Enhancing Photoluminescence and Mobilities in WS2 Monolayers with Oleic Acid Ligands.

Many potential applications of monolayer transition metal dichalcogenides (TMDs) require both high photoluminescence (PL) yield and high electrical mobilities. However, the PL yield of as prepared TMD monolayers is low and believed to be limited by defect sites and uncontrolled doping. This has led to a large effort to develop chemical passivation methods to improve PL and mobilities. The most successful of these treatments is based on the nonoxidizing organic "superacid" bis(trifluoromethane)sulfonimide (TFSI) which has been shown to yield bright monolayers of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) but with trap-limited PL dynamics and no significant improvements in field effect mobilities. Here, using steady-state and time-resolved PL microscopy we demonstrate that treatment of WS2 monolayers with oleic acid (OA) can greatly enhance the PL yield, resulting in bright neutral exciton emission comparable to TFSI treated monolayers. At high excitation densities, the OA treatment allows for bright trion emission, which has not been demonstrated with previous chemical treatments. We show that unlike the TFSI treatment, the OA yields PL dynamics that are largely trap free. In addition, field effect transistors show an increase in mobilities with the OA treatment. These results suggest that OA serves to passivate defect sites in the WS2 monolayers in a manner akin to the passivation of colloidal quantum dots with OA ligands. Our results open up a new pathway to passivate and tune defects in monolayer TMDs using simple "wet" chemistry techniques, allowing for trap-free electronic properties and bright neutral exciton and trion emission

Agenda 21.

A Agenda 21 Brasileira é um processo e, ao mesmo tempo, instrumento de planejamento participativo para o desenvolvimento sustentável e que tem como eixo central a sustentabilidade, compatibilizando a conservação ambiental, a justiça social e o crescimento econômico. O documento e resultado de uma vasta consulta a população brasileira, sendo construída a partir das diretrizes da Agenda 21 global. Trata-se, portanto, de um instrumento fundamental para a construção da democracia ativa e da cidadania participativa no pais. A primeira fase foi a construção da Agenda 21 Brasileira. Esse processo, que se deu de 1996 a 2002, foi coordenado pela Comissão de Politicas de Desenvolvimento Sustentável e da Agenda 21 Nacional - CPDS e teve o envolvimento de cerca de 40.000 pessoas de todo o Brasil. O documento Agenda 21 Brasileira foi concluído em 2002. A partir de 2003, a Agenda 21 Brasileira não somente entrou na fase de implementação assistida pela CPDS, como também foi elevada a condição de Programa do Plano Plurianual, PPA 2004-2007, pelo atual governo. Como programa, ela adquire mais foça politica e institucional, passando a ser instrumento fundamental para a construção do Brasil Sustentável, estando coadunada com as diretrizes da politica ambiental do Governo-transversalidade, desenvolvimento sustentável, fortalecimento do Sistema e participação social, adotando referenciais importantes como a Carta da Terra. Portanto, a Agenda 21, que tem provado ser um guia eficiente para processos de união da sociedade, compreensão dos conceitos de cidadania e de sua aplicação, e hoje um dos grandes instrumentos de formação de politicas públicas no Brasil.Agenda 21 Brazilian is a process and, at the same time, instrument of participative planning for the sustainable development and that it has as central axle the sustentabilidade, compatibizando the ambient conservation, social justice and the economic growth. The document is resulted of a vast one consults the Brazilian population, being constructed from the lines of direction of global Agenda 21. It is treated, therefore, of a basic instrument for the construction of the active democracy and the participative citizenship in the Country. The first phase was the construction of Agenda 21 Brazilian. This process, that if gave of 1996 the 2002, was co-ordinated by the Commission of Politics of Sustainable Development and the National Agenda 21 - CPDS and had the envolvement of about 40.000 people of all Brazil. The document Agenda 21 Brazilian was concluded in 2002. From 2003, Agenda 21 Brazilian not only entered in the phase of implementation attended for the CPDS, as also condition of Program of the Puritanical Plan was raised a, PPA 2004-2007, for the current government. As program, it it acquires more force institutional politics and, starting to be basic instrument for the construction of Sustainable Brazil, being coadunate with the lines of direction of the ambient politics of the Government-transversaldade, sustainable development, fortalecimento of the System and social participation, adopting referenciais important as the Letter of the Land. Therefore, Agenda 21, that it has proven being an efficient guide for processes of union of the society, understanding of the concepts of citizenship and its application, is today one of the great instruments of formation of public politics in Brazi

Rational Passivation of Sulfur Vacancy Defects in Two-Dimensional Transition Metal Dichalcogenides.

Structural defects vary the optoelectronic properties of monolayer transition metal dichalcogenides, leading to concerted efforts to control defect type and density via materials growth or postgrowth passivation. Here, we explore a simple chemical treatment that allows on-off switching of low-lying, defect-localized exciton states, leading to tunable emission properties. Using steady-state and ultrafast optical spectroscopy, supported by ab initio calculations, we show that passivation of sulfur vacancy defects, which act as exciton traps in monolayer MoS2 and WS2, allows for controllable and improved mobilities and an increase in photoluminescence up to 275-fold, more than twice the value achieved by other chemical treatments. Our findings suggest a route for simple and rational defect engineering strategies for tunable and switchable electronic and excitonic properties through passivation

Rational Passivation of Sulfur Vacancy Defects in Two-Dimensional Transition Metal Dichalcogenides.

Structural defects vary the optoelectronic properties of monolayer transition metal dichalcogenides, leading to concerted efforts to control defect type and density via materials growth or postgrowth passivation. Here, we explore a simple chemical treatment that allows on-off switching of low-lying, defect-localized exciton states, leading to tunable emission properties. Using steady-state and ultrafast optical spectroscopy, supported by ab initio calculations, we show that passivation of sulfur vacancy defects, which act as exciton traps in monolayer MoS2 and WS2, allows for controllable and improved mobilities and an increase in photoluminescence up to 275-fold, more than twice the value achieved by other chemical treatments. Our findings suggest a route for simple and rational defect engineering strategies for tunable and switchable electronic and excitonic properties through passivation

Correlation between systemic immune inflammatory index and prognosis of patients with hepatic alveolar hydatid disease and establishment of a nomogram prediction model

BackgroundTo explore the evaluation value of systemic immune inflammation index (SII) in the prognosis of patients with alveolar hydatid disease, and establish a nomogram prediction model.MethodsCollect the clinical data of 351 patients undergoing hepatic alveolar hydatid surgery admitted to the Department of Hepatobiliary and Pancreatic Surgery, Affiliated Hospital of Qinghai University from January 2015 to December 2020, calculate the SII value, and use the receiver operating characteristic curve (ROC curve) to determine According to the optimal clinical cut-off value of SII, patients were divided into two groups with high SII and low SII, and the relationship between SII and clinicopathological factors and prognosis of patients with alveolar echinococcosis was analyzed. Establish a nomogram prediction model based on independent risk factors for patient prognosis, and evaluate the prediction accuracy and discrimination ability of the nomogram through the consistency index (C-index) and calibration curve. The result is through the use of bootstrapping validation with 1,000 re-sampling Method for internal verification.ResultsThe ROC curve was used to determine the optimal cut-off value of SII before operation 761.192, and patients were divided into low SII group (n = 184) cases and high SII group (n = 167) cases. The 1, 3, and 5-year survival rates of patients with hepatic alveolar hydatid in the low SII group and the high SII group were 98.90%, 96.90%, 86.50% and 98.20%, 72.50%, 40.30%, respectively. The survival rate of worm disease patients was significantly better than that of the high SII group, and the overall survival rate difference between the two groups was statistically significant (P < 0.001). Multivariate Cox regression model analysis results showed that intraoperative blood loss (HR = 1.810, 95%CI: 1.227–2.668, P = 0.003), SII (HR = 5.011, 95%CI: 3.052–8.228, P < 0.001), Complications (HR = 1.720, 95%CI: 1.162–2.545, P = 0.007) are independent risk factors for the prognosis of patients with alveolar hydatid disease. Draw a nomogram and include statistically significant factors in the multivariate Cox regression model to predict the overall survival rate of patients with alveolar hydatid disease at 1, 3, and 5 years. The survival probability calibration curve is displayed. The nomogram is compared with The actual results have a high degree of agreement. The concordance index (C-index) of the nomogram model in the modeling sample is 0.777, and the C-index in the verification sample is 0.797, indicating that the nomogram model of this study has good accuracy and discrimination.ConclusionsSII has a clear correlation to the prognosis of patients with alveolar echinococcosis. The nomogram prediction model constructed on this basis is beneficial to the clinically individualized analysis of the patient's prognosis