Anti-bacterial, and antibiotic drugs are currently at a point where they are becoming increasingly ineffective. As such medicines to take their place have become a hot topic of research lately. One of the ways that it is being researched is in a multi-step or multi-component remedy instead of a one drug treatment. The driving force behind the process would be synergy between the substances being used to create the treatment. This method of treatment has been well documented and well tested within the Traditional Chinese Medicine (TCM) system. TCM is a collection of combinatorial remedies that usually consist of at least 3 components, often a number of herbs and a mineral. Using that premise this study was built. Antibacterial activity of five herbs (Garlic, Ginger, Echinacea, Oregano, and Turmeric) is presented in this study. Each of these herbs has different active ingredients and mechanisms of antibacterial activity which make them all potential candidates for this study in synergy. Various combinations were tested similar to the TCM method of treatments. Each of the five herbs have been separately extracted using a soxhlet extractor using solvents of dissimilar polarity to separate polar and nonpolar active ingredients. Combinations of two and three of these extracts were tested on Escherichia Coli (E. Coli) using diffusion methods. The ring of inhibition was measured around each of these combinations as well as positive and negative controls. The effectiveness of these combinations is presented here.

Anti-bacterial synergy of medicinal herbs

Intramammary infections caused by some stands of Escherichia coli have been known to acquire antibiotic resistance. Therefore, other methods should be sought out to find an effective therapy that does not include antibiotics. Information on how anti-inflammatories coupled with homeopathic practices affect Escherichia coli is insufficient. The objective of this experiment is to discover whether anti-inflammatories and organic compounds combined would have a detrimental affect on Escherichia coli. The Escherichia coli inhibiting power was evaluated both individually and combination of banamine, dexamethasone with either cinnamomum cassia oil or aromatic turmeric (curcuma aromatica) extract. Paper disks (8mm) was saturated in the different solutions and placed directly onto a lawn of Escherichia coli housed in a petri dish for each trial. Antibacterial activity results are presented here.

Enhancing antibacterial properties using herbal extracts

During the past decade, there has been a significant interest to use Co3O4 as an alternate anode material for lithium-ion batteries (LIB) due to its remarkably high theoretical capacity of 890 mAh g-1. The charge/discharge reaction of Co3O4 in LIB is found to be very reversible, however, a hysteresis of &gt;1.0 V vs. Li/Li+ is still a major issue that limits the usage of Co3O4 in a practical battery device. In this work, we first reveal the detailed charging mechanism of Co3O4 by combining first principle calculations with a derivative structure enumerating algorithm and ab initio molecular dynamic simulations. While the ground-state, equilibrium lithiation voltage of Co3O4 shows a large discrepancy compared to the experimental voltages, our calculated reaction pathway involving metastable phases of LixCo3O4 (x = 1, 2.5, 3, 4, 5, and 8) predicts a voltage profile in a much better agreement with experimental observations. By further examining the energetics of the metastable phases, we are also able to explain the large voltage hysteresis occurring during cycling of Co3O4 anode materials. Rearrangement of the close contact between Co and the surrounding lithia (Li2O) at the atomic scale and the facile Co-Li migration in the final Li8Co3O4 phase enable fast Co+O recombination and de-lithiation that can ultimately explain the good reversibility of Co3O4 in LIB during cycling.

Revealing the conversion mechanism of Co3O4 during lithiation from first principles calculations

The photo-oxidation of ethanol has been investigated over anatase TiO2(101) and rutile TiO2 (110) single crystals by STM and on-line mass spectrometry to determine the adsorbate species in the dark and post UV illumination in the presence of O2, and to extract initial reaction parameters under photo-excitation. On anatase (101) TiO2 single crystal the reaction rate for the photo-oxidation of ethanol to acetaldehyde is found to be strongly dependent on O2 partial pressures and surface coverage with an order of the reaction for O2 close to 0.15. Carbon-carbon bond dissociation leading to CH3 radicals in the gas phase was found to be a minor pathway, which is contrary to the case of TiO2 rutile (110) single crystal, as previously reported. Our STM images distinguished two types of surface adsorbates upon ethanol exposure that can be attributed to its molecular and dissociative modes. Upon UV exposure at (and above) 3×10-8 mbar O2, a third species is identified as a reaction end-product, which can be tentatively attributed to acetate/formate species, in line with XPS C1s measurements. The room temperature photo-oxidation of ethanol has also been investigated over a rutile TiO2(110) single crystal by STM and on-line mass spectrometry, in the presence of O2 to determine adsorbate species remaining post UV exposure and emitted gas phase products. In addition to acetaldehyde, methyl radical was detected in the mass spectrometry resulting from the photo-fragmentation of an acetaldehyde-O complex. Formic acid species bound to Ti5c in a bi-dentate mode were identified by STM on the surface after the reaction. The effect of O2 partial pressure on the reaction selectivity demonstrated a dominance of the photo-fragmentation process with increasing pressure unlike the case of anatase TiO2(101) single crystal.

Ethanol photoreaction over anatase TiO2(101) and rutile TiO2(110) single crystals. A combined STM and online mass spectrometry study

Presence of pharmaceuticals and other chemicals used worldwide in the environment is directly linked to the human impact. Potentially relevant group of environmental pollutants are antiviral drugs which have been put under a spotlight after a worldwide outbreak of swine influenza virus in 2009. But, antiviral drugs used for treatment of other viral infections like HIV, hepatitis or herpes could be equally significant. According to UNAIDS, 2.1 million new HIV infections have been reported in 2015. Although this number has been in moderate but constant decline in the last decades, still over 36 million people worldwide are living with HIV. Like other pharmaceuticals, antivirals are only partially metabolised in the human body and, once excreted, they can reach the aquatic environment via WWTPs. As a result, they can end up in surface water together with the mixture of their human metabolites and transformation products which are formed along the way. In order to evaluate their presence in the aquatic system, the aim of this work was to develop a target analytical method based on LC-MS. However, in order to avoid classical target method development which commonly relies on arbitrary selection of target compounds, here we used a suspect screening approach where a 100+ antivirals suspect list was matched to WWTP samples as a guarantee of environmental presence. This was especially advantageous since no data on drug consumption could be obtained. In our case, WWTP influent and effluent of the largest catalan WWTPs was sampled over three consecutive days. The samples were extracted using a generic SPE method and analysed using LC-QExactive-MS. Each positively detected exact mass was further rationalised with fragmentation logic for a specific compound/structure. A list of antivirals identified and detected in all three consecutive days were considered important and were advanced to the target method development step. The list was joined with compounds that have been reported to occur in high concentrations in other publications in order to check whether non-detection was due to lack of presence of lack of selectivity. Additionally, recently marketed compounds were also added to the method since its consumption rates were expected to grow over time. Finally, in order to decrease the analysis time, target method was developed using on-line SPE coupled to LC-MS for fast and reliable quantification of forty antiviral compounds in the aquatic environmental samples.

Smart target method development for detection of antiviral compounds in aqueous environmental samples based on suspect screening and HRMS

Herbertsmithite, ZnCu3(OH)6Cl2, is a two dimensional kagome lattice realization of a spin liquid, with evidence for fractionalized excitations and a gapped ground state. Such a quantum spin liquid has been proposed to underlie high temperature superconductivity and is predicted to produce a wealth of new states, including a Dirac metal at 1/3rd electron doping. Here we report the topochemical synthesis of electron doped ZnLixCu3(OH)6Cl2 from x = 0 to x = 1.8 (3/5th per Cu2+). Intercalation of Li ions is achieved through exposing herbertsmithite to a reducing solution of benzophenone and lithium under precise conditions. To obtain lower doping concentrations, the fully doped sample is systematically deintercalated by iodine in acetonitrile. X-ray diffraction studies demonstrate the underlying kagome structure of the doped herbertsmithite series is maintained, while X-ray photoelectron spectroscopy shows a change in the oxidation state and local chemical environment of the copper. This is consistent with a reduction of the copper kagome layer. Contrary to expectations, no metallicity or superconductivity is induced. Instead, we find a systematic suppression of magnetic behavior across the phase diagram. Our results demonstrate that significant theoretical work is needed to understand and predict the role of doping in magnetically frustrated narrow band insulators, particularly the interplay between local structural disorder and tendency toward electron localization, and pave the way for future studies of doped spin liquids.

Electron doping a kagome spin liquid

We are investigating a nanoparticle therapeutic silica-based (protocell) delivery system to overcome intracellular bacterial infections using bacteriophage. To aid in vivo visualization and tracking of bacteriophage delivery, we are employing fluorescent and electron-dense bioimaging nanoparticles. Bacteriophage are being used as templates to attach commercial and synthesized Quantum Dots (QDs) for future identification of bacteria within cells and tissue. The protein coat of MS2 phage, with exterior –NH2 groups from lysine residues, provides an ideal target for functionalization and conjugation of nanoparticles. QDs were selected due to their tunable emissions properties within the biological tissue optical window and their high quantum yields. Several conjugation strategies are being explored including EDC/NHS coupling to attach the QDs to the MS2 protein coat. Details on the results of viability studies using plaque assays and silica encapsulation will be presented.

Bacteriophage-conjugated quantum dots as in vivo luminescent bioimaging agents

Rare earth elements (REEs) are the backbone of clean energy technologies. However, REEs are mainly available through mining operations outside the U.S, which makes the future supply of these critical materials at risk. To ensure the U.S. energy security, it is now vital to develop domestic sources of REEs. Global phosphate deposits contain 27 million tons of REEs, equal to approximately 200 years of current world demand. Near 38% of these REEs end up in phosphogypsum (PG) waste during phosphate fertilizer production. PG stacks in central Florida occupy acres of potential farm land and pose adverse environmental effects to their surroundings. Recovering REEs from PG is the first step towards a trash-to-treasure transformation. Here we studied REEs location and stability in RE-doped CaSO4/Ca3(PO4)2 systems using solid state calorimetry. We also developed mixed solvent electrolyte simulations to predict and designed experiments to verify the solubility of NdPO4 (as a model compound) under various acidic conditions. This study provides insight into developing an efficient recovery process which could generate 25,000 tons of REEs annually from PG waste.

Rare earth recovery from phosphate fertilizer production waste

In order to develop nanoscintillators and bioimaging agents, we explored the synthesis of alkaline earth based chalcogenide (AEE, where AE = Ca, Sr, Ba; and E = S, Se, Te) phosphors. AEE materials have previously been investigated for infrared detectors, electroluminescent behavior, and radiation dosimetry devices. These materials emission properties can be fine-tuned by varying lanthanide activators. Recently, due to the promise of improved light emitting diodes (LED), scintillators, infrared detectors, biochips and bioimaging applications the demand for synthetic routes to doped AEE nanomaterials with tailored properties has increased. Therefore, we developed a general synthesis route to tailored AEE nanomaterials to enable the systematic exploration of the entire AEE family. A family of alkaline earth chalcogenide [AEE; where AE = Ca, Sr, Ba & E = S, Se, Te] and lanthanide doped strontium selenide (SrSe:Ln3+; Ln3+ = Tb, Dy) nanoparticles were synthesized under solution processing conditions. Crystalline nanoparticles were prepared from the stoichiometric reaction between various metal alkoxide and chalcogenide precursors heated in trioctylphosphine oxide (TOPO). The following metal alkoxides were synthesize and used: [Ca(DBP)2(THF)3] (1); [Sr5(μ4-O)(μ3-ONep)4(μ-ONep)4(HONep)(py)4] (2); [Ba2(μ3-ONep)(μ-ONep)2(ONep)(HONep)3(py)]2 (3); [Ln(µ-ONep)2(ONep)]4 [Ln = Tb (4), Dy (5)] (where ONep = OCH2C(CH3)3, DBP = OC6H3(C(CH3)3)2-2,6, THF = tetrahydrofuran, py = pyridine); along with chalcogenides: S(Si(CH3)3)2; TOP=Se; or TOP=Te (TOP = trioctylphosphine). Depending on processing conditions, the resultant nanoparticles were found to range from 5–50 nm by TEM analysis. Powder XRD revealed that all of the nanoparticles crystalized in the rock salt structure type and retained this structure under ambient conditions for a limited time. Through diffuse reflectance spectroscopy, room temperature indirect band gap energies from nanoparticle films were determined. The photoluminescence (PL) properties of 5% doped SrSe:Dy3+ and SrSe:Tb3+, in solution, were found to produced emission bands from the Tb3+ and Dy3+ dopants at excitation wavelengths of 315 and 317 nm, respectively. Full details on the synthesis and characterization will be presented.

Developing lanthanide doped alkaline earth chalcogenide nanoparticles for scintillators and bioimaging agents

Nickel and nickel based alloys are commonly used as metal surfaces in heterogeneous catalysts and in industrial applications. In industry, nickel metal alloys are used as the building material for various components in power plants because of their corrosion-resistant properties. In catalysis, nickel alloy surfaces are studied for applications such as the steam reforming of methane and the oxidation of hydrocarbon fuels in solid-oxide fuel cells. However, carbon deposition on the surface leads to coking and deactivation of the nickel catalyst while oxygen adsorption on the surface leads to the formation of a metal oxide which changes the chemistry of the surface. In order to make new nickel based alloys, it is therefore essential to understand the fundamental interactions of C, O, and CO species with the surface. Here density functional theory is used to analyze the interactions of C, O, and CO with the (100) and (111) facets of different nickel surface alloys. These interactions are discussed and compared to the pure nickel surface. For the nickel surface alloys, one surface Ni atom is substituted with the alloying atom to represent the surface alloy. Alloying elements include Al, Co, Cr, Cu, Fe, Mn, Mo, Nb, Ti, V, and W. The binding energies of each C, O, and CO on all twelve surfaces have been studied and reaction energies for the dissociation of CO into C and O have been calculated. The density of states for each nickel surface alloy has also been calculated, and the d-band center is compared to the binding energies of C, O, and CO on the surface. The addition of any of the alloying atoms to the Ni(100) facet has a destabilizing effect on the adsorption of C, O, and CO compared to the adsorption on the pure nickel surface. In contrast, on the (111) facet the addition of an alloying atom increases the stability of the adsorbates on the surface compared to the pure nickel surface. Overall, nickel surface alloys with Co, Cu, or Fe exhibit the weakest interactions between the surface and the C, O, and CO adsorbates while the nickel surfaces alloyed with Mo, W, V, or Ti induce the strongest binding of the adsorbates on the surface.

Density functional theory study of the interactions of C, O, and CO with nickel surface alloys

In order to provide affordable and sustainable energy to coastal regions the kinetic energy of waves, tides, and ocean currents are being harnessed through the development of Marine Hydrokinetic (MHK) technology. Since 2008, U.S. MHK devices tested in the open waters were found to have a number of materials and coating related issues. During their brief operation (8 weeks–1 year), the MHK industry noted mooring failure, connection failure (metal-composite), sediment fouling, sediment erosion, structural failure (composites), biofouling, and corrosion as materials and coatings problem areas.. These early stage demonstrations often employed designs using materials and coatings to primarily validate performance and not reliability. Coatings used were based upon meeting environmental policies that limited or negated the use of commercial coatings. The deployed projects also had limited or no structural health monitoring or non-destructive inspection of failed critical components during/after manufacture, delivery, setup, or during operation. To avoid and reduce these listed effects we have investigated how to improve current material selections and coatings formulations. This talk will review how materials chemistry is being used to advance MHK technology. The synthesis and characterization of antifouling and anticorrosion coatings as well as how salt water affects composite material’s resin, adhesive, and fiber (glass, carbon) properties will be discussed.

Advancing marine hydrokinetic energy technology through materials chemistry

We have designed new materials that integrate the photochemistry of metal-coordination complex into polymers. The inclusion of transition metal ions allowed for new photoreactivity in the polymers where the bonding interactions, and thus polymer cross-linking, was controlled with light. Depending on the type of metal and coordinated ligand, coordination complexes offer a diversity of reactivity due to the changing metal-ligand binding interactions (energy, geometry etc.). We have integrated such metal-coordination bonding into polysaccharide-based materials to create photoresponsive gels. These gels showed changes in mechanical properties and pore size after light irradiation, and could be used as scaffold materials for tissue engineering. We also created model polymer materials to understand how we could influence and control material properties by tuning the metal ion and ligand. We showed that by changing the geometry of ligand coordination, we could control the mechanical properties of the resulting materials. In addition, such metallopolymers showed reversible photoreactivity, where light irradiation led to softening of the materials.

Controlling mechanical properties of polymeric materials using photo-active metal coordination interactions

We have prepared metallo-supramolecular systems from linear ditopic ligands on short organic polymer chains with incorporated transition metal ions bound to these ligand termini. These labile metal-ligand interactions convert viscous liquid diamine-terminated hydrogenated poly(ethylene-co-butylene) polymer into photoresponsive viscoelastic materials with the terminal viscosity in the range of the glass viscosity (109 Pa s). Utilizing this approach we have created a series of supramolecular polymer melts and studied their mechanical and photo physical properties. We have shown that the photochemistry and photophysical properties of the metal center can be used to control the mechanical properties of the materails, and introduce new optical and mechanical properties not seen in the traditional covalent polymers. In particular, photo-induced metal-ligand bond labilization led to partial depolymerization of the supramolecular assembly, and softening of the materials. When the light stimulus was removed, the material recovered the initial stiffness back. We also investigated structure-property relationships in such systems where mechanical properties of the supramolecular polymers are controlled by coordination environment around metal cross-linking center.

Tuning photochemical and photophysical properties of metallosupramolecular materials

We have prepared hydrogen bonded supramolecular polymer melts via modification of soft non-polar hydrogenated poly(ethylene-co-butylene) polymer (HLBH-P 3000) termini groups with hydrogen bonding motifs. These interactions enhance the elastic properties of the material via supramolecular binding in the polymer matrix and result in a structurally dynamic supramolecular polymer network, whose properties could be temperature modulated. We have throughly studied the mechanical properties of the prepared material using oscillatory rheology. This supramolecular polymer exhibited interesting temperature-modulated behavior not seen in the previously reported systems. Namely, it had two switchable states with remarkably different mechanical properties that were achieved via reassembly of hydrogen bonding domains. To enhance the optical properties of these materials, we prepared a series of these supramolecular polymers with different organic and inorganic dyes incorporated into the polymer matrix. Introduction of the chromophores created materials that were capable of self-healing upon external light radiation. The healing rate was controlled by the light radiation power, time, and location as well as the nature of supramolecular interactions in the polymers.

Hydrogen bonding supramolecular polymers with temperature controlled switchable mechanical properties reveal photoheable effects

Layered double hydroxides (LDH) also referred to as anionic clays are a class of important materials comprising positively charged metal hydroxide layers with anions in the interlayer. Unlike hydrotalcite, which is a Mg-Al LDH whose structure is based on brucite, Li-Al LDH comprises monovalent Li and its structure is based on Al(OH)3. They can be crystallized with different compositions and have a potential for several applications. Among the others, recently it has been shown that it can be used for Li sequestration from brine. In the current work, we have examined the formation enthalpies of [Li-Al-Cl] LDHs with different compositions. We also determine the interaction energies of this material with several alkali chlorides in order to determine the LDH composition that interacts selectively with Li over the others cations which are present in the brine.

Thermochemistry of Layered double hydroxides of Li with Al

The raw bamboo (Phyllostachys mankinoi), with a moisture content of 13.54 % and an HHV of 17.657 MJ/kg, was subjected to torrefaction under a higee environment. The performance of the higee torrefaction was explored in two parts: (1) effect of rotation and temperature and (2) effect of duration on the solid yield, HHV and energy yield. By statistical analyses, the results indicated that the rotation, temperature and their interaction has a significant effect on the three responses. Same remarks on the effect of duration where when the duration (temperature and rotation) increases, the HHV increases, while the solid yield and energy yield decreases. Graphical interpretations showed that at 300 °C, the rotating speed has no evident effect on the responses. At 30-min holding time, the highest HHV reached (28.389 MJ/kg) was obtained in the most severe torrefaction condition (rotating speed at 1800 rpm and temperature at 300 °C) with an EF of HHV corresponding to 1.61 and an energy yield of 63.51%. Upon inspection, the recommended operating condition under a 30-min holding time is at 255 °C-1800 rpm since the EF (1.53), HHV (26.988 MJ/kg), and energy yield (65.21%) values are relatively close to that of the aforementioned torrefaction condition. The Van Krevelen diagram of the torrefied biomass showed that the ratios decrease as the torrefaction intensifies, hence improving the hydrophobicity of the product. The spreads of the results of the solid yield, EF of HHV, energy yield, and H/C and O/C ratios were in accordance to the trends of the responses. Overall, from the results presented, it can be concluded that the quality of the product from the process is at par to that of coal (i.e. HHV of coal is 21-35 MJ/kg). The FTIR results indicated that cellulose and lignin may have been degraded at a lower temperature at high rotating speed. The results suggested that torrefaction under higee environment indicates promising process for the utilization of bamboo.

Performance and structural evaluation of the torrefaction of bamboo under a high gravity (higee) environment using a rotating packed bed

Due to the increase in antibiotic resistant bacteria, alternative therapies that use bacteriophage are under investigation. Bacteriophage are viruses that infect bacteria and are ubiquitous in nature. To understand how bacteriophage can be used in phage therapy, we are developing several bioimaging nanoparticles that can be used to track them during cell studies. We selected quantum dots which have been previously investigated for bioimaging studies used in cancer research. Quantum dots of CdTe@ZnS were synthesized in trioctylphosphine and octadecene using a solution precipitation route. After, we performed surface exchange of the native ligands with 11-mercaptoundecanoic acid that allowed the particles to be dispersed in a buffer solution. The particles obtained were characterized using Powder X-ray Diffraction (PXRD), UV-vis Spectroscopy (UV-vis), and Transmission Electron Microscopy (TEM). Next particles were tested for their attachment to MS2 phage using EDC/NHS coupling strategies and we examined their viability using plaque assays. Full details on the synthesis and characterization will be presented.

Synthesis of quantum dot bioimaging agents to study bacteriophage

Alumina (Al2O3 or aluminum oxide) is an important metal oxide used in variety of applications due to its chemical and thermal stability. Nanoscale powders can be useful as an integral ink material used in direct write (robocasting) processes as well as in numerous commercial products such as electronics and paints. Critical to these applications is understanding how Al2O3 crystals grow under various processing conditions in order to control its properties. In order to understand growth behavior of Al2O3 nanoparticles, the effect of precursor on nanoparticle phase and morphology was examined within solution processing routes. Solution nanoparticle processing routes (e.g., glycothermal, solvothermal, and solution precipitation) were used to lower the temperatures and/or pressures required to reach the a-Al2O3. Powders were isolated and examined with X-ray Diffraction and Electron Microscopy. Depending on processing route, wires, plates, or spherical particles of boehmite or alumina were obtained. Full details on the synthesis and characterization on alumina and boehmite will be presented. This work was supported in part by Laboratory Directed Research and Development (LDRD), Department of Energy (DOE), Geothermal Technologies Office (GTO) under the Office of Energy Efficiency and Renewable Energy (EERE), and by the Sandia STAR Program. Sandia National Laboratories, a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Understanding growth behavior of alumina (Al2O3) and boehmite (AlO(OH)) nanoparticles

Tin phosphides (e.g., SnxPy or SnP, Sn3P4, Sn4P3) nanomaterials are being investigated for their use as battery anode materials and in semiconducting applications. Critical to their successful application is the development of synthetic routes that provide tight control over the final product. Current efforts in generating tin phosphide nano materials have explored precursors such as tin(II) acetate or elemental phosphorus and tin. These commercial precursors require high temperatures and pressures as well as long heating times to achieve phase purity of nanoparticles. To explore an alternative precursor to lower processing conditions, tin(bis(bisdiisopropylphosphinoamide) [Sn[N(P-Pri2)2]2 was synthesized and used to generate tin (Sn0) and SnxPy nanomaterials. Phase information of the nanoparticles was studied by removing aliquots of the reactions at different intervals for temporal analysis. Powder X-ray diffraction on the isolated temporal products revealed how [Sn[N(P-Pri2)2]2 yields Sn0 and SnxPy nanomaterials. Transmission electron microscopy (TEM) images showed that the particles ranged in size from 50-100 nm for Sn0 and from 0.1-0.2 um for SnxPy depending on reaction parameters. Additionally, TGA data on [Sn[N(P-Pri2)2]2shows the breakdown of outside functional groups.Using solution precipitation methods [Sn[N(P-Pri2)2]2was combined with coordinating (e.g. oleylamine, trioctylphosphine oxide, trioctylphosphine) or non-coordinating solvents (octadecene) to determine how these solvents boiling points, polarity, and functional groups affected the final nanomaterial phase. Solvothermal methods were also tested where results supported the previous findings of solution precipitation methods using [Sn[N(P-Pri2)2]2.

Synthesis of tin phosphide and tin nanomaterials

Designing well-defined, smart and dynamic nanostructures in solution through hierarchical assembly of materials has always been an exciting goal for many researchers. These nanoscale objects are very important in different aspects of nanotechnology since they are the key elements for making future advanced materials. Among various fabrication methods, ionic self-assembly has appeared as an important method in designing smart and stimuli responsive nanostructures. Although ionic interactions are important due to their abundance in nature, but incorporating them to design controlled artificial nanostructure has always been challenging. We proposed that through incorporation of zwitterionic functionalities it is possible to control the charged density of ionic building blocks and direct them into desired nanostructures. We showed that with controlling the electrostatic interaction of zwitterionic dendrimers and ionic surfactants by solution pH, we can design smart nanotubes through membrane fusion of bilayer vesicles which found to be responsive to ionic strength. Combination of atomic force microscopy (AFM), transmission and scanning electron microscopy (TEM, SEM) techniques were used to visualize nanotubes while dynamic light scattering (DLS) and isothermal titration calorimetry (ITC) provided information regarding self-assembly process in solution. Zwitterionic materials are important due to their unique behavior compare to typical polyelectrolytes which makes them a potential candidate in designing future novel nanostructures.

Bottom-up hierarchical self-assembly of zwitterionic dendrimers into stimuli responsive dynamic nanotubes

Attention! Our chemistry magic dog is missing! For over a decade, Sandia has invited 4th grade students from all over New Mexico to see a chemistry magic show. This workshop’s goal is to encourage interaction with scientists and engineers at our place of work during critical career path decisions, made as early as the 4th and 5th grade. The workshop includes 10 unique stations based on scientific principles that are used to identify the dognapping culprit. In order to track our impact, a survey was given to the workshop participants prior to a safety visit, immediately after the workshop, and two months after the workshop. The results from these surveys and a general description of the program will be presented.

CSI dognapping workshop: A Sandia outreach program

Two new isostructural double perovskites, Cs2AgSbCl6 and Cs2AgInCl6, have been synthesized and characterized. Cs2AgSbCl6 has an indirect band gap of 2.16 eV, while Cs2AgInCl6 possesses a direct bandgap of 3.29 eV. Cs2AgSbxIn1-xCl6 (x = 0.5, 0.4 and 0.2) solid solutions exhibit the transition from indirect to direct bandgaps at x = 0.4. Electronic structure calculations reveal that the transition from indirect to direct bandgaps is driven by an inversion of the unoccupied s- and p-states of Sb and In. These results open up an avenue for tuning the optical indirect to direct bandgaps in double perovskites based on less toxic elements and more air/moisture stable than hybrid lead halide perovskites. In addition, photoconductivity properties, temperature and wavelength dependence of structural and electronic properties have been performed and will be discussed.

Tuning indirect to direct bandgaps in double perovskites

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.