An integrated solar battery based on a charge storing 2D carbon nitride.

Solar batteries capable of harvesting sunlight and storing solar energy present an attractive vista to transition our energy infrastructure into a sustainable future. Here we present an integrated, fully earth-abundant solar battery based on a bifunctional (light absorbing and charge storing) carbon nitride (K-PHI) photoanode, combined with organic hole transfer and storage materials. An internal ladder-type hole transfer cascade via a transport layer is used to selectively shuttle the photogenerated holes to the PEDOT:PSS cathode. This concept differs from previous designs such as light-assisted battery schemes or photocapacitors and allows charging with light during both electrical charge and discharge, thus substantially increasing the energy output of the cell. Compared to battery operation in the dark, light-assisted (dis)charging increases charge output by 243%, thereby increasing the electric coulombic efficiency from 68.3% in the dark to 231%, leading to energy improvements of 94.1% under illumination. This concept opens new vistas towards compact, highly integrated devices based on multifunctional, carbon-based electrodes and separators, and paves the way to a new generation of earth-abundant solar batteries.

Electric-Field Control of a Single-Atom Polar Bond.

We expose the polar covalent bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) to an external electric field. For one field orientation, the Au─C bond is strong enough to sustain the mechanical load of partially detached graphene, while for the opposite orientation, the bond breaks easily. Calculations based on density-functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling bond forces that reflect the polar character of the bond. Field-induced charge transfer between the atomic orbitals modifies the polarity of the different electronegative reaction partners and the Au─C bond strength.

Virtual monoenergetic images from spectral detector computed tomography facilitate washout assessment in arterially hyper-enhancing liver lesions.

OBJECTIVES: To investigate whether the increased soft tissue contrast of virtual monoenergetic images (VMIs) obtained from a spectral detector computed tomography (SDCT) system improves washout assessment of arterially hyper-enhancing liver lesions. METHODS: Fifty-nine arterially hyper-enhancing lesions in 31 patients (age 65 ± 9 years, M/W 20/11) were included in this IRB-approved study. All patients underwent multi-phase SDCT for HCC screening. MRI, CEUS or biopsy within 3 months served as standard of reference to classify lesions as LiRADS 3 or 4/5. VMIs and conventional images (CIs) were reconstructed. Visual analysis was performed on 40, 60, and 80 kiloelectronvolt (keV) and CIs by 3 radiologists. Presence and visibility of washout were assessed; image quality and confidence of washout evaluation were evaluated on 5-point Likert scales. Signal-to-noise ratio (SNR), lesion-to-liver contrast-to-noise ratio (CNR) (|HUlesion-HUliver|/SDliver) and washout (|HUlesion-HUliver|) were calculated. Statistical assessment was performed using ANOVA and Wilcoxon test. RESULTS: On subjective lesion analysis, the highest level of diagnostic confidence and highest sensitivity for the detection of lesion washout were found for 40-keV VMIs (40 keV vs. CI, 81.3 vs. 71.3%). Image quality parameters were significantly better in low-kiloelectronvolt VMIs than in CIs (p < 0.05; e.g. SNRliver: 40 keV vs. CIs, 12.5 ± 4.1 vs. 5.6 ± 1.6). In LiRADS 4/5 lesions, CNR and quantitative washout values were significantly higher in 40-keV VMIs compared to CIs (p < 0.05; e.g. CNR and washout in 40 keV vs. CIs, 2.3 ± 1.6 vs. 0.8 ± 0.5 and 29.0 ± 19.1 vs. 12.9 ± 6.9 HU, respectively). CONCLUSION: By increasing lesion contrast, low-kiloelectronvolt VMIs obtained from SDCT improve washout assessment of hyper-enhancing liver lesions with respect to washout visibility and diagnostic confidence. KEY POINTS: • Low-kiloelectronvolt virtual monoenergetic images from spectral detector CT facilitate washout assessment in arterially hyper-enhancing liver lesions. • Image quality and quantitative washout parameters as well as subjective washout visibility and diagnostic confidence benefit from low-kiloelectronvolt virtual monoenergetic images.

Manipulation of the two-site Kondo effect in linear CoCu n CoCu m clusters.

Artificially assembled linear atomic clusters, CoCu n CoCu m , are used to explore variations of the Kondo effect at the two Co sites. For all investigated Cu n chain lengths ([Formula: see text]) the addition of a single Cu atom to one edge Co atom of the chain ([Formula: see text]) strongly reduces the amplitude of the Abrikosov-Suhl-Kondo resonance of that Co atom. Concomitantly, the resonance line width is more than halved. On the contrary, the Kondo effect of the opposite edge Co atom remains unaffected. Hybridization together with the linear geometry of the cluster are likely to drive the effect.

Exciting vibrons in both frontier orbitals of a single hydrocarbon molecule on graphene.

Vibronic excitations in molecules are key to the fundamental understanding of the interaction between vibrational and electronic degrees of freedom. In order to probe the genuine vibronic properties of a molecule even after its adsorption on a surface appropriate buffer layers are of paramount importance. Here, vibrational progression in both molecular frontier orbitals is observed with submolecular resolution on a graphene-covered metal surface using scanning tunnelling spectroscopy. Accompanying calculations demonstrate that the vibrational modes that cause the orbital replica in the progression share the same symmetry as the electronic states they couple to. In addition, the vibrational progression is more pronounced for separated molecules than for molecules embedded in molecular assemblies. The entire vibronic spectra of these molecular species are moreover rigidly shifted with respect to each other. This work unravels intramolecular changes in the vibronic and electronic structure owing to the efficient reduction of the molecule-metal hybridization by graphene.

Could FreeStyle Libre™ sensor glucose data support decisions for safe driving?

AIM: Many countries require individuals with diabetes to adhere to standards regarding blood glucose testing in order to be granted or retain a driving licence. Currently, interstitial glucose results may not be used. The aim of this study was to determine whether interstitial glucose measurements using flash glucose-sensing technology can provide additional information to augment safe driving. METHODS: Sensor data from two European studies (NCT02232698 and NCT02082184) of the FreeStyle Libre Glucose Monitoring System™ in insulin-treated Type 1 and Type 2 diabetes, 241 and 224 participants respectively, were used to determine the frequency of a low interstitial sensor glucose result (< 3.9 mmol/l) up to 4 h subsequent to a daytime (07:00-21:00 h) capillary blood glucose result ≥ 5 mmol/l. RESULTS: Within 4 h of a capillary blood glucose result ≥ 5 mmol/l a sensor glucose result of < 3.9 mmol/l occurred on 22.0% of occasions (2573 of 11 706 blood glucose readings) for those with Type 1 diabetes, and 8.4% of occasions (699/8352) for those with Type 2 diabetes; 13.8% (1610/11 628) and 4.4% (365/8203) within 2 h, and 10.0% (1160/11 601) and 3.1% (254/8152) within 1.5 h. Analysis of sensor glucose results 5-7 mmol/l demonstrated the glucose trend arrow descending on 14.7% (1163/7894, Type 1 diabetes) and 9.4% (305/3233, Type 2 diabetes) of occasions. CONCLUSIONS: Sensor-based glucose information with directional arrows has the potential to support assessment of safe glucose levels associated with driving and offers distinct advantages over blood glucose testing for individuals with Type 1 and Type 2 diabetes to concord with driving safety standards.

Ordered Superstructures of a Molecular Electron Donor on Au(111).

The molecular donor tetraphenyldibenzoperiflanthene (DBP) forms coverage-dependent superstructures on Au(111). At submonolayer coverage, the molecules align parallel to each other. They arrange in row-like structures, which exhibit a nearly rectangular primitive unit cell. By contrast, the molecular monolayer is characterized by a herringbone-type DBP arrangement spanned by an almost square unit cell containing two molecules. Both superstructures occur simultaneously in a narrow coverage range close to completion of the molecular monolayer. The adsorbate-substrate interaction is similar to other physisorbed molecular films on Au(111), but differs for the two adsorption phases as inferred from the different modification of the Au(111) surface reconstruction. Structural properties were consistently probed in real and reciprocal space by scanning tunneling microscopy and low-energy electron diffraction, respectively.

Impact of Atomic-Scale Contact Geometry on Andreev Reflection.

Charge transport has been examined in junctions comprising the normal-metal tip of a low-temperature scanning tunneling microscope, the surface of a conventional superconductor, and adsorbed C_{60} molecules. The Bardeen-Cooper-Schrieffer energy gap gradually evolves into a zero-bias peak with decreasing electrode separation. The peak is assigned to the spectroscopic signature of Andreev reflection. The conductance due to Andreev reflection is determined by the atomic termination of the tip apex and the molecular adsorption orientation. Transport calculations unveil the finite temperature and the strong molecule-electrode hybridization as the origin to the surprisingly good agreement between spectroscopic data and the Blonder-Tinkham-Klapwijk model that was conceived for macroscopic point contacts.

Asymmetry parameter of peaked Fano line shapes.

The spectroscopic line shape of electronic and vibrational excitations is ubiquitously described by a Fano profile. In the case of nearly symmetric and peaked Fano line shapes, the fit of the conventional Fano function to experimental data leads to difficulties in unambiguously extracting the asymmetry parameter, which may vary over orders of magnitude without degrading the quality of the fit. Moreover, the extracted asymmetry parameter depends on initially guessed values. Using the spectroscopic signature of the single-Co Kondo effect on Au(110) the ambiguity of the extracted asymmetry parameter is traced to the highly symmetric resonance profile combined with the inevitable scattering of experimental data. An improved parameterization of the conventional Fano function is suggested that enables the nonlinear optimization in a reduced parameter space. In addition, the presence of a global minimum in the sum of squared residuals and thus the independence of start parameters may conveniently be identified in a two-dimensional plot. An angular representation of the asymmetry parameter is suggested in order to reliably determine uncertainty margins via linear error propagation.

Lateral Electron Confinement with Open Boundaries: Quantum Well States above Nanocavities at Pb(111).

We have studied electron states present at the Pb(111) surface above Ar-filled nanocavities created by ion beam irradiation and annealing. Vertical confinement between the parallel crystal and nanocavity surfaces creates a series of quantum well state subbands. Differential conductance data measured by scanning tunneling spectroscopy contain a characteristic spectroscopic fine structure within the highest occupied subband, revealing additional quantization. Unexpectedly, reflection at the open boundary where the thin Pb film recovers its bulk thickness gives rise to the lateral confinement of electrons.

Superstructures and Electronic Properties of Manganese-Phthalocyanine Molecules on Au(110) from Submonolayer Coverage to Ultrathin Molecular Films.

The adsorption of manganese-phthalocyanine molecules on Au(110) was investigated using a low-temperature scanning tunneling microscope. A rich variety of commensurate superstructures was observed upon increasing the molecule coverage from submonolayers to ultrathin films. All structures were associated with reconstructions of the Au(110) substrate. Molecules adsorbed in the second molecular layer exhibited negative differential conductance occurring symmetrically around zero bias voltage. A double-barrier tunneling model rationalized this observation in terms of a peaked molecular resonance at the Fermi energy together with a voltage drop across the molecular film.

Ballistic Anisotropic Magnetoresistance of Single-Atom Contacts.

Anisotropic magnetoresistance, that is, the sensitivity of the electrical resistance of magnetic materials on the magnetization direction, is expected to be strongly enhanced in ballistic transport through nanoscale junctions. However, unambiguous experimental evidence of this effect is difficult to achieve. We utilize single-atom junctions to measure this ballistic anisotropic magnetoresistance (AMR). Single Co and Ir atoms are deposited on domains and domain walls of ferromagnetic Fe layers on W(110) to control their magnetization directions. They are contacted with nonmagnetic tips in a low-temperature scanning tunneling microscope to measure the junction conductances. Large changes of the magnetoresistance occur from the tunneling to the ballistic regime due to the competition of localized and delocalized d-orbitals, which are differently affected by spin-orbit coupling. This work shows that engineering the AMR at the single atom level is feasible.

Spectroscopy of transmission resonances through a C60 junction.

Electron transport through a single C60 molecule on Cu(1 1 1) has been investigated with a scanning tunnelling microscope in tunnelling and contact ranges. Single-C60 junctions have been fabricated by establishing a contact between the molecule and the tip, which is reflected by a down-shift in the lowest unoccupied molecular orbital resonance. These junctions are stable even at elevated bias voltages enabling conductance measurements at high voltages and nonlinear conductance spectroscopy in tunnelling and contact ranges. Spectroscopy and first principles transport calculations clarify the relation between molecular orbital resonances and the junction conductance. Due to the strong molecule-electrode coupling the simple picture of electron transport through individual orbitals does not hold.

Phthalocyanine adsorption to graphene on Ir(111): evidence for decoupling from vibrational spectroscopy.

Phthalocyanine molecules have been adsorbed to Ir(111) and to graphene on Ir(111). From a comparison of scanning tunneling microscopy images of individual molecules adsorbed to the different surfaces alone it is difficult to discern potential differences in the molecular adsorption geometry. In contrast, vibrational spectroscopy using inelastic electron scattering unequivocally hints at strong molecule deformations on Ir(111) and at a planar adsorption geometry on graphene. The spectroscopic evidence for the different adsorption configurations is supported by density functional calculations.

Association between erythrocyte membrane fatty acids and biomarkers of dyslipidemia in the EPIC-Potsdam study.

BACKGROUND/OBJECTIVE: Blood proportions of fatty acids (FAs) and FA-ratios reflecting desaturase activity are associated with the risk of chronic diseases like type 2 diabetes mellitus or cardiovascular diseases. Biomarkers of dyslipidemia are considered as potential mediators of this association. We evaluated associations of erythrocyte membrane proportions of individual disease-related polyunsaturated fatty acids (PUFAs), trans-FAs, dairy-derived saturated FAs (SFAs) (15:0, 17:0) and FA-ratios with biomarkers of dyslipidemia (high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, non-HDL-cholesterol, triglycerides). SUBJECTS/METHODS: We conducted a cross-sectional analysis of a subsample (n=1759) of the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study. Associations of individual FAs and FA-ratios with plasma biomarkers of dyslipidemia were evaluated by linear multivariable regression. RESULTS: Most notably, FA-ratios reflecting activity of Δ6-desaturase (D6D) and stearoyl-coenzyme A-desaturase (SCD) were positively associated with triglyceride and LDL-cholesterol concentrations (adjusted means (95% confidence interval (CI)) of triglycerides (mg/dl) across D6D tertiles: men--102 (94.7-110), 111 (104-120), 144 (134-156) and women--73.5 (70.0-77.2), 82.9 (79.0-86.9), 94.2 (89.7-98.9)); across SCD tertiles: men--99.0 (91.8-107), 115 (107-124), 144 (134-156) and women--72.4 (69.0-76.0), 81.5 (77.8-85.5), 97.2 (92.6-102)), whereas inverse associations with triglycerides were observed for the estimated Δ5-desaturase (D5D) activity (adjusted means (95% CI) of triglycerides (mg/dl) across D5D tertiles: men--128 (119-138), 121 (113-131), 106 (97.9-114) and women--92.0 (87.6-96.6), 82.8 (78.9-86.9), 75.3 (71.6-79.1), P-values for trend at least 0.0006). Furthermore, we observed generally weaker and less consistent associations of dairy-derived SFAs (mainly 17:0) with triglycerides and HDL-cholesterol. Individual PUFAs and trans-FAs were, if at all, only weakly associated with dyslipidemia markers. CONCLUSIONS: Our findings suggest that triglyceride and LDL-cholesterol concentrations may be mediators that link intake and metabolism of FAs to metabolic risk.

Associated factors of estimated desaturase activity in the EPIC-Potsdam study.

BACKGROUND AND AIMS: Altered activity of desaturase enzymes may be involved in the development of metabolic diseases like type 2-diabetes. Desaturase activities might be modifiable by diet and lifestyle-related factors, but no study has systematically investigated such factors so far. We aimed to evaluate the association of demographic, anthropometric, dietary and lifestyle characteristics with estimated Δ5-, Δ6- and Δ9-desaturase activity. METHODS AND RESULTS: A subsample (n = 1782) of the EPIC-Potsdam study was used for a cross-sectional analysis, involving men and women, mainly aged 35-65 years. Fatty acid (FA) product-to-precursor ratios, derived from the FA composition of erythrocyte membrane phospholipids, were used to estimate desaturase activities. Multiple linear regression models were used with estimated Δ5-, Δ6- and Δ9-desaturase activity as outcome and demographic (age, sex), anthropometric (BMI, WHR), dietary intake (FAs, carbohydrates) and lifestyle (physical activity, smoking, alcohol consumption) factors as exposure variables. Alcohol intake was positively associated with estimated Δ6- (explained variance in desaturase activity: 1.52%) and estimated Δ9-desaturase activity (explained variance: 5.53%). BMI and WHR showed a weak inverse association with estimated Δ5-desaturase activity (explained variance: BMI: 1.07%; WHR: 1.02%) and weak positive associations with estimated Δ6-(explained variance: BMI: 1.17%; WHR: 1.19%) and estimated Δ9-desaturase activities (explained variance: BMI: 0.70%; WHR: 0.96%). Age, sex, physical activity, smoking and dietary factors were only weakly associated with the estimated desaturase activities. CONCLUSION: Our findings suggest that alcohol intake as well as obesity measures are associated with the FA ratios reflecting desaturase activity.

Tunneling anisotropic magnetoresistance at the single-atom limit.

The tunneling anisotropic magnetoresistance (TAMR) of single Co atoms adsorbed on a double-layer Fe film on W(110) is observed by scanning tunneling spectroscopy. Without applying an external magnetic field the TAMR is found by comparing spectra of atoms that are adsorbed on the domains and domain walls of the Fe film. The TAMR can be as large as 12% and repeatedly changes sign as a function of bias voltage. First-principles calculations show that the hybridization between Co d states of different orbital symmetries depends on the magnetization direction via spin-orbit coupling. This leads to an anisotropy of the density of states and thus induces a TAMR.

Voltage-dependent conductance states of a single-molecule junction.

Ag-Sn-phthalocyanine-Ag junctions are shown to exhibit three conductance states. While the junctions are conductive at low bias, their impedance drastically increases above a critical bias. Two-level fluctuations occur at intermediate bias. These characteristics may be used to protect a nanoscale circuit. Further experiments along with calculations reveal that the self-limiting conductance of the junctions is due to reversible changes of the junction geometry.

Local gating of an Ir(111) surface resonance by graphene islands.

The influence of graphene islands on the electronic structure of the Ir(111) surface is investigated. Scanning tunneling spectroscopy (STS) indicates the presence of a two-dimensional electron gas with a binding energy of -160 meV and an effective mass of -0.18me underneath single-layer graphene on the Ir(111) surface. Density functional calculations reveal that the STS features are predominantly due to a holelike surface resonance of the Ir(111) substrate. Nanometer-sized graphene islands act as local gates, which shift and confine the surface resonance.