Shares of Nano Nuclear Energy (NNE -3.08%) sank 16% this week, according to data from S&P Global Market Intelligence. The nuclear energy start-up closed a private placement offering of common stock that will dilute shareholders, leading the stock to fall. Shares of the pre-revenue company are up 26% this year and up 500% since going public around one year ago.Here's why Nano Nuclear Energy stock was sinking this week, and whether the stock is a buy now.Raising money, new patentsNano Nuclear Energy wants to ...