Nicholas Pinto - US grants

With this award from the Major Research Instrumentation (MRI) Program, the Department of Chemistry at the University of Puerto Rico in Humacao will acquire a 300 MHz nuclear magnetic resonance (NMR) Spectrometer. This equipment will enable researchers to carry out studies on a) structural characterization of organometallic intermediates; b) enzyme mechanisms in organic solutions; c) solution-state dynamics for semiquinones in phospholipid membranes; d) kinetics of photochemical degradation of membranes by radical peroxidation; e) structure-function relationships of molecules of biological or pharmaceutical interest; and f) polymer structure.

Nuclear Magnetic Resonance (NMR) spectroscopy is the most powerful tool available to chemists for the elucidation of the structure of molecules. It is used to identify unknown substances, to characterize specific arrangements of atoms within molecules, and to study the dynamics of interactions between molecules in solution. Access to state-of-the-art NMR spectrometers is essential to chemists who are carrying out frontier research. The results from these NMR studies will have an impact in a number of areas including biochemistry.

This proposal presents a simple technique to controllably and reproducibly produce ultrafine fibers of conducting polymers. Many factors that control fiber diameter (like solvent viscosity) using this technique (electrospinning) will be investigated so that fibers with average diameters < 100 nm (1 nm = 10 -9 m) can be prepared. Electrospinning involves a high voltage source, a metal cathode collector and a glass pipette with the polymer solution to be electrospun. Single fibers will be captured on heavily doped silicon oxide coated wafers. The surface morphology will be studied with an optical microscope, a scanning electron microscope, a transmission electron microscope and an atomic force microscope. Fiber diameters and possible polymer chain alignment will be studied using these methods. Single fibers will also be characterized electrically via dc and ac conductivity measurements as a function of temperature. The PI's will study how the conduction mechanisms in these nanofibers differ from that in the bulk and could provide insights into the importance of interchain coupling that lead to charge delocalization. Finally, the fibers will be studied to check if the dc conductivity can be affected by applying a voltage to the heavily doped silicon. The purpose is to explore the possibility of fabricating nanodevices based on field effects, like nanoelectronic p.n junctions, Schottky junctions or field effect transistors (FET's).
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This project in materials research is directed at helping underrepresented students in academia to participate in scientific research during their undergraduate years. The equipment requested in this proposal will strengthen the institutional infrastructure and also have a broader impact of improving the research facilities on the South-East part of the island.

This award from the Instrumentation for Materials Research program provides funds to the University of Puerto Rico at Humacao, to purchase two instruments, a high power optical microscope with image processing capability and a semiconductor analyzer. The instruments will be used in nanoscience related research and training. The first project is the fabrication and electrical characterization of conducting polymer nanofibers using a simple electrospinning technique. In this method, the polymer dissolved in an appropriate solvent is placed in a hypodermic needle. By applying a high voltage to the needle, the polymer solution is forced out from the needle in the form of a jet, and as the solvent evaporates, ultra fine fibers of the polymer can be generated. The second project is the fabrication of carbon nanotubes using chemical vapor deposition (CVD) techniques. The nanofibers and nanotubes will be electrically connected in a field effect transistor configuration. The purpose is to be able to fabricate electronic devices. The optical microscope will be used in selecting good samples for characterization and to study electro chromic effects in the polymer nanofibers in-situ while there is an external current flowing through the fiber. Electro chromic effects on bulk conducting polymers have been done in the past but not in nanofibers. The instruments will also be used in Senior Lab for specialized experiments related to nanotechnology. The instruments are of the multi-user type and will enhance research collaboration with the Department of Physics and Electronics and the Biology Department. The acquisition will strengthen the undergraduate program in Physics and Electronics at the University and the research and education program in the Southeast part of the island

This award from the Instrumentation for Materials Research program supports the University of Puerto Rico at Humacao, with the acquisition a high power optical microscope with image processing capability and a semiconductor analyzer. The instruments will be used in nanoscience related research and training. The first project is the fabrication and electrical characterization of conducting polymer nanofibers. The second project is the fabrication of carbon nanotubes using chemical vapor deposition (CVD) techniques. The purpose is to be able to fabricate electronic devices. The optical microscope will be used in selecting good samples for characterization and also to study electro chromic effects in the polymer nanofibers in-situ with electric current flowing through the fiber. Electro chromic effects on bulk conducting polymers have been done in the past but not in nanofibers. The instruments will also be used in Senior Lab for specialized experiments related to nanotechnology. The instruments will enhance research collaboration with the Department of Physics and Electronics and the Biology Department. The acquisition will strengthen the undergraduate program in Physics and Electronics at the University and the research and education program in the South-East part of the island

This Nanotechnology in Undergraduate Education (NUE) award to the University of Puerto Rico at Humacao supports Dr. Nicholas Pinto, Dr. Claudio Guerra and Mr. Juan Gonzalez, Department of Physics and Electronics, to introduce new experiments into the undergraduate curriculum. Both the pedagogical theoretical concepts and modified experiments based on recently discovered techniques in the field of nanoscience, technology and engineering will be incorporated. The topics to be discussed fall in the fields of Physics, Chemistry, Biology and Electrical Engineering and are thus truly interdisciplinary.

New experiments related to the latest developments in nanotechnology, science and engineering will be included as part of the undergraduate curriculum. The intellectual scope of this proposal is that it will train students early in their careers in the field of nanotechnology. Also, opportunities to conduct research level experiments while enrolled in a core course is also proposed and this will give the students a flavor of how research is conducted together with the ups and downs in doing experimental research.

The proposed projects will enhance intradepartmental collaboration which is vital for a small Department like that at UPR-Humacao to stay competitive as an undergraduate institution in the areas of research and education. All of the experiments proposed will lie within the intellectual grasp of undergraduates. This has the broader impact of having a strong influence on the students desire to pursue higher education. Finally, having a strong research and teaching base at UPR-Humacao will have a broader impact on undergraduate education in the South-East part of the island in addition to increasing the number of underrepresented students in academic and research environments dedicated to nanoscience.

The proposal for this award was received in response to the Nanoscale Science and Engineering Education announcement, NSF 03-044, category NUE and was jointly funded by the Division of Engineering Education and Centers (EEC) in the Directorate for Engineering and the Division of Materials Research (DMR) in the Directorate for Mathematical and Physical Sciences (MPS),

This project began three years ago with NSF funding for the preparation of conducting polymer nanofibers, for device fabrication based on these nanofibers, and for motivating undergraduate students to pursue graduate degrees in science and engineering. The nanofibers were fabricated using the electrospinning technique. In this renewal proposal, we will extend the past work done on device fabrication based on polymer nanofibers and also include the use of the Atomic Force Microscope (AFM) to probe at the nanoscale level, the charge transport properties of these conducting polymer nanofibers. Polymer nanofibers will also be produced using the interfacial polymerization technique. Crossed polymer nanofibers will also be studied in order to understand the electrical properties of the resulting nanojunction, and how to join nanofibers together to form multiterminal devices and ultimately complex circuits.

The intellectual merit of this proposal is the ease with which nanofibers of conducting polymers can be prepared using the electrospinning technique or the interfacial polymerization technique as compared to other complex methods used to prepare for example carbon nanotubes. The processing and fabrication of devices based on conducting polymers is relatively easy and cheap. This has the potential of being able to fabricate large surface area flexible electronic devices. We will also use a biased AFM tip to locally probe (local gating) the conduction along the length of the polymer nanofiber in order to study the role of defects on electrical conduction and hence be able to shed additional light on the metallic state in conducting polymers. The use of the AFM as an active instrument in the electrical characterization of individual polymer nanofibers and crossed nanofibers has not been studied in detail as compared to carbon nanotubes and so the local gating effect proposed with the AFM is could lead to new results and suggest new experimental methods (using the AFM) of studying conducting polymers.

The broader impact of this proposal is significant. All of the experiments proposed are within the intellectual grasp of undergraduate students and are also aimed at motivating the students to pursue graduate studies in science and engineering. Modified experiments based on the proposed research are planned to be included into the Intermediate Laboratory course that the PI has taught for the last five years thus integrating research and education. The instrument requested in this proposal will strengthen the institutional infrastructure, increase faculty collaboration and also have a broader impact of improving the research facilities on the South-East part of the island. This proposal will also increase the number of undergraduate students that participate in scientific research and who are underrepresented in the fields of science and engineering. Finally, the PI and his Departmental colleagues have written a proposal to the UPR board of directors to begin a new Master's program in Materials Science. This program will be unique on the island. By improving the research infrastructure and enhancing research collaboration within the Department, this proposal will help us reach a critical mass of faculty that are active in research and hence boost our chances of having a successful MS program in Materials Science.

TECHNICAL SUMMARY: This award will expand the current work on polymers, which entails the fabrication of conducting and non-conducting polymer nanofibers via electrospinning or by the interfacial polymerization technique. Devices and sensors based on the use of these polymer nanofibers will be fabricated and tested. In addition, charge transport at nanofiber junctions, viz. junctions formed when two nanofibers overlap will be studied. Nanofibers of any polymer have a large surface to volume ratio. Because of their large surface area, they have the potential to be used in the fabrication of low power, supersensitive and fast response sensors. A range of experiments have been proposed using different instruments that will help in the complete characterization of the electronic devices and sensors using electrospun polymer nanofibers and of crossed polymer nanofibers. The approach to making polymer nanofibers via electrospinning is unique as it does not use templates or other cumbersome methods. The award encompasses polymer science, nanoscience and electronics and is multidisciplinary giving students a sound and direct research experience that will help them in graduate school and in job searches.

NON-TECHNICAL SUMMARY: Devices and sensors based on polymer nanofibers will be fabricated and tested. Since nanofibers have a large surface area they are very sensitive to the environment making it possible to detect minute amounts of gases very quickly. The small size of the devices and sensors imply comparatively low operating voltages and thus have the advantage of low power consumption. In addition, polymers are light weight, flexible and cheap to manufacture, hence this award has economic advantages. This award is directed at helping undergraduates with the goal of motivating them toward graduate school. Some of the experiments will be modified to be included into the course curriculum thereby integrating research and education. Finally, the majority of the students affected are minority students and this proposal will enhance their participation in the scientific arena.

TECHNICAL SUMMMARY:

This grant will expand research on conducting and semiconducting polymers and to include ferroelectric polymers and ceramic metal oxides. A simple technique called electrospinning will be used to prepare nanofibers of conducting/semiconducting/ferroelectric polymers and metal oxides and to use them as the active material in the fabrication of devices and sensors. Due to their small dimensions, nanofibers have a large surface to volume ratio and hence they have the potential to be used in the fabrication of low power consumption devices and supersensitive and rapid response sensors. Individual nanofibers that possess both semiconducting and ferroelectric properties are inherently multifunctional and will be used in non-volatile memory field effect transistors. The intellectual merit of this proposal also includes finding new ways of combining these materials that possess very different electronic, mechanical and optical properties, then using them in the form of nanofibers that have a large aspect ratio and even larger surface to volume ratio to fabricate and test devices and sensors. A range of experiments has been proposed using electrospun polymer and metal oxide nanofibers, and thin films and to study charge transport in crossed polymer nanofibers. The approach presented to making polymer nanofibers via electrospinning is unique and differs from the research of others who typically use templates or other complex methods. The proposed research includes polymer science, ceramics, physics, nanoscience and electronics and is multidisciplinary, giving students a sound and direct research experience that will help them in graduate school and in job searches.

NON-TECHNICAL SUMMARY:

This research will expose undergraduate students to various branches of science and engineering. The proposed experiments are within the intellectual grasp of undergraduate students. All of the students will be trained in the scientific method and will be motivated to pursue graduate studies in science and engineering by providing them with real opportunities to participate in scientific research. Modified experiments based on the proposed research are planned to be included into the Intermediate Laboratory course that the PI has taught for the last eight years, thereby integrating research and education. The instruments requested in this proposal will strengthen the institutional infrastructure, increase faculty collaboration and also have a broader impact of improving the research facilities in the southeastern region of the Island. New results will be published in a timely manner and an up-to-date web page will be maintained, thereby broadening the dissemination of results from this proposal. The University of Puerto Rico at Humacao is a minority serving institution. This proposal will therefore increase the number of undergraduate students that participate in scientific research and who are underrepresented in the fields of science and engineering.

TECHNICAL SUMMARY

In this project electrospinning will be used to prepare nanofibers of electroactive polymers and their composite blends. The PI's approach to making polymer nanofibers via electrospinning differs from common approaches that typically use templates or other complex methods. The electro-active polymers include those that exhibit conducting, semiconducting and ferroelectric properties at room temperature. The fundamental charge transport mechanisms and charge storage in these polymer nanofibers will be investigated via temperature-dependent conductivity and dielectric permittivity measurements. Nanofibers naturally possess a confined environment for charge flow, thus the presence of defects will lead to changes in charge transport and provide a handle on how best to prepare defect-free nanofibers. A better understanding of charge transport and charge storage in conducting, semiconducting and ferroelectric polymers as proposed here might then be exported to other macromolecules that exhibit similar physical properties. The composite nanofibers retain the properties of the individual components and are thus inherently capable of being used in devices that are multifunctional and hence more versatile. Modified experiments based on the proposed research will be included into the senior laboratory course for undergraduates, thereby integrating research and education.



NON-TECHNICAL SUMMARY

The principal investigator (PI) proposes to prepare fibers of electrically active polymers having a diameter roughly one-one thousandth that of a human hair using an inexpensive fiber-spinning technique called electrospinning. The materials to be studied are special polymers that are individually capable of carrying a current or storing charge while at the same time are light in weight, flexible, and inexpensive to manufacture. By combining these polymers as composites, the current carrying capacity of one together with the charge storage capacity of the other will lead to novel materials that are more versatile. Fabricating nanofibers of such composite materials is new and unexplored, and the PI's ultimate goal is to make devices and sensors with superior properties. Devices fabricated from nanofibers are also expected to be small in size and to consume less power. The proposed research is multidisciplinary across polymer science, physics, nanoscience, and electronics, thus giving students a sound and direct research experience that will train them in the scientific method and prepare them to be future scientists and engineers. This proposal will also increase the number of undergraduate students participating in scientific research from groups currently underrepresented in the fields of science and engineering and will extend the PI's outreach to include an international collaboration.