Ion Depletion Research Articles

Regulating Li<sup>+</sup> Transfer and Solvation Structure via Metal-Organic Framework for Stable Li Anode

Lithium metal batteries (LMBs) possess large application potential for advanced rechargeable batteries due to the high energy density (> 500 Wh kg−1) and alternative cathode materials. Random Li dendrite growth caused by uneven Li+ distribution and local ion depletion near surface of Li anode induces battery failure with inferior long-term stability. Therefore, regulation of ion distribution near anode surface is essential to realize dendrite-free and uniform Li deposition. Herein, a metal-organic framework (MOF), i.e., ZIF-8, is applied to regulate Li+ solvation structure via unsaturated metal-ion sites to achieve uniform Li+ distribution and Li deposition. A stable cycling performance over 800 h for Li symmetrical cell at 3 mA cm−2 and 3 mAh cm−2 without short circuit is realized. The facilitated Li+ solvation via the adsorption effect of metal-ion sites on anions is demonstrated, which further enhances the uniform Li+ distribution near Li anode surface. This work demonstrates an effective strategy for regulating ion coordination and Li+ distribution to stabilize Li anode via MOF-based materials.

DFT and ab-initio molecular dynamics of pyrochlore surface dissolution in aqueous media – Effect of cleavage plane and surface atomic vacancies

Pyrochlore, as a complex oxide mineral containing the critical niobium element, offers a rich diversity of surface chemical compositions in different cleavage directions. Hence, very little is known about the structure and stability of pyrochlore’s low-index surfaces. Accordingly, this study aims to investigate the hydration behavior of the defect-free and surface-depleted (110) and (111) Ca2Nb2O6F pyrochlore, terminated with F and Ca ions, under implicit and explicit consideration of water molecules using DFT and ab-initio molecular dynamics (AIMD) simulations. Our results revealed that the F&Ca-terminated (110) surface possesses strong hydrophilic characteristics compared to the (111) cleavage plane. The (110) surface becomes hydroxylated on the undercoordinated oxygen and niobium atoms by the dissociative reactions of water at the interface. Our simulations further captured a major intra-surface reconstruction in the (110) direction upon surface ion depletion. On the defect-free (111) surface, water-surface interactions were limited to a single hydrogen bond between each fluoride on the outermost layer and the water’s hydrogen. The ions removal from the (111) surface led to the exposure of Nb atoms and activated water-surface interaction by making the lower position oxygens accessible by the water molecules. The AIMD simulation results suggested that fluorides are prone to diffuse from the surface after solvation, while oxygen loss could also be an active mechanism for surface stability. Later, the insights could serve as the foundation for future studies to tailor advanced pyrochlore flotation procedures.

Mechanistic Study of the Conductance and Enhanced Single-Molecule Detection in a Polymer-Electrolyte Nanopore.

Solid-state nanopores have been widely employed in the detection of biomolecules, but low signal-to-noise ratios still represent a major obstacle in the discrimination of nucleic acid and protein sequences substantially smaller than the nanopore diameter. The addition of 50% poly(ethylene) glycol (PEG) to the external solution is a simple way to enhance the detection of such biomolecules. Here, we demonstrate with finite-element modeling and experiments that the addition of PEG to the external solution introduces a strong imbalance in the transport properties of cations and anions, drastically affecting the current response of the nanopore. We further show that the strong asymmetric current response is due to a polarity-dependent ion distribution and transport at the nanopipette tip region, leading to either ion depletion or enrichment for few tens of nanometers across its aperture. We provide evidence that a combination of the decreased/increased diffusion coefficients of cations/anions in the bath outside the nanopore and the interaction between a translocating molecule and the nanopore-bath interface is responsible for the increase in the translocation signals. We expect this new mechanism to contribute to further developments in nanopore sensing by suggesting that tuning the diffusion coefficients of ions could enhance the sensitivity of the system.

Origin of Late Cretaceous, enclave-bearing granitoids in southern Tibet: Implications for magma recharge and crustal thickening

Exposures of enclave-bearing granitoids can provide rare opportunities to directly evaluate the connection between compositional variability and the depth of origin of arc magmatic rocks. The ∼1000 km long Gangdese batholith is a composite batholith with composition from mafic to felsic; SiO2 ranges from 51 wt% to 70 wt%. New zircon U−Pb dating of the Nyemo plutons, Renbu plutons, and Xigaze plutons in the Gangdese batholith is consistent with their emplacement and crystallization in the Late Cretaceous (ca. 90−85 Ma). Mafic magmatic enclaves (MMEs) in the plutons are characterized by low SiO2 (50.9−56.0 wt%) and Nb/U, Ce/Pb, and Nb/La ratios coupled with enrichment in light rare earth elements and large ion lithophile elements and depletion in high field strength elements. These geochemical features, combined with depleted whole-rock εNd(t) (+4.2 to +4.7) and zircon εHf(t) (+9.0 to +13.8), suggest that they were derived by partial melting of a depleted mantle source associated with subduction-related fluids. The granitoids with high SiO2 (55.6−66.9 wt%) display adakitic geochemical characteristics, such as low Y and Yb contents, and high Sr/Y and La/Yb ratios. Their positive whole-rock εNd(t) (+4.0 to +5.5) and zircon εHf(t) (+6.9 to +14.3) values, as well as enrichment of incompatible elements, indicate that the granitoids were derived from partial melting of the juvenile lower crust. Geochemical modeling suggests that the compositional diversities of MMEs and adakitic granitoids were inherited from heterogeneous sources. This genetic relationship indicates that the underplated basaltic magmas could have supplied sufficient heat to trigger the melting of the thickened crust and thus formation of the enclave-bearing granitoid. In this regard, the origin of arc rocks can mirror the evolution of crustal thickness. Our results reveal that the crust was thickened to ∼50 km during the Late Cretaceous (90−85 Ma) and provide a magmatic record of crustal thickening prior to the Cenozoic Indo-Asia collision.

Characteristics of Typical Soil Acidification and Effects of Heavy Metal Speciation and Availability in Southwest China

Using a spatial instead of temporal approach, soil samples were collected from the main types and different stages of acidification in Southwest China, and the characteristics of soil physicochemical properties, acid-buffering properties, and heavy metal fugacity patterns were analyzed, combined with biological experiments in small cabbage pots, to explore the coupling relationship between soil acidification and changes in heavy metal morphological activity. The results showed that the exchangeable salt-based ions of the soil decreased with increasing acidification in purple and yellow soils, caused by the loss of exchangeable Ca2+. The acid-buffering capacity of purple and yellow soils was higher at pH>7.50 and pH<4.50. The acid-buffering capacity of yellow soils was strongly correlated with the content of soil exchangeable salt-based ions, and the increase in acid-buffering capacity was related to the rate of depletion of soil salt-based ions with the increase in acid addition. The distribution of Cd and Pb in the soil was closely related to the soil type and degree of acidification: in the purple and yellow soils, Cd and Pb were mainly in the exchangeable and residue states, and the proportions of the exchangeable state and residue state increased and decreased, respectively, with increasing acidification; in the red soils, the residue state and Fe-Mn bound state were predominant; the Fe-Mn bound state of Cd was 2.15 and 1.73 times higher than that of the purple and yellow soils, respectively, and the Fe-Mn bound state of Pb was 4.30 and 3.91 times higher than that of purple and yellow soils, which was related to the higher iron content in red soils. Pot experiments showed that soil acidification inhibited the growth of Chinese cabbage to a certain extent, and the biomass of Chinese cabbage in the heavily acidified yellow soil (pH<5.70) was significantly lower than that in the non-acidified yellow soil.

Influence of ion exchange membrane arrangement on dual-channel flow electrode capacitive deionization: Theoretical analysis and experimentations

Flow electrode capacitive deionization (FCDI) has emerged as a viable technology for brackish water desalination. However, the mutual restriction between desalination rate and energy consumption is the current bottleneck hindering the widescale and practical application of FCDI. At this point, the relationship between the complex electrical double layer and electrodialysis mechanism is still unclear. Herein, we have constructed two kinds of dual-channel FCDI systems to investigate the influence of ion exchange membranes (IEMs) arrangement on desalination performance. The diffusion coefficient of chlorine is higher than that of sodium, resulting in the improved salt removal rate and current efficiency of dual-channel FCDI based on the NaCl electrolyte. In contrast, both systems performed identically using KCl as the majority salt in the feed stream due to the similar diffusion coefficients of both the cation and anion. The higher salt removal capability of dual-channel FCDI was achieved by (i) the thicker ion depletion layer of cation exchange membrane (CEM) enabling higher salt removal efficiency and (ii) the higher concentration of the ion enrichment layer accelerating the electro-adsorption of flow-electrodes. Both the numerical simulation and experimental results indicate that the composite mechanisms of dual-channel FCDI are beneficial to the excellent desalination performance and great energy efficiency.

Late Carboniferous bimodal volcanic rocks of the West Junggar Terrane, NW China: Implications for the postcollisional tectonic setting of the southwestern CAOB

ABSTRACT The West Junggar terrain (WJT), as a crucial part of the Central Asian Orogenic Belt (CAOB), is distributed with numerous igneous rocks, which provide critical information for crustal growth. However, the closure of the Junggar Ocean (JO) and the beginning of the postcollisional tectonic stage of the WJT have been controversial. This study delimited the regional lithologic units based on remote sensing geological mapping and recognized a series of bimodal volcanic rocks (BVR) in Hala’alate Mountain of the WJT. LA-ICP‒MS zircon U‒Pb geochronology and geochemistry were used to discuss the petrogenesis of the BVR and determine the stage of regional tectonic evolution. Geochronological results yield crystallization ages of 302 ± 4 Ma, 298 ± 2 Ma, 304 ± 1 Ma, and 303 Ma± 2 Ma for the basaltic andesite, basalt, and two rhyolitic samples, respectively. Basalts and basaltic andesites are calc-alkaline, and display enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). Notably, basaltic andesites in this area were once misjudged as sanukitoids owing to their low contents of Mg#, Ni, Cr, and other characteristics that are inconsistent with the typical definition of sanukitoids. The rhyolites are A2-type granitoids with high SiO2 contents and are depleted in Nb, Ta, P, Ti, and Sr, showing enriched LREE patterns with negative Eu anomalies. These features indicate that the magma of the mafic end-member of the BVR is derived from the partial melting of the depleted lithospheric mantle, whereas the felsic end-member magma can be associated with the remelting of the lower crust due to the upwelling and underplating of mafic magma. In combination with previous studies of simultaneous basic dikes and felsic rocks, a postcollisional tectonic stage was proposed for the WTJ during the late Carboniferous, suggesting that the JO was closed.

Ion transport behavior in a vertically-oriented asymmetric Ti3C2Tx nanochannel membrane

Exceptional ion release and storage ability of biological ion channels are regarded as a prerequisite for various life activities. Constructing biomimetic nanochannels to modulate selective ion transport has received enormous attention. Herein, a study on ion transport behavior in a vertically-oriented three-sectional Ti3C2Tx membrane with asymmetric charge distribution was presented. The surface charge polarity of Ti3C2Tx nanosheet was changed from negativity to positivity by successfully grafting the silane molecules onto the surface. The heterogenous Ti3C2Tx nanochannel membrane consisting of three different charged sections was prepared to build up the nanofluidic device. The diode-like ion transport property was observed for the heterogenous membrane, and the maximum ion current rectification ratio reached approximately 32. The numerical simulation based on the Poisson-Nernst-Planck (PNP) equations indicated that the directional ion diffusion was attributed to the accumulation and depletion of ions in the nanochannels under different potential biases. Moreover, the application potential of desalination and ion storage of the heterogenous membrane was assessed. Our work paves the way for the design of heterogenous nanochannels for controllable ion transport and introduces a new perspective for ion sieving, energy conversion, and sensing applications.

Mechano-electrochemical coupling in flexible all-solid-state lithium metal batteries

Bending and stretching are critical mechanical behaviors affecting the electrochemical performance of flexible batteries in wearable electronic devices. Herein, a mechano-electrochemical model is developed for solid-state Li metal batteries under bending deformation. It is found that bending alters ion transport and electric potential in solid polymer electrolytes, and its influence relies on the bending direction. By means of the curvature and coupling coefficient, a phase map is constructed for the critical current density that leads to ion depletion at the Li metal-electrolyte interface. In addition, a positive curvature helps to decrease the overpotential for electrochemical reactions on the Li metal electrode. Though the direct influence of bending on electrochemical kinetics is limited, the bending deformation could substantially increase the stress and cause potential mechanical failure of electrodes and electrode-electrolyte interfaces, thereby degrading electrochemical performance.

Large‐Scale Depletion of Nighttime Oxygen Ions at the Low and Middle Latitudes in the Winter Hemisphere

AbstractBy analyzing the latitudinal distributions of ionospheric ions observed by the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions satellite at 670 km altitude in different seasons, we found that the large‐scale depletion of nighttime oxygen ions is prevalent at the low and middle latitudes of winter hemisphere (center ∼ 30°) under different geomagnetic conditions. The latitudinal width of the winter oxygen ion depletion (WOD) region is about 20°–60° at different longitudes, and its upper boundary latitudes are mostly lower than the midlatitude trough (|λ| ≥ 50°) of nighttime hydrogen ions (H+) near the plasmapause. In the WOD region, the density ratio of oxygen and hydrogen ions and that of their neutral densities (O and H) approximately agree with the chemical equilibrium relationship of charge exchange reactions (H + O+ ↔ H+ + O) predicted by previous theory, indicating that the charge exchange reactions are mainly responsible for the large‐scale oxygen ion depletion at the low and middle latitudes in winter hemisphere.

Petrogenesis and tectonic implications of Cenozoic mafic volcanic rocks in the Kahak area of central Urumieh–Dokhtar magmatic arc, Iran

• Mafic volcanic rocks in the Kahak area were erupted at ∼ 60–55 Ma and ∼ 21 Ma. • The Kahak basaltic rocks are divided into two groups of low and high Nb/Ta ratios. • The petrogenesis of the Kahak basaltic rocks involved slab dehydration and melting. • Slab rollback and mantle metasomatism occurred during the Paleocene–Eocene and Miocene . Cenozoic volcanic rocks are widely distributed in the Urumieh–Dokhtar magmatic arc (UDMA), Iran, but their petrogenesis and tectonic implications remain enigmatic. The volcanic rocks in the Kahak area of the central UDMA are mostly basalt and basaltic andesite. They show enrichment in light rare earth elements and large ion lithophile elements and depletion in the high-field-strength elements (Nb, Ta, and Ti), corroborating a subduction-related origin. U–Pb ages of zircon from these volcanic rocks demonstrate two episodes of magmatism during the Paleocene–Eocene (∼60–55 Ma) and Miocene (∼21.9–21.4 Ma). These rocks have 87 Sr/ 86 Sri values from 0.70485 to 0.70577, ɛ Nd (t) values from +2.0 to +5.0, and zircon Hf isotopes ε Hf (t) values from +8.3 to +10.2. These features with isotopic modeling support derivation from partial melting of an asthenospheric mantle wedge in an extensional intracontinental-arc basin. This mantle source was previously metasomatized by subducted slab components of the Neotethys Ocean. The mafic melts underwent fractional crystallization and minor crustal contamination during magma evolution. The Paleocene–Eocene basaltic rocks have subchondritic Nb/Ta ratios, indicating that the magma source was affected by fluids with low-Nb/Ta ratios, which were released during shallow metamorphism of a subducted slab. However, the Miocene basaltic rocks have unusual superchondritic Nb/Ta ratios, indicating slab melt involvement. Geochemical data and field relationship indicate that mafic volcanism in the Kahak area occurred in an extensional setting associated with the Paleogene shallowing of the northeastward-subducting Neotethyan oceanic lithosphere followed by Late Paleogene and Neogene slab rollback and eventual partial melting of a deeply subducted oceanic slab.

Influences of electroosmotic flow on ionic current through nanopores: A comprehensive understanding

Continuum simulations become an important tool to uncover the mysteries in nanofluidic experiments. However, fluid flow in simulation models is usually unconsidered. Here, systematical simulations are conducted to provide a quantitative understanding of influences from electroosmotic flow (EOF) on ionic transport through nanopores by both types of models with and without consideration of EOF. In nanopores of less than ∼10 nm in diameter, counterions dominate ionic current, which is always promoted obviously by the convective effect of EOF. In the diameter range from ∼10 to ∼30 nm, strong EOF induces ion concentration polarization or ion depletion inside nanopores, which causes significant decreases in ionic current. For nanopores larger than ∼30 nm, due to convective promotion and inhibition of EOF on the transport of counterions and anions, considerable nanopore selectivity to counterions maintains in cases with EOF. Though the difference in total current between both cases decreases with further pore size increasing, the difference in cation/anion current is still considerable. From our results under various pore parameters and applied conditions, the fluid flow should be considered in the simulation cases when EOF is strong. Our work may provide useful guidance for simulation conductance.

Constant phase element affected by ion transport in nanoporous electrodes

• A constant phase element (CPE) depends on the concentration of the electrolyte and ionic size at nanoporous electrodes. • Ion depletion in nanopores and the ion transport toward nanopores causes the non-ideality of the capacitance. • These findings are not observed at flat electrodes. A constant phase element (CPE) is an equivalent electrical circuit component that describes the behavior of a double layer formed at the electrode and electrolyte interface, which is a kind of imperfect capacitors. When the CPE concept is applied to model the behavior of the electrical double layer at nanoporous electrodes, the physical interpretation of the CPE becomes more complicated because of the morphological effect of the nanoporous electrode. Here we show that the CPE depends on the concentration of the electrolyte and ionic size at nanoporous electrodes. At low electrolyte concentration, the depletion of ions in the nanopore and the ion transport toward nanopores increase the dependence of capacitance on frequency. Moreover, larger ions have more restricted transport into the nanopore than smaller ions, leading to non-ideality of capacitance, which is significantly different from that of flat electrodes. The results suggest insight into the CPE at nanoporous electrodes.

Modelling the Alfvén eigenmode induced fast-ion flow measured by an imaging neutral particle analyzer

An imaging neutral particle analyzer (INPA) provides energy and radially resolved measurements of the confined fast-ion population ranging from the high-field side to the edge on the midplane of the DIII-D tokamak. In recent experiments, it was used to diagnose fast-ion flow in the INPA-interrogated phase-space driven by multiple, marginally unstable Alfvén eigenmodes (AEs). The key features of this measured fast-ion flow are: (I) a fast-ion flow from q min and the injection energy (81 keV) towards lower energies and plasma periphery.(II) A flow from the same location towards higher energies and the plasma core, (III) a phase-space ‘hole’ at the injected energy and plasma core and (IV) a pile-up at the plasma core at lower energies (∼60 keV). Ad hoc energetic particle diffusivity modelling of TRANSP significantly deviates from the observation. Comparably, a reduced modelling, i.e. a combination of NOVA-K and ASCOT5 code with the measured mode structure and amplitude, generally reproduce some key features of the observed phase-space flow, but largely failed to interpret fast ion depletion near the plasma axis. At last, self-consistent, first-principle multi-phase hybrid simulations that include realistic neutral beam injection and collisions are able to reproduce most features of the time-resolved phase-space flow. During consecutive hybrid phases, an RSAE consistent with the experiment grows and saturates, redistributing the injected fast ions. The resulting synthetic INPA images are in good agreement with the measurement near the injection energy. The simulations track the fast-ion redistribution within the INPA range, confirming that the measured fast-ion flow follows streamlines defined by the intersection of phase-space surfaces of constant magnetic moment μ and constant E′ = nE + ωP ϕ , where n and ω are the instability toroidal mode number and frequency, and E and P ϕ the ion energy and toroidal canonical momentum. Nonperturbative effects are required to reproduce the depletion of fast ions near the magnetic axis at the injection energy.

Long‐Term Field Screening by Mobile Ions in Thick Metal Halide Perovskites: Understanding Saturation Currents

Metal halide perovskite‐based semiconductor devices with micrometer‐to‐millimeter‐thick perovskite layers show a current response upon polarization which evolves up to several hours, transiting several regimes. This is the case of X‐ray detectors where the use of absorber perovskites produces instabilities in the dark reverse saturation current hindering the signal processing. Even though these phenomena are often attributed to the electronic–ionic conductivity and the interface phenomena in these perovskites, a proper theoretical description is missing. Herein, the numerical simulation study reproduces the main experimental trends and explains the origin of some of the apparently‐always‐increasing current transients in thick perovskite samples. The mobile ion concentration and mobility are correlated with three main transport regimes and interpretation and parameterization are provided to the current saturation time in terms of the ionic screening of the electric field toward the interfaces. The final steady‐state under reverse polarization is found as diffusion‐limited electronic current, which results from abrupt mobile ion depletion proportional to the Debye length in the vicinity of a contact. The conclusions suggest the material optimization of the contact interfaces as a pathway to reduce the long current saturation times in these devices.

Petrogenesis of newly identified Neoarchean granitoids in the Qingyuan of NE China: Implications on crustal growth and reworking of the North China Craton

• A new ca. 2.7–2.5 Ga granitoid suite was identified in the Qingyuan, NE China. • The 2.68 Ga TTG was derived from ancient lower crust as well as juvenile crust. • Qingyuan granitoids record two periods of crustal growth and reworking events. Discovery of ca. 2.7 Ga tonalite-trondhjemite-granodiorite (TTG) in the North China Craton (NCC) can provide the key clue to understanding the Neoarchean crustal evolution. Most recently, we mapped out ca. 2.7 Ga TTGs from the northern Qingyuan at the northeastern margin of NCC. Together with the associated ca. 2.6–2.5 Ga high-K granites and high-Mg diorites, this study provides new constraints on crustal growth and reworking during the Neoarchean. Zircon U–Pb dating indicates that the TTGs, high-K granites and high-Mg diorites were formed at ca. 2.68 Ga, ca. 2.56 Ga and ca. 2.54 Ga, respectively. All of these lithologies exhibit enrichments in large ion lithophile elements (e.g., Rb and Ba) but depletions in high field strength elements (e.g., Nb and Ta), with positive εHf(t) and εNd(t) values. The TTGs have moderate SiO 2 , low Al 2 O 3 and variable MgO contents with high Sr/Y and (La/Yb) N ratios. They were likely derived from partial melting of mafic lower crust. High SiO 2 and K 2 O but low MgO and Cr contents as well as high Sr/Y and (La/Yb) N ratios reflect an origin of recycling of ancient crustal rocks (e.g., pre-existing TTGs) for the high-K granites. The high-Mg diorites have high MgO and Cr contents but low Sr/Y and (La/Yb) N ratios, which indicate that they could be sourced from partial melting of metasomatized mantle peridotite. Combined with previous studies, the northeastern NCC experienced two major periods of ca. 2.7 Ga and ca. 2.6–2.5 Ga crustal growth and reworking events.

Unblocking Ion-occluded Pore Channels in Poly(triazine imide) Framework for Proton Conduction.

Poly(triazine imide) or PTI is an ordered graphitic carbon nitride hosting Å-scale pores attractive for selective molecular transport. AA'-stacked PTI layers are synthesized by ionothermal route during which ions occupy the framework and occlude the pores. Synthesis of ion-free PTI hosting AB-stacked layers has been reported, however, pores in this configuration are blocked by the neighboring layer. The unavailability of open pore limits application of PTI in molecular transport. Herein, we demonstrate acid treatment for ion depletion which maintains AA' stacking and results in open pore structure. We provide first direct evidence of ion-depleted open pores by imaging with the atomic resolution using integrated differential phase-contrast scanning transmission electron microscopy. Depending on the extent of ion-exchange, AA' stacking with open channels and AB stacking with closed channels are obtained and imaged for the first time. The accessibility of open channels is demonstrated by enhanced proton transport through ion depleted PTI.

Unblocking Ion‐occluded Pore Channels in Poly(triazine imide) Framework for Proton Conduction

AbstractPoly(triazine imide) or PTI is an ordered graphitic carbon nitride hosting Å‐scale pores attractive for selective molecular transport. AA’‐stacked PTI layers are synthesized by ionothermal route during which ions occupy the framework and occlude the pores. Synthesis of ion‐free PTI hosting AB‐stacked layers has been reported, however, pores in this configuration are blocked by the neighboring layer. The unavailability of open pore limits application of PTI in molecular transport. Herein, we demonstrate acid treatment for ion depletion which maintains AA’ stacking and results in open pore structure. We provide first direct evidence of ion‐depleted open pores by imaging with the atomic resolution using integrated differential phase‐contrast scanning transmission electron microscopy. Depending on the extent of ion‐exchange, AA’ stacking with open channels and AB stacking with closed channels are obtained and imaged for the first time. The accessibility of open channels is demonstrated by enhanced proton transport through ion depleted PTI.

Influence of a ‘shape/consolidation factor’ in unary, undoped oxide ceramics: Experimental evidence and associated benefits

In this work, we demonstrate the versatility of the ‘shape/consolidation factor’ effect in unary and/or undoped ceramics (chosen systems: TiO2 and BaTiO3). The phenomenon has been examined via suitable characterization techniques, e.g., X‐ray diffraction (XRD), Electron paramagnetic resonance (EPR), Raman Spectroscopy, Field emission scanning electron microscopy (FESEM) etc. In absence of the shape factor effect, undoped ceramics, e.g., TiO2 and BaTiO3 depicted a multitude of artifacts starting from issues with phase purity (i.e., emergence of extra/new phases), imbalance with stoichiometry, generation of unwanted vacancies (via depletion of ions) etc. The ‘shape factor’ effect, thus, proved to be beneficial for the control/mitigation of such defects. Dependencies of various possible factors on this ‘shape factor’ effect have also been highlighted.

On-Chip Electrokinetic Micropumping for Nanoparticle Impact Electrochemistry.

Single-entity electrochemistry is a powerful technique to study the interactions of nanoparticles at the liquid-solid interface. In this work, we exploit Faradaic (background) processes in electrolytes of moderate ionic strength to evoke electrokinetic transport and study its influence on nanoparticle impacts. We implemented an electrode array comprising a macroscopic electrode that surrounds a set of 62 spatially distributed microelectrodes. This configuration allowed us to alter the global electrokinetic transport characteristics by adjusting the potential at the macroscopic electrode, while we concomitantly recorded silver nanoparticle impacts at the microscopic detection electrodes. By focusing on temporal changes of the impact rates, we were able to reveal alterations in the macroscopic particle transport. Our findings indicate a potential-dependent micropumping effect. The highest impact rates were obtained for strongly negative macroelectrode potentials and alkaline solutions, albeit also positive potentials lead to an increase in particle impacts. We explain this finding by reversal of the pumping direction. Variations in the electrolyte composition were shown to play a critical role as the macroelectrode processes can lead to depletion of ions, which influences both the particle oxidation and the reactions that drive the transport. Our study highlights that controlled on-chip micropumping is possible, yet its optimization is not straightforward. Nevertheless, the utilization of electro- and diffusiokinetic transport phenomena might be an appealing strategy to enhance the performance in future impact-based sensing applications.