Current Nanoscience (v.13, #3)

Meet Our Editorial Board Member by Jian Liu (227-228).

Nanostructures for Antiviral Therapy: In the Last Two Decades by Afshan Siddiq, Ishrat Younus, Asma Shamim, Sehrish Badar (229-246).
Background: Viral infection is one of the global health problems and for the eradication of such infections no considerable antiviral agents are available. In addition, problem of emerging resistance to available antiviral agents is also rising day by day. The treatment of viral infection is indeed more complicated contrary to bacterial infection. So there is a dire need of identifying new type and technology to design dosage forms for antiviral drugs. In current scientific world, research works on Nanostructured particles are of huge significance because of its vital use in different fields of medical sciences and technology like biomedical, electronic and optical fields.

Methods: Research works and online contents related to nanostructures and nanotechnology that were designed for the advancement and effectiveness in antiviral therapy in the last two decades has been reviewed and presented in a summarized form. The efforts of scientists in the field of nanotechnology based antiviral drug design are written precisely to guide research workers, students and health care professionals.

Results: Regarding viral infections, identification of numerous nanostructured particles has been done. In last two decades, these particles have been reported with some potential activities against different viruses and exhibits potent role in preventing and curing different viral infections.

Conclusion: The antiviral systems based on nanotechnology can be designed with different and advanced functions like they might possess a different mechanism for releasing of the drug from its dosage design, more amount of drug might be available in biological fluid, improved activity with minimum adverse reactions and cost effectivity. Further, these designs might also provide specific and targeted drug delivery to the infected sites and viral pools in the body. Extensive research on receptor-based antiviral nanoparticles is going on which could reduce toxic and harmful effects of drugs in other normal tissues and ensure availability of accurate amount of dose to the targeted area.

New Bio-surfactant used in the Synthesis of Functionalized Nanoferrites as Potential Catalysts by Constantin Virlan, Ovidiu Florin Caltun, Doina Lutic, Aurel Pui (247-253).
Background: Organic dyes represented a serious pollutant in the past decades but does not present significant risk at the moment but still represents a model pollutant for the assessment of catalytic and photocatalytic activity of ferrite nanoparticles and more due to their ease in measurement.

Methods: Ferrite nanoparticles were obtained using the co-precipitation method and Palm Oil as biosurfactant. The nanoparticles were fully characterized using the relevant methods. Their catalytic activity was evaluated for the degradation of commonly used dyes.

Results: The nanoparticles present large magnetic moment and large specific surface suitable for environmental applications providing large adsorption surface and can be easily separated using an external magnetic field. The catalytic efficiency normalized to surface was maximum for copper ferrite.

Conclusion: Food grade palm oil can be used to reduce the synthesis cost of pure ferrite nanoparticles usable as catalyst in the degradation of organic pollutants as tested using model dyes.

Microwave Sensor for Ethanol Fuel Analysis Based on Single-Walled Carbon Nanotubes by Fatima S. Correra, Wesley Becari, Daniel B.R. Rodrigues, Henrique E. M. Peres (254-261).
Background: Ethanol is an important fuel for the automotive industry in different countries and an alternative to fossil non-renewable fuels. However, it is usual the malpractice of ethanol adulteration in many countries The illegal adulteration of ethanol fuel results in reduced engine lifetime and increases the production of toxic gases. The conventional ethanol analyses require expensive laboratory methodologies and equipment. This paper proposes a microwave sensor to analyze the complex permittivity of ethanol fuel by applying the cavity perturbation technique.

Methods: The sensor is a microstrip patch antenna coated with Single-Walled Carbon Nanotubes (SWCNTs). The SWCNTs deposited over the microstrip antenna allows characterizing the sample vapor-phase due to the change of the effective permittivity. When the ethanol-water vapor is injected, part of the Material Under Test (MUT) is adsorbed by the SWCNTs, increasing the charge transfer and changing the resonant frequency and Q factor. After the injection, the vapor is desorbed, returning to the initial values of frequency and Q factor of the device.

Results: The sensor presented a repetitive response, with no evidence of poisoning or drift. The measurements allowed to determine a relation between the resonant frequency for each fraction of ethanol-water sample and the real part of the complex permittivity. The same procedure was used with Q factor, which is related to the imaginary part of the complex permittivity. The sensor showed good sensitivity to detect small fractions of ethanol and water based on the complex permittivity of the mixtures.

Conclusion: The sensor was able to discriminate small fractions of ethanol-water with a fast response and good sensitivity. The proposed methodology allows in situ and real-time analysis of the ethanol fuel, towards the development of a compact, integrable, and portable electronic system. Therefore, the proposed microwave sensor presents consistent results related to the qualification of ethanol fuel, making it a promising tool for developing material characterization sensors and devices.

Background: Cells are typically crowded environments, affecting various properties of biomolecules such as diffusion, chemical binding, molecular structure and folding, and stability. Concentrated polymeric solutions serve as models to mimic these environments. In this study, we used ficoll, a water soluble, branched polysaccharide and we focused on probing its effect on the translational diffusion and the rotational diffusion of Alexa488 fluorophores. Here, we have a tertiary system (water, probes, polymers), introducing two lengthscales: the probe size and the mesh size of the polymer solution. It is unclear how the interplay between these two lengthscales would affect the nanoprobe translation and the rotation.

Methods: We combined standard fluorescence spectroscopy, fluorescence correlation spectroscopy (FCS), and fluorescence anisotropy (FA) techniques to probe changes of the fluorescence property, the translational diffusion, and the rotational diffusion of Alexa488 fluorophores (MW≈885 Da) mixed in non-fluorescent –hence 'invisible'- aqueous Ficoll (MW≈70 kDa) solutions. We measured changes of the emission spectrum, the lifetime, and the apparent rotational and translational diffusion coefficients of the fluorophores with systematic increase of Ficoll concentration up to 1200 mg/ml at room temperature. We also used a viscometer to measure changes of the viscosity of the ficoll solutions.

Results: We found that the spectrum and the lifetime of Alexa488 appeared to be insignificantly altered by the Ficoll solutions. The measured FCS functions were readily fitted with the expression describing normal particle diffusion. Notably, however, the changes of the diffusion coefficients could not be accounted for by the corresponding changes of the bulk viscosity of the Ficoll solutions as would suggest the Stokes-Einstein relations for both diffusion coefficients. Instead, we analyzed the data with the entropic model proposed by de-Gennes and his collaborators, and fitted each set of diffusion data with a stretched exponential [exp(-acn)] with n being related to the quality of the solvent. For both sets the fits yielded n-value close to one, suggesting a theta-like behavior of the host Ficoll-water system. However, the a-value for translation was larger than that of rotation, indicating dissimilar local entropic effects on the rotation and translation, which was not discussed by the proposers.

Conclusion: We demonstrated how FCS and FA can be applied to probe changes of the translational and rotational diffusions of a nanoprobe embedded in a polymeric solution. It appeared that the entropic model suggested by de Gennes and his collaborators was adequate to interpret the measured FCS and FA data. Further, taken altogether the results of the analysis of the data indicated that Ficoll polymers behaved as monodisperse non-interactive nanoparticles at low concentrations but were likely to interpenetrate and entangle at high concentrations.

Superparamagnetic Iron Oxide Nanoparticles Modified with Alanine and Leucine for Biomedical Applications: Development of a Novel Efficient Preparation Method by Isa Karimzadeh, Mustafa Aghazadeh, Taher Doroudi, Mohammad Reza Ganjali, Peir Hossein Kolivand, Davoud Gharailou (274-280).
Background: Magnetic nanoparticles (MNPs) are interesting candidates for biomedical areas of cell targeting and separation, magnetic resonance imaging (MRI), cancer therapy, hyperthermia, gene and drug delivery. Up now, various kind of surface coatings like polymers, polysaccharides, organic acids, silica and amino acids. The type of surface coating and their geometric connection onto the surface of MNPs determine the overall size, surface charge, magnetic characters, cytoxicity, bio-distribution, bio-compatibility and bio-performance. Amino acids can be interesting coating candidates for magnetite NPs because of their excellent bio-compatibility, stabilization and important role in the body. Hence, there has been increasing interest concerning amino acid coatings of MNPs.

Methods: Uncoated MNPs were electrodeposited by applying the current density of 10 mA/cm2. The bath temperature and deposition time were 25 A°C and 30 min, respectively. Then, the black deposit was scraped from the surface of steel electrode and then subjected to the purification process. For preparation of AMINO acid coated MNPs, 1g/L amino acids (alanine or leucine) were only added into the 0.01 M [FeCl2/Fe(NO3)3] solution. The purification steps were done for the prepared uncoated MNPs, alanine- and leucine coated MNPs. The obtained black powders were labeled amino acid-coated NPs (i.e. bare NPs, alanine- and leucine- coated- NPs) and evaluated by characterization analyses.

Results: The position and relative intensity of all XRD diffraction peaks are well-matched with a cubic spinel structure of magnetite (i.e. Fe3O4, JCPDS 01-088-0315). High magnification by TEM revealed that the prepared MNPs have size about 10 nm. It was found that the decrease in size and low agglomeration are due to the amino acid coating, which prevents agglomeration of the Fe3O4 fine particles during their deposition and growth on the cathode surface and hence reduces the size of the nanoparticles. The IR data completely specified the presence of the alanine and leucine on the surface of the electro-synthesized MNPs. VSM data revealed the amino acid coated NPs have very negligible Mr and Ce values, which indicated their better magnetic behavior as compared with naked NPs.

Zeptogram Mass Detection Using Triple Walled Carbon Nanotubes by Minesh T. Patel, Ajay M. Patel, Anand Y. Joshi (281-291).
Background: The aim of this paper is to use triple walled carbon nanotubes (TWCNT) as a sensor and explore the effect of change in the length of outer and middle tubes keeping smaller tubes length constant.

Methods: In this paper continuum models of TWCNTs are used, with the finite element procedure to evaluate the resonance frequencies of TWCNT. TWCNTs are treated as a number of concentric elastic cylindrical layers of SWCNTs. The interlayer interaction is described by the Van der Waals potential. The Van der Waals force field between the interfacial layers is represented by a spring element. Fixed free TWCNTs and bridged TWCNTs having attached mass at the end of their outer wall and at the center of the outer wall respectively have been analyzed with the variation in the mass.

Result: Fundamental frequencies in TWCNT resonators are in GHz which is much less than those of the DWCNT and/or SWCNT resonator in THz, because of the increasing inter tube interference. TWCNT resonators model was simulated and a decrease in the frequencies with decrease in length ratios was observed. Also, an increase in frequency shift is observed with an increase in the length ratio for different values of attached mass.

Conclusion: TWCNTs with different length variations can sense a mass up to zeptogram. TWCNTs with different wall lengths have been used for mass sensor may serve as a component in digital communication.

Sol-gel Synthesis of χTiO2/HZSM-5 Composite Photocatalyst on Degradation of Reactive Brilliant Red X3B by Huidong Su, Zheng Ma, Tingting Hu, Wenjie Zhang, Hongbo He (292-298).
Background: Different kinds of materials have been tried to support TiO2. The possible interactions between the supporting materials and the photocatalyst might put effect on photocatalytic activity. Synthesized zeolite with porous structure and large surface area has a long industrial history as adsorbent and catalyst. Photocatalytic degradation of Reactive Brilliant Red-X3B on χTiO2/HZSM-5 regarding TiO2 loading percentage and reaction time were investigated.

Methods: HZSM-5 supported TiO2 photocatalysts were prepared by a sol-gel method. XRD, SEM, FT-IR, and N2 adsorption-desorption analyses were measured to the materials. Decoloration of RBRX3B was conducted to evaluate the activity of the materials.

Results: Anatase TiO2 was found in both the XRD patterns of pure TiO2 and χTiO2/HZSM-5 samples. The supported χTiO2/HZSM-5 has enlarged surface area that is in accordance to the weight percentage of HZSM-5. Photocatalytic activity of TiO2 is enhanced after loading on HZSM-5 with the optimum TiO2 weight percentage of 50%. Total photocatalytic degradation of RBR-X3B dye molecules is achieved after 180 min of irradiation using 50%TiO2/HZSM-5. UV-Vis absorption spectra and FT-IR spectra of RBR-X3B solution during degradation prove the decomposition of RBR-X3B molecules, while the undecomposed triazine is the final residue remaining in the solution.

Conclusion: The external surface of HZSM-5 is coated with a layer of TiO2 in different thickness depending on TiO2 loading percentage. Anatase TiO2 forms in both pure TiO2 and the supported χTiO2/HZSM-5, while crystallite size of TiO2 shrinks after loading. The distribution of TiO2 on HZSM-5 is beneficial to both adsorption and photocatalytic oxidation of RBR-X3B. RBR-X3B is thoroughly decomposed into small organic substances during photocatalytic process.

Background: ZnO nanorod arrays (ZnO-NRA) are promising materials for the current research. The hydrothermal synthesis is considered as the most promising method for ZnO growth. ZnO-NRA-based UV sensors have been focused upon because of their use in the various fields. In this work, we fabricated zinc oxide (ZnO) nanorod array (NRA)-based metal–semiconductor–metal (MSM) UV sensors on glass substrates.

Methods: The ZnO-NRA was grown above ZnO-seed layer/glass using a low-temperature hydrothermal method. The MSM structure-based sensor was fabricated by depositing interdigitated contacts of Ag on NRA/glass samples. The crystalline structure and surface morphology of NRA were examined by X-ray diffraction and scanning electron microscopy. The values of responsivity and photocurrent to dark current ratio were obtained from the I-V characteristics of the MSM UV sensors.

Results: The grown single-crystalline ZnO nanorods were highly dense and uniform. The contrast ratio (C.R.) was found to be 9.20 at 1.50 V. The responsivity of UV sensors was found to be 0.122 mA/W at λ=365 nm.

Conclusion: ZnO nanorods were grown on glass substrates using a low-temperature hydrothermal method and the I-V characteristics of Ag/ZnO-NRA/Ag based MSM UV sensors were tested under UV light. The MSM UV sensors exhibited a photo current to dark current ratio of ~ 9.20 at 1.50 V, and a responsivity of 0.122 mA/W at 365 nm. These results can provide a deep insight into fabricating simpler, efficient, and inexpensive UV sensors for practical applications.

Activated Rice Bran Supported Preyssler Heteropolyacid: A New, Green and Recyclable Biocomposite for Adsorption of Toxic Dyes by Mitra Rohani, Fatemeh F. Bamoharram, Mohadeseh Bazoobandi, Morteza Khosravi, Javad Baharara (305-310).
A new, green and eco-friendly biocomposite based on Preyssler (H14[NaP5W30O110]) heteropolyacid supported on activated rice bran was prepared by a chemical impregnation method. The biocomposite catalyst was characterized by Fourier transform infrared and scanning electron microscopy. Decolorization of methyl red, methyl orange and methylene blue as carcinogenic and toxic dyes in textile wastewaters have been investigated in order to contribute toward clean technology, which is the most important need of the society. The performance of eco-friendly Preyssler/rice bran biocomposite was compared with rice bran and capability of the rice bran is found to be lower than the Preyssler/rice bran. In all cases, the synthesized biocomposite, was easily recovered and recycled with retention of their initial structure and activity. The results indicated that the decolorization of methyl red, methyl orange and methylene blue follows zero order kinetics.

Background: The heat transfer and fluid flow within a lid-driven, inclined, square cavity containing three circular heat sources are investigated. The enclosure is filled with DWCNT-water nanofluid. The effects of some important parameters, such as Richardson number, inclination angle, solid volume concentration and aspect ratio, are studied based on streamline, temperature field and average Nusselt number. The study is performed for Richardson numbers ranging from 0.01 to 100, inclination angles ranging from 0 to 60A°, aspect ratios ranging from 0.05 to 0.15 and solid volume fractions up to 0.004.

Method: The finite volume method and the SIMPLER algorithm are employed to solve the governing mass, momentum and energy equations numerically. The first step in discretizing the governing equations is to generate a finite difference mesh in the computational domain. A control volume is generated around each node of the mesh afterwards. The governing equations are then integrated over each control volume. In order to obtaine a stable solutions the diffusion terms are replaced using from the second-order central difference scheme, with a hybrid scheme for the convective terms for convection-dominated cases.

Results: According to the results, as the Richardson number increases, the average Nusselt number decreases. Furthermore, at a constant solid volume fraction for R/L=0.05 and R/L=0.1, as the inclination angle increases from 0 to 30o at Ri = 0.01, the average Nusselt number enhances. The maximum and minimum enhancements of the average Nusselt number for this case are 2.35% and 0.79%, occurring to φ=0.004 and 0, respectively.

Conclusion: The general behavior of the streamlines and isotherms for nanofluid and pure fluid is similar, but there are differences in terms of the lines. One of the differences is the formation of an inner vortex inside the larger vortex, which occurred for nanofluids at all Richardson numbers while was not observed for pure fluid. For all Richardson numbers, inclination angles and aspect ratios, as the solid volume fraction increases, the average Nusselt number is enhanced. For all the considered cases, as the Richardson number increases, the average Nusselt number decreases.

Prediction of Thermal Conductivity of Carbon Nanotube-EG Nanofluid Using Experimental Data by ANN by Mohammad Hemmat Esfe, Somchai Wongwises, Mousa Rejvani (324-329).
Background: The artificial neural network has been employed to predict the thermal conductivity of the carbon nanotube–ethylene glycol (CNT-EG) nanofluid based on experimental data. The main aim of this study is to find the best training algorithm for modeling the thermal conductivity of nanofluids.

Methods: Different activating functions and two training algorithms have been tested to train the neurons. The architecture of this modeling is the same and consists of one hidden layer with two neurons. The input parameters of the network include 20 data of temperatures (15–55oC) and volume concentrations (2.2–7.8 vol.%), and the output of the network is the thermal conductivity coefficient.

Results: The results indicate that the trainbr algorithm with the Elliotsig activating function responses have a higher regression coefficient and a lower mean square error. The results show also that an artificial neural network can estimate the experimental results with high precision in a wide range of temperatures and concentrations of carbon nanotubes.

Conclusion: The comparative graph with experimental data and artificial neural network modeling results in terms of temperature for different volume fractions revealed that the neural network can estimate the experimental results with high precision at a wide range of temperatures and concentrations of CNTs. Also, the results indicated that the neural network was not a proper tool for outside of the available data and should be used in the same range in which it was trained.