scholarly journals Electrochemical behavior of H3PW12O40/ acid-activated bentonite powders

2012 ◽  
Vol 18 (2) ◽  
pp. 329-338 ◽  
Author(s):  
Zorica Mojovic ◽  
Ljiljana Rozic ◽  
Tatjana Novakovic ◽  
Zorica Vukovic ◽  
Srdjan Petrovic ◽  
...  
Keyword(s):  
Electrochemical Behavior ◽  
Limit Of Detection ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Nitrite Oxidation ◽  
Face To Face ◽  
Force Microscopy ◽  
Atomic Force ◽  
Activated Bentonite ◽  
Adsorption Desorption

Electrochemical behavior of 12-tungstophosphoric acid (HPW)/acid-activated bentonite (AAB) powders with various loadings of HPW was investigated. The physicochemical properties of the prepared powders were examined by X-ray powder diffraction, nitrogen adsorption-desorption isotherms, atomic force microscopy and cyclic voltammetry measurements. The results indicated that the prepared powders are composed mainly of oriented domains of large rock blocks, probably resulting from a preferable deposition of bentonite particles having a face-to-face interaction. The particles had a mainly disordered mesoporous structure with a pore volume that varied according to the pore size in the range of 2-50 nm. In addition, the particles had crystallite size between 4.9 and 9.0 nm. The electrocatalytic activities of prepared HPW/Aelectrodes were studied in the oxidation of NO2-ions and the results revealed that the electrodes possessed relatively higher nitrite oxidation currents than Aelectrode. The best electroactivity was observed for HPW3/Aelectrode (AAB+20 wt. % HPW) and the limit of detection (3?) was determined as 8 ?M.

scholarly journals Surface Plasmon Resonance Based on Molecularly Imprinted Polymeric Film for l-Phenylalanine Detection

Biosensors ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 21
Author(s):  
Duygu Çimen ◽  
Nilay Bereli ◽  
Adil Denizli
Keyword(s):  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Limit Of Detection ◽  
Kinetic Studies ◽  
Force Microscopy ◽  
Spr Sensor ◽  
Atomic Force ◽  
Analysis Technique ◽  
Molecular Imprinting Technology

In this study, we designed a simple, rapid, sensitive and selective surface plasmon resonance (SPR) sensor for detection of L-phenylalaine by utilizing molecular imprinting technology. l-phenylalanine imprinted and non-imprinted poly(2-hydroxyethyl methacrylate-methacryloyl-l-phenylalanine) polymeric films were synthesized onto SPR chip surfaces using ultraviolet polymerization. l-phenyalanine imprinted and non-imprinted SPR sensors were characterized by using contact angle, atomic force microscopy and ellipsometry. After characterization studies, kinetic studies were carried out in the concentration range of 5.0–400.0 μM. The limit of detection and quantification were obtained as 0.0085 and 0.0285 μM, respectively. The response time for the test including equilibration, adsorption and desorption was approximately 9 min. The selectivity studies of the l-phenylalanine imprinted SPR sensor was performed in the presence of d-phenylalanine and l-tryptophan. Validation studies were carried out via enzyme-linked immunosorbent analysis technique in order to demonstrate the applicability and superiority of the l-phenylalanine imprinted SPR sensor.

scholarly journals ADSORPTION PROPERTIES OF TITANIA-SILICA MEMBRANES OBTAINED ON CERAMIC SUBSTRАTE

2018 ◽  
Vol 54 (3) ◽  
pp. 274-280
Author(s):  
T. F. Kouznetsova ◽  
A. I. Ivanets ◽  
J. D. Sauka
Keyword(s):  
Surface Area ◽  
Quartz Substrate ◽  
Cetylpyridinium Chloride ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Adsorption Properties ◽  
Molar Ratio ◽  
Silica Membranes ◽  
Metal Silicate ◽  
Adsorption Desorption

Titania-silica membranes on a porous quartz substrate are prepared by its direct contact with metal silicate sol at various Ti/Si ratios in the conditions of coagel sedimentation and presence of cetylpyridinium chloride. The study of textural and adsorption properties of membranes is conducted by low-temperature nitrogen adsorption-desorption, including methods of t-plots and DFT theory. It was shown that obtained membranes have mesoporous structure with the specific surface area and pore hydraulic diameter varied in intervals of 64–217 m2 /g and 4–11 nm, respectively. Developed values of surface area remain up to molar ratio of Ti/Si = 50/50.

scholarly journals A highly sensitive safrole sensor based on polyvinyl acetate (PVAc) nanofiber-coated QCM

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kuwat Triyana ◽  
Aditya Rianjanu ◽  
Doni Bowo Nugroho ◽  
Ahmad Hasan As’ari ◽  
Ahmad Kusumaatmaja ◽  
...  
Keyword(s):  
Response Time ◽  
Polyvinyl Acetate ◽  
Limit Of Detection ◽  
High Surface ◽  
High Surface Area ◽  
Average Diameter ◽  
Promising Alternative ◽  
Force Microscopy ◽  
Atomic Force ◽  
Highly Sensitive

Abstract A novel, highly sensitive and selective safrole sensor has been developed using quartz crystal microbalance (QCM) coated with polyvinyl acetate (PVAc) nanofibers. The nanofibers were collected on the QCM sensing surface using an electrospinning method with an average diameter ranging from 612 nm to 698 nm and relatively high Q–factors (rigid coating). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the PVAc nanofiber surface morphology, confirming its high surface area and roughness, which are beneficial in improving the sensor sensitivity compared to its thin-film counterpart. The as-spun PVAc nanofiber sensor could demonstrate a safrole limit of detection (LOD) of down to 0.7 ppm with a response time of 171 s and a sensitivity of 1.866 Hz/ppm. It also showed good reproducibility, rapid response time, and excellent recovery. Moreover, cross-interference of the QCM sensor response to non-target gases was investigated, yielding very low cross-sensitivity and high selectivity of the safrole sensor. Owing to its high robustness and low fabrication cost, this proposed sensing device is expected to be a promising alternative to classical instrumental analytical methods for monitoring safrole-based drug precursors.

scholarly journals Sputtered Pd as Hydrogen Storage for a Chip-Integrated Microenergy System

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
E. Slavcheva ◽  
G. Ganske ◽  
U. Schnakenberg
Keyword(s):  
Hydrogen Storage ◽  
Hydrogen Adsorption ◽  
Mechanical Stability ◽  
Water Electrolysis ◽  
Ambient Conditions ◽  
Force Microscopy ◽  
Atomic Force ◽  
Developed Surface ◽  
Adsorption Desorption ◽  
Sputtering Pressure

The work presents a research on preparation and physical and electrochemical characterisation of dc magnetron sputtered Pd films envisaged for application as hydrogen storage in a chip-integrated hydrogen microenergy system. The influence of the changes in the sputtering pressure on the surface structure, morphology, and roughness was analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AMF). The electrochemical activity towards hydrogen adsorption/desorption and formation of PdH were investigated in 0.5 M H2SO4using the methods of cyclic voltammetry and galvanostatic polarisation. The changes in the electrical properties of the films as a function of the sputtering pressure and the level of hydrogenation were evaluated before and immediately after the electrochemical charging tests, using a four-probe technique. The research resulted in establishment of optimal sputter regime, ensuring fully reproducible Pd layers with highly developed surface, moderate porosity, and mechanical stability. Selected samples were integrated as hydrogen storage in a newly developed unitized microenergy system and tested in charging (water electrolysis) and discharging (fuel cell) operative mode at ambient conditions demonstrating a stable recycling performance.

MESOPOROUS CARBON ELECTRODE: SYNTHESIS, CHARACTERIZATION AND ELECTROCHEMICAL PROPERTIES

2010 ◽  
Vol 03 (03) ◽  
pp. 161-164 ◽  
Author(s):  
XI LONG ◽  
CHUNXIA ZHAO ◽  
WEN CHEN
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Properties ◽  
Mesoporous Carbon ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Constant Current ◽  
Surface Areas ◽  
Constant Current Charge ◽  
Adsorption Desorption ◽  
Charge Discharge

The present paper studies a kind of mesoporous carbon (MC) with high electrochemical performance, which was prepared by vapor infiltration method. The microstructure and electrochemical properties of the mesoporous carbon were investigated by transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms, cyclic voltammetry (CV), constant current charge–discharge cycling (CD), and the long-term stability test. The results indicated that the mesoporous carbon has an ordered mesoporous structure, with pore size of about 3.87 nm and surface areas of 1087 m2 ⋅ g-1. The cyclic voltammetry curve reveals typical electrical double-layer capacitor property. After 200 cycles, the CV curves can almost be overlapped, which indicates excellent cycling stability. From the charge/discharge cycling, the specific capacitance of MC is 117 F ⋅ cm-1 in 1.0 M KNO3 electrolyte media at a scan rate of 1.0 mV ⋅ s-1, which decays with increasing current density. The charge–discharge efficiency also decays with it.

scholarly journals Electrochemical ELISA Protein Biosensing in Undiluted Serum Using a Polypyrrole-Based Platform

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2857 ◽  
Author(s):  
Sunil K. Arya ◽  
Pedro Estrela
Keyword(s):  
Serum Proteins ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Enzyme Linked Immunosorbent Assay ◽  
Protein Markers ◽  
Necrosis Factor Alpha ◽  
Force Microscopy ◽  
Atomic Force ◽  
Tnf Α ◽  
Undiluted Serum

An electrochemical enzyme-linked immunosorbent assay (ELISA) biosensor platform using electrochemically prepared ~11 nm thick carboxylic functionalized popypyrrole film has been developed for bio-analyte measurement in undiluted serum. Carboxyl polypyrrole (PPy-COOH) film using 3-carboxy-pyrrol monomer onto comb-shaped gold electrode microarray (Au) was prepared via cyclic voltammetry (CV). The prepared Au/PPy-COOH was then utilized for electrochemical ELISA platform development by immobilizing analyte-specific antibodies. Tumor necrosis factor-alpha (TNF-α) was selected as a model analyte and detected in undiluted serum. For enhanced performance, the use of a polymeric alkaline phosphatase tag was investigated for the electrochemical ELISA. The developed platform was characterized at each step of fabrication using CV, electrochemical impedance spectroscopy and atomic force microscopy. The bioelectrodes exhibited linearity for TNF-α in the 100 pg/mL–100 ng/mL range when measured in spiked serum, with limit of detection of 78 pg/mL. The sensor showed insignificant signal disturbance from serum proteins and other biologically important proteins. The developed platform was found to be fast and specific and can be applicable for testing and measuring various biologically important protein markers in real samples.

Synthesis of Ni(II)-imprinted Mesoporous Silica Adsorbents by Surface Imprinting Technology for Removal of Ni(II) from Aqueous Solution

2014 ◽  
Vol 997 ◽  
pp. 146-149
Author(s):  
Xiang Guo Meng ◽  
Wen Lu Guo ◽  
Min Luo ◽  
Ping Sun
Keyword(s):  
Aqueous Solution ◽  
Mesoporous Silica ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Surface Imprinting ◽  
Surface Imprinting Technique ◽  
Silica Adsorbents ◽  
Ft Ir ◽  
Surface Imprinting Technology ◽  
Adsorption Desorption

Ni(II)-imprinted polymer has been prepared by surface imprinting technique based on support matrix of mesoporous silica SBA-15. The obtained adsorbent was characterized by FT-IR, SEM, and nitrogen adsorption-desorption. The compound retained mesoporous structure and the polymer coated inside channels and outside surface hole wall. The adsorption behavior was carried out with Ni(II)-IIP in batch experiments. The results suggested that Ni(II)-IIP could be used as an excellent adsorbent for efficient removal of Ni(II) from aqueous solution.

Surface Cleaning, Topography, and Temperature Measurements of Single Crystal Diamond

1994 ◽  
Vol 339 ◽  
Author(s):  
Mark P. D'Evelyn ◽  
Lisa M. Struck ◽  
Robin E. Rawles
Keyword(s):  
Single Crystal ◽  
Surface Science ◽  
Surface Cleaning ◽  
Diamond Surfaces ◽  
Surface Hydroxyl ◽  
Force Microscopy ◽  
Atomic Force ◽  
Single Crystal Diamond ◽  
Adsorption Desorption ◽  
Internal Reflection Spectroscopy

ABSTRACTApplication of surface science methods to single crystal diamond surfaces requires the preparation of clean, well-ordered surfaces and accurate measurement of substrate temperature. Cleaning of diamond (100) in H2SO4/HNO3/HClO4 produced several infrared absorption features between 1025 and 1275 cm-1, as observed by infrared multiple-internal-reflection spectroscopy. These modes are assigned to surface hydroxyl and bridge-bonded oxygen. Heating an oxidized surface to ca. 1130 °C caused disappearance of a surface hydroxyl mode centered at 1080 cm-1. We show by atomic force microscopy that an as-polished diamond (100) sample is covered by grooves and ridges several nm in height, implying a modest density of atomic steps. The surface of a diamond that underwent etching via numerous adsorption/desorption experiments in ultrahigh vacuum and was acid cleaned several times was essentially unchanged, indicating a minimal perturbation of the surface topography. The capability of Fizeau interferometry for accurate measurement of single-crystal diamond temperatures is demonstrated.

scholarly journals SYNTHESIS AND ELECTROCHEMICAL PROPERTIES OF MESOPOROUS CARBON SUPPORTED WELL–DISPERSED COBALT OXIDES NANOPARTICLES

2018 ◽  
Vol 55 (1B) ◽  
pp. 230
Author(s):  
Nguyen Van Tu
Keyword(s):  
Electron Microscopy ◽  
Cobalt Oxide ◽  
Mesoporous Carbon ◽  
Good Control ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Oxide Nanoparticles ◽  
Cobalt Oxide Nanoparticles ◽  
Transmission Electron ◽  
Adsorption Desorption

In this article, well–dispersed cobalt oxide nanoparticles supported on mesoporous carbon (CMK–3) have been successfully synthesized. The composites were characterized by field emission scanning electron microscopy, transmission electron microscopy, X–ray diffraction and nitrogen adsorption–desorption analysis. The results have confirmed that, at a cobalt loading of 15 wt%, the composites have not only retained mesoporous structure of the support but also shown a good control of dispersed cobalt oxide nanoparticles with size of ~4 nm. The electrochemical property tests for the synthesized samples have shown significant improvement compared to the blank carbon (CMK–3) without cobalt oxide incorporation.

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