Screening of Wood/Forest and Vine By-Products as Sources of New Drugs for Sustainable Strategies to Control Fusarium graminearum and the Production of Mycotoxins

Fusarium graminearum is a fungal pathogen that can colonize small-grain cereals and maize and secrete type B trichothecene (TCTB) mycotoxins. The development of environmental-friendly strategies guaranteeing the safety of food and feed is a key challenge facing agriculture today. One of these strategies lies on the promising capacity of products issued from natural sources to counteract crop pests. In this work, the in vitro efficiency of sixteen extracts obtained from eight natural sources using subcritical water extraction at two temperatures was assessed against fungal growth and TCTB production by F. graminearum. Maritime pine sawdust extract was shown to be extremely efficient, leading to a significant inhibition of up to 89% of the fungal growth and up to 65% reduction of the mycotoxin production by F. graminearum. Liquid chromatography/mass spectrometry analysis of this active extract revealed the presence of three families of phenolics with a predominance of methylated compounds and suggested that the abundance of methylated structures, and therefore of hydrophobic compounds, could be a primary factor underpinning the activity of the maritime pine sawdust extract. Altogether, our data support that wood/forest by-products could be promising sources of bioactive compounds for controlling F. graminearum and its production of mycotoxins.     

Crystallization kinetics of Pd in composite films of PEDT

The crystallization of palladium in poly-3,4-ethylenedioxythiophene (PEDT) films is studied in order to obtain nanosized palladium clusters in PEDT composite layers with high electrocatalytic activity. Nucleation and growth of Pd is investigated for dependences on overpotential, polymer layer thickness d and chemical state (active or overoxidized) of the PEDT films. It is found that before the onset of diffusion limitations the growth occurs under charge transfer control. The observed induction period t₀ indicates crystallization at the metal | polymer interface. The linear relation I^1/3 versus t found in the initial stage of the deposition process gives evidence for three-dimensional growth of the metal crystals. The number N₀ of sites active for nucleation decreases strongly with increasing d. A saturation in N₀ is reached for continuous thicker films. The overoxidized layers are less active for metal deposition and exhibit a 50-fold lower number of active sites. The electrocatalytic properties of the Pd/PEDT composite layers are studied with respect to hydrogen sorption. High electrocatalytic activity is found for composites obtained with thin PEDT films polymerized in the low potential region.     

Copper-modified poly(3,4-ethylenedioxythiophene) layers for selective determination of dopamine in the presence of ascorbic acid: I. Role of the polymer layer thickness

The oxidation of ascorbic acid (AA) and dopamine (DA) is studied on non-modified and copper crystal-modified poly(3,4-ethylenedioxythiophene) (PEDOT)-coated electrodes. Both oxidation reactions are studied for different thickness of the polymer layers. For several microns thick PEDOT layers both PEDOT and Cu-modified PEDOT show the largest currents. A stable voltammetric response for AA oxidation is observed together with a linear dependence of the peak currents on concentration in the 0.3 to 6.0 mM range. For DA oxidation, however, a gradual loss of electroactivity is found with increasing number of voltammetric scans and concentration. This problem is overcome by using thinner (<1 µm) polymer layers. In the presence of both AA and DA, the Cu-modified PEDOT-coated electrodes provide better selectivity with respect to DA in comparison to non-modified PEDOT due to partial suppression of the AA oxidation currents. Thin PEDOT layers modified with electrodeposited Cu crystals show a stable and sensitive response for DA oxidation in the micromolar concentration range. A linear dependence of the voltammetric peak currents is found in a wide concentration range (from 6 to about 200 µM) of DA in the presence of a large excess (1 mM concentration) of AA. The sensitivity is 0.013 µA?µM^-1.     

Pd-modified PEDOT layers obtained through electroless metal deposition—electrooxidation of glycerol

Pd-poly(3,4-ethylenedioxythiophene) (PEDOT)-based electrocatalytic materials are obtained by coupling Pd ion reduction with oxidation of pre-reduced PEDOT coatings. Electroless metal deposition is carried out in single or triple electroless deposition steps resulting in Pd NPs with mean size ranging between 12 and 22 nm, respectively. The proposed method of dispersing the Pd catalytic phase provides the opportunity to obtain high electrocatalytic currents with Pd loadings as low as 10 μg cm^?2. The Pd-PEDOT catalyst obtained by triple-step metal deposition shows stable voltammetric behavior with respect to glycerol oxidation in alkaline solution. The established mass activity is between the highest values achieved at Pd-electrocatalysts without involving additional electrocatalytic materials or special supports.     

Theory of electrochemical nucleation and growth—revisited?

Journal of Solid State Electrochemistry -     

Copper-modified poly(3,4-ethylenedioxythiophene) layers for selective determination of dopamine in the presence of ascorbic acid: II Role of the characteristics of the metal deposit

The oxidation of ascorbic acid (AA) and dopamine (DA) is studied on non-modified and copper crystal-modified poly(3,4-ethylenedioxythiophene) (PEDOT)-coated electrodes. Both oxidation reactions are studied for different thickness of the polymer layers. For several microns thick PEDOT layers both PEDOT and Cu-modified PEDOT show the largest currents. A stable voltammetric response for AA oxidation is observed together with a linear dependence of the peak currents on concentration in the 0.3 to 6.0 mM range. For DA oxidation, however, a gradual loss of electroactivity is found with increasing number of voltammetric scans and concentration. This problem is overcome by using thinner (<1 μm) polymer layers. In the presence of both AA and DA, the Cu-modified PEDOT-coated electrodes provide better selectivity with respect to DA in comparison to non-modified PEDOT due to partial suppression of the AA oxidation currents. Thin PEDOT layers modified with electrodeposited Cu crystals show a stable and sensitive response for DA oxidation in the micromolar concentration range. A linear dependence of the voltammetric peak currents is found in a wide concentration range (from 6 to about 200 μM) of DA in the presence of a large excess (1 mM concentration) of AA. The sensitivity is 0.013 μA μM^-1.     

Electroless deposition of palladium nanoparticles on poly(3,4-ethylene-dioxythiophene)—role of the electrode substrate

Journal of Solid State Electrochemistry - Electroless deposition of Pd is studied comparatively on glassy carbon (GCE) and spectral graphite (SGE) electrodes modified with electrodeposited...     

Angular Dependence of Raman Spectra for Electroactive Polymer Films on a Platinum Electrode

Russian Journal of Electrochemistry - The redox transformations in a conducting polymer film on a platinum electrode were studied by Raman spectroelectrochemistry at fixed potentials depending on...