make text dependant on cell - Bold

hi guys i have some code where i need to make the text bold but not sure how to go about it

the formula is

="hello "&IF(ISBLANK('working sheet'!D2),"",'working sheet'!D2)

if cell d2 is empty then obviously there will be nothing there ie - hello

if d2 has steve in it, it should read - hello steve

its the steve part i need in bold
and im not sure
thanks in advance