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Poberznik M.,Institute of Environmental Protection and Sensors | Leis A.,Joanneum Research | Lobnik A.,University of Maribor
Water Science and Technology | Year: 2012

CO 2 gas with a special isotopic signature (δ 13C = -35.2‰vs. VPDB) was used as a marker to evaluate the efficiency of a drinking water treatment method and the effect of an ultrasonic (US) stirrer. This treatment was developed to prevent precipitation and corrosion effects in water-supply systems. The research work was performed using a laboratory-scale pilot plant that was filled with tap water. The stable isotope analyses of δ 13C-DIC (Dissolved Inorganic Carbon) in the water samples indicated that the maximum content of added CO 2 gas in DIC was in the range of 35 to 45%. The use of the US stirrer during the entire experiment decreased the method's overall efficiency by 10%, due to degassing at a late stage of the experiment but accelerated the dissolution process in the early experimental stage. © IWA Publishing 2012.

Urek S.K.,Institute of Environmental Protection and Sensors | Lobnik A.,University of Maribor
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

We present a new optical sensor for the detection of organophosphates by incorporating fluorescent indicator dye into sol-gel material. We used different configurations of immobilization matrices such as thin film and spherical nanoparticles. The sensor thin films were prepared by using acid-catalyzed sol-gel process and the spherical nanoparticles by modified Stöber method. The effects of configuration matrices on the sensor's characteristic were studied. The use of dye-doped nanoparticles improved the detection limit from 0.69 μM to 17 nM, response time from 600 s to 12 s, precision and sensitivity, but reduced the sensor's working rage from 6.9×10 -7 M - 6.9×10-3 M to 1.75×10-8 M - 2.3×10-7 M. © 2011 SPIE.

Lobnik A.,University of Maribor | Spela K.U.,Institute of Environmental Protection and Sensors | Turel M.,University of Maribor | Francic N.,University of Maribor
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

The growing activity in the field of optical chemical sensors has resulted in numerous sensing schemes, new indicator dyes, various polymeric matrix, size and shapes and highly diversified methods of immobilization. The sensor characteristics are dependent upon the choice of indicator, polymer, immobilization technique, and also size. Sol-gel technology provides a low-temperature method for obtaining porous silicate glass matrices. It enables to obtain material in the form of films, powders, monoliths, fibres or nanoparticles. Organic reagents and molecular receptors can be easily immobilized in the matrices. Moreover, one of the unique features of the sol-gel process is that the properties of the final network structure, such as hydrophobicity, thickness, porosity, flexibility, reactivity and stability can be easily tailored by controlling the process conditions, the type and the size of the precursors and catalysis. Here we will report about several sensor designed over the years based on sol-gel materials for monitoring and controlling different parameters, such as heavy metals, amines, phosphates, organophosphates. © 2011 SPIE.

Korent Urek S.,Institute of Environmental Protection and Sensors | Francic N.,University of Maribor | Turel M.,Institute of Environmental Protection and Sensors | Lobnik A.,University of Maribor
Journal of Nanomaterials | Year: 2013

Heavy metal pollution is one of the more serious environmental problems; therefore, there is a constant demand for the development of new analytical tools for its monitoring. An optical chemical sensor represents a good alternative to classical instrumental methods. The mesoporous materials used in optical chemical sensors' fabrications have properties such as high porosity, exceptional adsorption capacity, tuneable 3D shape, geometry, and morphology, which enable improved limit of detection, response time, and selectivity properties of optical sensors. In this review, we firstly present the properties of mesoporous materials, provide a brief description of sensing mechanisms, and briefly discuss the importance of continuous monitoring. Recent advances in those mesoporous silica-based optical sensors used for heavy metal detection have been reported and their advantages and limitations also discussed. This review covers publications that have appeared since 2008. © 2013 Špela Korent Urek et al.

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