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AFM Detection of an Alzheimer Marker: Different Stages of Amyloid Beta Peptide on a Mica Substrate
이주경,Hobin Jeong,Ahmed Busnaina,이혜연 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.12
Alzheimer’s disease is a progressive neurodegenerative disease that is characterized by the presence of extracellular amyloid plaques and intraneuronal neurofibrillary tangles within the brain. Biochemical analysis of amyloid plaques have revealed that the main constituents are fibrillary aggregates of 39-42 peptide residues referred to as the amyloid- protein (A). Here, we examined the consecutive aggregation stages of the A-42 peptide, as well as the fibril formation stages on a mica substrate by using atomic force microscopy. These results offer new tools for an analysis of the mechanisms of A aggregation.
Polypyrrole Films with Micro/Nanosphere Shapes for Electrodes of High-Performance Supercapacitors
Lee, JuKyung,Jeong, Hobin,Lassarote Lavall, Rodrigo,Busnaina, Ahmed,Kim, Younglae,Jung, Yung Joon,Lee, HeaYeon American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.38
<P>We demonstrate a simple and efficient one-step procedure for synthesizing a solid state polypyrrole (PPy) thin film for supercapacitor applications using alternating current impedance spectroscopy. By controlling the frequency and amplitude we were able to create unique PPy nano/Microstructures with a particular morphology of the loop. Our PPy micro/nanosphere shows extremely high capacitance of 568 F/g, which is close to the theoretical value of 620 F/g and 20-100% higher than that of other, reported PPy electrodes. Most of all, this material presents high capacitance and significantly improved electrochemical stability without pulverization of its :structure, demonstrating 77% retention of the capacitance value even after 10 000 charge/discharge cycles. These results are a consequence of the larger surface area and adequate porosity generated due to the balance between the nano/micro PPy loops. This created porous structure also allows the favored penetration of electrolyte and high ion mobility within the polymer and prevents the mechanical failure of the physical-structure during volume variation associated with the insertion/deinsertion of ions upon cycling.</P>
3-D Perpendicular Assembly of SWNTs for CMOS Interconnects
김태훈,Cihan Yilmaz,Sivasubramanian Somu,Ahmed Busnaina,연구자TEST 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.6
Due to their superior electrical properties such as high current density and ballistic transport, carbon nanotubes (CNT) are considered as a potential candidate for future very large scale integration (VLSI) interconnects. However,direct incorporation of CNTs into a complimentary metal oxide semiconductor (CMOS) architecture by the conventional chemical vapor deposition (CVD) growth method is problematic because it requires high temperatures that might damage insulators and doped semiconductors in the underlying CMOS circuits. In this paper, we present a directed assembly method to assemble aligned CNTs into pre-patterned vias perpendicular to the substrate. A dynamic electric field with a static offset is applied to provide the force needed for directing the SWNT assembly. It is also shown that by adjusting assembly parameters the density of the assembled CNTs can be significantly enhanced. This highly scalable directed assembly method is conducted at room temperature and pressure and is accomplished in a few minutes. I-V characterization of the assembled CNTs was conducted using a Zyvex nanomanipulator in a scanning electron microscope (SEM) and the measured value of the resistance was 270 kΩs.
Spin Coating Fabrication of Thin Film Transistors Using Enriched Semiconducting SWNT Solution
Jun Huang,Sivasubramanian Somu,Ahmed Busnaina 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.4
Semiconducting single wall carbon nanotubes (SWNT) are excellent candidates for thin film transistor (TFT)applications. Major obstacles in developing low cost separation techniques for high purity semiconducting SWNTs have hindered their incorporation into many low-end functional devices. For low-end transistor devices a moderate ON/OFF ratio and performance is sufficient. A mix of single wall nanotubes with enriched semiconducting tubes can meet these needs. Using such 90% semiconducting enriched SWNTs, we have fabricated thin film transistors with a maximum 104 ON/OFF ratio. The device-manufacturing yield was low due to inconsistencies in the distribution of the SWNTs across the wafer. Increasing the density of the SWNTs in the channel using the drop casting method increased the device-manufacturing yield but decreased the performance. Conducting multiple spin coating processes is expected to increase the device-manufacturing yield without sacrificing device performance.
Phospholipase-catalyzed hydrolysis in an artificial cell membrane in the presence of melittin.
Lee, Jinyoung,Lee, Joo-Kyung,Busnaina, Ahmed,Park, BaeHo,Lee, HeaYeon American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.1
<P>Biomimicry involves the use of the structure and function of biological systems as models for the design and engineering of materials and machines. An artificial cell membrane was developed using biomembrane components, and the membrane, formed by a lipid bilayer, was analyzed using surface plasmon resonance (SPR) to monitor hydrolysis by phospholipase (PL). The simultaneous atomic force microscope (AFM) images show that PL catalyzed the nanometer-scale hydrolysis of the artificial lipid biomembranes through enzymatic hydrolysis. In addition, it was confirmed that the combination of PL and melittin allowed the control of enzyme hydrolysis for the degradation of the lipid bilayer. Regarding the expected activating effect of melittin on hydrolysis, no difference with respect to the non-treated lipid membrane was observed in the AFM images. It is assumed that the partitioning of melittin into the membrane might prevent the binding or hydrolysis of Phospholipase A2 (PLA2). This study provides basic knowledge on a new approach for patterning biomimicking lipid membranes on a nano-scale.</P>
Collapse behavior and forces of multistack nanolines
Kim, Tae-Gon,Wostyn, Kurt,Mertens, Paul W,Busnaina, Ahmed A,Park, Jin-Goo IOP Pub 2010 Nanotechnology Vol.21 No.1
<P>Two types of multistack nanolines (MNLs), Si-substrate (Si)/siliconoxynitride (SiON)/amorphous Si (a-Si)/ SiO<SUB>2</SUB> and Si/ SiO<SUB>2</SUB> /polycrystalline Si (poly-Si)/ SiO<SUB>2</SUB> were used to measure the collapse force and to investigate their collapse behavior by an atomic force microscope (AFM). The Si/SiON/a-Si/ SiO<SUB>2</SUB> MNL showed a larger length of fragment in the collapse patterns at a smaller collapse force. The Si/ SiO<SUB>2</SUB> /poly-Si/ SiO<SUB>2</SUB> MNL, however, demonstrated a smaller length of fragment at a higher applied collapse force. The collapse forces increased by the square of the linewidth in both Si/SiON/a-Si/ SiO<SUB>2</SUB> and Si<I>/</I>SiO<SUB>2</SUB> /poly-Si/ SiO<SUB>2</SUB> MNLs. Once an AFM tip touches an Si/SiON/a-Si/ SiO<SUB>2</SUB> line, which is a softer MNL, it was delaminated first at the Si/SiON interface. One end of the delaminated line was first broken and then the other end was bent until it was broken. A harder MNL, Si/ SiO<SUB>2</SUB> /poly-Si/ SiO<SUB>2</SUB>, however, was broken at two ends simultaneously after the delamination occurred at the Si/ SiO<SUB>2</SUB> /poly-Si interface. The different collapse behaviors were attributed to the magnitude of adhesion forces at the stack material interfaces and the mechanical strength of MNLs. </P>
Acceleration of poly(L-lactide) degradation by TiO2 nanoparticles in sunlight.
Lee, Jinyoung,Lee, Ju-Kyoung,Park, Bae Ho,Busnaina, Ahmed,Lee, Hea Yeon American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.10
<P>Poly(L-lactide) (PLA) is known to eventually be degraded into water and carbon dioxide by the microorganisms of the natural world. Titanium dioxide (TiO2) has been used in the biomedical and bioengineering fields as a photocatalyst. The purpose of this research project is to evaluate the influence of TiO2 added to PLA films both before and after irradiation of the films with sunlight. The PLA-TiO2 films were prepared by the addition of TiO2 (size: > 100 nm) nanoparticles to PLA. The surface changes of the PLA film were investigated before and after the films were exposed to sunlight. Tiny holes were observed in the PLA film without TiO2 nanoparticles after irradiation with sunlight, whereas large pits formed in the PLA-TiO2 films. It is suggested that PLA was degraded by the ultraviolet rays in sunlight. In addition, the decomposition speed was thought to be enhanced by the addition of TiO2, which acted as a catalyst.</P>
전도성을 가지는 하이브리드 Ti<sub>2</sub>AlN 세라믹 복합체의 마이크로 방전드릴링에서 가공성 평가
허재영,정영근,강명창,Heo, Jae-Young,Jeong, Young-Keun,Kang, Myung-Chang,Busnaina, Ahmed 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.4
$Ti_2AlN$ composites are a laminated compounds that posses unique combination of typical ceramic properties and typical metallic(Ti alloy) properties. In this paper, the powder synthesis, SPS sintering, composite characteristics and machinability evaluation were systematically conducted. The random orientation characteristics and good crystallization of the $Ti_2AlN$ phase are observed. The electrical and thermal conductivity of $Ti_2AlN$ is higher than that of Ti6242 alloy. A machining test was carried out to compare the effect of material properties on micro electrical discharge drilling for $Ti_2AlN$ composite and Ti6242 alloy. Also, mixture table as a kind of tables of orthogonal arrays was used to know how parameter is main effective at experimental design. Consequently, hybrid $Ti_2AlN$ ceramic composites showed good machining time and electrode wear shape under micro ED-drilling process. This conclusion proves the feasibility in the industrial applications.