substring-after Not Working in apply-templates

Hi All,
I am trying this statement:

<xsl:apply-templates select="substring-after(@rdf:about,'#')">
</xsl:apply-templates>

But this gives an error saying:
MyXSLFile.xsl:39: value of expression cannot be converted to a node-set

Can anyone guide me how can I write the result of this substring-after thing
into an XML file. Do I have to use any other tag rather than
xsl:apply-templates or what?

Btw, I tried using following code:
<xsl:for-each select="@rdf:about">
<xsl:value-of select="substring-after(@about,'#')"/>
</xsl:for-each>

which (atleast) generates the XML file, but the file does not show any
substring extracted.

Please Help...