Effect of Linear Elongation on Carbon Nanotube and Polyelectrolyte Structures in PDMS-Supported Nanocomposite LbL Films

Kinetics, Electronic Properties of Filled Carbon Nanotubes Investigated with Spectroscopy for Applications

The paper is dedicated to the discussion of kinetics of growth, and electronic properties of filled carbon nanotubes investigated by spectroscopy for applications. The paper starts with discussion of growth of carbon nanotubes inside metallocene-filled carbon nanotubes. Nickelocene, cobaltocene are considered for growth of carbon nanotubes. Then, the investigations of filled carbon nanotubes by four spectroscopic techniques are discussed. Among them are Raman spectroscopy, near edge X-ray absorption fine-structure spectroscopy, photoemission spectroscopy, optical absorption spectroscopy. It is discussed that metal halogenides, metal chalcogenides, metals lead to changes in electronic structure of nanotubes with n- or p-doping. The filling of carbon nanotubes with different organic and inorganic substances results in many promising applications. This review adds significant contribution to understanding of the kinetics and electronic properties of filled SWCNTs with considering new results of recent investigations. Challenges in various fields are analyzed and summarized, which shows the author's viewpoint of progress in the spectroscopy of filled SWCNTs. This is a valuable step toward applications of filled SWCNTs and transfer of existing ideas from lab to industrial scale.

Carbon Nanotube Polymer Scaffolds as a Conductive Alternative for the Construction of Retinal Sheet Tissue

With the great success of graphene in the biomedical field, carbon nanotubes have attracted increasing attention for different applications in ophthalmology. Here, we report a novel retinal sheet composed of carbon nanotubes (CNTs) and poly(lactic-co-glycolic acid) (PLGA) that can enhance retinal cell therapy. By tuning our CNTs to regulate the mechanical characteristics of retina sheets, we were able to improve the in vitro viability of retinal ganglion cells derived from human-induced pluripotent stem cells incorporated into CNTs. Engrafted retinal ganglion cells displayed signs of regenerating processes along the optic nerve. Compared with PLGA scaffolds, CNT-PLGA retinal sheet tissue has excellent electrical conductivity, biocompatibility, and biodegradation. This new biomaterial offers new insight into retinal injury, repair, and regeneration.

A Comparison of Different Methods of MWCNTs Metalation in a Single Step Using Three Different Silver-containing Compounds

BACKGROUND

Synthesis and applications of Ag-coated carbon nanotubes are currently under intensive research, resulting in a series of recent patents. Silver nanoparticles are normally obtained from silver nitrate. However, there are also other silver-containing compounds that can facilitate the production of silver nanoparticles, such as silver(I) acetate and silver(II) oxide. Being combined with carbon nanotubes, silver nanoparticles can transfer to them some of their useful properties, such as conductivity and antibacterial properties, and contribute to improving their dispersion in solvents.

OBJECTIVE

To apply three different silver-containing precursors of Ag nanoparticles for the decoration of carbon nanotubes and study the morphology of formed composites by several methods.

METHOD

Three different silver compounds were used as Ag source to carry out the functionalization and decoration of carbon nanotubes under ultrasonic treatment of the reaction system, containing, commercial carbon nanotubes, organic peroxides as oxidants or hydrazine as a reductant, and a surfactant. Resulting samples were analyzed by XRD and XPS spectroscopy, as well as TEM and SEM microscopy to study the morphology of formed nanocomposites.

RESULTS

Silver nanoparticles can be produced without the presence of a reducing agent. Applying hydrazine, as a reducing agent, it is possible to obtain functionalized carbon nanotubes doped with silver nanoparticles, in which their sizes are smaller (1-5 nm) compared to those obtained without using hydrazine.

CONCLUSION

Silver nanoparticles having a size range between 2-60 nm can be produced without the presence of a reducing agent. The use of a reducing agent, such as hydrazine, affects the size of silver nanoparticles.

Elastic to Plastic Deformation in Uniaxially Stressed Polylelectrolyte Multilayer Films

Polyelectrolyte multilayer (PEM) are thin polymeric films produced by alternating adsorption of positively and negatively charged polyelectrolytes (PE) on a substrate. These films are considered drug delivery agents as well as coating material for implants, due to their antibiofouling and biologically benign properties. For these reasons the film mechanical properties as well as response to mechanical stress are important measurement parameters. Especially intriguing is the correlation of the mechanical properties of PEM on macroscopic level with the structure of PEM on molecular level, which is addressed here for the first time. This study investigates PEM from PDADMA/PSS produced by spraying technique with neutron and X-ray reflectometry. Reflectometry technique provides precise information on thickness and density (i.e., electron density or scattering length density, respectively), and, this way, allows to conclude on changes in film composition. Thus, neutron and X-ray reflectometry technique is suitable to investigate the overall and the internal transformations, which PEM films might undergo upon exposure to mechanical load. During uniaxial elongation two regimes of PEM-deformation can be observed: An elastic regime at small elongations (below ca. 0.2%), which is characterized by a reversible change of film thickness, and a plastic regime with a permanent change above this limit. Both regimes have in common, that the mechanical load induces an increase of the film thickness, which is accompanied by an uptake of water from the surrounding atmosphere. The strain causes a molecular rearrangement within the PEM-structure of stratified layers, which, even in elastic regime, is permanent, although the thickness change remains reversible.

Soft Thermal Sensor with Mechanical Adaptability

A soft thermal sensor with mechanical adaptability is fabricated by the combination of single-wall carbon nanotubes with carboxyl groups and self-healing polymers. This study demonstrates that this soft sensor has excellent thermal response and mechanical adaptability. It shows tremendous promise for improving the service life of soft artificial-intelligence robots and protecting thermally sensitive electronics from the risk of damage by high temperature.

Micro-contact printing of PEM thin films: effect of line tension and surface energies

A theory and method for calculating printing resolution limits for microcontact printing of a condensed polyelectrolyte multilayer thin film, based on surface energies and line tension is presented.

Small molecule-folic acid modification on nanopatterned PDMS and investigation on its surface property

Folic acid (or folate, FA) has attracted considerable attention for cancer therapy. As one small molecule, its receptor (folate receptor, FR) is significantly overexpressed on the surface of many human tumor cells compared with normal cells. In this work, physical and chemical coupled modification method, that is the combination of nanoimprinting technique and graft polymerization, was adopted to modify FA on nanopatterned polydimethylsiloxane (PDMS) surface for possible application in micro-nanofluidic cytology. The surface property of differently treated PDMS was characterized by FTIR, AFM and contact angle measurement. AO/PI double staining, cell counting and MTT method were performed to examine the potential influence of FA modified nanopatterned PDMS on human cervical carcinoma (HeLa) cell behavior. Both FA modification and nanostructure have positive effect on the growth and viability of HeLa cells. It is the first time that the small molecule-folic acid was used to immobilize on the surface of PDMS in order to improve its surface property.