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.     

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.     

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.     

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.     

Three-dimensionalization via control of laser-structuring parameters for high energy and high power lithium-ion battery under various operating conditions

Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery(LIB)electrodes.In this work,the effects of laser structuring parameters(groove pitch and depth)on the fundamental characteristics of LIB electrode,such as interfacial area,internal resistances,material loss and electrochemical performance,are investigated,LiNi_0.5Co_0.2Mn_0.3O₂ cathodes were structured by a femtosecond laser by varying groove depth and pitch,which resulted in a material loss of 5%-14%and an increase of 140%-260%in the in terfacial area between electrode surface and electrolyte.It is shown that the importance of groove depth and pitch on the electrochemical performance(specific capacity and areal discharge capacity)of laser-structured electrode varies with current rates.Groove pitch is more im porta nt at low current rate but groove depth is at high curre nt rate.From the mapping of lithium concentration within the electrodes of varying groove depth and pitch by laser-induced breakdown spectroscopy,it is verified that the groove functions as a diffusion path for lithium ions.The ionic,electronic,and charge transfer resistances measured with symmetric and half cells showed that these internal resistances are differently affected by laser structuring parameters and the changes in porosity,ionic diffusion and electronic pathways.It is demonstrated that the laser structuring parameters for maximum electrode performance and minimum capacity loss should be determined in consideration of the main operating conditions of LIBs.     

Mesh-like vertical structures enable both high areal capacity and excellent rate capability

In order to balance electrochemical kinetics with loading level for achieving efficient energy storage with high areal capacity and good rate capability simultaneously for wearable electronics,herein,2 D meshlike vertical structures(NiCo_2 S_4@Ni(OH)_2) with a high mass loading of 2.17 mg cm^-2 and combined merits of both 1 D nanowires and 2 D nanosheets are designed for fabricating flexible hybrid supercapacitors.Particularly,the seamlessly interconnected NiCo_2 S_4 core not only provides high capacity of 287.5 μAh cm^-2 but also functions as conductive skeleton for fast electron transport;Ni(OH)_2 sheath occupying the voids in NiCo_2 S_4 meshes contributes extra capacity of 248.4 μAh cm^-2;the holey features guarantee rapid ion diffusion along and across NiCO_2 S_4@Ni(OH)_2 meshes.The resultant flexible electrode exhibits a high areal capacity of 535.9 μAh cm^-2(246.9 mAh g^-1) at 3 mA cm^-2 and outstanding rate performance with 84.7% retention at 30 mA cm^-2,suggesting efficient utilization of both NiCo_2 S_4 and Ni(OH)_2 with specific capacities approaching to their theoretical values.The flexible solid-state hybrid device based on NiCo_2 S_4@Ni(OH)_2 cathode and Fe_2 O_3 anode delivers a high energy density of 315 μWh cm^-2 at the power density of 2.14 mW cm^-2 with excellent electrochemical cycling stability.     

Complete assignments of 1H and 13C NMR spectral data for benzylidenebenzyl butyrolactone lignans

The structures of three benzylidenebenzyl butyrolactone lignans (gossypifan, carthamogenin, and savinin) have been established on basis of 1H NMR and 13C NMR spectroscopic data. The 1H NMR and 13C NMR spectra of these lignans have been fully assigned by the use of techniques such as gCOSY, non-edited gHSQC, and gHMBC. Complete assignment and most homonuclear hydrogen coupling constant measurements were performed, also providing enough data for the determination of the relative stereochemistry.     

95Mo magic angle spinning NMR at high field: improved measurements and structural analysis of the quadrupole interaction in monomolybdates and isopolymolybdates

In this study, 95Mo quadrupole couplings in various molydbates were measured easily and accurately with magic angle spinning (MAS) NMR under a directing field of 19.6 T. The resonance frequency of 54 MHz was sufficiently high to remove acoustic ringing artifacts, and the spectra could be analyzed in the usual terms of chemical shift and quadrupolar line shapes. For monomolybdates and molybdite, the quadrupole coupling dominated the NMR response, and the quadrupole parameters could be measured with better accuracy than in previous lower field studies. Moreover, despite the low symmetry of the molybdenum coordination, the usefulness of such measurements to probe molybdenum environments was established by ab initio density functional theory (DFT) calculations of the electric field gradient from known structures. The experimental NMR data correlated perfectly with the refined structures. In isopolymolybdates, the resonances were shapeless and DFT calculations were impossible because of the large and low symmetry unit cells. Nevertheless, empirical but clear NMR signatures were obtained from the spinning sidebands analysis or the MQMAS spectra. This was possible for the first time thanks to the improved baseline and sensitivity at high fields. With the generalization of NMR spectrometers operating above 17 T, it was predicted that 95Mo MAS NMR could evolve as a routine characterization tool for ill-defined structures such as supported molybdates in catalysis.     

用于电子传输材料的含噻吩环噁二唑衍生物的合成(英文)

在有机电致发光器件研究中,电子传输材料占有特殊重要的地位。但现存的材料存在着不同的缺点。因噁二唑环的高的电子亲和性,噁二唑衍生物是常见的电子传输材料,如:2-(4- 叔丁苯基)-5-联苯基噁二唑(PBD),但容易结晶和低的电子亲和性限制了它的应用。为了得到新的有效的电子传输材料,本文以噻吩为起始反应物经过二碘代、羧酸化、酯化、氨解等步骤合成了噻吩二酰肼,再通过噻吩二酰肼与相应的取代苯甲酰氯缩合、关环的方法将富电子的噻吩环和高电子亲和性的噻吩环同时引入,合成了三种新的含噻吩环噁二唑衍生物2,5-双[2,2’-双(5-取代苯基)-1,3,4-噁二唑]噻吩(R-OXD R=H,OCH_3,CH_3)。同时,采用循环伏安法对其电化学性能进行了测定。这三种化合物都在负方向出现了-对可逆的氧化还原峰,由此得到其电子亲和势(EA)分别为-3.10eV,-3.07eV和-3.08eV,其EA值都高于常用的电子传输材料PBD。R-OXD的高电子亲和势有利于电子从阴极注入。并且由时间渡越法(TOF)测得R-OXD的电子迁移率达到10~(-4)cm~2/V.S(E=10~6V/cm)。所以R-OXD有可能是好的电子传输材料。     

用于电子传输材料的含噻吩环噁二唑衍生物的合成

在有机电致发光器伯研究中,电子传输材料占有特殊重要的地位。但现存在的材料存在着不同的缺点。因噁二唑环的高的电子亲和性,噁二唑衍生物是常见的电子传输材料,如：2-(4-叔丁苯基)-5-联苯基噁二唑(PBD),但容易结晶和低的电子? 缀托韵拗屏怂挠τ谩Ｎ说玫叫碌挠行У牡缱哟洳牧希疚囊脏绶晕鹗挤从ξ锞獯Ⅳ人峄Ⅴセ苯獾炔街韬铣闪肃绶远ｋ拢偻ü绶远ｋ掠胂嘤Φ娜〈郊柞Ｂ人鹾稀⒐鼗返姆椒ń坏缱拥泥绶曰泛透叩缱忧缀托缘泥绶曰吠币耄铣闪巳中碌暮绶曰穱f二唑衍生物2,5-双[2,2'-双(5-取代苯基)-1,3,4-噁二唑]噻吩(R-OXDR=H,OCH~3,CH~3)。同时,采用循环伏安法对其电? 阅芙辛瞬舛āＵ馊只衔锒荚诟悍较虺鱿至艘欢钥赡娴难趸乖澹纱说玫狡涞缱忧缀褪?EA)分别为-3.10eV,-3.07eV和-3.08eV,其EA值都高于常用? 牡缱哟洳牧螾BD。R-OXD的高电子亲和势有利于电子从阴极注入。并且由时间渡? 椒?TOF)测得R-OXD的电子迁移率达到10^-^4cm^2/V.S(E=10^6V/cm)。所以R-OXD有可能是好的电子传输材料。     

Synthesis of 3—Biaryl—1—ferrocenyl—2—propene—1—ones

The novel structures of organometallic compounds 3-biaryl-1-ferrocenyl-2-propene-1-ones 5 were synthesized for nonlinear optical chromophores by Suzuki cross-coupling reaction.Their structures were determined with elemental analyses,^1H NMR spectra and ^13C NMR spectra.     

Synthesis and characterization of Mn(II), Au(III) and Zr(IV) hippurates complexes

Mn(II), Au(III) and Zr(III) complexes with N-benzoylglycine (hippuric acid) (abbreviation hipH) were synthesized and characterized by elemental analysis, molar conductivity, magnetic measurements, spectral methods (mid-infrared, (1)H NMR, mass, X-ray powder diffraction and UV/vis spectra) and simultaneous thermal analysis (TG and DTG) techniques. The molar conductance measurements proved that all hippuric acid complexes are non-electrolytes. The electronic spectra and magnetic susceptibility measurements were used to infer the structures. The IR spectra of the ligand and its complexes are used to identify the type of bonding. The kinetic thermodynamic parameters such as: E*, DeltaH*, DeltaS* and DeltaG* are estimated from the DTG curves. The free ligand and its complexes have been studied for their possible biological antifungal activity.     

NMR Investigations of Temperature-Induced Phase Transition in Aqueous Polymer Solutions

The different dynamics of polymer segments forming phase-separated globular structures in aqueous (D₂O) solutions affects both the shape of NMR spectra and NMR relaxation times of polymer and solvent. Two types of the approach are discussed. The first one is based on the reduction of integrated intensities of polymer NMR lines in high-resolution NMR spectra in the system undergoing the coil-globule phase transition. The fraction p of phase-separated units (units with significantly reduced mobility) and subsequently, e.g., thermodynamic parameters ΔH and ΔS characterizing the coil-globule phase transition can be determined. The second approach is based on measurements of ¹H NMR relaxation times of water (HDO) which provide information on behaviour of water during phase transition. The power of both approaches is demonstrated on results obtained with solutions of several thermoresponsive homopolymers and copolymers.     

Molecularly ordered inorganic frameworks in layered silicate surfactant mesophases.

Self-assembled lamellar silica-surfactant mesophase composites have been prepared with crystal-like ordering in the silica frameworks using a variety of cationic surfactant species under hydrothermal conditions. These materials represent the first mesoscopically ordered composites that have been directly synthesized with structure-directing surfactants yielding highly ordered inorganic frameworks. One-dimensional solid-state 29Si NMR spectra, X-ray diffraction patterns, and infrared spectra show the progression of molecular organization in the self-assembled mesophases from structures with initially amorphous silica networks into sheets with very high degrees of molecular order. The silicate sheets appear to be two-dimensional crystals, whose structures and rates of formation depend strongly on the charge density of the cationic surfactant headgroups. Two-dimensional solid-state heteronuclear and homonuclear NMR measurements show the molecular proximities of the silica framework sites to the structure-directing surfactant molecules and establish local Si-O-Si bonding connectivities in these materials.     

两亲型聚L-亮氨酸-聚乙二醇单甲醚嵌段共聚物的合成与表征

开环聚合;生物降解共聚物;两亲型聚L-亮氨酸-聚乙二醇单甲醚嵌段共聚物的合成与表征     

Syntheses and characterization of Ru(III) with chelating containing ONNO donor quadridentate Schiff bases

Complexes of ruthenium(III) with N,N'-disalicylidene-l,2-phenylenediamine (H2dsp), N,N'-disalicylidene-3,4-diaminotoluene (H2dst), 4-nitro-N,N'-disalicylidene-1,2-phenylenediamine (H2ndsp) and N,N'-disalicylidene ethylenediamine (H2salen) have been prepared and characterized by elemental analysis, molar conductivity, spectral methods (mid-infrared, 1H NMR and UV-vis spectra) and simultaneous thermal analysis (TG and DTG) techniques. The molar conductance measurements proved that all these complexes are non-electrolytes. The electronic spectra measurements were used to infer the structures. The IR spectra of the ligands and their complexes are used to identify the type of bonding. The kinetic thermodynamic parameters such as: E*, DeltaH*, DeltaS* and DeltaG* are estimated from the DTG curves. The four ligands and their complexes have been studied for their possible biological antifungal activity.