Abstracts for Publications 81-100

101. H. F. Qian, Z. Zhao, J. C. Velazquez, L. A. Pretzer, K. N. Hecka, M. S. Wong, "Supporting palladium metal on gold nanoparticles improves its catalysis for nitrite reduction" Nanoscale, 59(12), 4474–4482 (2013). DOI: 10.1039/C3NR04540D

Abstract:

Nitrate (NO3) and nitrite (NO2) anions are often found in groundwater and surface water as contaminants globally, especially in agricultural areas due to nitrate-rich fertilizer use. One popular approach to studying the removal of nitrite/nitrate from water has been their degradation to dinitrogen via Pd-based reduction catalysis. However, little progress has been made towards understanding how the catalyst structure can improve activity. Focusing on the catalytic reduction of nitrite in this study, we report that Au NPs supporting Pd metal ("Pd-on-Au NPs") show catalytic activity that varies with volcano-shape dependence on Pd surface coverage. At room temperature, in CO2-buffered water, and under H2 headspace, the NPs were maximally active at a Pd surface coverage of 80%, with a first-order rate constant (kcat = 576 L gPd−1 min−1) that was 15x and 7.5x higher than monometallic Pd NPs ([similar]4 nm; 40 L gPd−1 min−1) and Pd/Al2O3 (1 wt% Pd; 76 L gPd−1 min−1), respectively. Accounting only for surface Pd atoms, these NPs (576 L gsurface-Pd−1 min−1) were 3.6x and 1.6x higher than monometallic Pd NPs (160 L gsurface-Pd−1 min−1) and Pd/Al2O3 (361 L gsurface-Pd−1 min−1). These NPs retained [similar]98% of catalytic activity at a chloride concentration of 1 mM, whereas Pd/Al2O3 lost [similar]50%. The Pd-on-Au nanostructure is a promising approach to improve the catalytic reduction process for nitrite and, with further development, also for nitrate anions.

100. J. C. Velázquez, S. Leekumjorn, Q. X. Nguyen, Y. L. Fang, K. N. Heck, G. D. Hopkins, M. Reinhard, M. S. Wong, "Chloroform Hydrodechlorination Behavior of Alumina-supported Pd and PdAu Catalysts" AIChE Journal, 59(12), 4474–4482 (2013). DOI: 10.1002/aic.14250

Abstract:

Chloroform is a common groundwater contaminant that is very difficult to remove. Chemically converting it into a less toxic form through heterogeneous catalysis is an attractive approach over conventional physical removal methods if it can be done economically. In this study, we explore the efficacy of supported precious metal catalysts for chloroform hydrodechlorination. We find that Pd/Al2O3 is catalytically active for this reaction (6.4 L/gPd/min) at room temperature, atmospheric pressure, in buffered water, and in the presence of hydrogen gas, and that Pd deposited on commercial Au/Al2O3 shows activities as high as 22.4 L/gPd/min, suggestive of some Pd metal located on top of Au domains. The primary reaction product is methane, with selectivity values exceeding 90%. Surface-enhanced Raman spectroscopy shows evidence of chloroform adsorption and dechlorination on the catalyst surface under aqueous conditions. The results highlight the potential of ambient-condition reductive catalysis to remove chloroform from water.

99. K. N. Heck, B. G. Janesko, G. E. Scuseria, N. J. Halas, M. S. Wong, "Using Catalytic and Surface-Enhanced Raman Spectroscopy-Active Gold Nanoshells to Understand the Role of Basicity in Glycerol Oxidation" ACS Catalysis, 3, 2430–2435 (2013). DOI: 10.1021/cs400643f

Abstract:

The origin of oxidation activity of gold catalysts has been a subject of great interest, particularly with the discovery of selective glycerol oxidation under water-phase alkaline conditions, for which neither small gold nanoparticles nor a catalyst support is necessary for activity. Little is known about the interactions among the catalyst surface, reactant, and hydroxyl species, which have never been examined spectroscopically because of a lack of developed in situ methods. In this work, we studied the room-temperature, water-phase reaction of glycerol oxidation using gold nanoshells (Au NSs), in which the gold substrate was active for surface-enhanced Raman spectroscopy (SERS) and catalysis. Analysis of glycerol solutions at high pH values and with oxygen content indicated that glycerol and glycerolate species did not bind directly to the catalyst surface in the absence of oxygen. However, glycerate surface species formed very rapidly when oxygen was present, suggesting an Eley–Rideal-type reaction mechanism with O2 (and/or O2-activated OH) as the adsorbed species. SERS analysis of carbon monoxide chemisorption on Au NSs indicated that higher pH values progressively weakened the C–O bond as the Au negative charge increased. The importance of high alkalinity to Au-catalyzed alcohol oxidation may result from both the activation of glycerol via deprotonation and the weakening of the adsorbed O2 double bond via induced Au negative charge.

98. Z. Zhao, Y.-L. Fang, P. J.J. Alvarez, M. S. Wong, "Degrading perchloroethene at ambient conditions using Pd and Pd-on-Au reduction catalysts," Appl. Catal. B-Environ., 140-141, 468-477 (2013). DOI: 10.1016/j.apcatb.2013.04.032

Abstract:

Perchloroethene (PCE) is a common groundwater contaminant, due to its common use as a dry-cleaning solvent. Current treatment methods are limited in their ability to remove PCE from contaminated sites in an efficient and cost effective manner. Palladium-on-gold nanoparticles (Pd-on-Au NPs) have been shown to be highly catalytically active in the hydrodechlorination (HDC) of trichloroethene (TCE) and other chlorinated compounds. However, the catalytic chemistry of such nanoparticles for PCE HDC in water has not been systematically addressed in the literature. In this paper, we assess the catalytic properties of ~4 nm Pd-on-Au NPs, ~4 nm Pd NPs, and Pd/Al2O3 for water-phase PCE HDC under ambient conditions. The Pd-on-Au NPs exhibited volcano-shape activity as a function of Pd surface coverage (sc). Maximum activity was at 80 ± 0.8 sc% (pseudo-first order rate constant of ~5000 L/gPd/min), which was ~20× and ~80× higher than that for Pd NPs and Pd/Al2O3 at room temperature and pH 7. A complete mechanistic model of PCE HDC that coupled gas–liquid mass transfer with the surface reactions was developed and found to be consistent with the observed concentration-time profiles for the 3 catalyst types. The formation and subsequent reaction of daughter products (TCE, dichloroethene isomers, vinyl chloride, and ethene) followed the stepwise dechlorination of the PCE chlorine groups. The final reaction products were ethane and minor amounts of n-butane/butenes. This study establishes the enhanced degradation chemistry of PCE using model Pd-on-Au catalysts and suggests the volcano-shape structure-activity dependence can be generalized from PCE and TCE to other organohalides.

97. S. S. Warudkar, K. R. Cox, M. S. Wong, G. J. Hirasaki, "Influence of stripper operating parameters on the performance of amine absorption systems for post-combustion carbon capture: Part II. Vacuum strippers," Int. J. Greenh. Gas. Con. 16, 351-360, (2013). DOI: 10.1016/j.ijggc.2013.01.049

Abstract:

The alkanolamine absorption process is viewed favorably for use in the separation of carbon dioxide (CO2) from point emission sources such as coal-fired power plants. At present, natural gas sweetening is the most important application for this technology. However, on a number of accounts such as the feed conditions of gas, its composition and process economics; natural gas sweetening and carbon capture are very different applications. Current technology is optimized toward providing a high performance for the former. As a part of this two-part study, we have used the process simulation software ProMax® to perform a detailed analysis on the effect of stripper operating pressure on factors like reboiler energy duty, absorber and stripper column sizing and parasitic power loss. We have examined the performance of monoethanolamine (MEA), diethanolamine (DEA) and diglycolamine (DGA) which are all commercial absorbents that can be reliably modeled in ProMax®. In part I of this study, we have analyzed the performance of strippers operated at pressures ranging from 150 kPa to 300 kPa. In this part of the study, we examine the performance of vacuum strippers operating under low vacuum at pressures of 30 kPa, 50 kPa and 75 kPa. Since vacuum strippers operate at lower temperatures than conventional stripper configurations, it is possible to use waste heat in the reboiler. In this study, we explore this possibility and consider 5 scenarios in which varying fractions of the reboiler steam are provided from waste heat sources located outside the turbine system. As with the cases presented in Part I, our comparisons of different configurations are based on energy consumption and column dimensions required for 90% CO2 capture (separation + compression) from a 400 MW coal-fired power plant. CO2 separated from the flue gas is compressed to a pressure of 16 MPa, typically maintained in the pipelines. On the basis of our findings, we report that vacuum stripping is an attractive alternative to conventional stripping. It is particularly attractive if significant sources of waste heat outside the turbine system can be located. We also conclude from our work that DEA and DGA have a superior performance than MEA when vacuum strippers are used. Use of vacuum strippers will certainly result in increased capital costs due to the need for larger equipment. However, in the view of potential savings in operating costs mainly by reduction in parasitic power loss; the increased capital expenditure may be justifiable.

96. S. S. Warudkar, K. R. Cox, M. S. Wong, G. J. Hirasaki, "Influence of stripper operating parameters on the performance of amine absorption systems for post-combustion carbon capture: Part I. High pressure strippers," Int. J. Greenh. Gas. Con. 16, 342-350, (2013). DOI: 10.1016/j.ijggc.2013.01.050

Abstract:

Amine absorption is a mature technology that is widely applied on a commercial scale for the removal of acid gases from gas mixtures. It is viewed as the most promising technology to separate carbon dioxide (CO2) at point emission sources such as fossil fuel fired power plants as a part of a strategy called ‘carbon capture and storage’ being deployed to mitigate climate change. However, there are major challenges in advancing its use for this application; the most prominent one being – cost. It is estimated that the application of current technology to CO2 capture will result in a 70–100% increase in the cost of electricity (COE). As a part of this two-part study, we have examined the influence of stripper operating parameters on carbon capture at a 400 MW pulverized coal-fired power plant retrofitted with amine absorption technology. We use the process simulation software, ProMax® to simulate the amine absorption process. Three commercial absorbents namely monoethanolamine (MEA), diethanolamine (DEA) and diglycolamine (DGA) are considered in this work. All the absorbents examined are studied at the typical working concentrations used in commercial operation. We also constrain the CO2 loading of rich amine solution to 0.4 mol-CO2/mol-amine to closely resemble the chemical environment in commercial operation. The main pointer used to compare system performance is the parasitic power loss due to the carbon capture. Parasitic power loss comprises of the loss of plant output due to withdrawal of reboiler steam from the low pressure turbine; the electricity required for CO2 compression and by the plant auxiliaries such as blowers and pumps. We also examine the absorber and stripper column sizes and heat exchanger parameters which are key components of the system. On the basis of our findings in the first part of this study, we report that operating the stripper at higher pressures has significant advantages but also some disadvantages and operational challenges. We also report that DEA and DGA have a superior performance to MEA when used in high pressure strippers. We conclude that increasing the stripper pressure reduces the parasitic losses and the equipment sizing but may result in higher solvent losses and equipment corrosion.

95. H. Qian, L. A. Pretzer, J. C. Velazquez, Z. Zhao, and M. S. Wong, "Gold nanoparticles for cleaning contaminated water," J. Chem. Tech. Biotech. (online). DOI: 10.1002/jctb.4030

Abstract:

Pollutants in the form of heavy metals, fertilizers, detergents, and pesticides have seriously reduced the supply of pure drinking water and usable water. Gold metal has intriguing potential to deal with the water pollution problem, as recent research on several fronts is advancing the concept of nanoscale gold as the basis for cost-effective nanotechnology-based water treatment. Nano-gold has special properties, such as enhanced catalytic activity, visible surface plasmon resonance color changes, and chemical stability, that make it more useful than other materials. This Perspective article highlights the current use of gold nanoparticles for the efficient removal and the selective and sensitive detection of a variety of pollutants in water. The challenges in further developing nano-gold to address water contamination are discussed, which should stimulate future research into improved removal and detection of undesirable chemical compounds.

94. L. A. Pretzer, H. J. Song, Y. L. Fang, Z. Zhao, N. Guo, T. Wu, I. Arslan, J. T. Miller, and M. S. Wong, "Hydrodechlorination catalysis of Pd-on-Au nanoparticles varies with particle size," J. Catal., 298, 206-217 (2013). DOI: 10.1016/j.jcat.2012.11.005

Abstract:

Trichloroethene (TCE), a common carcinogen and groundwater contaminant in industrialized nations, can be catalytically degraded by Au nanoparticles partially coated with Pd (“Pd-on-Au NPs”). In this work, we synthesized Pd-on-Au NPs using 3, 7, and 10 nm Au NPs with Pd surface coverages between 0–150% and studied how particle size and composition influenced their TCE hydrodechlorination (HDC) activity. We observed volcano-shape dependence on both Au particle size and Pd surface coverage, with 7 nm Au NPs with Pd coverages of 60–70% having maximum activity. Using extended X-ray absorption fine-structure spectroscopy, we found a strong correlation between catalytic activity and the presence of 2-D Pd ensembles (as small as 2–3 atoms). Aberration-corrected scanning transmission electron microscopy further confirmed the presence of Pd ensembles. The Pd dispersion and oxidation state generally changed from isolated, metallic Pd atoms to metallic 2-D Pd ensembles of varying sizes, and to partially oxidized 3-D Pd ensembles, as Pd surface coverage increased. These changes occurred at different surface coverages for different Au particle sizes. These findings highlight the importance of controlling particle size and surface coverage in bimetallic catalysts.

93. N. Soultanidis, and M. S. Wong, "Olefin impurity effect on n-pentane bimolecular isomerization over WOx/ZrO2," Catal. Commun., 32, 5-10 (2013). DOI: 10.1016/j.catcom.2012.11.017

Abstract:

Depending on the catalyst used, the reaction conditions and the molecules converted, alkane isomerization proceeds via a monomolecular or a bimolecular mechanism. n-Pentane isomerizes via both mechanisms which makes it an excellent probe molecule. In this study, n-pentane isomerization was investigated using WOx/ZrO2. Propylene and 1-pentene were co-fed separately to study the effect on n-pentane isomerization and it was identified that only 1-pentene increases the isomerization selectivity to isopentane. Our results support the model of a bimolecular mechanism that proceeds via a C10 intermediate on Zr-WOx Brønsted sites.

92. M. D. Blankschien, L. A. Pretzer, R. Huschka, N. J. Halas, R. Gonzalez, and M. S. Wong, "Light-triggered biocatalysis using thermophilic enzyme–gold nanoparticle complexes," ACS Nano, 7 (1), 654-663 (2013). DOI: 10.1021/nn3048445

Abstract:

The use of plasmonic nanoparticle complexes for biomedical applications such as imaging, gene therapy, and cancer treatment is a rapidly emerging field expected to significantly improve conventional medical practices. In contrast, the use of these types of nanoparticles to noninvasively trigger biochemical pathways has been largely unexplored. Here we report the light-induced activation of the thermophilic enzyme Aeropyrum pernix glucokinase, a key enzyme for the decomposition of glucose via the glycolysis pathway, increasing its rate of reaction 60% with light by conjugating the enzyme onto Au nanorods. The observed increase in enzyme activity corresponded to a local temperature increase within a calcium alginate encapsulate of 20 °C when compared to the bulk medium maintained at standard, nonthermophilic temperatures. The encapsulated nanocomplexes were reusable and stable for several days, making them potentially useful in industrial applications. This approach could significantly improve how biochemical pathways are controlled for in in vitro and, quite possibly, in vivo use.

91. N. Soultanidis, W. Zhou, C. J. Kiely, and M. S. Wong, "Solvothermal Synthesis of ultrasmall tungsten oxide nanoparticles," Langmuir, 28 (51), 17771–17777 (2012). DOI: 10.1021/la3029462

Abstract:

The synthesis of catalytically useful, ultrasmall oxide nanoparticles (NPs) of group 5 and 6 metals is not readily achievable through reported methods. In this work, we introduce a one-pot, two-precursor synthesis route to <2 nm MOx NPs in which a polyoxometalate salt is decomposed thermally in a high-boiling organic solvent oleylamine. The use of ammonium metatungstate resulted in oleylamine-coated, crystalline WOx NPs at consistently high yields of 92 ± 5%. The semicrystalline NPs contained 20–36 WOx structural units per particle, as determined from aberration-corrected high-resolution scanning transmission electron microscopy, and an organic coating of 16–20 oleylamine molecules, as determined by thermogravimetric analysis. The NPs had a mean size of 1.6 ± 0.3 nm, as estimated from atomic force microscopy and small-angle X-ray scattering measurements. Carrying out the synthesis in the presence of organic oxidant trimethylamine N-oxide led to smaller WOx NPs (1.0 ± 0.4 nm), whereas the reductant 1,12-dodecanediol led to WOx nanorods (4 ± 1 nm × 20 ± 5 nm). These findings provide a new method to control the size and shape of transition metal oxide NPs, which will be especially useful in catalysis.

90. S. Gullapalli, J. M. Grider, H. G. Bagaria, K.-S. Lee, M. Cho, V. L. Colvin, G. E. Jabbour, and M. S. Wong, "Molten-droplet synthesis of composite CdSe hollow nanoparticles," Nanotechnology, 23 (49), 495605-495615 (2012). DOI: 10.1088/0957-4484/23/49/495605

Abstract:

Many colloidal synthesis routes are not scalable to high production rates, especially for nanoparticles of complex shape or composition, due to precursor expense and hazards, low yields, and the large number of processing steps. The present work describes a strategy to synthesize hollow nanoparticles (HNPs) out of metal chalcogenides, based on the slow heating of a low-melting-point metal salt, an elemental chalcogen, and an alkylammonium surfactant in octadecene solvent. The synthesis and characterization of CdSe HNPs with an outer diameter of 15.6 ± 3.5 nm and a shell thickness of 5.4 ± 0.9 nm are specifically detailed here. The HNP synthesis is proposed to proceed with the formation of alkylammonium-stabilized nano-sized droplets of molten cadmium salt, which then come into contact with dissolved selenium species to form a CdSe shell at the droplet surface. In a reaction–diffusion mechanism similar to the nanoscale Kirkendall effect it is speculated that the cadmium migrates outwardly through this shell to react with more selenium, causing the CdSe shell to thicken. The proposed CdSe HNP structure comprises a polycrystalline CdSe shell coated with a thin layer of amorphous selenium. Photovoltaic device characterization indicates that HNPs have improved electron transport characteristics compared to standard CdSe quantum dots, possibly due to this selenium layer. The HNPs are colloidally stable in organic solvents even though carboxylate, phosphine, and amine ligands are absent; stability is attributed to octadecene-selenide species bound to the particle surface. This scalable synthesis method presents opportunities to generate hollow nanoparticles with increased structural and compositional variety.

89. M. Thakur, S. L. Sinsabaugh, M. J. Isaacson, M. S. Wong, and S. L. Biswal, "Inexpensive method for producing macroporous silicon particulates (MPSPs) with pyrolyzed polyacrylonitrile for lithium ion batteries," Scientific Reports, 2: 795, 1-7 (2012). DOI: 10.1038/srep00795

Abstract:

One of the most exciting areas in lithium ion batteries is engineering structured silicon anodes. These new materials promise to lead the next generation of batteries with significantly higher reversible charge capacity than current technologies. One drawback of these materials is that their production involves costly processing steps, limiting their application in commercial lithium ion batteries. In this report we present an inexpensive method for synthesizing macroporous silicon particulates (MPSPs). After being mixed with polyacrylonitrile (PAN) and pyrolyzed, MPSPs can alloy with lithium, resulting in capacities of 1000 mAhg-1 for over 600+ cycles. These sponge-like MPSPs with pyrolyzed PAN (PPAN) can accommodate the large volume expansion associated with silicon lithiation. This performance combined with low cost processing yields a competitive anode material that will have an immediate and direct application in lithium ion batteries.

88. S. Leekumjorn, S. Gullapalli, and M. S. Wong, "Understanding the solvent polarity effects on surfactant-capped nanoparticles," J. Phys. Chem. B, 116 (43), 13063–13070 (2012). DOI: 10.1021/jp307985c

Abstract:

Understanding the molecular interactions between suspended nanoparticles (NPs) and the suspending solvent fluid may provide a useful avenue to create and to study exotic NP ensembles. This study focused on using a coarse-grained computational model to investigate the molecular interactions between oleate-capped NPs in various solvents, and to relate the results to experimental features of solvent-suspended, oleate-capped CdSe quantum dots (QDs). The QDs were modeled as a closed-shell fullerene molecule with an oleate-like ligand attached to each vertex. Solvent polarity was found to correlate to the simulation and experimental results more strongly than either dielectric constant or dipole moment. Computational results showed that the nonpolar solvents of hexane, toluene, and benzene (polarity index ETN < 0.120) kept NPs in suspension and solvated the oleate chains such that the oleate layer swelled to full extension. In contrast, as the most polar solvent tested (ETN = 1.000), water caused NPs to aggregate and precipitate. It partially solvated the oleate chains and compressed the layer to 86% of full extension. For solvents of intermediate polarity like ethanol, acetone, and chloroform, the oleate layer swelled with decreasing polarity index values, with rapid swelling occurring close to ETN = 0.307 (50:50 vol % chloroform/acetone) below which QDs were colloidally stable. This study represents the first attempt to delineate the solvent effect on surfactant-coated NP hydrodynamic size, colloidal stability, and aggregation behavior.

87. G. C. Kini, S. L. Biswal, M. S. Wong, and C. A. Miller, "Characteristics of spontaneously formed nanoemulsions in octane/AOT/brine systems," J. Colloid Interface Sci., 385 (1), 111-121 (2012). DOI: 10.1016/j.jcis.2012.07.041

Abstract:

Nanoemulsions were formed spontaneously by diluting water-in-oil (W/O) or brine-in-oil (B/O) microemulsions of a hydrocarbon (octane), anionic surfactant (Aerosol-OT or AOT) and water or NaCl brine in varying levels of excess brine. The water-continuous nanoemulsions were characterized by interfacial tension, dynamic light scattering, electrophoresis, optical microscopy and phase-behavior studies. The mechanism of emulsification was local supersaturation and resulting nucleation of oil during inversion. For nanoemulsions formed at low salinities with Winsor I phase behavior, octane drops grew from initial diameters of 150–250 nm to 480–1000 nm over 24 h, depending on salinity. Growth was caused by mass transfer but seemed to approach the asymptotic stage of Ostwald ripening described by the Lifshitz–Slyozov–Wagner (LSW) theory only for dilution with salt-free water. Near the higher cross-over salinity (Winsor III), the nanoemulsions showed much slower growth with droplet size consistently remaining below 200 nm over 24 h and reaching 250 nm after 1 week. Birefringence indicated the presence of liquid crystal for these conditions, which could have contributed to the slow growth rate. At even higher salinity levels in the Winsor II domain, W/O/W multiple emulsions having drops greater than 1 μm in diameter were consistently recorded for the first 5–7 h, after which size decreased to values below 1 μm. The number and size of internal water droplets in multiple emulsion drops was found to decrease over time, suggesting coalescence of internal droplets with the continuous water phase and mass transfer of water from internal droplets to continuous phase as possible mechanisms of the observed drop shrinkage. Electrophoresis studies showed the nanoemulsions to be highly negatively charged (zeta potentials of −60 mV to −120 mV). The high charge on octane droplets helped assure stability to flocculation and coalescence, thereby allowing mass transfer to control growth in the Winsor I and III regions.

86. M. Thakur, R. B. Pernites, N. Nitta, M. Isaacson, S. L. Sinsabaugh, M. S. Wong, and S. L. Biswal, "Freestanding Macroporous Silicon and Pyrolyzed Polyacrylonitrile As a Composite Anode for Lithium Ion Batteries," Chem. Mater., 24 (15), 2998–3003 (2012). DOI: 10.1021/cm301376t

Abstract:

Silicon continues to draw great interest as an anode material for lithium ion batteries due to its large specific capacity for lithium. Macroporous silicon produced by electrochemical etching is one of several anode materials of interest, but its energy density is oftentimes limited due to its attachment to an unreactive silicon substrate. Here, we present a novel “lift-off” method by which a freestanding macroporous silicon film (MPSF) is electrochemically detached from the underlying bulk silicon and combined with pyrolyzed polyacrylonitrile (PAN), a conductive polymer that forms a conjugated-chain chemical structure. We report the performance of these silicon thin films with and without pyrolyzed PAN.

85. K. -P. Chao, H. Bagaria, M. S. Wong, and S. L. Biswal, "Templating CdSe tetrapods at the air/water interface with POPC lipids," J. Colloid Interface Sci., 378 (1), 58-63 (2012). DOI:10.1016/j.jcis.2012.04.028

Abstract:

Surfactants have been widely used as templating agents to pattern the orientation of nanoparticles of various conformations. Here we report the use of a lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), as a template to order CdSe tetrapods (TPs) at the air/water interface using a Langmuir–Blodgett trough. The surface pressure versus area isotherms for CdSe TPs and CdSe TPs/POPC are examined and monitored by Brewster angle microscopy (BAM). The transferred thin films are further characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Initially disc-like structures containing randomly oriented TPs form during solvent evaporation. Upon decreasing surface area, these discs merge into larger continental structures. In a mixed CdSe TPs/POPC system, these discs organize into wire-like networks upon compression. We detail how lipid molecules can be used to direct the two-dimensional assembly of TPs.

84. C. -C. Hwang, L. Wang, W. Lu, G. -D. Ruan, G. C. Kini, C. -S. Xiang, E. L. G. Samuel, W. Shi, A. T. Kan, M. S. Wong, M. B. Tomson, and J. M. Tour, "Highly stable carbon nanoparticles designed for downhole hydrocarbon detection," Energy Environ. Sci., 5, 8304-8309 (2012). DOI:10.1039/C2EE21574H

Abstract:

Sulfated polyvinyl alcohol functionalized carbon black, stable under high temperature and high salinity conditions, efficiently carries a hydrophobic compound through a variety of oil-field rock types and releases the compound when the rock contains hydrocarbons.

83. S. -J. Li, Y.-L. Fang, C. D. Romanczuk, Z.-H. Jin, T.-L, Li, and M. S. Wong, "Establishing the Trichloroethene Dechlorination Rates of Palladium-based Catalysts and Iron-based Reductants," Appl. Catal. B-Environ., 125, 95-102 (2012). DOI:10.1016/j.apcatb.2012.05.025

Abstract:

The removal of undesired chlorinated hydrocarbon contaminants through chemical destruction using ex situ Pd-based catalytic or in situ Fe-based reductive nanomaterials offers unique advantages over current physical displacement methods for groundwater treatment. While these two types of chemical methods has been studied in-depth in recent years, their respective hydrodechlorination and dechlorination transformations have not been analyzed together before. Here, the reactivities of Pd catalysts and Fe reductants were experimentally assessed for trichloroethene (TCE) degradation using room-temperature, atmospheric-pressure, dihydrogen-headspace-filled batch reactor studies under buffered and non-buffered conditions. Pseudo-first order reaction rate constants at pH 7 spanned 9 decades: 1.2 × 104, 1.0 × 103, 4.5 × 102, 2.41 × 10−4, 4.2 × 10−4, and 7.09 × 10−6 L/gactive-metal/min for Pd-on-Au nanoparticles (Pd/Au NPs), Pd NPs, Pd-on-alumina powder, and two nano-sized forms and one micron-sized form of commercial zerovalent iron, respectively. With rates measured in the range of commonly reported values, the Fe-based materials produced ethane, ethene, and vinyl chloride; ethene hydrogenated into ethane at sufficiently long reaction times. The much more active Pd-based materials produced ethane as the primary TCE degradation reaction product. This study presents, for the first time, a quantitative comparison of TCE degradation rates determined under identical experimental conditions.

82. O. Kuznetsov, Y.-Q. Sun, R. Thaner, A. Bratt, V. Shenoy, M. S. Wong, J. Jones, and W. E. Billups, "Water-Soluble Nanodiamond," Langmuir, 28 (11), 5243–5248 (2012). DOI:10.1021/la204660h

Abstract:

Reduction of the graphenic edges of annealed nanodiamond by sodium in liquid ammonia leads to a nanodiamond salt that reacts with either alkyl or aryl halides by electron transfer to yield radical anions that dissociate spontaneously into free radicals and halide. The free radicals were observed to add readily to the aromatic rings of the annealed nanodiamond. Nanodiamonds functionalized by phenyl radicals were sulfonated in oleum, and the resulting sulfonic acid was converted to the sodium salt by treatment with sodium hydroxide. The solubility of the salt in water was determined to be 248 mg/L. Nanodiamond functionalized by carboxylic acid groups could be prepared by reacting 5-bromovaleric acid with the annealed nanodiamond salt. The solubility of the sodium carboxylate in water was found to be 160 mg/L.