Search

The investigation of laser beam irradiation on different types of butterfly wings has been done previously by using the holographic method. The deformations due to the use of different laser wavelengths were observed. It is well-known that chitin is an abundant component of many complex structures in biological samples, such as butterfly wings. Consequently, as the influence of the chemical structure was taken into account, it was decided to examine the influence of chitin itself in laser-induced deformation in biological samples. Therefore, in this work, the same tests were performed on the film generated from chitin by using different wavelengths of laser. The results obtained strongly suggest that there are no effects of laser beam irradiation on chitin, indicating that chitin itself does not have an influence on the observed deformation of the butterfly wings. It was decided to make some additional measurements of such wings, which would be important for the further course of research in this direction. Some useful graphs were obtained by X-ray diffraction (XRD) and Fourier-Transform Infrared Spectroscopy (FTIR) measurements of particular butterfly wings. The obtained results contribute to a better knowledge of the structure and morphology and may have applications in the industry of artificial materials, especially polymers.

Thermal monitoring of a Briggs-Rauscher oscillatory reaction with a phase transition or the state I (low concentration of iodide and iodine) to the state II (high concentration of iodide and iodine) transition with formation of new solid iodine phase is presented. This is the very first time that an oscillatory reaction and the state I to state II transition have been monitored using a thermal camera. It should be pointed out, that the BR reaction solution is not homogenized by stirring, and that only oxygen production influence the solution mixing. Therefore, the analysis was done at three sampling points on the cuvette where temperature change over time was observed, and compared with average temperature distribution. The first point is chosen to correspond to the top of the solution in the cuvette, followed by one in the middle of the volume and one at the very bottom of the cuvette. Although the state I to the state II transition itself is not reproducible (investigated transition exhibits crazy clock behavior), the overall temperature pattern has shown a reproducible character.

Nowadays phosphate tungsten bronzes (PWBs) attract a lot of attention due to their interesting chemical, mechanical, and optical features. Moreover, tungsten bronzes as inert inorganic solids, with incorporated rare-earth ions in their structure, show interesting and useful electronic properties. Praseodymium doped phosphate tungsten bronze (Pr-PWB) is obtained in the process of phase transformations of PrPW12O40∙6H2O (Pr-PWA) salt. The green crystals of Pr-PWB are formed after the heating of Pr-PWA in a furnace, in a temperature range from room temperature to 650 °C. In the present paper the fluorescent properties are analyzed of Pr-PWB, its precursor – 12-tungstophosphoric heteropoly acid, H3PW12O40∙29H2O (PWA) with Keggin's anion structure, as well as the intermediate – Pr-PWA salt. The luminescent properties where characterized and the obtained results showed that both samples emit in the deep blue region, indicating their potential use as a blue emitting source for white light LED's.

Phosphate tungsten bronzes (PWBs), due to their intriguing and potentially valuable properties, have consistently garnered research attention [1]. In this study, we introduced two rare-earth metallic elements, namely cerium and praseodymium, as dopants for PWBs. This led to the successful synthesis of novel PWBs doped with cerium and praseodymium, which were subsequently subjected to various characterization techniques, including thermal analyses (TA), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDX), and hotoluminescence spectroscopy (PL). The behavior of cerium and praseodymium doped phosphate tungsten bronzes (Ce-PWB and Pr-PWB) [2], was investigated in the Briggs-Rauscher (BR) oscillatory reaction. The alterations in the oscillatory dynamics, brought about by the incorporation of cerium and praseodymium dopants, served as a means to distinguish between these bronzes. Additionally, this approach provided a method for assessing the catalytic properties of the bronzes. Apart from their nonlinear behavior, these bronzes also exhibited photoluminescence in the visible spectrum, specifically in the blue region.

Phosphate-tungsten bronzes (PWBs) constantly attract a lot of attention owing to their interesting chemical, mechanical, and optical properties. Furthermore, tungsten bronzes as inert inorganic solids, exhibit interesting and useful electronic properties when rare-earth ions are incorporated into their structure. Cerium doped phosphate-tungsten bronze (Ce-PWB) is obtained in the process of phase transformations of CePW12O40×6H2O (Ce-PWA) salt. The brown crystals of Ce-PWB are formed after heating of Ce-PWA in a furnace, in a temperature range from room temperature to 650 °C. In the present paper the luminescence properties of undoped PWB and Ce-PWB are analyzed and compared. Regarding the characterized luminescence properties of PWB and Ce-PWB, only PWB matrix showed luminescence, while dopant Ce3+ had no significant influence on the change of the emission spectra with characteristic spectra for this ion. The obtained CIE chromaticity diagrams showed that both samples emit in the deep blue region, suggesting their possible use as a blue emitting source for white light-emitting diodes (LEDs).

The transition from state I ( characterized by low iodide and iodine concentration) to state II (high iodide and iodine concentration) occurs in a nonlinear Briggs-Rauscher (BR) oscillatory reaction. This transition was studied by two methods: potentiometric and holographic. The first derivative technique was applied to the obtained electrochemical and holographic curves of the transition state I→state II to obtain the corresponding slopes. Based on these slopes, the results of the two methods are compared. The obtained holographic slope for the transition from state I to state II is higher than the potentiometric one in all selected reaction sections. In the initial phase of the transition from state I to state II, it is clear that the velocity of the holographic method is twice that of the potentiometric method. While this trend shows a twofold increase at the beginning of the phase transition, it deviates in the other phases, where the holographic measurements show a 1.5-fold higher rate in the middle. The obtained results could have a strong impact on the study of nonlinear systems in the future.

Due to the interesting and potentially useful properties, phosphate tungsten bronzes are constantly being studied and attract a lot of attention. In the present work, two different metallic elements, belonging to the group of rare-earth metals, cerium and praseodymium, were used as a dopants for phosphate tungsten bronzes. Novel cerium and praseodymium doped phosphate tungsten bronzes were successfully synthesized and further characterized by thermal analyses, Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometer and photoluminescence spectroscopy. The behavior of cerium and praseodymium doped phosphate tungsten bronzes were examined in the Briggs-Rauscher oscillatory reaction. The changes in the oscillatory dynamics, caused by the addition of cerium doped and praseodymium doped phosphate tungsten bronzes, are used for distinction of these bronzes and also as a method for testing the catalytic features of the bronzes. Beside the nonlinear behavior, the bronzes have shown photoluminescence in the visible region (blue region).

For the preparation of praseodymium doped phosphate tungsten bronze (Pr-PWB), as a starting material is used 12-tungstophosphoric heteropoly acid H3PW12O40×29H2O (PWA) [1]. PWA was first converted into H3PW12O40×6H2O (6-PWA) by heating it to 80 °C in a kiln. The aqueous PrCl3×H2O solution was prepared by dissolving 0.7102 g of PrCl3×H2O in distilled water. This solution is then mixed with aqueous solution of 6- PWA, slightly heated in order to start the crystallization process and left overnight to finish the crystallization. The produced greenish crystals of praseodymium doped phosphate tungsten bronze are created by heating the obtained salt PrPW12O40×nH2O in a furnace from room temperature to 600 °C. The conditions for thermal phase transformation of praseodymium salt of 12-tungstophosphoric heteropoly acid to produce new praseodymium phosphate tungsten bronze, have been investigated in the current work. The new material (Pr-PWB), synthesized from Keggin's anion structure as a precursor, is successfully formed. The potential practical application of Pr-PWB is in its installation in batteries and fuel cells, as a catalyst, and due to its specific green color it could also be used as a pigment.

The Briggs-Rauscher (BR) reaction is an oscillating reaction in which the oxidation of malonic acid (CH2(COOH)2) in the presence of hydrogen peroxide (H2O2) and potassium iodate (KIO3) is catalyzed with a metal ion (usually Mn2+) in acidic aqueous solution. The BR reaction is very sensitive to the addition of different types of analytes. Every change in oscillatory dynamics, caused by analyte addition, can be used for the appraisal of analyte concentration, as well as its potential antiradical or catalytic activity. The cerium doped phosphate tungsten bronze (Ce-PWB) was obtained by thermal treatment and characterized by TGA, DSC, FTIR, and XRPD technics. In this work, the behavior of Ce-PWB and its influence on BR oscillatory dynamics was examined. The results revealed that an increase in the mass of added Ce-PWB has slightly shortened the oscillation time duration with the minimal change in the form of the basic BR oscillogram, suggesting the catalytic effect of this bronze in oscillatory reaction

The calcium phosphate tungsten bronze (Ca-PWB) has been synthesized and characterized (TGA, DSC, XRPD, FTIR, SEM). The influence of solid insoluble materials Ca-PWB, as well as lithium doped (Li-PWB) and cation free phosphate tungsten (PWB) bronzes on the oscillatory Briggs-Rauscher (BR) reaction dynamics, is compared. The results show that doping with Li and Ca reduces sensitivity of the BR reaction towards bronzes addition. These findings suggest the usage of the BR reaction as an innovative method for testing of different properties of bronze material. The behavior of PWB in the BR reaction is significantly changed with divalent cation (Ca2+) doping. The reasons for the different bronzes behavior were found in their calculated unit cell volumes. Namely, the compressed Ca-PWB unit cell volume indicates the difficult availability of the active site for heterogeneous catalysis. Hence, the linear correlation (slope) of the BR oscillogram’s length (τosc) vs. mass of bronze in BR reaction might be considered as a new parameter for the evaluation of the bronzes catalytic activity., У овом раду синтетисана је и окарактерисана (TGA, DSC, XRPD, FTIR, SEM) нова калцијумом допирана фосфат волфрамова бронза (Ca-PWB). Испитан је и упоређен утицај фосфат волфрамове бронзе (PWB), литијумом допиране фосфат волфрамове бронзе (Li-PWB) и калцијумом допиране фосфат волфрамове бронзе (Ca-PWB) на осцилаторну динамику Briggs-Rauscher (БР) реакције. Резултати показују да допирање катјонима Li+ и Ca2+ смањује осетљивост БР реакције на додатак нерастворних бронзи, што се огледа у смањивању нагиба праве осцилаторног времена (τosc) БР реакције у функцији масе додате допиране бронзе. Добијени резултати сугеришу употребу БР реакције као иновативне методе за испитивање различитих својстава допираних и недопиране фосфат волфрамове бронзе. Разлози за различито понашање бронзи у осцилаторној реакцији пронађени су у различитим величинама јединичних ћелија PWB, Li-PWB и Ca-PWB. Наиме, најмања вредност, тј. сабијање јединичне ћелије допирањем калицијумом указује на тежу доступност активних места за хетерогену катализу. Каталитичка активност бронзи усмерена је ка реакцијама оксидације које укључују водоник-пероксид (један од реактаната БР реакције). Стога би се линеарна корелација (нагиб) τosc у функцији масе бронзе у БР реакцији могла сматрати новим параметром за процену каталитичке активности бронзе, али и других материјала.

The Briggs-Rauscher (BR) reaction is an oscillating reaction in which the oxidation of malonic acid (CH2(COOH)2) in the presence of hydrogen peroxide (H2O2) and potassium iodate (KIO3) is catalyzed with a metal ion (usually manganese ion (Mn2+)) in an acid solution (HClO4). It is well known that the BR reaction represents a chemical system that is extremely sensitive to the addition of different types of analytes. Every change in oscillatory dynamics, caused by analyte addition, can be used for the assessment of analyte concentration, as well as its potential antiradical activities. The basic idea of this work is to use the oscillatory reaction, as an unusual and novel system for distinguishing different types of insoluble materials such as bronzes, specifically phosphate tungsten bronze (PWB) and phosphate molybdenum bronze (PMoB). Regarding the results obtained, the increasing mass of PWB leads to a significant decrease of BR oscillatory time, while the addition of PMoB has not affected the BR reaction dynamics. The obtained different behavior of PWB and PMoB introduced the BR reaction as a systemdetector for these two types of bronzes. In order to investigate the mechanism of bronzes action in BR oscillatory reaction, the pH and electric conductivity measurements, as well as inductively coupled plasma and the cyclic voltammetry measurements were done. This work extends the practical aspect of the BR reaction for the examination of solid materials. Furthermore, the obtained results open a new section of oscillatory reaction usage in material science and catalysis in general.