Aljoša Košak

Removal of Pb(II) ions from aqueous systems using thiol-functionalized cobalt-ferrite magnetic nanoparticles

We have investigated the removal of Pb2+ ions from water using thiol-functionalized, cobalt-ferrite, magnetic nanoparticles. These magnetic nanoparticles were prepared using the co-precipitation method and their surfaces were modified with tetraethoxy silane and 3-mercaptopropyl trimethoxysilane in order to provide a sufficient surface concentration of the thiol (–SH) functional groups. The adsorption of the Pb2+ ions from the aqueous solutions onto the thiol-functionalized, cobalt-ferrite, magnetic nanoparticles was studied. The investigated parameters include the pH value of the model water, the concentration of the adsorbent, the contact time and the temperature of adsorption. The removal of the Pb2+ was found to be greater at the higher pH values and increasing the temperature was also found to increase the removal of Pb2+ ions.

The Preparation of Spinel Ferrite Nanoparticles Using Precipitation in Water-in-Oil Microemulsions

MnZn-ferrite nanoparticles with a narrow size distribution were prepared in situ in water-CTAB-hexanol microemulsions using a two-step process: the precipitation of the corresponding hydroxides, followed by the oxidation of the Fe2+. The influence of the temperature and the time of the precipitation step was systematically studied.

Nanostructured Materials Use in Sensors: Their Benefits and Drawbacks

The development of nanoscale materials for optical chemical sensing applications has emerged as one of the most important research areas of interest over the past decades. In this chapter we firstly present some general aspects of nanostructured materials and give a description on the analytical aspects of sensors and sensing principles. The broad variety of nanomaterials as well as sensors’ design made us to limit our presentation, which concentrates on nanomaterials, such as quantum dots, polymer- and sol-gel-based particles. The benefits and drawbacks of the properties of these nanomaterials used in optical sensing applications are given, and the recently developed optical chemical sensors and probes based on photoluminescence are overviewed. Finally, some future trends of the nanomaterial-based optical chemical sensors are given.

Syntheses of Ferrite Nanoparticles Using Ultrasound Irradiation

Sonochemically assisted co-precipitation has been used to prepare nanosized manganesezinc- ferrite powder. A suspension of constituent hydroxides was ultrasonically irradiated for various times with high-intensity ultrasound radiation (20 kHz, 750 W) using a direct-immersion titanium horn. The average grain size and magnetization of the synthesized MnZn-ferrite nanoparticles gradually increases with the time of ultrasonic irradiation.

Magnetic Silica Nanocomposites as Optical Tools in Biomedical Applications

As a result of their size and versatile chemistry, today’s nanomaterials represent powerful tools for several biomedical applications. Various types of nanomaterials have proven to be practical, not only for determining clinically relevant parameters, but also for diagnostics, drug delivery and the treatment of diseases (e.g., cancer). Of particular promise are those nanocomposite structures with multifunctional capabilities. In this chapter we focus on magnetic silica nanocomposites, combined with an optical component, such as organic fluorescent dyes or quantum dots. The most important characteristics of these nanomaterials are presented, together with their specific uses in biomedical applications. It was observed that findings based on in-vitro measurements were not always in agreement with in-vivo applications. Additionally, the use of these nanocomposites in clinical trials remains a long-term goal.

An optical biosensor based on His6-OPH for organophosphate detection

In this work we describe a method for immobilizing the hexahistidine-modified OPH (His6-OPH) enzyme via sol-gel technology in a porous material while retaining its catalytic activity. The potential use of each bio-sensing material was checked by quantifying the enzymatic properties, such as the relative activity of the immobilized enzyme, its Michaelis- Menten equation parameters and its stability under extreme working conditions (pH, T). The bio-sensor material was also characterised by SEM as well as in terms of its reversibility and sensitivity.