Synthesis, characterization and computational chemical study of novel pyrazole derivatives as anticorrosion and antiscalant agents

NASA Astrophysics Data System (ADS)

El-Taib Heakal, F.; Attia, S. K.; Rizk, S. A.; Abou Essa, M. A.; Elkholy, A. E.

2017-11-01

Metals corrosion and scales deposition are two serious problems of heavy burden in most industries. Both problems can be mitigated by adding special chemicals capable of being adsorbed on metallic surfaces as well as on scale growing crystal surfaces. Efficient materials should be rich in functional groups containing heteroatoms and/or π bonds for supporting their adsorbability on surfaces. In the present work, four novel pyrazole derivatives were synthesized and characterized for their structures using elemental analysis and spectroscopic tools. The tested compounds were fabricated by treating 2,3-diaryloxirane-2,3-dicarbonitriles with different nitrogen nucleophiles. The density functional theory (DFT) was then applied to explore the structural and electronic characteristics of these materials. Molecular dynamics simulation was also run to scrutinize the ability of the prepared compounds to act as corrosion inhibitors and antiscalant agents by adsorbing on Fe and CaSO4 surfaces.

Chloride (Cl-) ion-mediated shape control of palladium nanoparticles

NASA Astrophysics Data System (ADS)

Nalajala, Naresh; Chakraborty, Arup; Bera, Bapi; Neergat, Manoj

2016-02-01

The shape control of Pd nanoparticles is investigated using chloride (Cl-) ions as capping agents in an aqueous medium in the temperature range of 60-100 °C. With weakly adsorbing and strongly etching Cl- ions, oxygen plays a crucial role in shape control. The experimental factors considered are the concentration of the capping agents, reaction time and reaction atmosphere. Thus, Pd nanoparticles of various shapes with high selectivity can be synthesized. Moreover, the removal of Cl- ions from the nanoparticle surface is easier than that of Br- ions (moderately adsorbing and etching) and I- ions (strongly adsorbing and weakly etching). The cleaned Cl- ion-mediated shape-controlled Pd nanoparticles are electrochemically characterized and the order of the half-wave potential of the oxygen reduction reaction in oxygen-saturated 0.1 M HClO4 solution is of the same order as that observed with single-crystal Pd surfaces.

Adsorption of Halogenated Fire-Extinguishing Agents on Powders

NASA Technical Reports Server (NTRS)

Barduhn, Allen J.; Patel, Bhailal S.; Meyer, Walter; Smura, Bronislaw B.

1960-01-01

The amounts of four different Freons adsorbed by carbon, silica gel, alumina, and molecular sieves were determined at pressures up to 225 lb/sq in. The carbon adsorbed 50 to 100 percent and the silica gels, 30 to 50 percent of their own weight of Freon. Several adsorbed systems were tested in a standard dry-powder extinguisher on a 5-sq-ft gasoline fire for their effectiveness in putting out a fire. One of the Freons (bromotrifluoromethane) and carbon extinguished fires about as well as bicarbonate powder and nitrogen.

Capping agents in nanoparticle synthesis: Surfactant and solvent system

NASA Astrophysics Data System (ADS)

Gulati, Shivani; Sachdeva, M.; Bhasin, K. K.

2018-05-01

The preparation of nanomaterials by organometallic precursors require a capping agent, which primarily acts as stabilizing agent and provide colloidal stability along with preventing agglomeration and stopping uncontrolled growth. Final morphology of nanocrystal largely depends on the type of capping agent which is adsorbed on the surface of nanocrystal. Thus capping agents are the keys to obtain the small-sized nanoparticles and are very frequently used in colloidal synthesis of nanoparticles to avoid its overgrowth.

Synthesis and Characterization Pectin-Carboxymethyl Chitosan crosslinked PEGDE as biosorbent of Pb(II) ion

NASA Astrophysics Data System (ADS)

Hastuti, Budi; Siswanta, Dwi; Mudasir; Triyono

2018-01-01

Pectin and chitosan are biodegradable polymers, potentially applied as a heavy metal adsorbents. Unfortunately both biosorbents pectin and chitosan have a weakness in acidic media. For this purpose required modified pectin and chitosan. The modified adsorben is intended to obtain a stable adsorbent and resistance under acid. The research was done by experimental method in laboratory. The stages of this research are the synthesis of carboxymethyl chitosan (CMC), synthesis of Pec-CMC-PEGDE film adsorbent, stabily test under acid, the characterization of active group using FTIR, stability characterization of Pec-CMC-PEGDE powder adsorbent using XRD, termo stability using DTA-TGA. The results of the research have shown that: pectin and CMC can be cross-linked using PEGDE crosslinking agent, the film adsorbent was stable under HCl 1 M, the film adsorbent have active group comprise of carboxylate and amine groups. The result of characterization using XRD, shows that the adsorbent is semi-crystalline. Base on termo stability, the film adsorbent Pec-CMC-PEGDE stable up to 600°C. The film can be applied as an adsobent of Pb (II) ion remediation. The optimum pH of pec-CMC-PEGDE in adsorbed of Pb(II) was reached at pH 5 with 99.99% absorbent adsorbed and of and adsorption capacity was 46.11 mg/g.

Interfacial interactions between calcined hydroxyapatite nanocrystals and substrates.

PubMed

Okada, Masahiro; Furukawa, Keiko; Serizawa, Takeshi; Yanagisawa, Yoshihiko; Tanaka, Hidekazu; Kawai, Tomoji; Furuzono, Tsutomu

2009-06-02

Interfacial interactions between calcined hydroxyapatite (HAp) nanocrystals and surface-modified substrates were investigated by measuring adsorption behavior and adhesion strength with a quartz crystal microbalance (QCM) and a contact-mode atomic force microscope (AFM), respectively. The goal was to develop better control of HAp-nanocrystal coatings on biomedical materials. HAp nanocrystals with rodlike or spherical morphology were prepared by a wet chemical process followed by calcination at 800 degrees C with an antisintering agent to prevent the formation of sintered polycrystals. The substrate surface was modified by chemical reaction with a low-molecular-weight compound, or graft polymerization with a functional monomer. QCM measurement showed that the rodlike HAp nanocrystals adsorbed preferentially onto anionic COOH-modified substrates compared to cationic NH2- or hydrophobic CH3-modified substrates. On the other hand, the spherical nanocrystals adsorbed onto NH2- and COOH-modified substrates, which indicates that the surface properties of the HAp nanocrystals determined their adsorption behavior. The adhesion strength, which was estimated from the force required to move the nanocrystal in contact-mode AFM, on a COOH-grafted substrate prepared by graft polymerization was almost 9 times larger than that on a COOH-modified substrate prepared by chemical reaction with a low-molecular-weight compound, indicating that the long-chain polymer grafted on the substrate mitigated the surface roughness mismatch between the nanocrystal and the substrate. The adhesion strength of the nanocrystal bonded covalently by the coupling reaction to a Si(OCH3)-grafted substrate prepared by graft polymerization was approximately 1.5 times larger than that when adsorbed on the COOH-grafted substrate.

Coverage dependent non-adiabaticity of CO on a copper surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omiya, Takuma; Surface and Interface Science Laboratory, RIKEN, Wako 351-0198; Arnolds, Heike

2014-12-07

We have studied the coverage-dependent energy transfer dynamics between hot electrons and CO on Cu(110) with femtosecond visible pump, sum frequency probe spectroscopy. We find that transients of the C–O stretch frequency display a red shift, which increases from 3 cm{sup −1} at 0.1 ML to 9 cm{sup −1} at 0.77 ML. Analysis of the transients reveals that the non-adiabatic coupling between the adsorbate vibrational motion and the electrons becomes stronger with increasing coverage. This trend requires the frustrated rotational mode to be the cause of the non-adiabatic behavior, even for relatively weak laser excitation of the adsorbate. We attributemore » the coverage dependence to both an increase in the adsorbate electronic density of states and an increasingly anharmonic potential energy surface caused by repulsive interactions between neighboring CO adsorbates. This work thus reveals adsorbate-adsorbate interactions as a new way to control adsorbate non-adiabaticity.« less

Functionalization of CNTs surface with phosphonuim based deep eutectic solvents for arsenic removal from water

NASA Astrophysics Data System (ADS)

AlOmar, Mohamed Khalid; Alsaadi, Mohammed Abdulhakim; Hayyan, Maan; Akib, Shatirah; Hashim, Mohd Ali

2016-12-01

Herein, we present the use of deep eutectic solvent (DES) as functionalization agents for carbon nanotubes (CNTs) to form novel adsorbents for removal of arsenic ions (As3+) from water. Two DESs systems were prepared using methyltriphenylphosphonium bromide (MTPB) and benzyltriphenylphosphonium chloride (BTPC) as salts, in conjugation with glycerol (Gly) as a hydrogen bond donor. The resulting novel adsorbents were characterized using thermogravimetric analysis (TGA), Zeta potential, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, XRD, EDX, FESEM, and BET surface area. Optimization studies were carried out utilizing RSM-CCD experimental design to estimate the optimum removal conditions for each adsorbent. The adsorption experimental data of both adsorbents were found to fit well with pseudo-second-order kinetics model, as well as with Langmuir and Freundlich adsorption isotherm models. The maximum adsorption capacity of a MTPB-DES-functionalized CNTs adsorbent was 23.4 mg/g.

The possible magnetoelectric coupling induced by adsorption in SnTe films

NASA Astrophysics Data System (ADS)

Fu, Zhaoming; Liu, Meng; Zhang, Na; An, Yipeng; Yang, Zongxian

2018-01-01

Based on the recent discovery of the stable in-plane spontaneous polarization in SnTe films. We report the possible magnetoelectric (ME) coupling induced by adsorption in SnTe films by performing density functional calculations. Firstly, we investigate the adsorption-induced magnetic behaviors on the two-dimensional SnTe monolayer. Five kinds of adatoms (H, B, C, N and O) are taken into account. It is found that the SnTe with adsorbing H and B have nonzero magnetic moments and good stability. Secondly, the coexistence of the ferromagnetism and ferroelectrics (i.e. multiferroics) is observed in H-adsorbed SnTe. The magnetoelectric coupling in this system is studied by calculating the poralazition in different magnetic structures (antiferromagnetic and ferroelectric). According to our study, we propose that it is a possible method obtaining the multiferroicity and ME coupling to modify the SnTe films by chemical adsorption of single atoms.

Metal organic frameworks (MOFs) for degradation of nerve agent simulant parathion

USDA-ARS?s Scientific Manuscript database

Parathion, a simulant of nerve agent VX, has been studied for degradation on Fe3+, Fe2+ and zerovalent iron supported on chitosan. Chitosan, a naturally occurring biopolymer derivative of chitin, is a very good adsorbent for many chemicals including metals. Chitosan is used as supporting biopolymer ...

Metal organic frameworks (MOFs) for degrdation of nerve agent simulant parathion

USDA-ARS?s Scientific Manuscript database

Parathion, a simulant of nerve agent VX, has been studied for degradation on Fe3+, Fe2+ and zerovalent iron supported on chitosan. Chitosan, a naturally occurring biopolymer derivative of chitin, is a very good adsorbent for many chemicals including metals. Chitosan is used as supporting biopolymer ...

Evaluation of phosphorus adsorption capacity of sesame straw biochar on aqueous solution: influence of activation methods and pyrolysis temperatures.

PubMed

Park, J H; Ok, Y S; Kim, S H; Cho, J S; Heo, J S; Delaune, R D; Seo, D C

2015-12-01

The phosphorus (P) adsorption characteristic of sesame straw biochar prepared with different activation agents and pyrolysis temperatures was evaluated. Between 0.109 and 0.300 mg L(-1) in the form of inorganic phosphate was released from raw sesame straw biochar in the first 1 h. The release of phosphate was significantly enhanced from 62.6 to 168.2 mg g(-1) as the pyrolysis temperature increased. Therefore, sesame straw biochar cannot be used as an adsorbent for P removal without change in the physicochemical characteristics. To increase the P adsorption of biochar in aqueous solution, various activation agents and pyrolysis temperatures were applied. The amount of P adsorbed from aqueous solution by biochar activated using different activation agents appeared in the order ZnCl2 (9.675 mg g(-1)) > MgO (8.669 mg g(-1)) ⋙ 0.1N-HCl > 0.1N-H2SO4 > K2SO4 ≥ KOH ≥ 0.1N-H3PO4, showing ZnCl2 to be the optimum activation agent. Higher P was adsorbed by the biochar activated using ZnCl2 under different pyrolysis temperatures in the order 600 °C > 500 °C > 400 °C > 300 °C. Finally, the amount of adsorbed P by activated biochar at different ratios of biochar to ZnCl2 appeared in the order 1:3 ≒ 1:1 > 3:1. As a result, the optimum ratio of biochar to ZnCl2 and pyrolysis temperature were found to be 1:1 and 600 °C for P adsorption, respectively. The maximum P adsorption capacity by activated biochar using ZnCl2 (15,460 mg kg(-1)) was higher than that of typical biochar, as determined by the Langmuir adsorption isotherm. Therefore, the ZnCl2 activation of sesame straw biochar was suitable for the preparation of activated biochar for P adsorption.

Development of Reactive Topical Skin Protectants against Sulfur Mustard and Nerve Agents

DTIC Science & Technology

1997-06-01

Inorganic pollutants such as hydrogen cyanide, cyanogen chloride, and acid gases are not adsorbed well by activated carbon, and (3) Clean-up and...with Fe203 caused an increase in destructive adsorbent capacity of chlorocarbons, acid gases, and organophosphorus compounds. We attribute this...solution of distilled water, concentrated nitric acid , and methanol were added to methanol and neat titanium (IV) butoxide. The formed gel was aged

Electronic damping of anharmonic adsorbate vibrations at metallic surfaces

NASA Astrophysics Data System (ADS)

Tremblay, Jean Christophe; Monturet, Serge; Saalfrank, Peter

2010-03-01

The nonadiabatic coupling of an adsorbate close to a metallic surface leads to electronic damping of adsorbate vibrations and line broadening in vibrational spectroscopy. Here, a perturbative treatment of the electronic contribution to the lifetime broadening serves as a building block for a new approach, in which anharmonic vibrational transition rates are calculated from a position-dependent coupling function. Different models for the coupling function will be tested, all related to embedding theory. The first two are models based on a scattering approach with (i) a jellium-type and (ii) a density functional theory based embedding density, respectively. In a third variant a further refined model is used for the embedding density, and a semiempirical approach is taken in which a scaling factor is chosen to match harmonic, single-site, first-principles transition rates, obtained from periodic density functional theory. For the example of hydrogen atoms on (adsorption) and below (subsurface absorption) a Pd(111) surface, lifetimes of and transition rates between vibrational levels are computed. The transition rates emerging from different models serve as input for the selective subsurface adsorption of hydrogen in palladium starting from an adsorption site, by using sequences of infrared laser pulses in a laser distillation scheme.

SEPARATION OF PLUTONIUM

DOEpatents

Maddock, A.G.; Smith, F.

1959-08-25

A method is described for separating plutonium from uranium and fission products by treating a nitrate solution of fission products, uranium, and hexavalent plutonium with a relatively water-insoluble fluoride to adsorb fission products on the fluoride, treating the residual solution with a reducing agent for plutonium to reduce its valence to four and less, treating the reduced plutonium solution with a relatively insoluble fluoride to adsorb the plutonium on the fluoride, removing the solution, and subsequently treating the fluoride with its adsorbed plutonium with a concentrated aqueous solution of at least one of a group consisting of aluminum nitrate, ferric nitrate, and manganous nitrate to remove the plutonium from the fluoride.

Polymer-based adsorbent for heavy metals removal from aqueous solution

NASA Astrophysics Data System (ADS)

Mahmud, H. N. M. E.; Huq, A. K. O.; Yahya, R.

2017-06-01

A novel conducting polymer-based adsorbent, polypyrrole (PPy) fine powder has successfully been prepared as a new adsorbent and utilized in the adsorption of heavy metal ions like arsenic, zinc and cadmium ions from aqueous solution. PPy was chemically synthesized by using FeCl3.6H2O as an oxidant. The prepared PPy adsorbent was characterized by Brunauer-Emmet-Teller (BET) surface analysis, field emission scanning electron microscopy (FESEM) and attenuated total reflectance fourier transform infrared ATR-(FTIR) spectroscopy. The adsorption was conducted by varying different parameters such as, contact time, pH and adsorbent dosage. The concentrations of metal ions were measured by inductively coupled plasma mass spectroscopy (ICP-MS). The results show that PPy acts as an effective sorbent for the removal of arsenic, zinc and cadmium ions from aqueous solution. The as-prepared PPy fine powder is easy to prepare and appeared as an effective adsorbent for heavy metal ions particularly arsenic in wastewater treatment.

Primary, secondary, and tertiary amines for CO2 capture: designing for mesoporous CO2 adsorbents.

PubMed

Ko, Young Gun; Shin, Seung Su; Choi, Ung Su

2011-09-15

CO(2) emissions, from fossil-fuel-burning power plants, the breathing, etc., influence the global worming on large scale and the man's work efficiency on small scale. The reversible capture of CO(2) is a prominent feature of CO(2) organic-inorganic hybrid adsorbent to sequester CO(2). Herein, (3-aminopropyl) trimethoxysilane (APTMS), [3-(methylamino)propyl] trimethoxysilane (MAPTMS), and [3-(diethylamino) propyl] trimethoxysilane (DEAPTMS) are immobilized on highly ordered mesoporous silicas (SBA-15) to catch CO(2) as primary, secondary, and tertiary aminosilica adsorbents. X-ray photoelectron spectroscopy was used to analyze the immobilized APTMS, MAPTMS, and DEAPTMS on the SBA-15. We report an interesting discovery that the CO(2) adsorption and desorption on the adsorbent depend on the amine type of the aminosilica adsorbent. The adsorbed CO(2) was easily desorbed from the adsorbent with the low energy consumption in the order of tertiary, secondary, and primary amino-adsorbents while the adsorption amount and the bonding-affinity increased in the reverse order. The effectiveness of amino-functionalized (1(o), 2(o), and 3(o) amines) SBA-15s as a CO(2) capturing agent was investigated in terms of adsorption capacity, adsorption-desorption kinetics, and thermodynamics. This work demonstrates apt amine types to catch CO(2) and regenerate the adsorbent, which may open new avenues to designing "CO(2) basket". Copyright © 2011. Published by Elsevier Inc.

First-principles study of Au-decorated carbon nanotubes

NASA Astrophysics Data System (ADS)

Ju, Weiwei; Li, Tongwei; Zhou, Qingxiao; Li, Haisheng; Li, Xiaohong

2018-07-01

The electronic structures and spin-orbit (SO) coupling of carbon nanotubes with adsorbed Au atoms are investigated based on density functional theory. Three kinds of zigzag single-walled CNT (8,0), (10,0) and (12,0) are selected. The Au atoms prefer to adsorb on the top of C atoms. The adsorption of Au atoms can introduce impurity states in the band gap, modifying the electronic properties of systems. Furthermore, the influence of SO coupling on these impurity states is also explored. Considerable SO splitting (∼130 meV) can be obtained. We find that the SO splitting decreases with the increase of the concentration of Au atoms, which can be ascribed to the interaction between Au atoms, suppressing the SO splitting. Our work provides imperative understanding on the electronic properties and SO coupling effect in Au-decorated CNTs.

Adsorbate hopping via vibrational-mode coupling induced by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Ueba, H.; Hayashi, M.; Paulsson, M.; Persson, B. N. J.

2008-09-01

We study the heat transfer from femtosecond laser-heated hot electrons in a metal to adsorbates in the presence of vibrational-mode coupling. The theory is successfully applied to the experimental result of atomic oxygen hopping on a vicinal Pt(111) surface. The effective friction coupling between hot electrons and the vibrational mode relevant to the hopping motion depends on the transient temperature of the partner mode excited by hot electrons. The calculated two-pulse correlation and fluence dependence of the hopping probability reproduce the experimental results, which were previously analyzed using the hot-electron temperature (Te) -dependent friction ηa(Te) in a conventional heat transfer equation. A possible elementary process behind such a hypothetic modeling using ηa(Te) is discussed in terms of an indirect heating of the vibrational mode for hopping at the surface.

Analysis and treatment of industrial wastewater through chemical coagulation-adsorption process-A case study of Clariant Pakistan limited

NASA Astrophysics Data System (ADS)

Ali Shah, Syed Farman; Shah, Abdul Karim; Mehdi, Ahmad; Memon, Aziza Aftab; Harijan, Khanji; Ali, Zeenat M.

2012-05-01

Textile dye manufacture processes are known as the most polluting chemical processes of industrial sectors of the world. Colored wastewaters along with many polluting agents are troublesome. They are heavily polluted with dyes, textile auxiliaries and chemicals. Current study applies a coupled technology for wastewater treatment. Combined coagulation-adsorption process was utilized for treatment of complex nature effluents of dyes, binder emulsion, pigments and textile chemicals plants at Clariant Pakistan. Cost effective coagulant and adsorbent was selected by using waste material from a power generation unit of Water and Power Development Authority (WAPDA), Pakistan. The treated effluent could be reused. Alum+ Activated Carbon, Ferrous sulfate+ Activated Carbon, Ferric chloride + Activated Carbon. Almost complete decolourization was achieved along with reduction in COD up to 65%. Pre and post treatment, TDS, COD, Turbidity and suspended solids were improved.

The influence of activating agents on the performance of rice husk-based carbon for sodium lauryl sulfate and chrome (Cr) metal adsorptions

NASA Astrophysics Data System (ADS)

Arneli; Safitri, Z. F.; Pangestika, A. W.; Fauziah, F.; Wahyuningrum, V. N.; Astuti, Y.

2017-02-01

This research aims to study the influence of activating agents to produce rice husk based-carbon with high adsorption capacity and efficiency for either hazardous organic molecules or heavy metals which are unfriendly for the environment. Firstly, rice husk was burned by pyrolysis at different temperatures to produce rice husk-based carbon. To improve its ability as an adsorbent, carbon was treated with activating agents, namely, H3PO4 and KOH at room and high temperature (420 °C). The performance of carbon was then tested by contacting it with surfactant (SLS). Finally, the surfactant-modified active carbon was applied for chrome metal removal. The result shows that activation of carbon using phosphate acid (H3PO4) was more effective than potassium hydroxide (KOH) conducted at high temperature to adsorb sodium lauryl sulfate (SLS) and chrome metal with the adsorption capacity 1.50 mgg-1 and 0.375 mgg-1, respectively.

Environmental Effects on Zirconium Hydroxide Nanoparticles and Chemical Warfare Agent Decomposition: Implications of Atmospheric Water and Carbon Dioxide.

PubMed

Balow, Robert B; Lundin, Jeffrey G; Daniels, Grant C; Gordon, Wesley O; McEntee, Monica; Peterson, Gregory W; Wynne, James H; Pehrsson, Pehr E

2017-11-15

Zirconium hydroxide (Zr(OH) 4 ) has excellent sorption properties and wide-ranging reactivity toward numerous types of chemical warfare agents (CWAs) and toxic industrial chemicals. Under pristine laboratory conditions, the effectiveness of Zr(OH) 4 has been attributed to a combination of diverse surface hydroxyl species and defects; however, atmospheric components (e.g., CO 2 , H 2 O, etc.) and trace contaminants can form adsorbates with potentially detrimental impact to the chemical reactivity of Zr(OH) 4 . Here, we report the hydrolysis of a CWA simulant, dimethyl methylphosphonate (DMMP) on Zr(OH) 4 determined by gas chromatography-mass spectrometry and in situ attenuated total reflectance Fourier transform infrared spectroscopy under ambient conditions. DMMP dosing on Zr(OH) 4 formed methyl methylphosphonate and methoxy degradation products on free bridging and terminal hydroxyl sites of Zr(OH) 4 under all evaluated environmental conditions. CO 2 dosing on Zr(OH) 4 formed adsorbed (bi)carbonates and interfacial carbonate complexes with relative stability dependent on CO 2 and H 2 O partial pressures. High concentrations of CO 2 reduced DMMP decomposition kinetics by occupying Zr(OH) 4 active sites with carbonaceous adsorbates. Elevated humidity promoted hydrolysis of adsorbed DMMP on Zr(OH) 4 to produce methanol and regenerated free hydroxyl species. Hydrolysis of DMMP by Zr(OH) 4 occurred under all conditions evaluated, demonstrating promise for chemical decontamination under diverse, real-world conditions.

Modified silicas with different structure of grafted methylphenylsiloxane layer

NASA Astrophysics Data System (ADS)

Bolbukh, Yuliia; Terpiłowski, Konrad; Kozakevych, Roman; Sternik, Dariusz; Deryło-Marczewska, Anna; Tertykh, Valentin

2016-06-01

The method of a chemical assembly of the surface polymeric layer with high contents of the modifying agent was developed. Powders of nanodispersed silica with chemisorbed polymethylphenylsiloxane (PMPS) were synthesized by solvent-free chemical assembly technique with a dimethyl carbonate (DMC) as scission agent. Samples were characterized using FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis (CHN analysis). Coating microstructure, morphology, and hydrophilic-hydrophobic properties of nanoparticles were estimated. The results indicate a significant effect of the PMPS/DMC ratio at each modification stage on hydrophobic properties of modified silicas. Modification with a similar composition of the PMPS/DMC mixture, even with different polymer amount at each stage, provides the worst hydrophobicity. Results suggest that the highest hydrophobicity (contact angle θ = 135°-140°) is achieved in the case when silica modified with the PMPS/DMC mixture using multistage approach that providing a formation of the monomolecular layer of polysiloxane at the first modification step. The characteristics of surface structure were interpreted in terms of density of polymer-silica bonds at the interfaces that, usually, are reduced for modified surfaces, in a coupling with conformation model that accented the shape of chains (arch- and console-like) adsorbed on solid surfaces.

Facet-specific interaction between methanol and TiO2 probed by sum-frequency vibrational spectroscopy.

PubMed

Yang, Deheng; Li, Yadong; Liu, Xinyi; Cao, Yue; Gao, Yi; Shen, Y Ron; Liu, Wei-Tao

2018-04-24

The facet-specific interaction between molecules and crystalline catalysts, such as titanium dioxides (TiO 2 ), has attracted much attention due to possible facet-dependent reactivity. Using surface-sensitive sum-frequency vibrational spectroscopy, we have studied how methanol interacts with different common facets of crystalline TiO 2 , including rutile(110), (001), (100), and anatase(101), under ambient temperature and pressure. We found that methanol adsorbs predominantly in the molecular form on all of the four surfaces, while spontaneous dissociation into methoxy occurs preferentially when these surfaces become defective. Extraction of Fermi resonance coupling between stretch and bending modes of the methyl group in analyzing adsorbed methanol spectra allows determination of the methanol adsorption isotherm. The isotherms obtained for the four surfaces are nearly the same, yielding two adsorbed Gibbs free energies associated with two different adsorption configurations singled out by ab initio calculations. They are ( i ) ∼-20 kJ/mol for methanol with its oxygen attached to a low-coordinated surface titanium, and ( ii ) ∼-5 kJ/mol for methanol hydrogen-bonded to a surface oxygen and a neighboring methanol molecule. Despite similar adsorption energetics, the Fermi resonance coupling strength for adsorbed methanol appears to depend sensitively on the surface facet and coverage.

A machine learning approach to graph-theoretical cluster expansions of the energy of adsorbate layers

NASA Astrophysics Data System (ADS)

Vignola, Emanuele; Steinmann, Stephan N.; Vandegehuchte, Bart D.; Curulla, Daniel; Stamatakis, Michail; Sautet, Philippe

2017-08-01

The accurate description of the energy of adsorbate layers is crucial for the understanding of chemistry at interfaces. For heterogeneous catalysis, not only the interaction of the adsorbate with the surface but also the adsorbate-adsorbate lateral interactions significantly affect the activation energies of reactions. Modeling the interactions of the adsorbates with the catalyst surface and with each other can be efficiently achieved in the cluster expansion Hamiltonian formalism, which has recently been implemented in a graph-theoretical kinetic Monte Carlo (kMC) scheme to describe multi-dentate species. Automating the development of the cluster expansion Hamiltonians for catalytic systems is challenging and requires the mapping of adsorbate configurations for extended adsorbates onto a graphical lattice. The current work adopts machine learning methods to reach this goal. Clusters are automatically detected based on formalized, but intuitive chemical concepts. The corresponding energy coefficients for the cluster expansion are calculated by an inversion scheme. The potential of this method is demonstrated for the example of ethylene adsorption on Pd(111), for which we propose several expansions, depending on the graphical lattice. It turns out that for this system, the best description is obtained as a combination of single molecule patterns and a few coupling terms accounting for lateral interactions.

Amine-tethered solid adsorbents coupling high adsorption capacity and regenerability for CO2 capture from ambient air.

PubMed

Choi, Sunho; Gray, McMahan L; Jones, Christopher W

2011-05-23

Silica supported poly(ethyleneimine) (PEI) materials are prepared via impregnation and demonstrated to be promising adsorbents for CO(2) capture from ultra-dilute gas streams such as ambient air. A prototypical class 1 adsorbent, containing 45 wt% PEI (PEI/silica), and two new modified PEI-based aminosilica adsorbents, derived from PEI modified with 3-aminopropyltrimethoxysilane (A-PEI/silica) or tetraethyl orthotitanate (T-PEI/silica), are prepared and characterized by using thermogravimetric analysis and FTIR spectroscopy. The modifiers are shown to enhance the thermal stability of the polymer-oxide composites, leading to higher PEI decomposition temperatures. The modified adsorbents present extremely high CO(2) adsorption capacities under conditions simulating ambient air (400 ppm CO(2) in inert gas), exceeding 2 mol(CO (2)) kg(sorbent)(-1), as well as enhanced adsorption kinetics compared to conventional class 1 sorbents. The new adsorbents show excellent stability in cyclic adsorption-desorption operations, even under dry conditions in which aminosilica adsorbents are known to lose capacity due to urea formation. Thus, the adsorbents of this type can be considered promising materials for the direct capture of CO(2) from ultra-dilute gas streams such as ambient air. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Are biopolymers potential deodourising agents in wound management?

PubMed

Lee, G; Anand, S C; Rajendran, S

2009-07-01

To investigate the odour-adsorbing properties of biopolymers, with a view to using the findings to develop a novel dressing with odour-adsorbing properties. The odour-adsorbing properties of a selection of biopolymers (aloe vera, tea tree oil, neem oil and manuka honey) and three commercially available dressings containing activated charcoal cloth (ACC) were quantitatively assessed using laboratory test equipment. An aloe vera-containing composite dressing, designed and developed by the authors, was also compared with the ACC dressings. Aloe vera was the most adsorbent of the biopolymers and a 40% dilution had comparable values to those of the ACC dressings. Furthermore, values for the novel composite dressing were similar to those of the ACC dressings. The novel composite dressing may be a potential alternative to ACC dressings, and has the added advantages of having antimicrobial properties as well as the ability to promote a moist wound environment. However, more research is needed.

Determination of Adsorption Equations for Chloro Derivatives of Aniline on Halloysite Adsorbents Using Inverse Liquid Chromatography.

PubMed

Słomkiewicz, Piotr M; Szczepanik, Beata; Garnuszek, Magdalena; Rogala, Paweł; Witkiewicz, Zygfryd

2017-11-01

Chloro derivatives of aniline are commonly used in the production of dyes, pharmaceuticals, and agricultural agents. They are toxic compounds with a large accumulation ability and low natural biodegradability. Halloysite is known as an efficient adsorbent of toxic compounds, such as phenols or herbicides, from wastewater. Inverse LC was applied to measure the adsorption of aniline and 2-chloroaniline (2-CA), 3-chloroaniline (3-CA), and 4-chloroaniline (4-CA) on halloysite adsorbents. A peak division (PD) method was used to determine a Langmuir equation in accordance with the adsorption measurement results. The values of adsorption equilibrium constants and enthalpy were determined and compared by breakthrough curve and PD methods. The physical sense of the calculated adsorption enthalpy values was checked by applying Boudart's entropy criteria. Of note, adsorption enthalpy values for halloysite adsorbents decreased in the following order: aniline > 4-CA > 2-CA > 3-CA.

Photoluminescence Probing of Complex H2O Adsorption on InGaN/GaN Nanowires.

PubMed

Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Teubert, Jörg; Eickhoff, Martin

2017-02-08

We demonstrate that the complex adsorption behavior of H 2 O on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, H 2 O adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, H 2 O adsorbates act as efficient photoluminescence enhancers. We show that this behavior, which can only be detected due to the low operation temperature of the InGaN/GaN nanowires, can be explained on the basis of single H 2 O adsorbates forming surface recombination centers and multiple H 2 O adsorbates forming surface passivation layers. Reversible creation of such passivation layers is induced by the photoelectrochemical splitting of adsorbed water molecules and by the interaction of reactive H 3 O + and OH - ions with photoactivated InGaN surfaces. Due to electronic coupling of adsorbing molecules with photoactivated surfaces, InGaN/GaN nanowires act as sensitive nanooptical probes for the analysis of photoelectrochemical surface processes.

Direct structural evidence of commensurate-to-incommensurate transition of hydrocarbon adsorption in a microporous metal organic framework

DOE PAGES

Banerjee, Debasis; Wang, Hao; Gong, Qihan; ...

2015-10-27

Here, the efficiency of physisorption-based separation of gas-mixtures depends on the selectivity of adsorbent which is directly linked to size, shape, polarizability and other physical properties of adsorbed molecules. Commensurate adsorption is an interesting and important adsorption phenomenon, where the adsorbed amount, location, and orientation of an adsorbate are commensurate with the crystal symmetry of the adsorbent. Understanding this phenomenon is important and beneficial as it can provide vital information about adsorbate–adsorbent interaction and adsorption–desorption mechanism. So far, only sporadic examples of commensurate adsorption have been reported in porous materials such as zeolites and metal organic frameworks (MOFs). In thismore » work we show for the first time direct structural evidence of commensurate-to-incommensurate transition of linear hydrocarbon molecules (C 2–C7) in a microporous MOF, by employing a number of analytical techniques including single crystal X-ray diffraction (SCXRD), in situ powder X-ray diffraction coupled with differential scanning calorimetry (PXRD-DSC), gas adsorption and molecular simulations.« less

Adsorption of 1-naphthyl methyl carbamate in water by utilizing a surface molecularly imprinted polymer

NASA Astrophysics Data System (ADS)

So, Juhyok; Pang, Cholho; Dong, Hongxing; Jang, Paeksan; U, Juhyok; Ri, Kumchol; Yun, Cholyong

2018-05-01

Surface molecularly imprinting polymer (SMIP) was utilized in the removal of a residual pesticide (carbaryl (CBL)) in water and simulated fruit juice. Being the crosslinking agent, ethylene glycol dimethacrylate (EGDMA) was copolymerized with the monomer, methacrylic acid (MAA) and CBL as the template molecules on the surface of the silica gel particles to produce the SMIP adsorbents. The SMIP adsorbents showed good selectivity and good adsorption capacity for CBL in the competitive adsorptions with two structurally related carbamate pesticides. The effect of the pretreatment solvents on the adsorption capacity of the SMIP adsorbent was investigated with the results of the numerical simulations. The adsorption isotherms and the adsorption kinetics were well described by the Freundlich equilibrium model and the pseudo-second-order kinetic model, respectively. Scatchard plot analysis revealed that there were two classes of binding sites populated in the SMIP adsorbents. In addition, the good selective adsorption of CBL by the SMIP adsorbent in a simulated fruit juice containing vitamin C and fructose indicated the great potential of the SMIP adsorbents to remove residual pesticide in food industry and processing industry for agricultural products.

The uranium from seawater program at PNNL: Overview of marine testing, adsorbent characterization, adsorbent durability, adsorbent toxicity, and deployment studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gill, Gary A.; Kuo, Li -Jung; Janke, Christopher James

The Pacific Northwest National Laboratory's (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacitymore » and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 ± 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 ± 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage. Marine testing at Woods Hole Oceanographic Institution with the ORNL AF1 adsorbent produced 15% and 55% higher adsorption capacities than observed at PNNL for column and flume testing, respectively. Variations in competing ions may be the explanation for the regional differences. In addition to marine testing, a number of other efforts are underway to characterize adsorbents and impacts of deployment on the marine environment. Highlights include: Hydrodynamic modelling predicts that a farm of adsorbent materials will likely have minimal effect on ocean currents and removal of uranium and other elements from seawater when densities are < 1800 braids/km 2. A decrease in U adsorption capacity of up to 30% was observed after 42 days of exposure due to biofouling when the ORNL braided adsorbent AI8 was exposed to raw seawater in a flume in the presence of light. An identical raw seawater exposure with no light exposure showed little or no impact to adsorption capacity from biofouling. No toxicity was observed with column effluents of any absorbent materials tested to date. Toxicity could be induced with some non amidoxime-based absorbents only when the ratio of solid absorbent to test media was increased to highly unrealistic levels. Thermodynamic modeling of the seawater-amidoxime adsorbent was performed using the geochemical modeling program PHREEQC. Modeling of the binding of Ca, Mg, Fe, Ni, Cu, U, and V from batch interactions with seawater across a variety of concentrations of the amidoxime binding group reveal that when binding sites are limited (1 x 10 -8 binding sites/kg seawater), vanadium heavily out-competes other ions for the amidoxime sites. In contrast, when binding sites are abundant magnesium and calcium dominate the total percentage of metals bound to the sorbent.« less

The uranium from seawater program at PNNL: Overview of marine testing, adsorbent characterization, adsorbent durability, adsorbent toxicity, and deployment studies

DOE PAGES

Gill, Gary A.; Kuo, Li -Jung; Janke, Christopher James; ...

2016-02-07

The Pacific Northwest National Laboratory's (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacitymore » and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 ± 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 ± 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage. Marine testing at Woods Hole Oceanographic Institution with the ORNL AF1 adsorbent produced 15% and 55% higher adsorption capacities than observed at PNNL for column and flume testing, respectively. Variations in competing ions may be the explanation for the regional differences. In addition to marine testing, a number of other efforts are underway to characterize adsorbents and impacts of deployment on the marine environment. Highlights include: Hydrodynamic modelling predicts that a farm of adsorbent materials will likely have minimal effect on ocean currents and removal of uranium and other elements from seawater when densities are < 1800 braids/km 2. A decrease in U adsorption capacity of up to 30% was observed after 42 days of exposure due to biofouling when the ORNL braided adsorbent AI8 was exposed to raw seawater in a flume in the presence of light. An identical raw seawater exposure with no light exposure showed little or no impact to adsorption capacity from biofouling. No toxicity was observed with column effluents of any absorbent materials tested to date. Toxicity could be induced with some non amidoxime-based absorbents only when the ratio of solid absorbent to test media was increased to highly unrealistic levels. Thermodynamic modeling of the seawater-amidoxime adsorbent was performed using the geochemical modeling program PHREEQC. Modeling of the binding of Ca, Mg, Fe, Ni, Cu, U, and V from batch interactions with seawater across a variety of concentrations of the amidoxime binding group reveal that when binding sites are limited (1 x 10 -8 binding sites/kg seawater), vanadium heavily out-competes other ions for the amidoxime sites. In contrast, when binding sites are abundant magnesium and calcium dominate the total percentage of metals bound to the sorbent.« less

Affinity adsorption of glucose degradation products improves the biocompatibility of conventional peritoneal dialysis fluid.

PubMed

Ishikawa, Naoyoshi; Miyata, Toshio; Ueda, Yasuhiko; Inagi, Reiko; Izuhara, Yuko; Yuzawa, Hiroko; Onogi, Hiroshi; Nishina, Makoto; Nangaku, Masaomi; Van Ypersele De Strihou, Charles; Kurokawa, Kiyoshi

2003-01-01

Reactive carbonyl compounds (RCOs) present in peritoneal dialysis (PD) fluid have been incriminated in the progressive deterioration of the peritoneal membrane in long-term PD patients. They are initially present in fresh conventional heat-sterilized glucose PD fluid and are supplemented during dwell time by the diffusion of blood RCOs within the peritoneal cavity. In the present study, RCO entrapping agents were immobilized on affinity beads to adsorb RCOs both in fresh PD fluid and in PD effluent. The RCO trapping potential of various compounds was assessed in vitro first by dissolving them in the tested fluid and subsequently after coupling with either epoxy- or amino-beads. The tested fluids include fresh heat-sterilized glucose and non-glucose PD fluids, and PD effluent. Their RCOs contents, that is, glyoxal (GO), methylglyoxal (MGO), 3-deoxyglucosone (3-DG), formaldehyde, 5-hydroxymethylfuraldehyde, acetaldehyde, and 2-furaldehyde were monitored by reverse-phase high-pressure liquid chromatography. The biocompatibility of PD fluid was assessed by a cytotoxic assay with either human epidermoid cell line A431 cells or with primary cultured human peritoneal mesothelial cells. Among the tested RCO entrapping agents, hydrazine coupled to epoxy-beads proved the most efficient. It lowered the concentrations of three dicarbonyl compounds (GO, MGO, and 3-DG) and those of aldehydes present in fresh heat-sterilized glucose PD fluid toward the low levels observed in filter-sterilized glucose PD fluid. It did not change the glucose and electrolytes concentration of the PD fluid but raised its pH from 5.2 to 5.9. Hydrazine-coupled epoxy-bead also lowered the PD effluent content of total RCOs, measured by the 2,4-dinitrophenylhydrazone (DNPH) method. The cytotoxicity of heat-sterilized PD fluid incubated with hydrazine-coupled epoxy-beads was decreased to the level observed in filter-sterilized PD fluid as the result of the raised pH and the lowered RCOs levels. Hydrazine-coupled epoxy-beads reduce the levels of a variety of dicarbonyls and aldehydes present in heat-sterilized glucose PD fluid to those in filter-sterilized PD fluid, without altering glucose, lactate, and electrolytes contents but with a rise in pH. Incubated with PD effluents, it is equally effective in reducing the levels of serum-derived RCOs. RCO entrapping agents immobilized on affinity beads improve in vitro the biocompatibility of conventional heat-sterilized glucose PD fluid. Their clinical applicability requires further studies.

The environmental effect on the radial breathing mode of carbon nanotubes. II. Shell model approximation for internally and externally adsorbed fluids

NASA Astrophysics Data System (ADS)

Longhurst, M. J.; Quirke, N.

2006-11-01

We have previously shown that the upshift in the radial breathing mode (RBM) of closed (or infinite) carbon nanotubes in solution is almost entirely due to coupling of the RBM with an adsorbed layer of fluid on the nanotube surface. The upshift can be modeled analytically by considering the adsorbed fluid as an infinitesimally thin shell, which interacts with the nanotube via a continuum Lennard-Jones potential. Here we extend the model to include internally as well as externally adsorbed waterlike molecules, and find that filling the nanotubes leads to an additional upshift of two to six wave numbers. We show that using molecular dynamics, the RBM can be accurately reproduced by replacing the fluid molecules with a mean field harmonic shell potential, greatly reducing simulation times.

Application of carbon foam for heavy metal removal from industrial plating wastewater and toxicity evaluation of the adsorbent.

PubMed

Lee, Chang-Gu; Song, Mi-Kyung; Ryu, Jae-Chun; Park, Chanhyuk; Choi, Jae-Woo; Lee, Sang-Hyup

2016-06-01

Electroplating wastewater contains various types of toxic substances, such as heavy metals, solvents, and cleaning agents. Carbon foam was used as an adsorbent for the removal of heavy metals from real industrial plating wastewater. Its sorption capacity was compared with those of a commercial ion-exchange resin (BC258) and a heavy metal adsorbent (CupriSorb™) in a batch system. The experimental carbon foam has a considerably higher sorption capacity for Cr and Cu than commercial adsorbents for acid/alkali wastewater and cyanide wastewater. Additionally, cytotoxicity test showed that the newly developed adsorbent has low cytotoxic effects on three kinds of human cells. In a pilot plant, the carbon foam had higher sorption capacity for Cr (73.64 g kg(-1)) than for Cu (14.86 g kg(-1)) and Ni (7.74 g kg(-1)) during 350 h of operation time. Oxidation pretreatments using UV/hydrogen peroxide enhance heavy metal removal from plating wastewater containing cyanide compounds. Copyright © 2016 Elsevier Ltd. All rights reserved.

Adsorption behavior of optical brightening agent on microfibrillated cellulose studied through inverse liquid chromatography: The need to correct for axial dispersion effect.

PubMed

Serroukh, Sonia; Huber, Patrick; Lallam, Abdelaziz

2018-01-19

Inverse liquid chromatography is a technique for studying solid/liquid interaction and most specifically for the determination of solute adsorption isotherm. For the first time, the adsorption behaviour of microfibrillated cellulose was assessed using inverse liquid chromatography. We showed that microfibrillated cellulose could adsorb 17 mg/g of tetrasulfonated optical brightening agent in typical papermaking conditions. The adsorbed amount of hexasulfonated optical brightening agent was lower (7 mg/g). The packing of the column with microfibrillated cellulose caused important axial dispersion (D a  = 5e-7 m²/s). Simulation of transport phenomena in the column showed that neglecting axial dispersion in the analysis of the chromatogram caused significant error (8%) in the determination of maximum adsorbed amount. We showed that conventional chromatogram analysis technique such as elution by characteristic point could not be used to fit our data. Using a bi-Langmuir isotherm model improved the fitting, but did not take into account axial dispersion, thus provided adsorption parameters which may have no physical significance. Using an inverse method with a single Langmuir isotherm, and fitting the transport equation to the chromatogram was shown to provide a satisfactory fitting to the chromatogram data. In general, the inverse method could be recommended to analyse inverse liquid chromatography data for column packing with significant axial dispersion (D a   > 1e-7 m²/s). Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorption of heavy metals on amine-functionalized MCM-48

NASA Astrophysics Data System (ADS)

Taba, P.; Budi, P.; Puspitasari, A. Y.

2017-04-01

The ordered mesoporous silica with cubic structure, MCM-48 was synthesized by post-synthesis under basic media using colloidal silica, cetyltrimethylammonium bromide, and Triton X-100. The modified material, NH2-MCM-48 was prepared using 3-aminopropyl trimetoxysilane (3-APTMS). X-ray diffraction and FT-IR were used to characterize the samples. The modified material was utilized for adsorption of Cu2+and Mn2+ from aqueous solution. Parameters used for studying the adsorption process were pH, time of contact, and the initial concentrations of Cu2+ and Mn2+ ions. Desorption of ions from the adsorbent was also studied using several desorbing agents. The pseudo-second order was found to be the kinetic order for the metals adsorption. The adsorption of Cu2+ and Mn2+ on NH2-MCM-48 was fixed by the Langmuir model better than the Freundlich model with the capacity of 0.52 and 0.80 mmol g-1 for Cu2+ and Mn2+, respectively. The best desorbing agents for removing the adsorbed Cu2+ and Mn2+ from the adsorbent were 1 M HNO3 and 1 M HC1, respectively.

Behavior of Paramecium sp. in solutions containing Sr and Pb: Do Paramecium sp. alter chemical forms of those metals?

NASA Astrophysics Data System (ADS)

Kozai, Naofumi; Ohnuki, Toshihiko; Koka, Masahi; Satoh, Takahiro; Kamiya, Tomihiro

2011-10-01

The behavior of Paramecium sp. (Paramecium bursaria) in aqueous solutions containing Sr and Pb was investigated to determine the role of protozoa in the migration of radionuclides in the environment. Precultured living cells of P. bursaria were exposed to aqueous solutions containing 0.01 or 0.05 mM Sr or Pb at pH 7 for 24 h. For comparison, pre-killed cells were treated with the metal solutions in the same way. Two-dimensional elemental mappings of cells were obtained by micro-PIXE. Aquatic species of Sr and Pb were analyzed by size exclusion chromatography (SEC) coupled online to ultraviolet (UV) spectroscopy and inductivity coupled plasma mass spectroscopy (ICP-MS). The amounts of Sr adsorbed or taken up by the cells surviving for 24 h and adsorbed on pre-killed cells were below the detection limit. Cells of P. bursaria adsorbed or took up a fraction of Pb. The Pb adsorbed or taken up by the cells surviving for 24 h in the Pb solution was barely detectable, while the Pb adsorbed on pre-killed cells was clearly mappable. These findings suggest that living cells of P. bursaria have functions that reduce adsorption or uptake of Pb on the cells. Quantitative and SEC-UV-ICP-MS analyses of the Sr and Pb in aqueous phases showed no clear evidences that living cells of P. bursaria alter the chemical form of Sr or Pb remaining in the aqueous phases after the cell-solution contact.

Adlayer structure dependent ultrafast desorption dynamics in carbon monoxide adsorbed on Pd (111)

NASA Astrophysics Data System (ADS)

Hong, Sung-Young; Xu, Pan; Camillone, Nina R.; White, Michael G.; Camillone, Nicholas

2016-07-01

We report our ultrafast photoinduced desorption investigation of the coverage dependence of substrate-adsorbate energy transfer in carbon monoxide adlayers on the (111) surface of palladium. As the CO coverage is increased, the adsorption site population shifts from all threefold hollows (up to 0.33 ML), to bridge and near bridge (>0.5 to 0.6 ML) and finally to mixed threefold hollow plus top site (at saturation at 0.75 ML). We show that between 0.24 and 0.75 ML this progression of binding site motifs is accompanied by two remarkable features in the ultrafast photoinduced desorption of the adsorbates: (i) the desorption probability increases roughly two orders magnitude, and (ii) the adsorbate-substrate energy transfer rate observed in two-pulse correlation experiments varies nonmonotonically, having a minimum at intermediate coverages. Simulations using a phenomenological model to describe the adsorbate-substrate energy transfer in terms of frictional coupling indicate that these features are consistent with an adsorption-site dependent electron-mediated energy coupling strength, ηel, that decreases with binding site in the order: three-fold hollow > bridge and near bridge > top site. This weakening of ηel largely counterbalances the decrease in the desorption activation energy that accompanies this progression of adsorption site motifs, moderating what would otherwise be a rise of several orders of magnitude in the desorption probability. Within this framework, the observed energy transfer rate enhancement at saturation coverage is due to interadsorbate energy transfer from the copopulation of molecules bound in three-fold hollows to their top-site neighbors.

Anomalous Kondo resonance mediated by semiconducting graphene nanoribbons in a molecular heterostructure

DOE PAGES

Li, Yang; Ngo, Anh T.; DiLullo, Andrew; ...

2017-10-16

An unusually large spin-coupling of almost 100% is found in vertically stacked molecular hetrostructures composed of cobalt-porphyrin based magnetic molecules adsorbed on semiconducting armchair graphene nanoribbon on a Au(111) surface. Although the graphene nanoribbons are electronically decoupled from the gold substrate due to their band gaps and weak adsorption, they enable spin coupling between the magnetic moment of the molecule and the electrons from the substrate exhibiting a Kondo resonance. Surprisingly, the Kondo temperatures corresponding to three adsorption sites of the molecules on Au(111) surface are reproduced on the molecules adsorb on the graphene nanoribbons although the molecules are locatedmore » 7.5 Å away from the surface. This finding suggests that the molecules on graphene nanoribbons experience almost the same environment for spin-electron interactions as the ones directly adsorb on Au(111). This puzzling effect is further confirmed by density functional theory calculations that reveal no spin electron interactions if the molecule is left at the same height from the Au(111) surface without the graphene nanoribbon in between.« less

Anomalous Kondo resonance mediated by semiconducting graphene nanoribbons in a molecular heterostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yang; Ngo, Anh T.; DiLullo, Andrew

An unusually large spin-coupling of almost 100% is found in vertically stacked molecular hetrostructures composed of cobalt-porphyrin based magnetic molecules adsorbed on semiconducting armchair graphene nanoribbon on a Au(111) surface. Although the graphene nanoribbons are electronically decoupled from the gold substrate due to their band gaps and weak adsorption, they enable spin coupling between the magnetic moment of the molecule and the electrons from the substrate exhibiting a Kondo resonance. Surprisingly, the Kondo temperatures corresponding to three adsorption sites of the molecules on Au(111) surface are reproduced on the molecules adsorb on the graphene nanoribbons although the molecules are locatedmore » 7.5 Å away from the surface. This finding suggests that the molecules on graphene nanoribbons experience almost the same environment for spin-electron interactions as the ones directly adsorb on Au(111). This puzzling effect is further confirmed by density functional theory calculations that reveal no spin electron interactions if the molecule is left at the same height from the Au(111) surface without the graphene nanoribbon in between.« less

Electronic and magnetic properties of nonmetal atoms adsorbed ReS{sub 2} monolayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiaoou; Li, Qingfang, E-mail: qingfangli@nuist.edu.cn; Department of Physics, Nanjing University of Information Science and Technology, Nanjing 210044

2015-08-14

The stable configurations and electronic and magnetic properties of nonmetal atoms (H, N, P, O, S, F, and Cl) adsorbed ReS{sub 2} monolayers have been investigated by first-principles calculations. It is found that H, O, S, F, and Cl prefer to occupy the peak sites of S atoms, while both N and P atoms favor the valley sites of S atoms. The ReS{sub 2} sheet exhibits a good adsorption capability to nonmetal atoms. The reconstruction of the surface is pronounced in N- and P-adsorbed ReS{sub 2} monolayers. In H-adsorbed case, the Fermi level is pulled into the conduction band, whichmore » results in the semiconductor-metal transition. The same magnetic moment of 1μ{sub B} is found in the N-, P-, F-, and Cl-adsorbed ReS{sub 2} monolayers, while the mechanisms of forming magnetic moment for N (P)- and F (Cl)-adsorbed cases are different. In addition, the spatial extensions of spin density in P-, F-, and Cl-adsorbed cases are larger than that in N-adsorbed case, which is more suitable to achieve long-range magnetic coupling interaction at low defect concentrations. Our results provide insight for achieving metal-free magnetism and a tunable band gap for various electronic and spintronic devices based on ReS{sub 2}.« less

Improved purification of immunoglobulin G from plasma by mixed-mode chromatography.

PubMed

Chai, Dong-Sheng; Sun, Yan; Wang, Xiao-Ning; Shi, Qing-Hong

2014-12-01

Efficient loading of immunoglobulin G in mixed-mode chromatography is often a serious bottleneck in the chromatographic purification of immunoglobulin G. In this work, a mixed-mode ligand, 4-(1H-imidazol-1-yl) aniline, was coupled to Sepharose Fast Flow to fabricate AN SepFF adsorbents with ligand densities of 15-64 mmol/L, and the chromatographic performances of these adsorbents were thoroughly investigated to identify a feasible approach to improve immunoglobulin G purification. The results indicate that a critical ligand density exists for immunoglobulin G on the AN SepFF adsorbents. Above the critical ligand density, the adsorbents showed superior selectivity to immunoglobulin G at high salt concentrations, and also exhibited much higher dynamic binding capacities. For immunoglobulin G purification, both the yield and binding capacity increased with adsorbent ligand density along with a decrease in purity. It is difficult to improve the binding capacity, purity, and yield of immunoglobulin G simultaneously in AN SepFF chromatography. By using tandem AN SepFF chromatography, a threefold increase in binding capacity as well as high purity and yield of immunoglobulin G were achieved. Therefore, the tandem chromatography demonstrates that AN SepFF adsorbent is a practical and feasible alternative to MEP HyperCel adsorbents for immunoglobulin G purification. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon monoxide reaction with UO2(111) single crystal surfaces: A theoretical and experimental study

NASA Astrophysics Data System (ADS)

Senanayake, S. D.; Soon, A.; Kohlmeyer, A.; Söhnel, T.; Idriss, H.

2005-07-01

The reaction of CO has been investigated on the surfaces of UO2(111) single crystal. Over the stoichiometric surface CO does not adsorb at 300 K and no further reaction is noticed. Over UO2-x (prepared by Ar+ bombardment), CO molecules adsorb and in presence of traces of H2 they couple to form acetylene molecules that desorb in two temperature domains during temperature programmed desorption (TPD). In the presence of excess H2 the coupling product is found to be ethylene. X-ray photoelectron spectroscopy (XPS) of the core level shows the presence of an U 4f line at 377 eV on the UO2-x surface, attributed to U metal. This line disappears upon CO adsorption (5 L and above) at 300 K indicating oxidation of U metal atoms by O from dissociatively adsorbed CO. XPS C 1s shows that the only C containing species formed is carbide. Computation of a α-U metal 2d-periodic slab was also conducted using plane-wave pseudopotential in the density functional theoretical framework. Two modes of CO adsorption were considered: molecular and dissociative. The dissociative adsorption was found more energetically favoured by 0.46 eV. From TPD, XPS and computation results it is strongly suggested that CO is dissociatively adsorbed on UO2-x and that a stable U-C species is formed at 300 K.

Fibrinogen adsorption on blocked surface of albumin.

PubMed

Holmberg, Maria; Hou, Xiaolin

2011-05-01

We have investigated the adsorption of albumin and fibrinogen onto PET (polyethylene terephthalate) and glass surfaces and how pre-adsorption of albumin onto these surfaces can affect the adsorption of later added fibrinogen. For materials and devices being exposed to blood, adsorption of fibrinogen is often a non-wanted event, since fibrinogen is part of the clotting cascade and unspecific adsorption of fibrinogen can have an influence on the activation of platelets. Albumin is often used as blocking agent for avoiding unspecific protein adsorption onto surfaces in devices designed to handle biological samples, including protein solutions. It is based on the assumption that proteins adsorbs as a monolayer on surfaces and that proteins do not adsorb on top of each other. By labelling albumin and fibrinogen with two different radioactive iodine isotopes that emit gamma radiation with different energies, the adsorption of both albumin and fibrinogen has been monitored simultaneously on the same sample. Information about topography and coverage of adsorbed protein layers has been obtained using AFM (Atomic Force Microscopy) analysis in liquid. Our studies show that albumin adsorbs in a multilayer fashion on PET and that fibrinogen adsorbs on top of albumin when albumin is pre-adsorbed on the surfaces. Copyright © 2010 Elsevier B.V. All rights reserved.

Magnetite nanoparticles coated glass wool for As(V) removal from drinking water

NASA Astrophysics Data System (ADS)

Kango, Sarita; Kumar, Rajesh

2015-08-01

Arsenic (As) removal from contaminated groundwater is a key environmental concern worldwide. In this study, glass wool was coated with magnetite nanoparticles under argon gas flow and magnetite coated glass wool have been investigated for application as an adsorbent for As(V) removal from water. The adsorbent was characterized by using Scanning Electron Microscopy (SEM) and arsenic contaminated water treated with adsorbent was analyzed by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The ICP-MS results showed that 10 g/L of adsorbent removed 99.4% of As(V) within 5 hours at pH-7 and initial arsenic concentration of 360µg/L. Adsorption kinetics data fitted well in pseudo-first-order kinetics model with high correlation coefficient (R2 = 0.995). As magnetite nanoparticles coated glass wool showed favorable adsorption behavior for As(V), it can be a promising tool for water purification.

Magnetite nanoparticles coated glass wool for As(V) removal from drinking water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kango, Sarita; Kumar, Rajesh, E-mail: rajesh.kumar@juit.ac.in

2015-08-28

Arsenic (As) removal from contaminated groundwater is a key environmental concern worldwide. In this study, glass wool was coated with magnetite nanoparticles under argon gas flow and magnetite coated glass wool have been investigated for application as an adsorbent for As(V) removal from water. The adsorbent was characterized by using Scanning Electron Microscopy (SEM) and arsenic contaminated water treated with adsorbent was analyzed by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The ICP-MS results showed that 10 g/L of adsorbent removed 99.4% of As(V) within 5 hours at pH-7 and initial arsenic concentration of 360µg/L. Adsorption kinetics data fitted well inmore » pseudo-first-order kinetics model with high correlation coefficient (R{sup 2} = 0.995). As magnetite nanoparticles coated glass wool showed favorable adsorption behavior for As(V), it can be a promising tool for water purification.« less

Single magnetic adsorbates on s-wave superconductors

NASA Astrophysics Data System (ADS)

Heinrich, Benjamin W.; Pascual, Jose I.; Franke, Katharina J.

2018-02-01

In superconductors, magnetic impurities induce a pair-breaking potential for Cooper pairs, which locally affects the Bogoliubov quasiparticles and gives rise to Yu-Shiba-Rusinov (YSR or Shiba, in short) bound states in the density of states (DoS). These states carry information on the magnetic coupling strength of the impurity with the superconductor, which determines the many-body ground state properties of the system. Recently, the interest in Shiba physics was boosted by the prediction of topological superconductivity and Majorana modes in magnetically coupled chains and arrays of Shiba impurities. Here, we review the physical insights obtained by scanning tunneling microscopy into single magnetic adsorbates on the s-wave superconductor lead (Pb). We explore the tunneling processes into Shiba states, show how magnetic anisotropy affects many-body excitations, and determine the crossing of the many-body ground state through a quantum phase transition. Finally, we discuss the coupling of impurities into dimers and chains and their relation to Majorana physics.

NOVEL SYNTHETIC METHOD FOR NARROW DISTRIBUTED COLLOIDAL SILICALITE

EPA Science Inventory

Preparation of zeolites is important for a variety of applications such as microelectronics, separation agents, ion exchange, catalysis, adsorbents, nanocomposites and zeolite membranes. Silicalite-1 is a crystalline, microporous polymorph of silicon dioxide with the MFI framewo...

Characteristics of activated carbon and carbon nanotubes as adsorbents to remove annatto (norbixin) in cheese whey.

PubMed

Zhang, Yue; Pan, Kang; Zhong, Qixin

2013-09-25

Removing annatto from cheese whey without bleaching has potential to improve whey protein quality. In this work, the potential of two activated carbon products and multiwalled carbon nanotubes (CNT) was studied for extracting annatto (norbixin) in aqueous solutions. Batch adsorption experiments were studied for the effects of solution pH, adsorbent mass, contact duration, and ionic strength. The equilibrium adsorption data were observed to fit both Langmuir and Freundlich isotherm models. The thermodynamic parameters estimated from adsorption isotherms demonstrated that the adsorption of norbixin on three adsorbents is exothermic, and the entropic contribution differs with adsorbent structure. The adsorption kinetics, with CNT showing a higher rate than activated carbon, followed the pseudo first order and second order rate expressions and demonstrated the significance of intraparticle diffusion. Electrostatic interactions were observed to be significant in the adsorption. The established adsorption parameters may be used in the dairy industry to decolorize cheese whey without applying bleaching agents.

Phenol adsorption by activated carbon produced from spent coffee grounds.

PubMed

Castro, Cínthia S; Abreu, Anelise L; Silva, Carmen L T; Guerreiro, Mário C

2011-01-01

The present work highlights the preparation of activated carbons (ACs) using spent coffee grounds, an agricultural residue, as carbon precursor and two different activating agents: water vapor (ACW) and K(2)CO(3) (ACK). These ACs presented the microporous nature and high surface area (620-950 m(2) g(-1)). The carbons, as well as a commercial activated carbon (CAC) used as reference, were evaluated as phenol adsorbent showing high adsorption capacity (≈150 mg g(-1)). The investigation of the pH solution in the phenol adsorption was also performed. The different activating agents led to AC with distinct morphological properties, surface area and chemical composition, although similar phenol adsorption capacity was verified for both prepared carbons. The production of activated carbons from spent coffee grounds resulted in promising adsorbents for phenol removal while giving a noble destination to the residue.

Dynamic bed reactor

DOEpatents

Stormo, Keith E.

1996-07-02

A dynamic bed reactor is disclosed in which a compressible open cell foam matrix is periodically compressed and expanded to move a liquid or fluid through the matrix. In preferred embodiments, the matrix contains an active material such as an enzyme, biological cell, chelating agent, oligonucleotide, adsorbent or other material that acts upon the liquid or fluid passing through the matrix. The active material may be physically immobilized in the matrix, or attached by covalent or ionic bonds. Microbeads, substantially all of which have diameters less than 50 microns, can be used to immobilize the active material in the matrix and further improve reactor efficiency. A particularly preferred matrix is made of open cell polyurethane foam, which adsorbs pollutants such as polychlorophenol or o-nitrophenol. The reactors of the present invention allow unidirectional non-laminar flow through the matrix, and promote intimate exposure of liquid reactants to active agents such as microorganisms immobilized in the matrix.

Technical and Associated R&D Laboratory/Project Support to AFRL/RXQL Airbase Sciences Branch

DTIC Science & Technology

2011-10-01

the organophosphorus nerve agents . The coupons were allowed to sit overnight at room temperature to allow the phosphoric acid to adsorb into the...of chlorine and of ammonia across samples of several soil types; measurements of adsorption of two chemical agent surrogates (dimethyl...methylphosphonate and diisopropyl fluorophosphate) on cellulose and silica gel surfaces by inverse gas chromatography, to infer enthalpies of adsorption. Reactive

Hybrid adsorptive membrane reactor

NASA Technical Reports Server (NTRS)

Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

2011-01-01

A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

Hybrid adsorptive membrane reactor

DOEpatents

Tsotsis, Theodore T [Huntington Beach, CA; Sahimi, Muhammad [Altadena, CA; Fayyaz-Najafi, Babak [Richmond, CA; Harale, Aadesh [Los Angeles, CA; Park, Byoung-Gi [Yeosu, KR; Liu, Paul K. T. [Lafayette Hill, PA

2011-03-01

A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

Effect of Silane Coupling Agent on Tribological Properties of Hemp Fiber-Reinforced Plant-Derived Polyamide 1010 Biomass Composites

PubMed Central

Kajiyama, Tetsuto; Yamanaka, Toshiyuki

2017-01-01

We have studied the effects of silane coupling agents used for the surface treatment of fiber on the tribological properties of hemp fiber (HF) reinforced plant-derived polyamide 1010 (PA1010) biomass composites. Hemp fibers were surface-treated by two surface treatment methods: (a) alkali treatment by sodium hydroxide solution and (b) surface treatment by silane coupling agents. Three types of silane coupling agents, namely aminosilane, epoxysilane and ureidosilane were used. These HF/PA1010 biomass composites were extruded using a twin extruder, and injection-molded. The mechanical and tribological properties were evaluated by the ring-on-plate type sliding wear test. It was found that tribological properties of HF/PA1010 biomass composites improved with the surface treatment by the silane coupling agent. This may be attributed to the change in the mode of friction and wear mechanism by the interfacial adhesion between fiber and matrix polymer according to the type of silane coupling agent used. In particular, the ureidosilane coupling agent showed the best improvement effect for the tribological properties of these biomass composites in this study. PMID:28872624

Controlling the Electronic Structure of Graphene Using Surface-adsorbate Interactions

DTIC Science & Technology

2015-07-21

substrate via n doping, with or without intercalation, suggests that the graphene-to-substrate interaction could be controlled dynamically. DOI : 10.1103...which form a Dirac cone and are degenerate at the Fermi level [1]. These states change in response to atoms adsorbed on top of graphene (doping) or when...coupling to the substrate is strong. In the case of graphene on metals, the energy of the Dirac cone can change as a result of interfacial doping, or

Further development of high temperature-resistant graphite fiber coupling agents

NASA Technical Reports Server (NTRS)

Griffin, R. N.

1976-01-01

Potential coupling agents for graphite fibers were screened by their effect on the weight losses of Thornel 300, HMS, and HTS fibers at 588K for 200 and 400 hours. Unidirectional laminates were made from HMS and HTS fibers, untreated, and treated with each of the seven coupling agents. The matrix of all laminates was PMR polyimide (PMR-PR). On the basis of the best overall retention of elevated temperature interlaminar shear strength after 200 hours at 588K, composite weight after 200 hours at 588K, and fiber weight after 400 hours at 588K, ventromer T-1 applied from aqueous solution and pyrolyzed PPQ were selected for further evaluation as coupling agents for HTS fiber while ventromer T-2 and pyrolyzed PPQ were selected as coupling agents for HMS fiber. It was shown that pyrolyzed PPQ as a coupling agent improves the oxidative stability of HTS/PMR-PI composites.

Direct coupling between stress, strain and adsorption reactions - A study on coal-CO2 systems

NASA Astrophysics Data System (ADS)

Hol, S.; Peach, C. J.; Spiers, C. J.

2012-12-01

Though it is well-known that adsorption reactions frequently assist deformation of porous rocks, very little understanding exists on the direct coupling with stress state and strain. One of the materials in which adsorption plays a large role is coal, as is observed in the particular case of Enhanced Coalbed Methane Production (ECBM), which involves the geological storage of CO2 and the recovery of CH4. In this case, adsorption and the associated swelling cause significant injectivity problems, which is experienced in almost all pilot field projects to date. This suggests that indeed a strong fundamental coupling exists between CO2 sorption, changes in the mechanical state of the coal matrix and changes in the transport properties of the system, and illustrates the need to understand coupled stress-strain-sorption behaviour. In this contribution, we describe several important observations made on coal-CO2 systems that can learn us about many other natural, stressed adsorbate-adsorbent systems. In our experiments, first of all, the adsorption of CO2 in the coal matrix gave rise to swelling. Although this is well-known, we found that the total volumetric strain occurring under unconfined conditions can be realistically modelled (up to at least 100 MPa) as the sum of an adsorption-related expansion term and an elastic compression term. Second, effective in situ stresses will directly reduce the sorption capacity, and associated swelling of the coal matrix significantly. Our general thermodynamic model for the effect of a 3D stress state on adsorbed CO2 concentration supports this observation, and also shows that "self-stressing", as a result of CO2 adsorption occurring under conditions of restricted or zero strain (i.e. fully constrained conditions), will more than double the expected in situ stresses. A constitutive equation was developed to describe the full coupling between stress state, total strain (i.e. combined strain of adsorption processes and poroelasticity) and sorption, and was found to be consistent with experimental data. Third, it was observed that microfractures form in coal due to exposure to CO2 under unconfined conditions, which illustrates the potentially high forces and the large thermodynamic work term involved in adsorption reactions. The findings of this study all lead to the conclusion that direct effects of stress can have a considerable impact on adsorption processes. If this is the case for coal, also other adsorbate-rock interactions (e.g. clay-fluids in shale formations and deep fault rocks) may be subject to such a coupling. We believe that this topic deserved attention in future research.

Method for removing strongly adsorbed surfactants and capping agents from metal to facilitate their catalytic applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adzic, Radoslav R.; Gong, Kuanping; Cai, Yun

A method of synthesizing activated electrocatalyst, preferably having a morphology of a nanostructure, is disclosed. The method includes safely and efficiently removing surfactants and capping agents from the surface of the metal structures. With regard to metal nanoparticles, the method includes synthesis of nanoparticle(s) in polar or non-polar solution with surfactants or capping agents and subsequent activation by CO-adsorption-induced surfactant/capping agent desorption and electrochemical oxidation. The method produces activated macroparticle or nanoparticle electrocatalysts without damaging the surface of the electrocatalyst that includes breaking, increasing particle thickness or increasing the number of low coordination sites.

Study of TiO2 anatase nano and microstructures with dominant {001} facets for NO oxidation.

PubMed

Sofianou, Maria-Veronica; Trapalis, Christos; Psycharis, Vassils; Boukos, Nikos; Vaimakis, Tiverios; Yu, Jiaguo; Wang, Wenguang

2012-11-01

TiO(2) anatase nanoplates and hollow microspheres were fabricated by a solvothermal-hydrothermal method using titanium isopropoxide as a titanium precursor and hydrofluoric acid as a capping agent in order to enhance the formation of the {001} crystal facets of the anatase nanocrystals. These different morphological structures of TiO(2) anatase can be achieved by only changing the solvent, keeping the amount of the precursor and of the capping agent identical during the solvothermal-hydrothermal process. After calcination of the samples, the adsorbed fluoride atoms on the {001} crystal facets of the TiO(2) anatase nanocrystals were completely removed from their surface according to XPS analysis. The calcined TiO(2) anatase structures were higher crystallized and the specific surface area of the catalysts increased, enhancing their photocatalytic activity in comparison to the non-calcined TiO(2) anatase structures. All TiO(2) anatase samples with adsorbed as well as non-adsorbed fluoride atoms on their {001} crystal facets, exhibited a higher photonic efficiency than Degussa P25, which was used as a reference. The fluoride free TiO(2) anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO(2) and NO(3) (-).

Enhancement of plasmon-induced charge separation efficiency by coupling silver nanocubes with a thin gold film

NASA Astrophysics Data System (ADS)

Akiyoshi, Kazutaka; Saito, Koichiro; Tatsuma, Tetsu

2016-10-01

Plasmon-induced charge separation (PICS), in which an energetic electron is injected from a plasmonic nanoparticle (NP) to a semiconductor on contact, is often inhibited by a protecting agent adsorbed on the NP. We addressed this issue for an Ag nanocube-TiO2 system by coating it with a thin Au layer or by inserting the Au layer between the nanocubes (NCs) and TiO2. Both of the electrodes exhibit much higher photocurrents due to PICS than the electrodes without the Au film or the Ag NCs. These photocurrent enhancements can be explained in terms of PICS with accelerated electron transfer, in which electron injection from the Ag NCs or Ag@Au core-shell NCs to TiO2 is promoted by the Au film, or PICS enhanced by a nanoantenna effect, in which the electron injection from the Au film to TiO2 is enhanced by optical near field generated by the Ag NC.

The use of selective adsorbents in capillary electrophoresis-mass spectrometry for analyte preconcentration and microreactions: a powerful three-dimensional tool for multiple chemical and biological applications.

PubMed

Guzman, N A; Stubbs, R J

2001-10-01

Much attention has recently been directed to the development and application of online sample preconcentration and microreactions in capillary electrophoresis using selective adsorbents based on chemical or biological specificity. The basic principle involves two interacting chemical or biological systems with high selectivity and affinity for each other. These molecular interactions in nature usually involve noncovalent and reversible chemical processes. Properly bound to a solid support, an "affinity ligand" can selectively adsorb a "target analyte" found in a simple or complex mixture at a wide range of concentrations. As a result, the isolated analyte is enriched and highly purified. When this affinity technique, allowing noncovalent chemical interactions and biochemical reactions to occur, is coupled on-line to high-resolution capillary electrophoresis and mass spectrometry, a powerful tool of chemical and biological information is created. This paper describes the concept of biological recognition and affinity interaction on-line with high-resolution separation, the fabrication of an "analyte concentrator-microreactor", optimization conditions of adsorption and desorption, the coupling to mass spectrometry, and various applications of clinical and pharmaceutical interest.

Effect of clarification process on the removal of pesticide residues in red wine and comparison with white wine.

PubMed

Doulia, Danae S; Anagnos, Efstathios K; Liapis, Konstantinos S; Klimentzos, Demetrios A

2018-04-30

The aim of this study was to determine the potential of seven clarifying agents to remove pesticides in red wine. The presence of pesticides in wine consists a great problem for winemakers and therefore, results on pesticide removal by clarification are very useful for taking a decision on the appropriate adsorbent. The selection of an efficient adsorbent can be based on data correlating pesticide removal in red wine to pesticides' properties, given the great number and variety of pesticides used. So, this experimental work is focused on the collection of results with regard to pesticide removal by clarification using a great number of pesticides and fining agents. A Greek red wine, fortified with single solutions and mixtures of 23 or 9 pesticides was studied. The seven fining agents, used at two concentrations, were activated carbon, bentonite, polyvinylpolypyrrolidone (PVPP), gelatin, egg albumin, isinglass-fish glue, and casein. Pesticides were selected with a wide range of properties (octanol-water partition coefficient (log K ow ) 2.7-6.3 and water solubility 0.0002-142) and belong to 11 chemical groups. Solid phase extraction (SPE) followed by gas chromatography (GC) with electron capture detector (ECD) were performed to analyze pesticide residues of the clarified fortified wine. The correlation of the clarifying agents' effectiveness to pesticide's chemical structure and properties (log K ow , water solubility) was investigated. The antagonistic and/or synergistic effects, occurring among the pesticides in the mixtures, were calculated by indices. Pesticide removal effectiveness results of the red wine were compared to those obtained from a white wine under the same experimental conditions and discussed. The order of decreasing adsorbent effectiveness (mixture of 23 pesticides) was: activated carbon 40% > gelatin 23% > egg albumin 21% > PVPP 18% > casein 12% > bentonite 7%. Isinglass showed 12% removal at the highest permitted concentration. In the case of 9 pesticides mixture, the effectiveness was quite higher but the order remained the same compared to 23 pesticides mixture. The removal of each pesticide from its single solution was generally the highest (particularly for hydrophobic pesticides). Adsorption on fining agents is increased by increasing hydrophobicity and decreasing hydrophilicity of organic pesticide molecules.

Osteoinductive implants: the mise-en-scène for drug-bearing biomimetic coatings.

PubMed

Liu, Y; de Groot, K; Hunziker, E B

2004-03-01

In orthopaedic and dental implantology, novel tools and techniques are being sought to improve the regeneration of bone tissue. Numerous attempts have been made to enhance the osteoconductivity of titanium prostheses, including modifications in their surface properties and coating with layers of calcium phosphate. The technique whereby such layers are produced has recently undergone a revolutionary change, which has had profound consequences for their potential to serve as drug-carrier systems. Hitherto, calcium phosphate layers were deposited upon the surfaces of metal implants under highly unphysiological physical conditions, which precluded the incorporation of proteinaceous osteoinductive drugs. These agents could only be adsorbed, superficially, upon preformed layers. Such superficially adsorbed molecules are released too rapidly within a biological milieu to be effective in their osteoinductive capacity. Now, it is possible to deposit calcium phosphate layers under physiological conditions of temperature and pH by the so-called biomimetic process, during which bioactive agents can be coprecipitated. Since these molecules are integrated into the inorganic latticework, they are released gradually in vivo as the layer undergoes degradation. This feature enhances the capacity of these coatings to act as a carrier system for osteogenic agents.

Potential development of a new cotton-based antimicrobial wipe

USDA-ARS?s Scientific Manuscript database

The adsorption of alkyl-dimethyl-benzyl-ammonium chloride (ADBAC), a cationic surfactant commonly employed as an antimicrobial agent, on greige and bleached nonwoven cotton fabrics was investigated using UV/visible spectroscopy. Initial results have shown that greige cotton adsorbs roughly three tim...

Delay-dependent coupling for a multi-agent LTI consensus system with inter-agent delays

NASA Astrophysics Data System (ADS)

Qiao, Wei; Sipahi, Rifat

2014-01-01

Delay-dependent coupling (DDC) is considered in this paper in a broadly studied linear time-invariant multi-agent consensus system in which agents communicate with each other under homogeneous delays, while attempting to reach consensus. The coupling among the agents is designed here as an explicit parameter of this delay, allowing couplings to autonomously adapt based on the delay value, and in order to guarantee stability and a certain degree of robustness in the network despite the destabilizing effect of delay. Design procedures, analysis of convergence speed of consensus, comprehensive numerical studies for the case of time-varying delay, and limitations are presented.

Short communication: Adverse effect of surface-active reagents on the bioleaching of pyrite and chalcopyrite by Thiobacillus ferrooxidans.

PubMed

Huerta, G; Escobar, B; Rubio, J; Badilla-Ohlbaum, R

1995-09-01

Oxidation of Fe(II) iron and bioleaching of pyrite and chalcopyrite by Thiobacillus ferrooxidans was adversely affected by isopropylxanthate, a flotation agent, and by LIX 984, a solvent-extraction agent, each at ≤ 1 g/l. The reagents/l were adsorbed on the bacterial surface, decreasing the bacteria's development and preventing biooxidation. Both reagents inhibited the bioleaching of pyrite and LIX 984 also inhibited the bioleaching of chalcopyrite.

Allyl triphenyl phosphonium bromide based DES-functionalized carbon nanotubes for the removal of mercury from water.

PubMed

AlOmar, Mohamed Khalid; Alsaadi, Mohammed Abdulhakim; Hayyan, Maan; Akib, Shatirah; Ibrahim, Muhammad; Hashim, Mohd Ali

2017-01-01

Recently, deep eutectic solvents (DESs) have shown their new and interesting ability for chemistry through their involvement in variety of applications. This study introduces carbon nanotubes (CNTs) functionalized with DES as a novel adsorbent for Hg 2+ from water. Allyl triphenyl phosphonium bromide (ATPB) was combined with glycerol as the hydrogen bond donor (HBD) to form DES, which can act as a novel CNTs functionalization agent. The novel adsorbent was characterized using Raman, FTIR, XRD, FESEM, EDX, BET surface area, TGA, TEM and Zeta potential. Response surface methodology was used to optimize the removal conditions for Hg 2+ . The optimum removal conditions were found to be pH 5.5, contact time 28 min, and an adsorbent dosage of 5 mg. Freundlich isotherm model described the adsorption isotherm of the novel adsorbent, and the maximum adsorption capacity obtained from the experimental data was 186.97 mg g -1 . Pseudo-second order kinetics describes the adsorption rate order. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modification of eucalyptus pulp fiber using silane coupling agents with aliphatic side chains of different length

USDA-ARS?s Scientific Manuscript database

The objective of this work was to evaluate the effect of three silane coupling agents with different aliphatic chain lengths on the hydrophobicity of eucalyptus pulp fiber. The three silanes coupling agents used (isobutyltrimethoxysilane, methyltrimethoxysilane, and n-octyltriethoxysilane [OTES]) we...

Modification of zeolite 4A for use as an adsorbent for glyphosate and as an antibacterial agent for water.

PubMed

Zavareh, Siamak; Farrokhzad, Zahra; Darvishi, Farshad

2018-07-15

The aim of this work was to design a low cost adsorbent for efficient and selective removal of glyphosate from water at neutral pH conditions. For this purpose, zeolite 4A, a locally abundant and cheap mineral material, was ion-exchanged with Cu 2+ to produce Cu-zeolite 4A. The FTIR results revealed that the modification has no important effect on chemical structure of zeolite 4A. After modification, highly crystalline zeolite 4A was converted to amorphous Cu-zeolite 4A according to XRD studies. The SEM images showed spherical-like particles with porous surfaces for Cu-zeolite 4A compared to cubic particles with smooth surfaces for zeolite 4A. Adsorption equilibrium data were well fitted with non-linear forms of Langmuir, Freundlich and Temkin isotherms. The maximum adsorption capacity for Cu-zeolite 4A was calculated to be 112.7 mg g -1 based on the Langmuir model. The adsorption of glyphosate by the modified adsorbent had fast kinetics fitted both pseudo-first-order and pseudo-second-order models. A mechanism based on chemical adsorption was proposed for the removal process. The modified adsorbent had a good selectivity to glyphosate over natural waters common cations and anions. It also showed desired regeneration ability as an important feature for practical uses. The potential use of the developed material as antibacterial agent for water disinfection filters was also investigated by MIC method. Relatively strong antibacterial activity was observed for Cu-zeolite 4A against Gram-positive and Gram-negative model bacteria while zeolite 4A had no antibacterial properties. No release of Cu 2+ to aqueous solutions was detected as unique feature of the developed material. Copyright © 2018 Elsevier Inc. All rights reserved.

Adsorption of β-sitosterol on molecularly imprinted polymer

NASA Astrophysics Data System (ADS)

Soekamto, N. H.; Fauziah, St.; Taba, P.; Amran, M. B.

2017-04-01

Molecularly Imprinted Polymer (MIP) has been synthesized using methacrylate acid (MAA) as a monomer with hydroxyl and carbonyl functional groups that can react with ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent, and β-sitosterol as a template molecule. After the template was removed from the polymer, MIP_TFMAA was obtained. The MIP was used to adsorb β-sitosterol. The amount of β-sitosterol in solution after the adsorption was determined by HPLC. The results showed that the MIP was able to adsorb well the β-sitosterol at a pH 7 and the contact time of 90 min. The kinetic adsorption data obtained for β-sitosterol followed the pseudo-second-order model and consistent with the model of Feundlich isothermal with the adsorption capacity of 1.05 mg/g. The MIP was selective on β-sitosterol because it was able to adsorb β-sitosterol better than cholesterol.

Decomposition of adsorbed VX on activated carbons studied by {sup 31}P MAS NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishay Columbus; Daniel Waysbort; Liora Shmueli

2006-06-15

The fate of the persistent OP nerve agent O-ethyl S-(2-(diisopropylamino)ethyl) methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. Four types of activated carbon were used, including coal-based BPL. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) ((DES){sub 2}). Decomposition occurred irrespective of the phase from which VX was loaded,more » the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed. 17 refs., 6 figs., 3 tabs.« less

Allantoin as a solid phase adsorbent for removing endotoxins.

PubMed

Vagenende, Vincent; Ching, Tim-Jang; Chua, Rui-Jing; Gagnon, Pete

2013-10-04

In this study we present a simple and robust method for removing endotoxins from protein solutions by using crystals of the small-molecule compound 2,5-dioxo-4-imidazolidinyl urea (allantoin) as a solid phase adsorbent. Allantoin crystalline powder is added to a protein solution at supersaturated concentrations, endotoxins bind and undissolved allantoin crystals with bound endotoxins are removed by filtration or centrifugation. This method removes an average of 99.98% endotoxin for 20 test proteins. The average protein recovery is ∼80%. Endotoxin binding is largely independent of pH, conductivity, reducing agent and various organic solvents. This is consistent with a hydrogen-bond based binding mechanism. Allantoin does not affect protein activity and stability, and the use of allantoin as a solid phase adsorbent provides better endotoxin removal than anion exchange, polymixin affinity and biological affinity methods for endotoxin clearance. Copyright © 2013 Elsevier B.V. All rights reserved.

Heterogeneous Interaction of Peroxyacetyl Nitrate on Liquid Sulfuric Acid

NASA Technical Reports Server (NTRS)

Zhang, Renyi; Leu, Ming-Taun

1996-01-01

The uptake of peroxyacetyl nitrate (PAN) on liquid sulfuric acid surfaces has been investigated using a fast-flow reactor coupled to a chemical ionization mass spectrometer. PAN was observed to be reversibly adsorbed on sulfuric acid.

In vitro pyrogen test for toxic or immunomodulatory drugs.

PubMed

Daneshian, Mardas; Guenther, Armin; Wendel, Albrecht; Hartung, Thomas; von Aulock, Sonja

2006-06-30

Pyrogenic contaminations of some classes of injectable drugs, e.g. toxic or immunomodulatory as well as false-positive drugs, represent a major risk which cannot yet be excluded due to the limitations of current tests. Here we describe a modification of the In vitro Pyrogen Test termed AWIPT (Adsorb, Wash, In vitro Pyrogen Test), which addresses this problem by introducing a pre-incubation step in which pyrogenic contaminations in the test sample are adsorbed to albumin-coated beads. After rinsing, the beads are incubated with human whole blood and the release of the endogenous pyrogen interleukin-1beta is measured as a marker of pyrogenic activity. Intentional contaminations with lipopolysaccharide were retrieved from the chemotherapeutic agents paclitaxel, cisplatin and liposomal daunorubicin, the antibiotic gentamicin, the antifungal agent liposomal amphotericin B, and the corticosteroid prednisolone at lower dilutions than in the standard in vitro pyrogen test. This represents a promising new approach for the detection of pyrogenic contamination in drugs or in drugs containing interfering additives and should lead to improved safety levels.

Influence of Mycotoxins and a Mycotoxin Adsorbing Agent on the Oral Bioavailability of Commonly Used Antibiotics in Pigs

PubMed Central

Goossens, Joline; Vandenbroucke, Virginie; Pasmans, Frank; De Baere, Siegrid; Devreese, Mathias; Osselaere, Ann; Verbrugghe, Elin; Haesebrouck, Freddy; De Saeger, Sarah; Eeckhout, Mia; Audenaert, Kris; Haesaert, Geert; De Backer, Patrick; Croubels, Siska

2012-01-01

It is recognized that mycotoxins can cause a variety of adverse health effects in animals, including altered gastrointestinal barrier function. It is the aim of the present study to determine whether mycotoxin-contaminated diets can alter the oral bioavailability of the antibiotics doxycycline and paromomycin in pigs, and whether a mycotoxin adsorbing agent included into diets interacts with those antibiotics. Experiments were conducted with pigs utilizing diets that contained blank feed, mycotoxin-contaminated feed (T-2 toxin or deoxynivalenol), mycotoxin-contaminated feed supplemented with a glucomannan mycotoxin binder, or blank feed supplemented with mycotoxin binder. Diets with T-2 toxin and binder or deoxynivalenol and binder induced increased plasma concentrations of doxycycline administered as single bolus in pigs compared to diets containing blank feed. These results suggest that complex interactions may occur between mycotoxins, mycotoxin binders, and antibiotics which could alter antibiotic bioavailability. This could have consequences for animal toxicity, withdrawal time for oral antibiotics, or public health. PMID:22606377

Vibrational dynamics of adsorbed molecules under conditions of photodesorption: pump-probe SFG spectra of CO/Pt(111).

PubMed

Fournier, Frédéric; Zheng, Wanquan; Carrez, Serge; Dubost, Henri; Bourguignon, Bernard

2004-09-08

Interaction of CO adsorbed on Pt(111) with electrons and phonons is studied experimentally by means of a pump-probe experiment where CO is probed by IR + visible sum frequency generation under a pump laser intensity that allows photodesorption. Vibrational spectra of CO internal stretch are obtained as a function of pump-probe delay. A two-temperature and anharmonic coupling model is used to extract from the spectra the real time variations of CO peak frequency and dephasing time. The main conclusions are the following: (i) The CO stretch is perturbed by two low-frequency modes, assigned to frustrated rotation and frustrated translation. (ii) The frustrated rotation is directly coupled to electrons photoexcited in Pt(111) by the pump laser. (iii) There is no evidence of Pt-CO stretch excitation in the spectra. The implications for the photodesorption dynamics are discussed. Copyright 2004 American Institute of Physics

Vibrational dynamics of adsorbed molecules under conditions of photodesorption: Pump-probe SFG spectra of CO/Pt(111)

NASA Astrophysics Data System (ADS)

Fournier, Frédéric; Zheng, Wanquan; Carrez, Serge; Dubost, Henri; Bourguignon, Bernard

2004-09-01

Interaction of CO adsorbed on Pt(111) with electrons and phonons is studied experimentally by means of a pump-probe experiment where CO is probed by IR+visible sum frequency generation under a pump laser intensity that allows photodesorption. Vibrational spectra of CO internal stretch are obtained as a function of pump-probe delay. A two-temperature and anharmonic coupling model is used to extract from the spectra the real time variations of CO peak frequency and dephasing time. The main conclusions are the following: (i) The CO stretch is perturbed by two low-frequency modes, assigned to frustrated rotation and frustrated translation. (ii) The frustrated rotation is directly coupled to electrons photoexcited in Pt(111) by the pump laser. (iii) There is no evidence of Pt-CO stretch excitation in the spectra. The implications for the photodesorption dynamics are discussed.

Interfacial charge transfer absorption: Application to metal molecule assemblies

NASA Astrophysics Data System (ADS)

Creutz, Carol; Brunschwig, Bruce S.; Sutin, Norman

2006-05-01

Optically induced charge transfer between adsorbed molecules and a metal electrode was predicted by Hush to lead to new electronic absorption features, but has been only rarely observed experimentally. Interfacial charge transfer absorption (IFCTA) provides information concerning the barriers to charge transfer between molecules and the metal/semiconductor and the magnitude of the electronic coupling and could thus provide a powerful tool for understanding interfacial charge-transfer kinetics. Here, we utilize a previously published model [C. Creutz, B.S. Brunschwig, N. Sutin, J. Phys. Chem. B 109 (2005) 10251] to predict IFCTA spectra of metal-molecule assemblies and compare the literature observations to these predictions. We conclude that, in general, the electronic coupling between molecular adsorbates and the metal levels is so small that IFCTA is not detectable. However, few experiments designed to detect IFCTA have been done. We suggest approaches to optimizing the conditions for observing the process.

Optoacoustic detection of viral antigens using targeted gold nanorods

NASA Astrophysics Data System (ADS)

Maswadi, Saher; Woodward, Lee; Glickman, Randolph D.; Barsalou, Norman

2009-02-01

We are detecting antigens (Ag), isolated from infectious organisms, utilizing laser optoacoustic spectroscopy and antibody-coupled gold nanorod (NR) contrast agents specifically targeted to the antigen of interest. We have detected, in clinical ocular samples, both Herpes Simplex Virus Type 1 and 2 (HSV-1 and HSV-2) . A monoclonal antibody (Ab) specific to both HSV-1 and HSV-2 was conjugated to gold nanorods to produce a targeted contrast agent with a strong optoacoustic signal. Elutions obtained from patient corneal swabs were adsorbed in standard plastic micro-wells. An immunoaffinity reaction was then performed with the functionalized gold nanorods, and the results were probed with an OPO laser, emitting wavelengths at the peak absorptions of the nanorods. Positive optoacoustic responses were obtained from samples containing authentic (microbiologically confirmed) HSV-1 and HSV-2. To obtain an estimate of the sensitivity of the technique, serial dilutions from 1 mg/ml to 1 pg/ml of a C. trachomatis surface Ag were prepared, and were probed with a monoclonal Ab, specific to the C. trachomatis surface Ag, conjugated to gold nanorods. An optoacoustic response was obtained, proportional to the concentration of antigen, and with a limit of detection of about 5 pg/ml. The optoacoustic signals generated from micro-wells containing albumin or saline were similar to those from blank wells. The potential benefit of this method is identify viral agents more rapidly than with existing techniques. In addition, the sensitivity of the assay is comparable or superior to existing colorimetric- or fluorometric-linked immunoaffinity assays.

Modeling adsorption: Investigating adsorbate and adsorbent properties

NASA Astrophysics Data System (ADS)

Webster, Charles Edwin

1999-12-01

Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas adsorption and catalysis. These studies are also applicable to environmental cleanup applications, such as waste stream purification and separation procedures as well as decontamination of chemical warfare agents.

Water defluoridation by aluminium oxide-manganese oxide composite material.

PubMed

Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

2014-08-01

In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3.1 x 10(-2) g/min mg. It is concluded that AOMO is a highly promising adsorbent for the removal of excess fluoride from drinking water.

Molecular and dissociative adsorption of DMMP, Sarin and Soman on dry and wet TiO2(110) using density functional theory

NASA Astrophysics Data System (ADS)

Quintero, Yenny Cardona; Nagarajan, Ramanathan

2018-09-01

Titania, among the metal oxides, has shown promising characteristics for the adsorption and decontamination of chemical warfare nerve agents, due to its high stability and rapid decomposition rates. In this study, the adsorption energy and geometry of the nerve agents Sarin and Soman, and their simulant dimethyl methyl phosphonate (DMMP) on TiO2 rutile (110) surface were calculated using density functional theory. The molecular and dissociative adsorption of the agents and simulant on dry as well as wet metal oxide surfaces were considered. For the wet system, computations were done for the cases of both molecularly adsorbed water (hydrated conformation) and dissociatively adsorbed water (hydroxylated conformation). DFT calculations show that dissociative adsorption of the agents and simulant is preferred over molecular adsorption for both dry and wet TiO2. The dissociative adsorption on hydrated TiO2 shows higher stability among the different configurations considered. The dissociative structure of DMMP on hydrated TiO2 (the most stable one) was identified as the dissociation of a methyl group and its adsorption on the TiO2 surface. For the nerve agents Sarin and Soman on hydrated TiO2 the dissociative structure was by the dissociation of the F atom from the molecule and its interaction with a Ti atom from the surface, which could indicate a reduction in the toxicity of the products. This study shows the relevance of water adsorption on the metal oxide surface for the stability and dissociation of the simulant DMMP and the nerve agents Sarin and Soman on TiO2.

Measurement of breakthrough volumes of volatile chemical warfare agents on a poly(2,6-diphenylphenylene oxide)-based adsorbent and application to thermal desorption-gas chromatography/mass spectrometric analysis.

PubMed

Kanamori-Kataoka, Mieko; Seto, Yasuo

2015-09-04

To establish adequate on-site solvent trapping of volatile chemical warfare agents (CWAs) from air samples, we measured the breakthrough volumes of CWAs on three adsorbent resins by an elution technique using direct electron ionization mass spectrometry. The trapping characteristics of Tenax(®) TA were better than those of Tenax(®) GR and Carboxen(®) 1016. The latter two adsorbents showed non-reproducible breakthrough behavior and low VX recovery. The specific breakthrough values were more than 44 (sarin) L/g Tenax(®) TA resin at 20°C. Logarithmic values of specific breakthrough volume for four nerve agents (sarin, soman, tabun, and VX) showed a nearly linear correlation with the reciprocals of their boiling points, but the data point of sulfur mustard deviated from this linear curve. Next, we developed a method to determine volatile CWAs in ambient air by thermal desorption-gas chromatography (TD-GC/MS). CWA solutions that were spiked into the Tenax TA(®) adsorbent tubes were analyzed by a two-stage TD-GC/MS using a Tenax(®) TA-packed cold trap tube. Linear calibration curves for CWAs retained in the resin tubes were obtained in the range between 0.2pL and 100pL for sarin, soman, tabun, cyclohexylsarin, and sulfur mustard; and between 2pL and 100pL for VX and Russian VX. We also examined the stability of CWAs in Tenax(®) TA tubes purged with either dry or 50% relative humidity air under storage conditions at room temperature or 4°C. More than 80% sarin, soman, tabun, cyclohexylsarin, and sulfur mustard were recovered from the tubes within 2 weeks. In contrast, the recoveries of VX and Russian VX drastically reduced with storage time at room temperature, resulting in a drop to 10-30% after 2 weeks. Moreover, we examined the trapping efficiency of Tenax TA(®) adsorbent tubes for vaporized CWA samples (100mL) prepared in a 500mL gas sampling cylinder. In the concentration range of 0.2-2.5mg/m(3), >50% of sarin, soman, tabun, cyclohexylsarin, and HD were recovered, whereas <1% of VX and Russian VX were recovered in the same concentration range. The results indicate that CWA vapors, with the exception of VX and Russian VX, can be measured by an on-site collection procedure using the Tenax(®) TA resin tubes, followed by a subsequent TD-GC/MS analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

Computational design and fabrication of core-shell magnetic molecularly imprinted polymer for dispersive micro-solid-phase extraction coupled with high-performance liquid chromatography for the determination of rhodamine 6G.

PubMed

Xie, Jin; Xie, Jie; Deng, Jian; Fang, Xiangfang; Zhao, Haiqing; Qian, Duo; Wang, Hongjuan

2016-06-01

A novel core-shell magnetic nano-adsorbent with surface molecularly imprinted polymer coating was fabricated and then applied to dispersive micro-solid-phase extraction followed by determination of rhodamine 6G using high-performance liquid chromatography. The molecularly imprinted polymer coating was prepared by copolymerization of dopamine and m-aminophenylboronic acid (functional monomers), in the presence of rhodamine 6G (template). The selection of the suitable functional monomers was based on the interaction between different monomers and the template using the density functional theory. The ratios of the monomers to template were further optimized by an OA9 (3(4) ) orthogonal array design. The binding performances of the adsorbent were evaluated by static, kinetic, and selective adsorption experiments. The results reveal that the adsorbent possesses remarkable affinity and binding specificity for rhodamine 6G because of the enhanced Lewis acid-base interaction between the B(Ш) embedded in the imprinted cavities and the template. The nano-adsorbent was successfully applied to dispersive micro-solid-phase extraction coupled to high-performance liquid chromatography for the trace determination of rhodamine 6G in samples with a detection limit of 2.7 nmol/L. Spiked recoveries ranged from 93.0-99.1, 89.5-92.7, and 86.9-105% in river water, matrimony vine and paprika samples, respectively, with relative standard deviations of less than 4.3%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of binary gas mixtures in heterogeneous carbon predicted by density functional theory: on the formation of adsorption azeotropes.

PubMed

Ritter, James A; Pan, Huanhua; Balbuena, Perla B

2010-09-07

Classical density functional theory (DFT) was used to predict the adsorption of nine different binary gas mixtures in a heterogeneous BPL activated carbon with a known pore size distribution (PSD) and in single, homogeneous, slit-shaped carbon pores of different sizes. By comparing the heterogeneous results with those obtained from the ideal adsorbed solution theory and with those obtained in the homogeneous carbon, it was determined that adsorption nonideality and adsorption azeotropes are caused by the coupled effects of differences in the molecular size of the components in a gas mixture and only slight differences in the pore sizes of a heterogeneous adsorbent. For many binary gas mixtures, selectivity was found to be a strong function of pore size. As the width of a homogeneous pore increases slightly, the selectivity for two different sized adsorbates may change from being greater than unity to less than unity. This change in selectivity can be accompanied by the formation of an adsorption azeotrope when this same binary mixture is adsorbed in a heterogeneous adsorbent with a PSD, like in BPL activated carbon. These results also showed that the selectivity exhibited by a heterogeneous adsorbent can be dominated by a small number of pores that are very selective toward one of the components in the gas mixture, leading to adsorption azeotrope formation in extreme cases.

Recycling of spent adsorbents for oxyanions and heavy metal ions in the production of ceramics.

PubMed

Verbinnen, Bram; Block, Chantal; Van Caneghem, Jo; Vandecasteele, Carlo

2015-11-01

Spent adsorbents for oxyanion forming elements and heavy metals are classified as hazardous materials and they are typically treated by stabilization/solidification before landfilling. The use of lime or cement for stabilization/solidification entails a high environmental impact and landfilling costs are high. This paper shows that mixing spent adsorbents in the raw material for the production of ceramic materials is a valuable alternative to stabilize oxyanion forming elements and heavy metals. The produced ceramics can be used as construction material, avoiding the high economic and environmental impact of stabilization/solidification followed by landfilling. To study the stabilization of oxyanion forming elements and heavy metals during the production process, two series of experiments were performed. In the first series of experiments, the main pollutant, Mo was adsorbed onto iron-based adsorbents, which were then mixed with industrial sludge (3 w/w%) and heated at 1100°C for 30 min. Mo was chosen, as this element is easily adsorbed onto iron-based adsorbents and it is the element that is the most difficult to stabilize (i.e. the highest temperatures need to be reached before the concentrations in the leachate are reduced). Leaching concentration from the 97/3 sludge/adsorbent mixture before heating ranged between 85 and 154 mg/kg; after the heating process they were reduced to 0.42-1.48 mg/kg. Mo was actually stabilized, as the total Mo concentration after addition was not affected by the heat treatment. In the second series of experiments, the sludge was spiked with other heavy metals and oxyanion forming elements (Cr, Ni, Cu, Zn, As, Cd and Pb) in concentrations 5 times higher than the initial concentrations; after heat treatment the leachate concentrations were below the regulatory limit values. The incorporation of spent adsorbents in ceramic materials is a valuable and sustainable alternative to the existing treatment methods, saving raw materials in the ceramics production process and avoiding the use of stabilizing agents. Besides, spent adsorbents added to the raw material for ceramic products, may improve their aesthetic and structural properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

Development of resin adsorbents for blood purification at Nankai University in China.

PubMed

Wang, Yong-Jian; Yu, Yao-Ting

2011-04-01

Various types of porous resin adsorbents based on polystyrene, agarose, and cellulose as matrixes coupling with DNA, amino acids and other biological active molecules as ligands were extensively studied in China. Molecular recognition between the ligand and pathogenic molecule was investigated. Several commercialized products are now widely used in hospitals all over China. Whole blood hemoperfusion is used to treat patients suffering from autoimmune diseases, uremia acute intoxication, and hyperbilirubinemia. Clinical performances of hundreds and thousands of patients treated by whole blood sorption therapy show that the therapy is safe, efficient, and cost-effective.

DNA adsorption onto glass surfaces

NASA Astrophysics Data System (ADS)

Carlson, Krista Lynn

Streaming potential measurements were performed on microspheres of silica, lime silicate (SLS) and calcium aluminate (CA) glasses containing silica and iron oxide (CASi and CAFe). The silicate based glasses exhibited acidic surfaces with isoelectric points (IEP) around a pH of 3 while the calcium aluminates displayed more basic surfaces with IEP ranging from 8--9.5. The surface of the calcium aluminate microspheres containing silica reacted with the background electrolyte, altering the measured zeta potential values and inhibiting electrolyte flow past the sample at ˜ pH 4 due to formation of a solid plug. DNA adsorption experiments were performed using the microspheres and a commercially available silicate based DNA isolation filter using a known quantity of DNA suspended in a chaotropic agent free 0.35 wt% Tris(hydroxymethyl)aminomethane (Tris) buffer solution. The microspheres and commercial filter were also used to isolate DNA from macrophage cells in the presence of chaotropic agents. UV absorbance at ˜260 nm and gel electrophoresis were used to quantify the amount and size of the DNA strands that adsorbed to the microsphere surfaces. In both experiments, the 43--106 microm CAFe microspheres adsorbed the largest quantity of DNA. However, the 43--106 microm SLS microspheres isolated more DNA from the cells than the <43 microm CAFe microspheres, indicating that microsphere size contributes to isolation ability. The UV absorbance of DNA at ˜260 nm was slightly altered due to the dissolution of the calcium aluminate glasses during the adsorption process. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) determined that calcium and aluminum ions leached from the CA and CAFe microsphere surfaces during these experiments. Circular dichroism (CD) spectroscopy showed that the leached ions had no effect on the conformation of the DNA, and therefore would not be expected to interfere in downstream applications such as DNA replication. The 0.35 wt% Tris solution completely inhibited the formation of the hydrated crystalline layer that develops when the calcium aluminate glassess are incubated in deionized water. A Tris concentration of 0.24 wt% allowed for the formation of both hexagonal and cubic hydrates, however they were severely distorted and present in low amounts such that they were undectable by XRD.

Studies on a complex mechanism for the activation of plasminogen by kaolin and by chloroform: the participation of Hageman factor and additional cofactors

PubMed Central

Ogston, Derek; Ogston, C. Marie; Ratnoff, Oscar D.; Forbes, Charles D.

1969-01-01

As demonstrated by others, fibrinolytic activity was generated in diluted, acidified normal plasma exposed to kaolin, a process requiring Hageman factor (Factor XII). Generation was impaired by adsorbing plasma with glass or similar agents under conditions which did not deplete its content of Hageman factor or plasminogen. The defect could be repaired by addition of a noneuglobulin fraction of plasma or an agent or agents eluted from diatomaceous earth which had been exposed to normal plasma. The restorative agent, tentatively called Hageman factor-cofactor, was partially purified by chromatography and had an apparent molecular weight of approximately 165,000. It could be distinguished from plasma thromboplastin antecedent (Factor XI) and plasma kallikrein, other substrates of Hageman factor, and from the streptokinase-activated pro-activator of plasminogen. Evidence is presented that an additional component may be needed for the generation of fibrinolytic activity in mixtures containing Hageman factor, HF-cofactor, and plasminogen. The long-recognized generation of plasmin activity in chloroform-treated euglobulin fractions of plasma was found to be dependent upon the presence of Hageman factor. Whether chloroform activation of plasminogen requires Hageman factor-cofactor was not determined, but glass-adsorbed plasma, containing Hageman factor and plasminogen, did not generate appreciable fibrinolytic or caseinolytic activity. These studies emphasize the complex nature of the mechanisms which lead to the generation of plasmin in human plasma. PMID:4241814

Synthesis and characterization of protocatechuic acid-loaded gadolinium-layered double hydroxide and gold nanocomposite for theranostic application

NASA Astrophysics Data System (ADS)

Usman, Muhammad Sani; Hussein, Mohd Zobir; Kura, Aminu Umar; Fakurazi, Sharida; Masarudin, Mas Jaffri; Saad, Fathinul Fikri Ahmad

2018-03-01

A theranostic nanocomposite was developed using anticancer agent, protocatechuic acid (PA) and magnetic resonance imaging (MRI) contrast agent gadolinium nitrate (Gd) for simultaneous delivery using layered double hydroxide (LDH) as the delivery agent. Gold nanoparticles (AuNPs) were adsorbed on the surface of the LDH, which served as a complementary contrast agent. Based on the concept of supramolecular chemistry (SPC) and multimodal delivery system (MDS), the PA and Gd guests were first intercalated into the LDH host and subsequently AuNPs were surface adsorbed as the third guest. The nanohybrid developed was named MAPGAu. The MAPGAu was exposed to various characterizations at different stages of synthesis, starting with XRD analysis, which was used to confirm the intercalation episode and surface adsorption of the guest molecules. Consequently, FESEM, Hi-TEM, XRD, ICP-OES, CHNS, FTIR and UV-Vis analyses were done on the nanohybrids. The result of XRD analysis indicated successful intercalation of the Gd and PA as well the adsorption of AuNPs. The UV-Vis release study showed 90% of the intercalated drug was released at pH 4.8, which is the pH of the cancer cells. The FESEM and TEM micrographs obtained equally confirmed the formation of MAGPAu nanocomposite, with AuNPs conspicuously deposited on the LDH surface. The cytotoxicity study of the nanohybrid also showed insignificant toxicity to normal cell lines and significant toxicity to cancer cell lines. The developed MAGPAu nanocomposite has shown prospects for future theranostic cancer treatment.

Fibrous Filter to Protect Building Environments from Polluting Agents: A Review

NASA Astrophysics Data System (ADS)

Chavhan, Md. Vaseem; Mukhopadhyay, Arunangshu

2016-04-01

This paper discusses the use of fibrous filter to protect the building environments from air born polluting agents and especially of concern chemical, biological and radiological agents. Air-filtration includes removal of particulate from air and toxic gases from air. In air filtration, particulate which are mostly biological and radioactive types of agents can be removed by using mechanical and electrostatic filters. Some biological agents, which cannot be removed by air filtration alone, special techniques like antimicrobial finish, UV germicides, coated filters etc. are required. Biocide agent can be added into the fibre itself by grafting reaction to impart antimicrobial activity. Chemical agents like toxic gases can be removed by integrating adsorbents and sorbents in filters or by fibre modifications. It is also possible to impart catalytic conversion properties into the fibre to remove volatile gasous. Radioactive agents can be removed by particulate filter if present in the form of aerosol or by gas cleaning by the use of specific fibre impregnate.

Magnetic coupling of Fe-porphyrin molecules adsorbed on clean and c(2×2) oxygen-reconstructed Co(100) investigated by spin-polarized photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Weber, A. P.; Caruso, A. N.; Vescovo, E.; Ali, Md. E.; Tarafder, K.; Janjua, S. Z.; Sadowski, J. T.; Oppeneer, P. M.

2013-05-01

The spin-polarized electronic structure of iron octaethylporphyrin (FeOEP) molecules adsorbed on a pristine and on a c(2×2) oxygen-reconstructed Co(100) surface has been analyzed by means of spin-polarized photoemission spectroscopy (SPPES) and first-principles density functional theory with the on-site Coulomb repulsion U term (DFT+U) calculations with and without Van der Waals corrections. The aim is to examine the magnetic exchange mechanism between the FeOEP molecules and the Co(100) substrate in the presence or absence of the oxygen mediator. The results demonstrate that the magnetic coupling from the ferromagnetic substrate to the adsorbed FeOEP molecules is ferromagnetic, whereas, the coupling is antiferromagnetic for the FeOEP on the c(2×2)O/Co(100) system. Spin-resolved partial densities of states extracted from ab initio DFT+U modeling are in fairly good comparison with the electronic spectral densities seen in angle-integrated SPPES energy dispersion curves for submonolayer coverages of FeOEP. Through combined analysis of these spectra and theoretical results, we determine that hybridization of 2p orbitals of N and O with Co 3d orbitals facilitates indirect magnetic exchange interactions between Fe and Co, whereas, a direct Fe-Co interaction involving the Fe dz2 orbital is also found for FeOEP on Co. It is observed through SPPES that the spin polarization of the photoemission-visible molecular overlayers decreases to zero as coverage is increased beyond the submonolayer regime, indicating that only interfacial magnetic coupling is at work. Microspot low-energy electron diffraction and low-energy electron microscopy were performed to characterize the physical order of the molecular coverage, revealing that FeOEP structural domains are orders of magnitude greater in size on c(2×2)O/Co(100) than on clean Co(100), which coincides with reduced scattering from the disorder and sharper features seen in SPPES.

Magnetic graphene-carbon nanotube iron nanocomposites as adsorbents and antibacterial agents for water purification.

PubMed

Sharma, Virender K; McDonald, Thomas J; Kim, Hyunook; Garg, Vijayendra K

2015-11-01

One of the biggest challenges of the 21st century is to provide clean and affordable water through protecting source and purifying polluted waters. This review presents advances made in the synthesis of carbon- and iron-based nanomaterials, graphene-carbon nanotubes-iron oxides, which can remove pollutants and inactivate virus and bacteria efficiently in water. The three-dimensional graphene and graphene oxide based nanostructures exhibit large surface area and sorption sites that provide higher adsorption capacity to remove pollutants than two-dimensional graphene-based adsorbents and other conventional adsorbents. Examples are presented to demonstrate removal of metals (e.g., Cu, Pb, Cr(VI), and As) and organics (e.g., dyes and oil) by grapheme-based nanostructures. Inactivation of Gram-positive and Gram-negative bacterial species (e.g., Escherichia coli and Staphylococcus aureus) is also shown. A mechanism involving the interaction of adsorbents and pollutants is briefly discussed. Magnetic graphene-based nanomaterials can easily be separated from the treated water using an external magnet; however, there are challenges in implementing the graphene-based nanotechnology in treating real water. Copyright © 2015 Elsevier B.V. All rights reserved.

Silica/graphene oxide nanocomposites: Potential adsorbents for solid phase extraction of trace aflatoxins in cereal crops coupled with high performance liquid chromatography.

PubMed

Yu, Li; Ma, Fei; Ding, Xiaoxia; Wang, Hengling; Li, Peiwu

2018-04-15

Graphene oxide wrapped silica nanocomposites were synthesized and selected as solid phase extraction adsorbents for high performance liquid chromatography analysis of aflatoxins. The major parameters affecting extraction efficiency were optimized, including the amount of adsorbents, extraction time and desorption conditions. The limit of detections and the limit of quantifications were from 0.1 to 0.3 µg/kg and from 0.3 to 1.0 µg/kg, respectively. The recoveries of aflatoxins in the spiked maize and rice samples were in the range of 76.8-104.7% and 81.1-106.9%, respectively, and with the RSDs less than 12.4%. The proposed method was proven to be simple, rapid and reliable for routine analysis of aflatoxins in crops. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adsorption of amphipathic dendrons on polystyrene nanoparticles.

PubMed

Sakthivel, T; Florence, A T

2003-03-18

Adsorption of dendrons onto nanoparticles may provide new model structures which may be useful in drug and gene delivery. Tritiated amphipathic dendrons having three lipidic (C(14)) chains coupled to branched (dendritic) lysine head groups with 8, 16 or 32 free terminal amino groups have been synthesised by solid phase peptide techniques. The interaction between these tritiated dendrons and 200 nm polystyrene latex nanoparticles was investigated in phosphate buffered saline. The amount of dendron adsorbed increased with increasing concentration of dendrons and then decreased. Maximum adsorption of dendrons per gram of nanoparticles was found to be between 8.2 and 84 x 10(-6)M, the amounts adsorbed being inversely proportional to the number of amino groups present in the molecule. The number of dendron molecules adsorbed per nanoparticle was found to be between 430 and 4421. The degree of adsorption was found to be slightly altered by the temperature. Copyright 2002 Elsevier Science B.V.

STUDY OF THE ADSORPTION ON AND DESORPTION FROM POLYSTYRENE-HUMAN SERUM ALBUMIN CONJUGATES OF RABBIT ANTI-HUMAN SERUM ALBUMIN ANTIBODIES HAVING DIFFERENT SPECIFICITIES

PubMed Central

Webb, Tom; Lapresle, Claude

1961-01-01

An insoluble specific adsorbent for anti-human serum albumin antibodies was prepared by coupling human serum albumin (H.S.A.) to polystyrene by azo bonds. Rabbit anti-H.S.A. immune serum was passed through a column of the adsorbent. It was shown that different volumes of the immune serum were required for the saturation of the different determinant groups of H.S.A. by their corresponding antibodies. The elution of the anti-H.S.A. antibodies adsorbed on the column was achieved by passing successively through the column an acetate buffer pH 3.0 and a solution of 0.1 N HCl in 0.15 M NaCl. The antibodies were eluted in three different fractions, each of which was composed of γ-globulins only. These three fractions contained different proportions of antibodies of different specificities. PMID:13783579

Nanoalloy electrocatalysis: simulating cyclic voltammetry from configurational thermodynamics with adsorbates.

PubMed

Wang, Lin-Lin; Tan, Teck L; Johnson, Duane D

2015-11-14

We simulate the adsorption isotherms for alloyed nanoparticles (nanoalloys) with adsorbates to determine cyclic voltammetry (CV) during electrocatalysis. The effect of alloying on nanoparticle adsorption isotherms is provided by a hybrid-ensemble Monte Carlo simulation that uses the cluster expansion method extended to non-exchangeable coupled lattices for nanoalloys with adsorbates. Exemplified here for the hydrogen evolution reaction, a 2-dimensional CV is mapped for Pd-Pt nanoalloys as a function of both electrochemical potential and the global Pt composition, and shows a highly non-linear alloying effect on CV. Detailed features in CV arise from the interplay among the H-adsorption in multiple sites that is closely correlated with alloy configurations, which are in turn affected by the H-coverage. The origins of specific features in CV curves are assigned. The method provides a more complete means to design nanoalloys for electrocatalysis.

Nanoalloy electrocatalysis: Simulating cyclic voltammetry from configurational thermodynamics with adsorbates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lin -Lin; Tan, Teck L.; Johnson, Duane D.

2015-02-27

We simulate the adsorption isotherms for alloyed nanoparticles (nanoalloys) with adsorbates to determine cyclic voltammetry (CV) during electrocatalysis. The effect of alloying on nanoparticle adsorption isotherms is provided by a hybrid-ensemble Monte Carlo simulation that uses the cluster expansion method extended to non-exchangeable coupled lattices for nanoalloys with adsorbates. Exemplified here for the hydrogen evolution reaction, a 2-dimensional CV is mapped for Pd–Pt nanoalloys as a function of both electrochemical potential and the global Pt composition, and shows a highly non-linear alloying effect on CV. Detailed features in CV arise from the interplay among the H-adsorption in multiple sites thatmore » is closely correlated with alloy configurations, which are in turn affected by the H-coverage. The origins of specific features in CV curves are assigned. As a result, the method provides a more complete means to design nanoalloys for electrocatalysis.« less

Many-particle effects in adsorbed magnetic atoms with easy-axis anisotropy: the case of Fe on the CuN/Cu(100) surface

NASA Astrophysics Data System (ADS)

Žitko, R.; Pruschke, Th

2010-06-01

We study the effects of the exchange interaction between an adsorbed magnetic atom with easy-axis magnetic anisotropy and the conduction-band electrons from the substrate. We model the system using an anisotropic Kondo model and we compute the impurity spectral function, which is related to the differential conductance (dI/dV) spectra measured using a scanning tunneling microscope. To make contact with the known experimental results for iron atoms on the CuN/Cu(100) surface (Hirjibehedin et al 2007 Science 317 1199), we calculated the spectral functions in the presence of an external magnetic field of varying strength applied along all three spatial directions. It is possible to establish an upper bound on the coupling constant J: in the range of the magnetic fields for which the experimental results are currently known (up to 7 T), the low-energy features in the calculated spectra agree well with the measured dI/dV spectra if the exchange coupling constant J is at most half as large as that for cobalt atoms on the same surface. We show that for an even higher magnetic field (between 8 and 9 T) applied along the 'hollow direction', the impurity energy states cross, giving rise to a Kondo effect which takes the form of a zero-bias resonance. The coupling strength J could be determined experimentally by performing tunneling spectroscopy in this range of magnetic fields. On the technical side, the paper introduces an approach for calculating the expectation values of global spin operators and all the components of the impurity magnetic susceptibility tensor (including the out-of-diagonal ones) in numerical renormalization group (NRG) calculations with no spin symmetry. An appendix contains a density functional theory (DFT) study of the Co and Fe adsorbates on the CuN/Cu(100) surface: we compare magnetic moments, as well as orbital energies, occupancies, centers and spreads, by calculating the maximally localized Wannier orbitals of the adsorbates.

Preparation of RHA-silica/graphene oxide nanocomposite for removal of nickel ions from water

NASA Astrophysics Data System (ADS)

Tien, Tran Thi Thuy; Tu, Tran Hoang; Thao, Huynh Nguyen Phuong; Hieu, Nguyen Huu

2017-09-01

In this study, silica was synthesized from rice husk ash (RHA-SiO2) by precipitation method. Graphene oxide (GO) was prepared by modified Hummers method. RHA-SiO2/GO nanocomposite was fabricated by in-situ one-step method using 3-Aminopropyltriethoxysilane (APS) as a coupling agent. The nanocomposite was characterized by using X-ray Fluorescence, X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and Brunauer-Emmett-Teller (BET) specific surface area. The adsorption of RHA-SiO2/GO for Ni2+ ions from water was investigated and compared with the precursors. Ultraviolet-visible (UV-Vis) spectroscopy was used to quantify the amount of the initial and the residual Ni2+ concentration. The maximum adsorption capacity of the nanocomposite for Ni2+ calculated from Langmuir isotherm model, which was 256.4 mg/g. In addition, the adsorption data were well-fitted to the pseudo-second-order kinetic equation. Accordingly, this study demonstrated that RHA-SiO2/GO could be used as a highly efficient adsorbent for removal Ni2+ ions from aqueous solution.

Critical evaluation and comparison of enrichment efficiency of multi-walled carbon nanotubes, C18 silica and activated carbon towards some pesticides from environmental waters.

PubMed

El-Sheikh, Amjad H; Sweileh, Jamal A; Al-Degs, Yahya S; Insisi, Ahmad A; Al-Rabady, Nancy

2008-02-15

In this work, optimization of multi-residue solid phase extraction (SPE) procedures coupled with high-performance liquid chromatography for the determination of Propoxur, Atrazine and Methidathion from environmental waters is reported. Three different sorbents were used in this work: multi-walled carbon nanotubes (MWCNTs), C18 silica and activated carbon (AC). The three optimized SPE procedures were compared in terms of analytical performance, application to environmental waters, cartridge re-use, adsorption capacity and cost of adsorbent. Although the adsorption capacity of MWCNT was larger than AC and C18, however, the analytical performance of AC could be made close to the other sorbents by appropriate optimization of the SPE procedures. A sample of AC was then oxidized with various oxidizing agents to show that ACs of various surface properties has different enrichment efficiencies. Thus researchers are advised to try AC of various surface properties in SPE of pollutants prior to using expensive sorbents (such as MWCNT and C18 silica).

A unifying model for non-adiabatic coupling at metallic surfaces beyond the local harmonic approximation: From vibrational relaxation to scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Tremblay, Jean Christophe

2013-06-01

A model for treating excitation and relaxation of adsorbates at metallic surfaces induced by non-adiabatic coupling is developed. The derivation is based on the concept of resonant electron transfer, where the adsorbate serves as a molecular bridge for the inelastic transition between an electron source and a sink. In this picture, energy relaxation and scanning tunneling microscopy (STM) at metallic surfaces are treated on an equal footing as a quasi-thermal process. The model goes beyond the local harmonic approximation and allows for an unbiased description of floppy systems with multiple potential wells. Further, the limitation of the product ansatz for the vibronic wave function to include the position-dependence of the non-adiabatic couplings is avoided by explicitly enforcing detailed balance. The theory is applied to the excitation of hydrogen on palladium, which has multiple local potential minima connected by low energy barriers. The main aspects investigated are the lifetimes of adsorbate vibrations in different adsorption sites, as well as the dependence of the excitation, response, and transfer rates on an applied potential bias. The excitation and relaxation simulations reveal intricate population dynamics that depart significantly from the simplistic tunneling model in a truncated harmonic potential. In particular, the population decay from an initially occupied local minimum induced by the contact with an STM tip is found to be better described by a double exponential. The two rates are interpreted as a response to the system perturbation and a transfer rate following the perturbation. The transfer rate is found to obey a power law, as was the case in previous experimental and theoretical work.

Absorption properties of carbon dioxide enhanced-oil-recovery additives. Final Technical report, 12 May 1987-31 August 1989

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patton, J.T.; Holbrook, S.T.

1990-01-01

The selection of the optimum foaming agent (surfactant) for enhancing oil production by carbon dioxide flooding is based on foamability and adsorption. Measurement of adsorption on carbonate cores from New Mexico reservoirs showed large adsorption differences between three commercial, high-foaming surfactants. An ethoxylated alcohol structure was least adsorbed, 0.64 mg/cc pore volume; an ethoxylated alcohol sulfate was next, 0.74 mg/cc pore volume; the highest adsorbed was a glyceryl sulfonate, 2.30 mg/cc pore volume. Commercial application of the foaming additive involves injecting alternate slugs of surfactant solution and carbon dioxide. Surfactant concentration should be determined to allow for the adsorption above.

Collective motion patterns of swarms with delay coupling: Theory and experiment.

PubMed

Szwaykowska, Klementyna; Schwartz, Ira B; Mier-Y-Teran Romero, Luis; Heckman, Christoffer R; Mox, Dan; Hsieh, M Ani

2016-03-01

The formation of coherent patterns in swarms of interacting self-propelled autonomous agents is a subject of great interest in a wide range of application areas, ranging from engineering and physics to biology. In this paper, we model and experimentally realize a mixed-reality large-scale swarm of delay-coupled agents. The coupling term is modeled as a delayed communication relay of position. Our analyses, assuming agents communicating over an Erdös-Renyi network, demonstrate the existence of stable coherent patterns that can be achieved only with delay coupling and that are robust to decreasing network connectivity and heterogeneity in agent dynamics. We also show how the bifurcation structure for emergence of different patterns changes with heterogeneity in agent acceleration capabilities and limited connectivity in the network as a function of coupling strength and delay. Our results are verified through simulation as well as preliminary experimental results of delay-induced pattern formation in a mixed-reality swarm.

Collective motion patterns of swarms with delay coupling: Theory and experiment

NASA Astrophysics Data System (ADS)

Szwaykowska, Klementyna; Schwartz, Ira B.; Mier-y-Teran Romero, Luis; Heckman, Christoffer R.; Mox, Dan; Hsieh, M. Ani

2016-03-01

The formation of coherent patterns in swarms of interacting self-propelled autonomous agents is a subject of great interest in a wide range of application areas, ranging from engineering and physics to biology. In this paper, we model and experimentally realize a mixed-reality large-scale swarm of delay-coupled agents. The coupling term is modeled as a delayed communication relay of position. Our analyses, assuming agents communicating over an Erdös-Renyi network, demonstrate the existence of stable coherent patterns that can be achieved only with delay coupling and that are robust to decreasing network connectivity and heterogeneity in agent dynamics. We also show how the bifurcation structure for emergence of different patterns changes with heterogeneity in agent acceleration capabilities and limited connectivity in the network as a function of coupling strength and delay. Our results are verified through simulation as well as preliminary experimental results of delay-induced pattern formation in a mixed-reality swarm.

Development of high temperature resistant graphite fiber coupling agents

NASA Technical Reports Server (NTRS)

Griffin, R. N.

1975-01-01

Surface treatments were investigated as potential coupling agents to improve the elevated temperature shear strength retention of polyimide/graphite and polyphenylquinoxaline/graphite composites. The potential coupling agents were evaluated by fiber strand tensile tests, fiber and composite weight losses at 533 and 588K, and by interlaminar shear strength retention at 533 and 588K. The two surface treatments selected for more extensive evaluation were a coating of Ventromer T-1, a complex organometallic reaction product of titanium tetrachloride and trimethyl borate, and a polyphenylquinoxaline (PPQ) sizing which was pyrolyzed in nitrogen to form a carbonaceous layer on the fiber. Pyrolyzed polyphenylquinoxaline is a satisfactory coupling agent for polyimide/Thornel 300 graphite fiber composites. During 1000 hours aging at 588K such composites lose a little over half their transverse tensile strength, and suffer a slight loss in flexural modulus. No degradation of flexural strength or interlaminar shear strength occured during 1000 hours aging at 588K. None of the coupling agents examined had a markedly beneficial effect with polyphenylquinoxaline composites.

2010 Department of Defense (DoD) Chemical and Biological Defense Program (CBDP) Portfolio

DTIC Science & Technology

2010-03-01

a new oxime and (2) obtaining approval for use of pyridostigmine bromide , the component of Soman Nerve Agent Pretreatment Pyridostigmine (SNAPP) for...Pralidoxime Chloride Autoinjector N/A 6505-01-125-3248 11704-620-01 N/A DLA 8 Pyridostigmine Bromide Tabs USP 30 mg I.S. (SNAPP) N/A 6505-01-178-7903 N...Soman Nerve Agent Pretreatment Pyridostigmine (SNAPP) N/A 6505-01-483-7162 N/A N/A N/A N/A Vaccines Anthrax Vaccine Adsorbed (AVA) N/A 6505-01-399

Production And Artile Of Iron/Surfactant-Modified Zeolite Pellets To Retain And Destroy Water Pollutants

DOEpatents

BOWMAN, ROBERT S.; [et al

2001-07-17

A method of producing a pollutant adsorption and degradation article, and such article, are provided. At least one adsorbent is mixed with at least one pollutant transforming agent to form a mixture. This mixture is compacted to form a porous, highly permeable article. If necessary, the article can be modified with surfactant either after the compacting step or by adding the surfactant to the mixture prior to the compacting step. In addition, if necessary, a binding agent can be added to the mixture prior to the compacting step.

Polypropylene/Short Glass Fibers Composites: Effects of Coupling Agents on Mechanical Properties, Thermal Behaviors, and Morphology

PubMed Central

Lin, Jia-Horng; Huang, Chien-Lin; Liu, Chi-Fan; Chen, Chih-Kuang; Lin, Zheng-Ian; Lou, Ching-Wen

2015-01-01

This study uses the melt compounding method to produce polypropylene (PP)/short glass fibers (SGF) composites. PP serves as matrix while SGF serves as reinforcement. Two coupling agents, maleic anhydride grafted polypropylene, (PP-g-MA) and maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MA) are incorporated in the PP/SGF composites during the compounding process, in order to improve the interfacial adhesion and create diverse desired properties of the composites. According to the mechanical property evaluations, increasing PP-g-MA as a coupling agent provides the composites with higher tensile, flexural, and impact properties. In contrast, increasing SEBS-g-MA as a coupling agent provides the composites with decreasing tensile and flexural strengths, but also increasing impact strength. The DSC results indicate that using either PP-g-MA or SEBS-g-MA as the coupling agent increases the crystallization temperature. However, the melting temperature of PP barely changes. The spherulitic morphology results show that PP has a smaller spherulite size when it is processed with PP-g-MA or SEBS-g-MA as the coupling agent. The SEM results indicate that SGF is evenly distributed in PP matrices, but there are distinct voids between these two materials, indicating a poor interfacial adhesion. After PP-g-MA or SEBS-g-MA is incorporated, SGF can be encapsulated by PP, and the voids between them are fewer and indistinctive. This indicates that the coupling agents can effectively improve the interfacial compatibility between PP and SGF, and as a result improves the diverse properties of PP/SGF composites. PMID:28793710

Adsorption study of a macro-RAFT agent onto SiO2-coated Gd2O3:Eu3+ nanorods: Requirements and limitations

NASA Astrophysics Data System (ADS)

Zou, Hua; Melro, Liliana; de Camargo Chaparro, Thaissa; de Souza Filho, Isnaldi Rodrigues; Ananias, Duarte; Bourgeat-Lami, Elodie; dos Santos, Amilton Martins; Barros-Timmons, Ana

2017-02-01

The use of a macromolecular RAFT (macro-RAFT) agent to encapsulate anisotropic nano-objects via emulsion polymerization is an emerging route to prepare polymer/inorganic colloidal nanocomposites. However, a number of requirements have to be fulfilled. This work aims at highlighting the effects of the preparative procedure and dispersion method on the amount of macro-RAFT agent adsorbed onto SiO2-coated Gd2O3:Eu3+ nanorods. The adsorption of macro-RAFT agent was studied using the depletion method with UV-vis spectrophotometry. Measurements were performed at a fixed concentration of nanorods and varying concentrations of the macro-RAFT agent in aqueous dispersion at room temperature. The adsorption isotherms showed that for the same initial macro-RAFT agent concentration, the highest adsorption capacity of the macro-RAFT agent on nanorods was usually achieved for non-calcined thin SiO2-coated nanorods under mild bath sonication.

Macroscopic monolayer of plasmon coupled gold nanoparticles on mirror for fluorescence enhancement

NASA Astrophysics Data System (ADS)

Kaydashev, V. E.; Zolotukhin, P.; Belanova, A.; Anokhin, A. S.; Zharinov, V. S.; Kaidashev, E. M.

2018-04-01

We study an ability of a large quasi-homogeneous monolayer of Au plasmon coupled nanoparticles separated from continuous Au film by polymer spacer to enhance a fluorescence of adsorbed molecular species. A fluorescence response of Methylene Blue molecules is studied as a function of polymer film thickness. A change of plasmonic properties of a system, its ability to enhance a fluorescence and the possible heating of a structure upon light absorption are discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahle, J.J.; Buettner, L.C.; Mauer, S.

A series of experimental results are reported for breakthrough of the agent simulants DMMP and DIMP on coconut carbon. This adsorbent is used in filters for the Chemical Demiliterization program. The conditions were appropriate for a post treatment stack gas filter. Results indicate that high capacity and long filtration times are achievable under moderate humidity conditions up to 180 degrees F.

Biomarkers of cigarette smoking and DNA methylating agents: Raman, SERS and DFT study of 3-methyladenine and 7-methyladenine

NASA Astrophysics Data System (ADS)

Harroun, Scott G.; Zhang, Yaoting; Chen, Tzu-Heng; Ku, Ching-Rong; Chang, Huan-Tsung

2017-04-01

3-Methyladenine and 7-methyladenine are biomarkers of DNA damage from exposure to methylating agents. For example, the concentration of 3-methyladenine increases significantly in the urine of cigarette smokers. Surface-enhanced Raman spectroscopy (SERS) has shown much potential for detection of biomolecules, including DNA. Much work has been dedicated to the canonical nucleobases, with comparatively fewer investigations of modified DNA and modified DNA nucleobases. Herein, Raman spectroscopy and SERS are used to examine the adsorption orientations of 3-methyladenine and 7-methyladenine on Ag nanoparticles. Density functional theory (DFT) calculations at the B3LYP level are used to support the conclusions via simulated spectra of the nucleobases and of Ag+/nucleobase complexes. The results herein show that 7-methyladenine adsorbs upright via its N3 and N9 atoms side, similarly to adenine. 3-Methyladenine adsorbs in a very tilted or flat orientation on the Ag nanoparticles. These findings will be useful for future SERS or other nanoparticle-based bioanalytical assays for detection of these methyladenines or other modified nucleobases.

Determination of pyrazole and pyrrole pesticides in environmental water samples by solid-phase extraction using multi-walled carbon nanotubes as adsorbent coupled with high-performance liquid chromatography.

PubMed

Ma, Jiping; Lu, Xi; Xia, Yan; Yan, Fengli

2015-02-01

A solid-phase extraction (SPE) method using multi-walled carbon nanotubes as adsorbent coupled with high-performance liquid chromatography was developed for the determination of four pyrazole and pyrrole pesticides (fenpyroximate, chlorfenapyr, fipronil and flusilazole) in environmental water samples. Several parameters, such as extraction adsorbent, elution solvent and volume and sample loading flow rate were optimized to obtain high SPE recoveries and extraction efficiency. The calibration curves for the pesticides extracted were linear in the range of 0.05-10 μg L(-1) for chlorfenapyr and fenpyroximate and 0.05-20 μg L(-1) for fipronil and flusilazole, with the correlation coefficients (r(2)) between 0.9966 and 0.9990. The method gave good precisions (relative standard deviation %) from 2.9 to 10.1% for real spiked samples from reservoir water and seawater; method recoveries ranged 92.2-105.9 and 98.5-103.9% for real spiked samples from reservoir water and seawater, respectively. Limits of detection (S/N = 3) for the method were determined to be 8-19 ng L(-1). The optimized method was successfully applied to the determination of four pesticides of pyrazoles and pyrroles in real environmental water samples. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Separation and purification of enzymes by continuous pH-parametric pumping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, S.Y.; Lin, C.K.; Juang, L.Y.

1985-10-01

Trypsin and chymotrypsin were separated from porcine pancreas extract by continuous pH-parametric pumping. CHOM (chicken ovomucoid) was convalently bound to laboratory-prepared crab chitin with glutaraldehyde to form an affinity adsorbent of trypsin. The pH levels of top and bottom feeds were 8.0 and 2.5, respectively. Similar inhibitor, DKOM (duck ovomucoid), and pH levels 8.0 and 2.0 for top and bottom feeds, respectively, were used for separation and purification of chymotrypsin. e-Amino caproyl-D-tryptophan methyl ester was coupled to chitosan to form an affinity adsorbent for stem bromelain. The pH levels were 8.7 and 3.0. Separation continued fairly well with high yield,more » e.g., 95% recovery of trypsin after continuous pumping of 10 cycles. Optimum operational conditions for concentration and purification of these enzymes were investigated. The results showed that the continuous pH-parametric pumping coupled with affinity chromatography is effective for concentration and purification of enzymes. 19 references.« less

Surface Redox Chemistry of Immobilized Nanodiamond: Effects of Particle Size and Electrochemical Environment

NASA Astrophysics Data System (ADS)

Gupta, S.; McDonald, B.; Carrizosa, S. B.

2017-07-01

The size of the diamond particle is tailored to nanoscale (nanodiamond, ND), and the ND surface is engineered targeting specific (electrochemical and biological) applications. In this work, we investigated the complex surface redox chemistry of immobilized ND layer on conductive boron-doped diamond electrode with a broad experimental parameter space such as particle size (nano versus micron), scan rate, pH (cationic/acidic versus anionic/basic), electrolyte KCl concentration (four orders of magnitude), and redox agents (neutral and ionic). We reported on the significant enhancement of ionic currents while recording reversible oxidation of neutral ferrocene methanol (FcMeOH) by almost one order of magnitude than traditional potassium ferricyanide (K3Fe(CN)6) redox agent. The current enhancement is inversely related to ND particle diameter in the following order: 1 μm << 1000 nm < 100 nm < 10 nm ≤ 5 nm < 2 nm. We attribute the current enhancement to concurrent electrocatalytic processes, i.e. the electron transfer between redox probes and electroactive surface functional (e.g. hydroxyl, carboxyl, epoxy) moieties and the electron transfer mediated by adsorbed FcMeOH+ (or Fe(CN) 6 3+ ) ions onto ND surface. The first process is pH dependent since it depends upon ND surface functionalities for which the electron transfer is coupled to proton transfer. The adsorption mediated process is observed most apparently at slower scan rates owing to self-exchange between adsorbed FcMeOH+ ions and FcMeOH redox agent molecules in diffusion-limited bulk electrolyte solution. Alternatively, it is hypothesized that the surface functionality and defect sites ( sp 2-bonded C shell and unsaturated bonds) give rise to surface electronic states with energies within the band gap (midgap states) in undoped ND. These surface states serve as electron donors (and acceptors) depending upon their bonding (and antibonding) character and, therefore, they can support electrocatalytic redox processes in the presence of specific redox-active molecules via feedback mechanism. Apparently, FcMeOH+ tended to have electrostatic affinity for negatively charged ND surface functionalities, corroborated by present experiments. We also attempted to study biocatalytic process using model metalloprotein (cytochrome c; Cyt c) immobilized on ND particles for investigating interfacial electron transfer kinetics and compared with those of functionalized graphene (graphene oxide; GO and reduced GO). The findings are discussed in terms of interplay of sp 3-bonded C (ND core) and sp 2-bonded C (ND shell and graphene-based systems).

Pressure Dependence of the Radial Breathing Mode of Carbon Nanotubes: The Effect of Fluid Adsorption

NASA Astrophysics Data System (ADS)

Longhurst, M. J.; Quirke, N.

2007-04-01

The pressure dependence of shifts in the vibrational modes of individual carbon nanotubes is strongly affected by the nature of the pressure transmitting medium as a result of adsorption at the nanotube surface. The adsorbate is treated as an elastic shell which couples with the radial breathing mode (RBM) of the nanotube via van der Waal interactions. Using analytical methods as well as molecular simulation, we observe a low frequency breathing mode for the adsorbed fluid at ˜50cm-1, as well as diameter dependent upshifts in the RBM frequency with pressure, suggesting metallic nanotubes may wet more than semiconducting ones.

Adsorption geometry and core excitation spectra of three phenylpropene isomers on Cu(111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolczewski, C.; Williams, F. J.; Cropley, R. L.

Theoretical C 1s near edge x-ray absorption fine structure (NEXAFS) spectra for the C{sub 9}H{sub 10} isomers trans-methylstyrene, {alpha}-methylstyrene, and allylbenzene in gas phase and adsorbed at Cu(111) surfaces have been obtained from density functional theory calculations where adsorbate geometries were determined by corresponding total energy optimizations. The three species show characteristic differences in widths and peak shapes of the lowest C 1s{yields}{pi}* transitions which are explained by different coupling of the {pi}-electron system of the C{sub 6} ring with that of the side chain in the molecules as well as by the existence of nonequivalent carbon centers. The adsorbedmore » molecules bind only weakly with the substrate which makes the use of theoretical NEXAFS spectra of the oriented free molecules meaningful for an interpretation of experimental angle-resolved NEXAFS spectra of the adsorbate systems obtained in this work. However, a detailed quantitative account of relative peak intensities requires theoretical angle-resolved NEXAFS spectra of the complete adsorbate systems which have been evaluated within the surface cluster approach. The comparison with experiment yields almost perfect agreement and confirms the reliability of the calculated equilibrium geometries of the adsorbates. This can help to explain observed differences in the catalytic epoxidation of the three molecules on Cu(111) based on purely geometric considerations.« less

Removal of gadolinium-based contrast agents: adsorption on activated carbon.

PubMed

Elizalde-González, María P; García-Díaz, Esmeralda; González-Perea, Mario; Mattusch, Jürgen

2017-03-01

Three carbon samples were employed in this work, including commercial (1690 m 2  g -1 ), activated carbon prepared from guava seeds (637 m 2  g -1 ), and activated carbon prepared from avocado kernel (1068 m 2  g -1 ), to study the adsorption of the following gadolinium-based contrast agents (GBCAs): gadoterate meglumine Dotarem®, gadopentetate dimeglumine Magnevist®, and gadoxetate disodium Primovist®. The activation conditions with H 3 PO 4 were optimized using a Taguchi methodology to obtain mesoporous materials. The best removal efficiency by square meter in a batch system in aqueous solution and model urine was achieved by avocado kernel carbon, in which mesoporosity prevails over microporosity. The kinetic adsorption curves were described by a pseudo-second-order equation, and the adsorption isotherms in the concentration range 0.5-6 mM fit the Freundlich equation. The chemical characterization of the surfaces shows that materials with a greater amount of phenolic functional groups adsorb the GBCA better. Adsorption strongly depends on the pH due to the combination of the following factors: contrast agent protonated forms and carbon surface charge. The tested carbon samples were able to adsorb 70-90% of GBCA in aqueous solution and less in model urine. This research proposes a method for the elimination of GBCA from patient urine before its discharge into wastewater.

Isotherm modeling of organic activated bentonite and humic acid polymer used as mycotoxin adsorbents.

PubMed

Santos, R R; Vermeulen, S; Haritova, A; Fink-Gremmels, J

2011-11-01

The aim of the current study was to evaluate and compare two representative samples of different classes of adsorbents intended for use as feed additives in the prevention or reduction of the adverse effects exerted by mycotoxins, specifically ochratoxin A (OTA) and zearalenone (ZEN). The adsorbents, an organically activated bentonite (OAB) and a humic acid polymer (HAP), were tested in a common in vitro model with a pH course comparing the maximum pH changes that can be expected in the digestive system of a monogastric animal, i.e. pH 7.4 for the oral cavity, pH 3.0 for the stomach, and pH 8.4 for the intestines. In the first experiment, the concentration-dependent adsorbent capacity of OAB and HAB were tested using a fixed concentration of either mycotoxin. Thereafter, adsorption was evaluated applying different isotherms models, such as Freundlich, Langmuir, Brunauer-Emmett-Teller (BET) and Redlich-Peterson, to characterize the adsorption process as being either homo- or heterogeneous and representing either mono- or multilayer binding. At the recommended statutory level for the mycotoxins of 0.1 mg kg(-1) OTA and 0.5 mg kg(-1) ZEN, OAB showed an adsorbed capacity of >96% towards both mycotoxins, regardless of the pH. The HAP product was also able to absorb >96% of both mycotoxins at pH 3.0, but extensive desorption occurred at pH 8.4. Based on χ-square (χ(2)) values, Langmuir and Redlich-Peterson equations proved to be the best models to predict monolayer equilibrium sorption of OTA and ZEN onto the organically activated bentonite and the humic acid polymer. The applied methodology has a sufficient robustness to facilitate further comparative studies with different mycotoxin-adsorbing agents.

In-situ probing of coupled atomic restructuring and metallicity of oxide heterointerfaces induced by polar adsorbates

NASA Astrophysics Data System (ADS)

Ryu, S.; Zhou, H.; Paudel, T. R.; Irwin, J.; Podkaminer, J. P.; Bark, C. W.; Lee, D.; Kim, T. H.; Fong, D. D.; Rzchowski, M. S.; Tsymbal, E. Y.; Eom, C. B.

2017-10-01

Microscopic understanding of the surface-controlled conductivity of the two dimensional electron gas at complex oxide interfaces is crucial for developing functional interfaces. We observe conductivity and structural modification using in-situ synchrotron surface x-ray diffraction as the surface of a model LaAlO3/SrTiO3 (001) heterostructure is changed by polar adsorbates. We find that polar adsorbate-induced interfacial metallicity reduces polar distortions in the LaAlO3 layer. First-principles density functional theory calculations show that surface dipoles introduced by polar adsorbates lead to additional charge transfer and the reduction of polar displacements in the LaAlO3 layer, consistent with the experimental observations. Our study supports that internal structural deformations controlling functionalities can be driven without the application of direct electrical or thermal bias and offers a route to tuning interfacial properties. These results also highlight the important role of in-situ x-ray scattering with atomic resolution in capturing and exploring structural distortions and charge density changes caused by external perturbations such as chemical adsorption, redox reaction, and generation and/or annihilation of surface defects.

Comparison of the adjuvant activity of aluminum hydroxide and calcium phosphate on the antibody response towards Bothrops asper snake venom.

PubMed

Olmedo, Hidekel; Herrera, María; Rojas, Leonardo; Villalta, Mauren; Vargas, Mariángela; Leiguez, Elbio; Teixeira, Catarina; Estrada, Ricardo; Gutiérrez, José María; León, Guillermo; Montero, Mavis L

2014-01-01

The adjuvanticity of aluminum hydroxide and calcium phosphate on the antibody response in mice towards the venom of the snake Bothrops asper was studied. It was found that, in vitro, most of the venom proteins are similarly adsorbed by both mineral salts, with the exception of some basic phospholipases A2, which are better adsorbed by calcium phosphate. After injection, the adjuvants promoted a slow release of the venom, as judged by the lack of acute toxicity when lethal doses of venom were administered to mice. Leukocyte recruitment induced by the venom was enhanced when it was adsorbed on both mineral salts; however, venom adsorbed on calcium phosphate induced a higher antibody response towards all tested HPLC fractions of the venom. On the other hand, co-precipitation of venom with calcium phosphate was the best strategy for increasing: (1) the capacity of the salt to couple venom proteins in vitro; (2) the venom ability to induce leukocyte recruitment; (3) phagocytosis by macrophages; and (4) a host antibody response. These findings suggest that the chemical nature is not the only one determining factor of the adjuvant activity of mineral salts.

In-situ probing of coupled atomic restructuring and metallicity of oxide heterointerfaces induced by polar adsorbates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryu, S.; Zhou, H.; Paudel, T. R.

Microscopic understanding of the surface-controlled conductivity of the two dimensional electron gas at complex oxide interfaces is crucial for developing functional interfaces. We observe conductivity and structural modification using in-situ synchrotron surface x-ray diffraction as the surface of a model LaAlO3/SrTiO3 (001) heterostructure is changed by polar adsorbates. We find that polar adsorbate-induced interfacial metallicity reduces polar distortions in the LaAlO3 layer. First-principles density functional theory calculations show that surface dipoles introduced by polar adsorbates lead to additional charge transfer and the reduction of polar displacements in the LaAlO3 layer, consistent with the experimental observations. Our study supports that internalmore » structural deformations controlling functionalities can be driven without the application of direct electrical or thermal bias and offers a route to tuning interfacial properties. These results also highlight the important role of in-situ x-ray scattering with atomic resolution in capturing and exploring structural distortions and charge density changes caused by external perturbations such as chemical adsorption, redox reaction, and generation and/or annihilation of surface defects.« less

Fabrication of sub-diffraction-limit molecular structures by scanning near-field photolithography

NASA Astrophysics Data System (ADS)

Ducker, Robert E.; Montague, Matthew T.; Sun, Shuqing; Leggett, Graham J.

2007-09-01

Using a scanning near-field optical microscope coupled to a UV laser, an approach we term scanning near-field photolithography (SNP), structures as small as 9 nm (ca. λ/30) may be fabricated in self-assembled monolayers of alkanethiols on gold surfaces. Selective exposure of the adsorbate molecules in the near field leads to photoconversion of the alkylthiolate to a weakly bound alkylsulfonate which may be displaced readily be a contrasting thiol, leading to a chemical pattern, or used as a resist for the selective etching of the underlying metal. A novel ultra-mild etch for gold is reported, and used to etch structures as small as 9 nm. Photopatterning of oligo(ethylene glycol) (OEG) terminated selfassembled monolayers facilitates the fabrication of biomolecular nanostructures. Selective removal of the protein-resistant OEG terminated adsorbates created regions that may be functionalized with a second thiol and derivatized with a biomolecule. Finally, the application of SNP to nanopatterning on oxide surfaces is demonstrated. Selective exposure of monolayers of phosphonic acids adsorbed onto aluminum oxide leads to cleavage of the P-C bond and desorption of the adsorbate molecule. Subsequent etching, using aqueous based, yields structures as small as 100 nm.

Coupling loss characteristics of runoff-sediment-adsorbed and dissolved nitrogen and phosphorus on bare loess slope.

PubMed

Wu, Lei; Qiao, Shanshan; Peng, Mengling; Ma, Xiaoyi

2018-05-01

Soil and nutrient loss is a common natural phenomenon but it exhibits unclear understanding especially on bare loess soil with variable rainfall intensity and slope gradient, which makes it difficult to design control measures for agricultural diffuse pollution. We employ 30 artificial simulated rainfalls (six rainfall intensities and five slope gradients) to quantify the coupling loss correlation of runoff-sediment-adsorbed and dissolved nitrogen and phosphorus on bare loess slope. Here, we show that effects of rainfall intensity on runoff yield was stronger than slope gradient with prolongation of rainfall duration, and the effect of slope gradient on runoff yield reduced gradually with increased rainfall intensity. But the magnitude of initial sediment yield increased significantly from an average value of 6.98 g at 5° to 36.08 g at 25° with increased slope gradient. The main factor of sediment yield would be changed alternately with the dual increase of slope gradient and rainfall intensity. Dissolved total nitrogen (TN) and dissolved total phosphorus (TP) concentrations both showed significant fluctuations with rainfall intensity and slope gradient, and dissolved TP concentration was far less than dissolved TN. Under the double influences of rainfall intensity and slope gradient, adsorbed TN concentration accounted for 7-82% of TN loss concentration with an average of 58.6% which was the main loss form of soil nitrogen, adsorbed TP concentration accounted for 91.8-98.7% of TP loss concentration with an average of 96.6% which was also the predominant loss pathway of soil phosphorus. Nitrate nitrogen (NO 3 - -N) accounted for 14.59-73.92% of dissolved TN loss, and ammonia nitrogen (NH 4 + -N) accounted for 1.48-18.03%. NO 3 - -N was the main loss pattern of TN in runoff. Correlation between dissolved TN, runoff yield, and rainfall intensity was obvious, and a significant correlation was also found between adsorbed TP, sediment yield, and slope gradient. Our results provide the underlying insights needed to guide the control of nitrogen and phosphorus loss on loess hills.

Electron-Mediated Phonon-Phonon Coupling Drives the Vibrational Relaxation of CO on Cu(100)

NASA Astrophysics Data System (ADS)

Novko, D.; Alducin, M.; Juaristi, J. I.

2018-04-01

We bring forth a consistent theory for the electron-mediated vibrational intermode coupling that clarifies the microscopic mechanism behind the vibrational relaxation of adsorbates on metal surfaces. Our analysis points out the inability of state-of-the-art nonadiabatic theories to quantitatively reproduce the experimental linewidth of the CO internal stretch mode on Cu(100) and it emphasizes the crucial role of the electron-mediated phonon-phonon coupling in this regard. The results demonstrate a strong electron-mediated coupling between the internal stretch and low-energy CO modes, but also a significant role of surface motion. Our nonadiabatic theory is also able to explain the temperature dependence of the internal stretch phonon linewidth, thus far considered a sign of the direct anharmonic coupling.

Adsorption properties of carbon dioxide enchanced oil recovery additives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patton, J.T.; Holbrook, S.T.

1990-01-01

The selection of the optimum foaming agent (surfactant) for enhancing oil production by carbon dioxide flooding is based on foamability and adsorption. Measurements of adsorption on carbonate cores from New Mexico reservoirs showed large adsorption differences between three commercial, high-foaming surfactants. An ethoxylated alcohol structure was at least adsorbed, 0.64 mg/cc pore volume; an ethoxylated alcohol sulfate was next, 0.74 mg/cc pore volume; the highest adsorbed was a glyceryl sulfonate, 2.30 mg/cc pore volume. Commercial application of the foaming additive involves injecting alternate slugs of surfactant solution and carbon dioxide. Surfactant concentration should be determined to allow for the adsorptionmore » above. 9 refs., 27 figs., 6 tabs.« less

ION EXCHANGE PROCESS FOR THE RECOVERY AND PURIFICATION OF MATERIALS

DOEpatents

Long, R.S.; Bailes, R.H.

1958-04-15

A process for the recovery of certain metallic ions from aqueous solutions by ion exchange techniques is described. It is applicable to elements such as vanadium, chromium, nnanganese, and the like, which are capable of forming lower valent cations soluble in aqueous solutions and which also form ldgher valent anions soluble in aqueous acidic solutions. For example, small amounts of vanadium occurring in phosphoric acid prepared from phosphate rock may be recovered by reducing the vanadium to a trivalent cation adsorbing; the vanadium in a cationic exchange resin, then treating the resin with a suitable oxidizing agent to convert the adsorbed vanadium to a higher valent state, and finally eluting; the vanadium as an anion from the resin by means of an aqueous acidic solution.

Characterizing Environmental Transformation of Multi-walled Carbon Nanotubes and Carbon Nano-Fiber Composites using Thermal Analysis and Related Hyphenated Techniques

EPA Science Inventory

Thermogravimetric analysis (TGA) coupled with gas chromatography and mass spectroscopy (TGA/GCMS), for the evolved gas analysis, has given insight to the stability and kinetics of structural changes and determining adsorbed organics to nanomaterials and nanocomposites. TGA is als...

Gastrointestinal gas.

PubMed Central

Fardy, J; Sullivan, S

1988-01-01

Complaints related to gastrointestinal gas are commonly encountered in clinical practice. Various therapies have been proposed, yet none has appeared to be extremely effective. A review of the literature revealed little hard evidence to support the use of simethicone, pancreatic enzymes, anticholinergic agents or antibiotics. Evidence supporting the use of prokinetic agents has been the strongest, and there may be a pathophysiologic basis for the use of these agents if the complaints are related to abnormal intestinal motility. The use of activated charcoal for adsorbing intestinal gas has been effective in healthy subjects but has not been properly investigated in patients with gas complaints. Dietary modification may be beneficial in certain cases. Additional controlled trials are necessary to clarify the issues in the treatment of this common problem. PMID:3058280

Vibrational energy transfer from photoexcited carbon nanotubes to proteins observed by coherent phonon spectroscopy

NASA Astrophysics Data System (ADS)

Nakayama, Tomohito; Yoshizawa, Shunsuke; Hirano, Atsushi; Tanaka, Takeshi; Shiraki, Kentaro; Hase, Muneaki

2017-12-01

Vibrational energy transfer from photoexcited single-wall carbon nanotubes (SWCNTs) to coupled proteins is a key to engineering thermally induced biological reactions, for example, in photothermal therapy. Here, we explored vibrational energy transfer from photoexcited SWCNTs to different adsorbed biological materials by means of a femtosecond pump-probe technique. We show that the vibrational relaxation time of the radial breathing modes in SWCNTs depends significantly on the structure of the coupled materials, that is, proteins or biopolymers, indicating that the vibrational energy transfer is governed by overlapping of the phonon densities of states of the SWCNTs and coupled materials.

Coupling Fe0 nano particles with living and dead Azolla filicoloides to improve removal of methylene blue from aqueous solution

NASA Astrophysics Data System (ADS)

Rakhshaee, Roohan

2015-11-01

Fe0 nano particles (FNPs) were connected to the cell wall of the dead and living Azolla filicoloides as an aquatic fern, individually. FNPs mean size was decreased due to the stabilization, especially using the living one. It was compared the results of X-ray photoelectron spectroscopy (XPS), saturation magnetization (Ms), zeta potential (ZP) and thermal analysis (DSC and TGA) of the dead and living Azolla connected to FNPs, and also the findings of potentiometric titration (PT) of the cell wall's pectin of the dead and living Azolla. It was confirmed (by XRD and XPS) that Fe0 nano particles when were connected to the living Azolla did not produce Fe3O4 due to oxidation unlike the bare FNPs and the connected form to the dead Azolla, by reason of the more stabilization (more surface protection) of nano iron particles after connecting to the living Azolla. To adsorb methylene blue by these agents at the optimum pre-treatment pH 10 and adsorption pH 8, the parameters of equilibrium sorption, rate constant of second-order sorption and activation energy were obtained as: living Azolla-FNPs > dead Azolla-FNPs > FNPs > dead Azolla, while, their thermodynamic parameters (ΔG°, ΔH° and ΔS°) had the reverse arrangement. It was also studied the various factors rule such as photoperiod and the presence of heavy metals on the living Azolla growth coupled with FNPs and its MB removal ability.

Investigation of the in vitro photocatalytic antibacterial activity of nanocrystalline TiO2 and coupled TiO2/Ag containing copolymer on the surface of medical grade titanium.

PubMed

Györgyey, Ágnes; Janovák, László; Ádám, András; Kopniczky, Judit; Tóth, Krisztián L; Deák, Ágota; Panayotov, Ivan; Cuisinier, Frédéric; Dékány, Imre; Turzó, Kinga

2016-07-01

Antibacterial surfaces have been in the focus of research for years, driven by an unmet clinical need to manage an increasing incidence of implant-associated infections. The use of silver has become a topic of interest because of its proven broad-spectrum antibacterial activity and track record as a coating agent of soft tissue implants and catheters. However, for the time being, the translation of these technological achievements for the improvement of the antibacterial property of hard tissue titanium (Ti) implants remains unsolved. In our study, we focused on the investigation of the photocatalysis mediated antibacterial activity of silver (Ag), and Ti nanoparticles instead of their pharmacological effects. We found that the photosensitisation of commercially pure titanium discs by coating them with an acrylate-based copolymer that embeds coupled Ag/Ti nanoparticles can initiate the photocatalytic decomposition of adsorbed S. salivarius after the irradiation with an ordinary visible light source. The clinical isolate of S. salivarius was characterised with MALDI-TOF mass spectrometer, while the multiplication of the bacteria on the surface of the discs was followed-up by MTT assay. Concerning practical relevance, the infected implant surfaces can be made accessible and irradiated by dental curing units with LED and plasma arc light sources, our research suggests that photocatalytic copolymer coating films may offer a promising solution for the improvement of the antibacterial properties of dental implants. © The Author(s) 2016.

Superradiance of J-Aggregated 2,2'-Cyanine Absorbed onto a Vesicle Surface

NASA Technical Reports Server (NTRS)

Akins, Daniel L.; Ozcelik, Serdar

1995-01-01

Phospholipid vesicles are used as substrates to form adsorbed aggregates of 2,2'-cyanine, also referred to as pseudoisocyanine (PIC). In this paper, we report photophysical parameters of two putative adsorbed aggregates species (cis- and trans-aggregates, relating to their makeup from mono-cis and all-transstereoisomers, respectively). Phase modulation picosecond fluorescence decay measurements reveal that superradiance and energy transfer are dominant features controlling photophysical processes. Superradiance, coherence size, energy transfer and exciton-phonon coupling are discussed for the two types of aggregates; as regards photophysical parameters, the fluorescence lifetimes, fluorescence quantum yields, and nonradiative rate constants are determined. It is suggested that structure plays the crucial role in excited state dynamics.

Designing transition metal surfaces for their adsorption properties and chemical reactivity

NASA Astrophysics Data System (ADS)

Montemore, Matthew M.

Many technological processes, such as catalysis, electrochemistry, corrosion, and some materials synthesis techniques, involve molecules bonding to and/or reacting on surfaces. For many of these applications, transition metals have proven to have excellent chemical reactivity, and this reactivity is strongly tied to the surface's adsorption properties. This thesis focuses on predicting adsorption properties for use in the design of transition metal surfaces for various applications. First, it is shown that adsorption through a particular atom (e.g, C or O) can be treated in a unified way. This allows predictions of all C-bound adsorbates from a single, simple adsorbate, such as CH3. In particular, consideration of the adsorption site can improve the applicability of previous approaches, and gas-phase bond energies correlate with adsorption energies for similarly bound adsorbates. Next, a general framework is presented for understanding and predicting adsorption through any atom. The energy of the adsorbate's highest occupied molecular orbital (HOMO) determines the strength of the repulsion between the adsorbate and the surface. Because adsorbates with similar HOMO energies behave similarly, their adsorption energies correlate. This can improve the efficiency of predictions, but more importantly it constrains catalyst design and suggests strategies for circumventing these constraints. Further, the behavior of adsorbates with dissimilar HOMO energies varies in a systematic way, allowing predictions of adsorption energy differences between any two adsorbates. These differences are also useful in surface design. In both of these cases, the dependence of adsorption energies on surface electronic properties is explored. This dependence is used to justify the unified treatments mentioned above, and is used to gain further insight into adsorption. The properties of the surface's d band and p band control variations in adsorption energy, as does the strength of the adsorbate-surface coupling. A single equation, with only a single adsorbate-dependent fitting parameter as well as a few universal fitting parameters, is developed that can predict the adsorption energy of any radical on any close-packed transition metal surface. The surface electronic properties that are input into this equation can be estimated based on the alloy structure of the surface, improving prospects for high-throughput screening and rational catalyst design. The methods discussed in this thesis are used to design a novel catalyst for ethylene epoxidation, which is experimentally synthesized and tested. Initial tests indicate that this catalyst may have improved selectivity over pure Ag.

Effect of Silane Coupling Agent on the Creep Behavior and Mechanical Properties of Carbon Fibers/Acrylonitrile Butadiene Rubber Composites.

PubMed

Choi, Woong-Ki; Park, Gil-Young; Kim, Byoung-Shuk; Seo, Min-Kang

2018-09-01

In this study, we investigated the effect of the silane coupling agent on the relationship between the surface free energy of carbon fibers (CFs) and the mechanical strength of CFs/acrylonitrile butadiene rubber (NBR) composites. Moreover, the creep behavior of the CF/NBR composites at surface energetic point of view were studied. The specific component of the surface free energy of the carbon fibers was found to increase upon grafting of the silane coupling agent, resulting in an increase in the tensile strength of the CF/NBR composites. On the other hand, the compressive creep strength was found to follow a slightly different trend. These results indicate the possible formation of a complex interpenetrating polymer network depending on the molecular size of the organic functional groups of the silane coupling agent.

Time scale of random sequential adsorption.

PubMed

Erban, Radek; Chapman, S Jonathan

2007-04-01

A simple multiscale approach to the diffusion-driven adsorption from a solution to a solid surface is presented. The model combines two important features of the adsorption process: (i) The kinetics of the chemical reaction between adsorbing molecules and the surface and (ii) geometrical constraints on the surface made by molecules which are already adsorbed. The process (i) is modeled in a diffusion-driven context, i.e., the conditional probability of adsorbing a molecule provided that the molecule hits the surface is related to the macroscopic surface reaction rate. The geometrical constraint (ii) is modeled using random sequential adsorption (RSA), which is the sequential addition of molecules at random positions on a surface; one attempt to attach a molecule is made per one RSA simulation time step. By coupling RSA with the diffusion of molecules in the solution above the surface the RSA simulation time step is related to the real physical time. The method is illustrated on a model of chemisorption of reactive polymers to a virus surface.

Understanding Defect-Stabilized Noncovalent Functionalization of Graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Hua; Uysal, Ahmet; Anjos, Daniela M.

2015-09-01

The noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high-resolution interfacial X-ray scattering, and ab initio density functional theory calculations. The findings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. The structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogen bonding with terminalmore » hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton-coupled-electron-transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. These results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.« less

Graphene-encapsulated silica as matrix solid-phase dispersion extraction sorbents for the analysis of poly-methoxylated flavonoids in the leaves of Murraya panaculata (L.) Jack.

PubMed

Sun, Ting; Li, Xuwen; Yang, Jie; Li, Lanjie; Jin, Yongri; Shi, Xiaolei

2015-06-01

In this study, graphene-encapsulated silica was synthesized by a hydrothermal reduction strategy. The presence of silica in graphene was identified by Fourier-transform infrared spectrometry, X-ray diffraction and scanning electron microscopy. The graphene-encapsulated silica subsequently was used as adsorbent for matrix solid-phase dispersion extraction of poly-methoxylated flavonoids from the dried leaves of Murraya panaculata (L.) Jack. Compared with the other adsorbents (graphene, silica gel, C18 silica, neutral alumina, diatomaceous earth) and without any adsorbents, better results were obtained. Then a method for analysis of poly-methoxylated flavonoids was established by coupling matrix solid-phase dispersion extraction with ultra high performance liquid chromatography and UV detection. Compared with reflux extraction and ultrasonic extraction, the proposed method is quicker, more efficient and more environmental protection. Less than 10 min is needed from extraction to detection. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Understanding Defect-Stabilized Noncovalent Functionalization of Graphene

DOE PAGES

Zhou, Hua; Uysal, Ahmet; Anjos, Daniela M.; ...

2015-09-01

For the noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high-resolution interfacial X-ray scattering, and ab initio density functional theory calculations. The fi ndings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. Moreover, the structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogenmore » bonding with terminal hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton-coupled-electron-transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. Finally, these results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.« less

Spin polarization properties of benzene/graphene with transition metals as dopants: First principles calculations

NASA Astrophysics Data System (ADS)

Yuan, X. B.; Tian, Y. L.; Zhao, X. W.; Yue, W. W.; Hu, G. C.; Ren, J. F.

2018-05-01

First principles calculations are used to study the spin polarization properties of benzene molecule adsorbed on the graphene surface which doped with transition metals including Mn, Cr, Fe, Co, and Ni. The densities of states (DOS) of the benzene molecule can be induced to be spin split at the Fermi level only when it is adsorbed on Mn-, and Cr-doped graphene. The p-orbital of the benzene molecule will interact with the d orbital of the doped atoms, which will generate new spin coupling states and lead to obvious spin polarization of the benzene molecule. The spin-polarized density distributions as well as the differential charge density distributions of the systems also suggest that Mn-doped graphene will induce bigger spin polarization than that of Cr-doped graphene. Benzene molecule could be spin-polarized when it is adsorbed on the graphene surface with transition metal dopants, which could be a new method for researching graphene-based organic spintronic devices.

Phase properties of elastic waves in systems constituted of adsorbed diatomic molecules on the (001) surface of a simple cubic crystal

NASA Astrophysics Data System (ADS)

Deymier, P. A.; Runge, K.

2018-03-01

A Green's function-based numerical method is developed to calculate the phase of scattered elastic waves in a harmonic model of diatomic molecules adsorbed on the (001) surface of a simple cubic crystal. The phase properties of scattered waves depend on the configuration of the molecules. The configurations of adsorbed molecules on the crystal surface such as parallel chain-like arrays coupled via kinks are used to demonstrate not only linear but also non-linear dependency of the phase on the number of kinks along the chains. Non-linear behavior arises for scattered waves with frequencies in the vicinity of a diatomic molecule resonance. In the non-linear regime, the variation in phase with the number of kinks is formulated mathematically as unitary matrix operations leading to an analogy between phase-based elastic unitary operations and quantum gates. The advantage of elastic based unitary operations is that they are easily realizable physically and measurable.

Modulating the magnetic behavior of Fe(II)-MOF-74 by the high electron affinity of the guest molecule.

PubMed

Han, Sungmin; Kim, Heejin; Kim, Jaehoon; Jung, Yousung

2015-07-14

As a new class of magnetic materials, metal-organic framework (MOF) has received a significant attention due to their functionality and porosity that can provide diverse magnetic phenomena by utilizing host-guest chemistry. For Fe-MOF-74, we here find using density functional calculations that the O2 and C2H4 adsorptions result in the ferromagnetic (FM) and antiferromagnetic (AFM) orderings along the 1D chain of an hexagonal MOF framework, respectively, while their adsorption energies, pi-complexation, and geometrical changes are all similar upon binding. We reveal that this different magnetism behavior is attributed to the different electronic effects, where the adsorbed O2 greatly withdraws a minor spin electron from the Fe centers. The latter significant back donation opens a new channel for superexchange interactions that can enhance the FM coupling between Fe centers, where the strength of calculated intrachain FM coupling constrant (Jin) in O2 adsorbed Fe-MOF-74 is more than 10 times enhanced compared to bare Fe-MOF-74. This prediction suggests a possibility for the conceptual usage of Fe-MOF-74 as a gas sensor based on its magnetic changes caused by the adsorbed gases. Furthermore, the suggested mechanism might be used to control the magnetic properties of MOFs using the guest molecules, although concrete strategies to enhance such magnetic interactions to be used in practical applications would require further significant investigation.

Performance of waste-paper/PETG wood–plastic composites

NASA Astrophysics Data System (ADS)

Huang, Lijie; An, Shuxiang; Li, Chunying; Huang, Chongxing; Wang, Shuangfei; Zhang, Xiaoxiao; Xu, Mingzi; Chen, Jie; Zhou, Lei

2018-05-01

Wood-plastic composites were prepared from polyethylene terephthalate- 1,4-cyclohexanedimethanol ester (PETG) and waste-paper fiber that was unmodified, modified with alkyl-ketene-dimer (AKD), and modified with a silane-coupling agent. The mechanical properties, water absorption properties, surface structure, and thermal properties of the three prepared materials were compared. The results showed that the optimum amount of waste-paper powder is 10 wt%, while that of the waste-paper particles is 60-80 mesh. The use of AKD and coupling agent KH550 can reduce the water absorption of the composite; however, the reductive effect of the coupling agent is better, in that it is reduced by 0.3%. Modification using a 1-wt% KH550 coupling agent can effectively increase the tensile strength of a composite from 31.36 to 41.67 MPa (increase of 32.8%), while the bending strength increased from 86.47 to 98.31 MPa (increase of 13.7%). This also enhances the thermal stability of the composites. With the addition of the coupling agent, the composite material maintains good mechanical properties even after being immersed in water; this can enable the safe use of these composite materials in outdoor environments.

[Effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker].

PubMed

Zhu, Ming-yi; Zhang, Xiu-yin

2015-06-01

To evaluate the effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker (ABW). ABW was surface-treated with 0%, 1%, 2%, 3% and 4% silan coupling agent (γ-MPS), and mixed with resin matrix to synthesize 5 groups of composite resins. After heat-cured at 120 degrees centigrade for 1 h, specimens were tested in three-point flexure to measure strength according to ISO-4049. One specimen was selected randomly from each group and observed under scanning electron microscope (SEM). The data was analyzed with SAS 9.2 software package. The flexural strength (117.93±11.9 Mpa) of the group treated with 2% silane coupling agent was the highest, and significantly different from that of the other 4 groups (α=0.01). The amount of silane coupling agent has impact on the flexural strength of dental composite resins reinforced with whiskers; The flexual strength will be reduced whenever the amount is higher or lower than the threshold. Supported by Research Fund of Science and Technology Committee of Shanghai Municipality (08DZ2271100).

A Financial Market Model Incorporating Herd Behaviour.

PubMed

Wray, Christopher M; Bishop, Steven R

2016-01-01

Herd behaviour in financial markets is a recurring phenomenon that exacerbates asset price volatility, and is considered a possible contributor to market fragility. While numerous studies investigate herd behaviour in financial markets, it is often considered without reference to the pricing of financial instruments or other market dynamics. Here, a trader interaction model based upon informational cascades in the presence of information thresholds is used to construct a new model of asset price returns that allows for both quiescent and herd-like regimes. Agent interaction is modelled using a stochastic pulse-coupled network, parametrised by information thresholds and a network coupling probability. Agents may possess either one or two information thresholds that, in each case, determine the number of distinct states an agent may occupy before trading takes place. In the case where agents possess two thresholds (labelled as the finite state-space model, corresponding to agents' accumulating information over a bounded state-space), and where coupling strength is maximal, an asymptotic expression for the cascade-size probability is derived and shown to follow a power law when a critical value of network coupling probability is attained. For a range of model parameters, a mixture of negative binomial distributions is used to approximate the cascade-size distribution. This approximation is subsequently used to express the volatility of model price returns in terms of the model parameter which controls the network coupling probability. In the case where agents possess a single pulse-coupling threshold (labelled as the semi-infinite state-space model corresponding to agents' accumulating information over an unbounded state-space), numerical evidence is presented that demonstrates volatility clustering and long-memory patterns in the volatility of asset returns. Finally, output from the model is compared to both the distribution of historical stock returns and the market price of an equity index option.

Decoupling Coupled Constraints Through Utility Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, N; Marden, JR

2014-08-01

Several multiagent systems exemplify the need for establishing distributed control laws that ensure the resulting agents' collective behavior satisfies a given coupled constraint. This technical note focuses on the design of such control laws through a game-theoretic framework. In particular, this technical note provides two systematic methodologies for the design of local agent objective functions that guarantee all resulting Nash equilibria optimize the system level objective while also satisfying a given coupled constraint. Furthermore, the designed local agent objective functions fit into the framework of state based potential games. Consequently, one can appeal to existing results in game-theoretic learning tomore » derive a distributed process that guarantees the agents will reach such an equilibrium.« less

Ochratoxin degradation and adsorption caused by astaxanthin-producing yeasts.

PubMed

Péteri, Z; Téren, J; Vágvölgyi, C; Varga, J

2007-05-01

Ochratoxin degrading and adsorbing activities of Phaffia rhodozyma and Xanthophyllomyces dendrorhous isolates were tested. P. rhodozyma CBS 5905 degraded more than 90% of ochratoxin A (OTA) in 15 days at 20 degrees C. The data presented indicate that P. rhodozyma is able to convert OTA to ochratoxin alpha, and this conversion is possibly mediated by an enzyme related to carboxypeptidases. Chelating agents like EDTA and 1,10-phenanthroline inhibited OTA degradation caused by P. rhodozyma indicating that the carboxypeptidase is a metalloprotease, similarly to carboxypeptidase A. The temperature optimum of this enzyme was found to be above 30 degrees C, which is much higher than the temperature optimum for growth of P. rhodozyma cells, which is around 20 degrees C. The enzyme responsible for ochratoxin degradation was found to be cell-bound. Besides, both viable and heat-treated (dead) P. rhodozyma cells were also able to adsorb significant amounts (up to 250 ng ml(-1)) of OTA. Heat treatment enhanced OTA adsorbing activities of the cells. Further studies are in progress to identify the enzyme responsible for OTA degradation in P. rhodozyma.

Hafnium radioisotope recovery from irradiated tantalum

DOEpatents

Taylor, Wayne A.; Jamriska, David J.

2001-01-01

Hafnium is recovered from irradiated tantalum by: (a) contacting the irradiated tantalum with at least one acid to obtain a solution of dissolved tantalum; (b) combining an aqueous solution of a calcium compound with the solution of dissolved tantalum to obtain a third combined solution; (c) precipitating hafnium, lanthanide, and insoluble calcium complexes from the third combined solution to obtain a first precipitate; (d) contacting the first precipitate of hafnium, lanthanide and calcium complexes with at least one fluoride ion complexing agent to form a fourth solution; (e) selectively adsorbing lanthanides and calcium from the fourth solution by cationic exchange; (f) separating fluoride ion complexing agent product from hafnium in the fourth solution by adding an aqueous solution of ferric chloride to obtain a second precipitate containing the hafnium and iron; (g) dissolving the second precipitate containing the hafnium and iron in acid to obtain an acid solution of hafnium and iron; (h) selectively adsorbing the iron from the acid solution of hafnium and iron by anionic exchange; (i) drying the ion exchanged hafnium solution to obtain hafnium isotopes. Additionally, if needed to remove residue remaining after the product is dried, dissolution in acid followed by cation exchange, then anion exchange, is performed.

Advanced functional materials in solid phase extraction for ICP-MS determination of trace elements and their species - A review.

PubMed

He, Man; Huang, Lijin; Zhao, Bingshan; Chen, Beibei; Hu, Bin

2017-06-22

For the determination of trace elements and their species in various real samples by inductively coupled plasma mass spectrometry (ICP-MS), solid phase extraction (SPE) is a commonly used sample pretreatment technique to remove complex matrix, pre-concentrate target analytes and make the samples suitable for subsequent sample introduction and measurements. The sensitivity, selectivity/anti-interference ability, sample throughput and application potential of the methodology of SPE-ICP-MS are greatly dependent on SPE adsorbents. This article presents a general overview of the use of advanced functional materials (AFMs) in SPE for ICP-MS determination of trace elements and their species in the past decade. Herein the AFMs refer to the materials featuring with high adsorption capacity, good selectivity, fast adsorption/desorption dynamics and satisfying special requirements in real sample analysis, including nanometer-sized materials, porous materials, ion imprinting polymers, restricted access materials and magnetic materials. Carbon/silica/metal/metal oxide nanometer-sized adsorbents with high surface area and plenty of adsorption sites exhibit high adsorption capacity, and porous adsorbents would provide more adsorption sites and faster adsorption dynamics. The selectivity of the materials for target elements/species can be improved by using physical/chemical modification, ion imprinting and restricted accessed technique. Magnetic adsorbents in conventional batch operation offer unique magnetic response and high surface area-volume ratio which provide a very easy phase separation, greater extraction capacity and efficiency over conventional adsorbents, and chip-based magnetic SPE provides a versatile platform for special requirement (e.g. cell analysis). The performance of these adsorbents for the determination of trace elements and their species in different matrices by ICP-MS is discussed in detail, along with perspectives and possible challenges in the future development. Copyright © 2017 Elsevier B.V. All rights reserved.

Preconcentration of trace lead and iron on activated carbon functionalized by o-Anisic acid derivatives prior to their determination in environmental samples.

PubMed

Tian, Hua; Hu, Zheng; He, Qun; Liu, Xueliang; Zhang, Li; Chang, Xijun

2012-07-01

Two solid-phase adsorbents (phase I and phase II) were synthesized successfully that o-Anisic acid derivatives were evenly functionalized on the surface of activated carbon. It was certified that the two adsorbents were applied to preconcentrate and separate trace levels of Pb(II) and Fe(III) from natural liquid samples with satisfactory results. It can be found that the adsorption capacity of the ions adsorbed on phase I and phase II was 48.3 and 85.7 mg g(-1) for Pb(II), 39.5 and 72.5 mg g(-1) for Fe(III), respectively. The detection limit (3σ) of the method separated on phase I and phase II was 0.12 and 0.09 ng mL(-1) for Pb(II), 0.23 and 0.17 ng mL(-1) for Fe(III), respectively. The relative standard deviation (R.S.D.) of the method was lower than 3.0%. The adsorption and desorption property of two kinds of adsorbents was comparatively studied, respectively. The adsorption selectivity of heavy metal ions at certain pH, the adsorption kinetics, the condition of complete elution, the effect of coexisting ions, the adsorption capacity and adsorption isotherm modes were examined. Based on the experimental datum determined by inductively coupled plasma optical emission spectrometry (ICP-OES), it was certified that the adsorption on the surface of adsorbents was in strict accordance with the monolayer adsorption principle. The structural features of series of multidentate ligand modified on adsorption matrix had been obtained. These conclusions can provide reference for synthesizing an efficient adsorbent which is specific to remove a particular kind of contaminant. Copyright © 2012 Elsevier B.V. All rights reserved.

Evaluation of eggshell membrane-based bio-adsorbent for solid-phase extraction of linear alkylbenzene sulfonates coupled with high-performance liquid chromatography.

PubMed

Wang, Weidong; Chen, Bo; Huang, Yuming; Cao, Jia

2010-09-03

The potential of eggshell membrane (ESM) as a novel solid-phase extraction bio-adsorbent was investigated in the present study. The ESM with a unique structure of intricate lattice network showed a predominant ability to capture linear alkylbenzene sulfonates (LAS) as a model of organic pollutants by the hydrophobic interactions between ESM and LAS molecular at pH very close to the isoelectric point of ESM, which was similar to the most widely used trapping mechanism for SPE. Under the optimal conditions, the breakthrough capacities of the ESM packed cartridge for C10-C13 LAS homologues were found to be 30, 53, 50, and 43microgg(-1), respectively. On the basis of high-performance liquid chromatography separation and UV detection of LAS homologues, the proposed system could respond down to 0.027ngmL(-1) of LAS with a linear calibration range from 0.2 to 100ngmL(-1), showing a good LAS enrichment ability of eggshell membrane biomaterial with high sensitivity, and could be successfully used for the detection of residual LAS in environmental water samples. The reproducibility among columns was satisfactory (RSD among columns is less than 10%). A comparison study with ESM, C8 and C18 as adsorbents for LAS demonstrated that ESM-based bio-adsorbent was advantageous over C8 and C18, the widely used traditional adsorbents. 2010 Elsevier B.V. All rights reserved.

Impact of natural organic matter on arsenic removal by modified granular natural siderite: Evidence of ternary complex formation by HPSEC-UV-ICP-MS.

PubMed

Li, Fulan; Guo, Huaming; Zhou, Xiaoqian; Zhao, Kai; Shen, Jiaxing; Liu, Fei; Wei, Chao

2017-02-01

High arsenic (As) groundwater usually has high concentrations of natural organic matter (NOM). Effects of NOM on arsenic adsorption were investigated to evaluate the efficiency of modified granular natural siderite (MGNS) as an adsorbent for groundwater arsenic remediation. Humic and fulvic acids (HA/FA) were selected as model NOM compounds. In batch tests, HA or FA was either first adsorbed onto the MGNS, or applied together with dissolved arsenic to investigate effects of both adsorbed and dissolved NOM on arsenic removal. The kinetic data showed no significant effects of both adsorbed and dissolved HA/FA on As(III) adsorption. However, As(V) removal was inhibited, whereby the adsorbed NOM compounds had greater inhibitory effect. The inhibitory effect on As(V) removal increased with increasing NOM concentrations. FA exhibited higher inhibitory effect than HA at the same concentration. Steric Exclusion Chromatography-HPLC (SEC-HPLC), and High-Performance Size Exclusion Chromatography-UV-Inductively Coupled Plasma Mass Spectrometry (HPSEC-UV-ICP-MS) revealed that As(V) removal was mostly achieved by the oxyanion adsorption and adversely affected by dissolved FA via competitive adsorption for surface sites. In addition to oxyanion adsorption, removal of As(V) was related to scavenging of ternary HA-As-Fe complexes, which led to the less inhibitory effect of dissolved HA on As(V) removal than dissolved FA via competitive adsorption. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biology of Streptococcus mutans-Derived Glucosyltransferases: Role in Extracellular Matrix Formation of Cariogenic Biofilms

PubMed Central

Bowen, W.H.; Koo, H.

2011-01-01

The importance of Streptococcus mutans in the etiology and pathogenesis of dental caries is certainly controversial, in part because excessive attention is paid to the numbers of S. mutans and acid production while the matrix within dental plaque has been neglected. S. mutans does not always dominate within plaque; many organisms are equally acidogenic and aciduric. It is also recognized that glucosyltransferases from S. mutans (Gtfs) play critical roles in the development of virulent dental plaque. Gtfs adsorb to enamel synthesizing glucans in situ, providing sites for avid colonization by microorganisms and an insoluble matrix for plaque. Gtfs also adsorb to surfaces of other oral microorganisms converting them to glucan producers. S. mutans expresses 3 genetically distinct Gtfs; each appears to play a different but overlapping role in the formation of virulent plaque. GtfC is adsorbed to enamel within pellicle whereas GtfB binds avidly to bacteria promoting tight cell clustering, and enhancing cohesion of plaque. GtfD forms a soluble, readily metabolizable polysaccharide and acts as a primer for GtfB. The behavior of soluble Gtfs does not mirror that observed with surface-adsorbed enzymes. Furthermore, the structure of polysaccharide matrix changes over time as a result of the action of mutanases and dextranases within plaque. Gtfs at distinct loci offer chemotherapeutic targets to prevent caries. Nevertheless, agents that inhibit Gtfs in solution frequently have a reduced or no effect on adsorbed enzymes. Clearly, conformational changes and reactions of Gtfs on surfaces are complex and modulate the pathogenesis of dental caries in situ, deserving further investigation. PMID:21346355

A DFT study on photoinduced surface catalytic coupling reactions on nanostructured silver: selective formation of azobenzene derivatives from para-substituted nitrobenzene and aniline.

PubMed

Zhao, Liu-Bin; Huang, Yi-Fan; Liu, Xiu-Min; Anema, Jason R; Wu, De-Yin; Ren, Bin; Tian, Zhong-Qun

2012-10-05

We propose that aromatic nitro and amine compounds undergo photochemical reductive and oxidative coupling, respectively, to specifically produce azobenzene derivatives which exhibit characteristic Raman signals related to the azo group. A photoinduced charge transfer model is presented to explain the transformations observed in para-substituted ArNO(2) and ArNH(2) on nanostructured silver due to the surface plasmon resonance effect. Theoretical calculations show that the initial reaction takes place through excitation of an electron from the filled level of silver to the lowest unoccupied molecular orbital (LUMO) of an adsorbed ArNO(2) molecule, and from the highest occupied molecular orbital (HOMO) of an adsorbed ArNH(2) molecule to the unoccupied level of silver, during irradiation with visible light. The para-substituted ArNO(2)(-)˙ and ArNH(2)(+)˙ surface species react further to produce the azobenzene derivatives. Our results may provide a new strategy for the syntheses of aromatic azo dyes from aromatic nitro and amine compounds based on the use of nanostructured silver as a catalyst.

Effect of silane coupling agents on the chemical and physical properties of photocrosslinked poly(dimethylsiloxane) dimethacrylate/poly(ethylene glycol) diacrylate hydrogel

NASA Astrophysics Data System (ADS)

Lim, K. W.; Hamid, Z. A. A.

2017-07-01

Inorganic-organic hydrogels based on dimethacrylated polydimethylsiloxane (PDMSMA) and diacrylated poly(ethylene glycol) (PEGDA) macromers were prepared via photocrosslinking method. Silane coupling agent was incorporated into the hydrogel formulations to overcome the phase incompatibility. Pure PEGDA (0:100) hydrogels showed the highest value of ESR %, while pure PDMSMA (100:0) hydrogels showed no swelling as we expected. Inclusion of more hydrophobic domains resulted in a lower value of ESR %, i.e. in 75:25 hybrid hydrogels. Beside, we had noticed 50:50 and 75:25 hybrid hydrogels disintegrate during swelling period. However, their integrity was improved and sustained after the coupling agent was added. Similarly, the value of E* for the hybrid hydrogels showed an increment after the coupling agent was incorporated, and this is in a good agreement with the SEM micrograph which display an improved interfacial adhesion.

Aryl diazonium salts: a new class of coupling agents for bonding polymers, biomacromolecules and nanoparticles to surfaces.

PubMed

Mahouche-Chergui, Samia; Gam-Derouich, Sarra; Mangeney, Claire; Chehimi, Mohamed M

2011-07-01

This critical review summarizes existing knowledge on the use of diazonium salts as a new generation of surface modifiers and coupling agents for binding synthetic polymers, biomacromolecules, and nanoparticles to surfaces. Polymer grafts can be directly grown at surfaces through the so-called grafting from approaches based on several polymerization methods but can also be pre-formed in solution and then grafted to surfaces through grafting onto strategies including "click" reactions. Several routes are also described for binding biomacromolecules through aryl layers in view of developing biosensors and protein arrays, while the use of aryl diazonium coupling agents is extended to the attachment of nanoparticles. Patents and industrial applications of the surface chemistry of diazonium compounds are covered. This review stresses the paramount role of aryl diazonium coupling agents in adhesion, surface and materials sciences (114 references).

Detection and identification of alkylating agents by using a bioinspired "chemical nose".

PubMed

Hertzog-Ronen, Carmit; Borzin, Elena; Gerchikov, Yulia; Tessler, Nir; Eichen, Yoav

2009-10-12

Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical-warfare agents. The detection and identification of alkylating agents is not a trivial issue because of their high reactivity and simple structure. Herein, we report on a new multispot luminescence-based approach to the detection and identification of alkylating agents. In order to demonstrate the potential of the approach, seven pi-conjugated oligomers and polymers bearing nucleophilic pyridine groups, 1-7, were adsorbed onto a solid support and exposed to vapors of alkylators 8-15. The alkylation-induced color-shift patterns of the seven-spot array allow clear discrimination of the different alkylators. The spots are sensitive to minute concentrations of alkylators and, because the detection is based on the formation of new covalent bonds, these spots saturate at about 50 ppb.

Adsorption/desorption characteristics of lead on various types of soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, R.W.; Shem, L.

1994-09-01

Laboratory studies were conducted to address the phenomena of adsorption/desorption of lead onto various types of soils, both in the absence and presence of the chelating agent, ethylenediaminetetraacetic acid (EDTA). The linear and Freundlich isotherm models provided adequate description of the adsorption/desorption behavior. Over the range of EDTA concentrations employed in the study (0.01 to 0.10M), no significant difference in the isotherm parameters was observed as a result of the applied EDTA concentration. The presence of EDTA significantly altered the adsorption/desorption behavior of lead on the soil, resulting in less of the metal being adsorbed. The soil with the highermore » silt/clay content had a greater amount of lead adsorbed onto it (as compared with the sandy soil).« less

Identification of detergents for forensic fiber analysis.

PubMed

Heider, Emily C; Mujumdar, Nirvani; Campiglia, Andres D

2016-11-01

Trace fibers are an important form of trace evidence, and identification of exogenous substances on textile fibers provides valuable information about the origin of the fiber. Laundering textiles can provide a unique fluorescent spectral signature of the whitening agent in the detergent that adsorbs to the fiber. Using fluorescence microscopy, the spectral characteristics of seven detergents adsorbed to single fibers drawn from laundered textiles were investigated, and principal component analysis of clusters was used to characterize the type of detergent on the fiber. On dyed nylon fibers, spectra from eight different detergent pairs could be resolved and washed validation fibers correctly classified. On dyed acrylic fibers, five different detergent pairs could be resolved and identified. Identification of the detergent type may prove useful in matching a trace fiber to its bulk specimen of origin.

Production of activated carbons from waste tyres for low temperature NOx control.

PubMed

Al-Rahbi, Amal S; Williams, Paul T

2016-03-01

Waste tyres were pyrolysed in a bench scale reactor and the product chars were chemically activated with alkali chemical agents, KOH, K2CO3, NaOH and Na2CO3 to produce waste tyre derived activated carbons. The activated carbon products were then examined in terms of their ability to adsorb NOx (NO) at low temperature (25°C) from a simulated industrial process flue gas. This study investigates the influence of surface area and porosity of the carbons produced with the different alkali chemical activating agents on NO capture from the simulated flue gas. The influence of varying the chemical activation conditions on the porous texture and corresponding NO removal from the flue gas was studied. The activated carbon sorbents were characterized in relation to BET surface area, micropore and mesopore volumes and chemical composition. The highest NO removal efficiency for the waste tyre derived activated carbons was ∼75% which was obtained with the adsorbent treated with KOH which correlated with both the highest BET surface area and largest micropore volume. In contrast, the waste tyre derived activated carbons prepared using K2CO3, NaOH and Na2CO3 alkali activating agents appeared to have little influence on NO removal from the flue gases. The results suggest problematic waste tyres, have the potential to be converted to activated carbons with NOx removal efficiency comparable with conventionally produced carbons. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fabrication of a novel hydrophobic/ion-exchange mixed-mode adsorbent for the dispersive solid-phase extraction of chlorophenols from environmental water samples.

PubMed

Gao, Li; Wei, Yinmao

2016-08-01

A novel mixed-mode adsorbent was prepared by functionalizing silica with tris(2-aminoethyl)amine and 3-phenoxybenzaldehyde as the main mixed-mode scaffold due to the presence of the plentiful amino groups and benzene rings in their molecules. The adsorption mechanism was probed with acidic, natural and basic compounds, and the mixed hydrophobic and ion-exchange interactions were found to be responsible for the adsorption of analytes. The suitability of dispersive solid-phase extraction was demonstrated in the determination of chlorophenols in environmental water. Several parameters, including sample pH, desorption solvent, ionic strength, adsorbent dose, and extraction time were optimized. Under the optimal extraction conditions, the proposed dispersive solid-phase extraction coupled with high-performance liquid chromatography showed good linearity range and acceptable limits of detection (0.22∽0.54 ng/mL) for five chlorophenols. Notably, the higher extraction recoveries (88.7∽109.7%) for five chlorophenols were obtained with smaller adsorbent dose (10 mg) and shorter extraction time (15 min) compared with the reported methods. The proposed method might be potentially applied in the determination of trace chlorophenols in real water samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theory of raman scattering from molecules adsorbed at semiconductor surfaces

NASA Astrophysics Data System (ADS)

Ueba, H.

1983-09-01

A theory is presented to calculate the Raman polarizability of an adsorbed molecule at a semiconductor surface, where the electronic excitation in the molecular site interacts with excitons (elementary excitations in the semiconductor) through non-radiative energy transfer between them, in an intermediate state in the Raman scattering process. The Raman polarizability thus calculated is found to exhibit a peak at the energy corresponding to a resonant excitation of excitons, thereby suggesting the possibility of surface enhanced Raman scattering on semiconductor surfaces. The mechanism studied here can also give an explanation of a recent observation of the Raman excitation profiles of p-NDMA and p-DMAAB adsorbed on ZnO or TiO 2, where those profiles were best described by assuming a resonant intermediate state of the exciton transition in the semiconductors. It is also demonstrated that in addition to vibrational Raman scattering, excitonic Raman scattering of adsorbed molecules will occur in the coupled molecule-semiconductor system, where the molecular returns to its ground electronic state by leaving an exciton in the semiconductor. A spectrum of the excitonic Raman scattering is expected to appear in the background of the vibrational Raman band and to be characterized by the electronic structure of excitons. A desirable experiment is suggested for an examination of the theory.

Enhancement of anion-exchange chromatography of DNA using compaction agents

NASA Technical Reports Server (NTRS)

Murphy, Jason C.; Fox, George E.; Willson, Richard C.

2003-01-01

The use of adsorptive chromatography for preparative nucleic acid separations is often limited by low capacity. The possibility that the adsorbent surface area sterically accessible to nucleic acid molecules could be increased by reducing their radius of gyration with compaction agents has been investigated. The equilibrium adsorption capacity of Q Sepharose anion-exchange matrix for plasmid DNA at 600 mM NaCl was enhanced by up to ca. 40% in the presence of 2.5 mM spermine. In addition, compaction agent selectivity has been demonstrated. Spermine, for example, enhances the adsorption of both plasmid and genomic DNA, spermidine enhances binding only of plasmid, and hexamine cobalt enhances only the binding of genomic DNA. Compaction may be generally useful for enhancing adsorptive separations of nucleic acids.

Metal-organic frameworks for the removal of toxic industrial chemicals and chemical warfare agents.

PubMed

Bobbitt, N Scott; Mendonca, Matthew L; Howarth, Ashlee J; Islamoglu, Timur; Hupp, Joseph T; Farha, Omar K; Snurr, Randall Q

2017-06-06

Owing to the vast diversity of linkers, nodes, and topologies, metal-organic frameworks can be tailored for specific tasks, such as chemical separations or catalysis. Accordingly, these materials have attracted significant interest for capture and/or detoxification of toxic industrial chemicals and chemical warfare agents. In this paper, we review recent experimental and computational work pertaining to the capture of several industrially-relevant toxic chemicals, including NH 3 , SO 2 , NO 2 , H 2 S, and some volatile organic compounds, with particular emphasis on the challenging issue of designing materials that selectively adsorb these chemicals in the presence of water. We also examine recent research on the capture and catalytic degradation of chemical warfare agents such as sarin and sulfur mustard using metal-organic frameworks.

[Determination of three phenoxyalkanoic acid herbicides in blood using gas chromatography coupled with solid-phase extraction and derivatization].

PubMed

Xin, Guobin; Tan, Jiayi; Yao, Lijuan; Zhu, Yu; Jiang, Zhaolin; Song, Hui

2008-01-01

A method for the determination of three phenoxyalkanoic acid herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2,4-dichlorophenoxy)-propanoic acid (2,4-DP), and 4-chloro-2-methylphenoxy-acetic acid (MCPA), in blood was developed. The blood sample was diluted with 0.1 mol/L hydrochloric acid, and extracted by solid-phase extraction using porous resin GDX401 as adsorbent and ethyl ether as eluent. The extract was esterified with dichloropropanol in the presence of sulfuric acid as catalyst. The derivatives were analysed by gas chromatography with electron-capture detection. The detection limits of 2,4-D, 2,4-DP and MCPA were 20, 8 and 40 ng/mL, respectively. In quantitative analysis, 2,4-dichlorophenylacetic acid was used as an internal standard. The linear relationships and recoveries were satisfactory. The derivatization of the three herbicides with methanol, ethanol, n-propanol, n-butanol, and trifluoroethanol were also studied, and the analytical methods of these derivatization were compared with that of dichloropropanol as esterifying agent. The method is sensitive enough for the examination of the poison samples in actual.

Application of Solid Phase Microextraction Coupled with Gas Chromatography/Mass Spectrometry as a Rapid Method for Field Sampling and Analysis of Chemical Warfare Agents and Toxic Industrial Chemicals

DTIC Science & Technology

2003-01-01

PHASE MICROEXTRACTION COUPLED WITH GAS CHROMATOGRAPHY/MASS SPECTROMETRY AS A RAPID METHOD FOR FIELD SAMPLING AND ANALYSIS OF CHEMICAL WARFARE AGENTS...SAMPLING AND ANALYSIS OF CHEMICAL WARFARE AGENTS AND TOXIC INDUSTRIAL CHEMICALS 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...GAS CHROMATOGRAPHY/MASS SPECTROMETRY AS A RAPID METHOD FOR FIELD SAMPLING AND ANALYSIS OF CHEMICAL WARFARE AGENTS AND TOXIC INDUSTRIAL CHEMICALS

Spectral tuning of optical coupling between air-mode nanobeam cavities and individual carbon nanotubes

NASA Astrophysics Data System (ADS)

Machiya, H.; Uda, T.; Ishii, A.; Kato, Y. K.

2018-01-01

We demonstrate control over optical coupling between air-suspended carbon nanotubes and air-mode nanobeam cavities by spectral tuning. Taking advantage of the large dielectric screening effects caused by adsorbed molecules, laser heating is used to blueshift the nanotube photoluminescence. A significant increase in the cavity peak is observed when the nanotube emission is brought into resonance, and the spontaneous emission enhancement is estimated from the photoluminescence spectra. We find that the enhancement shows good correlation with the spectral overlap of the nanotube emission and the cavity peak. Our technique offers a convenient method for controlling the optical coupling of air-suspended nanotubes to photonic structures.

Synchronization control in multiplex networks of nonlinear multi-agent systems

NASA Astrophysics Data System (ADS)

He, Wangli; Xu, Zhiwei; Du, Wenli; Chen, Guanrong; Kubota, Naoyuki; Qian, Feng

2017-12-01

This paper is concerned with synchronization control of a multiplex network, in which two different kinds of relationships among agents coexist. Hybrid coupling, including continuous linear coupling and impulsive coupling, is proposed to model the coexisting distinguishable interactions. First, by adding impulsive controllers on a small portion of agents, local synchronization is analyzed by linearizing the error system at the desired trajectory. Then, global synchronization is studied based on the Lyapunov stability theory, where a time-varying coupling strength is involved. To further deal with the time-varying coupling strength, an adaptive updating law is introduced and a corresponding sufficient condition is obtained to ensure synchronization of the multiplex network towards the desired trajectory. Networks of Chua's circuits and other chaotic systems with double layers of interactions are simulated to verify the proposed method.

Effects of dyes, gold nanocrystals, pH, and metal ions on plasmonic and molecular resonance coupling.

PubMed

Ni, Weihai; Chen, Huanjun; Su, Jing; Sun, Zhenhua; Wang, Jianfang; Wu, Hongkai

2010-04-07

The effects of various factors on the resonance coupling between elongated Au nanocrystals and organic dyes have been systematically investigated through the preparation of hybrid nanostructures between Au nanocrystals and the electrostatically adsorbed dye molecules. A nanocrystal sample is chosen for each dye to match the longitudinal plasmon resonance wavelength with the absorption peak wavelength of the dye as close as possible so that the resonance coupling strength can be maximized. The resonance coupling strength is found to approximately increase as the molecular volume-normalized absorptivity is increased. It is mainly determined by the plasmon resonance energy of the Au nanocrystals instead of their shapes and sizes. Moreover, the resonance coupling can be reversibly controlled if the dye in the hybrid nanostructures is pH-sensitive. The coupling can also be weakened in the presence of metal ions. These results will be highly useful for designing resonance coupling-based sensing devices and for plasmon-enhanced spectroscopy.

Magnetic and Electronic Properties of h-BN Nanosheets with Nonmetal Atoms Adsorbed: an Ab Initio Study

NASA Astrophysics Data System (ADS)

Luo, M.; Yin, H. H.; Chu, J. H.

2018-04-01

The magnetic properties of the h-BN monolayer with nonmetal atoms are studied by ab initio methods. Different dopants (C, Cl, F, and O) and doping sites are considered. Magnetic behavior is observed in the two-dimensional (2D) BN system with C, Cl, and O atoms. On the other hand, the O adsorbed system shows a more stable formed structure among above three magnetic materials, we study the ferromagnetic (FM) interaction in 2D-BN system with two O adatoms. Interestingly, as the O-O distance increases, the interaction between two O adatoms prefers to a long-range FM coupling. This phenomenon could be well described by a simple Heisenberg model.

Thermal Degradation, Mechanical Properties and Morphology of Wheat Straw Flour Filled Recycled Thermoplastic Composites

PubMed Central

Mengeloglu, Fatih; Karakus, Kadir

2008-01-01

Thermal behaviors of wheat straw flour (WF) filled thermoplastic composites were measured applying the thermogravimetric analysis and differential scanning calorimetry. Morphology and mechanical properties were also studied using scanning electron microscope and universal testing machine, respectively. Presence of WF in thermoplastic matrix reduced the degradation temperature of the composites. One for WF and one for thermoplastics, two main decomposition peaks were observed. Morphological study showed that addition of coupling agent improved the compatibility between WFs and thermoplastic. WFs were embedded into the thermoplastic matrix indicating improved adhesion. However, the bonding was not perfect because some debonding can also be seen on the interface of WFs and thermoplastic matrix. In the case of mechanical properties of WF filled recycled thermoplastic, HDPE and PP based composites provided similar tensile and flexural properties. The addition of coupling agents improved the properties of thermoplastic composites. MAPE coupling agents performed better in HDPE while MAPP coupling agents were superior in PP based composites. The composites produced with the combination of 50-percent mixture of recycled HDPE and PP performed similar with the use of both coupling agents. All produced composites provided flexural properties required by the ASTM standard for polyolefin-based plastic lumber decking boards. PMID:27879719

Mechanical behavior of bioactive composite cements consisting of resin and glass-ceramic powder in a simulated body fluid: effect of silane coupling agent.

PubMed

Miyata, N; Matsuura, W; Kokubo, T; Nakamura, T

2004-09-01

Time-dependent strength behavior was investigated for bisphenol-a-glycidyl methacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) resin cements combined with glass-ceramic A-W filler treated with various kinds of silane coupling agents. The fracture strength of the composite resin cements was measured by three-point bending as a function of stressing rate in a simulated body fluid (SBF), and thereby the stress-corrosion susceptibility constant was evaluated. The fracture strength was found to depend on the kind of coupling agent used. For the present Bis-GMA/TEGDMA resin, the silane coupling agents without hydrophilic amine groups can be used to obtain good adhesion between resin and A-W filler owing to their nature of co-polymerizing with the resin. On the other hand, all the composite resin cements showed nearly the same degree of stress-corrosion susceptibility whether the A-W fillers were treated or untreated with silane coupling agents. This means that the stress-corrosion susceptibility of the present composite cements is predominantly affected by that of the matrix resin. Thus, the microcrack formation and growth at the resin matrix near particle - resin interface were thought to determine overall time-dependent strength behavior of the composite cements.

Adaptive tracking control of leader-following linear multi-agent systems with external disturbances

NASA Astrophysics Data System (ADS)

Lin, Hanquan; Wei, Qinglai; Liu, Derong; Ma, Hongwen

2016-10-01

In this paper, the consensus problem for leader-following linear multi-agent systems with external disturbances is investigated. Brownian motions are used to describe exogenous disturbances. A distributed tracking controller based on Riccati inequalities with an adaptive law for adjusting coupling weights between neighbouring agents is designed for leader-following multi-agent systems under fixed and switching topologies. In traditional distributed static controllers, the coupling weights depend on the communication graph. However, coupling weights associated with the feedback gain matrix in our method are updated by state errors between neighbouring agents. We further present the stability analysis of leader-following multi-agent systems with stochastic disturbances under switching topology. Most traditional literature requires the graph to be connected all the time, while the communication graph is only assumed to be jointly connected in this paper. The design technique is based on Riccati inequalities and algebraic graph theory. Finally, simulations are given to show the validity of our method.

Boundary Conditions for Diffusion-Mediated Processes within Linear Nanopores: Exact Treatment of Coupling to an Equilibrated External Fluid

DOE PAGES

Garcia, Andres; Evans, James W.

2017-04-03

In this paper, we consider a variety of diffusion-mediated processes occurring within linear nanopores, but which involve coupling to an equilibrated external fluid through adsorption and desorption. By determining adsorption and desorption rates through a set of tailored simulations, and by exploiting a spatial Markov property of the models, we develop a formulation for performing efficient pore-only simulations of these processes. Coupling to the external fluid is described exactly through appropriate nontrivial boundary conditions at the pore openings. This formalism is applied to analyze the following: (i) tracer counter permeation (TCP) where different labeled particles adsorb into opposite ends ofmore » the pore and establish a nonequilibrium steady state; (ii) tracer exchange (TE) with exchange of differently labeled particles within and outside the pore; (iii) catalytic conversion reactions where a reactant in the external fluid adsorbs into the pore and converts to a product which may desorb. The TCP analysis also generates a position-dependent generalized tracer diffusion coefficient, the form of which controls behavior in the TE and catalytic conversion processes. We focus on the regime of single-file diffusion within the pore which produces the strongest correlations and largest deviations from mean-field type behavior. Finally, behavior is quantified precisely via kinetic Monte Carlo simulations but is also captured with appropriate analytic treatments.« less

Direct Structural Identification of Gas Induced Gate-Opening Coupled with Commensurate Adsorption in a Microporous Metal-Organic Framework.

PubMed

Banerjee, Debasis; Wang, Hao; Plonka, Anna M; Emge, Thomas J; Parise, John B; Li, Jing

2016-08-08

Gate-opening is a unique and interesting phenomenon commonly observed in flexible porous frameworks, where the pore characteristics and/or crystal structures change in response to external stimuli such as adding or removing guest molecules. For gate-opening that is induced by gas adsorption, the pore-opening pressure often varies for different adsorbate molecules and, thus, can be applied to selectively separate a gas mixture. The detailed understanding of this phenomenon is of fundamental importance to the design of industrially applicable gas-selective sorbents, which remains under investigated due to the lack of direct structural evidence for such systems. We report a mechanistic study of gas-induced gate-opening process of a microporous metal-organic framework, [Mn(ina)2 ] (ina=isonicotinate) associated with commensurate adsorption, by a combination of several analytical techniques including single crystal X-ray diffraction, in situ powder X-ray diffraction coupled with differential scanning calorimetry (XRD-DSC), and gas adsorption-desorption methods. Our study reveals that the pronounced and reversible gate opening/closing phenomena observed in [Mn(ina)2 ] are coupled with a structural transition that involves rotation of the organic linker molecules as a result of interaction of the framework with adsorbed gas molecules including carbon dioxide and propane. The onset pressure to open the gate correlates with the extent of such interaction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemo-mechanical coupling in kerogen gas adsorption/desorption.

PubMed

Ho, Tuan Anh; Wang, Yifeng; Criscenti, Louise J

2018-05-09

Kerogen plays a central role in hydrocarbon generation in an oil/gas reservoir. In a subsurface environment, kerogen is constantly subjected to stress confinement or relaxation. The interplay between mechanical deformation and gas adsorption of the materials could be an important process for shale gas production but unfortunately is poorly understood. Using a hybrid Monte Carlo/molecular dynamics simulation, we show here that a strong chemo-mechanical coupling may exist between gas adsorption and mechanical strain of a kerogen matrix. The results indicate that the kerogen volume can expand by up to 5.4% and 11% upon CH4 and CO2 adsorption at 192 atm, respectively. The kerogen volume increases with gas pressure and eventually approaches a plateau as the kerogen becomes saturated. The volume expansion appears to quadratically increase with the amount of gas adsorbed, indicating a critical role of the surface layer of gas adsorbed in the bulk strain of the material. Furthermore, gas uptake is greatly enhanced by kerogen swelling. Swelling also increases the surface area, porosity, and pore size of kerogen. Our results illustrate the dynamic nature of kerogen, thus questioning the validity of the current assumption of a rigid kerogen molecular structure in the estimation of gas-in-place for a shale gas reservoir or gas storage capacity for subsurface carbon sequestration. The coupling between gas adsorption and kerogen matrix deformation should be taken into consideration.

The Dynamics of Interacting Swarms

DTIC Science & Technology

2018-04-04

Unlimited 16 Ira Schwartzt (202) 404-8359 Swarms are self-organized dynamical coupled agents which evolve from simple rules of communication. They are ...when delay is introduced to the communicating agents. One of our major findings is that interacting swarms are far less likely to flock cohesively if...they are coupled with delay. In addition, parameter ranges based on coupling strength, incidence angle of collision, and delay change dramatically

Mobilization of arsenite by dissimilatory reduction of adsorbed arsenate

USGS Publications Warehouse

Zobrist, J.; Dowdle, P.R.; Davis, J.A.; Oremland, R.S.

2000-01-01

Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite, a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was influenced by the method in which arsenate became associated with the mineral phases and may have been strongly coupled with arsenate desorption rates. The extent of release of arsenite into solution was governed by adsorption of arsenite onto the ferrihydrite or alumina phases. The results of these experiments have interpretive significance to the mobilization of arsenic in large alluvial aquifers, such as those of the Ganges in India and Bangladesh, and in the hyporheic zones of contaminated streams.Sulfurospirillum barnesii is capable of anaerobic growth using ferric iron or arsenate as electron acceptors. Cell suspensions of S. barnesii were able to reduce arsenate to arsenite when the former oxyanion was dissolved in solution, or when it was adsorbed onto the surface of ferrihydrite a common soil mineral, by a variety of mechanisms (e.g., coprecipitation, presorption). Reduction of Fe(III) in ferrihydrite to soluble Fe(II) also occurred, but dissolution of ferrihydrite was not required in order for adsorbed arsenate reduction to be achieved. This was illustrated by bacterial reduction of arsenate coprecipitated with aluminum hydroxide, a mineral that does not undergo reductive dissolution. The rate of arsenate reduction was influenced by the method in which arsenate became associated with the mineral phases and may have been strongly coupled with arsenate desorption rates. The extent of release of arsenite into solution was governed by adsorption of arsenite onto the ferrihydrite or alumina phases. The results of these experiments have interpretive significance to the mobilization of arsenic in large alluvial aquifers, such as those of the Ganges in India and Bangladesh, and in the hyporheic zones of contaminated streams.

M4FT-15OR03100421: Status Report on Alkaline Conditioning Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsouris, Costas; Brown, Suree; Janke, Christopher James

2015-05-01

Significant progress in understanding the role of alkaline conditioning of polyethylene-fiber adsorbent, developed at the Oak Ridge National Laboratory (ORNL), is demonstrated in this report, which is essentially a manuscript prepared for publication in the journal Industrial & Engineering Chemistry Research of the American Chemical Society. The manuscript describes the influence of various parameters involved in adsorbent alkaline conditioning, including base concentration and duration and temperature of conditioning, on the uranium uptake history by the adsorbent. Various solutions have been used to determine the influence of conditioning parameters including (i) a screening solution containing uranyl nitrate at approximately 8 ppmmore » and sodium bicarbonate and sodium chloride at concentrations similar to those found in seawater, (ii) seawater spiked with approximately 75 ppb uranium, and (iii) natural seawater. In addition to concentration measurements by inductively coupled plasma (ICP) spectroscopy to determine the uranium uptake capacity and kinetics, spectroscopic methods such as Fourier transformed infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy were employed to investigate the effect of base treatment on the various chemical bonds of the adsorbent. Scanning electron microscopy (SEM) has also been employed to determine structural effects of the alkali on the adsorbent. The results are summarized as follows: 1. Alkali conditioning is necessary to prepare the adsorbent for uranium uptake. ICP analysis showed that without alkali conditioning, no appreciable uranium adsorption occurs. 2. FTIR showed that the base converts amidoxime to carboxylate groups. 3. FTIR showed that formation of carboxylate groups is irreversible and reduces the selectivity of the adsorbent toward uranium. 4. NMR showed that alkali conditioning leads also to the formation of cyclic imidedioxime, which is suspected to bind uranium, vanadium, iron, copper, and other metals. 5. Uptake of V, Fe, and Cu follows the same trend as that of uranium. Uptake of Ca, Mg, and Zn ions increases with increasing KOH conditioning time due to formation of carboxylate groups. 6. SEM showed that long conditioning times may also lead to adsorbent degradation. 7. The optimal conditioning parameters are: 0.44 M KOH, 70 C, for 1 hour. The results of this study are useful in the selection of optimal values of the parameters involved in preparing amidoxime-based adsorbent for uranium uptake from seawater. Additional work is still ongoing to provide a complete understanding of the chemistry of base conditioning and its role on the functioning of the adsorbent.« less

Adlayer structure dependent ultrafast desorption dynamics in carbon monoxide adsorbed on Pd (111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Sung -Young; Xu, Pan; Camillone, Nina R.

Here, we report our ultrafast photoinduced desorption investigation of the coverage dependence of substrate–adsorbate energy transfer in carbon monoxide adlayers on the (111) surface of palladium. As the CO coverage is increased, the adsorption site population shifts from all threefold hollows (up to 0.33 ML), to bridge and near bridge (>0.5 to 0.6 ML) and finally to mixed threefold hollow plus top site (at saturation at 0.75 ML). We show that between 0.24 and 0.75 ML this progression of binding site motifs is accompanied by two remarkable features in the ultrafast photoinduced desorption of the adsorbates: (i) the desorption probabilitymore » increases roughly two orders magnitude, and (ii) the adsorbate–substrate energy transfer rate observed in two-pulse correlation experiments varies nonmonotonically, having a minimum at intermediate coverages. Simulations using a phenomenological model to describe the adsorbate–substrate energy transfer in terms of frictional coupling indicate that these features are consistent with an adsorption-site dependent electron-mediated energy coupling strength, η el, that decreases with binding site in the order: three-fold hollow > bridge and near bridge > top site. This weakening of η el largely counterbalances the decrease in the desorption activation energy that accompanies this progression of adsorption site motifs, moderating what would otherwise be a rise of several orders of magnitude in the desorption probability. Within this framework, the observed energy transfer rate enhancement at saturation coverage is due to interadsorbate energy transfer from the copopulation of molecules bound in three-fold hollows to their top-site neighbors.« less

Adlayer structure dependent ultrafast desorption dynamics in carbon monoxide adsorbed on Pd (111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Sung-Young; Camillone, Nina R.; Camillone, Nicholas, E-mail: nicholas@bnl.gov

We report our ultrafast photoinduced desorption investigation of the coverage dependence of substrate–adsorbate energy transfer in carbon monoxide adlayers on the (111) surface of palladium. As the CO coverage is increased, the adsorption site population shifts from all threefold hollows (up to 0.33 ML), to bridge and near bridge (>0.5 to 0.6 ML) and finally to mixed threefold hollow plus top site (at saturation at 0.75 ML). We show that between 0.24 and 0.75 ML this progression of binding site motifs is accompanied by two remarkable features in the ultrafast photoinduced desorption of the adsorbates: (i) the desorption probability increasesmore » roughly two orders magnitude, and (ii) the adsorbate–substrate energy transfer rate observed in two-pulse correlation experiments varies nonmonotonically, having a minimum at intermediate coverages. Simulations using a phenomenological model to describe the adsorbate–substrate energy transfer in terms of frictional coupling indicate that these features are consistent with an adsorption-site dependent electron-mediated energy coupling strength, η{sub el}, that decreases with binding site in the order: three-fold hollow > bridge and near bridge > top site. This weakening of η{sub el} largely counterbalances the decrease in the desorption activation energy that accompanies this progression of adsorption site motifs, moderating what would otherwise be a rise of several orders of magnitude in the desorption probability. Within this framework, the observed energy transfer rate enhancement at saturation coverage is due to interadsorbate energy transfer from the copopulation of molecules bound in three-fold hollows to their top-site neighbors.« less

Adlayer structure dependent ultrafast desorption dynamics in carbon monoxide adsorbed on Pd (111)

DOE PAGES

Hong, Sung -Young; Xu, Pan; Camillone, Nina R.; ...

2016-07-01

Here, we report our ultrafast photoinduced desorption investigation of the coverage dependence of substrate–adsorbate energy transfer in carbon monoxide adlayers on the (111) surface of palladium. As the CO coverage is increased, the adsorption site population shifts from all threefold hollows (up to 0.33 ML), to bridge and near bridge (>0.5 to 0.6 ML) and finally to mixed threefold hollow plus top site (at saturation at 0.75 ML). We show that between 0.24 and 0.75 ML this progression of binding site motifs is accompanied by two remarkable features in the ultrafast photoinduced desorption of the adsorbates: (i) the desorption probabilitymore » increases roughly two orders magnitude, and (ii) the adsorbate–substrate energy transfer rate observed in two-pulse correlation experiments varies nonmonotonically, having a minimum at intermediate coverages. Simulations using a phenomenological model to describe the adsorbate–substrate energy transfer in terms of frictional coupling indicate that these features are consistent with an adsorption-site dependent electron-mediated energy coupling strength, η el, that decreases with binding site in the order: three-fold hollow > bridge and near bridge > top site. This weakening of η el largely counterbalances the decrease in the desorption activation energy that accompanies this progression of adsorption site motifs, moderating what would otherwise be a rise of several orders of magnitude in the desorption probability. Within this framework, the observed energy transfer rate enhancement at saturation coverage is due to interadsorbate energy transfer from the copopulation of molecules bound in three-fold hollows to their top-site neighbors.« less

The adsorption of argon on ZnO at 77K

NASA Astrophysics Data System (ADS)

Marinelli, Francis; Grillet, Yves; Pellenq, Roland J.-M.

We have studied the adsorption of argon onto ZnO surfaces at 77K by means of quasiequilibrium adsorption volumetry coupled with high resolution microcalorimetry and Grand Canonical Monte-Carlo (GCMC) simulations. The adsorbate/surface adsorption potential function (PN type) used in the simulations, was determined on the basis of ab initio calculations (corrected for dispersion interactions). The first aspect of this work was to test the ability of a standard solid-state Hartree-Fock technique coupled with a perturbative semiempirical approach in deriving a reliable adsorption potential function. The dispersion part of the adsorbate/surface interatomic potential was derived by using perturbation theory-based equations while the repulsive and induction interactions were derived from periodic HartreeFock (CRYSTAL92) calculations. GCMC simulations based on this adsorption potential allow one to calculate adsorption isotherms and isosteric heat versus loading curves as well as singlet distribution functions at 77K for each type of ZnO (neutral and polar) faces. The combined analysis of the simulation data for all surfaces gives a good insight of the adsorption mechanism of argon onto ZnO surfaces at 77K in agreement with experiment. As far as neutral surfaces are concerned, it is shown that adsorption first takes place within the 'troughs' which cover ZnO neutral surfaces. At low chemical potentials, these semi-channels are preferential adsorption sites in which we could detect a nearly one-dimensional adsorbate freezing in a commensurate phase at 77K. The polar O faces are the most favourable surfaces for adsorption at higher chemical potentials.

Internal coating of zirconia restoration with silica-based ceramic improves bonding of resin cement to dental zirconia ceramic.

PubMed

Kitayama, Shuzo; Nikaido, Toru; Ikeda, Masaomi; Alireza, Sadr; Miura, Hiroyuki; Tagami, Junji

2010-01-01

Resin bonding to zirconia ceramic cannot be established by standard methods that are utilized for conventional silica-based dental ceramics. This study was aimed to examine the tensile bond strength of resin cement to zirconia ceramic using a new laboratory technique. Sixty-four zirconia ceramic specimens were air-abraded using Al2O3 particles and divided into two groups; the control group with no pretreatment (Control), and the group pretreated using the internal coating technique (INT), in which the surface of the zirconia specimens were thinly coated by fusing silica-based ceramic and air-abraded in the same manner. The specimens in each group were further divided into two subgroups according to the silane coupling agents applied; a mixture of dentin primer/silane coupling agent (Clearfil SE Bond Primer/Porcelain Bond Activator) or a newly developed single-component silane coupling agent (Clearfil Ceramic Primer). After bonding with dual-cured resin cement (Panavia F 2.0), they were stored in water for 24 h and half of them were additionally subjected to thermal cycling. The tensile bond strengths were tested using a universal testing machine. ANOVAs revealed significant influence of ceramic surface pretreatment (p<0.001), silane coupling agent (p<0.001) and thermal cycling (p<0.001); the INT coating technique significantly increased the bond strengths of resin cement to zirconia ceramic, whereas thermal cycling significantly decreased the bond strengths. The use of a single-component silane coupling agent demonstrated significantly higher bond strengths than that of a mixture of dentin primer/silane coupling agent. The internal coating of zirconia dental restorations with silica-based ceramic followed by silanization may be indicated in order to achieve better bonding for the clinical success.

Surfactant modified zeolite as amphiphilic and dual-electronic adsorbent for removal of cationic and oxyanionic metal ions and organic compounds.

PubMed

Tran, Hai Nguyen; Viet, Pham Van; Chao, Huan-Ping

2018-01-01

A hydrophilic Y zeolite was primarily treated with sodium hydroxide to enhance its cation exchange capacity (Na-zeolite). The organo-zeolite (Na-H-zeolite) was prepared by a modification process of the external surface of Na-zeolite with a cationic surfactant (hexadecyltrimethylammonium; HDTMA). Three adsorbents (i.e., pristine zeolite, Na-zeolite, and Na-H-zeolite) were characterized with nitrogen adsorption/desorption isotherms, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, cation exchange capacities, and zeta potential. Results demonstrated that HDTMA can be adsorbed on the surface of Na-zeolite to form patchy bilayers. The adsorption capacity of several hazardous pollutants (i.e., Pb 2+ , Cu 2+ , Ni 2+ , Cr 2 O 7 2- , propylbenzene, ethylbenzene, toluene, benzene, and phenol) onto Na-H-zeolite was investigated in a single system and multiple-components. Adsorption isotherm was measured to further understand the effects of the modification process on the adsorption behaviors of Na-H-zeolite. Adsorption performances indicated that Na-H-zeolite can simultaneously adsorb the metal cations (on the surface not covered by HDTMA), oxyanions (on the surface covered by HDTMA). Na-H-zeolite also exhibited both hydrophilic and hydrophobic surfaces to uptake organic compounds with various water solubilities (from 55 to 75,000mg/L). It was experimentally concluded that Na-H-zeolite is a potential dual-electronic and amphiphilic adsorbent for efficiently removing a wide range of potentially toxic pollutants from aquatic environments. Copyright © 2017 Elsevier Inc. All rights reserved.

Influence of pH on Cr(VI) ions removal from aqueous solutions using carboxymethyl cellulose-based hydrogel as adsorbent

NASA Astrophysics Data System (ADS)

Anah, L.; Astrini, N.

2017-03-01

The major problem in heavy metal pollution is that these metals are not biodegradable and accordingly accumulate in the bodies of living organisms, causing dangerous diseases and serious cell disorder. According to World Health Organization (WHO), the long term exposure of Cr(VI) levels of over 0.1 ppm causes respiratory problems, liver and kidney damage, and carcinogenicity.Due to its easy operation and of various cheap adsorbents development, adsorption has been proved to be efficient and most economically attractive technique and feasible to the removal of toxic heavy metal from wastewater. The study aimed to report the removal of Cr(VI) ions from aqueous solutions through adsorption process using carboxymethyl cellulose-graft-poly(acrylic acid) (CMC-g-PAA) hydrogel as adsorbent.Effect of pH was studied to remove hexavalent chromium.Graft copolymerization of poly(acrylic acid) onto carboxymethyl cellulose was carried out in the presence of benzoyl peroxide redox initiator and methylenbisacrylamide as crosslinker agent. Batch experiments were carried out to investigate the effects ofinitial pH.The adsorption of Cr(VI) ions as a function of pH was conducted in the initial pH range of 1 to 8. The results indicated that acidic pH strongly favored the adsorption. The optimum pH for adsorption of Cr(VI) ranged from 1 to 3, and the maximum uptake of Cr(VI) from the solution was 6.53 mg/g at pH 1 and 30°C. FTIR spectroscopy, SEM analyses were performed on the adsorbent before and after Cr(VI) binding. All analyses confirmed the complexation of Cr(VI) ions on the adsorbent.

Assessing Atmospheric CO2 Entrapped in Clay Nanotubes using Residual Gas Analyzer.

PubMed

Das, Sankar; Maity, Abhijit; Pradhan, Manik; Jana, Subhra

2016-02-16

A residual gas analyzer (RGA) coupled with a high-vacuum chamber has been explored to measure atmospheric CO2 entrapped in aminosilane-modified clay nanotubes. Ambient CO2 uptake efficacy together with stability of these novel adsorbents composed of both primary and/or secondary amine sites has been demonstrated at standard ambient temperature and pressure. The unprecedented sensitivity and accuracy of the RGA-based mass spectrometry technique toward atmospheric CO2 measurement has been substantiated with a laser-based optical cavity-enhanced integrated cavity output spectroscopy. The adsorption kinetics of atmospheric CO2 on amine-functionalized clay nanotubes followed the fractional-order kinetic model compared to that of the pseudo-first-order or pseudo-second-order rate equations. The efficiency along with stability of these novel adsorbents has also been demonstrated by their repetitive use for CO2 capture in the oxidative environment. Our findings thus point to a fundamental study on the atmospheric CO2 adsorption by amine-loaded adsorbents using an easy handling and low-cost benchtop RGA-based mass spectrometer, opening a new strategy for CO2 capture and sequestering study.

A genetically optimized kinetic model for ethanol electro-oxidation on Pt-based binary catalysts used in direct ethanol fuel cells

NASA Astrophysics Data System (ADS)

Sánchez-Monreal, Juan; García-Salaberri, Pablo A.; Vera, Marcos

2017-09-01

A one-dimensional model is proposed for the anode of a liquid-feed direct ethanol fuel cell. The complex kinetics of the ethanol electro-oxidation reaction is described using a multi-step reaction mechanism that considers free and adsorbed intermediate species on Pt-based binary catalysts. The adsorbed species are modeled using coverage factors to account for the blockage of the active reaction sites on the catalyst surface. The reaction rates are described by Butler-Volmer equations that are coupled to a one-dimensional mass transport model, which incorporates the effect of ethanol and acetaldehyde crossover. The proposed kinetic model circumvents the acetaldehyde bottleneck effect observed in previous studies by incorporating CH3CHOHads among the adsorbed intermediates. A multi-objetive genetic algorithm is used to determine the reaction constants using anode polarization and product selectivity data obtained from the literature. By adjusting the reaction constants using the methodology developed here, different catalyst layers could be modeled and their selectivities could be successfully reproduced.

Trap-state-dominated suppression of electron conduction in carbon nanotube thin-film transistors.

PubMed

Qian, Qingkai; Li, Guanhong; Jin, Yuanhao; Liu, Junku; Zou, Yuan; Jiang, Kaili; Fan, Shoushan; Li, Qunqing

2014-09-23

The often observed p-type conduction of single carbon nanotube field-effect transistors is usually attributed to the Schottky barriers at the metal contacts induced by the work function differences or by the doping effect of the oxygen adsorption when carbon nanotubes are exposed to air, which cause the asymmetry between electron and hole injections. However, for carbon nanotube thin-film transistors, our contrast experiments between oxygen doping and electrostatic doping demonstrate that the doping-generated transport barriers do not introduce any observable suppression of electron conduction, which is further evidenced by the perfect linear behavior of transfer characteristics with the channel length scaling. On the basis of the above observation, we conclude that the environmental adsorbates work by more than simply shifting the Fermi level of the CNTs; more importantly, these adsorbates cause a poor gate modulation efficiency of electron conduction due to the relatively large trap state density near the conduction band edge of the carbon nanotubes, for which we further propose quantitatively that the adsorbed oxygen-water redox couple is responsible.

Ferrocene adsorbed into the porous octakis(hydridodimethylsiloxy)silsesquioxane after thermolysis in tetrahydrofuran media: An applied surface for ascorbic acid determination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribeiro do Carmo, Devaney, E-mail: docarmo@dfq.feis.unesp.br; Lataro Paim, Leonardo; Ramos Stradiotto, Nelson

Highlights: Black-Right-Pointing-Pointer Octakis(hydridodimethylsiloxi)silsesquioxane was synthesized and Ferrocene was adsorbed. Black-Right-Pointing-Pointer Polymeric net through electrostatic interactions was observed. Black-Right-Pointing-Pointer The novel materials presents electroacatalytic activity for Ascorbic acid. -- Abstract: Octakis(hydridodimethylsiloxi)silsesquioxane (Q{sub 8}M{sub 8}{sup H}) was synthesized and Ferrocene was adsorbed in a polymeric net through electrostatic interactions, with anion forming after the cleavage of any siloxy groups (ESFc). The nanostructured materials (Q{sub 8}M{sub 8}{sup H} and EsFc) were characterized by Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Thermogravimetric analyses and Voltammetric technique The cyclic voltammograms of the graphite paste electrode modified with ESFc showed onemore » redox couple with E{sup 0} Prime = 0.320 V (1.0 mol L{sup -1} NaCl, v = 50 mV s{sup -1}), with a diffusion-controlled process and the redox process shows electrocatalytic activity for the oxidation of ascorbic acid.« less

Benzene carboxylic acid derivatized graphene oxide nanosheets on natural zeolites as effective adsorbents for cationic dye removal.

PubMed

Yu, Yang; Murthy, Bandaru N; Shapter, Joseph G; Constantopoulos, Kristina T; Voelcker, Nicolas H; Ellis, Amanda V

2013-09-15

Graphene oxide (GO) nanosheets were grafted to acid-treated natural clinoptilolite-rich zeolite powders followed by a coupling reaction with a diazonium salt (4-carboxybenzenediazoniumtetrafluoroborate) to the GO surface. Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) revealed successful grafting of GO nanosheets onto the zeolite surface. The application of the adsorbents for the adsorption of rhodamine B from aqueous solutions was then demonstrated. After reaching adsorption equilibrium the maximum adsorption capacities were shown to be 50.25, 55.56 and 67.56 mg g(-1) for pristine natural zeolite, GO grafted zeolite (GO-zeolite) and benzene carboxylic acid derivatized GO-zeolite powders, respectively. The adsorption behavior was fitted to a Langmuir isotherm and shown to follow a pseudo-second-order reaction model. Further, a relationship between surface functional groups, pH and adsorption efficiency was established. Results indicate that benzene carboxylic acid derivatized GO-zeolite powders are environmentally favorable adsorbents for the removal of cationic dyes from aqueous solutions. Copyright © 2013 Elsevier B.V. All rights reserved.

Evidence and implications of direct charge excitation as the dominant mechanism in plasmon-mediated photocatalysis

DOE PAGES

Boerigter, Calvin; Campana, Robert; Morabito, Matthew; ...

2016-01-28

Plasmonic metal nanoparticles enhance chemical reactions on their surface when illuminated with light of particular frequencies. It has been shown that these processes are driven by excitation of localized surface plasmon resonance (LSPR). The interaction of LSPR with adsorbate orbitals can lead to the injection of energized charge carriers into the adsorbate, which can result in chemical transformations. The mechanism of the charge injection process (and role of LSPR) is not well understood. Here we shed light on the specifics of this mechanism by coupling optical characterization methods, mainly wavelength-dependent Stokes and anti-Stokes SERS, with kinetic analysis of photocatalytic reactionsmore » in an Ag nanocube–methylene blue plasmonic system. We propose that localized LSPR-induced electric fields result in a direct charge transfer within the molecule–adsorbate system. Lastly, these observations provide a foundation for the development of plasmonic catalysts that can selectively activate targeted chemical bonds, since the mechanism allows for tuning plasmonic nanomaterials in such a way that illumination can selectively enhance desired chemical pathways.« less

Surface-enhanced Raman for monitoring toxins in water

NASA Astrophysics Data System (ADS)

Spencer, Kevin M.; Sylvia, James M.; Clauson, Susan L.; Bertone, Jane F.; Christesen, Steven D.

2004-02-01

Protection of the drinking water supply from a terrorist attack is of critical importance. Since the water supply is vast, contamination prevention is difficult. Therefore, rapid detection of contaminants, whether a military chemical/biological threat, a hazardous chemical spill, naturally occurring toxins, or bacterial build-up is a priority. The development of rapid environmentally portable and stable monitors that allow continuous monitoring of the water supply is ideal. EIC Laboratories has been developing Surface-Enhanced Raman Spectroscopy (SERS) to detect chemical agents, toxic industrial chemicals (TICs), viruses, cyanotoxins and bacterial agents. SERS is an ideal technique for the Joint Service Agent Water Monitor (JSAWM). SERS uses the enhanced Raman signals observed when an analyte adsorbs to a roughened metal substrate to enable trace detection. Proper development of the metal substrate will optimize the sensitivity and selectivity towards the analytes of interest.

Simultaneous determination of cadmium, lead and mercury ions at trace level by magnetic solid phase extraction with Fe@Ag@Dimercaptobenzene coupled to high performance liquid chromatography.

PubMed

Zhou, Qingxiang; Lei, Man; Liu, Yongli; Wu, Yalin; Yuan, Yongyong

2017-12-01

Pollution resulted from heavy metal ions have absorbed much attention, and it is of great importance to develop sensitive and simultaneous determination method for them with common technologies without highly sensitive instruments. We prepared a new and functional core-shell magnetic nano-material, Fe@Ag@dimercaptobenzene (Fe@Ag@DMB), by a one-step method with sodium borohydride as the reducing agent and transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS) were used for characterisation. The mercapto functional groups on the newly synthesised magnetic nanoparticles could interact with Cd 2+ , Pb 2+ , and Hg 2+ ions in water samples and then efficient extraction for Cd 2+ , Pb 2+ , and Hg 2+ ions was achieved. DDTC-Na solution was a good elutent for elution of these ions from Fe@Ag@DMB nanoparticles. Based on these, a sensitive method was developed for simultaneous preconcentration and determination of the aforementioned ions using magnetic Fe@Ag@DMB nanoparticles as the magnetic solid phase extraction adsorbent prior to high performance liquid chromatography coupled with variable wavelength detection. Under the optimal conditions, the detection limits of the three metal ions were in the range of 0.011-0.031μgL -1 , and precisions were below 2.37% (n=6). The proposed method was evaluated with real water samples, and excellent spiked recoveries achieved indicated that the developed method would be a promising tool for monitoring these heavy metal ions in water samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Generation of Rayleigh waves into mortar and concrete samples.

PubMed

Piwakowski, B; Fnine, Abdelilah; Goueygou, M; Buyle-Bodin, F

2004-04-01

The paper deals with a non-destructive method for characterizing the degraded cover of concrete structures using high-frequency ultrasound. In a preliminary study, the authors emphasized on the interest of using higher frequency Rayleigh waves (within the 0.2-1 MHz frequency band) for on-site inspection of concrete structures with subsurface damage. The present study represents a continuation of the previous work and aims at optimizing the generation and reception of Rayleigh waves into mortar and concrete be means of wedge transducers. This is performed experimentally by checking the influence of the wedge material and coupling agent on the surface wave parameters. The selection of the best combination wedge/coupling is performed by searching separately for the best wedge material and the best coupling material. Three wedge materials and five coupling agents were tested. For each setup the five parameters obtained from the surface wave measurement i.e. the frequency band, the maximal available central frequency, the group velocity error and its standard deviation and finally the error in velocity dispersion characteristic were investigated and classed as a function of the wedge material and the coupling agent. The selection criteria were chosen so as to minimize the absorption of both materials, the randomness of measurements and the systematic error of the group velocity and of dispersion characteristic. Among the three tested wedge materials, Teflon was found to be the best. The investigation on the coupling agent shows that the gel type materials are the best solutions. The "thick" materials displaying higher viscosity were found as the worst. The results show also that the use of a thin plastic film combined with the coupling agent even increases the bandwidth and decreases the uncertainty of measurements.

Cytocompatibility and Mechanical Properties of Short Phosphate Glass Fibre Reinforced Polylactic Acid (PLA) Composites: Effect of Coupling Agent Mediated Interface

PubMed Central

Hasan, Muhammad Sami; Ahmed, Ifty; Parsons, Andrew; Walker, Gavin; Scotchford, Colin

2012-01-01

In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ϕ = 20 µm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent’s within medical implant devices. PMID:24955744

Lateral hopping of CO molecules on Pt(111) surface by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Hayashi, M.; Ootsuka, Y.; Paulsson, M.; Persson, B. N. J.; Ueba, H.

2009-12-01

Theory of heat transfer between adsorbate vibrational degrees of freedom and ultrafast laser heated hot electrons including vibrational intermode coupling is applied to calculate two-pulse correlation, laser fluence dependence and time dependence of lateral hopping of CO molecules from a step to terrace site on a stepped Pt (111) surface. The intermode coupling is a key ingredient to describe vibrational heating of the frustrated translation mode responsible for the CO hopping. The calculated results are in good agreement with the experimental results, especially if we scale down the experimentally determined absorbed fluence. It is found that CO hopping is induced by indirect heating of the FT mode by the FR mode with a strong frictional coupling to hot electrons.

Synthesis of nanoporous TiO2 materials using a doubly surfactant system and applying them as useful adsorbents

NASA Astrophysics Data System (ADS)

Anbia, Mansoor; Khosravi, Faezeh

Hydrothermal and non-hydrothermal nanoporous TiO2 materials were synthesized via a doubly surfactant route by using cationic cetyltrimethylammonium bromide and anionic sodium dodecyl sulfate surfactants as the molecular template/structure directing agent. Hydrothermal treatment was performed for comparison. The bulk chemical and phase compositions, crystalline structures, particle morphologies, thermal stabilities and surface texturing were determined by means of X-ray powder analysis, SEM and N2 sorptiometry. The nanoporous TiO2 materials were found to have a spherical morphology with a diameter range of 50-200 nm and a high surface area (390 m2 g-1). Hydrothermal and non-hydrothermal nanoporous TiO2 materials were applied for adsorption of heavy metal cations and the toxic organic compound, copper phthalocyanine, from water for evaluation of their adsorption properties. Both nanoporous TiO2 materials were found to have similar adsorption capacities toward heavy metal cations and CuPc. Both hydrothermal and non-hydrothermal TiO2 nanoporous materials were found to have very good potential for application as a new adsorbent especially for adsorbing heavy metal cations from wastewaters.

In vitro and in vivo studies to assess the effectiveness of cholestyramine as a binding agent for fumonisins.

PubMed

Solfrizzo, M; Visconti, A; Avantaggiato, G; Torres, A; Chulze, S

2001-01-01

Several adsorbent materials were tested at I mg/ml for their in vitro capacity to adsorb fumonisin B1(FB1) from aqueous solutions. Cholestyramine showed the best adsorption capacity (85% from a solution containing 200 microg/ml FB1) followed by activated carbon (62% FB1). Bentonite adsorbed only 12% of the toxin from a solution containing 13 microg/ml FB1, while celite was not effective even at the lowest tested FB1 concentration (3.2 microg/ml). Cholestyramine was tested in vivo to evaluate its capacity to reduce the bioavailability of fumonisins (FBs) in rats fed diet contaminated with toxigenic Fusarium verticillioides culture material. Rats were exposed for one week to FBs-free diet, FBs-contaminated diet containing 6 or 20 microg/g FB1 + FB2 and the same FBs-contaminated diet added of 20 mg/g cholestyramine. The increase of sphinganine/sphingosine (SA/SO) ratio in urine and kidney of treated rats was used as specific and sensitive biomarker of fumonisin exposure. The addition of cholestyramine to the FBs-contaminated diets consistently reduced the effect of FBs by reducing significantly (P < 0.05) both urinary and renal SA/SO ratios.

Activated carbons as potentially useful non-nutritive additives to prevent the effect of fumonisin B1 on sodium bentonite activity against chronic aflatoxicosis.

PubMed

Monge, María Del Pilar; Magnoli, Alejandra Paola; Bergesio, Maria Virginia; Tancredi, Nestor; Magnoli, Carina E; Chiacchiera, Stella Maris

2016-06-01

Aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are mycotoxins that often co-occur in feedstuffs. The ingestion of AFB1 causes aflatoxicosis in humans and animals. Sodium bentonite (NaB), a cheap non-nutritive unselective sequestering agent incorporated in animal diets, can effectively prevent aflatoxicosis. Fumonisins are responsible for equine leukoencephalomalacia and porcine pulmonary oedema, and often have subclinical toxic effects in poultries. Fumonisin B1 and aflatoxin B1 are both strongly adsorbed in vitro on sodium bentonite. Co-adsorption studies, carried out with a weight ratio of FB1 to AFB1 that mimics the natural occurrence (200:1), showed that FB1 greatly decreases the in vitro ability of NaB to adsorb AFB1. The ability of two activated carbons to adsorb FB1 was also investigated. Both carbons showed high affinity for FB1. A complex behaviour of the FB1 adsorption isotherms with pH was observed. In vitro results suggest that under natural contamination levels of AFB1 and FB1, a mixture of activated carbon and sodium bentonite might be potentially useful for prevention of sub-acute aflatoxicosis.

Evaluation of spacecraft toxic gas removal agents

NASA Technical Reports Server (NTRS)

1972-01-01

A study of the decomposition of various compounds adsorbed on charcoal was made, with a view toward providing a critical appraisal of previous data from charcoal adsorption studies. It was found that thermal decomposition occurs at temperature lower than previously suspected during the charcoal stripping process. A discussion is presented dealing with the various types of reactions found. A rough, quantitative scheme for correcting previous analytical results is developed and presented.

Chemical and Biological Resistant Clothing

DTIC Science & Technology

2013-04-01

for DMMP Measurement (Data from Samples with and without the Addition of Particulate Zeolite Sorbents... zeolite -NaA particles (which is a nanoporous zeolite with composition of [Na12(H2O)27][Al12Si12O48]) as dehydrating agent was added to the solution to...adsorb/remove water from the solution completely. The zeolite had a uniform pore diameter of ~0.41 nm, too small to accommodate DMMP molecules

Process for the preparation of organoclays

DOEpatents

Chaiko, David J.

2004-11-23

A method for preparing organoclays for use as rheological control agents and in the preparation of nanocomposites. Typically, the clay is dispersed in water, and a specific amount of polymeric hydrotrope, ranging from 0.1 to 15 weight percent relative to the weight of the clay, is adsorbed onto the clay surface. Quaternary amine exchange is also performed on the clay to modify the surface hydrophilic/lipophilic balance (HLB) of the clay.

Role of quinones in electron transfer of PQQ–glucose dehydrogenase anodes—mediation or orientation effect

DOE PAGES

Babanova, Sofia; Matanovic, Ivana; Chavez, Madelaine Seow; ...

2015-06-16

In this study, the influence of two quinones (1,2- and 1,4-benzoquinone) on the operation and mechanism of electron transfer in PQQ-sGDH anodes has been determined. Benzoquinones were experimentally explored as mediators present in the electrolyte. The electrochemical performance of the PQQ–sGDH anodes with and without the mediators was examined and for the first time molecular docking simulations were used to gain a fundamental understanding to explain the role of the mediator molecules in the design and operation of the enzymatic electrodes. It was proposed that the higher performance of the PQQ–sGDH anodes in the presence of 1,2- and 1,4-benzoquinones introducedmore » in the solution is due to the shorter distance between these molecules and PQQ in the enzymatic molecule. It was also hypothesized that when 1,4-benzoquinone is adsorbed on a carbon support, it would play the dual role of a mediator and an orienting agent. At the same time, when 1,2-benzoquinone and ubiquinone are adsorbed on the electrode surface, the enzyme would transfer the electrons directly to the support, and these molecules would primarily play the role of an orienting agent.« less

Role of Quinones in Electron Transfer of PQQ–Glucose Dehydrogenase Anodes—Mediation or Orientation Effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babanova, Sofia; Matanovic, Ivana; Chavez, Madelaine Seow

2015-06-24

In this study, the influence of two quinones (1,2- and 1,4-benzoquinone) on the operation and mechanism of electron transfer in PQQ-dependent glucose dehydrogenase (PQQ–sGDH) anodes has been determined. Benzoquinones were experimentally explored as mediators present in the electrolyte. The electrochemical performance of the PQQ–sGDH anodes with and without the mediators was examined and for the first time molecular docking simulations were used to gain a fundamental understanding to explain the role of the mediator molecules in the design and operation of the enzymatic electrodes. It was proposed that the higher performance of the PQQ–sGDH anodes in the presence of 1,2-more » and 1,4-benzoquinones introduced in the solution is due to the shorter distance between these molecules and PQQ in the enzymatic molecule. It was also hypothesized that when 1,4-benzoquinone is adsorbed on a carbon support, it would play the dual role of a mediator and an orienting agent. At the same time, when 1,2-benzoquinone and ubiquinone are adsorbed on the electrode surface, the enzyme would transfer the electrons directly to the support, and these molecules would primarily play the role of an orienting agent.« less

Plexcitonics: Coupled and Plasmon-Exciton Systems with Tailorable Properties

DTIC Science & Technology

2013-11-14

demonstrated efficient steam generation from aqueous nanoparticles solutions without heating the bulk volume of the liquid. Application in ethanol ...solutions without heating the bulk volume of the liquid. Applications in ethanol distillation and sanitation have been demonstrated. Key Accomplishments...nanoparticle surface. This state-selective population of adsorbate resonances could be exploited to prepare reactants in specific states on nanoparticle

Impact of biofibers and coupling agents on the weathering characteristics of composites polymer degradation and stability

USDA-ARS?s Scientific Manuscript database

This paper explores the ultraviolet (UV) weathering performance of high density polyethylene (HDPE) composites with different biofiber fillers and coupling agent. Biofiber polymer composite (BFPC) material samples were prepared using oak, cotton burr and stem (CBS) or guayule bagasse as fiber source...

A first principles investigation of electron transfer between Fe(II) and U(VI) on insulating Al- vs. semiconducting Fe-oxide surfaces via the proximity effect

NASA Astrophysics Data System (ADS)

Taylor, S. D.; Marcano, M. C.; Becker, U.

2017-01-01

This study investigates how the intrinsic chemical and electronic properties of mineral surfaces and their associated electron transfer (ET) pathways influence the reduction of U(VI) by surface-associated Fe(II). Density functional theory (DFT), including the Hubbard U correction to the exchange-correlation functional, was used to investigate sorption/redox reactions and ET mechanisms between Fe(II) and U(VI) coadsorbed on isostructural, periodic (0 0 1) surfaces of the insulator corundum (α-Al2O3) vs. the semiconductor hematite (α-Fe2O3). Furthermore, the coadsorbed Fe(II) and U(VI) ions are spatially separated from one another on the surfaces (⩾5.9 Å) to observe whether electronic-coupling through the semiconducting hematite surface facilitates ET between the adsorbates, a phenomenon known as the proximity effect. The calculations show that the different chemical and electronic properties between the isostructural corundum and hematite (0 0 1) surfaces lead to considerably different ET mechanisms between Fe(II) and U(VI). ET on the insulating corundum (0 0 1) surface is limited by the adsorbates' structural configuration. When Fe(II) and U(VI) are spatially separated and do not directly interact with one another (e.g. via an inner-sphere complex), U(VI) reduction by Fe(II) cannot occur as there is no physical pathway enabling ET between the adsorbates. In contrast to the insulating corundum (0 0 1) surface, the hematite (0 0 1) surface can potentially participate in ET reactions due to the high number of electron acceptor sites from the Fe d-states near the Fermi level at the hematite surface. The adsorption of Fe(II) also introduces d-states near the Fermi level as well as shifts unoccupied d-states of the Fe cations at the hematite surface to lower energies, making the surface more conductive. In turn, electronic coupling through the surface can link the spatially separated adsorbates to one another and provide distinct ET pathways for an electron from Fe(II) to travel through the hematite surface and reach U(VI). The progression and extent of ET occurring on the semiconducting hematite (0 0 1) surface via the proximity effect depends on the electronic properties of the surface. ET between the spatially separated U(VI) and Fe(II) occurs most readily when orbitals between the Fe and U adsorbates overlap with those of neighboring O and Fe ions at the hematite surface, as shown by calculations without the Hubbard U correction. Analyses of the spins densities confirm that the U and Fe adsorbates were reduced and oxidized, respectively, (acquiring 0.33 μB and 0.11-0.20 μB, respectively), while Fe cations at the hematite surface were reduced (losing ⩽0.6 μB). If electrons are highly localized, the amount of orbital mixing and electronic coupling through the hematite surface decreases and in turn leads to a lower degree of spin transfer, as predicted by calculations with the Hubbard U correction. Thus, the proximity effect is a potential mechanism on semiconducting surfaces facilitating surface-mediated redox reactions, although its significance varies depending on the electronic properties and subsequent charge-carrying ability of the surface. These results provide insight into ET pathways and mechanisms on insulating Al- and semiconducting Fe oxide surfaces influencing the reduction U(VI) by Fe(II) that may subsequently limit uranium's transport in the subsurface.

Equilibrium isotherms, kinetics, and thermodynamics studies for congo red adsorption using calcium alginate beads impregnated with nano-goethite.

PubMed

Munagapati, Venkata Subbaiah; Kim, Dong-Su

2017-07-01

The present study is concerned with the batch adsorption of congo red (CR) from an aqueous solution using calcium alginate beads impregnated with nano-goethite (CABI nano-goethite) as an adsorbent. The optimum conditions for CR removal were determined by studying operational variables viz. pH, adsorbent dose, contact time, initial dye ion concentration and temperature. The CABI nano-goethite was characterized by Fourier transform infrared spectroscopy (FTIR), X- ray diffraction (XRD) and Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The CR sorption data onto CABI nano-goethite were described using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm model. The maximum adsorption capacity (181.1mg/g) of CR was occurred at pH 3.0. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CABI nano-goethite. The best desorbing agent was 0.1M NaOH with an efficiency of 94% recovery. The thermodynamic parameters ΔG°, ΔH°, and ΔS° for the CR adsorption were determined by using adsorption capacities at five different temperatures (293, 303, 313, 323 and 303K). Results show that the adsorption process was endothermic and favoured at high temperature. Copyright © 2017 Elsevier Inc. All rights reserved.

[Decorporation agents for internal radioactive contamination].

PubMed

Ohmachi, Yasushi

2015-01-01

When radionuclides are accidentally ingested or inhaled, blood circulation or tissue/organ deposition of the radionuclides causes systemic or local radiation effects. In such cases, decorporation therapy is used to reduce the health risks due to their intake. Decorporation therapy includes reduction and/or inhibition of absorption from the gastrointestinal tract, isotopic dilution, and the use of diuretics, adsorbents, and chelating agents. For example, penicillamine is recommended as a chelating agent for copper contamination, and diethylene triamine pentaacetic acid is approved for the treatment of internal contamination with plutonium. During chelation therapy, the removal effect of the drugs should be monitored using a whole-body counter and/or bioassay. Some authorities, such as the National Council on Radiation Protection and Measurements and International Atomic Energy Agency, have reported recommended decorporation agents for each radionuclide. However, few drugs are approved by the US Food and Drug Administration, and many are off-label-use agents. Because many decontamination agents are drugs that have been available for a long time and have limited efficacy, the development of new, higher-efficacy drugs has been carried out mainly in the USA and France. In this article, in addition to an outline of decorporation agents for internal radioactive contamination, an outline of our research on decorporation agents for actinide (uranium and plutonium) contamination and for radio-cesium contamination is also presented.

Application of insoluble fibers in the fining of wine phenolics.

PubMed

Guerrero, Raúl F; Smith, Paul; Bindon, Keren A

2013-05-08

The application of animal-derived proteins as wine fining agents has been subject to increased regulation in recent years. As an alternative to protein-based fining agents, insoluble plant-derived fibers have the capacity to adsorb red wine tannins. Changes in red wine tannin were analyzed following application of fibers derived from apple and grape and protein-based fining agents. Other changes in wine composition, namely, color, monomeric phenolics, metals, and turbidity, were also determined. Wine tannin was maximally reduced by application of an apple pomace fiber and a grape pomace fiber (G4), removing 42 and 38%, respectively. Potassium caseinate maximally removed 19% of wine tannin, although applied at a lower dose. Fibers reduced anthocyanins, total phenolics, and wine color density, but changes in wine hue were minor. Proteins and apple fiber selectively removed high molecular mass phenolics, whereas grape fibers removed those of both high and low molecular mass. The results show that insoluble fibers may be considered as alternative fining agents for red wines.

Synthesis, characterization and SERS activity of biosynthesized silver nanoparticles

NASA Astrophysics Data System (ADS)

Bindhu, M. R.; Sathe, V.; Umadevi, M.

2013-11-01

Silver nanoparticles were rapidly synthesized using Moringa oleifera flower extract as the reducing agent shows surface plasmon resonance peak at 439 nm. The size and shape of the nanoparticles controlled by varying the concentration of M. oleifera flower extract in the reaction medium. The synthesized silver nanoparticles were well-dispersed spherical nanoparticles with the average size of 14 nm. The retinoic acid present in M. oleifera flower extract used as reducing agent and proteins was responsible for capping of the bioreduced silver nanoparticles. The obtained nanoparticle shows size-dependent SERS activity. The SERS spectrum indicates that the pyridine adsorbed on the silver surface in a stand-on orientation via its nitrogen lone pair electrons.

Design, Synthesis, and Validation of an Effective, Reusable Silicon-Based Transfer Agent for Room-Temperature Pd-Catalyzed Cross-Coupling Reactions of Aryl and Heteroaryl Chlorides with Readily Available Aryl Lithium Reagents

PubMed Central

Martinez-Solorio, Dionicio; Melillo, Bruno; Sanchez, Luis; Liang, Yong; Lam, Erwin; Houk, K. N.; Smith, Amos B.

2016-01-01

A reusable silicon-based transfer agent (1) has been designed, synthesized, and validated for effective room-temperature palladium-catalyzed cross-coupling reactions (CCRs) of aryl and heteroaryl chlorides with readily accessible aryl lithium reagents. The crystalline, bench-stable siloxane transfer agent (1) is easily prepared via a one-step protocol. Importantly, this “green” CCR protocol circumvents prefunctionalization, isolation of organometallic cross-coupling partners, and/or stoichiometric waste aside from LiCl. DFT calculations support a σ-bond metathesis mechanism during transmetalation and lead to insights on the importance of the CF3 groups. PMID:26835838

INFLUENCE NETWORK AGENT EFFECTIVENESS IN PROMOTING COUPLES’ HIV COUNSELING AND TESTING IN KIGALI, RWANDA

PubMed Central

Wall, Kristin; Karita, Etienne; Nizam, Azhar; Bekan, Brigitte; Sardar, Gurkiran; Casanova, Debbie; Joseph, Dvora; De Clercq, Freya; Kestelyn, Evelyne; Bayingana, Roger; Tichacek, Amanda; Allen, Susan

2013-01-01

Objective To identify predictors of promotion of couples’ voluntary counseling and testing (CVCT) in Kigali, Rwanda Design Analysis of CVCT promotional agent (influential network leaders, INLs; influential network agents, INAs), and couple/invitation-level predictors of CVCT uptake. Methods Number of invitations and couples tested were evaluated by INL, INA, and couple/contextual factors. Multivariable logistic regression accounting for two-level clustering analyzed factors predictive of couples’ testing. Results 26 INLs recruited and mentored 118 INAs who delivered 24,991 invitations. 4,513 couples sought CVCT services after invitation. INAs distributed an average of 212 invitations resulting in an average of 38 couples tested/agent. Characteristics predictive of CVCT in multivariate analyses included the invitee and INA being socially acquainted (aOR=1.4;95%CI:1.2–1.6); invitations delivered after public endorsement (aOR=1.3;95%CI:1.1–1.5); and presence of a mobile testing unit (aOR=1.4;95%CI:1.0–2.0). In stratified analyses, predictors significant among cohabiting couples included invitation delivery to the couple (aOR=1.2;95%CI:1.0–1.4) in the home (aOR=1.3;95%CI:1.1–1.4), while among non-cohabiting couples predictors included invitations given by unemployed INAs (aOR=1.7;95%CI:1.1–2.7). Cohabiting couples with older men were more likely to test, while younger age was associated with testing among men in non-cohabiting unions. Conclusions Invitations distributed by influential people were successful in prompting couples to seek joint HIV testing, particularly if the invitation was given in the home to someone known to the INA, and accompanied by a public endorsement of CVCT. Mobile units also increased the number of couples tested. Country-specific strategies to promote CVCT programs are needed to reduce HIV transmission among those at highest risk for HIV in sub-Saharan Africa. PMID:22008653

First-Principles Integrated Adsorption Modeling for Selective Capture of Uranium from Seawater by Polyamidoxime Sorbent Materials

DOE PAGES

Ladshaw, Austin P.; Ivanov, Alexander S.; Das, Sadananda; ...

2018-03-27

Nuclear power is a relatively carbon-free energy source that has the capacity to be utilized today in an effort to stem the tides of global warming. The growing demand for nuclear energy, however, could put significant strain on our uranium ore resources, and the mining activities utilized to extract that ore can leave behind long-term environmental damage. A potential solution to enhance the supply of uranium fuel is to recover uranium from seawater using amidoximated adsorbent fibers. This technology has been studied for decades but is currently plagued by the material’s relatively poor selectivity of uranium over its main competitormore » vanadium. In this work, we investigate the binding schemes between uranium, vanadium, and the amidoxime functional groups on the adsorbent surface. Using quantum chemical methods, binding strengths are approximated for a set of complexation reactions between uranium and vanadium with amidoxime functionalities. Those approximations are then coupled with a comprehensive aqueous adsorption model developed in this work to simulate the adsorption of uranium and vanadium under laboratory conditions. Experimental adsorption studies with uranium and vanadium over a wide pH range are performed, and the data collected are compared against simulation results to validate the model. It was found that coupling ab initio calculations with process level adsorption modeling provides accurate predictions of the adsorption capacity and selectivity of the sorbent materials. Furthermore, this work demonstrates that this multiscale modeling paradigm could be utilized to aid in the selection of superior ligands or ligand compositions for the selective capture of metal ions. Furthermore, this first-principles integrated modeling approach opens the door to the in silico design of next-generation adsorbents with potentially superior efficiency and selectivity for uranium over vanadium in seawater.« less

First-Principles Integrated Adsorption Modeling for Selective Capture of Uranium from Seawater by Polyamidoxime Sorbent Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ladshaw, Austin P.; Ivanov, Alexander S.; Das, Sadananda

Nuclear power is a relatively carbon-free energy source that has the capacity to be utilized today in an effort to stem the tides of global warming. The growing demand for nuclear energy, however, could put significant strain on our uranium ore resources, and the mining activities utilized to extract that ore can leave behind long-term environmental damage. A potential solution to enhance the supply of uranium fuel is to recover uranium from seawater using amidoximated adsorbent fibers. This technology has been studied for decades but is currently plagued by the material’s relatively poor selectivity of uranium over its main competitormore » vanadium. In this work, we investigate the binding schemes between uranium, vanadium, and the amidoxime functional groups on the adsorbent surface. Using quantum chemical methods, binding strengths are approximated for a set of complexation reactions between uranium and vanadium with amidoxime functionalities. Those approximations are then coupled with a comprehensive aqueous adsorption model developed in this work to simulate the adsorption of uranium and vanadium under laboratory conditions. Experimental adsorption studies with uranium and vanadium over a wide pH range are performed, and the data collected are compared against simulation results to validate the model. It was found that coupling ab initio calculations with process level adsorption modeling provides accurate predictions of the adsorption capacity and selectivity of the sorbent materials. Furthermore, this work demonstrates that this multiscale modeling paradigm could be utilized to aid in the selection of superior ligands or ligand compositions for the selective capture of metal ions. Furthermore, this first-principles integrated modeling approach opens the door to the in silico design of next-generation adsorbents with potentially superior efficiency and selectivity for uranium over vanadium in seawater.« less

First-Principles Integrated Adsorption Modeling for Selective Capture of Uranium from Seawater by Polyamidoxime Sorbent Materials.

PubMed

Ladshaw, Austin P; Ivanov, Alexander S; Das, Sadananda; Bryantsev, Vyacheslav S; Tsouris, Costas; Yiacoumi, Sotira

2018-04-18

Nuclear power is a relatively carbon-free energy source that has the capacity to be utilized today in an effort to stem the tides of global warming. The growing demand for nuclear energy, however, could put significant strain on our uranium ore resources, and the mining activities utilized to extract that ore can leave behind long-term environmental damage. A potential solution to enhance the supply of uranium fuel is to recover uranium from seawater using amidoximated adsorbent fibers. This technology has been studied for decades but is currently plagued by the material's relatively poor selectivity of uranium over its main competitor vanadium. In this work, we investigate the binding schemes between uranium, vanadium, and the amidoxime functional groups on the adsorbent surface. Using quantum chemical methods, binding strengths are approximated for a set of complexation reactions between uranium and vanadium with amidoxime functionalities. Those approximations are then coupled with a comprehensive aqueous adsorption model developed in this work to simulate the adsorption of uranium and vanadium under laboratory conditions. Experimental adsorption studies with uranium and vanadium over a wide pH range are performed, and the data collected are compared against simulation results to validate the model. It was found that coupling ab initio calculations with process level adsorption modeling provides accurate predictions of the adsorption capacity and selectivity of the sorbent materials. Furthermore, this work demonstrates that this multiscale modeling paradigm could be utilized to aid in the selection of superior ligands or ligand compositions for the selective capture of metal ions. Therefore, this first-principles integrated modeling approach opens the door to the in silico design of next-generation adsorbents with potentially superior efficiency and selectivity for uranium over vanadium in seawater.

Influence of additional coupling agent on the mechanical properties of polyester–agave cantala roxb based composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ubaidillah, E-mail: ubaidillah@uns.ac.id; Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Jalan Sultan Yahya Petra, Kuala Lumpur; Raharjo, Wijang W.

The mechanical and morphological properties of the unsaturated polyester resins (UPRs)-agave cantala roxb based composite are investigated in this paper. The cantala fiber woven in 3D angle interlock was utilized as the composite reinforcement. Surface grafting of the cantala fiber through chemical treatment was performed by introducing silane coupling agent to improving the compatibility with the polymer matrix. The fabrication of the composite specimens was conducted using vacuum bagging technique. The effect of additional coupling agent to the morphological appearance of surface fracture was observed using scanning electron microscopy. Meanwhile, the influence of additional silane to the mechanical properties wasmore » examined using tensile, bending and impact test. The photograph of surface fracture on the treated specimens showed the residual matrix left on the fibers in which the phenomenon was not found in the untreated specimens. Based on mechanical tests, the treated specimens were successfully increased their mechanical properties by 55%, 9.67%, and 92.4% for tensile strength, flexural strength, and impact strength, respectively, at 1.5% silane coupling agent.« less

Density functional theory study of adsorption geometries and electronic structures of azo-dye-based molecules on anatase TiO2 surface for dye-sensitized solar cell applications.

PubMed

Prajongtat, Pongthep; Suramitr, Songwut; Nokbin, Somkiat; Nakajima, Koichi; Mitsuke, Koichiro; Hannongbua, Supa

2017-09-01

Structural and electronic properties of eight isolated azo dyes (ArNNAr', where Ar and Ar' denote the aryl groups containing benzene and naphthalene skeletons, respectively) were investigated by density functional theory (DFT) based on the B3LYP/6-31G(d,p) and TD-B3LYP/6-311G(d,p) methods The effect of methanol solvent on the structural and electronic properties of the azo dyes was elucidated by employing a polarizable continuum model (PCM). Then, the azo dyes adsorbed onto the anatase TiO 2 (101) slab surface through a carboxyl group. The geometries and electronic structures of the adsorption complexes were determined using periodic DFT based on the PWC/DNP method. The calculated adsorption energies indicate that the adsorbed dyes preferentially take configuration of the bidentate bridging rather than chelating or monodentate ester-type geometries. Furthermore, the azo compounds having two carboxyl groups are coordinated to the TiO 2 surface more preferentially through the carboxyl group connecting to the benzene skeleton than through that connecting to the naphthalene skeleton. The dihedral angles (Φ B-N ) between the benzene- and naphthalene-skeleton moieties are smaller than 10° for the adsorbed azo compounds containing one carboxyl group. In contrast, Φ B-N > 30° are obtained for the adsorbed azo compounds containing two carboxyl groups. The almost planar conformations of the former appear to strengthen both π-electrons conjugation and electronic coupling between low-lying unoccupied molecular orbitals of the azo dyes and the conduction band of TiO 2 . On the other hand, such coupling is very weak for the latter, leading to a shift of the Fermi level of TiO 2 in the lower-energy direction. The obtained results are useful to the design and synthesize novel azo-dye-based molecules that give rise to higher photovoltaic performances of the dye-sensitized solar cells. Copyright © 2017 Elsevier Inc. All rights reserved.

Preparation, characterization and application of Saussurea tridactyla Sch-Bip as green adsorbents for preconcentration of rare earth elements in environmental water samples

NASA Astrophysics Data System (ADS)

Zhang, Qiangying; He, Man; Chen, Beibei; Hu, Bin

2016-07-01

This paper deals with preparation, characterization and application of the Saussurea tridactyla Sch-Bip (STSB) as a new green adsorbent for separation of matrix elements and preconcentration of rare earth elements (REEs) in environmental water samples. The pretreated STSB adsorbent with 2 mol L- 1 NaOH is characterized with higher surface area and adsorption capacities in comparison with a raw STSB material. The new adsorbent was used for the development of on-line solid phase extraction (SPE) for the determination of REEs by radial viewing 27 MHz inductively coupled plasma optical emission spectrometry (ICP-OES). Various parameters affecting the adsorption/desorption procedure were optimized. The adsorption capacities for the STSB were found to be 62.2 (Y)-153 mg g- 1 (Tm). Under the optimized conditions, the limits of detection (LODs, 3σ) for REEs were in the range of 0.06 (Yb)-8.77 (Sm) ng mL- 1. The relative standard deviations (RSDs) for 7 replicate determinations of target REEs at low concentration level ranged from 2.4 (Yb) to 8.9 (Sm)%. The adsorption isotherm fitted Langmuir model and the adsorption kinetics fitted well with both Pseudo-first order and Pseudo-second order models. The predominant adsorption mechanism is ion exchange. The STSB pretreated with 2 mol L- 1 NaOH has been demonstrated to be low cost, green and environment friendly adsorbent, featuring with high adsorption capacity, wide pH range, and fast adsorption/desorption kinetics for target REEs with long lifetime. The proposed method was applied to the determination of REEs in East Lake, Yangtze River and rain water samples.

Exploring the core level shift origin of sulfur and thiolates on Pd(111) surfaces.

PubMed

Salvarezza, Roberto Carlos; Carro, Pilar

2015-10-07

Thiol molecules on planar metal surfaces are widely used for building sensing and electronic devices and also as capping agents to protect and to control the size and shape of nanoparticles. In the case of Pd the thiol molecules exhibit a complex behavior because C-S bond scission is possible, resulting in a significant amount of co-adsorbed S. Therefore identification of these species on Pd is a key point for many applications, a task that is usually achieved by XPS. Here we show, from DFT calculations, that the core level shift (CLS) of the S 2p binding energy (BE) of thiol and sulfur on different thiol-Pd(111) surface models strongly depends on the adsorbed or subsurface state of sulfur atoms. Our results reflect the complexity of S 2p BE behavior and contribute to understanding and reanalyzing the experimental data of thiolated Pd surfaces.

Studies on desorption and regeneration of natural pumice for iron removal from aqueous solution.

PubMed

Indah, S; Helard, D; Binuwara, A

2018-05-01

To make the adsorption process more economic and environmental friendly, it is necessary to study desorption and reutilization of the adsorbents. In the present study, the effectiveness of natural pumice in removal of iron from aqueous solution was investigated in several sorption-desorption cycles. The desorption characteristics of previously adsorbed iron ions on natural pumice were tested by various desorbing agents such as HCl, NaOH and aquadest. Among them, HCl showed the highest desorption efficiency (37.89%) with 0.1 M of concentration and 60 min of contact time. The removal efficiency of iron ions in reused natural pumice could be maintained up to 90% in the third cycle of adsorption. The results indicate that although complete desorption was not achieved, natural pumice from Sungai Pasak, West Sumatra, Indonesia, can be sufficiently reused up to three cycles of adsorption-desorption.

Studies on adsorption capacity of clay-Sargassum sp biosorbent for Cr (VI) removal in wastewater from electroplating industry

NASA Astrophysics Data System (ADS)

Aprianti, Tine; Aprilyanti, Selvia; Apriani, Rachmawati; Sisnayati

2017-11-01

Various raw biosorbents have been studied for pollutant treatment of heavy metals contained in wastewater. In this study, clay and brown seaweed, Sargassum sp, are used for hexavalent chromium [Cr (VI)] biosorption. The adsorption capacity is adequately improved by combining clay and Sargassum sp as the adsorbent agent. Ion exchange of metal ions has shown strong coordination cross-linkage due to organic functional hydroxyl groups (OH-) contained in brown seaweed that provide sites to capture and bind the metal ions. Clay is known as an inexpensive adsorbent due to its wide availability besides its large specific surface area. Combining clay and Sargassum sp as biosorbent resulting better adsorption, the adsorption capacity reaches most favorable results of 99.39% at Sargassum: clay ratio of 40:60 on contact time 10 h. This study has proven that composit biosorbent used has succeeded in reducing hexavalent chromium pollutant in wastewater.

Connection adaption for control of networked mobile chaotic agents.

PubMed

Zhou, Jie; Zou, Yong; Guan, Shuguang; Liu, Zonghua; Xiao, Gaoxi; Boccaletti, S

2017-11-22

In this paper, we propose a strategy for the control of mobile chaotic oscillators by adaptively rewiring connections between nearby agents with local information. In contrast to the dominant adaptive control schemes where coupling strength is adjusted continuously according to the states of the oscillators, our method does not request adaption of coupling strength. As the resulting interaction structure generated by this proposed strategy is strongly related to unidirectional chains, by investigating synchronization property of unidirectional chains, we reveal that there exists a certain coupling range in which the agents could be controlled regardless of the length of the chain. This feature enables the adaptive strategy to control the mobile oscillators regardless of their moving speed. Compared with existing adaptive control strategies for networked mobile agents, our proposed strategy is simpler for implementation where the resulting interaction networks are kept unweighted at all time.

Efficacy and safety testing of mycotoxin-detoxifying agents in broilers following the European Food Safety Authority guidelines.

PubMed

Osselaere, A; Devreese, M; Watteyn, A; Vandenbroucke, V; Goossens, J; Hautekiet, V; Eeckhout, M; De Saeger, S; De Baere, S; De Backer, P; Croubels, S

2012-08-01

Contamination of feeds with mycotoxins is a worldwide problem and mycotoxin-detoxifying agents are used to decrease their negative effect. The European Food Safety Authority recently stated guidelines and end-points for the efficacy testing of detoxifiers. Our study revealed that plasma concentrations of deoxynivalenol and deepoxy-deoxynivalenol were too low to assess efficacy of 2 commercially available mycotoxin-detoxifying agents against deoxynivalenol after 3 wk of continuous feeding of this mycotoxin at concentrations of 2.44±0.70 mg/kg of feed and 7.54±2.20 mg/kg of feed in broilers. This correlates with the poor absorption of deoxynivalenol in poultry. A safety study with 2 commercially available detoxifying agents and veterinary drugs showed innovative results with regard to the pharmacokinetics of 2 antibiotics after oral dosing in the drinking water. The plasma and kidney tissue concentrations of oxytetracycline were significantly higher in broilers receiving a biotransforming agent in the feed compared with control birds. For amoxicillin, the plasma concentrations were significantly higher for broilers receiving an adsorbing agent in comparison to birds receiving the biotransforming agent, but not to the control group. Mycotoxin-detoxifying agents can thus interact with the oral bioavailability of antibiotics depending on the antibiotic and detoxifying agent, with possible adverse effects on the health of animals and humans.

Water Transport in Bicontinuous, Phase-Separated Membranes Made from Reactive Block Copolymers

DTIC Science & Technology

2014-12-01

polyurethane foam impregnated with activated carbon, a design that allows perspiration to evaporate while chemical agents are adsorbed onto the activated... dispersed into a minimal volume (4–5 drops) of ethanol. The catalyst solution was then added to the polymer solution while stirring rapidly. The solution...substituted styrene monomer; one interior block with units of other styrene monomers which have been sulfonated; non- dispersible and solid in water

Annual Report 2013-2014: Theoretical Studies of Nerve Agents Adsorbed on Surfaces

DTIC Science & Technology

2014-07-08

of the solvation of sarin by water are underway. The results should clarify how water affects desorption properties and the extent of solvation of...platinum activated nanocrystalline ZnO thick films. Sensors and Actuators B-Chemical 2012, 161, 372- 380. 5. Bermudez, V. M., Computational Study of...Rauk, A.; Shishkov, I. F.; Vilkov, L. V.; Koehler, K. F.; Kostyanovsky, R. G., DETERMINATION OF THE STRUCTURE AND CHIROPTICAL PROPERTIES OF THE

Metal and Oxide Additives as Agents for Munitions Self-Remediation

DTIC Science & Technology

2010-07-01

properties of TiO2 can be modified by adding various dopants which serve to expand the range of light energy adsorbed into the visible part of the...spectrum. Photocatalyst development is an extremely active area of research with respect to both substrate and dopant . The selection of an anatase...based photocatalyst is largely due to its established dominance and chemical stability (Diebold 2003). Tungsten trioxide (WO3) is one of many dopants

Mixed reality framework for collective motion patterns of swarms with delay coupling

NASA Astrophysics Data System (ADS)

Szwaykowska, Klementyna; Schwartz, Ira

The formation of coherent patterns in swarms of interacting self-propelled autonomous agents is an important subject for many applications within the field of distributed robotic systems. However, there are significant logistical challenges associated with testing fully distributed systems in real-world settings. In this paper, we provide a rigorous theoretical justification for the use of mixed-reality experiments as a stepping stone to fully physical testing of distributed robotic systems. We also model and experimentally realize a mixed-reality large-scale swarm of delay-coupled agents. Our analyses, assuming agents communicating over an Erdos-Renyi network, demonstrate the existence of stable coherent patterns that can be achieved only with delay coupling and that are robust to decreasing network connectivity and heterogeneity in agent dynamics. We show how the bifurcation structure for emergence of different patterns changes with heterogeneity in agent acceleration capabilities and limited connectivity in the network as a function of coupling strength and delay. Our results are verified through simulation as well as preliminary experimental results of delay-induced pattern formation in a mixed-reality swarm. K. S. was a National Research Council postdoctoral fellow. I.B.S was supported by the U.S. Naval Research Laboratory funding (N0001414WX00023) and office of Naval Research (N0001414WX20610).

Textile/metal-organic-framework composites as self-detoxifying filters for chemical-warfare agents.

PubMed

López-Maya, Elena; Montoro, Carmen; Rodríguez-Albelo, L Marleny; Aznar Cervantes, Salvador D; Lozano-Pérez, A Abel; Cenís, José Luis; Barea, Elisa; Navarro, Jorge A R

2015-06-01

The current technology of air-filtration materials for protection against highly toxic chemicals, that is, chemical-warfare agents, is mainly based on the broad and effective adsorptive properties of hydrophobic activated carbons. However, adsorption does not prevent these materials from behaving as secondary emitters once they are contaminated. Thus, the development of efficient self-cleaning filters is of high interest. Herein, we report how we can take advantage of the improved phosphotriesterase catalytic activity of lithium alkoxide doped zirconium(IV) metal-organic framework (MOF) materials to develop advanced self-detoxifying adsorbents of chemical-warfare agents containing hydrolysable P-F, P-O, and C-Cl bonds. Moreover, we also show that it is possible to integrate these materials onto textiles, thereby combining air-permeation properties of the textiles with the self-detoxifying properties of the MOF material. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of hexavalent chromium on modified corn stalk using different cross-linking agents

NASA Astrophysics Data System (ADS)

Chen, Suhong; Zhu, Yi; Han, Zhijun; Feng, Gao; Jia, Yuling; Fu, Kaifang; Yue, Qinyan

2017-12-01

In this study, four different types of adsorbents modified from corn stalk were synthesized after the reaction with epichlorohydrin, N,N-dimethylformamide, triethylamine and different cross-linking agents. The surface functional groups and thermal stability of modified corn stalk (MCSs) were characterized using FTIR and TG analysis, respectively. The feasibility of using MCSs to remove Cr(VI) were evaluated. Adsorption isotherms were determined and modeled with Langmuir, Freundlich and Temkin equations. The experimental results showed that MCS modified using diethylenetriamine (DETA) had the best modification effect, and the adsorption capacity of Cr(VI) reached as high as 227.27 mg/g at 323 K. Thermodynamic study showed that the Cr(VI) adsorption onto MCSs was endothermic processes. As a result, MCS by using DETA as cross-linking agent has good potential for the removal of Cr(VI) from aqueous solutions.

Corrosion protection of galvanized steels by silane-based treatments

NASA Astrophysics Data System (ADS)

Yuan, Wei

The possibility of using silane coupling agents as replacements for chromate treatments was investigated on galvanized steel substrates. In order to understand the influence of deposition parameters on silane film formation, pure zinc substrates were first used as a model for galvanized steel to study the interaction between silane coupling agents and zinc surfaces. The silane films formed on pure zinc substrates from aqueous solutions were characterized by ellipsometry, contact angle measurements, reflection absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. The deposition parameters studied include solution concentration, solution dipping time and pH value of the applied solution. It appears that silane film formation involved a true equilibrium of hydrolysis and condensation reactions in aqueous solutions. It has been found that the silane film thickness obtained depends primarily on the solution concentration and is almost independent of the solution dipping time. The molecular orientation of applied silane films is determined by the pH value of applied silane solutions and the isoelectric point of metal substrates. The deposition window in terms of pH value for zinc substrates is between 6.0 and 9.0. The total surface energy of the silane-coated pure zinc substrates decreases with film aging time, the decrease rate, however, is determined by the nature of silane coupling agents. Selected silane coupling agents were applied as prepaint or passivation treatments onto galvanized steel substrates. The corrosion protection provided by these silane-based treatments were evaluated by salt spray test, cyclic corrosion test, electrochemical impedance spectroscopy, and stack test. The results showed that silane coupling agents can possibly be used to replace chromates for corrosion control of galvanized steel substrates. Silane coatings provided by these silane treatments serve mainly as physical barriers. Factors that affect the performance of a silane coupling agent in the application of corrosion control include chemical reactivity, hydrophobic character, siloxane crosslinker network, and film thickness. Good protections afforded by the silane treatments are a synergetic effect of all these factors.

TiO2 film/Cu2O microgrid heterojunction with photocatalytic activity under solar light irradiation.

PubMed

Zhang, Junying; Zhu, Hailing; Zheng, Shukai; Pan, Feng; Wang, Tianmin

2009-10-01

Coupling a narrow-band-gap semiconductor with TiO(2) is an effective method to produce photocatalysts that work under UV-vis light irradiation. Usually photocatalytic coupled-semiconductors exist mainly as powders, and photocatalytic activity is only favored when a small loading amount of narrow-band-gap semiconductor is used. Here we propose a heavy-loading photocatalyst configuration in which 51% of the surface of the TiO(2) film is covered by a Cu(2)O microgrid. The coupled system shows higher photocatalytic activity under solar light irradiation than TiO(2) and Cu(2)O films. This improved performance is due to the efficient charge transfer between the two phases and the similar opportunity each has to be exposed to irradiation and adsorbates.

Self-actuating heat switches for redundant refrigeration systems

NASA Technical Reports Server (NTRS)

Chan, Chung K. (Inventor)

1988-01-01

A dual refrigeration system for cooling a sink device is described, which automatically thermally couples the cold refrigerator to the sink device while thermally isolating the warm refrigerator from the sink device. The system includes two gas gap heat switches that each thermally couples one of the refrigerators to the sink device, and a pair of sorption pumps that are coupled through tubes to the heat switches. When the first refrigerator is operated and therefore cold, the first pump which is thermally coupled to it is also cooled and adsorbs gas to withdraw it from the second heat switch, to thereby thermally isolate the sink device from the warm second refrigerator. With the second refrigerator being warm, the second pump is also warm and desorbs gas, so the gas lies in the first switch, to close that switch and therefore thermally couple the cold first refrigerator to the sink device. Thus, the heat switches are automatically switched according to the temperature of the corresponding refrigerator.

Self bleaching photoelectrochemical-electrochromic device

DOEpatents

Bechinger, Clemens S.; Gregg, Brian A.

2002-04-09

A photoelectrochemical-electrochromic device comprising a first transparent electrode and a second transparent electrode in parallel, spaced relation to each other. The first transparent electrode is electrically connected to the second transparent electrode. An electrochromic material is applied to the first transparent electrode and a nanoporous semiconductor film having a dye adsorbed therein is applied to the second transparent electrode. An electrolyte layer contacts the electrochromic material and the nanoporous semiconductor film. The electrolyte layer has a redox couple whereby upon application of light, the nanoporous semiconductor layer dye absorbs the light and the redox couple oxidizes producing an electric field across the device modulating the effective light transmittance through the device.

Transcrystalline interphases in natural fiber-PP composites: effect of coupling agent

Treesearch

A.R. Sanadi; D.F. Caulfield

2000-01-01

The interest in lignocellulosic fiber composites has been growing in recent years because of their high specific properties. In this work, a new technique was used to prepare specimen to observe the transcrystalline zones in kenaf fiber-polypropylene composites. A maleated polypropylene (MAPP) coupling agent was used to improve the stress-transfer efficiency in the...

Improvements to hydroxymethylated resorcinol coupling agent for durable bonding to wood

Treesearch

Alfred W. Christiansen; E. Arnold Okkonen

2003-01-01

Improving the exterior quality bonding of wood to epoxy adhesive resins is important for bonding glass-fiber-reinforced vinyl ester resin laminae to glulam structural members, as well as for repairing glulam members in exterior applications on site. The coupling agent for these applications, hydroxymethylated resorcinol (HMR), was recently improved by using a novolak...

Progress in using hydroxymethylated resorcinol coupling agent to improve bond durability to wood

Treesearch

Alfred W. Christiansen

2001-01-01

In the mid-1990s, researchers at the Forest Products Laboratory developed a coupling agent, hydroxymethylated resorcinol (HMR), that has the ability to enhance adhesive bonds between wood and nontraditional adhesives (Vick and others 1995, 1996). HMR is also effective in promoting durable bonding of phenol-resorcinol- formaldehyde (PRF) adhesives to CCA-treated...

A Coupled Simulation Architecture for Agent-Based/Geohydrological Modelling

NASA Astrophysics Data System (ADS)

Jaxa-Rozen, M.

2016-12-01

The quantitative modelling of social-ecological systems can provide useful insights into the interplay between social and environmental processes, and their impact on emergent system dynamics. However, such models should acknowledge the complexity and uncertainty of both of the underlying subsystems. For instance, the agent-based models which are increasingly popular for groundwater management studies can be made more useful by directly accounting for the hydrological processes which drive environmental outcomes. Conversely, conventional environmental models can benefit from an agent-based depiction of the feedbacks and heuristics which influence the decisions of groundwater users. From this perspective, this work describes a Python-based software architecture which couples the popular NetLogo agent-based platform with the MODFLOW/SEAWAT geohydrological modelling environment. This approach enables users to implement agent-based models in NetLogo's user-friendly platform, while benefiting from the full capabilities of MODFLOW/SEAWAT packages or reusing existing geohydrological models. The software architecture is based on the pyNetLogo connector, which provides an interface between the NetLogo agent-based modelling software and the Python programming language. This functionality is then extended and combined with Python's object-oriented features, to design a simulation architecture which couples NetLogo with MODFLOW/SEAWAT through the FloPy library (Bakker et al., 2016). The Python programming language also provides access to a range of external packages which can be used for testing and analysing the coupled models, which is illustrated for an application of Aquifer Thermal Energy Storage (ATES).

Enzymatic functionalization of cork surface with antimicrobial hybrid biopolymer/silver nanoparticles.

PubMed

Francesko, Antonio; Blandón, Lucas; Vázquez, Mario; Petkova, Petya; Morató, Jordi; Pfeifer, Annett; Heinze, Thomas; Mendoza, Ernest; Tzanov, Tzanko

2015-05-13

Laccase-assisted assembling of hybrid biopolymer-silver nanoparticles and cork matrices into an antimicrobial material with potential for water remediation is herein described. Amino-functional biopolymers were first used as doping agents to stabilize concentrated colloidal dispersions of silver nanoparticles (AgNP), additionally providing the particles with functionalities for covalent immobilization onto cork to impart a durable antibacterial effect. The solvent-free AgNP synthesis by chemical reduction was carried out in the presence of chitosan (CS) or 6-deoxy-6-(ω-aminoethyl) aminocellulose (AC), leading to simultaneous AgNP biofunctionalization. This approach resulted in concentrated hybrid NP dispersion stable to aggregation and with hydrodynamic radius of particles of about 250 nm. Moreover, laccase enabled coupling between the phenolic groups in cork and amino moieties in the biopolymer-doped AgNP for permanent modification of the material. The antibacterial efficiency of the functionalized cork matrices, aimed as adsorbents for wastewater treatment, was evaluated against Escherichia coli and Staphylococcus aureus during 5 days in conditions mimicking those in constructed wetlands. Both intrinsically antimicrobial CS and AC contributed to the bactericidal effect of the enzymatically grafted on cork AgNP. In contrast, unmodified AgNP were easily washed off from the material, confirming that the biopolymers potentiated a durable antibacterial functionalization of the cork matrices.

Determination of malachite green in fish based on magnetic molecularly imprinted polymer extraction followed by electrochemiluminescence.

PubMed

Huang, Baomei; Zhou, Xibin; Chen, Jing; Wu, Guofan; Lu, Xiaoquan

2015-09-01

A novel procedure for selective extraction of malachite green (MG) from fish samples was set up by using magnetic molecularly imprinted polymers (MMIP) as the solid phase extraction material followed by electrochemiluminescence (ECL) determination. MMIP was prepared by using Fe3O4 magnetite as magnetic component, MG as template molecule, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent. MMIP was characterized by SEM, TEM, FT-IR, VSM and XRD. Leucomalachite green (LMG) was oxidized in situ to MG by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). And then MMIP was successfully used to selectively enrich MG from fish samples. Adsorbed MG was desorbed and determined by ECL. Under the optimal conditions, calibration curve was good linear in the range of 0.29-290 μg/kg and the limit of detection (LOD) was 7.3 ng/kg (S/N=3). The recoveries of MMIP extraction were 77.1-101.2%. In addition, MMIP could be regenerated. To the best of our knowledge, MMIP coupling with ECL quenching of Ru(bpy)3(2+)/TPA for the determination of MG has not yet been developed. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Surface-Modified TiO2 Nanoparticles on the Anti-Ultraviolet Aging Performance of Foamed Wheat Straw Fiber/Polypropylene Composites

PubMed Central

Xuan, Lihui; Han, Guangping; Wang, Dong; Cheng, Wanli; Gao, Xun; Chen, Feng; Li, Qingde

2017-01-01

Surface modification and characterization of titanium dioxide (TiO2) nanoparticles and their roles in thermal, mechanical, and accelerated aging behavior of foamed wheat straw fiber/polypropylene (PP) composites are investigated. To improve the dispersion of nanoparticles and increase the possible interactions between wheat straw fiber and the PP matrix, the surface of the TiO2 nanoparticles was modified with ethenyltrimethoxy silane (A171), a silane coupling agent. The grafting of A171 on the TiO2 nanoparticles’ surface was characterized by Fourier transform infrared spectroscopy (FTIR). The wheat straw fibers treated with A171 and modified TiO2 nanoparticles were characterized by FTIR and thermogravimetric analysis (TGA). FTIR spectra confirmed that the organic functional groups of A171 were successfully grafted onto the TiO2 nanoparticles and wheat straw fibers, and the modified TiO2 nanoparticles were adsorbed onto the wheat straw fibers. Thermogravimetric analysis showed that a higher thermal stability of the wheat straw fiber was obtained with the modified TiO2 nanoparticles. The flexural, tensile, and impact properties were improved. A higher ultraviolet (UV) stability of the samples treated with modified TiO2 nanoparticles was exhibited by the study of the color change and loss in mechanical properties. PMID:28772816

Ortho and para hydrogen dimers on G/SiC(0001): combined STM and DFT study.

PubMed

Merino, P; Švec, M; Martínez, J I; Mutombo, P; Gonzalez, C; Martín-Gago, J A; de Andres, P L; Jelinek, P

2015-01-01

The hydrogen (H) dimer structures formed upon room-temperature H adsorption on single layer graphene (SLG) grown on SiC(0001) are addressed using a combined theoretical-experimental approach. Our study includes density functional theory (DFT) calculations for the full (6√3 × 6√3)R30° unit cell of the SLG/SiC(0001) substrate and atomically resolved scanning tunneling microscopy images determining simultaneously the graphene lattice and the internal structure of the H adsorbates. We show that H atoms normally group in chemisorbed coupled structures of different sizes and orientations. We make an atomic scale determination of the most stable experimental geometries, the small dimers and ellipsoid-shaped features, and we assign them to hydrogen adsorbed in para dimers and ortho dimers configuration, respectively, through comparison with the theory.

Immunopotentiating reconstituted influenza virus virosome vaccine delivery system for immunization against hepatitis A.

PubMed Central

Glück, R; Mischler, R; Brantschen, S; Just, M; Althaus, B; Cryz, S J

1992-01-01

Hepatitis A virus (HAV) was purified from MRC-5 human diploid cell cultures, inactivated with formalin, and evaluated for safety and immunogenicity in humans. Three vaccine formulations were produced: (a) a fluid preparation containing inactivated HAV, (b) inactivated HAV adsorbed to Al(OH)3, and (c) inactivated HAV coupled to novel immunopotentiating reconstituted influenza virosomes (IRIV). IRIV were prepared by combining phosphatidylcholine, phosphatidylethanolamine, phospholipids originating from the influenza virus envelope, influenza virus hemagglutinin, and neuraminidase. The HAV-IRIV appeared as unilamellar vesicles with a diameter of approximately 150 nm when viewed by transmission electron microscopy. Upon intramuscular injection, the alum-adsorbed vaccine was associated with significantly (P < 0.01) more local adverse reactions than either the fluid or IRIV formulations. 14 d after a single dose of vaccine, all the recipients of the IRIV formulation seroconverted (> or = 20 mIU/ml) versus 30 and 44% for those who received the fluid and alum-adsorbed vaccines, respectively (P < 0.001). The geometric mean anti-HAV antibody titer achieved after immunization with the IRIV-HAV vaccine was also significantly higher (P < 0.005) compared with the other two vaccines. Images PMID:1334977

A Lectin Purified from Blood Red Bracket Mushroom, Pycnoporus sanguineus (Agaricomycetidae), Mycelium Displayed Affinity Toward Bovine Transferrin.

PubMed

Albores, Silvana; Moros, Maria; Cerdeiras, Maria Pia; de la Fuente, Jesus Martinez; Grazu, Valeria; Fraguas, Laura Franco

2016-01-01

Fungal lectins constitute excellent ligands for development of affinity adsorbents useful in affinity chromatography. In this work, a lectin was purified from Pycnoporus sanguineus (PSL) mycelium using 3 procedures: by affinity chromatography, using magnetic galactosyl-nanoparticles or galactose coupled to Sepharose, and by ionic exchange chromatography (IEC). The highest lectin yield was achieved by IEC (55%); SDS-PAGE of PSL showed 2 bands with molecular mass of 68.7 and 55.2 kDa and IEC displayed 2 bands at pi 5.5 and 5.2. The lectin agglutinates rat erythrocytes, exhibiting broad specificity toward several monosaccharides, including galactose. The agglutination was also inhibited by the glycoproteins fetal calf fetuin, bovine lactoferrin, bovine transferrin, and horseradish peroxidase. The lectin was then used to synthesize an affinity adsorbent (PSL-Sepharose) and the interaction with glycoproteins was evaluated by analyzing their chromatographic behaviors. The strongest interaction with the PSL-derivative was observed with transferrin, although lower interactions were also displayed toward fetuin and lactoferrin. These results indicate that the purified PSL constitutes an interesting ligand for the design of affinity adsorbents to be used (i.e., in glycoprotein purification).

An Evaluation of Technology to Remove Problematic Organic Compounds from the International Space Station Potable Water

NASA Technical Reports Server (NTRS)

Rector, Tony; Metselaar, Carol; Peyton, Barbara; Steele, John; Michalek, William; Bowman, Elizabeth; Wilson, Mark; Gazda, Daniel; Carter, Layne

2014-01-01

Since activation of the Water Processor Assembly (WPA) on the International Space Station (ISS) in November of 2008, there have been three events in which the TOC (Total Organic Carbon) in the product water has increased to approximately 3 mg/L and has subsequently recovered. Analysis of the product water in 2010 identified the primary component of the TOC as dimethylsilanediol (DMSD). An investigation into the fate of DMSD in the WPA ultimately determined that replacement of both Multifiltration (MF) Beds is the solution to recovering product water quality. The MF Beds were designed to ensure that ionic breakthrough occurs before organic breakthrough. However, DMSD saturated both MF Beds in the series, requiring removal and replacement of both MF Beds with significant life remaining. Analysis of the MF Beds determined that the adsorbent was not effectively removing DMSD, trimethylsilanol, various polydimethylsiloxanes, or dimethylsulfone. Coupled with the fact that the current adsorbent is now obsolete, the authors evaluated various media to identify a replacement adsorbent as well as media with greater capacity for these problematic organic contaminants. This paper provides the results and recommendations of this collaborative study.

A molecular model for cohesive slip at polymer melt/solid interfaces.

PubMed

Tchesnokov, M A; Molenaar, J; Slot, J J M; Stepanyan, R

2005-06-01

A molecular model is proposed which predicts wall slip by disentanglement of polymer chains adsorbed on a wall from those in the polymer bulk. The dynamics of the near-wall boundary layer is found to be governed by a nonlinear equation of motion, which accounts for such mechanisms on surface chains as convection, retraction, constraint release, and thermal fluctuations. This equation is valid over a wide range of grafting regimes, including those in which interactions between neighboring adsorbed molecules become essential. It is not closed since the dynamics of adsorbed chains is shown to be coupled to that of polymer chains in the bulk via constraint release. The constitutive equations for the layer and bulk, together with continuity of stress and velocity, are found to form a closed system of equations which governs the dynamics of the whole "bulk+boundary layer" ensemble. Its solution provides a stick-slip law in terms of the molecular parameters and extruder geometry. The model is quantitative and contains only those parameters that can be measured directly, or extracted from independent rheological measurements. The model predictions show a good agreement with available experimental data.

Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics.

PubMed

Anirudhan, T S; Divya, L; Suchithra, P S

2009-01-01

This study investigated the feasibility of using a new adsorbent prepared from coconut coir pith, CP (a coir industry-based lignocellulosic residue), for the removal of uranium [U(VI)] from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto CP using potassium peroxydisulphate-sodium thiosulphite as a redox initiator and in the presence of N,N'-methylenebisacrylamide as a crosslinking agent. IR spectroscopy results confirm the graft copolymer formation and carboxylate functionalization. XRD studies confirm the decrease of crystallinity in PGCP-COOH compared to CP, and it favors the protrusion of the functional group into the aqueous medium. The thermal stability of the samples was studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was determined using potentiometric titration. The ability of PGCP-COOH to remove U(VI) from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at the pH range 4.0-6.0. Maximum removal of 99.2% was observed for an initial concentration of 25mg/L at pH 6.0 and an adsorbent dose of 2g/L. Equilibrium was achieved in approximately 3h. The experimental kinetic data were analyzed using a first-order kinetic model. The temperature dependence indicates an endothermic process. U(VI) adsorption was found to decrease with an increase in ionic strength due to the formation of outer-sphere surface complexes on PGCP-COOH. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as DeltaG(0), DeltaH(0) and DeltaS(0) were derived to predict the nature of adsorption. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC-50, with carboxylate functionality for comparison. Utility of the adsorbent was tested by removing U(VI) from simulated nuclear industry wastewater. Adsorbed U(VI) ions were desorbed effectively (about 96.2+/-3.3%) by 0.1M HCl. The adsorbent was suitable for repeated use (more than four cycles) without any noticeable loss of capacity.

Adsorption-Induced Changes in Ribonuclease A Structure and Enzymatic Activity on Solid Surfaces

PubMed Central

2015-01-01

Ribonuclease A (RNase A) is a small globular enzyme that lyses RNA. The remarkable solution stability of its structure and enzymatic activity has led to its investigation to develop a new class of drugs for cancer chemotherapeutics. However, the successful clinical application of RNase A has been reported to be limited by insufficient stability and loss of enzymatic activity when it was coupled with a biomaterial carrier for drug delivery. The objective of this study was to characterize the structural stability and enzymatic activity of RNase A when it was adsorbed on different surface chemistries (represented by fused silica glass, high-density polyethylene, and poly(methyl-methacrylate)). Changes in protein structure were measured by circular dichroism, amino acid labeling with mass spectrometry, and in vitro assays of its enzymatic activity. Our results indicated that the process of adsorption caused RNase A to undergo a substantial degree of unfolding with significant differences in its adsorbed structure on each material surface. Adsorption caused RNase A to lose about 60% of its native-state enzymatic activity independent of the material on which it was adsorbed. These results indicate that the native-state structure of RNase A is greatly altered when it is adsorbed on a wide range of surface chemistries, especially at the catalytic site. Therefore, drug delivery systems must focus on retaining the native structure of RNase A in order to maintain a high level of enzymatic activity for applications such as antitumor chemotherapy. PMID:25420087

An experimental study of the effects of adsorbing and non-adsorbing gases on friction and permeability evolution in clay-rich fault gouge

NASA Astrophysics Data System (ADS)

Lisabeth, H. P.; Zoback, M. D.

2017-12-01

Understanding the flow of fluids through fractures in clay-rich rocks is fundamental to a number of geoengineering enterprises, including development of unconventional hydrocarbon resources, nuclear waste storage and geological carbon sequestration. High clay content tends to make rocks plastic, low-porosity and anisotropic. In addition, some gasses adsorb to clay mineral surfaces, resulting in swelling and concomitant changes in physical properties. These complexities can lead to coupled behaviors that render prediction of fluid behavior in the subsurface difficult. We present the results of a suite of triaxial experiments on binary mixtures of quartz and illite grains to separate and quantify the effects of hydrostatic pressure, differential stress, clay content and gas chemistry on the evolution of mechanical and hydraulic characteristics of the gouge material during deformation. Tests are run on saw-cut samples prepared with gouge at 20 MPa confining pressure, 10 MPa pore pressure and at room temperature. Argon or carbon dioxide is used as pore fluid. Sample permeability, stress and strain are monitored continuously during hydrostatic and axial deformation. We find that pressure and shearing both lead to reductions in permeability. Adsorbing gas leads to swelling and promotes permeability reduction, but appears to have no effect on frictional properties. These results indicate that the seal integrity of clay-rich caprocks may not be compromised by shear deformation, and that depletion and shear deformation of unconventional reservoirs is expected to result in production declines.

Preparation and evaluation of an adsorbent based on poly (muconic acid-co-divinylbenzene/ethylenedimethacrylate) for multiple monolithic fiber solid-phase microextraction of tetracycline antibiotics.

PubMed

Pei, Miao; Huang, Xiaojia

2017-09-29

To extract tetracycline antibiotics (TAs) effectively, a new adsorbent based on poly (muconic acid-co-divinylbenzene/ethylenedimethacrylate) monolith was fabricated and used as the extraction medium of multiple monolithic fiber solid-phase microextraction (MD/MF-SPME). The effect of the fabrication parameters on extraction efficiency was studied thoroughly. Elemental analysis, infrared spectroscopy, scanning electron microscopy and mercury intrusion porosimetry were used to check the physicochemical properties of the adsorbent. Some key parameters that affect the extraction performance of MD/MF-SPME for TAs were investigated systematically. Under the optimized experimental conditions, the prepared adsorbent could effectively extract the TAs through multiple interactions. At the same time, a simple and sensitive method for monitoring trace TAs in honey samples was developed by coupling MD/MF-SPME with high-performance liquid chromatography tandem mass spectrometry detection (MD/MF-SPME-HPLC-MS/MS). The limits of detection (S/N=3) for target compounds were in the range of 7.3-17.1ng/kg. The intra-day and inter-day precision (relative standard deviations, n=4, %) at 0.5μg/kg and 20.0μg/kg spiking concentrations were 5.0-9.5% and 3.6-10.0%, respectively. The mean recoveries of the target TAs in the real honey samples were between 70.5-111.0%. Copyright © 2017 Elsevier B.V. All rights reserved.

A decontamination system for chemical weapons agents using a liquid solution on a solid sorbent.

PubMed

Waysbort, Daniel; McGarvey, David J; Creasy, William R; Morrissey, Kevin M; Hendrickson, David M; Durst, H Dupont

2009-01-30

A decontamination system for chemical warfare agents was developed and tested that combines a liquid decontamination reagent solution with solid sorbent particles. The components have fewer safety and environmental concerns than traditional chlorine bleach-based products or highly caustic solutions. The liquid solution, based on Decon Greentrade mark, has hydrogen peroxide and a carbonate buffer as active ingredients. The best solid sorbents were found to be a copolymer of ethylene glycol dimethacrylate and n-lauryl methacrylate (Polytrap 6603 Adsorber); or an allyl methacrylate cross-linked polymer (Poly-Pore E200 Adsorber). These solids are human and environmentally friendly and are commonly used in cosmetics. The decontaminant system was tested for reactivity with pinacolyl methylphosphonofluoridate (Soman, GD), bis(2-chloroethyl)sulfide (Mustard, HD), and S-(2-diisopropylaminoethyl) O-ethyl methylphosphonothioate (VX) by using NMR Spectroscopy. Molybdate ion (MoO(4)(-2)) was added to the decontaminant to catalyze the oxidation of HD. The molybdate ion provided a color change from pink to white when the oxidizing capacity of the system was exhausted. The decontaminant was effective for ratios of agent to decontaminant of up to 1:50 for VX (t(1/2) < or = 4 min), 1:10 for HD (t(1/2) < 2 min with molybdate), and 1:10 for GD (t(1/2) < 2 min). The vapor concentrations of GD above the dry sorbent and the sorbent with decontamination solution were measured to show that the sorbent decreased the vapor concentration of GD. The E200 sorbent had the additional advantage of absorbing aqueous decontamination solution without the addition of an organic co-solvent such as isopropanol, but the rate depended strongly on mixing for HD.

Evaluation of Chlorella as a Decorporation Agent to Enhance the Elimination of Radioactive Strontium from Body.

PubMed

Ogawa, Kazuma; Fukuda, Tadahisa; Han, Jaegab; Kitamura, Yoji; Shiba, Kazuhiro; Odani, Akira

2016-01-01

Release of radionuclides, such as 137Cs and 90Sr, into the atmosphere and the ocean presents an important problem because internal exposure to 137Cs and 90Sr could be very harmful to humans. Chlorella has been reported to be effective in enhancing the excretion of heavy metals; thus, we hypothesized that Chlorella could also enhance the elimination of 137Cs or 90Sr from the body. We evaluated the potential of Chlorella as a decorporation agent in vitro and in vivo, using 85Sr instead of 90Sr. In vitro experiments of adsorption of 137Cs and 85Sr to Chlorella were performed under wide pH conditions. The maximum sorption capacity of Chlorella to strontium was estimated using the Langmuir model. A 85Sr solution was orally administrated to mice pretreated with Chlorella. At 48 h after 85Sr administration, the biodistribution of radioactivity was determined. In the in vitro experiments, although 85Sr barely adsorbed to Chlorella at low pH, the 85Sr adsorption ratio to Chlorella increased with increasing pH. The maximum sorption capacity of Chlorella to strontium was 9.06 mg / g. 137Cs barely adsorbed to Chlorella under any pH conditions. In the biodistribution experiments, bone accumulation of radioactivity after 85Sr administration was significantly decreased in the Chlorella pretreatment group compared with the non-treatment control group. In conclusion, these results indicated that Chlorella could inhibit the absorption of 90Sr into the blood and enhance the elimination of 90Sr from the body through adsorption in intestine. Further studies are required to elucidate the mechanism and the components of Chlorella needed for adsorption to strontium and could promote the development of more effective decorporation agents.

Evaluation of Chlorella as a Decorporation Agent to Enhance the Elimination of Radioactive Strontium from Body

PubMed Central

Ogawa, Kazuma; Fukuda, Tadahisa; Han, Jaegab; Kitamura, Yoji; Shiba, Kazuhiro; Odani, Akira

2016-01-01

Background Release of radionuclides, such as 137Cs and 90Sr, into the atmosphere and the ocean presents an important problem because internal exposure to 137Cs and 90Sr could be very harmful to humans. Chlorella has been reported to be effective in enhancing the excretion of heavy metals; thus, we hypothesized that Chlorella could also enhance the elimination of 137Cs or 90Sr from the body. We evaluated the potential of Chlorella as a decorporation agent in vitro and in vivo, using 85Sr instead of 90Sr. Methods In vitro experiments of adsorption of 137Cs and 85Sr to Chlorella were performed under wide pH conditions. The maximum sorption capacity of Chlorella to strontium was estimated using the Langmuir model. A 85Sr solution was orally administrated to mice pretreated with Chlorella. At 48 h after 85Sr administration, the biodistribution of radioactivity was determined. Results In the in vitro experiments, although 85Sr barely adsorbed to Chlorella at low pH, the 85Sr adsorption ratio to Chlorella increased with increasing pH. The maximum sorption capacity of Chlorella to strontium was 9.06 mg / g. 137Cs barely adsorbed to Chlorella under any pH conditions. In the biodistribution experiments, bone accumulation of radioactivity after 85Sr administration was significantly decreased in the Chlorella pretreatment group compared with the non-treatment control group. Conclusions In conclusion, these results indicated that Chlorella could inhibit the absorption of 90Sr into the blood and enhance the elimination of 90Sr from the body through adsorption in intestine. Further studies are required to elucidate the mechanism and the components of Chlorella needed for adsorption to strontium and could promote the development of more effective decorporation agents. PMID:26828430

The development, characterization, and application of biomimetic nanoscale enzyme immobilization

NASA Astrophysics Data System (ADS)

Haase, Nicholas R.

The utilization of enzymes is of interest for applications such as biosensors and biofuel cells. Immobilizing enzymes provides a means to develop these applications. Previous immobilization efforts have been accomplished by exposing surfaces on which silica-forming molecules are present to solutions containing an enzyme and a silica precursor. This approach leads to the enzyme being entrapped in a matrix three orders of magnitude larger than the enzyme itself, resulting in low retention of enzyme activity. The research herein introduces a method for the immobilization of enzymes during the layer-by-layer buildup of Si-O and Ti-O coatings which are nanoscale in thickness. This approach is an application of a peptide-induced mineral deposition method developed in the Sandhage and Kroger groups, and it involves the alternating exposure of a surface to solutions containing the peptide protamine and then an aqueous precursor solution of silicon- or titanium-oxide at near-neutral pH. A method has been developed that enables in situ immobilization of enzymes in the protamine/mineral oxide coatings. Depending on the layer and mineral (silica or titania) within which the enzyme is incorporated, the resulting multilayer biocatalytic hybrid materials retain 20 -- 100% of the enzyme activity. Analyses of kinetic properties of the immobilized enzyme, coupled with characterization of physical properties of the mineral-bearing layers (thickness, porosity, pore size distribution), indicates that the catalytic activities of the enzymes immobilized in the different layers are largely determined by substrate diffusion. The enzyme was also found to be substantially stabilized against heat-induced denaturation and largely protected from proteolytic attack. These functional coatings are then developed for use as antimicrobial materials. Glucose oxidase, which catalyzes production of the cytotoxic agent hydrogen peroxide, was immobilized with silver nanoparticles, can release antimicrobial silver ions. It is demonstrated that these two antimicrobial agents work in a synergistic manner for enhanced antimicrobial efficacy. Evidence of the proposed mechanism of synergy, namely enhanced release of silver ions by reaction of H2O2 with silver nanoparticles, is provided. Finally, the deployment of these materials in silk fibroins for development as wound dressings is also presented. Protamine cross-linking was then extended to the oxygen-reducing enzyme laccase to explore the use of this modified enzyme in an enzymatic biocathode. In this application laccase accepts electrons from the electrode and uses them to reduce oxygen to water molecules. The protamine-cross-linked enzyme exhibits a higher degree of immobilization, better retention of activity once immobilized, and superior electrochemical activity versus the native enzyme. Finally, preliminary research on the structure-function relationships of 16-mer peptides which adsorb to surfaces and deposit titanium oxide is presented. Specifically, the effect of content and distribution of arginine residues on the ability of peptides to adsorb to surfaces and subsequently deposit mineral oxides was investigated. The data demonstrate that surface adsorption of the peptides relies on both a critical number of arginine residues and their position within the peptide. Furthermore, the exchange of serine against arginine residues in surface-adsorbed peptides is detrimental to Ti-O deposition.

Granulated decontamination formulations

DOEpatents

Tucker, Mark D.

2007-10-02

A decontamination formulation and method of making that neutralizes the adverse health effects of both chemical and biological compounds, especially chemical warfare (CW) and biological warfare (BW) agents, and toxic industrial chemicals. The formulation provides solubilizing compounds that serve to effectively render the chemical and biological compounds, particularly CW and BW compounds, susceptible to attack, and at least one reactive compound that serves to attack (and detoxify or kill) the compound. The formulation includes at least one solubilizing agent, a reactive compound, a sorbent additive, and water. A highly adsorbent sorbent additive (e.g., amorphous silica, sorbitol, mannitol, etc.) is used to "dry out" one or more liquid ingredients into a dry, free-flowing powder that has an extended shelf life, and is more convenient to handle and mix in the field.

Protection of dried probiotic bacteria from bile using bile adsorbent resins.

PubMed

Mahbubani, Krishnaa T; Slater, Nigel K H; Edwards, Alexander D

2014-01-25

Enteric coated oral tablets or capsules can deliver dried live cells directly into the intestine. Previously, we found that a live attenuated bacterial vaccine acquired sensitivity to intestinal bile when dried, raising the possibility that although gastric acid can be bypassed, significant loss of viability might occur on release from an enteric coated oral formulations. Here we demonstrate that some food-grade lyophilised preparations of Lactobacillus casei and Lactobacillus salivarius also show temporary bile sensitivity that can be rapidly reversed by rehydration. To protect dried bacterial cells from temporary bile sensitivity, we propose using bile acid adsorbing resins, such as cholestyramine, which are bile acid binding agents, historically used to lower cholesterol levels. Vcaps™ HPMC capsules alone provided up to 830-fold protection from bile. The inclusion of 50% w/w cholestyramine in Vcaps™ HPMC capsules resulted in release of up to 1700-fold more live Lactobacillus casei into simulated intestinal fluid containing 1% bile, when compared to dried cells added directly to bile. We conclude that delivery of dried live probiotic organisms to the intestine may be improved by providing protection from bile by addition of bile adsorbing resins and the use of HPMC capsules. Copyright © 2013 Elsevier B.V. All rights reserved.

Green synthesis of palm oil mill effluent-based graphenic adsorbent for the treatment of dye-contaminated wastewater.

PubMed

Teow, Yeit Haan; Nordin, Nadzirah Ilyiani; Mohammad, Abdul Wahab

2018-05-12

Textile wastewater contains methylene blue (MB), a major coloring agent in textile industry. Activated carbon (AC) is the most widely used adsorbent in removing dyes from industrial wastewater. However, high production cost of AC is the major obstacle for its wide application in dye wastewater treatment. In this study, a sustainable approach in synthesizing graphenic adsorbent from palm oil mill effluent (POME), a potential carbonaceous source, has been explored. This new development in adsorption technique is considered as green synthesis as it does not require any binder during the synthesis process, and at the same time, it helps to solve the bottleneck of palm oil industry as POME is the main cause contributed to Malaysia's water pollution problem. The synthesized GSC was characterized through XRD, FESEM, and EDX. The adsorption performance of the synthesized GSC was evaluated by adsorption of MB. The effect of initial concentration of synthetic MB solution (1-20 mg/L) and weight of GSC (5-20 g) were investigated. A remarkable change in color of synthetic MB solution from blue to crystal clear was observed at the end of adsorption study. High efficiency of the synthesized GSC for dye-contaminated wastewater treatment is concluded.

Large zeolites - Why and how to grow in space

NASA Technical Reports Server (NTRS)

Sacco, Albert, Jr.

1991-01-01

The growth of zeolite crystals which are considered to be the most valuable catalytic and adsorbent materials of the chemical processing industry are discussed. It is proposed to use triethanolamine as a nucleation control agent to control the time release of Al in a zeolite A solution and to increase the average and maximum crystal size by 25-50 times. Large zeolites could be utilized to make membranes for reactors/separators which will substantially increase their efficiency.

Nanodiamonds of Laser Synthesis for Biomedical Applications.

PubMed

Perevedentseva, E; Peer, D; Uvarov, V; Zousman, B; Levinson, O

2015-02-01

In recent decade detonation nanodiamonds (DND), discovered 50 years ago and used in diverse technological processes, have been actively applied in biomedical research as a drug and gene delivery carrier, a contrast agent for bio-imaging and diagnostics and an adsorbent for protein separation and purification. In this work we report about nanodiamonds of high purity produced by laser assisted technique, compare them with DND and consider the prospect and advantages of their use in the said applications.

In situ capping for size control of monochalcogenides (ZnS, CdS, and SnS) nanocrystals produced by anaerobic metal-reducing bacteria

DOE PAGES

Jang, Gyoung Gug; Jacobs, Christopher B.; Ivanov, Ilia N.; ...

2015-07-24

Metal monochalcogenide quantum dot nanocrystals of ZnS, CdS and SnS were prepared by anaerobic, metal-reducing bacteria using in situ capping by oleic acid or oleylamine. Furthermore, the capping agent preferentially adsorbs on the surface of the nanocrystal, suppressing the growth process in the early stages, thus leading to production of nanocrystals with a diameter of less than 5 nm.

Gas and Particle Oxidation Products from Ozone Aging of Airborne Diesel Particles

NASA Astrophysics Data System (ADS)

Holmen, B. A.; Chen, Z.

2005-12-01

Diesel exhaust emissions contain fine particulate matter (PM2.5) composed of carbon-based particles with adsorbed compounds, including water soluble and insoluble substances. Many nonpolar organic compounds associated with diesel particulate matter (DPM) are known to be mutagenic and carcinogenic. In the presence of ozone, these DPM compounds can be transformed into polar species that are more toxic and poorly characterized. Understanding the gas and particle reaction products from DPM aging in the presence of tropospheric ozone is important for air quality, climate change and aerosol health effects. Aging experiments were conducted in a flow reactor to identify gas and particle-phase reaction products of DPM exposed to ambient levels of ozone. Diesel bus exhaust particles were collected on filters and then exposed to 0.1 - 0.5 ppm O3 for 0 to 72 h. Gaseous polar organic products formed during the aging experiments were collected on Tenax TA adsorbent coated with PFBHA derivatization agent. A thermal desorption gas chromatography mass spectrometry (TD/GC/MS) method was developed to determine gas-phase and particle-phase organic compounds. PFBHA and BSTFA derivatization agents converted polar species into less polar analogues prior to analysis. Preliminary results indicate that DPM hydrocarbons react with O3 to form many gas-phase polar products containing C=O (carbonyl) and COOH (carboxy) functional groups. Particle-phase PAH and alkane concentrations decreased significantly depending on time of exposure.

Fluorescent carbon dots as an efficient siRNA nanocarrier for its interference therapy in gastric cancer cells.

PubMed

Wang, Qing; Zhang, Chunlei; Shen, Guangxia; Liu, Huiyang; Fu, Hualin; Cui, Daxiang

2014-12-30

Fluorescent carbon dots (Cdots) have attracted increasing attention due to their potential applications in sensing, catalysis, and biomedicine. Currently, intensive research has been concentrated on the synthesis and imaging-guided therapy of these benign photoluminescent materials. Meanwhile, Cdots have been explored as nonviral vector for nucleic acid or drug delivery by chemical modification on purpose. We have developed a microwave assisted one-step synthesis of Cdots with citric acid as carbon source and tryptophan (Trp) as both nitrogen source and passivation agent. The Cdots with uniform size show superior water solubility, excellent biocompatibility, and high quantum yield. Afterwards, the PEI (polyethylenimine)-adsorbed Cdots nanoparticles (Cdots@PEI) were applied to deliver Survivin siRNA into human gastric cancer cell line MGC-803. The results have confirmed the nanocarrier exhibited excellent biocompatibility and a significant increase in cellular delivery of siRNA, inducing efficient knockdown for Survivin protein to 6.1%. In addition, PEI@Cdots complexes mediated Survivin silencing, the arrested cell cycle progression in G1 phase as well as cell apoptosis was observed. The Cdots-based and PEI-adsorbed complexes both as imaging agents and siRNA nanocarriers have been developed for Survivin siRNA delivery. And the results indicate that Cdots-based nanocarriers could be utilized in a broad range of siRNA delivery systems for cancer therapy.

Activated carbons from potato peels: The role of activation agent and carbonization temperature of biomass on their use as sorbents for bisphenol A uptake from aqueous solutions

NASA Astrophysics Data System (ADS)

Arampatzidou, An; Deliyanni, Eleni A.

2015-04-01

Activated carbons prepared from potato peels, a solid waste by product, and activated with different activating chemicals, have been studied for the adsorption of an endocrine disruptor (Bisphenol-A) from aqueous solutions. The potato peels biomass was activated with phosphoric acid, KOH and ZnCl2. The different activating chemicals were tested in order the better activation agent to be found. The carbons were carbonized by pyrolysis, in one step procedure, at three different temperatures in order the role of the temperature of carbonization to be pointed out. The porous texture and the surface chemistry of the prepared activated carbons were characterized by Nitrogen adsorption (BET), Scanning Electron Microscope (SEM), thermal analysis (DTA) and Fourier Transform Infrared Spectroscopy (FTIR). Batch experiments were performed to investigate the effect of pH, the adsorbent dose, the initial bisphenol A concentration and temperature. Equilibrium adsorption data were analyzed by Langmuir and Freundlich isotherms. The thermodynamic parameters such as the change of enthalpy (ΔH0), entropy (ΔS0) and Gibb's free energy (ΔG0) of adsorption systems were also evaluated. The adsorption capacity calculated from the Langmuir isotherm was found to be 450 mg g-1 at an initial pH 3 at 25 °C for the phosphoric acid activated carbon, that make the activated carbon a promising adsorbent material.

Surface modification of self-healing poly(urea-formaldehyde) microcapsules using silane-coupling agent

NASA Astrophysics Data System (ADS)

Li, Haiyan; Wang, Rongguo; Hu, Honglin; Liu, Wenbo

2008-12-01

Poly(urea-formaldehyde) (PUF) microcapsules, which are used as self-healing component of fibre reinforced resin matrix composites, were prepared by in situ polymerization method. The surface of PUF microcapsules was modified by using 3-aminopropyltriethoxy silane-coupling agent (KH550), and the interfacial interactions between PUF microcapsules and KH550 was also studied. Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectra (XPS) analyses showed that the silane-coupling agent molecular binds strongly to PUF microcapsules surface. Chemical bond (Si-O-C) was formed by the reaction between Si-OH and the hydroxyl group of PUF microcapsules, also there have chemical adsorption effect in the interface simultaneously because of the existence of hydrogen bond between Si-OH and the hydroxyl group of PUF microcapsules. Scanning electronic microscopy (SEM) observation showed that a thin layer was formed on the surface of modified PUF microcapsules. Additionally, fractured surface were observed under SEM to investigate the interfacial adhesion effect between PUF microcapsules and epoxy matrix. The result indicted that the silane-coupling agent play an important role in improving the interfacial performance between microcapsules and resin matrix.

Influences of surface modification of nano-silica by silane coupling agents on the thermal and frictional properties of cyanate ester resin

NASA Astrophysics Data System (ADS)

Chuang, Wang; Geng-sheng, Jiao; Lei, Peng; Bao-lin, Zhu; Ke-zhi, Li; Jun-long, Wang

2018-06-01

The surface of nano-silicon dioxide (nano-SiO2) particles was modified by small molecular coupling agent KH-560 and macromolecular coupling agent SEA-171, respectively, to change the surface activity and structure. The modified nano-SiO2 was then used for reinforcing cyanate ester resin (CE). Influences of the content of nano-SiO2 and the interfacial structure over the thermal and frictional properties of nano-SiO2/CE composites were investigated. The mechanism of the surface modification of silicon dioxide by KH-560 and SEA-171 was discussed. The experimental results show that the addition of coupling agents increased the interfacial bonding between nano-SiO2 particles and the CE resin so that the heat resistance and friction properties of the composites were improved. After surface treatment of nano-SiO2 by SEA-171, the thermal decomposition temperature of the 3.0 wt% nano-SiO2/CE composites increased nearly by 75 °C and the frictional coefficient was reduced by 25% compared with that of the pure CE, and the wear resistance increased by 77%.

The effects of low-tide rainfall on metal content of suspended sediment in the Sacramento-San Joaquin Delta

NASA Astrophysics Data System (ADS)

Moskalski, S. M.; Torres, R.; Bizimis, M.; Bergamaschi, B. A.; Fleck, J.; Goni, M. A.

2012-12-01

Rain falling near low tide is capable of eroding and transporting cohesive sediment from marsh and mudflat surfaces. Given that metals adsorb strongly to silt- and clay-sized particles, it is conceivable that lowtide rainfall may also liberate previously-deposited metals from storage in intertidal sediment. To investigate the potential for rainfall as an agent of remobilization of metals, this study tested the hypothesis of sediment, and therefore metals and nutrients, mobilization during these punctuated low-tide rainfall events. Water samples were collected during low-tide rain events in winter and wind resuspension events in summer from a marsh in central California. The concentrations of suspended sediment, particulate organic carbon and nitrogen, and total adsorbed concentration (mass of metal per volume of filtered water) of most metals were higher during a low tide rainfall event than during wind-only and fair-weather events. Metal contents (mass of metal per mass of sediment) were also greater during the rain event for most metals. Principle components analysis and the relationships between total adsorbed metals and SSC suggest rainfall during low tide can mobilize a different source of sediment than the background sediment available for tidal and wind-wave resuspension. The metal content of bulk sediment samples from around the study area could not be matched satisfactorily to the suspended sediment in any of the events, implying that bulk sediment should not be used to extrapolate to suspended sediment in terms of adsorbed metal content. Some of the adsorbed metals were present during the rain event in amounts that could be toxic, depending on the actual bioavailability of the metals.; Summary plots of measured organic parameters. (A) POC (B) PN (C) C:N (D) total leachable metal concentration, sum of all measured metals. The solid line inside box is the median and the dashed line is the mean.

Phosphorus recovery from biogas slurry by ultrasound/H2O2 digestion coupled with HFO/biochar adsorption process.

PubMed

He, Xuemeng; Zhang, Tao; Ren, Hongqiang; Li, Guoxue; Ding, Lili; Pawlowski, Lucjan

2017-02-01

Phosphorus (P) recovery from biogas slurry has recently attracted considerable interest. In this work, ultrasound/H 2 O 2 digestion coupled with ferric oxide hydrate/biochar (HFO/biochar) adsorption process was performed to promote P dissolution, release, and recovery from biogas slurry. The results showed that the optimal total phosphorus release efficiency was achieved at an inorganic phosphorus/total phosphorus ratio of 95.0% at pH 4, 1mL of added H 2 O 2 , and ultrasonication for 30min. The P adsorption by the HFO/biochar followed pseudo second-order kinetics and was mainly controlled by chemical processes. The Langmuir-Freundlich model matched the experimental data best for P adsorption by HFO/biochar at 298 and 308K, whereas the Freundlich model matched best at 318K. The maximum amount of P adsorbed was 220mg/g. The process was endothermic, spontaneous, and showed an increase in disorder at the solid-liquid interface. The saturated adsorbed HFO/biochar continually releases P and is most suitable for use in an alkaline environment. The amount of P released reached 29.1mg/g after five extractions. P mass balance calculation revealed that 11.3% of the total P can be made available. Copyright © 2016. Published by Elsevier Ltd.

Spin-orbit coupling and surface magnetism coexisting in spin-dependent low-energy He+-ion surface scattering

NASA Astrophysics Data System (ADS)

Suzuki, T. T.; Sakai, O.

2017-04-01

Surface magnetism is analyzed by spin-dependent He+-ion neutralization (the Auger neutralization) in the vicinity of a surface using an electron spin-polarized low-energy He+-ion beam [spin-polarized ion scattering spectroscopy (SP-ISS)]. Recently, spin-orbit coupling (SOC) has been found to act as another mechanism of spin-dependent low-energy He+-ion scattering. Thus, it is crucial for surface magnetism analyses by SP-ISS to separate those two mechanisms. In the present study, we investigated the spin-induced asymmetry in scattering of low-energy He+ ions on ultrathin Au and Sn films as well as the oxygen adsorbate on a magnetized-Fe(100) surface where these two mechanisms may coexist. We found that the Fe surface magnetism immediately disappeared with the growth of those overlayers. On the other hand, we observed no induced spin polarization in the Au and Sn thin films even in the very initial stage of the growth. We also observed that the spin asymmetry of the O adsorbate was induced by the magnetism of the underlying Fe substrate. The present study demonstrates that the two mechanisms of the spin-asymmetric He+-ion scattering (the ion neutralization and SOC) can be separated by an azimuthal-angle-resolved SP-ISS measurement.

Lab-on-a-bubble: direct and indirect assays with portable Raman instrumentation

NASA Astrophysics Data System (ADS)

Carron, Keith; Schmit, Virginia; Scott, Brandon; Martoglio, Richard

2012-10-01

Lab-on-a-Bubble (LoB) is a new method for SERS (Surface Enhanced Raman Scattering) assays that combines separationand concentration of the assay results. A direct LoB assay is comprised of gold nanoparticles coupled directly to the ~30 μm diameter buoyant silica bubble. The direct LoB method was evaluated with cyanide and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). An indirect assay uses the same ~ 30 μm diameter buoyant silica bubble and a silica coated SERS reporter. Both the bubble and SERS reporter are coated with a coupling agent for the analyte. The assay measures the amount of SERS reporter coupled to the bubble through a sandwich created by the analyte. The couling agent could consist of an immunological coupling agent (antibody) or a nucleic acid coupling agent (single strand DNA). The indirect LoB method was examined with Cholera toxin (CT) and antibodies against the β subunit. An LOD of ~ 170 pptrillion was measured for cyanide and a limit of detection of 1100 ng was found for CT. Instrumentation for the assay and a novel technique of dynamic SERS (DSERS) will also be discussed. The instrument is a small hand-held Raman device called the CBEx (Chemical Biological Explosive) with a novel raster system to detect heterogeneous or light sensitive materials. DSERS is a mathematical algorithm which eliminates background interference in SERS measurements with colloidal nanoparticles.

Importance of surface modification of γ-alumina in creating its nanostructured composites with zeolitic imidazolate framework ZIF-67.

PubMed

Liu, Yuanyuan; Gonçalves, Alexandre A S; Zhou, Yang; Jaroniec, Mietek

2018-05-07

Application of zeolitic imidazolate framework-67 (ZIF-67) as an adsorbent has been greatly hindered by slow mass transfer of adsorbate molecules due to its inherent microporosity. To address this limitation, we have developed binary nanostructures composed of ZIF-67 and γ-alumina (GA) containing respectively micropores and large mesopores. The nanostructured composites were successfully prepared by coupling ZIF-67 and GA with and without surface modification with imidazole silane that mimics the building blocks of ZIF-67 to obtain GA-Im-ZIF-67 (with imidazole silane) and GA-ZIF-67 (without imidazole silane). The sizes of ZIF-67 crystals in these composites were smaller as compared to those of pure ZIF-67, and the textural properties of these composites with and without surface modification were quite similar. However, the surface grafting of alumina with imidazole silane played an important role in improving interfacial coupling between GA and ZIF-67, which resulted in significant changes in the dispersion of ZIF-67 crystals and better adsorption properties. The presence of large mesopores in the alumina-based composites containing smaller ZIF-67 crystals improved their adsorption properties toward dyes such as Rhodamine B (RhB). The RhB adsorption capacity of GA-Im-ZIF-67 was much higher than that of GA-ZIF-67, suggesting that the imidazole silane modification of GA before its coupling with ZIF-67 and the GA mesoporosity were essential for a substantial increase in the adsorption capacity of RhB. Copyright © 2018 Elsevier Inc. All rights reserved.

Predicting the size-dependent tissue accumulation of agents released from vascular targeted nanoconstructs

NASA Astrophysics Data System (ADS)

de Tullio, Marco D.; Singh, Jaykrishna; Pascazio, Giuseppe; Decuzzi, Paolo

2014-03-01

Vascular targeted nanoparticles have been developed for the delivery of therapeutic and imaging agents in cancer and cardiovascular diseases. However, at authors' knowledge, a comprehensive systematic analysis on their delivery efficiency is still missing. Here, a computational model is developed to predict the vessel wall accumulation of agents released from vascular targeted nanoconstructs. The transport problem for the released agent is solved using a finite volume scheme in terms of three governing parameters: the local wall shear rate , ranging from to ; the wall filtration velocity , varying from to ; and the agent diffusion coefficient , ranging from to . It is shown that the percentage of released agent adsorbing on the vessel walls in the vicinity of the vascular targeted nanoconstructs reduces with an increase in shear rate , and with a decrease in filtration velocity and agent diffusivity . In particular, in tumor microvessels, characterized by lower shear rates () and higher filtration velocities (), an agent with a diffusivity (i.e. a 50 nm particle) is predicted to deposit on the vessel wall up to of the total released dose. Differently, drug molecules, exhibiting a smaller size and much higher diffusion coefficient (), are predicted to accumulate up to . In healthy vessels, characterized by higher and lower , the largest majority of the released agent is redistributed directly in the circulation. These data suggest that drug molecules and small nanoparticles only can be efficiently released from vascular targeted nanoconstructs towards the diseased vessel walls and tissue.

Influence of Chloride-Ion Adsorption Agent on Chloride Ions in Concrete and Mortar.

PubMed

Peng, Gai-Fei; Feng, Nai-Qian; Song, Qi-Ming

2014-04-30

The influence of a chloride-ion adsorption agent (Cl agent in short), composed of zeolite, calcium aluminate hydrate and calcium nitrite, on the ingress of chloride ions into concrete and mortar has been experimentally studied. The permeability of concrete was measured, and the chloride ion content in mortar was tested. The experimental results reveal that the Cl agent could adsorb chloride ions effectively, which had penetrated into concrete and mortar. When the Cl agent was used at a dosage of 6% by mass of cementitious materials in mortar, the resistance to the penetration of chloride ions could be improved greatly, which was more pronounced when a combination of the Cl agent and fly ash or slag was employed. Such an effect is not the result of the low permeability of the mortar, but might be a result of the interaction between the Cl agent and the chloride ions penetrated into the mortar. There are two possible mechanisms for the interaction between the Cl agent and chloride ion ingress. One is the reaction between calcium aluminate hydrate in the Cl agent and chloride ions to form Friedel's salt, and the other one is that calcium aluminate hydrate reacts with calcium nitrite to form AFm during the early-age hydration of mortar and later the NO₂ - in AFm is replaced by chloride ions, which then penetrate into the mortar, also forming Friedel's salt. More research is needed to confirm the mechanisms.

Influence of Chloride-Ion Adsorption Agent on Chloride Ions in Concrete and Mortar

PubMed Central

Peng, Gai-Fei; Feng, Nai-Qian; Song, Qi-Ming

2014-01-01

The influence of a chloride-ion adsorption agent (Cl agent in short), composed of zeolite, calcium aluminate hydrate and calcium nitrite, on the ingress of chloride ions into concrete and mortar has been experimentally studied. The permeability of concrete was measured, and the chloride ion content in mortar was tested. The experimental results reveal that the Cl agent could adsorb chloride ions effectively, which had penetrated into concrete and mortar. When the Cl agent was used at a dosage of 6% by mass of cementitious materials in mortar, the resistance to the penetration of chloride ions could be improved greatly, which was more pronounced when a combination of the Cl agent and fly ash or slag was employed. Such an effect is not the result of the low permeability of the mortar, but might be a result of the interaction between the Cl agent and the chloride ions penetrated into the mortar. There are two possible mechanisms for the interaction between the Cl agent and chloride ion ingress. One is the reaction between calcium aluminate hydrate in the Cl agent and chloride ions to form Friedel’s salt, and the other one is that calcium aluminate hydrate reacts with calcium nitrite to form AFm during the early-age hydration of mortar and later the NO2− in AFm is replaced by chloride ions, which then penetrate into the mortar, also forming Friedel’s salt. More research is needed to confirm the mechanisms. PMID:28788625

In Situ Probes of Capture and Decomposition of Chemical Warfare Agent Simulants by Zr-Based Metal Organic Frameworks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plonka, Anna M.; Wang, Qi; Gordon, Wesley O.

Recently, Zr-based metal organic frameworks (MOFs) were shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. Here, we report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination ofmore » DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. Our experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontamination materials.« less

In Situ Probes of Capture and Decomposition of Chemical Warfare Agent Simulants by Zr-Based Metal Organic Frameworks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plonka, Anna M.; Wang, Qi; Gordon, Wesley O.

Zr-based metal organic frameworks (MOFs) have been recently shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. We report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination ofmore » DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. These experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontamination materials.« less

In Situ Probes of Capture and Decomposition of Chemical Warfare Agent Simulants by Zr-Based Metal Organic Frameworks

DOE PAGES

Plonka, Anna M.; Wang, Qi; Gordon, Wesley O.; ...

2016-12-30

Recently, Zr-based metal organic frameworks (MOFs) were shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. Here, we report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination ofmore » DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. Our experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontamination materials.« less

Investigations Into Internal and External Aspects of Dynamic Agent-Environment Couplings

NASA Astrophysics Data System (ADS)

Dautenhahn, Kerstin

This paper originates from my work on `social agents'. An issue which I consider important to this kind of research is the dynamic coupling of an agent with its social and non-social environment. I hypothesize `internal dynamics' inside an agent as a basic step towards understanding. The paper therefore focuses on the internal and external dynamics which couple an agent to its environment. The issue of embodiment in animals and artifacts and its relation to `social dynamics' is discussed first. I argue that embodiment is linked to a concept of a body and is not necessarily given when running a control program on robot hardware. I stress the individual characteristics of an embodied cognitive system, as well as its social embeddedness. I outline the framework of a physical-psychological state space which changes dynamically in a self-modifying way as a holistic approach towards embodied human and artificial cognition. This framework is meant to discuss internal and external dynamics of an embodied, natural or artificial agent. In order to stress the importance of a dynamic memory I introduce the concept of an `autobiographical agent'. The second part of the paper gives an example of the implementation of a physical agent, a robot, which is dynamically coupled to its environment by balancing on a seesaw. For the control of the robot a behavior-oriented approach using the dynamical systems metaphor is used. The problem is studied through building a complete and co-adapted robot-environment system. A seesaw which varies its orientation with one or two degrees of freedom is used as the artificial `habitat'. The problem of stabilizing the body axis by active motion on a seesaw is solved by using two inclination sensors and a parallel, behavior-oriented control architecture. Some experiments are described which demonstrate the exploitation of the dynamics of the robot-environment system.

Extended Neural Metastability in an Embodied Model of Sensorimotor Coupling

PubMed Central

Aguilera, Miguel; Bedia, Manuel G.; Barandiaran, Xabier E.

2016-01-01

The hypothesis that brain organization is based on mechanisms of metastable synchronization in neural assemblies has been popularized during the last decades of neuroscientific research. Nevertheless, the role of body and environment for understanding the functioning of metastable assemblies is frequently dismissed. The main goal of this paper is to investigate the contribution of sensorimotor coupling to neural and behavioral metastability using a minimal computational model of plastic neural ensembles embedded in a robotic agent in a behavioral preference task. Our hypothesis is that, under some conditions, the metastability of the system is not restricted to the brain but extends to the system composed by the interaction of brain, body and environment. We test this idea, comparing an agent in continuous interaction with its environment in a task demanding behavioral flexibility with an equivalent model from the point of view of “internalist neuroscience.” A statistical characterization of our model and tools from information theory allow us to show how (1) the bidirectional coupling between agent and environment brings the system closer to a regime of criticality and triggers the emergence of additional metastable states which are not found in the brain in isolation but extended to the whole system of sensorimotor interaction, (2) the synaptic plasticity of the agent is fundamental to sustain open structures in the neural controller of the agent flexibly engaging and disengaging different behavioral patterns that sustain sensorimotor metastable states, and (3) these extended metastable states emerge when the agent generates an asymmetrical circular loop of causal interaction with its environment, in which the agent responds to variability of the environment at fast timescales while acting over the environment at slow timescales, suggesting the constitution of the agent as an autonomous entity actively modulating its sensorimotor coupling with the world. We conclude with a reflection about how our results contribute in a more general way to current progress in neuroscientific research. PMID:27721746

Extended Neural Metastability in an Embodied Model of Sensorimotor Coupling.

PubMed

Aguilera, Miguel; Bedia, Manuel G; Barandiaran, Xabier E

2016-01-01

The hypothesis that brain organization is based on mechanisms of metastable synchronization in neural assemblies has been popularized during the last decades of neuroscientific research. Nevertheless, the role of body and environment for understanding the functioning of metastable assemblies is frequently dismissed. The main goal of this paper is to investigate the contribution of sensorimotor coupling to neural and behavioral metastability using a minimal computational model of plastic neural ensembles embedded in a robotic agent in a behavioral preference task. Our hypothesis is that, under some conditions, the metastability of the system is not restricted to the brain but extends to the system composed by the interaction of brain, body and environment. We test this idea, comparing an agent in continuous interaction with its environment in a task demanding behavioral flexibility with an equivalent model from the point of view of "internalist neuroscience." A statistical characterization of our model and tools from information theory allow us to show how (1) the bidirectional coupling between agent and environment brings the system closer to a regime of criticality and triggers the emergence of additional metastable states which are not found in the brain in isolation but extended to the whole system of sensorimotor interaction, (2) the synaptic plasticity of the agent is fundamental to sustain open structures in the neural controller of the agent flexibly engaging and disengaging different behavioral patterns that sustain sensorimotor metastable states, and (3) these extended metastable states emerge when the agent generates an asymmetrical circular loop of causal interaction with its environment, in which the agent responds to variability of the environment at fast timescales while acting over the environment at slow timescales, suggesting the constitution of the agent as an autonomous entity actively modulating its sensorimotor coupling with the world. We conclude with a reflection about how our results contribute in a more general way to current progress in neuroscientific research.

Polyfibroblast: A Self-Healing and Galvanic Protection Additive

DTIC Science & Technology

2011-07-25

3 Key Accomplishments 3.1 Silane Formulation Processability Silane coupling agents may be added to the existing microcapsules either in low...constrained by the need to form stable microcapsules . To this end, we explored a number of recipes in which the following silane coupling agents were...Isocyanatopropyltrimethoxy silane (ITS). • Glycidoxypropyltrimethoxy silane (GPS) As expected, the lowest concentrations most readily formed stable microcapsules . The

Magneto-capillary dynamics of amphiphilic Janus particles at curved liquid interfaces.

PubMed

Fei, Wenjie; Driscoll, Michelle M; Chaikin, Paul M; Bishop, Kyle J M

2018-05-11

A homogeneous magnetic field can exert no net force on a colloidal particle. However, by coupling the particle's orientation to its position on a curved interface, even static homogeneous fields can be used to drive rapid particle motions. Here, we demonstrate this effect using magnetic Janus particles with amphiphilic surface chemistry adsorbed at the spherical interface of a water drop in decane. Application of a static homogeneous field drives particle motion to the drop equator where the particle's magnetic moment can align parallel to the field. As explained quantitatively by a simple model, the effective magnetic force on the particle scales linearly with the curvature of the interface. For particles adsorbed on small droplets such as those found in emulsions, these magneto-capillary forces can far exceed those due to magnetic field gradients in both magnitude and range. This mechanism may be useful in creating highly responsive emulsions and foams stabilized by magnetic particles.

Development of magnetic octadecylsilane particles as solid-phase extraction adsorbent for the determination of fat-soluble vitamins in fruit juice-milk beverage by capillary liquid chromatography.

PubMed

Hu, Chaofan; Jia, Li; Liu, Qingqing; Zhang, Sheng

2010-07-01

A sensitive, fast and simple method based on magnetic octadecylsilane particles was developed for the extraction of three fat-soluble vitamins followed by capillary LC (CLC) analysis with UV detection. Magnetic octadecylsilane particles were prepared based on three-step reactions including co-precipitation, sol-gel polymerization and alkylation. The characterization of the prepared product was studied by scanning electron microscope and Fourier-transform infrared spectrometry. The particles were used as magnetic SPE adsorbent for the extraction of fat-soluble vitamins in fruit juice-milk beverage. The extraction condition and efficiency of the particles for fat-soluble vitamins were investigated. By coupling magnetic SPE with capillary LC with UV detection, low concentrations of fat-soluble vitamins in fruit juice-milk beverage can be detected without the interference from other substances in the sample matrix.

Aluminium and titanium modified mesoporous TUD-1: A bimetal acid catalyst for Biginelli reaction

NASA Astrophysics Data System (ADS)

Pasupathi, M.; Santhi, N.; Pachamuthu, M. P.; Alamelu Mangai, G.; Ragupathi, C.

2018-05-01

Using a simple, non-surfactant template triethanolamine (TEA), bimetal (Al3+ and Ti4+ ions) incorporated mesoporous catalyst AlTiTUD-1 (Si/Al+Ti = 50) was synthesized. The catalyst was characterized by XRD (Low and High angle), N2 Sorption, FTIR, SEM, TEM, DR UV Visible, and pyridine adsorbed FT-IR techniques. The XRD and N2 sorption studies confirmed its amorphous, mesoporous nature, which possessed a BET surface area of 590 m2 g-1 and pore diameter of 4.4 nm. The Al3+ and Ti4+ co-ordination within the TUD-1 was evaluated by DR UV-Vis. Pyridine adsorbed FTIR revealed both Bronsted (B) and Lewis (L) acidity, which is responsible for the catalytic activity. The acid catalyst showed a good catalytic performance in Biginelli type multicomponent coupling reaction for the substituted aldehydes, ethyl acetoacetate and thiourea to yield about 70% in reflux condition.

Removal of salicylic acid as an emerging contaminant by a polar nano-dendritic adsorbent from aqueous media.

PubMed

Arshadi, M; Mousavinia, F; Abdolmaleki, M K; Amiri, M J; Khalafi-Nezhad, A

2017-05-01

A polar nano-dendritic adsorbent containing amine groups (SAPAMAA) was synthesized onto the nanoparticles of SiO 2 Al 2 O 3 and its uptake of salicylic acid (SA) from the synthetic and real water was investigated. The synthesized nanomaterials were fully studied by nuclear magnetic resonance spectrum ( 1 H NMR and 13 C NMR), Fourier transform infrared spectroscopy (FT-IR), zeta potential (ζ), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and elemental analysis. Various parameters such as the effect of the contact time, adsorbent dosage, initial SA concentrations, effect of solution's temperature, interfering ions, the hydrophobicity of the nanoadsorbent and initial pH were assessed. The contact time to approach equilibrium for higher adsorption was 15min (252.8mgg -1 ). The isotherms could be fitted by Sips model (with the average relative error of 6.6) and the kinetic data could be characterized by pseudo-second-order rate equation (with the average relative error of 13.0), implying chemical adsorption as the ratelimiting step of uptake process which was supported by the experimental data from the effect of interfering ions, zeta potential, and altering of the adsorbent's hydrophobicity. The uptake capacities decreased with temperature increasing, and showed that the uptake of SA was chemically exothermic in nature between 15 and 80°C. In addition, the spent SAPAMAA could be regenerated by the removal of adsorbed SA with NaOH and ethanol to regain the original SAPAMAA, the regenerated SAPAMAA also exhibited the high adsorption capacity after 10 runs. Moreover, SAPAMAA could also be applied to uptake SA from a real water (Anzali lagoon water). We envisage that the prepared nano-dendritic with remarkable characteristics such as environmentally friendly, low-cost, easy preparation in large quantity, high mechanical and chemical stability will play a significant role in developing a new generation of emerging contaminants adsorbent. Copyright © 2017 Elsevier Inc. All rights reserved.

Locating a silane coupling agent in silica-filled rubber composites by EFTEM.

PubMed

Dohi, Hidehiko; Horiuchi, Shin

2007-11-20

A silane coupling agent (SA) was added to silica/rubber composites at different mixing temperatures and the formation of a coupling layer at the silica/rubber interface was investigated by energy-filtering transmission electron microscopy. Bis(triethoxysilypropyl)tetrasulfane (TESPT), which was used as the SA, reacted with the silanol groups on the silica surface and with styrene-butadiene rubber to form an interfacial coupling layer. The silicon and sulfur elemental distributions were analyzed by electron energy loss spectroscopy (EELS) and elemental mapping. The amount of TESPT trapped in the rubber matrix could be qualitatively estimated by EELS, and the in situ formed coupling layer could be characterized by elemental mapping. The result indicated that the formation of the coupling layer was affected by the mixing temperature. The technique described here will contribute to the study of interface-property relationships and the evaluation of the role of SAs in polymeric composites.

Crosslinked, porous, polyacrylate beads

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

1976-01-01

Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

Crosslinked, porous, polyacrylate beads

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

1977-01-01

Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree. C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

Activation of water soluble amines by halogens for trapping methyl radioactive iodine from air streams

DOEpatents

Deitz, Victor R.; Blachly, Charles H.

1977-01-01

Gas adsorbent charcoals impregnated with an aqueous solution of the reaction product of a tertiary amine and elemental iodine or bromine are better than 99 per cent efficient in trapping methyl iodine.sup.131. The chemical addition of iodine or bromine to the tertiary amine molecule increases the efficiency of the impregnated charcoal as a trapping agent, and in conjunction with the high flash point of the tertiary amine raises the ignition temperature of the impregnated charcoal.

Photochemistry on, and Nature of Adsorbed Species on Colloidal Clay and Model Clay Systems.

DTIC Science & Technology

1987-09-25

polymethacrylic acid , PMA, have also been used to coat and stabilise colloidal particles( 24 ). The...readily repaired by electron-transfer agents such as ethylenediaminetetra- acetic acid (EDTA) and triethanolamaine (TEA). The data indicate that Elk. 5...8217% ,.• ***, %’SSpS5.% "W , ’ " "" % "a" ’ ".- "% S ,S ° - • S , .% " . ." . ," " % "."’V % % 8 to that of acid catalysis due to the highly acidic nature of

Small, porous polyacrylate beads

NASA Technical Reports Server (NTRS)

Yen, Shiao-Ping Siao (Inventor); Rembaum, Alan (Inventor); Dreyer, William J. (Inventor)

1976-01-01

Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

Characteristics of the iodide/triiodide redox mediator in dye-sensitized solar cells.

PubMed

Boschloo, Gerrit; Hagfeldt, Anders

2009-11-17

Dye-sensitized solar cells (DSCs) have gained widespread interest because of their potential for low-cost solar energy conversion. Currently, the certified record efficiency of these solar cells is 11.1%, and measurements of their durability and stability suggest lifetimes exceeding 10 years under operational conditions. The DSC is a photoelectrochemical system: a monolayer of sensitizing dye is adsorbed onto a mesoporous TiO(2) electrode, and the electrode is sandwiched together with a counter electrode. An electrolyte containing a redox couple fills the gap between the electrodes. The redox couple is a key component of the DSC. The reduced part of the couple regenerates the photo-oxidized dye. The formed oxidized species diffuses to the counter electrode, where it is reduced. The photovoltage of the device depends on the redox couple because it sets the electrochemical potential at the counter electrode. The redox couple also affects the electrochemical potential of the TiO(2) electrode through the recombination kinetics between electrons in TiO(2) and oxidized redox species. This Account focuses on the special properties of the iodide/triiodide (I(-)/I(3)(-)) redox couple in dye-sensitized solar cells. It has been the preferred redox couple since the beginning of DSC development and still yields the most stable and efficient DSCs. Overall, the iodide/triiodide couple has good solubility, does not absorb too much light, has a suitable redox potential, and provides rapid dye regeneration. But what distinguishes I(-)/I(3)(-) from most redox mediators is the very slow recombination kinetics between electrons in TiO(2) and the oxidized part of the redox couple, triiodide. Certain dyes adsorbed at TiO(2) catalyze this recombination reaction, presumably by binding iodine or triiodide. The standard potential of the iodide/triiodide redox couple is 0.35 V (versus the normal hydrogen electrode, NHE), and the oxidation potential of the standard DSC-sensitizer (Ru(dcbpy)(2)(NCS)(2)) is 1.1 V. The driving force for reduction of oxidized dye is therefore as large as 0.75 V. This process leads to the largest internal potential loss in DSC devices. We expect that overall efficiencies above 15% might be achieved if half of this internal potential loss could be gained. The regeneration of oxidized dye with iodide leads to the formation of the diiodide radical (I(2)(-*)). The redox potential of the I(2)(-*)/I(-) couple must therefore be considered when determining the actual driving force for dye regeneration. The formed I(2)(-*) disproportionates to I(3)(-) and I(-), which leads to a large loss in potential energy.

A Financial Market Model Incorporating Herd Behaviour

PubMed Central

2016-01-01

Herd behaviour in financial markets is a recurring phenomenon that exacerbates asset price volatility, and is considered a possible contributor to market fragility. While numerous studies investigate herd behaviour in financial markets, it is often considered without reference to the pricing of financial instruments or other market dynamics. Here, a trader interaction model based upon informational cascades in the presence of information thresholds is used to construct a new model of asset price returns that allows for both quiescent and herd-like regimes. Agent interaction is modelled using a stochastic pulse-coupled network, parametrised by information thresholds and a network coupling probability. Agents may possess either one or two information thresholds that, in each case, determine the number of distinct states an agent may occupy before trading takes place. In the case where agents possess two thresholds (labelled as the finite state-space model, corresponding to agents’ accumulating information over a bounded state-space), and where coupling strength is maximal, an asymptotic expression for the cascade-size probability is derived and shown to follow a power law when a critical value of network coupling probability is attained. For a range of model parameters, a mixture of negative binomial distributions is used to approximate the cascade-size distribution. This approximation is subsequently used to express the volatility of model price returns in terms of the model parameter which controls the network coupling probability. In the case where agents possess a single pulse-coupling threshold (labelled as the semi-infinite state-space model corresponding to agents’ accumulating information over an unbounded state-space), numerical evidence is presented that demonstrates volatility clustering and long-memory patterns in the volatility of asset returns. Finally, output from the model is compared to both the distribution of historical stock returns and the market price of an equity index option. PMID:27007236

Emergent Behavior of Coupled Barrier Island - Resort Systems

NASA Astrophysics Data System (ADS)

McNamara, D. E.; Werner, B. T.

2004-12-01

Barrier islands are attractive sites for resorts. Natural barrier islands experience beach erosion and island overwash during storms, beach accretion and dune building during inter-storm periods, and migration up the continental shelf as sea level rises. Beach replenishment, artificial dune building, seawalls, jetties and groins have been somewhat effective in protecting resorts against erosion and overwash during storms, but it is unknown how the coupled system will respond to long-term sea level rise. We investigate coupled barrier island - resort systems using an agent-based model with three components: natural barrier islands divided into a series of alongshore cells; resorts controlled by markets for tourism and hotel purchases; and coupling via storm damage to resorts and resort protection by government agents. Modeled barrier islands change by beach erosion, island overwash and inlet cutting during storms, and beach accretion, tidal delta growth and dune and vegetation growth between storms. In the resort hotel market, developer agents build hotels and hotel owning agents purchase them using predictions of future revenue and property appreciation, with the goal of maximizing discounted utility. In the tourism market, hotel owning agents set room rental prices to maximize profit and tourist agents choose vacation destinations maximizing a utility based on beach width, price and word-of-mouth. Government agents build seawalls, groins and jetties, and widen the beach and build up dunes by adding sand to protect resorts from storms, enhance beach quality, and maximize resort revenue. Results indicate that barrier islands and resorts evolve in a coupled manner to resort size saturation, with resorts protected against small-to-intermediate-scale storms under fairly stable sea level. Under extended, rapidly rising sea level, protection measures enhance the effect of large storms, leading to emergent behavior in the form of limit cycles or barrier submergence, depending on the relative rates of resort recovery from storms and sea level rise. The model is applied to Ocean City, Maryland and neighboring undeveloped Assateague Island National Seashore. Supported by the National Science Foundation, Geology and Paleontology Program, and the Andrew W. Mellon Foundation

Removal of Pb(II), Cd(II), Cu(II), and Zn(II) by hematite nanoparticles: effect of sorbent concentration, pH, temperature, and exhaustion.

PubMed

Shipley, Heather J; Engates, Karen E; Grover, Valerie A

2013-03-01

Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions (Pb(II), Cd(II), Cu(II), Zn(II)) to nanohematite was examined as a function of sorbent concentration, pH, temperature, and exhaustion. Adsorption experiments were conducted with 0.05, 0.1, and 0.5 g/L nanoparticles in a pH 8 solution and in spiked San Antonio tap water. The adsorption data showed the ability of nanohematite to remove Pb, Cd, Cu, and Zn species from solution with adsorption increasing as the nanoparticle concentration increased. At 0.5 g/L nanohematite, 100 % Pb species adsorbed, 94 % Cd species adsorbed, 89 % Cu species adsorbed and 100 % Zn species adsorbed. Adsorption kinetics for all metals tested was described by a pseudo second-order rate equation with lead having the fastest rate of adsorption. The effect of temperature on adsorption showed that Pb(II), Cu(II), and Cd(II) underwent an endothermic reaction, while Zn(II) underwent an exothermic reaction. The nanoparticles were able to simultaneously remove multiple metals species (Zn, Cd, Pb, and Cu) from both a pH 8 solution and spiked San Antonio tap water. Exhaustion experiments showed that at pH 8, exhaustion did not occur for the nanoparticles but adsorption does decrease for Cd, Cu, and Zn species but not Pb species. The strong adsorption coupled with the ability to simultaneously remove multiple metal ions offers a potential remediation method for the removal of metals from water.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Runhong; Fung, Victor; Zhang, Yafen

Perovskites are interesting materials for catalysis due to their great tunability. However, the correlation of many reaction processes to the termination of a perovskite surface is still unclear. In this paper, we use the methanol coupling reaction on the SrTiO 3(100) surface as a probe reaction to investigate direct C–C coupling from a computational perspective. We use density functional theory to assess methanol adsorption, C–H activation, and direct C–C coupling reactions on the SrTiO 3(100) surface of different terminations. We find that, although methanol molecules dissociatively adsorb on both A and B terminations with similar strength, the dehydrogenation and C–Cmore » coupling reactions have significantly lower activation energies on the B termination than on the A termination. The predicted formation of methoxy and acetate on the SrTiO 3(100) B termination can well explain the ambient-pressure XPS data of methanol on the single-crystal SrTiO 3(100) surface at 250 °C. Finally, this work suggests that a choice of B termination of perovskites would be beneficial for the C–C coupling reaction of methanol.« less

Influence of silane coupling agent on microstructure and properties of CCTO-P(VDF-CTFE) composites

NASA Astrophysics Data System (ADS)

Tong, Yang; Zhang, Lin; Bass, Patrick; Rolin, Terry D.; Cheng, Z.-Y.

Influence of the coupling agent on microstructure and dielectric properties of ceramic-polymer composites is systematically studied using CaCu3Ti4O12 (CCTO) as the filler, trichloro-(1H,1H,2H,2H-perfluorooctyl)-silane (Cl3-silane) as coupling agent, and P(VDF-CTFE) 88/12mol.% copolymer as the matrix. It is demonstrated that Cl3-silane molecules can be attached onto CCTO surface using a simple process. The experimental results show that coating CCTO with Cl3-silane can improve the microstructure uniformity of the composites due to the good wettability between Cl3-silane and P(VDF-CTFE), which also significantly improves the electric breakdown field of the composites. It is found that the composites using CCTO coated with 1.0wt.% Cl3-silane exhibit a higher dielectric constant with a higher electric breakdown field. For the composites with 15vol.% CCTO that is coated with 1.0wt.% Cl3-silane, an electric breakdown field of more than 240MV/m is obtained with an energy density of more than 4.5J/cm3. It is also experimentally found that the dielectric constant can be used to easily identify the optimized content of coupling agent.

Agent-based Model for the Coupled Human-Climate System

NASA Astrophysics Data System (ADS)

Zvoleff, A.; Werner, B.

2006-12-01

Integrated assessment models have been used to predict the outcome of coupled economic growth, resource use, greenhouse gas emissions and climate change, both for scientific and policy purposes. These models generally have employed significant simplifications that suppress nonlinearities and the possibility of multiple equilibria in both their economic (DeCanio, 2005) and climate (Schneider and Kuntz-Duriseti, 2002) components. As one step toward exploring general features of the nonlinear dynamics of the coupled system, we have developed a series of variations on the well studied RICE and DICE models, which employ different forms of agent-based market dynamics and "climate surprises." Markets are introduced through the replacement of the production function of the DICE/RICE models with an agent-based market modeling the interactions of producers, policymakers, and consumer agents. Technological change and population growth are treated endogenously. Climate surprises are representations of positive (for example, ice sheet collapse) or negative (for example, increased aerosols from desertification) feedbacks that are turned on with probability depending on warming. Initial results point toward the possibility of large amplitude instabilities in the coupled human-climate system owing to the mismatch between short outlook market dynamics and long term climate responses. Implications for predictability of future climate will be discussed. Supported by the Andrew W Mellon Foundation and the UC Academic Senate.

Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

NASA Astrophysics Data System (ADS)

Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

2015-12-01

In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

Effects of magnetic cobalt ferrite nanoparticles on biological and artificial lipid membranes

PubMed Central

Drašler, Barbara; Drobne, Damjana; Novak, Sara; Valant, Janez; Boljte, Sabina; Otrin, Lado; Rappolt, Michael; Sartori, Barbara; Iglič, Aleš; Kralj-Iglič, Veronika; Šuštar, Vid; Makovec, Darko; Gyergyek, Sašo; Hočevar, Matej; Godec, Matjaž; Zupanc, Jernej

2014-01-01

Background The purpose of this work is to provide experimental evidence on the interactions of suspended nanoparticles with artificial or biological membranes and to assess the possibility of suspended nanoparticles interacting with the lipid component of biological membranes. Methods 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid vesicles and human red blood cells were incubated in suspensions of magnetic bare cobalt ferrite (CoFe2O4) or citric acid (CA)-adsorbed CoFe2O4 nanoparticles dispersed in phosphate-buffered saline and glucose solution. The stability of POPC giant unilamellar vesicles after incubation in the tested nanoparticle suspensions was assessed by phase-contrast light microscopy and analyzed with computer-aided imaging. Structural changes in the POPC multilamellar vesicles were assessed by small angle X-ray scattering, and the shape transformation of red blood cells after incubation in tested suspensions of nanoparticles was observed using scanning electron microscopy and sedimentation, agglutination, and hemolysis assays. Results Artificial lipid membranes were disturbed more by CA-adsorbed CoFe2O4 nanoparticle suspensions than by bare CoFe2O4 nanoparticle suspensions. CA-adsorbed CoFe2O4-CA nanoparticles caused more significant shape transformation in red blood cells than bare CoFe2O4 nanoparticles. Conclusion Consistent with their smaller sized agglomerates, CA-adsorbed CoFe2O4 nanoparticles demonstrate more pronounced effects on artificial and biological membranes. Larger agglomerates of nanoparticles were confirmed to be reactive against lipid membranes and thus not acceptable for use with red blood cells. This finding is significant with respect to the efficient and safe application of nanoparticles as medicinal agents. PMID:24741305

Synergistic effect of PANI-ZrO2 composite as antibacterial, anti-corrosion, and phosphate adsorbent material: synthesis, characterization and applications.

PubMed

Masim, Frances Camille P; Tsai, Cheng-Hsien; Lin, Yi-Feng; Fu, Ming-Lai; Liu, Minghua; Kang, Fei; Wang, Ya-Fen

2017-11-03

The increasing number of bacteria-related problems and presence of trace amounts of phosphate in treated wastewater effluents have become a growing concern in environmental research. The use of antibacterial agents and phosphate adsorbents for the treatment of wastewater effluents is of great importance. In this study, the potential applications of a synthesized polyaniline (PANI)-zirconium dioxide (ZrO 2 ) composite as an antibacterial, phosphate adsorbent and anti-corrosion material were systematically investigated. The results of an antibacterial test reveal an effective area of inhibition of 14 and 18 mm for the Escherichia coli and Staphylococcus aureus bacterial strains, respectively. The antibacterial efficiency of the PANI-ZrO 2 composite is twice that of commercial ZrO 2 . In particular, the introduction of PANI increased the specific surface area and roughness of the composite material, which was beneficial to increase the contact area with bacterial and phosphate. The experimental results demonstrated that phosphate adsorption studies using 200 mg P/L phosphate solution showed a significant phosphate removal efficiency of 64.4%, and the maximum adsorption capacity of phosphate on the solid surface of PANI-ZrO 2 is 32.4 mg P/g. Furthermore, PANI-ZrO 2 coated on iron substrate was tested for anti-corrosion studies by a natural salt spray test (7.5% NaCl), which resulted in the formation of no rust. To the best of our knowledge, no works have been reported on the synergistic effects of the PANI-ZrO 2 composite as an antibacterial, anti-corrosion, and phosphate adsorbent material. PANI-ZrO 2 composite is expected to be a promising comprehensive treatment method for water filters in the aquaculture industry and for use in water purification applications.

Application of online measures to monitor and evaluate multiplatform fusion performance

NASA Astrophysics Data System (ADS)

Stubberud, Stephen C.; Kowalski, Charlene; Klamer, Dale M.

1999-07-01

A primary concern of multiplatform data fusion is assessing the quality and utility of data shared among platforms. Constraints such as platform and sensor capability and task load necessitate development of an on-line system that computes a metric to determine which other platform can provide the best data for processing. To determine data quality, we are implementing an approach based on entropy coupled with intelligent agents. To determine data quality, we are implementing an approach based on entropy coupled with intelligent agents. Entropy measures quality of processed information such as localization, classification, and ambiguity in measurement-to-track association. Lower entropy scores imply less uncertainty about a particular target. When new information is provided, we compuete the level of improvement a particular track obtains from one measurement to another. The measure permits us to evaluate the utility of the new information. We couple entropy with intelligent agents that provide two main data gathering functions: estimation of another platform's performance and evaluation of the new measurement data's quality. Both functions result from the entropy metric. The intelligent agent on a platform makes an estimate of another platform's measurement and provides it to its own fusion system, which can then incorporate it, for a particular target. A resulting entropy measure is then calculated and returned to its own agent. From this metric, the agent determines a perceived value of the offboard platform's measurement. If the value is satisfactory, the agent requests the measurement from the other platform, usually by interacting with the other platform's agent. Once the actual measurement is received, again entropy is computed and the agent assesses its estimation process and refines it accordingly.

Comparison of Zirconium Phosphonate-Modified Surfaces for Immobilizing Phosphopeptides and Phosphate-Tagged Proteins.

PubMed

Forato, Florian; Liu, Hao; Benoit, Roland; Fayon, Franck; Charlier, Cathy; Fateh, Amina; Defontaine, Alain; Tellier, Charles; Talham, Daniel R; Queffélec, Clémence; Bujoli, Bruno

2016-06-07

Different routes for preparing zirconium phosphonate-modified surfaces for immobilizing biomolecular probes are compared. Two chemical-modification approaches were explored to form self-assembled monolayers on commercially available primary amine-functionalized slides, and the resulting surfaces were compared to well-characterized zirconium phosphonate monolayer-modified supports prepared using Langmuir-Blodgett methods. When using POCl3 as the amine phosphorylating agent followed by treatment with zirconyl chloride, the result was not a zirconium-phosphonate monolayer, as commonly assumed in the literature, but rather the process gives adsorbed zirconium oxide/hydroxide species and to a lower extent adsorbed zirconium phosphate and/or phosphonate. Reactions giving rise to these products were modeled in homogeneous-phase studies. Nevertheless, each of the three modified surfaces effectively immobilized phosphopeptides and phosphopeptide tags fused to an affinity protein. Unexpectedly, the zirconium oxide/hydroxide modified surface, formed by treating the amine-coated slides with POCl3/Zr(4+), afforded better immobilization of the peptides and proteins and efficient capture of their targets.

Chemical activation of gasification carbon residue for phosphate removal

NASA Astrophysics Data System (ADS)

Kilpimaa, Sari; Runtti, Hanna; Lassi, Ulla; Kuokkanen, Toivo

2012-05-01

Recycling of waste materials provides an economical and environmentally significant method to reduce the amount of waste. Bioash formed in the gasification process possesses a notable amount of unburned carbon and therefore it can be called a carbon residue. After chemical activation carbon residue could be use to replace activated carbon for example in wastewater purification processes. The effect of chemical activation process variables such as chemical agents and contact time in the chemical activation process were investigated. This study also explored the effectiveness of the chemically activated carbon residue for the removal of phosphate from an aqueous solution. The experimental adsorption study was performed in a batch reactor and the influence of adsorption time, initial phosphate concentration and pH was studied. Due to the carbon residue's low cost and high adsorption capacity, this type of waste has the potential to be utilised for the cost-effective removal of phosphate from wastewaters. Potential adsorbents could be prepared from these carbonaceous by-products and used as an adsorbent for phosphate removal.

Surface Reactivity Enhancement on a Pd/Bi2Te3 Heterostructure through Robust Topological Surface States

PubMed Central

He, Qing Lin; Lai, Ying Hoi; Lu, Yao; Law, Kam Tuen; Sou, Iam Keong

2013-01-01

We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure. The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation. The surface reactivity of the adsorbed tellurium on this heterostructure is also intensified possibly benefitted from the effective transfer of the bath electrons. A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates. PMID:23970163

Adsorption of Heavy Metal Ions from Aqueous Solutions by Bentonite Nanocomposites.

PubMed

Ma, Jing; Su, Guojun; Zhang, Xueping; Huang, Wen

2016-08-01

A series of bentonite nanocomposites have been synthesized by modifying bentonite with hexadecyltrimethylammonium bromide (CTMAB) and the common complexing agents, complexone (ethylene diamine tetraacetic acid, EDTA) or mercaptocomplexant (2-Mercaptobenzothiazole, MBT). These adsorbents are used to remove heavy metal ions (Cu(2+), Zn(2+), Mn(2+),Co(2+)). The Bent-CTMAB-MBT adsorbed metal ions are higher than Bent-CTMAB-EDTA under the same ion concentration in AAS. Compared with the single ion system, the adsorption of the mixed ion system of Cu(2+), Zn(2+), Mn(2+), Co(2+) had decreased differently. In the mixed system, the adsorption of Mn(2+) is significantly lower, but the adsorption of Cu(2+) was highest. The adsorption sequence of these four metal ions was Cu(2+) > Zn(2+) > Co(2+) > Mn(2+), and the selective adsorption was closely related to the hydration energy of heavy metal ions. We could remove more metal ions in different stages with the adsorption sequence.

The Study of Blocking Agent on Lengkeng (Euphoria Logan Lour) Fruit Shell and Seed for Adsorption of Pb (II) from Aqueous Solution

NASA Astrophysics Data System (ADS)

Kurniawati, D.; Zein, R.; Chaidir, Z.; Aziz, H.

2018-04-01

The study focuses on the roles played by mayor functional groups(carboxyl) in the lengkeng shell for sorption of Pb (II). The biosorbent was characterized by FTIR and elemental analyses. The parameters such as pH, initial concentration, particle sizes, adsorbent dose and flow rate were also studied. The results showed that the optimum condition was at pH = 3, concentration 400 mg/l, 250 μm particle sizes, adsorbent dose 0,5 g and 2 ml/min flow rate with adsorption capacity 4,8933 mg/g(shell) and 5,2720 mg/g(seed). It is show that ion exchange play as a more important role in the sorption of Pb (II) on lengkeng shell and seed. Blocking of COOH groups by chemical esterification resulted in Pb important reduction in metal binding.The result showed that adsorption capacity of lengkeng shell uncreases until 63.67 % and lengkeng seed uncreases 98.70%.

Effects of heat exchanger tubes on hydrodynamics and CO 2 capture of a sorbent-based fluidized bed reactor

DOE PAGES

Lai, Canhai; Xu, Zhijie; Li, Tingwen; ...

2017-08-05

In virtual design and scale up of pilot-scale carbon capture systems, the coupled reactive multiphase flow problem must be solved to predict the adsorber's performance and capture efficiency under various operation conditions. This paper focuses on the detailed computational fluid dynamics (CFD) modeling of a pilot-scale fluidized bed adsorber equipped with vertical cooling tubes. Multiphase Flow with Interphase eXchanges (MFiX), an open-source multiphase flow CFD solver, is used for the simulations with custom code to simulate the chemical reactions and filtered sub-grid models to capture the effect of the unresolved details in the coarser mesh for simulations with reasonable accuracymore » and manageable computational effort. Previously developed filtered models for horizontal cylinder drag, heat transfer, and reaction kinetics have been modified to derive the 2D filtered models representing vertical cylinders in the coarse-grid CFD simulations. The effects of the heat exchanger configurations (i.e., horizontal or vertical tubes) on the adsorber's hydrodynamics and CO 2 capture performance are then examined. A one-dimensional three-region process model is briefly introduced for comparison purpose. The CFD model matches reasonably well with the process model while provides additional information about the flow field that is not available with the process model.« less

Synthesis of activated carbon-based amino phosphonic acid chelating resin and its adsorption properties for Ce(III) removal.

PubMed

Chen, Tao; Yan, Chunjie; Wang, Yixia; Tang, Conghai; Zhou, Sen; Zhao, Yuan; Ma, Rui; Duan, Ping

2015-01-01

This work aims to investigate the adsorption of Ce(III) onto chelating resin based on activated carbon (CRAC). The CRAC adsorbent was prepared from activated carbon (AC) followed by oxidation, silane coupling, ammoniation and phosphorylation, and characterized by Fourier transform-infrared spectrometry, nitrogen adsorption measurements and scanning electron microscopy. The effects of solution pH, adsorbent dosage and contact time were studied by batch technique. Langmuir and Freundlich isotherms were used to describe the adsorption behaviour of Ce(III) by CRAC, and the results showed that the adsorption behaviour well fitted the Langmuir model. The maximum uptake capacity (qmax) calculated by using the Langmuir equation for cerium ions was found to be 94.34 mg/g. A comparison of the kinetic models and the overall experimental data was best fitted with the type 1 pseudo second-order kinetic model. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) showed that the adsorption for Ce(III) was feasible, spontaneous and exothermic at 25-45 °C. The CRAC showed an excellent adsorptive selectivity towards Ce(III). Moreover, more than 82% of Ce(III) adsorbed onto CRAC could be desorbed with HCl and could be used several times.

Sequestration of toxic Pb(II) ions by chemically treated rubber (Hevea brasiliensis) leaf powder.

PubMed

Kamal, Megat Hanafiah Megat Ahmad; Azira, Wan Mat Khalir Wan Khaima; Kasmawati, Mohamed; Haslizaidi, Zakaria; Saime, Wan Ngah Wan

2010-01-01

Rubber leaf powder (an agricultural waste) was treated with potassium permanganate followed by sodium carbonate and its performance in the removal of Pb(II) ions from aqueous solution was evaluated. The interactions between Pb(II) ions and functional groups on the adsorbent surface were confirmed by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) coupled with X-ray energy dispersive spectroscopy (EDX). The effects of several important parameters which can affect adsorption capacity such as pH, adsorbent dosage, initial lead concentration and contact time were studied. The optimum pH range for lead adsorption was 4-5. Even at very low adsorbent dosage of 0.02 g, almost 100% of Pb(II) ions (23 mg/L) could be removed. The adsorption capacity was also dependent on lead concentration and contact time, and relatively a short period of time (60-90 min) was required to reach equilibrium. The equilibrium data were analyzed with Langmuir, Freundlich and Dubinin-Radushkevich isotherms. Based on Langmuir model, the maximum adsorption capacity of lead was 95.3 mg/g. Three kinetic models including pseudo first-order, pseudo second-order and Boyd were used to analyze the lead adsorption process, and the results showed that the pseudo second-order fitted well with correlation coefficients greater than 0.99.

Nanoscale carbon materials from hydrocarbons pyrolysis: Structure, chemical behavior, utilisation for non-aqueous supercapacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savilov, Serguei V., E-mail: savilov@chem.msu.ru; Strokova, Natalia E.; Ivanov, Anton S.

Highlights: • N-doped and regular carbon nanomaterials were obtained by pyrolitic technique. • Dynamic vapor sorption of different solvents reveals smaller S{sub BET} values. • Steric hindrance and specific chemical interactions are the reasons for this. • Nitrogen doping leads to raise of capacitance and coulombic efficiency with non-aqueous N-containing electrolyte. - Abstract: This work systematically studies adsorption properties of carbon nanomaterials that are synthesized through hydrocarbons that is a powerful technique to fabricate different kinds of carbon materials, e.g., nanotubes, nanoshells, onions, including nitrogen substituted. The adsorption properties of the as-synthesized carbons are achieved by low temperature nitrogen adsorptionmore » and organic vapors sorption. Heptane, acetonitrile, water, ethanol, benzene and 1-methylimidazole, which are of great importance for development of supercapacitors, are used as substrates. It is discovered that while nitrogen adsorption reveals a high specific surface area, this parameter for most of organic compounds is rather small depending not only on the size of its molecule but also on chemical interactions for a pair adsorbent–adsorbate. The experimental values of heat of adsorption for carbon and N-substituted structures, when Coulomb cross-coupling of nitrogen atoms in adsorbent and adsorbate takes place, confirms this supposition.« less

The Interplay between Information and Control Theory within Interactive Decision-Making Problems

ERIC Educational Resources Information Center

Gorantla, Siva Kumar

2012-01-01

The context for this work is two-agent team decision systems. An "agent" is an intelligent entity that can measure some aspect of its environment, process information and possibly influence the environment through its action. In a collaborative two-agent team decision system, the agents can be coupled by noisy or noiseless interactions…

Understanding Methanol Coupling on SrTiO 3 from First Principles

DOE PAGES

Huang, Runhong; Fung, Victor; Zhang, Yafen; ...

2018-03-19

Perovskites are interesting materials for catalysis due to their great tunability. However, the correlation of many reaction processes to the termination of a perovskite surface is still unclear. In this paper, we use the methanol coupling reaction on the SrTiO 3(100) surface as a probe reaction to investigate direct C–C coupling from a computational perspective. We use density functional theory to assess methanol adsorption, C–H activation, and direct C–C coupling reactions on the SrTiO 3(100) surface of different terminations. We find that, although methanol molecules dissociatively adsorb on both A and B terminations with similar strength, the dehydrogenation and C–Cmore » coupling reactions have significantly lower activation energies on the B termination than on the A termination. The predicted formation of methoxy and acetate on the SrTiO 3(100) B termination can well explain the ambient-pressure XPS data of methanol on the single-crystal SrTiO 3(100) surface at 250 °C. Finally, this work suggests that a choice of B termination of perovskites would be beneficial for the C–C coupling reaction of methanol.« less

Adsorbent Alkali Conditioning for Uranium Adsorption from Seawater. Adsorbent Performance and Technology Cost Evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsouris, Costas; Mayes, Richard T.; Janke, Christopher James

The Fuel Resources program of the Fuel Cycle Research and Development program of the Office of Nuclear Energy (NE) is focused on identifying and implementing actions to assure that nuclear fuel resources are available in the United States. An immense source of uranium is seawater, which contains an estimated amount of 4.5 billion tonnes of dissolved uranium. This unconventional resource can provide a price cap and ensure centuries of uranium supply for future nuclear energy production. NE initiated a multidisciplinary program with participants from national laboratories, universities, and research institutes to enable technical breakthroughs related to uranium recovery from seawater.more » The goal is to develop advanced adsorbents to reduce the seawater uranium recovery technology cost and uncertainties. Under this program, Oak Ridge National Laboratory (ORNL) has developed a new amidoxime-based adsorbent of high surface area, which tripled the uranium capacity of leading Japanese adsorbents. Parallel efforts have been focused on the optimization of the physicochemical and operating parameters used during the preparation of the adsorbent for deployment. A set of parameters that need to be optimized are related to the conditioning of the adsorbent with alkali solution, which is necessary prior to adsorbent deployment. Previous work indicated that alkali-conditioning parameters significantly affect the adsorbent performance. Initiated in 2014, this study had as a goal to determine optimal parameters such as base type and concentration, temperature, and duration of conditioning that maximize the uranium adsorption performance of amidoxime functionalized adsorbent, while keeping the cost of uranium production low. After base-treatment at various conditions, samples of adsorbent developed at ORNL were tested in this study with batch simulated seawater solution of 8-ppm uranium concentration, batch seawater spiked with uranium nitrate at 75-100 ppb uranium, and continuous-flow natural seawater at the Pacific Northwest National Laboratory (PNNL). Fourier Transform Infrared (FTIR) spectroscopy, Nuclear Magnetic Resonance (NMR) spectroscopy, Scanning Electron Microscopy (SEM), and elemental analysis were used to characterize the adsorbent at different stages of adsorbent preparation and treatment. The study can be divided into two parts: (A) investigation of optimal parameters for KOH adsorbent conditioning and (B) investigation of other possible agents for alkali conditioning, including cost analysis on the basis of uranium production. In the first part of the study, tests with simulated seawater containing 8 ppm uranium showed that the uranium adsorption capacity increased with an increase in the KOH concentration and conditioning time and temperature at each of the KOH concentrations used. FTIR and solid state NMR studies indicated that KOH conditioning converts the amidoxime functional groups into more hydrophilic carboxylate. The longer the KOH conditioning time, up to three hours, the higher was the loading capacity from the simulated seawater solution which is composed of only uranyl, sodium, chloride, and carbonate ions. Marine testing with natural seawater, on the other hand, showed that the uranium adsorption capacity of the adsorbent increased with KOH conditioning temperature, and gradually decreased with increasing KOH conditioning time from one hour to three hours at 80 C. This behavior is due to the conversion of amidoxime to carboxylate. The carboxylate groups are needed to increase the hydrophilicity of the adsorbent; however, conversion of a significant amount of amidoxime to carboxylate leads to loss in selectivity toward uranyl ions. Thus, there is an optimum KOH conditioning time for each temperature at which an optimum ratio between amidoxime and carboxylate is reached. For the case of base conditioning with 0.44 M KOH at 80 C, the optimal conditioning time is 1 hour, with respect to the highest uranium loading capacity from natural seawater. Uptake of other metal ions such as V, Fe, and Cu follows the same trend as that of uranium. Also, the uptake of Ca, Mg, and Zn ions increased with increasing KOH conditioning time, probably due to formation of more carboxylates, which leads to conversion of uranium-selective binding sites to less selective sites. In the second part of the study, inorganic based reagents such as sodium hydroxide (NaOH), sodium carbonate (Na 2CO 3), cesium hydroxide (CsOH), as well as organic based reagents such as ammonium hydroxide (AOH), tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), triethylmethylammonium hydroxide (TEMAOH), tetrapropylammonium hydroxide (TPAOH) and tetrabutylammonium hydroxide (TBAOH), in addition to KOH, were used for alkaline conditioning. NaOH has emerged as a better reagent for alkaline conditioning of amidoxime-based adsorbent because of higher uranium uptake capacity, higher uranium uptake selectivity ...« less

STM-induced light emission enhanced by weakly coupled organic ad-layers

NASA Astrophysics Data System (ADS)

Cottin, M. C.; Ekici, E.; Bobisch, C. A.

2018-03-01

We analyze the light emission induced by the tunneling current flowing in a scanning tunneling microscopy experiment. In particular, we study the influence of organic ad-layers on the light emission on the initial monolayer of bismuth (Bi) on Cu(111) in comparison to the well-known case of organic ad-layers on Ag(111). On the Bi/Cu(111)-surface, we find that the scanning tunneling microscopy-induced light emission is considerably enhanced if an organic layer, e.g., the fullerene C60 or the perylene derivate perylene-tetracarboxylic-dianhydride, is introduced into the tip-sample junction. The enhancement can be correlated with a peculiarly weak interaction between the adsorbed molecules and the underlying Bi/Cu(111) substrate as compared to the Ag(111) substrate. This allows us to efficiently enhance and tune the coupling of the tunneling current to localized excitations of the tip-sample junction, which in turn couple to radiative decay channels.

Mercury(II) removal from aqueous solutions and wastewaters using a novel cation exchanger derived from coconut coir pith and its recovery.

PubMed

Anirudhan, T S; Divya, L; Ramachandran, M

2008-09-15

A new adsorbent (PGCP-COOH) having carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto coconut coir pith, CP (a coir industry-based lignocellulosic residue), using potassium peroxydisulphate as an initiator and in the presence of N,N'-methylenebisacrylamide as a cross-linking agent. The adsorbent was characterized with the help of infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and potentiometric titrations. The ability of PGCP-COOH to remove Hg(II) from aqueous solutions was assessed using batch adsorption technique under kinetic and equilibrium conditions. Adsorbent exhibits very high adsorption potential for Hg(II) and more than 99.0% removal was achieved in the pH range 5.5-8.0. Adsorption process was found to follow first-order-reversible kinetics. An increase of ionic strength of the medium caused a decrease in metal removal, indicating the occurrence of outer-sphere surface complex mechanism. The equilibrium data were fitted well by the Freundlich isotherm model (R(2)=0.99; chi(2)=1.81). The removal efficiency was tested using chlor-alkali industry wastewater. Adsorption isotherm experiments were also conducted for comparison using a commercial carboxylate-functionalized ion exchanger, Ceralite IRC-50. Regeneration experiments were tried for four cycles and results indicate a capacity loss of <9.0%.

Combining human and machine intelligence to derive agents' behavioral rules for groundwater irrigation

NASA Astrophysics Data System (ADS)

Hu, Yao; Quinn, Christopher J.; Cai, Ximing; Garfinkle, Noah W.

2017-11-01

For agent-based modeling, the major challenges in deriving agents' behavioral rules arise from agents' bounded rationality and data scarcity. This study proposes a "gray box" approach to address the challenge by incorporating expert domain knowledge (i.e., human intelligence) with machine learning techniques (i.e., machine intelligence). Specifically, we propose using directed information graph (DIG), boosted regression trees (BRT), and domain knowledge to infer causal factors and identify behavioral rules from data. A case study is conducted to investigate farmers' pumping behavior in the Midwest, U.S.A. Results show that four factors identified by the DIG algorithm- corn price, underlying groundwater level, monthly mean temperature and precipitation- have main causal influences on agents' decisions on monthly groundwater irrigation depth. The agent-based model is then developed based on the behavioral rules represented by three DIGs and modeled by BRTs, and coupled with a physically-based groundwater model to investigate the impacts of agents' pumping behavior on the underlying groundwater system in the context of coupled human and environmental systems.

The application of single particle aerosol mass spectrometry for the detection and identification of high explosives and chemical warfare agents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Audrey Noreen

2006-01-01

Single Particle Aerosol Mass Spectrometry (SPAMS) was evaluated as a real-time detection technique for single particles of high explosives. Dual-polarity time-of-flight mass spectra were obtained for samples of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazinane (RDX), and pentaerythritol tetranitrate (PETN); peaks indicative of each compound were identified. Composite explosives, Comp B, Semtex 1A, and Semtex 1H were also analyzed, and peaks due to the explosive components of each sample were present in each spectrum. Mass spectral variability with laser fluence is discussed. The ability of the SPAMS system to identify explosive components in a single complex explosive particle (~1 pg) without the need formore » consumables is demonstrated. SPAMS was also applied to the detection of Chemical Warfare Agent (CWA) simulants in the liquid and vapor phases. Liquid simulants for sarin, cyclosarin, tabun, and VX were analyzed; peaks indicative of each simulant were identified. Vapor phase CWA simulants were adsorbed onto alumina, silica, Zeolite, activated carbon, and metal powders which were directly analyzed using SPAMS. The use of metal powders as adsorbent materials was especially useful in the analysis of triethyl phosphate (TEP), a VX stimulant, which was undetectable using SPAMS in the liquid phase. The capability of SPAMS to detect high explosives and CWA simulants using one set of operational conditions is established.« less

Controlled preparation of M(Ag, Au)/TiO2 through sulfydryl-assisted method for enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Xia, Hongbo; Wu, Suli; Bi, Jiajie; Zhang, Shufen

2017-11-01

Here a simple and effective method was explored to fabricate M/TiO2 (M = Ag, Au) composites, which required neither pre-treatment of TiO2 nor any additives as reducing agent. Using amorphous TiO2 spheres functionalized with SH groups as starting materials, the noble metallic ions (Ag, Au) can be adsorbed by TiO2 due to their special affinity with SH groups, which is beneficial to the uniform dispersion of metallic ions on the surface of TiO2. Then the adsorbed ions were reduced to form noble metal nanoparticles by heating process (95 °C) directly without additive as reduction agent. Meanwhile, the amorphous TiO2 was transformed into anatase phase during the heating process. Thus, the transformation of TiO2 along with the reduction of noble metallic ions (Ag, Au) was simultaneously carried out by heating. The XRD patterns proved the formation of anatase TiO2 after heating. The characterizations of XPS and TEM proved the formation of Ag and Au nanoparticles on the surface of TiO2. The element mapping indicated that Ag nanoparticles are dispersed uniformly on the surface of TiO2. The photocatalytic activity of the composites has been investigated by the degradation of methyl orange under visible light irradiation. The results showed that when Ag/TiO2 (2.8 wt%) was used as photocatalyst, about 98% of the MO molecules were degraded in 70 min.

Implications of interfacial characteristics of food foaming agents in foam formulations.

PubMed

Rodríguez Patino, Juan M; Carrera Sánchez, Cecilio; Rodríguez Niño, Ma Rosario

2008-08-05

The manufacture of food dispersions (emulsions and foams) with specific quality attributes depends on the selection of the most appropriate raw materials and processing conditions. These dispersions being thermodynamically unstable require the use of emulsifiers (proteins, lipids, phospholipids, surfactants etc.). Emulsifiers typically coexist in the interfacial layer with specific functions in the processing and properties of the final product. The optimum use of emulsifiers depends on our knowledge of their interfacial physico-chemical characteristics - such as surface activity, amount adsorbed, structure, thickness, topography, ability to desorb (stability), lateral mobility, interactions between adsorbed molecules, ability to change conformation, interfacial rheological properties, etc. -, the kinetics of film formation and other associated physico-chemical properties at fluid interfaces. These monolayers constitute well defined systems for the analysis of food colloids at the micro- and nano-scale level, with several advantages for fundamental studies. In the present review we are concerned with the analysis of physico-chemical properties of emulsifier films at fluid interfaces in relation to foaming. Information about the above properties would be very helpful in the prediction of optimised formulations for food foams. We concluded that at surface pressures lower than that of monolayer saturation the foaming capacity is low, or even zero. A close relationship was observed between foaming capacity and the rate of diffusion of the foaming agent to the air-water interface. However, the foam stability correlates with the properties of the film at long-term adsorption.

High efficiency removal of triclosan by structure-directing agent modified mesoporous MIL-53(Al).

PubMed

Dou, Rongni; Zhang, Junya; Chen, Yuancai; Feng, Siyuan

2017-03-01

In order to expand the potential applications of metal-organic frameworks (MOFs), structure directing agents modified mesoporous MIL-53(Al) (MIL-53(Al)-1) was investigated to adsorb triclosan (TCS) with two different initial concentrations. MIL-53(Al)-1 with high mesoporosity and total pore volume exhibited higher adsorption capacity and 4.4 times faster adsorption of TCS at low concentration (1 mg L -1 ) than that of microporous MIL-53(Al). Also, mesoporous as well as microporous MIL-53(Al) showed significant higher adsorption capacity and two orders of magnitude greater fast uptake of TCS than two kinds of mesoporous-activated carbon. The adsorption of TCS onto MIL-53(Al)-1 released more energy and had higher disorderliness than TCS on MIL-53(Al). The superior adsorption characteristics of MIL-53(Al)-1 were preserved over a wide pH range (4-9), at high concentration of ionic strengths, and in the presence of coexisting compounds (anions, cations, phenol, aniline, and humic acid). The selectivity adsorption and Fourier transform infrared (FT-IR) spectra revealed that TCS adsorption on MIL-53(Al)s was mainly driven by hydrophobicity interaction assisted with hydrogen bonding on MIL-53(Al)s. MIL-53(Al)s can be effectively regenerated several times by washing with 90% methanol-water (pH 11). All of the above results demonstrated MIL-53(Al)s are promising adsorbents for water purification. Graphical abstract.

Field validation of a free-agent cellular automata model of fire spread with fire–atmosphere coupling

Treesearch

Gary Achtemeier

2012-01-01

A cellular automata fire model represents ‘elements’ of fire by autonomous agents. A few simple algebraic expressions substituted for complex physical and meteorological processes and solved iteratively yield simulations for ‘super-diffusive’ fire spread and coupled surface-layer (2-m) fire–atmosphere processes. Pressure anomalies, which are integrals of the thermal...

Expansion Hamiltonian model for a diatomic molecule adsorbed on a surface: Vibrational states of the CO/Cu(100) system including surface vibrations

NASA Astrophysics Data System (ADS)

Meng, Qingyong; Meyer, Hans-Dieter

2015-10-01

Molecular-surface studies are often done by assuming a corrugated, static (i.e., rigid) surface. To be able to investigate the effects that vibrations of surface atoms may have on spectra and cross sections, an expansion Hamiltonian model is proposed on the basis of the recently reported [R. Marquardt et al., J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES), which was built for the CO/Cu(100) system with a rigid surface. In contrast to other molecule-surface coupling models, such as the modified surface oscillator model, the coupling between the adsorbed molecule and the surface atoms is already included in the present expansion SAP-PES model, in which a Taylor expansion around the equilibrium positions of the surface atoms is performed. To test the quality of the Taylor expansion, a direct model, that is avoiding the expansion, is also studied. The latter, however, requests that there is only one movable surface atom included. On the basis of the present expansion and direct models, the effects of a moving top copper atom (the one to which CO is bound) on the energy levels of a bound CO/Cu(100) system are studied. For this purpose, the multiconfiguration time-dependent Hartree calculations are carried out to obtain the vibrational fundamentals and overtones of the CO/Cu(100) system including a movable top copper atom. In order to interpret the results, a simple model consisting of two coupled harmonic oscillators is introduced. From these calculations, the vibrational levels of the CO/Cu(100) system as function of the frequency of the top copper atom are discussed.

Expansion Hamiltonian model for a diatomic molecule adsorbed on a surface: Vibrational states of the CO/Cu(100) system including surface vibrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Qingyong, E-mail: mengqingyong@dicp.ac.cn; Meyer, Hans-Dieter, E-mail: hans-dieter.meyer@pci.uni-heidelberg.de

2015-10-28

Molecular-surface studies are often done by assuming a corrugated, static (i.e., rigid) surface. To be able to investigate the effects that vibrations of surface atoms may have on spectra and cross sections, an expansion Hamiltonian model is proposed on the basis of the recently reported [R. Marquardt et al., J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES), which was built for the CO/Cu(100) system with a rigid surface. In contrast to other molecule-surface coupling models, such as the modified surface oscillator model, the coupling between the adsorbed molecule and the surface atoms is already included in themore » present expansion SAP-PES model, in which a Taylor expansion around the equilibrium positions of the surface atoms is performed. To test the quality of the Taylor expansion, a direct model, that is avoiding the expansion, is also studied. The latter, however, requests that there is only one movable surface atom included. On the basis of the present expansion and direct models, the effects of a moving top copper atom (the one to which CO is bound) on the energy levels of a bound CO/Cu(100) system are studied. For this purpose, the multiconfiguration time-dependent Hartree calculations are carried out to obtain the vibrational fundamentals and overtones of the CO/Cu(100) system including a movable top copper atom. In order to interpret the results, a simple model consisting of two coupled harmonic oscillators is introduced. From these calculations, the vibrational levels of the CO/Cu(100) system as function of the frequency of the top copper atom are discussed.« less

Integration agent-based models and GIS as a virtual urban dynamic laboratory

NASA Astrophysics Data System (ADS)

Chen, Peng; Liu, Miaolong

2007-06-01

Based on the Agent-based Model and spatial data model, a tight-coupling integrating method of GIS and Agent-based Model (ABM) is to be discussed in this paper. The use of object-orientation for both spatial data and spatial process models facilitates their integration, which can allow exploration and explanation of spatial-temporal phenomena such as urban dynamic. In order to better understand how tight coupling might proceed and to evaluate the possible functional and efficiency gains from such a tight coupling, the agent-based model and spatial data model are discussed, and then the relationships affecting spatial data model and agent-based process models interaction. After that, a realistic crowd flow simulation experiment is presented. Using some tools provided by general GIS systems and a few specific programming languages, a new software system integrating GIS and MAS as a virtual laboratory applicable for simulating pedestrian flows in a crowd activity centre has been developed successfully. Under the environment supported by the software system, as an applicable case, a dynamic evolution process of the pedestrian's flows (dispersed process for the spectators) in a crowds' activity center - The Shanghai Stadium has been simulated successfully. At the end of the paper, some new research problems have been pointed out for the future.

Electrophoretic nanotechnology of graphene-carbon nanotube and graphene-polypyrrole nanofiber composites for electrochemical supercapacitors.

PubMed

Shi, Kaiyuan; Zhitomirsky, Igor

2013-10-01

Thin films of multiwalled carbon nanotubes (MWCNT), graphene and polypyrrole (PPy) nanofibers were prepared by cathodic electrophoretic deposition (EPD) from aqueous suspensions, containing safranin (SAF) as a new dispersant. The results of Fourier transform infrared spectroscopy, UV-Vis spectroscopy studies and sedimentation tests, coupled with deposition yield and electron microscopy data showed that SAF adsorbed on MWCNT, graphene and PPy, provided their dispersion and charging in the suspensions and allowed efficient EPD. The deposition yield can be controlled by the variation of SAF concentration in the suspensions and deposition time. The use of SAF as a co-dispersant for MWCNT, graphene and PPy, allowed controlled EPD of composite graphene-MWCNT and graphene-PPy films. The proposed approach for the deposition of PPy paves the way for EPD of neutral polymers using organic dyes as dispersing and charging agents. The composite films were investigated for application in electrochemical supercapacitors (ES). The graphene-MWCNT and graphene-PPy films showed significant increase in capacitance, decrease in resistance and increase in capacitance retention at high charge-discharge rates compared to the films of individual components. The analysis of electrochemical testing results and electron microscopy data provided an insight into the influence of composite microstructure on electrochemical performance. The composites, prepared by EPD are promising materials for electrodes of ES. Copyright © 2013 Elsevier Inc. All rights reserved.

Magnetic solid phase extraction using ionic liquid-coated core-shell magnetic nanoparticles followed by high-performance liquid chromatography for determination of Rhodamine B in food samples.

PubMed

Chen, Jieping; Zhu, Xiashi

2016-06-01

Three hydrophobic ionic liquids (ILs) (1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6), 1-hexyl-3-methyl-imidazole hexafluoro-phosphate ([HMIM]PF6), and 1-octyl-3-methylimidazole hexafluorophosphate ([OMIM]PF6)) were used to coat Fe3O4@SiO2 nanoparticles (NPs) with core-shell structures to prepare magnetic solid phase extraction (MSPE) agents (Fe3O4@SiO2@IL). A novel method of MSPE coupled with high-performance liquid chromatography for the separation/analysis of Rhodamine B was then established. The results showed that Rhodamine B was adsorbed rapidly on Fe3O4@SiO2@[OMIM]PF6 and was released using ethanol. Under optimal conditions, the pre-concentration factor for the proposed method was 25. The linear range, limit of detection (LOD), correlation coefficient (R), and relative standard deviation (RSD) were found to be 0.50-150.00 μgL(-1), 0.08 μgL(-1), 0.9999, and 0.51% (n=3, c=10.00 μgL(-1)), respectively. The Fe3O4@SiO2 NPs could be re-used up to 10 times. The method was successfully applied to the determination of Rhodamine B in food samples. Copyright © 2016. Published by Elsevier Ltd.

Advanced buffer materials for indoor air CO2 control in commercial buildings.

PubMed

Rajan, P E; Krishnamurthy, A; Morrison, G; Rezaei, F

2017-11-01

In this study, we evaluated solid sorbents for their ability to passively control indoor CO 2 concentration in buildings or rooms with cyclic occupancy (eg, offices, bedrooms). Silica supported amines were identified as suitable candidates and systematically evaluated in the removal of CO 2 from indoor air by equilibrium and dynamic techniques. In particular, sorbents with various amine loadings were synthesized using tetraethylenepentamine (TEPA), poly(ethyleneimine) (PEI) and a silane coupling agent 3-aminopropyltriethoxysilane (APS). TGA analysis indicates that TEPA impregnated silica not only displays a relatively high adsorption capacity when exposed to ppm level CO 2 concentrations, but also is capable of desorbing the majority of CO 2 by air flow (eg, by concentration gradient). In 10 L flow-through chamber experiments, TEPA-based sorbents reduced outlet CO 2 by up to 5% at 50% RH and up to 93% of CO 2 adsorbed over 8 hours was desorbed within 16 hours. In 8 m 3 flow-through chamber experiments, 18 g of the sorbent powder spread over a 2 m 2 area removed approximately 8% of CO 2 injected. By extrapolating these results to real buildings, we estimate that meaningful reductions in the CO 2 can be achieved, which may help reduce energy requirements for ventilation and/or improve air quality. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Embodied cognition and circular causality: on the role of constitutive autonomy in the reciprocal coupling of perception and action

PubMed Central

Vernon, David; Lowe, Robert; Thill, Serge; Ziemke, Tom

2015-01-01

The reciprocal coupling of perception and action in cognitive agents has been firmly established: perceptions guide action but so too do actions influence what is perceived. While much has been said on the implications of this for the agent's external behavior, less attention has been paid to what it means for the internal bodily mechanisms which underpin cognitive behavior. In this article, we wish to redress this by reasserting that the relationship between cognition, perception, and action involves a constitutive element as well as a behavioral element, emphasizing that the reciprocal link between perception and action in cognition merits a renewed focus on the system dynamics inherent in constitutive biological autonomy. Our argument centers on the idea that cognition, perception, and action are all dependent on processes focussed primarily on the maintenance of the agent's autonomy. These processes have an inherently circular nature—self-organizing, self-producing, and self-maintaining—and our goal is to explore these processes and suggest how they can explain the reciprocity of perception and action. Specifically, we argue that the reciprocal coupling is founded primarily on their endogenous roles in the constitutive autonomy of the agent and an associated circular causality of global and local processes of self-regulation, rather than being a mutual sensory-motor contingency that derives from exogenous behavior. Furthermore, the coupling occurs first and foremost via the internal milieu realized by the agent's organismic embodiment. Finally, we consider how homeostasis and the related concept of allostasis contribute to this circular self-regulation. PMID:26579043

Use of absorbent materials in on-line coupled reversed-phase liquid chromatography-gas chromatography via the through oven transfer adsorption desorption interface.

PubMed

Flores, Gema; Díaz-Plaza, Eva María; Cortés, Jose Manuel; Villén, Jesús; Herraiz, Marta

2008-11-21

The use of absorbents as retaining materials in the through oven transfer adsorption desorption interface (TOTAD) of an on-line coupled reversed-phase liquid chromatography-gas chromatography system (RPLC-GC) is proposed for the first time. A comparative study of an adsorbent (Tenax TA) and two absorbents, namely polydimethylsiloxane and poly(50% phenyl/50% methylsiloxane) is performed to establish the best experimental conditions for the automated and simultaneous determination of 15 organophosphorus and organochlorine pesticide residues in olive oil. The proposed method provides satisfactory repeatability (RSDs lower, in general, than 8.5%) and sensitivity (limits of detection ranging from 0.6 to 81.9 microg/L) for the investigated compounds.

Photo-assisted cyanation of transition metal nitrates coupled with room temperature C-C bond cleavage of acetonitrile.

PubMed

Zou, Shihui; Li, Renhong; Kobayashi, Hisayoshi; Liu, Juanjuan; Fan, Jie

2013-03-07

It is a challenge to use acetonitrile as a cyanating agent because of the difficulty in cleaving its C-CN bond. Herein, we report a mild photo-assisted route to conduct the cyanation of transition metal nitrates using acetonitrile as the cyanating agent coupled with room-temperature C-C bond cleavage. DFT calculations and experimental observations suggest a radical-involved reaction mechanism, which excludes toxicity from free cyanide ions.

Shear Bond Strength of Resin Buttons to Lithium Disilicate and Leucite Reinforced Feldspathic Restorations

DTIC Science & Technology

2016-05-01

Hydrofluoric acid, silane coupling agent, light cured composite and ceramic restoration specimens (10 of each IPS e.max and Empress). The surface treatment...cured composite and ceramic restoration specimens (10 of each IPS e.max and Empress). The surface treatment in group C was applied to all specimens...and light cured for 20 seconds. 4) Group D: 5% Hydrofluoric acid, silane coupling agent, light cured composite and ceramic restoration (10 of

Surface-active agents from the group of polyoxyethylated glycerol esters of fatty acids. Part III. Surface activity and solubilizing properties of the products of oxyethylation of lard (Adeps suillus, F.P. VIII) in the equilibrium system in relation to lipophilic therapeutic agents (class II and III of BCS).

PubMed

Nachajski, Michał J; Piotrowska, Jowita B; Kołodziejczyk, Michał K; Lukosek, Marek; Zgoda, Marian M

2013-01-01

Research was conducted into the solubilization processes of diclofenac, ibuprofen, ketoprofen and naproxen in equilibrium conditions in the environment of aqueous solutions of oxyethylated lard's fractions (Adeps suillus, Polish Pharmacopoeia VIII). The determined thermodynamic (cmc, deltaGm(0)) and hydrodynamic (R0, R(obs), omega, M(eta)) parameters characterizing the micelle of the solubilizer and the adduct demonstrate that lipophilic therapeutic agents are adsorbed in a palisade structure of the micelle due to a topologically created so-called "lipophilic adsorption pocket". This shows that the hydrophilicity of the micelle and the adsorption layer decreases at the phase boundary, which is confirmed by the calculated values of coefficients A(m) and r x (a). The results obtained indicate the possibility of making use of the class of non-ionic surfactants which are not ksenobiotics for the modification of the profile of solid oral dosage forms with lipophilic therapeutic agents from the II class of Biopharmaceutics Classification System (BCS).

Use of phenyl/tetrazolyl-functionalized magnetic microspheres and stable isotope labeled internal standards for significant reduction of matrix effect in determination of nine fluoroquinolones by liquid chromatography-quadrupole linear ion trap mass spectrometry.

PubMed

Xu, Fei; Liu, Feng; Wang, Chaozhan; Wei, Yinmao

2018-02-01

In this study, the strategy of unique adsorbent combined with isotope labeled internal standards was used to significantly reduce the matrix effect for the enrichment and analysis of nine fluoroquinolones in a complex sample by liquid chromatography coupled to quadrupole linear ion trap mass spectrometry (LC-QqQ LIT -MS/MS). The adsorbent was prepared conveniently by functionalizing Fe 3 O 4 @SiO 2 microspheres with phenyl and tetrazolyl groups, which could adsorb fluoroquinolones selectively via hydrophobic, electrostatic, and π-π interactions. The established magnetic solid-phase extraction (MSPE) method as well as using stable isotope labeled internal standards in the next MS/MS detection was able to reduce the matrix effect significantly. In the process of LC-QqQ LIT -MS/MS analysis, the precursor and product ions of the analytes were monitored quantitatively and qualitatively on a QTrap system equipped simultaneously with the multiple reaction monitoring (MRM) and enhanced product ion (EPI) scan. Subsequently, the enrichment method combined with LC-QqQ LIT -MS/MS demonstrated good analytical features in terms of linearity (7.5-100.0 ng mL -1 , r > 0.9960), satisfactory recoveries (88.6%-118.3%) with RSDs < 12.0%, LODs = 0.5 μg kg -1 and LOQs = 1.5 μg kg -1 for all tested analytes. Finally, the developed MSPE-LC-QqQ LIT -MS/MS method had been successfully applied to real pork samples for food-safety risk monitoring in Ningxia Province, China. Graphical abstract Mechanism of reducing matrix effect through the as-prepared adsorbent.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurtubise, R.J.

Interaction models were developed for moisture effects on room-temperature fluorescence (RTF) and room-temperature phosphorescence (RTP) of compounds adsorbed on filter paper. The models described both dynamic and matrix quenching and also related the Young modulus of filter paper to quenching of phosphor on moist filter paper. Photophysical parameters for lumiphors in solution and on solid matrices were compared. Results showed that for some compounds, solid-matrix luminescence has greater analytical potential than solution luminescence. Also, the solid-matrix systems into one of two categories depending on how the intersystem crossing rate constants change with temperature. The first study was carried out onmore » effects of heavy atom on solid-matrix luminescence. With some heavy atoms, maximum solid-matrix phosphorescence quantum yield was obtained at room temperature, and there was no need to use low temperature to obtain a strong phosphorescence signal. By studying solid-matrix luminescence properties of phosphors adsorbed on sodium acetate and deuterated sodium acetate, an interaction model was developed for p-aminobenzoic acid anion adsorbed on sodium acetate. It was shown that the energy-gap law was applicable to solid-matrix luminescence. Also, deuterated phenanthrene and undeuterated phenanthrene were used to study nonradiative transition of excited triplet state of adsorbed phosphors. Heat capacities of several solid matrices were obtained vs temperature and related to vibrational coupling of solid matrix with phosphor. Photophysical study was performed on the hydrolysis products of benzo(a)pyrene-DNA adducts. Also, an analytical method was developed for tetrols in human lung fractions. Work was initiated on the formation of room temperature glasses with glucose and trehalose. Also, work has begun for the development of an oxygen sensor by measuring the RTP quenching of triphenylene on filter paper.« less

Charge-transfer excited state in pyrene-1-carboxylic acids adsorbed on titanium dioxide nanoparticles

NASA Astrophysics Data System (ADS)

Krawczyk, S.; Nawrocka, A.; Zdyb, A.

2018-06-01

The electronic structure of excited photosensitizer adsorbed at the surface of a solid is the key factor in the electron transfer processes that underlie the efficiency of dye-sensitized solar cells and photocatalysts. In this work, Stark effect (electroabsorption) spectroscopy has been used to measure the polarizability and dipole moment changes in electronic transitions of pyrene-1-carboxylic (PCA), -acetic (PAA) and -butyric (PBA) acids in ethanol, both free and adsorbed on colloidal TiO2, in glassy ethanol at low temperature. The lack of appreciable increase of dipole moment in the excited state of free and adsorbed PAA and PBA points that two or more single bonds completely prevent the expansion of π-electrons from the aromatic ring towards the carboxylic group, thus excluding the possibility of direct electron injection into TiO2. In free PCA, the pyrene's forbidden S0 → S1 transition has increased intensity, exhibits a long progression in 1400 cm-1 Ag mode and is associated with |Δμ| of 2 D. Adsorption of PCA on TiO2 causes a broadening and red shift of the S0 → S1 absorption band and an increase in dipole moment change on electronic excitation to |Δμ| = 6.5 D. This value increased further to about 15 D when the content of acetic acid in the colloid was changed from 0.2% to 2%, and this effect is ascribed to the surface electric field. The large increase of |Δμ| points that the electric field effect can not only change the energetics of electron transfer from the excited sensitizer into the solid, but can also shift the molecular electronic density, thus directly influencing the electronic coupling factor relevant for electron transfer at the molecule-solid interface.

The effect of interstitial pressure on therapeutic agent transport: coupling with the tumor blood and lymphatic vascular systems.

PubMed

Wu, Min; Frieboes, Hermann B; Chaplain, Mark A J; McDougall, Steven R; Cristini, Vittorio; Lowengrub, John S

2014-08-21

Vascularized tumor growth is characterized by both abnormal interstitial fluid flow and the associated interstitial fluid pressure (IFP). Here, we study the effect that these conditions have on the transport of therapeutic agents during chemotherapy. We apply our recently developed vascular tumor growth model which couples a continuous growth component with a discrete angiogenesis model to show that hypertensive IFP is a physical barrier that may hinder vascular extravasation of agents through transvascular fluid flux convection, which drives the agents away from the tumor. This result is consistent with previous work using simpler models without blood flow or lymphatic drainage. We consider the vascular/interstitial/lymphatic fluid dynamics to show that tumors with larger lymphatic resistance increase the agent concentration more rapidly while also experiencing faster washout. In contrast, tumors with smaller lymphatic resistance accumulate less agents but are able to retain them for a longer time. The agent availability (area-under-the curve, or AUC) increases for less permeable agents as lymphatic resistance increases, and correspondingly decreases for more permeable agents. We also investigate the effect of vascular pathologies on agent transport. We show that elevated vascular hydraulic conductivity contributes to the highest AUC when the agent is less permeable, but to lower AUC when the agent is more permeable. We find that elevated interstitial hydraulic conductivity contributes to low AUC in general regardless of the transvascular agent transport capability. We also couple the agent transport with the tumor dynamics to simulate chemotherapy with the same vascularized tumor under different vascular pathologies. We show that tumors with an elevated interstitial hydraulic conductivity alone require the strongest dosage to shrink. We further show that tumors with elevated vascular hydraulic conductivity are more hypoxic during therapy and that the response slows down as the tumor shrinks due to the heterogeneity and low concentration of agents in the tumor interior compared with the cases where other pathological effects may combine to flatten the IFP and thus reduce the heterogeneity. We conclude that dual normalizations of the micronevironment - both the vasculature and the interstitium - are needed to maximize the effects of chemotherapy, while normalization of only one of these may be insufficient to overcome the physical resistance and may thus lead to sub-optimal outcomes. Copyright © 2014 Elsevier Ltd. All rights reserved.

The effect of interstitial pressure on therapeutic agent transport: coupling with the tumor blood and lymphatic vascular systems

PubMed Central

Wu, Min; Frieboes, Hermann B.; Chaplain, Mark A.J.; McDougall, Steven R.; Cristini, Vittorio; Lowengrub, John

2014-01-01

Vascularized tumor growth is characterized by both abnormal interstitial fluid flow and the associated interstitial fluid pressure (IFP). Here, we study the effect that these conditions have on the transport of therapeutic agents during chemotherapy. We apply our recently developed vascular tumor growth model which couples a continuous growth component with a discrete angiogenesis model to show that hypertensive IFP is a physical barrier that may hinder vascular extravasation of agents through transvascular fluid flux convection, which drives the agents away from the tumor. This result is consistent with previous work using simpler models without blood flow or lymphatic drainage. We consider the vascular/interstitial/lymphatic fluid dynamics to show that tumors with larger lymphatic resistance increase the agent concentration more rapidly while also experiencing faster washout. In contrast, tumors with smaller lymphatic resistance accumulate less agents but are able to retain them for a longer time. The agent availability (area-under-the curve, or AUC) increases for less permeable agents as lymphatic resistance increases, and correspondingly decreases for more permeable agents. We also investigate the effect of vascular pathologies on agent transport. We show that elevated vascular hydraulic conductivity contributes to the highest AUC when the agent is less permeable, but leads to lower AUC when the agent is more permeable. We find that elevated interstitial hydraulic conductivity contributes to low AUC in general regardless of the transvascular agent transport capability. We also couple the agent transport with the tumor dynamics to simulate chemotherapy with the same vascularized tumor under different vascular pathologies. We show that tumors with an elevated interstitial hydraulic conductivity alone require the strongest dosage to shrink. We further show that tumors with elevated vascular hydraulic conductivity are more hypoxic during therapy and that the response slows down as the tumor shrinks due to the heterogeneity and low concentration of agents in the tumor interior compared with the cases where other pathological effects may combine to flatten the IFP and thus reduce the heterogeneity. We conclude that dual normalizations of the micronevironment - both the vasculature and the interstitium - are needed to maximize the effects of chemotherapy, while normalization of only one of these may be insufficient to overcome the physical resistance and thus leads to sub-optimal outcomes. PMID:24751927

The high throughput investigation of polyphenolic couplers in biodegradable packaging materials

NASA Astrophysics Data System (ADS)

Lochhead, Robert Y.; Haynes, Camille T.; Jones, Stephen R.; Smith, Virginia

2006-01-01

Our goal is to select and develop stimuli-responsive interfacial coupling materials for nanocomposites that will enhance substrate mechanical properties during use but cause triggered disintegration when exposed to the appropriate aqueous environment. The study could potentially provide the scientific underpinning for the development of an interfacially interacting nanocomposite alloy capable of enhanced biodegradation in the aqueous environment. In the first stage of this study it was shown that quaternary ammonium polymers adsorbed on the faces of the montmorillonite platelets, non-ionic polyacrylamides adsorbed on the faces and edges by hydrogen bonding, and anionic polyelectrolytes, carboxylates and sulfonates, did not adsorb at all on the montmorillonite [R.Y. Lochhead, C.L. McConnell-Boykin, An investigative study of polymer adsorption to smectite clay: polyelectrolytes and sodium montmorillonite, in: R. Krishnamoorti, R. Vaia (Eds.), Polymer Nanocomposites, American Chemical Society, 2002; R.Y. Lochhead, C.L. McConnell-Boykin, C. Haynes, Interaction of hydrophilic polymers with smectite clays, Polymer Materials Science and Engineering, vol. 85, American Chemical Society, 2001, p. 419]. The objective of the second part of the study was to examine model polymers in order to guide research aimed at designing coupling polymers that would cause exfoliation of the clay. Based upon the earlier study, polyvinylamine was chosen as the model on the basis that it is a simple polymer with primary amine groups and the polymer charge density could be modified by simply changing the system pH. The aim of this research was to determine the conditions under which polyvinylamine, and selected derivatives of this polymer, would penetrate the galleries of the stacked montmorillonite platelets. The knowledge gained could be applied to predict systems that would facilitate intercalation or exfoliation of sodium montmorillonite. The investigative approach of the third stage was to create a coupler from the hydrogen-bonded coacervate formed between a polyphenolic compound and polyvinylpyrrolidone, and to use this to exfoliate and couple montmorillonite nanoparticles to polycaprolactone. To achieve this, solubility parameter mapping of candidate polymeric couplers, polycaprolactone and target polyphenolic compounds was undertaken. This was used as a screening process in predicting incompatibilities and eliminating unpromising materials that were soluble in the same materials as the polycaprolactone and the polyvinylpyrrolidone. High throughput generation of Hansen-Hoy solubility diagrams coupled with simple techniques like high throughput FT-IR spectroscopy and polarized light microscopy provide a powerful tool for the evaluation of compatibility between formulation components. We were able to quickly evaluate over 110 food-contact-approved phenolic compounds, select the two promising candidates and eliminate all of the rest by evaluating their propensity for compatibility and hydrogen bonding.

The situated HKB model: how sensorimotor spatial coupling can alter oscillatory brain dynamics

PubMed Central

Aguilera, Miguel; Bedia, Manuel G.; Santos, Bruno A.; Barandiaran, Xabier E.

2013-01-01

Despite the increase of both dynamic and embodied/situated approaches in cognitive science, there is still little research on how coordination dynamics under a closed sensorimotor loop might induce qualitatively different patterns of neural oscillations compared to those found in isolated systems. We take as a departure point the Haken-Kelso-Bunz (HKB) model, a generic model for dynamic coordination between two oscillatory components, which has proven useful for a vast range of applications in cognitive science and whose dynamical properties are well understood. In order to explore the properties of this model under closed sensorimotor conditions we present what we call the situated HKB model: a robotic model that performs a gradient climbing task and whose “brain” is modeled by the HKB equation. We solve the differential equations that define the agent-environment coupling for increasing values of the agent's sensitivity (sensor gain), finding different behavioral strategies. These results are compared with two different models: a decoupled HKB with no sensory input and a passively-coupled HKB that is also decoupled but receives a structured input generated by a situated agent. We can precisely quantify and qualitatively describe how the properties of the system, when studied in coupled conditions, radically change in a manner that cannot be deduced from the decoupled HKB models alone. We also present the notion of neurodynamic signature as the dynamic pattern that correlates with a specific behavior and we show how only a situated agent can display this signature compared to an agent that simply receives the exact same sensory input. To our knowledge, this is the first analytical solution of the HKB equation in a sensorimotor loop and qualitative and quantitative analytic comparison of spatially coupled vs. decoupled oscillatory controllers. Finally, we discuss the limitations and possible generalization of our model to contemporary neuroscience and philosophy of mind. PMID:23986692

Combining Human and Machine Intelligence to Derive Agents' Behavioral Rules for Groundwater Irrigation

NASA Astrophysics Data System (ADS)

Hu, Y.; Quinn, C.; Cai, X.

2015-12-01

One major challenge of agent-based modeling is to derive agents' behavioral rules due to behavioral uncertainty and data scarcity. This study proposes a new approach to combine a data-driven modeling based on the directed information (i.e., machine intelligence) with expert domain knowledge (i.e., human intelligence) to derive the behavioral rules of agents considering behavioral uncertainty. A directed information graph algorithm is applied to identifying the causal relationships between agents' decisions (i.e., groundwater irrigation depth) and time-series of environmental, socio-economical and institutional factors. A case study is conducted for the High Plains aquifer hydrological observatory (HO) area, U.S. Preliminary results show that four factors, corn price (CP), underlying groundwater level (GWL), monthly mean temperature (T) and precipitation (P) have causal influences on agents' decisions on groundwater irrigation depth (GWID) to various extents. Based on the similarity of the directed information graph for each agent, five clusters of graphs are further identified to represent all the agents' behaviors in the study area as shown in Figure 1. Using these five representative graphs, agents' monthly optimal groundwater pumping rates are derived through the probabilistic inference. Such data-driven relationships and probabilistic quantifications are then coupled with a physically-based groundwater model to investigate the interactions between agents' pumping behaviors and the underlying groundwater system in the context of coupled human and natural systems.

Simulation of low temperature combustion mechanism of different combustion-supporting agents in close-coupled DOC and DPF system.

PubMed

Jiao, Penghao; Li, Zhijun; Li, Qiang; Zhang, Wen; He, Li; Wu, Yue

2018-07-01

In the coupled Diesel Oxidation Catalyst (DOC) and Diesel Particular Filter (DPF) system, soot cannot be completely removed by only using the passive regeneration. And DPF active regeneration is necessary. The research method in this paper is to spray different kinds of combustion-supporting agents to the DOC in the front of the DPF. Therefore, the low temperature combustion mechanism of different kinds of combustion-supporting agents in DOC was studied, in order to grasp the law of combustion in DOC, and the influence of follow-up emission on DPF removal of soot. During the study, CH 4 H 2 mixture and diesel (n-heptane + toluene) were used as combustion-supporting agents respectively. The simplified mechanisms of two kinds of gas mixtures used as the combustion-supporting agents in DPF have been constructed and testified in the paper. In this paper, the combustion and emission conditions of the two combustion-supporting agents were analyzed so as to meet the practical requirements of different working conditions. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Activities report in nuclear physics and particle acceleration

NASA Astrophysics Data System (ADS)

Jansen, J. F. W.; Demeijer, R. J.

1984-04-01

Research on nuclear resonances; charge transfer; breakup of light and heavy ions; reaction mechanisms of heavy ion collisions; high-spin states; and fundamental symmetries in weak interactions are outlined. Group theoretical methods applied to supersymmetries; phenomenological description of rotation-vibration coupling; a microscopic theory of collective variables; the binding energy of hydrogen adsorbed on stepped platinium; and single electron capture are discussed. Isotopes for nuclear medicine, for off-line nuclear spectroscopy work, and for the study of hyperfine interactions were produced.

Surface-Enhanced Raman Scattering for Redox-Active Adsorbates: Pentaammineosmium(III)/(II) and Pentaammineruthenium(II) Containing Nitrogen Heterocycle Ligands.

DTIC Science & Technology

1984-04-01

Ill) and Os(Il) as determined using SERS are in good agreement with those obtained from rapid cyclic voltametry . The bulk-phase Raman spectra exhibit...under conventional conditions -i ( sweep rates ca. 100-500 mV sec ; reactant concentration ca. 1 ml_ for which the contribution from any initially...couple can also be obtained using cyclic voltammetry. -1 This entails using sufficiently rapid sweep rates (Z 20 V sec ) and small bulk reactant

Controlled Interphases in Glass Fiber and Particulate Reinforced Polymers: Structure of Silane Coupling Agents in Solutions and On Substrates

DTIC Science & Technology

1993-01-01

to dissolve into water. Table 3. Typical industrially used silane coupling agents Organofunctional Chemical Formula Group Cationic styryl CH2...can also react with the surface as some unreacted silanol groups remain in the oligomers. The notion of physisorbed and chemisorbed silanes is used ...silanes use many silanol groups for covalent bonding with the substrate surface whereas the loosely chemisorbed silanes use only a few silanols to bond to

SERS+MEF of the anti-tumoral drug emodin adsorbed on silver nanoparticles

NASA Astrophysics Data System (ADS)

Sevilla, Paz; De Llanos, Raquel; Domingo, Concepción; Sánchez-Cortés, Santiago; García-Ramos, José V.

2010-02-01

Metal nanostructures are known to amplify the spontaneous emission of fluorescent molecules by resonant coupling to external electromagnetic fields. We have used spectroscopy to characterize the structural properties of emodin molecules, a natural anthraquinone dye, and bovine serum albumin, the most abundant protein in plasma, in the presence of silver nanoparticles. Aggregation of emodin at pH=10 and pH=6 gives rise to SERS and MEF effects in silver colloid. We have obtained MEF spectra at acidic pH=2.9 using two different silver nanostructures. We have also studied the change in the secondary structure of bovine serum albumin adsorbed on metal nanoparticles surface. Circular dichroism, fluorescence emission and fluorescence lifetime measurements indicate an increase in the alfa-helical content of the protein and a change in the environment of the tryptophan residues that bury in the interior of the biomolecule. This variation on the secondary structure could have further influence in the binding of the drug to form transport and regulatory complexes.

Electronic coupling in iron oxide-modified TiO2 leads to a reduced band gap and charge separation for visible light active photocatalysis.

PubMed

Nolan, Michael

2011-10-28

In recent experiments Tada et al. have shown that TiO(2) surfaces modified with iron oxide display visible light photocatalytic activity. This paper presents first principles simulations of iron oxide clusters adsorbed at the rutile TiO(2) (110) surface to elucidate the origin of the visible light photocatalytic activity of iron oxide modified TiO(2). Small iron oxide clusters adsorb at rutile (110) surface and their presence shifts the valence band so that the band gap of the composite is narrowed towards the visible, thus confirming the origin of the visible light activity of this composite material. The presence of iron oxide at the TiO(2) surface leads to charge separation, which is the origin of enhanced photocatalytic efficiency, consistent with experimental photoluminesence and photocurrent data. Surface modification of a metal oxide is thus an interesting route in the development of visible light photocatalytic materials. This journal is © the Owner Societies 2011

Preparation and application of poly 3, 4-ethylenedioxythiophene (PEDOT) nanofibers in the pretreatment of samples before the determination of elements in children fingernails

NASA Astrophysics Data System (ADS)

Qiu, J. L.; Kang, X. J.; Ma, L.; Huang, W. Y.; Ge, Q. Y.

2015-07-01

Solid phase extraction (SPE) has been used widely for sample preparation in the analytical process. Many efforts have focused on developing novel adsorbents to enrich and purify the analytes effectively. In this study, poly-3, 4-ethylenedioxythiophene (PEDOT) nanofiber was prepared and used as the SPE adsorbent. The fiber performed good in extraction of metal ions, Cd, Sn, Hg, Pb, Al, and As, with the extraction recoveries ranged from 53.9% to 99.6% in the wet digested samples of fingernails. A PEDOT namofibers SPE column coupled with ICP-MS was established for assay of elements in fingernails. The levels of elements (Cd, Sn, Hg, Pb, Al, and As) in the fingernails of 77 healthy Chinese children (6-7 and 10-11 years) were determined. Independent t test shows that no significance has been found between boys and girls. On the contrary, there was obvious difference on the levels of most elements between the two grade groups.

Tunable magnetism in metal adsorbed fluorinated nanoporous graphene

DOE PAGES

Kumar, Pankaj; Sharma, Vinit; Reboredo, Fernando A.; ...

2016-08-24

Developing nanostructures with tunable magnetic states is crucial for designing novel data storage and quantum information devices. Using density functional theory, we study the thermodynamic stability and magnetic properties of tungsten adsorbed tri-vacancy fluorinated (TVF) graphene. We demonstrate a strong structure-property relationship and its response to external stimuli via defect engineering in graphene-based materials. Complex interplay between defect states and the chemisorbed atom results in a large magnetic moment of 7 μ B along with high in-plane magneto-crystalline anisotropy energy (MAE) of 17 meV. Under the influence of electric field, spin crossover effect accompanied by a change in the MAEmore » is observed. The ascribed change in spin-configuration is caused by the modification of exchange coupling between defect states and a change in the occupation of d-orbitals of the metal complex. In conclusion, our predictions open a promising way towards controlling the magnetic properties in graphene based spintronic and non-volatile memory devices.« less

Postadsorption Work Function Tuning via Hydrogen Pressure Control

PubMed Central

2015-01-01

The work function of metal substrates can be easily tuned, for instance, by adsorbing layers of molecular electron donors and acceptors. In this work, we discuss the possibility of changing the donor/acceptor mixing ratio reversibly after adsorption by choosing a donor/acceptor pair that is coupled via a redox reaction and that is in equilibrium with a surrounding gas phase. We discuss such a situation for the example of tetrafluoro-1,4-benzenediol (TFBD)/tetrafluoro-1,4-benzoquinone (TFBQ), adsorbed on Cu(111) and Ag(111) surfaces. We use density functional theory and ab initio thermodynamics to show that arbitrary TFBD/TFBQ mixing ratios can be set using hydrogen pressures attainable in low to ultrahigh vacuum. Adjusting the mixing ratio allows modifying the work function over a range of about 1 eV. Finally, we contrast single-species submonolayers with mixed layers to discuss why the resulting inhomogeneities in the electrostatic energy above the surface have different impacts on the interfacial level alignment and the work function. PMID:26692915

Theoretical Study on Sers of Wagging Vibrations of Benzyl Radical Adsorbed on Silver Electrodes

NASA Astrophysics Data System (ADS)

Wu, De-Yin; Chen, Yan-Li; Tian, Zhong-Qun

2016-06-01

Electrochemical surface-enhanced Raman spectroscopy (EC-SERS) has been used to characterize adsorbed species widely but reaction intermediates rarely on electrodes. In previous studies, the observed SERS signals were proposed from surface benzyl species due to the electrochemical reduction of benzyl chloride on silver electrode surfaces. In this work, we reinvestigated the vibrational assignments of benzyl chloride and benzyl radical as the reaction intermediate. On the basis of density functional theoretical (DFT) calculations and normal mode analysis, our systematical results provide more reasonable new assignments for both surface species. Further, we investigated adsorption configurations, binding energies, and vibrational frequency shifts of benzyl radical interacting with silver. Our calculated results show that the wagging vibration displays significant vibrational frequency shift, strong coupling with some intramolecular modes in the phenyl ring, and significant changes in intensity of Raman signals. The study also provides absolute Raman intensity in benzyl halides and discuss the enhancement effect mainly due to the binding interaction with respect to free benzyl radical.

Real-space imaging of interfacial water with submolecular resolution

NASA Astrophysics Data System (ADS)

Jiang, Ying; Peking University Team

2014-03-01

Water/solid interfaces are vital to our daily lives and also a central theme across an incredibly wide range of scientific disciplines. Resolving the internal structure, i.e. the O-H directionality, of water molecules adsorbed on solid surfaces has been one of the key issues of water science yet remains challenging. Using a low-temperature scanning tunneling microscope (STM), we report the submolecular-resolution imaging of individual water monomers and tetramers on NaCl(001) films supported by a Au(111) substrate at 5 K. The frontier molecular orbitals of adsorbed water were directly visualized, which allowed discriminating the orientation of the monomers and the H-bond directionality of the tetramers in real space. Comparison with ab initio density functional theory calculations reveals that the ability to access the orbital structures of water stems from the electronic decoupling effect provided by the NaCl films and the precisely tunable tip-water coupling. Supported by National Basic Research Programs of China and National Science Foundation of China.

Photo-catalytic Activities of Plant Hormones on Semiconductor Nanoparticles by Laser-Activated Electron Tunneling and Emitting

PubMed Central

Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

2015-01-01

Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO2), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated. PMID:25749635

Glucose Oxidase Adsorption on Sequential Adsorbed Polyelectrolyte Films Studied by Spectroscopic Techniques

NASA Astrophysics Data System (ADS)

Tristán, Ferdinando; Solís, Araceli; Palestino, Gabriela; Gergely, Csilla; Cuisinier, Frédéric; Pérez, Elías

2005-04-01

The adsorption of Glucose Oxidase (GOX) on layers of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) deposited on Sequentially Adsorbed Polyelectrolyte Films (SAPFs) were studied by three different spectroscopic techniques. These techniques are: Optical Wave Light Spectroscopy (OWLS) to measure surface density; Fluorescence Resonance Energy Transfer (FRET) to verify the adsorption of GOX on the surface; and Fourier Transform Infrared Spectroscopy in Attenuated Total Reflection mode (FTIR-HATR) to inspect local structure of polyelectrolytes and GOX. Two positive and two negative polyelectrolytes are used: Cationic poly(ethyleneimine) (PEI) and poly(allylamine hydrochloride) (PAH) and anionic poly(sodium 4-styrene sulfonate) (PSS) and poly(acrylic acid) (PAA). These spectroscopic techniques do not require any labeling for GOX or SAPFs, specifically GOX and PSS are naturally fluorescent and are used as a couple donor-acceptor for the FRET technique. The SAPFs are formed by a (PEI)-(PSS/PAH)2 film followed by (PAA/PAH)n bilayers. GOX is finally deposited on top of SAPFs at different values of n (n=1..5). Our results show that GOX is adsorbed on positive ended SAPFs forming a monolayer. Contrary, GOX adsorption is not observed on negative ended film polyelectrolyte. GOX stability was tested adding a positive and a negative polyelectrolyte after GOX adsorption. Protein is partially removed by PAH and PAA, with lesser force by PAA.

Electroadsorption-assisted direct determination of trace arsenic without interference using transmission X-ray fluorescence spectroscopy.

PubMed

Jiang, Tian-Jia; Guo, Zheng; Liu, Jin-Huai; Huang, Xing-Jiu

2015-08-18

An analytical technique based on electroadsorption and transmission X-ray fluorescence (XRF) for the quantitative determination of arsenic in aqueous solution with ppb-level limits of detection (LOD) is proposed. The approach uses electroadsorption to enhance the sensitivity and LOD of the arsenic XRF response. Amine-functionalized carbonaceous microspheres (NH2-CMSs) are found to be the ideal materials for both the quantitative adsorption of arsenic and XRF analysis due to the basic amine sites on the surface and their noninterference in the XRF spectrum. In electroadsorptive X-ray fluorescence (EA-XRF), arsenic is preconcentrated by a conventional three-electrode system with a positive electricity field around the adsorbents. Then, the quantification of arsenic on the adsorbents is achieved using XRF. The electroadsorption preconcentration can realize the fast transfer of arsenic from the solution to the adsorbents and improve the LOD of conventional XRF compared with directly determining arsenic solution by XRF alone. The sensitivity of 0.09 cnt ppb(-1) is obtained without the interferences from coexisted metal ions in the determination of arsenic, and the LOD is found to be 7 ppb, which is lower than the arsenic guideline value of 10 ppb given by the World Health Organization (WHO). These results demonstrated that XRF coupled with electroadsorption was able to determine trace arsenic in real water sample.

Photo-catalytic Activities of Plant Hormones on Semiconductor Nanoparticles by Laser-Activated Electron Tunneling and Emitting

NASA Astrophysics Data System (ADS)

Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

2015-03-01

Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO2), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.

Ultrasound-assisted dispersive magnetic solid phase extraction for preconcentration and determination of trace amount of Hg (II) ions from food samples and aqueous solution by magnetic graphene oxide (Fe3O4@GO/2-PTSC): Central composite design optimization.

PubMed

Keramat, Akram; Zare-Dorabei, Rouholah

2017-09-01

In this work, the synthesis of the magnetic graphene oxide modified by 2-pyridinecarboxaldehyde thiosemicarbazone groups (Fe 3 O 4 @GO/2-PTSC) was utilized for preconcentration and determination of mercuric ions in a trace amount by inductively coupled plasma-optical emission spectrometry (ICP-OES). Characterization of the adsorbent was performed using various techniques, such as FT-IR, VSM, SEM and XRD analysis. Central composite design (CCD) under response surface methodology (RSM) was used for obtaining the most important parameters and probable interactions in variables. The variables such as adsorbent dosage, pH, desorption time, and eluent volume was optimized. These values were 8mg, 5.4min, 0.5mL (HCl, 0.1M), respectively. Sonication had an important role in shortening the adsorption time of Hg (II) ions by enhancing the dispersion of adsorbent in solution. Under the optimal conditions, the proposed method presented high enrichment factor of 193, an extraction percentage of 96.5, a detection limit of 0.0079µgL -1 and a relative standard deviation (RSD %) of 1.63%. Finally, the application of the synthesized material was evaluated for preconcentration and determination of mercuric ions from foods and environmental waters samples. Copyright © 2017 Elsevier B.V. All rights reserved.

SERS of semiconducting nanoparticles (TiO{sub 2} hybrid composites).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musumeci, A.; Gosztola, D.; Schiller, T.

Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules thatmore » lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.« less

SERS of semiconducting nanoparticles (TIO{sub 2} hybrid composites).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajh, T.; Musumeci, A.; Gosztola, D.

Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules thatmore » lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.« less

Reaction mechanism for oxygen evolution on RuO 2, IrO 2, and RuO 2@IrO 2 core-shell nanocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Zhong; Zhang, Yu; Liu, Shizhong

Iridium dioxide, IrO 2, is second to the most active RuO 2 catalyst for the oxygen evolution reaction (OER) in acid, and is used in proton exchange membrane water electrolyzers due to its high durability. In order to improve the activity of IrO 2-based catalysts, we prepared RuO 2@IrO 2 core-shell nanocatalysts using carbon-supported Ru as the template. At 1.48 V, the OER specific activity of RuO 2@IrO 2 is threefold that of IrO 2. While the activity volcano plots over wide range of materials have been reported, zooming into the top region to clarify the rate limiting steps ofmore » most active catalysts is important for further activity enhancement. Here, we verified theory-proposed sequential water dissociation pathway in which the O—O bond forms on a single metal site, not via coupling of two adsorbed intermediates, by fitting measured polarization curves using a kinetic equation with the free energies of adsorption and activation as the parameters. Consistent with theoretical calculations, we show that the OER activities of IrO 2 and RuO 2@IrO 2 are limited by the formation of O adsorbed phase, while the OOH formation on the adsorbed O limits the reaction rate on RuO 2.« less

Reaction mechanism for oxygen evolution on RuO 2, IrO 2, and RuO 2@IrO 2 core-shell nanocatalysts

DOE PAGES

Ma, Zhong; Zhang, Yu; Liu, Shizhong; ...

2017-10-28

Iridium dioxide, IrO 2, is second to the most active RuO 2 catalyst for the oxygen evolution reaction (OER) in acid, and is used in proton exchange membrane water electrolyzers due to its high durability. In order to improve the activity of IrO 2-based catalysts, we prepared RuO 2@IrO 2 core-shell nanocatalysts using carbon-supported Ru as the template. At 1.48 V, the OER specific activity of RuO 2@IrO 2 is threefold that of IrO 2. While the activity volcano plots over wide range of materials have been reported, zooming into the top region to clarify the rate limiting steps ofmore » most active catalysts is important for further activity enhancement. Here, we verified theory-proposed sequential water dissociation pathway in which the O—O bond forms on a single metal site, not via coupling of two adsorbed intermediates, by fitting measured polarization curves using a kinetic equation with the free energies of adsorption and activation as the parameters. Consistent with theoretical calculations, we show that the OER activities of IrO 2 and RuO 2@IrO 2 are limited by the formation of O adsorbed phase, while the OOH formation on the adsorbed O limits the reaction rate on RuO 2.« less

Magnetic nano graphene oxide as solid phase extraction adsorbent coupled with liquid chromatography to determine pseudoephedrine in urine samples.

PubMed

Taghvimi, Arezou; Hamishehkar, Hamed; Ebrahimi, Mahmoud

2016-01-15

This paper reports on a method based on magnetic solid phase extraction (MSPE) for the determination of pseudoephedrine. Magnetic nanographene oxide (MNGO) was applied as a new adsorbent for the extraction of pseudoephedrine from urine samples. Synthesis of MNGO was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The main factors influencing extraction efficiency, including the amounts of sample volume, amount of adsorbent, type and amount of extraction organic solvent, time of extraction and desorption, pH, ionic strength of extraction medium, and agitation rate, were investigated and optimized. Under optimized extraction conditions, a good linearity was observed in the range of 100-2000ng/mL with a correlation coefficient of 0.9908 (r(2)). Limit of detection (LOD) and limit of quantification (LOQ) were 25 and 82.7ng/mL, respectively. Inter-day and intra-day precision and accuracy were 6.01 and 0.34 (%), and 8.70 and 0.29 (%), respectively. The method was applied for the determination of pseudoephedrine in urine samples of volunteers receiving pseudoephedrine with the recovery of 96.42. It was concluded that the proposed method can be applied in diagnostic clinics. Copyright © 2015 Elsevier B.V. All rights reserved.

Split Flow Online Solid-Phase Extraction Coupled with Inductively Coupled Plasma Mass Spectrometry System for One-Shot Data Acquisition of Quantification and Recovery Efficiency.

PubMed

Furukawa, Makoto; Takagai, Yoshitaka

2016-10-04

Online solid-phase extraction (SPE) coupled with inductively coupled plasma mass spectrometry (ICPMS) is a useful tool in automatic sequential analysis. However, it cannot simultaneously quantify the analytical targets and their recovery percentages (R%) in one-shot samples. We propose a system that simultaneously acquires both data in a single sample injection. The main flowline of the online solid-phase extraction is divided into main and split flows. The split flow line (i.e., bypass line), which circumvents the SPE column, was placed on the main flow line. Under program-controlled switching of the automatic valve, the ICPMS sequentially measures the targets in a sample before and after column preconcentration and determines the target concentrations and the R% on the SPE column. This paper describes the system development and two demonstrations to exhibit the analytical significance, i.e., the ultratrace amounts of radioactive strontium ( 90 Sr) using commercial Sr-trap resin and multielement adsorbability on the SPE column. This system is applicable to other flow analyses and detectors in online solid phase extraction.

CO-CO coupling on Cu facets: Coverage, strain and field effects

DOE PAGES

Sandberg, Robert B.; Montoya, Joseph H.; Chan, Karen; ...

2016-08-21

We present a DFT study on the effect of coverage, strain, and electric field on CO-CO coupling energetics on Cu (100), (111), and (211). Our calculations indicate that CO-CO coupling is facile on all three facets in the presence of a cation-induced electric field in the Helmholtz plane, with the lowest barrier on Cu(100). The CO dimerization pathway is therefore expected to play a role in C 2 formation at potentials negative of the Cu potential of zero charge, corresponding to CO 2/CO reduction conditions at high pH. Both increased *CO coverage and tensile strain further improve C-C coupling energeticsmore » on Cu (111) and (211). Since CO dimerization is facile on all 3 Cu facets, subsequent surface hydrogenation steps may also play an important role in determining the overall activity towards C 2 products. Adsorption of *CO, *H, and *OH on the 3 facets were investigated with a Pourbaix analysis. Here, the (211) facet has the largest propensity to co-adsorb *CO and *H, which would favor surface hydrogenation following CO dimerization.« less

Three-body-wear resistance of the experimental composites containing filler treated with hydrophobic silane coupling agents.

PubMed

Nihei, Tomotaro; Dabanoglu, Alp; Teranaka, Toshio; Kurata, Shigeaki; Ohashi, Katsura; Kondo, Yukishige; Yoshino, Norio; Hickel, Reinhard; Kunzelmann, Karl-Heinz

2008-06-01

This paper evaluated the wear resistance of resin composite materials with fillers which were modified with a novel hydrophobic silane coupling agent. The novel silane coupling agent containing hydrophobic phenyl group 3-(3-methoxy-4-methacryloyloxyphenyl)propyltrimethoxysilane (p-MBS) was synthesized. The experimental light-cure hybrid composites containing 85wt% of filler modified with this silane were formulated. Twelve specimens were prepared for the three-body-wear test with the ACTA machine and the collected data were analyzed statistically using a one-way ANOVA and Tukey's multiple comparison test as the post hoc test. The wear of the composites containing fillers treated with p-MBS was significantly lower compared with the composite materials containing fillers pretreated with 3-methacryloyloxypropyltrimethoxysilane or the commercially composites (AP-X and ELS extra low shrinkage) after a wear test for 200,000 cycles (p<0.05). It is suggested that the resin composites containing fillers modified with the novel hydrophobic silane has high wear resistant, because of the coupling layers treated with this silane had an excellent affinity with the base resin and formed a highly hydrophobic layer on the filler surface.

Perfluorophenyl Azides: New Applications in Surface Functionalization and Nanomaterial Synthesis

PubMed Central

Liu, Li-Hong; Yan, Mingdi

2010-01-01

Conspectus A major challenge in materials science is the ongoing search for coupling agents that are readily synthesized, capable of versatile chemistry, able to easily functionalize materials and surfaces, and efficient in covalently linking organic and inorganic entities. A decade ago, we began a research program investigating perfluorophenylazides (PFPAs) as the coupling agents in surface functionalization and nanomaterial synthesis. The p-substituted PFPAs are attractive heterobifunctional coupling agents because of their two distinct and synthetically distinguishable reactive centers: (i) the fluorinated phenylazide, which is capable of forming stable covalent adducts, and (ii) the functional group R, which can be tailored through synthesis. Two approaches have been undertaken for material synthesis and surface functionalization. The first method involves synthesizing PFPA bearing the first molecule or material with a functional linker R, and then attaching the resulting PFPA to the second material by activating the azido group. In the second approach, the material surface is first functionalized with PFPA via functional center R, and coupling of the second molecule or material is achieved with the surface azido groups. In this Account, we review the design and protocols of the two approaches, providing examples in which PFPA derivatives were successfully used in material surface functionalization, ligand conjugation, and the synthesis of hybrid nanomaterials. The methods developed have proved to be general and versatile, and they are applicable to a wide range of materials (especially those that lack reactive functional groups or are difficult to derivatize) and to various substrates of polymers, oxides, carbon materials, and metal films. The coupling chemistry can be initiated by light, heat, and electrons. Patterned structures can be generated by selectively activating the areas of interest. Furthermore, the process is easy to perform, and light activation occurs in minutes, greatly facilitating the efficiency of the reaction. PFPAs indeed demonstrate many benefits as versatile surface coupling agents and offer opportunities for further exploration. PMID:20690606

New approach to resolve the humidity problem in VOC determination in outdoor air samples using solid adsorbent tubes followed by TD-GC-MS.

PubMed

Maceira, Alba; Vallecillos, Laura; Borrull, Francesc; Marcé, Rosa Maria

2017-12-01

This study describes the humidity effect in the sampling process by adsorbent tubes followed by thermal desorption and gas chromatography-mass spectrometry (TD-GC-MS) for the determination of volatile organic compounds (VOCs) in air samples and evaluates possible solutions to this problem. Two multi-sorbent bed tubes, Tenax TA/Carbograph 1TD and Carbotrap B/Carbopack X/Carboxen 569, were tested in order to evaluate their behaviour in the presence of environmental humidity. Humidity problems were demonstrated with carbon-based tubes, while Tenax-based tubes did not display any influence. Silica gel, a molecular sieve and CaCl 2 were tried out as materials for drying tube to remove air humidity, placed prior to the sampling tube to prevent water from entering. The pre-tubes filled with 0.5g of CaCl 2 showed the best results with respect to their blanks, the analytes recoveries and their ability to remove ambient humidity. To avoid the possible agglomeration of CaCl 2 during the sampling process in high relative humidity atmospheres, 0.1g of diatomaceous earth were mixed with the desiccant agent. The applicability of the CaCl 2 pre-tube as drying agent prior to Carbotrap B/Carbopack X/Carboxen 569 tubes was tested in urban and industrial locations with samplings of air at high relative humidity. In addition, the results were compared with those obtained using Tenax TA/Carbograph 1TD tubes. Copyright © 2017 Elsevier B.V. All rights reserved.

Formation and composition of adsorbates on hydrophobic carbon surfaces from aqueous laccase-maltodextrin mixture suspension

NASA Astrophysics Data System (ADS)

Corrales Ureña, Yendry Regina; Lisboa-Filho, Paulo Noronha; Szardenings, Michael; Gätjen, Linda; Noeske, Paul-Ludwig Michael; Rischka, Klaus

2016-11-01

A robust procedure for the surface bio-functionalization of carbon surfaces was developed. It consists on the modification of carbon materials in contact with an aqueous suspension of the enzyme laccase from Trametes versicolor and the lyophilization agent maltodextrin, with the pH value adjusted close to the isoelectric point of the enzyme. We report in-situ investigations applying Quartz Crystal Microbalance with Dissipation (QCM-D) for carbon-coated sensor surfaces and, moreover, ex-situ measurements with static contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) and Scanning Force Microscopy (SFM) for smooth Highly Oriented Pyrolytic Graphite (HOPG) substrates, for contact times between the enzyme formulation and the carbon material surface ranging from 20 s to 24 h. QCM-D studies reveals the formation of rigid layer of biomaterial, a few nanometers thin, which shows a strongly improved wettability of the substrate surface upon contact angle measurements. Following spectroscopic characterization, these layers are composed of mixtures of laccase and maltodextrin. The formation of these adsorbates is attributed to attractive interactions between laccase, the maltodextrin-based lyophilization agent and the hydrophobic carbon surfaces; a short-term contact between the aqueous laccase mixture suspension and HOPG surfaces is shown to merely result in de-wetting patterns influencing the results of contact angle measurements. The new enzyme-based surface modification of carbon-based materials is suggested to be applicable for the improvement of not only the wettability of low energy substrate surfaces with fluid formulations like coatings or adhesives, but also their adhesion in contact with hardened polymers.

Novel morphology change of Au-Methotrexate conjugates: From nanochains to discrete nanoparticles.

PubMed

Wang, Wei-Yuan; Zhao, Xiu-Fen; Ju, Xiao-Han; Wang, Yu; Wang, Lin; Li, Shu-Ping; Li, Xiao-Dong

2016-12-30

A novel morphology change of Au-methotrexate (Au-MTX) conjugates that could transform from nanochains to discrete nanoparticles was achieved by a simple, one-pot, and hydrothermal growth method. Herein, MTX was used efficiently as a complex-forming agent, reducing agent, capping agent, and importantly a targeting anticancer drug. The formation mechanism suggested a similarity with the molecular imprinting technology. The Au-MTX complex induced the MTX molecules to selectively adsorb on different crystal facets of gold nanoparticles (AuNPs) and then formed gold nanospheres. Moreover, the abundantly binding MTX molecules promoted directional alignment of these gold nanospheres to further form nanochains. More interestingly, the linear structures gradually changed into discrete nanoparticles by adding different amount of ethylene diamine tetra (methylene phosphonic acid) (EDTMPA) into the initial reaction solution, which likely arose from the strong electrostatic effect of the negatively charged phosphonic acid groups. Compared with the as-prepared nanochains, the resultant discrete nanoparticles showed almost equal drug loading capacity but with higher drug release control, colloidal stability, and in vitro anticancer activity. Copyright © 2016 Elsevier B.V. All rights reserved.

Graphene oxide/MnO2 nanocomposite as destructive adsorbent of nerve-agent simulants in aqueous media

NASA Astrophysics Data System (ADS)

Šťastný, Martin; Tolasz, Jakub; Štengl, Václav; Henych, Jiří; Žižka, David

2017-08-01

Graphene oxide/MnO2 nanocomposite was prepared by thermal hydrolysis of potassium permanganate (KMnO4) and 2-chloroacetamide aqueous solutions with graphene oxide (GO) suspension. The synthesized samples were characterized by specific surface area (BET) and porosity determination (BJH), X-ray Diffraction (XRD) and high-resolution electron microscopes (HRSEM, HRTEM). These nanocomposites were used in an experimental evaluation of their adsorption activity with nerve agent simulants dimethyl methyl phosphonate (DMMP) and triethyl phosphate (TEP) in aqueous media. The nanocomposites exhibited enhanced adsorptive degradation ability compared to pure manganese oxide (MnO2) and GO. The GO amount in the nanocomposites affected their degradation activity substantially. The best adsorption efficiency was observed for samples with moderate GO amount. Three methods were used to observe the mechanism of the nerve-agent simulants deactivation: Gas chromatography with mass spectrometry (GC-MS), High-Performance Liquid Chromatography (HPLC) and in situ Infrared spectroscopy (FTIR). It was shown that the hydrolysis on the surface of prepared nanocomposites yields volatile primary alcohols (methanol and ethanol) as the main hydrolysis products.

First passage times for multiple particles with reversible target-binding kinetics

NASA Astrophysics Data System (ADS)

Grebenkov, Denis S.

2017-10-01

We investigate the first passage problem for multiple particles that diffuse towards a target, partially adsorb there, and then desorb after a finite exponentially distributed residence time. We search for the first time when m particles undergoing such reversible target-binding kinetics are found simultaneously on the target that may trigger an irreversible chemical reaction or a biophysical event. Even if the particles are independent, the finite residence time on the target yields an intricate temporal coupling between particles. We compute analytically the mean first passage time (MFPT) for two independent particles by mapping the original problem to higher-dimensional surface-mediated diffusion and solving the coupled partial differential equations. The respective effects of the adsorption and desorption rates on the MFPT are revealed and discussed.

Microwave pyrolysis with KOH/NaOH mixture activation: A new approach to produce micro-mesoporous activated carbon for textile dye adsorption.

PubMed

Liew, Rock Keey; Azwar, Elfina; Yek, Peter Nai Yuh; Lim, Xin Yi; Cheng, Chin Kui; Ng, Jo-Han; Jusoh, Ahmad; Lam, Wei Haur; Ibrahim, Mohd Danial; Ma, Nyuk Ling; Lam, Su Shiung

2018-06-19

A micro-mesoporous activated carbon (AC) was produced via an innovative approach combining microwave pyrolysis and chemical activation using NaOH/KOH mixture. The pyrolysis was examined over different chemical impregnation ratio, microwave power, microwave irradiation time and types of activating agents for the yield, chemical composition, and porous characteristic of the AC obtained. The AC was then tested for its feasibility as textile dye adsorbent. About 29 wt% yield of AC was obtained from the banana peel with low ash and moisture (<5 wt%), and showed a micro-mesoporous structure with high BET surface area (≤1038 m 2 /g) and pore volume (≤0.80 cm 3 /g), indicating that it can be utilized as adsorbent to remove dye. Up to 90% adsorption of malachite green dye was achieved by the AC. Our results indicate that the microwave-activation approach represents a promising attempt to produce good quality AC for dye adsorption. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthesis of graphene aerogel for adsorption of bisphenol A

NASA Astrophysics Data System (ADS)

Trinh, Truong Thi Phuong Nguyet Xuan; Long, Nguyen Huynh Bach Son; Quang, Dong Thanh; Hieu, Nguyen Huu

2018-04-01

In this research, graphene aerogel (GA) was synthesized by chemical reduction method using ethylene diamine as a reducing agent. The morphology and properties of GA were characterized by calculating apparent density, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and Brunauer-Emmett-Teller (BET) specific surface area. High-performance liquid chromatography (HPLC) was used to quantify the amount of the residual bisphenol A (BPA) concentration. The analysis results showed that GA exhibited low density ranging from 4-8 mg/cm3, hydrophobicity, high porosity, and specific surface area of 1883 m2/g according to BET. The obtained GA was used as an adsorbent for BPA. The effects of pH, contact time, and initial BPA concentration on the adsorption were investigated. The adsorption equilibrium time could be reached within 240 minutes. The adsorption data were well-fitted to pseudo-second-order kinetic equation and Langmuir isotherm model. The maximum adsorption capacity of GA for BPA calculated by the Langmuir model was 185.185 mg/g at pH 7. Accordingly, GA could be considered as promising adsorbents for BPA in water.

Role of oil derived carbonaceous phase in the performance of sewage sludge-based materials as media for desulfurizaton of digester gas

NASA Astrophysics Data System (ADS)

Kante, Karifala; Qiu, Jieshan; Zhao, Zongbin; Chang, Yu; Bandosz, Teresa J.

2008-02-01

Desulfurization adsorbents for purification of digester gas were prepared by pyrolysis of sewage sludge impregnated with spent mineral oil. To evaluate the changes in the structural and chemical properties the pyrolysis time and temperature varied. The materials were characterized using adsorption of nitrogen, FTIR, XRD, ICP, SEM and thermal analysis. Their catalytic activity was tested in the removal of hydrogen sulfide from simulated mixture of digester gas. The results indicated the importance of new carbon phase from the oil precursor. It provided mesoporosity, which increased the dispersion of catalytic phase and space for storage of surface reaction products. The results indicated that the adsorbents obtained at 950 °C are much more active in the process of hydrogen sulfide oxidation than those obtained at 650 °C. Moreover, longer heat treatment is also beneficial for the development of surface catalytic properties. Extensive pyrolysis stabilizes carbon phase via increasing its degree of aromatization and provides activation agents for this phase coming from decomposition and rearrangement of inorganic phase.

Photocatalytic thin films coupled with polymeric microcapsules for the controlled-release of volatile agents upon solar activation

NASA Astrophysics Data System (ADS)

Oliveira, L. F.; Marques, J.; Coutinho, P. J. G.; Parpot, P.; Tavares, C. J.

2013-06-01

This work reportson the application of solar-activated photocatalytic thin films that allow the controlled-release of volatile agents (e.g., insecticides, repellents) from the interior of adsorbedpolymericmicrocapsules. In order to standardize the tests, a quantification of the inherent controlled-release of a particular volatile agent is determined by gas chromatography coupled to mass spectroscopy, so that an application can be offered to a wide range of supports from various industrial sectors, such as in textiles (clothing, curtains, mosquito nets). This technology takes advantage of the established photocatalytic property of titanium dioxide (TiO2) for the use as an active surface/site to promote the controlled-release of a specific vapor (volatile agentfrom within the aforementioned microcapsules.

Dye-sensitized solar cells

DOEpatents

Skotheim, T.A.

1980-03-04

A low-cost dye-sensitized Schottky barrier solar cell is comprised of a substrate of semiconductor with an ohmic contact on one face, a sensitizing dye adsorbed onto the opposite face of the semiconductor, a transparent thin-film layer of a reducing agent over the dye, and a thin-film layer of metal over the reducing agent. The ohmic contact and metal layer constitute electrodes for connection to an external circuit and one or the other or both are made transparent to permit light to penetrate to the dye and be absorbed therein for generating electric current. The semiconductor material chosen to be the substrate is one having a wide bandgap and which therefore is transparent; the dye selected is one having a ground state within the bandgap of the semiconductor to generate carriers in the semiconductor, and a first excited state above the conduction band edge of the semiconductor to readily conduct electrons from the dye to the semiconductor; the reducing agent selected is one having a ground state above the ground state of the sensitizer to provide a plentiful source of electrons to the dye during current generation and thereby enhance the generation; and the metal for the thin-film layer of metal is selected to have a Fermi level in the vicinity of or above the ground state of the reducing agent to thereby amply supply electrons to the reducing agent. 3 figs.

Dye-sensitized solar cells

DOEpatents

Skotheim, Terje A. [Berkeley, CA

1980-03-04

A low-cost dye-sensitized Schottky barrier solar cell comprised of a substrate of semiconductor with an ohmic contact on one face, a sensitizing dye adsorbed onto the opposite face of the semiconductor, a transparent thin-film layer of a reducing agent over the dye, and a thin-film layer of metal over the reducing agent. The ohmic contact and metal layer constitute electrodes for connection to an external circuit and one or the other or both are made transparent to permit light to penetrate to the dye and be absorbed therein for generating electric current. The semiconductor material chosen to be the substrate is one having a wide bandgap and which therefore is transparent; the dye selected is one having a ground state within the bandgap of the semiconductor to generate carriers in the semiconductor, and a first excited state above the conduction band edge of the semiconductor to readily conduct electrons from the dye to the semiconductor; the reducing agent selected is one having a ground state above the ground state of the sensitizer to provide a plentiful source of electrons to the dye during current generation and thereby enhance the generation; and the metal for the thin-film layer of metal is selected to have a Fermi level in the vicinity of or above the ground state of the reducing agent to thereby amply supply electrons to the reducing agent.

Dye-sensitized Schottky barrier solar cells

DOEpatents

Skotheim, Terje A.

1978-01-01

A low-cost dye-sensitized Schottky barrier solar cell comprised of a substrate of semiconductor with an ohmic contact on one face, a sensitizing dye adsorbed onto the opposite face of the semiconductor, a transparent thin-film layer of a reducing agent over the dye, and a thin-film layer of metal over the reducing agent. The ohmic contact and metal layer constitute electrodes for connection to an external circuit and one or the other or both are made transparent to permit light to penetrate to the dye and be absorbed therein for generating electric current. The semiconductor material chosen to be the substrate is one having a wide bandgap and which therefore is transparent; the dye selected is one having a ground state within the bandgap of the semiconductor to generate carriers in the semiconductor, and a first excited state above the conduction band edge of the semiconductor to readily conduct electrons from the dye to the semiconductor; the reducing agent selected is one having a ground state above the ground state of the sensitizer to provide a plentiful source of electrons to the dye during current generation and thereby enhance the generation; and the metal for the thin-film layer of metal is selected to have a Fermi level in the vicinity of or above the ground state of the reducing agent to thereby amply supply electrons to the reducing agent.

A Novel Anti-Pollution Filter for Volatile Agents During Cardiopulmonary Bypass: Preliminary Tests.

PubMed

Nigro Neto, Caetano; Landoni, Giovanni; Tardelli, Maria Angela

2017-08-01

Concerns regarding pollution of the operating room by volatile anesthetics and effects on atmospheric ozone depletion exist. Volatile agents commonly are used during cardiopulmonary bypass to provide anesthesia independent of any supposed myocardial protective effects. The authors' aim was to create and to assess the performance of a prototype filter for volatile agents to be connected to the cardiopulmonary bypass circuit to avoid the emission of volatile agents to the operating room, and also to the environment without causing damage to the membrane oxygenator. Observational trial. University hospital. Prototype filter for volatile agents. The prototype filter was tested in a single ex vivo experiment. The main data measured during the test were pressure drop to detect interference with the performance of the oxygenator, back pressure to detect overpressure to the outlet gas jacket of the oxygenator, analysis of exhaled sevoflurane after the membrane oxygenator, and after the filter to detect any presence of sevoflurane. The prototype filter adsorbed the sevoflurane eliminated through the outlet portion of the oxygenator. During the entire test, the back pressure remained constant (4 mmHg) and pressure drop varied from 243 mmHg to 247 mmHg. The prototype filter was considered suitable to absorb the sevoflurane, and it did not cause an overpressure to the membrane oxygenator during the test. Copyright © 2017 Elsevier Inc. All rights reserved.

Protein Diffusion on Charged Membranes: A Dynamic Mean-Field Model Describes Time Evolution and Lipid Reorganization

PubMed Central

Khelashvili, George; Weinstein, Harel; Harries, Daniel

2008-01-01

As charged macromolecules adsorb and diffuse on cell membranes in a large variety of cell signaling processes, they can attract or repel oppositely charged lipids. This results in lateral membrane rearrangement and affects the dynamics of protein function. To address such processes quantitatively we introduce a dynamic mean-field scheme that allows self-consistent calculations of the equilibrium state of membrane-protein complexes after such lateral reorganization of the membrane components, and serves to probe kinetic details of the process. Applicable to membranes with heterogeneous compositions containing several types of lipids, this comprehensive method accounts for mobile salt ions and charged macromolecules in three dimensions, as well as for lateral demixing of charged and net-neutral lipids in the membrane plane. In our model, the mobility of membrane components is governed by the diffusion-like Cahn-Hilliard equation, while the local electrochemical potential is based on nonlinear Poisson-Boltzmann theory. We illustrate the method by applying it to the adsorption of the anionic polypeptide poly-Lysine on negatively charged lipid membranes composed of binary mixtures of neutral and monovalent lipids, or onto ternary mixtures of neutral, monovalent, and multivalent lipids. Consistent with previous calculations and experiments, our results show that at steady-state multivalent lipids (such as PIP2), but not monovalent lipid (such as phosphatidylserine), will segregate near the adsorbing macromolecules. To address the corresponding diffusion of the adsorbing protein in the membrane plane, we couple lipid mobility with the propagation of the adsorbing protein through a dynamic Monte Carlo scheme. We find that due to their higher mobility dictated by the electrochemical potential, multivalent lipids such as PIP2 more quickly segregate near oppositely charged proteins than do monovalent lipids, even though their diffusion constants may be similar. The segregation, in turn, slows protein diffusion, as lipids introduce an effective drag on the motion of the adsorbate. In contrast, monovalent lipids such as phosphatidylserine only weakly segregate, and the diffusions of protein and lipid remain largely uncorrelated. PMID:18065451

Determination of six sulfonylurea herbicides in environmental water samples by magnetic solid-phase extraction using multi-walled carbon nanotubes as adsorbents coupled with high-performance liquid chromatography.

PubMed

Ma, Jiping; Jiang, Lianhua; Wu, Gege; Xia, Yan; Lu, Wenhui; Li, Jinhua; Chen, Lingxin

2016-09-30

Magnetic solid-phase extraction (MSPE) using magnetic multi-walled carbon nanotubes (mag-MWCNTs) as adsorbents, coupled with high-performance liquid chromatography-diode-array detector (HPLC-DAD), was developed for the simultaneous separation and determination of six types of sulfonylurea herbicides (SUs) in environmental water samples. Several variables affecting MSPE efficiency were systematically investigated, including the type and volume of desorption solvent, sample solution pH, salt concentration, amount of mag-MWCNTs, and extraction and desorption time. Response surface was employed to assist in the MSPE optimization. Under optimized conditions, excellent linearity was achieved in the range of 0.05-5.0μg/L for all six SUs, with coefficients of correlation r>0.9994, and preconcentration factors ranging from 178 to 210. Limits of detection and quantification were 0.01-0.04μg/L and 0.03-0.13μg/L, respectively. The intra-day and inter-day precision (relative standard deviations, n=6, %) at three spiked levels were 2.0-11.0% and 2.1-12.9% in terms of peak area, respectively. The method recoveries at three fortified concentrations were obtained within 76.7-106.9% for reservoir water samples and 78.2-105.4% for tap water samples. The developed MSPE-HPLC method demonstrated high sensitivity, repeatability, simplicity, rapidity, and excellent practical applicability. Copyright © 2016 Elsevier B.V. All rights reserved.

Analysis of electron beam induced deposition (EBID) of residual hydrocarbons in electron microscopy

NASA Astrophysics Data System (ADS)

Rykaczewski, Konrad; White, William B.; Fedorov, Andrei G.

2007-03-01

In this work we have developed a comprehensive dynamic model of electron beam induced deposition (EBID) of residual hydrocarbon coupling mass transport, electron transport and scattering, and species decomposition to predict the deposition of carbon nanopillars. The simulations predict the local species and electron density distributions, as well as the three-demensional morphology and the growth rate of the deposit. Since the process occurs in a high vacuum environment, surface diffusion is considered as the primary transport mode of surface-adsorbed hydrocarbon precursor. The governing surface transport equation (STE) of the adsorbed species is derived and solved numerically. The transport, scattering, and absorption of primary electron as well as secondary electron generation are treated using the Monte Carlo method. Low energy secondary electrons are the major contributors to hydrocarbon decomposition due to their energy range matching peak dissociation reaction cross section energies for precursor molecules. The deposit and substrate are treated as a continuous entity allowing the simulation of the growth of a realistically sized deposit rather than a large number of cells representing each individual atom as in previously published simulations [Mitsuishi et al., Ultramicroscopy 103, 17 (2005); Silvis-Cividjian, Ph.D. thesis, University of Delft, 2002]. Such formulation allows for simple coupling of the STE with the dynamic growth of the nanopillar. Three different growth regimes occurring in EBID are identified using scaling analysis, and simulations are used to describe the deposit morphology and precursor surface concentration specific for each growth regime.

Consequences of plasma oxidation and vacuum annealing on the chemical properties and electron accumulation of In2O3 surfaces

NASA Astrophysics Data System (ADS)

Berthold, Theresa; Rombach, Julius; Stauden, Thomas; Polyakov, Vladimir; Cimalla, Volker; Krischok, Stefan; Bierwagen, Oliver; Himmerlich, Marcel

2016-12-01

The influence of oxygen plasma treatments on the surface chemistry and electronic properties of unintentionally doped and Mg-doped In2O3(111) films grown by plasma-assisted molecular beam epitaxy or metal-organic chemical vapor deposition is studied by photoelectron spectroscopy. We evaluate the impact of semiconductor processing technology relevant treatments by an inductively coupled oxygen plasma on the electronic surface properties. In order to determine the underlying reaction processes and chemical changes during film surface-oxygen plasma interaction and to identify reasons for the induced electron depletion, in situ characterization was performed implementing a dielectric barrier discharge oxygen plasma as well as vacuum annealing. The strong depletion of the initial surface electron accumulation layer is identified to be caused by adsorption of reactive oxygen species, which induce an electron transfer from the semiconductor to localized adsorbate states. The chemical modification is found to be restricted to the topmost surface and adsorbate layers. The change in band bending mainly depends on the amount of attached oxygen adatoms and the film bulk electron concentration as confirmed by calculations of the influence of surface state density on the electron concentration and band edge profile using coupled Schrödinger-Poisson calculations. During plasma oxidation, hydrocarbon surface impurities are effectively removed and surface defect states, attributed to oxygen vacancies, vanish. The recurring surface electron accumulation after subsequent vacuum annealing can be consequently explained by surface oxygen vacancies.

Hyperpolarization of Frozen Hydrocarbon Gases by Dynamic Nuclear Polarization at 1.2 K.

PubMed

Vuichoud, Basile; Canet, Estel; Milani, Jonas; Bornet, Aurélien; Baudouin, David; Veyre, Laurent; Gajan, David; Emsley, Lyndon; Lesage, Anne; Copéret, Christophe; Thieuleux, Chloé; Bodenhausen, Geoffrey; Koptyug, Igor; Jannin, Sami

2016-08-18

We report a simple and general method for the hyperpolarization of condensed gases by dynamic nuclear polarization (DNP). The gases are adsorbed in the pores of structured mesoporous silica matrices known as HYPSOs (HYper Polarizing SOlids) that have paramagnetic polarizing agents covalently bound to the surface of the mesopores. DNP is performed at low temperatures and moderate magnetic fields (T = 1.2 K and B0 = 6.7 T). Frequency-modulated microwave irradiation is applied close to the electron spin resonance frequency (f = 188.3 GHz), and the electron spin polarization of the polarizing agents of HYPSO is transferred to the nuclear spins of the frozen gas. A proton polarization as high as P((1)H) = 70% can be obtained, which can be subsequently transferred to (13)C in natural abundance by cross-polarization, yielding up to P((13)C) = 27% for ethylene.

Evaluation of biosurfactant obtained from Lactobacillus pentosus as foaming agent in froth flotation.

PubMed

Vecino, X; Devesa-Rey, R; Cruz, J M; Moldes, A B

2013-10-15

This study analyzes the kinetics of sediment sorption on two chemical surfactants (Tween 20 and SDS) and a biotechnologically produced surfactant (obtained from Lactobacillus pentosus). Biosurfactants were produced by fermentation of hemicellulosic sugars from vineyard pruning waste supplied as a substrate to L. pentosus. Results obtained showed that almost no SDS was adsorbed onto the sediments, whereas Tween 20 and biosurfactants from L. pentosus were absorbed after a few minutes. Kinetic models revealed that adsorption of surfactant onto riverbed sediments is governed not only by an intra-particle diffusion model (evaluated by the Weber and Morris model), but also by surface reaction models (evaluated by first, second, third order equations and Elovich equation), showing the best fit when employing the Elovich model. The adsorption properties showed by biosurfactant from L. pentosus onto sediments present it as a potential foaming agent in froth flotation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Decontamination formulation with sorbent additive

DOEpatents

Tucker; Mark D. , Comstock; Robert H.

2007-10-16

A decontamination formulation and method of making that neutralizes the adverse health effects of both chemical and biological compounds, especially chemical warfare (CW) and biological warfare (BW) agents, and toxic industrial chemicals. The formulation provides solubilizing compounds that serve to effectively render the chemical and biological compounds, particularly CW and BW compounds, susceptible to attack, and at least one reactive compound that serves to attack (and detoxify or kill) the compound. The formulation includes at least one solubilizing agent, a reactive compound, a bleaching activator, a sorbent additive, and water. The highly adsorbent, water-soluble sorbent additive (e.g., sorbitol or mannitol) is used to "dry out" one or more liquid ingredients, such as the liquid bleaching activator (e.g., propylene glycol diacetate or glycerol diacetate) and convert the activator into a dry, free-flowing powder that has an extended shelf life, and is more convenient to handle and mix in the field.

Polymerization on the rocks: beta-amino acids and arginine

NASA Technical Reports Server (NTRS)

Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1998-01-01

We have studied the accumulation of long oligomers of beta-amino acids on the surface of minerals using the 'polymerization on the rocks' protocol. We find that long oligopeptides of beta-glutamic acid which cannot be formed in homogeneous aqueous solution are accumulated efficiently on the surface of hydroxylapatite using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as condensing agent. The EDAC-induced oligomerization of aspartic acid on hydroxylapatite proceeds even more efficiently. Hydroxylapatite can also facilitate the ligation of the tripeptide (glu)3. The 'polymerization on the rocks' scenario is not restricted to negatively-charged amino acids. Oligoarginines are accumulated on the surface of illite using carbonyldiimidizole (CDI) as condensing agent. We find that FeS2 catalyzes the CDI-induced oligomerization of arginine, although it does not adsorb oligoarginines. These results are relevant to the formation of polypeptides on the primitive earth.

Self-assembled high-strength hydroxyapatite/graphene oxide/chitosan composite hydrogel for bone tissue engineering.

PubMed

Yu, Peng; Bao, Rui-Ying; Shi, Xiao-Jun; Yang, Wei; Yang, Ming-Bo

2017-01-02

Graphene hydrogel has shown greatly potentials in bone tissue engineering recently, but it is relatively weak in the practical use. Here we report a facile method to synthesize high strength composite graphene hydrogel. Graphene oxide (GO), hydroxyapatite (HA) nanoparticles (NPs) and chitosan (CS) self-assemble into a 3-dimensional hydrogel with the assistance of crosslinking agent genipin (GNP) for CS and reducing agent sodium ascorbate (NaVC) for GO simultaneously. The dense and oriented microstructure of the resulted composite gel endows it with high mechanical strength, high fixing capacity of HA and high porosity. These properties together with the good biocompatibility make the ternary composite gel a promising material for bone tissue engineering. Such a simultaneous crosslinking and reduction strategy can also be applied to produce a variety of 3D graphene-polymer based nanocomposites for biomaterials, energy storage materials and adsorbent materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Isotopic effects in vibrational relaxation dynamics of H on a Si(100) surface

NASA Astrophysics Data System (ADS)

Bouakline, F.; Lorenz, U.; Melani, G.; Paramonov, G. K.; Saalfrank, P.

2017-10-01

In a recent paper [U. Lorenz and P. Saalfrank, Chem. Phys. 482, 69 (2017)], we proposed a robust scheme to set up a system-bath model Hamiltonian, describing the coupling of adsorbate vibrations (system) to surface phonons (bath), from first principles. The method is based on an embedded cluster approach, using orthogonal coordinates for system and bath modes, and an anharmonic phononic expansion of the system-bath interaction up to second order. In this contribution, we use this model Hamiltonian to calculate vibrational relaxation rates of H-Si and D-Si bending modes, coupled to a fully H(D)-covered Si(100)-( 2 × 1 ) surface, at zero temperature. The D-Si bending mode has an anharmonic frequency lying inside the bath frequency spectrum, whereas the H-Si bending mode frequency is outside the bath Debye band. Therefore, in the present calculations, we only take into account one-phonon system-bath couplings for the D-Si system and both one- and two-phonon interaction terms in the case of H-Si. The computation of vibrational lifetimes is performed with two different approaches, namely, Fermi's golden rule, and a generalized Bixon-Jortner model built in a restricted vibrational space of the adsorbate-surface zeroth-order Hamiltonian. For D-Si, the Bixon-Jortner Hamiltonian can be solved by exact diagonalization, serving as a benchmark, whereas for H-Si, an iterative scheme based on the recursive residue generation method is applied, with excellent convergence properties. We found that the lifetimes obtained with perturbation theory, albeit having almost the same order of magnitude—a few hundred fs for D-Si and a couple of ps for H-Si—, are strongly dependent on the discretized numerical representation of the bath spectral density. On the other hand, the Bixon-Jortner model is free of such numerical deficiencies, therefore providing better estimates of vibrational relaxation rates, at a very low computational cost. The results obtained with this model clearly show a net exponential decay of the time-dependent survival probability for the H-Si initial vibrational state, allowing an easy extraction of the bending mode "lifetime." This is in contrast with the D-Si system, whose survival probability exhibits a non-monotonic decay, making it difficult to define such a lifetime. This different behavior of the vibrational decay is rationalized in terms of the power spectrum of the adsorbate-surface system. In the case of D-Si, it consists of several, non-uniformly distributed peaks around the bending mode frequency, whereas the H-Si spectrum exhibits a single Lorentzian lineshape, whose width corresponds to the calculated lifetime. The present work gives some insight into mechanisms of vibration-phonon coupling at surfaces. It also serves as a benchmark for multidimensional system-bath quantum dynamics, for comparison with approximate schemes such as reduced, open-system density matrix theory (where the bath is traced out and a Liouville-von Neumann equation is solved) or approximate wavefunction methods to solve the combined system-bath Schrödinger equation.

Hardware accelerated high performance neutron transport computation based on AGENT methodology

NASA Astrophysics Data System (ADS)

Xiao, Shanjie

The spatial heterogeneity of the next generation Gen-IV nuclear reactor core designs brings challenges to the neutron transport analysis. The Arbitrary Geometry Neutron Transport (AGENT) AGENT code is a three-dimensional neutron transport analysis code being developed at the Laboratory for Neutronics and Geometry Computation (NEGE) at Purdue University. It can accurately describe the spatial heterogeneity in a hierarchical structure through the R-function solid modeler. The previous version of AGENT coupled the 2D transport MOC solver and the 1D diffusion NEM solver to solve the three dimensional Boltzmann transport equation. In this research, the 2D/1D coupling methodology was expanded to couple two transport solvers, the radial 2D MOC solver and the axial 1D MOC solver, for better accuracy. The expansion was benchmarked with the widely applied C5G7 benchmark models and two fast breeder reactor models, and showed good agreement with the reference Monte Carlo results. In practice, the accurate neutron transport analysis for a full reactor core is still time-consuming and thus limits its application. Therefore, another content of my research is focused on designing a specific hardware based on the reconfigurable computing technique in order to accelerate AGENT computations. It is the first time that the application of this type is used to the reactor physics and neutron transport for reactor design. The most time consuming part of the AGENT algorithm was identified. Moreover, the architecture of the AGENT acceleration system was designed based on the analysis. Through the parallel computation on the specially designed, highly efficient architecture, the acceleration design on FPGA acquires high performance at the much lower working frequency than CPUs. The whole design simulations show that the acceleration design would be able to speedup large scale AGENT computations about 20 times. The high performance AGENT acceleration system will drastically shortening the computation time for 3D full-core neutron transport analysis, making the AGENT methodology unique and advantageous, and thus supplies the possibility to extend the application range of neutron transport analysis in either industry engineering or academic research.

Tracking Site-specific C-C Coupling of Formaldehyde Molecules on Rutile TiO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Ke; Xia, Yaobiao; Tang, Miru

2015-06-25

Direct imaging of site-specific reactions of individual mole-cules as a function of temperature is a long-sought goal in molecular science. Here, we report the direct visualization of molecular coupling of formaldehyde on reduced rutile TiO2(110) surfaces as we track the same set of molecules when the temperature is increased from 75 to 170 K using scanning tunneling microscope (STM). Our recent study showed that formaldehyde preferably adsorbs on bridging-bonded oxygen (Ob) vacancy (VO) defect site. Herein, images from the same area as the temperature is increased show that VO-bound formaldehyde couples with Ti-bound formaldehyde forming a diolate intermediate. Exposure ofmore » formaldehyde at room temperature leads to diolate as the majority species on the surface and no VO-bound formaldehyde is observed. The diolate species are the key reaction intermediates in the formation of ethylene reported in previous ensemble-averaged studies.« less

Oxidation-induced spin reorientation in Co adatoms and CoPd dimers on Ni/Cu(100)

NASA Astrophysics Data System (ADS)

Chen, K.; Beeck, T.; Fiedler, S.; Baev, I.; Wurth, W.; Martins, M.

2016-04-01

Ultrasmall magnetic clusters and adatoms are of strong current interest because of their possible use in future technological applications. Here, we demonstrate that the magnetic coupling between the adsorbates and the substrate can be significantly changed through oxidation. The magnetic properties of Co adatoms and CoPd dimers deposited on a remanently magnetized Ni/Cu(100) substrate have been investigated by x-ray absorption and x-ray magnetic circular dichroism spectroscopy at the Co L2 ,3 edges. Using spectral differences, pure and oxidized components are distinguished, and their respective magnetic moments are determined. The Co adatoms and the CoPd dimers are coupled ferromagnetically to the substrate, while their oxides, Co-O and CoPd-O, are coupled antiferromagnetically to the substrate. Along with the spin reorientation from the pure to the oxidized state, the magnetic moment of the adatom is highly reduced from Co to Co-O. In contrast, the magnetic moment of the dimer is of similar order for CoPd and CoPd-O.

Diastereoisomers of 2-benzyl-2, 3-dihydro-2-(1H-inden-2-yl)-1H-inden-1-ol: potential anti-inflammatory agents.

PubMed

Sheridan, Helen; Walsh, John J; Cogan, Carina; Jordan, Michael; McCabe, Tom; Passante, Egle; Frankish, Neil H

2009-10-15

The synthesis and biological activity of the novel diastereoisomers of 2-benzyl-2,3-dihydro-2-(1H-inden-2-yl)-1H-inden-1-ol is reported. The 2,2-coupled indane dimers were synthesised by coupling of the silyl enol ether of 1-indanone with the dimethyl ketal of 2-indanone. The coupled product was directly alkylated to give the racemic ketone which was reduced to the diastereoisomeric alcohols. The alcohols were separated and their relative stereochemistry was established by X-ray crystallography. These molecules demonstrate significant anti-inflammatory activity in vivo and in vitro and may represent a new class of anti-inflammatory agent.

Simple fabrication of reduced graphene oxide -few layer MoS2 nanocomposite for enhanced electrochemical performance in supercapacitors and water purification

NASA Astrophysics Data System (ADS)

Raghu, M. S.; Yogesh Kumar, K.; Rao, Srilatha; Aravinda, T.; Sharma, S. C.; Prashanth, M. K.

2018-05-01

Expelling of heavy metal ions into water resource systems is extremely hazardous to the environment. Adsorption is one of the most cost effective and potential methods to remove the heavy metal ions from the effluents. Therefore, an attempt has been made to study the adsorption of metal particles of Cd and Hg from aqueous solution by using reduced graphene oxide-molybdenum disulphide (rGO-MoS2) nanocomposites as adsorbents. The rGO-MoS2 composites were synthesized by following simple physical methods; which involve the mixing of dispersions of MoS2 and graphene oxide (GO) by sonication, followed by subsequent reduction with hydrazine hydrate. Characterization of the nanocomposites was performed by FESEM, TEM, EDAX, raman spectroscopy, XRD and BET surface area analysis. Electron microscopic images validate the presence of homogeneity in the synthesized nanocomposite. Batch adsorption experiments were used to scrutinizethe effect of an array of parameters like effect of pH, initial concentration of the metal ions, adsorbent dose, and contact time on the adsorption capacity of metal ions on rGO-MoS2 nanocomposites. The thorough examination of adsorbed isotherm and energy demonstrates the best fitting of the adsorption data with the 'Langmuir adsorption isotherm model' and follows the pseudo-second-order kinetic in active condition. The synthesized materials havealso been tested against Gram-positive and Gram-negative bacterial strains and have showcased promising antimicrobial activities. At the same time, the nanocomposites were evaluated for electrochemical performance in supercapacitors. The rGO-MoS2 nanocomposite demonstrates better capacitance (440 Fg-1) at 5 mvs-1 scan rate. The inimitable surface property of MoS2 and good electrical conductivity of rGO results show versatile usage and formidable performance as an adsorbent, antibacterial agent and electrode material for supercapacitors.

Guanidinium ionic liquid-controlled synthesis of zeolitic imidazolate framework for improving its adsorption property.

PubMed

Fan, Chen; Liang, You; Dong, Hongqiang; Yang, Jiale; Tang, Gang; Zhang, Wenbing; Kong, Dandan; Li, Jianqiang; Cao, Yongsong

2018-05-30

The massive release of rhodamine B (RhB) to water system is an emerging problem, which dramatically threaten environment and human health. The development of an adsorbent with enhanced removal efficiency for RhB is urgently needed. Herein, we report an environment-friendly synthesis of high quality zeolitic imidazolate framework-8 (ZIF-8) and functional ionic liquid@ZIF-8 in water-based system without heat treatment for improving its adsorption property. Guanidinium ionic liquids (ILs) could not only act as greener agents instead of volatile bases and toxic surfactants to efficiently control the nucleation and growth rate of ZIF-8, but also were incorporated as shell material to add specific adsorption sites. The relationship between nanoparticle structure and adsorption performance for RhB was systematically investigated. Due to high surface area (1167 m 2  g -1 ), high porosity (0.79 cm 3  g -1 ), high crystallinity, nano size (about 100 nm) and monodispersity, the as-obtained ZIF-8 showed improved adsorption capacity toward RhB (80% removal efficiency). Heteropolyanion-based guanidinium IL@meso-ZIF-8 (HPAIL@meso-ZIF-8) exhibited the high RhB uptake capacity of 278 mg g -1 (higher than most of the reported adsorbents) and effectively removed 99% of RhB within 15 min. The results showed that the adsorption process of prepared materials fitted well with pseudo-second-order kinetics and Langmuir isotherm model. The existence of mesopores in ZIF-8 facilitated the diffusion of RhB and the incorporated guanidinium IL played a significant role in enhancing the adsorption affinity. Moreover, the reusability results revealed the HPAIL@meso-ZIF-8 as a highly efficient adsorbent for RhB removal with satisfactory performance and structural stability. Therefore, HPAIL@meso-ZIF-8 is one of the most promising adsorbents for organic dye removal from water. Copyright © 2018 Elsevier B.V. All rights reserved.

Single-molecule interfacial electron transfer dynamics in solar energy conversion

NASA Astrophysics Data System (ADS)

Dhital, Bharat

This dissertation work investigated the parameters affecting the interfacial electron transfer (ET) dynamics in dye-semiconductor nanoparticles (NPs) system by using single-molecule fluorescence spectroscopy and imaging combined with electrochemistry. The influence of the molecule-substrate electronic coupling, the molecular structure, binding geometry on the surface and the molecule-attachment surface chemistry on interfacial charge transfer processes was studied on zinc porphyrin-TiO2 NP systems. The fluorescence blinking measurement on TiO2 NP demonstrated that electronic coupling regulates dynamics of charge transfer processes at the interface depending on the conformation of molecule on the surface. Moreover, semiconductor surface charge induced electronic coupling of molecule which is electrostatically adsorbed on the semiconductor surface also predominantly alters the ET dynamics. Furthermore, interfacial electric field and electron accepting state density dependent ET dynamics has been dissected in zinc porphyrin-TiO2 NP system by observing the single-molecule fluorescence blinking dynamics and fluorescence lifetime with and without applied bias. The significant difference in fluorescence fluctuation and lifetime suggested the modulation of charge transfer dynamics at the interface with external electric field perturbation. Quasi-continuous distribution of fluorescence intensity with applied negative potential was attributed to the faster charge recombination due to reduced density of electron accepting states. The driving force and electron accepting state density ET dependent dynamics has also been probed in zinc porphyrin-TiO2 NP and zinc porphyrin-indium tin oxide (ITO) systems. Study of a molecule adsorbed on two different semiconductors (ITO and TiO2), with large difference in electron densities and distinct driving forces, allows us to observe the changes in rates of back electron transfer process reflected by the suppressed fluorescence blinking of molecule on ITO surface. Finally, the electric field effect on the interface properties has been probed by using surface-enhanced Raman spectroscopy and supported by density functional theory calculations in alizarin-TiO2 system. The perturbation, created by the external potential, has been observed to cause a shift and/or splitting interfacial bond vibrational mode, typical indicator of the coupling energy changes between alizarin and TiO2. Such splitting provides evidence for electric field-dependent electronic coupling changes that have a significant impact on the interfacial electron transfer dynamics.

Mesoporous silica originating from a gaseous ammonia epoxide ring opening and the thermodynamic data on some divalent cation adsorptions.

PubMed

Sales, José A A; Petrucelli, Giovanni C; Oliveira, Fernando J V E; Airoldi, Claudio

2007-11-15

An organofunctionalized mesoporous HMS-like compound has been synthesized by reacting the silylating agent 3-glycidoxypropyltrimethoxysilane with gaseous ammonia. The reaction path leads to the opening of the three membered epoxide ring to incorporate ammonia to give the modified silylating agent. This new silylating agent was used to synthesize a mesostructure inorganic-organic hybrid through the neutral template directing agent, dodecylamine, using a co-condensation process, and exploring the ability of the silicon source tetraethoxysilane. The final solid named HMS-NH has been characterized through elemental analysis, X-ray powder diffraction, nitrogen gas adsorption, infrared spectroscopy and solid state NMR for the 29Si nucleus. An amount of 1.06+/-0.10 mmol of pendant groups is covalently bonded to the inorganic backbone. The attached basic centers adsorbed divalent cations to give the maxima adsorption capacity of 0.74+/-0.03, 0.55+/-0.06, 0.53+/-0.05 and 0.51+/-0.06 mmolg(-1) for copper, nickel, zinc and cobalt, respectively. From calorimetric determinations the quantitative thermal effects for all these cation/basic center interactions gave exothermic enthalpy, negative Gibbs free energy and positive entropy. These thermodynamic data confirmed the energetically favorable condition of such interactions at the solid/liquid interface for all systems.

Quantitation of five organophosphorus nerve agent metabolites in serum using hydrophilic interaction liquid chromatography and tandem mass spectrometry

PubMed Central

Hamelin, Elizabeth I.; Schulze, Nicholas D.; Shaner, Rebecca L.; Coleman, Rebecca M.; Lawrence, Richard J.; Crow, Brian S.; Jakubowski, E. M.; Johnson, Rudolph C.

2015-01-01

Although nerve agent use is prohibited, concerns remain for human exposure to nerve agents during decommissioning, research, and warfare. Exposure can be detected through the analysis of the hydrolysis products in urine as well as blood. An analytical method to detect exposure to five nerve agents, including VX, VR (Russian VX), GB (sarin), GD (soman) and GF (cyclosarin), through the analysis of the hydrolysis products, which are the primary metabolites, in serum has been developed and characterized. This method uses solid phase extraction coupled with high performance liquid chromatography for separation and isotopic dilution tandem mass spectrometry for detection. An uncommon buffer of ammonium fluoride was used to enhance ionization and improve sensitivity when coupled with hydrophilic interaction liquid chromatography resulting in detection limits from 0.3–0.5 ng/mL. The assessment of two quality control samples demonstrated high accuracy (101–105%) and high precision (5–8%) for the detection of these five nerve agent hydrolysis products in serum. PMID:24633507

Simple D-A-D Structural Bisbithiophenyl Diketopyrrolopyrrole (TDPP) as Efficient Bioimaging and Photothermal Agents.

PubMed

Zong, Shan; Wang, Xin; Lin, Wenhai; Liu, Shi; Zhang, Wei

2018-06-20

Design and synthesis of biocompatible and multi-functional photothermal agents is crucial for effective cancer phototherapy. In order to achieve this ambition, simple D-A-D structural bisbithiophenyl diketopyrrolopyrrole (TDPP) was fabricated. In this molecule, the donor, 2-thiophenylboric acid, was conjugated via Suzuki coupling reaction, which could expand the emission wavelength to the red region of the spectrum. TDPP could self-assemble into stable and uniform nanoparticles (TDPP NPs) in the assistant of amphiphilic Pluronic F-127 polymer. Exposing the TDPP NPs (100 µg/mL) aqueous dispersion to 638 nm (0.61 W/cm2) laser irradiation resulted in a temperature elevation of approximately 30 oC within 5 min, which is high enough for inducing the cytotoxicity and tumor inhibition. Because of the bathochromic shift absorption of TDPP NPs in water, TDPP NPs could also act as a contrast agent for near-infrared fluorescence imaging (NIRF) to visualize the drug distribution in vivo. Coupled with the infrared thermal imaging properties of the photothermal agent, TDPP NPs were proved to be a multifunctional theranostic agent for dual-modal imaging-guided phototherapy.

SOx/NOx sorbent and process of use

DOEpatents

Ziebarth, M.S.; Hager, M.J.; Beeckman, J.W.; Plecha, S.

1993-01-19

An alumina sorbent capable of adsorbing NOx and SOx from waste gases and being regenerated by heating above 600 C. is made by incorporating an alumina stabilizing agent into the sorbent. A preferred method is to add the stabilizer when the alumina is precipitated. The precipitated powder is formed subsequently into a slurry, milled and dripped to form the stabilizing spheroidal alumina particles. These particles are impregnated with an alkali metal or alkaline earth metal to form the stabilized sorbent. Alumina stabilizers include one or more of silica, lanthana, other rare earths, titania, zirconia and alkaline earths.

Relative impact of H 2 O and O 2 in the oxidation of UO 2 powders from 50 to 300 °C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donald, Scott B.; Davisson, M. Lee; Dai, Zurong

Here, we studied the reaction of water and molecular oxygen with stoichiometric uranium dioxide (i.e. UO 2) powder at elevated temperature by high-resolution x-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, powder x-ray diffraction (XRD), and scanning electron microscopy (SEM). We observed and quatified oxidation resulting from the dissociative chemisorption of the adsorbing molecules and subsequent incorporation into the oxide lattice. Molecular oxygen was found to be a stronger oxidation agent than water at elevated temperatures but not at ambient.

SOX/NOX sorbent and process of use

DOEpatents

Ziebarth, M.S.; Hager, M.J.; Beeckman, J.W.; Plecha, S.

1995-05-09

An alumina sorbent capable of adsorbing NOx and SOx from waste gases and being regenerated by heating above 600 C is made by incorporating an alumina stabilizing agent into the sorbent. A preferred method is to add the stabilizer when the alumina is precipitated. The precipitated powder is formed subsequently into a slurry, milled and dripped to form the stabilized spheroidal alumina particles. These particles are impregnated with an alkali metal or alkaline earth metal to form the stabilized sorbent. Alumina stabilizers include one or more of silica, lanthana, other rare earths, titania, zirconia and alkaline earths. 3 figs.

SOX/NOX sorbent and process of use

DOEpatents

Ziebarth, Michael S.; Hager, Michael J.; Beeckman, Jean W.; Plecha, Stanislaw

1995-01-01

An alumina sorbent capable of adsorbing NOx and SOx from waste gases and being regenerated by heating above 600.degree. C. is made by incorporating an alumina stabilizing agent into the sorbent. A preferred method is to add the stabilizer when the alumina is precipitated. The precipitated powder is formed subsequently into a slurry, milled and dripped to form the stabilized spheroidal alumina particles. These particles are impregnated with an alkali metal or alkaline earth metal to form the stabilized sorbent. Alumina stabilizers include one or more of silica, lanthana, other rare earths, titania, zirconia and alkaline earths.

SOx/NOx sorbent and process of use

DOEpatents

Ziebarth, Michael S.; Hager, Michael J.; Beeckman, Jean W.; Plecha, Stanislaw

1993-01-19

An alumina sorbent capable of adsorbing NOx and SOx from waste gases and being regenerated by heating above 600.degree. C. is made by incorporating an alumina stabilizing agent into the sorbent. A preferred method is to add the stabilizer when the alumina is precipitated. The precipitated powder is formed subsequently into a slurry, milled and dripped to form the stabilizing spheroidal alumina particles. These particles are impregnated with an alkali metal or alkaline earth metal to form the stabilized sorbent. Alumina stabilizers include one or more of silica, lanthana, other rare earths, titania, zirconia and alkaline earths.

Relative impact of H2O and O2 in the oxidation of UO2 powders from 50 to 300 °C

NASA Astrophysics Data System (ADS)

Donald, Scott B.; Davisson, M. Lee; Dai, Zurong; Roberts, Sarah K.; Nelson, Art J.

2017-12-01

The reaction of water and molecular oxygen with stoichiometric uranium dioxide (i.e. UO2) powder at elevated temperature was studied by high-resolution x-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, powder x-ray diffraction (XRD), and scanning electron microscopy (SEM). Oxidation resulting from the dissociative chemisorption of the adsorbing molecules and subsequent incorporation into the oxide lattice was observed and quantified. Molecular oxygen was found to be a stronger oxidation agent than water at elevated temperatures but not at ambient.

Relative impact of H 2 O and O 2 in the oxidation of UO 2 powders from 50 to 300 °C

DOE PAGES

Donald, Scott B.; Davisson, M. Lee; Dai, Zurong; ...

2017-10-04

Here, we studied the reaction of water and molecular oxygen with stoichiometric uranium dioxide (i.e. UO 2) powder at elevated temperature by high-resolution x-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, powder x-ray diffraction (XRD), and scanning electron microscopy (SEM). We observed and quatified oxidation resulting from the dissociative chemisorption of the adsorbing molecules and subsequent incorporation into the oxide lattice. Molecular oxygen was found to be a stronger oxidation agent than water at elevated temperatures but not at ambient.

QENS investigation of filled rubbers

NASA Astrophysics Data System (ADS)

Triolo, A.; Lo Celso, F.; Negroni, F.; Arrighi, V.; Qian, H.; Lechner, R. E.; Desmedt, A.; Pieper, J.; Frick, B.; Triolo, R.

The polymer segmental dynamics is investigated in a series of silica-filled rubbers. The presence of inert fillers in polymers greatly affects the mechanical and physical performance of the final materials. For example, silica has been proposed as a reinforcing agent of elastomers in tire production. Results from quasielastic neutron scattering and Dynamic Mechanical Thermal Analysis (DMTA) measurements are presented on styrene-ran-butadiene rubber filled with silica. A clear indication is obtained of the existence of a bimodal dynamics, which can be rationalized in terms of the relaxation of bulk rubber and the much slower relaxation of the rubber adsorbed on the filler surface.

Cytocompatibility and response of osteoblastic-like cells to starch-based polymers: effect of several additives and processing conditions.

PubMed

Gomes, M E; Reis, R L; Cunha, A M; Blitterswijk, C A; de Bruijn, J D

2001-07-01

This work reports on the biocompatibility evaluation of new biodegradable starch-based polymers that are under consideration for use in orthopaedic temporary applications and as tissue engineering scaffolds. It has been shown in previous works that by using these polymers it is both possible to produce polymer/hydroxyapatite (HA) composites (with or without the use of coupling agents) with mechanical properties matching those of the human bone, and to obtain 3D structures generated by solid blowing agents, that are suitable for tissue engineering applications. This study was focused on establishing the influence of several additives (ceramic fillers, blowing agents and coupling agents) and processing methods/conditions on the biocompatibility of the materials described above. The cytotoxicity of the materials was evaluated using cell culture methods, according to ISO/EN 109935 guidelines. A cell suspension of human osteosarcoma cells (HOS) was also seeded on a blend of corn starch with ethylene vinyl alcohol (SEVA-C) and on SEVA-C/HA composites, in order to have a preliminary indication on cell adhesion and proliferation on the materials surface. In general, the obtained results show that all the different materials based on SEVA-C, (which are being investigated for use in several biomedical applications), as well as all the additives (including the novel coupling agents) and different processing methods required to obtain the different properties/products, can be used without inducing a cytotoxic behaviour to the developed biomaterials.

Microstructure and properties of FeSiCr/PA6 composites by injection molding using FeSiCr powders by phosphating and coupling treatment

NASA Astrophysics Data System (ADS)

Wang, Lulu; Qiao, Liang; Zheng, Jingwu; Cai, Wei; Ying, Yao; Li, Wangchang; Che, Shenglei; Yu, Jing

2018-04-01

FeSiCr/PA6 composites were prepared by injection molding using the FeSiCr powders modified by different phosphating agents and KH550 coupling agent. The resistivity, impact strength, magnetic permeability and magnetic loss of the FeSiCr/PA6 composites were measured. The morphologies of different FeSiCr powders and the FeSiCr/PA6 composites were also observed by scanning electron microscope (SEM). The results showed that 1-Hydroxyethylidene-1,1-diphosphonic acid, phytic acid and H3PO4 could improve the electrical resistivity of FeSiCr powders by forming the dense phosphating layer except diphenylphosphinic acid. However, the resistivity of FeSiCr/PA6 composites using the FeSiCr powders treated by all the four phosphating agents had no obvious increase though the phosphating layer on the surface of FeSiCr powder came into being. The nylon insulation layer had much stronger influence than the phosphating layer on electrical resistivity of the composites. After adding appropriate KH550 coupling agent, the impact strengths of FeSiCr/PA6 composites were significantly improved, which may be associated with the tiny gap between FeSiCr powder and PA6 matrix. The effects of the phosphating agents on the magnetic permeability and loss of the FeSiCr/PA6 were small and the mechanism were also discussed.

Photoenhanced uptakes of NO2 by indoor surfaces: A new HONO source

NASA Astrophysics Data System (ADS)

Gligorovski, S.; Bartolomei, V.; Soergel, M.; Gomez Alvarez, E.; Zetzsch, C.; Wortham, H.

2012-12-01

Nitrous acid (HONO) is a known household pollutant that can lead to human respiratory tract irritation. HONO acts as the nitrosating agent, e.g. by the formation of the so-called third-hand smoke after wall reactions of HONO with nicotine (1). HONO can be generated indoors directly during combustion processes or indirectly via heterogeneous NO2 reactions with adsorbed water on diverse surfaces (2). Recently a new source was identified as another path of HONO formation in the troposphere (3). Namely, the light-induced heterogeneous reaction of NO2 with adsorbed organics (known as photosensitizers) on various surfaces such as roads, buildings, rocks or plants leads to enhanced HONO production. The detected values of HONO indoors vary in the range between 2 and 25 parts per billion (ppb). However, like outdoors, the processes leading to HONO formation indoors are not completely understood (4). Indoor photolysis radiation sources include exterior sunlight (λ>350 nm) that enters typically through the windows and indoor illumination sources, i.e., rare gas/mercury fluorescent light bulbs and tungsten and tungsten/halogen light bulbs among others. The present work is showing the importance of indoor sources of HONO recently identified or postulated. We have tested a number of common household chemical agents commonly used for cleaning purposes or coatings of domestic surfaces to better identify different indoor HONO sources. We used a heterogeneous flow tube technique to test the HONO production potentials of these household chemical agents under different experimental conditions, namely with and without light and at different relative humidity levels and different NO2 concentrations. We report uptake kinetics measurements of the heterogeneous reaction of gas phase NO2 with lacquer and paint coated on the walls of the reactor. The flow tube was irradiated with four near-ultraviolet (UV) emitting lamps (range of wavelengths 300-420nm). We observed that the heterogeneous conversion of NO2 to HONO on lacquer surfaces and on white wall paints is substantially enhanced in the presence of light and at higher relative humidity (RH = 60%). In runs carried out applying experimental conditions typically found indoors, i.e., NO2 mixing ratios of 25 ppb and 60% RH%, the observed NO2 uptakes on a surface coated with lacquer and paint showed an enhancement of one order of magnitude in the presence of light as compared to the uptake observed in the dark. Our results indicate, contrary to other study that claimed that humidity does not influence the NO2 reactions with adsorbed organics, that actually both postulated HONO sources combined i.e. heterogeneous NO2 reactions with adsorbed organics (photosensitizers) in presence of elevated humidity leads to even more pronounced HONO production. Reference: 1. M., Sleiman, L. A., Gundel, J. F., Pankow, P., Jacob, B. C., Singer, H., Destaillats, P. Natl. Acad. Sci. USA, 107, 6576 (2010). 2. B. J. Finlayson-Pitts, L. M. Wingen, A. L. Sumner, D. Syomin, K. A. Ramazan, Phys. Chem. Chem. Phys. 5, 223 (2003). 3. K., Stemmler, M., Ammann, C., Donders, J., Kleffmann, C., George, Nature 440, 195 (2006). 4. E. Gomez Alvarez, H. Wortham, R. Strekowski, C. Zetzsch, S. Gligorovski, Environ. Sci. Technol., 46, 1955 (2012).

Molecular dynamics investigation of separation of hydrogen sulfide from acidic gas mixtures inside metal-doped graphite micropores.

PubMed

Huang, Pei-Hsing

2015-09-21

The separation of poisonous compounds from various process fluids has long been highly intractable, motivating the present study on the dynamic separation of H2S in acidic-gas-mixture-filled micropores. The molecular dynamics approach, coupled with the isothermal-isochoric ensemble, was used to model the molecular interactions and adsorption of H2S/CO2/CO/H2O mixtures inside metal-doped graphite slits. Due to the difference in the adsorption characteristics between the two distinct adsorbent materials, the metal dopant in the graphitic micropores leads to competitive adsorption, i.e. the Au and graphite walls compete to capture free adsorbates. The effects of competitive adsorption, coupled with changes in the gas temperature, concentration, constituent ratio and slit width on the constituent separation of mixtures were systematically studied. The molecule-wall binding energies calculated in this work (those of H2S, H2O and CO on Au walls and those of H2O, CO and CO2 on graphite walls) show good agreement with those obtained using density functional theory (DFT) and experimental results. The z-directional self-diffusivities (Dz) for adsorbates inside the slit ranged from 10(-9) to 10(-7) m(2) s(-1) as the temperature was increased from 10 to 500 K. The values are comparable with those for a typical microporous fluid (10(-8)-10(-9) m(2) s(-1) in a condensed phase and 10(-6)-10(-7) m(2) s(-1) in the gaseous state). The formation of H-bonding networks and hydrates of H2S is disadvantageous for the separation of mixtures. The results indicate that H2S can be efficiently separated from acidic gas mixtures onto the Au(111) surface by (i) reducing the mole fraction of H2S and H2O in the mixtures, (ii) raising the gas temperature to the high temperature limit (≥400 K), and (iii) lowering the slit width to below the threshold dimension (≤23.26 Å).

Facile synthesis of amine-functional reduced graphene oxides as modified quick, easy, cheap, effective, rugged and safe adsorbent for multi-pesticide residues analysis of tea.

PubMed

Ma, Guicen; Zhang, Minglu; Zhu, Li; Chen, Hongping; Liu, Xin; Lu, Chengyin

2018-01-05

Amine-functional reduced graphene oxide (amine-rGO) with different carbon chain length amino groups were successfully synthesized. The graphene oxides (GO) reduction as well as amino grafting were achieved simultaneously in one step via a facile solvothermal synthetic strategy. The obtained materials were characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy to confirm the modification of GO with different amino groups. The adsorption performance of catechins and caffeine from tea acetonitrile extracts on different amine functional rGO samples were evaluated. It was found that tributylamine-functional rGO (tri-BuA-rGO) exhibited the highest adsorption ability for catechins and caffeine compared to GO and other amino group functional rGO samples. It was worth to note that the adsorption capacity of catechins on tri-BuA-rGO was 11 times higher than that of GO (203.7mgg -1 vs 18.7mgg -1 ). Electrostatic interaction, π-π interaction and surface hydrophilic-hydrophobic properties of tri-BuA-rGO played important roles in the adsorption of catechins as well as caffeine. The gravimetric analysis confirmed that the tri-BuA-rGO achieved the highest efficient cleanup preformance compared with traditional dispersive solid phase extraction (dSPE) adsorbents like primary-secondary amine (PSA), graphitized carbon black (GCB) or C18. A multi-pesticides analysis method based on tri-BuA-rGO is validated on 33 representative pesticides in tea using gas chromatography coupled to tandem mass spectrometry or high-performance liquid chromatography coupled with tandem mass spectrometry. The analysis method gave a high coefficient of determination (r 2 >0.99) for each pesticide and satisfactory recoveries in a range of 72.1-120.5%. Our study demonstrated that amine functional rGO as a new type of QuEChERS adsorbent is expected to be widely applied for analysis of pesticides at trace levels. Copyright © 2017 Elsevier B.V. All rights reserved.

REMOTE BIOSENSOR FOR IN SITU MONITORING OF ORGANOPHOSPHATE NERVE AGENTS. (R823663)

EPA Science Inventory

A remote electrochemical biosensor for field monitoring of organophosphate nerve agents is described. The new sensor relies on the coupling of the effective biocatalytic action of organophosphorus hydrolase (OPH) with a submersible amperometric probe design. This combination resu...

Selective determination of gold(III) ion using CuO microsheets as a solid phase adsorbent prior by ICP-OES measurement.

PubMed

Rahman, Mohammed M; Khan, Sher Bahadar; Marwani, Hadi M; Asiri, Abdullah M; Alamry, Khalid A; Al-Youbi, Abdulrahman O

2013-01-30

We have prepared calcined CuO microsheets (MSs) by a wet-chemical process using reducing agents in alkaline medium and characterized by UV/vis., fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM) etc. The detailed structural, compositional, and optical characterizations of the MSs were evaluated by XRD pattern, FT-IR, X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy, respectively which confirmed that the obtained MSs are well-crystalline CuO and possessed good optical properties. The CuO MSs morphology was investigated by FESEM, which confirmed that the calcined nanomaterials were sheet-shaped and grown in large-quantity. Here, the efficiency of the CuO MS was applied for a selective adsorption of gold(III) ion prior to its detection by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of CuO MSs towards various metal ions, including Au(III), Cd(II), Co(II), Cr(III), Fe(III), Pd(II), and Zn(II) was analyzed. Based on the adsorption isotherm study, it was confirmed that the selectivity of MSs phase was mostly towards Au(III) ion. The static adsorption capacity for Au(III) was calculated to be 57.0 mg g(-1). From Langmuir adsorption isotherm, it was confirmed that the adsorption process was mainly monolayer-adsorption onto a surface containing a finite number of adsorption sites. Copyright © 2012 Elsevier B.V. All rights reserved.

Synthesis of surface Cr (VI)-imprinted magnetic nanoparticles for selective dispersive solid-phase extraction and determination of Cr (VI) in water samples.

PubMed

Qi, Xue; Gao, Shuang; Ding, Guosheng; Tang, An-Na

2017-01-01

A facile, rapid and selective magnetic dispersed solid-phase extraction (dSPE) method for the extraction and enrichment of Cr (VI) prior to flame atomic absorption spectrometry (AAS) was introduced. For highly selective and efficient extraction, magnetic Cr (VI)-imprinted nanoparticles (Fe 3 O 4 @ Cr (VI) IIPs) were prepared by hyphenating surface ion-imprinted with sol-gel techniques. In the preparation process, chromate (Cr(VI)) was used as the template ion; vinylimidazole and 3-aminopropyltriethoxysilane were selected as organic functional monomer and co-monomer respectively. Another reagent, methacryloxypropyltrimethoxysilane was adopted as coupling agent to form the stable covalent bonding between organic and inorganic phases. The effects of various parameters on the extraction efficiency, such as pH of sample solution, the amount of adsorbent, extraction time, the type and concentration of eluent were systematically investigated. Furthermore, the thermodynamic and kinetic properties of the adsorption process were studied to explore the internal adsorption mechanism. Under optimized conditions, the preconcentration factor, limit of detection and linear range of the established dSPE-AAS method for Cr (VI) were found to be 98, 0.29μgL -1 and 4-140μgL -1 , respectively. The developed method was also successfully applied to the analysis of Cr (VI) in different water samples with satisfactory results, proving its reliability and feasibility in real sample analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Adsorption mechanism of ester phosphate on baryum titanate in organic medium. Preliminary results on the structure of the adsorbed layer

NASA Astrophysics Data System (ADS)

Le Bars, N.; Tinet, D.; Faugère, A. M.; van Damme, H.; Levitz, P.

1991-05-01

The purpose of this work is to evidence the adsorption mechanism and the structure of commercial phosphate ester surfactant stabilized BaTiO3 in organic suspension, and to relate these characteristics to rheological behaviour. Binders and plasticizers are omitted to reduce the number of system components. Firstly adsorption isotherm were determined by inductively coupled argon plasma technique and interpretated based on transmission electron microscopy and ^{31}P nuclear magnetic resonance studies. Preliminary rheological measurements were then performed and related to suspension structure. Structure of the adsorption layer is critically discussed. L'objectif de cette étude est la compréhension du mécanisme d'adsorption d'agents dispersants phosphatés dans des suspensions organiques de BaTiO3, ainsi que la caractérisation de la structure, et du comportement rhéologique de ces suspensions. Liants et plastifiants ne sont pas utilisés, afin de réduire le nombre de composants dans le système. Dans un premier temps, l'isotherme d'adsorption est établie par dosage en émission plasma, puis interprétée sur la base de résultats de Microscopie Eloctronique à Transmission, et de spectroscopie par Résonance Magnétique Nucléaire du ^{31}P. Des mesures rhéologiques préliminaires sont effectuées pour caractériser la structure des suspensions.

Selective Adsorption of Pb(II) from Aqueous Solution by Triethylenetetramine-Grafted Polyacrylamide/Vermiculite

PubMed Central

Gu, Shiqing; Wang, Lan; Mao, Xinyou; Yang, Liping; Wang, Chuanyi

2018-01-01

Amine groups play significant roles in polymeric composites for heavy metals removal. However, generating a composite with a large number of functional and stable amine groups based on clay is still a challenge. In this work, a new amine-functionalized adsorbent based on acid-activated vermiculite (a-Verm) was prepared by organic modification of silane coupling agent as bridge, followed by in situ polymerization of acrylamide (AM) and further grafting of triethylene tetramine (TETA). The obtained polymeric composite g-PAM/OVerm was characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared (FTIR), thermal analysis (TG/DTG), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analyses, confirming that amine groups were successfully grafted onto the surface of Verm. The efficacy g-PAM/OVerm for removing Pb(II) was tested. The adsorption equilibrium data on g-PAM/OVerm was in good accordance with the Langmuir adsorption isotherms, and the adsorption maximal value of Pb(II) was 219.4 mg·g−1. The adsorption kinetic data fit the pseudo-second-order kinetic model well. Additionally, g-PAM/OVerm has better selectivity for Pb(II) ion in comparison with Zn(II), Cd(II) and Cu(II) ions. The present work shows that g-PAM/OVerm holds great potential for removing Pb(II) from wastewater, and provides a new and efficient method for the removal of heavy metal ions from industrial wastewater. PMID:29597288

Kinetic studies of adsorption of Cu (II) from aqueous solution by coriander seeds (Coriandrum Sativum)

NASA Astrophysics Data System (ADS)

Kadiri, L.; Lebkiri, A.; Rifi, E. H.; Ouass, A.; Essaadaoui, Y.; Lebkiri, I.; Hamad, H.

2018-05-01

The adsorption of copper ions Cu2+ by Coriandrum Sativum seeds (CSS) from aqueous solution was studied in order to highlight the importance of coriander seeds as a potential tool in the treatment of wastewaters containing heavy metals. The kinetic studies of adsorption of Cu (II) were discussed using the spectroscopic technique "Inducting Coupled Plasma" (ICP). The effects of initial copper ion concentration and contact time were determined. All results show that coriander seeds have, over their culinary and medicinal benefits, a significant adsorbent power of copper ions.

Time-resolved spectroscopy at surfaces and adsorbate dynamics:insights from a model-system approach

NASA Astrophysics Data System (ADS)

Boström, Emil; Mikkelsen, Anders; Verdozzi, Claudio

We introduce a finite-system, model description of the initial stages of femtosecond laser induced desorption at surfaces. Using the exact many-body time evolution and also results from a novel time-dependent DFT description for electron-nuclear systems, we analyse the competition between several surface-response mechanisms and electronic correlations in the transient and longer time dynamics under the influence of dipole-coupled fields. Our model allows us to explore how coherent multiple-pulse protocols impact desorption in a variety of prototypical experiments.

Encapsulant materials and associated devices

DOEpatents

Kempe, Michael D [Littleton, CO; Thapa, Prem [Lima, OH

2011-03-08

Compositions suitable for use as encapsulants are described. The inventive compositions include a high molecular weight polymeric material, a curing agent, an inorganic compound, and a coupling agent. Optional elements include adhesion promoting agents, colorants, antioxidants, and UV absorbers. The compositions have desirable diffusivity properties, making them suitable for use in devices in which a substantial blocking of moisture ingress is desired, such as photovoltaic (PV) modules.

Encapsulant materials and associated devices

DOEpatents

Kempe, Michael D [Littleton, CO; Thapa, Prem [Lima, OH

2012-05-22

Compositions suitable for use as encapsulants are described. The inventive compositions include a high molecular weight polymeric material, a curing agent, an inorganic compound, and a coupling agent. Optional elements include adhesion promoting agents, colorants, antioxidants, and UV absorbers. The compositions have desirable diffusivity properties, making them suitable for use in devices in which a substantial blocking of moisture ingress is desired, such as photovoltaic (PV) modules.

Synthesis of di-functional ligand and fluorescently labeling SiO2 microspheres

NASA Astrophysics Data System (ADS)

Chen, Kexu; Kang, Ming; Liu, Min; Shen, Simin; Sun, Rong

2018-05-01

In order to complete the fluorescent labeling of SiO2 microspheres, a kind of di-functional ligand was synthesized and purified, which could not only coordinate rare earth ions but also react with the active groups to bond host materials with an alkoxysilane groups. Fourier transform infrared spectroscopy (FT-IR), 1H NMR spectra, MS spectra, field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and luminescence spectrophotometer were used to study the structure of di-functional ligand and properties of fluorescent coupling agent and fluorescent labeled SiO2 microspheres. The optimal experiment conditions were acquired as follows: molar ratio as 1: 4 (MDBM: MICPTES), reaction time at 6 h and reaction temperature as 65 °C (yield up to 40%) through the orthogonal experiment and purification process. The results indicated that fluorescent coupling agent presented red photoluminesence of Eu3+ ions at 610 nm, and the absolute quantum yield was 11%. On the other hand, the hydrolysis of the coupling agent reacted on the surface of SiO2 microspheres and presented fluorescent labeling homogeneously.

Assessing groundwater policy with coupled economic-groundwater hydrologic modeling

NASA Astrophysics Data System (ADS)

Mulligan, Kevin B.; Brown, Casey; Yang, Yi-Chen E.; Ahlfeld, David P.

2014-03-01

This study explores groundwater management policies and the effect of modeling assumptions on the projected performance of those policies. The study compares an optimal economic allocation for groundwater use subject to streamflow constraints, achieved by a central planner with perfect foresight, with a uniform tax on groundwater use and a uniform quota on groundwater use. The policies are compared with two modeling approaches, the Optimal Control Model (OCM) and the Multi-Agent System Simulation (MASS). The economic decision models are coupled with a physically based representation of the aquifer using a calibrated MODFLOW groundwater model. The results indicate that uniformly applied policies perform poorly when simulated with more realistic, heterogeneous, myopic, and self-interested agents. In particular, the effects of the physical heterogeneity of the basin and the agents undercut the perceived benefits of policy instruments assessed with simple, single-cell groundwater modeling. This study demonstrates the results of coupling realistic hydrogeology and human behavior models to assess groundwater management policies. The Republican River Basin, which overlies a portion of the Ogallala aquifer in the High Plains of the United States, is used as a case study for this analysis.

A Study on the Rheological and Mechanical Properties of Photo-Curable Ceramic/Polymer Composites with Different Silane Coupling Agents for SLA 3D Printing Technology.

PubMed

Song, Se Yeon; Park, Min Soo; Lee, Jung Woo; Yun, Ji Sun

2018-02-07

Silane coupling agents (SCAs) with different organofunctional groups were coated on the surfaces of Al₂O₃ ceramic particles through hydrolysis and condensation reactions, and the SCA-coated Al₂O₃ ceramic particles were dispersed in a commercial photopolymer based on interpenetrating networks (IPNs). The organofunctional groups that have high radical reactivity and are more effective in UV curing systems are usually functional groups based on acryl, such as acryloxy groups, methacrloxy groups, and acrylamide groups, and these silane coupling agents seem to improve interfacial adhesion and dispersion stability. The coating morphology and the coating thickness distribution of SCA-coated Al₂O₃ ceramic particles according to the different organofunctional groups were observed by FE-TEM. The initial dispersibility and dispersion stability of the SCA-coated Al₂O₃/High-temp composite solutions were investigated by relaxation NMR and Turbiscan. The rheological properties of the composite solutions were investigated by viscoelastic analysis and the mechanical properties of 3D-printed objects were observed with a nanoindenter.

A Study on the Rheological and Mechanical Properties of Photo-Curable Ceramic/Polymer Composites with Different Silane Coupling Agents for SLA 3D Printing Technology

PubMed Central

Song, Se Yeon; Park, Min Soo; Lee, Jung Woo; Yun, Ji Sun

2018-01-01

Silane coupling agents (SCAs) with different organofunctional groups were coated on the surfaces of Al2O3 ceramic particles through hydrolysis and condensation reactions, and the SCA-coated Al2O3 ceramic particles were dispersed in a commercial photopolymer based on interpenetrating networks (IPNs). The organofunctional groups that have high radical reactivity and are more effective in UV curing systems are usually functional groups based on acryl, such as acryloxy groups, methacrloxy groups, and acrylamide groups, and these silane coupling agents seem to improve interfacial adhesion and dispersion stability. The coating morphology and the coating thickness distribution of SCA-coated Al2O3 ceramic particles according to the different organofunctional groups were observed by FE-TEM. The initial dispersibility and dispersion stability of the SCA-coated Al2O3/High-temp composite solutions were investigated by relaxation NMR and Turbiscan. The rheological properties of the composite solutions were investigated by viscoelastic analysis and the mechanical properties of 3D-printed objects were observed with a nanoindenter. PMID:29414912

Novel One-pot Fabrication of Lab-on-a-Bubble@Ag Substrate without Coupling-agent for Surface Enhanced Raman Scattering

NASA Astrophysics Data System (ADS)

Jiang, Jizhou; Ou-Yang, Lei; Zhu, Lihua; Zou, Jing; Tang, Heqing

2014-02-01

Through in-situ reduction of silver nitrate without using any coupling-agent, a substrate for surface-enhanced Raman scattering (SERS) was prepared by coating silver on hollow buoyant silica microspheres as a lab on a bubble (LoB). The silver coated LoBs (LoBs@Ag) floated on surface of a solution could provide a very convenient platform for the detection of target molecules in the solution. The LoBs@Ag substrate not only immobilized well-distributed Ag nanoparticles on the surface LoBs, but excluded the interference of coupling agents. This yielded high-resolution SERS spectra with excellent reproducibility. The adsorption of crystal violet (CV) on the LoBs@Ag substrate was investigated by means of SERS combined with density functional theory (DFT) calculations. The LoBs@Ag substrate exhibited a remarkable Raman enhancement effect for CV with an enhancement factor of 6.9 × 108 and wide adaptability from dye, pesticide to bio-molecules. On the basis of this substrate, a simple and sensitive SERS method was proposed for the determination of trace organic pollutants or bio-molecules.

Fabrication of boronate-decorated polyhedral oligomeric silsesquioxanes grafted cotton fiber for the selective enrichment of nucleosides in urine.

PubMed

Gao, Li; Wei, Yinmao

2016-06-01

Various cotton fiber based boronate-affinity adsorbents are recently developed for the sample pretreatment of cis-diol-containing biomolecules, but most do not have efficient capacity due to limited binding sites on the surface of cotton fibers. To increase the density of boronate groups on the surface of cotton fiber, polyhedral oligomeric silsesquioxanes were used to modify cotton fiber to provide plentiful reactive sites for subsequent functionalization with 4-formylphenylboronic acid. The new adsorbent showed special recognition ability towards cis-diols and high adsorption capacity (175 μg/g for catechol, 250 μg/g for dopamine, 400 μg/g for adenosine). The in-pipette-tip solid-phase extraction was investigated under different conditions, including pH and ionic strength of solution, adsorbent amount, pipette times, washing solvent, and elution solvent. The in-pipette-tip solid-phase extraction coupled with high-performance liquid chromatography was used to analyze four nucleosides in urine samples. Under the optimal extraction conditions, the detection limits were determined to be between 5.1 and 6.1 ng/mL (S/N  =  3), and the linearity ranged from 20 to 500 ng/mL for these analytes. The accuracy of the analytical method was examined by studying the relative recoveries of analytes in real urine samples with recoveries varying from 83 to 104% (RSD = 3.9-10.2%, n = 3). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theory of action spectroscopy for single-molecule reactions induced by vibrational excitations with STM

NASA Astrophysics Data System (ADS)

Frederiksen, T.; Paulsson, M.; Ueba, H.

2014-01-01

A theory of action spectroscopy, i.e., a reaction rate or yield as a function of bias voltage, is presented for single-molecule reactions induced by the inelastic tunneling current with a scanning tunneling microscope. A formula for the reaction yield is derived using the adsorbate resonance model, which provides a versatile tool to analyze vibrationally mediated reactions of single adsorbates on conductive surfaces. This allows us to determine the energy quantum of the excited vibrational mode, the effective broadening of the vibrational density of states (as described by Gaussian or Lorentzian functions), and a prefactor characterizing the elementary process behind the reaction. The underlying approximations are critically discussed. We point out that observation of reaction yields at both bias voltage polarities can provide additional insight into the adsorbate density of states near the Fermi level. As an example, we apply the theory to the case of flip motion of a hydroxyl dimer (OD)2 on Cu(110) which was experimentally observed by Kumagai et al. [Phys. Rev. B 79, 035423 (2009), 10.1103/PhysRevB.79.035423]. In combination with density functional theory calculations for the vibrational modes, the vibrational damping due to electron-hole pair generation, and the potential energy landscape for the flip motion, a detailed microscopic picture for the switching process is established. This picture reveals that the predominant mechanism is excitation of the OD stretch modes which couple anharmonically to the low-energy frustrated rotation mode.

Ultrafast Nanoscale Raman Thermometry Proves Heating Is Not a Primary Mechanism for Plasmon-Driven Photocatalysis.

PubMed

Keller, Emily L; Frontiera, Renee R

2018-06-08

Plasmonic materials efficiently convert light to various forms of energies for many applications, including photocatalysis, photovoltaics, and photothermal therapies. In particular, plasmonic photocatalysts hold incredible promise for highly selective sunlight-driven catalysis through the generation of highly energetic holes and electrons used to drive chemical reactions. However, plasmons are also known to generate heat, and the partitioning of photoexcitation energy into hot carriers and heat on molecularly relevant time scales is not well understood, yet plays a crucial role in designing and understanding these photocatalysts. Using an ultrafast surface-enhanced Raman thermometry technique, we probe the effective temperature, equivalent to the mode-specific increase of vibrational kinetic energy, of molecules adsorbed to gold nanoparticle aggregates in the most active hot spots on the picosecond time scale of chemical reactivity. This represents the first measurement of vibrational energy deposition for coupled molecular-plasmonic systems on the picosecond time scale of molecular motion. We find that upon plasmon excitation, the adsorbates in the hot spots undergo an initial energy transfer within several picoseconds that changes the effective temperature of the system by less than 100 K, even at peak flux values 10 8 times stronger than focused sunlight. The energy quickly dissipates from the adsorbates into the surroundings in less than 5 ps, even at the highest values of photoexcitation. This surprisingly modest energy transfer of the most active regions of the plasmonic materials on the ultrafast time scale decisively proves that most plasmonic photocatalysis is not primarily thermally driven.

Coupling of ultrasound-assisted extraction and expanded bed adsorption for simplified medicinal plant processing and its theoretical model: extraction and enrichment of ginsenosides from Radix Ginseng as a case study.

PubMed

Mi, Jianing; Zhang, Min; Zhang, Hongyang; Wang, Yuerong; Wu, Shikun; Hu, Ping

2013-02-01

A high-efficient and environmental-friendly method for the preparation of ginsenosides from Radix Ginseng using the method of coupling of ultrasound-assisted extraction with expanded bed adsorption is described. Based on the optimal extraction conditions screened by surface response methodology, ginsenosides were extracted and adsorbed, then eluted by the two-step elution protocol. The comparison results between the coupling of ultrasound-assisted extraction with expanded bed adsorption method and conventional method showed that the former was better than the latter in both process efficiency and greenness. The process efficiency and energy efficiency of the coupling of ultrasound-assisted extraction with expanded bed adsorption method rapidly increased by 1.4-fold and 18.5-fold of the conventional method, while the environmental cost and CO(2) emission of the conventional method were 12.9-fold and 17.0-fold of the new method. Furthermore, the theoretical model for the extraction of targets was derived. The results revealed that the theoretical model suitably described the process of preparing ginsenosides by the coupling of ultrasound-assisted extraction with expanded bed adsorption system. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

C-C Coupling on Single-Atom-Based Heterogeneous Catalyst.

PubMed

Zhang, Xiaoyan; Sun, Zaicheng; Wang, Bin; Tang, Yu; Nguyen, Luan; Li, Yuting; Tao, Franklin Feng

2018-01-24

Compared to homogeneous catalysis, heterogeneous catalysis allows for ready separation of products from the catalyst and thus reuse of the catalyst. C-C coupling is typically performed on a molecular catalyst which is mixed with reactants in liquid phase during catalysis. This homogeneous mixing at a molecular level in the same phase makes separation of the molecular catalyst extremely challenging and costly. Here we demonstrated that a TiO 2 -based nanoparticle catalyst anchoring singly dispersed Pd atoms (Pd 1 /TiO 2 ) is selective and highly active for more than 10 Sonogashira C-C coupling reactions (R≡CH + R'X → R≡R'; X = Br, I; R' = aryl or vinyl). The coupling between iodobenzene and phenylacetylene on Pd 1 /TiO 2 exhibits a turnover rate of 51.0 diphenylacetylene molecules per anchored Pd atom per minute at 60 °C, with a low apparent activation barrier of 28.9 kJ/mol and no cost of catalyst separation. DFT calculations suggest that the single Pd atom bonded to surface lattice oxygen atoms of TiO 2 acts as a site to dissociatively chemisorb iodobenzene to generate an intermediate phenyl, which then couples with phenylacetylenyl bound to a surface oxygen atom. This coupling of phenyl adsorbed on Pd 1 and phenylacetylenyl bound to O ad of TiO 2 forms the product molecule, diphenylacetylene.

Modeling of Internet Influence on Group Emotion

NASA Astrophysics Data System (ADS)

Czaplicka, Agnieszka; Hołyst, Janusz A.

Long-range interactions are introduced to a two-dimensional model of agents with time-dependent internal variables ei = 0, ±1 corresponding to valencies of agent emotions. Effects of spontaneous emotion emergence and emotional relaxation processes are taken into account. The valence of agent i depends on valencies of its four nearest neighbors but it is also influenced by long-range interactions corresponding to social relations developed for example by Internet contacts to a randomly chosen community. Two types of such interactions are considered. In the first model the community emotional influence depends only on the sign of its temporary emotion. When the coupling parameter approaches a critical value a phase transition takes place and as result for larger coupling constants the mean group emotion of all agents is nonzero over long time periods. In the second model the community influence is proportional to magnitude of community average emotion. The ordered emotional phase was here observed for a narrow set of system parameters.

Removal of Cd2+ and Cu2+ ions from aqueous solution by using Fe-Fe3O4/graphene oxide as a novel and efficient adsorbent

NASA Astrophysics Data System (ADS)

Le, Giang H.; Ha, Anh Q.; Nguyen, Quang K.; Nguyen, Kien T.; Dang, Phuong T.; Tran, Hoa T. K.; Vu, Loi D.; Nguyen, Tuyen V.; Lee, Gun D.; Vu, Tuan A.

2016-10-01

The nano Fe-Fe3O4/graphene oxide (GO) was successfully synthesized by the precipitation method and followed by chemical reduction using FeCl3 as iron sources and NaBH4 as reducing agent. The products were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), BET, x-ray photoelectron spectroscopy (XPS) and VMS. From the obtained XRD and XPS results, it revealed the formation of both Fe and Fe3O4 nano particles on GO surface. TEM images showed that both Fe3O4/GO and Fe-Fe3O4/GO had small particle size of 10-20 nm and uniform size distribution. Fe3O4/GO and Fe-Fe3O4/GO were used as adsorbents for removal of Cd2+ and Cu2+ ions from aqueous solution. Maximum adsorption capacity (Q max) of Fe-Fe3O4/GO for Cu2+ and Cd2+ are 90.0 mg g-1 and 108.6 mg g-1, respectively. These values are much higher as compared to those of Fe3O4/GO as well as those reported in the literature. Additionally, this novel adsorbent can be reused by washing with diluted Hcl solution and easily recovered by applying the magnetic field. The Cd2+ adsorption isotherm fits better for the Langmuir model that of the Freundlich model and it obeys the pseudo-second order kinetic equation.

Coupled replicator equations for the dynamics of learning in multiagent systems

NASA Astrophysics Data System (ADS)

Sato, Yuzuru; Crutchfield, James P.

2003-01-01

Starting with a group of reinforcement-learning agents we derive coupled replicator equations that describe the dynamics of collective learning in multiagent systems. We show that, although agents model their environment in a self-interested way without sharing knowledge, a game dynamics emerges naturally through environment-mediated interactions. An application to rock-scissors-paper game interactions shows that the collective learning dynamics exhibits a diversity of competitive and cooperative behaviors. These include quasiperiodicity, stable limit cycles, intermittency, and deterministic chaos—behaviors that should be expected in heterogeneous multiagent systems described by the general replicator equations we derive.

Effects of electrolytes and surfactants on the morphology and stability of advanced silver nano-materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obaid, Abdullah Yousif; AL-Thabaiti, Shaeel Ahmed; El-Mossalamy, E.H.

2013-03-15

Highlights: ► Stoichiometric ratio of S{sub 2}O{sub 3}{sup 2−} and Ag{sup +} ions are responsible to the formation of prefect transparent yellow colored silver sol. ► Higher S{sub 2}O{sub 3}{sup 2−} concentrations has damping effect. ► Head group of the surfactants and nature of the electrolytes have significant effect on the stability of silver nanoparticles. - Abstract: The impact of electrolytes, stabilizing and/or capping agents on morphology of colloidal silver nano-materials (AgNPs) has been studied spectroscopically. Sodium thiosulfate acts as reducing-, stabilizing- and damping-agents. Stoichiometric ratios of S{sub 2}O{sub 3}{sup 2−} and Ag{sup +} ions were responsible to the formationmore » stable and prefect transparent dark yellow colored AgNPs. The S{sub 2}O{sub 3}{sup 2−}-stabilized AgNPs were significantly more stable in inorganic electrolytes (NaNO{sub 3}, Na{sub 2}SO{sub 4}, Na{sub 2}CO{sub 3} and KBr). S{sub 2}O{sub 3}{sup 2−} is adsorbed more strongly than the used other anions. The addition of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) has significant effects on the absorbance of S{sub 2}O{sub 3}{sup 2−}-stabilized AgNPs which can be rationalized in terms of electrostatic attraction and repulsion between the adsorbed S{sub 2}O{sub 3}{sup 2−} ions on to the surface of AgNPs and cationic and/or anionic head groups of used surfactants, respectively. Transmission electron microscopy images suggest that AgNPs are polydispersed, spherical and exhibiting an interesting irregular morphology.« less

Characterization, sorption, and exhaustion of metal oxide nanoparticles as metal adsorbents

NASA Astrophysics Data System (ADS)

Engates, Karen Elizabeth

Safe drinking water is paramount to human survival. Current treatments do not adequately remove all metals from solution, are expensive, and use many resources. Metal oxide nanoparticles are ideal sorbents for metals due to their smaller size and increased surface area in comparison to bulk media. With increasing demand for fresh drinking water and recent environmental catastrophes to show how fragile water supplies are, new approaches to water conservation incorporating new technologies like metal oxide nanoparticles should be considered as an alternative method for metal contaminant adsorbents from typical treatment methods. This research evaluated the potential of manufactured iron, anatase, and aluminum nanoparticles (Al2O3, TiO2, Fe2O3) to remove metal contaminants (Pb, Cd, Cu, Ni, Zn) in lab-controlled and natural waters in comparison to their bulk counterparts by focusing on pH, contaminant and adsorbent concentrations, particle size, and exhaustive capabilities. Microscopy techniques (SEM, BET, EDX) were used to characterize the adsorbents. Adsorption experiments were performed using 0.01, 0.1, or 0.5 g/L nanoparticles in pH 8 solution. When results were normalized by mass, nanoparticles adsorbed more than bulk particles but when surface area normalized the opposite was observed. Adsorption was pH-dependent and increased with time and solid concentration. Aluminum oxide was found to be the least acceptable adsorbent for the metals tested, while titanium dioxide anatase (TiO2) and hematite (alpha-Fe2O3) showed great ability to remove individual and multiple metals from pH 8 and natural waters. Intraparticle diffusion was likely part of the complex kinetic process for all metals using Fe2O3 but not TiO 2 nanoparticles within the first hour of adsorption. Adsorption kinetics for all metals tested were described by a modified first order rate equation used to consider the diminishing equilibrium metal concentrations with increasing metal oxides, showing faster adsorption rates for nanoparticles compared to bulk particles. Isotherms were best fit with most correlations of r=0.99 or better using the Langmuir-Freundlich equation which describes a heterogeneous surface with monolayer adsorption. Calculated rate constants and distribution coefficients (Kd) showed TiO2 nanoparticles were very good sorbents and more rapid in removing metals than other nanoparticles studied here and reported in the literature. Desorption studies concluded Pb, Cd, and Zn appear to be irreversibly sorbed to TiO2 surfaces at pH 8. TiO2 and Fe2O3 nanoparticles were capable of multiple metal loadings, with exhaustion for both adsorbents at pH 6. Exhaustion studies at pH 8 showed hematite exhausted after four consecutive cycles while anatase showed no exhaustion after 8 cycles. Their bulk counterparts exhausted in earlier cycles indicating the lack of ability to adsorb much of the multiple metals in solution. The increased surface area of TiO2 and Fe 2O3 nanoparticles, coupled with strong adsorption at the pH of most natural waters and resistance to desorption of some metals, may offer a potential remediation method for removal of metals from water in the future.

Theoretical Study of Oxovanadium(IV) Complexation with Formamidoximate: Implications for the Design of Uranyl-Selective Adsorbents

DOE PAGES

Mehio, Nada; Ivanov, Alexander S.; Ladshaw, Austin P.; ...

2015-11-22

Poly(acrylamidoxime) fibers are the current state of the art adsorbent for mining uranium from seawater. However, the competition between uranyl (UO 2 2+) and vanadium ions poses a challenge to mining on the industrial scale. In this work, we employ density functional theory (DFT) and coupled-cluster methods (CCSD(T)) in the restricted formalism to investigate potential binding motifs of the oxovanadium(IV) ion (VO 2+) with the formamidoximate ligand. Consistent with experimental EXAFS data, the hydrated six-coordinate complex is predicted to be preferred over the hydrated five-coordinate complex. Here, our investigation of formamidoximate-VO 2+ complexes universally identified the most stable binding motifmore » formed by chelating a tautomerically rearranged imino hydroxylamine via the imino nitrogen and hydroxylamine oxygen. The alternative binding motifs for amidoxime chelation via a non-rearranged tautomer and 2 coordination are found to be ~11 kcal/mol less stable. Ultimately, the difference in the most stable VO 2+ and UO 2 2+ binding conformation has important implications for the design of more selective UO 2 2+ ligands.« less

Statistical Mechanical Model for Adsorption Coupled with SAFT-VR Mie Equation of State.

PubMed

Franco, Luís F M; Economou, Ioannis G; Castier, Marcelo

2017-10-24

We extend the SAFT-VR Mie equation of state to calculate adsorption isotherms by considering explicitly the residual energy due to the confinement effect. Assuming a square-well potential for the fluid-solid interactions, the structure imposed by the fluid-solid interface is calculated using two different approaches: an empirical expression proposed by Travalloni et al. ( Chem. Eng. Sci. 65 , 3088 - 3099 , 2010 ), and a new theoretical expression derived by applying the mean value theorem. Adopting the SAFT-VR Mie ( Lafitte et al. J. Chem. Phys. , 139 , 154504 , 2013 ) equation of state to describe the fluid-fluid interactions, and solving the phase equilibrium criteria, we calculate adsorption isotherms for light hydrocarbons adsorbed in a carbon molecular sieve and for carbon dioxide, nitrogen, and water adsorbed in a zeolite. Good results are obtained from the model using either approach. Nonetheless, the theoretical expression seems to correlate better the experimental data than the empirical one, possibly implying that a more reliable way to describe the structure ensures a better description of the thermodynamic behavior.

Sorption potential of alkaline treated straw and a soil for sulfonylurea herbicide removal from aqueous solutions: An environmental management strategy.

PubMed

Cara, Irina-Gabriela; Rusu, Bogdan-George; Raus, Lucian; Jitareanu, Gerard

2017-11-01

The adsorption potential of alkaline treated straw (wheat and corn) in mixture with soil, has been investigated for the removal of sulfonylurea molecules from an aqueous solutions. The surface characteristics were investigated by scanning electron microscopy and Fourier Transform Infrared - FTIR, while the adsorbent capacity was evaluated using batch sorption tests and liquid chromatography coupled with mass spectrometry. Surface analysis of alkaline treated straw samples by scanning electron microscopy - SEM showed the increasing of the surface roughness improving their functional surface activity. An increase (337.22 mg g -1 ) of adsorption capacity of sulfonylurea molecules was obtained for all studied straw. The Langmuir isotherm model was the best model for the mathematical description of the adsorption process indicating the forming of a surface sorption monolayer with a finite number of identical sites. The kinetics of sulfonylurea herbicide followed the pseudo-second order mechanism corresponding to strong chemical interactions. The results sustained that the alkaline treated straw have biosorption characteristics, being suitable adsorbent materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sorption and modeling of mass transfer of toxic chemical vapors in activated-carbon fiber-cloth adsorbers

USGS Publications Warehouse

Lordgooei, M.; Sagen, J.; Rood, M.J.; Rostam-Abadi, M.

1998-01-01

A new activated-carbon fiber-cloth (ACFC) adsorber coupled with an electrothermal regenerator and a cryogenic condenser was designed and developed to efficiently capture and recover toxic chemical vapors (TCVs) from simulated industrial gas streams. The system was characterized for adsorption by ACFC, electrothermal desorption, and cryogenic condensation to separate acetone and methyl ethyl ketone from gas streams. Adsorption dynamics are numerically modeled to predict system characteristics during scale-up and optimization of the process in the future. The model requires diffusivities of TCVs into an activated-carbon fiber (ACF) as an input. Effective diffusivities of TCVs into ACFs were modeled as a function of temperature, concentration, and pore size distribution. Effective diffusivities for acetone at 65 ??C and 30-60 ppmv were measured using a chromatography method. The energy factor for surface diffusion was determined from comparison between the experimental and modeled effective diffusivities. The modeled effective diffusivities were used in a dispersive computational model to predict mass transfer zones of TCVs in fixed beds of ACFC under realistic conditions for industrial applications.

Simultaneous trace multielement determination by ICP-OES after solid phase extraction with modified octadecyl silica gel.

PubMed

Karbasi, Mohamad-Hadi; Jahanparast, Babak; Shamsipur, Mojtaba; Hassan, Jalal

2009-10-15

Multielement simultaneous determination of 35 trace elements in environmental samples was carried out by inductively coupled plasma emission spectrometry (ICP-OES) after preconcentration with octadecyl silicagel, modified with aurin tricarboxylic acid (Aluminon). Optimal experimental conditions including pH of sample solution, sample volume, sample and eluent flow rate, type, concentration and volume of eluent and foreign ions effect were investigated and established. Trace element ions in aqueous solution were quantitatively adsorbed onto octadecyl silicagel modified with aurin tricarboxylic acid at pH 8.0 with a flow rate of 11.0 mL min(-1). The adsorbed element ions were eluted with 3-5 mL of 0.5 mol L(-1) HNO(3) at a flow rate of 10.0 mL min(-1) and analyzed by ICP-OES simultaneously. The proposed method has at least preconcentration factor of 100 in water samples, which results high sensitive detection of ultra-trace and trace analysis. The present methodology gave recoveries better than 70% and RSD less than 16%.

Resolving intramolecular-distortion changes induced by the partial fluorination of pentacene adsorbed on Cu(111)

NASA Astrophysics Data System (ADS)

Franco-Cañellas, Antoni; Wang, Qi; Broch, Katharina; Shen, Bin; Gerlach, Alexander; Bettinger, Holger F.; Duhm, Steffen; Schreiber, Frank

2018-04-01

We experimentally quantify the molecular bending of a partially fluorinated pentacene (PEN) compound, namely 2,3,9,10-tetrafluoropentacene (F4PEN), adsorbed on Cu(111). By means of the x-ray standing wave (XSW) technique, we directly measure the adsorption distance of three inequivalent carbon sites, the fluorine atoms as well as the total and backbone carbon average adsorption distances. The precise positioning of different sites within the carbon core allows us to resolve two adsorption behaviors, namely a PEN-like strong coupling between the backbone and the substrate, and a repulsive interaction involving the fluorinated short molecular edges, which are 0.91 ±0.09 Å above the central benzene ring. This finding is further supported by additional electronic and in-plane-structure measurements, thus showing that the selective fluorination of a PEN molecule has only a local conformational effect and it is not sufficient to modify its interface properties. Yet, in the multilayer regime, the electronic and growth properties of the film differ completely from those of PEN and its perfluorinated derivative.

Oxygen adsorption on the Al₉Co₂(001) surface: first-principles and STM study.

PubMed

Villaseca, S Alarcón; Loli, L N Serkovic; Ledieu, J; Fournée, V; Gille, P; Dubois, J-M; Gaudry, E

2013-09-04

Atomic oxygen adsorption on a pure aluminum terminated Al9Co2(001) surface is studied by first-principle calculations coupled with STM measurements. Relative adsorption energies of oxygen atoms have been calculated on different surface sites along with the associated STM images. The local electronic structure of the most favourable adsorption site is described. The preferential adsorption site is identified as a 'bridge' type site between the cluster entities exposed at the (001) surface termination. The Al-O bonding between the adsorbate and the substrate presents a covalent character, with s-p hybridization occurring between the states of the adsorbed oxygen atom and the aluminum atoms of the surface. The simulated STM image of the preferential adsorption site is in agreement with experimental observations. This work shows that oxygen adsorption generates important atomic relaxations of the topmost surface layer and that sub-surface cobalt atoms strongly influence the values of the adsorption energies. The calculated Al-O distances are in agreement with those reported in Al2O and Al2O3 oxides and for oxygen adsorption on Al(111).

Magnetic porous carbon derived from a bimetallic metal-organic framework for magnetic solid-phase extraction of organochlorine pesticides from drinking and environmental water samples.

PubMed

Liu, Yaxi; Gao, Zongjun; Wu, Ri; Wang, Zhenhua; Chen, Xiangfeng; Chan, T-W Dominic

2017-01-06

In this work, magnetic porous carbon material derived from a bimetallic metal-organic framework was explored as an adsorbent for magnetic solid-phase extraction of organochlorine pesticides (OCPs). The synthesized porous carbon possessed a high specific surface area and magnetization saturation. The OCPs in the samples were quantified using gas chromatography coupled with a triple quadrupole mass spectrometer. The experimental parameters, including the desorption solvent and conditions, amount of adsorbent, extraction time, extraction temperature, and ionic strength of the solution, were optimized. Under optimal conditions, the developed method displayed good linearity (r>0.99) within the concentration range of 2-500ngL -1 . Low limits of detection (0.39-0.70ngL -1 , signal-to-noise ratio=3:1) and limits of quantification (1.45-2.0ngL -1 , signal-to-noise ratio=10:1) as well as good precision (relative standard deviation<10%) were also obtained. The developed method was applied in the analysis of OCPs in drinking and environmental water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Investigation of Cr(VI) adsorption onto chemically treated Helianthus annuus: optimization using response surface methodology.

PubMed

Jain, Monika; Garg, V K; Kadirvelu, K

2011-01-01

In the present study, chemically treated Helianthus annuus flowers (SHC) were used to optimize the removal efficiency for Cr(VI) by applying Response Surface Methodological approach. The surface structure of SHC was analyzed by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Analysis (EDX). Batch mode experiments were also carried out to assess the adsorption equilibrium in aqueous solution. The adsorption capacity (qe) was found to be 7.2 mg/g. The effect of three parameters, that is pH of the solution (2.0-7.0), initial concentration (10-70 mg/L) and adsorbent dose (0.05-0.5 g/100 mL) was studied for the removal of Cr(VI) by SHC. Box-Behnken model was used as an experimental design. The optimum pH, adsorbent dose and initial Cr(VI) concentration were found to be 2.0, 5.0 g/L and 40 mg/L, respectively. Under these conditions, removal efficiency of Cr(VI) was found to be 90.8%. Copyright © 2010 Elsevier Ltd. All rights reserved.

High-Quality Metal–Organic Framework ZIF-8 Membrane Supported on Electrodeposited ZnO/2-methylimidazole Nanocomposite: Efficient Adsorbent for the Enrichment of Acidic Drugs

PubMed Central

Wu, Mian; Ye, Huili; Zhao, Faqiong; Zeng, Baizhao

2017-01-01

Metal–organic framework (MOF) membranes have received increasing attention as adsorbents, yet the defects in most membrane structures greatly thwart their capacity performance. In this work, we fabricated a novel ZnO/2-methylimidazole nanocomposite with multiple morphology by electrochemical method. The nanocomposite provided sufficient and strong anchorages for the zeolitic imidazolate frameworks-8 (ZIF-8) membrane. Thus, a crack-free and uniform MOF membrane with high performance was successfully obtained. In this case, 2-methylimidazole was believed to react with ZnO to form uniform ZIF nuclei, which induced and guided the growth of ZIF-8 membrane. The as-prepared ZIF-8 membrane had large surface area and good thermal stability. As expected, it displayed high adsorption capacity for acidic drugs (e.g., ibuprofen, ketoprofen and acetylsalicylic acid) as they could interact through hydrophobic, hydrogen bonding and π-π stacking interaction. Accordingly, by coupling with gas chromatography the ZIF-8 membrane was successfully applied to the real-time dynamic monitoring of ibuprofen in patient’s urine. PMID:28051129

Fabrication of a high selectivity magnetic solid phase extraction adsorbent based on β-cyclodextrin and application for recognition of plant growth regulators.

PubMed

Chen, Jiuyan; Cao, Shurui; Zhu, Ming; Xi, Cunxian; Zhang, Lei; Li, Xianliang; Wang, Guomin; Zhou, Yuantao; Chen, Zhiqiong

2018-04-27

An adsorbent, consisting of silica-coated Fe 3 O 4 grafted graphene oxide and β-cyclodextrin (Fe 3 O 4 @SiO 2 /GO/β-CD), which possessed the merits of antioxidation, superparamagnetism, high surface area, high supramolecular recognition and environment friendly, was successfully fabricated. Considering the synergy between β-CD and graphene oxide in adsorption mechanism, the synthesized adsorbent could grasp compounds especially with aromatic structures through π-π interaction, hydrophobic interaction and host-guest inclusion complex forming. Based on the advantages, a magnetic solid phase extraction (MSPE) method for 9 PGRs using Fe 3 O 4 @SiO 2 /GO/β-CD as adsorbents was developed in this study. The characterizations of Fe 3 O 4 @SiO 2 /GO/β-CD were performed on Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS), CHNS/O elemental analyzer, scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). Under the optimal MSPE condition, the Fe 3 O 4 @SiO 2 /GO/β-CD exhibited selectivity capability toward 9 PGRs when compared with Fe 3 O 4 @SiO 2 /GO. Meanwhile, the selectivity capability of Fe 3 O 4 @SiO 2 /GO/β-CD was higher than that of Fe 3 O 4 @SiO 2 /GO/α-CD except for 4-FPA. When the developed MSPE procedure was coupled with ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry (UHPLC-QTrap-MS/MS) to quantitative analysis of 9 PGRs, linearities ranging from 2 to 50 μg/kg were achieved for 9 PGRs with the correlation coefficients (r 2 ) in the range of 0.9975-0.9999. The limits of detection (LODs) for 9 analytes varied from 0.04 to 0.29 μg/kg. Finally, the proposed technique was applied to analyze PGRs residues in mutiple vegetable samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Pipette-tip solid-phase extraction using polypyrrole as efficient adsorbent for extraction of avermectins and milbemycins in milk.

PubMed

Florez, Diego Hernando Ângulo; Teixeira, Roseane Andrade; da Silva, Ricky Cássio Santos; Pires, Bruna Carneiro; Dutra, Flávia Viana Avelar; Borges, Keyller Bastos

2018-05-01

In this work, we developed a HPLC method for the multidetermination of avermectins (AVM) (abamectin-ABA 1b and ABA 1a, eprinomectin-EPR, and ivermectin-IVM) and milbemycins (moxidectin-MOX) in milk samples using polypyrrole (PPy) as adsorbent material in pipette-tip solid-phase extraction (PT-PPy-SPE). PPy was characterized by scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray diffraction and the data agreed with the literature. The sample preparation included the clean-up of the milk by protein precipitation (PP) with acetonitrile and extraction of the analytes by PT-PPy-SPE. The chromatographic method was developed in reverse phase and isocratic mode with flow rate at 1.2 mL min -1 and ultraviolet detection at 250 nm. The mobile phase composition was acetonitrile:methanol:water (55:25:20, v/v/v). The studied parameters and the optimized conditions for the sample preparation were washing solvent (300 μL water), volume and type of eluent (500 μL methanol), volume and pH of sample (1 mL and pH 10), amount of adsorbent material (50 mg PPy), and without addition of salt (NaCl). The method was linear over the concentration range from 20 to 3000 ng mL -1 with coefficients of correlation (r) ≥ 0.99 for all analytes and recoveries around 100%. The method developed and validated was used for the analyses of real milk samples from cow treated with Ivomec ® (IVM 3.5%), in which were found 21.51 ± 2.94 ng mL -1 of IVM. Finally, the results proved that PT-PPy-SPE coupled to HPLC-UV was economical, simple, and easy-to-perform technique. Graphical abstract Pipette-tip solid phase extraction using polypirrole as adsorbent material for determination of avermectins and milbemycins in milk.

Method of bonding functional surface materials to substrates and applications in microtechnology and anti-fouling

DOEpatents

Feng, Xiangdong; Liu, Jun; Liang, Liang

2001-01-01

A simple and effective method to bond a thin coating of poly(N-isopropylacylamide) (NIPAAm) on a glass surface by UV photopolymerization, and the use of such a coated surface in nano and micro technology applications. A silane coupling agent with a dithiocarbamate group is provided as a photosensitizer preferably, (N,N'-diethylamine) dithiocarbamoylpropyl-(trimethoxy) silane (DATMS). The thiocarbamate group of the sensitizer is then bonded to the glass surface by coupling the silane agent with the hydroxyl groups on the glass surface. The modified surface is then exposed to a solution of NIPAAm and a crosslinking agent which may be any organic molecule having an acrylamide group and at least two double bonds in its structure, such as N, N'-methylenebisacrylamide, and a polar solvent which may be any polar liquid which will dissolve the monomer and the crosslinking agent such as acetone, water, ethanol, or combinations thereof. By exposing the glass surface to a UV light, free radicals are generated in the thiocarbamate group which then bonds to the crosslinking agent and the NIPAAm. Upon bonding, the crosslinking agent and the NIPAAm polymerize to form a thin coating of PNIPAAm bonded to the glass. Depending upon the particular configuration of the glass, the properties of the PNIPAAm allow applications in micro and nano technology.

Method of bonding functional surface materials to substrates and applications in microtechnology and antifouling

DOEpatents

Feng, Xiangdong; Liu, Jun; Liang, Liang

1999-01-01

A simple and effective method to bond a thin coating of poly(N-isopropylacylamide) (NIPAAm) on a glass surface by UV photopolymerization, and the use of such a coated surface in nano and micro technology applications. A silane coupling agent with a dithiocarbamate group is provided as a photosensitizer, preferably, (N,N'-diethylamine)dithiocarbamoylpropyl-(trimethoxy)silane (DATMS). The thiocarbamate group of the sensitizer is then bonded to the glass surface by coupling the silane agent with the hydroxyl groups on the glass surface. The modified surface is then exposed to a solution of NIPAAm and a crosslinking agent which may be any organic molecule having an acrylamide group and at least two double bonds in its structure, such as N,N'-methylenebisacrylamide, and a polar solvent which may be any polar liquid which will dissolve the monomer and the crosslinking agent such as acetone, water, ethanol, or combinations thereof. By exposing the glass surface to a UV light, free radicals are generated in the thiocarbamate group which then bonds to the crosslinking agent and the NIPAAm. Upon bonding, the crosslinking agent and the NIPAAm polymerize to form a thin coating of PNIPAAm bonded to the glass. Depending upon the particular configuration of the glass, the properties of the PNIPAAm allow applications in micro and nano technology.

Dispersion measurement by the single introduction method coupled with the back-sorption procedure: A chemisorption and TPD study of the different chemisorbed hydrogen species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ragaini, V.; Giannantonio, R.; Magni, P.

1994-03-01

The Single Introduction (S.I.) method for the measurement by hydrogen chemisorption of metal dispersion in supported metal catalysts has been tested on two commercial 5% Pd/Al[sub 2]O[sub 3] catalysts. The S.I. results are compared with those obtained by the classical method of determining the adsorption isotherm (i.e., the multiple introduction method) and by O[sub 2]/H[sub 2] titration. As in Part I of this work, both chemisorption and thermal desorption have been used to find the best experimental conditions for the [open quotes]Back-Sorption[close quotes] procedure. It is shown that [alpha]- and [beta]-palladium hydrides can be decomposed by outgassing the samples formore » less than 5 min at 305 K and 10[sup [minus]6] Torr and that 30 min pumping at the same temperature and pressure is sufficient to eliminate from the catalyst surface the weakly adsorbed hydrogen as well. It has also been verified that chemisorption of hydrogen on these catalysts at room temperature is complete at pressures lower than those required for the [alpha] [yields] [beta] phase transition, so that it is possible to perform dispersion measurements by means of a simple S.I. of hydrogen coupled with Back-Sorption below 15 Torr at 305 K. Temperature-programmed desorption of hydrogen on one of the samples outlines the need to discriminate among the different adsorbed species for a more detailed characterization of supported metal catalysts. 44 refs., 10 figs., 2 tabs.« less

Coupled Geochemical Impacts of Leaking CO2 and Contaminants from Subsurface Storage Reservoirs on Groundwater Quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Hongbo; Qafoku, Nikolla; Lawter, Amanda R.

2015-07-07

The leakage of CO2 and the concomitant saline solutions from deep storage reservoirs to overlying groundwater aquifers is considered one of the major potential risks associated with geologic CO2 sequestration (GCS). Batch and column experiments were conducted to determine the fate of trace metals in groundwater in the scenarios of CO2 and metal contaminated brine leakage. The sediments used in this work were collected from an unconsolidated sand and gravel aquifer in Kansas, and contained 0-4 wt% carbonates. Cd and As were spiked into the reaction system to represent potential contaminants from the reservoir brine that could intrude into groundwatermore » aquifers with leaking CO2 at initial concentrations of 114 and 40 ppb, respectively. Through this research we demonstrated that Cd and As were adsorbed on the sediments, in spite of the lowered pH due to CO2 dissolution in the groundwater. Cd concentrations were well below its MCL in both batch and column studies, even for sediment samples without detectable carbonate to buffer the pH. Arsenic concentrations in the effluent were also significantly lower than influent concentration, suggesting that the sediments tested have the capacity to mitigate the coupled adverse effects of CO2 leakage and brine intrusion. However, the mitigation capacity of sediment is a function of its geochemical properties [e.g., the calcite content; the presence of adsorbed As(III); and the presence of P in the natural sediment]. The competitive adsorption between phosphate and arsenate may result in higher concentrations of As in the aqueous phase.« less

Simultaneous extraction and determination of phthalate esters in aqueous solution by yolk-shell magnetic mesoporous carbon-molecularly imprinted composites based on solid-phase extraction coupled with gas chromatography-mass spectrometry.

PubMed

Yang, Rui; Liu, Yuxin; Yan, Xiangyang; Liu, Shaomin

2016-12-01

A rapid, sensitive and accurate method for the simultaneous extraction and determination of five types of trace phthalate esters (PAEs) in environmental water and beverage samples using magnetic molecularly imprinted solid-phase extraction (MMIP-SPE) coupled with gas chromatography-mass spectrometry (GC-MS) was developed. A novel type of molecularly imprinted polymers on the surface of yolk-shell magnetic mesoporous carbon (Fe 3 O 4 @void@C-MIPs) was used as an efficient adsorbent for selective adsorption of phthalate esters based on magnetic solid-phase extraction (MSPE). The real samples were first preconcentrated by Fe 3 O 4 @void@C-MIPs, subsequently extracted by eluent and finally determined by GC-MS after magnetic separation. Several variables affecting the extraction efficiency of the analytes, including the type and volume of the elution solvent, amount of adsorbent, extraction time, desorption time and pH of the sample solution, were investigated and optimized. Validation experiments indicated that the developed method presented good linearity (R 2 >0.9961), satisfactory precision (RSD<6.7%), and high recovery (86.1-103.1%). The limits of detection ranged from 1.6ng/L to 5.2ng/L and the enrichment factor was in the range of 822-1423. The results indicated that the novel method had the advantages of convenience, good sensitivity, and high efficiency, and it could also be successfully applied to the analysis of PAEs in real samples. Copyright © 2016. Published by Elsevier B.V.

Rotary adsorbers for continuous bulk separations

DOEpatents

Baker, Frederick S [Oak Ridge, TN

2011-11-08

A rotary adsorber for continuous bulk separations is disclosed. The rotary adsorber includes an adsorption zone in fluid communication with an influent adsorption fluid stream, and a desorption zone in fluid communication with a desorption fluid stream. The fluid streams may be gas streams or liquid streams. The rotary adsorber includes one or more adsorption blocks including adsorbent structure(s). The adsorbent structure adsorbs the target species that is to be separated from the influent fluid stream. The apparatus includes a rotary wheel for moving each adsorption block through the adsorption zone and the desorption zone. A desorption circuit passes an electrical current through the adsorbent structure in the desorption zone to desorb the species from the adsorbent structure. The adsorbent structure may include porous activated carbon fibers aligned with their longitudinal axis essentially parallel to the flow direction of the desorption fluid stream. The adsorbent structure may be an inherently electrically-conductive honeycomb structure.

Adsorption characteristics of water vapor on gear-pellet and honeycomb-pellet types of adsorbents containing A-type zeolite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, A.; Munakata, K.; Hara, K.

2015-03-15

It is necessary to recover or process tritiated species that are extensively coexistent in nuclear fusion installations. A conventional way to recover tritium release to atmosphere is catalytic oxidation of tritiated species and adsorption of tritiated water vapor on adsorbents with high surface areas. Therefore, new adsorbents with low pressure loss and high surface areas need to be developed and utilized for such large-scale adsorption systems. In this study, attention was focused on new adsorbents, which are gear-type pellet MS5A adsorbent, gear-type pellet MS4A adsorbent and honeycomb-type pellet MS5A adsorbent. The adsorption characteristics of the new adsorbent were comparatively studiedmore » with conventional type of adsorbents (pellet-type MS5A adsorbent and pebble-type MS5A adsorbent), in terms of adsorption capacity, pressure loss and adsorption rate. It was found that the adsorption capacity of water vapor on the gear-type adsorbents is higher than that on a honeycomb-type adsorbent. The experimental breakthrough curves indicate that the adsorption rates of water vapor on gear-type and honeycomb-type adsorbents are smaller than that on conventional type adsorbents. Various adsorption models were also tested to correlate the experimental isotherms. It was found that the Langmuir-Freundlich model could properly correlate the experimental adsorption isotherms.« less

A facile reflux procedure to increase active surface sites form highly active and durable supported palladium@platinum bimetallic nanodendrites

NASA Astrophysics Data System (ADS)

Wang, Qin; Li, Yingjun; Liu, Baocang; Xu, Guangran; Zhang, Geng; Zhao, Qi; Zhang, Jun

2015-11-01

A series of well-dispersed bimetallic Pd@Pt nanodendrites uniformly supported on XC-72 carbon black are fabricated by using different capping agents. These capping agents are essential for the branched morphology control. However, the surfactant adsorbed on the nanodendrites surface blocks the access of reactant molecules to the active surface sites, and the catalytic activities of these bimetallic nanodendrites are significantly restricted. Herein, a facile reflux procedure to effectively remove the capping agent molecules without significantly affecting their sizes is reported for activating supported nanocatalysts. More significantly, the structure and morphology of the nanodendrites can also be retained, enhancing the numbers of active surface sites, catalytic activity and stability toward methanol and ethanol electro-oxidation reactions. The as-obtained hot water reflux-treated Pd@Pt/C catalyst manifests superior catalytic activity and stability both in terms of surface and mass specific activities, as compared to the untreated catalysts and the commercial Pt/C and Pd/C catalysts. We anticipate that this effective and facile removal method has more general applicability to highly active nanocatalysts prepared with various surfactants, and should lead to improvements in environmental protection and energy production.

Does 8-methacryloxyoctyl trimethoxy silane (8-MOTS) improve initial bond strength on lithium disilicate glass ceramic?

PubMed

Maruo, Yukinori; Nishigawa, Goro; Yoshihara, Kumiko; Minagi, Shogo; Matsumoto, Takuya; Irie, Masao

2017-03-01

Dental ceramic surfaces are modified with silane coupling agents, such as γ-methacryloxypropyl trimethoxy silane (γ-MPTS), to improve bond strength. For bonding between lithium disilicate glass ceramic and resin cement, the objective was to investigate if 8-methacryloxyoctyl trimethoxy silane (8-MOTS) could yield a similar performance as the widely used γ-MPTS. One hundred and ten lithium disilicate glass ceramic specimens were randomly divided into 11 groups (n=10) according to pretreatment regime. All specimens were pretreated with a different solution composed of one or a combination of these agents: 10 or 20wt% silane coupling agent of γ-MPTS or 8-MOTS, followed by a hydrolysis solution of acetic acid or 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP). Each pretreated surface was luted to a stainless steel rod of 3.6mm diameter and 2.0mm height with resin cement. Shear bond strength between ceramic and cement was measured after 24-h storage in 37°C distilled water. 8-MOTS produced the same bonding performance as γ-MPTS. Both silane coupling agents significantly increased the bond strength of resin cement, depending on their concentration. When activated by 10-MDP hydrolysis solution, 20wt% concentration produced the highest values (γ-MPTS: 24.9±5.1MPa; 8-MOTS: 24.6±7.4MPa). Hydrolysis with acetic acid produced lower bond strengths than with 10-MDP. Silane coupling pretreatment with 8-MOTS increased the initial bond strength between lithium disilicate glass ceramic and resin cement, rendering the same bonding effect as the conventional γ-MPTS. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Pilot scale treatment of chromite ore processing residue using sodium sulfide in single reduction and coupled reduction/stabilization processes.

PubMed

Velasco, Antonio; Ramírez, Martha; Hernández, Sergio; Schmidt, Winfried; Revah, Sergio

2012-03-15

Single Cr(VI) reduction and coupled reduction/stabilization (R/S) processes were evaluated at pilot scale to determine their effectiveness to treat chromite ore processing residue (COPR). Sodium sulfide was used as the reducing agent and cement, gypsum and lime were tested as the stabilizing agents. The pilot experiments were performed in a helical ribbon blender mixer with batches of 250 kg of COPR and mixing time up to 30 min. Na2S/Cr(VI) mass ratios of 4.6, 5.7 and 6.8 were evaluated in the single reduction process to treat COPR with Cr(VI) concentration of ≈4.2 g/kg. The R/S process was tested with a Na2S/Cr(VI) mass ratio of 5.7 and including stabilizing agents not exceeding 5% (w/w(COPR)), to treat COPR with a Cr(VI) content of ≈5.1g/kg. The single reduction process with a ratio of 6.8, reached Cr(VI) reduction efficiencies up to 97.6% in the first days, however these values decreased to around 93% after 380 days of storage. At this point the total Cr level was around 12.5 mg/L. Cr(VI) removal efficiencies exceeding 96.5% were reached and maintained during 380 days when the coupled R/S process was evaluated. Total Cr levels lower than 5 mg/l were attained at the initials days in all R/S batch tested, however after 380 days, concentrations below the regulatory limit were only found with gypsum (2%) as single agent and with a blend of cement (4%) and lime (1%). These results indicated that the coupled R/S process is an excellent alternative to stabilize COPR. Copyright © 2011 Elsevier B.V. All rights reserved.

Novel Cs-Based Upconversion Nanoparticles as Dual-Modal CT and UCL Imaging Agents for Chemo-Photothermal Synergistic Therapy.

PubMed

Liu, Yuxin; Li, Luoyuan; Guo, Quanwei; Wang, Lu; Liu, Dongdong; Wei, Ziwei; Zhou, Jing

2016-01-01

Lanthanide-based contrast agents have attracted increasing attention for their unique properties and potential applications in cancer theranostics. To date, many of these agents have been studied extensively in cells and small animal models. However, performance of these theranostic nanoparticles requires further improvement. In this study, a novel CsLu2F7:Yb,Er,Tm-based visual therapeutic platform was developed for imaging-guided synergistic cancer therapy. Due to the presence of the heavy alkali metal Cesium (Cs) in host lattice, the nanoplatform can provide a higher resolution X-ray CT imaging than many other reported lanthanide-based CT contrast agents. Furthermore, by using the targeted RGD motif, chemotherapy drug alpha-tocopheryl succinate (α-TOS), and photothermal coupling agent ICG, this nanoplatform simultaneously provides multifunctional imaging and targeted synergistic therapy. To demonstrate the theranostic performance of this novel nanoplatform in vivo, visual diagnosis in the small animal model was realized by UCL/CT imaging which was further integrated with targeted chemo-photothermal synergistic therapy. These results provided evidence for the successful construction of a novel lanthanide-based nanoplatform coupled with multimodal imaging diagnosis and potential application in synergistic cancer theranostics.

Synthesis of (+)-Antroquinonol: An Antihyperglycemic Agent.

PubMed

Sulake, Rohidas S; Lin, Hsiao-Han; Hsu, Chia-Yu; Weng, Ching-Feng; Chen, Chinpiao

2015-06-19

The total synthesis of antroquinonol has been accomplished through Suzuki-Miyaura cross-coupling and Barton-McCombie reaction, and the α,β-unsaturation was achieved through selenylation and oxidation protocols. In vitro and in vivo studies on the glucose-lowering properties of antroquinonol indicate that it is a potential antidiabetic agent.

Gas/vapour separation using ultra-microporous metal-organic frameworks: insights into the structure/separation relationship.

PubMed

Adil, Karim; Belmabkhout, Youssef; Pillai, Renjith S; Cadiau, Amandine; Bhatt, Prashant M; Assen, Ayalew H; Maurin, Guillaume; Eddaoudi, Mohamed

2017-06-06

The separation of related molecules with similar physical/chemical properties is of prime industrial importance and practically entails a substantial energy penalty, typically necessitating the operation of energy-demanding low temperature fractional distillation techniques. Certainly research efforts, in academia and industry alike, are ongoing with the main aim to develop advanced functional porous materials to be adopted as adsorbents for the effective and energy-efficient separation of various important commodities. Of special interest is the subclass of metal-organic frameworks (MOFs) with pore aperture sizes below 5-7 Å, namely ultra-microporous MOFs, which in contrast to conventional zeolites and activated carbons show great prospects for addressing key challenges in separations pertaining to energy and environmental sustainability, specifically materials for carbon capture and separation of olefin/paraffin, acetylene/ethylene, linear/branched alkanes, xenon/krypton, etc. In this tutorial review we discuss the latest developments in ultra-microporous MOF adsorbents and their use as separating agents via thermodynamics and/or kinetics and molecular sieving. Appreciably, we provide insights into the distinct microscopic mechanisms governing the resultant separation performances, and suggest a plausible correlation between the inherent structural features/topology of MOFs and the associated gas/vapour separation performance.

Quick and selective extraction of Z-ligustilide from Angelica sinensis using magnetic multiwalled carbon nanotubes.

PubMed

Zeng, Qiong; Jia, Yan-Wei; Xu, Pei-Li; Xiao, Meng-Wei; Liu, Yi-Ming; Peng, Shu-Lin; Liao, Xun

2015-12-01

A facile and highly efficient magnetic solid-phase extraction method has been developed for Z-ligustilide, the major therapeutic agent in Angelica sinensis. The solid-phase adsorbent material used was prepared by conjugating carbon nanotubes with magnetic Fe3 O4 nanoparticles via a hydrothermal reaction. The magnetic material showed a high affinity toward Z-ligustilide due to the π-π stacking interaction between the carbon nanotubes and Z-ligustilide, allowing a quick and selective exaction of Z-ligustilide from complex sample matrices. Factors influencing the magnetic solid-phase extraction such as the amount of the added adsorbent, adsorption and desorption time, and desorption solvent, were investigated. Due to its high extraction efficiency, this method was proved highly useful for sample cleanup/enrichment in quantitative high-performance liquid chromatography analysis. The proposed method had a linear calibration curve (R(2) = 0.9983) over the concentration between 4 ng/mL and 200 μg/mL Z-ligustilide. The accuracy of the method was determined by the recovery, which was from 92.07 to 104.02%, with the relative standard deviations >4.51%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

MIL-68 (In) nano-rods for the removal of Congo red dye from aqueous solution.

PubMed

Jin, Li-Na; Qian, Xin-Ye; Wang, Jian-Guo; Aslan, Hüsnü; Dong, Mingdong

2015-09-01

MIL-68 (In) nano-rods were prepared by a facile solvothermal synthesis using NaOAc as modulator agent at 100°C for 30 min. The BET test showed that the specific surface area and pore volume of MIL-68 (In) nanorods were 1252 m(2) g(-1) and 0.80 cm(3) g(-1), respectively. The as-prepared MIL-68 (In) nanorods showed excellent adsorption capacity and rapid adsorption rate for removal of Congo red (CR) dye from water. The maximum adsorption capacity of MIL-68 (In) nanorods toward CR reached 1204 mg g(-1), much higher than MIL-68 (In) microrods and most of the previously reported adsorbents. The adsorption process of CR by MIL-68 (In) nano-rods was investigated and found to be obeying the Langmuir adsorption model in addition to pseudo-second-order rate equation. Moreover, the MIL-68 (In) nanorods showed an acceptable reusability after regeneration with ethanol. All information gives an indication that the as-prepared MIL-68 (In) nanorods show their potential as the adsorbent for highly efficient removal of CR in wastewater. Copyright © 2015 Elsevier Inc. All rights reserved.

Effect of pH on the interaction of volatile compounds with the myofibrillar proteins of duck meat.

PubMed

Yang, Q L; Lou, X W; Wang, Y; Pan, D D; Sun, Y Y; Cao, J X

2017-06-01

In order to clarify the influence of curing agents on the flavor of duck, the effect of pH on the surface hydrophobicity, secondary structures, and adsorption capacity of myofibrillar proteins to alcohols, aldehydes, ketones, and esters was assessed using Raman spectroscopy, gas chromatography-mass spectrometer, and other methodologies. The hydrophobicity decreased as pH increased from 5.0 to 8.0; β-turn turned into α-helix and random coil as pH increased from 5.0 to 7.0, while α-helix and random coil turned into β-sheet and β-turn as pH increased from 7.0 to 8.0. With the increase of pH, the decreased adsorbing of alcohols could depend on hydrogen bonds. As pH increased from 5.0 to 8.0, the increase of aldehydes and esters was attributed to the unfolding of myofibrillar proteins and decreased hydrophobicity. The decreased adsorbing of ketones was due to the decreased hydrophobicity as pH increased from 5.0 to 8.0. The present work provided information about the correlation between structure and adsorption capacity of myofibrillar proteins to flavor compounds. © 2016 Poultry Science Association Inc.

Dynamics and Steady States in Excitable Mobile Agent Systems

NASA Astrophysics Data System (ADS)

Peruani, Fernando; Sibona, Gustavo J.

2008-04-01

We study the spreading of excitations in 2D systems of mobile agents where the excitation is transmitted when a quiescent agent keeps contact with an excited one during a nonvanishing time. We show that the steady states strongly depend on the spatial agent dynamics. Moreover, the coupling between exposition time (ω) and agent-agent contact rate (CR) becomes crucial to understand the excitation dynamics, which exhibits three regimes with CR: no excitation for low CR, an excited regime in which the number of quiescent agents (S) is inversely proportional to CR, and, for high CR, a novel third regime, model dependent, where S scales with an exponent ξ-1, with ξ being the scaling exponent of ω with CR.

Low-temperature thermally regenerative electrochemical system

DOEpatents

Loutfy, R.O.; Brown, A.P.; Yao, N.P.

1982-04-21

A thermally regenerative electrochemical system is described including an electrochemical cell with two water-based electrolytes separated by an ion exchange membrane, at least one of the electrolytes containing a complexing agent and a salt of a multivalent metal whose respective order of potentials for a pair of its redox couples is reversible by a change in the amount of the ocmplexing agent in the electrolyte, the complexing agent being removable by distillation to cause the reversal.

Low temperature thermally regenerative electrochemical system

DOEpatents

Loutfy, Raouf O.; Brown, Alan P.; Yao, Neng-Ping

1983-01-01

A thermally regenerative electrochemical system including an electrochemical cell with two water-based electrolytes separated by an ion exchange membrane, at least one of the electrolytes containing a complexing agent and a salt of a multivalent metal whose respective order of potentials for a pair of its redox couples is reversible by a change in the amount of the complexing agent in the electrolyte, the complexing agent being removable by distillation to cause the reversal.

TREATMENT FOR IMPROVING THE OPERATION OF STRONG BASE ANION EXCHANGE RESINS

DOEpatents

Stevenson, P.C.

1960-11-29

A process is offered for improving quaternary ammonium type strongly basic anion exchange resins so that centain zinc and cadmium residues, which normally stick to and "poison" this type of resin, can be removed by elution. Specifically, the resin as obtained commercially is treated with an aqueous solution of sodium hydroxide of about 1 to 4 M concentration by heating therein and periodically adding small amounts of oxidizing agent selected from hydrogen peroxide, sodium peroxide and hypochlorite. Zinc and cadmium values may then be adsorbed onto the resin from a 0.1 to 3 M HCl and thereafter eluted therefrom with very dilute HCl solutions.

Sox/Nox Sorbent And Process Of Use

DOEpatents

Ziebarth, Michael S.; Hager, Michael J.; Beeckman, Jean W.; Plecha, Stanislaw

1995-06-27

An alumina sorbent capable of adsorbing NOx and SOx from waste gases and being regenerated by heating above 650.degree. C. is made by incorporating an alumina stabilizing agent into the sorbent. A preferred method is to add the stabilizer when the alumina is precipitated. The precipitated powder is formed subsequently into a slurry, milled and spray dried to form the stabilized spheroidal alumina particles having a particle size of less than 500 microns. These particles are impregnated with an alkali metal or alkaline earth metal to form the stabilized sorbent. Alumina stabilizers include one or more of silica, lanthana, other rare earths, titania, zirconia and alkaline earths.

Sox/Nox Sorbent And Process Of Use

DOEpatents

Ziebarth, Michael S.; Hager, Michael J.; Beeckman, Jean W.; Plecha, Stanislaw

1996-12-17

An alumina sorbent capable of adsorbing NOx and SOx from waste gases and being regenerated by heating above 650.degree. C. is made by incorporating an alumina stabilizing agent into the sorbent. A preferred method is to add the stabilizer when the alumina is precipitated. The precipitated powder is formed subsequently into a slurry, milled and spray dried to form the stabilized spheroidal alumina particles having a particle size of less than 500 microns. These particles are impregnated with an alkali metal or alkaline earth metal to form the stabilized sorbent. Alumina stabilizers include one or more of silica, lanthana, other rare earths, titania, zirconia and alkaline earths.

Numerical analysis of the effect of the kind of activating agent and the impregnation ratio on the parameters of the microporous structure of the active carbons

NASA Astrophysics Data System (ADS)

Kwiatkowski, Mirosław

2015-09-01

The paper presents the results of the research on the application of the LBET class adsorption models with the fast multivariant identification procedure as a tool for analysing the microporous structure of the active carbons obtained by chemical activation using potassium and sodium hydroxides as an activator. The proposed technique of the fast multivariant fitting of the LBET class models to the empirical adsorption data was employed particularly to evaluate the impact of the used activator and the impregnation ratio on the obtained microporous structure of the carbonaceous adsorbents.

Nanostructured carbon materials for adsorption of methane and other gases

DOEpatents

Stadie, Nicholas P.; Fultz, Brent T.; Ahn, Channing; Murialdo, Maxwell

2015-06-30

Provided are methods for storing gases on porous adsorbents, methods for optimizing the storage of gases on porous adsorbents, methods of making porous adsorbents, and methods of gas storage of optimized compositions, as in systems containing porous adsorbents and gas adsorbed on the surface of the porous adsorbent. The disclosed methods and systems feature a constant or increasing isosteric enthalpy of adsorption as a function of uptake of the gas onto the exposed surface of a porous adsorbent. Adsorbents with a porous geometry and surface dimensions suited to a particular adsorbate are exposed to the gas at elevated pressures in the specific regime where n/V (density) is larger than predicted by the ideal gas law by more than several percent.

Strategies for the one-step immobilization-purification of enzymes as industrial biocatalysts.

PubMed

Barbosa, Oveimar; Ortiz, Claudia; Berenguer-Murcia, Ángel; Torres, Rodrigo; Rodrigues, Rafael C; Fernandez-Lafuente, Roberto

2015-01-01

In this review, we detail the efforts performed to couple the purification and the immobilization of industrial enzymes in a single step. The use of antibodies, the development of specific domains with affinity for some specific supports will be revised. Moreover, we will discuss the use of domains that increase the affinity for standard matrices (ionic exchangers, silicates). We will show how the control of the immobilization conditions may convert some unspecific supports in largely specific ones. The development of tailor-made heterofunctional supports as a tool to immobilize-stabilize-purify some proteins will be discussed in deep, using low concentration of adsorbent groups and a dense layer of groups able to give an intense multipoint covalent attachment. The final coupling of mutagenesis and tailor made supports will be the last part of the review. Copyright © 2015 Elsevier Inc. All rights reserved.

The Development of Novel Nanomaterials for Separation Science

NASA Astrophysics Data System (ADS)

Zewe, Joseph William

Separation efficiency is inversely proportional to the diameter of the particles of the stationary phase. Accordingly, a major aim of current separations research is focused on the reduction of both the diameter and particle-to-particle size variation of sorbent materials utilized as stationary phases. Herein, novel methods for the fabrication and application of various nanoscale stationary phases are described. Electrospinning is a simple and cost-effective method of generating nanofibers; here both polymeric and carbon electrospun nanofibers are applied as sorbent materials. Carbon nanofibers are of particular interest; graphite and glassy carbon are widely utilized in separation science due to their chemical and mechanical stability and unique selectivity. Electrospun carbon nanofibers have proven to be ideal for use as an extractive phase for solid phase microextraction (SPME) and have been successfully coupled to both gas and liquid chromatography. The high surface area nanofibrous mat provides extraction efficiencies for both polar and nonpolar compounds that range from 2-8 times greater than those attainable using currently available commercial SPME fibers. The electrospun nanofibrous SPME phases proved to be very stable when immersed in a range of solvents, demonstrating increased stability relative to conventional liquid SPME coatings. The chemical and mechanical stability of the electrospun carbon nanofiber SPME phases expands the range of compounds that are applicable to SPME while extending the lifetime of the SPME fibers. Molecularly imprinted (MI) electrospun polymeric and carbon nanofibers were also generated using the template molecule dibutyl butyl phosphonate (DBBP), a surrogate for chemical warfare agents. Nicotine was also used as a template molecule. The MI-nanofibers imprinted with DBBP were applied as an adsorbent for SPME. The MI-SPME fibers preferentially adsorbed the DBBP template molecule relative to the non-imprinted SPME fibers, demonstrating that imprinted surfaces containing analyte-specific recognition sites can be produced. MI-nicotine electrospun nanofibers were also studied as a solid phase extraction (SPE) adsorbent for the extraction of nicotine from water. The MI-nanofibers showed a greater extraction efficiency for nicotine relative to their non-imprinted counterparts. Electrospun nanofibers have proven to be effective stationary phases in ultra-thin layer chromatography (UTLC), giving more efficient separations in shorter analysis times than traditional particle-based stationary phases. This technology was further enhanced by aligning the nanofibrous mats in a single direction. Aligned electrospun UTLC (AE-UTLC) devices showed improved performance relative to non-aligned electrospun UTLC phases, demonstrating higher separation efficiency and reduced times of analysis. All currently utilized carbon sorbents, including the carbon nanofibers described in this work, possess at least two different surface sites for interaction with solutes, namely basal-plane and edge-plane sites. It is predicted that a more homogenous carbon surface, consisting entirely of either all-basal or all-edge plane sites, would produce a separation with a significant improvement in chromatographic efficiency. Progress toward homogenous carbon phases and their application and sorption behavior are also discussed.

Ortho Group Activation of a Bromopyrrole Ester in Suzuki-Miyaura Cross-Coupling Reactions: Application to the Synthesis of New Microtubule Depolymerizing Agents with Potent Cytotoxic Activities

PubMed Central

Gupton, John T.; Yeudall, Scott; Telang, Nakul; Hoerrner, Megan; Huff, Ellis; Crawford, Evan; Lounsbury, Katie; Kimmel, Michael; Curry, William; Harrison, Andrew; Juekun, Wen; Shimozono, Alex; Ortolani, Joe; Lescalleet, Kristin; Patteson, Jon; Moore-Stoll, Veronica; Rohena, Cristina C.; Mooberry, Susan L.; Obaidullah, Ahmad J.; Kellogg, Glen E.; Sikorski, James A.

2017-01-01

New microtubule depolymerizing agents with potent cytotoxic activities have been prepared with a 5-cyano or 5-oximino group attached to a pyrrole core. The utilization of ortho activation of a bromopyrrole ester to facilitate successful Suzuki-Miyaura cross-coupling reactions was a key aspect of the synthetic methodology. This strategy allows for control of regiochemistry with the attachment of four completely different groups at the 2, 3, 4 and 5 positions of the pyrrole scaffold. Biological evaluations and molecular modeling studies are reported for these examples. PMID:28433513

Synthesis of a New Titanate Coupling Agent for the Modification of Calcium Sulfate Whisker in Poly(Vinyl Chloride) Composite

PubMed Central

Yuan, Wenjin; Lu, Yunhua; Xu, Shiai

2016-01-01

A new titanate coupling agent synthesized from polyethylene glycol (PEG), isooctyl alcohol, and phosphorus pentoxide (P2O5) was used for the modification of calcium sulfate whiskers (CSWs) and the preparation of high-performance CSW/poly(vinyl chloride) (PVC) composites. The titanate coupling agent (sTi) and the modified CSWs (sTi–CSW) were characterized by Fourier transform infrared (FTIR) spectroscopy, and the mechanical, dynamic mechanical, and heat resistant properties and thermostability of sTi–CSW/PVC and CSW/PVC composites were compared. The results show that sTi–CSW/PVC composite with 10 wt. % whisker content has the best performance, and its tensile strength, Young’s modulus, elongation at break, break strength, and impact strength are 67.2 MPa, 1926 MPa, 233%, 51.1 MPa, and 12.75 KJ·m−2, with an increase of 20.9%, 11.5%, 145.3%, 24.6%, and 65.4% compared to that of CSW/PVC composite at the same whisker content. As the whisker content increases, the storage modulus increases, the Vicat softening temperature decreases slightly, and the glass transition temperature increases at first and then decreases. PMID:28773748