Highly Efficient Encapsulation and Phase Separation of Apolar Molecules by Magnetic Shell‐by‐Shell‐Coated Nanocarriers in Water

Hirsch

2019

Chemistry A European J

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A first series of examples for confined space interactions of electron‐rich and electron‐poor molecules organized in an internal corona of shell‐by‐shell (SbS)‐structured Al2O3 nanoparticle (NP) hybrids is reported. The assembly concept of the corresponding hierarchical architectures relies on both covalent grafting of phosphonic acids on the NPs surface (SAMs formation; SAM=self‐assembled monolayer) and exohedral interdigitation of orthogonal amphiphiles as the second ligand layer driven by solvophobic interactions. The electronic communication between the chromophores of different electron demand, such as pyrenes, perylenediimides (PDIs; with and without pyridinium bromide headgroups) and fullerenes was promoted at the layer interface. In this work, it is demonstrated that the efficient construction principle of the bilayer hybrids assembled around the electronically “innocent” Al2O3 core is robust enough to achieve control over electronic communication between electron‐donors and ‐acceptors in the interlayer region. The electronic interactions between the electron‐accepting and electron‐donating moieties approaching each other at the layer interface were monitored by fluorescence measurements.

Section: Resultsmentioning

confidence: 99%

Electronic Communication in Confined Space Coronas of Shell‐by‐Shell Structured Al₂O₃ Nanoparticle Hybrids Containing Two Layers of Functional Organic Ligands

Hirsch

2019

Chemistry A European J

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“…Our group has further exploited this construction principle and has also coined the term “shell‐by‐shell (SbS)‐assembly” [1a–c, 11] . We have recently investigated suitable building blocks for the SbS‐functionalization of metal oxide NPs containing phosphonic acids as first‐shell building blocks and amphiphilic molecules as second‐shell building blocks for the construction of water‐dispersible NP hybrid systems [1a] .…”

Section: Introduction and General Remarksmentioning

confidence: 99%

“…Furthermore, we created confined space coronas within SbS‐structured NP hybrids, in which an electronic communication between organic units with different electron demand was facilitated [11] . SbS‐systems could also be used as water‐cleaning materials [1c] and as X‐ray sensitizing agents in radiotherapy [1e] . Our Review describes first the general functionalization principle and then sets the focus on our recently published work with interesting implications and applications of such highly hierarchical ordered nano‐systems.…”

Section: Introduction and General Remarksmentioning

confidence: 99%

“…By applying a magnetic field, the SbS‐NPs can easily be removed from a dispersion medium by an external magnet. This has been demonstrated, for example, with the development of practical catalytic‐, or water‐cleaning materials [1c, 14] . Also, redox inactive Al 2 O 3 NPs have been intensively investigated, for example, as core for SbS‐architectures with interesting optical and electronic properties [1d, 11] .…”

Section: Introduction and General Remarksmentioning

confidence: 99%

“…This allows also for tuning of surface energies of the functionalized NPs [1b, 15] . An interesting field of application was established with ferromagnetic SbS‐architectures that were used to encapsulate small nonpolar molecules from contaminated water [1c] . The hydrophobic pocket between the first and second ligand shell of the NPs was used to accommodate hydrophobic molecules.…”

Section: Introduction and General Remarksmentioning

confidence: 99%

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Shell‐by‐Shell Functionalization of Inorganic Nanoparticles

Luchs

Hirsch

2020

Chemistry A European J

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The current state of the hierarchical chemical functionalization of inorganic nanoparticles (NPs) by shell-byshell (SbS)-assembly of organic layers around the NP cores is summarized. This supramolecular functionalization concept is based on two steps: 1) the covalent grafting of a first ligand-shell consisting of, for example, long chain phosphonic acids and 2) the noncovalent interdigitation of amphiphiles forming the second ligand shell. The latter process is guaranteed predominantly by solvophobic interactions. These highly order organic-inorganic hybrid architectures are currently an emerging field at the interface of synthetic chemistry, nanotechnology, and materials science. The doubly functionalized NPs display tunable materials properties, such a controlled dispersibility and stability in various solvents, highly efficient trapping of guest molecules in between the ligand shells (water cleaning) as well as compartmentalization and modification of electronic interactions between photoactive components integrated in such complex nano-architectures. Such SbS-functionalized NPs have a high potential as water-cleaning materials and also some first prototype applications as biomedicinal therapeutics have been presented.

Tunable Composition of Mixed Self‐Assembled Shell‐by‐Shell Structures on Nanoparticle Surfaces

Eigen

Gradl

et al. 2022

Adv Materials Inter

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of the individual molecules has a decisive influence on the final properties of the resulting suprastructure. In micelles, this can be the size and shape, for vesicles, the diffusion speed through the molecular bilayer, or for self-assembled monolayers (SAMs) the packing density and crystallinity. [1][2][3][4] Properties of such assemblies can be either modified by tuning the individual molecules or by a smart combination of multiple building blocks. [5][6][7][8][9][10][11][12][13] This concept is proven by nature as a highly reliable method to create, for example, cell membranes, which consist of hundreds of different molecules, even for the simplest organisms resulting in remarkably high functionality. [14,15] Among many other tasks, those molecules control the stability, the salt content in cells, the oxygen and nutrient uptake, and the size of these structures. [15] The exact selection of molecule types and stoichiometric composition of membranes play a decisive role in the functioning of the cells. Most prominent examples are amphiphiles that consist of two parts of different polarities, thus making them soluble in orthogonal solvents.All corresponding suprastructures are based on weak hydrophobic interactions as well as intermolecular recognition motifs such as stereo complexation, H-bonding, ionic interactions, etc. [16] But even in simple artificial micelles and vesicles (compared to biological systems), competing forces between two or more molecules can either lead to synergetic effects or segregation of the involved molecules into multiple structures with heterogeneous composition. [17,18] In particular for the combination of highly orthogonal amphiphiles bearing fluorophilic and lipophilic (alkyl-chained) residues, there are only a few examples of synergetic mixtures known. [18,19] However, such orthogonally chained molecules tend to self-assemble to mixed SAMs if they exhibit strong covalent binding anchor groups such as phosphonic acids. The covalent binding drives the self-assembly on, for example, oxide surfaces and prevent the individual molecules from segregating into multiple phases, which allows the formation of SAMs in any stoichiometric mixing ratio. [20] Based on such SAMs, vesicle-like structures (see Scheme 1) can be formed with nanoparticles as template by building up a second layer through non-covalent interactions to a shell-by-shell (SbS) system. [21][22][23][24][25][26] Such unique systems provide the opportunity to switch the polarity of core-shell nanoparticles for adjusted processing, [21] to prepare model bilayers The formation of mixed shell-by-shell (SbS) systems with tunable shell compositions is demonstrated by using molecular self-assembly driven by chemical recognition motifs. Aluminum oxide nanoparticles (AlOx-NPs) act as template surface for a self-assembled monolayer (SAM) of either partially fluorinated fluoroalkyl or alkyl chained phosphonic acid derivatives or defined stoichiometric mixtures of those. By providing an equimolar mixture of corresponding fluoroalkyl and a...