Use Of Borohydride Research Articles

Characterization and reactivity of novel silver/iron nanoparticles

Abstract One of critical aspects still limiting a wider use of zero-valent iron in large-scale application is the use of borohydride for the material synthesis, which is expensive and leads to the production of large quantities of hydrogen gas and toxic borates. A new bimetallic material was devised, whose synthesis employs eco-benign sulfur-based reducing agent and is of easy implementation and scalability. Our material consists of a core of zero-valent iron covered by a thin film of iron oxide, while silver is homogeneously distributed, and proved able to efficiently decolorize bromophenol blue outperforming zero-valent silver (ZVS) and nZVI obtained with the same method.

Synthesis of eco-compatible bimetallic silver/iron nanoparticles for water remediation and reactivity assessment on bromophenol blue

In the last decade, zero-valent iron nanoparticles (nZVI) have been applied for groundwater remediation and they proved to be effective towards a wide range of contaminants, both organic and inorganic. One of the critical aspects related to the synthesis of this material concerns the use of borohydride, which increases the cost of the final product and generates toxic borates. In this paper, a new synthesis method of bimetallic nanoscale zero-valent silver/iron (nZVSI), its properties and its reactivity towards a model compound are presented. The novel synthesis protocol employs benign hydrosulfite as reducing agent and it is of easy implementation and scalability. The resulting nanoparticles have narrow size distribution and show appropriate colloidal stability. They consist of a core of zerovalent iron and a thin shell of iron oxide, while silver is homogeneously distributed within the material. The nanoparticles showed effective reactivity, able to degrade bromophenol blue with suitable kinetics and using a low amount of material. Additionally, the bimetallic nanomaterial significantly outperformed nanometric zero-valent silver (nZVS) and nZVI obtained with the same protocol. The proposed synthesis would allow to significantly reduce the environmental and health impact of the stage prior to product application via injection in the subsoil. Also, the simplicity and the safety of the proposed synthesis procedure would allow the production of the bimetallic reactant directly on-site, thus streamlining the remediation process and maximizing its efficiency.

Stabilization of Enzymes by Multipoint Covalent Attachment on Aldehyde-Supports: 2-Picoline Borane as an Alternative Reducing Agent

Enzyme immobilization by multipoint covalent attachment on supports activated with aliphatic aldehyde groups (e.g., glyoxyl agarose) has proven to be an excellent immobilization technique for enzyme stabilization. Borohydride reduction of immobilized enzymes is necessary to convert enzyme–support linkages into stable secondary amino groups and to convert the remaining aldehyde groups on the support into hydroxy groups. However, the use of borohydride can adversely affect the structure–activity of some immobilized enzymes. For this reason, 2-picoline borane is proposed here as an alternative milder reducing agent, especially, for those enzymes sensitive to borohydride reduction. The immobilization-stabilization parameters of five enzymes from different sources and nature (from monomeric to multimeric enzymes) were compared with those obtained by conventional methodology. The most interesting results were obtained for bacterial (R)-mandelate dehydrogenase (ManDH). Immobilized ManDH reduced with borohydride almost completely lost its catalytic activity (1.5% of expressed activity). In contrast, using 2-picoline borane and blocking the remaining aldehyde groups on the support with glycine allowed for a conjugate with a significant activity of 19.5%. This improved biocatalyst was 357-fold more stable than the soluble enzyme at 50 °C and pH 7. The results show that this alternative methodology can lead to more stable and active biocatalysts.

Air Independent Fuel Cells Utilizing Borohydride and Hydrogen Peroxide

AbstractThe US Navy continues to pursue electrochemical power sources with high energy density for low rate, long endurance air independent, undersea applications. The use of borohydride and hydrogen peroxide as fuel and oxidant sources offer several different fuel cell configurations; each with their own advantages and technical challenges.The direct electro-oxidation and electro-reduction of sodium borohydride and hydrogen peroxide is conceptually a simple system. In the fuel cell configuration where Nafion 115 is used and both electrolyte solutions are allowed to have a pH >8, high efficiencies (>70%) can be maintained with careful control of the concentration of reactants in the flowing electrolyte, choice of catalyst and electrode architecture. The onset of borate precipitation is offset by diffusion of water created by the osmotic pressure between anode and cathode.The direct liquid/liquid system has the potential to be a “2V” system if the pH of the hydrogen peroxide catholyte is maintained at a pH<1. In order to make this a viable system for Naval applications, the amount of acid used in the catholyte to establish the desired pH needs to be minimized. The key enabling technology is the development of a suitable anion exchange membrane. The characteristics of the anion membrane are: 1) conduct hydroxides generated at the cathode to the anode in order to minimize its concentration buildup in the catholyte solution and to maintain the desired pH.<1, 2) minimize hydrogen peroxide cross-over and 3) afford high ionic conductivity.Efforts are currently underway to improve the understanding of the reaction mechanism of borohydride at the catalyst surface and to identify membranes with higher ionic conductivity. These efforts have been identified as critical paths for the successful development of a liquid/liquid borohydride/hydrogen peroxide fuel cell.

The labeling of proteins and LDL with 99mTc: a new direct method employing KBH 4 and stannous chloride

A new direct labeling technique for proteins with technetium-99m ( 99mTc) has been developed and makes use of borohydride and stannous chloride. The method is simple and reproducible and gives a high labeling efficiency and high retention of biological activity for proteins, including polyclonal immunoglobulin (Ig), antifibrin monoclonal antibody, tissue type plasminogen activator, fibrinogen and low density lipoprotein (LDL). This method can be used in kit-format and takes about 20 min preparation time at room temperature. Both in vitro and in vivo studies indicate good stability of the label. In vivo, mice and rabbit images show significant accumulation of 99mTc-Ig at an inflammation area, 99mTc-antifibrin at a thrombus site and 99mTc-LDL in atherosclerotic lesions. The method is attractive for routine research and clinical purposes.

L-iduronic acid, a major constituent of heparin

Heparin has been degraded by a sequence of several reactions to give as the major identifiable products, 1,6-anhydro- l-idopyranose ( 2) and 2,5-anhydro- d-mannitol ( 3), these products being attributed originally to l-idosyluronic acid and the 2-amino-2-deoxy- d-glucopyranosyl residues, respectively. Products such as methyl α- d-glucopyranoside ( 4), derivable from d-glucosyluronic acid residues, were relatively minor, the ratio of 2 to 3 to 4 being approximately 5:5:1. These findings are supported by periodate-oxidation experiments, which have led to the detection of threitol (5 parts) and erythritol (1 part). The latter results show also that the l-idosyluronic (as well as the d-glucosyluronic) acid residues are substituted at position 4, and other evidence indicates that a hexosaminyl residue frequently is the 4-substituent. By reducing carboxyl groups of heparin (as methyl esters) with borohydride in tritiated water, evidence has been obtained to indicate that little, if any, of 2 is derived through isomerization of d-glucosyluronic acid residues. By contrast, and as required by the above information, the use of borohydride- t affords isotopically labelled 2. It is suggested that the presence of l-idosyluronic acid residues as major components of heparin helps to explain what heretofore has been regarded as an anomalously low positive rotation for the polymer.