Layer-Dependent Gas Sensing Mechanism of 2D Titanium Carbide (TiCT) MXene.

Monolayers of TiCT MXene and bilayer structures formed by partially overlapping monolayer flakes exhibit opposite sensing responses to a large scope of molecular analytes. When exposed to reducing analytes, monolayer MXene flakes show increased electrical conductivity, i.e.

Porous Nanographenes, Graphene Nanoribbons, and Nanoporous Graphene Selectively Synthesized from the Same Molecular Precursor.

We demonstrate a family of molecular precursors based on 7,10-dibromo-triphenylenes that can selectively produce different varieties of atomically precise porous graphene nanomaterials through the use of different synthetic environments. Upon Yamamoto polymerization of these molecules in solution, the free rotations of the triphenylene units around the C-C bonds result in the formation of cyclotrimers in high yields. In contrast, in on-surface polymerization of the same molecules on Au(111) these rotations are impeded, and the coupling proceeds toward the formation of long polymer chains.

Tunable Magnetic Coupling in Graphene Nanoribbon Quantum Dots.

Carbon-based quantum dots (QDs) enable flexible manipulation of electronic behavior at the nanoscale, but controlling their magnetic properties requires atomically precise structural control. While magnetism is observed in organic molecules and graphene nanoribbons (GNRs), GNR precursors enabling bottom-up fabrication of QDs with various spin ground states have not yet been reported. Here the development of a new GNR precursor that results in magnetic QD structures embedded in semiconducting GNRs is reported.

Hybrid Edge Results in Narrowed Band Gap: Bottom-up Liquid-Phase Synthesis of Bent = 6/8 Armchair Graphene Nanoribbons.

Scalable fabrication of graphene nanoribbons with narrow band gaps has been a nontrivial challenge. Here, we have developed a simple approach to access narrow band gaps using hybrid edge structures. Bottom-up liquid-phase synthesis of bent = 6/8 armchair graphene nanoribbons (AGNRs) has been achieved in high efficiency through copolymerization between an -terphenyl monomer and a naphthalene-based monomer, followed by Scholl oxidation.

Interlayer Incorporation of A-Elements into MXenes Via Selective Etching of A' from MA'A″C MAX Phases.

MXenes are a large family of two-dimensional materials with a general formula MXT, where M is a transition metal, X = C and/or N, and T represents surface functional groups. MXenes are synthesized by etching A-elements from layered MAX phases with a composition of MAX. As over 20 different chemical elements were shown to form A-layers in various MAX phases, we propose that they can provide an abundant source of very diverse MXene-based materials.

Sub-5 nm Contacts and Induced p-n Junction Formation in Individual Atomically Precise Graphene Nanoribbons.

This paper demonstrates the fabrication of nanometer-scale metal contacts on individual graphene nanoribbons (GNRs) and the use of these contacts to control the electronic character of the GNRs. We demonstrate the use of a low-voltage direct-write STM-based process to pattern sub-5 nm metallic hafnium diboride (HfB) contacts directly on top of single GNRs in an ultrahigh-vacuum scanning tunneling microscope (UHV-STM), with all the fabrication performed on a technologically relevant semiconductor silicon substrate. Scanning tunneling spectroscopy (STS) data not only verify the expected metallic and semiconducting character of the contacts and GNR, respectively, but also show induced band bending and p-n junction formation in the GNR due to the metal-GNR work function difference.

Ultrafast electron diffraction instrument for gas and condensed matter samples.

We report the modification of a gas phase ultrafast electron diffraction (UED) instrument that enables experiments with both gas and condensed matter targets, where a time-resolved experiment with sub-picosecond resolution is demonstrated with solid state samples. The instrument relies on a hybrid DC-RF acceleration structure to deliver femtosecond electron pulses on the target, which is synchronized with femtosecond laser pulses. The laser pulses and electron pulses are used to excite the sample and to probe the structural dynamics, respectively.

Chiral photocurrent in a Quasi-1D TiS(001) phototransistor.

The presence of in-plane chiral effects, hence spin-orbit coupling, is evident in the changes in the photocurrent produced in a TiS(001) field-effect phototransistor with left versus right circularly polarized light. The direction of the photocurrent is protected by the presence of strong spin-orbit coupling and the anisotropy of the band structure as indicated in NanoARPES measurements. Dark electronic transport measurements indicate that TiSis n-type and has an electron mobility in the range of 1-6 cmVs.

[Changes in the type and amount of bone collagens in chronic suppurative otitis media].

Objective: Comparative assessment of the collagen-tissue interaction in the bone tissue of the middle ear structures in patients with chronic suppurative otitis media (CSOM).

Material And Methods: A prospective study of 42 patients aged 16-60 years with CSOM admitted for reconstructive sanitizing surgery was performed. To study the collagen-tissue interaction, intraoperative samples of the bone tissue of the middle ear were used.

UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS Nanoribbons: Detection of Isopropanol at ppm Concentrations.

The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors.

High-yield fabrication of electromechanical devices based on suspended TiCT MXene monolayers.

MXenes, two-dimensional transition metal carbides, nitrides, and carbonitrides, are known for their exceptional electronic and mechanical properties. Yet, the experimental efforts toward the realization of MXene-based nanoelectromechanical systems (NEMS) combining electrical and mechanical functionalities of MXenes at the nanoscale remain very limited. Here, we demonstrate a high-yield fabrication of the electromechanical devices based on individual suspended monolayer MXene flakes.

Surface Versus Bulk State Transitions in Inkjet-Printed All-Inorganic Perovskite Quantum Dot Films.

The anion exchange of the halides, Br and I, is demonstrated through the direct mixing of two pure perovskite quantum dot solutions, CsPbBr and CsPbI, and is shown to be both facile and result in a completely alloyed single phase mixed halide perovskite. Anion exchange is also observed in an interlayer printing method utilizing the pure, unalloyed perovskite solutions and a commercial inkjet printer. The halide exchange was confirmed by optical absorption spectroscopy, photoluminescent spectroscopy, X-ray diffraction, and X-ray photoemission spectroscopy characterization and indicates that alloying is thermodynamically favorable, while the formation of a clustered alloy is not favored.

- isomerization of dimethyl 2,3-dibromofumarate.

The isomerization of dimethyl 2,3-dibromofumarate in chloroform solutions was investigated by the combination of nuclear magnetic resonance (NMR) and density functional theory (DFT) calculations. The bromination of dimethyl acetylenedicarboxylate leading to dimethyl 2,3-dibromofumarate produces the isomer initially, which however converts into the more stable isomer. The conversion from to is spontaneous and greatly accelerated by light.

Bifunctional Amine- and Thiol-Modified TiCT MXene for Trace Detection of Heavy Metals.

Surface functionalization of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, also known as MXenes, is a powerful approach for modification of their physical and chemical properties for new applications. In this study, we demonstrate the synthesis of a bifunctional TiCT MXene modified with amine and thiol groups through a facile condensation reaction. We successfully employed the resulting NH/SH-TiCT MXene as a solid phase in the ultrasonic-assisted dispersive micro solid-phase extraction (d-μ-SPE) method for the analytical determination of heavy metals at trace levels in food and soil samples.

Ultralarge Flakes of TiCT MXene Soft Delamination.

Two-dimensional (2D) titanium carbide MXene (TiCT) has attracted significant attention due to its combination of properties and great promise for various applications. The size of the 2D sheets is a critical parameter affecting multiple properties of assembled films, fibers and 3D structures. The increased lateral size of MXene flakes can benefit not only their assemblies by improving the interflake contacts and alignment but also fundamental studies at the individual flake level, allowing for facile patterning and investigation of intrinsic physical properties of MXenes.

Negative photoresponse in TiCT MXene monolayers.

Two-dimensional transition metal carbides, nitrides, and carbonitrides, collectively known as MXenes, are finding numerous applications in many different areas, including optoelectronics and photonics, but there is limited information about their intrinsic photoresponse. In this study, we investigated the visible and near-infrared range photoresponse of TiCT , the most popular MXene material to date. The electrical measurements were performed on devices based on individual monolayer TiCT MXene flakes, which were characterized by a variety of microscopic and spectroscopic methods.

Ferroptosis as a mechanism of non-ferrous metal toxicity.

Ferroptosis is a recently discovered form of regulated cell death, implicated in multiple pathologies. Given that the toxicity elicited by some metals is linked to alterations in iron metabolism and induction of oxidative stress and lipid peroxidation, ferroptosis might be involved in such toxicity. Although direct evidence is insufficient, certain pioneering studies have demonstrated a crosstalk between metal toxicity and ferroptosis.

Effect of Au/HfS interfacial interactions on properties of HfS-based devices.

X-ray photoemission spectroscopy (XPS) has been used to examine the interaction between Au and HfS at the Au/HfS interface. XPS measurements reveal dissociative chemisorption of O, leading to the formation of an oxide of Hf at the surface of HfS. This surface hafnium oxide, along with the weakly chemisorbed molecular species, such as O and HO, are likely responsible for the observed p-type characteristics of HfS reported elsewhere.

Diffusion-controlled on-surface synthesis of graphene nanoribbon heterojunctions.

We report a new diffusion-controlled on-surface synthesis approach for graphene nanoribbons (GNR) consisting of two types of precursor molecules, which exploits distinct differences in the surface mobilities of the precursors. This approach is a step towards a more controlled fabrication of complex GNR heterostructures and should be applicable to the on-surface synthesis of a variety of GNR heterojunctions.

Mechanical Stress Modulation of Resistance in MoS Junctions.

Strain engineering is a powerful strategy to control the physical properties of material-enabling devices with enhanced functionality and improved performance. Here, we investigate a modulation of the transport behavior of the two-dimensional MoS junctions under the mechanical stress induced by a tip of an atomic force microscope (AFM). We show that the junction resistance can be reversibly tuned by up to 4 orders of magnitude by altering a tip-induced force.

Printed Electronic Devices with Inks of TiS Quasi-One-Dimensional van der Waals Material.

We report on the fabrication and characterization of electronic devices printed with inks of quasi-one-dimensional (1D) van der Waals materials. The quasi-1D van der Waals materials are characterized by 1D motifs in their crystal structure, which allow for their exfoliation into bundles of atomic chains. The ink was prepared by the liquid-phase exfoliation of crystals of TiS into quasi-1D nanoribbons dispersed in a mixture of ethanol and ethylene glycol.

Complexities at the Au/ZrS(001) interface probed by x-ray photoemission spectroscopy.

Interaction between the Au adlayers and ZrS(001) has been examined via x-ray photoemission spectroscopy (XPS). The angle-resolved XPS measurements reveal that ZrS(001) is disulfide (S) terminated and the Au thickness-dependent XPS indicates that the observed band bending, for low Au coverage, is consistent with formation of a Schottky barrier at the Au/ZrS(001) interface. This band bending, however, appears to be suppressed as the thickness of Au adlayer is increased, indicating varying interfacial interactions at the Au/ZrS(001) interface.

Modification of a spectrophotometric method for assessment of monoamine oxidase activity with 2,4-dinitrophenylhydrazine as a derivatizing reagent.

The aim of the study was to modify a simple and widely used spectrophotometric assay for MAO activity evaluation with 2,4-dinitrophenylhydrazine. A modified procedure includes molar absorption coefficients of 2,4-DNP-hydrazone benzaldehyde and 2,4-DNP-hydrazone 5-hydroxyindolylacetaldehyde as 2.3 × 10moll cm and 1.

Structure Formation and Coupling Reactions of Hexaphenylbenzene and Its Brominated Analog.

The on-surface coupling of the prototypical precursor molecule for graphene nanoribbon synthesis, 6,11-dibromo-1,2,3,4-tetraphenyltriphenylene (C Br H , TPTP), and its non-brominated analog hexaphenylbenzene (C H , HPB), was investigated on coinage metal substrates as a function of thermal treatment. For HPB, which forms non-covalent 2D monolayers at room temperature, a thermally induced transition of the monolayer's structure could be achieved by moderate annealing, which is likely driven by π-bond formation. It is found that the dibrominated carbon positions of TPTP do not guide the coupling if the growth occurs on a substrate at temperatures that are sufficient to initiate C-H bond activation.