Tunable Low Crystallinity Carbon Nanotubes/Silicon Schottky Junction Arrays and Their Potential Application for Gas Sensing

Highly ordered nanostructure arrays have attracted wide attention due to their wide range of applicability, particularly in fabricating devices containing scalable and controllable junctions. In this work, highly ordered carbon nanotube (CNT) arrays grown directly on Si substrates were fabricated, and their electronic transport properties as a function of wall thickness were explored. The CNTs were synthesized by chemical vapor deposition inside porous alumina membranes, previously fabricated on n-type Si substrates. The morphology of the CNTs, controlled by the synthesis parameters, was characterized by electron microscopies and Raman spectroscopy, revealing that CNTs exhibit low crystallinity (LC). A study of conductance as a function of temperature indicated that the dominant electric transport mechanism is the 3D variable range hopping. The electrical transport explored by I-V curves was approached by an equivalent circuit based on a Schottky diode and resistances related to the morphology of the nanotubes. These junction arrays can be applied in several fields, particularly in this work we explored their performance in gas sensing mode and found a fast and reliable resistive response at room temperature in devices containing LC-CNTs with wall thickness between 0.4 nm and 1.1 nm.

A Facile Way for Preparation of Cellulose Beads With High Homogeneity, Low Crystallinity, and Tunable - Internal Structure

The preparation of cellulose beads has attracted more and more attention in the application of advanced green materials. To obtain uniform and controllable cellulose beads, the dissolving pulp was dissolved in NMMO, and the cellulose beads were regenerated in various coagulation baths (water, alcohol, acid, NMMO, etc.) by phase conversion method. Results show that the crystal form of regenerated cellulose changes from cellulose I to cellulose II. NMMO swelling cellulose beads present low crystallinity and low water holding capacity. The coagulation mechanism of cellulose beads was clarified by a laser confocal microscopy. It is found that the whole coagulation process was from outside to inside gradually. It is a green and facile method for preparing cellulose beads with different structures and properties, which can be widely used in biomedicine, energy storage materials, and protein chromatography.