Prussian blue analogues of reduced dimensionality

Mixed-valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room-temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While molecule-based materials can combine physical and chemical properties associated with molecular-scale building blocks, their successful integration into real devices depends primarily on higher-order properties such as crystal size, shape, morphology, and organization. Herein a study of a new reduced-dimensionality system based on Prussian Blue analogues (PBAs) is presented. The system is built up by means of a modified Langmuir-Blodgett technique, where the PBA is synthesized from precursors in a self-limited reaction on a clay mineral surface. The focus of this work is understanding the magnetic properties of the PBAs in different periodic, low-dimensional arrangements, and the influence of the "on surface" synthesis on the final properties and dimensionality of the system.     

Mixed valency in rare-earth fullerides

Mixed-valence phenomena associated with the highly correlated narrow-band behaviour of the 4f electrons in rare earths are well documented for a variety of rare-earth chalcogenides, borides and intermetallics (Kondo insulators and heavy fermions). The family of rare-earth fullerides with stoichiometry RE2.75C60 (RE=Sm, Yb, Eu) also displays an analogous phenomenology and a remarkable sensitivity of the rare-earth valency to external stimuli (temperature and pressure) making them the first known molecular-based members of this fascinating class of materials. Using powerful crystallographic and spectroscopic techniques which provide direct indications of what is happening in these materials at the microscopic level, we find a rich variety of temperature- and pressure-driven abrupt or continuous valence transitions-the electronically active fulleride sublattice acts as an electron reservoir that can accept electrons from or donate electrons to the rare-earth 4f/5d bands, thereby sensitively modulating the valence of the rare-earth sublattice.     

Mixed valency in organic charge transfer complexes

Mixed-valence (partial charge transfer state) and segregated stacking are the key factors for constructing organic metals. Here, we discuss the ionicity phase diagrams for a variety of charge transfer systems to provide a strategy for the development of functional organic materials (Mott insulator, semiconductor, superconductor, metal, complex isomer, neutral-ionic system, etc.).     

Mixed valency character of bismuth in ferrite lattices

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Synthesis and characterization of Co-Fe Prussian blue nanoparticles within MCM-41

A Prussian blue analogue, K_0.84Co_1.08[Fe(CN)₆] is prepared by reaction between [Fe(CN)₆]³⁻ in aqueous solution and ion-exchanged Co²⁺ in the channels of MCM-41. Powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-vis absorption spectroscopy and magnetic measurements were employed to characterize the product. The results show that the Prussian blue analogue is in nanoparticles within the channels and the hexagonal phase of MCM-41 remains intact during the reactions. A particle size effect on optical and magnetic properties of the nanoparticles was observed.     

聚苯胺包覆CoFe类普鲁士蓝复合材料的超电容性能

制备了聚苯胺包覆CoFe类普鲁士蓝纳米立方（CoFePBA@PANI）复合材料,采用XRD、FTIR、SEM和TEM对CoFePBA@PANI复合材料的结构和形貌进行表征,利用循环伏安法（CV）、恒电流充放电法及交流阻抗法（EIS）对CoFePBA@PANI复合材料的电化学性能进行了考察。结果表明:通过植酸的配位作用促使苯胺在具有面心立方结构的CoFePBA表面发生聚合反应,形成了具有核-壳结构的CoFePBA@PANI复合材料。系统地研究了PANI的含量对CoFePBA@PANI复合材料电化学性能的影响,CoFePBA@PANI复合材料在0.5 mol/L Na₂SO₄和H₂SO₄的混合酸性介质中,在1 A/g电流密度下,比电容值达到401.2 F/g,电流密度增大至10 A/g时,比电容仍能保持在367.3 F/g。      

普鲁士兰恒电流法沉积在聚苯胺膜上的性能表征

在ITO玻璃上分别用循环扫描伏安法和恒电流法依次沉积了聚苯胺(PANI)和普鲁士兰(PB)薄膜,对PANI和PB单层膜及复合膜的红外光谱进行了分析,讨论了3种薄膜的循环伏安曲线和紫外-可见吸收光谱.结果表明,在所选沉积条件下,制备出了电活性高的电致变色复合薄膜,600nm处的着色效率η=57.3.用钾离子掺杂的聚(2-丙稀酰胺-2-甲基丙磺酸)(PAMPS)作为离子导体,电导率σ达到8.691×10-3S/cm,组装的器件循环50次后,CV曲线变化较小,性能稳定.     

Prussian blue modified Fe3O4 nanoparticles for Cs detoxification

Fe₃O₄ nanoparticles were surface modified with Prussian blue (PB) and the nanoparticles were used for the removal of cesium (Cs) ion. The attachment of PB with the Fe₃O₄ and their morphology were explained based on the studies by transmission electron microscope and BET measurements. The Cs ion adsorption studies have shown that the Cs removal efficiency reached maximum within 120 min. The adsorption kinetics studies using Lagergren pseudo-first-order kinetic model suggest the values of the amount of metal ion adsorbed at equilibrium (q _e) and adsorption rate constant (k ₁) as 22 mg/g and 0.015 min^?1, respectively. The capture efficiency of the prepared nanoparticles was studied by varying the flow channel diameter, applied magnetic field, and the fluid flow velocity. The study suggests that PB-Fe₃O₄ nanoparticles could be used for the detoxification of Cs where the flow velocity is in the range of few tens of cm/s.     

Fabrication of high-aspect-ratio Prussian blue nanotubes using a porous alumina template

Prussian blue nanotubes were fabricated by using a sequential deposition technique inside the 60-nm well-ordered pores of anodic alumina. By varying the deposition parameters and the dimensions of the template, we could tailor the length and the outer as well as the inner diameter of the tubes. The nanotubes were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD).     

Synthesis and characterization of nanodispersed molecular aggregates of Prussian blue in aerosol OT reverse micelle

Prussian Blue (PB) nanomolecular aggregates were prepared in a well-characterized, monodispersed biomimicking nanocavities formed by Aerosol OT (AOT) reverse micelle in H2O/AOT/heptane at different omega ([H2O]/[Surfactant]) employing coprecipitation technique. The formed nanomolecular aggregates of PB have been characterized by the UV-visible, Fourier Transformed Infrared (FTIR) spectroscopy as well as by Transmission Electron Microscopy (TEM) and Cyclic Voltammetric methods. Visible and FTIR spectroscopic measurements confirm the formation of PB nano aggregates. Experimental results reveal that the molar extinction coefficient of PB nanomolecular aggregates is different for two different regimes of omega of reverse micelles. TEM measurements show that the size of these reverse micellar entrapped nano aggregrates varied with hydration (omega). Studies on these nano sized particles indicate that Fe is present in a single mixed valence state along the Fe-C-N-Fe skeleton in PB and the half wave potential (E1/2) becomes more positive with increase in the size of the nano aggregates.     

Electrochemical deposition of Prussian blue on hydrogen terminated silicon(111)

Electrochemical deposition of Prussian blue (PB) was performed by cyclic voltammetry on hydrogen terminated n-type Si(111) surface. The characterization of the samples based on atomic force microscopy and X-ray diffraction spectroscopy showed a nanocrystal form of the PB films on the silicon surface. The thickness of PB films as a function of the potential cycling number was monitored simultaneously by Raman spectroscopy, proving that the growth of the films is in a good controllable manner.     

Co-Fe普鲁士蓝/多壁碳纳米管复合材料的超电容性能

Co-Fe普鲁士蓝(CoPBA)是目前被广泛研究的超级电容器正极材料,其比电容高循环性能好,但低导电性和较差的倍率性能限制了其在超级电容器中的应用。为了提高CoPBA的导电性和电化学性能,本文以Co-glycerate为前驱体,采用牺牲模板法制备了Co-Fe普鲁士蓝/多壁碳纳米管(CoPBA/MWCNT)复合材料,利用XRD、SEM和FTIR等对复合材料的结构和形貌进行表征,使用电化学工作站在三电极体系和非对称超级电容器中测定了复合材料的电化学性能。实验结果表明：采用牺牲模板法成功合成出形貌较好的球状复合材料,以中性溶液Na₂SO₄为电解液,测得在1 A/g的电流密度下复合材料的质量比电容达到391.5 F/g。在10 A/g的高电流密度下比电容达到312.6 F/g,为1 A/g时的79.8%。利用软件模拟得出电荷转移电阻由3.9Ω降低到1.1Ω。以CoPBA/MWCNT为正极,以活性炭为负极制成非对称电容器,在功率密度为1 092 W/kg时能量密度可达39.5 Wh/kg, 5 000次循环后容量保持率为85.2%。采用牺牲模板法制备的...     

类普鲁士蓝空心微米管的通用性制备及其作为高性能非对称超级电容器的研究

在电化学储能领域,具有可控组成的一维空心结构纳米材料引起了人们的极大关注.本文以静电纺丝制备的聚丙烯腈(PAN)-醋酸钴(Co(Ac)2)纳米纤维为模板,首次采用简易的自模板法制备了一维铁氰化钴(CoHCF)空心微米管.PAN-Co(Ac)2纳米纤维模板与铁氰化钾溶液反应,合成了核壳结构的PAN-Co(Ac)2@CoHCF纳米纤维;随后,选择性溶解去除PAN-Co(Ac)2芯部,从而得到CoHCF空心微米管.得益于其独特的结构优势,CoHCF空心微米管电极在Na2SO4电解液中表现出优异的电化学性能,如高比电容(281.8 F g^-1@1 A g^-1),良好的速率性能和长时间循环稳定性(5000次循环后电容保持率为93%).由CoHCF为正极和活性炭(AC)为负极组装的非对称超级电容器,具有43.9 W h kg^-1的高能量密度、20 k W kg^-1的功率密度以及长的循环寿命.更重要的是,这种通用性的自模板合成策略可以推广到其他组成可控的一维空心普鲁士蓝(PB)及其类似物(PBA)材料,因而在很多领域具有广泛的应用前景.     

A simple chemical method for deposition of electrochromic Prussian blue thin films

This paper is about a recently developed new chemical method for deposition of Prussian blue thin films. The films are easily prepared by successive immersion of the substrates into an acidic aqueous solution of Fe₂(SO₄)₃ and K₄[Fe(CN)₆]. It is calculated of the results from AFM analysis that the growth in the film thickness by one immersion cycle corresponds to an average increase of 6 nm. The characterization of the films with X-ray diffraction, SEM-EDS analysis and FTIR spectroscopy shows that the deposited material is amorphous hydrated Fe₄[Fe(CN)₆]₃. The electrochromic properties are characterized by cyclic voltammetry and VIS spectrophotometry. The PB thin films exhibit stability and excellent reversibility, which make these films favorable for electrochromic devices.     

Hierarchical sodium-rich Prussian blue hollow nanospheres as high-performance cathode for sodium-ion batteries

Recently, Prussian blue and its analogues (PBAs) have attracted tremendous attention as cathode materials for sodium-ion batteries because of their good cycling performance, low cost, and environmental friendliness. However, they still suffer from kinetic problems associated with the solid-state diffusion of sodium ions during charge and discharge processes, which leads to low specific capacity and poor rate performances. In this work, novel sodium iron hexacyanoferrate nanospheres with a hierarchical hollow architecture have been fabricated as cathode material for sodium-ion batteries by a facile template method. Due to the unique hollow sphere morphology, sodium iron hexacyanoferrate nanospheres can provide large numbers of active sites and high diffusion dynamics for sodium ions, thus delivering a high specific capacity (142 mAh/g), a superior rate capability, and an excellent cycling stability. Furthermore, the sodium insertion/extraction mechanism has been studied by in situ X-ray diffraction, which provides further insight into the crystal structure change of the sodium iron hexacyanoferrate nanosphere cathode material during charge and discharge processes.

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普鲁士蓝/氟化超支化聚氨酯复合涂层材料及其光热转换超疏水性能

首先制备氟化超支化聚氨酯(FHPU),然后与具有光热转化功能的普鲁士蓝(PB)纳米粒子复合,得到光热转换功能的PB/FHPU超疏水防结冰复合涂层材料。利用FTIR、TGA和DSC等测试分析了FHPU和PB/FHPU超疏水防结冰复合涂层材料的结构及性能,通过光热转换实验证明了复合涂层材料出色的光热性能;深入探究了PB纳米粒子的添加量对复合涂层材料表面性质和光热转化性能的影响。结果表明,当PB质量占FHPU的13%时,复合涂层材料可形成具有微纳结构的复合涂层,涂层表面最大接触角达157°,滚动角为1.8°。同时,该涂层在808 nm激光照射下10 s内温度可升高78.1℃,最高温度达到148.7℃。因而,光热转换功能性超疏水防结冰复合涂层材料具有良好的疏水、防结冰性能。      

Synthesis of two-dimensional micron-size single-crystalline Prussian blue nanosheets by hydrothermal methods assisted by glucose

Prussian blue Fe₄[Fe(CN)₆]₃ nanosheets have been successfully prepared by a simple hydrothermal process employing the reactions between K₃[Fe(CN)₆] and glucose (C₆H₁₂O₆). X-ray diffraction and transmission electron microscopy measurement results show that the Prussian blue nanosheets are highly crystalline with a face-centered-cubic structure of a = 10.26 Å. It was found the C₆H₁₂O₆ is not only a reductant, but also may be a template for synthesizing the nanosheets.     

"Green" synthesis of size controllable Prussian blue nanoparticles stabilized by soluble starch

"Green" and size-controlled Prussian blue (PB) nanoparticles have been synthesized using soluble starch as protective agent. The transmission electron images (TEM) showed that the average dimensions of the monodispersed.PB nanoparticles could be tuned from 5 to 20 nm by using different concentration of starch. X-ray diffraction (XRD) analysis further identified a face-centered cubic structure of the nanoparticles. Investigations of optical properties of nanoparticles were also conducted with FT-IR and UV-vis spectroscopy. Moreover, cyclic voltammograms (CV) showed that the starch-PB nanoparticles kept their intrinsic electrochemical properties. The utilization of environmentally benign and renewable starch as the protecting agents offers numerous benefits ranging from environmental safety to integration of these nanomaterials to biologically relevant systems.