Thermally stable carbon nanofibers functionalized with poly(dimethylsiloxane) for solid-phase microextraction of polycyclic aromatic hydrocarbons prior to GC analysis

The authors describe poly(dimethylsiloxane)-coated carbon nanofibers (CNF-PDMS) for solid-phase microextraction of polycyclic aromatic hydrocarbons (PAHs). The fibers were prepared by a sol–gel method and are stable at temperatures up to 350 °C, probably due to the chemical bonds between the coating and the fiber surface. The fibers can be re-used up to 180 times. The CNFs enhance the surface area of the coating compared to that of a plain PDMS fiber and, accordingly, provide higher extraction efficiency. Following thermal desorption, the PAHs were quantified by GC with FID detection. Under optimized experimental conditions, the detection limits of the method range from 5 to 20 pg mL−1, and response is linear in the 0.017 to 100 ng mL−1 range. The repeatability and reproducibility vary between 4.8 % and 8.6 %, and between 4.1 % and 10.2 %, respectively. The method was successfully utilized for the analysis of PAHs in (spiked) water samples, with satisfactory recoveries in the range of 90.1–99.9 %

Electrically doped nanoscale devices using first-principle approach: a comprehensive survey

Doping is the key feature in semiconductor device fabrication. Many strategies have been discovered for controlling doping in the area of semiconductor physics during the past few decades. Electrical doping is a promising strategy that is used for efective tuning of the charge populations, electronic properties, and transmission properties. This doping process reduces the risk of high temperature, contamination of foreign particles. Signifcant experimental and theoretical eforts are demonstrated to study the characteristics of electrical doping during the past few decades. In this article, we frst briefy review the historical roadmap of electrical doping. Secondly, we will discuss electrical doping at the molecular level. Thus, we will review some experimental works at the molecular level along with we review a variety of research works that are performed based on electrical doping. Then we fgure out importance of electrical doping and its importance. Furthermore, we describe the methods of electrical doping. Finally, we conclude with a brief comparative study between electrical and conventional doping methods

Synthesis of carbon nanotube-carbon nanosphere on the CF surface by CVD

In the current work, the synthesis of carbon nanotubes (CNTs) and carbon nanospheres (CNS’s) has been investigated by applying the chemical vapor deposition method in a one-step sample preparation. In this method, iron nitrate non-hydrate (Fe(NO3)3.9H2O) and acetylene (C2H2) have been used as the catalyst source and carbon source, respectively, to grow CNT directly on the CF surface at 700°C and then CNS’s were synthesized on the CNT layers at 900°C under a 250sccm gas flow rate (40%N2, 40%H2, 20% C2H2). According to the SEM and TEM micrographs from the resultant carbon nanoparticles, the diameters of the CNTs and CNS’s have been estimated about 30-50nm and 300-400nm, respectively

QCA based error detection circuit for nano communication network

This paper outlines low power nano-scale circuit design for even parity generator as well as even parity checker circuit using quantum-dot cellular automata (QCA). The proposed even parity generator and even parity checker is achieved by using a new layout of XOR gate. This new XOR gate is much denser and faster than existing ones in the state of the art. The proposed parity generator has out shined the existing design by reducing the cell count as 10proposed parity checker has also out shined the existing design with an improvement in cell count as 17.94circuits are denser and faster than existing one. Nanocommunication architecture with the proposed circuits is also demonstrated. The bit-error coverage by the proposed method is described. Besides, the defects in the circuits are explored to facilitate guide to proper implementation. The tests vectors are proposed to identify the defects in the designs and the defect coverage by those test vector are also described. The estimation of dissipated energy by the layouts established the very low energy dissipation nature of the designs. Different parameters like logic gate, density and latency are utilized to evaluate the designs that demonstrate the faster processing speed at nano-scale

Few-and multi-layer graphene on carbon fibers: synthesis and application

In the current study, we investigated the influences of chemical vapor deposition parameters on the formation of uniform structures of few- and multi-layer graphene (FLG and MLG) as a coating phase on carbon fiber (CF). To this end, the process conditions of the chemical vapor deposition method, such as catalyst concentration, reaction temperature and time, and also carbon source flow rate, were optimized. The resulting FLG and MLG with high yields led to the modification of the CF surface by improving its properties. By applying scanning electronic microscopy, transmission electron microscopy and Raman spectroscopy, the surface morphology and structural information of the G–CF were analyzed. It was observed that under different conditions the FLG–CF and MLG–CF were obtained with 54%, 58% yields and also 10.21 m2 g−1, 8.78 m2 g−1 BET surface areas, respectively. Besides that, the FLG–CF and MLG–CF were used as fillers in the polypropylene (PP) composite and the effects of the number of graphene layers on the mechanical and thermal properties of the composite were analyzed. It is noteworthy to mention, composites based on the CF coated with G with only a few layers presented the highest surface area, strength and thermal resistance compared to those based on multi layers

Comparative study of the electrochemical, biomedical, and thermal properties of natural and synthetics nanomaterials

In this research, natural nanomaterials including cellulose nanocrystal (CNC), nanofiber cellulose (NFC), and synthetic nanoparticles such as carbon nanofiber (CNF) and carbon nanotube (CNT) with different structures, sizes, and surface areas were produced and analyzed. The most significant contribution of this study is to evaluate and compare these nanomaterials based on the effects of their structures and morphologies on their electrochemical, biomedical, and thermal properties. Based on the obtained results, the natural nanomaterials with low dimension and surface area have zero cytotoxicity effects on the living cells at 12.5 and 3.125 μg/ml concentrations of NFC and CNC, respectively. Meanwhile, synthetic nanomaterials with the high surface area around 15.3–21.1 m2 /g and significant thermal stability (480 °C–600 °C) enhance the output of electrode by creating a higher surface area and decreasing the current flow resistance

Superheated steam pretreatment of cellulose affects its electrospinnability for microfibrillated cellulose production

In this study, oil palm mesocarp fiber (OPMF) was pretreated with (1) superheated steam (SHS) and (2) potassium hydroxide (KOH) to remove hemicellulose. Both SHS–OPMF and KOH–OPMF underwent delignification step to isolate the cellulose and dissolved in selected ionic liquid and its co-solvent before being electrospun to obtain microfibrillated cellulose (MFC). FE-SEM images showed that SHS–OPMF cellulose produced discontinuous MFC fiber with diameter ranging from 100 to 500 nm, of which 15.5% were in the range of 100–200 nm; while KOH–OPMF cellulose produced continuous MFC with sizes larger than 200 nm. The differences in fiber size and continuity of fiber produced were due to incomplete removal of hemicellulose from SHS–OPMF sample that inhibited fiber re-coalescence and resulted in interruption in fiber formation

Synthesis and comparative study of thermal, electrochemical, and cytotoxicity properties of graphene flake and sheet

Two types of graphene, namely few-layer flake and multilayer sheet, were produced by chemical vapor deposition on nickel catalyst at high temperature (1050 °C) using different reaction times and cooling rates and their properties characterized and compared. The number of layers, morphology, structure, graphitization, composition, and surface area were studied using scanning electron microscopy, transmission electron microscopy, electron-dispersive X-ray analysis, Raman spectroscopy, and Brunauer–Emmett–Teller (BET) surface area measurements, respectively. Further properties of these nanomaterials, including their thermal stability, electrochemical properties, and cytotoxicity, were also comprehensively investigated

Synthesis of different types of carbon nanostructure on carbon fiber and their application as fillers in polypropylene composite

The potential application of carbon nanoparticles such as carbon nanotubes (CNT),carbon nanofibers (CNF) and graphene (G) flakes grown on carbon fiber (CF) surface as fillers in polypropylene composite is discussed. Carbon fiber surface must be modified before it can be used as fillers in composites. A one-step process using the chemical vapor deposition (CVD) method has been used to synthesize CNT, CNF and G and also G-CNF and G-CNT on the carbon fiber to modify its surfaces. In this study, CFs (Toho Tenax Co. Ltd.) was utilized as a substrate to grow carbon nanostructures and also as a filler in polypropylene pellets (PP 600G) polymer matrix. To the best of our knowledge, so far nobody has reported any work being widely carried out on synthesizing G layers on the CNF and CNT grown on CF by using a bimetallic catalyst (Ni/Cu) in a one-step CVD method in order to increase the CF surface area as well as to improve its properties. The synthesis of nanostructures on CF was accomplished using high purity acetylene (C2H2) as a carbon source, and nitrogen (Air Product,99.9995) and hydrogen as carrier gases. Two types of catalysts namely copper nitrate trihydrate (Cu(NO3)2.3H2O) and nickel nitrate hexahydrate (Ni(NO3)2.6H2O) were utilized as bimetallic catalyst in the synthesis. All the operating parameters of CVD process for growing the carbon nanostructures were optimized in order to obtain uniform and high quality carbon nanostructures. These parameters include catalyst concentration (from 50 mM to 150 mM), reaction temperature (different for each kind of carbon nanomaterial), reaction time (from 10 to 50 min) and carbon source flow rate (from 25 sccm to 100 sccm). Based on the SEM,TEM, TGA, BET surface area and Raman spectroscopy results, it was concluded that the optimum conditions are at 100mM catalyst concentration at 50sccm acetylene flow rate for 30 min at 550oC, 800 oC and 1050 oC for CNF, CNT and G growth, respectively. The changes in the surface characteristics of CFs was studied with scanning electron microscopy (SEM), transmission electron microscope (TEM), Raman spectroscopy and BET surface area analyzer. By analyzing SEM and TEM images, the morphology,structure, size and diameter of the resulting carbon nanostructures were obtained. In Raman spectra, the ID/IG ratio of the samples decreases when graphene flakes are present. When the ratio of CF/catalyst was at the maximum value, the ID/IG ratio (≈1.13) coated with CNF, CNT and G, decreased to 0.94, 0.88, and 0.47 respectively. The ID/IG ratio of CF-CNF-G (0.85) and CF-CNT-G (0.81) indicates the effect of graphene growth on the crystallinity of the substrate. Based on the results obtained from the surface modification of CF with various nanostructures, it is concluded that the carbon fiber coated with CNT-G (CF-CNT-G) with 80% yield and 46 m2/g BET surface area is the best method for surface modification of CF. Other fillers such as CF-CNF produced 24% yield and 2.31 m2/g surface area, CF-CNT with 46% yield and 5.22 m2/g surface area, CF-CNF-G with 56% yield and 21 m2/g surface area and, CF-G with 54% yield and 10.21 m2/g surface area. Polypropylene (PP) composites with different carbon-based fillers such as G on CF (GCF),CNF on CF (CNF-CF), CNT on CF (CNT-CF) and also G-CNF-CF and G-CNTCF were prepared by the melt mixed method and the effects of these nanoparticles on the mechanical and thermal behavior of the composites were analyzed. The mechanical behavior and thermal resistance of the produced composites were evaluated using the tensile test and thermal gravimetric analysis (TGA), respectively. The Raman images were then used to explain the observed mechanical behavior of the different types of fillers/PP composites. The tensile stress and young’s modulus of neat PP are 28MPa and 1400MPa. The values increased when various nanostructures were grown on the CF, to about 8.9% and 14.5% for CF/PP, 21% and 30.5% for CF-CNF/PP, 30.7% and 50% for CF-CNF-G/PP, 58.9% and 58% for CF-CNT/PP, 98.2% and 114.2% for CFCNT-G and finally 82.8% and 97% for CF-G. Based on the results, the PP composite reinforced with CF-CNT-G showed the highest improvement in tensile stress at 55.5 MPa, young’s modulus at 2998.9 MPa and enhancement in thermal stability to 130oC

Methods for coating solid-phase microextraction fibers with carbon nanotubes

The presence of carbon nanotubes (CNTs) on the surfaces of solid-phase microextraction (SPME) fibers can enhance the efficiency of the extraction. Their unique properties, such as large surface area, and excellent chemical, mechanical and thermal stability, make such fibers very attractive as adsorbents in SPME. The current review concentrates on the different coating methods, such as chemical bonding, physical attachment, sol–gel technique, electrochemical deposition and electrophoretic deposition (EPD) that coat the SPME fibers with CNTs. We also briefly discuss the advantages and the disadvantages of these coating methods