Poster Session:  October 24,  5:30 - 6:30  in front of Salons (Student Activity Center)

P1:  Synthesis of Platinum Nanoparticles

M. Marín-Almazo¹, Luis Rendón², and M. José-Yacamán<sup>3

1</sup> Instituto Nacional de Investigaciones Nucleares, Km. 36.5 Carretera México-Toluca, C.P. 52045 Salazar, Edo. de México, México.² Instituto de Física, Universidad Nacional Autónoma de México, Apdo. Postal 20-364, Del. Álvaro Obregón, 01000 México, D.F., México.³ Texas Materials Institute and Department of Chemical Engineering University of Texas at Austin, Austin, Texas. 78712-1062, USA
 

The synthesis of nanoparticles of different materials has great importance because of all the possible applications in nanotechnology, from electronics, magnetism, photonic devices to catalysts. These potentialities are mainly due to the quantum size effect, which is derived from the dramatic reduction of the number of free electrons in particles in the range 1-10 nm.

The chemical synthesis methods appear to offer many advantages over other methods in the controlled production of nanoparticles. The use of hydrotriorganoborates as reducing agents leads to colloidal transition metals in organic phases. In the present work we display the growth of platinum nanoparticles stabilized with a 1-dodecanethiol using the reducing agent lithium trirthylborohydride in tetrahydrofuran. It was observed that particle growth likely occurs in the size range from 2 to 4 nm. It was also observed that most of the particles show an fcc structure.

The observation of high resolution electron microscopy (HREM) images with an image processor and the corresponding FFT of the images are discussed. These studies show small particles produced by a colloidal method and reveal the structural characteristics of obtained samples.

Contact Author: Presenting Author:  Margarita Marín-Almazo
Organization: ININ

Instituto Nacional de Investigaciones Nucleares,
Km. 36.5 Carretera México-Toluca,
C.P. 52045 Salazar, Edo. de México, México.

Phone: 53-29-72-00 Ext. 2893
Fax: 53-29-72-40
E-mail: mma@nuclear.inin.mx
 

P2:  Nanoscale Chemistry for Environmental Remediation in Soil and Groundwater

Bianca W. Hydutsky, Bettina Schrick, Benjamin Beckerman, Elizabeth B. Mack, and Thomas E. Mallouk
Department of Chemistry, The Pennsylvania State University, University Park, PA 16802

Kaiti Liao, Kiran Gill, Christopher Nelson, and Harch Gill
PARS Environmental, Inc., 6 S. Gold Dr., Robbinsville, NJ  08691

Soil and groundwater contain a legacy of chemical substances - including halogenated organics and toxic metal ions - from industrial and agricultural processes.  Several years ago, scientists at the University of Waterloo developed a remediation method based on zero-valent iron, which has since been investigated by numerous researchers.  Chemical reduction by iron converts halogen-containing compounds to relatively innocuous hydrocarbons, and reducible metal ions (Cr(VI), Pb(II), Hg(II), As(V), Tc(VII)) to less soluble forms.  Still, the inaccessibility of the deep subsurface and the large volume of soil or water affected by a chemical spill make the clean up of contaminants both costly and technically daunting.  To address this problem, we have developed chemical "delivery vehicles" that transport metal nanoparticles through soils.  This talk describes the design of these supported metal nanoparticles, their interaction with the complex matrix of natural soils, and the mechanism of their reactions with halocarbons and toxic metal ions.

 

P3:  Resists for Sub-100 nm Patterning at 193 nm Exposure

Kenneth E. Gonsalves, Nathan D. Jarnagin and Minxing Wang
Department of Chemistry
University of North Carolina
Charlotte, NC 28223

We are developing methacrylate based resists suitable for 193 nm exposure for sub-100 nm patterning. These resists feature a photoacid generator bound to the polymer chain. It has been reported that photoacid generators have limited compatibility with the chemically amplified resist matrix that leads to phase separation, non-uniform acid distribution and migration during the baking process. To alleviate these problems, it is proposed that PAG units be incorporated in the resist chain, rather than blending monomeric PAG with the resist polymer. Also, these methacrylate resists incorporate the lactone group for substrate adhesion, and the bulky ethyl adamantyl protecting group for improved lithographic performance.

The polymer bound PAG resists, poly (u-butyrolactone methacrylate-co-2-ethyl-2-adamantyl methacrylate-co-PAG), were synthesized using free radical polymerization. The average molecular weights of the polymers were 1700-2000 and the polydispersities were around 1.7. The glass transition temperatures were 112˚ to 137˚.

PAG incorporated resists, as well as PAG blended resists were exposed using the ASML 5500/9xx optical lithography system, with 0.63 NA. Exposed wafers were evaluated using SEM. The blended resists provided 140 nm isolated lines, while the PAG incorporated resists provided 80 nm isolated lines and 110 nm line/space features. Analysis shows polymers with the highest amount of EAMA, and 8% incorporated PAG provided the best features. The associated photospeed for the 110 nm line space features was 4.25 mJ/cm2. Faster photospeed provides system advantages such as less thermal management of the mirrors and mask, and potentially increased component lifetimes. Analogous resists are currently being developed for EUV.

Key Word: phenylmethacrylate dimethylsulfoniumtriflate photoacidgenerator (PAG)

Support of Intel Corp OR & SEMATECH INT TX is acknowledged. User Facilities at the NSF Nanofabrication Center at NCSU are also acknowledged
 

P4:  Nanoparticles from Diesel engine carbon soot by electron microscopy techniques

M.G. Cisniega-Rojas¹ , M.Marín – Almazo¹ , Y. Falcon.²
¹Instituto Nacional de Investigaciones Nucleares. Apdo. postal: 18-1027, México D.F.,C.P. 11801. ² Uam-Azc., Ave. San pablo 180, Col. Reynosa Tamaulipas. C.P. 02200 Mexico

Carbon soot is a scourge. It looks and smells bad, and it is a health hazard. It is also wasted energy, which is a paradox since soot forms in a diesel engine , where you will expect complete combustion and no waste.  The causes of soot production are among the most important unresolved problems of combustion science .

This paper outlines how electron microscopy methods are being used to complement the carbon soot analysis methods. Information is provided to illustrate how morphology and individual particle chemistry data offer the potential to provide greater insight into the concentrations and sources of organic and elemental carbon species.

Carbon soot is an agglomeration of particles impregnated with “tar” formed in the incomplete combustion of diesel engine. Carbonaceous material are present in high concentrations in the streets of Mexico City ( 1.5 – 30 µg/m³ ). Soot particles form aggregates of primary spheres of 15 to 35 nm in a chain structure, the chains can agglomerate and form particles up to a few micrometers. The actual structure may influence processes such as coagulation and condensation which depend on particle dimension . When soot particles are aged , they are internally mixed with other organic compounds by coagulation , condensation and in a cloud processing. This ageing processes are still in research, as is quite difficult to estimate the life time of the soot particles. Other important processes involving carbon particles are also interactions with: hν, O³, SO², NOx . Organic carbon (OC) can be directly emitted during combustion processes such as those ocurring in non catalyts vehicles in diesel engines. It can be formed also by transfer of mass to the aerosol phase of low volatility products that can result from oxidation of organic gases due to Secondary Organic aerosols. Although Primary Organic aerosols usually dominate, Secondary Organic aerosols are an important contribution to the atmospheric organic carbon sink. Also non-antropogenic sources of organic material are relevant. In fact, α – pirene, β- pirene and monoterpenes emitted from the forest, can contribute significantly to aerosol in presence of dense trees coverage. The concentration from OC ranges are 5 µg (C) m³ at the nuclear center to 4 – 35 µg (C) m³. In Mexico City located 35 km from south east from the Nuclear Center.


Contact Author: Presenting author: María Guadalupe Cisniega
Organization: Instituto Nacional de Investigaciones Nucleares (ININ).
Km. 36.5 Carret. Mexico – Toluca.
C.P. 52045 Salazar, edo. De Mexico, Mexico.

Ph: 55 53 29 73 67
Fax: 53 29 72 40
E-mail: gc@nuclear.inin.mx
 

P5:  Understanding and Manipulating Surface Chemsitry at the Atomic Scale

Charles Sykes

Department of Chemistry
Pearson Chemistry Laboratory
Tufts University
Medford, MA 02155

charles.sykes@tufts.edu

Our work is aimed at understanding how atoms and molecules interact with surfaces, and building novel nanoscale structures by controlling these interactions. We use Low-Temperature Scanning Tunneling Microscopy (LT-STM), a very powerful surface science technique, which enables direct visualization and control over single atoms and molecules on conductive surfaces. We will study how molecules interact with the electron density inside confined systems (Quantum Corrals) and investigate how we can tailor these interactions in order to spontaneously self-assemble molecules into new surface architectures.

Also, STM will be used to investigate the surface chemistry of model chiral systems with the aim of understanding mechanism by relating chemical reactivity to the atomic scale structure of these potentially important industrial catalysts.

P6:  Nanolithography and Probing of  Electronic Properties of Single Walled Carbon Nanotubes as Field Effect Transistor

H.Chaturvedi¹, J.C.Poler^1,2

¹Department of Physics and Optical Science,UNC,Charlotte,Charlotte,NC

²Department of Chemistry,UNC,Charlotte,Charlotte,NC

Carbon nanotubes and nanowires are important materials for new nanotechnology devices and sensors.  Future opotoelectronic devices can be made from assemblies of nanostructured materials. We have fabricated back-gated single walled carbon nanotube field effect transistors. .  Devices were processed with standard optical lithography and high resolution e-beam lithography.  These devices can potentially be used for fabricating future Optoelectronic devices.

 

 The Nanotubes were dispersed and ultra-Sonicated to obtain individual SWNT. These SWNT then form the gate channel of the fabricated field effect transistor. Our preliminary electronic results of the device will be presented. Also, our acquired capabilities in Nano-alignment and Nano-manipulation will be presented along with Atomic force Microscopy of Single Walled Carbon Nanotubes. We are using these devices to study charge injection into the nanotubes and the resultant effect on the tube’s transport properties

P7:  Light Transmission through a Set of One-dimensional Dielectric Slabs

Wei Guo

Department of Physics and Optical Science

University of North Carolina - Charlotte

Charlotte, NC 28223

Light transmission through identical dielectric slabs whose distribution is arbitrary is formulated in the one-dimensional space using the theory of multiple scattering. Two specific cases are considered after the light transmittance is derived. First, the slabs are assumed to be regularly arranged with a common spacing, so that they form a finite photonic crystal. It is revealed that bandgaps are caused by multiple scattering of light within and between the slabs, and that the more slabs in the crystal, the more bandgaps appear. Second, the defects in the crystal are mimicked via randomly shifting some slabs away from their regular locations. It is then found when more defects are presents some bandgaps in the crystal can be removed. The defects also effectively reduce the crystal into a discrete random medium, but, not as in continuous one-dimensional random media, resonance transmission occurs in the present case at fixed frequencies.

P8: Characterization , Imaging, and Degradation Studies of Quantum Dots in Aquatic Organisms

Sireesha Khambhammettu¹, Kenneth E. Gonsalves², Amy H. Ringwood³

University of North Carolina at Charlotte, NC-28223

1. Department of Mechanical Engineering

2. Department of Chemistry

3. Department of Biology

Nanoparticles may be introduced into aquatic environments during production processes and also as a result of release following their use in electronic and biological applications.  The purpose of these studies was to characterize and image the behavior of quantum dots (QD) in seawater, and the accumulation of and toxicity to potential biological receptors. For these studies, oyster embryos as well as isolated hepatopancreatic cells were used.   Fluorescent Confocal microscopy, electron diffraction and electron microscopy were used to determine the size distribution and composition of quantum dots and also to verify the accumulation and cellular localization inside these cells.

Furthermore, there are natural differences in environmental factors that may affect the degradation rates of QD’s, including salinity and pH conditions, as well as seasonal differences in temperature.  To determine the effects of salinity on degradation rates,  non functionalized QD’s composed of a Cd/Se core surrounded by layers of Zn (Evident Technologies) were added to 0.22 filtered seawater samples of different salinities (10, 20, and 30 parts per thousand), and the changes in emission spectra over time were determined; likewise, the potential effects of pH were evaluated under a range of environmentally realistic pH conditions (e.g. pH 7, 7.5, and 8); and the impacts of temperature (10, 20, and 30 degrees centigrade) were determined. These kinds of basic studies are essential for addressing the potential impacts of nano engineered particles on aquatic organisms.

 

P10:  Nanofabrication Using 193 nm Lithography at the Triangle National Lithography Center/NNIN

C. M. Osburn, J. O’Sullivan, D.G. Vellenga, and D.G. Yu

Triangle National Lithography Center

NCSU Nanofabrication Facility

Department of Electrical & Computer Engineering

North Carolina State University

Raleigh, NC 27695-7920

Leading-edge, optical photolithography facilities have been installed in the Triangle National Lithography Center (TNLC), which is part of the National Nanotechnology Infrastructure Network (NNIN). The ASML PAS 5500-950B 193 nm step and scan system can provide about 60 full-wafer exposures per hour on 6” substrates (wafers or glass).  The lithography process uses a 300 nm thick layer of acid-hardened resist (e.g. Rohm & Hass V41) on top of an 80 nm bottom anti-reflective coating (BARC) (e.g., Brewer Science AR29A-8).  After 18 mJ/cm² exposure, the chemically amplified resist is post-exposure baked for 90 sec at 120°C.  SEM metrology is used to verify pattern sizes and resist sidewall angles.   The scanner field size is 26 mm x 32 mm, making it possible to either expose a large area or, using a smaller field (e.g., 1 cm²),  to combine several (e.g., 6) pattern layers on one mask plate to dramatically reduce reticle-making costs.  Even without resist trimming, linewidths down to 80 nm and nano-dot arrays down to 130 nm have been demonstrated,  Resist trimming, under development now, is expected to reduce those sizes by as much as a factor of 4.  The TNLC, as well as the NCSU Nanofabrication Facility (NNF) are user facilities, where researchers from academia, industry, and government are welcome to come and use the equipment.  Exposures and processing can also be done for remote users.  Currently the scanner supports a variety of research programs in resist materials, CO₂-based processes, nano-particle drug delivery, optical systems, and advanced semiconductor technology.

 

Key Words: Nanolithography, Nanofabrication

 

Support of NSF under the National Nanotechnology Infrastructure Network is gratefully acknowledged

 

P11: Nano/Micro Fabrication of Novel Polymers for Tissue Engineering Applications

Y. Umar¹, C.E. Austin²,  M. Thiyagarajan¹, P.B. Nunes², C.R. Halberstadt², and K.E. Gonsalves¹*

¹Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC

²Department of General Surgery Research, Carolinas Medical Center, Charlotte, NC

Engineering functional tissues and organs successfully depends on the ability to control cell orientation and distribution. Materials used for such purposes have to be designed to facilitate cell distribution and eventually guide tissue regeneration in 3D.

Non-patterned cells are effectively not tissues. “Tissues require that cells be placed and hold precise places often with precise orientations”. Cell patterning is therefore very important for tissue engineering. The goal of this research is to develop a biocompatible, biostable chemically amplified bioresist, with which patterns can be generated without involving any harsh chemical treatment.

A combinatorial approach of polymer synthesis can be used to increase the number of available polymeric materials for any application and also to study the correlation between polymer structure, material property, and function. In this research, this approach was used in a limited manner, to synthesize and characterize the copolymers, 3-(t-butoxycarbonyl)-N-vinyl-2-pyrrolidone-co-methyl methacrylate, and t-butyl methacrylate-co- N-vinyl-2-pyrrolidone and a terpolymer of t-butyl methacrylate-co- N-vinyl-2-pyrrolidone-co- methyl methacrylate in different compositions. See scheme 1 below. Due to its hydrophilic and good biocompatibility character, N-vinyl-2-pyrrolidone was used in the polymer systems.

Photoresist solutions were prepared by dissolving a polymer and triarylsulfonium hexafluoroantimonate used as a photoacid generator in cyclohexanone. It was then spin-coated at 2000 rpm on a glass microscope slide and baked at 120^oC to remove the solvent. Exposures were done through two types of masks (25µm line by 25µm space and 25µm line by 50µm space) on a Contact Mask Printer. The exposed samples were immediately baked at 120^oC on a hot plate and developed in a dilute aqueous base solution (2.6 x 10^-3M) for 60s to reveal the patterns as shown in Figure 1.

Rat Fibroblast cells were cultured on patterned surfaces using DMEM containing 10% FBS. Glass slides with patterns were rinsed with sterile Phosphate Buffered Saline (PBS) several times and placed in a 1-well Lab-Tek chamber coverglass, which was precoated with poly (2-hydroxyehtyl methacrylate). Cells were washed with serum-free medium before seeding onto the samples at a density of 1.0 x 10⁵ cells/well.  Nonpatterned scaffolds were used as a control. After seeding, fibroblast cells were cultured on the materials at 37^oC in 8% CO₂ atmosphere for various periods of time. At the end of each incubation period, the samples were rinsed with PBS to remove nonattached cells. It was observed that on the patterned polymer substrate, cells were strongly aligned, elongated, and became bipolar along the engineered grooves (Figure 1 c & d). However, it appears that the 50µm space may prevent crossover of cells between the channels (1d).  These results imply one potential application of using this technique in combination with 3-D bioresorbable constructs to produce an oriented tissue-like structure from fibroblasts, which will have desirable mechanical strength and flexibility similar to that of normal tissue. AFM studies indicated that the developed regions consisted of grooves less than 250 nm in depth, providing contact guidance for cell alignment in addition to their hydrophilic character.

Finally 3-D porous scaffolds were attempted using PLA, PCL, and PLGA. Resist solutions of poly (t-BOC-NVP-co-MMA) were used to modify their surfaces. Cell culture studies were performed to illustrate the varying cell adhering properties of several different polymer surfaces.

 

P 12:  EUV Resists for sub 90 nm patterning- Moore’s law and the ITRS roadmap!

Muthiah Thiyagarajan and Kenneth E. Gonsalves,^a) 

Polymer Chemistry Nanotechnology Laboratory, Cameron Applied Research Center and Department of Chemistry, Center for Optoelectronics and Optical Communications, University of North Carolina, Charlotte, North Carolina 28223

Kim Dean

SEMATECH, 2706 Montopolis Drive Austin, Texas 78741

^a) Electronic mail: kegonsal@uncc.edu

            Extreme Ultraviolet (EUV) lithography at wavelength of 13.4 nm has emerged as a promising candidate to meet the resolution requirements of the microelectronics industry for the production of dense features with critical dimensions for the 45 nm technology node and beyond. In addition to developing the exposure tools themselves, significant challenges remain in developing photoresist materials with all of the required imaging properties. At the 45nm technology node, the sensitivity of a resist must be approximately 10mJ/cm2 or less and patterned features must exhibit a line edge roughness (LER) of less than 5 nm. In general the absorbance of hydrocarbon polymers containing aromatic rings is smaller than those of the hydrocarbon polymers. The presence of aromatic rings is also known to improve the etch resistance of a polymer.  It is known that the LER of the resist patterns is adversely influenced by postexposure bake (PEB) and by resist development. LER refers to interface roughness (IR) of the sidewalls projected onto the substrate plane, rather than two-dimensional IR of the sidewall interface. So reducing LER is indispensable for nanolithography. Roughening occurs due to factors related to the nonuniformity of polymers structures at the molecular level, such as oligomer components, polymer aggregates and phase separation structures and those related to statistical variations in photochemical events . It has also been found that size of aggregates depends on both molecular weight of a resist polymer  and its structure. In our approach, the photoacid generator was incorporated in the main chain of the polymer to enhance lithographic properties such as photospeed and LER.

            A polymer bound PAG resists, poly (HOST-co-EAMA-co-PAG1) and poly (HOST-co-EAMA-co-PAG2) has been synthesized and evaluated as potential components of EUV resist materials with enhanced lithographic properties such as photospeed and LER. The polymer bound PAG resist exhibited faster photospeed and less LER than the corresponding blend PAG resists, poly (HOST-co-EAMA) blend PAG3(Tf) and poly (HOST-co-EAMA)blend PAG4(Nf). These results imply that this novel resist has advantages over conventional resists and should be further explored for application in EUV lithography. Furthermore, use of different counter anions such as triflate and nonaflate influences the lithographic performance. Sub-100nm features were obtained with enhanced lithographic performance using EUV exposure.

 

P13:  Application of Amphiphilic Polymers for Gene Delivery

T. Doran¹, K. Gonsalves², C. Yengo³, Q. Lu¹

1. MDA/ALS Center, Cannon Research Center, Carolinas Medical Center, Charlotte, NC
2. Department of Chemistry, UNC Charlotte, Charlotte, NC
3. Department of Biology, UNC Charlotte, Charlotte, NC

Non ionic copolymers consisting of polypropylene glycol (hydrophobic) and polyethylene glycol (hydrophilic) in a triblock configuration hold a great potential for gene and nucleic acid delivery. They are easily synthesized and manipulated to produce polymers that vary widely in their physical properties. The number of blocks in each of the segments can be varied to produce a wide array of polymers with highly diverse physical properties and potential interactions with target transgenes or oligonucleotides.  The efficiency of gene delivery with amphiphilic polymers can be further improved by incorporating functional groups critical for gene delivery into cells which will induce DNA encapsulation and protection. We have recently examined several commercially available triblock polymers for their interaction with nucleic acid and effects on cell survival and gene delivery. Preliminary studies found that polymers improve efficiency of gene delivery in vivo and in vitro differentially. We were also able to demonstrate that polymers bind to nucleic acid differentially. Our results indicate that systematic investigation into the interaction between polymer and nucleic acid in connection with the effect of polymers on gene delivery could reveal the relationship between structure and function and lead to new designs of polymers that should increase delivery efficiency, provide specific targeting of cells, and reduce toxicity.

P14:  Novel Nanopatterned Surfaces to Investigate for Optimal SERS Enhancement

Tres Brazell¹, E. Charles Sykes², Mahnaz El-Kouedi¹

¹Department of Chemistry and ²Center for Optoelectronics and Optical Communications, University of North Carolina at Charlotte, Charlotte, NC, 28223

We will present the fabrication and characterization of novel nanopatterned surfaces that are employed as SERS substrates.  Commercial Reynolds™ aluminum foil is anodized to grow aluminum oxide. The growth of aluminum oxide on the surface creates nano-indentions or pores on the metal surface. The aluminum oxide is removed or etched using Cr(VI)oxide for several hours.  After etching, the surface of the anodized aluminum is now covered with indentations ranging in size from 20 to 120 nm, as dependent on controlled growth conditions.  By simply varying one parameter, the anodization voltage, one can test a wide range of pore spacings to determine optimal SERS enhancement. Aluminum has its plasmon resonance in the UV region.  Silver or gold can be electrodeposited onto the surface to shift the plasmon resonance into the visible region were Raman spectra can be collected.  An Atomic Force Microscope is employed to visualize the aluminum nanopatterned surface.  The AFM is also used to verify that enough Ag or Au has been deposited to conserve the overall topography of the nanopattern surface.  P-NDMA is adsorbed onto the Nanopatterned surface, and its SERS enhancement is investigated using a MicroRaman Spectrometer. Nanopatterned surfaces provide advantages in that they can be fabricated rapidly at low costs and exhibit a high level of homogeneity.  This allows us to fabricate a wide range of configurations to test for optimum SERS enhancement. 

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