Phosphorylating Tannin in Urea System: A Simple Approach for Enhanced Methylene Blue Removal from Aqueous Media.

Tannin, after lignin, is one of the most abundant sources of natural aromatic biomolecules. It has been used and chemically modified during the past few decades to create novel biobased materials. This work intended to functionalize for the first time quebracho Tannin (T) through a simple phosphorylation process in a urea system. The phosphorylation of tannin was studied by Fourier transform infrared spectroscopy (FTIR), NMR, inductively coupled plasma optical emission spectroscopy (ICP-OES), and X-ray fluorescence spectrometry (XRF), while further characterization was performed by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and thermogravimetric analysis (TGA) to investigate the morphology, composition, structure, and thermal degradation of the phosphorylated material. Results indicated the occurrence of phosphorylation, suggesting the insertion of phosphate-containing groups into the tannin structure, revealing a high content of phosphate for modified tannin (PT). This elevated phosphorus content serves as evidence for the successful incorporation of phosphate groups through the functionalization process. The corresponding PT and T were employed as adsorbents for methylene blue (MB) removal from aqueous solutions. The results revealed that the Langmuir isotherm model effectively represents the adsorption isotherms. Additionally, the pseudo-second-order model indicates that chemisorption predominantly controls the adsorption mechanism. This finding also supports the fact that the introduced phosphate groups via the phosphorylation process significantly contributed to the improved adsorption capacity. Under neutral pH conditions and at room temperature, the material achieved an impressive adsorption capacity of 339.26 mg·g-1 in about 2 h.

Nanocellulose-Bovine Serum Albumin Interactions in an Aqueous Medium: Investigations Using In Situ Nanocolloidal Probe Microscopy and Reactive Molecular Dynamics Simulations.

As a versatile nanomaterial derived from renewable sources, nanocellulose has attracted considerable attention for its potential applications in various sectors, especially those focused on water treatment and remediation. Here, we have combined atomic force microscopy (AFM) and reactive molecular dynamics (RMD) simulations to characterize the interactions between cellulose nanofibers modified with carboxylate or phosphate groups and the protein foulant model bovine serum albumin (BSA) at pH 3.92, which is close to the isoelectric point of BSA. Colloidal probes were prepared by modification of the AFM probes with the nanofibers, and the nanofiber coating on the AFM tip was for the first time confirmed through fluorescence labeling and confocal optical sectioning. We have found that the wet-state normalized adhesion force is approximately 17.87 ± 8.58 pN/nm for the carboxylated cellulose nanofibers (TOCNF) and about 11.70 ± 2.97 pN/nm for the phosphorylated ones (PCNF) at the studied pH. Moreover, the adsorbed protein partially unfolded at the cellulose interface due to the secondary structure's loss of intramolecular hydrogen bonds. We demonstrate that nanocellulose colloidal probes can be used as a sensitive tool to reveal interactions with BSA at nano and molecular scales and under in situ conditions. RMD simulations helped to gain a molecular- and atomistic-level understanding of the differences between these findings. In the case of PCNF, partially solvated metal ions, preferentially bound to the phosphates, reduced the direct protein-cellulose connections. This understanding can lead to significant advancements in the development of cellulose-based antifouling surfaces and provide crucial insights for expanding the pH range of use and suggesting appropriate recalibrations.

Phase Engineering via Aluminum Doping Enhances the Electrochemical Stability of Lithium-Rich Cobalt-Free Layered Oxides for Lithium-Ion Batteries.

Lithium-rich, cobalt-free oxides are promising potential positive electrode materials for lithium-ion batteries because of their high energy density, lower cost, and reduced environmental and ethical concerns. However, their commercial breakthrough is hindered because of their subpar electrochemical stability. This work studies the effect of aluminum doping on Li1.26 Ni0.15 Mn0.61 O2 as a lithium-rich, cobalt-free layered oxide. Al doping suppresses voltage fade and improves the capacity retention from 46% for Li1.26 Ni0.15 Mn0.61 O2 to 67% for Li1.26 Ni0.15 Mn0.56 Al0.05 O2 after 250 cycles at 0.2 C. The undoped material has a monoclinic Li2 MnO3 -type structure with spinel on the particle edges. In contrast, Al-doped materials (Li1.26 Ni0.15 Mn0.61-x Alx O2 ) consist of a more stable rhombohedral phase at the particle edges, with a monoclinic phase core. For this core-shell structure, the formation of Mn3+ is suppressed along with the material's decomposition to a disordered spinel, and the amount of the rhombohedral phase content increases during galvanostatic cycling. Whereas previous studies generally provided qualitative insight into the degradation mechanisms during electrochemical cycling, this work provides quantitative information on the stabilizing effect of the rhombohedral shell in the doped sample. As such, this study provides fundamental insight into the mechanisms through which Al doping increases the electrochemical stability of lithium-rich cobalt-free layered oxides.

Covalent bonding of N-hydroxyphthalimide on mesoporous silica for catalytic aerobic oxidation of p-xylene at atmospheric pressure.

The surface of SBA-15 mesoporous silica was modified by N-hydroxyphthalimide (NHPI) moieties acting as immobilized active species for aerobic oxidation of alkylaromatic hydrocarbons. The incorporation was carried out by four original approaches: the grafting-from and grafting-onto techniques, using the presence of surface silanols enabling the formation of particularly stable O-Si-C bonds between the silica support and the organic modifier. The strategies involving the Heck coupling led to the formation of NHPI groups separated from the SiO2 surface by a vinyl linker, while one of the developed modification paths based on the grafting of an appropriate organosilane coupling agent resulted in the active phase devoid of this structural element. The successful course of the synthesis was verified by FTIR and 1H NMR measurements. Furthermore, the formed materials were examined in terms of their chemical composition (elemental analysis, thermal analysis), structure of surface groups (13C NMR, XPS), porosity (low-temperature N2 adsorption), and tested as catalysts in the aerobic oxidation of p-xylene at atmospheric pressure. The highest conversion and selectivity to p-toluic acid were achieved using the catalyst with enhanced availability of non-hydrolyzed NHPI groups in the pore system. The catalytic stability of the material was additionally confirmed in several subsequent reaction cycles.

Activity and Stability of Nanoconfined Alpha-Amylase in Mesoporous Silica.

Mesoporous silica particles (MSPs) have been studied for their potential therapeutic uses in controlling obesity and diabetes. Previous studies have shown that the level of digestion of starch by α-amylase is considerably reduced in the presence of MSPs, and it has been shown to be caused by the adsorption of α-amylase by MSPs. In this study, we tested a hypothesis of enzymatic deactivation and measured the activity of α-amylase together with MSPs (SBA-15) using comparably small CNP-G3 (2-chloro-4-nitrophenyl alpha-d-maltotrioside) as a substrate. We showed that pore-incorporated α-amylase was active and displayed higher activity and stability compared to amylase in solution (the control). We attribute this to physical effects: the coadsorption of CNP-G3 on the MSPs and the relatively snug fit of the amylase in the pores. Biosorption in this article refers to the process of removal or adsorption of α-amylase from its solution phase into the same solution dispersed in, or adsorbed on, the MSPs. Large quantities of α-amylase were biosorbed (about 21% w/w) on the MSPs, and high values of the maximum reaction rate (Vmax) and the Michaelis-Menten constant (KM) were observed for the enzyme kinetics. These findings show that the reduced enzymatic activity for α-amylase on MSP observed here and in earlier studies was related to the large probe (starch) being too large to adsorb in the pores, and potato starch has indeed a hydrodynamic diameter much larger than the pore sizes of MSPs. Further insights into the interactions and environments of the α-amylase inside the MSPs were provided by 1H fast magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and 13C/15N dynamic nuclear polarization MAS NMR experiments. It could be concluded that the overall fold and solvation of the α-amylase inside the MSPs were nearly identical to those in solution.

Occupational Exposure of Employees in a Multispecialty Hospital to Factors Causing Contact Dermatitis-A Questionnaire Study.

Background and Objectives: Allergic contact dermatitis (ACD) is a serious health and socio-economic problem. Accurate and reliable assessment of exposure to ACD factors in the work environment would increase quality of life and work of employees. The aim of this study was to assess the level of exposure of workers of a multidisciplinary hospital to the factors causing ACD. Material and Methods: The proprietary OSDES-16 questionnaire was used. The effectiveness of the OSDES-16 was confirmed statistically. The study included 230 employees of the medical center in Polanica Zdrój, divided into groups. Results: The differences in the overall assessment of exposure between the individual groups in the OSDES-16 scale were statistically insignificant (p > 0.05). There was no significant correlation between the current workplace and the level of exposure to ACD (p > 0.05). The level of exposure to ACD in the group of employees with work experience in the current position for more than 10 years was significantly higher than those working less than 6 years (p < 0.05). Conclusions: Nurses, midwives and paramedics are the occupational group most exposed to the development of contact allergy related to exposure to factors present in the work environment. The seniority of more than 10 years in the current position was linked with a higher level of occupational exposure.

An Atomically Dispersed Mn-Photocatalyst for Generating Hydrogen Peroxide from Seawater via the Water Oxidation Reaction (WOR).

In this work, we have fabricated an aryl amino-substituted graphitic carbon nitride (g-C3N4) catalyst with atomically dispersed Mn capable of generating hydrogen peroxide (H2O2) directly from seawater. This new catalyst exhibited excellent reactivity, obtaining up to 2230 µM H2O2 in 7 h from alkaline water and up to 1800 µM from seawater under identical conditions. More importantly, the catalyst was quickly recovered for subsequent reuse without appreciable loss in performance. Interestingly, unlike the usual two-electron oxygen reduction reaction pathway, the generation of H2O2 was through a less common two-electron water oxidation reaction (WOR) process in which both the direct and indirect WOR processes occurred; namely, photoinduced h+ directly oxidized H2O to H2O2 via a one-step 2e- WOR, and photoinduced h+ first oxidized a hydroxide (OH-) ion to generate a hydroxy radical (•OH), and H2O2 was formed indirectly by the combination of two •OH. We have characterized the material, at the catalytic sites, at the atomic level using electron paramagnetic resonance, X-ray absorption near edge structure, extended X-ray absorption fine structure, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, magic-angle spinning solid-state NMR spectroscopy, and multiscale molecular modeling, combining classical reactive molecular dynamics simulations and quantum chemistry calculations.

Precapture of CO2 and Hydrogenation into Methanol on Heterogenized Ruthenium and Amine-Rich Catalytic Systems.

A heterogenized alternative to the homogeneous precapture of CO2 with amines and subsequent hydrogenation to MeOH was developed using aminated silica and a Ru-MACHOTM catalyst. Commercial mesoporous silica was modified with three different amino-silane monomers and used as support for the Ru catalyst. These composites were studied by TEM and solid-state NMR spectroscopy before and after the catalytic reaction. These catalytic reactions were conducted at 155 °C at a H2 and CO2 pressures of 75 and 2 bar, respectively, with the heterogeneous system (gas-solid) being probed with gas-phase infrared spectroscopy used to quantify the resulting products. High turnover number (TON) values were observed for the samples aminated with secondary amines.

The novel questionnaire assessing occupational exposure to the risk factors of contact allergy among health professionals.

Introduction: Skin diseases account for about 7% of all occupational diseases in Europe. Allergic contact dermatitis (ACD) is one of the most common occupational skin diseases. Therefore, it constitutes the major health and economic problem. Increasing the detectability of ACD would significantly improve the quality of life of patients and their work efficiency. Aim: To design a questionnaire facilitating the diagnosis of ACD in work environment of healthcare providers. Material and methods: The initial questionnaire consisted of 53 questions related to ACD and exposure to various occupational hazards. On its basis, a scale of exposure to occupational skin diseases (OSDES-49) was created. The reliability of the scale was measured using the internal consistency test of the scale. It was assumed that individual items of the scale would be correlated with the total score if the Kleine and Nunnally criteria were met. Results: The Kleine and Nunnally criteria were met by 16 out of 49 items on the scale. OSDES-49 results were strongly correlated with the assessment using a questionnaire consisting of only 16 items (OSDES-16). Spearman's rank correlation coefficient was rho = 0.850 and p < 0.001. Conclusions: Results of the study showed that in any further screening tests, the OSDES-16 scale is reliable. The use of OSDES-16 reduces the time of initial diagnostics and simplifies it.

Probing the electronic structure and hydride occupancy in barium titanium oxyhydride through DFT-assisted solid-state NMR.

Perovskite-type oxhydrides such as BaTiO3-xHy exhibit mixed hydride ion and electron conduction and are an attractive class of materials for developing energy storage devices. However, the underlying mechanism of electric conductivity and its relation to the composition of the material remains unclear. Here we report detailed insights into the hydride local environment, the electronic structure and hydride conduction dynamics of barium titanium oxyhydride. We demonstrate that DFT-assisted solid-state NMR is an excellent tool for differentiating between the different feasible electronic structures in these solids. Our results indicate that upon reduction of BaTiO3 the introduced electrons are delocalized among all Ti atoms forming a bandstate. Furthermore, each vacated anion site is reoccupied by at most a single hydride, or else remains vacant. This single occupied bandstate structure persists at different hydrogen concentrations (y = 0.13-0.31) and a wide range of temperatures (∼100-300 K).

Usability of Mobile Solutions Intended for Diagnostic Images-A Systematic Review.

Despite the growing popularity of mobile devices, they still have not found widespread use in medicine. This is due to the procedures in a given place, differences in the availability of mobile devices between individual institutions or lack of appropriate legal regulations and accreditation by relevant institutions. Numerous studies have been conducted and compared the usability of mobile solutions designed for diagnostic images evaluation on various mobile devices and applications with classic stationary descriptive stations. This study is an attempt to compare the usefulness of currently available mobile applications which are used in the medical industry, focusing on imaging diagnostics. As a consequence of the healthcare sector's diversity, it is also not possible to design a universal mobile application, which results in a multitude of software available on the market and makes it difficult to reliably compile and compare studies included in this systematic review. Despite these differences, it was possible to identify both positive and negative features of portable methods analyzing radiological images. The mobile application of the golden mean in hospital infrastructure should be widely available, with convenient and simple usage. Our future research will focus on development in the use of mobile devices and applications in the medical sector.

Application of artificial intelligence in diagnosing COVID-19 disease symptoms on chest X-rays: A systematic review.

This systematic review focuses on using artificial intelligence (AI) to detect COVID-19 infection with the help of X-ray images. Methodology: In January 2022, the authors searched PubMed, Embase and Scopus using specific medical subject headings terms and filters. All articles were independently reviewed by two reviewers. All conflicts resulting from a misunderstanding were resolved by a third independent researcher. After assessing abstracts and article usefulness, eliminating repetitions and applying inclusion and exclusion criteria, six studies were found to be qualified for this study. Results: The findings from individual studies differed due to the various approaches of the authors. Sensitivity was 72.59%-100%, specificity was 79%-99.9%, precision was 74.74%-98.7%, accuracy was 76.18%-99.81%, and the area under the curve was 95.24%-97.7%. Conclusion: AI computational models used to assess chest X-rays in the process of diagnosing COVID-19 should achieve sufficiently high sensitivity and specificity. Their results and performance should be repeatable to make them dependable for clinicians. Moreover, these additional diagnostic tools should be more affordable and faster than the currently available procedures. The performance and calculations of AI-based systems should take clinical data into account.

Deep and extensive pediatric burns: retrospective evaluation of scheme of patients at the Department of Children's Developmental Defects Surgery and Traumatology SUM.

<b> Introduction:</b> Burns are one of the most common injuries among children. Despite the scale of the problem, there is no generally accepted algorithm for dealing with burn wounds in children in Poland. </br></br> <b>Aim:</b> The aim of our study was to evaluate our treatment scheme as well as the long-term effects of burn treatment in our department. </br></br> <b>Material and methods:</b> We conducted a telephone survey with the parents of patients treated at our ward in 01.01.2016-01.01.2021 due to thermal burns. To assess the cosmetic effect of treatment, the modified Vancouver Scar Scale (mVSS) was used, as well as the evaluation of parents' satisfaction with the treatment of patients on a scale from 1 to 10. Criteria to be included were the thermal burn of the skin to at least a 2b degree and/or burns with not less than 8% of the Total Body Surface Area (TBSA), as well as answering all the questions included in the questionnaire. The inclusion criteria were met by 38 out of 97 hospitalized patients. </br></br> <b>Results:</b> 26.32% of patients achieved 0 points on the mVSS, 21.05% achieved 1 point, 15.79% achieved 2 points, 15.79% achieved 3 points, 2.63% patients received 4 points, 5.26% patients received 5 points, 5.26% patients received 7 points, 2.63% patients received 8 points, 2.63% patients received 9 points, 2.63% of patients received 10 points, none of the patients received 6 and 11 points higher. 3% of parents rated their satisfaction at 5 points, 3% of caretakers as 7 points, 8% as 8 points, 8% as 9 points, and 89% as 10 points. </br></br> <b>Discussion:</b> Our treatment algorithm brings good therapeutic effects and is also very well received by the patients' parents. In order to carry out a nationwide standardization of the treatment of childhood burn wounds, it would be necessary to conduct a similarly constructed study in a multicenter setting.

Electron correlation and vibrational effects in predictions of paramagnetic NMR shifts.

Electronic structure calculations are fundamentally important for the interpretation of nuclear magnetic resonance (NMR) spectra from paramagnetic systems that include organometallic and inorganic compounds, catalysts, or metal-binding sites in proteins. Prediction of induced paramagnetic NMR shifts requires knowledge of electron paramagnetic resonance (EPR) parameters: the electronic g tensor, zero-field splitting D tensor, and hyperfine A tensor. The isotropic part of A, called the hyperfine coupling constant (HFCC), is one of the most troublesome properties for quantum chemistry calculations. Yet, even relatively small errors in calculations of HFCC tend to propagate into large errors in the predicted NMR shifts. The poor quality of A tensors that are currently calculated using density functional theory (DFT) constitutes a bottleneck in improving the reliability of interpretation of the NMR spectra from paramagnetic systems. In this work, electron correlation effects in calculations of HFCCs with a hierarchy of ab initio methods were assessed, and the applicability of different levels of DFT approximations and the coupled cluster singles and doubles (CCSD) method was tested. These assessments were performed for the set of selected test systems comprising an organic radical, and complexes with transition metal and rare-earth ions, for which experimental data are available. Severe deficiencies of DFT were revealed but the CCSD method was able to deliver good agreement with experimental data for all systems considered, however, at substantial computational costs. We proposed a more computationally tractable alternative, where the A was computed with the coupled cluster theory exploiting locality of electron correlation. This alternative is based on the domain-based local pair natural orbital coupled cluster singles and doubles (DLPNO-CCSD) method. In this way the robustness and reliability of the coupled cluster theory were incorporated into the modern formalism for the prediction of induced paramagnetic NMR shifts, and became applicable to systems of chemical interest. This approach was verified for the bis(cyclopentadienyl)vanadium(II) complex (Cp2V; vanadocene), and the metal-binding site of the Zn2+ → Co2+ substituted superoxide dismutase (SOD) metalloprotein. Excellent agreement with experimental NMR shifts was achieved, which represented a substantial improvement over previous theoretical attempts. The effects of vibrational corrections to orbital shielding and hyperfine tensor were evaluated and discussed within the second-order vibrational perturbation theory (VPT2) framework.

Lignin-Supported Heterogeneous Photocatalyst for the Direct Generation of H2O2 from Seawater.

The development of smart and sustainable photocatalysts is in high priority for the synthesis of H2O2 because the global demand for H2O2 is sharply rising. Currently, the global market share for H2O2 is around 4 billion US$ and is expected to grow by about 5.2 billion US$ by 2026. Traditional synthesis of H2O2 via the anthraquinone method is associated with the generation of substantial chemical waste as well as the requirement of a high energy input. In this respect, the oxidative transformation of pure water is a sustainable solution to meet the global demand. In fact, several photocatalysts have been developed to achieve this chemistry. However, 97% of the water on our planet is seawater, and it contains 3.0-5.0% of salts. The presence of salts in water deactivates the existing photocatalysts, and therefore, the existing photocatalysts have rarely shown reactivity toward seawater. Considering this, a sustainable heterogeneous photocatalyst, derived from hydrolysis lignin, has been developed, showing an excellent reactivity toward generating H2O2 directly from seawater under air. In fact, in the presence of this catalyst, we have been able to achieve 4085 µM of H2O2. Expediently, the catalyst has shown longer durability and can be recycled more than five times to generate H2O2 from seawater. Finally, full characterizations of this smart photocatalyst and a detailed mechanism have been proposed on the basis of the experimental evidence and multiscale/level calculations.

Probing Molecular Motions in Metal-Organic Frameworks by Three-Dimensional Electron Diffraction.

Flexible metal-organic frameworks (MOFs) are known for their vast functional diversities and variable pore architectures. Dynamic motions or perturbations are among the highly desired flexibilities, which are key to guest diffusion processes. Therefore, probing such motions, especially at an atomic level, is crucial for revealing the unique properties and identifying the applications of MOFs. Nuclear magnetic resonance (NMR) and single-crystal X-ray diffraction (SCXRD) are the most important techniques to characterize molecular motions but require pure samples or large single crystals (>5 × 5 × 5 µm3), which are often inaccessible for MOF synthesis. Recent developments of three-dimensional electron diffraction (3D ED) have pushed the limits of single-crystal structural analysis. Accurate atomic information can be obtained by 3D ED from nanometer- and submicrometer-sized crystals and samples containing multiple phases. Here, we report the study of molecular motions by using the 3D ED method in MIL-140C and UiO-67, which are obtained as nanosized crystals coexisting in a mixture. In addition to an ab initio determination of their framework structures, we discovered that motions of the linker molecules could be revealed by observing the thermal ellipsoid models and analyzing the atomic anisotropic displacement parameters (ADPs) at room temperature (298 K) and cryogenic temperature (98 K). Interestingly, despite the same type of linker molecule occupying two symmetry-independent positions in MIL-140C, we observed significantly larger motions for the isolated linkers in comparison to those reinforced by π-π stacking. With an accuracy comparable to that of SCXRD, we show for the first time that 3D ED can be a powerful tool to investigate dynamics at an atomic level, which is particularly beneficial for nanocrystalline materials and/or phase mixtures.

Local energy decomposition analysis and molecular properties of encapsulated methane in fullerene (CH4@C60).

Methane has been successfully encapsulated within cages of C60 fullerene, which is an appropriate model system to study confinement effects. Its chemistry and physics are also relevant for theoretical model descriptions. Here we provide insights into intermolecular interactions and predicted spectroscopic responses of the CH4@C60 complex and compared them with results from other methods and with data from the literature. Local energy decomposition analysis (LED) within the domain-based local pair natural orbital coupled cluster singles, doubles, and perturbative triples (DLPNO-CCSD(T)) framework was used, and an efficient protocol for studies of endohedral complexes of fullerenes is proposed. This approach allowed us to assess energies in relation to electronic and geometric preparation, electrostatics, exchange, and London dispersion for the CH4@C60 endohedral complex. The calculated stabilization energy of CH4 inside the C60 fullerene was -13.5 kcal mol-1 and its magnitude was significantly larger than the latent heat of evaporation of CH4. Evaluation of vibrational frequencies and polarizabilities of the CH4@C60 complex revealed that the infrared (IR) and Raman bands of the endohedral CH4 were essentially "silent" due to the dielectric screening effect of C60, which acted as a molecular Faraday cage. Absorption spectra in the UV-vis domain and ionization potentials of C60 and CH4@C60 were predicted. They were almost identical. The calculated 1H/13C NMR shifts and spin-spin coupling constants were in very good agreement with experimental data. In addition, reference DLPNO-CCSD(T) interaction energies for complexes with noble gases (Ng@C60; Ng = He, Ne, Ar, Kr) were calculated. The values were compared with those derived from supramolecular MP2/SCS-MP2 calculations and estimates with London-type formulas by Pyykkö and coworkers [Phys. Chem. Chem. Phys., 2010, 12, 6187-6203], and with values derived from DFT-based symmetry-adapted perturbation theory (DFT-SAPT) by Hesselmann & Korona [Phys. Chem. Chem. Phys., 2011, 13, 732-743]. Selected points at the potential energy surface of the endohedral He2@C60 trimer were considered. In contrast to previous theoretical attempts with the DFT/MP2/SCS-MP2/DFT-SAPT methods, our calculations at the DLPNO-CCSD(T) level of theory predicted the He2@C60 trimer to be thermodynamically stable, which is in agreement with experimental observations.

The Structure, Morphology, and Complex Permittivity of Epoxy Nanodielectrics with In Situ Synthesized Surface-Functionalized SiO2.

Epoxy nanocomposites have demonstrated promising properties for high-voltage insulation applications. An in situ approach to the synthesis of epoxy-SiO2 nanocomposites was employed, where surface-functionalized SiO2 (up to 5 wt.%) is synthesized directly in the epoxy. The dispersion of SiO2 was found to be affected by both the pH and the coupling agent used in the synthesis. Hierarchical clusters of SiO2 (10-60 nm) formed with free-space lengths of 53-105 nm (increasing with pH or SiO2 content), exhibiting both mass and surface-fractal structures. Reducing the amount of coupling agent resulted in an increase in the cluster size (~110 nm) and the free-space length (205 nm). At room temperature, nanocomposites prepared at pH 7 exhibited up to a 4% increase in the real relative permittivity with increasing SiO2 content, whereas those prepared at pH 11 showed up to a 5% decrease with increasing SiO2 content. Above the glass transition, all the materials exhibited low-frequency dispersion effect resulting in electrode polarization, which was amplified in the nanocomposites. Improvements in the dielectric properties were found to be not only dependent on the state of dispersion, but also the structure and morphology of the inorganic nanoparticles.

Graphitic nitrogen in carbon catalysts is important for the reduction of nitrite as revealed by naturally abundant 15N NMR spectroscopy.

Metal-free nitrogen-doped carbon is considered as a green functional material, but the structural determination of the atomic positions of nitrogen remains challenging. We recently demonstrated that directly-excited solid state 15N NMR (ssNMR) spectroscopy is a powerful tool for the determination of such positions in N-doped carbon at natural 15N isotope abundance. Here we report a green chemistry approach for the synthesis of N-doped carbon using cellulose as a precursor, and a study of the catalytic properties and atomic structures of the related catalyst. N-doped carbon (NH3) was obtained by the oxidation of cellulose with HNO3 followed by ammonolysis at 800 °C. It had a N content of 6.5 wt% and a surface area of 557 m2 g-1, and 15N ssNMR spectroscopy provided evidence for graphitic nitrogen besides regular pyrrolic and pyridinic nitrogen. This structural determination allowed probing the role of graphitic nitrogen in electrocatalytic reactions, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and nitrite reduction reaction. The N-doped carbon catalyst (NH3) showed higher electrocatalytic activities in the OER and HER under alkaline conditions and higher activity for nitrite reduction, as compared with a catalyst prepared by the carbonization of HNO3-treated cellulose in N2. The electrocatalytic selectivity for nitrite reduction of the N-doped carbon catalyst (NH3) was directly related to the graphitic nitrogen functions. Complementary structural analyses by means of 13C and 1H ssNMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature N2 adsorption were performed and provided support to the findings. The results show that directly-excited 15N ssNMR spectroscopy at natural 15N abundance is generally capable of providing information on N-doped carbon materials if relaxation properties are favorable. It is expected that this approach can be applied to a wide range of solids with an intermediate concentration of N atoms.

LignoPhot: Conversion of hydrolysis lignin into the photoactive hybrid lignin/Bi4O5Br2/BiOBr composite for simultaneous dyes oxidation and Co2+ and Ni2+ recycling.

Valorization of lignin is still an open question and lignin has therefore remained an underutilized biomaterial. This situation is even more pronounced for hydrolysis lignin, which is characterized by a highly condensed and excessively cross-linked structure. We demonstrate the synthesis of photoactive lignin/Bi4O5Br2/BiOBr bio-inorganic composites consisting of a lignin substrate that is coated by semiconducting nanosheets. The XPS analysis reveals that growing these nanosheets on lignin instead on cellulose prevents the formation of Bi5+ ions at the surface region, yielding thus a modified heterojunction Bi4O5Br2/BiOBr. The material contains 18.9% of Bi4O5Br2/BiOBr and is effective for the photocatalytic degradation of cationic methylene blue (MB) and zwitterionic rhodamine B (RhB) dyes under light irradiation. Lignin/Bi4O5Br2/BiOBr decreases the dye concentration from 80 mg L-1 to 12.3 mg L-1 for RhB (85%) and from 80 mg L-1 to 4.4 mg L-1 for MB (95%). Complementary to the dye degradation, the lignin as a main component of the composite, was found to be efficient and rapid biosorbent for nickel, lead, and cobalt ions. The low cost, stability and ability to simultaneously photo-oxidize organic dyes and adsorb metal ions, make the photoactive lignin/Bi4O5Br2/BiOBr composite a prospective material for textile wastewaters remediation and metal ions recycling.