Rózsa Szűcs

Dibenzophosphapentaphenes: Exploiting P Chemistry for Gap Fine-Tuning and Coordination-Driven Assembly of Planar Polycyclic Aromatic Hydrocarbons

A synthetic route to planar P-modified polycylic aromatic hydrocarbons (PAHs) is described. The presence of a reactive σ(3),λ(3)-P moiety within the sp(2)-carbon scaffold allows the preparation of a new family of PAHs displaying tunable optical and redox properties. Their frontier molecular orbitals (MOs) are derived from the corresponding phosphole MOs and show extended conjugation with the entire π framework. The coordination ability of the P center allows the coordination-driven assembly of two molecular PAHs onto a Au(I) ion.

Synthesis, electronic properties and WOLED devices of planar phosphorus-containing polycyclic aromatic hydrocarbons.

We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P-containing PAHs exhibit properties expected for an emitter in white organic light-emitting diodes (WOLEDs).

Phosphorus-Containing Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are highly appealing functional materials in the field of molecular electronics. In particular, molecular engineering of these derivatives by using organic chemistry is a powerful method to tune their properties from the point of view of the band gap and supramolecular assemblies. Another way to achieve such control is to take advantage of the specific reactivity of heteroatoms placed within the sp2 -carbon framework. This strategy has been successfully applied to nitrogen, sulfur and boron. In this review, examples of phosphorus-containing PAHs and the effect of the phosphorus environment on the electronic properties from both experimental and theoretical points of view are discussed.

Green synthesis of gold nanoparticles by thermophilic filamentous fungi

Alternative methods, including green synthetic approaches for the preparation of various types of nanoparticles are important to maintain sustainable development. Extracellular or intracellular extracts of fungi are perfect candidates for the synthesis of metal nanoparticles due to the scalability and cost efficiency of fungal growth even on industrial scale. There are several methods and techniques that use fungi-originated fractions for synthesis of gold nanoparticles. However, there is less knowledge about the drawbacks and limitations of these techniques. Additionally, identification of components that play key roles in the synthesis is challenging. Here we show and compare the results of three different approaches for the synthesis of gold nanoparticles using either the extracellular fraction, the autolysate of the fungi or the intracellular fraction of 29 thermophilic fungi. We observed the formation of nanoparticles with different sizes (ranging between 6 nm and 40 nm) and size distributions (with standard deviations ranging between 30% and 70%) depending on the fungi strain and experimental conditions. We found by using ultracentrifugal filtration technique that the size of reducing agents is less than 3 kDa and the size of molecules that can efficiently stabilize nanoparticles is greater than 3 kDa.

Chemically coded time-programmed self-assembly

Dynamic self-assembly is of great interest in the fields of chemistry, physics and materials science and provides a flexible bottom-up approach to build assemblies at multiscale levels. We propose a method to control the time domain of self-assembling systems in a closed system, from molecular to material level using a driving chemical system: methylene glycol–sulfite pH clock reaction coupled to lactone hydrolysis. The time domain of the transient pH state (alkaline) and the time lag between the initialization of the reaction and the pH change can be efficiently fine-tuned by the initial concentration of the reagents and by the chemical composition of the lactone. The self-assembly of pH-responsive building blocks can be dynamically driven by this kinetic system, in which the time course of the pH change is coded in the system. This approach provides a flexible and autonomous way to control the self-assembly of pH responsive building blocks in closed chemical systems far from their thermodynamic equilibrium.

Synthesis and electronic properties of polycyclic aromatic hydrocarbons doped with phosphorus and sulfur

In this work, we report on the synthesis of polyaromatic hydrocarbons containing phosphole and thiophene rings at the edge. The ring-closure reactions have been investigated by theoretical calculations. The optical and electrochemical properties and density functional theory calculations showed that the properties depend on the relative position of these five membered rings in the PAH structure.

Strategies toward phosphorus-containing PAHs and the effect of P-substitution on the electronic properties

Abstract In this paper, we report on the different synthetic strategies which led to the preparation of a whole family of polyaromatic hydrocarbons containing a P-atom at the edge. In particular, we show from both experimental and theoretical perspective how the Scholl method has to be adapted to the specificity of organophosphorus derivatives. The P-modified PAHs possess the classical phosphane reactivity that allows fine-tuning of their electronic properties as evidenced by spectro-electrochemistry and theoretical calculations. In particular, the effect of P-substitution on the aromaticity of the different cycles of the PAH was studied.

pH mediated kinetics of assembly and disassembly of molecular and nanoscopic building blocks

Self-assembly occurs when building blocks of the system interact with one another through interactions existing between them. Proper temporal control of these interactions can lead to formation of transient self-assembled states. pH mediated self-assembly is one of the powerful tools to stabilize and destabilize structures consisting of different sized building blocks. Here we investigate the kinetics of pH triggered reversible transformation of two building blocks using a relaxation method, reversible vesicle–micelle transformation of oleic acid molecules and dispersion–aggregation of pH sensitive gold nanoparticles. We found significant differences in the characteristic times (two orders of magnitudes) between the disassembly processes—from an ordered structure to a less ordered structure (in the case of oleic acid molecules) or to single building blocks (in the case of nanoparticles)—and the self-assembly processes (bilayer formation or aggregation of nanoparticles). It can be explained by a sophisticated interplay between repulsive (electrostatic) and attractive (van der Waals) interactions.

Sensitivity enhancement for mycotoxin determination by optical waveguide lightmode spectroscopy using gold nanoparticles of different size and origin

Mycotoxins, present in a wide range of food and feed commodities, are toxic secondary metabolites produced by a number of different fungi. Certain mycotoxins do not readily degrade at high temperatures, therefore are resistant to food processing, and consequently are present in the human and animal food supply. Optical waveguide lightmode spectroscopy (OWLS) was applied for the detection of aflatoxin B1, in a competitive immunoassay format, to compare the analytical sensitivity achieved with an immunosensor design allowing signal enhancement by increasing the sensor surface through immobilization of gold nanoparticles (AuNPs) of different size and origin (obtained by chemical or biotechnological synthesis). The effects of AuNPs median size, the methods of sensitization and the biochemical parameters on immunosensor performace were examined. After optimization of the sensitized sensor surface, an immunosensing method was developed for the analysis of aflatoxin in paprika matrix and the results were compared with HPLC reference measurements.