Syntax Error Unexpected T_String In String Concatination

The syntax error Iam getting while editing the code in my theme’s functions.php is on line 88, where I added a new line of code ..

Here’s the code :

$popular .= '<a href="<?php the_permalink(); ?>"><img src="<?php echo bloginfo('template_url'); ?>/timthumbs.php?src=<?php echo catch_that_image() ?>&w=200&h=100&zc=3&q=100" alt="<?php the_title(); ?>" class="footer-thumb" width="200px" height="100px" /></a>'

Iam unable to figure out the correct escaping required ..

Kindly help ..