We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.

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Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

https://www.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/p85.pdf

Advances in the science and technology of carbon nanotubes and their composites: a review

Photoinduced reactivity of titanium dioxide

Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

Small but strong: A review of the mechanical properties of carbon nanotube–polymer composites

https://hal.archives-ouvertes.fr/hal-01003709/document

Specific surface area of carbon nanotubes and bundles of carbon nanotubes

Reference LNNME-ARTICLE-1999-004doi:10.1103/PhysRevLett.82.944View record in Web of Science Record created on 2007-04-23, modified on 2016-08-08

/pdf/elastic-and-shear-moduli-of-single-walled-carbon-nanotube-4fnqoxob6b.pdf

Elastic and shear moduli of single-walled carbon nanotube ropes

https://hal.archives-ouvertes.fr/hal-00926035/document

Gram-scale CCVD synthesis of double-walled carbon nanotubes

Nanocrystalline titania catalysts with high surface area (68–100 m 2 /g) with varying amounts of anatase and rutile phases were tested during the photocatalyzed degradation of p -coumaric acid. This is a pollutant found in agricultural waste waters originating from the wine and olive oil industry. The catalysts were prepared by the same route namely, the hydrolysis of alkoxides followed by densification under hydrothermal conditions (1500–4000 kPa). Hydrolysis of Ti-butoxide gives rise to predominantly anatase containing titania whereas the Ti-ethoxide hydrolysis leads to mixtures of anatase and rutile. Compared to pure anatase or rutile, titania containing both phases shows a significantly higher catalytic activity during the degradation of p -coumaric acid. After preliminary optimization experiments, the degradation of 0.1 mM p -coumaric acid was achieved in 45 min under light irradiation in the presence of H 2 O 2 . The most efficient catalyst is TiO 2 containing 30% rutile and 70% anatase and is prepared by the hydrolysis of tetraisopropyl–orthotitanate. Pore size distribution measurements indicate the presence of mesopores of radii in the range 6–25 A which were responsible for the effective adsorption of the pollutant on the catalyst. Electrophoretic mobility measurements show the isoelectric point for the most efficient catalyst at pH 5.5.

Effect of rutile phase on the photocatalytic properties of nanocrystalline titania during the degradation of p-coumaric acid

Doped TiO2 samples using different preparative procedures were synthesized using either urea or thiourea leading to N- or S-doped TiO2. Photocatalytic peroxidation and oxidation (mineralization) of phosphatidylethanolamine (PE) lipid with doped TiO2 were carried out under light irradiation lambda > 410 nm. The formation of conjugated double bonds in PE molecules was followed to detect the formation of peroxy radicals (peroxidation index) under light excitation (lambda > 410 nm) when doped TiO2 was used. The kinetics of CO2 production was monitored during the mineralization of PE. Colored TiO2 powders were studied in detail by different and complementary physicochemical techniques. The band gap energies of colored TiO2 were determined by diffuse reflectance spectroscopy (DRS). The visible absorption shoulder of TiO2 was observed to follow Urbach's law. The variation of the transient decay after 354 nm laser pulse excitation does not correlate with the different N- and S-TiO2 doping levels introduced by the addition of urea or thiourea. This suggests that the states (recombination centers or traps) introduced by the doping are not effective in varying the decay kinetics within the nanosecond and microsecond time scale. Elemental analysis shows comparable amounts of S- and N-doping of TiO2 when thiourea is used as dopant. X-ray diffraction reveals no rutile in S-TiO2 samples heated to 600 degrees C, suggesting that the addition of sulfur precludes rutilization during sample crystallization. X-ray photoelectron spectroscopy (XPS) of the S-TiO2 samples confirms the preferential localization of S on the 20 topmost layers of S-TiO2 upon calcination at 500 degrees C for 2 h.

Revathi Bacsa

Papers

Specific surface area of carbon nanotubes and bundles of carbon nanotubes

Elastic and shear moduli of single-walled carbon nanotube ropes

Gram-scale CCVD synthesis of double-walled carbon nanotubes

Effect of rutile phase on the photocatalytic properties of nanocrystalline titania during the degradation of p-coumaric acid

Preparation, testing and characterization of doped TiO2 active in the peroxidation of biomolecules under visible light.