Advances in the Field of Two-Dimensional Crystal-Based Photodetectors.

Two-dimensional (2D) materials have sparked intense interest among the scientific community owing to their extraordinary mechanical, optical, electronic, and thermal properties. In particular, the outstanding electronic and optical properties of 2D materials make them show great application potential in high-performance photodetectors (PDs), which can be applied in many fields such as high-frequency communication, novel biomedical imaging, national security, and so on. Here, the recent research progress of PDs based on 2D materials including graphene, transition metal carbides, transition-metal dichalcogenides, black phosphorus, and hexagonal boron nitride is comprehensively and systematically reviewed.

Towards ballistic transport CVD graphene by controlled removal of polymer residues.

Polymer-assisted wet transfer of chemical vapor deposited (CVD) graphene has achieved great success towards the true potential for large-scale electronic applications, while the lack of an efficient polymer removal method has been regarded as a crucial factor for realizing high carrier mobility in graphene devices. Hereby, we report an efficient and facile method to clean polymer residues on graphene surface by merely employing solvent mixture of isopropanol (IPA) and water (HO). Raman spectroscopy shows an intact crystal structure of graphene after treatment, and the x-ray photoelectron spectroscopy indicates a significant decrease in the C-O and C=O bond signals, which is mainly attributed to the removal of polymer residues and further confirmed by subsequent atomic force microscopy analysis.

Fabrication of BP2T functionalized graphene non-covalent π-π stacking interactions for enhanced ammonia detection.

Graphene has stimulated great enthusiasm in a variety of fields, while its chemically inert surface still remains challenging for functionalization towards various applications. Herein, we report an approach to fabricate non-covalently functionalized graphene by employing π-π stacking interactions, which has potentialities for enhanced ammonia detection. 5,5'-Di(4-biphenylyl)-2,2'-bithiophene (BP2T) molecules are used in our work for the non-covalent functionalization through strong π-π interactions of aromatic structures with graphene, and systematic investigations by employing various spectroscopic and microscopic characterization methods confirm the successful non-covalent attachment of the BP2T on the top of graphene.

Graphene-Oxide-Based Fluoro- and Chromo-Genic Materials and Their Applications.

Composite materials and their applications constitute a hot field of research nowadays due to the fact that they comprise a combination of the unique properties of each component of which they consist. Very often, they exhibit better performance and properties compared to their combined building blocks. Graphene oxide (GO), as the most widely used derivative of graphene, has attracted widespread attention because of its excellent properties.

Poly(vinyl pyridine) and Its Quaternized Derivatives: Understanding Their Solvation and Solid State Properties.

A series of N-methyl quaternized derivatives of poly(4-vinylpyridine) (PVP) were synthesized in high yields with different degrees of quaternization, obtained by varying the methyl iodide molar ratio and affording products with unexplored optical and solvation properties. The impact of quaternization on the physicochemical properties of the copolymers, and notably the solvation properties, was further studied. The structure of the synthesized polymers and the quaternization degrees were determined by infrared and nuclear magnetic spectroscopies, while their thermal characteristics were studied by differential scanning calorimetry and their thermal stability and degradation by thermogravimetric analysis (TG-DTA).

Review on Graphene-, Graphene Oxide-, Reduced Graphene Oxide-Based Flexible Composites: From Fabrication to Applications.

In the new era of modern flexible and bendable technology, graphene-based materials have attracted great attention. The excellent electrical, mechanical, and optical properties of graphene as well as the ease of functionalization of its derivates have enabled graphene to become an attractive candidate for the construction of flexible devices. This paper provides a comprehensive review about the most recent progress in the synthesis and applications of graphene-based composites.

Click Chemistry Enabling Covalent and Non-Covalent Modifications of Graphene with (Poly)saccharides.

Graphene is a material with outstanding properties and numerous potential applications in a wide range of research and technology areas, spanning from electronics, energy materials, sensors, and actuators to life-science and many more. However, the insolubility and poor dispersibility of graphene are two major problems hampering its use in certain applications. Tethering mono-, di-, or even poly-saccharides on graphene through click-chemistry is gaining more and more attention as a key modification approach leading to new graphene-based materials (GBM) with improved hydrophilicity and substantial dispersibility in polar solvents, e.

Mono- and Di-Quaternized 4,4'-Bipyridine Derivatives as Key Building Blocks for Medium- and Environment-Responsive Compounds and Materials.

Mono- and di-quaternized 4,4'-bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications. These applications correspond to various disciplines of research and technology. In their majority, two key features of these 4,4'-bipyridine-based derivatives are exploited: their redox activity and their electrochromic aptitude.

Nanoresolution patterning of hydrogenated graphene by electron beam induced C-H dissociation.

Direct writing of semi-conductive or insulative nanopatterns on graphene surfaces is one of the major challenges in the application of graphene in flexible and transparent electronic devices. Here, we demonstrate that nanoresolution patterning on hydrogenated graphene can be approached by using electron beam induced C-H dissociation when the electron accelerating voltage is beyond a critical voltage of 3 kV. The resolution of the patterning reaches 18 nm and remains constant as the accelerating voltage is beyond 15 kV.

Electrochemical Water Oxidation and Stereoselective Oxygen Atom Transfer Mediated by a Copper Complex.

Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal-oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with the use of H O as an oxygen source. To date, this strategy has not been reported for copper complexes.

Cyclopropyl Group: An Excited-State Aromaticity Indicator?

The cyclopropyl (cPr) group, which is a well-known probe for detecting radical character at atoms to which it is connected, is tested as an indicator for aromaticity in the first ππ* triplet and singlet excited states (T and S ). Baird's rule says that the π-electron counts for aromaticity and antiaromaticity in the T and S states are opposite to Hückel's rule in the ground state (S ). Our hypothesis is that the cPr group, as a result of Baird's rule, will remain closed when attached to an excited-state aromatic ring, enabling it to be used as an indicator to distinguish excited-state aromatic rings from excited-state antiaromatic and nonaromatic rings.

Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene.

The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S), becomes exergonic in the first triplet state (T). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T state and also in its first singlet excited state (S), opposite to S, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%).

Preferential Solvation of a Highly Medium Responsive Pentacyanoferrate(II) Complex in Binary Solvent Mixtures: Understanding the Role of Dielectric Enrichment and the Specificity of Solute-Solvent Interactions.

In this work, the preferential solvation of an intensely solvatochromic ferrocyanide(II) dye involving a 4,4'-bipyridine-based ligand was examined in various binary solvent mixtures. Its solvatochromic behavior was rationalized in terms of specific and nonspecific solute-solvent interactions. An exceptional case of solvatochromic inversion was observed when going from alcohol/water to amide/water mixtures.

The excited state antiaromatic benzene ring: a molecular Mr Hyde?

The antiaromatic character of benzene in its first ππ* excited triplet state (T1) was deduced more than four decades ago by Baird using perturbation molecular orbital (PMO) theory [J. Am. Chem.

Structural and magnetic characterization of a tetranuclear copper(II) cubane stabilized by intramolecular metal cation-π interactions.

A novel tetranuclear copper(II) complex (1) was synthesized from the self-assembly of copper(II) perchlorate and the ligand N-benzyl-1-(2-pyridyl)methaneimine (L(1)). Single-crystal X-ray diffraction studies revealed that complex 1 consists of a Cu4(OH)4 cubane core, where the four copper(II) centers are linked by μ3-hydroxo bridges. Each copper(II) ion is in a distorted square-pyramidal geometry.

Photoconductive properties of a π-conjugated α-cyclodextrin containing [2]rotaxane and its corresponding molecular dumbbell.

The photoconductive properties of an azo-containing [2]rotaxane, bearing a π-conjugated axial part and its corresponding dumbbell compound are investigated. Structural effects on the observed photoconductive behavior in both cases are discussed. The photoresponsive behavior of the title [2]rotaxane was proved to be more intense than that of its analogue lacking the α-cyclodextrin (α-CyD) macrocycle.

Spectroscopic investigation of the solvatochromic behavior of a new synthesized non symmetric viologen dye: study of the solvent-solute interactions.

This work deals with the design, synthesis, and characterization of a new solvatochromic dye. The intense solvatochromic behavior of this new synthesized non symmetric viologen was investigated using UV-Vis spectrophotometry. A further purpose was the study of the interactions between the solvent and solute molecules responsible for the solvatochromism.