Structural Diversity of 2D Molecular Self-Assemblies Arising from Carboxyl Groups Attached to a Molecule: An STM Study at the Liquid-Solid Interface.

Understanding the molecular self-assembly behavior, especially at the microscopic level, sheds light on the rational design of artificial supramolecular systems at surfaces. In this work, scanning tunneling microscopy (STM) and force field simulations were utilized to explore two molecular systems where two and four carboxyl groups are symmetrically modified onto a skeleton. The two target molecules are 4,4'-(ethyne-1,2-diyl) dibenzoic acid (EBA) and 1,1'-ethynebenzene-3,3',5,5,'-tetracarboxylic acid (TCA).

A Paradigm Shift from 2D to 3D: Surface Supramolecular Assemblies and Their Electronic Properties Explored by Scanning Tunneling Microscopy and Spectroscopy.

Exploring supramolecular architectures at surfaces plays an increasingly important role in contemporary science, especially for molecular electronics. A paradigm of research interest in this context is shifting from 2D to 3D that is expanding from monolayer, bilayers, to multilayers. Taking advantage of its high-resolution insight into monolayers and a few layers, scanning tunneling microscopy/spectroscopy (STM/STS) turns out a powerful tool for analyzing such thin films on a solid surface.

STM Study of the Self-Assembly of Biphenyl-3,3',5,5'-Tetracarboxylic Acid and Its Mixing Behavior with Coronene at the Liquid-Solid Interface.

We report a scanning tunneling microscopy (STM) study of the molecular self-assembly of biphenyl-3,3',5,5'-tetracarboxylic acid (BPTC) at the octanoic acid/graphite interface. STM revealed that the BPTC molecules generated stable bilayers and monolayers under high and low sample concentrations, respectively. Besides hydrogen bonds, the bilayers were stabilized by molecular π-stacking, whereas the monolayers were maintained by solvent co-adsorption.

Surface supramolecular assemblies tailored by chemical/physical and synergistic stimuli: a scanning tunneling microscopy study.

Supramolecular self-assemblies formed by various non-covalent interactions can produce diverse functional networks on solid surfaces. These networks have recently attracted much interest from both fundamental and application points of view. Unlike covalent organic frameworks (COFs), the properties of the assemblies differ from each other depending on the constituent motifs.

Flow-induced-crystallization: tailoring host-guest supramolecular co-assemblies at the liquid-solid interface.

Here, we report that using the method of simply contacting a sample solution droplet with a piece of tissue paper can create a solvent flow (capillary force). During this process, the dynamics and solvent removal can promote the formation and stabilization of a meta-stable linear quasi-crystal composed of -terphenyl-3,5,3',5'-tetracarboxylic acid (TPTC) molecules, which would otherwise pack into thermodynamically favored random tiling. The tailored quasi-crystal (linear) template allows atop it higher-efficiency accommodation of fullerene molecules (C) from 40.

An Assessment of MXenes through Scanning Probe Microscopy.

Recently, exploring the unique properties of 2D materials has constituted a new wave of research, which lead these materials to enormous applications ranging from optoelectronics to healthcare systems. Due to the profusion of surface terminated functionalities, MXenes have become an emerging class of 2D materials that can be easily integrated with other materials. The versatility of MXenes allows to tune their finest material properties for further device applications.

Odd-Even Effect on Supramolecular Co-Assemblies: Control over the Two-Dimensional Self-Assemblies of a Fluorenone Derivative with Asymmetrically Substituted Alkyl Chains.

The precise control of two-dimensional supramolecular co-assemblies presents a research topic related to advance nanotechnology. Here, we report a scanning tunneling microscopy (STM) study of the mixture behavior of three fluorenone derivatives at the liquid-solid interface. The target molecule is F-CC whose structure bears asymmetrical alkyls, whereas the regulating molecules, either F-CC or F-CC, are structurally symmetric.

Monolayer and Bilayer Formation of Molecular 2D Networks Assembled at the Liquid/Solid Interfaces by Solution-Based Drop-Cast Method.

In recent years, extending self-assembled structures from two-dimensions (2D) to three-dimensions (3D) has been a paradigm in surface supramolecular chemistry and contemporary nanotechnology. Using organic molecules of p-terphenyl-3,5,3',5'-tetracarboxylic acid (TPTC), and scanning tunneling microscopy (STM), we present a simple route, that is the control of the solute solubility in a sample solution, to achieve the vertical growth of supramolecular self-assemblies, which would otherwise form monolayers at the organic solvent/graphite interface. Presumably, the bilayer formations were based on π-conjugated overlapped molecular dimers that worked as nuclei to induce the yielding of the second layer.

Substrate Impact on MR Characteristics of Carbon Nano Films Explored via AFM and Raman Analysis.

Recent advances in the fabrication and classification of amorphous carbon (a-Carbon) thin films play an active part in the field of surface materials science. In this paper, a pulsed laser deposition (PLD) technique through controlling experimental parameters, including deposition time/temperature and laser energy/frequency, has been employed to examine the substrate effect of amorphous carbon thin film fabrication over SiO and glass substrates. In this paper, we have examined the structural and magnetoresistance (MR) properties of these thin films.

Supramolecular Chemistry: Host-Guest Molecular Complexes.

In recent times, researchers have emphasized practical approaches for capturing coordinated and selective guest entrap. The physisorbed nanoporous supramolecular complexes have been widely used to restrain various guest species on compact supporting surfaces. The host-guest (HG) interactions in two-dimensional (2D) permeable porous linkages are growing expeditiously due to their future applications in biocatalysis, separation technology, or nanoscale patterning.

Recent progress in hybrid perovskite solar cells through scanning tunneling microscopy and spectroscopy.

Currently, sustainable renewable energy sources are urgently required to fulfill the cumulative energy needs of the world's 7.8 billion population, since the conventional coal and fossil fuels will be exhausted soon. Photovoltaic devices are a direct and efficient means to produce a huge amount of energy to meet these energy targets.

Electric-field-induced supramolecular phase transitions at the liquid/solid interface: cat-assembly from solvent additives.

We demonstrate by using scanning tunneling microscopy that a series of trace organic solvent additives can efficiently promote the electrically triggered phase transition of trimesic acid (TMA), which would otherwise occur rather sporadically. DFT simulations taking into account the electric field effect elucidate such tailored phase transformations, based on the Gibbs activation and free energies of the deprotonation reactions of TMA.

Nanoscale tailoring of supramolecular crystals via an oriented external electric field.

The oriented external electric field of a scanning tunneling microscope (STM) has recently been adapted for controlling the chemical reaction and supramolecular phase transition at surfaces with molecular precision. However, to date, advance controls using such electric-fields for crystal engineering have not been achieved yet. Here, we present how the directional electric-field of an STM can be utilized to harness supramolecular crystallization on a solid surface.

One-step preparation of single-layered graphene quantum dots for the detection of Fe.

Single-layer graphene quantum dots are highly desirable while their facile and controllable preparations remain challenging. Herein, single-layered graphene quantum dots (sl-GQDs) were developed via a facile one-step hydrothermal synthesis, with citric acid and β-cyclodextrin (CD) as starting materials. The sl-GQDs decorated with CD molecules emit green fluorescence with a quantum yield of 5.

Newtonian flow inside carbon nanotube with permeable boundary taking into account van der Waals forces.

Here, water flow inside large radii semi-infinite carbon nanotubes is investigated. Permeable wall taking into account the molecular interactions between water and a nanotube, and the slip boundary condition will be considered. Furthermore, interactions among molecules are approximated by the continuum approximation.

A continuum study of layer analysis for single species ion transport inside double-layered graphene sheets with various separations.

We investigate the formation of thin ionic layers driven by electro-osmotic forces, that are commonly found in micro- and nano-channels. Recently, multi-layers have been reported in the literature. However, the relation between classical Debye layers and multi-layers, which is a practically and fundamentally important question, was previously unexplained.

Influence of Zn Doping on Ni-Based Nanoferrites; (Ni ZnFeO).

Nickel zinc nanoferrites (NiZnFeO) were synthesized via a chemical co-precipitation method having stoichiometric proportion (x) altering from 0.00 to 1.00 in steps of 0.

Hydrophobic surface modified HfO antireflective coatings.

A multifunctional antireflective (AR) thin film is always a prerequisite for growing high-tech applications. Herein we proposed a surface modification technique to transform the hydrophilic behaviour of HfO AR nanofilms into hydrophobic without influencing the nanostructure, morphology, refractive index (η) or AR efficacy of HfO nanofilms. Our experimental results demonstrate that the fabricated HfO AR nanofilms retain its AR efficiency after surface modification to <1% in the visible wavelength range (450-700 nm) on FTO and sapphire.

Synergic Effect: Temperature-Assisted Electric-Field-Induced Supramolecular Phase Transitions at the Liquid/Solid Interface.

Using trimesic acid (TMA) as a model system by means of scanning tunneling microscope (STM) equipped with a temperature controller, here, we report a temperature-assisted method to cooperatively control electric-field-induced supramolecular phase transitions at the liquid/solid interface. Octanoic acid is used as a solvent due to its good solubility for TMA and its less complicated pattern formed under negative STM bias (e.g.

Influence of Refractive Index on Antireflectance Efficiency of Thin Films.

In today's world, scientific development is tremendously strengthened by imitating natural processes. This development remarkably validates progressive and efficient operation of multifunctional thin films in variable ecological circumstances. We use TFCalc thinfilm software, a reliable and trustworthy simulation tool, to design antireflective (AR) coatings for solar cells that can operate in varying environmental conditions and can be functional according to user-defined conditions.

Superstructure manipulation and electronic measurement of monolayers comprising discotic liquid crystals with intrinsic dipole moment using STM/STS.

In this work, we studied the discotic liquid crystals (DLCs) of dibenzo[a,c]phenazine at the liquid-solid interface using scanning tunnelling microscopy/spectroscopy, by which we show how to tailor the DLC assemblies and in turn their electron-transfer efficiency. This study presents an alternative method for phase control and electronic measurements for DLCs, especially at the microscopic level.

Template-Assisted Proximity for Oligomerization of Fullerenes.

Demonstrated herein is an unprecedented porous template-assisted reaction at the solid-liquid interface involving bond formation, which is typically collision-driven and occurs in the solution and gas phases. The template is a TMA (trimesic acid) monolayer with two-dimensional pores that host fullerenes, which otherwise exhibit an insignificant affinity to an undecorated graphite substrate. The confinement of C units in the TMA pores formulates a proximity that is ideal for bond formation.

The Cyclic Hydrogen-Bonded 6-Azaindole Trimer and its Prominent Excited-State Triple-Proton-Transfer Reaction.

The compound 6-azaindole undergoes self-assembly by formation of N(1)-H⋅⋅⋅N(6) hydrogen bonds (H bonds), forming a cyclic, triply H-bonded trimer. The formation phenomenon is visualized by scanning tunneling microscopy. Remarkably, the H-bonded trimer undergoes excited-state triple proton transfer (ESTPT), resulting in a proton-transfer tautomer emission maximized at 435 nm (325 nm of the normal emission) in cyclohexane.

3D and 2D supramolecular assemblies and thermotropic behaviour of a carbo-benzenic mesogen.

Hexaalkoxy-di(phenylethynyl)-tetraphenyl-carbo-benzenes bearing six CH aliphatic chains (n = 12, 18) have been synthesized and characterized, including by single crystal XRD analysis. For n = 12, a liquid crystal behaviour was observed in the range of 109-130 °C. DSC, POM and PXRD analyses evidenced a rectangular columnar mesophase at 115 °C.

Reversible Local and Global Switching in Multicomponent Supramolecular Networks: Controlled Guest Release and Capture at the Solution/Solid Interface.

Dynamically switchable supramolecular systems offer exciting possibilities in building smart surfaces, the structure and thus the function of which can be controlled by using external stimuli. Here we demonstrate an elegant approach where the guest binding ability of a supramolecular surface can be controlled by inducing structural transitions in it. A physisorbed self-assembled network of a simple hydrogen bonding building block is used as a switching platform.