Publications by authors named "Mengyao Dong"

26 Publications

  • Page 1 of 1

Influences of aggressive ions in human plasma on the corrosion behavior of AZ80 magnesium alloy.

Mater Sci Eng C Mater Biol Appl 2021 Feb 21;119:111521. Epub 2020 Sep 21.

Integrated Composites Lab (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37966, USA. Electronic address:

Magnesium alloys can work as biomedical materials due to their Young's modules similar to that of bone. Nevertheless, in a human plasma, one of the major drawbacks of these materials is the low corrosion resistance. Here, AZ80 corrosion in the solutions containing chloride, bicarbonate, sulphate and hydrogen phosphate ions were investigated by a short-term immersion test and electrochemical techniques. The results showed that bicarbonate and hydrogen phosphate could retard corrosion rate, while chloride and sulphate accelerated corrosion rate. During the early immersion stage, the corrosion rate increased with the presence of bicarbonate. It was caused by the reaction of bicarbonate and hydroxide promoting the dissolution of magnesium and accelerating corrosion. In the later stage, the reduced corrosion rate was due to the formation of various protective films. The sample formed a new sparse porous MgSO·5HO compounds in the sulphate ion solution, which could not effectively prevent chloride ions from entering the matrix and thus accelerated the dissolution of magnesium. With the presence of hydrogen phosphate, magnesium phosphate with a much lower solubility was formed, preferentially precipitated on the surface and was not influenced by the chloride ions. The corrosion mechanisms of magnesium alloys in above ions were proposed.
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http://dx.doi.org/10.1016/j.msec.2020.111521DOI Listing
February 2021

One-pot microwave-hydrothermally synthesized carbon nanotube-cerium oxide nanocomposites for enhanced visible photodegradation of acid orange 7.

Phys Chem Chem Phys 2020 Oct;22(41):23743-23753

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA.

Carbon nanotubes (CNT)-cerium oxide (CeO2) nanocomposites were fabricated successfully by one-pot microwave hydrothermal growth of regular CeO2 nanoparticles with a size of 8 nm on hydroxyl-functionalized multi-walled CNTs. These nanocomposite photocatalysts demonstrated an acid orange (AO7) photocatalytic degradation efficiency of above 90% under solar-simulated light irradiation for 3 h, which was much higher than that of the pure CeO2 nanoparticles. The enhanced photocatalytic activity was observed to mainly originate from the ˙O2- and hole traps, while the hydroxyl radical ˙OH played a secondary role.
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http://dx.doi.org/10.1039/d0cp00431fDOI Listing
October 2020

Microwave Hydrothermally Synthesized Metal-Organic Framework-5 Derived C-doped ZnO with Enhanced Photocatalytic Degradation of Rhodamine B.

Langmuir 2020 Aug 16;36(33):9658-9667. Epub 2020 Aug 16.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States.

C-doped ZnO particles have been successfully prepared by the calcination using microwave hydrothermally prepared metal-organic framework-5 (MOF-5) as the precursor. MOF-5 was turned into C-doped ZnO through calcination at 500 °C, and its cubic shape was well-maintained. X-ray photoelectron spectroscopic studies confirmed the C-doping in the ZnO. The as-prepared C-doped ZnO demonstrated a Rhodamine B (RhB) degradation efficiency of 98% in 2 h under an solar-simulated light irradiation, much higher than that of C-doped ZnO derived from MOF-5 synthesized by the ordinary hydrothermal method. The trapping experiment revealed that the crucial factors in the RhB removal were photogenerated h and •O.
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http://dx.doi.org/10.1021/acs.langmuir.0c00395DOI Listing
August 2020

Bimetallic metal-organic frameworks anchored corncob-derived porous carbon photocatalysts for synergistic degradation of organic pollutants.

Chemosphere 2020 Nov 15;259:127389. Epub 2020 Jun 15.

Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou, China. Electronic address:

Metal-organic frameworks (MOFs) are promising for photocatalysis owing to their excellent structure and performance. Unfortunately, poor stability in both aqueous solutions and high temperatures and lack of adsorption centers during reactions limit their practical applications. Herein, a bimetallic MOF anchored corncob calcined derived activated carbon (CCAC) was successfully prepared by a one-step solvothermal method. Benefiting from unique structures and synergetic effect, the porous carbon provided a high specific surface area for stable MOF support and served as an organic pollutant buffer-reservoir, which was advantageous for efficient photocatalytic degradation of organic pollutants. The optimized MOF/CCAC-5 samples possessed excellent visible light degradation rate, i.e., 100% for Rh B, more than 96% for six mixed dyes, and 98% for tetracycline. This prominent photocatalytic activity was caused by active species, including photoelectrons (e), photo-holes (h) and superoxide free radicals (•O). The transient photocurrent response and electrochemical impedance tests showed that MOF/CCAC-5 exhibited a relatively high charge separation and low carrier recombination rate. Cyclic and simulation experiments indicated high reusability, stability and universality of the composite photocatalysts. These exciting results provide new pathways for the fabrication of MOFs anchored porous carbon materials.
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http://dx.doi.org/10.1016/j.chemosphere.2020.127389DOI Listing
November 2020

Binder-free CuS/ZnS/sodium alginate/rGO nanocomposite hydrogel electrodes for enhanced performance supercapacitors.

Int J Biol Macromol 2020 Nov 20;162:310-319. Epub 2020 Jun 20.

Key Laboratory of Materials Processing and Mold, Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou, China. Electronic address:

CuS/ZnS/sodium alginate/reduced graphene oxide nanocomposites (CZSrG) were prepared by physical crosslinking followed by one-step reduction and were justified as green binder-free hydrogel high-capacitance electrodes. The physical crosslinking was realized simply through the hydrogen-bond interaction between sodium alginate (SA) and graphene oxide (GO), avoiding the usage of traditional Ca crosslinking agent. The hydrogel structure made of CZSrG possessed the most beneficial effect of avoiding large volume change and increasing cycle stability for supercapacitors. When used as electrode, the specific capacitance of CZSrG was 992 F·g (10 mV·s) in a three-electrode system. Furthermore, the fabricated supercapacitors had a specific capacitance of 252.1 F·g (5 mV·s), and a power density of 1800 Wh·kg at the energy density of 2.05 Wh·kg. Thus, the CZSrG has a favorable electrochemical performance and wide application prospects in supercapacitors.
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http://dx.doi.org/10.1016/j.ijbiomac.2020.06.169DOI Listing
November 2020

Enteromorpha prolifera polysaccharide based coagulant aid for humic acids removal and ultrafiltration membrane fouling control.

Int J Biol Macromol 2020 Jun 24;152:576-583. Epub 2020 Feb 24.

Integrated Composites Lab (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA. Electronic address:

Polyacrylamide (PAM) has been used as a coagulant aid in water treatment process for past decades, but it has caused great damages to human nervous system. Developing new coagulant aid with high biological safety is urgently demanded. This study provides a natural biomacromolecule coagulant aid with good biosecurity-Enteromorpha prolifera polysaccharide (Ep). Its coagulant aid efficiency and mechanism were investigated in terms of organics removal, floc properties and membrane fouling degree. In addition, contrast experiments were conducted with PAM to evaluate its potential of industrial applications. Results showed that organics removal could be increased by 23% when 0.3 mg/L Ep was used, which exhibited comparable aid effects to PAM. Due to the bridging-sweep aid role of Ep, flocs sizes, growth rate and recovery factor reached 470 μm, 62.6 μm/min and 0.492, respectively, while only 170 μm, 14.0 μm/min and 0.326 were obtained by PAM. Additionally, flocs exhibited more porous and multi-branched structures when Ep was applied, which caused less ultrafiltration membrane fouling (eventual J/J value = 0.52). As a result, Ep could be considered as a potential substitute of PAM, since better biosecurity, higher organics removal and lower membrane fouling could be obtained simultaneously by Ep addition.
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http://dx.doi.org/10.1016/j.ijbiomac.2020.02.273DOI Listing
June 2020

Flexible silver nanowire/carbon fiber felt metacomposites with weakly negative permittivity behavior.

Phys Chem Chem Phys 2020 Mar 19;22(9):5114-5122. Epub 2020 Feb 19.

College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China.

Recently, flexible metacomposites with negative permittivity have triggered extensive interest owing largely to their promising applications in areas such as sensors, cloaking, and wearable and flexible electronic devices. In this paper, flexible silver nanowire/carbon fiber felt (AgNW/CFF) metacomposites with weakly negative permittivity were fabricated by adjusting their composition and microstructure. Along with the formation of a conductive AgNW network, the resulting composites gradually presented metal-like behavior. Interestingly, weakly negative permittivity with a small absolute value (as low as about 6.4) and good flexibility were observed in the composites with 3.7 wt% AgNWs. The one-dimensional silver nanowires contribute to reducing the overall electron density of the resulting composites, which is responsible for the weakly negative permittivity. As the AgNWs increased, the Drude-like negative permittivity got stronger owing to the enhancement of the electron density. Further investigation from the perspective of microelectronics revealed that the negative permittivity is dependent on the inductive characteristic. The proposed design strategy for AgNW/CFF composites with tunable negative permittivity opens up a new approach to flexible metacomposites.
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http://dx.doi.org/10.1039/c9cp06196gDOI Listing
March 2020

Sodium-ion capacitors: Materials, Mechanism, and Challenges.

ChemSusChem 2020 May 24;13(10):2522-2539. Epub 2020 Mar 24.

Integrated Composites Laboratory, Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, 37996, USA.

Sodium-ion capacitors (SICs), designed to attain high energy density, rapid energy delivery, and long lifespan, have attracted much attention because of their comparable performance to lithium-ion capacitors (LICs), alongside abundant sodium resources. Conventional SIC design is based on battery-like anodes and capacitive cathodes, in which the battery-like anode materials involve various reactions, such as insertion, alloying, and conversion reactions, and the capacitive cathode materials usually depend on activated carbon (AC). However, researchers have attempted to construct SICs based on battery-like cathodes and capacitive anodes or a combination of both in recent years. In this Minireview, charge storage mechanisms and material design strategies for SICs are summarized, with a focus on the battery-like anode materials from both inorganic and organic sources. Additionally, the challenges in the fabrication of SICs and future research directions are discussed.
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http://dx.doi.org/10.1002/cssc.201903440DOI Listing
May 2020

Dandelion-like CuCoO arrays on Ni foam as advanced positive electrode material for high-performance hybrid supercapacitors.

J Colloid Interface Sci 2020 Apr 21;566:79-89. Epub 2020 Jan 21.

Henan Key Laboratory of Utilization of Non-metallic Mineral in the South of Henan, College of Chemistry and Chemical Engineering, Xinyang Normal University, 464000 Xinyang, China.

In this paper, CuCoO dandelion arrays grown on nickel foam (CuCoO/NF) was successfully synthesized by a simple hydrothermal route with post-heat-treatment for emolying as a high-performance positive electrode material for hybrid supercapacitors. Due to the unique tree-dimension porous (3D) microstructure and binder-free electrode architecture, the CuCoO/NF electrode deliveries a large specific capacitance of 2656.7 F g at an areal current density of 1 mA cm. Moreover, it has an outstanding rate performance, as well as striking cycling stability. Additionally, a hybrid supercapacitors (HSCs) was fabricated using CuCoO as positive electrode and corals-like N-doping porous carbon (N-CCs) as negative electrode. The device exhibited a broad potential window of 1.55 V and a high specific capacitance of 273.9 F g, which result in a largest energy density of 91.4 Wh kg and a maximum power density of 13.4 kW kg. Finally, the assembled device manifests a preeminent electrochemical stability which maintained a 92.32% capacitance retention after 5000 cycles. The practical application was visually validated by lighting a blue light-emitting diode.
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http://dx.doi.org/10.1016/j.jcis.2020.01.077DOI Listing
April 2020

Advances in Template Prepared Nano-Oxides and their Applications: Polluted Water Treatment, Energy, Sensing and Biomedical Drug Delivery.

Chem Rec 2020 Jul 16;20(7):710-729. Epub 2020 Jan 16.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA.

The nano-oxide materials with special structures prepared by template methods have a good dispersion, regular structures and high specific surface areas. Therefore, in some areas, improved properties are observed than conventional bulk oxide materials. For example, in the treatment of dye wastewater, the treatment efficiency of adsorbents and catalytic materials prepared by template method was about 30 % or even higher than that of conventional samples. This review mainly focuses on the progress of inorganic, organic and biological templates in the preparation of micro- and nano- oxide materials with special morphologies, and the roles of the prepared materials as adsorbents and photocatalysts in dye wastewater treatment. The characteristics and advantages of inorganic, organic and biological template are also summarized. In addition, the applications of template method prepared oxides in the field of sensors, drug carrier, energy materials and other fields are briefly discussed with detailed examples.
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http://dx.doi.org/10.1002/tcr.201900093DOI Listing
July 2020

Antifouling and antibacterial behaviors of capsaicin-based pH responsive smart coatings in marine environments.

Mater Sci Eng C Mater Biol Appl 2020 Mar 1;108:110361. Epub 2019 Nov 1.

Integrated Composites Laboratory (ICL), Chemical and Biomolecular Engineering Department, University of Tennessee, Knoxville, TN, 37996, USA. Electronic address:

Antifouling biocides releasing restricts the longevity of antifouling coatings. Compared with the anchoring state, the releasing behavior of agents is much faster on the voyage, while the biofouling process is tougher. In this work, a series of capsaicin-based pH-triggered polyethylene glycol/capsaicin@chitosan (PEG/CAP@CS), polyvinyl alcohol (PVA)/CAP@CS and alginate (ALG)/CAP@CS multilayer films are prepared with controlling antimicrobial properties in marine environments. There are 23.70, 23.35 and 22.06 ppb CAP releasing from (PVA/CAP@CS), (PEG/CAP@CS) and (ALG/CAP@CS) films after immersing in pH 4 solutions for 60 days, while only 13.07, 12.95 and 11.55 ppb CAP have been found in alkaline solutions after immersing for the same time, respectively. All these three types of films exhibit extraordinary pH responsive properties. They can control the CAP release at a low level in alkaline solutions, and make the CAP release fast in acid solutions. Moreover, the antibacterial properties against P.aeruginosa are outstanding about 95.84%, 95.0% and 96.91% for (PVA/CAP@CS), (PEG/CAP@CS) and (ALG/CAP@CS) films, respectively. The bacteriostasis of (ALG/CAP@CS) film keeps 92.73% after 60 days in alkaline solution, which means it is steadily controlled in the marine environment. Although with similar antibacterial properties to those of (PEG/CAP@CS) film, (PVA/CAP@CS) film displays the maximum decrease with about 92% in acid solution after 60 days. The ALG/CAP@CS film with the best-controlled release performance and long-term antibacterial properties provides novel guidance for developing new antifouling coatings application in the marine environment.
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http://dx.doi.org/10.1016/j.msec.2019.110361DOI Listing
March 2020

Magnetic nanocellulose-magnetite aerogel for easy oil adsorption.

J Colloid Interface Sci 2020 Feb 31;560:849-856. Epub 2019 Oct 31.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37966, USA.

Hypothesis: Cellulose aerogels are a new category of high-efficiency adsorbents for treating oil spills and water pollution. However, the hydrophilic properties and recyclability of aerogels after adsorption hamper developments and applications. Combining both hydrophobic and magnetic properties are expected to improve their adsorption capacity and functionality.

Experiments: In this study, the effect of oleic acid (OA) and nanomagnetite on the preparation of magnetic nanocellulose aerogels (called as NCA/OA/FeO) by a mechanical mixing combined with freeze-drying method have been investigated.

Findings: It has been found that the optimal condition for fabricating this NCA/OA/FeO aerogel is 0.4 wt% nanocellulose, 3 mg mL OA and 0.5 wt% FeO in the aqueous solution. This aerogel has a very low density of 9.2 mg cm and demonstrates a high adsorption capacity of 68.06 g g for cyclohexane. In addition, this aerogel adsorbent demonstrates an excellent magnetic responsivity and can be easily recycled by a permanent magnet after adsorption. As a consequence, this hydrophobic magnetic NCA/OA/FeO aerogel is promising not only for easy oil and organic solvent adsorption but also potentially for other magnetic related applications.
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http://dx.doi.org/10.1016/j.jcis.2019.10.084DOI Listing
February 2020

Optimizing nanocarbon shell in zero-valent iron nanoparticles for improved electron utilization in Cr(VI) reduction.

Chemosphere 2020 Mar 30;242:125235. Epub 2019 Oct 30.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, United States. Electronic address:

A core-shell structured zero-valent iron@carbon (ZVI@C) nanocompoiste was designed to improve the electron utilization of ZVI in the Cr(VI) reduction. The porosity of carbon layer in ZVI@C was optimized for improving the efficiency of electron utilization of ZVI in the Cr(VI) reduction process. The porous structure of carbon layer was controllably synthesized by adjusting the carbon source and the ratio of C/Fe in the precursor. The glucose was suggested as the optimal carbon source, and a high specific surface area (37.067 m/g) was reached for the prepared ZVI@C when the ratio of C/Fe was controlled at 20. These ZVI@C performed well on Cr(VI) reduction, e.g. a complete reduction of Cr(VI) (2 mg/L) to Cr(III) within 10 min. The removal capacity (800 mg/g) exceeded previously recorded ZVI based adsorbents. The pH and initial Cr(VI) concentration were demonstrated as the key factors for the efficient electron utilization of ZVI. Furthermore, the efficiency of electron utilization of the ZVI increased up to 80% when the concentration of Cr(VI) was 2000 mg/L and the pH was controlled at 3, which was much higher than 8% of the naked ZVI.
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http://dx.doi.org/10.1016/j.chemosphere.2019.125235DOI Listing
March 2020

N,S-self-doped carbon quantum dots from fungus fibers for sensing tetracyclines and for bioimaging cancer cells.

Mater Sci Eng C Mater Biol Appl 2019 Dec 31;105:110132. Epub 2019 Aug 31.

Integrated Composites Laboratory (ICL), Department of Chemical and Bimolecular Engineering, University of Tennessee, Knoxville, TN, 37996, USA.

In this work, nitrogen and sulfur dual-doped carbon quantum dots (N,S-CDs) from naturally renewable biomaterial fungus fibers were prepared by a biosynthesis and hydrothermal method. The N,S-CDs displayed good water solubility, excellent stability, high quantum yield (QY = 28.11%) as well as remarkable features for fluorescence quenching-based detection and cellular imaging of cancer cells. It was worth mentioning that the heteroatoms doped carbon quantum dots made from the fungus fibers had a satisfactory QY and could be used as a selective, efficient, and sensitive fluorescent probe to determine tetracyclines by the synergistic effects of static quenching and internal filtration effect. The probe demonstrated a wide linear range and low detection limit. For tetracycline, the linear range was 0.5 μM to 47.6 μM, and the corresponding detection limit was 15.6 nM. Significantly, the test papers prepared by using N,S-CDs could detect tetracyclines in aquiculture wastewater rapidly. The produced N,S-CDs did not affect the cell viability and showed great promises for cellular imaging.
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http://dx.doi.org/10.1016/j.msec.2019.110132DOI Listing
December 2019

Sodium alginate templated hydroxyapatite/calcium silicate composite adsorbents for efficient dye removal from polluted water.

Int J Biol Macromol 2019 Dec 11;141:1035-1043. Epub 2019 Sep 11.

Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou, 450002, China. Electronic address:

In this work, natural polysaccharide product sodium alginate (SA) served as templates to prepare porous calcium silicate (CS) hydroxyapatite (HA) composite microspheres (CHCM) with high specific surface area by a new route combining ion exchange and calcination. CHCM played an important role in the fields of environmental protection with its large specific surface area, excellent adsorptive property, high mechanical strength and good regeneration performance. In order to explore its treatment capacity of wastewater, a series of eriochromeblue black R (EBBR) adsorption experiments were carried out. The equilibrium data fitted well with the Langmuir isotherm with a maximum adsorption capacity of 76.80 mg/g. Electrostatic interaction, ionic bonds and physical adsorption were responsible for the interactions between the EBBR and CHCM. Meanwhile, the CHCM maintained complete spherical and almost undamaged in the regeneration experiments, which confirmed its stability for cyclical usage. This paper demonstrates the role of natural polysaccharide product sodium alginate serving as templates to prepare useful products with potential wide applications.
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http://dx.doi.org/10.1016/j.ijbiomac.2019.09.082DOI Listing
December 2019

Boosted selectivity and enhanced capacity of As(V) removal from polluted water by triethylenetetramine activated lignin-based adsorbents.

Int J Biol Macromol 2019 Nov 28;140:1167-1174. Epub 2019 Aug 28.

Integrated Composites Laboratory (ICL), Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN 37996, USA. Electronic address:

Low-cost natural polymer lignin has been widely used to remove heavy metal ions from polluted water. But it still has some shortcomings, such as poor removal performance, and weak selective adsorption. Thus, in this study, the lignin prepared by Mannich reaction with black liquor was activated with triethylenetetramine (TETA) to achieve a novel adsorbent with high adsorption rates and a strong selectivity for specific oxygen-containing anions. The adsorption capacity of activated lignin (a-CL) on three oxygen-containing anions (i.e. As(V), P(V) and Cr(VI)) was investigated systematically. The adsorption mechanism of a-CL was elucidated theoretically by the density functional theory (DFT) method. Under the same conditions, the selectivity toward oxygen-containing anions by a-CL followed P(V) < Cr(VI) < As(V). Both FT-IR and DFT simulation results revealed that the hydrogen bond between HAsO and N dominated the remarkable selectivity of As (V), yielding a maximum adsorption capacity as high as 62.5 mg g. Moreover, the adsorption was very fast with a calculated large adsorption kinetic constant. The removal of As(V) reached 100% within 60 min. The As(V) adsorption kinetics and the adsorption isotherms followed the pseudo-second-order and the Langmuir model. This study provides a way for highly selecting removal of As(VI) from polluted water with the lignin.
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http://dx.doi.org/10.1016/j.ijbiomac.2019.08.230DOI Listing
November 2019

Anchoring carbon nanotubes and post-hydroxylation treatment enhanced Ni nanofiber catalysts towards efficient hydrous hydrazine decomposition for effective hydrogen generation.

Chem Commun (Camb) 2019 Aug 10;55(61):9011-9014. Epub 2019 Jul 10.

Integrated Composites Lab (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37966, USA.

For effective hydrogen generation with remarkable durability, carbon nanotubes (CNTs) grown on Ni nanofibers and their post hydroxylation treatment engendered active Ni nanofiber catalysts an efficient decomposition of hydrous hydrazine with a turnover frequency (TOF) of 19.4 h and an activation energy down to 51.05 KJ mol.
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http://dx.doi.org/10.1039/c9cc04559gDOI Listing
August 2019

Reduced Graphene Oxide Heterostructured Silver Nanoparticles Significantly Enhanced Thermal Conductivities in Hot-Pressed Electrospun Polyimide Nanocomposites.

ACS Appl Mater Interfaces 2019 Jul 3;11(28):25465-25473. Epub 2019 Jul 3.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering , University of Tennessee , Knoxville , Tennessee 37996 , United States.

Graphene presents an extremely ultra-high thermal conductivity, well above other known thermally conductive fillers. However, graphene tends to aggregate easily due to its strong intermolecular π-π interaction, resulting in poor dispersion in the polymer matrix. In this study, silver nanoparticles anchored reduced graphene oxide (Ag/rGO) were first prepared using one-pot synchronous reduction of Ag and GO solution via glucose. The thermally conductive (Ag/rGO)/polyimide ((Ag/rGO)/PI) nanocomposites were then obtained via electrospinning the in situ polymerized (Ag/rGO)/polyamide electrospun suspension followed by a hot-press technique. The thermal conductivity (λ), glass transition temperature (), and heat resistance index () of the (Ag/rGO)/PI nanocomposites all increased with increasing the loading of Ag/rGO fillers. When the mass fraction of Ag/rGO (the weight ratio of rGO to Ag was 4:1) fillers was 15%, the corresponding (Ag/rGO)/PI nanocomposites showed a maximum λ of 2.12 W/(m K). The corresponding and values were also enhanced to 216.1 and 298.6 °C, respectively. Furthermore, thermal conductivities calculated by our established improved thermal conduction model were relatively closer to the experimental results than the results obtained from other classical models.
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http://dx.doi.org/10.1021/acsami.9b10161DOI Listing
July 2019

Surface intercalated spherical MoSSe nanocatalysts for highly efficient and durable hydrogen evolution reactions.

Dalton Trans 2019 Jun 17;48(23):8279-8287. Epub 2019 May 17.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA.

An efficient hydrogen evolution reaction (HER) depends essentially on high-performing electrocatalysts. The aggregation of catalysts normally deteriorates their activity and stability. In this study, a two-step route was used to synthesize surface intercalated well-dispersed spherical MoSSe nanocatalysts. The resulting catalysts present a highly active and stable performance towards the HER with an overpotential of -143 mV at 10 mA cm, and a Tafel slope of 53.8 mV dec. The mechanism for the enhanced HER was analyzed and was attributed to three factors: (i) large numbers of defects and edge active sites arising from the coexistence of S and Se elements; (ii) enhanced electric conductivity arising from the phase transition from the semiconducting 2H-phase to metallic 1T-phase during the intercalation process; and (iii) enlarged contact areas between active sites and electrolyte caused by the increased surface roughness due to the surface intercalation. This work not only deepens our understanding of the improved HER performance of surface intercalated catalysts, but also provides novel strategies for preparing durable electrocatalysts through surface engineering.
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http://dx.doi.org/10.1039/c9dt01218dDOI Listing
June 2019

Synthesis and characterization of porous tree gum grafted copolymer derived from Prunus cerasifera gum polysaccharide.

Int J Biol Macromol 2019 Jul 17;133:964-970. Epub 2019 Apr 17.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA. Electronic address:

Porous grafted copolymer with excellent thermal stability and swelling capacity was synthesized from water soluble Prunus cerasifera gum polysaccharide (PG) and acrylamide (AM). The monosaccharide compositions and the structure of Prunus cerasifera tree gum were detected by a high-performance anion exchange chromatography (HPAEC) system and H NMR and C NMR, and the obtained PG-AM copolymer was characterized by Fourier transform infrared (FT-IR), scanning electron microscope (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. The results indicated that the water soluble polysaccharides obtained from Prunus cerasifera tree gum were mainly composed of l-arabinose (39.78%) and d-galactose (40.59%) with minor amount of xylose, mannose and uronic acids. The maximum percent and the grafting efficiency of grafting acrylamide (AM) onto PG to form PG-AM were obtained by copolymerization between polysaccharide and 3 times (weight) acrylamide with 3 mmol/L potassium persulfate initiator at 50 °C for 1 h. In addition, lots of isolated and conjoint pores were observed in the prepared PG-AM materials, with a diameters distribution between 2 and 10 μm. Compared with PG, the synthesized copolymer PG-AM showed an excellent performance in thermal stability and swelling capacity. The detailed structural characteristic together with excellent thermal stability and swelling properties will benefit efficient utilization of the synthesized copolymer as a precursor for preparation of large-scale environmentally friendly advanced materials with various potential applications.
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http://dx.doi.org/10.1016/j.ijbiomac.2019.04.128DOI Listing
July 2019

Zinc oxide/vanadium pentoxide heterostructures with enhanced day-night antibacterial activities.

J Colloid Interface Sci 2019 Jul 19;547:40-49. Epub 2019 Mar 19.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37934, USA. Electronic address:

Low photocatalytic efficiency of visible light and fast recombination of photo-generated carriers are two challenges facing the applications of photocatalyst sterilant zinc oxide (ZnO). Meanwhile, both light and dark photocatalytic activities are important. It is of great theoretical and practical significance to construct a day-night photocatalytic antibacterial material, which is beneficial to the effective use of energy and to tackle the limitation of using photocatalytic bacteriostat. ZnO nanoflowers decorated vanadium pentoxide (VO) nanowires heterojunction (ZVH) was firstly fabricated using a facile water-bathing method. The designed ZVH structure efficiently produced abundant reactive oxygen species (ROS) in both light and darkness. It yielded 99.8% and 99.0% of antibacterial rate against S. aureus due to oxidative stress induced by ROS in light and darkness, respectively. The generation of ROS played a major role in the antibacterial activities against S. aureus under both light and dark conditions. The prepared ZVH with improved antibacterial properties provides an alternative for day-night antibacterial agents.
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http://dx.doi.org/10.1016/j.jcis.2019.03.061DOI Listing
July 2019

Nanosheet-based NbO hierarchical microspheres for enhanced lithium storage.

Chem Commun (Camb) 2019 Feb;55(17):2493-2496

Institute of Materials for Energy and Environment, School of Materials Science and Engineering, Qingdao University, Qingdao 266071, China.

Conductive Nb12O29 hierarchical microspheres with nanosheet shells were synthesized based on a hydrothermal process and a high-temperature hydrogen reduction treatment. The obtained materials demonstrated comprehensively good electrochemical properties, including a significant pseudocapacitive contribution, safe operating potential, high reversible capacity, superior initial coulombic efficiency, increased rate capability, and durable cycling stability.
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http://dx.doi.org/10.1039/c8cc09924cDOI Listing
February 2019

Microwave solvothermal carboxymethyl chitosan templated synthesis of TiO/ZrO composites toward enhanced photocatalytic degradation of Rhodamine B.

J Colloid Interface Sci 2019 Apr 17;541:18-29. Epub 2019 Jan 17.

Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA. Electronic address:

A series of TiO/ZrO composites with various molar ratios of ZrO:TiO were synthesized by a facile and mild microwave hydrothermal method with carboxymethyl chitosan (CMCS) as templates. The as-obtained products were characterized with wide-angle powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectrophotometry (UV-vis-DRS), N adsorption-desorption isotherms (BET), and X-ray photoelectron spectrometer (XPS). The TiO/ZrO composites with heterogeneous structure consisted of particles which showed a better regularity and uniform with about 800 nm in diameter, and showed a larger specific surface area and smaller energy band gap than pure ZrO. Comparative experiments including varying the pH of the solution and the content of titania demonstrated that the 5% TiO/ZrO composites (n:n = 5:100) at pH = 10.3 possessed the best photocatalytic property. Moreover, the possible reasons for these phenomena were clarified. Cyclic experiments proved that the resulting TiO/ZrO composites as photocatalyst could be reused efficiently. Meanwhile, a possible mechanism of photocatalysis was proposed.
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http://dx.doi.org/10.1016/j.jcis.2019.01.069DOI Listing
April 2019

Structural characterization of lignin and its carbohydrate complexes isolated from bamboo (Dendrocalamus sinicus).

Int J Biol Macromol 2019 Apr 26;126:376-384. Epub 2018 Dec 26.

Integrated Composites Laboratory (ICL), Department of Chemical and Biomolecular Engineering, University of Tennessee, 322, Dougherty Engineering Bldg., Knoxville, USA. Electronic address:

Isolation of earth abundant biopolymer, Lignin, from Dendrocalamus sinicus and their structural properties were investigated to achieve its large-scale practical applications in value-added products. Two lignin fractions (MWL, DSL) were isolated with successive treatments of dioxane and dimethylsulfoxide (DMSO) from dewaxed and ball milled bamboo (D. sinicus) sample. The two-step treatments yielded 52.1% lignin based on the total lignin content in the dewaxed bamboo sample. Spectroscopy analyses indicated that the isolated bamboo lignin was a typical grass lignin, consisting of p-hydroxyphenyl, guaiacyl, and syringyl units. The major interunit linkages presented in the obtained bamboo lignin were β-O-4' aryl ether linkages, together with lower amounts of β-β', β-5', and β-1' linkages. The tricin was detected to be linked to lignin polymer through the β-O-4' linkage in the bamboo. In addition, phenyl glycoside and benzyl ether lignin-carbohydrate complexes (LCC) linkages were clearly detected in bamboo (D. sinicus), whereas the γ-ester LCC linkages were ambiguous due to the overlapping NMR signals with other substructures. The detailed structural properties of the obtained lignin fraction together with the light-weight will benefit efficient utilization of natural polymers as a possibly large-scale bio-based precursor for making polymeric materials, biochemicals, functional carbon and biofuels, and multifunctional polymer nanocomposites.
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http://dx.doi.org/10.1016/j.ijbiomac.2018.12.234DOI Listing
April 2019

In situ grown nickel selenide on graphene nanohybrid electrodes for high energy density asymmetric supercapacitors.

Nanoscale 2018 Nov;10(43):20414-20425

Electro-Materials Research Laboratory, Centre for Nanoscience and Technology, Pondicherry University, Puducherry - 605014, India.

Nickel selenide (NiSe) nanoparticles uniformly supported on graphene nanosheets (G) to form NiSe-G nanohybrids were prepared by an in situ hydrothermal process. The uniform distribution of NiSe on graphene bestowed the NiSe-G nanohybrid with faster charge transport and diffusion along with abundant accessible electrochemical active sites. The synergistic effect between NiSe nanoparticles and graphene nanosheets for supercapacitor applications was systematically investigated for the first time. The freestanding NiSe-G nanohybrid electrode exhibited better electrochemical performance with a high specific capacitance of 1280 F g-1 at a current density of 1 A g-1 and a capacitance retention of 98% after 2500 cycles relative to that of NiSe nanoparticles. Furthermore, an asymmetric supercapacitor device assembled using the NiSe-G nanohybrid as the positive electrode, activated carbon as the negative electrode and an electrospun PVdF membrane containing 6 M KOH as both the separator and the electrolyte delivered a high energy density of 50.1 W h kg-1 and a power density of 816 W kg-1 at an extended operating voltage of 1.6 V. Thus, the NiSe-G nanohybrid can be used as a potential electrode material for high-performance supercapacitors.
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http://dx.doi.org/10.1039/c8nr06345aDOI Listing
November 2018

Synthesis of unusual N-acylated aminosugar fragments of Mycobacterium marinum lipooligosaccharide IV.

J Org Chem 2015 Mar 16;80(5):2767-80. Epub 2015 Feb 16.

Alberta Glycomics Centre and Department of Chemistry, University of Alberta , Gunning-Lemieux Chemistry Centre, Edmonton, AB T6G 2G2, Canada.

A convergent strategy was developed for the stereoselective synthesis of four unusual N-acylated monosaccharides (5-8), which are fragments of lipooligosaccharide IV (LOS-IV) from Mycobacterium marinum. A critical substrate-controlled asymmetric cyclization of an amino acid derived oxazolidine provided a key lactam intermediate 11, which was successfully converted to targets 5-7. The key step in the synthesis of 8 was a one-pot cascade oxidation-cyclization-oxidation reaction of a Boc-protected amino alcohol, prepared from 3-butynol, which led to the formation of lactam 15. The five-membered ring lactam intermediates in these synthetic routes were sensitive to elimination side reactions, but careful manipulation of the reaction sequence allowed for the stereoselective synthesis of the targets. This work represents the first synthesis of these unusual motifs, which have been shown to be essential to the bioactivity of LOS-IV.
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http://dx.doi.org/10.1021/acs.joc.5b00064DOI Listing
March 2015