Pressure-Dependent Shape and Edge Configurations of MoS by Kinetic Monte Carlo Simulation.

Understanding the influence of precursor pressures is crucial for optimizing the properties of MoS grown through the chemical vapor deposition (CVD) process. In this study, we use kinetic Monte Carlo (KMC) simulations to investigate how varying the pressures of molybdenum () and sulfur () impacts the structural properties of MoS, such as grain shape and edge configurations. The simulations differentiate three distinct regimes─growth, steady-state, and etching─each defined by specific , , and the most probable atomic sites for filling or etching.

Real-Time Observation for MoS Growth Kinetics and Mechanism Promoted by the Na Droplet.

While the molten salt-catalyzed chemical vapor deposition (CVD) technique is recognized for its effectiveness in producing large-area transition metal chalcogenides, understanding their growth mechanisms involving alkali metals remains a challenge. Here, we investigate the kinetics and mechanism of sodium-catalyzed molybdenum disulfide (MoS) growth and etching through image analysis conducted using an integrated CVD microscope. Sodium droplets, agglomerated via the thermal decomposition of the sodium cholate dispersant, catalyze the precipitation of supersaturated MoS laminates and induce growth despite fragmentation during this process.

Spatiotemporally Controllable Electrical Stimulator via Independent Photobending and Upconversion Photoluminescence Using Two Different Wavelengths of Near-Infrared/Visible Light as Dual Stimuli.

Multistimuli responsive materials are advantageous in that they can enhance the desired response or bypass unwanted reactions. Light is one of the most attractive stimuli since it allows remote spatiotemporal control and multiplexing of properties (e.g.

Hierarchical van der Waals Heterostructure Strategy to Form Stable Transition Metal Dichalcogenide Dispersions.

Although various methods have been developed to disperse transition metal dichalcogenides (TMDCs) in aqueous environments, the methodology to generate stable TMDC dispersions remains challenging. Here, we developed a hierarchical van der Waals (vdW) heterostructure-based strategy to disperse few-layered TMDCs (WS, MoS, WSe, and MoSe) using both hexagonal boron nitride (hBN) and sodium cholate (SC) as synergistic vdW surfactants. By showing long-term stability of up to 3 years, the extinction spectra of these TMDC/hBN/SC dispersions exhibit the most blue-shifted excitonic transitions, low background extinction, good colloidal stability, and dispersion stability upon ultracentrifugation compared to other dispersion methods.

The Effects of Lengths of Flavin Surfactant -10-Alkyl Side Chains on Promoting Dispersion of a High-Purity and Diameter-Selective Single-Walled Nanotube.

Flavin with defined helical self-assembly helps to understand chemical designs for obtaining high-purity semiconducting ()-single-walled carbon nanotubes (SWNT) in a diameter ()-selective manner for high-end applications. In this study, flavins containing 8, 12, 16, and 20 -alkyl chains were synthesized, and their single/tandem effects on -selective -SWNT dispersibility were investigated at isomolarity. Flavins with -dodecyl and longer chain lengths (FC12, FC16, and FC20) act as good surfactants for stable SWNT dispersions whereas -octyl flavin (FC8) exhibits poor dispersibility owing to the lack of SWNT buoyancy.

Quantification and removal of carbonaceous impurities in a surfactant-assisted carbon nanotube dispersion and its implication on electronic properties.

Carbonaceous impurities (CIs) affect the optoelectronic properties as well as the ability to use absorption spectroscopy to estimate the metallic content of a single-walled carbon nanotube (SWNT) dispersion. Therefore, a method for the accurate quantification and removal of CIs is required. We have devised methods to characterize and quantify CIs present in SWNT batches and to determine the effects of CIs on the optical and electrical properties of SWNT.

Long-Term Exposure of MoS to Oxygen and Water Promoted Armchair-to-Zigzag-Directional Line Unzippings.

Understanding the long-term stability of MoS is important for various optoelectronic applications. Herein, we show that the long-term exposure to an oxygen atmosphere for up to a few months results in zigzag (zz)-directional line unzipping of the MoS basal plane. In contrast to exposure to dry or humid N atmospheres, dry O treatment promotes the initial formation of line defects, mainly along the armchair (ac) direction, and humid O treatment further promotes ac line unzipping near edges.

Flavin Mononucleotide-Mediated Formation of Highly Electrically Conductive Hierarchical Monoclinic Multiwalled Carbon Nanotube-Polyamide 6 Nanocomposites.

Although the multiwalled carbon nanotube (MWNT) is a promising material for use in the production of high electrical conductivity (σ) polymer nanocomposites, its tendency to aggregate and distribute randomly in a polymer matrix is a problematic issue. In the current study, we developed a highly conductive and monoclinically aligned MWNT-polyamide 6 (PA) nanocomposite containing interfacing flavin moieties. In this system, the flavin mononucleotide (FMN) initially serves as a noncovalent aqueous surfactant for individualizing MWNTs in the form of FMN-wrapped MWNTs (FMN-MWNT), and then partially decomposed FMN (dFMN) induces crystallization of the PA on the MWNTs.

Helical Assembly of Flavin Mononucleotides on Carbon Nanotubes as Multimodal Near-IR Hg(II)-Selective Probes.

The development of novel methods to detect mercury is of paramount importance owing to the impact of this metal on human health and the environment. We observed that flavin mononucleotide (FMN) and its helical assembly with a single-walled carbon nanotube (SWNT) selectively bind Hg arising from HgCl and MeHgCl. Absorption spectroscopic studies show that FMN preferentially forms a 2:1 rather than a 1:1 complex with Hg at high FMN concentrations.

Determination of the Absolute Enantiomeric Excess of the Carbon Nanotube Ensemble by Symmetry Breaking Using the Optical Titration Method.

Symmetry breaking of single-walled carbon nanotubes (SWNTs) has profound effects on their optoelectronic properties that are essential for fundamental study and applications. Here, we show that isomeric SWNTs that exhibit identical photoluminescence (PL) undergo symmetry breaking by flavin mononucleotide (FMN) and exhibit dual PLs and different binding affinities (K). Increasing the FMN concentration leads to systematic PL shifts of SWNTs according to structural modality and handedness due to symmetry breaking.

Affinity-mediated sorting order reversal of single-walled carbon nanotubes in density gradient ultracentrifugation.

Sorted single-walled carbon nanotubes (SWNTs) are of paramount importance for their utilization in high-end optoelectronic applications. Sodium cholate (SC)-based density gradient ultracentrifugation (DGU) has been instrumental in isolating small diameter (d t) SWNTs. Here, we show that SWNTs wrapped by flavin mononucleotide (FMN) as a dispersing agent are sorted in DGU, and show sorting order reversal behavior, departing from prototypical SC-SWNT trends.

Selective Dispersion of Highly Pure Large-Diameter Semiconducting Carbon Nanotubes by a Flavin for Thin-Film Transistors.

Scalable and simple methods for selective extraction of pure, semiconducting (s) single-walled carbon nanotubes (SWNTs) is of profound importance for electronic and photovoltaic applications. We report a new, one-step procedure to obtain respective large-diameter s- and metallic (m)-SWNT enrichment purity in excess of 99% and 78%, respectively, via interaction between the aromatic dispersing agent and SWNTs. The approach utilizes N-dodecyl isoalloxazine (FC12) as a surfactant in conjunction with sonication and benchtop centrifugation methods.

Trap density probing on top-gate MoS₂ nanosheet field-effect transistors by photo-excited charge collection spectroscopy.

Two-dimensional (2D) molybdenum disulfide (MoS₂) field-effect transistors (FETs) have been extensively studied, but most of the FETs with gate insulators have displayed negative threshold voltage values, which indicates the presence of interfacial traps both shallow and deep in energy level. Despite such interface trap issues, reports on trap densities in MoS₂ are quite limited. Here, we probed top-gate MoS₂ FETs with two- (2L), three- (3L), and four-layer (4L) MoS₂/dielectric interfaces to quantify deep-level interface trap densities by photo-excited charge collection spectroscopy (PECCS), and reported the result that deep-level trap densities over 10(12) cm(-2) may exist in the interface and bulk MoS₂ near the interface.

Few-Layer MoS2-Organic Thin-Film Hybrid Complementary Inverter Pixel Fabricated on a Glass Substrate.

Few-layer MoS2-organic thin-film hybrid complementary inverters demonstrate a great deal of device performance with a decent voltage gain of ≈12, a few hundred pW power consumption, and 480 Hz switching speed. As fabricated on glass, this hybrid CMOS inverter operates as a light-detecting pixel as well, using a thin MoS2 channel.

Multifunctional Schottky-diode circuit comprising palladium/molybdenum disulfide nanosheet.

Many electron devices using two-dimensional dichalcogenide MoS2 have been reported beyond graphene, but those were mostly field-effect transistors except few while P-N or Schottky diode form devices should be also important. In the present study, we have fabricated a Pd-driven MoS2 Schottky diode and its related circuits for multifunctional applications: dynamic electrical rectifier, visible light sensor, and hydrogen gas sensor.

The effects of dendrimer size and central metal ions on photosensitizing properties of dendrimer porphyrins.

A series of dendrimer porphyrins (G(n)DP(M); n = generation of dendrimer, n = 1-3; M = coordination metal, M = freebase, Zn, Pt) were prepared and their photosensitizing properties were compared. All G(n)DP(M) exhibited sharp absorption in organic solvents. However, the Soret absorptions of G(n)DP(M)(CO(2)H) in 10 mM phosphate buffer solution (pH = 7.

Effect of tight flavin mononucleotide wrapping and its binding affinity on carbon nanotube covalent reactivities.

The controlled functionalization of single-walled carbon nanotubes (SWNTs) is a key to using them in high-end applications. We show that nanotube reactivity after covalent diazonium modification is governed by a chirality-specific surfactant binding affinity to SWNTs. Both metallic and semiconducting SWNTs tightly organized by a helical flavin mononucleotide (FMN) assembly exhibit two hundred times slower reactivity toward 4-methoxy benzenediazonium (4-MBD) than those wrapped by sodium dodecyl sulfate and this reactivity enables chirality- and metallicity-specific behaviours to be probed, as confirmed by absorption, Raman, and photoluminescence (PL) spectroscopy.

Binding affinities and thermodynamics of noncovalent functionalization of carbon nanotubes with surfactants.

Binding affinity and thermodynamic understanding between a surfactant and carbon nanotube is essential to develop various carbon nanotube applications. Flavin mononucleotide-wrapped carbon nanotubes showing a large redshift in optical signature were utilized to determine the binding affinity and related thermodynamic parameters of 12 different nanotube chiralities upon exchange with other surfactants. Determined from the midpoint of sigmoidal transition, the equilibrium constant (K), which is inversely proportional to the binding affinity of the initial surfactant-carbon nanotube, provided quantitative binding strengths of surfactants as SDBS > SC ≈ FMN > SDS, irrespective of electronic types of SWNTs.

Handedness enantioselection of carbon nanotubes using helical assemblies of flavin mononucleotide.

In order to truly unlock advanced applications of single-walled carbon nanotubes (SWNTs), one needs to separate them according to both chirality and handedness. Here we show that the chiral D-ribityl phosphate chain of flavin mononucleotide (FMN) induces a right-handed helix that enriches the left-handed SWNTs for all suspended (n,m) species. Such enantioselectivity stems from the sp(3) hybridization of the N atom anchoring the sugar moiety to the flavin ring.

High-throughput graphene imaging on arbitrary substrates with widefield Raman spectroscopy.

Raman spectroscopy has been used extensively to study graphene and other sp(2)-bonded carbon materials, but the imaging capability of conventional micro-Raman spectroscopy is limited by the technique's low throughput. In this work, we apply an existing alternative imaging mode, widefield Raman imaging (WRI), to image and characterize graphene films on arbitrary substrates with high throughput. We show that WRI can be used to image graphene orders of magnitude faster than micro-Raman imaging allows, while still obtaining detailed spectral information about the sample.

Oxidation resistance of graphene-coated Cu and Cu/Ni alloy.

The ability to protect refined metals from reactive environments is vital to many industrial and academic applications. Current solutions, however, typically introduce several negative effects, including increased thickness and changes in the metal physical properties. In this paper, we demonstrate for the first time the ability of graphene films grown by chemical vapor deposition to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation.

Single-walled carbon nanotubes as excitonic optical wires.

Although metallic nanostructures are useful for nanoscale optics, all of their key optical properties are determined by their geometry. This makes it difficult to adjust these properties independently, and can restrict applications. Here we use the absolute intensity of Rayleigh scattering to show that single-walled carbon nanotubes can form ideal optical wires.

On-chip Rayleigh imaging and spectroscopy of carbon nanotubes.

We report a novel on-chip Rayleigh imaging technique using wide-field laser illumination to measure optical scattering from individual single-walled carbon nanotubes (SWNTs) on a solid substrate with high spatial and spectral resolution. This method in conjunction with calibrated AFM measurements accurately measures the resonance energies and diameters for a large number of SWNTs in parallel. We apply this technique for fast mapping of key SWNT parameters, including the electronic-types and chiral indices for individual SWNTs, position and frequency of chirality-changing events, and intertube interactions in both bundled and distant SWNTs.

Enrichment mechanism of semiconducting single-walled carbon nanotubes by surfactant amines.

Utilization of single-walled carbon nanotubes (SWNTs) in high-end applications hinges on separating metallic (met-) from semiconducting (sem-) SWNTs. Surfactant amines, like octadecylamine (ODA) have proven instrumental for the selective extraction of sem-SWNTs from tetrahydrofuran (THF) nanotube suspensions. The chemical shift differences along the tail of an asymmetric, diacetylenic surfactant amine were used to probe the molecular dynamics in the presence and absence of nanotubes via NMR.

Brightly fluorescent single-walled carbon nanotubes via an oxygen-excluding surfactant organization.

Attaining high photoluminescence quantum yields for single-walled carbon nanotubes (SWNTs) in order to broaden their optoelectronics and sensing applications has been a challenging task. Among various nonradiative pathways, sidewall chemisorption of oxygen provides a known defect for exciton quenching through nanotube hole doping. We found that an aliphatic (dodecyl) analog of flavin mononucleotide, FC12, leads to high dispersion of SWNTs, which tend to aggregate into bundles.