Metal nanoclusters were fabricated by inert-gas condensation in a sputtering reactor. From transmission electron microscopy, it was confirmed that copper nanoclusters with a high degree of monodispersity in size of about 5 nm were successfully produced. The conductance of the percolated nanocluster film was measured. In order to incorporate nano-scale arrangement characterizations in nano-devices being operated in air, aging experiments of the specimen after long time in air were carried. Negative temperature coefficient of resistance suggests that surface native copper oxide in core-shell structured nanoclusters was mainly responsible for the conductance, because copper oxide is known as semiconductor. After aged at higher than 100 degrees C, the conductance at room temperature didn't return to the original value. This irreversible phenomenon might be due to coarsening and/or coalescence of copper nanoclusters.