Narrow Results

An interest in the study of the structural and optical properties of topological insulators, led to the selection of Bismuth telluride thin films. Among the topological insulators, Bismuth telluride is one of the promising materials that exhibit applications in the field of thermoelectric power generation. The films were prepared using the thermal evaporation method under vacuum conditions of ${10}^{-5}$ mbar on glass substrates maintained at a temperature of 120^∘C. The thickness of the film samples ranges from 400 Å to 1400 Å. Pure phases of Bi₂Te₃ with a rhombohedral structure are confirmed using X-ray Diffraction. The crystallite size was calculated using Debye–Scherrer’s formula. Structural morphology and compositions are examined using SEM and EDAX. The UV–Vis study reflects the optical behavior of the thin film samples. The absorption spectra gives the direct and allowed transition band gap of the Bi₂Te₃ thin film samples for various thicknesses. The band gap decreases with the increase in the thickness of the Bi₂Te₃ thin films, suggesting that the material has significant absorption towards the visible spectrum. The Photoluminescence (PL) emissions for Bi₂Te₃ thin film samples of various thicknesses are examined and analysed. Raman study reveals the presence of two active modes.

Novel nanoprism-shaped manganese-doped copper sulfide (Mn–CuS) was fabricated by two-phase colloidal method (Mn percentages = 0%, 1%, 3%, and 5%). The Mn–CuS was analyzed by XRD, FTIR, UV–Vis spectrometer, and TEM. The XRD shows that the hexagonal covellite copper sulfide peaks appeared at 2$\theta =47.9^{\circ },31.9^{\circ },47.8^{\circ }$, and $31.8^{\circ }$ for 0%, 1%, 3%, and 5% respectively, and orthorhombic chalcocite copper sulfide appeared at the peaks that are corresponding the planes (412), (275), (029) and (106). According to UV–Vis analysis, the optical absorption of manganese-doped copper sulfide 0%, 1%, 3%, and 5% clearly appeared in the UV–Vis region at 518, 440, 478, and 477nm respectively, and there are broad peaks for localized surface plasmon resonances (LSPR) of CuS located at 970, 1061, 1002, and 1006nm for Mn–CuS 0%, 1%, 3%, and 5%, respectively. The favored nanoprism-shaped sample (manganese-doped copper sulfide 1%) was coated with gum Arabic (GA) in order to decrease the cytotoxicity and enhance the biocompatibility. The antibacterial activity of manganese-doped copper sulfide and GA@Mn–CuS 1% nanostructure toward Staphylococcus aureus and Escherichia coli bacteria was determined by inhibition zone. It was found that the fabrecated Mn–CuS 1% nanoprisms were more active toward both E. coli and S. aureus bacteria and the doping enhanced the antibacterial activity.

This study intended to synthesize Nickel-doped Cerium oxide (Ni-CeO₂ NPs) nanoparticles using Pedalium Murex leaf extract. X-ray diffraction (XRD) was used to investigate the structure of the Ni-CeO₂ NPs. The XRD measurements showed that the Ni-CeO₂ NPs crystallized into the face-centered cubic system. The Ni(1%)-CeO₂ and Ni(3%)-CeO₂ NP’s crystallite sizes were between 47nm and 59nm. FTIR and Raman spectral studies were conducted to investigate the sample’s atomic vibrations and chemical bonding. Energy-dispersive X-ray study and field-emission scanning electron microscopy were performed to examine the surface texture and chemical assembly of the Ni-CeO₂ NPs. UV–Vis DRS spectrum study was performed to ascertain the reflectance characteristics and bandgap of Ni-CeO₂ NPs. The Ni(1%)-CeO₂ and Ni(3%)-CeO₂ NPs were found to have bandgaps of 2.73eV and 2.82eV, respectively. Electrochemical impedance spectroscopy and cyclic voltammetry were employed to explore the electrochemical nature of Ni-CeO₂ NPs and their capacitive properties at various scanning rates. Using the agar well-diffusion technique, the antifungal activities of Ni-CeO₂ NPs were assessed. The experimental findings illustrate the utility of Ni-CeO₂ NPs for supercapacitor electrode material and healthcare applications.

Single crystals of pure and various amount of L-lysine doped KDP crystals were grown from aqueous solution. The doping of L-lysine was confirmed by CHN analysis and FT-IR spectroscopy. Powder XRD was carried out to assess the single phase nature of the samples. The effect of doping on thermal stability of the crystals was carried out by TGA and the kinetic and thermodynamic parameters of dehydration were evaluated. It was found that as the amount of doping of amino acid, L-lysine, increased the thermal stability of the grown crystals decreased. However, the second-harmonic generation (SHG) efficiency of Nd:YAG laser and UV-vis spectroscopy studies indicated that as the L-lysine doping increased in KDP crystals the SHG efficiency and optical transmission percentage increased. The dielectric constant and the dielectric loss of L-lysine doped KDP crystals are lower than the pure KDP crystals. Hence L-lysine doped KDP crystals are found to be more beneficial from an application point of view as compared to pure KDP crystals. The results are discussed.

The widespread use of nonlinear optical (NLO) materials for contemporary technologies has sparked intense interest in their production with the creation of materials with a continuous endeavor. In this theoretical study, we investigate the NLO responses of doped superalkali (SA) metal salts with planar boron sheets (PBSs). We consider four different substrates (B${}_{10}$, B${}_{10}$F₃, B${}_{16}$, and B${}_{16}$F₃) to create 12 new surfaces (1-12) by doping SAs (Li₂F, Li₂OF, Li₂O₂) with them. We optimize the geometries of these surfaces and analyze their frontier molecular orbitals (FMOs) and natural bond orbitals (NBO) to obtain insights into their global chemical reactivity. We also examined their NLO responses ranging as 1.22–$1.67\times 10^{-21}$, 3.39–$7.59\times 10^{-24}$, and $3.5\times 10^{-24}$e.s.u. Our results reveal that the doped surfaces exhibit stronger NLO responses compared to the undoped surfaces, and that the strongest NLO response is found in the B${}_{16}$F₃-doped surface. The role of various segments in FMOs is investigated using the TDOS and PDOS spectral analyses. To comprehend the relationship between the SA and the B${}_{10}$F₃ substrates molecule more effectively, non-covalent interaction (NCI) investigation is carried out. Additionally, Time-dependent DFT (TD-DFT) simulations are done for UV–Vis analysis to observe significant redshifts up to 1050nm. All the SA-doped surfaces are thermodynamically stable NLO materials with improved NLO responses, so these materials are proposed to be used during the construction of advanced NLO responses.

An infrared CO₂ laser was used for regional heating to study the heating effect on hot filament chemical vapor deposition of diamond-like carbon formation on Si(100) face substrates. The substrate surface temperature was about 450–500°C. The power of the laser called low, medium, and high raised the temperature of the substrate locally by 25, 45, and 55°C, respectively. At medium laser power, at the central laser beam region, a narrow Raman peak centered at 1438 cm^-1 was detected. It can be concluded that this region has good-quality DLC. This moderate high-frequency peak corresponds to a fourfold-rotation-symmetry atom in an amorphous carbon network from the tight-binding molecular dynamics simulation of Wang and Ho.

Nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium salt (NiTsPc) thin films were deposited on glass substrates at different substrate temperatures ($T_s$) by chemical spray pyrolysis (CSP) technique. The substrate temperature varied from 110^∘C to 310^∘C in 50^∘C steps. The substrate surface temperature is the main parameter that determines the film morphology and properties of the thin films. The structural properties of the deposited NiTsPc thin films were investigated by X-ray diffraction (XRD) and from the obtained results, it was shown that depositing thin films using 210^∘C as $T_s$ results in higher crystallinity. Atomic force microscope (AFM) was employed to obtain the surface topography and to calculate the roughness and grain size. The smoothest thin film surface was obtained when using at 160^∘C, while the highest roughness was obtained at 310^∘C. The optical properties were investigated by ultraviolet visible (UV-Vis) spectrophotometer and fluorescence spectrophotometer. From the absorption spectra recorded in the wavelength range 190–1100nm, two absorption bands were observed, which are known as Soret and Q-band. By observing the absorption spectrum, it can be concluded that the deposited thin films at 110^∘C–310^∘C have direct energy gap. From Tauc plot relation, the energy gap ($E_g$) was calculated. The values of the energy gap were between 3.05 and 3.14eV. It was observed that different $T_s$ highly affects the structural and optical properties of the deposited thin films. The crystallinity, grain size, roughness and the optical properties were strongly affected by the different substrate temperatures.

A five-coordinate chloroiron(III) complex has been synthesized and characterized by X-ray diffraction analysis and UV-Vis spectroscopy. The maximum one-photon absorption (OPA) wavelengths recorded by both linear optical measurements and quantum mechanical computations using the configuration interaction (CI) method are estimated to be shorter than 400 nm in the UV region, showing good optical transparency to visible light. To investigate the microscopic third-order nonlinear optical (NLO) behavior of the title compound, we have computed both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) at λ = 825–1125 nm and 1050–1600 nm wavelength areas using the time-dependent Hartree–Fock (TDHF) method. The ab-initio calculation results with non-zero values on (hyper)polarizabilities indicate that the synthesized molecule might possess microscopic third-order NLO phenomena.

The advancement of crystal growth and characterization methods allows us to investigate new substances with excellent nonlinear optical characteristics. To synthesize nonlinear optical material L-histidine hydrochloride hydrate (L-HHCLH), the gradual evaporation process was used. The produced samples were characterized by single-crystal X-ray crystallography, Fourier transform infrared (FTIR) and Raman spectroscopy, UV–visible (UV–Vis) spectroscopy, second harmonic generation (SHG) test, dielectric, and mechanical investigations. The L-HHCLH sample was crystallized in an orthorhombic structure with the P2₁2₁2₁ space group, as verified by the crystallographic data. FTIR and Raman spectroscopy were applied to examine the molecular vibrations and availability of the functional groups of the compound. The L-HHCLH is significantly transparent across the UV and visible ranges, as shown by the UV–Vis spectra measurements. The bandgap of L-HHCLH is 5.45 eV. The SHG test showed that the L-HHCLH crystals produced a significant amount of SHG output thrice that of the potassium dihydrogen phosphate (KDP) sample. The frequency dependences of the dielectric parameters were investigated in the dielectric tests. With increasing frequency, both the dielectric constant and loss dropped exponentially. The crystal hardness was determined using a microhardness test.

Composites of polyvinyl alcohol (PVA) containing silver nanoparticles were prepared using in situ synthesis of nanoparticles. Structure and properties of these composites were investigated using UV-Vis spectroscopy, XRD, DSC, SEM and AFM. The studies show that PVA can reduce the AgNO₃ to yield silver nanoparticles and in the process forms bonds with PVA chains. The anti-bacterial properties of these films were studied by qualitative as well as quantitative methods which gave the values of 98% for gram positive and 89% for gram negative bacteria.

In this work, we report the successful formation of MgO doped TiO₂ nanocrystals (NCs) by simple wet-chemical method. The XRD exhibits a marginal decrease in the crystalline size of TiO₂ nanosamples by the addition of MgO dopant. UV–Vis spectral analysis shows that the addition of MgO in TiO₂ resulted in the red shift of the absorption edge. The optical energy band-gap and molecular vibrational analysis of doped nanosample was ascertained from photoluminescence (PL) and micro-Raman scattering technique respectively. HR-TEM analysis reveals that the substitution has sharply reduced the particle size of TiO₂NCs.

Gold and silver nanoparticles (NPs) are physically synthesized using Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG)-pulsed laser ablation in liquid (PLAL) technique which is a rapid, simple and efficient one-step synthesis. The gold and silver colloidal solutions are separately prepared by 1064nm of pulsed laser ablation of metallic target (gold and silver) which is immersed in deionized water. Ultraviolet–visible spectroscopy (UV–Vis) analysis shows the absorption band of gold and silver NPs at $\sim 520$nm and $\sim 400$nm, respectively. The absorption spectra and color variations of gold and silver NPs at three different laser parameters (output laser energies, target distances from focal point and laser time exposures). High-resolution transmission electron microscopy shows the spherical shape of gold and silver NPs with 34nm and 33nm diameter of size, respectively, are reported. The aggregation and particle sizes of gold and silver NPs due to minimum energy (75mJ) and maximum energy (311mJ) are observed.

Stated work consisted synthesis of ZnO nanoparticles (NPs) by the irradiation of microwaves. Material is formed by a simple chemical precipitation method by using Zinc Acetate Dehydrate (Zn(CH₃COO)₂$\cdot$2H₂O) and Sodium hydroxide (NaOH) as base chemicals in aqueous media for two different pH (12 and 14) values. This synthesis was carried out at room temperature. Synthesized NPs are dried in Microwave oven for 3 min of duration each. X-ray Diffraction (XRD) study confirmed the trend of incremental crystallinity upon increasing pH. XRD reveals the existence of (100), (002), (101), (102) and (110) reflections at $32.7^{\circ }$, $35.3^{\circ }$, $37.2^{\circ }$, $48.4^{\circ }$ and $57.4^{\circ }$ two theta values, respectively. Crystallite size was determined by both Scherrer formula and W–H plot method. UV-Vis spectroscopy is utilized to probe the optical features of ZnO NPs. This confirms intrinsic excitonic transition properties of ZnO. UV absorbance shows decrement upon increasing pH value. Band gap depicts the decremental behavior upon increasing pH. Stated method is a novel and time saving method for ZnO NPs synthesis; a large scale production is also feasible by this method.

Pulsed laser ablation in liquid (PLAL) of metallic magnesium was used in this work to manufacture magnesium nanoparticles with varying average sizes (10–90nm). (2.07–3.44) $\times$ 10⁸W/cm² of laser intensity and pulse rates of 100 pulses were used to create the nanoparticles. Laser power increased the number of nanoparticles in magnesium oxide (MgO) at 204nm absorption spectroscopic absorbance linearly. When the UV–Vis absorbance of nanoparticles rose, so did their colloidal density (measured in mg/mL). Nanoparticles are more likely to be produced at higher laser scanning rates: UV–Vis absorbance and nanoparticle diameters. Field emission scanning electron microscopy (FESEM) revealed that nanoparticles created dendritic patterns when put upon metal foil. The nanoparticles were measured using dynamic light scattering. When MgO particles were used in antibacterial activity against (in vitro) various gram-positive and gram-negative strains of bacteria, they had a demonstrable impact on some strains of bacteria. MgO has been shown to have antibacterial properties.

The FTIR (4000–400cm${}^{-1}$) and the FT-Raman spectra (4000–50cm${}^{-1}$) of 4-Hydroxy-7-methyl-1,8-naphthyridine-3-carboxylic acid are recorded and investigated. The spectra are interpreted using anharmonic frequency computations by VPT2, VSCF and PT2-VSCF methods within DFT/6-311G(d,p) framework. The root mean square (RMS) values indicate that VSCF computed frequencies are in close agreement with the observed frequencies. The combination and overtone bands are also identified in the FTIR spectrum. The intermolecular O-H$\cdots$O hydrogen bonding interactions are discussed in the dimer structure of the molecule. The magnitudes of the coupling between pair of modes are also computed. The electronic spectra in water and ethanol solvents are analyzed using TD-B3LYP/6-311$++$G(d,p) level of theory. Molecular electrostatic potential (MEP) and HOMO-LUMO analysis are also performed.

The QCA paradigm is one of the approaches to decrease the size scale of computing devices. When molecules are used as QCA cells, they may be able to perform computing at room temperature. This paper describes a novel molecular QCA cell candidate which is a side-by-side iron phthalocyanine dimer, and an investigation of its optical and redox properties. The new dodeca(pentyloxy) substituted side-by-side iron phthalocyanine dimer, along with the octa(pentyloxy) iron phthalocyanine monomer, are soluble in non-polar organic solvents. These compounds were isolated by gel permeation chromatography (GPC) and high-performance liquid chromatography (HPLC) to final purities of 98% and 99%, respectively. The NMR spectra of both compounds in CDCl₃ are broad due to aggregation, but become well resolved after the addition of the coordinating solvent pyridine-d₅. Addition of pyridine also gives changes in the UV-vis spectra and electrochemical peaks of both monomer and dimer in dichloromethane indicative of axial iron coordination. The electrochemical data indicates the loss of pyridine ligands from the oxidized products of both monomer and dimer. The comproportionation constant of side-by-side phthalocyanine dimer shows that its oxidized and reduced mixed-valence complexes are fairly stable. The dimer is thus a candidate for molecular QCA systems.

Three novel hydroquinone-based symmetrically and unsymmetrically substituted subphthalocyanine (SubPc) dimers have been synthesized through the axial substitution of the macrocycle. The mono SubPc hydroquinone derivative (Hq-SubPc) first prepared acts as a nucleophile which replaces the chlorine atom of the second SubPc molecule to form the dimer. The dimers were obtained by reacting hydroquinone and the respective SubPcs in a 1:1 molar ratio in toluene at 180 °C in a pressure vessel. This new approach allowed stoichiometric quantities of reactants to be utilized. All dimers were characterized by ¹H NMR, ¹³C NMR, UV-vis, fluorescence and mass spectral analysis.

The role of the base nature during complexation of 2-hydroxy-9(10),16(17),23(24)-tri-tert-butyl-29H,31H-phthalocyanine ligand (1) with zinc acetate was studied by the UV-vis spectroscopy and DFT calculations. The latter allowed us to explain the selective formation of double-coordinated J-type dimer in the presence of lithium methoxide. Spectropotentiometry was used to study the nucleophilic properties of the dimeric complex in comparison with the corresponding monomer and has demonstrated the strong intramolecular interactions of macrocycles.

Six monophenyltripyridylporphyrin derivatives were synthesized and characterized by spectroscopy in order to demonstrate their potential usefulness as photosensitizers for anticancer therapy purposes. Compounds 1 and 3–5 are amphiphilic, thus they may be suitable for transfer inside cells. Photochemical parameters such as fluorescence yield and singlet oxygen yield were determined. The former parameter does not exceed 10% which makes them unsuitable for photodynamic diagnosis (PDD). However, singlet oxygen yields are high and sufficient for these compounds to be considered as potential photodynamic therapy (PDT) photosensitizers.

A presence of bulky 2,6-di-iso-propylphenoxy groups in bis-tert-butylisocyano adduct of 2(3),9(10),16(17),23(24)-tetrachloro-3(2),10(9),17(16),24(23)-tetra(2,6-di-iso-propylphenoxy)-phthalocyaninato iron(II) complex allows separation of two individual positional isomers and a mixture of the remaining two isomers using conventional chromatography. X-ray structures of “$D_{2h}$” and “$C_{4h}$” isomers were confimed by X-ray crystallography. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of each individual positional isomer allowed insight into their electronic structures and vertical excitation energies, which were correlated with the experimental UV-vis and MCD spectra.