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The first fully inorganic Pt(IV) carbonato-complex trans-[Pt(CO3)2(OH)2]2- with a {PtO6} coordination sphere was isolated as the (Me4N)2[Pt(CO3)2(OH)2] (1) salt. The compound 1 was characterized using single-crystal and powder X-ray diffraction, Raman spectroscopy, infrared spectroscopy (FTIR), electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance spectroscopy (NMR), and thermogravimetric analysis (TG). Density functional theory (DFT) calculations were also performed to analyze the spectral features of the complex. 1 crystallizes in the triclinic system (P-1) with a Z of 1. The trans-[Pt(CO3)2(OH)2]2- anion has axial hydroxo ligands and κ2-CO3 ligands, which form an equatorial plane. This anionic complex exhibits notable stability in aqueous solutions, while the axial hydroxo ligand can be readily modified, as exemplified by the acylation of the trans-[Pt(CO3)2(OH)2]2- into trans-[Pt(CO3)2(OAc)2]2- anion. Furthermore, it has been shown that rigid and glittering platinum coatings can be electrochemically deposited from an aqueous solution of 1 without the addition of surfactants.
RESUMO
A combination of multinuclear nuclear magnetic resonance spectroscopy and theoretical calculation based on density functional theory was used for a speciation study of Pt in solutions prepared either by the interaction of [Pt(OH)6]2- with gaseous CO2 in an alkaline solution of platinum(IV) hydroxide ([Pt(OH)4(H2O)2]) or by the dissolution of [Pt(OH)4(H2O)2] in an aqueous KHCO3 solution. The formed solutions contained coexisting Pt(IV) carbonato complexes with κ1- and κ2-coordination modes. The gradual condensation of mononuclear Pt species in such bicarbonate solutions resulted in the formation of PtO2 nanoparticles aggregating into a solid precipitate on prolonged aging. The deposition of PtO2 particles from bicarbonate solutions was adapted for the preparation of Pt-containing heterogeneous catalysts: bimetallic Pt-Ni catalysts were prepared using various supporting materials (CeO2, SiO2, and g-C3N4) and tested for the activity in hydrazine-hydrate decomposition. All prepared materials showed high selectivity with respect to H2 production from the hydrazine-hydrate with PtNi/CeO2 showing the highest rate of H2 evolution. In the long-range evaluation, the PtNi/CeO2 catalyst operating at 50 °C showed an exceptional turnover number value of 4600 producing hydrogen at a 97% selectivity level and with a mean turnover frequency value of about 470 h-1. In the case of the PtNi/g-C3N4 catalyst, for the first time, the photodriven decomposition of hydrazine-hydrate was shown to enhance the productivity of the catalyst by 40%.
RESUMO
The systematic study of the platinum speciation in sulfuric acid solutions of platinum (IV) hydroxide {[Pt(OH)4(H2O)2], HHPA} was performed with the use of a combination of methods. Depending on the prevailing Pt form, the three regions of H2SO4 concentration were marked: (1) up to 3 M H2SO4 forms unstable solutions gradually generating the PtO2·xH2O particles; (2) 4-12 M H2SO4, where the series of mononuclear aqua-sulfato complexes ([Pt(SO4)n(H2O)6-n]4-2n, where n = 0···4) dominate; and (3) 12 M and above, where, along with [Pt(SO4)n(H2O)6-n]4-2n species, the polynuclear Pt(IV) species and complexes with a bidentate coordination mode of the sulfato ligand are formed. For the first time, the salts of the aqua-hydroxo Pt(IV) cation [Pt(OH)2(H2O)4]SO4 (triclinic and monoclinic phases) were isolated and studied with a combination of methods, including the single-crystal X-ray diffraction. The formation of PtO2·xH2O particles in sulfuric acid solutions (1-3 M) of HHPA and their spectral characteristics and morphology were studied. The deposition of PtO2·xH2O was highlighted as a convenient method to prepare various Pt-containing heterogeneous catalysts. This possibility was illustrated by the preparation of Pt/g-C3N4 catalysts, which show an excellent performance in catalytic H2 generation under visible light irradiation with a quantum efficiency up to 5% and a rate of H2 evolution up to 6.2 mol·h-1 per gram of loaded platinum.
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The paper presents the experimental research findings for the integral characteristics of processes developing when two-phase liquid droplets collide in a heated gas medium. The experiments were conducted in a closed heat exchange chamber space filled with air. The gas medium was heated to 400-500 °C by an induction system. In the experiments, the size of initial droplets, their velocities and impact angles were varied in the ranges typical of industrial applications. The main varied parameter was the percentage of vapor (volume of bubbles) in the droplet (up to 90% of the liquid volume). The droplet collision regimes (coalescence, bounce, breakup, disruption), size and number of secondary fragments, as well as the relative volume fraction of vapor bubbles in them were recorded. Differences in the collision regimes and in the distribution of secondary fragments by size were identified. The areas of liquid surface before and after the initial droplet breakup were determined. Conditions were outlined in which vapor bubbles had a significant and, on the contrary, fairly weak effect on the interaction regimes of two-phase droplets.
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OBJECTIVE: Introduction: Ovarian tumours are an actual problem of present-day medicine, being one of the most difficult sections of modern oncology. The majority of ovarian tumours are of epithelial origin. The ovarian Brenner tumour represents a rare epithelial ovarian neoplasm and accounts for 1-2% of all ovarian neoplasms. The aim of the study is to identify clinical and morphological features of ovarian Brenner tumour. PATIENTS AND METHODS: Materials and methods: The material was 5 cases of Brenner ovarian tumour, diagnosed in the study of 4 cases of operational material and 1 case of autopsy observation for the period from 2007 to 2019. Histological and immunohistochemical staining methods were used. The microspecimens were examined on an Olympus BX-41 microscope (Japan). RESULTS: Results: Ovarian Brenner tumour is a rather rare pathology, the histogenesis of which is debatable. Morphological examination is the main method for its diagnosing. Ovarian Brenner tumours developed in women of middle and old age (the average age was 51.8 years). Women with a malignant ovarian Brenner tumour were older than women with a benign variant (the average age in women with a malignant variant was 55.8 years, with a benign variant - 49.3 years). Benign ovarian Brenner tumour occurred more frequently compared with a malignant one. Malignant and benign variants of ovarian Brenner tumour were characterized by a one-sided nature of the lesion with frequent involvement in the pathological process of the left ovary. Clinically, in patients with a benign variant of the Brenner tumour in all cases an abdominal pain syndrome was determined, combined in one case with metrorrhagia. A malignant ovarian Brenner tumour was clinically manifested by severe abdominal pain syndrome, combined in one case with complaints of an increase in the size of the abdomen, and in another case with intoxication syndrome and a clinic of small bowel obstruction. In all cases a malignant ovarian Brenner tumour metastasized to the omentum and in one case also to the small intestine wall. Macroscopically the ovarian Brenner tumour had the form of a node, the dimensions of which were significantly larger for the malignant variant compared with a benign, dense or soft consistency, on the cross section of a whitish-gray or brown color with cysts. A damaged ovary with a malignant variant of Brenner tumour significantly increased in size, while with a benign one, its size did not change or increased slightly. In all cases the malignant and benign variants of ovarian Brenner tumour were combined with various reproductive system organs pathologies (mucinous papillary cystadenoma of the ovary, serous ovarian cyst, ovarian endometriosis, endometrial hyperplasia, cervical nabothian cysts, uterine leiomyoma). CONCLUSION: Conclusions: A study conducted by the authors revealed clinical and morphological features of a rare ovarian tumour - Brenner tumour, which will contribute to a better understanding of this pathology by the doctors of various specialties, and improve the treatment and diagnostic process.
