Kaihong Qi

Artificial lotus leaf structures from assembling carbon nanotubes and their applications in hydrophobic textiles

Artificial lotus leaf structures were fabricated on cotton substrates via the controlled assembly of carbon nanotubes onto the surface of cotton substrates. Both pristine carbon nanotubes (CNTs) and surface modified carbon nanotubes (PBA-g-CNTs) were used as building blocks to biomimic the surface microstructures of lotus leaves at the nanoscale. Cotton fabrics, which otherwise have perfect water absorbabilities, have been endowed with super-hydrophobic properties—water contact angles greater than 150° were measured. The method provides a bionic route to create hydrophobic textiles. Furthermore, considering the novel mechanical and electric properties of carbon nanotubes, these carbon nanotubes coated cotton fabrics will find potential application in sensing, conducting and special textiles.

Self-cleaning cotton

Nanocrystalline titanium dioxide has been prepared under ambient pressure and at temperatures close to or approaching room temperature using hydrolysis of titanium tetraisopropoxide in an acidic aqueous solution. A transparent thin layer of nanocrystalline titania has been produced on cotton textiles by a dip-pad–dry-cure process. These TiO2 coated cotton textiles possess significant photocatalytic self-cleaning properties, such as bactericidal activity, colorant stain decomposition and degradation of red wine and coffee stains. The UV absorption and tearing strength of the TiO2 coated cotton has also been studied. Self-cleaning cotton may find potential commercialization in the textile industry.

Facile preparation of anatase/SiO2 spherical nanocomposites and their application in self-cleaning textiles

Anatase TiO2/SiO2 nanocomposites were prepared by a sol–gel process at a low temperature. The structural properties of these as-prepared nanocomposites were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD), showing that TiO2 nanoparticles were deposited on the surface of SiO2 spheres. The spherical TiO2/SiO2 nanocomposites were coated onto cotton fabrics by a simple dip-pad–dry-cure process. The treated cotton fabrics demonstrated higher photocatalytic activity in comparison to pure TiO2 treated cotton fabrics in a typical photocatalytic test using a model compound of Neolan Blue 2G dye. Our results demonstrate that this composite material is a step towards better self-cleaning performance of textile materials.

Functionalization of cotton with carbon nanotubes

Cotton is one of the most important raw materials for textile and clothing production. Compared with some synthetic polymer fibers, the main drawback of cotton fibers is its poor mechanical properties and its high flammability, and therefore it can not be used for special textiles. Cotton fabrics treated with modern flame-retardant and reinforcement finishes often can not meet rigid military specifications. In this paper, we show the functionalization of common cotton fibers with carbon nanotubes (CNTs). CNT network armors have been fabricated on the surface of cotton fibers using a simple dipping coating method. Due to the reinforcement and protection of CNTs, the cotton textiles exhibit enhanced mechanical properties, extraordinary flame retardancy, improved UV-blocking and super water repellent properties. Considering the exceptional electronic properties of CNTs, these CNTs functionalized cotton fibers will find a variety of applications in high performance fabrics and smart textiles. The method developed in this paper also provides a simple surface coating method to produce CNT–polymer hybrid materials.

Photocatalytic self-cleaning textiles based on nanocrystalline titanium dioxide

The anatase TiO2 in this study was prepared in an aqueous solution through a sol-gel process with a small amount of acid, which prevented the loss of the mechanical strength of the cotton fabrics when compared with previous methods. The application of the anatase TiO2 to textiles, which formed a transparent, thin film of nanocrystalline TiO2 on the fiber surface, was done via a simple dip-pad—dry-cure process. The adhesion between the TiO 2 thin film and the cotton substrates was high, indicated by good fastness at 20 home launderings. The bending rigidity was increased by 13% and the air permeability was reduced by 0.76% after TiO2 treatment, which indicated that the treatment did not significantly influence the fabric handling and the air permeability. The mechanical strengths of the treated cotton fabrics investigated indicated that the photocatalytic decomposition of the cellulosic chains of the cotton fibers is very limited after 20 h of irradiation.

Room-Temperature Synthesis of Single-Phase Anatase TiO2 by Aging and its Self-Cleaning Properties

A facile process to synthesize single-phase anatase titanium dioxide nanocrystallites at room temperature was presented. The process included a sol-gel reaction in an aqueous media followed by aging at room temperature. The anatase TiO2 was characterized using XRD, TEM and SEM. The cotton fabrics-coated by the anatase nanocrystallites possessed significant photocatalytic self-cleaning properties as demonstrated by their ability to decompose a colorant and degrade red wine and coffee stains, which was equivalent to that of prepared by heating or hydrothermal methods described previously. The anatase TiO2-coated cotton substrate also showed a high UPF rating of 50+, which means excellent UV protection to human wearers. The study of the adhesion between the anatase TiO2 and the cotton substrate showed that even after 20 times of repeated launderings, the-coated substrate was still capable of decomposing stains, which indicated its photocatalytic power, though this was reduced compared to that before laundering. The tensile strength results of the anatase TiO2-coated cotton fabrics indicate that the anatase TiO2 will not damage the cotton substrate even after 20 h of continuous UV irradiation. The method of preparing single-phase anatase TiO2 revealed in this study not only eliminates the need for high temperature processing, which means energy saving, but also broadens its applications to poor acid-resistant and low thermal stability materials such as many of the biomaterials and cellulosic materials.

Carboxymethyl chitosan coating to block photocatalytic activity of TiO2 nanoparticles

In order to lower photocatalytic degradation of TiO2 on skin and textiles, carboxymethyl chitosan (CMCH) was used to coat TiO2 nanoparticles. The polymer (CMCH) not only acted as the blocking agent of photocatalytic activity, but also dispersed TiO2 nanoparticles better to prohibit them from congregation by anchoring them. The structure of as-prepared nanocomposites was characterized by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The TiO2/CMCH nanocomposites were coated onto cotton fabrics by a dip-pad—drycure process. The treated cotton fabrics demonstrated lower photocatalytic activity in comparison to cotton fabrics treated by pure TiO2 in a typical photocatalytic test. The treated cotton showed a combination of bactericidal activity of TiO2 and CMCH, and excellent protection against UV radiation.

A direct route to active silica nanoparticles

Monodisperse silica particles containing available active C=C bonds were directly prepared by a simple two-step sol-gel method. In the first step the hydrolysis of vinyltrimethoxysilane (VTMS) was performed under acidic conditions in an aqueous solution. In the second step the condensation of the siloxane precursors progressed under basic conditions, resulting in production of silica nanoparticles containing available active C=C bonds. The products were characterized using SEM and FTIR.

Modified Cotton Fiber Surface for Apatite Growth and Cell Affinity

In order to bring widely distributed polysaccharides materials into more medical applications, cotton fiber surfaces were modified into substrates for apatite deposition. Using a solid phase reaction, cotton fibers were conveniently carboxylated in large scale. The carboxylated cotton fibers were coated by apatite in a biomimetic way. Through soaking in a concentrated simulated body fluid (SBF × 5), nano-size apatite particles rapidly and finely grew on the fiber surfaces. The nucleation and growth of apatite was investigated with the aid of scanning electron microscopy (SEM). In comparison to pure cotton, the cotton coated with apatite showed improved cell affinity to osteoblast-like cells.