Search

ZnZrOx solid solution is a promising catalyst for the hydrogenation of CO2 to methanol, but precise design of the nanostructure to enhance catalytic performance remains a significant challenge. Herein, a ZnZrOx-based solid solution (ZnZrOx-MD) nanoparticle catalyst with uniform metal dispersion and remarkable CO2 activation ability was developed via calcination of metal–organic frameworks [MOFs, viz., PCN-223-(Zn)] with mixed metal (Zr and Zn) as solid precursors. It was found that the ZnZrOx-MD nanoparticle catalyst outperformed its counterparts prepared using a traditional deposition–precipitation method (ZnZrOx-TD). Furthermore, the effects of the micromorphology and crystal composition on the catalytic performance of ZnZrOx-MD were systematically investigated. Comprehensive characterization results reveal that ZnZrOx-MD contained abundant oxygen vacancies, large specific surface area, and uniform metal dispersion, which collectively contributed to its excellent CO2 hydrogenation performance, resulting in a high methanol selectivity of 77.2% at 320 °C. In situ DRIFTS experiments confirm the mechanism for the CO2 hydrogenation to methanol over the ZnZrOx nanoparticle catalysts involved the initial formation of HCOO* species, followed by subsequent hydrogenation to generate CH3O* and ultimately produce methanol. Overall, this work highlights the potential benefits of MOFs as thermal decomposition precursors for the fabrication of solid-state catalysts with unique properties. [ABSTRACT FROM AUTHOR]

A Supported gold catalyst was prepared by reduction of HAuCl4 with the Cacumen Platycladi extract. This catalyst was then used for oxidation of 2-phenylethyl alcohol in a model reaction. Our study evaluated the effect of various preparation conditions, including the Au loading ratio and calcination temperature. Additionally, we explored the influence of the reaction temperature and reaction time on the catalytic performance of a Au/TiO2 catalyst. Our experimental findings revealed notable results for the Au/TiO2 catalyst characterized by the Au loading of 1.3 wt % and calcinated at 400°C. Under specific reaction conditions (0.3 g catalyst, 220°C, 3.0 MPa, 2.5 h), the conversion of 2-phenylethyl alcohol reached 45.3 and a 59.6% selectivity and a 27.0% yield of the target product (phenylacetaldehyde). In addition, catalytic performance remained stable after 8 repeated uses. [ABSTRACT FROM AUTHOR]

The innovation ability of students is one of the most important objectives that need to be cultivated in colleges and universities. The comprehensive evaluation of innovation ability discussed in the study can be divided into two stages: the first stage can be called preliminary evaluation and its main target is to identify students with innovative potential; in the second stage, the target objects found in the previous stage will be evaluated quantitatively and ranked. However, it is always difficult to quantitatively evaluate the innovation ability by using traditional algorithms. Based on the above analysis, the study proposes an algorithm to quantitatively evaluate the innovation ability with the help of management thought and fuzzy mathematics. Data are the basis of evaluation, and the accuracy of the data directly determines the quality of the algorithm; the data structure of the incompletely probabilistic fuzzy set is proposed in the study; the data structure can fully consider the fuzziness of the problem and the hesitation in the decision-making process; it can save the original detailed data to the maximum extent. Certainly, certain information may be lost or only the value range can be determined; there are usually some unknowns in the evaluation data, and the consistency optimization model is proposed for solving the problem. Usually, there are certain contradictions among the evaluation data; the definition of the consistency degree is proposed in the study; the consistency can be verified in time after all the unknowns are obtained, and the automatic adjustment module will be activated immediately if the value of the consistency degree exceeds the warning threshold. Finally, after verifying the data consistency, the solution can be obtained by solving the optimization model. Several experiments have been carried out to verify the effectiveness and high-discrimination ability of the algorithm proposed in the study; meanwhile, the superiority of the algorithm is further verified through comparisons with other outstanding algorithms. [ABSTRACT FROM AUTHOR]

From trivial matters in life to major scientific projects related to the fate of mankind, decision-making is everywhere. Whether high-quality decisions can be made often directly affects the development of affairs, especially when sudden disasters occur. As the basis of decision-making, data are crucial. The continuously probabilistic linguistic set, a data structure of the fuzzy mathematics, is selected in the paper to collect original data after careful comparisons, because this data structure can fully consider the hesitation of decision-makers and the fuzziness of complex problems. Although all alternatives are costly, the costs of different alternatives still vary greatly; obviously, the low-cost alternative is better than others when the same predetermined goal can be achieved, which is one of the research objectives and characteristics of this paper. Different from other researchers who only take the cost as one of the decision-making indicators, the algorithm proposed in the paper pays much more attention on the cost reduction. When dealing with an emergency, it is often difficult to solve the problem by taking measures only once; usually, multiple rounds of measures are needed. Each round of decision-making has both connections and differences, and the multiround decision-making model is proposed and built in the paper. Different from traditional linear structures, the model mainly adopts the closed-loop structure, which divides the whole process into multiple sub-decision-making points, the severities measured at the current time point will be compared with the values estimated at the latter time point, and then, the differences will be input into the system, the corresponding automatic adjustment modules will be activated immediately according to the values. The accuracy of the system can be verified and adjusted in time by the closed-loop control module. Finally, several experiments are carried out and the results show that the algorithm proposed in the paper is more effective and the cost is lower. [ABSTRACT FROM AUTHOR]

Emergencies often occur irregularly, such as infectious diseases, earthquakes, wars, floods, the diffusion and leakage of chemically toxic and harmful substances, etc. These emergencies can bring huge disasters to people, even worse, the time left for people to make critical decisions is usually very limited. When an emergency occurs, the most important thing for people is to make reasonable decisions as soon as possible to deal with the current problems, otherwise, the situation may deteriorate further. The paper proposes an emergency decision-making algorithm under the constraints of the limited time and incomplete information, the research is mainly carried out from the following aspects, firstly, we use the data structure of the hesitant fuzzy probabilistic linguistic set to collect the basic data after careful comparison, which has three advantages, (1) considering the hesitation in the decision-making process, each evaluation information is allowed to contain multiple values instead of just one value; (2) each evaluation value is followed by a probability value, which further describes the details of the evaluation information; (3) the data structure allows some probability information to be unknown, which effectively expands the application scope of the algorithm. Secondly, the maximization gap model is proposed to calculate unknown parameters, the model can distinguish alternatives with small differences. Thirdly, all the evaluation information will be aggregated by the dynamic hesitant probability fuzzy weighted arithmetic operator. Subsequently, an instance is given to illustrate the effectiveness and the accuracy of the algorithm proposed in the paper. Finally, the advantages of the proposed algorithm are further demonstrated by comparing it with other outstanding algorithms. The main contribution of the paper is that we propose the maximization gap model to obtain the unknown parameters, which can effectively and accurately distinguish alternatives with small differences. [ABSTRACT FROM AUTHOR]

At present, the whole world is facing the serious challenge of COVID-19, and it has reached a consensus that taking appropriate measures timely is the key to prevent and control infectious diseases. This paper proposes an algorithm to solve the problem of how to choose the most appropriate alternative from numerous alternatives in the limited time from the perspective of management. First of all, we have compared various data structures for keeping the comparison results of alternatives. After comparisons, we adopt the hesitant fuzzy incomplete probabilistic linguistic preference relation matrix to save the information which can keep the first-hand valuable collected data to the maximum extent; then, we can obtain the missing values with the help of the fault tree analysis method, which can consider both subjective evaluation data and objective historical data simultaneously. Meanwhile, the fault tree analysis method can find development laws with the help of similar infectious diseases that have occurred in the past. The definition of consistency index is also introduced which can measure whether there are contradictions and the degree of contradiction in the decision results. Only those data that meet the consistency requirements can be used for decision-making and then a method is proposed to effectively reduce the degree of inconsistency. The information aggregation method will be adopted subsequently, and we can obtain the ranking of alternatives. An instance with specific execution steps is also introduced to illustrate the feasibility and efficiency of the algorithm proposed in this paper; in the end, several types of comparisons with typical algorithms proposed by other scholars are carried out, and all the experimental results show that the algorithm proposed in this paper is effective and innovative in some aspects. [ABSTRACT FROM AUTHOR]

The influencing factors of chelator, reaction times, and Yb3+/Tm3+ -doped concentration on the formation of NaYF4:Yb,Tm crystals with various morphologies have been investigated and determined. It is found that NaYF4:Yb,Tm with various morphologies and different phases can be tuned. Compared with the addition of ethylene diamine tetra acetic acid, hexagonal nanoprism-like β-NaYF4:Yb,Tm with a mean length of ~ 1300 nm and diameter of ~ 100 nm is prepared in the presence of oleic acid, which preferentially orients along with the [0001] direction more quickly than others. Systematical research on the emission of Yb3+/Tm3+-doped NaYF4 crystals with microrod, hexagonal microprism, and nanoplate has implied that these obtained crystals with unique optical properties are closely related to their morphologies, phases, and sizes. In addition, a possible growth mechanism of co-existence of α- and β-NaYF4 phases is proposed. It can be expected to illustrate the formation mechanism for the upconversion crystals or other rare-earth upconversion materials and to import these highly luminescent microcrystals or nanocrystals to environmental remediation by full solar energy spectra. [ABSTRACT FROM AUTHOR]

Extensive application of vaterite in ceramics, biomedical implanting, encapsulation and drug delivery require the effectively controlling the size, morphology and polymorph of the obtained calcium carbonate. For this purpose, vaterite was synthesized by using histidine-grafted-chitosan (NHCS) as an organic matrix in this research. The effects of the initial concentration of NHCS, and the aging time on the morphology and polymorph were investigated. The prepared vaterite was characterized by field-emission scanning electron microscope, Fourier transform infrared spectrometer and X-ray diffraction. The result showed vaterite has presented as an advantage phase over calcite phase in presence of NHCS system, and the 91.6 wt% percentage of vaterite can be achieved when the initial concentration of NHCS is 1.000 mg L. Prolonging aging time from 0 to 24 h, the percentage of vaterite would be deduced from 94.4 to 86.2 wt%, in which the flaky-floret and multilayered vaterite transforms to calcite slowly. In contrast, a single crystalline rhombohedral calcite phase can only be obtained without adding NHCS in pure water system. The possible growth mechanism has been proposed by investigating the transition of crystal phase and formation of the vaterite during the growth process. The result indicates that NHCS is an effective template to biomimetic synthesis of vaterite, and provides a novel method for controlling synthesis other biomaterials. Graphical Abstract : [ABSTRACT FROM AUTHOR]

A double hydrolysis approach is first adopted to prepare yttrium aluminum garnet (YAG) powders using Y(NO) · 6HO and NaAlO as raw materials. A variety of techniques, such as thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to characterize the as-synthesized samples. The results show that pure-phase YAG powders are accurately available at 900 °C and above. Among these, the YAG powders, produced at 1100°C, are elliptic in shape, with an average particle size of ~44 nm. Pellets of pressed YAG powders are sintered in vacuum at 1700°C for 8 h, resulting in a dense and nearly pore-free microstructure with an average grain size of ~7 μm. [ABSTRACT FROM AUTHOR]

Pt catalysts and Co doped Pt catalysts with TiO2as the support were prepared by the sol immobilization method based on biological synthesis process, whereby Pt nanoparticles (PtNPs) were reduced from Na2PtCl4usingCacumen Platycladiextract (CPE). The catalytic performance of the catalysts was studied using hydrogenation of cinnamaldehyde as the model reaction. For comparison, Co doped Pt/catalysts were also prepared by traditional impregnation method, TEM observation, and XRD measurement were carried out to characterize the catalysts. The effects of different Pt loadings and Co doping amounts were investigated. The results showed that the PtNPs could be well dispersed onto the TiO2support with narrow size distribution between 4 and 6 nm. 1.0% was observed as the optimal Pt loading amount in our experiments showing a cinnamaldehyde conversion of 73.3% with 68.8% selectivity to cinnamyl alcohol. A proper Co doping amount was also essential to the catalytic performance of the prepared Pt/catalysts as well as a favorable for the reaction process, 1.0% doping amount showed the best activity in which a 70.4% conversion and 88.3% selectivity was achieved. Recyclability tests carried out revealed that the 1.0 Co–1.0 Pt/TiO2catalysts possessed possessing good durability. In this work, Co-Pt/TiO2catalysts prepared by the sol immobilization method based on biological reduction process, showed better selectivity than that from traditional impregnation method. [ABSTRACT FROM PUBLISHER]

BACKGROUND Biosynthesis of Ag nanoparticles ( AgNPs) utilizing renewable materials and nontoxic chemicals has become highly desirable and is currently receiving tremendous attention. In this study, a facile and cellulose-based approach was developed to biosynthesize AgNPs through tandem hydrolysis of silver sulfate and cellulose under hydrothermal conditions. RESULTS Well-defined AgNPs of about 72.0 nm in size were biosynthesized with 0.30 g of cellulose at 200°C for 10 h. The particle sizes of the as-synthesized AgNPs were positively affected by the reaction temperature and time, but on the contrary were negatively affected by the amount of cellulose employed. The results from Fourier transform infrared spectroscopy showed that the cellulose-hydrolyzed products (saccharides or aldehydes) were accountable for the bioreduction of the Ag ions, and the C = O (C-O) groups in the aldehydes or saccharides played critical roles in capping the AgNPs. Additionally, in the presence of the as-synthesized AgNPs, enhanced surface fluorescence of methyl orange was achieved. CONCLUSION A biological and maneuverable strategy was successfully developed for the synthesis of AgNPs by a hydrothermal route through tandem hydrolysis of silver sulfate and cellulose. Thus, this environmentally friendly method is anticipated to be utilized for the biosynthesis of AgNPs and opens up avenues to prepare other metal nanoparticles from metal sulfates. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]