Mechanistic aspects of hydrazine-induced Pt colloid instability and monitoring aggregation kinetics with nanoparticle impact electroanalysis

2016 ◽  
Vol 193 ◽  
pp. 293-312 ◽  
Author(s):  
D. A. Robinson ◽  
J. Duay ◽  
A. M. Kondajji ◽  
K. J. Stevenson
Keyword(s):  
Colloidal Stability ◽  
Catalytic Decomposition ◽  
Dlvo Theory ◽  
Open Circuit ◽  
General Mechanism ◽  
Layer Potential ◽  
Ph Buffer ◽  
The Stability ◽  
Citrate Capping ◽  
Exceptional Stability

Here we investigate the mechanistic aspects of Pt nanoparticle (NP) aggregation in solutions typically used for detecting NP/electrode impacts by electrocatalytic amplification (ECA). We previously proposed a general mechanism for Pt colloid destabilization that involved the participation of both the hydrazine redox probe and the pH buffer species as coagulants. Herein the Pt NP coagulation and aggregation mechanisms were further investigated with microscopic kinetic NP concentration monitoring and zeta potential measurements using nanoparticle tracking analysis (NTA), as well as open circuit potential experiments with a citrate-treated polycrystalline Pt surface to assess electrical double layer potential. After considering the combined results of these experiments we propose that the colloidal stability of citrate-capped platinum nanoparticles involves much more than the typical physicochemical interactions predicted by DLVO theory. A structure based on intermolecular H-bonding in the citrate capping layer is the most plausible explanation for the exceptional stability of large Pt NPs in high ionic strength buffers. Thus, the mechanism of Pt NP aggregation includes specific reactive contributions from hydrazine. The catalytic decomposition of hydrazine, in particular, is thought to occur to some extent at the citrate-coated Pt surface while the citrate remains adsorbed. Evolved gases such as ammonia and possible surface bound intermediates from Pt-catalyzed decomposition of hydrazine may disrupt the stability of the citrate layer, causing colloidal instability and thus promoting Pt NP coagulation. In the closing section, we demonstrate nanoparticle impact electroanalysis by ECA detection as a method to quantify Pt NP concentration with adequate time resolution for monitoring the kinetics of Pt NP coagulation.

scholarly journals Communication: On the Stability and Necessary Electrophoretic Mobility of Bare Oil Nanodroplets in Water

2020 ◽  
Author(s):  
Saranya Pullanchery ◽  
Sergey Kulik ◽  
halil okur ◽  
Hilton. B. de Aguiar ◽  
Sylvie Roke
Keyword(s):  
Electrophoretic Mobility ◽  
Dlvo Theory ◽  
Air Bubbles ◽  
Oil Droplets ◽  
Cleaning Procedure ◽  
Charged Droplets ◽  
Oil In Water ◽  
The Creation ◽  
The Stability ◽  
The 19Th Century

Hydrophobic oil droplets, particles and air bubbles can be dispersed in water as kinetically stabilized dispersions. It has been established since the 19th century that such objects harbor a negative electrostatic potential roughly twice larger than the thermal energy. The source of this charge continues to be one of the core observations in relation to hydrophobicity and its molecular explanation is still debated. What is clear though, is that the stabilizing interaction in these systems is understood in terms of electrostatic repulsion via DLVO theory. Recent work [Carpenter et al., PNAS 116 (2019) 9214] has added another element into the discussion, reporting the creation of bare near-zero charged droplets of oil in water that are stable for several days. Key to the creation of the droplets is a rigorous glassware cleaning procedure. Here, we investigate these conclusions and show that the cleaning procedure of glassware has no influence on the electrophoretic mobility of the droplets, that oil droplets with near-zero charge are unstable, and provide an alternative possible explanation for the observations involving glass surface chemistry.

scholarly journals Potentiometric Response of Ag/AgCl Chloride Sensors in Model Alkaline Medium

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Farhad Pargar ◽  
Hristo Kolev ◽  
Dessi A. Koleva ◽  
Klaas van Breugel
Keyword(s):  
Alkaline Medium ◽  
Open Circuit Potential ◽  
Dynamic Equilibrium ◽  
Chloride Concentration ◽  
Chloride Content ◽  
Cementitious Materials ◽  
Open Circuit ◽  
Potentiometric Response ◽  
Before And After ◽  
The Stability

The stability and reproducibility of an Ag/AgCl sensors’ response in an alkaline medium are important for the application of these sensors in cementitious materials. The sensors’ response, or their open circuit potential (OCP), reflects a dynamic equilibrium at the sensor/environment interface. The OCP response in an alkaline medium is affected by the presence of hydroxide ions. The interference of hydroxide ions leads to inaccuracies or a delay in the sensors’ response to a certain chloride content. In this article, the potentiometric response (or OCP evolution) of the chloride sensors is measured in model solutions, resembling the concrete pore water. The scatter of the sensors’ OCP is discussed with respect to the interference of hydroxide ions at varying chloride concentration in the medium. The deviation of the sensor’s response from its ideal performance (determined by the Nernst law) is attributed to dechlorination of the AgCl layer and the formation of Ag2O on the sensor’s surface. Results from the surface XPS analysis of the AgCl layer before and after treatment in alkaline medium confirm these observations in view of chemical transformation of AgCl to Ag2O.

Stability of a Class of Piezoelectric State-Switching Methods

2000 ◽  
Author(s):  
Andrew J. Kurdila ◽  
William W. Clark ◽  
Weijian Wang ◽  
Dwayne E. McDaniel
Keyword(s):  
Lyapunov Functions ◽  
Closed Loop ◽  
Control Strategies ◽  
Short Circuit ◽  
Open Circuit ◽  
Hybrid Dynamical Systems ◽  
Multiple Lyapunov Functions ◽  
Control Laws ◽  
State Switching ◽  
The Stability

Abstract Experimental and anecdotal evidences have shown that state-switched control strategies for piezoelectric actuators can be advantageous. However, most discussions of the stability of these systems has relied on heuristic, or physically motivated, arguments. In this paper, we show that recent open-circuit/short-circuit state-switching control laws can be viewed as hybrid dynamical systems of Witsenhausen type. Within this framework, the closed-loop stability of OC/SC switching is rigorously established using the method of multiple Lyapunov functions.

scholarly journals Effect of Ionic Compounds of Different Valences on the Stability of Titanium Oxide Colloids

2018 ◽  
Vol 2 (3) ◽  
pp. 32 ◽  
Author(s):  
Szabolcs Muráth ◽  
Szilárd Sáringer ◽  
Zoltán Somosi ◽  
István Szilágyi
Keyword(s):  
Titanium Oxide ◽  
Colloidal Stability ◽  
Heterogeneous Systems ◽  
Multivalent Ions ◽  
Aggregation Behaviour ◽  
Ionic Compounds ◽  
Oxide Particles ◽  
Synthetic Routes ◽  
The Stability

Titanium oxide particles of various morphologies have been prepared for applications of scientific or industrial interest in recent decades. Besides development of novel synthetic routes and solid-state characterization of the obtained particles, colloidal stability of titanium oxide dispersions was the focus of numerous research groups due to the high importance of this topic in applications in heterogeneous systems. The influence of dissolved ionic compounds, including monovalent salts, multivalent ions and polyelectrolytes, on the charging and aggregation behaviour of titanium oxide materials of spherical and elongated structures will be discussed in the present review.

Increase in Open-circuit Voltage and Improved Stability of Organic Solar Cells by Inserting a Molybdenum Trioxide Buffer Layer

2009 ◽  
Vol 1154 ◽  
Author(s):  
Hideyuki Murata ◽  
Yoshiki Kinoshita ◽  
Yoshihiro Kanai ◽  
Toshinori Matsushima ◽  
Yuya Ishii
Keyword(s):  
Solar Cells ◽  
Buffer Layer ◽  
Organic Solar Cells ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Type Material ◽  
Type Layer ◽  
Improved Stability ◽  
The Stability ◽  
P Type

AbstractWe report the increase in open-circuit voltage (Voc) by inserting of MoO3 layer on ITO substrate to improve built-in potential of organic solar cells (OSCs). In the OSCs using 5,10,15,20-tetraphenylporphyrine (H2TPP) as a p-type material and C60 as a n-type material, the Voc effectively increased from 0.57 to 0.97 V as increasing MoO3 thickness. The obtained highest Voc (0.97 V) is consistent with the theoretical value estimated from the energy difference between the LUMO (−4.50 eV) of C60 and the HOMO (−5.50 eV) of H2TPP layer. Importantly, the enhancement in the Voc was achieved without affecting the short-circuit current density (Jsc) and the fill-factor (FF). Thus, the power conversion efficiency of the device linearly increased from 1.24% to 1.88%. We also demonstrated that a MoO3 buffer layer enhances the stability of OSCs after photo-irradiation. We have investigated the stability of OSCs using H2TPP and N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine as a p-type layer. The both devices with MoO3 layer showed improved stability. These results clearly suggest that the interface at ITO/p-type layer affects the device stability.

scholarly journals Colloidal stability of (functionalised) fullerenes in the presence of dissolved organic carbon and electrolytes

2015 ◽  
Vol 2 (3) ◽  
pp. 280-287 ◽  
Author(s):  
Joris J.-H. Haftka ◽  
Patrick S. Bäuerlein ◽  
Erik Emke ◽  
Nienke Lammertse ◽  
Daria Belokhovstova ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Colloidal Stability ◽  
The Stability ◽  
Fullerene Clusters

Influence of various parameters on the stability and size of fullerene clusters is being investigated using DLS, MALS and flow cytometry.

scholarly journals Application of Ketone-Based Resins as Anticorrosive Coating

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Esma Sezer ◽  
Nilgün Kızılcan ◽  
Kerim Çoban
Keyword(s):  
Thin Film ◽  
Stainless Steel ◽  
Acidic Medium ◽  
Impedance Measurement ◽  
Metal Electrode ◽  
Open Circuit ◽  
Polymeric Coating ◽  
Anticorrosive Coating ◽  
The Stability ◽  
Ss 304

Effect of some newly synthesized modified ketonic resins on corrosion inhibition of stainless steel (SS) and copper (Cu) was investigated in acidic medium. Carboxyl, hydroxyl, and carbonyl functionalized resins have been coated on metal electrode as a thin film by dipping method. Corrosion characteristics of coating on SS (304 L) and Cu were investigated by polarization, open-circuit, and impedance measurement. These measurements performed at different time and the stability of polymeric coating were tested with time in acidic medium. The resin coating was able to protect both the SS and copper.

On the stability of alkali metal promoters in Co mixed oxides during direct NO catalytic decomposition

2017 ◽  
Vol 428 ◽  
pp. 33-40 ◽  
Author(s):  
K. Pacultová ◽  
V. Draštíková ◽  
Ž. Chromčáková ◽  
T. Bílková ◽  
K. Mamulová Kutláková ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Mixed Oxides ◽  
Catalytic Decomposition ◽  
The Stability

Hidden dimensions: the stability and structure of regional political cleavages in Poland

2000 ◽  
Vol 33 (3) ◽  
pp. 331-354 ◽  
Author(s):  
Tomasz Zarycki ◽  
Andrzej Nowak
Keyword(s):  
Survey Data ◽  
Spatial Data ◽  
Electoral Behavior ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Ecological Data ◽  
Surface Dimension ◽  
The Stability ◽  
Exceptional Stability ◽  
Political Scene

The main aim of this paper is to show that behind the complex and fluid surface dimension of the Polish political scene it is possible to reveal a relatively stable two-dimensional structure of deep political identities. The study is based on the analysis of ecological data — the results of elections from 1990 to 1997. The results prove the exceptional stability of the Polish electoral geography and appear to be consistent with other studies based mainly on the survey data. The use of the spatial data allowed us to reveal the historical and spatial determinants of electoral behavior in Poland.

Comparative Study of Structure and Pickling Characteristics of Oxide Scale Formed on Strips Produced by TSCR and Conventional Process

2011 ◽  
Vol 228-229 ◽  
pp. 77-82
Author(s):  
L. M. Zhu ◽  
J. H. Yang
Keyword(s):  
Oxide Scale ◽  
Open Circuit Potential ◽  
Steel Strip ◽  
Open Circuit ◽  
Conventional Process ◽  
Pickling Solution ◽  
Magnetite Fe3o4 ◽  
Structure Observation ◽  
The Stability ◽  
Hematite Fe2o3

The microstructure and pickling characteristics of oxide scale formed on hot-rolled SPHC steel strip produced by different processes were investigated based on structure observation, weight loss and corrosion potential measurements. The results show that the scale formed on strip produced by TSCR consists of mainly magnetite (Fe3O4) and little wustite (FeO), hematite (Fe2O3), and that in conventional process is composed mainly wustite (FeO) and little magnetite (Fe3O4), hematite (Fe2O3). The shape of the open-circuit potential transient is determined crucially by the oxide scale structure. Time to reach a steady-state value of open-circuit potential of strip produced by TSCR is longer than that in conventional process. Both the stability of the scale in pickling solution and the effectiveness of descaling could be evaluated and predicted by measuring the change of electrochemical potential during acid pickling.

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