Formation of Cobalt Nanoparticles from Co(OH)2 Suspension

2014 ◽  
Vol 974 ◽  
pp. 50-54
Author(s):  
Mary Donnabelle L. Balela ◽  
Shunsuke Yagi ◽  
Eiichiro Matsubara
Keyword(s):  
Room Temperature ◽  
Electroless Deposition ◽  
Reduction Potential ◽  
Particle Diameter ◽  
Mixed Potential ◽  
Potential Measurement ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Co Nanoparticles

Metallic cobalt (Co) nanoparticles with mean diameters in the range of 50-500 nm are formed by electroless deposition at room temperature in the presence of increasing concentration of NaOH. Co deposition was investigated by in situ mixed potential measurement. Increasing concentration of NaOH shifts the mixed potential negatively, leading to faster Co deposition and smaller apparent particle diameter. The decrease in mixed potential with increasing NaOH concentration is attributed to the decrease in the activity of Co2+ aquo ions in equilibrium with Co (OH)2. Consenquently, the oxidation-reduction potential of Co (II)/Co redox pair is reduced. This leads to more negative mixed potential.

Electroless Deposition of Nickel Nanoparticles at Room Temperature

2014 ◽  
Vol 974 ◽  
pp. 107-111 ◽  
Author(s):  
Mary Donnabelle L. Balela ◽  
Shunsuke Yagi ◽  
Eiichiro Matsubara
Keyword(s):  
Electroless Deposition ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Metallic Nickel ◽  
Mixed Potential ◽  
Ni Nanoparticles ◽  
Potential Measurement ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Reaction Solution

Metallic nickel (Ni) nanoparticles with a mean diameter of about 70 nm are successfully formed by electroless deposition in an aqueous solution at 273 K. The formation of Ni nanoparticles is investigated by in situ mixed potential measurement in combination with thermodynamic calculation. The deposition rate of Ni is measured using an electrochemical quartz crystal microbalance (EQCM). The mixed potential of reaction solution drastically decreases below the oxidation-reduction potential of Ni (II)/Ni redox pair at about-0.60 v vs SHE after 30 min reaction. This coincides with a sharp increase in the deposited mass, suggesting Ni deposition.

scholarly journals In situ measurements of oxidation–reduction potential and hydrogen peroxide concentration as tools for revealing LPMO inactivation during enzymatic saccharification of cellulose

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Adnan Kadić ◽  
Anikó Várnai ◽  
Vincent G. H. Eijsink ◽  
Svein Jarle Horn ◽  
Gunnar Lidén
Keyword(s):  
Reduction Potential ◽  
Enzymatic Saccharification ◽  
The State ◽  
Enzyme Inactivation ◽  
Ex Situ ◽  
Process Economics ◽  
Complete Inactivation ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

Abstract Background Biochemical conversion of lignocellulosic biomass to simple sugars at commercial scale is hampered by the high cost of saccharifying enzymes. Lytic polysaccharide monooxygenases (LPMOs) may hold the key to overcome economic barriers. Recent studies have shown that controlled activation of LPMOs by a continuous H2O2 supply can boost saccharification yields, while overdosing H2O2 may lead to enzyme inactivation and reduce overall sugar yields. While following LPMO action by ex situ analysis of LPMO products confirms enzyme inactivation, currently no preventive measures are available to intervene before complete inactivation. Results Here, we carried out enzymatic saccharification of the model cellulose Avicel with an LPMO-containing enzyme preparation (Cellic CTec3) and H2O2 feed at 1 L bioreactor scale and followed the oxidation–reduction potential and H2O2 concentration in situ with corresponding electrode probes. The rate of oxidation of the reductant as well as the estimation of the amount of H2O2 consumed by LPMOs indicate that, in addition to oxidative depolymerization of cellulose, LPMOs consume H2O2 in a futile non-catalytic cycle, and that inactivation of LPMOs happens gradually and starts long before the accumulation of LPMO-generated oxidative products comes to a halt. Conclusion Our results indicate that, in this model system, the collapse of the LPMO-catalyzed reaction may be predicted by the rate of oxidation of the reductant, the accumulation of H2O2 in the reactor or, indirectly, by a clear increase in the oxidation–reduction potential. Being able to monitor the state of the LPMO activity in situ may help maximizing the benefit of LPMO action during saccharification. Overcoming enzyme inactivation could allow improving overall saccharification yields beyond the state of the art while lowering LPMO and, potentially, cellulase loads, both of which would have beneficial consequences on process economics.

Effect of PVP on the Morphology and Growth of Cu Hierarchical Nanostructures Prepared by Electroless Deposition

2019 ◽  
Vol 821 ◽  
pp. 183-188
Author(s):  
Mary Donnabelle L. Balela ◽  
Vina Ingrid Cabiles
Keyword(s):  
Electroless Deposition ◽  
Reduction Rate ◽  
Particle Diameter ◽  
The Other ◽  
Mixed Potential ◽  
Cu Nanoparticles ◽  
Structure Directing Agent ◽  
Hierarchical Nanostructures ◽  
Mean Particle Diameter

Octahedral Cu hierarchical nanostructures were prepared by electroless deposition in aqueous solution at 80 °C. Polyvinyl pyrrolidone (PVP) was employed as the protective and structure directing agent to prevent oxidation and agglomeration of the Cu products. Addition of higher amounts of PVP (about 1.275 g) resulted in smaller but irregularly-shaped Cu nanoparticles. The Cu nanoparticles have a mean particle diameter of about 200 nm with excellent size distribution. On the other hand, Cu octahedrals were produced when 0.425 to 0.850 g PVP was used. In situ mixed potential monitoring of the solution during electroless deposition revealed that the mixed potential was more positive at larger amounts of PVP. This can be attributed to slower reduction rate due to the decrease in the activity of Cu(II) ions. Consequently, smaller Cu nanoparticles were produced.

Effects of oxidation reduction potential in the bypass micro-aerobic sludge zone on sludge reduction for a modified oxic–settling–anaerobic process

2014 ◽  
Vol 69 (10) ◽  
pp. 2139-2146 ◽  
Author(s):  
Kexun Li ◽  
Yi Wang ◽  
Zhongpin Zhang ◽  
Dongfang Liu
Keyword(s):  
Reduction Potential ◽  
Particle Diameter ◽  
Sludge Reduction ◽  
Anaerobic Process ◽  
Aeration Time ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Median Particle Diameter ◽  
Specific Oxygen Uptake Rate ◽  
Aerobic Sludge

Batch experiments were conducted to determine the effect of oxidation reduction potential (ORP) on sludge reduction in a bypass micro-aerobic sludge reduction system. The system was composed of a modified oxic–settling–anaerobic process with a sludge holding tank in the sludge recycle loop. The ORPs in the micro-aerobic tanks were set at approximately +350, −90, −150, −200 and −250 mV, by varying the length of aeration time for the tanks. The results show that lower ORP result in greater sludge volume reduction, and the sludge production was reduced by 60% at the lowest ORP. In addition, low ORP caused extracellular polymer substances dissociation and slightly reduced sludge activity. Comparing the sludge backflow characteristics of the micro-aerobic tank's ORP controlled at −250 mV with that of +350 mV, the average soluble chemical oxygen (SCOD), TN and TP increased by 7, 0.4 and 2 times, median particle diameter decreased by 8.5 μm and the specific oxygen uptake rate (SOUR) decreased by 0.0043 milligram O2 per gram suspended solids per minute. For the effluent, SCOD and TN and TP fluctuated around 30, 8.7 and 0.66 mg/L, respectively. Therefore, the effective assignment of ORP in the micro-aerobic tank can remarkably reduce sludge volume and does not affect final effluent quality.

Sign in / Sign up

Export Citation Format

Share Document