In this paper we aim to develop a summer garment with improved ultraviolet (UV) protection. Due to its lightweight and breathability, cellulose-based viscose rayon was selected to be covered with inorganic ZnO film. Atomic layer deposition (ALD) is a modern technique that delivers uniform coatings with controlled thickness. Viscose fragments were evenly covered with ZnO at 120°C in high vacuum, and their properties were tested against UV exposure and wettability. Morphological examination conducted by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) elemental analysis demonstrated the uniform deposition of ZnO onto the porous semi-synthetic material. The bond structure of cellulose-ZnO composite was assessed by Fourier-transform infrared spectroscopy (FTIR). High wettability of viscose was restrained by the ZnO superficial layer, as revealed by contact angle measurements. Optical absorbance and transmittance evaluated by diffuse reflectance spectroscopy (DRS) displayed the increase of the absorption peak below the 400 nm wavelength in dry and wet conditions, after the ZnO functionalization.
The present paper focuses on the obtaining of ZnO in powder form with a limited distribution of the nanoparticle size using different types of surface-active agents and optimizing the synthesis conditions. The coprecipitation process was chosen for the ZnO powder synthesis in the absence and in the presence of surface-active agents, being considered one of the most common synthesis and processing methods for producing nanostructured materials. The use of agents consists in preventing the nanoparticle size growth, but also in stabilizing the aggregation trend effectively by controlling structural features and by reducing the oxygen bridge bonds between particles. The anionic surfactant (SDS sodium dodecyl sulfate) and the cationic surfactant (CTAB cetyltrimethylammonium bromide) were used to modify the size, morphology and surface properties of the precipitated nanoparticles. Based on the structural characterization by FTIR, XRD, morphology by SEM, as well as UV absorption and PL analyses of ZnO in various versions, the significant influence of agents on ZnO particles, as well as the correlation of optical systems properties with particles morphology and size was revealed. The development of this type of material encourages the uses in many applications in nanotechnology, electronics, optics and other areas of modern science and technology.
Due to the honeycomb arrangement of carbon atoms, graphene exhibits unique properties, such as superior thermal conductivity, exceptionally large surface area and zero bandgap, and has become one of the fastest growing domains of scientific research. Many processes have been developed to obtain single layer graphene by chemical vapour deposition, but the main drawback of using graphene in large area industrial manufacturing processes is the transfer procedure from the transition metal to the target substrate. In the present paper we study the possibility to obtain single layer graphene by chemical vapour deposition (CVD) on copper catalyst and transfer it to different substrates. The quality of CVD graphene on copper catalyst and on substrate target after transfer was evaluated from the structural (by Raman spectroscopy), morphological (by SEM) and optical properties (UV-VIS) point of view. The transfer process proposed in this paper enable the use of this type of material in applications such as pressure sensors and field effect transistors, when proper control of the graphene/substrate interface is very important.
In this paper we propose the study of nanocomposites for white light emission in a semiconductor device, by incorporating the yttrium aluminum garnet doped with cerium ions (YAG:Ce3+), into a polymeric matrix of poly methyl methacrylate. The co-precipitation method was used for the synthesis of YAG:Ce yellow phosphor. The transition from the amorphous state to the crystalline was observed at a temperature of 1200°C. In order to obtain a better dispersion of the nanoparticles in the polymeric matrix has been chosen a capping agent. The structural analysis of the nanocomposite and the phosphor were studied by Fourier transform infrared spectroscopy and x-ray diffraction, morphological properties were investigated by scanning electron microscope, and photoluminescence spectrometry has highlighted the applicability of phosphors and, implicitly, of the nanocomposite for application in emitting optoelectronics.