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.     

基于翻转课堂的大学实验化学教学研究与实践

Experimental chemistry is an important public foundation course for the undergraduate student during their first year at Shihezi University. This paper introduces the teaching status and implementation of the experimental chemistry curriculum. Based on the student activities, this paper firstly constructs flipped learning mode of the experimental chemistry, combining the curriculum resource preparation with online and offline teaching. Secondly, the experimental chemistry curriculum takes deep integration of information technology and classroom teaching as an opportunity. Furthermore, the teaching implementation is carried out by the network teaching platform of Shihezi university. Finally, the student's questionnaire displays that it works well in improving the teaching quality.     

基于MOOC“一站式”有机化学在线翻转课堂实践

Under the case of novel coronavirus (COVID 19), and in response to the Ministry of Education's call for "postponement of school without suspension of learning", online teaching should be equivalent to the real class teaching. Based on Chinese University MOOC platform, this paper establishes SPOC on campus with the open online course Organic Chemistry as the online learning resource. Before class, students learn online video and self-testing. The teacher will answer questions and interact with students through live broadcasting. The student will practice and consolidate after school. "One-stop" solves the learning needs of the three stages of online flipped classroom and demonstrates online flipped classroom teaching effect.     

在线课程与翻转课堂相结合的大学化学混合式教学实践

介绍了自2017年以来天津大学大学化学课程使用在线课程和翻转课堂相结合的混合式教学实践,包括课程的组织模式、翻转课堂内容的选择、翻转课堂课时与课程总课时的比例、期末成绩分析和教学反思等。教学实践结果显示,选取学生在中学化学有一定基础的知识点作为教学内容,课时占课程总课时的30%–50%时进行翻转课堂教学,教学效果明显好于完全传统教学的平行对照班。     

现代教育技术构建氧化还原反应线上实验教学的策略探索与实践

In the era of "Internet +", with the help of national excellent MOOC course of Chinese university and Mlabs-virtual experimental software, Tencent classroom is built to provide a diversified and efficient online inorganic chemistry basic laboratory classroom by combining a variety of modern education technologies with the concept of flipped classroom. Taking the redox reaction experiment as an example, we designed a multi-link teaching process and carried out a multi-faceted assessment. The online teaching can not only strengthen the cultivation of students' comprehensive and innovating ability, but also help teachers to update the teaching mode and create the new experimental content in line with the development of the times, so as to realize the mutual learning between teachers and students in the exploration of experimental teaching reform.     

英才班基础化学原理自主学习模式的构建与实践

"Creative teaching" is the most suitable teaching pattern for the training of top-notch talents and the core is the cultivation of elite-class students' autonomous learning ability. We have tried to build the autonomous learning mode in the course of Principles of Basic Chemistry for the elite-class major in polymer materials engineering. The teaching practice has been carried out in six aspects that are "leading both teachers and students to change minds, constructing autonomous learning platform, activating the classroom teaching, complementary integration between PBL teaching method and 'the flipped classroom', 'a line' for extracurricular self-study, and 'point-line-face' generalization and summarization".     

利用有机波谱教学网站iSpec进行游戏化课堂教学的实践*

针对学生在有机化学波谱学学习过程中枯燥、难以形象化的具体情况,介绍一个利用有机波谱在线学习的网站进行游戏化课堂教学的学习活动,以期提升学生在该课程学习中的积极性及学习效果。该教学活动的实施分为课堂和课后进行,主要依托iSpec网站游戏竞赛的答题模式,结合教师课堂教学及学生自主学习,进行相关知识技能的教授,最终提升学生的学习效率与效果。     

激励机制辅助的翻转课堂教学模式的应用——以有机化学实验为例

针对我校有机化学实验课程传统教学模式中存在的弊端,探索了激励机制辅助的"翻转课堂"教学模式,并以正溴丁烷的制备实验为例,介绍了课前、课中以及课后的教师和学生工作内容以及教学评价。实践表明:激励机制辅助的"翻转课堂"教学模式,极大地调动了学生自主学习的积极性和主动性,且激励机制可以更有效地保证"翻转课堂"的顺利实施。     

翻转课堂在仪器分析教学中的应用

针对当前仪器分析课程普遍存在理论知识抽象、枯燥、难以理解,学生学习难度较大、学习积极性不高的问题,提出将翻转课堂的教学模式应用于仪器分析教学中。该教学模式通过学生课前预习、课中完成知识吸收与内化、课后教师布置练习作业或者拓展性学习任务,线上与线下学生与教师交流互动的方式,提高了学生学习该课程的兴趣,培养了学生自主学习、独立思考及创新的能力。同时,该教学模式适用于多民族学生的共同学习。     

SPOC模式下无机与分析化学课程教学实践

以无机与分析化学课程教学为例,探讨了SPOC混合教学模式下提高学生知识与能力的有效途径。在该课程教学中的应用和考核评价中,采用课堂教学与在线自主学习相结合的教学方式,实现了以能力培养为目标的本科教育模式的"三个转变":(1)以教为主向以学为主的转变;(2)以课堂教学为主向课内课外结合为主的转变;(3)以结果评价为主向以结果与过程评价相结合为主的转变。有效地提高了教学质量,突出地解决了目前高等院校本科教育模式面临的学生学习主动性差、参与度少的问题。     

从知识到智慧:有深度的教和学——化学生物交叉班分析化学课程教学思考

以面向本科化学生物学交叉班的专业基础必修课分析化学为例,从构建多维度关联的课程知识结构,营造意义丰富、身心沉浸以及层层剖析、步步推进的自主学习氛围,探索启发式与翻转式相结合的教学形式,以及教材分析和研究、课外实践、学习过程评价、课程资源建设等方面,探讨分析化学课程的深度学习与深度教学途径,使学生不仅获得高级认知和高阶思维能力,而且在动心用情的学习过程中,把握知识的本质和思想方法,促进知识向学科核心素养和关键能力的转化。