Analyzing the Impact of Physicochemical Factors on Chlorella vulgaris Growth Through Design of Experiment (DoE) for Carbon Capture System.

The CO2 emission is increasing every year and threatening both humans and the ecosystem. Carbon capture technological innovations have emerged as a potential solution to mitigate this emissions. Due to its high capacity of photosynthetic activity, CO2 sequestration by microalgae, such as Chlorella vulgaris has attracted much attention as a carbon capture system. The growth of this microalgae is influenced by various physicochemical factors. By designing the Design of Experiment (DoE) with Response Surface Methodology (RSM), the effect of several independent factor can be evaluated to optimize Chlorella vulgaris growth condition and CO2 conversion. This study aims to identify the most impact factors affecting C. vulgaris growth through investigating the variations in physicochemical factors of aeration, initial pH, dark light regime, saline, and substrates concentration using DoE. In this study, C. vulgaris was cultivated in batch culture for 10 days with 8 experiments that were designed under various conditions as per experimental run. Biomass growth was observed using optical density and analyzed by first order regression. The result shows that aeration parameters was statistically significant affect microalgae growth, evidence by p-value below 0.05 at all observation points. Runs with aeration treatment showed a prolonged exponential growth phase and delayed onset of the deceleration phase. Additionally, this study also found that the initial pH level also significantly affects growth at the last day of cultivation. Cultures with a higher initial pH reached the stationary phase earlier than those with a lower pH. Thus, the growth of C. vulgaris can be optimized by adding aeration treatment into culture media and regulating initial pH around 8 to enhancing carbon fixation and biomass yield.

S,N-GQD sensitization effect on the improvement of ZnO nanopencil photoelectrochemical properties.

ZnO photoanodes in photoelectrochemical (PEC) water splitting for green-hydrogen production are limited due to the large bandgap that is only confined to UV light. One of the strategies for broadening the photo absorption range and improving light harvesting is to modify a one-dimensional (1D) nanostructure to a three-dimensional (3D) ZnO superstructure coupling with a narrow-bandgap material, in this case, a graphene quantum dot photosensitizer. Herein, we studied the effect of sulfur and nitrogen co-doped graphene quantum dot (S,N-GQD) sensitization on the surface of ZnO nanopencil (ZnO NPc) to give a photoanode in the visible light spectrum. In addition, the photo energy harvesting between the 3D-ZnO and 1D-ZnO, as represented by neat ZnO NPc and ZnO nanorods (ZnO NRs), was also compared. Several instruments, including SEM-EDS, FTIR, and XRD revealed the successful loading of S,N-GQDs on the ZnO NPc surfaces through the layer-by-layer assembly technique. The advantages are S,N-GQDs's band gap energy (2.92 eV) decreasing ZnO NPc's band gap value from 3.169 eV to 3.155 eV after being composited with S,N-GQDs and facilitating the generation of electron-hole pairs for PEC activity under visible light irradiation. Furthermore, the electronic properties of ZnO NPc/S,N-GQDs were improved significantly over those of bare ZnO NPc and ZnO NR. The PEC measurements revealed that the ZnO NPc/S,N-GQDs stood out with a maximum current density of 1.82 mA cm-2 at +1.2 V (vs. Ag/AgCl), representing a 153% and 357% improvement over the bare ZnO NPc (1.19 mA cm-2) and the ZnO NR (0.51 mA cm-2), respectively. These results suggest that ZnO NPc/S,N-GQDs could have potential for water splitting applications.

3D-ZnO Superstructure Decorated with Carbon-Based Material for Efficient Photoelectrochemical Water-Splitting under Visible-Light Irradiation.

The depletion of fossil fuels is a worldwide problem that has led to the discovery of alternative energy sources. Solar energy is the focus of numerous studies due to its huge potential power and environmentally friendly nature. Furthermore, one such area of study is the production of hydrogen energy by engaging photocatalysts using the photoelectrochemical (PEC) method. 3-D ZnO superstructures are extensively explored, showing high solar light-harvesting efficiency, more reaction sites, great electron transportation, and low electron-hole recombination. However, further development requires the consideration of several aspects, including the morphological effects of 3D-ZnO on water-splitting performance. This study reviewed various 3D-ZnO superstructures fabricated through different synthesis methods and crystal growth modifiers, as well as their advantages and limitations. Additionally, a recent modification by carbon-based material for enhanced water-splitting efficiency has been discussed. Finally, the review provides some challenging issues and future perspectives on the improvement of vectorial charge carrier migration and separation between ZnO as well as carbon-based material, using rare earth metals, which appears to be exciting for water-splitting.

Development of differential pulse voltammetric method for determining samarium (III) through electroanalytical study of the metal ion in acetonitrile using Box-Behnken design.

The development of methods for the efficient and reliable separation and routine analysis of rare-earth elements (REEs), including samarium (Sm), proceeds to draw in the interest of the many researchers, attributable to the similar physical and chemical properties of these elements. Note that although the voltammetric determination of Sm has been described in the literature, thus far, no chemometric and voltammetric methods for the quantification of the element in its mixtures with other lanthanides in an acetonitrile solution have been reported. This work was aimed toward the advancement of a method for the detection of Sm in acetonitrile, the intended function of which was to obtain a selective current response of Sm by Differential Pulse Voltammetry, utilizing the Box-Behnken experimental design, to identify the best conditions for the determination. In particular, the three selected factors for the experiment, namely the potential range, amplitude modulation, and the deposition time, were found to have optimal conditions of -1.5 to +1.0 V, 0.075 V, and 60 s, consecutively. The optimal conditions were observed to result in a selective current response for samarium with a detection limit of 2.25 mg/L and a limit of quantitation of 7.50 mg/L. Furthermore, the accuracy was 98.70% and the precision was found to be 1.91% in relative standard deviation (RSD), while the recovery was found to be 98.70%.