Giant Enhancement of Photoluminescence Emission in WS2-Two-Dimensional Perovskite Heterostructures.

Transition metal dichalcogenides (TMDCs) and two-dimensional organic and inorganic hybrid lead halide perovskites (2DPVSKs) have emerged as highly promising materials for ultralight and ultrathin optoelectronics application. They both exhibit tunability of electronic properties such as band structure, and they can form heterostructures with various types of two-dimensional materials for novel physical properties not observed in single components. However, TMDCs exhibit poor emission efficiency due to defect states and direct-to-indirect interband transition, and 2DPVSKs suffer from poor stability in ambient atmosphere. Here we report that fabrication of TMDC-on-2DPVSK heterostructures using a solvent-free process leads to novel optical transitions unique to the heterostructure which arise from the hybrid interface and exhibit a strong photoluminescence. Moreover, a two orders of magnitude enhancement of the photoluminescence as compared to WS2 emission is observed. The TMDC on top of 2DPVSK also significantly improves the stability as compared to bare 2DPVSK. Enhanced emission can be explained by electronic structure modification of TMDC by novel interfacial interactions between TMDC and 2DPVSK materials, which shows promise of the heterostructure for high efficiency and stable optoelectronic devices.

Role of aggregation in the synthesis and polymerization activity of SalBinap indium alkoxide complexes.

The reaction of racemic SalBinap ligand, (±)-H2(ONN*OMe), with InCl3 and excess NaOEt generated a mixture of two dinuclear compounds [(µ-κ(2)-ONN*OMe)In(µ-OEt)]2 (1a) and [κ(4)-ONN*OMe)In(µ-OEt)]2 (1b), which were isolated and fully characterized. Polymerization of racemic lactide with 1a and 1b was slow in refluxing THF and showed only modest stereoselectivity. Catalyst 1b displayed better control than 1a, with the experimental molecular weights of the resulting poly(lactic acid) in agreement with the expected values. The higher-than-expected molecular weights observed in polymers formed by 1a were due to partial initiation of the catalyst. The reaction of (±)-H2(ONN*OtBu) with InCl3 yielded (κ(4)-ONN*OtBu)InCl (2); however, further reactivity of the compound formed a mixture of products. An attempt to prevent aggregation by reacting (±)-H2(ONN*OMe) with InCl3 and excess NaO(i)Pr yielded an intractable mixture, including [(µ-κ(2)-ONN*OMe)In]2(µ-Cl)(µ-OH) (3). The thermal stabilities of compounds 1a and 1b under polymerization conditions were investigated. Examination of the polymerization behavior of complexes 1a and 1b and the reaction equilibrium between the two illustrates the importance of aggregation in indium salen complexes compared to their aluminum counterparts.

Experimental and Theoretical Comparison of Potential-dependent Methylation on Chemically Exfoliated WS2 and MoS2.

Reductant-activated functionalization is shown to enhance the methylation of chemically exfoliated MoS2 (ceMoS2) and ceWS2 by introducing excess negative charge to facilitate a nucleophilic attack reaction. Relative to methylation in the absence of a reductant, the reaction produces a twofold increase in coverage of ceWS2, from 25 to 52% coverage per WS2. However, at every potential, the methyl coverage on ceWS2 was ∼20% lower than that on ceMoS2. We applied grand canonical density functional theory to show that at constant potential, more negative charge is present on 1T'-MoS2 than on 1T'-WS2, making methylation both thermodynamically and kinetically more favorable for 1T'-MoS2 than 1T'-WS2. This effect was moderated when the reactions were compared at constant charge, emphasizing the importance of comparing the reactivity of materials at nominally identical electrode potentials.

Long-term Patterns of Patient Portal Use for Pediatric Patients at an Academic Medical Center.

BACKGROUND: Patient portal adoption has increased over the last two decades. Most research about patient portals has focused on adult populations in the primary care and medical specialty settings. OBJECTIVE: We describe initial and long-term portal use by pediatric patients and their caregivers in a broadly deployed patient portal at an academic medical center. METHODS: We analyzed portal usage for pediatric patients and their caregivers from 2008 to 2014. We recorded usage events with time stamps; user role defined as self, surrogate (i.e., parent or guardian), or delegate; and functions accessed. Usage events were grouped into sessions to calculate descriptive statistics by patient age, user role, and active use over time. RESULTS: From 2008 to 2014, the number of portal accounts increased from 633 to 17,128. 15.9% of pediatric patients had their own account; 93.6%, a surrogate account; and 2.2% a delegate account. During the study period, 15,711 unique users initiated 493,753 sessions and accessed 1,491,237 functions. Most commonly used functions were secure messaging (accessed in 309,204 sessions; 62.6%); test results (174,239; 35.3%) and appointments (104,830; 21.2%). Function usage was greatest for patients ages 0-2 years (136,245 functions accessed; 23.1%) and 15-17 years (109,241;18.5%). Surrogate users conducted 83.2% of logins for adolescent patients. Portal accounts were actively used for < 1 year for 9,551 patients (55.8%), 1-2 years for 2,826 patients (16.5%), 2-3 years for 1,968 patients (11.5%) and over 3 years for 2,783 patients (16.3%). CONCLUSION: Pediatric patients and caregivers have avidly used messaging, test result, and appointment functions. The majority of access was done by surrogates. Adolescent portal usage increased with age. Most accounts for pediatric patients were only used actively for a few years, with peak usage for patients in early childhood and late adolescence.

Insertion of CO2 into the carbon-boron bond of a boronic ester ligand.

New Ru and Zn diazafluorenyl complexes undergo C-H borylation of the diazafluorenyl ligand to form the corresponding diazafluorenylboronic ester complexes, which can insert CO2 into their C-B bonds to form boryl ester functionalities. The relevance of these new reactivities towards catalytic CO2 reduction has also been explored.

Reduced release of nitric oxide to shear stress in mesenteric arteries of aged rats.

We hypothesized that aging is characterized by a reduced release of nitric oxide (NO) in response to shear stress in resistance vessels. Mesenteric arterioles and arteries of young (6 mo) and aged (24 mo) male Fischer 344 rats were isolated and cannulated. Shear stress (15 dyn/cm(2))-induced dilation was significantly reduced and shear stress (1, 5, 10, and 15 dyn/cm(2))-induced increases in perfusate nitrite were significantly smaller at all shear stress levels in vessels of aged rats. Inhibition of NO synthesis abolished shear stress-induced release of nitrite. Furthermore, shear stress (15 dyn/cm(2))-induced release of nitrate was significantly higher and total nitrite (nitrite plus nitrate) was significantly lower in vessels of aged rats. Tiron or SOD significantly increased nitrite released from vessels of aged rats, but this was still significantly less than that in young rats. Superoxide production was increased and the activity of SOD was decreased in vessels of aged rats. There were no differences in endothelial NO synthase (eNOS) protein and basal activity or in Cu/Zn-SOD and Mn-SOD proteins in vessels of the two groups, but extracellular SOD was significantly reduced in vessels of aged rats. Maximal release of NO induced by shear stress plus ACh (10(-5) M) was comparable in the two groups, but phospho-eNOS in response to shear stress (15 dyn/cm(2)) was significantly reduced in vessels of aged rats. These data suggest that an increased production of superoxide, a reduced activity of SOD, and an impaired shear stress-induced activation of eNOS are the causes of the decreased shear stress-induced release of NO in vessels of aged rats.