Please help me out with answer...
Can a diode be used 4 amplification purpose... If yes give me some specific applications...
Hope my information is sufficient.:)

No

No

YES.
See A.W. Holt "Diode Amplifiers" Bureau of Standards . Old research conducted in the 1950's. The Nov. 1954 issue of Radio Electronics has example designs and theory behind it.

Additionally, see: http://www.youtube.com/watch?v=3DA07A6BLDg and other links there concerning audio amplification using diodes.

I had the same doubt, becoz, if we luk at diode characteristics, ders a significant increase in current fr small increase in voltage...

So wudn't that account as amplification of current based on voltage..