Thank you mukeshchand ...i will see those review and will discuss if required

[1]A seed crystal is a small piece of single crystal/ polycrystal material from which a large crystal generally of the same material is to be grown.Now to obtain large sized Au nano rods, a seed crystal should either be some some soluble salt of Au (I) or Au (III). Both are found to unsuitable as seed crystal. Au (1) Cl is insoluble while Au (NO3) is very less soluble and there is some possibility of its changing into Au (III) in aqueous medium in atmospheric oxygen. More over, high Au (I)/Au(s) = 1.69V redox potential will not favour the easy formation Au(s) on the AuNP to increase its size to Au nano rods. Even the Au (III) salts will be unsuitable because higher Au (III)/Au(s) = 1.50 V redox potential will aso be unsuitable as there is large difference between the reduction half potential of this metal ion and oxidation half potential of water.

H2 (g) +2OH (-) = 2H20+2e; 0.83V.

So to aggregate AuNP to larger nano rod size, we have to make a typical seeding, i.e. provide a platform to AuNP of such a substance WHICH IS BOTH NOBLE AND POSSESSES HALF REDUCTION POTENTIAL OF THE RANGE OF HALF OXIDATION POTENTIAL OF WATER.Ag (I) [AgNO3 - the most soluble salt ] fits well in both these requirements as Ag(I)/Ag(s) half reduction potential (0.8V) is also of the range of half oxidation potential of water.

[11] There is still another point which should also be considered. The addition of HNO3 and AgNO3 was favourable for the formation of gold nano rods with long ASPECT RATIOS. The effect of the addition of Ag (I) is more than NO3 (-) .The ideal pH being 3-5-2.2; the lower side of pH being more favouable.

Mukeshchand Thakur please can you also send me the review articles.

Thank you