Stable Morphology Research Articles

Ampicillin-resistant bacterial pathogens targeted chitosan nano-drug delivery system (CS-AMP-P-ZnO) for combinational antibacterial treatment

Drug-resistant microorganisms are defeated using combinational drug delivery systems based on biopolymer chitosan (CS) and metal nanoparticles. Hence, PEGylated zinc oxide nanoparticles (P-ZnO NPs) decorated chitosan-based nanoparticles (CS NPs) were prepared to deliver ampicillin (AMP) for improved antibacterial activity. In comparison to ZnO NPs, P-ZnO NPs exhibit less aggregation and more stable rod morphologies in TEM. The size of the P-ZnO NPs decreased and was engulfed by the spherical CS-AMP NPs. The zeta potential of the CS-AMP-P-ZnO NPs was determined to be −32.93 mV and the hydrodynamic size to be 210.2 d. nm. Further, DEE and DLE of CS-AMP (2.0:0.2 w/w) showed 79.60 ± 2.62 % and 15.14 ± 2.11 %, respectively. The cumulative AMP release was observed at >50 % at 48 h at pH 5.4 and 7.4. Additionally, when compared to AMP, CS-AMP-P-ZnO NPs had better antibacterial activity against E. coli, due to the alternation of cell membrane permeability by CS and ZnO NPs. Moreover, the hemolytic properties of ZnO NPs were attenuated because of PEGylation and CS. Furthermore, due to the biocompatible behavior of CS, CS-AMP-P-ZnO NPs did not exhibit toxicity on HEK-293 cells, erythrocytes, and chick embryos. Hence, this study concludes that CS-AMP-P-ZnO NPs could be a promising antibacterial agent.

In Situ Metal Organic Framework (ZIF-8) and Mechanofusion-Assisted MWCNT Coating of LiFePO4/C Composite Material for Lithium-Ion Batteries

LiFePO4 is one of the industrial, scalable cathode materials in lithium-ion battery production, due to its cost-effectiveness and environmental friendliness. However, the electrochemical performance of LiFePO4 in high current rate operation is still limited, due to its poor ionic- and electron-conductive properties. In this study, a zeolitic imidazolate framework (ZIF-8) and multiwalled carbon nanotubes (MWCNT) modified LiFePO4/C (LFP) composite cathode materials were developed and investigated in detail. The ZIF-8 and MWCNT can be used as ionic- and electron-conductive materials, respectively. The surface modification of LFP by ZIF-8 and MWCNT was carried out through in situ wet chemical and mechanical alloy coating. The as-synthesized materials were scrutinized via various characterization methods, such as XRD, SEM, EDX, etc., to determine the material microstructure, morphology, phase, chemical composition, etc. The uniform and stable spherical morphology of LFP composites was obtained when the ZIF-8 coating was processed by the agitator [A], instead of the magnetic stirrer [MS], condition. It was found that the (optimum of) 2 wt.% ZIF-8@LFP [A]/MWCNT composite cathode material exhibited outstanding improvement in high-rate performance; it maintained the discharge capacities of 125 mAh g−1 at 1C, 110 mAh g−1 at 3C, 103 mAh g−1 at 5C, and 91 mAh g−1 at 10C. Better cycling stability with capacity retention of 75.82% at 1C for 100 cycles, as compared to other electrodes prepared in this study, was also revealed. These excellent results were mainly obtained because of the improvement of lithium-ion transport properties, less polarization effect, and interfacial impedance of the LFP composite cathode materials derived from the synergistic effect of both ZIF-8 and MWCNT coating materials.

Unveiling the Morphological and Physical Mechanism of Burn-in Loss Alleviation by Ternary Matrix Toward Stable and Efficient All-Polymer Solar Cells.

All-polymer solar cells (All-PSCs) are considered the most promising candidate in achieving both efficient and stable organic photovoltaic devices, yet the field has rarely presented an in-depth understanding of corresponding device stability while efficiency is continuously boosted via the innovation of polymer acceptors. Herein, a ternary matrix is built for all-PSCs with optimized morphology, improved film ductility and importantly, boosted efficiency and better operational stability than its parental binary counterparts, as a platform to study the underlying mechanism. The target system PQM-Cl:PTQ10:PY-IT (0.8:0.2:1.2) exhibits an alleviated burn-in loss of morphology and efficiency under light soaking, which supports its promoted device lifetime. The comprehensive characterizations of fresh and light-soaked active layers lead to a clear illustration of opposite morphological and physical degradation direction of PQM-Cl and PTQ10, thus resulting in a delicate balance at the optimal ternary system. Specifically, the enlarging tendency of PQM-Cl and shrinking preference of PTQ10 in terms of phase separation leads to a stable morphology in their mixing phase; the hole transfer kinetics of PQM-Cl:PY-IT host is stabilized by incorporating PTQ10. This work succeeds in reaching a deep insight into all-PSC's stability promotion by a rational ternary design, which booms the prospect of gaining high-performance all-PSCs.

Developing ternary composite phase change materials with two different phase change temperatures for battery thermal management

Paraffin wax (PW), as a phase change material (PCM), with high latent heat, is likely to be used in battery thermal management. However, the application of PW is remarkably limited due to its low thermal conductivity, poor mechanical properties, and easy leakage after melting. Here, we prepared a novel ternary composite phase change material (CPCM) to eliminate melt leakage with high thermal conductivity, stable morphology, and two different phase change temperatures. The step cooling data confirmed that when the proportions of myristic acid (MA), palmitic acid (PA), and PW are 3:1:4, there are two phase transition points at 35.88 ℃ and 46.26 ℃, respectively. The addition of short carbon fiber (SCF) and carbon black (CB) with different particle sizes significantly improved the thermal conductivity of the PCM up to 8.7 W/mK. The addition of silicone rubber (SR) film not only avoids the liquid PCM leakage but also improves its mechanical properties. At the highest discharge rate, the maximum temperature of a large capacity square terpolymer lithium battery is 47.03 ℃ due to excellent thermos conductivity. Furthermore, the ternary CPCM does not melt completely at the end of discharge. Compared with the CPCM with single phase transition temperature, the two different phase transition temperatures have excellent balanced performance. After two phase change temperature controlling processes, the rise of battery surface temperature is effectively delayed, and the working time of the CPCM is prolonged. Hence, the developed CPCM is more suitable for the battery thermal management system (BTMS).

Plant protein-based self-assembling core–shell nanocarrier for effectively controlling plant viruses: Evidence for nanoparticle delivery behavior, plant growth promotion, and plant resistance induction

The excessive use of non-renewable formulations, low utilization efficiency, and eco-unfriendly behavior are serious disadvantages of traditional pesticide formulations. Herein, a scalable and sustainable biopolymer-based core–shell (CS) nanocarrier loaded with an anti-viral candidate agent, Bingqingxiao (BQX), was investigated for plant disease management. Preliminary BQX@PyPHEMA@SWP nanoparticles (BQX@PP@S NPs) were manufactured through the noncovalent self-assembly of pyridine-grafted poly (hydroxyethyl methacrylate) (PyPHEMA) and natural soy whey protein (SWP), and exhibited a stable spherical morphology with a diameter of approximately 130 nm. Notably, encapsulation of BQX into the NPs increased the ultra-violet (UV) resistance of the compound by 8.7-fold, and the nanocarrier PyPHEMA@SWP (PP@S) enhanced the BQX foliar surface wettability, resulting in a slow, urea-responsive release. In vivo studies revealed that the protective activity of BQX@PP@S NPs was 1.4-fold higher than that of BQX against tobacco mosaic virus (TMV), and the antiviral efficiency was further improved by stimulation with 0.2 M urea. Furthermore, foliar application of BQX@PP@S NPs activated host plant defense responses by upregulating the expression of salicylic acid (SA)- and abscisic acid (ABA)-related genes. Interestingly, the developed BQX@PP@S NPs act as plant nutrition to enhance the crop fresh and dry weight by 24.7% and 19.9%, respectively. Consequently, PP@S is a promising biocompatible carrier that can enhance the potency of various pesticides, synergistically improve plant disease resistance, and simultaneously act as a fertilizer for crop growth.

Microglial morphology in the somatosensory cortex across lifespan. A quantitative study.

Microglia are long-lived cells that constantly monitor their microenvironment. To accomplish this task, they constantly change their morphology both in the short and long term under physiological conditions. This makes the process of quantifying physiological microglial morphology difficult. By using a semi-manual and a semi-automatic method to assess fine changes in cortical microglia morphology, we were able to quantify microglia changes in number, surveillance and branch tree starting from the fifth postnatal day to 2 years of life. We were able to identify a fluctuating behavior of most analyzed parameters characterized by a rapid cellular maturation, followed by a long period of relative stable morphology during the adult life with a final convergence to an aged phenotype. Detailed cellular arborization analysis revealed age-induced differences in microglia morphology, with mean branch length and the number of terminal processes changing constantly over time. Our study provides insight into microglia morphology changes across lifespan under physiological conditions. We were able to highlight, that due to the dynamic nature of microglia several morphological parameters are needed to establish the physiological state of these cells.

Lifetime over 10000 hours for organic solar cells with Ir/IrOx electron-transporting layer

The stability of organic solar cells is a key issue to promote practical applications. Herein, we demonstrate that the device performance of organic solar cells is enhanced by an Ir/IrOx electron-transporting layer, benefiting from its suitable work function and heterogeneous distribution of surface energy in nanoscale. Notably, the champion Ir/IrOx-based devices exhibit superior stabilities under shelf storing (T80 = 56696 h), thermal aging (T70 = 13920 h), and maximum power point tracking (T80 = 1058 h), compared to the ZnO-based devices. It can be attributed to the stable morphology of photoactive layer resulting from the optimized molecular distribution of the donor and acceptor and the absence of photocatalysis in the Ir/IrOx-based devices, which helps to maintain the improved charge extraction and inhibited charge recombination in the aged devices. This work provides a reliable and efficient electron-transporting material toward stable organic solar cells.

POLY(Amidoamine) Dendrimer-Induced 3D Crosslinked Network Binder For LiFePO4 Cathode: Endowing Battery With Superior Cycling Stability

The electronic and ionic conductivity inside electrode play a decision role in cell performance of lithium-ion batteries (LIBs). However, traditional polymer binder connecting the conductive network for active material often tends to lose its original structure and function after the immersion of electrolyte. This will make the conductive network collapse, thus affecting charge/discharge capacity and cycle stability of LIBs. Therefore, in this paper, Poly(amidoamine) (PAMAM) induced three-dimensional (3D) crosslinked polymer was designed and applied as binder for LIBs cathode. Compared with conventional linear Polyvinylidene fluoride (PVDF) binder, the 3D binder exhibits better bonding ability and electrolyte affinity, which respectively bring superior electronic and ionic conductivity for LiFePO4 cathode. So that the slighter polarization and better C-rate capability (140 mAh g−1 in 2C discharge) are achieved. In addition, the crosslinked network constructed in binder provides smooth and stable surficial morphology for electrode through stronger own strength and adhesion with substrate (average 7.69 N), which finally leads to improved cycling performance (98% retention after 250 cycles). Clearly, this 3D crosslinked polymer will bring new breakthrough for binder during the development of higher power LIBs.

Effect of donor groups on the photovoltaic performance of benzothiadiazole-core substituted small molecules for fullerene-based bulk heterojunction organic solar cells

Herein, two symmetric donor-π-acceptor-π-donor-type π-conjugated small molecule donors (BTM and BTP), based on a benzothiadiazole central acceptor core unit and end-capped with electron-donating triphenylamine and 3,5-dimethoxyphenyl)vinyl, are synthesized via a multistep coupling reaction. The structural, thermal, optical, and electrochemical properties of the small molecules are systematically analyzed; subsequently, the molecules are applied as electron donor materials for bulk heterojunction organic solar cell fabrication. Compared with BTM, BTP exhibits a strong absorption spectrum with a precisely tuned optical bandgap (approximately 1.87 eV), desired morphology, and improved interfacial properties. The solar devices fabricated with BTP:PC71BM (1:2.5, w/w) exhibit a higher power conversion efficiency (PCE) of approximately 7.08% with an enhanced current density (JSC) of approximately 12.90 mA/cm2, high open-circuit voltage (VOC) of approximately 0.989 V, and fill factor (FF) of approximately 55.5% compared with BTM-based devices (approximately 4.86%). Notably, the high VOC achieved for the BTP:PC71BM (1:2.5, w/w) devices is a result of the deep-lying HOMO energy level and low LUMO energy offset (approximately 0.51 eV) between the BTP donor and PC71BM acceptor. The high hydrophobicity and stable surface morphology of BTP:PC71BM (1:2.5, w/w) exhibits a high room temperature stability approximately > 94% and retain 6.70% of PCE of its original PCE (7.08%) after 288 hr.

Length‐Controlled Construction of Ceria Nanowires with Ultrafine Diameter and Stable Morphology for Targeted Acute Lung Injury Therapy

AbstractThe overproduction of reactive oxygen species (ROS) is one of the major reasons for the aggravation of acute lung injury (ALI). Smaller‐sized ceria nanoparticles featured with higher ROS scavenging capability than their bigger‐sized counterparts are potential candidates for ALI therapy. However, smaller‐sized ceria nanoparticles are more easily accumulated in spleen and liver rather than lung. Herein, it is reported that this obstacle can be addressed by constructing ceria into ultrafine nanowires, through which the ultrafine diameter ensures the high ROS scavenging activity and the high aspect ratio promotes the lung targeted accumulation. To demonstrate the feasibility of this conception, a platform is developed to realize length‐controlled ceria nanowires (diameter of ≈1.5 nm) synthesis. These nanowires are PEGylated using a carefully optimized procedure that can preserve their fragile crystal structures. The PEGylated nanowires exhibit higher ROS scavenging capabilities than the ≈3.9 nm sized nanoparticles. Most importantly, lung targeted accumulation can be realized through modulating the length of the nanowires, where the longer nanowires (>100 nm) show much higher lung accumulation. Due to these properties, the longer ceria nanowires can effectively scavenge the overproduced ROS during the progression of ALI, and thereby inhibit the edema and inflammation in the lung tissue.

Transforming vulcanized styrene–butadiene waste into valuable raw material: an opportunity for high-impact polypropylene production

Polypropylene (PP) compounds with styrene–butadiene rubber residue (SBRr) from the footwear industry were produced, adding styrene-(ethylene–butylene)-styrene (SEBS) as a compatibilizer, with 20% and 30% of styrene (St.). The PP/SBRr and PP/SBRr/SEBS compounds were processed in a co-rotating twin-screw extruder and injection molded. The addition of 30% SBRr did not compromise processability, as torque and melt flow index increased slightly compared to neat PP. Significant increases in impact strength were achieved for PP/SBRr/SEBS (10–20% St.) and PP/SBRr/SEBS (10–30% St.), with gains of 316% and 248% related to PP. The elastic modulus, tensile strength, elongation at break, and Shore D hardness indicated greater flexibility for the PP/SBRr/SEBS, especially in the copolymer with 20% St. When the PP/SBRr system was made compatible with SEBS (30% St.), the elastic modulus, tensile strength, and Shore D hardness increased in relation to the PP/SBRr/SEBS (20% St.). Such behavior suggested that the SEBS copolymer (30% St.) was more effective in increasing the resistance to elastic deformation of the PP/SBRr/SEBS compounds, compared to SEBS (20% St.). The heat deflection temperature (HDT) indicated that even adding high content of SBRr to PP, the HDT was not severely affected, possibly due to its crosslinked character. PP/SBRr compatibilization with SEBS (20% St.) inhibited the PP crystalline peaks, as verified through X-ray diffraction (XRD). Stable morphology was achieved upon 10% of SEBS addition to PP/SBRr, providing proper interfacial adhesion and fine particles, contributing to toughening PP. Acquired results are promising for rubber recycling, aiming to produce high-impact polypropylene for containers and furniture accessories applications.Graphic abstract

Development of a composite hydrogel incorporating anti-inflammatory and osteoinductive nanoparticles for effective bone regeneration

BackgroundBone tissue regeneration is regulated by complex events, including inflammation, osteoinduction, and remodeling. Therefore, to induce the complete restoration of defective bone tissue, biomaterials with the ability to regulate the collective bone regenerative system are beneficial. Although some studies conclude that reducing reactive oxygen species created a favorable environment for bone regeneration by controlling inflammation, biomaterials that can simultaneously promote osteogenesis and regulate inflammation have not been developed. Herein, we describe the development of a multi-functional nanoparticle and its hydrogel composite with osteoinductive, anti-inflammatory, and osteoclast-maturation regulatory functions for enhanced bone regeneration.MethodsTannic acid–mineral nanoparticles (TMP) were prepared by self-assembly of tannic acid in an ion-rich simulated body fluid containing Ca2+ and PO43-. Particles with a diameter of 443 ± 91 nm were selected for their stable spherical morphology and minimal tendency to aggregate. The particles were homogeneously embedded within a gelatin-based cryogel (TMP/Gel) to be used in further experiments. The osteoinductive properties, anti-inflammatory and osteoclast-maturation regulatory functions in vitro were tested by culturing corresponding cells on either TMP/Gel or a gelatin-based cryogel without the particles (Gel). For in vivo analyses, a murine calvarial defect model was used. Statistical analyses were carried out using a Graphpad Prism 7 software (San Diego, CA, USA) to perform one-way analysis of variance ANOVA with Tukey’s honest significant difference test and a Student’s t-test (for two variables) (P < 0.05).ResultsExcellent biocompatibility and radical scavenging abilities were exhibited by the TMP/Gel. The expression of osteogenic mRNA is significantly increased in human adipose-derived stem cells seeded on the TMP/Gel compared to those without the particles. Furthermore, RAW264.7 cells seeded on the TMP/Gel displayed significantly lower-than-normal levels of pro-inflammatory and osteoclastogenic genes. Finally, the in vivo results indicated that, compared with the cryogel with no anti-inflammatory effect, the TMP/Gel significantly enhanced both the quality and quantity of newly formed bone, demonstrating the importance of combining anti-inflammation with osteoinduction.ConclusionCollectively, these findings suggest our nanoparticle-hydrogel composite could be an effective tool to regulate complex events within the bone healing process.Graphical

Polymer-Assisted Compressed Flux Growth: A Universal and High-Yield Method for Dimension-Controlled Single Crystals.

Single crystals possess the most perfect and stable morphology and represent the intrinsic and upper limits of performance when integrated into various application scenarios. However, for a large portion of the newly emerging low-dimensional and molecular materials, the mass production of crystals with a desirable shape is still challenging. Here, a universal and high-yield method to grow functional single crystals with controlled dimensions is provided that can be directly integrated into a device. By utilizing a polymeric flux in combination with a compressed growth space, numerous materials can be grown into size-controllable single crystalline flakes, with millions produced in one batch. This scalable growth method shows promise for the large-scale integration of micro-single-crystals as functional components, as exemplified by the construction of a 5 in. field-effect transistor array.

The establishment of Boron nitride@sodium alginate foam/polyethyleneglycol composite phase change materials with high thermal conductivity, shape stability, and reusability

Adopting organic phase change materials (PCMs) for the management of electronic devices is restricted by low thermal conductivity. In this paper, the composite PCMs are established by freeze-drying and vacuum impregnation. Herein, polyethylene glycol (PEG) is induced as heat storage materials, Boron nitride (BN) is embedded as filler stacking in an orderly fashion on the foam walls to improve thermal conductivity and sodium alginate (SA) is formed as supporting material to keep the shape of the composite stable. X-ray diffractometry, scanning electron microscopy-energy dispersive spectrometer, thermal gravimetric analysis, thermal conductivity meter, differential scanning calorimeter, and Fourier transform infrared were used to characterize the samples and thermal cycles were employed to measure the shape stability. The results exhibit the BN@SA/PEG composite PCMs have good chemical compatibility, stable morphology, and thermal stability. Due to the high porosity of foam, PEG endows the composite PCMs with high latent heat (149.11 and 141.59 J∙g –1 ). Simultaneously, BN@SA/PEG shows an excellent heat performance with high thermal conductivity (0.99 W∙m –1 ∙K –1 ), reusability, and shape stability, contributing the composite PCMs to application in the energy storage field. This study provides a strategy to manufacture flexible, long-serving, and shape-stable PCMs via introducing BN@SA foam as a storage framework, and these PCMs have great potential in thermal management in the electronic field.

Long term culturing of CHO cells: phenotypic drift and quality attributes of the expressed monoclonal antibody

Establishing cell lines with enhanced protein production requires a deep understanding of the cellular dynamics and cell line stability. The aim of the study is to investigate the impact of long term culturing (LTC) on cell morphology and altered cellular functions possibly leading to phenotypic drift, impacting product yield and quality. Study highlights the orthogonal cellular and analytical assay toolbox to define cell line stability for optimal culture performance and product quality. We investigated recombinant monoclonal antibody (mAb) expressing CHO cells for 60 passages or 180 generations and assessed the cell growth characteristics and morphology by confocal and scanning electron microscopy. Quality attributes of expressed mAb is accessed by performing charge variants, glycan, and host cell protein analysis. We observed a 1.65-fold increase in viable cell population and 1.3-fold increase in cell specific growth rate. A 2.5-fold decrease in antibody titer and abatement of actin filament indicate cellular phenotypic drift. Mitochondrial membrane potential (∆ΨM) signified cell health and metabolic activity during LTC. Host cell protein production is reduced by 1.8-fold. Charge heterogeneity was perturbed with 12.5% and 43% reduction in abundance of acidic and basic charge variants respectively. Glycan profile indicated a decline in fucosylation with 17% increase in galactosylated species as compared with early passaged cells. LTC impinges on cellular phenotype as well as the quality of the expressed antibody, suggesting a defined subculturing limit to retain stable protein expression and cell morphology to achieve consistent product quality. Study signifies the changes in cellular and metabolic markers, suggesting cellular and analytical toolbox which could play a significant role in defining cell characteristics and ensured product quality.

Corrosion Induced Morphology Evolution in Stressed Solids

Corrosion morphology is a key factor that influences the reliability and service life of a structure. As most structures service under stress corrosion, there is a great need to understand the effect of stress on the formation conditions of different morphologies. This paper introduces a numerical method to simulate the evolution of surface morphologies. The results indicate that a corroded surface will become rougher and sharper with an increase in stress, and as a consequence, the corrosion morphology will transfer from a flatter surface to a pit and then a crevice. The critical stress values for different morphologies (crevice, pit, and a flatter surface) were captured. Among the three morphologies, the flatter surface and pit maintain a fixed shape, also known as stable morphology. As stress exceeds a critical value, crevices are generated, and the morphology evolution becomes unstable. On the basis of the simulation results, the influence of morphology on the service life of the structure was evaluated. The corrosion velocity of a rough surface exceeds that of a flat surface, and this reduces the service life of the structure more significantly. With a rise in applied stress, the acceleration of corrosion presents a quadratically increasing relationship with applied stress.

Fabrication of three-dimensional printed hybrid graphene oxide/calcium alginate network by 3D printing technology with outstanding U(VI) recycling capacity in acidic solution

In this study, a 3D-printed graphene oxide (GO)/calcium alginate (CA) hybrid network (3D GO/CA) with excellent U(VI) adsorption performance was constructed using direct ink writing-based 3D printing technology and in situ calcium ion cross-linking technology. The GO and CA sheets in 3D GO/CA were stacked layer by layer. Meanwhile, the 3D multilayered pore structure with large-scale characteristics was constructed. Furthermore, the pore structure was orderly arranged, with abundant active adsorption sites (oxygen-containing functional groups/Ca2+ binding sites) exposed. The adsorption experiment results showed that 3D GO/CA exhibited a wide valid pH range (3–12) and excellent adsorption capacity for U(VI) in a strongly acidic solution (for example, at pH = 2.8, the adsorption capacity is 200.1 mg/g). In addition, 3D GO/CA exhibited high adsorption kinetic reaction rate (adsorption equilibrium could be reached within 30 min). In the simulated acidic wastewater (pH = 2.8), 3D GO/CA exhibited an excellent adsorption capacity of UO22+ and an adsorption ratio of approximately 99.7 %. The 3D GO/CA retained its original stable structure morphology after it was reused eight times. In addition, the stable structure of 3D GO/CA was retained after it was soaked in the strong acid solution at different concentrations (1.59 × 10−3–2 mol/L) for 48 h. With the aid of 3D printing technology and Ca2+ cross-linking technology, the structure of 3D GO/CA was optimized, and more oxygen-containing functional groups were retained at the edge of the GO sheet. Therefore, 3D GO/CA has a promising application prospect for removing and recovering U(VI) in acidic solutions.

EVAPORATION HEAT TRANSFER OF SINGLE HYDROUS ETHANOL DROPLET IMPACTING ON A HEATED WALL

The phenomenon of droplet impact on heated wall along with its evaporation is encountered in a variety of scenarios in industrial production. The present work aims to experimentally study the evaporation heat transfer of single hydrous ethanol droplet impact on a heated wall at saturation temperature under lower velocity. Its dynamic evolution after the impact, along with the stable adhesion morphology, was studied at different wall temperatures. The characteristics of its heat transfer and evaporation were analyzed by focusing on the effects of wall temperature, ethanol concentration, and adhesion morphology. The results show that the wall temperature has little effect on the spreading time, but significant on the spreading area and retraction. The "pining effect" of the hydrous ethanol weakens with the ethanol concentration, until it completely disappears. The film thickness along with its contact angle in adhesion evaporation shows a linear decrease accompanied by oscillations at the later stage. Evaporation heat transfer rate gradually increases with the wall temperature and ethanol concentration, and shows a multiple power function with them. The saturation temperature in evaporation gradually increases with the wall temperature, while the ethanol concentration has a minor effect. The average heat flux in evaporation can reach the magnitude of 10E5, and increases with the wall temperature and ethanol concentration.

Study on ZnO quantum dot ligands for inkjet printing of light-emitting diodes

Inkjet printing as a contact-free, high material utilization, low cost, patternable solution processing technology, may become the future color quantum-dot light-emitting diodes (QLED) production of the key technology. However, owing to the existence of the pixel structure of the substrate array, the film prepared by inkjet printing technology is not so smooth and uniform as that by spin coating technology, which affects the luminescence performance of the device. Therefore, it is necessary to study the film forming mechanism and process of inkjet printing. In order to solve the above problems, this paper focuses on the material and process problems of preparing high-quality electronic transport layer ZnO thin films by inkjet printing. From the perspective of ligand, the ZnO quantum dot material, which is an indispensable electron transport layer, is optimized to prepare the thin films with good morphology and stability in air, and the methods to improve the performances of inkjet printing QLED devices are explored. Firstly, the drying process and influence mechanism of ZnO quantum dot ink in air are investigated. As the thickness of ZnO quantum dot film prepared by inkjet printing increases, the film becomes loose and the surface becomes rough with the continuous extension of the time in the air. These changes make the efficiency of the QLED device decrease and the luminous region uneven. The reason for this phenomenon is that after the ZnO quantum dots are printed into the pixel pit, the random Brownian motion of quantum dots will continue in the process of solvent evaporation. In this process, the ligand ethanolamine connected to the surface of ZnO quantum dots will fall off with the movement and cannot play the role in dispersing the quantum dots. Besides, the external water oxygen and carbon dioxide attach to the film. The combination between the two effects makes the ZnO quantum dots aggregate into large particles and the film becomes loose and porous. In this paper, we use ethylenediamine tetraacetic acid (EDTA) as ligand to synthesize ZnO quantum dots, which can effectively improve this phenomenon. The carboxyl group at the end of EDTA is more stable in connection with ZnO quantum dots. Moreover, the EDTA has multiple branch chains, which makes it have steric hindrance effect and can disperse ZnO effectively. A smooth and compact film with a roughness of 1.97 nm is prepared by inkjet printing. After 40 min exposure to air, the film is still able to maintain a stable morphology. Then, based on the EDTA-ZnO quantum dots synthesized above, red QLED devices with optimized performance are prepared. The current efficiency of the spin-coating device is 16.8 cd/A, which is better than that of the ZnO quantum dots before modification. The EDTA ligand passivates the surface defects of ZnO, alleviates the quenching phenomenon when contacting red quantum dots, and improves the fluorescence quantum efficiency and transient fluorescence lifetime of quantum dots on the electron transport layer. In addition, the EDTA regulates the carrier transport performance, making the carrier recombination of the device more balanced. In the inkjet printing device, the improvement of device morphology plays a leading role in improving the performance. The inkjet printing QLED based on EDTA-ZnO achieves a current efficiency of 9.24 cd/A, and maintains a current efficiency of 6.82 cd/A after 40 min in air, which are 23% and 89% higher than those of the control device. This work provides a reference for solving the problems of film thickness increase and morphology variation caused by particle agglomeration in the preparation of large area devices in inkjet printing.

Reversible transformation of peptide assembly between densified-polysarcosine-driven kinetically and helix-orientation-driven thermodynamically stable morphologies.

Stimuli-responsive transformable biomaterials development can be manipulated practically by fine-tuning the built-in molecular design of their structural segments. Here, we demonstrate a peptide assembly by the bola-type amphiphilic polypeptide, glycolic acid-polysarcosine (PSar)13-b-(L-Leu-Aib)6-b-PSar13-glycolic acid (S13L12S13), which shows morphological transformations between hydrophilic chain-driven and hydrophobic unit-driven morphologies. The hydrophobic α-helical unit (L-Leu-Aib)6 precisely controls packing in the hydrophobic layer of the assembly and induces tubule formation. The densified, hydrophilic PSar chain on the assembly surface becomes slightly more hydrophobic as the temperature increases above 70 °C, starting to disturb the helix-helix interaction-driven formation of tubules. As a result, the S13L12S13 peptide assembly undergoes a reversible vesicle-nanotube transformation following a time course at room temperature and a heat treatment above 80 °C. Using membrane fluidity analysis with DPH and TMA-DPH and evaluating the environment surrounding the PSar side chain with NMR, we clarify that the vesicle was in a kinetically stable state driven by the dehydrated PSar chain, while the nanotube was in a thermodynamically stable state.