Wizards who select a bonded object begin play with one at no cost. Objects that are the subject of an arcane bond must fall into one of the following categories: amulet, ring, staff, wand, or weapon. These objects are always masterwork quality. Weapons acquired at 1st level are not made of any special material. If the object is an amulet or ring, it must be worn to have effect, while staves, wands, and weapons must be held in one hand. If a wizard attempts to cast a spell without his bonded object worn or in hand, he must make a concentration check or lose the spell. The DC for this check is equal to 20 + the spell’s level. If the object is a ring or amulet, it occupies the ring or neck slot accordingly.
So, it is masterwork (both ends) and no special materials.
From there your GM can rule in one of two ways:1) You may pay the 90gp to have one end silvered.
2) You must purchase a new weapon and make that your arcane bond if you wish it to have special materials but that is not the free weapon you get at level 1.
The stricter interpretation is #2.
If you want an arcane bond made of special materials, you can simply buy or craft one, then perform the ritual to make it your new arcane bond. You'll have to save up 200 gp for the ritual in addition to the cost of your new bonded item.
In the case of a quarterstaff, though, it cannot strictly be made of silver:
A complex process involving metallurgy and alchemy can bond silver to a weapon made of steel so that it bypasses the damage reduction of creatures such as lycanthropes.
On a successful attack with a silvered slashing or piercing weapon, the wielder takes a –1 penalty on the damage roll (with a minimum of 1 point of damage). The alchemical silvering process can't be applied to nonmetal items, and it doesn't work on rare metals such as adamantine, cold iron, and mithral.
A quarterstaff is a simple piece of wood, about 5 feet in length.
Doh, good point blahpers. I was thinking more about the bonded object side and not 'can it be made of silver'. LOL