Paul E. Laibinis - US grants

Abstract - Laibinis - 9413894 Microwave-based heating of chemical systems holds the promise of increased energy efficiency and superior temperature control over chemical processes. Particular advantages of microwave heating appear to be the abilities to increase reaction rates (by seemingly superheating the reaction medium) and to heat systems uniformly (by applying heat from within a vessel rather than by conduction from its walls). In this work, surfactants will be used to structure fluids as a means for enhancing the desirable chemical processing features of microwave-based heating. The abilities to control and structure the polarity of a liquid phase through the formation of micellar domains are expected to yield new methods for tailoring and optimizing the heating liquid phases by incident microwaves. The methods will produce environmental and processing benefits by reducing energy consumption in the heating of chemical streams and by producing uniform heating profiles within reaction vessels. This latter ability will avoid exposing reaction mixtures to the elevated and spatially variant temperatures that typically reduce reaction specificity and lead to enhanced material decomposition and waste products. It is the goal of this work to develop new processing methods for controlling the heating of chemical systems by microwaves, in particular, for non-polar chemical phases where the use of microwave radiation for heating has been ineffective. The strategy uses the abilities of self-assembled polymer and surfactant systems -- micelles, reverse micelles, vesicles, liposomes, etc. -- to produce specific isolated micro-domains of different polarities within a liquid continuum. The resulting polar and non-polar domains represent specific regions within the liquid that will absorb the incident microwave radiation differently, with the polar regions being responsible for efficient energy absorption and subsequent rapid thermal dissipation to the contacting non-polar phase. In these self-assembled systems, the dielectric properties, contents, sizes, and relative amounts of the individual domains can each be readily changed, and their manipulation should provide a controlled method for modifying the microwave absorbing characteristics of a liquid phase. Aqueous dispersions should allow for the efficient absorption of the incident microwave radiation and the use of frequencies (2.45 GHz) and hardware presently dedicated for microwave heating. From an industrial standpoint, an important aspect of the work is that the energy absorbing properties of reaction/solvent systems will be varied by straightforward chemical means and will not require changes to the microwave hardware.

ABSTRACT Paul Labinis MIT CTS-9500149 The Chemical Engineering Department at MIT request support to purchase a scanning probe microscope (SPM) with the capabilities to perform high resolution imaging of organic materials and surfaces. The SPM will provide the needed means to interrogate chemical and biochemical interactions at surfaces and to determine relationships between chemical processing, surface structure (composition, roughness, etc.), and surface properties. Its primary application will be to problems involving various organic surfaces, including molecular and multilayer films and fluorinated, polyionic and biocampatible polymers.

Author: vjohn at nsf18 Date: 7/20/98 10:17 AM Priority: Normal TO: adthomas Subject: abstract - 9817221 Green ------------------------------- Message Contents ------------------------------- Abstract Proposal No: 9817221 Proposal Type: EPA-NSF Joint Initiative, 1998 Principal Investigator: William Green Affiliation: Massachusetts Institute of Technology This grant is awarded through the Separations and Purification Program sub-element of the Interfacial, Transport and Separations Program of the Chemical and Transport Systems Division. The principal investigator is Dr. William Green at the Massachusetts Institute of Technology. New technology is developed to remove sulfur compounds from gasoline and fuel oils. Traditionally, sulfur removal is done through catalytic technologies using hydrodesulfurization catalysts. The alternate route studied here involves the selective binding of these compounds to functionalized magnetic particles. These functional moieties attached to the magnetic particles are either polymers and/or surfactants adsorbed onto the particle surface. Various schemes for the selective extraction of the sulfur compounds onto the particles are considered. The final objective is incorporation of the sulfur compounds into the adsorbed layers of the particles. The particles are then removed through a magnetic field gradient, regenerated and cycled back. This technology of sulfur removal could be extremely cost effective since it does not involve high temperature reaction or multiphase extraction. The application of such technology could result in a paradigm shift for the petroleum and fuel processing industries.

9871996 Bawendi This project combines expertise in Chemistry, Physics, Chemical Engineering, and Materials Science to synthesize, process and characterize self-assembled quantum dot based nanostructures. It integrates activities for creating nanocrystalline quantum dots, surface derivatization, self- assembly, and ultra-sensitive electronic measurements and spectroscopy, to explore the chemistry and physics of single and coupled nanocrystalline quantum dots. The investigators will develop control of spatial positioning of nanocrystallites on a nanometer scale. Proteins or oligonucleotides which self-assemble will be used as directing agents for the formation of nanostructures. Each of these biomolecules can be engineered to bind to a specific ligand on the surface of a nanocrystalline quantum dot. The biological system then serves as a template for the controlled positioning of quantum dots on a surface. Ultra- sensitive charge sensing methods will be used to probe the electronic structure of such quantum dots. These measurements will address both the energetics and the extent of delocalizaton of charges inside or localized on the surface of the quantum dots. Additionally, it is planned to spectroscopically characterize charged single quantum dots. The spectroscopic properties of nanocrystalline dots are expected to strongly depend on the number of charges present in the dot, analogous to the filling of atomic orbitals; this may lead to control over the interaction of photons with the nanostructures through adjustment of the charge density on the dots. Such a capability opens the possibility of using nanocrystalline quantum dots as building blocks for microphotonic devices. The interdisciplinary collaboration combining sensitive electronic measurements with the chemical control of the dots, their environment, and their spatial positioning may allow optimization of the chemistry of the self-assembled nanostructures and the observation of new physics of confine d electrons. %%% The project addresses basic research issues in a topical area of science and engineering having high technological relevance. The research will contribute new knowledge at a fundamental level to important aspects of electronic/photonic devices. The basic knowledge and understanding gained from the research is expected to contribute to improving the performance of advanced devices by providing a fundamental understanding and a basis for designing and producing improved materials, and materials combinations. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. Graduate students will be co-advised by the four investigators across the disciplines of Chemistry, Physics, Chemical Engineering, and Materials Science integrating research and education from an interdisciplinary perspective. This research grant is made under the Nanotechnology Initiative (NSF 98-20), and is co-funded by the MPS Office of Multidisciplinary Activities(OMA), the Division of Chemical and Transport Systems, and the Division of Materials Research. ***

The Nanogate is a mechanism that creates and precisely maintains nano-meter level channel openings. This is accomplished by anchoring a cantilever beam at one end, then pivoting about a fulcrum surface; this creates an opening between the beam and an anvil. As part of an NSF exploratory research grant, a prototype was constructed from simply machined parts. In the prototype, 1 micron edge displacement of a 50mm silicon wafer pivoted abound a 15mm diameter anvil resulted in a 50nm gap opening. A diamond turned Nickel plated aluminum structure with 10nm surface finish is currently made for testing; the resulting small annular gap from the new design will allow control of gas flow rates on the order of 1e-12 moles/sec. This research will further develop the Nanogate mechanism and use it to precisely meter molecular flows and study the physics of such flows.

This work will result in a new class of instrumentation tools which will enable fundamental experimentation of basic physical phenomena related to fluid flow in very small gaps. Examples of questions that may be answered are: (1)How do molecules behave when a single layer is pulled apart to create force/displacement data? and (2) Why does apparent viscosity increase when the gap gets smaller and how does the boundary behave when one fluid pushes another? The answers to these questions and the enabling instrumentation that are proposed to be developed will have profound influence on areas of high technological importance such as the life sciences, in particular biophysics and biochemistry, energy handling systems such as microengines and micropumps, and new, more accurate metrology/calibration procedures.

This grant supports the acquisition of a scanning electron spectroscopy for chemical analysis (ESCA) instrument for interface characterization of bio- , geo- and nanomaterials at Rice University. ESCA, also known as x-ray photoemission spectroscopy (XPS), is a powerful and versatile method for evaluating the surfaces of complex materials. The characterization of material interfaces is an important activity in much of materials research; for bio-, geo- and nanomaterials it is essential for developing new materials and understanding their properties. It is intrinsically a surface technique sensitive only to the top several angstroms of a sample, but with the appropriate conditions can be used to probe depths up to 20 nanometers. Several projects require depth profiling of atomic concentrations at surfaces while others need information about the nature of chemical bonding at interfaces. Still others are interested in chemical mapping of interfaces at the tens of micron level. Nearly all participants must be able to measure the atomic composition of surfaces, and the ability to analyze multiple samples quickly and consistently is of particular value. ESCA can measure the relative amounts of carbon and nitrogen at a surface and can determine whether the carbon is graphitic or bound to nitrogen. ESCA works by bombarding surfaces with a controlled X-ray source and resolving the kinetic energy of the photoemitted electrons; these energies are then used to identify surface atoms and their chemical state. Both the relative amounts of atomic species at surfaces, as well as their chemical environment can be deduced from XPS data. Though samples are evaluated under vacuum conditions, the technique is flexible- conductive and non-conductive powders and thin films have been analyzed with this method. The specific system has a focused, intense x-ray source, leading to small spot sizes (10 microns and high x-ray flux. This feature speeds data collection and its large sample platforms allow for rapid analysis of multiple samples. The scanning capability also enables a wider range of surface chemical experiments, such as depth profiles of atomic composition near surfaces and chemical mapping at the tens of micron length scale.

The acquisition of a scanning ESCA will be especially significant to student training and development, specialized courses for undergraduates and graduates, and workshops. Over thirty graduate students, and tens of post-docs and undergraduates will be able to use this system to understand how surface chemistry plays a role in their research. The existence of a scanning ESCA will allow us to implement a set of programs that not only teaches students how to use the instrument, but also highlights the importance of interface chemistry in areas such as bio- and nanoengineering.