Solvent-free Strategy Research Articles

Significantly enhanced hydrogen desorption properties of Mg(AlH4)2 nanoparticles synthesized using solvent free strategy

Mg(AlH4)2 nanoparticles with a particle size less than 10nm have been successfully synthesized by mechanochemical method using LiAlH4 and MgCl2 as raw materials together with LiCl buffering additive. In comparison to Mg(AlH4)2 microparticles, Mg(AlH4)2 nanoparticles exhibit a faster hydrogen desorption kinetics and lower desorption temperature. The hydrogen desorption temperatures of the first and second dehydrogenation steps are 80 and 220°C for the Mg(AlH4)2 nanoparticles, which are about 65 and 60°C, respectively, lower than those of Mg(AlH4)2 microparticles. The decomposition activation energy is reduced from 135kJ/mol for Mg(AlH4)2 microparticles to 105.3kJ/mol for Mg(AlH4)2 nanoparticles. It is proposed that the shortened diffusion distance and enhanced diffusivity of Mg(AlH4)2/MgH2 nanoparticles provide an energy destabilization for lowering the dehydrogenation temperature, and thus being the key factor for promoting the hydrogen desorption kinetics. More importantly, it is demonstrated that the dehydrided nano MgH2 hydride with a particle size below 10nm can be formed after rehydrogenation process, resulting in the good cycling hydrogen desorption performance of nano MgH2.

Vapor-phase π–π molecular recognition: a fast and solvent-free strategy towards the formation of co-crystalline hollow microtube with 1D optical waveguide and up-conversion emission

1D molecular co-crystals with hollow micro-tubular morphology can be fabricated through a facile vapor deposition process, which have potential photonic and photofunctional applications.

An efficient organic solvent-free solution-processing strategy for high-mobility metal chalcogenide film growth

One of the primary challenges for high-quality metal chalcogenide film growth by a chemical solution approach is to avoid the use of volatile/hazardous organic solvents during the fabrication processes.

CuBr-ZnI2 Combo-Catalysis for Mild CuI-CuIII Switching and sp2 C-H Activated Rapid Cyclization to Quinolines and Their Sugar-Based Chiral Analogues: A UV-Vis and XPS Study.

An unprecedented CuBr–ZnI2 combo-catalyzed mild Cu1–CuIII switching activation of sp2 C–H of highly electron-rich arenes is reported. Anilines, aldehydes, and terminal alkynes were rapidly coupled together at ambient temperature to construct a ubiquitous quinoline framework through cyclization of the C≡C bond. This smart solvent-free strategy was exploited for the direct synthesis of valuable 4-substituted, 2,4-disubstituted, and thermally labile sugar-based chiral quinolines in good yields. In contrast to the frequently used imine–alkyne cyclization reaction, this uncommonly mild CuI–CuIII combo-catalysis for a rapid three-component cyclization is expected to proceed through the formation of a flexible propargyl amine intermediate, which provides a CuI-procatalyst for rapid sp2 C–H activation with cyclization involving transient CuIII species. The in situ generation of transient CuIII species was confirmed through online ultraviolet–visible spectroscopy (UV–vis), electrospray ionization mass spectrometry (ESI-MS), and X-ray photoelectron spectroscopy (XPS) analyses.

One-pot solvent-free synthesis of cross-linked anion exchange membranes for electrodialysis

Solvent-free strategy has attracted a broad interest in preparation of ion exchange membranes in recent years stemming from the no need of organic solvents and facilitated construction of highly crosslinking networks. However, post-functionalization is commonly required for further introducing ion-exchange groups. In this study, we report a one-pot solvent-free synthesis of cross-linked anion exchange membranes (AEMs) without the need for post-functionalization. We firstly dissolved brominated poly (2, 6-dimethyl-1, 4-phenylene oxide) (BPPO) in liquid monomers mixture of 4-vinylbenzyl chloride (VBC) and styrene without any organic solvent, then added appropriate amount of N-vinylimidazole and N-methylimidazole to introduce imidazolium groups into both of polyelectrolyte and solvents. The transparent, robust and crosslinked AEMs were obtained by the thermal crosslinking of the unsaturated moieties during the membrane forming process. This approach, distinct from the classical post-functionalization processes, performs crosslinking and functionalization simultaneously. Particularly, imidazolium cations locating on cross-links endow the resultant membrane a high concentration of charge carriers (ion-exchange capacity) for target low resistance, while maintain a high mechanical stability.

Solvent-Free Synthesis of Zeolite Crystals Encapsulating Gold-Palladium Nanoparticles for the Selective Oxidation of Bioethanol.

The conversion of bioethanol into valuable products is an important area in the conversion of biomass. We demonstrate the successful synthesis of bimetallic gold-palladium (Au-Pd) nanoparticles encapsulated within S-1 zeolite crystals (AuPd@S-1) by a solvent-free strategy. This strategy allows highly efficient use of the noble metals, with more than 96 % of the gold and palladium being loaded into the final samples. Electron microscopy characterization and investigations with probe molecules confirm that the Au-Pd nanoparticles are encapsulated inside the S-1 crystals. The AuPd@S-1 catalyst is very active for the aerobic oxidation of bioethanol, giving 100 % conversion and 99 % selectivity to acetic acid. Even in the presence of 90 % water, the catalyst still gives a conversion higher than 80 % and a selectivity of 95 %. More importantly, the AuPd@S-1 catalyst exhibits excellent stability in the oxidation of bioethanol. These features are important for future practical applications of the AuPd@S-1 catalyst.

Solvent-free thermoplastic-poly(dimethylsiloxane) bonding mediated by UV irradiation followed by gas-phase chemical deposition of an adhesion linker

Here, we introduce a solvent-free strategy for bonding various thermoplastic substrates with poly(dimethylsiloxane) (PDMS) using ultraviolet (UV) irradiation followed by the gas-phase chemical deposition of aminosilane on the UV-irradiated thermoplastic substrates. The thermoplastic substrates were first irradiated with UV for surface hydrophilic treatment and were then grafted with vacuum-evaporated aminosilane, where the alkoxysilane side reacted with the oxidized surface of the thermoplastic substrate. Next, the amine-terminated thermoplastic substrates were treated with corona discharge to oxidize the surface and were bonded with PDMS, which was also oxidized via corona discharge. The two substrates were then hermetically sealed and pressed under atmospheric pressure for 30 min at 60 °C. This process enabled the formation of a robust siloxane bond (Si–O–Si) between the thermoplastic substrate and PDMS under relatively mild conditions using an inexpensive and commercially available UV lamp and Tesla coil. Various thermoplastic substrates were examined for bonding with PDMS, including poly(methylmethacrylate) (PMMA), polycarbonate (PC), poly(ethyleneterephthalate) (PET) and polystyrene (PS). Surface characterizations were performed by measuring the contact angle and performing x-ray photoelectron spectroscopy analysis, and the bond strength was analyzed by conducting various mechanical force measurements such as pull, delamination, leak and burst tests. The average bond strengths for the PMMA–PDMS, PC–PDMS, PET–PDMS and PS–PDMS assemblies were measured at 823.6, 379.3, 291.2 and 229.0 kPa, respectively, confirming the highly reliable performance of the introduced bonding strategy.

Quaternized membranes bearing zwitterionic groups for vanadium redox flow battery through a green route

Novel quaternized membranes with zwitterionic groups applied in all-vanadium redox flow battery (VRB) have been prepared using a solvent free strategy, which is environmentally-friendly and different from traditional methods using organic solvents as reaction media. It was performed by dissolving cardopolyetherketone (PEK-C) in monomers mixture of 4-vinylbenzyl chloride (VBC) and divinylbenzene (DVB), and then in situ polymerization to incorporate PEK-C into the network of poly (VBC–DVB). The resulting copolymer was immersed in dimethylamine (DMA) followed by 1,3-propane sultone (PS) aqueous solution to obtain the target quaternized membranes bearing zwitterionic groups ([CH2N+(CH3)2CH2CH2CH2SO3−]), which greatly enhance the chain packing density, and consequently improve membrane stability. The optimized quaternized membrane with zwitterionic groups showed a 20% decrease in vanadium ion permeability as compared to the benchmark quaternized membrane without zwitterionic groups. It also possesses good mechanical strength even after immersion in VO2+ solution for as long as 20 days. Comparing the commercial Nafion117 with the optimized membrane, the vanadium ion permeability sharply decreased from 10.80×10−5cmmin−1 to 0.21×10−5cmmin−1 while the coulombic and energy efficiency increased from 89.7% and 68.3% to 97.1% and 73.4% at 50mAcm−2, respectively. The present quaternized membrane with zwitterionic groups shows good characteristics for application in VRBs.

A practical synthesis of trifluoromethyl alkyl ketones

A practical approach to TFMKs under mild conditions by “trifluoroacetic ester/ketone metathesis” was described. The i -Pr and t -Bu alkyl ketones were used to produce TFMKs with high boiling points by distillation or recrystallization. The solvent-free strategy was effective used to collect volatile TFMKs. • A trifluoroacetic ester/ketone metathesis was applied on alkyl alkyl ketones. • TFMKs with high boiling points were prepared from i -Pr/ t -Bu alkyl ketones. • The solvent-free condition is suitable for trifluoroacetic ester/ketone metathesis. • TFMKs with low boiling points can be easily gained with the solvent-free condition. Trifluoromethyl ketones (TFMKs) significantly contribute to biologically active compounds and special materials. TFMKs can be prepared by “trifluoroacetic ester/ketone metathesis” along with the accompanying products, aromatic acid esters. As an important extension of our previous studies on the use of aryl alkyl ketones, wherein the separation of the resulting TFMKs and aromatic acid esters proved problematic, i -Pr and t -Bu alkyl ketones were shown in this work to be competent reaction partners for easy TFMK separation from the product mixtures, thereby providing a practical synthesis route to TFMKs. With the removal of accompanying products, i -Pr and t -Bu carboxylic esters, TFMKs with high boiling points were efficiently obtained by distillation or recrystallization. Furthermore, a solvent-free condition was also effective for this reaction, which allowed TFMKs with low boiling points to be separated from the reaction mixture by distillation in good yield.

The beauty of frost: nano-sulfur assembly via low pressure vapour deposition

A low pressure vapour deposition (LPVD) technique is proposed as an environmentally friendly, cost-effective and versatile strategy for fabrication of sulfur nanomaterials. By controlling the characteristics of the deposit substrate for the LPVD, various sulfur-based nanomaterials have been obtained through a substrate-induced self-assembly process.

Cross-Linked Alternately Copolymerized Electrolyte Poly (styrene-a-maleic ester) Synthesized through Solvent-Free Strategy

A solvent-free cross-linked alternating copolymer electrolyte is synthesized through photo copolymerization of comb-like poly (ethylene glycol) ester maleate and styrene. Phase transitions, thermal properties, ionic conductivities and electrochemical stabilities are investigated to characterize the alternating copolymer electrolyte. The flexible solid polymer electrolyte (spe) with lithium salt content of 15 wt.% and MA/-OH = 1 has a good ionic conductivity of 1.45×10-5 S cm-1 at 35 °C and a superior electrochemical stability to 5.2 V. The maleic anhydride on the main chain increases the rigidity of the copolymer matrix and decreases the ionic conductivity.

Reacciones asimétricas organocatalizadas en ausencia de disolvente: una estrategia para hacer más “verde” la organocatálisis

According with the principles of “green” chemistry, asymmetric organocatalysis aims to become a sustainable strategy to catalyze a wide range of chemical transformations. Furthermore, during the last decade the application of solvent-free methodologies has transformed asymmetric organocatalysis into an even “greener” alternative, avoiding the use of volatile, toxic and expensive reaction media. In this article, we review some recent salient examples of solvent-free strategies that have converted asymmetric organocatalysis into a more sustainable synthetic methodology.

Cross-linked anion exchange membranes for alkaline fuel cells synthesized using a solvent free strategy

This article describes the preparation of cross-linked anion exchange membranes (AEMs) using a solvent free strategy. A novel casting solution is formed by dissolving cardo polyetherketone (PEK-C) as an essential polymer intensifier in a mixture of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) monomers without any organic solvent. Tetraethylenepentamine (TEPA) is added to act as a cross-linker between VBC and PKE-C. Polymerization and quaternization are successively implemented to obtain the cross-linked AEMs, whose properties are found to compare well to many referenced AEMs. Apart from improving the compatibility of PEK-C with poly(VBC-co-DVB), TEPA also effectively enhances the charge density, ionic conductivity and alkaline stabilities of the resulting AEMs, whilst simultaneously inhibiting the swelling ratio. The optimal membrane shows an ionic conductivity of 76 mS cm−1 at 70 °C and 100% relative humidity and can remain stable after immersing in 2 mol dm−3 KOH solution for 168 h. A power density of 6 mW cm−2 is achieved in a H2/O2 fuel cell test at 50 °C with an optimal AEM but a non-optimized membrane electrode fabrication process. Generally, the novel method herein highlights an environmentally friendly and economically attractive method for the preparation of AEMs used in alkaline fuel cells.

Miniaturization of Metal–Biomolecule Frameworks Based on Stereoselective Self‐Assembly and Potential Application in Water Treatment and as Antibacterial Agents

Miniaturization of metal-biomolecule frameworks (MBioFs) to the nanometer scale represents a novel strategy for fabricating materials with tunable physical and chemical properties. Herein, we demonstrate a simple, low-cost, and completely organic solvent-free strategy for constructing a dl-glutamic acid-copper ion-based three-dimensional nanofibrous network structure. The building blocks used are available in large quantities and do not require any laborious synthesis or modification. Importantly, we demonstrate with an intriguing example, that the self-assembly ability of supramolecular nanofibers could be finely tuned with the ligands' chirality. This offers opportunities for obtaining one-dimensional hierarchical nanostructures and expands the investigation scope of stereoselective self-assembly. Furthermore, the material displays good ability in removing anionic dyes from water and inhibits the growth of both Gram positive and Gram negative bacteria, possibly through the contact-killing mechanism; this indicates potential applications in environmental issues and antimicrobial nanotherapeutics.

Innovations in Food Technology Special Issue

The development of novel processing techniques to obtain healthier and safer food products is one of the major challenges facing the food industry in the new century. On one hand, novel processes and products are driven by the stunning technological advances of this global era, to which food science and technology are not alien. Such advances include not only the design and application of new equipment and process lines, which constitute what has been called “emerging technologies”, but also the biotechnological and nanotechnological applications of such cutting-edge disciplines for food production and control. On the other hand, innovation in food technology flows in parallel with consumers’ demand for healthier and safer foods with improved quality and shelf life. As a consequence of these developments, and in an effort to give a response to such challenges, food technologists have paid special attention to the development and application of minimal processing strategies to a myriad of food products, thus avoiding the nutritional shortcomings that occur from the application of traditional preservation methods such as intense heat processing. Nevertheless, although the nutritional components of minimally processed foods may be more intact in products subjected to such light preservation methods, the presence of spoilage and pathogenic bacteria that are able to survive such minimal processing may incur novel risks. These risks require the development of robust and sensitive control methods to ensure not only the quality but also, and especially, the safety of such novel food products. In such an actively changing food technology environment, scientists working in this field are ready to find solutions from different approaches. Some of the most relevant solutions have been compiled in this “Innovations in Food Technology Special Issue”. Among the most promising novel technologies with a higher transfer potential from research to development and innovation, the application of pulsed electric fields and high-pressure processing are still at the top. Nevertheless, more specific and still less known techniques, such as hydrodynamic cavitation, are also gaining increasing importance for certain applications in water and food processing, while thermosonication and ultraviolet radiation are also gaining attention as food processing strategies. Sometimes, the combination of novel techniques and the obtention of added value food ingredients goes together, such is the case with the application of solvent-free strategies to the extraction of antioxidants that are relevant to the food industry. Novel food biopreservation techniques constitute another innovative field that deserves special attention. Active packaging techniques extend the possibility of keeping food quality at its best during storage, whereas the development of novel bacteriocins and other novel inhibitory agents, such as essential oils or the so-called vitamin K5, which are able to inhibit spoilage and pathogenic bacteria and fungi, represent valuable steps toward hurdle technologies for the production of minimally processed food products. The ever changing field of biotechnology also provides us with selected and engineered enzymes and starter cultures for novel food applications, such as microbial proteases and selected lactic acid bacteria for wine production, respectively. Novel technologies for cell immoJ. Barros Velazquez (*) Food Technology Laboratory, Department of Analytical Chemistry, Nutrition and Food Science School of Veterinary Sciences/College of Pharmacy University of Santiago de Compostela, 15782 Santiago de Compostela, Spain e-mail: jorge.barros@usc.es Food Bioprocess Technol (2011) 4:831–832 DOI 10.1007/s11947-011-0576-9

An efficient strategy for highly loaded, well dispersed and thermally stable metal oxide catalysts

A family of metal oxides (Co 3 O 4 , NiO and CeO 2 ) confined in SBA-15 with high loadings (≥ 20 wt%) was prepared through a solvent-free method. Characterizations of X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that aggregation-free nanoparticles were obtained and N 2 physisorption confirmed they were studded in mesopores. It was proposed that the intermediate molten salt phases ensured successful encapsulation and homogeneous dispersion of metal oxides. Lastly, the importance of the strategy was exemplified by NiO, and the high thermal stability together with superior performance in hydrodechlorination of chlorobenzene suggested great potential of these samples in heterogeneous catalysis. A family of highly loaded, well dispersed and thermally stable metal oxide nanoparticles (Co 3 O 4 , NiO, CeO 2 ) confined in SBA-15 is fabricated via a solvent-free strategy. The preliminary catalytic test of NiO in hydrodechlorination of chlorobenzene suggests great potential of the samples in heterogeneous catalysis. ► Co 3 O 4 , NiO and CeO 2 are filled into SBA-15 through a solvent-free method. ► The method is facile but efficient. ► The key of the method is based on suppression of distribution of precursors. ► The obtained samples show promising applications in heterogeneous catalysis.

Environmentally friendly synthesis of alkaline anion exchange membrane for fuel cells via a solvent-free strategy

In this study, we described a solvent-free strategy for alkaline anion exchange membranes synthesis by in situ polymerization. Different from the available membrane synthesis by direct polymerization and post-polymerization modification, the non-solvent strategy demonstrated here was performed by dissolving brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) in monomers mixture of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) and then in situ polymerization to incorporate BPPO into the network of poly(VBC–DVB). After quaternization, a translucent, flexible and robust anion exchange membrane was obtained. The membrane morphology was confirmed by SEM-EDXA images. Factors such as quaternizing conditions and components of the casting solution were fully investigated. The optimized membranes exhibited favorable water uptakes (ranging from 19.9% to 29.3%) and hydrated hydroxyl conductivities (ranging from 0.017 to 0.028Scm−1) at room temperature, which allows its application in alkaline anion exchange membrane fuel cells (AAEMFCs). Moreover, this solvent-free strategy is not limited to the above BPPO/VBC/DVB system. It can be applied to other compatible systems of (aromatic) polymers and (aromatic) monomers as long as homogeneous cast solution of the monomers and polymers can be formed. Thus this research will provide a versatile environmentally friendly route to prepare anion exchange membranes with tailored properties for alkaline fuel cells.

Synthesis of Protein-Loaded Hydrogel Particles in an Aqueous Two-Phase System for Coincident Antigen and CpG Oligonucleotide Delivery to Antigen-Presenting Cells

Materials that effectively deliver protein antigens together with activating ligands to antigen-presenting cells are sought for improved nonviral vaccines. To this end, we synthesized protein-loaded poly(ethylene glycol) (PEG)-based hydrogel particles by cross-linking PEG within the polymer-rich phase of an emulsion formed by a poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer in saturated aqueous salt solution. These particles (500-nm diameter) contained high levels of encapsulated protein (approximately 75% of dry mass), which was selectively released by proteolytic enzymes normally present in the phagosomal/endosomal compartments of dendritic cells (DCs). For co-delivery of cellular activation signals, gel particles were surface-modified by sequential adsorption of poly(l-arginine) and CpG oligonucleotides. DCs pulsed with protein-loaded particles activated naïve T cells in vitro approximately 10-fold more efficiently than DCs incubated with soluble protein. This organic solvent-free strategy for protein encapsulation within submicron-sized hydrophilic particles is attractive for macromolecule delivery to a variety of phagocytic and nonphagocytic cells.