Home Institution: Loyola University Chicago
REU Mentor: Dan Frisbie
Self-Aligned, Capillary-Assisted Lithography for Facile Control for Printed Electronics
Printed electronics show promise for cost savings in large-area applications such as televisions and solar panels because printing is an additive process. Expensive materials are only printed where they are needed in the device unlike traditional photolithographic methods where material is coated over the entirety of the device and then removed where it is not needed. A drawback of printed electronics is the poor resolution, limiting practical feature sizes to the order of 20 micrometers. To improve upon this limit, a novel technique has been developed called self-aligned capillarity-assisted lithography for electronics (SCALE). The SCALE process utilizes imprint lithography to mold a series of reservoirs linked to capillary channels into a UV curable polymer. Electronic inks are easily printed into relatively larger (10’s-100’s of μm) reservoirs where they flow along the capillary channel to their feature. Channels are engineered at different levels in order to properly inkjet-print the necessary materials into a multilayered device. Feature sizes on the micron and sub-micron scale have already been successfully produced; however, I will be using the SCALE process to engineer large millimeter sized features in order to verify that a wide range of size requirements can be employed in a single device. I expect that the SCALE process can successfully manufacture operable, larger-sized transistors.
Home Institution: Utah State University
REU Mentor: Vlad Pribiag
Assistance with Microfabrication in the PAN Lab through E-Beam Lithography, Atomic-Force Microscopy, and Profilometry
The future looks very bright for the field of solid state physics because it involves the attempt at understanding the fundamentals of how semiconductors behave in special circumstances at the nanoscale. Thus, we turn to microfabrication processes and lithography, where micro-devices can be put together by means of etching and filling of substrate material over layers upon layers of wafer. We will mainly be using equipment in the laboratory such as the Atomic-Force Microscope, Profilometer, and Keyence Digital Microscope to take a closer look at structures such as nanowires that are applicable to nanoscale machines and devices. More specifically, the project will comprise of devices based on InSb nanowires, Si nanoparticles and InAs-based quantum wells.
Home Institution: University of Minnesota Twin Citites
REU Mentor: Paul Dauenhauer
Construction and Verification of an Automated Microcatalytic Reactor’s Accuracy Using Solid Acid Catalysts
Microreactors have made great improvements in reaction engineering research due to their ability to rapidly screen catalysts of interest for any desired chemistry. Evaluating the performance of a catalyst for a given chemical reaction usually requires a well-trained chemical engineer to continuously run and monitor multiple reactions in order to collect enough data to determine a certain reaction’s properties. The development of an automated microcatalytic reactor could significantly decrease the amount of manual labor and intensive training required to evaluate new catalysts for reactions, which do not have well known chemistries. The automated microcatalytic reactor will be housed within a gas chromatograph (GC), in which the GC inlet will contain the reactor and an automated liquid sampler (ALS) will deliver the reactant. The reactor will be a semi-continuous flow reactor with the ability to reach steady-state, inject the results, and quickly move on to new conditions. Once constructed, the automated microcatalytic reactor’s ability to obtain accurate data will be tested by running reactions with well-known chemistries, such as alcohol dehydration over solid acid catalysts. This will be performed by comparing reaction rates, activation energies, reaction orders and product selectivity to those in the literature. This validation will allow the automated microcatalytic reactor to potentially be standardized and be used in more diverse labs.
Home Institution: Georgetown College
REU Mentor: Jeff Derby
Analysis of Bridgman Growth of Scintillator Crystals
The work will render the modeling results for the design work for a five-heating-zone vertical Bridgman furnace, which is used for the crystal growth process of BaBrCl. CrysMAS (a code developed by the Crystal Growth Laboratory at Fraunhofer IISB) is employed to model global heat transfer in the furnace. The preliminary results would highlight the differences in the growth characteristics of various furnace designs. The Crystal Growth Laboratory led by Edith Bourret-Courchesne in Lawrence Berkeley National Laboratory (LBNL) has achieved notable success in the discovery of new scintillator crystals . The next step towards utilization is to produce these scintillator crystals with higher quality. Heat transfer modeling is used to optimize the design of the furnace and the strategies to control the heating zones. Crystal growth modeling is performed to improve the solid-melt interface shape and reduce the thermal stress in these new scintillator crystals that would result in cracking, one issue that hinders the growth of large-size crystals. These models would also be used to promote the design of the furnace to focus on the most important phenomena that affects crystal growth processes. Our work would allow cheaper, more efficient scintillator crystals to be produced.
 Bourret-Courchesne, E. D., Bizarri, G. A., Borade, R., Gundiah, G., Samulon, E. C., Yan, Z., & Derenzo, S. E. (2012). Crystal growth and characterization of alkali-earth halide scintillators. Journal of Crystal Growth, 352(1), 78–83.
Home Institution: University of Wisconsin-Green Bay
REU Mentor: Frank Bates
Crosslinking of Particle-forming PB-PLA Diblock Copolymers
Diblock copolymers are the covalently linked composition of two different polymers. Studying these is useful to understand structure-property relationships in soft matter. Asymmetric AB diblock copolymers (ƒA << 0.5) easily order into particle-forming structures; the most common is cubic symmetry. An exception to this is the newly discovered Frank-Kasper sigma phase that has been identified for strongly segregated, low molar mass diblock copolymers. These complex structures are able to fill space more efficiently by generating different size particle cores through chain exchange between particles. The purpose of this project is to understand the role of chain exchange in model poly(1,2-butadiene)-b-poly((±)-lactide) (PB-PLA) diblock copolymers through synthesis and characterization. To do this, PB-PLA diblock copolymers will be synthesized using sequential anionic polymerization followed by a ring-opening polymerization technique. 1H Nuclear Resonance Spectroscopy, Size Exclusion Chromatography, and Differential Scanning Calorimetry will be used to quantify the molecular characteristics of the samples. Additionally, the physical characteristics will be analyzed via X-ray scattering and rheology. After running these tests, the PB cores will be crosslinked by adding a small amount of photo-initiator (< 1 wt%) and activated by UV light. The physical properties will be examined during and after crosslinking to note the structural changes in the sample. We hypothesize the crosslinking will eliminate or decrease chain exchange, thus altering the disorder temperature (ODT) and possibly the morphology. This research will provide fundamental information about the physical effects of chain exchange in diblock copolymers, specifically regarding ordered structures and fluctuations in the disordered state.
Home Institution: Case Western Reserve University
REU Mentor: Uwe Kortshagen
Lifetime of Silicon Nanocrystals in Optoelectronic Applications
Solar cells and light emitting diodes (LEDs) are devices that rely on the photoluminescence (PL) of semiconductor materials. Silicon is earth abundant and non-toxic, making it a favorable candidate. Silicon nanocrystals (NCs) can improve the efficiency of devices because of our ability to alter their characteristics. Using a plasma reactor and adjusting the aperture within the plasma chamber, we control the residence time of NCs in the plasma. As a result, we change the particle size, thereby the photoelectric behavior and bandgap, of NCs. We can also conduct time-resolved photoluminescence (TRPL) tests using time-correlated single photon counting instrumentation. By studying the TRPL, we will better understand factors that impact PL lifetime, which refers to the time it takes for an exciton to return to its ground state. During this process, excitons may transfer to a nearby NC before emitting photons of a particular wavelength—dependent on the size of the NC—and recombining with holes. When excitons encounter other materials such as gold nanoparticles, however, the lifetime shortens significantly as a result of a trapping effect. The lifetime of NCs influences the efficiency of optoelectronic devices because we can generate current for solar cell applications or allow recombination to occur at higher efficiencies in LEDs. We expect that a decrease in NC size and concentration of gold should increase the lifetime of silicon NCs. We will also study the difference between interacting and non-interacting NCs within films and solutions, respectively, since interactions decrease the PL lifetime.
Home Institution: Rowan University
REU Mentor: Uwe Kortshagen
Exciton Diffusion in Doped Silicon Nanocrystal Films and Solutions
Excitons in crystalline semiconductors have become of interest for their applications in the light-emitting diode (LED) industry. This interest has led to the need for better understanding of how excitons are transported in silicon quantum dot (QD) films and solutions. Time-Resolved Photoluminescence (TRPL) was used to determine radiative and nonradiative free-charge carrier photoluminescence (PL) lifetimes of samples, to deduce characteristics of the material. Time-Resolved Emission Spectra (TRES) measured intensity of photon emission of samples to exhibit the decay of these emissions. By doping QD samples with gold nanocrystals, acting as exciton traps, exciton diffusion can be studied by observing the changes in PL lifetime, which is expected to decrease as concentration of gold increases. Additionally, the interactions of particles in the samples were observed when particles were in solution, as well as in a film. These interactions are effected by the proximity of neighboring particles to each other, which can be controlled by the functionalization of the films. Ligands increase the space between particles, and thus are expected to cause lower magnitudes of interparticle interactions and decrease inter-nanocrystal hopping rates.
Home Institution: University of Texas Rio Grande Valley
REU Mentor: Chris Leighton
Influence of particle size and stoichiometry on the magnetoelectronic properties of La1-xSrxCoO3 nanoparticles
Perovskite oxides have been shown to exhibit a plethora of interesting and important materials properties, ranging from high temperature superconductivity, colossal magnetoresistance, and ferroelectricity, to co-incident metal-insulator, structural, and magnetic phase transitions. Perovskite cobaltites doped with alkaline-earth metals, such as La1-xSrxCoO3, have shown a clear form of magneto-electronic phase separation which is heavily influenced by the chemical composition of the material. In addition to stoichiometric effects, magneto-electronic phase separation behavior could also be affected by constraining dimensionality of the material. In order to study this behavior, nanoparticles of La1-xSrxCoO3 are being studied in this project, as a function of composition and particle size. Magnetometry measurements on La1-xSrxCoO3 (x = 0, 0.05, 0.1, 0.2, 0.3) nanoparticles from year-old samples and recently-made samples were first studied and compared to analyses made a year ago. This was done to determine if there is any deterioration in the magnetic properties of the nanoparticles, and to further see how particle size affects these properties. Preliminary analysis demonstrates that there is little decay of the magnetic properties with time. Current work on the project focuses on the measurement and analysis of magnetometry data from the new batch of nanoparticle samples. Future characterization using scanning electron microscopy, energy dispersive analysis of x-rays, x-ray diffraction, and small angle neutron scattering will also provide a more concrete understanding on how the effects of particle size and composition affect the magnetoelectronic behavior of these size-constrained materials.
Home Institution: St. Catherine University
REU Mentor: Eray Aydil
Hydrothermal Synthesis and Characterization of Two-Dimensional Tin Sulfide Nanosheets
Layered metal chalcogenides are emerging as two-dimensional (2D) materials with a wide range of electronic, optical, chemical, mechanical, and catalytic properties. Like graphene, Tin(II) Sulfide may be separated to form single or few layer nanosheets. Tin Sulfide is promising because of its high theoretical efficiency at converting light into energy of 24% comparable to silicon, abundance in nature, and non-toxicity. Here we report on our efforts to synthesize nanosheets of tin monosulfide via a green hydrothermal synthesis. Specifically, we discuss strategies to control growth production of single or few layer nanosheets with large lateral dimensions (> 1 micron). Three different things were tested out when optimizing the synthesis; solvent type, sonication methods, and time dependence. First by looking at the morphologies of two different solvents; water, ethylene glycol, and then ethylene diamine. Time dependence was measured by synthesis of varying 4-24 hours in the hydrothermal bomb. Then sonication was used to separate the material into thin sheets. The resulting nanosheets were characterized by UV-visible and Raman spectroscopy. Morphologies were analyzed using AFM and SEM. The water synthesis was observed to yield large (several micron) nanosheets with the abundant side product of TinOxide. The synthesis using ethylene glycol as the solvent was observed to create flower-like nanospheres with very different morphologies than water, and without any TinOxide side product. The time dependence, sonication, and ethylene diamine solvent experiments are still in the process
Home Institution: University of St. Thomas
REU Mentor: Michael McAlpine
3D Printing of Organic Light Emitting Diodes (OLED) Matrix
For this project, I will be printing polydimethylsiloxane (PDMS) scaffolding in different arrays to then print quantum dot based organic light emitting diodes (QD-OLEDs) on top of the silicon structure. All of the designs for the project will be generated in solid works or CAD Fusion. The QD-OLEDs will be printed on top of the PDMS and and the first layer will be silver nanoparticles for conductivity, followed by polydioxyethylene thiophene and polystyrene sulfonate (PEDOT:PSS) as an anode, then poly[N,N’-bis(4-butylphenyl)-N,N’-(bis(phenyl)-benzidine] (Poly-TPD) as a hole transport layer, and subsequently the emissive layer will be deposited via solution (composed of various quantum dots and solvents), and finally a cathode made of gallium indium will be placed on top. The quantum dots being used will be composed of silicon or cadmium selenide/zinc sulfide. This is advantageous because quantum dots are more efficient than light emitting organic polymer LEDs. Some advantageous aspects of this route is that silicon nanocrystals are more sustainable due to silicon’s abundance and nontoxicity. Sustainability is becoming a prevalent concern throughout society; research in areas that are orientated around sustainability will aid in maintaining the prosperous longevity of the human population. By utilizing the recent advances in three-dimensional printing, another route to produce solid-state lighting is created, which is more environmentally friendly than the current manufacturing processes available. Also, OLEDs are much more flexible and even thinner than the modern LEDs used today. The flexibility of OLEDs allows for devices to be conformal to curvilinear surfaces, like human skin.
Home Institution: Drake University
REU Mentor: Marc Hillmyer
Polymer Transamidation Via Tert-Butoxycarbonyl Induced Destabilization of Amidic Resonance
Transamidation is of major interest in organic synthesis. However, this reaction is difficult to perform under mild conditions due to the high stability of the amide bond through amidic resonance. We seek to assess the effect of using tert-butoxycarbonyl (BOC) groups to weaken the amidic bond stability and thus increase its reactivity in transamidation reactions. This strategy is known in small molecule chemistry, but has yet to be applied to polymer chemistry. First, we will synthesize a highly activated monomer from commercially available acrylamide, and polymerize it to form a polymer with weakened amidic resonance. This polymer will then be tested in individual transamidation reactions with a primary amine, hindered primary amine, secondary amine, non-polymerizable amine, alcohol, and amino acid. The resulting polymers will be characterized by 1H-NMR, 13C-NMR, SEC, TGA, and DSC. We anticipate that, because of the weakened amide bond, these transamidation reactions will proceed with full conversion in mild conditions. We expect this method of transamidation to provide a gateway for generating polymers that would be otherwise difficult or impossible to generate through radical polymerization alone. Thus, this strategy will open the door to the creation of unique and novel acrylamide-based polymers with an extensive variety of properties, functionalities, and characteristics.
Home Institution: University of Texas Rio Grande Valley
REU Mentor: Tim Lodge
High modulus and Conductivity Polymer Electrolyte Membranes
Polymer electrolyte membranes (PEMs) with mechanical robustness and high ionic conductivity at room temperature are vital components of next-generation lithium-ion batteries. PEMs will be produced via polymerization-induced microphase separation (PIMS) facilitating long-range continuous conducting nanochannels, and a cross-linked mechanical phase. The design of PEMs involves the growth of cross-linked polystyrene phase off poly[oligo(ethylene glycol) methy ether acrylate] (POEGA). During the reaction, lithium salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and succinonitrile (SN), a plasticizer partitions to the POEGA phase to form the conducting domain, while a glassy polystyrene (PS) phase provides the mechanical stability to the PEMs. The addition of SN as a plasticizer increases the ionic conductivity and permits the miscibility of styrene/divinylbenzene monomers with POEGA and lithium salt. The current work will utilize POEGA at various molecular weights, variations concentrations of lithium salt and SN to simultaneously optimize the ionic conductivity and mechanical properties. The resultant PIMS PEMs will be tested and measured for its ion conductivity at different temperatures using an AC impedance spectroscopy, mechanical properties by a tensile bar loaded to obtain elastic tensile modulus at different temperature ranges, observe morphology by small-angle x-ray scattering(SAXS) imaging & transmission electron microscopy (TEM), and its thermal stability using a thermogravimetric analysis under nitrogen atmosphere. The system developed will help in the understanding and advancement of Lithium-ion batteries.
Home Institution: Louisiana Tech University
REU Mentor: James Johns
Growth of Single to Few Layer Black Phosphorous Through PVT and CVD
Black phosphorous is an allotrope of phosphorous with useful properties, including a layer dependent band gap, a high charge mobility, and chemical stability. Phosphorene is an atomic layer of black phosphorous, and because of this and the properties of black phosphorous, it has the potential to enhance electronics. One of the problems with black phosphorous is that all known techniques to manufacture phosphorene are “top down” approaches, including exfoliation of bulk black phosphorous. The limitations of exfoliation are that the orientation of black phosphorous grains are random, the thickness of the exfoliated film is not consistent or controllable, and the size of the film created is limited, making the process difficult to scale up. Also, at this point, the growth mechanism is unknown. Our hypothesis is that phosphorous and tin form a eutectic alloy at high temperatures, and that, as the mixture cools, black phosphorous precipitates out of this alloy. Our goal is to create a process to develop films of phosphorene in a more useful bottom up approach and to better understand the growth mechanism of black phosphorous. We will attempt two different methods to achieve growth. The first method is to sublimate bulk black phosphorous in a physical vapor transport furnace and deposit the material downstream. The second method is to sublimate black phosphorous in a CVD chamber and to attempt growth on molten tin. If these methods are successful, they will provide evidence for our proposed growth mechanism and provide a procedure to manufacture phosphorous for electronics.
Home Institution: Utah State University
REU Mentor: Sarah Swisher
Optimization of parameters for Zinc Oxide thin film synthesis for semiconductor application
ZnO thin films has potential as a multifunctional material to applied in PH sensors, surface acoustic wave devices, optical waveguides, solar cells, biosensors, etc. ZnO can be manufactured utilizing low-cost wet processing methods that include electrochemical, chemical bath, and sol-gel spin coating practices. The solution based deposition processes provides a cheap and basic production route for depositing ZnO layers because there is no need for vapor deposition equipment. Although the sol-gel method is a simple technique, many factors affect the quality of the ZnO film such as precursor concentration, pre-heating temperature, sol aging temperature, coating speed, etc. The effects of ‘precursor concentration, sol-aging time, and spin speed will be examined for their effects on film quality. Characterizations will include XPS to clarify chemical composition, UV visible transmission spectroscopy to determine film absorption, XRD to examine crystallinity. Due to stabilization of the solution as the sol ages, it is expected to see Zinc oxide increase compared to Zinc Hydroxide. The average thickness of films decreases with increases in spinning speed and the optical transmittance is expected to increase with the spin speed.
Home Institution: University of Puerto Rico Humacao
REU Mentor: Bharat Jalan
Understanding the electronic transport behavior in La-doped BaSnO3 thin films grown using hybrid molecular beam epitaxy
Barium stannate (BaSnO3) has a cubic perovskite structure with a lattice parameter of 4.116 Å and wide band gap of ~ 3 eV which makes it optically transparent. Recently, it has been shown to possess high room-temperature electron mobility. [1, 2] This makes it an impressive material for potential room-temperature applications including transparent conductors. My research will focus on the growth of epitaxial, single-crystalline BaSnO3 films grown on various substrates using hybrid molecular beam epitaxy (MBE) approach. Films will be characterized using x-ray diffraction (XRD) for determining the phase-purity, and crystal structure. Out-of-plane lattice parameter measured using XRD will be used as the measure of cation stoichiometry. Grazing incidence x-ray reflection (GIXR) will be utilized for determining thickness of the film. I will use GenX software for fitting the GIXR data to extract different parameters such as film thickness, interfacial roughness, and density of BaSnO3 films. Surface morphology of films will be studied using atomic force microscopy (AFM). Electronic properties will be measured using physical properties measurement system (PPMS) where I will study the temperature dependence of resistivity. Temperature dependent data will be analyzed to study the governing transport mechanisms at different temperatures for stoichiometric as well as non-stoichiometric films.
Home Institution: University of Michigan
REU Mentor: Cari Dutcher
Flocculation Performance Dependence on Ionic Strength and pH in the presence of Humic Acid
Polymer flocculation is commonly utilized in water treatment facilities to remove colloidal organic matter. Flocculate (floc) structure depends on a number of system properties such as pH, ionic strength, and natural organic material (NOM) content. Traditional flocculation experiments, also known as jar tests, will be conducted at varying pH levels, salt concentrations, and polymer dosages to determine the optimal dosage level at a number of system conditions and floc structure. Turbidity will be measured as a metric for flocculation performance. For structure characterization, experiments will be conducted with fluorescently-tagged polymer to visualize floc structure using laser confocal microscopy using a technique developed by this lab. Previous work has established the effect of ionic strength and pH on flocculation performance. Here we look at the effects of adding NOM- in the form of humic acid- on flocculation performance and structure. Preliminary results indicate that the addition of humic acid to the system creates a structural dependence on polymer dose not seen previously. We anticipate structural differences of the flocculate compared to previous trials due to the addition of adsorbed humic acid on the particle surface.
Home Institution: Tuskegee University
REU Mentor: Christy Haynes
Nanotoxicity evaluation of Doped silicon nanocrystals
Doped silicon nanocrystals (DSNcs) have demonstrated their biocompatibility compared to their alternatives quantum dots containing heavy metal content, and have drawn the attention of researchers as a result of its potential application in sensing, bio imaging, and energy conversion 1. Shewanella oneidensis MR-1 (S.oneidensis MR-1) is commonly used as the model microorganism in studying the nanomaterial toxicity of silver nanoparticles (Ag NPs), gold nanoparticle (Au NPs), and Li-ion battery materials 2. We synthesized NCs doped in boron and phosphorus of various concentration attempting to assess the bacterial toxicity in S.oneidensis MR-1. Hence, we used the colony counting assay (drop plate method) which includes a 10-fold serial dilution conducted to grow expected cell density.
Home Institution: University of Missouri Columbia
REU Mentor: Andre Mkhoyan
Infilling of Nanocrystal Networks Using (Plasma-Enhanced) Atomic Layer Deposition
Development and implementation of photodetection, photovoltaic, and photocatalysis technologies in the past decades have driven demand for transparent conductive substrates to an all-time high, with indium tin-oxide (ITO) glass being the substrate of choice. Though ITO glass boasts superior conductivity and transparency with respect to alternatives, indium production is dependent on zinc-sulfide ore mining, making production of ITO glass an expensive and environmentally-taxing endeavor. In searching for viable alternatives, we demonstrate the use of atomic layer deposition (ALD) and plasma-enhanced atomic layer deposition (PEALD) in infilling porous nanocrystal networks as an efficient and cost-effective method to synthesize metamaterials with desirable electrical and optical properties. By infilling ZnO with TiN using PEALD, we achieve a conductive, plasmonic material that absorbs strongly in the infrared region of the electromagnetic spectrum, allowing for possible applications in photodetection devices, photocatalysis, and photovoltaic energy conversion. Using ALD, we infill ZnO nanocrystals sequentially with further ZnO, followed by Al2O3, creating a robust, highly interconnected nanocrystal network, useful for physics studies of the insulator-metal transition in such networks. By comparing uniformity of elemental distribution throughout the thin films and their capacity to achieve desired properties, we discuss the potential and the limitations of ALD and PEALD as a nanocrystal network infilling technique.
Home Institution: Iowa State University
REU Mentor: Kevin Dorfman/ David Morse
Generation of Complex Morphologies in Diblock, Copolymers via blending using Self Consistent Field Theory (SCFT)
The combination of polymers to a single material can be done in different ways . These combination can lead to different phase behaviors . In recent years, Self-consistent field theory (SCFT) a powerful tool for the designing and interpretation of experiments on phase behavior of block polymer has been used to study and predict different morphologies of polymer blends. SCFT determines face behaviors by analyzing how the configuration of a test polymer chain is affected by the presence of other chains and vice versa. In this research a numerical implementation of SCFT known as Polymer Self Consistent Field (PSCF) is used to calculate phase diagrams of block copolymer by comparing free energies of competing ordered phase.The numerical evaluation of the different phases of block copolymer directly influences the physical properties and applications of polymers.
Home Institution: University of Puget Sound
REU Mentor: Russ Holmes
Lead Free Sn/Sr Halide Perovskites for Solar Cells
The term “perovskite” denotes a broad class of materials that have the stoichiometry ABX3 where A and B are cations (with A being larger than B) and X is an anion. Halide perovskite solar cells are one of the most exciting new technologies in the field of photovoltaics (PVs). Solar cells using these materials have improved in efficiency rapidly in the decade since their emergence and are approaching efficiency parity with more mature technologies like silicon PVs. They are also relatively simple to synthesize using a wide variety of techniques and some have properties that make them ideal as active PV materials, like excellent absorption properties, direct bandgaps and long carrier lifetimes. The main issues facing this promising new technology are rapid degradation in ambient conditions and a reliance on lead as the B cation in the most successful materials studied, such as the archetypal methylammonium lead iodide (CH3NH3PbI3). Lead perovskites are sensitive to light, heat and moisture, and can release toxic lead compounds during degradation, making industrial implementation a difficult prospect. To reduce problems with toxicity, several groups have replaced lead with tin. Unfortunately, tin perovskites appear to have worse stability than their lead counterparts. The work of this project will be to attempt to improve the stability of tin perovskites by partially replacing tin with another cation such as Sr. In lead perovskites, both experimental results and density functional theory calculations indicate that partial Sr replacement of Pb leads to improved stability. In addition, MAPbI3 showed a marked improvement in several factors important to photovoltaic use with just 2% strontium, making this method promising for continued study. This project seeks to optimize thin film synthesis methods and to identify the optical and degradation properties of tin halide perovskites with partial strontium replacement. This will shed more light on the ability of substituting strontium to improve stability and reduce the toxicity of perovskite materials for PVs, and thereby enhance the prospects of the commercial viability of perovskite solar cells.
Home Institution: University of Texas Rio Grande Valley
REU Mentor: Eray Aydil
Examination of the Size-Dependent Absorption Properties of CdSe Quantum Dots
In the past few years, Quantum Dots (QD) have increasingly drawn attention due to their variety of potential applications. Characteristics such as relatively small size, usually a few nanometers in diameter, and the ability to efficiently convert light waves into nearly any color in the visible spectrum by the mere adjustment of diameter size, make QD remarkably unique. These characteristics give QD the versatility to be implemented in different fields ranging from advanced electronic displays to biosensors, photovoltaics, and lasers. In order to further understand the particular behavior of QD, Cadmium Selenide (CdSe) QD will be synthezed by reacting, in a three-necked flask, a mixture of precursors including: Cadmium Oxide (CdO), Octadecylphosphonic acid (ODPA), and Tri-n-Octylphosphonic acid (TOPO). While subject to heat, this flask is connected to a Schlenk Line with the purpose of preventing the exposure to oxygen and removing any traces of water from the compound. This reaction will continue with a hot injection of Trioctylphosphine Selenide (TOPSe) into the fabricated compound, allowing it to react for the desired time, and quickly quenched to conclude with the synthesis. In order to demonstrate the effect that reaction time of TOPSe in the solution has on QD size, a series of synthesis will be performed where the time of reaction will be altered. Furthermore, this array of QD will later be analyzed via Ultraviolet–visible spectroscopy (UV-Vis) to determine their respective absorption peak and size distribution, and Dynamic Light Scattering (DLS) to determine QD interactions and behavior while disperse in solvent.
Home Institution: Saint John's University
REU Mentor: Steve Koester
Characterization of thin layered Gallium Oxide, Ga2O3, through Raman spectroscopy
Two dimensional semiconductors are of importance for their use in transistors and other devices. They provide an avenue for smaller functioning electronic devices and greater energy efficiency. Gallium oxide, Ga2O3, has a high energy bandgap which allows it to be implemented in thinner devices compared to other semiconductors. We will attempt to create monolayers of Gallium oxide though exfoliation techniques and then characterize them through Raman spectroscopy. Raman spectroscopy can identify multiple vibrational modes within Gallium oxide which can be used to determine the thickness of the material under observation. The Raman spectra will be recorded and compared to other thin layer semiconductors such as Molybdenum disulfide.
Home Institution: University of Delaware
REU Mentor: Paul Dauenhauer
Verification of an Automatic Microcatalytic Reactor’s Accuracy Using Solid Acid Catalysts
While industrial laboratories own expensive equipment to test catalyst activities over a wide range of conditions, catalyst screening in academic environments can be a tedious process that takes ample time and effort using traditional flow reactors. To solve this problem, a new reactor has been designed for rapid catalyst screening, solely within a gas chromatograph (GC). The new reactor is contained within a gas chromatograph quartz liner and is a semi-continuous flow reactor. It can quickly achieve steady state, where a sample is taken and then a new condition can be set. I will be testing the validity of the reactor by studying alcohol dehydrations, a common and well documented reaction, and comparing the results with known experimental data. Alcohol dehydration involves the reaction of an alcohol to form either an alkene or ether and water. The catalysts of interest are solid acid catalysts, which include industrial zeolite catalysts such as ZSM-5 and H-BEA. The results will be analyzed using gas chromatography and mass spectroscopy, and then compared to data found from scientific literature. We anticipate that the reactor will be successful, and that it will revolutionize the way data is collected from catalysis, making it a more affordable and efficient process.
Home Institution: University of Texas Rio Grande Valley
REU Mentor: Theresa Reineke
Synthesis of Poly(N-(2-(diethylamino) ethyl) acrylamide) for Cell Transfection
Poly(N-(2-(diethylamino) ethyl) acrylamide) is a novel water-soluble cationic polymer which exhibits thermo-responsive properties. We hypothesize that this polymer can form polyplexes with DNA that can be used to transfect cells. If the polymer crosses its LCST during transfection, the resulting destabilization of polyplexes may lead to in vitro gene delivery. The monomer N-[2-(diethylamino) ethyl] acrylamide (DEADEAM) will be synthesized according to a literature protocol. It will be purified by solvent extraction and column chromatography. Proton and 13C NMR as well as IR spectra will validate a successful synthesis. Subsequently, polymerization of the monomer will be performed using RAFT (Reversible Addition Fragmentation chain Transfer) polymerization. The final product will be precipitated and dried to obtain the pure material. The polymer obtained will be subjected to several characterization techniques such as Gel Permeation Chromatography (GPC) and 1H NMR, to determine the molecular weight and chemical structure of the material. The solution behavior of the polymer will be assessed in water. Lower Critical Solution Temperature (LCST) which, as its name states, determines the critical temperature at which the material is miscible will be determined as a function of pH. The pKa of the polymer will also be measured. For biological applications, it will be helpful to evaluate the bio-compatibility of the material. Toxicity of polyplexes will be measured by MTT assay. The polymer complexation with DNA will be analyzed using Dynamic Light Scattering (DLS) and a gel electrophoresis retention assay. Finally, the transfection efficiency of the polymer in primary human fibroblasts will be analyzed using a GFP reporter assay.
Home Institution: The University of Texas Austin
REU Mentor: Mahesh Mahanthappa
Investigating Lyotropic Liquid Crystal Phase Behavior of Hydrated Nonionic Surfactants
To bridge the gap between the phase behavior of polymers and the phase behavior ionic surfactants, we will investigate three nonionic surfactants: Brij O20, Brij 58, and TWEEN 40. Surfactants are “soap” molecules that contain both a hydrophilic and a hydrophobic portion. They spontaneously self-assemble into nanoscale structures in the presence of a solvent such as water. Under different concentrations, temperatures, and pressures, surfactant molecules will assemble into different lyotropic liquid crystal phases. Using polarized light microscopy and small angle x-ray scattering (SAXS), we will identify the phases that form upon various degrees of hydration. We aim to determine the conditions under which certain phases form and potentially discover some previously-unseen phases in these systems. An improved fundamental understanding of the liquid crystal phase behavior of hydrated nonionic surfactants will inform the design of soft materials for applications in in drug delivery, fuel cells, and catalysis.
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