Over the years,zinc-ion batteries(ZIBs)have attracted attention as a promising next-generation energy storage technology because of their excellent safety,long cycling performance,eco-friendliness,and high-power densi...Over the years,zinc-ion batteries(ZIBs)have attracted attention as a promising next-generation energy storage technology because of their excellent safety,long cycling performance,eco-friendliness,and high-power density.However,issues,such as the corrosion and dissolution of the Zn anode,limited wet-tability,and lack of sufficient nucleation sites for Zn plating,have limited their practical application.The introduction of a protective layer comprising of tellurium(Te)nanobelts onto the surface of Zn anode has emerged as a promising approach to overcome these limitations and improve the electrochemical behav-ior by enhancing the safety and wettability of ZIBs,as well as providing numerous nucleation sites for Zn plating.In the presence of a Te-based protective layer,the energy power density of the surface-engineered Zn anode improved significantly(ranging from 310 to 144 W h kg^(-1),over a power density range of 270 to 1,800 W kg^(-1)),and the lifespan capability was extended.These results demonstrate that the proposed strategy of employing Te nanobelts as a protective layer holds great promise for enhancing the energy storage performance of zIBs,making them even more attractive as a viable energy storage solution forthefuture.展开更多
AIM To investigate histologic abnormalities in the gastric smooth muscle of patients with diabetes mellitus(DM).METHODS Full-thickness gastric specimens were obtained from patients undergoing surgery for gastric cance...AIM To investigate histologic abnormalities in the gastric smooth muscle of patients with diabetes mellitus(DM).METHODS Full-thickness gastric specimens were obtained from patients undergoing surgery for gastric cancer. H&E stain and Masson's Trichrome stain were performed to assess the degree of fibrosis. Immunohistochemical staining using various antibodies was also performed [antibodies against protein gene product 9.5(PGP9.5), neuronal nitric oxide synthase(n NOS), vasoactive intestinal peptide(VIP), neurokinin-1(NK1) receptor, c-Kit, and platelet-derived growth factor receptor-alpha,(PDGFRα)]. Immunofluorescent staining and evaluation with confocal microscopy were also conducted.RESULTS Twenty-six controls and 35 diabetic patients(21 shortduration patients and 14 long-duration patients) were included. There were no significant differences in basic demographics between the two groups except in mean body mass index(BMI)(higher in the DM group). Proportions of moderate-to-severe intercellular fibrosis in the muscle layer were significantly higher in the DM group than in the control group(P < 0.01). On immunohistochemical staining, c-Kit- and PDGFRα-positive immunoreactivity were significantly decreased in the DM group compared with the control group(P < 0.05). There were no statistically significant differences in PGP9.5, n NOS, VIP, and neurokinin 1 expression. On immunofluorescent staining, cellularity of interstitial cells of Cajal(ICC) was observed to decrease with increasing duration of DM.CONCLUSION Our study suggests that increased intercellular fibrosis, loss of ICC, and loss of fibroblast-like cells are found in the smooth muscle of DM patients. These abnormalities may contribute to changes in gastric motor activity in patients with DM.展开更多
Barium titanate (BaTiO3) and silver (Ag) composite film with high dielectric constant was grown at room temperature by an aerosol deposition method.The dielectric constant increases by 0.5 times after adding Ag to the...Barium titanate (BaTiO3) and silver (Ag) composite film with high dielectric constant was grown at room temperature by an aerosol deposition method.The dielectric constant increases by 0.5 times after adding Ag to the BaTiO3 matrix,compared with pure BaTiO3.The high dielectric constant can be attributed to the percolation effect of Ag inclusions in the BaTiO3 matrix.The Ag was present in the form of discrete layer in the BaTiO3 film.The dielectric properties of BaTiO3 Ag were discussed in detail taking into account the changes in microstructures.展开更多
In order to obtain ultrafine Nd-Fe-B powder, a spray-dried precursor was treated by reduction-diffusion (R/D) process. And, unlike the conventional R/D process, calcium reduction that is a crucial step for the formati...In order to obtain ultrafine Nd-Fe-B powder, a spray-dried precursor was treated by reduction-diffusion (R/D) process. And, unlike the conventional R/D process, calcium reduction that is a crucial step for the formation of Nd2Fe14B was performed without conglomerating the precursor with Ca powder. By adopting this modified process, it is possible to synthesize the hard magnetic Nd2Fe14B at the reaction temperature as low as 850 ℃. The average size of Nd2Fe14B particles that are uniformly distributed in the optimally treated powder was <<1 μm. Most Nd2Fe14B particles were enclosed with thin layers of Nd-rich phase. Typical magnetic properties of such powder without eliminating impurity CaO were iHc=~5.9 kOe, Br=~5.5 kG, and (BH)max=~6 MGOe.展开更多
A graphene-CdSe composite was synthesized by a facile hydrothermal method,and characterized by X-ray diffraction,scanning electron microscopy with energy dispersive X-ray analysis,transmission electron microscopy and ...A graphene-CdSe composite was synthesized by a facile hydrothermal method,and characterized by X-ray diffraction,scanning electron microscopy with energy dispersive X-ray analysis,transmission electron microscopy and UV-vis diffuse reflectance spectrophotometry.The graphene-CdSe composite efficiently catalyzed the photodegradation of methylene blue(MB),methyl orange(MO) and rhodamine B(Rh.B) in aqueous solution under UV or visible light irradiation.The graphene-CdSe composite exhibited a higher photocatalytic activity for the MB solution.展开更多
The thermal conductivity of polymer composites can be enhanced by the vertical alignment of anisotropic aluminum nitride(AlN)platelet fillers in polymer matrices.The AlN platelets in polymer matrix were aligned in the...The thermal conductivity of polymer composites can be enhanced by the vertical alignment of anisotropic aluminum nitride(AlN)platelet fillers in polymer matrices.The AlN platelets in polymer matrix were aligned in the direction of in-plane and out-of-plane by using the doctor blading and the lamination process.The alignment of AlN plates in the out-of-plane or the in-plane direction has been confirmed by XRD and FE-SEM investigations.The polymer composite with the out-of-plane aligned AlN platelets showed almost 1.5 times or 2 times higher thermal conductivity than those with the AlN spheres or the in-plane aligned AlN platelets at the same filler content,respectively.This result could be attributed to the improvement of thermal pathway generated along the plane of platelets and the decrease of interfaces between the filler and the polymer.展开更多
A visible-light photocatalyst containing Ag2Se and reduced graphene oxide(RGO) was synthesized by a facile sonochemical-assisted hydrothermal method. X-ray diffraction, scanning electron mi-croscopy with energy-disper...A visible-light photocatalyst containing Ag2Se and reduced graphene oxide(RGO) was synthesized by a facile sonochemical-assisted hydrothermal method. X-ray diffraction, scanning electron mi-croscopy with energy-dispersive X-ray analysis, and ultraviolet-visible diffuse reflectance spectros-copy results indicated that the RGO-Ag2Se nanocomposite contained small crystalline Ag2Se nano-particles dispersed over graphene nanosheets and absorbed visible light. The high crystallinity of the nanoparticles increased photocatalytic activity by facilitating charge transport. N2 adsorp-tion-desorption measurements revealed that the RGO-Ag2Se nanocomposite contained numerous pores with an average diameter of 9 nm, which should allow reactant molecules to readily access the Ag2Se nanoparticles. The RGO-Ag2Se nanocomposite exhibited higher photocatalytic activity than bulk Ag2Se nanoparticles to degrade organic pollutant rhodamine B and industrial dye Texbrite BA-L under visible-light irradiation(λ > 420 nm). The generation of reactive oxygen spe-cies in RGO-Ag2Se was evaluated through its ability to oxidize 1,5-diphenylcarbazide to 1,5-diphenylcarbazone. The small size of the Ag2Se nanoparticles in RGO-Ag2Se was related to the use of ultrasonication during their formation, revealing that this approach is attractive to form po-rous RGO-Ag2Se materials with high photocatalytic activity under visible light.展开更多
Hair loss due to medical conditions,such as alopecia,male pattern baldness,and cancer chemotherapy treatment,has been a comm onproblem for many in dividuals.Cyclospori n A(CsA),a fungal metabolite,has been reported to...Hair loss due to medical conditions,such as alopecia,male pattern baldness,and cancer chemotherapy treatment,has been a comm onproblem for many in dividuals.Cyclospori n A(CsA),a fungal metabolite,has been reported to be a hair growth modulatory agent and is apotential drug for hair regeneration.However,the effect of topical application of CsA is limited by its poor water solubility.Several deliverysystems developed to enhance its solubility still showed poor skin penetration.To overcome these limitations,in this study,we have developed a novel chitosan nanocapsule platform using Pluro nic F127 and chitosan without any chemical crosslinking or complicated preparati on steps for the enhanced water solubility and high tran sdermal penetration of CsA.The chitosan nanocapsules(ChiNCs)optimized in terms of structural stability by using chitosan with various molecular weights ranging from 3 to 100 kDa enhanced the skin permeation of CsA through humancadaver skin in vitro.Topical administration of the CsA loaded ChiNCs in creased the hair follicles by c.a.7 times higher than that of thecontrol group,and effectively induced hair growth in C57BL/6 mice in vivo.These results suggest that ChiNCs could be used as a platform foreffective transdermal delivery of various hydrophobic drugs.展开更多
Perovskite quantum dots(PQDs)have been considered promising and effective photovoltaic absorber due to their superior optoelectronic properties and inherent material merits combining perovskites and QDs.However,they e...Perovskite quantum dots(PQDs)have been considered promising and effective photovoltaic absorber due to their superior optoelectronic properties and inherent material merits combining perovskites and QDs.However,they exhibit low moisture stability at room humidity(20-30%)owing to many surface defect sites generated by inefficient ligand exchange process.These surface traps must be re-passivated to improve both charge transport ability and moisture stability.To address this issue,PQD-organic semiconductor hybrid solar cells with suitable electrical properties and functional groups might dramatically improve the charge extraction and defect passivation.Conventional organic semiconductors are typically low-dimensional(1D and 2D)and prone to excessive self-aggregation,which limits chemical interaction with PQDs.In this work,we designed a new 3D star-shaped semiconducting material(Star-TrCN)to enhance the compatibility with PQDs.The robust bonding with Star-TrCN and PQDs is demonstrated by theoretical modeling and experimental validation.The Star-TrCN-PQD hybrid films show improved cubic-phase stability of CsPbI_(3)-PQDs via reduced surface trap states and suppressed moisture penetration.As a result,the resultant devices not only achieve remarkable device stability over 1000 h at 20-30%relative humidity,but also boost power conversion efficiency up to 16.0%via forming a cascade energy band structure.展开更多
NASICON (sodium (Na) superionic conductor) compounds have attracted considerable attention as promising solid electrolyte materials for advanced Na-based batteries. In this study, we investigated the improvement in io...NASICON (sodium (Na) superionic conductor) compounds have attracted considerable attention as promising solid electrolyte materials for advanced Na-based batteries. In this study, we investigated the improvement in ionic conductivities of von-Alpen-type NASICON (vA-NASICON) ceramic electrolytes by introducing a magnesium ion (Mg^(2+)) as a heterogeneous element. The optimal Mg-doped vA-NASICON exhibited a high ionic conductivity of 3.64×10^(−3) S·cm^(−1), which was almost 80% higher than that of un-doped vA-NASICON. The changes in physicochemical properties of the vA-NASICONs through the Mg introduction were systematically analyzed, and their effects on the ionic conductivities of the vA-NASICON were studied in detail. When the optimal ratio of Mg^(2+) was used in a synthetic process, the relative density (96.6%) and grain boundary ionic conductivity (σgb) were maximized, which improved the total ionic conductivity (σt) of the vA-NASICON. However, when Mg^(2+) was introduced in excess, the ionic conductivity decreased because of the formation of an undesired sodium magnesium phosphate (NaxMgyPO_(4)) secondary phase. The results of this study are expected to be effectively applied in the development of advanced sodium-based solid electrolytes with high ionic conductivities.展开更多
Cerium was extracted from rare earth slurry waste used for polishing a glass substrate.Initially,glass frit and flocculant were removed by froth flotation and dissolution.The recovered rare earth slurry exhibited almo...Cerium was extracted from rare earth slurry waste used for polishing a glass substrate.Initially,glass frit and flocculant were removed by froth flotation and dissolution.The recovered rare earth slurry exhibited almost the same particle size distribution as original slurry,which could be reused as slurry for glass polishing.From the rare earth slurry,the cerium solution was obtained by an oxidative thermal treatment and subsequent chemical leaching.The cerium solution was further purified up to 94% by selective precipitation of rare earth species.展开更多
Silicon carbide (SiC) fiber has recently received considerable attention as promising next-generation fiber because of its high strength at temperatures greater than 1300 ℃ in air.High-quality SiC fiber is primarily ...Silicon carbide (SiC) fiber has recently received considerable attention as promising next-generation fiber because of its high strength at temperatures greater than 1300 ℃ in air.High-quality SiC fiber is primarily made through a curing and heat treatment process.In this study,the chemical vapor curing method,instead of the thermal oxidation curing method,was used to prepare cured polycarbosilane (PCS) fiber.During the high temperature heat treatment of the cured PCS fiber,varied heating rates of 10,20,30,and 40 ℃/min were applied.Throughout the process,the fiber remained in the amorphous silicon carbide phase,and the measured tensile strength was the greatest when the oxygen content in the heat-treated fiber was low,due to the rapid heating rate.The fiber produced through this method was also found to have excellent internal oxidation properties.This fast,continuous process shows a great promise for the production of SiC fiber and the development of high-quality products.展开更多
High power light-emitting diodes (LEDs) lighting has drawn a great interest in the field of street light system in recent years. Key parameters for successful launching of LED street light in the commercial market a...High power light-emitting diodes (LEDs) lighting has drawn a great interest in the field of street light system in recent years. Key parameters for successful launching of LED street light in the commercial market are price and light efficiency, respectively, and they are greatly influenced by the materials and design factors used in high power LED package. This article presents a new design and materials processing technology to realize the solution of LED packaging with advantageous in price and performance. Cost effective materials and processing technology can be realized via thick film glass-ceramic insulating layer and silver conductor. Highly effective thermal design using direct heat dissipation to heat sink in LED package is demonstrated.展开更多
The development of CO_(2)into hydrocarbon fuels has emerged as a green method that could help mitigate global warning.The novel structured photocatalyst is a promising material for use in a photocatalytic and magneto-...The development of CO_(2)into hydrocarbon fuels has emerged as a green method that could help mitigate global warning.The novel structured photocatalyst is a promising material for use in a photocatalytic and magneto-electrochemical method that fosters the reduction of CO_(2)by suppressing the recombination of electron−hole pairs and effectively transferring the electrons to the surface for the chemical reaction of CO_(2)reduction.In our study,we have developed a novel-structured AgCuZnS_(2)–graphene–TiO_(2)to analyze its catalytic activity toward the selective evolution of CO_(2).The selectivity of each nanocomposite substantially enhanced the activity of the AgCuZnS_(2)–graphene–TiO_(2)ternary nanocomposite due to the successful interaction,and the selectivity of the final product was improved to a value 3 times higher than that of the pure AgCuZnS_(2)and 2 times higher than those of AgCuZnS_(2)–graphene and AgCuZnS_(2)–TiO_(2)under ultraviolet(UV)-light(λ=254 nm)irradiation in the photocatalytic process.The electrochemical CO_(2)reduction test was also conducted to analyze the efficacy of the AgCuZnS_(2)–graphene–TiO_(2)when used as a working electrode in laboratory electrochemical cells.The electrochemical process was conducted under different experimental conditions,such as various scan rates(mV·s^(–1)),under UV-light and with a 0.07 T magneticcore.The evolution of CO_(2)substantially improved under UV-light(λ=254 nm)and with 0.07 T magnetic-core treatment;these improvements were attributed to the facts that the UV-light activated the electron-transfer pathway and the magnetic core controlled the pathway of electrontransmission/prevention to protect it from chaotic electron movement.Among all tested nanocomposites,AgCuZnS_(2)–graphene–TiO_(2)absorbed the CO_(2)most strongly and showed the best ability to transfer the electron to reduce the CO_(2)to methanol.We believe that our newly-modeled ternary nanocomposite opens up new opportunities for the evolution of CO_(2)to methanol through an electrochemical and photocatalytic process.展开更多
The single-pot production of Pd@Pt core-shell structures is a promising approach as it offers large surface area,catalytic capability,and stability.In this work,we established a single-pot process to produce Pd@Pt cor...The single-pot production of Pd@Pt core-shell structures is a promising approach as it offers large surface area,catalytic capability,and stability.In this work,we established a single-pot process to produce Pd@Pt core-shell nanodendrites with tunable composition,shape and size for optimal electrochemical activity.Pd@Pt nanodendrites with diverse compositions were synthesized by tuning the ratios of Pd and Pt sources in an aqueous environment using cetyltrimethylammonium chloride,which functioned as both the surfactant and the reducing agent at an elevated temperature(90°C).The synthesized Pd5@Pt5 nanodendrites showed exceptional electrochemical action toward the methanol oxidation reaction related with another compositional Pd@Pt nanodendrites and conventional Pt/C electrocatalysts.In addition,Pd5@Pt5 nanodendrites exhibited good CO tolerance owing to their surface features and the synergistic effect among Pt and Pd.Meanwhile,nanodendrites with a Pt-rich surface provided exceptional catalytic active sites.Compared with the conventional Pt/C electrocatalyst,the anodic peak current obtained by Pd5@Pt5 nanodendrites was 3.74 and 2.18 times higher in relations of mass and electrochemical active surface area-normalized current density,respectively.This approach offers an attractive strategy to design electrocatalysts with unique structures and outstanding catalytic performance and stability for electrochemical energy conversion.展开更多
Three-dimensional (3D) host materials for lithium metal anodes (LMAs) have gained attention because they can mitigate volume expansion and local current density through their large surface area and suppress the dendri...Three-dimensional (3D) host materials for lithium metal anodes (LMAs) have gained attention because they can mitigate volume expansion and local current density through their large surface area and suppress the dendritic growth of lithium. Recent research on 3D host materials has focused on conductive materials;however, the benefits of 3D host materials cannot be fully utilized because lithium deposition begins at the top of the structure. Herein, we fabricate SiO_(2)-TiO_(2) composite microspheres with bimodal pore structures (bi-SiTiO) by simple spray pyrolysis. These microspheres effectively store lithium within the structure from the bottom of the electrode while preventing lithium dendrite formation. Focused ion beam-scanning transmission electron microscopy (FIB-STEM) analysis reveals that the lithiophilic properties of composite microspheres enhanced their effectiveness in storing lithium, with small pores acting as “lithium-ion sieves” for a uniform lithium-ion flux and large pores that provide sufficient volume for lithium deposition. The bi-SiTiO composite microspheres exhibit a high Coulombic efficiency of 98.5% over 200 cycles at 2.0 mA·cm^(−2) when operated in a lithium half-cell. With a high lithium loading of 5.0 mAh·cm^(−2), the symmetrical cell of the bi-SiTiO electrode sustains more than 900 h. A full cell coupled with an LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) (NCM811) cathode also exhibits enhanced electrochemical properties in terms of cycling stability and rate capability.展开更多
Wearable pressure sensors having versatile device structures have been extensively investigated to achieve high sensitivity under mechanical stimuli.Here,we introduce piezoelectric pressure sensors based on fabrics wo...Wearable pressure sensors having versatile device structures have been extensively investigated to achieve high sensitivity under mechanical stimuli.Here,we introduce piezoelectric pressure sensors based on fabrics woven using polyvinylidene fluoride(PVDF)weft and polyethylene terephthalate(PET)warp yarns with different weave structures:1/1(plain),2/2,and 3/3 weft rib patterns.The dependence of the pressure-sensing performance on the weave pattern is demonstrated with an actual large-scale fabric up to the~2 m scale.An optimized pressure sensor with a 2/2 weft rib pattern produced a high sensitivity of 83 mV N−1,which was 245%higher than that of the 1/1 pattern.The detection performance of the optimal fabric was extensively evaluated with a variety of ambient input sources,such as pressing,bending,twisting,and crumpling,as well as various human motions.Further,a large allfabric pressure sensor with arrayed touch pixel units demonstrated highly sensitive and stable sensing performance.展开更多
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea government(MOTIE)(RS-2023-00303581,Multiscale Simulation-Driven Development of Cost-Effective and Stable Aqueous Zn Ion Battery with Energy Density of 110 Wh/L for Energy Storage Systems:A Korea-USA Collaboration)。
文摘Over the years,zinc-ion batteries(ZIBs)have attracted attention as a promising next-generation energy storage technology because of their excellent safety,long cycling performance,eco-friendliness,and high-power density.However,issues,such as the corrosion and dissolution of the Zn anode,limited wet-tability,and lack of sufficient nucleation sites for Zn plating,have limited their practical application.The introduction of a protective layer comprising of tellurium(Te)nanobelts onto the surface of Zn anode has emerged as a promising approach to overcome these limitations and improve the electrochemical behav-ior by enhancing the safety and wettability of ZIBs,as well as providing numerous nucleation sites for Zn plating.In the presence of a Te-based protective layer,the energy power density of the surface-engineered Zn anode improved significantly(ranging from 310 to 144 W h kg^(-1),over a power density range of 270 to 1,800 W kg^(-1)),and the lifespan capability was extended.These results demonstrate that the proposed strategy of employing Te nanobelts as a protective layer holds great promise for enhancing the energy storage performance of zIBs,making them even more attractive as a viable energy storage solution forthefuture.
基金Supported by the National Research Foundation of Korea Grant funded by the Korean Government,No.2014R1A5A2010008
文摘AIM To investigate histologic abnormalities in the gastric smooth muscle of patients with diabetes mellitus(DM).METHODS Full-thickness gastric specimens were obtained from patients undergoing surgery for gastric cancer. H&E stain and Masson's Trichrome stain were performed to assess the degree of fibrosis. Immunohistochemical staining using various antibodies was also performed [antibodies against protein gene product 9.5(PGP9.5), neuronal nitric oxide synthase(n NOS), vasoactive intestinal peptide(VIP), neurokinin-1(NK1) receptor, c-Kit, and platelet-derived growth factor receptor-alpha,(PDGFRα)]. Immunofluorescent staining and evaluation with confocal microscopy were also conducted.RESULTS Twenty-six controls and 35 diabetic patients(21 shortduration patients and 14 long-duration patients) were included. There were no significant differences in basic demographics between the two groups except in mean body mass index(BMI)(higher in the DM group). Proportions of moderate-to-severe intercellular fibrosis in the muscle layer were significantly higher in the DM group than in the control group(P < 0.01). On immunohistochemical staining, c-Kit- and PDGFRα-positive immunoreactivity were significantly decreased in the DM group compared with the control group(P < 0.05). There were no statistically significant differences in PGP9.5, n NOS, VIP, and neurokinin 1 expression. On immunofluorescent staining, cellularity of interstitial cells of Cajal(ICC) was observed to decrease with increasing duration of DM.CONCLUSION Our study suggests that increased intercellular fibrosis, loss of ICC, and loss of fibroblast-like cells are found in the smooth muscle of DM patients. These abnormalities may contribute to changes in gastric motor activity in patients with DM.
基金supported by a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy,Korea
文摘Barium titanate (BaTiO3) and silver (Ag) composite film with high dielectric constant was grown at room temperature by an aerosol deposition method.The dielectric constant increases by 0.5 times after adding Ag to the BaTiO3 matrix,compared with pure BaTiO3.The high dielectric constant can be attributed to the percolation effect of Ag inclusions in the BaTiO3 matrix.The Ag was present in the form of discrete layer in the BaTiO3 film.The dielectric properties of BaTiO3 Ag were discussed in detail taking into account the changes in microstructures.
文摘In order to obtain ultrafine Nd-Fe-B powder, a spray-dried precursor was treated by reduction-diffusion (R/D) process. And, unlike the conventional R/D process, calcium reduction that is a crucial step for the formation of Nd2Fe14B was performed without conglomerating the precursor with Ca powder. By adopting this modified process, it is possible to synthesize the hard magnetic Nd2Fe14B at the reaction temperature as low as 850 ℃. The average size of Nd2Fe14B particles that are uniformly distributed in the optimally treated powder was <<1 μm. Most Nd2Fe14B particles were enclosed with thin layers of Nd-rich phase. Typical magnetic properties of such powder without eliminating impurity CaO were iHc=~5.9 kOe, Br=~5.5 kG, and (BH)max=~6 MGOe.
基金supported by Research Foundation of Hanseo University in2011
文摘A graphene-CdSe composite was synthesized by a facile hydrothermal method,and characterized by X-ray diffraction,scanning electron microscopy with energy dispersive X-ray analysis,transmission electron microscopy and UV-vis diffuse reflectance spectrophotometry.The graphene-CdSe composite efficiently catalyzed the photodegradation of methylene blue(MB),methyl orange(MO) and rhodamine B(Rh.B) in aqueous solution under UV or visible light irradiation.The graphene-CdSe composite exhibited a higher photocatalytic activity for the MB solution.
基金a financial support from Korean Ministry of Industry,Energy,and Commerce through the program of Industrial Core Material development.(Project No.10038631)。
文摘The thermal conductivity of polymer composites can be enhanced by the vertical alignment of anisotropic aluminum nitride(AlN)platelet fillers in polymer matrices.The AlN platelets in polymer matrix were aligned in the direction of in-plane and out-of-plane by using the doctor blading and the lamination process.The alignment of AlN plates in the out-of-plane or the in-plane direction has been confirmed by XRD and FE-SEM investigations.The polymer composite with the out-of-plane aligned AlN platelets showed almost 1.5 times or 2 times higher thermal conductivity than those with the AlN spheres or the in-plane aligned AlN platelets at the same filler content,respectively.This result could be attributed to the improvement of thermal pathway generated along the plane of platelets and the decrease of interfaces between the filler and the polymer.
文摘A visible-light photocatalyst containing Ag2Se and reduced graphene oxide(RGO) was synthesized by a facile sonochemical-assisted hydrothermal method. X-ray diffraction, scanning electron mi-croscopy with energy-dispersive X-ray analysis, and ultraviolet-visible diffuse reflectance spectros-copy results indicated that the RGO-Ag2Se nanocomposite contained small crystalline Ag2Se nano-particles dispersed over graphene nanosheets and absorbed visible light. The high crystallinity of the nanoparticles increased photocatalytic activity by facilitating charge transport. N2 adsorp-tion-desorption measurements revealed that the RGO-Ag2Se nanocomposite contained numerous pores with an average diameter of 9 nm, which should allow reactant molecules to readily access the Ag2Se nanoparticles. The RGO-Ag2Se nanocomposite exhibited higher photocatalytic activity than bulk Ag2Se nanoparticles to degrade organic pollutant rhodamine B and industrial dye Texbrite BA-L under visible-light irradiation(λ > 420 nm). The generation of reactive oxygen spe-cies in RGO-Ag2Se was evaluated through its ability to oxidize 1,5-diphenylcarbazide to 1,5-diphenylcarbazone. The small size of the Ag2Se nanoparticles in RGO-Ag2Se was related to the use of ultrasonication during their formation, revealing that this approach is attractive to form po-rous RGO-Ag2Se materials with high photocatalytic activity under visible light.
文摘Hair loss due to medical conditions,such as alopecia,male pattern baldness,and cancer chemotherapy treatment,has been a comm onproblem for many in dividuals.Cyclospori n A(CsA),a fungal metabolite,has been reported to be a hair growth modulatory agent and is apotential drug for hair regeneration.However,the effect of topical application of CsA is limited by its poor water solubility.Several deliverysystems developed to enhance its solubility still showed poor skin penetration.To overcome these limitations,in this study,we have developed a novel chitosan nanocapsule platform using Pluro nic F127 and chitosan without any chemical crosslinking or complicated preparati on steps for the enhanced water solubility and high tran sdermal penetration of CsA.The chitosan nanocapsules(ChiNCs)optimized in terms of structural stability by using chitosan with various molecular weights ranging from 3 to 100 kDa enhanced the skin permeation of CsA through humancadaver skin in vitro.Topical administration of the CsA loaded ChiNCs in creased the hair follicles by c.a.7 times higher than that of thecontrol group,and effectively induced hair growth in C57BL/6 mice in vivo.These results suggest that ChiNCs could be used as a platform foreffective transdermal delivery of various hydrophobic drugs.
基金This work was supported by National Research Foundation of Korea(NRF)grants funded by Ministry of Science and ICT(MSIT)(Nos.2021R1A2C3004420,2022M3J1A1085282,2020R1C1C1012256 and 2020R1C1C1003214)the NRF of Korea grant funded by the Korean Government(NRF-2019-Global Ph.D.Fellowship Program.
文摘Perovskite quantum dots(PQDs)have been considered promising and effective photovoltaic absorber due to their superior optoelectronic properties and inherent material merits combining perovskites and QDs.However,they exhibit low moisture stability at room humidity(20-30%)owing to many surface defect sites generated by inefficient ligand exchange process.These surface traps must be re-passivated to improve both charge transport ability and moisture stability.To address this issue,PQD-organic semiconductor hybrid solar cells with suitable electrical properties and functional groups might dramatically improve the charge extraction and defect passivation.Conventional organic semiconductors are typically low-dimensional(1D and 2D)and prone to excessive self-aggregation,which limits chemical interaction with PQDs.In this work,we designed a new 3D star-shaped semiconducting material(Star-TrCN)to enhance the compatibility with PQDs.The robust bonding with Star-TrCN and PQDs is demonstrated by theoretical modeling and experimental validation.The Star-TrCN-PQD hybrid films show improved cubic-phase stability of CsPbI_(3)-PQDs via reduced surface trap states and suppressed moisture penetration.As a result,the resultant devices not only achieve remarkable device stability over 1000 h at 20-30%relative humidity,but also boost power conversion efficiency up to 16.0%via forming a cascade energy band structure.
基金supported by Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Korea government(MOTIE)(20215610100040,Development of 20 Wh seawater secondary battery unit cell).
文摘NASICON (sodium (Na) superionic conductor) compounds have attracted considerable attention as promising solid electrolyte materials for advanced Na-based batteries. In this study, we investigated the improvement in ionic conductivities of von-Alpen-type NASICON (vA-NASICON) ceramic electrolytes by introducing a magnesium ion (Mg^(2+)) as a heterogeneous element. The optimal Mg-doped vA-NASICON exhibited a high ionic conductivity of 3.64×10^(−3) S·cm^(−1), which was almost 80% higher than that of un-doped vA-NASICON. The changes in physicochemical properties of the vA-NASICONs through the Mg introduction were systematically analyzed, and their effects on the ionic conductivities of the vA-NASICON were studied in detail. When the optimal ratio of Mg^(2+) was used in a synthetic process, the relative density (96.6%) and grain boundary ionic conductivity (σgb) were maximized, which improved the total ionic conductivity (σt) of the vA-NASICON. However, when Mg^(2+) was introduced in excess, the ionic conductivity decreased because of the formation of an undesired sodium magnesium phosphate (NaxMgyPO_(4)) secondary phase. The results of this study are expected to be effectively applied in the development of advanced sodium-based solid electrolytes with high ionic conductivities.
基金Project supported by the Energy & Resource R&D Program under the Ministry of Knowledge Economy,Republic of Korea (2008-R-RU02-P-02-0-000)
文摘Cerium was extracted from rare earth slurry waste used for polishing a glass substrate.Initially,glass frit and flocculant were removed by froth flotation and dissolution.The recovered rare earth slurry exhibited almost the same particle size distribution as original slurry,which could be reused as slurry for glass polishing.From the rare earth slurry,the cerium solution was obtained by an oxidative thermal treatment and subsequent chemical leaching.The cerium solution was further purified up to 94% by selective precipitation of rare earth species.
文摘Silicon carbide (SiC) fiber has recently received considerable attention as promising next-generation fiber because of its high strength at temperatures greater than 1300 ℃ in air.High-quality SiC fiber is primarily made through a curing and heat treatment process.In this study,the chemical vapor curing method,instead of the thermal oxidation curing method,was used to prepare cured polycarbosilane (PCS) fiber.During the high temperature heat treatment of the cured PCS fiber,varied heating rates of 10,20,30,and 40 ℃/min were applied.Throughout the process,the fiber remained in the amorphous silicon carbide phase,and the measured tensile strength was the greatest when the oxygen content in the heat-treated fiber was low,due to the rapid heating rate.The fiber produced through this method was also found to have excellent internal oxidation properties.This fast,continuous process shows a great promise for the production of SiC fiber and the development of high-quality products.
文摘High power light-emitting diodes (LEDs) lighting has drawn a great interest in the field of street light system in recent years. Key parameters for successful launching of LED street light in the commercial market are price and light efficiency, respectively, and they are greatly influenced by the materials and design factors used in high power LED package. This article presents a new design and materials processing technology to realize the solution of LED packaging with advantageous in price and performance. Cost effective materials and processing technology can be realized via thick film glass-ceramic insulating layer and silver conductor. Highly effective thermal design using direct heat dissipation to heat sink in LED package is demonstrated.
文摘The development of CO_(2)into hydrocarbon fuels has emerged as a green method that could help mitigate global warning.The novel structured photocatalyst is a promising material for use in a photocatalytic and magneto-electrochemical method that fosters the reduction of CO_(2)by suppressing the recombination of electron−hole pairs and effectively transferring the electrons to the surface for the chemical reaction of CO_(2)reduction.In our study,we have developed a novel-structured AgCuZnS_(2)–graphene–TiO_(2)to analyze its catalytic activity toward the selective evolution of CO_(2).The selectivity of each nanocomposite substantially enhanced the activity of the AgCuZnS_(2)–graphene–TiO_(2)ternary nanocomposite due to the successful interaction,and the selectivity of the final product was improved to a value 3 times higher than that of the pure AgCuZnS_(2)and 2 times higher than those of AgCuZnS_(2)–graphene and AgCuZnS_(2)–TiO_(2)under ultraviolet(UV)-light(λ=254 nm)irradiation in the photocatalytic process.The electrochemical CO_(2)reduction test was also conducted to analyze the efficacy of the AgCuZnS_(2)–graphene–TiO_(2)when used as a working electrode in laboratory electrochemical cells.The electrochemical process was conducted under different experimental conditions,such as various scan rates(mV·s^(–1)),under UV-light and with a 0.07 T magneticcore.The evolution of CO_(2)substantially improved under UV-light(λ=254 nm)and with 0.07 T magnetic-core treatment;these improvements were attributed to the facts that the UV-light activated the electron-transfer pathway and the magnetic core controlled the pathway of electrontransmission/prevention to protect it from chaotic electron movement.Among all tested nanocomposites,AgCuZnS_(2)–graphene–TiO_(2)absorbed the CO_(2)most strongly and showed the best ability to transfer the electron to reduce the CO_(2)to methanol.We believe that our newly-modeled ternary nanocomposite opens up new opportunities for the evolution of CO_(2)to methanol through an electrochemical and photocatalytic process.
基金the Basic Science Research Program of the National Research Foundation(NRF)of Korea(Nos.2019R1A6A1A11053838,2022R1A4A3033528,and 2022R1F1A1063285)Korea Agency for Infrastructure Technology Advancement(KAIA)funded by the Ministry of Land,Infrastructure,and Transport(No.21CTAP-C163795-01)Prof.M.Y.Choi acknowledges the Korea Basic Science Institute(National Research Facilities and Equipment Center)grant funded by the Ministry of Education(Nos.2019R1A6C1010042 and 2021R1A6C103A427).
文摘The single-pot production of Pd@Pt core-shell structures is a promising approach as it offers large surface area,catalytic capability,and stability.In this work,we established a single-pot process to produce Pd@Pt core-shell nanodendrites with tunable composition,shape and size for optimal electrochemical activity.Pd@Pt nanodendrites with diverse compositions were synthesized by tuning the ratios of Pd and Pt sources in an aqueous environment using cetyltrimethylammonium chloride,which functioned as both the surfactant and the reducing agent at an elevated temperature(90°C).The synthesized Pd5@Pt5 nanodendrites showed exceptional electrochemical action toward the methanol oxidation reaction related with another compositional Pd@Pt nanodendrites and conventional Pt/C electrocatalysts.In addition,Pd5@Pt5 nanodendrites exhibited good CO tolerance owing to their surface features and the synergistic effect among Pt and Pd.Meanwhile,nanodendrites with a Pt-rich surface provided exceptional catalytic active sites.Compared with the conventional Pt/C electrocatalyst,the anodic peak current obtained by Pd5@Pt5 nanodendrites was 3.74 and 2.18 times higher in relations of mass and electrochemical active surface area-normalized current density,respectively.This approach offers an attractive strategy to design electrocatalysts with unique structures and outstanding catalytic performance and stability for electrochemical energy conversion.
基金supported by the Bio and Medical Technology Development Program of the National Research Foundation(NRF)funded by the Korean government(No.NRF-2022M3A9I3082366)+1 种基金supported by the Technology Innovation Program(No.20026752)funded by the Ministry of Trade,Industry and Energy(MOTIE,Korea).
文摘Three-dimensional (3D) host materials for lithium metal anodes (LMAs) have gained attention because they can mitigate volume expansion and local current density through their large surface area and suppress the dendritic growth of lithium. Recent research on 3D host materials has focused on conductive materials;however, the benefits of 3D host materials cannot be fully utilized because lithium deposition begins at the top of the structure. Herein, we fabricate SiO_(2)-TiO_(2) composite microspheres with bimodal pore structures (bi-SiTiO) by simple spray pyrolysis. These microspheres effectively store lithium within the structure from the bottom of the electrode while preventing lithium dendrite formation. Focused ion beam-scanning transmission electron microscopy (FIB-STEM) analysis reveals that the lithiophilic properties of composite microspheres enhanced their effectiveness in storing lithium, with small pores acting as “lithium-ion sieves” for a uniform lithium-ion flux and large pores that provide sufficient volume for lithium deposition. The bi-SiTiO composite microspheres exhibit a high Coulombic efficiency of 98.5% over 200 cycles at 2.0 mA·cm^(−2) when operated in a lithium half-cell. With a high lithium loading of 5.0 mAh·cm^(−2), the symmetrical cell of the bi-SiTiO electrode sustains more than 900 h. A full cell coupled with an LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) (NCM811) cathode also exhibits enhanced electrochemical properties in terms of cycling stability and rate capability.
基金supported by grants from the National Research Foundation of Korea (NRF-2016M3A7B4910151 and NRF-2021R1A2C2013501).
文摘Wearable pressure sensors having versatile device structures have been extensively investigated to achieve high sensitivity under mechanical stimuli.Here,we introduce piezoelectric pressure sensors based on fabrics woven using polyvinylidene fluoride(PVDF)weft and polyethylene terephthalate(PET)warp yarns with different weave structures:1/1(plain),2/2,and 3/3 weft rib patterns.The dependence of the pressure-sensing performance on the weave pattern is demonstrated with an actual large-scale fabric up to the~2 m scale.An optimized pressure sensor with a 2/2 weft rib pattern produced a high sensitivity of 83 mV N−1,which was 245%higher than that of the 1/1 pattern.The detection performance of the optimal fabric was extensively evaluated with a variety of ambient input sources,such as pressing,bending,twisting,and crumpling,as well as various human motions.Further,a large allfabric pressure sensor with arrayed touch pixel units demonstrated highly sensitive and stable sensing performance.