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Functionalized mesoporous silica nanoparticles (MSNs) for applications in drug delivery and catalysis

Well-ordered mesoporous silica nanoparticles MSNs) feature a great number of important characteristics including large surface area and pore volume, tunable pore diameter, uniform particle size, and good biocompatibility. The feasibility of selective functionalization on the exterior and interior surface of MSNs makes them applicable in areas as diverse as sorption, separation, sensing, drug delivery, and catalysis. PolyL-lysine) was immobilized onto the outer surface of amine functionalized MSN via ring-opening polymerization. The poly L-lysine) coated MSN PLL-MSN) could be internalized by human cervical cancer HeLa) cells with extremely high efficiency, which made the delivery of a large amount of drugs into cells possible. The release of the drugs was regulated by the degradation of polyL-lysine). Trypsin, an enzyme abundant in the intestine where most molecules are absorbed by human body, could digest polyL-lysine) and open the pore channels of PLL-MSN. On the other hand, pepsin, an enzyme that accumulates in the stomach, had no impact on polyL-lysine) and therefore the loaded drugs could be kept inside the pore channels and protected from enzymatic hydrolysis. We envision that PLL-MSN has great potential as an oral drug delivery vehicle. MSNs were also used as catalyst supports in cellulose degradation reactions. We have synthesized a series of platinum nanoparticle immobilized mesoporous silica nanoparticles Pt NP-MSNs) by using N-2-aminoethyl)-3-aminopropyl AAP) and 3-[2-2-aminoethylamino)ethylamino]propyl AEP) functionalized MSNs as solid supports. Platinum nanoparticles were anchored on the MSNs by complexation between the Pt precursor and surface amine groups followed by hydrogen reduction. Pt NP-MSNs successfully catalyzed the conversion of cellulose into valuable polyols: sorbitol and mannitol and could be recycled at least three times under optimized reaction conditions. In order to expand the applications of MSNs, a series of organofunctionalized large pore mesoporous silica nanoparticles LPMSNs) were synthesized via the co-condensation method under acidic conditions using a triblock copolymer P104) as the structure-directing agent. The hydrothermal temperature, the amount of organosilanes, and the sequence of reagent additions were optimized to yield functionalized LPMSN with large pore size and well-controlled particle morphology. The sulfonic acid functionalized silica synthesized under optimum conditions showed better catalytic performance than traditional sulfonic acid functionalized SBA-15 in esterification reactions. A mesoporous aluminum silicate Al-MS) material has been synthesized via co-condensation by using NaAlO2 as aluminum source under basic conditions. The aluminum was tetrahedrally coordinated throughout Al-MS and, for the first time, the quantity of the surface aluminum sites was determined by solid-state NMR studies. The silicon to aluminum atomic ratios at the surface and in the bulk were around 100 and 60, respectively； indicating less chemically accessible aluminum sites on the surface. Despite the low surface concentration of aluminum. Al-MS showed excellent catalytic reactivity for the Claisen rearrangement of allyl phenyl ether.

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Ruthenium(II), osmium(II), and rhodium(II,II) complexes as potential photodynamic therapy agents

Photodynamic therapy PDT) is a cancer therapy that operates with greater selectivity than conventional chemotherapy by the combination of a photosensitizer and visible light irradiation. Localization of irradiation allows for specificity by selectively activating the photosensitizer in the tissue of interest, while leaving healthy cells undamaged. However, PDT drawbacks remain and in this document the photophysical properties and DNA interactions of dirhodium, ruthenium, and osmium complexes are investigated for their abilities to address some of the shortcomings of current cancer photochemotherapies. A series of dirhodiumII,II) complexes of the type cis-[Rh2&mgr；-O 2CCH3)2dppn)L)]2＋, where dppn ＝ benzo[i]dipyrido-[3,2-a:2&feet；,3&feet；-h]quinoxaline and L ＝ 2,2&feet；-bipyridine bpy), 1,10-phenanthroline phen), dipyrido[3,2-f:2&feet；3&feet；- h]quinoxaline dpq), dipyrido[3,2-a:2&feet；,3&feet；- c]phenazine dppz), and dppn, was synthesized and its photophysical properties investigated. The ability of the complexes to bind and photocleave DNA was also probed, along with their toxicity and photocytotoxicity toward human skin cells. Nanosecond time-resolved absorption measurements established that the lowest energy excited state in the series is dppn-localized 3pipi* in DMSO. All complexes except the bis-dppn complex photocleave DNA efficiently via a mechanism that is mostly mediated by reactive oxygen species. The DNA photocleavage by the bis-dppn complex is significantly lower than that measured for the others, however, it exhibits the largest increase between toxicity and photocytotoxicity within the series. A discussion of three new complexes [Rubpy)2dpqp)] 2＋ dpqp ＝ pyrazino[2&feet；,3&feet；:5,6]pyrazino-[2,3-f][1,10]phenanthroline), [Rubpy)2dppn)]2＋, and [Osbpy)2dppn)] 2＋ is also presented. These complexes provide improvement to current PDT shortcomings by utilizing longer lifetimes, dual mechanisms of reactivity, and longer wavelengths of absorption, respectively. [Rubpy)2dpqp)] 2＋ exhibits strong luminescence in water at room temperature, a striking deviation from that of the related non-emissive “DNA light-switch” prototype [Rubpy)2dppz)]2＋ under similar conditions. The combination of its strong DNA binding affinity and relatively long-lived triplet metal-to-ligand charge-transfer 3MLCT) excited state in water results in more efficient DNA photocleavage by [Rubpy)2dpqp)] 2＋ than [Rubpy)2dppz)]2＋. Irradiation of [Rubpy)2dppn)]2＋ with visible light results in nearly complete DNA cleavage within 30 s lambdairr &ge； 455 nm), likely from the combination of guanine oxidation from the 3MLCT state and photoproduction of 1O2 from population of the 3pipi*. [Osbpy)2dppn)]2＋ generates 1O2 with a quantum yield of 0.42 upon irradiation from its low-lying 3pipi* excited state, which results in efficient DNA cleavage with irradiation lambdairr &ge； 645 nm. The new complexes cis-[Rh2&mgr；-O2CCH3) 2C6H5CN)42＋] and cis-[Rh 2&mgr；-O2CCH3)24F-C6H 5CN)42＋] were synthesized and studied as potential photo-cisplatin analogs. Theoretical calculations were performed to assist in the understanding of the electronic structures of the complexes. Both complexes were inert to ligand exchange in the dark in H2O, CH3CN, and CH2Cl2. cis-[Rh2&mgr；-O2CCH 3)24F-C6H5CN)42＋ ], however, showed photosubstitution of its four equatorial 4F-C 6H5CN ligands for CH3CN with lambdairr &ge； 455 nm in 25 min, whereas tirr ＞ 2 hr was required for cis-[Rh2&mgr；-O2CCH3) 2C6H5CN)42＋]. The photosubstitution of the complexes with H2O was also investigated to assess their biological viability. Both complexes exhibit reduced ligand substitution in water due to their hydrophobicity and the pi-stacking of the benzonitrile ligands. The photoinduced DNA binding of cis-[Rh2&mgr；-O 2CCH3)2C6H5CN)4 2＋] was investigated by gel electrophoresis and compared to cis-[Rh2&mgr；-O2CCH3)2CH 3CN)62＋], a complex known to covalently bind DNA upon irradiation.

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Measurement of single transverse spin asymmetry via single hadrons and di-hadron correlations in the 200GeV p ＋ p collision in the PHENIX experiment at RHIC

The spin structure of the proton has been revealed to be extremely complex. The proton spin is composed of the spins and the orbital angular momenta of quarks and gluons in the proton. The first results from polarized deep inelastic scattering pDIS) experiments in the late 1980s and early 1990s revealed that quarks do not carry a significant fraction of the protons spin. The recent global analysis on gluon spin including RHIC results showed that gluons have a very small contribution on the spin of proton. Therefore, it is extremely important for physicists understanding the contribution from the orbital angular momenta of quarks and gluons. However, it is very difficult for the current experiments measuring the orbital angular momentum directly and accurately. The Sivers-type single transverse spin asymmetry provides us a window to study the orbital angular momentum. In this thesis, results for the single transverse spin asymmetry of forward charged hadrons in polarized proton collisions measured with the PHENIX detector are presented. A predicted sizable asymmetry has been observed which is consistent with the results from other experiments. A correlation between neutral pions and charged hadrons measured in the central region of the PHENIX detector has been used to extract the single transverse spin asymmetry due to the Sivers effect. The Sivers effect describes the relation of the protons spin and its intrinsic transverse momentum. The latter one has been thought to originate from the orbital angular momentum of proton.

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Flow and Acoustics of Jets from Practical Nozzles for High- Performance Military Aircraft

This research project examines supersonic jets from nozzles representative of the practical variable-geometry convergent-divergent nozzles used on high-performance military aircraft. The nozzles employed have conical convergent sections, sharp throats and conical divergent sections. Nozzles with design Mach numbers of 1.3, 1.5, 1.56 and 1.65 are tested and the flow and acoustics examined. Such nozzles are found to produce a double-diamond shock structure consisting of two overlapping sets of shock cells, one cast from the nozzle lip and one cast from the nozzle throat. These nozzles are found to produce no shock-free condition at or near the design condition. As a result they produce shock-associated noise at all supersonic conditions. The shock cell spacing, broad-band shock-associated noise peak frequency and screech frequency all match those of more traditional nearly isentropic convergent-divergent nozzles. A correlation is proposed which improves upon the Prandtl-Pack relation for shock cell spacing in that it accounts for differences in nozzle design Mach number which the Prandtl-Pack relation does not. This proposed relation reverts to the Prandtl-Pack equation for the case of a design Mach number of 1.0. Chevrons are applied to the nozzles with design Mach numbers of 1.5 and 1.56. The effective penetration of the chevrons is found to be a function of the jet Mach number. Increasing jet Mach number increases effective penetration of the chevrons and increases the magnitude of all chevron effects. Chevrons on supersonic jets are found to reduce shock cell length, increase mixing and spreading, decrease turbulent kinetic energy at the end of the potential core and increase it near the nozzle. Chevrons corrugate the shear layer but not the shock structures inside the jet which remain axisymmetric. Chevrons thicken the shear layer, reducing the sonic diameter and reducing the diameter of the shock cells. By reducing their diameter they also reduce the shock cell spacing. Chevrons reduce low-frequency mixing noise near the end of the potential core, increase high-frequency noise near the nozzle exit. They eliminate screech and reduce broad-band shock-associated noise and shift it to higher frequencies. Fluidic injection is applied to the nozzle with design Mach number of 1.5. Fluidic injection corrugates the shear layer, increases mixing and spreading, reduces low frequency mixing noise, increases high frequency noise, reduces broad-band shock-associated noise and shifts its peak to higher frequency.

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Enantioselective reduction by natural/engineered enzymes and synthesis of smart polymer-protein bioconjugates via raft

The research described in this dissertation focuses on the application of proteins in synthetic chemistry, with the discussion being divided into two discrete sections. The first half of the material covers the application of proteins as biocatalysts to achieve increased specificity and efficiency during the synthesis of small chiral chemicals. The latter half describes how synthetic polymer chemistry can be employed to covalently modify proteins, potentially leading to enhanced protein stability and versatility. Biocatalysts continue to play an increasingly significant role in the efficient and selective synthesis of drugs containing asymmetric moieties. However, suitable biocatalysts are not always readily available, and improvement of enzyme activity and enhancement of enantioselectivity via genetic engineering has become an important tool for obtaining the improved biocatalysts. An introduction to enzymatic catalysis in chemical synthesis is included in Chapter 1. Chapter 2 describes site-saturation mutagenesis being guided by the enzyme-substrate docking model to enhance the enantioselectivity of a carbonyl reductase from Sporobolomyces salmonicolor SSCR). The kinetic parameters of the mutant enzymes indicated that the identity of residues 242 and 245 greatly affected the proteins catalytic activity and enantioselectivity. Our investigation of variants with single mutations at M242 or Q245 and double mutations at M242/Q245 identified enzymes with greater preference for the formation of S)-enantiomeric alcohols than the wild type enzyme. SSCR and its mutants are also capable of catalyzing the enantioselective reduction of bulky substrates of diaryl ketones to give the corresponding chiral alcohols. Chapter 3 describes the results obtained while investigating these reactions for the dependence of conversion and enantioselectivity on the reaction medium cosolvent. Notably, diaryl ketones with a p-substituent on one of the phenyl groups were reduced with high enantioselectivity up to 99% ee), which is difficult to achieve using more traditional chemical methods, such as chiral borane reduction, asymmetric hydrogenation or hydrosilylation. In addition to the studies involving ketoreductase enzymes, Chapter 4 describes a leucine dehydrogenase from Bacillus sphaericus BSLeuDH) being used to convert aliphatic keto acids to the corresponding alpha-amino acids with high activity. After cloning this enzyme, it was determined that the sequence result resolved from an X-ray crystal structure in 1995 was, in fact, inaccurate. While Part 1 of this dissertation describes the utilization of enzymes to enhance the efficiency and enantioselective conversion of small molecule reactions, Part 2 involves synthetic polymer chemistry being employed to modify the activity, stability, and practical applicability of proteins for a variety of applications. The conjugation of biologically relevant molecules with synthetic polymers has been an important area of research for many years, and recently there has been significant interest in employing controlled radical polymerization techniques to prepare bioconjugates with synthetic polymer components of controlled molecular weight, low polydispersity, and complex chain architecture Chapter 5). My research focused on the application of aqueous reversible addition-fragmentation chain transfer RAFT) polymerization to synthesize thermoresponsive, polymer-protein hybrids by various combinations of the grafting-to and grafting-from conjugation techniques. Functional RAFT agents were used to prepare thermoresponsive polymers with activated ester end groups. Reaction of these polymers with primary amines on model proteins led to polymer-protein conjugates that retained the responsiveness of the immobilized polymer Chapter 6). Retention of the trithiocarbonate o–end groups distal to the protein allowed subsequent chain extension during block copolymerization with a hydrophilic monomer Chapter 7). To our knowledge, this is the first attempt to prepare block copolymer conjugates by a combination of grafting-to and grafting-from techniques. Another strategy for preparing block copolymer-protein conjugates relied solely on a grafting-from approach Chapter 8). Immobilization of the low molecular weight activated ester RAFT agent to proteins prior to polymerization resulted in protein macrochain transfer agents capable of chain extension during aqueous RAFT. After addition of a thermoresponsive homopolymer block by grafting directly from the surface of the protein, a second monomer was polymerized to yield an outer hydrophilic segment. As opposed to methods that rely on grafting preexisting polymers to proteins, this graftingfrom approach is not limited by steric hindrance and allows the synthesis of block copolymer conjugates of high molecular weight.

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Theoretical studies of H-passivated silicon nanowires, silicon surface systems and silicon/germanium core/shell nanowires

Global structural optimization with Genetic Algorithm and first principle analysis have been performed on the Silicon nanowires, Ag induced Si surface reconstruction systems and Si/Ge core/shell nanowires. By using genetic algorithm combined with ab-initio calculation, we determined the atomic structures H-passivated &lt；110＞ and &lt；112＞ silicon nanowires. We found that at certain values of the hydrogen chemical potential the nanowires can take relatively stable structures in &lt；112＞ SiNWs with rectangular cross sections bounded by monohydride {110} and {111} facets with dihydride wire edges. In &lt；110＞ SiNWs cross section of the nanowire evolves from chains of six-atom rings to fused pairs of such chains to hexagons bounded by {001} and {111} facets. Second, with the structural models of SiNWs, we further analyzed their electronic properties. We showed that the &lt；112＞ SiNWs have an indirect to quasi-direct band gap transition with the increasing sizes and the band gap properties under uniaxial stress and different aspect ratios. Third, we did a Ag-induced Si(111) (rt3xrt3) and (3×1) surface reconstruction search with our variablenumber GA with ab-initio relaxation. The (rt3xrt3) global search found the Inequivalent Triangle (IET) structure as the lowest energy. A model of combination of pure Ag films and IET structure is proposed to explain the islands-to-holes ratio (RIH) equals 3 situation observed in experiments. For the (3×1) reconstruction, a model with 2/3 ML Ag and 1Ml Si coverage has been found and it has lower surface energy than the widely accepted HCC model with only 1/3 ML Ag coverage. Finally, we did some DFT calculation on the Si/Ge and Ge/Si core/shell [112] nanowires. The charged localization inside the NWs reveals that the electrons and holes are seperated. The quantum confinement effect in the NWs is strongly modified by the band offsets. An indirect to quasi-direct band gap transition can be obtained with a compressive strain, and the depth of the quantum wells can be modulated by the aspect ratios.

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Development of a neutrino tracking detector using gas electron multiplier avalanche light production in neon

We describe a prototype time projection chamber for tracking recoil electrons from low energy neutrinos down to 100 keV using Gas Electron Multipliers (GEMs) in supercritical neon below the critical temperature. Under this condition, electron drift and diffusion approach the low values of the electron bubble state. Light output produced by Townsend avalanches in a stack of three GEMs operated in mixtures of neon and hydrogen has been measured as a function of the GEM operating voltage, hydrogen partial pressure, and total gas pressure at room temperature in this stage of measurement. The next step will be below the critical temperature. Light from avalanches in neon-hydrogen mixtures has not been observed previously. Using commercially available low cost CCD-based imaging devices, the tracks of electrons can be recorded. The light output contains strong emission of neutral atomic neon (Ne I), and most of the allowed transitions connecting the 10 2P states to the 4 1S states (in Paschen notation) are observed. A broad band of emission from about 560 nm to the cutoff of the optical system at 225 nm is also observed, especially at low hydrogen concentrations and high total pressure. The origin of this emission is discussed. The ratio of the number of photons emitted to the number of avalanche electrons is greater than 1 at low hydrogen concentrations, and is essentially independent of the GEM voltage at fixed total pressure but, due to the Penning effect, decreases monotonically with increasing partial pressure of hydrogen for all mixtures studied. A plasma-kinetic model of the neon-hydrogen system has been developed to explain the measurements and to estimate the charge gain and light production in supercritical conditions. The implications of these observations are discussed to use the light output from avalanches in GEMs to implement a high density, large volume, time projection tracking detector for low energy solar neutrinos from pp fusion which are 99.5% of all solar neutrinos and has not been extensively and completely measured so far.

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Model selection for good estimation or prediction over a user-specified covariate distribution

In many applications it is common to observe a response with corresponding potential explanatory variables or covariates. Regression models using either the frequentist or Bayesian paradigm for inference are often employed to model such data. To perform model selection in the frequentist paradigm, step-wise or all-subsets selection based on the Cp criterion, the Akaike information criterion (AIC), or the Bayesian information criterion (BIC) are often used. Also, strategies based on cross-validation are available. In the Bayesian paradigm, the deviance information criterion (DIC) or posterior model probabilities are the primary tools for model selection. One theme central to these methods is that they only consider model performance at the observed data. However, in some applications we wish to predict the response or estimate the mean response over a distribution of explanatory-variable values that are different from those in the observed data. We propose a new model selection strategy that focuses on estimation or prediction over a user-specified distribution of covariate values. The idea is that, if a model is to be used for inference over a specific portion of the covariate space, that study goal should be allowed to influence the selection procedure. The new methodology and its implementation are presented via examples for linear models under the frequentist and Bayesian paradigms and for generalized linear models under the Bayesian paradigm. Furthermore, under the Bayesian paradigm, the methodology can be modified to protect against predictions that are too high or too low. Finally, simulation studies comparing the predictive ability of the new methodology to some current methods are considered.

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Solubility and Spectroscopy of Unsaturated Hydrocarbons in Cryogenic Solvents

The exploration of Saturns moon, Titan has revealed an atmosphere rich in nitrogen as in Earth, and has established the presence of gaseous methane. Data from the Cassini-Huygens mission have shown the existence of liquid bodies of methane and ethane, such as lakes and rivers with geological structures similar to Earth, with bays, islands, and channels. Moreover, the Cassini-Huygens mission has shown strong evidence that Titans surface and atmosphere have an active hydrological cycle alike, with condensed hydrocarbons instead. Although identification of chemical species is hard, many organic molecules have been detected in the atmosphere, and in icy form on the surface. Spectroscopic properties and solubility of many unsaturated hydrocarbons dissolved in liquid methane and ethane is unknown. Thus, in this work, vibrational spectroscopy in the IR-NIR-Vis of small organic molecules such as benzene, ethene, 2-methyl-1,3-butadiene isoprene), and formaldehyde dissolved in liquid ethane, rare gases, and nitrogen under Titans conditions low temperatures, and concentrations in the order of 10-4 mole fraction) are presented. Our studies indicate that the presence of the solvent interacting with the solute produces frequency shift and change in the linewidth from that of the gas phase. Additionally, solubilities of unsaturated hydrocarbons in liquid ethane and liquid argon have been meassured. In order to study the weak fifth CH vibrational overtone of the selected molecules, Fourier Transform spectroscopy is not sensible enough. Thermal Lens spectroscopy has been found to be a very sensitive technique, good for detecting samples of low concentration in transparent solutions. In addition to the traditional double-beam configuration, whose absorption process is carried out with one photon absorption, we have also developed a new triple-beam thermal lens apparatus in a collinear configuration, in order to enhance the thermal lens signal upon two photon absorption.

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Green composites and coatings from agricultural feedstocks

Green composites have been produced from natural oils and agricultural co-products or residues. A variety of natural oil-based resins, both free radically- and cationically-cured, and agricultural filler/fiber reinforcements have been utilized in their production. The natural oils and agricultural filler/fibers of interest include tung, corn, soybean, fish, and linseed oils and spent germ, corn stover, wheat straw, and switchgrass. The structure, water absorption, and thermal and mechanical properties of the composites has been studied using Soxhlet extraction, thermogravimetric and dynamic mechanical analysis and tensile testing. These novel composites contain anywhere from 60 to 95% renewable materials and have properties suitable for nonstructural applications, such as automotive panels, wall panels, ceiling tiles, window frames, furniture and doors, in the automotive, construction and furniture industries.

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