Graphene performs the role of an electron donor in covalently interfaced porphyrin-boron azadipyrromethene dyads and manages photoinduced charge-transfer processes

Herein, we introduced the versatility of free-base and zinc-metallated porphyrin (H₂P and ZnP, respectively) to combine with boron azadipyrromethene (azaBDP) NIR absorbing species, for extending their photophysical interest and covalently anchored onto graphene. In particular, the covalent functionalization of graphene with those H₂P-azaBDP and ZnP-azaBDP dyads ensured an invariable structure, in which both chromophores and graphene are in intimate contact, free of aggregations and impurities. Both H₂P-azaBDP and ZnP-azaBDP dyads were found to perform energy transfer processes between the chromophores, however, only ZnP-azaBDP confirmed additional charge separation between the chromophores yielding the ZnP˙⁺-azaBDP˙^- charge-separated state. On the other hand, graphene in (H₂P-azaBDP)-graphene and (ZnP-azaBDP)-graphene hybrids was found to act as an electron donor, yielding (H₂P-azaBDP˙^-)-graphene˙⁺ and (ZnP-azaBDP˙^-)-graphene˙⁺ charge-separated states at an ultrafast timescale. The creation of such donor-acceptor systems, featuring graphene as an electron donor and Vis-to-NIR electron-acceptor dyads, expands their utility when considered in optoelectronic applications.

Laparoscopic and open surgery in patients with transverse colon cancer: short-term and oncological outcomes

BACKGROUND

Studies evaluating the outcomes after laparoscopic resections of transverse colon cancers are scant. This manuscript aimed to compare surgical and oncological outcomes after laparoscopic (Lap) and open procedures for transverse colon carcinomas.

METHODS

All consecutive patients who underwent resection for a cancer located in the transverse colon between 2003 and 2019 were reviewed. Patients were categorized according to the surgical approach (Lap versus open) and groups were compared. Outcome measures were the short-term results, complications and functional recovery; moreover, recurrence-free survival (RFS) and overall survival (OS) rates were compared overall and after propensity score matching (PSM) based on age, sex, ASA classification, BMI, carcinoembryonic antigen (CEA) level, use of postoperative chemotherapy, location of tumour, stage and grading, operation time, blood loss and complications.

RESULTS

Of 248 transverse resections reviewed, 146 (81 Lap and 65 open) were selected for data analysis. Blood loss, fluid intake and the incidence of wound infection were significantly lower and the hospital stay was significantly shorter in the Lap group (P < 0.001). The operation time and incidence of complications (Clavien-Dindo classification grade 3 or above) did not differ significantly between the two groups. Mean follow-up was of 75.4 months in the Lap group and 78.6 months in the open group. Regression analyses showed that OS was associated with the postoperative carcinoembryonic antigen (CEA) level (hazard ratio 1.18 (95 per cent c.i. 1.10 to 1.27); P < 0.001), BMI (hazard ratio 0.81 (95 per cent c.i. 0.68 to 0.96); P = 0.017), operation time (hazard ratio 0.99 (95 per cent c.i. 0.97 to 1.00; P = 0.010), and postoperative chemotherapy (hazard ratio 0.27 (95 per cent c.i. 0.08 to 0.96); P = 0.042), while RFS was associated with the postoperative CEA level (hazard ratio 1.13 (95 per cent c.i. 1.07 to 1.20); P < 0.001). PSM selected 42 patients for data comparison of long-term results, and showed no significant differences between groups (RFS: P = 0.530; OS: P = 0.561).

CONCLUSION

Lap and open resections for transverse colon cancer provided similar outcomes in terms of severe post-operative complication and long-term results.

Microscopic Mechanism of Van der Waals Heteroepitaxy in the Formation of MoS2/hBN Vertical Heterostructures

Recent studies have revealed that van der Waals (vdW) heteroepitaxial growth of 2D materials on crystalline substrates, such as hexagonal boron nitride (hBN), leads to the formation of self-aligned grains, which results in defect-free stitching between the grains. However, how the weak vdW interaction causes a strong limitation on the crystal orientation of grains is still not understood yet. In this work, we have focused on investigating the microscopic mechanism of the self-alignment of MoS₂ grains in vdW epitaxial growth on hBN. Using the density functional theory and the Lennard-Jones potential, we found that the interlayer energy between MoS₂ and hBN strongly depends on the size and crystal orientation of MoS₂. We also found that, when the size of MoS₂ is several tens of nanometers, the rotational energy barrier can exceed ∼1 eV, which should suppress rotation to align the crystal orientation of MoS₂ even at the growth temperature.

Diagnosing heart failure from chest X-ray images using deep learning

 

The development of deep learning technology has enabled machines to achieve high-level accuracy in interpreting medical images. While many previous studies have examined the detection of pulmonary nodules and cardiomegaly in chest X-rays using deep learning, the application of this technology to heart failure remains rare. In this study, we investigated the performance of a deep learning algorithm in terms of diagnosing heart failure using images obtained from chest X-rays. We used 952 chest X-ray images from a labeled database published by the National Institutes of Health. Two cardiologists respectively verified and relabeled these images, for a total of 260 “normal” and 378 “heart failure” images, and the remainder were discarded because they had been incorrectly labeled. In this study “heart failure” was defined as “cardiomegaly or congestion”, in a chest X-ray with cardiothoracic ratio (CTR) over 50% or radiographic presence of pulmonary edema. To enable the machine to extract a sufficient number of features from the images, we used the general machine learning approach called data augmentation and transfer learning. Owing mostly to this technique and the adequate relabeling process, we established a model to detect heart failure in chest X-ray by applying deep learning, and obtained an accuracy of 82%. Sensitivity and specificity to heart failure were 75% and 94.4%, respectively. Furthermore, heatmap imaging allowed us to visualize decisions made by the machine. The figure shows randomly selected examples of the prediction probabilities and heatmaps of the chest X-rays from the dataset. The original image is on the left and its heatmap is on the right, with its prediction probability written below. The red areas on the heatmaps show important regions, according to which the machine determined the classification. While some images with ambiguous radiolucency such as (e) and (f) were prone to be misdiagnosed by this model, most of the images like (a)–(d) were diagnosed correctly. Deep learning can thus help support the diagnosis of heart failure using chest X-ray images.

Heatmaps and probabilities of prediction

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): JSPS KAKENHI

Efficacy of fractional flow reserve-guided percutaneous coronary intervention for patients with angina pectoris: a network meta-analysis

Background

Evaluation of hemodynamic parameters, such as fractional flow reserve (FFR), is recommended before percutaneous coronary intervention (PCI) for patients with angina pectoris (AP). However, the advantage of FFR-guided PCI has not been fully established. A network meta-analysis (NMA) synthesizes the results of studies on multiple competing interventions. Moreover, no NMA has evaluated randomized controlled trials for AP to compare FFR-guided PCI and other treatments. To clarify whether FFR-guided PCI improves the prognosis in patients with AP, we performed this study.

Methods

Multiple databases were searched for studies published from 2000 to 2018. The search terms were based on Medical Subject Headings and keywords including “angioplasty”, “coronary artery bypass”, “percutaneous coronary intervention”, “coronary disease”, and “randomized controlled trial”. And an NMA was performed to compare outcomes of FFR-guided PCI, non-FFR-guided PCI, coronary artery bypass grafting (CABG), and medical treatment (MT) for AP based on estimated odds ratios (ORs). The primary endpoint was all-cause mortality. The secondary endpoints were the occurrence of MI. Treatments were ranked by the surface under the cumulative ranking curve.

Results

The study included 18,093 patients from 15 randomized controlled trials. No evidence of inconsistency was observed among the studies. The NMA showed that the all-cause mortality of FFR-guided PCI was not significantly different from that of the other treatment groups (CABG: OR, 1.1; 95% confidence interval [CI], 0.67–1.7; non-FFR-guided PCI: OR, 0.85; 95% CI, 0.53–1.4; and MT: OR, 0.83; 95% CI, 0.52–1.3). The NMA for myocardial infarction, which included 13,548 patients from 11 randomized controlled trials, showed that FFR-guided PCI tended to reduce the occurrence of myocardial infarction compared with MT (OR, 0.60; 95% CI, 0.36–1.0). According to the surface under the cumulative ranking curve, CABG was the best treatment, followed by FFR-guided PCI, non-FFR-guided PCI, and MT.

Conclusions

FFR-guided PCI for AP showed no significant prognostic improvement compared with non-FFR-guided PCI, CABG, and MT. CABG was the best treatment for AP, followed by FFR-guided PCI, non-FFR-guided PCI, and MT.

Network plot and interval plot

Funding Acknowledgement

Type of funding source: None

Impact of sarcopenia on glycemic control and atherosclerosis in Japanese patients with type 2 diabetes: Cross-sectional study using outpatient clinical data

AIM

This study examined the association among sarcopenia and various surrogate markers of atherosclerosis in Japanese patients with type 2 diabetes (T2D).

METHODS

Patients with T2D who visited the outpatient clinic comprised the study's participants. Handgrip strength (Grip), usual gait speed (GS) and skeletal muscle index, in addition to glycated hemoglobin, ankle-brachial index (ABI) and intima-media thickening (IMT), were measured in 1030 patients for the diagnosis of sarcopenia. From these results were obtained three categorical data (without sarcopenia [NS], sarcopenia with two factors [Sw2], sarcopenia with three factors [Sw3]), and continuous data for atherosclerosis.

RESULTS

Glycated hemoglobin was significantly high among patients in the Sw3 category, as well as among all patients with sarcopenia, compared with those in the NS group, after adjustment was made for age, gender, duration of diabetes, and medications for hypertension and dyslipidemia. ABI was significantly low among the Sw2 and Sw3 patients, as well as among all patients with sarcopenia, but mean and maximum IMT were not when compared with the NS category of patients after the adjustment described above. However, skeletal muscle index, Grip and GS were positively associated with ABI after the adjustment. Grip and GS were negatively associated with maximum IMT after the adjustment.

CONCLUSIONS

These results imply that measurements to diagnose sarcopenia could play an important role for early detection of preclinical atherosclerosis, specifically peripheral artery disease, among Japanese patients with T2D. Geriatr Gerontol Int 2020; 20: 1196-1201.

Efficient growth and characterization of one-dimensional transition metal tellurides inside carbon nanotubes

Atomically thin one-dimensional (1D) van der Waals wires of transition metal monochalocogenides (TMMs) have been anticipated as promising building blocks for integrated nanoelectronics. While reliable production of TMM nanowires has eluded scientists over the past few decades, we finally demonstrated a bottom-up fabrication of MoTe nanowires inside carbon nanotubes (CNTs). Still, the current synthesis method is based on vacuum annealing of reactive MoTe₂, and limits access to a variety of TMMs. Here we report an expanded framework for high-yield synthesis of the 1D tellurides including WTe, an previously unknown family of TMMs. Experimental and theoretical analyses revealed that the choice of suitable metal oxides as a precursor provides a useful yield for their characterization. These TMM nanowires exhibit a significant optical absorption in the visible-light region. More important, electronic properties of CNTs can be tuned by encapsulating different TMM nanowires.

Significance of body mass index for diagnosing sarcopenia is equivalent to slow gait speed in Japanese individuals with type 2 diabetes: Cross-sectional study using outpatient clinical data

Aims/Introduction

This study examined the association between body mass index (BMI) and the risk of sarcopenia in Japanese type 2 diabetes patients.

Materials and Methods

Patients with type 2 diabetes who visited an outpatient clinic comprised the study’s participants. Sarcopenia was defined using the definition of the Asian Working Group for Sarcopenia 2014. The area under the curve was examined for the presence of sarcopenia based on the receiver operating characteristic curve of BMI.

Results

Among 1,137 patients, 210 were diagnosed with low grip strength, 78 with slow gait speed, 444 with low muscle mass and 142 with sarcopenia. The optimal cut‐off point of BMI level for risk of sarcopenia was 24.4 kg/m² (area under the curve 0.729, 95% confidence interval 0.688–0.770, sensitivity 0.587, specificity 0.789). Furthermore, the receiver operating characteristic curve of BMI for sarcopenia did not significantly differ (P = 0.09) from that of gait speed, an established marker of sarcopenia. In both the male and female groups, there was no difference between the receiver operating characteristic curves of BMI and gait speed for sarcopenia. (P = 0.23 and P = 0.40, respectively).

Conclusions

These results suggest that a BMI <24 kg/m² among Japanese patients with type 2 diabetes could increase their risk of sarcopenia, the extent of which is equivalent to the risk for sarcopenia from slow gait speed in this study. Further prospective investigation, however, is required.

Concise, Single-Step Synthesis of Sulfur-Enriched Graphene: Immobilization of Molecular Clusters and Battery Applications

The concise synthesis of sulfur-enriched graphene for battery applications is reported. The direct treatment of graphene oxide (GO) with the commercially available Lawesson's reagent produced sulfur-enriched-reduced GO (S-rGO). Various techniques, such as X-ray photoelectron spectroscopy (XPS), confirmed the occurrence of both sulfur functionalization and GO reduction. Also fabricated was a nanohybrid material by using S-rGO with polyoxometalate (POM) as a cathode-active material for a rechargeable battery. Transmission electron microscopy (TEM) revealed that POM clusters were individually immobilized on the S-rGO surface. This battery, based on a POM/S-rGO complex, exhibited greater cycling stability for the charge-discharge process than a battery with nanohybrid materials positioned between the POM and nonenriched rGO. These results demonstrate that the use of sulfur-containing groups on a graphene surface can be extended to applications such as the catalysis of electrochemical reactions and electrodes in other battery systems.

Turning On the Near-Infrared Photoluminescence of Erbium Metallofullerenes by Covalent Modification

The photoluminescence of lanthanide ions inside fullerenes is usually very weak due to the quenching effect of the fullerene cage. In the case of Er@C₈₂, the near-infrared emission from the Er³⁺ ion is completely quenched by the C₈₂ fullerene cage. It remains challenging to turn on the photoluminescence of Er@C₈₂ and other monometallofullerenes. In this work, we adopt a covalent modification strategy to alter the electronic structure of the fullerene cage for sensitizing the near-infrared emission of Er³⁺ ions in metallofullerenes Er@C_2n (2n = 72, 76, and 82). After covalent modification with trifluoromethyl, phenyl, or dichlorophenyl groups, the erbium metallofullerenes exhibit photoluminescence at 1.5 μm, which is the characteristic emission of the Er³⁺ ion. Particularly, the otherwise nonfluorescent metallofullerene Er@C₈₂ is transformed into fluorescent derivatives by using this strategy. The photoluminescence from the Er³⁺ ion is ascribed to energy transfer from the fullerene cage to the Er³⁺ ion. According to theoretical calculations, the sensitization of the Er³⁺ ion by the fullerene cage is associated with the large HOMO-LUMO gap and the closed-shell electronic structure of the metallofullerene derivatives. This work provides useful guidance for the design and synthesis of new fluorescent metallofullerenes.

A novel surgical strategy for the resection of duodenal gastrointestinal stromal tumours located close to the duodenal ampulla: a case report

Although the optimal surgical procedure for the resection of duodenal gastrointestinal stromal tumours has not yet been characterised due to the low prevalence of these tumours and the anatomical complexity of the duodenopancreatic region, difficult surgical procedures such as pancreaticoduodenectomy are often proposed for stromal tumours located in the second portion of the duodenum. Our case report highlights a novel surgical strategy that can be implemented as an alternative to pancreaticoduodenectomy for such tumours close to the duodenal ampulla. A 70-year-old man incidentally diagnosed with a stromal tumour close to the duodenal ampulla in the second portion of the duodenum underwent local resection guided by an endoscopic nasobiliary drainage tube with primary closure. This tube was converted to a percutaneous trans-small intestinal biliary drainage tube during the procedure to prevent biliary leakage biliary stasis due to swelling of the duodenal ampulla. He also underwent a simple distal gastrectomy with Roux-en-Y reconstruction. This resulted in successful R0 resection. There were no procedure-related complications or post-surgery weight changes. Our simple novel surgical strategy may therefore be useful for avoiding pancreaticoduodenectomy and maintaining quality of life in patients with stromal tumours close to the duodenal ampulla.

Isolation of Single-Wired Transition-Metal Monochalcogenides by Carbon Nanotubes

The successful isolation of single layers from two-dimensional (2D) van der Waals (vdW)-layered materials has opened new frontiers in condensed matter physics and materials science. Their discovery and unique properties laid the foundation for exploring 1D counterparts. However, the isolation of 1D vdW-wired materials has thus far remained a challenge, and effective techniques are demanded. Here we report the facile synthesis of isolated transition-metal monochalcogenide MoTe nanowires by using carbon nanotubes (CNTs) as molds. Individual nanowires are perfectly separated by CNTs with a minimal interaction, enabling detailed characterization of the single wires. Transmission electron microscopy revealed unusual torsional motion of MoTe nanowires inside CNTs. Confinement of 1D vdW-wired materials to the nanotest tubes might open up possibilities for exploring unprecedented properties of the nanowires and their potential applications such as electromechanical switching devices.

Rock-salt and helix structures of silver iodides under ambient conditions

Many different phase structures have been discovered for silver iodides. The β and γ phases were found to be the most common ones at ambient conditions, while the rock-salt phase was found to be stable under pressures between 400 MPa and 11.3 GPa. Recently, the α phase was demonstrated to be stable under ambient conditions when the particle sizes were reduced to below 10 nm. However, no other phase has been reported to be stable for silver iodides under ambient conditions. Rock-salt and helix structures have been found to be stable under ambient conditions in this study. The structures have been characterized by elemental mapping, Raman scattering, and high-resolution transmission electron microscopy. The stabilities of these structures were also confirmed by molecular dynamics and density functional theory.

Excited-State Charge Transfer in Covalently Functionalized MoS2 with a Zinc Phthalocyanine Donor-Acceptor Hybrid

The functionalization of MoS₂ is of paramount importance for tailoring its properties towards optoelectronic applications and unlocking its full potential. Zinc phthalocyanine (ZnPc) carrying an 1,2-dithiolane oxide linker was used to functionalize MoS₂ at defect sites located at the edges. The structure of ZnPc-MoS₂ was fully assessed by complementary spectroscopic, thermal, and microscopy imaging techniques. An energy-level diagram visualizing different photochemical events in ZnPc-MoS₂ was established and revealed a bidirectional electron transfer leading to a charge separated state ZnPc^.+ -MoS₂ ^.- . Markedly, evidence of the charge transfer in the hybrid material was demonstrated using fluorescence spectroelectrochemistry. Systematic studies performed by femtosecond transient absorption revealed the involvement of excitons generated in MoS₂ in promoting the charge transfer, while the transfer was also possible when ZnPc was excited, signifying their potential in light-energy-harvesting devices.

Blister-based-laser-induced-forward-transfer: a non-contact, dry laser-based transfer method for nanomaterials

We show that blister-based-laser-induced forward-transfer can be used to cleanly desorb and transfer nano- and micro-scale particles between substrates without exposing the particles to the laser radiation or to any chemical treatment that could damage the intrinsic electronic and optical properties of the materials. The technique uses laser pulses to induce the rapid formation of a blister on a thin metal layer deposited on glass via ablation at the metal/glass interface. Femtosecond laser pulses are advantageous for forming beams of molecules or small nanoparticles with well-defined velocity and narrow angular distributions. Both fs and ns laser pulses can be used to cleanly transfer larger nanoparticles including relatively fragile monolayer 2D transition metal dichalcogenide crystals and for direct transfer of nanoparticles from chemical vapour deposition growth substrates, although the mechanisms for inducing blister formation are different.

Isolation and structure determination of missing fullerenes Gd@C74(CF3) n through in situ trifluoromethylation

Our trifluoromethyl functionalization method enables the dissolution and isolation of missing metallofullerenes of Gd@C74(CF3) n . After multi-stage high-performance liquid chromatography purification, Gd@C74(CF3)3 and two regioisomers of Gd@C74(CF3) are isolated. X-ray crystallographic analysis reveals that all of the isolated metallofullerenes react with CF3 groups on pentagons of the D 3 h-symmetry C74 cages. Highest occupied molecular orbital-lowest unoccupied molecular orbital gaps of these trifluoromethylated derivatives, estimated by absorption spectra, are in the range 0.71-1.06 eV, consistent with density functional calculations.

Determining addition pathways and stable isomers for CF3 functionalization of endohedral Gd@C60

Using density functional theory approaches, we follow the sequential addition of CF3 functional groups to the surface of the metallic endofullerene species Gd@C60. The presence of gadolinium in the interior of the cage strongly influences the addition sequence. The calculations are able to successfully identify end points in the addition sequence at Gd@C60(CF3) n , n = 3 and two isomers at n = 5, in predictive agreement with experiment. Inverting the algorithm to determine the most labile groups also identifies the correct positively charged Gd@ C 60 ( C F 3 ) 4 + isomer, as confirmed by experimental mass spectra. The importance of surface mobility, notably at later stage addition, is discussed.

Crystalline functionalized endohedral C60 metallofullerides

Endohedral metallofullerenes have been extensively studied since the first experimental observation of La@C60 in a laser-vaporized supersonic beam in 1985. However, most of these studies have focused on metallofullerenes larger than C60 such as (metal)@C82, and there are no reported purified C60-based monomeric metallofullerenes, except for [Li@C60]+(SbCl6)- salt. Pure (metal)@C60 compounds have not been obtained because of their extremely high chemical reactivity. One route to their stabilization is through chemical functionalization. Here we report the isolation, structural determination and electromagnetic properties of functionalized crystalline C60-based metallofullerenes Gd@C60(CF3)5 and La@C60(CF3)5. Synchrotron X-ray single-crystal diffraction reveals that La and Gd atoms are indeed encapsulated in the Ih-C60 fullerene. The HOMO-LUMO gaps of Gd@C60 and La@C60 are significantly widened by an order of magnitude with addition of CF3 groups. Magnetic measurements show the presence of a weak antiferromagnetic coupling in Gd@C60(CF3)3 crystals at low temperatures.

One-dimensional hydrogen bonding networks of bis-hydroxylated diamantane formed inside double-walled carbon nanotubes

1,6-Bis(hydroxymethyl)diamantane spontaneously aligns inside double-walled carbon nanotubes. The encapsulated molecules form a one-dimensional network within the double-walled carbon nanotubes through hydrogen bonding that leads to a highly dense filling as compared to unfunctionalized diamantane. Improving the encapsulation yields of precursors via functionalization is crucial to prepare novel one-dimensional materials.

Direct and Indirect Interlayer Excitons in a van der Waals Heterostructure of hBN/WS2/MoS2/hBN

A van der Waals (vdW) heterostructure composed of multivalley systems can show excitonic optical responses from interlayer excitons that originate from several valleys in the electronic structure. In this work, we studied photoluminescence (PL) from a vdW heterostructure, WS₂/MoS₂, deposited on hexagonal boron nitride (hBN) flakes. PL spectra from the fabricated heterostructures observed at room temperature show PL peaks at 1.3-1.7 eV, which are absent in the PL spectra of WS₂ or MoS₂ monolayers alone. The low-energy PL peaks we observed can be decomposed into three distinct peaks. Through detailed PL measurements and theoretical analysis, including PL imaging, time-resolved PL measurements, and calculation of dielectric function ε(ω) by solving the Bethe-Salpeter equation with G₀ W₀, we concluded that the three PL peaks originate from direct K-K interlayer excitons, indirect Q-Γ interlayer excitons, and indirect K-Γ interlayer excitons.

Correction: Band gap modification and photoluminescence enhancement of graphene nanoribbon filled single-walled carbon nanotubes

Correction for 'Band gap modification and photoluminescence enhancement of graphene nanoribbon filled single-walled carbon nanotubes' by A. I. Chernov et al., Nanoscale, 2018, DOI: 10.1039/c7nr07054c.

Band gap modification and photoluminescence enhancement of graphene nanoribbon filled single-walled carbon nanotubes

Molecule encapsulation inside the single-walled carbon nanotube (SWCNT) core has been demonstrated to be a successful route for the modification of nanotube properties. SWCNT diameter-dependent filling results in band gap modification together with the enhancement of photoluminescence quantum yield. However, the interaction between the inner structure and the outer shell is complex. It depends on the orientation of the molecules inside, the geometry of the host nanotube and on several other mechanisms determining the resulting properties of the hybrid nanosystem. In this work we study the influence of encapsulated graphene nanoribbons on the optical properties of the host single-walled carbon nanotubes. The interplay of strain and dielectric screening caused by the internal environment of the nanotube affects its band gap. The photoluminescence of the filled nanotubes becomes enhanced when the graphene nanoribbons are polymerized inside the SWCNTs at low temperatures. We show a gradual photoluminescence quenching together with a selective signal enhancement for exact nanotube geometries, specifically (14,6) and (13,8) species. A precise adjustment of the optical properties and an enhancement of the photoluminescence quantum yield upon filling for nanotubes with specific diameters were assigned to optimal organization of the inner structures.

Band-Gap Engineering of Graphene Heterostructures by Substitutional Doping with B3 N3

We investigated the energetics and electronic structure of B₃ N₃ -doped graphene employing density functional theory calculations with the generalized gradient approximation. Our calculations reveal that all of the B₃ N₃ -doped graphene structures are semiconducting, irrespective of the periodicity of the B₃ N₃ embedded into the graphene network. This is in contrast to graphene nanomeshes, which are either semiconductors or metals depending on the mesh arrangement. In B₃ N₃ -doped graphene, the effective masses for both electrons and holes are small. The band gap in the B₃ N₃ -doped graphene networks and the total energy of the B₃ N₃ -doped graphene are inversely proportional to the B₃ N₃ spacing. Furthermore, both properties depend on whether or not the graphene region possesses a Clar structure. In particular, the sheets with a Clar structure exhibit a wider band gap and a slightly lower total energy than those without a Clar structure.

Capturing the Unconventional Metallofullerene M@C66 by Trifluoromethylation: A Theoretical Study

The endohedral metallofullerenes M@C₆₆ (M=rare-earth metal) have a unique structure that violates the well-known "isolated pentagon rule" of fullerene science. Although the synthesis of M@C₆₆ has been achieved by using the arc discharge method, the solvent extraction and purification of M@C₆₆ remain challenges because of their radical character and extremely high reactivity. In this paper, the possibility of capturing these missing metallofullerenes by exohedral functionalization of the C₆₆ cage is demonstrated theoretically. Stable trifluoromethylated derivatives of Y@C₆₆ are revealed by density functional theory calculations. Mono- or poly-trifluoromethylation of Y@C₆₆ results in a closed-shell electronic configuration and a large band gap. Thus Y@C₆₆ can be greatly stabilized through trifluoromethylation. The trifluoromethyl group prefers to be attached to the fused pentagon region to relieve local steric strain. The mechanism of isomerization of Y@C₆₆ (CF₃ )₃ is also investigated and it is found that the attached trifluoromethyl group can migrate from a carbon atom to another via a transition state.

Modulation of thermal and thermoelectric transport in individual carbon nanotubes by fullerene encapsulation

The potential impact of encapsulated molecules on the thermal properties of individual carbon nanotubes (CNTs) has been an important open question since the first reports of the strong modulation of electrical properties in 2002. However, thermal property modulation has not been demonstrated experimentally because of the difficulty of realizing CNT-encapsulated molecules as part of thermal transport microstructures. Here we develop a nanofabrication strategy that enables measurement of the impact of encapsulation on the thermal conductivity (κ) and thermopower (S) of single CNT bundles that encapsulate C ₆₀, Gd@C ₈₂ and Er ₂@C ₈₂. Encapsulation causes 35-55% suppression in κ and approximately 40% enhancement in S compared with the properties of hollow CNTs at room temperature. Measurements of temperature dependence from 40 to 320 K demonstrate a shift of the peak in the κ to lower temperature. The data are consistent with simulations accounting for the interaction between CNTs and encapsulated fullerenes.

Non-Chromatographic Purification of Endohedral Metallofullerenes

The purification of endohedral metallofullerenes by high performance liquid chromatography is very time-consuming and expensive. A number of rapid and inexpensive non-chromatographic methods have thus been developed for large-scale purification of metallofullerenes. In this review, we summarize recent advances in non-chromatographic purification methods of metallofullerenes. Lewis acid-based complexation is one of the most efficient and powerful methods for separation of metallofullerenes from empty fullerenes. The first oxidation potential of metallofullerenes is a critical factor that affects the separation efficiency of the Lewis acid-based method. Supramolecular methods are effective for separation of fullerenes and metallofullerenes that are different in size and shape. Chemical/electrochemical reduction and exohedral functionalization are also utilized to separate and purify metallofullerenes on a large scale.

Observation of biexcitonic emission at extremely low power density in tungsten disulfide atomic layers grown on hexagonal boron nitride

Monolayer transition metal dichalcogenides (TMDCs) including WS₂, MoS₂, WSe₂ and WS₂, are two-dimensional semiconductors with direct bandgap, providing an excellent field for exploration of many-body effects in 2-dimensions (2D) through optical measurements. To fully explore the physics of TMDCs, the prerequisite is preparation of high-quality samples to observe their intrinsic properties. For this purpose, we have focused on high-quality samples, WS₂ grown by chemical vapor deposition method with hexagonal boron nitride as substrates. We observed sharp exciton emissions, whose linewidth is typically 22~23 meV, in photoluminescence spectra at room temperature, which result clearly demonstrates the high-quality of the current samples. We found that biexcitons formed with extremely low-excitation power (240 W/cm²) at 80 K, and this should originate from the minimal amount of localization centers in the present high-quality samples. The results clearly demonstrate that the present samples can provide an excellent field, where one can observe various excitonic states, offering possibility of exploring optical physics in 2D and finding new condensates.

Development of Gd3N@C80 encapsulated redox nanoparticles for high-performance magnetic resonance imaging

As novel magnetic resonance imaging (MRI) contrast agent, gadofullerene encapsulated redox nanoparticles (Gd₃NPs) were prepared by encapsulation of Gd₃N@C₈₀ in the core of core-shell-type polymer micelles composed of original polyamine with a reactive oxygen species (ROS)-scavenging ability. Because Gd₃NPs possess biocompatible PEG shell with a smaller size (ca. 50 nm), they had high colloidal stability in a physiological environment, and showed low cytotoxicity. Specific accumulation of Gd₃NPs in a tumor was confirmed in tumor-bearing mice after systemic administration. The tumor/muscle (T/M) ratio of the Gd ion reached five at 7.5 h after the administration. T₁-weighted MRI signal enhancement of the T/M ratio increased by 8% at 6 h postinjection of Gd₃NPs (Gd dose:14.35 μmol/kg). Although Gd₃NPs showed a tendency for extended blood circulation, they did not have severe adverse effects, probably due to the confinement of Gd in a hydrophobic fullerene in addition to the ROS-scavenging capacity of these nanoparticles. In sharp contrast, systemic administration of Gd-chelate nanoparticles (GdCNPs) to mice disrupts liver function, increases leukocyte counts, and destroys spleen and skin tissues. Leaking of Gd ions from GdCNPs may cause such adverse effects. Based on these results, we expect that Gd₃NPs is high-performance MRI contrast agents for tumor diagnosis.

Another big discovery-metallofullerenes

Several days after the first experimental observation of the 'magic number' soccerball-shaped C60 in a laser-vaporized cluster beam mass spectrum by Kroto and co-workers (Heath et al 1985 J. Am. Chem. Soc. 107, 7779-7780. (doi:10.1021/ja00311a102)) they also found a magic number feature owing to La@C60 in a mass spectrum prepared by laser vaporization of a LaCl3-impregnated graphite rod. With the advent of macroscopic synthesis and the following successful separation and purification of metallofullerenes, both experimental and theoretical studies of metallofullerenes have developed quite rapidly to date so as to elucidate their structural, electronic, magnetic and transport properties. Furthermore, a bottom-up closed network growth mechanism has experimentally been shown to play a crucial role in generating various types of metallofullerenes.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'.

Elastic and anelastic relaxation behaviour of perovskite multiferroics II: PbZr0.53Ti0.47O3 (PZT)-PbFe0.5Ta0.5O3 (PFT)

Elastic and anelastic properties of ceramic samples of multiferroic perovskites with nominal compositions across the binary join PbZr_0.53Ti_0.47O₃-PbFe_0.5Ta_0.5O₃ (PZT-PFT) have been assembled to create a binary phase diagram and to address the role of strain relaxation associated with their phase transitions. Structural relationships are similar to those observed previously for PbZr_0.53Ti_0.47O₃-PbFe_0.5Nb_0.5O₃ (PZT-PFN), but the magnitude of the tetragonal shear strain associated with the ferroelectric order parameter appears to be much smaller. This leads to relaxor character for the development of ferroelectric properties in the end member PbFe_0.5Ta_0.5O₃. As for PZT-PFN, there appear to be two discrete instabilities rather than simply a reorientation of the electric dipole in the transition sequence cubic-tetragonal-monoclinic, and the second transition has characteristics typical of an improper ferroelastic. At intermediate compositions, the ferroelastic microstructure has strain heterogeneities on a mesoscopic length scale and, probably, also on a microscopic scale. This results in a wide anelastic freezing interval for strain-related defects rather than the freezing of discrete twin walls that would occur in a conventional ferroelastic material. In PFT, however, the acoustic loss behaviour more nearly resembles that due to freezing of conventional ferroelastic twin walls. Precursor softening of the shear modulus in both PFT and PFN does not fit with a Vogel-Fulcher description, but in PFT there is a temperature interval where the softening conforms to a power law suggestive of the role of fluctuations of the order parameter with dispersion along one branch of the Brillouin zone. Magnetic ordering appears to be coupled only weakly with a volume strain and not with shear strain but, as with multiferroic PZT-PFN perovskites, takes place within crystals which have significant strain heterogeneities on different length scales.

Near-Infrared Photoluminescence Properties of Endohedral Mono- and Dithulium Metallofullerenes

The optical properties of endohedral metallofullerene molecules can be tuned by changing the fullerene size as well as the number of metal atoms inside the fullerene cages. In this work we have synthesized and isolated a series of mono- and dithulium metallofullerenes, including Tm@C82 (isomers I, II, III, IV), Tm@C88 (I-IV), Tm2@C82 (I-III), and (Tm2C2)@C82 (I-III). Near-infrared photoluminescence is observed from the thulium metallofullerenes. By changing the number of Tm ion in the fullerene cage, we have found that one can vary and tune the photoluminescence from 1200 to 1300-2000 nm observed for Tm(2+) (4f(13)) in Tm@C88 and Tm(3+) (4f(12)) in (Tm2C2)@C82, respectively. The photoluminescence intensity depends sensitively on the fullerene cages. (Tm2C2)@C82 (III) exhibits the highest photoluminescence intensity among the three structural isomers because of its large HOMO-LUMO energy gap.

Fabrication and In Situ Transmission Electron Microscope Characterization of Free-Standing Graphene Nanoribbon Devices

Edge-dependent electronic properties of graphene nanoribbons (GNRs) have attracted intense interests. To fully understand the electronic properties of GNRs, the combination of precise structural characterization and electronic property measurement is essential. For this purpose, two experimental techniques using free-standing GNR devices have been developed, which leads to the simultaneous characterization of electronic properties and structures of GNRs. Free-standing graphene has been sculpted by a focused electron beam in transmission electron microscope (TEM) and then purified and narrowed by Joule heating down to several nanometer width. Structure-dependent electronic properties are observed in TEM, and significant increase in sheet resistance and semiconducting behavior become more salient as the width of GNR decreases. The narrowest GNR width we obtained with the present method is about 1.6 nm with a large transport gap of 400 meV.

Oligothiophene/graphene supramolecular ensembles managing light induced processes: preparation, characterization, and femtosecond transient absorption studies leading to charge-separation

Advances in organic synthetic chemistry combined with the exceptional electronic properties of carbon allotropes, particularly graphene, is the basis used to design and fabricate novel electron donor-acceptor ensembles with desired properties for technological applications. Thiophene-based materials, which are mainly thiophene-containing polymers, are known for their notable electronic properties. In this frame moving from polymer to oligomer forms, new fundamental information would help for a better understanding of their electrochemical and photophysical properties. Furthermore, a successful combination of their electronic properties with those of graphene is a challenging goal. In this study, two oligothiophene compounds, which consist of three and nine thiophene-rings and are abbreviated 3T and 9T, respectively, were synthesized and noncovalently associated with liquid phase exfoliated few-layered graphene sheets (abbreviated eG), thus forming donor-acceptor 3T/eG and 9T/eG nanoensembes. Markedly, intra-ensemble electronic interactions between the two components in the ground and excited states were evaluated with the aid of UV-Vis and photoluminescence spectroscopy. Furthermore, redox assays revealed the one-electron oxidation of 3T accompanied by one-electron reduction due to eG in 3T/eG, whereas there were two reversible one-electron oxidations of 9T accompanied by one-electron reduction of eG9T/eG. The electrochemical band gap for the 3T/eG and 9T/eG ensembles were calculated and verified, in which the negative free-energy change for the charge-separated state of 3T/eG and 9T/eGvia the singlet excited state of 3T and 9T, respectively, were thermodynamically favorable. Finally, the results of transient pump-probe spectroscopy studies at the femtosecond time scale were supportive of charge transfer type interactions in the 3T/eG and 9T/eG ensembles. The estimated rates for intra-ensemble charge separation were found to be 9.52 × 10(9) s(-1) and 2.2 × 10(11) s(-1), respectively, for 3T/eG and 9T/eG in THF, which reveal moderate to ultrafast photoinduced events in the oligothiophene/graphene supramolecular ensembles.

Selective Formation of Zigzag Edges in Graphene Cracks

We report the thermally induced unconventional cracking of graphene to generate zigzag edges. This crystallography-selective cracking was observed for as-grown graphene films immediately following the cooling process subsequent to chemical vapor deposition (CVD) on Cu foil. Results from Raman spectroscopy show that the crack-derived edges have smoother zigzag edges than the chemically formed grain edges of CVD graphene. Using these cracks as nanogaps, we were also able to demonstrate the carrier tuning of graphene through the electric field effect. Statistical analysis of visual observations indicated that the crack formation results from uniaxial tension imparted by the Cu substrates together with the stress concentration at notches in the polycrystalline graphene films. On the basis of simulation results using a simplified thermal shrinkage model, we propose that the cooling-induced tension is derived from the transient lattice expansion of narrow Cu grains imparted by the thermal shrinkage of adjacent Cu grains.