DETERMINATION OF BOD USING A FIA SYSTEM WITH MICROBIAL SENSOR

A microbial amperometric sensor for the determination of the biochemical oxygen demand using Trichosporan cutaneum cells immmobilized in polyvinyl alcohol has been developed. The sensor has a response time of less than 1 min. A linear range is obtained up to 100 mg /1 BOD in the sample. For calibration a glucose/glutamic acid standard is used. A dilution of the waste water is necessary for practical application. Therefore a FIA system was coupled with the BOD sensor. In this way it is possible to analyse waste water up to 1000 mg 1 BOD with a serial coefficient of variation below 5 percent

Magnetic anisotropy in surface supported single ion lanthanide complexes

Single ion lanthanide organic complexes can provide stable magnetic moments with well defined orientation for spintronic applications on the atomic level. Here, we show by a combined experimental approach of scanning tunneling microscopy and x ray absorption spectroscopy that dysprosium tris 1,1,1 trifluoro 4 2 thienyl 2,4 butanedionate Dy tta 3 complexes deposited on a Au 111 surface undergo a molecular distortion, resulting in distinct crystal field symmetry imposed on the Dy ion. This leads to an easy axis magnetization direction in the ligand plane. Furthermore, we show that tunneling electrons hardly couple to the spin excitations, which we ascribe to the shielded nature of the 4f electron

Modifying the Magnetic Anisotropy of an Iron Porphyrin Molecule by an on Surface Ring Closure Reaction

The magnetic properties of adsorbed metalloporphyrin molecules can be altered or tuned by the substrate, additional axial ligands, or changes to the molecules’ macrocycle. These modifications influence the electronic configuration of the fourfold-coordinated central metal ion that is responsible for the metalloporphyrins’ magnetic properties. We report a substantial increase in the effective spin moment obtained from sum-rule analysis of X-ray magnetic circular dichroism for an iron metalloporphyrin molecule on Au(111) through its conversion from iron(II)-octaethylporphyrin to iron(II)-tetrabenzoporphyrin in a surface-assisted ring-closure ligand reaction. Density functional theory calculations with additional strong Coulomb correlation (DFT+U) show that the on-surface reaction alters the conformation of the molecule, increasing its planarity and the ion–surface distance. A spin-Hamiltonian fit of the magnetization as a function of field reveals a substantial increase in the intra-atomic magnetic dipole term (Tz) and a decrease in the magnitude of the easy-plane anisotropy upon ring closure. This consequence of the ring closure demonstrates how new magnetic properties can be obtained from on-surface reactions, resulting here in significant modifications to the magnetic anisotropy of the Fe ion, and sheds light onto the molecule–substrate interaction in these systems