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Paper is an important material for many applications. During the centuries, it has been the most widely used writing support and therefore paper degradation is a major issue for cultural heritage. The main component of paper is cellulose, one of the most abundant biomaterials on Earth. Cellulose oxidation is mainly responsible for the yellowing of the ancient samples, through the formation of chromophores. In order to investigate this issue and the chromophores’ role, we exploit the optical properties combining non-destructive experiments and theoretical calculations based on ab-initio techniques. In this paper, we illustrate the method and show its application to three ancient paper samples. The procedure we describe is a precious tool for cultural heritage preservation: indeed, the approach we present is based on non-invasive and non-destructive measurements that allows a microscopic understanding of cellulose-based artifacts degradation.

The objective of this research is to understand more fully the out-of-plane auxetic behavior of paper. In the reported research, initial characterization of the auxetic properties of common, commercially available papers is described. The results of these experiments suggest that the auxetic response seen in paper structures is related to the cellulose fiber network structure, as previously suggested, and is related to inter-fiber bonding and fiber organization in the sheet. These results also indicate that further study is needed to understand how materials and processing variables influence auxetic behavior. A mathematical model, attempting to explain auxetic response in an idealized arrangement of fibers is included. Ultimately, the fundamental understanding resulting from this research should lead to new product development opportunities for forest product-based paper materials as well as to the establishment of predictive structure–property relations for auxetic materials using paper as a model system.

In this article, we investigate the nanocomposite material formation, particularly the deposition of nanocrystalline diamond and carbon nanowalls (CNWs) on single-wall carbon nanotubes buckypaper (BP). One part of the buckypaper substrate was nucleated by nanodiamond powder. The growth was carried out in a hot filament chemical vapor deposition (HFCVD) system. Contact angle measurements, scanning electron microscopy, and Raman spectroscopy were used for the surface morphology analysis and characterization of carbon phases. Due to a different surface pretreatment, different carbon nanostructures were formed: diamond film was grown on the nucleated BP area; non-treated area of the BP was covered with a dense field of CNWs. Covering a part of the BP surface prevented an access of the HF-plasma and so the growth of any carbon structures.

Single-walled carbon nanotube (SWNT) networks have been irradiated with a '2C4 + ion beam (ion energy 23 MeV) to investigate changes to their properties. Measurements of the Raman D-line show that the irradiation produces structural defects throughout SWNT paper of thickness 40 μm, with a linear increase in defects at the back side of the sample, but a saturating tendency occurring at the front (irradiated) side. The resistance of the samples also increases linearly with irradiation dose. The temperature dependence of the conductivity of the samples is changed progressively by the irradiation: whereas the pristine sample exhibits mixed metallic-nonmetallic character consistent with the usual model of metallic conduction interrupted by thin barriers through which fluctuation-assisted tunnelling occurs, the temperature dependence loses its metallic character and follows three-dimensional variable-range hopping for the most irradiated sample.

The 7th International Workshop on Nonlinear Optics and Excitation Kinetics in Semiconductors (NOEKS 7) was held at Uni-versit�t Karlsruhe from 24-28 February 2003. Topics of NOEKS 7 were: Ultrafast dynamics (coherent effects, coherent control, quantum kinetics, THz-experiments), photonic crystals (2D and 3D photonic band gap materials), quantum dot physics (quantum dots, quantum wires), spin effects (spin dephasing, spin transport), disorder-related effects, organic semiconductors, semiconductor quantum optics (luminescence, photon statistics), device physics (quantum cascade lasers, superlattices, interband lasers), and Bose-Einstein condensation of excitons. The cover picture is taken from Ref. [1] and shows the spatial pattern of the indirect exciton PL intensity in GaAs/AlGaAs coupled quantum wells. Around the laser excitation spot, it ex-hibits an external ring structure with a periodic array of circular-shaped structures which is due to the formation of an exciton gas with macroscopic coherence. The full proceedings of NOEKS 7, guest-edited by Martin Wegener, are published in physica status solidi (c) 0, No. 5 (2003). Since 1988, all previous NOEKS proceedings have also appeared in physica status solidi.

Strain rate changes are used for analysing the flow stress of n-irradiated copper crystals and lead to the following conclusions: a) The “active crystal length”, i. e. the number of simultaneously active slip planes, increases with the strain rate , resulting in not being proportional to ⋖ (cross-head speed) [1]. b) The critical shear stress (css) varies with ⋖ more rapidly than is expected from theory [2]. In the preceding paper [3] arguments are advanced against both of these statements. All of these arguments will be invalidated. The proportionality ∼ ⋖ is shown to represent a rather special case from an atomic point of view. By far more general is a non-proportionality ≁ ⋖. Taking this into accont one succeeds in describing straightforwardly the results of b). New experiments supporting our former statements are going to be reported. All conclusions drawn previously [4, 5, 6] on the strengthening mechanism in copper and based on a) and b) can be fully maintained [7]. Geschwindigkeitswechselversuche zur Analyse der Fliesspannung n-bestrahlter Kupferkristalle fuhrten uns zu folgenden Aussagen: a) Die „aktive Kristallange”, d. h. die Zahl der gleichzeitig aktiven Gleitebenen, wachst mit der Abgleitgeschwindigkeit . Daraus folgt, das nicht proportional zu ⋖ (Verformungsgeschwindigkeit) ist [1]. b) Die kritische Schubspannung andert sich mit ⋖ starker, als die Theorie erwartet [2]. Gegen beide Aussagen werden in der vorhergehenden Arbeit [3] Argumente vorgebracht. Diese werden samtlich entkraftet und widerlegt. Es wird gezeigt, das die Proportionalitat ∼ ⋖ vom atomistischen Standpunkt aus einen Sonderfall darstellt. Der weitaus umfassendere Fall ist die Nichtproportionalitat ≁ ⋖. Gerade damit lassen sich die Ergebnisse b) zwanglos beschreiben. Alle fruher gezogenen Schlusse [4, 5, 6] uber die Art der Bestrahlungsverfestigung in Kupfer, die auf a) und b) basieren, bleiben daher bestehen [7].

Koppenaal's and Arsenault's analysis of the thermally activated glide processes in neutron irradiated copper is discussed and compared with a similar investigation of the present authors. It is shown that Koppenaal and Arsenault use a number of very restrictive and not very realistic assumptions, e.g. regarding the behaviour of the dislocations and the nature of the dislocation obstacles, which are not necessary in our investigations. Koppenaal's and Arsenault's arguments against our analysis can easily be refuted. Eine von Koppenaal und Arsenault durchgefuhrte Analyse der thermisch aktivierten Gleitvorgange in neutronenbestrahltem Kupfer wird diskutiert und mit eigenen Untersuchungen verglichen. Es wird gezeigt, das Koppenaal und Arsenault sehr einschrankende und wenig realistische Annahmen, z. B. uber das Verhalten der Versetzungen und die Natur der Versetzungshindernisse, verwenden, die in unserer Untersuchung nicht erforderlich sind. Koppenaal's und Arsenault's Kritik an unserer Analyse kann ohne weiteres widerlegt werden.

Few-layer graphene samples have been obtained by a thermal expansion of bromine-intercalated fluorinated graphite with a ∼C2F matrix composition at 600, 700, and 800 °C. X-ray photoelectron spectroscopy detected that the products contained almost the same quantities of foreign atoms independently on the exfoliation temperature. However, the Raman spectra showed a progressive increase in the relative intensity of the D mode with the temperature growth. This was attributed to more edge states developed in graphene planes at the higher temperature. Thin films from obtained samples were tested as sensors using 1000 ppm nitrogen dioxide (NO2) in argon. The film from few-layer graphene produced at 800 °C had the largest relative response, while its recovery was quite low at room temperature. The sensor performances were related with the structural characteristics of the exfoliated graphenes. Left: Relative response of gas sensors based on few-layer graphene products of an expansion of fluorinated graphite at 600, 700, and 800 °C toward 1000 ppm NO2. Right: Proposed structures of the products.

In situ Raman spectroelectrochemistry has been applied to study chemical vapor-deposition-grown single-layer graphene membrane on a patterned SiO2/Si substrate. The SiO2/Si substrate is known to dope graphene, thus the substrate can significantly influence the properties of the graphene during electrochemical charging. We analyzed the change of the Raman intensity of the G mode as a function of electrode potential for a single-layer graphene membrane and we compared the results to those obtained for the same graphene sample on a substrate. Because of the elimination of the influence of a supporting substrate we have been able to achieve more efficient doping of graphene by applied electrode potentials.

Ga nanoparticles (GaNPs) produced by thermal evaporation or epitaxial methods on graphene sheets present strong plasmonic effects that can couple to graphene phonons. In this work, GaNPs are deposited on graphene monolayers supported on Cu, quartz, and SiO2/Si substrates. The use of graphene increases the interparticle distance and improves the size uniformity. The enhancement of G and 2D graphene Raman lines is analyzed for the different substrates under excitation at 633 and 532 nm. The plasmonic effects are investigated using spectroscopic ellipsometry, finding a strong resonant mode at energies between 1.7 and 2.0 eV and an incidence angle of 55.6°. Finally, the heterogeneous surfaces are functionalized for the preparation of optical biosensors exposing the surface to 3,3′-dithiodipropionic acid di(N-succinimidyl ester) (DTSP). A significant energy shift of the ellipsometric signal on the Ga/graphene surfaces is observed in comparison to Ga/Si surfaces. Sketch of GaNPs atop graphene and biofunctionalizing agent (DTSP). Dip in the Psi ellipsometric function, and associated step in the Delta function, found around the GaNPs–graphene coupling resonance at an incident angle of 55.6°.