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The effects of rare earth site doping on the structural, superconducting and magnetic properties of SmFeAsO0.7F0.3 iron pnictide are investigated. Gd3+ and Ce3+ ions are chosen by virtue of their position being on either side of Sm3+. Doping of both smaller (Gd3+) and larger (Ce3+) ions at the Sm3+ site increases the TC up to 55 K. Doping with the smaller Gd3+ results in lattice contraction and thereby enhances TC. It is interesting to observe that though Ce3+ doping in SmFeAsO0.7F0.3 exhibits an increase in lattice parameters, a substantial enhancement of TC occurs. The enhancement in TC due to increased charge carrier concentration is also confirmed using Hall Effect measurement. Apart from TC enhancement, the simultaneous doping of both at oxygen and rare earth sites prominently increases the superconducting properties such as JC, HC1 and HC2. The co-doped samples also exhibit better magnetic field dependence of JC over the entire field of study. It is also observed that the Ce3+ doped sample shows higher JC in the high field region due to its enhanced flux pinning properties.

The influence of rare earth (RE – Ce, Gd) doping at the Nd site in the NdFeAsO0.7F0.3 superconductor wherein Ce and Gd have ionic radii in the order Ce > Nd > Gd is investigated. The structural and superconductivity characterization of the pure and doped samples show that Ce doping enhances the TC of Nd1−xRExFeAsO0.7F0.3 to a maximum of 53.6 K at x = 0.1 while Gd doping attains a TC of 55.1 K at x = 0.15. Interestingly, both Ce and Gd doping create neither secondary phases nor precipitates within the detection limit of XRD. However, the lattice defects due to Ce and Gd doping modifies NdFeAsO0.7F0.3 and assists in pinning the flux lines on these defects thereby exhibiting an enhanced JC(H) performance especially at high fields. It is also observed that the relatively small ionic size of Gd is more effective in TC enhancement, while the lattice defects due to larger ionic size of Ce favor the remarkable enhancement of JC(H).

The chromogenic complex 1 x Zn (where 1 is (E)-4-(4-dimethylamino-phenylazo)-N,N-bispyridin-2-ylmethyl-benzenesulfonamide) showed high affinity toward the phosphate ion in tetrabutylammonium phosphate in acetonitrile solution and could preferentially bind to adenosine triphosphate (ATP) in aqueous solution at physiological pH. This binding caused a visual change in color, whereas no such change was noticed with other related anions (adenosine monophosphate, adenosine diphosphate, pyrophosphate, and phosphate) of biological significance. Thus, 1 x Zn could be used as a staining agent for different biological cells through binding to the ATP, generated in situ by the mitochondria (in eukaryotes). For prokaryotes (bacteria) the cell membrane takes care of the cells' energy conversion, since they lack mitochondria. ATP is produced in their unique cell structure on the cell membrane, which is not found in any eukaryotes. These stained cells could be viewed with normal light microscopy. This reagent could even be used for distinguishing the gram-positive and the gram-negative bacteria (prokaryotes). This dye was found to be nonlipophilic in nature and nontoxic to living microbes (eukaryotes and prokaryotes). Further, stained cells were found to grow in their respective media, and this confirmed the maintenance of viability of the microbes even after staining, unlike with many other dyes available commercially.