Chiral Nanoparticles

Gautier, Cyrille; Brgi, Thomas

doi:10.1002/9783527625345.ch3

Cited by 7 publications

(8 citation statements)

References 117 publications

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“…Furthermore, other approaches utilize chiral templates or molecular changes affecting the conformation or shape of molecules and nanostructures to spontaneously promote helical structure formation. Examples range from inorganic subnm nanowires and nanocrystals − over polymers − and polymer networks to amphiphiles, surfactants, and a considerable variety of other organic, inorganic, − and organometallic molecules. , …”

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confidence: 99%

Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments

et al. 2021

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The coupling between molecular conformation and chirality is a cornerstone in the construction of supramolecular helical structures of small molecules across various length scales. Inspired by biological systems, conformational preselection and control in artificial helical molecules, polymers, and aggregates has guided various applications in optics, photonics, and chiral sorting among others, which are frequently based on an inherent chirality amplification through processes such as templating and self-assembly. The so-called B4 nano- or microfilament phase formed by some bent-shaped molecules is an exemplary case for such chirality amplification across length scales, best illustrated by the formation of distinct nano- or microscopic chiral morphologies controlled by molecular conformation. Introduction of one or more chiral centers in the aliphatic side chains led to the discovery of homochiral helical nanofilament, helical microfilament, and heliconical-layered nanocylinder morphologies. Herein, we demonstrate how a priori calculations of the molecular conformation affected by chiral side chains are used to design bent-shaped molecules that self-assemble into chiral nano- and microfilament as well as nanocylinder conglomerates despite the homochiral nature of the molecules. Furthermore, relocation of the chiral center leads to formation of helical as well as flat nanoribbons. Self-consistent data sets from polarized optical as well as scanning and transmission electron microscopy, thin-film and solution circular dichroism spectropolarimetry, and synchrotron-based X-ray diffraction experiments support the progressive and predictable change in morphology controlled by structural changes in the chiral side chains. The formation of these morphologies is discussed in light of the diminishing effects of molecular chirality as the chain length increases or as the chiral center is moved away from the core-chain juncture. The type of phase (B1-columnar or B4) and morphology of the nano- or microfilaments generated can further be controlled by sample treatment conditions such as by the cooling rate from the isotropic melt or by the presence of an organic solvent in the ensuing colloidal dispersions. We show that these nanoscale morphologies can then organize into a wealth of two- and three-dimensional shapes and structures ranging from flower blossoms to fiber mats formed by intersecting flat nanoribbons.

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Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments

et al. 2021

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“…1-5 Nanoparticles are promising candidates for a broad range of applications such as biosensing, labeling, environmental nanoassays and chiral memory as well as attractive building blocks for the bottom-up nanofabrication of chiroptical devices and nanoassemblies. 6-9 Chiroptical activity in semiconductor and metallic nanoparticles can originate from several distinct phenomena that can concurrently affect the resulting chiroptical properties.…”

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“…6-9 Chiroptical activity in semiconductor and metallic nanoparticles can originate from several distinct phenomena that can concurrently affect the resulting chiroptical properties. 1 The nanocrystals can be intrinsically chiral with mirror-image arrangement of atoms within the crystals. 10-13 Chiroptical activity of nanocrystals can also be induced by a chiral environment via binding of chiral organic ligands to the surface 14-19 or via an electronic coupling between nanocrystal and chiral ligands in its proximity.…”

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“…Chiral optically active semiconductor and metallic nanoparticles possess unique yet modular structural and optical properties not present in bulk materials. − Nanoparticles are promising candidates for a broad range of applications such as biosensing, labeling, environmental nanoassays and chiral memory as well as attractive building blocks for the bottom-up nanofabrication of chiroptical devices and nanoassemblies. − Chiroptical activity in semiconductor and metallic nanoparticles can originate from several distinct phenomena that can concurrently affect the resulting chiroptical properties . The nanocrystals can be intrinsically chiral with mirror-image arrangement of atoms within the crystals. − Chiroptical activity of nanocrystals can also be induced by a chiral environment via binding of chiral organic ligands to the surface − or via an electronic coupling between nanocrystal and chiral ligands in its proximity. ,,,, Coupled with quantum size effect, the postsynthetic ligand exchange introducing a chiral organic shell represents an appealing approach to induce and tune optical and chiroptical characteristics of achiral quantum dots (QDs).…”

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Ligand Induced Circular Dichroism and Circularly Polarized Luminescence in CdSe Quantum Dots

et al. 2013

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Chiral thiol capping ligands L- and D-cysteines induced modular chiroptical properties in achiral cadmium selenide quantum dots (CdSe QDs). Cys-CdSe prepared from achiral oleic acid capped CdSe by post-synthetic ligand exchange displayed size-dependent electronic circular dichroism (CD) and circularly polarized luminescence (CPL). Opposite CPL signals were measured for the CdSe QDs capped with D- and L-cysteine. The CD profile and CD anisotropy varied with size of CdSe nanocrystals with largest anisotropy observed for CdSe nanoparticles of 4.4 nm. Magic angle spinning solid state NMR (MAS ssNMR) experiments suggested bidentate interaction between cysteine and the surface of CdSe. Density functional theory (DFT) calculations verified that attachment of L- and D-cysteine to the surface of model (CdSe)13 nanoclusters induces measurable opposite CD signals for the exitonic band of the nanocluster. The chirality was induced by the hybridization of highest occupied CdSe molecular orbitals with those of the chiral ligand.

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“…Chiral, optically active nanoparticles (NPs) are promising candidates for biosensing, stereoselective reactions, and chiral memory applications as well as for the bottom-up fabrication of chiroptical nanomaterials. − Chirality in semiconductor quantum dots (QDs) can concurrently originate from (i) intrinsic dissymmetry of a nanocrystal, (ii) the ligand-induced chiral surface of QDs, (iii) the electronic coupling between chiral capping ligands and achiral QDs, or (iv) chiral assemblies of achiral QDs. − Since capping ligands can influence chemical and electronic properties of QDs, , the postsynthetic functionalization of achiral QDs with chiral capping ligands is an ideal approach to induce and control chirality in semiconductor nanomaterials. Some of us reported the first example of chiral QDs prepared by postsynthetic phase transfer ligand exchange on achiral QDs: d - and l -cysteine-functionalized CdSe displayed mirror-image circular dichroism (CD) as well as circularly polarized luminescence (CPL) spectra. , Here, for the first time, we report the inversion of the CD spectra of CdSe and CdS QDs induced by ligands of identical absolute configuration but different chemical structure.…”

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Chirality Inversion of CdSe and CdS Quantum Dots without Changing the Stereochemistry of the Capping Ligand

et al. 2016

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L-cysteine derivatives induce and modulate the optical activity of achiral cadmium selenide (CdSe) and cadmium sulfide (CdS) quantum dots (QDs). Remarkably, N-acetyl-L-cysteine-CdSe and L-homocysteine-CdSe as well as N-acetyl-L-cysteine-CdS and L-cysteine-CdS showed "mirror-image" circular dichroism (CD) spectra regardless of the diameter of the QDs. This is an example of the inversion of the CD signal of QDs by alteration of the ligand's structure, rather than inversion of the ligand's absolute configuration. Non-empirical quantum chemical simulations of the CD spectra were able to reproduce the experimentally observed sign patterns and demonstrate that the inversion of chirality originated from different binding arrangements of N-acetyl-L-cysteine and L-homocysteine-CdSe to the QD surface. These efforts may allow the prediction of the ligand-induced chiroptical activity of QDs by calculating the specific binding modes of the chiral capping ligands. Combined with the large pool of available chiral ligands, our work opens a robust approach to the rational design of chiral semiconducting nanomaterials.

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Chiral Nanoparticles

Cited by 7 publications

References 117 publications

Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments

Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments

Ligand Induced Circular Dichroism and Circularly Polarized Luminescence in CdSe Quantum Dots

Chirality Inversion of CdSe and CdS Quantum Dots without Changing the Stereochemistry of the Capping Ligand

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