Kunmei Su

Organically modified MCM-type material preparation and its usage in controlled amoxicillin delivery

MCM-41 was grafted with 3-aminopropyl trimethoxysilane (APTMS), 3-chloropropyltriethoxysilane (CPTMS) to give organic group modified samples, and l-tryptophane was covalently immobilized onto organic samples to improve the physicochemical properties of mesoporous silica to controlled amoxicillin delivery. Samples were characterized by X-ray diffraction (XRD), N(2) adsorption-desorption isotherms and Fourier transform infrared (FT-IR) spectroscopy, and characterized results demonstrated that organic groups were successfully grafted onto the samples. The results of amoxicillin release exhibited that 12.9wt% and 33.0wt% impregnated amoxicillin could be released from the post-grafting MCM-41 with APTMS and pure MCM-41 after 24h, however, 41.0wt% impregnated amoxicillin could be released from the post-grafting MCM-41 with CPTMS after 24h. When the samples modified with APTMS and CPTMS were further grafted by l-tryptophane, the slower drug release rate was achieved over samples with l-tryptophane immobilization. The release profiles of all samples indicated that the amoxicillin release was mainly regulated by the diffusion mechanism.

Selective oxidation of 5-hydroxymethylfurfural with H2O2 catalyzed by a molybdenum complex

Organic solvent free 5-hydroxymethylfurfural (HMF) oxidation into 2,5-furandicarboxylic acid (FDCA) with hydrogen peroxide using quaternary ammonium octamolybdate and quaternary ammonium dectungstate was studied. Tetra-1-ethyl-3-methylimidazolium octamolybdate ([EMIM]4Mo8O26), tetra-hexadecyltrimethyl ammonium octamolybdate ([CTAB]4Mo8O26) and tetra-ethylpyridinium octamolybdate ([EPy]4Mo8O26) displayed high activity for the selective oxidation of HMF to FDCA, and the selectivity of FDCA could reach 100% with a 99.5% conversion of HMF in the presence of [EMIM]4Mo8O26. The byproduct formed in competition with FDCA was identified as the intermediate 5-hydroxymethyl-2-furan carboxylic acid (HMFCA) and 5-formyl-2-furan carboxylic acid (FFCA), and neither 2,5-diformyl furan (DFF) nor any other byproducts from the oxidative cleavage of the HMF furan ring were detected during the oxidation process, which indicated that the aldehyde group of HMF oxidizes first, followed by the oxidation of the hydroxymethyl group in this reaction system. Although the quaternary ammonium salts, such as [EMIM]Br, EPyBr and CTAB, prevented FDCA formation from the HMFCA advanced oxidation, they could eliminate the oxidative cleavage of the furan ring and improve the affinity of HMF and catalysts, to make the catalytic active centers readily accessible to HMF molecules. However, tetra-1-ethyl-3-methylimidazolium dectungstate ([EMIM]4W10O32), tetra-hexadecyltrimethyl ammonium dectungstate ([CTAB]4W10O32) and tetra-ethylpyridinium dectungstate ([EPy]4W10O32) were unfavorable for FDCA formation. The great difference in performance of quaternary ammonium octamolybdate and quaternary ammonium dectungstate in HMF oxidation with H2O2 was attributed to their different structure.

Furan-based co-polyesters with enhanced thermal properties: poly(1,4-butylene-co-1,4-cyclohexanedimethylene-2,5-furandicarboxylic acid)

New co-polyesters of poly(butylene-co-1,4-cyclohexanedimethylene-2,5-furandicarboxylic acid) (PBCFs) were synthesized from 2,5-furandicarboxylic acid (FDCA), 1,4-butanediol (BDO) and 1,4-cyclohexanedimethanol (CHDM) via a two-step esterification–polycondensation procedure. The structure of the synthesized polymers were characterized by 1H NMR, and the characterization results revealed that the co-polymers had triad components in a random sequential structure. The average sequence length and monomer percentages in the co-polymer could be adjusted by changing the feed molar ratio of BDO to CHDM, however, the easy removal of BDO during the polycondensation procedure facilitates the formation of long chain links containing CHDM units. Co-polyester composition could be calculated from the quantitative 13C NMR spectra which are well consistent with the elemental analysis results. The incorporation of CHDM units into poly(butylene-2,5-furandicarboxylate) (PBF) can significantly influence the thermal transition behavior, thermal stability and crystallinity of PBCFs. PBCFs showed Tg monotonously increasing with CHDM content, and the characterized Tg by DSC method is consistent with the calculated value from the Fox equation. As the molar percent of CHDM unit in co-polymers increases from 20 to 70%, Tg changes from 45.7 to 74.4 °C, Tm from 140.1 to 251.9 °C and decomposition temperature from 380.6 to 388.0 °C. XRD results indicated that the crystallinity and crystal structure of the polyester was significantly changed by CHDM incorporation. When the content of CF units increases to 31%, PBC31F is almost amorphous and it is difficult to form long regular segments to form micro-crystals, and this co-polymer shows neither cold-crystallization nor melting behavior. However, multiple melting behaviors are observed in the DSC heating traces of PBC52F, PBC61F, PBC70F and PCF with a shoulder peak on the side of the main melting peak because of partial melting–recrystallization and final melting process taking place successively during the heating scan.

Rational design of N-doped carbon nanobox-supported Fe/Fe2N/Fe3C nanoparticles as efficient oxygen reduction catalysts for Zn–air batteries

Zn–air battery, as a low cost, high energy density, and safe energy device, has received significant attention in recent years. However, its wide application has been hindered due to the low oxygen reduction reaction (ORR) activity in air electrodes without excellent catalysts. Herein, N-doped porous and highly graphitic carbon nanobox-supported Fe-based nanoparticles (Fe–N-CNBs), which were synthesized from fructose, NH3, and FeCl3 by a self-propagating high-temperature synthesis (SHS) process followed by a heat treatment process, were used as ORR catalysts. Fe–N-CNBs calcined at 600 °C (Fe–N-CNBs-600) showed higher ORR activity (onset and half-wave potentials of 1.03 and 0.85 V vs. RHE, respectively), better electrochemical stability, and higher methanol tolerance than Pt/C under alkaline conditions. The outstanding ORR performance of Fe–N-CNBs-600 was attributed to the synergistic effect of Fe, Fe2N, and Fe3C nanoparticles, which was unambiguously confirmed by HRTEM and XRD characterization. Furthermore, Fe–N-CNBs-600 also exhibited higher electrochemical properties than the currently used expensive Pt/C catalyst in Zn–air batteries.

Direct catalytic conversion of glucose and cellulose

Biomass product 5-hydroxymethylfurfural (5-HMF) can be used to synthesize a broad range of value added compounds currently derived from petroleum. Thus, the effective conversion of glucose or cellulose (the major components of biomass) into fuels and chemical commodities has been capturing increasing attention. Previous studies have been extensively focused on a two-step process for producing 5-HMF from glucose or cellulose, i.e., the isomerization of glucose into fructose and then the dehydration of fructose. We herein discovered that heterogeneous sulfonated poly(phenylene sulfide) (SPPS) containing strong Bronsted acid sites is able to convert glucose and cellulose into 5-HMF with a high yield in ionic liquids (ILs). The optimal activity of glucose conversion to 5-HMF achieves a yield of 87.2% after 4 h reaction at 140 °C. For direct cellulose conversion, a 5-HMF yield of 68.2% can be achieved. The reaction mechanism over the SPPS catalyst in ILs was studied by DFT calculations, and the results indicated that the SO3H group of SPPS plays a crucial role in glucose conversion into 5-HMF, and it acts as a proton donor as a Bronsted acid and functions as a proton acceptor as the conjugate base. Furthermore, the anions and cations of ILs together with SO3H-SPPS helped in stabilizing the reaction intermediates and transition states, which also resulted in glucose facile conversion into 5-HMF. The new catalyst system highlights new opportunities offered by optimizing the production of 5-HMF directly from glucose and cellulose.

Hydrophilic Graphene Preparation from Gallic Acid Modified Graphene Oxide in Magnesium Self-Propagating High Temperature Synthesis Process

Hydrophilic graphene sheets were synthesized from a mixture of magnesium and gallic acid (GA) modified graphene oxide (GO) in a self-propagating high-temperature synthesis (SHS) process, and hydrophilic graphene sheets displayed the higher C/O ratio (16.36), outstanding conductivity (~88900 S/m) and excellent water-solubility. GO sheets were connected together by GA, and GA was captured to darn GO structure defects through the formation of hydrogen bonds and ester bonds. In SHS process, the most oxygen ions of GO reacted with magnesium to prevent the escape of carbon dioxide and carbon monoxide to from the structure defects associated with vacancies, and GA could take place the high-temperature carbonization, during which a large-area graphene sheets formed with a part of the structure defects being repaired. When only GO was reduced by magnesium in SHS process, and the reduced GO (rGO) exhibited the smaller sheets, the lower C/O ratio (15.26), the weaker conductivity (4200 S/m) and the poor water-solubility because rGO inevitably left behind carbon vacancies and topological defects. Therefore, the larger sheet, less edge defects and free structure defects associated with vacancies play a key role for graphene sheets good dispersion in water.

Formation of larger-area graphene from small GO sheets in the presence of basic divalent sulfide species and its use in biomass conversion

Basic divalent sulfide species exhibit unique chemical activity in that they react with organic matter and function as a redox reagent. Herein, graphene oxide (GO) was modified by basic divalent sulfide species, and the modified materials were characterized by FT-IR spectra, XRD, UV-Vis, SEM, HRTEM, XPS, TG-MS analysis, Raman spectroscopy and electrical conductivity measurements. The results indicated that basic divalent sulfide species removed the abundant oxygen-containing groups from the basal plane of GO, in which the π-conjugated structure was largely restored. The basic divalent sulfide species also react with marginal oxygen-containing groups and were doped into GO to form large-area π-conjugated structures, resulting in the high electrical conductivity of sulfur-modified GO (SGO). TG-MS analysis showed that the basic divalent sulfide in SGO can be removed by heating, which provides a new method for preparing larger-area graphene sheets from GO with a smaller average size. In addition, SGO prepared without annealing displayed better performance in converting fructose, glucose, cellobiose and cellulose to 5-hydroxymethylfurfural (HMF) because it retained some acidic marginal oxygen-containing groups and basic divalent sulfide species.

Higher UV-shielding ability and lower photocatalytic activity of TiO2@SiO2/APTES and its excellent performance in enhancing the photostability of poly(p-phenylene sulfide)

U–TiO2 is successfully coated with SiO2 and subsequently well modified by APTES, and the core–shell structure exists on TiO2@SiO2 and TiO2@SiO2/APTES, which greatly reduces aggregation of the TiO2 nanoparticles. The photocatalytic activities of U–TiO2, TiO2@SiO2, and TiO2@SiO2/APTES are evaluated using MB decomposition. Nearly 50% of the MB is degraded after 15 min in the presence of the U–TiO2 under UV radiation (300 W), and only 17.44% and 4.18% of the MB is degraded in the presence of the TiO2@SiO2-0.6 and TiO2@SiO2/APTES-1. However, TiO2@SiO2/APTES-0.6 and TiO2@SiO2-0.2 exhibit excellent UV absorbance capacities, and the TiO2@SiO2/APTES-0.6 achieves 80% of the UV-shielding ability of U–TiO2. Poly(p-phenylene sulfide) (PPS) is an easily photodegraded material and TiO2/PPS is more seriously photodegraded than PPS, however, the TiO2@SiO2/APTES nanoparticles can effectively protect the PPS from UV degradation, owing to their lower photocatalytic activities, higher UV-shielding abilities and easy dispersion in the PPS matrix. The breaking strength retention rate of the 1 wt% TiO2@SiO2/APTES/PPS film shows a maximum increase of 38.26%, and the breaking elongation retention rate increased by 41.64% at 2 wt% TiO2@SiO2/APTES loading. These results reveal that the incorporation of the TiO2@SiO2/APTES nanoparticles into the PPS matrix imparts excellent anti-UV properties to the PPS matrix, leading to a mechanical performance improvement.

The structure of organotin oxides playing a key role on the transesterification of dimethyl carbonate with hydrogenated bisphenol A

Transesterification of dimethyl carbonate (DMC) with hydrogenated bisphenol A (HBPA) was studied over various organotin oxides under pressured condition without removal of by-producing methanol. Bu2SnO displayed higher activities in HBPA conversion and bis-methylcarbonate of hydrogenated bisphenol-A (BMHBPA) synthesis, and HBPA conversion and BMHBPA selectivity reached 97.4% and 84.0%. However, when Ph2SnO was used as catalyst, HBPA conversion and BMHBPA selectivity decreased to 81.5 and 37.7%. Catalyst steric hindrance significantly influenced HBPA conversion and BMHBPA formation, and π-d interaction between phenyl ring and Sn was unfavorable for the transesterification of HBPA with DMC. Moreover, the catalytic system was further optimized.

Catalytic performance of metal oxide modified SiMCM-41 catalysts in diphenyl carbonate synthesis

Decomposition of CCl4 into diphenyl carbonate (DPC) was examined over metal oxides modified SiMCM-41. ZnO/SiMCM-41 and Fe2O3/SiMCM-41 showed high activity in DPC synthesis. Although many other metal oxides, such as La2O3, CuO, Al2O3 and alkali or alkaline earth oxide, were success in destruction of CCl4, they displayed nearly no activity on DPC synthesis. ZnO/SiMCM-41 and Fe2O3/SiMCM-41 were characterized by X-ray diffraction (XRD), UV-Raman, 29Si MAS NMR and N2 adsorption-desorption isotherms, and results showed that ferric and zinc oxide were supported onto SiMCM-41. The well ZnO dispersion in SiMCM-41 channels and the weak electrostatic interaction between chlorine anion and Zn2+ play an important role for the high activity of ZnO/SiMCM-41 in decomposition of CCl4 into DPC.