Structures and optical properties of zinc oxide nanoclusters: a combined experimental and theoretical approach.

CONTEXT: In this study, theoretical and experimental analysis of the electrical, optical, and structural properties of a wurtzite-like zinc oxide (ZnO) nanostructure has been done. To investigate how quantum confinement affects the optical characteristics, two distinct ZnO clusters in nanowire structures have been investigated. The [(ZnO)55(H2O)4] system's HOMO-LUMO band gap (BG) was calculated to be 2.99 eV, which is quite close to the experimental measurement. It was found that the BG decreases with the increase in the number of atoms in the cluster in connection with the quantum confinement in nanoclusters. In addition, the lowest excitation energy in TD-DFT calculations of the identical system is in fairly good agreement with the experimental value with a difference of 0.1 eV. We conclude that the CAM-B3LYP functional has highly successful in reproducing the experimental data reported in the present study and previously reported experimental data. METHODS: The geometrical optimization of two different sizes of ZnO clusters ([(ZnO)25(H2O)4] and [ZnO)55(H2O)4]) was performed using the CAM-B3LYP functional with no symmetry constraints applied in the gas phase. LANL2DZ basis sets were used for the Zinc (Zn) atom and 6-31G* basis sets for the O and H atoms. To determine their optical and electronic properties, excited state calculations of the pre-optimized structures were performed using the Time-Dependent DFT (TD-DFT) method. Multiwfn, Gaussum 3.0, and GaussView 5.0 programs were used to visualize the results.

Computational Study of Doping in Dopamine with Halogens to Control Optical and Spectroscopic Properties.

In this research, a comprehensive study of dopamine was conducted using the theoretical first principles method due to its crucial importance as a hormone for the neurotransmission process in the animal body. Many basis sets and functionals were used for optimization of the compound to attain stability and find the appropriate energy point for the overall calculations. Then, the compound was doped with the first three members of the halogen family (fluorine, chlorine, and bromine) to analyze the effect of their presence in terms of change in their electronic properties, such as band gap and density of states, and spectroscopic parameters, such as nuclear magnetic resonance and Fourier transform infrared. It was found that the band gap of the system changes depending on the doping of halogens.

Halogen Doping to Control the Band Gap of Ascorbic Acid: A Theoretical Study.

Ascorbic acid is an important antioxidant agent that acts as an electron donor and is involved in many physiological processes. Structural modification in ascorbic acid is a subject of extensive biochemical research due to its involvement in a variety of relevant phenomena including electron transport, complex redox reactions, neurochemical reactions, enzymatic reactions, and chemotherapeutic potential. In this work, the structure of ascorbic acid is modified via doping with the first three members of the halogen group to investigate the changes in the electronic structure and spectroscopic parameters using first-principles methods. To obtain the lowest-energy structures, different basis sets in density functional theory (DFT) and Hartree-Fock approaches were employed in the geometry optimization process. The potential energy maps of the structures were computed to study the molecular orientations and their optical and electrical properties. The spectroscopic properties were computed via UV-vis and nuclear magnetic resonance (NMR) spectroscopies to study the effects of doping into the compound. To obtain further insights into the chemical structure, the Fourier transform infrared (FT-IR) spectra of the materials were theoretically investigated. It was found that the band gap is sensitive to doping as we moved from fluorine to chlorine and then to bromine.

Effects of Yttrium Doping on Erbium-Based Hydroxyapatites: Theoretical and Experimental Study.

This is the first investigation of yttrium (Y) and erbium (Er) co-doped hydroxyapatite (HAp) structures, conducted using theoretical and experimental procedures. By using a wet chemical method, the materials were synthesized by varying the concentration of Y amounts of 0.13, 0.26, 0.39, 0.52, 0.65, and 0.78 at.% every virtual 10 atoms of calcium, whereas Er was kept fixed at 0.39 at.%. Spectroscopic, thermal, and in vitro biocompatibility testing were performed on the generated samples. Theoretical calculations were carried out to compute the energy bandgap, density of states, and linear absorption coefficient. The effects of Y concentration on thermal, morphological, and structural parameters were investigated in detail. Raman and Infrared (FTIR) spectroscopies confirmed the formation of the HAp structure in the samples. Theoretical investigations indicated that the increasing amount of Y increased the density from 3.1724 g cm-3 to 3.1824 g cm-3 and decreased the bandgap energy from 4.196 eV to 4.156 eV, except for the sample containing 0.39 at. % of the dopant, which exhibited a decrease in the bandgap. The values of linear absorption appeared reduced with an increase in photon energy. The samples exhibited cell viability higher than 110%, which revealed excellent biocompatibility for biological applications of the prepared samples.

Bioactive contents, In vitro antiradical, antimicrobial and cytotoxic properties of rhubarb (Rheum ribes L.) extracts.

Rheum ribes L. (rhubarb) is belonging to Polygonaceae, and its roots and fresh shoots are consumed as vegetable in Turkey. This plant is considered to be one of the most important pharmaceutical raw materials in Middle East. In this study, the antiradical, antimicrobial, cytotoxic and bioactive properties of water, ethanol, and methanol extracts of R. ribes stems were determined. R. ribes stems water, ethanol and methanol extracts are better scavenged ABTS•+ (99.27, 99.91, and 99.88%), DPPH• (83.11, 81.42, and 83.26%), and OH• radicals (93.49, 94.21, 95.86%) than standard antioxidant BHA (95.32, 80.49, and 93.78%). Stems of R. ribes abundantly include bioactive compounds, dominated by rutin, catechin, caffeic acid, ferulic acid, α-tocopherol and vitamin D. These extracts show effective cytotoxic properties against PC-3, A2780, HCT-116 and MCF-7 cancer cell lines at 24h. It is found that R. ribes contain high amount important bioactive contents, and has effective antiradical and cytotoxic properties.

Phytochemical compounds and antiradical, antimicrobial, and cytotoxic activities of the extracts from Hypericum scabrum L. Flowers.

Hypericum scabrum L. has been widely used in traditional medicine for the treatment of many diseases just as the other Hypericum species. In the present study, the antiradical, antimicrobial and cytotoxic activities of water and ethanol extracts of H. scabrum flowers were investigated. Their phytochemical contents and composition were also determined. The water and ethanol extracts are better scavenged ABTS (97.89 and 98.99%) and OH radicals (96.36 and 97.33%); the water extract is better scavenged DPPH radicals (91.66%) than the standard antioxidant BHA (94.33, 85.19, 90.16%, respectively). Flowers of H. scabrum contain flavonoids, phenolic acids, vitamins and phytosterols, dominated by catechin, vanillic acid, vitamin K and ergosterol. The extracts exhibit a strong cytotoxic activity against MCF-7, HCT-116, and LNCaP cancer cell lines. It is found that their antimicrobial activities are higher than the standard antibiotics. These results indicate that H. scabrum flowers have potent antiradical, antimicrobial and cytotoxic activities.

The effect of simulating body fluid on the structural properties of hydroxyapatite synthesized in the presence of citric acid.

In present work, the effect of citric acid (CA) addition in different amounts (0, 1, 5 and 10 ml) on the structure of hydroxyapatite (HAp) was investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. The crystallite dimensions, lattice parameters, unit cell volume, crystallinity percentage and Ca/P molar ratio were found to be affected by the CA content. To investigate the influence of CA on the bioactive properties of the HAp samples and to determine the optimum amount of CA, in vitro soaking tests in simulated body fluid (SBF) were performed. Although the samples' morphology was found to be affected by neither the amount of CA nor the soaking time in SBF, the soaking results revealed that the maximum changes in the Ca/P ratio were found for the HAp samples prepared in the presence of the highest amounts of CA, which pointed out to the highest bioactivity of these samples.

Controlling of dielectric parameters of insulating hydroxyapatite by simulated body fluid.

Hydroxyapatite (HAp) samples were synthesized under various amounts of citric acid using the sol-gel method. Before and after immersion in simulated body fluid (SBF) for 14 and 28 days, the structural properties of HAp samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy with energy dispersive X-ray (EDX) spectroscopy and dielectric measurements. The crystallite size (D) was found to be in the range of 25.17-33.06 nm with the crystallinity percent (XC%) of 69.53-86.09. The lattice parameters of a and c were calculated to be in the ranges of 9.373-9.434 Å and 6.828-6.896 Å, respectively. The morphology of the as-synthesized samples was changed with the amount of citric acid and soaking period in SBF. The Ca/P molar ratios indicated a decrease with increasing immersion time, and Ca-deficiency was observed. The relative permittivity (ε') and dielectric loss (ε″) were significantly affected by citric acid content and soaking period in SBF. It was seen that the alternating current conductivity (σac) increased with increasing frequency and the σac values changed with increasing soaking period and amount of citric acid.

Strontium substituted hydroxyapatites: Synthesis and determination of their structural properties, in vitro and in vivo performance.

The objective of this study is to present a detailed report related to the synthesis and characterization of strontium substituted hydroxyapatites. Based on this purpose, hydroxyapatite (HAp) bioceramics with different amounts of strontium (e.g., 0, 0.45, 0.90, 1.35, 1.80 and 2.25 at.%) were prepared using a sol-gel method. The effects of Sr substitution on the structural properties and biocompatibility of the samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques, in vitro and in vivo tests. All the samples composed of the nanoparticles ranging from 21 to 27 nm. The presence of Sr at low levels influenced the crystal size, crystallinity degree, lattice parameters and volume of the unit cell of the HAp. Both in vitro conditions and soaking period in simulated body fluid (SBF) significantly affected these properties. Especially, the (Ca+Sr)/P molar ratio gradually decreases with increasing soaking period in SBF. Animal experiments revealed the bone formation and osseointegration for all samples, and as compared with other groups, more reasonable, were observed for the sample with the lowest Sr content.

Structural and dielectric properties of yttrium-substituted hydroxyapatites.

Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content.

Synthesis and characterization of Ce-substituted hydroxyapatite by sol-gel method.

Both undoped hydroxyapatite (HAp) and three Ce-substituted HAp samples with variable amounts (from 0.5 to 2 at.%) of Ce were synthesized by sol-gel method. The samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy to determine the crystallite size, crystallinity degree, phases, functional groups, morphology and elemental composition. In all samples, the amount of HAp exceeded 92%, while the amount of admixture ß-TCP was always below 8% and no changes were observed by addition of Ce. The crystallinity degree of the samples was always within 84-89%, while the calculated dimensions of crystallites appeared to be within 26-35nm. The microstructure and elemental composition of all the samples were found to be affected by the addition of Ce.

Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications.

The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA.

In vitro characterization of polyvinyl alcohol assisted hydroxyapatite derived by sol-gel method.

The synthesis and characterization of sol-gel derived hydroxyapatite (HAp) were investigated with the effects of the addition of polyvinyl alcohol (PVA) to the structural and material in vitro behavior. All samples were soaked in simulated body fluid (SBF) for 14 and 28 days. The characterization of bioceramics before and after immersing in SBF was carried out by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis (DTA), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques. After the simulated body fluid period, the crystal structure and phase of HAp samples did not change significantly. The characteristic bands of hydroxyl, phosphate and carbonate groups were detected. HAp exhibited a thermal stability of room temperature to 1000 °C. The surface morphologies of the samples show an evident change with the soaking period in SBF.