How to include the icon inside the tooltip message

I need to include the download icon inside the tooltip message, I have tried the below code:

ObjectIconView: Ember.ContainerView.extend(childMOMixin, {
                iconDownload: function () {
                              model: 'download'
                },
                mouseEnter: function(e) {
                if(type == 'Text'){
                var textUrl = {content: 'Preview is Not Available, Use '+ this.iconDownload() +'Menu'};
                this.$().tooltip(textUrl);
}

In that I have called the iconDownload inside the tooltip. But it's saying undefined in the output. I'm using Ember 1.4.0 version. Can anybody please provide the suggestion for this. I'm new to the Ember. Thanks in advance