdIn2S4 (ZCIS) composites with excellent catalytic performance for atrazine (ATZ) degradation. The ZCIS-4 composite could degrade 99.82% of ATZ within 40 min, which showed 1.42 and 1.91 times better than blank ZnIn2S4 and CdIn2S4, respectively. The excellent catalytic performance is attributed to the built-in electric field in the in-situ self-assembled composite photocatalyst, which accelerates the rapid transfer of interfacial charges and the rapid separation of photogenerated electron hole pairs. The toxicity assessment shown that some intermediates exhibited decreased toxicities; however, the toxicities were still significant. Active radical capture experiments and electron spin resonance characterization demonstrated that h+, O2− were the main active free radicals. Differential charge density simulation calculations verified that interface photogenerated electrons were transported from CIS to the ZIS surface.

Plasma defect-engineering of bulk oxygen-deficient zirconia

Oxygen-deficient zirconia (ZrO2-x) has recently emerged as a promising material for light absorption and photocatalytic applications. However, the economic and environmentally friendly manufacture of bulk ZrO2-x remains challenging and has limited widespread adoption. In this study, we present a novel low-pressure (300 Pa) plasma treatment (H2 gas at 500 °C for 5 h) capable of producing fully-dense bulk ZrO2-x without significant structural modifications. EPR (electron paramagnetic resonance) and XPS (X-ray photoelectron spectroscopy) characterisation of the plasma treated zirconia indicate the formation of Zr3+ ions and F2+ (VO··) centres. The increase of oxygen vacancies is also supported by the greater exothermic heat flow and relative mass gain observed through TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry) analyses. Diffuse reflectance spectroscopy (DRS) reveals a substantial enhancement in light absorption, with an average increase of 66.2 % and >65 % absolute absorption across the entire spectrum (200–3000 nm). XPS and DRS measurements suggest significant reduction in both direct (from 4.84 to 2.61 eV) and indirect (from 3.19 to 1.45 eV) bandgap transition. By effectively enhancing the light absorption capability, reducing bandgap transitions, and maintaining the structural integrity of zirconia, low-pressure plasma treatments offer a promising and scalable approach for the environmentally friendly production of next-generation ZrO2-x materials.

Probing the Effect of Linear and Crosslinked POE-g-GMA on the Properties of Asphalt.

The copolymer ethylene-octene (POE) has good aging resistance and is an inexpensive asphalt additive compared to the styrene-butadiene-styrene copolymer (SBS). However, POE is easy to segregate in asphalt during storage at high temperatures. Grafting glycidyl methacrylate (GMA) onto the molecular backbone of POE (i.e., POE-g-GMA) may solve this problem, for the epoxy groups in GMA can react with the active groups in asphalt. Asphalt modified with linear and crosslinked POE-g-GMA were prepared, and the hot storage stability, physical properties and thermal oxidation aging properties were discussed in detail. The results show that linear and low-degree crosslinked POE-g-GMA-modified asphalts are storage-stable at high temperatures via measurements of the difference in softening points and small-angle X-ray scattering (SAXS) characterizations from macro and micro perspectives. The difference in softening points (ΔSP) between the upper and lower ends is no more than 3.5 °C for modified asphalts after 48 h of being in an oven at 163 °C. More importantly, the crosslinking modification of POE-g-GMA can further increase the softening point and reduce the penetration as well as rheological properties via conventional physical property, dynamic shear rheometer (DSR) and multiple-stress creep recovery (MSCR) tests. Furthermore, asphalt modified with crosslinked POE-g-GMA reveals better aging resistance via measurements of the performance retention rate and electron paramagnetic resonance (EPR) characterizations after a rolling thin film oven test (RTFOT). This work may provide further guidelines for the application of polymers in asphalt.

CuCo2S4 microporous composite membrane to activate peroxymonosulfate for carbamazepine removal

In this study, a CuCo2S4 microporous composite membrane (CCSM) was successfully prepared by loading CuCo2S4 nanoparticles on a membrane substrate, and then used to activate PMS to degrade carbamazepine (CBZ). Meanwhile, the physicochemical properties of the nanomaterial and the effects of various reaction parameters, such as, catalyst film loads, PMS dosage, initial pH value, and co-existing substances on the catalytic degradation performance were investigated. The results showed that CCSM/PMS exhibited admirable catalytic performance, and 90.3% CBZ could be degraded within 3 min under the optimum conditions ([CuCo2S4] = 0.05 g L−1, [PMS]=0.30 g L−1, [CBZ]0 =10 g L−1 and Initial pH = 6.95). Furthermore, the CCSM/PMS system could efficiently degrade various antibiotics (sulfamethoxazole, metronidazole, hydrochloride and ciprofloxacin). In addition, the reusable ability of CCSM without significant efficiency loss after 10 cycles. The quenching experiments and electron paramagnetic resonance (EPR) characterization showed that the main active species were SO4•-, •OH, O2•- and 1O2, and SO4•-played a dominant role in this system. Finally, based on the data analysis, the study proposed the possible degradation mechanism and four degradation routes of CBZ.

Enhancing biomass oxidation with carbon nitride nanosheets ring inserted on C. I. Pigment Yellow 53 photocatalysts for simultaneous CO and lactic acid production

Synchronously producing gas–liquid products from biomass conversion is an effective solution for addressing global energy depletion and environmental pollution. Here, we designed an efficient photocatalyst (CNs@PY53-x) to co-produce CO and lactic acid from biomass-derived sugars. Carbon nitride nanosheets were incorporated onto the surface of PY53 using an ultrasonic-assisted self-assembly coupled with evaporation-drying strategy. The CNs@PY53-x exhibited broader visible light absorption, stronger photocurrent density, and faster separation rate of photogenerated carriers as compared with CNs or PY53. The photocatalytic performance of CNs@PY53-x correlated well with its photoelectric characterization, achieving an CO evolution rate of 371.56 μmol g−1h−1 and a lactic acid yield of 86.9% in the xylose-alkaline system. Furthermore, CNs@PY53-2 demonstrated favorable applicability with various biomass-based sugars. Poisoning experiments, coupled with electron spin resonance (ESR) characterization, revealed that the superoxide radical (O2−) was the primary oxidation active species during this process. This work presents a new strategy for synchronously producing gas–liquid products during biomass conversion.