Korean Journal of Chemical Engineering (v.36, #1)
Recently developed methods to enhance stability of heterogeneous catalysts for conversion of biomass-derived feedstocks by Soosan Kim; Yiu Fai Tsang; Eilhann E. Kwon; Kun-Yi Andrew Lin; Jechan Lee (1-11).
Many processes for the conversion of biomass and its derivatives into value-added products (e.g., fuels and chemicals) use heterogeneous catalysts. However, the catalysts often suffer from deactivation under harsh reaction conditions, such as liquid phase at high temperatures and pressures. The catalyst deactivation is a big obstacle to developing industrially relevant biomass conversion processes, including leaching, sintering, and poisoning of metals and collapse of catalyst support. Different approaches have been applied to limit the reversible and irreversible deactivation, highly associated with the kind of catalyst, reactants, reaction conditions, etc. This review presents recent advances in strategies to stabilize heterogeneous catalysts against deactivation for biomass conversion reactions.
Keywords: Heterogeneous Catalyst; Catalyst Stability; Catalyst Deactivation; Biomass Conversion; Catalyst Design; Biorefinery
Design of a renewable energy system with battery and power-to-methanol unit by Riezqa Andika; Young Kim; Choa Mun Yun; Seok Ho Yoon; Moonyong Lee (12-20).
An energy storage system consisting of a battery and a power-to-methanol (PtM) unit was investigated to develop an energy storage system for renewable energy systems. A nonlinear programming model was established to optimize the energy storage system. The optimal installation capacities of the battery and power-to-methanol units were determined to minimize the cost of the energy system. The cost from a renewable energy system was assessed for four configurations, with or without energy storage units, of the battery and the power-to-methanol unit. The proposed model was applied to the modified electricity supply and demand based on published data. The results show that value-adding units, such as PtM, need be included to build a stable renewable energy system. This work will significantly contribute to the advancement of electricity supply and demand management and to the establishment of a nationwide policy for renewable energy storage.
Keywords: Battery Energy Storage; Electricity Supply and Demand; Nonlinear Programming; Power to Methanol; Renewable Energy
Asymmetrical breakup and size distribution of droplets in a branching microfluidic T-junction by Pengcheng Ma; Taotao Fu; Chunying Zhu; Youguang Ma (21-29).
The breakup and distribution of droplets at a branching T-junction were investigated experimentally by a high-speed camera. The effects of two-phase flow rates, two-phase Reynolds number and capillary number of the dispersed phase on droplet volume distribution were studied. The results indicated that the volume distribution ratio λ decreases first and then increases with the increase of two-phase flow ratio Qd/Qc. Similarly, as the Reynolds number Rec of the continuous phase increases, the volume distribution ratio λ also decreases at first and then increases. The increase of Reynolds number Red of the dispersed phase would lead to a reduction in the volume distribution ratio λ. Moreover, the increase of the capillary number Cad of dispersed phase could result in an increase in the volume distribution ratio λ. Correlations for predicting the volume distribution ratio were proposed, and the calculated results show good agreement with experimental data.
Keywords: Microchannel; Droplet; Breakup; Distribution; Interface
Synthesis of exo-tricyclopentadiene from endo-dicyclopentadiene over mesoporous aluminosilicate catalysts prepared from Y zeolite by Yongin You; Youri Park; Jeongsik Han; Tae Soo Kwon; Donguk Seo; Minjun Seong; Jong-Ki Jeon (30-36).
A highly ordered mesoporous aluminosilicate (MMZ Y ) was prepared by a top-down and bottom-up method using HY zeolite as a raw material. A pellet-type catalyst was prepared through extrusion using a twin-screw extruder. The effects of the Si/Al2 ratio of the HY zeolite used in the MMZ Y catalyst preparation on the physicochemical and acid properties of MMZ Y catalysts were investigated. The oligomerization of endo-dicyclopentadiene (endo-DCPD) was performed in a spinning basket reactor, and the deactivated catalyst was repeatedly regenerated to verify the possibility of reusing the catalyst. It was confirmed that ordered hexagonal arrays of mesopores were well developed in the MMZ Y (27) and MMZ Y (48) catalysts, whereas the mesoporous structure of the MMZ Y (6) and MMZ Y (12) materials with relatively large amounts of Al collapsed. As the Si/Al2 molar ratio of the MMZ Y catalyst was increased, the number of weak acid sites increased prominently and the acid strength decreased. MMZ Y (27) and MMZ Y (48) are more effective for the oligomerization of endo-DCPD to exo-tricyclopentadiene (exo-TCPD) compared to a microporous HY catalyst. This is attributed to the abundant acid sites and to the well-developed mesopore structure. Calcination in air was found to be effective for the regeneration of the deactivated MMZ Y pellet catalyst for synthesis of exo- TCPD from endo-DCPD.
Keywords: MMZ; Pellet-type Catalyst; Endo-dicyclopentadiene; Exo-tricyclopentadiene; Regeneration
Facile and simple synthesis of triethylenetetramine-modified mesoporous silica adsorbent for removal of Cd(II) by Atena Abedi; Hamidreza Ghafouri Taleghani; Mohsen Ghorbani; Hamed Salimi Kenari (37-47).
Monodispersed porous silica microspheres (SM) were synthesized and further functionalized with amine moieties using triethylenetetramine (TETA) in order to obtain a novel adsorbent for Cd(II) elimination from aqueous media. The morphology, texture and structure of samples were characterized with the aid of Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), energy dispersive spectroscopy (EDS), and N2 adsorption-desorption. The adsorption efficiency was investigated based on the effect of operational parameters including pH of the solution, the dose of adsorbent, adsorption time, initial concentration of Cd(II) ions and temperature. The equilibrium, kinetics and thermodynamics of Cd(II) adsorption were also studied. The maximum adsorption capacity of amine functionalized silica microspheres (AMSM) for Cd(II) was 35.6 mg g-1. Cd(II) adsorption onto AMSM had highest consistency with Sips and Langmuir isotherms, while adsorption kinetics was best fitted with pseudo-second order model. Thermodynamics of adsorption revealed that Cd(II) adsorption on AMSM was spontaneous, feasible and exothermic with physical interactions and pore diffusion being the dominant mechanisms in the adsorption process. Results confirmed that AMSM adsorbent has the potential to be a suitable candidate for Cd(II) removal from aqueous solutions.
Keywords: Mesoporous; Silica Microspheres; Amine Functionalized; Adsorption; Cd(II) Removal
Biosorption of Cu(II) from aqueous solution onto immobilized Ficus religiosa branch powder in a fixed bed column: Breakthrough curves and mathematical modeling by Madiha Tariq; Umar Farooq; Makshoof Athar; Muhammad Salman; Muqaddas Tariq (48-55).
We investigated the adsorption potential of powdered branches from Ficus religiosa, an abundantly available plant, for the removal of Cu(II) from aqueous solution via column studies. Biomass was used as silica immobilized form and characterized using available techniques, including Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Breakthrough curve approach was used to explain removal capacity of biomass in a continuous flow mode, using different operating parameters like bed height (5-30 cm), inlet metal concentration (100-300mg/L) and pH (3-5) of the solution, at a fixed flow rate of 2mL/min. Biosorption of Cu(II) favored with increased service time (breakthrough and exhaust time) of the column with an increase in pH of inlet solution. Maximum biosorption capacity (17.5mg/g) for Cu(II) was achieved at 5 cm bed height, pH 5 and 300 mg/L influent Cu(II) concentration. Findings suggested that Ficus religiosa branch powder takes less service time and thus triggers fast removal of metal ions. Bed depth service time (BDST), Thomas and Yoon-Nelson models were effectively applied to the breakthrough data. The study indicated that the immobilized powdered branches could be used for the effective removal of Cu(II) ions in a continuous flow mode.
Keywords: Ficus religiosa ; Copper; Breakthrough Curve; Biosorption; Fixed Bed; BDST Model
Superior dye degradation using SnO2-ZnO hybrid heterostructure catalysts by Shama Sehar; Iffat Naz; Irum Perveen; Safia Ahmed (56-62).
We investigated the efficiency of oxide based hierarchical heterostructure as adsorbent for the treatment of organic dyes, Methyl orange (MO) and Methylene Blue (MB), containing solution. Nanocrystals such as ZnO nanorods (at various temperatures of 30, 60 and 75 °C) and SnO2 nanoparticles were synthesized by electrodeposition method and hydrothermal approaches, respectively. SnO2-ZnO heterostructures were formed by spin coating SnO2 nanoparticles on ZnO nanorods matrix to form a heterostructured film. The surface morphologies and structural characterization of as-prepared heterostructures were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. While, absorption spectra of all samples were examined by UV-vis diffuse reflectance spectroscopy. The photocatalytic activities of as-prepared samples for organic dyes degradation were tested under UV light as model reaction. The SnO2-ZnO heterostructured photocatalyst showed superior activities than individual ZnO and SnO2 nanocrystals. This heightened behavior was attributed to its better charge separation capability and the slow charge recombination originating due to difference in energy values of conduction band edges of SnO2 and ZnO. The SnO2-ZnO heterostructure demonstrated better stability and recyclability up to five times, which is highly desirable for potential industrial applications including dye degradation and wastewater treatment systems.
Keywords: Organic Dye Degradation; Hydrothermal Approach; Metal Oxide Heterostructures; Photocatalysis; Electrochemical Deposition
Enhanced lipid content in Chlorella sp. FC2 IITG via high energy irradiation mutagenesis by Muthusivaramapandian Muthuraj; Baskar Selvaraj; Basavaraj Palabhanvi; Vikram Kumar; Debasish Das (63-70).
High energy ultra-violet radiation was used to induce mutations in the wild type strain Chlorella sp. FC2 IITG and the mutants obtained were screened for enhanced lipid content targeted towards biodiesel production. Screening of mutants under nitrogen starved photoautotrophic condition showed five mutant strains with higher lipid content as compared to the wild type strain. Maximum neutral lipid content of 22.26% (w/w, DCW) was found for FC2-25UV mutant strain, which was 48.4% higher than that of wild type culture. Further characterization under photoautotrophic two stage high cell density cultivation of lipid rich FC2-25UV resulted in total lipid content of 68% (w/w, DCW), which was 21.43% higher than the wild type strain with a marginal improvement of 11% in the total lipid productivity. Comparison of enzyme activity assays under nitrogen starved conditions in both the strains revealed an 18.2% and 31.25% increase in acetyl CoA carboxylase and di-acyl-glycerol transferase activity of mutant. The FAME composition analysis showed 41.5% and 24% increase in the fractions of C18:2 and C18:1 in the mutant strain when compared to the wild type strain with no significant difference in the other FAME fractions. Thus, the mutant strain could be a potential candidate for biodiesel production.
Keywords: Microalgae; Mutation; Ultraviolet Rays; High Cell Density Cultivation; Lipid Content
Continuous production of bioethanol using microalgal sugars extracted from Nannochloropsis gaditana by Ja Hyun Lee; Hee Uk Lee; Ju Hun Lee; Soo Kweon Lee; Hah Young Yoo; Chulhwan Park; Seung Wook Kim (71-76).
We developed a continuous production process of bioethanol from sugars extracted from Nannochloropsis gaditana. To improve algal sugar production, the reaction conditions of acid-thermal hydrolysis were investigated based on five different types of acid and their concentrations (1-4%), and the loading ratio of solid/liquid (S/L). As a result, the maximum hydrolysis efficiency (92.82%) was achieved under 2% hydrochloric acid with 100 g/L biomass loading at 121 oC for 15 min. The hydrolysates obtained from N. gaditana were applied to the main medium of Bretthanomyces custersii H1-603 for bioethanol production. The maximum bioethanol production and yield by the microalgal hydrolysate were found to be 4.84 g/L and 0.37 g/g, respectively. In addition, the cell immobilization of B. custersii was carried out using sodium alginate, and the effect of the volume ratio of cell/sodium alginate on bioethanol productivity was investigated in a batch system. The optimal ratio was determined as 2 (v/v), and the immobilized cell beads were applied in the continuous stirred tank reactor (CSTR). Continuous ethanol production was performed using both free cells and immobilized cells at 1 L CSTR. In both groups, the maximum bioethanol production and yield were achieved at dilution rate of 0.04 h-1 (3.93 g/L and 0.3 g/g by free cell, and 3.68 g/L and 0.28 g/g by immobilized cell, respectively).
Keywords: Bioethanol; CSTR; Fermentation; Hydrolysis; Nannochloropsis gaditana
Use of multiple inter-reboilers to achieve energy savings and improve thermodynamic efficiency of the distillation of N,N-dimethylformamide wastewater by Xiaoxin Gao; Xueming Yin; Song Yang; Deming Yang (77-83).
The purification of N,N-dimethylformamide wastewater involves an energy intensive distillation process. We propose a novel energy-saving process scheme involving multiple inter-reboilers sed. In this scheme, ideal thermodynamic model non-random two liquid (NRTL) model was used to calculate the phase equilibrium using Aspen Plus platform. While the relationship between important process parameters and energy consumption by the distillation process was studied, several parameters such as the most suitable positions for the inter-reboilers and the most reasonable steam extraction rates were obtained. The feasibility was detected under the same separation duties and main technological structure. For 10wt% DMF wastewater, the inter-reboilers were installed on the 37th, 38th and 39th plates, while the corresponding heat transferred values were 3,038 kW, 91 kW and 179kW, respectively. In comparison to the conventional distillation process, an energy consumption of 77.43% and thermodynamic efficiency of 65.69% were obtained. For 20 wt% DMF wastewater, the inter-reboilers were installed on the 21st and 25th plate, while the corresponding values for the heat transferred were 1,632kW, and 1,450kW, respectively. In comparison to the conventional distillation process, the energy consumption can be reduced by 71.31%, while the thermodynamic efficiency can be improved by 47.10%.
Keywords: Inter-reboiler; Energy-saving; Distillation; Thermodynamic Efficiency; N,N-dimethylformamide Wastewater
Sensitivity analysis of key factors in controlling absorption and desorption of oxygen to oxygen carriers by Limin Hou; Qingbo Yu; Kun Wang; Shuo Zhang; Qin Qin; Fan Yang (84-91).
Chemical looping air separation gives an oxygen resource for the oxy-fuel combustion system. To investigate the sensitivity of operation parameters and optimal operation parameters, with the consideration of the reactor temperature, we used the oxygen concentration, and reaction gas flow, an orthogonal experiment and multi-objective comprehensive evaluation method to analyze the results obtained by fixed-bed apparatus with the YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.5Dy0.5BaCo4O7+δ, and Y0.2Ti0.05Dy0.75BaCo4O7+δ oxygen carriers. The results showed that the effects of operating conditions on oxygen absorption/desorption properties varieds in the order: oxygen concentration>gas flow rate>absorption temperature=desorption temperature. Analysis of max-min difference showed that the optimum operating conditions such as absorption temperature, 350 °C, desorption temperature, 430 °C, gas flow rate, 200 ml/min, and oxygen concentration, 21% were confirmed.
Keywords: Orthogonal Test; Multi-objective Comprehensive Evaluation; Oxygen Carrier; Sensitivity; Optimum Analysis
Hierarchical Al2O3/SiO2 fiber membrane with reversible wettability for on-demand oil/water separation by Zhangdi Li; Tianhui Shi; Tao Zhang; Qing Guo; Fengxian Qiu; Xuejie Yue; Dongya Yang (92-100).
This work presents an effective method of fabricating hierarchical Al2O3/SiO2 fiber membrane with reversible wettability for on-demand oil/water separation. In this strategy, the superhydrophilic/underwater superoleophobic surfaces are fabricated by in-situ growing hierarchical Al2O3 nanosheets on the SiO2 fiber surfaces that can be used as water-removing materials for oil/water separation. Then, the superhydrophobic/oleophilic surfaces are obtained by surface chemical modification with sodium laurate, which can be used as oil-removing materials for oil/water separation. Interestingly, the reversible wettability transformation of Al2O3/SiO2 fiber membrane can be controlled by the annealing and modification treatment alternately. The as-prepared Al2O3/SiO2 fiber membrane, combining the advantages and overcoming disadvantages of two modes, achieves reversible wettability transitions and on-demand oil/water separation. In addition, the Al2O3/SiO2 fiber membrane shows a significant chemical stability and super-wettability even after five annealing and surface modification cycles, indicating its excellent durability. The separation efficiency in both oil-removing mode and water-removing mode is over 95% for various oil/water mixtures through multiple recycle separation processes. This work not only provides a simple and cost-effective method to fabricate separation membrane with reversible wettability, but also shows great potential in remediation of large-scale oil spillage or organic solvents discharge at different environmental conditions.
Keywords: Al2O3 Nanosheets Coating; Fiber Membrane; Reversible Wettability; Oil/Water Separation; Recyclability
Adsorption and precipitation of anionic dye Reactive Red 120 from aqueous solution by aminopropyl functionalized magnesium phyllosilicate by Yong-Woon Kim; Jung-Hun Kim; Deok Hyun Moon; Hyun-Jae Shin (101-108).
Dye wastewater causing destruction in ecosystem from a variety of plants an operation needs various factors for environmental cleanup. To improve removal efficiency of dye wastewater, various adsorbents including clay and nonclay-related materials have been tried. The use of soluble aminopropyl functionalized magnesium phyllosilicate (Mg-AMP clay) as an adsorbent for the textile anionic dye Reactive Red 120 (RR 120) was examined thermodynamically and kinetically. The adsorption kinetics followed the pseudo-second-order and Langmuir isotherm equation fitted best models. A maximum amount of adsorption was determined to be 229.9 mg/g, which is one of the highest values studied so far. An Mg-AMP clay dosage of 10 mg/mL obtained from Langmuir model a maximum adsorption capacity of 229.94, 182.26 and 156.54 mg/g at 298.15, 308.15 and 318.15 K, respectively. Moreover the thermodynamic activation parameters such as enthalpy and entropy were determined. We suggest the removal mechanism of RR 120 using Mg-AMP clay by adsorption and precipitation.
Keywords: Anionic Dyes; Magnesium Phyllosilicate; Clay; Adsorption; Precipitation; Reactive Red 120
Modified simulated moving bed chromatography with two pumps for sugar separation by Jae-Ryong Song; Hyukmin Park; Jin-Il Kim; Ngoc Lan Mai; Yoon-Mo Koo (109-114).
A modified SMB system composed of two pumps was developed for the separation of L-ribose and L-arabinose from its binary mixture. In two-pump SMB operation, the flow rates required for separation in every column zones and product ports are identical to those in conventional SMB equipped with four pumps and are controlled by appropriate operation of valves during a cycle of switching time. The purity, yield and enrichment of sugars obtained by two-pump SMB separation were comparable to that of conventional SMB. The two-pump SMB system is therefore considered to be more economically efficient than conventional SMB by reducing the cost for SMB installation and pump operation.
Keywords: Two-pump; SMB; Chromatography; Sugar Separation; Energy Efficient
Enhanced photocatalytic activity of TiO2/graphene by tailoring oxidation degrees of graphene oxide for gaseous mercury removal by Yu Guan; Tao Hu; Jiang Wu; Lili Zhao; Fengguo Tian; Weiguo Pan; Ping He; Xuemei Qi; Fangqin Li; Kai Xu (115-125).
We used a simple method of graphene oxide (GO) preparation with different oxidation levels, and control the properties of the TiO2 nanocrystals by tuning the content and oxidation degree of GO to enhance the photocatalytic performance. During the hydrothermal reaction, reduction of GO, formation of TiO2 and chemical bonds between TiO2 and reduced graphene oxide (RGO) was achieved simultaneously. Characterization results showed that TiO2 properties such as crystalline grain and particle size could be tailored by the amount of functional groups, and that crystallinity was also controlled by GO degrees of oxidation. TiO2/RGO photocatalysts showed great efficiency of mercury oxidation, which reached 83.7% and 43.6% under UV and LED light irradiation, respectively. The effects of crystalline grain size and surface chemical properties on Hg0 removal under LED and UV light irradiation were analyzed. In addition, the properties of the photocatalysts before and after UV illumination were investigated, finding that part of Ti-OH on TiO2 surface transformed to Ti-O-Ti. In a nutshell, this work could provide a new insight into enhancing activity of photocatalysts and understanding the photocatalytic mechanism.
Keywords: TiO2 ; Reduced Graphene Oxide; Photocatalysis; Chemical Bonds; Elemental Mercury
Nickel nanoparticles-doped rhodamine grafted carbon nanofibers as colorimetric probe: Naked eye detection and highly sensitive measurement of aqueous Cr3+ and Pb2+ by Dinesh Kumar; Neetu Talreja (126-135).
Nickel nanoparticle (NiNPs)-doped carbon nanofiber (CNF) grafted with Rhodamine-B (RhB) dye (Ni-CNF-RhB), was prepared and utilized as a colorimetric probe for detection and measurements of chromium (Cr3+) and lead (Pb2+) metal ions in aqueous systems. An intense pink solution was obtained within 30 s on the exposure of the colorless Ni-CNF-RhB probe to the metal ions (Cr3+ and Pb2+) solution. Briefly, the NiNPs-doped carbon beads were synthesized and applied as a substrate to grow CNFs by chemical vapor deposition. The Ni-CNF-RhB colorimetric probe exhibited fast response and selective determination towards Cr3+ and Pb2+ over the 0.1-10 ppm concentration range of their respective solution pH. The developed probe also showed the pH-dependent colorimetric response, thereby, selectivity determination of the metal ions. The detection limits of the colorimetric probe against Cr3+ and Pb2+ are 203 and 132 nM, respectively. The binding ability of the RhB-dye was augmented by CNF and NiNPs, while the carbon beads provided support to CNF to help probe in detection application and its re-usability. The method to prepare the colorimetric probe is simple, novel, selective, and the probe can be efficiently used for the fast detection (naked eye) and measurements of toxic metal ions in aqueous systems.
Keywords: Carbon Nanofibers; Rhodamine Dye; Colorimetric; Sensor; Toxic Metals
Effects of electrode compression on the water droplet removal from proton exchange membrane fuel cells by Gholam Reza Molaeimanesh; Mohammad Hassan Shojaeefard; Mohammad Reza Moqaddari (136-145).
Proton-exchange membrane (PEM) fuel cells are one of the main candidates for propulsion systems of modern electric vehicles. However, appropriate water management is crucial to performance. Cell compression can affect the performance and water management of PEM fuel cells. Although the influence of cell compression on the transport of continuous water flow through the porous electrodes has been investigated, the influence of cell compression on the droplet dynamic behavior through these electrodes is not investigated thoroughly. Employing a pore-scale simulation method such as lattice Boltzmann method (LBM) is an excellent means for such investigation. In this study, LBM was applied to investigate the influence of compression of gas diffusion layer (GDL) on the removal of a water droplet from an electrode of a cell with interdigitated flow field. During removal process the droplet dynamic movement through five different GDLs (one without compression and the other four with four different levels of compression) was depicted and analyzed. The results reveal that the droplet experiences a faster removal process when the GDL is compressed. However, more increasing of compression does not result in a faster removal process, which indicates the existence of an optimum compression level for which the fastest removal process occurs.
Keywords: Compression; Multiphase Flow; Water Droplet; Proton-exchange Membrane (PEM) Fuel Cell; Gas Diffusion Layer (GDL); Lattice Boltzmann Method (LBM)
Study of effective parameters for the polarization characterization of PEMFCs sensitivity analysis and numerical simulation by Sara Barati; Mohsen Mehdipour Ghazi; Behnam Khoshandam (146-156).
A three-dimensional model of a HT-PEMFC was simulated using Comsol Multiphysics software. Sensitivity was analyzed by using the three-level Box-Behnken experimental design. The effect of independent variables on the fuel cell performance including air and hydrogen velocity, temperature and amount of phosphoric acid doping level (PA dop ) on the membrane was investigated. The results showed that the PA dop is the most important variable. The simulation results showed that with the increasing of the PA dop from 2 to 16, the current density (at a voltage of 0.4 V) increased from 0.3 to 0.9A/cm2, which confirms the importance of the PA dop factor on the fuel cell performance.
Keywords: Design Expert; Sensitivity Analysis; Box-Behnken; High Temperature PEM Fuel Cell
Synthesis of high-quality carbon nanotubes by using monodisperse spherical mesoporous silica encapsulating iron oxide nanoparticles by Raji Atchudan; Bong Geun Cha; Nasreena Lone; Jaeyun Kim; Jin Joo (157-165).
Well-graphitized carbon nanotubes (CNTs) were grown by using monodisperse spherical mesoporous silica encapsulating single iron oxide (Fe3O4) nanoparticles (MSEINPs) as catalytic templates by chemical vapor deposition (CVD) and using acetylene as carbon source. The catalytic templates were synthesized by a sol-gel method. The MSEINPs exhibited better activity and selectivity in CNT synthesis than bare Fe3O4 catalysts. The synthesized multiwall carbon nanotubes (MWCNTs) were analyzed by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Raman spectroscopy. The carbon deposits are rich in MWCNTs, as confirmed by FESEM and TGA. The wall thickness of the MWCNTs is controlled primarily by the size of the spherical mesoporous silica layer encapsulating the Fe3O4 NPs, while the inner diameter of the CNTs is determined by the size of the Fe3O4 NPs at the center of the MSEINPs. The average diameter of the MWCNTs increased significantly with increases in the growth temperature and acetylene flow rate. The analytical results show that the CNTs prepared on MSEINPs are well graphitized with a narrow size distribution in thickness, and straight and longer tubes are obtained without major defects as compared to the CNTs grown on bare Fe3O4 NPs.
Keywords: Carbon Nanotubes; Mesoporous Silicas; Iron Oxide; Nanoparticles; CVD
pH-triggered intracellular release of doxorubicin from polyaspartamide-encapsulated mesoporous silica nanoparticles by Cheolwon Lim; Eun-Bum Cho; Dukjoon Kim (166-172).
Mesoporous silica nanoparticles (MSNs) conjugating doxorubicin (DOX) via a pH-sensitive cleavable linkage, hydrazine (HYD) were synthesized. MSN-HYD-DOX were encapsulated with the polyaspartamide (PASPAM) grafted with the hydrophilic o-(2-aminoethyl)-o′-methylpoly(ethylene glycol) (PEG) and the cell permeating ligand, biotin (Biotin). The chemical structure of the synthesized MSN-HYD-DOX and PASPAM-g-PEG/Biotin was confirmed using FT-IR and 1H-NMR spectroscopy. The mean diameter of the MSN-HYD-DOX@PASPAM-g-PEG/Biotin nanoparticle was 142 nm and 121 nm, respectively, examined by dynamic light scattering (DLS) and transmission electron microscope (TEM). The HYD bond was effectively cleaved in acidic condition, and thus DOX was released much faster at pH 5.0 than at pH 7.4. The cell viability in MSN-HYD-DOX@PASPAM-g-PEG/Biotin system was much lower than that of the free DOX drug because of efficient intracellular drug delivery associated with the biotin ligand.
Keywords: Mesoporous Silica Nanoparticle; Polysuccinimide; Hydrazone Bond; Doxorubicin