Search

Centrifugation is one of the most commonly used methods for separation in biology and chemistry. However, effective fractionation is not always easy to obtain, as preparative centrifuge experiments are mostly conducted in an empirical way, even when it is guided by the quantitative results from analytical ultracentrifuge (AUC). Very few works have been performed to enhance the fractionation resolution of the differential centrifugation method in a swing-out rotor. This is primarily due to the absence of a characterization tool for sedimentation in the preparative centrifuge. In this study, we utilized image analysis to map the particle concentration distribution throughout the preparative centrifuge tube, revealing an unexpected and abnormal sedimentation process. By characterizing the sedimentation coefficient distributions of the fractionated product via AUC, we demonstrated that the overall sedimentation efficiency in a swing-out preparative centrifuge was significantly reduced. Furthermore, effective fractionation was confined to the intermediate phase of the entire sedimentation process. We propose that the mechanism here is a combination of the inverse Boycott effect and droplet sedimentation. The actual sedimentation process within a preparative centrifuge can be described by modifying the Lamm equation phenomenologically, which simply results in an effective sedimentation coefficient. Our work builds a foundation for determining the optimal preparative centrifugation conditions for various systems.

Enhancing the fluorescence of organic dye by colloidal particles is one of the most promising routes to optimize fluorescence detection. However, in addition to metallic particles, which serve as the most frequently used particles and have been found to employ the plasmonic resonance to provide strong fluorescence enhancement, neither new types of colloidal particles nor new fluorescence mechanisms have been intensively explored in recent years. In this work, strongly enhanced fluorescence was observed when 2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI) molecules were simply mixed with zeolitic imidazolate framework-8 (ZIF-8) colloidal suspensions. Moreover, the enhancement factor ΔI= IHPBI+ZIF-8/IHPBIdoes not increase accordingly with the increasing amount of HPBI. To find out how the strong fluorescence was triggered and affected by the amount of HPBI, multiple techniques were applied to analyze the adsorption behavior. By combining analytical ultracentrifugation with first-principles calculations, we proposed that HPBI molecules were adsorbed onto the surface of ZIF-8 particles coordinatively and electrostatically, depending on the concentration of HPBI molecules. The coordinative adsorption would result in a new kind of fluorescence emitter. The new fluorescence emitters tend to distribute on the outer surface of ZIF-8 particles periodically. The distance between each fluorescence emitter is fixed and much smaller than the wavelength of the excitation light. Thus, it can be concluded that collective spontaneous emission might be triggered.

Significant progress has been made in the synthesis and application of core–shell nanoparticles in the past decade. But particle agglomerations are hard to avoid as the formation mechanisms of core–shell nanoparticles are still vague and not clear even for the simplest and most straightforward hard-templating method. Here, analytical ultracentrifugation (AUC) is applied to investigate the formation of polystyrene@ZIF-8 core–shell nanoparticles, as a model to understand the hard-templating method. It has been found that the concentration of the ZIF-8 precursor influences both the ZIF-8 shell formation and the agglomeration of the polystyrene (PS) template. An overdiluted ZIF-8 precursor is not suitable for ZIF-8 shell formation, while a highly concentrated ZIF-8 precursor causes strong aggregation of the PS core. By applying the optimal precursor concentration identified by AUC, well-dispersed polystyrene@ZIF-8 core–shell nanoparticles can be obtained.

An improved synthesis of Lacosamide 1with high purity has been developed. Critical parameters of each step were identified as well as the impurities generated. Moreover, a creative method to improve chiral purity and stability of the key intermediate (R)-2-amino-N-benzyl-3-methoxypropionamide 10by forming salt with an achiral acid (phosphoric acid) was discovered to ensure the chiral purity of (R)-Lacosamide. Phosphoric acid was further developed for the deprotection of the Boc group.

Understanding the piezoelectricity mechanism is crucial for developing new materials for better performance. Here, we developed a nanogenerator based on the ZnO thin films having various TC(002) values. The output current well correlated to the magnitude of (002) texture coefficient (TC(002)). Additionally, the TC(002)-dependent photovoltaic and rectification properties are observed. When the film is subjected to persistent compression, the photovoltaic, rectification, and piezoelectric properties fade away. Based on our observation that the ZnO polar structure always shows a spontaneous electron field (SEF), we thus propose a new piezoelectricity mechanism. The [001]-orientated ZnO thin film with the SEF is equivalent to a capacitor, the compression functions as a discharging process, and the removal of the external stress serves as a charging process. The physical mechanism provides an insight into various energy conversion processes that will inspire advanced designs of high-performance nanogenerators, solar cells, and other optoelectronic devices.

The concept of spontaneous electric field (Es) in polar structures is crucial for understanding the physical and chemical properties of compound semiconductors and improving their performanes. However, this concept has not been widely accepted so far. Here, we show the first observation of rectification and photovoltaic effects in the polar [0001] direction on the nonpolar ZnO (1010) crystal plane. However, no rectification and photovoltaic effects are observed in the nonpolar [1210] direction perpendicular to the [0001]. When a stress was applied in the [0001] direction of the ZnO single crystal, the rectification and photovoltaic effects are abated and disappeared. The disappearance of the two effects results from the pressure-induced disappearance of the polar structure. The results fully demonstrated that the rectification and photovoltaic effects arise from the existence of Es in the polar [0001] direction. The Es motivates the directional transfer of the electrons and photocreated charges along the [0001] direction, and the rectification and photovoltaic effects are thus observed. These results provide direct evidence for the polar structure theory and suggest that the polar structures can be employed to develop new types of photovoltaic and other electronic and photoelectronic devices.

Given a certain binary phase, its crystal structure can usually be rationalized by thermodynamics and packing rules. However, there is still no fundamental understanding of how metastable solids form and how this is influenced by kinetic factors. Furthermore, the very early stages of crystallization remain vague. We present an experimental study using a binary mixture of colloidal particles as a model. Particle assembly is provoked by centrifugation, and the degree of separation can be adjusted precisely. Between the scenarios of random mixture (glassy state) and complete phase separation, conditions could be realized to facilitate the occurrence of various periodic structures in a single experiment. Some of these structures can only be explained by a dynamic, nonequilibrium and dissipative state. Eventually, the formation of certain metastable lattices can be interpreted as an emergent, systemic phenomenon. Thus, centrifugation can be used for studying the chaos–order transition in complex particle systems.

Given the importance of promoting renewable energy, the Chinese government has enacted policies to encourage residents to install and use household distributed photovoltaic (PV) systems. However, only a few studies investigated factors influencing residents’ use intention for household PV systems. The present study therefore investigated the influence of Chinese residents’ environmental concern and innovativeness on their use intention for household PV system, as well as the mediating effects of perceived benefits and harm of household PV system in this process. Furthermore, the moderating role of residents’ monthly electricity consumption in the above-mentioned association was also examined. Questionaire data from 400 Chinese participants in Zhejiang Province were used for analysis. Results from structural equation modeling suggested positive associations between environmental concern and use intention, and between innovativeness and use intention, through the mediating of perceived benefits and harm. Residents’ monthly electricity consumption also moderate part of the associations. Based on the results, this paper calls on the government to regulate the safety standard of household PV nationwide to enhance social confidence. Conspicuous consumption, which comes with “traditional customs”, should also be reduced.

In this study, the effect of centrifugal force on the assembly and crystallization of binary colloidal mixtures is demonstrated. Monolithic pieces have been prepared which are characterized by a structural gradient along the direction of the centrifugal force. For a given number ratio of monodisperse 154 and 300 nm latex spheres, the absolute latex concentration was varied and with it the sedimentation velocity of the individual particle species. For three different concentrations it has been demonstrated that the structure of the binary colloidal assembly obtained after centrifugation is affected significantly. For the largest initial latex absolute concentrations, the structural variation along the packed latex column in the ultracentrifuge tube is minimal, while a decrease in the absolute concentrations leads to crystalline packing in defined regions of the column. The observation of the thermodynamically favored structure resembling NaCl, but also of the aluminum boride AlB2analog as well as unordered, glass-like packing depending on the mutual latex concentration under unchanged particle number and size ratio, shows that by centrifugation kinetically favored states can be realized. This result implies that centrifugation of binary latex mixtures is a promising route for investigating the self-organization of binary colloidal systems since the sedimentation velocities of the two particle species are different, and thus the local concentrations and mixing ratios vary continuously also enabling rare packing motifs.

A novel umami peptide, IPIPATKT, showed excellent dual dipeptidyl peptidase-IV (DPP-IV) and angiotensin I-converting enzyme (ACE) inhibitory activities, the IC50values were 64 and 265 μM, respectively. Molecular docking displayed that IPIPATKT was docked into the S1 and S2 pockets of ACE, and it was close to the active site pocket of DPP-IV. The insulin-resistant-HepG2 (IR-HepG2) cell model and human umbilical vein endothelial cell (HUVEC) model showed that the peptide significantly increased the content of glucose, the activities of hexokinase, pyruvate kinase, and the concentration of nitric oxide (p< 0.01), while it reduced the content of endothelin-1 (ET-1). IPIPATKT exhibited a hypotensive effect (−23.5 ± 2.2 mmHg) and attenuated the increase in glucose levels in vivo, as demonstrated using spontaneous hypertensive rats (SHRs) and C57BL/6N mice. We reported the in vivo activities of the umami peptide with dual hypertensive and hypoglycemic effects for the first time.