Molecular batteries: ferrocenylsilylation of dendrons, dendritic cores, and dendrimers: new convergent and divergent routes to ferrocenyl dendrimers with stable redox activity

The ferrocenylsilylation of the phenol triallyl dendron 2, of the phenol nonaallyl dendron 4, and of the 9-, 27-, 81-, and 243-allyl dendrimers 7-10 (monitored by the disappearance of the signals of the olefinic protons in 1H NMR spectra) has been achieved using ferrocenyldimethylsilane 1 and Karstedt's catalyst in diethyl ether at 40 degrees C, yielding the corresponding ferrocenyl dendrons and dendrimers. An alternative convergent synthesis of the nonaferrocenyl dendron 5 was carried out by reaction of the triferrocenyl dendron 2 with a protected triododendron followed by deprotection. Reaction of the nonaferrocenyl dendron 5 with hexakis(bromomethyl)benzene gave the 54-ferrocenyl dendron 6. All the ferrocenyl dendron and dendrimers produce a chemically and electrochemically reversible ferrocenyl oxidation wave at seemingly the same potential. Stable platinum electrodes modified with the high ferrocenyl dendrimers were fabricated. The soluble orange-red ferrocenyl dendrimers can also be oxidized in CH2Cl2 by [NO][PF6] to the insoluble deep blue polyferrocenium dendrimers. For instance, the 243-ferrocenium dendrimer has been characterized by its Mossbauer spectrum, which is of the same type as that of ferrocenium itself. The ferrocenium dendrimers can be reduced without any decomposition back to the ferrocenyl dendrimer, indicating that these multielectronic redoxstable dendrimers behave as molecular batteries.     

Application of relaxation periods during electrodialysis of a casein solution: Impact on anion-exchange membrane fouling

Electrodialysis (ED) is a membrane process used on a large scale. However, one of the common problems is fouling of ion-exchange membranes stacked in the cell. The use of pulsed power, consisting in applying a constant current density during a fixed time of application (T_on) followed by a pause duration (T_off), was demonstrated recently as an effective fouling mitigation method for electrodialysis. Up until now, no work has investigated the potential of electrodialysis using pulsed electric field on protein fouling. The aim of the present work was to study the influence of pulsed electric field (PEF) with a low frequency square shaped periodic signal (T_on = 10 s–T_off = 10 s, T_on = 10 s–T_off = 40 s) in comparison with dc current during electrodialysis of a casein solution at different current densities (10, 20 and 30 mA/cm²) on membrane fouling. It appeared from these results that PEF, under certain conditions of pulse, would avoid fouling on anion-exchange membranes. For 10 s–40 s pulsed electric field conditions, no fouling was observed with any density, while for 10 s–10 s PEF conditions, fouling appeared only at current density over 10 mA/cm². dc current, whatever the current density conditions, led to a fouling on the diluate side of the AEM. Furthermore, when fouling occurred, magnitude layer thickness and dry weight increased with the applied current density. The nature of the fouling was identified as 97% protein. The protein fouling would be due to the dissociation of water molecules and/or heat increase at the anion-exchange membrane interface. The relaxation time of the pulse would limit both phenomena on the membrane.     

Seedling Development and Evaluation of Genetic Stability of Cryopreserved Dendrobium Hybrid Mature Seeds

Vitrification, a simple, fast, and recommended cryopreservation method for orchid germplasm conservation, was evaluated for Dendrobium hybrid “Dong Yai” mature seeds. The genetic stability of regenerated seedlings was also evaluated using flow cytometry. Mature seeds from this hybrid were submitted to plant vitrification solution (PVS2) for 0, 0.5, 1, 2, 3, 4, 5, or 6 h at 0 °C. Subsequently, they were plunged into liquid nitrogen (LN) at ?196 °C for 1 h and recovered in half-strength Murashige and Skoog culture medium (1/2 MS), and seed germination was evaluated after 30 days. Seeds directly submitted to LN did not germinate after cryopreservation. Seeds treated with PVS2 between 1 and 3 h presented the best germination (between 51 and 58 %), although longer exposure to PVS2 returned moderated germination (39 %). Germinated seeds were further subcultured in P-723 culture medium and developed whole seedlings in vitro after 180 days, with no abnormal characteristics, diseases, or nutritional deficiencies. Seedlings were successfully acclimatized under greenhouse conditions with over 80 % survival. Flow cytometry analysis revealed no chromosomal changes on vitrified seedlings, as well as seedlings germinated from the control treatment (direct exposure to LN). These findings indicate that vitrification is a feasible and safe germplasm cryopreservation method for commercial Dendrobium orchid hybrid conservation.     

Turbulence in microfluidics: Cleanroom-free,fast, solventless,and bondless fabrication and application in high throughput liquid-liquid extraction

This paper addresses an important breakthrough in the deployment of ultra-high adhesion strength microfluidic technologies to provide turbulence at harsh flow rate conditions. This paper is only, to our knowledge, the second reporting on the generation of high flow rate-assisted turbulence in microchannels. This flow solves a crucial bottleneck in microfluidics: the generation of high throughput homogeneous mixings. We focused on the fabrication of bulky polydimethylsiloxane (PDMS) microchips (without any interfaces) rather than the laborious surface modifications that were employed in the first reporting about turbulence-assisted microfluidics. The fabrication is cleanroom-free, simple, low-cost, fast, solventless, and bondless requiring only a laboratory oven. More specifically, our method relies on the shaping of a nylon scaffold, cure of PDMS with embedded nylon, and removal of this scaffold. The scaffold was obtained by manually wrapping nylon threads. The withdrawing out of the scaffold was completed in few seconds using only a plier. Such microchannels endured flow rates of up to 60.0 mL min⁻¹ with a strikingly low elastic deformation. The importance in producing turbulence into microscale channels was successfully shown in liquid-liquid extractions. The great energy dissipation rate relative to the turbulence created high throughput and efficient extractions in microfluidics for the first time. The residence time was only 0.01 s at 25.0 mL min⁻¹ (total flow rate of the immiscible phases). In addition, the partition coefficient determined in a single run was similar to that obtained by the conventional batch shake-flask method that was realized in triplicate.     

Evaluation of low-dose irradiation on microbiological quality of white carrots and string beans

The minimally processed food provided the consumer with a product quality, safety and practicality. However, minimal processing of food does not reduce pathogenic population of microorganisms to safe levels. Ionizing radiation used in low doses is effective to maintain the quality of food, reducing the microbiological load but rather compromising the nutritional values and sensory property. The association of minimal processing with irradiation could improve the quality and safety of product. The purpose of this study was to evaluate the effectiveness of low-doses of ionizing radiation on the reduction of microorganisms in minimally processed foods. The results show that the ionizing radiation of minimally processed vegetables could decontaminate them without several changes in its properties.     

Synthesis and characterization of Pd(II) complexes of 2‐ and 3‐thiophenecarbaldehyde immobilized on silica obtained from sepiolite

Silica obtained by acid treatment of sepiolite was used as a support for catalysts consisting of palladium complexes of 2‐ and 3‐thiophenecarbaldehyde. The support and the catalysts were characterized by X‐ray diffraction, and solid‐state ²⁹Si and ¹³C nuclear magnetic resonance spectroscopies. The supported palladium catalysts were used in the Suzuki reaction of bromobenzene with phenylboronic acid. Copyright © 2013 John Wiley & Sons, Ltd.