Trace rare earth elements analysis in atmospheric particulates and cigar smoke by ICP-MS after pretreatment with magnetic polymers.

BACKGROUND: Some heavy metals could be ingested into human body through breathing besides diet and drinking. Atmospheric particulates and smoke are main sources of this kind for the metals' exposure to human. Compared with environmental water, the methodologies for trace metals in particulates and smoke samples with more complex matrix are much less. Magnetic functional sorbents can be designed to remove complex matrix and enrich target analytes. The combination of magnetic solid phase extraction (MSPE) with highly sensitive inductively coupled plasma mass spectrometry (ICP-MS) detection is a good alternative for the analytical purpose. (92). RESULTS: Magnetic polymers were synthesized through free radical polymerization with Fe3O4 nanoparticles as the core and 2-methyl-2-hydroxyethyl 2-acrylate-2-hydroxyethyl ester phosphate as external modifier. The sorbent showed a high phosphorus content (2.7 wt%) and good selectivity to target REEs, along with good reusability (at least 45 times) and chemical stability. With the consumption of 150 mL aqueous solution, an enrichment factor of 300 was obtained by the proposed method, leading to low detection limits (0.001-0.2 ng L-1) for 15 REEs. The application potential of the method was further evaluated by analyzing local atmospheric particulate and cigar smoke samples. Recovery of 86.3-107 % in digested total suspended particulate (TSP) was obtained for 15 REEs, demonstrating a good anti-interference ability of the method. Target REEs in TSP, PM2.5 and PM10 samples were found to be 0.01-2.81, 0.006-1.09 and 0.009-2.46 ng m-3, respectively, and none of them were detected in the collected cigar smoke. (148) SIGNIFICANCE: The method of MSPE-ICP-MS was demonstrated with good potential for trace analysis in complex sample matrix, probably due to the good selectivity of the functionalized polymers. With the design and fabrication of specific functionalized magnetic sorbents, other heavy metals can be monitored in those samples which would be intake by human breathing. It provided an efficient strategy for the evaluation of metals' health risk in particulates and smoke samples. (69).

Organocatalytic Atroposelective Synthesis of Axially Chiral Indolyl Ketosulfoxonium Ylides.

Despite recent advancements in catalytic synthesis of axial chirality, reports on non-biaryl atropisomers remain limited because of the stringent steric requirements necessary to establish effective rotational brakes. In this study, we present a novel class of monoaryl atropisomers, indolyl ketosulfoxonium ylides, and describe an organocatalytic protocol for their synthesis. We discovered that a chiral phosphoric acid (CPA) serves as an effective catalyst for the highly enantioselective iodination of ortho-aminophenylethynyl sulfoxonium ylides. Under the optimized reaction conditions, a strong preference for the intended iodination process over the competing protonation was observed. Subsequently, intramolecular amide cyclization enabled the formation of sterically congested indole fragments. Furthermore, the synthetic utility of the products was demonstrated by showcasing versatile transformations into other chiral scaffolds with complete retention of optical purity.

Efficient sequestration of cesium ions using phosphoric acid-modified activated carbon fibers from aqueous solutions.

In this study, acid-modified activated carbon fibers (ACF-Ps) were synthesized by phosphorylation. Three different types of ACF-based adsorbents functionalized with PO43-, P2O74-, or P3O105- ions, namely, ACF-P1, ACF-P2, and ACF-P3, were prepared by phosphorylating ACF with trisodium phosphate (Na3PO4), sodium dihydrogen pyrophosphate (Na2H2P2O5), and sodium tripolyphosphate (Na5P3O10), respectively, and utilized as adsorbents to remove cesium ions (Cs+) from aqueous solutions. Among the tested adsorbents, ACF-P3 exhibited the highest Cs+ adsorption capacity of 37.59 mg g-1 at 25 °C and pH 7 which is higher than that of ACF (5.634 mg g-1), ACF-P1 (19.38 mg g-1), and ACF-P2 (30.12 mg g-1) under the same experimental conditions. More importantly, the Cs+ removal efficiencies of ACF-P3 (82.90%), ACF-P2 (66.2%), ACF-P1 (34.2%) were 29.3-, 23.4-, and 12.11-fold higher than that of un-treated ACF (2.83%). The results suggested that the phosphorylation with Na5P3O10 is highly suitable for Cs+ adsorption which effectively functionalizes ACF with a greater number of phosphate functional groups. Adsorption and kinetic data well-fitted the Langmuir isotherm and pseudo-second-order model, respectively, which indicated the monolayer adsorption of Cs+ onto ACF-P1, ACF-P2, and ACF-P3 which were largely controlled by chemisorption. Overall, phosphoric acids containing different phosphate-based polyanions (PO43-, P2O74-, or P3O105-) enriched -OH and/or -COOH surface functional groups of ACF in addition to P-containing surface groups (PO, C-P-O, C-O-P, and P-O) and facilitated the Cs+ adsorption through surface complexation and electrostatic interactions.

A comparison of different cleaning approaches for blood contamination after curing universal adhesives on the dentine surface.

OBJECTIVE: This study compared the effectiveness of various cleaning approaches, including spray rinsing, repreparing with diamond burs, and using phosphoric acid or sodium hypochlorite alone or with polyphenols (resveratrol or myricetin), in removing blood contamination from the dentine after adhesive light-curing. METHODS: The contact angles of the treated surfaces were measured and scanning electron microscopy/ energy dispersive X-ray spectroscopy observation was performed. The bond strength and nanoleakage were assessed, and in situ zymography was performed before and after aging. Interactions between matrix metalloproteinase (MMP)-9 and polyphenols were evaluated using molecular dynamics and rhMMP-9 inhibition analyses. The destruction of sodium hypochlorite on collagen and the resistance of polyphenols-treated dentine collagen to enzymolysis were evaluated using the hydroxyproline (HYP) assay. The effect of polyphenols on dentine collagen crosslinking was assessed by Fourier Transform Infrared Spectroscopy. RESULTS: The repreparation group had the lowest contact angle compared to the other groups. The spray rinsing group had the lowest bond strength and highest amounts of nanoleakage. Cleaning with phosphoric acid or sodium hypochlorite alone removed the blood contaminants and parts of the adhesive; moreover, applying polyphenols further improved the bond strength and decreased nanoleakage and MMP activity after aging. Both polyphenols inhibited rhMMP-9 activity and promoted collagen crosslinking. Sodium hypochlorite showed the maximum HYP release when used alone, which was decreased after adding polyphenols. SIGNIFICANCE: Phosphoric acid or sodium hypochlorite cleaning can remove blood contamination from the dentine surface after adhesive curing, and the addition of polyphenols can improve the durability of dentine bonding.

All-cellulose composite yarn via welding engineering.

Due to the wide range of available raw materials and excellent biocompatibility, all-cellulose composites (ACCs) have received significant attention as a kind of renewable and biodegradable candidate to replace petroleum-based synthetic polymers. However, most current research of ACCs is limited to film and bulk materials. Herein, we present a simple, efficient, and scalable welding method for obtaining green, self-reinforced, high performance all-cellulose composite yarns by partially dissolving and regenerating cellulose yarns with phosphoric acid. The in-situ core-shell structure of the welded yarn results in improved strength (134.6 MPa), friction resistance (8000 cycles), moisture regain (11.89 %), and dyeing properties. Moreover, the regeneration and drying procedure can be optimized to further enhance the strength (190.5 MPa) of the welded yarn. This straightforward welding approach provides a promising and convenient route for manufacturing high-performance bio-based yarn.

Radiochemical neutron activation analysis of elemental contents in crude phosphoric acid samples and studies on adsorption removal of these elements using synthesized bionanocomposites.

Harmful elements in Egyptian phosphoric acid were identified by radiochemical neutron activation analysis. In the Second Egyptian Nuclear Research Reactor, precipitates were created and examined to identify many types of contaminants (Ce, Co, Cr, etc.). New bionanocomposite materials effectively removed with a high proportion each of Ce, Th, Pa, U, Np, Zn, and Co (100%) and a somewhat lower percentage (65-85%) for Cr, Sc, and Fe from simulated solutions, suggesting promise for purifying phosphoric acid.

Carbon nanotube-modified adhesive to caries affected dentin conditioned with Nd: YAP laser, phosphoric acid, and photoactivated-erythrosine.

AIM: Dentin conditioned with phosphoric acid (PA) Nd: YAP laser, and photoactivated-Ery(Erythrosine) on microleakage, shear bond strength (SBS) degree of conversion (DC), and rheological assessment of adhesive-infused with carbon nanotubes (CNTs). MATERIAL AND METHOD: Carious ninety-six human mandibular molars were included. Specimens were disinfected and allocated into three groups based on surface pretreatment (n = 32) Group 1 (PA), Group 2 (Nd: YAP) laser, and Group 3 (Photoactivated-Ery). Conditioned groups were further divided into two 2 subgroups based on the application of unmodified ERA and CNTs-modified ERA. Composite restorations were placed on the CAD surface and thermal aging of the samples was performed. The microleakage assessment was conducted using a dye penetration test. Universal testing machine (UTM) assessed SBS bond failure was evaluated using a stereomicroscope. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analyses of CNT, and Fourier Transform Infrared FTIR of adhesives were performed. One-way ANOVA and Tukey post hoc analyzed the outcomes. RESULTS: Group 1B samples (PA+ CNTs modified adhesive) presented the minimum marginal leakage and highest bond integrity. Group 2A (Nd:YAP laser+Unmodified adhesive) displayed the maximum scores of microleakage and lowest bond strength. CONCLUSION: Photoactivated Ery-PS can serve as an alternative to phosphoric acid for conditioning CAD. Incorporating CNT in adhesive significantly enhanced bond integrity and marginal seal with no significant difference in DC.

Facile Fabrication of Hierarchical Structured Anodic Aluminum Oxide Molds for Large-Scale Production of Superhydrophobic Polymer Films.

Anodized aluminum oxide (AAO) molds were used for the production of large-area and inexpensive superhydrophobic polymer films. A controlled anodization methodology was developed for the fabrication of hierarchical micro-nanoporous (HMN) AAO imprint molds (HMN-AAO), where phosphoric acid was used as both an electrolyte and a widening agent. Heat generated upon repetitive high-voltage (195 V) anodization steps is effectively dissipated by establishing a cooling channel. On the HMN-AAO, within the hemispherical micropores, arrays of hexagonal nanopores are formed. The diameter and depth of the micro- and nanopores are 18/8 and 0.3/1.25 µm, respectively. The gradual removal of micropatterns during etching in both the vertical and horizontal directions is crucial for fabricating HMN-AAO with a high aspect ratio. HMN-AAO rendered polycarbonate (PC) and polymethyl methacrylate (PMMA) films with respective water contact angles (WCAs) of 153° and 151°, respectively. The increase in the WCA is 80% for PC (85°) and 89% for PMMA (80°). On the PC and PMMA films, mechanically robust arrays of nanopillars are observed within the hemispherical micropillars. The micro-nanopillars on these polymer films are mechanically robust and durable. Regular nanoporous AAO molds resulted in only a hydrophobic polymer film (WCA = 113-118°). Collectively, the phosphoric acid-based controlled anodization strategy can be effectively utilized for the manufacturing of HMN-AAO molds and roll-to-roll production of durable superhydrophobic surfaces.

Self-Organization of Polyurethane Ionomers Based on Organophosphorus-Branched Polyols.

Based on organophosphorus branched polyols (AEPAs) synthesized using triethanolamine (TEOA), ortho-phosphoric acid (OPA), and polyoxyethylene glycol with MW = 400 (PEG), vapor-permeable polyurethane ionomers (AEPA-PEG-PUs) were obtained. During the synthesis of AEPAs, the reaction of the OPA etherification with polyoxyethylene glycol was studied in a wide temperature range and at different molar ratios of the starting components. It turned out that OPA simultaneously undergoes a catalytically activated etherification reaction with triethanolamine and PEG. After TEOA is fully involved in the etherification reaction, excess OPA does not react with the terminal hydroxyl groups of AEPA-PEG or the remaining amount of PEG. The ortho-phosphoric acid remaining in an unreacted state is involved in associative interactions with the phosphate ions of the AEPA. Increasing the synthesis temperature from 40 °C to 110 °C leads to an increase in OPA conversion. However, for the AEPA-PEG-PU based on AEPA-PEG obtained at 100 °C and 110 °C, ortho-phosphoric acid no longer enters into associative interactions with the phosphate ions of the AEPA. Due to the hydrophilicity of polyoxyethylene glycol, the presence of phosphate ions in the polyurethane structure, and their associative binding with the unreacted ortho-phosphoric acid, the diffusion of water molecules in polyurethanes is enhanced, and high values of vapor permeability and tensile strength were achieved.

Experimental and Chitosan-Infused Adhesive with Dentin Pretreated with Femtosecond Laser, Methylene Blue-Activated Low-Level Laser, and Phosphoric Acid.

Aim: To prepare experimental adhesive (EA) with 1% and without chitosan nanoparticles on dentin conditioned with a conventional technique phosphoric acid (PA) compared with two different contemporary techniques: photodynamic therapy (PDT) and femtosecond laser (FSL). Method: The methodology consisted of synthesis of EA and 1% chitosan-modified adhesive (CMA). Scanning electron microscopy, dentin adhesive interface assessment, energy-dispersive spectroscopy, shear bond strength (SBS), degree of conversion (DC), and bond failure were assessed. Teeth were selected, disinfected, and mounted in acrylic up to the cementoenamel junction. Occlusal enamel was removed and teeth were randomly allocated into groups and conditioned. These included Group 1: samples treated with PA; Group 2: specimens conditioned with methylene blue photosensitizer (MBP) activated by PDT; and Group 3: samples conditioned with FSL. Following different conditioning regimes, specimens were bonded using 1% CMA and EA. The composite buildup was followed by SBS testing and a bond failure assessment. DC was assessed for both EA and CMA. Analysis of variance and Tukey's post hoc test were used to compare the mean and standard deviation of SBS and DC in different experimental groups, with a significance level of p < 0.05. Results: Dentin pretreated with etch and rinse demonstrated the highest bond strength with 1% CMA. Dentin conditioned with MBP activated by PDT and bonded to EA showed the lowest bond scores. Overall SBS values of 1% CMA were better than EA irrespective of the conditioning regime of dentin. The DC was higher in EA adhesive. This was followed by DC in 1% CMA. DC in EA was found to be comparable with 1% CMA. Conclusions: PA remains the gold standard for dentin conditioning. The incorporation of 1% chitosan in adhesive improves SBS and results in no change in DC. The use of FSL in dentin conditioning can be used as an alternative approach as it results in SBS within acceptable limits. The study was approved by the ethical board of King Saud University.

High tensile regenerated cellulose fibers via cyclic freeze-thawing enabled dissolution in phosphoric acid for textile-to-textile recycling of waste cotton fabrics.

Recycling of waste cotton fabrics (WCFs) is a desirable solution to address the problems brought up by fast fashion, but it remains challenging due to inherent limitations in preparing stable and spinnable dopes by dissolving high molecular weight cellulose efficiently and cost effectively. Herein, we show that despite the prevailing concerns of cellulose degradation via glycosidic hydrolysis when dissolved in acids, fast and non-destructive direct dissolution of WCFs in aqueous phosphoric acid (a.q. PA) could be realized using a cyclic freeze-thawing procedure, which combined with subsequent adjustment of degree of polymerization (DP) and degassing yielded stable and spinnable dopes. Regenerated cellulose fibers (RCFs) with favorable tensile strength (414.2 ± 14.3 MPa) and flexibility (15.4 ± 1.5 %) could be obtained by carefully adjusting the coagulation conditions to induce oriented and compact packing of the cellulose chains. The method was shown to be conveniently extended to dissolve reactively dyed WCFs, showing great potential as a cheap and green alternative to heavily explored ionic liquids (ILs) and N-methylmorpholine-N-oxide (NMMO)-based systems for textile-to-textile recycling of WCFs.

Synergistic adsorption of methylene blue using ternary composite of phosphoric acid geopolymer, calcium alginate, and sodium lauryl sulfate.

The removal of dyes from the aquatic ecosystem is necessary being a major threat to life. For enhanced remediation of methylene blue (MB) dye, a new ternary biopolymer-geopolymer-surfactant composite adsorbent is synthesized by combining phosphoric acid geopolymer (PAGP), calcium alginate (Alg), and sodium lauryl sulfate (SLS). During the synthesis of the composites, PAGP and SLS were mixed with the alginate matrix, producing porous hybrid beads. The PAGP-SLS-alginate (PSA) beads prepared were characterized using different analytical tools, i.e., scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR), X-ray diffractometry (XRD), surface area and porosimetery (SAP), and thermogravimetric analysis (TGA). To ascertain the ideal conditions for the adsorption process, a batch reactor procedure was used to investigate the effects of several parameters on MB adsorption, including pH (2, 4, 6, 8, 10), PSA adsorbent dosage (0.06-0.12 g), MB concentration (50-500 mg/L), contact time (15 to 300 min), and temperature (25, 35, and 45 °C). The SEM investigation indicated that ~ 1860 µm-sized PSA beads with 6-8 µm voids are generated. Based on XRD, FTIR, and SAP examinations, the material is amorphous, having numerous functional groups and an average pore size of 6.42 nm. Variation of pH has a little effect on the adsorption process, and the pH of 7.44 was found to be the pHpzc of the PSA beads. According to the findings of the batch study, equilibrium adsorption was obtained in 270-300 min, showing that the adsorption process was moderately slow-moving and effective. The dye adsorption linearly increased with initial dye concentration over concentration range of 50-500 mg/L and reciprocally decreased with rise in temperature. 0.06 g adsorbent dose, 25 °C, pH10, and 270 min were found to be the better conditions for adsorption experiments. Langmuir isotherm fitted well compared to Freundlich, Temkin, and Dubinin-Radushkevich (DR) isotherm models on the experimental data, and the maximum adsorption capacity(qmax) calculated was 1666.6 mg. g-1. Pseudo-second-order (PSO) kinetics model and multi steps (two) intra particle diffusion (IPD) model fitted well on the adsorption kinetics data. The system's entropy, Gibbs free energy, and change in enthalpy were measured and found to be -109.171 J. mol-1. K-1, - 8.198 to - 6.014 kJ. mol-1, and - 40.747 kJ. mol-1. Thermodynamics study revealed that adsorption process is exothermic, energetically favorable and resulting in the decrease in randomness. Chemisorption is found to be the dominant mechanism as confirmed by pH effect, Langmuir isotherm, PSO kinetics, IPD model, and thermodynamics parameters. PSA beads were successfully regenerated using ethanol in a course of 120 min and re-used for five times. To sum up, the PSA adsorbent's impressive adsorption capability of 1666.66 mg/g highlights its potential as a successful solution for methylene blue removal. The results of this study add to the expanding corpus of information on sophisticated adsorption materials and demonstrate PSA's potential for real-world uses in wastewater treatment and environmental clean-up.

Introduction of polymeric ionic liquids containing quaternary ammonium groups to construct high-temperature proton exchange membranes with high proton conductivity and stability.

A series of membrane materials suitable for high-temperature proton exchange membranes (HT-PEM) were successfully prepared by introducing polymeric ionic liquids (PILs) containing quaternary ammonium groups into ether-bonded polybenzimidazole (OPBI). The structure of the cross-linked membrane has a strong interaction with phosphoric acid (PA), which enhances proton transport and PA retention. To ensure better overall performance of the cross-linked membrane, the optimal PIL content is 30 wt% (OPBI-PIL-30 %). The PA uptake of OPBI-PIL-30 % membrane was 323.24 %, and the proton conductivity at 180 â„ƒ was 113.94 mS cm-1, which was much higher than that of OPBI membrane. It is noteworthy that the PA retention of OPBI-PIL-30 % membrane could reach 71.38 % after 240 h of testing under the harsh environment of 80 â„ƒ/40 % RH. The membrane showed better acid retention capacity of 86.89 % at 160 â„ƒ under anhydrous environment. The OPBI-PIL-20 % membrane achieved the maximum power density of 436.19 mW cm-2, attributed to its favorable mechanical characteristics and proton conductivity. By these excellent properties, it is shown that OPBI-PIL-X membranes containing quaternary ammonium groups have the potential to be applied in high temperature proton exchange membrane fuel cells (HT-PEMFCs).

Aspects of glass and hybridization protocols for bonding of fiber posts to root dentine.

This study evaluated bond strength of glass fiber posts to root dentin using push-out (PO) and diametral compression (DC), testing glycolic acid as a conditioner and varying dentin moisture. An additional aim was to test whether DC can be an alternative test to PO for bond strength assessment. Eighty bovine teeth were divided into eight groups (n = 10) defined by the use of either 37% glycolic acid or 37% phosphoric acid (PA) on moist or wet dentin before bonding with either Adapter SingleBond/RelyX ARC or One Step Plus/Duo-Link Bisco. Each tooth provided discs with an internal diameter of 2 mm, external diameter of 5 mm, and height of 2 mm, which underwent PO and DC. Finite element analysis (FEA) was carried out on 3D models. When analyzing PO results through linear regression, the highest values of bond strength were observed using glycolic acid on wet dentin in the cervical and middle thirds of the teeth. Analyzing DC results, the only statistical influence on values was the dental thirds. The scatterplot of the DC results and the PO bond strength values indicated no relationship between the results of the two tests (r = 0.03; p = 0.64). PO test detected more sensitive changes in bond strength values than DC.

Study on the Application Performance of Polymer Electrolyte Membrane Functionalized with Triethyl Phosphite-Modified Graphene Oxide in Fuel Cells.

In this paper, we successfully synthesize phosphoric acid functionalized graphene oxide (PGO) based on acid modification of graphene oxide. The composite membrane is further prepared by adding PGO into sulfonated poly(aryl ether ketone sulfone) containing carboxyl groups matrix (C-SPAEKS). The PGO as well as the composite membranes were characterized by a series of tests. The prepared composite proton exchange membranes (PEMs) have good mechanical and electrochemical properties. Compared to the C-SPAEKS membrane, the best composite membrane has a tensile strength of 40.7 MPa while exhibiting superior proton conductivity (110.17 mS cm-1 at 80 °C). In addition, the open-circuit voltage and power density of C-SPAEKS@1% PGO are 0.918 V and 792.17 mW cm-2, respectively. Compared with C-SPAEKS (0.867 V and 166 mW cm-2), it can be seen that our work has a certain effect on the improvement of the single cell performance. The above results demonstrate that the functionalized graphene oxide has greatly improved the electrochemical performance and even the overall performance of PEMs.

Valorization of castor seed shell waste as lead adsorbent by treatment with hot phosphoric acid: Optimization and evaluation of adsorption properties.

Lead is used in many industries such as refining, mining, battery manufacturing, smelting. Releases of lead from these industries is one of the major public health concerns due to widespread persistence in the environment and its resulting poisoning character. In this work, the castor seed shell (CSS) waste was exploited for preparing a beneficial bio-adsorbent for removal of Pb(II) ions from water. The raw CSS was modified with H3PO4 at different acid concentrations, impregnation ratios, activation times, and temperatures. An optimum adsorption capacity was observed for CSS modified with 2 M acid, 5 mL g-1 solid to liquid ratio, treated at 95 °C for 160 min. Exploiting acid modification, the SEM, XRD, and FTIR analyses show some alterations in functional groups and the surface morphology of the biomass. The impacts of physiochemical variables (initial lead ions concentration, pH, adsorbent dose and adsorption time) on the lead removal percentage were investigated, using response surface methodology (RSM). Maximum removal of 72.26% for raw CSS and 97.62% for modified CSS were obtained at an initial lead concentration (50 mg L-1), pH (5.7), adsorption time (123 min) and adsorbent dosage (1.1 g/100 mL). Isothermal and kinetics models were fitted to adsorption equilibrium data and kinetics data for the modified CSS and the adsorption system was evaluated thermodynamically and from the energy point of view. Isothermal scrutinization indicated the mono-layer nature of adsorption, and the kinetics experimental outcomes best fitted with the pseudo-second-order, implying that the interaction of lead ions and hot acid-treated CSS was the rate-controlling phenomenon of process. Overall, results illustrated that the hot acid-treated biomass-based adsorbent can be considered as an alternative bio-adsorbent for removing lead from water media.

Effect of Phytic Acid Etching and Airborne-Particle Abrasion Treatment on the Resin Bond Strength.

Objective: This study aimed to evaluate the bond strength of a universal adhesive to dentin (µTBS) using different time periods of airborne particle abrasion (APA) and two types of acid etching. Methods: Seventy-two human third molars were divided into 9 groups (n=8) according to dentin pretreatment: APA duration (0, 5, or 10s) and acid etching (no acid - NA, 37% phosphoric acid - PhoA, or 1% phytic acid - PhyA). APA was performed at a 0.5 cm distance and air pressure of 60 psi using 50 µm aluminum oxide particles. Afterwards, two coats of Single Bond Universal adhesive (3M) were applied to the dentin surface. Composite blocks were built using the incremental technique, sectioned into 1×1 mm slices and subjected to microtensile bond strength (µTBS) testing. Fracture patterns and surface topography of each dentinal pretreatment were evaluated using a Scanning electron microscope (SEM). Bond strength data were analyzed using two-way ANOVA and Bonferroni post-hoc tests. Results: The group that received pretreatment with 5s APA and PhoA presented higher µTBS values among all groups, which was statistically different when compared with the PhoA, 10APA+PhoA, and 5APA+PhyA groups. PhyA did not significantly influence the bond strength of the air-abraded groups. Finally, adhesive failure was considered the predominant failure in all groups. Conclusion: Dentin pretreated by airborne particle abrasion using aluminum oxide demonstrated an increase in bond strength when abraded for 5 seconds and conditioned with phosphoric acid in a universal adhesive system.

Organocatalytic Enantioselective Synthesis of Inherently Chiral Calix[4]arenes.

Inherently chiral calix[4]arenes are an excellent structural scaffold for enantioselective synthesis, chiral recognition, sensing, and circularly polarized luminescence. However, their catalytic enantioselective synthesis remains challenging. Herein, we report an efficient synthesis of inherently chiral calix[4]arene derivatives via cascade enantioselective cyclization and oxidation reactions. The three-component reaction features a broad substrate scope (33 examples), high efficiency (up to 90 % yield), and excellent enantioselectivity (>95 % ee on average). The potential applications of calix[4]arene derivatives are highlighted by their synthetic transformation and a detailed investigation of their photophysical and chiroptical properties.

In-syringe homogeneous liquid-phase microextraction followed by filtration-based phase separation for on-site extraction of chloroanilines from water samples.

This study introduces a new in-syringe homogeneous liquid-phase microextraction method for the rapid on-site extraction of chloroanilines from water samples. Extraction was performed using a plastic syringe, eliminating the use of any electrical power source. Di-(2-ethylhexyl) phosphoric acid (DEHPA) served as the extractant. The process initially involved dissolving DEHPA in an alkaline solution to obtain a homogeneous solution. Subsequently, the sodium salt of DEHPA was precipitated by salting-out, and the resulting heterogeneous mixture was filtered using a syringe filter. The precipitate containing the analytes was then dissolved in methanol for analysis by high-performance liquid chromatography. Under optimal conditions, extraction recovery for chloroanilines ranged from 26% to 71%. Method linearity was evaluated within a concentration range of 1.0-100 µg/L, resulting in coefficients of determination exceeding 0.9987 for all analytes. Method detection limits ranged from 0.28 to 0.41 µg/L. Intra and inter-day precision values were below 9.5% and 10.8%, respectively. The developed method was applied to determine chloroanilines in real waters, yielding acceptable recoveries ranging from 80% to 109% for spiked tap, rain, and stream waters. Additionally, the method was successfully employed for on-site extraction of target contaminants, demonstrating no statistically significant differences compared to laboratory results.

Effectiveness of Different Etching Agents on Enamel Surface and Shear Bond Strength: An In Vitro Evaluation.

Background Enamel etching is of utmost importance during the orthodontic bonding procedure. Phosphoric acid, hydrofluoric acid, and citric acid are used in specific concentrations to create surface irregularities on enamel surfaces, enhancing the bond strength of the orthodontic attachment. Therefore, it is essential to evaluate the type of etchant for reliable orthodontic bracket bonding with minimal damage to the enamel surface. Aims and objectives This study aimed to investigate the morphological changes on the enamel surface after treatment with different surface etchants, assess the depth of penetration, and evaluate the shear bond strength (SBS) of orthodontic brackets. Materials and methods One hundred and one extracted premolar teeth were used to investigate morphological changes on the enamel surface treated with 37% phosphoric acid, 11% hydrofluoric acid, and 20% citric acid. It was evaluated on a scanning electron microscope (Jeol Scientific Equipment, Jeol Limited, Akishima, Japan), and the SBS of brackets on enamel treated with different etching agents was evaluated using an Instron Universal Testing Machine (UTM; Instron Model: 5982, Universal Testing Systems, Norwood, MA). Group A had 60 test samples. Group B had 40 test samples. One control without any acid etching was used in both groups. Subgroup A1 (n = 30) was evaluated for surface characteristics of acid-etched enamel. Subgroup A2 was assessed for the penetration depth of various etchants. Group B (n = 40) was tested for SBS. The results were tabulated and analyzed using IBM SPSS Statistics, version 20.0 (IBM Corp., Armonk, NY). Post hoc Tukey HSD test and one-way analysis of variance were used to assess SBS and penetration depth of etchants (P ≤ 0.05). Pearson's correlation test was used to correlate SBS, etching pattern, and penetration depth. The chi-square test was used to test the frequency of types of etching patterns.  Results Intergroup correlations between etching depth, etching pattern evaluated on SEM, and SBS evaluated on the UTM showed a high statistical correlation between etching depth & SBS, etching depth & etching pattern, and SBS & etching pattern between A1, A2, and group B (P ≤ 0.001). A highly significant negative correlation between SBS & etching pattern (P = 0.42) was observed among intra-group correlation. Non-significant correlations were found between etching depth & SBS and etching depth & etching pattern within the 20% citric acid etch group (P = 0.370 and 0.141, respectively). Conclusion Penetration depth obtained was highest with 11% hydrofluoric acid, followed by 37% phosphoric acid and 20% citric acid. In addition, 11% hydrofluoric acid showed the highest bond strength. Acid etching showed better penetration depth and bond strength than control.