Mikel Arteta's men moved five points clear of PSV at the top of Group A in a rescheduled game which was postponed last month following the death of Queen Elizabeth II.
The two sides meet again in a week's time, when a point for Arsenal would be enough to wrap up top spot and qualification directly into the last 16.
"I'm so happy to score. I don't know when I scored for the last time with the right foot but so happy," Xhaka told BT Sport.
"It doesn't matter which foot, or who scores. It gives us confidence and on to the next one."
A fourth victory in as many games in Europe means Arsenal have won 13 of their 14 matches in all competitions this season.
"Everything is going well at the moment but for us it is not a surprise, we're doing a lot of work," added Xhaka.
"We win and lose as a team and at the moment we are very dangerous. We wanted to go through and are very happy."
The Premier League leaders dominated for long periods but had to wait until 19 minutes from time to take the lead when Takehiro Tomiyasu chipped the ball back for Xhaka to drill home his third goal of the season.
Bukayo Saka and Gabriel Martinelli both came close to extending the advantage late on, but Ruud van Nistelrooy's PSV rarely threatened an equaliser.
Arsenal, who are four points clear of reigning champions Manchester City, return to Premier League action on Sunday with a visit to Southampton.