Structural elucidation, optical, magnetic and nonlinear optical properties of oxystyryl dyes

Structure, magnetic and optical properties of tetraphenylborate salts of 2,5-[1-methyl-4-[2-(4-hydroxyphenyl)ethenyl]piridinium]-propane and butane are performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV-vis and fluorescence methods, HPLC tandem ESI mess spectrometry (MS/MS), (1)H, (13)C and (1)H-(1)H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are used for performing of the structures, optical and nonlinear optical properties of the studied compounds.     

X-Shaped electro-optic chromophore with remarkably blue-shifted optical absorption. Synthesis, characterization, linear/nonlinear optical properties, self-assembly, and thin film microstructural characteristics

A novel type of "X-shaped" two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH(2)Cl(2)) while maintaining a very large first hyperpolarizability (beta). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a beta(zzz) value of 1840 x 10(-30) esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response (chi(2)(333) approximately 232 pm/V at 1064 nm; r(33) approximately 45 pm/V at 1310 nm). This work demonstrates an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs.     

Structural,morphological, optical and antibacterial properties of pentagon CuO nanoplatelets

Pentagon copper oxide (CuO) nanoplatelets formation employing Nephelium lappaceum L. extract was successfully developed. Characteristic X-ray diffraction peaks revealed a monoclinic and end-centered lattice structure of copper oxide belonging to ¹C⁶_2h (c²/c) space group. Three characteristic Raman peaks, A_g, B_g(1) and B_g(2), confirmed the monoclinic CuO structure. The pentagon CuO nanoplatelets formation increased proportionally with increase in calcination temperature from 600 to 800?°C and the particle size was noticeably increased from 30 to 250?nm. Strong photoluminescence emission peak was noticed in the UV region between 377 and 393?nm. The metal–oxygen Cu²⁺–O^2? vibration of the synthesized product in the range between 300 and 700?cm^?1 was confirmed using infrared studies. The CuO product obtained at 600?°C showed best antibacterial action due to its small particle size (30–60?nm) against both Gram-positive and Gram-negative bacteria. The obtained product cell morphology, proliferation and viability test were investigated with respect to control and 10, 50, 100, and 500?μg/ml. Cell viability of the product were respectively 74, 55.3, 50, and 27.3% and found suitable for biomedical applications.

Open image in new window

     

Topographic, electrochemical, and optical images captured using standing approach mode scanning electrochemical/optical microscopy

We developed a high-resolution scanning electrochemical microscope (SECM) for the characterization of various biological materials. Electrode probes were fabricated by Ti/Pt sputtering followed by parylene C-vapor deposition polymerization on the pulled optical fiber or glass capillary. The effective electrode radius estimated from the cyclic voltammogram of ferrocyanide was found to be 35 nm. The optical aperture size was less than 170 nm, which was confirmed from the cross section of the near-field scanning optical microscope (NSOM) image of the quantum dot (QD) particles with diameters in the range of 10-15 nm. The feedback mechanism controlling the probe-sample distance was improved by vertically moving the probe by 0.1-3 microm to reduce the damage to the samples. This feedback mode, defined as "standing approach (STA) mode" (Yamada, H.; Fukumoto, H.; Yokoyama, T.; Koike, T. Anal. Chem. 2005, 77, 1785-1790), has allowed the simultaneous electrochemical and topographic imaging of the axons and cell body of a single PC12 cell under physiological conditions for the first time. STA-mode feedback imaging functions better than tip-sample regulation by the conventionally available AFM. For example, polystyrene beads (diameter approximately 6 microm) was imaged using the STA-mode SECM, whereas imaging was not possible using a conventional AFM instrument.     

Syntheses, and optical, fluorescence, and nonlinear optical characterization of phosphine-substituted terthiophenes

Earlier studies of phosphine-substituted terthiophenes have demonstrated that some of these materials exhibit nonlinear absorption at 532 nm. However, this wavelength is significantly removed from the linear absorption maxima of the complexes, suggesting that better nonlinear absorption might be observed at wavelengths closer to the linear absorption maxima. To investigate this possibility, a library of compounds has been prepared either by varying the group attached to the nonbonding pair of electrons on the phosphorus atoms of 5,5'-bis(diphenylphosphino)-2,2':5',2'-terthiophene (PT(3)P), or by introducing additional substituents on the 5'-position of 5-(diphenylphosphino)-2,2':5',2'-terthiophene (PT(3)). All these compounds have been characterized using multinuclear NMR, UV-vis, and fluorescence spectroscopy. The compounds are strongly fluorescent, and both the fluorescence wavelength and the intensity depend upon the thiophene substituents. The nonlinear optical properties have also been evaluated at various wavelengths in the blue region. Each compound exhibits reverse saturable absorption, and the intensity of the reverse saturable absorption at a particular wavelength depends on the chemical structure of the compound.     

Syntheses, structural, electrochemical and optical studies of heterobinuclear ruthenium-osmium alkynyl complexes

The complexes trans-[Os(CCC₆H₄-4-CCR)Cl(dppe)₂] (R = SiPrⁱ₃1, H 2), trans,trans-[(dppe)₂ClOs(CCC₆H₄-4-CC)RuX(dppe)₂] (X = Cl 3, CCC₆H₄-4-CCSiPrⁱ₃4), trans-[Os(CCC₆H₄-4-CCC₆H₄-4-CCR)Cl(dppe)₂] (R = SiPrⁱ₃5, H 6), and trans,trans-[(dppe)₂ClOs(CCC₆H₄-4-CCC₆H₄-4-CC)RuCl(dppe)₂] (7) have been synthesized, and the identities of 1, 2, and 6 confirmed by single-crystal X-ray diffraction studies. Cyclic voltammetry shows that the mononuclear complexes 1, 2, 5, and 6 are oxidized at potentials within a narrow range (0.45-0.49 V), in processes centered on the osmium ethynyl neighbourhood and for simplicity assigned as Os^II/III, while the heterobinuclear complexes 3, 4, and 7 exhibit lower oxidation potentials for Os^II/III and a second oxidation process assigned in a similar fashion to Ru^II/III; the difference in potential between the Os- and Ru-localized processes decreases as the π-bridge is lengthened. UV-vis-NIR spectroelectrochemical studies on 1 and 5 reveal the appearance on oxidation of a low-energy band ascribed to chloro to metal-ethynyl charge transfer. Osmium-centered oxidation at the heterobinuclear complexes 4 and 7 results in appearance of a low-energy band, which blue-shifts and increases in intensity on further oxidation to 4²⁺ and 7²⁺.     

Structures, stabilities, and electronic and optical properties of C62 fullerene isomers

The 2385 classical isomers and four nonclassical isomers of fullerene C62 have been studied by PM3, HCTH/3-21G//SVWN/STO-3G, B3LYP/6-31G(d)//HCTH/3-21G, and B3LYP/6-31G(d)//B3LYP/6-31G(d). The Cs:7mbr isomer, with a chain of four adjacent pentagons surrounding a heptagon, is predicted to be the most stable isomer, followed by C2v:4mbr which is 3.15 kcal/mol higher in energy. C2:0032 with three pairs of adjacent pentagons is the most stable isomer in the classical framework. To clarify the relative stabilities of C62 isomers at high temperatures, the entropy contributions are taken into account on the basis of the Gibbs energy at the B3LYP/6-31G(d) level. Analyses reveal that Cs:7mbr prevails in a wide temperature range. The vibrational frequencies of the five most stable C62 fullerene isomers are also predicted at the B3LYP/6-31G(d) level, and the simulated IR spectra show important differences in positions and intensities of the vibrational modes for different isomers. The nucleus-independent chemical shift and the density of states of the three most stable isomers show that the square in C2v:4mbr and the adjacent pentagons in Cs:7mbr and C2:0032 possess high chemical reactivity. In addition, the electronic spectra and second-order hyperpolarizabilities are determined by means of ZINDO and the sum-over-states mode. The intensity-dependent refractive index gamma(-omega; omega, omega, -omega) at omega = 2.3305 eV of Cs:7mbr is very large because of resonance with the external field. The second-order hyperpolarizabilities of the five most stable isomers of C62 are predicted to be larger than those of C60.     

Preparation, characterization, and optical, electrochemical property research of CdS/PAM nanocomposites

CdS/PAM nanocomposites have been successfully synthesized in situ via a ultrasound-assisted route under ambient condition, employing CdCl(2) and Na(2)S(2)O(3) as Cd(2+) and S(2-) ion sources and acrylamide (AM) and (NH(4))(2)S(2)O(8) as organic monomers and initiating reagents, respectively. The results from X-ray powder diffraction (XRD) analysis and the IR spectrum of the final product showed the formation of CdS nanoparticles and the polymerization of AM monomers. SEM observations showed that the CdS/PAM nanocomposites could film on the quartz substrate and some holes in which many nanorods regularly arranged distributed on the film. The UV-vis absorption and PL spectra of CdS/PAM nanocomposites obviously differed from those of CdS nanoparticles prepared under the same conditions due to the presence of PAM. The electrochemical research showed that CdS/PAM nanocomposites had a stronger ability to promote electron transfers between Hb and the Au electrode than CdS nanoparticles prepared under the same conditions. A possible formation mechanism was also suggested based on the results of experiments.     

Morphology,optical properties,and curing behavior of UV-curable acrylate-siloxane polymer blends

UV-curable organic-inorganic blends have captured lots of attention recently due to leveraging the positive features of polymer blending and radiation curing. However, the optical properties of such blends, including transparency, which is an important attribute in many applications, have not been sufficiently explored. In this study, a series of UV-Curable acrylate-siloxanes blends were prepared using different compositions and processing variables to obtain blends with promising transparency, and acceptable stability before and after curing. The variables include speed and time of mixing, siloxane functionality (-OH versus –CH₃), the monomer/oligomer ratio in the acrylate phase, and the amount of compatibilizer.The spectrophotometric results revealed that blends containing 100 wt% of acrylate monomer as the acrylate phase and 10 wt% of compatibilizer in the siloxane phase, demonstrated the highest transparency regardless of the siloxane functionality. SEM illustrated that a two-phase droplet-in-matrix morphology was formed containing dispersed siloxane particles in an acrylate matrix. The incorporation of compatibilizer significantly reduced the average size of the droplets and increased the uniformity of their distribution. Additionally, Photo-DSC, RT-ATR, AFM, and refractometry methods respectively showed that the addition of the siloxane phase to the acrylate matrix, regardless of its functionality, reduced the heat of reaction and CC conversion, while increased the surface roughness and refractive index. The developed UV-Curable acrylate-siloxane blends showed promising stability and transparency, and present a potential platform for PDLCs.     

Elastic, dielectric and optical constants of 4'-pentyl-4-cyanobiphenyl

4'-n-Pentyl-4-cyanobiphenyl (5CB) is a room temperature nematic liquid crystal with a high positive dielectric anisotropy and a high chemical stability. Many experimental results concerning the elastic and dielectric constants of 5CB are available in the literature, although there is often no satisfactory agreement between the experimental data obtained by different groups, especially as far as the dielectric constants are concerned. Furthermore, no detailed investigation of the temperature dependence of the elastic and dielectric constants close to the nematic-isotropic transition temperature T_NI has yet been reported. In this paper, we report the measurement of the elastic and dielectric constants of 5CB, and the temperature behaviour close to T_NI has been investigated in detail. The experiment consists in the measurement of the director deformation induced by an electric field using simultaneously both a dielectric and an optical method. The simultaneous use of these two methods provides an indirect check on the reliability of the measurements. Special attention has been devoted to control possible sources of uncertainty. In particular, the effects of finite anchoring energy and of finite pretilt angle have been considered. The temperature dependence of the anisotropy of the refractive indices is also obtained in the experiment.     

Structural,morphological, optical and third order nonlinear optical response of spin-coated NiO thin films: An effect of N doping

The present work deals with the deposition of NiO and Nitrogen (N)-doped NiO thin films by sol-gel spin coating technique. Structural, morphological, linear and non-linear optical characteristics of undoped and N-doped (1–15 wt%) NiO films were studied. From XRD measurements, it is evident that single phase nano crystalline NiO is formed for all doping concentrations. Surface morphology study shows that higher concentration of N doped NiO thin films were of high quality and EDX mapping confirmed the doping of Nitrogen in films. The Raman spectra of the studied films were analyzed over the range of 1400-200 cm⁻¹. The optical studies confirm that as doping increases, transparency of the film decreases (except at 10% N doping) and the band gap narrows. Nonlinear parameters such as refractive index and susceptibilities also depend on N dopant concentration. Z-scan studies viz., absorption index, nonlinear refractive index were carried out on undoped and N doped NiO samples and the results were matched with theoretical calculated values.     

Silver hierarchical bowl-like array: synthesis, superhydrophobicity, and optical properties

We present a facile synthetic route to a silver bowl-like array film with hierarchical structures on glass substrate using the colloidal monolayer as a template. In these special hierarchical structures, microstructures were provided by a colloidal template of polystyrene latex spheres and nanostructures resulting from the thermal decomposition of silver acetate. These structures were chemically modified with 1-hexadecanethiol, and a corresponding self-assembled monolayer (SAM) was formed on their surfaces. Due to the lotus leaf-like morphology with hierarchical micro/nanostructures, the film displayed an extraordinary superhydrophobicity after chemical modification. Water contact angle and sliding angle were 169 degrees and 3 degrees (the weight of water droplets: 3 mg), respectively. Additionally, its optical property has also been investigated. This structure could be used in microfluidic devices, optical devices, and biological science.     

EPR, optical, infrared and Raman spectral studies of Actinolite mineral

Electron paramagnetic resonance (EPR), optical, infrared and Raman spectral studies have been performed on a natural Actinolite mineral. The room temperature EPR spectrum reveals the presence of Mn(2+) and Fe(3+) ions giving rise to two resonance signals at g = 2.0 and 4.3, respectively. The resonance signal at g = 2.0 exhibits a six line hyperfine structure characteristic of Mn(2+) ions. EPR spectra have been studied at different temperatures from 123 to 433 K. The number of spins (N) participating in the resonance at g = 2.0 has been calculated at different temperatures. A linear relationship is observed between log N and 1/T in accordance with Boltzmann law and the activation energy was calculated. The paramagnetic susceptibility (chi) has been calculated at different temperatures and is found to be increasing with decreasing temperature as expected from Curie's law. From the graph of 1/chi versus T, the Curie constant and Curie temperature have been evaluated. The optical absorption spectrum exhibits bands characteristic of Fe(2+) and Fe(3+) ions. The crystal field parameter Dq and the Racah parameters B and C have been evaluated from the optical absorption spectrum. The infrared spectral studies reveal the formation of Fe(3+)--OH complexes due to the presence of higher amount of iron in this mineral. The Raman spectrum exhibits bands characteristic of Si--O--Si stretching and Mg?OH translation modes.     

Organometal halide perovskite quantum dots: synthesis,optical properties,and display applications

In recent two years, organometal halide perovskites quantum dots are emerging as a new member of the nanocrystals family. From the chemical point of view, these perovskites quantum dots can be synthesized either by classical hot-injection technique for inorganic semiconductor quantum dots or the reprecipitation synthesis at room temperature for organic nanocrystals. From a physical point of view, the observed large exciton binding energy, well self-passivated surface, as well as the enhanced nonlinear properties have been of great interest for fundamental study. From the application point of view, these perovskites quantum dots exhibit high photoluminescence quantum yields, wide wavelength tunability and ultra-narrow band emissions, the combination of these superior optical properties and low cost fabrication makes them to be suitable candidates for display technology. In this short review, we introduce the synthesis, optical properties, the prototype light-emitting devices, and the current important research tasks of halide perovsktie quantum dots, with an emphasis on CH₃NH₃PbX₃ (X=Cl, Br, I) quantum dots that developed in our group.     

Synthesis, characterization, and optical properties of well-defined N-doped, hollow silica/titania hybrid microspheres

Well-defined nitrogen-doped, hollow SiO2/TiO2 hybrid spheres were successfully prepared through a two-step sol-gel synthesis combined calcination process using triethylamine as the nitrogen source. In this approach, polystyrene (PS)/silica microspheres were first synthesized. Subsequently, the amine-treated PS/SiO2/TiO2 hybrid spheres were obtained by sol-gel method. Finally, the elimination of the PS core, nitrogen-doping process, and crystallization of amorphous TiO2 were simultaneously conducted in the calcination process to acquire the final products. The as-prepared hybrid spheres were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. The results of XRD, FTIR, and XPS spectra indicated that nitrogen was really doped into the anatase TiO2 shell and confirmed that most nitrogen dopants might be present in the chemical environments of N-Ti-O and Ti-N-O. It was found that the absorption shoulder of nitrogen-doped hollow SiO2/TiO2 hybrid spheres vastly shifted to the visible region up to around 530 nm. The photoluminescence (PL) bands showed spectral lines at about 421, 472, and 529 nm, which were attributed to the self-trapped excitons, F and F+ centers. Moreover, the intensity of the PL spectra band of hollow SiO2/TiO2 hybrid spheres increased with as the amount of titanium tetrabutoxide (TBOT) precursor increased. However, the doping of nitrogen into hollow SiO2/TiO2 hybrid spheres led to the drastic quenching of photoluminescence because of the increase in the separation efficiency of the photoinduced electron and hole pairs.     

Synthesis, structure, optical properties, and electronic structure of NaLiCdS2

The new compound NaLiCdS₂ has been synthesized by the reaction of Cd and a Li₂S/S/Na₂S flux at 773 K. This compound, which has the Ce₂O₂S structure type, crystallizes with one formula unit in space group P3¯m1 of the trigonal system in a cell at T=153 K with a=4.1320(3) Å and c=6.8666(11) Å. The structure consists of two-dimensional layers stacked perpendicular to the [001] direction. The two-dimensional layers are formed by corner-sharing LiS₄ or CdS₄ tetrahedra. The Na atoms are between these layers. Li incorporation in the compound is confirmed by an SIMS chemical composition map and by ICP measurements. The Li and Cd atoms are disordered in the crystal structure. First-principles calculations show that the optical excitations arise primarily from S→Cd charge-transfer transitions at 1.0 eV (very weak) and 2.4 eV (strong). Calculations also indicate that Na contributions around the Fermi level are significant. Polarized single-crystal optical measurements indicate an indirect optical band gap of 2.37 eV for light perpendicular to the (001) crystal face, in good agreement with theory. The compound NaLiZnS₂ has also been synthesized and is found to be isostructural with NaLiCdS₂.     

Synthesis, optical resolution, and configurational assignment of novel axially chiral quateraryls

A one-pot general synthesis of highly functionalized quateraryls through carbanion-induced, base-catalyzed ring transformation of 5,6-diaryl-2H-pyran-2-ones and core-substituted phenylacetones is delineated. These conversions were found to give diversely functionalized benzenes bearing peripheral aryl rings, some of which possess inherent atropisomerism. Exemplarily for one of the quateraryls, the optical resolution of the respective atropo-enantiomers by HPLC on a chiral phase and the assignment of their absolute axial configurations succeeded by LC-CD coupling in combination with semiempirical CNDO/S and TDDFT CD calculations. This synthetic approach offers-in a transition metal-free environment-high flexibility in the construction of quateraryls with the desired conformational freedom along the molecular axis, which may help in exploring and developing new potential ligands for asymmetric synthesis.