Sang-Wha Lee

Remediation of petroleum-contaminated soils by fluidized thermal desorption

A novel type of fluidized bed desorber was developed for the remediation of petroleum-contaminated soils at low temperature with high efficiency. Cahn balance® was utilized to investigate the thermal desorption behavior of soils contaminated by various hydrocarbons. The performance of the fluidized-bed desorber was investigated at different operating modes. Batch operation of the fluidized-bed desorber exhibited 99.9% desorption efficiency at temperatures of ca. 300°C within a half hour. Continuous operation of the fluidized-bed indicated that Q/F (the ratio of the mass flow rate of fluidizing gas to feeding rate of contaminated soils) is less important at higher temperature (>300°C), if proper fluidization is ensured. The periodic operation of the fluidized bed desorber shows the possibility to reduce off-gas volume significantly.

Silicon/copper dome-patterned electrodes for high-performance hybrid supercapacitors

This study proposes a method for manufacturing high-performance electrode materials in which controlling the shape of the current collector and electrode material for a Li-ion capacitor (LIC). In particular, the proposed LIC manufacturing method maintains the high voltage of a cell by using a microdome-patterned electrode material, allowing for reversible reactions between the Li-ion and the active material for an extended period of time. As a result, the LICs exhibit initial capacities of approximately 42 F g−1, even at 60 A g−1. The LICs also exhibit good cycle performance up to approximately 15,000 cycles. In addition, these advancements allow for a considerably higher energy density than other existing capacitor systems. The energy density of the proposed LICs is approximately nine, two, and 1.5 times higher than those of the electrochemical double layer capacitor (EDLC), AC/LiMn2O4 hybrid capacitor, and intrinsic Si/AC LIC, respectively.

Employment of encapsulated Si with mesoporous TiO2 layer as anode material for lithium secondary batteries

Abstract Silicon composite of nano-capsule type is newly applied as an active anode material for lithium ion batteries. TiO 2 -encapsulated silicon powders were synthesized by a sol-gel reaction with titanium ethoxide. Silicon nanoparticles were successfully embedded into porous titanium oxide capsules that played as a buffer layer against drastic volume changes of silicon during the charge-discharge cycling, consequently leading to the retardation of the capacity fading of intrinsic silicon materials. The electrochemical and structural properties of silicon nanocomposites with different surface areas of encapsulating TiO 2 layer were characterized by X-ray diffraction(XRD), nitrogen gas adsorption analysis by the Brunauer-Emmett-Teller(BET) equation, transmission electron microscopy(TEM), and galvanostatic charge-discharge experiments.

Encapsulated Fe3O4 nanoparticles with silica thin layer as an anode material for lithium secondary batteries

Fe3O4 nanoparticles were coated with a SiO2 layer by using a modified sol?gel method. The synthetic procedures for Fe3O4 nanoparticles encapsulated with a SiO2 layer (SiO2@Fe3O4) consist of three consecutive steps: (i) fabrication of Fe3O4 by the co-precipitation method, (ii) stabilization of Fe3O4 with citrate as a capping agent, which is used to prevent particles from aggregating, and (iii) silica encapsulation by a modified sol?gel reaction. Based on the experimental range, SiO2@Fe3O4 exhibited higher cyclic performance than the intrinsic one. The reversible capacity of Fe3O4 with SiO2 at the first cycle was 363?mA?h?g?1 and the remaining discharge capacity was 321?mA?h?g?1 after the 30th cycle.

A prominent anchoring effect on the kinetic control of drug release from mesoporous silica nanoparticles (MSNs)

This work demonstrated kinetically controlled release of model drugs (ibuprofen, FITC) from well-tailored mesoporous silica nanoparticles (MSNs) depending on the surface charges and molecular sizes of the drugs. The molecular interactions between entrapped drugs and the pore walls of MSNs controlled the release of the drugs through the pore channels of MSNs. Also, polydopamine (PDA) layer-coated MSNs (MSNs@PDA) was quite effective to retard the release of large FITC, in contrast to a slight retardation effect on relatively small Ibuprofen. Of all things, FITC (Fluorescein isothiocyanate)-labeled APTMS (3-aminopropyltrimethoxysilane) (APTMS-FITC conjugates) grafted onto the MSNs generate a pinch-effect on the pore channel (so-called a prominent anchoring effect), which was highly effective in trapping (or blocking) drug molecules at the pore mouth of the MSNs. The anchored APTMS-FITC conjugates provided not only tortuous pathways to the diffusing molecules, but also sustained release of the ibuprofen over a long period of time (∼7days). The fast release kinetics was predicted by an exponential equation based on Ficks law, while the slow release kinetics was predicted by Higuchi model.

The characteristic ag core au shell nanoparticles as SerS substrates in detecting dopamine molecules at various ph ranges

AgcoreAushell nanoparticles (NPs) are a promising surface-enhanced Raman scattering (SERS) substrate, which can offer a high enhancement factor through the combined effect of the high SERS activity of the Ag core and the biocompatibility of the Au shell. In this study, AgcoreAushell NPs were examined as SERS substrates for the sensitive detection of dopamine (DA) molecules in an aqueous solution. The SERS activity of the AgcoreAushell NPs was strongly dependent on the pH of the solution. When the pH of the solution was acidic (pH <5) or basic (pH >9), the AgcoreAushell NPs exhibited negligible SERS activity toward the DA molecules, due to the weakened interactions (or repulsive forces) between the DA molecules and the core–shell NPs. On the other hand, the AgcoreAushell NPs exhibited a high SERS activity in the intermediate pH ranges (pH 7–9), due to the molecular bridging effect of DA molecules, which allows probe molecules to be located at the interstitial junctions (so-called hot spots) between the core–shell NPs. The results of this study highlight the importance of probe-induced clustering of core–shell NPs in the SERS measurements at physiological pH.

Additive effect of 1,8-diaminoctane as a bi-functional linker on the two-dimensional array of large gold nanoparticles

1,8-Diaminooctane ligand was investigated as a molecular bridging linker to induce a uniform array of gold nanoparticles (GNPs) (larger than 60 nm) via the lateral immobilization of GNPs on amine-functionalized glass substrate. The effects of array time and ligand amounts were optimized to obtain a uniform and two-dimensional (2D) array of large GNPs. With the increase of ligand dosage, the deposition of GNPs on glass substrate progressively increased, finally leading to a densely packed 2D array of GNPs. Excessive dosage of ligand, however, led to a multilayered array of GNPs on glass substrate.

Today's diverse nano-theranostic applications and tomorrow's promises

In 2004, the US Food and Drug Administration (FDA) released an important report entitled Innovation/Stagnation: Challenges and Opportunities on the Critical Path to New Medical Products.1 In this report, the FDA strongly expressed its interest in modernizing manufacturing processes (or scientific tools) for medical products. Theranostics was indicated as one of the best candidates that can epochally change such scientific tools toward a critical path to new medical products. Since the concept was first introduced in 1998 by John Finkhouser, theranostics has been generally considered as combining therapy and diagnosis into one approach in order to develop an efficient new targeted therapy for personalized medicine. Theranostics was a term created by combining the two words, therapy and diagnostics, into one to better present the early detection of various diseases and their respective personalized treatments. The following phrase also seems to reflect the core of theranostics – have your cake and eat it too – combining these two excellent ideas of nanotechnology and theranostics into inspiration for innovative creativities. Here, nano-theranostics extends further into the convergence with nanotechnology and personalized medicine, where many researchers and scientists have been developing cutting-edge nanotechnologies and applying them into tailored medicines for each individual. A concerted effort has been intensively invested to develop theranostic nanomaterials that can effectively combine therapeutic agents, targeting moieties, and imaging agents. For practical and clinical applications of nano-theranostics, all three components need to be cunningly integrated into nanoparticle-based carriers because of the three components feasible tailorability and functional diversity. Nanoparticle-based systems can be a useful theranostic platform that can combine all the required components because the particle core can be tailored to load multiple therapeutic drugs and imaging agents and the particle surface can also be easily modified to attach the targeting moieties and surface-enhancing factors (long circulation and penetration capability). Furthermore, various nanomaterials (such as graphene, carbon nanotube, biocompatible polymers, superparamagnetic materials, gold nanocomposites, etc.) are constantly designed as theranostic nanoparticles that can monitor treatment and simultaneously enhance drug efficacy. This special issue consists mainly of nanoparticle-based theranostics that combine therapeutic drugs, diagnostic imaging agents, and/or targeting moieties at the nanoscale. In addition, this issue is intended to highlight recent developments in nano-theranostics and provide useful information for the future research directions in theranostics. In this light, nano-theranostics could continue to have a promising future in cancer diagnoses and treatments as well as other emerging needs, such as infection.

Self-Assembled Two-Dimensional Array of Gold Nanoparticles with Different Size for the Sensing Application

Self-assembled two-dimensional array of gold nanoparticles (GNPs) on the glass substrate was systematically investigated in terms of glass cleaning, K2CO3 addition, GNP size, and pH of gold colloids. An ambient-air plasma treatment produced a highly-activated glass surface with the lowest air/water contact angles and K2CO3 addition is very effective to preserve the optical properties of gold nanoparticles for a long time. Small GNPs (≤40 nm) was uniformly arrayed on the amine-functionalized glass through the optimization process of electrostatic attractions between positively-charged glass and negatively-charged gold nanoparticles. For large GNPs (≥50 nm) that resulted in discrete (or loosely-packed) array on the glass substrate, pH adjustment of gold colloids (from pH 11 to 9) produced more densely-packed array of GNPs with less void areas, probably due to the reduction of electrostatic repulsion forces between large gold nanoparticles.

Effect of ion irradiation on internal stress of amorphic carbon films produced by pulsed laser

Abstract Amorphic carbon films either 50 or 160 nm thick were deposited on Si(100) and glass substrates at room temperature in a high-vacuum environment using a Q-switched Nd-YAG pulse laser focused on a graphite target. These films were irradiated with Ti+ or C+ ions having kinetic energies of 35 and 75 keV, and the changes in internal stresses of the films with varying ion influence were investigated by measuring substrate bending using stylus profilometry. The ion energy and the film thickness were chosen such that the ion penetration depth, Rp, corresponded to either the film thickness or one half of the film thickness. The results indicate that there is an optimum ion fluence leading to a stress-free film for a given ion species and energy. Interpretation of the resulting stress behavior from ion irradiation was made based on the relaxation resulting from damage inside the film together with interfacial mixing. The scanning electron microscopy pictures and surface roughness measurements showed a very smooth surface for both as-deposited and ion-irradiated films. The ion-irradiated films had a Vickers hardness greater than 22 GPa, and were adherent to both Si and glass substrates. An investigation of the film characteristics using Raman scattering and electron-energy loss spectra has revealed that high-energy ion irradiation of an intermediate ion fluence can be utilized successfully to deposit an adherent and hard carbon film with controlled internal stress without changing the film structure significantly.