Friday May 4th – Presentations

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Drug Discovery Efforts at UNF

Kenneth K. Laali

Department of Chemistry, University of North Florida

02:50 PM
Showcase

Parent curcumin CUR (a natural product constituent in turmeric) has a wide spectrum of biological activity as anti-inflammatory, anti-tumor, antioxidant, and antibacterial agent, but efforts to develop CUR as a therapeutic agent have not met with success due to major drawbacks associated with its low solubility, low bioavailability, and rapid metabolism.

In a quest to find "hit-compounds" inspired by CUR, but with improved physicochemical characteristics for clinical development, we are working on a multi-faceted project that combines synthesis, NMR studies and X-ray analysis with DFT optimizations, computational/docking studies and in-vitro bioassay.  To date several libraries of curcuminoids (over 80 compounds) have been synthesized and characterized, and a significant number have been tested for anti-tumor activity against a host of cancer cell lines. A progress review will be presented.

 

 

 

Electrospinning of natural and synthetic polymers

Nelly Mateeva, Jamie Hamilton, Brittney Jackson, Christopher Weider

Florida A&M University

09:25 AM
Physical Chemistry

Nanostructured materials with high surface area are of tremendous importance for many industrial applications, such as production of catalysts, sensors, and thermoelectric materials. Electrospinning, a method which applies high voltage to a solution, or melt of a polymeric material, allows for the synthesis of fibers from nano- to micro- size with versatile properties. High surface-to-volume ratio and the availability of functional groups enable post-modification and further processing of the material. Most synthetic polymers are easy to electrospin, however proteins are notoriously difficult to convert to individual, bead-less fibers. The reasons for this are not well understood and we explored the effect of many parameters, such as viscosity, delivery rate, solvent, etc., on the production of nanofibers from egg while lysozyme (HEWL). Our group also created several metal-polymer composite materials that involving transition metals, with possible application in catalysis.

One-Bead-Two-Compound Macrocyclic γ-AApeptide Screening Library against EphA2

Yan Shi, Jianfeng Cai*

University of South Florida

09:25 AM
Biochemistry / Chem Bio.

Identification of molecular ligands that recognize peptides or proteins is significant, but poses a fundamental challenge in chemical biology and biomedical sciences. Development of cyclic peptidomimetic library is scarce and thus discovery of cyclic peptidomimetic ligands for protein targets is rare. Herein we report the unprecedented One-Bead-Two-Compound (OBTC) combinatorial library based on a novel class of the macrocyclic peptidomimetics γ-AApeptides. In order to develop the library, we utilized the coding peptide tags synthesized with Dde-protected α-amino acids, which were proved to be orthogonal to solid phase synthesis of γ-AApeptides. Employing the thioether linkage, the desired macrocyclic γ-AApeptides were found to be effective for ligand identification. Screening the library against the receptor tyrosine kinase EphA2 led to the discovery of one lead compound which tightly bound to EphA2 (Kd: 81 nM) and potently antagonized EphA2-mediated signaling. This new approach of macrocyclic peptidomimetic library may lead to a novel platform which provides unique source of ligands for biomacromolecular surface recognition and function modulation.

Interfacial Dynamics in Additively Manufactured Polymer Matrix Composites

Kyle J. Johnson, Andrew Abbott, Lutz Wiegart, Jeff Baur, Hilmar Koerner

UES Inc., University of Dayton Research Institute, Brookhaven National Laboratory (NSLS II), Air Force Research Laboratory

10:55 AM
Additive Manufacturing

Additive manufacturing (AM) is pervasive across many disciplines at the Air Force Research Laboratory (AFRL). AFRL is investing in these novel manufacturing processes because of their appeal in rapid prototyping, part reduction and the ability to manufacture complex parts using design and topology optimization. Before AM is robust enough for metals, polymers, ceramics and composite manufacturing, morphology/processing/performance relationships have to be established. The presentation will give a brief overview of the different AM areas that AFRL is working on with focus on AM for polymer matrix composites. The road to road interface in additively manufactured composite parts is crucial for part performance. As an example, weakness and anisotropy at this interface have been key areas of study in the pursuit of more robust additively manufactured parts. Here, the dynamics and morphology at road-to-road interfaces were explored in an epoxy/nanoclay  composite ink using X-Ray photon correlation spectroscopy (XPCS). We observe a time scale associated with equilibrium dynamics, and observe substantially faster dynamics perpendicular to the road-to-road interface than parallel. This anisotropy in dynamics is shown to pass through a maximum both into the recently printed and previously printed road. The behavior is discussed relative to the alignment of the composite particles during shear of the ink through the extrusion head. The ultimate goal of this research is to use the in-situ data to calibrate more conventional techniques that can be implemented within an AM machine and use this to advance close-loop feedback control in AM processes in the future.

Assessment of potential markers of waste in wetland-treated wastewater

Emily C. Heider and Joseph Welch

University of Central Florida

04:55 PM
Environmental

Wastewater treatment facilities are remarkably effective in the removal of anthropogenic chemical components (e.g. caffeine) in waste. Even so, some compounds are persistent despite treatment with bacterial degradation, UV light, ozonation, and chlorination at the treatment facilities. Effluent from wastewater treatment facilities contains high concentrations of nitrogen (N) and phosphorus (P), yet these can be remediated with secondary water treatment wetlands that use natural processes to remove N and P nutrients and promote the health of natural waterways downstream. The Orlando Easterly Wetland (OEW) is an example such water polishing; this facility receives approximately 15 million gallons of treated wastewater per day, and through plant uptake, sedimentation, precipitation and bacterial denitrification, nutrients in the water are drastically decreased before the outflow to the St. Johns River. This research seeks to quantify sucralose (an artificial sweetener) and uric acid (the product of purine catabolism in animals and humans) at the Orlando Easterly Wetlands (OEW), to determine if these markers of human waste persist through wetland water polishing processes. Additionally, the uric acid in the water was studied to determine if its concentration increased through the excretions of avian, reptilian, and aquatic species.

Atomistic insight towards fragmentary interactions of PEG in bioconjugates – an atomistic molecular dynamics study

Aravinda Munasinghe1, Akash Mathavan1,2, Akshay Mathavan1,2, Ping Lin1 and Coray M. Colina1,2

1 Department of Chemistry, University of Florida, Gainesville, FL 32611
2 Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611

04:50 PM
Computational Chemistry

Currently many polymers and their different architectures are being investigated to synthesize bioconjugates. Due to its biocompatibility, polyethylene glycol (PEG) has emerged as an interesting polymer for bio-conjugate synthesis. Though PEG has been extensively studied, how its interact with biomolecules is yet to be fully clarified. The purpose of this work was to explore how PEG interacts with the Bovine Serum Albumin (BSA) protein using atomistic molecular dynamics simulations. To understand conditions which promote PEG – BSA interactions, conjugated systems with different molecular weights (i.e., 2, 5, 10, and 20 kDa) and unbound PEG were studied. PEGylated polymers were conjugated to N-terminal as well as Lys116 to explore the effect of the conjugate site. In each system, contacts between the polymer and the protein were monitored to explore PEG – BSA interactions and the affinity of PEG towards the BSA was evaluated based on the total number of formed contacts. It was found that the affinity of PEG towards the protein surface increases as a function of molecular weight. Further analysis of these interactions has revealed that PEG could adopt extended or coil-like conformations near the protein surface where mainly hydrophobic or hydrophilic residues are predominant.

Synthesis and Characterization of Nature-derived Polymers with Potential to Replace Commodity Plastics

Olivier Nsengiyumva, Stephen A. Miller

George & Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science & Engineering, Department of Chemistry, University of Florida, Gainesville, FL 32611, USA.

09:25 AM
PMSE/POLY

Over the last century, the commercial plastic industry burgeoned with a variety of finite resources allocated to polymer production. However, with their increased production and usage came a plethora of negative consequences to the environment, notably the inability of these polymers to degrade when disposed and only a small percentage being recycled. In addition, fossil fuel resources are dwindling, the key resource of most commercial polymers. This presentation will focus on new methods to access monomers from nature, and thus using them to synthesize renewable polymers. “Silicon acetal metathesis polymerization (SAMP)” is a methodology where silicon-based monomers and diols derived from plants are used to synthesize polysilicon acetals with glass transitions temperatures higher than that of polydimethylsiloxane (PDMS) and with relatively high melting points. SAMP also avoids the formation of deleterious byproducts such as corrosive acid (HCl). Other nature-derived monomers have also been used with the aim of replacing other non-renewable commodity plastics.

Development of the reductive enyne Cope rearrangement

Sarah K. Scott, Katherine E. White and Alexander J. Grenning

Department of Chemistry, University of Florida, Gainesville FL 32611-7200, USA

09:10 AM
Organic Chemistry

Although the enyne Cope rearrangement has been known for several decades, it has not seen applications in synthetic chemistry due to low yields and product instability. However, through the implementation of a reductive variant, this reaction is now being exploited to access functionalized allenyl malonates, which can be further manipulated to generate a range of carbocyclic frameworks commonly found in natural products. This work not only demonstrates the first potential application of the enyne Cope rearrangement in the synthesis of natural products and their analogs, but also provides significant insight into overcoming the challenges previously associated with the transformation.

Structure predictions of mixed-metal solid state compounds

Michael Lufaso

University of North Florida

04:55 PM
Materials Chemisry

Advances in solid-state chemistry benefit from synthesis of new materials and the characterization of their structures and properties. Both exploratory and targeted synthetic methods have unique advantages in the synthesis of new materials. These methods have been used to prepare mixed-metal solid state compounds, which exhibit structural variety and diverse physical properties. Structure prediction software based on the bond valence approach has been developed to predict the structure of a range of phase compositions. Developments include structure stability predictions and temperature dependent calculations, enabling the examination of structural phase transitions and the associated changes in unit cells, atomic positions, bond distances, bond angles, etc. Representative mixed metal solid state systems are examined in the context of the predicted and experimental structures.

AlFe2B2 as Water Oxidation Catalyst

Dallas K. Mann,a Yury V. Kolen’ko,b and Michael Shatruka

a Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306, United States
b International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga s/n, 4715-330 Braga, Portugal

09:25 AM
Inorganic Chemistry

Currently, many highly important catalytic processes depend critically on compounds that contain noble metals such as platinum or rhenium. Such catalysts, however, are non-sustainable in the long run, due to the low abundance and high cost of such metals. To counter this issue, we have developed a guided approach to the discovery of new sustainable catalysts.  This approach utilizes machine-learning analsyis (deep neural networks, or DNN) to identify potentially promising catalysts, in particular, among complex metallic alloys (CMAs). The DNN analyzes atomic fingerprints, i.e. radial distribution functions, around crystallographically unique sites to effectively screen through a vast database of intermetallic structures and identify materials with transition metal sites similar in their coordination topology to the active sites in known state-of-the-art catalyst. The approach also builds on the active site isolation concept, which has proven to be useful for the design of efficient heterogeneous catalysts. Guided by the DNN analysis, we began synthesizing several promising CMAs, which are characterized by extremely large unit cell volumes. CMAs are known to contain unique structural defects which might contribute to unconventional catalytic behavior. Our initial investigation has begun with AlFe2B2, a ternary boride known for its remarkably high magnetocaloric effect near room temperature with a composition consisting of light earth-abundant elements.1 In this contribution, we will demonstrate that AlFe2B2 acts as excellent catalyst for the oxygen evolution reaction (OER). In addition to the good catalytic activity, this material has remained remarkably stable under catalytic conditions, providing nearly constant OER rate for over 300 hours. The nature of our neural network approach and the catalytic performance of AlFe2B2 will be discussed in this presentation.

References

Tan, X.; Chai, P.; Thompson, C. M.; Shatruk, M. J. Am. Chem. Soc.2013, 117, 17399-17411.

Structural characterization of the Rous Sarcoma Virus capsid protein in its tubular assembly and simulations of the self-assemblies of the HIV capsid protein

Jaekyun Jeon, Ivan Hung, Alok K. Mitra, Ambroise Desfosses, Xin Qiao, Daniel Huang, Peter L. Gor’kov, Rebecca C. Craven, Richard L. Kingston, Zhehong Gan, Fangqiang Zhu, and Bo Chen

Department of Physics, University of Central Florida

11:10 AM
Biophysical

The capsid proteins (CAs) of ortho-retroviruses share a common tertiary fold but form distinct capsids. They are promising antiviral drug targets and templates for versatile nano-assemblies. However, they are tough to characterize due to the strong polymorphism. In this work, solid state NMR was applied to characterize the CA tubular assembly of Rous sarcoma (RSV), a prototype of retrovirus. A novel resonance assignment strategy was developed that exploits the well-resolved NCACX spectra to facilitate the assignment of congested NCOCX spectra, which led to a nearly complete assignment (234 residue out of the 237-residue protein). Based on this, site-specific dynamics and secondary structural information were determined. Combining with constraints from cryo-EM, we established an atomic resolution model of the tubular assembly by molecular dynamics flexible fitting. Our model shows that significant structural rearrangements take place at flexible loops and the 310 helix regions, while the rest of the protein retains its structure upon assembly. The analyses of our model suggests the assembly polymorphism is attributed to the disorder of the trimer interface between C-terminal domains. In addition, the different contact angles between helices at assembly interfaces of tubular and planar assemblies for HIV and RSV CA. Based on simulations of our novel coarse grain model, it suggests the two systems undergo different assembly pathways.

Detection of Adulterants in Drug Screening Analysis

Bianca Olivieri 

Mark Maric Ph.D.

Candice Bridge Ph.D.

Bianca Olivieri- University of Central Florida Chemistry Department
Mark Maric Ph.D. - National Center for Forensic Science
Candice Bridge Ph.D. - University of Central Florida Chemistry Department /National Center for Forensic Science

10:15 AM
Analytical Chemistry

Drug abuse has been problematic for centuries; however, the technology to detect drugs and their metabolites in bodily fluids has only been available for less than 50 years.1 To detect the use of illicit drugs in urinalysis, testing typically begins with a screening technique in the form of an immunoassay, such as Enzyme-Linked Immunosorbent Assay (ELISA). Although the response accuracy of immunoassays has increased, it remains only 95% accurate for urine screenings, which may be effectively lowered with the addition of adulterants into the urine matrix.2 To counteract a potential false-negative result, analysts will often use adulterant test strips to detect the presence of additional products. An understanding of this screening technique and the influence of adulterants on accurate results is crucial for workplace drug testing, criminal proceedings and the compliance of court probations.

In this study approximately thirty urine samples were obtained via volunteers under UCF IRB No: SBE-16-12568. Included with the samples were completed surveys detailing drug use, the frequency of stated drug use, and other contributing factors. Based on the provided information, samples were identified containing known types of illicit drugs and their metabolites (i.e. THC, cocaine, amphetamines, and benzodiazepines). No known samples contained traces of α-PVP, therefore a clean urine sample was taken and spiked with an α-PVP standard. Urine samples were then adulterated at set concentrations of 5, 10, 25, and 50 % v/v or w/v. Adulterants in this study included: bleach, vinegar, eye drops, Drano®, nitrite, table salt, and hand sanitizer. The adulterated and unadulterated samples were then analyzed via ELISA protocol. Results with ELISA revealed that certain adulterants (e.g. bleach, eye drops, Drano®) consistently decreased the detected concentration of drug metabolites to below cut-off thresholds. In conjunction, adulterant test strips AdultaCheck® 6 (AC6) and Intect™ 7 (I7), were utilized to determine if and at what concentration the adulterants could be detected. Data has revealed that the majority of the adulterants were unable to be detected at a low 5 % v/v adulteration level. This is a cause of concern, due to the ability of these adulterants to drastically decrease the drug/metabolite concentration using ELISA. The combination of these results suggest that a new urinalysis technique needs to be identified in order to effectively detect the presence of drug metabolites in the case of adulterant addition.

Keywords: ELISA, Adulterant Test Strips, Urinalysis

1.Bennett, J. B., Introduction. In Preventing Workplace Substance Abuse: Beyond Drug Testing to Wellness, Bennett, J. B.; Lehman, W. E. K., Eds. American Psychological Association: Washington, DC, 2003

2.Schütz, H.; Paine, A.; Erdmann, F.; Weiler, G.; Verhoff, M. A., Immunoassays for drug screening in urine. Forensic Science, Medicine, and Pathology 2006, 2 (2), 75-83.

 

 

Kinetic Measurements of CO+ and CO2+ Reactions with N and O Atoms for Models of the Martian Atmosphere

Jake Tenewitz1, Tri Le1, Shaun G. Ard2, Nicholas S. Shuman2, Albert A. Viggiano2, and Joshua J. Melko1

1. University of North Florida, Department of Chemistry, Jacksonville, FL
2. Air Force Research Laboratory, Kirtland Air Force Base, Albuquerque, NM

10:15 AM
Physical Chemistry

We have measured rate constants for CO+ and CO2+ reacting with N and O atoms using a flow tube apparatus equipped with a microwave discharge atom source. We report new room-temperature rate constants for these reactions that are much less efficient than previously thought, and the reaction of CO2+ + O is observed to yield O2+ exclusively, in contrast to an existing measurement in the literature. Experimental work was supplemented by molecular structure calculations. Calculated pathways show the sensitivity of kinetic barriers  to theoretical method, and indicate high level ab initio methods are required for accurate energetics. Our findings suggest that models of planetary atmospheres and the interstellar medium need to be updated accordingly. We will highlight a recently published model of the Martian atmosphere utilizing our new values.

Increased post-translation modification of eIF5A contributes to TDP43 proteinopathy

Shayna Smeltzer, Zain Quadri, Frank Zamudio, Jordan Hunter, Daniel C Lee, Maj-Linda B Selenica

College of Pharmacy, University of South Florida

10:15 AM
Biochemistry / Chem Bio.

The hallmark of TDP-43 proteinopathy is loss of nuclear function and accumulation as cytoplasmic inclusions. Recent evidence suggests for unique accumulation of TDP-43 in stress granules (SG) as disease progresses. In patients, TDP-43 pathology results in impairment of motor neuron function (ALS) and cognitive dysfunction (FTD). Hypusination of eIF5A (eIF5AhypK50) denotes its activation and cytoplasmic localization where it also binds to various RNA binding proteins. Its overall cellular function is translational elongation but translation inhibition in stress granules also occurs, as shown in stress-induced cellular models. While this is a common feature of SG biology, the activity of eIF5AhypK50 in SG can be problematic for TDP-43 proteinopathies. It can lead to further seeding of TDP-43 and translation of aberrant truncated TDP-43 forms adding to cytoplasmic aggregation once SGs dissolve. We show increased levels of enzymes responsible for hypusination in brain tissue from AD patient as well as in TDP-43 animal models. The animal model also displayed significant increase in hypusination levels, suggesting that its augmentation underlies the progression of the disease. Further, we know that protein–protein binding occurs between eIF5AhypK50 and TDP-43, and just by inhibiting hypusination, phosphorylated and total TDP-43 levels are reduced in the cytoplasm. It is however unknown the mechanism by which this occur. We predict that inhibition of hypusination will reduce TDP-43 burden and provide a strategy for therapies in TDP-43 proteinopathy. We hypothesize that eIF5AhypK50 regulates TDP-43 trafficking via several potential mechanisms, including protein-protein interactions, promoting cytoplasmic accumulation, translational regulation and the government of SG biology. We predict that it is through these mechanisms that eIF5AhypK50 orchestrates TDP-43 trafficking to cytoplasm and determines the biological signature of SGs. Our team has developed several unique tools to evaluate the efficacy of such approaches and dissect the mechanism of action through which eIF5AhypK50 affects TDP-43 pathology. We already know that pharmacological inhibition effectively reduces TDP-43 accumulation in SG in cells. However, we do not know if modulations of eIF5AhypK50 have neuronal efficacy or if it yields beneficial outcomes in the brain. Therefore, we have employed several innovative techniques, siRNA screening, antisense oligonucleotides and viral constructs to examine the neuronal role of eIF5AhypK50 in primary neurons and in TDP43 transgenic model.

Additive Manufacturing for the Future Warfighter

Jaret C. Riddick

Army Research Labs

04:00 PM
Additive Manufacturing

Army Research Lab is conducting research to enable the use of additive manufacturing to reduce the logistical burden of the future Warfighter.  ARL researchers are investigating additive manufacturing to establish research prototypes such as mission-matched UAS concepts built on-demand at the point-of-need and multifunctional components for maintenance-free air vehicle platforms.

Encapsulation of High Surface Particulates into Sol-gel Matrix and Their Use in Environmental Pollution Mitigation

Abuzar Kabir, Cassie-Jo McBride, Kenneth G. Furton.

Florida International University

05:45 PM
Environmental

Due to the explosive growth of human activities in recent years, thousands of toxic and hazardous synthetic organic compounds produced for industrial, domestic and agricultural purpose have continued to pollute fresh water systems. Many of these pollutants are classified as persistent organic pollutants (POPs). When POPs are released into the environment, they remain unchanged for a long period. Due to their prolonged presence in the environment, many of these pollutants finally find their way in the food chain, with severe implications in the health and well-being of human.  As such, it is imperative that these compounds be efficiently removed from environmental water through more efficient sewerage treatment processes and other reliable, yet inexpensive remediation techniques.

Among many classical processes used in removing pollutants from water, adsorption is one of the most effective removal techniques. A large number of carbonaceous adsorbents including activated carbon, carbon nanotube, biochar, graphene, calixarenes, poly(styrene-divinyl benzene), carboxen, fullerene, cation exchange resins, anion exchange resins and many others are used as adsorbents in sewerage treatment plants. These adsorbents offer a large variety of intermolecular interactions towards the analytes including µ-µ stacking interactions, cation-µ bonding interactions, electron donor-acceptor interactions, hydrophobic interactions, hydrogen bonding interaction, cation exchange, anion exchange, dipole-dipole interactions etc. Many of these adsorbents possess extremely high surface area and demonstrate strong tendency to form agglomeration. As such, when they are used in their pristine form, a large portion of their available surface area cannot be readily accessed by the analytes due to their agglomeration. As a result, the adsorption capacities of these adsorbents remain largely unexploited during their applications. The agglomeration of these unique particulate matters can be inhibited by encapsulated them into sol-gel silica network. Sol-gel chemistry provides a convenient and mild reaction pathway to create pure silica or organically modified silica 3-D network. Addition of adsorbent particles into the sol solution during sol-gel synthesis results in a sol-gel composite sorbent system with homogeneously trapped particulate matters. Due to the inherently porous and open architecture of sol-gel silica network, the encapsulated particulate matters maintain their high surface area as well as freely accessible interaction sites. As such, the synergistic combination of silica chemistry as well as the chemistry of particulate matters result in robust composite material systems capable of exerting intermolecular/ionic interactions towards a wide variety of analytes including polar, medium polar, nonpolar, ionic, and metal species and successfully trap them in the sol-gel composite sorbent matrices.

Analytical data obtained from a number of real-life applications of the sol-gel composite sorbents including endocrine disrupting chemicals (EDCs), Pharmaceuticals and personal care products (PPCPs), polycyclic aromatic hydrocarbon (PAHs) in environmental water will be presented showcasing their advantages, extraction characteristics, performance superiority, and analytical figures of merit.

Free Energy Sampling of Long-Timescale Biomolecular Dynamics: The Orthogonal Space Sampling Paradigm

Lianqing Zheng, Dongsheng Wu, Karen Corbett, Erick Aitchison, Steven Austin, Xubin Li, Chao Lv, William Harris, and Wei Yang

Department of Chemistry and Biochemistry & Institute of Molecular Biophysics
Florida State University

05:45 PM
Computational Chemistry

In the past decades, various enhanced sampling schemes and methods have been proposed towards the dream of practical sampling of free energy surfaces underlying biologically relevant biological processes. Despite victories declared by various mathematical methods, their ineffectiveness has been increasingly clear; physical basis of their limitation, particularly from the viewpoint of energy flow acceleration, is also more obvious to the community. At the same time, a physics-centered scheme, the orthogonal space sampling (OSS) theory, has been emerging. The recent development and large-scale tests shows that robust free energy sampling of long-timescale biomolecular processes has been achieved. This talk will serve as a part of official announcement of this breakthrough.

NSF 101: The Process of Preparing, Submitting, and Reviewing Proposals for The National Science Foundation

Tarek Sammakia

National Science Foundation and the University of Colorado

09:30 AM
Organic Chemistry

The process of preparing, submitting, and reviewing proposals for Chemistry Division of The National Science Foundation (NSF) will be described. This talk is geared at those in early stages of their careers and will provide some basic advice about the process of obtaining funding from the NSF.

Synthesis and Characterization of Lead Halide Perovskites for Solid State Lighting

Edward T. Nguyen

Florida State University

05:45 PM
Materials Chemisry

Down-shifting phosphors are routinely used in solid state lighting to convert higher energy UV or blue light to visible light. However, color quality of commercial LEDs are modest and new RGB phosphors are needed to tune the color of light. Commercial LEDs are composed of bulk semiconductors that typically contain materials on the DOE high risk index. For improving performance of down-shifting phosphors, size of the phosphor must be reduced to sub 10nm to reduce scattering of the pump led, the host lattice must minimize the amount of rare earth metals used, and must absorb pump LED irradiation and convert to pure red, green, and blue emission for optimal color quality. Here we present the synthesis of lanthanide-doped lead-halide perovskites (CsPbX3; X = Cl, Br, I). Lanthanide emission is accomplished by energy transfer from surface ligands to lanthanide metal centers by using the molecular antenna effect. Optical measurements of the nano-perovskites will be discussed including absorption, emission, lifetime, and quantum yields. Ligand exchanges were completed in efforts to improve quantum efficiencies and the nanoperovskites were characterized by pXRD, TEM, EPR, and FT-IR.

Terbium(III) doped nano-spinels as green emitters for solid state lighting.

David A. Hardy, Geoffrey F. Strouse

Florida State University

10:15 AM
Inorganic Chemistry

Down-shifting phosphors are routinely used in solid state lighting to convert higher energy UV or blue light to visible light. However, color quality of commercial LEDs are modest and new RGB phosphors are needed to tune the color of light. Commercial LEDs are composed of bulk semiconductors that typically contain materials on the DOE high risk index. For improving performance of down-shifting phosphors, size of the phosphor must be reduced to sub 10nm to reduce scattering of the pump led, the host lattice must be composed of earth abundant materials, and must absorb pump LED irradiation and convert to pure red, green, and blue emission for optimal color quality. Here we present the microwave synthesis of nanophosphors doped with Terbium(III) to accomplish green emission. Lanthanide emission is accomplished by energy transfer from surface ligands to lanthanide metal centers by using the molecular antenna effect. Optical measurements of the nano-spinel will be discussed including absorption, emission, lifetime, and quantum yields. Ligand exchanges were completed in efforts to improve quantum efficiencies and the nanospinels were characterized by pXRD, TEM, EPR, and FT-IR.

A gold nanoparticle/aptamer-based multi-channel paper microfluidic device designed for the scheduled drugs.

Ling Wang, Bruce McCord

Florida International University

10:35 AM
Analytical Chemistry

Designed aptamer has been developed to successfully identify some drugs of abuse in the last years.  Gold nanoparticles are usually used as a colorimetric detection or an electrical detection of drugs in the solutions.  These tests are based on the operations of chemical reactions, so they require the special knowledge of the chemical reactions.  We have been working on an alternative platform for the gold nanoparticles/ aptamers detection based on paper microfluidic devices.  Paper microfluidic devices are prepared with a wax-ink printer, thermal laminator, chromatography paper, gold nanoparticles and aptamers.  We have created a chip with a multiple-channel design which utilized the gold nanoparticles and special aptamers as a ready-to-use format.  In the field, samples are dissolved in a carrier solvent in vials and then applied to the paper just before the analysis.  The drug sample in the moving solution moved through the channel via capillary actions, reacted with the designed aptamers, and changed the color of gold nanoparticles with salted-induced aggregations.  Aptamers in each channel react with the target drug and the gold nanoparticles area turn from red to black indicating the presence of the target drug.  The entire process takes 5-10 minutes.  The devices can be used in different conditions where the suspected powders need the identification.   These devices are easy to prepare and inexpensive to operate without the special knowledge or training.

Tracking the ultrafast charge carrier dynamics at the surface of photocatalytic materials

Mihai E. Vaida1, Brett M. Marsh2, Bethany Lamoureux,2 and Stephen R. Leone2

1 Department of Physics, University of Central Florida, Florida 32816, USA
2 Departments of Physics and Chemistry, University of California, Berkeley, California 94720, USA and Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

10:35 AM
Physical Chemistry

The electronic structure of semiconductor substrates decorated with co-catalytic centers, i.e. metal and metal oxides small clusters and particles are important because of their many potential applications in photochemistry and catalysis. Understanding electronic structure and ultrafast photoinduced charge carrier dynamics at the co-catalytic particles is a defining principle that will guide advances in the next generation of photocatalysts to produce storable fuels from sustainable inputs.

Time resolution, surface sensitivity and element specificity are technical ingredients required to investigate ultrafast photoinduced processes of charge migration, localization and recombination at the surface of photocatalytic materials. All these requirements are fulfilled by a new experimental technique based on pump-probe photoelectron spectroscopy in conjunction with femtosecond extreme ultraviolet (XUV) laser pulses that will be presented in this contribution. The ultrafast electron and hole charge state dynamics at photocatalytic surfaces is investigated by monitoring the ultrafast photoinduced transient charging of the overlayers, particles, or clusters at surface.

Gold clusters grown on 10 ML MgO(100)/Mo(100) are investigated as a model system for using static XUV photoemission as a probe of electronic character versus cluster size. As the size of the Au clusters is increased, a gradual shift in the photoemission onset up to the Fermi energy indicates a change in the character of the gold clusters from non-metallic to metallic. The results are compared with theoretical work and previous investigations to validate the PES method. Static photoemission is then further utilized to monitor the electronic structure of Zn clusters on p-Si(100) as a function of Zn deposition. The transition from non-metallic to metallic Zn character is observed at 0.16 ML of Zn coverage. Furthermore, femtosecond pump-probe XUV photoemission spectroscopy technique is employed to induce a charge transfer from the p-Si(100) substrate to the Zn clusters and to measure in real time the charge trapping at the Zn cluster as well as the subsequent charge relaxation. The ultrafast charge carrier dynamics is investigated as the Zn dimensionality is increased from small clusters composed of a very few atoms to large particles to extended Zn films.

Identification of suramin as a potent and specific inhibitor of the mammalian high mobility group protein AT-hook 2 (HMGA2)-DNA interactions

Linjia Su1,2, Prem P. Chapagain1,3, Steve Vasile4, Layton Smith4, and Fenfei Leng1,2,*

1 Biomolecular Sciences Institute and 2 Department of Chemistry and Biochemistry, 3 Department of Physics, Florida International University, Miami, FL 33199
4 Sanford-Burnham Center for Chemical Genomics at Sanford-Burnham Medical Research Institute, Orlando, Florida 32827, USA

10:35 AM
Biochemistry / Chem Bio.

The mammalian high mobility group protein AT-hook 2 (HMGA2) is a nuclear protein associated with epithelial-mensenchymal transition (EMT) during cell development and differentiation. This protein plays an important role in the formation of a variety of tumors including malignant tumors, such as melanoma, lung cancer and hepatocellular carcinoma. These results suggest that HMGA2 is a potential therapeutic target of anticancer drugs. HMGA2 is a DNA minor-groove binding protein specifically recognizing the minor groove of AT-rich DNA sequences. Previous results showed that HMGA2-DNA interactions are a potential target for chemical intervention. In this study, we developed an AlphaScreen HTS Assay to screen inhibitors targeting HMGA2-DNA interactions. We are particularly interested in identifying non DNA-binding compounds that inhibit HMGA2-DNA interactions due to the fact that DNA-binding compounds are highly cytotoxic. After the HTS campaign, several non DNA-binding compounds have been identified to potently inhibit HMGA2-DNA interactions. Among them is suramin, a negatively charged antiparasitic drug. Suramin potently inhibits HMGA2-DNA interaction with an IC50 of 2.78±0.10 micro molar. We also found that suramin and analogues strongly bind to HMGA2, suggesting that the inhibition of HMGA2-DNA interactions is through suramin binding to HMGA2 and therefore blocking HMGA2’s DNA binding capacity. Suramin is an anticancer agent that inhibits tumor growth and metastasis for certain cancers including pancreatic cancer, prostate cancer, melanoma, and etc. The anti-cancer mechanism of suramin is still illusive. The discovery of suramin as a potent inhibitor of HMGA2-DNA interactions suggests that the anti-cancer activities of suramin may stem from its inhibition of HMGA2-DNA interactions in vivo and opens a door for future research in suramin as an anticancer agent.

Dielectric and magnetic properties of nanoparticle loaded polystyrene as a printable, low-k hybrid material

Faheem Muhammed,1 Subramanian Ramakrishnan1, Parth Vakil2, Geoffrey Strouse2

1 -Department of Chemical Engineering, Florida A&M University, Tallahassee FL, 32301
2 - Department of Chemistry, Florida State University, Tallahassee, FL, 32301

04:35 PM
Additive Manufacturing

The development and miniaturization of electronics has increased the need for low-k dielectric materials for use in interconnect shielding. The primary goal of this work was to systematically modify the printed material to strike the balance between magnetic (permeability) and dielectric properties that provides maximal electronic shielding. The key in these applications is maximizing particle loadings in a polymer matrix while maintaining low dielectric constants and losses. Magnetic nanoparticles were dispersed in low-k thermoplastics and the dielectric properties were systematically studied as a function of particle type, concentration (0 to 13 volume percent), and surface coating. By varying the volume percentage of filler in the matrix, it is shown that one can increase the magnetic properties of the materials while minimizing unwanted contributions to the dielectric constant and dielectric loss. The well dispersed nanoparticle systems were successfully modeled through the Maxwell-Garnett (MG) theory thus giving one a predictive ability for the dielectric properties. High-precision (100 μm resolution) additive manufacturing, combined with these materials, has demonstrated further reductions to the dielectric constant by controlled incorporation of air (k=1) in the system. The volume fraction of air present was tuned through topological optimization, computer aided structural design, and printing parameters. By treating the nanocomposite as a continuous matrix, and air as the filler, the MG theory was extended to the manufactured composites.

The effect of dual frequency sonolytic irradiation on the production of hydroxyl radicals and efficiency of degradation of model dye compounds

Zeynep EREN

Kevin O’Shea

Department of Chemistry and Biochemistry, Florida International University, Miami, Florida, 33199 USA

06:05 PM
Environmental

Ultrasonic irradiation of aqueous media generates tiny air bubbles which undergo rapid compression-expansion cycles leading to a violent collapse and three main reaction zones: the interior of the gaseous cavitation bubbles, the interface of gas bubble-liquid solution and the bulk solution. Pyrolysis of water vapor inside the cavitation bubbles and near the inerface leading to OH and H radicals which can diffuse among the different reaction zones leading to the degradation of a polluants and toxins. Only ~ 10 % of OH radicals can by transferred to the bulk solution where the majority of target compounds often reside. The interface processes hydrophobic solvating properties while the bulk solution processes hydrophilic properties. Therefore, the partitioning of hydrophilic and hydrophobic pollutants and subsequent radical attack can be dramatically different within the reaction zones. In this work, two frequencies of ultrasound (20 kHz and 670 khz) were applied in order to investigate the degradation effectiveness when applying a second frequency to promote mixing among the different reaction zones. To assess the efficiency of dual frequency ultrasound, the power intensity per mL of each equipments were calculated with colorimetry at different amplitudes and power outputs. The results are evaluated according to the sonochemical efficiency calculated from the ratio of dye degradation percentage to ultrasonic intensity, which have shown the radical production decreasing with increasing frequency.