Edi Suharyadi

Magnetic Properties and Microstructures of Polyethylene Glycol (PEG)-Coated Cobalt Ferrite (CoFe2O4) Nanoparticles Synthesized by Coprecipitation Method

Magnetic nanoparticles of cobalt ferrite (CoFe2O4) have been synthesized by co-precipitation method with various synthesis temperatures, concentration of NaOH and stirring duration. The results showed that nanoparticles have well crystallized structure with various grain sizes which depend on synthesis parameters. The grain size increased with increasing synthesis temperature, decreasing concentration of NaOH and decreasing stirring duration. Magnetic characterization of CoFe2O4 nanoparticles measured by Vibrating Sample Magnetometer (VSM) showed that coercive field was decrease with the decreasing of particle size. The saturation and remnant magnetization showed increasing when crystallinity increased. However, it also depends on presence of α-Fe2O3 phases and their grain size. Based on magnetic characterization analysis, sample with parameter of synthesis temperature 80°C, concentration of NaOH 5 M and stirring duration 120 minutes have been selected to be modified using polyethylene glycol (PEG)-4000. XRD and TEM analysis showed that surface modification with PEG-4000 could increase the crystallinity of nanoparticles, decrease agglomeration and control the shape to more spherical. VSM analysis showed that modification PEG-4000 could decrease the saturation magnetization which is due to the existence of α-FeO(OH) and γ-FeO(OH) phases from bonds at interface of CoFe2O4 as confirmed by XRD and Furrier Transform Infra Red (FTIR) analysis. Keywords: magnetic nanoparticles, CoFe2O4, copresipitation, PEG-4000

Influence of stabilizing agent and synthesis temperature on the optical properties of silver nanoparticles as active materials in surface plasmon resonance (SPR) biosensor

It has been successfully carried out the synthesis of colloidal silver nanoparticles by chemical reduction method. Silver nitrate (AgNO3) was used as metal precursors and trisodium citrate as the reducing agent. In the synthesis process, were varied the stabilizing agent of Polyvinyl Alcohol (PVA) and polyvinylpyrrolidone (PVP) and heating temperature. The formation of silver nanoparticles was observed visually with discoloration (yellowish). The formation and the structure of silver nanoparticles in colloidal solution were further examined through their optical properties by using a UV-Vis spectrometer. The wavelength absorption spectrum of colloidal silver nanoparticles shows that maximum surface plasmon absorption for the trisodium citrate-synthesized nanoparticles was at 429.43 nm for temperature of 90°C. The addition of the stabilizer sharpened spectrum curves and caused red shift in the maximum absorption peak of 429.01 nm and 427.09 nm for PVA and PVP respectively. Meanwhile, the addition of the sy...

Study of Heavy Metal Ions Mn(II), Zn(II), Fe(II), Ni(II), Cu(II), and Co(II) Adsorption Using MFe 2 O 4 (M=Co 2+ , Mg 2+ , Zn 2+ , Fe 2+ , Mn 2+ , and Ni 2+ ) Magnetic Nanoparticles as Adsorbent

Removal of heavy metal ions (Co2+, Cu2+, Zn2+, Fe2+, Mn2+, and Ni2+) from artificial wastewater has been successfully perfomed by adsorption process using magnetic ferrite (MFe2O4; M=Co2+, Mg2+, Zn2+, Fe2+, Mn2+, and Ni2+) nanoparticles. Ferrite nanoparticles were synthesized using coprecipitation method and used as absorbent in heavy metal ions removal with concentration of 5 g/L and 10 g/L. The adsorption and desorption ability of each ferrite nanoparticles, the effect of heavy metal ion in adsorption and desorption process, and the endurance of ferrite nanoparticles were investigated using atomic absorption spectroscopy (AAS). The removal process has been conducted for wastewater at pH 7.It showed the presence of heavy metal precipitate in solution. The result shows that MgFe2O4 has the highest adsorption ability than other ferrite and MnFe2O4 is the lowest. Desorption ability of all ferrites is high except for Fe ion removal. Desorption of Fe ion shows very low result which might due to FeO bond from Fe ion reaction in acid solution. The endurance of MnFe2O4 and Fe3O4 as adsorbent after repeated adsorption and desorption process is up to 4 times and more than 6 times. The MnFe2O4 nanoparticles show a stability in adsorption ability after 4 times repetition adsorption and desorption process.

The use of Fe3O4 magnetic nanoparticles as the active layer to detect plant’s DNA with surface plasmon resonance (SPR) based biosensor

The surface plasmon resonance (SPR) phenomenon has been observed on the silver-coated prism and Fe3O4 magnetic nanoparticles for detecting plant’s DNA. Fe3O4 nanoparticles were synthesized using temperature of 30°C and they were coated with PEG4000. The composite of Fe3O4+PEG4000 has a function as a DNA binding active layer and for optimizing the detection ability of SPR. SPR-based biosensor in this work using Kretschmann configuration and He-Ne laser beam (λ = 632.8 nm). The plant’s DNA used in this study has ratio 1.828. The plant’s DNA could be detected by SPR-based biosensor with the ratio of composite Fe3O4 : PEG4000 is 1:1. This work was done for the earlier study to approve that SPR can be used to detect DNA with the active layer on it (in this case: composite Fe3O4+PEG4000). Thus, the shift of SPR-angle was influenced by the DNA ratio, concentration of Fe3O4 and its refractive index.

The calcination temperature dependence of microstructural, vibrational spectra and magnetic properties of nanocrystalline Mn0.5Zn0.5Fe2O4

Effect of calcination temperature on microstructural, vibrational, and magnetic properties of Mn0.5Zn0.5Fe2O4 nanoparticles have been successfully investigated. The nanoparticles were synthesized via coprecipitation method and calcined at different temperatures varying from 400, 600, 800, and 1000°C. The X-ray diffraction (XRD) pattern confirmed the formation of cubic spinel structure Mn0.5Zn0.5Fe2O4 with crystallite size ranging from 18.3 nm to 24.8 nm. The TEM micrograph showed the morphology of nanoparticles change from nearly spherical to cubic form after calcination. The FTIR spectra confirmed the existence of vibrations at 416.6 cm-1 - 455.2 cm-1 and 555.5 cm-1 -578.6 cm-1 which corresponds to the intrinsic stretching vibration of metal-oxygen at octahedral and tetrahedral sites, respectively. The maximum specific magnetization and coercivity increase with increasing calcination temperature. The maximum specific magnetization value of 54.7emu/gram was obtained for sample calcined at 1000°C. The results showed that calcination treatment will facilitate the tunability of microstructural and magnetic properties of nanoparticles for expanding the field of application.

Effect of Co concentration on crystal structures and magnetic properties of Ni1-xCoxFe2O4 nanoparticles synthesized by co-precipitation method

ABSTRACT Cobalt substituted nickel ferrite nanoparticles (Ni1-xCoxFe2O4) with stoichiometric proportion (x) from 0.2 to 0.8 have been synthesized by co-precipitation method with synthesis temperature of 90°C. The crystallite size of Ni1-xCoxFe2O4 nanoparticles were within range of 14 – 27 nm. The X-ray diffraction (XRD) analysis informed that the lattice parameter of Ni1-xCoxFe2O4 nanoparticles at x = 0.3 was 8.423 Å, and then increased with increasing Co concentration. This is due to substitution of larger ionic radius of Co2+. The selected area electron diffraction (SAED) patterns showed that increasing Co concentration exhibited more prominent ring indicating well crystallinity. It could be confirmed from the crystallinity of the sample for x = 0.7 was higher than 0.5. The SAED patterns of Ni1-xCoxFe2O4 nanoparticles also displayed polycrystalline diffraction ring. The fourier transform infrared spectroscopy (FTIR) spectra of Ni1-xCoxFe2O4 showed the presence of vibration bands of metal ions within the range of 370.33 cm−1 – 601.79 cm−1 at the tetrahedral and octahedral sites, respectively. These two bands indicated the formation of a spinel ferrite structure. The magnetic hysteresis results showed that the maximum magnetization at 15 kOe of Ni1-xCoxFe2O4 nanoparticles at x = 0.2 was 7.0 emu/g, and then increase to 29.0 emu/g at x = 0.8 with increasing Co concentration. The results could be attributed to substitution of higher magnetic moment of Co2+. The coercivity (Hc) of Ni1-xCoxFe2O4 nanoparticles at x = 0.2 was 59.4 Oe, and then increase to 641.75 Oe at x = 0.6 with increasing Co concentration. This is due to cobalt having higher magnetic anisotropy than nickel.

Yttria-Stabilized Zirconia Ceramic Deposition on SS430 Ferritic Steel Grown by PLD - Pulsed Laser Deposition Method

Development of high temperature materials are one of the key issues for the deployment of advanced nuclear reactors due to higher temperature operation. One of the candidate materials for that purpose is ceramic-coated ferritic steel that one of the functions is to be a thermal barrier coating (TBC). Thin films of YSZ (Ytrria-Stabilized Zirconia) ceramic have been deposited on a SS430 ferritic steel using Pulsed Laser Deposition (PLD) at Center For Science and Technology of Advanced Materials laboratory – National Nuclear Energy Agency of Indonesia (BATAN). The thin film was deposited with the chamber pressure range of 200-225 mTorr, the substrate temperature of 800oC, and the number of laser shots of 3×104, 6×104 and 9×104. Afterward, the samples were analyzed using Scanning Electron Microscope – Energy Dispersive X-ray Spectroscope (SEM-EDS), X-Ray Diffractometer (XRD), Atomic Force Microscope (AFM) and Vickers hardness tester. The results showed that the YSZ could homogeneously and sticky deposited on the surface of the ferritic steel. The surfaces were very smoothly formed with the surface roughness was in the range of 70 nm. Furthermore, thickness, composition of Zr4+ dan Y3+, the crystallinity, and hardness property was increased with the increasing the number of the shots.

The Roles of Polyvinyl Alcohol (PVA) as the Capping Agent on the Polyol Method for Synthesizing Silver Nanowires

We report our investigation of roles of polyvinyl alcohol (PVA) as a high-performance capping agent in synthesizing silver nanowires (AgNWs) using polyol method. For this purpose, we varied the concentration of silver nitrate (AgNO3), from 0.3 M to 1.0 M, and molar ratios of [PVA:AgNO3] from 2 to 6. The UV-vis spectra show the AgNWs growth optimally at a molar ratio of 4.5 with the absorbance peaks of 378 nm and 380 nm. Meanwhile, from XRD patterns, it was found that the crystal structure of the AgNWs can be identified as a face-centered cubic (fcc) with a lattice constant according to the spacing distance between the {111} planes of 4.087 Å. Finally, scanning electron microscopy (SEM) and transmission electron microscopy TEM images show the diameter and length of the AgNRs are 150 to 230 nm and 50 to 120 µm, respectively. These results show that the AgNWs synthesized using PVA having a long size.

High-Performance Silver Nanowire Film on Flexible Substrate Prepared by Meyer-rod Coating

Flexible and transparent conducting (FTC) films based on silver nanowires (AgNWs) were fabricated onto a polycarbonate (PC) substrate by a simple Meyer-rod coating process. AgNWs were synthesized using polyvinyl alcohol by polyol process with a diameter and length of 500 nm and 10 µm, respectively. The FTC film was fabricated by varying the number of layers. The FTC film exhibited a sheet resistance of 12.1 Ω.sq-1 with a transparency of 89.5%. The optical conductivity of FTC films was obtained about 4.7 - 13.1 × 105 S.m-1 with a refractive index about 1.2 to 1.7. The number of layers is an important to influence on the sheet resistance and transmittance of the FTC films. The sheet resistance and transmittance decreases with the number of layers.

Giant magnetoresistance (GMR) sensors based on Co/Cu multilayers for biomaterial detection applications

In this study, a potential biomaterial detection technology was successfully developed based on giant magnetoresistance (GMR) sensors. The GMR sensors were performed using [Co(1.5 nm)/Cu(x)]20 multilayer structures (x = 0.8, 0.9 and 1.0 nm) fabricated by DC magnetron sputtering. The X-ray diffraction (XRD) patterns showed that Co/Cu film multilayer has a high degree of crystallinity with a single peak correspond to face-centered cubic (111) structure at 2θ = 44.1°. Co/Cu multilayers exhibit soft magnetic behavior with the saturation magnetization (Ms) of 1416, 1463 and 1489 emu/cc and the coercivity (Hc) of 1.5, 1.6, and 112 Oe for x = 0.8, 0.9 and 1.0 nm, respectively. The magnetoresistance (MR) of Co/Cu was about 4.3%, 6.9% and 14.8% for x = 0.8, 0.9 and 1.0 nm, respectively. Furthermore, we used magnetite (Fe3O4) nanoparticles as a biomolecular label (nanotag) synthesized by coprecipitation method. XRD patterns and transmission electron microscopy (TEM) images showed that Fe3O4 had well crystallized and grow in their inverse spinel structure, highly uniform morphology with grain size of about 12 nm. The M-H loop of Fe3O4 exhibit soft magnetic behavior with Ms of 77 emu/gram and Hc of 47 Oe. The GMR sensor design was used to detect a biomolecule such as formaldehyda and α-amylase enzyme with concentration 20 ppm captured using nanoparticles magnetite coated with polyethylene glycol (PEG) polymer for surface functionalization. Various applied magnetic field of 0-600 Gauss has been performed using electromagnetic with the various current of 0-4.5 A. Induction which cause a shift in MR ratio shown the best response with tCu = 0.9nm was about 18.3% and tCu = 1.0nm was about 4.7% for detection formaldehyda and α-amylase enzyme respectively. Furthermore, we present the linearly output signal and saturation signals in real time measurement from sensors. Based on this result, we can conclude that the combination of Co/Cu film multilayer, magnetite, and PEG polymer are potential in biodetection technology.