Simulation and Experimental Studies and Applications of Carbon Nanotubes and Graphenes in Engineering and Medicine

Abstract

It is a pleasure to come to a final editorial for the special issue on simulation, experimental studies, and applications of carbon nanotubes or graphenes in engineering and medicine. The issue of Vol. 3 No. 1 publishes four papers on this topic while the current Vol. 3 No. 2 issue hosts the remaining four papers. A wide range of fundamentally theoretical, computational, and experimental topics on modeling and applications of the two materials are covered in the special issue. It is my honor to highlight major contributions of each paper hereinafter.In the issue of No. 1, the first work by Derouiche and Mohamed is about the fabrication of a flexible organic solar cell. The PEDOT:PSS (poly(3,4-ethylene dioxythiophene) poly(4-styrenesulfonate), doped with EG (ethylene glycol) and single wall carbon nanotubes, is used as conductive transparent electrode rather than electron blocking layer. The presented idea can be helpful in developing disposable solar cells with improved photovoltaic characteristics into photovoltaic diodes applications. The second work presented by Lee and Hill introduces a nanocomputer component comprising a metallic single-walled carbon nanotube with three metallic inner tubes; two smaller fixed tubes symmetrically located, and a moveable third tube which has radius intermediate to that of the main tube and the two smaller fixed inner tubes. In the nanosystem, electrons can jump from one tube to another and a current can flow from the larger tube to the moveable one and finally to one of the smaller tubes. By applying a voltage input to produce an external electrical field and another voltage input to provide a charge on the moving tube, the moving tube provides an output signal. Based on different designs presented in the research, the multiwalled carbon nanotubes give rise to the possibility of being used either as a two-state memory device or as a logic gate for an AND or an OR gate. The findings by Ansari’s group are about the application of single-walled carbon nanotubes used as protective drug carriers which can decrease these severe side effects to some extent. It is shown that the equilibrium condition of the drug may be affected by the radius of nanotube, the orientation of cisplatin, and the distance between the central molecule of the drug and the left end of nanotube. The research provides practical guidance on design of carbon nanotubes as target carriers in drug delivery systems for cancer therapies. As is acknowledged, the unique properties of carbon nanotubes have made them very attractive as reinforcements in polymer nanocomposites to effectively improve the mechanical properties. In the last paper in No. 1, Hu’s group conducts tensile tests and single-edge notched bending tests for four types of carbon nanotube-reinforced nanocomposites to explore the effects of three appealing influencing factors, i.e., acid treatment, pressured curing, and liquid rubber (LR) on mechanical properties of nanocomposites. The interesting work provides much more choices for fabricating specific carbon nanotube-reinforced nanocomposites with desired properties by reasonably combining proper fabrication conditions including acid treatment, pressured curing, liquid rubber with polymer matrix, and reinforcement loading.In the current No. 2 issue, four more papers are hosted. In the first work, Arash et al. investigate the potential of carbon nanotubes as nanosensors in detection of genes through a vibration analysis with molecular dynamics. The carbon nanotube based nanosensor under investigation is wrapped by a gene whose structure includes a single strand DNA with a certain number of distinct nucleobases. Simulation results indicate that the nanosensor is able to differentiate distinct genes, i.e., small proline-rich protein 2A, small proline-rich protein 2B, small proline-rich protein 2D, and small proline-rich protein 2E, with a recognizable sensitivity. The research provides a rapid, effective, and practical method for detection of genes. Natsuki and his group explore the potential of using carbon nanotubes as atomic force microscope probes. The result shows that the buckling stability of the carbon nanotube-atomic force microscope probe can be largely enhanced by increasing the stiffness of elastic medium. The theoretical investigation on the buckling stability might give a useful reference for designing nanotubes as atomic force microscope probes. It has to be noted here however that pertinent validations on the theoretical simulations would be useful to justify the feasibility of continuum theory used in the study. The third research extends the work by Duan and Wang on water transportation with carbon nanotubes. Duan and his collaborators investigate the influences of nanotube pretwist angle, water mass, environmental temperature, tube diameter, tube channel length, and channel restrain condition on driving force and transportation efficiency. It is found that in order to initiate the transportation, the pretwist angle must be larger than certain threshold. Furthermore, driving force decreases with increasing water mass and it is more efficient to transport multiple water molecules than one water molecules. The water molecule is also found to have higher degrees of collisions in elevated environmental temperature. The research findings provide practical guidelines on design of carbon nanotubes for water transportation and are useful in applications of carbon nanotubes in atomic and molecular transportations. The last research conducted by Shi et al. reports the discovery of buckling instability and vibration of polyethylene/carbon nanotube matrices by molecular mechanics simulations. The buckling strains and the resonance frequencies are found to decrease with an increase in the number of polyethylene chains in the polyethylene/carbon nanotube matrices. The van der Waals forces between the polyethylene chains and the carbon nanotube in matrices are investigated to provide physical interpretations on the findings. The research findings would provide guidance on potential applications of carbon nanotube/polymer composites.Last but not the least, I would like to extend my sincere thanks to the authors for their contributions which provide a better understanding of the most recent developments in this field.