Plasmonic Imaging of Electrochemical Reactions at Individual Prussian Blue Nanoparticles

Prussian blue is an iron-cyanide-based pigment steadily becoming a widely used electrochemical sensor in detecting hydrogen peroxide at low concentration levels. Prussian blue nanoparticles (PBNPs) have been extensively studied using traditional ensemble methods, which only provide averaged information. Investigating PBNPs at a single entity level is paramount for correlating the electrochemical activities to particle structures and will shed light on the major factors governing the catalyst activity of these nanoparticles. Here we report on using plasmonic electrochemical microscopy (PEM) to study the electrochemistry of PBNPs at the individual nanoparticle level. First, two types of PBNPs were synthesized; type I synthesized with double precursors method and type II synthesized with polyvinylpyrrolidone (PVP) assisted single precursor method. Second, both PBNPs types were compared on their electrochemical reduction to form Prussian white, and the effect from the different particle structures was investigated. Type I PBNPs provided better PEM sensitivity and were used to study the catalytic reduction of hydrogen peroxide. Progressively decreasing plasmonic signals with respect to increasing hydrogen peroxide concentration were observed, demonstrating the capability of sensing hydrogen peroxide at a single nanoparticle level utilizing this optical imaging technique.

Effect of drying, composing and pelletizing of biowaste-based digestates on providing water soluble nutrients and stabilizing iron-cyanide (Fe-CN) complexes

<p>With recent policy developments under the German Renewable Energies Law (Erneuerbare‐Energien‐Gesetz, EEG) and the German Waste and Recycling Law (Kreislaufwirtschaftsgesetz, KrWG) increase in organic waste utilization is expected, which can be utilized for the waste sites restoration. We present a novel application of organic amendments to reduce the mobility of iron‐cyanide (Fe‐CN) complexes and simultaneously promote vegetation. Two batches of digestates from anaerobic treatment of separately collected municipal organic waste in a two-stage semi scale biogas plant have been conditioned by a) drying, b) composting and c) pelletisation. To evaluate the influence of post-treatment of digestates on nutrient and carbon release and contaminants sorption, two batch experiments were conducted, using I) deionized water and II) potassium hexacyanoferrate (II) solution. Batch experiment I resulted in a considerably higher nutrient and carbon elution from dried digestates. Batch experiment II revealed the highest significant tot. CN conc. reduction using not composted, air dried (100%) and oven dried (82%) biowaste digestates. The FTIR analysis of dried and mortared digestate materials indicated Fe-CN complexation on inorganic (K2Mn[FeII(CN)6], NH4Fe[FeII(CN)6]) and organic constituents, and possibly formation of nitriles. In terms of rapid soil fertility enhancement and feasibility to decrease Fe-CN complexes mobility, air and oven dried fresh biowaste digestates revealed the highest efficiency.</p>

Preparation of 15N-labeled Potassium Ferrocyanide for Tracer Studies

Isotopic labels are widely used to trace the fate and cycling of common environmental contaminants. Many of the labeled materials are not available commercially and, depending on the complexity of the substance, the label and the enrichment level, custom syntheses are costly. A simple, straightforward, and cost effective method for the preparation of a highly enriched, 15N-labeled potassium ferrocyanide (K4[Fe(C15N)6]*3H2O) has been developed to meet the requirements of related tracer experiments and minimize their costs. In this case, the 15N label was used to quantify iron cyanide detoxification (biodegradation and/or transformation) within soil-plant-systems. 15N-labeled potassium cyanide (KC15N) and a ferrous iron salt have been used for the synthesis. Extensive qualitative and quantitative analyses showed a product, entirely identical in its functional and elemental components to commercial non-labeled K4[Fe(CN)6]*3H2O and in its 15N enrichment to the KC15N used for its synthesis. To investigate their behavior and fate in various environmental compartments, other labeled iron or metal cyanide complexes might be synthesized in analogous manner.