Macroscopic Fibers of Oriented Vanadium Oxide Ribbons and Their Application as Highly Sensitive Alcohol Microsensors

Abstract

Recently, there has been a strong focus on inorganic morphosynthesis, leading to the concepts of "chemistry of shapes" or synthesis over "all length scales".[1] To achieve hierarchical architectures, mineralization can be confined to different length-scale interfaces, as demonstrated by the growing field of bioinspired materials. [2] In this context, three main strategies can be identified. The first makes use of macroscopic patterns via metastable thermodynamic systems (emulsions, [3] reverse emulsions, [4] or air-liquid foams [5] ), while generating mesotexturation using supramolecular organization. One can take advantage of mesoscopic supramolecular templating effects, where the induced inorganic texturation extends to higher length scales; for instance, the chirality information embedded in a molecule can be carried forward to shape architectures at longer length scales. [6] A second method involves the use of either a preformed microorganism [7] or preexisting colloidal opal-like organic textures.[8] Also, it has been recently been demonstrated that hierarchical systems can be generated with high-aspect-ratio carbon particles (possessing strong anisotropy), where organization at higher length scales is achieved through extrusion processes.[9]Furthermore, inorganic polymers, such as silica, titanium dioxide, vanadium oxide, etc., can be patterned using the abovementioned patterning strategies. Particularly, extensive interest has been focused on vanadium oxides mainly because of their structural diversity and potential applications in areas such as heterogeneous catalysis, cathode materials for advanced lithium batteries, visible-light photochromism, and electrochromic devices. [10,11] Also, it is worthwhile to note that this particular interest, beyond the structural and electronic properties, is certainly enhanced by the fact that aqueous V 2 O 5 gels are one of the best examples of materials synthesized by the sol-gel process, [12,13] where "chimie douce", or soft chemistry, [14] offers the possibility of shaping and organizing the inorganic polymer at different length scales. These soft-synthesis approaches allow the fabrication of either hybrid organic-inorganic materials whose properties are influenced by each individual constituent, [15,16] or gels with properties arising from textural singularity, i.e., the strong anisotropy of the nanoscopic ribbons constituting the gel promotes nematic liquid crystal behavior. [17][18][19][20] Making use of an extrusion strategy already applied in our laboratory for the unidirectional organization of carbon nanotubes, [9] we have generated for the first time macroscopic vanadium oxide fibers with strong intrinsic one-dimensional (1D) organization of vanadium oxide nanoscopic ribbon subunits. Using the general process described in the Experimental section and in the Supporting Information (Fig. S1), vanadium oxide macroscopic fibers can be obtained (Fig. 1).Beyond fabrication of vanadium oxide fibers we have observed good transversal flexibility, which allows for...

Self-assembled hierarchically structured organic–inorganic composite systems

“…Moreover, the composite structures on the nanometer to micrometer length scale remained visually intact after extended voltammetric cycling and storing the electrochromic devices for several weeks (see scheme 4, middle panel) [53]. Since vanadium oxides are functional materials with a fairly broad range of applications including catalytic applications [63][64][65][66][67][68] and the use as gas sensors [69][70][71][72], hierarchically organized V 2 O 5 /LC polymer composites (or their micro-/ nanoporous counterparts obtained after removal of the polymeric matrix) might potentially even feature further promising functions.…”

Flow-Orientation of Internal Structure and Anisotropic Properties on Hydrogels Consisted of Imogolite Hollow Nanofibers

“…These cables are typically produced by fluidic elongation processes, in which the nanofibers in the cable are oriented along the flow axis [8][9][10][11][15][16][17][18]. This orientational behavior provides many potential advantages, such as improvements in mechanical strength [8][9][10][11][13][14][15][16] or anisotropic ion conduction [19]. However, the possible shapes of the assembled materials having a uniform alignment of nanofibers have been limited typically to fibrous thin forms with submillimeter diameters, owing to the nature of the required preparative methods.…”

“…For instance, cables composed of nanofibers have recently attracted much attention as instances of materialization [8][9][10][11][12][13][14][15][16][17][18]. These cables are typically produced by fluidic elongation processes, in which the nanofibers in the cable are oriented along the flow axis [8][9][10][11][15][16][17][18]. This orientational behavior provides many potential advantages, such as improvements in mechanical strength [8][9][10][11][13][14][15][16] or anisotropic ion conduction [19].…”

“…For instance, cables composed of nanofibers have recently attracted much attention as instances of materialization [8][9][10][11][12][13][14][15][16][17][18]. These cables are typically produced by fluidic elongation processes, in which the nanofibers in the cable are oriented along the flow axis [8][9][10][11][15][16][17][18].…”

“…Practical applications of nanofiber assemblies have been attempted in various fields such as the production of electronic and optical devices [1][2][3] and scaffolds for living tissues [4,5] ; a considerable number of such nanofiber assemblies have been generated from various synthetic/bioorganic nanofibers (e.g., carbon nanotubes [6], organic nanofibers, [7] and vanadium oxide [8][9][10]). For instance, cables composed of nanofibers have recently attracted much attention as instances of materialization [8][9][10][11][12][13][14][15][16][17][18].…”