小 +
姓 ("Little + Surname") is the standard friendly address for a younger or junior colleague — like "young Smith" in workplace English. Pair it with
老 +
姓 (
老张,
老王) for older or senior colleagues.
詹 (Zhān) is a relatively uncommon Chinese surname; in pop culture, the actor
肖战 (Xiāo Zhàn) is sometimes nicknamed
小詹 by fans, though strictly his surname is
肖, not
詹.