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In the past few years, tellurium has attracted much attention as it is widely used in a large number of important industrial applications. Despite its importance, there is a lack of data on its salts in the literature. In this study, different sparingly soluble tellurite salts (e.g., Ag2TeO3, PbTeO3, CaTeO3, SrTeO3 and BaTeO3) were prepared and characterized using various techniques including powder X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometry, Fourier transform infrared spectroscopy and thermogravimetric analysis as well as differential scanning calorimetry. Moreover, the solubility and solubility product of these salts are studied by potentiometric method using carbon paste sensors. By applying standard and double standard addition methods, the tellurite ion content in the supernatant liquid (TeO32− ) was determined at 25 °C. The solubility products were confirmed by atomic absorption spectroscopy and complexometric titrations, which indicate the high sensitivity and accuracy of the proposed potentiometric method. In addition, thermodynamic parameters such as Gibbs free energy ∆G°, enthalpy ∆H° and entropy ∆S° of the dissociation process or solution were calculated using the Debye–Huckel equation via the determination of solubility of metal tellurite salts at different temperatures.

In this work, scanning electron microscopy (SEM) was used for the characterization of chemically modified carbon paste sensors (CMCPSs), with the aim of understanding their chemical and electrochemical properties. The work also provides a microscopic study on the role of the binder, type of carbon, amount and nature of modifier, composition of the carbon paste and its impact on the electrochemical performance of the sensor. In addition, energy dispersive X-ray spectroscopy (EDX) was utilized for the direct observation of the interaction between the chemical modifier and the carbon paste. This has enabled the fabrication of new sensitive and selective chemically modified carbon paste sensors that were successfully applied for the detection of tellurite ions in pure solutions, environmental and biological samples. This work provides new insights on the rational design and integration of carbon paste sensors for a variety of applications.

Determination of tellurium compounds is of particular interest because of the intrinsic toxicity associated with its water-soluble oxyanions, tellurite TeO32−. Among various analytical approaches, carbon paste sensors (CPSs) are widely used for the determination of heavy metals, nucleic acids and other organic compounds due to their simplicity, sensitivity and cost-effectiveness. In this study, chemically modified carbon paste sensor is developed for the analysis of tellurite ions in pure and in real samples. The sensor showed nearly Nernstian behavior (30 mV) with wide linear range and low detection limit. Moreover, the sensor was successfully applied to the determination of tellurite in environmental and biological samples such as wastewater, human serum, tellurite culture media, synthetic tellurite-cefotaxime and tellurite/tellurate mixtures. The results show high recovery rates, selective and highly reproducible response, indicating the suitability of the proposed sensor for practical applications. In addition, we studied how several parameters such as the type of carbon, type of the plasticizer, amount of the modifier and composition of the sensor affect its electrochemical performance. This was achieved by tracing the morphology and composition of the electrode using optical and atomic force microscopy. The combination of these techniques provides valuable information on the physical, mechanical and chemical properties of the sensor, which proved to be very helpful in understanding its behavior under different chemical conditions. The study also gives some insights on the optimization of chemical sensors based on chemically modified carbon paste sensors.

There is significant interest in the development of methods to create hybrid materials that transform capabilities, in particular for Earth-abundant metal oxides, such as TiO2, to give improved or new properties relevant to a broad spectrum of applications. Here we introduce an approach we refer to as ‘molecular cross-linking’, whereby a hybrid molecular boron oxide material is formed from polyhedral boron-cluster precursors of the type [B12(OH)12]2–. This new approach is enabled by the inherent robustness of the boron-cluster molecular building block, which is compatible with the harsh thermal and oxidizing conditions that are necessary for the synthesis of many metal oxides. In this work, using a battery of experimental techniques and materials simulation, we show how this material can be interfaced successfully with TiO2 and other metal oxides to give boron-rich hybrid materials with intriguing photophysical and electrochemical properties.

In the version of this Article originally published, Liban M. A. Saleh was incorrectly listed as Liban A. M. Saleh due to a technical error. This has now been amended in all online versions of the Article.