Materials Chemistry Commons^™

Mathematical Expression And Quantitative Analysis Of Impedance Spectrum On The Interface Of Glassy Carbon Electrode, Lei Cheng, Pu-Xuan Yan, You-Jun Fan, Hua-Hong Zou, Hong Liang

Journal of Electrochemistry

Glassy carbon electrode (GCE) is a common basic electrode for various electrochemical sensors, and the detection properties are determined by its interfacial characteristics. In this paper, we established an equivalent circuit including electrolyte resistance (R_el), charge transport resistance (R_ct), diffusion impedance (R_di, C_di), electrochemical (oxidation/reduction) reaction impedance (R_R, C_R), surface adsorption impedance (R_ads , C_ads), double-layer capacitance (C_DL), and derived the mathematical expression for the equivalent circuit. The R_el and C_DL are contributed by inactive …

Preparation Of Modified Titanium Based Pbo2 Electrode And Its Rapid Detection Of Cod, Qi Sun, Yan-He Han, Xiao-Lu Fu

Journal of Electrochemistry

In the traditional Ti/β-PbO₂ electrode, the crystal lattice difference between β-PbO₂ and Ti matrix is large, and the prepared electrode is easy to fall off and has a short service life. It needs to be modified in actual use. Based on the advantages of α-PbO₂ material and Ag material in terms of adhesion and conductivity, respectively, the above two materials are selected as the intermediate layer of Ti/β-PbO₂ electrode to improve electrode performance. In this paper, by preparing Ti/α/β-PbO₂ and Ti/Ag/β-PbO₂ electrodes …

Fundamentals Of Electrochemical Impedance Spectroscopy For Macrohomogeneous Porous Electrodes, Xiang Li, Qiu-An Huang, Wei-Heng Li, Yu-Xuan Bai, Jia Wang, Yang Liu, Yu-Feng Zhao, Juan Wang, Jiu-Jun Zhang

Journal of Electrochemistry

Electrochemical impedance spectroscopy (EIS) can be used to diagnose charge transfer reactions and mass transport in porous electrodes. The charge transfer reactions include interfacial charge accumulation and charge conduction as well as electrochemical reaction. In this paper, the complex phasor method is developed under the macrohomogeneous assumption to build an impedance model of porous electrodes for clarifying several vague expressions in the traditional approaches. The following researches are carried out: (1) Identifying characteristic parameters for the porous electrodes, including electrode electronic conductivity σ₁, electrolyte ionic conductivity σ₂, interface charge transfer conductivity g_ct, unit area …

Hemoglobin-Modified Core–Shell Fe3o4@Au Nanostructures For The Electrochemical Detection Of Acrylamide, Endang Saepudin, Tri Yuliani, Mochammad Arfin Fardiansyah Nasution, Munawar Khalil, Jong Wook Hong, Tribidasari Anggraningrum Ivandini

Makara Journal of Science

In this study, electrochemical detection of acrylamide using hemoglobin (Hb)-modified core–shell Fe₃O₄@Au nanostructures was conducted. Fe₃O₄ nanoparticles (~4.9 nm) and core–shell Fe₃O₄@Au (5.0–6.4 nm) nanostructures were successfully synthesized by the thermal decomposition method. Electrochemical investigation revealed that the optimum amount of Hb of 2 mg/mL could be immobilized in 0.1 M acetate buffer solution (pH = 6). Moreover, the detection of acrylamide using Fe₃O₄@Au/Hb was evaluated by the cyclic voltammetry technique. A linear calibration curve (R² = 0.98) in the concentration range of …

Two-Dimensional Monolayer Salt Nanostructures Can Spontaneously Aggregate Rather Than Dissolve In Dilute Aqueous Solutions, Wenhui Zhao, Yunxiang Sun, Weiduo Zhu, Jian Jiang, Xiaorong Zhao, Dongdong Lin, Wenwu Xu, Xiangmei Duan, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

It is well known that NaCl salt crystals can easily dissolve in dilute aqueous solutions at room temperature. Herein, we reported the first computational evidence of a novel salt nucleation behavior at room temperature, i.e., the spontaneous formation of two-dimensional (2D) alkali chloride crystalline/non-crystalline nanostructures in dilute aqueous solution under nanoscale confinement. Microsecond-scale classical molecular dynamics (MD) simulations showed that NaCl or LiCl, initially fully dissolved in confined water, can spontaneously nucleate into 2D monolayer nanostructures with either ordered or disordered morphologies. Notably, the NaCl nanostructures exhibited a 2D crystalline square-unit pattern, whereas the LiCl nanostructures adopted non-crystalline 2D hexagonal …

Doping Of Conjugated Polymers: Preparation, Characterization And Device Fabrication, Kan Tang

Dissertations

Semiconducting conjugated polymers (CPs) as emerging materials for advanced electronic applications such as sensors, OPVs, and OEFTs has become an intriguing research topic in the past decades. It opens a new avenue of “flexible” electronics, which has shown great potential in next-generation electronic devices.

However, due to the nature of CP materials and related solution processing techniques, unlike almost perfectly crystalline silicon materials, CPs in the solid-state often exhibit much lower crystallinity if it is not complete amorphous, which severely hinder the electronic property and optical property of the materials. The crystallinity of CPs in a film is often uniquely …

Degumming Of Hemp Fibers Using Combined Microwave Energy And Deep Eutectic Solvent, Bulbul Ahmed

LSU Master's Theses

Hemp is considered as one of the sustainable agricultural fiber materials. Degumming or surface modification of hemp bast is needed to produce single fibers for ensuing textile and industrial applications. The traditional degumming process necessitates a high amount of alkali, which causes detrimental environmental pollution. This study offers a new method to degum hemp fibers with reduced use of harmful alkali and precious water resources. In this work, hemp bast fibers were degummed by using combined microwave energy and deep eutectic solvent (DES). The properties of hemp fibers manufactured by this method were investigated and compared with the traditional alkali …

Microfabrication And Electrochemical Characterization Of A Novel Su-8 Probe With An Array Of Individually Addressable Electrodes Suitable For Redox Cycling Experiments In Ultra-Small Volumes, Mahsa Lotfi Marchoubeh

Graduate Theses and Dissertations

Redox cycling is an electrochemical technique that utilizes closely spaced generator and collector electrodes to cycle reversible redox species between their oxidative states. With advantages in signal amplification, selectivity of species based on their electrochemical reaction mechanism, and limited or no background subtraction, this technique is well suited for selective detection of important electrochemically active molecules such as dopamine at basal or slowly changing levels.

Miniaturized medical devices have become an area of great interest for measurement of chemicals in limited volumes with low concentrations or in sensitive tissues. A probe on a polymeric SU-8 substrate with suitable dimensions and …

Multiple Wetting−Dewetting States Of A Water Droplet On Dual- Scale Hierarchical Structured Surfaces, Yurui Gao, Yuan Liu, Jian Jiang, Chongqin Zhu, Craig Zuhlke, Dennis Alexander, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Surfaces with microscale roughness can entail dualscale hierarchical structures such as the recently reported nano/ microstructured surfaces produced in the laboratory (Wang et al. Nature 2020, 582, 55−57). However, how the dual-scale hierarchical structured surface affects the apparent wetting/ dewetting states of a water droplet, and the transitions between the states are still largely unexplored. Here, we report a systematic large-scale molecular dynamics (MD) simulation study on the wetting/dewetting states of water droplets on various dual-scale nano/near-submicrometer structured surfaces. To this end, we devise slab-water/slab-substrate model systems with a variety of dual-scale surface structures and with different degrees of intrinsic …

Electrochemical Oxidation Of Individual Silver Nanoparticles: Exploring The Effect Of Particle Shape, Capping Ligand, Electrolyte, And Potential On The Signal, Jazlynn Sikes

Graduate Theses and Dissertations

Nanomaterials have revolutionized science and technology. Their unique properties can be exploited, and nanoparticles are being used as catalysts, antimicrobials, drug delivery vehicles, sensors, and more. However, the fundamental properties of nanomaterials and their interactions with their surrounding environments are still poorly understood. In this work, a single-particle approach was used to observe the effects of capping ligand, surrounding solution, and particle shape on the oxidative process to gain deeper understanding of silver nanoparticle properties. When allowed the opportunity, the particles will adsorb to the electrode surface then oxidize in rapid succession upon electrode activation, regardless of capping ligand as …

Luminol/Sulfamic Acid Electrochemiluminescence And Its Application For Dopamine Detection, Tesfaye Hailemariam Barkae, Mohamed Ibrahim Halawa, Tadesse Haile Fereja, Shimeles Addisu Kitte, Xian-Gui Ma, Ye-Quan Chen, Guo-Bao Xu

Journal of Electrochemistry

Herein, sulfamic acid (SA) was utilized, for the first time, to enhance significantly the luminol electrochemiluminescence (ECL). With the SA concentration increased from 0.1 μmol·L^-1 to 500 μmol·L^-1 the ECL intensity increased proportionally. The developed luminol/SA ECL system was employed to detect dopamine (DA) based on its prominent quenching effect. The Stern-Volmer equation of I_o/I= 1+K_sv[DA] could be applied to express well the quenching mechanism of DA in the luminol/SA ECL system. The calibration plot showed that the increase in the DA concentration from 0.5 to 20 μmol·L^-1 decreased linearly the ECL intensity …

Electrochemical Surface-Enhanced Raman Spectroscopic Studies On Nickel Ultramicroelectrode, Li-Wen Wu, Wei Wang, Yi-Fan Huang

Journal of Electrochemistry

Nickel (Ni) electrodes are widely used in electrochemical researches. Understanding electrochemical processes on Ni electrodes through in-situ characterization of adsorbed species on their surfaces is helpful for rational optimization and application of Ni electrochemistry. Microelectrochemical surface-enhanced Raman spectroscopy (μEC-SERS) combines the mass transfer feature of ultramicroelectrode with high-sensitivity characterizations of molecular structures, which is a powerful method for studying Ni electrochemistry on polarization and non-equilibrium conditions. The key point of performing μEC-SERS is to make a SERS-active Ni ultramicroelectrode.
Here, we demonstrate a method of preparing a SERS-active Ni ultramicroelectrode through electrochemical deposition of several atomic layers of …

Molecular Design Of Three-Dimensional Metal-Free A(Nh4)X3 Perovskites For Photovoltaic Applications, Jie Bie, Dai-Bei Yang, Ming-Gang Ju, Qiang Pan, Yu-Meng You, Wei Fa, Xiao Cheng Zeng, Shuang Chen

Xiao Cheng Zeng Publications

The intense research activities on the hybrid organic−inorganic perovskites (HOIPs) have led to the greatly improved light absorbers for solar cells with high power conversion efficiency (PCE). However, it is still challenging to find an alternative lead-free perovskite to replace the organohalide lead perovskites to achieve high PCE. This is because both previous experimental and theoretical investigations have shown that the Pb²⁺ cations play a dominating role in contributing the desirable frontier electronic bands of the HOIPs for light absorbing. Recent advances in the chemical synthesis of three-dimensional (3D) metal-free perovskites, by replacing Pb²⁺ with NH₄^{+ …}

Physicochemical Studies Of Triazolyl Benzoate Amphiphile And The Effects Of Different Glycolipids Towards Its Critical Micellar Concentration, Nurul Faiezin Zul

Student Works (2020-2029)

Basic molecular structure of natural fatty acids consisted of polar carboxylic acid headgroup (hydrophilic) connected to non-polar hydrocarbon tail (hydrophobic). However, the addition of a heteroaromatic as a linker between the regions and how they interact within the molecules in self-assembling structure were not well explored. The structure has inspired us to prepare and investigated a synthetic amphiphile constructed from the similar headgroup and alkyl chain but connected by triazolyl group, named as para-decyloxymethyl triazolyl benzoate (p-DMTB). The triazolyl was sufficiently produced from Copper(I)-catalyzed cycloaddition between 4-azidobenzoic acid and alkyl acetylene. Purity and molecular elucidation of the amphiphile were analyzed …

Combined Applications Of Photocurrent Spectroscopy, Photoluminescence Spectroscopy And Uv-Vis Spectroscopy For Nano-Semiconductor Based Photoelectric Devices, Si-Da Bian, Jian-Zhang Zhou, Zhong-Hua Lin

Journal of Electrochemistry

The electronic structures and properties of nano-semiconductors are quite different from those of bulk semiconductors due to the nano-size effect (such as quantum size effect). Moreover, when the nano-semiconductor materials are deposited onto the substrate to construct a device, their electronic properties are also affected by the substrate or other components, which may lead to different performances of nano-semiconductors based photoelectric devices, and consequently, different corresponding characterization methods are needed. The combination of photocurrent spectroscopy, photoluminescence spectroscopy with UV-Vis absorption spectroscopy can provide a more comprehensive characterization for the electronic properties and photoelectrochemical performances of nano-semiconductors in photoelectric devices. Our …

Development Of Engineered Soil Surrogates For Modeling Natural Soil Sorption Behavior, Ghada Yehia Abdalla

LSU Doctoral Dissertations

The land produces more than 95% of the global food supply, and with a continuously growing population, we need to optimize the use of the available agricultural land. Soil organic matter (SOM) is an essential component of soils, especially concerning their fertility and sorption behavior. The chemical composition of the SOM consists of lipids, lignin, and cellulose. However, the heterogeneous and complex nature of SOM, and real soils, makes their study challenging and introduces uncontrollable factors.

Therefore, structural mimics of natural soils with increasing complexity representing the real soil functionality were synthesized and evaluated for bulk properties related to their …

Valorization Of Xylan In Agroforestry Waste Streams, Harrison Appiah

Graduate Theses, Dissertations, and Problem Reports (ETD)

Valorization of Xylan in Agroforestry Waste Streams.

Harrison Appiah

Microwave-assisted deep eutectic solvent and gamma-valerolactone metallic chloride catalyzed conversion of xylan to furfural were investigated using a 2x3 factorial experimental design at two levels of percent microwave power, reaction time, and catalyst concentration. The levels of each factor studied were (20%, 60% microwave power, 2, 4 minutes, and 10, 20mg) respectively. The effect of three metallic chloride catalysts (LiCl, FeCl3.6H20, CuCl2) on the conversion of xylan to furfural was also investigated. The gamma-valerolactone-ferric chloride sent system exhibited the highest mean yield of furfural (56.50%). The next highest furfural yield of …

Characterization Of Modern Ammunition And Background Profiles: A Novel Approach And Probabilistic Interpretation Of Inorganic Gunshot Residue, Korina Layli Menking-Hoggatt

Graduate Theses, Dissertations, and Problem Reports (ETD)

Gunshot residue (GSR) can provide essential clues in gun-related investigations. The standard practice for GSR analysis uses SEM-EDS, with the capability for single particle elemental and morphological analysis. However, the method is time-consuming and based on categorical classification models without considering case circumstances. Therefore, complementary and more encompassing methods are needed to improve evidence interpretation of modern ammunition. This research aims to fill these demands by developing standard materials and alternative methods to characterize and interpret IGSR.

This study developed primer GSR (pGSR) standards from sixty discharged primers that were fully characterized by three techniques. The number of GSR particles, …

Plasmon Enhanced Single Molecule Fluorescence In Zero Mode Waveguides (Zmws), Abdullah Masud

Theses and Dissertations--Chemistry

Plasmonic nanostructures are an extensive research focus due to their ability to modify the photophysical properties of nearby fluorophores. Surface plasmons (SP), defined as the collective oscillation of delocalized electrons, are the fundamental characteristic primarily responsible for altering those photophysical properties. Studying fluorophores at the single-molecule level has received significant attention since more specific information can be extracted from single molecule-based studies, which otherwise could be obscured in ensemble studies. However, single-molecule studies are inherently challenging because the signal from a single molecule is usually dim, making it difficult to detect. The situation is even worse in a crowded environment …

Cobalt, Molybdenum, And Nickel Complexes, Natural Zeolites, Epoxidation, And Free Radical Reactions, Nicholas K. Newberry

Dissertations, Master's Theses and Master's Reports

Chapter 2 is based on the synthesis and study of the compounds of the bidentate ligand ((5-phenyl-1H-pyrazol-3-yl)methyl)phosphine oxide with molybdenum and cobalt as the transition metal. The complexes were analyzed via FTIR, NMR, UV-Vis, Fluorescence Spectroscopy, TGA, DFT, and XRD. Chapter 3 resulted in the synthesis of the complexes [Ni(II)SSRRL](PF6)2 and [Ni(II)SRSRL](Cl)(PF6) of which [Ni(II)SRSRL](Cl)(PF6) had not been previously analyzed. Both products were analyzed via FTIR, NMR, UV-Vis, CV, DFT, and XRD. Chapter 5 contains the results of the characterization and modification of 4 natural zeolites (AZLB-Na, AZLB-Ca, NM-CA, NV-Na) from the United States in an attempt to increase the …

Multiple Wetting−Dewetting States Of A Water Droplet On Dual-Scale Hierarchical Structured Surfaces, Yurui Gao, Yuan Liu, Jian Jiang, Chongqin Zhu, Craig Zuhlke, Dennis Alexander, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Surfaces with microscale roughness can entail dualscale hierarchical structures such as the recently reported nano/ microstructured surfaces produced in the laboratory (Wang et al. Nature 2020, 582, 55−57). However, how the dual-scale hierarchical structured surface affects the apparent wetting/ dewetting states of a water droplet, and the transitions between the states are still largely unexplored. Here, we report a systematic large-scale molecular dynamics (MD) simulation study on the wetting/dewetting states of water droplets on various dual-scale nano/near-submicrometer structured surfaces. To this end, we devise slab-water/slab-substrate model systems with a variety of dual-scale surface structures and with different degrees of intrinsic …

Novel Electrochemical Sensor Based On Integration Of Nanoporous Gold With Molecularly Imprinted Polymer For Detection Of Arsenic Ion(Iii), Wu-Wei Ma, Qi-Gang Chang, Xiong-Fang Shi, Yan-Bin Tong, Li Zhou, Bang-Ce Ye, Jian-Jiang Lu, Jin-Hu Zhao

Journal of Electrochemistry

Arsenic, a toxic chemical element, is detrimental to environment and human health in particular. Therefore, the development of simple, fast, and accurate arsenic ion (As³⁺) detection methods has attracted extensive attention. In this work, an electrochemical sensor based on molecular imprinted polymer (MIP) and nano-porous gold (NPG) modified indium tin oxide (ITO) electrode (MIP/NPG/ITO) was developed for determination of As³⁺ in water with different quality. NPG with high conductivity, large specific surface area and high biocompatibility was prepared in situ on ITO surface by a green electrodeposition method using simple and controllable steps. Then, a layer of …

Carbon Dots As Artificial Peroxidases For Analytical Applications, Shih-Chun Wei, Yang-Wei Lin, Huan-Tsung Chang

Journal of Food and Drug Analysis

Nanozymes have become attractive in analytical and biomedical fields, mainly because of their low cost, long shelf life, and less environmental sensitivity. Particularly, nanozymes formed from nanomaterials having high surface area and rich active sites are interesting since their activities can be tuned through carefully controlling their size, morphology, and surface properties. This review article focuses on preparation of carbon dots (C dots) possessing peroxidase-like activity and their analytical applications. We highlight the important roles of the oxidation states and surface residues of C dots and their nanocomposites with metal, metal oxides, or metal sulfides playing on determining their specificity …

Functionalized Gold Nanoparticles For Sensing Of Pesticides: A Review, Wei-Bin Tseng, Ming-Mu Hsieh, Che-Hsie Chen, Tai-Chia Chiu, Wei-Lung Tseng

Journal of Food and Drug Analysis

Pesticides are a family of non-biodegradable chemical compounds which widely used in agriculture to control pests and increase yield production. However, overuse or abuse of pesticides and their metabolites may cause potential toxicity for the environment as well as human health and all other living organisms, even at deficient concentrations. Consequently, the development of sensors for monitoring these compounds is significant. Recently, nanoparticles-based sensors have been extensively employed as a potential alternative or complementary analytical tool to conventional detection methods for pesticides. Among them, gold nanoparticles (AuNPs) owing to their unique optical properties have been developed as smart sensors with …

Design, Synthesis And Application Of Janus Gold Nanoprisms For Directed Self-Assembly., Md. Emtias Chowdhury

Electronic Theses and Dissertations

Colloidal Janus particles that possess more than one type of surface chemistry or functionalities have drawn significant interest due to their enormous potential in bottom-up synthetic strategies for complex superstructures. Moreover, the property of molecular recognition, tunability, and predictability of the DNA-mediated interactions enable a high degree of control over particle assembly to generate highly ordered nanostructures with emergent applications. In this dissertation, we present our works on the synthesis of Janus particles from anisotropic gold nanoprisms, and DNA- mediated assembly of nanoprisms and polymer beads in four major areas: 1) Facet selective asymmetric functionalization of gold nanoprisms for Janus …

Structure And Dynamics Of Phospholipid Vesicles And The Dependence On Nanoscale Interactions With Molecules Of Varying Complexity, Lakshapathy Widanelage Judith Upeka De Mel

LSU Doctoral Dissertations

In this dissertation, molecular interactions and changes imposed by nano-scale structures on phospholipid vesicles were investigated. 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) large unilamellar vesicles (LUVs) were used as the model system. Understanding changes of the bilayer structure, interfacial properties, lipid dynamics, and self-assembly, allows bridging relationships between biological cell membrane structure and dynamics to cellular functionalities. For example, membrane curvature changes are linked to membrane protein functions, although the exact mechanisms of control are not yet understood. Moreover, the knowledge gained from vesicle models allows exploring novel strategies for drug delivery applications. To achieve this, DOPC LUVs were synthesized and characterized by a …

Fundamentals Of Distribution Of Relaxation Times For Electrochemical Impedance Spectroscopy, Jia Wang, Qiu-An Huang, Wei-Heng Li, Juan Wang, Quan-Chao Zhuang, Jiu-Jun Zhang

Journal of Electrochemistry

Electrochemical impedance spectroscopy (EIS) is a powerful electrochemical characterization technology, which has been widely used in the field of electrochemical energy, such as lithium-ion batteries, supercapacitors, fuel cells, etc. Distribution of relaxation time (DRT) is an EIS deconvolution technique which does not depend on the prior knowledge of the targeted research object. Furthermore, DRT can serve to separate and analyze physical and chemical processes which are highly overlapped in their EIS data. In order to encourage the application and popularization of DRT deconvolution technology, several core questions are addressed in this paper: (1) DRT deconvolution principle, implementation steps and important …

Hexacyanoferrate-Based Nanocomposites For The Electrochemical Sensing Of Hydrogen Peroxide And Nicotine, Lee Pui Kee

Student Works (2020-2029)

Metal hexacyanoferrate (MeHCF) is a unique material that not only acquired immense research interest in electrochemical sensing field but also possesses potential as energy storage material. As such, the present thesis sought to investigate the facile method to synthesis MeHCF-based nanocomposites and explore its possible applications. First, comparative research on the synthesis of Prussian blue-polypyrrole (PB-PPy) nanocomposite by novel self-assembly (SA) method and conventional electrodeposition technique was performed. PB-PPy nanocomposites were prepared by the novel self-assembly method and via the electrodeposition approach. The nanocomposites were compared in term of surface morphology and its electrochemical and electrocatalytic characteristics. The results indicated …

Synthesis And Characterization Of Water-Soluble Polyaniline For Hydrazine Detection / Hazira Hussin, Hazira Hussin

Student Works (2020-2029)

In this study, polyaniline (PAni) was synthesized through the chemical oxidation method using aniline (Ani) as a monomer, hydrochloric acid (HCl) as a dopant, and ammonium persulphate (APS) as an initiator. PAni was rendered water soluble through treating with cellulose derivatives. Cellulose derivatives such as methylcellulose (MC), hydroxypropyl cellulose (HPC), and hydroxypropyl methylcellulose (HPMC) were used as a stabilizer to improve the solubility of PAni in an aqueous medium. The water-soluble PAni-cellulose derivative was applied as a chemical sensor for hydrazine detection. The chemical structures and electrical conducting behaviours of PAni-cellulose derivatives were investigated using Fourier transform infrared (FTIR) and …

Detection Of Melamine Based On The Suppressed Anodic Response Of Uric Acid By A Au-Ag Nanoparticles Modified Glassy Carbon Electrode, Yu-Hui Peng, Tsunghsueh Wu, Yang-Wei Lin

Journal of Food and Drug Analysis

We demonstrated a sensitive electrochemical method for the determination of non-electroactive melamine (Mel) using a modified glassy carbon electrode (GCE), with uric acid (UA) as the signal reporter. To increase the anodic response of UA, GCE was coated with Au–Ag nanoparticles and a Nafion thin film (Au–Ag/Nafion/GCE). The sensing mechanism was based on the competitive adsorption behavior of Mel on the Au–Ag/Nafion/GCE, which reduces the electroactive surface area of nanoparticles and thus hinders anodic response of UA. Under optimal conditions and the use of an analytical method of differential pulse voltammetry, this modified electrode detected Mel concentrations ranging from 2.5 …