TOPO- and pyridine-capped cubic CdSe quantum dots were prepared, and the effect of surface ligand exchange on the photoluminescence (PL) peak shift was investigated. From the analysis of PL spectra and TEM images, it was found that the decrease in diameter in the CdSe quantum dot and redistribution of its surface electronic density play different roles in the PL peak shift. The reduction in size of CdSe by ligand exchange caused a blue shift of the PL peak due to the quantum confinement effect, whereas the redistribution of surface electronic density of CdSe by the exchange of TOPO with pyridine resulted in a red shift of 23 meV on the average for the samples investigated. The result was also supported by the XPS characterizations.
In this study, the issues of complicated interactions between process variables were solved by decoupling techniques; in particular, simplified decoupling was used due to its simplicity and robustness. A new approach to solving decoupling realizability was developed by using the modified particle swarm optimization (PSO) algorithm. However, time delays still existed in the diagonal elements of the decoupled matrix, and they resulted in a more sophisticated controller design and sluggish responses in the outputs. To overcome the adverse effects of time delays, a Smith predictor, also known as a dead time compensator, is normally used. In this work, a Smith predictor structure in combination with simplified decoupling for multivariable processes was proposed in order to enhance system performances in terms of the servomechanism problem. The proportional integral or proportional integral derivative (PI/PID) controller tuning rules for several common industrial processes, such as first-order, second-order, and second-order with negative zero systems, were obtained. Many multivariable industrial processes were adopted to simulate the effectiveness of the proposed method in terms of the servomechanism problem and robust response.
CuO thin films with broccoli-like structure were prepared using a facile hydrothermal method to construct photocathodes for water-splitting application. The morphological, structural, and optical properties of thin films were characterized and measured using several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and ultraviolet-visible spectroscopy (UV-Vis). The thickness, structure, and morphology of CuO thin films can be controlled by varying the precursor concentration (Cp) and reaction temperature (Tr), which are also discussed. Moreover, the electrical properties of CuO thin films were also measured in the three-electrode system. The photocurrent density of photocathodes, when synthesized by a 0.5 M solution at 150 °C for 12 h, was 0.5 mA/cm2 at −0.6 V vs. Ag/AgCl, which is 1.8 times higher than that of photocathodes synthesized in a 0.1 M solution at 100 °C with the same reaction time. In addition, increasing the reaction temperature and precursor concentration aided in the enhancement of the IPCE and APCE values, which peaked at a wavelength range of 330–400 nm.
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