Advanced Materials Research Vol. 686

Abstract: Several clinical studies have proved the triterpenes in this herb have therapeutic properties and posses significant to health such as antitumor and wound healing. Centella asiatica nanopowders (CANPs) have been produced via top down approach using Planetary Ball Mill (PBM) at 0.5, 4 and 8 hours of milling in optimized condition. CANPs have been characterized using Photo Correlation Spectroscopy (PCS), Field Emission Scanning Electron Microscope (FESEM) and High Performance Liquid Chromatography (HPLC). As a result significant reduction on size was observed as increased a milling time by comparing their z-Average (nm) and the morphology of CANPs exist in the agglomerated form. The HPLC results showed significant increase in concentration of asiatic acid by comparing the concentration of asiatic acid in extract of CANPs and coarse powders whereby the asiaticoside completely disappeared after milling. Thus, nanoherbal can be said as improving the extraction ratio of asiatic acid compared to the coarse powders due to the smaller particle size and larger surface area and the disappearance of asiaticoside still not completely understood.

Abstract: In this work, 10 nm gold nanoparticles (AuNPs) was successfully synthesized via seeded-growth method. The green chemically synthesis of this AuNPs becomes attractive because the growth process does not involve heat. Moreover, this technique has advantages of quick, simple, and low cost process. Sodium borohydrate (NaBH4) was used as a reducing agent while trisodium citrate was used as a source of OH- ions in the seed stage. Hydroxylamine hydrochloride (NH4.3H2O) was used as a slow reducing agent to enlarge 4 nm seeds to 10 nm AuNPs. A 4 ml AuNPs seed was the optimized volume to produce 10 nm AuNPs with great homogeneity and dispersity. A sharp peak of surface plasmon resonance (SPR) measurement at 517 nm proved that 10 nm AuNPs was successfully synthesized via this method. Optical properties of the seeds and grown AuNPs were analyzed using UV-Vis spectroscopy while size and surface morphology were observed using a transmission electron microscopy (TEM). Particle size distribution was measured using Zetasizer. 10 nm AuNPs was then conjugated with streptavidin and goat anti-human IgA. Depending on type of protein, 10 µg/ml of streptavidin and 11.2 µg/ml of goat anti-human IgA were required to conjugate with 10 nm AuNPs. The produced products had binding capability on lateral flow immunoassay (LFI). A few nanometer red-shifted absorption spectrum of 10 nm AuNPs conjugated protein revealed successful conjugation instead of agglomeration. 1% BSA was determined as the optimum concentration to stabilize 10 nm AuNPs conjugated biomolecules.

Abstract: The formation of self-organized and highly ordered Titania nanotubes was achieved by anodisation of Ti in a mixture of water-ethylene glycol electrolyte. Control over the dimensions and morphology of nanotubes was successfully established by changing the anodisation voltage, the ammonium fluoride (NH4F) concentration and the anodisation time. A threshold voltage of 5 V is required for nanotube formation. Collapsed tubes were formed by applying electrochemical etching at high fluoride concentration. This study also showed that the nanotube lengths ranging from 0.5 to 2.6 μm could be formed by controlling the voltage applied and fluoride concentration with preferred growth along the c-axis.

Abstract: One-dimensional (1D) titanium dioxide (TiO2) was synthesized using heat sol-dispersion immersion technique which is combination of four methods at lower temperature processing. The method is versatile with adjustable temperature, multi-ratio solution compositional and ability to tailor the structure into nanometer scale and small dimension of nanostructures. 1D TiO2 nanothorn-like structures assisted TiO2 template has been increased the performance of self-cleaning property with height of TiO2 nanostructures grew 17.5 nm at temperature 100oC. Further enhancing current work of coating function ability to the high performance and efficiency self-cleaning compared to present coating. The results showed a surface area for hydrophilic self-cleaning is 13.50 nm2 while the efficiency of 1D TiO2 nanostructures for self-cleaning through contact angle (CA) measurement indicated that 0.35 degrees after 2.30 minutes exposed to the water molecules droplets. The average of absorption coefficient (α) in UV region attribute 5.45 compared to another three heat immersions temperature.

Abstract: In this paper, carbon nanotubes on porous silicon substrate were developed in order to get high quality nanotubes for various kind of application. CNTs were deposited on porous silicon nanostructures (PSiN) at 750 0C on porous silicon by using double-furnace thermal chemical vapor deposition technique. Align carbon nanotubes with diameters of 15 to 30 nm were successfully synthesized on a porous silicon substrate. In this system, carbon nanotubes were grown directly on the p-type porous silicon surface at 750 0C for a total time of 30 minutes. The samples were characterized using field emission scanning electron microscopy and micro-Raman spectroscopy. Align carbon nanotubes (ACNTs) bundle with uniform diameter (~20 nm) were found grown on porous silicon at certain area. Based on micro-Raman spectroscopy result, the peak of silicon at ~520 nm and peak of carbon nanotube (around 1 300 to 1 600 nm) was detected.

Abstract: Hydroxyapatite (HA) is a bioceramics that commonly used as bone substitute materials, coating materials and scaffolds in orthopedics. It is well known for its remarkable biocompatibility with natural human tissue. However, synthetic HA is different from biological apatite whereby apatites contain carbonate ion which is about 3-8wt% of the hard tissues of human body which described as carbonated hydroxyapatite (CHA). Hence, synthetic CHA may have a better bioactivity than HA and more widely used as biomaterials. This study described the synthesis and characterization of nanoporous carbonated hydroxyapatite (CHA) by co-precipitation method through self-organization mechanism with different type of non-ionic surfactants (P123 and F127). Diammonium hydrogen phosphate, (NH4)2HPO4 and calcium nitrate tetrahydrate, Ca (NO3)2.4H2O were used as starting materials for preparing the precursor for CHA powder. The ammonium carbonate, NH4HCO3 was used as the main source for carbonate ion. Synthesized powder was characterized using XRD, FESEM, EDS and FTIR. From the XRD result, pure HA phase was obtained for all samples. FTIR analysis results obviously showed the substitution of carbonate ion into the apatite and confirm the formation of CHA. The FTIR results also demonstrated that the surfactants had been removed completely through calcination process. SEM image revealed a sphere-like particle shape of CHA was produced after the calcinations. The mesoporous CHA with pore size 2-12 nm (F127) and 2-8 nm (P123) was synthesized.

Abstract: This study aims to evaluate the effects of sintering temperature on the density and hardness of tetragonal zirconia polycrystals stabilized with 3 mol% 3Y-TZP dental ceramic type. Five cylindrical specimens were fabricated from zirconia powder of particle size 50 nm via colloidal processing. The specimens were sintered densely at the final sintering temperatures of 1000, 1100, 1200, and 1300 °C, respectively. The sintered density and hardness of the sintered specimen were then examined. The results showed that the sintered densities and hardness of the specimen increased as the temperature increased from 1000 °C to 1300 °C. Zirconia 3Y-TZP could gain near full density and reach hardness of as high as 11.30 GPa at the final sintering temperature of 1300 °C. The density and hardness of zirconia structured from 3Y-TZP can be improved by controlling the final sintering temperature.

Abstract: For this experiment, the main purpose of this experiment is to determine the electroluminescence of PSiNs samples with optimum electrolyte volume ratio of photo-electrochemical anodisation. PSiNs samples were prepared by photo-electrochemical anodisation by using p-type silicon substrate. For the formation of PSiNs on the silicon surface, a fixed current density (J=20 mA/cm2) and 30 minutes etching time were applied for the various electrolyte volume ratio. Volume ratio of hydrofluoric acid 48% (HF48%) and absolute ethanol (C2H5OH), HF48%:C2H5OH was used for sample A (3:1), sample B (2:1), sample C (1:1), sample D (1:2) and sample E (1:3). The light emission can be observed at visible range. The effective electroluminescence was observed for sample C. Porous silicon nanostructures light–emitting diode (PSiNs-LED) has high-potential device for future flat screen display and can be high in demand.

Abstract: Nanostructured Porous Silicon templates (NPSiT) were prepared by photo-electrochemical anodization of p-type crystalline silicon in HF electrolyte at different etching time. Five samples were prepared with etching time varied from 10 to 50 minutes at 20 mA/cm2 of current density. The effects of etching time on NPSiT were observed based on nanocrystallite size, photon energy and surface distribution. These studied was demonstrated by Raman spectroscopy, photoluminescence (PL) and Fourier transforms infrared spectroscopy (FTIR). It was found that NPSiT sample with large pore diameter, which is smaller nanocrystallites size of Si between pore. The optical properties of NPSiT were investigated by photoluminescence (PL) and PL peak broadening and shifting towards higher energy can be observed with increasing etching time. The optimum etching time with respect to PL intensity was obtained at 30 minutes, for which uniform pores and a shift of the PL maximum to a higher energy of 1.9 eV is observed.