Facile synthesis of hierarchically aloe-like gold micro/nanostructures for ultrasensitive DNA recognition.

Well-defined hierarchically aloe-like gold micro/nanostructures (HAG) are one-step electrochemically fabricated without introducing any template or surfactant. The formation kinetics of the HAG can be described as a nucleation and three-dimensional growth process controlled by the reactant diffusion from the solution side. As the applied electro-deposition potential moved in the negative direction, the gold crystal density increased, and the crystal shape changed from a quasi-spherical to dendritic fractal morphology. Under the optimal potential of -0.1 V and the time of 10 min, well-defined HAG possessing a hydrophilic surface with large effective area (ca. 8 times of its geometrical area) were obtained, which was used as the substrate for fabricating an ultrasensitive DNA biosensor. The DNA biosensor displayed a significantly enhanced detection limit of 12 aM, a wide linear response from 50 aM to 1 pM, as well as good selectivity, stability and reusability. This efficient DNA molecule immobilization platform may have implications in the preparation of many other gold micro/nanostructures (GMNs) with interesting properties and application potentials in many fields, such as biosensing, biocatalysis and biofuel cells.