I'm unaware of any research suggesting that UV light can be used to transform fullerenes into diamonds and, indeed, I can't think of any reason why such a transformation would occur.
Plenty of people have tried to create diamond-like structures from fullerenes but with little success. Yoo & Nellis, for example, claimed success using high shock pressures ('Phase Transformations in Carbon Fullerenes at High Shock Pressures', Science, 1991) but others failed to replicate their results. Webb, Qadri, et al tried high pressure techniques but with limited success. ('Novel techniques for the preparation of synthetic diamond', High Pressure Research, 1990). Bocquillon, Bogicevic, et al tried again in 1993. ('C60 Fullerene as Carbon Source for Diamond Synthesis', Journal of Physical Chemistry, 1993).
If you can achieve an alchemist's dream using UV, you'll probably win a Nobel Prize and make a fortune! Good luck in your efforts though ;-)