Nano

A precipitation–reduction synthesis method for silver nanoparticles (Ag NPs) was developed. Molten ε-caprolactam (CL) was used not only as solvent but also as reducing agent and stabilizer. At first, Ag₂O NPs was prepared by precipitation reaction of silver nitrate (AgNO₃) and sodium hydroxide (NaOH) using molten CL as solvent at 100°C. Then, Ag₂O NPs was in situ reduced into Ag NPs by molten CL at 120°C. Techniques of X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to monitor the synthesis process. With the increase of reduction time, monodispersed Ag₂O NPs (ca. 3.7 nm) were integrated and larger Ag NPs (10–90 nm) were formed. Fourier transform infrared (FT-IR) results showed that the surface of Ag NPs was capped with about 0.9 wt.% of CL molecules. Surface enhanced Raman scattering (SERS) effect of Ag NPs was investigated using Rhodamine 6G as a probe molecule.

Sensor application for detection of acetone molecule(s) present in human breath is developed for cantilevered single walled-boron nitride nanotube (SW-BNNT) and analyzed in the present work. The same can be used for continuous monitoring of diabetes. Biocompatibility nature of BNNTs justify their use in biomedical applications. The possible use of the BNNT as nanomechanical resonators is explored in the present study. An atomistic three dimensional (3D) space frame model of fixed-free SW-BNNT-based nanoresonator is developed. The proposed model investigates the feasibility of SW-BNNT for sensing acetone molecules present in human breath for detecting diabetes. Dynamic analysis of fixed-free SW-BNNT for variable aspect ratios of nanotubes is carried out. Presence of acetone molecule(s) causes a shift in the resonant frequency of SW-BNNT. It is observed that this frequency shift is quite significant with presence of more acetone molecules and shows mass sensitivity of SW-BNNT toward acetone molecules. Continuum mechanics-based analytical approach has been used to validate the newly developed sensor equations as the results are found to be in close proximity. The result thus paves new path for the application of SW-BNNTs as biosensor for detection of acetone molecule(s) present in human breath.

Molecular dynamics (MD) simulations are performed to study the fracture behavior of armchair and zigzag graphene sheets with V-shaped notches subjected to tensile loading. The effects of temperature and notches depth on the fracture characteristics of the graphene sheets are examined. The results show that the cracks propagate from the notch tip along the direction perpendicular to the loading axis for armchair sheets. This is different from the zigzag graphene propagating along the direction of 45° from the loading axis. In addition, the fracture energy of zigzag graphene sheets is larger than armchair one at the same temperature condition.

In this study, the adsorption of Paclitaxel (PTX) drug molecule onto graphene doped with nitrogen atoms (N-doped graphene) in vacuum and aqueous environments has been investigated. To do this, we have employed a series of very accurate molecular dynamics (MD) simulations to reveal the effect of N atoms concentration on drug molecule adsorption. The critical value of N adatoms is obtained. The water concentration, adsorption energy, and average distance of drug molecule from surface are calculated. Overall, our findings provide crucial information for the performance of N-doped graphene in drug delivery.

The influence of particle size on density, ultrasonic velocity and viscosity of magnetite nanofluids have been determined at (298.15 K, 303.15 K, 308.15 K and 313.15 K). Two different sized nanoparticles (commercially procured D = 20–30 nm and synthesized D = 9 ± 3 nm in the laboratory by co-precipitation method) were dispersed in a citric acid base fluid. The desired parameters have been experimentally determined by loading different concentrations of nanoparticles. It has been found that the influence of particle size and temperature on measured physical parameters (density, ultrasonic velocity and viscosity) is not negligible and can also be taken into account in any practical application. The analyzed physical parameters can describe qualitatively and quantitatively the particle size distribution of nanofluids at a specific temperature. Results are interpreted in terms of particle–particle and particle–fluid interactions.

In this paper, a highly catalytic and nanosized Ag/Co₃O₄ composite for rhodamine B(RhB) degradation was fabricated by using the co-precipitation method at room temperature. The Ag/Co₃O₄ structure and catalytic properties were characterized through scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) gas-sorption measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. The results showed that the Co₃O₄ nanosheets prepared by hydrothermal synthesis mainly exposed (2 2 0) and (1 1 1) facets, which played an important role in determining its catalytic oxidation performance. The Co₃O₄ nanosheets doped with Ag nanoparticles by a simple silver-mirror reaction exhibited a stable and well-dispersed property in dye solution. Compared to the Ag and Co₃O₄ nanostructure, the Ag nanoparticles with bigger diameter (10 nm) on Co₃O₄ surface also readily produced surface-active oxygen species and exhibited a higher catalytic activity for the degradation of RhB solution (5 mg ⋅ L^-1) under the visible light. The kinetic constant K of Ag/Co₃O₄ catalyst for RhB degradation reaction was evaluated to 0.02724 min^-1, which is relatively higher than those reported in the literatures.

In the present study, a candid approach using mechanical oxidation, for modification of multi-walled carbon nanotubes (CNTs) has been utilized, and its advantages over conventional acid oxidation methods have been established. Higher concentration of acidic groups was found in case of mechanically oxidized CNTs (i.e., McCNT) as compared to acid oxidized CNT (i.e., ACNT). Raman spectrum exhibited greater degree of transformation of sp² carbon into sp³ carbon. X-ray diffraction (XRD) analysis revealed maintained crystalline organization in McCNT. The major finding of the study was that, the mechanical oxidation method can be used easily to replace the conventional acid treatment method. This is because in the mechanical oxidation crystalline organization of CNTs can be maintained, relatively higher number of acid groups can be incorporated, no loss to the mass of CNTs is allowed etc.

Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries and so on. In this study, the process of Nickel filling into single wall CNTs was studied by molecular dynamics (MD) simulation. Three models consisting of Nickel atoms and CNTs were established. These models were cooled from 1500 K to 100 K to analyze the factors that influence the filling height, such as temperature, the force between Carbon and Nickel atoms, as well as CNTs diameter. The results showed that filling height increased as the temperature and the force between Carbon–Nickel atoms rised. Filling height reduced with the increasing diameter of CNTs.

A facile and effective approach based on magnetic separation was developed for the adsorption of Rhodamine B(RhB) from aqueous solution using magnetic oxidized multi-walled carbon nanotubes (magnetic o-MWCNTs) as adsorbent. The magnetic o-MWCNTs were simply synthesized by assembling magnetic nanoparticles onto the oxidized MWCNTs. Adsorption conditions such as pH values, the dosage of adsorbent added and adsorption time were investigated and optimized to achieve the best removal value. In addition, kinetics, adsorption isotherms and adsorption thermodynamics were studied to understand the mechanism by which the magnetic o-MWCNTs adsorbed RhB. The results indicated that the proposed method based on magnetic o-MWCNTs as magnetic absorbent was rapid and efficient for the removal of RhB. Furthermore, the magnetic o-MWCNTs could be easily removed after adsorption process and regenerated through desorption by ethanol.

The silicon-doped Bi₂O₂CO₃ nanorods with the interesting hierarchical structure are synthesized by a simple hydrothermal method. The samples are characterized by XRD, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), Ultraviolet-visible diffuse reflectance spectra (UV-DRS) and nitrogen sorption isotherms. It is found that with the increase of silicon content, the XRD peak of the sample significantly shifts toward a low diffraction angle and the particle morphologies change from nanosheets, nanoflowers to hierarchical nanorods. Moreover, the silicon-doped Bi₂O₂CO₃ hierarchical nanorods exhibit improved photocatalytic degradation activities for different types of dyes under simulated solar light irradiation. The improved activity has been mainly attributed to the unique hierarchical nanorods structure and the formation of Si–O–Bi bonds.

Poly(methyl methacrylate)-b-poly(vinyltriethoxysilane) (PMMA-b-PVTES) are synthesized using atom transfer radical polymerization (ATRP) and used as macromolecular coupling agents to modify silicon nitride nanoparticles (nano-Si₃N₄). The chemical composition of copolymers PMMA-b-PVTES and modified nano-Si₃N₄ are confirmed by various characterization techniques. The modified nano-Si₃N₄ shows excellent hydrophobic nature, which make nanoparticles (NPs) stably disperse in organic solvent. Transmission electron microscope (TEM), particle size testing, contact angle measuring and sedimentation experiment are employed to examine the dispersion of modified nano-Si₃N₄ in chloroform. By comparing the effects of copolymers with varied number-average molecular weight (M_n) and block length ratio on stabilizing nano-Si₃N₄, we discussed the mechanism of macromolecular coupling agent stabilizing NPs. In our experiments, the copolymer PMMA₈₈-b-PVTES₁₇ is found to be the most effective macromolecular coupling agent for stabilizing nano-Si₃N₄.

A novel sensitive and elective electrochemical sensor was developed to detect methyl parathion (MP) based on a glassy carbon electrode (GCE) modified with gold nanoparticles (AuNPs)/graphene nanocomposites film. The AuNPs were modified onto graphene sheets using NaBH₄ as a reductant. The obtained AuNPs/graphene nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of MP and interference studies were then investigated. Compared with metal ions and nitroaromatic compounds, which exist in environmental samples, the AuNPs/graphene/GCE exhibited high adsorption and strong affinity toward MP. Under optimized conditions, the oxidation peak current of MP was linear to its concentration within the range of 4.0 × 10^-7–8.0 × 10^-5 M, with a detection limit (S/N = 3) of 8.5 × 10^-8 M. These results indicated that the AuNPs/graphene nanocomposites displayed a synergic effect involving the catalytic characteristics of graphene and AuNPs nanocomposites, which can effectively improve the electrochemical properties of MP. Furthermore, the AuNPs also enhanced sensor sensitivity to MP. Therefore, the AuNPs/graphene/GCE could be a promising sensor for the fast, sensitive and selective detection of MP in real samples.

The nanocomposites of graphene loaded–ZnS nanoflowers (GR–ZnS) had been successfully prepared. Materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) spectra. A possible formation mechanism of this architecture was proposed. The experimental results revealed that these nanoflowers exhibited excellent UV-light photocatalytic activities for pollutant methyl orange (MO) dye degradation. These new nanostructures were expected to show considerable potential applications in the water treatment.

Over the past decade, functionalization with bimetallic catalysts have been studied owing to their excellent catalytic activities for various reactions, whereas few studies have been performed on cofunctionalization with two different types of metal catalysts despite its simplicity. This study examined the sensing performances of Nb₂O₅ nanorods cofunctionalized with Pd and Au nanoparticles. Pd, Au-cofunctionalized Nb₂O₅ nanorods were prepared by a hydrothermal technique. The Nb₂O₅ nanorods cofunctionalized with Pd and Au nanoparticles showed far stronger response to ethanol gas than the Pd or Au-functionalized counterpart. The origin for the enhanced response of the Pd, Au-cofunctionalized Nb₂O₅ nanorods is discussed.

We report on the sensitive detection of glucose using silicon nanowire array field-effect-transistor (SiNW-FET) upon illumination. The uniformly distributed and size-controlled SiNWs were fabricated by "top-down" approach. The fabricated SiNW-FET device was evaluated for detection of glucose in the range of 100–900 mg/dL. The SiNW-FET shows enhanced sensitivity of 0.988 ± 0.030 nA (mg/dl)^-1 upon illumination at 480 nm light as compared to without illumination as 0.486 ± 0.014 nA (mg/dL)^-1. The presented SiNW-FET device is fast, stable and sensitive to light as well as to bio analyte, and hence can be utilized as sensitive biological sensing platform.

A novel shear thickening fluid (STF) obtained from a halloysite nanotube (HNT) and SiO₂ compounded system was successfully prepared using HNT and nano-SiO₂ as dispersed phases and polyethylene glycol 200 (PEG200) as the dispersion medium. The steady rheological behavior of the STF was investigated using a high-speed rotational rheometer, and the dispersion states of SiO₂ and HNT in PEG200 were characterized by field emission scanning electron microscopy and transmission electron microscopy. Results show that HNT and SiO₂ coexisted in the compounded system, and presented a special state that was both uniformly dispersed and partially enriched. The shear thickening effect of the STF was significantly enhanced by the enrichment of SiO₂ loaded on the surface of HNTs in the compounded system.