Reaction Kinetics Mechanisms and Catalysis
·
2024
·Vol. 137
·期 3
·1701-1720
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IF 1.7
Guo Kailiang,Liu Shuang,Men Yong,Li Lin,Hu Jiajia,Xu Junzhe,Sun Chenghui,Wei Gaixia,Wang Jinguo,He Shan,Wu Bin,Huang Xiaohui
Herein, we prepared Pd nanoparticle (NP) catalysts using XC-72 carbon supports through a tailored deposition–precipitation method. Our primary objective was to unravel the size effects of Pd NPs on hydrogenation of tetraacetyldibenzylhexaazaisowurtzitane (TADBIW), a pivotal intermediate for synthesis of high energy density materials hexanitrohexaazaisowurtzitane (CL-20). The controlled modulation of Pd NP size ranged from a mere 1.8 nm to 7.4 nm. Remarkably, our investigations into TADBIW hydrogenation unveiled a fascinating trend: the ultrasmall-sized Pd NPs with a diameter of 1.8 nm exhibited excellent yield and reaction rates. In stark contrast, their larger-sized counterparts demonstrated diminished catalytic activities. To disclose the size-dependent nature, various characterization techniques were employed, including XRD, TEM, XPS, CO and H 2 pulse chemisorption. The comprehensive analysis revealed that the ultrasmall-sized Pd possessed more positively charged sites and exhibited higher dispersion. This unique configuration facilitated an accelerated adsorption of hydrogen and the electron-rich substrate TADBIW. Notably, this phenomenon led to a reduction in the activation energy through a thermodynamic effect, thereby enhancing overall catalytic performance. Our results strongly suggested that the ultrasmall-sized Pd NPs can exert a dominated influence on the physical and chemical states of the active sites, playing a key role in triggering the adsorption and activation of the substrate TADBIW. These findings not only deepen our understanding of the intricate connections between Pd NP size and catalytic activity but also open new avenues for advancing the design and optimization of catalysts in the hydrodebenzylation methodologies and synthesis of related compounds.
研究领域:
材料科学
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催化化学
·
能源材料
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DOI
高影响因子
Crystals
·
2020
·Vol. 10
·期 9
·781
·
IF 2.404
Qintong Huang,Rui Li,Guangying Fu,Jiuxing Jiang
ZSM-5 zeolites are commonly used as a heterogeneous catalyst for reactions. Four ZSM-5 catalysts (with various crystallite sizes and a similar ratio of Si/Al) and their ball-milling/surface-poisoning derivates were used to convert L-lactic acid to L, L-lactide. The reaction products were analyzed by three independent analytical methods (i.e., Proton nuclear magnetic resonance (1H NMR), high-pressure liquid chromatography (HPLC), and chiral gas chromatography (GC)) for determining the L, L-lactide yield and L-lactic acid conversion. A clear size effect, i.e., smaller catalysts providing better performance, was observed. Further ball-milling/surface-poisoning experiments suggested that the size effect of the ZSM-5 catalysts originated from the diffusion-controlled nature of the reaction under the investigated conditions.Keywords:ZSM-5 zeolites;L,L-lactide;size effect;diffusion control
研究领域:
催化化学
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材料科学
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DOI
高影响因子
Nanomaterials
·
2020
·Vol. 10
·期 6
·1035
·
IF 4.324
Xiang Nie,Guo Li,Zhao Jiang,Wei Li,Ting Ouyang,Jianfeng Wang
Exfoliation of two-dimensional boron nitride nanosheets (BNNSs) from parent bulk material has been receiving intensive attention because of its fascinating physical properties. Liquid exfoliation is a simple, scalable approach to produce single-layer or few-layer BNNS. In this paper, water/propanol co-solvent exfoliation of bulk boron nitride under the assistance of sonication was investigated in detail. Special attention was paid on the effect of raw bulk boron nitride size and co-solvent composition. The results show that sonication of small-size hexagonal boron nitride tends to generate large nanosheets, due to a predominant solvent wedge effect. In addition, it is found that the composition of water/propanol co-solvent has an important effect on exfoliation efficiency. Interestingly, although two isomers of 1-propanol (NPA) and 2-propanol (IPA) have the same molecular weight and similar surface tension, their aqueous solutions allow the formation of boron nitride nanosheets dispersion with markedly different concentrations. It is proposed that due to their spatial configuration difference, NPA with its longer molecular chain and fewer hydrophobic methyl group tends to form dynamic water-NPA clusters with larger size than water-IPA clusters. The hydrodynamic radius of the co-solvent “clusters” was calculated to be 0.72 nm for water/NPA system and 0.44 nm for water/IPA system at their maximum, respectively. Their size changes, represented by two curves, indicate a strong “cluster size” effect on exfoliation efficiency. Our work provides an insight into co-solvent exfoliation of hexagonal boron nitride and emphasizes the importance of co-solvent cluster size in exfoliation efficiency.Keywords:liquid phase exfoliation;boron nitride nanosheets;co-solvent cluster;size effect
研究领域:
材料科学
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纳米技术
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化学工程
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DOI
PubMed
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2016
·Vol. 27
·期 6
·5735-5740
·
IF 1.798
Liu Chang,Liu Yunfei,Lyu Yinong,Lyu Chongguang
Octahedra-like NaNd(MoO 4 ) 2 microcrystals with tetragonal scheelite-type structure were successfully synthesized by a low cost molten salt method using halons (NaCl or NaBr) as flux. The as-prepared products were characterized by powder X-ray diffractometer, field emission-scanning electron microscope and photoluminescence spectrometer (PL). The results show that the reaction parameters including calcining temperature, reaction time, and the type of salt play important roles on the morphologies and sizes of the NaNd(MoO 4 ) 2 microcrystals. The excitation spectra of the NaNd(MoO 4 ) 2 octahedron-like crystals were observed with a maximum peak at 585 nm (λ em = 1066 nm). The emission spectra were recorded under excitation wavelength of 585 nm and exhibit the strongest peak at 1066 nm. In addition, the results revealed the size effect on the PL intensity of NaNd(MoO 4 ) 2 crystals, that the PL intensity of microcrystals is higher than that of nanocrystals. These imply that NaNd(MoO 4 ) 2 microcrystals have potential application in the field of solid state laser materials.
研究领域:
材料科学
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光学
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DOI
高影响因子
Materials
·
2021
·Vol. 14
·期 21
·6342
·
IF 3.623
Ming Wei,Ye Tian,Lijun Wang,Yuankai Hong,Dan Luo,Yinlin Sha
The absorption and emission mechanisms of gold nanoclusters (AuNCs) have yet to be understood. In this article, 11-Mercaptoundecanoic acid (MUA) capped AuNCs (AuNC@MUA) were synthesized using the chemical etching method. Compared with MUA, AuNC@MUA had three obvious absorption peaks at 280 nm, 360 nm, and 390 nm; its photoluminescence excitation (PLE) peak and photoluminescence (PL) peak were located at 285 nm and 600 nm, respectively. The AuNC@MUA was hardly emissive when 360 nm and 390 nm were chosen as excitation wavelengths. The extremely large stokes-shift (>300 nm), and the mismatch between the excitation peaks and absorption peaks of AuNC@MUA, make it a particularly suitable model for studying the emission mechanism. When the ligands were partially removed by a small amount of sodium hypochlorite (NaClO) solution, the absorption peak showed a remarkable rise at 288 nm and declines at 360 nm and 390 nm. These experimental results illustrated that the absorption peak at 288 nm was mainly from metal-to-metal charge transfer (MMCT), while the absorption peaks at 360 nm and 390 nm were mainly from ligand-to-metal charge transfer (LMCT). The PLE peak coincided with the former absorption peak, which implied that the emission of the AuNC@MUA was originally from MMCT. It was also interesting that the emission mechanism could be switched to LMCT from MMCT by decreasing the size of the nanoclusters using 16-mercaptohexadecanoic acid (MHA), which possesses a stronger etching ability. Moreover, due to the different PL intensities of AuNC@MUA in methanol, ethanol, and water, it has been successfully applied in detecting methanol in adulterated wine models (methanol-ethanol-water mixtures).Keywords:gold nanocluster;source of absorption;emission mechanism;ligand;size effect
研究领域:
化学
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材料科学
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光学
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DOI
PubMed
高影响因子
AQUATIC TOXICOLOGY
·
2023
·
IF 4.5
Yuanyuan Su,Liu Gao,Licheng Peng,Xiaoping Diao,Shengyou Lin,Ruiqi Bao,Tariq Mehmood
Existing studies have shown that microplastics (MPs) as artificial surfaces can be colonized by plankton microorganisms. However, systematic research on exploring the aggregation formation process of MPs and microalgae is still lacking and particularly the influencing factors of aggregation remain to be elucidated. Therefore, this study investigated the heterogeneous aggregation process between various microalgal species (i.e., Chlorella vulgaris, Scenedesmus obliquus, Tetraselmis subcordiformis, Chaetoceros müelleri and Streptococcus westermani ) and MPs (i.e., mPS and mPLA) with different sizes (i.e., 74 μm and 613 μm), concentrations (i.e., 0.1 g/L, 1 g/L and 2 g/L) and shapes (i.e., the particle and sheet). The results showed that microalgae can first attach to the holes or protrusions of MPs and highly accumulate in the local region, and then multi-layer aggregation can be formed subsequently. The aggregation degree between MPs and microalgae was closely related to the MPs shape and size, and was less related to the MPs concentration. The aggregation speed of small-sized MPs (e.g., 74 μm) was faster than the large-sized ones (e.g., 613 μm). The MPs in a shape of sheet were more obvious than those in particle on their aggregation with microalgae. The density of aggregates was increased compared with pristine MPs, which is related to the cell density and cell number of attached microalgae. For the same type of MPs, the aggregation degree for the tested microalgae was as follows: Scenedesmus obliquus > C. vulgaris > T. subcordiformis > C. müelleri > S. westermani . Meanwhile, MPs inhibited cell growth of microalgae, particularly under the circumstance of their aggregation, by limiting the gas and mass transfer between microalgal cells and the extracellular environment. The heterogeneous aggregation of MPs and microalgae may provide new ideas for treatment and controlling of MPs in the environment.
研究领域:
环境科学
·
微生物学
✓ 已验证
DOI
PubMed
高影响因子
AQUATIC TOXICOLOGY
·
2019
·
IF 3.794
Ting Wang,Xizhi Huang,Xiaoyu Jiang,Menghong Hu,Wei Huang,Youji Wang
Titanium dioxide nanoparticles (TiO 2 NPs) are widely used in various products and inevitably released with different sizes and forms into aquatic environment. The purpose of this study was to assess the differential immune toxicity of TiO 2 NPs with size difference on mussel hemocytes using flow cytometry (FCM) assays. Hemocyte parameters, including total hemocyte count (THC), hemocyte mortality (HM), phagocytosis activity (PA), lysosomal content (LC), esterase activity (EA), mitochondrial number (MN), mitochondrial membrane potential (MMP) and reactive oxygen species content (ROS) were evaluated in the mussels Mytilus coruscus exposed to two types of TiO 2 NPs (25nm & 100nm: 0.1, 1, 10 mg/L, respectively). In general, size- and concentration-dependent toxicity was pronounced with 25nm-NP and highest concentration (10mg/L) being the most toxic. Alhough a slight recovery from the TiO 2 exposure was observed, significant carry-over effects were still detected. These results highlight the importance of differential size effects of metal oxide NPs on toxicity mechanisms in aquatic animals.
研究领域:
环境科学
·
免疫学
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DOI
PubMed
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
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2024
·
IF 5.8
Yuchao Fan,Xu Mei,Beibei Liu,Jianfeng Wang,Li Ye,Yingjiu Zhang,Xinjian Li
The size of reinforcements is a pivotal and conventional parameter in metal matrix composites . Based on the distinctive preparation process of MXene , this research introduces a novel strategy to tailor the size of Ti 3 C 2 T x through the controlled ball milling of its precursor, Ti 3 AlC 2 . This approach fabricated Ti 3 C 2 T x sheets with sizes of 4.7 µm, 1.8 µm, and 0.6 µm. Subsequently, these Ti 3 C 2 T x sheets are incorporated into a magnesium (Mg) matrix composite to investigate the effect of Ti 3 C 2 T x size on the strengthening performance. The findings reveal a trend wherein the compressive yield strength (CYS) of the Ti 3 C 2 T x /ZK61 composites increases and the failure strain decreases with the decreased size of Ti 3 C 2 T x . Incorporating 4.7 µm Ti 3 C 2 T x results in an 11.0% reduction in CYS coupled with a 50% increase in failure strain. Incorporating 1.8 µm Ti 3 C 2 T x leads to a 4.6% increase in CYS with a 6.5% increase in failure strain. Incorporating 0.6 µm Ti 3 C 2 T x leads to a 10.7% increase in CYS with a 3.2% increase in failure strain.
研究领域:
材料科学
·
力学
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产品关联
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2024
·
IF 8.3
Shuchao Jiang,Hongqi Shi,Yuzhe Xu,Jiaojiao Liu,Tie Yu,Guoqing Ren
Formic acid (FA, HCOOH) is regarded as one of the most promising carriers for hydrogen storage. However, the catalyst design for FA dehydrogenation into H2 with high efficiency is not clear. Here, we elucidate the rationale of size effect over the most commonly used Pd-based catalyst through supporting different Pd species, including single atoms, nanoclusters, and nanoparticles, on amine-functionalized active carbon (Pd/AC-NH2). The activity test presents that Pd/AC-NH2 with Pd nanoclusters exhibits the best turnover frequency (TOF) value of 40856 h–1 for 1 M FA at 328 K and even 1504 h–1 for neat FA at 308 K, which is comparable to the homogeneous catalysts and has been the first heterogeneous catalyst used in neat FA dehydrogenation under mild conditions. The comprehensive characterizations reveal that the size of Pd species affects the ratios of Pd0/Pd2+ and hydrogen spillover effect, which is crucial for the C–H cleavage and H2 desorption. Besides, the influences of amine groups on catalytic performance were further examined. This work provided an ingenious guideline to design efficient and practical catalysts for hydrogen storage under ambient conditions.
研究领域:
化学工程
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材料科学
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能源科学
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产品关联
DOI
PubMed
高影响因子
Advanced Composites and Hybrid Materials
·
2024
·Vol. 7
·期 2
·1-13
·
IF 23.2
Guo Jiang,Xi Shaohua,Sun Yukun,Dong Wenhao,Asiri Yazeed M.,Alqarni Nawal D.,Helal Mohamed H.,Zhou Fujian,Zhu Jianfeng
In this work, magnetoresistive nanomagnetite@polyaniline (Fe 3 O 4 @PANI) composites with a core-shell structure were prepared by in situ polymerization method with KH-550 as coupling agent. All the samples demonstrated the positive MR, and compared with PANI composites reinforced with small (diameter 80 nm) size or large (diameter 450 nm) size of Fe 3 O 4 , the PANI composites reinforced with medium (diameter 220 nm) size of Fe 3 O 4 exhibit the largest MR (8.41%) when the MK-F loading is 60 wt%. Moreover, the size effect of Fe 3 O 4 particles on the electrical conductivity and MR behavior was analyzed by the Mott VRH model and wave functional shrinkage model. The MR value of Fe 3 O 4 @PANI composites with different loading and size of Fe 3 O 4 particles mainly depends on localization length, density of state at Fermi level, and average hopping length. Moreover, the Fe 3 O 4 @PANI composites were systematically characterized by SEM, TEM, XRD, and FT-IR. This work could provide the guidance for fabrication of magnetic field sensors and information memory storage devices. Graphical Abstract The core-shell structured magnetite/polyaniline nanocomposites with tunable magnetoresistance by changing the size of magnetite nanoparticle.
研究领域:
材料科学
·
物理学
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DOI
高影响因子
APPLIED PHYSICS LETTERS
·
2019
·Vol. 115
·期 23
·
IF 3.521
Liang Hao,Peng Fang,Guan Shixue,Tan Lijie,Chen Haihua,Lei Li,He Duanwei,Lu Cheng
Hafnium diboride (HfB 2 ) is one of the most promising hard-brittle ceramic materials with unique physical properties. Here, we have synthesized the well-crystallized HfB 2 by a high-pressure solid-state reaction and employ in situ high-pressure synchrotron radiation angle-dispersive X-ray diffraction to investigate the size-effect of HfB 2 . An abnormal physical behavior of HfB 2 under high pressure is observed. The microsized HfB 2 shows slight anisotropy along a and c axes; however, the nanosized HfB 2 reveals a different compression behavior with pressure-induced shell structural transition from a disordered symmetric amorphous shell state to an asymmetric amorphous shell state. In addition, the results indicate that the pressure calibrations are sensitive to the grain size. The present findings offer insights into the physical behaviors of different sized HfB 2 , which may also provide valuable information for other transition metal borides under high pressure.
研究领域:
材料科学
·
凝聚态物理
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产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2014
·
IF 6.007
Peng Wang,Danzhen Li,Jing Chen,Xiaoyun Zhang,Jiangjun Xian,Xue Yang,Xiuzhen Zheng,Xiaofang Li,Yu Shao
In this paper, a facile and green method was employed to synthesize CdSe quantum dots (QDs)-modified TiO 2 . It exhibited much higher photocatalytic activities than both TiO 2 and bulk CdSe-modified TiO 2 on degrading malachite green (MG) aqueous solution under visible light irradiation. The vital role that quantum size effect of CdSe QDs plays in enhancing photocatalytic properties of CdSe QDs-modified TiO 2 is discussed in detail for the first time. Due to the more negative conduction band potentials of CdSe QDs than that of bulk CdSe, the electron transfer rate from CdSe QDs to TiO 2 is much faster than that from bulk CdSe to TiO 2 , which would be beneficial for an efficient charge carrier's separation. As a result, more quantities of active species (O 2 • − , H 2 O 2 , •OH) are generated during the photocataltytic reaction in CdSe QDs-modified TiO 2 system. This work could not only provide a facile and green strategy to fabricate semiconductor QDs-modified TiO 2 photocatalyst but also contribute to a deeper understanding of the specific role of semiconductor QDs during the photocatalytic reaction process.
研究领域:
材料科学
·
环境科学
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）