Aquathermolysis of Heavy Crude Oil with Amphiphilic Nickel and Iron Catalysts

Two amphiphilic catalysts (i.e., metal dodecylbenzenesulfonates, noted as C₁₂BSNi and C₁₂BSFe) were synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), element analysis (EA), atomic absorption spectroscopy (AAS), and thermogravimetric (TGA). Their interfacial activities were determined using a surface tensiometer and an interfacial tensiometer. Both catalysts are interfacial active and thermostable enough for heavy oil aquathermolysis. Their performance on heavy oil aquathermolysis was assessed in an autoclave. According to the viscosity reduction results, the synthesized amphiphilic catalysts are more effective than water-soluble or oil-soluble catalysts, with C₁₂BSNi more efficient than C₁₂BSFe. The average molecular weight, group compositions, and average molecular structure of heavy oil samples were analyzed using EA, FT-IR, and ¹H nuclear magnetic resonance (¹H NMR) before and after aquathermolysis reaction. And the results show that both catalysts caused the change of molecular structures in heavy oil. The change of asphaltene and resin molecular structures and decrease of their contents are crucially important to the reduction of viscosity. C₁₂BSNi causes more changes of the asphaltene than C₁₂BSFe, whereas C₁₂BSFe is beneficial to the breakage of C–S bonds in asphlatenes and resins

The Properties of Asphaltenes and Their Interaction with Amphiphiles

The functional groups on asphaltene surfaces of two kinds of Chinese residue oil were analyzed by X-ray photoelectron spectroscopy (XPS). The ζ potential and electrophoretic mobility of asphaltene solutions and residue solutions were measured through phase analysis light scattering (PALS) technique. The ability to stabilize asphaltenes of two typical ionic amphiphiles, dodecyl benzene sulfonic acid (DBSA) and dodecyl trimethyl ammonium bromide (DTAB), were investigated. Karamay asphaltenes contain large amount of carboxyl and calcium and are negatively charged; whereas Lungu asphaltenes are rich in nickel, vanadium, and pyrrolic structures and are positively charged. DBSA has good ability to stabilize Lungu asphaltenes but has no effect on Karamay asphaltenes. Differently, DTAB has good ability to disperse Karamay asphaltenes but has no obvious effect on Lungu asphaltenes. It is concluded from these results that the charges might derive from the dissociation of metal ions and the deprotonation of acid groups (such as COOH, OH, and SH) or basic groups (such as pyridinic groups) on asphaltene surface. The electric property of asphaltenes plays an important role in the interaction between asphaltenes and amphiphiles. The negatively charged asphaltenes tend to be dispersed by cationic amphiphiles, whereas the positively charged asphaltenes tend to be dispersed by anionic amphiphiles

Tuning the Self-Assembly of Short Peptides via Sequence Variations

Peptide self-assembly is of direct relevance to protein science and bionanotechnology, but the underlying mechanism is still poorly understood. Here, we demonstrate the distinct roles of the noncovalent interactions and their impact on nanostructural templating using carefully designed hexapeptides, I₂K₂I₂, I₄K₂, and KI₄K. These simple variations in sequence led to drastic changes in final self-assembled structures. β-sheet hydrogen bonding was found to favor the formation of one-dimensional nanostructures, such as nanofibrils from I₄K₂ and nanotubes from KI₄K, but the lack of evident β-sheet hydrogen bonding in the case of I₂K₂I₂ led to no nanostructure formed. The lateral stacking and twisting of the β-sheets were well-linked to the hydrophobic and electrostatic interactions between amino acid side chains and their interplay. For I₄K₂, the electrostatic repulsion acted to reduce the hydrophobic attraction between β-sheets, leading to their limited lateral stacking and more twisting, and final fibrillar structures; in contrast, the repulsive force had little influence in the case of KI₄K, resulting in wide ribbons that eventually developed into nanotubes. The fibrillar and tubular features were demonstrated by a combination of cryogenic transmission electron microscopy (cryo-TEM), negative-stain transmission electron microscopy (TEM), and small-angle neutron scattering (SANS). SANS also provided structural information at shorter scale lengths. All atom molecular dynamics (MD) simulations were used to suggest possible molecular arrangements within the β-sheets at the very early stage of self-assembly

Designed Short RGD Peptides for One-Pot Aqueous Synthesis of Integrin-Binding CdTe and CdZnTe Quantum Dots

We have designed a series of short RGD peptide ligands and developed one-pot aqueous synthesis of integrin-binding CdTe and CdZnTe quantum dots (QDs). We first examined the effects of different RGD peptides, including RGDS, CRGDS, Ac-CRGDS, CRGDS-CONH₂, Ac-CRGDS-CONH₂, RGDSC, CCRGDS, and CCCRGDS, on the synthesis of CdTe QDs. CRGDS were found to be the optimal ligand, providing the CdTe QDs with well-defined wavelength ranges (500–650 nm) and relatively high photoluminescence quantum yields (up to 15%). The key synthesis parameters (the pH value of the Cd²⁺-RGD precursors and the molar ratio of RGD/Cd²⁺) were assessed. In order to further improve the optical properties of the RGD-capped QDs, zinc was then incorporated by the simultaneous reaction of Cd²⁺ and Zn²⁺ with NaHTe. By using a mixture of CRGDS and cysteine as the stabilizer, the quantum yields of CdZnTe alloy QDs reached as high as 60% without any post-treatment, and they also showed excellent stability against time, pH, and salinity. Note that these properties could not be obtained with CRGDS or cysteine alone as the stabilizer. Finally, we demonstrated that the RGD-capped QDs preferentially bind to cell surfaces because of the specific recognition of the RGD sequence to cell surface integrin receptors. Our synthesis strategy based on RGD peptides thus represents a convenient route for opening up QD technologies for cell-specific tagging and labeling applicable to a wide range of diagnostics and therapy

77K fluorescence emission spectra of PS-I solubilized with different surfactants.

<p>The surfactants tested include lipopeptides C14DK and C16DK, DDM and FC14 as indicated and the concentrations of surfactants were kept the same as under RT. The concentration of PS-I added was 0.117 µmol/L (equal to 10 µg Chl/ml).</p

CD spectrum from 400 to 800 nm of PS-I solubilized with 5mM lipopeptide C14DK.

<p>The concentration of PS-I is 0.233µmol/L (equal to 20µg Chl/ml).</p