Synthesis of ytterbium bisphthalocyanines: Photophysicochemical properties and nonlinear absorption behavior

Herein we report on the syntheses, photophysico-chemical properties and nonlinear absorption parameters of bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-2-yloxy phthalocyaninato)} ytterbium (III) (3) and bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-4-yloxy phthalocyaninato)} ytterbium (III) (4). The fluorescence and singlet oxygen quantum yields obtained for complexes 3 and 4 are low. The triplet quantum yield obtained for complex 3 is high at Φ_T = 0.89 whereas for complex 4 Φ_T = 0.48. The third order optical susceptibility values are of the order: 10⁻¹¹ esu (for complex 3), and 10⁻¹³ esu (for complex 4) while the hyperpolarizability values are of the order: 10⁻²⁸ esu (for complex 3) and 10⁻³¹ esu (for complex 4). Complexes 3 and 4 show two-photon absorption coefficients of the order of 10⁻⁴⁶ cm⁴ s/photon and 10⁻⁴⁸ cm⁴ s/photon, and threshold intensities as low as 0.3 J cm⁻² and 0.0045 J cm⁻², respectively.     

The nonlinear absorption in new lanthanide double decker pyridine-based phthalocyanines in solution and thin films

The optical behavior of bis-{2(3), 9(10), 16(17), 23(24)-(tetrapyridin-4-yloxy phthalocyaninato)} lanthanum (III) (2) and its ytterbium (3) counterpart in dimethyl sulfoxide are presented and compared to bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-4-yloxy phthalocyaninato)} ytterbium (III) (4). We report on the third-order susceptibility, second-order hyperpolarizability and the limiting threshold values. The nonlinear optical limiting threshold values of complexes 2, 3 and 4 showed improvement in the solid state (thin films), with complex 4 giving the best value at 0.033 J cm⁻².     

Synthesis,z-scan and degenerate four wave mixing characterization of certain functionalized photosensitive polyesters containing ortho-hydroxyazo chromophores

The preparation and NLO characterization of photosensitive polyesters containing azoaromatic residues in the molecular backbone, functionalized with orthohydroxy chromophores is presented. Samples were studied for its UV–vis absorption, FT-IR and intensity dependent nonlinear absorption properties. Nonlinear characterization was carried out with z-scan using frequency doubled, Q-switched Nd:YAG laser operating at 532 nm. The closed aperture z-scan spectra reveal the self defocusing effects of the samples with negative nonlinearity coefficient (n₂) showing values as high as −1.28 × 10⁻¹⁰ (esu) for certain samples and the corresponding third order susceptibility coefficient of the order of 29.9 × 10⁻¹² (esu). Degenerate four wave mixing technique was employed to substantiate the findings. The numerical fits show that the molecules exhibit reverse saturable absorption. A study of beam fluence dependence of nonlinear absorption coefficient (β_eff) has been presented. All phenomena indicate that molecules are reverse saturable absorbers whose optical limiting property gets enhanced with increasing conjugation length.     

Utilization of residual CdCl2 in CBD-CdS to realize grain growth in CdTe: A novel route

CdTe films were deposited by thermal evaporation onto chemical bath deposited CdS (CBD-CdS) films. The composite films were subjected to rapid thermal annealing (RTA) to observe simultaneous grain growth in both the CdS and CdTe layers. The films were characterized by measuring the compositional, microstructural and photoluminescence (PL) properties. PL spectra is dominated by the characteristic peaks (∼1.42 eV and ∼1.26 eV) associated with the virgin CdTe film. Additional features located at ∼2.56 eV and ∼1.99 eV could also be detected. The Fourier Transform Infra Red (FTIR) peak at ∼482 cm⁻¹ appeared due to the simultaneous presence of absorption peaks for CdTe stretching mode as well as Cd-S modes. Appearance of the broad peak between 1000 cm⁻¹ and 1165 cm⁻¹ may be an indication of interfacial alloying. Secondary ion mass Spectroscopy (SIMS) measurements were done to observe the compositional uniformity in the film and to measure the interfacial mixing behaviour.     

Electroresistance and magnetoresistance in La0.9Ba0.1MnO3 thin films

The electroresistance and magnetoresistance effects have been investigated in La_0.9Ba_0.1MnO₃ epitaxial thin films. Tensile strain caused by substrate mismatch makes the Curie temperature T_C of the film at ∼300 K. The influence of an applied dc-current on the resistance in the absence of a magnetic field was studied. Significant change of the peak resistance at different currents was found. The reduction of the peak resistance reaches ∼27% with an electric current density up to 1.3 × 10⁵ A cm⁻². We also studied colossal magnetoresistance (CMR) effect in the films. Applying a magnetic field of 2 T could lead to a magnetoresistance as large as 42%. The reduction of resistance caused by a current density ∼1.3 × 10⁵ A cm⁻² was found to be equivalent to the CMR effect caused by 1.5 T near T_C. The phenomenon that the resistance in CMR manganites could be easily controlled by the electric current should be of high interest for both fundamental research and practical applications.     

Chemical bonding and optoelectrical properties of ruthenium doped yttrium oxide thin films

Highly infrared transparent conductive ruthenium doped yttrium oxide (RYO) films were deposited on zinc sulfide and glass substrates by reactive magnetron sputtering. The structural, optical, and electrical properties of the films as a function of growth temperature were studied. It is shown that the sputtered RYO thin films are amorphous and smooth surface is obtained. The infrared transmittance of the films increases with increasing the growth temperature. RYO films maintain greater than ∼65% transmittance over a wide wavelength range from 2.5 μm to 12 μm and the highest transmittance value reaches 73.3% at ∼10 μm. With increasing growth temperature, the resistivity changed in a wide range and lowest resistivity of about 3.36 × 10⁻³ Ω cm is obtained at room temperature. The RYO thin films with high conductivity and transparency in IR spectral range would be suitable for infrared optical and electromagnetic shielding devices.     

Electrical properties of lead zirconate titanate thick films prepared by hybrid sol–gel method with multiple infiltration steps

High-quality ferroelectric thick films are required for various piezoelectric applications including high-frequency transducers and microelectromechanical systems. In this work, we report the fabrication of dense crack-free lead zirconate titanate (PZT) thick films on Pt-coated Si substrates using commercial PZT powder dispersed in a sol–gel precursor solution without viscous additives. Preannealed films were infiltrated with the same solution and heat treated at 500 °C. Dielectric and ferroelectric properties of the films are found to be strongly dependent on the number of infiltration steps reaching sufficiently high values: dielectric constant ∼2270 and remanent polarization ∼35 μC cm⁻². Moderate coercive field of 60 kV cm⁻¹ and low dielectric loss ∼0.04 are observed in these films. Effective longitudinal piezoelectric coefficient d₃₃ also depends on the number of infiltrations demonstrating remanent value of ∼80 pm V⁻¹ for eight infiltration steps. The results show the suitability of hybrid sol–gel method for the fabrication of PZT thick films for dielectric and piezoelectric applications.     

Nonlinear optical properties of the PbS nanorods synthesized via surfactant-assisted hydrolysis

PbS nanorods were synthesized by surfactant-assisted homogenous hydrolysis. The products were characterized by UV–vis spectrophotometer, X-ray powder diffraction (XRD) and transmission electron microscope (TEM). PbS nanorods were measured by the Z-scan technique to investigate the third-order nonlinear optical (NLO) properties. The result of the NLO measurements shows that the PbS nanorods have the third-order nonlinear optical properties of both NLO absorption and NLO refraction with self-focusing effects. The nonlinear absorption coefficient and refractive index of the PbS nanorods are 2.16 × 10^− 9 m/W and 3.52 × 10^− 16 m²/W respectively.     

Optical nonlinearities of BaTiO3 matrix-embedded Au nanoparticles

Composite thin films Au/BaTiO₃ comprising nanometer-sized gold particles embedded in BaTiO₃ matrices were synthesized on MgO(1 0 0) substrates by co-depositing Au and BaTiO₃ targets using pulsed laser deposition technique. The nanostructure of the films and the size distributions of the Au particles were analyzed by high-resolution transmission electron microscopy. Crystal lattice fringes from the Au nanocrystals and BaTiO₃ matrices were observed. The nonlinear optical properties of the Au/BaTiO₃ films were measured using z-scan method at the wavelength of 532 nm with a laser duration of 10 ns. The nonlinear refractive index n₂ and the nonlinear absorption coefficient β were determined to be 2.72 × 10⁻⁶ esu and −1.1 × l0⁻⁶ m/W, respectively.     

Mixture design for evaluation of potassium sorbate and xanthan gum effect on properties of tapioca starch films obtained by extrusion

A mixture experimental design was used to study the physical and microbiological properties of tapioca starch–glycerol based edible films added with xanthan gum (XG) and potassium sorbate (PS) and obtained by extrusion technology. The results showed that PS presence decreased the ultimate tensile strength and elastic modulus and increased strain at break. XG produced a reinforcing effect on the films and also enhanced solubility in water and decreased moisture content. The analysis revealed significant interactions between components in the mixture. The water vapor permeability values ranged from 3.72 × 10^? 10 to 6.4 × 10^? 10 g/m s Pa. The PS concentration was not affected by the extrusion process and the preservative was available to act as an antimicrobial agent. Extruded films made from biopolymers showed a potential application in food technology as an active packaging.     

Synthesis of polypyrrole and carbon nano-fiber composite for the electrode of electrochemical capacitors

Nano-thin polypyrrole (PPy) films were deposited on vapor grown carbon fibers (VGCF) by using an in situ chemical polymerization of the monomer in the presence of FeCl₃ oxidant. An ultrasonic cavitational stream was used during polymerization of pyrrole, to enable the deposition of uniformly nano-thin PPy films on the surface of VGCF. The PPy/VGCF composite was characterized by FTIR spectroscopy. Surface morphology of the polymer films was characterized by using scanning electron microscopy and scanning transmission electron microscopy. The capacitance of the composite electrodes was investigated with cyclic voltammetry. As results of this study, thinner layer of PPy in the composite electrode (< 10 nm) was effective to obtain fully reversible and very fast Faradaic reaction. Hence, most mass of the PPy could contribute to the pseudo-capacitive charge storage. This nano-thin PPy layer exhibited higher specific capacitance of ∼588 F g^− 1 at 30 mV s^− 1 and ∼545 F g^− 1 at 200 mV s^− 1 along with an excellent power capability.     

Experimental and theoretical characterization of semiorganic nonlinear optical material l-leucine hydrobromide

Semiorganic nonlinear optical material l-leucine hydrobromide (LEHBr) has been synthesized and single crystals were grown by solvent evaporation method at a constant temperature of 35 °C. CHN test, FTIR and XRD analysis were performed for identification of the material. Thermal and mechanical stability of the grown crystal were investigated by DTA-TGA analysis and microhardness measurement respectively. Suitability of LEHBr for NLO application was studied by optical transmission study and second harmonic generation (SHG) efficiency measurement. SHG efficiency was found to be 4 times of KDP. First hyperpolarizability, dipole moment and polarizability of LEHBr were calculated at the framework of Hartree–Fock (HF) with 6-311G(d) basis set. First order hyperpolarizability was found to be 3.233 × 10⁻³³ esu which is 4.9 times of urea.     

Enhanced optical limiting performance in phthalocyanine-quantum dot nanocomposites by free-carrier absorption mechanism

Enhanced nonlinear optical properties (in dimethyl sulphoxide) is observed for 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy)phthalocyaninato indium(III) chloride (InPc) when covalently linked to CdSe/ZnS or CdSe quantum dots (QDs). The experimental nonlinear optical parameters were obtained from Z-Scan measurements. Contributions from two-photon absorption (2PA) due to the InPc, and free-carrier absorption (FCA) by QDS have been identified as the main factors responsible for the enhanced optical limiting. The effective nonlinear absorption coefficient for InPc-CdSe/ZnS was found to be 700.0 cm/GW. The FCA cross-sections for InPc-CdSe/ZnS and InPc-CdSe composites were found to be 1.52 × 10⁻¹⁹ and 6.00 × 10⁻²⁰ cm² respectively. A much lower limiting threshold of 92 mJ cm⁻² was observed for InPc-CdSe/ZnS nanocomposite, hence, making it suitable for use as optical limiting material. Density Functional Theory (DFT) calculations on similar phthalocyanine-quantum dots system was modeled in order to explain the enhancement in the observed nonlinear optical properties of the Pc in the presence of the QDs. The experimentally determined nonlinear optical properties are well within the range of the DFT calculated properties.     

A novel ratiometric fluorescent Yb3+ sensor based on a N′-(1-oxoacenaphthylen-2(1H)-ylidene)furan-2-carbohydrazide as a suitable fluorophore

N′-(1-oxoacenaphthylen-2(1H)-ylidene)furan-2-carbohydrazide (L) was synthesized for the first time and used as a ratiometric fluorescent chemosensor for high selective recognition of Yb³⁺ ions in acetonitrile (MeCN) solution. The L–Yb³⁺ complexation quench the fluorescence of L at 420 nm and induces new fluorescent enhancement at 516 nm. Due to the formation of a 2:1 metal ligand complex in acetonitrile solution, the red shift of fluorescent emission spectrum occurred. The sensor shows a linear response toward Yb³⁺ ion concentration in the range of 3.3 × 10^? 7 M to 1.0 × 10^? 4 M with detection limit of 1.2 × 10^? 7 M. The fluorescent probe exhibits high selectivity for Yb³⁺ ion over the other common mono-, di-, and trivalent cations.     

Quantitative monitoring of terbium ion by a Tb3+ selective electrode based on a new Schiff's base

Solution study showed N,N′-bis(5-nitrosalicylidene)-2-aminobenzylamin (L) trends toward Tb³⁺ ion. Then, it was used as a suitable ionophore in construction of terbium ion selective electrode. The electrode with composition of 30% PVC, 65% solvent mediator (NB), 3% ionophore (L) and 2% anionic additive (NaTPB) shows the best potentiometric response characteristics. It displays a Nernstian behavior (20.1 mV decade^?1) over the concentration range 1.0 × 10^? 6 to 1.0 × 10^? 2 mol L^?1. The detection limit of the electrode is 6.3 × 10^? 7 mol L^?1. It has a very short response time (~ 10 s) and a useful working pH range of 2.6–9.4 for at least 2 months. The proposed membrane sensor shows excellent discriminating ability towards Tb³⁺ ions with regard to several alkali, alkaline earth, transition and heavy metal ions. To investigate the analytical applicability of the sensor, it was successfully applied to the determination of terbium in certified reference material.     

Fine-tuning the photoluminescence and photocatalytic properties of CdS nanorods of varying dimensions

CdS nanorods having different aspect ratio viz., 17 (length ∼170 nm and width ∼10 nm) and 28 (length ∼140 nm and width ∼5 nm) has been synthesized by solvothermal technique at different time intervals (2–10 h). The effect of aspect ratio, crystallinity, band gap energy, surface area and Au/Ag loading on the various photoactive properties of these CdS nanostructures are discussed here. The photocatalytic activity for salicylic acid oxidation under UV irradiation is gradually improved with the increasing crystallinity of CdS nanostructures, length (140 < 170 nm), exposed area (2358 < 5722 nm²) per particle and decreasing surface area (158 < 122 < 76 m²g⁻¹), surface to volume ratio (0.82 < 0.41 nm⁻¹) and aspect ratio (28 < 17). The deposition of 1–2 wt% Au (∼3.5 nm) and Ag (∼1.8 nm) nanoparticles onto CdS drastically quenched the emission and enhanced the photocatalytic activity.     

Studies on the electrochemical preparation of MgCeCo alloy thin films on Cu substrates in urea–DMSO system

Cyclic voltammetry was used to investigate the electrochemical behaviors of Mg(II), Ce(III) and Co(II) in 3.00 mol L^− 1 urea–DMSO (dimethylsulfoxide). The electrode processes of Mg(II), Ce(III) and Co(II) reducing on Pt electrodes were irreversible steps. The transfer coefficient of Mg(II), Ce(III) and Co(II) in 3.00 mol L^− 1 urea–DMSO system was calculated as 0.07, 0.05 and 0.05 at 298.15 K, respectively. The diffusion coefficient of Mg(II), Ce(III) and Co(II) in 3.00 mol L^− 1 urea–DMSO system was calculated as 2.27 × 10^− 10, 1.77 × 10^− 10 and 3.16 × 10^− 10 m² s^− 1 at 298.15 K, respectively. The MgCeCo alloy thin films with smooth, uniform and metallic luster were obtained on Cu substrates by cyclic electrodeposition in 0.01 mol L^− 1 Mg(ClO₄)₂–0.01 mol·L^− 1 Ce(CH₃SO₃)₃₋0.01 mol L^− 1 CoCl₂–3.00 mol L^− 1 urea–DMSO system. The potential sweep rate was found to be important with respect to the adhesion of the thin films.     

Effect of magnetic fields on the abnormal electroresistance behavior in epitaxial thin films of La0.8Ca0.2MnO3

We report an unusual electroresistance (ER) behavior induced by a current and its response to magnetic fields in La_0.8Ca_0.2MnO₃ epitaxial thin films. These thin films were fabricated on SrTiO₃ (1 0 0) substrate using pulsed laser deposition (PLD) technique. It is found that the electric resistivity in these films is significantly enhanced by applying a dc current over a threshold value. Simultaneously, an abnormal electroresistance behavior appears in the temperature range from 10 to 300 K. The enhanced resistance turns out to be very sensitive to a weak current. Even a very small dc current can remarkably depress the high resistance, showing an unusual colossal ER effect. The ER reaches ∼1175% at temperatures lower than ∼50 K, and ∼705% at 300 K for a current changing from 0.72 to 10.5 μA. The influence of magnetic fields on the transport was also studied. The I–V curves can be strongly influenced by a low magnetic field even at room temperature. The deduced magnetoresistance (MR) reaches 120% at 300 K upon applying a magnetic field of 0.25 T. An interesting phenomenon is that the observed MR is current dependent.     

Off-resonant third-order nonlinear optical properties of multiply-bonded multinuclear organometallic complexes measured with femtosecond pulses

Third-order nonlinear optical properties of multinuclear organometallic complexes consisting of metal–metal multiple bonds previously studied by picosecond degenerate four-wave mixing (DFWM) are reexamined by femtosecond optical heterodyned optical Kerr effect (OHD-OKE) and femtosecond Z-scan techniques. The real part of off-resonant second hyperpolarizabilities are obtained at a wavelength of 1280 nm to be +3.0 ± 10⁻³³ esu for a Pt–Mo–Mo–Pt tetranuclear complex and less than 10⁻³³ esu for a Mo–Mo dinuclear complex. The present results clarify that the previously reported values are not off-resonant values and the off-resonant property of the tetranuclear complex is superior to that of the dinuclear one.     

Effect of oxygen partial pressure on microstructural and optical properties of titanium oxide thin films prepared by pulsed laser deposition

Nanocrystalline titanium oxide (TiO₂) thin films were deposited on silicon (1 0 0) and quartz substrates at various oxygen partial pressures (1 × 10⁻⁵ to 3.5 × 10⁻¹ mbar) with a substrate temperature of 973 K by pulsed laser deposition. The microstructural and optical properties were characterized using Grazing incidence X-ray diffraction, atomic force microscopy, UV–visible spectroscopy and photoluminescence. The X-ray diffraction studies indicated the formation of mixed phases (anatase and rutile) at higher oxygen partial pressures (3.5 × 10⁻² to 3.5 × 10⁻¹ mbar) and strong rutile phase at lower oxygen partial pressures (1 × 10⁻⁵ to 3.5 × 10⁻³ mbar). The atomic force microscopy studies showed the dense and uniform distribution of nanocrystallites. The root mean square surface roughness of the films increased with increasing oxygen partial pressures. The UV–visible studies showed that the bandgap of the films increased from 3.20 eV to 3.60 eV with the increase of oxygen partial pressures. The refractive index was found to decrease from 2.73 to 2.06 (at 550 nm) as the oxygen partial pressure increased from 1.5 × 10⁻⁴ mbar to 3.5 × 10⁻¹ mbar. The photoluminescence peaks were fitted to Gaussian function and the bandgap was found to be in the range ∼3.28–3.40 eV for anatase and 2.98–3.13 eV for rutile phases with increasing oxygen partial pressure from 1 × 10⁻⁵ to 3.5 × 10⁻¹ mbar.