Monolayer deposition of L10 FePt nanoparticles via electrospray route

The deposition monolayers of L1₀ FePt nanoparticles via an electrospraying method and the magnetic properties of the deposited film were studied. FePt nanoparticles in a size of around 2.5 nm in diameter, prepared by a liquid process, were used as a precursor. The size of the deposited particles can be controlled up to 35 nm by controlling the sprayed droplet size that is formed by adjusting the precursor concentration and the precursor flow rate. The droplets were heated in a tubular furnace at a temperature of up to 900 °C to remove all organic compounds and to transform the FePt particles from disordered face centered cubic to an ordered FCT phase. Finally, the particles were deposited in the form of a monolayer film on a silicon substrate by electrostatic force and characterized by scanning electron microscopy. The monolayer of particles was obtained by the high charge on particles obtained during the electrospraying process. The magnetic properties of the monolayer were investigated by magneto-optic Kerr effect measurements. Coercivity up to 650 Oe for a film consisting of 35 nm L1₀ FePt nanoparticles was observed after heat treatment at a temperature of 800 °C.     

Cytotoxic labdane diterpenes and bisflavonoid atropisomers from leaves of Araucaria bidwillii

Chemical investigation of a methanolic extract of leaves from Araucaria bidwillii (Araucariaceae) from Egypt afforded four new labdane diterpenoidal metabolites (1–4) together with one known diterpene, 7-oxocallitrisic acid (5), two triterpenoidal metabolites, 2-O-acetyl-11-keto-boswellic acid (6) and β-sitosterol-3-O-glucopyranoside (7), phloretic acid (8), and two methylated bisflavonoids, agathisflavone-4′,7,7″-trimethyl ether (9) and cupressuflavone-4′,7,7″-trimethyl ether (10). The new metabolites 1–4 were unambiguously identified by applying extensive 1D and 2D NMR spectroscopic studies as well as HRESIMS. The relative and absolute configurations of 1–4 were determined using ROESY and the modified Mosher's method, respectively. All isolated compounds were assessed for their antimicrobial, antitubercular and cytotoxic activities. Among the tested compounds, the new labdane diterpenes 1–4 revealed significant cytotoxic activity against mouse lymphoma L5178Y cell line with IC₅₀ values ranging from 1.4 to 12.9 μM, respectively.     

Ferrocene-peptido conjugates: from synthesis to sensory applications

The field of chemical and biological sensing is increasingly dependent on the availability of new functional materials that enhance the ability of the system to respond to chemical interactions. Organometallic bioconjugates derived from amino acids, peptides, proteins, peptide nucleic acids, and dendrimers have had a profound effect in this area and have endowed modern sensory systems with a superior performance. Owing to their fairly high stability, solubility in various solvents, and excellent redox properties, ferrocene and ferrocenyl conjugates have emerged as one of the most important classes of materials that enable direct observation of molecular interactions and as electron mediators. The low potential, reversible redox behavior of the ferrocene/ferrocenium couple is a unique property that finds widespread application in the design of sensory platforms. Currently, there is significant drive to exploit new organometallic systems, in which the presence of ferrocene acting as a redox center is critical and allows the design of highly sensitive electrochemical sensors for the sensing and recognition of a vast array of analytes.     

Synthesis and characterization of novel chromone Schiff base complexes as p53 activators

A series of chromone Schiff base complexes were prepared and analytically as well as spectroscopically characterized. The ligand was found to act as a monobasic tridentate ligand bonded covalently or coordinatively to the metal ion via deprotonated hydroxyl group, azomethine nitrogen atom and carbonyl oxygen atom of antipyrine moiety. Both electronic spectra and magnetic measurements indicated an octahedral or a distorted octahedral geometry around the metal ions for all metal complexes except the nickel complex, which had a tetrahedral geometry. In addition, the ability of the newly prepared compounds to activate the tumour suppressor p53 in cancer cells was studied, with zinc and copper complexes showing promising activities for p53 ubiquitination compared with diphenylimidazole (reference drug).     

Probing the role of the linker in ferrocene-ATP conjugates: monitoring protein kinase catalyzed phosphorylations electrochemically

The synthesis and electrochemical properties of ferrocene conjugates are presented for the purpose of investigating adenosine 5′‐[γ‐ferrocenoylalkyl] triphosphate ( 1 a – 4 a , ferrocene (Fc)–ATP) as co‐substrates for phosphorylation reactions. Compounds 1 a – 4 a were synthesized, purified by HPLC, and characterized by NMR spectroscopy and mass spectrometry. In solution, all Fc–ATP bioconjugates exhibit a reversible one‐electron redox process with a half‐wave potential (E_1/2) in the 390–430 mV range, peak separations (ΔE_p) in the 40–70 mV range, and the peak current ratio (i_pa/i_pc) near unity. The peptide‐modified surface Glu‐Gly‐Ile‐Tyr‐Asp‐Val‐Pro was used to study the sarcoma‐related protein (Src) kinase activity by employing the Fc–ATP bioconjugates as co‐substrates. Subsequent kinase‐catalyzed transfer of the γ‐Fc‐phosphate group to the tyrosine residues of the surface‐bound peptides was characterized by a formal potential (E^o) ≈390 mV (vs. Ag/AgCl). The Fc‐coverage, estimated by time‐of‐flight secondary‐ion mass spectrometry (TOF‐SIMS) and cyclic voltammetry (CV), suggested validity of Fc–ATP conjugates as kinase co‐substrates. Depending on the length of the alkyl spacer of the Fc–ATP conjugate, different current densities were obtained, pointing to a direct correlation between the two. Molecular modeling revealed that the structural constraint imposed by the short alkyl spacer ( 1 a ) causes a steric congestion and negatively affects the outcome of phosphorylation reaction. An optimal analytical response was obtained with the Fc–ATP conjugates with linker lengths longer than six CH₂ groups.     

On the medicinal chemistry of ferrocene

Organometallic chemistry and biochemistry have been merged in the last two decades into a new field: bioorganometallic chemistry. This new research area was devoted to the synthesis of new organometallic compounds and their biological and medical effects against some types of diseases, such as cancer and malaria. For several years, the use of ferrocene in bioorganometallic chemistry has been growing rapidly, and several promising applications have been developed since ferrocene is a stable, nontoxic compound and has good redox properties. This review will focus on ferrocenyl compounds which have been biologically evaluated against certain diseases. This area has attracted many researchers due to the promising results of some ferrocene compounds in the medicinal applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Characterization of dip-coated ITO films derived from nanoparticles synthesized by␣low-pressure spray pyrolysis

In₂O₃:Sn (Indium Tin Oxide; ITO) films were prepared from a sol solution with highly crystalline ITO nanoparticles (less than 20 nm in size with 10 at.% Sn) which had been prepared by low-pressure spray pyrolysis (LPSP) in a single step. The ITO sol solution was prepared by dispersing LPSP-prepared ITO nanoparticles into ultra pure water. The nanoparticle ITO film was deposited on a glass substrate using a dip-coating method and then annealed in air at various temperatures. The optical transmittances of the ITO films were measured by UV–Vis spectrometry, and the films were found to have a high transparency to visible light (in the case of a film thickness of 250 nm annealed at 400°C, the transparency was in excess of 95% over the range λ=450–800 nm, with a maximum value near 100% at wavelengths above λ=700 nm). The optical transmittances of the films were influenced by the size of the ITO particle used, the film thickness and the annealing temperature. The ITO films showed a minimum resistivity of 9.5×10⁻² Ω cm, and their resistivity was affected by both the ITO particle size and the annealing temperature used.