• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.475-476
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• 2012

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2567-2573
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• 2012

We successfully synthesized $Fe_3O_4@SiO_2$ nanoparticles with ultrathin silica layer of $1.0{\pm}0.5$ nm that polyethyleneimine (PEI) with low molecular weight of 2.0-4.0 kDa was covalently conjugated with the resulting $Fe_3O_4@SiO_2$ nanoparticles by silane coupling reaction. The PEI-$Fe_3O_4@SiO_2$ nanoparticles were further used as gene delivery vector for a human fibroblast cell (IMR-90) line. Gene transfection efficiency of the PEI-$Fe_3O_4@SiO_2$ complexes did not increase remarkably after magnetofection; however, the addition of Lipofectamine 2000 significantly increased the transfection efficiency of the PEI-$Fe_3O_4@SiO_2$ complexes. We believe that the present approach could be utilized for magnetofection as alternative to $Fe_3O_4$ nanoparticles conjugated with the PEI of high molecular weight thanks to its relatively low cytotoxicity and high transfection efficiency.

• Journal of Powder Materials
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• v.18 no.4
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• pp.347-358
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• 2011

Two different schemes were adopted to fabricate ordered macroporous structures with face centered cubic lattice of air spheres. Monodisperse polymeric latex suspension, which was synthesized by emulsifier-free emulsion polymerization, was mixed with metal oxide ceramic nanoparticles, followed by evaporation-induced self-assembly of the mixed hetero-colloidal particles. After calcination, inverse opal was generated during burning out the organic nanospheres. Inverse opals made of silica or iron oxide were fabricated according to this procedure. Other approach, which utilizes ceramic precursors instead of nanoparticles was adopted successfully to prepare ordered macroporous structure of titania with skeleton structures as well as lithium niobate inverted structures. Similarly, two different schemes were utilized to obtain disordered macroporous structures with random arrays of macropores. Disordered macroporous structure made of indium tin oxide (ITO) was obtained by fabricating colloidal glass of polystyrene microspheres with low monodispersity and subsequent infiltration of the ITO nanoparticles followed by heat treatment at high temperature for burning out the organic microspheres. Similar random structure of titania was also fabricated by mixing polystyrene building block particles with titania nanoparticles having large particle size followed by the calcinations of the samples.

• Computers and Concrete
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• v.21 no.4
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• pp.431-440
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• 2018

Fluid velocity analysis on the instability of pipes reinforced by silica nanoparticles ($SiO_2$) is presented in this paper. Mori-Tanaka model is used for obtaining the effective materials properties of the nanocomposite structure considering agglomeration effects. The well known Navier-Stokes equation is used for obtaining the applied force of fluid to pipe. Based on the Reddy higher-order shear deformation theory, the motion equations are derived based on energy method and Hamilton's principal. The frequency and critical fluid velocity of structure are calculated using differential quadrature method (DQM) so that the effects of different parameters such as volume fractions of SiO2 nanoparticles, SiO2 nanoparticles agglomeration, boundary conditions and geometrical parameters of pipes are considered on the nonlinear vibration and instability of the pipe. Results indicate that increasing the volume fractions of SiO2 nanoparticles, the frequency and critical fluid velocity of the structure are increased. Furthermore, considering SiO2 nanoparticles agglomeration, decreases the frequency and critical fluid velocity of the pipe.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.1-1
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• 2011

We developed a new generalized synthetic procedure, called as "heat-up process," to produce uniform-sized nanocrystals of many transition metals and oxides without a size selection process. We were able to synthesize uniform magnetite nanocrystals as much as 1 kilogram-scale from the thermolysis of Fe-oleate complex. Clever combination of different nanoscale materials will lead to the development of multifunctional nano-biomedical platforms for simultaneous targeted delivery, fast diagnosis, and efficient therapy. In this presentation, I would like to present some of our group's recent results on the designed fabrication of multifunctional nanostructured materials based on uniform-sized magnetite nanoparticles and their medical applications. Uniform ultrasmall iron oxide nanoparticles of <3 nm were synthesized by thermal decomposition of iron-oleate complex in the presence of oleyl alcohol. These ultrasmall iron oxide nanoparticles exhibited good T1 contrast effect. In in vivo T1 weighted blood pool magnetic resonance imaging (MRI), iron oxide nanoparticles showed longer circulation time than commercial gadolinium complex, enabling high resolution imaging. We used 80 nm-sized ferrimagnetic iron oxide nanocrystals for T2 MRI contrast agent for tracking transplanted pancreatic islet cells and single-cell MR imaging. We reported on the fabrication of monodisperse magnetite nanoparticles immobilized with uniform pore-sized mesoporous silica spheres for simultaneous MRI, fluorescence imaging, and drug delivery. We synthesized hollow magnetite nanocapsules and used them for both the MRI contrast agent and magnetic guided drug delivery vehicle.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.3957-3962
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• 2012

Iron-oxide nanoparticles (IONs) with biocompatible coatings are the only nanostructural materials which have been approved by the FDA for clinical use. Common biocompatible coatings such as hydrocarbons, polymers, and silica have profound influences on critical characteristics of IONs. Recently, amino acids were introduced as a novel biocompatible coating. In the present study, the effects of amino acids on IONs synthesis and characteristics have been evaluated. Magnetite nanoparticles with L-arginine and L-lysine coatings were synthesised by a coprecipitation reaction in aqueous solvent and their characteristics were compared with naked magnetite nanoparticles. The results showed that amino acids can be a perfect coating for IONs and would increase particle stability without any significant effects on the critical properties of nanoparticles such as particle size and magnetization saturation value.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3668-3674
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• 2010

Mesoporous SBA-15 was synthesized using tetraethylorthosilicate (TEOS) as the silica source and Pluronic (P123) as the structure-directing agent. The defective Si-OH groups present in SBA-15 were successively grafted with 3-chloropropyltrimethoxysilane (CPTMS) followed by tris-(2-aminoethyl) amine (TAEA) and/or tetraethylenepentamine (TEPA) for effective immobilization of silver nanoparticles. Grafting of TAEA and/or TEPA amine and immobilization of silver nanoparticles inside the channels of SBA-15 was verified by XRD, TEM, IR and BET techniques. The silver nanoparticles immobilized on TAEA and /or TEPA grafted SBA-15 was subjected for electrocatalytic reduction of hydrogen peroxide ($H_2O_2$). The TEPA stabilized silver nanoparticles show higher efficiency for reduction of $H_2O_2$ than that of TAEA, due to higher number of secondary amine groups present in TEPA. The amperometric analysis indicated that both the Ag/SBA-15/TAEA and Ag/SBA-15/TEPA modified electrodes required lower over-potential and hence possess high sensitivity towards the detection of $H_2O_2$. The reduction peak currents were linearly related to hydrogen peroxide concentration in the range between $3{\times}10^{-4}\;M$ and $2.5{\times}10^{-3}\;M$ with correlation coefficient of 0.997 and detection limit was $3{\times}10^{-4}\;M$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.6-7
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• 2008

Composite nanoparticles of silica-polyaniline were synthesized and tested as an electrochromic material. For the optical application, the size of the nanoparticle was intended to be less than 100 nm in diameter. The synthesis was done by using a microemulsion synthesis method where the silica-polyaniline composite nanoparticle was obtained by dispersing two acidic aqueous phases containing aniline and polymerization agent, respectively. Microstructure analysis such as TEM and BET surface area measurement showed the possibility that polyaniline is incorporated in porous silica structure. The composite structure of the particle was proved to enhance chemical stability of the prepared electrochromic film.

• Advances in nano research
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• v.1 no.3
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• pp.159-169
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• 2013

A preparation method for gadolinium compound (GdC) nanoparticles coated with silica ($GdC/SiO_2$) is proposed. GdC nanoparticles were prepared with a homogeneous precipitation method at $80^{\circ}C$ using $1.0{\times}10^{-3}$ M $Gd(NO_3)_3$, 0.5 M urea and $0-3.0{\times}10^{-4}$ M ethylenediarinnetetraacetic acid disodium salt dihydrate (ETDA) in water. As a result of preparation at various EDTA concentrations, GdC nanoparticles with a size as small as $40.5{\pm}6.2$ nm, which were colloidally stable, were prepared at an EDTA concentration of $2.0{\times}10^{-4}$ M. Silica-coating of the GdC nanoparticles was performed by a St$\ddot{o}$ber method at $35^{\circ}C$ using $1.0-10.0{\times}10^{-3}$ M tetraethylorthosilicate (TEOS), 11 M $H_2O$ and $1.5{\times}10^{-3}$ M NaOH in ethanol in the presence of $1.0{\times}10^{-3}$ M GdC nanoparticles. Performance of preparation at various TEOS concentrations resulted in production of $GdC/SiO_2$ particles with an average size of $106.1{\pm}11.2$ nm at a TEOS concentration of $5.0{\times}10^{-3}$ M. The gadolinium (Gd) concentration of $1.0{\times}10^{-3}$ M in the as-prepared $GdC/SiO_2$ particle colloid solution was increased up to a Gd concentration of 0.2 M by concentrating with centrifugation. The core-shell structure of $GdC/SiO_2$ particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated $GdC/SiO_2$ colloid solution showed images of X-ray and magnetic resonance with contrast as high as commercial Gd complex contrast agents.

• Advances in nano research
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• v.10 no.3
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• pp.295-312
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• 2021

A new ionic liquid functionalized magnetic silica nanoparticle was synthesized and characterized and tested as an adsorbent. The adsorbent was used for magnetic solid phase extraction on ICP-MS method. Simultaneous determination of precious metal Au has been addressed. The method is simple and fast and has been applied to standard water and surface water analysis. A new method for separation/analysis of trace precious metal Au by Magnetron Solid Phase Extraction (MSPE) combined with ICP-MS. The element to be tested is rapidly adsorbed on CoFe2O4@SiO2@[BMIM]PF6 composite nano-adsorbent and eluted with thiourea. The method has a preconcentration factor of 9.5-fold. This method has been successfully applied to the determination of gold in actual water samples. Hydrophobic Ionic Liquids (ILs) 1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6) coated CoFe2O4@SiO2 nanoparticles with core-shell structure to prepare magnetic solid phase extraction agent (CoFe2O4@SiO2@ILs) and establish a new method of MSPE coupled with inductively coupled plasma mass spectrometry for separation/analysis of trace gold. The results showed that trace gold was adsorbed rapidly by CoFe2O4@SiO2@[BMIM]PF6 and eluanted by thiourea. Under the optimal conditions, preconcentration factor of the proposed method was 9.5-fold. The linear range, detection limit, correlation coefficient (R) and relative standard deviation (RSD) were found to be 0.01~1000.00 ng·mL-1, 0.001 ng·mL-1, 0.9990 and 3.4% (n = 11, c = 4.5 ng·mL-1). The CoFe2O4@SiO2 nanoparticles could be used repeatedly for 8 times. This proposed method has been successfully applied to the determination of trace gold in water samples.