Nano

Nanotechnology is one of the most important emerging fields of science in this century. It deals with designing, construction, investigation, and utilization of systems at the nanoscale. Another interesting research discipline of current day is biotechnology, which gives us a way to understand biological system and to utilize our knowledge for industrial manufacturing. Nanobiotechnology lies at the interface of these two research fields. It exploits nanotechnology and biotechnology to analyze and create nanobiosystems to meet a wide variety of challenges and develops a wide range of applications.

In this study the response surface methodology (RSM) coupled with the central composite design (CCD) were used to optimize the mechanical strength properties of poly(L-lactide)/multi-walled carbon nanotube (MWCNT) scaffolds. The scaffolds were prepared by the freeze-extraction method. MWCNTs were incorporated into PLLA composite as a reinforcement agent in order to improve the strength properties of the scaffolds. The effect of process parameters such as ratio of PLLA/(PLLA + MWCNT) (93–100%), solvent amount (100–200 ml), freezing time (5–7 h) and immersing time (2–4 days) were studied using the design of experiment (DOE). Based on CCD, quadratic model was obtained and developed to correlate the process parameters to the strength of the scaffolds. An analysis of variance (ANOVA) was applied to determine the significant factors affecting the experimental design response (strength) of the scaffolds. The predicted values after optimization process were in good agreement with the experimental values. The model was able to accurately predict the response of strength with less than 5% error.

In this paper, we report a unique growth of nanofibrous structures and nanospheres of titanium using femtosecond laser in air and without the need for any type of catalyst. The femtosecond laser was used to generate nanoparts on a titanium substrate. The irradiated substrate is assumed to be subjected to plane stress type of temperature variation and a new method combining finite difference and Runge–Kutta 4 transient thermal model has been developed to calculate the temperature distribution on the top surface of the substrate during laser ablation. A Matlab code has been developed and validated with the known results from the literature. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffractograms (XRD) and micro-Raman analysis were conducted to characterize the microstructure and revealed metallic and oxide phases in the nanostructure analyses. Results showed that nanofibers and nanospheres were grown in the order of few hundreds nanometers or more. The effect of the laser power on the energy/pulse and hence the temperature was studied. It was found that high temperature results in the formation of nanofibers while lower temperature results in formation of nanospheres. This first time observation could have potential application in biomedical, optoelectronics and photocatalysis.

The single-phase nanostructure forsterite powder was successfully synthesized by mechanical activation of talc and magnesium carbonate powder mixture followed by annealing in the presence and absence of ammonium chloride. Mechanical activation was used as an efficient method for the optimization of powder properties by means of combination and uttermost homogenization of the powder mass. Besides, the presence of chlorine ion affected the forsterite formation rate via producing smaller particle size during subsequent annealing which is very important in the case of diffusion-controlled reactions. The single-phase nanostructure forsterite powder with crystallite size of about 36 nm was successfully synthesized by 10 h mechanical activation with subsequent annealing at 1000°C for 1 h. While in the presence of chlorine ion, the single-phase nanostructure forsterite powder with crystallite size of about 20 nm could be obtained by 5 h of mechanical activation with subsequent annealing at 1000°C for 2 min.

Combustion synthesis has emerged as a facile and economically viable technique for the preparation of advanced ceramics, catalysts and nanomaterials. This paper is the report of the investigations carried out on the synthesis of titania–rare-earth mixed oxide pigments: TiCe_1-xPr_xO_4-δ by the solution combustion method and their characterization by X-ray powder diffraction, transmission electron microscopy, reflectance spectral data, thermal analysis and surface area measurements. The synthesized nanopigments exhibit yellow to brick red color with the increase of praseodymium content. The dominant reflectance of these pigments lies above a wavelength of 600 nm. These pigments are found to be promising candidates as ecological pigments because of their high reflectance, lightness and intense coloration.

Fe₃O₄/Au composite nanoparticles were modified with α-thio-ω-carboxy poly (ethylene glycol). Results from XRD, selected area diffraction, high-resolution TEM images, and dynamic lighting scattering illustrate that the particles have a core/shell composite structure and were monodispersed. Surface plasmon resonance measured by UV–Vis indicates that the absorption peak of the modified composite particle characteristic at 532 nm can be stably suspended in a different buffer. The modified composite particles also have good response to external magnetic field. The Fe₃O₄/Au composite nanoparticles are magnetically and optically active, and are useful for simultaneous magnetic and optical detection. Coupled with biomolecules, the advantages of these composite particles make them very promising for biomedical applications in the near future.

The effect of a thin In_0.1Ga_0.9As underlying layer on the structural properties of single layer In_0.5Ga_0.5As quantum dots (QDs) was investigated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and high-resolution X-ray diffraction (HR-XRD) characterization. The size of dots formed on the surface is uniform but the density increases with the addition of In_0.1Ga_0.9As underlying between In_0.5Ga_0.5As QDs and GaAs buffer layer. This is consistent with the TEM characterization. The existence of thin underlying layer has caused the dots to have different crystal orientation as shown in TEM characterization. From the HR-XRD characterization, broad peak of In_0.1Ga_0.9As underlying layer and QDs has been observed. The wider width of the layer peak than the expected one has been attributed to the strain-relaxation-induced defects. The growth of a thin In_0.1Ga_0.9As underlying layer in the In_0.5Ga_0.5As/GaAs structures strongly affects the structural properties, which was also believed to influence the optical properties of QDs.

Cylindrical In_xGa_1-xAs nanowires (NWs) perpendicular to the substrate have been successfully grown using MOCVD. Morphology of In_xGa_1-xAs NWs has been observed using Field Emission-Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). Both FE-SEM and TEM results show that the NWs grown at low growth temperature and V/III ratio were via direct impinging mechanism. Energy Dispersive X-ray spectroscopy (EDX) results confirm that the cylindrical NWs grown via direct impinging mechanism and tends to have uniform chemical composition.

Nanocrystalline silicon carbide (SiC) thin films with 5 ~ 10 nm grain size, large Seebeck coefficient (-0.393 mV/K), and low electrical resistivity (3.2 ×10^-4 Ohm-m) have been successfully prepared on oxidized silicon substrates by magnetron sputtering of SiC and Al targets. It was found that the addition of a small amount of Al into the SiC film, the high deposition temperature (760 K), and the high thermal annealing temperature (1063 K) were necessary to achieve the goal. The Seebeck coefficient versus logarithm of temperature in the temperature range 383 K to 533 K was a straight line with a slope of -0.999 mV/K. The value of 0.999 mV/K is much larger than the theoretical value of 0.129 mV/K for conventional semiconductors.

Nanocrystalline ZnO particles substituted with different concentrations (0–30%) of Mn were synthesized by using a modified ceramic route and characterized by X-ray diffraction, transmission electron microscopy, selected area electron diffraction and energy dispersive X-ray analysis methods. Positron lifetime and coincidence Doppler broadening measurements were used as probes to identify the vacancy-type defects present in them and monitor the changes while doping. The predominant positron trapping center in the undoped ZnO is identified as the trivacancy-type cluster V_Zn+O+Zn, which is negatively charged, and it transformed to the neutral divacancy V_Zn+O on doping with Mn²⁺ ions. The intensity of the defect-specific positron lifetime component got reduced initially indicating partial occupancy of the vacancies by the doped cations but then recovered on further doping due to the additional Zn vacancies created as a result of the increasing strain introduced by the Mn ions of larger radius. The creation of a new phase ZnMn₂O₄ thereafter changed the course of variation of the annihilation parameters, as the positrons got increasingly trapped in the vacancies at the tetrahedral and octahedral sites of the spinel nanomanganite.