Charge Gradient Research Articles

Solvation modeling and optical properties of CdSO4-Doped L-Valine crystals

The utilization of computational solvation models for crystals proves effective in determining the amalgamation of molecular structures within the crystal medium, offering valuable insights into optimized crystal properties. This study focuses on identifying the arrangement of molecular strips within the crystal, crucial for recognizing active planes and the presence of non-linear optical (NLO) properties. To delve into the crystal's intricacies, a computational model was developed, and conformational analysis was conducted to ensure NLO property. The synthesis of the CdSO4-doped L-Valine metallo-organic complex crystal was achieved through the melt-freezing technique. The computational model was constructed to elucidate the formation of sub-planes within a confirmed orthorhombic crystal lattice. Mapping the molecular charge distribution with the dispersion of charge gradient facilitated the identification of chemical potential inhibition and its equipotential nodal domains. The estimation of electron density potential over critical points of the core carbons provided further insights. Chemical dynamics on the electron content of molecules for NLO properties were investigated by screening control parameters. The inelastic scattering ability of heteronuclear bonds for enhancing boosting potential was observed. Interactive frontier orbitals of degenerate energy states were illustrated, and the chemical potential of molecular zones was analyzed in-depth.

Long range self-transport of liquid droplets driven by electric field and roughness gradient

It is well known that roughness and charge gradients could be used for droplet self-transport. The key issue is how to synergize the two effects. The uniform density charge can form linearly increasing charge gradient on a roughness gradient surface. Under this condition, the influence on the droplet self-transport under the synergy of these two effects was obtained by statics analysis, and the driving function was presented. An energy equation was constructed to study the conditions for crossing periodic boundaries, and the problem of distance limitation on periodic surfaces due to energy dissipation was solved by converting electric potential into droplet kinetic energy. A periodic roughness gradient surface with K = 0.07 was designed and prepared via 3D printing. Water droplets can be transported over long distances and the maximum velocity increases with charge density up to 46 mm/s. Finally, the effect of different structures on the maximum charge density in the Cassie state was investigated by simulation. The biomimetic structures exhibit great compressive stability, which can increase the surface charge density of droplets in the Cassie state by 3.6 times compared to pillar structures. It can be widely used in the fields of materials science and interface chemistry, etc.

Enhancing Directional Droplet Transport via Surface Charge Gradient: Insights from Molecular Dynamics Simulations.

The phenomenon of spontaneous droplet transport has a wide range of implications in water collection, microfluidic manipulation, oil-water separation, and various other fields. Achieving efficient and controllable spontaneous droplet transport is therefore of paramount importance. This study investigates the potential of surface charge manipulation to enhance spontaneous droplet transport through comprehensive molecular dynamics simulations. Our findings reveal that the surface charge of the substrate significantly influences its wettability, reducing the contact angle of the droplet and increasing both the contact area and interaction energy. Moreover, we introduce a novel approach to enhance droplet mobility by creating a surface charge gradient on the substrate. By introducing bands with varying charges along a specific direction of the substrate, the droplet experiences a force directed toward regions of increasing charge, thereby facilitating its movement. Importantly, the driving mechanism of droplet motion is well explained by combining classical electrowetting theory with the analysis of the droplet's advancing and receding contact angles, which demonstrates that a more pronounced surface charge gradient generates greater force and enhances droplet mobility. These findings offer valuable insights into the design of microfluidic systems and related applications based on electrowetting.

Electrical Chain Rearrangement: What Happens When Polymers in Brushes Have a Charge Gradient?

Under the influence of electric fields, the chains in polyelectrolyte brushes can stretch and collapse, which changes the structure of the brush. Copolymer brushes with charged and uncharged monomers display a similar behavior. For pure polyelectrolyte and random copolymer brushes, the field-induced structure changes only the density of the brush and not its local composition, while the latter could be affected if charges are distributed inhomogeneously along the polymer backbone. Therefore, we systematically study the switching behavior of gradient polyelectrolyte brushes in electric fields for different solvent qualities, grafting densities, and charges per chain via coarse-grained molecular dynamics simulations. Similar to random copolymers and pure polyelectrolytes, these brushes show a mixed-phase transition: intermediate states between fully stretched and collapsed are characterized by a bimodal chain-end distribution. Additionally, we find that the total charge of the brush plays a key role in the critical field required for a complete transition. Finally, we find that gradient polyelectrolyte brushes are charge-enriched at the brush-solvent interface under stretched conditions and charge-depleted under collapsed conditions, allowing for control over the local composition and thus the surface charge of the brush due to the inhomogeneous charge along the grafted chains.

Programmable Droplet Manipulation on Superhydrophobic Surfaces with Charge Gradient

The controllable manipulation of droplets is pivotal for diverse applications spanning from microfluidics to biotechnology. In this paper, we present a novel droplet manipulation method leveraging a charge gradient on superhydrophobic surfaces. By shielding the charges on a superhydrophobic surface with uniform charges, a charge gradient is generated, which can drive a neutral droplet to move along the charge gradient. By controlling the motion trajectory of the metallic shield, a programmable droplet motion in a desired manner is achieved. This programmable droplet manipulation accompanied by non-contact, fast-responsive, ultrafast, and convenient performances is promising in many fluidic systems.

Soccer Ball‐like Assembly of Edge‐to‐edge Oriented 2D‐silica Nanosheets: A Promising Catalyst Support for High‐Temperature Reforming

AbstractControlled assembly of nanoparticles into well‐defined assembled architectures through precise manipulation of spatial arrangement and interactions allows the development of advanced mesoscale materials with tailored structures, hierarchical functionalities, and enhanced properties. Despite remarkable advancements, the controlled assembly of highly anisotropic 2Dnanosheets is significantly challenging, primarily due to the limited availability of selective edge‐to‐edge connectivity compared to the abundant large faces. Innovative strategies are needed to unlock the full potential of 2D‐nanomaterialsin self‐assembled structures with distinct and desirable properties. This research unveils the discovery of controlled self‐assembly of 2D‐silica nanosheets (2D‐SiNSs) into hollow micron‐sized soccer ball‐like shells (SA‐SiMS). The assembly is driven by the physical flexibility of the 2D‐SiNSs and the differential electricdouble‐layer charge gradient creating electrostatic bias on the edge and face regions. The resulting SA‐SiMS structures exhibit high mechanical stability, even at high‐temperatures, and exhibit excellent performance as catalyst support in the dry reforming of methane. The SA‐SiMS structures facilitate improved mass transport, leading to enhanced reaction rates, while the thin silica shell prevents sintering of small catalyst nanocrystals, thereby preventing coke formation. This discovery sheds light on the controllable self‐assembly of 2D nanomaterials and provides insights into the design and synthesis of advanced mesoscale materials with tailored properties.

Soccer Ball-like Assembly of Edge-to-edge Oriented 2D-silica Nanosheets: A Promising Catalyst Support for High-Temperature Reforming.

Controlled assembly of nanoparticles into well-defined assembled architectures through precise manipulation of spatial arrangement and interactions allows the development of advanced mesoscale materials with tailored structures, hierarchical functionalities, and enhanced properties. Despite remarkable advancements, the controlled assembly of highly anisotropic 2Dnanosheets is significantly challenging, primarily due to the limited availability of selective edge-to-edge connectivity compared to the abundant large faces. Innovative strategies are needed to unlock the full potential of 2D-nanomaterialsin self-assembled structures with distinct and desirable properties. This research unveils the discovery of controlled self-assembly of 2D-silica nanosheets (2D-SiNSs) into hollow micron-sized soccer ball-like shells (SA-SiMS). The assembly is driven by the physical flexibility of the 2D-SiNSs and the differential electricdouble-layer charge gradient creating electrostatic bias on the edge and face regions. The resulting SA-SiMS structures exhibit high mechanical stability, even at high-temperatures, and exhibit excellent performance as catalyst support in the dry reforming of methane. The SA-SiMS structures facilitate improved mass transport, leading to enhanced reaction rates, while the thin silica shell prevents sintering of small catalyst nanocrystals, thereby preventing coke formation. This discovery sheds light on the controllable self-assembly of 2D nanomaterials and provides insights into the design and synthesis of advanced mesoscale materials with tailored properties.

Light/pH dual-responsive magnetic metal-organic frameworks composites for phosphorylated peptide enrichment

Metal-organic frameworks (MOFs) combined with specific ligands are highly adaptable smart materials that can respond to external and physiological stimuli. In this study, we introduced a pyridinyl zwitterionic ligand with light/pH dual response into magnetic MOF composite (Fe3O4@ZW-MOF) for enrichment of phosphorylated peptides for the first time. The introduction of the developed ligand gives MOF material dual response properties. Light stimulation affects the generation/disappearance of free radicals of the pyridine derivative, resulting in a change in the charge gradient of the zwitterion, and zwitterion can also regulate the pH of the solution by adding acid or base. Therefore, the reversible capture and release of phosphorylated peptides can be easily achieved by adjusting light and pH. The established phosphorylated peptide enrichment platform exhibits high sensitivity (detection limit of 1 fmol), high selectivity (β-casein:BSA, 1:1000), and good reusability (7 cycles). In addition, the method was applied to the enrichment of phosphorylated peptides in complex systems (non-fat milk and human serum), demonstrating the feasibility of this method for phosphoproteom analysis. In conclusion, the synthesized Fe3O4@ZW-MOF is a promising MOF material, which provides the possibility to advance the application of responsive MOFs materials in proteomics.

Moving water droplets induced electricity on an electret surface with a charge gradient

In solid-liquid systems, a variety of electrokinetic effects can generate electricity utilizing diverse forms of gradients, for instance, pressure and salinity gradients. Here we report a new electrokinetic effect that moving a water droplet on an electret surface with a charge gradient can induce electricity in circuit between the droplet and an electrode underneath the electret film. While the droplet moves along the charge gradient, electric double layers at the solid-liquid interfaces continue to be charged or discharged through the circuit due to the change in surface charge density, leading to a direct-current output that can be quantitatively described by a proposed model. Furthermore, the direct correlation between the electrical output and the surface charge gradient endows the droplet with intelligence to sense the surface charge distribution, and the read of binary digital information stored in a charge matrix using a tiny water droplet was achieved. The reported electrokinetic effect not only promises a new sustainable avenue to deliver application-friendly direct-current electricity, distinct from the instantaneous pulsed output of traditional devices, but also extends the intelligent functionality of water droplets.

Electrokinetic ion rectification in the coupling asymmetric charged nanochannel

Ion transport in nanochannels attracts increasing attention with the advance of nanotechnology, where ion rectification has been intensively studied due to its diode-like electrokinetic behavior. However, the electrochemical interface in most ion rectification is not uniform but involves asymmetric-charged characteristics that offer new degrees of electrical double layer (EDL) confinement. Herein, we investigate the ion transport in coupling asymmetric charged nanochannel to evaluate how the asymmetric geometry and surface charge influences the ion rectification performance. The results show that at low surface charge gradient, the coupling effect enhances ion rectification performance. While at high surface charge gradient, an anomalous electrokinetic behavior is observed that coupling effect deteriorates ion rectification performance. Further analysis discloses that the enhancement-deterioration transition threshold depends on the coordination mechanism of asymmetric geometry and surface charge. It is found that the asymmetric geometry shaped nanochannel with low surface charge gradient and homogeneous geometry shaped nanochannel with high surface charge gradient have the better ion rectification performance. This work fills the gap in understanding the coupling asymmetry effect on ion rectification, providing the useful guidance to design nanofluidic energy devices.

Biomimetic Liquid Metal Mechatronic Devices

AbstractPerceiving mechanical stimuli and converting them into bioelectric signals to complete sensing information transmission and computation is a fundamental mechanism for survival and evolution of natural animals. This leads to a variety of intelligent behaviors, such as processing, learning, judgment, feedback, and so on when tackling complex and changeable environmental challenges. Until now, the realization of a bionic system to mimic the above activities has long been an important goal which is mainly based on the integration of distributed functional units, lacking the coordination between functional units and the whole systems. Herein, based on the mechano‐electronic coupling effect of liquid metals and by following the basic principle of perception and transduction of piezo proteins, a biomimetic functional liquid metal mechatronic device is proposed with the switching behavior via establishing the reversible charge gradient. Owing to flexible features of liquid metals, this all‐soft mechatronic device exhibits excellent compliance with the whole system. Based on electrochemical characteristics of liquid metals, the passive intelligent device demonstrates versatile behaviors, such as self‐energy supply, encoding, computation, sensing, information identification, communicating, and controlling functions etc. which can only possibly be achieved by living animals. This work opens a new strategy for developing intelligent mechatronic systems.

Study of drop mobility over a surface having electric charge gradient

Though different methodologies like thermal and magnetic fields have been tried to control a droplet's mobility in biochemical and medical applications, charge imprinted super-amphiphobic surface is the recent and promising development in which droplets can be transported through any predefined path over the surface. Such surfaces are electrified by impacting water droplets from varying release heights through triboelectrification. Impacting droplets on pillared surface dynamics of the same have been analyzed to understand the nature of electrostatic charge distribution generated. Further to this, droplet actuation on such surfaces with surface charge gradient has been simulated. Charge separation inside the liquid droplet and charge accumulation near the interface has been visualized to understand the phenomenon. Asymmetry in droplet shape and charge distribution has been analyzed as the reason behind the droplet actuation. The effect of different charge density gradients and surface wettability over droplet mobility has also been studied.

Biochemical Characterization of Caenorhabditis elegans Ferritins.

The nematode Caenorhabditis elegans contains genes for two types of ferritin (ftn-1 and ftn-2) that express FTN-1 and FTN-2. We have expressed and purified both proteins and characterized them by X-ray crystallography, cryo-electron microscopy, transmission electron microscopy, dynamic light scattering, and kinetically by oxygen electrode and UV-vis spectroscopy. Both show ferroxidase activity, but although they have identical ferroxidase active sites, FTN-2 is shown to react approximately 10 times faster than FTN-1, with L-type ferritin character over longer time periods. We hypothesize that the large variation in rate may be due to differences in the three- and four-fold channels into the interior of the protein 24-mer. FTN-2 is shown to have a wider entrance into the three-fold channel than FTN-1. Additionally, the charge gradient through the channel of FTN-2 is more pronounced, with Asn and Gln residues in FTN-1 replaced by Asp and Glu residues in FTN-2. Both FTN-1 and FTN-2 have an Asn residue near the ferroxidase active site that is a Val in most other species, including human H ferritin. This Asn residue has been observed before in ferritin from the marine pennate diatom Pseudo-mitzchia multiseries. By replacing this Asn residue with a Val in FTN-2, we show that the reactivity decreases over long time scales. We therefore propose that Asn106 is involved in iron transport from the ferroxidase active site to the central cavity of the protein.

INVESTIGATION OF THE PROPERTIES OF MICROPARTICLES IN THE GLOW DISCHARGE STRATUM IN A CROSSED ELECTRIC AND MAGNETIC FIELD

In this work, the behavior of charged micron-sized particles in the DC glow discharge stratum at low pressure in a crossed magnetic and electric field was experimentally studied. The experiment was conducted in a vertically oriented gas-discharge glass tube. A homogeneous magnetic field was created using a two-section Helmholtz coil. The results showed that the micron-sized dust particles move in the opposite direction to the ExB drift as the magnetic field induction increases. Once the induction reaches a specific threshold (B>10 mT), the dust particles start rotating and forming counter-rotating vortex pairs on the horizontal plane. Moreover, it was observed that the shape of the dust structures changes from a disk to an ellipsoid. The PIV (particle image velocimetry) method was employed to analyze the dust vortices' dynamic behavior, and the generation of the co-vortex rotation was explained through the dust particles' charge gradient, which was orthogonal to the ion drag force.

Effect of surface charge gradient on the concentration difference driven energy conversion in nanochannel

With the growing energy crisis, new energy conversion methods are receiving much attention. Among them, there has been increasing interest in the concentration gradient power generation due to its facile availability in nature. However, the effect of surface charge gradient on ions transport and energy conversion has not been fully studied so far. Herein, this work proposed nanofluid systems to show how the surface charge gradient influences the energy conversion behavior in nanochannel. The results show that the negative surface charge gradient (NSCG) exhibits the best energy conversion performance in contrast to homogeneous surface charge (HSC) and positive surface charge gradient (PSCG) conditions. The maximum output power of 1.2 pW and energy conversion efficiency of 49% are obtained at NSCG case. Such high performance mainly arises from its excellent ion selectivity during the energy conversion. For practical application, the output voltage of long nanochannel with NSCG condition almost maintains constant and the resistance decreases gradually when the high surface charge is fixed and tuning the low surface charge, which can be regarded as a steady voltage resource. These results provide a general strategy for tuning nanofluid power generation and are beneficial to understand the basic mechanism in fluidic energy device.

Moving dynamics of a nanorobot with three DNA legs on nanopore-based tracks.

DNA nanorobots have garnered increasing attention in recent years due to their unique advantages of modularity and algorithm simplicity. To accomplish specific tasks in complex environments, various walking strategies are required for the DNA legs of the nanorobot. In this paper, we employ computational simulations to investigate a well-designed DNA-legged nanorobot moving along a nanopore-based track on a planar membrane. The nanorobot consists of a large nanoparticle as the robot core and three single-stranded DNAs (ssDNAs) as the robot legs. The nanopores linearly embedded in the membrane serve as the toeholds for the robot legs. A charge gradient along the pore distribution mainly powers the activation of the nanorobot. The nanorobot can move in two modes: a walking mode, where the robot legs sequentially enter the nanopores, and a jumping mode, where the robot legs may skip a nanopore to reach the next one. Moreover, we observe that the moving dynamics of the nanorobot on the nanopore-based tracks depends on pore-pore distance, pore charge gradient, external voltage, and leg length.

Contributions of Ti-xTa cold spray composite interface to in-vitro cell growth

Surface charge of biomaterials is one of the most influential parameters on regulating the complex processes of cell responses in tissue engineering. This study explores the contributions of x Ta ( x ​= ​5; 10; 30 in wt %) interface with the Ti as matrix on the in-vitro cell growth when such composites were produced through cold spray additive manufacturing. Preliminary results reveal that formation of intimate contact between deposited Ti and Ta splats provides meaningful differences in work function, results in an estimated surface potential variation around 50 ​mV, that ultimately influence cell growth. Increasing mass fraction of Ta in the chosen cold sprayed Ti- x Ta composites was beneficial to initial cell attachment and proliferation upon the surface. Electrochemical response of cold sprayed coatings indirectly proves that Ta may act as anode and Ti performs as cathode in the electrochemical cells with possible surface charge gradient that allow to design and adapt biomaterials surfaces to a specific application. Understanding the mechanism of cell growth upon the surface of cold sprayed Ti- x Ta composites will contribute to design of biomaterial surface for promising osseointegrity in biomedical applications. • Cold spray establishes a Ti/Ta electrolytic cell with work function variations in guiding cell performance.

Dynamics of dust particles in the glow discharge stratum in crossed E × B field

AbstractIn this work, the dynamic behaviour of micron‐sized dust particles suspended in the glow discharge stratum at low pressure in the crossed magnetic and electric fields was experimentally studied. The observations showed that the dust particles move in the direction opposite to the ExB drift with increasing magnetic field induction. When the magnetic field induction reaches a threshold point (B > 10 mT), the dust particles begin to rotate, forming pair of counter‐rotating vortex in the horizontal plane. It was also found that the shape of the dust structures changes from a disk shape to an ellipsoid shape. The dynamic behaviour of the dust vortices was analysed using the PIV (particle image velocimetry) method. The quantitative explanation of the generation of the co‐vortex rotation observed in the experiment was explained on the basis of the charge gradient of the dust particles, which was orthogonal to the ion drag force.

Reversibly Migratable Fluorescent Probe for Precise and Dynamic Evaluation of Cell Mitochondrial Membrane Potentials.

The mitochondrial membrane potential (MMP, ΔΨmito) provides the charge gradient required for mitochondrial functions and is a key indicator of cellular health. The changes in MMP are closely related to diseases and the monitoring of MMP is thus vital for pathological study and drug development. However, most of the current fluorescent probes for MMP rely solely on the cell fluorescence intensity and are thus restricted by poor photostability, rendering them not suitable for long-term dynamic monitoring of MMP. Herein, an MMP-responsive fluorescent probe pyrrolyl quinolinium (PQ) which is capable of reversible migration between mitochondria and nucleolus is developed and demonstrated for dynamic evaluation of MMP. The fluorescence of PQ translocates from mitochondria to nucleoli when MMP decreases due to the intrinsic RNA-specificity and more importantly, the translocation is reversible. The cytoplasm to nucleolus fluorescence intensity ratio is positively correlated with MMP so that this method avoids the negative influence of photostability and imaging parameters. Various situations of MMP can be monitored in real time even without controls. Additionally, long-term dynamic evaluation of MMP is demonstrated for HeLa cells using PQ in oxidative environment. This study is expected to give impetus to the development of mitochondria-related disease diagnosis and drug screening.

Rapid and highly selective conversion of CO2 to methanol by heterometallic porous ZIF-8

Commercial application of CO2-to-fuel technology has been mainly restricted due to low-cut CO2 adsorption and activation by photocatalyst, thus contributing to low/impure fuel yield. Defect engineering of key CO2 activators onto excellent CO2 adsorbent along with in-situ & co-production of Hadatoms could address these issues. Herein, we report rapid conversion of CO2 to CH3OH in a photocatalytic system composed of CoxMoyZn1−x−yZIF-8 photocatalyst and NaBH4-assisted Hadatoms production. Doping of Co & Mo into ZIF-8 provided active centers for CO2 activation and structured highly efficient electron transport chains (ETCs) for selective conversion of continuous supply of CO2 into CH3OH (99%). Conversion of CO2 by CoxMoyZn1−x−yZIF-8 yields 9.96 mmole gcat-1 h-1 of CH3OH higher than reported ZIF-8 based photocatalyst in literature, and pristine ZIF-8, which only produced 94.2 µmole g-1 of carbon monoxide. Mechanistically, engineered doping of Co0.25/Mo0.25 in Zn-ZIF-8 enhanced visible light absorption and mechanized ETCs due to d-orbitals and multiple redox states, which largely expediated CO2 adsorption-activation. While in-situ & co-production of Hadatoms from NaBH4 and water spitting boost conversion of activated CO2 to CH3OH. Interestingly, the controlled release of Hadatoms from NaBH4 maintained a requisite charge gradient across ETCs, which was proven to be another reason for the high yield and selectivity of CH3OH.13CO2 analysis confirmed the source of C in CH3OH was supplied CO2, not by photocatalyst carbon that proved the stability of CoxMoyZn1−x−yZIF-8. We believe this work will be a step forward for commercializing revolutionary CO2-to-fuel technology, while results and novel interpretation will be key for multidisciplinary research.