Synthesis of Ag-Au/Reduced Graphene Oxide/TiO2 Nanocomposites: Application as a Non-enzymatic Amperometric H2O2 Sensor

2020 ◽  
Vol 16 (4) ◽  
pp. 485-492
Author(s):  
Long Han ◽  
Shoufang Cui ◽  
Dongmei Deng ◽  
Yuanyuan Li ◽  
Xiaoxia Yan ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Practical Significance ◽  
Quantitative Detection ◽  
Reduction Peak ◽  
Transmission Electron ◽  
H2o2 Detection ◽  
Reduced Graphene ◽  
Aseptic Packaging ◽  
Reducing Properties

Background: Owing to the strong oxidizing and reducing properties of hydrogen peroxide (H2O2), it has been widely used in many fields. In particular, H2O2 is widely used in the aseptic packaging of drinks and milk. The residue of H2O2 in food is harmful to human health. Therefore, the quantitative detection of H2O2 is of great practical significance. Methods: The Ag-Au/RGO/TiO2 nanocomposites were facilely synthesized by photo-reduction approach. Transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to characterize the synthesized Ag-Au/RGO/TiO2 nanocomposites. Cyclic voltammetry was used to analyze the electrochemical behavior of H2O2 on the Ag-Au/RGO/TiO2/GCE. Amperometry was applied for quantitative determination of the concentration of H2O2. Results: A novel Ag-Au/RGO/TiO2/GCE was prepared. The Ag-Au/RGO/TiO2/GCE displayed high electrocatalytic activity towards H2O2 reduction. An electrochemical reduction peak of H2O2 was achieved on the Ag-Au/RGO/TiO2/GCE. The current responses were linear with the concentrations of H2O2 in the range of 0.01-30 mM with the detection limit of 3.0 μM (S/N = 3). Conclusion: An amperometric sensor has been prepared for H2O2 detection using Ag- Au/RGO/TiO2/GCE. The Ag-Au/RGO/TiO2/GCE shows good performance for the determination of H2O2. The proposed sensor exhibits good selectivity and stability.

The electrocatalytic response of metallophthalocyanines when clicked to electrodes and to nanomaterials

2021 ◽  
Author(s):  
◽  
Lekhetho Simon Mpeta
Keyword(s):  
Hydrogen Peroxide ◽  
Silver Nanoparticles ◽  
Zinc Oxide ◽  
Photoelectron Spectroscopy ◽  
Electrocatalytic Activity ◽  
Electrochemical Impedance ◽  
Modified Electrodes ◽  
Transmission Electron ◽  
Reduced Graphene ◽  
Electrochemical Microscopy

Conjugates of nanomaterials and metallophthalocyanines (MPcs) have been prepared and their electrocatalytic activity studied. The prepared nanomaterials are zinc oxide and silver nanoparticles, reduced graphene oxide nanosheets and semiconductor quantum dots. The MPcs used in this work are cobalt (II) (1a), manganese(III) (1b) and iron (II) (1c) 2,9(10),16(17),23(24)- tetrakis 4-((4-ethynylbenzyl) oxy) phthalocyaninato, 2,9(10),16(17),23(24)- tetrakis(5-pentyn-oxy) cobalt (II) phthalocyaninato (2), 9(10),16(17),23(24)- tris-[4-tert-butylphenoxy)-2- (4-ethylbezyl-oxy) cobalt (II) phthalocyaninato (3), 9(10),16(17),23(24)- tris-[4-tertbutylphenoxy)-2-(pent-4yn-yloxy)] cobalt (II) phthalocyaninato (4), cobalt (II) (5a) and manganese (III) (5b) 2,9(10),16(17),23(24)- tetrakis [4-(4-(5-chloro-1H-benzo [d]imidazol-2-yl)phenoxy] phthalocyaninato and 9(10),16(17),23(24)- tris tert butyl phenoxy- 2- [4-(4-(5-chloro-1H-benzo[d]imidazole-2-yl)phenoxy] cobalt (II) phthalocyaninato (6). Some of these MPcs (1a, 3 and 4) were directly clicked on azide grafted electrode, while some (1b, 1c, 2, 5a and 5b) were clicked to azide functionalised nanomaterials and then drop-dried on the electrodes. One phthalocyanine (5b) was drop-dried on the electrode then silver nanoparticles were electrodeposited on it taking advantage of metal-N bond. Scanning electrochemical microscopy, voltammetry, chronoamperometry, electrochemical impedance spectroscopy are among electrochemical methods used to characterise modified electrodes. Transmission electron microscopy, X-ray photoelectron spectroscopy, Xray diffractometry, Raman spectroscopy and infrared spectroscopy were employed to study surface functionalities, morphology and topography of the nanomaterials and complexes. Electrocatalytic activity of the developed materials were studied towards oxidation of 2-mercaptoethanol, hydrazine and hydrogen peroxide while the reduction study was based on oxygen and hydrogen peroxide. In general, the conjugates displayed superior catalytic activity when compared to individual materials. Complex 2 alone and when conjugated to zinc oxide nanoparticles were studied for their nonlinear optical behaviour. And the same materials were explored for their hydrazine detection capability. The aim of this study was to develop sensitive, selective and affordable sensors for selected organic waste pollutants. Conjugates were found to achieve the aim of the study compared to when individual materials were employed.

FeYO3@rGO nanocomposites: Synthesis, characterization and application in photooxidative degradation of atrazine under visible light

2021 ◽  
Vol 11 (5) ◽  
pp. 706-716
Author(s):  
Nada D. Al-Khthami ◽  
Tariq Altalhi ◽  
Mohammed Alsawat ◽  
Mohamed S. Amin ◽  
Yousef G. Alghamdi ◽  
...  
Keyword(s):  
Visible Light ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Bandgap Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Reduced Graphene ◽  
Structural Surface ◽  
Adsorption Desorption

Different organic pollutants have been remediated photo catalytically by applying perovskite photocatalysts. Atrazine (ATR) is a pesticide commonly detected as a pollutant in drinking, surface and ground water. Herein, FeYO3@rGO heterojunction was synthesized and applied for photooxidation decomposition of ATR. First, FeYO 3nanoparticles (NPs) were prepared via routine sol-gel. After that, FeYO3 NPs were successfully incorporated with different percentages (5, 10, 15 and 20 wt.%) of reduced graphene oxide (rGO) in the synthesis of novel FeYO3@rGO photocatalyst. Morphological, structural, surface, optoelectrical and optical characteristics of constructed materials were identified via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), adsorption/desorption isotherms, diffusive reflectance (DR) spectra, and photoluminescence response (PL). Furthermore, photocatalytic achievement of the constructed materials was evaluated via photooxidative degradation of ATR. Various investigations affirmed the usefulness of rGO incorporation on the advancement of formed photocatalysts. Actually, novel nanocomposite containing rGO (15 wt.%) possessed diminished bandgap energy, as well as magnified visible light absorption. Furthermore, such nanocomposite presented exceptional photocatalytic achievement when exposed to visible light as ATR was perfectly photooxidized over finite amount (1.6 g · L-1) from the optimized photocatalyst when illuminated for 30 min. The advanced photocatalytic performance of constructed heterojunctions could be accredited mainly to depressed recombination amid induced charges. The constructed FeYO3@rGO nanocomposite is labelled as efficient photocatalyst for remediation of herbicides from aquatic environments.

scholarly journals Reduced Graphene Oxide–Epoxy Grafted Poly(Styrene-Co-Acrylate) Composites for Corrosion Protection of Mild Steel

Coatings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 666
Author(s):  
Xinchuan Fan ◽  
Yue Hu ◽  
Yijun Zhang ◽  
Jiachen Lu ◽  
Xiaofeng Chen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
X Ray Diffraction ◽  
Corrosion Properties ◽  
X Ray ◽  
Transmission Electron ◽  
Reduced Graphene ◽  
Scanning Electron

Reduced graphene oxide–epoxy grafted poly(styrene-co-acrylate) composites (GESA) were prepared by anchoring different amount of epoxy modified poly(styrene-co-acrylate) (EPSA) onto reduced graphene oxide (rGO) sheets through π–π electrostatic attraction. The GESA composites were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The anti-corrosion properties of rGO/EPSA composites were evaluated by electro-chemical impedance spectroscopy (EIS) in hydroxyl-polyacrylate coating, and the results revealed that the corrosion rate was decreased from 3.509 × 10−1 to 1.394 × 10−6 mm/a.

scholarly journals Efficient Method for the Concentration Determination of Fmoc Groups Incorporated in the Core-Shell Materials by Fmoc–Glycine

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3983
Author(s):  
Elżbieta Szczepańska ◽  
Beata Grobelna ◽  
Jacek Ryl ◽  
Amanda Kulpa ◽  
Tadeusz Ossowski ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Core Shell ◽  
Amino Groups ◽  
The Core ◽  
Transmission Electron ◽  
Model Sample ◽  
Vis Spectroscopy ◽  
Fmoc Group ◽  
Synthesis Procedure

In this paper, we described the synthesis procedure of TiO2@SiO2 core-shell modified with 3-(aminopropyl)trimethoxysilane (APTMS). The chemical attachment of Fmoc–glycine (Fmoc–Gly–OH) at the surface of the core-shell structure was performed to determine the amount of active amino groups on the basis of the amount of Fmoc group calculation. We characterized nanostructures using various methods: transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to confirm the modification effectiveness. The ultraviolet-visible spectroscopy (UV-vis) measurement was adopted for the quantitative determination of amino groups present on the TiO2@SiO2 core-shell surface by determination of Fmoc substitution. The nanomaterials were functionalized by Fmoc–Gly–OH and then the fluorenylmethyloxycarbonyl (Fmoc) group was cleaved using 20% (v/v) solution of piperidine in DMF. This reaction led to the formation of a dibenzofulvene–piperidine adduct enabling the estimation of free Fmoc groups by measurement the maximum absorption at 289 and 301 nm using UV-vis spectroscopy. The calculations of Fmoc loading on core-shell materials was performed using different molar absorption coefficient: 5800 and 6089 dm3 × mol−1 × cm−1 for λ = 289 nm and both 7800 and 8021 dm3 × mol−1 × cm−1 for λ = 301 nm. The obtained results indicate that amount of Fmoc groups present on TiO2@SiO2–(CH2)3–NH2 was calculated at 6 to 9 µmol/g. Furthermore, all measurements were compared with Fmoc–Gly–OH used as the model sample.

Nonenzymatic Electrochemical Immunosensor Using Ferroferric Oxide–Manganese Dioxide–Reduced Graphene Oxide Nanocomposite as Label for α-Fetoprotein Detection

NANO ◽  
2016 ◽  
Vol 11 (10) ◽  
pp. 1650116 ◽  
Author(s):  
Wensi Jian ◽  
Chunping Wang ◽  
Zuanguang Chen ◽  
Yanyan Yu ◽  
Duanping Sun ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Manganese Dioxide ◽  
Reduced Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
Low Cost ◽  
Synergetic Effect ◽  
Electrochemical Immunosensor ◽  
Quantitative Detection ◽  
Ferroferric Oxide ◽  
Reduced Graphene

A novel nonenzymatic electrochemical immunosensor was fabricated for quantitative detection of [Formula: see text]-fetoprotein (AFP). The immunosensor was constructed by modifying gold electrode with electrochemical reduction of graphene oxide-carboxyl multi-walled carbon nanotube composites (ERGO–CMWCNTs) and electrodeposition of gold nanoparticles (AuNPs) for effective immobilization of primary antibody (Ab[Formula: see text]. Ferroferric oxide–manganese dioxide–reduced graphene oxide nanocomposites (Fe3O4@MnO2–rGO) were designed as labels for signal amplification. On one hand, the excellent electroconductivity and outstanding electron transfer capability of ERGO–CMWCNTs/AuNPs improved the sensitivity of the immunosensor. On the other hand, introduction of rGO could not only increase the specific surface area for immobilization of secondary antibody (Ab[Formula: see text] but also build a synergetic effect to reinforce the electrocatalytic properties of catalysts. Fe3O4@MnO2–rGO nanocomposites were characterized by scanning electron microscope, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Using AFP as a model analyte, the proposed sandwich-type electrochemical immunosensor exhibited a wide linear range of 0.01–50[Formula: see text][Formula: see text] with a low detection limit of 5.8[Formula: see text][Formula: see text]. Moreover, the Fe3O4@MnO2–rGO-based peroxidase mimetic system displayed an excellent analytical performance with low cost, satisfactory reproducibility and high selectivity, which could be further extended for detecting other disease-related biomarkers.

SYNTHESIS AND CHARACTERIZATION OF Au NANOPARTICLES/REDUCED GRAPHENE OXIDE NANOCOMPOSITE: A FACILE AND ECO-FRIENDLY APPROACH

NANO ◽  
2014 ◽  
Vol 09 (03) ◽  
pp. 1450031
Author(s):  
MEILING ZOU ◽  
HAN ZHU ◽  
PAN WANG ◽  
SHIYONG BAO ◽  
MINGLIANG DU ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
Au Nanoparticles ◽  
Epigallocatechin Gallate ◽  
Chloroauric Acid ◽  
Mixed Solution ◽  
Atomic Force ◽  
Transmission Electron ◽  
Reduced Graphene

In this paper, epigallocatechin gallate (EGCG) was used as a green reductant both for the fabrication of soluble reduced graphene oxide (rGO) and the synthesis of Au nanoparticles/rGO nanocomposite. Fourier transform infrared (FTIR) spectra confirmed the efficient removal of the oxygen-containing groups in graphene oxide (GO) through the reduction act of EGCG. Au nanoparticles ( AuNPs ) were anchored onto the rGO sheets by heating the mixed solution of rGO and chloroauric acid at 65°C using EGCG as reductant. Transmission electron microscopy (TEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the resulting nanocomposite. Due to the chelating effect of polyhydroxy EGCG, AuNPs with diameters of ~20–50 nm were stably decorated onto both sides of the rGO sheets. Because this reduction method avoids the use of toxic reagents, AuNPs /rGO nanocomposite would be eco-friendly, and it might be useful not only for electronic devices but also for biocompatible materials in the future applications.

The study of the valence and distribution of radiogenic Pb in monazite by using XPS and TEM

2020 ◽  
Author(s):  
Xu Tang ◽  
Qiu-li Li ◽  
Lin-xin Gu
Keyword(s):  
Crystal Lattice ◽  
Photoelectron Spectroscopy ◽  
Atomic Scale ◽  
Laser Raman Spectroscopy ◽  
Heterogeneous Distribution ◽  
Laser Raman ◽  
Transmission Electron ◽  
Phosphate Mineral ◽  
Monazite Crystal

<p>Monazite((Ce,Y,La,Th)PO<sub>4</sub>) is an important phosphate mineral and is one of the widely used minerals for U-Th-Pb dating in geochronology. In this study, we have examined the crystallinity, the valence and coordination of radiogenic Pb in a natural RW-1 monazite standard (ThO<sub>2</sub> up to13.5 wt% and Pb up to ~5000 ppm) with a <sup>207</sup>Pb/<sup>235</sup>U age of 904.15 ± 0.26 Ma from a Norwegian pegmatite by using laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy (TEM). The Raman spectrum analysis revealed that this monazite is well crystalline and is not damaged by α-particles. The results of XPS and TEM suggest that the radiogenic Pb produced by the α-decay of U and Th is divalent and radiogenic Pb atom substitutes the Ce-site within the monazite crystal lattice. The qualitative analyses conducted on the HAADF-STEM data reveal heterogeneous distribution of radiogenic Pb within the monazite crystal lattice. This is the first work on the determination of the oxidation state, the atomic location and distribution of radiogenic Pb in a natural monazite (CePO<sub>4</sub>). The deeply study of radiogenic Pb in monazite at the nanoscale and atomic scale provides a good insight for us to understand the mechanisms of nano-isotopic mobility and the nano-geochronology  that has been poorly understood so far.</p>

scholarly journals 3D-Flower-Like Copper Sulfide Nanoflake-Decorated Carbon Nanofragments-Modified Glassy Carbon Electrodes for Simultaneous Electrocatalytic Sensing of Co-existing Hydroquinone and Catechol

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2289 ◽  
Author(s):  
Lina Abdullah Alshahrani ◽  
Liqiong Miao ◽  
Yanyu Zhang ◽  
Shengming Cheng ◽  
Palanivel Sathishkumar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Glassy Carbon ◽  
Photoelectron Spectroscopy ◽  
Copper Sulfide ◽  
Environmental Pollutants ◽  
Differential Pulse ◽  
Glassy Carbon Electrodes ◽  
X Ray ◽  
Transmission Electron

A copper sulfide nanoflakes-decorated carbon nanofragments-modified glassy carbon electrode (CuS-CNF/GCE) was fabricated for the electrocatalytic differentiation and determination of hydroquinone (HQ) and catechol (CC). The physicochemical properties of the CuS-CNF were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The electrocatalytic determination of HQ and CC over the CuS-CNF/GCE was evaluated by cyclic voltammetry and differential pulse voltammetry. An excellent detection limit and sensitivity of the CuS-CNF/GCE are obtained (0.293 µM and 0.259 µM) with a sensitivity of 184 nA µM−1 cm−2 and 208 nA µM−1 cm−2 (S/N=3) for HQ and CC, respectively. In addition, the CuS-CNF/GCE shows a selective identification of HQ and CC over potential interfering metal ions (Zn2+, Na+, K+, NO3−, SO42−, Cl−) and organic compounds (ascorbic acid, glucose), and a satisfactory recovery is also obtained in the spiked water samples. These results suggest that the CuS-CNF/GCE can be used as an efficient electrochemical sensor for the simultaneous determination of co-existing environmental pollutants such as HQ and CC in water environments with high selectivity and acceptable reproducibility.

Sign in / Sign up

Export Citation Format

Share Document