Piyapong Asanithi

Preparation and characterization of alumina nanoparticles in deionized water using laser ablation technique

Al2O3 nanoparticles were synthesized using laser ablation of an aluminum (Al) target in deionized water. Nd:YAG laser, emitted the light at a wavelength of 1064 nm, was used as a light source. The laser ablation was carried out at different energies of 1, 3, and 5 J. The structure of ablated Al particles suspended in deionized water was investigated using X-ray diffraction (XRD). The XRD patterns revealed that the ablated Al particles transformed into γ-Al2O3. The morphology of nanoparticles was investigated by field emission scanning electron microscopy (FE-SEM). The FE-SEM images showed that most of the nanoparticles obtained from all the ablated laser energies have spherical shape with a particle size of less than 100 nm. Furthermore, it was observed that the particle size increased with increasing the laser energy. The absorption spectra of Al2O3 nanoparticles suspended in deionized water were recorded at room temperature using UV-visible spectroscopy. The absorption spectra show a strong peak at 210nm arising from the presence of Al2O3 nanoparticles. The results on absorption spectra are in good agreement with those investigated by XRD which confirmed the formation of Al2O3 nanoparticles during the laser ablation of Al target in deionized water.

Carbon-Nanotube-Based Materials for Protein Crystallization

We report on the first use of carbon-nanotube-based films to produce crystals of proteins. The crystals nucleate on the surface of the film. The difficulty of crystallizing proteins is a major bottleneck in the determination of the structure and function of biological molecules. The crystallization of two model proteins and two medically relevant proteins was studied. Quantitative data on the crystallization times of the model protein lysozyme are also presented. Two types of nanotube films, one made with the surfactant Triton X-100 (TX-100) and one with gelatin, were tested. Both induce nucleation of the crystal phase at supersaturations at which the protein solution would otherwise remain clear; however, the gelatin-based film induced nucleation down to much lower supersaturations for the two model proteins with which it was used. It appears that the interactions of gelatin with the protein molecules are particularly favorable to nucleation. Crystals of the C1 domain of the human cardiac myosin-binding protein-C that diffracted to a resolution of 1.6 A were obtained on the TX-100 film. This is far superior to the best crystals obtained using standard techniques, which only diffracted to 3.0 A. Thus, both of our nanotube-based films are very promising candidates for future work on crystallizing difficult-to-crystallize target proteins.

Growth of silver nanoparticles by DC magnetron sputtering

Silver (Ag) nanoparticles are of great interest for many applications. However, their fabrications have been limited by the synthesis methods in which size, shape, and aggregation are still difficult to control. Here, we reported on using direct current (DC) magnetron sputtering for growing Ag nanoparticles on unheated substrates. Effects of sputtering condition on grain size of Ag nanoparticle were discussed. At constant sputtering current and deposition time, the average sizes of Ag nanoparticles were 5.9 ± 1.8, 5.4 ± 1.3, and 3.8 ± 0.7 nm for the target-substrate distances of 10, 15, and 20 cm, respectively. The morphology evolution from nanoparticles to wormlike networks was also reported. High-resolution transmission electron microscopy image represented clear lattice fringes of Ag nanoparticles with a d-spacing of 0.203 nm, corresponding to the (200) plane. The technique could be applied for growth of nanoparticles that were previously difficult to control over size and size uniformity.

Aligned, isotropic and patterned carbon nanotube substrates that control the growth and alignment of Chinese hamster ovary cells

Here we culture Chinese hamster ovary cells on isotropic, aligned and patterned substrates based on multiwall carbon nanotubes. The nanotubes provide the substrate with nanoscale topography. The cells adhere to and grow on all substrates, and on the aligned substrate, the cells align strongly with the axis of the bundles of the multiwall nanotubes. This control over cell alignment is required for tissue engineering; almost all tissues consist of oriented cells. The aligned substrates are made using straightforward physical chemistry techniques from forests of multiwall nanotubes; no lithography is required to make inexpensive large-scale substrates with highly aligned nanoscale grooves. Interestingly, although the cells strongly align with the nanoscale grooves, only a few also elongate along this axis: alignment of the cells does not require a pronounced change in morphology of the cell. We also pattern the nanotube bundles over length scales comparable to the cell size and show that the cells follow this pattern.

Blue photoluminescent carbon nanodots from limeade.

Carbon-based photoluminescent nanodot has currently been one of the promising materials for various applications. The remaining challenges are the carbon sources and the simple synthetic processes that enhance the quantum yield, photostability and biocompatibility of the nanodots. In this work, the synthesis of blue photoluminescent carbon nanodots from limeade via a single-step hydrothermal carbonization process is presented. Lime carbon nanodot (L-CnD), whose the quantum yield exceeding 50% for the 490nm emission in gram-scale amounts, has the structure of graphene core functionalized with the oxygen functional groups. The micron-sized flake of the as-prepared L-CnD powder exhibits multicolor emission depending on an excitation wavelength. The L-CnDs are demonstrated for rapidly ferric-ion (Fe(3+)) detection in water compared to Fe(2+), Cu(2+), Co(2+), Zn(2+), Mn(2+) and Ni(2+) ions. The photoluminescence quenching of L-CnD solution under UV light is used to distinguish the Fe(3+) ions from others by naked eyes as low concentration as 100μM. Additionally, L-CnDs provide exceptional photostability and biocompatibility for imaging yeast cell morphology. Changes in morphology of living yeast cells, i.e. cell shape variation, and budding, can be observed in a minute-period until more than an hour without the photoluminescent intensity loss.

Colloid-Assisted Self-Assembly of Robust, Three-Dimensional Networks of Carbon Nanotubes over Large Areas

Natural materials, such as bone and spider silk, possess remarkable properties as a result of sophisticated nanoscale structuring. They have inspired the design of synthetic materials whose structure at the nanoscale is carefully engineered or where nanoparticles, such as rods or wires, are self-assembled. Although much work has been done in recent years to create ordered structures using diblock copolymers and template-assisted assembly, no reports describe highly ordered, three-dimensional nanotube arrays within a polymeric material. There are only reports of two-dimensional network structures and structures on micrometer-size scales. Here, we describe an approach that uses plasticized colloidal particles as a template for the self-assembly of carbon nanotubes (CNTs) into ordered, three-dimensional networks. The nanocomposites can be strained by over 200% and still retain high conductivity when relaxed. The method is potentially general and so may find applications in areas such as sensing, photonics, and functional composites.

Surface porosity and roughness of micrographite film for nucleation of hydroxyapatite

Heterogeneous nucleation of hydroxyapatite (HAp) can be facilitated by physical and chemical properties of material surface. In this article, we reported how effective surface porosity and roughness are for inducing nucleation of HAp crystal in simulated body fluid. Two types of micrographite film (MGF) prepared from assembly of micrographite flakes were used as seeds to induce HAp crystal: uncompressed (high surface porosity) and compressed (low surface porosity) MGFs. Compressed MGF was prepared by applying mechanical compression to the uncompressed MGF. Uncompressed and compressed MGFs have similar surface wettability with the water contact angles (θ) of 113° and 107°, respectively. The number density of HAp crystals on the uncompressed MGF was higher than that of the compressed MGF by a factor of 6. This result implied that surface porosity and roughness were more effective parameters for inducing HAp crystal than surface wettability. Uncompressed MGF also induced HAp nucleation better than a cover glass although the glass had high wettability (θ = 64°). The effectiveness of uncompressed MGF on inducing HAp crystals was as high as that of the SiO2 -coated Si substrate. Our finding suggests that we do not require to functionalize material surface to be an effective seed; a surface with pores or roughness of the right scale is enough.

Raman spectroscopy of DLC/a-Si bilayer film prepared by pulsed filtered cathodic arc

DLC/a-Si bilayer film was deposited on germanium substrate. The a-Si layer, a seed layer, was firstly deposited on the substrate using DC magnetron sputtering and DLC layer was then deposited on the a-Si layer using pulsed filtered cathodic arc method. The bilayer films were deposited with different DLC/a-Si thickness ratios, including 2/2, 2/6, 4/4, 6/2, and 9/6. The effect of DLC/a-Si thickness ratios on the sp3 content of DLC was analyzed by Raman spectroscopy. The results show that a-Si layer has no effect on the structure of DLC film. Furthermore, the upper shift in G wavenumber and the decrease in ID/IG inform that sp3 content of the film is directly proportional to DLC thickness. The plot modified from the three-stage model informed that the structural characteristics of DLC/a-Si bilayer films are located close to the tetrahedral amorphous carbon. This information may be important for analyzing and developing bilayer protective films for future hard disk drive.

Variation of Color in Zirconium Nitride Thin Films Prepared by Reactive DC Magnetron Sputtering

This study is to evaluate a color variation of the zirconium nitride thin film, prepared from deposition technique of different N2 flow rates, ranging from 0.0 to 3.0 sccm, whereas the Ar flow rate is fixed at 3 sccm. The thin film was deposited on an unheated silicon wafer (100) via a reactive DC magnetron sputtering. The deposition current and deposition time were 0.6 A and 15 minutes, respectively. In the study, colors of film were changed from silver, gold, dark brown, brown, purple, pink to blue, when N2 flow rate further increase. Interestingly, the results indicate that gold color occurs in a very small interval of N2 flow rate.

A volumetric flask as a projector

A lens based on liquid in the confined volume of a volumetric flask was presented as a potential projector to observe microscopic floating organisms or materials. In this experiment, a mosquito larva from a natural pond was selected as a demonstration sample. By shining a light beam from a laser pointer of any visible wavelength through the volumetric flask filled with liquid, the movements of floating objects were clearly observed on a screen. The magnification was simply controlled by changing either the volume of the flask or the distance of the screen from the flask.