Variations In Surface Chemistry Research Articles

Surface chemistry characterization of AA2014 aluminum alloy powder through triboelectric charging

Traditional characterization techniques for powders primarily focus on bulk properties, often neglecting the critical role of surface chemistry variations that influence the performance in applications such as additive manufacturing. The method presented in this work addresses this gap by utilizing triboelectric charging concept to gain a comprehensive understanding of powder surface state under varying environmental conditions. In particular, the study investigates the detection of surface chemistry variations of AA2014 powder caused by an exposure to various relative humidity (RH) levels through a change in triboelectric charging behavior. The surface variations are analyzed in parallel with X-ray photoelectron spectroscopy (XPS). The findings reveal a direct correlation between elevated RH and increased hydroxide species content at the surface of the powder. The triboelectric charging experiments demonstrated a significant RH-dependent variations of charge accumulation, with higher humidity levels leading to reduced static charge buildup on the powder particles. The charge accumulation behavior in the powder was fitted with the compressed exponential relaxation model. The results showed that each surface chemical species exhibits a distinct correlation between charging rate and charge accumulation, confirming the method's effectivity to detect subtle variations in surface chemistry. The variations in the exponent of the fitted model were shown to be characteristics to the surface scale of the powder particles.

A universal packaging substrate for mechanically stable assembly of stretchable electronics

Stretchable electronics commonly assemble multiple material modules with varied bulk moduli and surface chemistry on one packaging substrate. Preventing the strain-induced delamination between the module and the substrate has been a critical challenge. Here we develop a packaging substrate that delivers mechanically stable module/substrate interfaces for a broad range of stiff and stretchable modules with varied surface chemistries. The key design of the substrate was to introduce module-specific stretchability and universal adhesiveness by regionally tuning the bulk molecular mobility and surface molecular polarity of a near-hermetic elastic polymer matrix. The packaging substrate can customize the deformation of different modules while avoiding delamination upon stretching up to 600%. Based on this substrate, we fabricated a fully stretchable bioelectronic device that can serve as a respiration sensor or an electric generator with an in vivo lifetime of 10 weeks. This substrate could be a versatile platform for device assembly.

Adhesion promotion and corrosion resistance of mixed phosphonic acid monolayers on AA 2024

Mixed monolayers were used to prepare surfaces of AA 2024 with precisely controlled corrosion protective and adhesive properties. In this study, the corrosion inhibition and adhesion promotion as a function of the composition of mixed phosphonic acid monolayers on AA 2024 was investigated. Mixed monolayers were formed by competitive adsorption of n-dodecylphosphonic acid (DPA) and 12-aminododecylphosphonic acid (ADPA) from ethanolic solution. Their compositions were determined by X-ray photoelectron spectroscopy. Atomic force microscopy studies and polarization modulation infrared reflection–absorption spectroscopy as well as contact angle studies proved the formation of monolayers with varying surface chemistry. The wet-adhesion strength was tested by 90° peel tests after application of an epoxy-amine adhesive. Linear sweep voltammetry was performed to evaluate the corrosion inhibition of the monolayers, and the corrosion resistance of the metal/adhesive composite was investigated by means of its corrosive delamination behavior. The electrochemical measurements demonstrated that reducing the surface concentration of ADPA improved the corrosion inhibition of the monolayer. However, the corrosive delamination experiments revealed that the improved corrosion inhibition by the self-organized DPA is of minor importance for the corrosion behavior of the metal/adhesive composite, as the adhesive properties dominate.

Benchmarking diamond surface preparation and fluorination via inductively coupled plasma-reactive ion etching

Diamond, renowned for its exceptional semiconducting properties, stands out as a promising material for high-performance power electronics, optics, quantum, and biosensing technologies. This study methodically investigates the optimization of polycrystalline diamond (PCD) substrate surfaces through Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). Various parameters, including gaseous species, flow rate, coil power, and bias power were tuned to understand their impact on surface morphology and chemistry. A thorough characterization, encompassing chemical, spectroscopic, and microscopic methods, shed light on the effects of different ICP-RIE conditions on surface properties. CF4/O2 plasma emerged as a viable treatment for achieving smooth PCD surfaces with minimal etch pit formation. Most notably, surface fluorination, a critical aspect of increasing chemical and thermal stability, was successfully accomplished using CF4, SF6, and other F-containing plasmas. The fluorine concentration and surface chemistry variations were studied, with high resolution X-ray Photoelectron Spectroscopy unveiling differences amongst the sp2 C phase, sp3 C phase, C–O, CO, and C–F bonds. Time-of-flight secondary Ion Mass Spectrometry (ToF-SIMS) and depth-profile analysis unveiled a consistent surface fluorination pattern with CF4/O2 treatment. Furthermore, contact angle measurements showcased heightened hydrophobicity. This study provides valuable insights into precise diamond surface engineering, important for the development of future diamond-based semiconductor technologies.

A bioinspired heterostructured nanochannel based on dendrimer-gold network and aluminum oxide arrays for sensitive detection of miRNA

BackgroundMicroRNAs, as oncogenes or tumor suppressors, enable to up or down-regulate gene expression during tumorigenesis. The detection of miRNAs with high sensitivity is crucial for the early diagnosis of cancer. Inspired by biological ion channels, artificial nanochannels are considered as an excellent biosensing platform with relatively high sensitivity and stability. The current nanochannel biosensors are mainly based on homogeneous membranes, and their monotonous structure and functionality limit its further development. Therefore, it is necessary to develop a heterostructured nanochannel with high ionic current rectification to achieve highly sensitive miRNA detection. ResultsIn this work, an asymmetric heterostructured nanochannel constructed from dendrimer-gold nanoparticles network and anodic aluminum oxide are designed through an interfacial super-assembly method, which can regulate ion transport and achieve sensitive detection of target miRNA. The symmetry breaking is demonstrated to endow the heterostructured nanochannels with an outstanding ionic current rectification performance. Arising from the change of surface charges in the nanochannels triggered by DNA cascade signal amplification in solution, the proposed heterogeneous nanochannels exhibits excellent DNA-regulated ionic current response. Relying on the nucleic acid's hybridization and configuration transformation, the target miRNA-122 associated with liver cancer can be indirectly quantified with a detection limit of 1 fM and a wide dynamic range from 1 fM to 10 pM. The correlation fitting coefficient R2 of the calibration curve can reach to 0.996. The experimental results show that the method has a good recovery rate (98%–105 %) in synthetic samples. SignificanceThis study reveals how the surface charge density of nanochannels regulate the ionic current response in the heterostructured nanochannels. The designed heterogeneous nanochannels not only possess high ionic current rectification property, but also enable to induce superior transport performance by the variation of surface chemistry. The proposed biosensor is promising for applications in early diagnosis of cancers, life science research, and single-entity electrochemical detection.

Ce-TiO2 nanoparticles with surface-confined Ce3+/Ce4+ redox pairs for rapid sunlight-driven elimination of organic contaminants from water

Industrial discharge of organic pollutants poses a severe threat to human health and aquatic life. Elimination of these pollutants from drinking and wastewater is imperative for a sustainable environment. To address this issue, pure and Ce3+-doped TiO2 nanoparticles are designed with stable tetragonal (anatase) lattices by a low-temperature sol–gel process. The spectroscopic and structural analyses reveal the formation of TiO2 and Ce-TiO2 nanocrystals with controlled crystallite size (3–6 nm), high surface areas, and varying surface chemistry. The effect of calcination (thermal (Δ) treatment at 450 °C) on the structure and photocatalytic performance of ΔTiO2 and ΔCe-TiO2 nanoparticles is also investigated. Simultaneous photocatalysis experiments over a 90-min exposure to natural sunlight show 240 % and 191 % improved elimination of methylene blue (MB), an organic pollutant, by Ce-TiO2 and ΔCe-TiO2 nanoparticles compared to their pure TiO2 analogs. Also, Ce-TiO2 and ΔCe-TiO2 nanoparticles exhibit 326 % and 229 % faster kinetics for the photocatalytic elimination of MB primarily due to the surface-confinement of Ce3+ in Ce-TiO2 nanocrystals, where Ce3+ ions play a dual role as reducing agent for adsorbed oxygen species and electron trap sites via Ce3+/Ce4+ interconversion. The mechanism of photocatalytic redox reactions is discussed. The study elaborates on the role of Ce-TiO2 nanoparticles as an effective photocatalyst for the elimination of organic pollutants in wastewater.

Effect of inorganic material surface chemistry on structures and fracture behaviours of epoxy resin

The mechanisms underlying the influence of the surface chemistry of inorganic materials on polymer structures and fracture behaviours near adhesive interfaces are not fully understood. This study demonstrates the first clear and direct evidence that molecular surface segregation and cross-linking of epoxy resin are driven by intermolecular forces at the inorganic surfaces alone, which can be linked directly to adhesive failure mechanisms. We prepare adhesive interfaces between epoxy resin and silicon substrates with varying surface chemistries (OH and H terminations) with a smoothness below 1 nm, which have different adhesive strengths by ~13 %. The epoxy resins within sub-nanometre distance from the surfaces with different chemistries exhibit distinct amine-to-epoxy ratios, cross-linked network structures, and adhesion energies. The OH- and H-terminated interfaces exhibit cohesive failure and interfacial delamination, respectively. The substrate surface chemistry impacts the cross-linked structures of the epoxy resins within several nanometres of the interfaces and the adsorption structures of molecules at the interfaces, which result in different fracture behaviours and adhesive strengths.

Virus-like Silica Nanoparticles Improve Permeability of Macromolecules across the Blood-Brain Barrier In Vitro.

The presence of the blood-brain barrier (BBB) limits the delivery of therapies into the brain. There has been significant interest in overcoming the BBB for the effective delivery of therapies to the brain. Inorganic nanomaterials, especially silica nanoparticles with varying surface chemistry and surface topology, have been recently used as permeation enhancers for oral protein delivery. In this context, nanoparticles with varying sizes and surface chemistries have been employed to overcome this barrier; however, there is no report examining the effect of nanoscale roughness on BBB permeability. This paper reports the influence of nanoscale surface roughness on the integrity and permeability of the BBB in vitro, using smooth surface Stöber silica nanoparticles (60 nm) compared to rough surface virus-like silica nanoparticles (VSNP, 60 nm). Our findings reveal that VSNP (1 mg/mL) with virus-mimicking-topology spiky surface have a greater effect on transiently opening endothelial tight junctions of the BBB than the same dose of Stöber silica nanoparticles (1 mg/mL) by increasing the FITC-Dextran (70 kDa) permeability 1.9-fold and by decreasing the trans-endothelial electrical resistance (TEER) by 2.7-fold. This proof-of-concept research paves the way for future studies to develop next-generation tailored surface-modified silica nanoparticles, enabling safe and efficient macromolecule transport across the BBB.

(Best Student Presentation) Impact of Surface Characteristics on Interfacial Stability in Lithium Metal Batteries

A comprehensive understanding of the morphology evolution of deposited lithium (Li) is a primary challenge in the commercialization of Li-metal batteries. Li-metal batteries, which contain a Li-metal anode, have a theoretical capacity that is an order of magnitude greater than that of a Li-ion battery helping to overcome their energy storage limitations. However, while Li-metal batteries have proven to have a much larger specific capacity, they are hindered by unstable deposition at the electrode-electrolyte interface and severe dendritic growth. Interfacial stability is a complex phenomenon that is influenced by many different factors, including local current densities, overpotentials, Li+ concentrations, and transport properties. Additionally, varying surface characteristics such as surface chemistries and the physical structure of the anode can affect Li deposition and could be used to design a more stable interface. Due to the nature of the anode surface, it is difficult to observe the complex physics experimentally. Thus, computational modeling is a powerful tool for understanding the deposition of Li on the anode surface. In this work we present a computational model to comprehensively study the morphology of dendrites when exposed to varying conditions. While transport properties1, electrolyte characteristics2, separator structures3, and charging protocols4 play significant roles in Li dendrite morphology and interfacial stability, this work focuses on the impact of the anode surface itself on stability. This includes patterned anode surfaces for guided lithium deposition and varying surface chemistries such as surface energy and reaction rate. We concentrate on the types of defects that are present along the anode surface including surface roughness, points of high convexity, breaks in the SEI layer, lattice defects leading to changes in surface energy and their impact on instability. We also look at guided deposition through modifications of the anode surface.1. J. Tan, A. M. Tartakovsky, K. Ferris, and E. M. Ryan, J Electrochem Soc, 163, A318–A327 (2016).2. J. Tan and E. M. Ryan, J Power Sources, 323, 67–77 (2016).3. A. Cannon and E. M. Ryan, ACS Appl Energy Mater, 4, 7848–7861 (2021).4. T. Melsheimer, M. Morey, A. Cannon, and E. Ryan, Electrochim Acta, 433 (2022).

Theoretical Interpretation of pH and Salinity Effect on Oil-in-Water Emulsion Stability Based on Interfacial Chemistry and Implications for Produced Water Demulsification

The petroleum industry produces thousands of barrels of oilfield waters from the initial stage driven by primary production mechanisms to the tertiary stage. These produced waters contain measurable amounts of oil-in-water emulsions, the exact amounts being determined by the chemistry of the crude oil. To meet strict environmental regulations governing the disposal of such produced waters, demulsification to regulatory permissible levels is required. Within the electric double layer theory, coupled with the analytical solutions to the Poisson–Boltzmann Equation, continuum electrostatics approaches can be used to describe the stability and electrokinetic properties of emulsions. In the literature, much of the surface charge density and zeta potential relationship to emulsion stability has been confined to systems with less salinity. In this paper, we have exploited the theoretical foundations of the electric double layer theory to carry out theoretical evaluations of emulsion salinity based on zeta potential and surface charge density calculations. Most importantly, our approaches have enabled us to extend such theoretical calculations to systems of the higher salinity characteristic of oil-in-water emulsions found in oilfield-produced waters, based on crude oil samples from the literature with varying surface chemistry. Moreover, based on the definition of acid crude oils, our choice of samples represents two distinct classes of crude oils. This approach enabled us to evaluate the stability of emulsions associated with these produced oilfield waters in addition to predicting the potential of demulsification using demulsifiers. Given that the salinity range of this study is that encountered with the vast majority of produced oilfield waters, the findings from our theoretical predictions are perfect guides as far as emulsion stability is concerned.

Linking Interfacial Bonding and Thermal Conductivity in Molecularly-Confined Polymer-Glass Nanocomposites with Ultra-High Interfacial Density.

Thermal transport in polymer nanocomposites becomes dependent on the interfacial thermal conductance due to the ultra-high density of the internal interfaces when the polymer and filler domains are intimately mixed at the nanoscale. However, there is a lack of experimental measurements that can link the thermal conductance across the interfaces to the chemistry and bonding between the polymer molecules and the glass surface. Characterizing the thermal properties of amorphous composites are a particular challenge as their low intrinsic thermal conductivity leads to poor measurement sensitivity of the interfacial thermal conductance. To address this issue here, polymers are confined in porous organosilicates with high interfacial densities, stable composite structure, and varying surface chemistries. The thermal conductivities and fracture energies of the composites are measured with frequency dependent time-domain thermoreflectance (TDTR) and thin-film fracture testing, respectively. Effective medium theory (EMT) along with finite element analysis (FEA) is then used to uniquely extract the thermal boundary conductance (TBC) from the measured thermal conductivity of the composites. Changes in TBC are then linked to the hydrogen bonding between the polymer and organosilicate as quantified by Fourier-transform infrared (FTIR)and X-ray photoelectron (XPS)spectroscopy. This platform for analysis is a new paradigm in the experimental investigation of heat flow across constituent domains.

Probing the interaction between coal particle and collector using atomic force microscope and density functional theory calculation

Revealing the interaction mechanism between coal and collector is essential for coal flotation. However, direct determination of the interaction force between coal and collector has rarely been reported. In this work, an atomic force microscope (AFM) was used to directly measure the interaction between collectors, i.e., n-dodecane, nonyl benzene and sub-bituminous coal (SC), bituminous coal (BC) and anthracite coal (BC) with different metamorphic degrees, and density functional theory calculation (DFT) was used to simulate the interaction mechanism of coal and collectors at the molecular level. The results indicate that the interaction force between coal and collector improves with the increase of coal metamorphic degrees for the same type of collector. Extended DLVO fitting reveals that the hydrophobic interaction decays exponentially. Consistent with the AFM force measurement results, the adsorption energy between the coal and the collector calculated by DFT all show that the interaction between n-dodecane and the three types of coals is weaker than that of nonyl benzene. This work provides quantitative information on the molecular interaction mechanism underlying the adsorption of collectors on the coal of varying surface chemistry at the nanoscale, with valuable implications for developing influential collectors for coal preparation and many other engineering processes.

Influence of reaction variables on the surface chemistry of cellulose nanofibers derived from palm oil empty fruit bunches

Nanocellulose from palm oil empty fruit bunch (EFB) fibers shows varied surface chemistry influenced by reaction time and primary oxidizing agent. EFB fibers are a valuable raw source to produce sustainable and functional materials.

Optimisation of a High-Throughput Model for Mucus Permeation and Nanoparticle Discrimination Using Biosimilar Mucus.

High-throughput permeation models are essential in drug development for timely screening of new drug and formulation candidates. Nevertheless, many current permeability assays fail to account for the presence of the gastrointestinal mucus layer. In this study, an optimised high-throughput mucus permeation model was developed employing a highly biorelevant mucus mimic. While mucus permeation is primarily conducted in a simple mucin solution, the complex chemistry, nanostructure and rheology of mucus is more accurately modelled by a synthetic biosimilar mucus (BSM) employing additional protein, lipid and rheology-modifying polymer components. Utilising BSM, equivalent permeation of various molecular weight fluorescein isothiocyanate-dextrans were observed, compared with native porcine jejunal mucus, confirming replication of the natural mucus permeation barrier. Furthermore, utilising synthetic BSM facilitated the analysis of free protein permeation which could not be quantified in native mucus due to concurrent proteolytic degradation. Additionally, BSM could differentiate between the permeation of poly (lactic-co-glycolic) acid nanoparticles (PLGA-NP) with varying surface chemistries (cationic, anionic and PEGylated), PEG coating density and size, which could not be achieved by a 5% mucin solution. This work confirms the importance of utilising highly biorelevant mucus mimics in permeation studies, and further development will provide an optimal method for high-throughput mucus permeation analysis.

Prediction of surface excess adsorption and retention factors in reversed-phase liquid chromatography from molecular dynamics simulations

An alternative method to the classical fit of semi-empirical, statistical, or artificial intelligence-based models to retention data is proposed to predict surface excess adsorption and retention factors in liquid chromatography. The approach is based on a fundamental, microscopic description of the liquid-to-solid adsorption of analytes taking place at the interface between a bulk liquid phase and a solid surface. Molecular dynamics (MD) simulations are performed at T=300 K in a 100 Å wide slit-pore model (β-cristobalite-C18 surface in contact with an acetonitrile/water mobile phase) to quantify a priori the retention factors of small molecules expected in reversed phase liquid chromatography (RPLC). Uracil is chosen as the reference “non-retained” marker, whereas benzyl alcohol, acetophenone, benzene, and ethylbenzene are four selected retained, neutral compounds. The MD simulations allow to determine the pore-level density profiles of these five compounds, i.e., the variation of the analyte concentration as a function of distance from the silica surface. The retention factors of the retained analytes are expressed using their respective calculated surface excess adsorption relative to uracil. By definition, the retention factors are proportional to the surface excess adsorbed and the proportionality constant is directly scaled to the retention time of the “non-retained” marker. Experimentally, a 4.6 mm × 150 mm RPLC-C18 column packed with 5 μm 100 Å High Strength Silica (HSS)-C18 particles is used and the retention times of these five compounds are measured. The volume fraction of acetonitrile in water increases from 20 to 90% generating a wide range of retention factors from 0.15 to 183 at T=300 K. The results demonstrate very good agreement between the MD-predicted surface excess adsorption data and measured retention factors (R2> 0.985). A systematic error is observed as the proportionality constant is not exactly scaled to the retention time of uracil. This is most likely caused by the differences between the chemical and morphological features of the slit-pore model adopted in the MD simulations and those of the actual HSS-C18 particles: the average surface coverage with C18 chains, the geometry of the mesopores, and the pore size distribution. Specifically, the impact on RPLC retention of slight, local variations in surface chemistry (e.g., functional group density and uniformity) and how this aspect is affected by the pore space morphology (e.g., pore curvature and size) is worth investigating by future MD simulations.

(Digital Presentation) Nanoscaffold Porosity and Surface Chemistry Effects on Li-Ion Conductivity in Metal Hydride Nanocomposite Electrolytes

The development of energy storage technologies, such as rechargeable batteries, is crucial for the transition to a sustainable energy supply. Lithium-ion batteries are an effective means of energy storage, which is demonstrated by their wide application ranging from mobile phones to laptops and electric vehicles. Unfortunately, Li-ion batteries suffer from safety issues arising from their combustible organic electrolytes. All-solid-state batteries, in which the common liquid organic electrolyte is replaced by a solid-state electrolyte, could potentially lead to safer batteries with increased energy density.[1] Recently, metal hydrides (e.g. LiBH4 and LiCB11H12) have gained attention as promising solid electrolytes due to their electrochemical and thermal stability, low density and high ionic conductivity albeit at elevated temperatures. However, for successful incorporation of metal hydride electrolytes in all-solid-state batteries, sufficient ionic conductivity at room temperature is a prerequisite. Therefore, the development of strategies that enhance the room temperature conductivity in complex hydrides (10-8 S cm-1 for LiBH4) is of major importance.In this contribution, we combined two promising strategies to enhance ion mobility in metal hydrides, namely, partial ionic substitution[2] and nanoconfinement[3], which led to highly conductive metal hydride-based nanocomposites (Figure 1). Specifically, via partial ion substitution with LiNH2, followed by nanoconfinement in a mesoporous oxide scaffold, LiBH4-LiNH2/metal oxide nanocomposites with conductivities reaching 5x10-4 S cm-1 at 30 °C were obtained[4], compared to 2x10-8 S cm-1 for pure LiBH4.Interestingly, the conductivity of the LiBH4-LiNH2/metal oxide nanocomposites is strongly influenced by the chemical and physical nature of the mesoporous metal oxide. We systematically studied the influence of the scaffold properties on the conductivity of nanoconfined LiNH2-substituted LiBH4 using mesoporous silica scaffolds (SBA-15) with varying surface chemistry and pore structure. The conductivity varied over three orders of magnitude when tuning both the porosity and surface chemistry of the metal oxide scaffold.[5] Our study reveals that the LiBH4-LiNH2/metal oxide conductivity is affected by the chemical nature of the scaffold, similar to LiBH4/metal oxide nanocomposites. A conductivity improvement of a factor of two is achieved by changing the SiO2 (SBA-15) surface chemistry through alumination (Figure 2a). On the other hand, different from nanoconfined LiBH4, the conductivity of LiBH4-LiNH2/metal oxide nanocomposites is largely dictated by the pore structure of the scaffold, especially the pore volume (Figure 2b). Notably, the conductivity can be varied from 4x10-7 S cm-1 to 5x10-4 S cm-1 by increasing the scaffold pore volume from 0.51 to 1.00 cm3 g-1.Our work demonstrates that the origin of the conductivity enhancement in anion-substituted complex hydride-based nanocomposite electrolytes is different from other nanoconfined complex hydrides, e.g. LiBH4. In particular, for nanoconfined LiBH4-LiNH2, the conductivity improvement is attributed to stabilization of a highly conductive phase inside the scaffold pores, rather than the formation of a conductive interfacial layer at the hydride/oxide interface as observed for nanoconfined LiBH4. Thus, it is clear that the conductivity of metal hydride-based nanocomposite ion conductors is closely linked to the properties of scaffold material. The fundamental insights on the influence of scaffold properties on ion mobility in nanocomposite materials could be applicable to other cation- and anion substituted ion conductors as well. Thereby, this work provides useful insights for the design novel solid-state electrolytes with excellent ionic conductivity, crucial for the development of next generation batteries.

Active coating for packaging papers with controlled thermal release of encapsulated plant oils

The surface properties and water repellence of paper substrates can be tuned by a waterborne nanoparticle coating containing hybrid organic nanoparticles with encapsulated vegetable oils. In particular, the release of oil from the deposited nanoparticle capsules can be activated upon thermal heating. The specific release temperature allows to control the amount of free oil at the surface and consequent tuning of required hydrophobicity. This study particularly focusses on a detailed monitoring of variations in chemical surface composition upon controlled oil release by means of micro-Raman mapping. The coverage of surfaces with both free oil and imide moieties originating from the organic nanoparticles can be quantified after a calibration between Raman spectra and extraction studies of the nanoparticles. As such, different thermal release profiles were observed depending on the type of encapsulated oils, i.e. polyunsaturated oil (e.g., soy oil, corn oil), mono-unsaturated oil (e.g., rapeseed oil, castor oil), or saturated oil (e.g., hydrogenated castor oil). The oil release can interestingly be related to variations in surface chemistry and water contact angles, as it seems that the surface hydrophobicity increases with the chemical heterogeneity that is quantified by oil content, imide content and iodine value of the oil.

Facet-dependent Fe(II) redox chemistry on iron oxide for organic pollutant transformation and mechanisms

Fe(II) redox chemistry is a pivotal process of biogeochemical Fe cycle and the transformation of organic pollutants in subsurface aquifers, while its interfacial reactivity on iron oxides with varying surface chemistries remains largely unexplored. In this study, the redox processes of Fe(II) on two hematite with highly exposed {001} and {110} facets and their impacts on the transformation of nitrobenzene were investigated. Results suggest that Fe(II) adsorption is the rate-limiting step of the redox chain reactions, controlling the reduction potential (EH). Nitrobenzene activates the facet electron transfer on hematite, leading to nitrobenzene reduction and Fe(II) oxidation. Moreover, {001} facet exhibits a higher reactivity and electron transport efficiency than {110} facet, which is attributed to a lower site density (0.809 #Fe/nm2) and a lower EH of hematite {001} facet than that of {110} facet. It is worth noting that the facet-dependent reduction activity is more intense at low pH or high Fe(II) activity. A slight dissolution of {110} facet was observed, indicating hematite {001} facet exhibits higher thermodynamic stability than {110} facet. This study confirms the facet-dependent reducing activity of surface bound Fe(II) on hematite, providing a new perspective for in-depth understanding of the interfacial reactions on hematite. The findings of this work broaden the biogeochemical process of Fe cycle in subsurface environments and its impact on the fate of organic pollutants in groundwater.

Laser Desorption/Ionization Mass Spectrometry Imaging: A New Tool to See through Nanoscale Particles in Biological Systems.

Understanding the fate of nanoscale particles (NPs) in biological systems is significant with the increasing risk for human exposure. Recent research endeavors in laser desorption/ionization mass spectrometry imaging (LDI-MSI) have enriched the toolbox for evaluation of NPs' behavior in biological tissues, especially in aspects including sub-organ bio-distribution, clearance, quantification and surface chemistry variation analysis. In recognition of the potential for advancement in LDI MSI, this concept provides a brief overview of recent research works in LDI MSI for NPs, illustrates new applications that demonstrate the superiority of this technique, and highlights a series of perspectives and directions to move the field forward.

Li-Ion Conductivity in Metal Hydride-Based Nanocomposite Electrolytes: The Effect of Nanoscaffold Porosity and Surface Chemistry

The development of energy storage technologies, such as rechargeable batteries, is crucial for the transition to a sustainable energy supply. Lithium-ion batteries are an effective means of energy storage, which is demonstrated by their wide application ranging from mobile phones to laptops and electric vehicles. Unfortunately, Li-ion batteries suffer from safety issues arising from their combustible organic electrolytes. All-solid-state batteries (ASSBs), in which the common liquid organic electrolyte is replaced by a solid-state electrolyte (SSE), could potentially lead to safer batteries with increased energy density.[1] Recently, metal hydrides (e.g. LiBH4 and LiCB11H12) have gained attention as promising solid electrolytes due to their electrochemical and thermal stability, low density and high ionic conductivity albeit at elevated temperatures. However, for successful incorporation of metal hydride SSEs in ASSBs, sufficient ionic conductivity at room temperature is a prerequisite. Therefore, the development of strategies that enhance the room temperature conductivity in complex hydrides (10-8 S cm-1 for LiBH4) is of major importance.In this contribution, we combined two promising strategies to enhance ion mobility in metal hydrides, namely, partial ionic substitution[2] and nanoconfinement[3], which led to highly conductive metal hydride-based nanocomposites (Figure 1). Specifically, via partial ion substitution with LiNH2, followed by nanoconfinement in a mesoporous oxide scaffold, LiBH4-LiNH2/metal oxide nanocomposites with conductivities reaching 5⸱10-4 S cm-1 at 30 °C were obtained[4], compared to 2⸱10-8 S cm-1 for pure LiBH4.Interestingly, the conductivity of the LiBH4-LiNH2/metal oxide nanocomposites is strongly influenced by the chemical and physical nature of the mesoporous metal oxide. We systematically studied the influence of the scaffold properties on the conductivity of nanoconfined LiNH2-substituted LiBH4 using mesoporous silica scaffolds (SBA-15) with varying surface chemistry and pore structure. The conductivity varied over three orders of magnitude when tuning both the porosity and surface chemistry of the metal oxide scaffold.[5] Our study reveals that the LiBH4-LiNH2/metal oxide conductivity is affected by the chemical nature of the scaffold, similar to LiBH4/metal oxide nanocomposites. A conductivity improvement of a factor of two is achieved by changing the SiO2 (SBA-15) surface chemistry through alumination (Figure 2a). On the other hand, different from nanoconfined LiBH4, the conductivity of LiBH4-LiNH2/metal oxide nanocomposites is largely dictated by the scaffold pore volume (Figure 2b). Notably, the conductivity can be varied from 4⸱10-7 S cm-1 to 5⸱10-4 S cm-1 by increasing the scaffold pore volume from 0.51 to 1.00 cm3 g-1.Our work demonstrates that the origin of the conductivity enhancement in anion-substituted complex hydride-based solid electrolytes is different from other nanoconfined complex hydrides, e.g. LiBH4. In particular, for nanoconfined LiBH4-LiNH2, the conductivity improvement is attributed to stabilization of a highly conductive phase inside the scaffold pores, rather than the formation of a conductive interfacial layer at the hydride/oxide interface as observed for nanoconfined LiBH4. Thus, it is clear that the conductivity of metal hydride-based nanocomposite ion conductors is closely linked to the properties of scaffold material. These fundamental insights on the influence of scaffold properties on ion mobility in nanocomposite materials could be applicable to other cation- and anion substituted ion conductors as well. Thereby, this work provides useful insights for the design novel solid-state electrolytes with excellent ionic conductivity, which are crucial for the development of next generation batteries. References Janek, Jürgen, and Zeier, Wolfgang G. "A solid future for battery development." Nature Energy 1.9 (2016): 1-4.Maekawa, Hideki, et al. "Halide-stabilized LiBH4, a room-temperature lithium fast-ion conductor." Journal of the American Chemical Society 131.3 (2009): 894-895.Blanchard, Didier, et al. "Nanoconfined LiBH4 as a fast lithium ion conductor." Advanced Functional Materials 25.2 (2015): 184-192Zettl, Roman, et al. "Combined Effects of Anion Substitution and Nanoconfinement on the Ionic Conductivity of Li-Based Complex Hydrides." The Journal of Physical Chemistry C 124.5 (2020): 2806-2816.de Kort, Laura M., et al. "The effect of nanoscaffold porosity and surface chemistry on the Li-ion conductivity of LiBH4–LiNH2/metal oxide nanocomposites." Journal of Materials Chemistry A 8.39 (2020): 20687-20697. Figure 1