Coupled spin states in armchair graphene nanoribbons with asymmetric zigzag edge extensions

Carbon-based magnetic structures promise significantly longer coherence times than traditional magnetic materials, which is of fundamental importance for spintronic applications. An elegant way of achieving carbon-based magnetic moments is the design of graphene nanostructures with an imbalanced occupation of the two sublattices forming the carbon honeycomb lattice. According to Lieb's theorem, this induces local magnetic moments that are proportional to the sublattice imbalance. Exact positioning of sublattice imbalanced nanostructures in graphene nanomaterials hence offers a route to control interactions between induced local magnetic moments and to obtain graphene nanomaterials with magnetically non-trivial ground states. Here, we show that such sublattice imbalanced nanostructures can be incorporated along a large band gap armchair graphene nanoribbon on the basis of asymmetric zigzag edge extensions, which is achieved by incorporating specifically designed precursor monomers during the bottom-up fabrication of the graphene nanoribbons. Scanning tunneling spectroscopy of an isolated and electronically decoupled zigzag edge extension reveals Hubbard-split states in accordance with theoretical predictions. Investigation of pairs of such zigzag edge extensions reveals ferromagnetic, antiferromagnetic or quenching of the magnetic interactions depending on the relative alignment of the asymmetric edge extensions. Moreover, a ferromagnetic spin chain is demonstrated for a periodic pattern of zigzag edge extensions along the nanoribbon axis. This work opens a route towards the design and fabrication of graphene nanoribbon-based spin chains with complex magnetic ground states

Emissive brightening in molecular graphene nanoribbons by twilight states

Carbon nanomaterials are expected to be bright and efficient emitters, but structural disorder, intermolecular interactions and the intrinsic presence of dark states suppress their photoluminescence. Here, we study synthetically-made graphene nanoribbons with atomically precise edges and which are designed to suppress intermolecular interactions to demonstrate strong photoluminescence in both solutions and thin films. The resulting high spectral resolution reveals strong vibron-electron coupling from the radial-breathing-like mode of the ribbons. In addition, their cove-edge structure produces inter-valley mixing, which brightens conventionally-dark states to generate hitherto-unrecognised twilight states as predicted by theory. The coupling of these states to the nanoribbon phonon modes affects absorption and emission differently, suggesting a complex interaction with both Herzberg–Teller and Franck– Condon coupling present. Detailed understanding of the fundamental electronic processes governing the optical response will help the tailored chemical design of nanocarbon optical devices, via gap tuning and side-chain functionalisation

Transvaginal natural orifice transluminal endoscopic surgery-assisted versus transumbilical laparoendoscopic single-site ovarian cystectomy for ovarian mature cystic teratoma. A randomized controlled trial

Objectives: Transvaginal natural orifice transluminal endoscopic surgery (vNOTES) and transumbilical laparoendoscopic single-site surgery (LESS) have shown the prospection as minimally invasive procedures. Here we aimed to compare ovarian cystectomy assisted by vNOTES and by LESS for ovarian mature cystic teratoma (OMCT). Material and methods: A total of 81 premenopausal women with OMCT were randomized to undergo ovarian cystectomy assisted by either vNOTES (n = 41) or LESS (n = 40). The main outcome was the operative time. Secondary outcomes included the length of hospital stay, visual analog scale (VAS) pain scores, abdominal contamination by teratoma contents, and intraoperative and postoperative complications. Results: There were no intergroup differences in age, body mass index, tumor size, or bilaterality of tumor. The operative time for the vNOTES group was significantly shorter than that for the LESS group (68.41 ± 20.92 min vs 85.05 ± 32.94 min, p = 0.008). The highest VAS pain score 24 hours postoperatively was 1.21 ± 0.48 in the vNOTES group and 2.43 ± 0.57 in the LESS group (p < 0.001). Twenty-four of the 40 patients in the LESS group experienced teratoma rupture intraoperatively, leading to abdominal contamination by the teratoma content, while 5 abdominal contamination was observed in the vNOTES group （p = 0.005. No significant differences between the two groups were observed in the other outcomes. Conclusions: vNOTES assisted ovarian cystectomy has short operative time, fast recovery, no scarring, less pain, and low rate of abdominal contamination. Consequently, vNOTES might be superior to LESS for treating OMCTs

Steering on-surface reactions through molecular steric hindrance and molecule-substrate van der Waals interactions.

UNLABELLED On-surface synthesis is a rapidly developing field involving chemical reactions on well-defined solid surfaces to access synthesis of low-dimensional organic nanostructures which cannot be achieved via traditional solution chemistry. On-surface reactions critically depend on a high degree of chemoselectivity in order to achieve an optimum balance between target structure and possible side products. Here, we demonstrate synthesis of graphene nanoribbons with a large unit cell based on steric hindrance-induced complete chemoselectivity as revealed by scanning probe microscopy measurements and density functional theory calculations. Our results disclose that combined molecule-substrate van der Waals interactions and intermolecular steric hindrance promote a selective aryl-aryl coupling, giving rise to high-quality uniform graphene nanostructures. The established coupling strategy has been used to synthesize two types of graphene nanoribbons with different edge topologies inducing a pronounced variation of the electronic energy gaps. The demonstrated chemoselectivity is representative for n-anthryl precursor molecules and may be further exploited to synthesize graphene nanoribbons with novel electronic, topological and magnetic properties with implications for electronic and spintronic applications. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s44214-022-00023-9

Nanographenes: Ultrastable, Switchable, and Bright Probes for Super-Resolution Microscopy

Super-resolution fluorescence microscopyh as enabled important breakthroughs in biology and materials science.Implementations such as single-molecule localization microscopy(SMLM) and minimal emission fluxes (MINFLUX) microscopyinthe localization mode exploit fluorophores that blink, i.e., switch on and off,stochastically.Here, weintroducenanographenes,namelylargepolycyclicaromatic hydrocarbons that can also be regarded as atomically precise graphene quantum dots,asanew class of fluorophores for super-resolution fluorescence microscopy. Nanographenes exhibit outstanding photophysical properties:intrinsic blinking even in air,excellent fluorescence recovery,and stability over several months.Asaproof of concept for super-resolution applications,weuse nanographenes in SMLM to generate 3D super-resolution images of silica nanocracks.O ur findings open the door for the widespread application of nanographenes in super-resolution fluorescence microscopy

Engineering of robust topological quantum phases in graphene nanoribbons

Here we present a flexible strategy to realize robust nanomaterials exhibiting valence electronic structures whose fundamental physics is described by the SSH-Hamiltonian. These solid-state materials are realized using atomically precise graphene nanoribbons (GNR). We demonstrate the controlled periodic coupling of topological boundary states at junctions of armchair GNRs of different widths to create quasi-1D trivial and non-trivial electronic quantum phases. Their topological class is experimentally determined by drawing upon the bulk-boundary correspondence and measuring the presence (non-trivial) or absence (trivial) of localized end states by scanning tunneling spectroscopy (STS). The strategy we propose has the potential to tune the band width of the topological electronic bands close to the energy scale of proximity induced spin-orbit coupling or superconductivity, and may allow the realization of Kitaev like Hamiltonians and Majorana type end states

Association of sleep behaviors, insulin resistance surrogates, and the risk of hypertension in Chinese adults with type 2 diabetes mellitus

ObjectiveOur aim was to evaluate the association between midday napping, combined sleep quality, and insulin resistance surrogates and the risk of hypertension in patients with type 2 diabetes mellitus (T2DM).MethodsData were collected using a standardized questionnaire. Binary logistic regression was performed to estimate the odds ratio (OR) and 95% confidence interval (CI) for the risk of hypertension. Systolic and diastolic blood pressure were grouped as categorical variables and unpaired two-sided Student’s t-test and Spearman correlation analysis were performed to estimate the association between different blood pressure levels and insulin resistance surrogates.ResultsThe overall prevalence rate of hypertension was 50%. Age (OR = 1.056, 95% CI:1.044–1.068), poor sleep quality (OR = 1.959, 95% CI:1.393–2.755), hyperlipidemia (OR = 1.821, 95% CI:1.462–2.369), family history of hypertension (OR = 2.811, 95% CI:2.261–3.495), and obesity (OR = 5.515, 95% CI:1.384–21.971) were significantly associated with an increased risk of hypertension. Midday napping for 1–30 min was negatively correlated with the risk of hypertension (OR = 0.534, 95% CI:0.305–0.936, P <0.05).ConclusionPoor sleep quality and obesity are independent risk factors for hypertension. Midday napping (1–30 min) is associated with a decreased risk of hypertension in patients with T2DM

Synthesis of Nonplanar Graphene Nanoribbon with Fjord Edges

As a new family of semiconductors, graphene nanoribbons (GNRs), nanometer-wide strips of graphene, have appeared as promising candidates for next-generation nanoelectronics. Out-of-plane deformation of π-frames in GNRs brings further opportunities for optical and electronic property tuning. Here we demonstrate a novel fjord-edged GNR (FGNR) with a nonplanar geometry obtained by regioselective cyclodehydrogenation. Triphenanthro-fused teropyrene 1 and pentaphenanthro-fused quateropyrene 2 were synthesized as model compounds, and single-crystal X-ray analysis revealed their helically twisted conformations arising from the [5]helicene substructures. The structures and photophysical properties of FGNR were investigated by mass spectrometry and UV–vis, FT-IR, terahertz, and Raman spectroscopic analyses combined with theoretical calculations

Regioselective Hydrogenation of a 60-Carbon Nanographene Molecule toward a Circumbiphenyl Core

Regioselective peripheral hydrogenation of a nanographene molecule with 60 contiguous sp 2 carbons provides unprecedented access to peralkylated circumbiphenyl (1). Conversion to the circumbiphenyl core structure was unambiguously validated by MALDI-TOF mass spectrometry, NMR, FT-IR, and Raman spectroscopy. UV-vis absorption spectra and DFT calculations demonstrated the significant change of the optoelectronic properties upon peripheral hydrogenation. Stimulated emission from 1, observed via ultrafast transient absorption measurements, indicates potential as an optical gain material