Quantum Dots — Characterization, Preparation and Usage in Biological Systems

The use of fluorescent nanoparticles as probes for bioanalytical applications is a highly promising technique because fluorescence-based techniques are very sensitive. Quantum dots (QDs) seem to show the greatest promise as labels for tagging and imaging in biological systems owing to their impressive photostability, which allow long-term observations of biomolecules. The usage of QDs in practical applications has started only recently, therefore, the research on QDs is extremely important in order to provide safe and effective biosensing materials for medicine. This review reports on the recent methods for the preparation of quantum dots, their physical and chemical properties, surface modification as well as on some interesting examples of their experimental use

Modern Natural Sciences Could Inspire from Classical Chinese Metaphysics to Better Understand the Nature of Being

Abstract According to the latest scientific estimates, all resources needed for survival of Humankind on Earth are already in a deficit of up to one and a half planet! To slow down this rapidly widening deficit we are morally obliged to correct our behaviors not only from one to another but, most of all, toward the Earth! For that reason a radical reevaluation of many misinterpretations in present astrophysics, quantum theory and common natural sciences (also because of some incorrect religious opinions) are required, too. To search for a fundamental model to solve these problems is therefore necessary not only to find the most modern scientific, metaphysical and astrophysical solutions but also with the help of a comparative analysis to consider answers to similar questions by some ancient cultures and civilizations on Earth. Hoping to be inspired in our modern world-view with a willingness to change our misinterpretation of Nature, I present in this paper an analysis of ancient Chinese worldview opinions as they contrast with our present prevalent scientific assumptions. However, all this is quite fatally linked with adopting a true metaphysical knowledge about the real substance of the everlasting Multiverse of being (as well as of our Universe in it) and with our acceptance of its bipolar dialectical patterns of all existing processes within it. Modern science considers only a one-directional, especially linearly occurring fundamental axioms, such as entropy, laws of thermodynamics, or the law of conservation of energy. Ancient Chinese concept of the Great Change explains the Universe as a cyclical, infinite flow of contradictory dialectical transformations of its basic Energy, the Energy which is originally a Nothing/Emptiness, stemming from its antipodal bipolar forces=gravitation which is periodically (but not mechanically) reversing its direction. If its anonymous "Nothing" in the Multiverse/Universe (also in the being of our Earth) is not an absolute "nothing" but if it is that pure Energy, full of movement as well as full of information, permanently changing its antinomic polarizations, we are forced to consider such metaphysical reality and synchronize our existence on Earth with its intrinsic laws

Study of intergranular corrosion in austenitic stainless steels using electrochemical impedance spectroscopy

Abstract Electrochemical impedance spectroscopy (EIS) has been used to detect sensitization in austenitic stainless steels that are heat treated in the temperature regime 600–820 °C to produce different degrees of sensitization in the material. The tests were conducted at five different DC potentials in the transpassive region. The quantitative determination of degree of sensitization has been done using double loop electrochemical potentiokinetic reactivation tests (DL-EPR). The correlation between EIS Nyquist diagrams and DL-EPR degree of sensitization values has been studied. The EIS technique can be used as a qualitative tool in determining the intergranular corrosion in austenitic stainless steels that are heat treated at a given temperature

Association interaction and voltammetric determination of 1-aminopyrene and 1-hydroxypyrene at cyclodextrin and DNA based electrochemical sensors

The aim of this work was voltammetric determination of 1-aminopyrene and 1-hydroxypyrene using carbon paste electrodes modified with cyclodextrin derivatives and double stranded deoxyribonucleic acid (dsDNA). The detection schemes based on a preconcentration and differential pulse voltammetric (DPV) determination at beta-cyclodextrin and gamma-cyclodextrin modified carbon paste electrode (beta-CD/CPE, gamma CD/CPE), neutral beta-cyclodextrin polymer and carboxymethyl-beta-cyclodextrin polymer modified screen-printed electrode (beta-CDP/SPE, beta-CDPA/SPE) and dsDNA modified screen-printed electrode (DNA/SPE) are proposed for the trace determination of studied analytes within the concentration range from 2 x 10(-8) to 4 x 10(-7) mol dm(-3) and from 2 x 10(-7) to 4 x 10(-6) mol dm(-3) with the limits of quantification down to 10-8 mol dm-3. Depending on pH, 1-aminopyrene interacts with both surface attached CD and DNA by electrostatic bonds and supramolecular complexation while 1-hydroxypyrene associates with the CD hosts via complexation. The 1-aminopyrene interaction with dsDNA was confirmed by fluorimetric measurements in the solution phase using a competing DNA-TO-PRO-3 dye complex. In addition, the effect of temperature on this association was investigated using an electrically heated DNA-modified carbon paste electrode (DNA/CPE). (c) 2005 Elsevier B.V. All rights reserved