The properties of sintered calcium phosphate with [Ca]/[P] = 1.50.

In order to obtain the properties of the sintered as-dried calcium phosphate with [Ca]/[P] = 1.50, the characteristics of sintered pellets have been investigated using X-ray diffraction (XRD), inductively coupled plasma-mass spectrometry (ICP-MS), Fourier-transform infrared (FT-IR) spectra, Vickers hardness indentation and scanning electron microscopy (SEM). When the pellet samples were sintered between 700 °C and 1200 °C for 4 h, the hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), HA) still maintained the major phase, accompanied with the rhenanite (NaCaPO(4)) as the secondary phase and ß-tricalcium phosphate (ß-Ca(3)(PO(4))(2), ß-TCP) as the minor phases. In addition, the HA partially transformed to α-tricalcium phosphate (α-Ca(3)(PO(4))(2), α-TCP) and tetracalcium phosphate (Ca(4)(PO4)(2)O, TTCP), when the pellet samples were sintered at 1300 °C and 1400 °C, respectively, for 4 h. The maximum density and Vickers Hardness (HV) of sintered pellet samples were 2.85 g/cm3 (90.18% theoretical density (T.D.)) and 407, which appeared at 1200 °C and 900 °C, respectively.

Photoelectric characteristics of natural pigments self-assembly fabricated on TiO2/FTO substrate.

Natural pigment can act as an inexpensive and biologically-friendly dye, which is fabricated on a TiO2/FTO substrate. Natural pigments promote the efficiency of the photoelectric conversion in water-based DSSC with the aqueous electrolyte of the Ce+4/+3 system. The open-circuit voltage (Voc) of natural pigment in water-based DSSC is 0.640 V. The short-circuit current (Isc) of natural pigment in water-based DSSC is 0.658 mA/cm2. The efficiency of the photoelectric conversion in water-based DSSC of natural pigment is up to 0.131%. The natural pigments in DSSC are potentially applicable to turning solar energy into environmentally-friendly energy.

Ellipsometric studies of optical properties of local surface plasmon resonance for Au nanoparticles on the substrate.

Few ellipsometric studies have been conducted on Au self-assembled monolayers (SAM), with large discrepancies obtained for refractive index values. Because the Au NPs layer is a kind of composite layer, Au NPs and void, the effective media approximate (EMA) model was employed to investigate the optical properties of Au NPs. The reflective coefficient (approximately 1.2) was smaller than the extinction coefficient (approximately 2.5), which is different from the previous reports and corresponds to the Drude model. The absorption peak of surface plasmon resonance for Au NPs on the glass substrate was shifted from 580 nm to 480 nm.

Morphology-controlled 2D ordered microstructure arrays by surface modification of colloidal template.

In this paper, we describe a convenient approach for fabricating two-dimensional, ordered TiO2 bowl-like structure and inverted-bowl-like structure patterns consisting of submicrometer arrays on a self-assembled monolayer film, for the first time using a surface-modified polystyrene colloidal monolayer as the template. Typically, the well-ordered two-dimensional TiO2 bowl-like structures were obtained by liquid phase deposition within the interstitial voids in assemblies of polystyrene spheres followed by the dissolution of the polystyrene template with dichloromethane. Otherwise, through a simple wet treatment by immersing in the sulfuric acid at 50 degrees C, the surface characteristics of polystyrene were turned from hydrophobic to hydrophilic. The ordered inverted-bowl-like structures could be prepared on this treated surface. We believe that this method could be extendable to colloidal template with smaller dimensions, and to periodic arrays made of other materials.

Ellipsometric advances for local surface plasmon resonance to determine chitosan adsorption on layer-by-layer gold nanoparticles.

The ellipsometric measurement of local surface plasmon resonance (LSPR) caused by the adsorption of chitosan on layer-by-layer gold nanoparticles (Au NPs) was investigated. Six nanometer (6 nm) Au NPs were prepared and layer-by-layer Au NPs were fabricated to shift the LSPR to 520, 540, and 560 nm, respectively, due to the Mie theory. The thicknesses and the fractions of the layer-by-layer Au NPs were measured accurately using a combination of the Fresnel equation and the Maxwell-Garnett equations for ellipsometry. Furthermore, the position of the LSPR was shifted by chitosan. Using trajectory to record the trace of polarized light for ellipsometry resulting from LSPR, it was found that LSPR is predominantly induced when the LSPR position is close to the wavelength of the ellipsometric measurement. The trajectory circle of LSPR is very large for an increase of chitosan adsorption on Au NPs when the LSPR position is close to the detected wavelength. The linear approximation aspect quantifying the trajectory corresponds with the change of LSPR for the adsorption of chitosan, except for cases with low incidence and Brewster angles. The aspects and technologies of ellipsometry will benefit from the findings in this study, with potential applications in the fields of determination of molecular adsorption.

Surfactants-aided syntheses of different sizes and triangular shape of gold nanoparticles using trisodium citrate in environmentally friendly and photoinduced methods.

We prepared gold nanoparticles (Au NPs) by only using trisodium citrate as the stabilizer. The detailed reaction mechanisms of S(N)1 and E1 reactions are examined and evidenced in this study by FTIR data. Citric acid is a kind of tertiary substrate. In aqueous solution, the substitution nucleophile path 1 (S(N)1) reaction and Elimination path 1 (E1) reaction usually occur simultaneously. Chloride ions, the substitution nucleophile, play a very important role to launch the mechanisms of S(N)1 and E1 reactions. Controlling the concentration of the chloride ions with the addition of HCl(aq) according to Le Chatelier theory, the average particle size of Au NPs (5.5 nm) was achieved to overcome the minimum limited size (approximately 10 nm). Two stages of the photoinduced method, aggregation into triangular conglomerates and growth into triangular particles, were determined form TEM observations. This preparation of Au NPs has potential in tuning the size, shape, and mechanism of Au NP formation by using only environmentally friendly trisodium citrate and the photoinduced method.

Fabrication of aligned TiO2 one-dimensional nanostructured arrays using a one-step templating solution approach.

In this letter, we report a one-step templating synthetic strategy to prepare aligned TiO2 nanotube and nanowire arrays on Si substrate from a solution at ambient temperature. The deposition of TiO2 and the selective-etching of the ZnO template proceeded at the same time through the careful control of process parameters. The different thickness of TiO2 sheaths, leading to the formation of nanotubes or nanorods, can be precisely controlled by the deposition time. The idea of selective etching and deposition is applicable to other oxide materials, and such a facile method is expected to find widespread applications.

Fabrication of Mesoporous CoS2 Nanotube Arrays as the Counter Electrodes of Dye-Sensitized Solar Cells.

Mesoporous cobalt sulfide nanotube arrays on FTO-coated glass were synthesized by combining three simple technologies: the selective etching of ZnO sacrificial templates, mesoporous Co3 O4 formation from cobalt-chelated chitosan, and ion-exchange reaction (IER). The mesoporous Co3 O4 nanotubes composed of the Co3 O4 nanoparticles possess a high surface area and are taken advantage for further removal of templates and IER. The morphologies and crystal structures of the CoS2 nanotube arrays were characterized by SEM, TEM, and XRD analyses. Their electrocatalytic properties were determined by electrochemical analyses including cyclic voltammetry measurements and Tafel polarization. The DSSCs assembled with a CoS2 counter electrode achieved a power conversion efficiency of 6.13 %, which was comparable to that of the DSSC with the Pt counter electrode (6.04 %). This indicates that the mesoporous CoS2 nanotube array can be a low-cost and efficient alternative for the reduction of electrolytes in DSSCs.

Sugar-mediated chitosan/poly(ethylene glycol)-beta-dicalcium pyrophosphate composite: mechanical and microstructural properties.

The microstructural and mechanical properties of sugar-mediated chitosan/poly(ethylene glycol)-based scaffolds and composites, which are composed of beta-dicalcium pyrophosphate (beta-DCP) and sugar-mediated scaffolds, were investigated. All of the scaffolds were prepared by various freeze-drying protocols. The differences in the freeze-drying process of the sugar-mediated chitosan/poly(ethylene glycol) scaffold for three types of sugar (sucrose, glucose, and D-fructose) were determined by scanning electron microscopic observation, water retention, density, and porosity analyses. The sugar-mediated scaffolds prepared by scheme I of the freeze-drying process show large pores, poorly connective interlayers, and disintegrated inner structures, different from the small pores and well-connective channel structures as shown in the scheme II freeze-drying process. The key factors for controlling pore structure and size in the scheme I freeze-drying process were formulation and composition, but for the scheme II freeze-drying process, the key factor was freeze protocol. The composite scaffolds were macroporous, and the microstructure changed considerably with added beta-DCP content. The incorporation of beta-DCP granules caused a significant enhancement of compressive modulus and yield strength. The increased mechanical strength may be attributable not only to the physical complexation between the sugar-mediated scaffold and beta-DCP, but also the chemical reaction to apatite formed on the cell wall.

Synthesis of nanosized chitosan-poly(acrylic acid) particles by a dropping method.

Deoxyribonucleic acid (DNA) vaccines are being investigated extensively because of their excellent potential over conventional protein ones. A suitable DNA carrier, consisting of uniformly dispersed chitosan-poly(acrylic acid) particles with an average size of 30 nm, was successfully synthesized by a dropping method with a ratio of chitosan solution to poly(acrylic acid) solution of 1:1 and was incubated in a buffer solution with a pH value of 3.0. The particle size increased from 35.76 to 45.90 nm when the pH value of the buffer solution was increased from 3.0 to 7.4. After freeze-drying, the non-incubated mixed solution showed a membranous morphology. A powdered product was formed from the mixed solution as incubated in buffer solution with pH values of 3.0 and 5.3. However, when the mixed solution was incubated in a buffer solution of pH 7.4, a mixture of membrane and powder was obtained.

Outstanding H2 sensing performance of Pd nanoparticle-decorated ZnO nanorod arrays and the temperature-dependent sensing mechanisms.

The nearly monodispersed Pd nanoparticles with controllable density on ZnO nanorod arrays were prepared by the unique PVP-mediated photochemical deposition (PCD). The changes in morphology and dispersion of Pd on ZnO surface are ascribed to the stabilizing property and self-assembly characteristic of PVP being exploited during PCD. There are three temperature-dependent H(2) sensing mechanisms in those Pd/ZnO NRs, including general oxygen adsorption/desorption mode within 200-300 °C, surface conductivity mode at 60-120 °C and palladium hydride (PdH(x)) formation at room temperature, which causes a significant discrepancy in sensitivity variations as a function of Pd density. It is also verified that the electronic sensitization related to the transition of Pd(2+)/Pd(0) redox couple predominates the promoting mechanism in Pd/ZnO NRs used for sensing H(2) at 200-300 °C. Therefore, the gas sensitivity to 500 ppm H(2) of Pd/ZnO NRs can be significantly improved by around 553-fold (S, R(a)/R(g) = 1106) at 260 °C through decorating an adequate amount of discrete Pd nanoparticles instead of the Pd clusters, moreover, the corresponding sensitivity at room temperature is 16.9 that is superior to some promising devices reported in the literatures.

Fabrication of ordered nanoporous anodic alumina prepatterned by mold-assisted chemical etching.

In this article, a simple and cost-effective method to create patterned nanoindentations on Al surface via mold-assisted chemical etching process is demonstrated. This report shows the reaction-diffusion method which formed nanoscale shallow etch pits by the absorption/liberation behaviors of chemical etchant in poly(dimethylsiloxane) stamp. During subsequent anodization, it was possible to obtain the ordered nanopore arrays with 277 nm pitch that were guided by the prepatterned etch pits. The prepatterned etch pits obtained can guide the growth of AAO nanopores during anodization and facilitate the preparation of ordered nanopore arrays.

Influence of humidity on the fabrication of high-quality colloidal crystals via a capillary-enhanced process.

Three-dimensional colloidal crystals have attracted a great deal of attention because of their potential use in photonic crystal, sensors, and other applications, but the bottlenecks in fabricating colloidal crystals include longer processing time and the lack of large-area ordered samples. A proposed capillary-enhanced method, which is a novel, efficient process for fabricating high-quality colloidal crystals in 24 h, is reported. It is necessary for increasing the processing rate by elevating the evaporation temperature but commonly resulted in the deposition of less-ordered crystals. However, high-quality colloidal crystals can be obtained in a controlled high-humidity system, resulting from the existence of secondary capillary forces present in high ambient humidity. Furthermore, the effect of secondary capillary forces will be confirmed, and it will increase with increasing humidity levels according to the semiquantitative analysis view of the surface thermodynamic behavior of small particles, including the modified Kelvin and Young-Laplace equations. Therefore, it can fine tune the relative position of the neighboring particles in the microarray and efficiently decrease the number of defects, resulting in the formation of perfect colloidal crystals with the assistance of enhanced secondary capillary forces.

Preparation and characterization of pH sensitive sugar mediated (polyethylene glycol/chitosan) membrane.

Novel biodegradable membrane based on chitosan matrix was prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and swelling test. Native sugar, which is commonly used in human life, was utilized to prepare the crosslinked hydrophilic chitosan-polyethylene glycol (PEG) polyblend. According to TGA and FTIR results, the chemical reaction occurred in imine bonds (C=N) between sugar and amino groups in chitosan. Chitosan blending with high swelling capacity of PEG increased the water affinity and reacted with sugar decreased the water affinity. The equilibrium water content (EWC) value of the sugar mediated membrane is in the sequence of sucrose>D-fructose>glucose and they all present much lower water uptake ability than polyblend. The chitosan was not degraded by lysozyme, but all of the sugar-mediated membranes were susceptible to lysozyme. Scanning electron microscope (SEM) morphology shows that the degradation rate not only was controlled by the chemical complexation between sugar and polyblends, but the surface morphology of membranes also has great influence. Sucrose-mediated membrane supports the attachment and growth of NIH 3T3 fibroblasts. The pH-sensitive and well degradable property of the sucrose-mediated membrane can be applied for biomedical application.

Effects of sugar cross-linking agents and thermal treatment on the culture of fibroblasts in vitro on a (PEG/chitosan) membrane.

The influences of sugar and a thermal treatment process on the properties of a PEG/chitosan membrane were investigated in this study. With increasing thermal treatment temperature, the cross-linking density was increased and the crystal structure was distorted in the sugar-mediated polyblend. The coloration of the samples intensified from yellow or brown to dark brown during the heat exposure, indicating that a Schiff base was formed. The presence of cross-linking was determined from the FTIR spectrum, a solubility test, and water uptake. The C=N bonding shown in the FTIR spectrum indicates that a Maillard reaction occurred in the sugar-mediated polyblend. The water uptake ability of the samples tested was in the following sequence: sucrose > glucose > D-fructose, which was inverse to the trend of the cross-linking density. The compatibility of the polyblend and the sugar-mediated polyblend with fibroblasts was demonstrated. The thermal treatment has an insignificant effect on cell attachment on chitosan and the other polyblends, but different types of sugar and the cross-linking density changed the cell behavior. Consequently, chitosan/PEG6K cross-linked with sucrose at a concentration of 10 wt% and 120 degrees C thermal treatment shows potential for biomedical applications.

Biodegradation behavior and cytotoxicity of the composite membrane composed of beta-dicalcium pyrophosphate and glucose mediated (polyethylene glycol/chitosan).

The purpose of this study is to prepare and evaluate the biodegradation behavior and cytotoxicity of a composite membrane, G-beta-DCP, combining beta-dicalcium pyrophosphate (beta-DCP) ceramic particles and glucose mediated chitosan-polyethylene glycol (PEG) membrane. The cytotoxicity of the G-beta-DCP was examined by the in vitro method of NIH 3T3 fibroblast cell culture. Extracts were obtained by soaking the G-beta-DCP composite in lysozyme containing phosphate buffer solution for 2, 7, 14, 21 and 28 days, respectively. The substances released from the G-beta-DCP composite were analyzed by gas chromatography-mass spectrometry (GC-MAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The change in morphologies, chemical composition and crystal structure was examined by scanning electron microscopy (SEM) and X-ray diffraction pattern (XRD). The results of extracts cocultured with fibroblasts show that the growth of fibroblasts would increase for the extracts obtained from different beta-DCP feeding weight G-beta-DCP composites after soaking for 7 days. After further increasing the soaking time, the cell number still increases. It is found that the glucose amine and calcium are gradually released from the G-beta-DCP composites, which is considered to be nutritious for the growth of the fibroblast. The release rate of calcium ion and glucosamine concentration can be regulated by feeding the beta-DCP. The degradation behavior of G-beta-DCP composite is considered as an "onion degradation model" that the G-beta-DCP degrades from outer layer to inner layer. The developed material should have a great potential as a cell substrate in the field of tissue engineering.