Nonequilibrium Dynamics of Electron Emission from Cold and Hot Graphene under Proton Irradiation.

Characteristic properties of secondary electrons emitted from irradiated two-dimensional materials arise from multi-length and multi-time-scale relaxation processes that connect the initial nonequilibrium excited electron distribution with their eventual emission. To understand these processes, which are critical for using secondary electrons as high-resolution thermalization probes, we combine first-principles real-time electron dynamics with irradiation experiments. Our data for cold and hot proton-irradiated graphene show signatures of kinetic and potential emission and generally good agreement for electron yields between experiment and theory. The duration of the emission pulse is about 1.5 fs, which indicates high time resolution when used as a probe. Our newly developed method to predict kinetic energy spectra shows good agreement with electron and ion irradiation experiments and prior models. We find that the lattice temperature significantly increases secondary electron emission, whereas electron temperature has a negligible effect.

Nanoflower-like NiCo2O4 Composite Graphene Oxide as a Bifunctional Catalyst for Zinc-Air Battery Cathode.

Developing efficient bifunctional catalysts for nonprecious metal-based oxygen reduction (ORR) and oxygen evolution (OER) is crucial to enhance the practical application of zinc-air batteries. The study harnessed electrostatic forces to anchor the nanoflower-like NiCo2O4 onto graphene oxide, mitigating the poor inherent conductivity in NiCo2O4 as a transition metal oxide and preventing excessive agglomeration of the nanoflower-like structures during catalysis. Consequently, the resulting composite, NiCo2O4-GO/C, exhibited notably superior ORR and OER catalytic performance compared to pure nanoflower-like NiCo2O4. Notably, it excelled in OER catalytic activity of the OER relative to the precious metal RuO2. As a bifunctional catalyst for ORR and OER, NiCo2O4-GO/C displayed a potential difference of 0.88 V between the ORR half-wave potential and the OER potential at 10 mA·cm-2, significantly lower than the 1.08 V observed for pure flower-like NiCo2O4 and comparable to the 0.88 V exhibited by precious metal catalysts Pt/C + RuO2. The NiCo2O4-GO/C-based zinc-air battery demonstrated a discharge capacity of 817.3 mA h·g-1, surpassing that of precious metal-based zinc-air batteries. Moreover, charge-discharge cycling tests indicated the superior stability of the NiCo2O4-GO/C-based zinc-air battery compared to its precious metal-based counterparts.

The impact of an innovative payment method on medical expenditure, efficiency, and quality for inpatients with different types of medical insurance: evidence from a pilot city, China.

BACKGROUND: Since 2020, China has implemented an innovative payment method called Diagnosis-Intervention Packet (DIP) in 71 cities nationwide. This study aims to assess the impact of DIP on medical expenditure, efficiency, and quality for inpatients covered by the Urban Employee Basic Medical Insurance (UEBMI) and Urban and Rural Residents Basic Medical Insurance (URRBMI). It seeks to explore whether there are differences in these effects among inpatients of the two insurance types, thereby further understanding its implications for health equity. MATERIALS AND METHODS: We conducted interrupted time series analyses on outcome variables reflecting medical expenditure, efficiency, and quality for both UEBMI and URRBMI inpatients, based on a dataset comprising 621,125 inpatient reimbursement records spanning from June 2019 to June 2023 in City A. This dataset included 110,656 records for UEBMI inpatients and 510,469 records for URRBMI inpatients. RESULTS: After the reform, the average expenditure per hospital admission for UEBMI inpatients did not significantly differ but continued to follow an upward pattern. In contrast, for URRBMI inpatients, the trend shifted from increasing before the reform to decreasing after the reform, with a decline of 0.5%. The average length of stay for UEBMI showed no significant changes after the reform, whereas there was a noticeable downward trend in the average length of stay for URRBMI. The out-of-pocket expenditure (OOP) per hospital admission, 7-day all-cause readmission rate and 30-day all-cause readmission rate for both UEBMI and URRBMI inpatients showed a downward trend after the reform. CONCLUSION: The DIP reform implemented different upper limits on budgets based on the type of medical insurance, leading to varying post-treatment prices for UEBMI and URRBMI inpatients within the same DIP group. After the DIP reform, the average expenditure per hospital admission and the average length of stay remained unchanged for UEBMI inpatients, whereas URRBMI inpatients experienced a decrease. This trend has sparked concerns about hospitals potentially favoring UEBMI inpatients. Encouragingly, both UEBMI and URRBMI inpatients have seen positive outcomes in terms of alleviating patient financial burdens and enhancing the quality of care.

Comparison of the market share of public and private hospitals under different Medical Alliances: an interrupted time-series analysis in rural China.

BACKGROUND: China initiated the Medical Alliances (MAs) reform to enhance resource allocation efficiency and ensure equitable healthcare. In response to challenges posed by the predominance of public hospitals, the reform explores public-private partnerships within the MAs. Notably, private hospitals can now participate as either leading or member institutions. This study aims to evaluate the dynamic shifts in market share between public and private hospitals across diverse MAs models. METHODS: Data spanning April 2017 to March 2019 for Dangyang County's MA and January 2018 to December 2019 for Qianjiang County's MA were analyzed. Interrupted periods occurred in April 2018 and January 2019. Using independent sample t-tests, chi-square tests, and interrupted time series analysis (ITSA), we compared the proportion of hospital revenue, the proportion of visits for treatment, and the average hospitalization days of discharged patients between leading public hospitals and leading private hospitals, as well as between member public hospitals and member private hospitals before and after the reform. RESULTS: After the MAs reform, the revenue proportion decreased for leading public and private hospitals, while member hospitals saw an increase. However, ITSA revealed a notable rise trend in revenue proportion for leading private hospitals (p < 0.001), with a slope of 0.279% per month. Member public and private hospitals experienced decreasing revenue proportions, with outpatient visits proportions declining in member public hospitals by 0.089% per month (p < 0.05) and inpatient admissions proportions dropping in member private hospitals by 0.752% per month (p < 0.001). The average length of stay in member private hospitals increased by 0.321 days per month after the reform (p < 0.01). CONCLUSIONS: This study underscores the imperative to reinforce oversight and constraints on leading hospitals, especially private leading hospitals, to curb the trend of diverting patients from member hospitals. At the same time, for private hospitals that are at a disadvantage in competition and may lead to unreasonable prolongation of hospital stay, this kind of behavior can be avoided by strengthening supervision or granting leadership.

Cell damage evaluation by intelligent imaging flow cytometry.

Essential thrombocythemia (ET) is an uncommon situation in which the body produces too many platelets. This can cause blood clots anywhere in the body and results in various symptoms and even strokes or heart attacks. Removing excessive platelets using acoustofluidic methods receives extensive attention due to their high efficiency and high yield. While the damage to the remaining cells, such as erythrocytes and leukocytes is yet evaluated. Existing cell damage evaluation methods usually require cell staining, which are time-consuming and labor-intensive. In this paper, we investigate cell damage by optical time-stretch (OTS) imaging flow cytometry with high throughput and in a label-free manner. Specifically, we first image the erythrocytes and leukocytes sorted by acoustofluidic sorting chip with different acoustic wave powers and flowing speed using OTS imaging flow cytometry at a flowing speed up to 1 m/s. Then, we employ machine learning algorithms to extract biophysical phenotypic features from the cellular images, as well as to cluster and identify images. The results show that both the errors of the biophysical phenotypic features and the proportion of abnormal cells are within 10% in the undamaged cell groups, while the errors are much greater than 10% in the damaged cell groups, indicating that acoustofluidic sorting causes little damage to the cells within the appropriate acoustic power, agreeing well with clinical assays. Our method provides a novel approach for high-throughput and label-free cell damage evaluation in scientific research and clinical settings.

Hybrid tunnel junction enabled independent junction control of cascaded InGaN blue/green micro-light-emitting diodes.

We demonstrate vertical integration of nitride-based blue/green micro-light-emitting diodes (µLEDs) stacks with independent junctions control using hybrid tunnel junction (TJ). The hybrid TJ was gown by metal organic chemical vapor deposition (p + GaN) and molecular-beam epitaxy (n + GaN). Uniform blue, green and blue/green emission can be generated from different junction diodes. The peak external quantum efficiency (EQE) of the TJ blue µLEDs and green µLEDs with indium tin oxide contact is 30% and 12%, respectively. The carrier transportation between different junction diodes was discussed. This work suggests a promising approach for vertical µLEDs integration to enhance the output power of single LEDs chip and monolithic µLEDs with different emission colors with independent junction control.

High external quantum efficiency (6.8%) UV-A LEDs on AlN templates with quantum barrier optimization.

AlGaN-based UV-A LEDs have wide applications in medical treatment and chemical sensing; however, their efficiencies are still far behind visible LEDs or even shorter wavelengths UV-C counterparts because of the large lattice mismatch between the low-Al-content active region and the AlN substrate. In this report, we investigated the composition and thickness of the quantum barrier in the active region in terms of LED performance. Due to the improved strain management and better carrier confinement, efficient UV-A LEDs (320 nm - 330 nm) with EQEs up to 6.8% were demonstrated, among the highest efficiencies at this wavelength range.

Cervical cancer screening aided by artificial intelligence, China.

Objective: To implement and evaluate a large-scale online cervical cancer screening programme in Hubei Province, China, supported by artificial intelligence and delivered by trained health workers. Methods: The screening programme, which started in 2017, used four types of health worker: sampling health workers, slide preparation technicians, diagnostic health workers and cytopathologists. Sampling health workers took samples from the women on site; slide preparation technicians prepared slides for liquid-based cytology; diagnostic health workers identified negative samples and classified positive samples based on the Bethesda System after cytological assessment using online artificial intelligence; and cytopathologists reviewed positive samples and signed reports of the results online. The programme used fully automated scanners, online artificial intelligence, an online screening management platform, and mobile telephone devices to provide screening services. We evaluated the sustainability, performance and cost of the programme. Results: From 2017 to 2021, 1 518 972 women in 16 cities in Hubei Province participated in the programme, of whom 1 474 788 (97.09%) had valid samples for the screening. Of the 86 648 women whose samples were positive, 30 486 required a biopsy but only 19 495 had one. The biopsy showed that 2785 women had precancerous lesions and 191 had invasive cancers. The cost of screening was 6.31 United States dollars (US$) per woman for the public payer: US$ 1.03 administrative costs and US$ 5.28 online screening costs. Conclusion: Cervical cancer screening using artificial intelligence in Hubei Province provided a low-cost, accessible and effective service, which will contribute to achieving universal cervical cancer screening coverage in China.

Metal-free sulfonylation of quinoxalinones to access 2-sulfonyl-oxylated quinoxalines via oxidative O-S cross coupling.

The C2 sulfonylation of quinoxalinones via a metal-free oxidative S-O cross-coupling strategy for synthesizing 2-sulfonyloxylated quinoxalines is established. It effectively solved the long-standing problems in the C2 transformation of quinoxalinones via a metal-free oxidative O-S coupling strategy. Compared with the traditional C2 transformed quinoxalinones-C2 chlorination method, this protocol is mild, facile, and environmentally friendly and exhibits good atomic economy and excellent functional group tolerance. Moreover, the utility of this methodology and the sulfonyloxyl handles was demonstrated through the synthesis of 2-substituted quinoxaline-based bioactive molecules.

Sensitive Room-Temperature Graphene Photothermoelectric Terahertz Detector Based on Asymmetric Antenna Coupling Structure.

A highly sensitive room-temperature graphene photothermoelectric terahertz detector, with an efficient optical coupling structure of asymmetric logarithmic antenna, was fabricated by planar micro-nano processing technology and two-dimensional material transfer techniques. The designed logarithmic antenna acts as an optical coupling structure to effectively localize the incident terahertz waves at the source end, thus forming a temperature gradient in the device channel and inducing the thermoelectric terahertz response. At zero bias, the device has a high photoresponsivity of 1.54 A/W, a noise equivalent power of 19.8 pW/Hz1/2, and a response time of 900 ns at 105 GHz. Through qualitative analysis of the response mechanism of graphene PTE devices, we find that the electrode-induced doping of graphene channel near the metal-graphene contacts play a key role in the terahertz PTE response. This work provides an effective way to realize high sensitivity terahertz detectors at room temperature.

First morning voided urinary gonadotropins in children: verification of method performance and establishment of reference intervals.

OBJECTIVES: Urinary luteinizing hormone (uLH) and urinary follicle-stimulating hormone (uFSH) have been shown to be useful screening and management tools for children with central precocious puberty. However, studies on uLH and uFSH reference intervals are scarce. Therefore, we aimed to establish reference intervals for uLH and uFSH, according to age, sex, and pubertal status in apparently healthy children aged 6-11 years. METHODS: We performed detection capability, precision, accuracy by recovery, linearity, agreement analysis, and stability testing to analyze the method performance of uLH and uFSH. The Clinical Laboratory Standards Institute's C28-A3 criteria was used to establish the reference intervals. RESULTS: Both uLH and uFSH were stable at 4 °C for 52.6 h and 64.8 days, respectively. The total imprecision of uFSH is within the manufacturer's claim, while the total imprecision of uLH remained within tolerable bias. Both uLH and uFSH could be measured with acceptable detection capability. The recovery rates of the hormones were 87.6-98.8% and 102.8-103.4%, respectively, and therefore within acceptable limits. There were significant correlations between the serum and urine concentrations (LH: r=0.91, p<0.001; FSH: r=0.90, p<0.001). The reference intervals of uLH and uFSH were established according to age, sex, and pubertal status. CONCLUSIONS: We established reference intervals for uLH and uFSH based on age, sex and pubertal status to provide a non-invasive clinical screening tool for precocious puberty in children aged 6-11 years.

Explicit-by-Implicit Treatment of Natural Orbital Occupations Using First- and Second-Order Optimization Algorithms: A Comparative Study.

To address the convergence issues in the natural occupation optimization of reduced density matrix functional theory (RDMFT), we recently proposed the explicit-by-implicit (EBI) idea to handle the ensemble N-representability constraint (Yao et al. J. Phys. Chem. Lett. 2021, 12, 6788). This work continues to focus on these issues that can affect the reliability of the electronic structure description in RDMFT; further explores the combination of EBI, as well as the (augmented) Lagrangian methods (both LM and ALM), with both first- and second-order numerical optimization algorithms; and carefully evaluates their performances in natural occupation optimizations of various systems, including strongly correlated systems and large molecules. By comparing both converged energies and elapsed times, it can be seen that the LM and ALM have serious convergence issues for systems of different sizes. In contrast, the optimizations of EBI can converge to better energies with fewer iterations. However, due to the local convergence nature of the Newton's Method (NM) algorithm, EBI@NM still suffers from the local minimum issue for both strongly correlated systems and large molecules. Overall, the combination of EBI with the simple first-order algorithm of gradient descent (GD), namely EBI@GD, consistently provides the lowest converged energies for different types of systems, with the lowest computational scaling. These tests demonstrate the advantages of EBI in the calculations of transition states, strongly correlated systems, and large molecules. Meanwhile, the insights gained from this work are helpful to further develop more efficient algorithms for RDMFT.

Association of depressive symptoms with ambient PM2.5 in middle-aged and elderly Chinese adults: A cross-sectional study from the China health and Retirement Longitudinal Study wave 4.

Depressive symptoms have become a serious public health issue worldwide. Several studies showed that air pollution, especially fine particulate matter (PM2.5), may be a risk factor of mental disorders. However, existing studies reported inconsistent results and little evidence is available in developing countries, like China. To fill the gap, in this study, we explored the relationship between ambient PM2.5 exposure and depressive symptoms among middle-aged and elderly Chinese adults in the Chinese Health and Retirement Longitudinal Study (CHARLS). The social and demographic variables and depressive symptoms were obtained from the Wave4 of CHARLS in 2018. PM2.5 concentrations were obtained from the national urban air quality real-time release platform of China Environmental Monitoring Station. We applied generalized linear mixed models to determine the association between PM2.5 exposure and depressive symptoms. A total of 15,105 middle-aged and elderly adults from CHARLS Wave4 were included in the analyses. We found positive impact of ambient PM2.5 on depressive symptoms for the exposure windows of 30-day, 60-day, 120-day, 180-day, 1-year and 2-year. The most significant increase was observed for 180-day moving average. For every 10 µg/m3 increment in PM2.5 exposure, the incidence of depressive symptoms increased by 9% (OR = 1.09; 95%CI: 1.05, 1.14) after adjusting for age, sex and residence. In interaction analyses, we found PM2.5 had weaker effect on depressive symptoms among people who used to drink alcohol (OR = 1.05; 95%CI: 1.00, 1.10) and exercise (OR = 1.10; 95%CI: 1.02, 1.18). People living in western China (OR = 1.09; 95%CI: 1.03, 1.16) were more vulnerable than those living in eastern China (OR = 0.99; 95%CI: 0.94, 1.05). In conclusion, exposure to PM2.5 was significantly associated with depressive symptoms in middle-aged and elder Chinese adults, particularly for people who never drink, with lower physical activity levels, or lived in western China.

Associations of long-term exposure to ambient air pollutants with metabolic syndrome: The Wuhan Chronic Disease Cohort Study (WCDCS).

BACKGROUND: Evidence on the associations between long-term exposure to ambient air pollutants (including particle with aerodynamic diameter ≤10 µm (PM10), particle with aerodynamic diameter ≤2.5 µm (PM2.5), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2)) and prevalence of metabolic syndrome (MetS) remains inconclusive. This study aimed to determine the associations based on a case-control study nested in the Wuhan Chronic Disease Cohort study (WCDCS), a population-based study with baseline survey in 2019. METHODS: A total of 10,253 residents living in Wuhan were recruited. The 3-year average concentrations of main pollutants (PM10, PM2.5, O3, NO2, and SO2) at residences prior to the survey date were estimated to evaluate the long-term exposures. The generalized linear mixed models were used to investigate the changes in MetS prevalence by an IQR increases in each air pollutant exposure concentrations. Interaction effects between air pollutants and demographic, lifestyle, and dietary factors on MetS were evaluated by including an interactive item in the main model. RESULTS: The prevalence of MetS in Wuhan was 9.8%, and the 3-year exposure concentrations of PM10, PM2.5, O3, NO2, and SO2 were 84.1 µg/m3, 50.5 µg/m3, 55.7 µg/m3, 46.0 µg/m3, and 9.4 µg/m3, respectively. Higher PM10, PM2.5 and O3 exposure concentrations were associated with an elevated MetS prevalence (e.g. an IQR increase in PM2.5, OR = 1.193, 95% confidence intervals (95%CIs): 1.028, 1.385; for O3, OR = 1.074, 95%CIs: 1.025, 1.124), whereas NO2, and SO2 were negatively or insignificant correlated with odds of Mets (e.g. an IQR increase in NO2, OR = 0.865, 95%CIs: 0.795, 0.941). Males, smokers, alcohol drinkers and individuals who intake fruits occasionally exposure to PM10 and PM2.5 were found had a higher risk of developing MetS. CONCLUSIONS: Long-term exposure to higher concentrations of ambient air pollutants may elevate the prevalence of MetS in populations in Central China. Susceptible individuals especially those with unhealthy lifestyles had a higher risk for MetS.

Highly Sensitive Strain Sensors Based on Molecules-Gold Nanoparticles Networks for High-Resolution Human Pulse Analysis.

High-performance flexible strain sensors are key components for the next generation of wearable health monitoring devices. Here, the authors have fabricated a novel strain sensor based on gold nanoparticles (AuNPs) interconnected by flexible and responsive molecular linkers. The combination of conductive AuNPs (25 nm in diameter) with tetra(ethylene glycol) dithiol (SH-TEG-SH) linkers yields a covalent 3D network which can be directly deposited onto prepatterned flexible supports exposing interdigitated Au electrodes. The electrically insulating nature of the linkers effectively defines the tunneling modulated charge transfer through the AuNPs network. When compressive/tensile strain is applied, the molecular linkers adopt a compressed/stretched conformation thus decreasing/increasing the interparticle distance, ultimately yielding an exponential increase/decrease of the tunneling current when voltage is applied. The strain sensor displays state-of-the-art performances including a highly sensitive response to both tensile and compressive strain, as quantified by a high gauge factor (GF≈126) combined with other superior sensing properties like high flexibility, short response time (16.1 ms), and good robustness (>2000 cycles). Finally, the applicability of the device for health monitoring is demonstrated: high-resolution artery pulse waves are acquired by placing the strain sensor onto the skin allowing the extraction of important physical parameters for human-health assessment.

Fully transparent metal organic chemical vapor deposition-grown cascaded InGaN micro-light-emitting diodes with independent junction control.

In this work, we present fully transparent metal organic chemical vapor deposition (MOCVD)-grown InGaN cascaded micro-light-emitting diodes (µLEDs) with independent junction control. The cascaded µLEDs consisted of a blue emitting diode, a tunnel junction (TJ), a green emitting diode, and a TJ, without using any conductive oxide layer. We can control the injection of carriers into blue, green, and blue/green junctions in the same device independently, which show high optical and electrical performance. The forward voltage (Vf) at 20 A/cm2 for the TJ blue µLEDs and TJ green µLEDs is 4.06 and 3.13 V, respectively. These results demonstrate the efficient TJs and fully activated p-type GaN in the cascaded µLEDs. Such demonstration shows the important application of TJs for the integration of µLEDs with multiple color emissions.

Lower testosterone levels predict increasing severity and worse outcomes of hepatitis B virus-related acute-on-chronic liver failure in males.

BACKGROUND: Hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF) is a serious liver disease with pathogenesis remaining unclear. This study aims to investigate the association between testosterone levels, stage (early, middle, or late, categorized according to clinical manifestation), severity scores, and clinical outcomes of HBV-ACLF. METHODS: This single-center observational study involved 160 male patients with HBV-ACLF, 151 chronic hepatitis B patients without liver failure (CHB) and 106 healthy controls (HC). Morning blood samples were collected and androgen levels analyzed by chemi-bioluminescent immunoassay. Time to death or liver transplantation within 90 days comprised the primary composite outcome. RESULTS: Serum levels of total testosterone (TT), free testosterone index (FTI), dehydroepiandrosterone sulfate and cortisol were significantly lower among HBV-ACLF than CHB and HC, while androstenedione was higher. Low TT, sex hormone binding globulin and FTI were associated with increased stage (of HBV-ACLF, ascites, and hepatic encephalopathy) and severity scores (Model for End-stage Liver Disease and Chinese Group on the Study of Severe Hepatitis B-ACLF scores). Low TT (< 142.39 ng/dL) was a risk factor for both the composite outcome and for death alone within 90 days. Multivariate analysis revealed TT to be an independent predictor for the composite outcome (hazard ratio 2.57, 95% CI 1.09-6.02; P = 0.030). CONCLUSION: Low serum testosterone is common among male patients with HBV-ACLF and predictive of increased severity and worse outcome of the disease and may play an important role in the progression of HBV-ACLF.

First-principles theoretical study on dry reforming of methane over perfect and boron-vacancy-containing h-BN sheet-supported Ni catalysts.

The entire reaction mechanism of the dry reforming of methane (DRM) as well as the competition processes over perfect and boron-vacancy-containing h-BN sheet-supported Ni-catalysts (labeled Ni2/h-BN and Ni2/h-BN-B-D) was studied by density functional theory calculations in the present work. Our calculation results show that B-defected h-BN strongly binds to the Ni2 active sites (i.e., shows a strong metal-support interaction (SMSI) character) due to the better electron transfer between Ni2 sites and the support. It was found that CH4 is easier to activate than molecular CO2. The activation of CO2 occurs on the surface of Ni2/h-BN through a direct route, whereas it is prone to follow a hydrogen-assisted path for Ni2/h-BN-B-D via the COOH* intermediate, and the results show that the oxidant O* is easily formed on the surface of Ni2/h-BN-B-D. It was also found that O* is the main oxidant agent for CHx* intermediates through the CH3-O oxidation mechanism. The reaction kinetic analysis indicated that the reverse water gas shift reaction (RWGS) is much more favorable than DRM (1.30 vs. 1.72 eV) over the Ni2/h-BN system, whereas the RWGS and DRM are comparable on Ni2/h-BN-B-D (1.77 vs. 1.66 eV), suggesting a high DRM activity on Ni2/h-BN-B-D. Moreover, neither methane cracking nor a Boudouard reaction to form C* species is thermodynamically and kinetically unfavorable over Ni2/h-BN-B-D; hence, Ni2/h-BN-B-D has strong resistance to carbon deposition. Compared to Ni(111), both Ni2/h-BN-B-D and Ni2/h-BN show strong resistance to carbon deposition. Our results provide a further mechanistic understanding of the DRM over an Ni-based catalyst through the SMSI characteristic and the SMSI favors strong resistance to carbon deposition.

Size-independent low voltage of InGaN micro-light-emitting diodes with epitaxial tunnel junctions using selective area growth by metalorganic chemical vapor deposition.

High performance InGaN micro-size light-emitting diodes (µLEDs) with epitaxial tunnel junctions (TJs) were successfully demonstrated using selective area growth (SAG) by metalorganic chemical vapor deposition (MOCVD). Patterned n + GaN/n-GaN layers with small holes were grown on top of standard InGaN blue LEDs to form TJs using SAG. TJ µLEDs with squared mesa ranging from 10×10 to 100×100 µm2 were fabricated. The forward voltage (Vf) in the reference TJ µLEDs without SAG is very high and decreases linearly from 4.6 to 3.7 V at 20 A/cm2 with reduction in area from 10000 to 100 µm2, which is caused by the lateral out diffusion of hydrogen through sidewall. By contrast, the Vf at 20 A/cm2 in the TJ µLEDs utilizing SAG is significantly reduced to be 3.24 to 3.31 V. Moreover, the Vf in the SAG TJ µLEDs is independent on sizes, suggesting that the hydrogen is effectively removed through the holes on top of the p-GaN surface by SAG. The output power of SAG TJ µLEDs is ∼10% higher than the common µLEDs with indium tin oxide (ITO) contact.

Spectroscopic Measurement of a Halogen Bond Energy.

Halogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br- anions is reported. The XB strength between the positively-charged σ-hole on the Br atom of the bromotrichloromethane (CCl3 Br) molecule and the Br- anion was found to be 0.63 eV (14.5 kcal mol-1 ). In the neutral complexes, Br(CCl3 Br)1,2 , the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl3 Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol-1 ) and 0.12 eV (2.8 kcal mol-1 ).