What should a candidate with no publications mention to professor for PhD admission or research position?
Remember that professors often get dozens of emails every day, so your chances to get an answer are higher if you keep things short.
Send an email saying that you are interested in a PhD in program XX under his supervision and ask a few short, relevant questions, e.g. if spaces are available at all.
Any longer questions, or even sending a whole portfolio, should not be done in the first email. If things go well, he agrees to talk to you about your application and there are spaces available, you can go on with your other questions.
If possible, a short visit in person might help; you can for example discuss most of your questions with PhD students or postdocs should the professor be too busy.