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Fabrication of Hierarchical, Porous, Bimetallic, Zeolitic Imidazolate Frameworks with the Incorporation of Square Planar Pd and Its Catalytic Application
No full textBimetallic zeolitic imidazolate frameworks (ZIFs) containing two different metal ions can exhibit superior performances when applied in heterogeneous catalysis. Herein, we present a facile one-pot synthesis method for PdCo-ZIFs with various Pd/Co ratios, where Pd(II) ions are successfully incorporated into the Co node sites of the ZIF structure. The local structure of the bimetallic ZIFs was comprehensively investigated by pore-structure, Xray absorption fine structure, and in situ CO adsorption Fourier transform infrared analyses. The results demonstrated that the framework comprises different coordination geometries of Co (tetrahedral) and Pd (square planar) ions connected by the benzimidazolate ligand. Notably, the inherently nonporous, 2D Co-ZIF structure was transformed into a hierarchical porous structure, and the PdCo-ZIFs exhibited a significantly increased concentration of defects and distorted Co sites. Based on these results, the catalytic performances of the synthesized ZIFs in the cycloaddition of CO2 to epoxides were evaluated under a cocatalyst and solvent-free conditions. The PdCo-ZIFs exhibited significantly higher catalytic activity (maximum turnover frequency, TOF = 2501 h-1) than Co-ZIF (TOF = 65 h-1) and Pd-ZIF (no activity), which revealed that the undercoordinated Co sites with distorted structure are the active sites rather than the incorporated Pd ions. This study provides a facile one-pot method for synthesizing bimetallic ZIFs with mixed-coordination modes, hierarchical porous structures, and modified defect concentrations, which would expand the library of structurally diverse bimetallic ZIFs toward various applications
Secured delivery of basic fibroblast growth factor using human serum albumin-based protein nanoparticles for enhanced wound healing and regeneration
No full textBackground
Basic fibroblast growth factor (bFGF) is one of the critical components accelerating angiogenesis and tissue regeneration by promoting the migration of dermal fibroblasts and endothelial cells associated with matrix formation and remodeling in wound healing process. However, clinical applications of bFGF are substantially limited by its unstable nature due to rapid decomposition under physiological microenvironment.
Results
In this study, we present the bFGF-loaded human serum albumin nanoparticles (HSA-bFGF NPs) as a means of enhanced stability and sustained release platform during tissue regeneration. Spherical shape of the HSA-bFGF NPs with uniform size distribution (polydispersity index???<???0.2) is obtained via a simple desolvation and crosslinking process. The HSA-bFGF NPs securely load and release the intact soluble bFGF proteins, thereby significantly enhancing the proliferation and migration activity of human dermal fibroblasts. Myofibroblast-related genes and proteins were also significantly down-regulated, indicating decrease in risk of scar formation. Furthermore, wound healing is accelerated while achieving a highly organized extracellular matrix and enhanced angiogenesis in vivo.
Conclusion
Consequently, the HSA-bFGF NPs are suggested not only as a delivery vehicle but also as a protein stabilizer for effective wound healing and tissue regeneration
Fabrication of p-type 2D single-crystalline transistor arrays with Fermi-level-tuned van der Waals semimetal electrodes
No full textHigh-performance p-type two-dimensional (2D) transistors are fundamental for 2D nanoelectronics. However, the lack of a reliable method for creating high-quality, large-scale p-type 2Dsemiconductors and a suitablemetallization process represents important challenges that need to be addressed for future developments of the field. Here, we report the fabrication of scalable p-type 2D single-crystalline 2H-MoTe2 transistor arrays with Fermi-level-tuned 1T'-phase semimetal contact electrodes. By transforming polycrystalline 1T'-MoTe2 to 2H polymorph via abnormal grain growth, we fabricated 4-inch 2H-MoTe2 wafers with ultra-large single-crystalline domains and spatially-controlled singlecrystalline arrays at a low temperature (similar to 500 degrees C). Furthermore, we demonstrate on-chip transistors by lithographic patterning and layer-by-layer integration of 1T' semimetals and 2H semiconductors. Work function modulation of 1T'-MoTe2 electrodes was achieved by depositing 3D metal (Au) pads, resulting in minimal contact resistance (similar to 0.7 k Omega.mu m) and near-zero Schottky barrier height (similar to 14meV) of the junction interface, and leading to high on-state current (similar to 7.8 mu A/mu m) and on/off current ratio (similar to 105) in the 2H-MoTe2 transistors
Controlling hydrophilic microenvironment of electrodes for gas-involving electrochemical reactions
No full text
Production of carbon nanotubes from plastic wastes and application in battery additives
No full textCarbon nanotubes (CNTs) were produced from two plastic waste feedstocks, a polypropylene (PP)-dominated mask and a solid recovered fuel (SRF) with a high content of non-recyclable mixed plastics, using a pyrolysis-chemical vapor deposition (CVD) process. FeMo/MgO and CoMo/MgO catalysts were used for CNT growth using pyrolysis gases containing various hydrocarbons. It was found that CoMo/MgO produced selective and small-walled CNTs, while FeMo/MgO produced high-yield multi-walled CNTs. The CNTs produced from the mask feedstock exhibited higher yield, diameter, and purity compared to those produced from the SRF feedstock. The resulting CNTs were tested as conductive additives in the cathode of a lithium-ion battery (LIB). Electrochemical measurements demonstrated that CNTs produced with FeMo/MgO outperformed commercially available carbon black. This study presents a novel approach for plastic waste utilization, where CNTs produced from plastic waste can be utilized as effective conductive additives for LIB cathodes
Catalytic CO2 Hydrogenation Using Cobalt Ferrite Nanoparticles for Selective Production of Light Olefins
No full textThe steady increase of CO2 in the atmosphere owing to the excessive use of fossil fuels is seriously threatening the future of humankind by accelerating climate change. However, catalytic chemistry can turn this harmful greenhouse gas into a renewable source of carbon to provide an alternative feedstock for producing high-value hydrocarbon fuels, chemicals, and polymers as a carbon capture and utilization (CCU) strategy. Among the proposed CCU options, catalytic CO2 hydrogenation is attractive because the process is very similar to the well-established CO hydrogenation. The CO2 hydrogenation process usually involves two consecutive steps: the reverse water???gas shift (RWGS) and subsequent CO hydrogenation reactions. In CO2 hydrogenation over Fe-based catalysts, the Fe3O4 phase catalyzes the RWGS reaction, and its reduced form, the Ha??gg iron carbide (??-Fe5C2) phase, provides active sites for CO hydrogenation and chain growth. To increase the CO2 conversion and light olefin selectivity, various strategies have been used to control the electronic and structural properties of Fe-based catalysts. Here, we synthesized monodisperse Fe3O4 and CoFe2O4 nanoparticles (NPs) with a size of 10???20 nm by the thermal decomposition of metal???oleate complexes and supported them on carbon nanotubes (CNTs). It was found that the Na and Co promoters played decisive roles in controlling the reaction rates and product selectivity of catalytic CO2 hydrogenation over these reduced CoFe2O4 NP/CNT catalysts
Seismic fragility assessments of fill slopes in South Korea using finite element simulations
No full textThis study evaluates the seismic fragilities in fill slopes in South Korea through parametric finite element analyses that have been barely investigated thus far. We consider three slope geometries for a slope of height 10 m and three slope angles, and two soil types, namely frictional and frictionless, associated with two soil states, loose and dense for frictional soils and soft and stiff for frictionless soils. The input ground motions accounting for four site conditions in South Korea are obtained from one-dimensional site response analyses. By comparing the numerical modeling of slopes using PLAXIS2D against the previous studies, we compiled suites of the maximum permanent slope displacement (&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;&#xfffd;) against two ground motion parameters, namely, peak ground acceleration (PGA) and Arias Intensity (IA). A probabilistic seismic demand model is adopted to compute the probabilities of exceeding three limit states (minor, moderate, and extensive). We propose multiple seismic fragility curves as functions of a single ground motion parameter and numerous seismic fragility surfaces as functions of two ground motion parameters. The results show that soil type, slope angle, and input ground motion influence these probabilities, and are expected to help regional authorities and engineers assess the seismic fragility of fill slopes in the road systems in South Korea
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Get PDFDepartment of Biomedical EngineeringGiven the concerning trends, it is clear that research focused on the mental health of individuals in their twenties is crucial. Understanding the factors contributing to poor mental health and effective interventions is vital for providing appropriate support. Therefore, this study aimed to develop a lifestyle questionnaire for early intervention and prevention of mental health issues among university students. The study consisted of two parts: developing a questionnaire to assess the overall lifestyle of university students and comparing mental health among demographic/socioeconomic groups and lifestyle groups identified by Latent Profile Analysis (LPA) using lifestyle factors screened by the developed lifestyle questionnaire. Data from 414 undergraduate and graduate students at UNIST were used for the analysis.
The study resulted in the development of a validated lifestyle questionnaire comprising 8 domains (personality problem, planning, consumption satisfaction, economic difficulty, relationship, career, stress and energy management, and physical health) to assess the overall lifestyle of university students. Furthermore, when comparing the mental health factors, the research revealed significant differences between demographic/socioeconomic groups and latent lifestyle groups. Specifically, economic difficulty, physical illness, and psychological experiences were associated with poorer mental health. In addition, students were categorized into four latent lifestyle profiles: Low consumption satisfaction group (31.5%), Worst lifestyle group (11.8%), Good lifestyle group (23.8%), and Bad lifestyle but high consumption satisfaction group (23.8%). There were significant differences in mental health factors across these lifestyle groups, including depression, anxiety, stress, social interaction anxiety, sleep disturbance, procrastination, smartphone use, social support, self-esteem, life value composite, and life value gap. These findings highlight the significant link between lifestyle and mental health, with healthier lifestyles associated with better mental health outcomes.
Integrating the lifestyle questionnaire into mental health screening offers the advantage of reducing the burden associated with multiple assessments, while still providing a comprehensive evaluation of mental health. This approach allows individuals to gain insights into their lifestyle and understand which lifestyle factors impact their mental wellbeing. Furthermore, the findings from this research can inform the development of interventions, such as personalized healthcare content recommendation services. By taking a holistic approach to mental health assessment and offering personalized support, it can contribute to improved mental wellbeing and overall quality of life for university students.clos
Ultrasensitive Quantification of Single Extracellular Vesicles in Unprocessed Plasma using Droplet Digital Nanoplasmonic Assay
No full textDepartment of Biomedical Engineeringclos