Effect of Bi contents on key physical properties of NiO NPs synthesized by flash combustion process and their cytotoxicity studies for biomedical applications

Nickel oxide has tremendous applications in the field of biomedicine. In this study, NiO nanoparticles were synthesized with different Bi contents (NiO@Bi; 0.0–7.5 wt%), and multifunctional usages were investigated. Structural confirmation was conducted through XRD and Raman studies, which revealed a monophasic cubic system. With increasing Bi content, broadening of the XRD and Raman peaks were observed, indicating a reduction in particle size. The crystallite size was found to be in the range of 10–26 nm. The decrease in particle size was confirmed through dynamic light scattering measurement. The homogeneous distribution of all elements and the presence of Bi were detected by an EDX/SEM e-mapping study. Field emission electron microscopy confirmed the formation of spherical shape nanoparticles. The grain size was reduced from 30 nm to 10 nm with Bi content, in accordance with XRD and Raman results. The Kubelka-Munk method was employed to determine the effect of Bi content on the optical band gap of NiO. The energy gap was reduced with Bi content in the range of 3.32–3.50 eV. Antimicrobial and in vitro cytotoxic characteristics of the prepared NPs were also studied. The results revealed that all NiO@Bi NPs had negligible antimicrobial activity and no cytotoxic effects on both normal and activated splenic cells. The in vivo acute cytotoxicity study indicated no cytotoxic effects on liver and kidney functions. The prepared NiO@Bi NPs were implanted in living organisms without hepatic/renal toxicity, demonstrating excellent biocompatibility, cell viability, and superior quality of nanocrystals, suggesting that the prepared NPs are ideal candidates for antibacterial and biomedical applications.     

Synthesis and physicochemical characterization of silica aerogels by rapid seed growth method

Thanks to the high optical transparency and ultra-low thermal conductivity, silica aerogels are ideal materials for energy-saving windows. However, their preparation is commonly based on either one-step base-catalyzed method, or two-step acid-base catalyzed method, which is difficult to inhibit the aggregation of clusters while keeping the size of clusters as small as possible and thus degrading silica aerogel's properties. Here, a new idea for synthesizing silica aerogels is presented from the viewpoint of controlling the growth and aggregation of silica clusters. A certain amount of Tetramethoxysilane (TMOS) used as seed precursor is firstly added into the mixture of methanol and distilled water for hydrolysis. A certain time later, the additional TMOS and a defined amount of ammonia are added to the obtained sol for promoting the rapid formation of the gel in several minutes. The silica aerogels prepared by this method have higher optical transparency and lower thermal conductivity than those prepared by the other two methods. This approach may also shed substantial light on controlling the microstructure of other materials prepared by sol-gel process.     

The Effect of Ethanol on Nanostructures of Mixed Cationic and Anionic Surfactants

Micellization of tetradecyl trimethyl ammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) in water–ethanol (ET) micellar solutions, with the weight percent of ET changing within the range 0–30, was studied by means of surface tension and conductivity measurements. Surface tension measurements also provided information about the dependence of the surface excess concentration, the minimum area per surfactant molecule, and the standard Gibbs energy of adsorption on the added weight percent of the organic solvent. Information about the degree of counterion dissociation and phase transition was obtained through conductivity measurements. Cyclic voltammetry (CV) and dynamic light scattering (DLS) was also employed to investigate the mixed micellar behavior of the binary mixtures. It was shown that an excess of cationic surfactant and ET resulted in a phase transition of vesicles and large micelles to mixed micelles. The regular solution theory approximation was used to determine various micellar parameters of ideal systems. The regular solution interaction parameter (β) suggests that the formation of mixed micelles is due to the synergistic interactions in the case of TTAB/SDS systems and becomes affected by the water/ET ratio.     

Research Impact on Emerging Quantum Materials for Electrochromic Applications

Electrochromic devices (ECDs), which can dynamically vary optical properties under applied specific voltage, have been actively studied for use in applications requiring human comfort and energy efficiency (i. e. smart windows and electronic displays). In order to improve the electrochromic (EC) performances, many researchers have been using nanomaterials. In this respect, in the present study, we highlight some of valuable examples using WO₃ from unique nanostructures to quantum dots (QDs) and discuss the core relationship between nanostructuring and EC performances. In particular, the present study proposes major impact on the novel approach using QDs to upgrade technical value and application of ECDs.     

Cellulose Aerogel Fibers Tested on a REXUS 18 Rocket – The ACTOR Project

Aerogels are high‐performance materials used for space and aviation purposes. Cellulose aerogel fibers have been investigated under real space conditions for their insulation properties. The experiments were carried out in a one‐stage high‐altitude research rocket of the improved ORION type. A cuboid module with measurement cells, camera modules, and electronic devices has been developed for monitoring the insulation behavior of cellulose aerogel non‐woven samples. The thermal behavior of these samples has been analyzed and compared to cellulose cloth (cotton) and aluminum for reference.     

Optimization of single mode fibre sensors to detect organic vapours

The construction of single mode optical fibre (SMF) sensors to handle with volatile organic compounds (VOCs), has been optimized to operate at the third telecommunication window (1550 nm). The main motivation is to take advantage of the photonic devices used in telecommunication systems that makes easier sensors multiplexing. Moreover, the low transmission attenuation at that wavelength offers the possibility of remote sensing. The sensing materials used suffer reversible structural alterations in the presence of VOC, such as colour change, which are detectable with a photonic system. Following the Electrostatic Self Assembly method (ESAm), a nanostructure is constructed onto cleaved ended SMF, which is doped with a sensing material. The fabrication of this type of sensors was focused on multimode fibres (MMF) and in the visible spectral range (VIS) so far. The implementation has been adapted to SMF and to operate around 1550 nm, specifically, by easing the adsorption of the VOCs molecules. It has been observed that the sensing material affects the morphology of the nanostructures as well and so, to the sensors response. The devices implemented show a potential use in the identification of single and complex mixtures of VOCs.     

Inorganic–Organic Hybrid Polymers for Information Technology: from Planar Technology to 3D Nanostructures

Sol‐gel synthesis allows inorganic–organic hybrid polymer materials (ORMOCER®s) to be produced, which can be functionalized to tailor their physical and chemical properties such as refractive index or optical loss. A particular material system is discussed here, which is synthesized without addition of water and is applied in optical communications. As examples for 2D and 2.5D technology, planar waveguides, stacked waveguides, and microlenses are shown. Using two‐photon polymerization initiated by femtosecond laser pulses, arbitrary 3D structures can be made in the submicrometer range. In particular, 3D photonic crystal structures are described and discussed.     

Co-synthesis of single-walled carbon nanotubes and carbon fibers

A new vertical floating catalytic technique is developed and used to prepare both single-walled carbon nanotubes (SWNTs) and carbon fibers (CFs). Scanning electron microscopy (SEM) observation shows a clear separation of these two materials. Thin films of SWNTs can be peeled easily from the CF substrate which just acts as a catalyst support for the SWNT growth. The production process is also semicontinuous, resulting in a yield of ∼1.0 g h⁻¹ of SWNTs film with high purity. Structure and vibrational properties of these materials are investigated by electron microscopy and Raman spectroscopy, respectively.     

Anelastic properties of aluminium thin films on silicon cantilevers

Thin films (thickness 40 to 250 nm) of Al on microstructurized Si substrates have been investigated by the vibrating-reed technique (typical frequencies 100 Hz to 10 kHz) with strain amplitudes in the range of 10⁻⁷ to 10⁻⁴ and for temperatures up to 850 K. The combined evaluation of flexural and torsional vibrations permits to separate the complex shear modulus and biaxial modulus of the thin layer, which helps to identify the damping mechanisms. For Al thin films with thickness <200 nm, in addition to the well-known damping peak due to grain boundary sliding (peak temperature about 370 K), a further maximum of damping has been observed around 600 K, the nature of which is discussed.