The effect of high power airborne ultrasound and microwaves on convective drying effectiveness and quality of green pepper

The effectiveness of hybrid drying based on convective drying with application of ultrasound and microwave enhancement is the main subject of the studies. The drying kinetics, energy consumption as well as the quality aspect of green pepper is analysed. It was shown that hybrid drying methods shorten significantly the drying time, reduce the energy consumption and affect positively the quality factors. Each of the analysed aspects depend on combination of the convective-ultrasound-microwave drying programs. Besides, based on the drying model elaborated earlier by one of the authors, the effects of ultrasound on convective drying assessed by such phenomena as “heating effect”, “vibration effect” and “synergistic effect” are presented.     

Polylactones. 13. Transesterification of Poly(L-Lactide) with Poly(Glycoude), Poly(β-Propio-Lactone), and Poly[ε -Caprolactone)

Homogeneous blends of poly(L-lactide) (M _n = 30 000 to 40 000) and poly(β-propiolactone) or poly(ε-caprolactone) were prepared in solution. The solvent-free blends were subjected to transesterification catalyzed by means of methyl triflate, triflic acid, boron trifluoride, or tributyltin methoxide at 100 or 150°C. At 100°C, transesterification was barely detectable even after 96 h. When poly(β-propiolactone) was used as the reactant at 150°C, degradation was faster than transesterification regardless of the catalyst. The same negative result was obtained for heterogeneous blends of poly(L-lactide) and poly(glycolide). In the case of poly(ε-caprolactone), copolyesters with slightly blocky sequences were obtained with tributyltin methoxide as catalyst, whereas the acidic catalysts caused rapid degradation. The copolyesters were characterized by means of ¹H-NMR spectroscopy with regard to their molar composition, by means of ¹³C-NMR spectroscopy with regard to their sequences, and by means of differential scanning calorimetry with regard to crystallinity.     

Polymeric Nanocomposites—Polyhedral Oligomeric Silsesquioxanes (POSS) as Hybrid Nanofiller

Abstract

Polyhedral oligomeric silsesquioxane (POSS), a hybrid nanostructured macromer has been used in the last decade for preparation of polymeric nanocomposites. Its versatile chemistry, which lends it for almost infinite chemical modification, sets it apart from other nanostructured fillers like nanoclays, carbon nanotubes, and carbon nanofibers. Depending on its functionality, 3‐D network, bead or pendant type‐POSS based polymeric nanocomposites can be synthesized. These have the potential to be designed for products with specific nanostructures for specific end‐use applications. This article discusses the trends in current research involving use of POSS macromers for modification of mainly thermal and viscoelastic properties of various polymers.     

Recent developments in polymer–block–polypeptide and protein–polymer bioconjugate hybrid materials

In the last few years, polymer bioconjugates have been shown to be useful in many emerging areas of materials science. Consequently, the synthesis of polymer bioconjugates has suddenly become a central topic in polymer chemistry. The versatility and robust nature of modern synthetic methods such as controlled radical polymerisation (CLRP),¹ ring-opening polymerisation (ROP), and ‘click’ chemistry make them excellent tools for the preparation of tailor-made polymer bioconjugates. CLRP in combination with other techniques has been shown to be a mature technology for building tailor-made block copolymers and protein–polymer conjugates with a wide range of applications, especially in biomedical domains. This review describes the recent advances and progress in the rapidly expanding field of bioconjugation, outlining the work performed up to 2012.     

Preparation and Characterization of the Hybrids Containing Silica Nanoparticles by Sol-Gel Crosslinking Process

The organic/inorganic hybrid nanomaterials containing silica nanoparticles are synthesized by sol-gel crosslinking process. The tetraethoxysilane (TEOS) and γ-aminopropyltriethoxylsilane as coupling agents are used as a precursor. The 2,4,6-tri [(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) as crosslinking agent is used to form covalent bonds among the inorganic nanoparticles. The chemical and morphological structures of the organic/inorganic hybrid are characterized with FTIR spectra, ²⁹Si-NMR, x-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscope (AFM). The results show that the organic/inorganic hybrid forms covalent bond between the inorganic nanoparticle and Tri-EBAC. The network organic/inorganic hybrid can form good film with even nanometer particles. The network organic/inorganic hybrids nanomaterial not only exhibits the thermal properties of inorganic compounds, but also exhibits the thermal properties of organic polymer.     

Hybrid phospholipid bilayer coatings for separations of cationic proteins in capillary zone electrophoresis

Protein separations in CZE suffer from nonspecific adsorption of analytes to the capillary surface. Semipermanent phospholipid bilayers have been used to minimize adsorption, but must be regenerated regularly to ensure reproducibility. We investigated the formation, characterization, and use of hybrid phospholipid bilayers (HPBs) as more stable biosurfactant capillary coatings for CZE protein separations. HPBs are formed by covalently modifying a support with a hydrophobic monolayer onto which a self‐assembled lipid monolayer is deposited. Monolayers prepared in capillaries using 3‐cyanopropyldimethylchlorosilane (CPDCS) or n‐octyldimethylchlorosilane (ODCS) yielded hydrophobic surfaces with lowered surface free energies of 6.0 ± 0.3 or 0.2 ± 0.1 mJ m^?2, respectively, compared to 17 ± 1 mJ m^?2 for bare silica capillaries. HPBs were formed by subsequently fusing vesicles comprised of 1,2‐dilauroyl‐sn‐glycero‐3‐phosphocholine or 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine to CPDCS‐ or ODCS‐modified capillaries. The resultant HPB coatings shielded the capillary surface and yielded reduced electroosmotic mobility (1.3–1.9 × 10^?4 cm² V^?1s^?1) compared to CPDCS‐ and ODCS‐modified or bare capillaries (3.6 ± 0.2 × 10^?4 cm² V^?1s^?1, 4.8 ± 0.4 × 10^?4 cm² V^?1s^?1, and 6.0 ± 0.2 × 10^?4 cm² V^?1s^?1, respectively), with increased stability compared to phospholipid bilayer coatings. HPB‐coated capillaries yielded reproducible protein migration times (RSD ≤ 3.6%, n ≥ 6) with separation efficiencies as high as 200 000 plates/m.     

线上线下混合式物理化学实验研究型教学改革

针对目前实验教学在创新型人才培养中存在的问题,介绍了北京航空航天大学化学学院物理化学实验教学的改革与实践情况。结合线上教学灵活、不受时空限制,以及线下教学培养学生动手操作能力和严谨求实的科学素养的特点,从递进式教学内容设计、个性化实验操作指导和训练、科研式论文报告总结、针对性展示和专题分析等方面进行了线上线下混合式研究型教学改革。将理论方法、虚拟操作、实际训练和总结提升等相结合,充分发挥教师指导和学生主体的优势,多维度培养和提升学生的科学素养、创新思维和综合创新能力,为提升实验教学质量和促进创新型人才培养提供了有益的借鉴。     

Green synthesis and characterization of copper and nickel hybrid nanomaterials: Investigation of their biological and photocatalytic potential for the removal of organic crystal violet dye

Nanotechnology deals with the materials at nanoscale to synthesize nanoparticles. The current study introduced a new green approach for the synthesis of Copper and Nickel hybrid nanoparticles by using Zingiber officinale rhizome extract as a capping and reducing agent. The nanoparticles were physico-chemically characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, Energy-dispersive X-ray spectroscopy, and Scanning electron microscopy. It was revealed by scanning electron micrograph that the Cu-Ni hybrid nanoparticles have spherical geometries with average grain size of 25.12 ± 1.2 nm. Furthermore, biocatalytic and photocatalytic applications of the biosynthesized nanoparticles were assessed. The results of antibacterial assay revealed that Cu-Ni hybrid nanoparticles had an inhibition zones of 28 ± 1.0, 25 ± 0.8, and 25 ± 1.5 mm against P. aeruginosa, E. coli and Proteus vulgaris. Commercially available antibiotics were purchased and coated with Cu-Ni hybrid nanoparticles, it was found that their antimicrobial efficacy was increased twice. To evaluate the antioxidant potential, nanoparticles having a concentration of 200 µg/mL were applied against 2,2-diphenyl-1-picrylhydrazyl free radicals and NPs showed 42.1 ± 0.71 % inhibition. Cu-Ni nanoparticles have shown a dose-dependent cytotoxicity against amastigote and promastigote in anti-leishmanial assay. The synthesized nanoparticles were found biocompatible and safe in nature to be used in vivo, as they showed no significant hemolysis of human red blood cells at their highest concentration. In antidiabetic assay, NPs inhibited alpha-amylase enzyme up to 38.07 ± 0.65 %. An organic crystal violet dye was successfully degraded by the synthesized nanoparticles in photocatalytic assay. Hence, it is concluded that Cu-Ni hybrid nanoparticles can be used both in vitro and in vivo for drug delivery in biomedical research. These nanoparticles can also be used in the remediation of organic dyes as a catalyst.     

Water-annealing regulated protein-based magnetic nanofiber materials: tuning silk structure and properties to enhance cell response under magnetic fields

In this study, flexible silk fibroin protein and biocompatible barium hexaferrite (BaM) nanoparticles were combined and electrospun into nanofibers, and their physical properties could be tuned through the mixing ratios and a water annealing process. Structural analysis indicates that the protein structure of the materials is fully controllable by the annealing process. The mechanical properties of the electrospun composites can be significantly improved by annealing, while the magnetic properties of barium hexaferrite are maintained in the composite. Notably, in the absence of a magnetic field, cell growth increased slightly with increasing BaM content. Application of an external magnetic field during in vitro cell biocompatibility study of the materials demonstrated significantly larger cell growth. We propose a mechanism to explain the effects of water annealing and magnetic field on cell growth. This study indicates that these composite electrospun fibers may be widely used in the biomedical field for controllable cell response through applying different external magnetic fields.     

Concerted effect of boron and porosity on shear thickening behavior of hybrid mesoporous silica dispersions

In the present work, the influence of porosity and boron on shear thickening behavior of hybrid mesoporous silica has been studied. Three different levels of boron modification were performed by varying the molar composition of boric acid viz., 1.5 mmol, 2.5 mmol, and 3.5 mmol in a co-condensation approach. The incorporation of boron in mesoporous silica network was confirmed by various techniques such as Fourier transform infra-red (FTIR), and ¹¹B solid- state nuclear magnetic resonance (NMR) spectroscopy. The morphology and particle size were confirmed by using scanning and transmission electron microscopy. To evaluate the effect of boron and porosity on the shear thickening behavior, dispersions were prepared from mesoporous boron- modified silica (MSiB), control mesoporous silica (MSi), non-porous boron-modified silica (SiB), and control non-porous silica (Si) in polyethylene glycol. The shear thickening behavior was studied using steady shear rheology. The dispersion prepared from different loadings of synthesized MSiB containing 1.5 mmol boron showed more than 16 times increase in viscosity (657.7 Pa.s) compared to that of MSi (39.2 Pa.s) at a fairly low volume fraction (φ = 0.15) of silica. It is expected that the highly ordered mesoporous architecture of hybrid silica has improved the interaction between the particle and the dispersing medium through hydrogen bonding. The porous morphology of the hybrid mesoporous silica as well as the incorporation of boron in the silica network favors the formation of a frictional contact network, and a transition from continuous shear thickening (CST) to discontinuous shear thickening (DST) behavior was observed. Therefore, silica prepared via incorporation of boron as well as porosity can be material of interest in variety of applications, for example, soft body armors, sporting goods, and shear thickening electrolytes for high impact resistant batteries.