Current Nanoscience - Volume 12, Issue 4, 2016

Background: Fluorescent film sensors utilizing immobilized fluorescent reporters possess more favorable properties from a practical viewpoint. Recent advances in fluorescent noble metal nanoclusters, e.g. Au and Ag, have greatly prompted the development of fluorescent film sensors. The aims of this paper are to introduce readers to the synthesis of Au and Ag fluorescent nanoclusters and the fabrication of the fluorescent film sensors, and to review research related to the potential application of the nanoclusters-based fluorescent film sensors. Methods: The synthesis of Au and Ag fluorescent nanoclusters, fabrication of fluorescent metal nanocluster film sensors and their application are reviewed. Outlook of the fluorescent film sensors is provided. Results: Au and Ag fluorescent nanoclusters can be synthesized by using different ligands,such as thiol-based ligands, polymers and dendrimers, proteins, etc. Fluorescent films based on nanoclusters can be fabricated by incorporation of the pre-synthesized nanoclusters into the films or direct generation of nanoclusters within the films. Fluorescent film sensors have been used to sensitively and selectively detect heavy metal ions (e.g., Hg2+, Cu2+), nitrite anion, and trinitrotoluene (TNT). Conclusion: Organic ligand shells of nanoclusters play a crucial role in stabilizing Au and Ag nanoclusters and impart the properties of the ligands to the encapsulated nanoclusters. The ligand shells of nanoclusters can be tailored independently, constituting versatile platforms for the development of simple and facile methods of immobilizing nanoclusters on solid substrates. Designing the immobilization strategy of clusters on substrates would have a profound effect on the construction of fluorescent nanocluster film sensors with optimal properties.

Background: Antibacterial materials have attracted much attention due to its important role in human health and safety. Therefore the development and exploitation of novel antibacterial materials and agents with highly effective antibacterial activity are very necessary. Methods: A simple method to prepare antibacterial multi-walled carbon nanotubes (MWCNTs) was described. MWCNTs were coated with a reactive polydopamine (PDA) layer by dispersing them in dopamine (DA) solution, followed with chemical deposition of silver nanoparticles (Ag NPs) on the PDA layer. Antibacterial activity of MWCNTs@PDA@Ag NPs towards E. coli and S. aureus was estimated by standard plate count method. Results: Spherical silver nanoparticles with size of 5-6 nm were uniformly decorated on the sidewalls of MWCNTs. The MWCNTs@PDA@Ag NPs composite shows a good antibacterial property towards E. coli and S. aureus, with an antibacterial rate of 93.8% at the concentration of 6.25μg/mL and an antibacterial rate of 93.1% at the concentration of 2μg/mL, respectively. Conclusion: The MWCNTs@PDA@Ag NPs composite exhibits excellent antibacterial activity towards E. coli and S. aureus, and it is an ideal material for sterilization.

Background: The present study has made great progress in multifunctional nanomaterials, which have great potential in cancer diagnosis and therapy. Methods: In this paper, we proposed a new multifunctional nanocomposite (HGN@RhB-BSA/DOX) which bovine serum albumin (BSA) and doxorubicin (DOX) were modified onto hollow gold nanosphere (HGN) by the electrostatic interaction, and fluorescent dye Rhodamine B (RhB) was combined with bovine serum albumin (BSA) by coupling agent 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide sodium salt (Sulfo-NHS). Results: Based on absorption spectrometer, fluorescence spectrometer, and ZetaSizer analyzer, the nanocomposite had strong surface plasmon resonance (SPR) absorption near 800 nm and revealed the success of RhB, BSA, and DOX were bound onto HGN. The significant rising of temperature was observed when multifunctional fluorescent drug-loaded nanoparticle were irradiated with near-infrared (NIR) light. Conclusion: We conclude that the nanocomposite presents a promising for photothermal therapy, fluorescence imaging and drug delivery.

Background: Carbon nanotube (CNT) nanofluidics have been studied theoretically and experimentally for more than a decade. Due to the unique geometrical, chemical and physical properties of CNTs, it is extremely interesting to understand the mass transport properties of these molecular scale nanochannels. In addition, the carbon nanotube based nanofluidic devices have great potentials for revolutionary applications in biosensing. Here, we review the recent research activities in the field of CNT nanofluidics. Methods: We will first give a brief introduction of this field. Then we will summarize various methods for the fabrication of CNT nanofluidic devices. After that, we will discuss the unique mass transport phenomenon, especially for small molecules, observed in these CNT nanofluidic devices. Finally, we will discuss the challenges and future prospects of CNT nanofluidics. Results: The current research in CNT nanofluidics mainly focused on developing fundamental understanding of the unique mass transport properties in molecular scale CNT. This is partially due to the difficulty of CNT sorting and device fabrication. The steady progress in the technology development of CNT synthesis and device fabrication will eventually promote the applications of CNT nanofluidics. Conclusion: CNT based nanofluidic devices are promising in biosensing and can perform better than typical solid state nanopores. Beside applications in biosensing, exciting applications of CNT nanofuidics can also arise in biology, medical and energy related fields in the near future.

Background: Research in to transparent super-hydrophobic surfaces is of considerable interest in the present scenario, as it finds plenty of applications in both fundamental research and industry. An extensive scattering of propagated light may take place through super hydrophobic surfaces because of very high surface roughness. Transparency and super hydro-phobicity are general conflicting properties whereby; the main requirement to satisfy both these properties is the precise control of roughness. Further, the wettability of the surface is another important property of the material that depends on both the surface composition and its roughness. Methods: Approaches for fabrication of transparent super-hydrophobic surfaces may be categories as; bottom-up, top-down, and combination of bottom-up with top-down approaches. Bottom-up approaches encompass mostly self-assembly and self-organization such as chemical vapor deposition (CVD), layer-by-layer (LBL) deposition, hydrogen bonding and colloidal assemblies. Top-down approaches involve lithographic and template-based techniques, as well as surface plasma treatment. Methods combining bottom-up with top-down approaches include casting of polymer solution, phase separation, and electro-spinning. Results: Present work reviews the preparation of transparent superhydrophobic surfaces by following different techniques and the developments over the years. This paper deals with the detailed discussion regarding the origins of water-repellent surfaces, examining how the surface characteristics can be controlled by using the shape and size of surface features, in particular, how techniques have progressed to create multiscaled roughness to mimic the lotus leaf effect. Conclusion: With the availability of several methods to fabricate superhydrophobic surfaces and coatings, important applications for super-hydro-phobicity have been identified but the use of super-hydrophobic surfaces at the large scale is still lacking due to the poor wear resistance. Artificial superhydrophobic surfaces are not able to recover and heal the damages, due to abrasion. Further, the fabrication of robust surfaces is one of the major points to be focused with super- hydrophobic and other functional surfaces, which can withstand in wearing conditions. Long-term durability and wear resistance, which are the key issues with super-hydrophobic cotton clothes, is another major challenge with super-hydrophobic surfaces. However, the use of paper products in superhydrophobic coatings is quite different from cotton fabrics due to the difference in their quality and manufacturing. Therefore, the varied nature of the substrate materials, demands to seek new methods which are suitable for mass production of super- hydrophobic surfaces than to focus on the durability of surface.

Background: Metal films in microwave-assisted, continuous-flow organic synthesis (MACOS) have shown to act as heterogeneous catalysts for a variety of reactions, but have difficulty due to difficult to control heating and occurrence of laminar flow which limits the contact of the reagents with the catalyst surface. The aim of this paper is to describe a microwave-transparent supported metal catalyst with high surface area and its use in MACOS. Methods: Millimeter sized, monodisperse, macroscopic spherical silica beads loaded with Ni, Cu, and Pd nanoparticles were prepared through use of a single-step emulsion procedure via a sol-gel process and used to perform Heck cross-coupling reactions in MACOS. Results: The size of the spheres was readily controlled to a maximum diameter of 1300 μm by varying the stirring rate of the emulsion mixture. Pd loadings of up to 4.3 wt.% were obtained, and confirmed to be present as nanoparticles through PXRD spectroscopy and TEM imaging. The metal-loaded spheres were found to be essentially microwave-transparent, allowing for use as catalytic beads in microwave flow reactors. In addition, no mechanical dislodgement of the nanoparticles or degradation of their catalytic activity was observed over repeated usage. Conclusion: Metal-nanoparticle-impregnated silica macrospheres were found to be an effective catalyst for use in MACOS by providing access to the use of heterogeneous metal catalysts with controllable heating. Further testing of various metals and reactions can be performed to increase the scope of possible reactions to be catalysed in MACOS using metal-impregnated macrospheres as catalysts.

Background: Magnetic nanoparticles (NPs) used in biomedical applications should be discrete with small particle sizes, narrow size distribution and superparamagnetic. NPs can be tailored to target, through chemical bonds, specific organs, cells, or even molecular markers of different diseases in vivo, with suitable surface chemistry modification. Methods: Nanoparticles are synthesized by a low cost coprecipitation reaction of ferrous and ferric salts with alkaline solution. The characteristics of the NPs are modified by varying the addition rate of the alkaline solution. NPs surface is silica coated using a modified Stöbe method. The conversion of the surface hydroxyl groups into amino-groups is performed by two different alkoxysilanes and the silanization reaction is conducted either in Methanol – Glycerol environment at elevated temperature, or in water at room temperature. The surface amine groups of the NPs are further converted, either to aldehyde groups by glutaraldehyde, or to carboxyl groups using glutaric anhydride. Bovine Serum Albumin and Vena human natural immunoglobulin are used in order to study the protein conjugation capacity of the functionalized NPs. The amount of protein attached to the nanoparticles is determined by UV–Vis spectroscopy of the supernatant. Conjugation of synthesized nanoparticles to protein BSA is examined by FTIR spectroscopy. SDS-PAGE electrophoresis followed by protein immunoblotting is used to test the effect of nano-conjugation to the antibodies. Results: Superparamagnetic Fe3O4 nanoparticles with saturation magnetization 60emu/g, a mean diameter 8-12 nm and BET surface areas between 100-250 m2/gr are obtained with total time of addition of the base between 1-5 minutes. They are coated with a thin and nearly uniform silica (SiO2) layer with thickness 1-2 nm. The most appropriate source for surface functionalization with amino groups is 3-aminopropyltriethoxysilane (APTES), while the two silanization methods used, proved to be equally efficient. NPs with surface aldehyde groups display better conjugation capacity than NPs functionalized with carboxyl groups. The FTIR spectra of the protein conjugated NPs samples, contain the two main peaks, at 1529 cm-1 and 1661 cm-1, attributed to the amide bond of the protein, which confirms the conjugation of the protein to the NPs. During a SDS-PAGE electrophoresis - protein immunoblotting experiment, the antibodies, after being conjugated to the nanoparticles, are selectively attached to their antigen, which indicates of lack of significant conformation changes secondary to the conjugation process. Conclusion: The conjugation capacity of the optimized nanoparticles is higher for Ig antibody than for BSA protein, under similar reaction conditions. The conjugational efficacy and conformational stability and the effect on electrophoretic mobility of the antibodies conjugated to the nanoparticles are verified by protein immunoblotting.

Background: This paper presents a series of theoretical studies about the influence of the size distribution and the effective magnetic anisotropy constants on the Néel relaxation time, the effective relaxation time and the Specific Loss Power of a magnetic nanoparticle system. Methods: We modelled the system by considering the dipolar magnetic interactions among the nanoparticles. Therefore, the Néel relaxation time has been modelled by considering the local magnetic field (i.e., the external magnetic field plus the local magnetic dipolar field) as oblique to each nanoparticle's anisotropy axis. The contribution of our studies have practical applications. In fact, our goal is to propose a robust and reliable model able to optimise the heating process and, consequently, the Specific Loss Power in magnetic hyperthermia applications. Results: In our work, we checked how the dynamic behaviour of monodomain nanoparticles is ifluenced not only by energy barriers but also by a number of other parameters that depend on the effective magnetic anisotropy constants, of the local magnetic field and thus implicitly of the nanoparticle sizes. Conclusion: Our studies contribute to a deeper understanding of the magnetic hyperthermia process and finding ways to control the system parameters for optimising the heating process and, consequently, the Specific Loss Power.

Background: Based on the resistive switching mechanism such as electrochemical migration and redox, chemical bonding character and structural distortion from elemental substitution may affect the resistive switching properties. Therefore, in this study, the resistive switching properties of a reactive metal Ti electrode and Ln0.7Sr0.3MnO3 films, which were synthesized with differently sized trivalent lanthanide cations (Pr and Sm), were investigated in terms of their structural, chemical, and electrical properties in order to elucidate the chemical and structural effects of the lanthanide cation on the resistive switching properties and the interface characteristics. Methods: Ln0.7Sr0.3MnO3 (Ln=Pr and Sm) films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by RF magnetron sputtering from powder targets. The crystal structures of the films were analyzed by glancing angle X-ray diffraction and the surface morphologies were investigated by atomic force microscopy analysis in non-contact mode. The chemical states of the films were analyzed by X-ray photoelectron spectroscopy and the current-voltage characteristics were measured using a semiconductor device analyzer. Results: An internal lattice strain in Ln0.7Sr0.3MnO3 (Ln=Pr and Sm) films was increased with decreasing trivalent cation size, orthorhombic structure for Pr3+ and monoclinic structure for Sm3+ as confirmed with XRD results. An increase in the covalent Mn-O bond character was confirmed by shifts in the binding energies of Mn 2p and Mn 3s. The Mn 3s splitting magnitude remained unchanged as the trivalent cation size was decreased and the formal oxidation state of Mn ions was calculated to be +3.33. The PSMO film shows a resistive switching curve with low resistance and this was related to the larger covalent character of the Mn-O bond, which obstructs a formation of interfacial oxide with Ti top electrode. Conclusion: Structural analysis with X-ray diffraction showed that larger internal lattice strain was developed with Sm0.7Sr0.3MnO3 film, crystallized with monoclinic structure. The Mn-O bond character became more covalent with increasing Ln3+ cation size in case of Pr3+ and this covalent bond character inhibited the formation of TiOx at the interface between Ti top electrode and Ln0.7Sr0.3MnO3 film, which affects the redox-based resistive switching characteristics and IV behavior. The smaller lattice strain with higher crystal symmetry and larger covalent character in Mn-O bond were found to induce enlarged resistive switching ratio and operating current level, respectively. The larger internal lattice strain with lower crystal symmetry by smaller size of Sm3+ trivalent cation in Ln0.7Sr0.3MnO3 film induced a reduced resistive switching ratio due to obstacled electrochemical migration.

Background: Silicon photonic structures (PSs) with inverse opal structures are favored due to their high refractive index at optical frequencies. However, the fabrication of monoliths of 3D amorphous silicon (a-Si) inverse opals with large band-gaps and photoluminescence at optical frequencies especially in the visible range is rarely reported in literatures. Methods: The monoliths of the ordered 3D polystyrene colloidal crystals are immersed into tetraethyl-orthosilicate solution for several hours and then dried. The resulting monolith of latex/silica is calcinated under an oxygen flow. Using the porous silica as templates and reactants, a-Si photonic structures with a face centered cubic crystal lattice are obtained through a magnesiothermic reduction procedure. Results: Large-scale monoliths of a-Si photonic materials with inverse opal macro-porous hierarchical nanostructures have been fabricated. This successful fabrication is mainly attributed to the lower-temperature (605 ºC) and the disordered amorphous morphology for Si. The obtained 3D a-Si inverse opals are with a full band-gap at optical frequencies. Conclusion: This facile fabrication of large-scale amorphous Si photonic materials with well-tailored optical properties would greatly extend the applications of a-Si in optoelectronics and other fields.

Background: The aim of this study is to design a new levodopa nanocomposite. A levodopa (dopa)- iron oxide nanoparticles (MNPs) nanocomposite was synthesized under an high basic environment using dopa, FeCl3 and FeCl2 as the precursors. Methods: iron oxide nanoparticles (MNPs) were prepared using an iron salt coprecipitation method in a sodium hydroxide medium and subsequently coated with the bioavailability polymer chitosan (CS) to form CS-MNP nanoparticles. CS-MNP was loaded with levodopa to form a dopa-CS-MNP nanocomposite. Results: A magnetization study shows that both MNPs and the dopa-CS-MNP nanocomposite were superparamagnetic with saturation magnetizations at 25 and 30 emu/g, respectively. The levodopa release was also studied at 25 and 37 °C with carbonic anion and showed 90 % release over 1000 minutes. The mean diameters of MNPs and dopa-CS-MNP are 57 nm and 43 nm, respectively. The cytotoxicity effects in normal cells (3T3) were investigated using an MTT assay for up to 72 hours. The IC50 values of dopa-CS-MNP and free dopa are 199 ±2 μg/ml and 40 ±2 μg/ml, respectively. Conclusion: The resulting dopa-CS-MNP nanocomposite can be used in a wide range of applications, such as biotechnology, MRI and drug delivery.

Background: As a B group vitamins, vitamin B9 is a Water-soluble vitamin which is produced by plants and microorganisms (bacteria and yeasts). Vitamin B9 plays an important role in the production of proteins and nucleic acids in body and also is one of the substances that prevents the development of neural tube defects in the fetus. Methods: Electrochemical behavior of vitamin B9 was studied using a potentiostat/galvanostat SAMA 500, electroanalyzer system, I. R. Iran. A three-electrode system was used, including a glassy carbon working electrode (d = 2.0 mm, purchased from Azar Electrode Co., Urmia, I.R. Iran), an Ag/AgCl (saturated KCl) reference electrode and a Pt wire auxiliary electrode. Electrochemical impedance spectroscopy (EIS) measurements were performed with a Potentiostat /Galvanostat/Frequency response analyser (FRA) EG model 273A. Scanning electron microscopy (SEM) experiments were performed on a VEGA\\TESCAN scanning electron microscope (Czech Republic). Results: An electrochemical sensor for vitamin B9 was developed by deposition of carbon nanoparticles-cellulose nanofibers (CNP-CNF) suspension on the GCE surface. Voltammetric experiments revealed good adherence of thin layer coating of CNP-CNF to the GCE surface which enhanced long-time stability and repeatability of modified electrode responses. Voltammetry results showed distinguish enhancement of vitamin B9 anodic peak current (27 fold) on the surface of CNP-CNF/GCE compared to the bare GCE. High uniform and quite porous structure formed on the surface of GCE through drop casting of CNP-CNF suspension produced very large active surface area which effectively improved characteristics of the electrode surface toward diffusion of electroactive species. Based on AFM measurements, the thickness of CNP-CNF layers was estimated below 100 nm. SEM image indicated the presence of nanoparticles on the GCE surface along with displaying uniform distribution of nanoparticles on the electrode surface. The average size of nanoparticles deposited on the GCE was estimated below 100 nm. Under the optimized conditions, CNP-CNF/GCE exhibited a wide linear dynamic range of 0.1 – 10 μM for the voltammetric determination of vitamin B9. The modified electrode was successfully applied for the accurate determination of vitamin B9 amounts in pharmaceutical preparations. Conclusion: The CNP-CNF modified glassy carbon electrode showed notable electrochemical advantages for vitamin B9 analysis such as high accuracy, good repeatability and reproducibility as well as low detection limit and wide linear range. Results of electrochemical investigations revealed that introducing the CNP-CNF to the electrode surface increased electroactive area and leaded to significant enhancement of oxidation peak current of vitamin B9. Therefore, it can be concluded that the prepared modified electrode has great potential to accurate analysis of vitamin B9 in pharmaceutical and clinical preparations.

In order to utilize the visible light of TiO2 effectively, the heterostructured TiO2 nanotube/ CdS nanocomposite was synthesized by a hydrothermal approach. Characterization of the prepared products were performed with scanning electron microscopy, transmission electron microscopy, X-ray diffraction and ultraviolet-visible spectroscopy. The results indicated that the heterostructured TiO2 nanotube/CdS nanocomposite exhibited a significant red shift while the CdS quantum dots were attached on the surface of the TiO2 nanotubes. Based on a quartz crystal microbalance array, TiO2 nanotubes and heterostructured TiO2 nanotube/CdS nanocomposite were used to fabricate a chemical prototype device to study the surface and interface properties of the heterostructured nanocomposite. The adsorption properties of the chemical prototype device to some typical organic volatiles were examined under the same micro-environment. The results showed that the attachment of CdS on the TiO2 nanotubes had enhanced the adsorption properties to those organic volatiles greatly. After the heterostructured TiO2 nanotube/CdS nanocomposite was casted on the surface of Au interdigital electrodes on flexible polyethylene terephthalate substrates, the photoresponse of the nanocomposite was examined with a low-power visible light source to explore the modification mechanism in detail. It was found that the CdS modification enhanced the photocurrent of the TiO2 nanotubes to weak visible light. Not only showing enhanced visible light response, but also possessing excellent adsorption properties to organic volatiles, the heterostructured TiO2 nanotube/CdS nanocomposite, has good potential applications in photocatalysts, self-cleaning coatings, photo detectors, chemical and bio- sensors.

Background: The current environment problem and energy crisis become two major bottleneck restricting the development of human. Photocatalytic technology is expected to become the effective approach to solve the problem of environment and energy. Since it is a ‘‘green’’ technology for removing toxic organic pollutants and photocatalytic degradation to solve the problem of environment. The aims of this paper are to introduce the new composite photocatalysts which improve photocatalytic activities and discuss reasons for mechanism of photocatalytic degradation. Methods: A series of Zn1-xCdxS solid solution nanoparticles were synthesized via the simple hydrothermal method. Then these samples were characterized by XRD, SEM, TEM, HRTEM, EDS and UV-vis techniques, while the photocatalytic activity of the samples for the degradation of RhB was evaluated under visible light illumination. Results: The band gaps of various Zn1-xCdxS were calculated. It was shown that when the redox power together with light absorption capacity in the Zn0.5Cd0.5S nanoparticles reach a balance which probably leads to a higher photocatalytic efficiency under visible light irradiation. When EDTA- 2Na is added to the solution, the photocatalytic activities of all the Zn1-xCdxS photocatalysts have been greatly enhanced compared with no EDTA-2Na system. The result indicates that the addition of EDTA improves the separation efficiency of electrons and holes. Conclusion: The Zn1-xCdxS solid solution nanoparticles as visible-light induced photocatalyst was successfully synthesized by a simple hydrothermal method. We got the best ratio of ZnS to CdS which possessed an appropriate band-gap structure and exhibited the enhanced and highest photocatalytic activities under visible light irradiation. In addition, the enhancement of the photocatalytic performance of Zn1-xCdxS solid solution by the addition of EDTA- 2Na may improve separation efficiency of electrons and holes.

Background: Photocatalytic degradation of organic pollutants on TiO2-based materials has become a research focus in environmental cleaning. It is worthy of studying the effects of pre-treating of zeolite on the properties of the supported TiO2 photocatalyst. However, hydrothermal treatment is still a new approach to prepare HZSM-5. Hydrochloric acid concentration is a key factor in the Na+- H+ exchanging process using NaZSM-5 as the raw material. Methods: HZSM-5 was treated in hydrochloric acid aqueous solution by hydrothermal method and was used to synthesize supported nanosized TiO2. Characterizations of the materials were conducted by means of XRD, SEM, XPS, BET and BJH analyses. Results: The distribution of TiO2 on the surface of HZSM-5 leads to shrinking crystallite size of anatase TiO2. 50%TiO2/ 0.3HZSM-5 has the maximum surface area of 243.1 m2/g among the supported 50%TiO2/xHZSM-5. Rising hydrochloric acid concentration during treating of NaZSM-5 zeolite can lead to enlarging pore size of the supported materials. The Ti2p and O1s electron binding energies in 50%TiO2/0.3HZSM-5 shift to higher energy due to the existence of HZSM-5. 92.8% of methyl orange is degraded in 100 min under irradiation on 50%TiO2/0.3HZSM-5. Conclusion: The composite TiO2/HZSM-5 materials were prepared for the purpose of photocatalytic decoloration of methyl orange. TiO2 is in the anatase phase in the supported 50%TiO2/HZSM-5. Photocatalytic activity of 50%TiO2/xHZSM-5 varies with hydrochloric acid concentration.

Background: A carbon nanotube field-effect transistor (CNTFET) is, however a field-effect transistor itself, which utilizes a single carbon nanotube or a multiple of carbon nanotubes act as the channel material instead of bulk silicon in the traditional MOSFET structure. A carbon nanotube is a tube-shaped material, made of carbon, having a diameter measuring on the nanometer scale. Multi-Valued Logic (MVL) is a calculus in which there exist more than two truth values. The ternary logic is a common MVL, which includes three significant logic levels. These logic levels are ‘0’, ‘1’ and ‘2’ symbols respectively. As such three different types of logics are used for the ternary logic, those include negative, positive and standard. The purpose of this paper is to introduce a new low-power ternary logic Ex-OR and Ex-NOR gates using CNTFETs. The proposed ternary logic circuits are designed based on the conventional static CMOS and pseudo nMOS architectures. Moreover, each of the proposed CNTFET based ternary logic gates includes all the possible types of ternary logic, that is, negative, positive and standard. Methods/Results: All the proposed ternary Ex-OR and Ex-NOR gates are simulated using Spectre Cadence with the supply rail voltage of +0.9 V using 32 nm CNTFET technology files. The transient response of all the CNTFET static and pseudo ternary Ex-OR and Ex-NOR logic gates are reviewed. The power consumption and the propagation delays of all the proposed Ex-OR and Ex-NOR circuits are calibrated. The results have indicated that the delays of pseudo gates are considered less than normal gates. Conclusion: In this paper CNTFET-based 2-input Ex-OR and Ex-NOR gate design are presented. The proposed CNTFET-based circuits have been designed by deploying multi-valued logic (ternary logic) and multiple threshold voltage nano devices. These circuits are designed at various carbon nanotube diameters having less than 3 nm. The simulation results confirm the authenticity and the superiority of the proposed circuits in terms of the propagation delays and power consumption. So, these are proven to be the best choice for low-power and low-voltage applications that require of small area, high performance, high noise margin and low power dissipation.

Background: Three tetracycline antibiotics (TCs), tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC), were extensively employed in human, veterinary medicine as well as feed additives to treat and prevent bacterial infections. Tetracycline antibiotics are widespectrum antibiotics active versus a wide range of gram-positive and gram-negative bacteria, as well as a range of organisms such as mycoplasma and chlamydia. As mentioned above, these drugs stay as residues in animals, fish, and birds are harmful to humans at quite low levels. Thus, it is important to develop an effective alternative procedure for the detection of tetracycline compounds. Methods: An electrochemical sensor based on the electrocatalytic activity of commercial screen-printed graphene electrode for sensitive detection of tetracycline was presented. The electrochemical behaviors of tetracycline on graphene screen-printed carbon electrodes (GRSPCEs) were researched by cyclic voltammetry and differential pulse voltammetry. The use of the commercially disposable graphene modified screen-printed carbon electrode for milk and honey sample assays obtained satisfactory results, which made it an encouraging alternative in routine sensing applications. Results: This study focuses the first application of GR modified SPCE as voltammetric sensors for the detection and quantification of TC. The large advantages of this type of sensor system are associated with their modest cost, potential portability, the simplicity of operation, reliability, and the compact detector arrangement containing the working electrode, auxiliary and reference electrodes. This sensor features speedy experimentation time, well suitability for field trace TC analysis and an admissible sensor lifetime. This proposed electrochemical approach was successfully adapted to determine the TC in honey and milk samples. Conclusions: The results suggest that the method developed for the determination of TC using GR modified SPCE is practicable for the sensing of the antibiotic at 0.08 μM levels with really good precision. This approach allows avoiding the electrode fouling that is noticed when evaluating this class of compound. The process, therefore, is very convenient for the daily routine assessment of tetracycline antibiotics. The proposed voltammetric approach is highly competitive for the detection of these antibiotics in foods, particularly as a screening method. It was not necessary to use solid phase extraction, we usually employ for a preliminary separation when assaying milk and honey samples.