Comprehensive Analysis of Lutein and Loroxanthin in Scenedesmus obliquus: From Quantification to Isolation.

Carotenoids are hydrophobic pigments produced exclusively by plants, fungi, and specific microbes. Microalgae are well suited for the production of valuable carotenoids due to their rapid growth, efficient isoprenoid production pathway, and ability to store these compounds within their cells. The possible markets for bio-products range from feed additives in aquaculture and agriculture to pharmaceutical uses. The production of carotenoids in microalgae is affected by several environmental conditions, which can be utilized to enhance productivity. The current study focused on optimizing the extraction parameters (time, temperature, and extraction number) to maximize the yield of carotenoids. Additionally, the impact of various nitrogen sources (ammonia, nitrate, nitrite, and urea) on the production of lutein and loroxanthin in Scenedesmus obliquus was examined. To isolate the carotenoids, 0.20 g of biomass was added to 0.20 g of CaCO3 and 10.0 mL of ethanol solution containing 0.01% (w/v) pyrogallol. Subsequently, the extraction was performed using an ultrasonic bath for a duration of 10 min at a temperature of 30 °C. This was followed by a four-hour saponification process using a 10% methanolic KOH solution. The concentration of lutein and loroxanthin was measured using HPLC-DAD at 446 nm, with a flow rate of 1.0 mL/min using a Waters YMC C30 Carotenoid column (4.6 × 250 mm, 5 µm). The confirmation of carotenoids after their isolation using preparative chromatography was achieved using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with an atmospheric pressure chemical ionization (APCI) probe and UV-vis spectroscopy. In summary, S. obliquus shows significant promise for the large-scale extraction of lutein and loroxanthin. The findings of this study provide strong support for the application of this technology to other species.

Tailoring p-Type Behavior in ZnO Quantum Dots through Enhanced Sol-Gel Synthesis: Mechanistic Insights into Zinc Vacancies.

The synthesis and control of properties of p-type ZnO is crucial for a variety of optoelectronic and spintronic applications; however, it remains challenging due to the control of intrinsic midgap (defect) states. In this study, we demonstrate a synthetic route to yield colloidal ZnO quantum dots (QD) via an enhanced sol-gel process that effectively eliminates the residual intermediate reaction molecules, which would otherwise weaken the excitonic emission. This process supports the creation of ZnO with p-type properties or compensation of inherited n-type defects, primarily due to zinc vacancies under oxygen-rich conditions. The in-depth analysis of carrier recombination in the midgap across several time scales reveals microsecond carrier lifetimes at room temperature which are expected to occur via zinc vacancy defects, supporting the promoted p-type character of the synthesized ZnO QDs.

Unlocking the full potential of citric acid-synthesized carbon dots as a supercapacitor electrode material via surface functionalization.

This research paper investigates the effect of functionalizing the surfaces of citric acid-synthesized carbon dots (CDs) with hyperbranched bis(methylol)propionic acid (bis-MPA) polyester hydroxyl polymers (HBPs) on their performance as electrode materials in a supercapacitor. Two types of HBPs with 16 and 64 peripheral hydroxyl groups were used to functionalize the CDs' oxygen-enriched surface. Here, CDs were used as electrode materials for the first time in symmetric supercapacitors without a composite material, and how surface modification affects the capacitance performance of CDs was investigated. Our results showed that the functionalization of green-emitting CDs with HBP resulted in the successful passivation of surface defects, which improved their stability and prevented further oxidation. The CDs with HBP passivation exhibited excellent electrochemical performance, with a high specific capacitance of 32.08 F g-1 at 0.1 A g-1 and good rate capability, indicating a faster ion transport rate at high current densities. Experimental EPR spectra of functionalized and non-functionalized CDs reveal distinct changes in g-factor values and line widths, confirming the impact of dangling bonds and spin-orbit interactions. The observed broader linewidth indicates a wider range of electron spin resonances due to energy-level splitting induced by spin-orbit coupling. The excellent electrochemical performance of CDs with HBP passivation can be attributed to the presence of oxygen-containing surface functional groups such as hydroxyl and carboxyl groups on their surfaces, which enhance the conductivity and charge transfer reactions. These results suggest that functionalization with polar HBPs is a promising strategy to enhance the electrochemical performance of CDs in supercapacitor applications.

Manipulation in Culture Conditions of Nanofrustulum shiloi for Enhanced Fucoxanthin Production and Isolation by Preparative Chromatography.

Microalgae produce a variety of high-value chemicals including carotenoids. Fucoxanthin is also a carotenoid that has many physiological functions and biological properties. For this reason, the cost-effective production of fucoxanthin at an industrial scale has gained significant attention. In the proposed study, fucoxanthin production was aimed to be increased by altering the culture conditions of N. shiloi. The effect of light intensity aeration rate, different nitrogen sources, and oxidative stress on the biomass and fucoxanthin productivity have been discussed. Based on these results, the fucoxanthin increased to 97.45 ± 2.64 mg/g by adjusting the light intensity to 50 µmol/m2s, and aeration rate at 5 L/min using oxidative stress through the addition of 0.1 mM H2O2 and 0.1 mM NaOCl to the culture medium. Fucoxanthin was then purified with preparative HPLC using C30 carotenoid column (10 mm × 250 mm, 5 µm). After the purification procedure, Liquid chromatography tandem mass spectrometry (LC-MS/MS) and UV-vis spectroscopy were employed for the confirmation of fucoxanthin. This study presented a protocol for obtaining and purifying considerable amounts of biomass and fucoxanthin from diatom by manipulating culture conditions. With the developed methodology, N. shiloi could be evaluated as a promising source of fucoxanthin at the industrial scale for food, feed, cosmetic, and pharmaceutical industries.

Boron Carbide as an Electrode Material: Tailoring Particle Morphology to Control Capacitive Behaviour.

In this study, boron carbide powders consisting mainly of nano/micro fibers or polyhedral-equiaxed particles were synthesized via the sol-gel technique, and the influence of particle morphology on electrochemical performance of boron carbide electrodes was investigated. Thermal decomposition duration of the precursors played a determinant role in the final morphology of the synthesized boron carbide powders. The morphology of boron carbide powders successfully tuned from polyhedral-equiaxed (with ~3 µm average particle size) to nano/micro fibers by adjusting the thermal decomposition duration of precursors. The length and thickness of fibers were in the range of 30 to 200 µm and sub-micron to 5 µm, respectively. The electrochemical performance analysis of boron carbide powders has shown that the particle morphology has a considerable impact on the boron carbide electrodes electrochemical performance. It was found that the synergetic effects of polyhedral-equiaxed and nano/micro fiber morphologies exhibited the best electrochemical performance in supercapacitor devices, resulting in the power and energy density of 34.9 W/kg and 0.016 Wh/kg, respectively.

All-in-One Electric Double Layer Supercapacitors Based on CH3NH3PbI3 Perovskite Electrodes.

Supercapacitors (SCs) are widely used energy storage devices in various applications that require instantaneous power supply and fast response times; however, the challenge for achieving high performance demands the continuous development and tailoring of electrode materials. Organic-inorganic halide perovskites (OIHPs) have recently received significant attention in electrochemical energy storage and conversion applications due to their unique properties including high charge carrier mobility, high mixed (electronic-ionic) conductivity, and presence of large oxygen vacancies. This study presents the fabrication and use of OIHPs based on methyl-ammonium lead iodide (CH3NH3PbI3) and its Co2+- and Bi3+-substituted derivatives (CH3NH3Pb1-x Co x I3 and CH3NH3Pb1-x Bi x I3, respectively, where x = 0.1) as electrodes for SCs. SC devices were constructed symmetrically by sandwiching the synthesized electrode materials in a quasi-solid-state electrolyte between two TiO2-coated FTO glasses. We discussed the optimization parameters (i.e., A-site doping, B-site doping, and controlling the stoichiometry of the anion and cation) to improve the electrochemical performance of the fabricated SCs. Furthermore, the effects of substitution ions (Co2+ and Bi3+) on the charge-discharge performance, energy and power density, defects, crystallinity, and microstructure were demonstrated. Electrochemical performances of the electrodes were analyzed by using CV, EIS, and GCPL techniques. The highest power density of 934.6 W/kg was obtained for Bi-substituted perovskite electrodes. Fabricated SC devices show good cyclability with 97.2, 96.3, and 86.6% retention of the initial capacitances after 50 cycles for pure, Co2+-substituted, and Bi3+-substituted perovskite electrodes, respectively.

ZnO and reduced graphene oxide electrodes for all-in-one supercapacitor devices.

Reduced graphene oxide/zinc oxide (rGO/ZnO) hybrid nanocomposites were prepared from synthesized GO and high energy ball milled (HEBM) ZnO for supercapacitor electrodes. Evolution of intrinsic point defects and defect-induced morphological, structural and size-dependent properties of rGO/ZnO hybrid nanocomposites were investigated using electron paramagnetic resonance (EPR) spectroscopy. CV, PEIS and GCPL techniques were employed to investigate the electrochemical behavior of the electrode materials and the effects of defects on the electrochemical performance of the electrodes by using the standard two-electrode cell in a 6 M KOH electrolyte. Analyses of the obtained CV and impedance profiles have shown the pseudocapacitive and EDLC-type contributions in the supercapacitors. Cycling stabilities were evaluated using galvanostatic charge-discharge curves at current densities between 0.10 and 2.40 A g-1. The capacitance retention of all electrodes was found to be 100% after 30 cycles at 0.30 A g-1. The electrochemical analyses revealed that the incorporation of ZnO that is rich in core defects improved the charge transfer performance and ion diffusion of the rGO electrode.

Links between airborne microbiome, meteorology, and chemical composition in northwestern Turkey.

The composition of atmospheric aerosols is dynamic and influenced by their emission sources, organic and inorganic composition, transport pathways, chemical and physical processes, microorganisms' content and more. Characterization of such factors can improve the ability to evaluate air quality and health risks under different atmospheric scenarios. Here we investigate the microbial composition of the atmospheric particulate matter (<10 µm; PM10), sampled in Bolu, Turkey, and the linkage to the chemical composition changes, and different environmental factors. We show distinct differences between aerosol composition of different sources and air-mass transport patterns, sampled in July-August 2017 and in February 2018. The summer samples had a typical northern component air mass trajectories and higher local wind speed. They were characterized by high PM10 levels, marine and mineral dust tracers and high relative abundance of Ascomycota, suggesting long-range transport of the particles from remote sources. In contrast, samples collected in February were characterized by a dominant contribution of southern air masses, and low wind speed. They had low PM10 values, higher relative abundance of antibiotic resistance genes and anthropogenic ions related to local industries and farming, suggesting a dominance of local sources. With the microbiome analyses reported here for the first time for this region, we show good agreement between airborne microbial composition, aerosol mass load, chemistry, and meteorology. These results allow better air quality evaluation and prediction capabilities.

A new exposure route to trace elements in indoor particulate matter.

Concentrations and emission rates of sixteen trace elements in emitted PM during heating soybean oil using three types of pans, including Teflon, granitium, and cast-iron, were investigated. Statistically significant decreases in Mn and Co emission rates were observed when the oil was heated in the cast-iron pan compared to Teflon and granitium pans. Among the released trace elements, Ni, Ba, Zn, and Cr had more contribution to the emission rate. The concentrations of Fe in the emitted PM1 were found to be higher when cast-iron pan (8.49 ± 3.35 µg/m3 ) was utilized compared to Teflon (8.05 ± 2.27 µg/m3 ) and granitium (7.45 ± 1.38 µg/m3 ). However, these increases were statistically insignificant. The results of our study support the hypothesis that the trace elements translocate from cooking pans into the heated oil and subsequently to the particulate phase. This translocation creates a new inhalation exposure route to trace elements in indoor environments.