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Benchmark Analysis on Magnetic and Photoluminescence Properties of Selective Metal Ions Doped ZnS Nanoparticles
摘要： The creation of diluted magnetic semiconductors (DMSs) at lower dimensions that exhibit room temperature ferromagnetism (RTFM) has been given immense significance for the fabrication of a new class of spintronic devices through utilizing spin degrees of freedom besides charge nature of electrons. In this view, nanocrystals of ZnS doped with 4% concentration of Fe, Co, Ni, Cr, Mn, Sr, Cu, and Ce have been synthesized at room temperature (RT) by chemical co-precipitation method. The samples were examined by various characterization techniques like energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and photoluminescence (PL). EDS spectra revealed the existence of parent elements in the prepared samples. XRD characterization disclosed hexagonal structures of nanocrystals, and no secondary phases were observed in all the samples except for Cu and Ni doped ZnS. FTIR data confirmed the proper substitution of dopants in the host lattice as all the graphs have almost same stretchings. The magnetic nature of each sample was evaluated from M-H graphs of VSM, and it corroborated the transition of magnetic properties due to doping. Pristine ZnS showed diamagnetic nature, while Fe and Sr doped ZnS evinced strong ferromagnetic and anti-ferromagnetic properties, respectively. Photoluminescence studies on Ce, Sr and Mn doped ZnS samples revealed strong emission peaks with enhanced luminescence properties compared to bare ZnS. Cu, Cr and Mn doped ZnS exhibited a red shift in emission wavelengths, whereas Co doped ZnS showed emission peak shifted towards the blue region as compared to the host lattice.
关键词： ZnS,Photoluminescence,DMS,RTFM,Transition metals
更新于2025-09-23 15:23:52
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Exploration of new birefringent crystals in bismuth d0 transition metal selenites
摘要： The first examples of bismuth fluoride selenites with d0-TM/Te(VI) polyhedrons, namely, Bi4TiO2F4(SeO3)4 (1), Bi4NbO3F3(SeO3)4 (2), Bi4TeO4F2(TeO3)2(SeO3)2 (3), Bi2F2(MoO4)(SeO3) (4) and Bi2ZrO2F2(SeO3)2 (5) have been successfully synthesized under hydrothermal reactions by aliovalent substitution. The five new compounds feature three different types of structures. Compounds 1-3, containing Ti(IV), Nb(V) and Te(VI) respectively, are isostructural, exhibiting a new 3D framework composed of 3D bismuth oxyfluoride architecture with intersecting tunnels occupied by d0-TM/Te(VI) octahedrons and selenite/tellurite groups. Compound Bi4TeO4F2(TeO3)2(SeO3)2 (3) is the first structure containing Se(IV) and mixed-valent Te(IV)/Te(VI) cations simultaneously. Compound 4 features a new 3D structure formed by 3D bismuth oxyfluoride network with MoO4 tetrahedrons and selenites groups embeded in the 1D tunnels. Compound 5 displays a novel pillar-layered 3D open framework consisted of 2D bismuth oxide layers bridged by the [ZrO2F2(SeO3)2]6- polyanions. Theoretical calculations revealed that the five compounds displayed very strong birefringence. The birefringence values of compounds 1-3, especially, are above 0.19 at 1064 nm, which are bigger than the mineral calcite. Based on the structure and property analysis, we found that the asymmetric SeO3 groups (and TeO3 in compound 3) displayed the largest anisotropy compared with the bismuth cations and the d0 TM/Te polyhedrons, which is beneficial to the birefringence.
关键词： metal selenites,d0 transition metals,aliovalent substitution,hydrothermal reactions,birefringent crystals
更新于2025-09-23 15:23:52
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TiO2 Modification with Transition Metallic Species (Cr, Co, Ni, and Cu) for Photocatalytic Abatement of Acetic Acid in Liquid Phase and Propene in Gas Phase
摘要： The commercial P25 titania has been modi?ed with transition metallic species (Cr, Co, Ni, and Cu), added by impregnation with aqueous solutions of the corresponding nitrates. The preparation procedure also includes a heat treatment (500 ?C) in argon to decompose the nitrates, remove impurities and to strengthen the metal–TiO2 interaction. The catalysts have been thoroughly characterized using N2 adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible diffuse-re?ectance spectroscopy (UV-vis DRS) and X-ray photoelectron spectroscopy (XPS), and have been tested in the aqueous phase decomposition of acetic acid and in the gas phase oxidation of propene, using an irradiation source of 365 nm in both cases. The photocatalytic activity of the four metal-containing catalysts varies with the nature of the metallic species and follows a similar trend in the two tested reactions. The effect of the nature of the added metallic species is mainly based on the electrochemical properties of the supported species, being Cu/P25 (the sample that contains copper) the best performing catalyst. In the photodecomposition of acetic acid, all the metal-containing samples are more active than bare P25, while in the gas phase oxidation of propene, bare P25 is more active. This has been explained considering that the rate-determining steps are different in gas and liquid media.
关键词： TiO2,P25,propene,photocatalysis,acetic acid,transition metals
更新于2025-09-23 15:22:29
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Optical properties and colorimetry of gelatine gels prepared in different saline solutions
摘要： Gelatine has been widely used in many multidisciplinary research fields due to its biocompatibility. Using saline solutions in the gelation of gelatine allows for new properties to be incorporated into the prepared gels. This study examined the optical and colour properties of gelatine gels prepared in saline solutions, containing three different metal chlorides (NiCl2·6H2O, CoCl2·6H2O, and CrCl3·6H2O) with concentrations of up to 50%, to prepare three groups of gels. FTIR spectroscopy indicated a loss in the helical structure of the metal-containing gelatine gels, and a shift in the amide bands towards lower wavenumbers. From the thermogravimetric analysis (TGA), the starting degradation temperatures (SDTs) of the prepared gelatine gels were found to be correlated to the concentration of the gelling solutions. All SDTs were above 250 °C, making these gels suitable for standing temperatures beyond the daily range. UV–vis spectroscopy showed that d-d transitions were responsible for the colour properties of the metal-containing gelatine gels. It is concluded that the studied properties and the measured parameters were found to depend on both salt type and concentration. With the current findings, the prepared gels can be used as optical thermometers, colour-selective corner cube retroreflectors, laser components, and coatings for OLEDs.
关键词： Colour parameters,Fourier transform infrared spectroscopy,Optical properties,Gelatine,Transition metals,Thermogravimetric analysis
更新于2025-09-23 15:22:29
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RECENT APPLICATIONS IN ORGANIC SYNTHESIS OF VISIBLE LIGHT PHOTOREDOX CATALYSIS
摘要： RECENT APPLICATIONS IN ORGANIC SYNTHESIS OF VISIBLE LIGHT PHOTOREDOX CATALYSIS. In the past few years, photoredox catalysis has become a powerful tool in the field of organic synthesis. Using this efficient method, it is possible to excite organic compounds from visible light and attain alternative mechanistic pathways for the formation of chemical bonds, a result which is not obtainable by classical methods. The rapid growth of work in the area of photoredox catalysis is due to its low cost, broad chemical utility protocols, and, especially, its relevancy from the green and sustainable chemistry viewpoints. Thus, this study proposes a brief theoretical discussion of and highlights recent advances in visible-light-induced photoredox catalysis through the analysis of catalytic cycles and intermediates.
关键词： visible light,photoredox catalysis,organocatalysis,organic synthesis,transition metals
更新于2025-09-23 15:21:21
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DFTB Investigations on Transition Metals Doped TiO2 Quantum Dots
摘要： The structural, optical and electronic properties of different-sized pure as well as transition metals doped TiO2 quantum dots were investigated using density functional tight binding (DFTB) methods. The self-consistent charge density functional tight binding theory (SCC-DFTB) was used to model the TiO2 quantum dots (QDs) of increasing size up to 3.03 nm. The size dependence of density of states, position of molecular orbitals, and gap between highest orbital molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of the QDs were studied. It appeared that, when the size of QDs approaches 3.03 nm, the energy gap narrowed down due to quantum confinement effects. The QD Ti27O54 was doped with 3d transition metals to further explore the possibility of tailoring the properties. The dopants introduced 3d impurity gap states which opens the opportunity to modify the band gap or positions of principal bands. The position of a shifted Fermi level was monitored to explore the changes in conductivity and n- or p-type behaviors of the doped QDs. It was observed that TiO2 QDs doped with V and Cr showed the n-type behavior while those doped with Sc, Mn and Fe showed p-type behavior. The findings are helpful to enhance the photocurrent efficiency of dye-sensitized solar cells and use the materials in electronic and optoelectronic properties.
关键词： LUMO,transition metals,DFTB,density of states,quantum dots,HOMO
更新于2025-09-23 15:19:57
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UV-induced macromolecular and optical modifications in gelatin solid films with transition metal chlorides
摘要： Gelatin solid films containing transition metal chlorides (NiCl2·6H2O, CoCl2·6H2O and CrCl3.6H2O) were prepared and UV-irradiated at different exposure times, to study the effect of irradiation on the structural properties at the molecular level, as well as the electronic level, using FT-IR and UV-visible spectroscopies. Results showed that modifications in the molecular and electronic structure due to UV-irradiations were possible even when applying the irradiation treatment to the films in the solid phase. These modifications also differ according to the additive’s type and concentration. The force constant of the CO bond tends to increase, and that for the OH bond tends to decrease, by increasing the irradiation exposure time. The colour difference tends to have higher values for the films with the higher additive concentration and higher exposure times, in the meantime, the brightness tends to increase for Gelatin-NiCl2 and Gelatin-CrCl3 films, and decrease for Gelatin-CoCl2 films. The samples of the Gelatin-NiCl2 group become more yellowish and more greenish by increasing concentrations and exposure times, whereas those of the Gelatin-CoCl2 group tend to become more bluish and more reddish. Moreover, the values of yellowness tend to increase for Gelatin-CoCl2 and Gelatin-NiCl2 films with increasing concentrations and exposure times. Our research concludes that UV-induced modifications in the microstructure and optical properties of the gelatin films are possible in the solid phase due to increasing the crosslinking effects. With the current findings, these films can be used as radiation biosensors.
关键词： UV-vis spectroscopy,Ultraviolet radiation,Transition metals,gelatin,macrostructure,FT-IR
更新于2025-09-19 17:15:36
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Single-Walled boron nitride nanotubes interaction with nickel, titanium, palladium, and gold metal atoms- A first-principles study
摘要： Ab initio calculations based on density functional theory was carried out to study the electronic properties of (3,3), (4,2), (5,2) and (6,0) boron nitride nanotubes when interacting with nickel, titanium, palladium and gold metal atoms. These interactions occurred via adsorption, intercalation, nitrogen substitutional doping and boron substitutional doping. The wide band gaps intrinsic to the pristine boron nitride nanotubes were successfully tuned upon interaction with the metal atoms irrespective of the type of interactions. However, for most of the interactions that occurred via intercalation and nitrogen substitutional doping, the boron nitride nanotube was found to possess semi-metallic properties. More states were added in the density of states upon interaction in which the d orbital of the transition metal atoms was found to be the major contributor to the increase in density of states.
关键词： Transition metals,Fermi energy,Density functional theory,Band gap,Boron nitride nanotubes
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Nonlinear Refraction and Nonlinear Absorption in Layered Transition Metals Dichalcogenides
摘要： The unique thickness- and composition-dependent properties of two-dimensional Transition Metal Dichalcogenides (TMDs) afford opportunities to a wide range of applications, as reviewed in [1]. Among the diverse methods to fabricate TMDs, redox exfoliation offers features critical to composite, coating and ink technologies, including low cost, low-energy, and a general framework for exfoliating TMDs from Groups IV, V, VI, and VII. Nonlinear (NL) optical absorption is a relevant effect in TMDs with potential applications in multiphoton microscopy, fluorescence imaging and optical limiting. For instance, two-photon absorption (TPA) saturation in MoS2 was reported in [2]. On the other hand, NL refraction may be exploited for all-optical switching and optical processing. In this communication, we describe the NL optical behavior of MoS2, WS2, NbS2 and ZrTe2 in the femtosecond regime. Details of the redox exfoliation and morphological characterization of the TMDs are given in [3]. For the experiments, the TMDs were suspended in acetonitrile with concentrations of (cid:26)(cid:19)(cid:3)(cid:541)(cid:74)(cid:18)(cid:80)(cid:79) (MoS2)(cid:15)(cid:3)(cid:23)(cid:19)(cid:3)(cid:541)(cid:74)(cid:18)(cid:80)(cid:79) (WS2), (cid:20)(cid:19)(cid:19)(cid:3) (cid:541)(cid:74)(cid:18)(cid:80)(cid:79)(cid:3) (NbS2) (cid:68)(cid:81)(cid:71)(cid:3) (cid:20)(cid:19)(cid:19)(cid:3) (cid:541)(cid:74)(cid:18)(cid:80)(cid:79) (ZrTe2). The mean lateral flakes’ sizes varied from 84 nm to 325 nm and thicknesses from 2.0±1.1 nm to 3.8±1.7 nm. Fig.1(a) shows the linear extinction spectra of the four samples. The effective NL refractive index (nNL) and effective NL absorption coefficient ((cid:68)NL) were measured. In principle, both parameters include contributions from NL susceptibilities and NL light scattering. The light source used was a Ti:Sapphire based regenerative amplifier (800 nm, 1 kHz, 100 fs). The beam was focused with a 15 cm focal length lens onto a 1 mm quartz cuvette. The peak intensity was varied up to (cid:1835) =120 GW/cm2. Z-scan measurements were also performed for pure acetonitrile which showed third-order refractive index equal to +1.9×10-17cm2/W. Fig.1(b) shows the ratio between the peak-to-valley Z-scan curve and the laser intensity (|(cid:959)(cid:1846)|/(cid:1835)) versus (cid:1835) that indicates an effective fifth-order nonlinearity of MoS2 - the values of the third- and fifth-order effective refractive indices are +(4.5±0.3)×10-16 cm2/W and - (7.1±0.2) × 10-25 cm4/W2, respectively. Fig. 1(c) shows that in the case of WS2 only the third-order nonlinearity is observed and nNL=+(3.4±0.2) ×10-16 cm2/W. Fig. 1(d), for NbS2, shows a change in the nNL sign from negative to positive as the intensity increases. Finally, Fig.1(e) for the novel ZrTe2 material shows third-order response with nNL=+(4.2±0.3)×10-16 cm2/W. NL absorption was only observed for NbS2 which presented the effective TPA changing to saturated absorption as the intensity is increased. The results were analyzed considering the sample’s characteristics and applying the Z-scan procedure as described in [4]. To fit the NL absorption curves of NbS2 we assumed homogeneous broadening relaxation and the saturation intensities obtained were 33 GW/cm2 for 1-photon and 39 GW/cm2 for 2-photon absorption. The effective TPA coefficient was 0.21 cm/GW for intensities below saturation.
关键词： Transition Metals Dichalcogenides,TMDs,redox exfoliation,Nonlinear Absorption,Nonlinear Refraction,femtosecond regime
更新于2025-09-12 10:27:22
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Substrate integrated waveguide‐slot wide‐angle scanning aperiodic phased array with low side‐lobe levels
摘要： The concentrations of Cr, Fe, Ni, and Cu in a cast-monocrystalline silicon ingot grown for solar cell applications are reported. Wafers taken from along the ingot are coated with silicon nitride ?lms and annealed, causing mobile impurities to be gettered to the ?lms. Secondary ion mass spectrometry is applied to measure the metal content in the silicon nitride ?lms. The bulk concentrations of the gettered metals in samples along the ingot are found to be: Cr (3.3 (cid:1) 1010–3.3 (cid:1) 1011 cm(cid:3)3), Fe (3.2 (cid:1) 1011–2.5 (cid:1) 1012 cm(cid:3)3), Ni (1.5 (cid:1) 1012–1.3 (cid:1) 1013 cm(cid:3)3), and Cu (7.1 (cid:1) 1011–3.2 (cid:1) 1013 cm(cid:3)3). For each metal, the lower limit is measured on the wafer from the middle of the ingot, and the higher limit is measured on wafers from the bottom or the top. The results are compared with similar data recently measured on a high-performance multicrystalline silicon ingot. The results provide insights into the total bulk concentrations of the metals in cast-grown ingots.
关键词： gettering,transition metals,cast-mono,silicon nitride
更新于2025-09-11 14:15:04