检索结果-南通市图书馆

Odd-even effects in the structure and properties of aryl-substituted aliphatic self-assembled monolayers

Nano research 2024年第5期17卷 4231-4243页

作者： Piotr Cyganik Andreas Terfort Michael Zharnikov Jagiellonian University Faculty of PhysicsAstronomy and Applied Computer ScienceSmoluchowski Institute of PhysicsŁojasiewicza 1130-348 KrakówPoland institut für Anorganische und Analytische chemie Universität FrankfurtMax-von-Laue-Straße 760438 FrankfurtGermany Applied Physical Chemistry Heidelberg UniversityIm Neuenheimer Feld 25369120 HeidelbergGermany

Self-assembled monolayers(SAMs)represent an important tool in context of nanofabrication and molecular engineering of surfaces and interfaces.The properties of functional SAMs depend not only on the character of the tail groups at the SAM-ambient interface,but are also largely defined by their structure.In its turn,the latter parameter results from a complex interplay of the structural forces and a variety of other factors,including so called odd-even effects,viz.dependence of the SAM structure and properties on the parity of the number(odd or even)of individual building blocks in the backbone of the SAM constituents.The most impressive manifestation of the odd-even effects is the structure of aryl-substituted alkanethiolate SAMs on Au(111)and Ag(111),in which,in spite of the fact that the intermolecular interaction is mostly determined by the aryl part of the monolayers,one observes a pronounced dependence of molecular inclination and,consequently,the packing density of the SAM-forming molecules on the parity of number of methylene units in the alkyl linker.Here we review the properties of the above systems as well as address fundamental reasons behind the odd-even effects,including the existence of a so-called bending potential,which is frequently disregarded in analysis of the structure-building forces.The generality of the odd-even effects in SAMs is additionally supported by the recent data for SAMs on GaAs,scanning tunneling microscopy data for SAMs on Ag(111),and the data for the monolayers with selenolate and carboxyl anchoring groups on Au(111)and Ag(111).The implications of these effects in terms of the control over the packing density and orientation of the tail groups at the SAM-ambient interface,structural perfection,polymorphism,temperature-driven phase transitions,and SAM stability toward such factors as ionizing radiation,exchange reaction,and electrochemical desorption are discussed.These implications place the odd-even effects as an important tool for the design of functional SAMs in context of

关键词： self-assembled monolayers molecular films surface and interface engineering odd-even-effects

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Sequence-sorted redox-switchable hetero[3]rotaxanes

引用

Organic Chemistry frontiers 2022年第1期9卷 64-74页

作者： Marius Gaedke Henrik Hupatz felix Witte Susanne M.rupf Clara Douglas Hendrik V.Schröder Lukas fischer Moritz Malischewski Beate Paulus Christoph A.Schalley institut für chemie und Biochemie der freien Universität Berlin Arnimallee 2014195 BerlinGermany institut für chemie und Biochemie der freien Universität Berlin Arnimallee 2214195 BerlinGermany institut für chemie und Biochemie der freien Universität Berlin Fabeckstr.34/3614195 BerlinGermany

from a library of five crown ether macrocycles with different ring sizes and redox-active moieties,such as tetrathiafulvalene(TTf)and naphthalene dimiide(NDI),directional heterocircuit[3]rotaxanes were constructed.Using an axle with two binding sites with different steric accessibility,the concept of integrative self-sorting was applied to program the sequence of functional units in heteropseudo[3]rotaxanes.Depending on binding strength and ring size of the smaller macrocycles,different heteropseudo[3]rotaxane selectivities and stabilities were determined by 2D NMr spectroscopy and tandem mass spectrometry.A heteropseudo[3]rotaxane with rotaxane-like behaviour was isolated chromatographically,displaying electrochemically“frustrated”properties.A robust synthetic procedure was developed allowing the synthesis of four new hetero[3]rotaxanes incorporating specific sequences of functional units.Sequence pseudoisomeric rotaxanes which have the naphthalene diimide subunit at two different positions show distinct electrochemical properties.DfT calculations suggest that this differences could arise from a folding of the structure,in which the redox-active moieties stack with a stopper unit.This study presents a blueprint for the construction of hetero[3]rotaxanes with sequential control of the functional units along the track of the axle and paves the way to extend the functionality of mechanically interlocked molecules.

关键词： properties redox Sequence

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

The stability of carbon from a maize-derived hydrochar as a function of fractionation and hydrothermal carbonization temperature in a Podzol

引用

Biochar 2022年第1期4卷 315-326页

作者： Megan de Jager frank Schröter Michael Wark Luise Giani institut für Biologie Und Umweltwissenschaften Carl Von Ossietzky Univer-sitätOldenburgGermany institut für chemie Carl Von Ossietzky UniversitätOldenburgGermany

Hydrochar(HC)produced by the hydrothermal carbonization(HTC)of typically wet biomass is generally considered to be less effective for carbon(C)sequestration in soils compared to biochar(BC)by pyrolysis,due to a higher content of more easily decomposable C.Although the recalcitrance of HC is suggested to improve with increasing HTC production temperature,the way it interacts and becomes associated with soil organic matter(SOM)fractions of different stabilities against decomposition,may also influence its effectiveness for C sequestration in soils.In that respect,this study aimed to verify the potential of HCs from maize silage produced at different HTC temperatures(190,210 and 230℃)for C sequestration in a HC-amended sandy loam Podzol.To do this,we conducted a pot trial experiment and traced the fate of HC-derived C(HC-C)within different SOM fractions,namely the free-and occluded particulate organic matter(POMf and POMO,respectively)fractions and that comprising organic matter(OM)bound to clays(OMCl).Approx.1 year after applying 5%of the different HTC temperature HCs to the soil,the SOM fractions were isolated by density fractionation for each HC treatment(HC190,HC210 and HC230)and the control(absent of HC).All fractions and the HCs were analyzed for organic C(OC)content and isotopic signatures(δ^(13)C).from the δ^(13)C signatures,the amount of HC-C and native soil organic carbon(SOC)within each fraction was calculated.Increased C contents and decreased H/C and O/C ratios were observed with increasing HTC production temperatures,which sug-gests a lower stability for the low temperature HC.After ca.1 year,a loss of~20-23%of the bulk soil TOC was found in the HC-amended soils.The POMf fraction of the HC-amended soils showed losses of 68-81%HC-C and 52-72%native SOC,which may be due to a positive priming effect caused by HC addition.The POM_(O) and OM_(Cl) fractions of the HC-amended soils contained more OC than the control,indicating the integration of HC-C together with SOM within these more stable fractions,while

关键词： Hydrochar Carbon sequestration Carbon stabilization Soil organic matter fractions Soil density fractionation δ^(13)C analysis

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Condensation of pyrylium salts with mixed anhydrides:aryl ethers,aryl amines and sterically congested aromatics

引用

Organic Chemistry frontiers 2022年第2期9卷 294-298页

作者： Daniel Grabowski Susanne Alef Steven Becker Ute Muller Gregor Schnakenburg Sigurd Hoger aKekulé-institut für Organische chemie und Biochemie Rheinische Friedrich-Wilhelms-Universität BonnGerhard-Domagk-Str.153121 BonnGermany binstitut für Anorganische chemie Universität BonnGerhard-Domagk-Str.153121 BonnGermany

The condensation of easily accessible and widely functionalizable 2,4,6-triaryl pyrylium salts with mixed anhydrides,formed in situ fromα-functionalized sodium acetates and an anhydride solvent,leads in good yields to the corresponding 2,4,6-triaryl benzenes functionalized at their 1-position.4-(Trifluoromethyl)benzoic anhydride has been proven as being the solvent of choice and ortho-disubstituted diphenyl ethers,triphenyl amines and phenyl carbazoles with different functionalizations are synthesized.In addition,sterically hindered anthracene diacetate is condensed with two bis-bromophenyl pyrylium salts which leads after intramolecular Yamamoto coupling to bicyclophanes.In these,the anthracene core is surrounded by phenylenes and protected from photooxidation,leading to a highly stable blue emitting material.

关键词： material. anhydride salts

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Isotopic labelling experiments and enzymatic preparation of iso-casbenes with casbene synthase from ricinus communis

引用

Organic Chemistry frontiers 2022年第3期9卷 795-801页

作者： Heng Li Jeroen S.Dickschat Kekulé-institut für Organische chemie und Biochemie Rheinische Friedrich-Wilhelms-Universität BonnGerhard-Domagk-Straße 153121 BonnGermany

Isotopic labelling experiments gave insights into the enzyme mechanism of casbene synthase from ricinus communis,showing a clear stereochemical course for the cyclisation reaction,in agreement with the reported absolute configuration of casbene.Two oligoprenyl diphosphate analogs with shifted double bonds were synthesised and enzymatically converted with casbene synthase to yield casbene isomers.

关键词： enzymatic isomers bonds

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Yb-and Er concentration dependence of the upconversion luminescence of highly doped NaYf_(4):Yb,Er/NaYf_(4):Lu core/shell nanocrystals prepared by a water-free synthesis

引用

Nano research 2022年第10期15卷 9639-9646页

作者： Christian Würth Bettina Grauel Monika Pons florian frenzel Philipp rissiek Kerstin rücker Markus Haase Ute resch-Genger federal institute for Materials research and Testing(BAM) Division BiophotonicsRichard-Willstaetter-Str.1112489 BerlinGermany institut für chemie Neuer Materialien Fachbereich Biologie/ChemieUniversität OsnabrückBarbarastraße 749076 OsnabrückGermany

High sensitizer and activator concentrations have been increasingly examined to improve the performance of multi-color emissive upconversion(UC)nanocrystals(UCNC)like NaYf_(4):Yb,Er and first strategies were reported to reduce concentration quenching in highly doped UCNC.UC luminescence(UCL)is,however,controlled not only by dopant concentration,yet by an interplay of different parameters including size,crystal and shell quality,and excitation power density(P).Thus,identifying optimum dopant concentrations requires systematic studies of UCNC designed to minimize additional quenching pathways and quantitative spectroscopy.Here,we quantify the dopant concentration dependence of the UCL quantum yield(ΦUC)of solid NaYf_(4):Yb,Er/NaYf_(4):Lu upconversion core/shell nanocrystals of varying Yb3+and Er3+concentrations(Yb3+series:20%‒98%Yb3+;2%Er3+;Er3+series:60%Yb3+;2%‒40%Er3+).To circumvent other luminescence quenching processes,an elaborate synthesis yielding OH-free UCNC with recordΦUC of~9%and~25 nm core particles with a thick surface shell were used.High Yb3+concentrations barely reduceΦUC from~9%(20%Yb3+)to~7%(98%Yb3+)for an Er3+concentration of 2%,thereby allowing to strongly increase the particle absorption cross section and UCNC brightness.Although an increased Er3+concentration reducesΦUC from~7%(2%Er3+)to 1%(40%)for 60%Yb3+.Nevertheless,at very high P(>1 MW/cm^(2))used for microscopic studies,highly Er3+-doped UCNC display a high brightness because of reduced saturation.These findings underline the importance of synthesis control and will pave the road to many fundamental studies of UC materials.

关键词： highly doped upconversion nanocrystals core/shell nanoparticles upconversion luminescence efficiency NaYf_(4):Yb Er concentration quenching

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

N-heterocyclic carbene-stabilized metal nanoparticles within porous organic cages for catalytic application

引用

National Science review 2022年第6期9卷 135-142页

作者： Tong Liu Sha Bai Le Zhang f.Ekkehardt Hahn Ying-feng Han Key Laboratory of Synthetic and Natural functional Molecule of the Ministry of Education Xi'an Key Laboratory of Functional Supramolecular Structure and Materials College of Chemistry and Materials ScienceNorthwest University institut für Anorganicshe und Analytische chemie Westf?lische Wilhelms-Universit?t Münster

Tuning the surface-embellishing ligands of metal nanoparticles(NPs) is a powerful strategy to modulate their morphology and surface electronic and functional features, impacting their catalytic activity and selectivity. In this work, we report the design and synthesis of a polytriazolium organic cage PIC-T, capable of stabilizing Pd NPs within its discrete cavity. The obtained material(denoted Pd@PCC-T) is highly durable and monodispersed with narrow particle-size distribution of 2.06 ± 0.02 nm, exhibiting excellent catalytic performance and recyclability in the Sonogashira coupling and tandem reaction to synthesize benzofuran derivatives. further investigation indicates that the modulation of N-heterocyclic carbene sites embedded in the organic cage has an impact on NPs’ catalytic efficiency, thus providing a novel methodology to design superior NP catalysts.

关键词： metal nanoparticle porous organic cage catalytic reaction N-heterocyclic carbene

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Gαq,Gγ1 and Plc21C Control Drosophila Body fat Storage

引用

Journal of Genetics and Genomics 2014年第5期41卷 283-292页

作者： Jens Baumbach Yanjun Xu Philip Hehlert ronald P.Khnlein Abteilung Molekulare Entwicklungsbiologie Forschungsgruppe Molekulare Physiologie Max-Planck-Institut fr biophysikalische Chemie Abteilung Molekulare Entwicklungsbiologie Forschungsgruppe Molekulare PhysiologieMax-Planck-Institut fr biophysikalische Chemie

mobilization of body fat is essential for energy homeostasis in animals. In insects, the adipokinetic hormone （Akh） systemically controls body fat mobilization. Biochemical evidence supports that Akh signals via a G protein-coupled receptor （GPCr） called Akh receptor （Akhr） using cyclic-AMP （cAMP） and Ca2＋ second messengers to induce storage lipid release from fat body cells. recently, we provided genetic evidence that the intracellular calcium （iCa2＋） level in fat storage cells controls adiposity in the fruit fly Drosophila melanogaster. However, little is known about the genes, which mediate Akh signalling downstream of the Akhr to regulate changes in iCa2＋. Here, we used thermogenetics to provide in vivo evidence that the GPCr signal transducers G protein α q subunit （Gαq）, G protein γ1 （Gγ1） and Phospholipase C at 21C （Plc21C） control cellular and organismal fat storage in Drosophila. Transgenic modulation of Gαq, Gγ1 and Plc21C affected the iCa2＋ of fat body cells and the expression profile of the lipid metabolism effector genes midway and brummer, which results in severely obese or lean flies. Moreover, functional impairment of Gαq, Gγ1 and Plc21C antagonised Akh-induced fat depletion. This study characterizes Gαq, Gγ1 and Plc21C as anti-obesity genes and supports the model that Akh employs the Gαq/Gγ1/Plc21C module of iCa2＋ control to regulate lipid mobilization in adult Drosophila.

关键词： Plc21C Gαq Gγ1 Calcium fat storage Adipokinetic hormone

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The 3,4-dimethoxybenzyl group as solubilizing protective group for the in situ deprotection/deposition of extended aromatic thiolate monolayers

引用

Nano research 2023年第1期16卷 1695-1702页

作者： Adrian Wiesner Sonja Katzbach Dariusz Bebej Martina Dettenhöfer Michael Zharnikov Andreas Terfort institut für Anorganische und Analytische chemie Johann Wolfgang Goethe Universität FrankfurtMax-von-Laue-Straße 7Frankfurt am Main D-60438Germany Angewandte Physikalische chemie Universität HeidelbergIm Neuenheimer Feld 253Heidelberg D-69120Germany

While self-assembled monolayers(SAMs)of aromatic thiolates are frequently used in a wide range of applications,their formation is often hampered by the low solubilities of their precursors.Here we introduce the 3,4-dimethoxybenzyl group as a protective group for the thiol moiety,which increases the solubility and stability of the precursor,but becomes cleaved off during monolayer formation,especially at elevated temperature(60°C)and in presence of protons(trifluoroacetic acid).for a series of substituted terphenylthiols as model systems,it could be demonstrated by using ellipsometry,infrared-reflection absorption spectroscopy,and scanning-tunneling microscopy that the resulting SAMs have the same structure and quality as the ones obtained from the respective unprotected thiols.The protective group has the additional advantage to be stable under Pdcatalyzed C–C bond formation reaction conditions,facilitating the syntheses of the respective precursors.

关键词： self-assembled monolayers protective group solubility scanning-tunneling microscopy infrared-reflection absorption spectroscopy

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Aromatic self-assembled monolayers with pentafluoro-λ^(6)-sulfanyl(−Sf_(5))termination:Molecular organization and charge transport properties

引用

Nano research 2023年第5期16卷 7991-8002页

作者： Yangbiao Liu Marc Zeplichal Sonja Katzbach Adrian Wiesner Saunak Das reas Terfort Michael Zharnikov Angewandte Physikalische chemie Universität HeidelbergIm Neuenheimer Feld 253D-69120 HeidelbergGermany institut für Anorganische und Analytische chemie Johann Wolfgang Goethe Universität FrankfurtMax-von-Laue-Straße 7D-60438 Frankfurt am MainGermany

A series of molecules with oligophenylene backbone,thiolate anchoring group,pentafluoro-λ^(6)-sulfanyl(−Sf_(5))tail group was synthesized and used as precursors to form self-assembled monolayers(SAMs)on Au(111)substrates.The resulting SAMs feature dense molecular packing,upright molecular orientation,chemically homogeneous SAM-ambient interface,comprised entirely of the−Sf_(5)moieties.These SAMs exhibit exceptional wetting and electrostatic properties,showing advancing water contact angles up to 103°and work function values up to 5.96 eV—probably the highest values reported for any aromatic monolayers on gold.They also feature a comparably low value of the tunnelling decay coefficient(0.38±0.07Å^(−1)),typical of oligophenylene backbone,which is not affected by the introduction of the−Sf_(5)group.The latter also hardly affects the current densities at a specific bias compared to analogous monolayers with other electronegative tail groups.The superior electrostatic and good charge transport properties of the designed,Sf_(5)-terminated SAMs make them potentially useful for interface engineering in organic electronics and photovoltaics.

关键词： backbone charge electrostatic

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：