Green synthesis of P - ZrO 2 CeO 2 ZnO nanoparticles using leaf extracts of Flacourtia indica and their application for the photocatalytic degradation of a model toxic dye, Congo red.

In the present work P - Z r O 2 C e O 2 Z n O nanoparticles were synthesised for the first time using phytochemical extracts from Flacourtia indica leaves and applied in the photocatalytic degradation of Congo Red in the presence of Light Emitting Diode warm white light. The photocatalytic degradation was optimized with respect to P - Z r O 2 C e O 2 Z n O nanoparticle dosage, initial Congo Red concentration, and degradation time. The optimum conditions for P - Z r O 2 C e O 2 Z n O nanoparticle synthesis was pH 9, leaves extracts of F. indica dosage 4 g 100 mL-1, Zirconia, Cerium and Zinc metal ion concentration 0.05 mg/L and metal ion to plant volume ratio of 1:4. The leaves extract dosage, pH and metal concentration had the most significant effects on the synthesis of the nanoparticles. The nanoparticles followed type III physisorption adsorption isotherms with surface area of 0.4593 m3g-1, pore size of 6.80 nm, pore volume 0.000734 cm g - 1 3 and average nanoparticle size 0.255 nm. A degradation efficiency of 86% was achieved and the optimum degradation conditions were 0.05 g/L of P - Z r O 2 C e O 2 Z n O nanoparticle dosage, 10 mg/L initial Congo red concentration, and 250 minutes irradiation time. Data from kinetic studies showed that the degradation followed pseudo first order kinetics at low concentration, with a rate constant of 0.069 min-1. The superoxide, h + holes and light were the main determinants of the reaction mechanisms for the degradation of Congo Red. The investigation outcomes demonstrated that P - Z r O 2 C e O 2 Z n O nanoparticles offer a high potential for photocatalytic degradation of Congo Red.

Lanthanide(III)-doped magnetite nanoparticles.

Nearly monodisperse lanthanide-doped magnetite nanoparticles were obtained by thermally decomposing a mixture of Fe(acac)(3) and Ln(acac)(3) (acac = acetylacetonate; Ln = Sm, Eu, Gd) in the presence of passivating surfactants. Magnetic studies revealed room-temperature ferromagnetic behaviors of these doped nanoparticles, distinctly different from those of the undoped parent magnetite or the doped nanoparticles prepared by a coprecipitation method.

Self-assembly of nanostructured diatom microshells into patterned arrays assisted by polyelectrolyte multilayer deposition and inkjet printing.

Individual shells of the diatom Coscinodiscus were self-assembled into a rectangular array on a glass surface that possessed a polyelectrolyte multilayer patterned through inkjet printing. This patterned thin film possessed hierarchical order with nanostructure provided by the diatom biosilica. The process used two polyelectrolytes with opposite electric potentials to control the surface charge of the substrate. The fine features of the diatom frustules were perfectly preserved as a result of the mild conditions of the deposition process. This technique has the potential to enable large-scale device applications that harness the unique properties of functionalized diatom biosilica.

Photoluminescence of silica nanostructures from bioreactor culture of marine diatom Nitzschia frustulum.

The marine diatom Nitzschia frustulum is a single-celled photosynthetic organism that uses soluble silicon as the substrate to fabricate intricately patterned silica shells called frustules consisting of 200 nm diameter pores in a rectangular array. Controlled photobioreactor cultivation of the N. frustulum cell suspension to silicon starvation induced changes in the nanostructure of the diatom frustule, which in turn imparted blue photoluminescence (PL) to the frustule biosilica. The photoluminescent properties were imbedded within a patterned substrate precisely ordered at the nano, submicron and microscales. The peak PL intensity increased by a factor of 18 from the mid-exponential to late stationary phase of the cultivation cycle, and the peak PL wavelength increased from 440 to 500 nm. TEM analysis revealed that the emergence of blue photoluminescence was associated with the appearance of fine structures on the frustule surface, including 5 nm nanopore arrays lining the base of the frustule pores, which were only observed at the late stationary phase when both silicon consumption and cell division were complete for two photoperiods. Photoluminescence was quenched by thermal annealing of diatom biosilica in air at 800 degrees C for 1.0 hr, commensurate with the loss of silanol (triple bond Si-OH) groups on the diatom biosilica, as confirmed by FT-IR. Consequently, the likely origin of blue photoluminescence in the diatom biosilica was from surface silanol groups and their distribution on the frustule fine structures.

Measurement of the intrinsic thermal conductivity of a multiwalled carbon nanotube and its contact thermal resistance with the substrate.

The intrinsic thermal conductivity of an individual carbon nanotube and its contact thermal resistance with the heat source/sink can be extracted simultaneously through multiple measurements with different lengths of the tube between the heat source and the heat sink. Experimental results on a 66-nm-diameter multiwalled carbon nanotube show that above 100 K, contact thermal resistance can contribute up to 50% of the total measured thermal resistance; therefore, the intrinsic thermal conductivity of the nanotube can be significantly higher than the effective thermal conductivity derived from a single measurement without eliminating the contact thermal resistance. At 300 K, the contact thermal resistance between the tube and the substrate for a unit area is 2.2 × 10(-8) m(2) K W(-1) , which is on the lower end among several published data. Results also indicate that for nanotubes of relatively high thermal conductance, electron-beam-induced gold deposition at the tube-substrate contacts may not reduce the contact thermal resistance to a negligible level. These results provide insights into the long-lasting issue of the contact thermal resistance in nanotube/nanowire thermal conductity measurements and have important implications for further understanding thermal transport through carbon nanotubes and using carbon nanotube arrays as thermal interface materials.

Enhanced and switchable nanoscale thermal conduction due to van der Waals interfaces.

Understanding thermal transport in nanostructured materials is important for the development of energy conversion applications and the thermal management of microelectronic and optoelectronic devices. Most nanostructures interact through van der Waals interactions, and these interactions typically lead to a reduction in thermal transport. Here, we show that the thermal conductivity of a bundle of boron nanoribbons can be significantly higher than that of a single free-standing nanoribbon. Moreover, the thermal conductivity of the bundle can be switched between the enhanced values and that of a single nanoribbon by wetting the van der Waals interface between the nanoribbons with various solutions.

Metabolic insertion of nanostructured TiO2 into the patterned biosilica of the diatom Pinnularia sp. by a two-stage bioreactor cultivation process.

Diatoms are single-celled algae that make silica shells or frustules with intricate nanoscale features imbedded within periodic two-dimensional pore arrays. A two-stage photobioreactor cultivation process was used to metabolically insert titanium into the patterned biosilica of the diatom Pinnularia sp. In Stage I, diatom cells were grown up on dissolved silicon until silicon starvation was achieved. In Stage II, soluble titanium and silicon were continuously fed to the silicon-starved cell suspension (approximately 4 x 10(5) cells/mL) for 10 h. The feeding rate of titanium (0.85-7.3 micromol Ti L(-1) h(-1)) was designed to circumvent the precipitation of titanate in the liquid medium, and feeding rate of silicon (48 micromol Si L(-1) h(-1)) was designed to sustain one cell division. The addition of titanium to the culture had no detrimental effects on cell growth and preserved the frustule morphology. Cofeeding of Ti and Si was required for complete intracellular uptake of Ti. The maximum bulk composition of titanium in the frustule biosilica was 2.3 g of Ti/100 g of SiO(2). Intact biosilica frustules were isolated by treatment of diatom cells with SDS/EDTA and then analyzed by TEM and STEM-EDS. Titanium was preferentially deposited as a nanophase lining the base of each frustule pore, with estimated local TiO(2) content of nearly 80 wt %. Thermal annealing in air at 720 degrees C converted the biogenic titanate to anatase TiO(2) with an average crystal size of 32 nm. This is the first reported study of using a living organism to controllably fabricate semiconductor TiO(2) nanostructures by a bottom-up self-assembly process.

Biological fabrication of photoluminescent nanocomb structures by metabolic incorporation of germanium into the biosilica of the diatom Nitzschia frustulum.

Diatoms are single-celled algae that make microscale silica shells or "frustules" with intricate nanoscale features such as two-dimensional pore arrays. In this study, the metabolic insertion of low levels of germanium into the frustule biosilica of the pennate diatom Nitzschia frustulum by a two-stage cultivation process induced the formation of frustules which strongly resembled double-sided nanocomb structures. The final product from the two-stage cultivation process contained 0.41 wt % Ge in biosilica and consisted of an equal mixture of parent frustule valves possessing a normal two-dimensional array of 200 nm pores and daughter valves possessing the nanocomb structure. The nanocomb structures had overall length of 8 mum, rib width of 200 nm, rib length of 500 nm, and slit width of 100 nm. Each slit of the nanocomb was most likely formed by a directed morphology change of a row of 200 nm pores to a single open slit following Ge incorporation into the developing frustule during the final cell division. The frustules possessed blue photoluminescence at peak wavelengths between 450 and 480 nm, which was attributed to contributions from nanostructured biosilica in both the parent valves and in the nanocomb daughter valves. This is the first reported study of using a cell culture system to biologically fabricate a photoluminescent nanocomb structure.