Hai-Min Shen

Surface immobilization of β-cyclodextrin on hybrid silica and its fast adsorption performance of p-nitrophenol from the aqueous phase

Renewable β-cyclodextrin (β-CD) was immobilized onto the surface of hybrid silica using ethylenediamine as linking groups to construct an adsorbent in water treatment (CD@Si), and the obtained CD@Si was characterized through FT-IR, XPS, EDX, contact angle measurement, TGA, solid-state 13C NMR, SEM, and XRD analyses. The effect of initial pH, contact time on the adsorption performance of CD@Si for p-nitrophenol, and the adsorption kinetics, adsorption isotherms, adsorption thermodynamics, reusability and adsorption mechanism were investigated systematically, which indicate that the adsorption of p-nitrophenol onto CD@Si is a very fast process. The adsorption equilibrium can be reached in 15 s with an acceptable equilibrium adsorption capacity of 69.6 mg g−1 at pH 7.0, which is much faster than many reported adsorbents based on β-CD. The adsorption of p-nitrophenol onto CD@Si follows the pseudo-second-order model, obeys the Freundlich model, and is a feasible, spontaneous, and exothermic process which is more favorable at lower temperatures. And the formation of an inclusion complex and a hydrogen bond interaction are two origins of p-nitrophenol being adsorbed onto CD@Si. Additionally, CD@Si can be recycled and reused for at least five runs with an acceptable adsorption capacity, and is a very promising adsorbent for the fast adsorption of p-nitrophenol or its analogues from the aqueous phase. Additionally, this work also provides a strategy to increase the adsorption rate of adsorbents based on β-CD.

Preparation of Silica Aerogel and Its Adsorption Performance to Organic Molecule

Hydrophobic and lipophilic silica aerogel was prepared from water-glass by gelling, aging, silylation, and drying under atmospheric pressure and characterized by FT-IR and SEM. The effect of preparation process on aerogel density and the aerogel density on contact angle of water on it were investigated in detail. pH 6 is most beneficial to shorten gelling time and to obtain the lowest density of silica aerogel. Increasing TEOS concentration of aging solution to 25 v% could decrease aerogel density to 0.093 g/cm3. The silica aerogel exhibits good hydrophobicity even though its density is 0.30 g/cm3. There are few changes in their adsorption capacities after 3 cycles of adsorption-desorption. The adsorption performance of the silica aerogel to organic solvent in water is different from in pure solvents. The critical surface tension () of the silica aerogel prepared here is about 30.8 mN/m. If the surface tension of aqueous solvent solution () is greater than , it will wet the aerogel surface partially. If   ≤  , the solution will wet all aerogel surface and be adsorbed well. This work delivers us a method to adsorb solvents from their waste water by adjusting the surface tension of the waste water to lower than of the adsorbent.

pH-Dependence of the Aqueous Phase Room Temperature Brønsted Acid-Catalyzed Chemoselective Oxidation of Sulfides with H₂O₂.

A pH-dependence of the Brønsted acid-catalyzed oxidation of sulfides to the corresponding sulfoxides with H2O2 is reported for the first time based on our systematic investigation of the catalytic performance of a series of Brønsted acids. For all of the Brønsted acids investigated, the catalytic performances do not depend on the catalyst loading (mol ratio of Brønsted acid to substrate), but rather depend on the pH value of the aqueous reaction solution. All of them can give more than 98% conversion and selectivity in their aqueous solution at pH 1.30, no matter how much the catalyst loading is and what the Brønsted acid is. This pH-dependence principle is a very novel perspective to understand the Brønsted-acid catalysis system compared with our common understanding of the subject.

Novel A–(π–D–π–A)1–3 branched fluorophores displaying high two-photon absorption

A series of novel acceptor–π–donor–π–acceptor branched fluorophores with a 1,3,5-triazine core (LB1, LB2, LB3, DB1, DB2, DB3, and EQ3) were synthesized and characterized by infrared, hydrogen-1 nuclear magnetic resonance, carbon-13 nuclear magnetic resonance, mass spectrometry, and elemental analysis. Their photophysical properties in different solvents were systematically investigated including linear absorption, single-photon excited fluorescence, two-photon absorption, and frequency up-converted fluorescence. When the number of branches increases, the spectral positions of the linear absorption and the single-photon excited fluorescence show red shifts, while the fluorescence quantum yields decrease. When the polarity of solvents increases, the spectral positions of the single-photon excited fluorescence and the Stokes shifts also show red shifts, while the linear absorption wavelengths slightly change and the fluorescence quantum yields decrease. Under the excitation of a femtosecond laser (690–890 nm, 80 MHz, 140 fs), all these compounds emit intense green frequency up-converted fluorescence, and the two-photon absorption cross-sections in THF are 236, 1149, 2250, 207, 1015, 2028, and 546 GM for LB1, LB2, LB3, DB1, DB2, DB3, and EQ3, respectively. The quantum chemical calculations based on density functional theory provide supporting evidence that significant enhancement of the two-photon absorption cross-section can be achieved by sufficient electronic coupling between the strong charge transfer acceptor–π–donor–π–acceptor quadrupolar branches through the 1,3,5-triazine core.

Synthesis of Branch Fluorinated Cationic Surfactant and Surface Properties

A novel fluorinated quaternary ammonium salt cationic surfactant N,N,N-trimethyl-2-[[4-[[3,4,4,4-tetrafluoro-2-[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]-1,3-bis(tri-fluoromethyl)-1-buten-1-yl]oxy]-benzoyl]amino]-iodide (FQAS) was synthesized successfully, and its structure was characterized by FTIR, 1H-NMR, 19F-NMR, and MS. The surface activities of FQAS and the effect of temperature, electrolyte, and combination with hydrocarbon surfactant were investigated. The results showed that FQAS exhibited excellent surface activity and combination with hydrocarbon surfactant.

Synthesis of novel perfluoroalkyl ether derivatives

A series of novel fluoroether-containing monomers has been designed and prepared based on the commercially available perfluoroalkyl ether acid fluoride. Treating acid fluoride with allyl alcohol, 2-hydroxyethyl methacrylate or N-allylmethylamine allowed for the direct formation of corresponding vinyl-containing fluorinated monomers. High yields of the fluorinated epoxy monomers could be obtained from acid chloride with glycidol; meanwhile, fluorinated diol was prepared from diethanolamine or 3-amino-1,2-propanediol. Moreover, fluorinated monoamine, fluorinated monoalcohol and fluorinated dichloride were also obtained. Most of these fluorinated monomers were liquid at room temperature and exhibited good solubility in common organic solvents.

A novel fluorinated diamine as an extender for polyurethanes

A novel environmentally friendly fluorinated diamine N-[2-[(2-aminoethyl) amino]ethyl]-perfluoro-2,5-dimethyl-3,6-dioxa-nonanamide(FDETA) was synthesized for the first time based on diethylenetriamine and ethyl perfluoro-2,5-dimethyl-3,6-dioxa-nonanoate (FEt). It was characterized by means of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and mass spectroscopy (MS). Subsequently, fluorinated polyurethanes (FPUs) containing various amounts of FDETA were then synthesized using hexamethylene diisocyanate (HDI), poly(tetramethylene oxide glycol) (PTMG), FDETA and 1,4-butanediol (BDO) as the main starting materials. Results of proton 1H NMR and FTIR had verified successful incorporation of the FDETA chain extenders into FPU backbones. The surface properties of FPUs were detected by contact angle measurement, scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). The thermal property of FPUs was also investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Results from EDX, SEM and contact angle studies indicated that fluorinated side chains in the hard segments had indeed migrated onto the surface. Results from DSC and TGA studies indicated that the thermal stability and the degree of phase separation were also improved.

Treatment of the Iron Surface and its Corrosion Resistance

Preparation and corrosion resistance of iron plate with micro-nano-structure were investigated. A clean iron plate was etched with a mixture of FeCl3, H2O, hydrochloric acid, H2O2 and H3PO4 to form a super hydrophilic surface which was treated with fatty acid solution to form a micro-nano-structure surface on which the water contact angle was about 147°. The super hydrophilic surface was treated with 3-aminopropyltriethoxysilane solution and then fatty acid solution (test plate) to turn to a super hydrophobic surface and the water contact angle was greater than 150°. This test plate coated with alkyd vamish exhibited better corrosion resistance to H2SO4 than blank iron plate.

Metal-free chemoselective oxidation of sulfides to sulfoxides catalyzed by immobilized L-aspartic acid and L-glutamic acid in an aqueous phase at room temperature

L-Aspartic acid and L-glutamic acid were immobilized on hybrid silica and characterized by FT-IR, XPS, contact angle measurements, TGA, SEM and XRD. Employed as heterogeneous catalysts in the selective oxidation of sulfides with 30% H2O2 at room temperature, 99% conversion and 97% selectivity were achieved with excellent substrate tolerance and recyclability.