TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Method: In the method for forming a nanostructure, the nanostructure is etched by contacting the outer surface of the nanostructure with a basic solution. The contacting is performed while controlling at least one selected from a concentration of the basic solution, a temperature of the basic solution and a contacting time. The contacting is performed at 100 degrees C or lower. The nanostructure is a nanorod, and the method further comprises providing a nanorod comprising the piezoelectric material on a substrate; and contacting an outer surface of the nanorod with the basic solution to etch at least a portion the surface of the nanorod. The substrate is at least one selected from a gallium nitride substrate, a glass substrate, a plastic substrate, an indium tin oxide layer-coated glass substrate, an indium tin oxide layer-coated plastic substrate and their combination. The basic solution comprises at least one selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, francium hydroxide, barium hydroxide, strontium hydroxide, calcium hydroxide, copper hydroxide, iron hydroxide, ammonium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, choline hydroxide, alanine, phosphazene, histidine, imidazole, benzimidazole, purine, pyridine, pyrimidine, methylamine and their combination. The piezoelectric material comprises zinc oxide and the basic solution is an aqueous solution comprising potassium hydroxide; the aqueous potassium hydroxide solution has a molar concentration of 0.05-0.1 M and a temperature of 30-80 degrees C; and the nanostructure is contacted with the basic solution for 0.5-48 hours. The piezoelectric material comprises zinc oxide and the basic solution is an aqueous solution comprising potassium hydroxide; the aqueous potassium hydroxide solution has a molar concentration of 0.3-0.35 M and a temperature of 40-100 degrees C; and the nanostructure is contacted with the basic solution for 0.5-2 hours. The piezoelectric material comprises zinc oxide and the basic solution is an aqueous solution comprising ammonia; the aqueous ammonia solution has a molar concentration of 0.02-0.1 mM; and the nanostructure is contacted with the basic solution for 5-60 minutes. The piezoelectric material comprises zinc oxide and the basic solution is an aqueous solution comprising ammonia; the aqueous ammonia solution has a molar concentration of 0.2-0.5 mM and a temperature of 50 degrees C or lower; and the nanostructure is contacted with the basic solution for 5-40 minutes. The piezoelectric material is selected from aluminum orthophosphate, quartz, Rochelle salt, topaz, gallium orthophosphate, lanthanum gallium silicate, barium titanate, bismuth titanate, lead titanate, zinc oxide, zirconium lead titanate, lanthanum bismuth titanate, tin oxide, potassium niobate, lithium niobate, lithium tantalate, sodium tungstate, sodium barium niobate, potassium lead niobate, sodium potassium niobate and bismuth ferrite. Preferred Nanostructure: The etched outer surface is on a top surface and on a lateral surface of the nanorod. Preferred Device: The device is selected from an energy generating system, a solar cell, a light emitting diode, a sensor and an electrochromic display device.