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3:Eu Phosphors by Various Synthesis Routes
Published in Vikas Dubey, Sudipta Som, Vijay Kumar, Luminescent Materials in Display and Biomedical Applications, 2020
Ruby Priya, O.P. Pandey, Vikas Dubey
Nanoparticles have sparked intense interest in the field of material science due to their size dependent properties. The physical and chemical properties vary drastically with size variation and thus making them suitable for different applications (Siegel 1993; Siegel et al. 1998; Sun and Murray 2010). At nanometer size range, properties of crystallites are influenced by the presence of significant number of surface atoms. Due to a quantum confinement effect in these nanoparticles, the electronic states become more channelized which exhibit novel properties compared with their corresponding bulk phases (Kruis et al. 1998; Suryanarayana 1995; Wakefield et al. 1999).
Synthesis of Humidity-Sensitive Metal Oxides
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2020
For some applications, especially solid-state gas humidity sensors, it is necessary to use nanoscaled grains with sizes smaller than 5–10 nm (Nayral et al. 2000; Leite et al. 2001). In principle, this is possible, since during the synthesis, crystallites with a size of 2–20 nm are formed. In many cases, however, the powders synthesized using dry and wet methods are agglomerated and are large in size up to several micrometers. Mechanical milling is an effective method of resolving this problem (Hadjipanayis and Siegel 1994; Koch 1997).
Relaxation transitions in some polymers
Published in Maxim Arzhakov, Relaxation in Physical and Mechanical Behavior of Polymers, 2019
A specific feature of semi-crystalline polymers is the coexistence of crystalline and amorphous phases. During crystallization, the same macromolecule participates in the formation of several crystalline regions (crystallites). The segments of the tie-chains connecting the crystallites, (through chains) form amorphous interlayers. Thus, in contrast to polycrystalline low-molecular-weight bodies, for example, metals for polycrystalline polymers, a cooperative relationship of crystalline and amorphous phases is characteristic. Any temperature and/or force perturbation of amorphous regions affects crystallites and vice versa. This dictates a number of distinctive physico-mechanical and relaxation properties of this class of substances and materials, some of which are discussed below.
Temperature dependent electrical and optical properties with higher photosensitivity of Cu2Se absorber thin films for photo voltaic application
Published in Inorganic and Nano-Metal Chemistry, 2021
J. Henry, T. Daniel, V. Balasubramanian, K. Mohanraj, G. Sivakumar
Figures 2–5 shows the FESEM images of as-deposited and Cu2Se films annealed at 100 °C, 200 °C and 300 °C. It is seen from the images that the deposited particles are homogenously distributed over the surface and it covers the entire substrate surface well without any voids, pinholes or cracks. The films composed of small size irregular shaped grains which are well defined boundaries and almost similar in size. The particle size is found to be increases with increase in annealing temperature. The observation supports the XRD analysis. The average size particle is found to be less than 500 nm. The calculated crystallite size from the XRD is several times smaller than that of FESEM. The difference is attributed to the fact that XRD measurements consider crystallite sizes as sizes of “coherently diffracting domains” of crystals while grains may contain several of these domains. The thickness was calculated using FESEM cross sectional images and it is given in Supporting Information (Figure S1, Supplementary material). From the cross sectional images it is found that thickness varies with annealing temperature.
Application of Co-doped copper oxide nanoparticles against different multidrug resistance bacteria
Published in Inorganic and Nano-Metal Chemistry, 2020
Naveen Thakur, Kuldeep Kumar, Kuldeep Kumar Sharma
In this study, the effect of Ag and Ni content on the structural, morphological and optical properties of CuO nanoparticles has been investigated. X-ray diffraction (XRD) and FTIR patterns revealed the formation of single phase nanoparticles of polycrystalline nature without changing their monoclinic structure even after co-doping with Ag and Ni. The average crystallite size varies in the range of 13–23 nm. Also, the fabricated nanoparticles exhibit high purity and crystallinity as reported by elemental analysis studies. SEM analysis shows the formation of various morphologies like rod, needle and spherical shaped nanoparticles and confirms the particle sizes of synthesized nanoparticles as 16.53, 21.99, 26.19, 25.88, and 29.81 nm. TEM images shows little bit aggregation of synthesized CuO nanoparticles and the average particle size measured form TEM images is found in close agreement with the average crystallite size calculated from XRD studies. The optical direct and indirect energy band gap of synthesized nanoparticles lies between 1.34-1.50 eV and 1.22 − 1.37 eV, respectively. In FTIR study, the stretching peak at 526 cm−1 due to Cu-O bond substantiate the formation of the CuO nanoparticles. The antibacterial activity results explained that the synthesized nanoparticles are good inhibitors for the bacterial growth of four pathogens viz. Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.
Influence of Zn incorporation on the microstructural and magnetic properties of La0.67Sr0.33Mn1−xZnxO3 nanoparticles synthesised by the sol–gel method
Published in Philosophical Magazine Letters, 2018
Hilal Ahmed, Shakeel Khan, Wasi Khan, M Ashiq, Swaleha Naseem
Figure 4 shows the field-dependent isothermal dc magnetization at room temperature for the Z0, Z10 and Z20 samples up to the maximum available field of 1.8 Tesla. The hysteresis loops for all the investigated samples measured at room temperature are closed and show almost no coercivity. This may be considered as typical superparamagnetic behaviour of the samples. Superparamagnetism arises on account of the tiny nanoscale size of the particles. Thermal energy is sufficient to modify the direction of magnetization of the whole crystal even though the temperature is less than the Curie or Néel temperatures. These fluctuations in the direction of magnetization are responsible for zero net magnetic field. However, sample shows a paramagnetic nature, as every individual atom comes under the influence of the magnetic field forcing the magnetic moment of the whole crystal to align with the applied magnetic field [23]. The energy required to transform the direction of magnetization of a crystallite is known as crystalline anisotropy energy. It is dependent on the properties of the material and the size of the crystallites. Hence, owing to the small crystallite size, this energy decreases, resulting in a lowering of the temperature at which the sample has a superparamagnetic nature [24,25]. Complete saturation behaviour is not detected even at the highest value of magnetic field (~1.8 Tesla) for all the samples, which can be explained by canting of the surface spins of the nanoparticles. The value of slope of the M-H curve increases with Zn doping up to 10%, but the slope of the curve is lower for 20% Zn doping.