The effect of increasing course of temperature and pressure on polypropylene （PP） degradation in supercritical water was investigated for developing a process of recycling waste plastic. A group of experiments was c...The effect of increasing course of temperature and pressure on polypropylene （PP） degradation in supercritical water was investigated for developing a process of recycling waste plastic. A group of experiments was carded out in a reaction system at a pressure of 26MPa, temperature of 380℃ or 400℃ for 30min, 70min, and 120min by Course One （the increasing course of temperature and pressure is via gaseous regions to supercritical regions）, and the other group was carried out at corresponding holding conditions by Course Two （the increasing course of temperature and pressure is via liquid regions to supercritical regions）. The time of the increasing courses was about 30min. Products were analyzed by Ostward-type viscometer, gaseous chromatography, and mass spectrometers （GC/MS）. Characterization results suggested that different increasing courses of temperature and pressure would give rise to different results, although they were treated under the similar holding conditions. It was also found that Course Two was more effective on PP degradation in supercritical water.展开更多
The novel sulfonated polyimide membranes were successfully synthesized by thermal imidization with monomers of 4,4＇-（hexafluoroisopropylidene）diphthalic anhydride （6FDA）, 4,4＇-diamino- diphenyl ether-2,2＇-disul...The novel sulfonated polyimide membranes were successfully synthesized by thermal imidization with monomers of 4,4＇-（hexafluoroisopropylidene）diphthalic anhydride （6FDA）, 4,4＇-diamino- diphenyl ether-2,2＇-disulfonic acid （SODA） and 3,3 ＇-diaminochalcone （3DAC）. Photosensitive chalcone moiety was introduced to the main chain of copolymers, and the photocrosslinking of resulting copolymer in aqueous electrolyte was attempted. A series of sulfonated copolyimide precursors containing chalcone functional groups in the main chain were prepared with different sulfonation degrees by controlling the molar ratio of SODA, 6FDA and 3DAC. The polymer membranes were prepared from these sulfonated aromatic precursors by solution casting and subsequent thermal imidization. The crosslinking with UV irradiation was attempted in the presence or absence of distilled water. The characterizations of the resulting membrane such as the ion-exchange capacity, water absorption and ionic conductivity were performed with respect to the copolymer compositions and the photocrosslinking conditions.展开更多
In order to improve the properties by chemical modification and to optimize the alkali concentration, we treated Borassus fruit fine fibers with aqueous sodium hydroxide solutions of different concentra- tions. In eac...In order to improve the properties by chemical modification and to optimize the alkali concentration, we treated Borassus fruit fine fibers with aqueous sodium hydroxide solutions of different concentra- tions. In each case, the tensile properties of the fibers were determined. The morphology of the untreated and alkali treated fibers was observed using scanning electron microscope. The surface of the fibers became rough on alkali treatment. The tensile properties of the fibers improved on alkali treatment. The fibers attained maximum tensile properties when treated with 15% aqueous sodium hydroxide solution and decreased thereafter. The crystallinity index of the fibers showed a similar trend. The thermal stability of the alkali treated fibers was found to be higher than that of untreated fibers. Further, the char content was maximum for fibers treated with alkali having concentration of 15% and above. The chemical composition indicated that the percentageof a-cellulose was maximum when the fibers were treated with 15% aqueous sodium hydroxide solution and then decreased thereafter thus indicating the beginning of degradation of the fibers at higher concentrations. Thus, the optimum concentration of NaOH was established as 15% for alkali treatment of the Borassus fibers.展开更多
Polymers are huge compounds made up of numerous monomers(repeated subunits).They have similar macro and micro properties,as well as electrical transport qualities,semiconductive capabilities,and optical features.With ...Polymers are huge compounds made up of numerous monomers(repeated subunits).They have similar macro and micro properties,as well as electrical transport qualities,semiconductive capabilities,and optical features.With the advent of conductive polyacetylene,conductive polymers have gotten a lot of interest.These conductors have a wide range of electrical conductivity,which may be produced by doping,while being mechanically flexible and having a high thermal stability.Polymers may be created using a variety of methods,including chemical and electrochemical polymerization.With advancement in material stability and greater property control,an increasing variety of new applications are now being investigated.展开更多
The aim of the present work is fabrication of dual cross linked sodium alginate(SA)/montmorillonite(MMT) microbeads as a potential drug vehicle for extended release of curcumin(CUR). The microbeads were prepared using...The aim of the present work is fabrication of dual cross linked sodium alginate(SA)/montmorillonite(MMT) microbeads as a potential drug vehicle for extended release of curcumin(CUR). The microbeads were prepared using in situ ion-exchange followed by simple ionotropic gelation technique. The developed beads were characterized by Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), X-ray diffraction(X-RD) and scanning electron microscopy(SEM). The effect of MMT on encapsulation efficiency of CUR and intercalation kinetics was investigated. Dynamic swelling study and in vitro release study were investigated in simulated intestinal fluid(pH 7.4) and simulated gastric fluid(pH 1.2) at 37 ℃. Results suggested that both the swelling and in vitro release studies were influenced by the pH of test media, which might be suitable for intestinal drug delivery. The release mechanism was analyzed by fitting the release data into KorsmeyerPeppas equation.展开更多
The coconut palm tree leaf sheath fibers were analyzed by FTIR spectral analysis, Chemical, X-ray and thermo gravimetric methods to assess their suitability as reinforcements in the preparation of green composites. Th...The coconut palm tree leaf sheath fibers were analyzed by FTIR spectral analysis, Chemical, X-ray and thermo gravimetric methods to assess their suitability as reinforcements in the preparation of green composites. The morphology of the untreated and alkali treated fibers was studied by scanning electron microscopic method. The FTIR and chemical analyses indicated lowering of hemi-cellulose content by alkali treatment of the fibers. The X-ray diffraction revealed an increase in crystallinity of the fibers on alkali treatment. The thermal stability of the fibers was found to increase slightly by alkali treatment. The tensile properties of these fibers increased on alkali treatment. The mechanical and other physical properties indicated that these fibers were suitable as reinforcements for making the green composites.展开更多
Introduction We all very accustomed to the emergency room of a crit-ical care unit,which is indeed captivated with accidental injury and internal bleeding,making the duo one of the highest causes of mortality to date.
The methods of preparation of magnetic chitosan microspheres have been introduced. In addition, their applications in the wastewater treatment, based on different kinds of wastewater, have been reviewed, and their mec...The methods of preparation of magnetic chitosan microspheres have been introduced. In addition, their applications in the wastewater treatment, based on different kinds of wastewater, have been reviewed, and their mechanisms have been discussed.展开更多
Objective: To investigate the chemical composition, in vitro antibacterial and antifungal activity of Mentha longifolia L. essential oils using aqueous extract. Methods: Mentha longifolia L. essential oils were extrac...Objective: To investigate the chemical composition, in vitro antibacterial and antifungal activity of Mentha longifolia L. essential oils using aqueous extract. Methods: Mentha longifolia L. essential oils were extracted using hydrodistillation with Clevenger apparatus for 3 h and the yield of the essential oil was calculated. Essential oils were qualitatively and quantitatively analyzed with gas chromatography and gas chromatography-mass spectrometer. For these essential oils, antibacterial and antifungal activity against human pathogens were evaluated. Results: Nineteen chemical constituents representing 99.72% of the essential oil were found, comprising menthone (39.55%), isopulegone (30.49%), eucalyptol (10.38%), and α-terpineol (3.15%);these were major components, and others were minor components. The essential oil showed strong antibacterial activity against Staphylococcus aureus [(35.24 ± 0.13) mm], Enterococcus faecalis [(32.12 ± 0.12) mm] and Bacillus cereus [(30.06 ± 0.04) mm], as well as antifungal activity against Aspergillus flavus [(38.02 ± 0.06) mm], Alternaria alternaria [(35.26 ± 0.12) mm], and Penicillum spp ((34.14 ± 0.02) mm)Conclusions: It seems that the essential oils derived from the Mentha longifolia L. species could be used as a natural source of antimicrobial agents.展开更多
Hydrogels are high-water-content soft materials with widely tunable physicochemical properties,resembling soft tissues.Tremendous progress in engineering hydrogels with good biocompatibility,suitable bioactivities,and...Hydrogels are high-water-content soft materials with widely tunable physicochemical properties,resembling soft tissues.Tremendous progress in engineering hydrogels with good biocompatibility,suitable bioactivities,and controlled geometries has made them promising candidates for broad applications.Nevertheless,conventional hydrogels usually suffer from weak mechanical properties,limiting their use in biomedical settings involving load-bearing and persistent mechanical deformations.Inspired by the extreme mechanical properties and multiscale hierarchical structures of biological tissues,mechanically robust tough hydrogels have been developed.Combining robust mechanical properties and other desired performance characteristics in functional tough hydrogels expands their opportunities in biomedical fields.This Account seeks to guide the readership regarding the recent progress in functional tough hydrogels with a focus on molecular/structural design and novel fabrications,particularly surrounding the works reported by our groups.Meanwhile,functional tough hydrogels for multiple biomedical applications are discussed,highlighting the underlying mechanisms governing their relevant applications.We begin by introducing the definition,measurements,and design principles of tough hydrogels and hydrogel adhesives in terms of soft materials mechanics.Various molecular and structural engineering approaches by building mechanical dissipation into stretchable hydrogels to realize stress homogenization or energy dissipation are exploited to fabricate tough hydrogels.Molecular engineering-based network architecture design of homogeneous hydrogels and structural engineering-based design of heterogeneous hydrogels are elaborated.The conventional energy-dissipation-based tough hydrogels are reinforced by the sacrificial bonds or components,leading to a substantial toughness reduction in subsequent loading cycles.To this end,new molecular designs,including highly entangled hydrogels and sliding-ring hydrogels,have been developed to resolve the toughness−hysteresis conflict.In addition,novel processing techniques,including salting out,freeze casting,and three-dimensional(bio)printing,are exploited to manipulate the multiscale structures and geometries for tough hydrogel fabrication.As some of the most actively studied materials in recent years,functional tough hydrogels are finding promising applications as bioadhesives/coatings,tissue-engineering scaffolds,soft robot/actuators,and bioelectronics interfaces.The development of tough bioadhesives/coatings lies in constructing strong interfacial linkages between the tough hydrogels and the underlying substrates,having broad applications in wound closure and drug delivery.Tough hydrogels have also been widely studied for use in tissue engineering and regenerative medicine,although the conflict of mechanical robustness−cellular function restricts their practical applications.The flexible and compliant tough hydrogels with stimuli-responsive shape shifting and pressure-triggered actuation make them good candidates as actuators and soft robots for biomedical devices dealing with soft tissues.Conductive tough hydrogels also have been widely exploited for utility in bioelectronics.In the end,we highlight the major challenges and emphasize the trends in developing the next-generation functional tough hydrogels for practical biomedical and medical applications.展开更多
ZrO2/Graphene nanocomposites are fabricated from graphene oxide by one-step, green, facile and low-cost SCCO2 method. The as-prepared nanocomposites are characterized by means of X-ray photoelectron, transmission elec...ZrO2/Graphene nanocomposites are fabricated from graphene oxide by one-step, green, facile and low-cost SCCO2 method. The as-prepared nanocomposites are characterized by means of X-ray photoelectron, transmission electron microscopy and catalytic chemiluminescence measurement. The ZrO2 nanoparticles with size of several nanometers are uniformly coated on the graphene surface. The chemiluminescence characteristic to ethanol of the as-prepared nanocomposite paper is also investigated. The nanocomposite paper obtained displays high catalytic chemiluminescence sensitivity and highly selectivity to the ethanol gas. This study provides a facile, green and low-cost route to prepare nanoscopic gas sensing devices with application in safe protection, food fermentation, medical process and traffic safe.展开更多
BACKGROUND： Bacteria endogenously residing within the plant tissues have attracted significant attention for production of biopolyester, polyhydroxyalkanoates （PHAs）. Bacillus cereus RCL 02 （MCC 3436）, a leaf end...BACKGROUND： Bacteria endogenously residing within the plant tissues have attracted significant attention for production of biopolyester, polyhydroxyalkanoates （PHAs）. Bacillus cereus RCL 02 （MCC 3436）, a leaf endophyte of oleaginous plant Ricinus communis L. accumulates 81% poly（3-hydroxybutyrate） [P（3HB）] of its cell dry biomass when grown in mineral salts （MS） medium. METHODS： The copolymer production efficiency of B. cereus RCL 02 was evaluated in valeric acid supplemented MS medium under biphasic cultivation condition. The copolymer so produced has been compared with the P（3HB） isolated from RCL 02 in terms of thermal, mechanical and chemical properties. RESULTS： Valeric acid supplementation as co-substrate in the medium has led to the production of copolymer of 3- hydroxybutyrate （3HB） and 3-hydroxyvalerate （3HV） [P（3HB-co-3HV）] with 14.6 mol% 3HV. The identity of the polymers has been confirmed by X-ray diffraction （XRD） analysis, Fourier transform infrared （FTIR） and nuclear magnetic resonance （NMR） spectroscopic studies. Thermogravimetric analysis （TGA） revealed that P（3HB） and P（3HB-co-3HV） films degraded at 278.66℃ and 273.49℃, respectively. The P（3HB-co-3HV） showed lower melting temperature （165.03℃） compared to P （3HB） （170.74℃） according to differential scanning calorimetry （DSC）. Incorporation of 3HV monomers decreased the tensile strength （21.52 MPa）, tensile modulus （0.93 GPa）, storage modulus （E＇） （0.99 GPa） and increased % elongation at break （12.2%） of the copolyester. However, P（3HB） showed better barrier properties with lower water vapor transmission rate （WVTR） of 0.55 g-mil/100 in2/24 h. CONCLUSION： These findings emphasized exploration of endophytic bacterial strain （RCL 02） to produce biodegradable polyesters which might have significant potential for industrial application.展开更多
The effect of benzoyl peroxide （BPO） on polypropylene （PP） degradation in supercritical water was investigated with the aim of developing a process for recycling of waste plastics. A series of experiments with and...The effect of benzoyl peroxide （BPO） on polypropylene （PP） degradation in supercritical water was investigated with the aim of developing a process for recycling of waste plastics. A series of experiments with and without BPO were carried out at temperatures of 653 K and 673 K under pressure about 26 MPa for 30, 75 and 120 min respectively. Products were analyzed by an Ostward-type viscometer, gas chromatography and spectrometry （GC/MS） etc. The results indicated that mean molecular weight of the samples decreased greatly along with the time elapsing or with the temperature increasing, and PP was decomposed to Miphatic and cycloparaftinic hydrocarbons but a few benzenoid hydrocarbons. By comparing the experiments with and without BPO, it was made clear that BPO is an effective additive on PP degradation in supercritical water.展开更多
Stretched polyethylene(PE)fibers are found to have super high thermal conductivity,while the bulk of polyethylene is usually thermal insulating even for those with high crystalline degree.A molecular dynamic simulatio...Stretched polyethylene(PE)fibers are found to have super high thermal conductivity,while the bulk of polyethylene is usually thermal insulating even for those with high crystalline degree.A molecular dynamic simulation is deliberately carried out to examine the relationship between chain configuration and thermal conductivity of polyethylene.In this simulation study,independent and interacting PE chains being stretched are compared with the aim to find out the effect of stretching on thermal conductivity of PE.Various crystallization conditions for PE bulk are considered.It is found that heat transports predominately along the covalent chain rather than across chains in PE crystals.Our simulation study helps to understand experimental findings on thermal conductivity of PE at different states.W e also predict that amorphous PE may be super thermally conductive if chains are strictly stretched along heat flux.展开更多
3D DNA origami holds tremendous potential for the encapsulation and selective release of therapeutic drugs. Observations of the real-time performance of these structures in physiological environments will contribute t...3D DNA origami holds tremendous potential for the encapsulation and selective release of therapeutic drugs. Observations of the real-time performance of these structures in physiological environments will contribute to the development of future applications. We investigated the degradation kinetics of 3D DNA box origami in serum by using high-speed atomic force microscope optimized for imaging 3D DNA origami in real time. The time resolution allowed to characterize the stages of serum effects on individual 3D DNA boxes origami with nanometer resolution. Our results indicate that the digestion process is a combination of rapid collapse and slow degradation phases. Damage to box origami occurs mainly in the collapse phase. Thus, the structural stability of 3D DNA box origami should be improved, especially in the collapse phase, before these structures are used in clinical applications.展开更多
Graphene is the most attractive carbon-based material at present and attracting increasing attention as promising candidates for applications in numerous areas, because of its extraordinary chemical, thermal and mecha...Graphene is the most attractive carbon-based material at present and attracting increasing attention as promising candidates for applications in numerous areas, because of its extraordinary chemical, thermal and mechanical properties. In this paper, we discussed an innovative and simple method to synthesize titanium dioxide （TiO2） nanoclusters, using graphene as a mid-step template not as a component of final product. Using this method, the graphene was firstly fully coated with TiO2 nanoparticles by the thermal decomposition of titanium （IV） isopropoxide in a supercritical carbon dioxide （SC-CO2） at 200 ℃; the developed TiO2/graphene composites then were heated in an oxygen atmosphere. Eventually the TiO2 nanoclusters were obtained. The prepared TiO2 nanoclusters showed irregular features with high surface coverage, providing promises in a wide range of applications, especially for photo-degradation of organic compounds in aqueous solution under the radiation of UV-light.展开更多
基金Supported by the National Natural Science Foundation of China （No.59972022） and the 0pening Foundation of the Environmental Engineering Key Discipline, Zhejiang University of Technology （No.56310503011）.
文摘The effect of increasing course of temperature and pressure on polypropylene （PP） degradation in supercritical water was investigated for developing a process of recycling waste plastic. A group of experiments was carded out in a reaction system at a pressure of 26MPa, temperature of 380℃ or 400℃ for 30min, 70min, and 120min by Course One （the increasing course of temperature and pressure is via gaseous regions to supercritical regions）, and the other group was carried out at corresponding holding conditions by Course Two （the increasing course of temperature and pressure is via liquid regions to supercritical regions）. The time of the increasing courses was about 30min. Products were analyzed by Ostward-type viscometer, gaseous chromatography, and mass spectrometers （GC/MS）. Characterization results suggested that different increasing courses of temperature and pressure would give rise to different results, although they were treated under the similar holding conditions. It was also found that Course Two was more effective on PP degradation in supercritical water.
基金Funded by the New & Renewable Energy R&D Program(2009T100100606) under the Ministry of Knowledge Economy of Koreathe National Research Foundation of Korea (NRF) through the Human Resource Training Project for Regional Innovation
文摘The novel sulfonated polyimide membranes were successfully synthesized by thermal imidization with monomers of 4,4＇-（hexafluoroisopropylidene）diphthalic anhydride （6FDA）, 4,4＇-diamino- diphenyl ether-2,2＇-disulfonic acid （SODA） and 3,3 ＇-diaminochalcone （3DAC）. Photosensitive chalcone moiety was introduced to the main chain of copolymers, and the photocrosslinking of resulting copolymer in aqueous electrolyte was attempted. A series of sulfonated copolyimide precursors containing chalcone functional groups in the main chain were prepared with different sulfonation degrees by controlling the molar ratio of SODA, 6FDA and 3DAC. The polymer membranes were prepared from these sulfonated aromatic precursors by solution casting and subsequent thermal imidization. The crosslinking with UV irradiation was attempted in the presence or absence of distilled water. The characterizations of the resulting membrane such as the ion-exchange capacity, water absorption and ionic conductivity were performed with respect to the copolymer compositions and the photocrosslinking conditions.
文摘In order to improve the properties by chemical modification and to optimize the alkali concentration, we treated Borassus fruit fine fibers with aqueous sodium hydroxide solutions of different concentra- tions. In each case, the tensile properties of the fibers were determined. The morphology of the untreated and alkali treated fibers was observed using scanning electron microscope. The surface of the fibers became rough on alkali treatment. The tensile properties of the fibers improved on alkali treatment. The fibers attained maximum tensile properties when treated with 15% aqueous sodium hydroxide solution and decreased thereafter. The crystallinity index of the fibers showed a similar trend. The thermal stability of the alkali treated fibers was found to be higher than that of untreated fibers. Further, the char content was maximum for fibers treated with alkali having concentration of 15% and above. The chemical composition indicated that the percentageof a-cellulose was maximum when the fibers were treated with 15% aqueous sodium hydroxide solution and then decreased thereafter thus indicating the beginning of degradation of the fibers at higher concentrations. Thus, the optimum concentration of NaOH was established as 15% for alkali treatment of the Borassus fibers.
文摘Polymers are huge compounds made up of numerous monomers(repeated subunits).They have similar macro and micro properties,as well as electrical transport qualities,semiconductive capabilities,and optical features.With the advent of conductive polyacetylene,conductive polymers have gotten a lot of interest.These conductors have a wide range of electrical conductivity,which may be produced by doping,while being mechanically flexible and having a high thermal stability.Polymers may be created using a variety of methods,including chemical and electrochemical polymerization.With advancement in material stability and greater property control,an increasing variety of new applications are now being investigated.
基金UGCe BSR, New Delhi, India, for the financial support provided。
文摘The aim of the present work is fabrication of dual cross linked sodium alginate(SA)/montmorillonite(MMT) microbeads as a potential drug vehicle for extended release of curcumin(CUR). The microbeads were prepared using in situ ion-exchange followed by simple ionotropic gelation technique. The developed beads were characterized by Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), X-ray diffraction(X-RD) and scanning electron microscopy(SEM). The effect of MMT on encapsulation efficiency of CUR and intercalation kinetics was investigated. Dynamic swelling study and in vitro release study were investigated in simulated intestinal fluid(pH 7.4) and simulated gastric fluid(pH 1.2) at 37 ℃. Results suggested that both the swelling and in vitro release studies were influenced by the pH of test media, which might be suitable for intestinal drug delivery. The release mechanism was analyzed by fitting the release data into KorsmeyerPeppas equation.
基金supported by University Grants Com-mission,India,Major Research Project(No:33-397/2007(SRF))
文摘The coconut palm tree leaf sheath fibers were analyzed by FTIR spectral analysis, Chemical, X-ray and thermo gravimetric methods to assess their suitability as reinforcements in the preparation of green composites. The morphology of the untreated and alkali treated fibers was studied by scanning electron microscopic method. The FTIR and chemical analyses indicated lowering of hemi-cellulose content by alkali treatment of the fibers. The X-ray diffraction revealed an increase in crystallinity of the fibers on alkali treatment. The thermal stability of the fibers was found to increase slightly by alkali treatment. The tensile properties of these fibers increased on alkali treatment. The mechanical and other physical properties indicated that these fibers were suitable as reinforcements for making the green composites.
文摘Introduction We all very accustomed to the emergency room of a crit-ical care unit,which is indeed captivated with accidental injury and internal bleeding,making the duo one of the highest causes of mortality to date.
基金Supported by the Key Natural Science Foundation of China (Grant No. 50633030)
文摘The methods of preparation of magnetic chitosan microspheres have been introduced. In addition, their applications in the wastewater treatment, based on different kinds of wastewater, have been reviewed, and their mechanisms have been discussed.
文摘Objective: To investigate the chemical composition, in vitro antibacterial and antifungal activity of Mentha longifolia L. essential oils using aqueous extract. Methods: Mentha longifolia L. essential oils were extracted using hydrodistillation with Clevenger apparatus for 3 h and the yield of the essential oil was calculated. Essential oils were qualitatively and quantitatively analyzed with gas chromatography and gas chromatography-mass spectrometer. For these essential oils, antibacterial and antifungal activity against human pathogens were evaluated. Results: Nineteen chemical constituents representing 99.72% of the essential oil were found, comprising menthone (39.55%), isopulegone (30.49%), eucalyptol (10.38%), and α-terpineol (3.15%);these were major components, and others were minor components. The essential oil showed strong antibacterial activity against Staphylococcus aureus [(35.24 ± 0.13) mm], Enterococcus faecalis [(32.12 ± 0.12) mm] and Bacillus cereus [(30.06 ± 0.04) mm], as well as antifungal activity against Aspergillus flavus [(38.02 ± 0.06) mm], Alternaria alternaria [(35.26 ± 0.12) mm], and Penicillum spp ((34.14 ± 0.02) mm)Conclusions: It seems that the essential oils derived from the Mentha longifolia L. species could be used as a natural source of antimicrobial agents.
基金funding from the National Institutes of Health(R01HL153857,R01HL165176)the Brigham Research Institute.M.O.A.also acknowledges funding support from the TÜBÍTAK 2214-A Program(1059B141801395).
文摘Hydrogels are high-water-content soft materials with widely tunable physicochemical properties,resembling soft tissues.Tremendous progress in engineering hydrogels with good biocompatibility,suitable bioactivities,and controlled geometries has made them promising candidates for broad applications.Nevertheless,conventional hydrogels usually suffer from weak mechanical properties,limiting their use in biomedical settings involving load-bearing and persistent mechanical deformations.Inspired by the extreme mechanical properties and multiscale hierarchical structures of biological tissues,mechanically robust tough hydrogels have been developed.Combining robust mechanical properties and other desired performance characteristics in functional tough hydrogels expands their opportunities in biomedical fields.This Account seeks to guide the readership regarding the recent progress in functional tough hydrogels with a focus on molecular/structural design and novel fabrications,particularly surrounding the works reported by our groups.Meanwhile,functional tough hydrogels for multiple biomedical applications are discussed,highlighting the underlying mechanisms governing their relevant applications.We begin by introducing the definition,measurements,and design principles of tough hydrogels and hydrogel adhesives in terms of soft materials mechanics.Various molecular and structural engineering approaches by building mechanical dissipation into stretchable hydrogels to realize stress homogenization or energy dissipation are exploited to fabricate tough hydrogels.Molecular engineering-based network architecture design of homogeneous hydrogels and structural engineering-based design of heterogeneous hydrogels are elaborated.The conventional energy-dissipation-based tough hydrogels are reinforced by the sacrificial bonds or components,leading to a substantial toughness reduction in subsequent loading cycles.To this end,new molecular designs,including highly entangled hydrogels and sliding-ring hydrogels,have been developed to resolve the toughness−hysteresis conflict.In addition,novel processing techniques,including salting out,freeze casting,and three-dimensional(bio)printing,are exploited to manipulate the multiscale structures and geometries for tough hydrogel fabrication.As some of the most actively studied materials in recent years,functional tough hydrogels are finding promising applications as bioadhesives/coatings,tissue-engineering scaffolds,soft robot/actuators,and bioelectronics interfaces.The development of tough bioadhesives/coatings lies in constructing strong interfacial linkages between the tough hydrogels and the underlying substrates,having broad applications in wound closure and drug delivery.Tough hydrogels have also been widely studied for use in tissue engineering and regenerative medicine,although the conflict of mechanical robustness−cellular function restricts their practical applications.The flexible and compliant tough hydrogels with stimuli-responsive shape shifting and pressure-triggered actuation make them good candidates as actuators and soft robots for biomedical devices dealing with soft tissues.Conductive tough hydrogels also have been widely exploited for utility in bioelectronics.In the end,we highlight the major challenges and emphasize the trends in developing the next-generation functional tough hydrogels for practical biomedical and medical applications.
文摘ZrO2/Graphene nanocomposites are fabricated from graphene oxide by one-step, green, facile and low-cost SCCO2 method. The as-prepared nanocomposites are characterized by means of X-ray photoelectron, transmission electron microscopy and catalytic chemiluminescence measurement. The ZrO2 nanoparticles with size of several nanometers are uniformly coated on the graphene surface. The chemiluminescence characteristic to ethanol of the as-prepared nanocomposite paper is also investigated. The nanocomposite paper obtained displays high catalytic chemiluminescence sensitivity and highly selectivity to the ethanol gas. This study provides a facile, green and low-cost route to prepare nanoscopic gas sensing devices with application in safe protection, food fermentation, medical process and traffic safe.
文摘BACKGROUND： Bacteria endogenously residing within the plant tissues have attracted significant attention for production of biopolyester, polyhydroxyalkanoates （PHAs）. Bacillus cereus RCL 02 （MCC 3436）, a leaf endophyte of oleaginous plant Ricinus communis L. accumulates 81% poly（3-hydroxybutyrate） [P（3HB）] of its cell dry biomass when grown in mineral salts （MS） medium. METHODS： The copolymer production efficiency of B. cereus RCL 02 was evaluated in valeric acid supplemented MS medium under biphasic cultivation condition. The copolymer so produced has been compared with the P（3HB） isolated from RCL 02 in terms of thermal, mechanical and chemical properties. RESULTS： Valeric acid supplementation as co-substrate in the medium has led to the production of copolymer of 3- hydroxybutyrate （3HB） and 3-hydroxyvalerate （3HV） [P（3HB-co-3HV）] with 14.6 mol% 3HV. The identity of the polymers has been confirmed by X-ray diffraction （XRD） analysis, Fourier transform infrared （FTIR） and nuclear magnetic resonance （NMR） spectroscopic studies. Thermogravimetric analysis （TGA） revealed that P（3HB） and P（3HB-co-3HV） films degraded at 278.66℃ and 273.49℃, respectively. The P（3HB-co-3HV） showed lower melting temperature （165.03℃） compared to P （3HB） （170.74℃） according to differential scanning calorimetry （DSC）. Incorporation of 3HV monomers decreased the tensile strength （21.52 MPa）, tensile modulus （0.93 GPa）, storage modulus （E＇） （0.99 GPa） and increased % elongation at break （12.2%） of the copolyester. However, P（3HB） showed better barrier properties with lower water vapor transmission rate （WVTR） of 0.55 g-mil/100 in2/24 h. CONCLUSION： These findings emphasized exploration of endophytic bacterial strain （RCL 02） to produce biodegradable polyesters which might have significant potential for industrial application.
基金the National Natural Science Foundation of China，the China Postdoctoral Science Special Foundation，UTC Exploration Project，the Harbin City Science and Technology Projects
基金Supported by the National Natural Science Foundation of China (No.59972022).
文摘The effect of benzoyl peroxide （BPO） on polypropylene （PP） degradation in supercritical water was investigated with the aim of developing a process for recycling of waste plastics. A series of experiments with and without BPO were carried out at temperatures of 653 K and 673 K under pressure about 26 MPa for 30, 75 and 120 min respectively. Products were analyzed by an Ostward-type viscometer, gas chromatography and spectrometry （GC/MS） etc. The results indicated that mean molecular weight of the samples decreased greatly along with the time elapsing or with the temperature increasing, and PP was decomposed to Miphatic and cycloparaftinic hydrocarbons but a few benzenoid hydrocarbons. By comparing the experiments with and without BPO, it was made clear that BPO is an effective additive on PP degradation in supercritical water.
基金supported by the National Key R&D Program of China(No.2017YFB0406204)the National Natural Science Foundation of China(No.51973002)University Institution of High Performance Rubber Materials of Anhui Province.
文摘Stretched polyethylene(PE)fibers are found to have super high thermal conductivity,while the bulk of polyethylene is usually thermal insulating even for those with high crystalline degree.A molecular dynamic simulation is deliberately carried out to examine the relationship between chain configuration and thermal conductivity of polyethylene.In this simulation study,independent and interacting PE chains being stretched are compared with the aim to find out the effect of stretching on thermal conductivity of PE.Various crystallization conditions for PE bulk are considered.It is found that heat transports predominately along the covalent chain rather than across chains in PE crystals.Our simulation study helps to understand experimental findings on thermal conductivity of PE at different states.W e also predict that amorphous PE may be super thermally conductive if chains are strictly stretched along heat flux.
文摘3D DNA origami holds tremendous potential for the encapsulation and selective release of therapeutic drugs. Observations of the real-time performance of these structures in physiological environments will contribute to the development of future applications. We investigated the degradation kinetics of 3D DNA box origami in serum by using high-speed atomic force microscope optimized for imaging 3D DNA origami in real time. The time resolution allowed to characterize the stages of serum effects on individual 3D DNA boxes origami with nanometer resolution. Our results indicate that the digestion process is a combination of rapid collapse and slow degradation phases. Damage to box origami occurs mainly in the collapse phase. Thus, the structural stability of 3D DNA box origami should be improved, especially in the collapse phase, before these structures are used in clinical applications.
基金financial support from iNANO through the Danish National Research Foundationthe National Natural Science Foundation of China to the Sino-Danish Center of Excellence on"The Self-assembly and Function of Molecular Nanostructures on Surfaces"+6 种基金the Carlsberg Foundationthe Villum Foundationthe National Natural Science Foundation of China(No.51003021)China Postdoctoral Science Special Foundation(Nos.201003420 and20090460067)UTC Exploration Project(CASC-HIT12-1C03)Opening Project of Key Laboratory of Solid Waste Treatment and Resource Recycle,Ministry of Education(12zxgk10)Harbin City Science and Technology Projects(2013DB4BP031)
文摘Graphene is the most attractive carbon-based material at present and attracting increasing attention as promising candidates for applications in numerous areas, because of its extraordinary chemical, thermal and mechanical properties. In this paper, we discussed an innovative and simple method to synthesize titanium dioxide （TiO2） nanoclusters, using graphene as a mid-step template not as a component of final product. Using this method, the graphene was firstly fully coated with TiO2 nanoparticles by the thermal decomposition of titanium （IV） isopropoxide in a supercritical carbon dioxide （SC-CO2） at 200 ℃; the developed TiO2/graphene composites then were heated in an oxygen atmosphere. Eventually the TiO2 nanoclusters were obtained. The prepared TiO2 nanoclusters showed irregular features with high surface coverage, providing promises in a wide range of applications, especially for photo-degradation of organic compounds in aqueous solution under the radiation of UV-light.
