Crystalline Species Research Articles

Ethanol-assisted kneading of apigenin with arginine for enhanced dissolution rate of apigenin: development of rapidly disintegrating tablets

Apigenin is a natural flavonoid which is claimed to have many pharmacological activities ranging from simple anti-inflammatory to anticancer action. However, poor dissolution slowed the advancement of this drug through the development pipelines. The objective of this work was to probe ethanol-aided kneading of apigenin with arginine as a new strategy for enhanced dissolution rate. The work was extended to develop rapidly disintegrating tablets of apigenin. Apigenin was mixed with increasing molar ratios of arginine before ethanol-aided kneading. The resulting products were examined using Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction in addition to probing the dissolution characteristics of apigenin. The analytical techniques highlighted the existence of new crystalline species with a possibility of salt formation. The recorded alterations in the crystalline properties were associated with a significant enhancement in the dissolution rate of apigenin. The presence of arginine did not have any negative effect of the cytotoxic power of apigenin. Optimum formulation was successfully prepared as rapidly disintegrating tablets which showed fast liberation of apigenin. The study introduced arginine as a potential excipient for enhanced dissolution of apigenin after ethanol-assisted kneading.

Molecular dynamics simulation of a nanocluster obtained from the mining industry

A dynamic molecular simulation is a straightforward and logical research tool governed by Newton’s movement equations. In this case, it is part of a new research line that explores the molecular interactions of a concentrate obtained from the mining industry (nanocluster). Mineragraphic and mineralogic analyses were performed, and 26 crystalline species were obtained and modeled, being chalcopyrite, pyrite, Cd-sulphide, quarts, and calcite the most representative structures due to their content. A geometry optimization applying the Quasi-Newton BFGS method was performed through the Materials Studio software version 8.0, obtaining the crystalline nanostructures. Finally, 95% of the structures were optimized, and more than 50% of these were validated based on X-ray diffraction (XRD) studies. Crystals that have not been validated have a different molecular weight and a different chemical composition and structure, affecting their crystallinity and X-ray diffraction patterns.

Carbon resistance of xNi/HTASAO5 catalyst for the production of H2 via CO2 reforming of methane

xNi/HTASAO5 catalysts (x = 2.5, 3.3, 4.4, 5.8, 8.2) were prepared for CO2 reforming of methane. No crystalline nickel species formed on the catalysts with lower nickel content (≤4.4%), and large Ni0 crystallite formed on 5.8% (10 nm) and 8.2 wt%Ni/HTASAO5 (17 nm), whereas the surface concentration of Ce3+ decreased with Ni loading. The initial conversion of CH4 increased from 29.5% to 46.9% with Ni loading. The xNi/HTASAO5 (x ≤ 4.4%) performed stably in the reaction due to the presence of dispersed Ni species and high surface Ce3+ content without coke formation, however, 5.8% and 8.2 wt%Ni/HTASAO5 exhibited decreased activity with time on stream, because of the formation of large Ni particles with lower surface Ce3+, leading to carbon accumulation. Thus, CH4 conversion stabilized at about 43% and no carbon formed on 4.4 wt%Ni/HTASAO5 with optimum Ni loading.

Deciphering of advantageous electrocatalytic water oxidation behavior of metal-organic framework in alkaline media

Carboxylic acid-based metal-organic frameworks (MOFs) are normally passed for the “pre-catalysts” for oxygen evolution reaction (OER) due to the hydroxides constructed in-situ during its alkaline hydrolysis process (AHP) in lye. Whereas, it remains a mystery that they show advantageous activity over prototypical hydroxides when they are directly acted as OER catalysts. Herein, we propose for the first time that the steric hindrance effect of Nafion can induce enhanced catalytic activity of such MOFs. Different from conventional catalysts without AHP, the Nafion with 3D structure weakens the AHP of Co-MOF nanoribbons, thus forming small size and low crystallinity species (cobalt hydroxide) with more active sites. And the existence of Nafion also optimizes its electronic structure, which is confirmed by transmission electron microscopy (TEM), in-situ UV absorption spectra, in-situ Raman spectroscopy and so on. Compared with Co-MOF-K obtained by directly immersing the Co-MOF nanoribbons in 1.0 M KOH, the Co-MOF-NK obtained by AHP of Co-MOF mixed with Nafion shows better catalytic activity. Based on the above inspiration, we realized the low overpotential of 268 mV at 10 mA·cm−2 by preparing CoFe-MOF-NK. This work provides a new understanding of the structural reconstruction of MOFs in the field of electrocatalysis.

Quantifying Preservation Potential: Lipid Degradation in a Mars-Analog Circumneutral Iron Deposit.

Comparisons between the preservation potential of Mars-analog environments have historically been qualitative rather than quantitative. Recently, however, laboratory-based artificial maturation combined with kinetic modeling techniques have emerged as a potential means by which the preservation potential of solvent-soluble organic matter can be quantified in various Mars-analog environments. These methods consider how elevated temperatures, pressures, and organic-inorganic interactions influence the degradation of organic biomarkers post-burial. We used these techniques to investigate the preservation potential of deposits from a circumneutral iron-rich groundwater system. These deposits are composed of ferrihydrite (Fe5HO8 · 4H2O), an amorphous iron hydroxide mineral that is a common constituent of rocks found in ancient lacustrine environments on Mars, such as those observed in Gale Crater. Both natural and synthetic ferrihydrite samples were subjected to hydrous pyrolysis to observe the effects of long-term burial on the mineralogy and organic content of the samples. Our experiments revealed that organic-inorganic interactions in the samples are dominated by the transformation of iron minerals. As amorphous ferrihydrite transforms into more crystalline species, the decrease in surface area results in the desorption of organic matter, potentially rendering them more susceptible to degradation. We also find that circumneutral iron-rich deposits provide unfavorable conditions for the preservation of solvent-soluble organic matter. Quantitative comparisons between preservation potentials as calculated when using kinetic parameters show that circumneutral iron-rich deposits are ∼25 times less likely to preserve solvent-soluble organic matter compared with acidic, iron-rich environments. Our results suggest that circumneutral iron-rich deposits should be deprioritized in favor of acidic iron- and sulfur-rich deposits when searching for evidence of life with solvent extraction techniques.

Geochemical changes of Mn in contaminated agricultural soils nearby historical mine tailings: Insights from XAS, XRD and, SEP

Manganese is ubiquitous in nature and essential for some metabolic reactions, but also it is present in the environment as a product of anthropogenic activities. Despite evidence linking high concentrations of Mn to several diseases, it is not commonly considered during environmental risk assessment of soils. Changes in chemical forms, oxidation state, and speciation of Mn in impacted agricultural soils by historical mine tailings in central Sonora in northwestern Mexico were studied using X-ray Absorption Near Edge Spectroscopy (XANES), X-ray Diffraction (XRD), and Sequential Extraction Procedures (SEP) techniques. Mn concentrations ranged from 1093 to 2919 mg·kg−1 in these soils, which exceeded the local geochemical background by up to six-fold. According to SEP, the tendency found in agricultural soils was reducible (42–66%) > soluble and exchangeable (16–42%) > residual (5–22%) > oxidizable (4–24%). In contrast, the tendency in sulfide-rich tailings samples was soluble and exchangeable (47–49%) > residual (35–41%) > oxidizable (5–11%) > reducible (5–7%), and in oxide-rich materials was residual (21–79%) > soluble and exchangeable (1–30%) > reducible (1–45%) > oxidizable (2–15%). The considerable percentage of the soluble forms indicated the potential of mobilization and availability to exposed organisms. No Mn-bearing mineral phases were identified with XRD, which suggested that manganese was mostly found in low-crystalline forms. XANES measurements indicated that the oxidation state of Mn in agricultural soil samples varied from Mn2+ through Mn4+. Conversely, the main oxidation state in mine tailings samples was Mn2+. Substantial changes were detected in Mn XANES spectra in the whole sample and residues left from SEP in agricultural soils, which confirmed the presence of all chemical forms (e.g., soluble and exchangeable, reducible, oxidizable, residual). A well-defined structure spectrum was obtained in soils once low crystallinity species and/or organic compounds were removed, which was similar to that acquired for mine tailings, suggesting mobility from tailings deposit to agricultural soils. Substantial contribution of compounds with mineral structures like birnessite (((Na, Ca, K)0.6(Mn4+, Mn3+)2O4·1.5H2O) and minor contributions of hausmannite (Mn3O4), spessartine (Mn3Al2(SiO4)3) and szmikite (MnSO4) were identified by Linear Combination Fitting (LCF) in soils, whereas the significant contribution of structures like hausmannite and spessartine, and minor contributions of rhodochrosite were found in tailings material. An LCF analysis in residues from SEP also suggests that the chemical species involved in the Mn mobilization were scachite and szmikite. In general, the results obtained indicate that leaching processes favored the presence of chemical species of Mn with a considerable potential of mobility and toxicity in agricultural soils interacting with historical mine tailings in central Sonora.

Sorption and Desorption of Vanadate, Arsenate and Chromate by Two Volcanic Soils of Equatorial Africa

Sorption of oxyanions by soils and mineral surfaces is of interest due to their role as nutrients or pollutants. Volcanic soils are variable charge soils, rich in active forms of aluminum and iron, and capable of sorbing anions. Sorption and desorption of vanadate, arsenate, and chromate by two African andosols was studied in laboratory experiments. Sorption isotherms were determined by equilibrating at 293 K soil samples with oxyanion solutions of concentrations between 0 and 100 mg L−1 V, As, or Cr, equivalent to 0−2.0 mmol V L−1, 0−1.3 mmol As L−1, and 0−1.9 mmol Cr L−1, in NaNO3; V, As, or Cr were determined by ICP-mass spectrometry in the equilibrium solution. After sorption, the soil samples were equilibrated with 0.02 M NaNO3 to study desorption. The isotherms were adjusted to mathematical models. After desorption with NaNO3, desorption experiments were carried out with a 1 mM phosphate. The sorption of vanadate and arsenate was greater than 90% of the amount added, while the chromate sorption was much lower (19–97%). The sorption by the Silandic Andosol is attributed to non-crystalline Fe and Al, while in the Vitric Andosol, crystalline iron species play a relevant role. The V and Cr sorption isotherms fitted to the Freundlich model, while the As sorption isotherms conformed to the Temkin model. For the highest concentrations of oxyanions in the equilibrating solution, the sorbed concentrations were 37–38 mmol V kg−1, 25 mmol As kg−1, and 7.2–8.8 mmol Cr kg−1. The desorption was low for V and As and high for Cr. The comparison of the sorption and desorption isotherms reveals a pronounced hysteresis for V in both andosols and for Cr in the Silandic Andosol. Phosphate induced almost no V desorption, moderate As desorption, and considerable Cr desorption.

Assessing poorly crystalline and mineral-organic species by extracting Al, Fe, Mn, and Si using (citrate-) ascorbate and oxalate

Poorly crystalline and mineral-organic species are commonly assessed by oxalate (Ox) extraction of aluminium (Al), iron (Fe), manganese (Mn), and silicon (Si). Drawbacks regarding selectivity towards analytical targets led to test alternatively, but mostly with topsoils, citrate-ascorbate (CA), combined with a separate citrate extraction. Here, we tested the extraction by Ox, CA, and citrate with 61 carbonate-free subsoils characterized by pedogenic element accumulation, and with 17 minerals, including primary silicates, clay minerals, and (Al, Fe) oxides. Iron extraction from the minerals, apart from pyrite, by citrate was negligible (≤2% of total Fe), like from Fe oxides (≤1.5% of total Fe), while oxalate-extractable Al, Fe, and Mn contents were larger than those extracted by CA, the relative fraction of which was below 9%, except for allophane. In subsoils, extractable element contents spanned several orders of magnitude whatever the extractant. With several samples, Mn was entirely solubilized by any extractant. The AlOx, FeOx, and MnOx amounts were very similar among soils lacking allophanic minerals. However, the ratio FeCA:FeOx increased with Bl and Bg horizons, which received Fe2+ by ground- or stagnic water. Citrate-extraction data revealed, depending on the soil type, a potentially large contribution of organic forms to CA- and Ox-extractable Al and Fe. Thus, we recommend combining Ox and CA extraction with citrate extraction to approximate the contents of poorly crystalline pedogenic Al and Fe species, rather than using CA- or oxalate-extraction data alone. Our results challenge the appropriateness of oxalate-extraction data for species identification and mineral quantification.

T1-T2* relaxation correlation measurements

The majority of low field Magnetic Resonance (MR) analyses rely on T2 lifetime measurements. Modification of the T2 measurement to include a T1 dimension has made the T1-T2 measurement a very powerful analytical technique. The T1-T2 measurement is uniquely well suited to characterization of different spin populations in porous materials, such as fluid bearing reservoir rocks, and in soft biopolymer materials, for example foods. However, the T1-T2 measurement is challenging or impossible if the T2 relaxation lifetime, or a component lifetime, is short-lived and the signal unobservable in an echo measurement. This occurs in many important classes of materials. A short lifetime T2 will not however, in general, preclude observation of a free induction decay with signal decay governed by T2*.As outlined in this paper a T1-T2* measurement is a useful analog to the T1-T2 experiment. T1-T2* measurement enables one to differentiate species as a function of T2* in one dimension and T1 in the other dimension. Monitoring changes of the T1-T2* coordinate, and associated signal intensity changes, has the potential to reveal structural changes in materials evolving in time. These methods may also be employed to discriminate and identify solid-like species present in static samples.The T1-T2* measurement is very general in application, but in this paper we focus on cement-based mortars to develop and illustrate the essential ideas. T1-T2* results show a multi-modal behaviour of the MR signal lifetimes, T1 and T2*, in mortar samples under study, indicating at least two different water populations. The short T2* lifetime was assigned to interlayer water (water between C–S–H layers) where the associated T1 is also short lived. The longer T2* lifetime was assigned to water in the pore space, where T1 is also longer lived. In addition to mortar samples we also show application of the method to a crystalline organic species, o-phenylenediamine, which features Sinc Gaussian and exponential decays of transverse magnetization.

Synergistic role of bulk carbon and iron minerals inherent in the sludge-derived biochar for As(V) immobilization

Sludge-derived biochar has been considered as a promising sorbent for As(V) due to its high content of Fe. However, role of different endogenous iron minerals and the bulk carbon in this process remained unclear. Here, biochar with different Fe content and species were prepared from two types of sludge (SSA and SSB) at 350 °C or 700 °C for As(V) immobilization. Although SSB biochar had considerable Fe (3.6%-8.6%), they showed limited sorption capacity for As(V) due to the electrostatic repulsion related to the negatively charged surface at the experimental pH. By contrast, SSA biochar demonstrated superior sorption abilities for As(V) with the maximum capacities of 60.2–90.2 mg g−1. Amorphous iron determined the removal of As(V) by SSA350 due to the adsorption and the co-precipitation of released Fe2+ with H2AsO4-, which accounted for 77.6% and 22.4%, respectively. For SSA700, iron minerals were converted to more crystalline species, including γ-FeOOH, Fe4(O,OH,SO4)9, and Fe2(SO3)3·xH2O, and the co-precipitation with As(V) caused 74.6% of As(V) removal by SSA700. The bulk carbon of biochar was proved to serve as heterogeneous nucleation sites for the co-precipitation, showing its synergistic effect with iron on As(V) removal, which raised the removal efficiency from 0.9–2.9% by Fe2+ alone to 13.9–25.5% by Fe2+ co-existing with bulk carbon. Findings of this study not only demonstrate the importance of iron species in biochar to As(V) removal, but also provide new insights on the synergistic effect of iron interaction with bulk carbon.

Bimodal effect of water on V2O5/TiO2 catalysts with different vanadium species in the simultaneous NO reduction and 1,2-dichlorobenzene oxidation

VOX/TiO2 catalysts with different vanadium loading were prepared in order to study the influence of vanadium species on the effect of water in the simultaneous NO reduction through NH3-SCR and o-DCB oxidation reactions. The presence of isolated, polymeric and crystalline species and their redox and acid properties were evaluated by N2-Adsorption, XRD, Raman, H2-TPR, XPS and NH3-TPD. Water has a bimodal and reversible effect in both NO reduction and o-DCB oxidation depending on vanadium species and temperature. In SCR, water has a detrimental effect at low temperature due to competitive adsorption with NO and NH3, while at high temperature it promotes an increase of NO conversion associated to the suppression of side-reactions, which increase the selectivity towards N2. In o-DCB oxidation, the effect of water is the sum of two contributions: one positive, related to the removal of surface adsorbed detrimental species; and one negative, associated to the competitive adsorption with o-DCB. Thus, at high temperature water acts as inhibitor, while at low temperature water has a promotional effect in the highly dispersed vanadium catalysts due to their tendency to suffer deactivation, mainly by carbonaceous materials. The presence of water also favors total oxidation and decreases the formation of chlorinated by products.

Light-Responsive Proton Conductor: Record High Gain of Proton Conductivity Achieved by Photoinduced Electron-Transfer Strategy

Light-Responsive Proton Conductor: Record High Gain of Proton Conductivity Achieved by Photoinduced Electron-Transfer Strategy

The role of the synthetic chromophore of GFP in generating polymorphism-dependent on/off photoluminescence

Polymorphism, i.e. the ability of a solid material to exist in more than one crystal form, gives unique opportunity to study the correlation between the solid-state molecular arrangement and the photoluminescence properties, and allows optimizing the performances of materials with reduced synthesis effort. Compound 1, which results from the combination of 2-phenylbenzoxazole (PBO) and benzylideneimidazolinone (BDI), was known to be weakly fluorescent in solution and in the solid state. Time-dependent density functional theory (TD-DFT) and spin-flip TD-DFT calculations were first used to revisit the behaviour of the isolated molecule in solution. It was shown that the relaxation pathway in the lowest singlet excited state leads to a thermally-accessible conical intersection (CI), which favours non-radiative deactivation. Then, crystallizing molecule 1 under precise experimental conditions allowed four distinct polymorphs and one solvate to be obtained. Remarkably, forms 1a and 1b exhibited strong photoluminescence (PL), while polymorphs 1c-e were virtually not emissive. Recrystallization allowed passing reversibly from one crystalline species to another. Mechanical stimuli, exhibition to solvent vapours and heating were not very effective, but a non-trivial effect of PL enhancement upon freezing was observed for 1a and 1b. The non-emissive polymorphs were characterized by the presence of a centrosymmetric dimer structured by hydrogen bonds, in which paired molecules vibrate with the same mode and are in turn subjected to maximum deformation, according to DFT calculations. Based on the whole set of results, possible deactivation mechanisms were proposed to account for the opposite PL behaviour of the two types of crystalline species. It is shown that the emergence of polymorphism and of a rare on/off PL mechanism may be attributed to the presence of the BDI unit in the molecule.

How the in situ monitoring of bulk crystalline phases during catalyst activation results in a better understanding of heterogeneous catalysis.

The present Highlight article shows the importance of the in situ monitoring of bulk crystalline compounds for a more thorough understanding of heterogeneous catalysts at the intersection of catalysis, materials science, crystallography and inorganic chemistry. Although catalytic action is widely regarded as a purely surface-bound phenomenon, there is increasing evidence that bulk processes can detrimentally or beneficially influence the catalytic properties of various material classes. Such bulk processes include polymorphic transformations, formation of oxygen-deficient structures, transient phases and the formation of a metal–oxide composite. The monitoring of these processes and the subsequent establishment of structure–property relationships are most effective if carried out in situ under real operation conditions. By focusing on synchrotron-based in situ X-ray diffraction as the perfect tool to follow the evolution of crystalline species, we exemplify the strength of the concept with five examples from various areas of catalytic research. As catalyst activation studies are increasingly becoming a hot topic in heterogeneous catalysis, the (self-)activation of oxide- and intermetallic compound-based materials during methanol steam and methane dry reforming is highlighted. The perovskite LaNiO3 is selected as an example to show the complex structural dynamics before and during methane dry reforming, which is only revealed upon monitoring all intermediate crystalline species in the transformation from LaNiO3 into Ni/La2O3/La2O2CO3. ZrO2-based materials form the second group, indicating the in situ decomposition of the intermetallic compound Cu51Zr14 into an epitaxially stabilized Cu/tetragonal ZrO2 composite during methanol steam reforming, the stability of a ZrO0.31C0.69 oxycarbide and the gas-phase dependence of the tetragonal-to-monoclinic ZrO2 polymorphic transformation. The latter is the key parameter to the catalytic understanding of ZrO2 and is only appreciated in full detail once it is possible to follow the individual steps of the transformation between the crystalline polymorphic structures. A selected example is devoted to how the monitoring of crystalline reactive carbon during methane dry reforming operation aids in the mechanistic understanding of a Ni/MnO catalyst. The most important aspect is the strict use of in situ monitoring of the structural changes occurring during (self-)activation to establish meaningful structure–property relationships allowing conclusions beyond isolated surface chemical aspects.

Effect of SrO on the Structure of Apatite and Wollastonite Phases of Na<sub>2</sub>O-CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> Glass System

Glasses in the system 24.5Na2O·24.5CaO·6P2O5·xSrO·(45-x)SiO2 have been studied in the composition region of x = 0 - 15 mol%. The as prepared glasses are transparent and have an amorphous network structure. On the otherhand, heat treated glasses are transformed to opaque white glass ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca3(PO4)2, wollastonite (calcium silicate, CaSiO3), and strontium calcium phosphate Ca2Sr(PO4)2 are the main well-formed crystalline species played the major role in material bioactivity. Increasing SrO leads to enhancing material crystallite and enhances the hardness of the host glass matrix. The change of XRD spectra, 31P NMR chemical shift and hardness number upon increasing SrO are considered due to modification of the apatit Ca(PO3)2 to involve Sr ions inducing Ca2Sr (PO4)2 apatite one. Such species play the role in enhancing material properties and hardness.

Synergistic Effect of Platinum Single Atoms and Nanoclusters Boosting Electrocatalytic Hydrogen Evolution

Maximizing atomic utilization of precious metal-based catalysts is of great significance in heterogeneous catalysis, also becoming a useful strategy to develop efficient electrocatalysts for hydrog...

Hydrophilic Sugars for Enhancing Dissolution Rate of Cilostazol: Effect of Wet Co-Processing

Background: Cilostazol is an anti-platelets drug with considerable antithrombotic effects in vivo. Therefore, it is widely used by elderly patients. However, it suffers from poor bioavailability due to its low aqueous solubility. The objective of this work was to enhance the dissolution of cilostazol with the aim of formulating fast dissolving tablets for geriatrics and those of swallowing difficulties. Methods: Ethanol-assisted co-grinding of cilostazol with sugar-based excipients was adopted. Sucralose and mannitol were used for this purpose as hydrophilic excipient as well as taste improving agents. The obtained products were investigated regarding differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and in vitro drug dissolution. Fast disintegrating tablets were prepared and evaluated. Results: Thermal behavior of the developed products reflected reduced crystallinity, it also suggested possible existence of new crystalline species with sucralose. Eutexia was also suggested for mannitol mixtures, that was supported by X-ray diffraction data. SEM indicated size reduction with the deposition of the drug as submicron particles over the excipient surface. Co-processing markedly improved cilostazol dissolution compared to unprocessed drug. The optimized formulations were successively formulated into fast disintegrating tablets. Conclusion: This investigation introduced the wet grinding strategy with sugar excipients as a platform for the formulation of easy to use tablets with optimum drug release.

An Advanced Dual‐Function MnO2‐Fabric Air Filter Combining Catalytic Oxidation of Formaldehyde and High‐Efficiency Fine Particulate Matter Removal

AbstractComprehensive treatment of indoor contaminants such as volatile organic compounds (VOCs) and fine particulate matter (PM2.5) using transition metal oxide catalysts or functional fibrous filters has gained substantial attention recently. However, coupling VOC oxidation catalysts into high‐performance filter systems remains a challenge. Herein, an overall solution to strongly bind manganese dioxide (MnO2) nanocrystals onto polypropylene (PP) nonwoven fabrics is provided. For the first time, uniform heterogeneous nucleation and growth of MnO2 onto PP nonwoven fabrics using intermediate inorganic nucleation films, including Al2O3, TiO2, and ZnO, formed conformally on the fabrics via atomic layer deposition (ALD) are demonstrated. How different ALD thin films influence the crystallinity, morphology, surface area, and surface oxygen species of the MnO2 grown ALD‐coated PP fibers is further investigated. In addition to uniformity and integrity, ZnO thin films give rise to MnO2 crystals with the largest fraction of available surface oxygen, enabling 99.5% catalytic oxidation of formaldehyde within 60 min. Moreover, the metal oxide filters provide excellent PM removal efficiencies (ePM), achieving ePM2.5 90% and ePM10 98%, respectively, making the approach an outstanding method to produce fully dual‐functional filtration media.

Multiscale characterization of exhaust and crankcase soot extracted from heavy-duty diesel engine and implications for DPF ash

Engine-dynamometer bench tests were performed to evaluate the severity of engine operation resulting in oil degradation, set limits for drain intervals and provide recommendations for oil formulators to develop an additive package offering enhanced engine hardware protection. Engine oil was sampled at specified intervals to monitor depletion of additives, changes in viscosity, soot agglomerates and wear elements. A myriad of characterization techniques such as temperature resolved XRD, TEM, EDS, BET, Raman, DLS, TGA and ICP-OES are employed to develop a holistic understanding of crankcase soot interaction with lubricant additives influencing soot-induced wear, and oxidative properties of exhaust soot trapped in the DPF. XRD phase analysis of residue left behind after crankcase soot oxidation showed the presence of crystalline compounds embedded in the soot structure (CaSO4, Ca3(PO4)2, and Zn3(PO4)2); exhaust soot showed no crystalline compounds and had 85 wt% less residue after oxidation compared to crankcase soot. The residue inevitably forms ash precursors that are trapped in the DPF (Diesel Particulate Filter) affecting the filtration performance and fuel efficiency of the vehicle in the longer run. The turbostratic structure of both soot samples remains the same prior to oxidation; however, the embedded crystalline and amorphous species in the crankcase soot structure are different compared to exhaust soot. Ex-situ experiments were performed on soot-ash mixture with heated microscopy stage to allow for better visualization of ash formation, sintering and transport properties in the DPF channels. Findings in the study help in developing a comprehensive insight into ‘soot ecosystem’ in diesel engine vehicles.

Quantification of Surface Reactivity and Step-Selective Etching Chemistry on Single-Crystal BiOI(001).

To bridge the gap between the cleanliness of a freshly cleaved surface of 2D BiOI and that available from a purely chemical-etching means, we subjected single-crystal BiOI to a series of surface treatments and quantified the resulting chemical states and electronic properties. Vapor transport syntheses included both physical vapor transport from single-source BiOI, as well as chemical vapor transport from Bi2O3 + BiI3 and from Bi + I2 + Bi2O3. Surface treatments included tape cleaving, rinsing in water, sonication in acetone, an aqueous HF etch, and a sequential HF etch with subsequent sonication in acetone. X-ray diffraction, XRD, and X-ray photoelectron spectroscopy, XPS, probed the resulting bulk crystalline species and interfacial chemical states, respectively. In comparison with overlayer models of idealized oxide-terminated or iodide-terminated BiOI, angle-resolved XPS elucidated surface terminations as a function of each treatment. Ultraviolet photoelectron spectroscopy, UPS, established work-function, and Fermi-level energies for each treatment. Data reveal that HF etching yields interfacial BiI3 at BiOI steps that is subsequently removed with acetone sonication. UPS establishes n-type behavior for the vapor-transport-synthesized BiOI, and surface work function and Fermi level shifts for each chemical treatment under study. We discuss the implications for processing BiOI nanofilms for energy-conversion applications.