Nano

The optical properties of CdSe quantum dots (QDs) capped by thioglycolic acid (TGA) before and after surface modification with poly (acrylic acid) grafted onto salep (salep-g-PAA), as a biopolymer-based multidentate ligand, were examined. The results showed that the fluorescence intensity as well as the stability of CdSe QDs was incredibly increased after surface modification with the biopolymer-based ligand. To provide more evidence for the occurrence of surface modification, the prepared CdSe–salep-g-PAA QDs were characterized by thermo-gravimetric analysis (TG), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR).

Bilayer structures of colloidal PbS quantum dots (QDs) with different sizes are fabricated by two methods: chemical bond anchoring and electrostatic adsorption. Unlike the sample prepared by chemical bond anchoring, we find that the electronic connection between different layers is suppressed in the samples prepared by electrostatic adsorption with charged polyelectrolytes. To clarify the electronic coupling between the QDs and the polyelectrolytes, QDs directly stabilized by charged polyelectrolytes were synthesized. Transmission electron microscopy investigation shows that cross-linked QD networks are formed. Time-resolved photoluminescence measurements indicate that the carrier lifetimes of QDs in networks were greatly reduced. The photoluminescence peak energy increases with a third root of the excitation power. All these observations can be consistently explained considering spatially separated photoexcited carriers in a type-II band alignment. The abnormal behaviors of electrostatic adsorption sample are discussed based on these results.

Oral chemotherapy is a great way to cancer treatment because it is less stressful being that the patient will have less hospital visits and can still maintain a close relationship with health care professionals. In this research, three types of nanoparticle formulation from commercial PCL and self-synthesized TPGS-b-(PCL-ran-PGA) diblock copolymer were fabricated for oral delivery of antitumor agents, including DDAB-modified PCL nanoparticles, unmodified TPGS-b-(PCL-ran-PGA) nanoparticles and DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticles. Firstly, the TPGS-b-(PCL-ran-PGA) diblock copolymer was synthesized and characterized. DDAB was adopted to increase retention time at the cell surface, thus increasing the chances of nanoparticle uptake by the gastrointestinal mucosa and improving drug absorption. The TPGS-b-(PCL-ran-PGA) nanoparticles were found by FESEM of spherical shape and around 200 nm in diameter. The surface charge of TPGS-b-(PCL-ran-PGA) nanoparticles was reversed from anionic to cationic after DDAB modification. The DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticles have significantly higher level of the cell uptake than that of DDAB-modified PCL nanoparticles and unmodified TPGS-b-(PCL-ran-PGA) nanoparticles. In vitro cell viability studies showed advantages of the DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticles over Taxotere^® in terms of cytotoxicity against A549 cells. In conclusion, oral chemotherapy by DDAB-modified TPGS-b-(PCL-ran-PGA) nanoparticle formulation may provide a promising outcome for lung cancer patients.

In this paper, we present a facile process for preparing 3 mol.% yttria-fully-stabilized zirconia (3Y-FSZ) nanopowders by molten salts/coprecipitation method at low temperature. By this method, precursor powders in molten salts have a high reactivity and diffusivity, and react easily and completely, which can greatly reduce the synthesis temperature. Furthermore, the synthesis procedure involves neither mechanical mixing nor repeated grinding and thus ultrapure nanopowders with a better uniformity and fewer agglomerates can be obtained. The results illustrated that 3Y-FSZ nanopowders particle diameters ranging from 7 nm to 10 nm were successfully synthesized at 500°C.

We present a simple method to prove the presence of an organic shell around silver nanoparticles (NPs). This method is based on the comparison between optical extinction measurements of isolated NPs and Mie calculations predicting the expected wavelength of the Localized Surface Plasmon Resonance of the NPs with and without the presence of an organic layer. This method was applied to silver NPs which seemed to be well protected from oxidation. Further experimental characterization via surface enhanced raman spectroscopy (SERS) measurements allowed to identify this protective shell as ethylene glycol. Combining LSPR and SERS measurements could thus give proof of both presence and identification for other plasmonic NPs surrounded by organic shells.

Stable dispersions of reduced graphene oxide (RGO) have been prepared by indole as a previously unreported reducing agent without employing any external stabilizing reagents. The obtained RGO can be individually dispersed in ethanol, N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), tetrahydrofuran (THF) and isopropanol. Several analytical techniques including Atomic force microscopy, X-ray diffraction, UV-Vis spectra, Raman spectroscopy and X-ray photoelectron spectroscopy indicate that a significant fraction of the oxygen-containing functional groups are removed, yields a C/O ratio as high as 7.4. The conductivity of RGO is 21.2 S/m and the thickness of RGO increases to 1.7 nm. Furthermore, this new reducing agent is of low toxicity, which makes the reduction much safer than hydrazine and this method is cost-effective to produce single-layered RGO on a large scale.

Effect of pristine and modified MCM-41 on the kinetics of styrene atom transfer radical polymerization (ATRP) was studied using a double bound containing modifier at 110°C. Conversion, molecular weight and PDI were obtained during the polymerization reactions to study the polymerization kinetics. Addition of the both types of MCM-41 has resulted in inconsiderable variations on the kinetics of polymerization. A similar trend is observed for the molecular weight of the free chains; however, increasing MCM-41 content results in higher PDI values. Also, surface modification of MCM-41 results in lower polymerization rates. In the case of grafted chains, molecular weight and PDI values increase by increasing MCM-41 content.

The linear and nonlinear optical properties in a wurtzite In_xGa_1-xN/Al_yGa_1-yN strained spherical quantum dot (QD) subjected to a uniform external electric field with a direction opposite to that of the built-in electric (BEF) within the framework of effective-mass approximation have been investigated. The results show that the BEF has great effects on the linear and nonlinear optical absorption coefficients (ACs) and refractive index (RI) changes. Moreover, the dependence of the linear and nonlinear optical properties on the In composition, on the Al composition and on the inner sphere radius has been studied in detail. It is indicated that the ACs and RI changes of the Wurtzite spherical QD have strongly affected by these factors. The results may make a significant contribution to designing some important photodetectors and photonic crystal devices.

Polypyrrole/manganese dioxide nanocomposite was deposited on graphite felt (GF) via electrodeposition to fabricate polypyrrole/manganese dioxide/graphite felt (PYMG), which can be used as novel free-standing electrode for supercapacitors. The microstructure and morphology of the as-prepared samples were characterized by Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cyclic voltammogram (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the electrochemical performance of the composites. The PYMG electrode displayed specific capacitance as high as 596.3 Fg^-1 at the current density of 0.5 Ag^-1, which is much higher than that of polypyrrole/manganese dioxide (PPy/MnO₂) composite reported previously. The high specific capacitance of PYMG may be attributed to the fact that the porous GF is a good conductive matrix for the dispersion of PPy/MnO₂ composite and it can facilitate easy access of electrolytes to the electrode, which results in enhancement of the electrochemical performance of the composite. Furthermore, the PYMG composite exhibited enhanced specific capacitance compared to MnO₂/GF (MGF) and PPy/GF, which may be ascribed to the synergistic effect of PPy and MnO₂.

The defect formation energies and magnetic properties in Co-doped ZnO nanowires (NWs) are studied using the first-principle density functional method within the generalized gradient approximation (GGA) and GGA + U schemes. It is found that Co impurity has lower formation energies in the surface sites, indicating that Co impurity occupies preferably surface sites of NWs. Ferromagnetic (FM) and antiferromagnetic (AFM) coupling are investigated by GGA and GGA + U methods. The results show that the AFM coupling in energy is lower than the FM coupling, which indicates that AFM coupling is more stable. The magnetic properties can be mediated by the vacancies [V_O(B) and V_Zn(B)] and interstitials [I_Zn(oct)]. The stability of the FM and AFM can be explained by the Co 3d energy level coupling.

BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄/Polypyrrole composite film [including three doping acids, dodecyl benzene sulfonic acid (DBSA), camphor sulfonic acid (CSA) and p-toluenesulfonic acid (TSA)] was prepared by sol–gel method and in situ chemical oxidative polymerization. The structure, morphologies, conductivities, magnetic properties and microwave absorption properties of the composite film were characterized by using XRD, FESEM, FTIR, Four-probe tester, VSM and Vector network analyzer. The results show that the conductivity of acid-doped Polypyrrole composite film is higher than that of pure Polypyrrole composite film. The saturation magnetization (M_s) and remanent magnetization (M_r) of the composite film are lower than those of BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄ film. However, the electromagnetic properties are in the contrary. The microwave absorption properties of the composite film are much better than those of BaFe₁₂O₁₉–Ni_0.8Zn_0.2Fe₂O₄, which mainly depends on the increasing of the dielectric loss. A minimum reflection loss of the DBSA-doped composite film is −17.6 dB at 9.3 GHz with the thickness at 3.0 mm.

For the first time, pyromilling synthesis for production of nanocrystalline titanium carbide was presented in this research. Raw materials containing stoichiometric ratio of titanium and carbon were milled and heated simultaneously. Samplings were done at different times. Then, phase transformation, crystallite size and strain of samples were estimated by XRD technique. Microstructures of milled samples were studied by SEM and TEM. Results showed that by increasing temperature, milling time for synthesizing of titanium carbide was reduced. Crystallite size of milled samples were in nanometer scale which were reduced by increasing of milling time and decreasing of temperature while strain was intensified. Existence of created strain changed lattice parameter of synthesized titanium carbide from standard value.