Corrosion Protection Properties of Co3O4 and CoFe2O4 Nanoparticles for Water-Based Epoxy Coatings on 2024-T3 Aluminum Alloys

Thu Thuy Thai,Anh Truc Trinh,Thi Thanh Tam Pham,Hoan Nguyen Xuan 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.2

In this study, cobalt oxide (Co3O4) and cobalt-doped magnetite (CoFe2O4) nanoparticles were synthesizedby a hydrothermal method. They were then used as corrosion inhibitors for corrosion protection ofAA2024-T3 aluminum alloys. These obtained nanoparticles were characterized by x-ray diffraction, fieldemissionscanning electron microscopy, and Zeta potential measurements. Corrosion inhibition activities ofCo3O4 and CoFe2O4 nanoparticles were determined by performing electrochemical measurements for bareAA2024-T3 aluminum alloys in 0.05 M NaCl + 0.1 M Na2SO4 solution containing Co3O4 or CoFe2O4nanoparticles. Corrosion protection for AA2024-T3 aluminum alloys by a water-based epoxy with or withoutthe synthesized Co3O4 or CoFe2O4 nanoparticles was investigated by electrochemical impedance spectroscopyduring immersion in 0.1 M NaCl solution. The corrosion protection of epoxy coating depositedon the AA2024-T3 surface was improved by incorporating Co3O4 or CoFe2O4 nanoparticles in the coating. The corrosion protection performance of the epoxy coating containing CoFe2O4 was higher than that of theepoxy coating containing Co3O4.

Preparation and Properties of Silicone Hydrogel Material Containing Silane Group with Cobalt Oxide Nanoparticles through Thermal Polymerization

Lee, Min-Jae,Kong, Ki-Oh,Sung, A-Young Materials Research Society of Korea 2020 한국재료학회지 Vol.30 No.6

This research is conducted to analyze the compatibility of used monomers and produce the high functional hydrogel ophthalmic polymer containing silane and nanoparticles. VTMS (vinyltrimethoxysilane), TAVS [Triacetoxy(vinyl)silane] and cobalt oxide nanoparticles are used as additives for the basic combination of SilM (silicone monomer), MMA (methyl methacrylate) and MA (methyl acrylate). Also, the materials are copolymerized with EGDMA (ethylene glycol dimethacrylate) as cross-linking agent, AIBN (thermal polymerization initiator) as the initiator. It is judged that the lenses of all combinations are optically excellent and thus have good compatibility. Measurement of the optical and physical characteristics of the manufactured hydrophilic ophthalmic polymer are different in each case. Especially for TAVS, the addition of cobalt oxide nanoparticles increases the oxygen permeability. These materials are considered to create synergy, so they can be used in functional hydrogel ophthalmic lenses.

Immobilized Co/Rh Heterobimetallic Nanoparticle-Catalyzed Pauson–Khand-Type Reaction

Park, Kang ,Hyun,Chung, Young ,Keun WILEY-VCH Verlag 2005 Advanced synthesis & catalysis Vol.347 No.6

<P>Co/Rh heterobimetallic nanoparticles were prepared from cobalt-rhodium carbonyl clusters [Co<SUB>2</SUB>Rh<SUB>2</SUB>(CO)<SUB>12</SUB> and Co<SUB>3</SUB>Rh(CO)<SUB>12</SUB>] and immobilized on charcoal. HR-TEM revealed that the size of the heterobimetallic nanoparticles was ca. 2 nm and ICP-AES analysis showed a 2 : 2 and a 3 : 1 cobalt-rhodium stoichiometry (Co<SUB>2</SUB>Rh<SUB>2</SUB> and Co<SUB>3</SUB>Rh<SUB>1</SUB>) in the heterobimetallic nanoparticles. The Co/Rh heterobimetallic nanoparticles immobilized on charcoal were used as a catalyst in the Pauson–Khand-type reaction under 1 atm of CO. The catalytic reactivity was highly dependent upon the ratio of Co : Rh with the highest reactivity being observed when the ratio was 2 : 2 (Co<SUB>2</SUB>Rh<SUB>2</SUB>). The Co<SUB>2</SUB>Rh<SUB>2</SUB> immobilized catalyst is quite an effective catalyst for intra- and intermolecular Pauson–Khand-type reactions. When the immobilized Co<SUB>2</SUB>Rh<SUB>2</SUB> catalyst was used as a catalyst in the Pauson–Khand-type reaction in the presence of an aldehyde instead of carbon monoxide, the catalytic system was highly efficient. When the reaction was carried out in the presence of chiral diphosphines, ee values up to 87% were observed. The catalytic system can be reused at least five times in the presence of chiral diphosphines without loss of catalytic activity and enantioselectivity. The addition of Hg(0), a known heterogeneous catalyst poison, completely inhibits further catalysis. Thus, an environmentally friendly and sustainable process was developed.</P>

Removal of Cr(VI) from aqueous media using magnetic Co-reduced graphene oxide

Nduduzo Nkanyiso Malinga,Alan Lawrence Leigh Jarvis 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.11

The adsorption of Cr(VI) from an aqueous medium using magnetically functionalized cobalt nanoparticles- reduced graphene oxide (Co-rGO) was studied. Co-rGO was synthesized using the co-precipitation method. Graphene oxide and cobalt acetylacetonate were reduced together in water using sodium borohydride as a reducing agent. CorGO was used as the adsorbent material for the removal of dichromate ions in water. The prepared Co-rGO was characterized using powder X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Brunauer-Emmett- Teller (BET) surface area analysis. Selected area electron diffraction was used to determine that the cobalt nanoparticles were on the surface of the reduced graphene oxide. The effect of the mass of the adsorbent material (Co-rGO), the concentration and pH of the Cr(VI) containing solution and the time of contact between the adsorbent and the Cr(VI) on the adsorption efficiency were investigated. It was found that the optimum adsorbent mass for the efficient removal of Cr(VI) from a fixed concentration of Cr(VI) of 100mg L1 was 0.015 g, the optimum pH of the solution was 8, and the optimum contact time was 90 minutes. The experimental data obtained were fitted to the Langmuir, Freundlich, and Lui isotherms to obtain the characteristic parameters of each model. The experimental data fitted well to the Freundlich isotherm. The thermodynamic data was used to evaluate the nature of the adsorption. It was determined that the sorption process was physisorption. The kinetics of the adsorption process followed pseudo-second-order kinetic model.

Structural and Magnetic Properties of Aluminium-Substituted Cobalt-Ferrite Nanoparticles Synthesised by the Co-precipitation Route

Budi Purnama,Anisa Khoiriah,Suharyana 한국자기학회 2018 Journal of Magnetics Vol.23 No.1

The crystal structure and magnetic properties of aluminium-substituted cobalt-ferrite nanoparticles synthesised by the co-precipitation are reported in this study. The single phase nanoparticles are obtained. Magnetic property Changes in these properties are clarified mainly by changes in parameters such as the crystalline constant, crystallite size and crystalline density. An increase of saturated magnetisation with annealing temperature is also observed. Results for the change in saturated magnetization at several elevated temperatures indicate that the available non-magnetic aluminium ions support redistribution of cation-trivalent Fe<SUP>3+</SUP> during the annealing process at octahedral sites.

A Synthesis of High Purity Single-Walled Carbon Nanotubes from Small Diameters of Cobalt Nanoparticles by Using Oxygen-Assisted Chemical Vapor Deposition Process

변혜령,Hyunseob Lim,Hyun Jae Song,최희철 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.11

A successful combination of oxygen-assisted chemical vapor deposition (CVD) process and Co catalyst nanoparticles to grow highly pure single walled carbon nanotubes (SWNTs) was demonstrated. Recently, it was reported that addition of small amounts of oxygen during CVD process dramatically increased the purity and yield of carbon nanotubes. However, this strategy could not be applied for discrete Fe nanoparticle catalysts from which appropriate yields of SWNTs could be grown directly on solid substrates, and fabricated into field effect transistors (FETs) quite efficiently. The main reason for this failure is due to the carbothermal reduction which results in SiO2 nanotrench formation. We found that the oxygen-assisted CVD process could be successfully applied for the growth of highly pure SWNTs by switching the catalyst from Fe to Co nanoparticles. The topological morphologies and p-type transistor electrical transport properties of the grown SWNTs were examined by using atomic force microscope (AFM), Raman, and from FET devices fabricated by photolithography.

A Synthesis of High Purity Single-Walled Carbon Nanotubes from Small Diameters of Cobalt Nanoparticles by Using Oxygen-Assisted Chemical Vapor Deposition Process

Byon, Hye-Ryung,Lim, Hyun-Seob,Song, Hyun-Jae,Choi, Hee-Cheul Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.11

A successful combination of “oxygen-assisted chemical vapor deposition (CVD) process” and Co catalyst nanoparticles to grow highly pure single walled carbon nanotubes (SWNTs) was demonstrated. Recently, it was reported that addition of small amounts of oxygen during CVD process dramatically increased the purity and yield of carbon nanotubes. However, this strategy could not be applied for discrete Fe nanoparticle catalysts from which appropriate yields of SWNTs could be grown directly on solid substrates, and fabricated into field effect transistors (FETs) quite efficiently. The main reason for this failure is due to the carbothermal reduction which results in SiO2 nanotrench formation. We found that the oxygen-assisted CVD process could be successfully applied for the growth of highly pure SWNTs by switching the catalyst from Fe to Co nanoparticles. The topological morphologies and p-type transistor electrical transport properties of the grown SWNTs were examined by using atomic force microscope (AFM), Raman, and from FET devices fabricated by photolithography.

Magnetothermal Properties of Triethylene Glycol-Coated Cobalt-Zinc-Ferrite Nanoparticles for Magnetic Hyperthermia Applications

Ashfaq AHMAD,배홍섭,이일수 한국물리학회 2019 새물리 Vol.69 No.2

Cobalt zinc ferrite (Co0:6Zn0:4Fe2O) nanoparticles were synthesized using a one-step hydrothermal method. Triethylene glycol (TREG) was used as a biocompatible coating material. The TREGcoated nanoparticles were spherical, with an average diameter of 9.82 nm. The Fourier-transform infrared spectra confirmed the presence of a TREG-coating on the surfaces of the nanoparticles. The particles had a saturation magnetization of 84 emu/g and a coercivity of 32 Oe. The heating capability of the particles was evaluated using an induction system, and the heating curves for aqueous samples with various particle concentrations were obtained. An alternating magnetic field with an amplitude of 4.5 kA/m and a frequency of 216 kHz was applied to the samples. The optimal particle concentration in water for achieving the hyperthermia target temperature of 42 ◦C was 4.58 mg/mL. The specific absorption rate (SAR) of the 2-mg/mL sample was 83 W/g. The linear relationship between the SAR and the square of the field strength was confirmed for a representative 10-mg/mL sample. These findings show that TREG-coated particles are suitable for magnetic hyperthermia applications owing to their superparamagnetic properties and high SAR values.

One-pot dual product synthesis of hierarchical Co₃O₄@N-rGO for supercapacitors, N-GDs for label-free detection of metal ion and bio-imaging applications

Atchudan, Raji,Edison, Thomas Nesakumar Jebakumar Immanuel,Chakradhar, Dasagrandhi,Karthik, Namachivayam,Perumal, Suguna,Lee, Yong Rok Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.3

<P><B>Abstract</B></P> <P>Cobalt oxide nanoparticles@nitrogen-doped reduced graphene oxide (Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO) composite and nitrogen-doped graphene dots (N-GDs) were synthesized by a one-pot simple hydrothermal method. The average sizes of the synthesized bare cobalt oxide nanoparticles (Co<SUB>3</SUB>O<SUB>4</SUB> NPs) and Co<SUB>3</SUB>O<SUB>4</SUB> NPs in the Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO composite were around 22 and 24nm, respectively with an interlayer distance of 0.21nm, as calculated using the XRD patterns. The Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO electrode exhibits superior capacitive performance with a high capability of about 450Fg<SUP>−1</SUP> at a current density of 1Ag<SUP>−1</SUP> and has excellent cyclic stability, even after 1000 cycles of GCD at a current density of 4Ag<SUP>−1</SUP>. The obtained N-GDs exhibited high sensitivity and selectivity towards Fe<SUP>2+</SUP> and Fe<SUP>3+</SUP>, the limit of detection was as low as 1.1 and 1.0μM, respectively, representing high sensitivity to Fe<SUP>2+</SUP> and Fe<SUP>3+</SUP>. Besides, the N-GDs was applied for bio-imaging. We found that N-GDs were suitable candidates for differential staining applications in yeast cells with good cell permeability and localization with negligible cytotoxicity. Hence, N-GDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe<SUP>3+</SUP>/Fe<SUP>2+</SUP>) and also for early detection of opportunistic yeast infections in biological samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dual product of Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO and fluorescent N-GDs by one-pot hydrothermal method. </LI> <LI> The Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO delivered a high C<SUB>s</SUB> of 450 F g<SUP>−1</SUP> at current density of 1 A g<SUP>−1</SUP>. </LI> <LI> First time, the byproducted N-GDs was used for label-free detection of Fe<SUP>3+</SUP>/Fe<SUP>2+</SUP>. </LI> <LI> N-GDs were used as a fluorescent probe for bio-imaging with good biocompatibility. </LI> <LI> N-GDs would offer a great potential for clinical applications in the near future. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Preparation and electrochemical properties of cobalt-phthalocyanine-decorated Fe ₃ O ₄ nanoparticles

Hong, Sun-Mi,Son, Hoseung,Park, Jong S. World Scientific Publishing Company 2018 Journal of porphyrins and phthalocyanines Vol.22 No.7

<▼1><P>Phthalocyanines (Pcs) have been known for excellent electron transfer properties owing to their extended <TEX>$ \pi $</TEX>-conjugated structures. In addition, functionalized iron oxide nanoparticles (Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX> NPs) have attracted considerable interest owing to their unique spectral and electronic properties. Hence, it can be reasonably expected that Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX> NPs decorated with Pc molecules could provide a useful electrocatalytic system. Herein, we present the preparation and electrochemical properties of cobalt-phthalocyanine (CoPc)-decorated Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX> NPs (CoPc@Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}})$</TEX>. The Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX> NPs were first coated with a silica layer to produce SiO<TEX>$ _{\text{2}}$</TEX>@Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX>. Subsequently, CoPc with a siloxane end group (CoPc-TEOS) was anchored to the outer surface of the SiO<TEX>$ _{\text{2}}$</TEX>@Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX>. The CoPc@Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX> thus prepared was fully analyzed using various characterization methods. Distinctive electrochemical responses of CoPc and CoPc@Fe<TEX>$ _{\text{3}}$</TEX>O<TEX>$ _{\text{4}}$</TEX> in the presence of picric acid were observed, demonstrating the potential application of the current approach to electrochemical catalysis.</P></▼1><▼2><P>We have prepared cobalt-phthalocyanine (CoPc)-decorated iron nanoparticles (Fe<SUB>3</SUB>O<SUB>4</SUB> NPs) by anchoring siloxane-terminated CoPc on silica-coated Fe<SUB>3</SUB>O<SUB>4</SUB> NPs. The prepared CoPc@Fe<SUB>3</SUB>O<SUB>4</SUB> exhibited distinctive electrochemical responses in the presence of picric acid and facile magnetic recovery behavior, demonstrating the potential for applications as electrochemical sensors and biological catalysts.</P></▼2>