scholarly journals Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

Biosensors ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Christopher J. Freeman ◽  
Borkat Ullah ◽  
Md. Shafiul Islam ◽  
Maryanne M. Collinson
Keyword(s):  
Ascorbic Acid ◽  
Uric Acid ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Nanoporous Gold ◽  
Redox Potentials ◽  
Biologically Relevant ◽  
Redox Sensing ◽  
Redox Molecules

Potentiometric redox sensing is a relatively inexpensive and passive approach to evaluate the overall redox state of complex biological and environmental solutions. The ability to make such measurements in ultra-small volumes using high surface area, nanoporous electrodes is of particular importance as such electrodes can improve the rates of electron transfer and reduce the effects of biofouling on the electrochemical signal. This work focuses on the fabrication of miniaturized nanoporous gold (NPG) electrodes with a high surface area and a small footprint for the potentiometric redox sensing of three biologically relevant redox molecules (ascorbic acid, uric acid, and cysteine) in microliter volumes. The NPG electrodes were inexpensively made by attaching a nanoporous gold leaf prepared by dealloying 12K gold in nitric acid to a modified glass capillary (1.5 mm id) and establishing an electrode connection with copper tape. The surface area of the electrodes was ~1.5 cm2, providing a roughness factor of ~16 relative to the geometric area of 0.09 cm2. Scanning electron microscopy confirmed the nanoporous framework. A linear dependence between the open-circuit potential (OCP) and the logarithm of concentration (e.g., Nernstian-like behavior) was obtained for all three redox molecules in 100 μL buffered solutions. As a first step towards understanding a real system, the response associated with changing the concentration of one redox species in the presence of the other two was examined. These results show that at NPG, the redox potential of a solution containing biologically relevant concentrations of ascorbic acid, uric acid, and cysteine is strongly influenced by ascorbic acid. Such information is important for the measurement of redox potentials in complex biological solutions.

Fabrication of Ag/ZnO Nanoparticles Using Ascorbic Acid as Reducing Agent

2016 ◽  
Vol 1133 ◽  
pp. 462-466 ◽  
Author(s):  
Jeyashelly Andas ◽  
Nor Wahida Subri
Keyword(s):  
Ascorbic Acid ◽  
Surface Area ◽  
Zno Nanoparticles ◽  
High Surface ◽  
High Surface Area ◽  
Absorption Spectrometry ◽  
Average Diameter ◽  
Reducing Agent ◽  
Bet Surface Area ◽  
Simple Method

High surface area Ag/ZnO with an average diameter of 13.95 nm was successfully synthesized through a facile route, using ascorbic acid and silica rice husk as reducing agent and amorphous support respectively. This nanomaterial was characterized by transmission electron microscopy, N2 adsorption-desorption, atomic absorption spectrometry and particle size analyzer. This simple method resulted in the production of almost spherical Ag/ZnO nanoparticles with high BET surface area and large pore volume of 341.46 m2g-1 and 0.59 cm3g-1 respectively. This preliminary study revealed the successful inclusion of metal cations into the silica framework without damaging the mesoporosity nature of silica.

scholarly journals Nanoporous Gold Electrodes and Their Applications in Analytical Chemistry

2013 ◽  
Vol 2013 ◽  
pp. 1-21 ◽  
Author(s):  
Maryanne M. Collinson
Keyword(s):  
Analytical Chemistry ◽  
Surface Area ◽  
Chemical Sensors ◽  
High Surface ◽  
High Surface Area ◽  
Pore Network ◽  
Nanoporous Gold ◽  
Dna Sensors ◽  
Porous Framework ◽  
Surface Areas

Nanoporous gold prepared by dealloying Au:Ag alloys has recently become an attractive material in the field of analytical chemistry. This conductive material has an open, 3D porous framework consisting of nanosized pores and ligaments with surface areas that are 10s to 100s of times larger than planar gold of an equivalent geometric area. The high surface area coupled with an open pore network makes nanoporous gold an ideal support for the development of chemical sensors. Important attributes include conductivity, high surface area, ease of preparation and modification, tunable pore size, and a bicontinuous open pore network. In this paper, the fabrication, characterization, and applications of nanoporous gold in chemical sensing are reviewed specifically as they relate to the development of immunosensors, enzyme-based biosensors, DNA sensors, Raman sensors, and small molecule sensors.

scholarly journals Morphological evolution of Pt-modified nanoporous gold after thermal coarsening in reductive and oxidative environments

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
A. A. El-Zoka ◽  
B. Langelier ◽  
G. A. Botton ◽  
R. C. Newman
Keyword(s):  
Surface Area ◽  
Morphological Evolution ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Atom Probe ◽  
Nanoporous Gold ◽  
Atomic Scale ◽  
Thermal Coarsening

AbstractNanoporous gold made by dealloying AgAuPt (NPG-Pt) has been shown to exhibit several interesting catalytic properties, tied to its exceptionally high surface area; however, structural degradation may occur owing to thermal coarsening. To understand the effect of atmosphere chemistry on thermal coarsening and degradation, and means of limiting it, this study focuses on the high-resolution characterization of NPG-Pt layers coarsened in reductive Ar-H2 atmosphere, and in oxidative air. Atom probe tomography (APT) analysis is performed on NPG-Pt, coarsened separately in either Ar-H2 or air, to characterize the atomic-scale chemical changes in the nanoligaments and to develop a mechanistic view of the inherent processes. A tendency of Ag to segregate to the surface during coarsening is found to lead to complete elimination of the nanoligament core-shell structures in both cases. Large Pt segregates form during coarsening in Ar-H2, but under the surface of the ligaments, having relatively little effect on the coarsening rate. The oxygen-induced segregation of Pt was observed to cause the inhibition of thermal coarsening after minor loss in surface area-to-volume ratio. Findings in this paper help in understanding further the thermal coarsening of heterogeneous nanomaterials made by dealloying, and the pertinent factors that come into play in different chemical environments.

scholarly journals Modified Polyaniline Nanofibres for Ascorbic Acid Detection

2011 ◽  
Vol 1312 ◽  
Author(s):  
Larisa Florea ◽  
Emer Lahiff ◽  
Dermot Diamond
Keyword(s):  
Ascorbic Acid ◽  
Carboxylic Acid ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Redox States ◽  
Sensing Applications ◽  
Ph Range ◽  
Surface Modified ◽  
Ascorbic Acid Detection

ABSTRACTPolyaniline nanofibres (PAni) can be surface modified to improve electroactivity over a broader pH range. The technique we describe here can be used to attach carboxylic acid terminated substituents. Modified nanofibres maintain their high surface area, and ability to switch between different redox states. These properties make the material suitable for sensing applications. Unlike unmodified PAni, the functionalised material is self-doping and hence more stable in higher pH solutions. Here we demonstrate how modified PAni fibres can be used for the detection of ascorbic acid.

scholarly journals Nanoporous gold assemblies of calixarene-phosphine-capped colloids

2017 ◽  
Vol 53 (79) ◽  
pp. 10870-10873 ◽  
Author(s):  
Christian Schöttle ◽  
Ezra L. Clark ◽  
Audrey Harker ◽  
Andrew Solovyov ◽  
Alexis T. Bell ◽  
...  
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Nanoporous Gold

Synthesis of high surface-area colloidal assemblies of calixarene-phosphine-capped nanoporous gold with a remarkably high surface-to-volume ratio is reported.

scholarly journals An easily modified method using FeCl3 to synthesize nanoporous gold with a high surface area

RSC Advances ◽  
2017 ◽  
Vol 7 (30) ◽  
pp. 18327-18332 ◽  
Author(s):  
Kenan Shao ◽  
Chun Fang ◽  
Yinfang Yao ◽  
Canyun Zhao ◽  
Zhi Yang ◽  
...  
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Nanoporous Gold ◽  
Modified Method

Illustration of the dealloying of nanoporous gold using FeCl3.

Cobalt ferrite (CoFe2O4) nanoparticles (size: ∼10 nm) with high surface area for selective non-enzymatic detection of uric acid with excellent sensitivity and stability

RSC Advances ◽  
2016 ◽  
Vol 6 (64) ◽  
pp. 59457-59467 ◽  
Author(s):  
Chumki Charan ◽  
Vinod K. Shahi
Keyword(s):  
Uric Acid ◽  
Surface Area ◽  
Cobalt Ferrite ◽  
High Surface ◽  
High Surface Area ◽  
Cofe2o4 Nanoparticles ◽  
Enzymatic Detection ◽  
Uric Acid Biosensor

A high surface area CoFe2O4 nanoparticle based non-enzymatic uric acid biosensor with excellent sensitivity, selectivity and LOD.

Tenacious Mass Transfer Limitations Drive Catalytic Selectivity during Electrochemical Carbon Dioxide Reduction

2019 ◽  
Author(s):  
Kailun Yang ◽  
Recep Kas ◽  
Wilson A. Smith
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Layer ◽  
Active Surface ◽  
Active Surface Area ◽  
High Concentration ◽  
Copper Electrodes ◽  
Surface Enhanced ◽  
Local Current

<p>This study evaluated the performance of the commonly used strong buffer electrolytes, i.e. phosphate buffers, during CO<sub>2</sub> electroreduction in neutral pH conditions by using in-situ surface enhanced infrared absorption spectroscopy (SEIRAS). Unfortunately, the buffers break down a lot faster than anticipated which has serious implications on many studies in the literature such as selectivity and kinetic analysis of the electrocatalysts. Increasing electrolyte concentration, surprisingly, did not extend the potential window of the phosphate buffers due to dramatic increase in hydrogen evolution reaction. Even high concentration phosphate buffers (1 M) break down within the potentials (-1 V vs RHE) where hydrocarbons are formed on copper electrodes. We have extended the discussion to high surface area electrodes by evaluating electrodes composed of copper nanowires. We would like highlight that it is not possible to cope with high local current densities on these high surface area electrodes by using high buffer capacity solutions and the CO<sub>2</sub> electrocatalysts are needed to be evaluated by casting thin nanoparticle films onto inert substrates as commonly employed in fuel cell reactions and up to now scarcely employed in CO<sub>2</sub> electroreduction. In addition, we underscore that normalization of the electrocatalytic activity to the electrochemical active surface area is not the ultimate solution due to concentration gradient along the catalyst layer.This will “underestimate” the activity of high surface electrocatalyst and the degree of underestimation will depend on the thickness, porosity and morphology of the catalyst layer. </p> <p> </p>

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