Plate-like hydroxyapatite nanoparticles synthesized by the hydrothermal method

In this article, calcium nitrate (Ca(NO₃)₂) and disodium hydrogen phosphate (Na₂HPO₄) are used as calcium and phosphorous sources to prepare hydroxyapatite nanoparticles by the hydrothermal method. Plate-like nanocrystals of hydroxyapatite are synthesized with the aid of sodium tripolyphosphate. The results show that sodium tripolyphosphate increases the diameters of the hydroxyapatite nanoparticles during the hydrothermal process. When the concentration of sodium tripolyphosphate reaches 0.015 M, the average aspect ratio of those nanoparticles is close to 1. The strong surface adsorption caused by sodium tripolyphosphate may answer for the morphological change of hydroxyapatite crystal.     

AOT微乳体系中纳米银的可控合成及其紫外-可见光谱研究

在以琥珀酸二异辛酯磺酸钠(AOT)为表面活性剂、环己烷为连续相形成的W/O型微乳体系中,用增溶于微乳液水核中的AgNO₃为银源、水合肼为还原剂制备了纳米银溶胶,利用UV-Vis光谱分析了AgNO₃的浓度、AOT的浓度、还原剂的种类和水与表面活性剂的物质的量比(W)等参数对形成粒子数量及平均粒径的影响,为纳米银粒子的可控合成和纳米银的UV-Vis光谱解析提供了新的依据。研究表明,适当增大AgNO₃的浓度,有利于形成粒径较小的纳米银粒子;W值增大,形成粒子的平均粒径和粒子数量明显增加。和NaBH₄相比,水合肼在反胶束中的溶解性能较好,有利于微乳液反胶束中Ag+的还原。增大AOT的浓度,在一定范围内胶束对反应物的增溶能力增强,胶束的半径也相应减小,有利于形成数量较多、平均粒径较小的纳米银粒子。     

The role of potassium tellurite as tellurium source in mercaptoacetic acid-capped CdTe nanoparticles

Water-soluble CdTe nanoparticles were synthesized in aqueous solution with the assistance of mercaptoacetic acid (MAA) molecules by wet chemical route and microwave-assisted method. A series of cadmium telluride (CdTe) nanoparticles capped with a bifunctional molecule, which contains both thiols and carboxylic acid groups were prepared using different pH values and using potassium tellurite as tellurium source. Thiol-capped nanocrystals of CdTe can be isolated as powders using 2-propanol. The synthesized thiol-capped CdTe were characterized with EDAX, TEM, Raman, FT–IR, UV–Visible absorption, fluorescence spectroscopy and X-ray diffraction (XRD) for the particle size determination and to understand their optical properties. The particles crystallize predominantly in cubic phase with narrow photoluminescence emission. Potassium tellurite as source of tellurium improves the photoluminescence efficiency and also avoids the cumbersome processes associated with H₂Te or NaHTe sources.     

Characterization and evaluation of cytotoxicity of biphasic calcium phosphate synthesized by a solid state reaction route

Calcium phosphate compounds have been widely studied for biomedical applications because of their chemical and structural similarity to the mineral phase constituting bone and teeth. In this work, biphasic calcium phosphate ceramics (HAP/β-TCP), with tunable phase composition ratio, were synthesized by a solid state reaction process. The effect of varying the heat treatment temperature (700, 800, 900, 1000, and 1100 °C) on the formation of the ceramic materials and their related cytotoxicity were examined. The phase composition and morphology of the prepared ceramic powders were characterized by X-ray diffraction and scanning electron microscopy, and the functional groups were analyzed using Fourier transform infrared spectroscopy and Raman spectroscopy. Cell culture experiments, using murine macrophages, showed that the synthesized HAP/β-TCP materials did not exhibit cytotoxicity regardless of the doses assayed or the differences in composition ratio of HAP/β-TCP, suggesting the potential of HAP/β-TCP for biological applications.     

羟基磷灰石团聚体的冲击波活化与烧结研究

 研究了经冲击波处理的羟基磷灰石粉末团聚体的活性及其烧结性能。X射线衍射（XRD）及扫描电镜（SEM）分析表明，冲击波对羟基磷灰石团聚体粉末具有明显的均化与细化作用，并产生了一定程度的晶格畸变，可促进羟基磷灰石陶瓷的烧结。粉体中储存的缺陷能在烧结过程中释放，使受冲击试样比未受冲击试样达到最大线收缩率时的温度降低70 ℃，羟基磷灰石陶瓷的强度和密度明显提高。     

原料加入顺序对制备Cu/Ag纳米粒子的影响

以硫酸铜为原料制备纳米级铜粉,再用化学还原法沉积生长Ag包覆层,制备Cu/Ag复合纳米粒子,使用紫外吸收光谱法监测反应过程.结果表明.加料方式对Cu粒子的粒径会产生影响,向水合肼中滴加聚乙烯吡咯烷铜与硫酸铜的混合液能制得粒径均匀的铜纳米粒子.同时,使用向聚乙烯吡咯烷铜与硫酸铜的混合液中滴加水合肼方法制得Cu2O继而得到...     

Laser-assisted production of tricalcium phosphate nanoparticles from biological and synthetic hydroxyapatite in aqueous medium

Pulsed laser ablation technique has attracted great attention as a method for preparing nanoparticles. In this work, calcined fish bones and synthetic hydroxyapatite, have been used as target to be ablated in de-ionized water with a pulsed CO₂ laser to produce calcium phosphate nanoparticles. The obtained nanoparticles were amorphous and spherical in shape with a mean diameter of about 25 nm. The microanalyses revealed that nanoparticles obtained from the synthetic HA undergo transformation to tricalcium phosphate. While nanoparticles obtained from the biological hydroxyapatite mostly preserve the composition of precursor material.     

Synthesis and characterization of bovine femur bone hydroxyapatite containing silver nanoparticles for the biomedical applications

Bovine femur bone hydroxyapatite (HA) containing silver (Ag) nanoparticles was synthesized by thermal decomposition method and subsequent reduction of silver nitrate with N,N-dimethylformamide (DMF) in the presence of poly(vinylacetate) (PVAc). The structural, morphological, and chemical properties of the HA–Ag nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). TEM images showed that the Ag nanoparticles with size ranging from 8 to 20 nm and were arranged at the periphery of HA crystals. Bactericidal activity of HA–Ag with different concentration of Ag nanoparticles immobilized on the surface of HA was investigated against gram-positive Staphylococcus aureus (S. aureus, non-MRSA), Methicillin resistant S. aureus (MRSA) and gram-negative Escherichia coli (E. coli) by the disc diffusion susceptibility test. The HA–Ag nanoparticles showed that broad spectrum activity against non-MRSA, MRSA, and E. coli bacterial strains.     

Synthesis of chitosan/hydroxyapatite membranes coated with hydroxycarbonate apatite for guided tissue regeneration purposes

Chitosan, which is a non-toxic, biodegradable and biocompatible biopolymer, has been widely researched for several applications in the field of biomaterials. Calcium phosphate ceramics stand out among the so-called bioceramics for their absence of local or systemic toxicity, their non-response to foreign bodies or inflammations, and their apparent ability to bond to the host tissue. Hydroxyapatite (HA) is one of the most important bioceramics because it is the main component of the mineral phase of bone. The aim of this work was to produce chitosan membranes coated with hydroxyapatite using the modified biomimetic method. Membranes were synthesized from a solution containing 2% of chitosan in acetic acid (weight/volume) via the solvent evaporation method. Specimens were immersed in a sodium silicate solution and then in a 1.5 SBF (simulated body fluid) solution. The crystallinity of the HA formed over the membranes was correlated to the use of the nucleation agent (the sodium silicate solution itself). Coated membranes were characterized by means of scanning electron microscopy - SEM, X-ray diffraction - XRD, and Fourier transform infrared spectroscopy - FTIR. The results indicate a homogeneous coating covering the entire surface of the membrane and the production of a semi-crystalline hydroxyapatite layer similar to the mineral phase of human bone.     

Initial stage of the explosion of ammonium nitrate and its powder mixtures

There is an obvious contradiction between the statistics of the devastating explosions that take place with the participation of ammonium nitrate and explosive properties of this material determined in standard tests. Pure ammonium nitrate does not burn under normal conditions and has a very low sensitivity to conventional mechanical and thermal stimuli. So far, ammonium nitrate has been detonated only by using high explosives. Causes of accidental explosions involving large masses of ammonium nitrate are likely to be found in a nonconventional behavior of ammonium nitrate. These changes may arise due to different chemical or physical factors, such as those associated with the presence of active additives, crushing of particles, etc., and lead to acceleration of the process at the initial stage of explosion. This work is devoted studying the convective burning and the initial stage of deflagration-to-detonation transition in dry and wet mixtures of ammonium nitrate with various, largely combustible additives. Experiments were conducted on loose-packed charges in a constant-volume bomb and by using the method of the critical bed height with recording pressure-time diagrams by a piezoelectric sensor. Ammonium nitrate of two different types was used: granular and powdered. The fuel additives were charcoal and aluminum powder, whereas the additives inhibiting the combustion of ammonium nitrate were water and monosodium salt of phosphoric acid. In addition, finely dispersed mixture of four components (ammonium nitrate, aluminum, powdered sugar, and TNT in a proportion of 76: 8: 12: 4) was used. The experiments in the constant-volume bomb were supplemented by numerical simulations, which made it possible to obtain a better understanding of the convective burning of the test mixtures and to evaluate the possibility of using a constant-volume bomb to collect quantitative information on the intensity of the combustion of the mixture at the initial stage of the explosion.     

Optical properties of hydroxyapatite obtained by mechanical alloying

Calcium phosphate based bioceramics, mainly in the form of hydroxyapatite (HA), have been in use in medicine and dentistry for the last 20 years. Applications include coatings of orthopaedic and dental implants, alveolar ridge augmentation, maxillofacial surgery, otolaryngology, and scaffolds for bone growth and as powders in total hip and knee surgery. These materials exhibit several problems of handling and fabrication, which can be overcome by mixing with a suitable binder. In this paper, mechanical alloying has been used successfully to produce nanocrystalline powders of HA using five different experimental procedures. The milled HA were studied by X-ray powder diffraction, infrared and Raman scattering spectroscopy. For four different procedures, HA was obtained after a couple of hours of milling (on an average, 20 h of milling depending on the reaction procedure). The XRD patterns indicate that the grain size is within the range of 29-103 nm. This milling process, used to produce HA, presents the advantage that melting is not necessary and the powder obtained is nanocrystalline with extraordinary mechanical properties. The material can be compacted and transformed in solid ceramic samples. The high efficiency of the process opens a way to produce commercial amount of nanocrystalline HA. Due to the nanocrystalline character of this powder, their mechanical properties have changed and for this reason a pressure of 1 GPa is enough to shape the sample into any geometry.     

In situ synthesis of silicon-substituted biphasic calcium phosphate and their performance in vitro

In situ preparation of silicon (Si) substituted biphasic calcium phosphate (BCP) of hydroxyapatite (HAp)/ β-tricalcium phosphate (β-TCP) were carried out through aqueous co-precipitation method. The concentrations of added silicon were varied with the phosphor in order to obtain constant Ca/(P+Si) ratios of 1.602. X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy were used to characterize the structure of synthesized silicon substituted BCP powders. The characterization revealed that the formation of biphasic mixtures of different HAp/ β-TCP ratios was dependent on the content of silicon. After immersing in Hanks' balanced salt solution (HBSS) for 1 week, 3 wt% silicon substituted BCP powders were degraded and precipitation started to be formed with small granules consisting of number of flake-like crystal onto the surface of synthesized powders. In the case of 1 wt% silicon substituted BCP powders, the degradation behavior was detected after immersion in HBSS for 3 weeks. On the other hand, silicon unsubtituted BCP powders were not degraded even after that duration. On the basis of these results, silicon substituted BCP is able to develop a new apatite phase on the surface in contact with physiological fluids faster than BCP does. This enhanced reactivity resulted in reduction for the stability of the β-TCP structure due to SiO₄ tetrahedral distortion and disorder at the hydroxyl site when silicon incorporates into BCP.     

Study of size dependent photoluminescence properties of copper doped sodium hexametaphosphate capped ZnS nanoparticles

Copper doped ZnS nanoparticles stabilized by sodium hexametaphosphate (SHMP) have been prepared via the wet chemical method using thiourea and sodium sulphide as chalcogenide sources. The XRD pattern showed that ZnS nanoparticles had zinc blende structure and line broadening suggests the formation of an amorphous compound. Absorption measurements were done for three different concentrations of dopant concentrations. The PL spectrum for the sample synthesized using Na₂S·9H₂O showed a sharp emission peak around 510 nm with full width at half maximum (FWHM)<10 nm. The role of the capping agent and sulphide source on optical properties of as synthesized nanoparticles by steady-state photoluminescence (PL) spectroscopy has been studied.     

Facile synthesis of calcium silicate hydrate using sodium dodecyl sulfate as a surfactant assisted by ultrasonic irradiation

Calcium silicate hydrate (CSH) consisting of nanosheets has been successfully synthesized assisted by a tip ultrasonic irradiation (UI) method using calcium nitrate (Ca(NO₃)·4H₂O), sodium silicate (Na₂SiO₃·9H₂O) and sodium dodecyl sulfate (SDS) in water. Systematic studies found that reaction time of ultrasonic irradiation and concentrations of surfactant (SDS) in the system were important factors to control the crystallite size and morphologies. The products were characterized by X-ray power diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrometry (FTIR). The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the CSH. These characterization techniques revealed the successful formation of a crystalline phase with an average crystallite size of about 13 nm and nanosheet morphology at a reaction time of 10 min UI with 0.2 g SDS in solvent which were found to be optimum time and concentrations of SDS for the synthesis of CSH powders.     

Preparation of nanostructured manganese-doped biphasic calcium phosphate powders via sol–gel method

Biphasic calcium phosphate ceramics doped with manganese (Mn-doped BCP) were prepared by using chemical doping via sol–gel technique. Four different concentrations of manganese (2, 5, 10, and 15 mol%) have been successfully incorporated into biphasic calcium phosphate (BCP) phases. X-ray diffraction analysis revealed that the phases present in the Mn-doped BCP powders are hydroxyapatite and β-tricalcium phosphate. The Mn-doped powders are more crystalline than Mn-free BCP powder as its crystallinity increased with increasing Mn content. Fourier transform infrared spectrum corresponded to this result as the peak resolutions of PO₄ bands are viewed with more intensity with the increased Mn. Particle size analysis resulted in nanoscale particles for the Mn-doped and Mn-free BCP powders. From field emission scanning electron microscope observation, Mn-doped BCP powders showed nanoscale individual particles but tightly agglomerated into microscale aggregates due to progressive fusion of particles. Hence, it can be concluded that Mn acts as calcination additives of the BCP powders.     

Synthesis,chemical and microstructural characterization of micro macroporous biphasic calcium phosphate granules

A route based on calcium phosphate emulsions with addition of glycolic acid as pore former was developed for synthesizing porous nanocrystalline biphasic calcium phosphate ceramics. The method is low cost and gives a biphasic calcium phosphate composed of 88% β‐tricalcium phosphate and 12% hydroxyapatite. The material obtained is characterized by scanning electron microscopy, X‐ray diffraction and X‐ray fluorescence techniques, and the specific surface area is determined by the Brunauer, Emmett and Teller method. The small crystalline domain sizes obtained (68 and 87 nm for β‐tricalcium phosphate and hydroxyapatite phases, respectively) allow a major contact reaction and stability in the interphase between the implanted material and natural bone, as well as a better promotion effect on the early bone in‐growth. The improvement of the physical, chemical and structural properties by the balanced combination of the ceramic phases, the small crystallite size, the high porosity and high specific surface area obtained is a desirable characteristic in bone tissue engineering and encourages the performance of animal studies in vivo to evaluate their use for applications such as bone replacement in humans. Copyright © 2017 John Wiley & Sons, Ltd.     

Synthesis of Ca-P nanoparticles and fabrication of Ca-P/PHBV nanocomposite microspheres for bone tissue engineering applications

As the first step in producing totally bioresorbable osteoconductive composite scaffolds for bone tissue engineering using the selective laser sintering technology, bioresorbable nanoparticles of calcium phosphate (Ca-P) similar in composition to β-tricalcium phosphate were synthesized and Ca-P nanoparticle filled poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) microspheres were fabricated. The pH of the chemical reaction for Ca-P particle synthesis was found to have significant effects on the morphology and chemical composition of Ca-P precipitated. Ca-P particles produced at the pH of 10.0-11.0 were amorphous, had a Ca:P molar ratio of about 1.5, were spherical in shape and had sizes in the range of 10-30 nm. The Ca-P particles were used to form Ca-P nanocomposite microspheres through a solid-in-oil-in-water (S/O/W) emulsion solvent evaporation process. Ca-P nanoparticles were mostly encapsulated inside the microspheres and some Ca-P nanoparticles were superficially embedded on the microspheres. The Ca-P/PHBV microspheres had an average diameter of about 48 μm which is suitable for selective laser sintering for constructing osteoconductive composite scaffolds.     

银和去合金银-金纳米粒子的SERS活性研究

用乙二醇还原硝酸银,聚乙烯吡咯烷酮作表面活性剂合成了大量的银纳米颗粒。银纳米颗粒和HAuCl4发生置换反应后形成去合金银-金纳米粒子。以吡啶和SCN-作为探针分子研究了它们的SERS活性。结果表明,当探针分子吸附于银纳米颗粒和去合金银-金纳米粒子上时,探针分子的特征振动峰强度增强、频率发生位移。SERS可表征纳米粒子物理和化学性质的变化。     

Rapid synthesis and characterization of silicon substituted nano hydroxyapatite using microwave irradiation

Nano sized hydroxyapatites with silicon substitution of three different silicon concentrations were successfully prepared first time by a rapid microwave assisted synthesis method, with a time saving and energy efficient technique. The effects of the Si substitution on crystallite size, particle size and morphology of the powders were investigated. The crystalline phase, microstructure, chemical composition, and morphology and particle size of hydroxyapatite and silicon substituted hydroxyapatites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and dynamic light scattering. The crystallite size and particle size decreases with increase in silicon content and particle morphology spheroidal for pure hydroxyapatite changes to elongated ellipsoidal crystals while silicon substitution increases. Fourier Transform Infrared Spectroscopy analysis reveals, the silicon incorporation to hydroxyapatite lattice occurs via substitution of silicate groups for phosphate groups. Substitution of phosphate group by silicate in the apatite structure results in a small increase in the lattice parameters in both a-axis and c-axis of the unit cell.     

Nano-MnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> powder synthesis by detonation of emulsion explosive

Nano-MnFe₂O₄ powders were synthesized by detonation of specially prepared emulsion explosives. X-ray diffraction and transmission electron microscopy were carried out to characterize the as-prepared powders. The results indicated that relatively finely dispersed spherical powders were obtained when the content of RDX in the emulsion explosives was 9.18 wt. %. A certain content of internal-phase ammonium nitrate was not only favorable to control the ingredients of the detonation products, but also advantageous to stabilize the detonation structure of the emulsion explosive according to differential thermogravimetry experimental results. PACS 81.07.Bc; 81.20.-n