Soft Solution Processing Research Articles

Antibacterial polyetheretherketone implants immobilized with silver ions based on chelate-bonding ability of inositol phosphate: Processing, material characterization, cytotoxicity, and antibacterial properties

We developed a novel antibacterial implant by forming a hydroxyapatite (HAp) film on polyetheretherketone (PEEK) substrate, and then immobilizing silver ions (Ag(+) ) on the HAp film based on the chelate-bonding ability of inositol phosphate (IP6). First, the PEEK surface was modified by immersion into concentrated sulfuric acid for 10 min. HAp film was formed on the acid-treated PEEK via the soft-solution process using simulated body fluid (SBF), urea, and urease. After HAp coating, specimens were immersed into IP6 solution, and followed by immersion into silver nitrite solution at concentrations of 0, 0.5, 1, 5 or 10 mM. Ag(+) ions were immobilized on the resulting HAp film due to the chelate-bonding ability of IP6. On cell-culture tests under indirect conditions by Transwell, MC3T3-E1 cells on the specimens derived from the 0.5 and 1 mM Ag(+) solutions showed high relative growth when compared with controls. Furthermore, on evaluation of antibacterial activity in halo test, elution of Ag(+) ions from Ag(+) -immobilized HAp film inhibited bacterial growth. Therefore, the above-mentioned results demonstrated that specimens had both biocompatibility and strong antibacterial activity. The present coating therefore provides bone bonding ability to the implant surface and prevents the formation of biofilms in the early postoperative period.

Synthesis of carbon films by electrochemical etching of SiC with hydrofluoric acid in nonaqueous solvents

Carbon films on SiC have many applications, ranging from tribology to electrical energy storage. Formation of epitaxial or heteroepitaxial layers of carbon on SiC by “soft solution process,” such as electro- or photochemical ones, is attractive for various fields of application, decreasing the energy consumption and making the process compatible with electronic device fabrication. We have demonstrated formation of a carbon layer on SiC ceramics by electrochemical etching in a nonaqueous electrolyte. The selective etching of Si from SiC in a single step reaction with hydrofluoric acid (HF) in different organic solvents has been carried out and the role of polarity, surface tension, density, and viscosity of the organic solvents in the formation of the carbon layer has been investigated. The solution of 1:4.6 ratio HF and ethanol at low current densities (10 and 20mA/cm2) allows the best control over selective etching of Si forming amorphous and ordered carbon on the SiC surface. The presence of an intense G band of graphitic carbon in Raman spectra and high resolution transmission electron microscopy analysis indicate formation of ordered carbon on the surface of SiC. X-ray diffraction shows that the etching rate of α-SiC is much higher when compared to β-SiC.

Growth of polycrystalline nickel hydroxide films from aqueous solution. Solution chemistry, deposition methods, film morphology and texture

Deposition of functional ceramic films on different substrates by using soft aqueous solution processing can represent a cheap, low- energy and environmental friendly alternative to other film technologies. In this study β-Ni(OH)2 polycrystalline films were grown on polytetrafluoroethylene, NiO, glass, copper, and Y:ZrO2 substrates from Ni2+–NH4OH aqueous solutions. A careful control of solution supersaturation was essential to induce heterogeneous nucleation on the substrate and film growth. This was realized through the gradual decomposition of the nickel amino complexes Ni(NH3)n2+ using two different methods. Thermodynamic modeling of the Ni–NH4OH–H2O system was used to provide some general indications for defining the experimental conditions most suitable for film deposition and understanding the role of solution chemistry on film formation. Film microstructure and texture can be controlled by varying the substrate, the ammonia concentration, the ammonia evaporation rate, the soaking time and by adding a surfactant like sodium dodecylbenzensulphonate. As a result, films with different morphologies and orientations, as well as a uniform decoration of the substrate surface with Ni(OH)2 crystals, were obtained. The proposed method can be extended to the preparation of oxide and hydroxide films of other transition metals forming moderately stable amino complexes.

Soft solution synthesis and intense visible photoluminescence of lamellar zinc oxide hybrids

In this study, we demonstrate the synthesis of layered zinc oxide films intercalated with dodecyl sulphate ions by a simple soft solution process. The presence of potassium (K+) and lithium (Li+) ions in the precursor solution of layered zinc hydroxide resulted in lamellar hybrid zinc oxide films instead of layered zinc hydroxides. On the other hand, the addition of nickel phthalocyanine induces zinc hydroxide host layers which exhibit an intense blue emission. This is also promoted by K+ and Li+ ions.

A novel approach for the preparation of phase-tunable TiO2 nanocomposite crystals with superior visible-light-driven photocatalytic activity

A series of novel TiO 2 nanocomposite crystals with superior visible-light-driven photocatalytic activity were successfully prepared using a soft chemical solution process involving direct reaction of aqueous H 2 O 2 with a 2-ethoxyethanol solution of tetraisopropyl titanate before calcination of the resulting peroxo-titanium complexes at 500 °C for 4 h. The synthesized TiO 2 samples are composed of anatase and rutile phases, and the ratio of rutile could be continuously tuned from 0 to 96% by altering the 2-ethoxyethanol volume. There are clear red-shifts in the UV-Vis absorption spectra and apparent band gap narrowing for the synthesized TiO 2 in comparison with Evonik P-25. The synthesized TiO 2 samples are found to be much more efficient for methylene blue degradation under visible-light irradiation. The optimized sample (2-ethoxyethanol: 5 ml; rutile in bulk: 46%) exhibits 5-fold higher adsorption capacity and 3-fold higher photocatalytic activity than those of Evonik P-25 (λ ≥ 400 nm). Characterizations including X-ray diffraction and Raman spectroscopy reveal that the surface of the optimized TiO 2 sample only contains a small quantity of rutile. It is concluded that the surface phase composition and distribution of the TiO 2 nanocomposite crystals are essential to their greatly enhanced photocatalytic activities and strong adsorption capacities. In addition, the concentration of defects existing in the synthesized TiO 2 is also regarded to account for these enhanced properties. 采用新的化学溶液法, 通过不同体积的钛酸四异丙酯的2-乙二醇单乙醚溶液与一定浓度的H 2 O 2 水溶液直接反应并对生成的钛过氧化配合物进行焙烧, 制备了一系列TiO 2 光催化剂. 表征发现, 所得TiO 2 样品为金红石和锐钛矿的纳米复合晶体, 改变2-乙二醇单乙醚的体积可实现金红石相比例在0–96%广范围的调变.与商业二氧化钛P-25相比, 所得的TiO 2 紫外-可见光吸收谱出现明显红移, 间隙能降低, 在可见光照射下, 该样品对亚甲基蓝有良好的降解活性. 当2-乙二醇单乙醚的添加量为5 ml时, 所得样品体相中金红石相比例接近50%, 其光催化活性和吸附性能最好, 可分别是P-25的3倍和5倍. 拉曼光谱结合X射线衍射等表征结果表明, 该样品的表面仅含少量的金红石相. TiO 2 纳米复合晶表面晶相的组成和分布对其光催化降解亚甲基蓝的活性及其吸附能力有直接的影响. 另外, TiO 2 纳米复合晶的缺陷浓度也是增强其光吸收能力, 提高其可见光光催化活性的原因之一. A novel approach for synthesis of phase-tunable TiO 2 is provided. The phase composition, distribution, and amount of oxygen vacancies are regarded as critical to the obtained superior visible-light-driven photocatalytic activity.

Soft solution processing of ZnO nanoarrays by combining electrophoretic deposition and hydrothermal growth

The use of seeded or pretreated substrates has been reported as a feasible way to control the morphology, texture and orientation of ZnO structures during hydrothermal growth. However, in a typical seeding procedure, high energy-consumption, high-cost, complexity and/or specific substrates are by now required. Electrophoretic deposition (EPD) is a soft solution process that may allow avoiding such problems of classical seeding procedures. In this work, the combination of these two soft solution processing techniques, EPD and hydrothermal growth, has been studied for growing ZnO nanostructures onto stainless steel substrates. The use of ZnO seed layers deposited by EPD as a way to control the evolution of ZnO structures during hydrothermal growth is discussed, showing that the seeding and its nature have an effect on the number of nucleation sites and consequently on the size and morphology of the obtained structures.

Photocatalytic oxidation of NO<SUB align="right">x gases using ZnO with superstructure by a low temperature soft solution process

Single phase of crystalline ZnO with controllable morphologies, including spindle–like, sunflower–like, dandelion–like and disk–like structures samples, have been successfully synthesised via a simple and effective low–temperature approach in a mixed solution of zinc nitrate and hexamethylenetetramine, with and without 2–aminoethanol as an accelerant. The ZnO crystal with different morphology can be obtained by simply varying the additive and reaction time. The samples were characterised by XRD, SEM, DRS and BET. The prepared ZnO with the sunflower–like superstructure showed excellent photocatalytic activity for the decomposition of NOx gas under UV light irradiation, being superior to that of a standard TiO2 (Aeroxide P25) powder.

Synthesis of carbon fibre-reinforced, silicon carbide composites by soft-solution approach

The aim of the present work centers on synthesizing and characterizing carbon fibre (Cf) reinforced, silicon carbide matrix composites which are considered to have potential applications in aerospace and automobile industry. A series of composites, namely the Cf-SiC, Cf-(SiC+ZrC), Cf-(SiC+ZrB2), and Cf-(SiC+ZrO2), have been prepared by a proposed soft-solution approach. This approach involves the use of water-soluble precursors of colloidal silica, sucrose, zirconium oxychloride, and boric acid as sources of silica, carbon, zirconia, and boron oxide, respectively to achieve the desired matrices through drying, carbonization and carbothermal reduction. The prepared powders and the composites were characterized by thermal analysis, X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses to assess the phase formation and microstructure of the materials, apart from assessment of their tensile properties. The study shows that the soft-solution process yields matrices with finer crystallite sizes, having homogeneous distribution of the constituent phases of either the powders or of the composite matrices. The role of the additional phases on the tensile properties of the composites has been discussed using consideration of thermal stresses at fibre-matrix interface; whereas the role of the carbothermal reduction temperature in determining these properties has been explained using the interfacial characteristics of the fibre-matrix. Addition of ZrO2 in the matrix of SiC has shown to improve the properties of Cf-SiC composites considerably. The results of this investigation unambiguously demonstrate that aqueous solution-based processing can be used for fabrication of these composites in relatively shorter time in an environmental friendly manner without using any expensive equipment. The approach is capable of yielding composites with different phases in the matrix by simple variation of precursor materials and solutions. The small crystallite sizes, fine particle distribution and low carbothermal reduction temperatures are some of the specific merits of the proposed method.

Novel solution routes of synthesis of metal oxide and hybrid metal oxide nanocrystals

Novel solution routes covering a wide range of processes like hydrothermal, solvothermal and supercritical techniques have been described in detail with reference to the processing of a wide range of advanced inorganic nanocrystalline materials and organic-inorganic hybrid nanocrystalline materials. The significance of the thermochemical calculations, in situ surface modification and the experimental parameters has been discussed. One step in situ fabrication of advanced functional nanocrystalline materials by soft solution processing has also been discussed briefly. Synthesis of nanocrystals of metal oxides and hybrid nanocrystals and also processing several nanocomposites like carbon nanotubes: metal oxide, activated carbon: metal oxide, etc. has been reviewed in relation to various process parameters. The effect of doping, size, shape and quality on the properties of nanocrystalline materials has been discussed in relation to the photoluminescence and photocatalytic characteristics.

Sr2ZnS3: Crystal Structure and Fluorescent Properties of a New Eu(II)-Activated Yellow Emission Phosphor

The new multicomponent sulfide material of Sr2ZnS3 composition was synthesized using combination of soft solution process and high-pressure synthesis. Its crystal structure belongs to K2AgI3 type. The Eu(II)-activated phosphor emits golden-yellow light under excitation by blue or near-UV radiation.

Soft-solution route to ZnO nanowall array with low threshold power density

ZnO nanowall array (ZNWA) has been directionally grown on the buffer layer of ZnO nanoparticles dip-coated on Si-wafer under a soft solution process. Nanowalls on substrate are in most suitable shape and orientation not only as an optical trap but also as an optical waveguide due to their unique growth habit, V[011¯0]⪢V[0001]≈V[0001¯]. Consequently, the stimulated emission at 384 nm through nanowalls is generated by the threshold power density of only 25 kW/cm2. Such UV lasing properties are superior to those of previously reported ZnO nanorod arrays. Moreover, there is no green (defect) emission due to the mild procedure to synthesize ZNWA.

ChemInform Abstract: Soft Solution Processing: Low-Energy Direct Fabrication of Advanced Inorganic Materials

Department of Fine Chemicals Engineering and Chemistry, Chungnam National University,220 kung-dong, Yusong-gu, Taejon 305-764, KoreaReceived March 27, 1999A new concept ‘‘soft solution processing’’ has been introduced to fabricate advanced solid state materials inan economical, environmentally friendly, and energy and material efficient way. The prepared films show thedesired and prospective properties despite of low temperature synthesis and no post-synthesis annealing. Suc-cessful examples demonstrate that soft solution processing is capable of preparing advanced materials withplanned properties through the easy control of reaction conditions in a suitable aqueous solution in a single syn-thetic step without huge energy consumption and without any sophisticated equipment.IntroductionAs advances in the instrumentation and material haveameliorated modern human life, the demand to developmore sophisticated and complicated functions increases.Especially, one of the most required techniques is a minia-turization of advanced inorganic materials such as micro-electronics. It means that technical improvements in thefabrication of functional thin films are important. However,although an intensive attention is being paid mainly to thefabrication of more delicate and advanced material, the eco-nomic, environmental, and energy factors of the fabricationprocesses have not been adequately considered. Since theearth is an almost closed system, the used materials wouldbe recycled, moreover wasted energy and heat should beminimized. Thus, if the production of desired substance, thesimultaneous shape-forming and in situ compositional andfunctional grading can be performed in only one syntheticstep at low temperature with high energy and material effi-ciency, it should be the most effective synthetic route.Unfortunately, the usual synthetic approaches described inprevious works to fabricate thin films have been mainlyfocused on multistep processes using gas phase and/or vac-uum system. These processes include the following: prepa-ration of a bulk material or its precursors; deposition orintegration onto/into substrates using chemical vapor deposi-tion, sputtering, or laser ablation deposition; the formation ofshape; size; and orientation. In addition, post-synthesis heattreatments are often required to allow proper functions.Since huge energy consumption and sophisticated instru-mentation are required in these methods, these techniquesare not economical nor environmentally friendly. In thecourse of trying to developing such a novel syntheticapproach, ‘‘soft solution processing’’ seems to fit these crite-ria. In this contribution, we explain what is soft solution pro-cessing and how soft solution processing can be realized toobtain advanced inorganic materials. In addition, severalsuccessful examples and some possible synthetic improve-ment using designed soft solution processing methods willbe given. Definition and Nature of “Soft Solution Processing’’‘‘Soft solution processing’’ is a term encompassing a widegroup of synthetic processes used to prepare advanced solidstate materials using a solution treatment at a low tempera-ture. Here, ‘‘soft’’ means less environmental charge, lowenergy and material consumption, no complicated instru-mentation, and no sophisticated multistep processes. Thesolution treatment of the starting substances can be easilycombined with different activation methods such as electro-chemical reactions, photochemical excitation, hydrothermalreactions at a low temperature, application of microwaves orultrasonics, chimie douce reactions, bioactivation or hot-pressing to prepare desired materials. Since all living organ-isms on earth consist of aqueous solution systems at ambienttemperature and pressure, water should be the most suitablesolvent for the soft solution processing. Therefore, spontane-ous chemical reactions in aqueous solution such as dissolu-tion, precipitation and/or interfacial reaction should beinvolved in the soft solution processing. In addition, themajor advanced ceramic materials contain at least one metalelement with its particular oxidation state, coordination, andchemical composition. It is attributed to the specialized elec-tronic configuration of the given metal species. Here, itshould be noted that the dissolved metal in aqueous solutionare generally combined with oxygen derivatives such ashydroxyl group to form a certain anion such as metalite ormetalate.

Synthesis of porous and nonporous ZnO nanobelt, multipod, and hierarchical nanostructure from Zn-HDS

Zn based hydroxide double salts (Zn-HDS) with an interlayer spacing of 20 Å was produced by dissolving dumbbell-like ZnO crystal. The resulting Zn-HDS with a ribbon-like shape has a suitable morphology to explore the remarkably mild procedure for synthesis of ZnO nanobelts. We found that the intercalated water molecules into the Zn-HDS could play a key role in the ZnO nanobelts porosity. The nonporous ZnO nanobelts were successfully synthesized from the Zn-HDS by soft-solution process at 95 °C through mild dehydration agent as Na 2CO 3. As-synthesized ZnO nanobelts were grown along not only the [0 1 −1 0], but also the [2 −1 −1 0]. On the other hand, the porous ZnO nanobelts were obtained from the Zn-HDS by calcinations at 200 and 400 °C. In addition, flower-like ZnO multipod and hierarchical nanostructures were produced from the Zn-HDS by using of strong dehydration agent (NaOH) through hydrothermal reaction at 150 and 230 °C.

Soft Solution Processing for the Synthesis of Alumina Nanoparticles in the Presence of Glucose

Alumina nanoparticles were synthesized following hydrothermal process at 170°C for 6 h, using glucose and other water‐based precursor materials. The uncalcined and calcined (550°–1200°C) particles were characterized by differential thermal analysis, thermogravimetry, Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and multipoint Brunauer–Emmett–Teller (BET) surface area. The microstructures of the calcined (at 550°C) particles were examined by field‐emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD and FTIR studies revealed that gamma‐alumina (γ‐Al2O3) persisted up to 1000°C followed by the appearance of alpha‐alumina (α‐Al2O3) at 1200°C. BET surface area analysis confirmed that the specific surface area of γ‐Al2O3 was higher compared with α‐Al2O3. Because of particle agglomeration, the crystallite sizes obtained by the BET method showed larger values than those determined by the XRD method for the samples calcined at 550°–1200°C. For 550°C‐treated sample, FESEM micrograph showed the aggregated particles of size 20–80 nm, while TEM image of the same sample revealed a particle size of 5–10 nm.

121Sb Mössbauer spectra of M or A-doped antimonic acid (M = Ta and Nb, A = Bi and Y) fine nanoparticles prepared by soft chemical solution process

121Sb Mössbauer spectroscopic studies on the pyrochlore-type M or A-doped antimonic acids (M = Ta and Nb, A = Bi and Y) nanoparticles were carried out at 12 K in order to determine the oxidation state of Sb and also find more useful information for making clear the detail mechanisms of the photocatalytic property and the proton conductivity. The 121Sb Mössbauer results indicated that all of Sb were Sb5+ in HSb1−xMxO3·nH2O (M = Ta and Nb) which Sb was partially substituted by M, however, small amount of Sb were Sb3+ in H1−3xAxSbO3·nH2O (A = Bi and Y) which H was partially substituted by A. The amounts of Sb3+ in the Bi-containing material were clearly larger than that in the Y-containing material. The photocatalytic properties and the proton conductivities of the pure and M or A-containing materials were discussed in relation to their 121Sb Mössbauer parameters, especially isomer shift (δ) and quadrupole coupling constant (e2qQ).

Room-temperature Synthesis of Monodispersed SnO2 Nanoparticles by Liquid Phase Deposition

Abstract We have successfully tailored a soft solution process for the synthesis of monodispersed SnO2 nanoparticles, applying a liquid phase deposition technique from an aqueous reaction mixture without any post-annealing treatment. The synthesis was carried out by varying poly(ethylene glycol) (PEG) content in the reaction mixture. The XRD patterns of the nanoparticles exhibited the formation of SnO2 cassiterite phase, irrespective of the PEG content in the composition of the reaction solution, the reaction time, and the reaction temperature. The mean size and the standard deviation of SnO2 nanoparticles exhibited a decreasing trend with increasing PEG concentration.

Processing of carbon-fiber reinforced (SiC + ZrC) mini-composites by soft-solution approach and their characterization

Carbon-fiber reinforced (SiC + ZrC) mini-composites have been prepared via soft-solution process using inorganic precursors. In this process, water-soluble compounds have been used to act as precursor materials to impregnate the fiber tow. Thermal analysis provided the temperature range for the pyrolysis to convert the precursors into the desired (SiC + ZrC) matrix. X-ray diffraction of the composites confirmed the phase formation and the crystallite size of these phases were in the range of 25–40 nm. Cross-sectional microstructures of the composites have shown the matrix formation around each individual fiber. The mechanical properties revealed that the tensile strength and fracture energy of the composites pyrolyzed at 1600 °C were significantly higher with typical composite failure behavior, as compared to those pyrolyzed at 1700 °C. The statistical size effects of the tensile strength were investigated on the basis of the Weibull statistics.

ChemInform Abstract: Features and Importance of Solution Processing for Ceramics: Merits and Demerits of Precipitation Method, Colloids, Sol—Gel, Soft Chemistry, Soft (Solution) Processing and Others

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

新素材：環境・エネルギー材料の新展開 セラミックスを溶液から作る意味と意義―ナノ粒子，薄膜，厚膜，パターンおよびバルク体―

Based upon thermodynamic considerations for various materials processing, solution processings appear to be the most energetically (environmentally) benign techniques. Various solution procesings for ceramics are critically reviewed with emphasis on their merits and demerits. Existing confusions and contradictions are pointed out in the definitions and concepts of various methods: i.e. precipitation, colloid, sol-gel, polymer-gel, complexed-gel (polymerized complex), soft process (soft solution process) and/or more widely, solution deposition, chemical solution deposition, bio-mimetic, bio-inspired, ink-jet, spray, etc. In particular, for ceramic films and patterns, the conventional methods where firing is essential after coating of powders from their suspensions or their solution precursors might be rather close to solid (powder) processes. This is especially true when significant chemical reactions are not involved during the coating processes, thus most reactions such as pyrolysis, compound formation (synthesis), crystallization, consolidation, substrate adhesion, etc., occur in the solid states by heat. In those solid state processes using firing of powders after shape-forming, the cracking/peeling of the film and/or the bulk is serious problems because volume shrinkage during firing is inevitable for packed powders. Those shrinkages practically limit the application of those powder processes. In order to overcome those limitations, alternative methods where chemical reactions at the interface between a solution and a substrate solid and/or a reactant are described here as typical Soft Processing Methods. They may lower the difficulties in powder processes by forming shaped materials in a single step at lower temperatures. In addition to the production of nano-crystals such as SrTiO3, Zr0.6Ce0.4O2, etc., direct fabrication of LiCoO2 and PbS films in solutions at room temperature to 150°C without post firing are described. “Direct Patterning of Ceramics” using ink-jet reaction or ink-jet deposition method has also been proposed.

Panoscopic Assembling and UV‐Shielding Properties of Calcia‐Doped Ceria with Micaceous Lepidcrocite Type Potassium Lithium Titanate via Soft Chemical Processes

In order to attain further performance improvements concerning UV‐shielding, calcia‐doped ceria (Ce0.8Ca0.2O1.8) nanoparticles were coated on micaceous lepidocrocite‐type potassium lithium titanate (K0.8Li0.27Ti1.73O4), 10–20 μm in diameter via soft solution processes, where the micaceous titanate was prepared by reacting K2CO3, Li2CO3 and TiO2 using K2MoO4 flux at 950°C. After putting micaceous potassium lithium titanate particles in deionized water at 40°C, appropriate quantities of 3 M NaOH aqueous solution and 0.8 M CeCl3‐0.2 M CaCl2 mixed aqueous solution were simultaneously dropped, where the solution was stirred and pH was kept at 12 through the reaction. Then, the desired amount of 2 M H2O2 solution was added and pH was also kept at 12. The slurry was filtrated and washed with water and methanol. The precipitate was fired at 700°C for 1 h to obtain micaceous K0.8Li0.27Ti1.73O4 coated with white Ce0.8Ca0.2O1.8 nanoparticles. Such panoscopic assembling successfully improved the comfort of the product when wearing it on the skin without compromising the UV‐shielding ability, meanwhile greatly reducing the oxidation catalytic activity.