Dong Wan Kim

Enhanced Lithium Storage in Hierarchically Porous Carbon Derived from Waste Tea Leaves

In this study, highly nanoporous carbon (HCl-TW-Car) was successfully synthesized using a facile procedure combining acid treatment with a carbonization process that uses waste tea leaves from spent tea bags as raw materials. The acid treatment not only promotes the efficient removal of unnecessary inorganic impurities but also increases the product porosity to enable synthesis of hierarchically porous carbon materials with various micro-, meso-, and macropores. When used as an anode material for lithium-ion batteries, HCl-TW-Car demonstrated a much higher discharge capacity than is theoretically possible using graphite [479u2009mAh g−1 after the 200th cycle at a rate of 0.2C (1Cu2009=u2009372u2009mAu2009g−1)] and exhibited greater rate capabilities compared with those of carbonated products from tea waste without acid treatment. It was shown that the good electrochemical properties of HCl-TW-Car can be ascribed to large Brunauer–Emmett–Teller (BET) surface area, well-formed hierarchical pores, and the prevention of unexpected electrochemical reactions from the reduction of metallic atoms.

Fe-based hybrid electrocatalysts for nonaqueous lithium-oxygen batteries

Lithium–oxygen batteries promise high energy densities, but are confronted with challenges, such as high overpotentials and sudden death during discharge–charge cycling, because the oxygen electrode is covered with the insulating discharge product, Li2O2. Here, we synthesized low–cost Fe–based nanocomposites via an electrical wire pulse process, as a hybrid electrocatalyst for the oxygen electrode of Li–O2 batteries. Fe3O4-Fe nanohybrids–containing electrodes exhibited a high discharge capacity (13,890u2009mAu2009h gc−1 at a current density of 500u2009mA gc−1), long cycle stability (100 cycles at a current rate of 500u2009mA gc−1 and fixed capacity regime of 1,000u2009mAu2009h gc−1), and low overpotential (1.39u2009V at 40 cycles). This superior performance resulted from the good electrical conductivity of the Fe metal nanoparticles during discharge–charge cycling, which could enhance the oxygen reduction reaction and oxygen evolution reaction activities. We have demonstrated the increased electrical conductivity of the Fe3O4-Fe nanohybrids using electrochemical impedance spectroscopy.

A higher aspect ratio enhanced bioaccumulation and altered immune responses due to intravenously-injected aluminum oxide nanoparticles

Abstract Aluminum oxide nanoparticles (AlO NP) have been widely utilized in a variety of areas, including in the optical, biomedical and electronic fields and in the overall development of nanotechnologies. However, their toxicological profiles are still not fully developed. This study compared the distribution and immunotoxicity of two rod-types of AlO NP. As reported previously, the two types of AlO NP had different aspect ratios (long-type: 6.2u2009±u20090.6, short-type: 2.1u2009±u20090.4), but the size and surface charge were very similar. On Day 14 after a single intravenous (IV) injection (1.25 or 5u2009mg/kg), both AlO NP accumulated primarily in the liver and spleen and altered the levels of redox response-related elements. The accumulated level was higher in mice exposed to the long-type AlO NP compared to the short-type. Additionally, it was noted that the levels of IL-1β, IL-8 and MCP-1 were enhanced in the blood of mice exposed to both types of AlO NP and the percentages of neutrophils and monocytes among all white blood cells were increased only in mice injected with the long-type AlO NP (5u2009mg/kg). In addition, as compared to the control, co-expression of CD80 and CD86 (necessary for antigen presentation) on splenocytes together with a decreased expression of chemotaxis-related marker (CD195) was attenuated by exposure to the AlO NP, especially the long-type. Taken together, the data suggest that accumulation following a single IV injection with rod-types of AlO NP is strengthened by a high aspect ratio and, subsequently, this accumulation has the potential to influence immune functions in an exposed host.

Comparison of distribution and toxicity following repeated oral dosing of different vanadium oxide nanoparticles in mice

Vanadium is an important ultra-trace element derived from fuel product combustion. With the development of nanotechnology, vanadium oxide nanoparticles (VO NPs) have been considered for application in various fields, thus the possibility of release into the environment and human exposure is also increasing. Considering that verification of bioaccumulation and relevant biological responses are essential for safe application of products, in this study, we aimed to identify the physicochemical properties that determine their health effects by comparing the biological effects and tissue distribution of different types of VO NPs in mice. For this, we prepared five types of VO NPs, commercial (C)-VO2 and -V2O5 NPs and synthetic (S)-VO2, -V2O3, and -V2O5 NPs. While the hydrodynamic diameter of the two types of C-VO NPs was irregular and impossible to measure, those of the three types of S-VO NPs was in the range of 125-170nm. The S- and C-V2O5 NPs showed higher dissolution rates compared to other VO NPs. We orally dosed the five types of VO NPs (70 and 210μg/mouse, approximately 2 and 6mg/kg) to mice for 28 days and compared their biodistribution and toxic effects. We found that S-V2O5 and S-V2O3 NPs more accumulated in tissues compared to other three types of VO NPs, and the accumulated level was in order of heart>liver>kidney>spleen. Additionally, tissue levels of redox reaction-related elements and electrolytes (Na(+), K(+), and Ca(2+)) were most clearly altered in the heart of treated mice. Notably, all S- and C-VO NPs decreased the number of WBCs at the higher dose, while total protein and albumin levels were reduced at the higher dose of S-V2O5 and S-V2O3 NPs. Taken together, we conclude that the biodistribution and toxic effects of VO NPs depend on their dissolution rates and size (surface area). Additionally, we suggest that further studies are needed to clarify effects of VO NPs on functions of the heart and the immune system.

Waste Windshield-Derived Silicon/Carbon Nanocomposites as High-Performance Lithium-Ion Battery Anodes

Silicon has emerged as the most promising high-capacity material for lithium-ion batteries. Waste glass can be a potential low cost and environmentally benign silica resource enabling production of nanosized silicon at the industry level. Windshields are generally made of laminated glass comprising two separate glass bonded together with a layer of polyvinyl butyral sandwiched between them. Herein, silicon/carbon nanocomposites are fabricated from windshields for the first time via magnesiothermic reduction and facile carbonization process using both waste glass and polyvinyl butyral as silica and carbon sources, respectively. High purity reduced silicon has unique 3-dimensional nanostructure with large surface area. Furthermore, the incorporation of carbon in silicon enable to retain the composite anodes highly conductive and mechanically robust, thus providing enhanced cycle stability.

Pulmonary persistence of graphene nanoplatelets may disturb physiological and immunological homeostasis

Accumulated evidence suggests that chronic pulmonary accumulation of harmful particles cause adverse pulmonary and systemic health effects. In our previous study, most of the graphene nanoplatelet (GNP) remained in the lung until 28u2009days after a single instillation. In this study, we sought to evaluate the local and systemic health effect after a long pulmonary persistence of GNP. As expected, GNP remained in the lung on day 90 after a single intratracheal instillation (1.25, 2.5 and 5u2009mgu2009kg−1). In the lung exposed at the highest dose, the total number of cells and the percentage of lymphocytes significantly increased in the BAL fluid with an increase in both the number of GNP‐engulfed macrophages and the percentage of apoptotic cells. A Th1‐shifted immune response, the elevated chemokine secretion and the enhanced expression of cytoskeletal‐related genes were observed. Additionally, the expression of natriuretic‐related genes was noteworthy altered in the lungs. Moreover, the number of white blood cells (WBC) and the percentage of macrophages and neutrophils clearly increased in the blood of mice exposed to a 5‐mgu2009kg−1 dose, whereas total protein, BUN and potassium levels significantly decreased. In conclusion, we suggest that the long persistence of GNP in the lung may cause adverse health effects by disturbing immunological‐ and physiological‐homeostasis of our body. Copyright

Comparison of subchronic immunotoxicity of four different types of aluminum-based nanoparticles

Nanoparticles (NPs) have recently emerged as an inhalable pollutant, owing to their applications, aluminum‐based NPs (Al‐NPs) have been prioritized for toxicity testing. In the current study, we compared the pulmonary biopersistence and subsequent toxicity of four different types of Al‐NPs (two rod‐type aluminum oxide NPs [AlONPs] with different aspect ratios [short (S)‐ and long (L)‐AlONPs], spherical aluminum cerium oxide NPs [AlCeO3, AlCeONPs] and spherical γ‐aluminum oxide hydroxide nanoparticles [AlOOHNPs]) 13weeks after a single intratracheal instillation, considering the importance of their properties in their toxicity. We found that the pulmonary biopersistence of Al‐NPs was strengthened by a high aspect ratio in the rod‐type AlONPs and by the presence of hydroxyl groups in the spherical‐type Al‐NPs. The highest toxicity was observed in the mice treated with AlOOHNPs, which showed low biostability. More importantly, we identified that the commercially available AlCeONPs were Al2O3‐coated CeO2 NPs, but not AlCeO3 NPs, although they have been sold under the trade name of AlCeONPs. In conclusion, the aspect ratio and biostability may be important factors in the determination of the biopersistence of NPs and the subsequent biological response. In addition, the physicochemical properties of NPs should be examined in detail before their release into the market to prevent unexpected adverse health effects.

Tissue distribution following 28 day repeated oral administration of aluminum‐based nanoparticles with different properties and the in vitro toxicity

The tissue distribution and toxicity of nanoparticles (NPs) depend on their physical and chemical properties both in the manufactured condition and within the biological system. We characterized three types of commercially available aluminum‐based NPs (Al‐NPs), two rod‐type aluminum oxide NPs (Al2O3, AlONPs), with different aspect ratios (short [S]‐ and long [L]‐AlONPs), and spherical aluminum cerium oxide NPs (AlCeO3, AlCeONPs). The surface area was in order of the S‐AlONPs > L‐AlONPs > AlCeONPs. Very importantly, we found that AlCeONPs is Al2O3‐coated CeO2 NPs, but not AlCeO3 NPs, and that the Al level in AlCeONPs is approximately 20% of those in S‐ and L‐AlONPs. All three types of Al‐NPs were slightly ionized in gastric fluid and rapidly particlized in the intestinal fluid. There were no significant differences in the body weight gain following 28 days of repeated oral administration of the three different types of Al‐NPs. All Al‐NPs elevated Al level in the heart, spleen, kidney and blood at 24 hours after the final dose, accompanied by the altered tissue level of redox reaction‐related trace elements. Subsequently, in four types of cells derived from the organs which Al‐NPs are accumulated, H9C2 (heart), HEK‐293 (kidney), splenocytes and RAW264.7 (blood), S‐AlONPs showed a very low uptake level and did not exert significant cytotoxicity. Meanwhile, cytotoxicity and uptake level were the most remarkable in cells treated with AlCeONPs. In conclusion, we suggest that the physicochemical properties of NPs should be examined in detail before the release into the market to prevent unexpected adverse health effects.

Pulmonary glass particles may persist in the lung suppressing function of immune cells

The health effects of silica may depend on the inherent properties of crystalline silica or on external factors affecting the biological activity or distribution of its polymorphs. Inhaled crystalline silica is classified as a Group I carcinogen, however, information on the health effects of amorphous silica is still insufficient. Considering that alveolar macrophages play a key role in both innate and adaptive immune responses for removal of foreign bodies that enter via the respiratory system, we treated sheet‐like glass particles (SGPs), a type of noncrystalline amorphous silica, to MH‐S cells, an alveolar macrophage cell line. SGPs reduced the generation of ROS and NO and induced cell death via multiple pathways. Although the expression of CD80, CD86, and CD40, increased by exposure to SGPs, the expression of MHC class II molecules had not notably changed. Additionally, expression of ICAM‐1 tended to decrease. In mice, SGPs were distributed in the interstitial region of the lung without notable pathological lesion on day 14 after a single intratracheal instillation. Pulmonary total cell number increased significantly with the highest dose, but the levels of all measured inflammatory cytokines and chemokines, except IL‐1, were lower in BAL fluid from SGP‐treated mice compared to control. More interestingly, the expression of antigen presentation‐related proteins was enhanced in the lungs of SGP‐exposed mice concomitant with an increase in the number of mature dendritic cells, whereas the expression of ICAM‐1, an important adhesion molecule for helper T cell recruitment, was suppressed. Taken together, we suggest that SGPs may induce adverse health effects by down‐regulating function of immune cells in the lungs. Furthermore, ICAM‐1 may play a key role in immune response to remove pulmonary SGPs.