Ahu Gümrah Dumanlı

Carbon fibres from cellulosic precursors: a review

The focus of this review is primarily on the sequence of structural changes at micro and molecular level during carbonization of cellulosic fibres. The influence of various operational parameters such as the pyrolytic temperature and the stabilization agents also discussed as is the effect of the initial properties of the cellulose fibre on the final properties of the carbon fibre.

Digital Color in Cellulose Nanocrystal Films

Cellulose nanocrystals (CNCs) form chiral nematic phases in aqueous suspensions that can be preserved upon evaporation of water. The resulting films show an intense directional coloration determined by their microstructure. Here, microreflection experiments correlated with analysis of the helicoidal nanostructure of the films reveal that the iridescent colors and the ordering of the individual nematic layers are strongly dependent on the polydispersity of the size distribution of the CNCs. We show how this affects the self-assembly process, and hence multidomain color formation in such bioinspired structural films.

Controlled, bio-inspired self-assembly of cellulose-based chiral reflectors

Layered transparent photonic stacks are known to give rise to highly brilliant color in a variety of living organisms.[1] The biomimetic replication of these structures not only offers a wide range of applications, but can also be used as a tool to gain understanding of the biological processes responsible for the self-assembly of these structures in nature. Recent studies showed that cellulose microfibrils form helicoidal stacks in the plant cell wall, which selectively reflect circularly-polarised light of a specific wavelength.[2]–[5] Such structures are responsible for the bright colors in fruits[2] and leaves[3] of very different species of plants.[4,5] Similar photonic structures can be artificially produced using the same constituent material, cellulose nano-crystals (CNCs).[6,7] Slow evaporation of a CNC suspension gives rise to their spontaneous assembly into a chiral nematic liquid crystalline phase that can be preserved in the dry state.[8,9] The self-assembly process is strongly dependent on the properties of the nanoscale building blocks and on the macroscopic parameters that characterise the assembly.[10]–[12] Many factors influence the optical and mechanical properties of the obtained film, including temperature and pressure[13,15,16] the substrate,[14] and the surface chemistry of the CNCs.[17,18] Nevertheless the self-assembly process is robust and can be coupled with a range of chemical processes.[19]–[21]

Recent advances in the biomimicry of structural colours

Nature has mastered the construction of nanostructures with well-defined macroscopic effects and purposes. Structural colouration is a visible consequence of the particular patterning of a reflecting surface with regular structures at submicron length scales. Structural colours usually appear bright, shiny, iridescent or with a metallic look, as a result of physical processes such as diffraction, interference, or scattering with a typically small dissipative loss. These features have recently attracted much research effort in materials science, chemistry, engineering and physics, in order to understand and produce structural colours. In these early stages of photonics, researchers facing an infinite array of possible colour-producing structures are heavily inspired by the elaborate architectures they find in nature. We review here the recent technological strategies employed to artificially mimic the structural colours found in nature, as well as some of their current and potential applications.

Nanocellulose and its Composites for Biomedical Applications

Cellulose is a natural linear biopolymer, which is constituted of an assembly of cellulose nanofibrils in a hierarchical order. Nanocelluloses in particular show great promise as a cost-effective advanced material for biomedical applications because of their biocompatibility, biodegradability, and low cytotoxicity. Moreover, with their chemical functionality they can be easily modified to yield useful products. While nature uses the hierarchical nanostructure of cellulose as the load-bearing constituent in plants, a significant amount of research has been directed toward the fabrication of advanced cellulosic materials with various nanostructures and functional properties. Such nanocelluloses are widely applied in medical implants, tissue engineering, drug delivery, wound healing, diagnostics, and other medical applications with real examples in this field. There are also emerging fields being developed to use nanocelluloses and their composites in more novel ways in biomedical applications such as 3D printing and magnetically responsive materials. In this mini-review, recent advances in the design and fabrication of nanocellulose-based materials and composites are presented with a special emphasis on their suitability for material requirements for biomedical applications as well as the new directions and challenges that the materials might face in the future.

Carbon Nanotube and Nanofiber Growth on Zn-Based Catalysts

Abstract In this study, acetylene gas was delivered to a catalyst network consists of NaCl-support and Zn nanoparticles in a temperature range of 500–700°C by means of a chemical vapor deposition (CVD). A principle feature that delineated this CVD study from prior studies lay first in the method used to support the catalyst and second in the choice of the catalyst metal. In particular, NaCl was deliberately retained and exploited in subsequent manipulations because it performed remarkably well as a support medium. The catalytic activity of Zn towards production of CNTs/CNFs appeared to be promoted as a result of using molten ionic substrate.

Research data supporting "Shape Memory Cellulose-based Photonic Reflectors"

Summary of available data Original or unprocessed data is provided in support of the article “Shape Memory Cellulose-based Photonic Reflectors”. The data is structured into two folders, each correlating to a specific data type presented in the published article. Folder 1: Polarised optical microscopy (POM) The polarised optical microscopy images (.png) used in Figures 1 and in Figure 2 of the Manuscript are provided into their corresponding folders. The scale bar is included in each folder for reference together with an image of the fiber used to collect the spectra. Both folder contain also the reflectivity spectra (.mat) used to plot the graph in Figure 1 and in Figure 2. The films were imaged under with polarizing filters, as described in the Experimental section of the Manuscript. Folder 2: Scanning electron microscopy (SEM) Micrographs cellulose films cross-sections showing the chiral nematic arrangement of cellulose nanocrystals retained after the shape memory polymer infiltration (.tif). The folder ‘Figure 3’ contains high and low magnification images, used for Figure 3 of the Manuscript, the folder ‘Figure S2’ contains the low magnification images, used for Figure S2 of the Supplementary Information. The folder ‘Table 2’ contains the low and high micrographs used to extrapolate the data presented in Table 2 of the Manuscript.