Single‐atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical ...reactions. In this Minireview, recent examples of single‐atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO2 reduction to methane or methanol production while suppressing H2 evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on TiN or TiC nanoparticles, defective graphene nanosheets, N‐doped covalent triazine frameworks, graphitic carbon nitride, S‐doped zeolite‐templated carbon, and Sb‐doped SnO2 surfaces. Scanning transmission electron microscopy, extended X‐ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single‐atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested.
Down to the atom: Single‐atom catalysts, in which metal atoms are dispersed on the support without forming nanoparticles, have recently been used for electrochemical reactions. In this Minireview, recent examples of single‐atom electrocatalysts for reactions including oxygen reduction, hydrogen oxidation, hydrogen evolution, formic acid oxidation, and methanol oxidation are introduced.
Abstract Purpose Alpha-lipoic acid is an essential cofactor for mitochondrial respiratory enzymes that improves mitochondrial function. We previously reported that alpha-lipoic acid markedly reduced ...body weight gain in rodents. The purpose of this study was to determine whether alpha-lipoic acid reduces body weight in obese human subjects. Methods In this randomized, double-blind, placebo-controlled, 20-week trial, 360 obese individuals (body mass index BMI ≥30 kg/m2 or BMI 27-30 kg/m2 plus hypertension, diabetes mellitus, or hypercholesterolemia) were randomized to alpha-lipoic acid 1200 or 1800 mg/d or placebo. The primary end point was body weight change from baseline to end point. Results The 1800 mg alpha-lipoic acid group lost significantly more weight than the placebo group (2.1%; 95% confidence interval, 1.4-2.8; P < .05). Urticaria and itching sensation were the most common adverse events in the alpha-lipoic acid groups, but these were generally mild and transient. Conclusion Alpha-lipoic acid 1800 mg/d led to a modest weight loss in obese subjects. Alpha-lipoic acid may be considered as adjunctive therapy for obesity.
Single‐atom catalysts (SACs) have attracted growing attention because they maximize the number of active sites, with unpredictable catalytic activity. Despite numerous studies on SACs, there is ...little research on the support, which is essential to understanding SAC. Herein, we systematically investigated the influence of the support on the performance of the SAC by comparing with single‐atom Pt supported on carbon (Pt SA/C) and Pt nanoparticles supported on WO3−x (Pt NP/WO3−x). The results revealed that the support effect was maximized for atomically dispersed Pt supported on WO3−x (Pt SA/WO3−x). The Pt SA/WO3−x exhibited a higher degree of hydrogen spillover from Pt atoms to WO3−x at the interface, compared with Pt NP/WO3−x, which drastically enhanced Pt mass activity for hydrogen evolution (up to 10 times). This strategy provides a new framework for enhancing catalytic activity for HER, by reducing noble metal usage in the field of SACs.
The influence of the support on the performance of a single‐atom catalyst was investigated by comparing single‐atom Pt supported on carbon and Pt nanoparticles supported on WO3−x (Pt NP/WO3−x). The support effect is maximized for single‐atom Pt on WO3−x, which drastically enhances the Pt mass activity for the hydrogen evolution reaction compared with Pt NP/WO3−x and Pt/C.
Although grounded theory and qualitative content analysis are similar in some respects, they differ as well; yet the differences between the two have rarely been made clear in the literature. The ...purpose of this article was to clarify ambiguities and reduce confusion about grounded theory and qualitative content analysis by identifying similarities and differences in the two based on a literature review and critical reflection on the authors’ own research. Six areas of difference emerged: (a) background and philosophical base, (b) unique characteristics of each method, (c) goals and rationale of each method, (d) data analysis process, (e) outcomes of the research, and (f) evaluation of trustworthiness. This article provides knowledge that can assist researchers and students in the selection of appropriate research methods for their inquiries.
Prevalence and importance of polymorphism occurring in pharmaceutical compounds are well recognized. It is of great importance to prepare and select the right form from the beginning during drug ...discovery and development. This review introduces the basic concepts of “What is polymorphism?”, addresses a fundamental question of “Why do polymorphs form?”, and provides practical guidelines of “How to prepare polymorphs?” “How to evaluate the relative thermodynamic stability between polymorphs?”, and “How to analyze polymorphs?”. Moreover, case studies of pharmaceutically important polymorphs are provided.
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•Salt-induced aggregation was employed to AuNP-aptasensor for bisphenol A detection.•Visible detection limit was 1 pg/mL with a broad linear range to 1000 ng/mL of BPA.•Colorimetric ...aptasensor exhibited high selectivity over the various BPA analogs.•The aptasensor was capable of detecting BPAin a contaminated grain of rice.
A colorimetric aptasensor was developed for the simple and rapid detection of bisphenol A (BPA). The aptasensor was designed to consist of colloidal gold nanoparticles (AuNPs) and a BPA-specific 24-bp aptamer. The AuNP-aptamer conjugates underwent an electrolyte-induced aggregation in the presence of sub-ppb levels of BPA. The surface plasmon resonance shift of AuNPs facilitated a color change from red to blue upon aggregation, which was visually observed by the naked eye. The corresponding visual limit of detection of BPA was as low as 1 pg/mL (0.004 nM). The aptasensor also achieved a selective detection of BPA over a variety of BPA analogs. The applicability of the aptasensor was verified via a successful detection of BPA in a single grain of rice. This result indicates that the colorimetric aptasensor can be used in a screening procedure for food and environmental monitoring, with reliable performance to sub-ppb levels of BPA detection.
Developing a highly efficient and durable proton exchange membrane fuel cell (PEMFC) using a low amount of platinum is essential for minimizing the total cost. Herein, the development of ...high‐performance PEMFC catalysts is demonstrated using ultra‐low Pt loaded (1 wt%) porous carbon with controlled channel diameters (Dch = 13–63 nm), produced from block copolymer particles. The single cell based on the catalyst with the largest Dch of 63 nm yields an initial maximum power density of 1230 mW cm−2 and high durability showing 1120 mW cm−2 after 30 000 cycles under H2/O2 flow, which outperforms those of commercial Pt/C catalysts despite 1/20 Pt usage. Furthermore, the catalyst shows outstanding performance with 51 kW per gram of Pt (kW gPt−1) after 30 000 cycles in H2/air flow, which is the highest performance reported to date. The channel structure and large Dch of the porous particles are the keys to enhancing the power density by improving the proton and mass transport.
A single fuel cell using ultra‐low Pt (1 wt%) loaded channeled mesoporous carbon particles shows exceptionally high activity, power density, and durability. The designed channels formed on the carbon particles allow effective transfer of the reactants and products, obtaining 51 kW gPt−1 after 30 000 cycles under H2/air flow, which is the highest performance reported to date.
Groundwater nitrate contamination has been the main water quality problem threatening the sustainable utilization of water resources in Jeju Island, South Korea. The spatially varying distribution of ...nitrate levels associated with complex environmental and anthropogenic factors has been a major challenge restricting improved groundwater management. In this study, we applied ordinary least squares (OLS) regression and geographically weighted regression (GWR) models to determine the relationships between the NO3–N concentration and various parameters (topography, hydrology and land use) across the island. A comparison between the OLS regression and GWR prediction models showed that the GWR models outperformed the OLS regression models, with a higher R2 and a lower corrected Akaike Information Criterion (AICc) value than the OLS regression models. Interestingly, the GWR model was able to provide undiscovered information that was not revealed in the OLS regression models. For example, the GWR model found that orchards (OR) and urban (UR) variables significantly contributed to nitrate enrichment in the certain parts of the island, whereas these variables were ignored as a statistically insignificant factor in the OLS regression model. Our study highlighted that GWR models are a useful tool for investigating spatially varying relationships between groundwater quality and environmental factors; therefore, it can be applied to establish advanced groundwater management plans by reflecting the spatial heterogeneity associated with environmental and anthropogenic conditions.
•Prediction of nitrate level based on geographical weighted regression (GWR) model.•GWR was used to study spatially varying nitrate level in a complex environment.•GWR showed higher prediction performance ability than ordinary least squares model.•GWR proposed groundwater management plans reflecting spatial heterogeneity.
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•FRET based QD-Aptasensor was successfully configured by employing a pair of QD525 and PoPo3 dye.•Highly sensitive detection of microcystin-LR was achieved in the analytical range of ...10−4–102 ng/mL.•Highly selective detection of microcystin-LR was demonstrated over seven congeners.•It was capable of quantifying microcystin-LR in both laboratory culture and eutrophic water.•It was compared by a high correlation with conventional ELISA.
A highly sensitive fluorescence resonance energy transfer (FRET)-based quantum dot (QD)-Aptasensor was developed for microcystin-LR (MC-LR) detection in eutrophic water. The FRET-based QD-Aptasensor was able to achieve an analytical limit of detection of 10−4 μg/L MC-LR with selectivity among different congeners (microcystin-YR, microcystin-LY, microcystin-LW, microcystin-RR, microcystin-LF, microcystin-LA, and Nodularin). The performance of QD-Aptasensor was demonstrated using both laboratory grown cyanobacterial culture (Microcystis aeruginosa) and environmental water samples. For the laboratory culture, the intracellular MC-LR concentrations changed according to the cyanobacterial growth curve. The QD-Aptasensor detected MC-LR up to 12.7–15.8 μg/L-cyanobacterial culture at early stationary phase. For the environmental samples, the MC-LR was measured at cell densities of 2.7 × 108 and 6.6 × 1010 cells/L-water, which correspond to 1.0 and 7.2 μg MC-LR/L-water, respectively. For comparison, the laboratory culture and environmental samples were analyzed by the conventional enzyme-linked immuno-sorbent assay (ELISA). The MC-LR concentrations of FRET-based QD-Aptasensor showed a strong positive correlation with those of ELISA (Pearson correlation coefficient, r = 0.981 and r = 0.862) for the laboratory culture and environmental samples, respectively.
Sensor measurements of civil structures provide basic information on their performance. However, it is impossible to install sensors at every location owing to the limited number of sensors ...available. Therefore, in this study, we propose an optimal sensor placement (OSP) algorithm while reducing the system order by using the constraint condition between the master and slave modes from the target modes. The existing OSP methods are modified in this study, and an OSP approach using a constrained dynamic equation is presented. The validity and comparison of the proposed methods are illustrated by utilizing a numerical example that predicts the OSPs of the truss structure. It is observed that the proposed methods lead to different sensor layouts depending on the algorithm criteria. Thus, it can be concluded that the OSP algorithm meets the measurement requirements for various methods, such as structural damage detection, system identification, and vibration control.
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