Investigation of Au SAMs Photoclick Derivatization by PM-IRRAS

2019 ◽  
Author(s):  
Mark Workentin ◽  
François Lagugné-Labarthet ◽  
Sidney Legge
Keyword(s):  
Cell Adhesion ◽  
Self Assembly ◽  
Materials Science ◽  
Fibroblast Cell ◽  
Fine Tuning ◽  
Chemical System ◽  
Infrared Reflection ◽  
Assembled Monolayers ◽  
One Step ◽  
High Degree

In this work we present a clean one-step process for modifying headgroups of self-assembled monolayers (SAMs) on gold using photo-enabled click chemistry. A thiolated, cyclopropenone-caged strained alkyne precursor was first functionalized onto a flat gold substrate through self-assembly. Exposure of the cyclopropenone SAM to UV-A light initiated the efficient photochemical decarbonylation of the cyclopropenone moiety, revealing the strained alkyne capable of undergoing the interfacial strain-promoted alkyne-azide cycloaddition (SPAAC). Irradiated SAMs were derivatized with a series of model azides with varied hydrophobicity to demonstrate the generality of this chemical system for the modification and fine-tuning of the surface chemistry on gold substrates. SAMs were characterized at each step with polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to confirm successful functionalization and reactivity. Furthermore, to showcase the compatibility of this approach with biochemical applications, cyclopropenone SAMs were irradiated and modified with azide-bearing cell adhesion peptides to promote human fibroblast cell adhesion, then imaged by live cell fluorescence microscopy. Thus, the “photoclick” methodology reported here represents an improved, versatile, catalyst-free protocol that allows for a high degree of control over the modification of material surfaces, with applicability in materials science as well as biochemistry.<br>

Investigation of Au SAMs Photoclick Derivatization by PM-IRRAS

2019 ◽  
Author(s):  
Mark Workentin ◽  
François Lagugné-Labarthet ◽  
Sidney Legge
Keyword(s):  
Cell Adhesion ◽  
Self Assembly ◽  
Materials Science ◽  
Fibroblast Cell ◽  
Fine Tuning ◽  
Chemical System ◽  
Infrared Reflection ◽  
Assembled Monolayers ◽  
One Step ◽  
High Degree

In this work we present a clean one-step process for modifying headgroups of self-assembled monolayers (SAMs) on gold using photo-enabled click chemistry. A thiolated, cyclopropenone-caged strained alkyne precursor was first functionalized onto a flat gold substrate through self-assembly. Exposure of the cyclopropenone SAM to UV-A light initiated the efficient photochemical decarbonylation of the cyclopropenone moiety, revealing the strained alkyne capable of undergoing the interfacial strain-promoted alkyne-azide cycloaddition (SPAAC). Irradiated SAMs were derivatized with a series of model azides with varied hydrophobicity to demonstrate the generality of this chemical system for the modification and fine-tuning of the surface chemistry on gold substrates. SAMs were characterized at each step with polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to confirm successful functionalization and reactivity. Furthermore, to showcase the compatibility of this approach with biochemical applications, cyclopropenone SAMs were irradiated and modified with azide-bearing cell adhesion peptides to promote human fibroblast cell adhesion, then imaged by live cell fluorescence microscopy. Thus, the “photoclick” methodology reported here represents an improved, versatile, catalyst-free protocol that allows for a high degree of control over the modification of material surfaces, with applicability in materials science as well as biochemistry.<br>

scholarly journals Two-step crystallization and solid–solid transitions in binary colloidal mixtures

2020 ◽  
Vol 117 (45) ◽  
pp. 27927-27933
Author(s):  
Huang Fang ◽  
Michael F. Hagan ◽  
W. Benjamin Rogers
Keyword(s):  
Free Energy ◽  
Self Assembly ◽  
Materials Science ◽  
Protein Structures ◽  
Free Energy Barrier ◽  
Enhanced Sampling ◽  
Homogeneous Fluid ◽  
Metastable Structures ◽  
One Step ◽  
Crystal Phases

Crystallization is fundamental to materials science and is central to a variety of applications, ranging from the fabrication of silicon wafers for microelectronics to the determination of protein structures. The basic picture is that a crystal nucleates from a homogeneous fluid by a spontaneous fluctuation that kicks the system over a single free-energy barrier. However, it is becoming apparent that nucleation is often more complicated than this simple picture and, instead, can proceed via multiple transformations of metastable structures along the pathway to the thermodynamic minimum. In this article, we observe, characterize, and model crystallization pathways using DNA-coated colloids. We use optical microscopy to investigate the crystallization of a binary colloidal mixture with single-particle resolution. We observe classical one-step pathways and nonclassical two-step pathways that proceed via a solid–solid transformation of a crystal intermediate. We also use enhanced sampling to compute the free-energy landscapes corresponding to our experiments and show that both one- and two-step pathways are driven by thermodynamics alone. Specifically, the two-step solid–solid transition is governed by a competition between two different crystal phases with free energies that depend on the crystal size. These results extend our understanding of available pathways to crystallization, by showing that size-dependent thermodynamic forces can produce pathways with multiple crystal phases that interconvert without free-energy barriers and could provide approaches to controlling the self-assembly of materials made from colloids.

From supramolecular chemistry to nanotechnology: Assembly of 3D nanostructures

2009 ◽  
Vol 81 (12) ◽  
pp. 2225-2233 ◽  
Author(s):  
Xing Yi Ling ◽  
David N. Reinhoudt ◽  
Jurriaan Huskens
Keyword(s):  
Supramolecular Chemistry ◽  
Self Assembly ◽  
Supramolecular Assembly ◽  
Fine Tuning ◽  
Nanoparticle Assembly ◽  
Layer By Layer ◽  
Surface Binding ◽  
Free Standing ◽  
Functionalized Nanoparticles ◽  
Assembled Monolayers

Fabricating well-defined and stable nanoparticle crystals in a controlled fashion receives growing attention in nanotechnology. The order and packing symmetry within a nanoparticle crystal is of utmost importance for the development of materials with unique optical and electronic properties. To generate stable and ordered 3D nanoparticle structures, nanotechnology is combined with supramolecular chemistry to control the self-assembly of 2D and 3D receptor-functionalized nanoparticles. This review focuses on the use of molecular recognition chemistry to establish stable, ordered, and functional nanoparticle structures. The host–guest complexation of β-cyclodextrin (CD) and its guest molecules (e.g., adamantane and ferrocene) are applied to assist the nanoparticle assembly. Direct adsorption of supramolecular guest- and host-functionalized nanoparticles onto (patterned) CD self-assembled monolayers (SAMs) occurs via multivalent host–guest interactions and layer-by-layer (LbL) assembly. The reversibility and fine-tuning of the nanoparticle-surface binding strength in this supramolecular assembly scheme are the control parameters in the process. Furthermore, the supramolecular nanoparticle assembly has been integrated with top-down nanofabrication schemes to generate stable and ordered 3D nanoparticle structures, with controlled geometries and sizes, on surfaces, other interfaces, and as free-standing structures.

Surface Dipoles Influence the Wettability of Terminally Fluorinated Organic Films

1998 ◽  
Vol 546 ◽  
Author(s):  
Ramon Colorado ◽  
Michael Graupe ◽  
Mitsuru Takenaga ◽  
Thomas Koini ◽  
T. Randall Lee
Keyword(s):  
Contact Angle ◽  
Organic Thin Films ◽  
Dipole Interaction ◽  
Contact Angles ◽  
Aprotic Solvents ◽  
Angle Measurements ◽  
Infrared Reflection ◽  
Contact Angle Measurements ◽  
Assembled Monolayers ◽  
High Degree

AbstractThe correlation of differences in the wettabilities of partially fluorinated self-assembled monolayers (SAMs) to changes in the chemical structure and composition of the films was explored by contact angle goniometry and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). SAMs of simple alkanethiols (CH3(CH2)nSH with n = 9-15) and their CF3-terminated analogs (CF3(CH2)nSH with n = 9-15) were prepared by adsorption from solution onto evaporated gold. Advancing contact angles of hexadecane were measured on both the terminally fluorinated surfaces and the hydrocarbon surfaces. These data were compared to those obtained using a series of polar aprotic contacting liquids. As expected, the contact angles of hexadecane were higher on the CF3-terminated SAMs than on the CH3-terminated SAMs. The contact angles of the polar aprotic solvents, however, were measurably lower on the CF3- terminated SAMs than on the CH3-terminated SAMs. These observations were rationalized on the basis that the introduction of the CF3 terminal groups yields oriented surface dipoles that interact with the dipoles of the polar contacting liquids. Further support for this model was provided by the observation of an inverse parity (“odd-even”) effect in the wettabilities of the polar aprotic solvents on the CF3-terminated surfaces. Analysis by PM-IRRAS revealed that both types of films consist of predominately trans-extended alkyl chains with relatively few gauche defects in a densely packed arrangement. The high degree of order is consistent with the detection of the parity effect, where small changes in the orientation of the tail groups can be sensed by contact angle measurements only in highly ordered organic thin films. The significance of the dipole-oriented dipole interaction in describing interfacial wettabilities is discussed.

scholarly journals Reconfiguring confined magnetic colloids with tunable fluid transport behavior

2020 ◽  
Author(s):  
Zhizhi Sheng ◽  
Mengchuang Zhang ◽  
Jing Liu ◽  
Paolo Malgaretti ◽  
Jianyu Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Drug Delivery ◽  
Self Assembly ◽  
Fluid Transport ◽  
Materials Science ◽  
Colloidal Suspension ◽  
Fine Tuning ◽  
Collective Dynamics ◽  
Theoretical Investigations ◽  
Magnetic Colloids

Abstract Collective dynamics of confined colloids is crucial in diverse scenarios such as self-assembly and phase behavior in materials science, microrobot swarms for drug delivery, and microfluidic control. Yet, fine-tuning the dynamics of colloids in microscale confined spaces is still a formidable task due to the complexity of the dynamics of colloidal suspension and to the lack of methodology to probe colloids in confinement. Here, we show that the collective dynamics of confined magnetic colloids can be finely tuned by external magnetic fields. In particular, the mechanical properties of the confined colloidal suspension can be probed in real-time and this strategy can be also used to tune microscale fluid transport. Our experimental and theoretical investigations reveal that the collective configuration characterized by the colloidal entropy is controlled by the colloidal concentration, confining ratio, and external field strength and direction. Indeed, our results show that mechanical properties of the colloidal suspension as well as the transport of the solvent in microfluidic devices can be controlled upon tuning the entropy of the colloidal suspension. Our approach opens new avenues for the design and applications of drug delivery, microfluidic logic, dynamic fluid control, chemical reaction, and beyond.

Stochastic Computing via In Operando Modulation of Rectification in Molecular Tunneling Junctions

2020 ◽  
Author(s):  
Xinkai Qiu ◽  
Sylvia Rousseva ◽  
Gang Ye ◽  
Jan C. Hummelen ◽  
Ryan Chiechi
Keyword(s):  
Self Assembly ◽  
Variable Temperature ◽  
Self Assembled Monolayers ◽  
Microfluidic Channels ◽  
Proof Of Concept ◽  
Glycol Ethers ◽  
Stochastic Computing ◽  
Assembled Monolayers ◽  
In Operando ◽  
Tunneling Junctions

This paper describes the reconfiguration of molecular tunneling junctions during operation via the self-assembly of bilayers of glycol ethers. We use well-established functional groups to modulate the magnitude and direction of rectification in assembled tunneling junctions by exposing them to solutions containing different glycol ethers. Variable-temperature measurements establish that rectification occurs by a bias-dependent tunneling-hopping mechanism and that glycol ethers, beside being an unusually efficient tunneling medium, behave identically to alkanes. We fabricated memory bits from crossbar junctions prepared by injecting eutectic Ga-In into microfluidic channels. Two 8-bit registers were able to perform logical AND operations on bit strings encoded into chemical packets as microfluidic droplets that alter the composition of the crossbar junctions through self-assembly to effect memristor-like properties. This proof of concept work demonstrates the potential for fieldable molecular-electronic devices based on tunneling junctions of self-assembled monolayers and bilayers.

scholarly journals Kinetic Constraints in the Specific Interaction between Phosphorylated Ubiquitin and Proteasomal Shuttle Factors

Biomolecules ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1008
Author(s):  
Ling-Yun Qin ◽  
Zhou Gong ◽  
Kan Liu ◽  
Xu Dong ◽  
Chun Tang
Keyword(s):  
Exchange Rate ◽  
Self Assembly ◽  
Solution Structure ◽  
Specific Interaction ◽  
Dissociation Rate ◽  
Fine Tuning ◽  
Binding Mechanism ◽  
Kinetics Analysis ◽  
Kinetic Constraint ◽  
Thermodynamic Basis

Ubiquitin (Ub) specifically interacts with the Ub-associating domain (UBA) in a proteasomal shuttle factor, while the latter is involved in either proteasomal targeting or self-assembly coacervation. PINK1 phosphorylates Ub at S65 and makes Ub alternate between C-terminally relaxed (pUbRL) and retracted conformations (pUbRT). Using NMR spectroscopy, we show that pUbRL but not pUbRT preferentially interacts with the UBA from two proteasomal shuttle factors Ubqln2 and Rad23A. Yet discriminatorily, Ubqln2-UBA binds to pUb more tightly than Rad23A does and selectively enriches pUbRL upon complex formation. Further, we determine the solution structure of the complex between Ubqln2-UBA and pUbRL and uncover the thermodynamic basis for the stronger interaction. NMR kinetics analysis at different timescales further suggests an indued-fit binding mechanism for pUb-UBA interaction. Notably, at a relatively low saturation level, the dissociation rate of the UBA-pUbRL complex is comparable with the exchange rate between pUbRL and pUbRT. Thus, a kinetic constraint would dictate the interaction between Ub and UBA, thus fine-tuning the functional state of the proteasomal shuttle factors.

scholarly journals Nucleation of Ga droplets self-assembly on GaAs(111)A substrates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Artur Tuktamyshev ◽  
Alexey Fedorov ◽  
Sergio Bietti ◽  
Stefano Vichi ◽  
Riccardo Tambone ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Size Distribution ◽  
Self Assembly ◽  
Cluster Size ◽  
Droplet Size Distribution ◽  
Local Environment ◽  
The Self ◽  
Critical Cluster ◽  
Droplet Nucleation ◽  
High Degree

AbstractWe investigated the nucleation of Ga droplets on singular GaAs(111)A substrates in the view of their use as the seeds for the self-assembled droplet epitaxial quantum dots. A small critical cluster size of 1–2 atoms characterizes the droplet nucleation. Low values of the Hopkins-Skellam index (as low as 0.35) demonstrate a high degree of a spatial order of the droplet ensemble. Around $$350\,^{\circ }\hbox {C}$$ 350 ∘ C the droplet size distribution becomes bimodal. We attribute this observation to the interplay between the local environment and the limitation to the adatom surface diffusion introduced by the Ehrlich–Schwöbel barrier at the terrace edges.

scholarly journals Constructing Large 2D Lattices Out of DNA-Tiles

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1502
Author(s):  
Johannes M. Parikka ◽  
Karolina Sokołowska ◽  
Nemanja Markešević ◽  
J. Jussi Toppari
Keyword(s):  
Self Assembly ◽  
Dna Nanotechnology ◽  
Building Blocks ◽  
High Yield ◽  
Dna Nanostructures ◽  
Liquid Interfaces ◽  
Basic Principles ◽  
Dna Tiles ◽  
One Step ◽  
Solid Liquid

The predictable nature of deoxyribonucleic acid (DNA) interactions enables assembly of DNA into almost any arbitrary shape with programmable features of nanometer precision. The recent progress of DNA nanotechnology has allowed production of an even wider gamut of possible shapes with high-yield and error-free assembly processes. Most of these structures are, however, limited in size to a nanometer scale. To overcome this limitation, a plethora of studies has been carried out to form larger structures using DNA assemblies as building blocks or tiles. Therefore, DNA tiles have become one of the most widely used building blocks for engineering large, intricate structures with nanometer precision. To create even larger assemblies with highly organized patterns, scientists have developed a variety of structural design principles and assembly methods. This review first summarizes currently available DNA tile toolboxes and the basic principles of lattice formation and hierarchical self-assembly using DNA tiles. Special emphasis is given to the forces involved in the assembly process in liquid-liquid and at solid-liquid interfaces, and how to master them to reach the optimum balance between the involved interactions for successful self-assembly. In addition, we focus on the recent approaches that have shown great potential for the controlled immobilization and positioning of DNA nanostructures on different surfaces. The ability to position DNA objects in a controllable manner on technologically relevant surfaces is one step forward towards the integration of DNA-based materials into nanoelectronic and sensor devices.

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