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.     

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.     

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.     

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.     

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.     

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.     

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.     

Core-shell lipid-polymer nanoparticles as a promising ocular drug delivery system to treat glaucoma

Nowadays,tremendous researches have been focused on the core-shell lipid-polymer nanoparticles(LPNs) due to the advantages of both liposomes and polymer nanoparticles.In this work,LPNs were applied to encapsulate brinzolamide(Brz-LPNs) for achieving sustained drug release,improving drug corneal permeation and enhancing drug topical therapeutic effect.The structure of Brz-LPNs was composed of poly(lactic-co-glycolic) acid(PLGA) nanocore which encapsulated Brz(Brz-NPs) and lipid shell around the core.Brz-LPNs were prepared by a modified thin-film dispersion method.With the parameters optimization of Brz-LPNs,optimal Brz-LPNs showed an average particle size of151.23±1.64 nm with a high encapsulation efficiency(EE) of 86.7%±2.28%.The core-shell structure of Brz-LPNs were confirmed by transmission electronic microscopy(TEM).Fourier transformed infrared spectra(FTIR) analysis proved that Brz was successfully entrapped into Brz-LPNs.Brz-LPNs exhibited obvious sustained release of Brz,compared with AZOPT^■ and Brz-LPs.Furthermore,the corneal accumulative permeability of Brz-LPNs significantly increased compared to the commercial available formulation(AZOPT^■) in vitro.Moreover,Brz-LPNs(1 mg/mL Brz) showed a more sustained and effective intraocular pressure(IOP) reduction than Brz-LPs(1 mg/mL) and AZOPT^■(10 mg/mL Brz) in vivo.In conclusion,Brz-LPNs,as promising ocular drug delivery systems,are well worth developing in the future for glaucoma treatment.     

Synthesis of Hollow Mesoporous TiO2 Microspheres with Single and Double Au Nanoparticle Layers for Enhanced Visible‐Light Photocatalysis

A facile method was used to prepare hollow mesoporous TiO₂ and Au@TiO₂ spheres using polystyrene (PS) templates. Au nanoparticles (NPs) were simultaneously synthesized and attached on the surface of PS spheres by reducing AuCl₄^? ions using sodium citrate which resulted in the uniform deposition of Au NPs. The outer coating of titania via sol‐gel produced PS@Au@TiO₂ core–shell spheres. Removing the templates from these core–shell spheres through calcination produced hollow mesoporous and crystalline Au@TiO₂ spheres with Au NPs inside the TiO₂ shell in a single step. Anatase spheres with double Au NPs layers, one inside and another outside of TiO₂ shell, were also prepared. Different characterization techniques indicated the hollow mesoporous and crystalline morphology of the prepared spheres with Au NPs. Hollow anatase spheres with Au NPs indicated enhanced harvesting of visible light and therefore demonstrated efficient catalytic activity toward the degradation of organic dyes under the irradiation of visible light as compared to bare TiO₂ spheres.     

Silver Nanoparticles Filling in TiO2 Hollow Nanofibers by Coaxial Electrospinning

This study investigated the coaxial electrospinning process of silver filling in TiO₂ ultrafine hollow fibers using polyvinyl pyrrolidone (PVP) sol/titanium n-butyloxide (Ti(OC₄H₉)₄) and PVP sol/silver nanoparticles as pore-directing agents. The bicomponent fibers were heat treated at 200 °C and calcined at 600 °C. Silver particles having diameters of 5 to 40 nm were deposited on the inner surface of the long hollow TiO₂ nanofibers (outer diameter of 150.300 nm) with mesoporous walls (thickness of 10.20 nm). The morphological structure of the filled ultrafine hollow fibers has been studied by means of infrared (IR) spectrum, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The diameters and wall thicknesses of the hollow fibers could be tuned by adjusting the electrospinning parameters. Compared with other nanostructured TiO₂ materials, such as mesoporous Ag-TiO₂ blending fibers, TiO₂ hollow nanofibers, TiO₂ nanofibers, and TiO₂ powders, the silver filled TiO₂ hollow fibers exhibited a higher photocatalytic activity toward the degradation of methylene blue.     

Preparation of Anatase Hollow TiO2 Spheres and Their Photocatalytic Activity in the Photodegradation of Chlorpyrifos

Hollow anatase titania (TiO₂) spheres were synthesized using fructose and tetrabutyl titanate (Ti(OC₄H₉)₄, TBT) as the precursors via the conventional hard template method. The morphological, structural and thermal properties of the products were characterized using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG‐DTA), Brunauer? Emmett? Teller (BET) surface area analysis and diffuse reflectance ultraviolet visible (DR UV? Vis) spectroscopy. XRD revealed that the hollow TiO₂ prepared was in the anatase phase and the BET surface area measured was about 22 m² g^?1. The photocatalytic activity of the synthesized hollow anatase TiO₂ in the photodecomposition of chlorpyrifos was 18.67 % higher than that obtained using commercial TiO₂.     

Physical properties of nano-titania hollow fibers and their photocatalytic activity in the decomposition of phenol

A series of nano-titania (TiO₂) photocatalytic materials with a hollow fiber structure were successfully prepared using tetra-n-butyl titanate (Ti(OC₄H₉)₄) as precursor and cotton fiber as the template. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and N₂ adsorption-desorption measurements were employed to characterize the morphology, crystal structure, and surface structure of the samples. The photocatalytic activities of the samples were studied by phenol photodegradation in water under UV irradiation. The effect of calcination temperature, photocatalyst dosage, initial concentration of phenol and irradiation time on the photodegradation of phenol was studied. Results showed that the TiO₂ fiber materials have hollow structures, indicating that these materials had a large specific surface area. The fiber structure material showed better photocatalytic properties for the degradation of phenol than pure TiO₂ under UV light, and the sample calcined at 500°C exhibited the highest phenol photodegradation efficiency. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed, the photocatalytic activity of TiO₂ fiber remained ca. 90% of photocatalytic activity of the fresh sample after being used four times. Moreover, TiO₂ fiber was easily recovered by centrifugal separation from water.     

Preparation of TiO2 nanocrystallites by hydrolyzing with gaseous water and their photocatalytic activity

TiO₂ nanocrystallites were prepared from precursors tetra-n-butyl titanate (Ti(OC₄H₉)₄) and titanium tetrachloride (TiCl₄). The precursors were hydrolyzed by gaseous water in autoclave, and then calcined at predetermined testing temperatures. The samples were characterized by X-ray diffraction (XRD), thermogravimetry–differential thermal analysis (TG–DTA), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectra (FT-IR), and UV–vis diffuse reflectance spectra (DRS). The photocatalytic activities of the samples were evaluated by the photobleaching of methylene blue (MB) in aqueous solution and the photocatalytic oxidation of propylene in gas phase at ambient temperature. The results showed that the anatase phase nanocrystalline TiO₂ could be obtained at relatively low temperatures (for precursor Ti(OC₄H₉)₄ at 110 °C and for TiCl₄ at 140 °C, respectively), and that the as prepared samples exhibited high photocatalytic activities to photobleach MB in aqueous solution. As the calcination temperatures increasing, the decolor ratio of MB increased and reached the maximum value of nearly 100% at 600 °C, and then decreased. The photobleaching of MB by all samples followed the pseudo-first-order kinetics with respect to MB concentration. The photodecomposition amount of propylene by TiO₂ nanocrystallites calcined at 600 °C from precursor of Ti(OC₄H₉)₄ is 21.6%, which is approaching to that by Degussa P25 TiO₂ (24.9%).     

具有分级多孔结构和光催化性质的核-壳纳米球(HP-Fe2O3@TiO2)

通过溶剂热和溶胶-凝胶涂层法, 设计并制备了具有分级多孔结构和光催化性质的核-壳纳米球(HP-Fe₂O₃@TiO₂). 透射电子显微镜(TEM)照片证明所得HP-Fe₂O₃@TiO₂样品具备分级多孔结构, 这是因为HP-Fe₂O₃@TiO₂的内核-Fe₂O₃具有大孔空隙, 同时外壳-TiO₂具有介孔空隙. 此外, 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)以及氮气吸附-脱附曲线深入研究了HP-Fe₂O₃@TiO₂的结构及其性质. 分别在可见及紫外光照下, 研究了样品在H₂O₂体系下的光催化降解亚甲基蓝(MB)的性质. 所观察到的HP-Fe₂O₃@TiO₂纳米球的光催化性能, 可归因于核-壳结构的协同作用, 这进一步表明, TiO₂外壳对α-Fe₂O₃的光催化活性有重要影响作用. 在可见光照射下, HP-Fe₂O₃@TiO₂ (1 mL Ti(OC₄H₉)₄ (TBT))具有较优异的光催化活性. 同时, HP-Fe₂O₃@TiO₂ (4mL TBT)具备优异的单分散形貌, 并在紫外光照射下, 表现出最优的光催化活性.     

Preparation,Characterization and Photocatalytic Activity of Lanthanum Doped Mesoporous Titanium Dioxide

Lanthanum doped mesoporous titanium dioxide photocatalysts with different La content were synthesized by template method using tetrabutyltitanate (Ti(OC₄H₉)₄) as precursor and Pluronic P123 as template. The catalysts were characterized by thermogravimetric dif-ferential thermal analysis, N₂ adsorption-desorption measurements, X-ray diffraction, and UV-Vis adsorption spectroscopy. The effect of La³⁺ doping concentration from 0.1% to 1% on the photocatalytic activity of mesoporous TiO₂ was investigated. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of about 10 nm with high surface area of 165 m²/g. X-ray photoelectron spectroscopy measurements in-dicated the presence of C in the doped samples in addition to La. Compared with pure mesoporous TiO₂, the La-doped samples extended the photoabsorption edge into the visible light region. The results of phenol photodecomposition showed that La-doped mesoporous TiO₂ exhibited higher photocatalytic activities than pure mesoporous TiO₂ under UV and visible light irradiation.     

Novel sol–gel synthesis of N-doped TiO<Subscript>2</Subscript> hollow spheres with high photocatalytic activity under visible light

Novel ammonia and triethanolamine assisted sol–gel synthesis method was developed to fabricate the N-doped TiO₂ hollow spheres. The prepared hollow spheres were in submicron size and had good morphology and high specific surface area. Polystyrene (PS) latexes in size of 470 nm were used as the templates to fabricate PS/TiO₂ core–shell spheres. Here ammonia and triethanolamine was first employed together to control the sol–gel process. The N-doped TiO₂ hollow spheres were got after calcinations of the core–shell spheres by using triethanolamine as N source, and the amount of doped N could be easily adjusted by changing the amount of triethanolamine. The hollow spheres had distinct visible light response, and the optical response shifted more to the visible region as the amount of doped N increases. The photodegradation of methylene blue expressed the high photocatalytic activity of the N-doped TiO₂ hollow spheres under visible light.     

Synthesis and photocatalytic activity of mesoporous SiO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>

Mesoporous SiO₂–TiO₂ was synthesized by the sol–gel method using Si(OC₂H₅)₄, Ti(OC₂H₅)₄, and stearyltrimethylammonium chloride. By using acetylacetone as the capping agent of Ti(OC₂H₅)₄, homogeneous SiO₂–TiO₂ composite was obtained. Spherical mesoporous SiO₂–TiO₂ was also synthesized by the sol–gel method using W/O emulsion under microwave irradiation. The specific surface area of these mesoporous SiO₂–TiO₂ materials decreased when the Ti/Si molar ratio was higher than 0.1, which indicated that Ti was homogeneously distributed in mesoporous SiO₂ matrix at Ti/Si ≦ 0.1. The photocatalytic activity of mesoporous SiO₂–TiO₂ materials was investigated by the degradation of methylene-blue in water under UV light irradiation. Mesoporous SiO₂–TiO₂ was effective for the adsorption–decomposition of methylene-blue.     

Characterization of anti-reflective and self-cleaning SiO2–TiO2 composite film

Sol–gel dip-coating technique can be used to fabricate SiO₂–TiO₂ composite film with self-cleaning and anti-reflectance properties from low-cost SiO₂ colloid solution and Ti(OC₄H₉)₄. The physical and structural properties have been investigated by UV–visible spectrophotometer, contact angle meter, XRD, FT-IR, FESEM. UV–vis spectra and methyl orange photodegradation experiments showed that the SiO₂–TiO₂ composite film had high light transmittance and photocatalytic activity.