Volume 7, Issue 6

Absorption of Pb ion on the (n, 0) carbon nanotube (CNT) (n=4, 5, 6) surface, pure and defected with single vacancy, is investigated based on density functional theory. Pristine (n, 0) CNTs can produce a certain degree of chemical adsorption of Pb ion. While a single vacancy is introduced, the adsorption ability of CNTs for Pb ion increases greatly, and the band gap changes significantly before and after adsorption. SV-(6, 0) CNTs have the strongest adsorption ability, and SV-(5, 0) CNTs are the potential material for the Pb ion detection sensor. It is expected that these could be helpful to the design of Pb filters and sensors.

The effect of carbon nanotube (CNT) functionalization in altering the properties of epoxy-CNT composites is presented. The presence of functional groups effectively influenced the colloidal behavior of CNTs in the precursor epoxy resin and the hardener triethylenetetramine (TETA), which affected the synthesis process and eventually the interfacial interactions between the polymer matrix and the CNTs. The physical, thermal, and electrical properties of the composites exhibited strong dependence on the nature of functionalization. At a 0.5-wt% CNT loading, the enhancement in tensile strength was found to be 7.2%, 11.2%, 11.4%, and 14.2% for raw CNTs, carboxylated CNTs, octadecyl amide-functionalized CNTs, and hydroxylated CNTs, respectively. Glass transition temperatures ( T g ) also varied with the functionalization, and composites prepared using hydroxylated CNTs showed the maximum enhancement of 34%.

Efficient selective extraction of semiconducting single-walled carbon nanotubes (s-SWCNTs) from as-synthesized SWCNTs is essential for their electronic and photovoltaic applications. In this study, we used a relatively simple copolymer backbone structure of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-thiophene] (PFT) for the selective extraction of s-SWCNTs from HiPCO SWCNTs. The absorption and Raman spectroscopies indicated that the PFT-sorted s-SWCNTs had high purity which was far beyond the sensitivity of the spectrometers. Photoluminescence excitation spectroscopy showed that PFT mainly extracted the chiralities of (n,m)=(9,5), (8,6), (7,5), and (10,5) s-SWCNTs with the ratios of about 53.1%, 24.8%, 11.5%, and 10.5%, respectively. Both steady-state and transient optical spectroscopies suggested that there was a strong interaction between PFT and s-SWCNTs. Molecular dynamics simulation results agreed well with the experimental data. Additionally, the photoinduced energy transfer behavior of the PFT-wrapped s-SWCNT resultant hybrid was assessed. This work indicated that the prepared PFT-wrapped s-SWCNT hybrid material was attractive for organic photovoltaic devices.

This paper presents a facile method of producing graphene nanosheets by organic liquid-assisted electrochemical exfoliation using tetramethyleammonium hydroxide (TMAH) as organic electrolyte. The process involves low-cost copper as ground electrode and carbon block as anode or cathode. The application of organic electrolyte eliminates the presence of unwanted metal ions on the graphene nanosheets. To the best of our knowledge, this is a maiden effort of producing graphene with pure organic electrolyte using TMAH with low-cost copper electrode. By the use of TMAH, conformal large-area graphene nanosheets of 4.3 nm thickness with an average sheet diameter of 3–4 μm have been obtained. Graphene nanosheets are characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared, Raman spectroscopy, and atomic force microscopy. Raman characterization confirms the conservation of the intrinsic nature of few-layer graphene. Graphene nanosheets are dissolved in a polar aprotic solvent dimethylformamide and are drop coated on the Si/SiO 2 substrate to make a thin film of graphene. Films are annealed to remove any residual solvent attached to it. Different annealing temperatures (50–200°C) were reported. Sheet resistances were measured before and after annealing, with a remarkable decrease afterward. Current-voltage characteristics were studied to evaluate the conductivity of the graphene nanosheets produced.

Background Nanosilver fluoride (NSF) was developed as an alternative in the prevention of dental caries. Purpose The aim of this study was to test the remineralizing action of NSF on incipient enamel caries and its antimicrobial action on the acid production and adhesion of Streptococcus mutans. Methods Deciduous enamel fragments were treated with sodium fluoride (NaF), NSF and deionized water. Microhardness, fluorescence spectroscopy and optical coherence tomography imaging were performed on each specimen before chemical caries induction, after caries induction and after 14 days of pH cycling. The treated enamel fragments were also placed into test tubes containing bacterial suspension and saliva. The pH readings and quantification of the adhered microorganisms to the dental enamel were determined. Analysis of variance, Kruskal-Wallis, Mann-Whitney, Tukey and mixed linear regression model were applied. Results NSF and NaF were effective in enamel remineralization, with a statistically significant difference (p<0.001) to deionized water, and they had no statistically significant difference between themselves (p>0.005). NSF had greater effectiveness compared to NaF in preventing decreases of pH and adhesion of S. mutans to the enamel surface, with statistically significant (p<0.001) differences. Conclusion NSF may be more effective than conventional fluorides in treating incipient caries lesions due to its remineralization and antibacterial actions.

The word “nanotechnology” has been exaggerated not only by media but also by scientist groups who have overstated the unforeseen benefits of nanotechnology to validate research funding. Even ecologists, who normally remain indulged in doom-and-gloom divinations, use this word to fuel their own motives. Such outcomes lead to widespread misinformation and an unaware public. This research work is a staunch effort to filter the Twitter-based public opinions related to this word. Our results clearly indicate more of positive sentiments attached to the subject of nanotechnology, as trust, anticipation and joy overweigh by many folds the anger, mistrust and anger related to nanotechnology.

The behavior of nanoparticle motion has a great influence on gas-liquid mass transfer. However, it has been very difficult to characterize the motion of nanoparticles from a micro view in mass transfer experiments. In this study, a novel method was proposed to investigate nanoparticle Brownian motion through the application of the total internal reflection fluorescence microscope in a self-designed sample (a quasi-static liquid micro-groove) and the mass transfer enhancement of nanoparticles. Nanoparticle movement behavior was photographed using an electron-multiplying charge coupled device, and 100 consecutive images were recorded using Micro-Manager software at a rate of 20 fps. The images were processed through the particle tracking velocimetry algorithm to calculate two-dimensional motion rates of nanoparticles caused by Brownian movement. It showed that nanoparticle loadings influenced the motion rates significantly, and the motion rates were larger with smaller particle sizes under the same operating condition. The mass transfer coefficients in the quasi-static gas-liquid mass transfer system were calculated and analyzed through microscopic measurement. Based on the above thought, three important non-dimensional numbers [Sherwood ( Sh p ), Reynolds ( Re p ), and Schmidt ( Sc p ) numbers] for mass transfer theory were studied.

Matrix metallopeptidases, commonly known as matrix metalloproteinases (MMPs), are a group of proteolytic enzymes whose main function is the remodeling of the extracellular matrix. Changes in the activity of these enzymes are observed in many pathological states, including cancer metastases. An increasing body of evidence indicates that nanoparticles (NPs) can lead to the deregulation of MMP expression and/or activity both in vitro and in vivo . In this work, we summarized the current state of knowledge on the impact of NPs on MMPs. The literature analysis showed that the impact of NPs on MMP expression and/or activity is inconclusive. NPs exhibit both stimulating and inhibitory effects, which might be dependent on multiple factors, such as NP size and coating or a cellular model used in the research.

In the past two decades, micro/nanomotor is emerging as a critical domain of nanoscale research. Light-driven micro/nanomotors have gained a wealth of attention from the academics because of their potential applications in various fields such as environment remediation, biomedical field and cargo delivery at microscale. In order to perform some more challenging and complex tasks, higher actuation force and more precise control are both indispensable for light-driven micro/nanomotors. In this review, we discussed about three major factors: actuation mechanism, structure of micro/nanomotors and the wavelength of light irradiation, to find out how to gain a higher actuation force and propel the motor in a relatively high speed under light irradiation. Besides, some common control strategies of light-driven micro/nanomotors are presented in details with the advantages and disadvantages of each control mechanism, which will help lead to a convenient and precise control. Finally, the future development approaches toward powerful thrust and precise control are discussed for light-driven micro/nanomotors.

In this review, the possibility of using pulsed, nanosecond laser heating of nanoparticles (NPs) is demonstrated, in order to investigate their thermo-physical properties. This approach is possible because the laser heating produces high NP temperatures that facilitate the observation of their thermal radiation (incandescence). This incandescence depends on the thermo-physical properties of the NPs, such as heat capacity, density, particle size, volume fraction and the refractive index of the particle material, as well as on the heat-mass transfer between the NPs and the surrounding gas media. Thus, the incandescence signal carries information about these properties, which can be extracted by signal analyses. This pulsed laser heating approach is referred to as laser-induced incandescence. Here, we apply this approach to investigate the properties of carbon, metal and carbon-encapsulated Fe NPs. In this review, the recent results of the measurements of the NP refractive index function, thermal energy accommodation coefficient of the NP surface with bath gas molecules and the NP evaporation temperature obtained using laser-induced incandescence are presented and discussed.

Nanoscience is a booming field incorporating some of the most fundamental questions concerning structure, function, and applications. The cutting-edge research in nanoscience requires access to advanced techniques and instrumentation capable of approaching these unanswered questions. Over the past few decades, atomic force microscopy (AFM) has been developed as a powerful platform, which enables in situ characterization of topological structures, local physical properties, and even manipulating samples at nanometer scale. Currently, an imaging mode called PeakForce Tapping (PFT) has attracted more and more attention due to its advantages of nondestructive characterization, high-resolution imaging, and concurrent quantitative property mapping. In this review, the origin, principle, and advantages of PFT on nanoscience are introduced in detail. Three typical applications of this technique, including high-resolution imaging of soft samples in liquid environment, quantitative nanomechanical property mapping, and electrical/electrochemical property measurement will be reviewed comprehensively. The future trends of PFT technique development will be discussed as well.

Nanoparticles are considered magic bullets because of their unique properties. Nowadays, the use of nanoparticles has emerged in almost every field of science and technology, owing to its potential of revolutionizing specific fields. In the field of food science and technology, the use of nanoparticles is being studied in diverse areas, starting with the harvesting of crops up to final food consumption. With the increased usage of nanoparticles in day-to-day life, concern over their safety has arisen in everyone’s mind. There is an imbalance between the increase in research to identify new nanoparticle applications and their safety, and this has triggered pressure on scientists to identify the possible effects of nanoparticles on human health. There are numerous studies on the use of nanotechnology in food and the effect of nanoparticles on human health, but there is a vacuum in the literature in terms of the combined analysis of such studies. This review is an attempt to present and analyze different studies on the use and the safety of nanoparticles in food.