Physicochemical properties, biological chemistry and mechanisms of action of caries-arresting diammine-silver(I) fluoride and silver(I)-fluoride solutions for clinical use: a critical review.

This paper serves as a Part II follow-up of our research investigations performed on the molecular structures of silver(I)-fluoride (SF) and diammine-silver(I) fluoride (SDF) complexes in solution-based commercial products for clinical application, their precise chemical compositions, and their nature in aqueous solution, the latter including rapid fluoride-exchange processes at the silver(I) ion centre monitored by 19F NMR analysis (Part I). Part I of this series also explores the mechanisms of action (MoA) of these complexes, and is therefore largely focused on their chemical reactions with constituents of human saliva, which has access to their sites of application. Such reactions were found to slowly promote the generation of potentially physiologically-active Ag/AgCl nanoparticles from primarily-generated discoloured silver(I) chloride (AgCl) precipitates, a process involving salivary electron-donors such as thiocyanate and L-cysteine. Since this research has shed new light on potential MoAs for these products, in this accompanying report (Part II), we have performed a critical review of scientific literature in order to rationalize our results in relation to current views on these mechanisms for SF and SDF products employed for the successful clinical arrest of dental caries. Following an Introduction to the subject matter ( Section 1), this paper comprises a generalized overview of silver coordination chemistry ( Section 2), which is followed by a section focused on the aqueous solution status and equilibria involved in SF chemistry ( Section 3), the latter including results acquired from an original simulation of the electronic absorption spectra of coloured SF complexes in aqueous solution (Section 3.1). Section 4 then investigates detailed rationales for the biologically-relevant ligand-exchange and redox chemistries, disposition and fates of SF, SDF and silver(I)-nitrate when employed for the treatment of dental caries, with emphasis placed on their therapeutic MoAs. This Section is supported by the provision of valuable information centralized on (1) relevant biomolecular chemistry involved in solution- and solid-state matrices ( Section 4.1); (2) SF and perhaps silver(I)-nitrate as more cost-effective alternatives to SDF therapies ( Section 4.2); and (3) the potential therapeutic benefits and effects offered by silver-based nanoparticles and their associated MoAs ( Section 4.3). Recommendations for future investigations in this area are proposed.

Rerefinement of the crystal structure of BiF5.

The crystal structure of bis-muth penta-fluoride, BiF5, was rerefined from single-crystal data. BiF5 crystallizes in the α-UF5 structure type in the form of colorless needles. In comparison with the previously reported crystal-structure model [Hebecker (1971 ▸). Z. Anorg. Allg. Chem. 384, 111-114], the lattice parameters and fractional atomic coordinates were determined to much higher precision and all atoms were refined anisotropically, leading to a significantly improved structure model. The Bi atom (site symmetry 4/m..) is surrounded by six F atoms in a distorted octa-hedral coordination environment. The [BiF6] octa-hedra are corner-linked to form infinite straight chains extending parallel to [001]. Density functional theory (DFT) calculations at the PBE0/TZVP level of theory were performed on the crystal structure of BiF5 to calculate its IR and Raman spectra. These are compared with experimental data.

Fluoride induces hepatointestinal damage and vitamin B2 mitigation by regulating IL-17A and Bifidobacterium in ileum.

INTRODUCTION: Fluorosis is a global public health disease affecting more than 50 countries and 500 million people. Excessive fluoride damages the liver and intestines, yet the mechanisms and therapeutic approaches remain unclear. OBJECTIVES: To explore the mechanisms by which fluoride-induced intestinal-hepatic damage and vitamin B2 alleviation. METHODS: Fluoride and/or vitamin B2-treated IL-17A knockout and wild-type mouse models were established, the morphological and functional changes of liver and gut, total bile acid biosynthesis, metabolism, transport, and regulation of FXR-FGF15 signaling pathways were evaluated, the ileal microbiome was further analyzed by 16S rDNA sequence. Finally, Bifidobacterium supplementation mouse model was designed and re-examined the above indicators. RESULTS: The results demonstrated that fluoride induced hepatointestinal injury and enterohepatic circulation disorder by altering the synthesis, transporters, and FXR-FGF15 pathway regulation of total bile acid. Importantly, the ileum was found to be the most sensitive and fluoride changed ileal microbiome particularly by reducing abundance of Bifidobacterium. While vitamin B2 supplementation attenuated fluoride-induced enterohepatic circulation dysfunction through IL-17A and ileal microbiome, Bifidobacterium supplementation also reversed fluoride-induced hepatointestinal injury. CONCLUSION: Fluoride induces morphological and functional impairment of liver and gut tissues, as well as enterohepatic circulation disorder by altering total bile acid (TBA) synthesis, transporters, and FXR-FGF15 signaling regulation. Vitamin B2 attenuated fluoride-induced enterohepatic circulation disorder through IL-17A knockout and ileal microbiome regulation. The ileum was found to be the most sensitive to fluoride, leading to changes in ileal microbiome, particularly the reduction of Bifidobacterium. Furthermore, Bifidobacterium supplementation reversed fluoride-induced hepatointestinal injury. This study not only elucidates a novel mechanism by which fluoride causes hepatointestinal toxicity, but also provides a new physiological function of vitamin B2, which will be useful in the therapy of fluorosis and other hepatoenterological diseases.

Metal fluorides-multi-functional tools for the study of phosphoryl transfer enzymes, a practical guide.

Enzymes facilitating the transfer of phosphate groups constitute the most extensive protein families across all kingdoms of life. They make up approximately 10% of the proteins found in the human genome. Understanding the mechanisms by which enzymes catalyze these reactions is essential in characterizing the processes they regulate. Metal fluorides can be used as multifunctional tools to study these enzymes. These ionic species bear the same charge as phosphate and the transferring phosphoryl group and, in addition, allow the enzyme to be trapped in catalytically important states with spectroscopically sensitive atoms interacting directly with active site residues. The ionic nature of these phosphate surrogates also allows their removal and replacement with other analogs. Here, we describe the best practices to obtain these complexes, their use in NMR, X-ray crystallography, cryo-EM, and SAXS and describe a new metal fluoride, scandium tetrafluoride, which has significant anomalous signal using soft X-rays.

Focus on cognitive impairment induced by excessive fluoride: an update review.

Fluorosis is a global public health concern. Prolonged exposure to excessive fluoride causes fluoride accumulation in the hippocampus, resulting in cognitive dysfunction. Cell death is necessary for maintaining tissue function and morphology, and changes in the external morphology of nerve cells and the function of many internal organelles are typical features of cell death; however, it is also a typical feature of cognitive impairment caused by fluorosis. However, the pathogenesis of cognitive impairment caused by different degrees of fluoride exposure varies. Herein, we provide an overview of cognitive impairment caused by excessive fluoride exposure in different age groups, and the underlying mechanisms for cognitive impairment in various model organisms. The mechanisms underlying these impairments include oxidative stress, synaptic and neurotransmission dysfunction, disruption of mitochondrial and energy metabolism, and calcium channel dysregulation. This study aims to provide potential insights that serve as a reference for subsequent research on the cognitive function caused by excessive fluoride.

A randomised clinical trial to arrest caries using silver diamine fluoride therapy with two postoperative instructions.

OBJECTIVE: The objective of this study is to investigate the beneficial effect of not rinsing for 30 minutes in arresting early childhood caries after SDF therapy. METHODS: This randomised clinical trial recruited 3- to 4-year-old kindergarten children with active (soft) dentine caries. A questionnaire was sent to the parents to collect children's demographic data and oral health-related behaviours. A dentist conducted an oral examination and measured the caries experience using dmft index and oral hygiene using visible plaque index. After 38% SDF therapy, the children were randomly allocated into two groups. Children in group A were instructed to rinse with water immediately, whereas children in group B were asked to refrain from rinsing, drinking, or eating for 30 minutes. After six months, the same examiner determined the lesion activity (active/arrest) of the SDF-treated carious tooth surface. Generalized Estimating Equations was used to compare the proportion of caries arrest (caries-arrest rate) between the two groups. RESULTS: This study recruited 298 children with 1,158 decayed tooth surfaces receiving SDF therapy at baseline and evaluated 275 (92%) children with 1,069 (92%) SDF-treated tooth-surface at the six-month examination. The demographic background, oral hygiene and caries status of two groups were comparable at baseline (p>0.05). The caries-arrest rate for group A and group B were 65% (337/519) and 61% (338/550), respectively (p=0.28). CONCLUSION: This randomised clinical trial found the postoperative instructions of immediate rinsing or refraining from rinsing, drinking, or eating for 30 minutes after SDF therapy had no significant effect on caries arrest in primary teeth. CONCLUSION: This randomised clinical trial found not rinsing for 30 minutes after SDF therapy is not better than immediate rinsing in arresting early childhood caries. CLINICAL SIGNIFICANCE: Topical SDF application leaves an unpleasant taste in the mouth, which may affect the acceptance or even rejection of SDF therapy among young children. This study provides clinicians with information to make their decision on postoperative instruction after SDF therapy.

Highly efficient recovery of phosphate and fluoride from phosphogypsum leachate: Selective precipitation and adsorption.

Phosphogypsum, a typical by-product in the phosphorus chemical industry, could generate a large amount of leachate containing phosphate and fluoride in the process of rainfall and long-term stacking, which not only causes serious environmental pollution, but also leads to a waste of resources. In this study, a united treatment of calcium hydroxide precipitation and lanthanum zeolite (La-ZFA) adsorption was proposed to achieve the recovery of phosphate and fluoride from phosphogypsum leachate. In phosphogypsum, most phosphorus could be leached except P in the residual occurrence form, while for fluoride, only water-soluble F could be effectively leached. The optimum leaching amounts of phosphate and fluoride were 22.59 and 4.64 mg/g, respectively, at liquid-solid ratio of 400:1, leaching time of 120 min, pH of 6.0, particle size of >200 mesh (<0.075 mm), and leaching temperature of 25°C. Using Ca(OH)2 as the precipitant, the phosphate could be precipitated selectively from phosphogypsum leachate by controlling pH and time, and the concentrations of it decreased significantly to 0.29 mg/L at pH 10.0, with a removal efficiency of 99.48%. XRD, SEM and Visual MINTEQ software analysis proved that the main component of the precipitate was hydroxyapatite (Ca5(PO4)3(OH)). After P precipitation, a series of sorbents for fluoride were investigated, and La-ZFA sorbent was chosen and utilized to recover the fluoride from the leachate through a cyclic fixed-bed column. The efficiency of La-ZFA was basically not affected by the high concentration sulfate, and it can selectively adsorb fluoride from phosphogypsum leachate, leading to a final fluoride concentration of 0.29 mg/L in the effluent. The characterization demonstrated that fluoride might be adsorbed onto the La-ZFA via ligand exchange with hydroxy groups. The proposed method in this study is expected to sequentially recover phosphate and fluorine from the leachate of phosphogypsum, and it has great guiding significance for resource utilization and management of phosphogypsum.

Apoptosis and Inflammation Involved with Fluoride-Induced Bone Injuries.

BACKGROUND: Excessive fluoride exposure induces skeletal fluorosis, but the specific mechanism responsible is still unclear. Therefore, this study aimed to identify the pathogenesis of fluoride-induced bone injuries. METHODS: We systematically searched fluoride-induced bone injury-related genes from five databases. Then, these genes were subjected to enrichment analyses. A TF (transcription factor)-mRNA-miRNA network and protein-protein interaction (PPI) network were constructed using Cytoscape, and the Human Protein Atlas (HPA) database was used to screen the expression of key proteins. The candidate pharmacological targets were predicted using the Drug Signature Database. RESULTS: A total of 85 studies were included in this study, and 112 osteoblast-, 35 osteoclast-, and 41 chondrocyte-related differential expression genes (DEGs) were identified. Functional enrichment analyses showed that the Atf4, Bcl2, Col1a1, Fgf21, Fgfr1 and Il6 genes were significantly enriched in the PI3K-Akt signaling pathway of osteoblasts, Mmp9 and Mmp13 genes were enriched in the IL-17 signaling pathway of osteoclasts, and Bmp2 and Bmp7 genes were enriched in the TGF-beta signaling pathway of chondrocytes. With the use of the TF-mRNA-miRNA network, the Col1a1, Bcl2, Fgfr1, Mmp9, Mmp13, Bmp2, and Bmp7 genes were identified as the key regulatory factors. Selenium methyl cysteine, CGS-27023A, and calcium phosphate were predicted to be the potential drugs for skeletal fluorosis. CONCLUSIONS: These results suggested that the PI3K-Akt signaling pathway being involved in the apoptosis of osteoblasts, with the IL-17 and the TGF-beta signaling pathways being involved in the inflammation of osteoclasts and chondrocytes in fluoride-induced bone injuries.

Impact of fluorosis on molecular predictors in pathogenesis of type 2 diabetes associated microvascular complications.

AIM: This review presents specific insights on the molecular underpinnings of the connection between fluorosis, type 2 diabetes, and microvascular complications, along with the novel biomarkers that are available for early detection. SUMMARY: Fluoride is an essential trace element for the mineralization of teeth and bones in humans. Exposure to higher concentrations of fluoride has harmful effects that significantly outweigh its advantageous ones. Dental fluorosis and skeletal fluorosis are the common side effects of exposure to fluoride, which affect millions of individuals globally. Alongside, it also causes non-skeletal fluorosis, which affects the population suffering from non-communicable diseases like diabetes by impacting the soft tissues and causing diabetic microvascular complications. Previous studies reported the prevalence range of these diabetic complications of neuropathy (3-65 %), nephropathy (1-63 %), and retinopathy (2-33 %). Fluoride contributes to the development of these complications by causing oxidative stress, cellular damage, degrading the functioning capability of mitochondria, and thickening the retinal vein basement. CONCLUSION: Early diagnosis is a prompt way of prevention, and for that, biomarkers have emerged as an innovative and useful technique. This allows healthcare practitioners and policymakers in endemic areas to comprehend the molecular complexities involved in the advancement of diabetic microvascular problems in the context of high fluoride exposure.

Effect of Silyl Ether Bulk on Excited-State Intramolecular Proton Transfer-Based Sensing of Extant Hydrogen Fluoride for G-Series Nerve Agent Detection.

Luminescence-based sensing provides a method for the rapid detection of nerve agents. Previous approaches have generally focused on sensing materials containing a nucleophilic group that can react with the electrophilic phosphorus atom found in nerve agents. Herein we report an alternative approach for the detection of phosphonofluoridate-based G-series nerve agents that utilizes the fact they contain hydrogen fluoride. We have developed silylated sensing materials based on an excited-state intramolecular proton transfer (ESIPT) reporter compound, 2-[benzo[d]thiazol-2-yl]phenol. Thin films of differently silylated 2-[benzo[d]thiazol-2-yl]phenol were found to react with the hydrogen fluoride found in di-iso-propyl fluorophosphate (DFP), a simulant of sarin (G-series nerve agent), and turn on the ESIPT emission of the reporter compound. The use of the ESIPT emission reduced the impact of background fluorescence and improved the sensitivity of the detection. The effectiveness of the approach was dependent on the stability of the silyl protecting group used, with the least sterically hindered (trimethylsilyl) found to be too unstable to the ambient environment while the most sterically hindered, e.g., tri-iso-propylsilyl and tert-butyldiphenylsilyl were found to be insufficiently reactive to be useful in a real detection scenario. The sensing material composed of the tert-butyl dimethylsilyl protected 2-[benzo[d]thiazol-2-yl]phenol was found to have the best balance between stability under ambient conditions, and reactivity and selectivity to hydrogen fluoride. In a 3 s exposure, it could detect hydrogen fluoride down to a concentration of around 23 ppm in DFP with 99% purity.

Silver diamine fluoride in preventing enamel erosion: An in vitro study with salivary pellicle.

OBJECTIVES: To compare the prevention of enamel erosion and discolouring effect with a single and two weekly topical applications of silver diamine fluoride (SDF) solution. METHODS: Human enamel blocks were divided into four groups. Group 1 (SDF2) received two weekly applications of SDF solution (Advantage Arrest: 260,000 ppm Ag, 44,300 ppm F, pH 9.1). Group 2 (SDF1) received a single application of SDF solution. Group 3 (SNF, Positive Control) received daily application of stannous-chloride/amine-fluoride/sodium-fluoride solution (Elmex® Enamel professional: 800 ppm Sn(II), 500 ppm F, pH 4.5). Group 4 (DW, Negative Control) received daily application of deionised water. The treated blocks were subjected to a 14-day erosive challenge. Crystal characteristics, elemental composition, surface morphology, percentage of surface microhardness loss (%SMHL), surface loss, and total colour change (ΔE) of the blocks were investigated using X-ray diffraction (XRD), energy-dispersive spectrometry (EDS) and scanning electron microscopy (SEM), Vickers' hardness testing, non-contact profilometry, and digital spectrophotometry, respectively. RESULTS: XRD and EDS revealed precipitates of silver for SDF2 and SDF1 and tin for SNF. SEM showed prominent etched enamel pattern on DW than the other three groups. The%SMHL (%) of SDF2, SDF1, SNF, and DW were 26.6 ± 2.9, 33.6 ± 2.8, 38.9 ± 2.9, and 50.5 ± 2.8 (SDF2SDF1=SNF>DW, p < 0.05). CONCLUSION: Two weekly applications was more effective than a single application of SDF in preventing enamel erosion, though it caused more discolouration. CLINICAL SIGNIFICANCE: Topical application of 38 % SDF with two weekly applications protocol is effective in preventing enamel erosion.

Salivary proteomic signatures in severe dental fluorosis.

The relationship between dental fluorosis and alterations in the salivary proteome remains inadequately elucidated. This study aimed to investigate the salivary proteome and fluoride concentrations in urine and drinking water among Thai individuals afflicted with severe dental fluorosis. Thirty-seven Thai schoolchildren, aged 6-16, were stratified based on Thylstrup and Fejerskov fluorosis index scores: 10 with scores ranging from 5 to 9 (SF) and 27 with a score of 0 (NF). Urinary and water fluoride levels were determined using an ion-selective fluoride electrode. Salivary proteomic profiling was conducted via LC-MS/MS, followed by comprehensive bioinformatic analysis. Results revealed significantly elevated urinary fluoride levels in the SF group (p = 0.007), whereas water fluoride levels did not significantly differ between the two cohorts. Both groups exhibited 104 detectable salivary proteins. The NF group demonstrated notable upregulation of LENG9, whereas the SF group displayed upregulation of LDHA, UBA1, S100A9, H4C3, and LCP1, all associated with the CFTR ion channel. Moreover, the NF group uniquely expressed 36 proteins, and Gene Ontology and pathway analyses suggested a link with various aspects of immune defense. In summary, the study hypothesized that the CFTR ion channel might play a predominant role in severe fluorosis and highlighted the depletion of immune-related salivary proteins, suggesting compromised immune defense in severe fluorosis. The utility of urinary fluoride might be a reliable indicator for assessing excessive fluoride exposure.

The influence of various sample storage conditions and sample bacterial contamination on concentrations of routine biochemical parameters.

Background: The pre-analytical (PA) phase is the most vulnerable phase of the laboratory testing procedure, with critical procedures-collection, handling, sample transport, and time and temperature of sample storage. This study aimed to examine the stability of basic biochemical parameters depending on the samples' storage conditions and the number of freeze-thaw cycles (FTCs). In parallel, the presence of sample bacterial contamination during routine laboratory work was examined. Methods: Two plasma pools (ethylenediaminetetraacetic acid (EDTA), and sodium-fluoride/potassium oxalate plasma (NaF)) were stored at +4 ˚C/-20 ˚C. Total chole - sterol (TC), glucose, triglycerides (TG), urea, and albumin concentrations were measured using BioSystems reagents (cholesterol oxidase/peroxidase, glucose oxidase/per - oxidase, glycerol phosphate oxidase/peroxidase, urease/ salicylate, and bromcresol green method, respectively) on Ilab 300+. Sample bacterial contamination was determined by 16S rRNA sequence analysis. The expe - riment encompassed a 5 day-period: Day 1-fresh sample, Day 2-1st FTC, Day 3-2nd FTC, Day 4-3rd FTC, Day 5-4th FTC. The appearance of bacteria in two consecutive samples was the experiment's endpoint.

High concentrations of NaF aggravate periodontitis by promoting M1 polarization in macrophages.

High-concentration fluoride treatment is commonly used to prevent dental caries in the oral cavity, and fluorine-containing protective paint is used to alleviate common root sensitivity symptoms in patients with periodontitis after periodontal treatment. Recent studies have confirmed its safe use in normal oral environments. However, whether fluoride treatment affects the progression of periodontitis in an inflammatory microenvironment remains unclear. Immunometabolism is crucial for maintaining bone regeneration and repair in periodontitis, and the precise regulation of macrophage polarisation is crucial to this process. Fluoride can influence the immune microenvironment of bone tissue by regulating immune metabolic processes. Herein, we investigated the effects of high concentrations of sodium fluoride (NaF) on periodontal tissues. We examined the expression of osteogenic and M1/M2 macrophage polarisation markers and glucose metabolism in macrophages. RNA sequencing was used to study differentially expressed genes related to M1 polarisation and glucose metabolism in treated macrophages. The results showed that NaF indirectly affects human periodontal ligament cells (hPDLCs), aggravating bone loss, tissue destruction, and submandibular lymph node drainage. Furthermore, NaF promoted glycolysis in macrophages and M1 polarisation while inhibiting osteogenic differentiation. These findings suggest that NaF has a direct effect on hPDLCs. Moreover, we found that high concentrations of NaF stimulated M1 polarisation in macrophages by promoting glycolysis. Overall, these results suggest that M1 macrophages promote the osteoclastic ability of hPDLCs and inhibit their osteogenic ability, eventually aggravating periodontitis. These findings provide important insights into the mechanism of action of NaF in periodontal tissue regeneration and reconstruction, which is critical for providing appropriate recommendations for the use of fluoride in patients with periodontitis.

Diffusion of Silver Diamine Fluoride Solution in Dentine: An In Vitro Study.

OBJECTIVES: The aim of this research was to assess the diffusion dynamics of silver and fluoride ions after 38% silver diamine fluoride (SDF) solution application on dentine of varying thicknesses over 24 weeks. METHODS: Bovine dentine discs of 5.5 mm in diameter were prepared and separated into 3 groups with thicknesses of 0.5 mm (group 1), 1.0 mm (group 2), and 1.5 mm (group 3). The diameter and number of dentinal tubules of discs were assessed. Each disc received a topical application of 0.05 mL 38% SDF solution. The deionised water in the tube was collected weekly for 24 weeks. The silver and the fluoride ion concentrations in the collected deionised water were determined. Generalised estimating equations was used to explore the potential effects of the key factors on the silver/fluoride diffusion. RESULTS: The amount of silver and fluoride ion diffusion through dentine almost levelled off after 4 weeks and showed a decline trend over 24 weeks. The mean (SD) 24-week cumulative ion diffusion through dentine in groups 1, 2, and 3 was as follows: 20 (4) µg, 10 (2) µg, and 5 (1) µg for silver (P < .05) and 18 (2) µg, 13 (2) µg, and 7 (1) µg for fluoride (P < .05), respectively. CONCLUSIONS: Silver and fluoride ion diffusion through dentine showed a decline trend over 24 weeks. The diameter and the number of dentinal tubules on dentine with different thicknesses affects the ion diffusion dynamics. This study provides indications on the pattern of silver/fluoride ions diffusion through dentine to pulp after 38% SDF application. An increased amount of silver/fluoride diffuses through dentine into the pulp with decreased remaining dentine thickness.

Antimicrobial effect of two fluoride-releasing adhesive tapes on Streptococcus mutans biofilm.

Fluoride-releasing adhesive tapes have been developed as a new fluoride delivery agent. However, application as caries prevention agents remains underexplored. This study aimed at evaluating the antimicrobial activity of two fluoride-releasing adhesive tapes against S. mutans biofilm. Two polyvinyl alcohol (PVA) tapes were investigated: (i) a fluoride-PVA (F-PVA) tape, (ii) a pullulan incorporated F-PVA (PF-PVA) tape. S. mutan strains were cultured and treated with the tapes. Antimicrobial effects were evaluated using the agar diffusion test, field-emission scanning electron microscopy (FE-SEM), and confocal laser scanning microscopy (CLSM). F-PVA tapes showed higher inhibition-zone diameters than PF-PVA at 48 h and 72 h. However, there were no significant differences (p > 0.05) between the effects of F-PVA and PF-PVA. The bio-volume of S. mutans and extracellular polymeric substances significantly decreased in the F-PVA tapes than in the PF-PVA tapes (p < 0.05). FE-SEM micrographs revealed less S. mutans colonization in F-PVA. F-PVA exhibited better antimicrobial activity against S. mutans than PF-PVA.

Revealing Roles of High-Electronegativity Fluorine Atoms in Boosting Redox Potential of Layered Sodium Cathodes.

The development of high-energy-density cathode materials is regarded as the ultimate goal of alkali metal-ion batteries energy storage. However, the strategy of regulating specific capacity is limited by the theoretical capacity, and meanwhile focusing on improving capacity will lead to structural destructions. Herein, a novel perspective is proposed that tuning the electronic band structure by introducing highly electronegative fluoride atoms in NaxTMO2-yFy (0 < x < 1, 0 < y < 2) model compounds to improve redox potential for developing high-energy-density layered oxides. Highly electronegative fluoride atoms is introduced into P2-type Na0.67Fe0.5Mn0.5O2 (NFM), and the thus fluoride NFM (F-NFM) cathode achieved high redox potential (3.0 V) and high energy density (446 Wh kg-1). Proved by structural characterizations, fluorine atoms are successfully incorporated into oxygen sites in NFM lattice. Ultraviolet photoelectron spectroscopy is applied to quantitatively analyze the improved redox potential of F-NFM, which is achieved by the decreased valence band energy in electronic band structure due to the strongly electrophilic fluoride ions. Moreover, fluoride atoms can stabilize the local environment of NFM and improve its redox potential. The work provides a perspective to improve redox potential by tuning the electronic band structure in layered oxides and developing high-energy-density alkali metal-ion batteries.

Synergistic Molecular Alignment and Dipole Polarization in Stretched Nafion/Poly(vinylidene fluoride) Blend Membranes for High Proton Conduction in PEMFCs.

The nanostructure of Nafion and poly(vinylidene fluoride) (PVDF) blend membranes is successfully aligned through a mechanical uniaxial stretching method. The phase-separated morphology of Nafion molecules distinctly forms hydrophilic proton channels with increased connectivity, resulting in enhanced proton conductivity. Additionally, the crystalline phase of PVDF molecules undergoes a successful transformation from the α- to ß-phase during membrane stretching, demonstrating an alignment of fluorine and hydrogen atoms with a TTTT(trans) structure. The aligned nanostructure of the blend film, combined with the dipole polarization of the ß-phase PVDF, synergistically enhances the proton conduction through the membrane for operating proton-exchange membrane fuel cells (PEMFCs). The controlled structures of the blend membranes are thoroughly investigated using atomic force microscopy and small-angle X-ray scattering. Furthermore, the improved in-plane proton conductivity facilitates increased proton conduction at the interface between the membrane and catalyst layer in the membrane-electrode assembly, ultimately enhancing the power generation of PEMFCs.

Antimicrobial polymer-based zeolite imidazolate framework composite membranes for uranium extraction from wastewater and seawater.

Extraction uranium (VI) (U(VI)) from wastewater and seawater is highly important for environmental protection and life safety, but it remains a great challenge. In this work, the growth of the zeolitic imidazolate framework-8 (ZIF-8) nanoparticles on the tannic acid (TA)-3-aminopropyltriethoxysilane (APTES) modified PVDF (TAP) membrane was designed to obtain an excellent U(VI) adsorbent. The zeolite imidazolate framework composite membrane (TAPP-ZIF-60) was prepared through polyethyleneimine (PEI) bridging strategy and temperature regulation strategy in solvothermal method. The coordination bond between PEI and ZIF-8 and the covalent bond between PEI and TAP are essential in forming stable composite membrane. TAPP-ZIF with different properties was synthesized through a temperature regulation process and the TAPP-ZIF prepared at 60 °C has the uniform morphology and good performance. The adsorption capacity of TAPP-ZIF-60 is 153.68 mg/g (C0 = 95.01 mg/L and pH = 8.0) and water permeability is 5459 L m-2 h-1 bar-1. After ten adsorption-desorption cycles, it is proved that TAPP-ZIF-60 has good repeatability and stability. In addition, the TAPP-ZIF-60 composites membrane has a good inhibitory effect on Staphylococcus aureus and Escherichia coli. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analysis reveal that the coordination between TAPP-ZIF-60 and uranyl ions is the primary factor contributing to the high adsorption capacity.

The factors associated with the knowledge of brushing teeth with fluoridated toothpaste among high school students in Al-Madinah, Saudi Arabia.

Objective: The use of fluoridated toothpaste (FT) is essential for controlling caries. This analytical cross-sectional study aimed to determine the proportion of students who brushed their teeth with fluoridated toothpaste/or do not know the content at least once a day and to determine the factors associated with the knowledge of brushing teeth with FT. Methods: An anonymous questionnaire was distributed during the academic year 2019-2020 among 439 high school students. The data collected included sociodemographic characteristics and oral-health-related variables [e.g., brushing teeth, knowledge of the effect of fluoride on caries (KEFC) and dental service utilisation (DSU)]. The dependent variable was the knowledge of using FT when brushing teeth (Yes or do not know). Descriptive, bivariate, and logistic regression analysis were performed. Results: The response rate was 98% (n = 432) and usable data was 88% (n = 385). The median (IQR) age of the students was 16.00 (1) years, and 190 (47%) were males. Eighty eight percent of the students brushed their teeth with toothpaste daily with no knowledge of toothpaste content and only 86 (21.8%) knew the content of the toothpaste used for brushing their teeth i.e., FT. The multivariable analyses revealed an association of family income and KEFC with brushing teeth with FT [adjusted odds ratio (AOR): 1.98, 95% confidence interval (CI): 1.14-3.43, p = 0.015 and AOR = 6.11, 95% CI: 3.45-10.83, p < 0.001, respectively]. Conclusions: While the brushing and use of toothpaste among high school students was common, the knowledge of the content of toothpaste used for brushing teeth was less common and was associated with family income and KEFC.