Pathway Complexity in Supramolecular Porphyrin Self-Assembly at an Immiscible Liquid|Liquid Interface

10.26434/chemrxiv.14170202.v1 ◽

2021 ◽

Author(s):

Iván Robayo-Molina ◽

Andrés F. Molina-Osorio ◽

Luke Guinane ◽

Syed A.M. Tofail ◽

Micheal D. Scanlon

Keyword(s):

Self Assembly ◽

Immiscible Liquid ◽

Bulk Solution ◽

Time Resolved ◽

Force Microscopy ◽

Atomic Force ◽

Aggregate Growth ◽

High Concentrations ◽

Thermodynamic Processes

<p>Nanostructures that are inaccessible through spontaneous thermodynamic processes may be formed by supramolecular self-assembly under kinetic control. In the past decade, the dynamics of pathway complexity in self-assembly have been elucidated through kinetic models based on aggregate growth by sequential monomer association and dissociation. Immiscible liquid|liquid interfaces are an attractive platform to develop well-ordered self-assembled nanostructures, unattainable in bulk solution, due to the templating interaction of the interface with adsorbed molecules. Here, we report time-resolved <i>in situ</i> UV/vis spectroscopic observations of the self-assembly of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrin (ZnTPPc) at an immiscible aqueous|organic interface. We show that the kinetically favoured metastable J-type nanostructures form quickly, but then transform into stable thermodynamically favoured H-type nanostructures. Numerical modelling revealed two parallel and competing cooperative pathways leading to the different porphyrin nanostructures. These insights demonstrate that pathway complexity is not unique to self-assembly processes in bulk solution, and equally valid for interfacial self-assembly. Subsequently, the interfacial electrostatic environment was tuned using a kosmotropic anion (citrate) in order to control the influence the pathway selection. At high concentrations, interfacial nanostructure formation was forced completely down the kinetically favoured pathway and only J-type nanostructures were obtained. Furthermore, we found by atomic force microscopy (AFM) and scanning electron microscopy (SEM) that the J- and H-type nanostructures obtained at low and high citric acid concentrations, respectively, are morphologically distinct, which illustrates the pathway-dependent material properties.</p>

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A Comparative Study on the Self-Assembly of Peptide TGV-9 by In Situ Atomic Force Microscopy

Microscopy and Microanalysis ◽

10.1017/s1431927620000082 ◽

2020 ◽

Vol 26 (2) ◽

pp. 319-325

Author(s):

Yaping Li ◽

Na Li ◽

Lei Wang ◽

Qinhua Lu ◽

Xiang Ji ◽

...

Keyword(s):

Atomic Force Microscopy ◽

Self Assembly ◽

The Self ◽

Peptide Sequence ◽

Bulk Solution ◽

Free Standing ◽

Atomic Lattice ◽

Force Microscopy ◽

Atomic Force

AbstractPrevious studies of amyloid diseases reported that the aggregating proteins share a similar conserved peptide sequence which can form the cross-β-sheet-containing nanostructures like nanofilaments. The template-assisted self-assembly (TASA) of peptides on inorganic substrates with different hydrophilicity could be an alternative approach to shed light on the fibrillization mechanism of proteins/peptides in vivo. To figure out the effect of interfaces on amyloid aggregation, we herein employed in situ atomic force microscopy (AFM) to investigate the self-assembling of a Parkinson disease-related core peptide sequence (TGV-9) on a hydrophobic liquid–solid interface via real-time observation of the dynamic fibrillization process. The results show that TGV-9 forms one-dimensional nanostructures on the surface of highly ordered pyrolytic graphite (HOPG) with three preferred growth orientations, which are consistent with the atomic lattice of HOPG, indicating an epitaxial growth or TASA. Conversely, the nanostructures formed in bulk solution can be free-standing nanofilaments, and the fibrillization mechanism is different from that on HOPG. These results could not only deepen the understanding of the protein/peptide aggregation mechanism but also benefit for the early diagnosis and clinic treatment of related diseases.

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In Situ Initial Growth Studies of SrTiO3 on SrTiO3 by Time Resolved High Pressure RHEED

MRS Proceedings ◽

10.1557/proc-526-33 ◽

1998 ◽

Vol 526 ◽

Cited By ~ 10

Author(s):

Gertjan Koster ◽

Guus J.H.M. Rijnders ◽

Dave H.A. Blank ◽

Horst Rogalla

Keyword(s):

High Pressure ◽

Pulsed Laser ◽

High Energy ◽

Initial Growth ◽

Time Resolved ◽

Force Microscopy ◽

Atomic Force ◽

Different Temperatures ◽

Substrate Surfaces

AbstractThe initial growth of pulsed laser deposited SrTiO3 on SrTiO3 has been studied using high pressure Reflection High Energy Electron Diffraction (RHEED) and Atomic Force Microscopy (AFM). For this, we developed a Pulsed Laser Deposition (PLD)-RHEED system, with the possibility to study the growth and to monitor the growth rates, in situ, at typical PLD pressures (10-50 Pa). Using perfect single crystal SrTiO3 substrate surfaces, we observe true 2D intensity oscillations at different temperatures. Simultaneously, information on the diffusion of the deposited material on the surface could be extracted from the relaxation of the intensity after each laser pulse. The characteristic times depend on pressure and temperature as well as the 2D coverage during growth.

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Guided Control of Cu2O Nanodot Self-Assembly on SrTiO3 (100)

MRS Proceedings ◽

10.1557/proc-811-e4.4 ◽

2004 ◽

Vol 811 ◽

Author(s):

Yingge Du ◽

Surajit Atha ◽

Robert Hull ◽

James F. Groves ◽

Igor Lyubinetsky ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Self Assembly ◽

Focused Ion Beam ◽

Ion Beam ◽

Photocatalytic Decomposition ◽

Process Conditions ◽

Photochemical Process ◽

Force Microscopy ◽

Atomic Force

ABSTRACTA method has been developed for specifying the growth location of Cu2O nanodotson SrTiO3 (100) substrates. Growth location has been specified by using a focused ion beam (FIB) to modify microscopic and nanoscopic regions of the SrTiO3substrate prior to Cu2O deposition. Deposition onto the modified regions under carefully selected process conditions has generated nanodot growth at the edge of microscopic FIB-induced features and on top of nanoscopic FIB-induced features. For this work, an array of evenly spaced FIB implants was first patterned into several regions of each substrate. Within each sub-division of the array, the FIB implants were identical in Ga+ energy and dosage and implant diameter and spacing. After FIB surface modification and subsequent in-situ substrate cleaning, Cu2O nanodots were synthesized on the patterned SrTiO3 substrates using oxygen plasma assisted molecular beam epitaxy. The substrates and nanodots were characterized using atomic force microscopy at various stages of the process; in-situ X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis demonstrated that the final stoichiometry of the nanodots was Cu2O. The photocatalytic decomposition of water on Cu2O under visible light irradiation has been reported. If the Cu2O can be located in the form ofislands on a carefully selected substrate, then it could be possible to greatly enhance the efficiency of the photochemical process.

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