qgis - Export raster layer in python to specific folder

I am trying to export existing raster layers as tif files. I just want to avoid saving each raster manually. this is the code I am trying to use, but it doesn't seem to work:

from PyQt4.QtCore import *
from qgis.core import *
from qgis.gui import *
import os
import sys


layers = iface.layerTreeView().selectedLayers()
for layer in layers:
    output='Desktop'%layer.name%'.tif'

As specified in a comment below, I modified my code to this:

from PyQt4.QtCore import *
from qgis.core import *
from qgis.gui import *
import os
import sys



layers = iface.layerTreeView().selectedLayers()

for layer in layers:
     file_name = 'D:\tif' + layer.name() + '.tif'
     file_writer = QgsRasterFileWriter(file_name)
     pipe = QgsRasterPipe()
     provider = layer.dataProvider()


     if not pipe.set(provider.clone()):
        print "Cannot set pipe provider"
     continue

     file_writer.writeRaster(
        pipe,
        provider.xSize(),
        provider.ySize(),
        provider.extent(),
        provider.crs())

I can't seem to get it to work and I am not getting any error.

I already selected the layers and it still does not work.