The aqueous biomolecule-silica interface is a technically important component present in many biosensors. For example, Biologically-sensitive Field Effect Transistors (BioFETs) are a class of biosensors designed to sense extremely small changes in the electric field at this interface. Understanding the physical and chemical nature of this surface region is crucially important to improving design of these devices. There are two influences on the electric field at this interface: surface charge from charging of silanol groups; and the structure/dynamics of mixed valency electrolytes near the charged silanolate surface. Density Functional Theory methods were used to explore the proton transfer rate to/from the surface, revealing a new reaction mechanism and demonstrating that it is limited by the rate of reorientation of nearby water molecules. Dynamic silica-surface charging can be therefore be modelled as an activationless, diffusion-limited process. [1] Classical Molecular Dynamics simulations were used to investigate electrolyte structure and dynamics under physiological conditions. The model showed that water polarisation plays an important role in determining the electric field near the interface, particularly for mixed valency magnesium/sodium electrolytes. This atomistic simulation work highlights the complexity of the silica-water interface, and provides detail which cannot be adequately described using conventional mean-field models such as the Poisson-Boltzmann description of the electric double layer. [1] Lowe, B. M., Skylaris, C.-K. & Green, N. G. Journal of Colloid and Interface Science 451, 231–244 (2015). doi: 10.1016/j.jcis.2015.01.094

Charge dynamics at the silica-electrolyte interface

Water purification is critical for many industrial and energy applications but most importantly it is also critical for people who live in arid climates or do not have access to clean drinking water. There are many classes of materials that are utilized for water purification, but regardless of material, nearly all sorbents operate with the same physical principles, i.e. all known materials show increased water capacity with increasing humidity. We imagine how water could be purified if a material were able to adsorb water at low humidity and release at high humidity. We present here a material that does just that. We have discovered a newly developed class of carbon rods that adsorb water vapor at low humidity, and expel half of the adsorbed water as liquid droplets spontaneously as the humidity passes a 50–80% threshold. This water expulsion is unprecedented, but more remarkably it is a reversible physical process, where decreasing the humidity around the sample increases its uptake of water. The rods perform this marvel simply by changing their available surface area for water to adhere to as a function of humidity, where there is more available surface area at low humidity than at higher humidity. Such behavior provides new means for water purification and separation, where water could be harvested from a low humidity vapor stream and then collected as a liquid when exposed to a pure water vapor stream. We present the physical and spectroscopic evidence for this behavior and discuss new potential processes that can purify water using these carbon rods.

Anomalous carbon rods that adsorb water vapor at low humidity and release liquid droplets at higher humidity

Industrial production and application of polyoxymethylene dimethyl ethers (PODEn, CH3O(CH2O)nCH3, where n&gt;1) play a central role on the use of the existing diesel engines, development of petrochemical industry technology and extension of C1 chemical industry. Ionic liquids (ILs) have been used to replace traditional liquid acids as the catalyst in chemical processes. In this work, a series of pyrrolidione based Brønsted acidities ionic liquids were synthesized, investigated and firstly used as the catalyst for the synthesis of PODEn from methylal and trioxane. The Hammett function values were measured to indicate the connection between catalytic performance and acidity-activity of ionic liquids. The optimal experimental conditions for synthesis of PODEn were analysed. The conversion of raw material and the selectivity of PODE3-8 have the maximum value with [NOP][TFO] (1-octyl-2-pyrrolidinone trifluoromethanesulfonate) as catalyst. The corresponding optimum reaction conditions is that the molar radio of methylal:trioxane:ILs is 180:90:1, temperature is 383.15K, pressure is 0.4Mpa, and reaction time is 5h. Moreover, the selectivity of PODE3-4 overides the traditional catalyst such as H2SO4 and CF3SO3H. In addition, the ionic liquids [NOP][p-ClBSA] (1-octyl-2-pyrrolidinone 4-chlorobenzenesulfonate), [NOP][DNBSA] (1-octyl-2-pyrrolidinone 2,4-dinitrobenzenesulfonate) and [NOP][HSO4] (1-octyl-2-pyrrolidinone hydrogen sulfate) also show a remarkable activity in the synthesis of PODEn.

Synthesis of polyoxymethylene dimethyl ethers catalyzed by the pyrrolidione-based ionic liquids

In hydraulically stimulated wells it is difficult, if not impossible, to precisely determine which fracture zones beyond the borehole wall are contributing to the production of the produced fluids. Improved exploitation of the natural resources in the wells requires greater understanding of which fractures are actively contributing to flow, as well as the rates of flow in these fractures. Accurate information concerning these parameters would allow the operator to monitor the engineered reservoir system and make informed decisions about increasing well efficiency over an extended period of time. It is therefore of high commercial interest to be able to determine quickly and accurately the regions of the rock mass that are not contributing to overall fluid flow. Our approach to address this critical problem is to develop unique, traceable “taggants” based on three general concepts: (i) rare-earth doped nanoparticles based on monocationic oxide matrices, (ii) bulk rare earth salts, and (iii) soluble coordination complexes. Each of these species can be independently loaded into a porous proppant and delivered underground. Once released, the identification of these nanoparticles or metal complexes above-ground can be realized through a combination of analytical tools (e.g., inductively-coupled plasma, resonance Raman spectroscopy) that allows both qualitative and quantitative information about the properties of the well flow to be determined.

New taggants for monitoring underground fluid flows

The batch reaction experiments have been made for the first time to investigate the effect of ionic structure on the reactivity and selectivity of the trioxane-forming reaction catalyzed by a Brønsted-acidic ionic liquid (IL). The ILs considered include 1-cyclohexyl-2-pyrrolidinone trifluoromethanesulfonate ([NCyP][TfO]), 1-cyclohexyl-2-pyrrolidinone benzenesulfonate ([NCyP][BSA]), 1-cyclohexyl-2-pyrrolidinone p-toluenesulfonate ([NCyP][p-TSA]), 1-octyl-2-pyrrolidinone 2,4-dinitrobenzenesulfonate ([NOP][DNBSA]), 1-octyl-2-pyrrolidinone benzenesulfonate ([NOP][BSA]), 1-octyl-2-pyrrolidinone methanesulfonate ([NOP][MSA]), and 1-octyl-2-pyrrolidinone hydrogen sulfate ([NOP][HSO4]). It is found that the yield and the selectivity of trioxane in the reaction solution correlate closely with the charge density of the anion of the corresponding ILs. Variation of the cation structure from [NCyP]+ to [NOP]+ exerts little influence on the yield and the selectivity of trioxane in the reaction solution. The continuous production experiments have been made to investigate the performance of [NOP][MSA], [NOP][DNBSA], [NCyP][TfO], and H2SO4 as an extraction distillation agent. Such effect of [NCyP][TfO] considerably overides that of H2SO4. The competitive green catalyst in production of trioxane is thus presented.

Novel brønsted-acidic ionic liquids as catalysts for synthesizing trioxane

Rutile TiO2 is a prototypical light-harvesting semiconductor showing promising potential in the application of photocatalysis. Nevertheless, it has proven difficult to establish the detailed processes involved in photocatalysis, partly because the excited states involved are difficult to study. Here, we present evidence for the existence of hydroxyl-induced states in the conduction band region that may also play a role in photocatalysis. In a two-photon photoemission (2PPE) experiment on rutile TiO2(110), an electron in the well-known defect states about 0.8 eV below EF is excited into an intermediate state by absorbing a photon, from which it is further excited above the vacuum level by a second photon. By varying the photon energy from about 3 to 4 eV, we observe a pronounced resonant enhancement of the 2PPE intensity when the photon energy is about 3.5 eV. It indicates an intermediate state at about 2.7 eV above EF. Further investigations show that this state is induced by the hydroxyls on the TiO2 surface with a lifetime shorter than 15 fs. The intensity of the resonance can be greatly enhanced by the adsorption of molecular water at 100 K. The energy of the hydroxyl-induced state is found to be 2 eV lower and less-influenced by water adsorption than that expected for a hydroxylated TiO2(110) surface.

Non-band-gap photoexcitation of hydroxylated TiO2

Rare earth elements (REEs) are vital to various emerging technologies, from wind turbines to solid state lighting. REEs are mainly available through mining operations outside the U.S. However, due to import shortages, the prices of these elements have increased drastically in the last decade and the future availability of these elements is at risk. It is now crucial to develop technology to establish domestic sources of REEs. Global phosphate deposits contain 27 million tons of REEs, equal to nearly 200 years of current world demand. More than 38% of REEs end up in phosphogypsum (PG) and sludge during phosphate fertilizer production - the former is a waste from phosphate rock processing and the latter is a secondary waste from PG processing. Therefore, both waste streams are excellent sources for REEs recovery. Here, we developed a liquid phase-based recovery process which could generate 25,000 tons of REEs per year. This is the equivalent of 20% of current world demand. To optimize REEs recovery, we studied NdPO4 solubility as a model aqueous system through both experimental and computational approaches. Calorimetry of REE-doped gypsum and PG was used to compare the energetics of surface adsorption versus phase stability of REEs in the solid phase, which provides insight into developing an effective recovery process.

Green Technology for REEs Recovery

Glycerol is a by-product of bio-diesel production, and the development of the down-stream products of glycerol has recently attracted much attention. Glycerol hydrogenolysis could convert glycerol into propanediols (PD, including 1,2-PD and 1,3-PD), which are value-added materials. Pd-Re bimetallic catalysts showed high activity in the hydrogenolysis of glycerol and Re exhibited obvious promoting effect on the performance of the catalysts. In this work, the influence of different precursors of Pd on the performance of Pd-Re catalyst in glycerol hydrogenolysis was investigated. Pd-Re/SBA-15 catalysts with different palladium precursors (PdCl2, Pd(NO3)2, Pd(OAc)2) were prepared by impregnation method. The contents of Pd and Re were all 5%, respectively. Before used in the reaction, the catalyst was reduced with H2 at 250 oC for 2 h. The reaction was carried out in a 100 ml stainless steel autoclave (reaction conditions: 200 oC, 8 MPa H2, 18 h). N2 adsorption-desorption, XRD, H2-TPR, TEM and NH3-TPD were used to characterize the physical and chemical properties of the catalysts. The catalysts showed the different reduction behaviors and had different particle sizes. Different Pd precursors changed the activities of Pd-Re catalysts in glycerol hydrogenolysis. 5Pd-5Re/SBA-15 with PdCl2 as palladium precursor had higher activity than those with Pd(NO3)2 and Pd(OAc)2 as precursor. The existence of Cl would affect the particle size, reduction behaviors and acid properties of Pd-Re catalysts.

Hydrogenolysis of biomass-derived glycerol to propanediols over Pd-Re catalyst: Influence of different Pd precursors

Compound 1 is a potent 5’-adenosine-monophosphate-activated protein kinase (AMPK) activator that was progressed to the clinic for the potential treatment of diabetic nephropathy. The development of the synthesis and the execution of the scale up campaigns to meet clinical and non-clinical studies will be described in addition to the synthesis of a major metabolite. Optimization of key steps included the formation of a methyl indole-3-carboxylate through acylation chemistry, palladium-mediated aryl-heteroaryl cross coupling, and an ester hydrolysis.

Development of the synthesis and scale-up of an AMPK activator clinical candidate

With the increasing demand for rare earth elements (REE) in many emerging clean energy technologies, there is an urgent need for the development of new approaches for efficient REE extraction and recovery. As one step towards this goal, we genetically engineered the aerobic bacterium Caulobacter crescentus for REE adsorption through high-density cell surface display of lanthanide binding tags (LBTs) on the S-layer. The engineered LBT-displayed strains exhibited enhanced and specific adsorption towards REE compared to other metals, as well as adsorption preference of heavy- versus light- REE. Additionally, adsorbed REE could be effectively recovered using citrate, with adsorption fully recycled multiple times. Together, our results demonstrated a rapid, efficient and reversible process for REE adsorption with potential industrial application towards REE enrichment and separation.

Enhanced bioadsorption of rare earth elements through cell surface display of lanthanide binding tag

251st National Meeting (2016)

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