In this work, we provide theoretical evidence on the existence of energetically stable chiral structures for bare gold clusters. Density functional theory calculations within the generalized-gradient approximation were performed to systematically study structural, vibrational, electronic, and optical properties of the lowestlying isomers of the Au 34 Z , (Z) +1, 0,-1), clusters. Our results show that for the neutral and charged clusters, the lowest-energy isomer has a C 1 (chiral) structure. In addition, a C 3 (chiral) isomer was found nearly degenerate in energy with the C 1 isomer. These results are in agreement with previous theoreticalexperimental studies done for the Au 34cluster; however, because our calculated molecular scattering functions for the C 1 and C 3 isomers of this cluster are almost indistinguishable, it is concluded that the actual resolution in trapped ion electron diffraction experiments is not enough to discriminate between them. On the other hand, the electronic density of states of the C 1 isomer shows better overall agreement with the measured photoelectron spectrum of the Au 34cluster than that one corresponding to the C 3 isomer. The electronic density of states of these isomers also shows different features in the energy region of the HOMO-LUMO gap, which would generate distinct behavior in their optical properties. In fact, the calculated absorption and circular dichroism spectra of the two chiral isomers show clear differences in their line shape. Another important property that distinguishes the C 1 and C 3 isomers is the different spatial distribution of the atomic coordination on the cluster surface. Our results confirm that the potential energy surface of bare gold clusters could have lowest-lying energy minima corresponding to intrinsically chiral structures.

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RESUMEN En el presente trabajo se estudió el proceso de fabricación de una serie de macroporos sobre obleas de silicio cristalino mediante la técnica wet etching. Se evaluó la incidencia de distintos factores como el voltaje, la temperatura y el agente de frenado sobre las características específicas de la formación. A partir de los datos obtenidos de la evolución de las corrientes fue posible estandarizar el proceso y determinar el momento de formación del poro, esencial en cuanto a la disponibilidad de un método compatible con las exigencias de la industria. Finalmente, se concluyó que para la fabricación de poros en forma controlada, las condiciones óptimas corresponden a una temperatura de 84 ˚C, HCl como agente de frenado y voltajes de 0,1V, 0,5V y 1V respectivamente. Los anteriores resultados son de gran importancia en los campos de la medicina y la biología en relación a la utilidad de los poros como dispositivos de sensado.