Journal of Metastable and Nanocrystalline Materials Vol. 35

Abstract: In this research, iron oxide nanoparticles were prepared by a new hydrothermal pyrolysis technique at different reaction times. X-ray diffractometer (XRD) characterization showed that the nanoparticles have high crystallinity with a combination of two crystal phases maghemite and magnetite, as the reaction time increase the ratio of magnetite phase to maghemite phase increased. The morphological properties of the samples showed an increase in the particle size from 58 to 108 nm due to the single domain–multidomain transition as showed by scanning electron microscope (SEM). Electron Dispersive X-ray (EDX) spectra showed only peaks of oxygen and iron that verified the formation of iron oxide nanoparticles. The Fourier transform infrared spectroscopy (FT-IR) showed that the absorption peaks at about 578 cm^-1 and 630 cm^-1 correspond to the stretching modes of the Fe-O in magnetite, as the reaction time increased the peak around 630 cm^-1 decreased due to the magnetite phase only. Finally, all the results showed the formation of iron oxide nanoparticles by this new technique that merges spray pyrolysis and hydrothermal techniques with many advantages such as spraying successive parameters in a short time, high-speed, good homogeneity, and pure material with small particle size.

Abstract: The production of nanocomposite tungsten carbide buttons was studied. Using the mechanically induced solid-state mixing technique, the nanopowders were mixed with Cobalt (Co) and Zirconium Oxide (ZrO₂). During the consolidation and manufacturing process, the nanocrystalline characteristics of the nanocomposite were improved by replacing Co with ZrO₂-2 mol% yttria (YO₃), and the average grain size was reduced to 23-49µm. With the advent of fast sintering techniques and the synthesis of nanocomposites from the consolidation of nanocomposite powders, full dense buttons with outstanding properties were produced. These buttons have a very high nano hardness value (24.41GPa) and a low Young's modulus (E) value (332.02 GPa).

Abstract: Biosensors must display high sensitivity and selectivity with fast response and be cost-effective. Silica nanoparticles are profoundly promising as versatile signal platforms opening up new possibilities for bioassays and dynamic units in biosensing systems. Fluorescent silica nanoparticles (FSNP) may be a key nanomaterial for labeling antibodies or antigens for biosensor application. Integration FSNP with functional molecules utilizing different surface modification techniques can bring out great improvements such as selective recognition, sensitive detection, and signal amplification because FSNP can bind with a large number of dye molecules within a silica matrix. The FSNP conjugated with anti-IgY can be applied for the detection of IgY antibody. FSNP was fabricated using the sol-gel method with hydrosilylation techniques for silica surface modification. N-H of amide groups from FSNP-anti-IgY ware observed in the FTIR spectra at 1648 cm^-1 indicating that the conjugation was successful. The fluorescence intensity of FSNP-anti-IgY after detection of IgY was applied for immunodetection and measured using fluorescence spectroscopy. The intensity of FSNP-anti-IgY was 156.82, 368.31, and 648.00 a.u for the 0.05, 0.1, 0.5 µg/ml of the sample concentrations, respectively. The results showed that the modified FSNP-anti-IgY may be used for the fluorescence detection of antibodies.

Abstract: The aim of this study was to compare the synthesis process of magnetic silica nanoparticles (Fe-SNP) through the analysis of X-ray Diffraction (XRD) results. Fe₃O₄ magnetic nanopowders was synthesized by ultrasonic assisted co-precipitation and Fe-SNP was synthesized by direct mixing method of sodium silicate (Na₂SiO₃) and magnetite (Fe₃O₄) and the sol-gel method. Silica sludge was used as a silica source from Indonesia geothermal power plant waste. The synthesized of Fe-SNP is the functionalization of Fe₃O₄ with silica. Variations concentration of Na₂SiO₃ is used for the direct mixing method and variations of Fe₃O₄ form is used for the sol-gel method. Particles formed and particle size were characterized by XRD. The XRD results showed that there is no SiO₂ phase in the sample synthesized by direct mixing method while two phases of SiO₂ and Fe₃O₄ were found in the sample synthesized by sol-gel method. The size of the Fe₃O₄ nanoparticles calculated with Scherer’s formula and it obtained 19.9 nm, while the Fe₃O₄ nanoparticles with the addition of 20 mL and 6 mL Na₂SiO₃ concentrations were 6,53 nm and 10,23 nm. For the sol-gel method the size of Fe₃O₄ nanoparticles obtained was 11,03 using Fe₃O₄ powders and 9,86 using Fe₃O₄ solutions.

Abstract: Silver nano/micro particles have been successfully produced via biosynthesis using sambiloto (Andrographis paniculata) leaves extract as the reductor agent. The obejctive of current was to study the effect of four different AgNO₃ solution concentrations (i.e. 0.0125, 0.025, 0.05, 0.075 M) on the production of silver nano/micro particles via biosynthtesis. The sambiloto extract concentration used in this study was 0.5% w/v. The silver nano/micro particles produced via biosynthesis was characterized using UV-Vis spectrophotometer and Scanning Electron Microscopy (SEM). The UV-Vis analysis results showed that absorbance peaks for all four samples were observed at wavelength around 450 nm, which can be attributed to the presence silver nano/microparticles. The absorbance peak values for all samples were 0.1115; 0.0876; 0.052; 0.0424 for AgNO3 solution concentration of 0.0125; 0.025; 0.05; 0.075 M, respectively. The UV-Vis analysis results could also qualitatively conclude that the size of silver nano/micro particles produced at lower AgNO₃ solution concentration were smaller than the size of silver nano/micro particles produced at higher AgNO3 solution concentration. In the other hand, SEM image showed that the size of silver particles prepared using AgNO₃ solution concentration of 0.075 M was in the range of 5 – 10 μm, hence it can be called silver micro-particles. It was assumed that the size of silver nano/micro particles produced at higher AgNO₃ solution concentration were bigger than the size of silver nano/micro particles produced at lower AgNO₃ solution concentration.