共查询到20条相似文献,搜索用时 13 毫秒
1.
Antonietta Cerulli Milena Masullo Cosimo Pizza Sonia Piacente 《Molecules (Basel, Switzerland)》2022,27(10)
Globe artichoke (Cynara cardunculus L. var. scolymus L.), is a perennial plant widely cultivated in the Mediterranean area, known for its edible part named capitula or heads. Its functional properties are related to its high levels of polyphenolic compounds and inulin. “Carciofo di Paestum”, an Italian traditional cultivar, is a labeled PGI (Protected Geographical Indication) product of the Campania region, representing an important economic resource. So far, a few chemical investigations were performed on this cultivar, mainly focused on the analysis of methanol extracts. Due to the increasing use of food supplements, in this study, a comprehensive analysis of green extracts of “Carciofo di Paestum” PGI heads was performed. EtOH, EtOH: H2O (80:20, 70:30, 60:40) extracts, as well as infusions and decoctions prepared according to Pharmacopeia XII were analyzed by LC-ESI/QExactive/MS/MS. A total of 17 compounds corresponding to caffeoylquinic acid derivatives, phenolics, flavonoids, and terpenoids were identified. The extracts were further submitted to NMR analysis to highlight the occurrence of primary metabolites. Both LCMS and NMR data were analyzed by Principal Component Analysis (PCA), showing significant differences among the extraction methods. Moreover, 5-caffeoylquinic acid and 1,5-dicaffeoylquinic acid were quantified in the extracts by LC-ESI/QTrap/MS/MS using the Multiple Reaction Monitoring (MRM) method. Furthermore, the phenolic content, antioxidant activity, and α-glucosidase inhibitory activity of C. cardunculus var. scolymus “Carciofo di Paestum” extracts were evaluated. 相似文献
2.
Xiao-Ning Liang 《Journal of Dispersion Science and Technology》2016,37(9):1360-1367
Aligned carbon nanotubes (CNTs) composites can be prepared by post-growth alignment or through the use of CNT bundles. Post-growth alignment requires stringent processing conditions (high-voltage electric field/high-strength magnetic field). In this study, we focused on well-aligned multi-walled CNT bundles (AMWNTs). Achieving a balance between dispersion and required orientation was the main aim of this study. Ultrasonic dispersion will inevitably produce heat, which will adversely affect dispersion. Hence, we developed and attached a temperature-control system to a water bath ultrasonic dispersion device. Further, we studied effects of additional factors such as the type and amount of surfactant on dispersion. 相似文献
3.
Brian P. Grady 《Macromolecular rapid communications》2010,31(3):247-257
The ability to control the dispersion of carbon nanotubes in polymers is key to most applications of nanotube‐polymer composites. This feature article describes recent advances in methods used to disperse carbon nanotubes and considers how these methods affect dispersion on different length scales. It is becoming increasing clear that perfect dispersion is not desired for many applications, in particular for electrical conductivity, and controlling the dispersion is key for proper function of the composite in its intended application.
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A facile and easily reproducible technique for assembling biohybrid nanoparticles is a core feature that is highly desired for biomedical applications, considering the nature and limited lifespan of the biopolymers used. Here we show a simple and effective method to enfold single‐walled carbon nanotubes (SWNTs) using an anionic polysaccharide, dextran sulfate. After their interactions, SWNTs were rendered dispersible in aqueous solution and were shortened and unbundled to their basic dimension. Atomic force microscopy analysis was extensively employed to elucidate the mechanism of their interfacing. This biohybrid nanoparticle holds promise for biological and biomedical applications due to the synergistic unique properties of SWNTs and dextran sulfate.
5.
Prof. Dr. Martin Goez Christoph Kerzig Robert Naumann 《Angewandte Chemie (International ed. in English)》2014,53(37):9914-9916
Hydrated electrons are highly aggressive species that can force chemical transformations of otherwise unreactive molecules such as the reductive detoxification of halogenated organic compounds. We present the first example of the sustainable production of hydrated electrons through a homogeneous catalytic cycle driven entirely by green light (532 nm, coinciding with the maximum of the terrestrial solar spectrum). The catalyst is a metal complex serving as a “container” for a radical anion. This active center is generated from a ligand through quenching by a sacrificial electron donor, is shielded by the complex such that it stores the energy of the photon for much longer than a free radical anion could, and is finally ionized by another photon to regenerate the ligand and recover the starting complex quantitatively. The sacrificial donor can be a bioavailable reagent such as ascorbic acid. 相似文献
6.
Eun Joo Park Jeongwoo Lee Dongsoo Jung 《Journal of Dispersion Science and Technology》2013,34(10):1485-1492
In order to achieve the dispersion stability of multi-walled carbon nanotubes (MWCNT) in a fluorinated refrigerant (FC-72) used in various cooling purposes, fluorinated MWCNT (MWCNT-F) was prepared by a combined process of oxidation and fluorination. As a fluorine source, (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane was used to react with hydroxyl groups on MWCNT (MWCNT-OH) generated by chemical oxidation. Pristine MWCNT, MWCNT-OH, and MWCNT-F were dispersed in FC-72 and MWCNT-F was also dispersed in polar and nonpolar solvents. The MWCNT-F has excellent colloidal stability in FC-72 because of the chemical affinity between FC-72 and functional groups (-CFn) on the side walls of MWCNT. Through surface modifications, we could obtain the enhanced dispersion stability of MWCNT in a refrigerant. This homogenous MWCNT solution in FC-72 may be used to increase the heat transfer in FC-72 based nanofluids. 相似文献
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The purpose of this review is to summarize the importance of microwave (MW) irradiation as a kind of catalyst in organophosphorus chemistry. Slow or reluctant reactions, such as the Diels-Alder cycloaddition or an inverse-Wittig type reaction, may be performed efficiently under MW irradiation. The direct esterification of phosphinic and phosphonic acids, which is practically impossible on conventional heating, may be realized under MW conditions. Ionic liquid additives may promote further esterifications. The opposite reaction, the hydrolysis of P-esters, has also relevance among the MW-assisted transformations. A typical case is when the catalysts are substituted by MWs, which is exemplified by the reduction of phosphine oxides, and by the Kabachnik–Fields condensation affording α-aminophosphonic derivatives. Finally, the Hirao P–C coupling reaction may serve as an example, when the catalyst may be simplified under MW conditions. All of the examples discussed fulfill the expectations of green chemistry. 相似文献
9.
Multi-drug resistant pathogens are a rising danger for the future of mankind. Iodine (I2) is a centuries-old microbicide, but leads to skin discoloration, irritation, and uncontrolled iodine release. Plants rich in phytochemicals have a long history in basic health care. Aloe Vera Barbadensis Miller (AV) and Salvia officinalis L. (Sage) are effectively utilized against different ailments. Previously, we investigated the antimicrobial activities of smart triiodides and iodinated AV hybrids. In this work, we combined iodine with Sage extracts and pure AV gel with polyvinylpyrrolidone (PVP) as an encapsulating and stabilizing agent. Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), Surface-Enhanced Raman Spectroscopy (SERS), microstructural analysis by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-Ray-Diffraction (XRD) analysis verified the composition of AV-PVP-Sage-I2. Antimicrobial properties were investigated by disc diffusion method against 10 reference microbial strains in comparison to gentamicin and nystatin. We impregnated surgical sutures with our biohybrid and tested their inhibitory effects. AV-PVP-Sage-I2 showed excellent to intermediate antimicrobial activity in discs and sutures. The iodine within the polymeric biomaterial AV-PVP-Sage-I2 and the synergistic action of the two plant extracts enhanced the microbial inhibition. Our compound has potential for use as an antifungal agent, disinfectant and coating material on sutures to prevent surgical site infections. 相似文献
10.
利用凝胶柱色谱技术, 研究者们通过两步或多步淋洗的方法实现了不同导电属性或电子结构单壁碳纳米管(SWCNTs)的分离, 并提出其分离机制主要是由不同导电属性和电子结构的SWCNTs 与凝胶填料之间作用力的差异所导致的. 基于凝胶柱色谱分离技术, 本文重点考察了超声时间对单壁碳纳米管单分散以及金属型/半导体型SWCNTs 分离的影响. 在一定的低超声功率下, 适当增加超声时间有利于SWCNTs 在十二烷基硫酸钠(SDS)溶液中的单分散. 紫外-可见-近红外(UV-Vis-NIR)吸收光谱、拉曼(Raman)光谱和荧光(PL)光谱表征结果表明, 2 h的超声条件是获得高纯度的金属型以及不同直径分布的半导体型SWCNTs 的最优条件. 我们认为不同超声时间对SWCNTs 分离的影响主要是改变了SWCNTs 的单分散性和长度, 调制了不同SWCNTs 与凝胶之间作用力的差异, 从而导致了不同SWCNTs分离结果. 相似文献
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Juliano B. Azeredo Filipe Penteado Vanessa Nascimento Luca Sancineto Antonio L. Braga Eder Joo Lenardao Claudio Santi 《Molecules (Basel, Switzerland)》2022,27(5)
Organoselenium compounds have been successfully applied in biological, medicinal and material sciences, as well as a powerful tool for modern organic synthesis, attracting the attention of the scientific community. This great success is mainly due to the breaking of paradigm demonstrated by innumerous works, that the selenium compounds were toxic and would have a potential impact on the environment. In this update review, we highlight the relevance of these compounds in several fields of research as well as the possibility to synthesize them through more environmentally sustainable methodologies, involving catalytic processes, flow chemistry, electrosynthesis, as well as by the use of alternative energy sources, including mechanochemical, photochemistry, sonochemical and microwave irradiation. 相似文献
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Marco A. Obregn-Mendoza William Meza-Morales Yair Alvarez-Ricardo M. Mirian Estvez-Carmona Raúl G. Enríquez 《Molecules (Basel, Switzerland)》2023,28(1)
The worldwide known and employed spice of Asian origin, turmeric, receives significant attention due to its numerous purported medicinal properties. Herein, we report an optimized synthesis of curcumin and symmetric curcuminoids of aromatic (bisdemethoxycurcumin) and heterocyclic type, with yields going from good to excellent using the cyclic difluoro-boronate derivative of acetylacetone prepared by reaction of 2,4-pentanedione with boron trifluoride in THF (ca. 95%). The subsequent cleavage of the BF2 group is of significant importance for achieving a high overall yield in this two-step procedure. Such cleavage occurs by treatment with hydrated alumina (Al2O3) or silica (SiO2) oxides, thus allowing the target heptanoids obtained in high yields as an amorphous powder to be filtered off directly from the reaction media. Furthermore, crystallization instead of chromatographic procedures provides a straightforward purification step. The ease and efficiency with which the present methodology can be applied to synthesizing the title compounds earns the terms “click” and “unclick” applied to describe particularly straightforward, efficient reactions. Furthermore, the methodology offers a simple, versatile, fast, and economical synthetic alternative for the obtention of curcumin (85% yield), bis-demethoxycurcumin (78% yield), and the symmetrical heterocyclic curcuminoids (80–92% yield), in pure form and excellent yields. 相似文献
14.
超支化聚酯修饰多壁碳纳米管 总被引:2,自引:0,他引:2
将碳纳米管先用V(H2SO4)∶V(HNO3)=3∶1混合溶液进行处理,再用V(H2SO4)∶V(H2O2=4∶1的混合溶液进一步酸化,制得含有羧基的碳纳米管。将羧基化碳纳米管与二氯亚砜反应使碳纳米管连接酰氯基团,利用酰氯基团与超支化聚酯上的羟基反应,将超支化聚酯接到碳纳米管的表面上,实现了碳纳米管的表面修饰。利用红外光谱、拉曼光谱、透射电镜观察分析测试结果表明,超支化聚酯以共价键形式连接到碳纳米管的表面。热失重分析结果表明,修饰密度为每321个C原子连接1个H20分子,每842个C原子上连接1个H40分子。修饰后的碳纳米管在有机溶剂中的溶解性能明显提高。 相似文献
15.
Zi-Shu Yang Yuhang Yao Adam C. Sedgwick Cuicui Li Ye Xia Yan Wang Lei Kang Hongmei Su Bing-Wu Wang Song Gao Jonathan L. Sessler Jun-Long Zhang 《Chemical science》2020,11(31):8204
We report here porphodilactol derivatives and their corresponding metal complexes. These systems show promise as “all-in-one” phototheranostics and are predicated on a design strategy that involves controlling the relationship between intersystem crossing (ISC) and photothermal conversion efficiency following photoexcitation. The requisite balance was achieved by tuning the aromaticity of these porphyrinoid derivatives and forming complexes with one of two lanthanide cations, namely Gd3+ and Lu3+. The net result led to a metalloporphodilactol system, Gd-trans-2, with seemingly optimal ISC efficiency, photothermal conversion efficiency and fluorescence properties, as well as good chemical stability. Encapsulation of Gd-trans-2 within mesoporous silica nanoparticles (MSN) allowed its evaluation for tumour diagnosis and therapy. It was found to be effective as an “all-in-one” phototheranostic that allowed for NIR fluorescence/photoacoustic dual-modal imaging while providing an excellent combined PTT/PDT therapeutic efficacy in vitro and in vivo in 4T1-tumour-bearing mice.We report here porphodilactol derivatives and their corresponding metal complexes as “all-in-one” phototheranostics by controlling the relationship between intersystem crossing (ISC) and photothermal conversion efficiency following photoexcitation. 相似文献
16.
Elvira M. Bauer Daniele Cecchetti Ettore Guerriero Simone Quaranta Francesca Ripanti Paolo Postorino Pietro Tagliatesta Marilena Carbone 《Molecules (Basel, Switzerland)》2022,27(11)
Due to the increasing tattoo practicing in Eastern countries and general concern on tattoo ink composition and safety, the green tattoo inks Green Concentrate by Eternal, for European and “for Asia Market Only” were analyzed, under the premise that only the former falls under a composition regulation. A separation of the additives from the pigment was carried out by successive extraction in solvents of different polarities, i.e., water, acetone and dichloromethane. The solid residues were analyzed by IR and Raman spectroscopies, the liquid fractions by GC/mass spectrometry. The relative pigment load and element traces were also estimated. We found that the European and the Asian inks are based on the same pigment, PG7, restricted in Europe, though at different loads. They have a similar content of harmful impurities, such as Ni, As, Cd and Sb and both contain siloxanes, including harmful D4. Furthermore, they have different physical-chemical properties, the European ink being more hydrophilic, the Asian more hydrophobic. Additionally, the Asian ink contains harmful additives for the solubilization of hydrophobic matrices and by-products of the phthalocyanine synthesis. Teratogenic phthalates are present as well as chlorinated teratogenic and carcinogenic compounds usually associated to the laser treatment for removal purposes, to a larger extent in the European ink. The composition of the inks does not seem to reflect regulatory restrictions, where issued. 相似文献
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以单壁碳纳米管和二茂铁为原料, 采用气相扩散法合成填充率较高的二茂铁掺杂单壁碳纳米管(Fc@SWNTs)的复合材料. 考察激光辐射对样品的影响, 结果表明, 当激光功率达到20 mW时, 对样品进行10 s辐照, 样品的拉曼光谱出现了稳定的新峰. 对比分析发现, 二茂铁在激光辐照后形成了碳化铁, 同时部分碳源转化成碳管形成了双层碳管. 表明碳化铁是二茂铁裂解向内层碳管转化的中间产物. 相似文献
18.
Jae Whan Cho Jeong Won Kim Yong Chae Jung Nam Seo Goo 《Macromolecular rapid communications》2005,26(5):412-416
Summary: Electro‐active shape‐memory composites were synthesized using conducting polyurethane (PU) composites and multi‐walled carbon nanotubes (MWNTs). Surface modification of the MWNTs (by acid treatment) improved the mechanical properties of the composites. The modulus and stress at 100% elongation increased with increasing surface‐modified MWNT content, while elongation at break decreased. MWNT surface modification also resulted in a decrease in the electrical conductivity of the composites, however, as the surface modified MWNT content increased the conductivity increased (an order of 10−3 S · cm−1 was obtained in samples with 5 wt.‐% modified‐MWNT content). Electro‐active shape recovery was observed for the surface‐modified MWNT composites with an energy conversion efficiency of 10.4%. Hence, PU‐MWNT composites may prove promising candidates for use as smart actuators.
19.
Sebastian Arndt Dominik Weis Kai Donsbach Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2020,59(21):8036-8041
High‐grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost‐efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported. The oxidation is conducted at boron‐doped diamond anodes, which are durable, metal‐free, and nontoxic. The avoidance of lead dioxide ultimately lowers the cost of purification and quality assurance. The electrolytic process was optimized by statistical methods and was scaled up in an electrolysis flow cell that enhanced the space–time yields by a cyclization protocol. An LC‐PDA analytical protocol was established enabling simple quantification of iodide, iodate, and periodate simultaneously with remarkable precision. 相似文献