If it makes you feel any better, I have not heard back from Duke either, and my stats are 3.6 undergrad GPA, one summer REU, 2 years of research and one paper in preparation. Also my Q/V GRE scores were 164/157. Judging by the results, it looks as though the only chem offers made from Duke so far has been to international students, so I'm thinking that maybe they haven't reviewed the domestic apps or haven't sent out those offers/rejections yet. I wouldn't worry about it just yet. You're definitely still in the running!