Growth of segmented gold nanorods with nanogaps by electrochemical wet etching technique

Optimized growth of segmented nanorods comprised of gold (Au) segments (Au-gap-Au) using electrochemical wet etching method is reported. The nanorods were fabricated using alumina (AAO) template of thickness 100 ¿m and pore size of 200 nm. A thin silver (Ag) sacrificial layer was grown on one side of the AAO template to act as cathode. Electrochemical process was used to grow Au segments sandwiching the Ag segments. Three segment nanorods (Au-Ag-Au) with different lengths of Ag segment were grown inside the AAO template. AAO template having multisegment nanorods within its interior was mixed with sodium hydroxide to dissolve the template to separate out the multisegment nanorods. The middle Ag segment was selectively etched to create segmented nanorods with nanogaps. Different gaps between the Au segments were created by growing Ag segments at different Coulomb exchanged charges during the electrochemical process. Scanning electron microscope revealed that exchanged charges below 1 mC could result in the formation of nanogap size ~ 5 nm. This process allows a cost-effective way to fabricate electrodes with sub-10 nm gap size.