Nanocrystalline hydroxyapatite bioceramic using microwave radiation: Synthesis and characterization

In this work, we synthesized bioactive hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) ceramic powder in the lower-end of nano-regime using microwave radiation, which offers several advantages. The powder was synthesized using calcium nitrate tetrahydrate and sodium phosphate dibasic anhydrous as the starting materials. EDTA served as the complex reagent. The pH of the final suspension was adjusted to 9 by adding ammonium hydroxide. Applied microwave power of 600 W, pH of the suspension, mole ratio of Ca/P in the staring chemicals, and the chelating effect of EDTA served as the factors in the synthesis of nanocrystalline HAp powder. The synthesized powder was studied using various characterizing techniques viz., XRD, SEM, HR-TEM, EDS, TG/DTA and FT-IR to determine powder morphology, particle-size, crystallinity, phases, elemental composition and thermal behavior. Results confirmed highly crystalline nano-powder (5–30 nm) with elemental composition of Ca and P in HAp phase and possessed mixed (elliptical and rod-shape) morphology. Using the Scherrer formula, the average crystallite size was found to be 12 nm. The FT-IR confirmed that the powder is of typical apatite structure. Thermal analysis showed a remarkably lower initial dehydroxylation temperature, compared to micron sized HAp, as reported in literature.     

Synthesis,characterization and modelling of zinc and silicate co-substituted hydroxyapatite

Experimental chemistry and atomic modelling studies were performed here to investigate a novel ionic co-substitution in hydroxyapatite (HA). Zinc, silicate co-substituted HA (ZnSiHA) remained phase pure after heating to 1100°C with Zn and Si amounts of 0.6 wt% and 1.2 wt%, respectively. Unique lattice expansions in ZnSiHA, silicate Fourier transform infrared peaks and changes to the hydroxyl IR stretching region suggested Zn and silicate co-substitution in ZnSiHA. Zn and silicate insertion into HA was modelled using density functional theory (DFT). Different scenarios were considered where Zn substituted for different calcium sites or at a 2b site along the c-axis, which was suspected in singly substituted ZnHA. The most energetically favourable site in ZnSiHA was Zn positioned at a previously unreported interstitial site just off the c-axis near a silicate tetrahedron sitting on a phosphate site. A combination of experimental chemistry and DFT modelling provided insight into these complex co-substituted calcium phosphates that could find biomedical application as a synthetic bone mineral substitute.     

Nanocrystalline copper doped zinc oxide produced from copper doped zinc hydroxide nitrate as a layered precursor

Undoped and copper doped nanostructured zinc oxides were synthesized by using a series of synthetic layered material, undoped and copper doped zinc hydroxide nitrates at various molar percentages of copper (2–10) within the layers as precursors. The layered materials were heat-treated at 500 °C to produce zinc oxide nanostructures with crystallite sizes in the range of 23–35 nm. Optical studies of the nanostructured copper doped zinc oxides showed the decrease in band gap with increasing content of the doping agent, copper.     

Synthesis and characterization of a new layered magnesium zinc phosphate hydrate

A new layered magnesium zinc phosphate hydrate, MgZn(HPO₄)₂·H₂O, with a zinc phosphate framework isostructural with the one of Na₂Zn(HPO₄)₂·4H₂O, was prepared by the direct ambient pressure and temperature reaction between zinc 2,4-pentanedionate, phosphoric acid and hexahydrated magnesium chloride. The as-prepared sample is monoclinic (a = 8.780(7) Å, b = 13.240(7) Å, c = 11.123(0) Å and β = 116.21(2)°). The prepared solid undergoes two thermal transformations when it is heated from 110 to 600 °C. The first transformation is due to the release of intercalated water molecules and the second one is due to the HPO₄²⁻ → P₂O₇⁴⁻ transition.     

Edge luminescence from zinc selenide doped with isovalent magnesium impurity

The electric and luminescent properties of zinc selenide crystals doped with the isovalent magnesium impurity were studied. It is demonstrated that low-resistivity n-type ZnSe layers with a dominating edge luminescence component can be obtained.     

Synthesis and characterization of carbonate hydroxyapatite

Substituted apatite ceramics are of clinical interest as they offer the potential to improve the bioactive properties of implants. Carbonate hydroxyapatite (CHA) has been synthesized by an aqueous precipitation method and precipitates with two different levels of carbonate, processed as powders. Sintering experiments were performed to establish the influence of carbonate in significantly reducing the temperature required to prepare high-density ceramics when compared with stoichiometric hydroxyapatite (HA). High-temperature X-ray diffraction was used to characterize the phase stability of the apatites on sintering. Increasing carbonate content was shown to reduce the temperature at which decomposition occurred, to phases of CaO and -TCP. Mechanical testing, performed using biaxial flexure, showed that the CHA specimens had strengths similar to stoichiometric HA. © 1998 Kluwer Academic Publishers     

Synthesis and characterization of hydroxyapatite, fluoride-substituted hydroxyapatite and fluorapatite

Powders of hydroxyapatite (HA), partially fluoride-substituted hydroxyapatite (fHA), and fluorapatite (FA) were synthesized in house using optimum methods to achieve relatively pure powders. These powders were assessed by the commonly used bulk techniques of X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and FT-Raman spectroscopies, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and F-selective electrode. In addition, the current study has employed transmission electron microscopy (TEM), involving morphological observation, electron diffraction and energy-dispersive X-ray spectrometry (EDX), as an effective analytical technique to evaluate the powders at a microscopic level. The HA and fHA particles were elongated platelets about 20×60 nm in size, while FA particles were over twice this size. Calcination of the HA and fHA powders at 1000 °C for 1 h resulted in increased grain size and crystallinity. The calcined fHA material appeared to possess a crystal structure intermediate between HA and FA, as evidenced by the (3 0 0) peak shift in XRD, as well as by the position of the hydroxyl bands in the FTIR spectra. This result was consistent with electron diffraction of individual particles. Small levels of impurities in some of the powders were identified by EDX and electron diffraction, and the carbonate content was detected by FTIR. The use of TEM in conjunction with the bulk techniques has allowed a more thorough assessment of the apatites, and has enabled the constituents in these closely related apatite powders to be identified.     

Long-term in vivo experimental investigations on magnesium doped hydroxyapatite bone substitutes

Despite several efforts to find suitable alternatives to autologous bone, no bone substitute currently available provides the same characteristics and properties. Nevertheless, among the wide range of materials proposed as bone substitutes, calcium phosphate materials represent the most promising category and the present study is aimed at improving the knowledge on non-stoichiometric magnesium-doped hydroxyapatite substitutes (Mg-HA), tested in two different formulations: Mg-HA Putty and Mg-HA Granules. These bone substitutes were implanted bilaterally into iliac crest bone defects in healthy sheep and comparative histological, histomorphometric, microhardness and ultrastructural assessments were performed 9, 12, 18 and 24 months after surgery to elucidate bone tissue apposition, mineralization and material degradation in vivo. The results confirmed that the biomimetic bone substitutes provide a histocompatible and osteoconductive structural support, during the bone formation process, and give essential information about the in vivo resorption process and biological behavior of biomimetic bone substitutes.     

羟基磷灰石的可控制备及其研究

以CTAB为表面活性剂,利用模板技术水热反应合成了平均粒径为68 nm的近球形颗粒和宽为26～35 nm,长为790～960 nm的纳米羟基磷灰石.通过对合成粉体的X射线衍射、红外光谱和透射电镜分析,探讨了CTAB在水热反应中对羟基磷灰石合成的影响机理.结果表明:通过控制反应温度、pH值、反应时间和CTAB的浓度等工艺条件,可以实现纳米羟基磷灰石粒径大小和形貌的可控生长.     

PSS-VS共聚物掺杂PEDOT的合成与表征

以苯乙烯磺酸钠(SSS)和乙烯磺酸钠(SVS)的共聚物PSS-VS为掺杂剂,过硫酸铵(APS)为氧化剂,采用化学氧化法制备了PEDOT/PSS-VS分散体,研究了PSS-VS的共聚比、分子量和用量等因素对PEDOT/PSS-VS导电性能及平均粒径的影响,分析了PEDOT/PSS-VS粒子形成过程。结果表明,SSS/SVS共聚摩尔比为5/5,单体与APS摩尔比为60时制得的PSS-VS掺杂PEDOT具有较好的导电性和分散稳定性,SO3-/EDOT=2,APS/EDOT=1.5,PEDOT/PSS-VS固含量为2.8%时制得的PEDOT/PSS-VS电导率可达11.74S/cm,分散体平均粒径为447nm。     

W doped vanadium oxide nanotubes: Synthesis and characterization

W doped vanadium oxide nanotubes (VONTs) were prepared via a rheological phase reaction followed by self-assembling process. The nanotubes were characterized by elemental analysis, IR, XRD, SEM, TEM, HRTEM, SAED and XPS. Elemental analysis, IR, XRD, SAED and XPS could confirm the crystalline characteristic of the W doped VONTs, while the SEM, TEM, and HRTEM confirmed their morphology and microstructure.     

Sonochemical synthesis and photocatalytic property of zinc oxide nanoparticles doped with magnesium(II)

Mg-doped ZnO nanoparticles were successfully synthesized by sonochemical method. The products were characterized by scan electron microscopy (SEM) and X-ray powder diffraction (XRD). SEM images revealed that ZnO doped with Mg(II) nanoparticles and ZnO nanoparticles synthesized by the same strategy all had spherical topography. XRD patterns showed that the doped nanoparticles had the same crystals structures as the pure ZnO nanoparticles. The Mg-doped ZnO nanoparticles had larger lattice volume than the un-doped nanoparticles. X-ray photoelectron spectroscopy (XPS) not only demonstrated the moral ratio of Mg and Zn element on the surface of nanoparticles, but their valence in nanoparticles as well. The Mg-doped ZnO nanoparticles presented good properties in photocatalyst compared with pure ZnO nanoparticles.     

Synthesis and characterization of hydroxyapatite nanobelts and nanoparticles

In the present paper, the nanobelts and sphere nanoparticles of hydroxyapatite (HA) had been synthesized using normal (oil in water) surfactant. The experimental results showed that the nanobelts consisted of uniform one-dimensional nanofibers with a width of 1.37 nm. The particle size of the sphere nanoparticles was about 55–60 nm. The presence of these resonance of phosphorus was in at least two types of phosphorus environments. The spectra of the nanobelts and sphere nanoparticles contained two typical bands of hexahedra Ca²⁺ at 200 and 210 nm. The Eg values for the HA of microcrystalline, sphere nanoparticles, and nanobelts samples were 1.60, 1.69 and 1.70 eV, respectively.     

HA晶须的制备及在HA/Mg生物复合材料中的应用

利用水热法合成羟基磷灰石晶须(HA_W), 采用浆料-粉末冶金法制备羟基磷灰石晶须/镁金属基复合材料(HA_W/Mg)。用XRD、 FTIR、 FESEM和TG对材料进行表征。分析了尿素含量对HA物相和晶体结构的影响, 以及HA_W/Mg复合材料的热稳定性和显微结构。结果表明: 在本实验条件下, 得到的产物均为带状、 含碳酸根的HA_W; 随着尿素添加量的增加, HA_W逐渐变长且结晶度增加; HA_W与Mg之间在600 ℃以下无化学反应, 且HA不会加剧Mg的氧化; HA_W在HA_W/Mg复合材料中分散均匀, 不易折断。      

Synthesis and characterization of biocompatible hydroxyapatite coated ferrite

Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical composition (CaO)_0.75(La₂0₃)_0.20(Fe₂O₃)₆ was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO₃)₂ and (NH₄)₂HPO₄ maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites could be useful for hyperthermia.     

四针状ZnO晶须的掺杂及其表征

在平衡气量法制备四针状ZnO晶须过程中添加金属锡以研究其对晶须形貌的影响，采用高温固熔表面处理法制备了铝掺杂ZnO晶须。用X射线衍射分析方法和扫描电子显微镜分别对其结构和形貌进行了表征。结果发现，锡在反应过程中起催化剂的作用，添加10％～15％(质量分数)的单质锡能促进ZnO的C轴择优生长，更多锡的加入则抑制C轴生长。铝以置换固溶体和ZnAl2O4两种形式存在于ZnO晶体中。     

Structural and optical characterization of potassium doped zinc oxide nanosheets

This paper presents the synthesis of potassium (K) doped zinc oxide nano sheets at room temperature by wet chemical method. The structure and morphology of the crystals prepared for different molar concentrations of K were analysed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Lattice strain and grain size were calculated from the Williamson–Hall (WH) Plot and Debye–Scherrer’s formula for different concentrations of potassium. Absorption studies reveal that absorption is minimum in the visible region and band gap energy is found to decrease with increase in K concentration. The photoluminescence (PL) spectra were used to study the luminescence behavior and the nature of defects in the samples and the overall emission is white for all the samples except the one prepared with 1.2 M potassium doping.     

Synthesis and characterization of dysprosium-doped magnesium tetraborate

We have identified optimal conditions for the synthesis of highly sensitive MgB₄O₇:Dy thermoluminescent phosphor and examined the effect of alkali metals (lithium and sodium) as additional dopants that improve the performance of the thermoluminescent phosphor.     

Copper and iron doped zinc oxide: chemical synthesis,characterization and their properties

We report here the synthesis of Cu and Fe doped ZnO nano-particles. Cu and Fe doped ZnO nanoparticles were successfully synthesized and structurally, optically and morphologically characterized using X-ray diffractometer, optical spectroscope and scanning electron microscope. The crystal size is in the range of 15–20 nm for both the Cu and Fe doped ZnO nanoparticles. Nanoparticles are not below the critical size where quantum confinement effect is observed. ZnO has hexagonal, wurtzite structure. Synthesis was carried out at 60 °C. The light orange and gray color powder of Cu and Fe doped ZnO nanoparticles were obtained.     

活性炭模板法制备锡酸锌掺杂磷化合物及表征

选用磷酸活化后的活性炭为模板,NaSnO₃·3H₂O、ZnSO₄·7H₂O为原料,通过生物质模板法制备了锡酸锌掺杂磷(Zn₂SnO₄/P)化合物。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和N_2吸脱附等温线对制备的Zn₂SnO₄/P的结构、形貌进行表征。结果表明:Zn₂SnO₄/P为尖晶石结构,其形貌基本上和活性炭相匹配。其比表面积、孔体积和平均孔径分别为87m²/g、0.20cm³/g和9.0nm。