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In this work the perillaldehyde aldoxime electrochemical determination on an anode, modified by squaraine dye composite with copper sulfide nanoparticles is analyzed. The electroanalytical process involves the formation of trivalent copper species, capable to oxidize the analyte by two parallel mechanisms. The correspondent mathematical model, correspondent to both of them, has been developed and analyzed by means of linear stability theory and bifurcation analysis. The model analysis clearly shows that the composite of a squaraine dye in organic phase and bivalent copper sulfide in the inorganic phase may be an efficient electrode modifier for perillaldehyde aldoxime electrochemical determination on an anode. The electroanalytical process will be mostly kinetically-controlled with the possibility of the transfer to diffusion-controlled mode. On the other hand, both oscillatory and monotonic instabilities may be realized in the electroanalytical process, and their probability will depend on the direction of the electroanalytical scenario in the concrete conditions, due to the possibility of the formation of ionic compounds in the pre-surface layer. DOI: http://dx.doi.org/10.17807/orbital.v13i5.1501

A novel electroanalytical process for sucralose determination has been theoretically suggested. Sucralose is immobilized over an acridine derivative 9-9´-diacridyl, yielding a quaternary salt, which is thereby gradually electrochemically reduced to an N-N´-disubstituted acridone derivative. The correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis, and this analysis has shown the high probability of the oscillatory and monotonic instabilities, due to the double electric layer structure changes during all of the stages of the process. Nevertheless, it also confirms the efficiency of 9-9´-diacridyl-modified electrode for sucralose determination in an electroanalytical system, which may be coupled with a fluorescent indicator. DOI: http://dx.doi.org/10.17807/orbital.v13i3.1584

The theoretical description for the chlorantraniliprole electrochemical determination, assisted by the hybrid composite of squaraine dye with CuS nanoparticles has been described. The correspondent reaction mechanism has been proposed, and the correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It has been shown that the chlorantraniprole electrochemical anodical determination on high potential may be efficiently provided by cupper sulfide nanoparticles, stabilized by the squaraine dye. On the other hand, the oscillatory and monotonic instability is also possible, being caused by DEL influences of the electrochemical stage. DOI: http://dx.doi.org/10.17807/orbital.v13i3.1518

In this work, the electrochemical description for metformin electrochemical determination, assisted by Ag2O2 composite with squaraine dye, is evaluated from the theoretical point of view. Metformin oxidation is realized via assisted electrochemical 1,2,4-triazole formation, followed by its polymerization and N-oxidation. The correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It has shown that the neutral and basic media are more efficient for metformin electrochemical determination than acidic media, due to the absence of the influences of non-protonated aminogroupsand, furtherly, pyridinic nitrogen atoms to double electric layer (DEL) ionic force, conductivity and impedance. In these conditions, the electrochemical instabilities are less capable to realize and, therefore, the linear dependence between the analyte concentration and the current of the system will be easier to obtain and maintain, as no side reaction or additional process, capable to compromise the monomer and (or) modifier stability is realized. DOI: http://dx.doi.org/10.17807/orbital.v12i4.1537

An interesting electroanalytical process for magnesium chlorate electrochemical determination has been described theoretically. The process involves the complex formation of magnesium cation with the azo dye Magnezone XC and the electropolymerization of the resulting complex compound in the presence of the chlorate-ion by two parallel mechanisms. The correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It has been shown that from both electroanalytical and electrosynthetical points of view the system is efficient. The linear dependence between the electrochemical parameter and salt concentration is obtained easily, and the material formed during the electroanalytical process is highly conductive and catalytic. On the other hand, the oscillatory behavior in this system will be caused by double electric layer influences on both complexation and electropolymerization stages. DOI: http://dx.doi.org/10.17807/orbital.v12i4.1534

For the first time, the perillaldehyde aldoxime electrochemical determination has been evaluated from the theoretical point of view. The correspondent mathematical model, including different scenarios of the electroanalytical process, has been developed and analyzed by means of linear stability theory and bifurcation analysis. The model analysis clearly shows that the composite of a squaraine dye in organic phase and vanadium oxyhydroxide in the inorganic phase may be an efficient electrode modifier for perillaldehyde aldoxime electrochemical determination. On the other hand, both oscillatory and monotonic instabilities may be realized in the electroanalytical process, and their probability will strongly depend on the direction of the electroanalytical scenario in the concrete conditions. DOI: http://dx.doi.org/10.17807/orbital.v12i3.1498

This work describes the synthesis, structural characterization and emissive behavior of a new copper (I) complex based on 1-thiocarbamoyl-5-(4-methoxiphenyl)-3-phenyl-4,5-dihydro-1H-pyrazole ligand. A dimeric self-assembling via hydrogen bonding was determined by analyzing the short contacts present in the solid-state structure by means of X-ray crystallography. The spectroscopic properties were determined using UV-Vis and fluorescence experiments and an interesting behavior as bluish luminescence was assigned mainly to the mixed (MLCT + IL) electronic transitions of the Cu(I)d10 ® (S=C–Nligand) type. The complete characterization of the new copper (I) complex also included elemental analyses and IR spectroscopy. DOI: http://dx.doi.org/10.17807/orbital.v9i1.952

O uso intensivo e descarte irregular de agrotóxicos na agricultura têm causado sérios problemas ambientais e de saúde. Neste trabalho foi avaliada a eficiência de UV e de alguns processos de oxidação avançada que envolva reação de foto-Fenton, O3 e O3/UV para o tratamento de soluções aquosas contendo pesticidas comerciais e padrão. Os resultados mostraram que a combinação da radiação UV em meios alcalinos com O3 aumentou significativamente a eficiência do processo de degradação e o sistema foto-Fenton é uma alternativa promissora para o tratamento de efluentes contendo pesticidas.

The theoretical description of the fluoxetine electrochemical determination over a CoO(OH) – Squaraine Dye composite has been carried out in this work. The correspondent mathematical model has been developed and analyzed by means of the linear stability theory and bifurcation analysis. It has been shown that the cobalt(III) oxyhydroxide, stabilized by squaraine dye layer, may be efficient electrode modifier for fluoxetine electrochemical determination. The possibility for the oscillatory and monotonic instabilities has also been verified. DOI: http://dx.doi.org/10.17807/orbital.v13i1.1573

The present study aimed to evaluate the feasibility of developing low-cost N- and Fe-doped TiO2 photocatalysts for investigating the mineralization of 2,4-dimethylaniline (2,4-DMA). With a single anatase phase, the photocatalysts showed high thermal stability with mass losses of less than 2%. The predominant oxidative state is Ti4+, but there is presence of Ti3+ associated with oxygen vacancies. In materials with N, doping was interstitial in the NH3/NH4+ form and for doping with Fe, there was a presence of Fe-Ti bonds (indicating substitutional occupations). With an improved band gap energy from 3.16 eV to 2.82 eV the photoactivity of the photocatalysts was validated with an 18 W UVA lamp (340–415 nm) with a flux of 8.23 × 10−6 Einstein s−1. With a size of only 14.45 nm and a surface area of 84.73 m2 g−1, the photocatalyst doped with 0.0125% Fe mineralized 92% of the 2,4-DMA in just 180 min. While the 3% N photocatalyst with 12.27 nm had similar performance at only 360 min. Factors such as high surface area, mesoporous structure and improved Ebg, and absence of Fe peak in XPS analysis indicate that doping with 0.0125% Fe caused a modification in TiO2 structure.