Defect passivation through electrostatic interaction for high performance flexible perovskite solar cells

The light weight,good bending resistance and low production cost make flexible perovskite solar cells(PSCs)good candidates in wearable electronics,portable charger,remote power,and flying objects.High power conversion efficiency(PCE)plays a crucial role on obtaining the high mass specific power of flexible devices.However,the performance for flexible PSCs is still having a large room to be improved.Here,we added the 2-amino-5-cyanopyridine(ACP)molecule with a polar electron density distribution in the perovskite precursor solution to improve the performance of flexible PSCs.The cyano groups with electron-withdrawing ability are expected to passivate positively charged point defects,while amines with electron donating ability are expected to passivate negatively charged point defects in perovskite films.Thanks to the effective passivation of defects at the grain boundary and surface of perovskite films,the PCE of flexible PSCs is obviously increased from 16.9%to 18.0%.These results provide a universal approach to improve performance of flexible PSCs by healing the defects in perovskite films through electrostatic interactions.

Electrostatic Interaction Tailored Anion-Rich Solvation Sheath Stabilizing High-Voltage Lithium Metal Batteries

Through tailoring interfacial chemistry,electrolyte engineering is a facile yet effective strategy for highperformance lithium(Li)metal batteries,where the solvation structure is critical for interfacial chemistry.Herein,the effect of electrostatic interaction on regulating an anion-rich solvation is firstly proposed.The moderate electrostatic interaction between anion and solvent promotes anion to enter the solvation sheath,inducing stable solid electrolyte interphase with fast Li+transport kinetics on the anode.This asdesigned electrolyte exhibits excellent compatibility with Li metal anode(a Li deposition/stripping Coulombic efficiency of 99.3%)and high-voltage LiCoO_(2) cathode.Consequently,the 50μm-thin Li||high-loading LiCoO_(2) cells achieve significantly improved cycling performance under stringent conditions of high voltage over 4.5 V,lean electrolyte,and wide temperature range(-20 to 60℃).This work inspires a groundbreaking strategy to manipulate the solvation structure through regulating the interactions of solvent and anion for highperformance Li metal batteries.

Minimizing electrostatic interactions from piezoresponse force microscopy via capacitive excitation

Piezoresponse force microscopy(PFM)has emerged as one of the most powerful techniques to probe ferroelectric materials at the nanoscale,yet it has been increasingly recognized that piezoresponse measured by PFM is often influenced by electrostatic interactions.In this letter,we report a capacitive excitation PFM(ce-PFM)to minimize the electrostatic interactions.The effectiveness of ce-PFM in minimizing electrostatic interactions is demonstrated by comparing the piezoresponse and the effective piezoelectric coefficient measured by ce-PFM and conventional PFM.The effectiveness is further confirmed through the ferroelectric domain pattern imaged via ce-PFM and conventional PFM in vertical modes,with the corresponding domain contrast obtained by ce-PFM is sharper than conventional PFM.These results demonstrate ce-PFM as an effective tool to minimize the interference from electrostatic interactions and to image ferroelectric domain pattern,and it can be easily implemented in conventional atomic force microscope(AFM)setup to probe true piezoelectricity at the nanoscale.

An approach to prepare uniform graphene oxide/aluminum composite powders by simple electrostatic interaction in water/alcohol solution

The homogenous dispersion of graphene in Al powders is a key challenge that limits the development of graphene-reinforced metal matrix composites with high performance.Here,uniform distribution of graphene oxide(GO)coated on flake Al powders were obtained by a simply stirring and ultrasonic treatment in the water/alcohol solution.The effect of water volume content on the formation of GO/Al composite powders was investigated.The results showed that GO adsorbed with synchronous reduction on the surface of Al powders,but when the water content was higher than 80%in the solution,Al powders were totally changed into Al(OH)3.With optimizing the water content of 60%in the solution,reduced GO was homogenously coated onto the surface of flake Al powders.The formation mechanism can be ascribed to the balance control between the liquid/solid interaction and the hydrolysis reaction.

Nanofriction characteristics of h-BN with electric field induced electrostatic interaction

The nanofriction properties of hexagonal boron nitride(h-BN)are vital for its application as a substrate for graphene devices and solid lubricants in micro-and nano-electromechanical devices.In this work,the nanofriction characteristics of h-BN on Si/SiO_(2) substrates with a bias voltage are explored using a conductive atomic force microscopy(AFM)tip sliding on the h-BN surface under different substrate bias voltages.The results show that the nanofriction on h-BN increases with an increase in the applied bias difference(V_(t–s))between the conductive tip and the substrate.The nanofriction under negative V_(t–s) is larger than that under positive V_(t–s).The variation in nanofriction is relevant to the electrostatic interaction caused by the charging effect.The electrostatic force between opposite charges localized on the conductive tip and at the SiO2/Si interface increases with an increase in V_(t–s).Owing to the characteristics of p-type silicon,a positive V_(t–s) will first cause depletion of majority carriers,which results in a difference of nanofriction under positive and negative V_(t–s).Our findings provide an approach for manipulating the nanofriction of 2D insulating material surfaces through an applied electric field,and are helpful for designing a substrate for graphene devices.

Effect of ionic strength and mixing ratio on complex coacervation of soy protein isolate/Flammulina velutipes polysaccharide

Soy protein isolate(SPI)is a commercial protein with balanced amino acids,while the poor solubility impedes its use in traditional foods.To overcome the problem,the complex coacervation of SPI/Flammulina velutipes polysaccharide(FVP)were investigated.Initial results revealed that the suitable amounts of FVP contributed to reducing the turbidity of SPI solution.Under electrostatic interaction,the formation of SPI/FVP coacervates were spontaneous and went through a nucleation and growth process.Low salt concentration(C_(NaCl)=10,50 mmol/L)led to an increase in the critical pH values(pHc,pHφ1)while the critical pH values decreased when C_(NaCl)≥100 mmol/L.The concentration of NaCl ions increased the content ofα-helix.With the increase of FVP,the critical pH values decreased and the content ofβ-sheet increased through electrostatic interaction.At SPI/FVP ratio of 10:1 and 15:1,the complex coacervation of SPI/FVP were saturated,and the coacervates had the same storage modulus value.SPI/FVP coacervates exhibited solid-like properties and presented the strongest storage modulus at C_(NaCl)=50 mmol/L.The optimal pH,SPI/FVP ratio and NaCl concentration of complex coacervation were collected,and the coacervates demonstrated a valuable application potential to protect and deliver bioactives and food ingredients.

Fabrication of graphene oxide-keratin-chitosan nanocomposite as an adsorbent to remove turbidity from tannery wastewater

Excessive turbidity in water is aesthetically unappealing and severely malfunctions the photosynthesis process of aquatic ecosystems. This study aimed to evaluate the effectiveness of a nanocomposite adsorbent made of graphene oxide-keratin-chitosan for removing turbidity from tannery influent. The nanocomposite was fabricated with simple solution casting methods. Material dispersibility, bonding between composite materials (amide linkage), and the surface morphology of the nanocomposite were analyzed with the ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. At pH of 6, 2 g/L of adsorbent and a 25-min contact time resulted in about 88% of turbidity elimination. After the adsorption process, the total suspended solids, total dissolved solids, salinity, biochemical oxygen demand, and chemical oxygen demand of the tannery wastewater were reduced by 55%, 29%, 12%, 58%, and 75%, respectively. The optimum dosage of the nanocomposite with the maximum turbidity removal capacity was 12.62 mg/g. According the adsorption kinetic and isotherm models, the graphene oxide-keratin-chitosan nanocomposite played a key role in the turbidity removal process with chemisorption and electrostatic multilayer adsorption. This study provided methodological and mechanistic insights into the procedures of investigating the removal of turbidity from tannery wastewater with a novel composite material.

Effect of carboxymethyl konjac glucomannan coating on curcumin-loaded multilayered emulsion:stability evaluation

The stability against various environmental stresses of the curcumin-loaded secondary and tertiary emulsions that was emulsified by whey protein isolate(WPI)and coated by chitosan(CHI),carboxymethyl konjac glucomannan(CMKGM),or their combination through layer-by-layer assembly was investigated.Generally,the multilayered emulsions were destabilized in high Na Cl concentrations or medium p H that could interrupt the electrostatic interaction between the three polyelectrolytes or deprotonate CHI,indicating that electrostatic interaction played an important role in the stability of emulsions.Compared with the primary emulsion that was solely stabilized by WPI,extra coating with CHI and CMKGM generally increased the stability of the emulsion against repeated freezing-thawing,improved the retention of curcumin against heating,UV irradiation,and long-term storage,and the effects were more remarkable in the tertiary emulsion with CMKGM locating in the outmost layer.Since CMKGM has shown the colon-targeted delivery potency,the multilayered emulsions assembled by layer-by-layer deposition,especially the tertiary emulsion,could be used as an effective carrier for the targeted delivery of curcumin.

Molecular simulations of charged complex fluids: A review

Molecular simulation plays an increasingly important role in studying the properties of complex fluid systems containing charges,such as ions,piezoelectric materials,ionic liquids,ionic surfactants,polyelectrolytes,zwitterionic materials,nucleic acids,proteins,biomembranes and etc.,where the electrostatic interactions are of special significance.Several methods have been available for treating the electrostatic interactions in explicit and implicit solvent models.Accurate and efficient treatment of such interactions has therefore always been one of the most challenging issues in classical molecular dynamics simulations due to their inhomogeneity and long-range characteristics.Currently,two major challenges remain in the application field of electrostatic interactions in molecular simulations;(i)improving the representation of electrostatic interactions while reducing the computational costs in molecular simulations;(ii)revealing the role of electrostatic interactions in regulating the specific properties of complex fluids.In this review,the calculation methods of electrostatic interactions,including basic principles,applicable conditions,advantages and disadvantages are summarized and compared.Subsequently,the specific role of electrostatic interactions in governing the properties and behaviors of different complex fluids is emphasized and explained.Finally,challenges and perspective on the computational study of charged systems are given.

Polar Phase Formation and Piezoelectricity of PVDF by Hot-pressing under Electrostatic Intermolecular Interactions

Piezoelectric poly(vinylidene fluoride)(PVDF)has received considerable attention due to its ability of interconverting mechanical into electric energies and potential applications in wearable electronics.To achieve piezoelectricity,it is important to simultaneously control the formation of polar phases,crystallinity,and dipole alignments in PVDF-based films.Here we demonstrate that piezoelectricity can be obtained by directly hot-pressing PVDF films sandwiched between chitosan or cellulose films.The electrostatic interactions between PVDF and chitosan or cellulose enabled an exceptional high content of polar phases(β-andγ-phases)up to 90%and a measured piezoelectric charge coefficient d_(33)of up to-30 pC/N.This study provides a simple and low-cost approach for obtaining piezoelectric PVDF films used for sensors,actuators,and energy harvesters.

Bifunctional LiI additive for poly(ethylene oxide)electrolyte with high ionic conductivity and stable interfacial chemistry

The development of polymer-based solid-state batteries is severely limited by the low ionic conductivity of solid polymer electrolyte and the instable interface between polymer electrolyte and Li-metal anode.In this work,lithium iodide(LiI)as a bifunctional additive was introduced into the poly(ethylene oxide)(PEO)-based electrolyte to improve the ionic conductivity and to construct a stable interphase at the Li/PEO interface.I-anions offer a strong electrostatic interaction with hydrogen atoms on PEO chains(HPEO)and forming massive I–H bonds that cross-link PEO chains,decrease crystallinity of PEO,and thus improve Li~+interchain transport.In addition,LiI participates in the formation of an inorganic-rich interphase layer,which decreases the energy barrier of Li+transport across the interface and thus inhibits the growth of lithium dendrites.As a result,the composite PEO electrolyte with 2 wt%LiI(PEO-2 LiI)presents a very high ionic conductivity of 2.1×10^(-4) S cm-1 and a critical current density of 2.0 m A cm^(-2) at 45°C.Li symmetric cell with this PEO-2 LiI electrolyte exhibits a long-term cyclability over 600 h at 0.2 m A cm^(-2).Furthermore,solid-state LiFePO_(4) and LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2) batteries with the PEO-2 LiI electrolyte show an impressive electrochemical performance with outstanding cycling stability and rate capability at 45°C.

Layer-by-layer nanostructured protein loaded nanoparticles: A feasibility study using lysozyme as model protein and chitosan as coating material

Stabilization of proteins in delivery devices and design of appropriate protein carriers are major research issues due to the extreme sensitivity of proteins.Previously,negatively charged nanoparticles,consisting of poly(lactic-co-glycolic acid)(PLGA)and poly(styrene-co-4–styrene-sulfonate)(PSS),showed considerably high loading capacity for positively charged model protein lysozyme depending on the surface charge density of nanoparticles.

Evaluation on performance of MM/PBSA in nucleic acid-protein systems

The molecular mechanics/Poisson-Boltzmann surface area(MM/PBSA) method has been widely used in predicting the binding affinity among ligands,proteins,and nucleic acids.However,the accuracy of the predicted binding energy by the standard MM/PBSA is not always good,especially in highly charged systems.In this work,we take the protein-nucleic acid complexes as an example,and showed that the use of screening electrostatic energy(instead of Coulomb electrostatic energy) in molecular mechanics can greatly improve the performance of MM/PBSA.In particular,the Pearson correlation coefficient of dataset Ⅱ in the modified MM/PBSA(i.e.,screening MM/PBSA) is about 0.52,much better than that(<0.33)in the standard MM/PBSA.Further,we also evaluate the effect of solute dielectric constant and salt concentration on the performance of the screening MM/PBSA.The present study highlights the potential power of the screening MM/PBSA for predicting the binding energy in highly charged bio-systems.

Probing the electrostatic aggregation of nanoparticles with oppositely charged molecular ions

The co-assembly of charged nanoparticles with oppositely charged molecular ions has emerged as a promising technique in the fabrication of nanoparticle superstructures.However,the underlying mechanism behind these molecular ions in mediating the repulsion between these charged nanoparticles remains elusive.Herein,coarsegrained molecular dynamics simulations are used to elucidate the effects of valency,shape,and size of molecular anions on their co-assembly with gold nanoparticles coated with positively charged ligands.The findings suggest that the valency,shape,and size of molecular anions significantly influence the repulsion and aggregating dynamics among these positively charged nanoparticles.Moreover,the free energy calculations reveal that ring-shaped molecular anions with higher valences and larger sizes are more effective at reducing the repulsion between these gold nanoparticles and thus enhance the stability of the aggregate.This study contributes to a better understanding of the critical roles of valence,shape,and size of ions in mediating the electrostatic co-assembly of nanoparticles with oppositely charged ions,and it also guides the future design of DNA templates and DNA origami in co-assembly with oppositely charged nanoparticles.

AB022.Membrane binding properties of the C-terminal segment of retinol dehydrogenase 8

Background:Retinol dehydrogenase 8(RDH8)is a 312-amino acid(aa)protein involved in the visual cycle.Bound to the outer segment disk membranes of photoreceptors,it reduces all-trans-retinal to all-trans-retinol1 as one of the rate-limiting steps of the visual cycle2.RDH8 is a member of the short-chain dehydrogenase/reductase family.Its C-terminal segment allows its membrane-anchoring through the postulated presence of an amphipathicα-helix and of 1 to 3 acyl groups at positions 299,302 and 3043.The secondary structure and membrane binding characteristics of RDH8 and its C-terminal segment have not yet been described.Methods:To evaluate the membrane binding of RDH8,the full-length protein(aa 1-312),a truncated form(aa 1-296),its C-terminal segment(aa 281-312 and 297-312)as well as different additional variants of this segment were used.The truncated protein binds membranes less efficiently than the full-length form.Thus,the C-terminal segment of RDH8 is essential for the binding and has thus been further examined.The intrinsic fluorescence of tryptophan residues at positions 289 and 310 of the wild-type C-terminal segment of RDH8 and the mutants W289F,W310F and W310R have thus been used to determine their extent of binding to lipid vesicles and to monitor their local environment.Unilamellar lipid vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC)or a mixture of POPC and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine(POPS)were used to mimic the phospholipid content of the outer segment disk membranes of photoreceptors.Results:An increase in fluorescence intensity and in fluorescence lifetime is observed upon increasing the concentration of lipid vesicles.These data allowed calculating values of partition coefficient of the C-terminal segment of RDH8 varying between Kp=1.1 E6 to 1.7 E6.It is noteworthy that the observation of a more intense shift to lower wavelengths upon membrane binding of the mutant W310R and W310F indicates a deeper incorporation of the remaining tryptophan residue at position 289 into the lipid bilayer.The secondary structure of the C-terminal segment of RDH8 observed by circular dichroism and infrared spectroscopy shows a superposition ofα-helical,β-turn and unordered structures.Conclusions:The peptides derived from the C-terminal segment of RDH8 show a strong binding to lipid vesicles.These strength of binding is independent of the type of lipid and the presence of a mutation.

Nonlinear Oscillations of a Pair of Charged Rings

Two electrically charged rings of different sizes are assembled along their common vertical symmetry axis through their centers. The bottom ring is secured on a horizontal support while the top one is loose. For a set of practical values characterizing the charged rings we envision a scenario where the mutual electric repulsion between the rings and the weight of the top ring results in stable nonlinear oscillations. To quantify the characteristics of the oscillations, we utilize a Computer Algebra System specifically Mathematica [1]. We accompany the analysis with a simulation for a comprehensive visual understanding.

Electrified Bow and Arrow

We consider an electrostatic bow and arrow both charged positively. The bow is circular and horizontal the massive arrow is vertically aligned with the bow’s symmetry axis with its head up. The arrow is released freely, the electrically charged ring repels the arrow and the gravity slows its uprise. The mass, length, and charge of the arrow as well as the size of the ring and its charge adjusted making the arrow oscillate up and down. The kinematic and dynamic quantities of the oscillations are calculated, and the relevant phase diagrams are depicted. In pursuing these goals, a Computer Algebra System (CAS) specifically Mathematica [1] is used. Among various scenarios, the case of a charged ring and a point charge is discussed.

Vesicle fusion induced by zwitterionic amphiphilic channels

A new strategy to induce vesicle fusion has been developed by employing pillar[5]arene derivatives that were channel-like and were prepared by appending side chains onto pillar[5]arenes backbones.The channels feature with hydrophilic negatively and positively charged groups at both ends and hydrophobic Trp residues at the outer surface,which endows the channels with amphiphilicity.The zwitterionic amphiphilic channels could spontaneously incorporate into the bilayer membranes of lipid vesicles to induce vesicle fusion driven by the electrostatic interactions between negatively charged and positively charged groups.

Recent progress in polymerization-induced self-assembly:From the perspective of driving forces

Polymerization-induced self-assembly(PISA)enables the simultaneous growth and self-assembly of block copolymers in one pot and therefore has developed into a high-efficiency platform for the preparation of polymer assemblies with high concentration and excellent reproducibility.During the past decade,the driving force of PISA has extended from hydrophobic interactions to other supramolecular interactions,which has greatly innovated the design of PISA,enlarged the monomer/solvent toolkit,and endowed the polymer assemblies with intrinsic dynamicity and responsiveness.To unravel the important role of driving forces in the formation of polymeric assemblies,this review summarized the recent development of PISA from the perspective of driving forces.Motivated by this goal,here we give a brief overview of the basic principles of PISA and systematically discuss the various driving forces in the PISA system,including hydrophobic interactions,hydrogen bonding,electrostatic interactions,andπ-πinteractions.Furthermore,PISA systems that are driven and regulated by crystallization or liquid crystalline ordering were also highlighted.

Flame-retardant and Self-healing Biomass Aerogels Based on Electrostatic Assembly

It remains a significant challenge to fabricate self-healing aerogels with excellent flame retardancy.Herein,we develop a class of biomass aerogels by electrostatically assembling chitosan(CS),phytic acid(PA),and itaconic acid(IA).The electrostatic interaction between CS and IA is weak and dynamic,so freeze-drying the solution of CS and IA enables the formation of continuous aerogel skeleton with self-healing ability and re-programmability;in comparison,the electrostatic interaction between CS and PA is strong and less dynamic,and thus mixing PA with CS in aqueous solution leads to fine precipitates of high flame retardancy due to the synergistic phosphorus-nitrogen effect.Integrating the continuous skeleton and the fine precipitates results in self-healing aerogles with UL-4 V-0 rating of flame retardancy aerogels and autoextinguishable feature.Interestingly,the aerogels after burning in flame for 30 s form a skin-core structure,and the carbonized skin protects the integrity of the aerogels and the self-healing ability of the internal parts.Therefore,this work provides a facile strategy to develop multifunctional aerogels which hold great promise for advanced applications.