排序方式: 共有61条查询结果,搜索用时 15 毫秒
31.
P. Dennis Christy N. Melikechi N. S. Nirmala Jothi A. R. Baby Suganthi P. Sagayaraj 《Journal of nanoparticle research》2010,12(8):2875-2882
The synthesis of TiO2 nanorods with anatase structure has been achieved from the necking of truncated nanoparticles by oriented attachment using titanium ethylenediaminetetraacetic acid (EDTA) chelated complex as a molecular precursor. The preparation was carried out under mild conditions using a simple solvothermal process. The influence of EDTA over the growth of nanocrystallites and the various other factors which contribute to the development of 1D TiO2 nanostructure are investigated. At a relatively lower temperature, titania nanopowders are obtained, and the anatase phase crystallization is verified by wide angle X-ray diffraction. The evolution of rod-shaped TiO2 with tapered edges has been confirmed by transmission electron micrographs. The well aligned lattice fringes of TiO2 nanorod towards [001] direction is investigated by HRTEM. The SEM images show the surface configuration of overall aggregates of titania crystallites consisted of primary particles which are densely packed in an orderly texture. The moderate shift in the absorption band towards higher energy region of the absorption spectrum confirms the weak carrier confinement effect in the sample. 相似文献
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Reversible Mechanical Interlocking of D‐Shaped Molecular Karabiners bearing Coordination‐Bond Loaded Gates: Route to Self‐Assembled [2]Catenanes 下载免费PDF全文
Soumyakanta Prusty Dr. Shobhana Krishnaswamy Sreenivasulu Bandi Dr. Baby Chandrika Dr. Jingwei Luo Prof. Dr. J. Scott McIndoe Prof. Dr. Garry S. Hanan Prof. Dr. Dillip Kumar Chand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15174-15187
Complexation of 1,4‐phenylenebis(methylene) diisonicotinate, L1 , with cis‐protected PdII components, [Pd( L′ )(NO3)2], in an equimolar ratio yielded binuclear complexes, 1 a – d of [Pd2( L′ )2( L1 )2](NO3)4 formulation where L′ stands for ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′‐bipyridine (bpy), and phenanthroline (phen). The combination of 4,4′‐bipyridine, L2 , with the cis‐protected PdII units is known to yield molecular squares, 2 a – d . However, 2 b – d coexist with the corresponding molecular triangles, 3 b – d . Combination of an equivalent each of the ligands L1 and L2 with two equivalents of cis‐protected PdII components in DMSO resulted in the D ‐shaped heteroligated complexes [Pd2( L′ )2( L1 )( L2 )](NO3)4, 4 a – d . Two units of the D ‐shaped complexes interlock, in a concentration dependent fashion, to form the corresponding [2]catenanes [Pd2( L′ )2( L1 )( L2 )]2(NO3)8, 5 a – d under aqueous conditions. Crystal structures of the macrocycle [Pd2(tmeda)2( L1 )( L2 )](PF6)4, 4 b′′ , and the catenane [Pd2(bpy)2( L1 )( L2 )]2(NO3)8, 5 c , provide unequivocal support for the proposed molecular architectures. 相似文献
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Mariana Mandelli de Almeida Nádia Araci Bou-Chacra Cibele Rosana Ribeiro de Castro Lima Jivaldo do Rosário Matos Elder Moscardini Filho Lucildes Pita Mercuri André Rolim Baby Telma Mary Kaneko Maria Valéria Robles Velasco 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2401-2406
The ursolic acid (UA) increases the skin’s barrier function and acts in epidermal differentiation of keratinocytes in the epidermis, promoting cell renewal. Besides the mentioned properties UA also has antioxidant, antimicrobial, and anti-irritant functions to cosmetic formulations. Thus, it is necessary formulation studies to insure the development of quality cosmetic products containing this active, increasing its antioxidant potential within nanoparticles. This study aims to characterize and evaluate the thermal behavior of UA in free and nanostructured forms, and both incorporated into a cosmetic base formulation, using thermogravimetry and differential scanning calorimetry. Through the study were observed that free UA, in the embedded nanoparticles and in base formulation exhibited different behavior in similar thermal profile and relative to the presence of UA. The UA remained stable to a temperature of 250 °C and the technique has been shown to be effective for characterizing UA, evaluate water content, and stability of the formulation base. 相似文献
34.
Fabiana Vieira Lima Trcio Elyan Azevedo Martins Ana Lucia Morocho‐Jcome Isabel Filipa Almeida Catarina Fialho Rosado Maria Valria Robles Velasco Andr Rolim Baby 《Journal of separation science》2021,44(1):438-447
Urocanic acid is a chromophore found in the skin that has been identified as an important immunosuppressant and carcinogenesis mediator through its photoisomerization from trans to cis form induced by ultraviolet radiation. Research on analytical methods that explore urocanic acid isomerization is indispensable to fully understand the deleterious effects mediated by this biomarker. In this context, the current relevant analytical methods for determination of these isomers in human samples are summarized in this review. The methods presented here are applicable to human samples collected by noninvasive methods (or minimally invasive), encompassing an array of analytical techniques, including high‐performance capillary electrophoresis, confocal Raman spectroscopy, gas chromatography, high‐performance liquid chromatography, and mass spectrometry, among others. Developed high‐performance liquid chromatography methods have proven to be advantageous, allowing noninvasive collections for in vivo analysis and the confocal Raman, specially, for real‐time analysis. Among all these methods, high‐performance liquid chromatography is the most investigated one with mass spectrometry or ultraviolet detector, and the mass spectrometry detector being the most studied in the last years, demonstrating high sensitivity, very low detection limits, and accurate identification, especially for clinical investigations. 相似文献
35.
Loïc Roupnel Régis Guillot Didier Gori Baby Viswambharan Cyrille Kouklovsky Valérie Alezra 《Helvetica chimica acta》2021,104(10):e2100127
We describe here an asymmetric aldol reaction based on the principle of Memory of Chirality. From α-amino acids such as leucine and methionine, we have synthesized in two steps quaternary α-amino acid derivatives with high diastereoselectivity and enantioselectivity, using the chirality of the initial α-amino acid as the only chirality source. Furthermore, we were able to determine the relative and absolute configurations of the aldol products thanks to crystallographic structures and thus showed that the relative configuration depended on the aldehyde employed. We proposed a stereoselectivity explanation and obtained also quaternary β-hydroxy α-amino acids after acidic hydrolysis. 相似文献
36.
4-Aryl-2,3-dihydro-4H-pyrimido[2,3-b]benzothiazoles (4-Ar-DHPBs) were synthesized and their catalytic activity and selectivity in kinetic resolution of a secondary alcohol as well as in the Steglich rearrangement and related reactions were evaluated. 4-Aryl-DHPBs showed low enantioselectivity in the acylative kinetic resolution of 1-phenylethanol. Conversely, they catalyzed the Steglich rearrangement with moderate to excellent enantioselectivity, demonstrating the possibility for remote stereocontrol by introduction of a substituent at the 4-position of DHPB. 相似文献
37.
Ponnusamy Shanmugam Paramasivan Rajasingh Baby Viswambharan Vadivel Vaithiyanathan 《合成通讯》2013,43(14):2291-2299
The synthesis of 3‐heteroaryl‐substituted tetrahydrofurans from the propargyl derivative of Baylis–Hillman adducts of heteroaryl aldehydes by n‐Bu3SnH‐mediated 5‐exo‐trig vinyl radical cyclization in high yield is reported. 相似文献
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Matea I Georgiev G Daugas JM Hass M Neyens G Astabatyan R Baby LT Balabanski DL Bélier G Borremans D Goldring G Goutte H Himpe P Lewitowicz M Lukyanov S Méot V Santos Fde O Penionzhkevich YE Roig O Sawicka M 《Physical review letters》2004,93(14):142503
We report on the g factor measurement of an isomer in the neutron-rich (61)(26)Fe (E(*)=861 keV and T(1/2)=239(5) ns). The isomer was produced and spin aligned via a projectile-fragmentation reaction at intermediate energy, the time dependent perturbed angular distribution method being used for the measurement of the g factor. For the first time, due to significant improvements of the experimental technique, an appreciable residual alignment of the nuclear spin ensemble has been observed, allowing a precise determination of its g factor, including the sign: g=-0.229(2). In this way we open the possibility to study moments of very neutron-rich short-lived isomers, not accessible via other production and spin-orientation methods. 相似文献
40.
Arppitha Baby Sainaba Mangili Venkateswarulu Pallab Bhandari Jack K. Clegg Prof. Partha Sarathi Mukherjee 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202315572
Through coordination-driven self-assembly, aesthetically captivating structures can be formed by tuning the length or flexibility of various components. The self-assembly of an elongated rigid terphenyl-based tetra-pyridyl ligand ( L1 ) with a cis-Pd(II) acceptor produces an [M12 L1 6]24+ triangular orthobicupola structure ( 1 ). When flexibility is introduced into the ligand by the incorporation of a -CH2- group between the dipyridylamine and terphenyl rings in the ligand ( L2 ), anunique [M8 L2 4]16+ water-soluble ‘intertwined cubic structure’ ( 2 ) results. The inherent flexibility of ligand L2 might be the key factor behind the formation of the thermodynamically stable and ′intertwined cubic structure′ in this scenario. This research showcases the ability to design and fabricate novel, topologically distinctive molecular structures by a straightforward and efficient approach. 相似文献