Styling category dropdown menu

Is it possible to bold all of the categories listed in a dropdown? I’ve tried:

<span style="font-weight:bold;">

<?php wp_dropdown_categories('show_option_none=Title&title_li=&hide_empty=0&exclude=1&orderby=name'); ?>

<script type="text/javascript"><!--
    var dropdown = document.getElementById("cat");
    function onCatChange() {
		if ( dropdown.options[dropdown.selectedIndex].value > 0 ) {
			location.href = "<?php echo get_option('home');
?>/?cat="+dropdown.options[dropdown.selectedIndex].value;
		}
    }
    dropdown.onchange = onCatChange;
--></script>
</span>

and

<?php wp_dropdown_categories('show_option_none=<span style="font-weight:bold;">Title</span>&title_li=&hide_empty=0&exclude=1&orderby=name'); ?>

<script type="text/javascript"><!--
    var dropdown = document.getElementById("cat");
    function onCatChange() {
		if ( dropdown.options[dropdown.selectedIndex].value > 0 ) {
			location.href = "<?php echo get_option('home');
?>/?cat="+dropdown.options[dropdown.selectedIndex].value;
		}
    }
    dropdown.onchange = onCatChange;
--></script>

With no results.