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Strain at surfaces and interfaces play an important role in the optical and electronic properties of materials. MeV ion-induced strain determination in single crystal silicon substrates and in Ag (nanoisland)/Si(111) at surface and interfaces has been carried out using transmission electron microscopy (TEM) and surface-sensitive X-ray diffraction. Ag nanoislands are grown under various surface treatments using thermal evaporation in high vacuum conditions. Irradiation has been carried out with 1.5 MeV Au 2+ ions at various fluences and impact angles. Selected area electron diffraction (SAED) and lattice imaging (using TEM) has been used to determine the strain at surface and interfaces. Preliminary results on the use of surfacesensitive asymmetric x-ray Bragg reflection method have been discussed. The TEM results directly indicate a contraction in the silicon lattice due to ion-induced effects. The nanoislands have shadowed the ion beam resulting in lesser strain beneath the island structures in silicon substrates. High-resolution lattice imaging has also been used to determine the strain in around amorphization zones caused by the ion irradiation.

Fabrication of Hg nanoparticles (NPs) templated on plasmid DNA has been investigated here. The Hg NPs get embedded inside the DNA scaffold through local melting of double helix due to the strong and exclusive interaction of the NPs with the nitrogen of the nucleic acid bases. The interaction of the Hg NPs with the guanine-cytosine base pair sites is responsible for the formation of two Hg metal-base complexes that can find application as the signature of ion-DNA interactions. The modifications in the transport properties of metal conjugated DNA can be utilized as sensor for mercury contamination.