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Flavin with defined helical self-assembly helps to understand chemical designs for obtaining high-purity semiconducting (s)-single-walled carbon nanotubes (SWNT) in a diameter (dt)-selective manner for high-end applications. In this study, flavins containing 8, 12, 16, and 20 n-alkyl chains were synthesized, and their single/tandem effects on dt-selective s-SWNT dispersibility were investigated at isomolarity. Flavins with n-dodecyl and longer chain lengths (FC12, FC16, and FC20) act as good surfactants for stable SWNT dispersions whereas n-octyl flavin (FC8) exhibits poor dispersibility owing to the lack of SWNT buoyancy. When used with small-dt SWNT, FC8 displays chirality-selective SWNT dispersion. This behavior, along with various flavin helical motifs, prompts the development of criteria for 'side chain length (lS)' required for stable and dt-selective SWNT dispersion, which also explains lS-dependent dt-enrichment behavior. Moreover, SWNT dispersions with flavins with dodecyl and longer lS exhibit increased metallic (m)-SWNT, background absorption-contributing carbonaceous impurities (CIs) and preferential selectivity of s-SWNT with slightly larger dt. The increased CIs that affect the SWNT quantum yield were attributed to a solubility parameter. Furthermore, the effects of flavin lS, sonication bath temperature, centrifugal speed, and surfactant concentration on SWNT purity and s-/m-SWNT ratio were investigated. A tandem FC8/FC12 provides fine-tuning of dt-selective SWNT dispersion, wherein the FC8 ratio governs the tendency towards smaller dt. Kinetic and thermodynamic assemblies of tandem flavins result in different sorting behaviors in which wide dt-tunability was demonstrated using kinetic assembly. This study highlights the importance of appropriate side chain length and other extrinsic parameters to obtain dt-selective or high-purity s-SWNT. [ABSTRACT FROM AUTHOR]

Understanding the long-term stability of MoS2 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 MoS2 basal plane. In contrast to exposure to dry or humid N2 atmospheres, dry O2 treatment promotes the initial formation of line defects, mainly along the armchair (ac) direction, and humid O2 treatment further promotes ac line unzipping near edges. Further incubation of MoS2 for a few months in an O2 atmosphere results in massive zz-directional line unzipping. The photoluminescence and the strain-doping plot based on two prominent bands in the Raman spectrum show that, in contrast to dry-N2-treated MoS2, the O2-treated MoS2 primarily exhibits hole doping, whereas humid-O2-treated MoS2 mainly exists in a neutral charge state with tension. This study provides a guideline for MoS2 preservation and a further method for generating controlled defects. [ABSTRACT FROM AUTHOR]

Although successfully implemented for optoelectronic devices of two‐dimensional materials, deterministic transfer for thin single‐walled carbon nanotube (SWNT) film has not been realized. Herein, we report a transfer method of few hundreds nanometer‐thick SWNT film to a desired prepatterned substrate position with few micrometer precision. This method comprises poly(methyl methacrylate) (PMMA)‐coated SWNT film, creating surface anisotropy on both sides for SWNT film transfer, and two sets of translators manipulating the film to desired position and angle. Especially, adsorption and desorption of PMMA‐coated SWNT film by each translator were modulated by use of interfacial water which not only promotes PMMA side to the transient sample loader via water capillary and releases the final substrate with capillary assisted sliding. Successful transfer of thin SWNT film with few tens of micrometer precision was achieved and will be beneficial for the preparation of high‐end optoelectronic devices. [ABSTRACT FROM AUTHOR]

Although solvent governed stability, selection and optical behavior of single walled carbon nanotubes (SWNTs) brought about by using specialized surfactants have importance in relation to various optoelectronic and biological applications, their origins and solvatochromism have not been thoroughly explored owing to the lack of ideal surfactant dispersing SWNTs. We show that solvent driven SWNT selection and solvatochromism occurs in SWNTs wrapped by two flavin derivatives in solvents with dielectric constants (ε) ranging from 2.3 to 80.4. Flavin-SWNT nanocomposite dispersions exhibit near-armchair and chirality-specific enrichment in lower ε aromatic solvents, and those with broader chirality selectivity are formed in higher ε solvents. Those trends are also observed by controlling flavin concentration. Consideration of optical spectra provides relative quantum yields of flavin-SWNT in each solvent, showing toluene and p -xylene dispersions as best owing to highly individualized SWNT. The selectivities and relative stabilities of the flavin-SWNT nanoconjugates are associated with the solubility parameter (δ), which controls the respective morphology of the side chains and the relative Gibbs energies of the nanoconjugates relative to those of the free flavin and SWNTs. Differences between δ of side chains vs. the media results in extended and collapsed side chain conformations in respective lower and higher ε solvents, leading to diameters (d t) selection of SWNT owing to diameter modulation of the isoalloxazine assembly. In addition, with increasing ε optical transitions of flavin/SWNT exhibit lower bathochromic shifts owing to a passivating role played by the isoalloxazine that does not take place with other surfactants. The results suggest new guidelines for the design of good SWNT dispersions that take into consideration self-association of the surfactant, conformations of side chains and the nature of the solvent. [Display omitted] [ABSTRACT FROM AUTHOR]

Facile construction of graphene nanostructures are potentially important for fundamental studies and various applications owing to its transparency and mechanical strength. Here we found that focused laser irradiation of a graphene/entrapped water/hydrophobic substrate leads to vaporization of entrapped water and consequent formation of graphene nanostructures. Graphene mechanically exfoliated on a hydrophobicized Si substrate was served as a transformable and impermeable nanocontainer in which water anisotropically and slowly diffuses from the weak edges into the van der Waals (vdW)-coupled interstitial volume between graphene and the substrate. Time-lapsed Raman mappings show that water entrapment promotes progressive lowering of the frequencies of the G and 2D bands of graphene and exhibits slower diffusion owing to vdW decoupling of substrate-induced doping and biaxial strain of graphene with hydrophobic substrate. Moreover, vaporized entrapped water promotes nanostructures by graphene sliding and bulging actions. This methodology represents viable approach to produce nanostructures from two dimensional materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Sorting single‐walled carbon nanotubes (SWNTs) that are heterogeneous into homogeneous groups based on their electronic type, chirality, and handedness is crucial for optoelectronic and biological applications. To achieve this, researchers have utilized dispersants with different binding affinities to sort SWNTs according to their chiralities. This review article provides an overview of the methods developed for sorting SWNTs using dispersants, with a particular focus on the role played by dispersant binding affinities. The article is organized into six sections, including an introduction, a background on SWNTs and dispersant‐based individualization of SWNTs, information on dispersants and their binding affinities, separation methods for SWNTs based on controlling the dispersant binding affinity, parameters used to control dispersant binding affinity, and a conclusion. It is hoped that this review will enhance understanding of the intricate interactions between dispersants and SWNTs, leading to the development of new SWNT sorting methods for future applications. [ABSTRACT FROM AUTHOR]

Abstract High-end applications of single-walled carbon nanotube (SWNT) require detailed understanding of their binding affinity (K d) with surfactants. Here, we quantitatively determined the comprehensive K d and aggregation number (γ) of nine nonionic and anionic surfactants according to SWNT chirality. Photoluminescence (PL)-based titration using flavin mononucleotide (FMN)-SWNT complexes showing the largest redshifted optical transition enabled quantitative comparison of the surfactants and displayed distinct first and second regimes which correspond to partial and full replacements of FMN, respectively. Especially, the second transition exhibited sigmoidal PL change whose middle point denoted by the inverse of K d slightly differs from critical micelle concentration of surfactant alone, depending on its functional groups. Moreover, nonionic surfactants displayed larger K d and lower γ values than the anionic did. Specifically, K d values between Pluronic F108 and sodium dodecyl sulfonate differ by four orders of magnitude. Such differences were rationalized in terms of the occupied volume of the micelle based on the hydrodynamic volume and γ. During the replacement, K d and γ were affected by the degree of surfactant rearrangement induced by aging process, leading to more stable complex. Scaling the interactions between surfactant and SWNT provides useful guidelines to design novel SWNT sorting method using more than two surfactants. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Few atom thick, twisted bilayer graphene (tBLG) possesses a rotation angle (θ) dependent van Hove singularity (vHs). Fine-tuning vHs serves a potential method to enhance charge transfer (CT) in surface enhanced Raman spectroscopy. This study shows that tBLG having a specific θ promotes as high as a 1.7 times enhancement of the Raman signals of copper phthalocyanine (CuPc) as compared to that caused by single layer graphene (SLG). The results of a combination of reflection imaging spectroscopy and widefield Raman provide spatial and spectral information about both tBLG with θ ranging from 10.9 to 13.7° and the corresponding vHs. Comparison of Raman spectra of CuPc in presence and absence of tBLG demonstrates that a significant enhancement of certain CuPc vibrational modes occurs when the underlying tBLG possesses a θ = 12.2°, showing as high as 6.8 and 1.7 times enhancements of certain vibrational mode as compared to those of CuPc on bare and SLG substrates, respectively. Theoretical calculations indicate that a match between the energies of vHs of tBLG with those of frontier orbitals of CuPc facilitates CT from the distant SLG to CuPc. [Display omitted] [ABSTRACT FROM AUTHOR]

Despite the many advances that have been made in using anionic surfactants to disperse and sort single-walled carbon nanotubes (SWNTs) for optoelectronic applications, one-pot methods for deposition of SWNTs in a diameter (d t) and position controlled manner from as-dispersed sample are essential. Here, we designed and prepared flavin-containing self-assembled monolayers (flavin-SAMs) that can be used to assemble d t -selective individualized SWNT networks directly from SWNT dispersions by using the widely-used anionic surfactant. For a given glass substrate, the dimethallylsilane-linked azide, along with surface immobilization was employed to have Click reaction with terminal acetylene tethered to flavin group known to have strong affinity with SWNT. As demonstrated by atomic force microscopy and other methods, along successful assembly of individualized networks, the SWNTs are either fully or partially wrapped in a d t selective manner by isoalloxazine moieties tethered to the surface, displaying Langmuir isotherm adsorption behaviors in a dipping method dependent manner. The assembled SWNT network secures photoluminescence and electrical conductivity albeit its intimacy to underlying substrate and near monolayer coverage of SWNT network, respectively, and, furthermore, preferentially takes place on flavin-SAM over hydrophobic surface. Functional self-assembled monolayer captures single-walled carbon nanotube network with diameter selectivity from as-dispersed suspension. Image 1 [ABSTRACT FROM AUTHOR]

A commonly used phase rotation beamforming (PRBF) technique in medical ultrasound scanners requires four multipliers to realise phase rotation (PR) in addition to two lowpass filters for quadrature demodulation for each channel. A new scheme is presented to reduce the computational complexity of PRBF without sacrificing image quality that uses only 16 PRs located behind inter‐channel adders, regardless of the number of channels, each of which is dedicated for one of 16 quantised PR values using a step size of 2π/16. [ABSTRACT FROM AUTHOR]

In article number 1808731, Du Yeol Ryu, In Hwan Jung, Sung‐Yeon Jang, and co‐workers report parallel‐like ternary organic solar cells via simultaneous improvement in charge generation and transport. The synergetic effects by fullerene/nonfullerene binary acceptors optimize the morphology of ternary active blends. The judicious control of the effective donor:acceptor composition also minimizes the energy loss in ternary devices. [ABSTRACT FROM AUTHOR]

Ternary organic photovoltaic (OPV) devices with multiple light‐absorbing active materials have emerged as an efficient strategy for realizing further improvements in the power conversion efficiency (PCE) without building complex multijunction structures. However, the third component often acts as recombination centers and, hence, the optimization of ternary blend morphology poses a major challenge to improving the PCE of these devices. In this work, the performance of OPVs is enhanced through the morphological modification of nonfullerene acceptor (NFA)‐containing binary active layers. This modification is achieved by incorporating fullerenes into the layers. The uniformly dispersed fullerenes are sufficiently continuous and successfully mediate the ordering of NFA without charge or energy transfer. Owing to the simultaneous improvement in the charge generation and extraction, the PCE (12.1%) of these parallel‐linked ternary devices is considerably higher than those of the corresponding binary devices (9.95% and 7.78%). Moreover, the additional energy loss of the ternary device is minimized, compared with that of the NFA‐based binary device, due to the judicious control of the effective donor:acceptor composition of the ternary blends. A high‐efficiency parallel‐like ternary organic photovoltaic device is developed through synergetic effects among a wide‐bandgap donor polymer, a narrow‐bandgap nonfullerene acceptor, and fullerene acceptors. Morphological optimization of the ternary devices via the incorporation of fullerenes yields simultaneous enhancement of the charge generation and extraction. An efficiency of 12.1% at an energy loss of 0.61 eV is realized. [ABSTRACT FROM AUTHOR]