Palladium Paste Nanocomposite Electrode as a New Metallic Electrocatalyst for Ethanol Oxidation and Nonenzymatic Amperometric Sensor in Alkaline Medium

Palladium paste nanocomposite electrode was employed as an efficient electrocatalyst for ethanol oxidation and nonenzymatic amperometric ethanol sensor, in alkaline media. The combined application of unique properties of nanomaterials and ionic liquids results in electrodes with interesting advantages compared to the conventional Pd disk electrodes. High tolerance towards accumulation of carbonaceous species (CO‐like intermediates) and poisoning by strongly adsorbed species suggests this electrode suitable for many applications. The sensor has the advantages of high sensitivity, low detection limit (20.0 µM), wide linear range (30.0 µM–1.6 M), ease of renewing the electrode surface, good long‐term stability and reproducibility for ethanol determination.     

Pencil Lead Electrode Modified with Hemoglobin Film as a Novel Biosensor for Nitrite Determination

In the present paper, the electrochemical reduction of nitrite at a hemoglobin modified pencil lead electrode (Hb/PLE) is described. The electrochemical properties of nitrite were studied by cyclic voltammetry and chronoamperometry. Results showed that the hemoglobin film has an excellent electrochemical activity towards the reduction of nitrite. By using voltammetric and chronoamperometric methods, α, n_α and n were calculated. Then the ability of the electrode for nitrite determination was investigated using differential pulse voltammetry. The electrocatalytic reduction peak currents were found to be linear with the nitrite concentration in the range from 10 to 220 µM with a detection limit of 5 µM. The relative standard deviation is 2 % for 3 successive determinations of a 100 µM nitrite solution. This modified electrode was successfully used for the detection of low amounts of NO₂^? in spinach sample and a spiked sample of tap water.     

Dodecatungstocobaltate heteropolyanion encapsulation into MIL‐101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides

A heterogeneous catalyst was synthesized by encapsulation of a Keggin‐type heteropolytungstate, potassium dodecatungstocobaltate trihydrate, K₅[CoW₁₂O₄₀]·(Co‐POM), into chromium(III) terephthalate (MIL‐101). Encapsulation was achieved via a ‘build bottle around ship’ strategy in aqueous media, following a hydrothermal method. The structure of the resulting crystalline solid was characterized using X‐ray diffraction, correlated with Fourier transform infrared and UV–visible spectroscopy. The metal content was analysed using optical emission spectroscopy. Transmission electron microscopy was used to measure particle size and N₂ adsorption in a Brunauer–Emmett–Teller instrument to characterize the specific surface area. The catalytic activity was investigated using methanolysis of epoxides under mild conditions as a test reaction. The turnover frequency of the heterogeneous Co‐POM@MIL‐101 catalyst was more than 20 times higher than that of the homogeneous Co‐POM catalyst. The Co‐POM@MIL‐101 catalyst was reused several times with negligible leaching of Co‐POM and with no considerable loss of its initial efficiency. The simplicity of preparation, extraordinary stability and high reactivity make Co‐POM@MIL‐101 an exceptional catalytic matrix that is easily separable from reaction media.     

Investigation of boiling heat transfer coefficients of different refrigerants for low fin,Turbo-B and Thermoexcel-E enhanced tubes using computational smart schemes

Journal of Thermal Analysis and Calorimetry - The design and manufacture of highly efficient evaporators and heat exchangers in cooling machinery need an accurate estimation of the boiling heat...     

A PVC-membrane bulk optode for gallium(III) ion determination

An optical probe responsive to gallium(III) ion has been developed. The gallium sensing system was prepared by incorporating 4-(p-nitrophenyl azo)-pyrocatechol (NAP) as ionophore in a plasticized PVC membrane containing tributylphosphate (TBP) as plasticizer. The sensing membrane in contact with gallium ion at pH 3.5, changes color from yellow-brown to pink-brown. Under optimum conditions, the proposed membrane displayed a linear range of 5-83 μM with a limit of detection of 4 μM. The response time of the membrane was within 10-15 min depending on the concentration of Ga³⁺ ions. The selectivity of the probe towards gallium determination was found to be very good. Experimental results showed that the probe could be used as an effective tool in analyzing the gallium content of water samples.     

The assessment of boron nitride nanotubes and functionalized carbon nanotubes as containers for anticancer drug delivery of dacarbazine and effect of urea on adsorption process by molecular dynamics

Structural Chemistry - The adsorption mechanism of dacarbazine (DAC) onto outer surfaces of boron nitride nanotubes (BNNTs) and functionalized carbon nanotubes (FCNTs) with one and three drug...     

Electrochemical Sensors,a Bright Future in the Fabrication of Portable Kits in Analytical Systems

Analysis of food, pharmaceutical, and environmental compounds is an inevitable issue to evaluate quality of the compounds used in human life. Quality of drinking water, food products, and pharmaceutical compounds is directly associated with human health. Presence of forbidden additives in food products, toxic compounds in water samples and drugs with low quality lead to important problems for human health. Therefore, attention to analytical strategy for investigation of quality of food, pharmaceutical, and environmental compounds and monitoring presence of forbidden compounds in materials used by humans has increased in recent years. Analytical methods help to identify and quantify both permissible and unauthorized compounds present in the materials used in human daily life. Among analytical methods, electrochemical methods have been shown to have more advantages compared to other analytical methods due to their portability and low cost. Most of big companies have applied this type of analytical methods because of their fast and selective analysis. Due to simple operation and high diversity of electroanalytical sensors, these types of sensors are expected to be the future generation of analytical systems. Therefore, many scientists and researchers have focused on designing and fabrication of electroanalytical sensors with good selectivity and high sensitivity for different types of compounds such as drugs, food, and environmental pollutants. In this paper, we described the mechanism and different examples of DNA, enzymatic and electro‐catalytic methods for electroanalytical determination of drug, food and environmental compounds.     

Wide range pH measurements using a single H(+)-selective chromoionophore and a time-based flow method

A hydrophilic transparent triacetyl cellulose membrane was adopted as a pH optode by immobilizing highly selective and sensitive Nile blue indicator on the membrane. Contrary to the common procedure for determinations using optodes, in which a steady state response is measured, a new approach is introduced in which the dynamic response of the optode is used as the analytical signal. While in common procedures, pH optodes exhibit limited linear dynamic range (often 2–4 pH units only), it is shown that in a time-based flow method, an optode with only one acid-base indicator can be used for measurement in the pH range of 0–10. The procedure is simple, inexpensive and rapid.     

Electrochemical Design of Ultrathin Palladium Coated Gold Nanoparticles as Nanostructured Catalyst for Amperometric Detection of Formaldehyde

An underpotential deposition (UPD) replacement tactic was employed to design a Pd overlayer on gold (Au) nanoparticles electrodeposited on a carbon ionic liquid electrode (CILE). Pd/Au/CILE was applied as an amperometric sensor for the determination of formaldehyde in aqueous solutions. The sensor displayed two linear ranges from 15 µM–1.4 mM and 1.4–56.7 mM of formaldehyde. The limit of detection was 3 µM of formaldehyde and the sensitivity of the sensor was 2.35 µA mM^?1, using the calibration graph in the lower range. The presence of 20 mM of formic acid and methanol and 10 mM ethanol did not interfere with the determination of formaldehyde solution.     

Design and evaluation of a thorium (IV) selective optode

A novel optical sensor has been proposed for sensitive determination of thorium (IV) ion in aqueous solutions. The thorium sensing membrane was prepared by incorporating 4-(p-nitrophenyl azo)-pyrocatechol (NAP) as ionophore in the plasticized PVC membrane containing tributyl phosphate (TBP) as plasticizer. The membrane responds to thorium ion by changing color reversibly from yellow to red-brown in glycine buffer solution at pH 3.5. The proposed sensor displays a linear range of 8.66 × 10⁻⁶-2.00 × 10⁻⁴ M with a limit of detection of 6 × 10⁻⁶ M. The response time of the optode was about 8.8-12.5 min, depending on the concentration of Th (IV) ions. The selectivity of optode to Th (IV) ions in glycine buffer is good. The sensor can readily be regenerated by exposure to a solution mixture of sodium fluoride and 5-sulfosalicylic acid (dihydrate) (0.01 M each). The optode is fully reversible. The proposed optode was applied to the determination of thorium (IV) in environmental water samples.