Date Published: April 10, 2014
Publisher: Public Library of Science
Author(s): Raoul R. Nigmatullin, Sergey I. Osokin, Dumitru Baleanu, Sawsan Al-Amri, Ameer Azam, Adnan Memic, Vipul Bansal.
Over the past couple of decades there have been major advances in the field of nanoscience and nanotechnology. Many applications have sprouted from these fields of research. It is essential, given the scale of the materials, to attain accurate, valid and reproducible measurements. Material properties have shown to be a function of their size and composition. Physiochemical properties of the nanomaterials can significantly alter material behavior compared to bulk counterparts. For example, metal oxide nanoparticles have found broad applications ranging from photo-catalysis to antibacterial agents. In our study, we synthesized CuO nanoparticles using well established sol-gel based methods with varying levels of Ni doping. However, upon analysis of measured infrared data, we discovered the presence of quasi-periodic (QP) processes. Such processes have previously been reported to be tightly associated with measurement memory effects. We were able to detect the desired QP process in these measurements from three highly accurate repetitive experiments performed on each Ni (1–7%) doped CuO sample. In other words, successive measurements performed in a rather short period of time remember each other at least inside a group of neighboring measurements.
Copper oxide is a technologically important material which is mostly found in two oxidation states, cupric oxide (CuO) and cuprous oxide (Cu2O). Both are p-type semiconductors and the preferred structure of CuO is monoclinic, while that of Cu2O is cubic. The energy band gap of CuO ranges between 1.2–1.9 eV  and Cu2O has an energy band gap between 1.8–2.5 eV ,. As a result of some of the fascinating properties exhibited by copper oxide, it finds its application in high Tc superconductors , lithium ion electrode , gas sensors , , solar cells –, field emission emitters –, catalysis ,, antibacterial agents  etc. Because CuO is a semiconductor, having a low band gap, it has also been applied for photoconductive and photothermal applications . Nanomaterials, which have attracted major interest in recent years, possess a large amount of surfaces and interfaces and exhibit enhanced properties in comparison to their bulk counterparts. The properties of these materials can be further fine-tuned by controlling the particle sizes in the nano range or by playing with the crystal morphologies of the final product. Moreover, the doping of the semiconductor nanoparticles with impurity metal ions is one of the most important methods to modify the characteristics of the material. The engineering of band gap and influencing physical, chemical, and electronic properties of the semiconductors are possible by the use of the right amount of dopants. Several authors have reported the improvement in a material’s properties using various dopants. The band gap narrowing of Ni doped SnO2 nanoparticles was observed by Ahmed et al. . Das et al. reported the tuning of emission properties of Mn doped Cu2O nanoparticles . Various methods have been developed for the synthesis of both pure and doped nanocrystalline CuO such as sol–gel method , one-step solid state reaction method , sonochemical method , electrochemical method , thermal decomposition of precursors  etc.. Out of these methods, sol–gel method is widely used for the synthesis of nanomaterials because of the various advantages associated with this method such as low cost, low temperatures processing, short annealing times, as well as higher purity of produced materials.