Korean Journal of Chemical Engineering (v.34, #12)

We investigated the effect of solvents on the formation of amorphous paclitaxel and proposed an efficient strategy for the removal of residual solvents from solvent-induced amorphous paclitaxel. Amorphous paclitaxel was produced by solvent-induced method using non-polar solvents (methylene chloride, toluene, pentane, methyl t-butyl ether, chloroform, and acetonitrile/hexane (1 : 2, v/v)). The residual pentane and hexane levels easily met the International Conference on Harmonization (ICH)-specified values (5,000 and 290 ppm) by simple rotary evaporation. When the vacuum-dried sample was subjected to microwave-assisted drying, the ICH requirements for methylene chloride (600 ppm) and acetonitrile (410 ppm) were met by drying for 23 hr at 200 W and 3 hr at 200 W, respectively. However, residual toluene, methyl t-butyl ether, and chloroform concentrations did not meet the ICH-specified values (890, 5,000, and 60 ppm). The shape and size of amorphous paclitaxel particles were examined by SEM and XRD.
Keywords: Solvent-induced Amorphous Paclitaxel; Residual Solvent; Removal; Rotary Evaporation; Vacuum Drying; Microwave-assisted Drying

Analysis of air blast effect for explosives in a large scale detonation by Hweeung Kwon; Kyungjae Tak; Sanjeev Maken; Hyounsoo Kim; Jungsu Park; Il Moon (3048-3053).
Open Burning/Open Detonation (OB/OD) has been widely used for demilitarization of expired explosives. However, OB/OD effects a variety of hazardous damages to environment. Therefore, using incinerators to treat expired explosives is required instead of OB/OD. To guarantee the safety of these demilitarization methods, the blast wave of the explosives should be previously recognized to evaluate the impact of detonations. Although various materials are used to produce explosives, most researches have focused on trinitrotoluene (TNT). Other representative explosives such as research department explosives (RDX) and high melting explosives (HMX) are seldom studied in the literature. Therefore, our aim was to understand the blast wave of three materials under different geometry throughout simulations. To improve accuracy and reduce computational time, a zoning technique with Euler-Lagrange coupling method was used. Due to limitations and difficulties of detonation experiments, simulations were verified by theoretical models. In case of semi-confined bunker, the simulation results were compared with experimental data, showing a close match. As a result, cylinder type is the safest incinerator among semi-confined bunker, cylinder, and cube incinerators, in terms of the blast wave.
Keywords: Explosion; Blast Effect; TNT; RDX; Detonation; Scaled Distance

Vulnerability assessment index at process-level for the identification of adaptive strategies in wastewater treatment plants under climate change by Dongwoo Kim; Gabriel Jacome; SeungChul Lee; Wladimir Moya; KiJeon Nam; Changkyoo Yoo (3054-3066).
Many studies have been conducted on climate change vulnerability assessments to develop adaptive strategies for climate change on a national or global scale. The development of an assessment tool for climate change on a process-level is necessary for evaluating vulnerability and to suggest an effective adaptive strategy in wastewater treatment plants (WWTP). Therefore, we proposed a vulnerability assessment index at the process-level in a WWTP to evaluate adaptive strategies for climate change in this study. The suggested process-level vulnerability assessment index is based on three performance WWTP indices: the effluent quality index (EQI), global warming potential (GWP), and operational cost index (OCI). Four different advanced WWTP processes were evaluated using the suggested vulnerability assessment index based on the A2 scenario, which is one of the carbon emission scenarios making predictions out to 2100 developed by the intergovernmental panel on climate change (IPCC). The adaptive strategies were evaluated at four conventional treatment processes to see the improvement of vulnerability of their processes, where the changes of their vulnerabilities are compared together. Suggested adaptive strategies in case studies showed that the process-level vulnerabilities were significantly decreased in the anaerobic/anoxic/aerobic (A2O) and Virginia initiative project (VIP) processes, especially during the flood and winter seasons. Therefore, it is expected that the proposed vulnerability assessment index can be useful as a decision-supporting tool for selecting the appropriate adaptive strategy for each process.
Keywords: Climate Change Vulnerability Assessment; Effluent Quality Index (EQI); Greenhouse Gas (GHG); Operational Cost Index (OCI); Wastewater Treatment Process; Adaptive Strategy

This paper proposes the closed-form analytical design of proportional-integral (PI) controller parameters for the optimal control of an open-loop unstable first order process subject to operational constraints. The main idea of the design process is not only to minimize the control performance index, but also to cope with the constraints in the process variable, controller output, and its rate of change. To derive an analytical design formula, the constrained optimal control problem in the time domain was transformed to an unconstrained optimization in a parameter space associated with closed-loop dynamics. By taking advantage of the proposed analytical approach, a convenient shortcut algorithm was also provided for finding the optimal PI parameters quickly, based on the graphical analysis for the optimal solution of the corresponding optimization problem in the parameter space. The resulting optimal PI controller guarantees the globally optimal closed-loop response and handles the operational constraints precisely.
Keywords: Optimal Control; Operational Constraints; Open-loop Unstable Process; Industrial Proportional-Integral (PI) Controller; Analytical Design Approach

Effects of organic and inorganic metal salts on thermogravimetric pyrolysis of biomass components by Shilin Zhao; Meng Liu; Liang Zhao; Jianhong Lu (3077-3084).
Thermogravimetric analyzer (TGA) was employed to elucidate the catalytic effects of organic and inorganic metal salts (K2CO3, KAc, Na2CO3 and NaAc) on the pyrolysis of three biomass components (cellulose, hemicellulose and lignin). In case of cellulose, TG analysis results showed that all the four metal salts increased the yield of char products and decreased the weight loss rates of cellulose pyrolysis, which followed the order of Na2CO3>K2CO3>NaAc>KAc. In contrast to cellulose, the four organic and inorganic salts employed had no significant effects on the remaining two biomass components:, hemicellulose and lignin. However, the four metal salts led to the devolatilization reaction of hemicellulose to occur at lower temperature region, and the dehydration reaction of lignin was promoted more or less. An increase in the heating rate might augment the maximum degradation rate. Different mixing ratios had little influence on the progress of catalytic pyrolysis. Based on the observations, the potential mechanism of the catalytic pyrolysis of biomass components with metal salts was discussed.
Keywords: TGA; Biomass; Metal Salts; Catalytic; Pyrolysis

CO and CO2 methanation over Ni catalysts supported on alumina with different crystalline phases by Thien An Le; Tae Wook Kim; Sae Ha Lee; Eun Duck Park (3085-3091).
The effect of alumina crystalline phases on CO and CO2 methanation was investigated using alumina-supported Ni catalysts. Various crystalline phases, such as α-Al2O3, θ-Al2O3, δ-Al2O3, η-Al2O3, γ-Al2O3, and κ-Al2O3, were utilized to prepare alumina-supported Ni catalysts via wet impregnation. N2 physisorption, H2 chemisorption, temperature-programmed reduction with H2, CO2 chemisorption, temperature-programmed desorption of CO2, and X-ray diffraction were employed to characterize the catalysts. The Ni/θ-Al2O3 catalyst showed the highest activity during both CO and CO2 methanation at low temperatures. CO methanation catalytic activity appeared to be related to the number of Ni surface-active sites, as determined by H2-chemisorption. During CO2 methanation, Ni dispersion and the CO2 adsorption site were found to influence catalytic activity. Selective CO methanation in the presence of excess CO2 was performed over Ni/γ-Al2O3 and Ni/δ-Al2O3; these substrates proved more active for CO methanation than for CO2 methanation.
Keywords: CO Methanation; CO2 Methanation; Ni/Al2O3 ; Alumina; Crystalline Phase

A reaction kinetic study of CO2 gasification of petroleum coke, coals and mixture by Jin Woo Kook; In Seop Gwak; You Ra Gwak; Myung Won Seo; See Hoon Lee (3092-3101).
Characteristics of Char-CO2 gasification were compared in the temperature range of 1,100–1,400 °C using a thermogravimetric analyzer (TGA) for petroleum coke, coal chars and mixed fuels (Petroleum coke/coal ratios: 0, 0.25, 0.5, 0.75, 1). The results showed that reaction time decreased with increasing gasification temperature, BET surface area and alkali index of coal. Mixed fuels composed of petroleum coke/coal exhibited reduced activation energies. Modified volumetric reaction model and shrinking core model might be suitably matched with experimental data depending on coal type and petroleum coke/coal ratio. Rate equations were suggested by selecting gas-solid reaction rate models for each sample that could simulate CO2 gasification behavior.
Keywords: Gasification; Coal; Petroleum Coke; Mixed Fuel; Kinetic

Multilateral approaches for investigation of particle stickiness of coal ash at low temperature fouling conditions by Hueon Namkung; Hyung-Taek Kim; Fuchen Wang; Kuangfei Lin; Guangsuo Yu (3102-3110).
Particle stickiness is a key parameter for increasing ash deposition in gasification process. We conducted multilateral investigations to evaluate particle stickiness of coal ash at low temperature fouling conditions through Watt and Fereday’s viscosity model, dilatometry (DIL) and laser flash apparatus (LFA) technique. Seventeen coals were employed for ash deposition experiments under gasification condition through drop tube furnace (DTF). The low viscosity not only led to increasing ash deposition behavior, but also increasing the particle size of deposited ash. From DIL analysis, the ash sintering behavior increased with increasing temperature due to increase of particle stickiness. The high amount of Fe2O3, CaO and MgO components resulted in low sintering temperature and high reduction of physical length. Through LFA analysis, the thermal conductivity increased with increasing temperature, because of increasing particle stickiness. In addition, its value was correlated with the propensity of common fouling indices.
Keywords: Ash Fouling; Gasification; Stickiness; Sintering; Thermal Conductivity

Compositional and structural variations of bitumen and its interactions with mineral matters during Huadian oil shale pyrolysis by Zhibing Chang; Mo Chu; Chao Zhang; Shuxia Bai; Hao Lin; Liangbo Ma (3111-3118).
Thermal bitumen is an important intermediate derived from kerogen decomposition during oil shale pyrolysis. In this study, free bitumen (FB) and bound bitumen (BB) were obtained by extracting oil shale chars (300–550 °C) before and after demineralization, and then analyzed by liquid chromatography fractionation, Fourier transform infrared spectroscopy, and gas chromatography/mass spectrometry. The FB yield first increased and then decreased with increasing temperature, and the maximum value was 2.10% at 400 °C. The decarboxylation of acids and decomposition of esters at 350–450 °C decreased the content of these compounds. Meanwhile, the intense cracking reactions of aliphatic compounds and alkyl chains at 400–450 °C decreased the carbon chain lengths and molecular weights of these compounds. From the analytical results obtained for the BB fractions, we suggest that some carboxylic acids or carboxyl group-containing compounds may be trapped on carbonate particles by the formation of Ca2+COO bonds, whereas other oxygenated compounds (e.g., esters and phenols) can be adsorbed preferentially by clay minerals through Lewis acid-base interactions.
Keywords: Oil Shale Pyrolysis; Bitumen; Chemical Structure; Chemical Composition; Mineral Matters

Investigating the effect of nano-silica on efficiency of the foam in enhanced oil recovery by Seyyed Ahmadreza Amirsadat; Babak Moradi; Ali Zeinolabedini Hezave; Siamak Najimi; Mehdi Hojjat Farsangi (3119-3124).
Due to the vast production of crude oil and consequent pressure drops through the reservoirs, secondary and tertiary oil recovery processes are highly necessary to recover the trapped oil. Among the different tertiary oil recovery processes, foam injection is one of the most newly proposed methods. In this regard, in the current investigation, foam solution is prepared using formation brine, C19TAB surfactant and air concomitant with nano-silica (SiO2) as foam stabilizer and mobility controller. The measurements revealed that using the surfactant-nano SiO2 foam solution not only leads to formation of stable foam, but also can reduce the interfacial tension mostly considered as an effective parameter for higher oil recovery. Finally, the results demonstrate that there is a good chance of reducing the mobility ratio from 1.12 for formation brine and reservoir oil to 0.845 for foam solution prepared by nanoparticles.
Keywords: Surfactant Foam; Interfacial Tension; Foam Stability; Nano-silica Dioxide; Enhanced Oil Recovery; Mobility Ratio

A comparison of fluidized bed pyrolysis of oil sand from Utah, USA, and Alberta, Canada by Dowon Shun; Jong-Seon Shin; Dal-Hee Bae; Ho-Jung Ryu; Jaehyeok Park (3125-3131).
Characterization and thermal pyrolysis of oil sand was conducted. The experiment was performed on Circle Cliffs, Utah, U.S.A. and the results were compared with the data from Alberta, Canada. The reaction character identified by TGA was dual mode of vaporization of light hydrocarbon and thermal cracking of high molecular hydrocarbon. The pyrolysis experiment was performed in a 2 kg/h capacity fluidized bed externally heated by electricity. The process variables investigated were a temperature range of 723-923 K, fluidization gas velocity of 1.5-2 times of the minimum fluidization velocity, solid retention time of 15-30 minutes, and average particle size of 435 microns. The results of TGA and elemental analysis of bitumen provided necessary information regarding maximum liquid yield from the pyrolysis prior to pyrolysis experiment. The oil yield was maximum at 823 K. The yield of liquid was not exceeding the weight percent of maltenes in original bitumen. The optimum reaction condition should be fast vaporization of light hydrocarbon and minimizing thermal cracking of high molecular hydrocarbon. To maximize the liquid yield, fast heating and vaporization of oil sand bitumen and then the rapid removal of the vaporized product from the heating zone is recommended, i.e., operation in a fluidized bed reactor.
Keywords: Oil Sand; Circle Cliffs; Pyrolysis; Bitumen

Deep desulfurization of model oil by photocatalytic air oxidation and adsorption using Ti(1−x)M x O2 (M=Zr, Ce) by Wei Zhang; Xin Li; Hong Wang; Yongji Song; Shenghong Zhang; Cuiqing Li (3132-3141).
Deep desulfurization of model oil by photocatalytic air oxidation and adsorption using Ti(1−x)M x O2 (M=Zr, Ce) was investigated. Ti(1−x)M x O2 (M=Zr, Ce) was prepared by urea gelation/co-precipitation method, and characterized by N2 adsorption, XRD and UV-vis spectra. UV irradiation greatly enhanced the adsorptive capacity and selectivity of TiO2-ZrO2 for organosulfur in model oil because organosulfur compounds were first photocatalytically oxidized to sulfoxides and sulfones over TiO2-ZrO2, which were then selectively adsorbed on the bifunctional material due to much higher polarities of generated sulfoxides and sulfones. The Ti/Zr molar ratio and calcination temperature were optimized to 5 : 5 and 500 °C with the sulfur removal of 99.6% after reaction for 2 h under UV irradiation. After adding 25 wt% toluene into model oil, the sulfur removal could still reach 97.2% after reaction for 7 h. TiO2-ZrO2 could be well regenrated by washing with acetonitrile followed by thermal treatment in air.
Keywords: Adsorptive Desulfurization; Photocatalysis; Dibenzothiophene; Selectivity; TiO2-ZrO2

Styrene monomer is a volatile organic compound that has many applications in plastics, rubber, and paint manufacturing industries. Exposure to styrene vapor has certain effects, including suppression of the central nervous system, loss of concentration, weakness and fatigue, and nausea and there is a possibility of carcinogenesis in long-term exposure. Therefore, it is necessary to control and eliminate this vapor. The aim of this study was to investigate the performance of zinc oxide nanoparticles on modified natural zeolites in removing styrene vapor from the air. Natural zeolites of clinoptilolite were modified using hydrochloric acid and diphenyldichlorosilane. Next, zinc oxide nanoparticles with different ratios of 3, 5, and 10 wt% were stabilized on the zeolites. To determine their characteristics, samples were used from BET, SEM and XRD analyses. The input styrene concentration and the ratio of nanoparticles stabilized on zeolites were studied as effective functional parameters on the removal process. The efficiency results of natural zeolites (Ze) and modified zeolites (Mze) in styrene adsorption from the air show that the styrene breakthrough in the bed of MZe compared to that of Ze increases approximately two times. Also, the results showed that the removal by the process of UV/MZe-ZnO 3%, UV/MZe-ZnO 5%, and UV/MZe-ZnO 10%, was 36.5%, 40%, and 26%, respectively. From the results it can be concluded that MZe can increase the efficiency of photocatalytic degradation. Clinoptilolites of Iran can be used as an adsorbent to remove polluted air in industries that have low concentrations and flow rates.
Keywords: Photocatalytic Degradation; Zinc Oxide Nanoparticles; Styrene; Zeolite

We investigated the effects of initial pH (2≤pH0≤6) and sewage sludge compost content (5≤[SSC]≤25 g/kg) on leaching characteristics of lead (Pb) and zinc (Zn) in contaminated field soil. pH0 and [SSC] significantly affected the leaching of Pb and Zn in soils contaminated with them. The pH in the solution increased as reaction time and [SSC] increased. The leached amounts of Pb and Zn were highest at pH0=2 and increased with reaction time. As [SSC] increased, the leached amount of Pb decreased (50.4 mg/kg at control condition ([SSC]=0 g/kg); 22.9 mg/kg at [SSC]=25 g/kg at pH0=2) and the leached amount of Zn increased (20.1 mg/kg at [SSC]=0 g/kg; 31.7 mg/kg at [SSC]=25 g/kg at pH0=2). The change increased as pH0 decreased. Within the design boundaries, minimum leaching of Pb (14.7 mg/kg) occurred at pH0=5.1 and [SSC]=25 g/kg, and minimum leaching of Zn (5.0 mg/kg) occurred at pH0=5.1 and [SSC]=5 g/kg.
Keywords: Biosolids; Heavy Metals; Optimization; Pb; Zn

Anti-melanogenic effect of Prunus davidiana extract in melan-a melanocyte through regulation of OCA-2, TRP-1 and tyrosinase by Birendra Kumar Singh; Vivek Kumar Morya; Hyang-Bok Lee; Jun-Shub Kim; Eun-Ki Kim (3156-3162).
Prunus spp. and locally available plants (used as folkloric medicine) were screened to find a novel and natural anti-melanogenic agent. Based on p-protein promoter reporter assay (PPRA) the candidate plants were screened in the quest for p-protein inhibitor. Expression profiling of key proteins revealed the molecular mechanism of the melanin inhibition as well as TEM analysis revealed melanosome structure. The screened plant extract through PPRA showed significant down regulation of p-protein, which led to melanin inhibition. Another key melanosomal protein like tyrosinase and TRP-1 was also found to be down-regulated. However, TRP-2 was not affected. TEM analysis of treated cells also revealed that the stage IV melanosomes were lowered in number compared to control. The present study shows the plants used in this study possess good anti-melanogenic properties. However, the P. davidiana has the highest anti-melanogenic property among screened plant extracts.
Keywords: Pink-eyed Dilution (p) Protein; Melanosome; TEM; P. davidiana ; Anti-melanogenic Agent

Gracilaria species produce agars with low quality due to their high sulfate concentrations. For this reason, the gel properties of many Gracilaria agars must be improved by appropriate processes. In this study, we developed an improved agar extraction process for Gracilaria verrucosa by alkali soaking extraction and microwave thawing and drying. Variables such as the seaweed to alkali volume ratio, extraction time, and alkali concentration were adjusted to optimize the yield and agar quality. The yield of the agar was maximized (34.5±0.6%) using 3% alkali concentration; the lowest yield (17.0±1.7%) was obtained with 1% alkali concentration. Agar gel strengths ranged from 462.0±7 to 627.3±11 g·cm−2. We have developed a process for quickly producing an agar gel through thawing and drying using microwave radiation. This study shows the possibility of producing a high-value agar using alkali soaking extraction methods for nonedible G. verrucosa.
Keywords: Gracilaria verrucosa ; Agar; Alkali Soaking; Seaweed-alkali Solution Ratio; Microwave Drying

Preparation of mesh-reinforced cellulose acetate forward osmosis membrane with very low surface roughness by Seyyed Mostafa Mirkhalili; Seyyed Abbas Mousavi; Ahmad Ramazani Saadat Abadi; Masoud Sadeghi (3170-3177).
Mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting compositions such as CA percent and 1, 4-dioxane/acetone ratio and also preparation conditions such as evaporation time, coagulation bath and annealing temperatures were tested for membranes’ performance. The results were compared with commercially CTA membranes. The best membrane (17.9% polymer and 1, 4-dioxane/acetone ratio of 1.89) showed water flux of 9.3 L/m2h (LMH) and RSF of 0.536 mol NaCl/m2h. Moreover, the membrane structure was reinforced by a polyester mesh, which created micro pores in the back of the membrane. This caused higher water flux and RSF compared to membranes without mesh. FO membrane prepared under best conditions, had a smoother surface than commercial ones. This feature enhances the fouling properties of the membrane, which can be appropriate for wastewater treatment applications.
Keywords: Forward Osmosis; Cellulosic Membrane; Internal Concentration Polarization; Mesh-reinforced Membrane

Effect of support layer on gas permeation properties of composite polymeric membranes by Hamid Reza Afshoun; Mahdi Pourafshari Chenar; Ahmad Fauzi Ismail; Takeshi Matsuura (3178-3184).
PES/Pebax and PEI/Pebax composite membranes were prepared by coating the porous PES and PEI substrate membranes with Pebax-1657. The morphology and performance of the prepared membranes were investigated by SEM and CO2 and CH4 permeation tests. The CO2 permeances of 28 and 52 GPU were achieved for PES/Pebax and PEI/Pebax composite membranes, respectively, with CO2/CH4 selectivities almost equal to that of Pebax (26). The experimental data were further subjected to a theoretical analysis using the resistance model. It was found that the porosity and the thickness of the dense section of PES substrate were an order of magnitude higher than those of PEI substitute. The porosity/thickness ratio of PEI substrate was, however, higher than PES, explaining the higher permeance of PEI/Pebax composite membrane. Substrates with porosities much higher than the Henis-Tripodi gas separation membrane were used in this work, aiming to achieve the selectivity of Pebax, rather than those of the substrate membrane materials.
Keywords: PES/Pebax; PEI/Pebax; Gas Permeation; Permeability; Substrate Effect

Preparation and characterization of a porous silicate material from silica fume by Yinmin Zhang; Haiping Qi; Yaqiong Li; Yongfeng Zhang; Junmin Sun (3185-3194).
A porous silicate material derived from silica fume was successfully prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, Thermogravimetry and Differential thermal gravity (TG-DTG), N2 adsorption and desorption isotherms, and scanning electron microscopy (SEM). Raw silica fume was analyzed by XRD, FT-IR and SEM. The analysis results of silica fume indicated that SiO2 in silica fume is mainly determined as amorphous state, and that the particles of raw silica fume exhibited characteristic spherical structure with a diameter of from 50 nm to 200 nm. The preparation of the porous silicate material involved two steps. The first step was the extraction of the SiO32− leachate from raw silica fume. The maximum value of SiO32− extraction yield was obtained under the following conditions: reaction temperature of 120 °C, reaction time of 120 min, NaOH concentration of 15%, and alkali to SiO2 molar ratio of 2. The second step was the preparation of the porous silicate material though the reaction of SiO32− leachate and Ca(OH)2 suspension liquid. The optimum preparation conditions were as follows: preparation temperature of 90 °C, preparation time of 1.5 h, Si/Ca molar ratio of 1 : 1, and stirring rate of 100 r/min. The BET surface area and pore size of the porous silicate material were 220.7 m2·g−1 and 8.55 cm3/g, respectively. The porous silicate material presented an amorphous and unordered structure. The spectroscopic results indicated that the porous silicate material was mainly composed of Si, Ca, O, C, and Na, in the form of Ca2+, SiO32−, CO32− and Na+ ions, respectively, which agreed with the XRD, TG-DSC, and FT-IR data. The N2 adsorption-desorption isotherm mode indicates that the porous silicate material belonged to a typical mesoporous material. The porous silicate material presented efficiency for the removal of formaldehyde: it showed a formaldehyde adsorption capacity of 8.01 mg/g for 140 min at 25 °C.
Keywords: Silica Fume; Porous Silicate Material; Preparation; Mesoporous Material

Silicon/carbon composite electrodes are in the spotlight as an anode with a high capacity and a long cycle life. For this purpose, it is important to make a uniformly dispersed composite material. We fabricated spherical composite particles of reduced graphene oxide (rGO) and silicon nanoparticle (Si NP) using a spray drying method. The composite microparticle fabricated by drying the suspended droplets forms a well-agglomerated rGO/Si NP composite and forms a pore structure by crumpled rGO. The rGO/Si NP microparticles were applied as the anode of the lithium-ion battery. We achieved a reversible capacity of 1,246 mAh/g at 1A/g after 200 charge/discharge cycles and a capacity retention of 83%. Considering that the Si NP microparticle without rGO showed a capacity of 365 mAh/g and a retention of 12%, the rGO matrix improves the electrical conductivity and effectively alleviates stress during charge and discharge cycles.
Keywords: Silicon Nanoparticles; Reduced Graphene Oxides; Lithium Ion Batteries

Plasmon-enhanced ZnO nanorod/Au NPs/Cu2O structure solar cells: Effects and limitations by Il-Han Yoo; Shankara Sharanappa Kalanur; Kiryung Eom; Byungmin Ahn; In Sun Cho; Hak Ki Yu; Hyeongtag Jeon; Hyungtak Seo (3200-3207).
Cu-based compounds can be a good candidate for a low cost solar cell material. In particular, Cu x O (x : 1–2) has a good visible light absorbing bandgap at 1–2 eV. As for using nanostructures in solar cell applications, metal nanoparticle-induced localized plasmon resonance is a promising way to increase light absorbance, which can help improve the efficiency of solar cells. We fabricated ZnO nanorod/Au nanoparticles/Cu2O nanostructures to study their solar cell performance. ZnO nanorods and Cu2O layer were synthesized by the electrodeposition method. Size-controlled Au nanoparticles were deposited using E-beam evaporator for localized surface plasmon resonance (LSPR) effect. By inserting Au plasmon nanoparticles and annealing Au NPs in solar cells, we could tune the maximum incident photon-to-current efficiency wavelength. However, the potential well formed by Au NP at the ZnO/Cu2O junction leads to charge-trapping, based on the constructed electronic band analysis. LSPR-induced hot carrier generation is proposed to promote carrier transport further in the presence of Au NPs.
Keywords: Au Plasmon Nanoparticle; LSPR; ZnO/Cu2O Solar Cells; Oxide Solar Cells; Electronic Band Analysis

Feasibility study on the differentiation between engineered and natural nanoparticles based on the elemental ratios by Woocheol Kim; Changju Yeom; Hyejin Lee; Hwakyung Sung; Eunhye Jo; Ig-chun Eom; Younghun Kim (3208-3213).
To understand the fate and exposure of engineered nanoparticles (ENPs) to environmental media, it is important to identify ENPs in the natural occurring nanoparticles (NNPs). Although nanomaterials have unique physical properties such as uniform particle size, hierarchical nanostructure, well-defined crystalline structure, and high surface area, compared to bulk materials, these properties are not suitable references to differentiate between ENPs and NNPs. Therefore, the identification and quantification of ENPs pose a big challenge to analysis. Herein, we did a feasibility study to distinguish between ENPs and NNPs based on the elemental ratio of target elements (Ti and Zn) to background elements (Fe and Al). Morphologies, particle size, and elemental analysis for 12 NNPs, 4 ENPs, and 3 NPs contained in consumer products were conducted. NPs were extracted from raw materials via density gradient ultracentrifugation and alkaline digestion. In a logarithm plot for the elemental ratio of {Ti+Zn} to {Ti/Zn}/{Fe+Al} and ternary plot of {Ti+Zn}, Fe, and Al ions for all samples, ENPs have a distinct contrast with NNPs. Therefore, it is expected that the suggested analysis for elemental ratio could be a preliminary screening tool to differentiate between ENPs and NNPs.
Keywords: Engineered Nanoparticles; Natural Nanoparticles; Nano-consumer Products; Density Gradient Ultracentrifugation; Alkaline Digestion

Expanding depletion region via doping: Zn-doped Cu2O buffer layer in Cu2O photocathodes for photoelectrochemical water splitting by Kangha Lee; Cheol-Ho Lee; Jun Young Cheong; Seokwon Lee; Il-Doo Kim; Han-Ik Joh; Doh Chang Lee (3214-3219).
We report photoelectrochemical hydrogen evolution reaction using a Cu2O-based photocathode with a layer doped with Zn ions. The doping results in the shift of the onset flat-band potential of the photocathode, likely a consequence of maximized band-bending in the Cu2O/Zn : Cu2O heterojunction. Systematic electrochemical analysis reveals that expansion of depletion region is responsible for the enhanced photoelectrochemical performance, e.g., the increase of photocurrent and reduced internal resistance.
Keywords: Cu2O; Zn-doped Cu2O; Photocathode; Water Splitting; Photoelectrochemistry

Various thin films for photoelectrochemical (PEC) water splitting were prepared and their PEC performance was tested. The precursor solutions for WO3 and BiVO4 photocatalysts were synthesized by solution processes, and the graphene oxide (GO) was prepared by Tour’s method and was calcined and converted to reduced graphene oxide (rGO). The composite photocatalyst thin films of WO3, BiVO4, WO3/BiVO4 and WO3/BiVO4-rGO were prepared on fluorine doped tin oxide glass by spin coating and calcination processes and the PEC performances were analyzed for those photocatalyst layers. The controlled WO3/BiVO4 heterojunction layer showed better PEC performance than the WO3 or BiVO4 single layer by the combined effects of photocatalysts. The WO3/BiVO4-rGO film with the optimum concentration of rGO showed a noticeable increase in photocurrent density because of the increased electrical conductivity by rGO and reduced recombination rate in BiVO4 layer.
Keywords: Production of Hydrogen; PEC Water Splitting; Heterojunction Photocatalyst Layers; Reduced Graphene Oxide (rGO); WO3/BiVO4-rGO Thin Film