[Air-L] NLP for sentiment analysis of social media comment

Dear all, most sentiment analyses of social media comments I know use dictionary-based approaches (e.g. sentigstrength). However, I am wondering if researchers also use Natural Language Processing approaches to examine the sentiment of social media comments; I am still an absolute beginner in this field, hence I would be very glad if somebody could point me to useful papers/tutorials/software for doing NLP based sentiment analyses? Many thanks, Nina