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.     

Synthesis of Eu3+-doped core and core/shell nanoparticles and direct spectroscopic identification of dopant sites at the surface and in the interior of the particles

A variety of redispersible Eu(3+)-doped LaPO(4) nanoparticles have been prepared in a high-boiling coordinating solvent mixture, and the Eu(3+) lattice sites of these materials have been investigated by luminescence line-narrowing measurements. In this spectroscopic method, Eu(3+) ions occupying different lattice sites are selectively excited with a tunable narrow-bandwidth laser system and distinguished by their luminescence spectra ("site-selective spectroscopy"). Depending on the concentration of the dopant, up to three different lattice sites could be identified in the interior of the LaPO(4) nanoparticles. These sites correspond to those known from bulk LaPO(4). In addition, a variety of surface sites is observed, which could be converted completely into bulk sites by overgrowing the nanoparticles with a shell of pure LaPO(4). The surface sites are identical to those obtained by reacting Eu(3+) with the surface of pure LaPO(4) nanoparticles. The spectroscopic properties of Eu(3+)-doped LaPO(4) nanoparticles differ from those of pure EuPO(4) nanoparticles, which were also investigated. Remarkably, the core/shell synthesis investigated in this paper allows one to prepare doped nanoparticles that contain no other dopant sites than those known from the corresponding bulk material.     

沉淀转化法制备多孔片状纳米LaF3

采用实验中所合成的LaPO4纳米棒为前驱体,通过沉淀的转化作用,大面积地制备了单分散的片状纳米LaF3。采用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、BET(Brunauer-Emmett-Teller)测试对片状纳米LaF3的形貌、结构、相组成及表面性质进行了分析。片状纳米LaF3底边长约为40 nm,片的厚度约为35 nm,大小均一,具有多孔结构。通过改变反应溶剂,可以控制LaF3粒子的成核、生长和团聚,从而有效地调控多孔片状纳米LaF3的颗粒尺寸和分散性。对多孔片状纳米LaF3的生长机制进行了研究,结果表明LaPO4和LaF3的溶度积常数差导致了片状纳米LaF3的生成;体系中自身存在的Ostwald ripening作用使片状纳米LaF3出现了多孔结构。     

液相浸渗法制备Y-TZP/LaPO4可加工复相陶瓷

通过往ZrO2多孔陶瓷浸渗LaPO4液态先驱液制备了具有可加工性的Y－TZP／LaPO4复相陶瓷。加入30％（体积分数）石墨可以得到具有35％（体积分数）开孔气孔率的ZrO2预烧结陶瓷体。采用不同浸渗和热分解周期可以得到不同LaPO4含量的Y－TZP／LaPO4复相陶瓷。研究了该材料的可加工性和力学性能。结果表明，含有3.5%-7.5%(体积分数）LaPO4的Y－TZP／LaPO4复相陶瓷具有良好的可加工性，同时保持优良的力学性能。     

Eu~(3+)-doped LaPO_4 and LaAlO_3 nanosystems and their luminescence properties

Eu3+ ion-doped LaPO4 nanowires or nanorods have been successfully synthesized by a simple hydrothermal method.The influence of varying the hydrothermal and subsequent sintering conditions on the morphology and structure of the LaPO4 host has been investigated by scanning electron microscopy(SEM) and X-ray diffraction(XRD).For comparison,the Eu3+ ions were also doped into monoclinic monazite LaPO4 nanoparticles and perovskite LaAlO3 nanoparticles.The relative intensities of the emission lines of the LaPO4:Eu...     

低成本LaPO4-LnPO4核壳结构荧光颗粒的合成与表征

LnPO4( LnPO4=LaPO4:Ce,Tb)是被广泛应用的绿色荧光材料,由于所用的主要原材料之一Tb4O7的价格较为昂贵,导致其生产成本居高不下.如能有效合理地降低稀土磷酸盐绿色荧光粉的生产成本,则可望为照明工业带来显著的效益.报道了一种新型的核壳结构材料LaPO4-LnPO4,该材料以较为廉价的LaPO4作为内部核层,三聚磷酸盐水解缓慢释放的磷酸根与稀土离子通过均相沉淀异相成核的方法在LaPO4表面结合形成LnPO4壳层.所得核壳结构颗粒的荧光发射光谱与纯LnPO4完全一致.在还原性气氛中灼烧后,其发光强度可与市售LnPO4商业产品相当.本方法可将稀土磷酸盐绿色荧光粉的合成成本降低45％左右,而且操作简单,易于进行大规模工业化生产推广,对发光照明行业具有潜在的重要应用价值.     

共沉淀法合成稀土正磷酸盐(La,Gd)PO4:RE3+(RE=Eu,Tb)及其真空紫外光谱特性

采用共沉淀法制备了稀土正磷酸盐荧光粉(La,Gd)PO4:RE3+(RE=Eu,Tb).红外光谱分析发现GdPO4的红外光谱吸收峰与LaPO4一致,只是峰位向高波数方向移动.(La,Gd)PO4:RE3+的真空紫外光谱特性研究表明,Gd3+在能量传递过程中起中间体作用.XPS研究揭示,LaPO4的价带由O2-的2p能级构成,而GdPO4的价带则是由O2-的2p能级和Gd3+的4f能级共同构成.     

Epitaxial synthesis of uniform cerium phosphate one-dimensional nanocable heterostructures with improved luminescence

Uniform CePO(4)@LaPO(4) and CePO(4):Tb(3+)@LaPO(4) one-dimensional single-crystalline nanocable heterostructures with highly enhanced photoluminescent emission have been synthesized via a mild and simple hydrothermal approach. The resulting one-dimensional single-crystalline nanocable heterostructures have smooth and uniform LaPO(4) sheaths, which is of great significance in effectively eliminating surface trap-states and suppressing the energy quenching in energy-transfer processes. The photoluminescence results for these one-dimensional nanocable heterostructures illustrate that the uniform LaPO(4) sheaths remarkably increase the luminescent efficiency.     

季铵盐修饰磷钼酸铵纳米微粒的制备、结构表征及摩擦学性能

在醇 -水体系中采用同阴离子共沉淀法制备了季铵盐修饰的 (NH4 ) 3PMo12 O4 0 纳米微粒 ,采用TEM ,XRD ,FTIR ,TGA&DSC等多种分析手段表征了这种纳米微粒的形貌和结构 ,在四球试验机上考察了它们的摩擦学性能。结果表明所合成的杂多化合物具有Keggin骨架结构 ,微粒粒径约 2 0nm ,在有机溶剂中可良好分散 ,作为一类新型润滑油添加剂 ,具有良好的抗磨性能。     

基于LaPO_4∶Ce,Tb-Au发光共振能量转移测定细胞色素C

以膦酰基羧酸共聚物为修饰剂,采用水热法制备了LaPO_4∶Ce,Tb发光纳米粒子,该粒子具有良好的水溶性和生物相容性。对合成的纳米粒子进行了发光光谱、X-射线衍射、透射电子显微镜和红外光谱表征。以制备的纳米粒子为能量供体,纳米金为能量受体,细胞色素C(Cyt C)为桥,构建了LaPO_4∶Ce,Tb-Au发光共振能量转移(LRET)体系,据此建立了测定Cyt C的新方法。实验结果表明,当Cyt C的浓度在0.333~21.0μg·mL~(-1)范围时,LRET体系发光猝灭程度与Cyt C浓度呈良好线性关系,检出限(S/N=3)为0.2μg·mL~(-1),相对标准偏差(RSD)为0.46%(c=10.0μg·mL~(-1),n=11)。该方法用于实际样品的测定,回收率范围为100%~101%。     

A simple mixed-solvothermal route for LaPO4 nanorods: synthesis, characterization, affecting factors and PL properties of LaPO4:Ce3+

In this paper, LaPO(4) nanorods have been successfully synthesized via a simple water-ethyleneglycol (H(2)O-EG) mixed-solvothermal route, employing lanthanum nitrate (La(NO(3))(3)·xH(2)O) as a La(3+) ion source and monobasic sodium phosphate (NaH(2)PO(4)·2H(2)O) as a PO(4)(3-) ion source. The as-obtained products were characterized by means of X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), (high resolution) transmission electron microscopy (HR/TEM), selected area electron diffraction (SAED) and field emission scanning electron microscopy (FESEM). Some factors influencing the formation of LaPO(4) nanorods, including the reaction temperature, the volume ratio of water/EG and the original amount of H(2)PO(4)(-) ions, were investigated. Experiments showed that the volume ratio of water/EG and the original amount of H(2)PO(4)(-) ions could markedly affect the morphology of the final product.