get latest post by category

hi i have a custom wordpress theme and i’m trying to get the latest past (just one) by a specific category. I found this code:
` <?php $my_query = new WP_Query(‘category_name=videos&posts_per_page=1’);
while ($my_query->have_posts()) : $my_query->the_post();
$do_not_duplicate = $post->ID; ?>
<!– Do stuff… –>
<?php endwhile; ?>

but it does not work. It shows up blank. any solutions?