Teguh Endah Saraswati

High-efficiency plasma surface modification of graphite-encapsulated magnetic nanoparticles using a pulsed particle explosion technique

A high-efficiency surface modification of graphite-encapsulated iron compounds magnetic nanoparticles using an inductively coupled radio-frequency plasma with a pulsed particle explosion technique was studied. A significant increase in N 1s peak intensity in the X-ray photoelectron spectroscopy spectra was obtained by applying a negative pulsed bias voltage of ?1 kV to the substrate stage for 15 s or less at a repetition frequency of 1 kHz and a duty ratio of 50% in ammonia plasma. The intensity of the N 1s peak and the N/C ratio of the nanoparticles treated in a pulsed particle explosion system were 3?4 times higher than those of the particles treated without bias. The amino group population of nanoparticles treated using the present technique was determined to be about 8.2 ? 104 molecules per nanoparticle, roughly four times higher than that of particles treated without bias. The dispersion of the plasma-treated nanoparticles was significantly improved compared with those of the untreated and treated particles in the nonbiasing system. The surface structure analysis by transmission electron microscopy showed no significant damage on the structure or morphology of the treated nanoparticles, indicating that the present technique is applicable to the high-efficiency surface modification of magnetic nanoparticles.

Improvement of UV emission from highly crystalline ZnO nanoparticles by pulsed laser ablation under O2/He glow discharge

Pulsed laser ablation under an O2/He glow discharge was studied to improve the surface crystallinity and UV luminescence of ZnO nanoparticles ∼10 nm in size. X-ray photoemission spectroscopy, scanning transmission electron microscopy, and cathodoluminescence spectroscopy were used to analyze the crystalline structures and chemical components. The results indicated that highly crystalline ZnO nanoparticles were fabricated under the O2/He plasma discharge. The near band gap UV emission intensities from these particles were roughly five times those of samples fabricated under O2 gas. The present results suggest the possibility of synthesize high quality ZnO quantum dots or nanoparticles without requiring any post-treatment.

Bifunctional catalyst of graphite-encapsulated iron compound nanoparticle for magnetic carbon nanotubes growth by chemical vapor deposition

The carbon nanotube has widely taken great attractive in carbon nanomaterial research and application. One of its preparation methods is catalytic chemical vapor deposition (CCVD) using catalyst i.e. iron, nickel, etc. Generally, except the catalyst, carbon source gasses as the precursor are still required. Here, we report the use of the bifunctional material of Fe3O4/C which has an incorporated core/shell structures of carbon-encapsulated iron compound nanoparticles. The bifunctional catalyst was prepared by submerged arc discharge that simply performed using carbon and carbon/iron oxide electrodes in ethanol 50%. The prepared material was then used as a catalyst in thermal chemical vapor deposition at 800°C flown with ethanol vapor as the primer carbon source in a low-pressure condition. This catalyst might play a dual role as a catalyst and secondary carbon source for growing carbon nanotubes at the time. The synthesized products were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The successful formation of carbon nanotubes was assigned by the shifted X-ray diffracted peak of carbon C(002), the iron oxides of Fe3O4 and γ-Fe2O3, and the other peaks which were highly considered to the other carbon allotropes with sp2 hybridization structures. The other assignment was studied by electron microscopy which successfully observed the presence of single-wall carbon nanotubes. In addition, the as-prepared carbon nanotubes have a magnetic property which was induced by the remaining of metal catalyst inside the CNT.The carbon nanotube has widely taken great attractive in carbon nanomaterial research and application. One of its preparation methods is catalytic chemical vapor deposition (CCVD) using catalyst i.e. iron, nickel, etc. Generally, except the catalyst, carbon source gasses as the precursor are still required. Here, we report the use of the bifunctional material of Fe3O4/C which has an incorporated core/shell structures of carbon-encapsulated iron compound nanoparticles. The bifunctional catalyst was prepared by submerged arc discharge that simply performed using carbon and carbon/iron oxide electrodes in ethanol 50%. The prepared material was then used as a catalyst in thermal chemical vapor deposition at 800°C flown with ethanol vapor as the primer carbon source in a low-pressure condition. This catalyst might play a dual role as a catalyst and secondary carbon source for growing carbon nanotubes at the time. The synthesized products were characterized by transmission electron microscopy (TEM) and X-ray di...

Surface Functionalization of Graphene Layer-Encapsulated Magnetic Nanoparticles by Inductively Coupled Plasma

The graphene layer-encapsulated iron nanoparticles were modified by pre-treatment of Ar plasma and post-treatment of NH3 plasma using an inductively coupled RF plasma. Analysis of XPS spectra have been carried out to study the effect of the plasma treatment on the improvement of enrichment of nitrogen-containing groups. The morphology of nanoparticles has been also analyzed by using a Scanning Transmission Electron Microscope (STEM) together with Energy Dispersive X-Ray Spectroscopy (EDS) elemental mapping to observe the distribution of elements.

The Modification of Carbon with Iron Oxide Synthesized in Electrolysis Using the Arc Discharge Method

The modification of carbon-based nanomaterials with metals is widely studied due to its unique properties. Here, the modification of carbon nanomaterial with iron oxide has been successfully carried out. This modification was achieved using arc discharge in 50% ethanol liquid media. The anode used in the arc discharge was prepared from a mixture of carbon and iron oxide that was synthesized in electrolysis and was then calcined at 250°C with silicon binder with a mass ratio of 3:1:1, and the cathode used was graphite rod. Both electrodes were set in the nearest gap that could provide an arc during arc-discharging, leading to carbon-based nanoparticle formation. The diffractogram pattern of the X-ray diffraction of the fabricated nanoparticles confirmed the typical peak of carbon, iron oxide and iron. The magnetization value of the result analysis of the vibrating sample magnetometer was 9.9 emu/g. The bandgap energy measurement using diffuse reflectance ultra violet was estimated to be 2.18 eV. Using the transmission electron microscopy, the structure of the nanomaterial produced was observed as carbon-encapsulated iron compound nanoparticles.

Size dependence effect of carbon-based anode material on intercalation characteristics of Li-ion battery

This work aims to study the effect of the different size of Li-ion battery anode during charging state. Carbon-Based nanomaterial using arc-discharge in a liquid which is much simpler and cheaper compared to other techniques, i.e., CVD, laser vaporization, etc. The experiment was performed using intermediate DC power supply (1300 W) to produce an arc, and commercial graphite pencils (with 5 mm diameter) as negative and positive electrodes. Deionized water mixed with ethanol was used as a heat absorber. The result shows that arc discharge in deionized water could effectively produce carbon nanomaterial (i.e., nano-onions). In addition, finite element method-based simulation of the different intercalating process of Li-ion to the different shape of the anode, i.e., bulk semi-porous and porous anode materials for battery application is also presented. The results show that intercalation of Li ions depends on the anode structure due to the different potential density at anode region. This finding will provide...

Covalent Functionalization of Amino Group onto Carbon-Based Magnetic Nanoparticles Using Pulsed-Powder Explosion Technique

In order to enhance the treatment processing for powder of nanoparticle, we developed a modified setup using an inductively coupled radio frequency plasma with a pulsed explosion technique. Applying a negative pulsed bias voltage of -1 kV to the substrate stage in 15 seconds with a repetition frequency of 1 kHz and a duty ratio of 50 % in ammonia plasma, a significant increase of N 1s peak intensity in the X-ray photoelectron spectroscopy spectra was observed. The intensity of N 1s peak treated in the pulsed-biasing system raised both about four times higher than those of the particles treated without bias. After plasma treatment, the amino group was suggested to be covalently functionalized onto the nanoparticle surface and quantitatively examined by chemical derivatization. The amino group population attached onto treated nanoparticles was determined about 8.2 x 104 molecules per nanoparticle, roughly four times higher than that of particle without biasing which was about 1.9 x 104 molecules per nanoparticle. The surface structure analysis by a high resolution-transmission electron microscopy showed no significant damages were found on the nanoparticles, indicating that the present technique is suitable mainly for surface modification of powder materials without bringing any damages on their structural and morphological surface.