Poster Abstracts

Nanotechnology ReTs

Wet Thermal Etching of Boron Nitride Nanomaterials: Unlocking their Activation Energies

Robert Black, Jesus Acapulco Jr., PhD, and Matteo Pasquali PhD

Boron nitride nanotubes (BNNTs) exhibit properties of insulating, sustaining high temperatures, and Strength, all promising for engineering and medical applications. The key to these applications is to refine the material to just BNNTs versus nanosheets or nanocages. Previous methods of separating BNNTs out of the existing boron nitride material from the team have resulted in a yield around 10 percent. This project specifically addresses the details of wet thermal etching with boron nitride nanomaterials, specifically BNNTs. The specimens will be analyzed to determine the initial size and morphologies of BN nanomaterial by using the scanning electron microscopy (SEM) and atomic force microscopy (AFM). For the wet thermal etching process, the specimen will be subjected to a set temperature level and water will be injected to react with the boron nitride nanomaterials for etching. The goal is to answer the question why do different boron nitride nanomaterials, (nanotubes, nanosheets, nanocages), etch out in different rates? In the study, we will provide an answer to the question by showing that different boron nitride nanomaterials have different activation energies in wet thermal etching reaction. Activation energy can be calculated by acquiring the slope of the plot temperature versus the change in length by using Arrhenius equation. This can be translated to other nanomaterials to provide fundamental understanding in chemical reactions. Wet thermal etching can be optimized to get high levels of purity in BNNTs to be applied to engineering purposes.

Neural Patterning of Stem Cells

Donna Booker, Miguel Angel, Dr. Aryeh Warmflash

Hippocrates, On the Sacred Disease, (Fourth Century B.C.E.) concluded “…In these ways I am of the opinion that the brain exercises the greatest power in man.” The brain is perhaps the most powerful organ in the body. With the spinal cord, it composes the central nervous system. When studying the central nervous system, one must understand its origin. At conception, one single cell divides and divides again to become the different types of cells that make up the tissues that make up organs. The focus of our research has been how do cells pattern and establish the complex structures of the brain. How does a cell know that it will be part of the forebrain or the hindbrain? Using embryonic stem cells, we examine how proteins and genes interact with each other to establish instructions for the proper development of the brain. Cells are treated so that they become different sections of the central nervous system. We seek to know exactly how this pattern of development takes place.

Spectra of Plasmonic Gold Nanoparticles

Rafferty Deeds,

Plasmonics has proven applications in improving photocatalysis, photothermal and photovoltaic cells. There are some issues with optimizing energy transfer and the decay of the plasmon oscillation in conjunction with semiconductors. Direct charge transfer results in chemical interface damping of plasmon and occurs during the plasmon lifetime. In the case of sequential charge transfer the plasmon has already decayed into energetic electrons and holes. The focus of our research is to explore the material properties of plasmonic gold nanorods such as aspect ratio and plasmon wavelength and semiconductor Schottky barriers. We are using dark-field spectroscopy and photoluminesce spectroscopy to acquire line spectra data, and optimize the energy output of the plasmon and quantify charge transfer from the direct charge transfer mechanism versus sequential charge transfer mechanism.

The Role of pH in Single-Wall Carbon Nanotube Functionalization by NaClO

Usha N Devathosh, V. B.Espinoza, R.B. Weisman

Single-wall carbon nanotubes (SWCNTs) are 1D cylindrical nanomaterials that resemble a rolled up graphene sheet and have many interesting properties, including the strong fluorescence emission of semi-conducting SWCNTs in the near-infrared region. Different approaches have been used to tailor the optical properties of SWCNTs, which previously resulted in the discovery of O-doped SWCNTs. More recently, sodium hypochlorite (NaClO) has been used to make doped SWCNTs. This method of SWCNT functionalization by (NaClO) has shown promise for more efficient optical tailoring because this method is much faster than previous work done to obtain O-doped SWCNTs. However, previous literature shows that the reactive agent of NaClO can vary depending on the pH environment. Therefore, to explore how pH variation effects the doping of SWCNTs with NaClO, we varied between acidic, neutral, and basic conditions. The functionalization of surfactant-suspended CoMoCAT SWCNTs was carried out with NaClO and a 300 nm LED as the light source. Here we show that changes in the pH environment does influence the doped (6, 5) species.

Building and Testing a Component of a Synthetic Genetic Circuit in Mammalian Cells

Ariel Delos Reyes, Tsvetelina Baryakova, and Laura Segatori

Oscillations in protein levels within cells help facilitate a variety of biological processes, from circadian rhythm to cell cycle progression. The Segatori lab is investigating a platform for creating oscillatory circuits in mammalian cells by using several interrelated DNA constructs. The “activator” is one of these constructs and consists partly of a fusion between tetracycline transactivator (tTA) protein and green fluorescent protein (GFP) under the control of a tetracycline-response element (TRE) promoter. We aim to build this complex construct using molecular cloning methods and show that it can transiently carry out its intended function in mammalian cells prior to the integration of other circuit elements.

Engineered Alginate-based Hydrogels for Biomedical Tissue Repair Applications

Francisco Padron, Joseph Swain, Adam Farsheed, Viridiana Leyva, and Jeffrey Hartgerink

Sodium alginate (SA) is a natural hydrophilic biopolymer, typically obtained from marine brown macroalgae, and suitable for making hydrogels for biomedical applications due to its biocompatibility, chelating ability, water solubility, and low-cost. The material properties of the alginate hydrogels can be engineered by different gelation methods and can be combined with nanoparticles or copolymers to form fibers, films, or a variety of shapes. The gels can be used in tissue repair and as a bioprinting material for damaged cartilage, herniated discs, synovial membranes, and implants. Naturally occurring alginates have random sequences of mannuronic (M) and guluronic (G) acid blocks with different ratios of M and G. The gelation process varies with different G/M ratios and block-length. For this investigation, we prepared six different hydrogels casted into Petri dishes with SA (2% w/v) and a G/M ratio of 40:60 via ionic crosslinking using CaCl₂ and CuSO₄ solutions at two concentrations (0.05M and 0.1M); two of the hydrogels were prepared with sodium bentonite clay (2% w/v of SA) using 0.1M ionic solutions. The hydrogels were inspected for visual appearance and shrinkage, analyzed with oscillatory rheology, and imaged using SEM to show nanostructures. The results show significant differences in the rheological properties of the hydrogels (storage and loss moduli, linear viscoelastic range, and flow point) as a result of the different crosslinking concentrations, the addition of nanoparticles, and metallic ions. The results also indicate excellent recovery and stability of the hydrogels up to 30 minutes after a 200% shear strain for one minute.

Aggregation Effect of Near-Infrared Boron Difluoride Formazanate Dyes

Jessica Robicheaux, Axel Loredo, Schichao Wang, and Dr. Han Xiao

The development of near-infrared (NIR) dyes are desired for their enhanced capability in fluorescence detection and imaging, tissue penetration depth and low background with minimal fluorescence from surrounding tissues. Previous research has led to the assumption that NIR dyes must contain large, bulky substituents that require multi-step synthesis. However, conventional dyes result in reduced emission intensity due to the possibility of containing strong intermolecular ℼ- ℼ stacking interactions because of their bulky size. This enables the formation of excimers and leads the fluorophore to experience aggregation-caused quenching (ACQ), which quenches the excited states via non-radiative pathways. Boron difluoride (BF₂) formazanate dyes are relatively small compounds that can be conjugated with targeting moieties. For our research, we have made structural modifications to the functional groups of boron difluoride complexes of 3-cyanoformazanates in THF-water mixtures. We observed that difluoride complexes exhibit absorption and fluorescence in the NIR region, and wavelengths were red-shifted despite its simple structure. This is caused by the addition of a para-substituted amine, which allows the compound to shift farther towards the red end of the spectrum. We also discovered that boron difluoride complexes of 3-cyanoformazanates exhibit aggregation-induced emission (AIE). Specifically, our asymmetrical compound, NMe2-MOR Formazanate, had the greatest intensity due to its structure preventing ℼ- ℼ stacking and aggregation restricting motion. The strategic development of these formazanate dyes offers a unique opportunity to use near-infrared fluorescence imaging techniques to detect and visualize fluorescent probes that are even able to pass through the blood brain barrier in-vivo.

Optical properties of Crystals give insight to Band Gap size in Hydrous Alum

Aerielle Rodriguez, Kevin Allen, and Dr. Emilia Morosan

When the band theory was proposed in the 20th century it revolutionized the world of solid-state physics. The size of the band gaps between the valence and conduction bands successfully explains many of the properties possessed by solids. We tested different crystals with varying band gaps in order to demonstrate the relationship between observable optical properties and physical properties. The slow evaporation method was used for growing all the crystals used. We then verified the structural composition through powdered x-ray diffraction. Using the X-ray data and TOPAS software, we fit the peaks to the ICSD database and found that we grew impure hydrate crystals. The resistance of the crystals was measured as a function of temperature using a two-probe method. Both Potassium phosphate and Cupric sulfate had resistance measurements outside the range at which the voltmeter can measure from 25oC-90oC. The Alum, Chrome Alum, and Chrome Alum doped Alum all had measurable resistances once heated. All crystals measured showed the same relationship in that as temperature increases their resistance decreases at an exponential rate when measured on cooling and on heating. The drop in resistance when heating had a much steeper slope than the increase in resistance when cooling. This could be due to residual heat on the crystal causing slower cooling rates or it may suggest structural reconstruction of the crystal at higher temperatures. The temperature at which this resistance decrease starts is different for each sample with the Chrome Alum’s measurable resistance starting at around 58oC and the Alums (100%, 95%, 70%) at around 82oC-84oC. This suggests that the Chrome Alum has the smallest band gap. The 70% Alum’s resistance decrease starts at the highest temperature suggesting that it has the biggest band gap. Doping of the Alum crystal with Chrome Alum may have played a part in the increased resistance measurements. Gaining a better understanding of the relationship between optical properties and electrical properties of crystals could have important implications for the future of technology, as tuning between insulating and conductive states may lead to more diverse uses in technology.

Measuring Boronic Acid Binding to Diols Using Alizarian Red S

Kaylene Thomas; Mentor - Michael Swierczynski; and PI - Dr. Zachary Ball

Boronic Acids (BOH) are promising molecules for site specific bioconjugation with proteins under mild aqueous conditions. Boronic Acids bind reversibly to diols, giving potential to use for reversible modification.Biomolecule-BOH attachment/diol binding is difficult to detect due to the small size difference. Alizarin Red S (ARS) is a color changing dye that can detect BOH in solutions.Salicylhydroxamic acids (SHA) bind strongly, yet reversibly, to BOH, thus is a promising diol for BOH binding.SHA should bind more strongly to BOH than ARS, allowing for an easy detection system.