等浓度的氯化铵和硫酸铵溶液哪个pH高

有中学化学参考资料题:0.10 mol/L的NH4Cl和(NH4)2SO4溶液哪个pH值高?这似乎是个中学生可做的简单题目,仔细考虑不是如此.如果简单地认为盐酸和硫酸都是强酸,而硫酸是二元酸,硫酸铵溶液中铵盐浓度为0.20 mol/L,那么NH4Cl溶液pH高,那是不妥的.硫酸是二元酸,第一个氢离子能完全电离,第二个氢离子部分电离,如此考虑情况怎么样呢?是不是答案发生变化?这要通过计算来说明.     

Enhanced efficiency and stability in Sn-based perovskite solar cells with secondary crystallization growth

The conversion efficiencies reported for Tin(Sn)halide-based perovskite solar cells(PSCs)fall a large gap behind those of lead halide-based PSCs,mainly because of poor film quality of the former.Here we report an efficient strategy based on a simple secondary crystallization growth(SCG)technique to improve film quality for tin halide-based PSCs by applying a series of functional amine chlorides on the perovskite surface.They were discovered to enhance the film crystallinity and suppress the oxidation of Sn²⁺remarkably,hence reduce trap state density and non-irradiative recombination in the absorber films.Furthermore,the SCG film holds the band levels matching better with carrier transport layers and herein favoring charge extraction at the device interfaces.Consequently,a champion device efficiency of 8.07% was achieved alo ng with significant enhancements in VOC and JSC,in contrast to 5.35% of the control device value.Moreover,the SCG film-based devices also exhibit superior stability comparing with the control one.This work explicitly paves a novel and general strategy for developing high performance lead-free PSCs.     

Energy level engineering of charge selective contact and halide perovskite by modulating band offset:Mechanistic insights

Mixed cation and anion based perovskites solar cells exhibited enhanced stability under outdoor conditions,however,it yielded limited power conversion efficiency when TiO₂ and Spiro-OMeTAD were employed as electron and hole transport layer(ETL/HTL)respectively.The inevitable interfacial recombination of charge carriers at ETL/perovskite and perovskite/HTL interface diminished the efficiency in planar(n-i-p)perovskite solar cells.By employing computational approach for uni-dimensional device simulator,the effect of band offset on charge recombination at both interfaces was investigated.We noted that it acquired cliff structure when the conduction band minimum of the ETL was lower than that of the perovskite,and thus maximized interfacial recombination.However,if the conduction band minimum of ETL is higher than perovskite,a spike structure is formed,which improve the performance of solar cell.An optimum value of conduction band offset allows to reach performance of 25.21%,with an open circuit voltage(VOC)of 1231 mV,a current density JSC of 24.57 mA/cm² and a fill factor of 83.28%.Additionally,we found that beyond the optimum offset value,large spike structure could decrease the performance.With an optimized energy level of Spiro-OMeTAD and the thickness of mixed-perovskite layer performance of 26.56% can be attained.Our results demonstrate a detailed understanding about the energy level tuning between the charge selective layers and perovskite and how the improvement in PV performance can be achieved by adjusting the energy level offset.     

A new strategy to access Co/N co-doped carbon nanotubes as oxygen reduction reaction catalysts

Carbon nanotubes(CNTs),as one-dimensional nanomaterials,show great potential in energy conversion and storage due to their efficient electrical conductivity and mass transfer.However,the security risks,time-consuming and high cost of the preparation process hinder its further application.Here,we develop that a negative pressure rather than a following gas environment can promote the generation of cobalt and nitrogen co-doped CNTs(Co/N-CNTs) by using cobalt zeolitic imidazolate framework(ZIF-67) as a precursor,in which the negative pressure plays a key role in adjusting the size of cobalt nanoparticles and stimulating the rearragement of carbon atoms for forming CNTs.Importantly,the obtained Co/N-CNTs,with high content of pyridinic nitrogen and abundant graphitized structure,exhibit superior catalytic activity for oxygen reduction reaction(ORR) with half-wave potential(E_1/2) of 0.85 V and durability in terms of the minimum current loss(2%) after the 30,000 s test.Our development provides a new pathway for large-scale and cost-effective preparation of metal-doped CNTs for various applications.     

Recent Advances of Pure Organic Room Temperature Phosphorescence Materials for Bioimaging Applications

Bioimaging,as a powerful and helpful tool,which allows people to investigate deeply within living organisms,has contributed a lot for both clinical theranostics and scientific research.Pure organic room temperature phosphorescence(RTP)materials with the unique features of ultralong luminescence lifetime and large Stokes shift,can efficiently avoid biological autofluorescence and scattered light through a time-resolved imaging modality,and thus are attracting increasing attention.This review classifies pure organic RTP materials into three categories,including small molecule RTP materials,polymer RTP materials and supramolecular RTP materials,and summarizes the recent advances of pure organic RTP materials for bioimaging applications.     

酵母对抑制剂耐受的系统分析

纤维素生产乙醇的关键问题之一是水解产生的抑制性物质对乙醇发酵具有明显的抑制效应,因而引起了国内外研究者的广泛关注.研究发现,在抑制剂存在下,酵母在基因表达水平,蛋白水平和代谢物水平都有相应的耐受响应,且这些响应错综复杂.从系统角度运用组学的方法研究这一体系将有助于全面深入了解酵母的耐受机制.本文综述了系统研究的思路和方法在酵母对抑制剂耐受方面的研究状况;对主要研究手段和成果进行了回顾;并对酵母发酵乙醇系统分析的前景进行了展望.     

Miniaturized electrochemical sensors and their point-of-care applications

Most of the current analytical methods depend largely on laboratory-based analytical techniques that require expensive and bullky equipment,potentially incur costly testing,and involve lengthy detection processes.With increasing requirements for point-of-care testing(POCT),more attention has been paid to miniaturized analytical devices.Miniaturized electrochemical(MEC)sensors,including different material-based MEC sensors(such as DNA-,paper-,and screen electrode-based),have been in strong demand in analytical science due to their easy operation,portability,high sensitivity,as well as their short analysis time.They have been applied for the detection of trace amounts of target through measuring changes in electrochemical signal,such as current,voltage,potential,or impedance,due to the oxidation/reduction of chemical/biological molecules with the help of electrodes and electrochemical units.MEC sensors present great potential for the detection of targets including small organic molecules,metal ions,and biomolecules.In recent years,MEC sensors have been broadly applied to POCT in various fields,including health care,food safety,and environmental monitoring,owing to the excellent advantages of electrochemical(EC)technologies.This review summarized the state-of-the-art advancements on various types of MEC sensors and their applications in POCT.Furthermore,the future perspectives,opportunities,and challenges in this field are also discussed.     

Stabilizing High-voltage Cathode Materials for Next-generation Li-ion Batteries

The pressing demand for high-energy/power lithium-ion batteries requires the deployment of cathode materials with higher capacity and output voltage.Despite more than ten years of research,high-voltage cathode mate-rials,such as high-voltage layered oxides,spinel LiNi0.5Mn1.5O4,and high-voltage polyanionic compounds still cannot be commercially viable due to the instabilities of standard electrolytes,cathode materials,and cathode electrolyte interphases under high-voltage operation.This paper summarizes the recent advances in addressing the surface and interface issues haunting the application of high-voltage cathode materials.The understanding of the limitations and advantages of different modification protocols will direct the future endeavours on advancing high-energy/power lithium-ion batteries.     

Suppressing trap states and energy loss by optimizing vertical phase distribution through ternary strategy in organic solar cells

Suppressing the trap-state density and the energy loss via ternary strategy was demonstrated.Favorable vertical phase distribution with donors(acceptors)accumulated(depleted)at the interface of active layer and charge extraction layer can be obtained by introducing appropriate amount of polymer acceptor N2200 into the systems of PBDB-T:IT-M and PBDB-TF:Y6.In addition,N2200 is gradiently distributed in the vertical direction in the ternary blend film.Various measurements were carried out to study the effects of N2200 on the binary systems.It was found that the optimized morphology especially in vertical direction can significantly decrease the trap state density of the binary blend films,which is beneficial for the charge transport and collection.All these features enable an obvious decrease in charge recombination in both PBDB-T:IT-M and PBDB-TF:Y6 based organic solar cells(OSCs),and power conversion efficiencies(PCEs)of 12.5%and 16.42%were obtained for the ternary OSCs,respectively.This work indicates that it is an effective method to suppress the trap state density and thus improve the device performance through ternary strategy.     

Conformational Properties of Comb-shaped Polyelectrolytes with Negatively Charged Backbone and Neutral Side Chains Studied by a Generic Coarse-grained Bead-and-Spring Model

A generic coarse-grained bead-and-spring model,mapped onto comb-shaped polycarboxylate-based(PCE)superplasticizers,is developed and studied by Langevin molecular dynamics simulations with implicit solvent and explicit counterions.The agreement on the radius of gyration of the PCEs with experiments shows that our model can be useful in studying the equilibrium sizes of PCEs in solution.The effects of ionic strength,side-chain number,and side-chain length on the conformational behavior of PCEs in solution are explored.Single-chain equilibrium properties,including the radius of gyration,end-to-end distance and persistenee length of the polymer backbone,shape-asphericity parameter,and the mean span dimension,are determined.It is found that with the increase of ionic strength,the equilibrium sizes of the polymers decrease only slightly,and a linear dependenew of the persistence length of backbone on the Debye screening length is found,in good agreement with the theory developed by Dobrynin.Increasing side-chain numbers and/or side-chain lengths increases not only the equilibrium sizes(radius of gyration and mean span)of the polymer as a whole,but also the persistence length of the backbone due to excluded volume interactions.     

以“联合大作业”实践加强学生创新创业能力的培养

以联合大作业的实践项目,通过校企合作、项目驱动、兴趣引导、文献查阅、市场调研、实验研发等实践训练,激发学生的创新创业意识,加强课内外联动,培养学生的自主学习能力、团队协作能力和创新能力。改革实践教学模式和方法,构建产学研创新实践平台,探索符合社会转型发展需要的复合型、创新型人才课外培养的有效途径。     

构建化学实验教学新体系,培养创新创业人才

基于创新创业型人才培养的需要,针对当前化学化工专业大学生实验教学中的能力培养问题,通过实验教学内容与科学研究和生产应用互动,构建了化学实验教学新体系,将训练实验技能、训练知识转移能力、训练创新创业意识等环节相互融合、相互支撑,从课内延伸到课外,做到大学四年创新创业训练不断线,并在本科生的实验教学过程中进行了实施,取得了良好的教学效果。     

大学生创新创业训练计划助推化学专业双创育人

以四川大学化学学院大学生创新创业训练计划为例,从学生创新创业理念培养、教育条件支撑建设和制度保障完善三个方面简要介绍以大学生创新创业训练计划为突破口的双创教育模式。本文剖析了四川大学化学学院2015–2019年大创实施成效,探讨了大学生创新创业训练计划实施过程中存在的不足,结合线上主题问卷调查结果进一步指出了今后改进的方向。     

"新工科"视角下以学生为中心"一纵三横"创新人才培养模式

Under the new economic background, social development needs more high-quality innovative talents with strong engineering practice ability, strong innovation ability and international competitiveness. Based on "emerging engineering education" perspective, the student-centered and "Yi-Zong and San-Heng" education mode has been proposed by analyzing the traditional talent training mode, which will better improve the "new system" of military engineering education.     

大学生实习实训与实践活动的融合与探索

为促进学生学思结合、知行统一,培养合格人才,近年来,武汉大学化学与分子科学学院对本科生实习实训与实践活动进行了融合与探索,形成了几大类别:科研院所实习实训实践类、企业公司实习实训类、志愿服务实践类、国情调研实践类、海外创新实训类。在探索中始终坚持协同与创新两大理念,通过整合各方资源、构建课程体系等,统筹推进大学生实习实训与实践活动,满足学生个性化发展需求,助力学生成才。     

用新工科理念做强做优盐湖化工特色专业

In order to better serve the local economic construction, the specialty of Salt Lake chemical industry is strengthened and optimized based on the concept of emerging engineering education (3E). The education reform has been carried out actively so as to meet the new needs of industrial development. The improvement of curriculum system was made by enhancing the multi-discipline education, updating the teaching contents, setting up school enterprise cooperation for teaching, research and application with strengthening innovation and engineering practice ability training. The reform has achieved good results and laid solid foundation for the future development of a new 3E major of Science and Technology of Salt Lake.     

高分子材料与工程专业生产实习环节的教学改革与实践

本文结合高分子材料与工程专业教学实践,分析了生产实习教学实际情况及存在的问题,对生产实习课程进行改革,提出了校外实习与校内实习协同进行的新生产实习模式,重点建设校内生产实习内容体系,切实解决校外实习内容更新慢,缺乏前沿成型技术这一问题。校内实习基地的建设结合了制度保障体系、教师队伍和信息化平台建设等进行了深入实践,学生参与生产实习的热情提高明显,各项创新创业大赛、考研和就业情况表明,本专业学生具有较好的工程实践和创新能力,改革实施效果明显。     

新工科背景下湖南大学应用化学专业教学改革研究与实践

新工科背景下我国高校强调宽口径、跨学科和复合型的应用化学学科人才培养。结合我校近年来应用化学专业教学改革研究的实际情况,从专业综合改革、实践教学、创新创业及海外课程等几个方面,总结了应用化学专业本科教学的改革成果。     

大学化学课程德育的设计与实践

Based on the teaching practice of chemistry courses in university and guided by the training specifications of talents, this paper carried out the ideology of moral education in the course and designed the moral education contents. Specifically, there were five aspects, including the patriotism sentiment, the collaborative spirit, the social responsibility, the innovation and entrepreneurship, the logical thinking and dialectical thinking. Moreover, this paper also putted forward the implementation strategy with combination of the teaching and the self-education.     

在化学实验课程教学中引入模拟创业的探索和体会

Under the background of the times when the state promotes innovation and entrepreneurship, the department of chemistry of Fudan University has introduced the concepts of innovation and cost accounting into the laboratory course of analytical chemistry to cultivate students' awareness of entrepreneurship and environmental protection etc. At the same time, it can further enhance students' interest in the laboratory course.