Charge Engine Research Articles

Surface Charge Engineering of Β-Glucosidase Using Rational Design Improves Catalytic Capacity and Ionic Liquid Tolerance

Surface Charge Engineering of Β-Glucosidase Using Rational Design Improves Catalytic Capacity and Ionic Liquid Tolerance

Surface salt bridges contribute to the extreme thermal stability of an FN3-like domain from a thermophilic bacterium.

This study uses differential scanning calorimetry, X-ray crystallography, and molecular dynamics simulations to investigate the structural basis for the high thermal stability (melting temperature 97.5°C) of a FN3-like protein domain from thermophilic bacteria Thermoanaerobacter tengcongensis (FN3tt). FN3tt adopts a typical FN3 fold with a three-stranded beta sheet packing against a four-stranded beta sheet. We identified three solvent exposed arginine residues (R23, R25, and R72), which stabilize the protein through salt bridge interactions with glutamic acid residues on adjacent strands. Alanine mutation of the three arginine residues reduced melting temperature by up to 22°C. Crystal structures of the wild type (WT) and a thermally destabilized (∆Tm -19.7°C) triple mutant (R23L/R25T/R72I) were found to be nearly identical, suggesting that the destabilization is due to interactions of the arginine residues. Molecular dynamics simulations showed that the salt bridge interactions in the WT were stable and provided a dynamical explanation for the cooperativity observed between R23 and R25 based on calorimetry measurements. In addition, folding free energy changes computed using free energy perturbation molecular dynamics simulations showed high correlation with melting temperature changes. This work is another example of surface salt bridges contributing to the enhanced thermal stability of thermophilic proteins. The molecular dynamics simulation methods employed in this study may be broadly useful for in silico surface charge engineering of proteins.

Enhanced acidic resistance ability and catalytic properties of Bacillus 1,3-1,4-β-glucanases by sequence alignment and surface charge engineering

High stability at acidic environment is required for 1,3-1,4-β-glucanase to function in biofuel, brewing and animal feed industries. In this study, a mesophilic β-glucanase from Bacillus terquilensis CGX 5-1 was rationally engineered through sequence alignment and surface charge engineering to improve its acidic resistance ability. Nineteen singly-site variants were constructed and Q1E, I133L and V134A variants showed better acidic stability without the compromise of catalytic property and thermostability. Furthermore, four multi-site variants were constructed and one double-site variant Q1E/I133L with better stability at acidic environment and higher catalytic property was obtained. The fluorescence spectroscopy and structural analysis showed that more surface negative charge, decreased exposure degree of residue No.1, shifted side chain direction of residue No.133 and the lower total and folding free energy might be the reason for the improvement of acidic stability of Q1E/I133L variant. The obtained Q1E/I133L variant has potential applications in industries.

Amino Acid‐Induced Interface Charge Engineering Enables Highly Reversible Zn Anode

AbstractDespite the impressive merits of low‐cost and high‐safety electrochemical energy storage for aqueous zinc ion batteries, researchers have long struggled against the unresolved issues of dendrite growth and the side reactions of zinc metal anodes. Herein, a new strategy of zinc‐electrolyte interface charge engineering induced by amino acid additives is demonstrated for highly reversible zinc plating/stripping. Through electrostatic preferential absorption of positively charged arginine molecules on the surface of the zinc metal anode, a self‐adaptive zinc‐electrolyte interface is established for the inhibition of water adsorption/hydrogen evolution and the guidance of uniform zinc deposition. Consequently, an ultra‐long stable cycling up to 2200 h at a high current density of 5 mA cm−2 is achieved under an areal capacity of 4 mAh cm−2. Even cycled at an ultra‐high current density of 10 mA cm−2, 900 h‐long stable cycling is still demonstrated, demonstrating the reliable self‐adaptive feature of the zinc‐electrolyte interface. This work provides a new perspective of interface charge engineering in realizing highly reversible bulk zinc anode that can prompt its practical application in aqueous rechargeable zinc batteries.

Sheet Charge Engineering Towards an Efficient Hole Injection in 290 nm Deep Ultraviolet Light-Emitting Diodes

The hole injection efficiency is one of the bottlenecks that restrict the external quantum efficiency (EQE) and optical power of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). The polarization-induced positive sheet charges at the last quantum barrier (LQB)/electron blocking layer (EBL) interface reflect the holes back to the p-type layer and weaken the hole injection capability into the active region. In this work, we designed and incorporated a polarization-engineered Al_xGa_1-xN/Al_yGa_1-yN superlattice layer at the LQB/EBL interface. The positive sheet charges at the LQB/EBL interface can be inverted into negative charges with optimal Al compositions in the Al_xGa_1-xN/Al_yGa_1-yN superlattice layer. The electron confinement and hole injection efficiency can also be improved through increasing the effective barrier height for electrons and decreasing the effective barrier height for holes, resulting in an enhanced optical power by 29.4% and alleviated efficiency droop by 78.4% for the proposed device with an Al_0.67Ga_0.33N/Al_0.7Ga_0.3N superlattice insertion layer. The sheet charge engineering method by polarization provides an alternative approach to boost the hole injection efficiency towards an enhanced device performance for DUV LEDs.

Normally-off operations in partially-gate-recessed AlTiO/AlGaN/GaN field-effect transistors based on interface charge engineering

We report normally-off operations in partially-gate-recessed AlxTiyO(AlTiO)/AlGaN/GaN metal-insulator-semiconductor (MIS) field-effect transistors (FETs), where aluminum titanium oxide AlTiO, an alloy of Al2O3 and TiO2, is employed as a gate insulator. Since AlTiO is useful for interface charge engineering owing to a trend that the AlTiO/AlGaN interface fixed charge is suppressed in comparison with Al2O3, we investigated combining the interface charge engineering with a partial gate recess method for AlTiO/AlGaN/GaN MIS-FETs. For AlTiO with a composition of x/(x+y)=0.73, a suppressed positive interface fixed charge at the AlTiO/recessed-AlGaN interface leads to a positive slope in the relation between the threshold voltage and the AlTiO insulator thickness. As a result, we successfully obtained normally-off operations in partially-gate-recessed AlTiO/AlGaN/GaN MIS-FETs with favorable performances, such as a threshold voltage of 1.7 V, an on-resistance of 9.5Ωmm, an output current of 450 mA/mm, a low sub-threshold swing of 65 mV/decade, and a rather high electron mobility of 730cm2/Vs. The results show that the interface charge engineering in combination with partial gate recess is effective for the GaN-based normally-off device technology.

Surface charge engineering for two-dimensional Ti2CTx MXene for highly efficient and selective removal of cationic dye from aqueous solution

• Few-layer Ti 2 CT x was synthesized by selective etching and ultrasonic exfoliation. • Ti 2 CT x showed excellent adsorption selectivity towards methylene blue removal. • The maximum adsorption capacity could reach as high as 2460.9 mg g −1 . • The primary adsorption mechanism was associated with electrostatic interaction. Exploring versatile materials that efficiently adsorb pollutants from wastewater is of critical importance for environmental remediation. As an emerging 2D material, MXene features a hydrophilic surface with abundant oxygen-containing groups that render a negatively charged surface, implying its great potential for removing cationic pollutants from wastewater. Given its remarkable properties, a novel Ti 2 CT x MXene as an adsorbent is synthesized through selective etching of Al layer from Ti 2 AlC and then ultrasonic exfoliation. The adsorption studies indicate that Ti 2 CT x exhibits highly efficient methylene blue (MB, cationic dye) removal performance, the maximum adsorption capacity can reach as high as 2460.9 mg g −1 , which is considerably higher than the values of graphene (83.2 mg g −1 ) and anionic dye removal (methyl orange, 122.6 mg g −1 ). Furthermore, the adsorption behavior fits well with the pseudo-second-order kinetic and Langmuir isotherm models, and thermodynamic analysis indicates that the adsorption is spontaneous and endothermic. Based on scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra analysis, the principal adsorption mechanism is related to the electrostatic interaction between Ti 2 CT x and MB molecules. Meanwhile, the result is also confirmed by adsorption experiments at different pH values and background ions. This work shows that the MXene family materials can be applied as high efficiency adsorbent for removing cationic dyes from wastewater.

Exciton generation and recombination dynamics of quantum dots embedded in GaNAsP nanowires

Semiconductor quantum dots (QDs) acting as single-photon-emitters are potential building blocks for various applications in future quantum information technology. For such applications, a thorough understanding and precise control of charge states and capture/recombination dynamics of the QDs are vital. In this work, we study the dynamics of QDs spontaneously formed in GaNAsP nanowires, belonging to the dilute nitride material system. By using a random population model modified for these highly mismatched materials, we analyze the results from photoluminescence and photon correlation experiments and show a general trend of disparity in positive and negative trion populations and also a strong dependence of the capture/recombination dynamics and QD charge states on its surroundings. Specifically, we show that the presence of hole-trap defects in the proximity to some QDs facilitates formation of negative trions, which also causes a dramatic reduction of the neutral exciton lifetime. These findings underline the importance of proper understanding of the QD capture and recombination processes and demonstrate the possibility to use highly mismatched materials and defects for charge engineering of QDs.

Surface charge engineering of Thermomyces lanuginosus lipase improves enzymatic activity and biodiesel synthesis.

This study was aimed at engineering charged residues on the surface of Thermomyces lanuginosus lipase (TLL) to obtain TLL variant with elevated performance for industrial applications. Site-directed mutagenesis of eight charged amino acids on the TLL surface were conducted and substitutions on the negatively charged residues D111, D158, D165, and E239 were identified with elevated specific activities and biodiesel yields. Synergistic effect was not discovered in the double mutants, D111E/D165E and D165E/E239R, when compared with the corresponding single mutants. One TLL mutant, D165E, was identified with increased specific activity (456.60 U/mg), catalytic efficiency (kcat/Km: 44.14s-1mM-1), the highest biodiesel conversion yield (93.56%), and comparable thermostability with that of the TLL. Our study highlighted the importance of surface charge engineering in improving TLL activity and biodiesel production, and the resulting TLL mutant, D165E, is a promising candidate for biodiesel industry.

Analysis of supercapacitor as a battery substitute in motorcycle

Lead acid battery is the main resource of motorcycle. It has some disadvantages, look like long charging time, short cycle life and also is not environment friendly. Supercapacitor is an electronic tool which can conserve electric current. It has higher power density compared to lead acid battery, but lower energy density. It is also faster in terms of charging, environment friendly, and has longer life cycle than lead acid battery. In this article, supercapacitor is used to substitute battery. The model is able to charge, discharge, and support engine starter in motorcycle. The result of this research shows that supercapacitor is able to substitute battery in motorcycle.

A Study of Mesh Sheets of 3-kW Stirling Engine

In recent years, the interest in low-pollution and high-efficiency heat engines has been increasing due to the growing awareness of environmental protection, and power generation at relatively low temperatures, such as use of exhaust heat and sunlight, has been attracting attention. Compared with other heat engines, Stirling engine is very important because it can be driven by any heat source at low temperatures, such as exhaust heat, and it does not emit exhaust gas. In order to realize a more efficient Stirling engine, it is essential to design a heat exchange system that is suitable for each component. Performance measurement and analysis on a new mesh regenerator material at low temperature difference using a 2-piston alpha-type 3-kW Stirling engine, NS03T are carried out. Mesh sheets developed for high performance Stirling engines can be designed with CAD and CAM technologies by etching process. For this study, M5 and M7 mesh sheets which are thin sheets of stainless steel with square holes in a grid arrangement, are used. With nitrogen and helium as the working fluid, the engine performance is measured by changing the charge pressure, heating temperature, and engine speed to clarify the flow resistance and heat transfer characteristics of the M5 and M7.

Power Prediction‐Based Model Predictive Control for Energy Management in Land and Air Vehicle with Turboshaft Engine

In recent years, the green aviation technology draws more attention, and more hybrid power units have been applied to the aerial vehicles. To achieve the high performance and long lifetime of components during varied working conditions, the effective regulation of the energy management is necessary for the vehicles with hybrid power unit (HPU). In this paper, power prediction‐based model predictive control (P2MPC) for energy management strategy (EMS) is proposed for the vehicle equipped with HPU based on turboshaft engine in order to maintain proper battery’s state of charge (SOC) and decrease turboshaft engine’s exhaust gas temperature (EGT). First, a modeling approach based on data‐driven method is adopted to obtain the mathematical model of turboshaft engine considering time delay and inertial of states. An integrated power predictor consisting of the classification of input status and the subpredictors are developed based on the deep learning method to improve the accuracy of the prediction model of the model predictive control (MPC). Subsequently, an EMS based on MPC using the proposed power predictor is introduced to regulate the SOC of battery and the EGT of turboshaft engine. The comparison with experimental results shows the high accuracy of mathematical model of turboshaft engine. The simulation results show the effectiveness of the proposed EMS for the vehicle, and the effects of different weight coefficients of objective function on the proposed EMS are discussed.

Test validated 0D/1D engine model of a swinging valve internal combustion engine

In the quest for reaching ever higher power density of IC engines a much simpler solution has been investigated that allows vehicles to reach a comparable power level with cars equipped with turbo charged engines. The new Swinging Valve (SwV) arrangement enables the unhindered gas exchange process through an engine. In this experiment a flow bench was used to examine a normal poppet valve cylinder head and a cylinder head constructed for the same engine but with Swinging Valves. The flow parameters of the original cylinder head were obtained then the SwV head was investigated in the same way. To examine the practical use of a SwV system a 0D/1D engine simulation had been created, first using the engine with conventional cylinder head. That model had been validated with dynamometer tests. After this stage the results of the Swinging Valve flow measurements were fed in the same 0D/1D engine simulation then the results were compared and examined.

Computational investigations on port injected DEE in a biogas inducted HCCI engine

Owing to global climate change and atmospheric pollution, several automobile manufacturing companies look for homogeneously charged engines to satisfy strict emission levels. In the present work, computational fluid dynamics (CFD) investigations have been carried out to showcase the homogeneity of air-fuel mixture formation by port fuel injection and manifold fuel injection of a Biogas-Diethyl Ether (DEE) homogeneous charge compression engine (HCCI). The distributions of equivalence ratio based on fuel and the total air-fuel mixture is formulated and found to be in close agreement with the literature. Earlier investigations have shown that the use of biogas as a single fuel causes lower power output compared to other alternative fuels. Hence the present study is planned to use biogas with DEE as an ignition improver via fuel injection systems to find the best suitable fuel injection system. In the mesh independent study, port injection mode is found to perform better against the manifold injection mode when compared with the homogeneity factor. Iso-volumes of excess-air ratio based on biogas, diethyl ether and other variables such as the density, turbulent kinetic energy, turbulent dissipation rate of air-fuel mixture influencing the homogeneity and equivalence ratio are studied for better in-cylinder distribution under the port injection mode.

Enhanced Fe 3d delocalization and moderate spin polarization in Fe[sbnd]Ni atomic pairs for bifunctional ORR and OER electrocatalysis

Charge and spin manipulations of electrons are considered to be of great significance in boosting the catalytic activity of MNC electrocatalysts. However, to the best of our knowledge, most current studies focus only on the charge engineering, the interplay between spin and charge is not well understood, and the simultaneous manipulation of both charge and spin remains challenging. Herein, we show that the cooperative interplay between charge itineration and spin-polarization of electrons has a profound impact on the catalytic behavior through density functional theory (DFT) calculations for the first time. Following this concept, we report a Fe-Ni atomic pair as a superior bifunctional catalyst for high performance ORR and OER, with a very small potential difference (ΔE) of 0.691 V. We confirm that the coexistence of Fe 3d itinerant charge and moderate spin polarization (magnetic moment: 1.48 μB) is responsible for the superior functional catalytic activity for the FeNi atomic pairs.

Nanowire Transistors with Bound-Charge Engineering.

Low-dimensional electronic systems such as silicon nanowires exhibit weak screening which is detrimental to the performance and scalability of nanodevices, e.g., tunnel field-effect transistors. By atomistic quantum transport simulations, we show how bound charges can be engineered at interfaces of Si and low-κ oxides to strengthen screening. To avoid compromising gate control, low-κ and high-κ oxides are used in conjunction. In Si nanowire tunnel field-effect transistors, we demonstrate that bound charge engineering increases the on-state current by orders of magnitude, and the combination of oxides yields minimal subthreshold swing. We conclude that the proposed bound-charge engineering paves a way toward improved low-power transistors.

Exerting charge transfer to stabilize Au nanoclusters for enhanced photocatalytic performance toward selective oxidation of amines

Atomically precise gold nanoclusters have received increasing attention in photocatalysis but suffered from self-oxidation coalescence induced by photo-generated holes. Herein, we report an efficient charge engineering strategy to improve the photo-oxidation activity and stability of Au25(PPh3)10(SC3H6Si(OC2H5)3)5Cl2 nanocluster (AuNC) taking advantage of Z-scheme AuNC/ultrathin BiOCl nanosheets (2D-BiOCl) heterojunction for visible light oxidative self-coupling of amines. The turnover frequency (TOF) over AuNC/2D-BiOCl for benzylamine can reach 1916 h―1, much higher than that of most previously reported gold catalysts with a TOF usually less than 500 h―1. Moreover, the heterojunction can be stabilized for six cycles with the intact structure of AuNC remained. The enhanced photocatalytic activity of AuNC/2D-BiOCl was predominantly attributed to the formation of Z-scheme heterojunction, which effectively accelerated the transfer and separation of photo-generated carriers. Especially, the consumption of holes in AuNC by injected electrons from 2D-BiOCl can inhibit the self-oxidation of AuNC, thus improve its stability. This study provides some insights into the design of metal nanocluster catalysts with Z-scheme charge transfer for the application of photocatalysis.

Black Men in Engineering Graduate Programs: A Theoretical Model of the Motivation to Persist

Background A growing body of research highlights the experiences of Black men students who successfully navigate science, technology, engineering, and mathematics (STEM) educational pathways. Many Black men graduate students in engineering describe moments when their advisors, peers, and, at times, community members make them feel different because of their race and gender. Needed is a better understanding of what motivates Black men to persist in graduate school despite such challenges. Purpose This study advances a new theoretical model, “Black Men's Graduate Engineering Motivation” (BMGEM), to describe the overlaying factors and sources of motivation—and their interrelations—that influence Black men in engineering graduate programs to persist. Research Design To explore the motivational factors that influence Black men in graduate engineering programs at predominantly White institutions (PWIs) to persist, this study of 42 students used an eight-item demographic form, one-on-one semi-structured interviews, and follow-up focus groups. Data analysis was conducted using adapted grounded theory techniques. After the completion of data collection and multiple iterations of analyses (both inductive and deductive), existing conceptualizations of motivation were used to help make sense of data. The connection to existing literature, code development, their placement into categories, and placing categories into themes led to the creation of a substantive, practice-informing theory: Black Men's Graduate Engineering Motivation. Findings Data analysis resulted in the theory of Black Men's Graduate Engineering Motivation (BMGEM). The BMGEM explains the overlaying factors that influence individuals’ experiences and motivations to persist (i.e., sociocultural factors, personal factors, social identities, pre-graduate school experiences), and external and internal motivational sources that also influence students’ motivations to persist (i.e., desire to earn a graduate degree, desire to become an engineer, challenges during graduate school, peers, family members, [under]representation, self-coaching practices, career and professional goals). Conclusions and Recommendations The findings from this study inform future research, and practice-based strategies around broadening participation, that aid in Black men's progress through science and engineering pathways. With this new information, we charge engineering colleges to make true commitments to broadening participation, which means centering students—in this case, Black men—as contributors to STEM. In doing so, engineering colleges need to commit to helping Black men succeed. Assisting in their motivation to persist is a key to meeting this charge.

Advanced Methods to Handle LSPI in TGDI Engines

<div class="section abstract"><div class="htmlview paragraph">In order to meet the stringent emission norms like EU6 and EU7 together with CAFÉ/CAFC norms, down-sizing of the engine is one of the thrust areas of focus among the OEMs. To this end, keeping the engine size small but to achieve the required power output, advanced Turbo charged Gasoline Direct Injection engine technology (TGDI) has emerged. However, TGDI technology is susceptible to an abnormal combustion phenomenon termed as Low Speed Pre-Ignition (LSPI) event. This event happens prior to the intended combustion, which causes the catastrophic engine damage. Several studies in terms of simulation and experiments to understand this phenomenon are reported in the literature. The main factors influencing this occurrence are found to be engine design and calibration, fuel types and engine oil formulation (in terms of calcium content). In this paper, advanced methods to handle the LSPI occurrence severity and component level advances in design robustness to avoid the engine damage are reported. The developed techniques include robust piston design, Piston ring design and coating technologies. In overall, the techniques related to engine design to predict the LSPI occurrence in terms of peak cylinder pressure (PCP) and number of events are summarized.</div></div>

Surface Charge Engineering for Covalently Assembling Three-Dimensional MXene Network for All-Climate Sodium Ion Batteries

MXenes, as excellent candidate anode materials for sodium ion batteries (SIBs), suffer from sluggish ion-diffusion kinetics resulting from the anchoring effect of the negatively charged functional groups on their surface on sodium ions. Herein, we introduce positively charged conductive polyaniline (PANI) to induce self-assembly of Ti3C2Tx MXenes into a three-dimensional PANI/Ti3C2Tx network. In this PANI/Ti3C2Tx network, PANI not only intercalates into Ti3C2Tx nanosheets to enlarge the interlayer spacing, but also promotes negative-to-positive transition of the surface charges of the Ti3C2Tx nanosheets, significantly improving ion-diffusion kinetics. Electrochemical test results further confirm the superb ion-diffusion kinetics of the PANI/Ti3C2Tx network. Meanwhile, a covalent interaction (Ti-N) between PANI and Ti3C2Tx, proved by X-ray photoelectron spectra (XPS) and X-ray absorption near-edge structure (XANES) tests, plays a key role in stabilizing this network structure. Therefore, PANI/Ti3C2Tx exhibits excellent sodium storage performances with a high specific capacity, superior rate performance and ultralong lifespan at high current density. More importantly, when operated at rigorous temperatures from +50 to -30 °C, PANI/Ti3C2Tx also exhibits good electrochemical performances. The present work presents a simple strategy for designing 3D porous MXene-based materials to realize high rate performance and all-climate energy storage device.