As a new and promising reinforcing filler, electrospun glass nanofibers (EGNFs) have attracted at... more As a new and promising reinforcing filler, electrospun glass nanofibers (EGNFs) have attracted attention in the field of polymer composite materials. However, the reinforcing effectiveness of surface-modified EGNFs using different silane coupling agents in epoxy resin is still not quite clear. In this research, a series of silane coupling agents with increasing chain lengths in the order of methyl trimethoxysilane (MTMS), (3-aminopropyl) triethoxysilane (APTES), (3-glycidyloxypropyl) trimethoxysilane (GPTMS), and dual silane coupling agent APTES–GPTMS were employed to carry out surface treatment on the EGNFs. The pristine and silane functionalized EGNFs were then incorporated into epoxy resin as reinforcing fillers at low loading levels, i.e., 0.25 wt.%, 0.5 wt.%, and 1 wt.%, and the mechanical properties of the resultant epoxy nanocomposites, including strength, stiffness, ductility, and toughness, were evaluated. A commercial product of glass nanoparticles (GNPs) was used as a con...
Epoxy is the most prevalent thermosetting resin in the field of polymer composite materials. Ther... more Epoxy is the most prevalent thermosetting resin in the field of polymer composite materials. There has been a growing interest in the development of bio-based epoxy resins as a sustainable alternative to conventional petrochemical epoxy resins. Advances in this field in recent years have included the use of various renewable resources, such as vegetable oils, lignin, and sugars, as direct precursors to produce bio-based epoxy resins. In the meantime, bio-oils have been produced via the decomposition of biomass through thermochemical conversion and mainly being used as renewable liquid fuels. It is noteworthy that bio-oils can be used as a sustainable resource to produce epoxy resins. This review addresses research progress in producing bio-oil-based epoxy resins from thermochemical processing techniques including organic solvent liquefaction, fast pyrolysis, and hydrothermal liquefaction. The production of bio-oil from thermochemical processing and its use to inject sustainability i...
Presently, dental composites have been widely adopted by the profession as the restorative materi... more Presently, dental composites have been widely adopted by the profession as the restorative material of choice; as compared to dental amalgams, the composites possess better esthetic property, have less safety concern, and have shown reasonably satisfactory clinic results. Dental composites consist of resin matrices and inorganic fillers. The monomer of 2,20-bis-[4-(methacryloxypropoxy)-phenyl]propane (Bis-GMA) has been used as an important dental base monomer since it was invented in the 1960s [1, 2]; for example, Bis-GMA is the base monomer in the Z100 Restorative Dental Composite produced by the 3M Corporate. Bis-GMA is a very viscous, honey-like liquid. To improve handling qualities, a diluent monomer of tri(ethylene glycol) dimethacrylate (TEGDMA) is added to thin the resin. In the Bis-GMA/TEGDMA dental resin systems, Bis-GMA functions to limit the polymerization-induced volumetric shrinkage and to enhance the resin reactivity, whereas TEGDMA provides for the increased vinyl double bond conversion [3, 4]. Albeit dental resins have been reinforced with inorganic fillers of glass/ceramic powders containing surface-silanized particles, relatively low strength and durability of the composites have limited their uses [5–8]: dental composites have flexural strengths typically ranging from 80 to 120 MPa, which can fulfill the requirement of filling tooth cavities but cannot survive large stress-bearing restorations such as crowns and bridges; furthermore, the strength of dental composites decreases substantially after being used for a period of time. The average service lifetime of dental composites is considerably shorter than that of dental amalgams [9, 10]. Investigations of the failures revealed that, among numerous issues, the inorganic filler was a major contributor [11, 12]. Many inorganic filler particles currently used for dental composites are spherical or irregular in shape. Such filler particles at occlusal surfaces are susceptible to dislodgement from the resin matrix during wear with food boluses. This would cause the reinforcement effect to be lost. Chopped glass fibers and/or high strength whiskers with diameters of 5–50 lm and aspect ratios larger than 10 have also been investigated to reinforce dental resins [13–16], and the resulting composites showed higher mechanical properties. Several reinforcement mechanisms including ‘‘Bridging,’’ ‘‘Pull-out,’’ and ‘‘Load Transfer’’ were proposed for understanding the fiber/whisker reinforcement [17, 18]; in particular, ‘‘Bridging’’ is a powerful reinforcement mechanism. If a micro-crack is initiated in a resin matrix under contact wear and/or other stresses, the fillers remain intact across the crack planes supporting the applied load. Crack-opening is resisted by the bridging fillers; thus the resin matrix is reinforced. Requirements for fillers to achieve effective ‘‘Bridging’’ reinforcement include high strength and large aspect ratio values; tooth enamel rods are an example of elongated fillers, and crystalline platelets in dental glass/ceramics are another example [19]. Nonetheless, the dental composites reinforced with fibers/whiskers generally possess mechanical properties that still need further improvements; this is L. Zhang Y. Gao Q. Chen H. Fong (&) Department of Chemistry, South Dakota School of Mines and Technology, 501 East St. Joseph Street, Rapid City, SD 57701, USA e-mail: [email protected]
As a short-chain PFAS (per- and polyfluoroalkyl substance), GenX was produced in recent years to ... more As a short-chain PFAS (per- and polyfluoroalkyl substance), GenX was produced in recent years to replace traditional long-chain PFASs, such as perfluorooctanoic acid (PFOA). However, GenX turns out to be more toxic than people originally thought, posing health risks as a persistent environmental pollutant. In this research, for the first time, we incorporated chlorella, a single-celled green freshwater microalga that grows worldwide, with polyacrylonitrile (PAN) in equal amounts in electrospun nanofibers and studied the capability of the electrospun PAN/Algae bicomponent nanofibrous membrane (ES(PAN/Algae)) to bind and remove GenX from water. The incorporation of algae demonstrated a synergistic effect and significantly improved the GenX removal efficiency of the nanofibrous membrane. The maximum GenX removal capacity reached 0.9 mmol/g at pH 6, which is significantly higher than that of most of the reported GenX adsorbents as well as activated carbon. The GenX removal mechanism was...
Due to a massive amount of plastic waste from municipal and industrial sources accumulates in lan... more Due to a massive amount of plastic waste from municipal and industrial sources accumulates in landfills, landfill leachate is becoming a significant reservoir of microplastic (MPs)/ Nanoplastics (NPs), and MPs/NPs in landfill leachate released to the environment can pose detrimental effects on humans and biota. This study critically reviewed most available up-to-date scientific literature on MPs/NPs in landfill leachate and provides the state-of-the-science regarding their detection and quantification, occurrence and characteristics, and remediation. MPs/NPs in landfill leachate can be classified into primary source that is in micro- or nano- scale when manufactured, and secondary source that is made as regular sized plastic but fragmented in to micro- or nano- scale in landfills. In the global scale, the concentration of MPs/NPs in raw and treated landfill leachate varied between 0-382 item/L and 0-2.7 item/L, respectively. Occurrence of MPs/NPs in raw landfill leachate is largely ...
A Photocurable Leaky Dielectric Material for Highly Electrical Insulating Electrohydrodynamic Mic... more A Photocurable Leaky Dielectric Material for Highly Electrical Insulating Electrohydrodynamic Micro-/Nanopatterns Guolong Wang,† Guowei Lv,† Shihu Zhang,† Jinyou Shao,‡ Xiangming Li,‡ Hongmiao Tian,‡ Demei Yu,*,† and Lifeng Zhang*,§ †Department of Applied Chemistry, School of Science, State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, and ‡Microand Nanotechnology Research Center, State Key Laboratory of Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Biomass-derived biochar was used as the precursor to synthesize porous carbons for supercapacitor... more Biomass-derived biochar was used as the precursor to synthesize porous carbons for supercapacitor electrodes. The biochar was first activated with KOH to generate porous carbon material and then fabricated into highly flexible porous carbon nanofibers (ECNF) by electrospinning technique. Activated carbons with a surface area of around 2258 m 2 /g were found. The resultant biochar based ECNF mats exhibited outstanding mechanical flexibility and electrochemical properties as free-stranding and binder free electrodes of supercapacitor. The PAN/BCK3 ECNFs, which were made from the composite of polyacrylonitrile (PAN) and KOH-activated biochar (mass ratio of Biochar/KOH =1:3) exhibited the highest gravimetric capacitance (108 F/g at current density of 0.5 A/g) with high retention (96% at 1 A/g) due to its well-developed micro-mesoporosity. The results indicated that biomass-derived biochar is a promising material which can be used for the production of low cost high performance electrode materials for supercapacitor.
ABSTRACT Carbon nanofibers with controllable surface-attached Pt nanoparticles (ECNFs-PtNPs) were... more ABSTRACT Carbon nanofibers with controllable surface-attached Pt nanoparticles (ECNFs-PtNPs) were prepared by electrospinning followed by carbonization and subsequent Pt nanoparticle growth via redox reaction.•The hierarchical ECNFs-PtNPs were employed as cost-effective counter electrode in dye-sensitized solar cells (DSCs).•The effects of size, morphology, and loading of Pt nanoparticles on performance of DSCs were investigated.•DSCs with ECNFs-PtNPs counter electrode demonstrated excellent solar power conversion efficiency which is equivalent or even higher than that of conventional DSCs made with Pt counter electrode.
The concept of phase separation was coupled with electrospinning to generate polyacrylonitrile (P... more The concept of phase separation was coupled with electrospinning to generate polyacrylonitrile (PAN) and poly (ethylene oxide)(PEO) bicomponent fibres that, upon removal of the phase-separated PEO domains, became nanoporous. Electrospinning of ...
ABSTRACT Carbon nanofibers with diameters that fall into submicron and nanometer range have attra... more ABSTRACT Carbon nanofibers with diameters that fall into submicron and nanometer range have attracted growing attention in recent years due to their superior chemical, electrical, and mechanical properties in combination with their unique 1D nanostructures. Unlike catalytic synthesis, electrospinning polyacrylonitrile (PAN) followed by stabilization and carbonization has become a straightforward and convenient route to make continuous carbon nanofibers. This paper is a comprehensive and state-of-the-art review of the latest advances made in development and application of electrospun PAN-based carbon nanofibers. Our goal is to demonstrate an objective and overall picture of current research work on both functional carbon nanofibers and high-strength carbon nanofibers from the viewpoint of a materials scientist. Strategies to make a variety of carbon nanofibrous materials for energy conversion and storage, catalysis, sensor, adsorption/separation, and biomedical applications as well as attempts to achieve high-strength carbon nanofibers are addressed.
Amidoxime surface functionalized polyacrylonitrile (ASFPAN) nanofibers were prepared by electrosp... more Amidoxime surface functionalized polyacrylonitrile (ASFPAN) nanofibers were prepared by electrospinning polyacrylonitrile (PAN) solution followed by surface treatment in hydroxylamine aqueous solution. The interaction between ASFPAN nanofibrous mat and fungus (yeast) was investigated for the first time and viability of yeast cells on the nanofibrous mat was evaluated. The biological assay revealed that yeast cells died on the ASFPAN nanofibrous mats after 30 min of contact while they were still alive on both of PAN and ASFPAN cast film. The observations indicated that differentiated cell adhesion on ASFPAN nanofibrous mat might be the reason for the death of yeast cells.
h i g h l i g h t s Electrospun carbon nanofiber mats were made from a natural product of alkali ... more h i g h l i g h t s Electrospun carbon nanofiber mats were made from a natural product of alkali lignin. The mats were free-standing and/or mechanically flexible. The mats had the BET specific surface area up to 583 m 2 g À1. The mats were studied as binder-free supercapacitor electrodes. Electrochemical performances of the electrodes were high.
In this study, hybrid multi-scale composites were developed from glass microfiber fabrics (GFs) a... more In this study, hybrid multi-scale composites were developed from glass microfiber fabrics (GFs) and nano-epoxy resins containing electrospun glass nanofibers (EGNFs). The hypothesis was that, through dispersing a small amount of EGNFs into epoxy resin, mechanical properties (particularly out-of-plane mechanical properties) of the resulting hybrid multi-scale composites would be significantly improved. The composites were fabricated by the technique of vacuum assisted resin transfer molding (VARTM). The interlaminar shear strength, flexural properties, impact absorption energy, and tensile properties of the composites were evaluated, and the results were compared to those acquired from GFs/epoxy composite as well as GFs/epoxy composites containing chopped glass microfibers (GMFs); additionally, the reinforcement and/or toughening mechanisms were investigated. The study revealed that the nanoepoxy resin with 0.25 wt.% of EGNFs resulted in substantial improvements on mechanical properties of the resulting hybrid multi-scale composites.
We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2 -... more We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2 -ethyl hexyloxy)-p-phenylene vinylene] (MEH-PPV) and polyethylene oxide (PEO) nanofibers. MEH-PPV/PEO nanofibers with different compositions have been fabricated by the electrospinning technique. The fluorescence spectra of the nanofibers show that the emission shoulder at ∼630 nm blue-shifts ∼45 nm, whereas the main emission peak around 590 nm blue-shifts ∼15 nm with decreasing concentration of MEH-PPV in the nanofiber. In addition, confocal microscopic studies of a single MEH-PPV/PEO electrospun nanofiber indicate that the fluorescence spectra of the nanofiber do not show any polarization dependence. The results are discussed in terms of the aggregation of MEH-PPV in an inert matrix.
We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2-e... more We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene] (MEH-PPV) and polyethylene oxide (PEO) nanofibers. MEH-PPV/PEO nanofibers with different compositions have been fabricated by the electrospinning technique. The fluorescence spectra of the nanofibers show that the emission shoulder at ∼630 nm blue-shifts ∼45 nm, whereas the main emission peak around 590 nm blue-shifts ∼15 nm with decreasing concentration of MEH-PPV in the nanofiber. In addition, confocal microscopic studies of a single MEH-PPV/PEO electrospun nanofiber indicate that the fluorescence spectra of the nanofiber do not show any polarization dependence. The results are discussed in terms of the aggregation of MEH-PPV in an inert matrix.
A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R... more A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R 2), and core atoms (X) were studied as light-harvesting sensitizers for dye-sensitized solar cells (DSSCs). DSSCs were fabricated using these porphyrins as well as TiO2 nanoparticles with a particle diameter of around 25 nm. A dense layer of TiO2 was deposited as an interfacial layer on fluorine-doped tin dioxide (FTO) substrates. A TiO2 nanocrystalline film was then deposited on the dense layer by spin coating. The comparison of DSSC performance from different core-modified porphyrins was studied. The UV-vis absorption spectroscopy of porphyrin films attached on TiO2 and porphyrin solutions were also measured. The results indicated that both anchoring and meso aryl groups impacted on cell performance. The cell efficiency was correlated to the absorption of porphyrin films attached on TiO2 at the Soret band.
A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R... more A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R 2), and core atoms (X) were studied as light-harvesting sensitizers for dye-sensitized solar cells (DSSCs). DSSCs were fabricated using these porphyrins as well as TiO2 nanoparticles with a particle diameter of around 25 nm. A dense layer of TiO2 was deposited as an interfacial layer on fluorine-doped tin dioxide (FTO) substrates. A TiO2 nanocrystalline film was then deposited on the dense layer by spin coating. The comparison of DSSC performance from different core-modified porphyrins was studied. The UV-vis absorption spectroscopy of porphyrin films attached on TiO2 and porphyrin solutions were also measured. The results indicated that both anchoring and meso aryl groups impacted on cell performance. The cell efficiency was correlated to the absorption of porphyrin films attached on TiO2 at the Soret band.
Electrospun carbon nanofibers (ECNs) have been explored as an electrocatalyst and low-cost altern... more Electrospun carbon nanofibers (ECNs) have been explored as an electrocatalyst and low-cost alternative to platinum (Pt) for triiodide reduction in dye-sensitized solar cells (DSCs). The results of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry measurements indicated that the ECN counter electrodes exhibited low charge-transfer resistance (R ct), large capacitance (C), and fast reaction rates for triiodide reduction. Although the efficiency (η) of ECN-based cells was slightly lower than that of Ptbased cells, their short circuit current density (J sc) and open circuit voltage (V oc) were comparable. The ECN-based cells achieved an energy conversion efficiency (η) of 5.5 % under the AM 1.5 illumination at 100 mW cm-2. The reason for lower cell performance using the ECN electrode was because of its lower fill factor (FF) than that of Pt-based cells, probably caused by high total series resistance (R Stot) at ∼15.5 Ω cm 2 , which was larger than that of ∼4.8 Ω cm 2 in the Pt-based devices. Simulated results showed that the fill factor (FF) and η could be substantially improved by decreasing R Stot , which might be achieved by using thinner and highly porous ECNs to reduce the thickness of the ECNs counter electrode.
Formation of cellulose acetate (CA) and poly(ethylene oxide) (PEO) bicomponent fibers by electros... more Formation of cellulose acetate (CA) and poly(ethylene oxide) (PEO) bicomponent fibers by electrospinning of binary mixtures of these polymers was strongly influenced by their chain lengths, concentrations and mixed ratios as well as the solvents employed. Individually, the threshold molecular weights that supported fiber generation were 50 kDa and 100 kDa for CA and PEO, respectively. Adding dioxane, a lower dielectric constant co-solvent, enabled fiber formation from CA alone at a lower 30 kDa as well as from binary systems with one low molecular weight polymer that was not fiber forming. While bicomponent fiber formation generally improved with longer polymers and higher concentrations, fiber sizes also increased with both these factors. PEO in the bicomponent fibers was clearly phase-separated and the phase separation of long chains was facilitated by DMF, whereas that of shorter chains by DMF/dioxane. A phase-separated CA core and PEO sheath structure of the bicomponent fibers was strongly supported by experimental evidence.
As a new and promising reinforcing filler, electrospun glass nanofibers (EGNFs) have attracted at... more As a new and promising reinforcing filler, electrospun glass nanofibers (EGNFs) have attracted attention in the field of polymer composite materials. However, the reinforcing effectiveness of surface-modified EGNFs using different silane coupling agents in epoxy resin is still not quite clear. In this research, a series of silane coupling agents with increasing chain lengths in the order of methyl trimethoxysilane (MTMS), (3-aminopropyl) triethoxysilane (APTES), (3-glycidyloxypropyl) trimethoxysilane (GPTMS), and dual silane coupling agent APTES–GPTMS were employed to carry out surface treatment on the EGNFs. The pristine and silane functionalized EGNFs were then incorporated into epoxy resin as reinforcing fillers at low loading levels, i.e., 0.25 wt.%, 0.5 wt.%, and 1 wt.%, and the mechanical properties of the resultant epoxy nanocomposites, including strength, stiffness, ductility, and toughness, were evaluated. A commercial product of glass nanoparticles (GNPs) was used as a con...
Epoxy is the most prevalent thermosetting resin in the field of polymer composite materials. Ther... more Epoxy is the most prevalent thermosetting resin in the field of polymer composite materials. There has been a growing interest in the development of bio-based epoxy resins as a sustainable alternative to conventional petrochemical epoxy resins. Advances in this field in recent years have included the use of various renewable resources, such as vegetable oils, lignin, and sugars, as direct precursors to produce bio-based epoxy resins. In the meantime, bio-oils have been produced via the decomposition of biomass through thermochemical conversion and mainly being used as renewable liquid fuels. It is noteworthy that bio-oils can be used as a sustainable resource to produce epoxy resins. This review addresses research progress in producing bio-oil-based epoxy resins from thermochemical processing techniques including organic solvent liquefaction, fast pyrolysis, and hydrothermal liquefaction. The production of bio-oil from thermochemical processing and its use to inject sustainability i...
Presently, dental composites have been widely adopted by the profession as the restorative materi... more Presently, dental composites have been widely adopted by the profession as the restorative material of choice; as compared to dental amalgams, the composites possess better esthetic property, have less safety concern, and have shown reasonably satisfactory clinic results. Dental composites consist of resin matrices and inorganic fillers. The monomer of 2,20-bis-[4-(methacryloxypropoxy)-phenyl]propane (Bis-GMA) has been used as an important dental base monomer since it was invented in the 1960s [1, 2]; for example, Bis-GMA is the base monomer in the Z100 Restorative Dental Composite produced by the 3M Corporate. Bis-GMA is a very viscous, honey-like liquid. To improve handling qualities, a diluent monomer of tri(ethylene glycol) dimethacrylate (TEGDMA) is added to thin the resin. In the Bis-GMA/TEGDMA dental resin systems, Bis-GMA functions to limit the polymerization-induced volumetric shrinkage and to enhance the resin reactivity, whereas TEGDMA provides for the increased vinyl double bond conversion [3, 4]. Albeit dental resins have been reinforced with inorganic fillers of glass/ceramic powders containing surface-silanized particles, relatively low strength and durability of the composites have limited their uses [5–8]: dental composites have flexural strengths typically ranging from 80 to 120 MPa, which can fulfill the requirement of filling tooth cavities but cannot survive large stress-bearing restorations such as crowns and bridges; furthermore, the strength of dental composites decreases substantially after being used for a period of time. The average service lifetime of dental composites is considerably shorter than that of dental amalgams [9, 10]. Investigations of the failures revealed that, among numerous issues, the inorganic filler was a major contributor [11, 12]. Many inorganic filler particles currently used for dental composites are spherical or irregular in shape. Such filler particles at occlusal surfaces are susceptible to dislodgement from the resin matrix during wear with food boluses. This would cause the reinforcement effect to be lost. Chopped glass fibers and/or high strength whiskers with diameters of 5–50 lm and aspect ratios larger than 10 have also been investigated to reinforce dental resins [13–16], and the resulting composites showed higher mechanical properties. Several reinforcement mechanisms including ‘‘Bridging,’’ ‘‘Pull-out,’’ and ‘‘Load Transfer’’ were proposed for understanding the fiber/whisker reinforcement [17, 18]; in particular, ‘‘Bridging’’ is a powerful reinforcement mechanism. If a micro-crack is initiated in a resin matrix under contact wear and/or other stresses, the fillers remain intact across the crack planes supporting the applied load. Crack-opening is resisted by the bridging fillers; thus the resin matrix is reinforced. Requirements for fillers to achieve effective ‘‘Bridging’’ reinforcement include high strength and large aspect ratio values; tooth enamel rods are an example of elongated fillers, and crystalline platelets in dental glass/ceramics are another example [19]. Nonetheless, the dental composites reinforced with fibers/whiskers generally possess mechanical properties that still need further improvements; this is L. Zhang Y. Gao Q. Chen H. Fong (&) Department of Chemistry, South Dakota School of Mines and Technology, 501 East St. Joseph Street, Rapid City, SD 57701, USA e-mail: [email protected]
As a short-chain PFAS (per- and polyfluoroalkyl substance), GenX was produced in recent years to ... more As a short-chain PFAS (per- and polyfluoroalkyl substance), GenX was produced in recent years to replace traditional long-chain PFASs, such as perfluorooctanoic acid (PFOA). However, GenX turns out to be more toxic than people originally thought, posing health risks as a persistent environmental pollutant. In this research, for the first time, we incorporated chlorella, a single-celled green freshwater microalga that grows worldwide, with polyacrylonitrile (PAN) in equal amounts in electrospun nanofibers and studied the capability of the electrospun PAN/Algae bicomponent nanofibrous membrane (ES(PAN/Algae)) to bind and remove GenX from water. The incorporation of algae demonstrated a synergistic effect and significantly improved the GenX removal efficiency of the nanofibrous membrane. The maximum GenX removal capacity reached 0.9 mmol/g at pH 6, which is significantly higher than that of most of the reported GenX adsorbents as well as activated carbon. The GenX removal mechanism was...
Due to a massive amount of plastic waste from municipal and industrial sources accumulates in lan... more Due to a massive amount of plastic waste from municipal and industrial sources accumulates in landfills, landfill leachate is becoming a significant reservoir of microplastic (MPs)/ Nanoplastics (NPs), and MPs/NPs in landfill leachate released to the environment can pose detrimental effects on humans and biota. This study critically reviewed most available up-to-date scientific literature on MPs/NPs in landfill leachate and provides the state-of-the-science regarding their detection and quantification, occurrence and characteristics, and remediation. MPs/NPs in landfill leachate can be classified into primary source that is in micro- or nano- scale when manufactured, and secondary source that is made as regular sized plastic but fragmented in to micro- or nano- scale in landfills. In the global scale, the concentration of MPs/NPs in raw and treated landfill leachate varied between 0-382 item/L and 0-2.7 item/L, respectively. Occurrence of MPs/NPs in raw landfill leachate is largely ...
A Photocurable Leaky Dielectric Material for Highly Electrical Insulating Electrohydrodynamic Mic... more A Photocurable Leaky Dielectric Material for Highly Electrical Insulating Electrohydrodynamic Micro-/Nanopatterns Guolong Wang,† Guowei Lv,† Shihu Zhang,† Jinyou Shao,‡ Xiangming Li,‡ Hongmiao Tian,‡ Demei Yu,*,† and Lifeng Zhang*,§ †Department of Applied Chemistry, School of Science, State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, and ‡Microand Nanotechnology Research Center, State Key Laboratory of Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Biomass-derived biochar was used as the precursor to synthesize porous carbons for supercapacitor... more Biomass-derived biochar was used as the precursor to synthesize porous carbons for supercapacitor electrodes. The biochar was first activated with KOH to generate porous carbon material and then fabricated into highly flexible porous carbon nanofibers (ECNF) by electrospinning technique. Activated carbons with a surface area of around 2258 m 2 /g were found. The resultant biochar based ECNF mats exhibited outstanding mechanical flexibility and electrochemical properties as free-stranding and binder free electrodes of supercapacitor. The PAN/BCK3 ECNFs, which were made from the composite of polyacrylonitrile (PAN) and KOH-activated biochar (mass ratio of Biochar/KOH =1:3) exhibited the highest gravimetric capacitance (108 F/g at current density of 0.5 A/g) with high retention (96% at 1 A/g) due to its well-developed micro-mesoporosity. The results indicated that biomass-derived biochar is a promising material which can be used for the production of low cost high performance electrode materials for supercapacitor.
ABSTRACT Carbon nanofibers with controllable surface-attached Pt nanoparticles (ECNFs-PtNPs) were... more ABSTRACT Carbon nanofibers with controllable surface-attached Pt nanoparticles (ECNFs-PtNPs) were prepared by electrospinning followed by carbonization and subsequent Pt nanoparticle growth via redox reaction.•The hierarchical ECNFs-PtNPs were employed as cost-effective counter electrode in dye-sensitized solar cells (DSCs).•The effects of size, morphology, and loading of Pt nanoparticles on performance of DSCs were investigated.•DSCs with ECNFs-PtNPs counter electrode demonstrated excellent solar power conversion efficiency which is equivalent or even higher than that of conventional DSCs made with Pt counter electrode.
The concept of phase separation was coupled with electrospinning to generate polyacrylonitrile (P... more The concept of phase separation was coupled with electrospinning to generate polyacrylonitrile (PAN) and poly (ethylene oxide)(PEO) bicomponent fibres that, upon removal of the phase-separated PEO domains, became nanoporous. Electrospinning of ...
ABSTRACT Carbon nanofibers with diameters that fall into submicron and nanometer range have attra... more ABSTRACT Carbon nanofibers with diameters that fall into submicron and nanometer range have attracted growing attention in recent years due to their superior chemical, electrical, and mechanical properties in combination with their unique 1D nanostructures. Unlike catalytic synthesis, electrospinning polyacrylonitrile (PAN) followed by stabilization and carbonization has become a straightforward and convenient route to make continuous carbon nanofibers. This paper is a comprehensive and state-of-the-art review of the latest advances made in development and application of electrospun PAN-based carbon nanofibers. Our goal is to demonstrate an objective and overall picture of current research work on both functional carbon nanofibers and high-strength carbon nanofibers from the viewpoint of a materials scientist. Strategies to make a variety of carbon nanofibrous materials for energy conversion and storage, catalysis, sensor, adsorption/separation, and biomedical applications as well as attempts to achieve high-strength carbon nanofibers are addressed.
Amidoxime surface functionalized polyacrylonitrile (ASFPAN) nanofibers were prepared by electrosp... more Amidoxime surface functionalized polyacrylonitrile (ASFPAN) nanofibers were prepared by electrospinning polyacrylonitrile (PAN) solution followed by surface treatment in hydroxylamine aqueous solution. The interaction between ASFPAN nanofibrous mat and fungus (yeast) was investigated for the first time and viability of yeast cells on the nanofibrous mat was evaluated. The biological assay revealed that yeast cells died on the ASFPAN nanofibrous mats after 30 min of contact while they were still alive on both of PAN and ASFPAN cast film. The observations indicated that differentiated cell adhesion on ASFPAN nanofibrous mat might be the reason for the death of yeast cells.
h i g h l i g h t s Electrospun carbon nanofiber mats were made from a natural product of alkali ... more h i g h l i g h t s Electrospun carbon nanofiber mats were made from a natural product of alkali lignin. The mats were free-standing and/or mechanically flexible. The mats had the BET specific surface area up to 583 m 2 g À1. The mats were studied as binder-free supercapacitor electrodes. Electrochemical performances of the electrodes were high.
In this study, hybrid multi-scale composites were developed from glass microfiber fabrics (GFs) a... more In this study, hybrid multi-scale composites were developed from glass microfiber fabrics (GFs) and nano-epoxy resins containing electrospun glass nanofibers (EGNFs). The hypothesis was that, through dispersing a small amount of EGNFs into epoxy resin, mechanical properties (particularly out-of-plane mechanical properties) of the resulting hybrid multi-scale composites would be significantly improved. The composites were fabricated by the technique of vacuum assisted resin transfer molding (VARTM). The interlaminar shear strength, flexural properties, impact absorption energy, and tensile properties of the composites were evaluated, and the results were compared to those acquired from GFs/epoxy composite as well as GFs/epoxy composites containing chopped glass microfibers (GMFs); additionally, the reinforcement and/or toughening mechanisms were investigated. The study revealed that the nanoepoxy resin with 0.25 wt.% of EGNFs resulted in substantial improvements on mechanical properties of the resulting hybrid multi-scale composites.
We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2 -... more We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2 -ethyl hexyloxy)-p-phenylene vinylene] (MEH-PPV) and polyethylene oxide (PEO) nanofibers. MEH-PPV/PEO nanofibers with different compositions have been fabricated by the electrospinning technique. The fluorescence spectra of the nanofibers show that the emission shoulder at ∼630 nm blue-shifts ∼45 nm, whereas the main emission peak around 590 nm blue-shifts ∼15 nm with decreasing concentration of MEH-PPV in the nanofiber. In addition, confocal microscopic studies of a single MEH-PPV/PEO electrospun nanofiber indicate that the fluorescence spectra of the nanofiber do not show any polarization dependence. The results are discussed in terms of the aggregation of MEH-PPV in an inert matrix.
We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2-e... more We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene] (MEH-PPV) and polyethylene oxide (PEO) nanofibers. MEH-PPV/PEO nanofibers with different compositions have been fabricated by the electrospinning technique. The fluorescence spectra of the nanofibers show that the emission shoulder at ∼630 nm blue-shifts ∼45 nm, whereas the main emission peak around 590 nm blue-shifts ∼15 nm with decreasing concentration of MEH-PPV in the nanofiber. In addition, confocal microscopic studies of a single MEH-PPV/PEO electrospun nanofiber indicate that the fluorescence spectra of the nanofiber do not show any polarization dependence. The results are discussed in terms of the aggregation of MEH-PPV in an inert matrix.
A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R... more A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R 2), and core atoms (X) were studied as light-harvesting sensitizers for dye-sensitized solar cells (DSSCs). DSSCs were fabricated using these porphyrins as well as TiO2 nanoparticles with a particle diameter of around 25 nm. A dense layer of TiO2 was deposited as an interfacial layer on fluorine-doped tin dioxide (FTO) substrates. A TiO2 nanocrystalline film was then deposited on the dense layer by spin coating. The comparison of DSSC performance from different core-modified porphyrins was studied. The UV-vis absorption spectroscopy of porphyrin films attached on TiO2 and porphyrin solutions were also measured. The results indicated that both anchoring and meso aryl groups impacted on cell performance. The cell efficiency was correlated to the absorption of porphyrin films attached on TiO2 at the Soret band.
A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R... more A series of core-modified porphyrins with different meso aryl groups ( R 1), anchoring groups ( R 2), and core atoms (X) were studied as light-harvesting sensitizers for dye-sensitized solar cells (DSSCs). DSSCs were fabricated using these porphyrins as well as TiO2 nanoparticles with a particle diameter of around 25 nm. A dense layer of TiO2 was deposited as an interfacial layer on fluorine-doped tin dioxide (FTO) substrates. A TiO2 nanocrystalline film was then deposited on the dense layer by spin coating. The comparison of DSSC performance from different core-modified porphyrins was studied. The UV-vis absorption spectroscopy of porphyrin films attached on TiO2 and porphyrin solutions were also measured. The results indicated that both anchoring and meso aryl groups impacted on cell performance. The cell efficiency was correlated to the absorption of porphyrin films attached on TiO2 at the Soret band.
Electrospun carbon nanofibers (ECNs) have been explored as an electrocatalyst and low-cost altern... more Electrospun carbon nanofibers (ECNs) have been explored as an electrocatalyst and low-cost alternative to platinum (Pt) for triiodide reduction in dye-sensitized solar cells (DSCs). The results of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry measurements indicated that the ECN counter electrodes exhibited low charge-transfer resistance (R ct), large capacitance (C), and fast reaction rates for triiodide reduction. Although the efficiency (η) of ECN-based cells was slightly lower than that of Ptbased cells, their short circuit current density (J sc) and open circuit voltage (V oc) were comparable. The ECN-based cells achieved an energy conversion efficiency (η) of 5.5 % under the AM 1.5 illumination at 100 mW cm-2. The reason for lower cell performance using the ECN electrode was because of its lower fill factor (FF) than that of Pt-based cells, probably caused by high total series resistance (R Stot) at ∼15.5 Ω cm 2 , which was larger than that of ∼4.8 Ω cm 2 in the Pt-based devices. Simulated results showed that the fill factor (FF) and η could be substantially improved by decreasing R Stot , which might be achieved by using thinner and highly porous ECNs to reduce the thickness of the ECNs counter electrode.
Formation of cellulose acetate (CA) and poly(ethylene oxide) (PEO) bicomponent fibers by electros... more Formation of cellulose acetate (CA) and poly(ethylene oxide) (PEO) bicomponent fibers by electrospinning of binary mixtures of these polymers was strongly influenced by their chain lengths, concentrations and mixed ratios as well as the solvents employed. Individually, the threshold molecular weights that supported fiber generation were 50 kDa and 100 kDa for CA and PEO, respectively. Adding dioxane, a lower dielectric constant co-solvent, enabled fiber formation from CA alone at a lower 30 kDa as well as from binary systems with one low molecular weight polymer that was not fiber forming. While bicomponent fiber formation generally improved with longer polymers and higher concentrations, fiber sizes also increased with both these factors. PEO in the bicomponent fibers was clearly phase-separated and the phase separation of long chains was facilitated by DMF, whereas that of shorter chains by DMF/dioxane. A phase-separated CA core and PEO sheath structure of the bicomponent fibers was strongly supported by experimental evidence.
Uploads
Papers by Lifeng Zhang