scholarly journals Voltammetric Detection of Caffeine in Beverages at Nafion/Graphite Nanoplatelets Layer-by-Layer Films

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 221 ◽  
Author(s):  
Sandra Hernandez-Aldave ◽  
Afshin Tarat ◽  
James D. McGettrick ◽  
Paolo Bertoncello
Keyword(s):  
Thin Films ◽  
Hydrogen Bonding ◽  
Hydrophobic Interactions ◽  
Carbon Electrodes ◽  
Layer By Layer ◽  
Graphite Nanoplatelets ◽  
Glassy Carbon Electrodes ◽  
X Ray ◽  
Voltammetric Detection ◽  
Lbl Films

We report for the first time a procedure in which Nafion/Graphite nanoplatelets (GNPs) thin films are fabricated using a modified layer-by-layer (LbL) method. The method consists of dipping a substrate (quartz and/or glassy carbon electrodes) into a composite solution made of Nafion and GNPs dissolved together in ethanol, followed by washing steps in water. This procedure allowed the fabrication of multilayer films of (Nafion/GNPs)n by means of hydrogen bonding and hydrophobic‒hydrophobic interactions between Nafion, GNPs, and the corresponding solid substrate. The average thickness of each layer evaluated using profilometer corresponds to ca. 50 nm. The as-prepared Nafion/GNPs LbL films were characterized using various spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), FTIR, and optical microscopy. This characterization highlights the presence of oxygen functionalities that support a mechanism of self-assembly via hydrogen bonding interactions, along with hydrophobic interactions between the carbon groups of GNPs and the Teflon-like (carbon‒fluorine backbone) of Nafion. We showed that Nafion/GNPs LbL films can be deposited onto glassy carbon electrodes and utilized for the voltammetric detection of caffeine in beverages. The results showed that Nafion/GNPs LbL films can achieve a limit of detection for caffeine (LoD) of 0.032 μM and linear range between 20‒250 μM using differential pulse voltammetry, whereas, using cyclic voltammetry LoD and linear range were found to be 24 μM and 50‒5000 μM, respectively. Voltammetric detection of caffeine in beverages showed good agreement between the values found experimentally and those reported by the beverage producers. The values found are also in agreement with those obtained using a standard spectrophotometric method. The proposed method is appealing because it allows the fabrication of Nafion/GNPs thin films in a simple fashion using a single-step procedure, rather than using composite solutions with opposite electrostatic charge, and also allows the detection of caffeine in beverages without any pre-treatment or dilution of the real samples. The proposed method is characterized by a fast response time without apparent interference, and the results were competitive with those obtained with other materials reported in the literature.

Selective Hydrogen Bonding Controls Temperature Response of Layer-by-Layer Upper Critical Solution Temperature Micellar Assemblies

Soft Matter ◽  
2021 ◽  
Author(s):  
Aliaksei Aliakseyeu ◽  
Victoria Albright ◽  
Danielle Yarbrough ◽  
Samantha Hernandez ◽  
Qing Zhou ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Methacrylic Acid ◽  
Temperature Response ◽  
Solution Temperature ◽  
Layer By Layer ◽  
Critical Solution Temperature ◽  
Hydrogen Bonding Interactions ◽  
Upper Critical Solution Temperature ◽  
Lbl Films

This work establishes a correlation between the selectivity of hydrogen-bonding interactions and the functionality of micelle-containing layer-by-layer (LbL) assemblies. Specifically, we explore LbL films formed by assembly of poly(methacrylic acid)...

scholarly journals Voltammetric Detection of Oxalic Acid by Using Glassy Carbon Electrodes with Covalently Attached Nitrogen-containing Functional Groups

2015 ◽  
Vol 31 (7) ◽  
pp. 733-735 ◽  
Author(s):  
Hiroaki MATSUURA ◽  
Syuhei AKABE ◽  
Tsubasa KITAMURA ◽  
Takuto TAKAHASHI ◽  
Shunichi UCHIYAMA
Keyword(s):  
Oxalic Acid ◽  
Functional Groups ◽  
Glassy Carbon ◽  
Carbon Electrodes ◽  
Glassy Carbon Electrodes ◽  
Voltammetric Detection

scholarly journals Non-invasive Electrochemical Detection of Glucose using CuO-NiO/MXene Modified Electrode

2020 ◽  
Author(s):  
Alaa Mohamed Elsafi ◽  
Vinotha Krishnasamy ◽  
Karthik Kannan ◽  
John-John Cabibihan ◽  
Abdulaziz Khalid AlAli ◽  
...  
Keyword(s):  
Morphological Analysis ◽  
High Selectivity ◽  
Proton Conductor ◽  
Carbon Electrodes ◽  
Electrochemical Studies ◽  
X Ray Diffraction ◽  
Characterization Methods ◽  
Glassy Carbon Electrodes ◽  
X Ray ◽  
Non Invasive

High levels of glucose or acetone in breath confirms diabetes disease. One of the analytical devices that detect changes in breath is the electrochemical sensor having high selectivity, easy to use and being able to meet diabetic patient’s needs. In this study, sensors were made by fabricating metal oxide coated glassy carbon electrodes and using nafion as a proton conductor. Characterization methods such as X-ray diffraction, FTIR and morphological analysis have been performed for metal oxides to characterize their atomic arrangement and composition. In addition, electrochemical studies were done using Gamry instrument and curves plotted as current in amperes versus voltage to test the coated electrodes conductivity. High selectivity sensors provide promising applications in any field.

Growth of CaFeOX/LaFeO3 Superlattice on SrTiO3(100) Substrates

2011 ◽  
Vol 1292 ◽  
Author(s):  
Nobuyuki Iwata ◽  
Mark Huijben ◽  
Guus Rijnders ◽  
Hiroshi Yamamoto ◽  
Dave H. A. Blank
Keyword(s):  
Thin Films ◽  
Pulsed Laser Deposition ◽  
Pulsed Laser ◽  
Layer Growth ◽  
Laser Deposition ◽  
Growth Mode ◽  
Layer By Layer ◽  
X Ray Diffraction ◽  
Reciprocal Space Mapping ◽  
X Ray

ABSTRACTThe CaFeOX(CFO) and LaFeO3(LFO) thin films as well as superlattices were fabricated on SrTiO3(100) substrates by pulsed laser deposition (PLD) method. The tetragonal LFO film grew with layer-by-layer growth mode until approximately 40 layers. In the case of CFO, initial three layers showed layer-by-layer growth, and afterward the growth mode was transferred to two layers-by-two layers (TLTL) growth mode. The RHEED oscillation was observed until the end of the growth, approximately 50nm. Orthorhombic twin CaFeO2.5 (CFO2.5) structure was obtained. However, it is expected that the initial three CFO layers are CaFeO3 (CFO3) with the valence of Fe4+. The CFO and LFO superlattice showed a step-terraces surface, and the superlattice satellite peaks in a 2θ-θ and reciprocal space mapping (RSM) x-ray diffraction (XRD) measurements, indicating that the clear interfaces were fabricated.

scholarly journals Hydrophilic and hydrophobic interactions in concentrated aqueous imidazole solutions: a neutron diffraction and total X-ray scattering study

2020 ◽  
Vol 22 (9) ◽  
pp. 5105-5113
Author(s):  
Laila H. Al-Madhagi ◽  
Samantha K. Callear ◽  
Sven L. M. Schroeder
Keyword(s):  
Hydrogen Bonding ◽  
Neutron Diffraction ◽  
Hydrophobic Interactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Ray Scattering

A study of 5 M aqueous imidazole solutions combining neutron and X-ray diffraction with EPSR simulations shows dominance of hydrogen-bonding between imidazole and water and negligible hydrogen-bonding between imidazole molecules.

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