自组装协同催化高选择性合成卤代芳烃

卤代芳烃是非常重要的合成砌块,广泛应用于农用化学品、材料和药物等的合成。芳烃的亲电取代卤化反应是制备芳基卤化物最简单的方法,但是富电子芳烃的卤化反应存在区域选择性差的挑战。本实验采用自组装协同催化策略,以环己基苯溴化反应为模型反应,高选择性合成溴代芳烃,进而应用于卤代芳烃的高选择性合成。在加深学生芳烃亲电取代卤化反应的同时,也向学生传授自组装、协同催化和路易斯酸碱催化等重要知识,加深学生对亲电取代反应机理和离子型中间体的了解。实验主要由卤代芳烃的合成、机理探究及实验普适性三部分组成,包含多种有机实验基本操作,涉及反应监测、分离纯化、产物表征等多个重要环节,实验整体时长7小时,安全性高,可操作性强,适合本科实验教学开设。本实验秉持科研反哺教学的理念,将新的科研成果转化为人才培养内容,有助于提高学生的科研创新与实践能力。

Assessment of the three representative empirical models for zenith tropospheric delay(ZTD)using the CMONOC data

The precise correction of atmospheric zenith tropospheric delay(ZTD)is significant for the Global Navigation Satellite System(GNSS)performance regarding positioning accuracy and convergence time.In the past decades,many empirical ZTD models based on whether the gridded or scattered ZTD products have been proposed and widely used in the GNSS positioning applications.But there is no comprehensive evaluation of these models for the whole China region,which features complicated topography and climate.In this study,we completely assess the typical empirical models,the IGGtropSH model(gridded,non-meteorology),the SHAtropE model(scattered,non-meteorology),and the GPT3 model(gridded,meteorology)using the Crustal Movement Observation Network of China(CMONOC)network.In general,the results show that the three models share consistent performance with RMSE/bias of 37.45/1.63,37.13/2.20,and 38.27/1.34 mm for the GPT3,SHAtropE and IGGtropSH model,respectively.However,the models had a distinct performance regarding geographical distribution,elevation,seasonal variations,and daily variation.In the southeastern region of China,RMSE values are around 50 mm,which are much higher than that in the western region,approximately 20 mm.The SHAtropE model exhibits better performance for areas with large variations in elevation.The GPT3 model and the IGGtropSH model are more stable across different months,and the SHAtropE model based on the GNSS data exhibits superior performance across various UTC epochs.

A survey on large language model(LLM)security and privacy:The Good,The Bad,and The Ugly

Large Language Models(LLMs),such as ChatGPT and Bard,have revolutionized natural language understanding and generation.They possess deep language comprehension,human-like text generation capabilities,contextual awareness,and robust problem-solving skills,making them invaluable in various domains(e.g.,search engines,customer support,translation).In the meantime,LLMs have also gained traction in the security community,revealing security vulnerabilities and showcasing their potential in security-related tasks.This paper explores the intersection of LLMs with security and privacy.Specifically,we investigate how LLMs positively impact security and privacy,potential risks and threats associated with their use,and inherent vulnerabilities within LLMs.Through a comprehensive literature review,the paper categorizes the papers into‘‘The Good’’(beneficial LLM applications),‘‘The Bad’’(offensive applications),and‘‘The Ugly’’(vulnerabilities of LLMs and their defenses).We have some interesting findings.For example,LLMs have proven to enhance code security(code vulnerability detection)and data privacy(data confidentiality protection),outperforming traditional methods.However,they can also be harnessed for various attacks(particularly user-level attacks)due to their human-like reasoning abilities.We have identified areas that require further research efforts.For example,Research on model and parameter extraction attacks is limited and often theoretical,hindered by LLM parameter scale and confidentiality.Safe instruction tuning,a recent development,requires more exploration.We hope that our work can shed light on the LLMs’potential to both bolster and jeopardize cybersecurity.

Electron-transporting boron-doped polycyclic aromatic hydrocarbons:Facile synthesis and heteroatom doping positions-modulated optoelectronic properties

While heteroatom doping serves as a powerful strategy for devising novel polycyclic aromatic hydrocarbons(PAHs), the further fine-tuning of optoelectronic properties via the precisely altering of doping patterns remains a challenge. Herein, by changing the doping positions of heteroatoms in a diindenopyrene skeleton, we report two isomeric boron, sulfur-embedded PAHs, named Anti-B_(2)S_(2) and Syn-B_(2)S_(2), as electron transporting semiconductors. Detailed structure-property relationship studies revealed that the varied heteroatom positions not only change their physicochemical properties, but also largely affect their solid-state packing modes and Lewis base-triggered photophysical responses. With their low-lying frontier molecular orbital levels, n-type characteristics with electron mobilities up to 1.5 × 10^(-3)cm^(2)V^(-1)s^(-1)were achieved in solution-processed organic field-effect transistors. Our work revealed the critical role of controlling heteroatom doping patterns for designing advanced PAHs.

Association between socio-economic factors and the risk of overweight and obesity among Chinese adults:a retrospective cross-sectional study from the China Health and Nutrition Survey

Background:With the rising prevalence of obesity and overweight,increasing number of scholars paid attention to the negative effects on human health and life.Recent years,many studies have focused on the relation of socio-economic factors with the risk of overweight or obesity,but findings have been inconsistent.This study investigated the relationship between socio-economic factors and the risk of overweight and obesity among Chinese adults.Methods:This study was based on the survey of the China Health and Nutrition Survey in 2015,with 9245 Chinese adults aged 18-65 years old.Overweight and obesity were assessed by physical measurements of weight,height,and waist circumference.Multiple logistic models were used to estimate the odds ratios(ORs)and 95%confidence intervals(CIs)of the association.Results:Overall,the prevalence rates of general obesity and abdominal obesity were 15.5%and 22.6%,respectively.We found that education and per capita household income were positively associated with overweight and obesity risk in men.However,the association between education and obesity status was negative in women[general obesity:OR=0.64,95%CI(0.50-0.81);abdominal obesity:OR=0.62,95%CI(0.51-0.76)].Occupational status was only associated with general overweight in men.Conclusions:Results suggested that higher education and per capita household income were associated with an increased risk of overweight and obesity among Chinese men,whereas the associations were negative for women.We recommended that men with high levels of education and income,women with low levels of education,can engage in some physical activity,modify dietary,and adopt a new way of life to maintain their weight and general health.

High performance organic transistors and phototransistors based on diketopyrrolopyrrole-quaterthiophene copolymer thin films fabricated via low-concentration solution processing

Conjugated polymers have received considerable attentions over the past years due to their large-area potential applications via low-cost solution processing. Improving crystallinity of conjugated polymer molecules in solution-processed thin films is crucial for their efficient charge transport and thus high performance optoelectronic devices. Herein, with diketopyrrolopyrrole-quaterthiophene （PDQT） copo/ymer as an example, it is found that by simply reducing the solution concentration for spincoating meanwhile with the assistance of post-annealing, significantly enhanced film crystallinity with formation of typical single crystalline domains is obtained, which benefits from the enough space for better molecular assembly especially at the semiconductor/dielectric interface. High performance polymer transistors and phototransistors were finally constructed based on the optimal lowconcentration （2 mg/mL） spin-coated PDQT films （～12 nm）, which giving a high charge carrier mobility of 2.28 cm2 V-1 s-1 and a photoresponse on/off ratio of 2.1 ×107 at VG = 0 V under white light irradiation of 6mW/cm2. The results suggest that the bright future of PDQT crystalline films for large-area flexible integrated optoelectronic devices and the application of effective low-concentration processing approach in solution-processed organic electronics with reduced material waste.

Organic photodetectors based on supramolecular nanostructures

Self‐assembly of semiconducting(macro)molecules enables the development of materials with tailored‐made properties which could be used as active components for optoelectronics applications.Supramolecular nanostructures combine the merits of soft matter and crystalline materials:They are flexible yet highly crystalline,and they can be processed with low‐cost solution methods.Photodetectors are devices capable to convert a light input into an electrical signal.To achieve high photoresponse,the photogenerated charge carriers should be transported efficiently through the self‐assembled nanostructures to reach the electrodes;this can be guaranteed via optimalπ–electron overlapping between adjacent conjugated molecules.Moreover,because of the high surface‐to‐bulk ratio,supramolecular nanostructures are prone to enhance exciton dissociation.These qualities make supramolecular nanostructures perfect platforms for photoelectric conversion.This review highlights the most enlightening recent strategies developed for the fabrication of high‐performance photodetectors based on supramolecular nanostructures.We introduce the key figure‐of‐merit parameters and working mechanisms of organic photodetectors based on single components and p–n heterojunctions.In particular,we describe new methods to devise unprecedented planar and vertical devices to ultimately realize highly integrated and flexible photodetectors.The incorporation of ordered mesoscopic supramolecular nanostructures into macroscopic optoelectronic devices will offer great promise for the next generation of multifunctional and multiresponsive devices.

Configurable microcavity-enhanced graphene photothermoelectric terahertz detectors

Terahertz(THz)detectors with high sensitivity,fast response speed,room temperature operation,and self-powered feature are the key component for many THz applications.Microcavity resonators can effectively improve the sensitivity of THz detectors.However,it is difficult to precisely evaluate the microcavity resonator induced such improvement in experiment.Here,we realize a configurable microcavity–antenna-integrated graphene photothermoelectric(PTE)THz detector.Through the microcavity–antenna hybrid structure,THz radiations are localized and enhanced at one end of the graphene channel,and the temperature difference along the channel is greatly increased,resulting in the strong enhancement of PTE response.At the resonant frequency,the device has a high responsivity(976 V/W),low noise equivalent power(2.87 pW∕Hz1∕2),and fast response speed(300 ns)at room temperature and in zero-bias operation mode.The microcavity-induced peak enhancement factor of 13.14 is accurately extracted.The microcavity–antenna introduced enhancement is further confirmed by using a two-temperature heat transfer model.The strategy of using a configurable microcavity is useful for further optimizing THz detectors by introducing the critical coupling mechanism.