CHANGE IN THE SURFACE STRUCTURE OF SEMICONDUCTOR POLYMER FILMS DURING REVERSE OXIDATION-REDUCTION

Методом растровой электронной микроскопии исследована морфология поверхности пленок полупроводниковых полимеров: полианилина, поли-о-толуидина, поли- α -нафтиламина. Пленки получены электрохимическим синтезом из подкисленных минеральными кислотами растворов их мономеров методом циклической вольтамперометрии. Пленки сформированы на платиновых подложках, сделанных по принципу биметаллических пластинок. Процессы обратимого окисления и восстановления полученных пленок осуществляли с применением электрического тока в водных растворах соляной кислоты, что приводило к допированию полимеров хлорид анионами. Показано, что поверхность пленок полианилина и поли-о-толуидина имеет схожую структуру, состоящую из многочисленных сферических зерен размером от 1 до 5 мкм. Поверхность пленок поли- α -нафтиламина существенно отличается и состоит из дендронов и крупных пор. При этом, во всех случаях наблюдаемые надмолекулярные образования для пленок в окисленном состоянии имеют несколько больший размер, чем для пленок в восстановленном состоянии, что обусловлено изменением конформации макромолекул. The surface morphology of films of semiconducting polymers: polyaniline, poly-o-toluidine, poly-α-naphthylamine was studied by scanning electron microscopy. The films were obtained by electrochemical synthesis from solutions of their monomers acidified with mineral acids by the method of cyclic voltammetry. The films are formed on platinum substrates made according to the principle of bimetallic plates. The processes of reversible oxidation and reduction of the obtained films were carried out using an electric current in aqueous solutions of hydrochloric acid, which led to the doping of polymers with chloride anions. It was shown that the surface of films of polyaniline and poly-o-toluidine has a similar structure, consisting of numerous spherical grains ranging in size from 1 to 5 pm. The surface of poly-α-naphthylamine films is significantly different and consists of dendrons and large pores. In this case, in all cases, the observed supramolecular formations for films in the oxidized state are somewhat larger than for films in the reduced state, which is due to a change in the conformation of macromolecules.

Acid Treated Montmorillonite—Eco-Friendly Clay as Catalyst in Carvone Isomerization to Carvacrol

Acid-treated montmorillonites (MMT) were used as catalysts of carvone isomerization to carvacrol. Mineral acids—sulfuric, hydrochloric, nitric acids and organic acids (acetic and chloroacetic)—were used for the acid treatment. Prepared materials were characterized by available characterization methods, namely XRD, EA, TPD, TPO, UV-Vis, laser light scattering and nitrogen physisorption. The structure of montmorillonite remained intact after treatment. However, TPD proved the increase of acidity of acid-treated materials comparing pure montmorillonite. All materials were tested in the isomerization of carvone, producing carvacrol as the desired product. The initial reaction rate increased using the materials in the row MMT-COOH < MMT-HNO3 < MMT-ClCOOH < MMT-H2SO4 < MMT-HCl, which is in accordance with the pKa of acids used for the treatment. The number of weak acid sites strongly influenced the selectivity to carvacrol. The optimal solvent for the reaction was toluene. Total conversion of carvone and the selectivity to carvacrol 95.5% was achieved within 24 h under 80 °C, with toluene as solvent and montmorillonite treated by chloroacetic acid as catalyst. The catalyst may be reused after calcination with only a low loss of activity.

Bioinspired Cellulase-Mimetic Solid Acid Catalysts for Cellulose Hydrolysis

Glucose produced by catalytic hydrolysis of cellulose is an important platform molecule for producing a variety of potential biobased fuels and chemicals. Catalysts such as mineral acids and enzymes have been intensively studied for cellulose hydrolysis. However, mineral acids show serious limitations concerning equipment corrosion, wastewater treatment and recyclability while enzymes have the issues such as high cost and thermal stability. Alternatively, solid acid catalysts are receiving increasing attention due to their high potential to overcome the limitations caused by conventional mineral acid catalysts but the slow mass transfer between the solid acid catalysts and cellulose as well as the absence of ideal binding sites on the surface of the solid acid catalysts are the key barriers to efficient cellulose hydrolysis. To bridge the gap, bio-inspired or bio-mimetic solid acid catalysts bearing both catalytic and binding sites are considered futuristic materials that possess added advantages over conventional solid catalysts, given their better substrate adsorption, high-temperature stability and easy recyclability. In this review, cellulase-mimetic solid acid catalysts featuring intrinsic structural characteristics such as binding and catalytic domains of cellulase are reviewed. The mechanism of cellulase-catalyzed cellulose hydrolysis, design of cellulase-mimetic catalysts, and the issues related to these cellulase-mimetic catalysts are critically discussed. Some potential research directions for designing more efficient catalysts for cellulose hydrolysis are proposed. We expect that this review can provide insights into the design and preparation of efficient bioinspired cellulase-mimetic catalysts for cellulose hydrolysis.

1300 Years Since the Birth of Geber – Beginning and Foundation of Arabic Alchemy

Geber (Latinized name of Jabir ibn Hayyan (c. 721 – c. 815)) is among the most notable representatives of medieval chemistry. The article, dedicated to the 1300th anniversary of his birth, tries to depict his work as the beginning and groundwork for Arabic alchemy, also serving as a push for the formation of chemistry in the future. The article touches upon his life, characteristics, evaluation of his works, doubts about his identity and authorship. His influences are examined and his achievements in the area of metallurgy (sulfur-mercury theory, characterizing all known metals), knowledge of `secret` (stimulating the transmutation of metals) substances, mineral acids, salts, chemical processes and apparatus, his contributions to practical chemistry prove the broadness of his interests. His rational and practical approach is acknowledged and also his “outer” spiritualism present in the terminology inherited by the authors of Alexandria. The legacy he leaves – his authority, influence on the development of chemistry and followers – Arabic medical alchemists. In the conclusion his services to science and civilization are summarized.

Acid dissolution behavior of ferritic FeCrAl tubes candidates for nuclear fuel cladding.

The international materials community is engaged in finding safer alternatives to zirconium alloys for the cladding of fuel in light water reactors. One solution is to replace the zirconium cladding using ferritic iron-chromium-aluminum -FeCrAl- alloys, which offer extraordinary resistance to high temperature reaction with air or steam due to the formation of a protective alumina layer on the external surface. It is important to characterize the behavior of FeCrAl not only during accident conditions but in the entire fuel cycle, which may include reprocessing of the used fuel after it is removed from the power reactors. The reprocessing may involve the dissolution of the fuel rods in mineral acids. Little or nothing is known on the dissolution of FeCrAl alloys in common mineral acids, therefore the objective of this research was to study the dissolution of typical cladding tubing having two compositions of FeCrAl (APMT & C26M) in three acids (H2SO4, HNO3 & HCl) as a function of the temperature using both standard ASTM immersion tests as well as electrochemical tests. The dissolution behavior of the FeCrAl alloys is compared to the dissolution capability of other traditional nuclear materials such as austenitic stainless steels (304SS & 316SS) and austenitic nickel alloys (Alloy 600 and Hastelloy C-276). Results show that both C26M and APMT have a higher dissolution capability in the studied mineral acids, which will be beneficial for reprocessing procedures.

Lead Electrodeposition from Triethylenetetramine Solution Containing Inhibitors

Lead can be efficiently electrodeposited from a number of common leaching agents such as mineral acids, carboxylic acids, and bases (hydroxides and ammonia). This paper reports the possibility to deposit lead from a triethylenetetramine solution, which is also a powerful extracting agent for lead sulfate. The high affinity of triethylenetetramine towards lead sulfate molecules makes it a promising candidate for lead recovery from various solid materials, including industrial secondary resources, sewages, and wastes. A popular methodology that can be found in the literature to recover metal from amine is based on purging a solution with carbon dioxide, resulting in lead carbonate precipitation. Here, the direct electrodeposition of lead from an amine solution was reported. The effects of the main process parameters, i.e., current density, temperature, and presence of additives, were examined to enhance the product quality. Bone glue, ethylene glycol, and polyvinylpyrolidone were used as perspective inhibitors of dendritic lead formation. It was shown that the addition of ethylene glycol can significantly reduce their formation as well as discoloration resulting from amine, producing lead metal with a 99.9% purity.

Electric Energy Potential from Pineapples and Potatoes

Basically, the voltage can be obtained from various sources, including fruit. Fruit is often used as food, drink and a source of vitamins for the body's defense system. It turns out that it has the ability to generate electricity, especially for fruit that has a high acidity level. The acidity in some types of fruit is able to generate electricity because it is electrolyte. Fruits which contain mineral acids in the form of hydrochloric acid and citric acid, are strong electrolytes that break down completely into ions in a water solution. Besides having acid, fruits also contain a lot of water, so that when two different metals are immersed, the fruit solution will create a potential difference between the metal and water so that there is an electrode potential that can generate electric current as well. The purpose of making a rough draft of this practicum is to prove the existence of electrical energy in pineapples and potatoes. In this experiment, it has been proven that pineapples and potatoes can produce an electric current, indicated by the presence of a voltage when measured by a voltmeter.