Table of contents

The rapid and successful development of the research on graphene and graphene-based nanostructures has been substantially enlarged to include many other two-dimensional hexagonal semiconductors (THS): phosphorene, silicene, germanene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) such as MoS₂, MoSe₂, WS₂, WSe₂ as well as the van der Waals heterostructures of various THSs (including graphene). The present article is a review of recent works on THSs beyond graphene and van der Waals heterostructures composed of different pairs of all THSs. One among the priorities of new THSs compared to graphene is the presence of a non-vanishing energy bandgap which opened up the ability to fabricate a large number of electronic, optoelectronic and photonic devices on the basis of these new materials and their van der Waals heterostructures. Moreover, a significant progress in the research on TMDCs was the discovery of valley degree of freedom. The results of research on valley degree of freedom and the development of a new technology based on valley degree of freedom-valleytronics are also presented. Thus the scientific contents of the basic research and practical applications os THSs are very rich and extremely promising.

Nanomagnetism is a subject of great interest because of both application and fundamental aspects in which understanding of the physical and electromagnetic structure of magnetic nanostructures is essential to explore the magnetic properties. Transmission electron microscopy (TEM) is a powerful tool that allows understanding of both physical structure and micromagnetic structure of the thin samples at nanoscale. Among TEM techniques, in situ TEM is the state-of-the-art approach for imaging such structures in dynamic experiments, reconstructing a real-time nanoscale picture of the properties–structure correlation. This paper aims at reviewing and discussing in situ TEM magnetic imaging studies, including Lorentz microscopy and electron holography in TEM, applied to the research of magnetic nanostructures.

The research on magnetic resonances in typical meta-atoms has led to the discovery of electromagnetic metamaterials (MMs). These new materials played a crucial role in achieving extraordinary phenomena as well as promised potential applications. In this paper, we numerically and experimentally investigated two different MM effects: the absorption and the negative refraction, which induced by magnetic resonances in a symmetric structure. The meta-atom sandwich model that includes two parallel flat rings separated by an insulating slab was designed. Firstly, three resonances in sub-wavelength range were demonstrated, revealing the negative permittivity and permeability effects. Notably, negative refractive index (NRI) was gained at the third-gap resonance, resulting from superposition of the rest of the electric resonance and the magnetic one accompanied by multi-plasmon. Moreover, the manipulation of the structural parameters could control the NRI behavior and, interestingly, a nearly perfect absorption peak arises in shallow sub-wavelength regime.

The photocatalytic BiFeO₃ perovskite nanoparticles were fabricated by gel combustion method using polyvinyl alcohol and corresponding metal nitrate precursors under the optimum mild conditions such as pH 2, gel formation temperature of 80 °C, metal/polyvinyl alcohol molar ratio of 1/3, metal molar ratio Bi/Fe of 1/1 and calcination temperature at 500 °C for 2 h. The prepared sample was characterized by x-ray diffraction, field scanning electron microscopy, transmission electron microscopy, Brunauer–Emmetl–Teller nitrogen adsorption method at 77 K, energy dispersive x-ray spectroscopy, ultraviolet-visible light spectrophotometry, and thermal analysis. The effects of molar ratios of starting material and calcination temperature on phase formation and morphology were investigated. The degradation of methylene blue, methylene orange and some toxic organic compounds such as phenol and diazinon under visible light irradiation by photocatalytic BiFeO₃ nanoparticles were evaluated at different parameters and conditions such as the light intensity determined from the light source to the measured sample, the addition H₂O₂, reaction time and the regeneration performance. Obtained results showed that the synthesized perovskite BiFeO₃ nanoparticles for the optimized sample have a size smaller than 50 nm and the high mean surface area of 50 m² g⁻¹. Degradation efficiency was almost 90.0% for methylene blue and 80.0% for methylene orange with added H₂O₂ after 30 min of reaction. After the 3rd time of regeneration, the BiFeO₃ nanoparticles still have 92.8% of the degradation performance for removing methylene blue. Phenol and diazinon toxic compound were degraded with the performance of 92.42% and 85.7%, respectively, for 150 min

Green function technique is a very efficient theoretical tool for the study of dynamical quantum processes in many-body systems. For the study of dynamical quantum processes in graphene ribbons it is necessary to know two-point Green functions of free Dirac fermions in these materials. The purpose of present work is to establish explicit expressions of two-point Green functions of free Dirac fermions in single-layer graphene ribbons with zigzag and armchair edges. By exactly solving the system of Dirac equations with appropriate boundary conditions on the edges of graphene ribbons we derive formulae determining wave functions of free Dirac fermions in above-mentioned materials. Then the quantum fields of free Dirac fermions are introduced, and explicit expressions of two-point Green functions of free Dirac fermions in single-layer graphene ribbons with zigzag and armchair edges are established.

The present scientific endeavour focuses on the optimization of process parameters using central composite design towards development of an efficient technique for the biosynthesis of silver nanoparticles. The combined effects of three process variables (days of fermentation, duration of incubation, concentration of AgNO₃) upon extracellular biological synthesis of silver nanoparticles (AgNPs) by Aspergillus wentii NCIM 667 were studied. A single absorption peak at 455 nm confirming the presence of silver nanoparticles was observed in the UV-visible spectrophotometric graph. Using Fourier transform infrared spectroscopic analysis the presence of proteins as viable reducing agents for the formation AgNPs was recorded. High resolution transmission electron microscopy showed the realization of spherically shaped AgNPs of size 15–40 nm. Biologically formed AgNPs revealed higher antimicrobial activity against gram-negative than gram-positive bacterial strains. We present the enumeration of the properties of biosynthesized nanoparticles which exhibit photocatalysis exhausting an organic dye, the methyl orange, upon exposure to sunlight thereby accomplishing the degradation of almost (88%) the methyl orange dye within 5 h.

A disposable card incorporating specific DNA probes targeting the 16 S rRNA gene of Streptococcus suis was developed for magnetically labeled target DNA detection. A single-stranded target DNA was hybridized with the DNA probe on the SPA/APTES/PDMS/Si as-prepared card, which was subsequently magnetically labeled with superparamagnetic beads for detection using an anisotropic magnetoresistive (AMR) sensor. An almost linear response between the output signal of the AMR sensor and amount of single-stranded target DNA varied from 4.5 to 18 pmol was identified. From the sensor output signal response towards the mass of magnetic beads which were directly immobilized on the disposable card surface, the limit of detection was estimated about 312 ng ferrites, which corresponds to 3.8 μemu. In comparison with DNA detection by conventional biosensor based on magnetic bead labeling, disposable cards are featured with higher efficiency and performances, ease of use and less running cost with respects to consumables for biosensor in biomedical analysis systems operating with immobilized bioreceptor.

The inhibition effect of magnetic nanofluid  on carbon steel in acid solutions was investigated using gravimetric, potentiodynamic and SEM measurement. The inhibition efficiency increases up to 95% and 75% for 51.7 mM concentration, respectively, in 1 M HCl and 1 M H₂SO₄ medium. The adsorption of nanoparticles to the steel surface forms a barrier between the metal and the aggressive environment, which is responsible for observed inhibition action. The adsorption of nanoparticles on steel surface is supported by the Langmuir and Freundlich adsorption isotherm and surface morphology scanned through SEM.

ZnO and potassium doped ZnO nanoparticles were synthesized through wet chemical method. The samples were characterized by UV, XRD, SEM, TEM and EDAX. XRD analysis reveals that the prepared nanoparticles exhibit hexagonal wurtzite structure. TEM and SEM analyses disclose that synthesized samples were porous structure with needle shape. It also confirms that potassium was dispersed on ZnO surface. The influence of potassium on ZnO surface modulates the degradation of textile dyeing wastewater by improving its rate of decomposition to 0.007 min⁻¹ with decoloration. A better zone of inhibition of about 20 mm against Staphylococci aureus and Pseudomonas aernginosa by ZnO and potassium doped ZnO nanoparticles were measured. The findings suggest that these nanoparticles have the potential to be a good photocatalyst and applied in water treatment to inhibit the bacterial growth.

The present study focuses on the biosynthesis of silver nanoparticles (AgNPs) along with its antibacterial and photocatalytic activity. The AgNPs were synthesized using Cordia dichotoma leaf extract and were characterized using UV-vis spectroscopy to determine the formation of AgNPs. FTIR was done to discern biomolecules responsible for reduction and capping of the synthesized nanoparticles. Further, DLS technique was performed to examine its hydrodynamic diameter, followed by SEM, TEM and XRD to determine its size, morphology and crystalline structure. Later, these AgNPs were studied for their potential role in antibacterial activity and photocatalytic degradation of azo dyes such as methylene blue and Congo red.

In this work anti-cancer drug curcumin-loaded superparamagnetic iron oxide (Fe₃O₄) nanoparticles was modified by chitosan (CS). The magnetic iron oxide nanoparticles were synthesized by using reverse micro-emulsion (water-in-oil) method. The magnetic nanoparticles without loaded drug and drug-loaded magnetic nanoparticles were characterized by XRD, FTIR, TG-DTA, SEM, TEM, and VSM techniques. These nanoparticles have almost spherical shape and their diameter varies from 8 nm to 17 nm. Measurement of VSM at room temperature showed that iron oxide nanoparticles have superparamagnetic properties. In vitro drug loading and release behavior of curcumin drug-loaded CS-Fe₃O₄ nanoparticles were studied by using UV-spectrophotometer. In addition, the cytotoxicity of the modified nanoparticles has shown anticancer activity against A549 cell with IC₅₀ value of 73.03 μg/ml. Therefore, the modified magnetic nanoparticles can be used as drug delivery carriers on target in the treatment of cancer cells.

Electrical conductivity of zinc oxide nanoparticles (ZnO NPs)-decorated bacterial nanowires is investigated in the present work. The ZnO NPs are prepared through a simple precipitation method and characterized by UV–vis spectrophotometer, Fourier transform infrared spectroscopy, x-ray diffraction, atomic force microscopy (AFM), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The SEM analysis discloses that the prepared ZnO NPs are spherical in shape with an average particle size of 3.5 nm. The ZnO NPs are decorated on the surface of bacterial nanowires and the same are characterized by AFM and HRTEM. The electrochemical performance of the bare bacterial nanowires and ZnO NPs-decorated bacterial nanowires is analyzed by cyclic voltammetry and linear sweep voltammetry, whereas their electrical conductivity is measured by electrochemical impedance spectroscopy. The results of the electrochemical investigations indicate that the ZnO NPs coating on the surface of bacterial nanowires improve the electrical conductivity of the bacterial nanowires.

The syntheses of Ag/M (M is Co, Ni, Pd, Pt and Ru) alloyed nanobimetallic particles in tri-n-octylphosphine oxide and oleic acid matrices were successfully carried out by the successive reduction of ligand capped metal ions with polyols, which resulted in rapid precipitation of some fractal high index faceted hybrid Ag/M bimetal nanoparticles. The optical measurements revealed the existence of modified surface plasmon band and peak broadening resulting from reaction-limited growth processes of the metal sols, making it possible to monitor the changes spectrometrically. The bimetallic nanoparticles were further characterized by powder x-ray diffraction, x-ray photoelectron spectroscopy and electron microscopy techniques which confirmed the formation of novel core–shell and alloyed clusters. The Ag/M nanoparticles thus synthesized within TOPO/OA matrices indicated significant reduction potential as a result of their energy band gap 2.65–2.77 eV which points to the fact that they could serve as reducing agents for electrocatalytic reaction.

The clinical utility of important therapeutic agents is often limited by the poor permeability of biological membranes. Cell penetrating peptides are usually employed to circumvent this challenge. This approach, coupled with gold nanoparticles, are a promising vehicle for drug delivery due to its good biocompatibility profile, negligable toxicity and possibility for multi-functionalization. Here we report the functionalization and intracellular tracking of gold nanoparticles decorated with a TAT cell penetrating peptide and a fluorescein tag in a simple, two step process. Fluorescence microscopy has confirmed the localization of the functionalized nanoparticles to be inside the cells, specifically within, or in close proximity to the nuclei of MT-4 lymphocytes; a HIV-relevant cell line in which this has not been previously demonstrated. The results of this study demonstrate that TAT has been efficiently conjugated to gold nanoparticles to facilitate both cellular and targeted nuclear entry.

Soybean crop losses due to fungal diseases are considerable and directly depend on the severity of the disease. The objective of this study was to assess antifungal activity of silver/silica (Ag/SiO₂) nanocomposite against crop pathogenic fungi (Fusarium oxysporium and Rhizoctonia solani) in soybean farming. Firstly, silica particles with a size ranging from 20 to 30 nm were modified with 3-aminopropyl triethoxysilane (APTES) for 2 h. Then these amino acid - functionalized silica particles were exposed to silver ion solution followed by reduction of silver ions with sodium borohydride to form Ag/SiO₂ nanocomposite. The formation of the linkage between APTES and silica particles was confirmed by Fourier transform infrared (FTIR) spectroscopy. The surface plasmon absorption maximum at 400 nm confirmed the nano essence of the silver particles on silica particles. For the seed coating, bentonite from Lam Dong deposit, Vietnam, was used as an encapsulation substance, while carboxymethyl cellulose (CMC) was used as a binding agent. The assessment of fungicidal activity of the Ag/SiO₂ nanocomposite produced showed that this product is effective in inhibition of the pathogenic fungi in soybean plant.

This study aims to enhance the mechanical properties, thermal stability, weathering resistance and antibacterial property of a styrene acrylic polyurethane coating by adding rutile titania dioxide (R-TiO₂) nanoparticles in coating formulation. The styrene acrylic polyurethane/R-TiO₂ nanocomposite had been prepared by using ultrasonication. The effects of nanoparticles on the mechanical properties, thermal stability and weathering resistance of as-prepared coatings were investigated by using the adhesion strength and ball impact tests, the Fourier transform infrared and UV–vis analyses, thermogravimetric analysis (TGA), and UV/condensation weathering chamber equipped with UVA-340 fluorescent lamps, respectively. The disperse quality of nanoparticles in the coating was examined by using the field emission scanning electron microscope (FESEM). The mechanical test results showed that suitable content of R-TiO₂ nanoparticles in the nanocomposite coating was 2 wt%. The FESEM images indicated that the nanoparticles were dispersed homogeneously into the entire volume of the coating. For the nanocomposite prepared by 3 h of ultrasonication, the average size of nanoparticles was in range of 40–50 nm. The ball impact and adhesion tests showed that the incorporation of nanoparticles into the coating significantly enhanced the impact strength from 120 to 145 kg cm and increased the adhesion from level 1 to level 0. The TGA test illustrated that in presence of nanoparticles, the decomposition temperature of coating increased from 146.9 °C to 154.21 °C. For the temperature at 50% loss in mass (T_50%), it was found that the T_50% of the neat coating is 351.86 °C. Adding the 2 wt% R-TiO₂ nanoparticles into coating increased the T_50% value to 360.06 °C. After UV/condensation accelerated weathering test (30 cycles), the significant improvement in weight loss, impact strength and adhesion of the neat coating was observed with the presence of nanoparticles. The antibacterial test showed that in the nanocomposite coating, R-TiO₂ nanoparticles exhibited their photocatalytic effect in the inhibition against E. coli bacterial growth. Incorporating 2 wt% of R-TiO₂ nanoparticles into the coating reduced the bacterial concentration by 6.1% after 60 min of culture.

Supercapacitors are highly promising energy devices with superior charge storage performance and a long lifecycle. Construction of the supercapacitor cell, especially electrode fabrication, is critical to ensure good performance in applications. This work demonstrates direct growth of vertically aligned carbon nanotubes (CNTs) on Fe–Ni based metal alloy foils, namely SUS 310S, Inconel 600 and YEF 50, and their use in symmetric vertically aligned CNT supercapacitor electrodes. Alumina and cobalt thin film catalysts were deposited onto the foils, and then CNT growth was performed using alcohol catalytic chemical vapour deposition. By this method, vertically aligned CNTs were successfully grown and used directly as a binder-free supercapacitor electrode to deliver excellent electrochemical performance. The device showed relatively good specific capacitance, a superior rate capability and excellent cycle stability, maintaining about 96% capacitance up to 1000 cycles.

Two-dimensional (2D) arrays of gold nanodisks (Au NDs) with different sizes of 75, 95 and 115 nm, with the distances between NDs of 10, 30 and 50 nm were fabricated on square-inch substrates. The optimal conditions regarding the thickness of anodic aluminum oxide (AAO) template, sputtering time and annealing temperature for Au, lift-off the walls of AAO template for getting the highest quality 2D arrays of Au NDs have been determined. Morphology and surface plasmon resonance (SPR) absorption of the 2D arrays of Au NDs were examined by using appropriate techniques. The 2D arrays of fabricated Au NDs show different SPRs peaking in the spectral range of 600–1600 nm, which are very promising for surface-enhanced Raman scattering (SERS)-based sensor applications. As an example for the potential use of fabricated SERS substrates, we have demonstrated the detection of methamidophos at various concentrations ranging from 1 ppb to 10³ ppm. Moreover, the method we have used to fabricate the 2D arrays of Au NDs can be applied to other kinds of metals or alloys just by varying the targets in the sputtering process.

This study describes the bioengineering of phycomolecule-coated zinc oxide nanoparticles (ZnO NPs) as a novel type of plant-growth-enhancing micronutrient catalyst aimed at increasing crop productivity. The impact of natural engineered phycomolecule-loaded ZnO NPs on plant growth characteristics and biochemical changes in Gossypium hirsutum L. plants was investigated after 21 days of exposure to a wide range of concentrations (0, 25, 50, 75, 100, and 200 mg l^−l). ZnO NP exposure significantly enhanced growth and biomass by 125.4% and 132.8%, respectively, in the treated plants compared to the untreated control. Interestingly, photosynthetic pigments, namely, chlorophyll a (134.7%), chlorophyll b (132.6%), carotenoids (160.1%), and total soluble protein contents (165.4%) increased significantly, but the level of malondialdehyde (MDA) content (73.8%) decreased in the ZnO-NP-exposed plants compared to the control. The results showed that there were significant increases in superoxide dismutase (SOD, 267.8%) and peroxidase (POX, 174.5%) enzyme activity, whereas decreased catalase (CAT, 83.2%) activity was recorded in the NP-treated plants compared to the control. ZnO NP treatment did not show distinct alterations (the presence or absence of DNA) in a random amplified polymorphic DNA (RAPD) banding pattern. These results suggest that bioengineered ZnO NPs coated with natural phycochemicals display different biochemical effects associated with enhanced growth and biomass in G. hirsutum. Our results imply that ZnO NPs have tremendous potential in their use as an effective plant-growth-promoting micronutrient catalyst in agriculture.

Curcumin is a polyphenol from turmeric Curcuma longa L that has been proved to possess numerous biological and pharmaceutical activities, including anti-cancer properties. However, curcumin has only limited clinical applications due to the aqueous insolubility characteristic that reduces its biological availability. On the other hand, using nanoparticles as drug delivery system has potential as it increases solubility of hydrophobic substances such as curcumin. Furthermore, nanoparticles can protect and control release of drug. Therefore, the objective of this project is to prepare nanoparticles by polymeric encapsulating curcumin by 1-3/1-6 β-glucan extracted from Vietnamese mushrooms to increase drug delivery efficiency and biological effect. Method of the preparation is nano-precipitation. The produced curcumin-β-glucan-nanoparticles (NanoGluCur) takes spherical shape with 60–70 nm in diameter. As expected, water solubility of curcumin increases about 180 times, from 0.6 μg ml⁻¹ to 0.11 mg ml⁻¹. Loading capacity of NanoGluCur is 18.16%. In vitro cytotoxicity and anti-tumor promoting effects of NanoGluCur were also investigated. Results revealed that NanoGluCur is able to inhibit the growth of two human cancer cell lines Hep-G2 and LU-1 with IC₅₀ values of 6.82 and 15.53 mg ml⁻¹, respectively, while free curcumin expresses the activity with IC₅₀ values of 7.41 and 18.82 mg ml⁻¹. At the concentration of 40 mg ml⁻¹, NanoGluCur showed anti-tumor promoting effects in reducing tumor size by 59.93% and tumor density by 40.52%, while the percentages caused by pristine curcumin were 41.36% and 29.14%, respectively. These results demonstrated dual effect of 1-3/1-6 β-glucan encapsulated curcumin nanoparticles: higher water solubility and better in vitro anti-cancer effects compared to free curcumin and 1-3/1-6 β-glucan, expectedly. This observation can potentially open a new approach in research and manufacture of functional foods from medicinal mushrooms.