Choice of Antenna

A number of factors must be considered during the designing of luminescent lanthanide complexes, some of the most important factors will now be discussed. These factors include the nature of the lanthanide ion, choice of antenna, degree of coordination, solvent, etc. 

So our choices of the two antennas is not unique for separately emphasizing the Lorenz vector and scalar potentials. All that is required is for the two to have the same exterior fields (say, electric dipole fields, or more general multipole fields) with different potentials (related by the gauge condition). In a classical electromagnetic sense, these antennas cannot be distinguished by exterior measurements. This is a classical nonuniqueness of sources. In a QED sense, the same is the case due to gauge invariance in its currently accepted form. 

The formation of luminescent lanthanide complexes relies on a number of factors. The choice of coordinating ligand and the method by which the antenna chromophore is attached to it, as well as the physical properties of the antenna, are important. In order to fully coordinate a lanthanide ion, either a high-level polydentate ligand such as a cryptate 1 or a number of smaller ligands (such as 1,3-diketones, 2) working in cooperation are required. Both 1 and 2 are two of the simplest coordination complexes possible for lanthanide ions. In both cases there are no antennae present. However, the number of bound solvent molecules is decreased considerably from nine (for lanthanide ions in solution) to one to two for the cryptate and three for the 1,3-diketone complexes. 

Example calculation for diffusion of multiple chemicals Consider a mix of chemicals that differ greatly in molecular mass (and hence in their diffusion coefficients), such as a 3 1 ratio of ethanolihexadecanol in the air surrounding a sensory hair or filiform antenna. The 16-carbon alcohol will be approximately eight times as massive as the 2-carbon alcohol. The diffusion coefficients (D) are 1.32 x 10 5 m2/s for ethanol (Welty el al., 1984) and 2.5 x 10 6 m2/s for hexadecanol (using the value for bombykol), both in air at 298 K. What will the rate of interception be at the level of a sensory hair for these two chemicals The answer (and choice of equation) depends on the boundary conditions. 

The luminescence intensity and decay time of EuCls in carboxymethyl cellulose membranes is decreased in presence of heavy metal ions like Cu" or Cu ", but also Cr " and Fe " exert a distinct quenching effect [111]. It is not likely that a sensor with high specificity can be prepared on the basis of LLCs that is free of interferences from other metal ions. However, an adequate choice of the ligand system may help to improve the selectivity of the response. Another approach uses a sol-gel technique to embed a complex of Eu " and silanized 2,6-pyridine-dicarboxylic acid as antenna in a silica network. This luminescent material can sense copper ion concentrations in water down to 50 pg but the sensor was not evaluated with respect to interferences of other metal ions or in environmental samples [112]. 

The basic horizontahy polarized panel antenna can be modihed to produce circular polarization through the addition of verticahy polarized radiators. Panel designs offer broad bandwidth and a wide choice of radiation patterns. By selecting the appropriate number of panels located around the tower, and the proper phase and amphtude distribution to the panels, a number of azimuth patterns can be realized. The primary drawback to the panel is the power distribution network required to feed the individual radiating elements. 

Dielectric properties of the nonconductive material play an important role. A wrong choice of material would compromise the performance of the antenna. The dielectric properties are affected by several physical parameters snch as temperature,... 

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