Three novel input logic gates supported by fluorescence studies: organic nanoparticles (ONPs) as chemo-sensor for detection of Zn²âº and Al³âº in aqueous medium.

Organic nanoparticles (ONPs) of N,N'-ethylenebis(salicylimine) (salen) were synthesized and applied for specific recognition of Zn(2+) and Al(3+) ions in an aqueous medium. The results show that fluorescence intensity rises with the increasing concentration of Zn(2+) in salen solution, proving that salen-ONPs detect Zn(2+) efficiently in the aqueous medium as chemo-sensor. Furthermore, the salen-ONPs/Zn(2+) system performs as an ON-OFF switch between pH 6.0 and 4.0. Amusingly, although salen-ONPs/Al(3+) does not show any significant effect in the fluorescence spectra, highest fluorescence intensity was observed when Al(3+) ion was added to salen-ONPs/Zn(2+) in a sequential order (addition of Zn(2+) to salen-ONPs, followed by Al(3+)). This system can be applied as a novel three inputs logic gate supported by the fluorescence for the detection of Zn(2+) and Al(3+) in biological and environmental samples. It appears that photo induced electron transfer (PET) occurs in the salen-ONPs when the fluorophore is excited. For salen/Zn(2+) system, the PET is being inhibited considerably by lowering the receptor HOMO energy due to the formation of a bond between the metal ion and ligand, enhancing the fluorescence emission. This is consistent with the theoretical study that the energy of HOMO of the ligand is lower than that of Zn(salen)(2+) complex.

Theoretical studies on iron surface coating: adsorption of furan derivatives over Fe(n) clusters (n = 1-4).

In the transition from small molecules to solids, atomic clusters are studied widely not only because they can own unique properties due to the nanosized effect but also because they represent an intermediate stage. A systematic study on the structures and properties of clusters as a function of size could give information on the transition from clusters to bulk and determine at what size a cluster can mimic the bulk solid at least to some extent. The adsorption capability of furan derivatives 2-furfurylamine, 2-furfuryl alcohol and 2-furfuryl mercaptan with different iron-clusters was studied by DFT. The results show that since the compounds possess suitable structural and electronic parameters for the metal adhesion, it is observed that the functional group (NH2, OH and SH) of furan derivatives strongly adsorb over the metal clusters. Moreover, the calculated binding energy supports the existence of a bond between furan derivatives and metal, indicating the transfer of high charge density which in the delocalization region of furan ring to the metal (L(sigma) --> Fe). In the molecular orbital studies by detecting the overlap of HOMO (furan ring and functional group) with LUMO (iron), the binding nature of the compounds is then confirmed.

Synthesis, structure, spectra and redox activities of model compounds for methanogenic bacteria.

Synthetically accessible benzimidazoles have been synthesized and the benzimidazole ligands were complexed with nickel(II) nitrate. A nickel(II) complex of N,N'-bis(benzimidazole-2-ylethyl)ethylenediamine was crystallized in single-crystal form and the structure was investigated by X-ray crystallography. The structure of the complex is bicapped axial coordinated octahedral. Ni(bbes)(2+)(2)[bbes=bis(benzimidazole-2-ylethyl)sulfide] exhibits broad low energy bands in electronic spectra and high redox potential in cyclic voltammetry (CV) rather than Ni(enbzim)(2+) [enbzim =N,N'-bis(benzimidazol-2-ylethyl)ethylenediamine], where high energy well separated bands were observed in the visible region and a more negative redox potential was detected in CV. Experimental studies show that an increasing amount of pi-orbital interaction with the Ni(2+)ion, irrespective of chelate ring may favour the higher redox potential. The higher redox potential of methanogenic bacterial [Ni(II)/Ni(I)] than nickel compounds is one of the main factors for the degradation of organic biodegradable compounds and the further transformation to methane.