Good Retention Rate Research Articles

Chitosan nanoparticles loaded with clove essential oil: Characterization, antioxidant and antibacterial activities

One of the recent trends in the food industry is application of natural antioxidant/antimicrobial agents. In this study, essential oil of clove buds was extracted and encapsulated in chitosan nanoparticles using a two-step technique of emulsion-ionic gelation. A good retention rate (55.8–73.4 %) of clove essential oil (CEO) loaded in chitosan nanoparticles was confirmed. Also, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses revealed the success of CEO encapsulation. Scanning electron microscopy (SEM) images illustrated regular distribution and spherical shape of nanoparticles with a size range of 223−444 nm. The antioxidant activity of CEO-loaded chitosan nanoparticles was higher than free CEO. Similarly, CEO-loaded chitosan nanoparticles had a high antibacterial activity against L. monocytogenes and S. aureus (inhibition halo diameter of 4.80–4.78 cm). This technique could improve the efficiency of CEO in food products and a delivery system for novel applications such as active packaging.

Preparation of Porous Carbon Nanofibers with Tailored Porosity for Electrochemical Capacitor Electrodes.

Porous carbon electrodes that accumulate charges at the electrode/electrolyte interface have been extensively investigated for use as electrochemical capacitor (EC) electrodes because of their great attributes for driving high-performance energy storage. Here, we report porous carbon nanofibers (p-CNFs) for EC electrodes made by the formation of a composite of monodisperse silica nanoparticles and polyacrylonitrile (PAN), oxidation/carbonization of the composite, and then silica etching. The pore features are controlled by changing the weight ratio of PAN to silica nanoparticles. The electrochemical performances of p-CNF as an electrode are estimated by measuring cyclic voltammetry and galvanostatic charge/discharge. Particularly, the p-CNF electrode shows exceptional areal capacitance (13 mF cm−2 at a current of 0.5 mA cm−2), good rate-retention capability (~98% retention of low-current capacitance), and long-term cycle stability for at least 5000 charge/discharge cycles. Based on the results, we believe that this electrode has potential for use as high-performance EC electrodes.

Sulfur source-inspired synthesis of β-NiS with high specific capacity and tunable morphologies for hybrid supercapacitor

A novel β-NiS active material with tunable morphologies is synthesized through a facile one-step hydrothermal approach by choosing a special substance 2-mercaptopropionic acid as sulfur source. It is found that the introduced sulfur source has a great influence on phase structure and morphology of nickel sulfides. Benefiting from the selection of an excellent sulfur source, pure β-NiS was obtained and the morphology modification from microsphere to microflower and then to urchin-like structure was successfully achieved. More remarkably, the products at all morphologies indicate excellent energy storage capability, among which a highest specific capacity of 313.1 mAh g−1 is attained. In addition, the fabricated asymmetric supercapacitor indicates an attractive energy density of 49 W h kg−1 at a power density of 399 kW kg−1 and a good capacitance retention rate of 98 % after 5000 cycles. Our work opens another avenue for phase-controlled synthesis of pure nickel sulfide with tunable morphologies for various applications.

Nanostructure-modified in-situ synthesis of nitrogen-doped porous carbon microspheres (NPCM) loaded with FeTe2 nanocrystals and NPCM as superior anodes to construct high-performance lithium-ion capacitors

Lithium-ion capacitors (LICs) are the new generation of hybrid energy storage devices because they combine the advantages of both lithium-ion batteries and supercapacitors. This paper reports a three-dimensional N-doped porous carbon microspheres (NPCM) prepared from polymers with aromatic skeletons, and in-situ growth of FeTe2 nanocrystals in carbon microspheres to form 3D network nano-hybrid FeTe2@NPCM-2 composite. This porous microsphere structure facilitates the provision of sufficient room to buffer the large volume expansion effects of the FeTe2 cycle, the unique carbon matrix NPCM has numerous active sites, excellent electrical conductivity and stable tap density. Simultaneously, using biomass mung-bean shells as precursor to prepare hierarchical porous carbon (HPC) as cathode material of LIC, it exhibits a huge specific surface area (SSA) (2103.31 m2 g−1), abundant micro-mesopores and possible oxygen-containing functional groups. The constructed LIC FeTe2@NPCM-2//HPC and NPCM//HPC have ultrahigh energy density (228.29 and 192.96 W h kg−1) and superior power density (10 and 10 kW kg−1) and good cycle retention rate. Hence, we hope that lithium-ion capacitors with transition metal tellurides as anodes have broad application prospects in the fields of new energy 3C electronic products and hybrid vehicles.

Facile preparation of porous carbons derived from orange peel via basic copper carbonate activation for supercapacitors

A facile activation method has been illustrated for the synthesis of porous carbons derived from orange peels using basic copper carbonate as activation agent. The resulting carbon material possesses a high specific surface area of 912.4 m2 g−1, hierarchical pore architecture with interconnected meso-/macropores, and a rich amount of nitrogen, oxygen and sulfur heteroatoms. Benefiting from to its unique pore structure and the co-existence of redox-active nitrogen, oxygen and sulfur functionalities, the obtained porous carbon shows outstanding electrochemical performance when used as electrode material for supercapacitors. The as-prepared porous carbon exhibits a high specific capacitance of 375.7 F g−1 at 1 A g−1 and good rate retention of 50.9% from 1 to 100 A g−1. Additionally, the assembled carbon-based symmetric supercapacitor delivers a high energy density of 31.3 W h kg−1 at a power density of 499.5 W kg−1 in 1.0 M Na2SO4 electrolyte as well as superior long-term cyclic stability (only 7.3% of capacitance loss after 50,000 cycles within a voltage window of 0–2.0 V). This work provides an easy and feasible way for the synthesis of hierarchical porous carbon materials with both high power and energy density.

Preparation and Properties of Flame Retardant ABS/POK Alloy

<i>Background</i> ABS material has excellent mechanical properties, but its solvent resistance is poor. Acid solvents are prone to cracking, which will affect the normal use of the product. Technical research is needed to improve this performance defect and solve the technical bottleneck of poor solvent resistance of ABS material, so as to meet the technical demand of energy and other fields and improve the market application field of ABS material. <i>Subject</i> Using ABS and POK resin alloy as matrix resin, a high performance flame retardant ABS alloy material was prepared by developing a high efficiency flame retardant system of brominated antimony. <i>Methods</i> The mechanical properties, crystallization behavior, wear resistance, solvent resistance and heat resistance of the alloy materials were characterized by Fourier infrared spectroscopy, differential scanning calorimeter, universal testing machine, scanning electron microscope and friction tester. <i>Result</i> ABS has a good compatibility with POK, and the alloy material containing 20% POK has excellent mechanical properties and heat resistance, good ice acetic acid resistance and excellent solvent resistance. Through the DSC curve of the alloy material, the relationship between the melting peak area and the content of POK resin was obtained. POK resin can significantly improve the wear resistance of ABS and has a good glossiness retention rate.

Comparing experiential versus conventional learning on knowledge retention for teaching surgery to medical graduates

BackgroundThe study aims to evaluate and see if experiential learning theory for teaching cataract surgery can improve the ability of students to retain more knowledge compared to the classical or traditional way of teaching. MethodsA pre and post control group design of 32 graduates at --------------------------------------, Riyadh, Saudi Arabia was conducted. The total of graduates including males and females were divided into control and experimental groups to which the educational materials about cataract surgery were presented as a lecture and as wet lab session respectively. All the data collected were entered in SPSS version 22 for analysis and a p ≤ 0.05 was considered significant. This study was approved by the Institutional Review Board, ---------------------------------------, Riyadh, KSA. Also a written consent form was obtained from all participants. Data were secured and participants received a number to secure their identity.The study was done during the academic year 2016 to examine the effect of experiential learning as an applicable way for teaching cataract surgery. ResultsBoth control and experimental groups showed good retention rate of knowledge. However, the gain of knowledge was more in the Wet lab group. The scores mean increased more than 5 points in this group compared to 2.5 points only in the lecture groups. ConclusionBoth teaching modalities were effective in improving the knowledge rate of the students. However, in the experiential learning group (Wet lab group), the gain of knowledge was higher compared to that in the traditional group (lecture group).

Comparing experiential versus conventional learning on knowledge retention for teaching surgery to medical graduates.

PURPOSE:The study aims to evaluate and see if experiential learning theory for teaching cataract surgery can improve the ability of students to retain more knowledge compared to the classical or traditional way of teaching.METHODS:A pre and post control group design of 32 graduates was conducted in 2016 at King Saud University, Riyadh, Saudi Arabia to examine the effect of experiential learning as an applicable way for teaching cataract surgery. The total of graduates including males and females were divided into control and experimental groups to which the educational materials about cataract surgery were presented as a lecture and as wet lab session respectively. All the data collected were entered in SPSS version 22 for analysis and a P ≤ 0.05 was considered significant.RESULTS:Both control and experimental groups showed good retention rate of knowledge. However, the gain of knowledge was more in the Wet lab group. The scores mean increased more than 5 points in this group compared to 2.5 points only in the lecture groups.CONCLUSION:Both teaching modalities were effective in improving the knowledge rate of the students. However, in the experiential learning group (Wet lab group), the gain of knowledge was higher compared to that in the traditional group (lecture group).

Construction of K-doped mixed-phase TiO2 nanowires@MoS2 nanosheets core-shell structure for researching on supercapacitors

To enhance the specific capacitance of titanium-based supercapacitor, a novel binder-free titanium supported electrode material is first assembled with K-doped mixed-phase (anatase and rutile) TiO2 nanowires coated by MoS2 nanosheets (K-TNW@MNs). The K-TNW@MNs core-shell structure is prepared by chitosan-assisted hydrothermal reaction. The soft template of chitosan is chosen to grow MNs uniformly on K-TNW and reduce the agglomeration of MNs. K-TNW backbone structure provides a large surface area for attaching and anchoring the MoS2 nanosheets. As a result, The K-TNW@MNs exhibits a high specific capacitance of 123.53 mF cm−2 at 0.4 mA cm−2, desirable rate capability, and outstanding cycling stability of 84.49% capacitance retention over 6000 cycles. A novel all-solid-state symmetrical supercapacitor assembled with two pieces of K-TNW@MNs electrodes and KCl/polyvinyl alcohol gel electrolyte exhibits a good capacitance retention rate of 78.44% after 6000 cycles. The researches offer a novel strategy to reduce the agglomeration of MoS2 nanosheets on TiO2 nanowires by chitosan-assisted.

Development of a novel cross-axis countercurrent chromatographic instrument with six separation columns: Design, dynamics, optimization, prototyping, and experiment.

This paper presents the development of a novel cross-axis countercurrent chromatographic instrument (CCCI) with six separation columns, including design, dynamics, optimization, prototype construction, and experimental validation. The conceptual design and the structural design of the cross-axis CCCI are performed while considering the requirements for the separation operation and design. The dynamic analysis is carried out in order to guarantee the local balance and the global balance for the CCCI. The relationship between the mechanical structure parameters and partition efficiency is investigated by analyzing the effect of mechanical structure parameters on the centrifugal force field. By virtue of the modal analysis of the mechanical structure, the critical speed and the weak link of the CCCI are achieved. Aiming at the problem of the weak link, the structural optimization is done. The presented CCCI has six separation columns distributed around the central revolution axis, and it has more separation columns than that of the existing chromatographic instrument. The CCCI has an axial symmetry structure in the three-dimensional space. Thus it can have better dynamics stability than the CCCI having less separation columns with a symmetry structure in the plane. A physical prototype is built, and then the partition efficiency and its effect factors are tested by the single experimental variable method. The results show that the CCCI runs smoothly and has a good retention rate of stationary phase. It is also proved that the developed CCCI has a good partition efficiency on bovine serum albumin and lysozyme.

SrLi2Ti6O14@AlF3 composite as high performance anode materials for lithium ion battery application

Titanate anode materials are usually considered as zero strain materials because of the very small volume change during cycling. SrLi2Ti6O14, one material of this family with a low potential plateau, is a promising candidate. In this work, a pure phase SrLi2Ti6O14 was successfully synthesized by a simple sol-gel method. To further improve the overall performance of this material, different amount of AlF3 was coated on its surface. Relying on different techniques, the structural details of SrLi2Ti6O14@AlF3 were revealed. The electrochemical tests showed that SLTO@AF0, SLTO@AF3, SLTO@AF5, and SLTO@AF8 samples can deliver a reversible capacity of about 193.3, 246.1, 280.9, and 223.7 mA h g−1 at 0.05 A g−1, which decrease to 74.2, 143.3, 155.7 and 107.6 mA h g−1 at the rate of 2.62 A g−1. Furthermore, the rate capability and cycling stability of the coated samples are all improved obviously. The SLTO@AF5 sample exhibit the best performance, and it shows a high specific capacity (>100 mA h g−1) and a good retention rate (45.2%) after 2000 cycles at an ultrahigh current density of 5.24 A g−1. Our experiments confirmed that AlF3 coating is an effective method to boost the electrochemical performance of SrLi2Ti6O14, which also provides some hints for the optimization of the titaniate-based materials.

Monodisperse starburst carbon spheres-intercalated graphene nanohybrid papers for supercapacitor electrodes

Here we report a nanohybrid of reduced graphene oxide (rGO) nanosheets at which monodispersed starburst carbon spheres (MSCSs) are intercalated for the use in high-performance supercapacitor electrodes. MSCSs that have large electrolyte ions-accessible surface area enlarge the interspacing between rGO nanosheets as a result of intercalation so that a hybrid electrode can increasingly form electrical double layers that store energy. Such electrode organization provides facilitated transport paths for both electron and ion. The volumetric capacitance of the hybrid electrode is 25 F cm−3 that is obtained at a constant current of 0.073 A cm−3, at least 2.5-fold greater than that of rGO electrode. The hybrid electrode also shows a good rate-retention capability of 81% as specific currents change from 0.073 to 1.5 A cm−3. The initial capacitance of the hybrid electrode remains unchanged, nearly 100% for at least 5000 charge/discharge cycles. The electrode also delivers high energy density, 1.7 × 10−3 Wh cm−3, and power density, 2.7 W cm−3.

WO3 Nanorods/MXene composite as high performance electrode for supercapacitors

Tungsten oxide (WO3) as electrode material has the drawbacks including poor rate capability and low capacitance. We firstly report a facile strategy to prepare WO3/MXene composite by intimately electrostatic attraction between the positively charged WO3 nanorods (WNRs) and the negatively charged transition metal carbides (MXene). This type composite shows higher specific capacitance (297 F g−1) compared with pure WNRs (121 F g−1) at a current density of 1 A g−1 in 0.5 M H2SO4 aqueous electrolyte. In addition, the as-prepared composite electrode displays good retention rate (82.2% retention at 5 A g−1) and cyclic stability (73.4% even after 5000 cycles at 4 A g−1). The attractive electrochemical performance of WNRs/MXene may be attributed to the main reasons as follows: The MXene acts as electrons collector effectively improving the electrical conductivity and supplying more electrons to participate redox reactions happened on the surface and interior of WNRs; The electrostatic self-assembly improves the stability of WNRs/MXene.

Facile synthesis of nitrogen self-doped hierarchical porous carbon derived from pine pollen via MgCO3 activation for high-performance supercapacitors

The development of simple and green synthetic strategies to obtain porous carbon with both high energy density and power density for carbon-based supercapacitors has motivated the utilization of sustainable biomass materials, due to their unique microstructures and high heteroatom contents. Herein, a novel, green and efficient activation agent magnesium carbonate is proposed to prepare nitrogen self-doped hierarchical porous carbon materials derived from pine pollen for superior carbon-based supercapacitors. The obtained carbon has a large surface area of 1311.2 m2 g−1, hierarchical porous structure with interconnected meso-/macropores and high nitrogen, oxygen contents. When applied as supercapacitor electrode in a three-electrode system, the carbon-based electrode exhibits a high specific capacitance of 419.6 F g−1 at a current density of 1 A g−1, good rate retention of 60.3% from 1 to 100 A g−1 and superior long-term cycling stability with 2.6% loss of its initial capacitance after 10,000 cycles in 6 M KOH aqueous electrolyte. Additionally, the assembled symmetric supercapacitor can work at a high voltage of 2.0 V in 1 M Na2SO4 aqueous electrolyte, and deliver an ultrahigh energy density of 34.9 Wh kg−1 at a power density of 181.0 W kg−1.

Ni-Bi-S nanosheets/Ni foam as a binder-free high-performance electrode for asymmetric supercapacitors

Supercapacitors are attracting tremendous interests in electrochemical energy storage and binary metal sulfides are attracting increasing attention due to higher electrochemical activities over their monometal counterparts. In this report, we show a novel Ni-Bi-S nanosheets/Ni foam electrode with superior performance for supercapacitors. In the synthetic process, Ni foam is utilized as current collector as well as Ni source for the Ni-Bi-S. Bi source plays a crucial role to achieve desired morphology for the Ni-Bi-S and uniform nanosheets network can be obtained by controlling the amount of the Bi (NO3)2. The Ni-Bi-S nanosheets/Ni electrode demonstrates a high specific capacitance of 4.81 F/cm2 at 5 mA/cm2 and an outstanding cycling performance. After 3000 cycles, 97.6% of the initial capacitance can be retained at 20 mA/cm2 and the retention is still as high as 83.4% even after 6500 cycles. An asymmetric supercapacitor constructed with Ni-Bi-S cathode and commercial conductive cloth (CC) anode demonstrates with a high energy density of 2.96 mWh/cm3 and a good retention rate after 2000 cycles.

Interfacial engineering of 0D/2D SnS2 heterostructure onto nitrogen-doped graphene for boosted lithium storage capability

The interfacial engineering plays an important role in enhancing the electrochemical properties of graphene-based hybrid materials for energy conversion and storage. Herein, we propose a facile interfacial engineering route for achieving a novel type of SnS2/N-doped graphene (SnS2/NG) composite with superior lithium storage capability. Interestingly, the SnS2 particles formed show two totally different morphologies including ultrasmall nanoparticles about 5 nm and ultrathin nanosheets, and they are strongly coupled with nitrogen-doped graphene, giving rise to a unique 0D/2D heterostructure. In the process, the multiple roles of the 3-aminophenol (AP) linker are well identified by combining the experimental results with the theoretical calculations, where a strong interface is successfully constructed between SnS2 and functionalized graphene. The electrochemical test results demonstrate that the as-made SnS2/NG composite exhibits a high lithium storage capacity (1101.3 mAh g−1 at 100 mA g−1), superior cycling stability (a capability fading of 0.04% per cycle for 200 cycles at 100 mA g−1), as well as a good rate retention. Such a unique hierarchical nanostructure and the strong interfacial interaction between 0D/2D SnS2 and nitrogen-doped graphene highlight the lithium storage performance of SnS2/NG.

Preparation and characterization of coenzyme Q10 loaded solid lipid-based formulations for enhancement of gastrointestinal solubilization

The aim of current research was to develop two types of solid lipid-based formulations to enhance solubility and stability of poorly water-soluble coenzyme Q10 (CoQ10). The powders of solid self-microemulsifying delivery system (SMEDS) were produced by rotational evaporation with magnesium aluminum silicate. And silica lipid hybrid (SLH) microparticles were developed by lyophilization of oil-in-water emulsions with Aerosil 300 silica nanoparticles as solid carrier. The in vitro dissolution experiment indicated that the dissolution behavior of solid SMEDS and SLH microparticles could be explained by Rigter-Peppas and Weibull model respectively. The in vitro lipolysis study revealed that compared with pure CoQ10, solid SMEDS and SLH microparticles significantly enhanced the solubility of CoQ10 in the aqueous medium under fasted and fed conditions. During a 30-day stability study, solid formulations showed good stability and high retention rate of CoQ10 (above 80%) after stored at three different temperatures. Besides, CoQ10 in solid formulations also exhibited good photostability. These results demonstrated that solid lipid-based formulations could be identified as appropriate strategies to improve solubility and stability of CoQ10.

High-performance lithium storage properties based on molybdenum trioxide nanobelts

Orthorhombic molybdenum trioxide (α-MoO3) nanobelts were successfully synthesized via a facile hydrothermal approach, and the lithium storage properties of α-MoO3 nanobelts were investigated. The α-MoO3 nanobelts anode delivered a high first specific discharge (lithiation) capacity of 1351 mA h g−1 at 0.2 A g−1, good capacity retention (over 900 mA h g−1 after 60 cycles at 0.2 A g−1) and impressive rate performance. The excellent electrochemical properties of the α-MoO3 electrode enable its application in the fields of energy storage and conversion.

Three dimensional network Si–C composite coating constructed by porous skeletons as an integrated anode for lithium-ion batteries

This paper reports a facile knife coating route to synthesize Cu-supported Si–C composite as an integrated anode for lithium-ion batteries. The composite displays a three dimensional (3D) network structure constructed by porous skeletons with Si nano-particles encapsulated in carbon matrix. The Cu-supported Si–C composite electrode demonstrates good capacity retention performance and rate performance. It delivers a high capacity of 1429 mA h g−1 at a current density of 1 A g−1 after 100 cycles and a capacity of 677 mA h g−1 at a high current density up to 20 A g−1. There are two facts responsible for its excellent electrochemical performance: (1) 3D network structure produced by volatilization of polymethylmethacrylate (PMMA) improves structure stability of the electrode; (2) abundant tunnels in skeletons made by volatilization of polyethylene glycol (PEG) increases diffusion of lithium-ions in the electrode.

Flower-like Cu₂SnS₃ Nanostructure Materials with High Crystallinity for Sodium Storage.

In this study, ternary Cu2SnS3 (CTS) nanostructure materials with high crystallinity were successfully prepared via a facile solvothermal method, which was followed by high-temperature treatment. The morphology of the as-synthesized samples is uniform flower-like spheres, with these spheres consisting of hierarchical nanosheets and possessing network features. Sodium storage measurements demonstrate that the annealed CTS electrodes have high initial reversible capacity (447.7 mAh·g−1 at a current density of 100 mA·g−1), good capacity retention (200.6 mAh·g−1 after 50 cycles at a current density of 100 mA·g−1) and considerable rate capability because of their high crystallinity and unique morphology. Such good performances indicate that the high crystallinity CTS is a promising anode material for sodium ion batteries.