Current Nanoscience - Volume 14, Issue 2, 2018

Background: Bimetallic silver-gold nanoparticles (Ag/Au NPs) with different structures have recently gained scientific attention due to their new and superior properties in comparison with metallic NPs made from a single metal. Ag/Au NPs (alloy or core-shell structures) have been applied to several biomedical, technological, and environmental applications. The potential applications of Ag/Au NPs are widespread yet poorly investigated in comparison with monometallic NPs. Besides traditional chemical and physical routes to synthesize bimetallic Ag/Au NPs, biogenic protocols are considered cost-effective, simple, and environmentally friendly. Despite their simplicity, biogenic routes to synthesize Ag/Au NPs are less explored than traditional synthetic protocols. Methods: In this context, we present a review and discuss recent progress in the preparation of bimetallic Ag/Au NPs with different morphologies, structures, and size distributions using biogenic synthetic protocols. Results: Biogenic synthesis using plant extracts, algae, bacteria, fungi, and other biological agents are presented and discussed. The characterization and potential applications of biogenically synthesized Ag/Au NPs in the different areas of medicine and biological applications, such as antibacterial, anticandidal, anticancer, antidiabetes, and as sensors for clinical diagnosis are presented and discussed. Conclusion: Finally, challenges and drawbacks in the biological routes for the preparation of Ag/Au NPs for industrial applications are also discussed.

Background: Nanotechnology has demonstrated great potential for the cure of bone infections through the development of antibacterial nanomaterials. The bone diseases include many skeletal- related illnesses such as arthritis, bone cancer, osteosarcoma and osteoarthritis, which are the major causes of mortality in human beings. Moreover, there are no effective treatment strategies available for such bone diseases. However, these limitations create pressing need to search safe and efficient novel drugs for clinical treatments. In this context, nanotechnology- based targeted drug delivery is widely proposed as an effective treatment strategy. Objective: Recently, various nanomaterials have been extensively used in the management of bone diseases. Therefore, we aimed to write a comprehensive review on the role of nanotechnology in bone diseases. Methods: We searched Google and PubMed portals extensively concerning literature of the following subjects so as to get latest updated information related to current developments in the field of nanotechnology in the context of bone diseases. Results: In the present review, we have discussed the role of the various nanomaterials, which can be promisingly used in the diagnosis and treatment of dentistry and bone cancer. Further, biomedical applications of nanomaterials like imaging, diagnostic, drug delivery and their use as regenerative bone substitutes have also been discussed. Conclusions: Considering the recent advances in the field, it can be concluded that the development of nano-based approaches can be possible, which will play important role in the diagnosis and treatment of bone diseases, bone regeneration, and tissue reconstruction.

Background: Because of nanofluids applications in improvement of heat transfer rate in heating and cooling systems, many researchers have conducted various experiments to investigate nanofluid's characteristics more accurate. Thermal conductivity, electrical conductivity, and heat transfer are examples of these characteristics. Method: This paper presents a modeling and validation method of heat transfer coefficient and pressure drop of functionalized aqueous COOH MWCNT nanofluids by artificial neural network and proposing a new correlation. In the current experiment, the ANN input data has included the volume fraction and the Reynolds number and heat transfer coefficient and pressure drop considered as ANN outputs. Results: Comparing modeling results with proposed correlation proves that the empirical correlation is not able to accurately predict the experimental output results, and this is performed with a lot more accuracy by the neural network. The regression coefficient of neural network outputs was equal to 99.94% and 99.84%, respectively, for the data of relative heat transfer coefficient and relative pressure drop. The regression coefficient for the provided equation was also equal to 97.02% and 77.90%, respectively, for these two parameters, which indicates this equation operates much less precisely than the neural network. Conclusion: So, relative heat transfer coefficient and pressure drop of nanofluids can also be modeled and estimated by the neural network, in addition to the modeling of nanofluid's thermal conductivity and viscosity executed by different scholars via neural networks.

Background: Electrical probe memory using chalcogenide alloy has recently become the research focus due to its potential for the future archival storage. Objective: In spite of its extraordinary electro-thermal characteristics, the stability of the chalcogenide alloy remains questionable because of the well-known resistance drift effect. Method: Therefore, we here investigated the possibility of using TePdO media that was previously implemented for Blu-Ray disc as an alternative material for electrical probe memory application. Result: A parametric approach was first deployed to find out the appropriate deposition conditions to optimize the TePdO resistivity around 100 ohm·cm. Subsequently the thickness of the TePdO film was optimized in terms of the amorphous resistivity, stability and threshold voltage. Conclusion: Finally, the write and readout performances of the electrical probe memory were reevaluated with the use of TePdO film with respect to the proposed optimized parameters.

Background: A new type of photocatalyst with a perovskite structure is recently utilized. The one-dimensional nanostructure of photocatalysts holds great charge mobility along the crystal longitudinal dimension and can hence provide the direct pathways of charge carriers. Graphene holds a superior electrical conductivity and high specific surface area. The aims of this paper are to make LaMnO3 nanorods disperse on the graphene surface. The synergistic effect between graphene and LaMnO3 nanorods enhances the photocatalytic performance. Method: LaMnO3 nanorods–graphene is fabricated using cetyltrimethyl ammonium bromide as template by a simple hydrothermal reaction followed by heat treatment. Results: XRD result indicates that the appropriate calcination temperature for the perovskite structure formation is 650°C. Electron microscopy reveals the LaMnO3 nanorods exhibit a good dispersion behavior on the surface of graphene and the specific surface area of LaMnO3 nanorods-graphene is higher than that of LaMnO3 nanorods. The activities of LaMnO3 nanorods–graphene and TiO2 are compared for degradation of Direct Green BE, the decolorizing rates are 99.93% and 79.45%, respectively. Conclusion: The photocatalytic results for Direct Green BE degradation showed that LaMnO3 nanorods– reduced graphene oxide exhibit a superior photocatalytic performance than that of LaMnO3 nanorods and TiO2 powders. The one-dimensional nanorod structure of LaMnO3 can provide a direct pathway for electronic transmission, and the increased aspect ratio is favorable for reducing the recombination probability of the electron and hole. Meanwhile, the photoelectron transport along the graphene sheets can promote the separation of the e−–h+ pairs.

Background: Recombinant human keratinocyte growth factor (rHuKGF) is a protein used to treat oral mucositis caused by radio and chemotherapy in patients with hematologic malignancy. The rHuKGF is available in the form of intravenous bolus injection. In this study, new formulation of rHuKGF-loaded chitosan nanoparticles was developed to improve patient compliance. Methods: Chitosan nanoparticles (CNPs) loaded with rHuKGF were prepared by ionic gelation method. The tripolyphosphate (TPP) cross-linked with chitosan molecules at pH >5.0 and form the nanoparticles. An infrared spectroscopic technique was conducted to confirm the formation of nanoparticles as a result of ionotropic interaction between TPP and chitosan. Zeta Sizer was used to determine the size, polydispersity index (PdI) and zeta potential of the prepared nanoparticles. The morphological characteristics of CNPs were measured by field emission scanning electron microscope. During the formation of CNPs, the rHuKGF was entrapped in the nanoparticles. The loading capacity of rHuKGF in CNPs was observed to be dependent on how much amount of rHuKGF/TPP solution was added to convert all the chitosan molecules to form nanoparticles. A double beam UV/Vis spectroscopic method was used to detect the formation of these rHuKGF loaded CNPs based on their optical properties. Results: The produced rHuKGF-loaded CNPs were colorless, cloudy, and positively charged monodisperse with a spherical shape. The prepared CNPs have particles size of 119 ± 74.62 nm, surface charge of +20.3 ± 6.46 mV and 0.217 polydispersity index. The shape of prepared CNPs was found to be spherical using field emission scanning electron microscope (FESEM). The interfacial polyelectrolyte complexation between TPP and chitosan was confirmed by comparing the FTIR spectra of TPP, chitosan, physical mixture of chitosan and TPP and CNPs. The loading capacity of the rHuKGF in CNPs was found to be 93.3 ± 2.02%. The formation of rHuKGF loaded CNPs was detected by double beam UV/Vis Spectroscopy at 232.2 nm. Conclusion: The results of the current work were utilized for designing a continuous monitoring and detection system for the formation of CNPs. The outcomes of this technique are useful to avoid the loss of rHuKGF during nanoparticle formation and improving the loading capacity of CNPs.

Background: Hydrogen sensors are micro/nano-structure that are used to locate hydrogen leaks. They are considered to have fast response/recovery time and long lifetime as compared to conventional gas sensors. In this paper, fabrication of sensitive capacitive-type hydrogen gas sensor based on Ni thin film has been investigated. The C-V curves of the sensor in different hydrogen concentrations have been reported. Method: Dry oxidation was done in thermal chemical vapor deposition furnace (TCVD). For oxidation time of 5 min, the oxide thickness was 15 nm and for oxidation time 10 min, it was 20 nm. The Ni thin film as a catalytic metal was deposited on the oxide film using electron gun deposition. Two MOS sensors were compared with different oxide film thickness and different hydrogen concentrations. Results: The highest response of the two MOS sensors with 15 nm and 20 nm oxide film thickness in 4% hydrogen concentration was 87.5% and 65.4% respectively. The fast response times for MOS sensors with 15 nm and 20 nm oxide film thickness in 4% hydrogen concentration was 8 s and 21 s, respectively. Conclusion: By increasing the hydrogen concentration from 1% to 4%, the response time for MOS sensor (20nm oxide thickness), was decreased from 28s to 21s. The recovery time was inversely increased from 237s to 360s. The experimental results showed that the MOS sensor based on Ni thin film had a quick response and a high sensitivity.

Description: Design methods of nanoparticle formulations are divided into break-down methods and build-up methods. The former is further divided into dry and wet processes. For drug nanoparticle preparations, the wet process is generally employed, and organic solvents are used in most formulations. Method: In this study, we investigate the preparation of nifedipine (IB) and griseofulvin (GF) nanoparticles without using organic solvent. Both IB and GF nanoparticles, with a mean particle size of approximately 50 nm, were prepared without organic solvent by employing a combination of roll milling and high-pressure homogenization. Result: The X-ray diffraction peak of the IB and GF samples prepared by roll milling was present at a position (2) identical to that of IB and GF crystals, indicating that no peak shift was induced by interaction with phospholipids. Conclusion: These findings demonstrate that most IB and GF nanoparticles exist as crystals in phospholipids.

Background: The conversion of sunlight to electrical power has been dominated by solidstate junction devices, often made of silicon. However, this dominance is now being challenged by the emergence of the new generation of water splitting cell (integration of photovoltaic system with an electrolyzer to generate clean and portable H2 energy carrier. This cell normally is based on nanocrystalline materials, which offers the prospect of cheap fabrication together with other attractive feature such as high chemical stability and flexibility in aqueous solution under evolving oxygen (O2) gases. However, nanocrystalline materials are facing few drawback such as recombination losses of charge carriers and less response under visible spectrum. Therefore, an effort to minimize the recombination losses of charge carriers and extended the spectral response of TiO2 NTs into visible spectrum by incorporating an optimum amount of lower band gap and suitable band edge position semiconductor (cadmium selenide [CdSe]) into the lattice of TiO2 NTs. Methods: An efficient approach has been demonstrated in this research work to enhance the solardriven photoelectrochemical (PEC) water splitting performance by decorating CdSe species into highly ordered TiO2 nanotubes (NTs) film through a facile and cost-effective chemical bath deposition. Morphology, chemical properties, and electronic structures have been studied. Results: A maximum photocurrent density of ~2.50 mA/cm2 at 0.6V versus Ag/AgCl electrode was exhibited by TiO2 NTs with the presence of approximately 1 at % of CdSe species. The presence of CdSe species offered an improvement of photocurrent density under solar irradiation due to the effective mediators to trap the photo-induced electrons and minimizes the recombination of charge carriers within the lattice of TiO2 NTs. Conclusion: Hybrid CdSe-TiO2 NTs were successfully fabricated through chemical bath deposition method in order to study the synergistic coupling effect of CdSe with TiO2 NTs on the PEC performance. By bathing pure TiO2 NTs film in a 5 mM CdSe precursor solution extensively covered by approximately 1 at % CdSe exhibited the highest jp of 2.50 mA/cm2 among the samples. However, excessive deposition (≥5 mM) was neither negatively affected by the self-organized NTs nor decreased in jp. This condition inferred that higher ionic product (Cd and Se ions) leaded to rapid ion-by-ion condensation or adsorption of colloidal particles clogged the opening pore's mouth of TiO2 NTs. Thus, an improvement in the photoresponse was observed when optimum amount (~ 1 at %) of the CdSe was deposited on TiO2 NTs film.

Background: Nano-Co3O4 has been used in various technological areas and applications such as electrochemical sensors and electrochemical water splitting. Even though many efforts have been expended to prepare nano-Co3O4, the development of novel methods to prepare Co3O4 using simple processes and at low cost remain a topic of interest. Besides, it could be economic and useful if the synthesized nanoparticle could be applied as efficient electrocatalyst upon its immobilization on a cheap base electrode material by very simple method for various practical applications including renewable energy. Method: We prepared nano-Co3O4 by a direct thermal decomposition of an inexpensive, simple and widely available cobalt inorganic precursor, such as Co(NO3)2·6H2O without any type of prereaction or processing. The nano-Co3O4 was immobilized on filter-paper-derived carbon electrode by drop-drying method for applying as electrode materials toward water electrooxidation. Results: The X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy analysis confirmed the formation of short nanorods of single-phase Co3O4 upon thermal decomposition of Co(NO3)2·6H2O at 520°C. The electrocatalytic properties of the nano- Co3O4 were evaluated after immobilizing it on a cheap carbon electrode derived from normal filter paper. The modified electrode showed good electrocatalytic properties toward water oxidation in an alkaline solution. Conclusion: In conclusion, we developed a very simple, straight-forward and economic method for preparation of nano-Co3O4 and immobilized it on very cheap carbon electrode for evaluating its electrocatalytic properties. Due to the high electrocatalytic properties, the prepared nano-Co3O4 could potentially play an important role in various practical fields.

Background: Metal chalcogenide nanomaterials represent an important group of efficient materials, in which the subtle variations in shape, size and phase of nano-powders resulted in physical properties (e.g., electronic and optical) differing from their bulk counterparts, which makes them useful materials for various technological devices. Objective: Synthesis and growth of chalcogenide nano powders from novel single source molecular precursors (i.e., Cd(II) bis-(aminopropane) selenide, Cd(II) bis-(aminoethane) telluride) for the production of cadmium chalcogenide (CdE, E= Se/Te) at nano scale. Method: Single source molecular precursor inserted in quinoline, acting as a coordinating solvent at suitable temperature, yielded vacuum dried powders of CdSe and CdTe nanomaterials. Results: The average particle size was estimated as CdSe ≈ 3 nm, and CdTe ≈ 29 nm from powder X-ray diffraction pattern of synthesized nanoparticles. The produced nanomaterials possess optical properties and calculated energy band gap of nanoparticles as CdTe = 5.2 eV and CdSe = 4.0 eV from UV-Visible spectra. Conclusion: The economical, harmless single source molecular method may be a striking technique to fabricate metal chalcogenide nanoparticles.