The Argentinian forward's 24th-minute strike handed Samp all three points and their sixth league win of the campaign.
Lopez, who joined Samp on loan from Catania last week for a second spell with the Blucerchiati, after spending part of last season with the Genoa outfit, was elated.
"I dedicate this goal to my children, my team-mates and our fans," Lopez said to Sampdoria.it.
"I am delighted for the goal and for the victory. I could not have asked for more.
"I dreamed of scoring in the derby and I'm over the moon.
"It was important for the squad to win such an important game as the derby is.
"I want to thank Sampdoria and coach Sinisa Mihajlovic for giving me this opportunity.
"I need to regain my confidence and needed playing time.
"I am sure if we continue to play as we did against Genoa, we will achieve our aims this season."
The Blucerchiati have climbed to 13th place, eight points clear of the relegation zone ahead of their clash with Cagliari on Sunday.