Applied Nanoscience (v.8, #4)

Tribological study on rapeseed oil with nano-additives in close contact sliding situation by Rajeev Nayan Gupta; A. P. Harsha; Sagar Singh (567-580).
The present work deals with the tribological evaluation of three types of nano-additives, i.e., copper oxide (CuO; ≈ 151.2 nm), cerium oxide (CeO2; ≈ 80 nm) and polytetrafluoroethylene (PTFE; ≈ 90.4 nm) with rapeseed oil under steel–steel sliding contacts. The nano-additives concentrations in the base oil were 0.1, 0.25 and 0.5% w/v for the lubricant formulation. Further, the rapeseed oil was also epoxidized by a chemical method and the tribological behavior was compared with the base oil (unmodified oil) at similar nano-additives concentrations. The ASTM standards were followed for the study of wear preventive and extreme-pressure analysis of nanolubricants, and it was carried out using four-ball tester. In the antiwear test, CeO2 and PTFE nano-additives have shown the significant reduction in the wear scar diameter at the concentration of 0.1% w/v. In the extreme-pressure test, 0.5% w/v concentration was optimum for oxide nanoparticles; however, PTFE nanoparticles did not show positive effect with both the base oils. Different characterization techniques were employed to confirm the oil modification and for the study of the worn surfaces.
Keywords: Nano-additive; Epoxidation; Antiwear; Extreme-pressure; Nanolubricant

In this paper, experiments were conducted to study the tribological behavior of synthetic oil containing nanodiamond (ND) with molybdenum disulphide (MoS2) and tungsten disulphide (WS2) nanoparticles. The experiments were performed in boundary lubrication regime for steel/steel contacts. A ball on disc configuration was used to obtain the frictional characteristics of the lubricating oils at a constant velocity of 0.58 m/s. Scanning electron microscopy and energy dispersive spectroscopy were carried out to evaluate the wear behavior of the worn out disc samples. The results obtained from the investigation exhibited an improvement in both wear and friction coefficient. On addition of 0.2% ND in the oil containing MoS2 and WS2 nanoparticles, the coefficient of friction (COF) and wear volume decreased around two times in comparison to the PAO oil. The enhancement in overall lubrication behavior is mainly due to the synergism between the MoS2/ND and WS2/ND nanoparticles.
Keywords: Boundary lubrication; Wear; Friction; Nanodiamond

Comparison of magnetic properties and high-temperature phase stability of phosphate- and oleic acid-capped iron oxide nanoparticles by T. Muthukumaran; S. S. Pati; L. H. Singh; A. C. de Oliveira; V. K. Garg; John Philip (593-608).
We study the influence of dynamic capping of Fe3O4 nanoparticles with phosphate and oleic acid, on their structure, magnetic properties and thermal stability of magnetic nanoparticles. It is observed that the phosphate coating on iron oxide lowers the dipole–dipole interaction significantly, as compared to oleic acid capping. The Mössbauer results show that the spin canting order of oxidized shell and the mean hyperfine field values follow the order Fe0 (uncoated) > FeOA (oleic acid capped) > FP1 (phosphate capped). The uncoated Fe3O4 nanoparticle is non-stoichiometric in nature due to oxidation, whereas FP1 and FeOA are of the correct stoichiometry. Mössbauer and photoacoustic spectroscopic studies on air-annealed phosphate-coated magnetite nanoparticles confirm that the magnetic iron oxide phase is preserved up to 833 K and a complete conversion of Fe3O4 into the non-magnetic hematite phase occurs at 1173 K. The iron oxide air annealed at 833 K is found to have a shell of orthorhombic α-Fe2O3 over the magnetite core. However, in oleic acid-coated nanoparticles, the magnetic to non-magnetic phase transformation commences at 623 K and the conversion was complete at 823 K. The photoacoustic spectra of the air-annealed phosphate-coated Fe3O4 particles showed a flipping of the absorption intensity between 500−700 nm and 800−1000 nm, due to the conversion of Fe3O4 to γ-Fe2O3 at 923 and γ-Fe2O3 to α-Fe2O3 at 1173 K, respectively. The γ-Fe2O3 showed an intense absorption peak above 750 nm, whereas the α-Fe2O3 showed a peak broadening in the wavelength range of 600–700 nm, in addition to the strong peaks at a wavelength above 750 nm. This study suggests that the photoacoustic spectroscopy can distinguish clearly the three polymorphs of iron oxide i.e., Fe3O4, γ-Fe2O3 and α-Fe2O3. Our results confirm the ability of phosphate-capped iron oxide particles to retard the oxidation of Fe2+ contents during the crystal growth process.
Keywords: Nanomaterials; Nanoparticle; Oxide; Phase transformation; Surface coating; Stability

One can design a robust optical device by engineering the optical band gap of the quantum dots (QDs) owing to their size-tunable quantum confinement effect. To do this, understanding the optical effects of QDs and composite materials is crucial. In this context, various sizes (2.8–4.2 nm) of CdSe QDs–PMMA nanocomposite are fabricated in a two-step process and their absorbance, luminescence and optical constants studied systematically. The ellipsometry spectroscopic analysis exhibits the heterogeneous medium feature of Ψ value and also the measured refractive index (1.51–1.59) values are increased with decreased band gap (2.24–2.10 eV). The observed red shift in the UV–Vis and photoluminescence spectra is indicative of early stage CdSe QD followed by a nucleation process of bigger size QD. In addition, the growth kinetics of the reaction and the band gap of the QDs are evaluated with respect to the time to testify the colloidal QDs formation. The thickness and QD composition of the nanocomposite thin films calculated by effective medium approximation are 100 nm and 8–12%, respectively. Morphology and structural feature transmission electron microscopy study of the fabricated nanocomposite demonstrated that spherical CdSe QDs are well dispersed in PMMA.
Keywords: Quantum dots; Optical property; Nanocomposite; Ellipsometry; Absorbance; Luminescence

Phototoxicity free quantum dot-based niosome formulation for controlled drug release and its monitoring by Sunil Kumar; T. W. Kang; Suman Bala; Sunil Kamboj; H. C. Jeon (617-625).
A novel niosomes-based system composed of Hypromellose (HPMC) functionalized fluorescent, biocompatible ZnS:Mn quantum dots (QDs), and anti-HIV drug Tenofovir disoproxil fumarate (TDF) was designed. An appropriate ratio of surfactant Sorbitan Monostearate (SPAN-60) and cholesterol was used to obtain an optimal entrapment efficiency. Initially, after observing the successful interaction of HPMC with SPAN-60, the noisome formulation including (QDs + drug) and HPMC-coated QDs was synthesized by a wet chemical route and characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM) and Selected Electron Diffraction (SAED). Secondly, (QDs + drug) loaded niosome formulations were studied by varying the ratio of SPAN-60 and cholesterol. Multiple studies were done to characterize the shape, size, viscosity, colloidal stability, and entrapment efficiency of (QDs + drug) loaded niosomes. Lastly, pH-dependent (QDs + drug) release profiles were studied by a spectroscopic technique considering the pH of the human gastrointestinal region to obtain the formulation stability of (QDs + drug) release from the niosome vesicles. These studies also include pH-dependent photo-stability measurements based on laser-induced multiphoton excitation technique in the Infrared region. The multiphoton time-resolved studies were completed to avoid the UV induced phototoxicity in the drug delivery modules. Current studies on the formulation of niosomes-based (QDs + drug) system laid a foundation to make a complete phototoxicity free system for tracking controlled drug release and its imaging.
Keywords: HPMC; ZnS:Mn QDs; SPAN-60; Niosomes; Phototoxicity

Monitoring dynamic electrochemical processes with in situ ptychography by George Kourousias; Benedetto Bozzini; Michael W. M. Jones; Grant A. Van Riessen; Simone Dal Zilio; Fulvio Billè; Maya Kiskinova; Alessandra Gianoncelli (627-636).
The present work reports novel soft X-ray Fresnel CDI ptychography results, demonstrating the potential of this method for dynamic in situ studies. Specifically, in situ ptychography experiments explored the electrochemical fabrication of Co-doped Mn-oxide/polypyrrole nanocomposites for sustainable and cost-effective fuel-cell air-electrodes. Oxygen-reduction catalysts based on Mn-oxides exhibit relatively high activity, but poor durability: doping with Co has been shown to improve both reduction rate and stability. In this study, we examine the chemical state distribution of the catalytically crucial Co dopant to elucidate details of the Co dopant incorporation into the Mn/polymer matrix. The measurements were performed using a custom-made three-electrode thin-layer microcell, developed at the TwinMic beamline of Elettra Synchrotron during a series of experiments that were continued at the SXRI beamline of the Australian Synchrotron. Our time-resolved ptychography-based investigation was carried out in situ after two representative growth steps, controlled by electrochemical bias. In addition to the observation of morphological changes, we retrieved the spectroscopic information, provided by multiple ptychographic energy scans across Co L3-edge, shedding light on the doping mechanism and demonstrating a general approach for the molecular-level investigation complex multimaterial electrodeposition processes.
Keywords: Coherent diffractive imaging; Fresnel CDI; Ptychography; In situ; Oxygen reduction reaction; Electrocatalysis; Fuel cells

Defects are inevitable most of the times either at the synthesis, handling or processing stage of graphene, causes significant deviation of properties. The present work discusses the influence of vacancy defects on the quantum capacitance as well as thermodynamic stability of graphene, and the nitrogen doping pattern needs to be followed to attain a trade-off between these two. Density Functional Theory (DFT) calculations have been performed to analyze various vacancy defects and different possible nitrogen doping patterns at the vacancy site of graphene, with an implication for supercapacitor electrodes. The results signify that vacancy defect improves the quantum capacitance of graphene at the cost of thermodynamic stability, while the nitrogen functionalization at the vacancy improves thermodynamic stability and quantum capacitance both. It has been observed that functionalizing all the dangling carbons at the defect site with nitrogen is the key to attain high thermodynamic stability as well as quantum capacitance. Furthermore, the results signify the suitability of these functionalized graphenes for anode electrode of high energy density asymmetric supercapacitors.
Keywords: Supercapacitor; Graphene; Quantum capacitance; Thermodynamic stability; Defects

Impact of microwave-assisted synthesis on the morphology and rhodamine B oxidation properties of ZnO nanocomposites by Ponnusamy Rajeswari; Sivasubramanian Dhanuskodi; K. Jothi Venkatachalam (645-654).
Nanocomposites of ZnO–NiO and ZnO–SnO2 were synthesized by the microwave-assisted method. The formation of ZnO–NiO nanocomposite [ZnO (hexagonal), NiO (cubic)], and ZnO–SnO2 nanocomposite [ZnO (hexagonal), SnO2 (tetragonal)] is confirmed by XRD. FTIR evidences the molecular vibrations of Ni–O (428 cm−1), Zn–O (477 cm−1), and Sn–O (485 and 618 cm−1). FESEM micrographs show hexagonal-faceted nanocrystals (ZnO) and spherical nanoparticles (ZnO–NiO). Photoluminescence study identifies the defect states due to oxygen vacancies. Photocatalytic activity for the degradation of RhB under UV irradiation shows better efficiency for pristine ZnO (100%) and NiO (80%) nanocomposite.
Keywords: Nanocrystals; Nanocomposites; Photocatalysis; Charge trapping

Ketamine nano-delivery based on poly-lactic-co-glycolic acid (PLGA) nanoparticles by Sota Hirano; Michele Bovi; Alessandro Romeo; Flavia Guzzo; Cristiano Chiamulera; Massimiliano Perduca (655-663).
This work describes a novel method for the generation of a ketamine nano-delivery, to improve brain blood barrier permeability and increase drug therapeutic window as anaesthetic, analgesic and potential antidepressant. The approach herein described is based on ketamine-loaded poly-lactic-co-glycolic acid (PLGA) nanoparticles coupled to an apolipoprotein E (ApoE) peptide for delivery to the central nervous system. PLGA particles were synthesized with amount of drug, coupled with the ApoE peptide on the surface, and validated by physical characterization. The produced nanodevice showed a good colloidal stability in water, confirmed by zeta potential measurements, with a diameter in the range of 185–205 nm. The ketamine encapsulation was verified by liquid chromatography–mass spectrometry analyses obtaining an encapsulation efficiency up to 21.2 ± 3.54%. Once the occurrence of ApoE peptide functionalization was confirmed with fluorescence spectroscopy, the thermal stability and morphological information were obtained by differential scanning calorimetry and further dynamic light scattering measurements. The spherical shape and a rough nanoparticles surface were observed by atomic force microscopy. The reliability of this approach may be further developed as a protocol to be used to generate PLGA nanoparticles greater than 100 nm able to better penetrate blood brain barrier and release a neuroactive molecule at lower doses.
Keywords: Poly(lactic-co-glycolic acid) nanoparticles; Ketamine; Apolipoprotein E; Double emulsion; Nanodrug delivery; Anaesthesia

Impact of the titania nanostructure on charge transport and its application in hybrid solar cells by Alejandro Koffman-Frischknecht; Fernando Gonzalez; Juan Plá; Ianina Violi; Galo J. A. A. Soler-Illia; M. Dolores Perez (665-673).
Porous titania films are widely studied in a number of optoelectronic applications due to its favorable optical and electronic characteristics. Mesoporous titania thin films (MTTFs) with tunable pore size, pore order, accessibility and crystallinity are of interest in electronic devices due to the potential for optimization of the desired characteristics for charge separation and carrier transport. In this work, several MTTFs were prepared by sol–gel chemistry with different structural properties tuned by post-synthesis thermal treatment. The effect of the structural properties (pore diameter, order and accessibility) on the electrical properties of the material was studied by films fabrication onto a transparent conducting electrode, ITO, such that it enables optoelectronic applications. The performance as photoanode was explored by the fabrication of hybrid polymer (P3HT): titania solar cells. Not only does structural properties affect polymer impregnation inside the titania pores as expected and hence impacts charge separation at the interface, but also the thermal treatment affects crystallinity and the films electronic properties. A more complete picture about the electronic properties of the different MTTFs prepared in this work was studied by mobility measurement by space charge limited current and impedance spectroscopy.
Keywords: Mesoporous titania; Hybrid solar cells; Transport properties

A simple method for the synthesis of magnetite nanoparticles using the leaf extract of Calliandra haematocephala has been developed. UV–Vis spectrum showed a characteristic strong absorption band. SEM image revealed the bead-like spherical nanoparticles. EDS showed the prominent peaks for elemental iron and oxygen. PXRD patterns confirmed the crystalline nature and the average crystallite size of 7.45 nm. In addition, the lattice parameter value was calculated to be 8.413 Å, close to Fe3O4 nanoparticles. BET analysis disclosed the total specific surface area of the nanoparticles as 63.89 m2/g and the mesoporous structure of the nanoparticles with a pore radius of 34.18 Å. FTIR studies showed the specific bands at 599.82 and 472.53 cm−1, typical for Fe3O4 nanoparticles. The photocatalytic efficacy of the nanoparticles was demonstrated against the degradation of malachite green dye under sunlight irradiation and the photocatalytic degradation constant was calculated as 0.0621 min−1.
Keywords: Calliandra haematocephala ; Magnetite nanoparticles; Green synthesis; Dye degradation; Mesoporous nanoparticles; BET analysis

In the present research, a simplified mathematical model is presented to study the heat transfer and entropy generation analysis of thermal system containing hybrid nanofluid. Nanofluid occupies the space over an infinite horizontal surface and the flow is induced by the non-linear stretching of surface. A uniform transverse magnetic field, Cattaneo–Christov heat flux model and thermal radiation effects are also included in the present study. The similarity technique is employed to reduce the governing non-linear partial differential equations to a set of ordinary differential equation. Keller Box numerical scheme is then used to approximate the solutions for the thermal analysis. Results are presented for conventional copper oxide–ethylene glycol (CuO–EG) and hybrid titanium–copper oxide/ethylene glycol ($${ ext {TiO}}_2$$ TiO2 –CuO/EG) nanofluids. The spherical, hexahedron, tetrahedron, cylindrical, and lamina-shaped nanoparticles are considered in the present analysis. The significant findings of the study is the enhanced heat transfer capability of hybrid nanofluids over the conventional nanofluids, greatest heat transfer rate for the smallest value of the shape factor parameter and the increase in Reynolds number and Brinkman number increases the overall entropy of the system.
Keywords: Casson fluid model; Hybrid nanofluid; Cattaneo–Christov heat flux model; Entropy generation; Heat transfer

Multidimensional dose–response toxicity exploration of silver nanoparticles from Nocardiopsis flavascens RD30 by Anandan Ranjani; Ponnusamy Manogaran Gopinath; Selvaraju Ananth; Ganesan Narchonai; Perumal Santhanam; Nooruddin Thajuddin; Dharumadurai Dhanasekaran (699-713).
In recent decades, silver nanoparticles (AgNPs) are progressively being used in various applications, nevertheless, their environment-based toxicity studies remain deficient. Hence this article shows the toxicity analysis of AgNPs synthesized from Nocardiopsis flavascens RD30 on Chloroccocum humicola, Artemia salina and Swiss albino mouse. AgNPs were extracellularly synthesized from N. flavascens RD30 extract with sunlight irradiation and the synthesized AgNPs were roughly spherical in shape, with the size range between 5 and 50 nm. Further, the toxicity study on green algae proves that, at 50 µg AgNPs concentration, there was no effect on C. humicola, however, increasing the concentration lead to the cell aggregation which is proposed as a defense mechanism by the algal populations. Similarly, in the case of A. salina, the mortality increased with the increasing concentration of AgNPs, wherein abnormalities such as the improper development of mandibles and underdeveloped endopod and endite were observed in concentrations 60 and 70 µg/mL. Finally, the oral toxicity of AgNPs was evaluated in the mouse model which is portrayed through serum biochemistry and histopathological observations of vital organs. There was no major effect on the liver function in the treated mice, while the negligible reaction was observed in kidneys and intestine of the mice treated with AgNPs after 10 days of oral exposure. Overall results indicate that the biogenic AgNPs are less/non-hazardous to the phytoplanktons, zooplanktons and higher animals when released at a minimal concentration and it could be possibly used in human and environmental applications.
Keywords: Silver nanoparticles; Nocardiopsis flavascens RD30; Toxicity; Chloroccocum humicola ; Artemia salina ; Swiss albino mouse

The study of colloidal lead bromide perovskite nanocrystals and its application in hybrid solar cells by Khurram Usman; Shuaiqiang Ming; Xiaohui Liu; Xiaodong Li; Zhenzhen Gui; Qiaomu Xie; Wenxiao Zhang; Yulei Wu; Hai-Qiao Wang; Junfeng Fang (715-721).
In this study, we investigated inorganic cesium lead halide perovskite semiconductor and tested its application in photovoltaics. Highly crystalline material was synthesized by two different approaches, including a high temperature route and a low temperature method. Inorganic-polymer hybrid solar cells based on solution-deposited layers of CsPbBr3 nanocrystals were successfully fabricated in ambient, with and without post treatments. The solar cells employing nanocrystals with short ligands, obtained from low temperature route, outperformed the devices with long ligands. The devices exhibited an efficiency up to 1.16%, with an open circuit voltage (V oc) of 0.87 V, a fill factor of 56.2% and a short-circuit current density (J sc) of 2.38 mA/cm2.
Keywords: CsPbBr3 ; Inorganic perovskite; Metal lead halide perovskite; Hybrid solar cells

Ultrasound-assisted co-precipitation has been used to prepare nano-sized Ni0.4Cu0.2Zn0.4Fe2O4 ferrite. Continuous (C-US) and pulsed (P-US) ultrasound modes are used at constant frequency = 20 kHz, reaction time = 2 h and pulse durations of 10 s on and 10 s off. All experiments were conducted at two temperatures 90 and 100°C. Samples were characterized by X-ray diffraction (XRD), Fourier transform spectroscopy (FT-IR), N2 adsorption isotherms at 77 k analysis (BET), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM) techniques. A nanocrystalline single-phase with particle size in the range 12–18 nm is obtained in both modes: continuous and pulsed ultrasound mode. FT-IR measurements show two absorption bands assigned to the tetrahedral and octahedral vibrations (ν1 and ν2) characteristics of cubic spinel ferrite. The specific surface area (S BET) is in the range of 110–140 m2 g−1 and an average pore size between 5.5 and 6.5 nm. The lowest values are obtained in pulsed mode. Finally, this work shows that the magnetic properties are affected by the ultrasound conditions, without affecting the particle shape. The saturation magnetization (Ms) values obtained for all samples are comparable. In P-US mode, the saturation magnetization (Ms) increases as temperature increases. Moreover, P-US mode opens a new avenue for synthesis of NiCuZn ferrites.
Keywords: Ni0.4Cu0.2Zn0.4 ferrite synthesis; Continuous and pulsed ultrasound; Structural and magnetic properties

The present work reports the electrochemical synthesis of polysaccharide-functionalized ZnO nanoparticles using sodium hydroxide, starch, and zinc electrodes for the degradation of cationic dye (Rhodamine-B) under sunlight. Physiochemical properties of synthesized sample have been characterized by different techniques such as XRD, TEM, FESEM, EDS, IR, and UV–visible spectroscopic techniques. The influence of various factors such as effect of dye concentration, contact time, amount of photocatalyst, and pH has been studied. The results obtained from the photodegradation study showed that degradation rate of Rhodamine-B dye has been increased with increase of amount of photocatalyst and decreased with increase in initial dye concentration. Furthermore, the kinetics of the degradation has been investigated. It has been found that the photodegradation of Rhodamine-B dye follows pseudo-first-order kinetics and prepared photocatalyst can effectively degrade the cationic dye. Thus, this ecofriendly and efficient photocatalyst can be used for the treatment of dye-contaminated water. This catalyst also showed the antibacterial activity against Bacillus pumilus and Escherichia coli bacterial strains, so the synthesized nanoparticles also have the pharmaceutical properties.
Keywords: ZnO; Starch; Electrochemical synthesis; Photocatalytic activity; Antibacterial activity

To fabricate a broad range of practical periodic nanostructures for biotechnological applications, colloidal lithography (nanosphere lithography) techniques are commonly used. Therefore, two-dimensional (2-D) colloidal arrays have been a significant area of research in these biotechnology applications. Simple and scalable colloidal transferring techniques allow the fabrication of 2-D highly ordered nanoarrays based on non-close-packed colloidal crystals on a large variety of substrates, such as plastics and glass. There are not many mass fabrication techniques for monolayer structures that use the current top-down and bottom-up approaches. Using the transfer technique for monolayer arrays, the mixture of urethane and acrylate monomers might be one of the most common materials as a transfer material or even a nano pore membrane. In this study, it is demonstrated that the transfer method might achieve mass production of monolayer nanostructures for potential applications, for example nanopores used to filtrate biomolecules such as miRNAs and tRNAs.
Keywords: Bioseparation; Biotechnology; LbL transfer; Nanomembrane filtration; Nanostructured surfaces; Nanosphere lithography; Spin-coating

In the present work, graphite was processed to graphene oxide (GO) using modified Hummer’s method by volumetric titration approach, without attaining zero temperature and the addition of toxic chemicals (NaNO2/NaNO3). The complete oxidation of graphite to graphene oxide was obtained by controlled addition (volumetric titration) of KMnO4. The addition of higher KMnO4 resulted in partial oxidation and 2–3 mono-layers with less defects/disordered structure of reduced graphene oxide (RGO) sheets were achieved. Samples were analyzed by XRD, FT-IR, Raman analysis, and TEM analysis. X-ray diffraction displayed the oxidized peak of graphene oxide at 11.9° and reduced graphene oxide at 23.8°. The prolonged stability of the synthesized GO with lower mole ratios of oxidizing agent was confirmed from UV–visible spectroscopy. Based on the results, processed graphene oxide is found to be a candidate material for thermally stable capacitor application.
Keywords: Graphene oxide; Reduced graphene oxide; Raman; TEM; Spectroscopy

Rapid synthesis of gold and silver nanoparticles using tryptone as a reducing and capping agent by Sourabh M. Mehta; Marilyn P. Sequeira; Harries Muthurajana; Jacinta S. D’Souza (759-769).
Due to its eco-friendliness, recent times have seen an immense interest in the green synthesis of metallic nanoparticles. We present here, a protocol for the rapid and cheap synthesis of Au and Ag nanoparticles (NPs) using 1 mg/ml tryptone (trypsinized casein) as a reducing and capping agent. These nanoparticles are spherical, ~ 10 nm in diameter and relatively monodispersed. The atoms of these NPs are arranged in face-centered cubic fashion. Further, when tested for their cytotoxic property against HeLa and VERO cell lines, gold nanoparticles were more lethal than silver nanoparticles, with a more or less similar trend observed against both Gram-positive and Gram-negative bacteria. On the other hand, the NPs were least cytotoxic against a unicellular alga, Chlamydomonas reinhardtii implying their eco-friendly property.
Keywords: Tryptone; Reducing agent; Green synthesis; Gold nanoparticle; Silver nanoparticle

Biogenic, eco-friendly, reliable, and cost-effective metal nanostructures were synthesized using Trigonella foenum-graecum leaf extract, which acted as reducing and stabilizing agent with no additional chemical surfactants. Nanoparticle formation was confirmed from UV–Vis absorption, XRD, and FTIR spectra. Morphology and crystallinity of spherical silver nanoparticles (Ag NPs) and gold nanoparticles (Au NTs) were further confirmed from TEM analysis. Luminescence enhancement and quenching of lanthanide ion complexes were observed and found to be dependent on metal nanostructure concentration. The factors relay on the energy transfers between nanostructures and rare-earth ions (RE). The nonlinear optical studies of Ag NPs and Au NTs were studied using Z-scan and degenerate four wave mixing (DFWM) techniques with picosecond and femtosecond lasers. The surface-enhanced Raman scattering (SERS) of the test molecule, rhodamine 6G, was studied to check the performance of Ag NPs and Au NTs in enhancing the Raman scattering signals. In vitro cytotoxic effect of the Ag NPs and Au NTs has been checked against A549 lung cancer cell lines and the efficiency of toxicity depended on the dosage. These experiments demonstrate that the nanostructures are ideal candidates for applications in optics and biology as PL based devices with appropriate concentrations of RE ions, optical switches, SERS substrates, and therapeutic agents towards cancer cell lines.
Keywords: Green synthesis; Metal nanoparticles; Fluorescence; SERS; NLO and MTTA

Polarized luminescence of nc-Si–SiO x nanostructures on silicon substrates with patterned surface by Katerina Michailovska; Viktor Mynko; Ivan Indutnyi; Petro Shepeliavyi (785-791).
Polarization characteristics and spectra of photoluminescence (PL) of nc-Si–SiO x structures formed on the patterned and plane c-Si substrates are studied. The interference lithography with vacuum chalcogenide photoresist and anisotropic wet etching are used to form a periodic relief (diffraction grating) on the surface of the substrates. The studied nc-Si–SiO x structures were produced by oblique-angle deposition of Si monoxide in vacuum and the subsequent high-temperature annealing. The linear polarization memory (PM) effect in PL of studied structure on plane substrate is manifested only after the treatment of the structures in HF and is explained by the presence of elongated Si nanoparticles in the SiO x nanocolumns. But the PL output from the nc-Si–SiO x structure on the patterned substrate depends on how this radiation is polarized with respect to the grating grooves and is much less dependent on the polarization of the exciting light. The measured reflection spectra of nc-Si–SiO x structure on the patterned c-Si substrate confirmed the influence of pattern on the extraction of polarized PL.
Keywords: Silicon grating; Silicon nanostructure; Photoluminescence; Polarization memory

Acacia gum–Fe0Np–silica nanocomposite (GFS1) has been crafted through sol–gel technique using a two-step process that involved the reduction of iron salt to zerovalent iron nanoparticles (Fe0Nps) followed by their impregnation within Acacia gum–silica matrix. GFS1 was characterized using Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS) techniques. GFS1 is decorated with Fe0Nps of ~ 5 nm average size. The VSM study revealed that GFS1 has ferromagnetic nature. GFS1 was used as a heterogeneous Fenton-like catalyst for the degradation of azo dyes using Remazol Brilliant Violet (RBV) dye as a model dye. In first 5 min of operation, > 86% dye degradation was achieved and 94% dye (from 100 mg L−1 dye solution) was successfully degraded in 50 min. The dye degradation followed pseudo-first-order kinetics. The GFS1 performed efficiently well over the wide range of dye concentrations (25–200 mg L−1). The catalyst was reused for eight repeated cycles where 12.5% dye degradation was possible even in the eighth cycle. The catalyst behaved fairly well for the degradation of Metanil Yellow (MY) and Orange G (OG) dyes also. Under the optimum conditions of RBV dye degradation, Metanil Yellow (MY) and Orange G (OG) dyes were degraded to the extent of 97 and 26.3%, respectively.
Keywords: Fenton-like degradation; Acacia gum–Fe0Np–silica nanocomposite; Sol–gel process; Remazol Brilliant Violet dye; Mango leaf extract

Polyethylenimine-coated iron oxide magnetic nanoparticles for high efficient gene delivery by Anh H. Nguyen; Gaser N. Abdelrasoul; Donghai Lin; Hamid Maadi; Junfeng Tong; Grace Chen; Richard Wang; Afreen Anwar; Lian Shoute; Qiang Fang; Zhixiang Wang; Jie Chen (811-821).
Properties of magnetic nanoparticles (MNPs) are of notable interest in many fields of biomedical engineering, especially for gene therapy. In this paper, we report a method for synthesis and delivery of MNPs loaded with DNAs, which overcomes the drawbacks of high cost and cytotoxicity associated with current delivery techniques (chemical- and liposome-based designs). 24-nm MNPs (Fe3O4) were synthesized, functionalized and characterized by analytical techniques to understand the surface properties for DNA binding and cellular uptake. The simple surface functionalization with polyethylenimine (PEI) through glutaraldehyde linker activation gave the complex of PEI-coated MNPs, resulting in high stability with a positive surface charge of about + 31 mV. Under the guidance of an external magnetic field, the functionalized MNPs with a loaded isothiocyanate (FITC) or green fluorescent protein (GFP) will enter the cells, which can be visualized by the fluorescence of FITC or GFP. We also examined the cytotoxicity of our synthesized MNPs by MTT assay. We showed that the IC50s of these MNPs for COS-7 and CHO cells were low and at 0.2 and 0.26 mg/mL, respectively. Moreover, our synthesized MNPs that were loaded with plasmids encoding GFP showed high transfection rate, 38.3% for COS-7cells and 27.6% for CHO cells. In conclusion, we established a promising method with low cost, low toxicity, and high transfection efficiency for siRNA and gene delivery.
Keywords: Magnetic nanoparticles; Gene delivery; Cell transfection; Cell toxicity

Nonlinear optical properties of metal alkanoate composites with hybrid core/shell nanoparticles by V. Rudenko; A. Tolochko; D. Zhulai; G. Klimusheva; T. Mirnaya; G. Yaremchuk; V. Asaula (823-829).
New composites with hybrid CdSe/ZnS and Au/CdSe nanoparticles (NPs) were chemically synthesized in the thermotropic liquid crystalline phase (smectic A) of cadmium octanoate. Features of structure and nonlinear optical properties of glassy cadmium octanoate composites with hybrid core/shell NPs were studied using small-angle X-ray scattering method and Z-scan technique. Experimental optical setup (Z-scan) is based on a Nd: YAG laser, generating 9 ns pulses with a repetition rate of 0,5 Hz on a wavelength of 532 nm. The effects of the influence of hybrid NPs on the nonlinear optical properties of nanocomposites are considered in this study.
Keywords: Optical nonlinearity; Structure of nanoparticles; Cadmium octanoate; Hybrid core/shell nanoparticles

An effective approach to study the biocompatibility of Fe3O4 nanoparticles, graphene and their nanohybrid composite by Ashwani Kumar Singh; Pallavi Singh; Rajiv Kumar Verma; Suresh Yadav; Kedar Singh; Amit Srivastava (831-838).
The present manuscript describes a simple, facile and effective solvothermal route to synthesize Fe3O4 nanoparticles (Fe3O4 NPs), reduced graphene oxide nanosheets (rGO NSs) and Fe3O4/reduced graphene oxide nanohybrid composite (Fe3O4/rGO nanohybrid composite) and subsequently examines their comparative biocompatibilities. The as-obtained Fe3O4 NPs, rGO NSs and Fe3O4/rGO nanohybrid composite have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The XRD studies and scanning electron microscope confirmed the proper phase formation and the surface morphology of the as-synthesized products, respectively. The Raman spectra of Fe3O4 NPs show the strongest peak at 673 cm−1 which can be assigned to A1g peak of bare Fe3O4 NPs and it complements the XRD studies. Furthermore, the increment in the I D/I G ratio in the Fe3O4/rGO nanohybrid composite suggests the creation of defects in graphene sheets due to strain caused by Fe3O4 NPs. The biocompatibility of these samples has been tested using Lung cancer cell line H1299 through MTT assay. The MTT assay reveals that the nanohybrid composite endows more biocompatible and effectiveness than rGO NSs and Fe3O4 NPs individually, as anti-proliferative agent for cancer treatment.
Keywords: Fe3O4 nanoparticles; Reduced graphene oxide nanosheets; Fe3O4/reduced graphene oxide nanohybrid composite; Anti-proliferative agent; MTT assay

An insight into the dopant selection for CeO2-based resistive-switching memory system: a DFT and experimental study by Fayyaz Hussain; Muhammad Imran; Anwar Manzoor Rana; R. M. Arif Khalil; Ejaz Ahmad Khera; Saira Kiran; M. Arshad Javid; M. Atif Sattar; Muhammad Ismail (839-851).
The aim of this study is to figure out better metal dopants for CeO2 for designing highly efficient non-volatile memory (NVM) devices. The present DFT work involves four different metals doped interstitially and substitutionally in CeO2 thin films. First principle calculations involve electron density of states (DOS) and partial density of states (PDOS), and isosurface charge densities are carried out within the plane-wave density functional theory using GGA and GGA + U approach by employing the Vienna ab initio simulation package VASP. Isosurface charge density plots confirmed that interstitial doping of Zr and Ti metals truly assists in generating conduction filaments (CFs), while substitutional doping of these metals cannot do so. Substitutional doping of W may contribute in generating CFs in CeO2 directly, but its interstitial doping improves conductivity of CeO2. However, Ni-dopant is capable of directly generating CFs both as substitutional and interstitial dopants in ceria. Such a capability of Ni appears acting as top electrode in Ni/CeO2/Pt memory devices, but its RS behavior is not so good. On inserting Zr layer to make Ni/Zr:CeO2/Pt memory stacks, Ni does not contribute in RS characteristics, but Zr plays a vital role in forming CFs by creating oxygen vacancies and forming ZrO2 interfacial layer. Therefore, Zr-doped devices exhibit high-resistance ratio of ~ 104 and good endurance as compared to undoped devices suitable for RRAM applications.
Keywords: Density functional theory; CERIA; Resistive switching; Doping; Charge density

Synthesis of pH-sensitive poly(β-amino ester)-coated mesoporous silica nanoparticles for the controlled release of drugs by William A. Talavera-Pech; Adriana Esparza-Ruiz; Patricia Quintana-Owen; Alfredo R. Vilchis-Nestor; Jesus A. Barrón-Zambrano; Alejandro Ávila-Ortega (853-866).
This report describes the synthesis of a controlled drug delivery system that was obtained by coating mesoporous silica nanoparticles (MSNs) with poly(β-amino ester) (PbAE), which is a solid and stable material at physiological pH, but is dissolved at acidic pH values, such as those in tumor tissues (from 5.0 to 6.5). To synthesize the system, PbAE chains were grafted onto amino-functionalized MSNs through a reaction between the surface amino groups of MSNs and the ends of acrylate chains of a PbAE. The system was physicochemically characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectrometry, and X-ray diffraction analyses. In addition, the in vitro release of doxorubicin (DOX) and doxycycline (DXY) in acidic and physiological media was evaluated. It was observed that the PbAE modification did not affect the mesoporous structure of MSNs. When the amount of 3-aminopropyltriethoxysilane was increased during functionalization, the amount of PbAE binding to MSNs increased as well. With respect to drug release, the sample with the highest amount of PbAE showed better control in the delivery of DXY and DOX in acidic media, because at pH 5.5, the release of both drugs was 40% higher than that at pH 7.4. These results reveal two aspects about the presence of PbAE in MSNs: PbAE does not affect the mesoporous structure of the nanoparticles, and PbAE is the main factor controlling the delivery of drugs in acidic media.
Keywords: Mesoporous silica nanoparticles; Poly(β-amino ester); pH-sensitive; Drug delivery system; Doxorubicin

Nanosized silica–titanium oxide as a potential adsorbent for C.I. Acid Yellow 219 dye removal from textile baths and wastewaters by Małgorzata Wiśniewska; Monika Wawrzkiewicz; Ewelina Polska-Adach; Gracja Fijałkowska; Olena Goncharuk (867-876).
The mixed SiO2–TiO2 oxide obtained by the pyrogenic method with the silica:titanium percentage ratio equal to 80:20 (ST20) was used as a potential adsorbent for the removal of hazardous azo dye C.I. Acid Yellow 219 (AY219) from aqueous solutions. Based on the values of determination coefficients (r 2), it can be stated that the Freundlich (r 2 = 0.929) model fitted the experimental data better than the Langmuir (r 2 = 0.920) and Tempkin (r 2 = 0.848) ones. In the system containing 20 mg/L AY219, the amount of dye adsorbed (q t ) by ST20 was equal to 9.7 mg/g and the time necessary to reach equilibrium was 120 min. The sorption of AY219 on ST20 may be described by the pseudo-second-order model (r 2 = 0.999) as the adsorption capacity was calculated as 9.69 mg/g. The amount of AY219 adsorbed decreased with the increasing concentration of additives such as anionic and non-ionic (Triton X-100) surfactants. In the presence of cationic surfactant, the reverse dependence was observed. Anionic dye additions influence the structure of electrical double layer formed on the surface of mixed oxide particles. The presence of negative charges in adsorbed AY219 molecules results in increase of the solid surface charge density with simultaneous decrease of the zeta potential of ST20 particles. The addition of surfactants with different ionic character causes formation of complexes whose presence at the mixed oxide–liquid interface influences considerably both the solid surface charge density and the zeta potential of ST20 particles dispersed in aqueous solution.
Keywords: Nanosized mixed oxide; Silica–titanium oxide; Acid yellow; Removal; Sorption; Electrokinetic properties

Superconductivity and weak localization of PdxBi2Se3 whiskers at low temperatures by Anatoly Druzhinin; Igor Ostrovskii; Yuriy Khoverko; Krzysztof Rogacki; Natalia Liakh-Kaguy (877-883).
The temperature dependencies of Bi2Se3 whiskers’ resistance with Pd doping concentration of (1÷2)×1019 cm−3 where measured in the temperature range 1.5÷77 K. At temperature 5.3 K a sharp drop in the whisker resistance was found. The observed effect is likely connected with the contribution of two processes such as the electron localization and superconductivity at temperatures below 5.3 K. The magnetoresistance in the n-type conductivity Bi2Se3 whiskers with different doping concentration of palladium that correspond to metal side of the metal–insulator transition was studied at low temperatures and magnetic field 0÷10 T. The whisker magnetoconductance is considered in the framework of the weak antilocalization model and connected with subsurface layers of Bi2Se3 whiskers.
Keywords: Bi2Se3 whiskers; Magnetoresistance; Superconductivity; Weak antilocalization

Effect of elastic deformation and the magnetic field on the electrical conductivity of p-Si crystals by R. Lys; B. Pavlyk; R. Didyk; J. Shykorjak; I. Karbovnyk (885-890).
It is shown that at a deformation rate of 0.41 kg/min, the characteristic feature of the dependence of the surface resistance of the p-Si sample on the magnitude of its elastic deformation (R(σ)) is the reduction of the resistance during compression and unclamping. With the increase in the number of “compression-unclamping” cycles, the difference between the positions of the compression and unclamping curves decreases. The transformation of two types of magnetically sensitive defects occurs under the impact of a magnetic field on p-Si crystals. The defects are interrelated with two factors that cause the mutually opposite influence on the conductivity of the crystal. The first factor is that the action of the magnetic field decreases the activation energy of the dislocation holders, which leads to an increase in the electrical conductivity of the sample. The second factor is that due to the decay of molecules of oxygen-containing impurities in the magnetic field, the stable chemisorption bonds appear in the crystal that leads to a decrease in its conductivity. If the sample stays in the magnetic field for a long time, the one or the other mechanism predominates, causing a slow growth or decrease in resistance around a certain (averaged) value. Moreover, the frequency of such changes is greater in the deformed sample. The value of the surface resistance of p-Si samples does not change for a long time without the influence of the magnetic field.
Keywords: Uniaxial deformation; Magnetic field; Dislocation; Silicon

CdTe epitaxial thin films, for use as a buffer layer for HgCdTe defectors, were grown on GaAs (211)B using the molecular beam epitaxy method. Wet chemical etching (Everson method) was applied to the epitaxial films using various concentrations and application times to quantify the crystal quality and dislocation density. Surface characterization of the epitaxial films was achieved using Atomic force microscopy and Scanning electron microscopy (SEM) before and after each treatment. The Energy Dispersive X-Ray apparatus of SEM was used to characterize the chemical composition. Untreated CdTe films show smooth surface characteristics with root mean square (RMS) roughnesses of 1.18–3.89 nm. The thicknesses of the CdTe layers formed were calculated via FTIR spectrometry and obtained by ex situ spectroscopic ellipsometry. Raman spectra were obtained for various temperatures. Etch pit densities (EPD) were measured, from which it could be seen that EPD changes between 1.7 × 108 and 9.2 × 108 cm−2 depending on the concentration of the Everson etch solution and treatment time. Structure, shape and depth of pits resulting from each etch pit implementation were also evaluated. Pit widths varying between 0.15 and 0.71 µm with heights varying between 2 and 80 nm were observed. RMS roughness was found to vary by anything from 1.56 to 26 nm.
Keywords: CdTe films; CdTe buffer layer; Etch pit density; Raman spectroscopy; Atomic force microscopy; Scanning electron microscopy

Microfluidics technology offers a new platform to control liquids under flow in small volumes. The advantage of using small-scale reactions for droplet generation along with the capacity to control the preparation parameters, making microfluidic chips an attractive technology for optimizing encapsulation formulations. However, one of the drawback in this methodology is the ability to obtain a wide range of droplet sizes, from sub-micron to microns using a single chip design. In fact, typically, droplet chips are used for micron-dimension particles, while nanoparticles’ synthesis requires complex chips design (i.e., microreactors and staggered herringbone micromixer). Here, we introduce the development of a highly tunable and controlled encapsulation technique, using two polymer compositions, for generating particles ranging from microns to nano-size using the same simple single microfluidic chip design. Poly(lactic-co-glycolic acid) (PLGA 50:50) or PLGA/polyethylene glycol polymeric particles were prepared with focused-flow chip, yielding monodisperse particle batches. We show that by varying flow rate, solvent, surfactant and polymer composition, we were able to optimize particles’ size and decrease polydispersity index, using simple chip designs with no further related adjustments or costs. Utilizing this platform, which offers tight tuning of particle properties, could offer an important tool for formulation development and can potentially pave the way towards a better precision nanomedicine.
Keywords: Microfluidics; Nanoparticles; Microparticles; Polymeric particles; Focused flow