Механизм роста монослоя на верхней грани Ga-каталитических нитевидных нанокристаллов GaAs и GaP

The growth mechanism of monolayer on the top facet of Ga-catalyzed GaAs and GaP nanowires is investigated. Within the framework of a theoretical model, the maximal monolayer coverage due to the material in the catalyst droplet, the nanowire growth rate and the content of group V atoms in the droplet are found depending on the growth conditions. The estimates of the phosphorus re-evaporation coefficient from neighboring nanowires and substrate are obtained by comparing the theoretical and experimental growth rate of Ga-catalyzed GaP nanowires.

Effect of Coverage on Adsorptions of CO on Ni(110) Surface

The adsorptions of CO on Ni(110) surface at different coverages have been investigated by first-principle calculations. The results show that CO will be bonded at short bridge site preferentially. And CO preferentially absorbs upright at short bridge sites and top sites at 1/6 monolayer coverage. With increasing coverage to 0.5 ML, the enhanced steric repulsion leads to the slope of CO. For 1/6 and 1/2 monolayer coverage, CO is mainly bonded at short bridge site and atop site simultaneously at a certain ratio. When CO coverage is 1 monolayer, CO absorbs at short bridge site and forms p2mg configuration. As the coverage of CO is increased to finally form the p2mg structure, there is a continuous frequency shift up to the value 1962.27 cm-1. The vibration frequencies we calculated are consistent with relative experimental results. DOS of CO molecules and Ni atoms are discussed too.

Highly efficient adsorption of uranyl ions using hydroxamic acid-functionalized graphene oxide

A chelating matrix prepared by immobilizing N-hydroxyl amine onto graphene oxide functionalized with aspartic acid (GO-HDX) was applied to recover UO2 2+ from their SO4 2− leach liquor. SEM-EDAX, FT-IR, TGA, and XRD instruments, in addition, Raman spectroscopy (IR-Raman), were used to analyze the synthesized GO-HDX. The static extraction technique optimized various physicochemical parameters that impacted the UO2 2+ extraction. The optimal pH, time of contact, initial concentration, GO-HDX dose, temp., foreign ions, and eluting agents were gained. The experimental equilibrium documents were assessed using Langmuir and Freundlich equations. The Langmuir equation model quite fits the investigational adsorption data with a maximum uptake of 277.78 mg/g, and it implied the attending of monolayer coverage of adsorbed molecules. Pseudo-first- and pseudo-second-order analyses were done to inspect the kinetic results. The data indicated that pseudo-second-order kinetics fit all concentrations. The intended thermodynamic factors were ∆G° negative values and ∆H° positive value. The data signified that the UO2 2+ extraction onto GO-HDX was spontaneous adsorption and endothermic at higher temperatures. The regeneration efficiency of GO-HDX was 98% using 1 M HCl.

Efficient anionic surfactant treatment of cork for cationic dye removal from aqueous media

<p>Sodium dodecyl sulfate sulfate modified Algerian cork powder (SDS-ACP) with interesting biosorption capacity was prepared for dye removal from aqueous media. The decolorization performance of SDS-ACP was studied using methylene blue (MB) as a model dye. Experiments were conducted in batch sysytem. The effects of initial pH, biosorbent dose, dye concentration, contact time and temperature were investigated. The kinetic modelling study showed that the experimental data are perfectly adjustable to the pseudo-second order model, with regression coefficients close to the unity and the intraparticle diffusion is not only the key controlling-step in the biosprption process. Langmuir isotherm was the most suitable model for describing the biosorption equilibrium results, which confirm the monolayer coverage and the maximum biosorption uptake of SDS-ACP was 117mg/g. Thermodynamic parameters such as Gibbs free energy, entropy and enthalpy were also evaluated showing that the biosorption process was spontaneously feasible and exothermic in nature. The application treatment has shown that SDS-ACP is a suitable lignocellulosic-type biosorbent for the decolorization of MB-colored solutions</p>

APTES monolayer coverage on self-assembled magnetic nanospheres for controlled release of anticancer drug Nintedanib

The use of an appropriate delivery system capable of protecting, translocating, and selectively releasing therapeutic moieties to desired sites can promote the efficacy of an active compound. In this work, we have developed a nanoformulation which preserves its magnetization to load a model anticancerous drug and to explore the controlled release of the drug in a cancerous environment. For the preparation of the nanoformulation, self-assembled magnetic nanospheres (MNS) made of superparamagnetic iron oxide nanoparticles were grafted with a monolayer of (3-aminopropyl)triethoxysilane (APTES). A direct functionalization strategy was used to avoid the loss of the MNS magnetization. The successful preparation of the nanoformulation was validated by structural, microstructural, and magnetic investigations. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to establish the presence of APTES on the MNS surface. The amine content quantified by a ninhydrin assay revealed the monolayer coverage of APTES over MNS. The monolayer coverage of APTES reduced only negligibly the saturation magnetization from 77 emu/g (for MNS) to 74 emu/g (for MNS-APTES). Detailed investigations of the thermoremanent magnetization were carried out to assess the superparamagnetism in the MNS. To make the nanoformulation pH-responsive, the anticancerous drug Nintedanib (NTD) was conjugated with MNS-APTES through the acid liable imine bond. At pH 5.5, which mimics a cancerous environment, a controlled release of 85% in 48 h was observed. On the other hand, prolonged release of NTD was found at physiological conditions (i.e., pH 7.4). In vitro cytotoxicity study showed dose-dependent activity of MNS-APTES-NTD for human lung cancer cells L-132. About 75% reduction in cellular viability for a 100 μg/mL concentration of nanoformulation was observed. The nanoformulation designed using MNS and monolayer coverage of APTES has potential in cancer therapy as well as in other nanobiological applications.

Coating of Conducting and Insulating Threads with Porous MOF Particles through Langmuir-Blodgett Technique

The Langmuir-Blodgett (LB) method is a well-known deposition technique for the fabrication of ordered monolayer and multilayer thin films of nanomaterials onto different substrates that plays a critical role in the development of functional devices for various applications. This paper describes detailed studies about the best coating configuration for nanoparticles of a porous metal-organic framework (MOF) onto both insulating or conductive threads and nylon fiber. We design and fabricate customized polymethylmethacrylate sheets (PMMA) holders to deposit MOF layers onto the threads or fiber using the LB technique. Two different orientations, namely, horizontal and vertical, are used to deposit MIL-96(Al) monolayer films onto five different types of threads and nylon fiber. These studies show that LB film formation strongly depends on deposition orientation and the type of threads or fiber. Among all the samples tested, cotton thread and nylon fiber with vertical deposition show more homogenous monolayer coverage. In the case of conductive threads, the MOF particles tend to aggregate between the conductive thread’s fibers instead of forming a continuous monolayer coating. Our results show a significant contribution in terms of MOF monolayer deposition onto single fiber and threads that will contribute to the fabrication of single fiber or thread-based devices in the future.

Fabrication of open type carbonizer for the preparation of activated carbon from rice husk

Activated carbon has been prepared from rice husk using laboratory fabricated open type carbonizer. The raw rice husk powder was named as RRH whereas chemically activated rice husk was named as CARH. Both samples were characterized by methylene blue number (MBN), iodine number (IN) and surface area. The MBN and IN of RRH was found to be 83 mg/g and 415 mg/g whereas CARH was 99 mg/g and 716 mg/g respectively which indicate the presence of mesoporosity and microporosity of the samples. The surface area of RRH was found to be 206 m2/g while CARH was found to be 531 m2/g. XRD analysis showed that the prepared materials were amorphous with some crystalline state while FTIR spectra showed the presence of different functional groups such as hydroxyl, carbonyl, Si-O-Si bond and aromatic group on the material. The adsorption properties of prepared samples were studied by using Langmuir and Freundlich isotherm models. Langmuir adsorption isotherm model was found to be best fitted. It showed that prepared materials have homogenous surface with monolayer type of adsorption. The maximum monolayer coverage (Qm) for RRH was found to be 55 mg/g and for CARH 143 mg/g. Thus, results revealed that laboratory fabricated low cost open type carbonizer is suitable for the preparation of activated carbon. BIBECHANA 18 (2021) 10-18