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The present work intends to study the
properties of magnesia based refractory aggregates developed from Indian magnesite
by changing lime/silica ratio. The material has been sintered in the
temperature range of 1550C - 1700C. The sintered samples are characterized in
terms of bulk density, apparent porosity, true density, percentage
densification, mechanical, thermo-mechanical properties like cold modulus of
rupture, hot modulus of rupture and thermal shock resistance and structural
properties by XRD. The developed microstructures at different temperatures are
studied through FESEM study and compositional analysis of the developed phases is
done by EDX study.
The citrate reduction method of synthesis of gold nanoparticles (AuNP) is standardized with the assistance of instruments like spectrophotometer and TEM. A correlation has been developed between the particle diameter and the fractional concentration of the reductant. This enables one to assess the diameter of the AuNP to be synthesized, in advance, from the composition of the reaction mixture and the diameter of the synthesized particles can be confirmed simply from spectrophotometry. Further, it has been demonstrated that the synthesized AuNPs serve as excellent acceptors for a super-efficient energy transfer (ET) from the donor coumarin 153, leading to a quenching of fluorescence of the latter. The Stern-Volmer constants determined from the fluorescence lifetimes are in the range 107 - 109 mol-1·dm3 and are orders of magnitude higher than the normal photochemical quenching processes. The energy transfer efficiency increases radically with an increase in the size of the metal nanoparticle. The highly efficient energy transfer and the variation of the efficiency of the ET process with a variation of the particle size is ascribed to a large enhancement in the extinction coefficient and an increase in the spectral overlap between the plasmon absorption band of AuNPs and the fluorescence spectrum of C153 with an increase in the size of the nanoparticles. The impact of the work remains in providing a demonstration of a super quenching effect of the AuNPs and projects that they can be exploited for developing biosensors with high degree of sensitivity, if tagged to the biomacromolecules.