Hyun Jung

Electromagnetic fields and nanomagnetic particles increase the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) are widely used in a number of cell therapies and have osteogenic differentiation capacity. Exposure to electromagnetic fields (EMFs) increases the osteogenic differentiation of hBM-MSCs. Nanomagnetic particles (MPs) also promote the differentiation potential of stem cells. In the present study, we investigated the effects of EMFs and MPs on the osteogenic differentiation of hBM-MSCs. hBM-MSCs were treated with 50 µg/ml of Fe3O4 MPs or exposed to a frequency of 45 Hz and an intensity of 1 mT EMF twice every 8 h per day for 7 days. MP incorporation, EMF exposure and MP incorporation with exposure to EMFs did not induce cytotoxic effects. A strong expression of osteogenic markers (osteocalcin, osteopontin and osteonectin) and von Kossa staining intensity was observed in the cells treated with MPs, the cells exposed to EMFs and in the cells treated with MPs and exposed to EMFs compared with the control group, as shown by immunohistochemical staining. Quantitative RT-PCR revealed that the mRNA expression levels of osteoblast markers [osteocalcin, osteopontin, osteonectin, collagen Ⅰ, collagen Ⅲ, bone morphogenetic protein 2 (BMP-2), bone sialoprotein (BSP) and runt-related transcription factor 2 (runx-2)] were markedly increased in the cells treated with MPs and exposed to EMFs. Furthermore, the mRNA expression of calcium channels (CACNA1C, CACNA1E, CACNA1G and CACNA1I) was activated during osteogenic differentiation. The expression levels of osteogenesis-related proteins (BSP, BMP-2, osteopontin and osteonectin) and phosphorylated extracellular signal-regulated kinase (p-ERK) were increased in the cells treated with MPs, those exposed to EMFs and in the cells treated with MPs and exposed to EMFs compared with the control group, as shown by western blot analysis. Fluorescence-activated cell sorting (FACS) analysis was performed for the hBM-MSC markers, CD73, CD90 and CD105. The expression levels of hBM-MSC surface antigens were decreased in the cells treated with MPs, those exposed to EMFs and in the cells treated with MPs and exposed to EMFs compared with the control group. The cell numbers were determined to be approximately 3.4 x 10(5) cells in the control group, 3.7 x 10(5) cells in the MP-treated group, 3.1 x 10(5) cells in the group exposed to EMFs and 3.9 x 10(5) cells in the group treated with MPs and exposed to EMFs. The cell mitochondrial activity among the 4 experimental groups was similar. The hBM-MSCs treated with MPs and exposed to EMFs showed an increase in alkaline phosphatase (ALP) activity. Taken together, these results suggest that the treatment of hBM-MSCs with MPs or exposure to EMFs increases osteogenic differentiation, and that treatment with MPs in conjunction with EMF exposure is more effective in increasing osteogenic differentiation.

Ultrathin graphene nanosheets derived from rice husks for sustainable supercapacitor electrodes

Graphene nanosheets are synthesized via the carbonization of brown-rice husks followed by a one-stage KOH-activation process for the design of a sustainable electrochemical energy-storage electrode. The graphene nanosheets exhibit an ultra-thin crumpled-silk-veil-wave, sheet-like structure with a high surface area of ∼1225 m2 g−1 and a high porosity. The graphene-nanosheet electrode shows a specific capacitance of 115 F g−1 at 0.5 mA cm−2 and a high energy density of 36.8 W h kg−1 at a power density of 323 W kg−1, with an excellent cyclic stability of 88% over 2000 cycles. The observed good electrochemical energy-storage performance of the biomaterial-derived graphene-nanosheet electrode is due to the synergistic effect of the intrinsically large electrochemically active surface area, an enhanced ion diffusion, and an improved electrical conductivity.

Simultaneous reduction and nitrogen doping of graphite oxide by using electron beam irradiation

Nitrogen-doped graphenes (NGs) were successfully obtained by electron beam (e-beam) irradiation from graphite oxide (GO) colloid solution in the presence of aqueous ammonia at room temperature under ambient conditions. The morphology, structure, and components of the obtained NGs were characterized by scanning electron microscopy, Raman spectroscopy, powder X-ray diffraction, elemental analysis, and X-ray photoelectron spectroscopy. The amount of incorporated nitrogen was in the range ∼3.20–3.54 wt% with pyrrolic-N as the main nitrogen configuration. The results of this study show that nitrogen was simultaneously doped into graphene as the GO was reduced by e-beam irradiation. Herein, the ratio of nitrogen sites (pyridinic-N, pyrrolic-N, graphitic-N, and pyridinic-N-oxide) and specific surface area were controlled for various applications of the NGs as a function of irradiation dose. Increasing concentrations of graphitic-N and pyridinic-N-oxide enhanced the electrical conductivity and improved the kinetic performance of supercapacitor. The highest capacitance of 90.5 F g−1 at a charge/discharge current of 0.1 A g−1 in organic media was achieved for NG-300 because of a high BET specific surface area of 470 m2 g−1.

Effect of charge-transfer complex on the energy level alignment between graphene and organic molecules

We performed density-functional theory calculations to study the electronic structures at the interfaces between graphene and organic molecules that have been used in organic light-emitting diodes. In terms of work function, graphene itself is not favorable as either anode or cathode for commonly used electron or hole transport molecular species. However, the formation of charge transfer complex on the chemically inert sp2 carbon surface can provide a particular advantage. Unlike metal surfaces, the graphene surface remains non-bonded to electron-accepting molecules even after electron transfer, inducing an improved Fermi-level alignment with the highest-occupied-molecular-orbital level of the hole-injecting-layer molecules.

Charge transferred doping of single layer graphene by mono-dispersed manganese-oxide nanoparticles adsorption

We report an efficient and controllable method to introduce p-type doping in graphene by decoration with Mn3O4 nanoparticles (NPs) on mechanically exfoliated single layer graphene. A monolayer of Mn3O4 NPs, with a diameter in the range of 5–10 nm, was decorated on a graphene film using an ex-situ method, whereas by controlling the coverage of the NPs on the graphene surface, the carrier concentration could be continually adjusted. The p-type of the NP-decorated single layer graphene was confirmed by the Raman G-band. It was found that the carrier concentration could be gradually adjusted up to 26.09 × 1012 cm−2, with 90% coverage of Mn3O4 NPs. The Dirac point of the pristine graphene at the gate bias of 27 V shifted to 150 V for Mn3O4 NP decorated graphene. The p-type graphene doped with Mn3O4 NPs demonstrated significant high air-stability, even under an oxygen atmosphere for 60 days. This approach allows for the opportunity for simple, scalable, and highly stable doping of graphene for future high-perfo...

Effect of the Addition of Mesogenic Thiol Ligand Modified Gold Nanoparticles on the Thermal Stabilization of Blue Phases

In this paper, we introduce surface modified gold nanoparticles with mesogenic thiol ligands in liquid crystal, for expansion of the temperature range of blue phases (BPs). We have used polarized optical microscope and UV-vis spectrophotometer to identify the thermal stabilization of BPs. The BPs range of nanoparticles doped liquid crystal is significantly dependent upon the addition amount of gold nanoparticles, and the molar ratios of attached ligands [4′-(10-mercaptodecyloxy)biphenyl-4-carbonitrile and dodecanethiol]. This study could provide a new and facile strategy to stabilize BPs, from the aspect of the surface modification of nanoparticles.

Selective stabilisation of blue phase liquid crystal induced by distinctive geometric structure of additives

ABSTRACT We successfully stabilised liquid crystalline blue phases (BPs) by introducing two suitable additives with different geometric molecular structures, linear-shaped cobalt oleate complex (Co-OL) or tetrahedral-shaped tetraoctadecylammonium bromide (TODAB), into a liquid crystal (mixture of 4ʹ-pentyl-4-biphenylcarbonitrile, JC-1041XX and chiral dopant). The BPs temperature range and phase sequence depending on the addition amount and shape of additives were systematically investigated to determine the optimal concentration and shape dependency required to achieve a stabilising effect for BPs. From the polarising optical microscope results, the BPs temperature range for all of the samples with additives was not only broadened but also shifted to room temperature compared to that of BPs without additives. The widest BPs temperature range was increased to 15.3°C by the addition of 3 wt% Co-OL. According to the UV-vis reflection spectroscopy results, the Co-OL has a more significant stabilisation effect on BP I than on BP II, and the widest BP I range increases to 11.0°C. On the other hand, TODAB is effective for BP II stabilisation with the broadest BP II range reaching 1.8°C. These selective stabilisation effects are attributed to the specific shape of additives that closely match the structures of the disclination lines of the BPs. Graphical Abstract

Pore Parameters-Dependent Adsorption Behavior of Volatile Organic Compounds on Graphene-Based Material

Mesoporous graphenes (MPGs) with interpenetrating porous networks are successfully obtained by the pyrolysis of composite gel consisting of graphite oxide (GO) and the amphiphilic triblock copolymer (Pluronic P123) under Ar atmosphere, wherein P123 is used as a soft-template. The as-prepared composite gel is obtained following self-assembly and freeze-drying. The obtained MPGs have high BET specific surface area (531-746 m2 g-1 and ink-bottle like pores with three dimensional interconnected network. Furthermore, the specific surface area and porous parameters such as pore volume, pore size, and pore size distribution of MPGs can be rationally controlled by regulating the initial mass ratio of P123 to GO. With the increase of P123 ratio, the average mesopore size is decreased from ∼16.4 nm to ∼9.5 nm, which is similar to the diameter size of P123 micelles. Also, the adsorption capacities of MPG-20 for 52 indoor air standard components (100 μg mL-1, Supelco) are compared with two different materials, namely commercial porous polymers (2,6-diphenyleneoxide) and reduced graphene oxide (RGO). The result shows that MPG-20 has significantly better adsorption capacity than RGO but also similar or slightly better than commercial porous polymer. The mesoporous structure and surface chemistry of MPGs were the most important factors for the enhancement of the adsorption efficiency for volatile organic compounds.

Development of Latent Fingermarks on Nonporous and Semiporous Substrates Using Photoluminescent Eu(Phen)2 Complex Intercalated Clay Hybrids with Enhanced Adhesion

In forensic science, developing latent fingermarks using powders is a critical, general method to identify individuals. Photoluminescent Eu(Phen)2 complex intercalated clay hybrids have been used to improve the visualization of fingermarks on nonporous (glass and polymer film) and semiporous (euro and dollar banknotes) substrates. An ion exchange reaction has been successfully used to intercalate Eu(Phen)2 complex ions into the interlayer spacing of two different Na+‐clays, Na+‐montmorillonite and Na+‐hectorite, with different primary particle sizes. To change the surface properties of the obtained hybrid to be more lipophilic, the hydroxyl groups at the edge of the hectorite hybrid were modified with hexadecyltrimethoxysilane via silylation. We investigated the correlation of the size and surface properties of the hybrids with their adhesion to fingermark residues. Fingermarks were successfully visualized using hybrids under UV illumination. In particular, ridge details on semiporous substrates can be more clearly seen using hybrids with smaller primary particles and greater lipophilicity.