Table of contents

Over the last several decades, interest in quasi-one dimensional charge transport has progressed from the seminal discoveries of Landauer quantization of conductance as a function of carrier density, to significant finer-scale phenomena. Those include: (i) fractional conductance, or '0.7 anomaly'; (ii) zero-bias anomaly; (iii) Rashba-effect anomalies; and (iv) apparent violation of the Landauer upper bound on conductance. In this work we present a very short summary of the first three items. The last anomaly, which remained theoretically unexamined until recently, is discussed in detail with emphasis on novel low-dimensional physics.

Multi-walled carbon nanotubes (MWCNTs) were prepared by thermal chemical vapor deposition at 750 °C, and WO₃ nanobricks with an average size of 80 nm were synthesized by a hydrothermal route. MWCNTs and WO₃ were mixed at different mass ratios in dimethylformamide solution to obtain composite materials. The WO₃/MWCNT composite-based sensors were used for detection of NH₃ gas. The gas-sensitive properties of the sensors were compared with those of pure CNT- and WO₃-based sensors. The fabricated WO₃/CNT composite sensors exhibited higher response, and faster response/recovery time than the other sensors at room temperature. In this work a possible mechanism conducting to the improvement of the hybrid sensors performance is proposed.

In this paper, a nanosensor has been developed to detect metal Fe3 + ions based on gold nanorods. The gold nanorods used in this research were synthesized using a modified seed-mediated growth method that minimizes the presence of spherical gold nanoparticles in the solution and, with controlled growth of nanorods, uniformly distributes them in the solution. Under reaction conditions, iron metal ions react with gold nanorods, resulting in a change in the structure of the nanoparticles and, consequently, their plasmonic properties. The detection of Fe³⁺ ions was carried out solely by the absorption mechanism and due to the changes in the longitudinal plasmon wavelength of the gold nanorods. One of the important achievements of this method is the detection limit of water-soluble Fe³⁺ ions, which is obtained at 0.1 ppm. The properties of gold nanorods and the interaction of Fe³⁺ ions with nanosensors were studied using a UV–vis spectrophotometer; FT-IR, XRD and transmission electron microscopy (TEM) spectroscopies were used to investigate the morphology and nature of synthetized gold nanorods. In this research, a new nanosensor was introduced to detect water-soluble Fe³⁺ ions at a concentration of parts per million (ppm), which could eliminate the need for complex chemical sensors and advanced expensive equipment, and provide a simple, low-cost and highly selective detection platform.

Density of charge carriers, introduced due to nitrogen vacancies, is estimated for SmN and EuN thin films. SmN is found to be weakly doped by nitrogen vacancies with an estimated carrier density of the order of 10²⁴−10²⁵ m⁻³ whereas the EuN thin film is heavily doped with the carrier density of the order 10²⁷ m⁻³. The free carriers cause the significant optical absorption in the sub-gap region and mask the true energy gap. Further, the onset of the interband transition for the SmN is around 1.2 eV and for the EuN it is 0.9 eV. The results indicate a disagreement in the theoretical and the experimental values.

Electrohydrodynamic jet (E-jet) printing is an advanced printing technique using an electric field to create the flow of inks from a nozzle via electrohydrodynamics. This technique can deliver very small droplets or flows of inks for high resolution printing. Here, we describe the fabrication of an anode functional layer for an electrolyte-supported solid oxide fuel cells using E-jet printing technique. An ink containing nickel oxide and 10% scandia-stabilized zirconia (10ScSZ) was used to print on an electrolyte plate. Different printing parameters were investigated to vary the structure and morphology of the printed layer. A multiple anode functional layer was fabricated following the optimal printing parameters. The results showed that the thickness of the lines of the printed grid-structured layer could be altered by changing the printing speed. In addition, the grid interval could be easily adjusted. Moreover, multiple overlapped grid layers could be quickly fabricated by printing another layer on a printed dried layer. This anode structure is very beneficial for fuel cell since it possesses a high porosity for quick diffusion of fuel gas and an increased active surface area for enhancing electrochemical reactions. The results showed that the open-circuit voltage (OCV) values of both cells were approximately 1.1 V although the anode functional layer fabricated by using E-jet printing was 7–10 times thinner than that using screen printing.

By embedding a thin ZnO layer sandwiched between the hole transport and photoactive layers, organic solar cells (OSC) based on poly(3-hexylthiophene) (P3HT) were prepared by spincoating. UV–vis spectra of the composite films showed that ZnO exhibited a suitable buffer layer that could block holes movement throughout the heterojunction of ITO/ZnO. The enhancement in the fill factor (FF) of the buffer-OSC (BOSC) is attributed to the presence of nanoheterojunctions of ZnO/PCBM and ZnO/ITO. For the normal temperature, the increase of the open-circuit potential and short-circuit current resulted in an overall increase of the energy conversion efficiency. Comparing to OSCs without buffer layer (WOSC), the laminar structure of ITO/ZnO/P3HT/PCBM/Li/Al cells possess a much larger photovoltaic energy conversion efficiency, namely 2.12% (for BOSC) compared to 1.75% (for WOSC).

In this study the novel approach for fabricating thin film Ag/AgCl electrodes was proposed using electron beam evaporation method for potential measurements as reference electrodes. A silver and silver/silver chloride (Ag/AgCl) thin films with a thickness of 300 nm were evaporated on the silicon substrate which had been initially oxidized to create the insulating silicon dioxide (SiO₂) layer. The dimension of the electrodes was about 0.5 mm × 2.0 mm. The characterization of AgCl layers was performed with field emission scanning electron microscopy, x-ray diffraction and energy dispersive x-ray spectroscopy, Raman spectroscopy and optical microscopy. The open circuit potential (OCP) measurements in buffer solution pH 7 were investigated between the fabricated Ag/AgCl electrodes and a commercial Ag/AgCl electrode as the reference electrode. The measured OCP values had insignificant disparity. The good reproducibility and potential stability with the average potential value and deviation were within 334.0 mV ± 4.07 mV. In addition, a pH sensing test was also performed by using a laboratory-made potentiometer, which showed a sensitivity of 48.01 mV pH⁻¹, with the correlation coefficient being greater than 0.99. The results showed that the fabricated thin film Ag/AgCl electrodes which could be obtained by a simple and fast process had high purity and could be used as reference electrodes for potential measurements.

Green synthesis of materials have received increasing attentions in the field of nanotechnology due to its characteristics of low-cost, high-efficiency, non-toxicity, and eco-friendly manner. In the present study, iron oxide nanoparticles (IONPs) were successfully synthesized using aqueous leaf extract of Teucrium polium as a low-cost and simple green technique to evaluate their effective applicability as dye degradation nanomaterial. The synthesis part comprises the reaction of Fe³⁺ to obtain spherical-shaped iron oxide nanoparticles with sizes in the range of 5.68 to 30.29 nm, which were further characterized using various techniques such as transmission electron microscopy (TEM), particle size analysis (PSA), x-ray diffraction pattern (XRD), Fourier transform infrared (FT-IR) spectroscopy, vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA). Additionally, the dye degradation activity of these nanoparticles was studied with the degradation of model dye methyl orange (MO). Remarkably, the results showed that the green synthesized IONPs were able to decolorize MO dye with 73.6% efficiency in a 6-h reaction, and so have the potential to serve as effective catalyst for environmental remediation.

Magnetic nanoparticles (MNPs) have attracted significant interest thanks to their small size, supermagnetism and low toxicity. However, with their large surface area, MNPs tend to aggregate and are sensitive to oxidation. To overcome this drawback, one of the solutions is surface modification of MNPs using many kinds of coating materials. Among them, carboxymethyl dextran is commonly used due to its high density of carboxymethyl groups which provide negative charge for stabilizing the ferrofluid and are available for attaching bioactive molecules. In this study we describe new methods of using microwave in carboxymethylation and Fe₃O₄ MNPs synthesis. Curcumin was then loaded on the coated MNPs to form a drug delivery system. The systems then were characterized and tested for cytotoxicity on cancer cells. Results show that our drug delivery system had small size of about 15–20 nm and saturation magnetization of 48.6 emu g⁻¹. Moreover, our system had strong anticancer effect against Hep-G2 and LU-1 cancer cell lines. Therefore, it can be a promising candidate for a novel anticancer treatment.

Nano-photocatalysis offers an environmentally friendly method, low cost process, and easy handling operation. In addition, converting cellulose as an abundant waste of agricultural side-product into glucose and alcohol sugar is interesting and challenging. LaCrO₃ nano photocatalyst was prepared using sol-gel and freeze-drying method. After the gelation and freeze-drying process, the precursors were subjected directly to the calcination treatment at 600, 700, and 800 °C, respectively. Then, the samples were subsequently characterized using x-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy (DRS), Fourrier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The results proved that LaCrO₃ crystalline phase is formed and its grain size is approximately 30 nm. DRS analysis also proved that band gap energy is affected by temperature calcination, and its value is around 2.9 eV. Its activity test said that the calcination temperature affected the conversion of cellulose. The cellulose conversion is more than 20% with the yield of alcohol sugar more than 600 ppm in 45 min exposure of the UV irradiation.

Recently, high residue of antibiotics in aquaculture products, which is a serious problem in aquaculture industry, has caused not only difficulties for export but also human health problems. In fact, many publications mentioned solutions for alleviating antibiotic content in disease treatment. Application of metal and metal oxides nanoparticles in bacterial treatment has been attracted abundant interests because of their distinctive properties in killing bacteria. For example, TiO₂ nanoparticles exhibit photocatalytic property in water producing reactive radicals for killing bacteria. Silver nanoparticles can interact with bacterial membrane and molecular structure leading to dysfuction of bacteria. In this study, a drug delivery system combining doxycycline (an antibiotic), TiO₂ and silver nanoparticles was prepared by multi-step procedure with the aim of improving bacterial treatment effectiveness. Morphology, size, zeta potential, compositions, doxycycline content of the nanoparticles were characterized by field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and UV-visible spectrometer (UV-Vis) methods. The results showed that doxycycline loaded Ag decorated TiO₂ nanoparticles have spherical shape with diameter in the range of 50–100 nm, zeta potential of −34 mV. In vitro tests on White-leg shrimp (Litopenaeus vannamei) infected Vibrio parahaemolyticus demonstrated the potential of nanoparticles in preventing and treating disease induced by Vibrio parahaemolyticus on white-leg shrimp.

This paper utilized urea functionalized multiwalled carbon nanotubes fertilizer as plant nutrition for rice to understand fully their mechanism of interaction. Surface modification of multiwalled carbon nanotubes was treated by nitric acid at different reflux times. The individual and interaction effects between the design factors of functionalized multiwalled carbon nanotube amount and functionalization reflux time with the corresponding responses of nitrogen uptake and nitrogen use efficiency were structured via the Response Surface Methodology based on five-level central composite design. The urea functionalized multiwalled carbon nanotubes fertilizer with optimized 0.5 weight% functionalized multiwalled carbon nanotubes treated at 21 h of reflux time achieve tremendous nitrogen uptake at 1180 mg/pot and NUE up to 96%. The FT-IR results confirm the formation of acidic functional groups of functionalized MWCNTs and UF-MWCNTs. The morphological observation of transmission electron microscopy shows extracellular regions to be the preferred localization of functionalized multiwalled carbon nanotubes in fresh plant root cells independent of their size and geometry. Penetration into the plant cell results in breaching of graphitic tubular structure of functionalized multiwalled carbon nanotubes with their length being shortened until ∼50 nm and diameters becoming thinner until less than 10 nm. The capability to agglomerate after translocation into the plant cells alarms potential cytotoxicity effect of functionalized multiwalled carbon nanotubes in agriculture. These work findings have suggested using urea functionalized multiwalled carbon nanotubes for effective nutrient delivery systems in rice plant.

A liquid flame spray (LFS) nanoparticle deposition process was used to generate glass surfaces with silver (Ag) and titania (TiO₂) nanoparticles for antibacterial activity against two common pathogenic bacteria causing community-associated and hospital-acquired infections, gram positive Staphylococcus aureus (S aureus) and gram negative Escherichia coli (E coli). All nanoparticle coatings increased antibacterial activity compared to a reference glass surface. The Ag nanoparticle coatings showed the highest antibacterial activity with E coli. On the contrary, TiO₂ nanoparticle coatings were found to have a higher antibacterial activity against S aureus than E coli. No significant differences in antibacterial activity were observed between the two used nanoparticle deposition amounts.

This paper develops a novel and convenient approach to deposit poly(3,4-ethylenedioxythiophene)-reduced graphene oxide (PEDOT-rGO) hybrid film in aqueous solution through electrochemical process. The PEDOT-rGO film exhibited supperior charge transfer capability with charge transfer resistance of 1333 Ω.cm⁻² and standard transfer rate constant of 0.145 s⁻¹, which makes it a promising material for electrochemical sensing applications. The glassy carbon electrode modified with PEDOT-rGO showed good electrocatalytic performance towards acetaminophen with limit detection of 5.74 μM, linear concentrations ranging from 10 to 60 μM and sensitivity of 23.5 μA.μM⁻¹.cm⁻². The use of acetaminophen sensor based on PEDOT-rGO in analysing Vietnamese traditional medicaments was demonstrated.

Fe₂O₃/TiO₂ composite has been extensively studied for heavy metals removal and photocatalysis. In photocatalysis, this composite was used for the degradation of organic dye pollutants. Herein, we reported a green approach to fabricate Fe₂O₃/TiO₂ nanoparticles from ilmenite ore. The Fe₂O₃/rutile was synthesized by one-step reaction of ilmenite at 700 °C in 3 h, the raw Fe₂O₃/rutile composite was, then, grounded by a ball-milled process in 4 h to obtain nanostructured composite. The obtained Fe₂O₃/rutile nanoparticles have the diameter of 50–100 nm with the BET surface area of 7 m² g⁻¹. The adsorption behaviour of the nanostructured Fe₂O₃/TiO₂ composite as adsorbent toward arsenic (particularly, oxidized form of arsenic [As(V)]) was investigated by carrying out batch adsorption. The adsorption isotherm was investigated by using both the Langmuir and Freundlich models. The sorption kinetics of adsorbent toward arsenic adsorption was found to be pseudo-second order. The Fe₂O₃/TiO₂ composite exhibited fast and high adsorption capacity of 47.12 mg g⁻¹ toward arsenic in various solution pHs. The composite was also found to be durable and recyclable for arsenic adsorption. Therefore, this as-prepared Fe₂O₃/TiO₂ composite could be promising and cost-effective adsorbent for effective removal of arsenic contaminant from aqueous environment.

In this work, we reported on the development of a sensor platform for the detection of 17β-Estradiol (E2). The artificial receptors for targets were fabricated on gold nanoparticles (AuNPs)-modified screen-printed carbon ink electrode. This is an applicable technical solution to overcome main limitations of current membrane molecularly imprinted polymer (MIP) technology. The AuNPs layer will increase specific area of electrode, hence increasing number of imprinted analyte molecules to polymer membrane. Especially, the harmonic distribution of AuNPs on the electrode helps to generate a single oriented monomer layer on the electrode. In turn, this layer helps to generate a highly homogeneous membrane of polymer with thickness of only several single layers to easily remove imprinted molecules from polymer matrix to form highly specific cavities, thus increasing the efficiency of the fabrication of artificial MIP bioreceptors. Our fabricated sensors showed the capability of detection limit (LOD) of 2 fM. The sensor also demonstrated reduced cost (cost of carbon ink printed electrode but can use as gold ink printed electrode), detection platform simplicity, and high reproducibility.