Multilayers film of nanostructured citrate-stabilized gold particles (AuNPs) has been fabricated based on the layer-by-layer (LBL) technique using a self-assembled monolayer of 1,4-benzenedimethanethiol (BDMT). The formation of AuNPs and BDMT self-assemblies as alternative multilayers was confirmed by transmission electron microscopy (TEM), X-ray photoelectron spectroscope (XPS), and quartz crystal microbalance (QCM). The formation of uniform AuNP layers with an average monolayer thickness of 5-6 nm was obvious in the TEM images. The existence of BDMT molecules as cross linkers for the AuNPs' layers was proved by XPS measurements. The greater affinity of AuNPs' layers to bind BDMT molecules in comparison with the bare Au bulk electrode was revealed by QCM measurements. Electrochemically, the AuNPs' layers on the electrode surface did not only catalyze the reduction of oxygen (ca. 100-mV positive shift of the reduction peak potential compared with that at the bare Au bulk electrode) but also showed a fascinating nature of working as a renewed activated-electrode surface; a zigzag response was observed for oxygen reduction during alternative immobilization of BDMT and the AuNP layer. The self-assembly of a new AuNPs layer restored the catalytic activity that was entirely blocked by the preceding BDMT layer. © 2006 American Chemical Society.

Fluorescent semiconductor quantum dots (QDs) are nanocrystals with a diameter that usually ranges from 1 to 10 nm. QDs can be prepared by many techniques including plasma synthesis, mechanical fabrication, or colloidal synthesis. The current paper presents the synthesis of CdTe quantum dots (QDs) with wet chemical method at variable reaction time, variable temperature and variable trioctylphosphine (TOPO) concentration, to control the size of the produced QDs. Structural characterization was carried out with conventional transmission electron microscopy (TEM) and X-ray diffraction (XRD). Optical characterization was performed with optical spectrometer and Spectrofluorometre. TEM images revealed that the size of QDs increases with the increase in the three parameters’ reaction time, temperature and TOPO concentration. This represents a new achievement in comparison to the previously produced similar QDs with random size ranges. Furthermore, the optical properties of the CdTe QDs showed that the characteristic emission and absorption of light could be controlled by changing these parameters as well. The observed results are very important and can be applied to increase the efficiency of solar cells. © 2019 National Institute of Optoelectronics. All rights reserved.